Motor field strength variable brush pressure apparatus and method

Claim 2

In a direct current or universal electric motor having an armature and commutator brushes, a method of increasing motor efficiency while operating the motor at loads less than rated loads by (a) detecting motor load, and (b) modifying the pressure of the brushes on the communtator of the motor as a function of the detected motor load.

Claim 3

The method of claim 1 wherein the pressure of the brushes is modified by varying the current in a solenoid coupled to the brushes as a function of the current in the field winding of the motor.

Claim 4

The method of claim 1 wherein the pressure of the brushes is modified by varying the current in a solenoid coupled to the brushes as a function of the current in the armature winding of the motor.

Claim 5

The method of claim 1 wherein the pressure of the brushes is modified by the steps of: varying the magnetic strength of a pole shoe as a function of motor load; and camming the brushes against the commutator of the motor by magnetic repulsion of a permanent magnet by the pole shoe.

Claim 6

In an electric motor of a direct current or universal type having a housing, field windings, armature windings, a commutator for the armature windings, and electrically conductive brusHes in pressural engagement with the commutator, the improvement comprising means carried by the housing of the motor and responsive to the motor load for dynamically varying the pressure with which the motor brushes engage the commutator of the motor to thereby modify the frictional drag of the motor brushes on the commutator as a function of the load of the motor.

Claim 7

In an electric motor of a direct current or universal type having a housing, field windings, armature windings, a commutator for the armature windings, and electrically conductive brusHes in pressural engagement with the commutator, the improvement comprising means carried by the housing of the motor and responsive to the motor load for dynamically varying the pressure with which the motor brushes engage the commutator of the motor to thereby modify the frictional drag of the motor brushes on the commutator as a function of the load of the motor.

Claim 8

The motor of claim 5 wherein said brushed pressure varying means is responsive to the amplitude of the current in the field windings of the motor.

Claim 9

The motor of claim 5 wherein said brushes pressure varying means is responsive to the amplitude of current in the armature windings of the motor.

Claim 10

The motor of claim 7 wherein the brush pressure varying means is also responsive to the amplitude of the current in the field windings of the motor.

Claim 11

The motor of claim 5 wherein said brush pressure varying means includes cam surfaces and permanent magnet means positioned to react to the magnetic strength of the motor poles for camming the brushes against the commutator.

Claim 14

Apparatus for enhancing the life of the brushes of an electric motor while operating the motor comprising: means for applying a predetermined contact pressure to the motor brushes; means for sensing motor load; and, means responsive to said motor load sensing means for varying the contact pressure of the motor brushes at loads below rated loads to thereby enhance brush life.

Claim 15

Apparatus for enhancing the life of the brushes of an electric motor while operating the motor comprising: means for applying a predetermined contact pressure to the motor brushes; means for sensing motor load; and, means responsive to said motor load sensing means for varying the contact pressure of the motor brushes at loads below rated loads to thereby enhance brush life.