A position detection system detects a position of a lens of a camera using a code plate provided with a plurality of electrodes arranged to form a plurality of patterns. The ends of the electrodes are respectively connected to a connecting point of a plurality of resistors connected in series, and a predetermined voltage is applied across the resistors. A conductive brush is provided such that, depending on the position of the lens, two of the electrodes are electrically connected by the brush, which short-circuits at least one of the plurality of resistors. Be detecting voltage at one of the connecting points of the resistors, which varies depending upon which resistor is short-circuited, the lens position is determined.

1. Field of the Invention
The present invention relates to an electronically controlled camera in which a lens is electronically driven to move within a movable range along an optical axis thereof.
2. Description of the Related Art
Conventionally, electronically controlled cameras have a photographing lens that is driven by a motor and moves within a predetermined movable range. In such a camera, for example, a zoom lens can move within a zooming range, which is defined as a range between a wide end and a tele end. The zoom lens is driven to move between the wide and tele extremities to change the focal length of the photographing lens.
In such a type of camera, the lens is positioned in the movable area when a main switch, or a power switch of the camera, is turned ON and the camera is in the condition where photographing can be performed. The lens is positioned at a retracted, or accommodated position (housed position) where the lens is retracted and barrier blades cover the lens when the power switch of the camera is turned OFF.
In the conventional camera as described above, when the power switch of the camera is operated and the operating condition of the camera changes from an OFF condition to an ON condition, the photographing lens, which was positioned at the housed position is extended and located within the movable range (i.e., a zooming range).
Within the zooming range, the lens is moved towards the tele extremity (tele end) or the wide extremity (wide end) in accordance with operation of a zoom lever or the like. When a user stops operating the zoom lever, the movement of the lens stops. In this situation, when the power switch is turned OFF, the lens positioned in the zooming range is moved to the housed position as described above.
In the electronically controlled camera, especially one which controls the motor to move the lens, the position of the lens should be detected to determine the focal length of the lens. For this purpose, a code plate is generally employed.
An example of the conventional code plate is a plate on which a certain pattern forming a plurality of codes corresponding to the lens position is provided. Each code consists of a plurality of conductive and non-conductive elements. Further, a detector for detecting a code is provided. The detector may have a plurality of brushes which simultaneously contact different portions of the code plate, and detect the conductivity of respective portions. That is, each brush detects the conductivity of the portion where it contacts. Combinations of the conductive and non-conductive portions represent the code which indicates the position of the lens. As the lens moves, relative movement between the code plate and the detector occurs. Based on the detected code, i.e., the detected combination of the conductive and non-conductive portions, the position of the lens, which corresponds to the focal length of the lens, is detected.
In a code detecting system as described above, if the code is not detected correctly, a wrong lens position may be detected as the lens position. In such a case, the lens may not be driven correctly, and may be driven to be positioned at a wrong place. Therefore, in the camera employing the code plate and the detector of the code, the code should be detected correctly, to ensure that the correct lens position is detected.
In order to obtain the accurate position of the lens, various methods have been suggested.
For example, a conventional lens position detection system is provided with a code plate having conductive and non-conductive portions forming various codes, and a plurality of brush members which contact the code plate to detect a code as described above. One of the brushes and the code plate move in accordance with the movement of the lens, and the other does not move (i.e., the positional relationship is fixed with respect to the body of the camera). Depending on the position of the lens, the brush contacts a pattern of the conductive and non-conductive portions indicative of the lens position. In other words, each code consists of a plurality of conductive and non-conductive portions, and the brushes detects the combination of the conductive and non-conductive portions. Therefore, each code represents a binary information indicating a plurality of ON and OFF states.
However, with the conventional lens position detection device as described above, in order to identify a number of lens positions, the large number of brushes and corresponding conductive and non-conductive positions should be provided since the plurality of positions are to be indicated with a binary information (i.e., a combination of conductive and non-conductive portions).
In the detection device constructed as above, it is highly probable that one of the brushes may not contact the code plate, i.e., the brush is lifted from the code plate. Under such a situation, the detected code is different from the actual code since the bit corresponding to the lifted brush always indicates the OFF state, and the wrong lens position is detected.
Further, in the conventional lens position detecting device constructed as above, one of the brushes should be grounded regardless of the lens position, and the other brushes contact the conductive and non-conductive portions in order to determine the conductivity of each of the portions contacting the brushes. In order to achieve this, a signal from each brush is input into a control unit, e.g., a CPU (central processing unit), and accordingly, relatively complicated wiring is required.
A further problem is that when the lens is driven and extended from the housed position to the wide end, the control unit of the camera continues driving the lens until a code indicating the wide end is detected. In response to the detection of the code indicating the wide end, the control unit stops driving the lens. If an error occurs, however, and the code indicating the wide end is not detected even through the lens reaches the wide end, the control unit continues driving the lens past the wide end. In such a case, the lens may move beyond the originally designed movable range, which is defined by, for example, the wide and the tele extremities (ends), and the lens may contact a mechanical stopper or the like which may be provided at the end of the movable range. Further, in a worse case, a screw part of the lens driving mechanism may be driven excessively or may be fastened at a part beyond the movable range.
A similar problem may occur when the lens is moved to the wide end. When the zoom lens is moved towards the wide end while the lens is located within the movable range, in response to the detection of the code indicating the wide end, the control unit stops driving the lens. In other words, the lens is prevented from moving towards the accommodated position (housed position), beyond the wide end when the camera operates. However, if the control unit fails to detect the wide end while the zoom lever is being operated and the lens moved towards the wide end, the control unit keeps driving the lens. In such a situation, fastening of the driving mechanism (i.e., the screw mechanism) at the housed position may occur, and/or an excessive load may be placed on the driving motor.
A similar problem may also occur when the main switch of the camera is turned OFF and the lens is to be retracted into the housed position. Conventionally, when the lens is moved to the housed position, it is detected whether the lens has reached the wide end. When the lens has reached the wide end, a predetermined operation such as a preparation operation for lens accommodation is performed. Thereafter, the lens is further moved to the housed position. In such a camera, if the detection of the wide end fails, the lens continues to be driven since the wide end code is not detected, which may cause damage to the motor and/or mechanical fastening of the lens driving mechanism.
Furthermore, with the above type of camera, when the lens is moving the code changes and the detection device detects various codes one-by-one. If the movement of the lens is prevented while attempting to move the lens, the codes stop changing even though the driving motor continues performing the lens driving operation. If the driving mechanism continues the lens movement operation under such a situation, the driving mechanism may be damaged or break. To avoid such a problem, in a camera in which the lens position is detected with use of the code plate and the code detection device, it is determined whether the code changes within a predetermined period of time. If the code does not change within the predetermined period, it is judged that an error has occurred, and the control unit stops the lens driving operation.
In the above-described situation, the load applied to the lens driving motor may be less if the predetermined period is set shorter. It is desirable to set the predetermined period as short as possible since it is desirable that the motor is stopped if the movement of the lens is prevented.
Generally, the lens is prohibited from stopping within an area between the accommodated position and the wide end. In a camera in which the lens position is detected using the code plate, there is no need to detect the lens position within the above-described area where the lens is prohibited from stopping, and therefore, there is no need to provide a code within the area.
Accordingly, a code is not formed in the area where the lens is prohibited from stopping. In other words, since the code does not change while the lens is moving the area between the accommodated position and the wide end, it takes a relatively long time for code change to occur. The code change occurs only after the lens has reached the wide end. Thus, the above-described predetermined period for detection of the code change should be set to a relatively long period. In order to wait the code change when the lens moves between the accommodated position and the wide end, the above-described predetermined period should be set to a relatively long period of time contrary to the desired short period.
The period of time set for detection of the code change therefore should be set to a relatively long value. Accordingly, if the lens movement is prevented while the lens driving motor is driven until the larger predetermined period has elapsed, and the motor is continuously driven during this period, the burden on the motor is increased.
Further, there has conventionally been known a zoom lens camera in which zoom lens is moved when a user operates an operable member, such as a zoom lever so that the focal length of the photographing lens can be changed. In such a camera, generally two types of movement control of the zoom lens are known.
A first is that when the user stops operating the operable member, the lens stops moving immediately. Then, when the user pushes a shutter button of the camera, the zoom lens remains where it is located. In other words, the zoom lens is capable of stopping anywhere within its movable range.
Another type is such that the zoom lens stops at only one of a plurality of predetermined positions when the user stops operating the operable member. In other words, in the latter type, the zoom lens moves in a stepwise fashion.
Further, the amount of movement of a focusing lens and an aperture value, which is used for exposure control, vary as function of the focal length. Accordingly, the latter type has an advantage in that the processing performed by a controller of the camera is less since the amount of information to be used in the exposure control. Additionally, exposure calculation parameters and the like are less than in the former type. Therefore, the latter type of the zoom lens and movement control thereof are widely employed in cameras, especially in compact cameras.
In the latter type, however, since the zoom lens stops at a position within the movable range of the lens, the lens position may deviate from the position where the lens is expected to stay after the user stops operating the operable member to stop the lens, and before the shutter button is depressed. When the lens deviates from the predetermined position, the focal length, which the exposure and focusing controls are performed based upon, changes and therefore the exposure and focusing controls become inaccurate.
Furthermore, the conventional camera may employ a "relative" code system, which has an advantage such that the number of lens positions can be identified using a fewer number of codes. In the relative code pattern system, the actual lens position is determined with reference to the detected relative code and the reference code.
In the camera employing the relative code system, when the lens is forcibly moved, the control unit may determine the wrong position as the lens position. If the lens movement is performed with reference to incorrectly determined position, the resultant position is also in correct.


