GB656926A - Improvements in dynamometers - Google Patents

Abstract

656,926. Electric indicating systems. METROPOLITAN - VICKERS ELECTRICAL CO., Ltd. Nov. 8, 1948, No. 28979. [Class 40 (i)] [Also in Group XIX] Forces acting on a cutting tool are measured by mounting the tool at the free end of a hollow cantilever and measuring the displacement of the free end in the required direction by means mounted within the cantilever. As shown, Fig. 3, a cantilever tube 3 preferably of steel, extends from a base 1, and at its free end is provided with a jaw 6 and clamping screw 7 for the cutting tool. Deflections of the tool in two directions XX, YY, Fig. 4, are measured by means of corresponding coil pairs 28, 29 and 28<SP>1</SP>, 29<SP>1</SP> disposed diametrally on the central legs of E-shaped magnetic cores 20, 21, 20<SP>1</SP>, 21<SP>1</SP> mounted within the cantilever by end rings 22, 23 and a spacing sleeve 21, and co-operating E-shaped magnetic cores 24, 25, 241, 25<SP>1</SP> mounted on a preferably non-magnetic, e.g. "Inconel" (Registered Trade Mark) hub 26 secured to a column 8 rigid with the base 1. A sleeve 11 secured to base 1 at one end is connected at its other end with the internal surface of the cantilever 3 by a flexible joint comprising, e.g. a rubber ring 12 bonded to metal rings 13, 14 secured respectively to the sleeve 11 and tube 3. The space between the sleeve and tube 3 is filled with oil or other viscous fluid to damp oscillations of the cantilever. Each coil pair is connected in series, with the secondary 30 of a transformer in a separate circuit, Fig. 6. A measuring instrument 32 connected across the mid-point of the transformer secondary and the common point of the measuring coils 28, 29 is adjusted for zero deflection in the absence of any force on the cutting tool and will indicate directly the force in the associated direction XX or YY by the differential displacement effect of the magnetic circuit on the measuring coils. Vibrational forces acting on the tool, e.g. up to 500 cycles per second may be indicated on a cathode-ray tube in lieu of the meter. Condensers 33, 34 provide a capacitative reactance equal to the leakage reactance of the coils to render the instrument scale linear.