US2326175A - Air eliminator - Google Patents

Description

All@ 10, 1943- D. sAMlRAN 2,326,175

AIR ELIMINATOR Original Filed May 16, 1940 2 Sheets-Sheet l Patented Aug. 10, 1943 UNITED STATES PATENT OFFICE 335,646. Divided and this 1942, Serial No. 446,028

Granted under the m of March 3, 1883, as amended April 30, 1928; 370 O. G. 757) 2 Claims.

The invention described herein may be manufactured and used by or for the Government for governmental purposes, without the payment to me of any royaltythereon.

The present invention is a division of my copending application Serial No. 335,646, nled May 16, 1940, and relates in general to fuel feeding systems, such as employed in connection with airplanes, automobiles and Diesel engines. More particularly the present invention is directed to certain novel apparatus for use in conjunction with such systems.

The presence of air, fumes and vapor has long been a serious problem in fuel systems for internal combustion engines of airplanes or automobiles, and also Diesel engines, wherein such air, fumes or vapor enters, or is created in the fuel supply conduits and is subsequently fed -into the carburetor or injector apparatus. This ccndition obviously is of more serious nature in connection with engines of airplanes, such as when the airplane approaches relatively high altitudes, under which condition the fuel in the system vaporizes to a much higher degree than at lower altitudes. As is well known, at certain altitudes the fuel in effect boils, thereby developing bubbles and air and vapor pockets in the fuel being fed through the system to the carburetor or injector apparatus. I'his condition results in varying the ratio ofthe fuel mixture, producing a lean mixture which causes faltering of the engine, with consequent reduction in speed and lack of power. Such effects upon the engine of an airplane are extremely serious and render the plane more dinicult to maneuver and may result in serious mishaps. Moreover at high altitudes, in addition to the conditions above mentioned, the fuel in the supply system, in effect, becomes expanded cr stretched due to the tendency to continuously supply an adequate amount of fuel to the carburetor or injector apparatus, thus causingpartial starving of the carburetor or injector, and thereby varying the ratio of fuel mixture entering the carburetor or injector apparatus. Such conditions also cause a reduction in speed and lack of power, with the attendant dangers above indicated.

As is well known, in airplane constructions at the present time, there is employed a plurality of fuel supply tanks and when one of the tanks is exhausted, another tank of fuel is connected into the fuel supply system. During this interva1 of switch-over there is a possibility of air and vapor getting into the system, which also produces the diiiiculties above mentioned.

While the present invention isadapted for use in connection with internal combustion engines, such as in airplanes and automobiles, as well as Diesel engines, the following explanation of the application June 6,

construction and operation of the apparatus constituting this invention will be treated primarily in connection with problems resulting from such conditions of the fuel systems of airplanes.

One of the objects of this invention resides in the provision of novel apparatus adapted for constantly eliminating air, fumes and vapor from a fuel supply system, prior to the supplying of fuel to the carburetor or injector apparatus and also capable of functioning at various altitudes.

A further object is to provide a novel form of apparatus of the character indicated for constantly eliminating air, fumes and vapor from the fuel system, together with a vent conduit for carrying off said air, fumes and vapor for discharge thereof into the upper part of a fuel supply tank above the fuel therein, the space above the fuel in turning being vented to atmosphere.

Still another object is to provide a novel device of the character indicated, .which is so constructed as to provide a small auiliary reserve supply of fuel for the carburetor or injector apparatus, adapted to be utilized for maintaining operation of the engine for a short period of time after the main fuel source is exhausted during which time air is being pumped into the system, or when, for various reasons, the pump is unable to supply the requisite quantity of fuel to the carburetor or injector apparatus of the engine.

A still further object of this invention resides inthe provision of a novel device of the character indicated having associated therewith and actuated responsively thereto a pressure actuated switch for controlling other apparatus associated with the fuel supply system.

