SLIDE ADJUSTING DEVICE FOR A PRESS

Abstract: A slide adjusting device for a press comprises a slide adjusting screw (4) connected via a connecting rod (3) to a crank shaft (1) attached to a crown (2) of a press. The screw (4) includes a bearing (5) connected to a worm wheel (10) which is driven by a motor (18). At the lower end of the bearing (5) there is a cylindrical screw (8) which is internally and externally threaded. A press slide (30, 31, 32) is screwed to the outer periphery of the screw (8) whilst a piston (33) is engaged with the internal thread of the screw (8). An oil pressure chamber (35) is formed between the bottom of the piston and the slide. Should sticking of the press occur, the oil pressure in the chamber (35) is released to allow the slide to move vertically and release the sticking.

Description: The present invention relates to a slide adjusting device which enables adjustment of slide height and release of sticking. If the so-called sticking of a die, due to the material to be processed, occurs during a press operation, the press stops operating under elastic deformation (under pressure) due to sticking of the die with the material or its counter force and the slide becomes inoperable. Generally, a crank is operated in the reverse direction by increasing the clutch torque capacity to release this sticking between the die and the material. However, such procedure is often ineffective and it becomes necessary to employ other methods; for example, the die is cooled to release the stuck portion, or a jack is inserted between the slide and the bed to move the slide away. Alternatively, in a press having an assembled frame structure, the slide is moved by elongating the tie rod by heating, or the die holder or the connecting rod of the press is cut to release the stuck portion. The press itself or the die must be broken under certain circumstances. Overload protectors utilizing oil pressure are found to exhibit not only overload protection but a function to release sticking and are therefore effective in general purpose presses. In case of high speed blanking, precision punching, multi-functional progressing and the like operations where high precision press processes are required, the conventional overload protector is not, however, applicable because of difficulties in terms of mechanical precision and safety of its performance. Still another method of releasing sticking is by interposing a wedge member between a member which moves up and down with the rotation of the crank shaft and the slide, so that the wedge member can be displaced whenever sticking occurs and the press stops operating due to insufficient energy or excessive torque. The length of the slide is thus reduced to release the sticking. The above discribed device results in too complicated a construction, as it requires an additional wedge member which is irrelevant to the essential functions of a press. The method in which sticking is released by displacing the wedge member is defective in that since the wedge member must be displaced overcoming the pressure occurring at the time of sticking, a large size oil pressure cylinder and the like must be provided, thereby inconveniently increasing the size of the press. When a die attached to a slide is changed, the slide is accordingly adjusted to a height to suit the die. As a method for doing this, a worm wheel which is held vertically unmovable is provided on a connecting rod which connects a crank shaft and the slide so as to displace the slide relative to the connecting rod by rotating the worm wheel via a worm shaft driven by a motor. Generally in the prior art, as the worm shaft is axially provided to the slide, the motor which actuates the worm shaft is also provided on the slide. However, since the slide moves up and down when the press is in operation and is constantly exposed to impact, the driving motor mounted on the slide is very likely to deteriorate in its performance. West German Patent specification DE-A-2416102 discloses a slide adjustment device for a press for adjusting slide height, the device having a slide adjusting screw which is connected to one end of a connecting rod rotatably mounted at an eccentric portion of a crank shaft at a press crown, and which is connected to a slide, the slide height being adjustable by rotating the slide adjusting screw. Mounted on the outer periphery of the slide adjusting screw for rotation thereof is a worm wheel which is engaged for rotation thereof by a motor driven worm shaft, the slide adjusting screw being formed at its lower end with a cylindrical portion having outer peripheral threads screwed into a cylindrical member provided on the slide and there being a control mechanism for maintaining at a predetermined level the pressure in an oil chamber. With this prior art press the slide adjusting screw with which the worm wheel engages is a solid, externally threaded rod, and the oil chamber is formed as an annulus disposed below the worm wheel. The worm wheel constitutes the means for adjusting the slide height, and as it is in direct engagement with the threaded rod, the press drive force is directly transmitted via this engagement to the press slide. Transmission of the press drive force via this single screw-threaded connection, involving possibly very large forces, causes a problem in that the screw-threads become damaged quite quickly. An object of the present invention is to provide a device which not only quickly releases sticking of the die, but also enables high precision adjustment of the slide, provides overload protection and overcomes the problem of screw-thread damage. According to the present invention there is provided a slide height adjustment device for a press for adjusting slide height