US20130220112A1 - Cryogenic refrigerator - Google Patents
Cryogenic refrigerator Download PDFInfo
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- US20130220112A1 US20130220112A1 US13/755,269 US201313755269A US2013220112A1 US 20130220112 A1 US20130220112 A1 US 20130220112A1 US 201313755269 A US201313755269 A US 201313755269A US 2013220112 A1 US2013220112 A1 US 2013220112A1
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- Prior art keywords
- displacer
- cylinder
- cryogenic refrigerator
- circumferential surface
- movement
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
- F04B9/00—Piston machines or pumps characterised by the driving or driven means to or from their working members
- F04B9/02—Piston machines or pumps characterised by the driving or driven means to or from their working members the means being mechanical
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
- F04B37/00—Pumps having pertinent characteristics not provided for in, or of interest apart from, groups F04B25/00 - F04B35/00
- F04B37/06—Pumps having pertinent characteristics not provided for in, or of interest apart from, groups F04B25/00 - F04B35/00 for evacuating by thermal means
- F04B37/08—Pumps having pertinent characteristics not provided for in, or of interest apart from, groups F04B25/00 - F04B35/00 for evacuating by thermal means by condensing or freezing, e.g. cryogenic pumps
Definitions
- An aspect of this disclosure relates to a cryogenic refrigerator.
- Japanese Laid-Open Patent Publication No. 3-843608 discloses a cryogenic refrigerator where valves are opened and closed while causing a displacer to reciprocate in a cylinder.
- “coldness” is generated by causing a refrigerant gas in an expansion space to expand via a clearance between the displacer and the cylinder, the “coldness” is transferred to a cooling stage on the periphery of the clearance and the expansion space by heat exchange, and as a result, an object is frozen.
- a cryogenic refrigerator that includes a cylinder; a displacer configured to reciprocate in the cylinder; a driving unit configured to drive a rotational shaft having an axial direction oriented in a direction of reciprocating movement of the displacer; and a movement conversion unit configured to convert rotational movement of the rotational shaft into the reciprocating movement of the displacer.
- the movement conversion unit is a screw unit including a male thread and a female thread one of which is a part of the displacer.
- FIG. 1 is a schematic diagram illustrating an exemplary configuration of a cryogenic refrigerator according to a first embodiment
- FIG. 2 is a schematic diagram illustrating an exemplary configuration of a live load packing of the cryogenic refrigerator of the first embodiment
- FIG. 3 is a schematic diagram illustrating an exemplary configuration of a cryogenic refrigerator according to a second embodiment.
- a cryogenic refrigerator 1 of a first embodiment may be implemented, for example, as a Gifford-McMahon (GM) refrigerator that uses a helium gas as the refrigerant gas.
- the cryogenic refrigerator 1 includes a cylinder 2 , a displacer 3 , a motor shaft (rotational shaft) 4 , a motor (driving unit) 5 , a sleeve 6 , a live load packing 7 , a housing 8 , a valve plate 9 , a valve body 10 , and a gas path 11 .
- GM Gifford-McMahon
- the cylinder 2 is a closed-end cylinder that encloses the displacer 3 .
- the upper end (in FIG. 1 ) of the cylinder 2 is hermetically closed by the housing 8 .
- An expansion space 12 is formed by the displacer 3 and the cylinder 2 in the lower part of FIG. 1 .
- the cylinder 2 includes a cooling stage that is disposed adjacent to and surrounds the expansion space 12 .
- the displacer 3 faces the cooling stage across a clearance.
- the cooling stage may be composed of, for example, copper, aluminum, or stainless steel.
- the displacer 3 is housed in the cylinder 2 so as to be able to reciprocate in the longitudinal direction or the axial direction of the motor 5 .
- a material such as stainless steel may be used taking into account strength, thermal conductivity, and helium blocking capability.
- the motor 5 causes the displacer 3 to reciprocate and is disposed at a hot end of the cylinder 2 such that the motor shaft 4 is oriented in the axial direction of the displacer 3 and the cylinder 2 (or in the direction of the reciprocating movement of the displacer 3 ).
- the outer circumferential surface of the displacer 3 is shaped like a cylinder, and the displacer is filled with a cold storage medium.
- the internal volume of the displacer 3 constitutes a regenerator.
- An upper flow smoother for smoothing the flow of the helium gas is provided at the upper end of the regenerator, i.e., the end closer to the ambient temperature chamber, and a lower flow smoother is provided at the lower end of the regenerator.
- An upper opening is formed at the hot end of the displacer 3 .
- the refrigerant gas flows from the ambient temperature chamber, which is located above the displacer 3 in FIG. 1 , through the upper opening into the displacer 3 .
- the ambient temperature chamber is a space formed by the cylinder 2 and the hot end of the displacer 3 , and the volume of the ambient temperature chamber changes as the displacer 3 reciprocates.
- An intake and exhaust system implemented by a rotary valve composed of the valve plate 9 and the valve body 10 is provided in the housing 8 that is disposed, in the axial direction, between the motor 5 and the cylinder 2 .
- a high-pressure flexible pipe HF connected to the high-pressure side of a compressor (not shown) and a low-pressure flexible pipe LF connected to the low-pressure side of the compressor are connected to one end of the intake and exhaust system.
- the gas path 11 implementing a supply and exhaust pipe and leading to the ambient temperature chamber is connected to the other end of the intake and exhaust system.
- the live load packing 7 is disposed between the cylinder 2 and a part of the displacer 3 near the hot end.
- the live load packing 7 includes a chevron packing 7 a (intermediate layer, triangle-shaped), upper and lower packings 7 b (sandwich layers), a ground 7 c , and bolts 7 d .
- the chevron packing 7 a includes a pair of string- or fiber-like elements. The elements have a cross-section shaped like a right triangle and their sloping surfaces are in contact with each other. The elements contain a lubricant.
- the upper and lower packings 7 b sandwich the chevron packing 7 a in the axial direction.
- the lower packing 7 b is disposed in a recess formed in the cylinder 2 adjacent to the hot end of a male thread 3 a of the displacer 3 .
- the chevron packing 7 a is disposed above the lower packing 7 b
- the upper packing 7 b is disposed above the chevron packing 7 a
- the ground 7 c is disposed above the upper packing 7 b as a spacer.
- a wall part of the housing 8 is disposed above the ground 7 c .
