GB724323A - Improvements in the construction of indicating or measuring instruments - Google Patents

Abstract

724,323. Instrument casings. SANGAMO WESTON, Ltd. March 27, 1953 [March 28, 1952], No. 8572/53. Class 106 (4). In a measuring instrument with a cup-like case, a moulded member of resilient material, such as rubber, extending round and in contact with the bottom and inner walls supports the mechanism and co-operates with the transparent cover to form an annular seal. In an electrical instrument, Figs. 4, 9, permanent magnet 28 to which the coil-bearing bridges, scale plate and stops are fixed rests on the block 30 and is bolted to three pillars 32, the lower ends of which are riveted to plate 31 moulded in the block. The whole assembly is thus insulated from shock and electrically insulated from the case. Connections to the coil are made through a pair of rods 35 moulded into the block concentric with and extending through the holes through which the block is extruded. These extrusions being of greater diameter than the holes outside'the case hold the block firmly thereto. The rods have threaded holes running axially from either end, through which the instrument may be flushed out and filled with inert gas and which accommodate screws holding soldering tags 22 and 37. In another embodiment the upper screws are slotted and shortened to give clearance in the holes which are connected with the lower holes allowing the interior to be flushed before final assembly, the lower holes being then sealed off by short screws 66, Fig. 9. The transparent cover 11 is of plate form and has an annular ridge 11<1> which mates with and is sealed to the annular rubber extensions 41 with cement or other known means and rests on the flanged lip 24 of the cup. It is fixed thereto by 6 hollow-headed rivets 45 (see Fig. 6) reduced in diameter where they engage countersunk holes in the flange. The tails of these rivets are spun out into the countersink, thus fixing the cover without straining it, as the broad part of the rivet is longer than the cover thickness. The plate shape of the cover permits illumination of the scale by 'exterior edge lighting, and enables the plane of the scale plate to be level with the lip of the case, thus facilitating its assembly beneath the pointer.