GB2120122A

GB2120122A - Air filter element

Info

Publication number: GB2120122A
Application number: GB08214063A
Authority: GB
Inventors: Dennis Albert George Marshall
Original assignee: Marshall D A G
Current assignee: Marshall D A G
Priority date: 1982-05-14
Filing date: 1982-05-14
Publication date: 1983-11-30
Also published as: GB2120122B

Abstract

An air filter element comprises a sleeve of pleated filter paper which is sealed in end caps (12 and 14) made of a substantially rigid synthetic plastics. One of the end caps (14) is annular and carries a projecting spigot (22) having an external screw thread (26), which enables the element to be screwed into an opening in a wall (28). A sealing ring or annular ridge (20) is also provided on the end cap (14) so as to be compressed between that end cap and the wall when the element is screwed into the opening. The screw thread (26) may be of square section, continuous or discontinuous. <IMAGE>

Description

SPECIFICATION Air filter element This invention relates to an air filter element comprising a cylinder or other annulus of air filtering material which is sealed in end caps at its two ends.

It has already been proposed to provide at least one of the end caps in such a filter with a tubular spigot or projection to permit the filter element to be plugged into a wall, the wall having an opening of such a diameter in comparison with the outer diameter of the spigot that the latter forms a tight fit once the filter element has been pressed towards the wall. In one such construction, the spigot has a portion on its external periphery which yields or "gives" as the spigot is pressed into the hole in the wall, and in this way a tight fit is ensured.

Sealing of the air filter element with respect to the wall surface is provided by an annular seal in the form of a ring or ridge interposed between the wall and the end cap having the spigot. Preferably, this sealing ring or ridge is provided on that end cap although it could equally well be provided on the wall.

Although such filters have worked well in practice, it has been found that the filter element can sometimes shift with respect to the wall so that leakage occurs where the spigot passes through the wall. Further, heavy pressure is sometimes required to force a filter spigot into the wall, this being due to manufacturing tolerances which can result in one filter element of a batch being a good fit in the wall while another one does not fit quite so well.

In order to avoid these disadvantages, an air filter element in accordance with the present invention has a spigot provided with an external screw thread so as to permit the spigot to be screwed into the wall instead of being pushed into the wall as hitherto. The hole in the wall will accordingly be shaped so as to take the screw thread on the spigot.

An example of an air filter element in accordance with the invention is shown in the accompanying drawing, in which~ Figure 1 is a vertical section through the air filter element; Figure 2 is an enlarged view of part of Fig.

1; and Figure 3 is a section taken on the line Ill-Ill in Fig. 1.

The air filter element shown in the drawing comprises filtering material 10 in the form of pleated air filtering paper, the pleated form of the paper being shown in Fig. 3. The upper end of the air filtering material is sealed in a circular end cap 12 while the lower end of the air filtering material is sealed in an annular end cap 14, the two caps 12 and 14 being made of a substantially rigid moulded synthetic plastics material. The end caps are in fact moulded on to the filtering material 10 so that an excellent seal is formed between them.

In order to give the filter element sufficient strength, the air filtering material 10 is bounded on its outer and inner peripheries by perforated metal screens 16 and 18. The upper and lower ends of these two screens are likewise embedded in the end caps 12 and 14 as shown in Figs. 1 and 2.

It will be seen from Fig. 1 that the lower annular end cap 14 has a sealing ring or ridge 20 provided on its lower surface. The sealing ring or ridge 20 is made of a soft synthetic or rubbery material which yields or deforms very easily under pressure. This material is therefore quite different from the substantially rigid material of the caps 12 and 14. In order that the sealing ring or ridge 20 may be appropriately secured to the end cap 14, the latter has an annular groove 21 formed in its lower surface to receive the root portion of the sealing ring or ridge 20. The sealing ring or ridge can accordingly be moulded in situ on the end cap 14 so that it bonds itself to the end cap as it cools down from its liquid state.