- Female screw holes are formed through the wall part of the housing 8 c in the vertical direction in FIG. 2 .
- the bolts 7 d are screwed into the female screw holes.
- the end of the male thread part (male thread end) of each bolt 7 d is in contact with the upper surface of the ground 7 c .
- the sloping surfaces of the elements constituting the chevron packing 7 a are pressed with a stronger force, and the inner one of the elements is pressed with a stronger force against the outer circumferential surface of the displacer 3 and thereby seals the displacer 3 while supplying the lubricant.
- a lower opening for introducing the refrigerant gas via the clearance into the expansion space 12 is formed at a cold end of the displacer 3 .
- the expansion space 12 is a space formed by the cylinder 2 and the displacer 3 , and the volume of the expansion space 12 changes as the displacer 3 reciprocates.
- the cooling stage is disposed on the outer circumferential surface of the cylinder 2 at a position corresponding to the expansion space 12 and is thermally connected to an object to be cooled. The cooling stage is cooled by the refrigerant gas passing through the clearance.
- a material such as Bakelite (fabric-filled phenolic material) may be used taking into account specific gravity, abrasion resistance, strength, and thermal conductivity.
- a wire mesh may be used as the cold storage medium.
- the male thread 3 a is formed on a part of the outer circumferential surface of the displacer 3 closer to the hot end, and a female thread 2 a that engages the male thread 3 a is formed on the inner circumferential surface of the cylinder 2 .
- a fitting hole is formed in the hot end surface of the displacer 3 .
- the sleeve 6 is shaped like a cylinder and is fitted into the fitting hole, and the movement of the sleeve 6 relative to the displacer 3 in the circumferential direction and the axial direction is thereby prevented.
- the outer circumferential surface of the sleeve 6 is, for example, serrated.
- An inner hole having an inner circumferential surface corresponding to the sleeve 6 is formed in the valve plate 9 , and the inner circumferential surface of the inner hole is also serrated to correspond to the serration on the outer circumferential surface of the sleeve 6 .
- a cylindrical inner hole having a diameter greater than the maximum diameter of the sleeve 6 is formed in the valve body 10 .
- valve plate 9 when the motor 5 rotates in the forward direction or the reverse direction, the valve plate 9 is rotated via the sleeve 6 relative to the valve body 10 and thereby functions as a supply valve and a return valve during the operations of the cryogenic refrigerator 1 .
- the inner circumferential surface of the sleeve 6 is also serrated, and the outer circumferential surface of the motor shaft 4 is serrated to correspond to the serration on the inner circumferential surface of the sleeve 6 . Accordingly, the movement of the sleeve 6 relative to the motor shaft 4 is not prevented in the axial direction but is prevented in the circumferential direction.
- the motor 5 is implemented by, for example, a three-phase AC synchronous motor, and is driven (rotated) in the forward and reverse directions by an inverter (not shown).
- the motor shaft 4 rotates in the forward direction and as a result, the sleeve 6 and the displacer 3 drivably coupled to the motor shaft 4 are rotated in the forward direction.
- the displacer 3 is caused to move from the bottom dead point (upper position in FIG. 1 ) to the top dead point (lower position in FIG. 1 ) by a screw unit composed of the male thread 3 a and the female thread 2 a .
- the displacer 3 is located at the top dead point (lower position in FIG. 1 ) in the cylinder 2 .
- the supply valve implemented by the rotary valve is opened.
- high-pressure helium gas is supplied via the supply valve through the gas path 11 (supply and exhaust pipe) into the cylinder 2 .
- the high-pressure helium gas flows through the upper opening at the upper end of the displacer 3 into the regenerator in the displacer 3 .
- the high-pressure helium gas flowing into the regenerator is cooled by the cool storage medium, flows through the lower opening at the lower end of the displacer 3 and the clearance, and is supplied into the expansion space 12 .
- the supply valve When the expansion space 12 is filled with the high-pressure helium gas, the supply valve is closed. At this timing, the displacer 3 is located at the bottom dead point (upper position in FIG. 1 ) in the cylinder 2 . At the same timing or at a slightly different timing, the return valve implemented by the rotary valve is opened, the pressure of the helium gas in the expansion space 12 is reduced and the helium gas expands. Due to the expansion, the helium gas in the expansion space 12 is cooled and absorbs the heat of the cooling stage via the clearance.
- the displacer 3 moves toward the top dead point (lower position in FIG. 1 ) and the volume of the expansion space 12 decreases.
- the helium gas in the expansion space 12 returns via the clearance, the lower opening, the regenerator, and the upper opening to the intake side of the compressor.
- the helium gas refrigerant gas
- the cold storage medium is cooled by the helium gas.
- the above process is referred to as a “cooling cycle”, and the cryogenic refrigerator 1 repeats the cooling cycle to cool the cooling stage.
- the driving force of the motor 5 is converted into the reciprocating movement of the displacer 3 between the bottom dead point and the top dead point by the screw unit composed of the male thread 3 a and the female thread 2 a .
- the configuration of the first embodiment makes it possible to eliminate the need to use a Scotch yoke mechanism or a ball screw mechanism.
- the configuration of the first embodiment makes it possible to orient the axis of the motor 5 in the vertical direction. This in turn makes it possible to prevent excessive thrust load on the motor shaft 4 of the motor 5 .
- the configuration of the first embodiment makes it possible to use a normal motor as the motor 5 and thereby makes it possible to reduce the costs of the cryogenic refrigerator 1 .
- the screw unit i.e., a movement conversion unit, is implemented by the male thread 3 a and the female thread 2 a that are disposed to overlap the displacer 3 in the axial direction, it is possible to reduce the size in the axial direction and the number of parts of the cryogenic refrigerator 1 compared with the related-art configuration.
- the screw unit is composed of the male thread 3 a formed on the outer circumferential surface of the displacer 3 and the female thread 2 a formed on the inner circumferential surface of the cylinder 2 , and therefore the screw movement is achieved by the male thread 3 a and the female thread 2 a that are in close contact with each other.
- This configuration makes it possible to reduce the leakage of helium gas flowing through the clearance from the hot side to the cold side. Also with this configuration, since even leaked helium gas flows helically, it is possible to increase the contact time of the helium gas with the outer circumferential surface of the displacer 3 and thereby increase the flow-path resistance in the clearance. In other words, this configuration makes it possible to reduce penetration of heat into the cooling stage due to the leakage of helium gas.
