WO2000078426A2

WO2000078426A2 - Filter with vacuum cleaning heads

Info

Publication number: WO2000078426A2
Application number: PCT/CA2000/000758
Authority: WO
Inventors: Robert Koopmans; Kevin Graydon Mccauley
Original assignee: Ontario Power Generation Inc.
Priority date: 1999-06-22
Filing date: 2000-06-22
Publication date: 2000-12-28
Also published as: CA2278433A1; JP2003502139A; GB2367258A; WO2000078426A3; CA2278433C; GB0130620D0; GB2367258B; AU5667200A

Abstract

A filter is taught having a filter element sealed in a housing and a cleaning apparatus capable of suctioning material from the filter element, wherein each cleaning head corresponds to a cleaning conduit. Also taught is a deflector plate located between the outlet and the filter element.

Description

TITLE OF THE INVENTION

FILTER WITH VACUUM CLEANING HEADS

FIELD OF THE INVENTION

This invention relates to improved fluid filter systems, and more particularly to self- cleaning filter systems.

CROSS REFERENCETO RELATED APPLICATION

This application claims priority from Canadian patent application serial number 2,278,433, filed June 22, 1999.

BACKGROUND OF THE INVENTION

Known methods of self-cleaning a filter element often involve scraping or brushing the filter element. U.S. patent number 5,569,383 to Vander Ark, Jr. et al, PCT patent application number WO95/00230, U.S. patent number 4,156,647 to Nieuwenhuis and U.S. patent number 5,614,093 to Mueggenburg et al. all teach filters which use a rotor with cleaning blades or brushes to scrape clean the pre-filtration side of the filter element. The use of scrapers or brushes for cleaning can damage the filter element either directly or by forcing material through the filter elements.

Other methods of self-cleaning a filter element involve backwashing, i.e. reversing the pressure differential between the pre- and post-filtration sides of the filter element to expel particular matter trapped in the filter element. Typically, such backwashing requires closing the main inlet and outlet valves and opening backwashing valves to reverse the pressure differential (see, for example, U.S. patent number 5,312,544 to Kinney). U.S. patent numbers 4,045,345 and 5,228,993 to Drori and U.S. patent number 5,108,592 to Wilkins et al. teach filters which use a series of valves and other mechanical devices to automate a backwashing procedure for cleaning the filter element. Cleaning is accomplished by reversing the flow of water through the filter element (i.e. exposing the post- filtration side of the filter element to a high pressure) to expel particulate matter caught in the filter element. In U.S. patent number 4,045,345 Drori teaches the reverse flow is induced by pressure at the outlet of the filter, and particulate matter is expelled through a slotted purging chamber which rotates, along with the filter housing, around the filter element. U.S. patent number 5,228,993 to Drori and U.S. patent number 5,108,592 to Wilkins et al. teach cleaning using a reverse flow through the filter achieved by pressure from a supply pipe. In all of these teachings, particulate matter is expelled from the filter element by spraying the post-filtration side of the filter element through rotating nozzles. The use of spray force for cleaning can damage the filter element either directly or by forcing material through the filter elements. All of these methods of self-cleaning require the cessation and reversal of normal filter flow. All of these methods teach a plurality of cleaning heads all in flow communication with one backwash conduit.

SUMMARY OF THE INVENTION

The present invention teaches a filter (10) for filtering liquids comprising a housing (12) having an inlet (21), an outlet (22) and an inner surface, said housing containing:

(i) a filter element (33) having an inner face (31), an outer face (32) and first and second ends (35,36), each end having a sealing face (50); (ii) a first sealing face (43) on said housing inner surface, said first sealing face being sealable with said first end sealing face of the filter element;

(iii) a second sealing face (49) on said housing inner surface, said second sealing face being sealable with said second end sealing face of the filter element, said sealing faces sealable to define a liquid flowpath through said inlet, through said inner face of said filter element to said outer face of said filter element and out said outlet; and

(iv) a cleaning member for cleaning said inner face of said filter element, said cleaning member having: a plurality of cleaning heads (129) positioned adjacent said inner face; a discharge aperture (82) extending through said housing; a plurality of conduits (70), each said conduit in flow communication respectively with one of said plurality of cleaning heads from said cleaning head to the discharge aperture; and vacuum means for providing suction to the conduits and cleaning heads to suction material from the inner face of said filter element, through the conduits and out the discharge aperture.

