Chucks or sockets – With fluid-pressure actuator – Radially reciprocating jaws
Reexamination Certificate
1998-04-16
2001-10-09
Bishop, Steven C. (Department: 3722)
Chucks or sockets
With fluid-pressure actuator
Radially reciprocating jaws
C279S121000, C279S157000
Reexamination Certificate
active
06299179
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to pneumatic and hydraulic actuated chucks.
BACKGROUND OF THE INVENTION
Fluid actuated chucks, both pneumatic and hydraulic, are known in the art. U.S. Pat. Nos. 3,770,287, 4,114,909, 4,139,207, 4,147,312, 4,200,301, 4,229,014, 4,317,577, 4,387,906, 4,697,966, 4,771,963, 4,793,053, 4,890,541, 4,946,178, 4,953,877, 4,979,853, 5,030,048, 5,110,146, 5,125,776, 5,127,780, 5,141,370, 5,174,585, 5,237,895, 5,249,815 and 5,259,630 are believed to be representative of the prior art. In general, fluid actuated chucks include a piston which axially drives a centrally located wedge which engages chuck jaws. The axial movement of the wedge causes the jaws to move radially inwards or outwards.
One of the problems of prior art fluid actuated chucks is that the jaws are generally not sealed from possible contamination from chips and machining fluids. In certain machining operations, such as grinding, chips can degrade the performance of the chuck.
In general, the inner sliding portion of the jaws of prior art fluid actuated chucks has a T-shaped cross section. The plurality of tolerances in machining the sliding portion of the jaws and the corresponding channels in the chuck limits the accuracy and repeatability of the chuck usually to no better than one micron.
It is believed that the same plurality of tolerances is the cause of another problem associated with prior art chucks. The problem is that during operation at relatively high rotational speeds, the chuck jaws sometimes have a tendency to “self-open”, that is, to loosen their grip on the workpiece.
In a perfectly manufactured chuck, the chuck jaws lie along axes which are coplanar. In actuality, due to the above mentioned tolerances, each chuck jaw does not lie exactly on its corresponding ideal axis. Rather, each end of each chuck jaw lies out of the ideal common plane of the ideal axes. During operation at relatively high rotational speeds, it is believed that relatively large centrifugal forces develop which cause the ends of the chuck jaws to become further displaced from the ideal common plane, thereby causing loosening of the workpiece.
SUMMARY OF THE INVENTION
The present invention seeks to provide a novel fluid actuated chuck which has better sealing properties, accuracy and repeatability than prior art fluid actuated chucks. A chuck constructed in accordance with a preferred embodiment of the present invention may have submicron repeatability even when it is made using the same conventional manufacturing techniques used in constructing prior art chucks.
In addition, a chuck constructed in accordance with a preferred embodiment of the present invention substantially prevents loosening of a workpiece even during relatively high rotational speeds.
There is thus provided in accordance with a preferred embodiment of the present invention a chuck actuated by a fluid including a body, a plurality of master jaws slidably mounted in the body, a fluid driven piston mounted for axial motion relative to the body along an axis, the piston including a plurality of bores extending therethrough along bore axes inclined with respect to the axis, and a plurality of shafts, each slidably mounted in one of the plurality of bores and being coupled to one of the master jaws, and wherein axial movement of the piston along the axis causes the plurality of shafts to move and to cause the plurality of master jaws to move therewith.
There is also provided in accordance with a preferred embodiment of the present invention a fluid actuated chuck including a body, a plurality of master jaws mounted for radial motion in a plane with respect to the body, a fluid driven piston mounted for axial motion relative to the body along an axis substantially perpendicular to the plane, the piston comprising a plurality of bores extending therethrough along bore axes inclined with respect to the axis and with respect to the plane, and a plurality of shafts, each slidably mounted in one of the plurality of bores and being coupled to one of the master jaws, and wherein axial movement of the piston along the axis causes the plurality of shafts to move radially relatively to the body and to cause the plurality of master jaws to move radially therewith.
In accordance with a preferred embodiment of the present invention, the plurality of bores and the plurality of shafts have corresponding generally circular cross sections.
Additionally in accordance with a preferred embodiment of the present invention, each master jaw is mounted for radial motion in a radial jaw bore, the plurality of master jaws and the plurality of radial jaw bores having corresponding generally circular cross sections. Preferably, each radial jaw bore is substantially sealed.
Further in accordance with a preferred embodiment of the present invention, the fluid actuated chuck also includes a plurality of seals operative to substantially seal the body, the plurality of master jaws, the piston and the plurality of shafts.
Still further in accordance with a preferred embodiment of the present invention, the fluid used to actuate the chuck is operative to lubricate the body, the plurality of master jaws, the piston and the plurality of shafts.
In accordance with a preferred embodiment of the present invention, a central shaft is provided for supplying pressurized air or hydraulic fluid to the piston for driving thereof.
Additionally in accordance with a preferred embodiment of the present invention, the plurality of master jaws are mounted such that displacement thereof is substantially prevented during operation at relatively high rotational speeds.
Further in accordance with a preferred embodiment of the present invention, a plurality of work jaws are fastened to the plurality of master jaws, such that the plurality of work jaws substantially seals the plurality of master jaws.
In accordance with a preferred embodiment of the present invention, each work jaw includes a generally axial tongue and each master jaw has a corresponding generally axial slot, such that the tongue fits into the slot.
The work jaws may be any shaped jaws such as soft jaws, pie jaws or half round jaws, and may be of different sizes and formed from a variety of materials.
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Bishop Steven C.
Helfgott & Karas, PC
R. S. R. Adtec Ltd.
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