GB2160442A

GB2160442A - Filter with by-pass system

Info

Publication number: GB2160442A
Application number: GB08514015A
Authority: GB
Inventors: Paul Jennison
Original assignee: Bendix Ltd
Current assignee: Honeywell UK Ltd
Priority date: 1984-06-22
Filing date: 1985-06-04
Publication date: 1985-12-24
Also published as: GB8415933D0; GB8514015D0; GB2160442B; IN161879B

Abstract

A filter for a compressed air line, through which flow may occur in either direction, is constructed to allow by-passing of the filter element(s) if the pressure drop in either direction is excessive. In Fig. 1 concentric filter elements 6, 9 are biassed by springs in opposite directions and are movable by fluid pressure against their respective springs. In Fig. 2 (not shown) a single filter element is similarly spring-biased and encloses a spring-biassed valve. <IMAGE>

Description

SPECIFICATION Fluid Filters This invention relates to fluid filters and relates especially but not exclusively to filters for use in compressed air systems.

In compressed air systems, especially compressed air braking systems used on heavy vehicles, the valves and other controlling components are becoming increasingly complex and sophisticated. As a result such components tend to be increasingly susceptible to malfunction due to ingress of foreign particulate matter carried through in the air supply. Whilst precautions are taken involving the use of filters and condensers or air driers to ensure the air is clean it is considered desirable to protect certain components by additional in-line filters. On the other hand risk of the flow of air to such an additionally protected device being interrupted by filter blockage has to be minimised and in-line filters have been proposed wherein a filter element is spring biassed to provide a bypass capability if the filter element becomes blocked.

According to the present invention there is provided a fluid filter device capable of filtering fluid flowing in either one of two directions between the ports of a housing including a filter element so spring biassed against a first seat that fluid pressure in one direction across it can unseat the filter element and characterised in that a check valve element is provided so biassed against a second seat substantially concentric with the first element that fluid pressure in the opposite direction across it can unseat the check valve element from the seat.

In order that the invention may be more clearly understood and readily carried into effect the same will be further described by way of example with reference to the accompanying drawing of which: Fig. 1 illustrates an in-line filter employing two elements and, Fig. 2 illustrates an alternative wherein one filter is replaced by a simple biassed check valve element.

Referring to Fig. 1 the in-line filter element comprises a generally cylindrical housing formed of a main body part 1 and a screw attached closure part 2. The body part 1 has a first port 3 and the closure part 2 has a second port 4. These ports are conveniently identical in the sense that the housing may be connected for flow in either direction through a compressed air line. More or less sealingly engageable with the inner end face 13 around the port 3 is an annular flange 5 of a solid part of a top-hat shaped filter element 6, the flange 5 being held so engaged by a biassing spring 7 compressed there between and the face 13 of the closure part 2.The top-hat shaped filter element 6 has an aperture 8 and within it a further smaller top-hat shaped element 9 having a flange 10 which is retained more or less sealingly engaged by means of a further biassed spring 10 retained between it and the end 12 of the housing. The spring 7 is appreciably stronger than the spring 10 the strength of these springs being determined in accordance with the effective areas of elements 6 and 9 presented to the respective ports 3 and 4 and determined in accordance with the pressure gradient specified for which the elements are required to become unseated on occurrence of blockage of the filter portions of these elements.

The flange 5 of element 6 is provided with a castellated periphery 15 to loosely centralise it in the housing and to provide for the possibility of airflow around it when unseated. Similarly, the flange 10 of element 9 is provided with a castellated periphery 16 to loosely centralise it in the element 6 but also provide for the possibility of air flow around it when it is unseated by air pressure.

The normal operation of the filter device is quite clear but in the albeit rare event of blockage, assuming port 3 to be the higher pressure port giving rise to a predetermined pressure gradient, the element 6 lifts off the end 12 of the housing to allow a bypass flow of compressed air albeit at slightly depleted pressure. If the filter device has been connected the opposite way in relation to the fluid pressure, the predetermined pressure gradient causes the element 9 to be unseated from the element 6 to permit a bypass flow of compressed air.

In an alternative embodiment the element 9 of Fig.

1 maybe replaced by a simple one-way check valve as shown for example in Fig. 2 wherein the spring 20 of a check valve element 21 is trapped by means of a crimped-on intermediate apertured guide member 22 attached to the flange 23 of the top-hat shaped element 24. This construction may be more appropriate for smaller versions of devices according to the invention.

In a further or alternative embodiment of the filter device of Fig. 1 the element 6 may comprise a non-filtering shell and all the normally filtered air flow then takes place via the inner element 9.

By virtue of the invention a widely adaptable in-line fluid filter device is provided having the particular merit of not being required to be connected in line in any particular sense in relation to fluid flow.

1. A fluid filter device capable of filtering fluid flowing in either one of two directions between the ports of a housing including a filter element so spring biassed against a first seat that fluid pressure in one direction across it can unseat the filter elemerit and characterised in that a check valve element is provided so biassed against a second seat substantially concentric with the first element that fluid pressure in the opposite direction across it can unseat the check valve element from the seat.

