WO2000028214A1

WO2000028214A1 - Peristaltic fluid pumping and/or separation apparatus

Info

Publication number: WO2000028214A1
Application number: PCT/GB1999/003703
Authority: WO
Inventors: Keith Crane; David Arthur Hoare
Original assignee: Albury Bourne Limited
Priority date: 1998-11-06
Filing date: 1999-11-08
Publication date: 2000-05-18
Also published as: US20010055534A1; EP1129289A1; AU1059700A

Abstract

Peristaltic pumping apparatus (5) has a cage with rollers (59) circumferentially spaced around its periphery rotatable within a casing, there being at least two flexible tubes extending around the cage, a first, evacuation tube having an inlet end held open within the casing (43) and an opposite end connected to a first outlet in the casing (33) and a second pumping tube extending between an inlet in the casing (37) adapted to be connected to a liquid to be pumped and a second outlet from the casing (31), whereby, upon rotation of the cage, e.g. by an electric motor, a negative pressure will be generated within the casing (7) and the liquid will be pumped through the apparatus. If the apparatus is to be used as a separator for separating solids suspended in/mixed with the mixture being pumped, filtering means (29) may be provided at the downstream end of the pumping tube outside the casing or within the tube itself. To prevent the tubes from wandering laterally and becoming worn within the casing, a plurality of guide spools (57) is located on the cage, preferably circumferentially alternating with the rollers on the cage. Instead of using a filtering means, the separation of solids from the liquid in the mixture may be achieved by generating an electrostatic charge within the mixture, or an electrical charge, using electrodes and a low voltage AC current.

Description

PERISTALTIC FLUID PUMPING AND/OR SEPARATION APPARATUS

The present invention relates to an apparatus for and method of pumping fluids and more particularly, an apparatus for and method of separating liquids from solids in a mixture of liquids and solids. The method and apparatus can be used for the processing of waste water or waste liquids carrying solids or particulate matter in any proportion. For example, the invention can be used for the dewatering of animal slurries, sewage slurries and for the treatment of liquid effluent from a vegetable washing plant, from a mushroom farm, or for the treatment of the liquid effluent from poultry packing plants, dairies, creameries and cheese making factories. It can also be used for treating industrial, municipal and commercial waste liquids, municipal sewage sludges, including digested and non-digested primary and secondary sludges, industrial sludges such as paper slurries and the like.

Furthermore, the invention can be used for the extraction of juices from citrus fruits and other fruit products, such as current and apple pulp, or even for separating the juice and fruit flesh from pips, stalk, branches and leaves during the harvesting of grapes, blackcurrants and the like.

The invention makes use of known peristaltic pumping principles. In DE-A-2234592, and US-A-5281112, a peristaltic pump is used to separate solids from liquids. In these specifications, an external vacuum source is used to generate a reduced pressure within the peristaltic pumping chamber. Alternative constructions of peristaltic pumping apparatus are disclosed in EP-A-0470333 and JP 61016282.

In our own earlier patent specification, WO 96/31269, a peristaltic fluid pumping or sludge separation device similar to that of the present invention is disclosed. In this device, at least two lay-flat tubes are entrained around a plurality of rollers supported on a roller cage and rotatable within a sealed casing. One of the lay-flat tubes is used to generate a reduced pressure within the casing and the other tube is used for pumping a fluid mixture of liquids and solids. The liquids are separated from the solids in this apparatus by using a composite lay-flat tube for the separation process, the composite lay-flat tube having a tapered filter tube therein through which the mixture to be separated is forced. The present invention is an improvement over the apparatus and method disclosed in WO 96/31269.

According to the broadest aspect of the present invention, we provide peristaltic pumping apparatus comprising at least two flexible deformable tubes entrained around a cage, rotatable within a part arcuate casing and supporting a plurality of rollers which push fluid through the tubes by squeezing the tubes, a first one of the tubes having a first end held open to the interior of the casing and an opposite end connected to a first outlet from the casing, whereby, upon operation of the apparatus, a pressure (hereinafter called negative pressure) which is less than that surrounding the casing will be generated within the casing, a second one of the tubes being connected at one end to an inlet in the casing, adapted to be connected to a fluid to be pumped and its opposite end being connected to a second outlet therein, whereby upon operation of the apparatus, the negative pressure will cause the second tube to move from a flattened state to a tubular state, whereby the fluid will be pumped through the second tube to the outlet.

