US2763253A

US2763253A - Fuel pressure release and valve therefor

Info

Publication number: US2763253A
Application number: US528220A
Authority: US
Inventors: Paul C Murrah
Original assignee: Individual
Current assignee: Individual
Priority date: 1955-08-12
Filing date: 1955-08-12
Publication date: 1956-09-18
Anticipated expiration: 1973-09-18

Description

Sept. 18, 1956 P. c. MURRAH FUEL PRESSURE RELEASE AND VALVE THEREFOR 3 Sheets-Sheet 1 Filed Aug. l2, 1955 FZ/EL PUMP zNvENToR Pn uz. 6i /17 UHR/QH ATTORNEYS BY M Sept.v 18,'195'6 P. c. MURRAH 2,763,253

FUEL. PRESSURE RELEASE AND VALVE THEREFOR Filed Aug. 12, 1955 5 sneets-sheet 2 10,401. 0. Maggy/f ATTORNEYS Sept 18', T956 P. c. MURRAH l 2,763,253

FUEL. PRESSURE RELEASE AND VALVE THEREFOR Filed. Aug. l2, 1955 5 Sheets-Sheet 3 e; f 3 ro /A/mA/f M4N/Fao 1NVBNT0R pam C Mogen# ATTORNEYS United States Patent O f7 FUEL PRESSURE RELEASE AND VALVE THEREFOR Paul C. Murrah, Corinth; Miss. Application August 12, 195s, serial No. Sia-220 12 claims. (c1. 12s-e139) The present invention relates in" general to pressure relief apparatus, and more particularly to apparatus for relieving excessive pressure in the fuel feed line of an internal combustion engine between the fuel pump and the carburetor thereof.

This application .is a continuation-in-part of my co'- pending application Ser. No. 460,609, filed October 6; 1954, and now abandoned.

In conventional internal combustion engines, the' fuel ptunp supplies fuel to the carburetor at a pressure of several pounds to the square inch. The conventional fuel 2 pump includes a diaphragm associated withinta'ke and outlet valves, al diaphragm actuating cam lever controlled by a cam driven in accordance with rotation of the en gine cam shaft for shifting the diaphragm through` its intake stroke, and a diaphragm return spring which is compressed on the intake stroke and supplies power for the pumping stroke of the diaphragm. The admission of fuel from the fuel feed line to the carburetor is controlled by a lioat valve which should maintain a specific fuel level in the carburetor at all times. To achieve proper starting characteristics of the internal combustion engine, the carburetor oat valve should also hold the specific fuel level in the carburetor after the engine hasceased operation and consumption of fuel fed' to the carburetor has terminated, in order to prevent fuel from overiiowing through the carburetor intake nozzle and other passages' into the intake manifold which produces a rich or engine-flooding fuel condition making itV dii-li-A cult to start the engine.

In practice, it has been found that the carburetor and intake manifold of internal combustion engines frequently become iooded in a short time after the engine is stopped, asa volume of fuel becomes trapped in the fuel line between the fuel pump and carburetor when the engine stops and the force of the diaphragm returnv spring in the fuel pump urges the diaphragm toward thefuel-'pump inlet and outlet valves and pumps the fuel trapped inthe feed line into the carburetor intake manifold. Aithough this movement of the fuel pump diaphragm is only to the extent permitted by the diaphragm actuating cani lever as it is shifted under the dominating force of. the diaphragm return spring from the high point on its associated cam to the lower point on the cam at whi'chythe` cam shaft stops, this movement is frequently sufficient to o'od the carburetor and intake manifold. Residual pressure in the fuel feed line after the engine stops,V arising from the fact that fuel pumps provide somewhat greater pressure than is necessary to feed the fuel, is anothersus-V pected cause of this iiooding.

Further, under current design practice, the temperature in the upper regions underv the hood of an automobile adjacent the carburetor and fuel lines isiincreased for a' short time after the engine ceases operation due to ter mination of the' ow of air. through the cooling: systemf and:` the excess heat that rises into the region fromI the exhaust manifold and engine, this region beingY poorly ventilated'. This increased temperature further boosts thepressure head in the fuel line supplying the carburetor, thereby` further implementing the expansion of fuel trapped between the fuel line and carburetor into the carburetor and the consequent establishment of the flooding conditions.

An object of the present invention, therefore, is the provision of apparatus associated with internal combustion engines which is conditioned upon cessation of engine operation to` maintain preselected static fuel conditions in the' fuel supply line to the engine carburetor while the engine is idle and thereby improve starting characterist'i'csi of the engine'.

