A peroxidase-activating oral care composition, in accordance with an embodiment of the invention, includes a non-enzymatic, water-soluble hydrogen peroxide precursor and a pH-adjusting agent capable of producing a selected pH in an aqueous solution. The composition facilitates the rapid release of hydrogen peroxide and results in the activation of a peroxidase enzyme in an oral cavity. A process for manufacturing the oral care composition including obtaining the precursor, dispersing it in a non-hygroscopic material so as to coat or encapsulate it, obtaining and associating the coated or encapsulated particles with a pH-adjusting agent, and formulating the particles into an oral care composition is provided in another embodiment. In addition, a method for activating a peroxidase system in an oral cavity of an animal, including selecting a non-enzymatic water soluble hydrogen peroxide precursor, mixing the precursor with a pH-adjusting agent, and administering the precursor and pH-adjusting agent in a suitable formulation to the oral cavity, is provided in a further embodiment of the invention.

This present invention relates to a method for activating a peroxidase enzyme system in situ.
A number of naturally occurring antimicrobial systems rely upon the ability of certain oxidizing agents to disrupt metabolic processes of bacteria, fungi and viruses. Examples of such oxidizing agents include hypothiocyanite (OSCNxe2x80x94/HOSCN), hypochlorite (OClxe2x80x94 HOCl), and hypoiodite (OIxe2x80x94 HOI). These agents are known to inhibit glycolysis, penetrate prokaryotic cell walls, and generally disrupt a wide variety of processes crucial to the survival of lower organisms at concentrations greater than or equal to about 100 micromoles per liter. The oxidizing agents are formed from the detoxification of hydrogen peroxide by mammalian peroxidase systems, such as those found in saliva, cervical fluid, lachrymal fluid, and leukocytes. Examples of such peroxidase system enzymes are myeloperoxidase, lactoperoxidase, and salivary peroxidase.
Attempts to exploit these natural antimicrobial systems have been directed to both the oral care field and the gastrointestinal tract. U.S. Pat. No. 4,150,113 and U.S. Pat. No. 4,178,362 (Hoogendorn, et al.) describe dentifrice compositions containing glucose oxidase that react with plaque and salivary glucose to produce low levels of hydrogen peroxide. Hydrogen peroxide production by such systems is, however, highly irregular due to the non-uniform distribution and unpredictable availability of substrate, namely glucose, in the oral cavity.
U.S. Pat. No. 4,269,822, U.S. Pat. No. 4,564,519 and U.S. Pat. No. 4,578,265 (Pellico, et al.) further describe dentifrice compositions containing an oxidoreductase enzyme and its specific substrate in an aqueous solution for the purpose of producing hydrogen peroxide or other antimicrobial oxidizing compounds such as hypothiocyanite ion. A more predictable amount of hydrogen peroxide (and subsequently hypothiocyanite ions) is produced by the compositions of Pellico et al., compared with those of the Hoogendorn references. The differences between the two compositions reflect the availability of glucose in the oral cavity as substrate for glucose oxidase.
There are, however, a number of disadvantages associated with the compositions of Pellico et al. These include: the limited rate of enzymatically-produced hydrogen peroxide that in turn produces the hypothiocyanite ion. The short duration of oral contact time, namely during toothbrushing, means that insufficient amounts of hypothiocyanite is available to effectively eliminate microbes in the oral cavity. In addition, the references utilize glucose oxidase as the oxidoreductase enzyme that in turn relies upon the availability of a sufficient concentration of glucose in solution to produce hydrogen peroxide. However, the glucose itself is a microbial substrate and is potentially cariogenic when present in an oral care product.
U.S. Pat. No. 4,564,519 describes a chewable dentifrice, such as a chewing gum or lozenge, which contains a dual enzyme system for producing hypothiocyanite ions upon being chewed or otherwise activated by the moisture in saliva. Such compositions suffer from similar drawbacks to those mentioned immediately above namely a slow rate of enzymatically-produced hydrogen peroxidase as well as a reliance on a cariogenic compound.
Other solid or chewable compositions capable of producing hydrogen peroxide or other oxidizing agents upon activation with moisture are taught in U.S. Pat. No. 4,320,116, U.S. Pat. No. 4,726,948, and U.S. Pat. No. 4,929,466. These compositions are foodstuffs intended for consumption by livestock in order to limit the growth of harmful bacterial within the animal""s gastrointestinal tract. These references describe the use of various enzymatic and non-enzymatic sources for hydrogen peroxide, where the enzymatic sources are glucose oxidase/glucose and the non-enzymatic sources are sodium perborate, sodium percarbonate, and calcium peroxide. However, it is known that sodium percarbonate and potassium percarbonate have extremely alkaline pH and are thus of little use in activating the peroxidase enzymes until exposed to the acidic environment within the gastrointestinal tract. Thus, the foodstuff compositions described in the reference cannot be used as a therapeutic or otherwise peroxidase-activating effect in the oral cavity.
It would thus be advantageous to provide substantially non-cariogenic compositions capable of rapidly producing hydrogen peroxide in conditions that are suitable for peroxidase enzyme activation in the oral cavity.
It would also be advantageous to provide compositions capable of rapidly producing antimicrobial hypohalite ions within the limited contact time available in most oral hygiene procedures.
It would also be advantageous to provide compositions capable of rapidly producing antimicrobial hypohalite ions upon contact with saliva within the limited contact time available in most oral hygiene procedures.
This invention satisfies the above needs. A novel oral care composition is provided.
A preferred embodiment of the invention is a non-enzymatic, water-soluble hydrogen peroxide precursor, capable of rapidly releasing an effective amount of hydrogen peroxide for activating the peroxidase system in the oral cavity, upon contact with an aqueous solution; and a pH adjusting agent capable of producing a selected pH in the aqueous solution for facilitating the rapid release of the hydrogen peroxide from the hydrogen peroxide precursor and the activation of the peroxidase enzyme in the oral cavity.
In a further embodiment of the invention, a process is provided for manufacturing an oral care product, comprising the steps of obtaining an alkali metal percarbonate; dispersing the percarbonate in a non-hygroscopic material so as to encapsulate the percarbonate; obtaining particles of percarbonate encapsulated in the non-hygroscopic material; associating the percarbonate particles with a pH adjusting agent; and formulating the particles into an oral care product.
In a further embodiment of the invention, a method is provided for activating a peroxidase system in an oral cavity of an animal, including the steps of selecting a non-enzymatic water soluble hydrogen peroxide precursor capable of rapidly releasing an effective amount of hydrogen peroxide for activating the peroxidase system in the oral cavity upon contact with an aqueous solution; mixing the precursor with a pH adjusting agent capable of producing a selected pH in the aqueous solution for facilitating the rapid release of the hydrogen peroxide from the hydrogen peroxide precursor and the activation of the peroxidase enzyme in the oral cavity; and administering to the oral cavity the precursor and pH-adjusting agent in a suitable formulation.
The present invention relates to oral care compositions which upon contact with an aqueous solution, are capable of rapidly activating a peroxidase enzyme so as to release hydrogen peroxide.
The concentrations of the components of the oral composition are given in molar units which denote the concentration of the component in the aqueous contact solution.
The limiting factor in all of the mammalian antimicrobial peroxidase systems is the availability of the substrate, namely hydrogen peroxide. Furthermore, the pH of the aqueous environment determines not only the effective release of hydrogen peroxide from the precursor but also the activity of the peroxidase system and the efficacy of the resulting oxidizing agents in penetrating the cell walls of microorganisms.
It is known, for example, that the non-ionized species of hypohalite ions more readily penetrates the cell walls of microorganisms then does the ionized species thereby having increased efficiency in inhibiting the metabolism of the microorganisms. The distribution of ionized versus non-ionized species (for instance HOCl, or hypochlorous acid, versus OClxe2x80x94, or hypochlorite ion) is highly pH dependent.
The pH activity profiles of the peroxidase enzymes lactoperoxidase, salivary peroxidase, and myeloperoxidase is maximum between pH 5 and 6, but drop off sharply below pH 4.0 and above pH 7.5. Thus, in order to maintain peroxidatic function, it is here concluded that the pH of the medium surrounding the peroxidase enzymes must be within the range of about pH 4.0 to about pH 7.5. This pH range also favors the anti-microbial, non-ionized hypohalite species which prevail at lower pH levels.
Consequently, the compositions of the invention include a non-enzymatic water-soluble hydrogen peroxide precursor and a water-soluble pH adjusting component capable of providing a pH to an aqueous contact solution of between about 4.0 and 7.9. The aqueous contact solution may commonly be saliva, but may also include an aqueous solution that is mixed with the precursor and pH adjusting agent prior to contact with the oral cavity.
The non-enzymatic water-soluble precursor may be selected from the group of stable persalts including, but not limited to, alkali metal percarbonates, for example, sodium and potassium percarbonate, alkali metal perborates, alkali metal peroxides, and hydrogen peroxide complexes such as carbamide peroxide. Preferred non-enzymatic hydrogen peroxide precursors are sodium percarbonate and carbamide peroxide due to their solubility characteristics and relatively benign toxicity in limited concentrations. The most preferred non-enzymatic hydrogen peroxide precursor is sodium percarbonate.
Sodium percarbonate is a relatively stable complex containing 2 moles of sodium carbonate complexed with 3 moles of hydrogen peroxide (27% hydrogen peroxide by weight). It is highly water soluble (120 grams per liter at 20xc2x0 C.) and produces a pH upon dissolution of between 10 and 11 (for a 1% solution). Thus, although sodium percarbonate possesses the desirable hydrogen peroxide-releasing properties for the practice of the present invention, alone they are of little utility for the activation of a peroxidase enzyme due to their high in-solution pH properties. Accordingly, a pH adjusting agent has been utilized to normalize the pH to a range of 4.0-7.9.
