GB2067425A - Filter elements - Google Patents

Abstract

A filter element comprises a roll of filter medium wrapped around a perforated centre tube 10 with end caps held in sealing engagement with the ends of the roll. The roll is composed of or at least includes, a substantial proportion of thermo-plastic material, and the free edge of the roll is welded to the adjacent turn of the roll at 15. End caps may be secured to the roll by welding or adhesive or may be clamped thereto with interposed felt sealing washers. <IMAGE>

Description

SPECIFICATION Filter elements This invention relates to filter elements of the kind comprising a roll of filter medium, end caps disposed at the opposite ends of the roll in sealing engagement therewith and a perforated centre tube about which the roll is positioned.

Filter elements of this type are well known and in use the fluid to be filtered passes through the filter medium forming the adjacent turns of the roll and contaminent in the fluid is retained on or in the filter medium.

It is essential to ensure that there should be no leakage of fluid along the path between the turns of the roll because if this should occur, there is a risk that contaminent may also pass. It is known to provide a perforated tube about the roll so that the turns are firmly pressed together between the tubes but this makes assembly of the element difficult besides requiring an extra component. It is also known to stitch the outer end of the length of filter medium forming the roll to the adjacent turn, but again this involves an extra operation during the manufacture of the element. It is also known to provide a metal clip which is used to secure the free outer end portion of the length of filter medium to the body of the roll but again this requires the provision of an additional component together with an extra operation during the assembly of the element.

The object of the invention is to provide a filter element of the kind specified in a simple and convenient form.

According to the invention a filter element comprises a perforated centre tube, a length of filter medium wound about the centre tube to form a roll, the filter medium being formed from or having a substantial content of a thermo-plastic material, a weld serving to secure a free end of the length of filter medium to the adjacent turn of the roll and end caps positioned at the opposite ends of the roll and in sealing engagement with the end edges of the roll.

One example of a filter element in accordance with the invention will now be described with reference to the accompanying drawings in which: Figure 1 is a vertical section through the element; and Figure 2 is a cross-section of the element.

Referring to the drawings the filter element comprises a perforated tube 10 conveniently formed from metal and a pair of metal end caps 11 which are positioned at the opposite ends of the tube. The end caps have inwardly directed rim portions 12 and are also provided with apertures 13 through which fluid can flow.

Surrounding the tube 10 is a roll of filter medium and this is wound as tightly as possible upon the centre tube 10. The roll of filter medium which is indicated at 14, fills the annular space defined between the tube 10 and the rim portions 12 of the end caps 11. The end caps are in sealing engagement with the edges of the roll 14 and to ensure a fluid tight seal, a heat softenable adhesive is applied to the inner faces of the end caps prior to location of the end caps in position. One convenient adhesive is a nitrile phenolic resin The roll comprises a number of turns and the filter medium is a felt which is composed of or at least includes, a substantial proportion of a thermo-plastic material. Examples of such material are polypropylene and polyester.

It is essential to ensure that no fluid should be able to pass along the spiral path defined between the turns of filter medium, and in order to prevent this the outer free end of the roll of filter medium is heat sealed to the adjacent turn so as to form a weld which is referenced 15. The fact that the roll is tightly wound about the tube 10 and that its outer end is held and sealed to the adjacent turn means that fluid is unable to flow along the spiral path mentioned above.

It is convenient to form the weld during the operation of winding the length of filter medium about the perforated tube.

One way in which this can be done is to use a heated blade which softens the thermo-plastic material to effect the weld whilst at the same time severing the wound length of material from the supply of material. As mentioned above after the winding operation the end caps are placed in position and the adhesive used between the end caps and the edges of the roll is softened to form the seal.

In the example described above the end caps are formed from metal they can however be formed from a thermo-plastic material and welded to the felt. It is also possible to retain the end plates by means of a through bolt and in this case annular pieces of felt may be located between the end caps and the edges of the roll of felt. The clamping action ensures the seal between the edges of the filter medium and the end caps.

1. A filter element comprising a perforated centre tube, a length of filter medium wound about the centre tube to form a roll, the filter medium being formed from or having a substantial content of a thermo-plastic material, a weld serving to secure a free end of the length of filter medium to the adjacent turn of the roll and end caps positioned at the opposite ends of the roll and in sealing engagemenu with the end edges of the roll.

2. A filter element according to claim 1 in which said end caps are retained in position by means of adhesive applied to the inner faces of the end caps, said adhesive acting to seal the edges of the roll to the end caps.

3. A filter element according to claim 1 including annular pieces of felt disposed between the ends of the roll and the end caps respectively and means clamping the end caps against the ends of the roll, said pieces of felt acting to ensure a seal between the edges of the roll and the end caps.

