US 4,734,604 AGranted

Friction braking system and apparatus for appliance induction motor drive

AssigneeCuisinarts, Inc.

InventorsCarl G. Sontheimer, William R. Smith-Vaniz

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Abstract

A friction braking system located entirely inside an induction motor of an appliance quickly stops rotation of the rotor in the appliance motor, for example such as a food processor, whenever the A.C. electrical power is turned off. Thus, rotation of any tool being operated in the appliance is quickly stopped, whenever the electrical power is interrupted. The rotor in the induction motor is axially slidably mounted on the motor shaft and is keyed to the shaft for permitting axial shifting displacement of the rotor relative to the stator while preventing any angular displacement of the rotor relative to the shaft. Consequently, the rotor and shaft always turn and stop as a function unit. A friction brake lining is affixed within the motor housing offset from the axis of the motor shaft as far as practicable. A disc brake mounted onto the rotor has an annular friction braking surface positioned for engagement against the brake lining. The rotor is arranged for an axial thrust to shift the rotor in an axial direction away from its normal operating position aligned with the stator, whenever the electrical power is interrupted, thereby applying friction braking action quickly and at a relatively large moment arm as compared with the radius of the rotor for effective braking. The brake disc may include motor-cooling fan blades. An inverted V-shaped brake surface configuration is also shown for enhancing braking action.

In an induction motor in a home electrical appliance, said induction motor including a housing, bearing means associated with the housing, a motor shaft within the housing mounted by said bearing means for rotation about its axis, said motor shaft extending outside of the housing and having power take-off means thereon external of said housing for enabling mechanical power to be delivered from said motor shaft to a working tool, a rotor in said housing mounted on said motor shaft, an electrically energizable electromagnetic stator fixed in said housing concentric with said rotor and encircling said rotor for causing said rotor to turn when said stator is electrically energized by alternating current, a friction braking system located totally inside of said housing for frictionally braking rotation of the rotor whenever the flow of electrical power to the motor ceases, said friction braking system comprising:

said rotor being shiftable in axial position relative to said stator,
said rotor being shiftable in axial position relative to said motor shaft,
a first coupling affixed to the motor shaft for the motor shaft and said first coupling to rotate as a unit,
a second coupling affixed to the rotor for the second coupling and the rotor to relate as a unit and to shift axially as a unit,
said second coupling being mechanically engaged with said first coupling for transmitting the rotary motion of the rotor to the motor shaft while permitting the rotor and said second coupling to shift axially with respect to said first coupling for preventing any angular displacement of said rotor relative to said shaft regardless of the axial position of said rotor,
said rotor during running of said induction motor being drawn into axial alignment with the stator by the electromagnetic effect of the stator when electrically energized,
said rotor being subjected to an axial thrust in a predetermined axial direction for shifting the rotor in a first axial direction out of aligment with the stator upon cessation of electrical energization of the stator,
a brake lining mounted in fixed position within said housing,
a brake disc secured to said rotor for causing said rotor and brake disc to rotate together and to stop together,
said brake disc having an annular frictional surface concentric about said axis,
said annular frictional surface being in opposed relationship with said brake lining and being spaced closely therefrom when said rotor is in axial alignment with said stator during running of said motor,
said shifting of said rotor in said first axial direction bringing said annular frictional surface against said brake lining for frictionally braking the rotor to stop turning, and
said rotor shifting in a second direction opposite to said first direction separating said annular frictional surface from said brake lining for releasing the friction braking upon electrical energization of said stator as said rotor is drawn into axial alignment with the stator and starts running.

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Abstract

Claims7