Patent GB-1174791-A (GB)
Title: Improvements in or relating to Carburettors for Internal Combustion Engines
Inventor: PITRA JIRI
IPC: F02M1/10
Filed: 1967-03-23
Abstract: 1,174,791. Spray carburettors. MOTOR, NARODNI PODNIK. March 23, 1967 [March 25, 1966], No.13727/67. Heading F1B. In an automatic device for controlling the starting slide valve or strangler valve of a carburettor in which the valve is moved by a servomotor driven by the depression in the induction manifold downstream of the carburettor in dependence of engine temperature, the depression transferred from the induction manifold to the servomotor chamber as governed by a temperaturecontrolled temperature detecting element. Operation: When the engine is cold the choke control mechanism assumes the starting position in Fig. 2, in which the rotatable slide valve 1, Fig.2a opens communication for the enrichment mixture to a passage 18 leading to a space 19 downstream of throttle 20. The end of a bimetallic spring 22 acts on a pin (35), Fig.1a (not shown) in the end of a pivoted retaining lever 30 to rotate the latter clockwise in Fig.2 whilst a stop dog 33, carried by lever 30, is engaged in a cuto-out portion 44 of a gate 6. The latter, which is mounted on the shaft 4 with slide valve 1, is articulated through a link 45 to a piston rod 7 of a spring-loaded diaphragm 8. A needle valve 24 is opened by its spring 25 whereby chamber 13 can communicate with ambient air via channel 27. Immediately upon starting, the depression in space 19 is introduced via channels 18, 17, 16, cavity 15 and channel 14 into chamber 13 and thence to atmosphere thereby causing a reduced depression which is communicated through channel 12 into chamber 11. The resultant flexing of diaphragm 8 causes partial turning of gate 6 and slide valve 1 to reduce the enrichment. Air from intake chamber 37 passes into chamber 28 via an exhaust-manifold-heated pipe 38. The resultant heading of bi-metallic spring 22 further reduces the choke operation whilst the spring end (23, Fig.1a, not shown) acts on needle valve 24 which closes on seat 26 so that the depression in chambers 13 and 11 increase thus causing increased flexing of diaphragm 8. The simultaneous release of the free end 31 of lever 30 causes the latter under the weight of bob-weight 32 to abut stop 43, as soon as permitted by the position of gate 6. The occurs in the position of Fig.1 (not shown) when stop dog 33 is in the cut-out above upper claw 34 and the enrichment is ceased. When the hot engine is stopped claw 34 engages stop-dog 33 to prevent turning of gate 6 by spring 10 into the enriched starting position. When the bi-metallic spring 22 cools its end (23) ceases to hold valve 24 closed and begins to move lever 30 so that stop dog 33 is disengaged from claw 34 allowing gate 6 to be partially turned by spring 10. Turning of gate 6 is again arrested when stop dog 33 is engaged by the lower claw 36 so that the device is set for partial enrichment. Continued cooling of the bi-metallic spring 22 causes further movement of lever 30 whereby the stop-dog 33 disengages from lower claw 36 and the gate 6 is turned by spring 10 as fast as allowed by the engagement of the lower edge of cutout 44 with stop-dog 33. The device then gradually assumes the position of Fig. 2 for starting a cold engine. In modifications the diaphragm 8 is replaced by a spring-loaded piston (42, Fig. 4, not shown) or the control mechanism actuates on air-strangler valve (41, Fig. 3, not shown).