Linear actuator

[0002] 1. Field of the Invention

[0003] The present invention relates to a linear actuator. In particular, the present invention relates to a linear actuator in which centralized piping can be achieved on either of a pair of end blocks.

[0004] 2. Description of the Related Art

[0005] In conventional linear actuators of this type, the piping for supplying and discharging a pressure fluid acting on a piston is provided for each of a pair of right and left end blocks. Centralized piping is made on only either of the right and left end blocks. Therefore, it has been hitherto necessary to prepare two types of linear actuators, i.e., a linear actuator having a left side outlet port in which supplying and discharging piping passages are concentrated on the left end block, and a linear actuator having a right side outlet port in which supplying and discharging piping passages are concentrated on the right end block.

[0006] Substantial equipment investment is required since the two types of linear actuators, which have different outlet ports based on the one-side centralized piping, are prepared. Further, in this case, two types of end blocks, which use different positions of piping ports, are required. Therefore, the number of parts is increased, and it is difficult to reduce the cost of production and maintenance.

[0007] A general object of the present invention is to provide a linear actuator in which one-side centralized piping can be made on either of a pair of right and left end blocks by displacing an attachment position of a connecting member attached to the pair of right and left end blocks provided for the linear actuator, and the pair of right and left end blocks can be used commonly.

[0008] The above and other objects, features, and advantages of the present invention will become more apparent from the following description when taken in conjunction with the accompanying drawings in which a preferred embodiment of the present invention is shown by way of illustrative example.

[0009] FIG. 1 is a perspective view schematically illustrating a linear actuator according to an embodiment of the present invention;

[0010] FIG. 2 is a longitudinal sectional view taken along a line II—II shown in FIG. 1;

[0011] FIG. 3 is, with partial cutout, a plan view illustrating the linear actuator shown in FIG. 1;

[0012] FIG. 4 is, with partial cutout, a plan view illustrating a state in which an attachment position of a sensor attachment rail shown in FIG. 3 is displaced in the rightward direction;

[0013] FIG. 5 is a perspective view schematically illustrating a linear actuator according to another embodiment of the present invention;

[0014] FIG. 6 is a longitudinal sectional view taken along a line VI—VI shown in FIG. 5;

[0015] FIG. 7 is a schematic lateral sectional view illustrating the linear actuator shown in FIG. 5; and

[0016] FIG. 8 is a schematic lateral sectional view illustrating a state in which an attachment position of a sensor attachment rail shown in FIG. 7 is displaced in the rightward direction.

[0017] In FIGS. 1 to 4, reference numeral 10 indicates a linear actuator 10 according to an embodiment of the present invention.

[0018] The linear actuator 10 basically comprises a driving section 12 which is composed of a magnet-based rodless cylinder, a slider 14 (movable member) which reciprocates linearly under the driving action of the driving section 12, a guide rail 16 (guide member) which guides the slider 14, a pair of end blocks 18a, 18bwhich are connected by screw members 20 to both end portions of the guide rail 16 respectively, and a sensor attachment rail 22 (connecting member) which is fixed to the pair of end blocks 18a, 18brespectively and which is arranged substantially in parallel to the guide rail 16.

[0019] As shown in FIG. 2, the driving section 12 includes a cylindrical member 28, a piston 30, and a slide block 32. The cylindrical member 28 has a through-hole 24 which functions as a cylinder chamber. The cylindrical member 28 is supported by the pair of end blocks 18a, 18bby the aid of end caps 26a, 26binserted in both end portions of the through hole 24 respectively. The piston 30 is formed of a magnetic material and slidably fitted to the through-hole 24 in the cylindrical member 28. The slide block 32 surrounds the outer circumferential surface of the cylindrical member 28. The slide block 32 is displaceable in the axial direction of the cylindrical member 28 in unison with the piston 30.

