US3104617A

US3104617A - Diaphragm pump

Info

Publication number: US3104617A
Application number: US48190A
Authority: US
Inventors: Edward J Barr
Original assignee: Mcculloch Corp
Current assignee: Mcculloch Corp
Priority date: 1960-08-08
Filing date: 1960-08-08
Publication date: 1963-09-24
Anticipated expiration: 1980-09-24

Description

- Sept. 24, 1963 E. J. BARR 3,104,617

` l DIAPHRAGM PUMP l I Filed Aug. 8. 1960 2 Sheets-Sheet l INVENTOR. MHA/N McMQ/v/Gm. arneysfarpp//can Sept. 24, 1963v E. J. BARR 3,104,617

DIAPHRAGM PUMP Filed Aug. a. 1960 2 Sheets-sheet 2 n/Alep Il ,3Q/ee INVENTOR MANN McMAw/@QL forneys for .QOp//-an United States Patent O Corporation, Los Angeles, Calif., a corporation of Wisconsin Filed Aug. 8, 1960, Ser. No. 48,190 2 Claims. (Cl. 10S-150) This invention relates to a diaphragm pump, and more particularly to a pump for .delivering .fuel to a small carburetor in a small ygas engine.

While the invention has particular utility as a fuel supply means lfor internal combustion engines of thetwocycle type which are used with chain saws, lawn mowers, and outboard types of rnarine engines, it is to be understood that its utility is not confined thereto.

'ilhe fuel pumps for supplying Ifuel to two-cycle internal combustion engines are for the most part loper-ated by a diaphragm; that is, the diaphragm is pulsed at a high rate to charge and discharge the pump. The diaphragms are generally pulsed by the alternate gas pressure and partial vacuum developed in the crankcase of the engine, and the rate of pulsing is equivalent to and determined by the stroke speed of the pistons. Thus, in an engine operating at 10,000 rpm., there are an equal number of cyclic strokes of each piston per minute and there are the same number of cyclic pumping strokes of the diaphragm.

These diaphragms in the past have been made of a rubber-like material, such as Buma-rubber or neoprene reinforced by some woven material, such as cotton fabric. The pump valves, one being in the fuel inlet and the other being in the fuel discharge, are made of the same piece of material as the diaphragm. The valves are generally in the form of a pair of tongues fitted over passages in the fuel portion of the pump and are alternately opened and closed according to Whether the pulse of the diaphragm charges :or discharges the pump. In other words, each time the diaphragm is pulsed in one direction, one of the valves opens and the other valve is held closed.

Over a long period of years, there have been excessive valve and diaphragm failures for various reasons. During the normal operation of the valves, there is a tendency of the reinforcing fabric or of the rubber or plastic coatings to swell, and when this occurs in the valve stresses are created to cause the valves to curl, either toward or away from the ports they control. When a valve curls away from the port the pump fails because the valve no longer properly closes. Thus, iduring a long period there has been unsatisfactory fuel pump oper-ation in the aforesaid type of .engine with accompanying unsatisfactory operation of the engines. These expensive .failures have resulted in considerable research on the part of the manufacturers concerned. One of the first things that was found was that the new synthetic materials which were recommended for use as a sin-gle s-heet, that is, unreinforced, swelled vduring operation more than the reinforced materials and tended to ooze out of the pump and, consequently, cause leaks. Durable materials, such as nylon, were tested, but after a short time they fatigued and the diaphrag-ms rupture-d.

However, according to the invention, it was surprisingly found that a diaphragm with integral valves stamped 4from one sheet of polytetrauoroethylene, sold commercially as Teflon, functioned successfully under operating test conditions for 800 hours. Diaphragms made of polytetraliuoroethylene were further tested successfully on engines which were operated at 11,000 to 15,000 rpm. These speeds are far in excess .of previous maximum successful Ioperating speeds.

It is an object of the present invention to provide an improved diaphragm pump for operation with two-cycle internal combustion engines.

