Chucks or sockets – Radially reciprocating jaws – Jaws
Reexamination Certificate
1999-09-02
2001-07-24
Bishop, Steven C. (Department: 3722)
Chucks or sockets
Radially reciprocating jaws
Jaws
C279S123000, C279S152000, C269S282000
Reexamination Certificate
active
06264210
ABSTRACT:
The present invention is related to a jaw assembly for a jaw chuck for holding a workpiece to a spindle of a machine.
BACKGROUND OF THE INVENTION
A jaw chuck for holding a work piece to the spindle of a rotary machine, such as a lathe, includes three or more jaw assemblies coupled to a chuck body for simultaneous reciprocating radial movement with respect to the chuck body to provide self-centering gripping of the workpiece. In a typical construction, each jaw assembly is attached to a master jaw disposed for radial movement within one of a number of radial jaw guides formed in the body. Each master jaw is coupled to a draw bar, disposed within the spindle of the machine, by a pivoting lever arm that actuates the master jaws by converting axial movement of the draw bar into the simultaneous reciprocating radial movement of the master jaws.
While the master jaws are rarely disassembled from the chuck body, the jaw assemblies or workpiece gripping jaws, are often removed from and reattached to the master jaws so that different jaw assemblies can be installed on the chuck so as to accommodate work pieces of different sizes and/or shapes. Each master jaw has a slot formed therein with retaining flanges extending along opposite edges of the slot. A top jaw is attached to the master jaw by means of two or more threaded fasteners extending through spaced-apart holes formed in the top jaw and into a single T-nut having two or more threaded holes or two or more one-hole T-nuts disposed in the master jaw slot. The fasteners are tightened into the T-nut(s) to draw the top jaw down into bearing contact with the master jaw. The respective surfaces of the master jaw and the top jaw that bear against each other are serrated to prevent sliding of the top jaw with respect to the master jaw.
This conventional method of attaching a top jaw to a master jaw has a number of disadvantages. Since the top jaw is attached to the master jaw with two or more threaded fasteners, the time required to change out the top jaws is greater than it would be if only one fastener were required to securely attach the top jaw to the master jaw. To attach a top jaw to the master jaw, each fastener must be placed through a hole formed in the top jaw and then aligned with and threaded into a T-nut disposed in the master jaw slot. Alternatively, the T-nuts can be started onto the ends of the fasteners protruding from the top jaw and then the loosely attached T-nuts are slid into the master jaw slots. The top jaw is then properly positioned with respect to the master jaw and both fasteners are tightened to secure the top jaw.
To remove the top jaw and install a new top jaw, both fasteners must be loosened, and the fasteners and T-nut(s) must be transferred to the next top jaw or the next top jaw must have its own dedicated fasteners and T-nut(s).
Also, to ensure rotational symmetry of the chuck and self centering gripping of the jaws, each top jaw must be positioned in the same location on its respective master jaw. For example, if the third serration of the top jaw is aligned with the first serration of the master jaw, then all top jaws should be aligned the same way. Aligning the top jaws can be cumbersome, because the serrated bearing surfaces makes it difficult to slide the top jaws with respect to the master jaws; both threaded fasteners must be sufficiently loose to permit adequate play between the top jaw and the master jaw.
SUMMARY OF THE INVENTION
These disadvantages are overcome in accordance with the present invention by a quick-change jaw assembly for a jaw chuck for holding a workpiece to the spindle of a machine, the jaw chuck including a rotatable chuck body with radially-extending jaw guides formed therein and a master jaw disposed for reciprocal radial movement within each of the jaw guides, the master jaw having a master jaw slot formed therein with retaining flanges formed along opposed sides of the master jaw slot. The jaw assembly comprises an intermediate coupling member that is slidable into the master jaw slot. The intermediate coupling member has a first flange structure that co-acts with the retaining flanges of the master jaw to retain the intermediate coupling member in the master jaw slot and a second flange structure.
A top jaw has a top jaw slot formed therein and retaining tabs disposed along opposite sides of the top jaw slot. The top jaw slot can receive a portion of the intermediate coupling member with the retaining tabs in overlying relation with the second flange structure of the intermediate coupling member.
A retaining mechanism secures the intermediate coupling member within the master jaw slot, thereby retaining the top jaw to the master jaw by co-action of the retaining tabs of the top jaw and the second flange structure of the intermediate coupling member.
The intermediate coupling member and the retaining mechanism stay coupled to the master jaw as the top jaw is changed out. Therefore, changing the top jaw is dramatically simplified. To remove a top jaw from the chuck, the retaining mechanism is released, thereby permitting the top jaw to be disengaged from the intermediate coupling member. The new top jaw is then engaged with the intermediate coupling member already disposed in the master jaw and the retaining mechanism is again tightened, thereby securing the intermediate coupling member and the new top jaw to the master jaw. Furthermore, the intermediate coupling member and the top jaw preferably include positioning protrusions for accurate and repeatable positioning of the intermediate coupling member with respect to the master jaw and the top jaw with respect to the intermediate coupling member.
In a preferred embodiment, the jaw assembly includes a spring plunger disposed between the intermediate coupling member and the master jaw. When the retaining mechanism is released, the bias of the plunger holds the intermediate coupling member somewhat elevated with respect to the master jaw. Accordingly, when a top jaw is engaged with the intermediate coupling member while the retaining member is released, the intermediate coupling member holds the top jaw out of contact with the master jaw, thereby permitting the top jaw to be easily slid into it proper position with respect to the master jaw.
Other objects, features, and characteristics of the present invention, as well as the methods of operation of the invention and the function and interrelation of the elements of structure, will become more apparent upon consideration of the following description and the appended claims with reference to the accompanying drawings, all of which form a part of this disclosure, wherein like reference numerals designate corresponding parts in the various figures.
REFERENCES:
patent: Re. 29533 (1978-02-01), Parsons
patent: 4387905 (1983-06-01), Brown
patent: 4667971 (1987-05-01), Norton et al.
patent: 4722536 (1988-02-01), Lane et al.
patent: 5464232 (1995-11-01), Chizmadia
patent: 47096 (1982-03-01), None
Difasi Anthony J.
Roberts, Jr. Matthew C.
Bishop Steven C.
Hardinge Inc.
Pillsbury & Winthrop LLP
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