Another object of the present invention is the provision of apparatus associated with internal combustion engines which isI activated in response to cessation of engine operation and deactivated in response to starting of the engine'toregulate fuel pressure conditions in the feed line to the carburetor and prevent fuel expansion into the carburetor establishing a ooded condition therein While the eligiiie'is'v idle.` v

Another object of the present invention is the provision of apparatus associated with internal combustion engines whichV is responsive to conditions incident to the idle state of an internal combustion engine to regulate pressure conditions in the' fuelfeed line tothe engine carburetor while the engine isidle and prevent delivery of fuel into the carburetor which would establish a iiooding condition impairing starting characteristics'.

Another object of the present invention is the provision of apparatus' associated with internal combustion engines which is responsive to and activated by the pressure conditions in the intake manifoldv when the engine is idle to relieve the pressure in the fuel line supplying the carburetor and prevent delivery of fuel into the carburetor which would flood the carburetor.

Another object of the present invention is the provision ofapparatusV associated with internal combustion engines which is responsiveV to open-circuiting of the ignition switch associated with the engine and activated upon open-circuitin'g' ofthe switch to relieve the pressure head in the fuel. line supplying the carburetor and prevent de'- liv'ery of the fuel to the carburetor and prevent delivery of the fuel to the carburetor while the ignition switch is open-circuited.

Another objectof the present invention isk the' provision of apparatus associated with internal combustion engines activated by pressure conditions present when the engine is idle to relieve the pressure in the fuel line supplying' the carburetor to prevent delivery of fuel into the carburetor, wherein means are provided to maintain the apparatus de-activated during transitory variations in such pressure conditionsv during operation of the engine.

Other objects; advantages and capabilities of the present inventionwill become apparent from the following detail description, taken in conjunction with the accompanying drawings showing several preferred embodiments of the invention.

In thef drawings:

Fi'gu-re 1 is a systematic view of fuel pressure relief apparatus embodying the present invention in association with theS pertinent components of internal combustion engine fuel system, the pressure relief apparatus being i1- lustratedV in section; k

Figure 2 is a view, partly in elevation and partly in section, showinga modified form of the present invention;

Figure 3 isl a view, partly in elevation and partly insection, showing anothermodified formof the presento, invention; and,

Figure 4 is a view, partly in elevation and partly in Patented sept. 1e, lese Y sa section, showing another modified form of the present invention.

Referring to the drawings, wherein like reference characters designate the corresponding parts throughout the several figures, and particularly to Figure l, there is illustrated a conventional carburetor 10, an intake manifold 11, a fuel pump l2 and an oil pump 13 constituting the pertinent components in the fuel supply system of an internal combustion engine with which the apparatus of the present invention is designed to be associated, the fuel pump 12 supplying conventional fuel through the feed line 14 to the conventional float valve chamber of the carburetor 1t).

As will be understood by those skilled in the art, the conventional fuel pump 12 associated with internal combustion engines includes a reciprocative diaphragm which is associated with intake and outlet valves in thefuel pump housing in such a manner that upon movement of the diaphragm away from the valves, a charge of fuel is delivered to the fuel pump from the gasolene tank of the vehicle, and upon return of the diaphragm toward the valves, the intake valve is closed by the pressure produced in the fuel pump created by the approaching diaphragm and the charge of fuel in the fuel pump is pumped through the feed line 14 to the carburetor 10. The diaphragm is actuated during its charging or withdrawing stroke by means of a cam lever actuated by a cam driven from the cam shaft of the internal combustion engine, and a diaphragm return spring is associated with the diaphragm to be compressed during this charging or withdrawing stroke of the diaphragm and to be released when the cam lever passes the high point on its associated cam to supply power for the pumping or approaching stroke of the diaphragm. When the internal combustion engine ceases operation, the diaphragm return spring is frequently in a compressed condition with a charge of fuel in the fuel pump, and the force of this spring is such that it can drive the diaphragm through a substantial portion of the pumping stroke to expel fuel through the feed line 14 to the carburetor 10 while the engine is in process of achieving a static condition, this pumping movement of the diaphragm being in accordance with the movement permitted upon rotation of the cam by the force of the diaphragm return spring from the position wherein the high point of the cam engages the cam lever to the lower point on the cam at which the cam shaft completely ceases rotation. vThis action of the fuel pump diaphragm produces a high pressure head in the fuel line 14 which overcomes the desired fuel level regulating action of the carburetor float valve and produces an enriched fuel condition in the carburetor and intake manifold which will interfere with proper restarting characteristics of the engine.

