Patent GB-784263-A (GB)
Title: Apparatus for measuring rotational speeds or velocities
IPC: G01P3/28
Filed: 1955-08-30
Abstract: 784,263. Measuring speed of shaft rotation. WAHLI, W. Aug. 30, 1955 [Aug. 31, 1954], No. 24819/55. Class 106 (3). [Also in Groups XXVIII and XXIX] Rotational speeds are measured by means of a liquid pump driven at a speed proportional to the rotational speed to be measured and discharging quantities of liquid through a control valve into a liquid measuring system responsive to the quantity of liquid which is discharged into it for operating a speed indicating device. The drive is imparted from a shaft 11, Fig. 1, through bevel gears 15, 16 and gearing 18, 19 to a shaft 20 and either spur gears 20, 21, 22 and 24 or 20, 21, 22, 25 and 24 to drive the gear 24 in the same direction irrespective of the direction of rotation of the shaft 11. The shaft 26 on which the gear 24 is mounted winds up a driving spring in a chamber 270 of a clockwork mechanism 27 and also extends into a liquid-tight casing 29 to drive, by means of a wheel 30 and toothed rim 32 the rotor 31 of an eccentric piston pump. The rotor 31, Fig. 3, has five bores 33 each with a piston 34 urged by a spring 35 to abut with a ball 37 against the cylindrical inner surface of an eccentric ring 38. The ring 38 may have its eccentricity with respect to the rotor adjusted by means of a screw 45. The rotor 31 revolves on a hollow member 47 and during rotation each bore 33 is, during the suction stroke of its piston 34, put into communication with the liquid-containing cavity via grooves 48, 49, 50, then cut off by the member 47, then communicates during the discharge period via groove 48 and slot 51 with the valve cavity 52 of a rotary valve 53 and finally cut off again by the member 47. The valve body 53 has a flange in the form of a six slot star wheel 57 driven by a pin wheel 59 in turn driven by the clock mechanism 27 to impart to the valve an intermittent rotary motion in six rotational steps. The hollow member 47 is formed as a projection on a fixed member 42 having three bores 62, 621, 6211, Fig. 4, extending radially at 120 degree angles from the valve bore 54, each bore opening at its end into a cavity 63, 631, 6311 of a cylindrical sleeve 64 via an opening 65. Each sleeve 64 has an associated sleeve 67 telescopically mounted thereon and connected thereto by a spring 68 normally urging the sleeve 67 into a position where its flange 72 abuts against an adjustable screw 73 screwed into the member 47. The axes of the three pairs of sleeves 64, 67 are in a common plane vertical to the axis of the rotary valve and together define an equilateral triangle through the centre of which passes the valve axis. The valve body 53 houses a coaxial equalization piston 76, Fig. 5, subjected to the pressure of a spring 77 abutting against an apertured port 78 through which liquid may flow into the open. end of the valve body 53. The body 53 has an opening 74 communicating fully with the bores 62, 62<SP>1</SP>, 62<SP>11</SP> in the 30-degree, 150-degree and 270-degree positions thus permitting direct discharge by the pump into these bores at those points but which is completely closed by the wall of member 42 at positions 90 degrees, 210 degrees and 330 degrees. At these points the liquid discharged by the pump is stored in the valve cavity 52 and added to the direct discharge into the next bore 62, 62<SP>1</SP> or 62<SP>11</SP> by the action of the piston 76. At subsequent positions in the valve cycle the bores 62, 62<SP>1</SP> or 62<SP>11</SP> discharge, under the return of cylinder 67 by the spring 68, to the liquid-containing cavity 29 through a port 75 in the valve body 53. Between the intake and discharge positions the position of cylinder 67 is governed by the rate of discharge of the pump and hence by the speed of the shaft 11 and this position is transferred to an indicator by means of a feeler or scanning disc 83, Fig. 4. The disc 83 is provided with three pins 84 each contacting the face 85 of the flange 72 of an associated sleeve 67 in such a manner that the disc 83 is angularly located in accordance with the greatest displace. ment of any one of the three sleeves 67. The disc 83 has a toothed segment 86 engaging a pinion 87 driving, through gears 91, 92 a shaft 93 on which is carried a pointer 97.