Handling: hand and hoist-line implements – Grapple
Reexamination Certificate
1999-03-05
2001-03-13
Kramer, Dean J. (Department: 3652)
Handling: hand and hoist-line implements
Grapple
C901S041000, C279S900000, C403S373000
Reexamination Certificate
active
06199928
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a motor-actuable coupler for connecting workpiece grippers with a manipulating device, in particular for the interlinking of stamping presses, consisting of a fixed element on the drive side and a connecting element on the gripper side.
BACKGROUND OF THE INVENTION
The workpiece grippers of manipulating devices, or respectively robots, must be individually matched to the workpieces. In connection with sheet metal parts, for example for motor vehicles, they normally have the form of a tube-shaped boom of, for example, 2 m length, with several boom extensions, to which suction grippers and/or clamping grippers are attached. Since the sheet metal parts are being deformed in several stamping presses, which are linked with each other, until they have their final shape, and since a specially designed workpiece gripper in accordance with the respective intermediate stage is required for a transfer to the next stamping press, 120 different workpiece grippers are required in order to produce 20 different sheet metal parts for a defined vehicle model on a line with, for example six stamping presses. So that the stocks of sheet metal parts can be kept as low as possible, the press tools are mostly exchanged in the course of only a few hours. Accordingly, in one work day it is often necessary to change the workpiece grippers of all transfer robots at the stamping presses ten times.
There are simple connections, which can be manually made by attachment screws, between the boom of a workpiece gripper and the portion of the robot supporting it, which is driven in a controlled manner. However, in view of the very high capital cost of a stamping press line per unit of time, a rapid exchange of the workpiece grippers must be relied upon. This requires quick acting couplers, which are motor-actuated when automatic gripper changing systems are used.
Such known couplers of this kind typically consist of a housing-like fixed element on the drive side, into which a matched connecting element coupled with the boom can be inserted and locked in place by means of interlocking connecting elements, for example stop bolts or hooks extending behind transverse pins. Since all workpiece grippers must be equipped with such a connecting element, considerable total costs result because of the multitude of grippers.
OBJECT AND SUMMARY OF THE INVENTION
It is the object of the invention to create a motor-actuable coupler of the type mentioned at the outset, which permits very rapid coupling and uncoupling, but which has a very simple structure.
The above object is attained in accordance with the invention in that the fixed element of the coupler has a collet chuck and the connecting element is a tube section, which can be centered in the fixed element spaced apart from the clamping area located at the front end of the collet chuck.
Collet chucks are used, for example, for clamping workpieces during lathe operations. In that process only comparatively low bending moments occur, because the cutting tools act on the workpiece at a short distance from the chuck.
In contrast to this workpiece grippers have to absorb considerable moments in particular at stamping presses. At the same time very high demands are made on accuracy. In spite of a long boom, large load stresses and great accelerations, a very narrowly delimited repetitive accuracy of the positioning movements is demanded. For this reason comparatively large connecting elements are provided on the gripper side of known quick change couplers, through which all forces are transferred from the boom to the robot arm, and which must be produced with several fitting surfaces in order to assure exact seating in the fixed element. In contrast to this, with the proposed coupler the structure can be much simpler, since no additional connecting element and no fitting surfaces are required at the point where the collet chuck of the fixed element of the coupler grips a tube section of the boom and clamps it. On the gripper side, a bezel on the front face of the end of the boom which can be inserted into the coupler is sufficient for centering the two coupler elements at a place spaced apart from the clamping place. Alternatively or additionally it is possible to use a collet chuck with two clamping areas arranged at a distance from each other. In both cases no additional connecting element is needed on the gripper side. The frontmost tube section of the boom is simply used as such.
In a preferred embodiment, on the gripper side the conical centering surface is provided on a cover, which is fitted or pressed into the end of the tube section which can be inserted into the collet chuck. This embodiment has the advantage that the cover can support the plug connector elements for compressed air or other power or control connections of the workpiece gripper on the gripper side.
In a further preferred embodiment of the invention, the collet chuck consists in a manner known per se of a bushing, which is conically widened on a longitudinally slit end, of a fitted inner cone on a housing receiving the slit bushing, and of a power cylinder for the axial movement of the slit bushing in relation to the housing. The centering cone surface is located on the side of the fixed element on a holder connected with the slit bushing and the portion of the power cylinder, which can be moved in relation to the housing. Usefully the piston of the power cylinder slides directly in a bore of the housing, so that no additional part is required for the cylinder. A very simple construction of the fixed element of the coupler as a whole is obtained if the housing has a stepped, continuous bore, which is closed at the rear end by a cover and into which a tight separating wall is inserted between the piston of the power cylinder and the holder.
Surprisingly, neither the coupling process nor the centering function is negatively affected if in an advantageous embodiment of the invention the conical centering surface on the side of the fixed element of the coupler is formed on the holder or on another part which is moved in the course of tightening the collet chuck. The reason for this is on the one hand the radial guidance of the holder or another part in the cylinder bore of the housing, on the other hand that a comparatively short axial displacement path of the longitudinally slit bushing of the collet chuck and the holder connected with it is sufficient for causing the clamping and the release of the tube section inserted into the collet chuck. During the short axial displacement it is possible to assure the mutual contact of the conical centering surfaces by means of a force exerted on the boom, if not anyhow after the insertion of its end into the collet chuck the boom is taken along by friction in the course of the axial movement of the slit bushing.
It has been found that it is advantageously possible to connect power-carrying lines, and possibly even control lines, with the holder, in spite of the necessary movements of the holder for tightening and releasing the collet chuck. In a further preferred embodiment of the invention it is therefore provided that the holder is equipped with several compressed air and/or vacuum connections, which extend outward through holes in the housing, which holes are of sufficient size for making the axial movements of the holder in the housing possible. Axially oriented plug connectors, which suitably are furthermore provided on the holder are connected with the compressed air and/or vacuum connections and in the course of inserting the connecting element into the collet chuck can be tightly connected with counter plug connectors arranged on the closing cover of the boom, which are connected with pneumatically actuable elements on the workpiece gripper.
Exemplary embodiments of the invention will be explained in more detail in what follows by means of the drawings.
REFERENCES:
patent: 4545723 (1985-10-01), Clark
patent: 4636135 (1987-01-01), Bancon
patent: 4664588 (1987-05-01), Newell et al.
patent: 4793053 (1988-12-0
Kramer Dean J.
Larson & Taylor PLC
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