The pressure relief apparatus of the present invention is designed to relieve the pressure condition thus created in the feed line 14 and prevent this influx of fuel into the carburetor 10. In the embodiment illustrated in Figure 1, the pressure relief apparatus is indicated generally by the reference character 15 and includes an expansion chamber 16 and a regulating chamber 17 interconnected together. The expansion chamber 16 is formed as a closed housing by means vof a cylindrical housing portion 1S of relatively large diameter having a smaller diameter integral cylindrical projection 19 extending from the rear thereof and a connecting integral frusto-conical portion 20 flaring outwardly from the cylindrical portion 19 and forming a portion of the wall of the regulating chamber 17. The larger diameter cylindrical portion 18 is peripherally flanged at its forward open end, to which a frusto-conical front cover 21 is secured to form the closed expansion chamber 16, the cover 21 being connected with an intake tube 22 which communicates with the feed line 14 through a T-ftting Z3 on the feed line 14. A flexible diaphragm 24 is provided in the expansion chamber 16 and is peripherally supported between the adjacent edges of the expansion chamber housing portions 1S and 21. A frusto-conical member 25 cooperates with the frusto-conical portion 20 to form a complete enclosure for the regulating chamber 17, a flexible diaphragm 26 being marginally supported within the regulating chamber 17 between the cover member 25 and cover portion 20.

A connecting rod 27 is interconnected between the diaphragms 24 and 26 to coordinate movement thereof, the forward end of the rod 27 having a reduced end 28 which projects through a frusto-conical support and guide 29 corresponding in diameter to the internal diameter of the rear cylindrical body portion 18 and slidable therein, and through the diaphragm 24, a washer 30 being fitted about the reduced rod portion 28 and a nut 31 being threaded thereto to couple the diaphragm 24 to the forward end of the rod 27. The rear end of the rod 27 is provided with a reduced portion 32 which passes through the diaphragm 26, a supporting plate 33, and a washer 34, a nut 35 being threaded onto the reduced rod portion 32 to secure the same to the diaphragm 26. A vacuum seal 36 is fitted about an intermediate portion of the connecting rod 27 and is located within the intermediate smaller diameter cylindrical body portion 19 to isolate the chamber 17 from the expansion chamber 16. A conduit 37 extends from the cover portion 20 of the regulating chamber 17 to the intake manifold 11 to expose the front face of the diaphragm 26 to the vacuum conditions in the intake manifold 11.

The regulating chamber 17 may, if desired, be provided with a secondary chamber 38 connected through a conduit 39 to the oil pump 13 of the internal combustion engine to expose the rear face of the diaphragm 26 opposite that face exposed to the intake manifold conditions to the oil pressure conditions.

In the operation of this embodiment, the diaphragms 24 and 26 are located in the positions illustrated in Figure 1 when the engine is idle and the pressure conditions in the intake manifold 11 are at approximately atmospheric pressure. When the engine commences operation, the vacuum produced in the cylinders of the internal combustion engine establishes a negative pressure condition in the intake manifold 11 which is coupled to the regulating chamber 17 through the conduit 37, drawing the regulating chamber diaphragm 26 to the right as viewed in Figure 1. This movement of the regulating chamber diaphragm 26 is imparted to the expansion chamber diaphragm 24 through the connecting rod 27, thereby reducing the volume in the portion of the expansion chamber 16 lying to the right of the diaphragm 24. When the engine ceases operation, the pressure in the intake manifold 11 rises toward atmospheric pressure, forcing the regulating chamber diaphragm 26 toward the left to the position illustrated in Figure 1 which movement is communicated to the expansion chamber diaphragm 24 to increase the volume to the right of the diaphragm 24 in communication through the intake tube 22 with the feed line 14. This expansion of the volume in the expansion chamber 16 communicating with the feed line 14 is sufllcient to relieve the pressure head existing in the feed line 14 due to the terminal pumping action of the fuel pump 12 and the thermal expansion of the fuel in the feed line 14 due to the increased temperature under the hood of the vehicle so as to prevent delivery of fuel into the carburetor and therefore avoid flooding conditions which would interfere with proper starting of the engine.

In order to provide trouble-free operation and prevent interference with normal fuel supply to the carburetor 10 during transitory variations in intake manifold pressure as when the internal combustion engine is heavily loaded by the vehicle travelling up an incline, the secondary regulating chamber 38 responsive to oil pressure .in the internal .combustion engine .isprovided to .dampen the transitory effect .on .the .regulating .chamber `dia- .phragm 26 which the .temporary reduction in fthe yintake manifold .pressure would ,.produce. IDuring .such tem- Mporary :heavy loading .of the .internal combustion engine, the .increase .in .oil pressure fis vsuiiciently related .to .the :loss of .intake .manifold .vacuum .so .thatth-e increased .pressure on .the .rear face of the :regulatingchamber diaphragm y26 y.during .such .periods substantially balances out the increased y.pressure :on the front vface of the regulating chamber .diaphragm 26.10 prevent any substantial expansion in `the .volumetof .that zportion of the .expansion .chamber .16 .in communication with-thefuel .feedfline 214.

