PISTON-FORMAT WORKING-FLUID-PRESSURE ACTUATOR AND CONTROL VALVE

[Problem] To provide a piston-format working-fluid-pressure actuator capable of commonly using components when the piston-format working-fluid-pressure actuator is used for a reverse action or a normal action and decreasing a length dimension, in the forward/backward movement direction of the output shaft and to provide a control valve using the piston-format working-fluid-pressure actuator and a valve member. [Solution] A piston-format working-fluid-pressure actuator (10) includes a casing (30) provided with a cylinder chamber (33) by including a cover portion (31) and a body portion (32), an output shaft (40) supported by the casing so as to be movable forward or backward, a piston (50) attached to the output shaft and defining the cylinder chamber, a spring member (60) applying an elastic force of moving the output shaft to the piston, and a working-fluid supply opening (70) supplying a working fluid. The piston includes an accommodating recess (51) accommodating the spring member and is attachable to the output shaft so that an opening (52) of the accommodating recess is selectively directed toward the cover portion or the body portion.

The present invention relates to a piston-format working-fluid-pressure actuator and a control valve using the piston-format working-fluid-pressure actuator and a valve member.

BACKGROUND ART

Various control valves are disposed in the course of a pipe through which a gas or a liquid flows in order to adjust a pressure or a flow rate. The control valve includes a piston-format working-fluid-pressure actuator which is operated by a fluid pressure of a working fluid such as air or oil and a valve member that includes a valve body opening or closing a flow channel. An output shaft of the piston-format working-fluid-pressure actuator is connected to the valve body of the valve member. As the action type of the piston-format, working-fluid-pressure actuator, a backward action type only using a working fluid pressure or a reverse or normal action type using an elastic force of a spring is known. The “reverse action type” is a type that opens the valve body by moving the output shaft up through the supply of the working fluid pressure, and the “normal action type” is a type that closes the valve body by moving the output shaft down through the supply of the working fluid pressure.

The piston-format working-fluid-pressure actuator includes a casing which is provided with a cylinder chamber by including a cover portion and a body portion and an output shaft which is supported by the casing so as to be movable forward or backward. A piston which defines the cylinder chamber into two compartments is attached to the output shaft. In the piston-format working-fluid-pressure actuator for the reverse action or the normal action, a spring member such as a compression coil spring is disposed between the piston and the casing so as to apply an elastic force of moving the output shaft to the piston. Further, in order to apply a force of moving the output shaft to the piston against the elastic force applied from the spring member, the casing is provided with a working-fluid supply opening which supplies the working fluid into the cylinder chamber.

In order to commonly use the casing regardless of the different action type of the piston-format working-fluid-pressure actuator, each of the cover portion and the body portion of the casing is provided with a recess having a hole shape or a groove shape accommodating the spring member. Then, in the case of the casing in which the cover portion is provided in the upper portion of the body portion, the spring member is accommodated in the recess of the body portion during the normal action, and the spring member is accommodated in the recess of the cover portion during the reverse action (see Patent Literature 1).

CITATION LIST

Patent Literatures

Patent Literature 1: JP 2006-329333 A

SUMMARY OP INVENTION

Technical Problem

However, since each of the cover portion and the body portion is provided with the recess accommodating the spring member, the length dimension (hereinafter, referred to as the “height dimension”) in the forward/backward movement direction of the output shaft increases in the piston-format working-fluid-pressure actuator. For example, when the spring member is accommodated in the recess of the cover portion in order to change the action type of the piston-format working-fluid-pressure actuator to the reverse action type, the height dimension of the piston-format working-fluid-pressure actuator increases by the depth dimension of the recess of the body portion.

The invention is made in view of the above-described circumstances, and an object thereof is to provide a piston-format working-fluid-pressure actuator capable of commonly using components when the piston-format working-fluid-pressure actuator is used for a reverse action or a normal action and decreasing a length dimension in the forward/backward movement direction of the output shaft and to provide a control valve using the piston-format working-fluid-pressure actuator and a valve member.

Means for Solving Problem

The above-described object is attained by the following means.

