GB2167696A

GB2167696A - A press with automatic gripper bar exchange system

Info

Publication number: GB2167696A
Application number: GB08523283A
Authority: GB
Inventors: Wolfgang Hartung; Alfred Kempf; Klaus Miethbauer; Ulf Zschocher
Original assignee: Umformtechnik Herbert Warnke VEB
Current assignee: Umformtechnik Herbert Warnke VEB
Priority date: 1984-11-29
Filing date: 1985-09-20
Publication date: 1986-06-04
Also published as: FR2573680A1; DD229320A1; GB2167696B; DE3530848C2; FR2573680B1; GB8523283D0; DE3530848A1

Abstract

A press provided with gripper bars for conveying workpieces therethrough, has an automatic gripper bar exchange system. A gripper bar consisting of a central portion 7 and extendable end portions 8 is released from an operative position in a press by clamps 14 and is lowered by a lifting beam 4 onto a sliding table 1.Take-up members 10 engage tongues 11 on the gripper bar end portions 8 and they are retracted by operating cylinders 9. The table 1 is then moved from the press and another gripper bar on a similar table is slid into position and offered up into the operative position in the press. A stop 18 and a marker 20 ensure correct alignment of the lifting beam 4 and the gripper bar. <IMAGE>

Description

SPECIFICATION A press with automatic gripper bar exchange system The invention relates to a press with an automatic gripper bar exchange system.

Trains of presses are known from German Offenlegungsschrift 2 411 447 in which the workpieces are conveyed by three-dimensional short gripper bar systems disposed within each press. By means of these short gripper bars the workpieces are taken up outside of the press, conveyed to the machining room and after machining placed on separate intermediate conveyors or storage tables again outside of the presses. If it is necessary to change the tools, these are conveyed out of the press room by means of a sliding table and exchanged. A second sliding table may in this respect already be prepared with the new tool.

However, the required exchange of the short gripper system takes place manually in the press room. This exchange of the short gripper system is consequently very intensive in terms of work and time.

German Auslegeschrift 1 964 326 and German Offenlegungsschriften 3 150 508, 3 213 381 and 3 233 102 disclose transfer presses with three-dimensional workpiece conveyor devices which comprise several independent sliding tables whose direction of movement is perpendicular to the conveyor direction of the workpieces. The continuous workpiece conveyor devices have respective detachable connection elements at the points of intersection between the sliding table and the press locations.

During tool exchange, the gripper bars belonging to the sliding table are moved out of the press room with the latter and exchanged by detaching these connection elements. These solutions are not, however, suitable for use with short gripper systems in the presses of a train as a result of the principal functional differences and the different bearing and guiding methods for the gripper bars.

An object of the invention is to automate the exchange of the gripper bars during tool exchange in presses in order to reduce setting up times.

According to the invention there is provided a press provided with a gripper bar for conveying workpieces and a system for automatically exchanging the gripper bar during tool exchange in the press, the exchange system comprising gripper bar support means movable to and from the press, and control means for releasing the gripper bar from operative connection in the press such that it is received by the support means to be conveyed thereby from the press, said control means further being operative to receive a gripper bar from a said support means into operative connection with the press, whereby to facilitate said automatic exchange.

Preferably the gripper bar comprises a central portion and an end portion slidable longitudinally of the end portion, and including contracting means on the support means for contracting the end portion of the gripper bar relative to said central portion. As a result of the fact that the end portion of the gripper bar is displaceable, it has variable end positions, i.e. the longitudinal extension of the gripper bar may be selected in accordance with the parts to be conveyed within the limits of the adjustment range.

It also lies within the scope of the invention to clamp and convey one-piece gripper bars.

Preferably the support means comprises a sliding table on which is mounted a lifting beam to receive the gripper bar. The slidable end portion of the gripper bar can be provided with a transverse tongue. A take-up member for the tongue is mounted on the lifting beam, and the take-up member is driven by a fluid actuated operating cylinder. A marker is provided on the gripper bar and a stop is provided on the lifting beam. The control means may include clamp levers for locking and releasing the gripper bar in the press. Alternatively, screw connectors may be provided.