[0020] Orifices 36a, 36b, which throttle the flow rate of the fluid flowing through passages 34a, 34b, are formed in the end caps 26a, 26b. The passages 34a, 34bare provided to make communication with fourth pressure fluid inlet/outlet ports 48a, 48b(see FIG. 3) which is formed in the end caps 26a, 26bas described later on.

[0021] As shown in FIG. 3, the end blocks 18a, 18bare formed with first pressure fluid inlet/outlet ports 38a, 38band second pressure fluid inlet/outlet ports 40a, 40bwhich are substantially in parallel to the axis of the cylindrical member 28, and third pressure fluid inlet/outlet ports 42a, 42bwhich are disposed substantially perpendicularly to the first pressure fluid inlet/outlet ports 38a, 38bto make communication therewith.

[0022] Further, first pressure fluid passages 44a, 44bare formed, which are disposed substantially perpendicularly to the second pressure fluid inlet/outlet ports 40a, 40bto make communication therewith. The first pressure fluid passages 44a, 44bcommunicate with the through-hole 24 of the cylindrical member 28.

[0023] Second pressure fluid passages 46a, 46bare formed substantially in parallel to the third pressure fluid inlet/outlet ports 42a, 42brespectively, and they communicate with the first pressure fluid passages 44a, 44b. The fourth pressure fluid inlet/outlet ports 48a, 48b, which communicate with the passages 34a, 34b, are connected to the first pressure fluid passages 44a, 44brespectively.

[0024] In this arrangement, the first pressure fluid inlet/outlet ports 38a, 38band the third pressure fluid inlet/outlet ports 42a, 42b, which communicate with each other, function as the first pressure fluid communicating passage. Further, the second pressure fluid inlet/outlet ports 40a, 40b, the first pressure fluid passages 44a, 44b, and the second pressure fluid passages 46a, 46bfunction as the second pressure fluid communicating passage. Reference numeral 50 indicates a seal ring.

[0025] As shown in FIG. 2, wear rings 52 and scrapers 54 are installed to both end portions of the piston 30 in the axial direction respectively. A first yoke, which is composed of five annular plates 56ato 56eformed of magnetic members, is externally fitted to the outer circumferential surface of the piston 30. Ring-shaped inner magnets 58ato 58dare interposed between the adjoining annular plates 56ato 56erespectively.

[0026] A second yoke, which is constructed by a plurality of divided annular plates 60ato 60ecomposed of magnetic members, is internally fitted to the inner circumferential surface of the slide block 32. Ring-shaped outer magnets 62ato 62dare interposed between the adjoining annular plates 60ato 60erespectively. The annular plates 60ato 60eand the ring-shaped outer magnets 62ato 62dare fastened to the inner circumferential surface of the slide block 32 by retaining rings 80 by the aid of wear rings 76 and spacers 78.

[0027] In this arrangement, the inner magnets 58ato 58dinstalled to the piston 30 and the outer magnets 62ato 62dinstalled to the slide block 32 are arranged so that they are opposed to one another with the cylindrical member 28 intervening therebetween respectively. Further, their magnetic poles are set so that they are attracted to one another.

[0028] As shown in FIG. 3, a passage 64, which extends in the axial direction, is formed in the sensor attachment rail 22. The passage 64 is provided to make communication with the third pressure fluid inlet/outlet port 42aof the end block 18aand the second pressure fluid passage 46bof the end block 18brespectively by the aid of piping studs 70a, 70bwhich are fitted to a pair of holes formed on the lower side of a sensor attachment long groove 68 (see FIG. 1) respectively.

[0029] Both ends of the passage 64 formed in the sensor attachment rail 22 are closed in an air-tight manner by steel balls 74 respectively. Reference numeral 84 (see FIG. 2) indicates screw members which are screw-fastened to the end blocks 18a, 18b. The displacement amount of the slider 14 is adjusted by increasing/decreasing the screwing amount of the screw member 84. Elastic members 86 (see FIG. 2), which are screw-fastened to the slider 14, effect the buffering function when the screw members 84 make abutment thereagainst.

