EP0879078A1

EP0879078A1 - Filter apparatus

Info

Publication number: EP0879078A1
Application number: EP96941767A
Authority: EP
Inventors: David John Tebbutt
Original assignee: Scapa Group Ltd
Current assignee: Madison Filter 981 Ltd
Priority date: 1995-12-29
Filing date: 1996-12-11
Publication date: 1998-11-25
Also published as: GB9526629D0; ZA9610480B; CN1209078A; YU70096A; AU1104497A; WO1997024170A1; AU713908B2

Abstract

A filter apparatus (2) for filtering solids from liquid media. The filter apparatus comprises a filter medium (8) secured to an elongate retaining body (9). The retaining body is inserted into slotted tubes (6), which are placed on the supporting structure of the filter apparatus thus securing the filter media to the supporting structure of the filter apparatus. This allows easy insertion and exchange of filter media to the filter apparatus.

Description

Filter Apparatus

The present invention relates to filter apparatus such as drum filters

and pan filters and to a method of installing a filter medium on the

supporting structure of a filter apparatus.

At present, filter media such as filter cloths are retained to their

supporting apparatus, usually a drum or pan, by wedging the filter media

into a groove around the edge of the filtration area with synthetic ropes or

similarly configured extrusions. Metal mesh or soft wound wire cable has

also been used. The installation of the filter media down into the groove is

normally achieved by means of caulking tools, such as a bolster-shaped

device with a perspex blade that is struck by a large rubber mallet.

US 5,124,037 describes a filter cloth retaining device for a pan filter

comprising a tubular gasket which is expandable and which locks the filter

media inside the groove on inflation. US 4,308,143 describes a filter cloth

retaining device for a drum filter comprising a flexible metal device inserted

over the filter cloth which is retained in axial slots spaced circumferentially

around the drum. UK Patent No. GB 2088809A describes the use of metal

mesh or soft wound wire cable to enhance the hold of the cable in the

caulking groove. Numerous problems are associated with these known devices and

methods for filtration. Firstly, the rope wedging the filter media into the

groove needs to be a very tight fit in order to be maintained within the

groove, particularly when air is blown back through the filter media in order

to discharge the filter cake. Furthermore considerable strength and effort is

required to fit the rope within the caulking groove. This can lead to injuries

being inflicted on the filter media installation personnel, in particular finger

and hand injuries, elbow and ligament strains, and so forth. This problem is

further exacerbated when installing filter media on pan filters as the

installers have to kneel, which is another common reason for injury.

A further problem relating to known caulking methods is that the

caulking rope needs to absorb a significant amount of the product being

filtered in order to swell, so that full pressure can be applied to blow back

air for filter cake discharge. Production time is lost after initial start-up of

the process due to the waiting time taken for the rope to swell. Further to

this, the rope may become hard depending on the process conditions and

subsequently require several hours of washing in order for it to soften and

allow it to be removed during replacement of the filter media. Alternatively

pneumatic chisel guns are required to remove the hard ropes, resulting in

damage to the caulking grooves.

An object of the present invention is to provide a retaining method which eliminates the need for repetitive, intensive, physically demanding

and somewhat dangerous manual labour while reducing the risk of cloth

damage during installation.

A further object of the present invention is to provide devices for

filtering which eliminate the need for lengthy washes to soften caulking

devices such as ropes and allow the filter to be run at full capacity right

from start-up.

According to a first aspect of the present invention there is provided

a filter apparatus comprising a filter medium and a supporting structure for

the filter medium, wherein the filter medium is secured to an elongate

retaining body for securing the filter medium to a slotted tube of the

supporting structure, wherein the slotted tube is configured solely to

receive the retaining body therein on sliding the retaining body into the

tube, the filter medium extending through the slot of the slotted tube.

The elongate retaining body preferably extends along a significant

portion of the filter medium and may be elastomeric. The elastomeric

retaining body may be bonded to the filter medium by conventional means

such as stitching, hot air welding or ultra-sonic bonding, or may be

extruded directly onto the fabric. The retaining body may comprise natural

or synthetic rubber. The elongate retaining body may extend along two opposing edges of

the filter media and is ideally between 6mm and 10mm in diameter and is

ideally substantially 8mm in diameter. Preferably, the elongate retaining

body extends along two of the filter media edges and the remaining filter

media edges may be secured to the supporting structure of the filter

apparatus by conventional caulking methods. Alternatively, a simple bolt-

down metal strip may be used to secure the remaining edges of the filter

media to the supporting structure of the filter apparatus.

The slotted tube may be inserted into grooves along two of the edges

of the filter apparatus. The size of the assembly formed by two adjacent

slotted tubes is preferably from 30mm to 35mm in diameter and is ideally

substantially 32mm in diameter.

