GB2434619A

GB2434619A - Self priming centrifugal pump

Info

Publication number: GB2434619A
Application number: GB0519408A
Authority: GB
Inventors: Kevin Stone; Martyn Jenkins
Original assignee: Kautex Textron CVS Ltd
Current assignee: Kautex Textron CVS Ltd
Priority date: 2005-09-22
Filing date: 2005-09-22
Publication date: 2007-08-01
Also published as: EP1957801A1; GB0519408D0; WO2007039139A1

Abstract

A centrifugal pump which may be used to pump wash fluid for an automobile has an inlet 10 with a hollow tube 12 connected to a radial portion 14. The tube 12 has two holes 16,18 which extend along the tube 12 towards the radial portion 14. One of the holes 18 extendes further along the tube 12 than the other hole 16. An impeller (30, fig 3) sits inside the inlet 10 and extends along the tube 12. A line made by joining the end of the impeller (30, fig 3) with the end of the longer hole 18 forms an angle of up to 45{ against the axis of the impeller (30, fig 3). In another embodiment, the ratio of the distance between the end of the impeller (30, fig 3) and the end of the longer hole 18, and the distance between the end of the longer hole 18 and the top of the tube 12 is less than 1 to 10.

Description

1 2434619 Liquid Pump System The present application relates to a

liquid pump system and more particularly to a pump for a wash system for automobiles and headlamps.

Many liquid pumps fall into the category of centrifugal pumps. A centrifugal pump uses an impeller to rotate the liquid rapidly in a casing, chamber, or housing. This rotating action moves the liquid through the pump by means of centrifugal force.

In order to operate satisfactorily a centrifugal pump must have a wet inlet, that is, there must be liquid in both the intake (or inlet) pipe and the casing when the pump is started. They have difficulty sucking liquid up into the intake pipe. Therefore they must be primed before the first use. To prime the pump it is normally necessary to fill the intake pipe with liquid and then quickly to turn the pump on. If there is no liquid already in the pump it will typically have great difficulty in pulling any liquid up into it.

Automotive screen wash and headlamp cleaning systems are well known in the automotive industry. They are used to provide cleaning liquid from a reservoir to the windscreen or the head lights via a nozzle. This is with an aim to help remove unwanted dirt or stains which may restrict the transparency of the surfaces.

Transparency of the surfaces enables the driver to see clearly through the windscreen and the headlight beani to shine more brightly, therefore improving the overall road safety of the vehicle.

Typically these wash systems utilise a small DC motor driven impellor pump to transfer wash fluid, at pressure, from a container to delivery nozzles. Such pumps have a variety of designs and can for example incorporate a single or a dual outlet.

The pumps are designed to niove wash fluid but are not generally suitable for pumping gaseous material such as air against any kind of back pressure. Though they perform perfectly adequately in service, they can be difficult to prime initially when the system is full of air, especially since the outlet nozzles are often fitted with anti-return valves that to some extent resist the flow of air out of the system. This can pose a particular difficulty for the automotive manufacturer and for auto repair facilities after the system has for any reason been drained.

In general these pumps employ one of two types of inlet, firstly a side inlet where the fluid is allowed to fill the pump chamber directly from a point level with the chamber, and secondly bottom inlet. In the second case the impellor is tapered and extended downwards from the pump chamber inside a hollow tube. It is these bottom inlet designs that can be particularly difficult to prime.

Current inlet designs have small hole s at opposite sides of the lower end of the inlet that allows fluid to enter the inlet whilst the impellor is spinning. However in the worst cases there is nowhere for the air that fills the pump chamber to be expelled and in such cases it can be observed that this air is expelled down the inlet at the same time that the fluid is required to be drawn up. Pulsing the pump is one way to achieve the simultaneous expulsion of air and ingress of fluid. However this can be time consuming and is not always effective.

An aim of the present invention is to provide an inlet design for use with a pump that enhances the ability of the pump to prime itself even in the most adverse conditions.

