US3789279A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Work and feed control system for cutting machines
Assignee: CONCRETE CORING Co EQUIPMENT PROGRAM Inc A CORP OF CA
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Filing: 1972-07-21
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Granted: 1974-01-29
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Expires: 1992-07-21
Abstract
Abstract A control system for cutting machines is disclosed in which a desired load is maintained on the cutting motor by use of a servo system regulating power to a feed motor which produces relative motion between the cutting tool and the work. The input to the servo system is a load-level signal proportional to the load current to the cutting motor. That signal is derived by adding signals from current transformers on the power lines to the cutting motor. If the load-level signal exceeds a predetermined threshold, the feed motor is reversed and the servo system is forced to a full speed level. Once the overload condition is relieved, the feed motor is restored to forward drive, but the servo system is limited to a low level for a predetermined period to assure feeding into the work slowly.
Inventors
- 👤 P Hudspeth
- 👤 E Dempsey
- 👤 D Kent
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-24 22:45
CPC Classifications
B; B23; B23Q; B23Q15/00; B23Q15/007; B23Q15/12; B23D; B23D47/00; B23D47/08; B23D59/00; B23D59/001; G; G05; G05B; G05B2219/00; G05B2219/30; G05B2219/37; G05B2219/37525; Y; Y10; Y10T; Y10T83/00; Y10T83/141; Y10T83/768; Y10T83/7755; Y10T83/7763; Y10T83/7776; Y10T83/778; Y10T83/869; Y10T83/8719
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
222 words
In a machine having two motors for cutting material, a feed motor for producing relative motion between a cutting tool and material being cut at a rate proportional to electrical power applied, thereby feeding material to said cutting tool, and a cutting motor for producing a cutting motion of said tool at a rate proportional to the level of current to said cutting motor, which level is in turn proportional to the load on said cutting tool, a load-control servo system comprised of means for continuously detecting said level of current to said cutting motor, means for continuously comparing said level of current to said cutting motor with a reference level and for producing an error signal proportional to the difference between said level of current and said reference level, where said reference level is set for a desired cutting tool load, means responsive to said error signal for controlling said electrical power applied to said feed motor to maintain the load on said cutting motor constant, means for detecting when current to said cutting motor exceeds a predetermined threshold level and for producing an overload signal when that condition is detected, and means responsive to said overload signal for reversing the direction of drive of said feed motor to reverse relative motion between said cutting tool and said material being cut.
Claim 2
Dependent Claim
222 words
In a machine having two motors for cutting material, a feed motor for producing relative motion between a cutting tool and material being cut at a rate proportional to electrical power applied, thereby feeding material to said cutting tool, and a cutting motor for producing a cutting motion of said tool at a rate proportional to the level of current to said cutting motor, which level is in turn proportional to the load on said cutting tool, a load-control servo system comprised of means for continuously detecting said level of current to said cutting motor, means for continuously comparing said level of current to said cutting motor with a reference level and for producing an error signal proportional to the difference between said level of current and said reference level, where said reference level is set for a desired cutting tool load, means responsive to said error signal for controlling said electrical power applied to said feed motor to maintain the load on said cutting motor constant, means for detecting when current to said cutting motor exceeds a predetermined threshold level and for producing an overload signal when that condition is detected, and means responsive to said overload signal for reversing the direction of drive of said feed motor to reverse relative motion between said cutting tool and said material being cut.
Claim 3
Dependent Claim
33 words
The combination of claim 1 including means responsive to said overload signal for applying maximum power to said feed motor, thereby applying full reverse power to said feed motor during an overload condition.
Claim 4
Dependent Claim
38 words
The combination of claim 2 including means responsive to said overload signal for delaying operation of said feed motor at high speed after a detected overload condition is terminated for a predetermined period after said overload signal terminates.
Claim 5
Dependent Claim
36 words
The combination of claim 3 wherein said high-speed delaying means includes means which responds to said overload signal for limiting said error signal to said controlling means to a predetermined low level for said predetermined period.
Claim 6
Dependent Claim
70 words
The combination of claim 4 wherein said means responsive to said error signal for controlling said electrical power applied to said feed motor is comprised of means for pulse-width modulating pulses inversely proportional to said error signal amplitude, means for applying said pulses at a constant rate to said modulating means, and means responsive to pulse-width modulated pulses from said modulating means for gating electrical power to said feed motor.
Claim 7
Dependent Claim
37 words
The combination of claim 5 wherein said feed motor is a series DC motor and said gating means is a gated full-wave rectifying means for receiving alternating line current and delivering DC current to said feed motor.
Claim 8
Dependent Claim
34 words
The combination of claim 6 wherein said reversing means is comprised of relay switching means responsive to said overload signal for reversing connections from said gated full-wave rectifying means to said series DC motor.
Claim 9
Dependent Claim
55 words
The combination of claim 7 wherein said means responsive to said overload signal for applying maximum power to sAid feed motor includes means for limiting only the rate of change of forward speed of said feed motor to prevent surging in the forward direction without limiting the rate at which said feed motor is reversed.
Claim 10
Dependent Claim
118 words
The combination of claim 8 wherein said means responsive to said overload signal for limiting said error signal to a predetermeined low level for said predetermined period is comprised of an RC timing means set to start timing said predetermined period by charging a capacitor in response to said overload signal and allowing said capacitor to discharge through a resistor when said overload signal terminates, and means coupled to said RC timing means by unidirectional conducting means for conducting discharge current from said capacitor, and in response to said discharge current for clamping said error signal to a predetermined low level until said capacitor discharges sufficiently to be unable to maintain discharge current through said unidirectional conducting means.
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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) | 1977-01-28 | 1977-07-30 | 1978-01-29 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-01-28 | 1981-07-30 | 1982-01-29 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-01-28 | 1985-07-30 | 1986-01-29 | $7700.00 | Window Closed / Lapsed |