Other objects and advantages of this invention will be apparent from the following description, taken in connection with the accompanying drawings in which- Figure l is a diagrammatic, fragmentary representation of certain elements of a fuel supply system, including the apparatus constituting the present invention;

Figure 2 is an enlarged cross sectional view of one embodiment of my novel air-vapor eliminator and pressure-responsive switch device;

Figure 2 is an enlarged sectional view of the upper and lower ends of the float and valve structure of Figure 2 showing the parts in an initial position;

Figure 2b is a similar View of the upper portion of Figure 2a showing the float valve in an intermediate position;

Figure 2c is a similar view showing the oat valve in final'closed position as in Figure 2, the details of Figure 2 being more clearly shown in this figure;

Fig. 2d is an enlarged view ofthe switch mechanism of Fig. 2.

Figure 3 is a cross sectional view of a further embodiment of air-vapor eliminator, especially adapted for use in connection with high pressure fuel systems, such as in connection with supercharged engines.

Referring now to Figure l of the drawings, I have shown a fuel supply or. storage tank indicated at 30, having a supply outlet 3l, adapted for connection to a fuel pump (not shown), the upper end of the tank being provided with a down-turned conduit' 32 constituting the usual air vent. The novel air-vapor eliminator unit is indicated generally at 33, and has connected thereto a fuel supply conduit 34, adapted to be connected to the pump, and also a fuel discharge conduit 35 adapted to be connected to a carburetor or fuel injector apparatus, (notshown).

The upper end of the air-vapor eliminator 33 is connected by a conduit 3B to the top of the fuel storage tank 30 and serves to constantly convey air, fumes, and vapor from the fuel system, for discharge into the top of the storage tank, and thereby precludes. passage of any appreciable amount of air, fumes or vapor into the carburetor or injector apparatus. This arrangement thereby permits the escape of the air, through ventI pipe 32 of the storage tank, and any of the vapors that again become condensed into liquid form within the tank are thereby salvaged.

It is to be understood that Figure 1 is merely a diagrammatic illustration, and any practical number of fuel supply tanks may 'be employed in connection with the fuel supply system, such as used in connection with airplanes.

The air-vapor eliminator as represented in Figures 1 and 2 of the drawings is of the type having directly mounted on top thereof a pressure-responsive switch, indicated generally at 40, which, it may be understood, may be employed for controlling an electrical circuit for other apparatus used in conjunction with a fuel supply system. An air-eliminator of this type is preferably used in connection with low pressure fuel systems utilizing either a carburetor or injector apparatus.

The air-vapor eliminator 33 is composed of a cup-shaped housing 44, surmounted at its open end by a cover plate 45. 'Ihe cover plate 45 also serves as a supporting base for the pressure responsive switch indicated at 40, and includes provision for a pipe fitting attachment. The cup-shaped housing 44 is provided at its lowermost extremity with a horizontal inlet 46, adapted to be connected to conduit 34 from the pump, a vertical outlet 41 adapted to be connected by conduit 35 to the carburetor or injector apparatus, a drain boss 48 and a drain plug 49. The upper end of the outlet 41 is recessed to receive and xedly hold the tube-like bottom extremity of a cup-shaped deector 50. A cylindrical sieve or screen 5I, sealed to Athe open upper end of the housing 44 by means of a gasket 52 and the cover plate 45, has its lower tube-like extremity adapted to be piloted into that portion of the deiiector 50 which projects downwardly into the upper end of the outlet 41. The underside of the cover plate 45 is provided with an annular iiange 53 to which is attached the open end of a cupshaped float guide 54. The bottom of the iioat guide 54 is provided with a small cup-shaped guide 55 adapted to receive the lower extremity of a valve mechanism indicated generally at 56.

