Pump assemblies

April 29, 1958

2,832,292 & sLO

M. L. EDWARDS

PUMP ASSEMBLIES

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April 29, 1958

2,832,292

M. L. EDWARDS

PUMP ASSEMBLIES

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2,832,292

April 29, 1958

M. L. EDWARDS

PUMP ASSEMBLIES

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MLlea Lowell Edwards

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2,832,292

April 29, 1958

M. L. EDWARDS

PUMP ASSEMBLIES

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United States Patent Office

2,832,292

Patented Apr, 29,1958

2,832,292

PUMP ASSEMBLIES Miles Lowell Edwards, Portland, Oreg. Application March 23, 1955, Serial No. 496,268 13 Claims. (Cl. 103—87) boil within the altitude range of the aircraft. Further, jet engines consume less fuel at high altitudes in proportion to the fuel requirements for the same speeds at lower altitudes and efficient pump design should, there5 fore, avoid a power wastage in pumping fuel beyond the demands of the engine. In addition, the rapid rate of climb of a jet engine, enhances the problem of release of dissolved air from the fuel before the fuel actually begins to boil at the higher altitudes. The pump must la be capable of getting rid of the released air while still supplying enough fuel to permit the aircraft to climb at higa rates. Since release of dissolved air is not initiated until altitudes are reached where the fuel demand is less than the take-off demand, the pumps of this invention 15 effectively utilize auxiliary inlets as air outlets when the flow rate demand decreases.

It is then a feature of this invention to provide the most efficient, lightest and most compact booster pump assembly for meeting a particular specification without, 20 however, altering the basic design of the pump.

Another feature of this invention is to provide a high speed fuel booster pump assembly which is streamlined to meet the requirements of a particular engine without wasting power. This invention thus avoids the hereto25 fore followed general practice of overdesigning the pump to meet tne most rigid specifications and then using this pump for engines not having such stringent fuel demands.

An object of the invention is to provide fuel booster pump units with standardized housing and mounting parts 30 together with a series of special components fitting the basic parts to cooperate therewith for meeting particular specifications.

Another object of the invention is to provide a fuel booster pump for jet engines having a standardized 35 mounting base, inlet and pump casing, together with a series of components for the standardized parts which will cooperate therewith to impart different characteristics to the resulting pump.

A still further object of this invention is to provide a 40 jet engine. fuel booster pump for submerged mounting in a fuel cell, wherein the pump casing is arranged to selectively receive components which will cooperate therewith to produce a pump capable of delivering the required fuel flow to the jet engine and capable of removing air and 45 vapors within the operating altitude range of the engine without consuming power in waste recirculation and vapor removal action beyond the demands of the engine.

A general object of the invention is to provide pump \ assemblies designed for a wide variety of altitude pumping ai) conditions without involving wastage of operating power.

A specific object of the invention is to provide a fuel booster pump having a basic high speed hydraulic design to efficiently deliver high rates of fuel and to selectively add to said design components which will increase the 55 vapor separating capacity of the pump.

A further object of the invention is to provide a telescoped impeller hub, motor shaft and bearing arrangement for pumps which reduces the required overall pump length, minimizes support weight and increases resist60 ance to deflection whereby the pump is especially adapted for vertical mounting in thin airplane wing tanks.

A further object of the invention is to provide a new pump impeller which is drawn up tightly against the sup_g. porting shaft adjacent the surrounding shaft bearing for increasing the rigidity of the impeller mounting in a pump.

Another object of the invention is to provide a booster pump having a main inlet supplying liquid to an impeller 7Q chamber and a diffuser outlet immediately downstream from the inlet surrounding the impeller in the chamber to act as a secondary inlet at high rates of flow through

This invention deals with pump assemblies having standardized body parts adapted* to receive different types of pump components for producing pumps capable of meeting . widely different specifications. More particulaily, this invention deals with fuel booster pumps for jet type airplane power plants wherein pump components can be substituted as required to meet the demands of a particular jet engine to insure adequate fuel delivery when the airplane climbs with hot fuel from sea level up through intermediate altitudes where dissolved air is released by the fuel to the highest operating altitudes where actual boiling of the fuel occurs.

