An active matrix type of twisted nematic liquid crystal display is provided with a lower alignment layer rubbed in rubbing directions RD3, RD4 opposite to each other, an upper alignment layer rubbed in rubbing directions RD5, RD6 opposite to each other, a liquid crystal layer arranged between the lower and upper alignment layers and filled with liquid crystal molecules set in a nematic liquid crystal phase, a pixel electrode and a common electrode for inducing a vertical electric field in the liquid crystal layer, and a source line and gate line driving a switching device for applying an electric potential to the pixel electrode. The rubbing direction on the substrate with the switching device is at an angle of 1.degree.-44.degree. to either the source or gate line. In this case, major axes of a group of liquid crystal molecules arranged above the pixel electrode are twisted in a clockwise direction, and major axes of other group of liquid crystal molecules are twisted in a counterclockwise direction.

1. Field of the Invention
The present invention relates to an active matrix type of twisted nematic liquid crystal display in which large pieces of lights are circularly polarized by pieces of liquid crystal arranged in an orderly matrix of picture elements to display a colored image.
2. Description of the Related Art
A liquid crystal display is conventionally utilized to display a colored image. In the liquid crystal display, liquid crystal is arranged along an optical path of a piece of incident light while twisting an orientation of the liquid crystal. Therefore, the incident light is circularly polarized in the liquid crystal display.
Also, an active matrix type of twisted nematic liquid crystal display in which a large number of picture elements are arranged in an orderly matrix has been recently utilized as one of the liquid crystal displays. In each of the picture elements of the active matrix type of twisted nematic liquid crystal display, liquid crystal set in a nematic phase is filled up to twist the orientation of the liquid crystal along the optical path, and a switching device is equipped to control the orientation of the liquid crystal. The twisted nematic liquid crystal display can be easily manufactured in a thin shape, and electric power consumed to operate the twisted nematic liquid crystal display is low. In addition, a contrast between a bright light and a dark light is superior in the twisted nematic liquid crystal display. Therefore, a colored image can be displayed in a high contrast on the twisted nematic liquid crystal display. Accordingly, the twisted nematic liquid crystal display has been developed for use as a television display in place of a cathode-ray tube of the television.
2.1. Previously Proposed Art
The active matrix type of twisted nematic liquid crystal display conventionally utilized is briefly described with reference to the drawings.
FIG. 1 is a plan view of the matrix type of twisted nematic liquid crystal display conventionally utilized.
As shown in FIG. 1, the matrix type of twisted nematic liquid crystal display 10 is provided with an array substrate 11 formed of transparent glass material, a large number of gate lines 12 arranged in parallel with each other on the array substrate 11, and a large number of source lines 13 arranged at right angles to the gate lines 12 on the array substrate 11. Therefore, a large number of picture elements 14 which each are surrounded by both one of the gate lines 12 and one of the source lines 13 are formed on the array substrate 11 in an orderly matrix.
In the above configuration, a pulse signal is transmitted through each of the gate lines 12, and a changeable electric potential is applied to the source lines 13.
FIG. 2 is a plan view of one of the picture elements 14 of the twisted nematic liquid crystal display 10 shown in FIG. 1. FIG. 3 is a sectional view of the picture element 14 shown in FIG. 2, the sectional view being taken generally along the line III--III of FIG. 2.
As shown in FIGS. 2, 3, each of the picture elements 14 is provided with the array substrate 11, a plate type of lower polarizer 15 arranged just under the array substrate 11 for linearly polarizing an incident white light with which the picture element 14 is irradiated, a thin type of amorphous silicon transistor 16 turned on by the pulse signal transmitted from the gate line 12, a picture element electrode 17 (or a pixel electrode 17) arranged on the array substrate 11 for receiving the changeable electric potential transmitted from the source line 13 through the amorphous silicon transistor 16 turned on by the pulse signal, and a passivation film 18 arranged between the source line 13 and the picture element electrode 17 for insulating the picture element electrode 17 from the source line 13.
The picture element electrode 17 is formed of an indiumtin oxide thin film so that the electrode 17 is transparent.
Also, the passivation film 18 is transparent.
In the above configuration, when a pulse signal is transmitted to the gate line 12, the amorphous silicon transistor 16 is turned on by the pulse signal as shown in FIG. 4 so that the changeable electric potential applied in the source line 13 is applied to the picture element electrode 17 through the amorphous silicon transistor 16 turned on. Thereafter, even though the amorphous silicon transistor 16 is turned off, the picture element electrode 17 is maintained to the changeable electric potential because the picture element electrode 17 is insulated by the passivation film 18. Also, the lower polarizer 15 is irradiated with the incident white light functioning as a back light. In this case, the incident white light is linearly polarized in a first polarizing direction PD1.
Also, each of the picture elements 14 is further provided with a lower alignment layer 19 arranged on the passivation film 18 in which polymers are oriented in a first rubbing direction RD1, an upper alignment layer 20 arranged over the lower alignment layer 19 through a spacer formed of glass beads in which polymers are oriented in a second rubbing direction RD2 normal to the first rubbing direction RD1, and a liquid crystal layer 21 arranged between the lower and upper alignment layer 19, 20.
A distance between the lower and upper alignment layers 19, 20 ranges from 2 .mu.m to 10 .mu.m.
The lower and upper alignment layers 19, 20 are transparent.
In the above configuration, liquid crystal filled in the liquid crystal layer 21 is crystallized in a nematic type of orientation. Also, the liquid crystal is a dielectric substance having an anisotropic dielectric constant, and the anisotropic dielectric constant is positive. In addition, a surface of the lower alignment layer 19 facing to the upper alignment layer 20 is rubbed to orient the polymers of the film 19 in the first rubbing direction RD1, and a surface of the upper alignment layer 20 facing to the lower alignment layer 19 is rubbed to orient the polymers of the film 20 in the second rubbing direction RD2. That is, when the alignment layers 19, 20 are rubbed in the rubbing directions RD1, RD2, a large number of small grooves are produced so that the polymers are extended towards the rubbing directions.
The rubbing directions RD1, RD2 of the alignment layers 19, 20 are set at 45 degrees to the gate and source lines 12, 13 as shown in FIG. 2 according to a conventional rubbing process. The reason that the rubbing directions RD1, RD2 are set at 45 degrees to the gate and source lines 12, 13 is to uniformly adjust the contrast of the image displayed on the entire picture element 14.
Therefore, when the liquid crystal is filled in a region between the lower and upper alignment layers 19, 20 after the lower and upper alignment layers 19, 20 are attached to each other through the spacer, major axes of liquid crystal molecules in the liquid crystal directly attached on the alignment layer 19 are oriented in the rubbing direction RD1 of the film 19 because the liquid crystal molecules oriented in the rubbing direction RD1 is energetically stable on the alignment layer 19. Also, major axes of liquid crystal molecules directly attached on the alignment layer 20 are oriented in the rubbing direction RD2 of the film 20 because the liquid crystal molecules oriented in the rubbing direction RD2 is energetically stable on the alignment layer 20.
Accordingly, the major axes of the liquid crystal molecules are gradually twisted like a spiral staircase along the optical path of the incident white light oriented from the lower alignment layer 19 to the upper alignment layer 20. As a result, the liquid crystal molecules are twisted 90 degrees in the liquid crystal layer 21. Therefore, in cases where any electric potential is not applied to the picture element electrode 17, the incident white light is circularly polarized 90 degrees in the liquid crystal layer 21 after the liquid crystal layer 21 is irradiated with the incident white light linearly polarized by the lower polarizer 15.
The major axes of the liquid crystal molecules are uniformly twisted either in a clockwise direction or in a counterclockwise direction in the entire liquid crystal layer 21 of the twisted nematic liquid crystal display 10.
In addition, the major axes of liquid crystal molecules are tilted in an upper direction at a pretilt angle .theta. having a tilt value. As shown in FIG. 5, the pretilt angle .theta. of a liquid crystal molecule is generally defined as an angle between the surface of the alignment layer 19 or 20 and a major axis of the liquid crystal molecule. The arrangement of the liquid crystal molecules at the pretilt angle .theta. is generally generated by a repulsive dipole-dipole interaction between a dipole of the polymer and another dipole of the liquid crystal molecule. Also, there are two types of twist conditions. One condition is called a normal twist condition, and another condition is called a reverse twist condition. The tilt value of the pretilt angle generally ranges from about 1 degree to 5 degrees in the normal twist condition.
Also, each of the picture elements 14 is further provided with a common electrode 22 for generating an electric field between the picture element electrode 17 charged to the changeable electric potential and the common electrode 22, a colored filter 23 arranged on the common electrode 22 for coloring the incident white light passing through the liquid crystal layer 21 red, green or blue (RGB), an opposite substrate 24 formed of transparent glass material for mounting the common electrode 22 and the colored filter 23, and a plate type of upper polarizer 25 for linearly polarizing colored light produced in the colored filter 23 in a second polarizing direction PD2 normal to the first polarizing direction PD1 of the lower polarizer 15.
The common electrode 22 is formed of an indium-tin oxide thin film so that the electrode 22 is transparent.
In the above configuration, in cases where any electric potential is not applied to the picture element electrode 17, no electric field is generated between the element picture electrode 17 and the common electrode 22. Therefore, the major axes of the liquid crystal molecules remain twisted 90 degrees in the liquid crystal layer 21. In this case, the incident white light is circularly polarized 90 degrees in the liquid crystal layer 21 after the incident white light is linearly polarized in the first polarizing direction PD1 by the lower polarizer 15. Therefore, the incident white light passing through the liquid crystal layer 21 is linearly polarized in the same direction as the second polarizing direction PD2 of the output polarizer 25 normal to the first polarizing direction PD1. Thereafter, the incident white light is colored red, green or blue in the colored filter 23 to produce a piece of colored light, and the colored light produced is linearly polarized in the second polarizing direction PD2. In this case, because the colored light has been linearly polarized in the same direction as the second polarizing direction PD2 in the liquid crystal layer 21, quantity of the colored light is not varied in the upper polarizer 25.
Accordingly, the colored light is radiated from each of the picture elements 14.
