Work holders – With fluid means – Cylinder-piston means in series with additional positioning...
Reexamination Certificate
2000-04-25
2001-05-29
Hail, III, Joseph J. (Department: 3723)
Work holders
With fluid means
Cylinder-piston means in series with additional positioning...
C269S024000, C269S027000
Reexamination Certificate
active
06237905
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a hold-down clamp. More particularly this invention concerns such a clamp used to secure a workpiece to a surface.
BACKGROUND OF THE INVENTION
For many machining and woodworking operations it is necessary to secure a workpiece to a machine bed or work surface. It is standard when the bed is formed of steel to provide it with upwardly open grooves of inverted T-section into which is fitted a T-nut or T-bolt that secures the clamp in place.
Such a clamp typically comprises a post having a lower end that is secured to the work surface. A body is displaceable vertically and axially along this post and normally has an arm whose free end can be brought to bear on the tool or workpiece being clamped to the surface to press it down against the work surface.
In U.S. Pat. No. 4,238,124 of Eichfeld the body is formed as a split ring which can be clamped by circumferential tightening at any angular or axial position on the post. Thus the position, both angular and axial, can be adjusted steplessly. Such a system does not make it possible to accurately duplicate a given angular position which is needed in many setups.
German patent 3,333,813 of Schmid discloses a double-jaw work-surface clamp. A collet arrangement is used to control the height or axial position of the upper jaw, and the lower jaw is movable axially by a bolt extending between the jaws. This system is also steplessly adjustable with no way to reproduce a given angular position.
German patent document 4,321,387 of Wurche describes a positioner having an upright post on which is mounted a ring carrying a radially projecting arm. The post has a single radially outwardly open and axially extending groove in which engages a spring-loaded ball mounted in the spring so as to define one standard angular position for the arm. Such a device is not a hold-down clamp; instead it serves merely for accurately setting the position of a workpiece that is then secured in place by standard hold-down clamps. The vertical or axial position of the arm-carrying ring is changed by moving a pair of abutment rings that axially closely flank it and that are each secured in place by a respective set screw, so that adjusting the vertical position is a laborious operation.
German utility model 297 03 707 assigned to HMC-Brauer Ltd. describes a hold-down clamp having a body that is vertically displaceable to a limited significant extent on the post, and whose free end is provided with an extensible bolt acting as a hold-down foot. The angular position of the arm with respect to the post is fixed by an interfitting axially extending groove and rib respectively formed on the body and post. A tightening lever can vertically displace the body through a short stroke so that, once the device is set the clamping can be effected with a single turn of this lever. This device must be carefully adjusted for each setup and, for a new setup, all the adjustments must be changed. There is no simple way to change the angular orientation of the arm relative to the post.
OBJECTS OF THE INVENTION
It is therefore an object of the present invention to provide an improved hold-down clamp.
Another object is the provision of such an improved hold-down clamp which overcomes the above-given disadvantages, that is which is easy to set up, which can accurately assume any of a plurality of different angular positions, and which is of simple and easy-to-service construction.
SUMMARY OF THE INVENTION
A hold-down clamp has according to the invention a post extending along an axis and having a lower end adapted to be secured to a work surface and an upper end and a clamping body axially displaceable along the post and formed offset from the axis with at least one seat. A locator ring engaged around the post can be fixed to the post adjacent the body in any of a multiplicity of angularly and axially offset positions. A locator element fixed on the ring is engaged in the seat.
Thus with this system the locator element can be positioned and locked in place. The body can be pivoted limitedly, depending on the diameter of the pin and the angular dimension of the seat, between two fixed end positions. Thereafter one workpiece after another can be secured with the hold-down body always assuming the exact same angular position with respect to the post. This is very useful for a run of similar machining operations.
The seat in accordance with the invention is a radially outwardly open notch and the locator element is a small-diameter pin extending parallel to the axis from the locator ring engaged in the seat. The angular dimension of the notch is greater than the diameter of the pin.
The body according to the invention is formed with a plurality of such seats angularly offset from one another. Thus it is possible to establish a series of uniformly offset standard angular positions for the clamp body. In addition it is possible to completely release the means securing the ring to the post so that the body can rotate freely on the post if that is desired.
The body of the clamp in accordance with the invention is formed with a radially inwardly open annular groove and is provided in the groove with a spring ring. The post is formed with an axially downwardly directed surface engageable with the spring ring to limit axial upward movement of the body. Thus the body will not slip accidentally upward off the post. More particularly the post is formed with a radially outwardly open annular groove having an upper flank extending generally perpendicular to the axis and forming the downwardly directed surface engageable with the spring ring and a frustoconical lower surface extending at a small acute angle to the axis so that the spring ring can slide out of the outwardly open groove over the lower flank. This groove system is particularly useful if the clamp is mounted with its axis horizontal or vertical but upside-down, as it prevents an overly loosened clamp from falling apart. The spring ring also increases the friction between the body and post somewhat so that it holds in any set position.
The body is axially displaced along the post by a screw threaded axially in the post and having an arm extending radially from the screw. A roller bearing is braced between the screw and the body. A spring is braced axially between the post and the body and urges the body axially upward.
REFERENCES:
patent: 2650523 (1953-09-01), Zwick
patent: 3572216 (1971-03-01), Seesody
patent: 4238124 (1980-12-01), Eichfeld
patent: 5927700 (1999-07-01), Yonezawa
Halder Werner
Hummel Dieter
Dubno Herbert
Hail III Joseph J.
Halder KG Erwin
Wilford Andrew
Wilson Lee
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