Control circuit for reversible electric motors

• US 4,365,189 A
• Filed: 08/20/1979
• Issued: 12/21/1982
• Est. Priority Date: 08/20/1979
• Status: Expired due to Term

• Current Assignee: Tennant Company
• Original Assignee: Tennant Company
• Inventors: Haub, Donald J., Seim, Howard N., Hawkins, Raymond C.
• Primary Examiner(s): Mitchell, David M.
• Application Number:
  US06/068,161
• Time in Patent Office: 1,219 Days
• Field of Search: 318/284, 318/139, 318/263, 318/273, 318/283, 180/65 R, 180/65 F, 180/272, 180/271
• US Class Current: 318/284
• CPC Class Codes: H02P 7/03 for controlling the direction of rotation of DC motors

Abstract

A reversible electrically driven motor is disclosed together with circuitry for controlling the direction of the motor such that the current to the drive motor cannot be reversed to an opposite direction while the motor continues operation in a first direction. Once the motor slows to predetermined speed, which may approximate near-stop condition, the circuitry permits the voltage to operate in the opposite direction thereby reversing the motor. The control apparatus may include the portion of the electric motor which operates as a generator when the motor is not being electrically driven, a solid state sensor for sensing the voltage generated, and a lock-out circuit which responds to the sensed voltage to disable the operation of the driving circuit which reverses the motor.

Claims

1. A circuit comprising, in combination, an electrically reversible DC motor having field and armature coils, means for reversing the flow of current through said field coil to reverse the direction of the motor, and a control circuit for sensing the rotation of said motor in a coasting state wherein said motor is rotating without voltage applied to said coils and for preventing the application of voltage to said field coil which would reverse the direction of said motor until said motor has slowed to a predetermined rotational velocity, said control circuit including detecting means connected in parallel with said armature coil for detecting voltage generated therein when said motor is in said coasting state, and preventing means responsive to said detecting means for preventing application of said reversing voltage to said motor while said detecting means is sensing said generated voltage.

3. The circuit of claims 1 or 2 wherein said motor is capable of sustaining residual magnetism when no current is flowing in said field coil so that a voltage will be induced in said armature coil when rotated.

2. A circuit comprising;

an electrically reversible DC motor having field and armature coils in series, said armature coil having one side at ground potential;

means for reversing the flow of current through said field coil for reversing the rotation of the motor;

a control circuit for sensing rotation of said motor, said control circuit serving to prevent application of electrical power to said motor until it has slowed to a predetermined rotational velocity, said control circuit including a transistor having its base connected to the ungrounded side of said armature coil and its emitter grounded.

4. A circuit comprising, in combination, an electrically reversible motor having field and armature coils and capable of sustaining residual magnetism when no current is flowing in said field coil, means for reversing the flow of current through said field coil to reverse the direction of the motor, and a control circuit for sensing the rotation of said motor in a coasting state wherein said motor is rotating without voltage applied to said coils and for preventing the application of voltage to said field coil which would reverse the direction of said motor until said motor has slowed to a predetermined rotational velocity, said control circuit including detecting means connected in parallel with said armature coil for detecting voltage generated therein when said motor is in said coasting state, and preventing means responsive to said detecting means for preventing application of said reversing voltage to said motor while said detecting means is sensing said generated voltage.

5. In combination, an electrically reversible motor and control circuit for sensing the rotation of said motor while the armature of said motor is rotating without voltage applied and means for preventing the application of voltage to said motor until said armature has slowed to a predetermined rotational velocity, said motor being capable of generating an electric voltage when the motor is in said coasting state, said control circuit comprising:

a first control circuit for applying voltage to said motor causing said armature to rotate in a first direction;

a second control circuit for applying voltage to said motor causing said armature to rotate in a second direction being opposite to said first direction,

means for detecting said generated voltage;

said preventing means including;

a first normally closed relay contact in series with said first circuit, and second normally closed relay contact in series with said second circuit;

first holding circuit means controlling said first relay contact, a second holding circuit means controlling said second relay contact;

said preventing means being responsive to said detecting means for preventing completion of said first circuit when said armature is rotating in said second direction and for preventing completion of said second circuit when said armature is rotating in said first direction;

said first holding circuit means being responsive to said detecting means for holding said first relay contact in its open-circuit state until said armature has slowed to said predetermined speed when said armature is coasting in said first direction;

said second holding circuit means being responsive to said detecting means for holding said second relay contact in its open-circuit state until said armature has slowed to said predetermined speed when said armature is coasting in said second direction;

and wherein said second holding circuit means includes;

a first relay coil for controlling said second relay contact;

a third relay contact responsive to said first relay coil and being in series with said first relay coil;

a fourth relay contact in parallel with said third relay contact;

a second relay coil in series with said first control circuit for controlling said fourth relay contact;

and wherein said first holding circuit means includes;

a third relay coil for controlling said first relay contact;

a fifth relay contact responsive to said third relay coil in series with said third relay coil;

a sixth relay contact in parallel with said fifth relay contact; and

a fourth relay coil in series with said second control circuit for controlling said sixth relay contact.

6. The apparatus of claim 5 wherein said first and second holding circuit means are in parallel with each other and in series with said detecting means.