(1) A piston-format working-fluid-pressure actuator including: a casing provided with a cylinder chamber by including first and second casing bodies; an output shaft supported by the casing so as to be movable forward or backward; a piston attached to the output shaft and defining the cylinder chamber; a spring member applying an elastic force of moving the output shaft to the piston; a working-fluid supply opening supplying a working fluid applying a force of moving the output shaft to the piston against the elastic force applied from the spring member; and at least one seal, member sealing the leakage of the working fluid, wherein the piston includes an accommodating recess accommodating the spring member and is attachable to the output shaft so that an opening of the accommodating recess is selectively directed toward the first casing body or the second casing body, wherein the output shaft extends so as to penetrate one casing body of the first casing body and the second casing body and is connected to a subject operation member, and wherein the piston is disposed so as to establish a relation of L1=L2when the distance L1is a distance between a seating surface connected to the output shaft and a contact surface contacting one casing body during a reverse action and the distance L2is a distance between a seating surface connected, to the output shaft and a contact surface contacting one casing body during a normal action.

(2) A control valve including: the piston-format working-fluid-pressure actuator of (1); and a valve member including a valve body opening or closing a flow channel, wherein the output shaft of the piston-format working-fluid-pressure actuator is connected to the valve body of the valve member, and wherein when the piston is attached to the output shaft so that the opening of the accommodating recess is selectively directed toward the first casing body or the second casing body, the valve member is operated as a reverse acting valve in which the valve body is opened by the working fluid supplied from the working-fluid supply opening or a normal acting valve in which the valve body is closed by the working fluid supplied from the working-fluid supply opening.

Advantageous Effect of the Invention

According to the invention, since the piston includes the accommodating recess accommodating the spring member and is attachable to the output shaft so that the opening of the accommodating recess is selectively directed toward the cover portion or the body portion, it is possible to commonly use the components (at least the casing, the output shaft, and the piston) when the piston-format working-fluid-pressure actuator is used for the reverse action or the normal action. Further, since the accommodation space for the spring member disposed for the reverse action and the accommodation space for the spring member disposed for the normal action may be commonly used, it is possible to decrease the length dimension (the height dimension) of the piston-format working-fluid-pressure actuator in the forward/backward movement direction of the output, shaft compared to the case where each of the cover portion and the body portion is provided with the recess accommodating the spring member. Accordingly, it is possible to provide the piston-format working-fluid-pressure, actuator capable of commonly using the components when the piston-format working-fluid-pressure actuator is used for the reverse action or the normal action and decreasing the length dimension (the height dimension) in the forward/backward movement direction of the output shaft. Since the piston is disposed so chat the equation of the distance L1=the distance L2is established, the output shaft may be used for both the reverse action and the normal action.

Further, the control valve is configured by connecting the output shaft of the piston-format working-fluid-pressure actuator to the valve body of the valve member. Since the piston is attached to the output shaft so that the opening of the accommodating recess is selectively directed coward the cover portion or the body portion, the valve member may be operated as the reverse acting valve in which the valve body is opened by the air supplied from the working-fluid supply opening or the normal acting valve in which the valve body is closed by the air supplied, from the working-fluid supply opening. Accordingly, it is possible to decrease the size of the control valve by decreasing tine size of the piston-format working-fluid-pressure actuator.

Further, the backward acting valve which is opened or closed by the air supplied from the working-fluid supply opening may be provided by separating, the spring member from the reverse acting valve or the normal acting valve.

DESCRIPTION OF EMBODIMENTS

Hereinafter, an embodiment of the invention will be described. Furthermore, the description in this section does not limit the technical scopes or the meanings of the terms of claims.

Embodiment

FIGS. 1 and 2are cross-sectional views illustrating the configuration of a control valve100including a piston-format working-fluid-pressure actuator10and a valve member20according to an embodiment, and are views illustrating a case where the valve member20is operated as a reverse acting valve.FIG. 1illustrates a state (a state where a valve body22is opened) where a working fluid is supplied to the piston-format working-fluid-pressure actuator10, andFIG. 2illustrates a state (a state where the valve body22is closed) where the working fluid is not supplied to the piston-format working-fluid-pressure actuator10. Further,FIGS. 3 and 4are views illustrating a case where the valve member20is operated as a normal acting-valve,FIG. 3illustrates a state (a state where the valve body22is closed) where the working fluid is supplied to the piston-format working-fluid-pressure actuator10, andFIG. 4illustrates a state (a state where the valve body22is opened) where the working fluid is not supplied to the piston-format working-fluid-pressure actuator10.FIG. 5is a top view illustrating a piston50.