[0030] The linear actuator 10 according to the embodiment of the present invention is basically constructed as described above. Next, its operation, function, and effect will be explained.

[0031] At first, it is assumed that the one-side centralized piping for supplying and discharging the pressure fluid is effected for the first end block 18adisposed on the left side.

[0032] With reference to FIG. 3, the first pressure fluid passage 44aof the end block 18a, and the second pressure fluid inlet/outlet port 40band the first pressure fluid passage 44bof the end block 18bare closed by plugs 82ato 82crespectively.

[0033] On the other hand, the piping studs 70a, 70bare screw-fastened to the third pressure fluid inlet/outlet port 42aof the end block 18aand the second pressure fluid passage 46bof the end block 18brespectively. The third pressure fluid inlet/outlet port 42aand the second pressure fluid passage 46bcommunicate with each other via the passage 64 of the sensor attachment rail 22.

[0034] Accordingly, the first pressure fluid inlet/outlet port 38aof the end block 18acommunicates with the passage 34bof the end cap 26bvia the third pressure fluid inlet/outlet port 42a, the communicating passage 72aof the piping stud 70a, the passage 64 of the sensor attachment rail 22, and the communicating passage 72bof the piping stud 70b, and via the second and first pressure fluid passages 46b, 46band the fourth pressure fluid inlet/outlet port 48bof the end block 18b.

[0035] On the other hand, the second pressure fluid inlet/outlet port 40aof the end block 18acommunicates with the passage 34aof the end cap 26avia the first pressure fluid passage 44aand the fourth pressure fluid inlet/outlet port 48a.

[0036] The pressure fluid, for example, compressed air, which is supplied from an unillustrated pressure fluid supply source, is introduced from the piping port P1 into the first pressure fluid inlet/outlet port 38aof the end block 18a. The second pressure fluid inlet/outlet port 40aof the end block 18ais open to the atmospheric air under the action of an unillustrated directional control valve.

[0037] The supplied compressed air passes from the first pressure fluid inlet/outlet port 38athrough the third pressure fluid inlet/outlet port 42a, the communicating passage 72aof the piping stud 70a, the passage 64 of the sensor attachment rail 22, and the communicating passage 72bof the piping stud 70b. The compressed air passes through the second and first pressure fluid passages 46b, 44band the fourth pressure fluid inlet/outlet port 48b, and it is introduced from the passage 34band the orifice 36binto the first end portion of the through-hole 24 of the cylindrical member 28 which functions as the cylinder chamber.

[0038] On the other hand, the second end portion of the through-hole 24 as the cylinder chamber is open to the atmospheric air via the orifice 36a, the passage 34a, the fourth pressure fluid inlet/outlet port 48a, and the first pressure fluid passage 44a, and via the second pressure fluid inlet/outlet port 40a.

[0039] Accordingly, the piston 30 is pressed under the action of the compressed air introduced into the through-hole 24 of the cylindrical member 28. The inner magnets 58ato 58dand the piston 30 are displaced integrally in the direction of the arrow Y (see FIG. 3) along the through-hole 24 of the cylindrical member 28 by the aid of the first yoke composed of the annular plates 56ato 56e. During this process, the outer magnets 62ato 62dare attracted under the action of the magnetic fields of the inner magnets 58ato 58dinstalled to the piston 30 by the aid of the first yoke. The slide block 32, which retains the outer magnets 62ato 62d, is displaced integrally with the piston 30.

[0040] When the compressed air is supplied from the piping port P2 to the second pressure fluid inlet/outlet port 40ato open the first pressure fluid inlet/outlet port 38ato the atmospheric air, the compressed air in the flow passages for supplying and discharging flows in the opposite directions, and the compressed air is introduced into the through-hole 24 of the cylindrical member 28. Therefore, the piston 30 and the slide block 32 are displaced integrally in the direction of the arrow X shown in FIG. 3.

