TURRET PUNCH PRESS

Abstract: A turret punch press has a motor (5) which drives a rotatable shaft (8) to which is keyed a gear ring (9). Separately journalled for rotation on the shaft (8) is a turret (4) around the periphery of which are mounted a plurality of rotatable tool holders (10). Each tool holder has a peripheral gear which is permanently engaged with the gear ring (9). By driving the shaft (8) and holding the turret (4) stationary, the tool holders (10) can be rotated about their own axes. A pneumatic, electromagnetic or hydraulic clutch can be operated selectively to couple the gear ring (9) and the turret (4), in which position the turret rotates with the shaft, so allowing indexing of the position of the tool holders.

Description: TURRET PUNCH PRESS The present invention relates to turret punch presses, for example those controlled by numerical methods which punch or stamp holes or impressions in- wor pieces. Such punch presses may be provided with tools of varying sizes and shapes which are adjustable for punching into the material wor piece at selected indexed or rotated orientations. It has been known for many years to work material , for example flat sheets of material such as steel by punching or stamping with a tool. In more recent times it has become practice to provide machines with a powered (for example, hydraulic) ram to produce the physical punching force required. A punch tool is usually positioned above a material workpiece with a corresponding die or anvil positioned underneath, and the tool is then punched by the ram to shape the workpiece. To increase productivity, it has become practice to produce machines with tool holders for fitting several different punch tools and corresponding dies to the machine at once, and to provide means for positioning a required punch tool and die in the correct position below the hydraulic ram. To this end, machines have been provided with a rotating turret on each side of the workpiece, with one turret having several punch tools and the other having corresponding dies. It is usual to position the workpiece relative to the punch tool to be punched by means of numerically controlled computer means before punching. Often this is achieved by gripping and moving the workpiece relative to the frame and ram of the machine and translating it along two "XY" axis numerically controlled slides. The upper and lower turrets are rotated to position the correct punch tool and corresponding die below the ram before punching. In more recent machines, it has become necessary to produce machines with tools and dies which can be rotated or indexed relative to the rotable turret, and therefore the ram and ultimately the workpiece. This enables, for example, more accurate and quicker punching of curved profiles which required several punches. Whereas before it had been necessary to provide special curved tools for producing curves, it became possible to produce curves with a set of fewer and more standardised tools, thus reducing machine operating costs. It is vital that, before punching, the punch tool and die are positioned correctly above one another. It must be ensured, therefore, that the upper and lower turrets are rotated to position the correct and corresponding punch tool and die beneath the ram; and the punch tool and die must also be rotated to the same angle relative to one another. If both these conditions are not met, the punching of the ram, which is often enormously powerful, is likely to destroy expensive machinery. It is therefore usual to provide means such as electronic circuitry to provide signals which indicate when punching may proceed safely. To rotate the turrets, the punch tool and die it is usual to use electric servo motors, although it is also possible to use any other type of motor for producing rotation, such as a hydraulic and rack and pinion type unit. Now motors are generally expensive and it is therefore desirable to minimise their number. To this end, machines have been provided with one motor to rotate both the upper and lower turrets in unison. Since the workpiece is positioned between the turrets and the mechanical drive has to be passed fully around the workpiece, either a right-angled gearbox arangement, or a sprocket wheel with shafts and chain drive arrangement is normally provided to ensure that the two turrets maintain the same angular rotation. It is also practice to provide only one motor to rotate the tool holder on the upper turret and the die on the lower turret simultaneously, and a similar right-angled or chain drive is usually provided to do this. Such a unit is illustrated in GB 2052342A. Manufacturers nowadays therefore produce turret punch presses with either two motors (or even three motors where separate motors are used to rotate punch tools and dies in their respective turrets) and at least one right-angled gearbox or chain and sprocket arrangement to link the upper and lower halves of the machine. A Problem with right-angled gearbox or chain and sprocket arrangements is that a