4. A filter element according to claim 1 in which said end caps are formed from a thermo-plastic material and are welded to the edges of the roll.

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

Claims (6)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Filter elements This invention relates to filter elements of the kind comprising a roll of filter medium, end caps disposed at the opposite ends of the roll in sealing engagement therewith and a perforated centre tube about which the roll is positioned. Filter elements of this type are well known and in use the fluid to be filtered passes through the filter medium forming the adjacent turns of the roll and contaminent in the fluid is retained on or in the filter medium. It is essential to ensure that there should be no leakage of fluid along the path between the turns of the roll because if this should occur, there is a risk that contaminent may also pass. It is known to provide a perforated tube about the roll so that the turns are firmly pressed together between the tubes but this makes assembly of the element difficult besides requiring an extra component. It is also known to stitch the outer end of the length of filter medium forming the roll to the adjacent turn, but again this involves an extra operation during the manufacture of the element. It is also known to provide a metal clip which is used to secure the free outer end portion of the length of filter medium to the body of the roll but again this requires the provision of an additional component together with an extra operation during the assembly of the element. The object of the invention is to provide a filter element of the kind specified in a simple and convenient form. According to the invention a filter element comprises a perforated centre tube, a length of filter medium wound about the centre tube to form a roll, the filter medium being formed from or having a substantial content of a thermo-plastic material, a weld serving to secure a free end of the length of filter medium to the adjacent turn of the roll and end caps positioned at the opposite ends of the roll and in sealing engagement with the end edges of the roll. One example of a filter element in accordance with the invention will now be described with reference to the accompanying drawings in which: Figure 1 is a vertical section through the element; and Figure 2 is a cross-section of the element. Referring to the drawings the filter element comprises a perforated tube 10 conveniently formed from metal and a pair of metal end caps 11 which are positioned at the opposite ends of the tube. The end caps have inwardly directed rim portions 12 and are also provided with apertures 13 through which fluid can flow. Surrounding the tube 10 is a roll of filter medium and this is wound as tightly as possible upon the centre tube 10. The roll of filter medium which is indicated at 14, fills the annular space defined between the tube 10 and the rim portions 12 of the end caps 11. The end caps are in sealing engagement with the edges of the roll 14 and to ensure a fluid tight seal, a heat softenable adhesive is applied to the inner faces of the end caps prior to location of the end caps in position. One convenient adhesive is a nitrile phenolic resin The roll comprises a number of turns and the filter medium is a felt which is composed of or at least includes, a substantial proportion of a thermo-plastic material. Examples of such material are polypropylene and polyester. It is essential to ensure that no fluid should be able to pass along the spiral path defined between the turns of filter medium, and in order to prevent this the outer free end of the roll of filter medium is heat sealed to the adjacent turn so as to form a weld which is referenced 15. The fact that the roll is tightly wound about the tube 10 and that its outer end is held and sealed to the adjacent turn means that fluid is unable to flow along the spiral path mentioned above. It is convenient to form the weld during the operation of winding the length of filter medium about the perforated tube. One way in which this can be done is to use a heated blade which softens the thermo-plastic material to effect the weld whilst at the same time severing the wound length of material from the supply of material. As mentioned above after the winding operation the end caps are placed in position and the adhesive used between the end caps and the edges of the roll is softened to form the seal. In the example described above the end caps are formed from metal they can however be formed from a thermo-plastic material and welded to the felt. It is also possible to retain the end plates by means of a through bolt and in this case annular pieces of felt may be located between the end caps and the edges of the roll of felt. The clamping action ensures the seal between the edges of the filter medium and the end caps. CLAIMS

1. A filter element comprising a perforated centre tube, a length of filter medium wound about the centre tube to form a roll, the filter medium being formed from or having a substantial content of a thermo-plastic material, a weld serving to secure a free end of the length of filter medium to the adjacent turn of the roll and end caps positioned at the opposite ends of the roll and in sealing engagemenu with the end edges of the roll.

2. A filter element according to claim 1 in which said end caps are retained in position by means of adhesive applied to the inner faces of the end caps, said adhesive acting to seal the edges of the roll to the end caps.

3. A filter element according to claim 1 including annular pieces of felt disposed between the ends of the roll and the end caps respectively and means clamping the end caps against the ends of the roll, said pieces of felt acting to ensure a seal between the edges of the roll and the end caps.

4. A filter element according to claim 1 in which said end caps are formed from a thermo-plastic material and are welded to the edges of the roll.

5. A filter element according to any one of the preceding claims in which said end caps have inwardly directed rim portions which surround the roll.

6. A filter element comprising the combination and arrangement of parts substantially as hereinbefore described with reference to the accompanying drawings.