In one embodiment, the filter has four cleaning heads and four conduits. In a further embodiment, each of the conduits is located in a quarter of a hollow shaft quartered lengthwise. In a further embodiment, the cleaning heads are arranged in a first and second pair each with a first and second cleaning head, and each said first and second cleaning head extend from said shaft in parallel, and said first pair extends from said shaft in a direction opposition said second pair. In one embodiment, the cleaning heads are arranged in pairs, each pair having a first and a second cleaning head, and the first cleaning head is structurally secured to said second cleaning head.

The invention also teaches a filter (10) for filtering liquids comprising a housing (12) having an inlet (21), an outlet (22) and an inner surface, said housing containing:

(i) a filter element (33) having an inner face (31), an outer face (32) and first and second ends (35, 36), each end having a sealing face (50);

(ii) a first sealing face (43) on said housing inner surface, said first sealing face being sealable with said first end sealing face of the filter element; (iii) a second sealing face (49) on said housing inner surface, said second sealing face being sealable with said second end sealing face of the filter element; said sealing faces sealable to define a liquid flowpath through said inlet, through said inner face of said filter element to said outer face of said filter element and out said outlet; and

(iv) a deflector plate (170) located between said outlet and said filter element.

In one embodiment, the deflector plate has a shape similar to a cross section of said outlet perpendicular to said flowpath through said outlet. In another embodiment, the deflector plate has a surface area similar to a cross section of an area of said outlet perpendicular to said flowpath through said outlet. In another embodiment , the deflector plate has a surface area which is about 1.5 times an area of a cross section of the outlet perpendicular to said flowpath through said outlet.

In one embodiment, the filter element is cylindrical. In another embodiment, the filter has a pre-screen filter positioned in the flowpath between said inlet and said filter element, and a pre-screen drain positioned in the flowpath between said pre-screen and said inlet.

In one embodiment, the filter further comprises a motor (77) connected to said cleaning member, and said motor moves said cleaning head parallel to said inner face of said filter element. In another embodiment, the filter element is cylindrical and said cleaning member moves rotationally. In an embodiment, the cleaning head does not contact said inner face. In an embodiment, the cleaning member passes through said housing and said motor is located outside of said housing.

In an embodiment, the cleaning member further comprises a plurality of cleaning heads in communication with said conduit, said cleaning heads positioned along said cleaning member such that substantially all of said inner face is subjected to vacuum from said cleaning heads when said motor is operated. In one embodiment, the cleaning head is a triangular fin nozzle. In one embodiment, the housing is oriented vertically.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a perspective partially broken away view of an embodiment of the invention.

Figure 2 is a side cross sectional view of the device shown in Figure 1. Figure 3 is an end plan view taken along line 3-3 of Figure 2. Figure 4 is a cross sectional view taken along line 4-4 of Figure 2.

Figure 5 is a cross sectional view taken along line 5-5 of Figure 2. Figure 6 is a cross sectional view taken along line 6-6 of Figure 2. Figure 7 is a detailed view taken at station 7 of Figure 2.

Figure 8 is a detailed view taken at station 8 of Figure 2.

Figure 9 is a detailed view taken at station 9 of Figure 2.

Figure 10 is a cross sectional view of some features of an alternative embodiment of the device of Figure 1.

Figure 11 is a detailed view taken at station 11 of Figure 10.

Figure 12 is a detailed view taken at station 12 of Figure 10.

Figure 13 is a cross sectional view of some features taken along line 13-13 of Figure 10. Figure 14 is a detailed view taken at station 14 of Figure 13.

Figure 15 is a side view of an alternate embodiment of the cleaning member of Figure 10.

Figure 16 is a cross sectional view of some features taken along line 16-16 of Figure 15. Figure 17 is a cross sectional view of some features taken along line 17-17 of Figure

15.

Figure 18 is a cross sectional view of some features taken along line 18-18 of Figure

15. Figure 19 is a cross sectional view of some features taken along line 19-19 of Figure

15. Figure 20 is a cross sectional view of some features taken along line 20-20 of Figure

15. Figure 21 is a cross sectional view of some features taken along line 21-21 of Figure

15. Figure 22 is a cross sectional view of some features taken along line 22-22 of Figure

15.