Filtering means may be located at or adjacent the outlet end of the second tube so that as the fluid is pumped through the tube, solids will be separated from liquids within the fluid. The filtering means may comprise a flexible sleeve, which may be formed of textile material, at the outlet end of the tube, one end of the sleeve being connected to the tube and the opposite end being connected to an outlet pipe of the filtering means, the sleeve being located within a casing having a liquid outlet therein through which filtered liquids can pass. The sleeve may be of tapered construction so that its outlet end is of reduced cross-sectional area, relative to its inlet end.

Also according to the present invention, we provide an apparatus for separating solids from liquids in a mixture of solids and liquids comprising a closed casing having a side wall, at least part of which is arcuate, and a pair of spaced opposed end walls, connected by said part arcuate side wall, a cage rotatable within the casing, the cage having rollers spaced around its periphery, and a first resilient tube extending around the cage and located between the peripheries of the rollers and the internal surface of the arcuate side wall, one end of the first tube being connected to a first outlet in a wall of the casing and the opposite end of the tube being connected to means within the casing to hold open said end of the tube, there being a non-return valve located within, or at the outlet end of, the first tube, means to cause rotation of the cage such that air within the casing will be drawn into the held-open end of the tube and pumped along the tube in peristaltic manner to the outlet, the non-return valve preventing air from re-entering the tube, whereby the pressure within the casing is reduced, relative to that around the casing, at least one further resiliently deformable tube entrained over at least some of the rollers of the cage, so as to extend between the rollers and the arcuate part of the side wall of the casing, one end of said further tube being connected to a second outlet in a wall of the casing and an opposite end thereof being connected to an inlet in a wall of the casing, said inlet being adapted to be connected to said mixture, whereby rotation of the cage not only reduces the pressure within the casing to cause the at least one further tube to expand into a tubular state, but also pushes said mixture to be pumped along the further tube from the inlet to the outlet, there being means to separate liquid from solids in said mixture. In one arrangement, said means may comprise filtering means located at the outlet end of the further tube, whereby the mixture pumped along the further tube is separated into liquids and solids by said filtering means.

In another arrangement, said means may comprise means for generating an electrical or electrostatic charge, which causes separation of solids from liquid in the mixture, e.g. by causing flocculation of the solid. In another arrangement, both means to generate an electrical charge or an electrostatic charge and filtering means may be provided.

The filtering means may comprise a perforated tubular member secured to the outlet end of the further tube, the perforated member preferably being flexible and formed of textile material and preferably tapering from its inlet end to its outlet end, the outlet end being connected to an outlet pipe in a filter casing, and there being a liquid outlet in said casing for liquids separated from said mixture. Alternatively, the filtering means may be a sieve-like filter sleeve located within said at least one further resiliently deformable tube, and incorporate at least two electrodes therein, or on the surface of the sleeve, and the other running centrally of the sleeve,^' each extending the full length of the sleeve.

Also according to the present invention, we provide a method of pumping peristaltically and a method of separating solids peristaltically from liquids in a mixture of solids and liquids, including the steps of locating a pair of flexible tubes within a casing having an at least part arcuate side wall, entraining the tubes around a cage having a plurality of rollers supported thereon, whereupon the flexible tubes are located between some of the rollers and the part arcuate side wall, one of said tubes being an evacuating tube and the other being a pumping tube, connecting an inlet end of the evacuating tube to means to hold open that end of the tube and connecting the other end of the tube to a non-return valve in the wall of the casing, causing rotation of the cage within the casing to generate a reduced pressure, relative to external pressure, within the casing, and connecting an inlet end of the further tube to an inlet in the casing, which inlet is adapted to be connected to a mixture to be pumped, whereby the reduced pressure will cause said mixture to be drawn into the further tube and then be pumped through the further tube and out of the casing, and optionally providing means to cause solids in said mixture to be separated from solids therein. Said means may comprise means to generate an electrical or electrostatic charge in the mixture, and/or filtering means at the outlet end of the further tube through which the mixture is passed, or within said tube.

