GB2031126A - Improvements relating to valves for windscreen washers - Google Patents

Abstract

One-way valves currently used in vehicle windscreen washer installations usually comprise a type of spring loaded valve member which is prone to leakage unless a strong spring is used. This invention provides a simple and cheap form of one-way valve which has improved flow and sealing characteristics. A resilient valve member 14, (17) Fig. 11 (not shown) of rubber or plastics in the form of a hollow cylindrical tube of circular cross-section in its free state is compressed in a valve chamber (6), Fig. 4 (not shown) (19) which has a semi-cylindrical valve seat 7. In operation water enters the chamber through an inlet 3, (20) in the valve seat 7 forcing the tube 14, (17) to collapse and provide free flow to an adjacent outlet (10), 13. The valve may be incorporated in a pump 50 as a unit. <IMAGE>

Description

SPECIFICATION Improvements relating to valves for windscreen washers This invention relates to one-way valve assemblies, primarily for use in vehicle windscreen washer installations.

A windscreen washer installation usually includes a liquid reservoir, a pump, and a nozzle through which a jet of water is ejected towards the windscreen or rear window of the vehicle. It is impractical to arrange for the level of water in the reservoir to be level with the nozzle, so that when the pump is not in operation there is a tendency for water to drain back to the reservoir giving rise to delay before water is ejected from the nozzle, when the pump is operated.

Usually this problem is alleviated by incorporating a one-way valve in the installation between the reservoir and the nozzle. The requirements of such a valve are that it should offer a reliable seal against drain-back, yet permit free forwards flow of water, when the pump is being operated. The drain-back pressure is of course very small, being merely due to the head of water between the nozzle and the reservoir. This pressure is thus not reliably effective to assist in sealing the valve so that it is usual to load the valve member with a spring. It will be realised that the washer may remain unused for a considerable time, during which it will often be subject to shocks and vibrations of the vehicle, so that a very efficient seal is necessary to inhibit drain back.The valve should also seal against leakage from the nozzle when the vehicle is parked on an incline and the water level in the tank is higher than the nozzle.

Known valve assemblies have been for example of flap or diaphram construction and have required quite strong springs to seal reliably against drain back, so that they have also significantly interfered with the free flow of pumped water. They have also been relatively expensive.

According to the invention a one-way valve assembly, comprises a housing provided with a chamber in which is located a resilient valve member, the valve member having the form of a hollow cylindrical tube of substantially circular cross-section in its free state, the walls of the chamber being provided with a valve seat connected to an inlet port and being so shaped and dimensioned that a part of the radially outer surface of the tube is urged against the valve seat.

The chamber may be so shaped that the tube is deformed to an ellipse, the major axis of which is greater than the diameter of the free circle of the tube, and the minor axis is smaller. The minor axis is preferably in line with the valve seat.

Preferably, however, that part of the wall of the chamber which contains the valve seat is made to substantially the same curvature as the outside of the tube in its free state. The radial deformation of the tube then involves little distortion of the tube in that part of it which contacts the seat. Hence it is an easy matter to ensure that the deformed tube "fits" the seat all round its periphery. The more complex the distortion induced, the less easy it is to predict the configuration required of the seat to ensure a reliable seal.

The chamber may be formed in part by a separate member which serves to compress valve member when assembled.

The invention further consists in a vehicle windscreen washer installation incorporating such a valve assembly. Such a valve assembly is very cheap to make, since a shaped chamber can easily be incorporated into a moulded plastics housing, and since the moving part of the valve is simply a length of resilient tube, which has a very small cost. The tube may be made for example of rubber; the material should retain its resiliency during prolonged contact with the liquid, which in the case of a windscreen washer is water, perhaps with detergent and anti-freeze additives. If a rubber tube is used care should be taken to select a grade of rubber which is not affected by antifreeze additives and E.P.D.M. has been found suitable.

Preferably, the valve assembly is incorporated in the windscreen washer pump but may be provided as a separate unit.

It has been found that such a valve assembly can provide a reliable seal against drainback and yet not interfere significantly with the pumped flow.

