Rodless cylinder

Abstract: The rodless cylinder includes a cylinder body, a piston, and a slide table connected to the piston. The slide table and the piston are united with each other due to a coupling part which projects through a slit formed in a longitudinal direction of the cylinder body. The slide table includes first and second load transmitting means, whereas the cylinder body includes first and second load receiving means corresponding to the first and second load transmitting means. When a lateral load is applied to the slide table, the load is transmitted via one of the first and second load transmitting means to a corresponding one of the first and second load receiving means so as to transmit the force to a direction in which the slit of the cylinder body can be widened.

Description: BACKGROUND OF THE INVENTION Field of the Invention: The present invention relates generally to rodless cylinders, and more particularly to a rodless cylinder in which a slide table and a cylinder body are made as small as possible to minimize their occupied space, the cylinder body sufficiently supporting any load applied to the slide table and smoothly displacing the slide table in accordance with piston's reciprocating motion. Prior Art: Many factories have recently used rodless cylinders for various workpiece transfer devices. The rodless cylinder has an advantage over a roded cylinder in a short stroke length, thus, in a sufficiently small occupied area for a convenient fabrication. In addition, the rodless cylinder has an advantage over the roded cylinder in preventing dust from entering the cylinder, and consequently in positioning an object with high-precision. Such rodless cylinders can be seen in U.S. Patent No. 4,373,427 and German Patent No. 3,124,915. In particular, the rodless cylinder disclosed in the German Patent No. 3,124,915 includes a guide groove, provided between an outer circumferential surface of a cylinder tube and a top surface with a slit of the cylinder, and distinct guide means, provided at a leg member extending from both sides of the slide table to the cylinder tube, which are engaged with the guide groove. According to the German Patent No. 3,124,915, the guide means are engaged with each other so as to prevent the width of slit from widening when the lateral force is applied. However, according to the German Patent No. 3,124,915, it is necessary to extend the leg member from the slide table to a part more external than an outer slide surface of the cylinder tube, so as to hold the guide means. Therefore, when the lateral force is applied to the slide table and the guide means are engaged with each other, one end surface of the cylinder tube which defines the slit is compulsively approached the other end surface of the cylinder tube which defines the other side slit; consequently the bore is wholly reduced only to compulsively stop the piston. That is, the piston comes to stop in response to the lateral force, and thus the workpiece transfer operation comes to unexpectedly stop, and the device is forced to be reluctantly made large due to the leg member. The EP-A-0 476 265 representing a state of the art under Article 54 (1), (3) and (4) EPC describes a fluid-actuated cylinder having a longitudinally slotted cylinder tube closed at the end which is limited on the slot side by an outer surface at right angles to the slot, and in which a piston, sealed by means of two piston seals arranged near its ends, is movably guided, this piston being fixably connected in the region between the piston seals by means of a connecting means passing through the slot, to a driver located at the outside of the cylinder tube in front of the slot, having a sealing strip arranged on the inner side of the cylinder tube and covering the slot in a fluid-tight manner outside the section included by the two piston seals and a cover strip covering the slot on the outside with the exception of the penetration region of the connecting means, having a power output element, guided axially movably on the outside of the cylinder, which engages over the driver remote from the slot and laterally, wherein the guideway of the power output element constructed symmetrically to a central plane extending to the slot and containing the cylinder axis has, on both sides of the slot two flat guide rails extending axis-parallel to each other at an angle, each having a guide groove arranged on the cylinder tube and a guide strip arranged adjustably on the power output element and having a coupling device arranged between the driver and the power output element and transmitting axial forces between these parts with the transverse and rotary mobility limited. The guideway of the power output element on both sides of the slot has one guide rail inside the guide groove and the other guide rail on the outer surface, the one guide rail not being adjustable and extending inclined to the central plane, and the other guide rail extending parallel to the outer surface and having the guide strip adjustable in the direction perpendicular to the outer surface. As one of the guide rails is provided on the outer surface on the cylinder body remote from the guide groove comprising the other guide rail two separate load transmitting means have to be provided at each side of the slot thereby increasing the overall dimensions of the cylinder and complicating its structure. SUMMARY OF THE INVENTION It is an object of the present invention to provide a rodless cylinder in which a piston never stops even when the lateral force is applied to a slide table, the slide