Carbamide peroxide is a 1 to 1 molar complex between urea and hydrogen peroxide (35% hydrogen peroxide by weight) with a molecular weight of 94.07. It is usually manufactured in the form of crystals which are highly soluble in water (800 grams per liter of water at 20xc2x0 C. to yield a saturated solution of 44.4% carbamide peroxide, equivalent to a hydrogen peroxide concentration of 15.5%). However, when carbamide peroxide is solubilized in water, a pH of approximately 3.40 (for a saturated solution) to approximately 4.05 (for a 1% solution) is obtained. This pH is slightly below the desirable range, according to the invention, for activating a peroxidase enzyme in the aqueous contact solution absent a pH adjusting agent.
The pH adjusting agent of the present invention may include any toxicologically acceptable and preferably water-soluble ingredient which is capable of producing an aqueous contact solution pH of between about 4.0 and about 7.5. Most preferably, the pH adjusting agent will provide a pH of between 5.0 and 6.0. Such pH adjusting agents include a wide variety of common buffers, acidulants, and/or alkalizers which are well known to those skilled in the art. Examples include organic acids and their alkali metal salts, such as citric acid, malic acid, butyric acid, gluconic acid, adipic acid, glutaric acid, and malonic acid; amines such as triethanolamine and tris(hydroxyaminomethane); alkali metal hydroxides, such as sodium hydroxide, potassium hydroxide, and ammonium hydroxide; and combinations thereof. Preferably, these pH adjusting agents are free of water of hydration in order to achieve long-term stability in the presence of the hydrogen peroxide precursor. The optimum concentration of the pH-adjusting agent is the lowest level necessary to achieve the desired pH adjustment of the aqueous contact solution to between 4.0 and 7.5. This concentration of the pH adjusting agent is in the range of about 0.01% by weight of the composition to about 1% by weight of the composition. However, higher and lower amounts may have utility in circumstances where the buffering capacity of the surrounding medium is either very strong or very weak, respectively.
The oral care composition described above generates hydrogen peroxide to be used as substrate for the peroxidase system in a manner that permits the concentration of hydrogen peroxide generated overall to be reduced while increasing the rate of its production. This provides a safe and effective antimicrobial composition. While the prior art describes antimicrobial activity associated with oral care products containing or generating hydrogen peroxide, the present invention provides for the first time the particular advantages of both limiting the concentration of hydrogen peroxide to a level which is suitable for the activation of a peroxidase enzyme (less than about 10 millimoles per liter in situ) and providing or limiting the pH range of the in situ composition/saliva fluids to that which is also most advantageous for activation of a peroxidase enzyme.
The antimicrobial activity of the oral compositions depend on the presence of an oxygen acceptor. The preferred oxygen acceptor for oral care applications (i.e., in the presence of salivary peroxidase or lactoperoxidase) is the thiocyanate ion, which can be provided to the composition through the inclusion of non-toxic levels of a thiocyanate salt, such as potassium or sodium thiocyanate. In general, the level of thiocyanate salt included in said compositions will be from about 1.0 millimolar to about 10.0 millimolar (again, as above, based upon the concentration achieved in the aqueous contact solution). However, the composition of the invention may be further enhanced by incorporating halide ions in the aqueous contact solution. One or more oxygen-accepting halide or pseudohalide ions, including any of chloride, iodide, bromide, and thiocyanate and combinations thereof, may be incorporated in the aqueous contact solution. These ions may already be present in solution (such as thiocyanate ion, which is present in saliva), or alternatively they may be provided as auxiliary components in the inventive compositions.
In general, oral care product use results in a dilution, of composition components on the order of 1 part composition to from about 1 part aqueous contact solution to about 5 parts aqueous contact solution (from about 1 to 1 to about 1 to 5). It is desirable that the non-enzymatic hydrogen peroxide precursors should be present at a level sufficient to release a minimum amount of hydrogen peroxide of approximately 100 micromoles per liter. A preferred range of hydrogen peroxide released is in the range of from about 500 micromoles per liter to about 2,000 micromoles per liter. The determination of the amounts of hydrogen peroxide that are released from a given composition in vitro (for instance, under controlled conditions in contact with distilled water as a diluent) are relatively simple to predict. However, the determination of amounts of hydrogen peroxide released in vivo indicates that in vivo levels are well below those predicted in vitro. This difference may result from the destruction of hydrogen peroxide by salivary catalase, interaction of hydrogen peroxide with various organic matter and non-enzymatic reducing agents in saliva, and the destructive effect of dissolved metal ions in saliva. Thus, while an upper limit of 2.0 millimoles of hydrogen peroxide per liter is predictive of an in vitro effectiveness, concentrations as high as 30 millimoles per liter may be desirable to produce much lower observed in vivo concentrations of hydrogen peroxide.
It should also be noted that an accumulation of high concentrations of hydrogen peroxide (greater than about 0.1 percent or about 29 millimoles per liter) ate not desirable due to the evidence that hydrogen peroxide is mutagenic and can cause cellular DNA damage at elevated concentrations. The prior art describes broad concentration ranges of hydrogen peroxide as halving utility in oral hygiene and tooth whitening applications, but makes little reference to the potential harmful effects of hydrogen peroxide at concentrations, for instance, in the range of 1.5 to 3.0 percent by weight (441 to 882 millimolar).
Although the peroxidase enzyme may typically be present in the aqueous contact solution (such as salivary peroxidase, which is resent in saliva), additional peroxidase enzyme, preferably lactoperoxidase, may be included in the inventive compositions in a range of from about 10 ABTS (2,2xe2x80x2-Azinobis(3-ethylbenzthiazoline sulfonic acid) units per gram of composition to about 1,000 ABTS units per gram of composition [under the assay conditions described in Pruitt, et al., Analytical Biochemistry 191, pp. 278-286 (1990)].
In a preferred embodiment of the invention, compositions may be non-aqueous, dry, or otherwise substantially water-free mixtures, which can be applied or deposited on or within an orally acceptable carrier, such as a chewing gum, dental floss, anhydrous dentifrice, or animal chew. These compositions, once dissolved in the aqueous solution at a selected pH, are capable of producing, in the absence of additional enzyme preparations, hydrogen peroxide that results in the rapid activation of an antimicrobial peroxidase enzyme system in vivo.
The hydrogen peroxide precursors of the invention, such as the alkali metal percarbonates, may be processed with little or no loss of activity from moisture pick-up if, prior to being deposited onto or into an orally acceptable carrier, the alkali metal percarbonate is first dispersed in a non-hygroscopic fluid or solid in order to coat or encapsulate each particle of the percarbonate prior to being entered into a manufacturing process. Alkali metal percarbonates processed in this manner show very little degradation during processing cycles due to moisture absorption and/or temperature exposure. Although the concept of coating moisture-sensitive materials with water-insoluble or non-hygroscopic outer layers is not new to the art, the inventive aspect of the present invention stems from the requirement that said coating must necessarily consist of a moisture-resistant fluid which has mobility and will form a fluid interface in contact with bulk moisture. Only through the formation of a thin interfacial layer in contact with bulk moisture will the intimately admixed alkali metal percarbonate and non-hygroscopic fluid release the alkali metal percarbonate (as hydrogen peroxide and an alkali metal carbonate) into the neighboring aqueous phase.
Preferred non-hygroscopic fluids and solids are non-solvents for alkali metal percarbonates. These fluids are water-insoluble, yet low enough in viscosity to be readily dispersed into a thin film or interface in the presence of bulk moisture. Such non-hygroscopic liquids include, but are not limited to, mineral oils, vegetable oils, fatty esters, silicone fluids, fluorinated hydrocarbons, and fluorosilicones. Preferred non-hygroscopic solids are also water insoluble and must be capable of being melt processed at a temperature suitable for maintaining the stability of the alkali metal percarbonate. Suitable non-hygroscopic solids include, but are not limited to, waxy solids such as mineral oils, vegetable oils, fatty esters, silicone fluids, fluorinated hydrocarbons, fluorosilicones, stearic acid, glyceryl monostearate, paraffin wax, microcrystalline wax, and fatty alcohols. An example of an applicable melt process includes batch melt processing, whereby the non-hygroscopic solid carrier is simply melted in bulk, whereupon the alkali metal percarbonate is added and dispersed. Another example of an applicable melt process is the fluid-bed processing technique described in U.S. Pat. No. 4,421,669, whereby the alkali metal percarbonate (in the form of a powdered or granular particle) is floated on an airstream and subsequently sprayed with melted droplets of the non-hygroscopic solid carrier.
Both non-hygroscopic fluid and solid carriers may also include the pH-adjusting agents of the present invention, so as to simplify the application of both inventive components (i.e., the hydrogen peroxide precursor and the pH-adjusting agent) onto or into the oral care product delivery system. Alternatively, the hydrogen peroxide precursor and the pH-adjusting agent may be dispersed separately within two different non-hygroscopic carriers and subsequently applied onto or into the oral care product delivery system in a stepwise fashion.
The choice of non-hygroscopic fluid or solid carrier for the alkali metal percarbonate is dependent upon the final oral care product delivery system contemplated. Where the formulation is an animal chew, such as a rawhide animal chew, the percarbonate may be dispersed in a non-hygroscopic fluid carrier before being deposited on the surface of the chew. Where the formulation is a chewing gum, the alkali metal percarbonate may be dispersed in either a non-hygroscopic liquid or solid, to be subsequently added batchwise to the gum base and thence kneaded to achieve homogeneity. Alternatively, the finished chewing gum may be coated with a layer of either a liquid or solid dispersion of alkali metal percarbonate.


