Vent Filter And Pure Liquid Storage Tank

Abstract

A vent filter (1), preferably for a pure liquid storage tank, comprising a cylindrical shell (2), at least one compartment (A) for accommodating granular filter material (3), said at least one compartment (A) defined between an inner peripheral surface (4) of the shell (2) and a pair of spaced apart separator plates (5) arranged in the shell (2) such that the spacing of the separator plates (5) in the axial direction of the shell (2) can be changed and fixed so as to apply a pressure on the granular filter material (3) in the at least one compartment (A). An air inlet (6) and an air outlet (7) are respectively arranged to allow a flow of air through the granular filter material (3) in the at least one compartment (A).

Claims

1. A vent filter, comprising: a cylindrical shell; at least one compartment for accommodating granular filter material, said at least one compartment defined between an inner peripheral surface of the shell and a pair of spaced apart separator plates arranged in the shell such that the spacing of the separator plates in the axial direction of the shell can be changed and fixed so as to apply a pressure on the granular filter material in the at least one compartment; and an air inlet and an air outlet respectively arranged to allow a flow of air through the granular filter material in the at least one compartment.

2. The vent filter according to claim 1, further comprising a support member and a locking mechanism for allowing fixing of at least one of the separator plates in a plurality of defined positions in the axial direction of the shell on the support member.

3. The vent filter according to claim 2, wherein the at least one of the separator plates respectively comprises a frame and a screen supported by the frame, wherein the screen is configured to be air permeable and to retain the granular filter material.

4. The vent filter according to claim 3, wherein the frame comprises a circumferential rim configured to slidingly seal against the inner peripheral surface of the shell.

5. The vent filter according to claim 2, wherein the support member comprises a shaft extending in the axial direction of the shell and supporting the at least one of the separator plates thereon.

6. The vent filter according to claim 5, wherein the separator plate(s) has/have a hub supported on the shaft so as to be movable in the axial direction.

7. The vent filter according to claim 6, wherein the locking mechanism comprises one or more protrusions provided on the hub and configured to be engaged with plural recesses provided on the shaft to define the plural axial fixing positions for the hub.

8. The vent filter according to claim 1, wherein the separator plates are identical.

9. The vent filter according to claim 1, wherein the granular filter material comprises soda-lime, activated carbon, LiOH and/or zeolithe.

10. The vent filter according to claim 1, comprising a further compartment upstream and/or downstream of the at least one compartment with respect to the flow direction of air through the vent filter from the inlet to the outlet.

11. The vent filter according to claim 1, wherein the inlet and/or the outlet is/are respectively formed on a lid member to close a respective axial end opening(s) thereof.

12. A pure liquid storage tank, comprising a vent filter according to claim 1 having the outlet communicating with the interior volume of the tank and arranged on a top side of the tank such that the axial direction of the cylindrical shell of the vent filter extends in a substantial horizontal direction.

13. The pure liquid storage tank according to claim 12, comprising a link for connecting the vent filter to the tank so as to allow pivotal movement of the vent filter into and from the substantial horizontal orientation.

14. The vent filter of claim 5, wherein said shaft is a central shaft.

15. The vent filter of claim 11, wherein the inlet and/or the outlet is/are respectively formed on the lid member non-removably attached to the shell.

Description

[0041] The present invention will be described in connection with the preferred embodiment by reference to the attached drawing. In the drawing:

[0042] FIG. 1 is a perspective partial view of the vent filter cartridge of a preferred embodiment;

[0043] FIG. 2 is a cross-sectional view of the vent filter cartridge of FIG. 1;

[0044] FIG. 3 is a partial sectional view of the vent filter cartridge of FIGS. 1 and 2; and

[0045] FIGS. 4A and 4B are magnified detail cross sectional views of the two extremities of the shaft with the locking mechanism of the embodiment of FIGS. 1 to 3.

[0046] The vent filter 1 in the form of a vent filter cartridge according to a preferred embodiment shown in the drawing is in particular intended for use with the pure liquid storage tank, in particular a pure water storage tank for use in a laboratory environment.

[0047] The vent filter or vent filter cartridge comprises a cylindrical shell or container 2 surrounding at least one compartment A for accommodating granular or particular filter material 3. The at least one compartment A is defined between an inner peripheral wall surface 4 of the cylindrical shell 2 and a pair of spaced apart separator plates 5 arranged in the shell 2 such that the spacing of the separator plates 5 in the axial direction of the shell can be changed and fixed so as to apply a certain pressure on the granular filter material 3 in the at least one compartment A and maintain a given packing state.

