| 摘要 |
828,131. Control systems for resistance welding. BUDD CO. Feb. 6, 1958 [Feb. 6, 1957], No. 3982/58. Class 38 (4). A method of controlling a resistance welding operation comprises supplying the workpieces to be welded with energy at a uniform rate until fusion of the workpieces commences and thereafter automatically adjusting the energy input to the workpieces in such a manner that the resistance across the workpieces varies in accordance with a predetermined function. The resistance across the workpieces is assessed by developing two signals W e and W i which are derived by measuring respectively the voltage across the workpieces and the current flowing therethrough, these signals being used to control the energy input to the welder. Before fusion of the workpieces takes place the resistance across the workpieces does not change appreciably; in consequence the energy input to the workpieces remains substantially uniform. Immediately fusion occurs a radical change takes place in the resistance across the workpieces whereby the derived signals W e and W i change. A signal W r is derived in a resistance signal generator from the signals We, W i and from this signal W r is derived a further signal F r by means of a function signal generator. The signal F r is representative of the function which the resistance across the workpieces is required to follow after fusion has taken place. The signal F r and the signal W r are compared in a change signal generator, therefore when the signals W e and W i and hence the signal W r change after fusion has taken place, the comparison of signals F r and W r produce a signal C g which, in an input control device, is compared with a reference quantity REF, thereby to control the energy input to the welder such that the weld is made in the desired manner. |