[0041] As described above, when the first pressure fluid inlet/outlet port 38aand the second pressure fluid inlet/outlet port 40aformed in the end block 18aare open to the atmospheric air for the supply and the discharge of the compressed air under the action of the unillustrated directional control valve respectively, the piston 30 and the slide block 32 are integrally displaced linearly. Thus, the reciprocating motion of the slider 14 is carried out.

[0042] Next, it is assumed that the flow passages are changed to effect the one-side centralized piping for supplying and discharging the pressure fluid for the second end block 18bdisposed on the right side, by further displacing the sensor attachment rail 22 in the direction of the arrow X from the position shown in FIG. 3.

[0043] FIG. 4 shows a state in which the piping studs 70a, 70bare screw-fastened to the second pressure fluid passage 46aof the end block 18aand the third pressure fluid inlet/outlet port 42bof the end block 18brespectively to displace the sensor attachment rail 22 in the rightward direction.

[0044] In this arrangement, the second pressure fluid inlet/outlet port 40aand the first pressure fluid passage 44aof the end block 18aand the first pressure fluid passage 44bof the end block 18bare closed by the plugs 82ato 82crespectively. Practically, the plug 82binstalled to the end block 18bis simply detached to install it to the end block 18adisposed on the opposite side.

[0045] The second pressure fluid passage 46aof the end block 18aand the third pressure fluid inlet/outlet port 42bof the end block 18bcommunicate with the passage 64 of the sensor attachment rail 22 by the aid of the piping studs 70a, 70b.

[0046] The first pressure fluid inlet/outlet port 38bof the end block 18bcommunicates with the passage 34aof the end cap 26avia the communicating passage 72bof the piping stud 70band the passage 64 of the sensor attachment rail 22, and via the communicating passage 72aof the piping stud 70aand the second and first pressure fluid passages 46a, 44aand the fourth pressure fluid inlet/outlet port 48aof the end block 18a.

[0047] The second pressure fluid inlet/outlet port 40bof the end block 18bcommunicates with the passage 34bof the end cap 26bby the first pressure fluid passage 44band the fourth pressure fluid inlet/outlet port 48b.

[0048] The compressed air is supplied from the piping port P1 to the second pressure fluid inlet/outlet port 40bof the end block 18b. The first pressure fluid inlet/outlet port 38bof the end block 18bis open to the atmospheric air under the action of the unillustrated directional control valve.

[0049] The supplied compressed air passes from the second pressure fluid inlet/outlet port 40bthrough the first pressure fluid passage 44band the fourth pressure fluid inlet/outlet port 48b, and it is introduced from the passage 34binto the first end portion of the through-hole 24 as the cylinder chamber. The second end portion as the cylinder chamber is open to the atmospheric air via the passage 34a, the fourth pressure fluid inlet/outlet port 48a, and the first and second pressure fluid passages 44a, 46a, via the communicating passage 72aof the piping stud 70a, the passage 64 of the sensor attachment rail 22, and the communicating passage 72bof the piping stud 70b, and via the first pressure fluid inlet/outlet port 38b.

[0050] Accordingly, the piston 30 is pressed under the action of the compressed air introduced into the through-hole 24 of the cylindrical member 28. The inner magnets 58ato 58dand the piston 30 are displaced in the direction of the arrow Y by the aid of the annular plates 56ato 56e.

[0051] When the compressed air is supplied from the piping port P2, and the piping port P1 is open to the atmospheric air, the compressed air in the passages for supplying and discharging flows in the opposite directions, and the compressed air is introduced into the through-hole 24 of the cylindrical member 28. Accordingly, the slide block 32 and the piston 30 are displaced integrally in the direction of the arrow X shown in FIG. 4.

