Patent GB-1196089-A (GB)
Title: Resilient Support for Yieldably Withstanding Forces
IPC: G01L9/00
Filed: 1968-04-16
Abstract: 1,196,089. Springs. REVERE CORP. OF AMERICA. 16 April, 1968 [23 May, 1967], No. 18011/68. Heading F2S. [Also in Division G1] A force measuring or resisting device comprises a resilient structure 1 (with or without strain gauges 18-21 connected to portions which develop strains in response to applied stresses) formed from an integral block of material e.g. steel by removing material mainly by turning, drilling or sawing whereby a hollow cylinder is obtained closed at the top which is then pierced by two pairs of diametrically opposite holes 5, 6; 7, 8 and by slots 3a, 3b each intersecting two adjacent holes 6, 7; 5, 8, thus leaving webs of which a peripheral web 1b at the bottom is joined to a top bridge piece 13 by alternate webs 9, 11 and to top flanges 1b by the other alternate webs 10, 12, the bridge 13 having a central post 14 to receive an applied force 16 opposed by a reactive force 17 received under the flanges 1b. More than two pairs of holes may be used. A device without strain gauges, Fig. 19, mayprovide, within limits two degrees of freedom of movement between a supported and a supporting structure and, to prevent the transmission of angular loads, two may be used in series with a load cell, one between a load and the cell and the other between the cell and its support. A pressure gauge, Fig. 5, incorporates a device 1, with strain gauges, to measure the pressure on a diaphragm 46 against the reaction of a ring 24, threaded in the housing 15 and supporting the flanges 1b on shims 23 spaced so that the bridge 13 can pass freely until obstructed by the ring 24, which prevents overloading. Leads to the strain gauges pass through insulating bushings 67 sealed in a metal header soldered to the housing 15, providing access to calibrating resistors 69 by removing a cover 26 outside the hermetically sealed unit. A universal load cell for measuring forces applied in tension of compression, Fig. 22 (not shown), has a device 1 with an elongated central post (70) extending upwards from its bridge and also a downward extension (76) each of which is welded to the inner periphery of an annular metal diaphragm (73, 78) which is welded at its outer periphery to a surrounding tubular housing (71). The diaphragms are stiff enoughtransversely to the post to transmit transverse components of applied forces directly to the housing and so protect the weaker parts of the device 1. Shims, to prevent overload, and access for calibration are also provided. In one embodiment of the strain sensitive device, Figs. 2, 3, a strain gauge is provided on each web, preferably on a milled flat surface 22, alternate gauges being subjected to tension, the others to compression, when stress is applied. In another embodiment, Fig. 11, a strain gauge is provided below each hole 5-8 in a portion joining a web in tension to a web in compression and consequently subjected to shear. The device can be made more sensitive by machining the peripheral web 1a to form a scallop (28c) aligned with each hole 5-8 and also a concave recess 28d connecting each scallop with its aligned hole. The inner and outer surfaces of the web 1a may be provided with strain gauges 33- 36; 29-32. Alternate holes may be joined to their adjacent scallops by slots and the number of strain gauges halved. In a further embodiment, Fig. 12, slots 37, 38 in the web 1a open opposite holes 5, 6 and strain gauges are fixed on the inner surfaces of holes 7, 8, where they respond to bending stresses.