US3559680A - Fuel pressure relief assembly - Google Patents

Abstract

A normally-open valved bypass line of small capacity is added around the fuel pump of a liquid-fuel engine. Upon cessation of pump action, the still open bypass equalizes pressure of the fuel on both sides of the pump; then it closes in response to decrease of back pressure in the bypass so as to retain an unbroken column of unpressured liquid in the whole line. This prevents forward drainage into the carburetor of otherwise trapped and pressurized fuel after the pump has stopped, and also prevents its rearward drainage into the fuel reservoir which might occur if the valve remained open. The bypass being S-shaped and connected to pick up the liquid fuel from the lowest level of the pump outlet line, also minimizes vapor lock during pump operation. A ball-check valve also opens the tapered bypass orifice progressively, in proportion to increased back pressure.

Description

United States Patent Neil C. Norton PO. Box 104.

Los Angeles County, Calif.

Gardena. Calif. 90247 [21] Appl. No. 726,308

[22] Filed May 3, 1968 Feb. 2, 1971 Continuation-impart of application Ser. No. 616,594, Feb. 16, 1967, now abandoned.

[72] Inventor [45] Patented [54] FUEL PRESSURE RELIEF ASSEMBLY Primary Examiner-William R. Cline Attorney-Howard L. Johnson ABSTRACT: A normally-open valved bypass line of small capacity is added around the fuel pump of a liquid-fuel engine. Upon cessation of pump action, the still open bypass equalizes pressure of the fuel on both sides of the pump; then it closes in response to decrease of back pressure in the bypass so as to retain an unbroken column of unpressured liquid in the whole line. This prevents forward drainage into the carburetor of otherwise trapped and pressurized fuel after the pump has stopped, and also prevents its rearward drainage into the fuel reservoir which might occur if the valve remained open. The bypass being S-shaped and connected to pick up the liquid fuel from the lowest level of the pump outlet line, also minimizes vapor lock during pump operation. A ball-check valve also opens the tapered bypass orifice progressively, in proportion to increased back pressure.

. l FUEL PRESSURE RELIEF ASSEMBLY This is a continuation-in-part of Ser. No. 616,594, filed Feb. l6, I967. now abandoned.

BACKGROUND OF THE INVENTION This invention relates to a valved bypass assembly used with conventional liquid-fuel pumps of an internal combustion engine Such small capacity bypass inserted in the fuel line may remain open during normal engine operation, but its particular effectiveness arises immediately after the pump and engine have stopped, which action leaves pressurized liquid in that portion of the main fuel line which is between the pump and the carburetor. Since this trapped fuel cannot go back into the pump, (without a bypass) it tends to dribble into the carburetor and may flood the same and overflow into the engine manifold as well as outside. This creates a fire hazard, makes subsequent engine starting more difficult, and by throwing off wet gasoline and/or vapor into a closed and unvented engine compartment, such as in a motor boat, it all too frequently supports'an explosion which may totally destroy such craft upon theaccidental introduction of a spark (as in a motor start-up). Suchslow spill-out of fuel is of course accentuated by the presence of a worn needle valve in the carburetor, and the slow increase of such inexact valve seating and hence the accentuation of such fire hazard may go undetected for a considerable period of time. By the present valved bypass, however, the pressurized liquid on the carburetor side of the pump is equalized with the unpressurized liquid on the reservoir side of the pump, and the bypass then automatically closes in response to fall of back pressure, so as to retain an essentially unpressurized but unbroken liquid, column throughout the whole fuel line.

It has been suggested in the past to provide a fuel pump bypass having a valve which is opened by excess" pump pressure (i.e., when the motor is operating at less then full throttle) so as to equalize the fuel flow and mufile its fluctuations; however such valve closes when the pressure decreases, and in any case as soon as the pump stops, which is when the present open valve is most useful or needed. Altemately, it has been suggested to bypass the fuel pump with a permanently-open bleed line, that is, unvalved; however, if the fuel reservoir is lower than the carburetor line, the standing fuel may be sucked back due to siphon action; if it is higher than the carburetor line, fuel may continue to dribble out. In addition, a permanently-open bypass obviously lowers the efiiciency of the pump in proportion to its flow capacity, but if valved for use in only certain periods of engine operation, it must carry appreciable flow to be then effective. However, when of small capacity such as the present open line, it has small effect on continuous pump efiiciency, but such negligible effect is more than overcome by the advantages of maintaining a dry carburetor and eliminating (especially marine) fire hazards, which may occur in any start-up subsequent to engine stoppage of a motor vehicle.

SUMMARY OF THE INVENTION Accordingly it is an object of the invention to provide a relatively simple assembly composed of a few easily installed elements which may be simply installed in most existing engine installations with a minimum of effort and inconvenience. In other words, the present assembly can merely be inserted in an automobile or boat engine, so as to couple the fuel line at both its pump ports, thus to insert a bypass formed therearound the pump, such bypass carrying a nonnally-open valve which .is responsive to fall of residual bypass back pressure for closing. Such valve is typified by a gravitational-opening, spring-tensioned ball valve, which should it be rendered inoperative for any reason, still leaves the previous function of the main fuel line unimpaired. In addition, the invention provides an S- shaped bypass conduit which, by its pickup from the lowest liquid level of the carburetor-side fuel line, is found effective to minimize vapor lock in the pump such as otherwise might occur under overheated operating conditions. The construction further provides a tapered bypass orifice along which the check ball progressively unseats to increase the backflow in proportion to its pressure, thus more quickly equalizing any pressure differential.

