Work holders – With fluid means – Cylinder-piston means in series with additional positioning...
Reexamination Certificate
1999-10-14
2001-03-13
Watson, Robert C. (Department: 3723)
Work holders
With fluid means
Cylinder-piston means in series with additional positioning...
C269S227000
Reexamination Certificate
active
06199848
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a fluid power gripper comprising a housing having a receiving space in which two pistons are located able to be moved by fluid power to perform oppositely directed axial drive movements, which pistons are connected or adapted to be respectively connected with a gripper element, a synchronization means, including a body of revolution, for synchronization of the drive movements of the two pistons, such synchronization means having first mesh means, provided on the two pistons, and second mesh means simultaneously in engagement with the first mesh means, such second mesh means being provided on the body of revolution, and axial tails provided on the two adjacent end regions of the two pistons, such axial tails overlapping one another axially and being opposite to each other with a clearance athwart the longitudinal axis of the receiving space, such tails furthermore bearing, on facing lateral surface thereof, the first mesh means, the body of revolution bearing the second mesh means being arranged in an intermediate space present between the two axial tails and being mounted for rotation about an axis of rotation extending athwart the longitudinal axis of the receiving space in relation to the housing
THE PRIOR ART
A fluid power gripper of this type, which is also termed a parallel gripper, is disclosed in the German patent publication (utility model) U 9,214,477. This gripper possesses a housing with an elongated receiving space, in which two pistons are arranged, which are respectively connected with the aid of a guide pin, which extends through the end wall of the housing, with a gripper element. When the inner section of the receiving space between the two pistons is put under pressure, the two pistons are moved away from one another and if the two outer receiving space sections are put under pressure simultaneously the pistons are moved toward each other. It is in this manner that an opening or closing movement of the gripper elements may be produced, the synchronization means ensuring ganged motion of the two pistons and consequently of the gripper elements.
In the case of a known gripper as disclosed in the U.S. Pat. No. 5,657,973 the synchronization means comprises a threaded rod, which extends through the two pistons and makes threaded engagement with them. Since a left hand screw thread is provided in the engagement zone with the one piston and in the engagement zone with the other piston a right hand screw thread is provided, there is a synchronized coupling of the movements of the two pistons via the threaded rod. A disadvantage of this arrangement is however the high friction at the screw threaded engagement zones making it necessary for the piston to provide large setting forces, and this is an obstacle to designing on a small and miniature scale. Furthermore elaborate sealing means are required in the zones where the screw threaded rod extends through the piston in order to provide a fluid-tight seal between the inner receiving space and the outer receiving spaces.
SHORT SUMMARY OF THE INVENTION
One object of the invention is to provide a gripper of the type initially mentioned which while having a simple structure is characterized ba low friction operation and which simplifies the design of small overall sizes of grippers.
In order to achieve these and/or other objects appearing from the present specification, claims and drawings, in the present invention in the peripheral part of the two pistons the housing is respectively provided with an axially extending longitudinal slot which is open on the one hand radially inward into the receiving space and on the other hand radially outward to an outer face of the housing and each of such longitudinal slots has an entraining means extending through it, such entraining means producing an entraining connection between the respectively associated piston and one of two gripper carriers, arranged to slide on the outer region of the housing, or gripper elements, the entraining means running at a right angle to the axis of rotation of the body of revolution.
This means that the mesh engagement between the mesh means provided on the pistons and on the body of revolution extends along only an extremely small axial length of the receiving space, this leading to low friction losses. Owing to the mutual arrangement at a right angle to one another of the entraining means and the axis of rotation of the body of revolution it is furthermore possible for the tendency to run skew in the mesh engagement to be reduced. Even relatively small drive forces are sufficient to move the piston with the associated gripper elements, something which favors design on a small scale. The assembly of the components in meshing engagement with one another of the gripper is relatively simple and furthermore the constructional complexity is reduced, because a sealed arrangement of the body of revolution where it extends through the pistons is unnecessary. This is something which increases functional reliability because the number of seals is diminished.
Further advantageous developments of the invention are defined in the claims.
A design which is more particularly suitable for products with large dimensions is such that the axial tails are designed like racks, their mutually facing teeth constituting the first mesh means. The body of revolution is in this case best designed in the form of a gear wheel such as a pinion.
More particularly in the case of minimum overall sizes a design is to be recommended in the case of which the first mesh means have respectively only one single recess, the second mesh means arranged on the body of revolution being constituted by only two mutually diametrally opposite projections, which fit respectively into one of the recesses of the first mesh means. It would be feasible as well to have a reversed arrangement having projections arranged on the piston and recesses provided in the body of revolution.
In order to ensure simple assembly an arrangement is to be recommended in which the body of revolution is rotatably mounted on a bearing journal or pin, which extends through the receiving space and has its two axial end region locked in the housing to prevent mutual rotation. In this respect it is possible for the body of revolution to be mounted on the bearing journal so that axial sliding motion is possible.
The attachment of the bearing journal is best such that it is swaged into a transverse hole extending through the housing athwart and through the receiving space. In addition or alternatively there may also be a provision such that the bearing journal ends in the transverse hole at a distance within the housing, closure elements being provided in the outer terminal sections of the transverse hole, such closure elements being more particularly constituted by screw elements and being anchored to the housing.
Further advantageous developments and convenient forms of the invention will be understood from the following detailed descriptive disclosure of embodiments thereof in conjunction with the accompanying drawings.
REFERENCES:
patent: 5657973 (1997-08-01), Zajac, Jr. et al.
patent: 38 06 148 A1 (1988-09-01), None
patent: 92 14 477 (1992-12-01), None
patent: 0 344 953 A1 (1989-12-01), None
patent: 1257813 (1961-02-01), None
Bellandi Giuseppe
Maffeis Giuseppe
Festo AG & Co.
Hoffman & Baron LLP
Watson Robert C.
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