A none intrusive pressure sensing device that clamps on to a pressure line and detects the internal pressure of the pressure line by detecting the resultant changes in the diameter of the pressure line. The clamp is held together by a fastener having a sensing element, such as a strain gage, that is able to detect the change in length of the fastener as the pressure line and the clamp expand and contract with the internal pressure of the pressure line.

Most conventional pressure transducers used to detect pressures in the pressure lines of machinery are intrusive, requiring exposure to the pressurized fluid or gas in the pressure line. This involves an assembly process requiring a breach in the wall of the pressure line or some other method of direct exposure of the pressure transducer to the pressurized fluid or gas.


A diaphragm-type sensor is disclosed which comprises a substrate including a cavity, a diaphragm formed on the cavity and supported by the substrate, a heater element arranged on the diaphragm, two sensor elements arranged on both sides of the heater means and slits between the heater means and the respective sensor means. The slits are effective in completely preventing the deformation of the diaphragm due to a heat propagated from the heater element, from influencing the sensor elements, whereby the diaphragm-type sensor exhibits stable output characteristics.

1. Field of the Invention
This invention relates to a diaphragm-type sensor for use in a flow detecting apparatus.
2. Description of the Prior Art
FIG. 1 is a perspective view of a conventional flow sensor of a type known as a microbridge flow sensor. The flow sensor as illustrated comprises a semiconductor substrate 1 made, for example, of silicon which is formed with a cavity 4 at a central portion thereof communicating openings 2, 3 at both side portions. A bridge 5 is formed over the cavity 4 so as to be thermally insulated from the semiconductor substrate 1. The bridge 5 includes a thin-film heater element 7 and two thin-film thermally sensitive resistor elements 8, 9 aligned on both sides of the heater element 7, the three elements being formed by a known thin-film forming technique. The semiconductor substrate 1 further comprises another thin-film thermally sensitive resistor element 10 formed at a corner portion thereof. A slit-like central opening 11 is also formed in addition to the side openings 2, 3 such that portions exposed by these openings 2, 3 and 11 are etched by an anisotropic etchant such as KOH to form the cavity 4 in an inverted trapezoidal shape as well as the bridge 5 supported by the semiconductor substrate 1, wherein the heater element 7 and the thermal sensor elements 8, 9 are thermally insulated from the semiconductor substrate 1 by the cavity 4. The elements 7, 8 and 9 are further encapsulated by a protective layer (6 in FIG. 2) made of a material having a low thermal conductivity ratio such as silicon nitride.
FIGS. 2a and 2b shows the operation of the microbridge flow sensor shown in FIG. 1. FIG. 2a illustrates a temperature distribution of the respective elements 7, 8 and 9 while FIG. 2b a cross-sectional view of the sensor taken along a line B--B' of FIG. 1.
If the heater element 7 is controlled to remain at a constant temperature higher than an ambient temperature, for example 63.degree. C., the thermal sensor element 8, 9 exhibit a substantially equal temperature as shown in FIG. 2a, for example, 35.degree. C. In this circumstance, if a fluid flows in the direction indicated by an arrow 12 shown in FIG. 1, the upstream sensor element 8 is cooled down by a temperature .DELTA.T.sub.3 while the downstream sensor element 9 is heated by .DELTA.T.sub.4. Consequently, a temperature difference is produced between the upstream sensor element 8 and the downstream sensor element 9. Thus, the microbridge flow sensor is used for detecting flow rates by incorporating the thermal sensor elements 8, 9 in a Wheatstone bridge to convert the temperature difference to a voltage signal corresponding to a flow rate of a fluid under measurement.
The microbridge flow sensor, as mentioned above, has a thin film bridge structure with an extremely small thermal capacitance formed by the thin film technique and the anisotropic etching technique and is advantageous in a very high response speed, a high sensitivity, a low power consumption, a good adaptability to a mass production, and so on.
However, the conventional microbridge flow sensor includes relatively large openings 2, 3 on both sides which are necessarily formed for etching semiconductor substrate 1 to form the cavity 4. The large openings 2, 3 causes a fluid flow to go into the cavity 4, whereby dust in the fluid may be attached in vicinity of the openings or in cavity 4 to badly affects the sensor characteristics.


A memory transistor including a substrate, a tunnel insulating pattern on the substrate, a charge storage pattern on the tunnel insulating pattern, a blocking insulating pattern on the charge storage pattern, and a gate electrode on the blocking insulating pattern, the blocking insulating pattern surrounding the gate electrode and methods of operating and fabricating the same. A nonvolatile memory may further include a plurality of memory transistors in series and a plurality of auxiliary structures between each of the plurality of unit transistors in series. Each of the plurality of auxiliary structures may be a dummy mask pattern or an assistant gate structure.

1. Field
Example embodiments relate to a storage device, for example, to a device and a method for operating and manufacturing a non-volatile and electrically erasable semiconductor memory device, for example, a flash memory.
2. Description of the Related Art
Non-volatile memory retains information stored in its memory cells even when no power is supplied. Examples include mask ROM, EPROM, and EEPROM.
Non-volatile memory is widely used in various kind of electronic products, for example, personal computers, personal digital assistants (PDAs), cellular phones, digital still cameras, digital video cameras, video game players, memory cards, and other electronic devices.
Memory cards types may include multimedia cards (MMC), secure digital (SD) cards, compact flash cards, memory sticks, smart media cards, and extreme digital (xD) picture cards.
Among non-volatile memory devices, a flash memory is widely used. Flash memory may be divided into a Not-OR (NOR) type and a Not-AND (NAND) type based on a connection structure of cells and bit lines. Because a read speed is faster and a write operation is slower, a NOR-type flash memory may be used as a code memory. Because a write speed is faster and a price per unit area is lower, a NAND-type flash memory may be used as a mass storage device.
NOR-type flash memory may be used in BIOS/networking in a PC, a router, or a hub or in a telecommunications switcher. NOR-type flash memory may also be used to store code or data for cellular phones, personal digital assistants (PDAs), POS, or PCA.
NAND-type flash memory may be used in memory cards for mobile computers, digital cameras, both still and moving, near-CD quality voice and audio recorders, rugged and reliable storage, for example, solid-state disks.
The programming method for NOR-type flash memory is hot carrier injection and the programming method for NAND-type flash memory is Fowler-Nordheim (FN) tunneling.
Advances in consumer electronics cause demand for higher density memory devices. Efforts to manufacture devices meeting this demand often involve scaling down the sizes of gate structures and reducing or minimizing the space between adjacent gate structures.
With the reduction in channel length of transistors, the influence of a source and drain upon an electric field or potential in the channel region may increase. This is referred to as the 'short channel effect'.
Other related problems include trap-assisted leakage current. As shown in FIG. 37, in a conventional charge trap memory device 10, including a substrate 12, a tunnel insulating pattern 14, a charge storage pattern 16, a blocking insulating pattern 18, and a conductive pattern 20, electrons e− may leak from the charge storage pattern 16 through blocking insulating pattern 18 to the conductive pattern 20, for example, as a result of one or more defects D in the blocking insulating layer.
Conventional art publications have studied the characteristics of non-overlapped MOSFETs, and reported that performance degradation was suppressed by using a short non-overlap distance, for example, less than 10 nm. These results indicate that a non-overlapped structure is practically applicable.
Referring now to a conventional device from U.S. patent application Ser. No. 11/643,022, filed on Nov. 20, 2006, the entire contents of which are hereby incorporated by reference in their entirety, shown in FIG. 38, a memory may include a substrate 10, a channel region 40cC, a fringing field 90, an inversion layer 410, and an inversion layer at a source/drain region 430. As shown, a pass voltage of 5 V may be applied to memory transistors MTn−1 and MTn+1, and a select voltage Vsel may be applied to memory transistors MTn. The fringing field 90 from the cell gate potential may cause source/drain inversion, which enables the channel region to conduct a charge.
Referring now to a conventional device from U.S. Pat. No. 7,081,651, shown in FIG. 39, a gate conductive pattern may be patterned to form a plurality of wordlines 140 crossing the first active regions 103 in the cell array region "a", and to form a gate electrode 240 at least on the second active region 203 in the peripheral circuit region "b".
The third insulating pattern 106 exposed between the plurality of wordlines 140 may be overetched or attacked by plasma while etching the gate conductive pattern. Therefore, a defect site may be created in the third insulating pattern 106 around an edge of a wordline 140. Subsequently, a trap-to-trap tunneling may occur through the defect site. Charges stored in a later-formed charge storage pattern may then be discharged to a gate electrode, having an undesirable influence on device operation.
Referring now to a conventional device from U.S. Pat. No. 6,674,122, shown in FIG. 40, a semiconductor integrated circuit device may include nonvolatile memory cells, each of which includes one memory transistor TMC and two switch transistors TSW, wherein the memory transistor TMC includes a memory gate electrode 7 connected to a word line 5. The switch transistors TSW may each include a switch gate electrode 6-1 and 6-2, an inversion layer 20-1 and 20-2 which is formed below the switch gate electrode 6-1 and 6-2 by applying a voltage to the switch gate electrode 6-1 and 6-2, the inversion layer 20-1 and 20-2 functioning as a source or a drain of the memory transistor TMC.

Memory device and method of operating and fabricating the same


Transistor devices which include semiconductor layers with integrated hole collector regions are described. The hole collector regions are configured to collect holes generated in the transistor device during operation and transport them away from the active regions of the device. The hole collector regions can be electrically connected or coupled to the source, the drain, or a field plate of the device. The hole collector regions can be doped, for example p-type or nominally p-type, and can be capable of conducting holes but not electrons.