Figure 23 is a cross sectional view of some features taken along line 23-23 of Figure

15. Figure 24 is a cross sectional view of some features taken along line 24-24 of Figure

15.

Figure 25 is a perspective partially broken away view of an embodiment of hollow shaft 70 of Figure 15. Figure 26 is a top perspective view of filter elements 33 of Figure 10.

Figure 27 is a top perspective view of an alternate embodiment of filter elements 33 of Figure 10.

DESCRIPTION OF EMBODIMENTS

The invention will be described as it applies to a large capacity, high flow rate continuous filter for water. The skilled person will appreciate that the invention has broad application to a variety of liquid filtration situations, and the scope of the invention should not be restricted because of the description of the embodiment which follows.

As shown in Figures 1 and 2, the liquid filtration device 10 of the invention has a housing 12 which is preferably cylindrical and which has a first end 14 provided with a liquid-tight door 15, and a second end 17. The filtration device 10 may be oriented vertically, horizontally or otherwise. Fluid flow ports are preferably provided through the housing wall 19 of the housing 12. Thus, an inlet 21 is provided near the first end 14 of the housing 12, an outlet 22 for filtered water is provided midway along the length of the housing 12, and a discharge aperture 23 is provided near the second end 17 of the housing 12.

A partition 25 is fixed within the housing 12 and spaced from the second end 17 to thereby define a discharge chamber 28 between the partition 25 and the second end 17. The discharge aperture 23 has a valve 30 which is opened only during the vacuumed cycle of operation. Preferably, the operation of the valve 30 is governed by an electronic controller.

One or more metal filter elements 33 are positionable within the housing 12. An embodiment will be described as shown in Figure 2 as having two filter elements 33. One of the advantages of the invention is its capability to be sized with the appropriate number of filter elements 33 to meet the specifications of a particular application. The utilization of a plurality of relatively small filter elements 33 in the device 10 of the invention has a number of decided advantages which will be described. Each filter element 33 has a panel with an inner face 31 and an outer face 32, and first and second flanged ends 35 and 36 with sealing surfaces formed to provide metal to metal water seals about the filtration zone 40. Filtration zone 40 is defined as the zone between the housing wall 19 and the outer face 32 of filter elements 33. Filtration zone 40 is in flow communication with outlet 22. Pre-filtration zone 85 is defined as the zone between the housing wall 19 and the inner face 31 of filter elements 33. Pre-filtration zone 85 is in flow communication with inlet 21.

As shown in an embodiment in Figures 10 and 11, the invention can also comprise a pre-screen 94 located between inlet zone 60 and pre-filtration zone 85. The pre-screen 94 is a filter means with a mesh size greater than that of filter elements 33. Pre-screen 94 is secured to pre-screen frame 101 by means of pre-screen bolt 98. Pre-screen 94 functions to prevent larger impurities, for example, seaweed, fish or shells from entering the prefiltration zone 40, where it might obstruct filter elements 33. Generally, objects filtered by pre-screen 94 will be large enough that they will fall to the bottom of inlet zone 60, where they may be periodically purged from the filter housing 12 by opening pre-screen drain 90 to a lower pressure than the pressure in inlet zone 60. In other embodiments, pre-screens may be located in the flow path prior to inlet 21, or, depending on the operating conditions, pre-screens may not be required at all.

As shown in an embodiment in perspective views of the filter elements 33 in Figure 26, the invention can also comprise a deflector plate 170. Deflector plate 170 is located between an interior mouth 175 of outlet 22 and the portion of filter element 33 closest to the interior mouth of interior mouth 175. Deflector plate 170 is a static fluid directing means arranged to cause the fluid coming into the interior mouth 175 of the outlet 22 to be drawn from a plurality of directions predominantly perpendicular to the outlet 22. Without deflector plate 170, the fluid stream into the mouth of the outlet 22 may be drawn predominantly from fluid passing from pre-filtration zone 85 to filtration zone 40 through the portion of filter element 33 closest to the interior mouth 175 of outlet 22. Deflector plate 170 is preferrably the same shape as interior mouth 175 and as large or larger than the interior mouth 175. In the embodiment shown, deflector plate 170 is circular with a diameter about 1.5 times the diameter of mouth 175. Deflector plate 170 is secured to filter element 33 by any means known in the art, for example spot welding to flanged ends 35 and 36 or filter element guide rods 92. The dispersal and redirection of the incoming fluid stream, now drawn from a range of directions, rather than directly from the filter screen 33 immediately adjacent mouth 175, facilitates efficient generation of an entrained fluid stream. This entrained fluid stream draws from filtration zone 40 in multiple directions, and at an angle primarily perpendicular to the face of filter element 33, thus one does not generate a flow path which flows primarily through only one portion of the filter screen 33, namely that portion closest to mouth 175.