- the displacer 3 rotates in the circumferential direction with respect to the cylinder 2 .
- the live load packing 7 configured as described above can effectively seal the clearance that is a gap in the radial direction between the displacer 3 and the cylinder 2 .
- the live load packing 7 can increase the lubricity and reduce the frictional resistance of the displacer 3 that rotates in the circumferential direction with respect to the cylinder 2 .
- the live load packing 7 may be replaced with an O-ring or a slipper seal.
- FIG. 3 is a schematic diagram illustrating an exemplary configuration of a cryogenic refrigerator 21 of a second embodiment.
- the same reference numbers are used for components corresponding to those in the first embodiment, and descriptions of those components are omitted.
- differences between the first embodiment and the second embodiment are mainly described.
- the cryogenic refrigerator 21 of the second embodiment may also be implemented as a Gifford-McMahon (GM) refrigerator. As illustrated in FIG. 3 , the cryogenic refrigerator 21 includes a cylinder 22 , a displacer 23 , a motor shaft (rotational shaft) 4 , a motor (driving unit) 5 , a sleeve 6 , a slipper seal 27 , a housing 8 , a valve plate 9 , a valve body 10 , and a gas path 11 .
- GM Gifford-McMahon
- the cylinder 22 is a closed-end cylinder that encloses the displacer 23 .
- the upper end of the cylinder 22 is hermetically closed by the housing 8 .
- An expansion space is formed by the displacer 23 and the cylinder 22 in the lower part of FIG. 3 .
- the cylinder 22 includes a cooling stage that is disposed adjacent to and surrounds the expansion space.
- the displacer 23 faces the cooling stage across a clearance.
- the cooling stage may be composed of, for example, copper, aluminum, or stainless steel.
- the displacer 23 is housed in the cylinder 22 so as to be able to reciprocate in the longitudinal direction or the axial direction of the motor 5 .
- a material such as stainless steel may be used taking into account strength, thermal conductivity, and helium blocking capability.
- the motor 5 causes the displacer 23 to reciprocate and is disposed at a hot end of the cylinder 22 such that the motor shaft 4 is oriented in the axial direction of the displacer 23 and the cylinder 22 .
- the outer circumferential surface of the displacer 23 is shaped like a cylinder, and the displacer 23 is filled with a cold storage medium.
- the internal volume of the displacer 23 constitutes a regenerator.
- An upper flow smoother for smoothing the flow of the helium gas is provided at the upper end of the regenerator, i.e., the end closer to the ambient temperature chamber, and a lower flow smoother is provided at the lower end of the regenerator.
- An upper opening is formed at the hot end of the displacer 23 .
- the refrigerant gas flows from the ambient temperature chamber, which is located above the displacer 23 in FIG. 3 , through the upper opening into the displacer 23 .
- the ambient temperature chamber is a space formed by the cylinder 22 and the hot end of the displacer 23 , and the volume of the ambient temperature chamber changes as the displacer 23 reciprocates.
- a high-pressure flexible pipe HF connected to the high-pressure side of a compressor (not shown), a low-pressure flexible pipe LF connected to the low-pressure side of the compressor, and an intake and exhaust system implemented by a rotary valve composed of the valve plate 9 and the valve body 10 are provided.
- the gas path 11 implementing a supply and exhaust pipe of the intake and exhaust system is connected to the ambient temperature chamber.
- a lower opening for introducing the refrigerant gas via the clearance into the expansion space is formed at a cold end of the displacer 23 .
- the expansion space is formed by the cylinder 22 and the displacer 23 , and the volume of the expansion space changes as the displacer 23 reciprocates.
- the cooling stage is disposed on the outer circumferential surface of the cylinder 22 at a position corresponding to the expansion space 12 and is thermally connected to an object to be cooled. The cooling stage is cooled by the refrigerant gas passing through the clearance.
- a material such as Bakelite (fabric-filled phenolic material) may be used taking into account specific gravity, abrasion resistance, strength, and thermal conductivity.
- a wire mesh may be used as the cold storage medium.
- An upper cup 23 b shaped like a disk is provided at the hot end of the displacer 23 .
- the slipper seal 27 is disposed on the outer circumferential surface of the displacer 23 at a position closer than the upper cup 23 b to the cold end of the displacer 23 .
- a hole (or recess) extending toward a cold-end surface of the displacer 23 is formed in the center of a hot-end surface of the displacer 23 .
- a female thread 23 a is formed on the inner circumferential surface of the hole.
- a male thread 26 a corresponding to the female thread 23 a is formed on the outer circumferential surface of a sleeve (cylindrical part) 26 .
- a part of the outer surface of the sleeve 26 which is positioned higher than the male thread 26 a in FIG. 3 , is serrated.
- An inner hole having an inner surface corresponding to the sleeve 26 is formed in the valve plate 9 , and the inner surface of the inner hole is also serrated to correspond to the serration on the outer circumferential surface of the sleeve 6 .
- a cylindrical inner hole having a diameter greater than the maximum diameter of the sleeve 26 is formed in the valve body 10 .
- the movement of the sleeve 26 relative to the valve body 10 is not prevented in the circumferential direction and the axial direction.
- the movement of the sleeve 26 relative to the valve plate 9 is not prevented in the axial direction but is prevented in the circumferential direction.
- the valve plate 9 is rotated via the sleeve 26 relative to the valve body 10 and thereby functions as a supply valve and a return valve during the operations of the cryogenic refrigerator 21 .
- the inner circumferential surface of the sleeve 26 is also serrated, and the outer circumferential surface of the motor shaft 4 is serrated to correspond to the serration on the inner circumferential surface of the sleeve 6 . Accordingly, the movement of the sleeve 26 relative to the motor shaft 4 is not prevented in the axial direction but is prevented in the circumferential direction.
- the motor 5 is implemented by, for example, a three-phase AC synchronous motor, and is driven (rotated) in the forward and reverse directions by an inverter (not shown).
- an inverter not shown
- the motor shaft 4 rotates in the forward direction and as a result, the sleeve 26 drivably coupled to the motor shaft 4 is rotated in the forward direction.
- the displacer 23 is caused to move from the bottom dead point (upper position in FIG. 3 ) to the top dead point (lower position in FIG. 3 ) by a screw unit composed of the male thread 26 a and the female thread 23 a .
