Claims
- 1. A fuel pump for incorporation in an i.c. engine air/fuel induction system which includes a carburetter having a driver operable throttle valve as well, the fuel pump comprising a hollow casing, a movable wall which divides the interior of the hollow casing into an air chamber and a fuel chamber which is for connection to a source of liquid fuel and the air/fuel induction system, resilient means which urge the movable wall to minimise the volume of the fuel chamber and thermostatically controlled means which are adapted to be responsive to the temperature of the engine to which the fuel pump is fitted when used, wherein the improvement comprises the provision of pressure regulating means for regulating a depression in said air chamber in accordance with a function of the depression that is established in the inlet manifold of the engine to which the pump is fitted when used and to the temperature of that engine, the pressure regulating means including a valve which is operatively associated with said thermostatically controlled means and which is adapted to be urged to restrict communication between the air chamber and the inlet manifold of the engine in response to a tendency for the depression in said air chamber to exceed a predetermined maximum when said predetermined maximum depression acts within the air chamber and the depression in the inlet manifold of the engine is at or above said predetermined maximum whilst, at least when the temperature of the engine is less than the normal working temperature, permitting relatively free communication between the air chamber and the inlet manifold of the engine when the depression in the inlet manifold of the engine is less than said predetermined maximum, the thermostatically controlled means co-operating with the valve and with an air bleed into the air chamber such that the volume of the air chamber, when communication between the air chamber and the inlet manifold is restricted, increases as the temperature of the engine increases.
- 2. A fuel pump according to claim 1, wherein the valve is adapted to be seated by the thermostatically controlled means to shut off communication between the air chamber and the inlet manifold of the engine when the engine has warmed up to its normal working temperature.
- 3. A fuel pump according to claim 1, wherein the pressure regulating means comprise a suction port in the air chamber, the suction port being for connection to the inlet manifold of the engine to which the pump is fitted when used; means for providing a regulated air flow into the air chamber from a separate source which is at a pressure which is higher than that in the air chamber, the regulated air flow comprising said air bleed, and a control member which extends movably through a wall portion of the casing into the air chamber and which is adapted to be linked to said thermostatically controlled means which are operable to move the control member relative to the casing when the temperature of the engine changes so that the location of the control member relative to the casing is dependent upon the temperature of the engine; said valve comprising a shut-off valve for the suction port, said valve being resiliently biassed open and co-operating with a control beam which is pivotally connected to the control member and which has a portion which co-operates with the movable wall so that it follows movement of the movable wall, the suction port shut-off valve and the control beam being orientated with respect to the movable wall and the suction port such that the suction port shut-off valve is moved in the closing direction by movement of the control beam that follows movement of said movable wall to enlarge the volume of the fuel chamber; and the forces that act upon the suction port shut-off valve to tend to seat it when the pump is in use, once it is located adjacent the suction port to restrict flow through the suction port and limit further increase in the volume of the fuel chamber, comprising a reaction applied to it from the control beam and the action upon it of the depression in the suction port and the forces tending to move it away from the suction port comprising the biassing load by which it is biassed open and the action upon it of the depression that is established within the air chamber.
- 4. A fuel pump according to claim 3 wherein the means for providing a regulated air flow into the air chamber provide such an air flow continuously.
- 5. A fuel pump according to claim 4, wherein the means for providing a continuous regulated air flow into the air chamber comprise a passage of restricted dimensions which is formed in the casing and by which the air chamber is placed in restricted communication with the surrounding atmosphere which comprises said separate source of air.
- 6. A fuel pump according to claim 5, wherein the restricted passage comprises the clearance between the control member and a bore in said casing wall portion within which that control member is a sliding fit.
- 7. A fuel pump according to claim 3, wherein said suction port shut-off valve is a needle valve which is urged into abutment with the control beam by a coil spring which reacts against the casing around the suction port and serves as the biassing means by which said valve is biassed open.
- 8. A fuel pump according to claim 3, wherein the control beam portion that co-operates with the movable wall comprises a lobe which abuts the movable wall and which is profiled so that it maintains contact with the movable wall during rocking movement of the control beam relative to the movable wall.
- 9. A fuel pump according to claim 8, wherein the control beam has two such lobes each formed by a respective one of two bowed limbs which extend on either side of said resilient means, the bowed limbs being joined together by bridge pieces adjacent their ends on either side of said resilient means.
- 10. A fuel pump according to claim 9, wherein said suction port shut-off valve is a needle valve which is urged into abutment with the control beam by a coil spring which reacts against the casing around the suction port and serves as the biassing means by which said valve is biassed open, the pivotal connection between the control member and the control beam is adjacent to one of the bridge pieces and the needle valve is urged into abutment with the other bridge piece which is flat.
