Work holders – With fluid means – Cylinder-piston means in series with additional positioning...
Reexamination Certificate
2000-04-24
2001-10-30
Hail, III, Joseph J. (Department: 3723)
Work holders
With fluid means
Cylinder-piston means in series with additional positioning...
C269S024000, C269S136000
Reexamination Certificate
active
06308943
ABSTRACT:
PRIORITY CLAIM
This application is based on and claims the priority under 35 U.S.C. §119 of German Patent Application 199 18 770.3, filed on Apr. 24, 1999, the entire disclosure of which is incorporated herein by reference.
FIELD OF THE INVENTION
A clamping device holds a workpiece in place by a clamping bolt which in turn is locked in place by a locking piston cooperating with the clamping bolt through a wedging incline and a tongue and groove combination.
BACKGROUND INFORMATION
Clamping tools in which a clamping bolt is slidably mounted in a housing are known in the art. A locking piston is also slidably movable in the housing preferably at right angles to the clamping bolt. The position of the clamping bolt is accomplished by the cooperation of wedging inclines. One wedging incline is provided on the locking piston or rather on its piston rod, while the other wedging incline is provided on an inner end of the clamping bolt.
These clamping tools must make sure that the workpiece is securely held in place on a surface in such a way that during a machining operation the forces effective on the workpiece do not diminish or remove the clamping force.
European Patent Publication EP 0,620,084 and corresponding German Patent Laying-Open Publication 43 11 857 disclose a clamping tool for clamping workpieces by a clamping head that is slidingly guided on an inclined plane in such a way that the frictional forces between the plane and the clamping head are larger than the forces effective on the clamping head. The inclined plane is formed between a lower section of the clamping head that is formed into a pestle and the piston rod of a clamping force holding element extending crosswise to the force direction of the clamping head. In order to increase the frictional force in the area of the inclined plane a V-groove is formed in the wedging incline of the piston rod and the pestle is formed with wedging bevels sliding in the V-groove. In order to move the clamping head against the workpiece two hydraulic drives are required, one for the clamping head and one for the holding piston. The need for separate hydraulic drives results in a relatively large structural assembly. U.S. Pat. No. 5,746,420 (Kohlbert) discloses a similar device as just described.
U.S. Pat. No. 5,915,679 (Kohlert) discloses a support element for securing a workpiece on a supporting surface, for example in a machine tool. The support element comprises a support or holding bolt movably mounted in a housing. The bolt is moved into contact with a workpiece by an air stream. Once contact is established, the holding bolt is held in place by a hydraulic piston extending in the same housing at right angles to the holding bolt. When the hydraulic locking piston is released, the holding bolt is reset into a rest position by a spring. The workpiece is contacted under a manual throttle control of the air stream and firmly held in place by hydraulic pressure. Here again two sources of pressure, one hydraulic one pneumatic are required for the operation of the clamping tool.
There is a trend in the technology of clamping tools to make these tools ever smaller while maintaining their high efficiency in a structurally compact component.
OBJECTS OF THE INVENTION
In view of the above it is the aim of the invention to achieve the following objects singly or in combination:
to construct the clamping tool as a compact element in which the required movements of a clamping bolt and a locking piston are accomplished by a single hydraulic drive system;
to construct the clamping bolt and locking piston in such a way that a self-locking is effective when the clamping bolt is in its work position without any elastic yielding;
to provide a compact workpiece holding tool that is easily adapted to all requirements that must be met by such clamping tools;
to utilize a self-locking effect in such a way that the clamping bolt and locking piston will retain their working positions even if the hydraulic pressure that moved the locking piston into its working position becomes unavailable for whatever reason; and
to keep the locking piston solely by a self-locking action in its working position independently of any reaction forces caused by the forces occurring when machining the workpiece.
SUMMARY OF THE INVENTION
According to the invention the above objects have been achieved by the combination of the following features. The present clamping device is characterized by a housing with a first bore in which a clamping bolt is slidably mounted to project out of the housing for contacting a workpiece. The housing has a second bore crossing the first bore and a locking piston is slidably movable in the second bore. The locking piston includes a piston rod provided with a first wedging incline. A second wedging incline is provided on an inner end of the clamping bolt inside the housing. The two wedging inclines cooperate with each other for locking the clamping bolt in a fixed working position in response to moving the locking piston and piston rod into a bolt locking position. A tongue and groove combination is provided between the piston rod and the inner end of the clamping bolt. The tongue and groove combination includes a tongue and a groove in which the tongue is guided in a force transmitting manner for facilitating the positioning of the clamping bolt by the locking piston. The groove comprises first and second groove portions interconnected by an open neck. The tongue comprises first and second tongue sections slidingly received in the first and second groove portions for slidingly guiding the tongue in the groove when the piston and piston rod are moved relative to the clamping bolt by pressure, such as hydraulic pressure applied either to one end or to the other end of the piston and piston rod.
It is an advantage of the invention that the locking piston with its rod assumes a self-locking position or condition when the clamping bolt has reached a workpiece contacting position. At that point the locking piston with its piston rod will retain this position independently of reaction forces generated by the machining of the workpiece and independently of any hydraulic pressure that brought the locking piston into its working position. The self-locking effect prevents the clamping bolt from moving out of the interlocking position until a release hydraulic pressure is introduced into a pressure chamber on the piston rod side of the locking piston in the second bore in the housing. The self-locking effect also is free of any elastic yielding.
REFERENCES:
patent: 4506871 (1985-03-01), Yonezawa
patent: 4932640 (1990-06-01), Shirkawa
patent: 5096009 (1992-03-01), Hirmann
patent: 5174554 (1992-12-01), Yonezawa
patent: 5374041 (1994-12-01), Bernstein
patent: 5746420 (1998-05-01), Kohlert
patent: 5915679 (1999-06-01), Kohlert
patent: 251439 (1912-01-01), None
patent: 332373 (1920-03-01), None
patent: 1646420 (1952-02-01), None
patent: 1552707 (1970-07-01), None
patent: 4311857 (1994-10-01), None
patent: 0620084 (1994-10-01), None
patent: 814647 (1981-03-01), None
Fischer David
Kohlert Rudolf
A. Roemheld GmbH & Co KG
Fasse W. F.
Fasse W. G.
Hail III Joseph J.
Shanley Daniel
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