PALLET REPLACING APPARATUS

Abstract: This invention relates to a pallet replacing apparatus most suitable for use in machine tools and the like. Conventional pallet replacing apparatuses are large in scale and complicated in structure. If a large-scale hydraulic cylinder or motor is used, a pallet replacing speed cannot be increased. This invention solves the problems described above. This invention uses driving means (3) for a table (2). A moving mechanism (12) consists of a chain (66), sprockets (64), (65), and the like. A pallet (4) is moved in the same direction as the moving direction of the table (2) when the driving mechanism (12) is driven by the driving force of the driving means (3).

Description: This invention relates to a pallet changer for a machine tool provided with pallets according to the preamble of claim 1. Such a pallet changer with means for feeding work to a machine tool is disclosed in GB 2 092 487 corresponding to JP-B-61013937. The machine tool includes a machining table comprising a base table drivable in the y-direction and a co-ordinating table which is movable under NC-control on the base table in the x-direction. A table part is secured to the co-ordinating table. The means for feeding work include pallets movable from a base frame on to the table part or the co-ordinating table under the positive direction of the controlled relative movement at the base table and the co-ordinating table. The x-axis driving means and the y-axis driving means of the machine tool are used to perform the pallet-changing function so that no special drive means is required for this. It is required, however, that the pallets have surfaces which, together with the surface of the base table part, form machining surfaces whereby at least the machining surfaces at the pallets are uniplanar. FMS (flexible manufacturing system) has a machine tool and a pallet changer. The pallet changer exchanges a pallet on a table of the machine tool for another pallet. The conventional pallet changer is a hydraulic cylinder type or a chain type. In case of the pallet changer of a hydraulic cylinder type, a rod of the hydraulic cylinder is extended so that a pallet is settled on the table of the machine tool. After a work on the pallet is machined, the rod is contracted so that the pallet is returned. In case of the pallet changer of a chain type, a plurality of pallets are set to the chain at regular intervals. The chain is drived by a motor so that the pallet is transfered to a pallet changing place near the table of the machine tool. But, the pallets and the works are considerably heavy. In case of the pallet changer of a hydraulic cylinder type, a large hydraulic cylinder is needed. In case of the pallet changer of a chain type, a large motor and a big chain are needed. In both cases, the pallet changer is big in size and it's construction is complicated. When the large hydraulic cylinder or the large motor in the pallet changer starts or stops, the pallet changer is shokked. The shock is caused by the inertia of the heavy pallets and the works on the pallets. To avoid the shock, the large hydraulic cylinder and the large motor must be slowly operated. The technical problem of the invention is to provide an improved pallet changer whose construction is simple. This problem is solved by a pallet changer according to the preamble of claim 1, and wherein the transfer means comprises a guide body fixed to said table; a slide body slidably supported along said first axis by the guide body; a first sprocket and a second sprocket provided at one end and at the other end of the slide body; a chain connecting the first sprocket and the second sprokket; an engagement means for detachably engaging the chain and the pallet; a mechanism part for moving the chain comprising a pinion engaging a rack, a chain hook fixed on said chain and a stopper pin removably engaging said chain hook so that the slide body slides relative to the table in the first direction or the second direction and that the pallet slides in said first direction or in said second direction as the table moves in the first direction or the second direction by means of said driving means. In the pallet changer according to this invention, the pallet moves in the same direction as the table's movement by means of the simple drive means such as the chain and the sprokkets, so that a large hydraulic cylinder and a large motor are not required. The construction of the pallet changer according to this invention is simple and the pallet changer is small in size. Using the pallet changer