The invention will hereinafter be described as embodied in a submerged type fuel booster pump for mounting in the fuel cell of a turbo-jet aircraft fuel system but it should be understood that the principles of this invention are generally applicable to pumps, especially of the vapor separating type and, therefore, the scope of this invention is not limited to any specific usage of the pump.

_ According to this invention, a standard main pump casing and mounting base is arranged for selectively receiving different types of pump impellers designed to meet dirieient specifications, different types of electric motors for driving the impellers, and auxiliary vapor diffusing units to ^augment the vapor separating capacity of the pump. The standard pump casing and mounting base includes a base plate adapted to cover an opening in the bottom of a fuel cell and be bolted to said bottom. This base has upstanding legs supporting an annular pump casing with a volute chamber surrounding a central impeller chamber. The volute chamber has a peripheral outlet integrally cast with an upstanding coupling member on the base plate. This coupling member opens through the base plate and is adapted to receive a. pipe fitting on the outside of the tank. The pump casing provides an axial inlet or eye spaced just above the base plate. Radially extending diffuser passages are formed in the casing immediately adjacent the axial inlet. These passages act as a secondary inlet or alternately, as a vapor discharge outlet, depending upon the rate of flow through the pump. The pump casing is adapted to receive various types of motors which are secured to the top wall of the casing and these motors carry different types of impellers designed for meeting various specifications. The impellers operate in an impeller chamber in the pump casing. The motors are arranged with end heads that carry impeller hub bearings which project into the pump casing to surround the impeller hub. I_n order to meet high vapor separating demands, the motor casing is adapted to carry a secondary diffuser attachment cooperating with the top of the pump casing.

While jet engine fuel is less volatile than the high test gasolines used for piston aircraft engines, the altitude range of jet engines and the rate of climb of such engines, is so much greater than piston driven aircraft engines, that even the less volatile jet engine fuel, unless confined in a pressurized tank, will release dissolved air and will

2,833,292 the pump and as a vapor and air outlet at lower rates of flow.

A further object of the invention is to provide a vapor separating pump capable of swallowing gas and air bubbles at high rates of flow where these bubbles cannot create a vapor lock and capable of efficiently separating the bubbles from the liquid before the liquid becomes trapped in a feed line whenever the rate of flow is low enough to permit accumulation of vapor and air which might disturb normal pump operation.

Another object of the invention is to provide a fuel booster pump which will deliver high rates of flow at low altitudes at high efficiency, will supply intermediate rates of flow at intermediate altitudes while removing air bubbles which are released from the fuel at these altitudes and will supply relatively small rates of fuel flew at still higher altitudes where boiling of the fuel occurs while effectively separating vapors from the boiling fuel.

Other and further objects of this invention will be apparent to those skilled in this art from the following description of the annexed sheets of drawings which, by way of preferred examples, illustrate several embodiments of the invention.

On the drawings:

Figure 1 is a vertical cross-sectional view, with parts in elevation, of a jet engine fuel booster pump assembly having components designed for high speed operation with nominal gas-removing capacity.

Figure 2 is a horizontal cross-sectional view taken along the line II—Π of Figure 1.

Figure 3 is a bottom end view of the impeller in the pump of Figure 1.

Figure 4 is a side view of the impeller of Figure 3.

Figure 5 is a bottom end view of an alternate impeller for the pump of Figure 1 to increase the vapor removing capacity of the pump.

Figure 6 is a side view of the impeller of Figure 5.

Figure 7 is a top view of the impeller of Figure 5.

Figure 8 is a vertical cross-sectional view of a further pump assembly of this invention showing departures from the pump of Figure 1 to further increase the vapor separating capacity of the pump to accommodate higher altitude performance of the pump.

Figure 9 is a horizontal cross-sectional view taken along the line IX—IX of Figure 8.

Figure 10 is a bottom end view of the impeller of the pump of Figure 8.

Figure 11 is a vertical cross-sectional view of an alternate motor and impeller assembly for the pumps of Figures 1 and 8.

