System for controlling the advance of a rotary machine tool
AssigneeBuderus'sche Eisenwerke Aktiengesellschaft
InventorJurgen Schreiber
Life of this patent
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Abstract
A rotary machine tool, such as a grinding wheel, is mounted on a movable support serving to advance the tool toward a workpiece, such as a pipe to be severed thereby. The tool is driven by an electric motor whose operating current is measured by a sensor controlling the fluid supply to a hydraulic servomotor which is linked with the support. When the advance is too rapid, the resulting rise in load resistance increases the operating current and causes a throttling of the fluid pressure, the rate of advance being thus optimized in conformity with the shape and/or composition of the workpiece.
Claims2
A system for machining a workpiece, comprising:
- a workpiece holder;
- a rotary machine tool engageable with a workpiece on said holder;
- p1 a support for said tool movable relatively to said holder for advancing said tool toward said workpiece;
- an electric motor coupled with said tool for rotating same about an axis;
- current-sensing means in circuit with said motor;
- a reversible hydraulic servomotor linked with said support and provided with a high-rate fluid-supply circuit including a first valve and with a low-rate fluid-supply circuit including a second valve, each of said valves having a forward-flow position, a neutral position and a reverse-flow position;
- control means responsive to said current-sensing means for placing said first valve in its forward-flow position to advance said tool rapidly toward the workpiece under low-current conditions during an approach phase and for actuating said second valve while maintaining said first valve in its neutral position to displace said tool more slowly under high-current conditions, indicative of an engagement of the tool with the workpiece, at speeds tending to maintain the motor current in a predetermined range during a working phase following said approach phase, with reversal of the flow in said low-rate fluid-supply circuit upon detection of an overload condition by said current-sensing means;
- and
- switchover means responsive to a predetermined advance of said tool from a starting position for modifying the operation of said control circuit to hold said second valve in its neutral position while shifting said first valve into its reverse-flow position upon a recurrence of said low-current conditions due to severance of the workpiece for rapidly retracting said tool to said starting position in a withdrawal phase following said working phase.
Dependencies are inferred from the claim text.