US3236496A

US3236496A - Fuel flow control valve

Info

Publication number: US3236496A
Authority: US
Inventors: Aaron D Rosenstein; Richard C Edwards; Eugene P Wise; Frank L Fisher
Original assignee: Chrysler Corp
Current assignee: Old Carco LLC
Priority date: 1963-02-20
Filing date: 1963-02-20
Publication date: 1966-02-22
Anticipated expiration: 1983-02-22

Description

United States Patent 3,236,496 FUEL FLOW CONTROL VALVE Aaron D. Roseustein, Detroit, Richard C. Edwards, Grosse Pointe Farms, Eugene P. Wise, Bloomfield Hills, and Frank L. Fisher, Highland Park, Mich., assignors to Chrysler Corporation, Highland Park, Mich., a corporation of Delaware Filed Feb. 20, 1963, Ser. No. 264,996 15 Claims. (Cl. 251--357) The present application is a continuation-in-part of our copending application Serial No. 817,307 filed June 1,

1959 and now abandoned.

This invention relates to improvements in fuel flow control devices or means and in particular to carburetor float or diaphragm actuated flow control valve means and related structure operably located between the carburetor fuel bowl or fuel reservoir of an internal combustion engine and the fuel pump or other fuel supply means thereof, for regulating the inlet flow of fuel into said fuel bowl or reservoir whereby to maintain a substantially constant level of fuel in the bowl or reservoir. Such inlet flow control valve means conventionally comprises metallic port restricting means such as a tapered metallic valve member or needle movable relative to port means comprising a port and surrounding metallic seat in the body of the valve means.

The invention is specifically concerned with valve means of the above character wherein one of the valve member or seat is of elastomeric character and the other is rigid as metal and wherein the elastomeric material is essentially constituted of polymeric compounds containing a major portion of units of hexafluoropropylene and vinylidene fluoride.

A major problem encountered with conventional inlet needle valves having metal to metal contact of their port restricting elements is their inability to satisfactorily cope with minute dirt particles ever present in engine fuels which may hold the valve member open when it should be closed thereby permitting leakage of a portion of the fuel pump delivery past the valve seat and through the port to the fuel bowl. This leakage is often suflicient to raise the fuel level or pressure in the carburetor bowl and cause flooding of the carburetor through the main metering system thereof, so enriching the air-fuel mixture or charge fed to the engine as to produce stalling and/or subsequent difficult starting of the engine.

We are aware that it has heretofore been proposed to provide a valve member or needle having a flexible tip of rubber-like material working with a metallic seat or a metal needle with a rubber seat. Such constructions have, for example, been previously suggested in the patents to Adair et al. 2,414,577, Hieger 2,752,937, and Phillips 2,953,347, for the purpose of overcoming leakage of fuel in cases of severe wear or engine vibration or misalignment of the valve structure where rneta'l valve members and seats had previously been employed. However, the synthetic rubber-like materials suggested for these constructions, for instance, neoprene (polychloroprene), Thiokol (thiorubber), nylon (superpolymeric amide), Buna N (butadienea-crylonitrile) and GR-S (buta diene styrene) will not provide a satisfactory valve function and also meet the dirt problem enumerated above or even the vibration and misalignment difficulties mentioned in said prior patents. We are also aware that flexible O-ring or Washer seats as of Teflon (tetrafluoroethylene) or Kel-F (polytriflu-orochloroethylene) have been proposed for conventional sealing purposes in other applications where leakage would not be vital or effect quantative delivery. In the presence of gasoline and fuels of high aromatic character, for example, a standard reference fuel containing by volume 50% iso-octane and 3,236,496 Patented Feb. 22, 1966 ice % toluene and under the operative temperature conditions to which carburetors are conventionally subjected, for example, temperatures even in the order of 216 F, these synthetic rubber tips and valve parts of the prior art may become soft and pudgy and either stick to the valve port seat or become swollen to an extent to upset the fuel control characteristics of the carburetor and indiscriminately change the flow rate to the carburetor bowl. Similar flow rate changes occur due to heat or compression set and especially due to volume changes in the rubber-like parts brought on by alternate wetting of these parts with the fuel at carburetor operating temperatures and drying out thereof at ambient temperatures when the carburetor is not functioning.