The valve mechanism includes a tube 51 fixedly secured to casing halves 58a and 58h of a float 59, which may be internally reinforced, if desired, by enclosing therein a body of lightweight material, such as Wood. Said tube is provided at its lower extremity with an outer collar 6D and an inner collar 6I, xedly connected thereto by means of a pin 62. A collar 63 is soldered or otherwise fixed interiorly of the uppermost extremity of said tube 51, and provides guidance for a needle valve 64, which is connected to a valve stem 65. A coil spring 66 surrounds the stem 65, within the tube 51, with the ends of said spring reacting against the base of valve 64 and the inner collar 6I at the lower end of saidV tube. The base of the needle valve 6 4 is flanged outwardly to abut the end of collar 63 limiting upward valve movement with respect to the tube 51 under inuence of the spring 66. A passageway 61 is provided through a boss 68 formed in the cover plate 45, and a valve seat 69 is fixed therewithin. Thus, with the valve 64 in down position, as in Figure 28, the interior of the housing 44 is in direct communication with the vent conduit 38 through passageways 1l, 12, 13 and 14. The vent conduit 38 is in turn in communication with the atmosphere through the fuel storage container 30 and vent pipe 32, as shown in Figure 1.

In Figure 2 three positions of the float 59 are shown. These are indicated, respectively, by dotted lines 59a, the full line position 59b of the iioat and dotted lines 59c. The float at position 558 causes the parts of its valve structure to remain in the position of Figure 2'3 by gravity. This position will be maintained all during the time fuel is rising within the eliminator to the fuel level indicated by the line 2B at the left side of Figure 2. When the fuel level rises to the level 2b, the oat 59 will rise from position 59B to its full line position 59h, and the float valve will assume the position shown in Figure 2b. In this position the valve 64 has just been closed against the seat 69, but there has not been enough buoyancy produced in the oat to compress the spring 66. Therefore, the flange on the lower end of the valve 64 is still in contact with the lower end of the stop collar v63.

When the liquid level rises higher, as to the line 2c in Figure 2, then the iioat will rise to position 59 as its buoyancy has overcome the spring 66. The valve 64 is now under spring pressure and also under pressure as a result of the buoyancy of the iioat, the parts of the oat valve being then in the position illustrated in Figure 2 with the lower end of the stem 65 against the pin 62. The significance of this particular position will hereinafter appear.

Finally the liquid level rises higher within the eliminator 33 as seepage of air and vaporsI occur through the valve seat 69 surrounding the valve 64. The buoyancy of the float thereby eifects further compression of the valve against the seat.

In the pressure responsive switch 40, a. cylindrical housing 15 is separated into an upper and a ,lower chamber 16 and 11, by means of a common ,wall 18. A bellows or multiple diaphragm 8U is designedto divide the lower chamber 11 into an upper and a lower compartment, 11a and 11b, the compartment 11B being sealed from uid intercommunication with a tapped hole 8| in the cover plate 45, leading directly into the interior of the housing 44 of the air-vapor eliminator 33. The outermost edges of the bellows are firmly clamped between a flange 82 formed integrally assaut with the lower end of the housing 15, and the upper outermost surface of the cover plate 45 with a gasket 83 interposed therebetween. The space 11a above the top surfaces of the bellows 80 is directly vented to the atmosphere by means of a passageway 84 formed in flange 82. Two electrical binding posts 85 and 86 are riveted to the outer ends 81 of a bridge 81 of insulating material which has a central opening `19 which provides clearance for the adjusting nut 93, the bridge being supported at the ends on layers 93 of insulation cemented or otherwise secured to the bridge and to each other. Clearance openings 88 are provided in the -bridge near the ends for installation of a fixed contact 89, short coupled to the binding post 86 by a conductive blade 89B, and a movable contact 98, long coupled to the binding post 85 by means of spring leaves 9|. The mid-portion of the leaves 9| is raised or lowered with reference to the base of a bellows stem 92 by vertical adjustment of the nut' 93 threaded on the upper end of the bellows stem 92. By means of this adjustment, spacing of the contacts -89 and 90 may be varied to any desired gap Prior to assembly of the above electrical parts, a washer 94 is slipped over the reduced upper portion of the bellows stem 92, a gasket 95 is placed in thebottom of the upper cavity 16, and a thin flexible diaphragm 96 is placed over the aforesaid two parts. A spring 91 and spring retaining washers 98 and 99 are next added, after which the switch assembly described above is positioned as shown in Figures 2 and 2d, and the nut 93 is screwed down to the desired adjustment, the function of the spring l" 91 being merely to maintain the adjusted relation of the parts between the nut 93 and the shoulder on the stem 92. The assembly is completed and mechanism enclosed within the upper cavity by final addition of a dust cover |00.