A Vibration damping device for a microscope comprises a housing. In the housing a foam rubber defining a cavity is formed which encloses a weight. The foam rubber has a plurality of interconnected pores. The housing is of the vibration damping device has in one embodiment a rectangular shape.

The present invention refers to a vibration damping device for microscopes especially the invention relates to a vibration damping device for confocal scanning microscopes and confocal laser scanning microscopes.
It is vital for all the microscopic application that the distance between the objective and the object is constant during image capture. Vibration may cause a non-constant distance during image capture which may result in a reduced image quality. Vibration is a great inhibitor of microscope performance and it becomes a greater problem as the expected magnification and desired image quality increase, being particularly sensitive in the field of confocal laser scanning microscopy. At the threshold of the problem are vibrations which derive from the environment, such as footsteps, power applications, vehicles and other movements in the vicinity. It is assumed that suitable isolation means has been provided to reduce the effect of such vibrations on the microscope base or the table a microscope rests on. There remain, nonetheless, inherent vibrations, i.e., those deriving from devices built in the microscope itself, for example, electric motors, fans and other dynamics of microscope accessories.
The prior art provides several solution for the reduction of vibrations in microscope stands or in special elements of the whole microscope. U.S. Pat. 4,168,881 by Harold E. Rosenberger et. al., granted Sep. 25, 1979, discloses a construction of a microscope stand which reduces vibration effects. Here the objective mount is isolated from the superstructure. The microscope stage is mounted upon the pillar by means chosen to lend the stage a large measure of the pillar""s rigidity. The stage has a relatively wide, vertical span of mounting bearings in contact with the pillar and the interface is relatively low on the pillar. The objective lens is also mounted in rigid relation to the pillar, by a strong cantilever arm rising at a low angle from the pillar and stoutly and rigidly held on the pillar. The eyepiece lens, or other viewing apparatus, is mounted on an arm, also cantilevered from the pillar, which extends over and around the objective mounting arm but which does not touch it anywhere. When the microscopist, or a bystander, touches the eyepiece mounting arm or the superstructure, vibrations and deflections which he might thereby introduce are to a large extent absorbed by the eyepiece mounting arm before they can be transmitted to the pillar or through it to the objective or stage mounts An introduced complexity in structure enables the reduction of vibrations.
U.S. Pat. No. 5,764,409 by James B. Colvin, entitled: ELIMINATION OF VIBRATION BY VIBRATION COUPLING IN MICROSCOPY APPLICATIONS, granted Jun. 09, 1998 shows a base for the microscope being placed over an opening in the wafer sorter. A translational apparatus is attached to the base for lowering a charge coupled device camera into an opening in the wafer sorter. A compact housing containing microscope optics is coupled to the camera. A vibration reducing apparatus is coupled to the microscope optics for preventing movement of the camera relative to the chip.
U.S. Pat. No. 5,731,896 by Hans Baumann et. al. entitled: MICROSCOPE, granted Mar. 24, 1998 shows a microscope which has the optically imaging portion of its optical arrangement separated from the object to be observed. The microscope has at least one force exerting drive element for the compensation of vibrations acting on the optical arrangement from its surroundings in at least one direction perpendicular to the optical axis. The drive element is installed in or on the microscope. The elimination of vibrations requires complicated control electronics and increases the cost of a microscope.
An additional vibration preventing device for a microscope is disclosed in the JP-Patent Application JP10148235. The disclosed device generates a noise which supplies an acoustic wave of reverse phase to this noise, which is for example generated in the sample chamber. The two kinds of sounds are negated each other. Vibration is remarkably reduced. Again, the system requires a complicated set-up to achieve the elimination of the vibrations.
It is therefore the object of the present invention to provide means which effectively reduce the inherent vibrations of a microscope.
The aforesaid object is achieved by vibration damping device for a microscope comprising a piece of foam rubber and a weight attached to said piece of foam rubber.
It is an other object of the invention to provide a microscope which allows, despite the inherent vibrations of the microscope, the capturing of high quality images
This object is achieved by a microscope comprising a stand, at least one focusing device movably mounted to the stand, and a vibration damping device attached to at least one focusing device.
What has been recognized according to the present invention is firstly that by mechanically coupling the vibration damping device to a movable part of a microscope, the inherent vibrations and vibrations induced by external sources are reduced efficiently. The external sources for example are: air condition, fans used for external electronic devices, airplanes, vibrations of the building etc. The inherent vibrations arouse from electromotors and/or mechanical gears mounted in the stand of the microscope. The stage and/or the objective is moved by the electromotors along the optical axis in order to focus on one sample plane. Once the focus on the selected sample plane is achieved it is vital for the capturing of high quality images that the focus stays at this plane during the whole image capturing process. The vibration damping device is coupled to the stage and/or the objective to minimize the effect of the inherent vibrations on the constant focus during image capture.
It has proven advantageous that the housing of the vibration damping device is attached directly to the part of the microscope of which the vibrations should be reduced. To achieve a efficient vibration damping the vibration damping device need to be mechanically coupled to the part of the microscope which requires the damping. It is advantageous as well to attach the foam rubber with the mounted weight to the part of the microscope which requires damping. Consequently, the housing is not necessary to achieve the damping effect. It provides a better appearance of the whole vibration damping device and does not allow any manipulations of the vibration damping device.
The present invention is advantageous since with the vibration damping device a significant reduction of the vibrations is achieved. This enables that the image capture is done in one single plane of the object and is not disturbed by vibrations caused for example by the electromotor for moving the stage or the electromotor for moving the objective. The movement for the stage and the objective is along the optical axis.

Vibration damping device for microscopes and microscope with a vibration damping device


The present invention is to provide an electronic component where positional accuracy for arranging members constituting a circuit element such as a resistor element and the like is mitigated and corrosion of a terminal electrode caused by sulfur in the atmosphere is reduced. The four chips connected resistor device 1 as an electronic component comprises: an insulating substrate 2 including a front surface 2a, a back surface 2b and a side surface 2c connecting the front surface 2a with the back surface 2b; a pair of terminal electrodes placed on the front and back surfaces 2a and 2b and the side surface 2c; a resistor element 5 including a resistor member 4 connected to the pair of terminal electrodes, and a protective layer (a glass film 6 and an overcoating film 7) for protecting the resistor member 4: the auxiliary electrode 9 placed with covering the interface 8 between the overcoating film 7 and the terminal electrode 3; and a nickel plated layer 10 and a solder plated layer 11 placed on the surfaces of the terminal electrode 3 and the auxiliary electrode 9. The interface 8 is placed at the end portion 2c of the insulating substrate 2.

1. Technical Field
The present invention relates to an electronic component and a method of manufacturing the electronic component.
2. Related Art
A method of barrel plating is generally applied to forming a plated layer such as solder plated layer on a surface of a terminal electrode of an electronic component. In the barrel plating method, many electronic components are put into a basket dipped into a plating solution with metal grains called as dummy balls and plated by oscillating or rotating the basket and applying electricity to it. Even if dummy balls contact an insulating protective layer included in an electronic component, they do not contribute to plating layer formation. Hence, it is difficult to form a plating layer in an area of a terminal electrode close to the interface between a protective layer and a terminal electrode. As a result, a plated layer becomes thinned or unfinished in such area. This means that the area is exposed to the atmosphere, corroding the terminal electrode (a part including Ag in particular) with sulfur in the atmosphere.
In order to restrain such corrosion, JP-A-2004-253467 discloses the technology in that an auxiliary electrode is placed at the interface between a protective layer and a terminal electrode of a resistor element as a chip resistor device on a surface of a substrate where the resistor element is formed. The auxiliary electrode is connected to the terminal electrode.
On the other hand, other members of the resistor element such as a resistor member, a glass film for protecting the resistor member and the like are also placed on the surface of the substrate where the resistor element is formed. Hence, there is difficulty in that many members must be accurately arranged in a extremely narrow area if the auxiliary electrode further is placed at the interface between the protective layer and the terminal electrode.

Electronic component and manufacturing the same


A slider-position detector for a disk player having a slider whose friction coefficient is low on a guide rail and for carrying a pickup and capable of moving in radial direction of a disk, which detector comprises a locking mechanism for locking the slider in accordance with a locking signal, and controller for providing a locking signal to the locking mechanism while the disk player is in a stop mode. The controller further detects the movement of the slider and causes the locking to lock the slider only upon the detection of movement of the slider while the disk player is in the stop mode. While reducing unwanted operating noises, the slider-position detector is capable of surely detecting the position of the slider easily moved due to external vibrations.

1. Field of the Invention
The present invention relates to a slider-position detector for detecting the position of the slider of a disk player.
2. Description of the Prior Art
In a disk player for playing an information recording disk (hereinafter referred to simply as "disk") such as a video disk, a digital audio disk, etc., a slider carrying a pickup is linearly moved in the radial direction of a disk. The slider is driven by a rotary motor through a mechanical transmission. A rack-and-pinion mechanism, for example, reduces the speed of the rotary motion of the rotary motor and converts the rotary motion into a linear motion to drive the slider for a linear motion.
The speed of the searching operation of the slider with the pickup, namely, an operation for searching a disk for a desired recording track while moving the slider at a high speed, is restricted since the response speeds of the mechanical transmission and the rotary motor are limited. Nevertheless, increase in the speed of the searching operation has been strongly desired in the industry. The speed of the searching operation of the slider may be increased by using a linear motor which has excellent response characteristics, instead of a rotary motor, as a driving source for driving the slider for a linear motion.
The friction coefficient between the slider using the linear motor and the guide rail is smaller than that using the conventional combination of the rotary motor and the rack-and-pinion mechanism, although the disk player is usually put on a stationary place. In the disk player employing the slider driven by the linear motor, the slider is liable to be accidentally moved due to external vibrations, in the stop mode. Therefore, the slider is shifted from a position to be stopped in the stop mode when the external vibrations acts on the disk player. In this case, the next movement of the slider is not smoothly executed.