These conditions are not tolerable in an automotive fuel supply system for automotive vehicles. They may occur where small changes in excess of about forty thousandths of an inch (0.040) occurs in the fuel level or hydraulic head from normal in the fuel bowl due to an abnormal change in poistion of the float or diaphragm. Such a change will usually result in an undesirable fuel mixture delivery to the engine fuel induction system. In this connection, it will be observed that the leverage connections, for example, between the float and valve memher are such that a total change of as little as ten thousandths (0.010") of an inch due to swelling, and/or set and/or shrinkage will result in a total change of about fifty thousandths of an inch (0.050) in the float level. In a float type carburetor, raising of the fuel level due to shrinkage or compression set of the valve member will induce over enrichment of the charge while lowering of the fuel level or decrease in the size of the port due to swelling of the valve member will produce starving of the engine intake system with consequent loss of efliciency and maximum power when most needed and even fuel cut-off when the swelling causes bottoming of the float. It is preferred that in normal service operations that the total float level change not exceed about 0.032".

We have discovered that a completely satisfactory float control valve means for carburetor fuel flow control may be provided by valve means such as the foregoing where one of the valve member or valve seat comprises a relatively soft molded and iured fluoro-elestomerii type material specifically a composition wherein the elastomeric constituent consists essentially of a polymeric compound of hexafluoropropylene and vinylidene fluoride such as a copolymer of these monomers containing 30 to by weight of hexafluoropropene monomer and 70 to 40% by weight of vinylidene fluoride monomer or a terpolymer thereof with tetrafiuoroethylene in which there is a major portion, between to 97% by weight, of units of hexafluoropropylene and vinylidene fluoride and wherein the cooperating structure of the valve means is a metal seat or metal valve member respectively. These polymeric compounds are commercially available under the trade names Viton and Fluorel. VitOn is made by the E. I, du Pont de Nemours and Company and Fluorel is produced by the Minnesota Mining and Manufacturing Co.

Valve means using these compositions as the soft needle tip or the soft seat in combination with either a rigid seat or a rigid needle tip respectively, will alleviate the aforementioned problems. They will be able to handle dirt and will have a sealing ability equivalent to that of a steel needle valve and seat even after the dirt concentration in the fuel in which the valve means functions is increased in the order of 1000% over that which could be handled by a metal needle valve and seat before flooding occurs. The valve means of our invention will be especially capable of substantially maintaining a specified fuel level in the carburetor bowl throughout the service life thereof with various fuels, in particular fuels having substantial aromatic content, for example, 15 to 60% aromatics in their makeup. A combination using a soft needle tip and metal seat provides best results in that there is less change in float position by its use.

The elastomeric composition of our invention exhibits unusual stability against undesirable swelling and shrinkage when subjected to alternate wetting in such fuels at temperature as high as 216 F. and drying at room or higher temperatures, conditions which a carburetor encounters in actual operation. The elastomeric composition used in the structures of the invention undergoes some initial swelling tendency within a short time after the parts are first soaked in fuel of substantial aromatic content after which it becomes stabilized and does not return to its original dimension even after a 96-hour period of drying at room temperature. Thereafter any changes in dimension due to alternate wetting in the fuel and drying are insufficient to adversely effect the control operation. Such total change in float level in normal service will rarely exceed twenty thousandths of an inch .020") and has not been found to be greater than 0.032 even under severe test conditions. This unusual and unexpected characteristic of the elastomeric composition used in the valve means of the invention makes it possible to either pretreat the valve means prior to assembly in a carburetor or make a compensating adjustment of the float setting before or after installation thereof in a carburetor, after which the device requires no further attention by reason of swelling or shrinkage of the parts from its stabilized condition. Rubber-like materials heretofore suggested as in the Adair et al., Hieger, and Phillips patents, supra not only exhibit such undesirable properties as prohibitive swell on initial wetting distorting the structure, compression set or shrinkage but are continually subjected to wide changes in dimension upon subsequent alternate wetting in the fuel at operating temperatures and drying thus producing float level variations in excess of forty thousandths of an inch (0.040") which are objectionable in a carburetor and are, therefore, not suited for the purposes of the present invention. With the valve means of the present invention, it is possible to effect a substantially accurate float level adjustment, maintain a substantially constant specified fuel level in the bowl, shut off the fuel supply with a minimum fuel level change upon engine shut down, handle large quantities of dirt without resulting flooding and resist undersirable sticking when closed under service or storage conditions.

An object of the invention is therefore to substantially inhibit the effect of dirt particles on the regulation of fuel flow into the bowl or reservoir of internal combustion engine carburetors.