- 11. A fuel pump according to claim 3, wherein the pivotal connection between the control member and the control beam comprises at least one substantially V-shaped part which is carried by the control member and which is engaged in the manner of a knife edge in a corresponding notch formed in the control beam.
- 12. A fuel pump according to claim 11, in which the control beam portion that co-operates with the movable wall comprises two lobes, each lobe being formed by a respective one of two bowed limbs which extend one on either side of said resilient means, the bowed limbs being joined together by bridge pieces adjacent their ends on either side of said resilient means, and the lobes abutting the movable wall and being profiled so that they maintain contact with the movable wall during rocking movement of the control beam relative to the movable wall, wherein said at least one substantially V-shaped part is one of two such V-shaped parts which are carried by the control member in the manner of trunnions and which each rest in a respective notch which is formed by a respective one of the bowed limbs.
- 13. A fuel pump according to claim 12, wherein the V-shaped parts are formed by a body which has a through bore through which the control member extends, the body being urged onto a stop carried below it by the control member and being so urged by resilient means which react against an abutment carried above it by the control member.
- 14. A fuel pump according to claim 13, wherein the stop comprises a self-locking nut fitted onto the control member.
- 15. A fuel pump according to claim 14, wherein the self-locking nut comprises a U-shaped component bent up from sheet material with an aligned pair of holes formed in each of its two sheet material limbs, the control member having a screw-threaded portion which is screwed into the aligned pair of holes and the limbs being deflected from the relative locations to which they are urged by the inherent resilience of the component.
- 16. A fuel pump according to claim 1, wherein the movable wall comprises a diaphragm of flexible impervious material.
- 17. A fuel pump according to claim 16, wherein at least that part of the diaphragm that extends across the interior of the hollow casing to separate the air chamber from the fuel chamber is a non-apertured sheet of the flexible impervious material.
- 18. A fuel pump according to claim 17 in which the control beam portion that co-operates with the movable wall comprises two lobes, each lobe being formed by a respective one of two bowed limbs which extend one on either side of said resilient means, the bowed limbs being joined together by bridge pieces adjacent their ends on either side of said resilient means, and the lobes abutting the movable wall and being profiled so that they maintain contact with the movable wall during rocking movement of the control beam relative to the movable wall, wherein the movable wall includes a disc which is within the air chamber, which is urged against the diaphragm by the resilient means and which is abutted by the or each bowed limb of the control beam.
- 19. A fuel pump according to claim 16, wherein a major part of the diaphragm, including its central portion, is adapted to seat upon the opposed wall of the fuel chamber so that the volume of that fuel chamber is negligible when it is minimised.
- 20. A fuel pump according to claim 1, wherein the fuel chamber has a single port through which fuel is both drawn into the fuel chamber and discharged from the fuel chamber.
- 21. A fuel pump according to claim 20, wherein the fuel chamber port is in communication with a conduit length of flow restricting dimensions.
- 22. A fuel pump according to claim 1, in combination with a cold start fuel/air mixture supply device, the cold start fuel/air mixture supply device comprising an air supply passage which has one end for connection to the inlet manifold of the internal combustion engine so that air can be drawn through that passage by engine suction when the device is fitted to the engine, an automatically operable throttle valve in the air supply passage, the automatically operable throttle valve being adapted to co-operate with an orifice which is formed within the air supply passage in order to throttle fluid flow through that orifice and being arranged to be urged to reduce the effective area of the orifice by engine suction when the device is fitted to the engine and the engine is running under its own power, a fuel passage which terminates in a fuel discharge nozzle which is formed in the air supply passage upstream of the orifice, the fuel passage including fuel metering means for metering flow of fuel drawn through the fuel passage from a source of liquid fuel by a depression which is established within part of the air supply passage upstream of the orifice, and thermostatically controlled means comprising a movable stop for limiting movement of the automatically operable throttle valve in the direction in which it is moved to reduce the effective area of the orifice, the position of the stop being controlled automatically in relation to the temperature of the engine to which the cold start fuel/air mixture device is fitted when used by control means which are responsive to the temperature of the engine in use so that the stop is moved to allow following movement of the automatically operable throttle valve in said direction as the engine warms up towards its normal working temperature whereat movement of said automatically operable throttle valve to close the orifice is permitted, whereby, when the device is fitted to the engine the constitution of the air/fuel mixture drawn from the device by the engine is changed firstly at the end of the engine cranking period, when the engine begins to run under its own power, and, when the engine has started to run under its own power, both the air flow in the air supply passage and the flow of fuel into the air supply passage through the fuel passage are decreased progressively with increase in engine temperature, the fuel pump being arranged so that fuel is displaced from the fuel chamber into the air/fuel induction system when the depression established in the inlet manifold of the engine is at or below the predetermined maximum and that depression falls and fuel is drawn into the fuel chamber from said source when the depression established in the inlet manifold of the engine increases up to said predetermined maximum.