Preferably, in order to prevent wear and tear of the tubes entrained around the rollers on the cage and to prevent the tubes from moving laterally along the rollers within the casing, the cage supports a plurality of guide spools for the respective tubes. Preferably there are a plurality of shafts circumferentially spaced around the cage, alternate shafts being used to support the rollers and the guide spools for the tubes.

In a preferred arrangement, an evacuating tube is located within the casing between a pair of pumping tubes, and hence, on each guide spool shaft, three separate guide spools are provided, a central one being for the evacuating tube and located on either side thereof, there is a lateral guide spool for the respective pumping tube. Preferably, also, each roller for the tubes is divided into a central portion for the evacuating tube and spaced to either side thereof, a lateral portion for the respective pumping tube.

Several embodiments of peristaltic pumping and separating apparatus of the present invention are now described by way of example with reference to the accompanying drawings in which: - FIGURE 1 : is a side elevation of one embodiment of a portable pump/separator,

FIGURE 2: is a plan view of the pump/separator,

FIGURE 3: is a front elevation of the pump/separator,

FIGURE 4: is a scrap plan view looking in the direction of the arrow A in Figure 1,

FIGURE 5: is a vertical section, to an enlarged scale, of filtering means shown at F in Figure 1,

FIGURE 6: is a plan view looking in the direction of the arrow B in Figure 5,

FIGURE 7: is a front elevation of the filtering means shown in Figures 5 and 6,

FIGURE 8: is a side elevation showing a rotor drum which is located within the casing of the pump/separator shown in Figures 1 to 4,

FIGURE 9: is a section on the line IX-IX shown in Figure 8,

FIGURE 10: is a section on the line X-X in Figure 8,

FIGURE 11: is a schematic view of an alternative embodiment of pumping and separating apparatus,

FIGURE 12: is a section to an enlarged scale through a preferred construction of filter sleeve having electrodes incorporated therein,

FIGURE 13: is a schematic scrap view showing a rotor drum having one pumping tube entrained around it and connected to an inlet and an outlet,

FIGURE 14: is an enlarged scrap view showing the inlet of Figure 13 in greater detail, FIGURE 15: is a view similar to Figure 14 but showing the outlet of Figure 13 and

FIGURE 16: is a schematic view of a sludge charging tank.

Referring to Figures 1 to 4, the peristaltic pump/separator is a mobile version having a wheeled support chassis 1 carrying an electric motor 3 driving the pump which is shown generally at 5, generally in known manner. The pump 5 has an overall casing 7 formed of sheet steel, having a part arcuate side wall 9 and a pair of end walls 11 , which are split as shown at 13 and support split bearing members 15 for a central drum shaft 17. The casing 5 is braced by a stiffening frame 19. The shaft 17 supports a drum 21 which is shown in greater detail in Figures 8 to 10.

The casing 5 has an upper cantilever portion 23 fitted with a removable inspection cover 24 and a lower cantilever portion 25 fitted with a removable inspection cover 26. Projecting arms 27 extend outwardly from each side of the cantilever portion 23 to support two filter chambers 29, as shown in Figure 2. On a front wall of the upper cantilever portion 23, two tube or hose coupling members 31 are provide for a pair of pumping tubes and a further tube or hose connector 33 for an evacuation tube (to be described hereinafter). As can clearly be seen in Figures 1 and 2, the ends of the coupling members 31 located outside the casing 5 are connected with proprietary coupling members to respective ones of the filter chambers 29, whereas a non-return valve 35 is mounted on the outer end of the connector 33.

As can clearly be seen from Figure 4, the cantilever portion 25 supports two further hose coupling members 37 for the peristaltic pumping hoses (not shown). Located internally of the casing 5 within the cantilever portion 25 is an evacuation hose support member 39. This is mounted on upstanding brackets supported on the base of the casing 5 and has an end open to the interior of the casing 5, as shown at 43.

