DC powered surgical handpiece having a motor control circuit

• US 5,268,622 A
• Filed: 03/22/1993
• Issued: 12/07/1993
• Est. Priority Date: 06/27/1991
• Status: Expired due to Term

• Current Assignee: Stryker Corporation
• Original Assignee: Stryker Corporation
• Inventors: Philipp, Christopher D.
• Primary Examiner(s): Ro, Bentsu
• Application Number:
  US08/034,277
• Time in Patent Office: 260 Days
• Field of Search: 318/138, 318/254, 318/439, 318/434, 318/432, 318/471, 388/934
• US Class Current: 318/400.08
• CPC Class Codes: A61B 17/1626 Control means; Display units
• CPC Class Codes: H02P 6/24 Arrangements for stopping
• CPC Class Codes: Y10S 388/934 Thermal condition

Abstract

A compact surgical handpiece comprises a motor energizable for moving a tool member, electric energy supply actuable for energizing the motor and a manually actuable trigger actuable to control motor operation. A motor control circuit interconnects the motor electric energy supply and trigger for running and braking the motor in response to actuation and release of the trigger. The control circuit includes a compact regulated voltage supply, a motor overcurrent limiting feature and a motor braking feature which is effective even if the operator fails to fully disconnect the electrical supply to the motor upon releasing the trigger.

Claims

1. A surgical handpiece, comprising:

electric energy supply means;

an electric motor having a winding;

electronic switch means connected in series with said winding to flow current therethrough from said electric energy supply means;

speed control means for turning said electronic switch means on and off wherein the longer the electronic switch means in on, the more energy is applied to the motor and the higher the speed and load handling capacity of the motor is;

means responsive to current through said electronic switch means and winding and also responsive to the temperature of said electronic switch means for producing a representative voltage signal;

means responsive to a change in said voltage signal beyond a threshold, in response to at least one of winding current and electronic switch means temperature going past a limit, for reducing the amount of energy applied to said winding by said electronic switch means, such that motor efficiency, in mechanical power output per unit electrical power input, can be increased by reducing motor winding resistance without increasing the danger of motor winding burnout and electronic switch means burnout.

2. The apparatus of claim 1 in which said electronic switch means comprises a SENSFET having a high current drain connected to said winding and a low current drain, said voltage signal producing means comprising a voltage dropping resistance connecting said low current drain to a ground side of said electric energy supply means, said resistance being connected to said means for reducing the amount of energy applied to said winding.

3. The apparatus of claim 1 in which said motor has three windings, said electronic switch means comprises three corresponding FETs, said FETs having gates arranged to be turned on in sequence and drains connected to said windings, Zener means connected to a nongrounded side of said electric energy supply means, said drains being connected through respective diodes to said Zener means for bypassing high voltage spikes from said drains to recharge said electric energy supply means.

4. The apparatus of claim 1 including manually actuable trigger means actuable for requesting motor operation, said speed control means being actuable by said manually actuable trigger means for energizing said motor from said electric energy supply means, said speed control means including a plurality of motor drive terminals actuable for providing motor drive signals suitable for full wave motor operation, said plurality comprising first half wave motor drive terminals and second half wave motor drive terminals, said first terminals being interconnected for running said motor in a half wave mode in response to actuation of said manually actuable trigger means.

5. The apparatus of claim 4 including brake actuating means connected to said second half wave motor drive terminals and responsive to cessation of said motor drive signals for producing a braking signal, and means responsive to said braking signal for braking said motor.

6. The apparatus of claim 5 in which said brake actuating means comprising delay timing means operatively connected to said second half wave motor drive terminals and enabled in response to running of said motor by said speed control means and responsive to said cessation of said motor drive signals on said second half wave motor drive terminals for timing an interval sufficient to allow said motor to be braked to a stop, said delay timing means disabling said braking means and thereby preventing further braking of said motor, upon completion of said time delay;

said delay timing means permitting braking of said motor by said braking means during timing of said interval.

7. The apparatus of claim 5 in which said brake actuating means includes gate means responsive to the absence of the motor drive signals from said motor drive terminals for providing said braking signal, means responsive to rotor position in said motor for applying commutation signals to said speed control means for proper timing of the motor drive signals to said motor by said speed control means, means connecting said commutation signals applying means to said gate means for modulating said braking signal to increase the braking torque on the motor as the motor slows, so as to prevent the motor from trying to jerk the handpiece out of the hand of the user upon initiation of braking of the motor.

8. The apparatus of claim 5 in which said trigger means includes a manual on/off switch actuable to an "on" position for connecting said electric energy supply means to said speed control means, further gate means responsive to turning on of said motor for establishing a shunt across said on/off switch for maintaining connection of said electric energy supply means to said speed control means despite opening of said on/off switch, and time delay means responsive to turn off of said motor by said speed control means for timing a delay, means connecting said time delay means to said further gate means causing same to disconnect said shunt across said on/off switch upon termination of said time delay and in the absence of turning on of said motor during said time delay.