.A .second embodiment 'of the present :invention .is .1'1- llustrated :in .Figure .2 wherein .the expansion chamber diaphragm .is .electromagnetically disabled from .reliev- .ing the pressure .head .in the :fuel .feed .line while .the .lignition switch associated withthe-internal `combustion engine .is on 'The fuel .pressure reliefapparatus .of this .embodiment .is indicated by .the .reference-character 40, .and is associated with .a carburetor .10 supplying an .intake .manifold 11, a :fuel .pump 12 having inlet and outlet valves 12a `and 12b, respectively, .-a fuel gfeed line .14 .extending from the fuel pump outlet vvalve 12b .to .the .carburetor 1-0, and a fuel .supply line 41 extending :from the fuel tank (not shown) to the .fuel pump .inlet valve 12a.

The expansion chamber 42 lis Vformed Yof .a `ipair of mating housing members 43 .and 44 forming a Iclosed chamber and supporting therebetween "within thevcham- .ber a iiexible diaphragm 45. .A.conduit`46.extendsfrom `the intake mani-fold ..11 4to .the section .of the Ychamber 4 2 below theV diaphragm 45 .to :subject .the .lower .'diaphragm `face -to .th-e pressure in the intake manifold .1-1. .The upper housing 'member-43 .-is provided --With .a `check valve extension 47 .having a valve seat .conduit 48 extending 'therethrough in vcommunication with the -cham- [ber area above the diaphragm 45 and a ball check 'valve 49 seated thereon. The upper end of the 'valve .seat conduit 48 -remote from the diaphragm i-s connected through a tube 50 with :the fuel .line 14. vA feedback .conduit 51 .also extends from the upper :chamber :section of `.expansion 'chamber -42 to the rline 41 .supplying .the fuelpump.

.A check valve*y plunger .52 slidaiblyextending through supporting plates .53 -o'n opposite 'faces fthe vdiaphragm 45 V.and yhaving .a shoulder bearing .on the uppermost plate 53 'projects into .the -valv'e :seat conduit I48 in operative relation lwith the check "valve 49. A reduced diameter .lower .end .of the plunger 52 is ysurrtmn'ded by :a return spring .54 bearing Yagainst the =lower'wall of the `.housing member 444 and Vthe lower plate T53 to `urge. the plunger 52 upwardly.

Magnetizablecore -rnembers 55 depend-from the lower diaphragm supporting plate 53 .andare each surrounded b y .electromagnetic coils 56 iixed on the Ahousing .member -44 and `connected .in series relation with fthe .ignition circuit lead 57 lof theigni-tion switch 58 of :the engine to bev energized `from the vbattery orgenerator only when the ignition :switchis"on.

vIn .the operation of this embodiment, Ythe portion of the expansion chamber 42 below the .diaphragm l45 is responsive to the pressure conditions in the .intake manifold to draw Athe .diaphragm 45 and plunger 52 Ydownwardly .tothe jposition Yillustrated in Figuref wherein the check valve 49 lis gravity-seated .on .its vassociated seat .in the conduit 4S to close olf this conduit. When'theengine ceases Yopera-ting .the .rising pressure -in the .intake manifold 11 .communicated .to the .lower diaphragm Yface through the conduit 46 4elevates the lcentral portion of the diaphragm 45 .and the plunger .52 .thereon lto lift the check valve 49 `olf .its .associatedseat .A .return path for ...reliefof fuel pressure from the fuel line =14 .to .the supply line 4l .iis .then provided :through ithe tube 50, the valve seat conduit 48, the upper section of the expansion ychamber 42 and .the feedback line i51, by which the formation of any such .fuel 4pressure head :in the :fuel line y14 which would vflood thevcarburetor V-is prevented.

The electromagnetic components associated vwit-h this structure are to prevent transitory 'variations in .intake manifold -pressure from actuating the diaphragm V45 .in such a manner as to `interfere with proper fuel feed. When the .ignition switch 58 :is on, the current :in :the electromagnetic coils 56 sets up 'a Ymagnetic iield .attracting the core members 55 to such an extent that Vthe .freducti-ons `in intake manifold 'vacuum when the engine :is loaded -which are 'somewhat less than total vacuum collapse, a-re insufcient to overcome the magnetic'attraction and force the diaphragm 45 'and plunger -52 to valve unseating position.