As can be seen from Figures 8 to 10, the drum 21 has a drive shaft 17 rotatable in the bearing members 15, supported by the end walls of the casing 5 and supported on the drive shaft 17 towards respective ends thereof are two spaced support plates 45, having four arcuate side walls at the junctions of which are four mounting channels, each to accommodate a roller support shaft 49. To either side of each mounting channel 47, a slot 51 is provided to enable mounting plates fixed on either end of the support shaft 49 to be adjustably located in the channel 47 in known manner, using suitable fixing screws 53. Located midway along each side wall of each drum support plate 45 is a further mounting channel 55 for a support shaft 56 for a plurality of tube guide spools 57 (see Figures 2 and 10). The shafts 56 are located in their respective mounting channels 55 in the same manner as the shafts 49.

As can be seen more clearly in Figure 9, each of the roller support shafts 49 rotatably supports two pumping tube rollers 59 towards each end thereof, and a centrally located evacuation tube roller 61, each of the rollers 59 and 61 being provided with its own bearings and the respective rollers being separated from one another by suitable spacers 63. Whereas the pumping rollers 59 are of regular cylindrical construction, the evacuation tube roller 61 is contoured so as to have a central region with a uniform diameter, but tapered end regions, as shown at 65.

As can more clearly be seen from Figure 10, each of the shafts 56 supports a centrally located guide spool 58 for the evacuation tube and, located to either side thereof, a guide spool 57 for the respective pumping tubes. As can be seen from Figure 10, the two spools 57 for the pumping tubes are somewhat wider than that for the evacuation tube since in the preferred arrangement, the pumping tubes are of larger diameter than the evacuation tube. Each of the spools is provided with its own bearing so as to be able to rotate freely on its respective support shaft 56.

An inlet end of a resiliently deformable evacuation tube or hose 71 is connected in fluid tight manner using a screw connector 73 to the hose support member 39 and the hose 71 is then entrained around respective ones of the rollers 61 and guides 58 of the drum 21 and its outlet end is then connected in fluid-tight manner to that end of the connector 33 located within the casing 5 by a screw connector 75. Likewise, an inlet end of a pumping hose or tube 77 is connected by a screw connector 79 to that end of each tube connector 39 located within the casing 5 and is then entrained around respective ones of the rollers 59 and guide spools 57, and its outlet end is then connected using a respective screw connector 81 to that end of the respective tube coupling member 31 located within the casing 5. Tension in the respective hoses can be adjusted by adjusting the radial spacing of the shafts 49 and 56 from the shaft 17 of the drum 21.

The flexible tubes 71 and 77 may either be suitably reinforced, resiliently deformable, tubular hoses which when collapsed will spring back to their tubular form or alternatively, may be reinforced, lay-flat hosing, such as that used by fire brigades. It is preferred that the evacuation hose 71 be in the form of a lay-flat hose, and the chamfered lateral portion 65 of the roller 61 are provided so as not completely to squash the two lateral edge regions of the lay-flat hose during use.

As will be apparent from Figure 1 and Figure 8, the pump is operated by rotating the drum 21 clockwise. Such rotation will cause the evacuation tube 71, as each roller 61 rolls around the tube, to be squashed substantially completely flat so as to drive any air within the tube from the inlet end of the tube connected to the tube support member 39 around the tube and out of the outlet hose connector 33. The presence of the member 39 will ensure that at no time is the inlet end of the evacuation tube 71 collapsed. Because the member 39 is located within the casing 5 which is a totally sealed casing, each time a roller passes over the evacuation tube, a little bit more air from within the casing will be evacuated therefrom, so that eventually, the pressure within the casing 5 will be reduced substantially from normal atmospheric pressure outside the casing. Because the inside of the casing is therefore, during normal operation of the pump, at a pressure substantially reduced relative to external pressure, the stiffening frame 19 for the casing is most important. At the same time as the rollers 61 are rolling over the evacuation tube 71, partially to evacuate the interior of the casing 5, so the two other rollers 59 will be rolling over the two pumping hoses 77. Because the pressure within the casing has been reduced, the two pumping hoses will be fully inflated, i.e. completely tubular, except where they are engaged by the rollers 59 (because, of course, the interior of the pumping tubes 77 are in communication with the exterior of the casing 5 through there respective coupling members 31 and 37). If the coupling members 37 are connected outside the casing 5 to a suitable fluid to be pumped, the passage of the rollers 59 around the pumping tube 77 within the casing will cause any fluid within the tubes 77 to be pushed around the tube 77 from their inlet ends, towards their outlet ends connected by the connectors 81 to the coupling members 31. This in turn will cause fluid to be drawn into the casing through the tube inlets 37 and fluid to be pumped out of the casing through the couplings 31. Because the pressure within the casing 5 is reduced relative to atmospheric pressure, the two pumping hoses 77 will always be caused to return to their fully tubular configuration, immediately after a roller 59 has rolled over the tube. Hence, using the peristaltic pumping principles described, the pump will generate a negative pressure within the casing and at the same time, cause fluid to be pumped through the casing, through the two pumping tubes 77.