It is another object of the invention to provide an improved diaphragm having integral check valves for use in the high pulse rate pump.

It is still another object of the invention to provide a new combination of a diaphragm pump having a diaphra-gm made of a single sheet of homogenous material, said diaphragm having check valves integral therewith.

It is a further object of the invention to provide an improved single sheet diaphragm yfor a fuel pump, said diaphragm being made from polytetrailuoroethylene.

It is still another object of the invention to provide an improved pump diaphragm having integral check valves and made from a single sheet of material which operates successfully for a longer period than was heretofore believed possible.

Further objects and advantages of the invention may be brought out in the following part of the specification wherein small details have been -described for the competence of disclosure, without intending to limit the scope of the invention which is set `forth in the appended claims.

Referring to the accompanying drawings which are for illustrative purposes only:

FIG. 1 is a plan view of a carburetor having a fuel pump according to present invention attached to its unshown underside;

FIG. 2 is a side view of the carburetor and the fuel pump;

FIG. 3 is a cross-sectional view of the carburetor and fue-l pump Itaken as indicated along the line 3 3 of FIG. l;

FIG. 4 is a cross-sectional view taken =as indicated along the liuc 4 4 in FIG. 3;

FiG. 5 is a partially cutaway view illustrating the air or `gas part of the pump, taken las indicated along the line 5 5 of FIG. 3;

FIG. 6 is a partially cutaway plan view illustrating the -fuel part of the pump, take-n as indicated along the line 6 6 of FIG. 3;

FIG. 7 is an enlarged fragmentary cross-sectional view illustrating the fuel inlet and inlet check valve, taken as indicated along the line 7 7 of FIG. 6;

FIG. 8 is `an enlarged Ifragmentary View illustrating the fuel pump outlet and outlet valve, taken substantially along the line 8 8 of FIG. 6; and

FIG. 9 is a plan view of the Teflon diaphragm according to the present invention.

Referring now tothe drawings, the fuel pump yaccording to the present invention and the carburetor herein shown and described, is particularly adapted for use with an engine of the so-called two-cycle type wherein pulsing pressures are available, 4although it is to be understood that this apparatus may be used with other types of internal combustion engines or in Iconnection with other devices Where pulsating pressures are available.

In FIGS. 1-4, there is shown a carburetor 10 having lan induction passage therethrough which includes an inlet portion 11 and a mixture outlet portion 12 with va venturi 13 interposed therebetween and connecting said passage portions. At the outlet end of the carburetor body is a flange 16 which is adapted to be secured to a boss 17 of the inlet of the mechanism to which a fuel mixture is supplied. As shown, the boss 17 is on the wall of crankcase 18 of -an internal combustion engine of the ltwo-cycle type, the engine inlet being in said boss 17.

Means for controlling the liow of fluid through the induction passage comprises a throttle valve 19, shown as being of the butterfly type, which is mounted on the usual throttle shaft 21, journaled in bearings 22. One end of the shaft 21 is provided with a throttle lever V23 which is in the shape of `a bell crank. The lever 23 is secured to the shaft in the usual well known manner whereby it has -a fixed predetermined position on the shaft relative .to the position of the throttle valve 19.

There is an .arm '24 on the body 1t) which extends outward- '1y substantially parallel to the throttle shaft and which is provided with a tapped opening adjacent the end for the reception of a screw 27 having an idle screw spring Z8 between the head of the screw and the arm 24. The screw '217 is adapted to be turned toward :and away from Ithe free'end of the adjacent arm of the throttle lever 23 to serve as a stop, limiting closing movement ofthe Ithrottle valve so that said valve may be adjusted in a cracked position for idling.