Slider-position detector for detecting the position of the slider of a disk player


A cable connector clamp for an insulated electrical cable is preferably integrally moulded from a resilient plastic material. It has a cylindrical housing defining a passage for the cable, and a slot to permit its insertion into a knock out or opening of an enclosure wall. Within the housing, there is a clamping element extending across the passage and resiliently deflectable, to permit insertion of a cable. The clamping element includes a clamping lip that is resiliently pressed against the cable to prevent its withdrawal from the connective clamp. To assist in clamping the cable, one or both of a clamping lip of reduced thickness at the free end of the clamping element, and additional projections on the inner wall of the housing are provided. The additional projections have abutment faces, perpendicular to the axis of the housing and facing the second end of it.

Electrical cables are used to connect together a variety of pieces of electrical equipment. In both domestic and industrial usage, it is common for fixed wiring cables to be inserted through an opening or hole in the wall of an enclosure, in which the cable terminates and is connected to electrical devices contained within the enclosure. Commonly, the enclosure can comprise an outlet box, in which an electrical receptacle, switch, etc., is mounted. It is desirable that the cable be clamped to prevent any mechanical loads being applied to the actual electrical connections and the opening should be substantially closed.
Electrical codes commonly require the cable to be clamped and the opening at least partially closed after insertion of the cable. At least for outlet boxes, and for a number of other enclosures, it is common to provide a number of knockouts, i.e. disc-shaped portions of the enclosure or housing, which are partially precut, to enable easy removal to form an opening. This provides a great degree of flexibility, since an end user can form the number of openings required, in the sides of the enclosure that are most advantageous.
Once the opening has been formed, it is then necessary to provide some sort of a clamp. Such a clamp can be a separate element that is secured to the housing, as by having two elements that are screwed together, in the wall of the housing. This is relatively inconvenient and time consuming.
More recently, single unit, plastic strain relief cable connector clamps, including a self-locking mechanism have become widely used. These have the advantage that they are relatively cheap and simple to make, since they are formed as a single unit component, moulded in plastic. Installation is also relatively quick and simple. The cable clamp is essentially tubular with a slit along one side, to enable it to be squeezed, for insertion into the knockout or opening of an enclosure. It then resiliently returns to its original shape, and is provided with protruding ribs to lock it in the opening.
Within the cable connector, there is a clamping element, which simply resiliently deflects as a cable is inserted. Its free end is resiliently biased against the cable sheath, with the intention that it will engage the cable, to prevent the cable being withdrawn. Thus, no separate clamping action is required.
However, in order to accommodate a wide variety of different cable sizes, it is desirable for the clamp to have a larger clamping range. Such a known design, because of its geometry, provides a substantially higher initial clamping pressure or load for a small cable, as opposed to a large cable. For a large cable, the clamping element is at a poor angle to provide a significant clamping force.
An additional problem is that electrical codes commonly stipulate that openings in connectors should be practically closed after the cable has been inserted. In this known design, the clamping element is largely circular. For larger cables, when the clamping element is deflected, it interferes with the sides of the connector clamp, which in turn interferes with insertion of the cable and the clamping action.


An organic EL element which has no layer that prevents penetration of holes and electrons to the counter electrode. The organic EL element includes: an anode, a hole injecting and transporting layer formed on the anode, a light emitting layer formed on the hole injecting and transporting layer, an electron injecting and transporting layer formed on the light emitting layer, and a cathode formed on the electron injecting and transporting layer. Ip2≧Ip3 is established when an ionization potential of a constituent material for the light emitting layer is Ip2 and an ionization potential of a constituent material for the electron injecting and transporting layer is Ip3. Ea1≧Ea2 is established when an electron affinity of a constituent material for the hole injecting and transporting layer is Ea1 and an electron affinity of the constituent material for the light emitting layer is Ea2.

The organic electroluminescence element (hereinafter, "electroluminescence" may be occasionally abbreviated as "EL") generally has a multilayer structure wherein plural layers are laminated using materials having a hole or electron injecting, transporting and blocking functions in order to achieve long-lasting life and high efficiency. Further, the organic EL element having the multilayer structure generally has a blocking layer, which prevents penetration of holes and electrons to the counter electrode, provided between an electrode and a light emitting layer to efficiently block holes and electrons in the light emitting layer.
However, there is a concern with the organic EL elements having the multilayer structure that deterioration caused during its driving at interfaces of the respective layers will lower the luminous efficiency or will deteriorate the elements to lower its luminance. In particular, charges are easily builtup at interfaces with the organic EL element comprising a blocking layer so that deterioration is easily caused at interfaces and the luminance deterioration of the element is a concern.
In order to restrain the deterioration from causing at interfaces of the respective layers during driving, methods to arrange materials used for the hole injecting and transporting layer and the electron injecting and transporting layer are proposed.
For example, the Patent Document 1 discloses a method to improve the injection properties of holes from an anode and the injection properties of electrons from the cathode, wherein an organic semiconductor layer (hole injecting and transporting layer or electron injecting and transporting layer) is constituted from either of the followings: an organic compound and an oxidizing dopant, an organic compound and a reducing dopant, or an organic compound and a conducting fine particle.
However, the organic EL element of the Patent Document 1 has the above-mentioned concerns of lowering in the luminous efficiency of causing and the deterioration of elements because an inorganic charge blocking layer (blocking layer) is provided between the organic semiconductor layer (hole injecting and transporting layer or electron injecting and transporting layer) and the organic light emitting layer.
Further for example, the Patent Document 2 discloses a method of doping an electron accepting dopant to an organic compound layer contacting to an anode, and an object thereof is to lower the energy barrier caused in injecting holes from the anode to the organic compound layer (hole injecting and transporting layer). Moreover, for example, the Patent Documents 3 and 4 discloses a method of doping an electron donating dopant to an organic compound layer contacting to a cathode, and their respective object is to lower the energy barrier caused in injecting electrons from the cathode to the organic compound layer (electron injecting and transporting layer).
Patent Document 1: Japanese Patent Application Laid-Open (JP-A) No. 2000-315581
Patent Document 2: JP-A No. 11-251067
Patent Document 3: JP-A No. 10-270171
Patent Document 4: JP-A No. 10-270172

Yamagata Promotional Organization for Industrial Technology


Provided are techniques that may include a disposable magnetic cell isolation holder having one or more passages that accommodate a magnetic retention material to facilitate magnetic cell isolation without adjustment of magnetic field parameters between isolation procedures using different magnetic particle sizes. When the magnetic cell isolation holder is coupled to a magnetic field generator, a first passage corresponding to a smaller particle size is positioned in a magnetic field where the magnetic field characteristics are different relative to a second passage, of a second holder or in the same holder, for use with another bead size.

The subject matter disclosed herein relates to the field of cell isolation and, particularly, to the field of magnetic particle-based cell selection.
Magnetic particle-based cell selection, or more simply referred to as magnetic cell isolation or magnetic cell selection, is a procedure used to isolate cells (e.g., T-cells or stem cells) from a cell mixture. In this procedure, cells in a biological sample (i.e., a cell mixture) are incubated with magnetic particles coated with antibodies or ligands designed to react with a particular surface antigen(s) of a target cell type. The antibodies or ligands recognize and bind to receptors on the surface of the target cell type, and the resulting cell suspension is passed through an external magnetic field generated by a magnetic isolation device. The target cells bound, via the antibodies or ligands, to the magnetic particles, are retained in the magnetic isolation device via magnetic force while the unlabeled cells pass through. With removal from the magnetic field, the target cells of interest can then be collected, thus isolating, or selecting out, the target cell population from the initial cell mixture.


An optimizer circuit is interposed between a DC bus and a battery of a power supply system, including two converters in parallel, one that can lower the battery voltage below the bus voltage or directly connect the bus to the battery and one that can raise the voltage to the battery above the bus voltage. A controller actuates the two converters for optimizing battery charging and maintenance and for providing the battery power to the bus if other sources supplying the bus are not available.

In some applications, such as aircraft applications, batteries are used as a power source for engine starting or as an emergency power source for a DC bus. Obviously, it is important to maintain the battery in a fully charged condition and to charge it after use. In known systems, a DC bus to which the battery is connected may itself be powered by a DC source, such as an engine-driven AC generator and a transformer rectifier unit (TRU) to convert AC to DC. During normal operation, the DC power source provides power for electrical loads of the system, in addition to providing power for charging the battery. If the DC power is interrupted, the battery immediately provides power to the DC bus. In order to reduce the voltage variation on the DC bus, the battery nominal voltage is usually selected to be close to the DC bus voltage.
The battery system with these components is simple and low cost so it is widely used in aircraft, electrical vehicle, and telecommunications applications. However, in this configuration, the battery is maintained in a float mode where the battery is fully charged and is essentially being topped off continuously because the DC power feeding the bus almost always is available. Therefore, the battery may be overcharged for long periods of time, resulting in battery overheating and electrolyte loss. On the other hand, if the bus voltage is too low the battery could be undercharged, resulting in capacity fade. In both cases this results in reducing system reliability, as well as increasing battery system maintenance cost. In addition, it may be undesirable to keep a completely discharged battery floating on the bus because the battery may draw a large transient current during initial charging and overloading the DC source.
One approach to these problems is to regulate the DC bus voltage in a way that is better for charging the battery. For example, the DC bus voltage may be initially reduced following battery discharge to prevent large current in-rush transients. The voltage may then be raised above a normal charging level to increase the battery charging rate. Such systems provide better control over battery charging to prevent overheating of the battery, and allow the battery to be recharged more quickly. However, there is substantial increased cost and complexity in regulating the DC bus voltage, and other aircraft systems connected to the bus may be affected.
More often, the DC bus is powered with an unregulated source, such as a TRU. In these systems, attempts have been made to intermittently connect the battery to the bus, as described, for example, in U.S. Pat. No. 3,703,675, which uses a contactor to control the battery charge and a parallel diode to provide a discharge path, and U.S. Pat. No. 5,969,436, which uses a MOSFET in series with a diode in order to control battery discharging. Another approach has been to add a "boost" circuit in series with an intermittently charged battery, to provide a voltage higher than the DC bus voltage for battery charging. See, for example, U.S. Pat. No. 4,061,956. Also, U.S. Pat. No. 4,443,752 describes a similar technique using a MOSFET as a switch. In either of these systems, two series-connected power components are provided on the high current path between the DC bus and the battery, which may increase power dissipation during operation.