certain amount of mechanical play is always evident between the upper and lower halves of the machine. Another problem is that these arrangements limit the operating speed of the machine. In particular, such arrangements produce a great deal of noise and vibration when run at high speed. This vibration shortens the service interval and ultimate life of the machine. Gearboxes and chainwheelε are also of limited efficiency, and larger motors have to be provided to overcome the loss of mechanical effort. EP 0215644 illustrates a turret punch press which requires at least three motors to provide rotation of turrets, punch tools and dies. The upper and lower turrets are each provided with a separate motor for rotating punch tool or die as the case may be. The motor is only capable of rotating one punch tool or die at a time. This requires that the motor has means for engaging or disengaging with punch tools or dies, and any punch tool or die which is not engaged with the motor has to be provided with a rotation brake so that the knowledge of the angular position of each punch tool or die can be maintained. If either of the motor engagement/disengagement means or a punch tool or die rotation brake were to malfunction, serious mishaps could occur. It is a first object of the present invention at least to alleviate the problems inherent in the prior art. It is a further objection to reduce the number of motors required to operate a turret punch press. It is another object to improve the efficiency, accuracy and working life of turret punch presses. It is yet a further object to provide a turret punch press which can be operated for long periods at high speeds. According to the present invention there is provided a turret punch press comprising a frame, a motor, a turret mounted for rotation with respect to the frame, and a tool holder mounted for rotation with respect to the turret; characterised by selectable drive means arranged in a first position to cause the motor to drive the turret and in a second position to cause the motor to drive the tool holder. The axis of rotation of the turret with respect to the frame is preferably parallel to the axis of rotation of the tool holder with respect to the turret. The drive is desirably selectable between a first state in which the turret can rotate and the tool holder is rotatably fixed relative to the turret, and a second state in which the turret is held stationary and the tool holder can rotate with respect to turret. Of course, it would also be possible to provide an arrangement with one state in which the turret rotates and the tool holder at the same time rotates relative to the turret. An epicyclic arrangement could be envisaged. The important feature is that the rotational speed of the tool holder relative to the turret differs between the two states. In this way, by using the two states, the tool holder can be positioned at any indexed angle and position on the turret relative to the frame. A clutch may be provided in the drive to select the first and second states. It is of course, not critical whether the clutch is activated to select the first state, or to select the second state. The clutch could be actuated by any convenient means, for example, an electromagnetic solenoid or by a hydraulic or pneumatic arrangement. Alternatively, a simple mechanical engagement might be suitable. The motor may rotate on a shaft with an axis concentric with that of the turret and the shaft may be arranged to drive a concentric gear ring which engages the gear on the periphery of the tool holder. There may be more than one tool holder arranged on the turret. The or each tool holder may be provided with a gear on its periphery which engages the gear ring. In this manner, knowledge of the rotational position of the gear ring or of a tool holder provides knowledge of the angular position of any component in the gear ring arrangement. The shaft is preferably connected through the clutch to the turret, with the shaft being rotationally fixed to the gear ring. Accordingly, the shaft is thus desirably permanently engaged with the gear ring, although this is not absolutely necessary. Alternatively, it is envisaged that the shaft could instead be connected through the clutch to the tool holder. Preferably, the turret is arranged so that a punch tool held in or by the tool holder can be struck towards a workpiece by a ram, preferably a hydraulic ram In the type of turret punch press where there are corresponding upper and lower turrets, the tool holder of the upper turret may hold the punch tool while the tool holder of the lower turret may hold an anvil or die. In such an arrangement, when the ram is actuated, the punch is pressed through the workpiece against the anvil or die. The die may be configured specifically to correspond to a particular punch tool in the turret above, and it is preferred that the die is mounted in a lower turret which rotates co-axially with the above turret. Automatic control means may be provided to operate the turret punch