Another object is to inhibit undesirable changes in fuel level within a carburetor fuel bowl due to the changes in level of the fuel bowl float caused by marked changes in the dimensions of the valve structure during operation by alternate wetting in the fuel and drying.

A further object of the invention is to provide a carburetor inlet fuel flow control or regulating valve means in which the valve member or valve port seat thereof comprises a soft molded and cured synthetic elastomeric material essentially constituted of polymeric compounds containing a major portion of units of hexfluoropropylene and vinylidene fluoride and the other part of said valve means is of metal.

A specific object is to provide valve means as in the preceding object wherein the valve member is a tapered needle tipped with said elastomeric composition.

Further objects and advantages of the present invention will become apparent from the following description and the drawings in which:

FIGURE 1 represents a cross sectional view a carburetor float bowl and a fuel flow regulating valve means embodying the invention and wherein the movable valve member or needle is tipped with the elastomeric composition of the invention;

FIGURE 2 represents a transverse cross sectional view of the valve structure of FIGURE 1 taken along the line 2-2 thereof in the direction of the arrows;

FIGURE 3 represents a variation of the tip attaching structure of the valve of FIGURE 1;

FIGURE 4 represents another variation of the valve structure wherein the needle mounts an O-ring;

FIGURE 5 represents a valve means embodying the invention and constructed according to the flexible seat principle;

FIGURE 6 represents a variation in the valve means structure of FIGURE 5;

FIGURE 7 represents a view showing the effect of minute dirt particles in the fuel when valve means employing metal or other non-flexible material needles and seats are employed;

FIGURE 8 is a graphical representation showing by a series of connected points the swelling and shrinkage characteristic in percent by volume versus time of the composition employed in the valve means of the inver1- tion as compared to materials of the prior art when subjected to alternate wetting (aging) in a standard reference fuel of 50% toluene and 50% iso-octane at 216 F. for 48 hours and air drying at room temperature for 96 hours; and

FIGURE 9 is an enlarged fragmentary portion of the structure of FIGURE 3 embodying a further structural feature and designating by the letter A the distance from the metal body of the needle against which the shoulder on the elastomeric tip may seat to the line of contact with the seat when the tip fills the seat opening. For purposes of illustration only the elastomeric tip in this figure has its shoulder backed off slightly from the metal body.

Referring to FIGURE 1, a carburetor float bowl 10 is provided with a float 12 which is secured to hanger means 14 pivotally mounted on the bowl defining wall structure 15 at 16 and is provided with a valve needle actuator portion 18. As the float 12 moves up or down the actua tor portion 18 will move either to the right or to the left as viewed in FIGURE 1. It will be understood that in some carburetor structures the actuator may operate by a diaphragm (not shown) in which case the actuator or diaphragm may be spring loaded. An insert or needle housing structure 20 is threadedly received in a portion of the bowl structure 15 and is provided with a recess 22 which houses the valve needle 24. This needle 24 is provided with hearing ribs 26 which provide the needle with several flow paths 28. Secured to a reduced end portion 30 of this needle in FIGURE 1 is a relatively soft, flexible (i.e. resilient) tip 31 made of the elastomeric composition described above which is secured to the end 30, preferably by an integral molding procedure whereby locking means such as apertures 32 within the reduced end portion of the needle are filled with the uncured elastomeric material which when cured as by heat is locked to the needle end due to the projection of the cured material into these apertures 32.

As shown in FIGURE 3 the locking means may be in the form of an internal thread 33 and the elastomeric tip 31 may be integrally molded therein in essentially the same manner as shown in FIGURE 1. It is noted that especially in the structure of FIGURE 3, the needle tip) could be readily replaced by unscrewing it from its; threaded receptacle. To facilitate optimum seating of the tip 31 the forward end of the thread 33 in the metal. body 24 is as seen in FIGURE 9 cut away as by the: chamfer 33a. A fuel inlet port 34 is provided in insert; 20 and is adapted to be operatively connected to fuelt source such as the tank and fuel pump (not shown) to, receive fuel therefrom. The needle 24 in FIGURE 1* cooperates with a rigid valve seat designated 36, general-. ly of metal, which may be sharp as shown in FIGURES l and 9 or may have a slight bevel as is shown in FIG- URE 3. Generally, the sharper the seat the less pressure is required to seat the needle tip in the presence of dirt particles.