Referring toFIGS. 1 to 4, the control valve100includes the piston-format working-fluid-pressure actuator10which is operated by a working fluid pressure of a working fluid such as air or oil and the valve member20which includes the valve body22opening or closing a flow channel21. An output shaft40of the piston-format working-fluid-pressure actuator10is connected to the valve body22of the valve member20.

Specifically, the piston-format working-fluid-pressure actuator10includes a casing30which is provided with, a cylinder chamber33by including a cover portion31(corresponding to a first casing body) and a body portion32(corresponding to a second casing body), the output shaft40which is supported by the casing30so as to be movable forward or backward, the piston50which is attached to the output shaft40so as to define the inside of the cylinder chamber33into two compartments, a spring member60which applies art elastic force of moving the output shaft40to the piston50, a working-fluid supply opening70which supplies a working fluid applying a force of moving the output shaft40against the elastic force applied from the spring member60to the piston50, and seal members37,38,45,46, and57which seals the leakage of the working fluid. The piston50includes an accommodating recess51which accommodates the spring member60and is attachable to the output shaft40by selectively directing an opening52of the accommodating recess51toward the cover portion31or the body portion32. In the control valve100, the piston is attached to the output shaft40by selectively directing the opening52of the accommodating recess51toward the cover portion31or the body portion32. Accordingly, the valve member20is operated as a reverse acting valve in which the valve body22is opened by the working fluid supplied from a second port72of the working-fluid supply opening70or a normal acting valve in which the valve body22is closed by the working fluid supplied from a first port71of the working-fluid supply opening70. In the embodiment, compressed air is used, as the working fluid. Hereinafter, this configuration will be described in detail.

The casing30includes the body portion32which is provided with a recessed position, and the cover portion31which is provided, at the upper portion of the body portion32. The cylinder chamber33is formed by covering the upper opening of the body portion32by the cover portion31. The external shape of the casing30substantially has a cylindrical shape. Center holes34and39penetrate the center portion of the casing30. The seal member37such as an O-ring which seals the leakage of air from the cylinder chamber33is provided in a portion contacting the cover portion31.

The output shaft40is supported inside the center holes34and39of the casing30so as to be movable forward or backward. The seal member45such as an O-ring which seals the leakage of air from the cylinder chamber33is provided between the output shaft40and the body portion32. The seal member38such as an O-ring which seals the leakage of air from the cylinder chamber33is provided between the output shaft40and, the cover portion31. In the embodiment, the O-ring groove is provided in each of the body portion32and the cover portion31, but may be provided in the output shaft40. The output shaft40includes a small-diameter portion41and a large-diameter portion42, and a stepped portion43is provided between the small-diameter portion41and the large-diameter portion42. The piston50is supported by the stepped portion43. A male screw is formed in the outer peripheral surface of the small-diameter portion41, and a nut44is threaded thereinto.

An attachment hole53penetrates the center portion of the piston50. The piston50is supported by the stepped portion43of the output shaft40by inserting the output shaft40through the attachment hole53. The piston50and the output shaft40are connected to each other by threading the nut44into the male screw of the small-diameter portion41. The nut44corresponds to a connection member that connects the piston50and the output shaft40to each other. The cylinder chamber33is divided into two compartments, that is, a first chamber35which is illustrated at the upper side of the drawing in relation to the piston50and a second chamber36which is illustrated at the lower side of the drawing in relation to the piston50. The seal member46such as an O-ring which seals the leakage of air between the first, chamber35and the second chamber36is provided between the output shaft40and the piston50. In the embodiment, the O-ring groove is provided in the output shaft40, but may be provide in the piston50.

The external shape of the piston50substantially has a cylindrical shape. The piston50includes a plurality of the accommodating recesses51which accommodate the spring member60. Each accommodating recess51has a bottomed circular hole shape. Referring toFIG. 5, six accommodating recesses51are formed at the equal interval in the circumferential direction of the piston50illustrated, in the drawing. The piston may be attached to the output shaft40by selectively directing the opening52of the accommodating recess51toward, the cover portion31or the body portion32in a manner such that the front and rear surfaces of the piston50are inverted and the output shaft40is inserted through the attachment hole53.FIGS. 1 and 2illustrate a state where the piston is attached to the output shaft40by directing the opening52of the accommodating recess51toward the cover portion31, andFIGS. 3 and 4illustrate a state where the piston is attached to the output shaft40by directing the opening52of the accommodating recess51toward the body portion32.