An aluminum-based material and method of manufacturing products from the aluminum-based material formed by a solid solution of zinc, magnesium and copper in aluminum with dispersed phase particles of aluminum, zinc, magnesium and copper essentially evenly distributed in the solution and particles of nickel aluminide being essentially evenly distributed in the matrix of the aluminum-based material that contains particles, essentially evenly distributed in the matrix, of at least one of the aluminides group such as chromium aluminide and zirconium aluminide, with a total content of 0.1-0.5% of the volume with the maximum amount of nickel aluminide particles being 3 xcexcm and the proportion between the maximum and minimum amount of nickel aluminide particles of no more than 2 and with the maximum amount of chromium aluminide and zirconium aluminide particles is 0.05 xcexcm, resulting in the aluminum-based material having a microhardness of no less than 170 HV, a tensile strength of no less than 530 MPa and elongation of no less than 2%.

The innovation belongs to the area of metallurgy of aluminum-based materials and a method of manufacturing products from such materials that can be used for recreational equipment, in various vehicles and their parts, and as an additive material for welding articles produced from aluminum-based material.
There are known aluminum-based materials that contain a matrix formed by a solid solution of certain elements, in particular, by a solid solution of copper in aluminum, and solidified particles of aluminide, including, according to (US-A N 5300157, cl. MKI(5) C22C 21/00, cl. NKI 148/437, 1994), nickel aluminides that are essentially uniformly distributed in the matrix. Such materials exhibiting a high degree of hardness and wear resistance are complex to produce and require laser technology of powder-coating materials in an inert gas atmosphere.
Also known are aluminum-based materials having a matrix formed by a solid solution of zinc, magnesium and copper in aluminum with the magnesium content being higher than the copper content and being lower than the zinc content, and containing solidified aluminides, such as particles of nickel aluminide (SU-AI N 1061495, cl. MKI(5) C 22 C 21/10, 1992), all these particles being essentially uniformly distributed in the matrix.
Such materials exhibit high strength properties with satisfactory ductility but they are also difficult to produce, because their production requires casting by granulation technique that provides the solidification of materials at a rate no less than 1000 K/s.
The material that seems closest to the claimed material is an aluminum-based material having a matrix formed by a solid solution of zinc, magnesium and copper in aluminum with dispersed particles of phases formed by aluminum, zinc, magnesium and copper essentially uniformly distributed in this solution. The material has a magnesium content that is higher than the copper content and lower than the zinc content. The material also contains solidified particles of nickel aluminides that constitute 3.5-11% of the total volume of the material and are essentially uniformly distributed in the matrix. (N. A. Belov et al. xe2x80x9cThe Effect of Nickel Aluminide and Magnesium Silicide on the Structure, Mechanical and Casting Properties of an Alxe2x80x94Znxe2x80x94Mgxe2x80x94Cu Alloy,xe2x80x9d Izv. Ross. Akad Nauk, Metally, No. 1, 1992, pp. 146-151).
This material combines high strength and ductility with satisfactory technological properties providing the possibility of manufacture articles by shaped castings and low pressure. However, in some cases, the durability and casting properties of such a material proved to be insufficient.
Also known is the process of making articles from an aluminum-based material by casting them from a molten mixture of aluminum, zinc, magnesium, and nickel which includes heating, holding, quenching, and aging. (N. A. Belov, V. S. Zolotorevskii, E. E. Tagiev. xe2x80x9cThe Effect of Nickel Aluminide and Magnesium Silicide on the Structure, Mechanical and Casting Properties of an Alxe2x80x94Znxe2x80x94Mgxe2x80x94Cu Alloy,xe2x80x9d Izv. Ross. Akad. Nauk, Metally, no. 1, 1992, pp. 146-151). However, this process does not allow one to obtain articles with required level and stability of mechanical properties.
The main objective of the present invention is to develop an aluminum-based material exhibiting a high strength and ductility properties, namely, a tensile strength no less than 530 MPa and an elongation of no less than 2%, which provide, in combination with good technological properties, the possibility of producing items, including thin-walled articles, by means of shaped casting into metallic molds, for example under low pressure, or by liquid forging. Another objective of the invention is to develop a method for manufacturing aluminum-based articles, including thin-walled articles, having said strength and ductility properties.
In accordance with an embodiment of the present invention, an aluminum-based material having a matrix formed by a solid solution of zinc, magnesium and copper in aluminum with uniformly distributed dispersed particles of phases formed by aluminum, zinc, magnesium and copper with the magnesium content being higher than the copper content and being lower than the zinc content, and contains solidified particles of nickel aluminide are essentially uniformly distributed in the matrix and constitute 3.5-11% of the volume of the material. The material additionally contains particles of at least one of the aluminides group consisting of chromium aluminide and zirconium aluminide, with a total content of 0.1-0.5% of the material volume, which are essentially uniformly distributed in the matrix. The matrix has a microhardness of no less than HV 170; the size of nickel aluminide particles does not exceed 3 xcexcm, and the maximum-to-minimum size ratio of no more than 2.
The particles of chromium aluminides and zirconium aluminides are no larger than 0.05 xcexcm. In this case, the tensile strength will be no less than 530 MPa and the elongation will be no less than 2% because the particles of chromium aluminide and/or zirconium aluminide, in combination with other strengthening phases, provide an additional strengthening of the matrix, increasing its microhardness up to a value no less than 170 HV. This value is chosen with the aim to provide the prescribed strength of the material, while the content of aluminide particles is chosen from the following considerations. If the content of the particles is lower than the minimum value, the prescribed microhardness value of the matrix is not attained; if, however, the content of the particles exceeds the maximum value, the elongation decreases below the prescribed value. The limitation on the size of the particles of nickel aluminides is set to prevent cracking and the lowering of strength and ductility of the material.
The formulated task is solved also in such a way that in order to manufacture products from aluminum-based material with tensile strength no less than 530 MPa and elongation no less than 2% by means of casting from a molten mixture of aluminum, zinc, magnesium, copper and nickel. In the process, solidification of the material is followed by heat treatment of the material, including heating, holding, quenching, and aging. According to an embodiment of the innovation, at least one of the elements from a group that includes chromium and zirconium is introduced into the molten mixture. The solidifaiton of the material is released at a rate of 2 to 90 K/s, and the heating of articles before quenching is accomplished in two steps. In the first step, the temperature is established at a level of 5-10 K lower than the temperature of nonequilibrium solidus of the material. In the second step, at a level that is higher than the nonequilibrium solidus temperature lower than the temperature of the equilibrium solidus of the material. Articles obtain, after aging, the material comprising (1) a matrix that has a microhardness no less than HV 170 and is formed by a solid solution of zinc, magnesium, and copper in aluminum and dispersed particles of phases formed by aluminum, zinc, magnesium, and copper uniformly distributed in the matrix, with a volume fraction of 3.5-11%, the maximum size no larger than 3 xcexcm, and the maximum-to-minimum size ratio no higher than 2; and (3) particles of at least one of the aluminides selected from a group consisting of chromium aluminides and zirconium aluminides with a total volume fraction of 0.1 to 0.5% of the material volume, these particles being also uniformly distributed in the matrix.
The introduction of chromium and/or zirconium to the molten mixture of aluminum, zinc, magnesium, copper and nickel provides the formation in the material of an article of particles of chromium aluminide and/or zirconium aluminide, which increases the strength of the material. The rate of solidification indicated above makes it possible to fabricate articles by shaped casting, for example by low pressure or using liquid die forging. The temperatures prescribed for the regimes of heating and annealing before quenching enables one to obtain the structure of the material with a specified strength and ductility.

Aluminum-based material and a method for manufacturing products from aluminum-based material


A medical device for treatment for overweight or obesity is presented. The medical device is attached or implanted in patient's target body organs, wherein in each one of the device attachments, or daily in the case of long continuous attachment, the device removes up to 100 grams of energy containing materials from the body. The medical device optionally contains needles or alternatively contains crawling worm-like arm. The energy containing materials may be fat cells, fatty acid molecules driven out from the fat cells or lipids or carbohydrates molecules such as glucose from the blood stream.

The present invention, in some embodiments thereof, relates to obesity treatment and, more particularly, but not exclusively, to liposuction and fat removal treatments.
Excess body weight is now widely recognized as one of today's leading health threats in most countries around the world and as a major risk factor for type 2 diabetes, cardiovascular disease, certain types of cancer and hypertension. Recent studies show that on average, obesity reduces life expectancy by six to seven years. A BMI of 30-35 reduces life expectancy by two to four years, while severe obesity (BMI>40) reduces life expectancy by 10 years.
Conservative treatment for obesity consists of dieting and physical exercise. However, due to the low success rate, medical treatments are extensively explored. Both medication and surgeries treatments are being used.
Most current medication treatments work by suppressing the appetite or decreasing absorption of fats eaten. Apart from its questionable success, current available medication suffers from major side effects and many medication did not get FDA approval or withdrawn from the market by the FDA after new risks and side effects revealed after FDA approval.
Surgical procedure are divided to bariatric surgeries that reduce the capacity or the opening of the stomach and liposuction, in many cases, considered more as a cosmetic surgery, that remove fat from many different sites on the human body such as abdomen, hips, thighs etc. Both types of surgeries are risky and have side effects and are not recommend for non extreme cases in general.
It is well recognized that new effective, less expensive, less risky and with as less as possible side effects obesity treatment are highly required.
The present invention addresses the issues of obesity by introducing a new type of medical treatment performed by a matching medical device.

