Patent GB-947909-A (GB)
Title: Leak test equipment
Inventor: MARTIN FREDERICK W
IPC: G01M3/32
Filed: 1961-10-09
Abstract: 947,909. Brake testing apparatus. BENDIX CORPORATION. Oct. 9, 1961, No. 36148/61. Heading F2E. Apparatus for testing a vacuum or compressed air servomotor or other pneumatic component of a fluid-pressure braking system to determine its rate of leakage comprises a source of vacuum or pressure to which the component is connected together with a pressuresensitive switch, the switch being connected in a circuit including a " pass " and a " reject " circuit, means for connecting the source to the component and pressure-sensitive switch for a predetermined time after which the " pass " or " reject " circuit is energized according to whether or not a predetermined vacuum or pressure has been reached, and further means for subsequently disconnecting the source if the " pass " circuit has been energized to initiate a further step of the test whereby, if after a further predetermined time the vacuum or pressure remaining is above the predetermined value, the " pass " circuit is again energized, otherwise the " reject " circuit is energized. As shown, the flow of air exhausted from a vacuum servo 22 to be tested by a vacuum source 11 is adjusted to a predetermined rate by a valve 14, the flow being initiated by a solenoid-operated valve 16 which is opened upon energization of its winding 34 resulting from the depression of a START switch and the consequent energization of relay CR1 and closure of contacts CR1-c. This initiates the first step during which a relay TD2 having delayed action contacts TD2 -DAE is also energized. As the degree of vacuum increases the pressure in chamber 46 of pressure-sensitive switch 42 is reduced and acts on a diaphragm 41 which in turn acts on the plunger of a two-way micro-switch VS-1 via a spring 44 which normally maintains its contacts 1, 2 closed. If after the expiry of the time delay the vacuum reached is insufficient to release the plunger of switch VS-1 the contacts TD2-DAE close to energize the " reject " circuit comprising red light R and relay CR2 which opens contacts CR2-b in the " pass " circuit. If, however, the plunger of switch VS-1 is released before expiry of the time delay contacts 1, 2 open and contacts 2, 3 close so that relay TD1 is energized. This relay has instantaneous and delay contacts, the former including contacts TD1-DAE which energize the " pass " circuit to illuminate green light G, contacts TD1-a which open the circuit of relay TD2, and contacts TD1-b which open to de-energize the solenoid valve 16. As a result, the vacuum source is cut off and the pressure in chamber 46 will rise if leakage is present. If, before the expiry of the time delay of relay TD1, the plunger of switch VS-1 is again depressed the " reject " circuit is completed by way of its contacts 1, 2. If, however, the plunger of switch VS-1 is not again depressed before this time has expired the delay contacts TD1-DAE close to energize the " pass " circuit whereupon relay CR3 opens contacts CR3-a in the " reject " circuit. The final result of the test as indicated by the light R of G therefore remains after the component has been removed from the test apparatus until the circuit network is reset by depression of a RESET button.