To date, most transistors used in power electronic applications have typically been fabricated with silicon (Si) semiconductor materials. Common transistor devices for power applications include Si CoolMOS, Si Power MOSFETs, and Si Insulated Gate Bipolar Transistors (IGBTs). While Si power devices are inexpensive, they suffer from a number of disadvantages, including relatively low switching speeds and high levels of electrical noise. More recently, silicon carbide (SiC) power devices have been considered due to their superior properties. III-Nitride or III-N semiconductor devices, such as gallium nitride (GaN) devices, are now emerging as attractive candidates to carry large currents, support high voltages, and to provide very low on-resistance and fast switching times.
FIGS. 1A and 1B illustrate a plan view and a cross-sectional view, respectively, of a III-N transistor of the prior art having source electrode 14, drain electrode 15, gate electrode 13, and access regions 23 and 24. As used herein, the "access regions" of a transistor refer to the two regions between the source and gate electrodes, and between the gate and drain electrodes of the transistor, i.e., regions 23 and 24, respectively, in FIGS. 1A and 1B. Region 23, the access region on the source side of the gate, is typically referred to as the source access region, and region 24, the access region on the drain side of the gate, is typically referred to as the drain access region. As used herein, the "gate region" 31 of a transistor refers to the portion of the transistor between the two access regions 23 and 24 in FIGS. 1A and 1B.
While numerous III-N transistors and diodes have been demonstrated, improvements in device reliability are still necessary in order to enable large scale manufacturing and more widespread adoption of these devices. In particular, in III-N devices configured to support high voltages and/or large currents, large electric fields present in the device during operation can lead to deleterious effects such as threshold voltage shifts and breakdown, as well as other effects that degrade device performance or otherwise render the device inoperable. Device structures that reduce such degradation and improve device reliability are therefore desirable.

Semiconductor devices with integrated hole collectors


Provided is a method for manufacturing carrier core particles for electrophotographic developer capable of stably maintaining high chargeability over a long time. The method for manufacturing carrier core particles includes a granulation step of granulating a mixture of raw materials containing manganese, iron, strontium, and calcium and a firing step of firing the mixture granulated in the granulation step. The firing step includes a heating process of heating the granular mixture with an increase in temperature to a predetermined degree and a cooling process of cooling the granular mixture, after the heating process, in an atmosphere with an oxygen concentration ranging from 5000 ppm to 20000 ppm. The molar ratio of the sum of strontium and calcium to the sum of the manganese, iron, strontium, and calcium is 0.0026 to 0.013.

1. Field of the Invention
This invention relates to a method for manufacturing carrier core particles for electrophotographic developer (hereinafter, sometimes simply referred to as "carrier core particles"), the carrier core particles for electrophotographic developer, carrier for electrophotographic developer (hereinafter, sometimes simply referred to as "carrier"), and electrophotographic developer (hereinafter, sometimes simply referred to as "developer"). More particularly, this invention relates to carrier core particles contained in electrophotographic developer used in copying machines, MFPs (Multifunctional Printers) or other types of electrophotographic apparatuses, a method for manufacturing the carrier core particles, carrier in the electrophotographic developer and the electrophotographic developer.
2. Description of the Related Art
Electrophotographic dry developing systems employed in copying machines, MFPs or other types of electrophotographic apparatuses are categorized into a system using a one-component developer containing only toner and a system using a two-component developer containing toner and carrier. In either of these developing systems, toner charged to a predetermined level is applied to a photoreceptor. An electrostatic latent image formed on the photoreceptor is rendered visual with the toner and is transferred to a sheet of paper. The image visualized by the toner is fixed on the paper to obtain a desired image.
A brief description about development with the two-component developer will be given. A predetermined amount of toner and a predetermined amount of carrier are accommodated in a developing apparatus. The developing apparatus is provided with a rotatable magnet roller with a plurality of south and north poles alternately arranged thereon in the circumferential direction and an agitation roller for agitating and mixing the toner and carrier in the developing apparatus. The carrier made of magnetic powder is carried by the magnet roller. The magnetic force of the magnet roller forms a straight-chain-like magnetic brush of carrier particles. Agitation produces triboelectric charges that attract a plurality of toner particles to the surfaces of the carrier particles. The magnetic brush abuts against the photoreceptor with rotation of the magnet roller to supply the toner to the surface of the photoreceptor. Development with the two-component developer is carried out as described above.
Fixation of the toner on a sheet of paper results in successive consumption of toner in the developing apparatus, and new toner in the same amount as that of the consumed toner is supplied, whenever needed, from a toner hopper attached to the developing apparatus. On the other hand, the carrier is not consumed for development and is used as it is until the carrier comes to the end of its life. The carrier, which is a component of the two-component developer, is required to have various functions including: a function of triboelectrically charging the toner by agitation in an effective manner; insulation properties; and a toner transferring ability to appropriately transfer the toner to the photoreceptor.
The recently dominating carrier includes carrier core particles, which are the core or the heart of the carrier particles, and resin that covers the outer surface of the carrier core particles.
The carrier core particles, which are cores of the carrier particles carried on the magnet roller and agitated and mixed in the developing apparatus, are required to have excellent magnetic characteristics and high mechanical strength as well as excellent electrical characteristics in order to improve triboelectric chargeability for the toner. The improvement of the electrical characteristics, that is, triboelectric chargeability for toner mainly have been made by resin that coats the carrier core particles as described above. However, the long-term use of the developer may cause the coating resin to be partially peeled off or may cause fracturing or chipping of the carrier core particles, which expose bare parts of the carrier. This means that long-term use of the developer deteriorates the triboelectric chargeability of the carrier, which is unfavorable.
The carrier core particles are thus required to improve their various characteristics and performance. Especially to improve the triboelectric chargeability, there is a tendency for the carrier core particles to be desired to have a somewhat rough surface rather than a smooth or slick one. Techniques developed by focusing on asperities on the surface of the carrier core particles are disclosed in Japanese Unexamined Patent Application Publications No. 2006-337828 and No. 2010-243798.

Method for manufacturing carrier core particles for electrophotographic developer, carrier core particles for electrophotographic developer, carrier for electrophotographic developer, and electrophotographic developer


The invention relates to an aqueous dispersion containing a cellulose-reactive sizing agent and a dispersant system comprising a low molecular weight cationic organic compound having a molecular weight less than 10,000 and an anionic stabilizer, its preparation and use in the production of paper. The invention further relates to a substantially water-free composition containing a cellulose-reactive sizing agent, a low molecular weight cationic organic compound having a molecular weight less than 10,000 and an anionic stabilizer, its preparation and use in the preparation of an aqueous dispersion of cellulose-reactive sizing agent.

Cellulose-reactive sizing agents, such as those based on alkyl ketene dimer (AKD) and alkenyl succinic anhydride (ASA), are widely used in papermaking at neutral or slightly alkaline stock pH's in order to give paper and paper board some degree of resistance to wetting and penetration by aqueous liquids. Paper sizes based on cellulose-reactive sizing agents are generally provided in the form of dispersions containing an aqueous phase and finely divided particles or droplets of the sizing agent dispersed therein. The dispersions are usually prepared with the aid of a dispersant system consisting of an anionic compound, e.g. sodium lignosulfonate, in combination with a high molecular weight amphoteric or cationic polymer, e.g. cationic starch, polyamine, polyamideamine or a vinyl addition polymer. Depending on the overall charge of the compounds of the dispersant system, the size dispersions will be cationic or anionic in nature. However, dispersions of these types usually exhibit rather poor stability and high viscosity, even at relatively low solids contents, which evidently lead to difficulties in handling the dispersions, for example on storage and in use. A further drawback is that the products have to be supplied as low concentration dispersions which further increases the costs of transportation of the active sizing agent.
Cellulose-reactive sizing agents generally provide good sizing with low dosages of the sizing agent. However, it has been experienced that the efficiency of conventional cellulose-reactive sizing agents is deteriorated when they are used with stocks having a high cationic demand and containing substantial amounts of lipophilic wood extractives, such as, for example, resin acids, fatty acids, fatty esters, triglycerides, etc. Due to the anionic character of lipophilic substances containing carboxylate or carboxylic acid groups, stocks containing substantial amounts of lipophilic extractives usually have a rather high cationic demand. It has been found that the lipophilic substances can be detrimental to the adsorption of sizing agents onto the fibers which may cause the poor sizing results. In order to improve sizing with such stocks the papermaker has had to increase the dosage of sizing agent, which of course is less favourable economically and can increase the accumulation of sizing agent in the white water recirculating in the papermaking process. These problems are even more pronounced in paper mills where white water is extensively recirculated with the introduction of only low amounts of fresh water into the process, thereby increasing the cationic demand and the accumulation of lipophilic extractives and non-retained sizing agent in the white water and the stock to be dewatered.


A multistage oxygen-added catalytic partial oxidation process and apparatus for converting H2S in an acid gas stream to elemental sulfur and water are disclosed. Each staged addition of oxygen or air at the top of the catalyst bed and at points along the catalyst bed maintain oxygen-limited H2S catalytic partial oxidation conditions whereby incidental SO2 production is minimized.

