BY-PASS AND PRESSURE RELIEF VALVE

1,230,004. Purifying exhaust gases; silencing gaseous flow. ACF INDUSTRIES Inc. July 26, 1968 [Jan.16, 1968], No.35804/68. Heading F1B. [Also in Division F2] A valve, which is adapted to be used in an antipollution system of an internal combustion engine, includes an air inlet 24 which is connected to an engine driven pump, (11), Fig. 1 (not shown), an outlet 26 which is connected to an exhaust manifold (16), a vacuum duct 30a which is connected to a position downstream of the carburetter (17), a by-pass outlet 28 which communicates with atmosphere via a felted muffler element 30 channel 114 and slots, (116), Fig.2 (not shown), formed in casing 110, and two valve members 52 and 54 carried by a stem 50 which has connected thereto, and is responsive to movements of a diaphragm assembly 70. Under normal conditions of operation, the valve attains the state shown wherein inlet 24 and outlet 26 are connected to each other, and the pressures within cap 64a and chamber 26a are equal. Upon the engine being subjected to a deceleration, the vacuum in line 30a increases, a pressure differential is created across assembly 70 and consequently valve members 52 and 54 are seated and unseated respectively the resulting shut-off of air-flow to the manifold serving to eliminate objectionable backfire. The new state of the valve is maintained for a short period of time only in view of the presence of a bleed aperture 89 formed in the assembly, the aperture at all times communicating cap 64a and chamber 26a, and its size determining the time interval necessary for the valve to return to its original state under the action of spring 64. Should the vehicle speed exceed a certain predetermined valve, the quantity of air supplied to the inlet 24 becomes greater than that required at the outlet 26 and the excess is then passed through outlet 28, this change of state of the valve being made possible by making valve member 54 of greater cross-sectional area than that of member 52, so that the by-pass is opened and the outlet throttled. In the event of a sudden acceleration immediately following a deceleration, diaphragm flaps 103 permit a rapid equalization of pressure between chamber 26a and cap 64a via ports 87 and 97 formed in the diaphragm backing plates.