press, for example a microprocessor. In one embodiment, the control means ensures that the upper and lower turrets always rotate together, and that the corresponding upper tool holders and lower dies are always maintained in their correct rotational positions relative to the turret. Inhibiting means may be provided to inhibit actuation of an operating ram in the event that the upper tool holder and the lower die which are to be used are not in position. The control means may conveniently actuate one motor for movement of the upper turret and tool holders, and a second motor for movement of the lower turret and dies or die holders. Feedback loops may be provided from one or both motors, and/or the positions of the turrets and/or tool holders, tools, die holders or dies to ensure that the upper and lower gearing arrangements always remain in synchronisation with each other. The invention may be carried into practice in a number of ways and three different embodiments will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a schematic representation of a turret punch press which is applicable to all three specific embodiments; Figure 2 is a schematic representation of the drive, clutch and gear assembly of the first embodiment; Figure 3 shows in detail the gears and clutch assembly of the first embodiment; Figure 4 shows in detail the gears and clutch assembly of the second embodiment; Figure 5 is a schematic representation of the drive, clutch and gear assembly of the third embodiment; Figure 6 shows in detail the locking assembly mechanism of the third embodiment; Figure 7 shows in detail the clutch assembly of the third embodiment; and Figure 8 shows in detail, the turret back valve and locking valve seat assembly of the third embodiment. To illustrate the general principles behind the present invention, reference will first be made to Figure 1 which is a schematic illustration of a turrent punch press. The specific features shown in this figure, and the corresponding description, are applicable to all three detailed embodiments which are to be described later. The turret punch press of Figure 1 is assembled on a C-shaped frame, generally designated by the numeral 1. The frame comprises a lower bed 2 and a cantilevered overhead beam 3. Mounted for rotation respectively to the overhead beam 3 and the bed 2 are upper and lower rotatable turrets 4, 14. The upper turret 4 is mounted for rotation on a shaft 8 which itself is driven via a reduction gearbox 7 by a servomotor 5 and encoder 6. Above the upper turret 4 is a gear ring 9 which is fixedly secured with respect to the shaft 8 for rotation therewith. A plurality of punching tools 12, for example punch assemblies, are located in corresponding upper tool holders 10 which are mounted for rotation on the upper turret 4. A clutch (not shown) is provided between the shaft 8 and the upper turret 4. When this clutch is engaged, the upper turret 4 is fixedly secured to the shaft and to the gear ring 9 and accordingly rotates when they rotate. In this way, by rotation of the shaft 8, a selected punch assembly 12 can be rotated into the operating position beneath a ram 13. The ram 13 is operated by a controllable impact device 28. The teeth of the gear ring 9 are in permanent meshing engagement with corresponding teeth of the various rotating upper tool holders 10. When the clutch (not shown) is de-energised, and the upper turrent 4 is held stationary, rotation of the shaft 8 simply causes rotation of the .gear ring 9 and accordingly rotation of the punch assemblies about their own axes. In this way, a selected punch assembly which has already been positioned beneath the ram 13 can be rotated about its own axis to provide (for example) square holes punched into a workpiece at a variety of different orientations. As will be seen from the figure, there is a corresponding arrangement for the drive mechanism of the lower turrent 14 which is mounted on the bed 2 below and co-axial with the upper turret 4. Rotation of a drive shaft 18 is effected by means of a servomotor 15 with encoder 16 acting through a reduction gearbox 17. When a lower clutch (not shown) is energised, a lower gear ring 19 and the lower turrent 14 rotate together with the shaft 18. In this way, lower tool holders 20 with lower parts for tools, for example die assemblies 22, can be selectively rotated about the axis of the shaft 18 until they lie in the operating position immediately below the ram 13. When the clutch (not shown) is deactivated and the lower turret 14 held stationary, rotation of the shaft 18 causes rotation of the lower gear ring 19. Since this gear is permanently coupled to corresponding planetary gears on the lower tool holders 20, rotation of the shaft 18 then causes rotation of the die assemblies 22 about their own axes. A workpiece 23 to be punched is positioned between the upper and lower turrets 4, 14. The workpiece is manoeuvered into position by a feeding mechanism 24 having separate controls and clamps 25 on the X and Y axes. In operation, the