Figur-e 3 illustrates a further embodiment operating generally on the same principle as that illustrated :in Figure 2 but wherein the pressure relief v`apggiaratus components are incorporated into a single assembly lwith the fuel pump. In .this embodiment, there is ,provided in the lower port-ion of a housing 60 the conventional fuel pump components including la pumping chamber 61 'terminated at its lower 'end by a reciprocative flexible Vdiaphragm -62 from which a diaphragm control plunger 63 depends, the plunger being reciprocated by a lpivotal fuel .pump operating lever y64 lcontrolled lby the fuel pump cam 65 on the cam 'sha-ft :of vthe lengine. Resiliently biased Aintake valve 66 and -outlet Valve 67 are provided -in the upper wall Aof the pumpingchamber 61 yand are fcontrolled by thepressure .conditions created in'the pumping `chamber 61 by the fuel pump diaphragm 62. The fuel pump inlet valve 66 .is seated in an .inlet conduit 68 :which .communicates with the supply line 69 extending .from the -fuel tank or reservoir (not shown) Iand the outlet valve 67 is seated .in an outlet conduit .'70 inthe housing 60which communicates with the fuel .feed

:line 7.1 extending to the `canburetor 10.

A by-pass conduit 72 extends 'through the housing 60 between the -inlet .conduit 63 .and the-outlet conduit 7 0, at

.an intermediate point in which a pressure relief valve 73 is provided which is resiliently biased to closed-condition. The intermediate portion of the `by-pass yconduit 72 is further provided immediately above the pressure relief valve '73 with anenlarged expansion chamber 74, across ythe upper portion of which in non-.intercepting relation with the by-pass conduit 72 is a flexible diaphragm 75 having a depending plunger 76 axed thereto 'and ex tending into operative relation with the pressure grelief `valve 73 -to unseat lthe pressure relief valve 73 when the .diaphragm 75 is forced downward-ly under atmospheric pressure conditions at the upper face of the diaphragm. A conduit 77 extends from the upper portion of the ex'- pansion chamber 74 above the diaphragm 75, 4which is hereinafter termed the regulating chamber 78 and which, inthe embodiment shown herein, is formed in a lcapping member 79 aflixed to the housing body 6i?, to the intake manifold 1-1 to subject theuppersurfaceof ythe diaphragm 75 to the pressure conditions in the intake manifold. Also disposed within `the regulating chamber '7S ;is lan electromagnetic coil 80 'surrounding a xed Amagnetizable core 81 disposed to attract the diaphragm plunger 76 when the-core @Gis-energized. The electromagnetic core 8i) is connected through the Wire'SZ in series circuit relation with the conventional ignition switch of the internal combustion engine .in the samejmanner as that illustrated inFigure 2 'so as to maintain the electromagnetic coil 80 energized while the ignition switch is on The operation of this `embodiment is identical with that described in connection with Figure 2, the existence of low pressure conditions in the intake manifold 11 when the engine .is operating being communicated through the tube- 77 lto the regulating .chamber 78 to draw the diaphragm 75 upwardly to the vposition illustrated in :Figure 3 wherein the diaphragm plunger 761is :free Vof Contact with the pressure relief valve 73 so that the valve 73 is resiliently held against its associated valve seat to close :off the by-pass conduit 72. When the engine ceases operating and the vacuum in the intake manifold 11 collapses, the resulting atmospheric pressure communicated to the upper face of .the diaphragm 75 ilexes the diaphragm downwardly to shift the plunger 76 so as to unseat the by-pass pressure relief valve 73 and open the by-pass conduit 72. In this condition, the fuel pressure head in the fuel feed line 71 and outlet conduit 70 is relieved through vthe by-pass conduit 72 to the inlet conduit 68 and supply line 69 to prevent existence of such pressure conditions in the fuel feed line 71 as would cause the carburetor to 'become flooded. The electromagnetic coil 70 which is energized when the ignition switch is on supplies sufficient magnetic attraction to the plunger 76 to overcome the small transitory increases of pressure in the intake manifold 11 when the engine is heavily loaded so as to prevent opening of the by-pass conduit 72 during such 'transitory operating conditions of the engine and prevent interruption of normal fuel supply at such times.

Figure 4 illustrates another embodiment wherein transitory fluctuations in manifold pressure are prevented from relieving fuel pressure in the fuel feed line by a lockout lmechanism operative when the throttle valve of the engine is open. The expansion chamber and regulating chamber are integrated into one assembly in a housing 8S of mating sections having a flexible diaphragm 86 marginally supported therebetween dividing the interior of the housing 85 into an upper expansion or by-pass chamber 87 and a lower regulating chamber 88. The regulating chamber 88 is in communication with the intake manifold by means of a tube 89. A check valve seat conduit 90 is provided in the upper section of the housing 85 between the expansion chamber 87 and the fuel feed line between the fuel pump and carburetor, having a ball check va'lve 91 gravity-seated therein, and a return line 92 extends from the expansion chamber 87 to the fuel tank.