Figure 12 is an exploded somewhat diagrammatic elevational view illustrating the manner in which the various pump components can be assembled in the standardized mounting base and casing to produce the pumps of this invention.

As shown on the drawings:

As shown in Figure 1, the submerged fuel booster pump 10 is basically composed of a mounting base and pump casing part 11, a cover or end head part 12, a motor casing 13, and an impeller 14.

The part 11 includes a flat plate-like base 15 with apertures 16 therethrough around the periphery thereof. The plate underlies the bottom wall 17 of a fuel cell or tank and covers an opening or hole 18 through this bottom wall. A mounting ring 19 is mounted on the bottom wall 17 around the hole 18 and is tapped to register with the holes 16 around the periphery of the plate 15. Mounting screws 20 threaded into the tapped holes of the ring 19 extend through the bottom wall 17 and through the apertures 16 to mount the unit 10 in the fuel cell.

The base 15 has a depressed portion 21 with a central boss 22 carrying a drain plug 23. This depressed portion 21 provides a sump S below the bottom 17 of the fuel cell. Legs 24 extend upwardly at intervals from the depressed portion 21 of the base plate 15 to support an annular pump casing 25 in spaced relation above the bottom of the sump.

The pump casing 25 is a generally annular body with an 5 axial inlet throat 26 communicating with the sump S at a level below the tank wall 17 so as to be submerged in fuel from the tank even when the tank is substantially empty. The inlet 26 is cylindrical and preferably has an outwardly flared or beveled mouth 26fl, for smooth flow 10 to the inlet. The cylindrical wall 26 of the inlet is intersected by a plurality of diffuser passages 27 which extend radially outwardly and axially downwardly from the inlet to the generally cylindrical periphery 28 of the pump casing. An upwardly curved lip 29 is formed around the 15 periphery 28 below the passageways 27 for directing discharge from the passageways away from the inlet 26.

As shown in Figure 2, the passageways 27 are separated by ribs 3® providing diffuser vanes. The passages 27 thus have inner ends in advance of the outer ends to diffuse 20 a centrifugally whirling flow from the vanes of the impeller 14 to a laterally outward flow over the lip 29 at a relatively high velocity.

The cylindrical inlet 26 tapers outwardly above the passages 27 as illustrated at 26b in Figure 1 to provide 25 a gradually widening passage. The upper end of the portion 26 b merges into a widely beveled or flattened wall 26c having a substantial horizontal component. An annular volute chamber 31 surrounds the wall 26c so that the inlet 26 discharges into the volute and is in full com30 munication therewith around the entire inner circumference of the volute chamber.

The volute chamber 31 has a peripheral outlet conduit 32 extending from the periphery 28 of the casing 25 to an inverted bell-shaped coupling 33 on top of the plate 35 15 and having an open bottom end bounded by a rim flange 34 on the bottom of the plate. The top of the coupling 33 has an internally threaded boss 35. An Lshaped pipe coupling 36 snugly fits in the rim 34 and has a boss 37 receiving a bolt 38 therethrough which is 10 threaded into the boss 35 to draw the coupling 36 tightly against the gasket 39 between the bolt 38 and the coupling thereby uniting the parts. The volute chamber thus discharges to the pipe coupling 36.

The pump casing 25 has a flat top 39 with a cylindrical 45 aperture 4® therethrough aligned with the inlet 26 and terminating at the volute chamber 31. The top wall 39 is tapped at intervals to provide screw holes such as 41 around the opening 40.

A screen 42 surrounds the periphery 28 of the casing 59 25 and is bottomed on the side wall of the depressed portion 21 of the base 15 to surround the passages 27 and the inlet 26 so that fuel from the tank must be screened before it enters the sump and reaches the passages or the inlet.

⁵⁵ The cover or end head 12 of the pump assembly 10 is composed of a flat plate-like portion 43 overlying the top wall 39 of the pump casing and apertured at intervals to receive mounting screws 44 threaded into the holes 41. This plate portion 43 extends beyond the periphery ' ’ 28 of the pump casing 25 to provide a projecting flange.

