Metal deforming – By plural tool-couples – With means to feed work between plural tool stations
Reexamination Certificate
2003-04-01
2004-12-07
Crane, Daniel C. (Department: 3725)
Metal deforming
By plural tool-couples
With means to feed work between plural tool stations
C198S621100
Reexamination Certificate
active
06826944
ABSTRACT:
TECHNICAL FIELD
The invention relates to a transfer device according to the preamble of claim
1
and a method for controlling a transfer device according to the preamble of claim
6
.
It is in particular known in the mass production of punch or press parts to use multistage presses, wherein one workpiece is subsequently moved through the individual stations of the press at which a certain processing is performed. The workpieces are gripped at all stations of the press, lifted, transferred and transported to the next station by so-called transfer devices during the opening lift of the press. Accordingly, it is required that a transfer device normally performs a movement of the workpieces in three subsequently following vertical moving directions. Starting from an open position, which the transfer device assumes when the lift of the press was just completed, the transfer device must close. This usually means that so-called gripper rails extending in the travel direction of the workpiece are moved towards the workpieces from both sides thereof, and catching fingers, which are usually provided at the gripper rails will grip the workpieces. Then, the gripper rails, and, thus, the workpieces are lifted in order to move them out of mesh from the processing tools. Thereupon follows the feed of all workpieces in the travel direction of the press. When all workpieces have reached the correspondingly next processing station, the gripper rails and, thus, the workpieces are lowered. Finally, the grippe rails open and return to their starting position by a movement opposite to the direction of feed, so that a new further transfer of all workpieces may follow after the end of the lift of the presses.
PRIOR ART
U.S. Pat. No. 5,307,666 discloses a transfer device which performs a movement with only two axes. The workpieces are gripped by a movement of the gripper rails towards each other and transferred to the next station by a movement in the direction of feed. No lifting is provided therein.
According to U.S. Pat. No. 5,586,464, the workpieces are additionally lifted, with the closing movement as well as the lifting movement of the gripper rails being performed by a common driving apparatus and by means of a cam mechanism.
In U.S. Pat. No. 5,423,202, the closing and the lifting of the gripper rails is carried out by separate driving apparatus. However, the driving apparatus for closing the gripper rails is situated on that component part which is lifted by the lift drive. This has the deficiency that the lift drive must be designed comparatively large. Further, the electric cables and the like, which lead to the closing drive, must be moved in each lifting movement and are therefore subject to considerable wear.
These disadvantages likewisely apply to the subject matter of EP 0 701 872 A1, in which a lift drive is also provided in order to lift the gripper rails together with the drives for the closing movement.
According to EP 0 849 015 A2, a ball bearing spindle is provided for the movement in one of the two required directions. Such a ball bearing spindle is, on the one hand, very noisy in operation. On the other hand, very high driving speeds are required for the rotation of the ball spindle which makes a complicated design of the drive necessary.
These disadvantages also apply to the arrangement according to DE 197 21 613 A1, in which the gripper rail is supported on parallel steerings which are rotatably attached to a slide. By a further slide having a lever which acts on one of the parallel steerings through a nut connected to the further slide a lifting of the gripper rails is effected by the rotation of a spindle.
JP-A-06031358 discloses a drive of a gripper element which has toothed racks and pinions. Herein, the lift drive must also be moved with the close drive in the close direction. A lifting is performed by moving the lift drive which is suitably connected to the gripper element by additional pinions and toothed racks.
DE 39 33 775 A1 discloses a device according to the preamble of claim
1
and a method according to the preamble of claim
6
. The close drive is performed by a fixed cam disk through a suitable crank gear. The drive of the lift is also performed by a cam disk through a crank gear which is connected to a rail which is transversely arranged. A vertical guide column is shiftable supported at the upper end of which the gripper elements are situated.
SUMMARY OF THE INVENTION
The invention is based on the objective problem to create a transfer device and a method for controlling a transfer device, wherein the arrangement of the transfer device and, in particular, of the required drives may be designed in a particularly simple manner.
The solution of this objective problem is realized by the transfer device according to claim
1
.
Accordingly, a lift drive for lifting the gripper rail, which is generally designated gripper, is provided, on the one hand. On the other hand, the transfer device according to the invention has a close drive for moving the gripper in lateral direction. In addition, a controller is provided, which is required for the connection according to the invention of both drives with the elements to be moved, which is explained in the following.
According to the invention, both drives are namely fixedly mounted, so that none of the two motors must be designed such that it must also drive the respective other drive mechanism apart from the parts to be moved. It is in particular not required that the lift drive must inter alia lift the close drive. Consequently, the drives may be designed comparatively small and compact which means a first simplification of the transfer device according to the invention and the reduction of the manufacturing costs. In addition, this arrangement offers the advantage that the electrical cables and the like which lead to the drives do not need to be moved during normal operation so that they do not need to be designed excessively wear-resistant either, which means a further reduction of cost.
As was stated above, it is conceivable with fixed drives that the engagement with the elements to be moved is performed via ball bearing spindles which have, however, certain disadvantages. Further, it is known to realize the transmission of the motion of rotation of an electromotor into the translational movement of the gripper rail via toothed racks and toothed belts. However, those belts must have an extremely great cross section in order that they are not excessively extended when loaded. This is required for a sufficiently precise movement without risk of vibrations and the like. Finally it would be conceivable to connect the lift drive with the part to be moved by means of an element, which is shiftably provided on a drive element of the motor. In this case, the lift drive remains in engagement with the element to be lifted also during the opening and closing movement. However, such a construction is comparatively complex.
According to the invention, it is provided that the two drives are constantly in engagement with the parts to be moved in an exclusively articulated manner. No additional ball bearing spindle is therefore provided, as it is the case with DE 197 21 613 A1. Rather, according to the invention, the transmission of the motion of rotation of the motor into a translational movement of the elements to be moved is realized in that a comparatively simple lever and bracket mechanism is provided the elements of which are connected with each other in an exclusively articulated manner. The required translational movement is realized by means of a suitable guidance of the parts to be moved. The described exclusively articulated connection of the respective drive to the element to be moved is comparatively simple to realize and is a further contribution to the simplification of the construction.
It should be mentioned that in view of the described connection between the two drive motors and the elements to be moved a compensation must take place such that the gripper rail is, for example, not lowered when it is opened. Base
Crane Daniel C.
Wolf Greenfield & Sacks P.C.
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