GB1574998A

GB1574998A - Filter assemblies

Info

Publication number: GB1574998A
Application number: GB41039/77A
Authority: GB
Original assignee: AMBIC DAIRY EQUIP
Current assignee: AMBIC DAIRY EQUIP
Priority date: 1977-10-03
Filing date: 1977-10-03
Publication date: 1980-09-17
Also published as: IE780040L; IE46136B1; AU3598078A; AU518577B2; NZ186166A

Description

(54) IMPROVEMENTS IN OR RELATING TO FILTER ASSEMBLIES (71) We, AMBIC DAIRY EQUIPMENT LIMITED, a Company organized and existing under the Laws of Great Britain, of Minster Lovell, Oxfordshire, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to a filter assembly suitable for filtering a sediment-containing liquid such as milk.

Conventional milk filters often comprise two conical filter elements mounted one within the other in a spaced-apart relationship inside a housing. Milk flows into the housing and is then forced through both the filter elements from the outside to the inside thereof, finally to flow out from the inside of the inner conical filter element.

Such an arrangement has the disadvantage that it cannot withstand high pressures without risk of the filter elements collapsing, which tends to limit the flow-rate through the filter. In addition, the removal of the filters is a time-consuming job. which often interrupts the supply of milk at crucial periods.

Accordingly, the invention provides a filter assembly comprising two filter elements arranged coaxially one inside the other in a spaced-apart relationship and mounted within a housing having an inlet and an outlet, the inlet communicating with the interior of the inner filter element and the outlet communicating with a space surrounding the outer filter element such that, in use, liquid under pressure flows from the inlet to the outlet by way of a path extending radially outwardly through both filter elements, in which the filter elements each comprise a mesh sleeve and an integrally moulded cage of plastics material having longitudinally extending bars integrally formed with axially-spaced ringlike parts, the mesh sleeve, at its ends, being held in respective ring-like parts by portions of the moulded plastics material which have flowed into inter-stices in the mesh from both sides, such moulded plastics portions preventing the mesh from being buckled away from the ring-like parts.

Preferably, the inner filter element is coarser than the outer filter element. Also, the housing may have a transparent wall to allow visual inspection of the filter elements.

Conveniently the housing includes a screw-on cap on which the inlet and outlet are provided. The screw-on cap may be provided with a cylindrical depending sleeve which co-operates with an upstanding spigot and an 0-ring seal on one filter element to seal it to the cap.

The base of the housing may also be provided with upstanding cylindrical wall portions to enable the bases of the filter elements to be readily sealed thereto by means of O-rings. Preferably, the filter elements are cylindrical and coaxial.

Conveniently a drain is provided in the base of the housing. In the preferred arrangement the drain comprises a hole in the base of the housing which is provided with an internally threaded upstanding boss surrounding the hole. The hole receives the drain plug which is screwed upwardly into the boss from beneath. The top of the boss is preferably provided with an inwardly turned rim and the plug is suitably provided at its upper end with an encircling O-ring which is compressed between the rim and the plug when screwed fully in position to close the drain.

Beneath the O-ring, but spaced above the threaded portion of the plug, are suitable openings extending through the plug wall to an interior wall. When the plug is partially unscrewed, the spacing between the rim and the O-ring allows liquid to flow down and through the openings so as to flow out via the interior of the plug. A controlled drain, suitable for sampling purposes can be achieved by connecting a pipe or vessel to catch liquid dripping from the interior of the plug when partially unscrewed.

By locking the end-portions of the screen to the frame as described above, there is no risk of buckling of the screen under pressure causing openings to occur between the ends of the screen and the frame. Also the screen is held to the frame without the use of compression fittings which can damage the screen if made of a soft material such as plastics. The screen may be a metal or a plastics mesh.

The invention will now be described in more detail, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a perspective view of a filter assembly housing; and Figure 2 is a perspective view of two filter elements, shown separately.

The filter assembly comprises a housing including a transparent cylindrical container 1 for receiving the filter elements 2 and 3 and which has a base 4 provided with a drain hole 5 normally stopped up by means of a drain plug 6.