A plunger 93 supported centrally on the diaphragm 86 at a point intermediate its ends projects upwardly into the valve seat conduit 90 to unseat the check valve 91 when atmospheric pressure conditions are coupled to the regulating chamber 88 from the intake manifold. The portion 94 of the plunger 93 depending from the diaphragm through a sealing gasket in the lower wall of the housing 85 terminates in a lateral shoulder 95 disposed below the periphery of a lockout cam 96 on the throttle valve shaft 97 of the engine. The lockout cam 96 has a small relieved section 98 which faces the shoulder 95 when the throttle is closed.

In the operation of this embodiment, the presence of negative pressure conditions in the intake manifold when the engine is operating draws the diaphragm 87 and plunger 93 down from the position illustrated in Figure 4 to a position permitting the check valve 91 to seat and close off the valve seat conduit 90. The open condition of the carburetor throttle valve when the engine is operating under heavy load, as when the vehicle is travelling up an incline, disposes the larger radius portions of the lockout cam 96 toward the shoulder 95 of the plunger portion 94, maintaining the plunger in lowered position wherein the check valve is seated. When the intake manifold pressure collapses upon termination of engine operation, the plunger 93 is projected upwardly by the rising pressure on the lower face of the diaphragm 86 to unseat the check valve 91. The fuel pressure in the fuel feed line is thereupon relieved through the valve seat conduit 9), the eX- pansion chamber 87 and the return line 92 to the fuel tank.

While several preferred embodiments have been specifically shown and described herein, it is apparent that other modifications may be made in the invention without departing from the spirit and scope thereof, and it is desired, therefore, that only such limitations shall be placed thereon as are imposed by the prior art and are set forth in the appended claims.

I claim: Y

1. In combination with an internal combustion engine having fuel pump means, an intake manifold, a carburetor, and a fuel feed line between said fuel pump means and said carburetor, fuel pressure relief means for selectively reducing the pressure in said fuel feed line comprising fuel accommodating means communicating with said fuel feed line into which fuel may be displaced from said feed line, displaceable means regulating the volume of said fuel accommodating means directly communicating with said feed line, and means for subjecting said displaceable means to the pressure in said intake manifold to position said displaceable means to establish a minimum volume condition in said fuel accommodating means when the intake manifold pressure is low during f ducing the pressure existing in said fuel feed line upon cessation of the operation of the engine comprising a fuel-receiving branch communicating with said fuel feed line into which fuel is displaceable for varying the effective volume of the fuel feed line between said fuel pump means and said carburetor, displaceable means for controlling the effective volume of said fuel-receiving branch means accessible to receive fuel from said fuel line, and means associated with said displaceable means rendering said displaceable means responsive to the pressure in said intake manifold so as to condition said displaceable means to expose a minimum volume of said fuel-receiving branch means to admission of fuel from said fuel feed line during occurrence of sub-atmospheric pressure conditions in said intake manifold and to increase the volume of said fuel-receiving branch means accessible to receive fuel from said feed line when the pressure in said intake manifold approaches atmospheric pressure.

3. In combination with an internal combustion engine having fuel pump means, an intake manifold, a carburetor, and a fuel feed line between said fuel pump means and said carburetor, fuel pressure relief means for reducing the pressure existing in said fuel feed line upon cessation of the operation of the engine comprising a fuel-receiving branch communicating with said fuel feed line into which fuel is displaceable for varying the effective volume of the fuel feed line between said fuel pump means and said carburetor, displaceable means for controlling the effective volume of said fuel-receiving branch means accessible to receive fuel from said fuel line, and means associated with said displaceable means rendering said displaceable means responsive to the pressure in said intake manifold so as to condition said displaceable means to expose a minimum volume of said fuel-receiving branch means to admission of fuel from said fuel feed line during occurrence of sub-atmospheric pressure conditions in said intake manifold while said engine is operating and to increase the volume of said fuel-receiving branch means accessible to receive fuel from said feed line when the pressure in said intake manifold approaches atmospheric pressure upon cessation of engine operation.

4. In combination with an internal combustion engine having fuel pump means, an intake manifold, a carburetor, and a fuel feed line between said fuel pump means and said carburetor, fuel pressure relief means for reducing the pressure established in said fuel feed line upon cessation of operation of the engine comprising expansible chamber means having a exible diaphragm controlling the volume thereof, a conduit communicating said chamber with said fuel feed line, and regulating means ntercoupled with said diaphragm and responsive to the agregarse engine operation and to increase the volume of said ex,-

pansible chamber when the pressure rises in said` intake manifold upon cessation of engine operation and accom-l modate fuel from said fuel feed line reducing the pressure therein.

