US2250674A - Diaphragm for fuel pumps - Google Patents

Description

July 29,1941. QMCBURNY' g 2,250,674

DIAPHRAGM FOR FUEL PUMPS Filed Nov.- 12, 1938 l'lldl? |NvENToR- y BY 5C c C'Tv 7 ARNEY Patented 'July 29, 1941 .UNITED sTATsls PATENT Vorinar.v

i 2,?5074 l s i Dorman Mcurney, Newburgh, N. Y., assignor to E. I. du' Pont de Nemours and Company, Wilmington, Del, a corporation of Delaware Application November 12, 193s, semi No. 240,203

1 claim. (ci. isi-157) This invention relates to pump diaphragms and more particularly -to diaphragms such as are used in pumps for feeding gasoline and similar `liquids to internal combustion engines.

In the manufacture of diaphragms for fuel pumps it has been proposed to coat fabric materials with certain coating compositions to obtain properties which are conducive to long life.

soluble in any liquid fuel such as gasoline, benzol.

alcohol, etc. or mixtures thereof. The pliability oflthe coated fabric must not stiften appreciably upon prolonged use and must .have a minimum of change in exibility at the extreme operating temperatures.

It has been proposed to employ drying Qil compositions and blends thereof as the filxn-forming material in the manufacture of fuel lpump diaphragms. While this type of coating has some of the-desiredproperties for application as fuel pump diaphragm material it is not completely satisfactory. Such-coatings have a tendency to crack when vsubjected to flexing in cold weather.

As a result of this behavior the fuel pump diaphragm failure occurs on starting the motor in cold weather. It is also common practice to-employ aplu'rality of layers of drying oil coated fabric to assemble. a fuel pump diaphragm. Sucha laminated assembly is objectionable in 'general advance in the art which will appear hereinafter are also contemplated.

The objectives of this invention are accomplished by treating a closely woven textile fabric with a plasticized polyvinyl alcohol composition or molding an unsupported iilm of plasticized polyvinyl alcohol to the desired shape.

, In Figure 1, which is a cross-section view of a fuel pump diaphragm assembly, Vl representsa laminated polyvinyl alcohol diaphragm, 2 cork gaskets located at the perifery of diaphragm l, 3 and 3' cup-like metal supports for the dlaphragm I held in position by washers 5 and 6'. and bolt il, and l represents the plunger arm' which vlbrates the diaphragm. In Figure 2, which is a plan View of the cork gaskets 2, 8 represents openings which register with the top and 'bottom housing (not shown) for the diato air and liquid fuels should be as nearly perfeet as possible. This is accomplished by thorough impregnation of a suitable fabric such as grade A airplane cloth with an aqueous plasticized polyvinyl alcohol solution. Such plasticized compositions as disclosed by Watkins in application led November 1'7, 1937; S N. 175,041 have been found advantageous in this'connection. The plasticized polyvinyl alcohol composithat at the upper temperature range of cperation the coating on the individual plies has a tendency to soften and become adhesive thereby fusing the individual plies into a composite' or combined structure. 'Ihe multi-ply diaphragm is thereby greatly stiifened and results in unsatisfactory behavior of the fuel pump.

A- primary object of this invention is to provide a fuel pump diaphragm which will retain its i tion is squeezed through the pores or interstices of the fabric to give a verycomplete union between the fabric and polyvinyl alcohol.

Grade A airplane fabric is'an example of one that is very suitable and is an unbleached mercerized cotton fabric of two ply yarn having at least 80 warp and 80 llerthreads per inch, the

welghtbeing 4.5 ounces per square yard. The fabric has a minimum tensile strength of 80 pounds per inch width- (strip method). The fabric is impregnated or coated on both sides .with a plurality ofcoats of any one of the examoriginal pliability, at the extreme operating temperatures after prolonged use.. A further object of this invention is to provideV a fuel pump dia-V phragm having a coating material, which is insoluble in liquid fuels. such as, e. g.. gasoline.` benzol, and the like. A still further object is to' provide a fuel pump diaphragm consisting of a plurality of fabric layers impregnated with a composition which will not coalesce at high temv peraturesand cause the separated layers to become fused or amalgamated into ya composite ples listed below in such a manner that' the com'- position permeates the fabric and the'coating or impregnant meets in the interstices. The fabric" l is actually imbedded in the polyvinylalcohol coating. The amount of coating` may vary over rather wide limits depending upon how the materialis to be used. In the preferred embodiment the 'amount vof coating or impregnant may vary between 6.0 ounces and 9.0 ounces (based article. These and other objects as 'well as a` f on nonvolatile components) per square yard;

however, some variation is permissible. 'I'he diaphragm assembly consists' of one or more layers of the treated fabric the thickness of the separate layers being such that 0? the assembly is' approximately .045".4 m

the total thickness -pmuceitmsbeenfcumderlrabietousethree separate layers of the treated fabric. each layer having a thickness of approximately .015". If asingleply diaphragmistobeusedthe total thickness (coating plus fabric) .should be approximately .045".

