Valve For Evaporative Loss Control

Abstract

Diaphragm valve spring biased into a closed position and responsive to fuel tank vapor pressure to effect opening of valve, and to fuel tank vacuum as the valve is closed, to vent the tank to atmosphere.

Parent Case Text

This application is a division of my application, Ser. No. 783,821, filed Dec. 16, 1968, now U.S. Pat. No. 3,628,517 and entitled "Valve For Evaporative Loss Control."

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to evaporative loss control apparatus, and in particular to valve apparatus for controlling evaporative loss in the fuel system of an automotive engine.

2. Description of the Prior Art

Evaporative loss control devices have found particular use in automotive fuel systems to purge fuel vapors from the fuel reservoirs during engine operation; to store vapors after engine operation when the fuel system is in an immediate overheat condition; and to return vapors to fuel reservoirs for condensation after cool down of the system, in cooperation with the carburetor and a vent switch of the automotive engine.

Heretofore, such apparatus employed at least two separate, but cooperable valves to channel the air and fuel vapors between the plurality of fuel reservoirs and the carburetor. In addition to the obvious disadvantage of requiring additional parts, the provision of a plurality of valves to provide the purging and venting operations, has a number of other disadvantages. One of these is the added design requirements for each valve and the cooperable parts thereof. Furthermore, the additional number of parts requires longer per unit assembly time. It is therefore desirable for evaporative loss control apparatus to employ a single valve for providing the venting and purging operations.

SUMMARY AND OBJECTS OF INVENTION

At the top of the housing are first and second passageways in communication with the chamber. The first passageway is adapted for connection to a carburetor line and through a vent switch to the upper throat portion of a carburetor. The second passageway is adapted for connection to a purge line which is in communication with a vacuum port adjacent the butterfly valve in a lower throat portion of the carburetor as a vacuum input to the device.

Evaporative loss control valve for the fuel control tank of an internal combustion engine in which the valve is in the form of a diaphragm biased into a closed condition, and opened by fuel tank vapor pressure. The valve is seated on an outlet port connected with a carburetor purge line and has a fuel tank inlet connection on the underside of the diaphragm which effects opening of the outlet port upon positive fuel tank vapor pressure conditions. The inlet connection to the fuel tank also supplies vacuum to the underside of the diaphragm valve to flex the valve when closed and open a passageway leading through the valve to connect the fuel tank to atmosphere until the pressure in the tank is balanced.

A principal object of the present invention, therefore, is to provide a simplified form of single diaphragm valve particularly adapted for controlling the evaporative loss from a fuel tank and operable to effect different operations by vapor pressure or vacuum in the fuel tank.

Another object of the invention is to improve upon the evaporative control valves, for fuel tanks for internal combustion engines heretofore known, by so arranging the valve that a single diaphragm can control the purging of the tank under certain pressure conditions and the venting of the tank to atmosphere under certain other pressure conditions.

Other objects, features and advantages of the invention will be readily apparent from the following description of a preferred embodiment thereof, taken in conjunction with the accompanying drawings, although variations and modifications may be effected without departing from the spirit and scope of the novel concepts of the disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention, its organization, construction and operation, according to one illustrative embodiment thereof, will be best understood from the following description taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a top plan view of an evaporative loss control device according to the present invention;

FIG. 2 is an elevational view, in section, of the apparatus of FIG. 1 taken along the line II--II;

FIGS. 3 and 4 are more detailed views of the valve apparatus shown in FIG. 2;

FIG. 5 is a modification of the apparatus of FIGS. 2, 3 and 4; and

FIGS. 6-9 are schematic diagrams of an evaporative loss fuel vapor system according to the present invention shown in various operational modes of the associated automobile engine.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In FIGS. 1-5, an evaporative loss control device is generally shown at 10 as comprising a hollow canister-type housing 11 defining a chamber 14 therein. Mounting flanges 12 having slotted tabs 13 are provided for securing the device within the engine compartment of an automobile.

Chamber 14 is filled with an absorbent material, preferably activated charcoal or a shredded rubber compound for collecting fuel vapors. At the lower end of device 10 and against the absorbent material is a screen or porous material 15 against which is located a pressure plate 16 having a plurality of holes 17 therein. A spring retainer 19 having a raised ridge portion 20 compresses spring 18 against the bottom of the pressure plate 16 and is secured to the hollow housing 11 by edge portions 22 and 23 which form a groove for accepting an annular ridge 24 at the lower end of the housing. A removable plastic cover 25 having a large opening 28 in the center thereof holds a filter 29 against the spring retainer 19 and releasably engages the spring retainer 19 by the overlapping portions 26 and 27 which overlappingly engage portions 22 and 23 of the retainer. The air passage into the bottom of the device 10 is therefore defined by opening 28, filter 29, hole 21, holes 17 and screen 15.

