US 4,398,326 AGranted

Collet unclamping mechanism

AssigneeKearney & Trecker Corporation

InventorJohn R. Joerger

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Abstract

Pressurized hydraulic fluid for energizing the collet unclamping mechanism of a machining center is supplied through a first solenoid valve from an accumulator which is charged by a piston pump. The piston pump is attached to the machining center between the Z axis slide and the Z bed so that as the Z axis slide is moved to a home position at the outset of a tool change cycle, the pump charges the accumulator, allowing pressurized hydraulic fluid to be admitted into the collet unclamping cylinder through the solenoid control valve in response to machining center control system commands. Following pressurization of the unclamping mechanism from the accumulator, both the unclamping mechanism and the piston pump drain to the oil sump to reduce any drag on the Z axis slide or on the unclamping mechanism itself.

Claims5

Dependent claims

In combination with a numerically controlled machine tool having a bed, a member movable on said bed between a forward and a home position, a rotary driven cutting-tool carrying spindle rotatably carried in said member and a collet unclamping cylinder associated with said spindle for releasing a toolholder engaged in said spindle when said unclamping cylinder is pressurized with hydraulic fluid, an improved apparatus for pressurizing said unclamping cylinder with hydraulic fluid comprising:

a source of hydraulic fluid;
an accumulator containing a volume of inert gas and hydraulic fluid;
pump means fastened to said machine tool between said bed and said movable member for pumping hydraulic fluid from said source of hydraulic fluid into said accumulator to increase the volume of hydraulic fluid in said accumulator, thereby increasing the pressure of said fluid, as said movable member moves on said bed from its forward to its home position;
means for preventing hydraulic fluid pumped into said accumulator by said piston pump from flowing back into said piston pump from said accumulator;
and
means responsive to numerical control commands for coupling said collet unclamping cylinder between said accumulator and said source of hydraulic fluid to conduct hydraulic fluid from said accumulator into said unclamping cylinder to pressurize said unclamping cylinder at predetermined intervals and to conduct the hydraulic fluid from said unclamping cylinder into said source of hydraulic fluid during intervals other than said predetermined intervals, respectively.

3 more elements

Dependencies are inferred from the claim text.