Further explanation of the invention is given l in the following detailed description and illustrative speciilcexamples, in which the parts are given by'weight. Throughout the examples the proportions of the ingredients on a solids basis (i. e., in the absence of volatile liquidslis indicated by enclosing the percent of each solid material in parentheses.

In the case of Examples I, II and III the components of the compositions are added together in a suitable container and subjected to a simple mixing operation until a homogeneous solution is obtained. After the composition has been thoroughly mixed it is appliedlto both sides of the textile fabric heretofore described by conventional means such as dipping, spraying, doctor coating, etc. It is very important that the ilrst coats on each side of the fabric be driven into the pores or interstices of' the fabric for the reason heretofore mentioned. After the coating has been dried the diaphragm is die cut to the desired shape and is then ready for use.

It has been found that if the fabric Vhas beenY wetted with a 10% aqueous solution of saponin and dried, a single application of plastlcized polyvinyl composition may be applied and it will penetrate the interstices of the fabric and even run out on the other side although the position of the doctor knife or the method of applying the vinyl alcohol is usually controlled so that this does not take place, although complete impregnation is desirable. y

Example IV Per cent Polyvinyl alcohol 50.0' Ethanol formamide 50.0

These ingredients are milled together and molded at a temperature atabout 135 C. and under a pressure of 300 pounds per square inch forabout ten to fifteen minutes. The illm so produced is suitable for a fuel pump diaphragm. The polyvinyl alcohol in this example had a saponiilcation number of 200. v

Example V Per cent Polyvinyl alcohol 80.0 Ethanol formamide 20.0

Example VI Per cent Polyvinyl alcohol 79.0 Ethanol formamide ...v.. 19.8 5 Water soluble dye 0.2` Carbon black l 1.0

Ijhe polyvinyl alcohol in this example has a saponiilcation number of 250. A diaphragm film was prepared from this material in the same manner as indicated in the previous example.

Example VII I Per cent Polyvinyl alcohol 50.0 Ethanol acetamide -50.0

The polyvinyl alcohol in this example is the same as in the previous example and the materials were milled together and molded at a temperature of 135 C. under a pressure of 750.

pounds per square inch.

` Example Vm l Per cent Polyvinyl alcohol 60.0 Ethanol acetamide 40.0

The polyvinyl alcohol and the method of procedure in this example ls the same as in the previous example.

Example IX l Per cent Polyvinyl alcohol 70.0 Ethanol acetamide s 30.0

In this example the ingredients and the method' of molding a film are the same as in the previous example.

' Example X n f Per cent Polyvinyl alcohol 68.8 Ethanol acetamide 30.0 Water soluble dye 0.2 Carbon black 1.0

The polyvinyl alcohol in this example had a saponiilcation number of and 'a iilm was molded from this composition at, 140 C. under a pressure of 1000 pounds per square inch. Otherwise themethod of procedure is the same as in the previous examples.

Example XI A y Per cent Polyvinyl alcohol 74.8 Ethanol formamide 20.0 Dye 0.2 -F'erric oxide 5,0

The polyvinyl alcohol in this example is the same as in the Iprevious example and the method of mixing and preparing a film is the same except that a slightly lower temperature may be used in molding if desired.

In the above examples the polyvinyl alcohol is prepared by saponifying polymerized vinyl acetate. Widely different properties may be imparted to the alcohol by controlling the degree of saponification. For example the maximum water solubility of polyvinyl alcohol is observed in one having a saponiilcation number of and which is saponifled to an extent that the The ingredients .in this example are the same' v as in the previous example and are milled together and molded at a temperature of C.

and under a pressure of 1000 pounds per square inch for ten to fifteen minutes.