At the top of the device 10, and adjacent the top surface of the absorbent material is a screen 30 which is spaced from the top of the chamber 14 by spacers 33 to define chamber 34 therebetween. The top of the housing further defines a plurality of passageways including a first passageway 37 which is defined by wall 36 of top portion 35. Passageway 37 is adapted for connection to a fuel tank line for venting and purging vapors with respect to the fuel tank. Passageway 37 is in communication with a chamber 38 which is formed between the top portion 35 of housing 11 and a rubber diaphragm 39 which is secured by its bead portion 51 which is held in groove 50 by a spring housing 57. The spring housing 57 is secured to the top portion 35 by means of portions 59 forming a snap fit with an annular groove 58 of the top portion 35.

Spring housing 57 holds spring 64 against a pressure plate 56 having an aperture 55a therein for receiving a snap button 55 of diaphragm 39. The spring 64 therefore urges diaphragm 39 downwardly against rounded end portion 49 of cylinder 41 formed in the upper portion 35, the cylinder 41 extending downwardly into a well 32 of screen 30 within the chamber 14.

Under conditions of positive pressure, symbolized by arrows 65 and 66, from the fuel tank line through passageway 37 into chamber 38, diaphragm 39 and pressure plate 56 operate against the action of the spring to open the seal between the flat portion 53 of the diaphragm and the rounded end portions 49 of cylinder 41 to permit fluid communication between the fuel tank and chamber 14 via a path including passageway 37, chamber 38, passageway 40 of cylinder 41, slots 42 at the lower end of cylinder 41 and screen well 32.

Under conditions of negative pressure within the fuel line and accordingly within passageway 37 and chamber 38, the spring 64 closes the above-mentioned path at end 49 of cylinder 41. Further, ambient air pressure transmitted through slot 63 of portion 35, filter 62, and holes 61 in spring housing 57 into chamber 60 acts on a first flexible portion 52 of diaphragm 39 to flex portion 53 thereof sufficiently to provide a continuation of the just-traced path through holes 54 of diaphragm 39 into chamber 38 and on through passageway 37 to the fuel tank line.

FIG. 5 illustrates a variation of the valve shown in detail in FIGS. 3 and 4 wherein a diaphragm 39a includes an annular upstanding ridge as a seal against the pressure plate 56. The operation of diaphragm 39a is substantially the same as that of the diaphragm 39.

A top portion 35 has two additional passageways formed therein. One of these passageways 43 is adapted for connection to a carburetor line and communicates the carburetor line with chamber 14 by way of slots 42 (for greater vapor dispersion) of a downwardly extending portion of passageway 43. This passageway is for communication between the carburetor and the chamber 14 by way of a purge line 79, as illustrated in FIGS. 6-9, whereby a vacuum may be supplied to the chamber 14.

Another passageway 45 has a depending cylindrical portion 47 defining a further passageway 46 having a slotted end (slots 48) extending into screen well 31 of screen 30 within chamber 14, the passageway 45 being adapted for connection to a line 73 for providing communication between the chamber 14 and a vent switch 74 and a fuel bowl 75 of a carburetor, as also illustrated in FIGS. 6-9.

OPERATION

The various operational modes of the evaporative loss control vapor system according to the present invention are shown in FIGS. 6-9 wherein a limited number of reference characters are employed for sake of clarity.

FIG. 6 describes a condition wherein the automotive engine is inoperative and cold, the fuel system also being cold and no fuel vapors being generated in the fuel tank 81 or in the carburetor hole 75.

Under such conditions, the butterfly valve 78 of carburetor 71 is closed there being no vacuum supplied through purge line 79 to passageway 43 of device 10. The vent switch 74 is positioned to close line 72 which extends to the upper throat area of the carburetor 71 and open to line 73 to place the fuel bowl 74 in communication with chamber 14 via passageway 45. In FIGS. 6-9 reference 76 indicates fuel level and reference 77 indicates a fuel line extending between the carburetor and the fuel of the fuel bowl 75. There being no pressure difference between the fuel tank 81 and ambient conditions, diaphragm 39a is closed.

