Fuel pumping apparatus

A fuel pumping apparatus of the rotary distributor type is provided with a spill control muff on the distributor member and which controls flow of fuel from a bore containing the pumping plungers to a chamber. Slidable in the chamber is a spring loaded piston formed with a valve element which controls flow of fuel from the bore into the chamber through a spill passage. With the spill passage closed by the valve element deliver of fuel through an outlet takes place until fuel is admitted to the chamber under the control of the spill muff. The admission of fuel causing the piston to move the valve element to allow fuel into the spill passage through the spill passage.

This invention relates to a liquid fuel injection pumping apparatus of the 
kind comprising a rotary cylindrical distributor member mounted in a body, 
a bore formed in the distributor member and a pumping plunger mounted 
therein, a cam for imparting inward movement to the pumping plunger as the 
distributor member rotates, means for supplying fuel to the bore from a 
source of fuel under pressure to effect outward movement of the pumping 
plunger, further means for conveying fuel displaced by the pumping plunger 
to a plurality of outlet ports in turn and a control sleeve slidable on 
the distributor member for controlling the flow of fuel through a passage 
connected to said bore whereby the quantity of fuel which is delivered by 
the apparatus during inward movement of the pumping plunger can be 
controlled. 
In known forms of apparatus of the aforesaid kind the fuel which flows 
through said passage flows to the interior of the apparatus. As a result 
the low pressure pump which constitutes the source of fuel under pressure 
even when only a small quantity of fuel is being supplied to the 
associated engine, must always supply fuel at the desired pressure and at 
a rate which is more than the maximum rate of fuel which can be supplied 
to the engine. Moreover, with modern fuel systems operating at high 
pressures, it is necessary to have high rates of spillage of fuel. The 
sleeve or the distributor member is provided with a groove or grooves and 
the distributor member or the sleeve is provided with a port which is 
uncovered by said groove to allow the spillage of fuel through said 
passage to occur. In order to increase the rate of spillage of fuel the 
port and groove must be increased in size and this can lead to excessive 
leakage of fuel during periods when the passage is closed. The object of 
the present invention is to provide an apparatus of the kind specified in 
a simple and convenient form. 
According to the invention an apparatus of the kind specified comprising a 
spill passage communicating with said bore, said spill passage opening 
into a chamber, a spring loaded piston movable in said chamber and a valve 
element mounted on said piston, said valve element in use engaging a 
seating defined about said spill passage to prevent flow of fuel through 
the spill passage, said first mentioned passage communicating with said 
chamber whereby during inward movement of the plunger when fuel flows 
through said first mentioned passage into the chamber, the piston will be 
moved to lift the valve element from the seating thereby to open the spill 
passage, the spilled fuel collecting in said chamber and being returned to 
the bore prior to the next inward movement of the pumping plunger.