according to this invention, large cost saving can be obtained. In a preferred embodiment of the invention the driving means comprises a ball screw part having a nut fixed to the table and a feed screw connected to a servomotor. It is preferred that the table moves along a second axis perpendicular to the first axis. A preferred embodiment of the invention is now described in detail with reference to the accompanying drawings in which Fig. 1 is a diagrammatic view showing a pallet changer according to this invention. Fig. 2 is a front view showing a machining center equipped with a pallet changer according to this invention. Fig. 3 is a side view showing the machining center. Fig. 4 is a perspective view showing a pallet table. Fig. 5 is a front view showing a transfer means and so on. Fig. 6 is a top view showing the transfer means. Fig. 7 is a perspective view showing the transfer means. Fig. 8 is a sectional view taken along line A-A of Fig. 5, in which a pallet is clamped. Fig. 9 is a sectional view in which the pallet is unclamped. Fig. 10 is a sectional view taken along B-B of Fig. 5. Fig. 11 is a view showing the pallets on the pallet table. Fig. 12 is a view showing the pallet on the table. Fig. 13 to Fig. 19 are explanatory views showing pallet changing operations. The function at an embodiment on the invention is first briefly illustrated with reference to Fig. 1 and 2. Fig. 1 shows the pallet changer PC comprising a work carrier pallet 4 detachably and movably mounted to an table 2, and another work carrier pallet 14 set at a separate location (pallet table 30 in an embodiment of Fig. 2). The table 2 is provided on a support 1 (a support of machine tool in the embodiment) of the pallet changer. The table 2 moves along at least a first axis (the X-axis in the embodiment). The table 2 can reciprocately move along the first axis by means of drive means 3 such as a servomotor. The work carrier pallet 4 is detachably mounted to the table 2, and the work carrier can move on the table 2. A transfer means 12 transfers the work carrier pallet 4 on the table 2 in a first direction of arrow X1 and a second direction of arrow X2 opposite to the first direction. The pallet 4 moves by a drive power means 3 when the table 2 moves in the first direction of arrow X1 or the second direction of arrow X2. Pallet 4 is transfered by the drive means 3 only. No other drive means such as a hydraulic cylinder and a motor is required. The transfer means 12 has a guide body 62, a slide body 69, a first and a second sprocket 64, 65, a chain 66, an engagement means 67 and a mechanism part 100. The slide body 69 is supported by the guide body 62 fixed to the table 2 and can slide along the first axis. The first sprocket 64 and the second sprocket 65 are provided to one portion and another portion of the slide body 69. The chain 66 is set between the first and the second sprokkets 64, 65. By means of the engagement means 67, the chain 66 detachably engages the work carrier pallet 4. When the table 2 moves in the first direction of arrow X1 or in the second direction of arrow X2 by means of drive means 3, the mechanism part 100 drives the chain 66 so that the slide body 69 slides in the first direction of arrow X1 or in the second direction of arrow X2 relative to the table 2. Accordingly, the work carrier pallet 4 slides on the table 2 in the first direction of arrow X1 or in the second direction of arrow X2. The best mode for carrying out the invention is now described in detail. In Fig. 1 the pallet changer PC has a support 1 of a machine tool, a table 2, a drive means 3, a work carrier pallet 4 and a transfer means 12. The support 1 is settled on a floor. The table 2 is provided on the support 1. A work 5 is fixed to the work carrier pallet (hereinafter called the pallet for short) 4. The pallet 4 is mounted to the table 2 and movably along the X-axis. The table 2 can move along the X-axis, or in a first direction of arrow X1 or in a second direction of arrow X2 opposite to the first direction, by means of drive means 3 relative to the support 1. The transfer means 12 transfers the pallet 4 on the table 2 in the first direction of arrow X1 or in the second direction of arrow X2 when the table 2 moves in the first direction of arrow X1 or in the second direction of arrow X2. Fig. 2 shows a vertical machining center equipped with the pallet changer according to this invention. The support 1 has a bed 7 and a saddle 8. A servo motor 9 (for a movement along the Y-axis) is attached to the bed. The drive means 3 has a servo moter 10 (for a movement along