GB2196268A

GB2196268A - Edge filter

Info

Publication number: GB2196268A
Application number: GB08724550A
Authority: GB
Inventors: David John Gaskell
Original assignee: Lucas Industries Ltd
Current assignee: ZF International UK Ltd
Priority date: 1986-10-25
Filing date: 1987-10-20
Publication date: 1988-04-27
Also published as: GB8724550D0; GB8625578D0

Abstract

An edge filter comprises a tube 10 enclosing as axially grooved bar 12, filtering gaps being defined between the raised lands, between the grooves 14, and the inside surface 11 of the tube. Plugs 15 and 16 close alternate grooves at one end of the bar and the intermediate grooves at the other. The plugs fit over spigots 19 or may be welded in place. <IMAGE>

Description

SPECIFICATION Edge filter This invention relates to a so-called edge filter for trapping particles of dirt or other solid matter which are suspended in a flowing liquid.

In an edge filter the liquid is constrained to flow through a slit defined by components of the filter, the width of the slit depending upon the size of solid matter to be retained. Such filters are often used in fuel injection nozzles for internal combustion engines, the purpose of the filter being to provide a barrier to prevent blocking of the very small orifices which are often found in such nozzles.

The production of such filters can present problems since where the gap between the components is very small it is necessary to provide a long slit or a plurality of slits in order to minimise the pressure drop across the filter.

The object of the invention is to provide an edge filter and a method of making same in a simple and convenient form.

According to the invention an edge filter comprises means defining a bore through which in use liquid flow takes place, a longitudinally fluted bar located in said bore, the outer surfaces of the flutes forming with the wall of said bore, a plurality of slits and means for closing alternate ones of the grooves defined between the flutes at one end of the bar and the other grooves at the opposite end of the bar.

An example of an edge filter in accordance with the invention will now be described with reference to the accompanying drawings in which: Figure 1 shows the individual parts of the filter prior to assembly, and Figure 2 shows three sections through various parts of the filter.

Referring to the drawings the filter comprises a tubular member 10 defining a bore 11 through which in use liquid takes place.

The tubular member may be part of the fuel supply conduit to a fuel injection nozzle for a compression ignition engine or it may form part of the body of the nozzle. Mounted within the bore is a filter element which comprises a cold drawn steel bar 12 which has a section as shown in the left hand view of Fig.

2. The bar has a plurality of flutes 13 there being an even number of flutes and between adjacent flutes are defined grooves 14. The bar is located within the bore so that the wall of the bore and the outer surfaces of the flutes define slits of a size chosen to retain all solid matter contained in the fuel which is above a predetermined size. The ends of alternate grooves at one of the bar are closed as are the ends of the other grooves at the other end of the bar and the closure is conveniently effected by end members 15, 16 which may themselves be formed from cold drawn bar but in this case the bar has half the number of grooves 17 as there are grooves 14.

The end members are located at the ends of the grooves 14 so as to achieve closure of the ends of the grooves in the manner described above. As a result liquid can flow between adjacent grooves 14 through the slit defined by the intervening flute 13 and the wall of the bore 11. In the particular example therefore with six flutes 13, six slits are formed through which the liquid flow can take place and solid matter will tend to be retained in those grooves which are connected to the inlet end of the bore. It is found that the retained solid matter does tend to be reduced in size during operation of the nozzle and may then pass through the slits.

Conveniently the end members 15, 16 are provided with central drillings 18 and are located on spigots 19 machined at the opposite ends of the bar 12. The end members may be an interference fit on the spigots 19. Alternatively they may be secured as by welding which can overcome the problem of ensuring the required concentricity of the end members and the bar.

An alternative way of closing the ends of the grooves is to pinch the ends of the flutes 13 and to secure the pinched ends by welding.

The bar is located within the bore by arranging that one of the end members or one of the pinched ends is a sliding fit in the bore while the other end member or the other pinched end is an interference fit in the bore in order to minimise the amount of material which may be removed from the bore during the process of inserting the insert into the bore.