The plate has an integral thickened central portion or head 45 snugly fitting through the bore or aperture 40 in the top of the pump casing and projecting into the upper portion of the volute cavity 31 to form a cylindrical ' inner periphery for the cavity. The head 45 has a flat bottom 46 with a central cylindrical aperture 47 extending to a radial shoulder 48 which terminates at a larger diameter bore 49 extending through the head to a counterbore 59 through the plate portion 43. A well is thus 70 provided in the head 45 and has an open bottom 47 with a shoulder 48 surrounding this open bottom.

A groove 51 is formed around the head 45 to register with the wall of the aperture 40. This groove 51 is joined with the volute 31 through a bleed hole 52 in the pump 75 casing and is joined with the top of the plate 43 through

2,833,292

OjJ a bleed hole 53. Fluid from the pump casing will, therefore, be bled through the plate to flood the motor casing for lubricating the motor bearings and cooling the motor.

A bushing sleeve 54 is press fitted into the bore 49 of the head 45 and is bottomed on the shoulder 48. A carbon bearing ring 55 is carried in the bushing 54 and is also bottomed on the shoulder 43. If desired, the carbon bearing could be replaced with any other suitable bearing ring or with an anti-friction bearing assembly.

The motor part 13 is composed of a generally cylindrical casing 56 with an outturned flange 57 at the bottom, thereof apertured at intervals to receive fastening screws 58 which are threaded into the extended flange portion of the plate 43 thereby uniting the part 12 to the casing 13.

The top of the casing 56 also has an outturned flange 59 therearound and a cover plate 60 on the top of the casing 56 is apertured around the periphery thereof to receive fastening screws 61 threaded into the flange 59. This cover plate 60 has a cup-shaped raised central portion 62 providing a recess 63. An annular skirt 64 depends from the cover portion to provide a cylindrical bore 65 in the cover carrying a bushing sleeve 66 which is bottomed on a shoulder 67 between the bore 65 and the recess 63. A carbon bearing ring or other suitable bearing 68 is mounted in the bushing 66. A screened port P is provided in the plate 69 to vent the interior of the motor casing to the tank so that fluid from the bleed hole 53 can be circulated through the motor casing.

A hollow motor shaft 69 has one reduced end 69α thereof rotatably mounted in the bearing ring 55 carried by the end head 12 and a second reduced end 69b rotatably carried in the bearing ring 68 mounted in the end cap 60. An integral collar portion 70 on the shaft provides a shoulder overlying the bearing ring 55 to thrust thereagainst. A shoulder 71 on the upper end of the shaft bottoms a washer 72 thrusting against the bearing ring 68. The shaft is thereby rotatably supported in the bearing rings 55 and 68 and is held against axial shifting by the thrust collar 70 and washer 72.

A thickened portion 74 in the shaft 69 above the collar 79 provides a reduced diameter splined bore 75 and a flat top shoulder 76. A self-locking nut 77 bottomed on the shoulder 76 has a splined portion 78 anchored against rotation in the bore 75. A relatively thin mounting bolt 79 is threaded into the nut 77 and depends into the inlet mouth 26 of the pump casing.

A motor armature 80 is secured around the shaft 69 and a motor field winding 81 is mounted in the casing 56 to surround the armature SO. The shaft 69 is thus driven by the resulting motor.

As shown in Figures 1, 3 and 4, the impeller 14 has a hub S2 snugly fitting in the open bottom end of the shaft 69. A key 83 carried in a groove in the hub 82 is seated in a groove 84 of the shaft 69 to join the hub and shaft for co-rotation. The mounting bolt 79 extends through the hub and has its head thrusting against the underface of a disk-like impeller head 85 fitting freely in the aperture 47. The bolt draws the head tightly against shims or a washer 86 on the bottom of the shaft 69. The tensioned bolt firmly holds the head 85 in thrusting relation with the end of the shaft which is surrounded by the bearing 55. The shims 86 provide the desired clearance between the impeller and the bottom wall 46 of the head 45. The telescoped hub 82, shaft 69, bearing 55 and bearing sup-, port 54 provide a firm support for the impeller without occupying any appreciable vertical space. A firm, rigid, lightweight, compact impeller support is thus provided.