- the displacer 23 has a sufficient weight with respect to the circumferential frictional force of the screw unit so that the displacer 23 is not rotated by the rotation of the sleeve 26 in the circumferential direction relative to the cylinder 22 .
- a mechanism such as a key may be provided to more reliably prevent the rotation of the displacer 23 relative to the cylinder 22 .
- the downward movement of the sleeve 26 is absorbed by the relative movement between the sleeve 26 and the motor shaft 4 . Meanwhile, when the motor 5 is driven in the reverse direction, the displacer 23 is caused to move from the top dead point to the bottom dead point.
- Other operations of the cryogenic refrigerator 21 are substantially the same as those of the cryogenic refrigerator 1 of the first embodiment.
- the driving force of the motor 5 is converted into the reciprocating movement of the displacer 23 between the bottom dead point and the top dead point by the screw unit composed of the male thread 26 a and the female thread 23 a .
- the configuration of the second embodiment also makes it possible to eliminate the need to use a Scotch yoke mechanism or a ball screw mechanism.
- the configuration of the second embodiment makes it possible to orient the axis of the motor 5 in the vertical direction. This in turn makes it possible to prevent excessive thrust load on the motor shaft 4 of the motor 5 .
- the configuration of the second embodiment makes it possible to use a normal motor as the motor 5 and thereby makes it possible to reduce the costs of the cryogenic refrigerator 21 .
- the screw unit i.e., a movement conversion unit, is implemented by the male thread 26 a and the female thread 23 a that are disposed to overlap the displacer 23 in the axial direction, it is possible to reduce the size in the axial direction and the number of parts of the cryogenic refrigerator 21 compared with the related-art configuration.
- the number of stages of a cryogenic refrigerator is one.
- the present invention may also be applied to a cryogenic refrigerator having any number of stages.
- the screw unit may be provided only in the first stage.
- the cryogenic refrigerator 1 , 21 is a GM refrigerator.
- the present invention may be applied to any type of refrigerator including a displacer such as a Stirling refrigerator or a Solvay refrigerator. The above definitions of the top dead point and the bottom dead point may be interchanged with each other.
- An aspect of this disclosure provides a cryogenic refrigerator where neither a Scotch yoke mechanism nor a ball screw mechanism is used to cause a displacer to reciprocate, and thereby makes it possible to reduce the size, the number of parts, and the costs of the cryogenic refrigerator.
- a screw unit constituted by a part of a displacer is used to convert the driving force (rotational movement) of a driving unit into reciprocating movement of the displacer.
- This configuration makes it possible to use a normal motor as the driving unit and to reduce the size, the number of parts, and the costs of a cryogenic refrigerator.
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Abstract
A cryogenic refrigerator includes a cylinder; a displacer configured to reciprocate in the cylinder; a driving unit configured to drive a rotational shaft having an axial direction oriented in a direction of reciprocating movement of the displacer; and a movement conversion unit configured to convert rotational movement of the rotational shaft into the reciprocating movement of the displacer. The movement conversion unit is a screw unit including a male thread and a female thread one of which is a part of the displacer.
Description
- The present application is based upon and claims the benefit of priority of Japanese Patent Application No. 2012-039245 filed on Feb. 24, 2012, the entire contents of which are incorporated herein by reference.
- 1. Field of the Invention
- An aspect of this disclosure relates to a cryogenic refrigerator.
- 2. Description of the Related Art
- Japanese Laid-Open Patent Publication No. 3-84368, for example, discloses a cryogenic refrigerator where valves are opened and closed while causing a displacer to reciprocate in a cylinder. In this cryogenic refrigerator, “coldness” is generated by causing a refrigerant gas in an expansion space to expand via a clearance between the displacer and the cylinder, the “coldness” is transferred to a cooling stage on the periphery of the clearance and the expansion space by heat exchange, and as a result, an object is frozen.
- However, with the related-art configuration where a complex mechanism such as a Scotch yoke mechanism or a ball screw mechanism is used to reciprocate the displacer, the number of components and the outside dimensions of a cryogenic refrigerator tend to become large. Also, when a ball screw mechanism is used, it is necessary to use an axial gap motor or a motor with a hollow rotor and therefore the costs of a cryogenic refrigerator may increase.
- In an aspect of this disclosure, there is provided a cryogenic refrigerator that includes a cylinder; a displacer configured to reciprocate in the cylinder; a driving unit configured to drive a rotational shaft having an axial direction oriented in a direction of reciprocating movement of the displacer; and a movement conversion unit configured to convert rotational movement of the rotational shaft into the reciprocating movement of the displacer. The movement conversion unit is a screw unit including a male thread and a female thread one of which is a part of the displacer.
-
FIG. 1 is a schematic diagram illustrating an exemplary configuration of a cryogenic refrigerator according to a first embodiment; -
FIG. 2 is a schematic diagram illustrating an exemplary configuration of a live load packing of the cryogenic refrigerator of the first embodiment; and -
FIG. 3 is a schematic diagram illustrating an exemplary configuration of a cryogenic refrigerator according to a second embodiment. - Preferred embodiments of the present invention are described below with reference to the accompanying drawings.
