Abstract:
A magnet-type rodless cylinder ( 1 ) is provided with a guide mechanism having an outer rolling groove ( 26 ), an inner rolling groove ( 29 ), a cylinder body ( 32 ), a pair of connection paths ( 34 ) for connecting an area between the outer rolling groove and the inner rolling groove with the cylinder body, and a plurality of steel bails ( 36 ) that can roll within an endless circuit ( 35 ) formed of the cylinder body, the connection paths and the area between the outer rolling groove and the inner rolling groove, wherein the connection paths ( 34 ) are formed at a pair of inner members, i.e. return caps ( 33 ), disposed on the inner sides of metal end plates ( 12 ) that are attached to the front and rear ends in the sliding direction of a sliding body ( 4 ).

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to a magnet-type rodless cylinder comprising a base with a U-shaped cross-section which is provided with a left and right air of side wall parts, a cylinder tube which holds a piston which is provided parallel to side wall parts inside it, a slide member which can slide along the cylinder tube at an outer circumferential surface of the cylinder tube, the piston and side member being integrally joined by a magnetic coupling force and the slide member being able to move tracking movement of the piston, and guide mechanisms which are provided between the side wall parts and the slide member. 
       BACKGROUND ART 
       [0002]    Known in the art is a magnet-type rodless cylinder which is provided with a base with a U-shaped cross-section which is provided with a left and right pair of side wall parts, a pair of end caps which are provided at the two ends of the base, a cylinder tube which holds a piston to be able to move back and forth in the axial direction and which is provided parallel to the side wall parts between the same, and a slide member which is passed over the cylinder tube and which is arranged between the side wall parts of the base, the piston and the slide member being magnetically coupled. Accordingly, if supplying the inside of the cylinder tube with compressed air or other fluid to make the piston move inside of the cylinder tube, the slide member can move integrally with the piston. 
         [0003]    In such a magnet-type rodless cylinder, guide mechanisms are given for guiding the slide member with respect to the cylinder tube with a high precision. As such guide mechanisms, for example, PLT 1 discloses structures which provide inside load ball-use guide grooves at the two side surfaces of a driven table (slide member) and outside load ball-use guide grooves at inside surfaces of guide rails (base), which provide no-load ball-use guide bores at the inside of the slide member, which provide circulating paths which connect the inside load ball-use guide grooves and no-load ball-use guide bores at end caps which are fastened to the two end faces of the slide member, and which hold ball-shaped rollers at endless circulating paths which are comprised of these guide grooves, guide bores, and circulating paths. 
       CITATIONS LIST 
     Patent Literature 
       [0004]    PLT 1: Japanese Patent No 3767648 
       SUMMARY OF INVENTION 
     Technical Problem 
       [0005]    However, in the above conventional guide mechanisms, circulating paths which form endless circulating paths are directly formed at the plastic end caps of the slide member. At the end caps, reamer bolts are screwed into the locations which abut against shock absorbers at the stroke ends. Accordingly, the total length of the slide member becomes longer and conversely the stroke ends up being limited. Further, to form internal threads for the reamer bolts to be screwed into, it is necessary to enlarge the width direction of the slide member. Further, it is necessary to arrange shock absorbers at the end sides of the end caps so as to correspond to the reamer bolts. There is therefore the problem of the magnet-type rodless cylinder becoming larger in size. Further, if removing the end caps for maintenance of the piston, scraper, etc, inside the slide member, the steel balls are liable to fall out from the circulating paths, so the work becomes troublesome. Furthermore, there is no place for attaching members which lubricate the grooves in which the rollers roll at the end caps. Accordingly, to provide these members, it is necessary to provide attachment members to the outsides of the end caps. There is therefore the problem that the total length of the slide member becomes longer. 
         [0006]    Therefore, the present invention has as its object the provision of a magnet-type rodless cylinder which has a longer total length of a slide member and is free of restrictions on its stroke and which can be made smaller overall and can be easily maintained. 