Referring toFIG. 2, the depth H1of the accommodating recess51is set to a depth equal to or larger than 50% and equal to or smaller than 70% with respect to the height H2of the spring which is assembled as the piston-format working-fluid-pressure actuator10and is set when air is not supplied thereto. When the depth is equal to or larger than 50%, the buckling or the bending of compression coil springs61may be prevented, by inserting a compression coil spring61into the accommodating recess51of the piston50, and hence a stable thrust force may be obtained. Further, the interference between the adjacent compression coil springs61may be prevented and abnormal noise is suppressed. Accordingly, a compact actuator may be provided. Further, when the depth is equal or smaller than 70%, the operation length necessary for opening or closing the valve may be easily obtained.

A center plate54which is provided with, the attachment hole53and to which the output shaft40is connected is substantially disposed at the central position of the piston50in the height direction. The nut44which serves as a connection means, that is, a means for connecting the output shaft40to the center plate54does not protrude toward one side of the piston50in the height direction, and hence the size of the piston50in the height direction may be decreased.

The output shaft40extends so as to penetrate one casing body among the first casing body and the second casing body, that is, the body portion32, and is connected to a subject operation member, that is, the valve body22. The piston50is disposed so that the relation of L1=L2is established when the distance L1(seeFIG. 1) is a distance between a contact surface501of the piston50contacting the body portion32and a seating surface551of a depressed portion55connecting the piston50to the output shaft40by the nut44during the reverse action and the distance L2(seeFIG. 4) is a distance between a contact surface502of the piston50contacting the body portion32and a seating surface552connecting the piston50to the output shaft40by the nut44during the normal action. Accordingly, the output shaft40may be used in both the reverse action and the normal action.

The center plate54is substantially disposed at the central position of the piston50in the height direction, and is disposed so as to establish the relation of L1=L2, thereby further compactly designing the size in the height direction.

The diameter of the center plate54is larger than that of the nut44. The depth from the end of the accommodating recess51in the height direction to the center plate54is larger than the height of the nut44. Thus, the piston50is provided with the depressed portion55which accommodates the nut44as a connection member.

In the embodiment, the nut44is used, as the connection member. However, as the connect ion member, a O type snap ring, an E-type snap ring, a parallel pin, a taper pin, a grooved spring pin, a split pin, or the like may be employed as long as the piston50and the output shaft40may be fixed to each other by the connection member. That is, the connection member is appropriately designed by a necessary thrust force, the number of operation times, and the like.

The spring member60is formed as, for example, a compression coil spring. Referring toFIGS. 1 and 2, the spring member60which, is disposed, in the first chamber35applies an elastic force of moving the output shaft40in the downward direction of the drawing to the piston50, Further, referring toFIGS. 3 and 4, the spring member60which is disposed in the second chamber36applies an elastic force of moving the output shaft40in the upward direction of the drawing to the piston50.

The working-fluid supply opening70includes the first port71which communicates with the first chamber35and the second port72which communicates with the second chamber36. When air is supplied to the second chamber36by connecting the second port72to a working fluid supply source, a force of moving the output shaft40in the upward direction of the drawing is applied to the piston50against the elastic force applied by the spring member60(seeFIG. 1). When air is supplied to the first chamber35by connecting the first port71to a working fluid supply source, a force of moving the output shaft40in the downward direction, of the drawing is applied to the piston50against the elastic force applied by the spring member60(seeFIG. 3).

A ring groove56is formed in the outer peripheral surface of the piston50. A seal member that seals the leakage of air is attached to the ring groove56. The seal member is, for example, the O-ring57. Furthermore, the ring groove may be formed in the inner surface of the cylinder chamber33, and the seal member may be attached to the ring groove. A plurality of seal members may be disposed if necessary.

The piston50includes a rib59. The rib59is provided as a pair of ribs, and is provided at two separated positions in both ends in the height direction. The O-ring57such as a seal member that seals the leakage of air is attached between the pair of ribs59. The dimension of the rib59protruding from the outer peripheral surface of the piston50is set to a dimension smaller than the dimension when the O-ring57is attached thereto. Since the ribs59are respectively provided at both ends in the height direction so as to be separated from each other, it is possible to suppress the piston50from partially contacting the inner surface of the cylinder chamber33when the piston, slides on the inner surface of the cylinder chamber33. As the shape of the rib, a semi-circular shape, a trapezoid shape, a triangular shape, or the like which protrudes in the cylinder direction may be exemplified.