The drain hole 5 is formed by the interior of a hollow boss 30 which extends upwards from the centre of the floor of the container and is internally threaded. An inwardly directed rim flange 31 extends around the top of the boss 30. The drain plug 6 has an externally threaded spigot 32 which screws into the boss interior, and is formed with a well 33 in its under surface which extends upwardly beyond the threaded portion of the spigot to an end-portion 34 of reduced diameter. Two parallel chordal slots 35 are formed in the end-portion 34 which intercept the wall of the well 33 so as to provide two lateral outlets 36. Above the outlets 36 the end-portion 34 is formed with a groove which receives an O-ring 37 whose external diameter is slightly greater than the internal diameter of the rim flange 31 so that, when the plug is screwed upwardly as far as it will go into the hollow boss, the O-ring forms a seal with the rim flange 31, However, to open the drain hole in a controlled manner, the plug can be unscrewed sufficiently for the O-ring 37 to clear the flange 31 and allow liquid to flow out via the lateral outlets 36 and the interior well of the plug 6.

The container is closed by a cap 38 provided with an outer lip 7 which seals on the rim 8 of the container 1.

Two cylindrical sleeves 9, 10 depend from the cap 6 and define between them a gap 12, and a central chamber 14. An inlet pipe connection 15 communicates with the cen tral chamber 14 and an outlet pipe connection 16, in-line with the inlet pipe connection 15, communicates with the outer annular gap 12.

The base 4 of the container 1 is stepped to provide an annular sealing surface 17 on which abuts (see Fig. 2) an O-sealing ring 22 carried in a groove in the underside of the filter element 3. About half-an-inch above the bottom of the inside wall of the container 1 is a slight annular step 39, the inner face of which is engaged by an Oring 27 provided around the lower end of the outer filter element 2. The resilient pressure exerted by the inner face of the step 39 on the O-ring 27 serves to positively locate the outer filter element 2 in position while providing a seal around its lower end.

The space between the lower ends of the two filter elements is sealed by the O-ring 22 from the interior of the inner filter element 3, and by the O-ring 27 from the outside of the outer filter element 1.

The inner filter element 3 is a coarse filter element mounted within a cage or framework consisting of longitudinal.plastics bars 18 integrally moulded with rings 19, 20, 21.

The upper end of the filter element 3 is provided with a spigot 24 surrounded by an O-ring seal 25. The ring 19 is not truly circular at its outer edge but is of elliptical plan. The bars 18 are formed with respective rounded ribs 40A and 40B which are arranged in two diametrically arranged pairs. One pair of ribs 40A projects at their upper ends radially beyond the minor diameter of the ellipse whereas the other pair of ribs 40B extend radially nearly to the major diameter of the ellipse and the outer portion of the elliptical ring 19 is slotted at each side of the said other pair of ribs, as shown at 41.

The filter element 2 is of similar construction to the filter element 3, but is much finer and of larger diameter; similar parts have been referenced with primed reference numerals.

The bars 18' are internally channelled at 42 to receive respective ribs 40A, 40B of the inner filter element, and the rings 19', 20' and 21' are all circular.

In the case of both filter elements the filtering is accomplished by a wire mesh cylindrical screen 50 and 50' held in place by being moulded in situ when the rings and bars are moulded from plastics material. Some of the plastics material flows through the interstices in the mesh from both sides and coalesces so that the mesh is firmly held in place by being actually moulded into the plastics material of the bars 18, 18' and the rings 19, 20 and 21 and 19', 20' and 21'. Thus the screen is divided into part-cylindrical windows 52 each of which is firmly held along its four edges to the surrounding frame of plastics material provided by the rings and bars.

Deformation of buckling of the meshes along the circular ends by internal pressure in the filter element is thus resisted in a way which prevents leak channels occurring around or through the mesh unless it is physically torn. The "weld" lines of the plastics to the mesh may be continuous or intermittent and the mesh itself may be metal or made of a plastics material such as nylon or other plastics substance able to withstand the moulding process used for forming the bars and rings.

The filtering apparatus is assembled by inserting the inner filter element 3 into the underside of the outer filter element 2 so that its ribs are received in respective channels of the latter. When pushed home the inner filter element 3 is held in place by the engagement of its O-ring 25 with the cylindrical inside wall of the spigot 24'.

