GB2187232A - Rotary impeller pump for liquids - Google Patents

Abstract

A pump, in particular for fuel for a vehicle engine, comprises an impeller 4 having a first portion 5 provided with at least one radial through hole 27 and a second portion 18 provided with an axial inlet hole 26 in communication with the radial hole(s) 27. The diameter of the radial hole 27 may increase progressively towards its outer end. The pump housing has an axial inlet 23 in communication with a liquid reservoir 25 and an outlet 32 containing a breather opening 60 and an adjacent baffle member 35 which operate to facilitate priming. The pump impeller may be rotated in either direction. <IMAGE>

Description

SPECIFICATION A rotary pump for liquids The present invention relates to a rotary pump for liquids, particularlyforthe supply of fuel to heat engines.

As is known, pumps of the above-indicated type currently in commercial use include an impeller of blade type driven by a DC electric motor. Such pumps are installed in the fuel supply circuit outside the fuel tankorwithin it.

The pump described has several disadvantages, in particularthe blade impeller is of low efficiency because oftheturbulance which causes the flow of fuel, and moreover is subjected to radial thrusts which stress it in a non-uniform manner. Finally, the blade impellar is of relatively complex construction and of relatively high production cost.

The object ofthe present invention is that of providing a rotary pump for liquids which will be free from the above cited disadvantages, that is to say which will be of high efficiency, have an extended working life, and be of simple construction and low cost.

Further objects and advantages ofthe present inventionwill become apparentduringthe course of the following description.

According to the present invention there is provided a rotary pump for liquids, characterised bythe fact that it includes a substantially cylindrical chamber in which is installed a first portion of a substantially cylindrical impeller driven by motor means and including a second portion in which isformed an axial hole in hydraulic communication at its lower end with a liquid reservoir and at its upper end extending as far as the said first portion where it is in hydrauliccommunica- tion with at least one radial hole formed in the said first portion and open towards the said chamber having the outlet opening.

For a better understanding ofthe present invention a preferred embodiment will now be described, by way of non-limitative example only, with reference to the attached drawings, in which: Figure lisa section side view of a pump formed according to the principles of the present invention; and Figures 2 and 3 are sections taken on the lines ll-ll and Ill-Ill respectively of Figure 1.

As illustrated in Figure l,a pump unitforliquids, in particularforfuel of vehicle heat engines, is generally indicated with the reference numeral 1 and comprises an electric motor 2 the casing of which is connected to a rotary pump 3 formed according to the principles of the present invention, having an impeller 4 of plastics material, a central portion 5 ofwhich is disposed within a cylindrical chamber 6 delimited by upper and lower end caps 7 and 8 respectively, and by a peripheral ring 1 liThe casing ofthe motor 2 is connected by screws 12 to the upper end cap 7 which has an axial through hole 13 traversed by an output spindle 14 ofthe motor2.The hole 13 has an upper section 15 of hexagonal cross-section (Figure 3) and a lower section 16 of cylindrical cross-section. The shaft 14 is cylindrical and therefore forms a contact along the intermediate zones ofthe said faces which delimit the section 15. This contact causes a low rotary friction and allows the centring of the spindle 14withoutthe aid of bearings. The impeller4 is cylindrical and coaxial with the spindle 14 by which it is driven to rotate, for example at 6,000 revolutions per minute.

The impeller4 has an upper portion 17 within the section 16 (wherethe clutching connection between this portion 17 and the free end ofthe spindle 14 is formed), the said central portion 5 being of greater diameter than thatofthe portion 17, and a lower portion 18 of diameter iessthan that of the portion 5.

Theendcaps7 and 8, the ring 11 and the impeiler4 are made of plastics material, and in particularthe end cap8andthe ring 11 areformed in one piece. The end cap 8 includes a plate 21 from the perimetral border of which the ring 11 extends upwardly and is fixed rigidly to the end cap 7. The plate 21 has a central hole 22 downwardly from the end ofwhich extends a tubular sleeve 23 which houses within it the lower portion 18 ofthe impeller 4. The free end of the sleeve 23 constitutes an input opening 19 for the fuel, and for this reason a filter 24 is installed therein. The pump unit 1 is conveniently installed within a tank close to the bottom thereof, indicated 25 and illustrated in broken outline in Figure 1.

