Patent GB-973778-A (GB)
Title: Temperature sensing device and manufacture thereof
IPC: B21D39/00
Filed: 1962-09-26
Abstract: 973,778. Punching; coiling; making temperature sensitive devices; stamping. KING- SEELEY THERMOS CO. Sept. 26, 1962 [Oct. 19, 1961], No. 36504/62. Headings B3A, B3E, B3R and B3W. [Also in Division G1] . In a temperature sensitive device, Fig. 2, adapted to be concentrically located with respect to a surface heater (not shown) such as a gas burner or an electrical heating element, an upper member 30 is yieldingly biased for relative movement with a base member 14, and a sensing element 34 comprises a top plate 36, of e.g. aluminium or brass, peripherally connected within an aperture in upper member 30, a backing plate 40, and a wire 44 having a high temperature coefficient of resistance sandwiched between the two plates. As shown, the upper member 30 comprises a skirted cap of, e.g. stainless steel, and is secured to an insulating base member 14, e.g. of ceramic material, by tabs (not shown) which engage the underside of a flange 74 on the base member 14, relative rotation of members 14 and 30 being prevented by ears 75 on flange 74 which engage grooves 32 in the cap 30. Cap 30 is biased upwards by a coil spring 72 in order to urge sensing element 34 into engagement with a cooking utensil being heated by the surface heater. The ends 48, 50 of sensing wire 44 are connected to a suitable temperature indicating or control system by a pair of uninsulated serpentine spring conductors 56 of high nickel alloy, spaced apart by a spring support block 60 of high thermal storage capacity. To ensure that the backing plate 40 is absolutely flat, it is stamped out of a sheet having an annular dent concentric with the location of a central aperture 39 in the backing plate to counteract dishing during stamping. The sensing element 34 is made by placing the central aperture 39 in the backing plate 40 over an arbor 42 projecting from the top plate 36, so that the backing plate 40 abuts a central shoulder portion 38 on the top plate 36. The arbor'is spun at 42a to hold plates 36, 40 together, and wire 44 is located in the annular groove 46 between the plates, and secured therein by deformation of plate 40 at 47; alternatively the wire 44 is secured in a chordal groove 104, Fig. 12, in the underside of top plate 36<SP>1</SP> and the backing plate is placed over the arbor and secured by punching the arbor with a punch as shown in Fig. 14. Wire 44 is then bifilarly wound within groove 46, as shown in Fig. 9; the wire is held in tension between cantilever spring arms 51 while the element 34 is rotated, arms 51 closing limit switches 55 when a pre-selected length of wire has been wound, to energize indicating means. The element is then subjected to pressure to join the outer edges of plate 36, 40 (except where the wire emerges) and to press the wire into intimate engagement with the plates; the wire may be embedded in one or both plates. The support block 60 is disposed on the arbor 42, the end of the latter being deformed to secure the block, and the sensing element is secured in the aperture in cap 30 by spinning; alternatively, the element has a re-entrant edge 68, Fig. 8, which is a snap fit in the upwardly turned periphery 70 of the aperture. Modifications..-The spring conductors 56 may be of sufficient gauge to replace the coil spring 72 as biasing means. In the Fig. 5 embodiment, the spring conductors are connected to the external circuit via a coaxial arrangement comprising a tubular conductor 94 and an insulated conductor 98, extending through base 90. Reference has been directed by the Comptroller to Specification 936,748.