Patent GB-1151083-A (GB)
Title: Thermoelectric Conversion Module.
IPC: H01L35/06
Filed: 1966-07-12
Abstract: 1,151,083. Shielded containers for radio-active material. MARTIN-MARIETTA CORP. 12 July, 1966 [26 July, 1965], No. 31256/66. Heading B4Q. [Also in Divisions G6 and H1] A planar thermo-electric conversion device comprises an array of thermo-electric elements positioned between two plates, with a side wall coupling the plates and exerting force so as to maintain the elements under compression. The embodiment consists of thermo-electric generator comprising a radio-active heat source, capsule 16 enclosed in a shield 20, with an array 92 of thermo-electric elements 98 set in holes in an insulating disc 94 disposed at one end of the container 20, separated from the capsule 16 by a shielding lid 22. Thermal insulation, in the form of a series of discs and rings 36 of a fibrous insulator, surround the shield 20, and the generator is housed in a cast iron container 38. A heat sink 46, comprising fins 72 attached to a disc 70, dissipates excess heat from the capsule 16. The thermoelectric elements 98 are urged by spring-biased pistons 78 situated in apertures 76 in the disc 70, into contact with a thin electrically insulating disc (108), Fig. 3 (not shown), e.g. of mica. Hemispherical metal buttons (84), seated in depressions in the pistons (78), press against copper bus-bars (90) attached to the elements (98). Each button (84) carries an electrically insulating layer (86), e.g. of oxide, to insulate the elements from the heat sink. Between the disc (108) and a metal cover (118) of the thermo-electric conversion unit, a disc (110), e.g. of zirconium, is provided to adsorb undesirable reactive gases emanating from the fibrous thermal insulation surrounding the indication shield. The cover (118), which is urged into thermal contact with the lid (22) of the radiation shield, is joined to the disc 70, Fig. 2, of the heat sink by a metal bellows, which encloses the array of elements 98, permitting the space around the array to be evacuated through a conduit 142. Thus the insulating disc 94 may be outgassed, and an inert gas such as argon may be introduced into the space surrounding the elements 98. Similar outgassing means are provided in the container 38, to permit outgassing of the insulation 36, and introduction of an inert gas. The gas introduced to the container 38 may be varied to adjust the degree of thermal insulation of the walls surrounding the capsule 16, and hence to control the power output of the generator. Each element 98 may be formed of a telluride, doped to provide the required P and N characteristics, and may be joined in pairs by hot shoes (102), Fig. 1 (not shown). The cold shoes are provided by cast iron discs bonded to the ends of the elements (98) remote from the heat source, and are linked for either series or parallel operation by the bus-bars (90). The radio-active heat source capsule 16, Fig. 2, comprises a fluid-tight metal cylinder enclosing a fuel source such as strontium 90, plutonium 238, cerium 144, cesium 137 &c. A second embodiment is described in which thermo-electric conversion units (12<SP>1</SP>, 12<SP>11</SP>), Fig. 4 (not shown), are situated at both ends of the heat source capsule (16<SP>1</SP>), which is provided with cylindrical shield (20<SP>1</SP>) thermal insulation (36<SP>1</SP>) and outer container (38<SP>1</SP>).