- A cryogenic refrigerator 1 of a first embodiment may be implemented, for example, as a Gifford-McMahon (GM) refrigerator that uses a helium gas as the refrigerant gas. As illustrated in
FIG. 1 , the cryogenic refrigerator 1 includes acylinder 2, adisplacer 3, a motor shaft (rotational shaft) 4, a motor (driving unit) 5, asleeve 6, alive load packing 7, ahousing 8, avalve plate 9, avalve body 10, and agas path 11. - The
cylinder 2 is a closed-end cylinder that encloses thedisplacer 3. The upper end (inFIG. 1 ) of thecylinder 2 is hermetically closed by thehousing 8. Anexpansion space 12 is formed by thedisplacer 3 and thecylinder 2 in the lower part ofFIG. 1 . Although not illustrated inFIG. 1 , thecylinder 2 includes a cooling stage that is disposed adjacent to and surrounds theexpansion space 12. The displacer 3 faces the cooling stage across a clearance. The cooling stage may be composed of, for example, copper, aluminum, or stainless steel. - The
displacer 3 is housed in thecylinder 2 so as to be able to reciprocate in the longitudinal direction or the axial direction of themotor 5. For thecylinder 2, a material such as stainless steel may be used taking into account strength, thermal conductivity, and helium blocking capability. - The
motor 5 causes thedisplacer 3 to reciprocate and is disposed at a hot end of thecylinder 2 such that themotor shaft 4 is oriented in the axial direction of thedisplacer 3 and the cylinder 2 (or in the direction of the reciprocating movement of the displacer 3). The outer circumferential surface of thedisplacer 3 is shaped like a cylinder, and the displacer is filled with a cold storage medium. The internal volume of thedisplacer 3 constitutes a regenerator. An upper flow smoother for smoothing the flow of the helium gas is provided at the upper end of the regenerator, i.e., the end closer to the ambient temperature chamber, and a lower flow smoother is provided at the lower end of the regenerator. - An upper opening is formed at the hot end of the
displacer 3. The refrigerant gas flows from the ambient temperature chamber, which is located above thedisplacer 3 inFIG. 1 , through the upper opening into thedisplacer 3. The ambient temperature chamber is a space formed by thecylinder 2 and the hot end of thedisplacer 3, and the volume of the ambient temperature chamber changes as the displacer 3 reciprocates. - An intake and exhaust system implemented by a rotary valve composed of the
valve plate 9 and thevalve body 10 is provided in thehousing 8 that is disposed, in the axial direction, between themotor 5 and thecylinder 2. A high-pressure flexible pipe HF connected to the high-pressure side of a compressor (not shown) and a low-pressure flexible pipe LF connected to the low-pressure side of the compressor are connected to one end of the intake and exhaust system. Meanwhile, thegas path 11 implementing a supply and exhaust pipe and leading to the ambient temperature chamber is connected to the other end of the intake and exhaust system. Thelive load packing 7 is disposed between thecylinder 2 and a part of thedisplacer 3 near the hot end. - As illustrated in
FIG. 2 , thelive load packing 7 includes achevron packing 7 a (intermediate layer, triangle-shaped), upper andlower packings 7 b (sandwich layers), aground 7 c, andbolts 7 d. The chevron packing 7 a includes a pair of string- or fiber-like elements. The elements have a cross-section shaped like a right triangle and their sloping surfaces are in contact with each other. The elements contain a lubricant. - The upper and
lower packings 7 b sandwich the chevron packing 7 a in the axial direction. Thelower packing 7 b is disposed in a recess formed in thecylinder 2 adjacent to the hot end of amale thread 3 a of thedisplacer 3. Thechevron packing 7 a is disposed above thelower packing 7 b, theupper packing 7 b is disposed above thechevron packing 7 a, and theground 7 c is disposed above theupper packing 7 b as a spacer. - A wall part of the
housing 8 is disposed above theground 7 c. Female screw holes are formed through the wall part of the housing 8 c in the vertical direction inFIG. 2 . Thebolts 7 d are screwed into the female screw holes. The end of the male thread part (male thread end) of eachbolt 7 d is in contact with the upper surface of theground 7 c. When thebolts 7 d are screwed into the female screw holes and the male tread ends are moved downward, the force of the upper andlower packings 7 b sandwiching thechevron packing 7 a is increased. As a result, the sloping surfaces of the elements constituting thechevron packing 7 a are pressed with a stronger force, and the inner one of the elements is pressed with a stronger force against the outer circumferential surface of thedisplacer 3 and thereby seals thedisplacer 3 while supplying the lubricant. - A lower opening for introducing the refrigerant gas via the clearance into the
expansion space 12 is formed at a cold end of thedisplacer 3. Theexpansion space 12 is a space formed by thecylinder 2 and thedisplacer 3, and the volume of theexpansion space 12 changes as the displacer 3 reciprocates. The cooling stage is disposed on the outer circumferential surface of thecylinder 2 at a position corresponding to theexpansion space 12 and is thermally connected to an object to be cooled. The cooling stage is cooled by the refrigerant gas passing through the clearance. - For the
displacer 3, a material such as Bakelite (fabric-filled phenolic material) may be used taking into account specific gravity, abrasion resistance, strength, and thermal conductivity. As the cold storage medium, for example, a wire mesh may be used. Themale thread 3 a is formed on a part of the outer circumferential surface of thedisplacer 3 closer to the hot end, and afemale thread 2 a that engages themale thread 3 a is formed on the inner circumferential surface of thecylinder 2. A fitting hole is formed in the hot end surface of thedisplacer 3. Thesleeve 6 is shaped like a cylinder and is fitted into the fitting hole, and the movement of thesleeve 6 relative to thedisplacer 3 in the circumferential direction and the axial direction is thereby prevented. - The outer circumferential surface of the
sleeve 6 is, for example, serrated. An inner hole having an inner circumferential surface corresponding to thesleeve 6 is formed in thevalve plate 9, and the inner circumferential surface of the inner hole is also serrated to correspond to the serration on the outer circumferential surface of thesleeve 6. A cylindrical inner hole having a diameter greater than the maximum diameter of thesleeve 6 is formed in thevalve body 10. Thus, the movement of thesleeve 6 relative to thevalve body 10 is not prevented in the circumferential direction and the axial direction. Meanwhile, the movement of thesleeve 6 relative to thevalve plate 9 is not prevented in the axial direction but is prevented in the circumferential direction. In other words, when themotor 5 rotates in the forward direction or the reverse direction, thevalve plate 9 is rotated via thesleeve 6 relative to thevalve body 10 and thereby functions as a supply valve and a return valve during the operations of the cryogenic refrigerator 1. - The inner circumferential surface of the
sleeve 6 is also serrated, and the outer circumferential surface of themotor shaft 4 is serrated to correspond to the serration on the inner circumferential surface of thesleeve 6. Accordingly, the movement of thesleeve 6 relative to themotor shaft 4 is not prevented in the axial direction but is prevented in the circumferential direction. - The