In cases where the picture element 14 having the red-colored filter 23, the picture element 14 having the green-colored filter 23, and the picture element 14 having the blue-colored filter 23 are arranged in a set, a viewer can feel colored lights provided from the above three picture elements 14 as a white light.
In contrast, in cases where a changeable electric potential is applied to the picture element electrode 17 from the source line 13, a vertical electric field is generated between the element picture electrode 17 and the commonelectrode 22. In this case, the major axes of the liquid crystal molecules twisted 90 degrees in the liquid crystal layer 21 are forcibly oriented in the same direction as the vertical electric field on condition that the intensity of the vertical electric field is high enough to forcibly orient the major axes of the liquid crystal molecules in a vertical direction parallel to the vertical electric field. Therefore, the incident white light is not circularly polarized at all in the liquid crystal layer 21 after the incident white light is linearly polarized in the first polarizing direction PD1 by the lower polarizer 15. Thereafter, the incident white light not circularly polarized is colored red, green or blue in the colored filter 23 to produce a colored light, and the colored light is transmitted to the second polarizing direction PD2. In this case, because the colored light is linearly polarized in the first polarizing direction PD1, the incident white light can not pass through the upper polarizer 25 because the colored light is linearly polarized in the second polarizing direction PD2 normal to the first polarizing direction PD1 by the upper polarizer 25. Therefore, the incident white light radiated to the picture element 14 can not transmit through the picture element 14.
Accordingly, in cases where the picture element 14 having the red-colored filter 23, the picture element 14 having the green-colored filter 23, and the picture element 14 having the blue-colored filter 23 are arranged in a set, one of three light source colored lights can be obtained by applying the changeable electric potential to two of the three picture elements 14 arranged in a set.
Also, in cases where the changeable electric potential applied to the source line 13 is controlled, major axis directions of the liquid crystal molecules of which major axes are twisted 90 degrees can be changed by a suitable angle. Therefore, the incident white light can be circularly polarized in the liquid crystal layer 21, dependent on the intensity of the changeable electric potential. As a result, the quantity of the colored light transmitted from the picture element can be controlled.
Accordingly, any type of colored light can be obtained by combining a piece of red light, a piece of green light, and a piece of blue light radiated from the set of three picture elements 14. Therefore, a colored image can be displayed on the matrix type of twisted nematic liquid crystal display 10.
2.2 Problems to be Solved by the Invention
However, the gate line 12 and the source line 13 is arranged adjacent to the picture element electrode 17 because a large number of picture elements 14 must be arranged in close formation to display a fine image. For example, the distance between the gate or source line 12, 13 and the picture element electrode 17 is within several micro meters (.mu.m).
Also, the electric potential applied to the source line 13 is always changed to control the polarization direction of the incident white light circularly polarized in the liquid crystal layer 21 by changing major axis directions of the liquid crystal molecules. Therefore, when the transistor 16 is turned off, an electric potential difference between the picture element electrode 17 and the source line 13 is necessarily generated, dependent on the change of the electric potential applied to the source line 13. As a result, not only the vertical electric field is induced between the picture element electrode 17 and the common electrode 22, but also a first lateral electric field is induced between the picture element electrode 17 and the source line 13.
In addition, the electric potential of the gate line 12 is always changed because a pulse signal is intermittently transmitted in the gate line 12. Therefore, another electric potential difference between the picture element electrode 17 and the gate line 12 is necessarily generated. As a result, a second lateral electric field is induced between the picture element electrode 17 and the gate line 12. The first and second lateral electric fields are called a lateral electric field for convenience in this specification hereinafter.
Because the lateral electric field is inevitably generated in each of the picture elements 14 in the twisted nematic liquid crystal display 10, even though the alignment layers 19, 20 are rubbed in the rubbing directions RD1, RD2 normal to each other, the liquid crystal molecules in the liquid crystal layer 21 are irregularly oriented. In other words, the normal tilt condition of the liquid crystal molecules is changed to the reverse tilt condition to stably arrange the liquid crystal molecules. Therefore, even though no vertical electric field is induced between the picture element electrode 17 and the common electrode 22, the major axes of the liquid crystal molecules in the liquid crystal 21 are not accurately twisted 90 degrees so that the contrast of the image displayed on the twisted nematic liquid crystal display 10 deteriorates.
Also, because the rubbing direction RD1 of the alignment layer 19 is generally set at 45 degrees to the gate and source lines 12, 13 and because the major axes of the liquid crystal molecules are twisted from the rubbing direction RD1 to the rubbing direction RD2, adverse influence of the lateral electric field such as a dipole-dipole interaction is easily affected on the liquid crystal molecules.
Also, because the tilt value of the pretilt angle is small, a dipole moment adversely influenced on each of the liquid crystal molecules by the lateral electric field is comparatively large.
Also, because the major axes of the liquid crystal molecules are uniformly twisted either in a clockwise direction or in a counterclockwise direction, the elastic deformation of the liquid crystal molecules is not enough to change the liquid crystal molecules irregularly oriented in the liquid crystal layer 21 to the liquid crystal molecules regularly oriented.
As a result, the liquid crystal molecules are irregularly oriented in the liquid crystal layer 21 adjacent to the picture element electrode 17 by the lateral electric field.
In addition, as a result of the liquid crystal molecules irregularly oriented in the liquid crystal layer 21, a reverse tilt disclination line is generated in the liquid crystal layer 21 adjacent to the picture element electrode 17. In cases where the reverse tilt disclination line is generated, even though any electric potential is not applied to the picture element electrode 17 by the source line 17, the incident white light polarized by the lower polarizer 15 can not be circularly polarized by liquid crystal molecules arranged adjacent to the reverse tilt disclination line so that any colored light can not be radiated from the picture element 14. Also, even though an electric potential is applied to the picture element electrode 17 by the source line 17, the incident white light polarized by the lower polarizer 15 is circularly polarized to some extent by liquid crystal molecules arranged adjacent to the reverse tilt disclination line so that a piece of colored light is radiated from the picture element 14. Therefore, the contrast of the image deteriorates.
The mechanism that the reverse tilt disclination line is generated by the lateral electric field induced between the picture element electrode 17 and the gate line 12 or between the picture element electrode 17 and the source line 13 is described with reference to FIG. 6.
FIGS. 6A, 6B explanatorily show the diffusion of the liquid crystal molecules set to the reverse tilt condition.
In cases where the intensity of the lateral electric field is low, liquid crystal molecules arranged adjacent to the picture element electrode 17 are regularly oriented. In other words, the liquid crystal molecules directly arranged on the lower alignment film 19 are set in the normal tilt condition as shown in FIG. 5. Therefore, the liquid crystal molecules in the liquid crystal layer 21 are set in a normal twist condition.
In contrast, in cases where the intensity of the lateral electric field is high, liquid crystal molecules arranged adjacent to edges of the picture element electrode 17 are irregularly oriented because the lateral electric field is concentrated at the edges of the picture element electrode 17. In other words, the liquid crystal molecules are set in the reverse tilt condition as shown in FIG. 5. Therefore, other liquid crystal molecules arranged on the liquid crystal molecules which are arranged adjacent to the edges of the picture element electrode 17 are set in a reverse twist condition.
Therefore, as shown in FIG. 6A, when the intensity of the lateral electric field becomes high, liquid crystal molecules arranged adjacent to edges of the picture element electrode 17 are strongly set in the reverse tilt condition. In contrast, liquid crystal molecules arranged on the picture element electrode 17remain set in the normal tilt condition.
Thereafter, as shown in FIG. 6B, the liquid crystal molecules strongly set in the reverse tilt condition is changed to the liquid crystal molecules weakly set in the reverse tilt condition while the liquid crystal molecules set in the normal tilt condition on the picture element electrode 17 is changed to the liquid crystal molecules weakly set in the reverse tilt condition. Therefore, the reverse tilt condition is diffused to the liquid crystal molecules arranged on the picture element electrode 17.
Thereafter, when a vertical electric field is induced between the picture element electrode 17 and the common electrode 24, major axes of the liquid crystal molecules weakly set in the reverse tilt condition are vertically oriented along the vertical electric field on the picture element electrode 17 while the liquid crystal molecules remain set in the reverse tilt condition. In contrast, major axes of other liquid crystal molecules set in the normal tilt condition are vertically oriented along the vertical electric field on the picture element electrode 17 while the liquid crystal molecules remain set in the normal tilt condition.
As a result, the reverse tilt disclination line is generated in a boundary line between the liquid crystal molecules set to the reverse tilt condition and the liquid crystal molecules set to the normal tilt condition.
Accordingly, the incident white light passing through the liquid crystal molecules arranged adjacent to the reverse tilt disclination line is irregularly poralized regardless of whether an electric potential is applied to the picture element electrode 17. Therefore, the contrast of the image displayed on the twisted nematic liquid crystal display 10 deteriorates.
In addition, a shielding film is generally equipped in a display domain of the picture element 14 to shield the incident white light passing through the liquid crystal molecules arranged adjacent to the reverse tilt disclination line. In this case, the incident white light passing through the liquid crystal molecules arranged adjacent to the reverse tilt disclination line can not transmit through the picture element 14 regardless of whether or not an electric potential is applied to the picture element electrode 17. Therefore, the contrast is improved. However, the ratio of an opening area which is not shielded by the shielding film to the entire area of the picture element 14 deteriorates so that the image can not displayed in a high brightness.

Active matrix twisted nematic liquid crystal display with rubbing direction 1-44 degrees to the electrodes

Matsushita Electric Industrial Co., Ltd.


A new and distinct Spathiphyllum plant named xe2x80x98Sweet Darioxe2x80x99 characterized by dark and glossy leaves, high shoots, most shoots producing inflorescences, shell-shaped inflorescences with large spadix.