Other objects and advantages of the present invention will become apparent from the following description of a presently preferred embodiment of the device as particularly used in marine installations.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevational view of my bypass assembly connected to an automotive fuel pump (shown in broken lines), with the fuel reservoir and carburetor indicated schematically; and

FIG. 2 is an axial sectional view of the bypass valve unit alone, seen in upright, operative position.

DESCRIPTION OF A PREFERRED EMBODIMENT As here illustrated, a conventional liquid-fuel pump P is located intermediate the length of the fuel line L which extends from a fuel reservoir R (i.e., gasoline tank) to the carburetor C of an internal combustion engine (not shown) which utilizes the carburetor-atomized fuel in the usual manner. The portion of the fuel line extending from the reservoir to the pump may be designated as the inlet conduit 10, and the portion from the pump to the carburetor as the outlet conduit 12. It will be understood that an unbroken stream or column is maintained in the line, whether moving or not. The liquid in the reservoir R is ordinarily under ambient atmospheric pressure, while the fuelin the outlet conduit 12 is under the pressure added by the pump P, which is usually on the order of about 1 to l 0 p.s.i.g. with diaphragm-type pumps.

Essentially the present assembly consists of a pair of T fittings l4, 16, a (S-shap'ed) bypass conduit 18 and a valve assembly 20. One Tee, l6,is connected between the inlet conduit 10 and the inlet port 6 of pump P, with its upstanding nipple 7 coupled to the valve assembly 20 above it. The other Tee, 14, is inserted between the outlet conduit 12 and the outlet port 8 of the pump P with its downturned nipple 17 joined to the downwardly concave segment 19 of the bypass conduit 18. The successive convex segment 21 of the bypass conduit is received in the aperture mount 9 of the upper housing piece 24 of the valve assembly 20.

The valve assembly proper 20 is fonned of a longitudinally apertured, two-piece housing shell or tube 24, 26 threadedly coupled together at the insertion neck 27 of the lower piece 26. A metering plug 28 is formed with an axial bore 11 which defines the flow capacity of the bypass 18, being threadedly mounted at 25 in a tapped end-socket 12 of the lower housing 26. A slotted end 31 enables axial adjustment of the plug 28, which at its inner end 23 forms a seat for the lower end of a compression spring 30 which is loosely disposed within the housing chamber 29. At the upper end of the housing 26, it is peripherally relieved at 15 and axially drilled partway to form a restricted bore 33. At the inner end of the bore 33 an outstepped annular shoulder 32 fonns a seat for a check ball 22, the underface of which is supported by the terminal coil 34 of the spring 30. Below the stepped area, the channel tapers outwardly at 36; into which tapered or conic section the valve 22 partially projects even when seated, and into which it is progressively thrust by increased back-pressure from the passage 35. It will be seen that the ball is in a position of gravitational descent, supported only by the weak spring 30, so that a comparatively small back-pressure (e.g. one-eighth p.s.i.g. or less) in the line 18-35-33 will serve to open it. However, when such minimum back pressure fails, it is immediately closed by the tension of spring 30 (which tension can be set or adjusted by positioning the plug 28).

Thus it will be seen that the added assembly has a dual function: When the pump P is operating, the return flow of liquid through the open bypass 18, which is actually metered to a small trickle by the small diameter of the passage 33, does not appreciably curtail the main fuel flow through the supply line L; but the bottom-level pickup provided by the descendingly bowed segment [9 of the bypass has been found to be particularly effective (from comparison with a top-side pickup from the same outlet conduit location by an over-the-top-of-pump C-shape conduit) to ininimize or eliminate vapor lock in the operating pump. Secondly. the valve 22 which is lightly loaded by the spring 29 so as to open at a low back-pressure in the bypass 18, although continually open during normal pump operation, is successively functional after cessation of pump action has stopped the main fluid flow through the supply line 12-10. At such time, the still-open valve first equalizes the line pressure of the carburetor side 12 against the unpressurized feed line 10, and then automatically closes so as to still retain liquid in the whole line (even in the event of a leaking carburetor needle valve). On the other hand, if for any reason the pressure on the reservoir side of the pump should exceed that on the opposite side after the pump has stopped, the valve 22 would close at once so as not to exert this additional pressure against the carburetor needle valve. It is notable that this overall or composite result is obtainable without any alteration of an existing or installed pump, and merely by incorporation-because of the Tees l4, 16 at connections already present on the fuel pump-of the present simplified and highly effective, self-operating structure.