The invention will now be further described, by way of example, with reference of the accompanying drawings, in which: Figure 1 is a section taken on the line I-I of Fig. 2 of a valve assembly embodying the invention and shown incorporated in a windscreen washer pump; Figure 2 is a section of the valve assembly taken on the line Il-Il of Fig. 1 but omitting the pump; Figure 3 is a sectional illustration showing the valve assembly partly exploded; Figure 4 is a plan view of Fig. 3 with parts A and B removed for clarity; Figure 5 is a cross-section taken on the line V-V of Fig. 4; Figure 6 is a cross-section similar to that of Fig. 1 but omitting the pump parts; Figure 7 is a plan view of Fig. 6 but omitting part A; Figure 8 is a plan view of the part A; Figure 9 is a plan view of the part B; Figure 10 is a plan view similar to Figs. 4 and 7 but with parts A and B fitted;; Figure 11 is a section taken on the centre line of a modified form of the valve assembly; and Figure 12 is a section taken on the line Xll-XlI of Fig. 11.

As shown in Fig. 1 a shaft 1 of a pump 50 carries an impeller 2 for conveying water from a reservoir (not shown), connected to an inlet 3, to one or more nozzles (not shown), connected to an outlet 4.

A housing part 5 of the pump body which houses the valve assembly is an integral plastics moulding and includes a valve chamber 6 having a part-cylindrical lower portion 7 and an upper portion having substantially parallel sides 8 tangential to the cylindrical sides of the lower portion. As shown in Fig. 2, the chamber 6 has flat end walls 9, one of which has a relief or cut-out 10. The sides and end walls 8 and 9 may be slightly divergent, for moulding purposes. The chamber 6 is defined in part by a removable disc 11, also part A in Figs. 3, 6 and 10, which rests against a flat surface 12 of the body at the bottom of a cylindrical recess 16. The disc 11 has a hole 13 in register with the cut-out 10.The upper part of the pump housing 5, defines the cylindrical recess 16 which receives a plastics bushing part 5a for mounting the shaft 1 and impeller 2 in the housing part 5 above the disc 11, as seen in Fig. 1.

The two body parts 5 and 5a of the pump 50 are assembled with the disc 11 interposed between the bushing 5a and the flat surface 12. The two parts 5 and 5a are secured together by any suitable means such as screws or bolts and made fluid tight by means of an '0' ring 21.

In the chamber 6 there is a short length of rubber tube 14, also reference 'B' in Figs. 3, 6, 7 and 10. The tube 14 is of circular crosssection in its free state, as shown in Fig. 3.

The chamber 6 is so shaped and dimensioned with respect to the tube 14 that the tube is compressed slightly when the disc 11 is brought into contact with the surface 12, as shown in Figs. 1, 2 and 6. The inlet 3 terminates in a port 15 of the chamber 6, so positioned that the tube 14 is urged towards the port 15 as the tube 14 is squashed by the assembly of the disc 11.

The disc 11 is held down on the surface 12 by being a tight fit in the recess 16. The disc 11 serves as a closure member for the valve chamber 6 and ensures also that the tube 14 does not come into contact with the rotating shaft 1 and impeller 2. When the pump assembly is in use, water enters the inlet 3 and deflects radially inwardly that part of the tube 14 which lies over and adjacent to the port 15. Thus a fluid connection is established between the port 15 and the cut-out 10, and thence through the hole 13 in the disc 11 to the impeller 2 and outlet 4.

When the pump assembly is not in use, the inherent resilie'nce of the tube 14 causes the tube to try to regain its free shape, and thus the rubber of the tube is urged against the port 15, effectively sealing it and preventing water from draining back down the inlet 3.

The relevant parameters of the chamber 6 and tube 14 in one example of the above described embodiment of the invention are as follows. The outer diameter of the tube 14 is 5.3 mm, its wall thickness 0.5 mm, its length 5.0 mm, and its material a special grade of rubber not affected by anti-freeze additives.

The diameter of the part-cylindrical portion 7 of the chamber 6 is 5.3 mm, and the distance between the end walls 9 is 5.3 mm. The port 15 is of 3.2 mm diameter. The distance between the undersurface of the disc 11 and the lowermost extent of the portion 7 is 4.9 mm.

It will be seen from Figs. 1 and 2 that the body 5 is easy to mould, in that its internal configuration has no horizontally (as drawn) re-entrant features. As a consequence of this, the axis of the tube 14 has been arranged horizontally to permit it to be compressed vertically downwards onto a vertical inlet 3.