Latin name of the genus and species of the plant claimed: Spathiphyllum hybrid.
Variety denomination: xe2x80x98Sweet Darioxe2x80x99.
The present invention relates to a new and distinct cultivar of Spathiphyllum plant, hereinafter referred to by the cultivar name xe2x80x98Sweet Darioxe2x80x99. The new cultivar originated from a cross made in a controlled breeding program in Monster, The Netherlands. The female parent is xe2x80x98991274-26xe2x80x99 (unpatented). The male parent is xe2x80x9893161-95xe2x80x99 (unpatented). xe2x80x98Sweet Darioxe2x80x99 was discovered and selected by the inventor, Petrus C. M. Olsthoorn, as a flowering plant within the progeny of the stated cross in a controlled environment in Monster, The Netherlands.
Asexual reproduction of the new cultivar was first performed by tissue culture in week 16 of 1997 in Honselersdijk, The Netherlands and has demonstrated that the combination of characteristics as herein disclosed for the new cultivar are firmly fixed and retained through successive generations of asexual reproduction and reproduce true-to-type.
The following traits have been repeatedly observed and are determined to be basic characteristics of xe2x80x98Sweet Darioxe2x80x99 which in combination distinguish this Spathiphyllum as a new and distinct cultivar:
1. Dark and glossy leaves;
2. Most shoots producing inflorescences;
3. Shell-shaped inflorescence; and
4. Large spadix.
xe2x80x98Sweet Darioxe2x80x99 has not been observed under all possible environmental conditions. The phenotype of the new cultivar may vary significantly with variations in environment such as temperature, light intensity, and day length without any change in the genotype of the plant. The following observations, measurements and values describe the new cultivar as grown in Honselersdijk, The Netherlands under conditions which closely approximate those generally used in commercial practice.
Of the many commerical cultivars known to the present inventor, the most similar in comparison to xe2x80x98Sweet Darioxe2x80x99 is the cultivar xe2x80x98Cupidoxe2x80x99 (unpatented). Compared to xe2x80x98Cupidoxe2x80x99, the leaves of xe2x80x98Sweet Darioxe2x80x99 are much darker and glossier. xe2x80x98Sweet Darioxe2x80x99 produces much more shoots than xe2x80x98Cupidoxe2x80x99. About 9 seeds of xe2x80x98Cupidoxe2x80x99 are needed to produce the same amount of shoots from a single plant of xe2x80x98Sweet Darioxe2x80x99. Nearly all shoots of xe2x80x98Sweet Darioxe2x80x99 produce inflorescences whereas only the main shoots of xe2x80x98Cupidoxe2x80x99 produce inflorescences. The inflorescences of xe2x80x98Sweet Darioxe2x80x99 are approximately 10 percent bigger than the inflorescences of xe2x80x98Cupidoxe2x80x99. The inflorescence shape of xe2x80x98Sweet Darioxe2x80x99 is shell-shaped whereas the inflorescence shape of xe2x80x98Cupidoxe2x80x99 is more oval. The spadix of xe2x80x98Sweet Darioxe2x80x99 is approximately 10-15% larger than the spadix of xe2x80x98Cupidoxe2x80x99. The inflorescence stem of xe2x80x98Sweet Darioxe2x80x99 is also much darker than the inflorescence stem of xe2x80x98Cupidoxe2x80x99. In order to force the shoots of a Spathiphyllum to flower gibberalic acid is added. xe2x80x98Cupidoxe2x80x99 needs more than twice the concentration of this hormone than xe2x80x98Sweet Darioxe2x80x99 to get the same result. The main vein of the leaves of xe2x80x98Sweet Darioxe2x80x99 is lighter than the color of the leaves whereas the main vein of the leaves of xe2x80x98Cupidoxe2x80x99 is the same color as the leaves. Finally, xe2x80x98Cupidoxe2x80x99 is more sensitive to light than xe2x80x98Sweet Darioxe2x80x99 causing the leaves of xe2x80x98Cupidoxe2x80x99 to lighten in color faster than those of xe2x80x98Sweet Darioxe2x80x99.


A method is disclosed for denitrification of compounds containing nitrogen present in aqueous waste streams. The method comprises the steps of (1) identifying the types of nitrogen compounds present in a waste stream, (2) determining the concentrations of nitrogen compounds, (3) balancing oxidized and reduced form of nitrogen by adding a reactant, and (4) heating the mixture to a predetermined reaction temperature from about 300.degree. C. to about 600.degree. C., thereby resulting in less harmful nitrogen and oxygen gas, hydroxides, alcohols, and hydrocarbons.

Compounds containing nitrogen including but not limited to nitrates, nitrites, nitro-organic compounds, ammonia, amines, and amides are often present together in various combinations in non-radioactive aqueous mixed waste streams such as sewage, sewage sludge, nitrate or nitrite wastes at metal finishing plants, and chemical and munitions plants. Nuclear materials production facilities also generate waste streams containing both nitrogen bearing compounds and radioactive materials.
In many waste or process streams, the concentration of nitrogen compounds is below 1% which is insufficient for cost effective removal of nitrogen compounds by traditional means. Removal of nitrogen from nitrogen bearing streams of higher concentration may be precluded by the presence of hazardous chemicals and/or radioactivity. Moreover, nitrogen compounds at any concentration in a waste stream, present problems such as nitrous oxide (NO.sub.x) emission upon disposal by incineration, and algae bloom induced eutrophication upon disposal by drainage into bodies of water.
Of the many methods of denitrification, very few are effective for anything other than a single nitrogen containing compound For example, The Nalco Water Handbook, 1979, pp. 6-11, states that "[t]he only chemical process that removes nitrate is anion exchange". However, the anion exchange process suffers from a number of disadvantages including 1) other nitrogen compounds are unaffected by the anion exchange, 2) additional chemicals are required to regenerate the anion exchange resin and 3) additional chemicals are required to regenerate the anion exchange resin and a waste stream is produced upon resin regeneration.
Further examples of single nitrogen compound removal include methods of ammonia removal The Handbook (pp. 6-10) also states that "[a]mmonia can be removed by degasification, by cation exchange on the hydrogen cycle, and by adsorption on certain clays, such as clinoptilolite". The disadvantage of these processes is that since they are primarily directed toward removal of ammonia, other compounds containing nitrogen are generally unaffected. A further disadvantage of these processes is that the pH of the waste stream must be raised to increase the vapor pressure of aqueous ammonia.
Another method of ammonia removal is by addition of chlorine to form nitrogen gas and hydrochloric acid. For purposes of toxic waste remediation, it is undesirable to handle chlorine or produce hydrochloric acid, and not all nitrogen compounds will release nitrogen gas upon addition of chlorine.
Hydrazine (N.sub.2 H.sub.4), may be removed by reaction with dissolved oxygen to produce nitrogen gas and water. However, any other nitrogen compounds that may be present remain unaffected by this reaction.
Each of the denitrification processes described so far are effective for removing one type of nitrogen compound. Removal of multiple nitrogen compounds by these methods requires use of multiple methods.
There are currently two methods capable of removing multiple nitrogen compounds, bacterial processing and incineration. Conventional bacterial systems usually require a settling pond or biological reactor, are carried out at temperatures below 30.degree. C., require equipment to handle great quantities of air and require residence times on the order of days to reduce nitrogen compound concentrations below acceptable limits.
In cases where nitrogen bearing waste streams are incinerated, undesirable nitrous oxide (NO.sub.x) emissions, components of smog, are produced. NO.sub.x can be combined with ammonia and destroyed by gas phase reactions at temperatures between 1000.degree. C. and 1100.degree. C. (known as thermal deNOx) or by selective catalytic reduction, at temperatures between 650.degree. C. and 750.degree. C. in the presence of a catalyst to convert the NO.sub.x to nitrogen, oxygen, and water. Disadvantages of treating nitrous oxides in the gas phase include, but are not limited to, 1) the size of the equipment required for handling gases, 2) the high temperature operation, 3) handling potentially corrosive condensate after the gas stream is cooled and 4) the cost of disposal of a spent catalyst after processing radioactive wastes.
Nitrogen compounds may be converted to a second nitrogen compound, but this does not fully remove nitrogen compounds. For example, cases where waste streams have a high chemical oxygen demand (COD) from the presence of carbonaceous and nitrogenous compounds, wet air oxidation can be used to oxidize most or all of the carbon portion of the waste. J. R. Heimbuch and A. R. Wilhelmi stated in their publication "Wet Air Oxidation--A Treatment Means for Aqueous Hazardous Waste Streams", December, 1985, Journal of Hazardous Materials, page 192: "A significant advantage of wet air oxidation is that there are minimal air pollution problems. Contaminants tend to stay in the aqueous phase. The small amount of gas that is discharged consists mainly of spent air and carbon dioxide. NOx emissions are not observed because nitrogen compounds are converted to ammonia." Thus, while wet air oxidation is effective for destroying the carbonaceous portion of the waste and converting the nitrogenous portion to ammonia, wet air oxidation as currently practiced, does not remove the nitrogen in the ammonia present in the aqueous stream.
In cases of waste streams having a plurality of nitrogen compounds, removal of nitrogen is a difficult and expensive task. Prior to the instant invention, only bacterial action and incineration were capable of removing a plurality of nitrogen compounds from an aqueous waste stream. However, neither of these approaches have nitrogen gas as the predominant nitrogenous end product and both of these approaches suffer from the previously mentioned disadvantages, especially when radioactive waste streams are considered.
The present invention is therefore, directed toward a method of removing a plurality of nitrogen containing compounds from an aqueous waste stream resulting in release of nitrogen as nitrogen gas without formation of nitrous oxides such as NO, NO.sub.2 and N.sub.2 O.sub.4. The method of the present invention relies upon aqueous phase reactions at moderate temperatures and pressures without the use of a catalyst and without the subsequent regeneration and/or disposal of a catalyst in both non-radioactive and radioactive waste treatment.

Aqueous phase removal of nitrogen from nitrogen compounds


A process for synthesizing enantiomerically pure chiral secondary alcohol compounds linked to a heterocyclic core moiety, using a natural chiral molecule starting material. The inventive process is particularly useful for bulk manufacturing of chiral secondary alcohol compounds.