the X-axis) and a bail screw 11. The table 2 is attached on the saddle 8. The pallet 4 is mounted to the table 2 detachably and movably along the X-axis. The transfer means 12 provided near the table 2. A column 20 has a spindle head 21. A tool 23 is attached to a spindle 22 of the spindle head 21. The spindle 22 rotates by means of a motor 24. The spindle head has a automatic tool changer 25. The column 20 also has a control panel 26, a CNC unit 27 and a control boad 28. The table 2 can move in the first direction of arrow X1 or in the second direction of arrow X2 by means of servomotor 10. A pallet table 30 is placed beside the table 2. Another pallet 14 is placed on the pallet table 30. In Fig. 3, a feed screw 34 of a ball screw part 33 is connected to the servomoter 9. The feed screw engages a nut 35. The nut 35 is mounted to the under portion of the saddle 8 so that the the saddle 8 can move along the X-axis by means of the servomotor 9. The spindle head 21 can move along the Z-axis by means of a servomotor 31. Fig. 3 shows a part of the transfer means 12, which is hereinafter explained. Fig.4 illustrates that the pallets 4 and 14 can be set side by side on the pallet table 30. The work 5 is fixed to the pallet 4 and another work 5 is fixed to the pallet 14. The pallet table 30 is equipped with two air cylinders 40, 41. Each air cylinder 40, 41 has a stopper pin 42, 43. Each stopper pin 42, 43 can be inserted into a hole 44, 45 of the pallet 4, 14. Thus, the pallet 4, 14 is placed in precise position. When the pallet 4, 14 is transfered, the stopper pin 42, 43 is extracted from the hole 44, 45. A pallet hook 63 is attached to the front portion of the pallet 4 along the longitudinal direction of the pallet 4. A pallet hook 91 is attached to the pallet 14 in the same way. Fig. 5 shows the saddle 8, the table 2, the pallet 4 which is also called a pallet table, and the transfer means 12. Fig 6 shows the transfer means 12. Fig 7 is a perspective view showing the transfer means 12. Fig. 5 shows that the transfer means 12 has a guide body 62, a slide body 69, an engagement means 67, a chain 66, a first and a second sprocket 64 and 65, and a mechanism portion 100. The guide body 62 is fixed to a base bracket 61. The base bracket is fixed to the table 2. The cylindrical guide body 69 is slidably supported by the guide body 62. The slide body 69 can slide along X-axis. The first and second sprocket is provided to one end and the other end of the slide body 69, respectively. The chain is provided between the sprockets 64 and 65. The chain 66 has a chain hook 90 for engaging the engagement means 67 and a chain hook 68 for engaging the mechanism part 100. The engagement means comprises the pallet hook 63 and the chain hook 90. The chain hook 90 is fixed to the chain 66. The chain hook 90 of convex shape engages the pallet hook 63 of concave shape. When the pallet hook 63 moves along the Y-axis (Fig. 3) relative to the chain hook 90, the pallet hook 63 disengages from the chain hook 90. The Y-axis is perpendicular to the X-axis. The chain hook 68 of concave shape is located above a stopper cylinder 92. The stopper cylinder 92 is upwardly fixed to the saddle 8. A pin 93 of the stopper cylinder 92 can be inserted into the chain hook 68. A rack 94 is fixed to the base bracket 61 along the X-axis. The rack 94 engages a pinion 95. The pinion 95 and the sprocket 64 are connencted to /or associated with to a shaft 96. The mechanism part 100 comprises the pinion 95, the rack 94, the chain hook 68 and the stopper pin 93. A proximity sensor 101 is associated with to the stopper cylinder 92. When the proximity sensor 101 detects the position of the chain hook 68, the pin 93 of the stopper cylinder 92 expands according to a command signal from the CNC device 27 (Fig. 2). The transfer mechanism 12 is covered by a cover 102. The pallet hook 63 is also covered by a cover 103. Because of these covers, cutting debris and a cutting oil can not enter inside these covers. Figs. 6 and 7 show the chain 66, the slide body 69, the guide body 62, the rack 94, the pinion 95, the sprocket 64, 65. The shaft 96 is rotatably attached to a connecting part 105. The connecting part 105 is fixed to one end of the slide body 69. A shaft 106 of the sprocket 65 is attached to the other end of the slide body 69. When the shaft is shifted by adjusting screws 104, 104, the tension of the chain 66 can be controlled. Fig. 8 is a sectional view taken along line A-A of Fig. 5. The table 2 in Fig. 8 has a slide portion 50, two clamp cylinders 51, a clamp unit 52, a clamp plate 