If it is desired to separate liquids from solids in the fluid being pumped by the pump, then suitable means to achieve this, such as the two filter chambers 29, are required. However, it is possible to dispense with these chambers altogether if the apparatus is merely to be used as a pump or alternatively, to dispense with the filters within the filter chambers, or alternatively, to use a different filter arrangement, or to use other means to achieve this.

Referring now to Figures 5 and 6, each filter chamber 29 is generally trough-shaped (as shown in Figure 7) with there being a liquid outlet 85 in the bottom of the trough. An inlet end of each filter chamber 29 is connected by a suitable screw connector 87 to a respective one of the hose coupling members 31, there being a suitable spigot 89 projecting inwardly into the interior of the chamber. At its opposite end, the chamber has an outlet pipe 91 for solids welded therein and during use, a suitable filter sleeve 93 which is preferably tapered, as shown in Figure 6, is connected, e.g. with Jubilee clips or the like, between the spigot 89 and the outlet pipe 91. As the fluid being pumped through the pumping tubes 77 is pumped into the respective filter chambers 29, so it will be forced into the sleeve-like filter 93 and liquids within the fluid will pass through the filter 93, whereas solids will pass down through the filter 93 and exit from the exit end 95 of the tube 91. Liquids can be collected from the liquid outlet 85, whereas solids can be collected from the outlet end 95, e.g. for further processing, in known manner. A clear inspection cover 97 is provided for each filter chamber 27 to enable users to inspect the filtering process and to enable users to see when the filter members 93 need to be changed. Figure 11 shows an alternative construction of pumping and separating apparatus schematically, with sludge to be pumped and separated indicated generally at 101 and the pumping and separating apparatus, which is largely identical to that shown generally at 5 in Figure 1, shown at 105. Although a negative pressure is created within the apparatus 105, as in the embodiment of Figure 1, only a single pumping tube 107 is illustrated which is entrained around some of the rollers of the drum 121. The tube 107 is connected at an inlet end to the sludge 101 by an inlet pipe 103 and at its outlet end, the tube 107 is connected to an outlet pipe 109 which deposits the sludge in a settling tank 111.

In order to impart an electrostatic charge to the sludge being pumped through the tube 107, a plurality of lengths of polypropylene twine 113 are entrained within the tube 107, one end of the polypropylene strands being anchored to the tube 107 at their inlet ends and the other ends being allowed to "stream" out of the outlet end of the tube 107. Material other than polypropylene and which is also known to generate an electrostatic charge could be used as an alternative. In order to increase the electrical charge of the pumped sludge which is deposited in the settling tank 111, two electrodes 115 and 117, which act alternately as a cathode and an anode, are supported above the settling tank 111, which is earthed as shown at 119. An AC current of low voltage, e.g. about 12 volts, is supplied to the electrodes 115,117. In order to increase still further the electrical/electrostatic charge applied to the sludge within the settling tank 111, a proportion of the sludge being pumped from the apparatus 105 into the outlet line 109 is taken from the pipe 109 and into a further pipe 122, an outlet end of which discharges into a further tank 123. The tank 123 has a semi-arcuate metallic screen 125 therein, the apertures in which are approximately 2 or 3 millimetres in diameter, and rotatable within the screen 125 are a plurality of paddles supported on an axis of rotation 127, each of the paddles extending across the full width of the screen 125 and being comprised of a plurality of polypropylene bristles 129 which contact the surface of the screen 125. These bristles impart further electrostatic charge to the sludge which exits from the tank 125 through an outlet pipe 131 for discharge into the settling tank 111.