It is common practice to synthesize and market a drug possessing a chiral center as its racemate. If an enantiomerically pure molecule is needed, one often synthesizes the racemate and then chirally separates the enantiomers. Manufacturing racemates means that a quantity of compound contains an equivalent weight (approximately) of isomers, one of which often has no therapeutic value and potentially may cause unsuspected side effects. For example, the sedative thalidomide was marketed as a racemate. Sedative activity resided in the R-isomer, but the contaminating S-isomer is a teratogen and is thought to cause birth defects in babies born to mothers using this drug. The R,R-enantiomer of the tuberculostatic Ethambutol can cause blindness. The lethal side effects associated with the nonsteroidal anti-inflammatory drag benoxaprofen (Oraflex) might have been avoided had the drug been sold as a pure enantiomer.
However, the issue of enantiomeric purity is not limited to the field of pharmaceuticals. For example, ASANA (.sup.i Pr=isopropyl) is a synthetic pyrethroid insecticide which contains two asymmetric centers. The potent insecticidal activity resides overwhelmingly in just one of four possible stereoisomers. Moreover, the three non-insecticidal stereoisomers exhibit cytotoxicity in certain plant species. Therefore, ASANA can only be sold as a single stereoisomer because the mixed stereoisomers would not be suitable. Therefore, there is a need to manufacture certain compounds with at least one chiral center as pure specific enantiomeric compounds and not as a racemate.
The pharmaceutical compound (R)-1-(5-hydroxyhexyl)-3,7-dimethylxanthine (described in WO93/17684, and in U.S. patent application 08/307,554, filed Sep. 16, 1994, the disclosure of which is incorporated in its entirety by reference herein) is useful for a wide variety of therapeutic indications, including, for example, sepsis and sepsis syndrome, trauma, increasing the production of multilineage cells after cytoreductive therapies, promoting engraftment after bone marrow transplantation, and alleviating the toxic side effect of interleukin-2 (IL-2), amphotericin B, cyclosporin A or FK506 therapy and granulocyte macrophage colony stimulating factor (GM-CSF) therapy. The synthesis procedure described in the foregoing International and U.S. Patent Applications is capable of achieving a chiral purity of about 95% for the R enantiomer. Also, the process disclosed has limited application for producing larger quantities of product. Therefore, there is a need in the art to improve upon this commercially viable synthetic process for producing a compound of higher enantiomeric purity.
Large-scale manufacturing of synthetic compounds, particularly compounds having a high enantiomeric purity, is usually not a simple process of increasing reagent quantitites or reaction vessel volumes. In fact, often the scale-up of synthetic protocols results in unexpected and undesirable results and/or contaminants, failing to provide commercially viable manufacturing methods. The invention addresses this need, providing a less expensive synthetic process utilizing readily available (or readily prepared) starting materials. The inventive process is directed to synthetic procedures for preparing products and isolating certain intermediates in significantly larger quantities with far higher yields and greater purity, being heretofore unknown.
Others have described synthetic processes for making chiral enantiomers using stereo specific routes involving catalytic activation, one such process is discussed in Lampilas et al., "Convergent Stereospecific Total Synthesis of Monochiral Monocillin I Related Macrolides," Tetrahedran Letters, Vol. 33, No. 6, pp. 777-780 (1992). However, Lampilas et al. is limited to reacting R (or S) propylene oxide with a lithium salt of a branched alkoxyalkynyl and subsequent preparation of a primary alcohol used in successive synthetic steps to obtain the disclosed monochiral Monocillin I and corresponding derivatives.
Mori et al., "Synthesis of the Enantiomers of cis-2-Methyl-5-Hexanolide, the Major Component of the Sex Pheromone of the Carpenter Bee," Tetrahedron, vol. 41, No.3, pp. 541-546 (1985), discloses synthesis of bichiral (2R,5S)-2-Methyl-5-hexanolide from an ethyl (2)-lactate starting material. Using a published process for preparing (S-)-propylene oxide, Mori et al. discloses converting an intermediate ester product to the corresponding (R-)-propylene oxide, having an optically determined enantiomeric purity of 97.3%. Mori et al. is limited to preparing the disclosed pheromone via the propylene oxide intermediate.
Johnston et al., "Facile Syntheses of the Enantiomers of Sulcatol," Can. J. Chem., vol. 75, pp. 233-235 (1979), discloses a synthesis for an aggregation pheromone, Sulcatol, prepared from methyl oxirane enantiomers. The R-(+)-methyl oxirane was prepared from S-(-)-ethyllactate, first converting it to tosylate and subsequently reacting the tosylate to obtain a the corresponding oxirane. The disclosed tosylate yield is 71% (based on a lactate starting material) and the resulting methyloxirane was obtained in a disclosed 50% yield (based on tosylate starting material). Johnston et al. specifically requires depressed reaction temperatures and very long reaction times (8 days). Johnston et al. is limited to specific process conditions that are non-scalable for commercial purposes and that require reaction conditions not embraced in the inventive synthetic procedure for preparing chiral propylene oxide.
Hillis et al,. "Improved Preparation of (+)-(R)-Methyloxirane," J. Org. Chem., vol. 46, pp. 3349-3352 (1981), disclose processes for preparing (+)-R-methyloxirane from (+)-(S)-lactate in several process steps. In the disclosed process steps, methanesulfonyl chloride was allowed to react with the lactate starting material in toluene, producing an intermediate, ethyl (-)-(S)-2-(mesyloxy)propanoate. The intermediate was then reacted with LiAlH.sub.4 in THF, resulting in an alcohol precursor. The alcohol precusor was reacted in a distillation process with KOH to obtain the desired oxirane product. Hillis et al. is limited to a process for obtaining the disclosed oxirane product via the specific steps provided. Hillis et al. do not disclose a method for preparing chiral secondary alcohols or derivatives thereof. Furthermore, the disclosed process for preparing the oxirane products is not the inventive process. The disclosed process requires formation of a sulfonyl intermediate and distillation of a final product, the latter of which is particularly unadaptable for commercial preparation.
Ellis et al., "Optically Active Epoxides from Vicinal Diols via Vicinal Acetoxy Bromides: The Enantiomeric Methyl oxiranes," Org. Syn., vol. 63, pp. 140-145 (1984), discloses synthetic protocols for preparing S-(-)-methyloxirane from ethyl-L-(-)-lactate through esterification, halogenation and corresponding reduction reactions. Disclosed yields for the propylene oxide intermediate are substantially less than the yields permitted by the inventive method. The disclosed synthesis requires reducing the lactate ester using lithium aluminum hydride, followed by simultaneously esterifying and halogenating an intermediate diol.
The process disclosed in Ellis et al. is limited to the specifc synthetic steps disclosed. These disclosed steps differ from the inventive process in that they do not disclose preparing R-(+)-propylene oxide via the inventive process or subsequently reacting in the R-(+)-propylene oxide in a series of reactions to obtain a secondary chiral alcohol.
Nokami et al., "A New Approach to the Synthesis of .alpha.-Hydroxy-.alpha.,.beta.-unsaturated Macrolides and (-)-Pyrenophorin...", Chem. Letters, pp. 1103-1106 (1994), discloses a process for preparing (+)- and (-)-Pyrenophorin, in which a first process step includes treating S-(-)-propylene oxide with lithium 3-tetrahydropyranyloxypropynylide to obtain an optically active alcohol. The resulting alcohol is converted to a corresponding benzl ether, and the THP-ether hydrolyzed to the corresponding alcohol. Other resulting intermediates are prepared in sequential synthetic steps to obtain a final product, (+)-/(-)-pyrenophorin. Nokami et al. is limited to preparing S-(-)-propylene oxide and other intermediates in process steps different than permitted by the inventive process to obtain a chemically different product from compounds produced by the inventive process.
The inventive process therefore provides a heretofore unknown method for preparing chiral secondary alcohols and selectively preparing and isolating intermediates thereof. The process addresses known, commercially-limiting process steps, including restrictive and unscalable reaction conditions, undesireable yields and by product contamination of desired products.

Asymmetric synthesis of chiral secondary alcohols


An electric power steering apparatus comprising a torque detector 6 for detecting a steering torque applied to a steering wheel (not shown) and a steering assist motor 8 which is driven under control based on a drive current corresponding to the steering torque detected by the torque detector 6. By further comprising an angle detector 20 for detecting a turn angle of the steering wheel, angular velocity calculating means 23 for calculating an angular velocity of turn of the steering wheel from the turn angle detected by the angle detector 20, friction compensating unit 24 for calculating an angular acceleration of turn of the steering wheel for friction compensation from the angular velocity of turn calculated by the angular velocity calculating means 23 and adding means 24d, 25 for adding a current related to the angular velocity of turn and a current related to the angular acceleration of turn calculated by the friction compensating unit 24 to the drive current, friction compensation is performed at the start of steering, more accurate friction compensation of a steering system is carried out, and an electric power steering apparatus having a good feel of steering is achieved.