53. The clamp unit 52 is fixed on the slide portion 50. One clamp cylinder 51 is located behind the other one. The clamp plate 53 is fixed to a rod 51a of the clamp cylinder 51. A nut 54 is fixed to an under surface of the slide portion 50. The feed screw 55 of the ball screw part 11 engages the nut 54. The feed screw 55 is connected to the servomoter 10. In Fig. 8, the rod 51a of the clamp cylinder 51 is contracted. The clamp plate clamps the pallet 4 against pins 54a, 54a. In Fig. 8, the transfer mechanism 12 comprises the chain 66, the sprocket 64, the slide body 69, the guide body 62, the chain hook 90, and the pallet hook 63. The clamp cylinder 92 is fixed to a bracket 57 which is fixed to the saddle 8. A pin 93 is guided by a pin guide 58. The chain hook 68 is located in a long groove 59 of the base bracket 61. In Fig. 9, the rod 51a of the clamp cylinder 51 expands and the clamp plate 53 unclamps the pallet 4. In this condition, the table 2 can move along the saddle 8 by means of servomotor 10. Fig. 10 is a sectional view taken along line B-B of Fig. 5. In Fig. 10, the transfer mechanism 12 has the pinion 95, the rack 94, a connecting portion 105, the chain 66, and the sprocket 64. In Fig. 11, the pallet 4 is located on the pallet table 30. The table 2 is located at a right end of the saddle 8. The table 2 moves in the first direction of arrow X1 by means of the servomotor 10. In this case, the pin 93 of the clamp cylinder 92 engages the chain hook 68 of the chain 66. The chain 66 rotates in the counter-clockwise direction so that the pinion 95 moves on the rack 94 in the first direction of arrow X1. The slide body 69 moves in the first direction of arrow X1 relative to the guide body 62 or the table 2. When the chain hook 90 engages the pallet hook 63 and the table 2 moves in the first direction of arrow X1, the pallet 2 moves in the first direction of arrow X1 relative to table 2. In such a manner, the pallet 4 is transfered from pallet stand to the table 2 as shown in Fig. 12. The pallet 4 is clamped at the table 2 as shown in Fig. 8. The pin 93 of the clamp cylinder 92 in Fig. 11 is removed from the chain hook 68. When the table moves along the X-axis to machine the work 5, the chain does not rotate. Accordingly, the pallet 4 does not move relative to the table 2. The work 5 is machined by predetermined tools. After the work is machined, the table 2 is transfered from the place in Fig. 12 to the other place in Fig. 11 in the following manner. The pin 93 of the clamp cylinder 92 is engaged with the chain hook 68 of the chain 66. The pallet 4 is unclamped as shown in Fig. 9. In this condition, the chain hook 90 engages the pallet hook 63. The table 2 is moved in the second direction of arrow X2 by means of the servomotor 10. At this time, the pin 93 of the clamp cylinder 92 engages the chain hook 68 of the chain 66. The chain 66 rotates clockwise so that the pinion moves in the second direction of arrow X2 in engaging with the rack 94. The slide member 69 moves in the direction of arrow X2 relative to the guide body 62 or the table 2. The chain hook 90 engages the pallet hook 63 so that the pallet 4 moves in the second direction of arrow X2 relative to the table 2 which moves in the direction of arrow X2. Thus, the pallet 4 is transfered from the table 2 to the pallet table 30 as shown in Fig. 11. By the before-mentioned manner, the pallet 4 is located at the table 2, and the work 5 is machined, and the pallet is transfered to the pallet stand 30. The process to transfer the pallet 4 and the pallet 14 to the table 2 is explained by referring to Fig. 13 and 19. In Fig. 13, the pallets 4, 14 are located on the pallet stand 30, and the table 2 is located in the initial position IP. The chain hook 90 is located at the left end of the chain 66. The table 2 moves in the second direction of arrow X2, and then next in the first direction of arrow Y1. Accordingly, the chain hook 90 moves at the right end of the chain 66 as shown in Fig. 14 and engages the pallet hook 63. The table 2 is then moved in the first direction of arrow X1. In Fig. 15, the pallet 4 is located on the table 2. The table 2 is located at the machining position P1. The spindle head 21 shown in Fig. 2 goes down so that a hole H (in Fig. 16) is machined in the work 5 by the tool 23. In Fig. 16, after the work 5 is machined, the table 2 is transfered to an another place SP. The table 2 moves in the second direction of arrow X2. When the table 2 moves, the pallet moves in the second direction of arrow X2 relative to the table 2. In Fig. 17, the pallet 4 is returned