GB491166A - Improvements in or relating to strain gauges for machine frames and the like - Google Patents

Abstract

491,166. Linear - dimension gauges. UNITED ENGINEERING & FOUNDRY CO. March 6, 1937, No. 6709. Convention date, May 20, 1936. Addition to 485,227. [Class 106 (ii)] Relates to the strain gauge described in the parent Specification in which a bar attached at one end to a machine frame extends along a length thereof, relative movement between the free end and the frame being measured and the bar being maintained at the same temperature as the frame, and consists in providing the bar with an armature movement which in an adjacent magnetic field operates the indicating mechanism. A vertical rod 2 is attached at the lower end by a bolt 3 to the housing post 1 of the mill. The upper end is reduced in section and guided in the groove 11 of a channel bar 12 secured to the housing 1. A frame 7 of magnetic material has mounted upon it a pair of parallel transverse polepieces 14, 15 and is secured at 8 to a support 9 guided in the groove 11. Upon the polepieces 14, 15 are mounted solenoids 16, 17 forming with them electromagnets 18, 19. Between the polepieces is mounted an armature 21 carried by a support 5 secured at 4 to the upper end of the rod 2. The support 9 is slotted and may be finely adjusted by a differential screw device 32, 33 and clamped by a main screw 29 to the housing 1. The solenoids 16, 17 are connected up in a bridge circuit with resistances or reactances 20 and an ammeter 26, and supplied with alternating current by leads L1, L2. When the frame or housing is under strain due to work passing through the rolls, the coils 16, 17 move relatively to the armature 21 and the balance of the bridge is disturbed and restored in the usual manner by adjustment of the resistance 20 such adjustment being a measure of the deformation. For calibration purposes, the rolls may be moved apart by hydraulic jacks and the load to produce a predetermined deformation noted. The bar 2 is housed in a casing 44 containing oil and this in turn enclosed by the insulated lower half of a two part casing 47. The oil is poured in at the top of the casing 44 while the upper half of the casing 47 is secured and the oil may be withdrawn through a plug-hole 45. In a modification the whole instrument is located in a recess formed in the housing which recess is closed by a cover plate. The bridge may assume various forms, one passing rectified current to the indicating instrument, another having several indicating instruments for location at various points and a third having each polepiece 14, 15 supplied with primary and secondary coils which function as transformers.