For the exchange of the gripper bars, the stop is brought up against the marker so that the gripper bar consequently brings the sliding table into a predetermined position. The lifting beam is raised as a result of which the tongue is positively taken up by the take-up member. After the release of all the clamp levers or the release of the screw connections the lifting beam is lowered with the gripper bars which it has taken up and moved back to the centre of the sliding table. The gripper bar end portions are subsequently contracted by means of the operating cylinder and the automatic tool exchange with the gripper bar is able to begin. The introduction of new gripper bars prepared outside of the presses for a new workpiece takes place in the reverse sequence.

The invention is now described by way of example with reference to an embodiment. In the attached drawings: Figure 1 shows a gripper bar exchange device with the gripper bar end portions retracted and clamping devices which consist of spring clamps and levers, in which the gripper bar are separated from the bracket and lie on the lowered lifting beams. The stop and the marker are separated from one another; Figure 2 is a section along the line A-A of Figure 1; Figure 3 shows a gripper bar exchange device with the gripper bar end portions extended, in which the gripper bars are moved into the brackets by means of lifting beams and are clamped to the brackets by the spring clamp with levers, in which the stop and the marker are moved together along the path y.

Figure 4 is a section along the line B-B of Figure 3; Figure 5 shows a gripper bar exchange device in which the gripper bars are clamped in an operative position by means of spring clamps and levers and the lifting beam (not shown) is lowered; Figure 6 shows a detail of the spring clamp with the lever and a section through the gripper bars; Figure 7 shows a gripper bar exchange device with the gripper bar end portions retracted and clamping devices which comprise clamp screws and screw connections, in which the gripper bars are separated from the brackets and rest on the lowered lifting beam; Figure 8 shows a gripper bar exchange device with the gripper bar end portions extended, in which the gripper bars are moved into the brackets by means of lifting beams and are clamped on the brackets by the clamp screws;; Figure 9 shows a gripper bar exchange device in which the gripper bars are clamped in an operative position by the clamp screws and the lifting beam (not shown) is lowered.

The gripper bar exchange device for automatic tool exchange in mechanised trains of presses, whose presses utilise short gripper bar workpiece transfer devices, comprises a respective lifting device, which is rigidly disposed on a sliding table 1, on each side of the press room in the throughput direction. The lifting device includes a lifting beam 4 which is vertically moved by an operating cylinder 2 and a lever gear 3. The gripper bars 7, 8 which are held in the guide blocks 5 are positively connected with the lifting device by means of a take-up in brackets 6. These brackets 6 are disposed on the lifting beam 4. The gripper bars comprise a gripper bar central portion 7 to whose ends the guide blocks 5 are fastened. In addition, displaceable gripper bar end portions 8 are held by the guide blocks 5.Displacement of the gripper bar end portions 8 takes place by means of an operating cylinder 9 which drives take-up members 10 which engage tongues 11 on the gripper bar end portions 8. In the operative condition of the gripper bar in the press after operation of the exchange device, the gripper bar central portion 7 and the gripper bar end portions 8 are frictionally and positively clamped on the bracket 12 by clamp levers 13 and 14, as shown in Figure 6. The lifting device is in this respect lowered and the connection between the take-up members 10 and the expanding tongues 11 is detached. This ensures that there is no connection between the gripper bars and the sliding table 1, i.e. the workpieces may be conveyed unhindered into the press tool room.

The clamping device of the gripper bars comprises, for example, an operating cylinder 16 with a piston rod 17 which is in operative connection with the clamp levers 13 or 14 formed as double levers.

The clamping force may then be provided by pressure springs 15. By means of a corresponding lever ratio, the clamping force may be set to any desired value. The detachment of the clamping levers 13 and 14 is achieved pneumatically or hydraulically by means of a force which is opposite to the clamping force in the operating cylinder 16.

The movement of the pistion rod 17 is transmitted to the clamp levers 13, 14 which are therefore released from their clamping position.