Referring to the drawings the apparatus comprises a rotary cylindrical 
distributor member 10 which is mounted within a sleeve 11 secured within a 
housing 12. The distributor member is provided with in the particular 
example, a pair of diametrically disposed bores 13 in each of which is 
mounted a pumping plunger 9 only one of which is shown. At their outer 
ends the plungers are engaged in the usual manner, by cam followers (not 
shown), which in turn engage cam lobes formed on the internal peripheral 
surface of an annular cam ring 8 which is secured in the housing. The 
distributor member is driven in timed relationship with the associated 
engine. 
At the inner ends of the plungers the bores communicate with an axially 
disposed passage 14 formed in the distributor member and which 
communicates with a delivery passage 15 opening onto the periphery of the 
distributor member. The passage 15 is arranged to register in turn with a 
plurality of outlet ports 16 which are formed in the sleeve and which 
communicate with outlets 17 formed in the housing. The outlets 17 in use 
are connected to the fuel injection nozzles respectively of the associated 
engine. 
The passage 14 also communicates with four equiangularly spaced inlet 
passages 18 which extend to the periphery of the distributor member and 
which can communicate with inlet ports 19 formed in the sleeve and 
connected to the outlet of a low pressure fuel supply pump 20. 
Conveniently, the pump 20 is a vane type pump the rotary part of which is 
mounted on the distributor member. The pump 20 delivers fuel at a pressure 
which varies in accordance with the speed at which the apparatus is 
driven. 
A portion of the distributor member lying between the sleeve 11 and an 
enlarged portion of the distributor member in which the bores 13 are 
formed, is surrounded by a sleeve 21. The sleeve commonly known in the art 
as a "spill muff" is utilised to control the amount of fuel which is 
supplied by the apparatus to the associated engine and it may be axially 
movable upon the distributor member by means of a governor mechanism not 
shown to vary the quantity of fuel delivered. It can also be angularly 
adjustable to vary the timing of fuel delivery. 
On the internal peripheral surface of the sleeve 21 there is provided as 
shown in FIG. 3, two grooves 22 and 23. In the example, groove 22 is a 
simple rectangular groove with the longer sides being disposed parallel to 
the axis of rotation of the distributor member. The longer sides of the 
groove 23 are obliquely disposed. Moreover, communicating with the passage 
14 are four radially extending passages 24 which open onto the periphery 
of the distributor member and formed in the distributor member at the 
outer end of each passage 24 is a recess 25 which is narrower than the 
grooves 22 and 23. During operation of the apparatus the sleeve 21 is 
restrained from rotation and the movement of the recess 25 relative to the 
sleeve and the grooves therein is indicated by the arrow in FIG. 3. 
Also formed in the distributor member is an axially disposed cylindrical 
chamber 26 in which is slidably mounted a cup shaped piston 27. Opening 
into the base wall of the chamber is a spill passage 28 which communicates 
with the bores 13 intermediate their ends and formed on the piston member 
for engagement with a seating defined about the passage 28 is a valve 
element 29. The piston and valve element are biased by means of a coiled 
compression spring 30 so that the valve element engages the seating. 
Also opening through the base wall of the chamber 26 are four passages 31 
which open onto the periphery of the distributor member in ports 32 as 
illustrated in FIG. 3. The ports 32 are cirumferentially spaced from the 
recesses 25 in the direction of rotation of the distributor member. 
In operation, as the distributor member rotates the delivery passage 15 
will be brought into register with a delivery port 16 and during continued 
rotation of the distributor member the pumping plungers in the bores 13 
will be moved inwardly by the cam lobes. Providing the passages 24 are 
closed, fuel will flow along the passage 14 to the respective outlet 17 
and to the associated injection nozzle. This flow of fuel will continue 
until the recess 25 is brought into communication with the groove 23. As 
soon as this communication is established fuel will flow along one of the 
passages 31 into the chamber 26 and displacement of the piston 27 against 
the action of the spring 30 will take place. As soon as the piston starts 
to move the valve element 29 is lifted from its seating and fuel can then 
flow through the spill passage 28 into the chamber. The result is that 
there is a rapid reduction in the pressure of fuel which is supplied to 
the injection nozzle and the valve in the injection nozzle closes to 
terminate delivery of fuel to the engine. The flow of fuel into the 
chamber will continue until the cam followers move over the crests of the 
cam lobes. Shortly after the cam followers have moved over the crests of 
the cam lobes the delivery passage 15 moves out of register with the 
delivery port 16 and the inlet passages 18 move into register with the 
inlet ports 19. 
The fuel contained within the cylindrical chamber is returned to the bores 
13 to move the plungers outwardly and to permit the valve element to seat 
with the seating. Any fuel which has been lost due to leakage and also 
displaced to the engine, is made up with fresh fuel supplied by way of the 
passages 18 from the low pressure pump 20. During continued rotation of 
the distributor member the recess 25 moves over the groove 23 and the 
following recess 25 will then start to move over the groove 22. At this 
time filling of the bores is complete and the plungers have moved 
outwardly their maximum extent. The passages 18 will move out of register 
with the ports 19 and the delivery passage 15 will move into register with 
the following outlet port 16. As the plungers start to move inwardly by 
the cam lobes, the recess 25 will be in communication with the groove 22 
and the groove 22 is in communication by way of a drilling, with the 
interior of the housing of the apparatus. Such fuel as is displaced by the 
plungers will flow through the drillings to the interior of the apparatus 
but this flow of fuel will cease when the recess 25 moves out of register 
with the groove 22. Delivery of fuel can take place and the cycle as 
described is repeated. 
In FIG. 3 the axial setting of the sleeve is such that the recess 25 is in 
communication with either the groove 22 or the groove 23 and in this 
situation no fuel will be supplied to the associated engine. However, if 
the sleeve 21 is moved towards the right as seen in the drawings there 
will be an interval during which the recess 25 is out of communication 
with both grooves and it is during this interval that fuel is supplied to 
the associated engine. 
It will be appreciated that some fuel is lost to the interior of the 
housing through the aforesaid drilling which connects the groove 22 with 
the interior of the housing and a further slight loss of fuel will occur 
through a restricted drilling 33 which is formed in the base wall of the 
piston. In addition, there can be a loss of fuel to the interior of the 
housing when during the filling of the bores 13, a recess 25 and a port 32 
cross the groove 22. To minimise this loss of fuel the drilling which 
connects the groove 22 to the interior of the housing incorporates a 
spring-loaded pressurising valve 34. This valve can open to allow spillage 
of fuel displaced by the plungers but it remains closed at other times. 
The purpose of the drilling 33 is to ensure that the valve element 29 
seats properly against the seating prior to the delivery of fuel and also 
to ensure that if any leakage occurs between the valve element and the 
seating there will not be a sufficient increase of pressure within the 
cylinder 26, to effect movement of the piston. 
By the arrangement described rapid spillage of fuel during the inward 
movement of the plungers takes place and furthermore, most of the fuel 
which is spilled is returned to the bores 13 at the start of a filling 
strokes of the plungers.