US3673371A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Gap monitoring electric-discharge-machining apparatus
Assignee: Sparcatron Ltd
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Filing: 1971-03-26
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Granted: 1972-06-27
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Expires: 1991-03-26
Abstract
Abstract The invention provides electrical discharge machining apparatus including in combination, a gap monitoring circuit registering machining energy flow across a working gap between a tool electrode and a workpiece in terms of voltage and/or current; a servo system which effects advance and retraction of the tool electrode to maintain the working gap within predetermined dimensions; a retraction detection means registering the extent of retraction of the tool electrode. In addition there is provided a subsidiary control circuit which is effective to operate at least one of (i) a warning device which may be visible or audible, (ii) means for disconnecting the supply of machining power to the inter-electrode gap, (iii) means for fully retracting the tool electrode; this subsidiary circuit being effective only when the following conditions exist simultaneously: the gap monitoring circuit registers machining energy flow at normal working levels and the retraction detection means registers retraction of the tool electrode to such an extent that the tool electrode and the workpiece are separated by more than a predetermined distance.
Inventors
- 👤 Gordon Victor Smith
- 👤 Eric John Ward
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 19:17
CPC Classifications
B; B23; B23H; B23H7/00; B23H7/14; B23H7/18
Claims Analysis
Total Claims: 9
Claim 1
Independent Claim
171 words
Electrical discharge machining apparatus including in combination: a. a gap monitoring circuit registering machining energy flow across a working gap between a tool electrode and a workpiece in terms of voltage and/or current; b. a servo system which effects advance and retraction of the tool electrode to maintain the working gap within predetermined dimensions; c. a retraction detection means registering the extent of retraction of the tool electrode and d. a subsidiary control circuit which is effective to operate at least one of: i. a warning device which may be visible or audible, ii. means for disconnecting the supply of machining power to the inter-electrode gap, iii. means for fully retracting the tool electrode; e. said subsidiary circuit being effective only when the following conditions exist simultaneously: 1. the gap monitoring circuit registers machining energy flow at normal working levels and 2. the retraction detection means registers retraction of the tool electrode to such an extent that the tool electrode and the workpiece are separated by more than a predetermined distance
Claim 2
Dependent Claim
171 words
Electrical discharge machining apparatus including in combination: a. a gap monitoring circuit registering machining energy flow across a working gap between a tool electrode and a workpiece in terms of voltage and/or current; b. a servo system which effects advance and retraction of the tool electrode to maintain the working gap within predetermined dimensions; c. a retraction detection means registering the extent of retraction of the tool electrode and d. a subsidiary control circuit which is effective to operate at least one of: i. a warning device which may be visible or audible, ii. means for disconnecting the supply of machining power to the inter-electrode gap, iii. means for fully retracting the tool electrode; e. said subsidiary circuit being effective only when the following conditions exist simultaneously: 1. the gap monitoring circuit registers machining energy flow at normal working levels and 2. the retraction detection means registers retraction of the tool electrode to such an extent that the tool electrode and the workpiece are separated by more than a predetermined distance
Claim 3
Dependent Claim
29 words
the retraction detection means registers retraction of the tool electrode to such an extent that the tool electrode and the workpiece are separated by more than a predetermined distance
Claim 4
Dependent Claim
29 words
the retraction detection means registers retraction of the tool electrode to such an extent that the tool electrode and the workpiece are separated by more than a predetermined distance
Claim 5
Dependent Claim
98 words
Electrical discharge machining apparatus according to claim 1, wherein the retraction detection means comprises in combination a block resiliently urged in frictional engagement against the surface of a bar member arranged to move with the tool electrode as the latter is advanced and retracted, the block being permitted movement, between a pair of stops, such movement being in a direction parallel to the movement of the tool electrode, and wherein said stops are separated by a gap such that the movement permitted to the block corresponds to predetermined maximum size of the working gap under normal working conditions.
Claim 6
Dependent Claim
36 words
Electrical discharge machining apparatus according to claim 2, wherein the stop abutted by the block during movement in retraction of the tool electrode, carries a micro switch adapted to be actuated by contact with the block.
Claim 7
Dependent Claim
26 words
Electrical discharge machining apparatus according to claim 2,wherein at least one of the stops is adjustable so that the gap separating the stops may be varied.
Claim 8
Dependent Claim
122 words
Electrical discharge machining apparatus according to claim 1, wherein the retraction detection means comprises in combination, a roller carried on an axle and resiliently urged in frictional engagement against the surface of a bar member arranged to move with the tool electrode as the latter is advanced and retracted, a disc of high friction material secured to one side of said roller, an arm journalled on the axle and urged against said disc and a portion of said arm spaced radially from said axle being free to move arcuately between a pair of stops, the spacing between said stops being adjustable so that it may be made to correspond to a predetermined maximum size of the working gap under normal working conditions.
Claim 9
Dependent Claim
28 words
Electrical discharge machining apparatus according to claim 5, wherein at least one of the stops carries a micro switch adapted to be actuated by contact with the arm.
References Cited (Backward Citations)
US3125700A
Cited
US3462576A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1975-06-27 | 1975-12-27 | 1976-06-27 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1979-06-27 | 1979-12-27 | 1980-06-27 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1983-06-27 | 1983-12-27 | 1984-06-27 | $7700.00 | Window Closed / Lapsed |