and releasing sticking, comprising a slide adjusting screw which is connected to one end of a connecting rod rotatably mounted at an eccentric portion of a crank shaft mounted on a press crown, and which is connected to a slide, the slide height being adjustable by rotating the slide adjusting screw, wherein: a worm wheel is mounted on the outer periphery of the slide adjusting screw for rotation thereof; a worm shaft in engagement with the worm wheel for rotation thereof is driven by a motor provided at the press crown; said slide adjusting screw is formed at its lower end with a cylindrical portion having outer peripheral threads, said outer peripheral threads being screwed into a cylindrical member provided on the slide; a control mechanism is provided for maintaining at a predetermined level the pressure in an oil pressure chamber between said cylindrical member and a piston part; characterised in that the worm wheel and the worm shaft are mounted at the press crown, the worm wheel being held fixed in the vertical direction relative to the press crown, whereby the slide adjusting screw is slidable in the vertical direction in said worm wheel; in that said cylindrical portion is tubular, having said peripheral threads on its exterior and also having threads on its inner periphery; in that a piston rod of the piston part is received within said tubular portion, with external threads on the piston rod being engaged with said inner peripheral threads of the tubular portion, so that, in use, press drive force is transmitted to the slide via the two screw threaded connections from the cylindrical portion; and in that the piston rod is housed within the cylindrical member, the oil pressure chamber being defined between the piston and the cylindrical member. During normal operation of the press, an oil pressure higher than the pressure of the press is supplied and maintained in the oil pressure chamber to eliminate backlash of the slide adjusting screw. When sticking occurs as the press stops operating due to insufficient energy or excessive torque, pressure in the oil pressure chamber is released to allow vertical movement of the slide to thereby release the stuck portion. Since, in the present invention, the pressing force is applied on the slide via the oil pressure in the oil pressure chamber, overload can be prevented by controlling the pressure in the oil pressure chamber at an adequate level. At the same time, by releasing the pressure in the oil pressure chamber, the slide is allowed to move vertically and thereby absorb the pressure caused by sticking between the slide die and the material thereby to release sticking. Further, as the backlash of the slide adjusting screw can be eliminated by the upward pushing force acting on the piston, the connecting rod and the slide can be co-ordinated for their relative positions constantly at higher precision to enable high precision operations at high speed. Further, as the driving motor for rotating the worm shaft which engages therewith for adjusting the slide height is mounted on the crown, the motor will not be exposed to impact from the press operation and thus can be protected against deterioration in the performance. The invention will now be described, by way of example, with reference to the accompanying drawings in which: Fig. 1 is a sectional view showing a slide adjusting device of the present invention when assembled, Fig. 2 is a diagram showing an oil pressure circuit of the device, Fig. 3 is a part-sectional view showing a driving mechanism of a worm shaft of the device, and Fig. 4 is a part-sectional view showing the installed part of a motor of the device. Figure 1 shows an embodiment of a device of the invention in which a crank shaft 1 is attached to a crown 2 of a press and is rotatably driven by a rotation driving mechanism. A connecting rod 3 is engaged to an eccentric portion 1a of the crank shaft 1 and a spherical portion 3a formed at the lower end of the connecting rod 3 is fixed to a slide adjusting screw 4, which its itself connected to a slide, to be described later. The slide adjusting screw 4 comprises a bearing 5 which contacts the lower face of the spherical portion 3a, and a bearing cap 6, which contacts the upper face of the portion 3a, the cap 6 being connected to the bearing 5 by bolts 7. At the lower end of the bearing 5, a cylindrical screw 8 is connected thereto by means of a bolt 9. Thus, as the crank shaft 1 rotates, the slide adjusting screw 4 moves vertically up and down via the connecting rod 3. At the outer periphery of the bearing 5 of the slide adjusting screw 4, there is a worm wheel 10 which is rotatable but is held against other movement in the crown 2. An axially extending key groove 11 is provided on the inner surface of the worm wheel 10. A pin 12 secured to the bearing 5 is inserted in the key groove 11, and the slide adjusting screw 4 thus rotates about the spherical portion 3a of the connecting rod 3 upon rotation of the worm wheel 10. Also, vertical movement of the connecting rod 3 can be effected independently of the worm wheel 10. A worm shaft 13 engaged with the worm wheel 10 is provided in the crown 2, with a bevel gear 14 (Figures 3 and 4) attached to the shaft end engaging with a bevel gear 16 of a driving shaft 15. A timing belt 19 is provided between a gear 17 of the driving shaft 15 and a driving shaft of a motor 18 so that the worm shaft 13 is rotationally driven by the motor 18. In the present embodiment, the motor 18 is an air motor. Referring to Figure 3, the worm shaft 13 extends laterally to both sides of the motor 18. This construction is used when two connecting rods 3 are provided to drive the slide. A cylindrical screw 8 (Figures 1 and 2) of the slide adjusting screw 4 is threaded