The air-vapor eliminator 33 and the pressure responsive switch 40 described immediately above oper-ate as follows:

Under empty tank condition, the lowermost extremity of the valve mechanism 56 rests against the bottom of the cup-shaped guide 55 as shown in Figure 2a. Under such down conditi-on of the Valve mechanism 56, the interior of the housing 44 is freely vented to the atmosphere through the passage 61, seat 69, passages 1l, 12` 13 and 14, vent conduit 38, fuel container 30, and vent pipe 32, as may be readily seen by joint reference to Figures 1, 2, and 2a. Under this condition the resiliency of the bellows 89 and spring leaves 9! brings the switch contacts 89 and 90 together. The circuit thus established may be used to signal an empty tank or to operate a motor for automatically makingconnection to a full tank. Upon introduction of fuel through the inlet 46 provided in the base of the air-vapor eliminator 33, the fuel level within the housing 44 builds up to the level 2a within the housing 44, and the float 59 thereafter starts to rise, ultimately assuming its full up position, with the needle valve 64 sealing the central aperture provided in the valve seat I69, as already described.

Considerable importance is attached to the operation of the needle v-alve 64 with relation to the ilow of fuel from the reservoir 50 to the carburetor and with relation to the venting of air or vapors through the conduit 38. After the level of fuel has reached the line 2C and the buoyant force of the iioat is at maximum, since the upper end of the tube 51 is stopped against a shoulder in the valve seat 69 as shown in Figure 2c, it

will be obvious that the needle valve 64 is main- -tained under predetermined pressure of the spring 68 and the buoyant force of the liquid displaced by the iloat in its uppermost position against the valve seat 69.

I have found that where a line contact of metal-to-metal faces is employed, as in my diS- closure, there is slight seepage of air past the needle valve and through the valve seat. Accordingly the air and vapors above the line 2c will gradually be eliminated so that the entire eliminator 33 above the line 2c to the valve seat .69 will ultimately become filled with liquid. Actual oper-ation of my fuel system in airplanes indicates that the trapped air just referred to, is thus gradually driven out through the vent conduit 38 until the housing 44 is completely liquid filled. Apparently when the liquid reaches the valve seat, it forms a nlm which prevents seepage of fuel -but will permit any seepage of air when once the level of the fuel recedes below the level of the valve seat.

Assuming that the chamber of the air eliminator is completely filled with liquid and the buoyant force of the float is positioning the needle valve in seated relation with the valve seat under whatever tension has been built up in the spring 66 by the buoyant force of the float 59, should further air or gas vapor enter the eliminator, one of two operations will take place. If the air or gas vapor accumulates in the eliminator at a rate equal to or less than the rate of elimination thereof by seepage through the valve seat 69, the necessary seepage of air or vapor will take place and the housing 44 will remain iilled with liquid fuel up to the valve seat.

On the other hand, if the air or gas vapor accumulation is at a rate greater than the rate of elimination by seepage, the accumulated an` and/or vapor will cause a displacement of the fuel through the discharge opening 41, which leads to the carburetor and the fioat 59 as soon as the level of the fuel begins to fall below the position 59.

