US4329561A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Method of ensuring the maintenance of constant quality of spot welds
Assignee: Individual
•
Filing: 1979-02-14
•
Granted: 1982-05-11
•
Expires: 1999-02-14
Abstract
Abstract A method of improving the reproducibility of the welds in an electric spot welding machine comprises prior to the initiation of a welding operation passing a preheating current of lower magnitude than the welding current through the parts to be welded. When either the total electrical workpiece resistance of the parts to be welded has fallen below a given limit or when its rate of decrease is slower than a predetermined limit the changeover from preheating current to welding current is effected.
Inventors
- 👤 Rolf Schafer
- 👤 Sumanjit Singh
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-27 08:52
CPC Classifications
B; B23; B23K; B23K11/00; B23K11/34; B23K11/24; B23K11/25
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
83 words
A method of improving the reproducibility of the welds produced by an electric spot welding machine, which comprises (a) passing a preheating current of lower magnitude than a subsequent welding current through the workpieces to be welded; (b) monitoring the resistance of the weld starting with the first cycle of preheating current; (c) determining when the rate of decrease of the total weld resistance has fallen below a predetermined limit; and (d) then switching over from said preheating current to said welding current.
Claim 2
Independent Claim
83 words
A method of improving the reproducibility of the welds produced by an electric spot welding machine, which comprises (a) passing a preheating current of lower magnitude than a subsequent welding current through the workpieces to be welded; (b) monitoring the resistance of the weld starting with the first cycle of preheating current; (c) determining when the rate of decrease of the total weld resistance has fallen below a predetermined limit; and (d) then switching over from said preheating current to said welding current.
Claim 3
Dependent Claim
51 words
A method according to claim 1 further comprising, after initiation of said welding current, measuring the electrode displacement as determined by the thermal expansion of the workpieces and the size of the generated weld nugget and switching off said welding current when a predetermined amount of electrode displacement has been achieved.
Claim 4
Dependent Claim
26 words
A method according to claim 1 wherein said preheating current passed through the workpieces to be welded is between 20 and 50% of said welding current.
Claim 5
Dependent Claim
40 words
A method according to claim 2 further comprising stepwise raising or lowering of the welding current for subsequent spot welds if the prescribed upper or lower limits of a standard welding time have once or repeatedly been reached or exceeded.
Claim 6
Dependent Claim
36 words
A method according to claim 4, wherein predetermined electrode displacement during the welding time is prescribed as a reference and the welding current raised or lowered by continuous comparison of the reference with the actual displacement.
Claim 7
Dependent Claim
38 words
A method according to claim 5, comprising indicating that an electrode change is required when the desired electrode displacement cannot be achieved by raising the welding current even after an extension of welding time to a prescribed maximum.
Claim 8
Dependent Claim
44 words
A method according to claim 6, wherein the prescribed reference value of electrode displacement is corrected by hand or automatically by the control system when fluctuations of the electrical mains voltage and/or of the electrode pressure occur in excess of a prescribed tolerance limit.
Claim 9
Independent Claim
93 words
A method of improving the reproducibility of the welds produced by an electric spot welding machine, which comprises (a) passing a preheating electrical current of lower magnitude than a subsequent welding current through workpieces to be welded at an interface between said workpieces to be welded; (b) monitoring the resistance of the weld starting with the first cycle of the preheating current; (c) determining when the total resistance of the interface of said workpieces has fallen below a predetermined limit; and (d) then switching over from said preheating current to said welding current.
Claim 10
Independent Claim
93 words
A method of improving the reproducibility of the welds produced by an electric spot welding machine, which comprises (a) passing a preheating electrical current of lower magnitude than a subsequent welding current through workpieces to be welded at an interface between said workpieces to be welded; (b) monitoring the resistance of the weld starting with the first cycle of the preheating current; (c) determining when the total resistance of the interface of said workpieces has fallen below a predetermined limit; and (d) then switching over from said preheating current to said welding current.
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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) | 1985-05-10 | 1985-11-09 | 1986-05-11 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1989-05-10 | 1989-11-09 | 1990-05-11 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1993-05-10 | 1993-11-09 | 1994-05-11 | $7700.00 | Window Closed / Lapsed |