       Solution to Problem 
       [0007]    To achieve the above object, one aspect according to the present invention provides a magnet-type rodless cylinder comprising a base with a U-shaped cross-section which is provided with a left and right pair of side wall parts, a cylinder tube which holds a piston, which cylinder tube is provided in the base parallel to side wall parts of the base, a slide member which can slide along the cylinder tube and is provided at an outer circumferential surface of the cylinder tube, which slide member is integrally joined with the piston by a magnetic coupling force and can move tracking movement of the piston, and guide mechanisms for the slide member which are provided between. the pair of side wall parts and the slide member, wherein each of the guide mechanisms includes an outside rolling groove which is provided in the side wall part and which is parallel with the cylinder tube, an inside rolling groove which is provided in the slide member facing the outside rolling groove, a guide path which is parallel with the cylinder tube and provided at the slide member, a U-shaped pair of connecting paths which connect the space between the outside rolling groove and the inside rolling groove and the guide path, and a plurality of rollers which can roll inside an endless circulating path which is formed by the space between the outside roiling groove and the inside rolling groove, the guide path, and the connecting paths, and wherein the connecting paths are formed with a pair of inside members which are arranged at insides of metal end plates which are attached to the front and back ends of the slide member in the slide direction. In the present invention, lubricating members which lubricate the outside rolling grooves may be attached to the end plates. 
       Advantageous Effects of Invention 
       [0008]    According to the invention according to claim  1 , metal end plates are attached to the front and back ends of the slide member in the slide direction. At the insides of the end plates, inside members which form connecting paths are arranged and end plates are made to directly abut against the shock absorbers etc. at the stroke ends, so the total length of the slide member becomes shorter compared with the past. Further, it is not necessary to arrange shock absorbers at the end sides of the end caps so as to correspond to the bolt members attaching the end plates to the slide member, so the magnet-type rodless cylinder as a whole becomes smaller in size. Further, at the time of maintenance work on the inside of the slide member, even if detaching the end plates, the rollers will not fall out from the circulating paths and the maintenance of the piston, scraper, etc. can be easily performed. According to the invention according to claim  2 , in addition to the effect of claim  1 , it is possible to attach lubricating members which lubricate the outside rolling grooves at the end plates, so the total length of the slide member does not become longer. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0009]      FIG. 1  is a front view of a magnet-type rodless cylinder. 
           [0010]      FIG. 2  is a plan view which shows part of a magnet-type rodless cylinder in cross-section. 
           [0011]      FIG. 3  is a left side view of a magnet-type rodless cylinder. 
           [0012]      FIG. 4(   a ) is a cross-sectional view along the line A-A of  FIG. 2 , ( b ) is a cross-sectional view along the line B-B of  FIG. 2 , and (c) is a cross-sectional view along the line CC of  FIG. 2 . 
           [0013]      FIG. 5  is a cross-sectional view along the line DD of  FIG. 2 . 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0014]    Below, embodiments of the present invention will be explained. with reference to the drawings.  FIG. 1  is a front view which shows one example of a magnet-type rodless cylinder,  FIG. 2  is a plan view of the same, and  FIG. 3  is a left side view. A magnet-type rodless cylinder (below simply called a “rodless cylinder”)  1  includes a base  2  with a U-shaped cross-section which is provided with a left and right pair of side wall parts  3 ,  3 , a slide member  4  which is arranged between the side wall parts  3 ,  3  of the base  2  and can slide along the base  2 , and guide mechanisms  5 ,  5  which are provided between the side wall parts  3 ,  3  and the slide member  4 . 
         [0015]    At the two ends of the base  2  in the longitudinal. direction, a pair of end caps  6 ,  6  are provided. Between the facing surfaces of the end caps  6 ,  6 , a. cylinder tube  7  which is comprised of a nonmagnetic material is laid. Over the cylinder tube  7 , a slide member  4  which is comprised of a nonmagnetic material is run. The cylinder tube  7 , as shown in  FIGS. 4 and 5 , has a circular cross-sectional shape and forms inside it a circular cross-section cylindrical bore  8 . The two end parts of the cylindrical bore  8  are air-tightly fit with engagement members  9  which are attached to the end caps  6 ,  6  through O-rings  10 . Reference notations  11 ,  11  are shock absorbers which are provided at the end caps  6  and which abut against the end plates  12 ,  12  of the slide member  4  in the front and back of the slide direction at the stroke ends so as to absorb shock. Note that, the end plates  12 ,  12  are made of metal (here, iron) and are fastened to the side members  4  by bolts  12   a,    12   a.    