When the level of the fuel recedes to a position approximately as indicated by the fuel level line 2b, the lost motion between the flange on the lower end of the needle valve 64 and the lower end of the stop collar 63 in Figure 2C will be taken up as in Figure 2b, and any further lowering of the fuel level will open the valve. Thus, as the float moves downward in response to a decrease in the volume of fuel in the housing 44 and increase in the volume of gas or vapor, the oat arrives lat a position where its buoyant force no longer acts upon the valve to keep it closed. Just prior to opening of the valve however it remains seated under the force of the spring 66 while the lost motion above referred to is being taken up, and all during such movement there will be seepage of a portion of the gas or vapor. The lower en-d of .the stop collar 63 aiTords a position engagement between the float and the ange on the lower end of the valve B4 for eventually opening .the valve as the float is further lowered, due to the displacement of the fuel by the accumulating vapor and gases. There will be a rapid discharge of the vapor and `gases during the short interval of time that the level of the fuel lowers from the line 2b to the line 2a Which, it will be noted, is a relatively short distance, thus providing a relatively close differential of operation for the float oper-ated valve. Thus, for a limited displacement of the float due to displacement of the fuel by the accumulating gas or vapor, the

needle valve is held in closed position by the action of the spring which varies in its resistance from a maximum when the :doat raises the tube 51 to the position shown in Figure 2 and to a minimum when the oat is positively engaged with the valve (lower end of the collar 63 with the flange ofthe valve 64 in Figure 2) for .there- -aflter unseating the valve as the float lowers further. It is desirable that the distance of travel of the float from the position of maximum spring pressure on the float valve 64 to .the position of positive unseating engagement of the ioai;v with the valve will be of a substantial length so that comparable quantities of gas and air are permitted to accumulate in the eliminator during the transfer of fuel from the source or supply tank to the carburetor, without bringing about a complete opening of the valve. 'Ihe time delay in the opening of the valve, brought about by .the action of the spring during the time that the float is being lowered, serves .to prevent the discharge of liquid through the air or vapor ydischarge seat 69 which would otherwise take place were the valve to open immediately with the accumulation of air and vapor in the eliminator and particularly where the vpressure in the eliminator is of comparatively high value.

Furthermore, .the delay in opening of the valve serves to maintain in the fluid path from the source to the carburetor a substantially constant pressure at such time when the fuel is supplied to the carburetor only from the reservoir. The delay in opening of the valve also serves toprovide an interval of time during which, when the reservoir chamber is being emptied, an indication or signal m-ay be given to the operator under control of the switch contacts 89 and 90 while the carburetor is still acting under normal pressure.

It is of course important not to delay the opening of the float valve too long as it is desired to prevent the complete displacement of the fuel from the reservoir in order to avoid a failure of supply of fuel .to the carburetor. In other words, it is desired to open the oat valve completely at a. time when there is still a small quantity of fuel in the reservoir cup 50.

Repositioning of the switch parts by the restored pressure acting against the underside of .the bellows 80 causes contacts 89 and 99 to be I separated to the position shown in Figures 2 and 2B. S0 long -as the aforesaid predetermined fuel pressure is maintained or exceeded, the contacts 89 and 99 will lremain in this open position.

However, in the eventl of continued operation of i the fuel system with ythe fuel storage container or tank 39 in an empty condition, the fuel pump will no longer be -able to deliver fuel to the inlet 46 and the housing 44, and more particularly the cup-defiector 50 of the air-vapor eliminator 33 will serve as a Ireserve reservoir for limited auxiliary fuel delivery to the carburetor or fuel injector apparatus, t maintain operation of the engine for a short period of time after the main fuel supply in tank 30 is exhausted.

After predetermined depletion of the auxiliary vsupply of fuel in the bowl 50. the valve mechanism 56 will assume the down position previously referred to above, and the bellows 80 will expand to a down position," resulting in closing of the contacts 89 and 90. As before indicated, contacts 89 and 90 may control an electrical circuit for actuating a selector valve for automatically connecting another tank of fuel in the fuel supply system. It will therefore be apparent that "closed Contact condition of the pressure responsive `switch 40 is maintained as long as the fuel pump remains continuously connected with an empty fuel container, and open contact condition of the pressure responsive switch 40 is maintained as long as an uninterrupted supply of fuel is delivered tothe fuel pump, and thence to the air-vapor eliminator 33.

When the valve is closed, the gases can accumulate within the chamber and displace the liquid, thereby lowering the level thereof and consequently the position of the float, without opening the valve until such time as the noat has approached the position when the float and valve are no longer relatively displaceable. Further displacement of the float by the accumulated gases will then cause opening of the valve.