It has been found that by applying an electric/electrostatic charge to the sludge which has been pumped to the tank 111 that this causes flocculation of the sludge, i.e. separation of nodules of solids which settle to the base of the settling tank, leaving a liquid at the upper end thereof. It is believed that the electric charge causes the fine solids to be attracted to one another so that they no longer remain in suspension within the sludge. The solids which settle to the bottom of the settling tank can then be withdrawn through an outlet 133, whereas liquid can be withdrawn through a further outlet 135.

In the construction shown in Figure 11, satisfactory separation of solids from liquids in a sludge mixture has been achieved without the use of a physical filter.

An alternative embodiment of pumping and separating apparatus is disclosed in Figures 12 to 15. Figure 13 shows a pump 205 similar to the pump 5 of Figure 1 and having a drum 221 rotatable therein, similar to that shown in Figure 2 and Figures 8 to 10. As in the embodiment of Figure 1, the pump 205 generates a negative pressure in the same manner as the pump of Figure 1, and it also has one or more pumping tubes 207 entrained around the drum 221. The or each pumping tube 207 comprises a resiliently deformable external tube 209 within which a filter sleeve 211 is located. The intention is that as the sludge to be separated is pumped through the or each tube 207, so the solids within the sludge will be separated out from the liquids therein, as will now be hereinafter described in greater detail with reference to Figures 12, 14 and 15.

Referring now to Figure 14, the or each pumping tube 207 is connected at its inlet end to a coupling member 237 comprising an external cylindrical portion 239 which may be formed of metal and an internal cylindrical coupling spigot 241 which forms a fluid tight joint with the external portion 239 and has an inner end with which one end of the filter sleeve 211 is connected in known manner, and an outer end to which a hose leading from a supply of sludge 201 to be pumped is connected in fluid tight manner. The coupling spigot 41 is formed of electrically insulating material.

As can be seen more clearly from Figure 12, the filter sleeve 211 is of generally circular cross section and diametrically opposed to each other, a pair of pockets are formed in the sleeve. In each of these pockets, an electrode 215 is located, typically a copper tape, and internally of the sleeve 211, a further electrode 217 is located, this electrode 217 being surrounded by a permeable sleeve-like envelope 219 which protects the electrode 217. The envelope 219 is manufactured from a liquid permeable electrically insulating material so as to prevent either of the electrodes 215 coming into contact with the electrode 217 when the filter sleeve 215 is collapsed during the peristaltic pumping operation.

Referring again to Figure 14, the filter sleeve 211 must be in sealing engagement with the inner end of the spigot 241 and its two electrodes must be electrically connected to respective terminals 223, whereas the electrode 217 must be connected to a separate terminal 225. The two terminals 223 are connected to a low voltage supply of AC electricity, e.g. of 12 volts.

Referring now to Figure 15, the outlet end of the pumping tube 207 is connected to a coupling member 231 comprised of an external cylindrical collar 233, which may be formed of metal, and an internal spigot 235 sealingly engaged with the external collar 233 and formed of electrically insulating material. The coupling member 231 has an outlet for liquid shown generally at 243 and an outlet for solids shown generally at 245. As with the coupling member 237, so with the coupling member 231, the electrodes 211 are connected to terminals on the spigot 235 as is the electrode 217.