Five fingers 85α radiate from the bottom of the head 85 in spaced spiral paths and pumping vanes 87 depend from the fingers. Each vane 87 has a sharp inner leading edge 87α sloping to the head 79α of the bolt 79 along a beveled path simulating the drainage path of liquid through an opening thereby accommodating smooth flow into the pump. The peripheral portions of the vanes closely confront the cylindrical· wall 26 of the inlet and follow the contour of the inlet portion 266.

Each vane 87 is arcuately curved for efficient centrifugal pumping action and is also axially pitched for induced axial flow through the inlet.

The vanes 87 have relatively deep major inner end portions and relatively shallow outer end portions. The deep inner end portions constitute about 50% to 65% of the area of each vane and lie within the diameter of the main inlet 26 while the shallow portions span the opening into the volute chamber 31. The leading corners between the leading ends 87α and the bottoms 87A span the mouths of the diffuser passages 27. The bottoms 87 b closely overlie the inlet wall 26Z&gt; and upright peripheral ends 87c project into the gap between the end wall 46 of the head and the top edge 26c of the inlet. Of course, the impeller can be inserted into the casing 25 with the head 45 and has an overall diameter less than the head. This arrangement produces high speed efficiencies at high flow rates and the axial pitch of the vanes produces a propeller effect to enhance the high speed efficiency.

At high rates of flow, the pump 10 receives fuel from the sump S through the inlet 26 and through the passages ‘TJ· At such high rates of flow little or no vapor separation will occur and the pump is adapted to swallow the gases and. vapors and force them through the conduit 36 at such high rates that they cannot accumulate to form a pocket or trap within the pump.

When the rate of flow through the pump is slowed down to deliver fuel at lower rates as for example, when the engine demand is lessened, the flow through the passages 27 will be reversed and vapors removed from the fuel by the agitating effect of the impeller on the fuel will flow outwardly to be discharged over the lip 29 and out of the path of the incoming fuel to the inlet 26.

Thus, at 100% pump capacity (sea level rate of flow for jet engines), the velocity in all pump passages is very high. Through the entrance part of the impeller there is practically no rotation of the fuel. As a natural hydraulic consequence, the flow of fuel through the inlet diffuser is inward from the tank to the impeller. Velocities are too high for separation of bubbles at any point m the pump.

At intermediate altitudes (20,000 to 30,000 feet altitude), the jet engine demand may be reduced from 45% to 75% of maximum pump capacity. Flow velocities in the pump are reduced accordingly, and the fuel rotates immediately upon entering the impeller. The combination of reduced inlet velocities and fuel rotation brings about a reversal of flow through the diffuser passages 27.

At high altitudes, the jet engine fuel demand may be reduced considerably below 40% of the pump capacity and flow through the pump is reduced to such an extent that maximum rotation and centrifuging of the fuel occurs.

The rate of climb of the aircraft and the degree, if any, of pressurization of the fuel tank, will vary widely with different types of aircraft so that to meet different specifications such as increased vapor removing capacity the impeller S3 of Figures 5, 6, and 7, may be substituted lor the impeller 14. The impeller 88 extends further into me pump inlet 26 to increase the size of the centrifuging chambers. The extended centrifuging chambers do not have the pumping efficiency of the impeller 14 and for the same amount of pumping, the impeller 88 will require more power than the impeller 14. The impeller 88 has the same small diameter hub 82 as the impeller but has a hollow shank portion 89 receiving a longer mounting bolt than the bolt 79. This shank 89 is surrounded by propeller-like vanes 90 which have a screw-like configuration. Four vanes 90 are provided each with a substantially flat bottomed end spanning the mouth of the inlet 26 and having an edge 90α extending radially from the shank 89. Each edge 90α serves to slice liquid in the 75, inlet and feed it to a spirally inclined wall 90b of the

2;832,292 vane which merges into an upstanding wall 90c at the outer periphery of the vane. The upstanding wall 90c is integral with fingers 90d which radiate from the hub 82 like curved teeth.

Vapor separating chambers are provided between the vanes 90 and gas bubbles are allowed to accumulate in greater quantity without interfering with the pump flow. These gas bubbles will be ejected through the passages 27 more effectively than by the impeller 14.