According to a second aspect of the present invention there is

provided a method of securing a filter medium to the supporting structure of

a filter apparatus, wherein the filter medium is secured to an elongate

retaining body for securing the filter medium to a slotted tube of the

supporting structure, and wherein the slotted tube is configured solely to

receive the retaining body therein on sliding the retaining body into the

tube, the filter medium extending through the slot of the slotted tube, the

method comprising the step of sliding the retaining body into the tube to

obtain a tensioned filter medium retained to the filter apparatus. Preferably the elongate retaining body of the filter medium is inserted

at one opening of the slotted tube of the supporting structure and the filter

medium is pulled to the other end of the slotted tube thereby obtaining a

tensioned filter medium retained to the filter apparatus. Further to this,

clamps are preferably used which allow the installers to pull the filter

medium along the slotted tube.

The present invention may be used in connection with devices for

filtering on a substantially horizontal plane as well as rotary devices for

filtering i.e., pan filters as well as drum filters.

In the case of a pan filter, the elongate retaining body of the filter

medium is fed into the slotted tube at the narrow end (neck) of the filter

panel and then the filter medium is pulled outwardly from the pan filter

centre to the wide end of the panel. The filter media is inserted via the two

edges along which the elongate retaining body is secured, into the two

slotted tubes which extend along the longitudinal edges of the pan filter.

Preferably, the remaining edges of the filter medium are secured at the inner

and outer perimeters of the pan filter via a bolt-down metal strip.

Altematively, conventional caulking methods may be used to secure the

filter medium at the inner and outer perimeters of the pan filter, wherein the

edges of the filter medium which are secured to the inner and outer

perimeters of the pan filter preferably do not have an elongate retaining body secured thereto.

The method used to install filter fabrics to a vacuum drum filter is

similar to that mentioned above in relation to a pan filter. A slotted tube is

installed longitudinally along the drum, and the elongate retaining body of

the filter medium is fed into the slotted tube and pulled along the length of

the drum. A slotted tube is preferably installed between every second panel

of a drum filter. The groove remaining between each slotted tube is used to

provide tension to the filter media via a bolt-down metal strip which is

secured to each central groove. A simple bolt-down metal strip may also be

used to secure the filter medium to the drum filter at the periphery of the

drum filter.

Alternatively, conventional caulking methods may be used in place of

a bolt-down metal strip at the central groove and at the peripheral edges of

the drum filter.

The retaining system according to the invention is preferably sized to

allow it to fit into the same area as the existing caulking grooves used in

conventional pan and drum filters. Consequently, there is no loss of

filtration area and installation costs are minimised.

In order that the present invention may be more readily understood specific embodiments thereof will now be described by way of example

only and with reference to the accompanying drawings in which:-

Fig. 1 is a perspective view of a part of a pan filter table in

accordance with the present invention;

Fig. 2 is an enlarged view along line A-A of Fig. 1 ;

Fig. 3 is an enlarged view along line B-B of Fig. 1 ;

Fig.4 is a perspective view of a rotary drum filter in accordance with

the present invention; and

Fig. 5 is an enlarged view along line C-C of Fig. 4.

Figures 2 and 3 also illustrate the enlarged views along lines A-A and

B-B respectively of Fig. 4.

Referring to the drawings and in particular Fig. 1 , a part 1 of a

circular pan filter table comprises two filtering apparatus in accordance with

the present invention, each filter apparatus 2 having a groove 3 provided

around the edge thereof. The filtering apparatus is shaped to form a narrow

end 4 at the centre of the pan filter table and a wide end 5 at the periphery of the pan filter table.

Referring also to Fig. 2, a slotted tube 6, having a slot 7, is inserted

into the groove 3 along the longitudinal edges 10 of the filter apparatus 2.

The slotted tube 6 is placed in the groove 3 so that the slot opening 7 faces

upwardly.

A filter medium such as a filter cloth 8, has secured thereto an

elongate retaining body 9, such as an elastomeric extrusion, along two

opposing edges of the filter cloth. Said elastomeric extrusion 9 is slidably

inserted into the slotted tube 6 at the narrow end 4 of the filter apparatus

2.

Once inserted, the elastomeric extrusion 9 being circular in cross

section and larger than the size of the slot 7 of the slotted tube 6, is thus

retained within the slotted tube. The filter cloth 8 extends through the slot

7 and is retained over the whole surface of the filter apparatus 2.

Once the filter cloth is inserted and the elastomeric extrusions 9

retained along the longitudinal edges 10 of the filter apparatus, the

remaining edges of the filter cloth 8 are secured along groove 3 at the

narrow end 4 and the wide end 5 of the filter apparatus 2. Referring to Fig. 3, the securing mechanism at the wide end 5 of the

filter apparatus 2 is shown. The filter cloth 8 is placed in the groove 3 and

a metal strip 14 secures the filter cloth into the groove via a bolt 15. The

tension on the filter cloth can be altered at this securing point.

Fig. 4 shows a rotary drum filter 16, wherein the drum filter is made

up of a series of filter panels 17. A slotted tube 19 is inserted between

every second filter panel along grooves 18.

