GB2063097A

GB2063097A - Filter for filtering compressed air

Info

Publication number: GB2063097A
Application number: GB8013063A
Authority: GB
Original assignee: Orion Machinery Co Ltd
Current assignee: Orion Machinery Co Ltd
Priority date: 1979-11-13
Filing date: 1980-04-21
Publication date: 1981-06-03
Also published as: JPS5676018U; FR2469196A1; DE3017852A1

Abstract

A filter, primarily for collecting impurities such as dust and oil mist from compressed air, has a main filter element 11, for fine particle collection, disposed on the inner circumferential surface of a rigid air permeable outer cylinder 10, and an auxiliary filter element 15, for collecting larger size particles, disposed inside the main element and having a corrugated cross section. The corrugations of element 15 may run axially or circumferentially. <IMAGE>

Description

SPECIFICATION Filter element for filtering compressed air The present invention concerns a filter element used in devices for collecting and removing dust and mist of air and oil contained in compressed air. Compressed air often contains suspended dusts, water, and oil mist which became mixed therewith inside the compressor. Accordingly, it was necessary in the prior art to use a filter device to obtain pure compressed air by removing these impurities. Figure 1 illustrates, in cross-section, part of a conventional filter having a filter layer 4 made of a filter material 3 shaped and supported in cylindrical form by using support screens 1, 1' and filter supports 2, 2'. The filter layer is attached to the inner peripheral surface of the outer cylinder 5 made, for example, of plastic foam, which is both air permeable and rigid. The reference number 7 denotes a bottom plate.

The filter element 6 constructed in the above manner takes in the compressed air containing impurities and sends out the clean compressed air through the outer cylinder 5.

As the life of the filter element depends on the degree of clogging of the filter layer, it is desirable to connect together filter 8, 8' housing filter elements 6, 6' which have different degrees of filtering capacity in multiple stages and thus improve the purity of the compressed air in successive steps. Figure 2 is a side view of one such arrangement.

However, when the filter device is constructed by combining a plurality of filters 8, 8', the cost of joints and piping between the filters increases and the filter device as a whole becomes larger, requiring a larger space for its installation. Furthermore, the use of a plurality of filters was uneconomical since it was necessary to provide such accessories as drains for each of the filters.

An object of the present invention is to provide an improved filter element in which the aforesaid defects and disadvantages of the aforesaid conventional filter are minimised or avoided.

According to the present invention, a filter element for filtering compressed air comprises a main filter layer for collecting fine particles, the main filter being disposed on the inner circumferential surface of a rigid air permeable outer cylinder, and an auxiliary filter layer having a corrugated cross section for collecting particles of a larger size than the said fine particles disposed inside the main filter layer.

An embodiment of the invention will now be described, by way of example, with reference to Figures 3 and 4 of the accompanying drawings which are respectively a cross sectional view of part of the filter element of the invention and a cross sectional view of part of the filter element of Figure 3. In Figures 3 and 4 of the drawings, the reference 10 denotes an outer cylinder with a high air permeability and rigidity, on the inner circumferential surface of which is formed a main filter layer 11.

The main filter layer 11 is cylindrical in shape and includes a filter material 12 to trap and collect fine particles, support screens 13, 13' and filter supports 14 14' to shape and support the said filter material 12 in such a way that the cylinder is inserted snugly inside the inner circumferential surface of the outer cylinder 10.

inside the main filter layer 11 is formed an auxiliary filter layer 15 to collect impurities of a larger diameter than those collected by the main filter layer 11. As shown in Figure 4, the auxiliary filter layer has a corrugated transverse cross section forming numerous flutes extending in the axial direction. Alternatively, it may be corrugated in longitudinal cross-section to provide numerous peripherally extending flutes. The bottom plate of the outer cylinder 10 is designated by the reference 16.

In the filter element constructed as above, when the compressed air containing impurities enters the auxiliary filter layer 15, the filtered air is subsequently discharged through the outer cylinder 10 after having passed through the auxiliary filter layer 15 and the main filter layer 11. At this time, the air from which larger impurities have been removed by the auxiliary filter layer 15 is passed to the main filter layer 11, and it is possible to prevent clogging of the main filter layer 11 even though the filtering capacity of the filter element as a whole may be raised.On the other hand, the auxiliary filter layer 15 which conducts preliminary filtering achieves the effect of enlarged filter area since it has a corrugated crosssection, and since it collects only the large particles of which the diameter is bigger than that of the particles collected by the main filter 11, clogging of the auxiliary filter layer 15 can also be prevented.

In other words, the filtering is not performed in one stage as in the conventional type filter element previously described, but it is conducted in two stages respectively by the auxiliary filter layer 15 and the main filter 11, the impurities of different particle sizes being thus collected in two stages. As the cross section of the auxiliary filter layer which catches and collects more impurities than the other is corrugated to enlarge the filter area, the filtering degree of the filter element, and thus the purity of the compressed air filtered thereby, may be improved without excessive clogging of the element and consequent shorter life.

When the pressure of the compressed air supplied to the filter element is raised, the volume of the air flow passing through the respective layers becomes increased, or the collected impurities tend to pass through the filter layers accompanied by the air.

However, if the pressure of the compressed air supplied in this manner becomes higher, the auxiliary filter layer 15 is pressed outwardly and compresses the main filter 11 against the outer cylinder 10. Accordingly, no matter how much the airflow through the auxiliary filter layer 15 increases, the filtering action of the main filter layer 11 becomes on the contrary improved, and the filtering action of the filter element as a whole does not deteriorate.

Accordingly, the present invention enables filtration of a more stable and reliable degree than those conventional filters in which two types of filter element have simply been put together.

As mentioned above, the filter element of the present invention conducts a two stage filtering within one element, and therefore improves the filtering action without its life being excessively shortened by clogging. Since a filtering operation is stable against the pressure changes of the compressed air being supplied thereto, it is possible to impart one filter element with the function of two or more filter elements of the conventional type.

Accordingly, it is possible to obtain the compressed air of a desired cleanness without joining a plurality of filters as in the conventional art, and to simplify and reduce the size of the filter device, as well as the appended devices and piping, and to reduce the costs thereof.

Claims

1. A filter element for filtering compressed air comprising a main filter layer for collecting fine particles, the main filter being disposed on the inner circumferential surface of a rigid air permeable outer cylinder, and an auxiliary filter layer having a corrugated cross section for collecting particles of a larger size than the said fine particles disposed inside the main filter layer.

2. A fiiter element according to Claim 1 wherein the auxiliary filter layer is corrugated in transverse cross section to form longitudinally extending flutes.

3. Afilter element according to Claim 1 wherein the auxiliary filter layer is corrugated in longitudinal cross section to form peripherally extending flutes.

4. A filter element according to any one of the preceding claims wherein the main filter is disposed between a pair of filter supports.

5. A filter element according to Claim 4 wherein the filter supports are concentrically arranged cylinders of different diameters and the main filter is disposed in the space therebetween.

6. A filter element according to any one of the preceding claims wherein the auxiliary filter is radially outwardly compressible by the pressure of compressed air supplied to the filter element so as to compress the main filter against the rigid outer cylinder.

7. A filter element substantially as hereinbefore described with reference to Figures 3 and 4 of the accompanying drawings.