The double filter element combination is then inserted into the container 1 and is pushed down until the O-ring 27 rides onto the inner face of the shallow step 39 of the container. This ensures an effective liquidtight seal at O-ring 27.

The screw threaded cap 38 is then placed on the container 1 and a threaded portion 28 on the sleeve 9 is screwed into an internally threaded zone provided in the upper wall portion of the container 1. The spigot 24' enters the chamber 14 and its O-ring 25' makes a tight seal against the chamber wall. The axial length of the sleeve 10 is such that final screwing motion of the cap causes the rim of the sleeve 10 to bear down on the ring 19' around the spigot 24' to effect the seal between the O-ring 22 of the inner filter element and the annular surface 17 of the container.

In use, liquid under pressure enters the filter assembly through the inlet pipe 15 and flows through the chamber 14 into the interior of the inner coarse filter element 3. The liquid is then forced radially through the two filter elements, passing firstly through the coarse element and then through the fine element 2, to a space between the wall of the container 1 and the outer element 2. The liquid then flows out of the assembly through the annular gap 12 and the outlet pipe connection 16.

The use of the cylindrical meshes divided into rectangular windows united with the supporting bars and rings around the edges of the windows means that the filter assembly can withstand much higher pressures than has previously been the case, which leads to a higher-flow rate. Furthermore, the transparent container 1 enables a constant watch to be kept on the filter elements.

Also, filter elements may be readily replaced simply by unscrewing the cap 38.

The fact that the inlet and outlet pipe connections are aligned means that the filter can be rapidly and simply inserted in a milk supply hose.

Finally, the design of the drain plug 6 ensures that a sample of the milk in the container can be taken without actually removing the plug 6.

Although the assembly specifically described with reference to the drawings uses cylindrical filter elements in a cylindrical transparent container, it is to be understood that the filter assembly of the invention may use frusto-conically shaped screens in place of cylindrically shaped screens and therefore the invention is not to be construed as being limited to cylindrically shaped filter elements.

WHAT WE CLAIM IS: - 1. A filter assembly comprising two filter elements arranged coaxially one inside the other in a spaced-apart relationship and mounted within a housing having an inlet and an outlet, the inlet communicating with the interior of the inner filter element and the outlet communicating with a space surrounding the outer filter element such that, in use, liquid under pressure flows from the inlet to the outlet by way of a path extending radially outwardly through both filter elements, in which the filter elements each comprise a mesh sleeve and an integrally moulded cage of plastics material having longitudinally extending bars integrally formed with axially-spaced ring-like parts, the mesh sleeve, at its ends, being held in respective ring-like parts by portions of the moulded plastics material which have flowed into inter-stices in the mesh from both sides, such moulded plastics portions preventing the mesh from being buckled away from the ring-like parts.

2. A filter assembly as claimed in Claim 1, in which the housing comprises a hollow container closed by a cap provided with the inlet and the outlet which open, respectively, into a chamber formed in the cap and into an annular space surrounding a sleeve within which the chamber is formed, circular O-ring seals being located between the upper ends of the two filter elements and between the sleeve and the outer filter element, and further circular O-ring seals being located between respective lower endportions of the two filter elements and the container.

3. A filter assembly as claimed in Claim 2, in which a shallow step formed on the inside wall of the container above its floor positively locates the lower O-ring of the outer filter element, and the lower O-ring