2. A fluid filter device as claimed in claim 1 characterised in that the first seat comprises the inner surface of the housing surrounding one said port and the second seat comprising an inner surface surrounding an aperture of the filter element.

3. A fluid filter device as claimed in claim 1 characterising in that the second seat comprising the inner surface of the housing surrounding one said port across the first seat comprising an inner

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Fluid Filters This invention relates to fluid filters and relates especially but not exclusively to filters for use in compressed air systems. In compressed air systems, especially compressed air braking systems used on heavy vehicles, the valves and other controlling components are becoming increasingly complex and sophisticated. As a result such components tend to be increasingly susceptible to malfunction due to ingress of foreign particulate matter carried through in the air supply. Whilst precautions are taken involving the use of filters and condensers or air driers to ensure the air is clean it is considered desirable to protect certain components by additional in-line filters. On the other hand risk of the flow of air to such an additionally protected device being interrupted by filter blockage has to be minimised and in-line filters have been proposed wherein a filter element is spring biassed to provide a bypass capability if the filter element becomes blocked. According to the present invention there is provided a fluid filter device capable of filtering fluid flowing in either one of two directions between the ports of a housing including a filter element so spring biassed against a first seat that fluid pressure in one direction across it can unseat the filter element and characterised in that a check valve element is provided so biassed against a second seat substantially concentric with the first element that fluid pressure in the opposite direction across it can unseat the check valve element from the seat. In order that the invention may be more clearly understood and readily carried into effect the same will be further described by way of example with reference to the accompanying drawing of which: Fig. 1 illustrates an in-line filter employing two elements and, Fig. 2 illustrates an alternative wherein one filter is replaced by a simple biassed check valve element. Referring to Fig. 1 the in-line filter element comprises a generally cylindrical housing formed of a main body part 1 and a screw attached closure part 2. The body part 1 has a first port 3 and the closure part 2 has a second port 4. These ports are conveniently identical in the sense that the housing may be connected for flow in either direction through a compressed air line. More or less sealingly engageable with the inner end face 13 around the port 3 is an annular flange 5 of a solid part of a top-hat shaped filter element 6, the flange 5 being held so engaged by a biassing spring 7 compressed there between and the face 13 of the closure part 2.The top-hat shaped filter element 6 has an aperture 8 and within it a further smaller top-hat shaped element 9 having a flange 10 which is retained more or less sealingly engaged by means of a further biassed spring 10 retained between it and the end 12 of the housing. The spring 7 is appreciably stronger than the spring 10 the strength of these springs being determined in accordance with the effective areas of elements 6 and 9 presented to the respective ports 3 and 4 and determined in accordance with the pressure gradient specified for which the elements are required to become unseated on occurrence of blockage of the filter portions of these elements. The flange 5 of element 6 is provided with a castellated periphery 15 to loosely centralise it in the housing and to provide for the possibility of airflow around it when unseated. Similarly, the flange 10 of element 9 is provided with a castellated periphery 16 to loosely centralise it in the element 6 but also provide for the possibility of air flow around it when it is unseated by air pressure. The normal operation of the filter device is quite clear but in the albeit rare event of blockage, assuming port 3 to be the higher pressure port giving rise to a predetermined pressure gradient, the element 6 lifts off the end 12 of the housing to allow a bypass flow of compressed air albeit at slightly depleted pressure. If the filter device has been connected the opposite way in relation to the fluid pressure, the predetermined pressure gradient causes the element 9 to be unseated from the element 6 to permit a bypass flow of compressed air. In an alternative embodiment the element 9 of Fig. 1 maybe replaced by a simple one-way check valve as shown for example in Fig. 2 wherein the spring 20 of a check valve element 21 is trapped by means of a crimped-on intermediate apertured guide member 22 attached to the flange 23 of the top-hat shaped element 24. This construction may be more appropriate for smaller versions of devices according to the invention. In a further or alternative embodiment of the filter device of Fig. 1 the element 6 may comprise a non-filtering shell and all the normally filtered air flow then takes place via the inner element 9. By virtue of the invention a widely adaptable in-line fluid filter device is provided having the particular merit of not being required to be connected in line in any particular sense in relation to fluid flow. CLAIMS

3. A fluid filter device as claimed in claim 1 characterising in that the second seat comprising the inner surface of the housing surrounding one said port across the first seat comprising an inner surface of the check valve element surrounding an aperture thereof.

4. Afluid filter device as claimed in claim 2 characterised in that the check valve element comprises a further filter element.

5. A fluid filter device as claimed in claim 1, 2 or 4 characterised in that one elements are biassed by respective spring captive between them and opposed inner end surfaces of the housing.

6. A fluid filter device as claimed in claim 1 characterised in that the check valve element is captive within the filter element.

7. A fluid filter device substantially as described herein with reference to Fig. 1 or Fig. 2 of the accompanying drawing.