1. An edge filter for trapping particles of dirt or other solid matter which are suspended in a flowing liquid comprising means defining a bore through which in use a flow of liquid takes place, a longitudinally fluted bar located in said bore, the outer surfaces of the flutes forming with the wall of said bore, a plurality of slits and means for closing alternate ones of the grooves defined between the flutes at one end of the bar and the other grooves at the opposite end of the bar.

2. A filter according to Claim 1 in which said means comprises a pair of end members located at the opposite ends of the bar respectively, said members being provided with longitudinal grooves, there being half the number of grooves on the end members as there are grooves on the bar.

3. A filter according to Claim 2 in which the end members are of annular form and are mounted on spigots at the ends of the bar respectively.

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

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Edge filter This invention relates to a so-called edge filter for trapping particles of dirt or other solid matter which are suspended in a flowing liquid. In an edge filter the liquid is constrained to flow through a slit defined by components of the filter, the width of the slit depending upon the size of solid matter to be retained. Such filters are often used in fuel injection nozzles for internal combustion engines, the purpose of the filter being to provide a barrier to prevent blocking of the very small orifices which are often found in such nozzles. The production of such filters can present problems since where the gap between the components is very small it is necessary to provide a long slit or a plurality of slits in order to minimise the pressure drop across the filter. The object of the invention is to provide an edge filter and a method of making same in a simple and convenient form. According to the invention an edge filter comprises means defining a bore through which in use liquid flow takes place, a longitudinally fluted bar located in said bore, the outer surfaces of the flutes forming with the wall of said bore, a plurality of slits and means for closing alternate ones of the grooves defined between the flutes at one end of the bar and the other grooves at the opposite end of the bar. An example of an edge filter in accordance with the invention will now be described with reference to the accompanying drawings in which: Figure 1 shows the individual parts of the filter prior to assembly, and Figure 2 shows three sections through various parts of the filter. Referring to the drawings the filter comprises a tubular member 10 defining a bore 11 through which in use liquid takes place. The tubular member may be part of the fuel supply conduit to a fuel injection nozzle for a compression ignition engine or it may form part of the body of the nozzle. Mounted within the bore is a filter element which comprises a cold drawn steel bar 12 which has a section as shown in the left hand view of Fig. 2. The bar has a plurality of flutes 13 there being an even number of flutes and between adjacent flutes are defined grooves 14. The bar is located within the bore so that the wall of the bore and the outer surfaces of the flutes define slits of a size chosen to retain all solid matter contained in the fuel which is above a predetermined size. The ends of alternate grooves at one of the bar are closed as are the ends of the other grooves at the other end of the bar and the closure is conveniently effected by end members 15, 16 which may themselves be formed from cold drawn bar but in this case the bar has half the number of grooves 17 as there are grooves 14. The end members are located at the ends of the grooves 14 so as to achieve closure of the ends of the grooves in the manner described above. As a result liquid can flow between adjacent grooves 14 through the slit defined by the intervening flute 13 and the wall of the bore 11. In the particular example therefore with six flutes 13, six slits are formed through which the liquid flow can take place and solid matter will tend to be retained in those grooves which are connected to the inlet end of the bore. It is found that the retained solid matter does tend to be reduced in size during operation of the nozzle and may then pass through the slits. Conveniently the end members 15, 16 are provided with central drillings 18 and are located on spigots 19 machined at the opposite ends of the bar 12. The end members may be an interference fit on the spigots 19. Alternatively they may be secured as by welding which can overcome the problem of ensuring the required concentricity of the end members and the bar. An alternative way of closing the ends of the grooves is to pinch the ends of the flutes 13 and to secure the pinched ends by welding. The bar is located within the bore by arranging that one of the end members or one of the pinched ends is a sliding fit in the bore while the other end member or the other pinched end is an interference fit in the bore in order to minimise the amount of material which may be removed from the bore during the process of inserting the insert into the bore. CLAIMS

4. A filter according to Claim 2 in which said end members are secured to the ends of the bar as by welding.

5. A filter according to Claim 1 in which the ends of the grooves in the bar are closed by pinching together the ends portions of the flutes forming the grooves.

6. An edge filter for trapping particles of dirt or other solid matter suspended in a liquid comprising the combination and arrangement of parts substantially as hereinbefore described with reference to the accompanying drawings.