[0048] The vent filter 1 in the form of a vent filter cartridge further has an air inlet 6 and an air outlet 7 respectively arranged at the ends of the vent filter 1 to allow a flow of air through the granular filter material 3 in the at least one compartment A (or optionally through further compartments and filter media as described below). The air inlet 6 is typically for ambient air and the air outlet 7 is for directing filtered air to the inner volume of the liquid storage tank to which the vent filter is mounted.

[0049] The variable spacing of the separator plates 5 in the shell 2 and the fixation of the separator plates 5 in their respective axial positions is achieved my means of a support member 8 and a locking mechanism for allowing fixing of at least one of the two separator plates 5 delimiting the at least one compartment A in a plurality of defined positions in the axial direction of the shell 2 on the support member 8. In the broadest understanding one of the separator plates 5 can be maintained in a fixed and unmovable position of the support member whereas only the other separator plate 5 can be movable and fixable in plural defined positions in the axial direction to allow filling of the granular filter material 3 into the compartment A and applying the defined pressure on the granular filter material.

[0050] In the preferred embodiment the separator plates 5 respectively comprise a frame 13 and a screen 16 supported by the frame 13. The screen 16 is designed to be air permeable and to retain the granular filter material 3 in the compartment. The frame 13 preferable comprises a circumferential rim or edge 15 configured to slideably seal against the inner prereferral wall surface 4 of the shell 2. An additional sealing device including an O-Ring, elastic sealing material or labyrinth-seal maybe provided at the interface between the circumferential rim 15 and the wall surface 4 of the shell 2. The separator plates 5 (i.e. at least the one of the plates that is movable) respectively have a central hub 11 connected to the peripheral rim 13 by means of an arrangement of stays or spokes 14 which are designed to maximise the air throughput through the screen 16 and provide sufficient rigidity and stability of the separator plate 5. The separator plates can be different or can be preferably identical.

[0051] In the preferred embodiment the support member 8 comprises a preferably central shaft 9 extending in the axial direction of the shell 2 and supporting the at least one or both of the separator plates 5 thereon. The support of the separator plate(s) 5 on the enteral shaft 9 is by means of the central hub 11 and the hub 11 is either fixedly mounted on the central shaft at a single position, which can be the case for one of the separator plates, or is movable in the axial direction of the shaft 9 (which can thus be the case for one or both of the separator plates depending on the design of the vent filter).

[0052] The fixation of the movable separator plate(s) 5 is realized by means of a locking mechanism which, in case of the preferred embodiment shown in FIG. 4, comprises one or more protrusions 12 formed on or adjacent to the central bore of the hub 11 and configured to be engaged with plural recesses 10 provided over axial portions of the shaft 9 to define the plural axial fixing positions for the hub.

[0053] The protrusion(s) 12 and recesses 10 defining the locking mechanism for the separator plates on the shaft 9 can be respectively formed as circular notching spaced apart in parallel along the axial direction of the shaft 9 as shown in FIG. 4A/B or can be in the form of a spiral thread or other mechanical locking mechanisms along a portion of the axial length of the shaft. The locking mechanism in the form of the protrusions/recesses in the form of the notching is advantageous in that the movement and fixation of the movable separator plate(s) 5 in the plural defined positions can be achieved by only an axial movement without requiring rotation of the separator plate(s) 5 which could potentially grind, abrade or otherwise damage the granular material.

[0054] Another solution for the locking mechanism would be to provide a locking mechanism that engages with the axial portions of the shaft whereas the hub 11 is not directly fixed to the shaft, i.e. in the form of a nut or clamp placed outside the compartment A and engaging a thread of other mating engaging features to press the hub in the axial direction. The finer the axial spacing of the locking positions of the locking mechanism, the finer is the setting of the compression or compaction of the granular material in the compartment A. A threaded mechanism, for example, provides an unlimited number of locking positions within the threaded moving range.

[0055] The shaft 9 may have a seat 20 (see FIG. 4B) for defining an axial end position for the hub 11. Likewise, the inner peripheral wall surface of the shell 2 may also have a seat 21 (see FIG. 2) for one of the separator plates which may thus be the one that is not axially movable along the shaft 9.