FIGURE 4 shows a modification where the needle 24 is provided with an annular groove 38 adjacent the reduced end of the needle and with a flexible fiuorohydrocarbon rubber ring 40 of the elastomeric composition of the invention frictionally secured in this groove. The valve seat 36 on the body portion 20 in FIGURE 4 may be sharp as shown in FIGURE 1 or slightly tapered as shown in FIGURE 3.

FIGURE 5 shows the needle 24 provided with a conventional tapered metal tip 42 but the body 20 is provided with a circular groove 44 in which an annular flexible fluorohydr-ocarbon rubber ring seat 46 of the elastomeric composition of the invention is frictionally secured. The ring may be inserted in to the groove 44 by reducing its diameter by pressure and then allowing it to snap out to frictionally engage the sides of the groove 44.

FIGURE 6 shows a flexible seat 48 of the elastomeric composition of the invention in the form of an annular washer which is secured against a shelf or ledge portion 50 of the body 20 and this washer 48 is secured into the body 20 by means of a retaining insert 52 frictionally secured in recess 22. As in FIGURE 5, the needle tip 42 is rigid and preferably of metal.

Although the forms of the invention shown in FIG-

URES

4, 5 and 6 have practical application to fuel feeding devices for many low powered gasoline driven engines the structures in FIGURES 1 and 3 are found to be preferred for high volume automotive vehicle carburetors since in the ring and washer types some form of separate retainer is found desirable or necessary for the elastomeric structure. Moreover, the O ring and washer forms exhibit some difficulty of continually remaining concentric and true relative to the valve member tip.

The effect of dirt particles 54 as shown in enlarged scale in FIGURE 7 is particularly significant when both parts of the valve, seat 36 and needle tip 42, are made of an inflexible material such as metal.

The polymeric compound providing the elastomeric constituent of the soft molded and cured portion of the valve means of the invention is described in and may be prepared in the manner described for example in Patent 3,051,677 of O. R. Rexford granted August 28, 1962 and in Patent 2,968,649 of I. R. Pailthrop et al. granted January 17, 1961. These elastomeric polymers may be suitably compounded With conventional curing and filler materials for hardening and reinforcing the molded and cured product. Examples of these are given in these patents. A preferred curing agent is ethylenediamine carbamate and a preferred filler thermal carbon black. However, other curing agents such as hexamethylene diamine carbamate, peroxide, and polyfunctional amines and other fillers such as silica, precipitated whiting, and blame fixe may readily be used.

The amount of filler may vary considerably depending upon the degree of hardness and viscosity of the base polymer. It is preferred that the quantities be selected to give a hardness in the cured product of about 60 to about 92 Shore A durometer reading preferably 75 to 85, the softer side of this range being considered best for molding purposes. Thus the composition may for example utilize between 0 to 90 parts by weight of filler for each 100 parts by weight of uncured elastomeric compound, and between about /2 to 2 parts by weight of curing agent for each 100 parts by weight of uncured elastomeric compound.

Typical formulations which have been found to be especially suitable for the purposes of this invention are set forth below. These are by way of example only and not of limitation:

6 EXAMPLE I Grams Copolymer of hexafluoropropene and vinylidene fluoride 1 1000 Magnesium oxide 150 Thermal carbon black 3 550 Ethylene diamine carbamate 4 8.5

Available as Viton A-HV. Viton A-HV has a Moody viscosity of about 15 and a Shore A durometer hardness when cured in the range 727S.

2 Available as Maglite D from Merck & CO., Inc.

3 Available as Thermax MT from R. '1. Vanderbilt Co.

iAvailable as Dial: #2 from E. I. du Pont de Nemours &: Co., Inc.

The above composition when molded and cured as hereinafter described has a Shore A durometer hardness of about 86.

EXAMPLE II Grams Copolymer of hexafluoropropene and vinylidene fluoride 5 1000 Magnesium oxide 200 Thermal carbon black 500 Hexamethylenediamine carbamate 6 10 5 Available as Viton A or Fluorel.

Available as Diak #1 from E. I. du Pont de Nemours 8: 60., Inc.

This copolymer has a Moody viscosity of about 65:6 and a Shore A durometer hardness when cured of about 72 to 78.

This composition when molded and cured has a Shore A durometer hardness of about 82.

EXAMPLE III Grams Terpolymer of hexafluoropropene, vinylidene fluoride, and tetrafluoroethylene 1000 Magnesium oxide 150 Thermal carbon black 550 Ethylenediamine carbamate 8.5

Available as Viton B. It has a Shore A durometer hardness when cured of about 72 to 78.

