Tool driving or impacting – Automatic control of power operated means – Tool advance causing or controlling means
Patent
1979-04-04
1982-02-23
Nerbun, Peter P.
Tool driving or impacting
Automatic control of power operated means
Tool advance causing or controlling means
B25B 23147
Patent
active
043165125
ABSTRACT:
A self-contained impact wrench having an adaptive control system for determining the yield point or some similarly significant tightened condition of a fastener assembly by detecting a signal representative of the forward rotation angle of the fastener assembly is disclosed. One embodiment utilizes a computed signal of time over a fixed interval of forward rotation angle, as an estimate of the torque applied by the impact wrench, and the torque estimate vs. rotation angle curve is differentiated to obtain the gradient thereof. Successive gradient values are stored and compared, and when the present gradient value has attained a predetermined relationship relative to a stored value of a gradient in a tightening region of the curve, further tightening of the fastener assembly is discontinued. This ensures that the yield point or other similarly significant tightened condition of the assembly has been reached.
REFERENCES:
patent: 4008772 (1977-02-01), Boys
patent: 4104778 (1978-08-01), Vliet
patent: 4106176 (1978-08-01), Rice et al.
Kibblewhite, "Impact Phenomena with Screw Fasteners", 1976, pp. 41-53, University of Canterbury Engineering Library, Christchurch, New Zealand.
Boys John T.
Kibblewhite Ian E.
Tambini Angelo L.
Nerbun Peter P.
Nerenberg Aaron
SPS Technologies, Inc.
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