When ease of moulding is of less consequence, other ways of shaping the chamber so as to compress the tube onto the inlet port may be used. For example, in the embodiment of Figs. 11 and 1 2, the tube 17 is received end-on in the valve chamber 19 and the walls 18 of the chamber 19 are shaped so as to compress the free circle of the tube 17 onto the inlet port 20, which is now horizontally disposed in a housing part 25. The tube 17 becomes extended in a direction at right angles to the direction in which the tube is compressed onto the port 20.

It might be considered that the performance of the valve described could be assessed by assuming that the rubber tube behaves in an equivalent manner to the known sipring and flap type of valve, so that the benefit of the invention lies only in the reduced cost of construction. However, we have found that the effectiveness of the drain back seal, as well as the resistance to leakage from the nozzles when the vehicle is on a slope, with the invention, is comparable with a very strongly sprung conventional flap valve, whereas the interference with pumped flow is comparable with a very lightly sprung flap valve.

We believe that this characteristic of the valve may be explained as follows; when the pump is being operated, the rubber tube 14, 17 is subject to a radial force by the flowing liquid which acts to compress it even further in the same direction that it is squashed by the chamber and it collapses radially inwardly in the region of the inlet valve seat 7. This gross movement creates a large passage through which the liquid may flow with little interference. When the flow stops, the tube "snaps" back to the position illustrated in Figs. 1, 6 and 12, against the valve seat which has a comparatively large sealing area, once again providing high security against drain-back.

It will be appreciated that other minor mod ifications may be made to the valve assembly without departing from the scope of this invention as defined by the claims appended hereto; For example, although plastics is a suitable material for providing injection mouldings of both valve body and the parts of the pump, metal could be used for special applications. Also, the means of connecting the valve body and the pump bushing may be varied such as by providing plastics mouldings with friction detents the snap connection of the two parts.

Claims (16)

1. A one-way valve assembly comprising a housing provided with a chamber in which is located a resilient valve member, the valve member having the form of a hollow cylindrical tube of substantially circular cross-section in its free state, the walls of the chamber being provided with a valve seat connected to an inlet port, and being so shaped and dimensioned that a part of the radially outer surface of the tube is urged against the valve seat.

2. An assembly as claimed in claim 1, wherein the chamber is so shaped that the tube is deformed to an ellipse the major axis of which is greater than the diameter of the free circle of the tube.

3. An assembly as claimed in claim 1, wherein that part of the wall of the chamber which provides the valve seat is of substantially the same curvature as the outside of the tube in its free state.

4. An assembly as claimed in claim 1 wherein the chamber is of substantially cylindrical shape and is defined by a substantially cylindrical side wall and by opposed end walls.

5. An assembly as claimed in claim 4 wherein said side wall comprises opposed substantially flat side wall portions, and the axis of the valve seat is directed substantially parallel to the planes of the side wall portions.

6. An assembly as claimed in claim 4 or claim 5 wherein the housing comprises a removable closure member which defines a further portion of the side wall that faces said valve seat across the chamber.

7. An assembly as claimed in claim 6 wherein the closure member forms one wall of the pump chamber in which an impeller is located.

8. An assembly as claimed in claim 6, wherein the chamber is so shaped and dimensioned with respect to the cylindrical tube that the tube is compressed by the removable member and urged towards the valve seat.

9. An assembly as claimed in any one of claims 6, 7, or 8 wherein the removable member comprises a disc located in a recess in the housing.

10. An assembly as claimed in claim 9, wherein the disc is provided with a hole and one end wall of the chamber with a cut-out, said hole and cut-out being in register and providing a fluid path between the inlet port and an outlet from the housing in operation.

11. An assembly as claimed in claim 4 wherein the housing comprises a removable closure member which defines one of the end walls.

12. A one-way valve assembly as claimed in any one of the preceding claims in combination with a vehicle windscreen washer installation including a liquid reservoir, a pump and at least one nozzle through which water is ejected towards the windscreen or rear window.

13. A one-way valve assembly as claimed in any one of claims 1 to 11, wherein the valve assembly and a pump are combined as a unit.

14. A one-way valve assembly substantially as hereinbefore described with reference to Figs. 2 to 10 of the drawings.

15. A one-way valve assembly substantially as hereinbefore described with reference to Figs. 11 and 12 of the drawings.

16. A one-way valve assembly in combination with a pump substantially as hereinbefore described with reference to Fig. 1 of the drawings.