These typical formulations may be compounded and molded according to standard rubber procedures as follows for the compounding of Formula I above:

The four ingredients are weighed out separately according to the above formulation. The Viton A-HV raw polymer is broken down for approximately 5 minutes on a cold (45 F.) rubber mill. The magnesium oxide is added and milled-in for approximately 3 minutes. The thermal carbon black is then gradually added and the batch milled until complete dispersion has taken (approximately 8 minutes). The ethylenediamine carbamate is added and the batch milled for 5 additional minutes and then removed in sheet form from the mill.

A pre-form approximately the volume of the elastomer in the final part is separated from the batch and placed on, and partially in, the heated (300 F.) cavity of the forming mold. The metal needle body is placed into the mating cavity in the other heated plate of the two-plate mold. The mold is closed and put in a curing press (300 F.) which applies a load onto the mold so that the pressure on the entrapped rubber is approximately 1000 p.s.i. The initial cure at 300 F. lasts for 30 minutes.

The part is removed from the mold and placed, unsupported, in a 400 F. oven for 24 hours for post curing. The part is then :cooled and any excessflash removed.

FIGURE 8 shows in graph form by a series of connected points derived by test, the volumetric changes (as determined by ASTM standard procedures) that occur when standard ASTM volume swell specimens 1 x 2" X 0.075" thick of the compositions used in the invention and of other compositions suggested as valve or other sealing means are aged, alternately, for 48 hours in a high aromatic ASTM standard reference fuel (50% by volume toluene and 50% by volume iso-octane) at a temperature of 216 F. (the approximate boiling point of the fuel), and then dried in air at ambient temperature for 96 hours and this cycle repeated at least two more times, determinations being made at the end of 48 hours when aging in the fuel and at the end of 24 hours and 96 hours respectively during drying. Each determination is plotted as a point in the graph and the points connected. The connecting lines are used solely for ease of comparing the results obtained with different specimens. Moreover, it is to be noted that although a determination of swell volume change is not made until the end of a 48 hour period it may well be that the specimen actually reaches its maximum swell in a lesser time. In the case of the compositions used in the present invention the maximum swell condition is substantially attained in 4 to 6 hours.

In FIGURE 8 the full line B records the results obtained with a composition of the invention set forth in Example I. The full line BB records the results obtained with a similar composition containing somewhat less filler (420 parts per 1000 copolymer) and somewhat softer (about 77 Shore A durometer). The dash, dash, dot line C records the result when the specimen was a proprietary commercial composition using thiorubber (Thiokol) as the elastomer and having the following approximate composition in parts by weight:

Thioru-bber (Thiokol ST) 93 Stearic acid 0.5 Organic polysulfide liquid polymer (LP-3) 7 p-Quinonedioxime (G-M-F) 1.5 Zinc oxide 0.

Furnace carbon black (Philblack A) 40 Fine furnace carbon black (Statex B) 40 The dash, dot, dot line D records the results when the specimen was a proprietary composition using Buna N rubber as the elastomer and having the following composition in parts by weight:

Buna N rubber (50% Paracril B, 50% Paracril n-Cyclohexyl-Z-benzothiazole sulfenamide (Santocure) 0.30

The long dash, dot, long dash line E records the results when the specimen was a proprietary composition using a copolymer of chlorotrifiuoroethylene and vinylidene fluoride as the elastomer and having the following composition in parts by weight:

Copolymer of chlorotrifiuoroethylene and vinylidene fluoride (Kel-F 3700) 100 Zinc oxide 1O Di-basic lead phosphite (Dyphos) 10 Hexamethylenediamine carlbamate (HMDA-C") 3 Furnace carbon black (Philblack O) 25 The dash, dash, dash line F records the results when the specimen was a proprietary composition using polychloroprene as the elastomer and having the following composition in parts by weight:

