Metal deforming – By plural tool-couples – With means to feed work between plural tool stations
Reexamination Certificate
1999-05-05
2001-02-13
Crane, Daniel C. (Department: 3725)
Metal deforming
By plural tool-couples
With means to feed work between plural tool stations
C072S405130, C198S621100
Reexamination Certificate
active
06185979
ABSTRACT:
BACKGROUND AND SUMMARY OF THE INVENTION
The present invention relates to a transfer system for multi-station presses and/or press working lines.
In for example, multi-station presses or press working lines, transfer systems have the task of transporting sheet metal parts or other workpieces from one press station to another. A workpiece passes successively through all press stations. The transfer system has the task of moving the opening tool over, i.e. below the top tool lifting off the workpiece, of picking up the workpiece, of moving it into the still open tool of the next press station and of depositing the workpiece there. Before the top tool is placed on the workpiece, the corresponding part of the transfer system must have been moved out of the tool.
During this operation, the gripper devices of the transfer system must cover considerable distances and move relatively large masses. Particularly with large-part presses, vehicle body presses and comparable facilities, very high accelerations and braking decelerations result and cannot easily be infinitely increased when the running speed (stroke number) of the press is to be raised.
EP 0388610 B1 describes a press facility which has a two-axis transfer system. The transfer system has two running rails which extend on both sides of the tools along the entire length of the press facility and on which travelling carriages are disposed. The running rails are connected with lifting devices which move the running rails synchronously up and down in the timing of the hybrid press facility. Two mutually opposite travelling carriages respectively are connected with one another by suction bridges or cross traverses. These are provided with vacuum suction devices so that a workpiece can be taken up and deposited in a controlled manner. By way of a transport linkage, the travelling carriages are connected with a drive to provide them with a longitudinal movement. By superimposing the lifting and lowering movement of the running rails on the longitudinal movement of the travelling carriages, the suction bridges negotiate the desired transfer curve by which the parts are transported.
When the tools close, the suction bridges must stand between the tools. Because of the finite moving and transporting speed of the suction bridges, this means that a maximal number of strokes cannot be exceeded. With smaller press strokes, higher stroke numbers are frequently desirable.
In addition, so-called three-axis transfer systems are known, in which, instead of the running rails, transfer bars are provided. In addition to the lifting and lowering movement, the transfer bars can also carry out a transfer movement in the transport direction and an opening and closing movement laterally with respect to the transport direction. The transfer bars carry blades which can reach laterally under the sheet metal parts.
Transfer systems of this type can carry out, for example, a return stroke when the tools of the individual press stations are closed. In the third axis, the blades held on the transfer bars carry out a lateral escape movement and move laterally past the closed tools. However, the blades grip the workpieces only on the edge. For this type of parts transport, the stability of the workpieces must therefore be sufficiently high. If parts are separated in a press station, i.e., if two sheet metal parts are cut out of a blank which are to be transported, e.g., side-by-side, the parts transport cannot be carried out only by means of the blades which reach into the tools from the sides. This limits the application possibilities of the three-axis transfer system.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a transfer system which permits high stroke numbers of the presses and a high flexibility.
This object has been achieved by a transfer system having at least one transfer carrier extending along at least two press stations, workpiece receiving devices operatively arranged to interact for receiving a workpiece, the workpiece receiving devices being carried by the transfer carrier and arranged to be moved toward one another into a workpiece receiving position, and away from one another into a workpiece-release position.
The transfer system according to the invention has at least one transfer carrier which moves past several tools and on which at least two workpiece receiving devices are provided. These can be moved toward one another and away from one another in order to pick-up and release a workpiece. For the transport of the workpiece, the workpiece receiving devices are advanced one more tool position. The transfer curve covered in this manner has two components, namely a lifting/lowering movement and a translational movement. The movement of the workpiece receiving devices toward one another and away from one another represents a third movement component, whose direction preferably coincides with the direction of the translational movement.
The transfer system of the present invention permits shortened transfer times and therefore higher stroke numbers. The shortening of the transfer times is the result of the minimizing of the required moving path for picking up and depositing the parts. While conventional suction bridges must be moved a long distance to the tool center into the opening tool, in the case of the transfer system according to the invention, the short-distance moving of the receiving devices into the opening tool can be started relatively early. The moving-in path amounts is short, for example, only a few centimeters.
A further saving of transfer time is achieved by the possibility of positioning the receiving devices in a preparatory manner for the subsequent transfer step during the press stroke, i.e., when the tools are closed. While, with a conventional two-axis transfer system with cross traverses (suction bridges), during the working stroke of the press station, the cross traverse must stand in a waiting position therebetween, the receiving devices of the transfer system according to the invention can be guided past the closing or closed tools. A portion of the required path to be covered by the receiving devices can therefore be covered during the working stroke of the press, which saves a considerable amount of time. Particularly when the presses are set to a low stroke, this permits the carrying-out of high stroke numbers.
In their receiving movement, the receiving devices are aligned toward and away from one another in the transport direction. As a result, the receiving devices can hold a front and a rear edge of the workpiece with respect to the transport direction. In contrast to holding devices which are applied laterally to the workpiece, the transfer of less stable parts and, in the case of a corresponding setup, also the transfer of parts guided in parallel through the press stations is permitted. This results in multiple application possibilities.
In a preferred embodiment, the workpiece receiving devices can be changed not only into a workpiece receiving position and a workpiece release position but also into an overtaking position which allows or facilitates the moving of the workpiece receiving devices past closed tools. This provides the basis for workpiece receiving devices which are relatively wide in the transverse direction. For the movement past closed tools, these can be folded for example, in the longitudinal direction or in the vertical direction but definitely into a position in which they require only very little space in the lateral direction. In addition to swivelling and folding movements, telescopable devices or the like can be used. The large transverse dimension of the receiving devices situated in the workpiece receiving position is particularly suitable for handling several parts guided in parallel or instable parts.
Swivel arms can, for example, also be used as receiving devices which, in each case at one end, are swivellably disposed on the transfer carrier. For receiving the workpiece, the swivel arms are swivelled toward one another until they are aligned parallel
Crane Daniel C.
Evenson, McKeown, Edwards & Lenahan P.L.L.C.
Schuler Pressen GmbH & Co. KG
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