The modifiedform of air-eliminator shown in Figure 3, and designated 33h, and pressure switch 49h, are especially adapted for use in high pressure fuel supply systems, such as in connection with a super-charged engine.

Due to the more or less schematic nature of Figure 3, I have reduced to a minimum the showing of details not involving modification, over the structure shown in Figure 2. The essence of novelty in Figure 3, over the showing of Figure 2, concerns slidable mounting of a oat guide 336, which functions in a manner so that upon seating of the valve 64 in the valve seat 69, further increase in the liquid fuel level in the cup-shaped housing 44 will cause vertical bodily movement of said float guide 336, against the compressive restraint of a spring 331, to a level resulting in opening of a switch composed of a xed contact 333 connected to a binding post 339 and a movable contact 340 connected to a binding post 34|. The contacts 338 and 340 perform. the same functions as the contacts 89 and 90 of Figure 2. Upon exhaustion of the fuel container 30, operably connected to the passageway 14 of the airvapor eliminator 33h (the same as in Figure 1), the reserve fuel contained in the cup-shaped housing 44 is pressure-fed through the outlet 41 by the spring 331, since continuing operation of the fuel pump prevents fuel escapage from the inlet 41 of housing 44.

In the construction represented in Figure 3, the following new or substitute parts employed include the slidable float guide 336 which consists of an annular ring 342 with vent holes 343 and 344, a lower housing 345` depending from said ring, and provided with vent holes 346, and an upper housing 341 fixed to the top surface of the annular ring 342. 'I'he bottom of the lower housing 345 is sleeved at 51a to form a journal guide for the tube 51 of the float 59. The valve seat 69 is fixed in an aperture provided in the top of the upper end of an inverted cup-shaped housing 341, so that it acts as a base guide for the spring 331. The outer diameter of the annular ring 342 is in turn guided by a cupped sleeve 348. Said sleeve is provided with vent holes 349a and 3491), and its upper end continues into an outwardly, extending. flange 350, supported 0n a mounting gasket 35|, which in turn is seated upon the upper end of the housing 44. Immediately upon the top of the mounting flange 350 I place a thin annular disk 352 to the lower inner surface of which I x the upper end of a flexible liquid sealing element or bellows portion 353. The lower end of the bellows portion 353 is also fixed to the top surface of the annular ring 342. The utility of the latter bellows portion will be discussed in detail hereinbelow.

Mounted on the cup-shaped housing 44 is a cover plate-housing 354, secured thereto by conventional screw-lockwasher means 354a. Formed in the housing 354 is a vertical cavity 355 in which is mounted a sleeve 356, adapted to act as a primary guide for the float guide 33B. The top of the housing 354 includes a spring cavity 351; vent line passageways 12, 13 and 14, and a contactor pin hole 358. A contactor pin 359, of insulating material, is mounted for sliding guidance in said hole and has a major portion thereof depending from the bottom surface of a contactor housing 360. Upward movement of the pin 359 serves to open the circuit controlled by contacts 338 and 340, by engagement of said pin with the insulated movable contact 340, with respect to the grounded fixed contact 338. Obviously, the fixed contact 338 may be insulated from the housing 360, if desired. The contactor housing 380 can be fixed to a shelf 36| provided upon the top outer surface of the cover plate housing 354 by any of several well known conventional means.