motor 5 is implemented by, for example, a three-phase AC synchronous motor, and is driven (rotated) in the forward and reverse directions by an inverter (not shown). When themotor 5 is driven in the forward direction, themotor shaft 4 rotates in the forward direction and as a result, thesleeve 6 and thedisplacer 3 drivably coupled to themotor shaft 4 are rotated in the forward direction. When rotated in the forward direction, thedisplacer 3 is caused to move from the bottom dead point (upper position inFIG. 1 ) to the top dead point (lower position inFIG. 1 ) by a screw unit composed of themale thread 3 a and thefemale thread 2 a. In this case, downward movement of the sleeve is absorbed by the relative movement between thesleeve 6 and themotor shaft 4. Meanwhile, when themotor 5 is driven in the reverse direction, thedisplacer 3 is caused to move from the top dead point to the bottom dead point. - Next, exemplary operations of the cryogenic refrigerator 1 are described. At a timing in a refrigerant gas supplying step, the
displacer 3 is located at the top dead point (lower position inFIG. 1 ) in thecylinder 2. At the same timing or at a slightly different timing, the supply valve implemented by the rotary valve is opened. As a result, high-pressure helium gas is supplied via the supply valve through the gas path 11 (supply and exhaust pipe) into thecylinder 2. Then, the high-pressure helium gas flows through the upper opening at the upper end of thedisplacer 3 into the regenerator in thedisplacer 3. The high-pressure helium gas flowing into the regenerator is cooled by the cool storage medium, flows through the lower opening at the lower end of thedisplacer 3 and the clearance, and is supplied into theexpansion space 12. - When the
expansion space 12 is filled with the high-pressure helium gas, the supply valve is closed. At this timing, thedisplacer 3 is located at the bottom dead point (upper position inFIG. 1 ) in thecylinder 2. At the same timing or at a slightly different timing, the return valve implemented by the rotary valve is opened, the pressure of the helium gas in theexpansion space 12 is reduced and the helium gas expands. Due to the expansion, the helium gas in theexpansion space 12 is cooled and absorbs the heat of the cooling stage via the clearance. - Then, the
displacer 3 moves toward the top dead point (lower position inFIG. 1 ) and the volume of theexpansion space 12 decreases. As a result, the helium gas in theexpansion space 12 returns via the clearance, the lower opening, the regenerator, and the upper opening to the intake side of the compressor. When the helium gas (refrigerant gas) flows through the regenerator, the cold storage medium is cooled by the helium gas. The above process is referred to as a “cooling cycle”, and the cryogenic refrigerator 1 repeats the cooling cycle to cool the cooling stage. - In the cryogenic refrigerator 1 of the first embodiment, the driving force of the
motor 5 is converted into the reciprocating movement of thedisplacer 3 between the bottom dead point and the top dead point by the screw unit composed of themale thread 3 a and thefemale thread 2 a. Thus, the configuration of the first embodiment makes it possible to eliminate the need to use a Scotch yoke mechanism or a ball screw mechanism. Unlike a Scotch yoke mechanism, the configuration of the first embodiment makes it possible to orient the axis of themotor 5 in the vertical direction. This in turn makes it possible to prevent excessive thrust load on themotor shaft 4 of themotor 5. Also, unlike a ball screw mechanism, the configuration of the first embodiment makes it possible to use a normal motor as themotor 5 and thereby makes it possible to reduce the costs of the cryogenic refrigerator 1. Further, since the screw unit, i.e., a movement conversion unit, is implemented by themale thread 3 a and thefemale thread 2 a that are disposed to overlap thedisplacer 3 in the axial direction, it is possible to reduce the size in the axial direction and the number of parts of the cryogenic refrigerator 1 compared with the related-art configuration. - The screw unit is composed of the
male thread 3 a formed on the outer circumferential surface of thedisplacer 3 and thefemale thread 2 a formed on the inner circumferential surface of thecylinder 2, and therefore the screw movement is achieved by themale thread 3 a and thefemale thread 2 a that are in close contact with each other. This configuration makes it possible to reduce the leakage of helium gas flowing through the clearance from the hot side to the cold side. Also with this configuration, since even leaked helium gas flows helically, it is possible to increase the contact time of the helium gas with the outer circumferential surface of thedisplacer 3 and thereby increase the flow-path resistance in the clearance. In other words, this configuration makes it possible to reduce penetration of heat into the cooling stage due to the leakage of helium gas. - In the configuration of the first embodiment, the
displacer 3 rotates in the circumferential direction with respect to thecylinder 2. Even in this case, the live load packing 7 configured as described above can effectively seal the clearance that is a gap in the radial direction between thedisplacer 3 and thecylinder 2. Particularly, the live load packing 7 can increase the lubricity and reduce the frictional resistance of thedisplacer 3 that rotates in the circumferential direction with respect to thecylinder 2. Alternatively, the live load packing 7 may be replaced with an O-ring or a slipper seal. - In the first embodiment, the screw unit is formed at the outer side of the
displacer 3. Alternatively, the screw unit may be formed at the inner side of thedisplacer 3.FIG. 3 is a schematic diagram illustrating an exemplary configuration of acryogenic refrigerator 21 of a second embodiment. The same reference numbers are used for components corresponding to those in the first embodiment, and descriptions of those components are omitted. Here, differences between the first embodiment and the second embodiment are mainly described. - The
cryogenic refrigerator 21 of the second embodiment may also be implemented as a Gifford-McMahon (GM) refrigerator. As illustrated inFIG. 3 , thecryogenic refrigerator 21 includes acylinder 22, a displacer 23, a motor shaft (rotational shaft) 4, a motor (driving unit) 5, asleeve 6, aslipper seal 27, ahousing 8, avalve plate 9, avalve body 10, and agas path 11. - The
cylinder 22 is a closed-end cylinder that encloses the displacer 23. The upper end of thecylinder 22 is hermetically closed by thehousing 8. An expansion space is formed by the displacer 23 and thecylinder 22 in the lower part ofFIG. 3 . Although not illustrated inFIG. 3 , thecylinder 22 includes a cooling stage that is disposed adjacent to and surrounds the expansion space. The displacer 23 faces the cooling stage across a clearance. The cooling stage may be composed of, for example, copper, aluminum, or stainless steel. - The displacer 23 is housed in the
cylinder 22 so as to be able to reciprocate in the longitudinal direction or the axial direction of themotor 5. For thecylinder 22, a material such as stainless steel may be used taking into account strength, thermal conductivity, and helium blocking capability. - The
