| 摘要 |
952,986. Making thermostats. TEXAS INSTRUMENTS Inc. April 8, 1960 [April 8, 1959], No. 12663/60. Heading B3A. [Also in Division G1] To increase the electrical resistance of a bimetal or other composite conductive sheet which flexes on heating, at least a portion of at least one face of a conductive part has a collection of closely-spaced discrete recesses 23 which as indicated in the four parts of Fig. 2 may extend part of the way into one layer 3, to the face of the other layer 5, into the other layer or through the two layers. The recesses may be formed on one face of the bimetal or on both faces with different patterns. The layer 5 may be the high expansion layer and be an alloy of iron with 22% nickel and 3% chromium and need not be of the same thickness as layer 3. There may be 17,000 recesses per square inch in a bimetal 0.008 inches thick. The recesses may be produced by fine mechanical blanking or by liquid honing or blasting through a resist, stencil or lattice or by etching, with acid or electrolytically, through a resist lattice 21, Fig. 4, in which case the resist material 19, Fig. 2, photographic emulsion or greasy ink, may be left on after etching. The bimetal may be snap-acting and may or may not be automatically re-setting. It may be of dished form, Figs. 5, 6 (not shown), and be mounted by a central hole on a post, rotation being prevented by a fixed pin cooperating with an edge notch. In another form, Figs. 7, 8 (not shown), a circular middle portion of a strip mounted on a post is dished and is formed with the recesses but the ends of the strip are flat and unrecessed. Fixed pins at the edge of the strip prevent rotation about the post. Specification 851,721 is referred to. |