FIG. 7 illustrates the conditions of fuel system when the automotive engine is in operation, the engine being on and hot and the fuel system being sufficiently warm so that fuel vapors are generated in the fuel tank 81 and the carburetor bowl 75.

Under these conditions, the diaphragm 39a is opened to the positive pressures developed in fuel tank 81, symbolized by arrows 90. The butterfly valve 78 is opened providing a vacuum through purge line 79 to passageway 43 of the loss control device 10. The vent switch 74 is opened to the carburetor, but closed to line 73 and passageway 45. Therefore, vapors from tank 81 pass to the carburetor over a path comprising line 80, passageway 57, chamber 38, passageway 40, chamber 14, passageway 43 and purge line 79. In chamber 14 air is drawn in through hole 21, (symbolically representing the holes and filters at the lower part of the canister), the air being mixed with the fuel vapors 90 and the material of chamber 14 being purged of fuel vapors by the vacuum supplied by the carburetor.

FIG. 8 illustrates the condition of immediate overheat wherein the engine has just been turned off and is still hot and the system is hot wherein fuel vapors are still being generated to positive pressures in the fuel tank 81 and the carburetor bowl 75.

In this situation, the butterfly valve 78 is closed and no vacuum is supplied to chamber 14. The vent switch is closed to the carburetor, but opened to lines 73 and passageway 43 into chamber 14 so that fuel vapors 90 may traverse this path into chamber 14. Also fuel vapors 90 from fuel tank 81 establish a positive pressure on the lower side of disphragm 39a urging the diaphragm against the action of spring 64 so that these vapors are also passed into the chamber 14. In such a case the activated charcoal or shredded rubber compound absorb these fuel vapors until the fuel system is cool enough to re-accept these vapors for condensation.

FIG. 9 illustrates the venting of the system to the atmosphere under conditions of negative pressure wherein the engine is off and has cooled down and the system fuel vapors are cooling sufficiently for condensation.

In FIG. 9, a negative pressure is established in chamber 38 (see FIG. 4) so that diaphragm 39a is flexed to the extent that fluid communication is established between the atmosphere and the fuel tank 81 over a path comprising holes 61, chamber 60, holes 54 of diaphragm 39a, passageway 37 and fuel tank line 80. By this action, any vapors within chamber 38, passageway 37 and fuel tank line 80 are forced back into the fuel tank 81 for condensation.

Inasmuch as the engine is off and the butterfly valve 78 is closed, no vacuum is supplied to the chamber 14 via passageway 43; however, fluid communication is established between the atmosphere and fuel bowl 75 since vent switch 74 is opened to the evaporative loss control device. Such communication comprises the path of hole 21, chamber 14, passageway 43 and carburetor line 73, the negative pressures established in the fuel bowl drawing air through hole 21 to force vapors over the just-traced path for condensation within the fuel bowl.

Although I have described my invention by reference to specific illustrations, many changes and modifications thereof will be evident to those skilled in the art without departing from the spirit and scope of my invention as set forth in the appended claims.

Claims

What I claim as my invention is:

1. A vacuum and pressure operated valve apparatus comprising:

a housing defining a chamber therein having a first passage opened to the atmosphere and a second passage cmmmunicating pressure or vacuum to said apparatus;

a diaphragm secured within said housing and dividing said first chamber into second and third chambers, said first passage communicating with said second chamber and said second passage communicating with said third chamber;

said diaphragm having continuous inner and outer area portions, said inner portion having a thicker cross section than said outer portion to define a diaphragm more flexible over said outer portion than said inner portion, said inner portion further having a plurality of openings adjacent its outer extremity;

a plate affixed to one side of said diaphragm and of sufficient area to extend over said openings in said inner portion to prevent communication between said first and second passages when said second passage is at pressure at least equal to atmosphere;

spring means in said second chamber biasing said plate toward said third chamber; and

means forming a third passage in said third chamber communicating with said second passage when said second passage is at pressure at least equal to atmosphere and sealed from said second passage by said inner portion when said second passage is at vacuum.

2. The valve apparatus of claim 1 wherein said inner portion of said diaphragm has a raised annular rib construction at its outer extremity in sealing engagement with said plate when said second passage is at positive pressure, said openings in said inner portion being disposed inwardly of said rib.

3. The valve apparatus of claim 2 wherein said inner portion of said diaphragm has a raised projection extending from one side at its center and said plate has a central opening which snugly receives said projection to maintain said plate in position.