The lower or underside of the body l0, as shown in FIGS. 3 and 4, is recessed to provide a fuel chamber 29. The fuel chamber is typically connected to

idling ports

30 and 31 by unshown passages and to an air inlet passage 33, also connected to `the idling ports 3) and 3l. The flow of fuel is regulated between chamber '29 and the idling ducts by means of a needle valve 32. y

The main fuel discharge orifice 35 is similarly con nected to the chamber 29 by unshown passage means and the flow of fuel thereto is regulated by a needle valve similar to valve 32. but not shown.

The chamber 2.9 is closed by la flexible diaphragm 36, having a stifening disc 37 ou its upper face, and which has its marginal edge portion clamped between the body 1t) and a pump plate 39 which on its lower side forms the air or gas pulsing portion of the fuel pump, generally designated as 40. The side of plate 39 facing diaphragm 36 is provided with a recess 41 of substantially the same diameter as the recess 29, said recess 41 serving as an air pressure balancing chamber which is connected to the atmosphere by passage 42, shown in FriG. 3.

The fuel pump 40, according to the invention, is comprised of three principal parts, namely, the aforesaid plate 39 having the operating or driving portion of the pump formed in its underside; the fuel carrying portion of the pump formed in a lower plate 45 complementary to the plate 39; and a diaphragm 46 composed of a single sheet of thin polytetrafluoroethylene. As best seen in FIG. 2, the pump di) is secured to the carburetor by means of cap screws 47. In the pump the diaphragm 46 is spaced between two sealing gaskets 4S and 49, the gaskets and the flexible polytetrailuoroethylene diaphragm being marginally clamped between the plate 39 and the fuel plate or body 45.

in the lower surface of plate 39 is a pressure pulsation chamber 51 formed by a dish-shaped recess covered by the polytetrauoroethylene diaphragm 46. The pulsation chamber 51 is connected with the engine crankcase by means of a passageway 52 which is formed in part between a recess in the bottom of plate 39 and the gasket 4S, as shown in FIG. 5, and then extends outwardly through the diaphragm 36 at a position outwardly of chamber 29 in the carburetor body it). The passageway 52 terminates at a port S3, shown in FIG. 2, and communicates with the engine crankcase in the well known manner :through a passage 54 in the boss 17.

The fuel plate 45 is provided in its upper side, as best seen in FIG. 6, with a fuel chamber 57 substantially complementary to the pulsation chamber 51, and covered by the diaphragm 46. As indicated in FIG. 2, the fuel from any suitable source is conducted Ito a fuel inlet 58 in a stem 59 of the body. The inlet 58 is connected with a fuel chamber 60 by a passage 63, best seen in FIGS. 6 and 7, in the stem and in the body 45. The chamber 60 has a connection with the main fuel chamber 57, said connection comprising a port 64 at the upper side of the body 45. Between the two

plates

45 and 39, the gaskets and diaphragm are cut away -to provide a chamber 65, along with recess 65h in plate 39, and which is connected to the chamber 57 by means of a passage 66 in the fuel plate 45 and open to recess 65.

As best seen in FIGS. 6 and 9, the marginal portion of diaphgram 46 has a cutout portion 65a, forming a portion of the cutaway part 65, in which is left a tongue 69. The tongue serves as a check valve member which is 4 operable within the chamber 65 and is adapted to permit the flow of fuel from the chamber 6i) to the chamber 57 but which prevents the counter ow of fuel. The gasket 49 has a slot 7i) into which tongue 69 is inserted and :the

outer bar 71, forming one side portion of the slot, limits the opening pivoting movement of -the tongue 69, said tongue being adapted to seat on the upper surface area of plate 45 about port 64, -the bottom or open end of the chamber 65 being of sufficient size to permit such engagement of the tongue with the area about the port 64.

The fuel chamber 57 in the pump is connected with the fuel chamber 29 in the carburetor by means of a passage 72 in fuel plate 45, shown in FIGS. 6 and 8; a chamber 74, formed by cutting away the

gaskets

48 and 49, a portion 74a of the diaphragm 46 and by forming a relieved portion Mb in the bottom surface of plate 39; and a passage 75 in body 1G extending through diaphragm 36, as shown -in FIG. 4.

