Patent GB-637256-A (GB)
Title: Improvements in or relating to apparatus for indicating or measuring torsional vibrations of a rotating body
IPC: G01H1/10
Filed: 1947-07-25
Abstract: 637,256. Indicating torsional vibrations; accelerometers. TRUMPER, R. D. July 25, 1947, No. 20036. [Classes 106 .(iii) and 106 (iv)] Apparatus for indicating or measuring torsional vibrations of a rotating body comprises a member driven by the body and an inertia element flexibly driven from and carried by the member, the member and element having slots in adjacent portions, one at right angles to the direction of rotation and the other at an angle thereto so that they intersect, light passing continuously through the point of intersection from a source within the member. A cylindrical member 10 has a hollow axial extension 11 bolted to a rotating body 9 with bearings 23 for a shaft 22 projecting from an inertia element 20 which is driven by flexible elements 24 attached to inwardly projecting lugs 25 and to the end of the member 10, small bushes 26 being provided. Arcuate slots 27 permit relative movement between the member 10 and inertia element 20 which serves as a measure of torsional vibrations and is indicated by the point of intersection 30 of two slots 28, 29 illuminated from a lamp 31 secured in a tubular member 18a, the moving spot of light producing a visual wave trace 34 observed through a translucent shield 35 provided with a graduated scale for reading the amplitude of vibration. The magnification depends on the slope of the slot 29 and, if desired, several slots with different inclinations may be provided in the inertia element which may be adjusted to obtain the required magnification. The member 18a is mounted in bearings 19 in a tubular extension 17 of a back plate 15 bolted to the casing 10 and is secured to an outer sleeve 18 by a grub-screw 18b. In lieu of the positive drive from the body 9 through bolts 13, the shaft 11 may terminate in a conical friction head engaging a similar shaped recess in the body 9 and to prevent slipping the crosssection of head and recess may be polygonal. A semi-cylindrical lens 37 may be mounted,in the inertia element to concentrate the rays of light from the lamp 31 on the slot 29. Small felt pads 38 soaked in lubricant may be provided to project through holes 39 with blade springs 40 to urge them against the casing 10 to damp free vibrations occurring upon sudden changes of speed. To minimize the rotating masses, the casing 10 and axial extension 11 may be stationary, the latter forming a bearing for a light shaft driven from the body and carrying and driving the inertia element, the light shaft being provided with a counterpoised pointer having a flange in which the slot is formed. In another embodiment shown in Fig. 5, a disc 41 closes the mouth of a funnelshaped member 43 which is secured at its narrow end to the rotating body 9. A central hub member 48 attached to the disc 41 forms a bearing for a cylindrical shoe 50 to which is attached an inertia disc 52 which is driven from the disc 41 by U-shaped wire elements 53 anchored to pins on the two discs. A lamp 59 is held by a member 61 rotatably mounted in the hub member and held stationary by the depending guide 64 for the leads. Intersecting slots 57, 58 are provided in the discs for indicating the vibrations and to correct wave deformation a curved or helical slot may be substituted for the straight radial slot 57 in the disc 41.