The present invention relates to an electric power steering apparatus for detecting a steering torque applied to a steering wheel and controlling driving of a steering assist motor according to the detected steering torque.
An electric power steering apparatus, which controls driving of a steering assist motor based on a result of detection of steering torque applied to a steering wheel and assists power required for steering an automobile by the torque of the motor so as to give a comfortable steering feel to a driver, has spread.
FIG. 1 is a block diagram showing an example of the constitution of xe2x80x9ca power steering apparatusxe2x80x9d proposed by the assignee of the present application in Japanese Patent No. 2694213.
In this power steering apparatus as an electric power steering apparatus, an output signal of a torque sensor 6 is inputted to a control unit 7. The control unit 7 supplies a drive signal to a steering assist motor 8 based on this output signal. The steering assist motor 8 transmits its torque to the lower shaft of a steering shaft.
The torque sensor 6 detects, as the steering torque applied to a steering wheel, a relative displacement in a circumferential direction which is generated between the upper and lower shafts of the steering shaft turning about the axis of the steering wheel according to turn of the steering wheel with twist of a torsion bar interposed between the upper and lower shafts.
A rotation detector 17 for detecting a rotational position of the motor 8 is attached to the rotation shaft of the motor 8.
The control unit 7 is supplied with a rotation detection signal of the rotation detector 17 and an output signal of a vehicle speed detector 18 for detecting a vehicle speed as well as the above-mentioned output signal of the torque sensor 6, and outputs a drive signal for driving the motor 8 and an electromagnetic clutch 16.
A torque detection signal outputted by the torque sensor 6 is supplied to each of a phase compensating unit 71a for stabilizing a system by advancing the phase of the torque detection signal, an angular acceleration calculating unit 71b for calculating an angular acceleration xcfx89xe2x80x2 of turn of the steering wheel, a middle point determining unit 71c for determining the middle point of the steering wheel of a vehicle traveling in a straight direction, and a lock detecting unit 71f for detecting whether the motor 8 is locked.
Moreover, a vehicle speed detection signal outputted by the vehicle speed detector 18 is supplied to each of the lock detecting unit 71f, middle point determining unit 71c, directing current function unit 73a, correction current function unit 73b and change current function unit 73c.
The directing current function unit 73a is supplied with an output signal of the phase compensating unit 71a and a later-described change current Ia, determines a directing current I for the motor 8 based on the steering torque, change current Ia and vehicle speed detection signal, and outputs the determined directing current I.
The correction current function unit 73b is supplied with the angular acceleration xcfx89xe2x80x2 of the steering wheel outputted by the angular acceleration calculating unit 71b, determines a correction current Ic for correcting the force of inertia of the motor 8 during acceleration and deceleration and the force of inertia of the traveling system of the vehicle based on the angular acceleration xcfx89xe2x80x2 and vehicle speed detection signal, and outputs the determined correction current Ic.
The change current function unit 73c is supplied with a steering angle xcex8 outputted from a later-described steering angle determining unit 71d, determines a change current Ia for changing the characteristic of the directing current I based on the steering angle xcex8 and vehicle speed detection signal, and outputs the determined change current Ia.
The rotation detection signal of the rotation detector 17 is supplied to the lock detecting unit 7 If, middle point determining unit 71c, angular acceleration calculating unit 71b and steering angle determining unit 71d.
The steering angle determining unit 71d determines a steering angle xcex8 based on the rotation detection signal and the middle point determined by the middle point determining unit 71c, and outputs the determined steering angle xcex8.
The lock detecting unit 71f detects whether the motor 8 is locked, based on the rotation detection signal, when the supplied torque detection signal and vehicle speed detection signal are larger than their predetermined values, respectively. When the lock detecting unit 71f detects that the motor 8 is locked, a driving circuit 72b disconnects the electromagnetic clutch 16.
The output signal of the directing current function unit 73a and the output signal of the correction current function unit 73b are added together by an adder 74a, and the result of addition is supplied to an error amplifier 74b. The error amplifier 74b calculates the difference between the result of addition and a feedback signal from a current detecting circuit 71e for detecting a current flowing in the motor 8, and a voltage corresponding to the calculation result is supplied to the motor 8 by a PWM (Pulse Width Modulation) driving circuit 72a.
The following description will explain an operation of an electric power steering apparatus having such structures.
The directing current function unit 73a determines a directing current I for the motor 8 based on the torque detection signal whose phase has been compensated by the phase compensating unit 71a, the change current Ia outputted by the change current function unit 73c and the vehicle speed detection signal outputted by the vehicle speed detector 18, and outputs the determined directing current I.
Meanwhile, the change current function unit 73c determines a change current Ia for changing the characteristic of the directing current I, based on the steering angle xcex8 given by the steering angle determining unit 71d and the vehicle speed detection signal outputted by the vehicle speed detector 18, and outputs the determined change current Ia.
The angular acceleration calculating unit 71b reads a torque detection signal T supplied from the torque sensor 6 and a motor rotational speed xcfx89m of the motor 8 supplied from the rotation detector 17, and calculates the angular acceleration xcfx89xe2x80x2 of the steering wheel according to the following equation.
xcfx89xe2x80x2=Txe2x80x3/K+xcfx89mxe2x80x2/nxe2x80x83xe2x80x83(1)
Here, equation (1) can be given by the following equations.
T=K(xcex8ixe2x88x92xcex8o)
where
xcex8i: a steering angle of the upper shaft of the steering shaft,
xcex8o: a steering angle of the lower shaft of the steering shaft,
K: a spring constant of the torsion bar.
xcex8ixe2x88x92xcex8o=T/K
xcex8ixe2x80x3xe2x88x92xcex8oxe2x80x3Txe2x80x3/K
xcex8ixe2x80x3=Txe2x80x3K+xcex8oxe2x80x3xe2x80x83xe2x80x83(2)
Meanwhile,
xcex8oxe2x80x2=xcfx89m/n
xcex8oxe2x80x3=xcfx89mxe2x80x2/n
(n: the deceleration ratio of the motor rotation shaft to the lower shaft)
∴ According to equation (2),
xcex8ixe2x80x3=xcfx89xe2x80x2=Txe2x80x3/K+xcfx89mxe2x80x2/nxe2x80x83xe2x80x83(1)
The correction current function unit 73b calculates a correction current Ic for correcting the effects of the force of inertia of the motor 8 and the force of inertia of the traveling system of the vehicle, based on the angular acceleration xcfx89xe2x80x2 calculated by the angular acceleration calculating unit 71b and a vehicle speed detection signal V outputted by the vehicle speed detector 18.
The adder 74a adds the correction current Ic calculated by the correction current function unit 73b to the directing current I calculated by the directing current function unit 73a, and outputs the resultant current. Hence, it is possible to improve a feel of steering.
The error amplifier 74b calculates the difference between the result of addition outputted by the adder 74a and a current flowing in the motor 8 detected by the current detecting circuit 71e, and supplies a voltage corresponding to the calculation result to the PWM driving circuit 72a. The PWM driving circuit 72a controls driving of the motor 8 according to the supplied voltage.
In the above-described electric power steering apparatus, the effects of the force of inertia of the motor 8 and the force of inertia of the traveling system of the vehicle are compensated using the motor rotational speed xcfx89m of the motor 8 supplied from the rotation detector 17, and thus there is a problem that the cost of the parts of the rotation detector 17 is required.
Moreover, although not shown in the drawings, friction compensation of the steering system is performed by controlling a motor current flowing in the motor 8 based on the motor rotational speed xcfx89m of the motor 8 detected by the rotation detector 17, but the torsion bar of the torque sensor 6 twists and the motor 8 does not rotate from the start of steering made by the driver until the friction compensation overcomes the friction torque of the motor 8 and reduction gear. Therefore, friction compensation is not carried out at the start of steering and control of friction compensation is started slightly later, resulting in a problem that the effect of friction compensation is small.
An object of the present invention is to provide an electric power steering apparatus capable of solving the above problems.
An electric power steering apparatus according to the first invention, being provided with a torque detector for detecting a steering torque applied to a steering wheel and a steering assist motor which is driven under control based on a drive current corresponding to the steering torque detected by the torque detector, is characterized by comprising: an angle detector for detecting a turn angle of the steering wheel; angular velocity calculating means for calculating an angular velocity of turn of the steering wheel from the turn angle detected by the angle detector; friction compensating means for calculating an angular acceleration of turn of the steering wheel for friction compensation from the angular velocity of turn calculated by the angular velocity calculating means; and adding means for adding a current related to the angular velocity of turn and a current related to the angular acceleration of turn calculated by the friction compensating means to the drive current.
In this electric power steering apparatus, the torque detector detects a steering torque applied to the steering wheel, and driving of the steering assist motor is controlled based on a drive current corresponding to the detected steering torque. The angle detector detects a turn angle of the steering wheel, and the angular velocity calculating means calculates an angular velocity of turn of the steering wheel from the detected turn angle. The friction compensating means calculates angular acceleration of turn of the steering wheel for friction compensation from the angular velocity of turn calculated by the angular velocity calculating means, and the adding means adds a current related to the angular velocity of turn and a current related to the angular acceleration of turn calculated by the friction compensating means to the drive current.
Accordingly, friction compensation is performed at the start of steering and more accurate friction compensation of a steering system is carried out, thereby achieving an electric power steering apparatus having a good feel of steering.
An electric power steering apparatus according to the second invention, being provided with a torque detector for detecting a steering torque applied to a steering wheel and a steering assist motor which is driven under control based on a drive current corresponding to the steering torque detected by the torque detector, is characterized by comprising: a current detecting circuit for detecting a current flowing in the motor; a voltage detecting circuit for detecting a voltage applied to the motor; motor rotational speed calculating means for calculating a rotational speed of the motor based on the current detected by the current detecting circuit and the voltage detected by the voltage detecting circuit; angular acceleration calculating means for calculating an angular acceleration of turn of the steering wheel by adding up a value corresponding to first-order differentiation of the rotational speed calculated by the motor rotational speed calculating means and a value corresponding to second-order differentiation of the steering torque; and adding means for adding a current determined in relation to the angular acceleration of turn calculated by the angular acceleration calculating means to the drive current.
In this electric power steering apparatus, the torque detector detects a steering torque applied to a steering wheel, and driving of the steering assist motor is controlled based on a drive current corresponding to the detected steering torque. The current detecting circuit detects a current flowing in the motor, and the voltage detecting circuit detects a voltage applied to the motor. The motor rotational speed calculating means calculates a rotational speed of the motor based on the current detected by the current detecting circuit and the voltage detected by the voltage detecting circuit, and the angular acceleration calculating means calculates angular acceleration of turn of the steering wheel by adding up a value corresponding to first-order differentiation of the rotational speed calculated by the motor rotational speed calculating means and a value corresponding to second-order differentiation of the steering torque. The adding means adds a current determined in relation to the angular acceleration of turn calculated by the angular acceleration calculating means to the drive current.
Accordingly, it is possible to achieve an electric power steering apparatus which requires no rotation detector and enables a reduction in the cost of parts.
An electric power steering apparatus according to the third invention, being provided with a torque detector for detecting a steering torque applied to a steering wheel and a steering assist motor which is driven under control based on a drive current corresponding to the steering torque detected by the torque detector, is characterized by comprising: a current detecting circuit for detecting a current flowing in the motor; a voltage detecting circuit for detecting a voltage applied to the motor; motor rotational speed calculating means for calculating a rotational speed of the motor based on the current detected by the current detecting circuit and the voltage detected by the voltage detecting circuit; angular velocity calculating means for calculating an angular velocity of turn of the steering wheel by adding up a value related to the rotational speed calculated by the motor rotational speed calculating means and a value related to first-order differentiation of the steering torque; angular acceleration calculating means for calculating an angular acceleration of turn of the steering wheel from the angular velocity of turn calculated by the angular velocity calculating means; and adding means for adding a current related to the angular velocity of turn and a current related to the angular acceleration of turn calculated by the angular acceleration calculating means to the drive current.
In this electric power steering apparatus, the torque detector detects a steering torque applied to the steering wheel, and driving of the steering assist motor is controlled based on a drive current corresponding to the detected steering torque. The current detecting circuit detects a current flowing in the motor, and the voltage detecting circuit detects a voltage applied to the motor. The motor rotational speed calculating means calculates a rotational speed of the motor based on the current detected by the current detecting circuit and the voltage detected by the voltage detecting circuit, and the angular velocity calculating means calculates an angular velocity of turn of the steering wheel by adding up a value related to the rotational speed calculated by the motor rotational speed calculating means and a value related to first-order differentiation of the steering torque. The angular acceleration calculating means calculates angular acceleration of turn of the steering wheel from the angular velocity of turn calculated by the angular velocity calculating means, and the adding means adds a current related to the angular velocity of turn and a current related to the angular acceleration of turn calculated by the angular acceleration calculating means to the drive current.
Accordingly, friction compensation is performed at the start of steering and more accurate friction compensation of a steering system is carried out, thereby achieving an electric power steering apparatus having a good feel of steering. Moreover, it is possible to achieve an electric power steering apparatus having a good feel of steering by only changing software, without changing conventional hardware.
The above and further objects and features of the invention will more fully be apparent from the following detailed description with accompanying drawings.