In another embodiment, shown in Figure 27, the deflector plate comprises two plates

171 and 172. Deflector plate 171 is secured to a first filter means 33 while deflector plate 171 is secured to a second filter means 33, such that the deflector plates 171 and 172 align and form a circular plate when the first and second filter means are placed together in the liquid filtration device. This embodiment of deflector plate is used where the location of mouth 175 and the size of filter elements 33 of the liquid filtration device are such that, upon assembly, the flanged ends 35 and 36 of two filter elements meet along a line which corresponds to a line bisecting mouth 175. Thus, upon assembly, the deflector plates 171 and

172 join to form a deflector plate which is centered in relation to mouth 175.

The filter elements 33 are preferably of metal wire mesh type wherein a fine wire mesh defining a desired pore size is applied to a structural screen made of sheet metal (detail not shown). The structural screen acts as a support for the finer mesh. In one embodiment, the structural screen consists of a rigid or semi-rigid plate having multiple apertures, and the mesh is fixed to the structural screen by a sintering process, such as the proprietary process performed by Purolator Products Company (Tulsa, OK, USA). By use of this embodiment, any damage to the fine mesh is restricted to the mesh at a given aperture of the structural screen, because the adjacent mesh is fixed to the structural plate. Isolated damage of this type may be easily repaired by simply soldering over a given structural screen aperture. Also, the use of this embodiment increases the ease with which the mesh may be cleaned, as compared to filter elements of the prior art. In one embodiment, the mesh side of the filter element faces the pre-filtration zone. In an alternative embodiment the filter elements 33 are of a stainless steel wire mesh type in which a fine wire mesh defining a desired pore size is sandwiched between inner and outer structural screens also made of stainless steel. In another embodiment, the filter elements 33 comprise an outer structural screen, an inner filter mesh, and an intermediate structural screen sandwiched between the inner and outer layers.

By selecting the size of the openings in the filter element, the filter may be used, for example, to filter out zebra mussels, silt, algae, or other particulate matter. In one embodiment, the mesh size is 40 microns or less. A mesh size of 40 microns allows the filter to remove zebra mussel larva. In the embodiments described above, the filters are constructed with metal and stainless steel rings complete the flanged ends 35 and 36 of the filter element. However, those skilled in the art will appreciate that for other applications, materials as diverse as ceramics or poly vinyl chlorides may be used. Alternatively, electrostatic or ionic filters may be used for other applications.

In the embodiments shown, the filter elements are cyclindrical, however, it will be appreciated that other dimensions may be used for the filter elements, so long as the filter element has an inner and outer face and ends having sealing surfaces capable of sealing in the manner described below.

As shown in Figure 8, the flanged end 35 of filter element 33 has a chamfered surface 42 which abuts a mating surface 43 about the sealing surfaces of second flanged end 36 to provide a nesting engagement of two filter elements 33. The water seal between the abutting flanges 35 and 36 is assisted by the addition of a small cross sectional diameter O-ring 44 carried in a groove 45 formed in the surface 43. Likewise, as shown in Figure 9, the partition 25 is provided with a chamfered partition seal surface 47 which aligns with and provides a sealing engagement with the mating surface 43 of a second flanged end 36. As shown in Figure 7, a water seal is provided for the filtration zone 40 about the endmost first flanged end 35 of the filter element 33 positioned nearest the first end 14 of the housing 12 by a housing flange 48. Housing flange 48 has a sealing surface 49 which aligns with sealing surface 50 of endmost first flanged end 35. Housing flange 48 is fixed to the wall 19. An O- ring 52 is carried in a groove 53 formed in the surface 50 to provide a sealing engagement of the circumferential sealing surface 50 with the housing flange 48. These sealing arrangements thus are capable of forming a complete seal between filtration zone 40 and pre- filtration zone 85.