Even when the seal member is disposed at two separate positions of the outer peripheral surface of the piston50, the partial contact of the piston50may be suppressed. In order to prevent the partial, contact, any one of or both the seal member and the rib59may be appropriately provided depending on the required specifications or the like (seeFIG. 6).

The piston50serves as a stopper which limits the movement of the output shaft40while contacting the inner surface of the cover portion31or the body portion32. When the valve member20is operated as the reverse acting valve, the surface (the front surface of the piston50) near the opening52of the accommodating recess51contacts the cover portion31so as to limit the movement of the output shaft40in the upward direction of the drawing (seeFIG. 1), and the bottom side surface (the rear surface of the piston50) of the accommodating recess51contacts the body portion32so as to limit the movement of the output shaft40in the downward direction of the drawing (seeFIG. 2). When the valve member20is operated as the normal acting valve, the front surface of the piston50contacts the body portion32so as to limit the movement of the output shaft40in the downward, direction of the drawing (seeFIG. 3), and the rear surface of the piston50contacts the cover portion31so as to limit the movement of the output shaft40in the upward direction of the drawing (seeFIG. 4). Since the upward or downward movement is limited, an excessive force is not applied to the valve body22, and hence the product lifetime of the valve body22may be increased. Then, since the contact surfaces501and502as the end. surfaces of the piston50widely come into plane-contact with the cover portion31or the body portion32, the concentration of stress is suppressed. Accordingly, a material may be decreased in thickness or a synthetic resin or the like may be used. Further, a useless space is not provided in the cover portion31or the body portion32, and hence a compact actuator may be provided.

In the piston50, a portion which contacts the cover-portion31or the body portion32is formed as a rounded portion58having a round shape. In the embodiment, the portion contacting the cover portion31or the body portion32in the piston50is formed in a round shape, but may be chamfered, When, the piston serves as the stopper, it is possible to alleviate, a state where the stress acting on the piston50is intensively applied to the edge, and hence to improve the durability of the piston50.

An elastic force which is applied from the spring member60to the piston50when the opening52of the accommodating recess51is directed toward, the cover portion31is different from an elastic force which is applied from the spring member60to the piston50when the opening52of the accommodating recess51is directed toward the body portion32. This is because an elastic force suitable for the action type of the piston-format working-fluid-pressure actuator10is applied. When the valve member20is operated as the reverse acting valve, the valve body22is closed by the elastic force of the spring member60(seeFIG. 2). Compared to the case where the valve member20is operated as the normal acting valve, the spring member60of the piston-format working-fluid-pressure actuator10requires a large elastic force.

The elastic force which is applied from the spring member60to the piston50may be appropriately adjusted by increasing the number of types of the spring members (having different materials, diameters, and the like). However, the embodiment has the following configuration so as to commonly use the spring member60.

The spring member60includes the same compression coil springs61. Then, the number of the compression coil springs61disposed when the opening52of the accommodating recess51is directed toward the cover port ion31is set to be different from the number of the compression, coil springs61disposed when the opening52of the accommodating recess51is directed toward the body portion32. Specifically, when the valve member20is operated as the reverse acting valve, the number of the compression coil springs61is set to, for example, six. When the valve member20is operated as the normal acting valve, the number of the compression coil springs61is set to, for example, three. Since the number of the disposed spring members60is set so as to be suitable for the action type of the piston-format working-fluid-pressure actuator10, the spring members60may be commonly used, and hence cost may be decreased. In the embodiment, although the number of springs is defined , the diameter, the coil average diameter, the free height, and the spring material of the spring or various combinations of the spring factors are appropriately designed depending on a necessary thrust force, cost, or the like.

Next, the action will be described.

Referring toFIGS. 1 and 2, the piston50is attached to the output shaft40so that the opening52of the accommodating recess51is directed toward the cover portion31when the valve member20is operated as the reverse acting valve. The piston50is supported by the stepped portion43of the output shaft40. The piston50and the output shaft40are connected to each other by threading the nut44into the male screw of the small-diameter portion41. The compression coil springs51are respectively disposed in the six accommodating recesses51. The number of the disposed compression coil springs61is six. The piston50is disposed in the recessed position of the body portion32, and the cover portion31is attached to the upper portion of the body portion32. The spring member60which is disposed in the first chamber35applies an elastic force of moving the output shaft40in the downward direction of the drawing to the piston50. Te second port72of the working-fluid supply opening70is connected to the working fluid supply source.

