Patent Publication Number: US-6038959-A

Title: Cylinder device for displacing workpiece

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a cylinder device disposed between feed lines, for example, for displacing a workpiece a predetermined distance. 
     2. Description of the Related Art 
     It has heretofore been customary for factories to have workpiece feed systems which comprise a plurality of feed conveyors or feed rollers. Such a workpiece feed system has a plurality of feed lines including first and second feed lines that extend perpendicularly to each other and a transfer unit disposed at the junction of the first and second feed lines for lifting a workpiece fed from the first feed line and transferring the lifted workpiece to the second feed line. 
     The present invention is concerned with an improvement in a cylinder device disclosed in U.S. patent application Ser. No. 08/582,911, which is used as a transfer unit and has a low profile for space-saving purpose. 
     SUMMARY OF THE INVENTION 
     It is a general object of the present invention to provide a cylinder device which is capable of producing an increased output power for displacing a workpiece. 
     A major object of the present invention is to provide a cylinder device which can handle an increased variety of workpieces with an increased output power for greater performance. 
     Another object of the present invention is to provide a cylinder device which is capable of dampening shocks produced when a piston or a cylinder reaches ends of the stroke of displacement thereof. 
     Still another object of the present invention is to provide a cylinder device which has a low profile or a reduced height or vertical dimension to allow effective utilization of a vertical space. 
     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 preferred embodiments of the present invention are shown by way of illustrative example. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a cylinder device according to a first embodiment of the present invention; 
     FIG. 2 is a perspective view of the cylinder device shown in FIG. 1, with a top plate thereof being elevated; 
     FIG. 3 is a bottom view of the cylinder device shown in FIG. 1; 
     FIG. 4 is a vertical cross-sectional view taken along line IV--IV of FIG. 3; 
     FIG. 5 is a vertical cross-sectional view of the cylinder device shown in FIG. 4, with the top plate thereof being elevated; 
     FIG. 6 is a plan view of a workpiece feed system which incorporates the cylinder device shown in FIG. 1 that is disposed at the junction of first and second feed lines; 
     FIG. 7 is a front elevational view of the cylinder device that is incorporated in the workpiece feed system shown in FIG. 6; 
     FIG. 8 is a perspective view of a cylinder device according to a second embodiment of the present invention; 
     FIG. 9 is a vertical cross-sectional view taken along line IX--IX of FIG. 8; and 
     FIG. 10 is a vertical cross-sectional view of the cylinder device shown in FIG. 9, with a top plate thereof being elevated. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     As shown in FIG. 1, a cylinder device 10 according to a first embodiment of the present invention basically comprises a substantially square base plate 12, a casing 20 fastened to a stepped surface of the base plate 12 by four screws 14 (see FIG. 3) and having a through hole 16 (see FIGS. 4 and 5) of substantially circular cross section defined therein which receives a cylinder 18 for vertical movement therein, and a top plate 22 having a shape substantially which is the same as the shape of the base plate 12 and fixed to an upper end of the cylinder 18. 
     As shown in FIGS. 4 and 5, a pair of ring-shaped first gaskets 24a, 24b is disposed between joined surfaces of the top plate 22 and the cylinder 18. A ring-shaped second gasket 26 is disposed between joined surfaces of the base plate 12 and the casing 20. A ring-shaped third gasket 28 is disposed between sliding surfaces of the cylinder 18 and the casing 20, the ring-shaped third gasket 28 being received in an annular groove defined in the casing 20. 
     As shown in FIGS. 1 and 2, four threaded attachment holes 30a-30d are defined in respective four corners of the base plate 12, and four threaded attachment holes 32a-32d are defined in respective four corners of the top plate 22. The cylinder device 10 may be fastened to another device by screws threaded into the attachment holes 30a-30d in the base plate 12, and similarly may be fastened to another device by screws threaded into the attachment holes 32a-32d in the top plate 22. The casing 20 has its four corners 34 near the respective attachment holes 30a-30d, which are recessed as concave surfaces to expose the attachment holes 30a-30d. 
