Abstract: In an electric motor, a conductive ring surrounds, and shields, each pole of stationary magnet. When a changing magnetic flux, produced by an armature, penetrates the ring, by Lenz's Law, the changing flux causes the ring to produce a counter-flux, which adds to the changing flux. Consequently, the total flux within the ring tends to remain constant. Maintaining this constant flux tends to reduce noise and vibration which the changing rotor flux otherwise causes.

Abstract: In an ordinary DC motor in a windshield wiper, operating speed tends to increase as the motor brushes become seated. The invention counteracts this tendency by providing a brush geometry which causes the effective angular position of a brush to change during seating. The change is in a direction which tends to reduce speed.

Abstract: The invention concerns an improved system for windshield wipers in vehicles. An induction motor is used, in which speed is accurately controlled by controlling frequency of power supplied to the motor. The induction motor may be of the consequent-pole type, which ordinarily does not produce sufficient torque. Addition of (a) auxiliary tooth slotting and (b) skew has raised the torque produced to acceptable levels.The invention includes a control system, which senses excess load on the motor, which occurs as the windshield dries, and reduces motor speed, subject to a minimum, in response.

Abstract: A windshield wiper system having variable frequency induction motor control for reducing wipe speed at reversal points includes an induction motor, a wiper and blade assembly operatively connected to the motor, a sensing means for detecting when the position of the wiper and blade assembly is within a preselected range of one of the reversal points, and a motor control responsive to the control signal generated by the sensing means for causing the motor to reduce wipe speed during the preselected range prior to the reversal point to reduce pattern growth, noise, and water expulsion. The sensing means takes the form of a cam or plate operated switch driven by the induction motor. The control signal derived from the cam operated switch is provided as an input to a voltage controlled oscillator, whose variable frequency output is used to vary the frequency of the excitation voltage applied to the windings of the three phase induction motor.