US3168044A

US3168044A - Pressure relief device for fuel pumps

Info

Publication number: US3168044A
Application number: US288299A
Authority: US
Inventors: David B Stevens; Shermeister Eugene
Original assignee: Individual
Current assignee: Individual
Priority date: 1963-06-17
Filing date: 1963-06-17
Publication date: 1965-02-02
Anticipated expiration: 1982-02-02

Description

1965 o. 5.. STEVENS ETAL 3,168,

PRESSURE RELIEF DEVICE FOR FUEL PUMPS Filed June 1'7, 1963 mdnmfiow .Uavzd .Ev. EZEVETZE' Eu EI'IE Shermezster 9 i k. Q

United States Patent Ofifice 3,168,044 Patented Feb. 2, 1965 3,168,044 PRESSURE RELIEF DEVICE FOR FUEL PUMPS David B. Stevens, Mequon, and Eugene Shermeister, Sheboygan, Wis. (both of Rte. 2, Box 449A, Thiensville, Wis.

Filed June 17, 1963, Ser. No. 288,299 '2 Claims. (Cl. 103-41) This invention relates to pressure relief devices and has as its purpose to provide means for quickly relieving pressure in the fuel line leading from the fuel pump to the carburetor of an automobile engine when the engine is stopped.

Automobile engines are now practically universally equipped with engine-driven fuel pumps which pump fuel from the supply tank to the carburetor of the engine; and while the pumps used on different engines may vary in design and construction, they all have an inlet connectible with the fuel supply tank and an outlet which connects with the carburetor, and in all cases during operation of the pump suction is manifested at its inlet and pressure exists in its outlet.

When the engine ignition is turned off to stop the engine, no further fuel should be delivered to the carburetor or from it to the intake manifold, but heretofore the residual pressure which existed at the outlet of the fuel pump when the ignition was turned off always forced some fuel into the carburetor. This resulted in an overly rich mixture being present in the carburetor the next time the engine was started, and made it difficult to start the engine. In addition, this pumping of fuel after the ignition was shut 01f wasted a significant amount of fuel.

Although this problem has been recognized for years and many attempts have been made to cope with it, heretofore all expedients intended for the purpose have been costly, complicated, and generally unsatisfactory. By contrast, this invention solves the problem by means of a simple by-pass connection around the fuel pump from its inlet to its outlet, which though effective at all times, nevertheless does not interfere with proper delivery of fuel to the carburetor during operation of the pump.

With the above and other objects in view which will appear as the description proceeds, this invention resides in the novel construction, combination and arrangement of parts substantially as hereinafter described and more particularly defined by the appended claims, it being understood that such changes in the precise embodiment of the herein disclosed invention may be made as come within the scope of the claims.

The accompanying drawing illustrates one complete example of the physical embodiment of the invention constructed according to the best mode so far devised for the practical application of the principles thereof, and in which:

FIGURE 1 is a vertical sectional view through a conventional fuel pump equipped with the pressure relief device of this invention; and

FIGURE 2 is a fragmentary enlarged detail cross sectional view through FIGURE 1 on the plane of the line 22.

Referring now particularly to the accompanying drawing, the numeral 5 designates a fuel pump which may be considered representative of those employed on automobile engines to pump fuel from the fuel tank of the automobile (not shown) to the carburetor of the engine (also not shown). The specific construction of the fuel pump forms no part of this invention, but as in all such fuel pumps the one illustrated has an inlet 6 which is connectible through a line 7 with the fuel tank (not shown), an outlet 8 connectible through a line 9 with the carburetor of the engine (also not shown), and a diaphragm 10, flexure of which alternately draws fuel through the inlet 6 into the pump and expels the same under pressure through the outlet 8. Suitable inlet and outlet valves 11 and 12 are provided to enable the diaphragm to perform its pumping function.

The diaphragm 10 is pulled downwardly to draw fuel into the pump by a cam 13 on a rotating shaft 14 of the engine acting through a lever 15 pivoted as at 16 and connected with the diaphragm through a plunger 17. As the cam rotates and the lever 15 rides onto the low point thereon, a compression spring 18 hearing against the underside of the diaphragm forces the same upwardly to expel the fuel from the pump through the outlet 8 and, in so doing, establishes a pressure zone at the outlet.

Without the benefit of this invention the residual pressure in the outlet 8 which obtains at the instant the engine stops is suflicient to cause an appreciable amount of fuel to be delivered to the carburetor, thereby flooding the carburetor and perhaps also forcing some of this raw fuel into the intake manifold. In any event, when the engine is again started, this excess fuel in the carburetor produces an overly rich mixture which makes starting diflicult and also wastes fuel.

