Rodless cylinder

Abstract: The rodless cylinder includes a cylinder body (12), a piston (70), and a slide table (14) connected to the piston (70). The slide table (14) and the piston (70) are united with each other due to a coupling member (82) which projects through a slit (18) formed in a longitudinal direction of the cylinder body (12). The slide table (14) includes first and second load transmitting means (312), whereas the cylinder body (12) includes first and second load receiving means (304) corresponding to the first and second load transmitting means (312). 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 slider 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 quide 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. A similar rodless cylinder is disclosed in DE 34 03 830 A. The EP-A-0 476 265 representing a state of the art under Article 54 (3) 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 which comprises the features of independent claim 1. Further object of the present invention is to provide a rodless cylinder wherein the first and second load transmitters each comprise bearings, and the first and second load receivers each comprise bearing rolling surfaces mounted on the cylinder body. Another object of the present invention is to provide a rodless cylinder wherein the first and second load receivers each comprise guide surfaces each displaced by a predetermined angle against a surface which includes an axis line along which the piston reciprocates. Further object of the present invention is to provide a rodless cylinder wherein the guide surfaces of the first and second load receivers are each displaced by 45° against the surface which includes the axis line along which the piston reciprocates. Still further object of the present invention is to provide a rodless cylinder wherein a guide surface of the first and second load receivers is displaced by 90° against the guide surfaces displaced by 45°. Further object of the present invention is to provide a rodless cylinder wherein the guide surfaces of the guide members each comprise ball bearings to be engaged with the guide surfaces of the rail member. Still further object of the present invention is to provide a rodless cylinder wherein the guide surfaces of the rail members each comprises ball bearings to be engaged with the guide surfaces of the guide members. 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 the slide table and the cylinder body of the rodless cylinder according to the present invention; FIG . 4 shows a perspective view depicting the slide table shown in FIG. 3; 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; and 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. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 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 bypass passages 22a and 22b are formed for concentrated piping while extending in its longitudinal direction. FIG. 3 and FIG. 4 show a preferred 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°. 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. 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 and/or the slide table 14. Next follows a description of the slide table 14. The slide table 14 includes a relatively thick plate 308, as shown in FIGS. 3 and 4; 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. 3, 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 this embodiment with the above construction, if an unexpected load, for example, a load from a direction F1 shown in FIG. 3, is applied during the workpiece transferring, the load is first transmitted via a plurality of ball bearings 316 to the rail member 304b, and then transmitted to the cylinder body 12. Consequently, since the load enforces to widen the slit 18, the undesirable case disclosed in the prior art in which the diameter of the bore 16 is reduced and the piston 70 is stopped never happens during the workpiece transferring. This is likewise applied to a load in a direction F2. Incidentally, if a load in the direction G is applied to the slide table 14, it is transmitted by the right and left guide members 312a and 312b, via a plurality of ball bearings 316, to the right and left rail members 304a and 304b, and then transmitted to the cylinder body 12. Consequently, since the operating load is divided into such two directions as widen the slit 18, the undesirable case disclosed in the prior art in which the diameter of bore 16 is reduced and the piston 70 is stopped during the workpiece transferring never happens. 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 141 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. 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 comprising: a cylinder body (12), extending in a longitudinal direction of a cylinder tube with both ends thereof closed, which defines a slit (18) communicating a bore (16) to the exterior of the cylinder body (12); 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 is spaced a predetermined distance from the top surface of said cylinder body and which moves in accordance with 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 at least partially cover the slit (18); first (312a) and second (312b) load transmitters extending from said slide table (14) to said cylinder body (12) and first (304a) and second (304b) load receivers provided on said cylinder body (12) so as to correspond to said first (312a) and second (312b) load transmitters, wherein said first load transmitter (312a) transmits, when a first lateral load is applied to said slide table (14), the first lateral load to said first load receiver (304a) so as to at least partially widen said slit (18), whereas said second load transmitter (312b) transmits, when a second lateral load directed opposite to the first lateral load is applied to said slide table (14), the second lateral load to the second load receiver (304b) so as to at least partially widen said slit (18); characterized in that said first and second load receivers (304a, 304b) comprise a pair of rail members (304a, 304b) each having guide surfaces (306a, 306b), one of said surfaces (306b) being disposed opposite to a surface of said cylinder body (12) at a side of said slide table (14), whereas said first and second load transmitters (312a, 312b) are each engaged with said guide surfaces (306a, 306b) of the respective rail members (304a, 304b) on a surface of said slide table (14) at a side of said cylinder body (12) and each comprise guide members (312a, 312b) having guide surfaces (314a, 314b) so as to displace said slide table (14) in response to the piston's (70) reciprocating motion, and that when a load is applied in a direction (G) perpendicular to the directions (F1, F2) of the first and second lateral loads to a top surface of said slide table (14), said load results in a force applied via said first and second load transmitters (312a, 312b) fixed on said slide table (14) to said first and second load receivers (304a, 304b), said force acting to spread said first and second load receivers (304a, 304b) outwardly from each other so as to at least partially widen said slit (18). A rodless cylinder according to claim 1, wherein said first and second load transmitters (312a, 312b) each comprise bearings (316), and said first and second load receivers (304a, 304b) each comprise bearing rolling surfaces (314a, 314b) mounted on said cylinder body (12). A rodless cylinder according to claims 1 or 2, wherein said first and second load receivers (304a, 304b) each comprise guide surfaces (306a, 306b) each displaced by a predetermined angle against a surface including an axis line along which the piston (70) reciprocates. A rodless cylinder according to claim 3, wherein said guide surfaces (306a, 306b) are each displaced by 45° against a surface including the axis line along which the piston (70) reciprocates. A rodless cylinder according to claim 4, wherein a guide surface (306a) of said first and second load receivers (304a, 304b) is displaced by 90° against the guide surfaces (306b) displaced by 45°. A rodless cylinder according to claim 1, wherein said guide surfaces (314a, 314b) each comprise ball bearings (316) to be engaged with said guide surfaces (306a, 306b) of the rail member (304a, 304b). A rodless cylinder according to claim 1, wherein said guide surfaces (306a, 306b) of the rail members (304a, 304b) each comprise ball bearings (316) to be engaged with said guide surfaces (314a, 314b) of the guide members (312a, 312b).

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