It will be noted that the impeller vanes 87 and 90 span the inner ends of the passages 27 at a diameter which is approximately equal to the main inlet diameter 26. Since liquid entering the pump is picked up by the propeller part or pitched part of the vanes, at high rates of flow the angle of lead of the propeller part is about 15 equal to the angle of advance of the liquid about to enter the passages 27. The liquid, at this high entrance velocity, does not immediately start revolving with the impeller and the non-revolving liquid tends to enter the passage in a direction parallel to the face of the vanes. The 20 non-revolving liquid passing into the impeller at high velocity with respect to the impeller vanes, does not have sufficient rotation to be centrifugally discharged outwardly through the passages 27. This high entrance velocity of the liquid creates a reduction in pressure at the pas- 25 sages 27 thereby drawing the liquid inwardly into the pump.

Thus, at high rates of flow, there is a minimum centrifugal force effect and a minimum time delay within the impeller to cause centrifugal separation and the gathering of large gas bubbles. There is also a sufficient inlet velocity to draw the fuel through the passages 27 and augment the feed from the inlet 26.

When the flow through the pump is reduced, the velocity through the impeller passages is proportionately reduced and there is an accompanying increase in the rotative speed of the liquid as it becomes enclosed between the propeller-shaped entrance vanes. This increase of rotating liquid speed increases the centrifugal force outwardly in the liquid to bring about an outward flow of liquid through the passages 27. Further, at the reduced rates of flow in the pump, there is an accompanying time delay within the impeller passages which gives more time for the centrifuging of bubbles and the merging of many small bubbles into a fewer number of larger ones. When the volume of gas or the rate of bubble accumulation is normal, the outward liquid flow through the inlet 26 sweeps the bubbles outwardly through the passages 27 to prevent gas accumulation which will interfere with normal pumping. As the flow through the pump, decreases to very small quantities in proportion to the full capacity of the pump, the centrifugal and vapor sweeping factors near the pump entrance become increasingly active to prevent air or gas binding.

Fuel under pressure in the volute 31 is held through the hole 52 into the groove 51 and thence through the hole 53 to. flood thecasing 13 thereby cooling the motor and lubricating the bearings 55 and 68 with the fuel being pumped.

The pump 10 can be further modified to increase its vapor separating capacity by the addition of more power to accommodate the increased vapor separation power demands as shown in Figure 8. The modified pump 100 of Figure 8, includes the same mounting base and pump casing part 11 as the pump 10 and common parts of both pumps have: been marked with the same reference numerals. The pump 100, however, includes a diffuser type cover or end head 101, a larger motor 102, and a more effective bubble-removing impeller 103.

The diffuser cover 101 is mounted on the pump casing 25 in. the same manner as the cover 12 and carries the motor casing 56 in the same manner as the part 12 of the pump 10. The member 101, also supports the motor shaft 69 in the same manner as described in connection with the pump 10.

The member 101, however, has a thicker top wall 104 than the wall 43 of the part 12 and this thicker wall has diffuser passages 105. These diffuser passages 105 have radial portions 105α discharging through the cylindrical periphery 28 of the; pump casing 25 at the top of the casing and have tapered inner portions 1055 sloping axially downward and radially inward from the inner ends of the. portions 105« to provide inlet ends in the bottom face of the head portion 106 of the member 101.

This head portion 106 fits through the aperture 40 in the top of ths pump casing. 25 in the same manner as the head portion 45 of the member 12.

The diffuser passages 105, as best shown in Figure 9, are separated by ribs 107. These ribs or vanes 107 have side walls shaped so that the passages 105 are, in effect, tangential gaps designed for centrifugal discharge. These passages have inner ends in advance of the outer ends so as to diffuse the centrifugally whirling flow into a lateral outward flow at relatively high velocities.

It will be noted that the inner or feed ends of the passageway portions 1055, are at a diameter smaller than the diameter of the inlet 26 so as to receive fluid from the impeller 103 which is rotating at a relatively high speed effected by a full forced rotation from the impeller vanes. In addition, the fluid is under a positive pressure resulting from the pumping effect of the propeller action of the vanes and the centrifugal force of the impeller vanes.