motor 5 causes the displacer 23 to reciprocate and is disposed at a hot end of thecylinder 22 such that themotor shaft 4 is oriented in the axial direction of the displacer 23 and thecylinder 22. The outer circumferential surface of the displacer 23 is shaped like a cylinder, and the displacer 23 is filled with a cold storage medium. The internal volume of the displacer 23 constitutes a regenerator. An upper flow smoother for smoothing the flow of the helium gas is provided at the upper end of the regenerator, i.e., the end closer to the ambient temperature chamber, and a lower flow smoother is provided at the lower end of the regenerator. - An upper opening is formed at the hot end of the displacer 23. The refrigerant gas flows from the ambient temperature chamber, which is located above the displacer 23 in
FIG. 3 , through the upper opening into the displacer 23. The ambient temperature chamber is a space formed by thecylinder 22 and the hot end of the displacer 23, and the volume of the ambient temperature chamber changes as the displacer 23 reciprocates. - In the
housing 8 disposed between themotor 5 and thecylinder 22 in the axial direction, a high-pressure flexible pipe HF connected to the high-pressure side of a compressor (not shown), a low-pressure flexible pipe LF connected to the low-pressure side of the compressor, and an intake and exhaust system implemented by a rotary valve composed of thevalve plate 9 and thevalve body 10 are provided. Thegas path 11 implementing a supply and exhaust pipe of the intake and exhaust system is connected to the ambient temperature chamber. - A lower opening for introducing the refrigerant gas via the clearance into the expansion space is formed at a cold end of the displacer 23. The expansion space is formed by the
cylinder 22 and the displacer 23, and the volume of the expansion space changes as the displacer 23 reciprocates. The cooling stage is disposed on the outer circumferential surface of thecylinder 22 at a position corresponding to theexpansion space 12 and is thermally connected to an object to be cooled. The cooling stage is cooled by the refrigerant gas passing through the clearance. - For the displacer 23, a material such as Bakelite (fabric-filled phenolic material) may be used taking into account specific gravity, abrasion resistance, strength, and thermal conductivity. As the cold storage medium, for example, a wire mesh may be used. An
upper cup 23 b shaped like a disk is provided at the hot end of the displacer 23. Theslipper seal 27 is disposed on the outer circumferential surface of the displacer 23 at a position closer than theupper cup 23 b to the cold end of the displacer 23. - In the center of a hot-end surface of the displacer 23, a hole (or recess) extending toward a cold-end surface of the displacer 23 is formed. A female thread 23 a is formed on the inner circumferential surface of the hole. A
male thread 26 a corresponding to the female thread 23 a is formed on the outer circumferential surface of a sleeve (cylindrical part) 26. - A part of the outer surface of the
sleeve 26, which is positioned higher than themale thread 26 a inFIG. 3 , is serrated. An inner hole having an inner surface corresponding to thesleeve 26 is formed in thevalve plate 9, and the inner surface of the inner hole is also serrated to correspond to the serration on the outer circumferential surface of thesleeve 6. A cylindrical inner hole having a diameter greater than the maximum diameter of thesleeve 26 is formed in thevalve body 10. - Thus, the movement of the
sleeve 26 relative to thevalve body 10 is not prevented in the circumferential direction and the axial direction. Meanwhile, the movement of thesleeve 26 relative to thevalve plate 9 is not prevented in the axial direction but is prevented in the circumferential direction. In other words, when themotor 5 rotates in the forward direction or the reverse direction, thevalve plate 9 is rotated via thesleeve 26 relative to thevalve body 10 and thereby functions as a supply valve and a return valve during the operations of thecryogenic refrigerator 21. - The inner circumferential surface of the
sleeve 26 is also serrated, and the outer circumferential surface of themotor shaft 4 is serrated to correspond to the serration on the inner circumferential surface of thesleeve 6. Accordingly, the movement of thesleeve 26 relative to themotor shaft 4 is not prevented in the axial direction but is prevented in the circumferential direction. - The
motor 5 is implemented by, for example, a three-phase AC synchronous motor, and is driven (rotated) in the forward and reverse directions by an inverter (not shown). When themotor 5 is driven in the forward direction, themotor shaft 4 rotates in the forward direction and as a result, thesleeve 26 drivably coupled to themotor shaft 4 is rotated in the forward direction. When thesleeve 26 is rotated in the forward direction, the displacer 23 is caused to move from the bottom dead point (upper position inFIG. 3 ) to the top dead point (lower position inFIG. 3 ) by a screw unit composed of themale thread 26 a and the female thread 23 a. Here, it is assumed that the displacer 23 has a sufficient weight with respect to the circumferential frictional force of the screw unit so that the displacer 23 is not rotated by the rotation of thesleeve 26 in the circumferential direction relative to thecylinder 22. Also, a mechanism such as a key may be provided to more reliably prevent the rotation of the displacer 23 relative to thecylinder 22. - The downward movement of the
sleeve 26 is absorbed by the relative movement between thesleeve 26 and themotor shaft 4. Meanwhile, when themotor 5 is driven in the reverse direction, the displacer 23 is caused to move from the top dead point to the bottom dead point. Other operations of thecryogenic refrigerator 21 are substantially the same as those of the cryogenic refrigerator 1 of the first embodiment. - In the
cryogenic refrigerator 21 of the second embodiment, the driving force of themotor 5 is converted into the reciprocating movement of the displacer 23 between the bottom dead point and the top dead point by the screw unit composed of themale thread 26 a and the female thread 23 a. Thus, the configuration of the second embodiment also makes it possible to eliminate the need to use a Scotch yoke mechanism or a ball screw mechanism. Unlike a Scotch yoke mechanism, the configuration of the second embodiment makes it possible to orient the axis of themotor 5 in the vertical direction. This in turn makes it possible to prevent excessive thrust load on themotor shaft 4 of themotor 5. Also, unlike a ball screw mechanism, the configuration of the second embodiment makes it possible to use a normal motor as themotor 5 and thereby makes it possible to reduce the costs of thecryogenic refrigerator 21. Further, since the screw unit, i.e., a movement conversion unit, is implemented by themale thread 26 a and the female thread 23 a that are disposed to overlap the displacer 23 in the axial direction, it is possible to reduce the size in the axial direction and the number of parts of thecryogenic refrigerator 21 compared with the related-art configuration. - The present invention is not limited to the specifically disclosed embodiments, and variations and modifications may be made without departing from the scope of the present invention.