1. Technical Field of the Invention
The present invention generally relates to sulfur recovery processes and to apparatus for removing sulfur from H2S-containing gas streams and producing elemental sulfur. More particularly, the invention relates to H2S catalytic partial oxidation processes that include staged addition of oxygen, and to apparatus for carrying out such processes.
2. Description of the Related Art
Sulfur removal from H2S-containing gas streams is a field of endeavor that is receiving a great deal of attention today, particularly in the petroleum industry. Considerable quantities of H2S are created from the refining of petroleum in processes such as crude oil hydrodesulfurization, gasification of coal and desulfurization of natural gas. The removal of sulfur from natural gas is a particular concern because utilization of the enormous supply of natural gas existing in underground reservoirs all over the world is hindered due to the presence of naturally-occurring H2S along with the methane and other light hydrocarbons that make up natural gas. Some natural gas formations contain only a relatively small concentration of H2S, yet even those types of natural gas wells typically remain shut-in today because the cost of removal of the H2S using existing methods and apparatus exceeds the market value of the gas. A further deterrent to full utilization of H2S-containing natural gas resources is the corrosive effect of the H2S component of liquefied natural gas on the transportation pipes and storage vessels that are needed to bring the H2S-containing natural gas from remote locations to existing sulfur treatment plants.
The removal of sulfur from naturally occurring and industrially produced H2S-containing gas streams is necessitated by the high demand for clean energy sources, and by increasingly stringent clean air standards for industrial emissions that restrict or prohibit the release of H2S into the environment due to its high toxicity and foul odor. Since the amount of sulfur recovered from an industrial H2S-containing stream may be quite large, the elemental sulfur product can have significant commercial value.
Many processes have been described for accomplishing the removal and recovery of sulfur from H2S-containing gases. The sulfur plants in common use today employ a modification of a process that was developed over 200 years ago in which H2S was reacted over a catalyst with air (oxygen) to form elemental sulfur and water (the Claus process). Sulfur recovery was low and the highly exothermic reaction was difficult to control. Modified Claus processes were introduced to overcome the deficiencies of the original Claus process, and today are generally referred to as "Claus Processes." In a conventional Claus process, the H2S-containing gas stream is contacted with air or a mixture of oxygen and air in a flame. One third (⅓) of the H2S is burned according to the equation:H2S+ 3/2 O2→SO2+H2O  (1)The remaining ⅔ of the H2S is converted to sulfur via the (Claus) reaction:2H2S+SO2⇄3/x Sx+2H2O  (2)
(x=2, 6, or 8 depending on temperature and pressure). The gases are cooled in a fire tube boiler after the burner. Typically, this step converts 55 to 70% of the H2S to elemental sulfur. The equilibrium of the reaction of equation (2), referred to as the "Claus reaction," limits the conversion. To improve the yield, elemental sulfur is condensed from the gas stream. After sulfur condensation and separation from the liquid sulfur, the unreacted gases are heated to the desired temperature, passed over a catalyst that promotes the Claus reaction, and cooled again to condense and separate the sulfur. Generally, two to three stages of Claus reheater, reactor, and condenser stages are employed. Over the years, most of the modifications to the Claus process have involved improvement of burner design, use of more active and durable catalysts, and use of different types of reheaters. Anywhere from 90 to 98% of the H2S fed to the unit is recovered as elemental sulfur. Any remaining H2S, SO2, sulfur, or other sulfur compounds in the Claus plant effluent are either incinerated to SO2 and discharged to the atmosphere, or incinerated to SO2 and absorbed by chemical reaction, or converted by hydrogen to H2S and recycled or absorbed by an alkanolamine solution. This is accomplished by various Claus "tail gas" treatment units, which improve the efficiency of sulfur removal from the gas discharged to the atmosphere.
Claus processes are generally efficient for processing large quantities of gases containing a high concentration (i.e., >40 vol. %) H2S in plants producing more than 100,000 tons of sulfur per year. The Claus-type processes are not suitable for use in cleaning up hydrogen or light hydrocarbon gases (such as natural gas) that contain H2S, however. Not only is the hydrocarbon content lost in the initial thermal combustion step of the Claus process, but carbon, carbonyl sulfide and carbon disulfide byproducts cause catalyst fouling and dark sulfur. Moreover, carbonyl sulfide is difficult to convert to elemental sulfur. In the past, others have usually addressed the problem of purifying hydrogen sulfide contaminated hydrogen or gaseous light hydrocarbon resources by employing an initial amine extraction technique.
Typically, alkanolamine absorption of the H2S component of a gas stream is performed, followed by H2S regeneration and conventional multistage Claus sulfur recovery, usually including tail gas treatments. According to conventional industrial practices, a hydrocarbon or hydrogen containing gas stream containing a low concentration of H2S is contacted with a water solution containing an alkanolamine. Alkanolamines commonly employed in the industry are monoethanolamine (MEA), diethanolamine (DEA), methyldiethanol amine (MDEA), diglycolamine (DGA), and diisopropanolamine (DIPA). These are basic nitrogen compounds. The basic alkanolamine reacts with the H2S and other gases that form acids when dissolved in water to form alkanolamine salts, according to the following generic reaction:Alkanolamine+Acid Gas=Protonated alkanolamine+weak acid anionWhen ethanolamine is the basic alkanolamine, the reaction is:H2N—CH2CH2OH+H2S→+NH3—CH2CH2OH+HS−  (3)The hydrogen or hydrocarbon gas, substantially freed of H2S, is recovered and may be used as fuel or routed to another system for processing. After absorbing the H2S from the gas, the alkanolamine solution is transported, heated, and placed in a stripping tower. Steam generated from boiling the alkanolamine solution at the bottom of the stripping tower, lowers the vapor pressure of the acid gas above the solution, reversing the equilibrium of the acid gas/alkanolamine reaction described above. The acid gases leaving the stripper are cooled to condense most of the remaining steam. The acid gas stream then goes to a Claus sulfur recovery plant, as described above.
The major problem with the Claus process is the inherent equilibrium constraint of the Claus reaction caused by the necessity of generating the SO2 intermediate. Others have addressed this problem by attempting to directly oxidize H2S to sulfur using alumina based catalysts and low temperature operating conditions. SUPERCLAUS™ processes such as the STRETFORD™ process are examples of low temperature direct oxidation methods. Typically, these processes are catalytic oxidations operating at temperatures below about 454° C., so that the reaction can be contained in ordinary carbon steel vessels. Usually these catalytic oxidation processes are limited to Claus tail gas operations or sulfur recovery from streams that have very low H2S content (i.e., about 1–3%). One reason for this limited use is that the heat evolved from the oxidation of a concentrated stream of H2 S would drive the reaction temperatures well above 454° C. requiring refractory lined vessels such as the conventional Claus thermal reactor. Low concentration H2S streams will not produce enough energy release from oxidation to sustain a flame as in a thermal reactor stage. The existing catalytic oxidation technologies are thus limited to low concentration H2S-containing streams using non-refractory lined vessels. Existing processes are also limited in the amount of sulfur that can be handled because the heat transfer equipment needed to remove the heat of reaction becomes extremely large due to the low temperature differential between the process and the coolant streams.
Some techniques for improving efficiency of sulfur removal that have been described in the literature for purifying hydrogen sulfide contaminated hydrogen or gaseous light hydrocarbon resources include: 1) adsorbing sulfur cooled below the freezing point on a solid material followed by releasing the trapped sulfur as a liquid by heating the solid adsorbent; 2) selectively oxidizing the remaining H2S to sulfur using air; and 3) selectively oxidizing the H2S to sulfur employing aqueous redox chemistry utilizing chelated iron salts or nitrite salts. According to the latter methods, the H2S-contaminated hydrogen or hydrocarbon stream is contacted directly with the redox reagent such as chelated iron (III) ions. The iron (III) is reduced to iron (II) ion while the H2S is converted to elemental sulfur. The sulfur in liquid form is separated from the solution. These types of desulfurization units have been shown to be practical when the amount of sulfur to be removed from the stream is below 5 long tons per day. The SULFUROX™ and LO-CAT™ processes are examples of this type of H2S conversion process. Some of these direct oxidation processes use a liquid medium to carry out the oxidation or to act as a carrier for the oxidizer. These processes are also limited in the amount of sulfur recovered due to the heat removal constraints at low temperatures and the need to maintain low temperatures to keep the liquid from boiling. For at least these reasons, existing direct oxidation processes have not proved to be viable substitutes for the Claus process in most industrial applications.
U.S. Pat. No. 5,700,440, U.S. Pat No. 5,807,410 and U.S. Pat. No. 5,897,850 describe some of the limitations of existing tail gas treatment (TGT) processes and the difficulty of meeting increasingly stringent government requirements for desulfurization efficiency in the industry. J. B. Hyne (Oil and Gas Journal Aug. 28, 1972: 64:78) gives an overview of available processes for effluent gas stream desulfurization and discusses economical and environmental considerations. R. H. Hass et al. (Hydrocarbon Processing May 1981:104–107) describe the BSR/Selectox™ process for conversion of residual sulfur in Claus tail gas or for pre-Claus treatment of a gas stream. K-T Li at al. (Ind. Eng. Chem. Res. 36:1480–1484 (1997)) describe the SuperClaus™ TGT system which uses vanadium antimonate catalysts to catalyze the selective oxidation of hydrogen sulfide to elemental sulfur.
U.S. Pat. No. 5,603,913 describes several oxide catalysts that have been suggested for catalyzing the reactionH2S+½O2→½S2+H2O  (4)Because reaction (4) is not a thermodynamically reversible reaction, direct oxidation techniques offer potentially higher levels of conversion than is typically obtainable with thermal and catalytic oxidation of H2S. As mentioned above, conventional direct oxidation methods are applicable to sour gas streams containing relatively small amounts of H2S and large amounts of hydrocarbons, but are not particularly well suited for handling more concentrated acid gas streams from refineries. For this reason direct oxidation methods have been generally limited to use as tail gas treatments only, and have not found general industrial applicability for first stage sulfur removal systems from gases containing large quantities of H2S.
U.S. Pat. No. 6,372,193 (Ledoux et al.) describes a process for catalytically oxidizing a gas stream containing a low concentration (up to 25 vol. %) H2S directly to sulfur over a catalytically active phase carried on a silicon carbide-based support. The catalytically active phase is an oxysulfide of Fe, Cu, Ni, Co, Cr, Mo or W.
Even though the Claus process still finds widespread industrial use today for recovering elemental sulfur from H2S that is generated in many industrial processes, such as petroleum refinery processes, and for reducing sulfur emissions from refineries, the Claus process is generally viewed as relatively costly for routine use on a commercial scale. As a result, the Claus process is currently performed mainly for the purpose of complying with government mandated environmental air quality standards. Most of the existing alternative desulfurization processes and systems must resort to use of a number of additional pre-treatments or post-treatment catalytic stages and tail gas treatment units (TGTUs) in order to adequately clean the waste gas that is vented into the air sufficiently to meet current environmental regulations for venting of cleaned H2S-containing gas streams. Multi-stage tail gas treating units (TGTUs) typically convert the H2S that did not react in the Claus unit to elemental sulfur by (a) oxidizing completely to SO2, (b) reacting the SO2 with H2S in smaller concentrations to form elemental sulfur (S0), and (c) reacting very small concentrations of H2S with oxygen to form S0 at low temperatures using a catalyst. A number of TGTUs are usually needed to achieve the 99+% conversion of H2S to S0, and involves a large initial investment and appreciable maintenance costs.
Significant capital and maintenance costs are associated with conventional multi-stage treatment units. More economical and efficient ways of recovering elemental sulfur from an H2S-containing gas stream and of removing environmentally harmful H2S from industrial vent stack exhaust gases are needed. Conventional desulfurization operations are also not practical for use at small operations such as remote well sites or on natural gas producing off shore oil platforms.
The basic SPOC™ technology, as described in co-owned U.S. patent application Ser. No. 09/625,710 (abandoned), Ser. No. 10/024,679 (U.S. Pat. No. 6,946,111) and Ser. No. 10/024,167 (U.S. Pat. No. 6,800,269), which are hereby incorporated herein by reference, provides an alternative to the conventional Claus process to handle H2S-containing fluid streams. U.S. Pat. Nos. 6,946,111 and 6,800,269 (Keller et al.) describe a method of selectively converting even high concentrations of hydrogen sulfide in H2S-containing gas streams to elemental sulfur via a short contact time catalytic partial oxidation process (SPOC™) that is more economic and efficient than a Claus type process. The process is carried out in a more compact system than a conventional Claus plant. Conversion of H2S to elemental sulfur by the SPOC™ process may be accompanied by the formation of some SO2 as a result of gas-phase reactions between S0 and O2 that occur both downstream from the catalyst zone and within the catalyst zone. This secondary production of SO2 is typically observed when higher than stoichiometric O2/H2S ratios are used to increase the H2S conversion. An apparatus and process that further improve the conversion of H2S to elemental sulfur would be valuable in the art, particularly for meeting stringent Federal environmental standards and the demands for cleaner industrial waste gas emissions as required by the Environmental Protection Agency.