[0052] Accordingly, when the first pressure fluid inlet/outlet port 38band the second pressure fluid inlet/outlet port 40bformed in the end block 18bare open to the atmospheric air for the supply and the discharge of the compressed air under the action of the unillustrated directional control valve respectively, the piston 30 and the slide block 32 are integrally displaced linearly. Thus, the reciprocating motion of the slider 14 is carried out.

[0053] In the embodiment of the present invention, the third pressure fluid inlet/outlet port 42band the second pressure fluid passage 46acommunicate with each other via the passage 64 by displacing the sensor attachment rail 22 in the rightward direction as shown in FIG. 4, and screw-fastening the piping studs 70a, 70bto the second pressure fluid passage 46aof the end block 18aand the third pressure fluid inlet/outlet port 42bof the end block 18brespectively.

[0054] As described above, the piping studs 70a, 70bhave the function to attach the sensor attachment rail 22 to the end blocks 18a, 18b.

[0055] Further, the communicating passages 72a, 72b, which are formed in the piping studs 70a, 70b, have the function to make communication with the passage 64 of the sensor attachment rail 22 for the third pressure fluid inlet/outlet port 42aof the end block 18aand the second pressure fluid passage 46bof the end block 18band for the second pressure fluid passage 46aof the end block 18aand the third pressure fluid inlet/outlet port 42bof the end block 18brespectively.

[0056] Therefore, in the embodiment of the present invention, the centralized piping can be concentrated on either of the end blocks 18a, 18bby only displacing the attachment position of the sensor attachment rail 22. Accordingly, the piping is simplified, and it is possible to shorten the time required for the piping operation.

[0057] Next, a linear actuator 90 according to another embodiment of the present invention is shown in FIGS. 5 to 8. The same components of the linear actuator 90 as the components shown in FIGS. 1 to 4 described above are designated by the same reference numerals, detailed explanation of which will be omitted.

[0058] With reference to FIG. 5, the linear actuator 90 comprises a body 92 (guide member) (see FIG. 6) which has a rectangular parallelepiped configuration, a pair of end blocks 96a, 96bwhich are connected to both end portions of the body 92 in the longitudinal direction by the aid of screw members 94a, 94b, and a slide table 100 (movable member) which makes linear reciprocating motion along a guide section 98 formed in an integrated manner while being exposed over the upper surface of the body 92.

[0059] As shown in FIG. 6, a first opening 102, which has a substantially elliptic configuration in order to displace a joint member 118 as described later on, is formed in the guide section 98 disposed along the upper surface of the body 92. A second opening 104 is formed at the bottom surface of the body 92. Further, a through-hole 106 having a substantially circular cross section, which communicates with the first and second openings 102, 104 respectively, is formed in the axial direction in the body 92.

[0060] As shown in FIGS. 6 and 7, cylindrical sections 108a, 108b, which protrude along the through-hole 106 formed in the body 92, are formed for the respective end blocks 96a, 96b. Holes 110a, 110b, which make penetration in the axial direction, are formed in the cylindrical sections 108a, 108b.

[0061] Seal members 114 are fitted to the outer circumferential surfaces of the cylindrical sections 108a, 108bby the aid of annular grooves. The seal members 114 make sliding contact with cap members 122a, 122bas described later on, and thus the seal members 114 function to retain, in an air-tight manner, pressure chambers 124a, 124bwhich are closed by the cap members 122a, 122bas described later on.

[0062] A bolt member 116 having a columnar configuration is screw-fastened to the slide table 100 in a direction perpendicular to the bottom surface portion thereof. An angular barrel-shaped joint member 118 is externally fitted to the outer circumferential surface of the bolt member 116. A damper member 120 having a substantially rectangular cross section is installed to the outer circumferential surface at one end of the joint member 118. The damper member 120 is displaceable integrally with the slide table 100, the bolt member 116, and the joint member 118, and it has a buffering function by making abutment against the inner wall surface of the first opening 102.