table itself can smoothly reciprocate, and a device can be made compact as a whole. This object is achieved with a rodless cylinder according to claim 1. Further object of the present invention is to provide a rodless cylinder wherein the first and second load transmitting means each comprise bearings, and the first and second load receiving means each comprise bearing rolling surfaces mounted on the cylinder body. Still further object of the present invention is to provide a rodless cylinder wherein the bearing rolling surfaces functioning as the first and second load receiving means each comprise rail members mounted on the cylinder body. Yet further object of the present invention is to provide a rodless cylinder wherein the first and second load receiving means each comprise side surfaces each of which receives, when a load is applied to a top surface of the slide table, a force spreading toward the exterior via the first and second load transmitting means fixed on the slide table. Another object of the present invention is to provide a rodless cylinder wherein a side surface of the first and second load receiving means is displaced by a predetermined angle of 45° against a surface which includes an axis line along which the piston reciprocates, wherein the other side surface of the first and second load receiving means is displaced by 90° against the side surfaces displaced by 45°. Yet further object of the present invention is to provide a rodless cylinder wherein the bearings each have substantially hexagonal sections. Another object of the present invention is to provide a rodless cylinder wherein the first and second load receiving means are each provided on one surface of the cylinder body at a side of the slide table, and each comprise guide grooves having a pair of first oblique surfaces each directing a vertical surface which includes the axis line of the cylinder body, whereas the first and second load transmitting means are engaged with the guide grooves on a surface of the slide table at a side of cylinder body, and each comprises guide means having second oblique surfaces engaged with the first oblique surfaces and directing the exterior of the cylinder body so as to displace the slide table in response to the piston's reciprocating motion. Further object of the present invention is to provide a rodless cylinder wherein the guide means comprise a pair of projecting parts each having oblique surfaces directing a direction along which the guide grooves open each other. Still further object of the present invention is to provide a rodless cylinder wherein at least one of a pair of projecting parts is displaceable against the other projecting part. Yet further object of the present invention is to provide a rodless cylinder wherein the projecting parts each have synthetic resin films on a surface which is slidably in contact with the guide grooves. Other objects and further features of the present invention will be fully understood from the detailed description of the preferred embodiments of the present invention with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows a perspective view depicting a rodless cylinder according to the present invention; FIG. 2 shows a perspective view depicting a cylinder tube of the rodless cylinder according to the present invention; FIG. 3 shows a longitudinal sectional view of a slide table and a cylinder body of the rodless cylinder according to the present invention; FIG. 4 shows a perspective view depicting the slide table of the rodless cylinder according to the present invention; FIG. 5 shows a perspective view depicting a piston of the rodless cylinder according to the present invention; FIG. 6 shows a longitudinal sectional view depicting a side of the rodless cylinder; FIG. 7 shows a longitudinal sectional view of a part of an engagement state between a first sealing member and a slit of the rodless cylinder according to the present invention; FIG. 8 shows a longitudinal sectional view of the slide table and the cylinder body of the rodless cylinder of another embodiment according to the present invention; and FIG. 9 shows a perspective view depicting the slide table shown in FIG. 8. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 1, numeral 10 denotes a rodless cylinder according to the present invention. The rodless cylinder 10 includes a tube body 12 and a slide table 14. The tube body 12 includes a bore 16 which extends, inside the tube body 12, in a longitudinal direction thereof (see FIG. 2); the bore 16 communicates to the exterior via a slit 18 formed on a top surface part shown in FIG. 2. On side surface parts of the tube body 12, as shown in FIGS. 2 and 3, long grooves 20a to 20d are formed to install sensors thereto, while extending in its longitudinal direction; in addition, fluid bypath passages 22a and 22b are formed for concentrated piping while extending in its longitudinal direction. Above the long grooves 20a and 20c, projecting parts 24 and 26 are formed by expanding corner parts of the cylinder tube; a first guide groove 28 is formed between the projecting part 24 and the slit 18, whereas a second guide groove 30 is formed between the projecting part 26 and the slit 18. As is easily understood from FIG. 3, a side wall part of the rodless cylinder 10 which forms the first guide groove 28 has a first side surface 32a and a second side surface 32b which are displaced by 45° against a vertical surface including an axis line along which the undermentioned piston reciprocates, the first side surface 32a being displaced by 90° against the second