1. Field of the Invention
This invention relates to a chuck for clamping and holding hollow bodies and more particularly to a fluid actuated holding device including a plurality of individual, annularly arranged, clamping fingers which have yieldably mounted terminal ends movable between inoperative positions and workpiece clamping position by a pliant, fluid actuated flexible annular ring.
2. Description of the Prior Art
Workpieces having a thin walled cylindrical or tubular surface to be machined are easily distortable and are frequently "out of round" on either or both of their outside diameter or their inside diameter. With one prior art type clamping device used to hold the workpiece during machining, the chuck is unable to adequately grip a hollow workpiece without distorting the workpiece. Such prior art holding devices typically comprise a diaphragm chuck having a mechanical sleeve in combination with a pliant sleeve to clamp the part. In one such prior art device, disclosed in U.S. Pat. No. 3,542,354 issued to Paul Fitzpatrick on or about Nov. 24, 1970, as the sleeve engages the workpiece, the workpiece would distort. The pressure which must be exerted in the prior art clamping devices, such as disclosed in the Fitzpatrick patent, to adequately flex the diaphragm chuck is so great that the "full wrapped sleeve" disclosed therein, cannot adequately grip the workpiece without concurrently distorting the workpiece.
Accordingly, in one instance, the outside diameter and/or the inside diameter" of the prior art clamped workpiece is "out of round" when it is being clamped and machined. Although the outside diameter of the hollow workpiece, which is chucked on its internal diameter surface, is machined perfectly round, when the clamping pressure is released, the distorted part contracts or retracts to its original shape and thus the outside diameter is out of round.
Accordingly, it is an object of the present invention to provide a new and novel chuck which clamps without distorting hollow parts having a thin cylindrical wall.
It is another object of the present invention to provide a chuck for holding workpieces, which may have an eccentric workpiece holding surface, without distorting the workpiece.
The U.S. Pat. No. 3,608,161, issued to E. Kost, et al on Sept. 28, 1971 and the U.S. Pat. No. 3,542,354 issued to Paul Fitzpatrick on Nov. 24, 1970, each disclose another clamping system using both a pliant sleeve and a full wrap mechanical sleeve in combination to clamp a hollow part.
This type of prior art system has the necessary mechanical stiffness to resist the cutting forces which tend to move the workpiece, however, it is unable to conform to the outline of the part gripping surface without workpiece distortion at the required clamping pressures. Also, with this type prior art systems, the inherent stiffness of the full wrapped mechanical sleeve severely limits the sleeve excursion which in turn limits the part size variation which is clampable.
Another prior art system is of the type disclosed in U.S. Pat. No. 3,677,559 issued to Andre, et al on July 18, 1972. This prior art system utilizes only a pliant sleeve to hold a workpiece and the forces exerted tending to hold a workpiece are not sufficient to resist the radial and axially forces created by the cutting tools. This prior art system results in the part moving during machining. This, is obviously unacceptable. The movement can be reduced, but not totally eliminated, by increasing chucking pressure.
Also, in this last mentioned prior art system, it is difficult to control the axial position of the part. If the part is moved off its axial locating surface, the result is a loss of dimensional stability and clamping rigidity.
It is another object of the present invention to provide a new and novel holding device which significantly increases the radial and axial holding forces exerted on the workpiece.
It is another object of the present invention to provide a new and novel holding device of the type described which will improve locational accuracy for machining.
The following prior art patents are cited as being of interest:
______________________________________ 2,534,527 Myers Dec. 19, 1950 2,753,388 Bjerkas Jul. 3, 1956 2,901,013 Freeman Aug. 25, 1959 3,144,064 Polk Aug. 11, 1964 3,176,439 Gabriel et al Apr. 6, 1965 3,542,434 Fitzpatrick Nov. 24, 1970 3,608,161 Kost et al Sep. 28, 1971 3,677,559 Andre et al Jul. 18, 1972 3,751,050 Hayes et al Aug. 7, 1973 4,422,653 Piotrowski Dec. 27, 1983 ______________________________________
Briefly, the U.S. Pat. No. 2,534,527 is an older basic showing while the Hayes Pat. No. 3,751,050, discloses a chuck provided with a plurality of separate annular elastomeric gooves which are inflated through various ports.
Also briefly, the Freeman Pat. No. 2,901,013, is of interest in illustrating an internal expansible bladder tube which grips a fruit workpiece to be externally peeled. The remaining patents likewisely do not disclose or remotely suggest Applicants' construction.
It is yet another object of the present invention to provide a new and novel chuck which can grip a part which is out of round without distorting the part but yet exerting sufficient clamping pressure thereon to hold the part during machining.
It is still another object of the present invention to provide a new and novel chuck of the type described including a plurality of individual, independently movable, flexible fingers which can grip a part which is out of round without distorting the part.
Still another object of the present invention to provide a new and novel chuck of the type described which includes a plurality of individual, independently movable, flexible fingers, which include a portion that swings radially and axially to exert radial and axial clamping forces on the workpiece.
A further object of the present invention to provide a fluid actuated chuck of the type described including an inflatable ring which actuates a plurality of circumferentially disposed, individually movable, independent flexible fingers which are fixed at one end and include a flexible free end which is radially moved by the ring, when inflated, to grip the part.
A still further object of the present invention is to provide a holding device of the type described which includes individual fingers which are flexible to allow the chucking fingers to conform to the part without distorting the part.
Other objects and advantages of the present invention will become apparent to those of ordinary skill in the art as the description thereof proceeds.