     The casing 20 also has three pairs of substantially parallel, spaced attachment grooves 36a, 36b, 36c (see FIG. 3) defined in respective three outer side surfaces thereof and each having a modified T-shaped cross section. The attachment grooves 36a, 36b, 36c extend in the directions indicated by the arrow X (see FIG. 1), i.e., the direction perpendicular to the base and top plates 12, 22. The casing 20 also has three pairs of substantially parallel sensor attachment grooves 38a, 38b, 38c defined in the respective three outer side surfaces thereof and extending in the directions indicated by the arrow X. The pair of sensor attachment grooves 38a is positioned intermediate between the attachment grooves 36a, the pair of sensor attachment grooves 38b intermediate between the attachment grooves 36b, and the pair of sensor attachment grooves 38c intermediate between the attachment grooves 36c. 
     The cylinder device 10 can horizontally be supported by headed retainers (not shown) fitted in the respective attachment grooves 36a, 36b, 36c, the headed retainers being shaped complementarily to the attachment grooves 36a, 36b, 36c. Since the attachment grooves 36a, 36b, 36c extend in the directions indicated by the arrow X, the headed retainers can be adjusted in their vertical positions along the attachment grooves 36a, 36b, 36c. 
     The casing 20 has a pair of fluid inlet/outlet ports 40a, 40b defined in an outer side surface thereof other than the other three outer side surfaces where the attachment grooves 36a-36c, 38a-38c are defined. As shown in FIGS. 3 and 4, the fluid inlet/outlet port 40a communicates with first and third cylinder chambers 46a, 46c (described later on) through a first fluid passage 42 defined in the base plate 12 and a second fluid passage 44 branched from the first fluid passage 42. 
     The other fluid inlet/outlet port 40b communicates with a second cylinder chamber 46b (described later on) through a third fluid passage 47 defined in the base plate 12 and a fourth fluid passage 48 branched from the third fluid passage 47. A cylindrical bushing (guide member) 50 made of synthetic resin or the like is coaxially fitted in an inner wall surface of the through hole 16 of circular cross section that is defined in the casing 20. 
     The first and second fluid passages 42, 44 serve as a first communication passageway, and the third and fourth fluid passages 47, 48 as a second communication passageway. 
     A piston 54 is fixedly mounted substantially centrally on the base plate 12, i.e., centrally in the casing 20, by screws 52a, 52b. The piston 54 is disposed in a large-diameter hole defined in the cylinder 18 and extending axially in the directions indicated by the arrow X. The piston 54 has a larger-diameter end portion on which there is mounted a seal ring 56 that is received in an annular groove defined in an outer circumferential edge of the larger-diameter end portion. The cylinder 18, which is of a substantially cylindrical shape, slidably disposed in the through hole 16 for sliding movement guided by the bushing 50. The large-diameter hole defined in the cylinder 18 is divided into the first cylinder chamber 46a and the second cylinder chamber 46b by the larger-diameter end portion of the piston 54 and the seal ring 56. 
     The first cylinder chamber 46a communicates with the fluid inlet/outlet port 40a through the first fluid passage 42 defined in the base plate 12 and the second fluid passage 44 that is defined axially in the piston 54. The second cylinder chamber 46b communicates with the fluid inlet/outlet port 40b through the third fluid passage 47 defined in the base plate 12 and the fourth fluid passage 48 that is defined axially in the piston 54. 
     A rod cover 58 is secured by staking to a lower end of the cylinder 18 in surrounding relation to the piston 54 for displacement in unison with the cylinder 18. An O-ring 60 is fitted in an annular groove defined in an inner circumferential surface of the rod cover 58 which is held in sliding contact with the piston 54. The third cylinder chamber 46c is defined below the rod cover 58 and surrounded by the cylinder 18, the rod cover 58, the piston 54, and the base plate 12. The third cylinder chamber 46c is held in communication with the fluid inlet/outlet port 40a through a communication passageway 62 that is branched from the first fluid passage 42 defined in the base plate 12. The first cylinder chamber 46a serves as a chamber defined between the top plate 22 and a piston-head end of the piston 54, and the second cylinder chamber 46b and the third cylinder chamber 46c serve as chambers defined between the base plate 12 and a piston-rod end of the piston 54. 
     The fluid inlet/outlet port 40a communicates with the first cylinder chamber 46a and the third cylinder chamber 46c through the first fluid passage 42, the second fluid passage 44, and the communication passageway 62, and the other fluid inlet/outlet port 40b communicates with the second cylinder chamber 46b through the third fluid passage 47 and the fourth fluid passage 48. The first, second, and third gaskets 24a, 24b, 26, 28, the seal ring 56, and the O-ring 60 serve as sealing means for hermetically sealing the first, second, and third cylinder chambers 46a, 46b, 46c. 