side surface 32b. On the other hand, as is applied to the second guide groove 30, a third side surface 34a and a fourth side surface 34b are displaced by 45° against the vertical surface including the axis line along which the piston reciprocates, the third side surface 34a being displaced by 90° against the fourth side surface 34b. The bore 16 communicates with the exterior through the slit 18, as mentioned above; side walls which define the slit 18 each include step part 36a and 36b which spread toward the bore 16. Surfaces which extend from an internal surface of the slit 18 to the above are formed as horizontal surfaces, then once elected, and connected to the first guide groove 28 and the second guide groove 30. Both ends of the tube body 12 which is constructed as mentioned above, are airtightly occluded by the end caps 40a and 40b having ports 38a and 38b (see FIG. 1). Incidentally, in FIG. 3, numeral 42 denotes a sensor which detects a position of the piston or the slide table 14. Next follows a description of the slide table 14. The slide table 14 includes a relatively thick plate 50, as shown in FIGS. 3 and 4; the plate 50 includes four rods 52a to 52d downwardly extending from its corner parts, and abacus-ball-shaped guide rollers 54a to 54d rotatably fixed on the corresponding rods at their top parts. The guide rollers 54a to 54d each include rolling surfaces 60a and 60b which are in contact with rail members 56a, 56b, 58a and 58b, the rail members 56a, 56b, 58a, and 58b being inserted into grooves formed on the first to fourth side surfaces 32a, 32b, 34a, and 34b of the tube body 12. The rolling surfaces 60a and 60b are in contact, by predetermined pressure, with the rail members 56a, 56b, 58a, and 58b which have the same oblique angles with the first side surface 32a, and second side surface 32b, the third side surface 34a, and the fourth side surface 34b. A groove 62 is defined to extend in the center part of and in the longitudinal direction of the slide table 14; elliptical space 64 opens at the center part of the groove 62. Incidentally, the groove 62 has, as easily understood from FIG. 4, a curved concave part 66 directing a surface 50a of the plate 50 at the opposite side of the tube body 12. FIG. 5 shows a piston 70. The piston 70 has a first pressure-receiving surface 72 and a second pressure-receiving surface 74 opposite thereto, which include therein cushion seals 76a and 76b (see FIG. 6). Belt separators 78a and 78b are fixed on a piston yoke 80 on the cylindrical piston; a roller 84 is fixed via a coupler 82 on the piston yoke 80. The coupler 82 has an elliptical shape so as to be inserted into the space 64 formed at the center part of the slide table 14. Therefore, as shown in FIG. 5, when the slide table 14 couples to the piston 70 via the coupler 82, firmly in the direction X, however, individually movably against the piston 70 in the directions Y and Z. As is easily understood by FIG. 6, the slide table 14 includes therein scrapers 84a and 84b. As is easily understood by FIG. 6, the coupler 82 has a plane circle shape, and is inserted into the elliptical space 64. Incidentally, in FIG. 6, reference numeral 86 denotes a passage through which the undermentioned first sealing member engages with the piston; numeral 97 denotes a cushion ring. FIG. 7 shows sealing members to be inserted into the step parts 36a and 36b. A first sealing member 90 has tongue parts 92a and 92b, and extending parts 94a and 94b above the tongue parts 92a and 92b. Engaging parts 96a and 96b extend from the extending parts 94a and 94b towards the above while somewhat opening. The extending parts 94a and 94b are engaged with each other when internal pressure is applied to the step parts 36a and 36b in the piston; the engaging parts 96a and 96b are engaged with internal surfaces 98a and 98b so as to define the slit 18. The first sealing member 90 is made, as one member, of flexible synthetic resin material. On the other hand, a second sealing member 100 occludes the slit 18, and is inserted into a groove 102 which extends above and in the longitudinal direction of the slit formed on the top end surface of the tube body 12. The first sealing member 90 enters the passage 86 of the piston 70; its both end parts are fixed by the second sealing member 100 and the end caps 40a and 40b. The rodless cylinder according to the present invention is thus constructed as mentioned above; next follows a description of its operation. When compressed air is applied from the port 38a, and compressed air pushes the first pressure-receiving surface 72 via the passage formed inside the cushion ring. Thereby, the piston is displaced to the left side in FIG. 6. Then, since the coupler 82 is inserted into the space 64 of the slide table 14, the piston 70 displaces the slide table 14 as a whole, and likewise transfers the same to the left side. Simultaneously, the belt separators 78a and 78b separate the first sealing member 90 from the second sealing member 100 between the slide table 14 and the piston 70. Therefore, only if a workpiece is placed on the slide table 14, the workpiece can be transferred to the left side in FIG. 6. Needless to say, when compressed air is applied to the port 38b, an operation reverse to the above description is performed. Incidentally, the roller 84 is slidably in contact with the second sealing member 100 during it transferring, and facilitates to transfer the slide table 14. By the way, suppose, in the above reciprocating activity, that an unexpected load is applied to the slide table 14 while a workpiece is being