WO1996017173A1

WO1996017173A1 - A tubular diaphragm for a flowable material handling device

Info

Publication number: WO1996017173A1
Application number: PCT/AU1995/000786
Authority: WO
Inventors: Joseph Bertony
Original assignee: Material Transportation Technologies Pty. Limited
Priority date: 1994-11-29
Filing date: 1995-11-28
Publication date: 1996-06-06
Also published as: AUPM975894A0

Abstract

A membrane (2) for use in a flowable material handling device, the membrane body has an elongated through bore (3) with a major and a minor axis to provide four longitudinally extending bore surfaces, end flanges (5, 7) on the body whereby the membrane (2) can be end connected into a flowable material handling device, said membrane body includes at least one flex zone (9, 11) provided by four channel forming sections of the respective surfaces of said bore (3) where the channels are end aligned circumferentially around the membrane body and each channel has a cross-sectional area which decreases from a maximum at the ends of the minor axis of the bore cross section to a minimum adjacent the ends of the major axis of the bore cross section.

Description

A TUBULAR DIAPHRAGM FOR A FLOWABLE MATERIAL HANDLING DEVICE

FIELD OF THE INVENTION.

The present invention relates to membrane for flowable material handling devices. Such membranes are adapted to move a fluid or flowable material and are suited for use in peristaltic pumps, mixing apparatus or valves. Materials typically handled are food slurries, coal slurries and ash slurries and other mining slurries.

BACKGROUND ART

Membranes for peristaltic pumps have been made in a variety of shapes over the years to suit the compression and expansion cycles of the pumps. In a peristaltic pump, tubular membranes are arranged end to end to form a flow path and are sequentially compressed to thereby pass through them or prevent passage through them of a flowable material being pumped by the peristaltic pumps. The closing of peristaltic pump membranes produces stresses in the wall section of the membrane with the value of the stress depending to a large degree on the shape of the membrane.

It has been found that stresses can be reduced by the use of a membrane shape which assists in the compression of the membrane. A lozenge shape with a cross-section having a minor and a major axis has bee n used with some success. However, even such membranes can suffer localised stress due to the intrinsic nature and shape of the membrane. The localised stress with which this invention is concerned is that resulting from stretching of the membrane in localised areas. Under operating conditions this can cause stress fractures and substantially decreased service life of the membrane

BROAD STATEMENT OF THE INVENTION.

The present invention can be said to provide a membrane for use in a flowable material handling device, said membrane including a body with a normally open through bore extending between ends of the body and defined by a generally uniform thickness flexible body wall, securement means at each end of the body whereby the membrane can be end connected into a flowable material handling device, said body and bore except for a portion associated with a flex zone in said body is of substantially uniform cross-sectional shape and symmetrical throughout its length with a major and a minor axis generally at right angles thereby providing said body with four longitudinally extending sides and said bore with four longitudinally extending surfaces, said body flex zone is provided by four channel forming sections of the respective sides of said body where the channels formed are circumferentially aligned and each has a cross-sectional area which decreases from a maximum at the e nds of the minor axis of the bore cross-section to a minimum adjacent the ends of the major axis of the bore cross-section

BRIEF DESCRIPTION OF THE DRAWINGS.

Two presently preferred embodiments of the invention will now be described with reference to the accompanying drawings in which : Fig.1 is a perspective view of a first embodiment of the membrane of the invention in which a wire frame pattern has been used to show the contours of the membrane body surface,

Fig.2 is a longitudinal sectional elevation of the membrane of Fig.1 , Fig.3 is an end elevation of the membrane of Fig.1 ,

Fig.4 is diagrammatic representation of the membrane of Fig.1 and Fig.5 is a view similar to Fig.1 showing a second embodiment of the invention.

DETAILED DESCRIPTION OF THE DRAWINGS.

Illustrated in Figure 1 there is a membrane 2 for a flowable material handling device as would be used to handle a slurry. Such a device might be a pump, a mixing device or a valve. The membrane 2 has a normally open lozenge shaped passage 3 therethrough. Around a first open passage end 4 is a flange 5 whilst around a second open passage end 6 there is a second flange 7. The flanges 5 and 7 can be used to secure the membrane 2 into a flowable material handling device body. The membrane body between the flanges 5 and 7 is a walled structure having five general zones. The first zone 8 is longitudinal and of generally constant cross-section and substantially straight sided. The second zone 9 is a flex zone and is curved. The third zone 10 is again straight sided and of generally constant cross- section similar to the cross-section of the zone 8. The fourth zone 11 is another flex zone and is curved similarly to flex zone 9. The fifth zone 12 is similar to the first zone 10. The flex zones 9 and 11 can be likened to bulbous reservoirs of wall material to be unfolded and refolded as the membrane body is flexed. The flex zones 9 and 11 are sized to provide a linear length of wall between lines 13 and 14 which is greater than the linear length of wall between lines 14 and 15. The perpendicular distance between lines 13 and 14 is substantially equal to the perpendicular distance between lines 14 and 15.