Process for the catalytic partial oxidation of H


A ring-shaped gasket for making high-purity fluid pathway connections between opposing fluid delivery apparatus elements having at least one simple flat surface in contact with the gasket. The face of at least one apparatus element typically has a circular counterbore depression to receive the gasket, but is not required. The gasket has a body, pierced through by a hole creating a fluid pathway and defining a radial inner surface, and additionally having a radial outer surface, a first axial end surface and a second axial end surface. At least one of the first and second axial end surfaces has a stress concentration feature radially adjacent to a gasket sealing region, the sealing region constructed to be in contact with a face surface of a corresponding fluid conduit port. The stress concentration feature may be a groove or a plurality of cavities disposed adjacent the gasket axial end surface sealing region.

Embodiments of the present invention are related to malleable, primarily metallic, gaskets for sealing joints between portions of a fluid pathway. Many combinations of interface structures and associated gaskets are well known in the design of fluid delivery apparatus. These structures include flanges, glands, component connections, and other functions that enable mechanical assembly of various apparatus elements forming a collection of interconnected fluid pathways. Representative fluid delivery apparatus are found among industrial equipment producing fine chemicals, petroleum products, flat panel electronic displays, or semiconductors, and may be subjected to vacuum, or pressure, or purity requirements, and combinations thereof. Fluid pathways among elements intended for manipulating process materials within semiconductor manufacturing equipment usually require attention to maintaining high purity of the delivered reactants and also typically have a much smaller cross-section than fluid pathways used in petrochemical plants, for example. In many cases practitioners have found metallic gaskets provide superior performance, particularly regarding diffusion of process fluid or contaminants through the gasket and consequent resistance to undesirable leakage, in preference over polymer materials.
One known type of fluid pathway joint uses a ring-shaped gasket, initially flat in a radial direction, axially compressed between nominally identical shaped annular projections that surround circular conduit openings of opposing apparatus elements. The annular projections are urged axially toward each other causing permanent plastic deformation of the ductile metallic gasket creating a seal that will resist leakage of even difficult to contain fluids such as helium. Representative examples of such joints may be seen in U.S. Pat. No. 3,208,758 issued to Carlson and Wheeler (familiarly known as the Varian® Conflat® flange), in U.S. Pat. No. 3,521,910 issued to Callahan and Wennerstrom (familiarly known as the Swagelok® VCR® fitting), and in U.S. Pat. No. 4,303,251 issued to Harra and Nystrom.
Another known type of fluid pathway joint uses a ring-shaped gasket of predetermined cross sectional profile compressed between nominally identical shaped annular projections that surround circular conduit openings of opposing apparatus elements. Representative examples of such joints may be seen in U.S. Pat. No. 4,854,597 issued to Leigh, in U.S. Pat. No. 5,505,464 issued to McGarvey, and in U.S. Pat. No. 6,135,155 issued to Ohmi et al. (an early version of the W-Seal joint type). The patent to Ohmi et al. additionally provides a separate retainer means for holding and centering the gasket during joint assembly. Other separate retainer structures may also be seen in U.S. Pat. Nos. 5,673,946 and 5,758,910 both issued to Barber and Aldridge, and in U.S. Pat. No. 7,140,647 issued to Ohmi et al.
Yet another known type of fluid pathway joint (familiarly known as the C-Seal joint type) uses a ring-shaped metallic gasket of complex shape compressed between opposing apparatus elements having simple flat surfaces in contact with the gasket. Most usually the face of at least one apparatus element has a circular counterbore depression to receive the gasket. Representative examples of such joints may be seen in U.S. Pat. No. 5,797,604 issued to Inagaki et al., in U.S. Pat. Nos. 6,357,760 and 6,688,608 both issued to Doyle, and in U.S. Pat. No. 6,409,180 issued to Spence & Felber. The '180 patent issued to Spence and Felber additionally provides a separate retainer means for holding and centering the gasket during joint assembly. Other separate retainer structures may also be seen in U.S. Pat. No. 5,984,318 issued to Kojima and Aoyama, in U.S. Pat. No. 6,845,984 issued to Doyle, and in U.S. Pat. No. 6,945,539 issued to Whitlow et al. Additionally, U.S. Pat. No. 5,992,463 issued to the present inventor Kim Ngoc Vu et al, and U.S. Pat. No. 5,730,448 issued to Swensen et al., show a suitably thick retainer may instead provide the compression limiting function of a counterbore sidewall and allow use of a gasket between simple flat opposing faces.
High purity fluid delivery components and fluid pathway elements are often made from a vacuum refined variation of type 316L stainless steel or nickel alloys such as Hastelloy® C-22®. Both of those metallic materials can only be hardened by mechanical work rather than heat treatments and consequently are at risk of being damaged by the localized forces accompanying metallic gaskets. High purity fluid delivery components made from polymer materials are also well known and often used when controlling flow of certain liquid fluids where potential contamination with metallic ions is a concern. In many polymer apparatus designs, fluid pathway joints also use opposed flat surfaces (with or without counterbores) with an interposed gasket. Gaskets made from polymer materials for use in such joints may also benefit from the inventive designs described in this disclosure.

This patent is subject to a terminal disclaimer.

Ultra-seal gasket for joining high purity fluid pathways


The present invention relates to a direct current relay, and more particularly, to a direct current relay capable of reducing an electronic repulsive force generated between a fixed contact and a movable contact by a permanent magnet installed to extinguish an arc. The direct current relay includes: a frame; first and second fixed contacts spaced from each other with a predetermined distance there between; first and second magnetic substances formed to enclose a lower part of the first and second fixed contacts; a movable contact movable to contact or to be separated from the first and second fixed contacts, having a first movable contact contactable to the first fixed contact, and having a second movable contact contactable to the second fixed contact; and a pair of permanent magnets installed on long sides of the frame.