transferred. In this case, the load is transmitted to the guide rollers 54a and 54d via the rods 52a to 52d. Since the guide rods 54a to 54d include the first side surface 32a, the second side surface 32b, the third side surface 34a, and the fourth side surface 34b, they can transmit, via the oblique angle thereof, the force to the rail members 56a, 56b, 58a, and 58b. The rail members 56a, 56b, 58a, and 58b assist the guide rollers 54a to 54d to rotate during the workpiece transferring, and sufficiently receive such an overweight load. Therefore, since the sufficient transfer operation can be retained even when an unexpected load is applied to the slide table 14, the undesirable case disclosed in the prior art in which the diameter of bore is reduced and the piston is stopped never happens. The sensor 42 detects the respective positions of the piston 70 and the slide table 14. FIGS. 8 and 9 show another embodiment according to the present invention. Those elements which are the same as corresponding elements in the above embodiments are designated by the same reference numerals, and a detail description thereof will be omitted. Above the long grooves 20a and 20b, the projecting parts 24 and 26 are formed by expanding the corner parts of the cylinder body 12; the first guide groove 28 is defined between the projecting part 24 and the slit 18; the second guide groove 30 is formed between the projecting part 26 and the slit 18. The first guide groove 28 includes an oblique surface 200 directing the vertical surface including the axis line of the cylinder body 12, whereas the second guide groove 30 likewise includes an oblique surface 202. Incidentally, the first guide groove 28 further includes a horizontal surface 204 connected to the oblique surface 200; the second guide groove 30 likewise includes a horizontal surface 206 connected to the oblique surface 202. Next follows a description of the slide table 14 of this embodiment. As shown in FIGS. 8 and 9, the slide table 14 includes a relatively thick plate 208; long grooves 210a and 210b are provided along the longitudinal direction of the plate 208. The respective long groove 210a and 210b are engaged, as shown in FIG. 8, with the leg members 212 and 214; the leg members 212 and 214 respectively include an oblique surface 216 which is slidably in contact with an oblique surface 200, and an oblique surface 218 which is slidably in contact with an oblique surface 202. It is preferable to coat friction-proof and durable synthetic resin material 220 and 222 around the part of the leg members 212 and 214. As is easily understood from FIG. 8, a distance between the leg members 214 and 212 can be adjusted by inserting a bolt (not shown) into a hole part indicated by a broken line and tightening the bolt. Thus, according to this embodiment with the above construction, suppose that an unexpected load is applied to the slide table 14 during the workpiece transferring. The unexpected load is indicated by numeral G in FIG. 8. At this time, the load G is transmitted via the leg member 212 and 214 so as to spread the oblique surfaces 200 and 202 of the cylinder body 12 (see broken line in FIG. 8). That is, the leg members 212 and 214 transmit the force via the synthetic resin material 220 and 222 while opening the expanding parts 24 and 26 via the oblique surfaces 200 and 202. These oblique surfaces 216, 218, 200 and 202 sufficiently receive such an overweight load. Therefore, even if the unexpected load G is applied to the slide table 14, the undesirable case disclosed in the prior art in which the diameter of the bore is reduced and the piston is stopped never happens. The sensor 42 detects the respective positions of the piston 70 and the slide table 14. FIG. 10 and FIG. 11 show still another embodiment according to the present invention. Above the long grooves 20a, 20b, 20c, and 20d, the projecting parts 24 and 26 are formed by expanding the corner parts of the cylinder body 12; a concave portion 300 is formed between the projecting part 24 and the slit 18. On both side parts of the concave part 300, a pair of rail members 304a and 304b are fixed while extending in its longitudinal direction by a bolt 302. The rail members 304a and 304b respectively include oblique surfaces 306a and 306b which are formed to be slanted by approximately 45°. Next follows a description of the slide table 14. The slide table 14 includes a relatively thick plate 308, as shown in FIGS. 10 and 11; the plate 308 includes, at a side surface opposite to the cylinder body 12, long grooves 310a and 310b which extend in its longitudinal direction. The long grooves 310a and 310b include therein guide members 312a and 312b. As is easily understood by FIG. 10, the guide members 312a and 312b include oblique surfaces 314a and 314b which are concave parts corresponding to the oblique surfaces 306a and 306b; ball bearings 316 are provided in the longitudinal direction of the oblique surface 314a and 314b with a predetermined interval, the part of the spherical surface of the ball bearings 316 touches the oblique surfaces 306a and 306b. According to the present invention, even if an overweight load is applied to the slide table, the smooth operation can be retained without stopping the slide table and the piston. In addition, the leg member is not necessarily formed to be extended from the slide table to the cylinder tube body, a width of the slide table can be made equal to or smaller than that of the cylinder tube body. Therefore, the present invention has a remarkable advantage in that the device can be made small in size.