The combined air-vapor eliminator 33h and pressure responsive switch 340 operate as follows: Assuming initial tank empty condition, fuel from the fuel pump first enters the inlet 46, spills over the top of the deilector 50, and then rises in the latter until it flows through vent holes 343, 343, 344, 349a and 3491) to an upward level approximating the middle of the last named vent hole. So far, air originally occupying the empty air-vapor eliminator 33h has found ready escape through the open valve seat 69 and vent passageways 61, 12, 13 and 14. Thereafter, further, fuel flow divides itself in inner zone A and outer zone B. Due to air trap, the fuel in zone B does not usually progress to the top of the cup-shaped housing 44. In zone A, however, fuel ultimately and completely fills the upper part of housing 341. When fuel in the inner zone A reaches a point slightly above the buoyancy level of the float 50, the valve 64 closes the valve seat 69. Thereafter, pressure from the fuel pump must be relied upon, if further liquid rise is to be accomplished within zones A and B. Ingress of further fuel, under steadily increasing pump pressure, causes the spring 331 to steadily compress, permitting corresponding upward movement of -the float guide 338 and associated elements, until its uppermost surface engages the pin 359. So long as the fuel pump continues normal functioning, the contacts 338 and 340 will remain in "open-circuit condition and the engine fuel in- Jector or carburetor connected with the outlet 41 of the housing 44 will continue to receive fuel under a predetermined pressure. During the time interval of switch-over between an exhausted fuel container and another container of fuel, the engine fuel injector or carburetor will continue to be fed reserve fuel under pressure from the cup-shaped housing 44 of the eliminator 33h, the volume of which is effectively increased by the volume of fuel within the elevated housing 341. As the fuel passes out of the lower passageway 41, the housing. 341 will be pressed downwardly by' the spring 331 while the valve 64 remains closed and the pressure of the spring thus maintains pressure on the fuel itself. The quantity of fuel within the elevated housing 341 is F thus moved bodilydownward to supplement the supply within the reservoir cup 50 with the spring 331 furnishing pressure for the supplemental fuel. Finally, however, the level of the fuel recedes to such a. point that the valve 64 opens and thereafter there can be only gravity feed of the reserve fuel. Long prior to this however and, in fact, when the housing 341 starts to move downwardly, the switch 340 is closed for operating an indicator or means to supply further fuel to the eliminator.

Although I have herein shown and described certain preferred forms of my invention, manifestly it is capable 0f further modification and rearrangement without departing from the spirit and scope thereof. I do not, therefore, wish to be understood as limiting this invention to the precise embodiments herein disclosed, except as I may be so limited by the appended claims.

I claim:

l. A pressure responsive electric switch for use in an air-vapor eliminator of a fuel dispensing system, said switch comprising a housing on the upper end of the eliminator, a wall separating' said housing into an upper and a lower chamber, a bearing hub in said wall, a switch-operating stern slidable in said hub and extending through and into the upper chamber, a diaphragm in the lower chamber having its outer edge sealed to the housing and its central part sealed to said stem, thereby dividing said lower chamber into an upper and a lower compartment, said upper compartment being connected by an opening to the atmosphere, and said lower compartment being connected by an opening to the inside of the eliminator, two binding posts insulatedly mounted in spaced-apart positions in said upper chamber, a resilient strip of conductive material electrically joined at one end to one binding post. the free end being near the second binding post, a contact pointon said free end, a cooperating point on said second binding post, means insulatedly joining the resilient strip intermediate its ends to the said stem, and adjusting means-to raise or lower the point on said stem at which the said strip is secured.

2. A float-operated switch in an air-vapor eliminator `of a fuel dispensing system comprising, in combination, a pressure-tight eliminator housing, a piston-like float cage movable vertically within said housing, a float movable vertically within said cage, cage guide means in said housing, float guide means in said cage, passageways connecting the pressure-tight housing with the inside of the float cage, means for pressuresealing the pressure-tight housing from the space above the float cage, a valve in its open position connecting the space within said float cage with the space above said float cage operative to be closed by rise of said float with respect to said cage, a spring positioned for opposing upward movement of said float cage, a switch casing on the top of said housing, a stationary contact member in said casing, a movable contact member in said casing normally resiliently held in engagement with said stationary contact member, a switch-operating stem vertically slidable in an opening connecting the switch casing with the space above the float cage, the upper end of said stem being positioned so that its upward movement will move said movable contact out of engagement with said fixed contact and its lower end extending into the space above the float cage and positioned to be moved upwardly by upward movement of said float cage, and a vent passageway connecting the space above the float cage with the outside of said eliminator.

DAVID

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