I claim:

1. ln combination with a liquid-fuel pump which is connected to a liquid-fuel reservoir by an inlet conduit and connected to a carburetor of an engine by an outlet conduit so as to move liquid fuel to the carburetor from the reservoir at a normal operating pressure of said pump:

a small capacity bypass conduit having a very small crosssectional flow area in respect to an internal cross section of the outlet conduit, the bypass conduit joining said inlet and outlet conduits so as to bypass said pump; and

valve means associated with said bypass conduit, for maintaining said bypass conduit open upon cessation of pump operation until the pressure in said outlet conduitis substantially equalized with the pressure in said inlet conduit, and then closing the same in response to decline of back pressure in said outlet conduit so as to retain unpressurized liquid in both conduits, thereby preventing the pump-pressurized liquid which was in the outlet conduit from draining into the carburetor after the pump has stopped, the valve means comprising a tubular housing having an internally tapered portion terminated in a valve seat and a spring-pressed ball valve adapted to seat therein and upon being unseated, progressively to permit fluid flow proportionate to the back-pressure in the outlet conduit. I

2. The combination of the preceding claim' 1' wherein said valve means is positioned at a junction of said bypass conduit and said inlet conduit.

3. The combination of the preceding claim 1 wherein said bypass conduit is dependently connected to said outlet conduit so as to draw off liquid from the lowest level thereof.

4. In combination with a liquid-fuel pump which is connected to a liquid-fuel reservoir by an inlet conduit and connected to a carburetor of an engine by an outlet conduit so as to move liquid fuel to the carburetor from the reservoir at a normal operating pressure of said pump:

a small capacity bypass conduit joining said inlet and outlet conduits so as to bypass said pump, wherein said bypass conduit is generally S-shaped, with a downwardly concave segment being dependently connected to said outlet conduit, and a successive, upwardly convex portion terminally connected to said inlet conduit, thereby minimizing occurrence of vapor lock in said pump; and

valve means associated with said bypass conduit, for maintaining said bypass conduit open upon cessation of pump operation until the pressure in said outlet conduit is substantially equalized with the pressure in said inlet conduit, and then closing the same in response to decline of back pressure in said outlet conduit so as'to retain unpressurized liquid in both conduits, thereby preventing the pump-pressurized liquid which was in the outlet conduit from draining into the carburetor after the pump has stopped. 5. The combination of claim 4 wherein the convex segment of said S-shaped bypass conduit is functionally coupled to said valve means which latter comprise a tubular housing having an internally tapered portion and a spring-pressed ball valve adapted to seat therein and upon being unseated, progressively to pennit fluidflow proportionate to the back-pressure in the bypass conduit.

Claims (5)

1. In combination with a liquid-fuel pump which is connected to a liquid-fuel reservoir by an inlet conduit and connected to a carburetor of an engine by an outlet conduit so as to move liquid fuel to the carburetor from the reservoir at a normal operating pressure of said pump: a small capacity bypass conduit having a very small crosssectional flow area in respect to an internal cross section of the outlet conduit, the bypass conduit joining said inlet and outlet conduits so as to bypass said pump; and valve means associated with said bypass conduit, for maintaining said bypass conduit open upon cessation of pump operation until the pressure in said outlet conduit is substantially equalized with the pressure in said inlet conduit, and then closing the same in response To decline of back pressure in said outlet conduit so as to retain unpressurized liquid in both conduits, thereby preventing the pump-pressurized liquid which was in the outlet conduit from draining into the carburetor after the pump has stopped, the valve means comprising a tubular housing having an internally tapered portion terminated in a valve seat and a spring-pressed ball valve adapted to seat therein and upon being unseated, progressively to permit fluid flow proportionate to the back-pressure in the outlet conduit.

2. The combination of the preceding claim 1 wherein said valve means is positioned at a junction of said bypass conduit and said inlet conduit.

3. The combination of the preceding claim 1 wherein said bypass conduit is dependently connected to said outlet conduit so as to draw off liquid from the lowest level thereof.

4. In combination with a liquid-fuel pump which is connected to a liquid-fuel reservoir by an inlet conduit and connected to a carburetor of an engine by an outlet conduit so as to move liquid fuel to the carburetor from the reservoir at a normal operating pressure of said pump: a small capacity bypass conduit joining said inlet and outlet conduits so as to bypass said pump, wherein said bypass conduit is generally S-shaped, with a downwardly concave segment being dependently connected to said outlet conduit, and a successive, upwardly convex portion terminally connected to said inlet conduit, thereby minimizing occurrence of vapor lock in said pump; and valve means associated with said bypass conduit, for maintaining said bypass conduit open upon cessation of pump operation until the pressure in said outlet conduit is substantially equalized with the pressure in said inlet conduit, and then closing the same in response to decline of back pressure in said outlet conduit so as to retain unpressurized liquid in both conduits, thereby preventing the pump-pressurized liquid which was in the outlet conduit from draining into the carburetor after the pump has stopped.

5. The combination of claim 4 wherein the convex segment of said S-shaped bypass conduit is functionally coupled to said valve means which latter comprise a tubular housing having an internally tapered portion and a spring-pressed ball valve adapted to seat therein and upon being unseated, progressively to permit fluid flow proportionate to the back-pressure in the bypass conduit.

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