The enlarged view along line A-A showing how a filter cloth is

retained to the drum filter panel is shown in Fig. 2 and is identical to that of

a pan filter table. A filter cloth is inserted to the drum filter panel at either

end 19 or 20.

Referring to Fig. 5, the filter cloth 8 is retained in the central groove

21 via a metal strip 22 which is placed on top of the filter cloth and a bolt

23 which holds the metal strip 23 and filter cloth 8 in place.

The above embodiments have been described by way of example

only. Many modifications and variations are possible.

Claims

CLAIM?

1. A filter apparatus comprising a filter medium and a supporting structure

for the filter medium, wherein the filter medium is secured to an elongate

retaining body for securing the filter medium to a slotted tube of the

supporting structure, wherein the slotted tube is configured solely to receive

the retaining body therein on sliding the retaining body into the tube, the filter

medium extending through the slot of the slotted tube.

2. A filter apparatus as claimed in claim 1 , wherein the elongate retaining

body extends along a substantial portion of the filter medium.

3. A filter apparatus as claimed in claim 1 or claim 2, wherein the elongate

retaining body is elastomeric.

4. A filter apparatus as claimed in claim 3, wherein the elongate retaining

body comprises natural or synthetic rubber.

5. A filter apparatus as claimed in any preceding claim, wherein the

retaining body is bonded to the filter medium by stitching, hot air welding,

ultrasonic bonding or extrusion directly onto the filter medium.

6. A filter apparatus as claimed in any preceding claim, wherein the elongate retaining body extends along two opposing edges of the filter media.

7. A filter apparatus as claimed in any preceding claim, wherein the

elongate retaining body is approximately 6mm to 10mm in diameter.

8. A filter apparatus as claimed in claim 7, wherein the elongate retaining body is approximately 8mm in diameter.

9. A filter apparatus as claimed in any of claims 6 to 8, wherein the

elongate retaining body extends along two opposing edges of the filter media

and the remaining filter media edges are secured to the supporting structure

of the filter apparatus by conventional caulking methods.

10. A filter apparatus as claimed in claim 9, wherein a bolt-down metal strip

is used to secure said remaining edges of the filter media to the supporting

structure of the filter apparatus.

11 . A filter apparatus as claimed in any preceding claim, wherein the slotted

tube is inserted into grooves along two edges of the supporting structure.

12. A filter apparatus as claimed in claim 11 , wherein the size of an

assembly formed by two adjacent slotted tubes is approximately 30mm to

35mm in diameter.

13. A filter apparatus as claimed in claim 12, wherein the size of the

assembly is approximately 32mm in diameter.

14. A method of securing a filter medium to the supporting structure of a

filter apparatus, wherein the filter medium is secured to an elongate retaining

body for securing the filter medium to a slotted tube of the supporting

structure, and wherein the slotted tube is configured solely to receive the

retaining body therein on sliding the retaining body into the tube, the filter

medium extending through the slot of the slotted tube, the method comprising

the step of sliding the retaining body into the tube to obtain a tensioned filter

medium retained to the filter apparatus.

15. A method of securing a filter medium to the supporting structure of a

filter apparatus as claimed in claim 14, wherein the elongate retaining body of

the filter medium is inserted at one opening of the slotted tube of the

supporting structure and the filter medium is pulled to the other end of the

slotted tube thereby obtaining a tensioned filter medium retained to the filter

apparatus.

16. A method of securing a filter medium to the supporting structure of a

filter apparatus as claimed in any one of claims 14 or 15, wherein clamps are

used to pull the filter medium along the slotted tube.

17. A filter apparatus as claimed in any one of claims 1 to 13, comprising

a pan filter apparatus for filtering on a substantially horizontal plane, wherein

the pan filter apparatus comprises at least one filter panel having a narrow end

at the centre of a pan filter table and a wide end at the perimeter of the pan

filter table.

18. A method of securing a filter medium to the pan filter apparatus of claim

17, wherein the elongate retaining body of the filter medium is fed into slotted

tubes, which extend along two longitudinal edges of the filter panel, at the

narrow end of the filter panel and pulled from the pan filter centre to the wide

end of the filter panel.

19. A method as claimed in claim 18, wherein the remaining edges of the

filter medium are secured at inner and outer perimeters of the pan filter via a

bolt-down metal strip.

20. A method as claimed in claim 19, wherein the remaining edges of the

filter medium are secured at the inner and outer perimeters via conventional

caulking methods.

21 . A filter apparatus as claimed in any of claims 1 to 13, comprising a

rotary filter, wherein at least one slotted tube is installed longitudinally along

a drum, said drum comprising a plurality of filter panels.

22. A method of securing a filter medium to the rotary filter apparatus of

claim 21 , wherein the elongate retaining body of the filter medium is fed into

the slotted tube, said slotted tube being positioned between the drum filter

panels, the filter medium is then pulled along the length of the drum.

23. A filter apparatus substantially as hereinbefore described with reference

to the accompanying drawings.

24. A method of securing a filter medium to a filter apparatus substantially

as hereinbefore described with reference to the accompanying drawings.