Patent GB-373170-A (GB)
Title: Improvements in or relating to devices for measuring acceleration
IPC: G01P15/04
Filed: 1931-02-13
Abstract: 373,170. Accelerometers. TUSTIN, A., 257A, Fulwood Road, Sheffield. Feb. 13, 1931, No. 4646. [Classes 106 (iii) and 106 (iv).] Apparatus for attachment to a vehicle or other body whose acceleration is required to be known comprises a cylinder 2 which slides against the action of a spring 3, a non-rotating piston 1 having a rack 16 meshing with a pinion 15 the spindle 13 of which rotates in a gland 14 and carries a pointer 19 moving over a scale 20 adjustable through a clamping screw 34 and arcuate slot 35. The pinion 15 is maintained in mesh with the rack 16 by an idle guide wheel 17 engaging in a groove 18 in the piston. A spiral spring 21 anchored at one end on the gland 14 and connected at the other end to the pointer 19 takes up backlash between the pinion 15 and rack 16. The piston is kept in its position of maximum displacement by a ring of hardened steel balls 6 in the cage 7 being frictionally gripped between the conical ground case-hardened surface 4 of the piston and the ground case-hardened inner surface of the cylinder 2. The cage 7 is attached to a disc 9 and the balls 6 are kept in contact with the piston by a spring 8 in a sleeve 11 pressing against the disc 9 and against the head of a bolt 10 screwed axially into the piston. The balls 6 and cage 7 can be moved out of engagement with the piston through a finger grip 12 to allow the piston to resume its normal position. A suitable transparent cover 22 is provided over the pointer mechanism and on removing this cover the pointer mechanism may be removed from the apparatus as a unit by unscrewing the gland 14 from the cylinder. The mass of the piston 1 is adjusted by screwing in a hole 5 an additional mass. The cover 23 of the cylinder 2 is drilled with an axial hole 24 through which a rod may be passed and screwed into the threaded hole 5, or hooked on to a hook screwed into the hole 5. The hole 24 may be plugged by a screw during normal operation of the device or it may be left open to provide a vent hole for the cylinder. The sensitiveness of the instrument can be changed by varying the strength of the spring 3. The cylinder 2 is provided with lugs 25, and the cover 23 with lugs 26 for attachment to any part of a machine or vehicle, the impact forces on which, knowing the mass, can be determined. In an alternative arrangement two conical surfaces such as 4 may be provided on the piston 1 each having an appropriate ring of balls 6. In the modification shown in Fig. 3 a central insulating bush 29 has mounted within it a metal bush 30 through which passes a metal adjusting screw 31. A releasing device similar to the device 8, 10, 11, 12 of Fig. 2 passes through the end 28, to one side of the central bush 30, and co-operates with a disc secured to the ball-retaining cage as in Fig. 2. A terminal 32 is connected by a metal strip to the metal bush 30. The head of the piston 1 has mounted therein a bolt 33 adapted to contact with the adjusting screw 31 due to pressure of the spring 3. When a predetermined acceleration is reached the bolt 33 and the adjusting screw 31 separate to break an electric circuit and extinguish a lamp or actuate other alarm signalling devices.