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US3609281A
Expired / Lapsed
US
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Method and apparatus for detecting short circuits in the machining gap in an edm process
Assignee: Milacron Inc
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Filing: 1969-12-15
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Granted: 1971-09-28
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Expires: 1989-12-15
Abstract
Abstract A method and apparatus for accurately determining the presence and magnitude of a short circuit condition in an electrodischarge machining (EDM) process. An electrically conductive tool and an electrically conductive workpiece are connected to a pulseproducing power supply and positioned in a dielectric medium to form a machining gap therebetween. The machining gap is placed in an impedance-measuring circuit as the impedance to be measured. The impedance-measuring circuit checks the gap condition by measuring the impedance of the machining gap between pulses from the power supply. In the embodiment disclosed, changes in gap impedance between output pulses are detected by a modified wheatstone bridge. During the time between pulses, a voltage less than the ionization voltage is applied to the bridge. If there is no short circuit condition, the bridge is balanced; and the bridge output is zero. A short circuit condition will cause an imbalance in the bridge producing a resultant error signal on the bridge output. This output is fed back within the power supply causing a change in its output parameters which will tend to alleviate the short circuit condition.
Inventors
- 👤 Harry D Kauffman
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-28 03:45
CPC Classifications
B; B23; B23H; B23H1/00; B23H1/02; B23H1/024
Claims Analysis
Total Claims: 14
Claim 1
Independent Claim
87 words
A method for detecting short circuit magnitudes in a machining gap being supplied with machining pulses from an EDM power supply having timewise predetermined OFF and ON times, said method comprising the steps of: a. applying an electric signal to the machining gap only during the OFF times of the machining pulses; b. measuring the gap impedance in response to the electric signal and producing an output signal as a function of the impedance measurement; and c. modifying successive machining pulses in response to the output signal.
Claim 2
Independent Claim
87 words
A method for detecting short circuit magnitudes in a machining gap being supplied with machining pulses from an EDM power supply having timewise predetermined OFF and ON times, said method comprising the steps of: a. applying an electric signal to the machining gap only during the OFF times of the machining pulses; b. measuring the gap impedance in response to the electric signal and producing an output signal as a function of the impedance measurement; and c. modifying successive machining pulses in response to the output signal.
Claim 3
Independent Claim
97 words
A method for detecting short circuit magnitudes in a machining gap being supplied with machining pulses from an EDM power supply having timewise predetermined OFF and ON times, said method comprising the steps of: a. applying an electric signal to the machining gap only during the OFF times of the machining pulses; b. measuring in response to the electric signal gap impedance only during the OFF times and producing a number of outputs signals in response to a corresponding number of predetermined gap impedance magnitudes; and c. modifying successive machining pulses in response to the output signals.
Claim 4
Independent Claim
97 words
A method for detecting short circuit magnitudes in a machining gap being supplied with machining pulses from an EDM power supply having timewise predetermined OFF and ON times, said method comprising the steps of: a. applying an electric signal to the machining gap only during the OFF times of the machining pulses; b. measuring in response to the electric signal gap impedance only during the OFF times and producing a number of outputs signals in response to a corresponding number of predetermined gap impedance magnitudes; and c. modifying successive machining pulses in response to the output signals.
Claim 5
Independent Claim
138 words
An apparatus for use with an EDM power supply of the type producing low-power pulses for initiating the generation of machining pulses having timewise predetermined OFF and ON times, said machining pulses producing electric discharges across a machining gap formed between an electrically conductive tool and an electrically conductive workpiece, the apparatus comprising: a. means connected to the power supply for producing a control signal only during the OFF times of the machining pulses; b. means responsive to the control signal and connected across the machining gap for measuring gap impedance and generating an output signal proportional to the gap impedance only during the OFF times of the machining pulses; and c. means responsive to the output signal and having an output connected to the power supply for modifying the machining pulses in response to the output signal.
Claim 6
Independent Claim
138 words
An apparatus for use with an EDM power supply of the type producing low-power pulses for initiating the generation of machining pulses having timewise predetermined OFF and ON times, said machining pulses producing electric discharges across a machining gap formed between an electrically conductive tool and an electrically conductive workpiece, the apparatus comprising: a. means connected to the power supply for producing a control signal only during the OFF times of the machining pulses; b. means responsive to the control signal and connected across the machining gap for measuring gap impedance and generating an output signal proportional to the gap impedance only during the OFF times of the machining pulses; and c. means responsive to the output signal and having an output connected to the power supply for modifying the machining pulses in response to the output signal.
Claim 7
Independent Claim
135 words
An apparatus for use with an EDM power supply of the type producing low-power pulses for initiating the generation of machining pulses having timewise predetermined OFF and ON times, said machining pulses producing electrical discharges across a machining gap formed betwEen an electrically conductive tool and an electrically conductive workpiece, the apparatus comprising: a. means connected to the power supply for producing a control signal only during the OFF times of the machining pulses; b. means responsive to the control signal and connected across the machining gap for measuring gap resistance only during the OFF times and producing an output signal in response to a predetermined gap resistance magnitude; and c. means responsive to the output signal and the connected to the power supply for modifying the machining pulses in response to the output signal.