     As illustrated in FIG. 4, the cylinder 18 has a width W greater than a height H thereof. The cylinder 18 can be lifted in the direction indicated by the arrow X 1  by a fluid under pressure introduced into the first cylinder chamber 46a and the third cylinder chamber 46c as shown in FIG. 5, and lowered in the direction indicated by the arrow X 2  by a fluid under pressure introduced into the second cylinder chamber 46b as shown in FIG. 4. 
     Two axially spaced ring-shaped dampers 64a, 64b are mounted on the piston 54 respective at the larger-diameter end portion thereof and at the base plate 12. When the piston 54 is lifted and lowered, the rod cover 58 abuts against the dampers 64a, 64b to dampen shocks and reduced noise at ends of the stroke of displacement of the piston 54. The rod cover 58 serves as a stop at the stroke end of upper movement of the cylinder 18 when engaging the larger-diameter end portion of the piston 54. 
     As can be seen from FIG. 3, the piston 54, the rod cover 58, and the cylinder 18 are coaxial with each other around a point O where the diagonal lines of the substantially square base plate 12 intersect with each other. 
     Magnets 66 (see FIGS. 3 through 5) are supported on or closely to an outer circumferential surface of the cylinder 18 near the sensor attachment grooves 38a, 38b, 38c defined in the casing 20. Sensors 66 (see FIGS. 1 through 3) held in the sensor attachment grooves 38a, 38b, 38c at given positions act magnetically with the magnets 66 to detect the vertical position of the cylinder 18 with respect to the casing 20. The cylinder 18 has a vertical guide hole 70 (see FIGS. 3 and 4) defined therein and spaced a predetermined distance from the point O, and a guide rod (rotation prevention means) 72 fixed to the base plate 12 is slidably inserted in the guide hole 70. The guide rod 72 serves to prevent the cylinder 18 from rotating with respect to the casing 20 and also to guide the cylinder 18 to move with respect to the casing 20. The guide hole 70 and the guide rod 72 may be dispensed with if the outer surface of the cylinder 18 and the inner surface of the casing 20 are not cylindrical, but angular, in shape. 
     Operation and advantages of the cylinder device 10 according to the first embodiment will be described below. 
     As shown in FIG. 6, a workpiece feed system which incorporates the cylinder device 10 has a first feed line 76 which comprises a plurality of substantially parallel feed rollers 74a-74f that can be rotated about their own axes by a driver source (not shown), and a second feed line 80 which comprises a plurality of substantially parallel feed rollers 78a-78c extending substantially perpendicularly to the feed rollers 74a-74f and rotatable about their own axes by a driver source (not shown) for feeding a workpiece in a direction substantially perpendicular to the first feed line 76. 
     The cylinder device 10 is fixedly mounted on a base 82 (see FIG. 7) below the first feed line 76 by screws threaded in the attachment holes 30a-30d. The top plate 22 of the cylinder device 10 supports thereon a workpiece feeder 88 that comprises a pair of substantially parallel feed belts 86a, 86b trained around guide rollers 84a, 84b. The feed belts 86a, 86b can be moved in a circulatory manner in the direction indicated by the arrow (FIG. 7) by a drive source (not shown) operatively coupled to the guide rollers 84a, 84b. The feed belts 86a, 86b extend substantially parallel to the feed rollers 74a-74f, and are positioned between the feed rollers 74b, 74c and between the feed rollers 74d, 74e. The fluid inlet/outlet ports 40a, 40b are connected to a pressurized fluid source (not shown) through tubes or the like. 
     After the above preparatory process, a workpiece W is fed in the direction indicated by the arrow A (FIG. 6) and detected by a detector (not shown) when it reaches a predetermined position above the feed belts 86a, 86b. In response to an output signal from the detector, a directional control valve (not shown) is operated to supply the fluid inlet/outlet port 40a with a fluid under pressure, e.g., air under pressure, from the pressurized fluid source. At the same time, the other fluid inlet/outlet port 40b is vented to the atmosphere by the directional control valve. 