As the sludge 201 is pumped peristaltically through the pumping tube 207, so the filter sleeve 211 will maintain solids therein but allow liquids to pass therethrough. Because of the presence of the electrodes 215,217 located respectively externally of the sludge and internally of the sludge, which electrodes are fed with the low voltage AC current, so there will be an electric charge set up in the sludge as it passes through the filter sleeve 211, this charge tending to cause small solid particles in the sludge to be attracted to one another, thus causing these particles to flocculate, i.e. to form into larger particles which tend to separate out from the liquids in the sludge. As a result, the filtering performance of the filter sleeve 211 is enhanced, thus causing liquids to be expressed from the sludge and passed from within to without the filter sleeve 11 as the sludge is pumped around the pump from the inlet coupling member 231 to the outlet coupling member 237. Hence, by the time the sludge reaches the outlet coupling member 231, only solids will exit at 245 and relatively clean liquid will exit at 243. In order to assist passage of the solids through the outlet 245, a source of compressed air may be led to the inner end of the spigot 235 by an air line 247, extending internally of the spigot 235.

Figure 16 shows a modification at the inlet end of the pumping and separating apparatus. Instead of the inlet coupling member 237 being connected direct to the supply of sludge 201 to be pumped and separated, the sludge 201 is passed through a charging tank 249. The charging tank has two compartments 251 and 253 separated by a weir 255 which is removable. In the compartment 251 a pair of closely spaced electrodes 257,259 are provided which are connected to a source of low voltage AC current, e.g. at 12 volts.

In the compartment 253, a plurality of aeration pipes 261 are provided, each having at spaced intervals along their length a plurality of outlet nozzles 263 through which gentle jets of compressed air may exit into the base of the chamber 253. Located immediately above the air pipes 261 is at least one pair of rod-like electrodes 265, the electrodes of each pair being connected to a further source of low voltage AC electric current, e.g. of 12 volts. These electrodes impart further electrical charge to the sludge before it enters the filter tube, thus assisting in the separation of solids from the liquid in the sludge.

It will be appreciated from the foregoing that in the various embodiments described electrical or electrostatic charge has been imparted to the sludge to be separated by various different means. These various different means are not mutually exclusive and could be used either alone or together in any one or more of the embodiments described. For example, in the embodiments of Figures 13 and 16, the strands of polypropylene could be located within the pumping tubes and, in the embodiment of Figure 11, the charging tank 249 could be located somewhere within the supply line 103.

The present invention also extends to the filter sleeve described with reference to Figures 11 to 15, and to the charging tank described with reference to Figure 16.

It will, of course, be understood that the present invention has been described above purely by way of example, and modifications of detail can be made within the scope of the invention.

Claims

1. A peristaltic pumping apparatus comprising at least two flexible deformable tubes entrained around a cage, rotatable within a casing and supporting a plurality of rollers which push fluid through the tubes by squeezing the tubes, a first one of the tubes having a first end held open to the interior of the casing and an opposite end connected to a first outlet from the casing, a second one of the tubes being connected at one end to an inlet in the casing, adapted to be connected to a fluid to be pumped and its opposite end being connected to a second outlet therein, whereby, upon operation of the apparatus, a pressure (hereinafter called negative pressure) which is less than that surrounding the casing will be generated within the casing, and the negative pressure will cause the second tube to move from a flattened state to a tubular state, whereby the fluid will be pumped through the second tube to the outlet.

2. Apparatus according to claim 1, wherein filtering means is located at the outlet end of the second tube, outside the casing so that as the fluid is pumped through the tube, solids will be separated from liquids within the fluid.

3. Apparatus according to claim 2, wherein the filtering means comprises a flexible sleeve, one end of the sleeve being connected to an outlet end of the tube and the opposite end being connected to an outlet pipe of the filtering means, the sleeve being located within a casing having a liquid outlet therein through which filtered liquids can pass.

4. Apparatus according to claim 3, wherein the sleeve is of tapered construction so that its outlet end is of reduced cross-sectional area, relative to its inlet end.

5. Apparatus according to any one of claims 1-4, and further comprising means for generating an electrical charge within the fluid.

6. Apparatus according to claim 5, wherein a receptor tank is provided for said fluid and said means comprises a pair of electrodes in the receptor tank for said fluid, said electrodes being connected to a source of low voltage AC current, and wherein said tank is earthed.

7. Apparatus according to any one of claims 1-6, and further comprising means for generating an electrostatic charge within said fluid.

8. Apparatus according to claim 7, wherein said means comprises a plurality of strands of polypropylene secured within said second tube.