5. In combination with an internal combustion engine having a fuel pump, an intake manifold, a carburetor, and a fuelV feed line between saidv fuelpumppand, said carburetor, fuel line pressure relief means including, a pressure relief assembly having a reary chamber and a fron-t chamber separated by a marginally supported peripheral diaphragm, means directly communicating said front chamber with said fuelgfeed line, means directly communicating said rear chamber with said intake manifold to subject the surface ofv said diaphragm facing said rear chamber to the pressure in said intake manifold for positioning said diaphragm to establish a selected minimum volume condition in said front chamber when subatmospheric pressure conditions exist in said intake-manifold' and shift said diaphragm to increase the volumeA in said front chamber when the-pressure in said intake manifold approaches atmospheric conditions upon cessation of engine operation. l

6. In combination with an internalVl combustion engine having a fuel pump, an intake manifold, a carburetor; and a fuel feed line between said fuel pump' and saidl carburetor, fuel pressure relief means includ-ing a pressure relief assembly having a rear chamber and a front chamber isolated fromV each other, means directly cornmunicating said front chamber with said fuel feed line, means communicating said rear chamber with said intake manifold, said front chamber having a flexiblediaphragmfor. controllingA the volume of front chamber accessible to receive. fuel from said fuel feed line, and4 said' rear chamber having a exible diaphragmr therein exposedto the pressure insaid intakeA manifold, andv means interconnecting said diaphragms for coordinating movement' thereof, said diaphragms being positioned by sub-atmospheric pressure from said' intake manifold in said rear chamber to establish a selected minimum volume condition in said front chamber and said diaphragms being shifted when the pressure coupled -to said rear chamber from said intake manifold approaches atmospheric pressure upon cessation of engine operation to increase the volume of said front chamber exposed to receive fuel from said fuel feed line.

7. In combination with an internal combustion engine having fuel pump means, an intake manifold, a carburetor, and a fuel feed line between said fuel pump means and said carburetor, fuel pressure relief means for reducing the pressure existing in said fuel feed line upon cessation of the operation of the engine comprising a fuel-receiving branch communicating with said fuel feed line into which fuel is displaceable for varying the effective volume of the fuel feed line between said fuel pump means and said carburetor, displaceable means for controlling the effective volume of said fuel-receiving branch means accessible to receive fuel from said fuel line, means associated with said displaceable means rendering said displaceable means responsive to the pressure in said intake manifold so as to condition said displaceable means to expose a minimum volume of said fuel-receiving branch means to admission of fuel from said fuel feed line during occurrence of sub-atmospheric pressure conditions in said intake manifold and to increase the volume of said fuelreceiving branch means accessible to receive fuel from said feed line when the pressure in said intake manifold approaches atmospheric pressure, and means conditioned continuously during operation of said engine for restraining said displaceable means against alteration of said minimum volume condition to render said displaceable t 10 l means-` insensitive to transitory variations, in intake, f old pressure. t p, 8j. In combination with, an internal, combustion engine havingfuel'pump means, anrintake manifold, acartburetqr, a fuel feed line between said fuel pump means and said carburetor and an ignition switch'for said engine, fuel pressure relief means for reducing the pressure existingtin said fuel feed line upon cessation ofI theoperationof the. engine comprising a fuel-receiving. branchA com.- municating with saidY fuel feed line into whichfuell is displaceable for Varying. the eifective volumeof the fuel feed line between said fuel pump means` and said carburetor.; displaceable means for controlling the effective volume 'of said fuel-receiving branch means accessible to receive fuel from said fuel line, means associated with, said displaceable means rendering said displaceable means responsive to the pressure in said intake manifold so asY to condition said displaceable means to expose a minimum volume of said fue'l-receivingy branch means t'o admis.- sion of' fuel from said fuel feed line during occurrenceA of sub-atmospheric pressure conditions, in said intake manifold' andto increase the volume of said` fuel-receiving branch` means accessible to receive fuel from` said feed line when the pressure in said intake manifold' approaches atmospheric pressure, and electromagnetic lockout means conditioned continuously while said' ignition switch is clos'ecircuited to restrain said displaceable means against movement altering said minimum volume condition and renderthe` same insensitive to transitory variations in intake manifold' pressure.

9. In combination with an internalL combustion engine having fuel pump means, an intake manifold, a` carburetor; a fuel feed line between said fuel pump means, and' saidcarb'uretor, and a throttle valve for'said engine, fuel pressure relief meansfor reducing'the pressureexifsting'in siaid fuel feed lineupon cessation ofthe operation of the` engine comprising a fuel-receiving branch communicating with said fuel` feed linev int'oA which fuel is displaceable' for varyingA the effective volume of therfuel feed line between sai'd fuel pump means andsaidcarburet'or', displaceable"meansv for controlling the effective volume of said fuel-receiving branchrneans accessible to'receive fuel from' said fuel'lihe, means associated with said displaceable'-means rendering. said displaceable means responsive to the pressure in said intake manifold so as to condition said displaceable means to expose a minimum volume of said fuel-receiving branch means to admission of fuel from said fuel feed line during occurrence of sub-atmospheric pressure conditions in said intake manifold and to increase the volume of said fuelreceiving branch means accessible to receive fuel from said feed line when the pressure in said intake manifold approaches atmospheric pressure, and magnetic lockout means conditioned by said throttle valve to restrain said displaceable means against movement altering said minimum volume condition and render the same insensitive to transitory variations in intake manifold pressure.