As illustrated in Figures 1 and 2, through the impeller4, and more precisely th rough the portions 5 and 18thereof, there is formed an axial hole 26 open at the bottom and from which, in the portionS, extend six radial through holes 27.The diameter ofthe portion 5 is less than the inner diameter of the chamber 6 so that, in the chamber 6, between the portion 5 and the ring 11,there is defined an annularspace 28. It is to be noted that between the upperface of the portion 5 of the impeller4 and the lower face ofthe end cap 7, and between the lowerface of the portion 5 and the upper face ofthe plate 21 ofthe end cap 8there is a respective clearance which must be not less than 0.2 mm so that no friction occurs due to the viscosity of the fuel, which would reduce the efficiency of the pump 3. In the upperface ofthe plate21 along the edgeofthe hole22thereisformedaseatforathrust bearing 31 supporting the portion 5 of the impeller4.

The clearance between the lower portion 18ofthe impeller4andthe central hole2ofthetubularsleeve 23 must not be greaterthan 0.1 mm to obtain a sufficient sea I for the an nular space 28.

With reference to Figures 1 and 2, an outlet opening 32 which is radial with the chamber6 is formed in the pump3. In particular, the opening 32 is formed with a first hollow section 33 provided in a radial portion 43 ofthe end cap 8 and closed atthetop by a portion 44 of the end cap 7, and has a second hollow section 34 formed by a sleeve portion 45 ofthe end cap 8 coaxial with the portion 43. The outlet opening 32 is adapted for connection onto the sleeve 45 of a tube (not shown) for the supply offuel to the heat engine. In correspondencewith the outlet opening 32 there is installed a diaphragm 35 of decreasing cross-sectional thickness.

In particular the diaphragm 35 extends from the annularspace28totheinterioroftheoutletopening 32 which, for an initial part ofthe section 33, is divided into two channels. In the end cap 7, after the position ofthe diaphragm 35, there is provided an external breather hole 60 ofsmall diameter, for example 1 mm.

The pump 3 is a centrigual pump in that, in use, the rotation ofthe impeller 4 causes expulsion ofthe liquid from the holes 27 towards the annular space 28 from where,through the opening 32, it flows towards the heat engine. The outward flow from the holes 27 causes a depression therein which draws in the fuel which flows through the inlet opening 19 to the holes 27 through the hole 26. Its to je notedthatthe pump 3 performs its pumping action both with the impeller4 turning in one directional sense and with it turning in the opposite sense.The diaphragm 35 allows self priming ofthe pump 3 in that, if there is air present in the chamber 6, this is conveyed towards the outlet opening 32 and morerapidlythroughthe hole 6 towards the outside since the diaphragm 35 interrupts the circulation ofthe air around the annular space 28.

From what has been described above the advantages achieved with the embodiment ofthe present invention will be apparent.

Among otherthingsthe pump 3 does not require close tolerances and can be made in plastics material.

Moreover,the impeller4does not experience radial thrusts in that a ring offuel around the portion 5 is present, nor axial thrusts in that the impeller4 is self-centring by the effect ofthe liquid present between the lower and upper sides ofthe portion 5. It is moreover, to be noted that the pump 3 is self priming and self draining, particularlythanks to the diaphragm 35 which allows any possible quantities of air drawn in, for example, when the vehicle is taking curves at high speed andthefuel level inthetankis rather low, to expelled.In normal operation of the pump 3there is a laminarflow offuel along the annular space 28 towards the outlet opening 32 unlike the turbulentflow which takes place in pumps with blade type impellers, which allows the efficiency ofthe pump 3 to be raised forthe same dimensions. The liquid present in the annular space 28 and which arrives, through the section 16, into the section 15 of the hole 13, furthercausesthe cooling ofthe spindle 14 of motor2. Finally, it is clearthatthe pump 3 described and illustrated here can have modifications and variations introduced thereto without bythis departing from the protective scope ofthe present invention.