The thickness of the membrane wall in the several zones is substantially the same. The flex zones 9 and 11 are located at the high stress points ( or points at which maximum flexibility is required) of the membrane when the membrane body is in the compressed state. When the membrane body is in compressed state (indicated 16 in figure 1 in phantom line) the region between the lines 13 and 14 unfolds to form a curved profile 17 which does not compromise the integrity of the membrane wall between the lines 13 and 14. There is sufficient material available in the flex zones 9 and 11 to enable the membrane body to be compressed without any stretching of the membrane taking place. If the flex zones 9 and 11 were not present the membrane body would have to achieve the compressed shape illustrated in phantom lines 16 and 17.

As illustrated in figure 2 the pocket in the membrane passage formed by the flex zone at 9 is dimension 18 above the passage in line with the minor axis 19 of the membrane passage. The pocket dimension decreased in both directions away from the axis 19 indicated as distances 20, 21 & 22.

In figure 4, the membrane 2 of figures 1 and 2 is diagrammatically represented. The symbols which appear in figure 4 are as follows:

DX is the minor axis or nominal bore of the membrane passage

DY is the major axis of the membrane passage which is in the order of 1.8 times DX to 3.5 times DX

DL is the overall length of the membrane which is in the order of 2.8 times DX to 6.2 times DX

DZ is the distance to the centre of the flex zones 14 and 18 from the open passage ends 6 and 10, this distance is in the order of

0.8 times DX to 2.2 times DX.

The ratios and relationships between DX, DY, DL, and DZ can be varied within the ranges given to suit particular slurry characteristics and the operational parameters of the flowable material handling device which will utilise the membrane 2.

The flex zones 9 and 11 whilst providing relief from stretching stresses also improve the effective displacement of the membrane. When the membrane having the characteristics described above is placed in a flowable material handling device such as a pump, mixing apparatus or valve, there is improved performance results, improved reliability and durability.

The preferred shape for the flex zones 9 and 11 is curved as shown presenting a concave surface to passage 3. The concavity of the flex zones 9 and 11 increase the volume of the passage 3 and there is no obstruction in the passage 3 when the membrane is in the uncompressed state. An alternative but less desirable profile for the flex zones 9 and 11 is one in which there is a convex surface projecting into the passage 3. If this profile is used there will be a reduction in the nominal size and cross-sectional area of the passage 3, thereby providing a restriction in the passageway decreasing the volume or capacity of the passage 3 of the membrane 2. If a convex form is utilised the overall size of the membrane 2 may need to be increased to compensate for the factors detailed above.

Whilst in figures 1 and 2 the flex zones 9 and 11 are illustrated as curved or part circular it would be possible to achieve a similar result with angled flanks for the flex zones 9 and 11 which would provide a greater length between lines 13 and 14 than between 14 and 15.

Where the quantity of additional membrane material needed to accommodate the compression of the membrane could be provided by one flex zone 9, 11 then only one such zone need be provided. That flex zone can be similar to the flex zone 9 or can be as shown and indicated by the numeral 23 in Fig.5.

Claims

CLAIMS:

1. A membrane for use in a flowable material handling device, said membrane including a body with a normally open through bore extending between ends of the body and defined by a generally uniform thickness flexible body wall, securement means at each end of the body whereby the membrane can be end connected into a flowable material handling device, said body and bore except for a portion associated with a flex zone in said body is of substantially uniform cross-sectional shape and symmetrical throughout its length with a major and a minor axis generally at right angles thereby providing said body with four longitudinally extending sides and said bore with four longitudinally extending surfaces, said body flex zone is provided by four channel forming sections of the respective sides of said body where the channels formed are circumferentially aligned and each has a cross-sectional area which decreases from a maximum at the ends of the minor axis of the bore cross-section to a minimum adjacent the ends of the major axis of the bore cross-section.

2. A membrane as claimed in claim 1 wherein the channels are curved in cross-section.

3. A membrane as claimed in claim 1 wherein the channels are of Vee cross-section.

4. A membrane as claimed in any one of claims 1 to 3 wherein the channel forming sections of the body wall extend into the body bore.

5. A membrane as claimed in any one of claims 1 to 3 wherein the channel forming sections extend above the body sides.

6. A membrane as claimed in any one of claims 1 to 5 wherein the membrane has two flex zones disposed adjacent the respective ends of the membrane.

7. A membrane as claimed in claim 6 where the relationship between the overall length of the membrane and the minor axis dimension DX of the membrane bore is 2.8 to 6.2 DX and the length of the major axis of the bore is 1.8 to 3.5 DX and proportionally the spacing of the flex zones from the respective ends of the membrane is 0.8 to 2.2 DX.