workpiece 23 is moved by the feeding mechanism into the correct place for punching to occur immediately beneath the ram 13, and it is then held in that position. The appropriate punch assembly 12 and corresponding die 22 are then moved into the operating position by actuating both the upper and lower motors 5, 15 and the corresponding upper and lower clutches (not shown) . When the punch and die are in the correct indexed position, the upper and lower turrents 4, 14 are locked in position by means of upper and lower locking mechanisms 26, 27. The clutches are then deactivated so that continued operation of the motors 5, 15 causes rotation of the punch and die about their own axes. When both are correctly positioned, the workpiece 23 is punched by operation of the ram 13. Overall control of the turret punch press is provided by an electronic control unit 29. This is desirably a microcomputer providing numerical control. In particular, the unit 29 ensures that the ram 13 is actuated only when it has received confirmation that the workpiece 23 is in position, the upper and lower turrets 4, 14 are properly locked in place, and that the selected punch 12 and corresponding die 22 have been correctly indexed and then rotated about their own axes so as to be in the desired position for punching. A more detailed description of each of the three specific embodiments will now follow. Figure 2, first of all, schematically shows the arrangement of drive members for the first embodiment. As has previously been described, the upper and lower gear rings 9, 19 are fixedly secured to the upper and lower shafts 8, 18 for rotation therewith. In contrast, the upper and lower turrets 4, 14 are journalled for rotation on their respective shafts 8, 18. The teeth of the gear rings 9, 19 remain permanently engaged with corresponding teeth of planetary gears of the upper punches 12 and the lower dies 22. Upper and lower electromagnetic clutches are provided respectively to couple the upper turret 4 to the upper shaft 8 and the lower turrent 14 to the lower shaft 18. The couplings are effected when the respective coils 11, 21 of the electromagnetic clutches are actuated. Further detail of the first embodiment is shown in Figure 3. As will be seen, the coil 11 of the upper electromagnetic clutch is contained within a retaining ring 32 which itself is permanently coupled to the fixed upper beam 3. The gear ring 9 is keyed at 34 to the drive shaft 8 so as to rotate therewith. In a circumferential groove running around the lower surface of the gear ring 9 is a friction disk 33. The clutch plate 30 is very slightly moveable in the vertical plane and has beneath it a wafer spring 35. The clutch plate 30 is screwed at intervals to the wafer spring 35 which in turn is screwed at intervals to the upper turret 4 to prevent the clutch plate rotating relative to the upper turret when the electromagnetic clutch is applied. When the clutch is energised the clutch plate 30 is pulled up into contact with the friction disk 33, so preventing relative rotation between the gear ring 9 and the upper turret 4. Although not clearly shown in the diagram, there is of course a small air gap between the gear ring 9 and the upper turret so that there is no mutual friction between them when the clutch is not actuated. The lower clutch mechanism is virtually identical, comprising as it does a lower electromagnetic clutch * having a coil 21. There is also a corresponding friction disk 37, clutch plate 31 and wafer spring 39. The lower gear ring 19 is fixedly coupled to the lower shaft 18 by means of a key 38. Rotation of the upper and lower turrets 4, 14 can be prevented by means of pins 40, 41 which are arranged for reception in corresponding indexed recesses 42, 43 around the peripheries of the turrets. Naturally, the control unit 29 (Figure 1) ensures that the clutches are always disengaged when the pins are located within their respective recesses. In the second embodiment, illustrated in detail in Figure 4, identical or substantially identical parts are given the same reference numerals as before. Parts which are somewhat different, but which perform a similar role to a part in the previous embodiment are given identical reference numerals with the addition of a prime. In this embodiment, the electromagnetic clutch arrangement is replaced by a pneumatic clutch. Such a clutch has the advantage that the working parts of the turret punch press are not then affected by the residual magnetism that electromagnetic clutches are liable to produce. The pneumatic clutch is here contained within an annular support 32' which is permanently secured to the fixed upper beam 3. The air for operating the clutch enters via one or more blind bores 50, and passes down through a plurality of vertical bores 52 to the upper surface of a continuous annular seal 55 which is itself secured to a continuous annular thrust bearing 54. This bearing has a plurality of downwardly extending spigots 56, spaced around the periphery, these spigots passing through