amount of acetate converted to alcohol is about 88%. In the above examples the polyvinyl alcohol having asaponiflcatlon number of 200 represents a polymer which has been converted to the. extent of 81.5% alcohol. In-the case of the alcohol having a saponiilcation number of 250, the conversion is 76.0% and in the case of the 'drocarbona carbon tetrachloride,

an unsupported film of plasticized polyvinyl alcohol. It is sometimes desirable to mold a. supporting gasket of dissimilar material, such as a cork composition, around the-edge `of the diaphragm to prevent cold flow of the film around the edges when under pressure. In this case the dry polyvinyl alcohol and plasticizer are mixed together andplaced in a mold, then subjected to heat and pressure whereby a homogeneous lm of plasticized polyvinyl alcohol is obtained. A nlm of approximately .045" thickness is satisfactory for this purpose. However, lms of greater or lesser thicknesses may be used, de-l pending upon the operating conditions of the pump. f

The plasticized polyvinyl alcohol compositions may also be calendered onto the textile fabric base, which may or may not be previously impregnated with a polyvinyl alcohol' composition in a manner similar to that employed inthe rubber industry. In this case the polyvinyl alcohol and plasticizer are subjected to a mixing operation at an elevated temperature until a doughy plastic mass is obtained and then calendering the plastic mass on each side of the fabric, squeezing the said mass into the pores or interstices of the fabric.

In still another embodiment of the invention l' the plasticized polyvinyl alcohol composition may be formed into sheets. A layerv of textile fabric is sandwiched between two sheets of the plasticized polyvinyl alcohol and the assembly subjected to the iniiuence of heat and pressure, whereby a composite integral union is obtained with the than cotton fabric where a supporting base is desired. In this connection nely woven wire fabrics having the proper degree of suppleness may be used as the supporting base for the polyvinyl alcohol.

bons, esters, ketones, carbon disulde and most,

other organic solvents. For example, the diaphragms of the invention are ideally suited for use in diaphragm-valves of the type where the diaphragm is exposed to the action of organic solvents. In addition polyvinyl alcohol coated ,Y fabrics are useful as "draw sheets` for rotary printing presses. The polyvinyl alcohol compositions may also be applied to unwoven felts to produce a "Printers Blanket for the rotary type printing presses. In addition to being resilient the polyvinyl alcohol fabrics are non-penetrable by printing inks and ink removers (such as hyetc.) and a non-cracking, non-peeling flexible. surface capable of withstanding millions of pressure cylinder), which properties'are extremely insoportant for draw sheets and printers blankets employed in rotary printing presses. For this purpose fabric or felt is usually coated on one side y only and the polyvinyl alcohol is applied in suiiicient quantity to obtain a smooth uninterrupted, continuous nlm.

An important advantage of this invention is the provision of a fuel pump diaphragm which l0 will retain it original flexibility-after prolonged,

use and further advantage isl the absence oi' any. -substantial variation of flexibility atl thev extrei'xyie operating temperatures. A still further advan'- tage is the fact that the coatings described are so completely insoluble in fuel liquids such as gasoline, benzol, and other hydrocarbons that they do not exhibit any swelling upon prolonged exposure thereto. -A still further advantage is that.

with a fuel pump diaphragm consisting of a plurality of separate layers the coating on the separate layers does not coalesce under operating conditions and become stiif.

The term polyvinyl alcohol as used herein and in the appended claim denotes not only the com- ,25 pund but it also includes derivatives thereof in which t the hydroxyl groups have been partially substituted byother groups such as ester, ether, or

acetal groups in proportions insuincient to render the compound insoluble in water. Such deriva- 35. tives may be prepared conveniently by the partial 40 capable of reacting with hydroxyly groups. In the I case of the partial saponiilcation products of polyvinyl acetate it has been found that products having a saponification number of less than about 300 (corresponding to approximately 70 mole per cent conversion of the acetate to the fabric embedded in the plasticized polyvinyl alco hol sheets. It'is also contemplated to use other alcohol) .are soluble in water and are particularly well suited for the purposes of-the present inven- V tion.

` In the preparation of fuel pumps the impreg-4 nated fabric is cut usually by die stamping into a circle which may or may not have anarrow `cork gasket at its perifexy. A small hole is also cut at the center of the diaphragm through which a `metal member is inserted. This may be a rivet or a washer on each side of the diaphragm held in f center of the diaphragm. Thisl member also is used to join two or more of the diaphragm laminations when more than one is used. It is apparent that'man'y widely diuerent embodiments of this invention may be made without departing from the spirit and scope thereof,

and therefore'it is not intended to be limited except as indicated in the appended claim.

I claim: n

A fuel pump diaphragm capable of withstanding repeated flexings at a high rate comprising a textile fabric impregnated with a composition containing POlyvinyl alcohol and a plasticizer selected from the class consisting of ethanol acet- 5 amide and ethanol formamidc.

applications of crest manmade (by tha ,pme 7 nomme MosUaNsr.

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