Title: Variable-speed drill

Abstract: A housing accommodates a motor and a tool shaft which is to be driven by the same. A gear drive is interposed between the motor and the tool shaft and transmits power from the former to the latter. The gear drive has at least two gear sets providing different gear ratios, and an intermediate shaft. An axial safety coupling is associated with each of the gear sets and provided on the intermediate shaft to be rotatable with the same. Each safety coupling includes axially extending projections which are distributed about the axis of rotation of the intermediate shaft and which have circumferentially defined flanks. Each safety coupling has a diameter and a flank inclination at least one of which is accommodated to the torque generated by the gear ratio associated with the safety coupling. A biasing spring urges the projections of the safety couplings into engagement with one another.

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Inventors: Grozinger, Dieter (Echterdingen, DT)

Application Number: 531616
Filing Date: 1974-12-11
Publication_date: 1976-08-24
Assignee: Robert Bosch G.m.b.H. (Stuttgart, DT)
Primary Class(es): 74/329 74/333, 74/337
Other Classes:
US Patent Ref:

2370885	Mar, 1945	Sohm	74/329.
2772576	Dec, 1956	Ross	74/337.
2861460	Nov, 1958	Lips et al.	74/322.
3436980	Apr, 1969	Loge et al.	74/329.

Other Refs:
Primary Examiner: Gerin, Leonard H.
Assistant Examiner:
Attorney: Striker; Michael J.