1. Field of the Invention
The present invention relates to a direct current relay, and more particularly, to a direct current relay capable of reducing an electronic repulsive force generated between a fixed contact and a movable contact by a permanent magnet installed to extinguish an arc.
2. Background of the Invention
Generally, a direct current (DC) relay or a electromagnetic contactor is a type of electric circuit switching apparatus for performing a mechanical driving and transmitting a current signal using a principle of an electromagnet. The DC relay or the electromagnetic contactor is installed at various types of industrial equipment, machines, vehicles, etc.
FIG. 1 is a sectional view of a direct current relay in accordance with the conventional art, and FIG. 2 is an inner perspective view illustrating an upper part of FIG. 1.
The conventional direct current relay includes a lower frame 1, an upper frame 2, a pair of fixed contacts and a pair of movable contacts installed in the upper frame 2, and an electric actuator 5 installed in the lower frame 1 and configured to drive the movable contacts 4 so that a connected state between the fixed contacts 3 and the movable contacts 4 can be switched by an electric signal. Permanent magnets 6a, 6b are provided in the upper frame 2 so as to effectively control an arc generated when the contacts are separated from each other.
The pair of fixed contacts 3 are configured as a first fixed contact 3a and a second fixed contact 3b, and have polarities of (+), (−), respectively. The permanent magnets 6a, 6b installed in the upper frame 2 form a magnetic field (B), and are fixed by a permanent magnet holder (not shown). The magnetic field (B) generated from the permanent magnets 6a, 6b interacts with a current (+I, −I), thereby generating a force (+f, −f) to push out an arc generated when the contacts are separated from each other. This can reduce damage of a contact part.
However, the conventional direct current relay has the following problems.
Firstly, when the permanent magnets 6a, 6b for controlling an arc are provided at the direct current relay, a current (I) flows on the movable contacts 4 from a first movable contact 4a to a second movable contact 4b as shown in FIG. 2. Thus, a force (F) is applied to the movable contacts 4 in a downward direction by Fleming's law. The force (F) is applied in a direction to separate the movable contacts 4 from the fixed contacts 3. Such a force is called an 'electrodynamic repulsion force'. In a normal current state, no problem occurs. However, when an over-current flows due to a fault current, the electrodynamic repulsion force is drastically increased, resulting in separation of the contact part. As a result, the fixed contact 3 and the movable contact 4 are separated from each other, and thus an inferior contact state may be caused.
FIG. 3 illustrates a magnetic flux density in a direct current relay in accordance with the conventional art, which shows a flow of a magnetic field (B) formed by the permanent magnets 6a, 6b. The magnetic field (B) flows in a direction toward the lower permanent magnet 6b from the upper permanent magnet 6a. It can be shown that a magnetic flux density within a range between the upper permanent magnet 6a and the lower permanent magnet 6b is almost constant.


The invention is directed to a method for performing a high throughput test to determine the presence of PrPsc in a tissue sample taken post mortem from brain, the test comprising the workflow of (A) sample preparation, (B) sample treatment, (C) sample analysis, (D) controls, and (E) classifying the results of the analysis as positive or negative. The invention is further directed to preparing a treated biological sample suspected of containing PrPsc such that it is suitable for specific detection of PrPsc, if present, the method comprising the steps of (a) homogenizing the sample; followed by (b) digesting the sample proteolytically by adding to the homogenate Proteinase K and incubating the sample; followed by (c) adding a peptidic protease inhibitor to the incubated mixture of step (b), thereby obtaining a treated biological sample suitable for specific detection of PrPsc, if present. The invention further provides a conditioned microwell plate. In addition, the invention provides a soluble fusion protein comprising one or more epitopes of prion protein as well as a carrier polypeptide.