An electronic device display may have a display cover layer. The cover layer may have a border that has an opaque masking material with an opening defining a light window for an ambient light sensor. The ambient light sensor may have a photodetector mounted in a light sensor housing. A molded clear plastic light diffuser may be used to diffuse light for the ambient light sensor that is passing through the light window. The light diffuser may reduce directionality in the ambient light sensor. The light diffuser may have an array of molded protrusions such as flat-topped cones. Alignment features may be formed in the light sensor housing and the light diffuser. Clips and other molded structures for attaching the light sensor to a mounting bracket or other structures may be molded into the light diffuser and light sensor housing.

This relates generally to light sensors and, more particularly, to structures for diffusing light for light sensors in electronic devices.
Electronic devices often include light sensors. For example, light sensors can be used to make ambient light measurements. An electronic device may use ambient light data to control display brightness under a variety of ambient lighting conditions.
If care is not taken, ambient light sensors may exhibit different sensitivities for incoming light from different directions. This directionality is generally not desired in an ambient light sensor, as it can make a device overly sensitive to its orientation relative to concentrated light sources rather than being responsive to the overall level of ambient light in the vicinity of the sensor.
To reduce directionality, an ambient light sensor may be provided with a diffuser. The diffuser is typically formed from a polymer film that is coated with acrylic beads. The film is attached to the ambient light sensor using pressure sensitive adhesive, which can lead to assembly challenges due to potential misalignment during attachment, difficulty in removing backing material from the pressure sensitive adhesive, and other handling issues.
It would therefore be desirable to be able to provide improved ways to diffuse light for a light sensor within an electronic device.

Electronic device having light sensor package with diffuser for reduced light sensor directionality


There are systems and methods for monitoring a vehicle in a fleet of vehicles and a worker that is driving the vehicle, the system comprising a headless check-in switch and a headless check-in indicator; a headless vehicle monitoring device, mounted in the vehicle, comprising: a communication module configured to communicate with a worker monitoring server; a processor, executing computer-readable instructions stored on a non-transitory medium, configured to: obtain a start monitoring signal from the headless check-in switch to launch a monitoring session; communicate the start monitoring signal to the worker monitoring server; prompt, via the headless check-in indicator, a worker to check-in; receive, via the headless check-in switch, a check-in signal; send the check-in signal to the worker monitoring server; and confirm, via the headless check-in indicator, a check-in status received from the worker monitoring server.

At any given time, an owner of a fleet of vehicles may employ several workers who travel alone in vehicles. There are risks and potential dangers that arise when a worker is alone, and it is desirable to have solitary workers check-in with a supervisor, at periodic intervals, to confirm their safety.
Currently there check-in systems that have a display interface that allows a worker to check into a back end system and provides the worker with a confirmation that he or she has checked in. These systems can be expensive. Other low cost check in systems without displays allow the ability for worker to check in but do not provide end to end communication—i.e. the worker receives no confirmation that he or she has successfully checked in.
As such, improvements to address such problems are desirable.

Systems and method for lone worker monitoring


The present invention relates to an extension cord comprising a lead having a first end and a second end. The first end comprises a socket having a cover and the second end comprises a plug. The cover is attached to the socket by a hinged joint possessing a force which resists opening of the cover. The cover comprises a retainer. The present invention also relates to a socket having a cover and a cover of a socket.

Some prior art solutions are known. For example, U.S. Pat. No. 5,336,107 discloses a device for retaining an electrical plug and extension cord to another plug and extension cord employs fastener strip elements secured to the cord adjacent to the plug by a circumferential clamping element. When the electrical plug is engaged with a corresponding socket, the mechanical fastener elements secured to the plug engage cooperating fastening elements affixed to the corresponding socket to retain the assembly in its connected state.
The aim of the prior art solution is to keep the plug and the socket firmly attached. A problem related to the above-mentioned device is that it requires a counterpart, i.e. both the plug and the socket have to have fastener elements that fit to each other.

Extension cord, socket and cover of a socket


An image forming method has steps of transferring a toner image formed on an image bearing member onto an intermediate transfer member and simultaneously transferring and fixing the toner image on the intermediate transfer member onto a recording medium. The toner contains a binder resin and a colorant, and has a storage elastic modulus (Gxe2x80x2) of 2xc3x97102 to 6xc3x97103 Pa at a temperature at which a loss elastic modulus (Gxe2x80x3) reaches 1xc3x97104 Pa, and the simultaneous transfer and fixing is conducted using a transfer and fixing unit which has a nip between a fixing roll coated with an elastic member and a heat-resistant belt laid across support rolls, and the heat-resistant belt is urged against the fixing roll and the elastic member of the fixing roll is twisted at an exit of the nip with a pressure roll mounted inside the heat-resistant belt.

