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).
The function of an accelerator pump and a starting device for a carburetter system.
| Identifier | ExFiles\Box 13\3\ 03-page228 | |
| Date | 23th July 1930 guessed | |
| -2- 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. The piston valve if given sufficient stroke could be used as an alternative delay action device, but this is not intended. The novel features of this scheme we believe are the provision in the pump plunger of the means of obtaining any desired lag in the operations of the pump and the means of distributing equal quantities of fuel to two or more nozzles from one pump by the use of calibrated restrictions. STARTING DEVICE. When set for starting or slow running the throttle will be just slightly open, and air will be drawn past the throttle disc on each side, and also rich mixture from the passageway masked by the clubfoot on one side of the disc. The mixture from this slow running orifice may be varied by raising and lowering the choke tube in the slow running carburetter, which action is under the control of the driver from the steering wheel controls, but the variation thus provided is only intended to be in the operational mixture range of the engine and is therefore not strong enough for starting under cold conditions. It is therefore proposed to have a small valve of some description operated by a special starting control to entirely shut off the normal supply of air to the slow running carburetter so that neat fuel is drawn up past the choke. It should be here mentioned that there is an orifice in the throttle barrel on each side of the throttle disc both connected to the slow running carburetter, but the second one comes in later. | ||