- For example, in the above embodiments, it is assumed that the number of stages of a cryogenic refrigerator is one. However, the present invention may also be applied to a cryogenic refrigerator having any number of stages. When a cryogenic refrigerator includes two or more stages, the screw unit may be provided only in the first stage. Also in the above embodiments, it is assumed that the
cryogenic refrigerator 1, 21 is a GM refrigerator. However, the present invention may be applied to any type of refrigerator including a displacer such as a Stirling refrigerator or a Solvay refrigerator. The above definitions of the top dead point and the bottom dead point may be interchanged with each other. - An aspect of this disclosure provides a cryogenic refrigerator where neither a Scotch yoke mechanism nor a ball screw mechanism is used to cause a displacer to reciprocate, and thereby makes it possible to reduce the size, the number of parts, and the costs of the cryogenic refrigerator.
- According to an aspect of this disclosure, a screw unit constituted by a part of a displacer is used to convert the driving force (rotational movement) of a driving unit into reciprocating movement of the displacer. This configuration makes it possible to use a normal motor as the driving unit and to reduce the size, the number of parts, and the costs of a cryogenic refrigerator.
Claims (6)
1. A cryogenic refrigerator, comprising:
a cylinder;
a displacer configured to reciprocate in the cylinder;
a driving unit configured to drive a rotational shaft having an axial direction oriented in a direction of reciprocating movement of the displacer; and
a movement conversion unit configured to convert rotational movement of the rotational shaft into the reciprocating movement of the displacer,
wherein the movement conversion unit is a screw unit including a male thread and a female thread one of which is a part of the displacer.
2. The cryogenic refrigerator as claimed in claim 1 , wherein the male thread is formed on an outer circumferential surface of the displacer and the female thread is formed on an inner circumferential surface of the cylinder.
3. The cryogenic refrigerator as claimed in claim 1 , wherein the female thread is formed on an inner circumferential surface of a hole extending from a hot-end surface toward a cold-end surface of the displacer.
4. The cryogenic refrigerator as claimed in claim 3 , further comprising:
a cylindrical part that is drivably coupled to the rotational shaft such that the cylindrical part is movable in the axial direction relative to the rotational shaft,
wherein the male thread is formed on an outer circumferential surface of the cylindrical part.
5. The cryogenic refrigerator as claimed in claim 2 , further comprising:
a seal disposed in a clearance formed between the displacer and the cylinder,
wherein the seal includes an intermediate layer containing a lubricant and sandwich layers sandwiching the intermediate layer in the axial direction.
6. The cryogenic refrigerator as claimed in claim 1 , further comprising:
a rotary valve configured to control intake and exhaust of gas into and from an expansion space formed by the cylinder and the displacer,
wherein the driving unit is configured to drive the rotary valve.
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP2012039245A JP2013174394A (en) | 2012-02-24 | 2012-02-24 | Ultra-low temperature freezer |
JP2012-039245 | 2012-02-24 |
Publications (1)
Publication Number | Publication Date |
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US20130220112A1 true US20130220112A1 (en) | 2013-08-29 |
Family
ID=49001424
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
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US13/755,269 Abandoned US20130220112A1 (en) | 2012-02-24 | 2013-01-31 | Cryogenic refrigerator |
Country Status (3)
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US (1) | US20130220112A1 (en) |
JP (1) | JP2013174394A (en) |
CN (1) | CN103292507A (en) |
Families Citing this family (1)
Publication number | Priority date | Publication date | Assignee | Title |
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CN109185093B (en) * | 2018-10-30 | 2024-02-20 | 郑州黄河众工机电科技有限公司 | Plunger pump and combined pump |
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US4180984A (en) * | 1977-12-30 | 1980-01-01 | Helix Technology Corporation | Cryogenic apparatus having means to coordinate displacer motion with fluid control means regardless of the direction of rotation of the drive shaft |
JPS60169657A (en) * | 1984-02-14 | 1985-09-03 | Toshiba Corp | Sealing mechanism |
JPH0384368A (en) * | 1989-08-25 | 1991-04-09 | Toshiba Corp | Refrigerator |
JPH08159583A (en) * | 1994-12-07 | 1996-06-21 | Daikin Ind Ltd | Cryogenic refrigerator |
JPH08284750A (en) * | 1995-04-07 | 1996-10-29 | Yoshihiko Haramura | Stirling engine having optional waveform driving displacer |
JP3588644B2 (en) * | 2000-03-07 | 2004-11-17 | 住友重機械工業株式会社 | Regenerator refrigerator |
JP2003028526A (en) * | 2001-05-09 | 2003-01-29 | Sumitomo Heavy Ind Ltd | Cool storage unit and refrigerating machine |
JP3851929B2 (en) * | 2002-04-17 | 2006-11-29 | 岩谷瓦斯株式会社 | Cryogenic refrigerator |
JP2008169910A (en) * | 2007-01-11 | 2008-07-24 | Fuji Koki Corp | Motor-operated valve |
JP2010216711A (en) * | 2009-03-16 | 2010-09-30 | Sumitomo Heavy Ind Ltd | Cold storage device type refrigerator |
-
2012
- 2012-02-24 JP JP2012039245A patent/JP2013174394A/en active Pending
-
2013
- 2013-01-31 US US13/755,269 patent/US20130220112A1/en not_active Abandoned
- 2013-02-25 CN CN2013100594274A patent/CN103292507A/en active Pending
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US2083009A (en) * | 1934-03-12 | 1937-06-08 | Hart E Delvin | Pump |
US2389918A (en) * | 1939-07-21 | 1945-11-27 | Barr & Stroud Ltd | Reciprocating pump |
US2471596A (en) * | 1945-04-04 | 1949-05-31 | John C Williams | Pump |
US5062547A (en) * | 1989-05-26 | 1991-11-05 | Metrohm Ag | Volume measurement and dosage device |
US6568923B2 (en) * | 2000-12-21 | 2003-05-27 | Kazumasa Ikuta | Fluid suction and discharge apparatus |
US7293967B2 (en) * | 2002-10-22 | 2007-11-13 | Smc Kabushiki Kaisha | Pump apparatus |
US7537437B2 (en) * | 2004-11-30 | 2009-05-26 | Nidec Sankyo Corporation | Linear actuator, and valve device and pump device using the same |
Also Published As
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JP2013174394A (en) | 2013-09-05 |
CN103292507A (en) | 2013-09-11 |
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