Polychloroprene (50% Neoprene W, 50% Neoprene WHV) 100 Buna N rubber (Paracril B) 50 Zinc oxide Sulfur 1 Thermal carbon black (Thermax MT) 20 Furnace black (FEF black) 40 Stearic acid 1 Polymerized trimethyldihydroquinoline (Age-Rite Resin D) 1.5 Tetramethylthiuram mono-sulfide (Thionex) 0.6 Dioctyl phthalate (DOP) l0 Coumarone-indene resin (Picco 25 Resin) 10 n-Cyclohexyl-Z-benzothiazole sulfenamide (Santocure) ()3 Referring again to FIGURE 8, each two squares plotted as abscissa represents a 24 hour period or one day and each square measured as an ordinate represents a 4 percent change in volume. Moreover, all measurements above the horizontal zero base line represents percent volume swell, and those below the zero base line represent percent volume shrinkage from the condition of the material as initially molded and cured. A consideration of the recorded data of tests on the Viton specimens B and BB indicates that these specimens on soaking for 48 hours in the standard reference fuel increased in volume by 16 and 20% respectively. This substantial change in volume if repeated on continued alternate drying and Wetting would have rendered this composition unusable for the purposes of the invention. However, as seen, subsequent alternate periods of 96 hours of drying at room temperature and of 48 hours soaking in the reference fuel indicate a surprising pattern wherein each of the Viton specimens remained in a range of approximately a 4% change in volume from their condition at the end of the initial 48 hour soak. Moreover, each Viton specimen at no time exhibited a volume change substantially exceeding its condition at the end of the initial 48 hour soak and at no time indicated shrinkage to a volume below that in its molded and cured condition prior to soaking. As previously described these surprising results make it possible when employing Viton in the valve means of the invention to anticipate the initial swell and to preset the carburetor to compensate for the initial swell so that subsequent volumetric changes in actual operation stay within the approximate 4% volume range. A consideration of the volumetric changes for specimens B and BB also show that changes in the percentage of filler do not materially alter the effects obtained upon alternate soaking and drying and that the softer material (less filler) only has a somewhat larger initial change in volume.

A similar consideration of the volumetric effects of alternate drying and swelling on the other materials plotted in FIGURE 8, clearly shows that the Thiokol rubber has a volumetric change of approximately 29% in the initial 48 hour period of soak and exhibits a volumetric shrinkage of approximately 26% in the 96 hours of drying following the initial soak and that this condition is followed by a volumetric swell of at least 20% in the next 48 hours of soaking and approximately 25% shrinkage thereafter on 96 hours of drying and so on. Moreover, the pattern of swelling and shrinking is erratic. The same type of pattern is evident for Buna N rubber as represented in the graph D, Kel-F rubber as shown in the graph E and neoprene as shown in the graph F from which it will be evident that each of these materials other than Viton had extremely high changes in percent volume upon alternate soaking and drying and had a pattern of behavior completely foreign to that obtained with Viton composition employed in the invention. In many instances the percentages of change in volume after the initial 48-hour soak even exceeded the initial change.

The table below presents data obtained by actual soak and dry tests of Viton needles as shown in FIGURE 9 wherein the Viton tip is held in the body of the movable valve member 24 by a thread 33, the tip having a cone angle of 70. These Viton tips were prepared from the compositon of Example I which exhibited the volumetric changes shown by the graph B in FIGURE 8. Similar tests were made with tips of KelF and Thiokol composition discussed in connection with FIG- URE 8, and only initial soak readings taken for Buna N and neoprene. In the table column (a) records the distance (A) measured from the end of the metallic body of the needle to the plane of contact of the elastomeric cone of the valve needle with the metallic valve seat for each of the materials for which data is given in FIG- URE 8. Moreover, column (b) records the distance (A) after a 8-hour period of soak in the standard reference fuel; column (c), the change in inches between the values in columns (a) and (b). Columns (d), (f), (h) and (7') record the value for (A) following subsequent alternate periods of drying and soaking and columns (2), (g), (i) and (k) give the respective differences for (A) between the value in (b) and those respectively in (d), (f), and (h) and (i). It will be noted that in no instance in the case of Viton is the dimensional change from the (b) reading more than .003" and the difference between the highest and lowest reading is only .006". This would correspond to a maximum change in the float level once the initial volumetric change had been compensated for of .030", well below the allowable limit. No additional reading beyond column (b are indicated for any of the materials other than Viton, Thiokol and Kel-F and as to the latter two materials only one further reading was taken after the initial 48-hour soak, to wit, that after a 96-hour period of drying. This was because first, some of the material such as neoprene and Buna N became badly distorted on initial soaking and further testing was useless. Secondly, with respect to Thiokol and Kel-F it will be apparent from the volumetric changes recorded in FIGURE 8 and the readings recorded in columns (b), (c), (d) and (e) in the table below that the changes in dimension (A) between that recorded after the initial soaking and that recorded after the first drying are so great for these materials that they far exceed the allowable float level limits set forth for satisfactory carburetor control. Thus, it will be seen that the dimensional changes recorded for each of the materials C, D, E and F in FIGURE 8 follow the same pattern in the case of valve needles tipped with these materials. Assuming that compensating carburetor settings were made for the initial swell change in Thiokol and Kel-F noted in column (c) in the table below, it will be apparent that the dimensional change recorded in column (e) is substantially as great as that in column Furthermore, if these values in (c) and (e) be multiplied by (5:1-leverage in the connecting link system between the needle and float) the result in values would be at least 5 times as great as any allowable float variation.