In the preferred embodiment of the invention, the gripper bar is in its shortened and lowered condition and its guide blocks 5 lie on the brackets 6. The required longitudinal extension of the gripper bar end portions by means of the movement of the gripper bar end portions 8 is achieved by means of the movement of the operating cylinder 9 and the operational connection between the tongue 11 and the take-up member 10. The guide blocks 5 reach the clamping area of the clamp levers 13 and 14 by raising of the gripper bar via the lifting system. By means of the pressure springs 15, one of the guide blocks 5 and the extended gripper bar end portions 8 are clamped respectively by the clamp levers 13 and 14 simultaneously or individually in a positive and, if necessary, by means of grooves, frictional manner on the bracket 12.

After lowering of the lifting device, uncoupling of the guide blocks 5 from the brackets 6 and uncoupling of the tongues 11 from the take-up members 10 and the movement of the operating cylinder 9 into the initial position, the coupled gripper bar is ready for operation.

The gripper bar exchange begins with the removal of gripper bars already present to the tool room after the shutdown of the press ram in a predetermined position. The presses, which are equipped with a short gripper transfer system, operate preferably in the three-dimensional cycle of the gripper bars. According to the type of press drive, the gripper bars move at the time of the predetermined position of the ram into or into the vicinity of the centre of their return stroke in the open and lowered condition. This means, as a rule, that the centre of the gripper bars must be moved exactly into the centre of the machine. This takes place by means of a predetermined movement of the gripper bars of a size x, as shown in Figure 1, as the stop 20 of the gripper bars is moved against the marker 18 on the lifting device.As during this supply movement, a further movement y is possible, as shown in Figure 3, it is necessary for the lifting beam 4 to be able to carry out a corresponding relative movement with respect to the sliding table 1. It is possible to stabilise the position reached between the gripper bars 7, 8 and the lifting beam 4 via the marker 18 by means of the system of pressure springs 19.

In this position, the lifting system is raised by the operating cylinder 2, the take-up members 10 engaging with the respective tongues 11. In the same way, the guide blocks 5 are positively taken up by the brackets 6. After the release of all the clamp levers 13, 14 the lifting beam 4 is lowered together with the gripper bars which have been taken up. At the same time the spring system 19 has to travel back along the subsequent path y to the centre of the sliding table. The bracket 12 remains a compo nent of the mechanization device on the press.

After lowering or during lowering the gripper bar end portions 8 are retracted by means of the operating cylinder 9 in the direction of the centre of the sliding table in order to shorten the overall length of the gripper bars. In this way it is possible to carry out an automatic tool exchange in trains of presses, in which the spacing of the presses has been optimized in accordance with current technology.

The introduction of new gripper bars prepared outside of the presses for a new workpiece takes place in the reverse sequence. The sliding tables 1 are retracted into the press tool room and positioned with retracted gripper bar end portions 8. In this respect, the gripper bar central portion 7 with the gripper bar end portions 8 is disposed on the brackets 6 via the guide blocks 5. The gripper bar end portions 8 are then extended by means of the operating cylinder 9 via the take-up member 10 and the tongues 11 retracted respectively therein into an end position which may be selected in advance. The gripper bars are then simultaneously or subsequently completely lifted by means of the lifting beam 4 until the guide blocks 5 contact the brackets 12.

During the lifting operation, the tongues 11 are drawn out of the take-up members 10. In this position, the clamping lever 13 for the guide block 5 and the clamping lever 14 for the gripper bar end portions 8 are actuated by the release of the operating cylinder 16 and the action of the pressure springs 15. In this way the gripper bars are connected into the mechanization drive of the presses.

The lifting beam 4 is then lowered again. This releases the positive connection of the guide blocks 5 with the brackets 6. The gripper bars are then completely exchanged and ready for operation.

In cases in which it is necessary for the mecahnization drive of the press to be off centre, it must firstly be moved back in the longitudinal direction by the value x in order to move from a predetermined direction towards the marker 18. This provides positional conformity between the entire lifting system including the gripper bars and the brackets 12.