         [0016]    Further, inside the cylindrical bore  8  of the cylinder tube  7 , a piston  13  is housed to be able to move back and forth in the cylinder tube  7  in the axial direction and divides the cylindrical bore  8  into cylinder chambers  14 ,  14  at the front and back in the axial direction. The end caps  6  are formed with feed/eject ports  15 ,  15  which are communicated with the cylinder chambers  14  through passages formed at the axial centers of the engagement members  9 . 
         [0017]    Furthermore, the piston  13  is constructed from a center piston shaft  16  around which donut-shaped inside magnets  17 ,  17  . . . and similar shaped yokes  18 ,  18  . . . are alternately fit. The inside magnets  17  and yokes  18  are clamped and fastened from the two ends by the piston ends  19 ,  19 , The poles of the inside magnets  17  are arranged as SN, NS, SN, NS so that the same poles face each other in the axial direction. 
         [0018]    On the other hand, at the portion of the slide member  4  passing over the cylinder tube  7 , a circular cross-section bore  20  one size larger than the cylinder tube  7  is provided. Inside this bore  20 , donut-shaped outside magnets  21 ,  21  . . . which surround the circumference of the cylinder tube and similarly shaped yokes  22 ,  22  . . . are alternately arranged in the axial direction. By fastening end plates  12 ,  12  through tubular spacers  23 ,  23  which are arranged at the two ends of these outside magnets  21 ,  21  . . . and yokes  22 ,  22  . . . , the outside magnets  21  and yokes  22  are held inside the bore  20 . The poles of the outside magnets  21  are arranged as NS, SN, NS, SN so that the same poles face each other in the axial direction and different poles face the poles of the inside magnets  17  of the piston  13 . Accordingly, the piston  13  and the slide member  4  are integrally joined over the cylinder tube  7  by the magnetic coupling force between the inside magnets  17  and the outside magnets  21 . 
         [0019]    Next, the guide mechanisms  5  will be explained. However, side wall parts  3 ,  3  both have the same structures, so mainly one side will be explained. First, at the inside surface of each side wall part  3  of the base  2 , as shown in  FIGS. 2 and 4 , an outer groove  24  parallel with the cylinder tube  7  is formed over the entire length. Inside the outer groove  24 , an outer rail  25  is press fit or bonded. At the inner surface side of this outer rail  25  (slide member  4  side), a semicircular cross-section outside rolling groove  26  is provided across the entire length. 
         [0020]    On the other hand, at the side surface of the slide member  4  which faces the outer groove  24 , an inner groove  27  parallel with the outer groove  24  is formed. Inside of this inner groove  27 , an inner rail  28  is press fit or bonded. This inner rail  28  is smaller in thickness in the left-right direction compared with the outer rail  25 . At the outer surface side (side wall part  3  side), a semicircular cross-section inside roiling groove  29  is provided over the entire length. 
         [0021]    Furthermore, at the inside from each inner rail  28  at the slide member  4 , a bore  31  is formed parallel with the inner rail  28  and a tubular member  32  is housed in the bore  31 . At the front and back of this tubular member  32 , plastic return caps  33  which have U-shaped connecting paths  34  which connect the space between the outer rail  25  and inner rail  28  and the tubular member  32  are fastened at the insides of the end plates  12 ,  12  by screwing them in. Accordingly, by the space between the outer rail  25  and inner rail  28 , the tubular member  32 , and the connecting paths  34  of the return caps  33 , an endless circulating path  35  which is formed long in the front-back direction is formed. Inside this circulating path  35 , rollers constituted by a plurality of steel balls  36 ,  36  . . . are held. Reference numerals  37 ,  37  are lubrication members constituted as wipers which are provided at the end plates  12  and which fit at their front ends into the outside rolling grooves  26  of the outer rails  25 . 