In the formation of the chamber 74 the marginal portion of the `diaphragm 46 has a cutaway portion 74a in which is left a tongue 73. This tongue serves as a check valve operable within chamber 74 and is adapted to permit the ow of fuel from the f-uel chamber 57 in the pump to the fuel cham-ber 29 in the carburetor but which prevents counter iiow of fuel'l valve 73 is inserted through a slot 70` in the gasket 49 and the bar 7i, forming par-t of the slot, limits the opening of the tongue 73, said tongue being adapted to seat on the upper surface area of the pump body 45A about the port 72, the bottom or open end of the chamber 74 being of sufficient size to permit such engagement of the tongue with the area about said last mentioned port.

Passage 75 includes an enlarged downwardly inclined portion in which is fitted securely a tubular member 76 which serves as a valve seat and cooperating with the seat is a valve 77. An inlet control lever 80 is disposed in the chamber 29 and .is pivoted at 81. The lever 8G is biased by a sp-ring 82 so that one end 83 is forced against stiifening plate 37 of diaphragm 36 and the other end 86 is forced against the end of valve 77 to hold it in a closed position. k

In operation, the carburetor 10 operates in a well known manner and as buttery valve 19 is opened, the amount of air going through the venturi 13 increases so as to increase the suction on the main fuel port 35 to draw fuel'out of the chamber 29. This rtends to cause diaphragm 36 to raise and in turn raise end 83 of lever charge by the action of one piston, for example, then, each time the Ypiston moves away from the crankcase in the compressive part of .the stroke air is drawn from pulsation chamber 51 and this causes the polytetrafluoroethylene diaphragm 46 to increase the size of the fuel chamber 57 so as to charge the pump through the fuel inletk 58. Thus, the suction created in fuel chamber 57 is effective in chamber 65 to open check valve 69 if it does not open by the force of the fuel in the inlet 58. Simultaneously, the suction which causes the chamber 57 to fill, also exerts a suction on valve 73 through passage 72 to cause it to be held closed in a sealed position. When the piston is then fired, it increases the pressure in the crankcase, in line 54 and in the pulsa-tion chamber 51, and the diaphragm 46 is caused to be pulsed downwardly` to increase the pressure in fuel chamber 57. As this occurs,

the pressure causes the fuel in passage 66 to be forcedV The remarkable, unexpected effect of .the use of a In chamber 74,

polytetrauoroethylene diaphragm with its integral valves has changed the pump operation and that of fthe engine te which it supplies fuel from one of embarrassing failure and unreliability to one of complete operational reli` ability. Such pumps, according to the present invention, have been completely successful in ambient temperatures of minus F. and in engine operating temperatures of more than 200 F. regardless of the type of fuel used. Moreover, the capabilities of the pump as to operating speeds and total hours of operation have far exceeded pumps in the prior art and have far exceeded what was expected for a successful pump.

The length-to-thickness ratio of the diaphragm and valves is predicated on the cyclic response per minute necessary and the pumping volume required in each particular application. Practical thicknesses of the polytetrafluoroethylene sheets used have been found to be from approximately 0.0025 inch to 0.060 inch. The desirable crystallinity range of the polytetratluoroethylene used has been found to be from approximately percent -to percent.

I claim:

1. In a gas operated diaphragm fuel pump, a flexible diaphragm dividing the pump into a gas part and a fuel part, a gas inlet and outlet operably connected to one side of the diaphragm and to a gas chamber on said one side in said gas part, a fuel inlet and a fuel discharge operably connected to the other side of the diaphragm and to a fuel chamber on said other side in said -fuel part, a check valve in said `fuel inlet for closing said fuel chamber to said fuel inlet when ythe pump discharges through said fuel discharge, a second check valve in said Ifuel outlet for closing said fuel chamber to said fuel outlet when said pump is taking a suction, said pump discharging when gas pressure is increased to flex said diaphragm 0n Said one side and toward said -fuel chamber and said pump taking a suction when said gas pressure is reduced to flex said diaphragm on said one side away fr0-m said fuel cham-ber, said check valves being in the form of tongues integrally connected with and of the same piece of material as said diaphragm, the improvement comprising: said diaphragm and valves being of a single sheet of polytetraiiuoroethylene having a thickness range of from approximately 0.0025 inch to 0.060 inch.

