US4847721A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Safety device for a tool powered by an electric motor
Assignee: C&E Fein GmbH and Co
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Filing: 1987-08-12
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Granted: 1989-07-11
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Expires: 2007-08-12
Abstract
Abstract A safety device for a tool powered by an electric motor. It has a main switch, electronic controls, and a tachometer-generator. In order to provide a device for switching off a motor as a function of motor speed that is simple and economical and that will retain the same nominal switch-off value for the total life of the device, a relay is wired in parallel with the motor and controls the supply of power to the motor through a relay contact.
Inventors
- 👤 Michael Nothofer
- 👤 Malcolm J. Bishop
- 👤 Nigel Bleasdale
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-02 20:06
CPC Classifications
H; H02; H02H; H02H7/00; H02H7/08; H02H7/093
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
214 words
Safety device for a tool, comprising: a tool and an electric motor for driving said tool; a relay with a contact on said relay, said relay controlling supply of power to said motor through said relay contact, said relay having a coil connected in series with means for actuating said coil, said motor being connected in series with control means and said control means being connected in series with said relay contact, the series circuit of said coil and said means for actuating said coil being connected substantially in parallel with the series circuit of said motor, said control means and said relay contact; said safety device switching off said motor when said control means malfunctions; tachometer-generator means and safety circuit means connected in series with said tachometer-generator means for controlling said relay; an auxiliary contact on said relay, said relay being switchable into a self-maintaining state through said auxiliary relay contact; said safety circuit comprising a resonance circuit connected to said tachometer-generator means; a rectifier connected to said resonance circuit, an adjustable threshold switch connected to said recifier, an ignition amplifier connected to said threshold switch, said means for actuating said coil comprising a thyristor connected to said ignition amplifier, said thyristor being also connected in series with said coil of said relay.
Claim 2
Dependent Claim
214 words
Safety device for a tool, comprising: a tool and an electric motor for driving said tool; a relay with a contact on said relay, said relay controlling supply of power to said motor through said relay contact, said relay having a coil connected in series with means for actuating said coil, said motor being connected in series with control means and said control means being connected in series with said relay contact, the series circuit of said coil and said means for actuating said coil being connected substantially in parallel with the series circuit of said motor, said control means and said relay contact; said safety device switching off said motor when said control means malfunctions; tachometer-generator means and safety circuit means connected in series with said tachometer-generator means for controlling said relay; an auxiliary contact on said relay, said relay being switchable into a self-maintaining state through said auxiliary relay contact; said safety circuit comprising a resonance circuit connected to said tachometer-generator means; a rectifier connected to said resonance circuit, an adjustable threshold switch connected to said recifier, an ignition amplifier connected to said threshold switch, said means for actuating said coil comprising a thyristor connected to said ignition amplifier, said thyristor being also connected in series with said coil of said relay.
Claim 3
Dependent Claim
329 words
Safety device for a tool, comprising: a tool and an electric motor for driving said tool; a relay with a contact on said relay, said relay controlling supply of power to said motor through said relay contact, said relay having a coil connected in series with means for actuating said coil, said motor being connected in series with control means and said control means being connected in series with said relay contact, the series circuit of said coil and said means for actuating said coil being connected substantially in parallel with the series circuit of said motor, said control means and said relay contact; said safety device switching off said motor when said control means malfunctions; tachometer-generator means and safety circuit means connected in series with said tachometer-generator means for controlling said relay; an auxiliary contact on said relay, said relay being switchable into a self-maintaining state through said auxiliary relay contact; said safety circuit comprising a resonance circuit connected to said tachometer-generator means; a rectifier connected to said resonance circuit, an adjustable threshold switch connected to said rectifier, an ignition amplifier connected to said threshold switch, said means for actuating said coil comprising a thyristor connected to said ignition amplifier, said thyristor being also connected in series with said coil of said relay; said tachometer-generator means supplying an analog signal dependent on actual motor speed, said analog signal being converted to a direct-current signal by said rectifier and transmitted to said threshold switch; said threshold switch applying a signal to said ignition amplifier when said signal received by said threshold switch exceeds a predetermined limit; said resonance circuit comprising an inductor and a capacitor for determining frequency of said resonance circuit; said threshold switch being influenced by rapid increase in voltage from said tachometer-generator means about said predetermined limit; said voltage from said tachometer-generator means being rectified and adjusted by said rectifier for eliminating motor scatter; a zener diode for determining threshold voltage corresponding to said predetermined limit.