         [0022]    In the above configured rodless cylinder  1 , the base  2  is fastened to a mounting member for use. Further, in the state with the top surface of the slide member  4  carrying a workpiece or other object, if feeding compressed air from either of the feed/eject ports  15 ,  15  of the left and right end caps  6 ,  6 , the piston  13  moves linearly through the cylindrical bore in the cylinder tube  7  in the axial direction. This being so, the slide member  4  which is integrally joined with the piston  13  by the magnetic coupling force between the inside magnets  17  and the outside magnets  21  tracks it and moves along the cylinder tube  7  back and forth in the axial direction. 
         [0023]    At the time of back and forth movement of this slide member  4 , at the guide mechanisms  5 ,  5 , the steel balls  36 ,  36  roll between the outer rails  25  and the inner rails  28  while circulating through the circulating paths  35 , so the inner rails  28  are guided to move along the outer rails  25  through the steel balls  36 . Accordingly, the slide member  4  moves back and forth by a stable posture. 
         [0024]    Here, when the slide member  4  reaches the stroke ends, the metal end plates  12  directly abut against the shock absorbers  11 , so the bolts  12   a  are not liable to loosen. Further, the return caps  33 ,  33  which are positioned at the two ends of the circulating paths  35  are arranged at the insides of the end plates  12 , so impact at the end plates  12  is hard to be transmitted to the return caps  33 . Accordingly, the circulating paths  35  are maintained. 
         [0025]    In this way, according to the rodless cylinder  1  of the above embodiment, by attaching metal end plates  12  to the front and back ends of the slide member  4  in the slide direction and arranging inside members forming the connecting paths  34  (return caps  33 ) at the insides of the end plates  12  to thereby make the end plates  12  directly abut against the shock absorbers  11  at the stroke ends, compared with the prior art, the total length of the slide member  4  becomes shorter. Further, there is no need to arrange shock absorbers  11  at the end sides of the end caps so as to correspond with the bolts  12   a  which attach the end plates  12  to the slide member  4 , so this leads to a reduced size of the rodless cylinder  1  as a whole. Further, at the time of maintenance work at the inside of the slide member  4 , even if removing the end plates  12 , the steel balls  36 ,  36  . . . will not fall out from the circulating paths  35  and the piston  13 , scraper, etc. can be easily maintained. 
         [0026]    In particular, here, the end plates  12  are provided with the wipers  37  which lubricate the outside rolling grooves  26 , so the total length of the slide member  4  does not become longer. 
         [0027]    Note that, in the above embodiment, the outside rolling grooves and the inside rolling grooves are formed at the outer rails and the inner rails, but it is also possible to eliminate these rails and directly form the outside rolling grooves and the inside rolling grooves at the side wall parts and the slide member. Further, tubular members are used to form the guide paths, but it is also possible to eliminate the tubular members and use the bores as they are as the guide paths. Furthermore, it is not necessary to provide wipers between the end plates and return caps. 
         [0028]    Further, in the rodless cylinder of the above embodiment, a structure has been explained where the piston is made to advance and retract inside a single cylindrical bore of a slide tube with a circular cross-section so as to make it magnetically couple with the slide member, but the invention is not limited to this. For example, the present invention can also be applied to a rodless cylinder which forms a pair of cylindrical bores inside a slide tube with an elliptical cross section and houses pistons in the cylindrical bores to be magnetically coupled with the slide member. 
         [0029]    Note that, the present invention has been explained in detail based on specific embodiments, but a person skilled in the art could make various changes, corrections, etc. without, departing from the claims and concepts of the present invention. 
       REFERENCE SIGNS LIST 
       [0000]    
       
           1  magnet-type rodless cylinder 
           2  base 
           3  side wall part 
           4  slide member 
           5  guide mechanism 
           6  end cap 
           7  cylinder tube 
           8  cylindrical bore 
           12  end plate 
           13  piston 
           14  cylinder chamber 
           17  inside magnet 
           21  outside magnet 
           24  outer groove 
           25  outer rail 
           26  outside rolling groove 
           27  inner groove 
           28  inner rail 
           29  inside rolling groove 
           32  tubular member 
           33  return cap 
           34  connecting path 
           35  circulating path 
           36  steel ball