l0. In combination with an internal combustion engine having fuel pump means, an intake manifold, a carburetor, and a fuel feed line between said fuel pump means and said carburetor, fuel pressure relief means for reducing the pressure in said fuel feed line upon cessation of the engine comprising expansible chamber means communicating with said fuel feed line, a marginally supported flexible diaphragm in said chamber means controlling the volume thereof accessible to said fuel feed line, normally seated check valve means between said chamber and said fuel feed line interrupting the communicaiton therebetween, means projecting from said diaphragm for unseating said check valve means when said diaphragm is iiexed in a preselected direction, and means subjecting said diaphragm to the pressure in said intake manifold for flexing said diaphragm in a direction -to free said check valve to occupy its normally seated position upon occurrence of subatmospheric pressure conditions in said intake manifold incident to engine operation and to ex said diaphragm 1 1 to unseat said check valve and increase the volume of said `expansible chamber means exposed to said fuel feed line when the pressure in said intake manifold approaches atmospheric pressure upon cessation of engine operation to admit fuel to said expansible chamber and relieve pressure in said fuel feed line.

1l. In combination with an internal combustion engine having fuel pump means, an intake manifold, a carburetor, a fuel feed line between said fuel pump means and said carburetor, and an ignition switch for said engine, fuel pressure relief means for reducing the pressure in said fuel -feed line upon cessation of the engine comprising expansi-ble chamber means communicating with said fuel feed line, a marginally supported flexible diaphragm in said chamber means controlling the volume thereof accessible to said fuel feed line, normally seated check valve means between said chamber and said fuel feed line interrupting the communication therebetween, means projecting from said diaphragm for unseating said check valve means when said diaphragm is flexed in a preselected direction, means subjecting said diaphragm to the pressure in said intake manifold for flexing said diaphragm in a direction to free said check valve to occupy its normally seated position upon occurrence of subatmospheric pressure conditions in said intake manifold incident to engine operation and to flex said diaphragm to unseat said check valve and increase the volume of said expansible chamber means exposed to said fuel feed line when the pressure in said intake manifold approaches atmospheric pressure upon cessation of engine operation to admit fuel to said expansible chamber and relieve pressure in said fuel feed line, an electromagnetic coil disposed adjacent said diaphragm, magnetizable means fixed on said diaphragm, and means electrically connecting said electromagnetic coil with said ignition switch to energize said coil upon close circuiting of said ignition switch and magnetically attract said magnetizable member on said diaphragm toward said coil to restrain said diaphragm against check valve unseating movement during transitory small pressure increases in said intake manifold while said engine is operating.

12. In combination with an internal combustion engine having fuel pump means, an intake manifold, a carburetor, a fuel'feed line between said fuel pump means and said carburetor, and a rotatable throttle valve and Qshaft therefor controlling fuel supply to said carburetor, fuel pressure relief means for reducing the pressure in said fuel feed line upon cessation of the engine comprising expansible chamber means communicating with said fuel feed line, a marginally supported flexible diaphragm in said chamber means controlling the volume thereof accessible to said fuel feed line, normally seated check valve means between said chamber and said fuel feed line interrupting the communication therebetween, plunger means projecting from said diaphragm for unseating said check valve means when said diaphragm is exed in a preselected direction, means subjecting said diaphragm to the pressure in said intake manifold for flexing said diaphragm in a direction to free said check valve to occupy its normally seated position upon occurrence of subatmospheric pressure conditions in said intake manifold incident to engine operation and to flex said diaphragm to unseat said check valve and increase the volume of said expansible chamber means exposed to said fuel feed line when the pressure in said intake manifold approaches atmospheric pressure upon cessation of engine operation to admit fuel to said expansible chamber and relieve pressure in said fuel feed line, said throttle valve shaft having a cam thereon including a relieved peripheral portion, and said plunger means having a shoulder thereon projecting into proximity with said cam to be restrained by the unrelieved peripheral portions of said cam against move ment shifting said diaphragm into check valve unseating condition during transitory small pressure increases in said intake manifold while said throttle valve is positioned to supply fuel to said carburetor, and said relieved peperipheral portion of said cam being positioned relative to said throttle valve and to said shoulder to be disposed in the path of movement of said shoulder when said diaphragm and plunger means undergo check valve unseating movement to free said plunger means and diaphragm for unseating said check valve when said diaphragm is flexed in response to rising intake manifold pressure.

No references cited.