[0063] A pair of cap members 122a, 122b, which extend in the axial direction of the through-hole 106 and each of which has a bottom-equipped cylindrical configuration, are arranged and opposed to one another on side wall surfaces of the joint member 118. The joint member 118 is retained in a surface-to-surface contact manner in a state in which the joint member 118 does not forcibly contact with the cap members 122a, 122b.

[0064] Pressure chambers 124a, 124b, each of which is formed by the cap member 122a, 122band the cylindrical section 108a, 108b, communicate with the holes 110a, 110bwhich penetrate through the cylindrical sections 108a, 108b. In this arrangement, the pressure fluid is supplied to the pressure chamber 124a, 124bvia the hole 110a, 110b, and thus the pressure fluid presses the inner wall surface of the cap member 122a, 122b.

[0065] Accordingly, the cap members 122a, 122bare slidably displaceable along annular gaps 126a, 126bwhich are formed by the through-hole 106 of the body 92 and the outer circumferential surfaces of the cylindrical sections 108a, 108b. When the cap members 122a, 122bare displaced along the outer circumferential surfaces of the cylindrical sections 108a, 108b, the slide table 100 makes the reciprocating motion in the direction of the arrow X or Y by the aid of the joint member 118 which is interposed by the cap members 122a, 122bin the surface-to-surface contact manner. In this arrangement, the cylindrical sections 108a, 108b, the seal members 114, the bolt member 116, the joint member 118, and the cap members 122a, 122bfunction as the driving section for making the reciprocating motion of the slide table 100 in the direction of the arrow X or Y.

[0066] The linear actuator 90 according to the another embodiment of the present invention is basically constructed as described above. Next, its operation, function, and effect will be explained.

[0067] At first, it is assumed that the one-side centralized piping for supplying and discharging the pressure fluid is effected for the first end block 96adisposed on the left side.

[0068] With reference to FIG. 7, the first pressure fluid passage 44aof the end block 96a, the first pressure fluid passage 44bof the end block 96b, and the first end of the hole 110bopen to the end block 96bare closed by plugs 82ato 82c.

[0069] Further, the piping studs 70a, 70bare screw-fastened to the third pressure fluid inlet/outlet port 42aof the end block 96aand the second pressure fluid passage 46bof the end block 96brespectively. Accordingly, the third pressure fluid inlet/outlet port 42aand the second pressure fluid passage 46bcommunicate with each other via the passage 64 of the sensor attachment rail 22.

[0070] The first pressure fluid inlet/outlet port 38aof the end block 96acommunicates with the hole 110bof the cylindrical section 108bvia the communicating passage 72aof the piping stud 70aand the passage 64 of the sensor attachment rail 22, and via the communicating passage 72bof the piping stud 70band the second and first pressure fluid passages 46b, 46bof the end block 96b. The hole 110aof the cylindrical section 108acommunicates with the pressure chamber 124aof the cap member 122a.

[0071] The pressure fluid, for example, compressed air, which is supplied from an unillustrated pressure fluid supply source, is introduced into the hole 110aof the cylindrical section 108afrom the piping port P2. The first pressure fluid inlet/outlet port 38aof the end block 96ais open to the atmospheric air under the action of an unillustrated directional control valve.

[0072] The supplied compressed air is introduced into the hole 110aof the cylindrical section 108a, and the compressed air is further supplied to the pressure chamber 124awhich is closed by the cap member 122ato press the inner wall surface of the cap member 122a. Therefore, the cap member 122ais slidably displaced in the direction (direction of the arrow X) to make separation from the cylindrical section 108a, while maintaining the state in which the pressure chamber 124ais retained in the air-tight manner by the aid of the seal member 114. Accordingly, the cap member 122apresses the joint member 118, and thus the slide table 100 is displaced in the direction of the arrow X by the aid of the bolt member 116 installed and fitted to the joint member 118.

[0073] The pressure chamber 124b, which is closed by the cap member 122b, is open to the atmospheric air via the first pressure fluid inlet/outlet port 38a. The joint member 118 is displaced in the direction of the arrow X in unison with the slide table 100, while maintaining the state in which the joint member 118 is interposed by the cap members 122a, 122b.

