Mechanical brake hold circuit for an electric motor

• US 5,394,069 A
• Filed: 03/08/1993
• Issued: 02/28/1995
• Est. Priority Date: 03/08/1993
• Status: Expired due to Fees

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Kishi, Gregory T., Rockwell, Scott M., McIntosh, Michael P., Mery, Hector E., Danielson, Craig T.
• Primary Examiner(s): Ro, Bentsu
• Application Number:
  US08/028,066
• Time in Patent Office: 722 Days
• Field of Search: 318/372, 318/375, 318/376, 318/377, 318/378, 318/379, 318/380, 318/362, 318/370, 318/371
• US Class Current: 318/371
• CPC Class Codes: H02P 3/26 by combined electrical and mechanical braking

Abstract

An automated tape library employing a motorized robotic picker wherein the electric motor driving the robotic picker is equipped with two brakes that act simultaneously. The first is a mechanical brake which uses a spring to push a brake pad against the rotating motor. During normal motor operation, an electric solenoid is used to overcome the spring and disengage the brake pad from the motor. When the robotic picker is to be mechanically stopped, the solenoid voltage is turned off and the solenoid releases the spring placing the brake pad in contact with the motor. The second brake is a dynamic electrical brake which makes use of the back emf of the motor to drive a current back into its own windings such that the motor decelerates.

Claims

1. A dynamic braking circuit for an electric motor comprising:

a mechanical brake power supply having first and second terminals;

a first relay having first, second, third and fourth movable contacts and a coil, said coil having first and second terminals;

a brake solenoid having first and second terminals;

said first movable contact of said first relay being connected between said first terminal of said coil of said first relay and said first terminal of said brake solenoid;

said second movable contact of said first relay being connected between said second terminal of said coil of said first relay and said second terminal of said brake solenoid;

said third movable contact of said first relay being connected between said second terminal of said brake solenoid and said first terminal of said brake power supply;

said fourth movable contact of said first relay being connected between said first terminal of said brake solenoid and said second terminal of said brake power supply;

a first resistor having a first and second terminal and being connected to a conversion means and being further connected to said electric motor, and said conversion means being connected to said first relay.

2. The circuit of claim 1 wherein said conversion means converts a voltage source from alternating current to direct current.

3. The circuit of claim 2 wherein said conversion means is a rectifier bridge.

4. The circuit of claim 1 further including:

a second resistor having a first terminal connected to said first terminal of said first resistor and a second terminal connected to said electric motor;

a third resistor having a first terminal connected to said first terminal of said second resistor and a second terminal connected to said electric motor.

5. The circuit of claim 4 further including a second relay having first and second movable contacts and a coil, said first movable contact connected between said first terminal of said first resistor and said first terminal of said second resistor and said second movable contact connected between said first terminal of said second resistor and said first terminal of said third resistor.

6. The circuit of claim 1 wherein said electric motor is an AC motor.

7. The circuit of claim 1 wherein said electric motor is a DC motor.

8. The circuit of claim 1 wherein said mechanical brake power is disconnected from said circuit when an emergency power off button is depressed.