Conveyors: power-driven – Conveyor section – Reciprocating conveying surface
Reexamination Certificate
2002-05-01
2004-03-30
Crawford, Gene O. (Department: 3651)
Conveyors: power-driven
Conveyor section
Reciprocating conveying surface
C198S750120, C414S732000, C414S733000, C901S021000
Reexamination Certificate
active
06712198
ABSTRACT:
The invention relates to a transport system for transporting workpieces from a machining station into the next machining station or intermediate store of a press, press line, simulator, or the like.
PRIOR ART
Where the manufacture of a workpiece calls for a plurality of work operations, such as cutting or shaping, then for economic production the necessary individual operations are carried out in a transfer press or press line, as they are known. The number of tools then corresponds to the number of work stages which are necessary for the manufacture. In the presses there are transport devices with which the workpieces are transported from one workstation to the next.
In the case of transfer presses or large-component transfer presses, the transport devices comprise gripper or load bearing rails which extend through the entire length of the shaping machine. In order to transport the components, the load bearing rails are fitted with gripper or holding elements. In this case, a distinction is made, depending on the movement sequence, between a two-axis transfer fitted with suction crossmembers or a three-axis transfer fitted with gripper elements. As an additional movement, pivoting in order to change the attitude of the component during the transport step may be required. This attitude change can also be carried out by an orientation station arranged between the shaping stages.
The transfer movement is initiated via cams, which are forcibly synchronized with the ram drive via movement transmission elements. The manufacture of large-area components, in particular, has led to the development of large-component transfer presses of greater and greater dimensions, based on the shaping force and the transport paths. Tool spacings of the order of magnitude of 5000 mm are entirely normal nowadays, and therefore corresponding transport steps are also necessary.
As a result of this development, the masses to be accelerated and braked in the transfer systems are completely opposed to the low masses of the components to be transported. Since the transport step is to be executed in an extremely short time, in order to achieve the greatest possible number of press strokes and therefore output of components, the system must have a high speed and therefore also acceleration and retardation.
A further disadvantage is the rigid movement sequence which is predefined by the cam drives. The optimum utilization of the free spaces between the lower and upper tool during the ram stroke to transport the parts is not possible.
In order to avoid these indicated disadvantages, intellectual rights applications nowadays concern the replacement of the previous transfer system by a corresponding number of transfer systems arranged between the machining stages and equipped with their own drive. Such an arrangement is disclosed by EP 0 672 480 B1. Transfer systems arranged on the uprights are equipped with a number of drives which, in operative connection with the movement transmission means, carry out the transport of the components. As a special feature, the system can be re-equipped both as a two-axis transfer with suction beams and as a three-axis transfer with grippers. However, this universal use requires a corresponding outlay on construction.
Likewise arranged in each upright area is a transfer device disclosed by DE 196 544 75 A1. In this application, elements which are known as—parallel cinematics—are used for the drive. In a modification of these known movement elements, however, telescopic lengthening of the drive rods is not performed, but, with a constant rod length, the attachment points are changed and therefore the transport movements are achieved. The attachment points that accommodate the forces or torques are not constant in terms of their distance from one another and, in particular when these points are close to one another because of the desired travel curve, support problems can occur. In order to increase the stiffness of the system, further mutually parallel links are also proposed, which are connected to one another by transverse crossmembers. In order to achieve functionally reliable transport of large-area components, the proposed system becomes correspondingly complicated and has a large overall height.
In DE 100 10 079, not previously published, the applicant proposes a system having transport devices arranged in the press upright area, which operate in a way comparable with a pivoting-arm principle. Crossmembers which are provided with component pick-up and holding means and are arranged transversely with respect to the transport direction are in each case held and moved at their ends by these pivoting-arm robots. Thus, the pivoting-arm robots are in each case arranged in pairs and opposite each other in the upright area. Because of the overall height and the vertical movement required by the drive concept, the transport system proposed is in particular suitable for presses with a relatively large overall height. The pivoting arm comprises a rigid piece which results in a correspondingly large pivoting radius. Since the intention is for the workpieces to be removed at the earliest possible time after the start of the ram upward movement, the large pivoting radius and the resulting obstructing edges are unfavorable. With this system, a desirable flat entry or exit curve can be implemented only with difficulty.
OBJECT AND ADVANTAGE OF THE INVENTION
The invention is based on the object of providing a highly flexible and precise transport system with a low overall height which ensures advantageous utilization of the free movement between the upper and lower tool for the purpose of insertion and removal of workpieces.
The invention is based on the idea, instead of using a rigid transport system, to design the latter from two parts which are connected to each other, mounted in an articulated fashion. In order to achieve a flat entry and exit curve, the pivoting angle of the first part arm can be selected to appropriately large.
On the basis of the proposed design, in conjunction with controlled drives, the pivoting angle can be selected within any technically practical range. As a result, in the tool area the transport arm is located in a very flat attitude oriented toward the horizontal plane.
Thus, with a relatively small opening stroke of the press ram bearing the upper tool, the articulated arm can advantageously move into the clearance which forms between the upper and lower tool.
Particularly advantageous is a design of the two articulated arm parts with equal lengths, since then a horizontal transport movement is executed. The suction spider carrying the workpiece therefore carries out a distortion-free horizontal movement. The vertical movement necessary to deposit and raise the workpieces is executed by a stationary lifting drive.
Given superimposition of the horizontal and the vertical movements, an appropriately beneficial flat curve course can be implemented at the start and end of the transport movement. The large-component transfer press or press line can be run without difficulty with phase-shifted ram positions, which results in a beneficial force distribution with a low drive power. This measure likewise increases the component output by reducing the transport times.
During the actual shaping operation, the articulated-arm transport system should be located in a lowered position in the upright area, as a result of which beneficial accessibility to the rising ram is provided for the following component transport. This accessibility permits an early inward movement and, as a result, in addition reduces the idle times. This lowered parking position is also made possible by superimposing the horizontal and the vertical movements.
Depending on the task set, it may be necessary for the attitude of the components to be changed between two shaping stations. In a press line, the attitude change takes place by means of intermediate stores, orientation stations as they are known. Since the intermediate stores lead to an enlargement of the overall press length, attempts are made
Harsch Erich
Reichenbach Rainer
Crawford Gene O.
Müller Weingarten AG
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