The clamping devices of the gripper bars may be formed as shown for example, in Figures 7 to 9.

For this purpose clamp screws 21 are disposed on the lifting beam 4. The clamp screws 21 receive either top nuts 22 or top screws 24. The corresponding counter-elements, the stud bolts 23 and the thread portions 25 are disposed on the brackets 12.

The entire gripper bar exchange takes place with this solution in the same way as in the example described above. After release of the screw connections 22, 23 and 24, 25 the gripper bars may be lowered by the lifting beam 4 by means of the clamp screws 21 and conveyed away. During the clamping of new gripper bars, these are fastened after raising to the bracket 12 by the screw connections 22, 23 and 24, 25 which are produced by the screw clamp 21.

Claims

1. A press provided with a gripper bar for conveying workpieces and a system for automatically exchanging the gripper bar during tool exchange in the press, the excange system comprising gripper bar support means movable to and from the press, and control means for releasing the gripper bar from operative connection in the press such that it is received by the support means to be conveyed thereby from the press, said control means further being oeprative to receive a gripper bar from a said support means into operative connection with the press, whereby to facilitate said automatic exchange.

2. A press according to claim 1 wherein said support means comprises a sliding table on which is aranged lifting means for raising and lowering a gripper bar to and from a position for operative connection to the press.

3. A press according to claim 2 wherein said lifting means comprises a lifting beam extending across the table, and a fluid actuated lifting device arranged to raise and lower the lifting bar.

4. A press according to any preceding claim wherein the gripper bar comprises a central portion and an end portion slidable longitudinally of the end portion, and including contracting means on the support means for contracting the end portion of the gripper bar relative to said central portion.

5. A press according to claim 4 wherein said end portion includes a transversely extending tongue, and said contracting means includes a take-up member for the tongue, and fluid actuated means for moving the take-up member.

6. A press according to any prceceding claim including a marker on the gripper bar in the press, and a stop on the support means, said stop and marker being arranged to cooperate to align said support means to receive the gripper bar.

7. A gripper bar exchange device for the automatic exchange of tools in presses, whose sliding tables are moved out from the presses parallel to the direction in which the workpieces are conveyed, preferably for a train of presses, whose mutual spacing is optimised in accordance with current technology, comprising in each case a sliding table and a short gripper transfer device with cam members, movement transmission elements, gripper bars and gripper elements, characterised in that gripper bar end portions are connected via guide blocks with a gripper bar central portion, in that the gripper bar end portions may be displaced by means of expanding tongues disposed at their ends and by means of an operating cylinder in operational connection therewith via take-up members axially parallel to the gripper bar central portion and may be locked in a positive andlor frictional manner by clamping devices to the brackets of the slide rails of the short gripper transfer device and in that on the sliding table an operating cylinder is in operational connection via a lever gear with a lifting beam, on which beam brackets are disposed and are in positive operational connection with the guide blocks.

8. A gripper bar exchange device as claimed in claim 7 characterised in that a stop disposed on the bracket is in operational connection with a marker disposed on the lifting beam for determining the central position of the bracket with respect to the lifting beam and in that a pre-tensioned pressure spring system is disposed on the lifting beam in order to maintain the operational contact during a common movement condition of the lifting beam and the bracket and, after release of the operational contact, to eliminate the subsequent path.

9. A gripper bar exchange device as claimed in claim 7, characterised in that the clamping devices disposed on the brackets comprise spring clamps whose respective piston rods are in operational connection with one end of a clamp lever formed as a double lever or with one end of a clamp lever formed as a double lever, whilst the other end of the clamp lever clamps the guide block and the other end of the clamp lever clamps the gripper bar end portions in a positive andlor frictional manner.

10. A gripper bar exchange device as claimed in claim 7 characterised in that clamp screws are disposed on the lifting beam as clamping elements, which screws detachably connect the bracket with the gripper bar central portion and the gripper bar end portions by means of top nuts and top screws and stud bolts and thread sections disposed in the bracket.

11. A press provided with a gripper rod exchange system, substantially as herein described with reference to the accompanying drawings.