Patent GB-960822-A (GB)
Title: Improvements relating to brake testing apparatus
Inventor: CLARKE WALTER WILSON HUGH
IPC: G01P15/04
Filed: 1960-07-18
Abstract: 960,822. Accelerometers. INERTIA SWITCH Ltd Sept. 29, 1961 [July 18, 1960], No. 24945/60. Heading G1K. Brake testing apparatus for mounting on a vehicle comprises a flywheel 18 mounted for rotation, means wherby the flywheel 18 receives a first acceleration, means to impose a predetermined second acceleration on the flywheel opposite in direction to the first acceleration, the arrangement being such that finally the flywheel comes to rest, and means to indicate the position at which the flywheel comes to rest, the position being dependent on the retardation applied to the vehicle. The flywheel 18 is mounted by means of stub-axles 16 and pinions 14 received by racks 12 supported in the frame 1, which is pivoted on a rubber-soled base 4 and levelled by means of screw 5. The base 4 is mounted in the vehicle with the racks 12 running longitudinally thereof, so that the flywheel 18, when released, runs from their rear ends to a stopping position near their forward ends, at which position a stirrup lever 24 is mounted. The stirrup 24 is pivoted on pins 26 in the frame 1 and has V-pulleys 30 secured outside its arms. Two springs 32 are adjustably secured to a bar 33 fixed in the frame 1 and are secured to the arms 25 by fine steel wires 34 trained over the pulleys 30. When the flywheel 18 reaches the stopping position pins 29 thereon strike projections 28 of the lever 24 and the stirrup turns with the flywheel extending the springs 32 which absorb their kinetic energy and bring them to rest. An extension of the stirrup contacts the tail of a pointer pivoted with friction to turn over a scale when driven by the lever 24, stopping as soon as the flywheel comes to rest and being unaffected by reverse movement of the stirrup. To set the apparatus for a brake test the pointer is set to initial position and the flywheel is moved to the rear ends of the racks. During this movement the pins 29 on the flywheel rock pivoted arms 52 to tension spring 54 and finally a catch 45 enters a recess in the periphery of the flywheel to lock it. Now when the brake pedal is depressed a switch is operated which causes a solenoid 50 to release the catch 45 so that the springs 54 give the flywheel a small initial acceleration to which is added the acceleration due to the inertia of the flywheel which is imparted as soon as the brakes operate. When the pins 29 strike the projections 28 the springs 32 apply a predetermined deceleration so that the pointer turns through an angle dependent on the deceleration of the vehicle. The scale may be calibrated in terms of braking efficiency. In the embodiment of Fig. 4, a flywheel 106 is mounted for rotation about a vertical axis and is held by a catch 111 with a pin 110 abutting a lever 107 against the tensing of a spring 109. A nylon string attached to a lever 121 carrying a weight 123 is wound around and attached to the spindle 126 of the flywheel 106 and is held in tension by a spring 124 acting on the lever 121. When the brake pedal is depressed a solenoid 116 releases the catch 111 and the release of the tension in spring 109 imparts a predetermined acceleration to the flywheel. As the brakes come into action the retardation of the vehicle tends to move the weight 123 in a direction to increase the tension in the string 125 and thence to apply a retarding torque to the flywheel 106 which comes to rest and is prevented from reversing by means not shown. The flywheel 106 carries a scale 127 which indicates against a fiduciary mark the efficiency of the brakes. A resetting knob 128 on the spindle 126 allows for the manual return of the flywheel 106.