on its outer periphery as well as its inner periphery. A screw member 32 fixed to a slide 31 via a cylindrical member 30 engages with outer periphery of the cylindrical screw 8, while a rod 34 of a piston 33, which is inserted and retained inside the cylindrical member 30 in a vertically movable manner, engages with the inner periphery of the cylindrical screw 8. Thus, the bottom of the piston 33 and the cylindrical member 30 form an oil pressure chamber 35 therebetween. The oil pressure chamber 35 is connected to an oil pressure tank 37 via an oil pressure circuit provided with an oil pressure pump 36, for example, as shown in Figure 2, and is normally supplied with an oil pressure of a predetermined level which is higher than the pressure of the press. The oil pressure chamber 35 and the oil pressure tank 37 are connected by means of a control valve 38 which is normally closed. Accordingly, when sticking occurs, the control valve 38 is opened to release the pressure in the oil pressure chamber 38 into the oil pressure tank 37. The reference number 39 denotes a relief valve provided between the control valve 38 and the oil pressure chamber 35. When the press is operating under normal conditions, the above contruction allows the oil pressure chamber 35 to be filled with an oil pressure of predetermined level supplied from the oil pressure pump 36 as the control valve 38 is closed, as shown in Figure 2. The piston 33 is pushed upward by the oil pressure, so that the connecting rod 3 and the slide 31 correspond with each other positionally at high precision. The pressing force applied by the connecting rod 3 is transmitted to the cylindrical member 30 (slide 30) via the piston 33 with the oil pressure in the chamber 35. When sticking occurs, the oil pressure pump 36 is stopped and the control valve 38 is opened. As a result, the oil pressure chamber 35 opens into the oil pressure tank 37 via the control valve 38 and the pressure in the chamber 35 is released to cancel the pushing force acting on the piston 33. As pressure in the chamber 35 is released and the pushing force on the piston 33 is cancelled, the pressure acting in the slide, die and the material due to sticking is absorbed to release the sticking. In the embodiment described, the oil pressure circuit having the control valve 38 for relieving the pressure in the chamber 35 is provided independently. However, it is possible that this circuit can be incorporated in an oil pressure circuit which includes the oil pressure pump 36.

Claims: A slide height adjustment device for a press for adjusting slide height and releasing sticking, comprising a slide adjusting screw (4) which is connected to one end of a connecting rod (3) rotatably mounted at an eccentric portion (1a) of a crank shaft (1) mounted on a press crown (2), and which is connected to a slide (31), the slide height being adjustable by rotating the slide adjusting screw (4), wherein: a worm wheel (10) is mounted on the outer periphery of the slide adjusting screw (4) for rotation thereof; a worm shaft (13) in engagement with the worm wheel (10) for rotation thereof is driven by a motor (18) provided at the press crown (2); said slide adjusting screw (4) is formed at its lower end with a cylindrical portion (8) having outer peripheral threads, said outer peripheral threads being screwed into a cylindrical member (30, 32) provided on the slide (31); a control mechanism (36, 37, 38, 39) is provided for maintaining at a predetermined level the pressure in an oil pressure chamber (35) between said cylindrical member (30) and a piston part (33); characterised in that the worm wheel (10) and the worm shaft (13) are mounted at the press crown (2), the worm wheel being held fixed in the vertical direction relative to the press crown, whereby the slide adjusting screw is slidable in the vertical direction in said worm wheel; in that said cylindrical portion (8) is tubular, having said peripheral threads on its exterior and also having threads on its inner periphery; in that a piston rod (34) of the piston part (33) is received within said tubular portion (8), with external threads on the piston rod (34) being engaged with said inner peripheral threads of the tubular portion, so that, in use, press drive force is transmitted to the slide (31) via the two screw threaded connections from the cylindrical portion (8); and in that the piston rod is housed within the cylindrical member, the oil pressure chamber (35) being defined between the piston (33) and the cylindrical member. A device as claimed in Claim 1, characterised in that an inner peripheral surface of the worm wheel (10) has a groove (11) therein parallel to the axis thereof, and in that said slide adjusting screw (4) has a pin (12) therein engaged in said groove. A device as claimed in Claim 1 or Claim 2, characterised in that said connecting rod (3) has a spherical end (3a) thereon, in that said slide adjusting screw (4) has a bearing (5) engaged by a lower portion of said spherical end, in that a bearing cap (6) on said bearing (5) engages an upper portion of said spherical end, and in that said bearing (5) has a hollow cylindrical portion (8) on its lower end with which said cylindrical member (30, 32) and said piston rod (34) are threadedly engaged, so that press drive force, in use, is transmitted to the slide (31) via the two threaded connections from the cylindrical portion (8). A device as claimed in any one of Claims 1 to 3, characterised in that the oil pressure chamber (35) is defined between an end face of the piston (33) and an inside end face of said cylindrical member (30, 32).

Inventors: IMANISHI, SHOZO, SATO, MITSUO
Applicants: AIDA ENGINEERING LTD.
Application year: 1985
Main classification: B21J9
IPC codes: B30B15