From the foregoing description it will be apparent that a novel valve means has been provided from which the many advantages described above are secured. It will be understood that modifications and different arrangements may be made other than herein disclosed without departing from the spirit and intent of the invention. All such modifications, arrangements and changes coming within the purview of the accompanying claims and equivalents are therefore contemplated.

We claim:

1. A liquid fuel flow regulating valve means comprising port means including a valve seat and port restricting means including a valve member, said valve seat and valve member being relatively movable for effecting engagement and disengagement thereof, one of said valve seat and valve member being of a relatively soft elastomeric material and the other being of a hard and relatively inflexible material, said elastomeric material being essentially constituted of the cured product of a polymeric compound containing a major portion of units of hexafluoropropene and vinylidene fluoride.

2. A fuel flow regulating valve means as claimed in claim 1 wherein the composition of said valve member includes an inert filler material in minor amount.

3. A fuel flow regulating valve means as claimed in claim 1 wherein said polymeric compound is a copolymer of hexafluoropropene and vinylidene fluoride.

4. A fuel flow regulating valve means as claimed in claim 1 wherein said polymeric compound is a terpolymer of hexafluoropropene, vinylidene fluoride and tetrafluor-oethylene.

5. A fuel flow regulating valve means as claimed in claim 1 wherein said valve member is of said elastomeric material.

6. A fuel flow regulating valve means as claimed in claim 1 wherein said valve seat is of said elastomeric material.

7. A liquid fuel flow regulating valve means for use in carburetors for controlling the inlet flow of fuel into the carburetor bowl comprising a valve body having an inlet port therein defined by an annular valve seat, a valve member having bearing ribs thereon for making sliding contact with said valve body and providing fuel flow paths between said valve member and said body, said valve member also having a conical tip adapted to control the flow of fuel through said inlet port by adjusting the flow area thereof, one of said valve seat and tip being of a relatively soft elastomeric material and the other being of a hard and relatively inflexible material, said elastomeric material being esentially constituted of the cured product of a polymeric compound containing a major portion of units of hexafiuoropropene and vinylidene fluoride.

8. A fuel flow regulating valve means as claimed in Dry 48 Hr. 96 Hr. 48 Hr. 96 Hr. I 48 Hr. Material (a)* Soak (0) Dry (e) Soak (g) Dry (1) Soak (k) (d) (I) (J) B. Viton 036 050 014 .048 002 053 003 .047" 003 053" 003 C. Thiokol 044" 081 037 057 024 D. Buna-N 024 106 .082 E. Kel-F .025 .070 +.045 .045 025 .024" 133 +.109

*Sarne mold was used for all specimens. (0.) Distance (A) before any soak.

Variation in initial reading of dimension (A) is due to variability in mold shrinkage.

(b) Distance (A) after initial period (48 hours) of soaking in standard reference fuel at 216 F.

(c) Difierence in inches between (a) and (b) (d) Distance (A) after subsequent 96 hours (6) Difierence in inches between (d) and (b). v v

(f) Distance (A) after a second 48 hour period of soaking as in (b). (9) Difference in inches between (1') and (b).

(h) Distance (A) aiter a second 96 hour period of drying.

(i) Diflerence in inches between (h) and (b).

(j) Distance (A) after a third 48-hour period of soaking.

(/1) Difference in inches between (j) and (b).

of drying at room temperature.

claim 7 wherein said valve member tip is of said elastomeric material.

9. A fuel flow regulating valve means as claimed in claim 7 wherein said valve seat has a sharp bearing surface and resilient and of said elastomeric material.

10. A fuel flow regulating valve means as claimed in claim 8 wherein said valve member has a threaded bore and said conical tip has a coaxial threaded shank releasably engaged in said threaded bore.