Claim 8
Independent Claim
135 words
An apparatus for use with an EDM power supply of the type producing low-power pulses for initiating the generation of machining pulses having timewise predetermined OFF and ON times, said machining pulses producing electrical discharges across a machining gap formed betwEen an electrically conductive tool and an electrically conductive workpiece, the apparatus comprising: a. means connected to the power supply for producing a control signal only during the OFF times of the machining pulses; b. means responsive to the control signal and connected across the machining gap for measuring gap resistance only during the OFF times and producing an output signal in response to a predetermined gap resistance magnitude; and c. means responsive to the output signal and the connected to the power supply for modifying the machining pulses in response to the output signal.
Claim 9
Independent Claim
139 words
An apparatus for use with an EDM power supply of the type producing power pulses for initiating the generation of machining pulses having timewise predetermined OFF and ON times, said machining pulses producing electrical discharges across a machining gap formed between an electrically conductive tool and an electrically conductive workpiece, the apparatus comprising: a. means connected to the power supply for producing a control signal only during the OFF times of the machining pulses; b. means responsive to the electric signal and connected across the machining gap for measuring gap resistance only during the OFF times and producing a number of output signals in response to a corresponding number of predetermined gap resistance magnitudes; and c. means responsive to the output signals and connected to the power supply for modifying successive machining pulses in response to the output signals.
Claim 10
Independent Claim
139 words
An apparatus for use with an EDM power supply of the type producing power pulses for initiating the generation of machining pulses having timewise predetermined OFF and ON times, said machining pulses producing electrical discharges across a machining gap formed between an electrically conductive tool and an electrically conductive workpiece, the apparatus comprising: a. means connected to the power supply for producing a control signal only during the OFF times of the machining pulses; b. means responsive to the electric signal and connected across the machining gap for measuring gap resistance only during the OFF times and producing a number of output signals in response to a corresponding number of predetermined gap resistance magnitudes; and c. means responsive to the output signals and connected to the power supply for modifying successive machining pulses in response to the output signals.
Claim 11
Independent Claim
140 words
An apparatus for use with an EDM power supply of the type producing low-power pulses for initiating the generation of machining pulses having timewise predetermined OFF and ON times, said machining pulses producing electrical discharges across a machining gap formed between an electrically conductive tool and an electrically conductive workpiece, the apparatus comprising: a. means responsive to the low-power pulses for producing a control signal only during the OFF times of the machining pulses; b. a power supply for producing a direct current; c. a resistance bridge responsive to the control signal and the direct current and connected across the machining gap for producing an output signal in response to a predetermined gap resistance magnitude; and d. means responsive to the output signal and connected to the power supply for modifying the machining pulses in response to the output signal.
Claim 12
Independent Claim
140 words
An apparatus for use with an EDM power supply of the type producing low-power pulses for initiating the generation of machining pulses having timewise predetermined OFF and ON times, said machining pulses producing electrical discharges across a machining gap formed between an electrically conductive tool and an electrically conductive workpiece, the apparatus comprising: a. means responsive to the low-power pulses for producing a control signal only during the OFF times of the machining pulses; b. a power supply for producing a direct current; c. a resistance bridge responsive to the control signal and the direct current and connected across the machining gap for producing an output signal in response to a predetermined gap resistance magnitude; and d. means responsive to the output signal and connected to the power supply for modifying the machining pulses in response to the output signal.
Claim 13
Independent Claim
193 words
An apparatus for use with an EDM power supply of the type including in part a pulse generator for producing control pulses having timewise predetermined OFF and ON times, said control pulses initiating the generation of machining pulses for producing electrical discharges across a machining gap formed between an electrically conductive tool and an electrically conductive workpiece, the apparatus comprising: a. a switching element connected to the pulse generator for producing a control signal in response to the OFF times of the control pulses; b. a drive circuit having an input connected to the switching element for producing a direct current in response to the control signal; c. a resistance bridge responsive to the direct current and connected across the machining gap for measuring gap resistance between discharges and producing an output signal as a function of a gap resistance magnitude; d. an electronic coupling circuit connected to the bridge for producing an isolated output signal in response to the output signal; and e. a switching circuit having inputs connected to the coupling circuit and an output connected to the power supply modifying the machining pulses in response to the isolated output signal.
Claim 14
Independent Claim
193 words
An apparatus for use with an EDM power supply of the type including in part a pulse generator for producing control pulses having timewise predetermined OFF and ON times, said control pulses initiating the generation of machining pulses for producing electrical discharges across a machining gap formed between an electrically conductive tool and an electrically conductive workpiece, the apparatus comprising: a. a switching element connected to the pulse generator for producing a control signal in response to the OFF times of the control pulses; b. a drive circuit having an input connected to the switching element for producing a direct current in response to the control signal; c. a resistance bridge responsive to the direct current and connected across the machining gap for measuring gap resistance between discharges and producing an output signal as a function of a gap resistance magnitude; d. an electronic coupling circuit connected to the bridge for producing an isolated output signal in response to the output signal; and e. a switching circuit having inputs connected to the coupling circuit and an output connected to the power supply modifying the machining pulses in response to the isolated output signal.
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) | 1974-09-27 | 1975-03-29 | 1975-09-28 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-09-27 | 1979-03-29 | 1979-09-28 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-09-27 | 1983-03-29 | 1983-09-28 | $7700.00 | Window Closed / Lapsed |