Patent GB-297460-A (GB)
Title: Improvements in or relating to charge forming devices for internal combustion engines
IPC: F02M21/00
Filed: 1928-09-22
Abstract: 297,460. Delco-Remy Corporation, (Assignees of Teeter, W. H.). Sept. 22, 1927, [Convention date]. Dashpots.-In a charge forming device for internal-combustion engines an air valve 91, Fig. 7, is loaded by a spring and its movements are controlled by a dashpot. The structure 34 has an arm 140 with tubular extension 141 around which is a sleeve 142, a grooved flange 143 on which supports the valve loading spring 92. The groove in the flange is engaged by pins 144 on a yoked lever 145 mounted on a shaft 147, Fig. 5, cranked so as to be actuated by a choke rod attached to the end 148, an adjustable stop limiting the return movement. To choke the carburettor at starting, the sleeve is raised to compress the spring 92. The stem 160 of the air valve passes through guides 141, 161, Fig. 7, and; at its lower end is attached to a piston rod 164 on which a dashpot piston 165 is mounted for sliding movement. A spring 166 is inserted between the piston and a nut 167 on the rod, against a flange 168 on which the piston is forced. The piston has holes 169 leading to the space between piston and flange and the latter provides a seat for a relief valve. The flange has holes 171 adapted to be closed by a check valve disc 172. The piston is enclosed in a cylinder 175 located in the float chamber and guided for vertical movement in a sleeve 177. A port 178 in the wall of the sleeve is adapted to register with a port 179 in the wall of the cylinder in the different positions thereof so as to permit of the passage of liquid fuel. A by-pass around the piston is provided by an external pipe 180, Fig. 13, with a constriction in its bore if desired. The pipe moves in a slot 181 and prevents relative rotation of cylinder and guide sleeve. A groove 182 in the upper end of the cylinder is engaged by pins 183 on an arm 184 mounted on a shaft 185 which carries a lever 186, Fig. 4. This lever is resiliently connected through stud 188, slotted block 189, spring 192, washer 193 and rod 194 with a lever 197 pivoted on a stud 198. This lever is in the path of the cam 118 mounted on the air valve spindle. If the valve 103 be opened suddenly, there will be a sudden increase of depression tending to open the air valve 91. The resistance to the downward movement of the valve however is at first large, but decreases as soon as the piston 165 has descended far enough to uncover the upper end of the by-pass 180. Consequently a lag occurs in the valve opening which gives a sufficiently rich mixture for accelerating. If acceleration involves the opening of the air throttle 101, means are provided for increasing still further the resistance to opening of valve 91, such means residing in the mechanism, Fig. 4, for raising the dash-pot cylinder upon opening of the valve 101 and producing an increase of liquid pressure on piston 165. Under certain conditions the liquid pressure may be great enough to cause compression of spring 166, in which case the flange 168 is separated from the piston and the resistance to opening reduced. The greater the opening of the air throttle at the time it is suddenly opened to accelerate, the less will be the damping action. To ensure ample fuel supply for acceleration at speeds above that at which valve 101 begins to open, a pipe 206, Fig. 7, leads from the float chamber and is adapted upon movement of the dashpot cylinder and piston to inject fuel on the air valve 91.