Alternatively, the sealing ring or ridge 20 can be made as a separate item and then bonded in position on the end cap 14 by means of an appropriate adhesive. Further information in regard to the sealing ring or ridge 20 can be derived from my co-pending Patent Application No. 82.12911 filed on 5th May 1982 for "Air Filter Element".

As already indicated in the introductory part of the specification, the invention is concerned with so-called "plug-in" filter elements which have a spigot at one end which is plugged into an opening in a wall. The filter element shown in the drawing is of this general construction and accordingly has a cylindrical spigot 22 formed integrally on the annular end cap 14 and extending co-axially of the longitudinal axis 24 of the filter element.

However, in contrast to earlier filter elements of this construction where the spigot is pressed or forced into the hole in the wall, the spigot 22 is provided with an external screw thread 26 which permits it to be screwed into an appropriately sized hole in a wall 28. It is not necessary for the wall itself to be provided with anything more than a single screw-turn which can be formed by slightly deforming a portion of the material bounding the hole in the wall.

The advantage of such a spigot 22 is that it no longer requires force to press the spigot into the hole in the wall. Instead, the spigot 22 can be steadily and gently screwed into the hole in the wall until the sealing ring or ridge 20 makes contact with the opposing surface of the wall 28. The axial position of the spigot 22 with respect to the wall 28 can therefore be very carefully controlled so that the pressure on the sealing ring or ridge can likewise be carefully controlled to give an excellent seal between the filter element and the wall 28. Yet another advantage is that the spigot is unlikely to become loose in the wall 28 as sometimes happens with spigots which are merely pressed into a wall.

In the particular air filter element shown in the drawing, the spigot has a screw thread of square section as this has certain practical advantages. It is to be understood however that various other forms of screw thread could be used instead, and it is not essential that the screw thread should be continuous. Thus, for example, the screw thread on the spigot 22 could be formed by spaced-apart projections or ridges which, together, would have the same effect as a screw thread as the spigot is rotated in the hole formed in the wall 28.

Claims

1. An air filter element comprising a cylinder or other annulus of air filtering material which is sealed in end caps at its two ends, in which the air filter element has a spigot provided with an external screw thread or the equivalent so as to permit the spigot to be screwed into a wall opening.

2. An air filter element according to claim 1, in which the screw thread is continuous from one end to the other end.

3. An air filter element according to claim 2, in which the screw thread is of square section.

4. An air filter element according to claim 1, in which the spigot is provided with external spaced-apart projections or ridges which, together have the same effect as a screw thread.

5. An air filter element according to any preceding claim, in which the spigot is of tubular form and projects axially of the element from one of the end caps.

6. An air filter element according to claim 5, in which a seal in the form of a ring or annular ridge is carried on the end cap from which the spigot projects, the annular seal lying radially outwardly of the spigot and concentric with it.

7. An air filter element according to any preceding claim, in which the air filtering material comprises pleated paper.

8. An air filter element according to any preceding claim, in which one of the end caps is of circular shape so as to close one end of the cylinder of air filtering material, while the other end cap is of annular form so as to serve as an air inlet or air outlet.

9. An air filter element according to claim 8 when appendant to claim 5 or claim 6, in which the spigot projects from the annular end cap.

10. An air filter element according to any preceding claim, in which the end caps are made of a substantially rigid moulded synthetic plastics material.

11. An air filter element according to any preceding claim, in which the air filtering material is bounded on its outer and inner peripheries by perforated metal screens.

12. An air filter element according to claim 11, in which the ends of the two metal screens are embedded in the end caps.

13. An air filter element according to claim 6 or any claim appendant thereto, in which the sealing ring or annular ridge is made of a soft synthetic rubbery material which yields or deforms very easily under pressure.

14. An air filter element according to claim 13, in which the sealing ring or annular ridge is attached to the respective end cap by being moulded in situ on the end cap so that it bonds itself to the latter as it cools down from its liquid state, the sealing ring or annular ridge having a root portion received in an annular groove formed in the end cap.

15. An air filter element substantially as described herein with reference to the accompanying drawing.