In particular, the outlet opening 32 from the chamber 6 can be radial, tangetial, or lateral in any way. Moreover, the electric motor2 can be of DC type orothertype. The coupling between the spindle 14 and the impeller 4can be differentfrom that described, as can the conformation of the impeller 4, providing the principle of having at least one hole and radial duct27 remains. Conveniently, this duct 27 can have its diameter increasing progressively towards the exterior ofthe impeller4,for examplefrom 2.5 mm atthe inner end to 3.5 mm atthe outer end so asto avoid increases in speed of the liquid senttowards the annular space 28 which could give rise to turbulent motions; moreover pressure losses ofthe pump are reduced. The pump 3 can be submerged in the tank or outsidethetank itself, as long as it is disposed below thefreesurface ofthe liquid in the tank. Finally, the pump3 can pump any liquid andtherefore can be utilised for the supply of any type of fuel (petrol, diesel, alcohol etc).

It will of course be understood that the present invention has been described above purely byway of example, and modifications of detail can be made within the scope ofthe invention.

Claims (16)

1. A rotary pump for liquids, characterised bythe fact that it includes a substantially cylindrical chamber in which is installed a first portion of a substantially cylindrical impeller driven by motor means and including a second portion in which is formed an axial hole in hydraulic communication at its lower end with a liquid reservoir and at its upper end extending as far as the said first portion where it is in hydraulic communication with at least one radial hole formed in the said first portion and open towards the said chamber provided with an outletopening.

2. A pump according to Claim 1, characterised by thefactthatthe said chamber is delimited by an external body of the said pump, there being defined an annular space between the said outer body and the said first portion of the said impeller, from which annular space the said outlet opening extends; there being a clearance between the lower and upper surfaces ofthe said first portion ofthe impeller and those ofthe said outer body such as not to cause substantial frictional forces due to the viscosity of the liquid.

3. A pump according to Claim 2, characterised by thefactthatthe said outer body has a plate having a central through holefrom the outer edge of which a tubularsleeveextendsdownwardly,thetubular sleeve constituting an inlet opening and housingthe said second portion ofthe said impellerwithin its interior.

4. A pump according to Claim 3, characterised by thefactthatthe radiai clearance ofthe said second portion of the impellerwithin the said central through hole is such as notto cause significant loss of seal at the said annularspace.

5. Apump according to Claim 3 or Claim 4, characterised by the fact that on the upper face ofthe said plate around the said central holethere is formed a seatfor a thrust bearing supporting the said first portion ofthesaid impeller.

6. A pump according to at least one of Claims from 2 to 5, characterised by the fact that within the said chamber and in correspondence with the said outlet opening there is a diaphragm which extends from the annular space towards the interior of the said outlet opening.

7. A pump according to any preceding Claim, characterised bythe factthatthe said motor means comprise an electric motor.

8. A pump according to Claim 7, characterised by the fact that the said electric motor has an output shaft to which the said impeller its fixedly connected.

9. A pump according to Claim 8, characterised by the factthatthe said outer body has an axial hole traversed by the said shaft and having a portion of hexagonal cross-section.

10. A pump accordingto at least one ofthe preceding Claims, characterised by the fact that in the said first portion ofthe impellerthere are formed six uniformly distributed radial holes.

11. A pump according to any preceding Claim, characterised by the fact that the said radial holes have a progressively increasing section towards the outside of the said impeller.

12. A pump according to at least one of the preceding Claims, characterised by the factthat it is made of plastics material.

13. A pump according to any preceding Claim, characterised by the fact that the said liquid is fuel for a motor vehicle engine.

14. A pump unit, characterised by the fact that it comprises electric motor drive means and a rotary pump according to any preceding Claim.

15. A rotary pump for liquids substantially as described with reference to the attached drawings.

16. A pump unit substantially as described hereinbefore with reference to the accompanying drawings.