corresponding spaced bores in the gear ring 9. Screwed into the lower ends of these spigots is a continuous annular wedge 58. Disk springs 60, located between a lower shoulder of the spigots 56 and the gear ring 9 ensure that in the rest position the wedge 58 is biased upwardly against the lower surface of the gear ring. The wedge 58 is located within a correspondingly wedge-shaped recess in a clutch plate 30'. To ensure good metal-to-metal contact between the wedge 58 and the thrust plate 30', the thrust plate is separated into four, six or eight separate sections around the periphery, each section being very slightly moveable in a radial direction. Accordingly, the sections can move slightly to take up slight machining errors in the surface of the wedge and/or the recess into which the wedge fits. Alternatively, it would be possible for the clutch plate 30' to be continuous, and the wedge 58 to be split up into a plurality of separate sections. When compressed air is applied to the bore 50, the pressure on the upper surface of the seal 55 overcomes the biasing force of the springs 60, so moving the wedge 58 down into contact with the thrust plate 30'. In this position, the upper turret 4 is coupled for rotation with the gear ring 9. In this embodiment, the gear ring 9 is shown as being manufactured from two separate sections 9a, 9b, which are simply screwed together. Of course, a continuous gear ring could also be used here, as was shown in Figure 3. In the same way, a two-part gear ring could also be used in Figure 3. The lower gear ring arrangements for this embodiment will not be described since, as will be appreciated, they resemble the arrangements shown in Figure 4 in the same way as the lower part of Figure 3 resembles the upper part of Figure 3. The third and final embodiment will now be described with reference to Figures 5 to 8. Again, identical and substantially identical items will be referred to by the same reference number, and items having the same function will be referred to by the same number but with the addition of a prime. This embodiment, like the embodiment for Figure 2, features an air clutch but in this case the air for operating the clutch is fed into the system via the upper and lower locking pins 40, 41. Reference will first be made to Figure 5, which shows a schematic arrangement of the drive mechanism. In this embodiment, connections beteen the upper turrent 4 and the gear ring 9, and the lower turret 14 and the lower gear ring 19, are effected by respective air-controlled clutch plates 60, 61. These extend circumferentially of the turrets and, when in their operational position, press respectively upwardly, and downwardly on the lower and upper surfaces of the gear rings 9 and 19. Air pressure is provided by a plurality of circumferentially arranged pneumatic cylinders 65, 69 which are coupled via radial bores to upper and lower ring channels 63, 67. These in turn, are coupled by further radial channels 62, 66 to valves 76, 77, the seats of which are the locking recesses 42', 43' into which are received the corresponding locking pins 40' and 41'. The locking pins 40', 41' in this case are hollow, and are arranged to supply air via control valves 81, 91. The actuation of the pins themselves is effected by further air-operated control valves 74, 75. In use, when the turrets 4, 14 have been indexed to the correct position, control valves 74, 75 are actuated to insert the pins into the corresponding recesses. The control valves 81, 91 are then actuated causing air to flow through the pins, via the valves 76, 77 to the respective upper and lower pneumatic cylinders 65, 61. This forces the clutch plates 60, 61 away from the gear rings 9, 19 (as will be described in more detail below) so allowing the gear rings to rotate independently of the turrets. Figure 6 shows the upper locking mechanism 26 in more detail. It comprises a stepped cylinder 78 having within it a hollow locking pin 40' with an outwardly-extending piston flange 80. The piston is biased to its inoperative or rectracted position by means of a spring 84 which extends between the piston flange 80 and a front cover 89. The cover is held in position by screws 82 and includes an O ring seal 83 around to the periphery of the pin. A pressure-balancing aperture 85 extends from one side of the cover to the other. Actuation of the pin 40' is,effected by supplying air via a control valve 74 through a bore in the side of the cylinder 78 to the rear of the piston flange 80. When the pin is in position, and sealed against the surface of the recess 42' (Figure 5) , further air pressure is supplied via a second control valve 81, this pressure passing via the longitudinal bore within the pin to the conduits within the turret 4. The lower locking mechanism is similar. Figure 7 shows in more detail the actual clutch mechanism. The circumferential friction disk 60, positioned in a corresponding annular cavity in the upper surface of the turret 4 , has screwed to it by screws 104 a plurality of circumferentially