According to a first aspect of the present invention there is provided a liquid pump system having an inlet tube, an impeller extending into the inlet tube and able to rotate relative to the inlet tube, there being a passage extending through the wall of the inlet tube, the passage being located such that hole the angle between the axis of the impeller and a line connecting the distal end of the impeller and the proximal wall of the passage is less than 45 degrees.

The said line preferably intersects the inner point of the proximal wall of the passage.

The said line preferably intersects the most proximal point on the proximal wall. The said line preferably intersects the most radially outward point on the distal end of the impeller.

This arrangement can offer the advantage that in use there can be created a vortex of sufficient depth to allow the pump to reliably prime itself in a fast time.

Preferably the said angle is less than 40 degrees, 35 degrees, 30 degrees, 25 degrees, degrees, 15 degrees, 10 degrees 5 degrees.

Preferably the inlet is a hollow tube and the passage hole is in the form of an elongate slit. Preferably the slit runs along the axis of the tube. Preferably the slit extends to the distal end of the tube. Alternatively the passage may be of another form, for example a hole having a distal as well as a proximal wall.

Preferably the hollow tube has two hole passages through the wall thereof, one on each side of the tube, only one of which creates the angle greater than 45 degrees.

Preferably one of the passages has its proximal wall further from the distal end of the inlet tube than the other of the passages. This can assist in supporting a vortex in the tube.

Advantages of this arrangement include that such a hole passage can be effective in simultaneous expelling air and delivering fluid faster than previous devices and even under the most adverse of conditions. The fluid may be drawn closer to the pump chamber on start up. The air in the system upon start up maybe forced out of the hole over a reduced distance and through a reduced thickness of water due to the increased inclination of the vortex.

Preferably the hole preferably is more than 6 mm, preferably more than 10mm, most preferably 12mm or more in length along the axis of the tube.

Preferably the liquid pump system is for use in an automotive washer system.

Advantageously the automotive washer system is the windscreen washer system.

Advantageously the automotive washer system is the headlight washer system.

Preferably the inlet is made of a plastics material.

Preferably the inlet is formed from one moulding.

This can allow the inlet to be manufactured quickly and efficiently.

According to a second aspect of the present invention there is provided a liquid pump system having an inlet tube, an impeller extending into the inlet tube and able to rotate relative to the inlet tube, there being a passage extending through the wall olthe inlet lube, the passage being located such that the ratio of the distance between the proximal wall of the passage and the top of the inlet tube and the distance between the distal end of the impeller and the proximal wall of the passage is less than 10.

Preferably the ratio is less than 9, preferably less than 8, preferably less than 7, preferably less than 6, preferably less than 5, preferably less than 2, most preferably less than 1.5 or less than 1. Preferably the said distances are the distances between the said points parallel to the axis of the impeller (i.e. as projected on to that axis).

An inlet made in accordance with the present invention will now be described herewith by way of example with reference to the accompanying drawing, in which Figure 1 shows a perspective view of an inlet made in accordance with the present invention; Figure 2 shows a pump assembly; and Figure 3 shows a cross section of a pump assembly.

In Figure 1 a pump inlet 10 is made of plastics material or similar. The inlet 10 includes a hollow tube 12 connected to a radial portion 14. The tube 12 has two hole s 16 and 18 in the end furthest from the radial portion 14. The cuts outs 16 and 18 are positioned opposite to one another on the circumference of the tube. One of the hole s 18 has its distal wall closer to the radial portion 14 than the other hole 16.

Figure 2 shows the radial portion 14 connected to a pump body 22 from which there projects a fluid outlet 20. The pump body is in turn also connected to a motor housing 24 with an electrical connector 26.

Figure 3 shows a cross section through the pump assembly. The inlet is connected to the pump body by any suitable means such as welding or bolts 38. A motor 36 is connected via a seal 34 to an impeller 30. The impellor sits within a pump chamber 32 and extends down through almost the entire length of the tube 12.

The hole is located so that a line connecting its proximal wall -that is the wall closest to the pump body -and the distal end of the impeller makes an angle of 45 degrees, or preferably even less, with the axis of the impeller.