Fat removal device and obesity treatment


The transducer (1) includes a support structure (2, 3) in which a metal body (8) is mounted, having a flat surface (8a) and on the opposite side a cavity (8b) for exposure to a pressure to be transduced. A thin wall (8c), resiliently deformable like a membrane under the effect of the pressure, is defined between the bottom of the cavity (8b) and the flat surface (8a). An inductor (10) a body of ferromagnetic material (11)is securely fixed to the metal body (8) and has a flat surface (11a) facing the flat surface (8a) of the metal body (8) and an annular recess (12) which defines a central core (13) with a winding (16) arranged therein and a surrounding sleeve (14). A spacer wing (9) of paramagnetic or diamagnetic material, and a calibrated thickness, is interposed between the metal body (8) and the ferromagnetic body (11).

The present invention relates to an inductive pressure transducer.
More specifically, the invention relates to a pressure transducer which can be used to detect the pressure of a fluid,for example in an air conditioning or climate control system, such as the passenger compartment of a motor vehicle.
The object of the present invention is to produce a pressure transducer offering a high degree of reliability and accuracy in operation, which is also easy to assemble and calibrate at the production site.


Furniture including a cushion comprising padding material, and upholstery material covering the padding material and releasably secured thereto. Such construction may advantageously be utilized for forming a cushion essentially in the form of an open-ended bag which is slipped over a cushion-receiving part of a frame for an item of furniture. The frame may include a base pan which is covered by padding material in turn covered by upholstery material. The upholstery material includes flaps releasably joined together on the underside of the base pan, and at least part of the upholstery material on the underside of the base pan is releasably secured to the base pan.

This invention relates to furniture construction, and more particularly to a unique chair or similar article fabricated from easily assembled and easily removed cushioning.
The present invention utilizes a base pan of a chair or similar article which is covered with padding material. Upholstery material covers the padding material and is formed with flaps that are releasably joined together on the underside of the base pan after the upholstery material is positioned in place over the padding material on the base pan. Selected parts of the upholstery material on the underside of the base pan are releasable secured to adjacent parts of the base pan to secure the entire cushion assembly to the base pan.
The base pan advantageously includes one or more upwardly extending cushion-receiving frame members. One or more cushions having openings therein to removably receive the cushion-receiving frame parts are utilized.
In this fashion a chair can be simply constructed with removable cushions that simply slip into place over frame parts, in combination with a uniquely upholstered base pan to which a part of an upholstery covering is releasably secured.
The cushions that receive the upwardly extending frame parts are advantageously formed from upholstery material that covers one surface of a padding material and which is releasably secured to an opposite surface of the padding material for ease in removing the upholstery material for cleaning.
The invention finds particular application with frame members of the type disclosed in my copending application Ser. No. 363,798 filed May 25, 1973, identified above.
In the prior art, cushions having openings therein for securing frame parts are known. See U.S. Pat. No. to Briggs 3,680,918 issued Aug. 1, 1972. Neither the unique releasable securing of upholstery material to padding nor the upholstering of a base pan as described above is disclosed or suggested in this patent.
The invention will be better understood by reference to the following detailed description, to be read in conjunction with the appended drawings .


A road gully or inspection cover assembly comprises an outer frame having an upstanding outer wall and integrally formed support structure extending inwardly of the lower regions of the outer wall over part at least of the peripheral extent of the outer wall, a first temporary inner frame for location within the outer frame, the outer frame and the first temporary inner frame co-operating to support a cover for the assembly in a first, lowermost position associated with the base course level of the road, and a second inner frame which, on removal of the first inner frame from within the outer frame, can be located within the outer frame to support the cover at a higher position associated with the wearing course level of the road.

This invention relates to a road gully or inspection cover assembly, and more particularly to such an assembly that permits ready adjustment of the vertical position of the cover of the assembly.
It is a necessary part of the construction of new roads to incorporate water gullies and manholes therein all of which have to be covered, the covers eventually needing to be at the finished level of the road.
Common practice is initially to construct a road to a base course level and thereafter to apply a wearing course of substantial thickness to complete the road.
The gullies and manholes are incorporated prior to application of the wearing course, and invariably extend above the base course with their covers located at a level anticipating that of the final wearing course.
There is often a considerable period of time, particularly in new housing estates, between laying of base courses and wearing courses, and this can create a number of problems.
As the covers project above the surface of the base course by the thickness of the wearing course, they constitute serious obstacles to vehicles with low clearance as well as to pedestrians. They can cause damage to, and can themselves be damaged by, vehicles, particularly road cleaning vehicles incorporating mechanical front shovels. In such situations, the assemblies, or at least the covers thereof, often have to be replaced and the associated manhole or gully cleared of rubble to prevent blockage.
Additionally, the finished level of the water gullies, being above that of the base course prior to the application of the wearing course, results in the accumulation of large pools of water on the roads during wet weather.
It has been proposed, for example in my European patent no. 0715028, to provide a road gully or inspection cover assembly the position of the cover of which can be adjusted to accommodate the difference in levels between the base course and the wearing course of the road.
More particularly, the known assembly comprises a fixed outer frame and an adjustable inner frame slidably supported in the outer frame and capable of being located at any position between a lowermost position and an uppermost position, the inner frame supporting the cover of the assembly whereby the cover can initially be located at the base course level of the road, and subsequently raised and located at the wearing course level of the road.
Such an assembly is suitable for situations in which the depth of the wearing course is within certain defined limits whereby strict regulations relating to the extent of overlap of the components of the assembly can be satisfied.
In particular, it is necessary to provide a minimum 50 mm vertical overlap of the cover with its supporting frame, and a minimum 50 mm overlap between the inner and outer frames.
The standard depth of the outer frame is 100 mm, the thickness of the base plate of the outer frame is 6 mm, and the recommended thickness of the wearing course is 40 mm. The overall relationship between the inner and outer frames of this known assembly is such as to provide a maximum adjustability between the lowermost and uppermost positions of the inner frame, and therefore the maximum depth of wearing course that can be accommodated by the assembly, of 44 mm.
It would be desirable to be able to provide a road gully or inspection cover assembly capable of accommodating thicker wearing courses than heretofore, whilst still satisfying British Standard regulations.
According to the present invention there is provided a road gully or inspection cover assembly comprising an outer frame having an upstanding outer wall and integrally formed support means extending inwardly of the lower regions of the outer wall over part at least of the peripheral extent of said outer wall, a first temporary inner frame for location within the outer frame, the outer frame and the first temporary inner frame co-operating to support a cover for the assembly in a first, lowermost position associated with the base course level of the road, and a second inner frame which, on removal of the first inner frame from within the outer frame, can be located within the outer frame to support the cover at a higher position associated with the wearing course level of the road.
There may be a plurality of second inner frames, one associated with each of a number of different higher positions.
Alternatively, the position of the second inner frame relative to the outer frame may be vertically adjustable, for example by providing selectively variable support means reacting between the outer frame and the underside of the second inner frame.
In a first embodiment of the invention, the outer frame is of upwardly-open channel shape in transverse section over said part at least of the peripheral extent of the outer wall thereof, the inner wall of the section comprising said support means, the lowermost position of the cover being determined by abutment of the cover with the inner wall of the channel section, the first temporary inner frame surrounding the cover in its lowermost position to close the hollow interior of the outer frame, the second inner frame being received within the channel section of the outer frame to determine the higher position of the cover.
In a second embodiment of the invention, the outer frame is of substantially L-shape in transverse section over said part at least of the peripheral extent of the outer wall thereof, the inwardly extending lower leg of the section comprising support means having a horizontal upper surface thereto.
The lowermost position of the cover may be determined by abutment of the cover with the upper surface of the support means, the first temporary inner frame also seating on the upper surface of the support means to surround the cover in its lowermost position and to close the outer frame, the second inner frame seating on the upper surface of the support means to determine the higher position of the cover.
Alternatively, the first temporary frame may seat on the upper surface of the support means and may be configured to receive thereon the cover, typically a gully grate, to determine the lowermost position of the cover, the second inner frame again seating on the upper surface of the support means to determine the higher position of the cover.
The invention is particularly suited to assemblies incorporating covers of generally rectangular shape, it being preferred that the inwardly extending support means are provided at the corner regions only of the outer frame.
Accordingly the first and second inner frames will include downwardly extending leg portions at the corner regions thereof adapted to seat on, and co-operate with, the support means on the outer frame, the extents of the first and second inner frames between the corner regions being of lesser depth than the corner regions.
Conveniently the outer frame and the second inner frame include adjustable attachment means operable to effect a connection between the sidewalls thereof once the inner frame is located at a desired level relative to the outer frame, for example one or more vertical slots in one of the frames and a locking bolt on the other frame.