2. A gas operated fuel pump comprising: a pump casing; a flexible diaphragm in said casing dividing the pump into two parts, one of said parts to carry an operating gas and the other of said parts to carry the fuel being pumped; a gas inlet and outlet oper-ably connected to one side of said diaphragm and to a gas chamber on said one side in said gas part; a fuel inlet and a fuel :discharge operably connected to the other side of the diaphragm and to a fuelchamber on said other side in said fuel part; a check valve in said fuel inlet for closing said fuel chamber to said fuel inlet when the pump discharges through said fuel discharge; and a second check valve in Said fuel outlet for closing said fuel chamber to said fuel outlet when said pump is being charged, said pump discharging when gas pressure is increased -to liex said diaphragm on said one side toward said fuel chamber and said pump being charged when said gas pressure is reduced to iiex said diaphragm on said one side away from said fuel chamber, said check valves being in the form of tongues integrally connected with and of the same piece of material as said diaphragm, said diaphragm and said valves being of a single sheet of polytetrafluoroethylene, and said sheet having a thickness of from approximately 0.0025 inch to 0.060 inch, and a crystallinity range of approximately 45 percent to 70 percent.

References Cited in the le of this patent UNITED STATES PATENTS Berry Dec. 8, 1953 Phillips June 25, -7

OTHER REFERENCES

Claims

1. IN A GAS OPERATED DIAPHRAGM FUEL PUMP, A FLEXIBLE DIAPHRAGM DIVIDING THE PUMP INTO A GAS PART AND A FUEL PART, A GAS INLET AND OUTLET OPERABLY CONNECTED TO ONE SIDE OF THE DIAPHRAGM AND TO A GAS CHAMBER ON SAID ONE SIDE IN SAID GAS PART, A FUEL INLET AND A FUEL DISCHARGE OPERABLY CONNECTED TO THE OTHER SIDE OF THE DIAPHRAGM AND TO A FUEL CHAMBER ON SAID OTHER SIDE IN SAID FUEL PART, A CHECK VALVE IN SAID FUEL INLET FOR CLOSING SAID FUEL CHAMBER TO SAID FUEL INLET WHEN THE PUMP DISCHARGES THROUGH SAID FUEL DISCHARGE, A SECOND CHECK VALVE IN SAID FUEL OUTLET FOR CLOSING SAID FUEL CHAMBER TO SAID FUEL OUTLET WHEN SAID PUMP IS TAKING A SUCTION, SAID PUMP DISCHARGING WHEN GAS PRESSURE IS INCREASED TO FLEX SAID DIAPHRAGM ON SAID ONE SIDE AND TOWARD SAID FUEL CHAMBER AND SAID PUMP TAKING A SUCTION WHEN SAID GAS PRESSURE IS REDUCED TO FLEX SAID DIAPHRAGM ON SAID ONE SIDE AWAY FROM SAID FUEL CHAMBER, SAID CHECK VALVES BEING IN THE FORM OF TONGUES INTEGRALLY CONNECTED WITH AND OF THE SAME PIECE OF MATERIAL AS SAID DIAPHRAGM, THE IMPROVEMENT COMPRISING: SAID DIAPHRAGM AND VALVES BEING OF A SINGLE SHEET OF POLYTETRAFLUOROETHYLENE HAVING A THICKNESS RANGE OF FROM APPROXIMATELY 0.0025 INCH TO 0.060 INCH.