To eliminate this objection the inlet 6 and the outlet 8 of the fuel pump are interconnected by duct means, indicated generally by the numeral 20. This duct means is so designed and constructed that although it is at all times open and capable of returning fuel from the outlet to the inlet or suction side of the pump and in a few seconds will so return all fuel under pressure in the outlet of the pump when the ignition for the engine is shut off, it does not interfere with adequate and proper delivery of fuel to the carburetor during operation of the pump.

Specifically, the duct means 20 comprises two identical pipe couplings 21, one of which is threaded into the inlet port and the other into the outlet port of the pump, and each of which is adapted to have its respective fuel line 7-9 attached thereto in the conventional manner.

Each fitting 21 also has a nipple 22 secured in its side and projecting therefrom. Preferably the nipples are driven into slightly undersized holes in the fittings; but, in any event, their connections with the fittings must be fluid tight and to this end a sealing compound 23 or the like may be applied around the base of the nipples where they join the fittings.

A flexible tube, desirably of a plastic material which is impervious to gasoline, has its opposite end portions snugly telescoped over the nipples. If desired, clamps (not shown) may be applied to the end portions of the tube to assure against detachment from the nipples; but if the outer ends of the nipples are flared, as at 25, and the tube 24 is made of a material which retains its resilience, clamps are not necessary.

At least one of the nipples-and preferably bothhave a constriction 26 in the bore thereof; and while this constriction may be located anywhere along the length of the nipple bore, it is most conveniently placed at the inner end of the nipple where it can be formed by simply compressing or shrinking the end portion of the nipple.

Since a fuel pump in normal operation ordinarily de livers approximately sixty gallons per hour, the constriction 26or, more accurately, the effect of the constriction 26should be such that it will not reduce the flow by more than on the order of three and one-half percent. This would be a reduction in flow of about two gallons per hour. Such slight reduction in flow does not noticeably affect the operation and performance of an automobile engine, but a more serious reduction will begin to starve the engine at higher speeds. It has been found that if the constriction 26 provides a passage on the order of forty-thousandths of an inch (.040") in diameter for the short distance involved in reducing the diameter of the end of the nipple, as shown, entirely satisfactory results are obtained, and that to the extent indic'ated'the size of the constriction and its length are critical factors.

From the foregoing description taken in connection with,

the accompanying drawing, it will be apparent to those skilled in thisart that this invention provides an extremely simple device for eliminating a very trying and troublesome condition which aifects most all automobile en'- gines wherein the fuel is delivered to the carburetor by an engine-driven fuel pump, since it avoids flooding the carburetor fuel delivered thereto after ignition of the engine is'shutbif. V

Experience with the pressure relieving device of this invention has also demonstrated that, in city driving, which is characterized by numerous starts and stops, asaving in fuel of as much as ten percent (10%) has been achieved. What isclaimed as our invention is:

1. A device for relieving the pressure at the outlet of a fuel pump and returning fuel 'thereat to the inletof'the pump, comprising: a "pair of tubular pipe fittings, each 20 having means for connecting the same with a port in a -fuel pump so that one of said fittings may be located at the inlet of the fuel pump and the other at its outlet; a nipple embedded in each fitting and projecting laterally therefrom, said nipples being secured to their respective fittings in a fluid-tight manner and opening into the interior of the fittings; a tube'having its opposite end portions telescoped onto and tightly secured to the nipples so as to connect one fitting with the other; and a constriction in the bore of at least one of said nipples.

2. The pressure relieving device of claim l,'wherein said constriction is located at the inner end of each nipple and forms an orifice on the order of forty-thousandths of aninch in diameter.

References Cited in the file of this patent UNITED STATES PATENTS 2,249,326 Rabe July 15, 1941 2,648,285 Johnson Aug. 11, 1953 2,693,114 Tapp et a1. Nov. 2, 1954 2,763,253 Murrah Sept. 18, 1956

Claims

1. A DEVICE FOR RELIEVING THE PRESSURE AT THE OUTLET OF A FUEL PUMP AND RETURNING FUEL THEREAT TO THE INLET OF THE PUMP, COMPRISING: A PAIR OF TUBULAR PIPE FITTINGS, EACH HAVING MEANS FOR CONNECTING THE SAME WITH A PORT IN A FUEL PUMP SO THAT OF SAID FITTINGS MAY BE LOCATED AT THE INLET OF THE FUEL PUMP AND THE OTHER AT ITS OUTLET; A NIPPLE EMBEDDED IN EACH FITTING AND PROJECTING LATERALLY THEREFROM, SAID NIPPLES BEING SECURED TO THRIE RESPECTIVE FITTINGS IN A FLUID-TIGHT MANNER AND OPENING INTO THE INTERIOR OF THE FITTINGS; A TUBE HAVING ITS OPPOSITE END PORTIONS TELESCOPED ONTO AND TIGHTLY SECURED TO THE NIPPLES SO AS TO CONNECT ONE FITTING WITH THE OTHER; AND A CONSTRICTION IN THE BORE OF AT LEAST ONE OF SAID NIPPLES.