Work holders – With fluid means – Cylinder-piston means in series with additional positioning...
Reexamination Certificate
2000-09-19
2001-08-28
Banks, Derris H. (Department: 3723)
Work holders
With fluid means
Cylinder-piston means in series with additional positioning...
C269S228000, C269S091000, C269S239000
Reexamination Certificate
active
06279887
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a toggle lever clamping device comprising a bearing head terminally arranged on an actuating means and on which a pivot unit, which has a clamping arm, is pivotally mounted for pivotal movement about a pivot axis between a release position and a clamping position, an actuating rod, plunging into the bearing head, of the actuating means, furthermore an intermediate member articulated on the one hand at a first bearing point with the actuating rod and on the other hand at a distance from the pivot axis at a second bearing point with the pivot unit, and an abutment face provided on the bearing head and serving for presetting the clamping position of the clamping arm.
A toggle lever clamping device of this type is disclosed in the European patent publication 0 575 888 B1. It possesses a toggle lever arrangement constituted by the pivot unit and the intermediate member, and operated by the actuating rod, pivoted on the intermediate member, of the actuating means. On outward movement of the actuating rod the clamping arm of the pivot unit is shifted into the clamping position, whereas inward movement of the actuating rod leads to retraction into the release position. In order to preset the clamping position a stationary or adjustable terminal abutment (which has an abutment face on the bearing head) is provided, against which the actuating rod strikes on reaching clamping position at the end thereof. This impact leads to a high load on the actuating rod and on the piston, which is normally connected with the rod, of the actuating means.
SUMMARY OF THE INVENTION
One object of the invention is to provide a toggle lever clamping device of the type initially mentioned in the case of which loads prone to produce wear are reduced.
In order to achieve this aim there is the provision that the abutment face is in the path of motion of the pivot unit and cooperates with the pivot unit for presetting the clamping position.
It is in this manner that the clamping position is predetermined by the cooperation between an abutment face on the bearing head and the pivot unit comprising clamping arm. This is responsible for a reduction of impacts otherwise occurring during operation on reaching the clamping position and correspondingly of the load on the actuating means and the components thereof. Owing to the leverage normally present the impact velocity is substantially reduced to below that in the prior art.
Further advantageous developments of the invention are defined in the dependent claims.
It is convenient for the pivot unit to comprise a pivot lever connected in such a manner as to prevent relative rotation with the clamping arm, on which lever the second bearing point is located and which cooperates with the abutment face on the bearing head. This pivot lever may be a component separate from the clamping arm, and be mounted in such a manner as to prevent relative rotation on a bearing pin (which is rotatably mounted on the bearing head) defining the pivot axis, on which pin the clamping arm is mounted in such a manner as to prevent relative rotation. Such an arrangement proves advantageous as regards accommodating the pivot lever in the interior of the bearing head and in the immediate neighborhood of the actuating rod. The clamping arm itself can be located clear of the bearing head so that the bearing head may be designed with compact dimensions.
It is preferred for the abutment face to be provided on the inner side of the bearing head's wall which is located radially short or in front of the pivot axis and extends in parallelism to the pivot axis of the pivot unit. In the case of a pivot unit provided with a pivot lever the said wall preferably extends in front of the pivot lever and aligned at a right angle to the pivot plane.
In the case of a particularly preferred design there is a provision such that the pivot unit comes into engagement with the abutment face just prior to reaching the dead center position of the toggle lever arrangement. The dead center position is defined by a state in which the angle between on the one hand the imaginary connecting line between the two bearing points and on the other hand the longitudinal axis of the actuating rod is a right angle. As the actuating rod moves out of the release setting of the clamping arm the enclosed angle, which is initially still obtuse decreases gradually until the dead center position is reached, the actuating rod conveniently moving on further to a small extent until the enclosed angle is somewhat less than 90 degrees. This terminal position of the actuating rod may for instance be preset by arranging a piston (of the actuating means) connected with the actuating rod comes into engagement with a cover of the actuating means. Since however the contrivance, which was moved, is braked, the load on the piston is in this case small.
In order to ensure that the toggle lever arrangement can move past the dead center setting without difficulty, the joint connection at one of the two bearing points at least is preferably so designed that there is a possibility of a small relative movement in the radial direction in relation to the pivot axes between the components which are articulated together. This is something which may be achieved by a suitable design of the bearings and/or by the provision of suitable elastic means.
In order to minimize the load on the actuating means even on displacement of the clamping arm into the release position, there is preferably a second abutment face provided clear of the actuating means on the actuating rod, such second abutment face being able to run up against a counter face on the bearing head.
The invention will now be described in the following with reference to the accompanying drawings in detail.
REFERENCES:
patent: 4637597 (1987-01-01), McPherson et al.
patent: 4905973 (1990-03-01), Blatt
patent: 5575462 (1996-11-01), Blatt
patent: 5996984 (1999-12-01), Takahashi
patent: 297 13 944 U1 (1997-11-01), None
patent: 296 14 630 U1 (1998-02-01), None
patent: 0849047A1 (1998-06-01), None
patent: 0894573A2 (1999-02-01), None
Glasenapp Uwe
Lichtenberger Thomas
Banks Derris H.
Festo AG & Co.
Hoffmann & Baron , LLP
Wilson Lee
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