Referring toFIGS. 1 and 2, in the piston50to which the elastic force of the spring member60(six compression coil springs61) is applied, the rear surface as the contact surface501contacts the body portion32until air is supplied to the second chamber36. Accordingly, the movement of the output shaft40in the downward direction of the drawing is limited. The valve body22of the valve member20closes the flow channel21while receiving the elastic force of the spring member60.

Referring toFIG. 1, when air is supplied from she second port72to the second chamber36, a force of moving the output shaft40in the upward direction of the drawing is applied to the piston50against the elastic force applied from the spring member60. The front surface of the piston50contacts the cover portion31. Accordingly, the movement of the output shaft40in the upward direction of the drawing is limited. The valve body22of the valve member20opens the flow channel21.

Referring toFIGS. 3 and 4, when the valve member20is operated as the normal acting valve, the piston50is attached to the output shaft40so that the opening52of the accommodating recess51is directed toward the body portion32. The piston50is supported by the stepped portion43of the output shaft40. The piston50and the output shaft40are connected to each other by threading the nut44into the male screw of the small-diameter portion41. The compression coil spring61is disposed at every other accommodating recess among the six accommodating recesses51. The number of the disposed compression coil springs61is three. The piston50is disposed in the recessed position of the body portion32, and the cover portion31is attached to the upper portion of the body portion32. The spring member60which is disposed in the second chamber36applies an elastic force of moving the output shaft40in the upward direction of the drawing to the piston50. The first port71of the working-fluid supply opening70is connected to the working fluid supply source.

Referring toFIG. 4, in the piston50to which the elastic force of the spring member60(three compression coil springs61) is applied, the rear surface thereof contacts the cover portion31until air is supplied to the first chamber35. Accordingly, the movement of the output shaft40in the upward direction of the drawing is limited. The valve body22of the valve member20opens the flow channel21while receiving the elastic force of the spring member60.

Referring toFIG. 3, when air is supplied from the first port71to the first chamber35, a force of moving the output shaft40in the downward direction of the drawing is applied to the piston50against the elastic force applied from the spring member60. In the piston50, the front surface as the contact surface502contacts the body portion32. Accordingly, the movement of the output shaft40in the downward direction of the drawing is limited. The valve body22of the valve member20closes the flow channel21.

As described above, in the piston-format working-fluid-pressure actuator10of the embodiment, the piston50includes the accommodating recess51accommodating the spring member60, and is attachable to the output shaft40so that the opening52of the accommodating recess51is selectively directed toward the cover portion31or the body portion32. For this reason, in the case of the piston-format working-fluid-pressure actuator10used for the reverse action or the normal action, the components (at least the casing30, the output shaft40, and the piston50) may be commonly used. Further, the accommodation space of the spring member60disposed for the reverse action and she accommodation space of the spring member60disposed for the normal action may be commonly used. For this reason, the height dimension of the piston-format working-fluid-pressure actuator10may be decreased compared to the case where a recess for accommodating the spring member is provided in each of the body portion32and the cover portion31. Accordingly, in the case of the piston-format working-fluid-pressure actuator10used for the reverse action or the normal, action, the components may be commonly used, and hence the piston-format working-fluid-pressure actuator10capable of decreasing the height dimension thereof may be provided. Since the O-rings37,38,45,46, and57as the seal members are provided, so as to seal the leakage of air, the piston50may be reliably operated by supplying air thereto.

Further, the piston-format working-fluid-pressure actuator10further includes the nut44as the connection member connecting the piston50and the output shaft40to each other, and the piston50includes the depressed portion55accommodating the nut44. Since the nut44does not protrude from the piston50, there is no need to provide a depressed portion in the cover portion31or the body portion32so as to prevent the contact with respect to the nut44, and hence the casing30may be easily processed.

Further, an elastic force which is applied from the spring member60to the piston50when the opening52of the accommodating recess51is directed toward the cover portion31is set to be different from an elastic force which is applied from the spring member60to the piston50when the opening52of the accommodating recess51is directed toward the body-portion32. For this reason, it is possible to apply an elastic force suitable for the action type of the piston-format working-fluid-pressure actuator10.