Claims: A rodless cylinder comprises: a cylinder body (12), extending in a longitudinal direction of a cylinder tube with both ends occluded, which defines a slit (18) communicating a bore (16) to the exterior; a piston (70) which reciprocates inside the bore (16) of said cylinder body (12); a slide table (14), connected to said piston (70) via a coupling member (82) extending through said slit (18), which moves in accordance with the reciprocating motion of said piston (70); a sealing member (90, 100) engaged with said piston (70) and/or said slide table (14) so as to occlude the slit (18); first (54a, 54c, 212) and second (54b, 54d, 214) load transmitting means for extending from said slide table (14) to said cylinder body (12) and for holding the coupling part; and first (56a, 56b, 24) and second (58a, 58b, 26) load receiving means provided on said cylinder body (12) so as to correspond to said first (54a, 54c, 212) and second (54b, 54d, 214) load transmitting means, said first load transmitting means (54a, 54c, 212) transmitting, when a first lateral load is applied to said slide table (14), the first lateral load to said first load receiving means (56a, 56b, 24) so as to widen said slit (18), whereas said second load transmitting means (54b, 54d, 214) transmitting, when a second lateral load directing opposite to the first lateral load is applied to said slide table (18), the second lateral load to the second load receiving means (58a, 58b, 26) so as to widen said slit (18); whereby the first (56a, 56b, 24) and second (58a, 58b, 26) load receiving means comprise guide grooves (28, 30) provided in the cylinder body (12) at both sides of the slit (18) and each having a pair of guide surfaces (32a, 32b, 34a, 34b; 200, 202, 204, 206) capable to support lateral loads as well as vertical loads applied from the slide table (14) by load transmitting means extending from said slide table (14) which are engaged and in contact to the guide surfaces (32a, 32b, 34a, 34b; 200, 202, 204, 206) of the guide grooves (28, 30). A rodless cylinder according to claim 1, wherein said first (54a, 54c) and second (54b, 54d) load transmitting means each comprise bearings, and said first and second load receiving means (56a, 56b, 58a, 58b) each comprise bearing rolling surfaces mounted on said cylinder body (12). A rodless cylinder according to claim 2, wherein said bearing rolling surfaces functioning as said first and second load receiving means each comprise rail members (56a, 56b, 58a, 58b) mounted on said cylinder body (12). A rodless cylinder according to claim 1 or 2, wherein said first and second load receiving means (56a, 56b, 58a, 58b) each comprise side surfaces each of which receives, when a load is applied to a top surface of said slide table (14), a force spreading toward the exterior via said first and second load transmitting means (54a, 54b, 54c, 54d) fixed on said slide table (14). A rodless cylinder according to one of claims 1 to 4, wherein a side surface of said first and second load receiving means (56a, 56b, 58a, 58b) is displaced by an angle of 45° against a vertical surface including the axis line along which the piston (70) reciprocates, the other side surface of said first and second load receiving means (56a, 56b, 58a, 58b) is displaced by 90° against the side surfaces displaced by 45°. A rodless cylinder according to claim 2, wherein said bearings each have substantially hexagonal sections. A rodless cylinder according to claim 1, wherein said first and second load receiving means (24, 26) are each provided on one surface of said cylinder body (12) at a side of said slide table (14), and each comprise guide grooves (28, 30) having a pair of first oblique surfaces (200, 202) each directing a vertical surface which includes an axis line of said cylinder body (12), whereas said first and second load transmitting means (212, 214) are engaged with the guide grooves (28, 30) on a surface of said slide table (14) at a side of said cylinder body (12), and each comprise guide means having second oblique surfaces (216, 218) engaged with said first oblique surfaces (200, 202) and directing the exterior of said cylinder body (12) so as to displace said slide table (14) in response to the piston's (70) reciprocating motion. A rodless cylinder according to claim 7, wherein said guide means comprise a pair of projecting parts (212, 214) each having oblique surfaces (216, 218) directing a direction along which the guide grooves (28, 30) open each other. A rodless cylinder according to claim 8, wherein at least one of a pair of projecting parts (212, 214) is displaceable against the other projecting part (212, 214). A rodless cylinder according to one of claims 8 or 9, wherein said projecting parts (212, 214) each have synthetic resin films (220, 222) on a surface which is slidably in contact with said guide grooves.

Inventors: MIYAMOTO MICHIKAZU, TAKADA YOSHIYUKI, MIYAMOTO, MICHIKAZU, TAKADA, YOSHIYUKI, Miyamoto, Michikazu, c/o SMC K.K.Tsukuba Gijutsu, Takada, Yoshiyuki, c/o SMC Kabushiki Kaisha
Applicants: SMC KK, SMC KABUSHIKI KAISHA
Application year: 1992
Main classification: F15B15
IPC codes: F16C29, F15B15