Patent US3926264A successfully refreshed from Google Patents.
US3926264A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Control circuit for a power tool
Assignee: Thor Power Tool Co
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Filing: 1973-11-23
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Granted: 1975-12-16
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Expires: 1993-11-23
Abstract
Abstract This disclosure deals with a control circuit for a tool including a motor for turning a rotatable power output shaft of the tool. A torque measuring device is coupled to the shaft and generates a signal which is a function of the torque output. The control circuit responds to the torque output and to a reference signal representing a preselected torque, and automatically turns off the motor when the torque output reaches the preselected torque. Further, the control circuit may cyclically turn the tool on and off at very short time intervals as the preselected torque value is being approached, in order to reduce the reaction torque felt by an operator of the tool. In addition, the lengths of the on times in successive cycles may be gradually decreased as the torque output level increases, with the result that the average reaction torque remains substantially constant even though the peak torque output increases.
Inventors
- 👤 Francis G Bardwell
- 👤 Edmund C Dudek
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 21:10
CPC Classifications
B; B25; B25B; B25B23/00; B25B23/14; B25B23/145; B25B23/1456; G; G05; G05D; G05D17/00; G05D17/02
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
175 words
A handheld torque applying power tool, comprising a power output shaft, a drive motor connected to said shaft, means for sensing the torque output of said shaft and for providing a torque signal having a characteristic which represents the torque output level, means for providing a maximum torque reference level signal, reactive reference signal means providing a reference signal of a desired value below said maximum torque level signal, means for comparing said reactive reference signal and said torque output level signal, said means for comparing said reactive reference signal and said torque level signal being operable to turn said motor on and off a plurality of times until the maximum torque is achieved, means for comparing said torque signal and said maximum torque reference signal and providing an output signal when said maximum outut torque level is attained, and motor control switch means connected to control energization of said motor, said switch means being responsive to said maximum torque comparing means for turning said motor off when said maximum output torque level is attained.
Claim 2
Dependent Claim
175 words
A handheld torque applying power tool, comprising a power output shaft, a drive motor connected to said shaft, means for sensing the torque output of said shaft and for providing a torque signal having a characteristic which represents the torque output level, means for providing a maximum torque reference level signal, reactive reference signal means providing a reference signal of a desired value below said maximum torque level signal, means for comparing said reactive reference signal and said torque output level signal, said means for comparing said reactive reference signal and said torque level signal being operable to turn said motor on and off a plurality of times until the maximum torque is achieved, means for comparing said torque signal and said maximum torque reference signal and providing an output signal when said maximum outut torque level is attained, and motor control switch means connected to control energization of said motor, said switch means being responsive to said maximum torque comparing means for turning said motor off when said maximum output torque level is attained.
Claim 3
Dependent Claim
25 words
A power tool as in claim 1, wherein said reactive comparing means operates said control switch means for cyclically turning said motor on and off.
Claim 4
Dependent Claim
26 words
A power tool as in claim 2, wherein said reactive comparing means is operable only after a minimum torque level is being produced by said tool.
Claim 5
Dependent Claim
27 words
A power tool as in claim 2, wherein the lengths of the on times of said motor are gradually decreased as the torque output level is increased.
Claim 6
Dependent Claim
61 words
A power tool as in claim 1, wherein said motor in an air motor which is powered by a supply of compressed air and said tool further includes air valve means connected between said supply and said motor, said valve means being of the poppet type, and said switch means includes solenoid means connected to control operation of said valve means.
Claim 7
Dependent Claim
19 words
A power tool as in claim 5, wherein said valve means comprises a pilot valve and a control valve.
Claim 8
Dependent Claim
39 words
A power tool as in claim 5, wherein said valve means is fast acting in operation, and further including modulating means connected to said solenoid means for opening and closing said valve means at a high rate of speed.
Claim 9
Dependent Claim
134 words
A power tool and control therefor, comprising; a power tool having drive motor means, an output member driven by said drive motor means, control means for controlling the torque generated by said drive motor means, said control means inclUding means for sensing torque, said control means having means for sensing the desired maximum output torque of the tool, means for sensing a threshold torque below said maximum desired torque and providing a threshold torque signal, said control means including means for rapidly pulsing said drive motor in response to said control means sensing said threshold signal until the maximum torque level is achieved, said threshold signal initiating each pulse, said control means including means for automatically terminating operation of said drive motor means upon the application of a predetermined torque to said output member.
Claim 10
Dependent Claim
134 words
A power tool and control therefor, comprising; a power tool having drive motor means, an output member driven by said drive motor means, control means for controlling the torque generated by said drive motor means, said control means inclUding means for sensing torque, said control means having means for sensing the desired maximum output torque of the tool, means for sensing a threshold torque below said maximum desired torque and providing a threshold torque signal, said control means including means for rapidly pulsing said drive motor in response to said control means sensing said threshold signal until the maximum torque level is achieved, said threshold signal initiating each pulse, said control means including means for automatically terminating operation of said drive motor means upon the application of a predetermined torque to said output member.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1978-12-15 | 1979-06-16 | 1979-12-16 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-12-15 | 1983-06-16 | 1983-12-16 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-12-15 | 1987-06-16 | 1987-12-16 | $7700.00 | Window Closed / Lapsed |