spaced shanks 100. The lower ends of these shanks are connected by a circumferentially continuous diaphragm 99. Air pressure within the cylinders 65 is prevented from reaching the clutch plate 60 by virtue of a fixed intermediate insert 96 which has seals 97 allowing the shanks 100 to move slightly up and down, taking with them, of course, the clutch plate 60. Below each of the shanks 100, on the other side of the diaphragm, there is a smaller diameter cylinder containing a shouldered spigot 101 and a biasing spring 102. An air equalising vent 103 extends between each of the cylinders 105 and the atmosphere. When air pressure is applied to the inside of the cylinders 65, the diaphragm 99 bends slightly, so forcing the shank 101 downwardly against the force of the spring 102. This pulls the clutch plate 60 away from the gear ring 9 and opens the clutch. When the air pressure is removed, the spring re-exerts itself and closes the clutch. In the embodiment shown, the interior surface of each of the cylinders 65 is lined with an insert 98. Figure 8 shows in detail the locking pin seat assembly of the upper turret 4. As has previously been described, the turret includes a plurality of circumferentially spaced recesses 42' which define seats for the locking pin 40'. At the base of each of the recesses 42' there is a back valve generally designated by the numeral 126 which connects the bore of the pin 40' with the internal channel 62. The back valve 126 has a biasing spring 119 which acts to press a moveable valve member 128 into sealing contact with an annular seal 110 on the turret. When the locking pin 40' is engaged with one of the seats 42', it presses against the forward end of the valve member 128, so mechanically opening the valve. In this position, air can pass from the pin 40' to the air clutch (Figure 7) . When it is desired to engage the clutch, air pressure is released from the channel 62 back through the bore in the locking pin. Any excess pressure remaining when the pin is withdrawn from the seat 42 prime is vented via a slot 111. An additional slot 112 at the rear of the moveable valve member ensures that the pressures are maintained constant between the chamber of the spring 119 and the channel 62. The lower turret has a corresponding mechanism.

Claims: CLAIMS : 1. A turret punch press comprising a frame, a motor, a turret mounted for rotation with respect to the frame, and a tool holder mounted for rotation with respect to the turret; characterised by selectable drive means arranged in a first position to cause the motor to drive the turret and in a second position to cause the motor to drive the tool holder. 2. A turret punch press as claimed in Claim 1 in which in the first position the tool holder remains stationary with respect to the turret and in the second position the tool holder rotates while the turret is held fixed relative to the frame. 3. A turret punch press as claimed in any one of the preceding claims in which the drive means includes a shaft, driven by the motor, having an axis co-incident with the axis of rotation of the turret, the shaft having a concentric gear ring which engages a gear on the tool holder. 4. A turret punch press as claimed in Claim 3 in which in the first position the turret is held fixed in relation to the gear ring and in the second position the gear ring is free to rotate independently of the turret. 5. A turret punch press as claimed in any one of the preceding claims in which the selectable drive means includes a clutch. 6. A turret punch press as claimed in Claim 5 in which the clutch is of the electromagnetic type. 7. A turret punch press as claimed in Claim 5 in which the clutch is of the pneumatic type. 8. A turret punch press as claimed in any one of Claim 5 to 7 in which the clutch includes a wedge-shaped annular first clutch plate and a second annular clutch plate having a co-operating channel for receipt of the wedge-shaped clutch plate. 9. A turret punch press as claimed in Claim 8 in which the first clutch plate, the second clutch plate, or both, is or are divided into a plurality of circumferential sections. 10. A turret punch press as claimed in any one of the preceding claims, including a further motor, a further turret mounted for rotation with respect to the frame, a die holder mounted for rotation with respect to the further turret, and further selectable drive means arranged in a first position to cause the further motor to drive the further turret and in a second position to cause the further motor to drive the die holder. 11. A turret punch press as claimed in Claim 10, including control means arranged to determine when the tool holder and the die holder are in the operating positions, and then to operate a ram causing a punch mounted to , the tool holder to punch through a workpiece located between the tool holder and the die holder .

Inventors: MILLS PETER, POTEMKIN BORIS, MILLS, PETER, POTEMKIN, BORIS
Applicants: SHAPE MACHINES LIMITED
Application year: 1990
Main classification: B21D28
IPC codes: B21D28