Patent GB-711862-A (GB)
Title: Improvements in or relating to pneumatically operated linear dimension gauges
Inventor: BOOSEY FREDERICK ROBERT
IPC: G01B13/00
Filed: 1951-07-19
Abstract: 711,862. Fluid-pressure gauging-apparatus; indicating-apparatus. SIGMA INSTRUMENT CO., Ltd. July 18, 1952 [July 19, 1951], No. 17180/51. Classes 106 (2) and 106 (4) [Also in Group XXIX] A pneumatically-operated linear-dimension gauge comprises a flexible member disposed in a container to divide the latter into two compartments, means for indicating the deflection of the flexible member, a control orifice, and conduits for leading air through one of the compartments and thence through the orifice, the downstream side of the orifice communicating with the other compartment, the arrangement being such that when air at constant pressure is fed through the first compartment to the orifice and when a measuring jet is connected to receive the air passing through the orifice, a variation in the amount of air passing through the jet causes deflection of the member and hence an alteration of the indication of the indicating means. The gauge, Fig.1, comprises a capsule 1 of thin flexible material whose walls 2, 3 are annularly corrugated, located in a box 4 with air inlet 5 and outlet 6. The central part 2A of the wall 2 is secured to the head 7 of a pin 8 whose shank 9 passes freely through a hole 10 in the wall 3. The upper end of the pin 8 has a threaded hole 11 in which the enlarged end 12A of a link 12 is secured by a plug 13 screwed in the hole 11, the link 12 passing upwardly through a tube 14 projecting from the top of the box 4. The upper end of the link 12 is secured in a collar 18 which is gripped in :a hole 15 in a block 16 by grub screws 17, the lower part of the collar 18 being surrounded by a tube 16A projecting down from the block 16. A flexible tube 55 of e.g. rubber joins the tubes 14, 16A to form a seal. The central part 3A of the wall 3 is secured to a threaded collar 19 passing through a hole 20 in the bottom of the box 4 with a shoulder 21 bearing on the box 4. The collar 19 is screwed into the upper end of a hollow cylinder 22 with a packing ring 23 gripped against the :box 4. In two holes 24, 25 in the wall of the cylinder 22 are secured a short tube 26, 28 connected to a flexible tube 27 leading to a measuring jet and a short tube 28 having a control orifice 29 therein, and its outer end joined by a flexible :pipe 30 to the air outlet 6 of the box 4. The lower end of the cylinder 22 is closed by a cap 31 leaving a space 32 in which are located nuts 33, 34 threaded on the lower end of the pin 9, the nut 33, locked by the nut 34, engaging the cylinder 22 to limit expansion of the capsule 1, while a screw 35 in the cap 31, locked by a nut 36, limits contraction of the capsule 1. The cylinder 22 is fixed by means of a bracket 37. The block 16 is secured to the lower end of a belt 38, the other end of which is secured to the far side 39 of a segment 40 of a cylinder, the segment 40 being pivoted, at the centre of its arc, to a fixed member 41 by means of crossed lath springs 42. The belt 38 meets the curved surface of the segment 40 tangentially thereto and the upper end is in contact with the curved surface. The lower ends of two belts 43 are connected to the side 44 of the segment 40 being disposed one each side of the belt 38 while their upper ends are connected to a cross bar 43A suspended from one end of a coiled spring 45 the other end of which is connected to a belt 46 wound onto a drum 47, which can be rotated by a worm drive 48. The segment 40 carries two arms 49, 50 whose free ends are connected by a flexible belt 51 wrapped round a roller 52 mounted on a spindle 53 carrying the pointer 54 of the gauge. Adjustments of zero may :be made by means of the spring 45 and drum 47 arrangement. In operation, high .pressure air above 4 lb. per square inch at constant pressure is delivered to the inlet 5 of the box 4 and air escapes from a measuring jet communicating with the flexible tube 27 at a rate depending on the dimensions or shape of work being gauged and causes a corresponding pressure drop across the control orifice 29. The low pressure side communicates with the inside of the capsule 1 via the annular space between the cylinder 22 and the pin 9 and the high pressure side communicates with the interior of the box 4 to act on the outside of the capsule. Since the apparatus measures a pressure difference it is possible to use a very thin walled capsule whilst still using a high pressure sufficient to force coolants, used in grinding or honing, off the surface being gauged. If it is necessary to have the measuring jet at a distance from the gauge, the control orifice may conveniently be arranged near the jet, Fig. 3. Specification 711,865 is referred to.