     The fluid under pressure supplied to the fluid inlet/outlet port 40a flows through the first and second fluid passages 42, 44 into the first cylinder chamber 46a, where there is developed a pressure buildup that moves the top plate 22 in the direction indicated by the arrow X 1 . The fluid under pressure supplied to the fluid inlet/outlet port 40a is also introduced through the communication passageway 62 into the third cylinder chamber 46c substantially at the same time that the fluid under pressure is introduced into the first cylinder chamber 46a. Therefore, the cylinder 18 is also moved in the direction indicated by the arrow X 1  under a pressure buildup developed in the third cylinder chamber 46c. 
     Since the fluid under pressure supplied to the fluid inlet/outlet port 40a is also introduced through the communication passageway 62 into the third cylinder chamber 46c substantially at the same time that the fluid under pressure is introduced into the first cylinder chamber 46a, the pressure-bearing area in the first cylinder chamber 46a and the pressure-bearing area in the third cylinder chamber 46c are combined to bear the pressure of the fluid introduced into the cylinder device 10. Consequently, the cylinder device 10 can produce an increased output power for lifting the top plate 22. 
     The top plate 22 is elevated together with the cylinder 18 in the direction indicated by the arrow X 1  while being guided by the guide rod 72, until it reaches an end of its stroke of displacement when the rod cover 58 engages the larger-diameter end portion of the piston 54 as shown in FIG. 5. At this time, inasmuch as the rod cover 58 abuts against the damper 64a, shocks are dampened and not large noise is generated. 
     The feeder 88 is also lifted in unison with the top plate 22 in the direction indicated by the arrow X 1 . The feed belts 86a, 86b project upwardly between the feed rollers 74b, 74c and between the feed rollers 74d, 74e, as indicated by the two-dot-and-dash lines in FIG. 7. The workpiece W is lifted a certain distance off the feed rollers 74a-74f and is supported by the feed belts 86a, 86b. The feed belts 86a, 86b are then moved to transfer the workpiece W onto the second feed line 80 perpendicular to the first feed line 76, after which the workpiece W is fed to a desired position by the second feed line 80. 
     After the workpiece W has been transferred onto the second feed line 80, the directional control valve is operated to supply the fluid under pressure to the other fluid inlet/outlet port 40b, from which it is introduced through the third and fourth fluid passages 47, 48 into the second cylinder chamber 46b. The top plate 22 is now lowered in unison with the cylinder 18 in the direction indicated by the arrow X 2  until it returns to its original position as shown in FIG. 4. At this time, the fluid inlet/outlet port 40a is vented to the atmosphere by the directional control valve. 
     According to the first embodiment, as described above, the fluid under pressure supplied to the fluid inlet/outlet port 40a is also introduced through the communication passageway 62 into the third cylinder chamber 46c substantially at the same time that the fluid under pressure is introduced into the first cylinder chamber 46a, so that the pressure-bearing area in the first cylinder chamber 46a and the pressure-bearing area in the third cylinder chamber 46c are combined to bear the pressure of the fluid introduced into the cylinder device 10. As a result, the cylinder device 10 can produce an increased output power for lifting the top plate 22 and hence can lift heavy workpieces W. Because the cylinder device 10 can produce an increased output power, it exhibits increased performance or an increased workpiece lifting capability for handling an increased range of workpieces S. 
     Furthermore, inasmuch as the height H of the cylinder 18 is small relatively to the width W thereof, the cylinder device 10 has a relatively low profile or small vertical dimension for effective utilization of a vertical space. The cylinder device 10 can thus be used in limited vertical spaces with large freedom. 
     FIGS. 8 through 10 show a cylinder device 90 according to a second embodiment of the present invention. Those parts shown in FIGS. 8 through 10 which are identical to those shown in FIGS. 1 through 7 are denoted by identical reference numerals, and will not be described in detail below. 
     As shown in FIG. 8, the cylinder device 90 differs from the cylinder device 10 in that the piston 54 is positioned such that its central axis is displaced eccentrically from the point O, and no guide rod is used to prevent a cylinder 92 from rotating with respect to the casing 20. Other structural details of the cylinder device 90 are the same as those of the cylinder device 10. 
     In the first and second embodiments, the cylinder 18 (92) is vertically displaced with respect to the piston 54 fixedly mounted on the base plate 12. However, the base plate 12 may be oriented such that its plane extends vertically to displace the cylinder 18 (92) horizontally with respect to the piston 54 fixedly mounted on the base plate 12. 
     Although certain preferred embodiments of the present invention has been shown and described in detail, it should be understood that various changes and modifications may be made therein without departing from the scope of the appended claims.