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

Claims

**WARNING** start of CLMS field may overlap end of DESC **. and 19', 20' and 21'. Thus the screen is divided into part-cylindrical windows 52 each of which is firmly held along its four edges to the surrounding frame of plastics material provided by the rings and bars. Deformation of buckling of the meshes along the circular ends by internal pressure in the filter element is thus resisted in a way which prevents leak channels occurring around or through the mesh unless it is physically torn. The "weld" lines of the plastics to the mesh may be continuous or intermittent and the mesh itself may be metal or made of a plastics material such as nylon or other plastics substance able to withstand the moulding process used for forming the bars and rings. The filtering apparatus is assembled by inserting the inner filter element 3 into the underside of the outer filter element 2 so that its ribs are received in respective channels of the latter. When pushed home the inner filter element 3 is held in place by the engagement of its O-ring 25 with the cylindrical inside wall of the spigot 24'. The double filter element combination is then inserted into the container 1 and is pushed down until the O-ring 27 rides onto the inner face of the shallow step 39 of the container. This ensures an effective liquidtight seal at O-ring 27. The screw threaded cap 38 is then placed on the container 1 and a threaded portion 28 on the sleeve 9 is screwed into an internally threaded zone provided in the upper wall portion of the container 1. The spigot 24' enters the chamber 14 and its O-ring 25' makes a tight seal against the chamber wall. The axial length of the sleeve 10 is such that final screwing motion of the cap causes the rim of the sleeve 10 to bear down on the ring 19' around the spigot 24' to effect the seal between the O-ring 22 of the inner filter element and the annular surface 17 of the container. In use, liquid under pressure enters the filter assembly through the inlet pipe 15 and flows through the chamber 14 into the interior of the inner coarse filter element 3. The liquid is then forced radially through the two filter elements, passing firstly through the coarse element and then through the fine element 2, to a space between the wall of the container 1 and the outer element 2. The liquid then flows out of the assembly through the annular gap 12 and the outlet pipe connection 16. The use of the cylindrical meshes divided into rectangular windows united with the supporting bars and rings around the edges of the windows means that the filter assembly can withstand much higher pressures than has previously been the case, which leads to a higher-flow rate. Furthermore, the transparent container 1 enables a constant watch to be kept on the filter elements. Also, filter elements may be readily replaced simply by unscrewing the cap 38. The fact that the inlet and outlet pipe connections are aligned means that the filter can be rapidly and simply inserted in a milk supply hose. Finally, the design of the drain plug 6 ensures that a sample of the milk in the container can be taken without actually removing the plug 6. Although the assembly specifically described with reference to the drawings uses cylindrical filter elements in a cylindrical transparent container, it is to be understood that the filter assembly of the invention may use frusto-conically shaped screens in place of cylindrically shaped screens and therefore the invention is not to be construed as being limited to cylindrically shaped filter elements. WHAT WE CLAIM IS: -

1. A filter assembly comprising two filter elements arranged coaxially one inside the other in a spaced-apart relationship and mounted within a housing having an inlet and an outlet, the inlet communicating with the interior of the inner filter element and the outlet communicating with a space surrounding the outer filter element such that, in use, liquid under pressure flows from the inlet to the outlet by way of a path extending radially outwardly through both filter elements, in which the filter elements each comprise a mesh sleeve and an integrally moulded cage of plastics material having longitudinally extending bars integrally formed with axially-spaced ring-like parts, the mesh sleeve, at its ends, being held in respective ring-like parts by portions of the moulded plastics material which have flowed into inter-stices in the mesh from both sides, such moulded plastics portions preventing the mesh from being buckled away from the ring-like parts.

of the inner filter element, which is located in its underside, abuts the container floor and is pressed against it by the cap.

4. A filter assembly as claimed in Claim 3, in which a drain hole is provided in the container floor and is closed by a hollow plug having a threaded spigot which is screwable into a threaded zone of the drain hole and has its upper portion formed with a lateral opening located beneath a circular O-ring which fits sealingly inside a sealing rim provided around the portion of the drain hole above the threaded zone, whereby, by partially unscrewing the drain plug, a controllable flow of liquid is released via the lateral opening in the drain plug and its hollow interior.

5. A filter assembly as claimed in any one of Claims 2 to 4, in which the two filter elements and their container are all cylindrical and all coaxially arranged.

6. A filter assembly as claimed in any one of Claims 2 to 5, in which the container is made of a transparent plastics material.

7. A filter assembly as claimed in Claim 6, in which the longitudinally extending bars of one filter element are formed with ribs which are a sliding fit in longitudinally extending channels provided in the bars of the other filter element.

8. A filter assembly as claimed in any one of Claims 5 to 7, in which the mesh sleeve of each filter element is divided by the bars and ring-like parts into partcylindrical windows through which filtering takes place, each said window being framed by portions of moulded plastics material extending from the bars and rings through interstices in the mesh and coalesced on their opposite side to lock the mesh to the bars and ring-like parts.

9. A filter assembly as claimed in any one of Claims 5 to 8, in which the mesh is metal.

10. A filter assembly as claimed in Claim 1, arranged and adapted to operate substantially as described with reference to the accompanying drawings.