Gear cutting – milling – or planing – Milling – Process
Reexamination Certificate
2000-02-17
2001-10-30
Howell, Daniel W. (Department: 3722)
Gear cutting, milling, or planing
Milling
Process
C409S233000
Reexamination Certificate
active
06309150
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a chuck actuator and to a method of operating a chuck actuator. More particularly this invention concerns a spindle assembly used to actuate a chuck at an outer end of the spindle assembly.
BACKGROUND OF THE INVENTION
A spindle assembly used to rotate and hold a machine tool or workpiece typically comprises inner and outer coaxial shafts having front and rear ends and extending along a common axis with the inner shaft axially displaceable in the outer shaft, a holding device or chuck on the front ends adapted to grip a tool or workpiece in an axially outwardly displaced position of the inner shaft relative to the outer shaft, a coupling ring fixed on the rear end of the outer shaft, and an actuator having a piston axially engageable with the rear end of the inner shaft and operable to axially shift the inner shaft in the outer shaft. Springs normally urge the inner shaft inward so, absent pressurization of the cylinder surrounding the piston, these springs maintain the assembly in the holding position in which it solidly grips the workpiece or tool. When thus held, the shafts are rotated at high speed for the desired machining operation.
The spindle assembly described in US Pat. No. 5,865,578 has inner and outer coaxial shafts having front and rear ends and extending along a common axis with the inner shaft axially displaceable in the outer shaft, a holding assembly on the front ends adapted to grip a tool or workpiece in an axially outwardly displaced position of the inner shaft relative to the outer shaft, a coupling ring fixed on the rear end of the outer shaft, and an actuator having a piston axially engageable with the rear end of the inner shaft and operable to axially shift the inner shaft in the outer shaft. Complementarily interengaging formations on the actuator and the coupling ring including a is groove and a projection are displaceable between a holding position axially securing the ring on the actuator and a freeing position allowing the ring to be axially separated from the actuator.
When the actuator is connected with the shafts, the formations can be engaged together to allow the actuator to operate the chuck. In this position the holding device can be opened to allow a workpiece or tool to be taken off or set in place, to which end the actuator axially displaces the piston into an outer end position. Once the tool or workpiece is properly engaged in the holding device, the shafts can be rotated to perform the desired machining operation.
In order to prevent the actuator from rotating with the shafts and to surely separate the rotating parts—the shafts and holding device—from the nonrotating parts—the actuator—the two relatively movable parts of the housing are pushed apart by compression springs so that the formations can move out of contact with one another. To dechuck the tool or workpiece the piston is moved oppositely so that the formations are again engaged and as a result the shaft bearings are relieved of forces from the piston. This relief is not complete since the bearings must at least take up the force of the springs used to relatively displace the housing parts.
OBJECTS OF THE INVENTION
It is therefore an object of the present invention to provide an improved chuck actuator.
Another object is the provision of such an improved chuck actuator which overcomes the above-given disadvantages, that is which is of simple construction certain to have a long service life.
Another object is to provide an improved method of operating a chuck actuator which eliminates the need for the above-described springs between the housing parts
SUMMARY OF THE INVENTION
A chuck actuator has according to the invention a main housing, a tube shaft having an outer end adjacent the main housing and an inner end remote from the main housing, and centered on an axis, a core shaft axially displaceable in the tube shaft between advanced and retracted positions and also having an inner end at the main housing and an outer end, and a holding device on the outer ends engageable with a tool or workpiece for holding same in the retracted position of the core shaft. A coupling member fixed on the core-shaft rear end and a housing member limitedly axially displaceable relative to the main housing and juxtaposed with the coupling member have formations including a radially projecting lug on one of the members and a radially open groove on the other of the members receiving the lug and of an axial dimension substantially greater than an axial dimension of the lug so that the lug can move limitedly axially in the groove. An actuating body axially displaceable in the main housing has a surface axially engageable with the core-shaft rear end and a pair of inwardly directed surfaces respectively engageable with the housing member and main housing. The surfaces are spaced such that, when one of the surfaces bears axially inward on the main housing, the other of the surfaces bears axially inward on the housing member to displace it axially inward and generally center the lug in the groove. The actuating body is moved outward to displace the core shaft into the advanced position and inward to allow the core shaft to move into the retracted position and displace the housing member to center the lug in the groove.
The system of this invention has the advantage that there are no springs at all between the two relatively movable housing parts. The housing member is positively positioned by the actuating body relative to the main housing so that the axial coupling formations are wholly out of contact with each other and the shafts can rotate freely relative to the actuator. This centered position is accurately set without the use of springs so the system is not normally under any spring load.
According to the invention the main housing and housing member form a cylinder and the actuating body is a piston axially displaceable in the cylinder and having an outer face forming the other surface. More particularly the main housing is provided with a pair of inlets connected to respective compartments formed by the piston in the cylinder. Thus pressurization of one or the other compartments effects the clamping or releasing actions. Only one of the compartments needs to be pressurized; the other can simply be connected to the sump. Once a new tool or workpiece is in place, the pressurization can be wholly relieved with the parts staying in the positions they were moved into
The piston has a stem projecting axially inward through the main housing and housing member and formed with the surface engageable with the main housing. This protruding stem can even be used to feed a fluid under pressure through the piston and core shaft to the chuck at the outer ends of the shafts.
The main housing in accordance with the invention is formed with a sleeve extending axially outward and forming a guide on which the housing member is slidable. Thus the main housing, which is typically stationary, carries the housing member that is limitedly axially movable relative to it.
According to the invention the main housing is formed with a radially inwardly open pocket, normally an annular groove, and the housing member is provided with a radially outwardly projecting lug engaged in the pocket and limitedly axially displaceable therein so that axial travel of the housing member relative to the main housing is limited by the lug and pocket. Thus the two housing parts form a simple subassembly.
The chuck actuator further has according to the invention a detectable element axially fixed on the outer shaft, and means in including a sensor for detecting the element on the housing member. This allows a controller that operates the valves connected between a source of pressurized fluid and the two inlets for the compartments to be operated in accordance with the actual position of the chuck.
With the system of this invention a workpiece or tool is secured in a holding device of a chuck actuator by pressurizing the outer compartment to shift the piston inward, move the core shaft
Dubno Herbert
Howell Daniel W.
Rohm GmbH
Wilford Andrew
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