9. Apparatus according to claim 7 or 8, and including a tank through which at least part of said fluid is pumped, said tank incorporating an arcuate screen through which the fluid is forced by a plurality of brush heads having polypropylene bristles and supported on a rotor.

10. Apparatus for separating solids from liquids in a mixture of solids and liquids, comprising a closed casing having a side wall, at least part of which is arcuate, and a pair of spaced opposed end walls, connected by said part arcuate side wall, a cage rotatable within the casing, the cage having rollers spaced around its periphery, and a first resilient tube extending around the cage and located between the peripheries of the rollers and the internal surface of the arcuate side wall, one end of the first tube being connected to a first outlet in a wall of the casing and the opposite end of the tube being connected to means within the casing to hold open said end of the tube, there being a non-return valve located within, or at the outlet end of, the first tube, means to cause rotation of the cage such that air within the casing will be drawn into the held-open end of the tube and pumped along the tube in peristaltic manner to the outlet, the non-return valve preventing air from re- entering the tube, whereby the pressure within the casing is reduced, relative to that around the casing, at least one further resiliently deformable tube entrained over at least some of the rollers of the cage, so as to extend between the rollers and the arcuate part of the side wall of the casing, one end of said further tube being connected to a second outlet in a wall of the casing and an opposite end thereof being connected to an inlet in a wall of the casing, said inlet being adapted to be connected to said mixture, whereby rotation of the cage not only reduces the pressure within the casing to cause the at least one further tube to expand into a tubular state, but also pushes said mixture to be pumped along the further tube from the inlet to the outlet, and means to separate liquids from solids in said mixture.

11. Apparatus according to claim 10, wherein said means comprises filtering means located outside the casing at the outlet end of the further tube, whereby the mixture pumped along the further tube is separated into liquids and solids by said filtering means.

12. Apparatus according to claim 10 or 11, wherein said means comprises means for generating an electrical charge within the fluid.

13. Apparatus according to claim 12, wherein a receptor tank is provided for said fluid and said means comprises a pair of electrodes in the receptor tank for said fluid, said electrodes being connected to a source of low voltage AC current, and wherein said tank is earthed.

14. Apparatus according to any one of claims 10-13, and further comprising means for generating an electrostatic charge within said fluid.

15. Apparatus according to claim 14, wherein said means comprises a plurality of strands of polypropylene secured within said second tube.

16. Apparatus according to claim 14 or 15, and including a tank through which at least part of said fluid is pumped, said tank incorporating an arcuate screen through which the fluid is forced by a plurality of brush heads having polypropylene bristles and supported on a rotor.

17. Apparatus according to any one of claims 2-9 or any one of claims 10-16, wherein the filtering means comprises a perforated tubular member secured at its inlet end to the outlet end of the further tube, and its outlet end being connected to an outlet pipe in a filter casing, and there being a liquid outlet in said filter casing for liquids separated from said mixture.

18. Apparatus according to any one of claims 1-17, wherein the cage supports a plurality of guide spools for the respective tubes, there being a plurality of shafts circumferentially spaced around the cage.

19. Apparatus according to claim 18, wherein the shafts for guide spools are circumferentially spaced, around the cage, by shaft for the rollers.

20. Apparatus according to any one of claims 1-19, wherein an evacuating tube is located within the casing between a pair of pumping tubes, and hence, on each guide spool shaft, three separate guide spools are provided, a central one being for the evacuating tube and located on either side thereof, there is a lateral guide spool for the respective pumping tube and wherein, on each roller shaft, there is a central roller for the evacuating tube and spaced to either side thereof, a lateral roller for the respective pumping tube.

21. Apparatus according to claim 1, wherein filtering means is located within the second tube.

22. Apparatus according to claim 10, wherein said means to separate liquids from solids comprises filtering means located within said at least one further resiliently deformable tube.

23. Apparatus according to claim 21 or 22, wherein the filtering means located within said tube incorporates at least two electrodes therein, one on the surface of the sleeve, and the other running centrally of the sleeve, each extending the full length of the sleeve, and the electrodes being connected to a source of low voltage AC current.