Variant Creutzfeldt-Jakob disease (vCJD) is a rare and fatal human neurodegenerative condition. As with Creutzfeldt-Jakob disease, vCJD is classified as a transmissible spongiform encephalopathy (TSE) because of characteristic spongy degeneration of the brain and its ability to be transmitted. vCJD is a new disease that was first described in March, 1996. In contrast to the traditional forms of CJD, vCJD has affected younger patients (average age 29 years, as opposed to 65 years), has a relatively longer duration of illness (median of 14 months as opposed to 4.5 months) and is strongly linked to exposure, probably through food, to a TSE of cattle called Bovine spongiform encephalopathy (BSE). TSEs are also known in other animals. For instance, scrapie affects sheep and goats and has been found in many sheep-producing countries throughout the world for over 250 years. Chronic wasting disease (CWD) is a contagious fatal TSE in cervids (members of the deer and elk family).
The hypothesis of a link between vCJD and BSE was first raised because of the association of these two TSEs in time and place. More recent evidence supporting a link includes identification of pathological features similar to vCJD in brains of macaque monkeys inoculated with BSE. A vCJD-BSE link is further supported by the demonstration that vCJD is associated with a molecular marker that distinguishes it from other forms of CJD and which resembles that seen in BSE transmitted to a number of other species. Studies of the distribution of the infectious agent in the brains of mice artificially infected with tissues from humans with vCJD and cows with BSE showed nearly identical patterns. The most recent and powerful evidence comes from studies showing that the transmission characteristics of BSE and vCJD in laboratory mice are almost identical, strongly indicating that they are due to the same causative agent. In conclusion, the most likely cause of vCJD is exposure to the BSE agent, most plausibly due to dietary contamination by affected bovine central nervous system tissue.
The infectious agents involved in TSE are usually referred to as prions. These pathogens are characterized by unusual properties and, in particular, by their strong resistance to common procedures of disinfection used against conventional microorganisms. Prions that cause BSE in cattle and vCJD in humans are transmitted through infected food products. While the incubation period of the disease is quite long, the onset of symptoms leads to extreme neurological debilitation within a few months. All animals possess normal prion proteins, which are known by a variety of acronyms in the scientific literature, e.g., PrP or PrPc. PrPc are found on the surface of many cell types including nerves, lymphocytes, and macrophages. All proteins "fold" themselves into specific three-dimensional shapes. Sometimes normal prion proteins become abnormally folded. Then the abnormal prions can "infect" normal ones by physical contact in which the abnormally-folded prion causes the normal one also to become misfolded, thus spreading the diseased state.
A major component of highly infectious prion protein fractions is a Proteinase K-resistant prion protein, termed PrPsc. The normal host prion protein PrPc is sensitive to Proteinase K. The biochemical behavior of PrPsc under denaturing conditions and in the presence of Proteinase K provides a biochemical means for assaying the presence of PrPsc in tissue samples, thereby diagnosing TSE disease. Identification of infected farm animals such as cattle or sheep post mortem is of particular importance in order to prevent potentially hazardous meat and other products from entering the human food chain. As the number of animals slaughtered and processed by the meat industry is high, TSE assays which are to be performed by foodstuff monitoring centers and reference laboratories have to meet the needs of high throughput testing.
A general workflow to assay for TSE essentially comprises the following steps:    (1) Removing sample tissue from a sacrificed animal            In the exemplary case of BSE the sample is preferably a piece of brain; usually, a part of the brain stem is removed when the animal is cut up. Preferably, the piece of brain includes the obex. However, other tissues are possible including spinal chord tissue and also lymph node or tonsil tissue.            (2) Taking a defined amount of tissue, which in the following will be referred to as "the sample", "the sampled tissue", or "the tissue sample"    (3) Homogenizing th tissue sample    (4) Treating the homogenized sample such that it is suitable for specific detection of PrPsc, if present            A preferred pretreatment uses proteolytic digestion of the homogenized sample with Proteinase K and denaturation with a chaotropic agent.            (5) Incubating the treated sample with one or more specific binding agents            Usually the binding agent is an antibody or an antibody fragment. The amount of complex formed by the binding agent(s) and the analyte is measured to result in a measurement value. In case a sample treated with Proteinase K and chaotropic agent is analyzed, the binding agents are specific for a fragment of PrPsc which resists the Proteinase K treatment.            (6) In order to assign a quantitative value to a positive or negative test result, using an algorithm which takes into account reference data and/or measurement values generated in one or more control experiments
The present invention focuses on steps (3), (4), (5) and (6) of the workflow. Step (5) according to the invention includes pretreatment with a proteolytic enzyme and chaotropic agent.
With respect to commercialized test systems, there exist several ways of performing steps (3) to (6). Generally, the processing of infective tissue often requires complex equipment in order to fulfill the needs of laboratory safety on the one hand and technical requirements on the other.
A first test system developed by Prionics AG (Schlieren, Switzerland) is distributed under the commercial name PRIONICS-Check WESTERN and PRIONICS-Check LIA (=luminescence immunoassay, described further below). The PRIONICS-Check LIA test system comprises (i) homogenization of sample tissue using a complex device and apparatus, (ii) proteolytic sample treatment, and (iii) immunological detection of PrPsc, whereby steps (ii) and (iii) are performed in the 96-well format.
According to the user's manual of the test system, for the homogenization step a deconstituting device for the preparation of biological samples as described in WO 02/48679 is used. The device comprises a container in the form of a cup for holding the tissue to be deconstituted. A shaft is mounted for rotation inside the container with a blade on the end inside the container. The shaft is supported axially by ball coupling means and has engagement means on its end outside the container for coupling the shaft to a motor. The device is used in an automatic apparatus (FASTH PCPM4, cod. 80040, Consul A R, Villeneuve, Switzerland), which includes at least one support element with a plurality of housings for receiving the container; a deconstitution station which includes at least one motor with a drive shaft for engaging the engagement means of the shaft of the deconstituting device, whereby the motor is movable between a position disengaged from the shaft and one position engaging it; and conveyor means for transporting the support element to the deconstitution station. The FASTH device simultaneously processes 4 containers which are placed in a rack. The rack takes up eight containers which are processed in two subsequent steps. Another device (MEDIFASTH, Consul) is commercially available which works similarly but processes only two containers at a time. The containers are placed in racks, whereby each rack takes up two containers.
The containers are commercially available as disposable items (PRYPCONS, Consul A R, Villeneuve, Switzerland) made of plastic. Each container has a sliding gate in the lid through which the sampled brain tissue is transferred into the container. The FASTH device is capable of taking up and subsequently processing 6 racks, i.e., 48 containers. Racks with processed containers can be removed from the running device; similarly, the device can be loaded with new racks. According to the manufacturer the device is capable of homogenizing up to 250 samples/h.
In each container a sample of 350-700 mg of tissue is homogenized together with a ten-fold volume of homogenization buffer. In order to ensure a proper sample vs. buffer ratio, the weight of the sample tissue is determined before. Following the homogenization process, an aliquot of the homogenate (1 ml) is taken manually from the container, usually with a hand pipet using disposable pipet tips, and is transferred to a 96-well "sample master plate". Alternatively, the homogenate can be removed and transferred by means of an automatic pipetting device (e.g., supplied by TECAN Group Ltd., Switzerland). However, the sliding gate of each container has to be opened manually.
In a cavity of a microwell plate (the "digestion" plate), a volume of 100 μl of the homogenate is mixed with 50 μl of a digestion solution containing a protease. The mixture is then sealed and incubated. Following an incubation, 10 μl of a stop solution are added to the digested homogenate and mixed. A volume of 15 μl of the mixture is transferred to a cavity of another microwell plate (the "preincubation plate") which contains 15 μl of an "assay buffer". Transfer and mixing of samples with assay buffer have to be completed within 2-5 min. After 2-5 min a volume of 10 μl "preincubation buffer" is added, mixed, and incubated for about 2 min. Subsequently, 200 μl of "detection antibody solution" are added and mixed. The plate is sealed and incubated on a shaker for about 60 min. Subsequently, a volume of 200 μl of each cavity is transferred to the corresponding cavity of a "capture plate". The plate is then incubated for about 90 min on a shaker. After that, the capture plate is washed with wash buffer four times using an ELISA washer. Remaining liquid is removed (preferably by clapping), and each cavity is filled with 100 μl of a chemiluminescent substrate working solution. After an incubation period of 5-10 min, the light signals are read in a chemiluminometer, and the signals are recorded.
A different test system is the Enfer TSE diagnostic kit which is distributed by Abbott Laboratories, USA. The homogenization method depends on the Stomacher apparatus (Seward Stomacher 80). The apparatus provides a mechanical action in which contoured paddles apply pressure to a sample bag. Sample tissue in the sample bag is subjected to homogenization in the presence of a sample buffer. This method is suited for soft tissue such as obex. A single apparatus is capable of processing 2 bags at a time. Homogenization of a tissue sample typically takes 2 min. For each single sample preparation a new blade, tongue depressor, weighing boat, and homogenizer bag must be used to prevent cross-contamination. The tissue sample is a thin cross-section of CNS tissue weighing between at least 0.5 g and 1.0 g. Weighing and transferring the sample into the bag require extensive manual work. Per 1 g of tissue, 15 ml of sample buffer are added into the bag. When dispensing the sample buffer, care must be taken to avoid contact of the dispenser with the bag. Homogenization is controlled by visual inspection. After the homogenization step, the homogenizer bag is left between 5 min and 40 min to allow bubbles to subside.
Following the homogenization process, the homogenization bag is opened and an aliquot (180 μl) of the liquid homogenate is taken manually out of the bag with a hand pipet using disposable pipet tips. At this point care must be taken not to allow the pipette to be contaminated on the outside by material from the homogenizer bag. The homogenate is transferred to a 96-well microwell plate. The plate is sealed and subjected to centrifugation at 4,000×g at room temperature for 5 min. One hundred μl of the supernatant are then transferred to a second 96-well microwell plate containing 20 μl of a Proteinase K solution. According to the user's manual, the Proteinase K solution has a tendency to stick to the side of the cavities. In order to prevent this, the buffer has to be pipetted to the very bottom of the cells. When transferring the supernatant, care must be taken not to disturb the pellet because transfer of solid particles must be prevented. The plate is then covered with a plate sealer, and samples are then incubated for 60 min on a shaker. During this step, PrPsc aggregates are hydrophobically bound to the cavities of the microwell plate while the Proteinase K digests away the PrPc, thus allowing the distinction of PrPsc from PrPc. The pipetting steps of this protocol can be automated.
The cavities of the microwell plate are washed, and the plate is clapped to remove remaining liquid. Subsequently, the sample cavities are incubated with 150 μl of Enfer buffer 3 for 15 min. The plate is washed again, clapped, and after that, rabbit polyclonal antibody specific for the PrP protein in a volume of 150 μl is added to the cavities. The plate is sealed again and incubated for 40 min. After that, the cavities are washed again and then incubated with an enzyme-conjugated second antibody. After incubation with the conjugate, the cavities are washed, and chemiluminescent substrate is added. The light signal is read in a chemiluminometer and the signal is recorded.
Another commercially available test system is the TeSeE BSE test distributed by Bio-Rad Laboratories (Munich, Germany; catalogue numbers 3551144 [purification kit], 3551145 [detection kit], 3551120 [calibration syringe and needle]). This method is adapted for processing two times 45 samples (plus controls) at a time, whereby in the beginning test tubes in racks in the 6*8 format are used.
An amount of 350 μg±40 μg of brain stem tissue, preferred obex tissue, is transferred to a grinding tube. This is a test vial with a volume of about 2 ml containing about 1.5 ml homogenization buffer and grinding beads. Test vials pre-filled with beads and buffer are part of the Bio-Rad kit. The grinding beads have a diameter of between 0.5 mm and 1 mm. The tube is filled with grinding beads up to about the 200 μl marking. Upon transfer of sample tissue, each test vial is closed manually with a screw cap, and the vial is placed in a rack which holds 48 vials in total. The homogenization step is performed by using a RIBOLYSER or a TeSeE Precess 48 device. Basically, the device agitates the racks with the vials, and the movement of the beads in each vial homogenizes the sample tissue contained therein.
Following the homogenization step, the rack is removed from the agitation device, each vial is opened manually, and a volume of 250 μl of the homogenate is removed using a syringe for single use which is fitted with a calibrated blunt end needle. The needle needs to be immersed in the pellet of beads to avoid taking up poorly homogenized tissue fragments.
The homogenates are transferred to reaction vials for further treatment. An equal volume of Proteinase K solution is added, mixed, and incubated at 37° C. for 10 min. Mixing is done manually by inverting the tubes 10 times. According to the user's manual, the time between adding Proteinase K solution and the incubation at 37° C. must not exceed 2 min. After the incubation, a volume of 250 μl of a "clarifying solution" (reagent B) is added and mixed. It is noted that for this step, the Eppendorf vial has to be manually opened and closed again. It is also noted that according to the user's manual, the time after the incubation until the point when the clarifying solution is mixed must not exceed 2 min. Within 30 min, the Eppendorf reaction vials are centrifuged for 5 min at 20,000×g. The vials are opened again, and the supernatants are discarded. The vials are dried by inverting onto absorbent paper for 5 min. Subsequently, a volume of 25 μl of "resolving buffer" (reagent C) is added to each vial, the vial is closed again and then immediately incubated at 100° C. for 5 min. After that, in another manual step, the vials are agitated on a vortex mixer for 5 seconds.
The treated sample is then diluted with 125 μl PBS containing BSA and mixed by vortexing just before transfer to a microwell plate. One hundred μl of the diluted sample are transferred to the microwell plate which is coated with a monoclonal capture antibody. The plate is sealed with adhesive tape. After incubation of the plate for about 75 min at 37° C., the plate is washed using an automatic washer, and subsequently 100 μl of a solution containing an enzyme-conjugated detection antibody are added to each cavity. The plate is sealed again with adhesive tape. After incubation of the plate for about 1 h, the plate is washed again, and a volume of 100 μl of a substrate solution is added to each cavity. After 30 min, the enzyme reaction is stopped by adding a stop solution. Signals are read in a microwell plate reader, and the signals are recorded.
The methods of the state of the art have certain disadvantages. Particularly the homogenization process represents a bottleneck with regard to both susceptibility to contamination and sample throughput. It is noted that a test system which would be performed entirely in the standardized 8×12 (i.e., 96-well) format would be advantageous. Also, a cost-effective workflow in this format with reduced hands-on time is desired.
For the PRYPCON container it is noted that the tissue is homogenized in the container in the presence of a homogenization buffer by means of fast rotating (20,000 r.p.m.) blades. As a consequence, an aerosol containing components of possibly prion-infected brain tissue is generated in the airspace in the inner compartment of the container. Regarding the container it is noted in addition that both (i) the opening of the lid with the shaft inserted and (ii) the sliding gate do not provide completely airtight (i.e., pressure-tight) sealing of the inner compartment where the homogenization takes place. The sample bags used for homogenization with the Stomacher apparatus may also give rise to contamination, particularly when the homogenate is removed from the bag.
Regarding throughput, the FASTH device is capable of simultaneously processing 4 PRYPCON containers. While this system already provides a partly automated homogenization process, the alternative system using Stomacher bags is capable of processing only 2 bags at a time per device. The Bio-Rad system, in contrast, homogenizes 48 samples at a time.
However, during the sample preparation procedure of the Bio-Rad system, each grinding tube is closed manually with a screw cap. Twisting of the screw cap presses a seal onto the mouth of the container; the stronger the screw cap is twisted, the tighter the tube is sealed. That is to say, depending on the force exerted when twisting the cap to close the vial, the sealing effect of the screw cap may be imperfect. As a consequence of imperfect sealing, liquid contents of the vial may be released from a screw-capped vial, e.g., in case the pressure inside the vial rises relative to the outside due to a rise of temperature in the vial or a drop of air pressure outside. Thus, the use of screw caps poses a problem when "sealing" as a defined (i.e., standardized) state or result is to be obtained. An exemplary parameter for standardized sealing is air-tightness over a defined time interval against a measured relative difference of higher air pressure within the container and lower air pressure outside of the sealed container.
In addition, the use of screw caps requires increased manual handling by lab technicians and prevents rapid processing. Consequently, screw caps pose a problem when larger number of vials have to be opened and closed, or when it is desired to seal the vials automatically. In addition, the more manual handling is involved, the higher are the chances that vials with sample material are mistakenly interchanged.
The amount and the complexity of the material for single use which is needed to perform a TSE assay influence the price of an assay system. However, the amount of single use items and the material of which these are made particularly impact on the costs of waste disposal. Depending on national regulations, any waste material which has come in contact with infective TSE agent has to be subjected to chemical and/or heat treatment, autoclaving, or incineration. Due to the difficulties to inactivate infective prions, these processes are more cost-intensive compared to the inactivation of usual infective waste. Therefore, it is desired to minimize expenditure on waste disposal when running TSE tests at high throughput.