to the pallet stand 30. The table 2 is then moved in the direction of arrow Y2. As seen in Fig. 18 the chain hook 90 disengages the pallet hook 63, and engages a pallet hook 91 of the pallet 14. The table 2 moves in the first direction of arrow X1. The table 2 moves so that the pallet 14 also moves in the first direction of arrow X1 relative to the table 2. In Fig. 19 the table 2 is transfered at the machining position P1. The spindle head 21 in Fig. 2 goes down so that the work 5 is machined by a tool. In this a manner, the pallets 4 and 14 are located to the table 2 one by one, and the work 5 are machined. This invention is not restricted to the described embodiment. In case of the before-mentioned vertical machining center, a plurality of pallets are provided on the pallet stand placed on the side of the machining center. The table moves along the X-axis so that a plurality of pallets are exchanged. The pallet table can be settled in front of the vertical machining center, and a plurality of pallets can be placed on the pallet table. In this case, the table moves along the Y-axis so that the pallets are exchanged. Further, the pallet table can be settled on the side of a horizontal machining center, and a plurality of pallets can be placed on the pallet stand. In this case, the table moves along the X-axis so that the pallets are exchanged. The pallet stand may be settled in front of the horizontal machining center. In this case, the table moves along the Z-axis so that the pallets are exchanged. The number of the pallets is not restricted to two. Three or more pallets may be used. Furthermore, the pallet changer according to this invention can be applied to a general industrial machine such as a automatic tool assembly machine with X, Y table as well as a machine tool. In the embodiment in the drawings, the table 2 moves along the Y-axis and accesses the pallet 4 and 14 one by one. Furthermore, the pallet 4 and 14 on the pallet stand 30 can be moved (along the Y-axis) relative to the table 2. INDUSTRIAL APPLICABILITY This invention is useful as a pallet changer, and is compact in size and it's construction is simple.

Claims: A pallet changer for a machine tool provided with pallets (4, 14) comprising: a support (1), which is the support of said machine tool; a table (2) movable along a first axis (X) and supported by the support (1); a pallet (4) detachably mounted on said table (2) and being movable along said table; a pallet table (30) for holding at least one of said pallets (4, 14), said pallet table (30) being positioned next to the support (1); driving means (3) for moving the table (2) along the first axis (X) between the machine tool (1) and the pallet table (30); transfer means (12) for moving one of said pallets (4, 14) on the table (2) in a first direction (X1) along the first axis (X) or in a second direction (X2) along the first axis (X) but opposite to the first direction (X1) by means of a driving force of said driving means (3) as the table moves in the first direction (X1) or in the second direction (X2) wherein the pallet is moved only by the driving force of the driving means (3), characterised by that the transfer means (12) comprises: a guide body (62) fixed to said table (2); a slide body (69) slidably supported along said first axis (X) by the guide body (62); a first sprocket (64) and a second sprocket (65) provided at one end and at the other end of the slide body (69); a chain (66) connecting the first sprocket (64) and the second sprocket (65); an engagement means (67) for detachably engaging the chain and the pallet (4); a mechanism part (100) for moving the chain comprising a pinion (95) engaging a rack (94), a chain hook (68) fixed on said chain (66) and a stopper pin (93) removably engaging said chain hook (68) so that the slide body (69) slides relative to the table in the first direction (X1) or the second direction (X2) and that the pallet (4) slides in said first direction (X1) or in said second direction (X2) as the table moves in the first direction (X1) or the second direction (X2) by means of said driving means (3). A pallet changer according to claim 1, wherein the driving means comprises a ball screw part (10) having a nut fixed to the table and a feed screw/connected to a servomotor. A pallet changer according to claim 1, wherein the table moves along a second axis perpendicular to the first axis.

Inventors: KITAMURA KOICHIRO, KITAMURA, KOICHIRO
Applicants: KITAMURA MACHINERY CO LTD, KITAMURA MACHINERY CO.,LTD.
Application year: 1988
Main classification: B23Q7
IPC codes: B23Q7