GB2212412A

GB2212412A - Spin-on filter

Info

Publication number: GB2212412A
Application number: GB8726988A
Authority: GB
Inventors: John Harris
Original assignee: COOPERS AP FILTERS Ltd
Current assignee: COOPERS AP FILTERS Ltd
Priority date: 1987-11-18
Filing date: 1987-11-18
Publication date: 1989-07-26
Also published as: GB8726988D0

Abstract

A spin-on filter comprises a housing enclosing an annular filter element 2 which is biassed by a spring 13, enclosed by a rubber tube 14, towards the closed end 11 of the housing. Excessive fluid pressure between inlets 7 and outlet 6 moves the element to the left, against spring 13, to open a bypass passage between housing end 11 and a sealing ring 10 surrounding opening 9 in the element end cap 8 (Fig 2). In Fig 3 the rubber tube 14 is extended to incorporate a non-return valve. <IMAGE>

Description

Spin-on Filters This invention relates to spin-on fluid filters. Such filters are well known; they comprise a casing containing a filter element, the casing having means for detatchably mounting it to associated hardware so that the inlet and outlet fluid flow through the same end of the casing. It is normal to provide such spin-on filters with an internal pressure relief valve which serves to enable fluid to by-pass the filter element when the latter becomes occluded. In the case of automotive filters this is particularly important, to prevent moving parts of an engine being starved of oil.

Filter relief valves usually comprise a disc member which is biased by means of a spring so that under normal conditions the filter element is not by-passed by fluid. It is an object of the present invention to provide an improved construction for a spin-on filter incorporating a relief valve.

According to the present invention, a spin-on fluid filter comprises a generally tubular filter element inside a casing which is closed at one end and has a mounting cap at the other end, said cap including inlet and outlet ports and a means for securing the filter in use, characterised in that the element is axially displacable inside the casing between a position in which fluid flowing from inlet to outlet by-passes the element and a position in which said fluid can only flow through the filter element.

Preferably the element is biassed towards the position in which the fluid is obliged to flow through the element, for example by means of a spring. The spring is preferably a coil spring and to prevent leakage between the coils, it is preferably enclosed in a flexible sleeve such as a rubber tube or boot.

Advantageously the outlet port communicates with the centre of the tubular filter element via a central apperature in the mounting cap. The central apperature, preferably also includes the means whereby the filter is mounted, in use. The inlet is then to the outside of the element through one or more apperatures disposed around the central apperature. The flexible sleeve in such case preferably incorporates a resilient flap constituting a valve member which under no-flow conditions covers the inlet apperature, thereby limiting reverse flow due to gravity and/or syphonic action and/or suction.

The filter element may be a relatively close fit in the casing, but preferably it includes radial location means co-operating with the casing to guide the movement of the element in a direction axially of the casing. The end of the filter element directly opposite to the outlet through the central apperature preferably incorporates an end cap provided with a apperature provided with a peripheral ceiling member which is directed towards the end of the casing, the latter being preferably configured so that the ceiling member engages with it under normal circumstances, thereby preventing leakage from the outside of the element through the end cap apperature to the inside of the element and then to the outlet.For example, the end of the casing may be slightly concave as seen from the outside, with a region configured to act as a sealing surface.

In order that the invention be better understood, preferred embodiments of it will now be described with reference to the accompanying drawing in which, figure 1 is a schematic side view in cross section, with the filter relief valve closed.

Figure 2 is a view of the filter of figure 1, but with the relief valve open, and Figure 3 is a side view in cross section of a modified version of the filter of figure 1 and 2.

In the interest of simplicity like parts in each of the figures have been given like reference numerals. In figure 1, a filter casing 1, contains a tubular filter element 2. The casing is closed at end 11 and has a mounting cap 3 at the opposite end. The cap is provided with a central apperature 6 the margin of which is screw-threaded 5 to enable the filter to be mounted to associated hardware (not shown). The end cap also has a plurality of inlet apperatures 7 as well as a marginal seal 4. It will be appreciated that when the filter is screwed hone into position the marginal seal served to prevent leakage.

Inside the casing, the filter element is located radially by means of lugs 16. It is otherwise free to move a short distance inside the casing axially with respect to the outlet The helical spring 13 is provided to bias the element towards the opposite end of the casing, the spring being enclosed by a rubber boot 14 to prevent leakage between the coils of the spring.

The other end of the element has an end cap 8 provided with a central aperture 9 having a rubber peripheral sealing ring 10.

The adjacent end 11 of the casing is concave, as seen from outside, and incorporates a central area 12 against which the sealing ring 10 abuts, in normal operation to effect a seal.

It will be appreciated that the opposite end of the filter element also incorporates an end cap 15 which not only supports the lugs 16 but also constitutes an abuttment for the spring 13 to act upon. In operation fluid enters through the apperatures 7 flows through the filter element 2 and out through the outlet 6. However when the filter element becomes occluded, for example, by grit or dirt present in the fluid, the pressure differential across the filter element exceeds the force due to the spring 13 causing the filter element to move to the left as best seen in figure 2. The resultant gap 17 between the seal 10 and its seat 12 is sufficient to enable fluid to by-pass the filter element completely.

Referring now to figure 3, the rubber boot 14 includes a flap 18. The periphery of this flap 19, seats against the inside of the mounting cap 3 and under static conditions effectively closes the inlet apperatures 7. This minimises or eliminates the risk of fluid flow in the reverse direction from outlet to inlet through these apperatures.

Claims

1. A spin-on fluid filter comprising a generally tubular filter element inside a casing which is closed at one end and has a mounting cap at the other, said cap including inlet and outlet ports and means for securing the filter in use, characterised in that the element is axially displacable in the casing between a position in which fluid flowing from inlet to outlet by-passes the element and a position in which said fluid can only flow through the filter element.

2. A filter according to claim 1, characterised in that the element is biassed towards the position in which the fluid is obliged to flow through the element.

3. A fluid filter according to claim 2, characterised in that the element is biassed towards the position in which said fluid can only flow through the filter element by means of a spring.

4. A fluid filter according to claim 3, characterised in that the spring is a coil spring enclosed in a flexible sleeve.

5. A fluid filter according to any preceeding claim characterised that the outlet communicates with the centre of the tubular filter element via a central apperature in the mounting cap and the inlet is to the outside of the element via one or more apperatures disposed around the central apperature.

6. A fluid filter according to claim 5, characterised in that the flexible sleeve incorporates a resilient flap which extends radially outwards to cover the inlet apperature, thereby preventing or substantially limiting reverse flow through the filter.

7. A fluid filter according to any preceeding claim characterised in that the element incorporates radial location means, whereby it is constrained to move axially of the casing.

8. A fluid filter according to any preceeding claim, characterised in that the end of the filter element remote from the inlet and outlet ports includes an end cap provided with an apperature, the margin of which incorporates sealing means which in normal operation seat against the end of the casing.

9. A fluid filter according to claim 8, characterised in that the end of the casing against which the sealing means seat is configured to provide a sealing surface.

10. A fluid filter substantially as described with reference to and as illustrated by the accompanying drawings.