Gatehouse of fleet, Castle Douglas GF7 2DU


A method and system for providing real-time, closed-loop control of the induction hardening process. A miniature magnetic sensor located near the outer surface of the workpiece measures changes in the surface magnetic field caused by changes in the magnetic properties of the workpiece as it heats up during induction heating (or cools down during quenching). A passive miniature magnetic sensor detects a distinct magnetic spike that appears when the saturation field, Bsat, of the workpiece has been exceeded. This distinct magnetic spike disappears when the workpiece""s surface temperature exceeds its Curie temperature, due to the sudden decrease in its magnetic permeability. Alternatively, an active magnetic sensor can measure changes in the resonance response of the monitor coil when the excitation coil is linearly swept over 0-10 MHz, due to changes in the magnetic permeability and electrical resistivity of the workpiece as its temperature increases (or decreases).

This invention relates generally to the field of heat treatment of metals, and more specifically to a method and system of providing real-time, closed-loop control of an induction heating machine by using a miniature magnetic sensor to measure the local changes in magnetic field close to a workpiece during induction heating.
Induction heating is a well-known process for efficiently applying energy directly to metals and other conductive materials for heat treating, melting, welding, brazing, tempering, normalizing, aging, or pre-heating prior to hot working.
Induction heating can also be used in non-metal applications, including adhesive bonding, graphitizing carbon, drying, curing, and superheating glass. In induction heating, alternating electric current is passed through an induction heating coil that is positioned closely to a workpiece. Where the lines of magnetic flux produced by the induction heating coil enter the workpiece, the alternating magnetic fields induce an alternating electric potential (e.g. voltage) in the workpiece. The alternating electric potential drives eddy currents in a thin surface layer. These eddy currents dissipate some of their energy within the surface layer by resistive Joule heating losses. The depth of resistive heating (e.g. skin depth) is inversely proportional to the square root of the product of three parameters: applied induction frequency, magnetic permeability, and electrical conductivity. The resultant temperature rise in the resistively heated surface layer is related to the specific heat, density, thermal conductivity, power level, and duration of heating. Magnetic coupling of the induction heating coil to the workpiece depends strongly on the geometrical arrangement, among other properties.
A common use of induction heating is case hardening of medium-carbon steel parts, such as gears, axles, and driveshafts. Many industrial applications require a steel part having a hardened outer surface (e.g. xe2x80x9ccasexe2x80x9d) and an interior region of higher toughness to provide improved strength, wear resistance, fatigue life, and toughness. Other applications include induction hardening of crankshafts, valve seats, railroad rails, rolling-mill rolls, and hand tools. Induction heating rapidly heats the outer surface layer of the steel workpiece in a short period of time (e.g. 5 seconds). Above a critical transition temperature (about 760 C for 1050M steel with 0.45% C) the initial ferrite-pearlite microstructure (BCC) transforms into the austenite phase (FCC).
Upon continued heating of the part, the transformed austenite layer thickens and extends deeper from the surface. Optimum peak surface temperatures can be 870-925 C, depending on the carbon concentration, and the desired depth of hardening. For some applications, the peak surface temperature can be as high as 1200xc2x0 C. Final hardening of the outer layer occurs when the heating power is shut off and the part is quenched (e.g. rapidly cooled from the outside to less than 200-400xc2x0 C. in 10-20 seconds). This converts the austenitic layer into a hard, metastable martensitic phase with a Rockwell hardness of Rc=50-60. An optional tempering step can follow the quench cycle, which can further improve the metallurgical properties.
Induction hardened steel parts are designed to have a case hardened layer with a specific desired depth. For example, a 25 mm diameter 1050 M steel automobile axle may be designed with a hardened layer from 4-5 mm thick, as defined by a Rockwell hardness of at least Rc=50. Should the layer be too thin, the axle would wear too quickly or have insufficient strength; should the layer be too thick, the axle would be too brittle. During mass production, the measured case depth should be repeatable to within +/xe2x88x920.1 mm. This requires close control of the induction heating process, as well as tight control of material properties, chemistry, workpiece alignment, etc.
Closed-loop control of the induction heating and hardening processes has been an elusive goal of the industry for many years. Existing induction hardening equipment is typically operated with open-loop process controllers, wherein an operator manually selects power and time (e.g. heating duration). Production users of this equipment monitor the process by destructively sectioning finished parts and inspecting the results; i.e., a finished part is cut apart and the case depth is directly measured radially across the cross-section by using a Rockwell hardness indentor, metallographic inspection, or chemical analysis of the carbon concentration profile. Process development for new parts is accomplished by time-consuming and expensive trial-and-error; for a given coil and part design, heating and quenching parameters are varied until destructive analysis reveals that the desired hardness profile is being produced.
These parameters are then utilized in the production run and the hardened parts are sampled and analyzed at regular intervals for quality control and assurance. If the tested part is bad, the production run from the previously tested good part is sampled to determine where the process failed. Production equipment may be taken out of service until subsequent parts test satisfactory. Since each test can take a minimum of several minutes by a trained technician, this process is quite inefficient for mass production. Unfortunately, small variations in the steel""s chemistry and microstructure can produce unacceptably large variations in the measured case depths, even for nominally acceptable material specifications. The cause of these variations is not well understood.
Other sources of variability include improper part positioning (e.g. misalignment relative to the heating coil), defects in the part (e.g. cracks), and damaged or aged heating coils. Low hardness values measured on a finished part may be caused by: surface decarburization; lower carbon content than specified; inadequate austenitizing temperature; prior structure; retained austenite (mostly in high-carbon steels); and unsatisfactory quenching.
Eddy current testing is a commonly used non-destructive method in the automotive manufacturing industry for measuring case depth. Eddy current testing can measure case depths in hardened shafts over a range from 0.2 mm to 9 mm, with an accuracy of about 0.15 mm RMS error. See Automotive Application of Eddy Current Testing, in Electromagnetic Testing, Vol. 4, 2nd ed., Nondestructive Testing Handbook, American Society of Nondestructive Testing, Inc., 1986, p 424-426. However, to achieve this level of accuracy requires the use of a master shaft for calibration purposes. This requires destructive measurement of the case depth in the master shaft by conventional hardness scans. All eddy current responses for the batch of test shafts are then normalized to the response for the master. A computer uses the responses at a few different frequencies to estimate the case depth using multiple linear regression fits. However, this type of eddy-current test is only performed after the part has been induction hardened (e.g. on finished parts); it is not used to provide real-time process control.
What is needed is a real-time, non-destructive, non-contact diagnostic technique that can respond quickly to the temperature changes and phase transformations in the workpiece during the induction heating process. The diagnostic should be small enough to provide sufficient spatial resolution, and robust enough to withstand the hostile environment (high temperatures, high fields, large volumes of quenching fluids, etc.). Use of an active feedback of process information measured directly from the part, coupled with closed-loop control of the heating process, would greatly improve the efficiency of induction hardening systems, while increasing accuracy and reducing part rework.
Direct measurement of the workpiece""s surface temperature during induction heating could provide a useful signal for closed-loop feedback control. However, use of contact thermocouples is impractical for mass production, especially since cylindrical parts are often rotated at significant rpm""s to create uniform heating profiles. Non-contact optical pyrometry could be used, however the accuracy is affected by surface conditions (e.g. emissivity) and the operating environment (e.g. smoke, dust, vapors). Coating of the pyrometer""s window by the quenching fluid can also degrade accuracy. Commercially available pyrometers do not have a sufficiently fast response time to monitor the rapid changes in surface temperature during induction heating. Neither pyrometry, nor surface-attached thermocouples, can directly measure the internal temperatures within a workpiece.
Indirect measurement of the workpiece""s temperature, and/or temperature profile through the depth, can be inferred by measuring corresponding changes in the electrical and magnetic properties of the workpiece as it heats up during induction heating. It is well known that the electrical resistivity increases with temperature for typical metals, including steel. For example, the resistivity of medium-carbon steels can increase as much as 800% as the temperature increases from 20xc2x0 C. to 900xc2x0 C. See ASM Handbook, Vol. 4, Heat Treating, 1991, p. 187.
The average electrical resistance of the workpiece (e.g. averaged over the cross-sectional area) can be measured indirectly by monitoring the voltage, current, and phase of the induction heating coil. This approach is described in U.S. Pat. No. 5,630,957 (commonly assigned to Sandia Corporation), which is herein incorporated by reference. In this patent, Adkins et al. teach a method of closed-loop control of an induction hardening machine that uses a trained neural network processor, combined with real-time measurement of the voltage, current, and phase in the induction coil, as measured by a Rogowski coil surrounding a current lead. The depth of hardening is controlled, in part, by computing the energy absorbed by the workpiece, and the changes in the average resistance of the coil plus the workpiece during the heating duration. However, this method does not provide any information regarding the temperature profile through the depth, or local information at a specific point on the workpiece.
A non-contacting, miniature magnetic sensor could be used for measuring the changes in surface magnetic fields near the workpiece in real-time during induction heating. A magnetic sensor responds to a time-varying magnetic field by generating a time-varying EMF (e.g. voltage) in the sensor""s monitor coil. As the workpiece heats up, changes in the electrical, magnetic, and microstructural properties of the heated surface layer affect the surrounding surface magnetic fields. A magnetic sensor positioned in close proximity to the surface could detect these changes. The output signals from such a sensor could provide useful information for controlling and optimizing the operation of an induction heating machine.
Magnetic sensors can be divided into two groups: active and passive. Active sensors provide their own excitation fields by using a driving coil (e.g. transmission coil or excitation coil). A second sensor coil (e.g. a monitor coil or probe coil responds to the time-varying magnetic field generated by the driving coil, which it is coupled through the workpiece. The excitation frequency of active sensors could be independently varied (e.g. 0-10 MHz), and could be much faster than the frequency of induction heating (e.g. 7 kHz). Use of a variable excitation frequency could provide the ability to probe the workpiece at varying depths, since the skin depth is inversely proportional to the square root of the driving frequency. Active sensors could also be used when the induction heating coil is temporarily at rest (e.g. during periodic pulsed heating), or during the cooling cycle (e.g. during quenching), when the induction heating coil is turned off. This is because active sensors provide their own source of excitation.
