Patent GB-689605-A (GB)
Title: Improvements in continuous reading dead-weight pressure gauges
IPC: G01L7/16
Filed: 1951-02-08
Abstract: 689,605. Pressure - gauges. BRITISH THOMSON-HOUSTON CO., Ltd. Feb. 8, 1951 [Feb. 10, 1950], No. 3108/51. Class 106 (ii). [Also in Group XXXII] A dead-weight pressure-gauge comprises a vertically reciprocable plunger adapted to be positioned by a pressure to be measured having variable biasing means for applying an auxiliary force to the plunger in the opposite direction to the force being measured including a weighted lever system, a frictionless spring suspension device for freely suspending the lever system for limited rotation about a horizontal pivot axis normal to the path of movement of the plunger and spaced transversely therefrom the lever system including a first radially adjustable weight spaced horizontally from the pivot axis for compensating the tare weight of the plunger, a second vertically adjustable weight disposed below the pivot and having a neutral position directly below the pivot, a second spring suspension device connecting the plunger to a portion of the lever system spaced from the pivot at the side opposite the first weight, so that movement of the plunger vertically from its neutral position causes rotation of the lever system about its pivot, causing the second weight to move away from the neutral position to produce a biasing force, tending to move the plunger and weight back to their neutral positions, the variable biasing force being proportional to the movement of the plunger from the neutral position. A double dead-weight pressure-gauge, which may be used for measuring the differential pressures in a flow-meter, comprises two hydraulic cylinders 1, 2 with plungers 9, 22, limited in movement by flanges 11, 23. An air vent for the lower cylinder 1 comprises a passage in a projection 13 closed by a removable plug 15, while the upper cylinder contains a vent port 17 closed by a removable plug 18. An annular groove 24 in a bushing 20 for the upper plunger 22 collects oil which drains through a conduit 25 to a recess 26 in the top of the lower cylinder. The plunger 9 carries a platform 12 for calibrated weights which has an upwardly projecting rod 30 carrying a radially projecting pin 31 for engaging the lower end of a rod 29 projecting downwardly from a bushing 28 secured to the plunger 22 which may thus be rotated to reduce friction by turning the platform 12. Operative connection between the plungers is made through a ball 33 engaging opposed spherical surfaces of the plunger 23 and rod 30 with cylindrical shields 34 to exclude dirt. The " tare weight " of the moving system is counterbalanced by an adjustable weight 42 on a lever 36 and the differential pressure between the cylinders is nearly balanced by calibrated weights on the platform 12. The lever 36 is suspended from a bracket by a pair of blade-springs 39 and in neutral position an adjustable weight 44 on an arm 37 at right-angles to the lever is disposed vertically below the pivot point at the junction of the springs 39 with a union 38, the free end of the lever 36 being connected to the plunger 9. Any unbalance in the moving system causes movement of the plunger and displacement of the weight 44 until the system is counterpoised, the displacement being a measure of the force required more or less than the calibrated weight. This force may be indicated upon a dial by a pointer with a string attached to the plunger 9 and weight 44 wrapped round its spindle, the device being calibrated to read in tenths of the difference between successive weights, the system being preferably arranged so that the arm 37 rotates through an arc of only plus or minus ten degrees. Indication may be by a dial gauge 80 with its spring removed, its spindle 80a being maintained in contact with a horizontal arm 83, attached to the arm 37, by a small permanent magnet 84 made, e.g., of " Alnico." Optical indicating means may be used. The lever 36 is connected to the plunger 9 by a spring suspension comprising a ballbearing whose inner race is carried by a depending hub portion 12b of the platform 12 and outer race by a yoke 54, Fig. 3, with radial extensions 56 to which are clamped, between blunt knife-edges, horizontal blade-springs 57 supported by a transverse member 62 and parallel arms 67 secured thereto by arms 66, vertical blade-springs 71 also being clamped to the ends of the extensions 56 and suspended from L-shaped arms 70 secured to the transverse member 62, into the centre of which the lever 36 is screwed. The invention is applicable to a gauge for a single pressure, the upper cylinder being omitted.