Here, the spring member60includes the same type of compression coil springs61, and the number of the compression coil springs61disposed when the opening52of the accommodating recess51is directed toward the cover portion31is set to be different from the number of the compression coil springs61disposed, when the opening52of the accommodating recess51is directed toward the body portion32. Thus, the spring members60may be commonly used, and hence cost may be further decreased, Further, specifications such as a diameter, a coil average diameter, a free height, and a spring material may be changed at any time depending on a necessary thrust force, cost, or the like. Further, various combinations may be employed in order to get a balance of the spring factors.

The piston50includes the rib59which suppresses the piston from partially contacting the inner surface of the cylinder chamber33. Accordingly, it is possible to suppress the piston50from partially contacting the inner surface of the cylinder chamber33when the piston50slides on the inner surface of the cylinder chamber33, and hence to ensure the smooth sliding action of the piston50.

Even by the configuration, in which the seal members are respectively disposed at two separated positions of the outer peripheral surface of the piston50, it is possible to suppress the piston50from partially contacting the inner surface of the cylinder chamber33when the piston slides on she inner surface of the cylinder chamber33, and hence to ensure the smooth, sliding action of the piston50.

Here, in order to suppress the piston50from partially contacting the inner surface of the cylinder chamber33, the seal members are respectively disposed at two separated positions of the outer peripheral surface of the piston50, and the rib59may be provided so as to suppress the piston from partially contacting the inner surface of the cylinder chamber33.

The piston SO has a function as the stopper that limits the movement of the output shaft40while contacting the cover portion31or the body portion32. There is no need to provide a dedicated stopper, and hence the number of components or processing steps may be decreased. There is no need to mention that a dedicated stopper may be provided.

Here, the contact surfaces501and502as the end surfaces of the piston50come into plane-contact with the cover portion31or the body portion32. Since the contact surfaces501and502as the end surfaces of the piston50widely come into plane-contact with the cover portion31or the body portion32, the concentration of stress is suppressed. Accordingly, a material may be decreased in thickness or a synthetic resin or the like may be used. Further, a useless space is not provided in the cover portion31or the body portion32, and hence a compact actuator may be provided.

Furthermore, a portion contacting the cover portion31or the body portion32in the piston50is formed in a round shape. In the embodiment, the portion contacting the cover portion31or the body portion32in the piston50is formed in a round shape, but may be chamfered. When the piston serves as the stopper, it is possible to alleviate a state where the stress acting on the piston50is intensively applied to the edge, and hence to improve the durability of the piston50.

The center plate54which is provided in the piston50and to which the output shaft40is connected is disposed at the central position of the piston50in the height direction. A means for connecting the output shaft40to the center plate54, for example, the nut44does not protrude toward, one side of the height direction of the piston50, and the size of the piston50in the height direction may be decreased.

The output shaft40extends so as to penetrate one casing body among the first casing body and the second casing body, that is, the body portion32, and is connected to the subject, operation member, that is, the valve body22. The piston50is disposed so that the relation of L1=L2is established when the distance L1is a distance between the contact surface501contacting the body portion32and the seating surface551connected to the output shaft40during the reverse action and the distance L2is a distance between the contact surface502contacting the body portion32and the seating surface552connected to the output shaft40during the normal action. In this way, since the piston is disposed so as to establish the relation of the distance L1=the distance L2, the output shaft40may be used in both the reverse action and the normal action.

The depth HI of the accommodating recess51is set to a depth equal to or larger than 50% and equal to or smaller than 70% with respect to the height H2of the spring which is assembled, as the piston-format, working-fluid-pressure actuator10and is set when a working fluid such as air is not supplied. When the depth is equal to or larger than 50%, the buckling or the bending of compression coil springs61may be prevented by inserting a compression, coil spring61into the accommodating recess51of the piston50, and hence a stable thrust force may be obtained. Further, the interference between the adjacent compression coil springs61may be prevented and abnormal noise is suppressed. Accordingly, a compact actuator may be provided. Further, when the depth is equal or smaller than 70%, the operation length necessary for opening or closing the valve may be easily obtained.

