From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Description and patent suggestions for a non-expanding carburetter's accelerator pump.
| Identifier | WestWitteringFiles\U\2January1930-September1930\ Scan228 | |
| Date | 23th July 1930 | |
| BY.{R.W. Bailey - Chief Engineer} FROM E.{Mr Elliott - Chief Engineer} C. to SG.{Arthur F. Sidgreaves - MD} HS.{Lord Ernest Hives - Chair} BY/NW.{N. Walker - Patents} C. to Mr. CLAREMONT. ORIGINAL NON-EXPANDING CARBURETTERS. E1/M23.7.30. X7080. In connection with the above R.{Sir Henry Royce} has made one or two suggestions which appear to be novel, and useful, and he thinks it would be wise to embody them in patent form as far as possible. The points in question are as follows:- ACCELERATOR PUMP. The piston of this pump when forced downwards by the sudden opening of the carburetter throttle, (with which it is mechanically coupled), ejects petrol through the twin diffuser nozzles of the carburetter via the main jet passages. The petrol flows from the pump to these passages through a needle valve operated by a small piston subject to the pump pressure. This needle valve will only open when the pump is exerting sufficient pressure and at other times acts as an effective means of cutting off the pump from the effects of the choke tube suction on the main jets. After leaving the needle valve the petrol flow has to be divided into two approximately equal parts so that each half of the twin carburetter will receive an equal share of fuel. It is proposed to accomplish this by having two restrictions, one in each fuel passage, of equal resistance. These take the form of drilled extensions added to the plugs which close the ends of the fuel passages to the nozzles. On the upstroke of the pump piston (which occurs when the carburetter throttle is closed) petrol is drawn past the piston into the cylinder via the clearance between the piston and cylinder. Should the throttle be closed or opened very suddenly the pump piston may lag behind by virtue of the springs above and below the spherical end of the connecting rod. These springs may be individually varied in loading etc to give any desired period of lag for charging or discharging the accelerator pump in conjunction with a given piston clearance. This latter must be such as to allow of effective discharging and charging of the pump, yet the piston must be able to move up and down slowly without ejecting any fuel into the carburetter nozzles, as under such conditions extra fuel is not desired. The spring loading of the piston operated needle valve plays an important part in fixing the rate of opening at which fuel is discharged. (1) | ||