- 23. A combination of a fuel pump and a cold start fuel/air mixture supply device according to claim 22, wherein the cold start fuel/air mixture supply device includes an air valve which co-operates with a valve seat to vary the area of part of the air supply passage upstream of the orifice and thereby controls the depression that is established within that portion of the air supply passage between the orifice and the valve seat, which is the portion of the air supply passage in which the fuel discharge nozzle is formed, and that serves as the fuel demand signal that draws fuel into the passage from the source of liquid fuel, and yieldable biassing means for urging the air valve towards the valve seat against the action upon the air valve of any such depression which is established within the air supply passage between the valve seat and the orifice and which tends to unseat the air valve.
- 24. A combination of a fuel pump and a cold start fuel/air mixture supply device according to claim 23, wherein the air valve carries a part which has a surface which is exposed to the pressure that is existent in a space which is for connection to a suitable source of suction, the part and the space being orientated with reference to the yieldable biassing means and said air valve seat so that, when the device is fitted to the engine in use, the biassing effect of said yieldable biassing means upon said air valve is opposed by the thrust due to the action on said surface of suction from said source, the arrangement being such that the effective cross-sectional area of said part of the air supply passage is dependent upon the depression that is established within the air supply passage between the orifice and the valve seat, upon the biassing effect exerted upon the air valve by the yieldable biassing means and upon the opposing thrust exerted upon the air valve due to the action on said surface of suction from said source.
- 25. A combination of a fuel pump and a cold start fuel/air mixture supply device according to claim 22, wherein the fuel chamber is connected to the fuel passage of the cold start fuel/air mixture supply device upstream of the fuel metering means so that it is adapted to be connected to the same source of liquid fuel as is that fuel passage and so that fuel displaced from the fuel chamber is fed into the air/fuel induction system through the fuel metering means of the cold start fuel/air mixture supply device.
- 26. A combination of a fuel pump and a cold start fuel/air mixture supply device according to claim 22, wherein the fuel pump is adapted to be rendered inoperative to pump liquid fuel into the air/fuel induction system when the engine with which the combination is used has warmed up to the temperature at which the cold start fuel/air mixture supply device ceases to supply extra fuel and air to the engine.
- 27. A combination of a fuel pump and a cold start fuel/air mixture supply device according to claim 22, wherein the fuel pump is adapted to continue to function to pump extra fuel into the air/fuel induction system of an engine with which the combination is used when the depression in the inlet manifold of that engine falls and the engine has warmed up to its normal working temperature.
- 28. A fuel pump for incorporation in an i.c. engine air/fuel induction system which includes a carburetter having a driver operable throttle valve as well; the fuel pump comprising a hollow casing, a diaphragm of flexible impervious material which divides the interior of the hollow casing into an air chamber and a fuel chamber, resilient means which urge the diaphragm to minimise the volume of the fuel chamber, the air chamber having a suction port which is for connection to the inlet manifold of the engine to which the pump is fitted when used, and a valve for the suction port which is resiliently biassed open and which co-operates with a control beam which has a portion which co-operates with the diaphragm so that the beam follows movement of the diaphragm, the suction port valve and the control beam being oriented with respect to the diaphragm and the suction port such that the suction port valve is urged towards the suction port by movement of the control beam that follows movement of said diaphragm to enlarge the volume of the fuel chamber, the arrangement being such that, once the suction port valve reaches a location relative to the suction port in which it restricts flow through the suction port so that the pressure in the air chamber is maintained substantially constant and further increase in the volume of the fuel chamber is prevented, the forces acting upon it to urge it towards the suction port comprise a reaction applied to it from the control beam and the action upon it of the depression in the suction port and the forces tending to move it away from the suction port comprise the biassing load by which it is biased open and the action upon it of the depression that is established within the reference pressure chamber.
Priority Claims (1)
Number |
Date |
Country |
Kind |
9467/78 |
Mar 1978 |
GBX |
|
Parent Case Info
This is a continuation of application Ser. No. 624,623 filed 10-22-75 now abandoned which in turn is a continuation of U.S. Ser. No. 367,291 filed June 5, 1973, now abandoned.
US Referenced Citations (7)
Foreign Referenced Citations (1)
Number |
Date |
Country |
2908783 |
Sep 1979 |
DEX |