Alternatively the hole is located such that the the ratio of the distance between the distal end of the impeller and the proximal wall of the hole and the proximal wall of the hole and the top of the inlet tube -that is the point at which the inlet tube broadens into the pump chamber 32 -end adjacent the radial portion 14 -is less than ltolO(l:l0). The In use the lower end of the inlet 10 is inserted into a liquid container such that the level of the liquid in the container sits flush with the base of the radial portion 14.

The liquid will enter the tube 12 and because the pump system is a closed unit the water rise up to the highest point of the hole 18. The angle between the lowest point of the impeller and the highest point of the hole 18, and therefore the level of the liquid, is such that when the motor is turned on and the impeller 30 is caused to rotate, the friction between the impeller and the water creates a centrifugal force and causes a higher vortex to be formed in the liquid around the impeller than has previously been appreciated. The point of the vortex closest to the impeller will move downwards in the axial direction of the impellor and away from the radial portion 14. The point of the impeller closest to the inside of the wall of the tube 12 will move upwards in the axial direction of the impeller and towards the radial portion 14. Due to the greater angle of the vortex this quickly becomes sufficient to push liquid into the pump chamber 32 and draw more liquid into the hollow tube 14. Air trapped in the system will move downwards into the space created by the vortex and past the point of hole 18. When the pressure of the air within the vortex is sufliciently great the air will pass out through the hole 18. Because the angle of the hole 18 and the impeller 30 is greater, the angle of the vortex will be greater and the distance the air has to travel before it can release is reduced in comparison to prior art designs. Therefore over a shorter period of time the trapped air passes from the pump chamber 32 and the hollow tube 14 out through the hole 18. It has also been noted that visually, small bubbles are dispersed when the pump is operated than with comparable prior art designs. It is observed that such a hole 18 is effective in simultaneously expelling air and delivering fluid even under the most adverse of conditions. The liquid that moves into the pump chamber 32 is then delivered under increased pressure through the fluid outlet 20 to a delivery nozzle (not shown).

The applicant hereby discloses in isolation each individual feature described herein and any combination of two or more such features, to the extent that such features or combinations are capable of being carried out based on the present specification as a whole in the light of the common general knowledge of a person skilled in the art, irrespective of whether such features or combinations of features solve any problems disclosed herein, and without limitation to the scope of the claims. The applicant indicates that aspects of the present invention may consist of any such individual feature or combination of features. In view of the foregoing description it will be evident to a person skilled in the art that various modifications may be made within the scope of the invention.

Claims

Claims 1. A liquid pump system having an inlet tube, an impeller

extending into the inlet tube and able to rotate relative to the inlet tube, there being a passage extending through the wall of the inlet tube, the passage being located such that the angle between the axis of the impeller and a line connecting the distal end of the impeller and the proximal wall of the passage is less than 45 degrees. hole.
2. A liquid pump system according to claim 1 in which the inlet tube has two passages therethrough, only one of which creates the said angle greater than 45 degrees.
3. A liquid pump system having an inlet tube, an impeller extending into the inlet tube and able to rotate relative to the inlet tube, there being a passage extending through the wall of the inlet tube, the passage being located such that the ratio of the distance between the proximal end of the passage and the top of the inlet tube and the distance between the distal end of the impeller and the proximal wall of the passage is less than 10.
4. A liquid pump system according to claim 3 wherein the ratio is less than
5.

5. A liquid pump system according to claim 3 wherein the ratio is less than 2.
6. A liquid pump system according to claim 3 wherein the ratio is less than I.
7. A liquid pump system according to any preceding claim in which the hole passage is in the form of an elongate slit.

8. A liquid pump system according to any preceding claim in which the hole is greater than 6mm in length 9. A liquid pump system according to any preceding claim for use in an automotive washer system.

10. A liquid pump system according the claim 9 in which the washer system is the windscreen washer system.

11. A liquid pump system according to claim 9 in which the washer system is the headlight washer system.

12. A liquid pump system according to any preceding claim in which the inlet is made of a plastics material.

13. A liquid pump system according to any preceding claim in which the inlet is formed from one moulding.

14. A liquid pump system substantially as described herein and with reference to the accompanying drawings.