The present invention relates to an image forming method in which an electrostatic latent image is developed and transferred onto an intermediate transfer member and the image is transferred and fixed onto a recording medium through heating in an electrophotographic method or an electrostatic recording method, and an image forming apparatus used in this method.
In an image forming apparatus of an ordinary electrophotographic system, for example, an image forming apparatus in which an electrostatic latent image is formed on an image bearing member and developed with a dry toner to form a toner image and the toner image is then electrostatically transferred and fixed onto a recording medium to obtain the image, there arise often problems that non-uniform density occurs in the image or a toner powder is scattered to impair the resolution of the image or the dot reproducibility. The non-uniform density or the toner scattering mainly occurs while the toner image on the image bearing member is electrostatically transferred onto the recording medium.
In the electrostatic transfer method, a toner transfer efficiency is increased in proportion to an intensity of an electric field to be applied to the toner layer. However, when the intensity of the electric field becomes higher than a certain degree, so-called Paschen discharge occurs to decrease the transfer efficiency. That is, the transfer efficiency shows a peak value in a certain intensity of the electric field. Generally, the peak value of the transfer efficiency, in many cases, does not reach 100%, and remains approximately 95% at the highest.
The transfer efficiency of the toner layer thus depends on the intensity of the electric field. Accordingly, as the intensity of the electric field is changed owing to a non-uniform thickness of the toner layer, or an uneven surface or non-uniform electric properties of a recording medium such as paper, the transfer efficiency is also changed. When the toner image formed on the recording medium is monochromic and a layer is thin, the intensity of the electric field is mainly changed owing to the uneven surface or the non-uniform electric properties of the recording medium, with the result that the image mottle occurs. When monochromic toner images formed independently on the image bearing member are overlaid and transferred onto the recording medium to form a color image, the image mottle also occurs owing to the uneven surface or the non-uniform electric properties of the recording medium. In the electrostatic transfer method, a difference in transfer efficiency by the change in a thickness of a layer between a portion of a high layer thickness formed by overlaying and transferring plural toner images and a portion of a low layer thickness formed by transferring a monochromic toner image is small, but the transfer efficiency is greatly changed and the image mottle tends to occur owing to the uneven surface or the non-uniform electric properties of the recording medium.
Meanwhile, in a so-called color image forming apparatus of an intermediate transfer system in which plural toner images formed independently on an image bearing member are electrostatically transferred primarily onto an intermediate transfer member having a less uneven surface with less non-uniform electric properties to be overlaid thereon in order and the multicolor toner image formed on the intermediate transfer member is secondarily transferred onto a recording medium, the transfer efficiency is less changed, so that an image with less image mottle can be obtained.
For transferring a toner image onto a recording medium such as paper electrostatically uniformly, it is required to apply a fixed electric field. With respect to a multicolor toner image formed on an intermediate transfer member, there is an area in which a toner image with plural layers, such as three or more layers is formed, while there is an area in which no toner image layer is formed. Accordingly, it is difficult to apply a fixed electric field to the toner image of which the layer thickness varies greatly, and the intensity of the electric field tends to be non-uniform. Consequently, in the secondary transfer by the electrostatic transfer method, not all of the multicolor toner images formed on the intermediate transfer member are transferred onto the recording medium, and a part thereof remain on the intermediate transfer member. The amount of the toner remaining on the intermediate transfer member varies depending on the thickness of the toner layer on the intermediate transfer member. As a result, the color balance of the color images obtained on the recording medium is lost, and desired color images are hardly obtained. Besides, due to the uneven surface of the recording medium, the recording medium and the intermediate transfer member are not completely adhered. The transfer electric field becomes non-uniform owing to a non-uniform gap generated therebetween, or the transfer efficiency is decreased with a Coulomb repulsion force of toners to decrease the image quality.
In order to solve these problems, Japanese Patent Publication No. 41679/1971 discloses an image forming method which has steps of adhesively transferring a toner image formed on an image bearing member onto a surface of an elastic intermediate transfer member, then heating a recording medium fed between the intermediate transfer member and a heating roller using the heating roller, and fusing the toner image on the intermediate transfer member to thermally transfer the toner image on the transfer member onto the recording medium. Further, Japanese Patent Publication Nos. 1024/1989 and 1027/1989 disclose a method in which an endless belt-like intermediate transfer member and a recording medium superposed with a toner image transferred onto the intermediate transfer member therebetween are urged with a heating roll and a pressure roll to transfer and fix the toner image on the intermediate transfer member onto a recording medium. Still further, Japanese Patent Publication Nos. 20632/1982, 36341/1983 and 1023/1989 disclose a method which has steps of heating a toner image transferred onto an endless belt-like intermediate transfer member to a temperature above a melting point of a toner, and then urging the intermediate transfer member against a recording medium to transfer and fix the toner image on the intermediate transfer member onto the recording medium, wherein after the intermediate transfer member is urged against the recording medium, the intermediate transfer member and the recording medium are circulated and moved while being contacted with each other for a long period of time, and heat transfer from the intermediate transfer member to the recording medium is satisfactorily conducted in this contact state to surely transfer and fix the toner image on the intermediate transfer medium onto the recording medium.
In these non-electrostatic transfer methods, the troubles caused by the non-uniformity of the electric field which are found in the foregoing electrostatic transfer method do not occur, so that a high-quality image with a good color balance can be obtained in a color image with a high transfer efficiency of a toner image and a high sharpness. However, in the methods disclosed in Japanese Patent Publication Nos. 41679/1989, 1024/1989 and 1027/1989, there are problems that since a pressure roll mounted on the reverse side of the recording medium is not provided with a heating unit, the recording medium takes out a large amount of heat so that the toner of the toner image in contact with the recording medium is hardly fused on the recording medium and insufficient fixing tends to occur in the image formation at a high speed in particular.
Furthermore, in the methods disclosed in Japanese Patent Publication Nos. 20632/1982, 36341/1983 and 1023/1989, there are problems that while the intermediate transfer member and the recording medium are moved in contact with each other for a long period of time, they come sometimes out of contact with each other, and therefore image disorder occurs or a pressure applied to the intermediate transfer member and the recording medium becomes non-uniform to cause image disarray.
Besides these methods, Japanese Patent Publication Nos. 63756/1991, 63757/1991 and 63758/1991 disclose a transfer and fixing method wherein in an image forming apparatus in which an intermediate transfer member carrying a toner image is urged against a recording medium with a pair of pressure rolls to transfer and fix the toner image on the intermediate transfer member onto the recording medium, a heater for preheating the recording medium is, separately from the pair of pressure rolls, mounted on an upstream side of a transfer and fixing zone to enable the high-speed fixing. Among the transfer-fixing methods using the heater for preheating as disclosed in these three documents, the method disclosed in Japanese Patent Publication No. 63756/1991 is a method in which the toner image on the intermediate transfer member is heated at a temperature lower than the fusing temperature of the toner, the pressure rolls heated at a temperature higher than the fusing temperature of the toner is urged against the intermediate transfer member, and the recording medium heated at the temperature higher than the fusing temperature of the toner is fed to the urged portion to transfer and fix the toner image onto the recording medium.
The method disclosed in Japanese Patent Publication No. 63757/1991 is, unlike the method of Japanese Patent Publication No. 63756/1991, a method in which the toner image on the intermediate transfer member is heated to a temperature lower than the fusing temperature of the toner, the pressure rolls heated at a temperature lower than the fusing temperature of the toner is urged against the intermediate transfer member, and the recording medium heated to a temperature higher than the fusing temperature of the toner is fed to the urged portion to transfer and fix the toner image onto the recording medium. Further, the method disclosed in Japanese Patent Publication No. 63758/1991 is, unlike the methods of Japanese Patent Publication Nos. 63756/1991 and 63757/1991, a method in which the toner image on the intermediate transfer member is heated to a temperature lower than the fusing temperature of the toner, the pressure rolls heated to a temperature higher than the fusing temperature of the toner are urged against the intermediate transfer member, and the recording medium heated at a temperature lower than the fusing temperature of the toner is fed to the urged portion to transfer and fix the toner image onto the recording medium.
In the transfer and fixing method using the heater for preheating as disclosed in these three documents, the excessive heating of the pressure rolls can be controlled to improve the thermal efficiency. However, it is difficult to completely eliminate the non-uniform melting of the toner image.
A fixing method and a fixing unit having a pair of pressure members and a pressure member heater that heats the pressure members as employed in an image forming apparatus are described in, for example, Japanese Patent Publication No. 4699/1984 and Japanese Patent Laid-Open Nos. 74579/1984 and 129768/1985. In the fixing method and the fixing unit, a main part has a rotatable heat-fixing roll having a heating source therein, a rotatable pressure roll mounted by being urged against the heat-fixing roll and a release agent feeding unit mounted on the heat-fixing roll to feed a release agent for preventing offset to the outer periphery of the heat-fixing roll, and a transfer paper that carries an unfixed toner image is passed between the heat-fixing roll and the pressure roll to fix the toner image. The heat-fixing roll includes a substrate roll having a heating source therein, an inner elastic layer formed on the substrate roll and an outer elastic layer mounted on the inner elastic layer and formed of an elastic material having an affinity for the release agent for preventing offset and an abrasion resistance, such as a fluororubber. The heat-fixing roll is brought into contact with the transfer paper by the elasticity of the inner elastic layer with an appropriate pressure and an appropriate contact width, and the offset phenomenon is prevented with the action of the release agent fed to the outer elastic layer.
Moreover, to meet the high speed, a method using a belt is proposed as described in Japanese Patent Laid-Open No. 132972/1986 (this method is hereinafter referred to as a belt nip method). In the belt nip method, using a fixing unit having an endless belt rotatably tensioned with plural support rolls and a heat-fixing roll that forms a belt nip in contact with the endless belt, a paper having an unfixed toner image formed thereon is passed through a belt nip between the heat-fixing roll and the endless belt to fix the image with the pressure and the heat energy in the belt nip. After passed through the belt nip, the paper is peeled off with a peel nail, and discharged outside the fixing unit. In this construction, the greater width of the belt nip between the endless belt and the heat-fixing roll can easily be secured than in the ordinary roll nip method to cope with the high speed. Further, at the same fixing speed, the heat-fixing roll in the belt nip method can be downsized in comparison with that in the roll nip method.
Nevertheless, a so-called offset phenomenon tends to occur that when the surface of the heat-fixing roll is contacted with the toner surface, the toner fused is adhered to the surface of the heat-fixing roll and migrates to a transfer medium such as paper to be fed later. In order to prevent the offset phenomenon, the surface of the heat-fixing roll is coated with a material having a good releasability from the toner fused, such as a silicone rubber or a fluororesin or with a liquid release agent such as silicone oil.
On the other hand, in recent years, an electrophotographic process has found wide acceptance in not only copying machines but also printers because of the development of appliances or the improvement of communication network in society of information technology, and downsizing, weight reduction, high speed and reliability of apparatus used have been increasingly required strictly. Especially in case of color electrophotography, an image formed is required to have a high quality and a high level of color formation. For obtaining a high-quality image with a high level of color formation, it is required, in view of a light transmission and a gloss, that a toner is satisfactorily fused and a surface of an image after fixed is smooth. To this end, a fixing step in the electrophotographic process is especially important.
As a contact-type fixing method which has been often used, a method using a heat and a pressure in the fixing (hereinafter referred to as a heat-pressing method) is generally employed. In case of the heat-pressing method, a surface of a fixing member and a toner image on a transfer medium are contacted under pressure. Accordingly, a thermal efficiency is quite good, and the fixing can quickly be conducted. This method is quite effective in a high-speed electrophotographic copying machine.
However, since the surface of the fixing member is contacted with the toner image under pressure in a heat-fused state in the heat-pressing method, an offset or wrapping phenomenon in which a part of the toner image migrates to the surface of the fixing member by being adhered thereto is liable to occur. In particular, in the color toner fixing in which plural color toners have to be fused and mixed, it is required, in comparison with the monochromic toner fixing, that sufficient heat and pressure are applied to the toner to make the toner flowable and that a toner layer in a fused state which is thick with plural colors overlaid is released without an offset or wrapping phenomenon. Thus, the releasing in the fixing of the color toner is more difficult than that in the fixing of the monochromic toner.
With respect to a simple method for preventing the adhesion of the toner to the surface of the fixing member, the surface of the fixing member is coated with silicon oil as a liquid for preventing offset. However, the use of oil involves a problem of adhesion of oil to the transfer medium and the image after the fixing. Further, it is problematic in that a tank for storing oil is required in the fixing unit which makes it difficult to downsize the fixing unit and that supply of oil is troublesome to restrict the cost reduction.
Ordinarily, the amount of oil coated on a general transfer medium in the color fixing is as large as approximately 8.0xc3x9710xe2x88x922 mg/cm2, while oil is not used at all in monochromic printers or even when oil is used, its amount is less than 8.0xc3x9710xe2x88x924 mg/cm2 which is {fraction (1/100)} of the amount of oil coated in the color fixing. Thus, the foregoing defect is not given in practice. Thus, it has been earnestly demanded that even the color fixing is enabled with the same amount of oil as in monochromic printers. Accordingly, various methods have been proposed in which the releasability of the toner is improved not by a fixing unit but by modification of a toner resin or a wax.
For example, Japanese Patent Laid-Open No. 158340/1981 discloses a monochromic toner that exhibits an excellent oilless fixing suitability by effects of a resin containing a low-molecular component and a high-molecular component and thus having a wide molecular weight distribution and a wax. The resin for the monochromic toner is adapted to endure a peel strength exerted on a toner layer in an interface of a fixing unit, namely to prevent offset with an elasticity of a rubber given by entanglement of the high-molecular component diluted with the low-molecular component.
However, when this technique is developed in the fixing of a color image, there are some problems. That is, (1) since the binder resin having the rubber elasticity given by entanglement of the high-molecular component is used, a gloss level of an image fixed is lowered to decrease color formation of a color image. (2) The binder resin is elastic but is itself soft and liable to deformation because it contains the low-molecular component in the molecule. Accordingly, when the number in toner layer is increased and 3 or 4 layers are used as in a color image, the binder resin tends to cause wrapping of the toner layers around a fixing unit in deformation by peeling to decrease a peelability. (3) In case of a color image with multiple toner layers, a wax is bled out between toner layers having different colors, with the result that the peeling of the toner layers, namely the offset tends to occur. Thus, the effect of preventing the offset is not so obtained as in the fixing of the monochromic image.
In the color toner as well, various fixing units such as a fixing unit using a high-molecular component and a fixing unit using a wax have been proposed. It is however difficult to overcome the foregoing problems. Even though a releasability is somewhat improved, the improvement with no practical problem by using oil in the same amount as in the fixing of the monochromic toner has not yet been attained.
Moreover, when the wrapping of the toner layer around the fixing unit by the adhesion of the toner can be prevented, a hot offset resistance is obtained by the viscoelasticity properties though somewhat controlling the color formation. However, in the resin of which the molecular weight distribution is widened using the mere combination of the high-molecular component and the low-molecular component, no sufficient releasability is obtained, and the large amount of oil is therefore needed for preventing the wrapping of the toner layer as stated above. Further, a styrene-acrylic resin tends to cause wrapping phenomenon around a fixing unit because of a low elastic modulus of a rubber due to a resin composition, even though a molecular weight is increased. Thus, no sufficient peelability is provided.
In addition, a fixing unit using a high-molecular component or a toner with a wax is problematic in that a gloss level is decreased. Especially when a ratio of a high-molecular component is increased, a gloss level is extremely decreased. This cannot be controlled by increasing a fixing temperature, and it is ascribable to the material.
In the mechanism of heating the intermediate transfer member and the belt nip method, not all of toners can be used in view of controlling the gloss level. The heating of the intermediate transfer member is advantageous in that a high gloss level can be obtained regardless of a type of a toner material. However, when the intermediate transfer member is preheated to decrease image unevenness and obtain a transfer efficiency, an image tends to be disarrayed on the intermediate transfer member heated in case of, for example, a toner using a resin having a low glass transition point (Tg). Further, in case of a toner using a resin containing a large amount of a high-molecular component, there is a tendency that an excessive amount of electricity is required to fuse the toner. In the pressure fixing area also, a gloss level which is an important factor of an image quality is restricted by the type of the toner material in the belt nip method alone. For example, when a low-molecular resin is used, a high gloss level is provided. Meanwhile, when a high-molecular resin is used, a low gloss level is provided. It is thus difficult to control the gloss level.
The invention has been made in view of the foregoing circumstances, and provides an image forming method and an image forming apparatus. That is, the invention provides, upon solving the problems in the related art, an image forming method in which without substantially feeding a release agent, neither image disarray in image transfer nor non-uniform melting of a toner occurs and a gloss level of an image can be controlled, and an image forming apparatus used in this method.
According to an aspect of the invention, an image forming method has steps of: transferring a toner image formed on an image bearing member onto an intermediate transfer member; and simultaneously transferring and fixing the toner image on the intermediate transfer member onto a recording medium using a transfer and fixing unit. The toner forming the toner image contains a binder resin and a colorant, and the toner has a storage elastic modulus (Gxe2x80x2) of 2xc3x97102 to 6xc3x97103 Pa at a temperature at which a loss elastic modulus (Gxe2x80x3) of the toner reaches 1xc3x97104 Pa, and the transfer and fixing unit has a nip between a fixing roll coated with an elastic member and a heat-resistant belt laid across in a tensioned condition with support rolls, and the heat-resistant belt is urged against the fixing roll and the elastic member of the fixing roll is twisted at an exit of the nip with a pressure roll mounted inside the heat-resistant belt through the heat-resistant belt.
In the binder resin of the toner, a number average molecular weight (Mn) is in the range of 2,500 to 20,000, a weight average molecular weight (Mw) is in the range of 9,000 and 90,000, a softening point (Tm) is in the range of 60xc2x0 C. to 120xc2x0 C., and a glass transition point (Tg) is in the range of 45xc2x0 C. to 70xc2x0 C.
According to another aspect of the invention, an image forming apparatus has: a transfer unit that transfers a toner image formed on an image bearing member onto an intermediate transfer member; and a simultaneous transfer and fixing unit that transfers and fixes the toner image on the intermediate transfer member onto a recording medium. The toner forming the toner image contains a binder resin and a colorant, and the toner has a storage elastic modulus (Gxe2x80x2) of 2xc3x97102 to 6xc3x97103 Pa at a temperature at which a loss elastic modulus (Gxe2x80x3) of the toner reaches 1xc3x97104 Pa, and the transfer and fixing unit has a nip between a fixing roll coated with an elastic member and a heat-resistant belt laid across in a tensioned condition with support rolls, and the heat-resistant belt is urged against the fixing roll and the elastic member of the fixing roll is twisted at an exit of the nip with a pressure roll mounted inside the heat-resistant belt through the heat-resistant belt.