[0074] When the compressed air is supplied from the piping port P1 to the first pressure fluid inlet/outlet port 38aunder the action of the unillustrated directional control valve to open the hole 110ato the atmospheric air, the compressed air in the flow passages for supplying and discharging flows in the opposite directions, and the slide table 100 is displaced in the direction of the arrow Y as shown in FIG. 7.

[0075] Next, it is assumed that the flow passages are changed to effect the one-side centralized piping for supplying and discharging the pressure fluid for the second end block 96bdisposed on the right side, by further displacing the sensor attachment rail 22 in the direction of the arrow X from the position shown in FIG. 7.

[0076] FIG. 8 shows a state in which the piping studs 70a, 70bare screw-fastened to the second pressure fluid passage 46aof the end block 96aand the third pressure fluid inlet/outlet port 42bof the end block 96brespectively to displace the sensor attachment rail 22 in the rightward direction.

[0077] In this arrangement, the first pressure fluid passage 44aof the end block 96a, the first end of the hole 110aopen to the end block 96a, and the first pressure fluid passage 44bof the end block 96bare closed by the plugs 82.

[0078] Further, the second pressure fluid passage 46aof the end block 96aand the third pressure fluid inlet/outlet port 42bof the end block 96bcommunicate with the passage 64 of the sensor attachment rail 22 via the piping studs 70a, 70b.

[0079] Accordingly, the hole 110bof the cylindrical section 108bformed in the end block 96bcommunicates with the pressure chamber 124bof the cap member 122b. The first pressure fluid inlet/outlet port 38bof the end block 96bcommunicates with the hole 110aof the cylindrical section 108avia the communicating passage 72bof the piping stud 70b, the passage 64 of the sensor attachment rail 22, and the communicating passage 72aof the piping stud 70a, and via the second and first pressure fluid passages 46a, 44aof the end block 96a.

[0080] The unillustrated compressed air is introduced from the piping port P2 into the first pressure fluid inlet/outlet port 38b. The hole 110bis in open to the atmospheric air under the action of the unillustrated directional control valve.

[0081] The supplied compressed air is introduced into the hole 110aof the cylindrical section 108afrom the second and first pressure fluid passages 46a, 44avia the first pressure fluid inlet/outlet port 38b, the communicating passage 72bof the piping stud 70b, the passage 64 of the sensor attachment rail 22, and the communicating passage 72aof the piping stud 70a. Further, the compressed air is supplied to the pressure chamber 124awhich is closed by the cap member 122ato press the inner wall surface of the cap member 122a. Therefore, the cap member 122ais slidably displaced in the direction (direction of the arrow X) to make separation from the cylindrical section 108a, while maintaining the state in which the pressure chamber 124ais retained in the air-tight manner by the aid of the seal member 114. Accordingly, the cap member 122apresses the joint member 118, and thus the slide table 100 is displaced in the direction of the arrow X by the aid of the bolt member 116 which is installed and fitted to the joint member 118.

[0082] The pressure chamber 124b, which is closed by the cap member 122b, is open to the atmospheric air via the hole 110b. The joint member 118 is displaced in the direction of the arrow X in unison with the slide table 100, while maintaining the state in which the joint member 118 is interposed by the cap members 122a, 122b.

[0083] When the compressed air is supplied from the piping port P1 to the hole 110bunder the action of the unillustrated directional control valve, and the first pressure fluid inlet/outlet port 38bis open to the atmospheric air, the compressed air in the flow passages for supplying and discharging flows in the opposite directions, and the slide table 100 is displaced in the direction of the arrow Y as shown in FIG. 8.

[0084] While the invention has been particularly shown and described with reference to preferred embodiments, it will be understood that variations and modifications can be effected thereto by those skilled in the art without departing from the spirit and scope of the invention as defined by the appended claims.