Claim 4
Dependent Claim
329 words
Safety device for a tool, comprising: a tool and an electric motor for driving said tool; a relay with a contact on said relay, said relay controlling supply of power to said motor through said relay contact, said relay having a coil connected in series with means for actuating said coil, said motor being connected in series with control means and said control means being connected in series with said relay contact, the series circuit of said coil and said means for actuating said coil being connected substantially in parallel with the series circuit of said motor, said control means and said relay contact; said safety device switching off said motor when said control means malfunctions; tachometer-generator means and safety circuit means connected in series with said tachometer-generator means for controlling said relay; an auxiliary contact on said relay, said relay being switchable into a self-maintaining state through said auxiliary relay contact; said safety circuit comprising a resonance circuit connected to said tachometer-generator means; a rectifier connected to said resonance circuit, an adjustable threshold switch connected to said rectifier, an ignition amplifier connected to said threshold switch, said means for actuating said coil comprising a thyristor connected to said ignition amplifier, said thyristor being also connected in series with said coil of said relay; said tachometer-generator means supplying an analog signal dependent on actual motor speed, said analog signal being converted to a direct-current signal by said rectifier and transmitted to said threshold switch; said threshold switch applying a signal to said ignition amplifier when said signal received by said threshold switch exceeds a predetermined limit; said resonance circuit comprising an inductor and a capacitor for determining frequency of said resonance circuit; said threshold switch being influenced by rapid increase in voltage from said tachometer-generator means about said predetermined limit; said voltage from said tachometer-generator means being rectified and adjusted by said rectifier for eliminating motor scatter; a zener diode for determining threshold voltage corresponding to said predetermined limit.
Claim 5
Dependent Claim
196 words
Safety device for a tool, comprising: a tool and an electric motor for driving said tool; a relay with a contact on said relay, said relay controlling supply of power to said motor through said relay contact, said relay having a coil connected in series with means for actuating said coil, said motor being connected in series with control means and said control means being connected in series with said relay contact, the series circuit of said coil and said means for actuating said coil being connected substantially in parallel with the series circuit of said motor, said control means and said relay contact; said safety device switching off said motor automatically when said control means malfunctions; tachometer-generator means and safety circuit means connected in series with said tachometer-generator means for controlling said relay; said safety circuit comprising a resonance circuit connected to said tachometer-generator means; a rectifier connected to said resonance circuit, an adjustable threshold switch connected to said rectifier, an ignition amplifier connected to said threshold switch, said means for actuating said coil comprising a thyristor connected to said ignition amplifier, said thyristor being also connected in series with said coil of said relay.
Claim 6
Dependent Claim
196 words
Safety device for a tool, comprising: a tool and an electric motor for driving said tool; a relay with a contact on said relay, said relay controlling supply of power to said motor through said relay contact, said relay having a coil connected in series with means for actuating said coil, said motor being connected in series with control means and said control means being connected in series with said relay contact, the series circuit of said coil and said means for actuating said coil being connected substantially in parallel with the series circuit of said motor, said control means and said relay contact; said safety device switching off said motor automatically when said control means malfunctions; tachometer-generator means and safety circuit means connected in series with said tachometer-generator means for controlling said relay; said safety circuit comprising a resonance circuit connected to said tachometer-generator means; a rectifier connected to said resonance circuit, an adjustable threshold switch connected to said rectifier, an ignition amplifier connected to said threshold switch, said means for actuating said coil comprising a thyristor connected to said ignition amplifier, said thyristor being also connected in series with said coil of said relay.
Claim 7
Dependent Claim
233 words
Safety device for a tool, comprising: a tool and an electric motor for driving said tool; a relay with a contact on said relay, said relay controlling supply of power to said motor through said relay contact, said relay having a coil connected in series with means for actuating said coil, said motor being connected in series with control means and said control means being connected in series with said relay contact, the series circuit of said coil and said means for actuating said coil being connected substantially in parallel with the series circuit of said motor, said control means and said relay contact; said safety device switching off said motor when said control means malfunctions; tachometer-generator means and safety circuit means connected in series with said tachometer-generator means for controlling said relay; an auxiliary contact on said relay, said relay being switchable into a self-maintaining state through said auxiliary relay contact; said safety circuit comprising a resonance circuit connected to said tachometer-generator means; a rectifier connected to said resonance circuit, an adjustable threhsold switch connected to said rectifier, an ignition amplifier connected to said threshold switch; and an output stage connected to said ignition amplifier, said means for actuating said coil comprising said output stage, said means for actuating said coil comprising a thyristor connected to said ignition amplifier, said thyristor being also connected in series with said coil of said relay.
Claim 8
Dependent Claim
233 words
Safety device for a tool, comprising: a tool and an electric motor for driving said tool; a relay with a contact on said relay, said relay controlling supply of power to said motor through said relay contact, said relay having a coil connected in series with means for actuating said coil, said motor being connected in series with control means and said control means being connected in series with said relay contact, the series circuit of said coil and said means for actuating said coil being connected substantially in parallel with the series circuit of said motor, said control means and said relay contact; said safety device switching off said motor when said control means malfunctions; tachometer-generator means and safety circuit means connected in series with said tachometer-generator means for controlling said relay; an auxiliary contact on said relay, said relay being switchable into a self-maintaining state through said auxiliary relay contact; said safety circuit comprising a resonance circuit connected to said tachometer-generator means; a rectifier connected to said resonance circuit, an adjustable threhsold switch connected to said rectifier, an ignition amplifier connected to said threshold switch; and an output stage connected to said ignition amplifier, said means for actuating said coil comprising said output stage, said means for actuating said coil comprising a thyristor connected to said ignition amplifier, said thyristor being also connected in series with said coil of said relay.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1992-07-10 | 1993-01-09 | 1993-07-11 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1996-07-10 | 1997-01-09 | 1997-07-11 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2000-07-10 | 2001-01-09 | 2001-07-11 | $7700.00 | Window Closed / Lapsed |