11. In a carburetor having a liquid fuel reservoir, a fuel passage connecting with said reservoir, a float in said reservoir operable in response to the level of fuel in said reservoir, a valve seat formed in a portion of said passage, and a valve member operatively connected to said float and having a seating surface cooperating with said valve seat to close and to open said passage, the improvement which consists in one of said valve seat and seating surface being of a relatively soft elastomeric material and the other of a relatively hard and inflexible material, said elastomeric material being essentially constituted of the heat cured product of a polymeric compound containing a major portion of units of hexafluoropropene and vinylidene fluoride said elastomeric surface being adapted to temporarily embed dirt particles while inhibiting leakage of fuel past said seat when the valve is closed and having a volume change upon alternate wetting by the fuel and drying insuflicient to produce a change of more than .032" in the fuel level in said reservoir from normal.

12. A liquid fuel flow regulating valve means for use in carburetors for controlling the inlet flow of fuel into the carburetor bowl comprising a valve body having an inlet port therein defined by an annular valve seat, a valve member slidably mounted in said body and movable relative to said inlet port and having bearing ribs thereon for making sliding contact with said valve body and providing fuel flow paths between said valve member and said body and a flexible ring of relatively soft elastomeric material secured over an end portion of said valve member and adapted to selectively contact or be spaced from said valve seat for adjusting the flow area of said port said elastomeric material being essentially constituted of the cured product of a polymeric compound containing a major portion of units of hexafluoropropene and vinylidene fluoride.

13. A liquid fuel flow regulating valve means for use in carburetors for controlling the inlet flow of fuel into the carburetor bowl comprising a valve body having an inlet port therein defined by a passage in said body and a resilient O-ring seat surrounding said passage and a valve member slidably mounted in said body and movable relative to said seat for adjusting the flow area of said port, said valve member having bearing ribs thereon for making sliding contact with said valve body and providing fuel flow paths between said valve member and said body, and said O-ring being of elastomeric material essentially constituted of the cured product of a polymeric compound containing a major portion of units of hexafluoropropene and vinylidene fluoride.

14. A liquid fuel flow regulating valve means for use in carburetors for controlling the inlet flow of fuel into the carburetor bowl comprising a valve body having an inlet port therein defined by a passage in said body and an annular seat surrounding said passage said seat being of a hard and inflexible material, a valve member having a body portion with bearing ribs thereon for making sliding contact with said valve body and providing flow paths between said valve member and said body, and said member having a conical tip secured to the body thereof movable relative to said seat to control the flow through said inlet port by adjusting the flow area thereof, said seat being substantially complementary in shape to said tip and said tip being of elastomeric material essentially constituted of the cured product of a polymeric compound containing a major portion of units of hexafluoropropene and vinylidene fluoride.

15. A liquid fuel flow regulating valve means for use in carburetors for controlling the inlet flow of fuel into the carburetor bowl comprising a valve body having an inlet port therein defined by a passage in said body and a resilient seat surrounding said passage, said seat being constituted by a substantially flat annular washer, there being an annular recess in said body surrounding said passage for receiving said washer, and a ring securing said washer in said recess, and a valve member slidably mounted in said body and movable relative to said seat for adjusting the flow area of said inlet, said valve member having bearing ribs thereon for making sliding contact with said valve body and providing fuel flow paths between said valve member and said body, said washer being of a relative-1y soft elastomeric material essentially constituted of the cured product of a polymeric compound containing a major portion of units of hexaflouropropene and vinylidene fluoride.

References Cited by the Examiner UNITED STATES PATENTS 2,414,577 1/1947 Adair et al. 137434 2,645,449 7/1953 Gulick 251360 X 2,700,307 1/1955 Thoresen 251360 X 2,701,119 2/1955 Smith 25136O X 2,704,650 3/1955 Rand 251-357 X 2,865,596 12/1958 Monnig 251368 X 2,890,711 6/1959 Parker 137434 2,930,401 3/1960 Cowan 251368 X 2.933,481 4/1960 Rugg 26087.7 2,941,987 6/1960 Dewey 26087.7 2,953,347 9/1960 Phillips 251361 2,955,104 10/1960 Smith 26087.7 2,968,649 1/1961 Pailthorp 26041.S X 3,013,576 12/1961 Read 137449 X 3,051,677 8/1962 Rexford 260--41 OTHER REFERENCES Industrial and Engineering Chemistry: volume 49, No.

10, October, 1957, pages 1687l690.

Rubber Age: 82, October 1957, pages l02104.

M. CARY NELSON, Primary Examiner.

LAVERNE D. GEIGER, Examiner.