[0056] The granular filter material 3 filled into the at least one compartment A may comprise soda lime or other suitable granular filter material depending on the filter purpose as described before and as known in the art. The form of the filter media may be for example irregular granular particles, spherical or non-spherical particles. Suitable filter material for CO.sub.2 absorption are for example LiOH or sodalime. For the absoprtion of organic molecules suitable filter materials may be selected from granular activated carbon or zeolithe and combinations thereof.

[0057] The vent filter or vent filter cartridge 1 according to the invention may comprise a further compartment B upstream of the at least one compartment A containing the granular filter material 3 and/or a further compartment C downstream of the at least one compartment A with respect to the flow direction of the air through the vent filter 1 from the inlet 6 to the outlet 7 (see FIG. 2). The upstream compartment B may contain a filter to filter volatile organic and inorganic substances or solvents or particles, and the downstream compartment C may contain a filter for filtering bacteria, dust and other particles.

[0058] In the preferred embodiment as shown in FIGS. 2 and 3 the inlet 6 and the outlet 7 are respectively formed on separate lid or end members or covers 17, 18. The downstream compartment C in the preferred embodiment is integrated into the inner volume of the shell 2. The upstream compartment B is received in the lid member 17. This is advantageous in that the compartments may be opened and are easily accessible for filter replacement and it facilitates the mounting.

[0059] A further lid member or cover 19 with a communication opening for the air may be provided to close part of an axial end of the shell 2 on the side of the movable separator plate 5 as show in FIG. 2. The lid members 17, 18 and the further lid member or cover 19, if provided, are preferable non-removably attached to the shell 2 to close the respectively axial ends thereof, by vibration or thermal or ultrasonic welding.

[0060] The inlet 6 in this embodiment is in the form of a plurality of axially extending long-holes formed in the lid member 17 on an outer circumferential surface thereof (see FIGS. 1 and 3). This arrangement is preferable as it does not require further space on the axial end of the lid member in the mounted state on a tank. The inlet 6 may be, however, formed in a variety of configurations determined just by the requirement of introducing a sufficient amount of air into the vent filter and allowing the air to pass through the compartment(s) in sequential order.

[0061] The outlet 7 in this case is formed on the lid member 18 and is provided in the form of a central hub or port. As shown in FIG. 3 an outer peripheral surface of the port is provided with a thread-like feature 23 for allowing a simple engagement/disengagement of the cartridge with a mating holder or receptacle on a tank. Other connecting means in the form of a bayonet or by means of a separate locking member are feasible.

[0062] Since the shaft 9 supports the separator plates in a fixed axial spacing, the sealing effect at the outer peripheral rim of the separator plates 5 with respect to the inner peripheral wall 4 of the shell 2 does not have to be very tight as the forces imparted on the separator plates are mainly born by the central shaft 9.

[0063] Although a single central shaft 9 is used in the preferred embodiment, a plurality of shafts, preferably equally distributed about the circumference are possible, in particular in connection with the locking mechanism with the notching that allows movement and fixation of the separator plates along the axial direction in a plurality of defined positions without a rotational movement thereof.

[0064] The vent filter is in the form of a self-supporting cartridge that can be easily mounted to and removed from a corresponding receptacle or holder on the tank.

[0065] In order to reduce the head space requirement for the vent filter above the tank, the vent filter cartridge of the invention can be mounted in a position on the top side of the tank such that the axial direction of the cylindrical shell of the vent filter extends in a substantially horizontal orientation. In this orientation the vent filter can be mounted and replaced by horizontal movement from a front side.

[0066] In a preferred embodiment (not shown) the pure liquid storage tank designed for use with the filter cartridge of the invention may be provided with a link member for connecting the vent filter cartridge to the tank so as to allow a pivotal movement of the vent filter into and from the horizontal orientation, i.e. from a horizontal working orientation to a substantially vertical orientation in order to facilitate the replacement of the vent filter cartridge and/or allow operation in such upright or vertical orientation. The link member may provide a direct communication between the outlet 7 for filtered air of the vent filter cartridge and the interior volume of the tank, but may be functionally combined with a valve or switch that is opened once the vent filter cartridge is pivoted in a particular working orientation. This allows for an exchange or replacement of the filter cartridge in the closed position of the valve without the risk of contaminating the interior volume of the tank during a replacement of the vent filter cartridge.