Image forming method and image forming apparatus


A tool (10) for inserting large studs (80) into and removing them from nuclear reactor pressure vessel closures and the like. The tool includes an air motor and gear reducer assembly (16) for rotating the stud (80), and an air cylinder assembly (14) for applying a predetermined upward preload to the stud (80) to prevent the weight of the stud (80) from binding the threads thereof. Regulator means (130) is provided for maintaining the preload constant as the stud (80) is threaded into or out of the closure.

Tools for inserting and removing heavy studs used to fasten the cover on nuclear reactor pressure vessels must be capable of handling stud assemblies weighing up to 1000 lbs. Because of the weight of these studs, the stud threads have a tendency to bind unless an upward preload is applied to the stud during the removing and inserting operation. Most prior art tools use sets of springs to apply this preload and rotate the stud with a leadscrew and nut arrangement. In this approach the leadscrew and nut arrangement must have the same thread pitch as the stud in order to maintain a constant preload for the full travel of the stud as it is threaded into or out of the pressure vessel cover flange. Thus, these tools are limited to use on studs having the same pitch unless the leadscrew assembly is changed. These prior art tools are also inherently slow to operate since the leadscrew nut must be threaded back to the opposite end of its travel to position it for the next stud. And lastly, the size and number of springs required varies with the size of the stud, thus requiring a time consuming change of springs, or the use of different tool for each stud size.
Because of the inherent problems associated with the use of the prior art tools for inserting and removing heavy studs, it has become desirable to develop a tool that can be used on any number of different sizes of studs and which will apply an upward preload to the stud in order to prevent the threads formed thereon from binding in the threaded bore into which the stud is inserted and removed.


An apparatus for detecting the starting or ending terminus of a tape by determining the rotatory state of a reel, includes a supply reel pulse generator for generating first pulses in response to rotation of the supply reel, a take-up reel pulse generator for generating second pulses in response to rotation of the take-up reel, a supply reel stop state determination circuit for determining the stop state of the supply reel on the basis of the first pulses, a take-up reel stop state determination circuit for determining the stop state of the take-up reel on the basis of the second pulses, and a tape terminus detection circuit for detecting the starting or ending terminus of the tape on the basis of the outputs of the supply and take-up reel stop state determination circuits. The apparatus for detecting tape termini does not require a sensor lamp and a photo-transistor, and thereby enables the miniaturization of a tape recorder.

The present invention relates generally to a method and an apparatus for detecting tape termini in a tape recorder, and more particularly, to a method and an apparatus for detecting the starting and ending points of a tape by checking the rotatory states of a take-up reel and a supply reel.
A video tape recorder ordinarily performs an automatic rewinding function such that if a tape is completely wound on the take-up reel in a reproducing mode, that is, the end of the tape has been reached, the tape is automatically rewound onto the supply reel, and once the rewinding is complete, that is, the tape is at the starting position again, tape operation stops. To perform such an automatic rewinding function, a transparent section of tape, called a lead tape, is secured to the opposite ends of a length of video tape. A tape terminus detecting circuit is utilized to check for light-transmission through the tape, which travels between a sensor lamp and a photo-transistor, thereby detecting starting and ending states of a tape. More particularly, a light signal emanating from the sensor lamp is received by the opposingly situated photo-transistor via the transparent lead tape section, thereby detecting the start or end of a tape.
However, the tape terminus detecting circuit using such an optical detecting method has suffered from a problem of abnormal operation when the sensitivity thereof is decreased by strain in the lead tape and even slight changes in the luminosity of the sensor lamp. Also, the photo-transistor is generally placed in a special case for preventing ambient light from causing abnormal operation of the photo-transistor. As a result, extra space is necessary for the installation of the case, which inhibits the miniaturization of the video tape recorder (VTR).
Based on the above, it can be appreciated that there presently exists a need in the art for a tape terminus detection method and apparatus which overcomes the above-described shortcomings and disadvantages of the presently available tape terminus detection technology. The present invention fulfills this need.

Method and apparatus for detecting tape termini in a tape recorder