Patent GB-643823-A (GB)
Title: Improvements in or relating to torque measuring devices
IPC: G01L3/10
Filed: 1948-05-11
Abstract: 643,823. Measuring shaft power. YATES, H. G., and PARSONS & MARINE ENGINEERING TURBINE RESEARCH & DEVELOPMENT ASSOCIATION. May 11, 1948, No. 12918. [Class 40 (i)] [Also in Group XIX and XL (b)] A torque measuring device for measuring the aggregate of work transmitted by a shaft in a given period of time independent of the rate of working, comprises a contact a1 fixed to the shaft at the driving end co-operating with a fixed contact a and a similar pair of contacts b1, b, at the driven end of the shaft d. The two pairs of contacts are arranged to make simultaneously when the shaft is transmitting no power. A drum f is driven by means of gearing g, h, or directly, from the shaft d, and a light endless band of ferromagnetic material e slotted at n, as shown in Fig. 1, passes over the drum f and a sprocket j. Two electromagnets o, p, are arranged to pull the ferromagnetic band in contact with the drum, to cause rotation, or in contact with a fixed plate q, to keep it stationary, respectively. The sprocket j is arranged to drive a counting mechanism (not shown) which registers the accumulated total of small movements over any desired period of time. Electrical connections are provided (not .shown) whereby in the interval between the operation of contacts a, a1, and the subsequent operation of contacts b, b1, when the shaft d is loaded the first electromagnet o is energized and the second p is free, whereas during the remainder of each revolution of the shaft d the first electromagnet o is free and the second p is energized. In this manner the belt is held stationary during most of each revolution of the shaft d and is driven at the peripheral speed of the drum f only during the small part of each revolution performed during the interval between the closing of contacts a, a<SP>1</SP> and the closing of contacts b, b<SP>1</SP>. In a modification, Fig. 2, suitable for high speeds of rotation, a toothed wheel r is driven by the gearing g, hand co-operates with a spring contact s to produce a series of pulses which are counted by suitable means (not shown) during the period between the operation of contacts a, a<SP>1</SP> and b, b<SP>1</SP> as before. In a further modification, Fig. 3, the two pairs of contacts a, a<SP>1</SP> and b, b<SP>1</SP> are driven through similar gearing at a higher speed of rotation than the shaft d in order to repeat the sequence of operation more than once during each revolution of the shaft d to overcome errors due to irregular movement of the shaft' in its bearings or to the presence of torsional vibration in the shaft. In a further modification, Fig. 7, electromagnets 7 are arranged to co-operate with slots 9 or projections on the shaft in place of the pairs of contacts in the previous examples. The counting mechanism may be arranged to commence counting at a desired moment of time and cease counting after a prescribed number of revolutions of the shaft d giving a measure of average torque. To obtain increased accuracy the series of pulses produced by the toothed wheel r may be arranged to vary periodically during each revolution of the wheel so as to vary the rate of impulses above and below a mean value giving rise to a high count or a low count according to circumstances at any particular time. The counts are averaged out over a considerable time to give an accurate measure of work transmitted during the period even if the number of impulses occurring during the time interval between the operation of the first and second pairs of contacts is relatively small. The invention is not restricted to the electrical means of initiating and interrupting the integrating or counting mechanism, for example obstruction of the open end of a pipe transmitting fluid, or alternative mechanical means, or a light beam and a photocell may be employed. In an alternative arrangement a thyratron may be employed to discharge an electric condenser into a second. condenser of much larger capacity each time that an electrical impulse occurs in the interval between the initiating pulse and the interrupting pulse. A relay circuit is provided to discharge the second condenser when its voltage reaches a predetermined value, at the same time operating a mechanical counter and subsequently opening the discharging circuit to allow the second condenser to recommence charging. The first condenser is connected to a source of positive supply through a resistance of suitable value so that it is recharged before the next impulse arrives. This ensures that the mechanical counter is only required to operate at a relatively low speed. An instrument adapted to indicate the average value of the current by which the first condenser is charged, but having a relatively high mechanical or electrical inertia so that it will not respond to individual pulses, may be employed to give an indication of the instantaneous rate of power transmission through the shaft.