Electricity: measuring and testing – Electrical speed measuring – Including speed-related frequency generator
Patent
1981-10-26
1983-05-24
Strecker, Gerard R.
Electricity: measuring and testing
Electrical speed measuring
Including speed-related frequency generator
310 47, 310 50, 310 68R, 318326, H02K 714, G01P 348
Patent
active
043852769
ABSTRACT:
A counterbalanced rotor is mounted on a rearward extension of the armature shaft of a portable electric tool. The rotor is nested within the annular portion of a ring member which is piloted on the rearward bridge portion of the motor field case. An end cap is secured to the field case and engages the annular portion of the ring, thereby retaining the ring against the bridge on the field case. The annular portion of the ring has an external boss with a notch formed therein substantially tangential to the annular portion. A printed circuit board is received in the notch and carries a semiconductor sensing device, such as a Hall-Effect generator, for cooperation with a magnet carried by the rotor. A spider member is retained in the bridge and has a bearing nested therein for journaling the commutator end of the armature shaft. The spider has a number of openings formed therein. The end cap has a plurality of ventilating openings formed therein, and a fan carried by the armature shaft draws cooling air in through the openings in the end cap. The cooling air is confined by the annular portion of the ring, is subjected to a turbulance by the rotor therein, and flows through the openings in the spider for purposes of cooling the bearing.
REFERENCES:
Wehmer, "Electromagnetic Tachometer", Dec. 1968, pp. 746-747, IBM Technical Disclosure Bulletin, vol. 11, No. 7.
Black & Decker Inc.
Murphy Edward D.
Ottesen Walter
Snow Walter E.
Strecker Gerard R.
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