A method of protecting a data network from denial of service (DOS) attacks is described. The method may use various network tools to selectively block or disable portions of a data trunk experiencing a DOS attack, thereby preventing the DOS attack from reaching at least some resources on the network. In one embodiment, a network switch identifies a virtual LAN (VLAN) carrying suspect data on a data trunk. The network switch then adjusts a spanning tree for the network so that one or more ports on the compromised VLAN are blocked or disabled, while non-compromised VLANs are allowed to continue carrying data. Other approaches are also presented for avoiding the loss of valid data when a network blocks one or more VLANs or other portions of a network in response to a DOS attack or other intrusion.

1. Field of the Invention
The invention relates generally to the field of networked data communications, and specifically to the field of network resilience and security.
2. Description of the Related Art
Virtual local area networks (VLANs) may be used to arrange communications among a group of devices so that the devices communicate as if they were connected by a common local area network (LAN). The devices in a VLAN may reside on one or more LANs, with non-local networks connecting the traditional LANs. The VLAN facilitates communications among the various machines, allowing users and network administrators to more readily expand operations beyond the confines of a single traditional LAN. In one sense, a VLAN may be identified as a collection of physical ports on one or more bridges and/or switches, with the ports associated together as sharing a local network structure.
Network administrators can benefit from tools that help prevent unwanted intrusions on their networks from external sources. One type of intrusion is a denial-of-service (DOS) attack. In a DOS attack, an outside party attempts to prevent legitimate users from being able to access or use resources on a network. DOS attacks commonly take the form of a large amount of incoming network traffic that floods network resources, such as central processing units (CPUs), ports, bridges, switches, and routers.
The goal of attackers in this type of attack is generally to prevent legitimate network traffic from reaching the network resources. In various situations, a DOS attack may attempt to maliciously disrupt connections to a machine, thereby disabling services provided by that machine. In other situations, a DOS attack may be an attempt to prevent a particular individual from accessing a service. DOS attacks may also be attempted as a part of a larger coordinated attack.
Most commonly, a DOS attacker may direct a large number of data packets to one or more devices on a target network. The flood of packets may generally be an attempt to consume much or all the available bandwidth or capacity on one or more portions of the target network. This type of attack may have a large variety of forms. For example, the DOS packets may be simple ICMP ECHO packets, but may alternatively be any other type of data that would be received by the target network. Also, the attacker may launch the attack from a single machine or from multiple machines. One trend in DOS attacks has been to mask the origin of attacks through the use of widely distributed "zombie" machines—computers that are maintained by unsuspecting owners, but which have been infected by a virus programmed to launch a coordinated DOS attack at a predetermined future time.
DOS attacks may also be an unintended consequence of improper but non-malicious activity. For example, a legitimate user may have unintentionally but incorrectly configured a remote system in such a way that repeatedly transmits data to a network server in a rapid endless loop. In some circumstances, the resulting flow of data may flood a resource on the network. Regardless of their source or purpose, DOS attacks may hinder or disrupt a network or a network resource if an appropriate response is not made to the attack.
VLANs generally share ports so that multiple VLANs may communicate through a common resource. Such shared resources, or trunks, may be shared physical connections between two switches or between other network devices. Trunks may be carried on physical connections such as twisted-pair cables, optical fibers, or wireless links. In some circumstances, multiple trunks may share a single physical connection. Alternatively, or in addition, trunks may be logical constructions that use more than one physical connection. To protect network resources from DOS attacks, a network may automatically disconnect a trunk to prevent the propagation of the attack on that trunk. Such a measure may disrupt the flow of the DOS attack, and protect network devices that are downstream from the attack. However, this protection also disrupts other traffic on the trunk, causing a loss of valuable data flows.
While the invention is susceptible to various modifications and alternative forms, specific embodiments of the invention are provided as examples in the drawings and detailed description. It should be understood that the drawings and detailed description are not intended to limit the invention to the particular form disclosed. Instead, the intention is to cover all modifications, equivalents and alternatives falling within the spirit and scope of the invention as defined by the appended claims.

Method and apparatus for preventing DOS attacks on trunk interfaces


Techniques are described for responding to aggregate queries using optimizer statistics already available in the data dictionary of the database in which the database object targeting by the aggregate query resides, without the user creating any additional objects (e.g. materialized views) and without requiring the objects to be loaded into volatile memory in a columnar fashion. The user query is rewritten to produce a transformed query that targets the dictionary tables to form the aggregate result without scanning the user tables. “Accuracy indicators” may be maintained to indicate whether those statistics are accurate. Only accurate statistics are used to answer queries that require accurate answers. The accuracy check can be made during runtime, allowing the query plan of the transformed query to be used regardless of the accuracy of the statistics. For queries that request approximations, inaccurate statistics may be used so long as the statistics are “accurate enough”.

It is common for a database server to receive simple queries with aggregate functions like count, min, max etc. on the table. For these simple queries, database servers typically scan the table to aggregate the column data.
It is possible to use a materialized view to return the results of these kind of queries with aggregation functions. A materialized view is a database object (e.g. another table) that contains the results of a query. For example, it may be a local copy of data located remotely, or may be a subset of the rows and/or columns of a table or join result, or may be a summary using an aggregate function.
When a user query can be answered by data maintained in a materialized view, the user query is rewritten by the database server to obtain the data from the materialized view, which has fewer rows than the original base table, and can be scanned faster than the original base table.
The use of materialized views to answer queries that contain aggregate functions requires the user to create the materialized view object. This additional object has to be refreshed/maintained whenever Data Manipulation Language (DML) operations (e.g. delete, insert and update) are performed on the base table. The maintenance of the materialized views requires additional objects like materialized view logs (a journal of rows modified, etc.). The maintenance causes more overhead on DMLs and uses space on disk for storing the materialized view and its logs. Materialized views and techniques for maintaining them are described in detail in U.S. Pat. No. 6,125,360, the contents of which is incorporated herein by reference.
Another technique used for increasing the performance of aggregate queries involves storing a copy of data in volatile memory in columnar fashion. Along with that columnar data, aggregate information can be stored for each columnar unit. When a query requires aggregation across a table, the result may be aggregated from the aggregated information available in each columnar unit, as is described, for example, in U.S. patent application Ser. No. 15/987,619, filed May 23, 2018, the contents of which are incorporated herein by reference.
Unfortunately, in-memory columnar units are limited to the memory available, so some of the database objects that are targeted by aggregate queries may not be available in the in-memory columnar storage. Further, even if the object targeted by an aggregate query is stored in an in-memory columnar unit along with corresponding aggregate information, there is a cost of going through all the columnar units for a particular column to derive an aggregate value for that column.
The approaches described in this section are approaches that could be pursued, but not necessarily approaches that have been previously conceived or pursued. Therefore, unless otherwise indicated, it should not be assumed that any of the approaches described in this section qualify as prior art merely by virtue of their inclusion in this section.


A magnetic actuator includes: a movable unit, movable between a first position and a second position, and including an integrally formed eddy-current component and first magnet yoke component; a second magnet yoke component to form a magnetic circuit with the first magnet yoke component; an electromagnetic coil capable of generating an exciting magnetic field when being energized, magnetic lines generated thereby being energized penetrating the magnetic circuit formed by the first and second magnet yoke components; an eddy-current coil to enable an eddy current to be generated in the eddy-current component, to produce an electromagnetic repulsive force to the movable unit; and a permanent magnetic holding component to hold the movable unit in the first position or the second position. The magnetic actuator can simplify the actuator, reduce the number of components and the size thereof, as well as reducing the energy consumption and improving the stability thereof.

Actuators are important components of the circuit breaker and the high-speed reversing switch. At present, there are spring actuators, electromagnetic actuators, and permanent magnetic actuators, etc. The spring actuators have the advantage that there is no need for a high-power direct-current power supply and have the defects of relatively complicated structure, more parts, and poor reliability. The electromagnetic actuators have a cumbersome structure and a relatively long switching-off and switching-on time.
The permanent magnetic actuators use a permanent magnet as a component for keeping the switching-off and switching-on positions. When the permanent magnetic actuators work, only one main moving component is provided, the switching-off and switching-on current is small, the mechanical service life is long, but the movement inertia of the moving component when in a switching-off state is relatively large, and a higher action speed cannot be achieved.
A typical actuator of a vacuum circuit breaker is disclosed in China patent CN 101315836 A (published on Feb. 13, 2008), the actuator mainly comprising an eddy-current disc, a switching-off coil, a switching-on coil and a charging circuit. When the charging circuit is excited, the rapidly-increased current would flow through the switching-off coil or the switching-on coil, and the switching-off coil or the switching-on coil will induce an eddy current in the eddy-current disc. In this way, a relatively large electromagnetic repulsive force can drive the eddy-current disc to leave the corresponding coil. The actuator further comprises a spring mechanism for keeping the switching-off state and the switching-on state. Although the switching-off operation can be rapidly realized by virtue of the electromagnetic repulsive force, the actuator has a large energy consumption and poor controllability.