The impeller 103, as best shown in Figures 8 and 10, ³⁰ is similar to the impeller 88 but has five screw vanes 108.

These vanes are spiralled or helically arranged around the central post 109 which receives the mounting bolt 79. The vanes 108 have substantially flat forward lower ends with sharp end edges 108α adapted to slice into the liquid in the inlet 23 and raise this liquid along the top helical faces 1085 of the vanes to the vertical faces 108c which depend from the fingers 10M. The impeller 103 functions in the same manner as the impeller 88 except that it has an additional vane for inducing vapor ⁴⁰ separation. The five vanes accelerate the liquid axially and discharge it centrifugally into the volute of the pump. The rapid axial acceleration sweeps bubbles to the diffuser passages 1055. As indicated, these passages have inlet ends positioned at the terminal end of the impeller 45 cavity where the fluid is always rotating at a high speed and is under a positive pressure. The vapors will be swept through the passages 1055 into the passages 105α and discharged radially from the pump.

Since vapor separation involves consumption of en50 ergy, the motor 102 is larger than the motor of the pump 10 so as to be capable of driving the impeller at high speeds even under the increased load imparted by vapor separation. Thus, the pump 100, while still having the basic housing component 11 as the pump 10, has an added 55 vapor diffuser and a vapor separating impeller for coacting with the diffuser to enhance the high altitude performance of the pump. The larger motor 102 can also be used with the four-vane impeller 88.

The telescoped impeller hub, motor shaft, shaft bearG0 ing, and bearing support, for the pumps 10 and 100, will provide a firm stable impeller support within a very compact area. The thrusting of the impeller shoulder against the end face of the shaft enhances the rigidity of the assembly. The contacting thrust faces are of rela65 tively large diameter compared with the hub so that tilting or cocking of the impeller is prevented even if the hub has a free fit in the shaft. This makes possible an impeller of smaller overall diameter since the mounting screws 79 can be very thin or can be quite short in the 70 type of impeller indicated at 14 for the pump 10.

If desired, as shown in Figure 11, the mounting bolt 79 for the impeller such as the impeller 103, can be replaced with a bolt 110 extending through the hollow shaft. In this arrangement the impeller hub 82 is in75 ternally threaded at 111 to receive the threaded end of

2,832,292 the bolt 110 and a cover disk 112 overlies the upper end of the motor shaft 69. The head of the bolt is bottomed on this disk. Notches 113 are preferably provided in the end of the shaft under the disk 112 to receive a lock wire (not shown) to hold the bolt 11Θ. The bolt 110 will 5 draw the head of the impeller tightly against the gasket 86 in the same manner as described in connection with Figure 1. Here again, the impeller hub, motor shaft, bearing, and bearing supports are nested and telescoped while the shoulder of the impeller is firmly bottomed on ’ the shaft.

As illustrated in Figure 12, the pumps of this invention are built up from a basic mounting plate and pump casing part 11 which can selectively receive a. high flow rate impeller 14 with a moderate vapor separating capacity, a lower flow rate impeller 88 with a higher vapor separating capacity or an impeller 103 with a still higher vapor separating capacity. Further, an end head part 12, or a diguser end head part IM, can be used in the pump. In addition, the pump can have any one of a number of motor components including small motors such as 13 and a larger motor such as 102.

From the above descriptions it should thus be understood that this invention provides pump assemblies which can be selectively built up from basic parts to meet various specifications and thereby eliminate wastage of power. The pumps of this invention have secondary inlets which firaction to augment intake at high rates of flow and which will serve as difiuser outlets for bubbles of gas or vapor at lower rates of flow through the pump. The pumps can be equipped with secondary difiuser outlets to cope with severe vapor conditions to the end that fully liquid fuel in desired amounts will always be delivered regardless of altitude. The motors and impellers of the pumps of this invention are adapted to be changed or substituted to meet requirements of different engine fuel systems. Thus, the invention provides basic pump components which can be used in various combinations to modify the pump characteristics.

It will be understood that variations and modifications may be effected without departing from the scope of the novel concepts of this invention.