The control valve100is configured by connecting the output shaft40of the piston-format working-fluid-pressure actuator10to the valve body22of the valve member20. Since the piston is attached to the output shaft40so that the opening52of the accommodating recess51is selectively directed toward the cover portion31or the body portion32, the valve member20may be operated as the reverse acting valve in which the valve body22is opened by the air supplied from the working-fluid supply opening72or the normal acting-valve in which the valve body22is closed by the air supplied from the working-fluid supply opening71. The control valve100may be decreased in size by decreasing the size of the piston-format working-fluid-pressure actuator10.

A case has been described in which the piston-format working-fluid-pressure actuator10is used for the reverse action or the normal action, but the piston-format working-fluid-pressure actuator may be used for a backward action without using the spring members60and90.FIGS. 7 and 8are cross-sectional views illustrating the configuration of a control valve102including the piston-format working-fluid-pressure actuator10and the valve member20according to the other variant, and illustrate a case where the valve member20is operated as a backward acting valve. The other variant is different from the embodiment in that the spring member60is not used, and the piston-format working-fluid-pressure actuator10is used for the backward action. The same reference numerals are given to the members and the parts common to the embodiment, and the description thereof will not be presented. Referring toFIG. 7, when air is supplied from the second port72of the working-fluid supply opening70to the second chamber36, a force of moving the output shaft40in the upward direction of the drawing is applied to-the piston50. The front surface of the piston50contacts the cover portion31. Accordingly, the movement of the output shaft40in the upward, direction of the drawing is limited. The valve body22of the valve member20opens the flow channel21. Referring toFIG. 8, when air is supplied from the first port71of the working-fluid supply opening70to the first chamber35, a force of moving the output shaft40in the downward direction of the drawing is applied to the piston50. The rear surface of the piston50contacts the body portion32. Accordingly, the movement of the output shaft40in the downward direction of the drawing is limited. The valve body22of the valve member20closes the flow channel21. In the embodiment, the piston50has the same configuration as the case of the reverse action, but may be operated in the same direction as the case of the normal action. In this way, even when the valve member is used for any one of the piston-format working-fluid-pressure actuators for the reverse action, the normal action, and the backward action, the components, (at least the casing30, the output shaft40, and the piston50) may be commonly used, and hence cost may be further decreased.

Further, the valve member20is not limited to the example of the drawings. For example, a valve member may be employed which opens or closes the flow channel by rotating a valve body such as a ball valve or a butterfly valve through a rack-and-pinion mechanism interposed between the piston-format working-fluid-pressure actuator10and the valve member.

Moreover, the valve member20is exemplified as the member driven by the piston-format, working-fluid-pressure actuator10, but the invention is not limited thereto. The piston-format working-fluid-pressure actuator10may be used to drive a member other than the valve member.

As the materials of the cover portion31, the body portion32, and the piston50of the invention, glass reinforced polypropylene (hereinafter, PPG) or aluminum may be used. However, if the strength or the characteristic required as the actuator is satisfied, polyvinylidene fluoride (hereinafter, PVBF), polyphenylene sulfide (hereinafter, PPS), polytetrafluoroethylene (hereinafter, PTFE), perfluoroalkoxylalkans (hereinafter, PFA), polycyelopentadiene (hereinafter, PDCPD), polyamide (hereinafter, PA), or a synthetic resin obtained by glass-reinforcing the synthetic resins (PVDF, PPS, PTFE, PFA, PDCPD, and PA) may be used. Alternatively, metal such as stainless steel, copper, cast iron, or cast steel may be used.

The materials of the output shaft40and the connection member44of the invention are not particularly limited as long as any problem in strength does not occur. Examples thereof may be cast iron, cast steel, carbon steel, copper, copper alloy, brass, aluminum, stainless steel, titanium, and the like.

The materials of the seal members37,38,45,46, and57of the invention may be a rubber-like elastic body, and are not particularly limited. Preferably, ethylene-propylene rubber, isoprene rubber, chloroprene rubber, chlorosulfonated rubber, nitrile rubber, styrene-butadiene rubber, chlorinated polyethylene, fluorine-contained rubber, and the like may be exemplified.

The spring members60and90of the invention may be formed as any known spring steel as long as a necessary thrust force may be obtained. Further, the spring members may be painted or coated by a resin if necessary.

The present application claims priority on Japanese Patent Application No. 2012-63106, filed Mar. 23, 2012, the contents of which are incorporated herein by reference.

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