This page supplements the details of Blackstone and Carter's patent "Spring Injection" given on the Heavy-Fuel-Oil Engines page. What follows is a summary of some of the advantages of the system and an explanation of its operation.
The advantages of "Spring Injection" were summarised in a Paxman catalogue as being:
The following diagrams explain the action of the "Spring Injection" device.
In Diagram 1 above, the Injector Lever, which is operated by an eccentric on the half time shaft, has been withdrawn, and a measured quantity of fuel has been delivered to the Fuel Chamber from the governed fuel pump pushing the Injector Plunger and Main Spring member bodily outwards.
In Diagram 2 above, rotation of the half time shaft has brought the roller on the Injector Lever into contact with the outer portion of the Main Spring member, compressing the main spring, forcing the Injector Plunger against the oil in the Fuel Chamber and closing the non-return valves.
The oil in the Fuel Chamber is now imprisoned and under pressure. This takes place just before the piston reaches in-dead centre.
The Injector Valve is held on its seat by the combined action of an internal spring and an external spring - the latter operating through a rod and bell crank lever.
In Diagram 3 above, the tip of the Injector Lever has compressed the external spring slightly taking its pressure off the Injector Valve. The pressure on the oil in the Fuel Chamber is now sufficient to overcome the internal spring and lift the Injector Valve off its seat, when injection takes place. The fuel is thus under full pressure when the injection starts and there is consequently no dribble. The valve is open only so long as the oil is under pressure, and closes instantly on completion of the charge. There is consequently no dribble when injection stops.
Page updated: 29 APR 2002