Active magnetic sensors can utilize a ferrite core to concentrate the magnetic flux, which improves overall performance. In this case, the monitor coil can sense four components of the total magnetic field: (1) the induction heating field, coupled through the workpiece and the ferrite core; (2) the magnetic field produced by eddy currents in the workpiece, in response to the induction heating field; (3) the high frequency excitation field, coupled through the ferrite core and workpiece; and (4) the magnetic field produced by eddy currents induced in the workpiece by the high frequency excitation field. Generally, the very small currents induced in the ferrite core can be neglected because of its high electrical resistance. Therefore, the only significant eddy currents are those inside of the workpiece. The magnetic loop includes the ferrite core and some portion of the workpiece. The magnetic field in the ferrite core depends, therefore, on all of the fields generated inside the workpiece, coupled through the magnetic loop.
Frequency filters could be used to eliminate either the high frequency (e.g. sensor excitation) or the low frequency (e.g. induction heating) components, as well as to control electromagnetic interference (EMI). Also, examination of the phase shift could be used to distinguish between these different magnetic components. Additionally, changes in the orientation of the excitation coil, the monitor coil, the ferrite core, and/or the workpiece could be used to selective emphasize either the coupled applied field, the eddy-current field, or both.
Passive magnetic sensors, on the other hand, do not have an independent excitation coil. Rather, they respond xe2x80x9cpassivelyxe2x80x9d to time-varying changes in the local surface magnetic field produced by two sources: (1) the magnetic field of the induction heating coil interacting (e.g. coupling) with the workpiece, and (2) the magnetic fields generated by the induced eddy currents that heat the workpiece. Consequently, the frequency measured by the passive magnetic sensor is nominally fixed by the induction heating frequency (e.g. 7 kHz). Despite the fixed frequency limitation, a passive sensor could be simpler, less expensive, and easier to instrument than an active sensor. Passive sensors could also detect the Curie temperature effect (to be discussed later).
Passive magnetic sensors could be used to monitor intra-cycle changes (e.g. during an active heating cycle) in the surface magnetic field during induction heating.
Magnetic sensors could be miniaturized (e.g. 1-2 mm diameter coil), to provide enhanced spatial and temporal resolution. Additionally, multiple sensors could be placed at various axial locations along an axle or driveshaft to monitor axial variations in the process. This could be applied for a continuous hardening process, where the workpiece is moving sequentially through a fixed set of induction heating coils and quench stations. Alternatively, multiple sensors could be used avantageously for complicated parts that are being heated simultaneously with multiple induction heating coils, each being controlled by individual controllers coupled to their own sensors.
Although the use of active magnetic sensors have been proposed for controlling induction heating machines, numerous problems exist with these methods. In U.S. Pat. Nos. 5,250,776 and 5,373,143, Pfaffmann teaches a method of using an eddy current sensor to xe2x80x9cmeasurexe2x80x9d the temperature of a part during the induction heating process. The method relies on the known increase in electrical resistivity as the workpiece heats up, causing a corresponding change in the impedance of an electromagnetic test coil placed adjacent to the metal part. See Introduction to Electromagnetic Nondestructive Test Methods, by H. L. Libby, John Wiley and Sons, Inc., 1971, p. 272.
Pfaffmann teaches that because of significant electromagnetic interference (EMI) produced by the induction heating machine, useful analysis of the eddy currents sensed by the eddy current sensor is impaired and, hence, real-time monitoring is not attainable. To get around this problem, Pfaffmann""s method specifically restricts the use of the eddy current sensor to periods of time when the induction heating coil is deliberately turned off.
Pfaffmann""s method is illustrated in FIG. 1. Here, the induction heating coil power is turned off at periodic intervals for short periods of time (e.g. 10 milliseconds). During the period of no heating, the excitation coil of the eddy current sensor is energized, thereby inducing eddy currents in the workpiece, which are detected by the sensor coil. Pfaffmann thereby eliminates the problem of electromagnetic interference by operating the eddy current sensor only when the induction heating coil is deliberately turned off.
Unfortunately, Pfaffmann""s method eliminates the possibility of using a simpler and cheaper passive magnetic sensor, since there is no excitation field to drive the passive sensor when the induction heating coil is deliberately turned off. Another disadvantage of Pfaffmann""s method is that additional electronic equipment is required to create, control, and synchronize the timing of the coordinated patterns for turning on and off the induction heating power, while simultaneously activating the eddy current sensor, thereby adding additional costs and system complexity.
Important process information may not be gathered because the large magnetic field created by the induction heating coil is missing. For example, the saturation of the induced magnetic field, Bsat (in ferromagnetic materials) inside of the heated surface layer is artificially missing when the induction heating coil is deliberately turned off. Additionally, commonly used commercial induction heating machines that operate on a continuous xe2x80x9charmonicxe2x80x9d cycle do not have a natural downtime in the heating cycle. Therefore, costly modifications of their electronics and control circuitry would be required to create the downtime period. Pfaffmann does not discuss the important effects of the Curie Temperature on the magnetic permeability, which strongly influences the induction heating process (to be discussed later).
In addition to detecting electrical properties, miniature magnetic sensors could be used to detect changes in the magnetic properties of a workpiece, including: (1) hysteresis in the magnetic permeability, and (2) the Curie temperature effect.
Changes in the relative magnetic permeability, mu, (e.g. relative to the free space permeability) that occur during heating are important to understand because the depth of induction heating is inversely proportional to the square root of the magnetic permeability. For soft ferromagnetic materials the permeability is a strong non-linear function of the applied magnetic field. The permeability is defined as the ratio of the Induced Field, B (Teslas), divided by the Applied Field, H (A/m). Above a certain applied field, the induced field saturates at an essentially constant value, Bsat, which is about 1.5-2 Teslas for medium-carbon steels. This is important because the magnetic field applied by the induction heating coil typically drives the surface of the workpiece well beyond magnetic saturation twice during each cycle (both positively and negatively). During saturation, when all of the magnetic domains align with the magnetic field, the induced eddy currents penetrate more deeply into the part because the permeability, mu, is much smaller inside the saturated zone.
Because alternating current drives the induction heating coil, the workpiece is subjected to an alternating applied magnetic field. Soft ferromagnetic materials respond with a hysteresis in their induced field, B, when the applied field, H, is cycled between maximum and minimum values, as shown in FIG. 2. Energy lost during AC magnetization is converted into heat in the ferromagnetic material, and can be represented, in part, by the area inside the hysteresis loop. The slope (e.g. permeability) of the hysteresis loop, and the flat-top (saturation field, Bsat), both depend on the temperature, driving frequency, carbon content, microstructure, and other properties of the workpiece. FIG. 3 shows an example of how a typical B-H hysteresis loop changes with temperature for 1050M medium-carbon steel at 5000 Hz. Increasing the temperature from 100 C to 700 C decreases the saturation field (Bsat) by roughly a factor of two. The permeability is also affected by temperature changes. These changes in magnetic properties significantly affect the heating profile through the depth, and, therefore, the temperature rise during induction heating.
Ferromagnetic materials undergo a dramatic transition from being a xe2x80x9cmagneticxe2x80x9d material with a large relative magnetic permeability (muxcx9c100-1000), to being a xe2x80x9cnon-magneticxe2x80x9d material (mu=1) when heated above the Curie temperature. The cause of the Curie effect is closely related to the phase transformation that occurs during heating, passing from a 100% ferrite-pearlite BCC microstructure when the temperature is below the Ac1line, to a 100% austenitic FCC microstructure when above the Ac3 line. For steels with carbon concentrations less than about 0.45 wt %, the Curie temperature is relatively constant at about 770xc2x0 C. In higher carbon steels the Curie temperature follows the A3 line on the Fe-C phase diagram to the eutectoid composition; thereafter, it coincides with the A1 line.
Both the Curie temperature and the ferrite-to-austenite phase transformation during heating are affected by many factors, including the rate of heating, the starting microstructure (e.g. annealed, normalized, quenched and tempered), grain size, carbon content, trace elemental composition, and possibly magnetic field, frequency, and stress state. When the heated surface exceeds the Curie temperature, austenite begins to form and the magnetic permeability rapidly drops to mu=1. Consequently, the induction heating magnetic field rapidly penetrates more deeply into the part. Continued heating increases the thickness of the austenite layer, until the desired depth is reached. Finally, the heating coil is turned off and the part is quenched, thereby forming a hard martensite surface layer.
Because the Curie temperature effect coincides closely with the beginning of austenite formation upon heating, the time after start of heating at which the Curie temperature is reached at the surface could be used as a sensitive indicator of how fast the workpiece is heating up. For example, if the Curie temperature is reached too quickly, this could indicate that too much power is being delivered to the workpiece, resulting in too great a case hardening depth. Likewise, if the Curie temperature signal is detected too late in the process, the case depth could be too shallow. Either condition could result in rejection of the part.
The heating process could be adjusted after the Curie temperature has been reached (and detected) by changing the power level of the induction heating coil, or by adjusting the heating duration (e.g. stop time), so that the desired depth of case hardening is precisely achieved. Because miniature magnetic sensors can detect the Curie temperature effect, they are well suited to provide critical information useful for actively controlling the induction heating process. This applies not only for induction hardening, but also for high temperature annealing or normalizing of steel and cast iron parts, using similar induction heating methods.
Additionally, analysis of the sensor""s response throughout the induction heating process could provide important information regarding the temperature profile through the depth, and the rate of heating over time, before the Curie temperature point has been reached. Likewise, similar information could be obtained during cooling when the Curie point is traversed when cooling down from a temperature above the Curie temperature point.

Closed loop control of the induction heating process using miniature magnetic sensors