The flanged ends 35 and 36 of the filter elements 33 have a plurality of holes 55 spaced around them for receiving filter guide rods 56. In most applications, four filter guide rods 56 are sufficient for the intended purpose. In the embodiments illustrated, the rods are cylindrical. However, it will be appreciated that the rods may be other dimensions, so long as they allow the filter elements to be installed or removed along the length of the rod. The filter guide rods 56 extend through and are fixed to the partition 25. The filter guide rods 56 are sized to extend just beyond the endmost first flanged end 35, and the filter guide rods 56 are threaded at their ends so that the filter elements 33 can be secured in place by means of nuts 57 (Figure 7). Preferably, a precision machined threadless fastening nut is used. However, it will be appreciated that any suitable releasable fastening means known in the art may be used, for example threaded bolts or latch mechanisms.

When installing and removing the filter elements 33 from the housing 12, filter guide rod extensions 59 may be added to the ends of the filter guide rods 56 by a precision machined threadless fastening coupling arrangement as shown in Figure 7. These filter guide rods 56 provide a significant advantage over the prior art as they facilitate the proper positioning of the filter elements 33 within the housing 12, they ensure that the sealing surfaces of the filter elements 33 are aligned and mated properly, and by virtue of the tightening of the nuts 57 at the end of each filter guide rod 56, the filter elements 33 are compressed together to provide the necessary water seals to separate filtered water in the filtration zone 40 from unfiltered water in the pre-filtration zone 85. The extensions 59 when attached to the filter guide rods 56 assist with the installation and removal of filter screens. Preferably, these extensions are long enough to exit the front of the filter housing 12.

In the embodiment shown in Figure 10, filter element guide rods 92 are used in place of filter guide rods 56. Filter element guide rod 92 extends between annular flanged ends 35 and 36 of filter element 33. Filter element guide rod 92 provides structural support to filter element 33, as well as a grip for manipulating filter element 33. As seen in Figure 12, filter element guide rods 92 are fixed to flanged ends 35 and 36 by means of welds 117. A guide projection 131 of filter element guide rod 92 projects outwardly from flanged end 36. When the filter elements 33 are assembled, guide projection 131 is received by guide rod receptacle 113, thus aligning one filter element 33 with the next during assembly and reassembly.

In one embodiment, the seals between the pre-filtration zone 85 and the filtration zone 40 can be tightened and secured by means of the structure shown in Figure 11. As in the first embodiment, housing flange 48 extends circumferentially along the inner surface of housing wall 19, and is attached thereto by means of, for example, weld 133. When all filter elements

33 are installed, the endmost first flanged end 35 is proximal to housing flange 48. Position pin 96 is held in position pin receptacle 114. Position pin 96 projects outwardly from endmost first flanged end 35 and is received by a support structure frame 105. A seal between endmost first flanged end 35 and support structure frame 105 is assisted by the addition of a small cross sectional diameter O-ring 135 carried in a groove 137 formed in the surface 139 of support structure frame 105. Pre-screen frame 101 is placed over support structure frame 105 and secured to housing flange 48 by means of pre-screen frame bolt 98. An O-ring 111 is carried in a groove 112 formed in the pre-screen frame 101 to provide a sealing engagement of the circumferential sealing surface 109 with the circumferential housing flange 48. An O-ring 52 is carried in a groove 53 formed in the support structure frame 105 to provide a sealing engagement of the support structure frame 105 with the pre- screen frame 101. These sealing arrangements thus form a seal between filtration zone 40 and pre-filtration zone 85 when frame bolt 103 is tightened. To ensure a tight and secure seal between flanged ends 35 and 36 seen in Figures 12 and 10, a jack screw 107 is received through pre-screen frame 101. When tightened, jack screw 107 applies force to support structure frame 105, and this force is transmitted to the flanged ends of each filter element 33 in the series.

Having regarding to the above description, it will be appreciated that other functional equivalents of the sealing structure of Figure 11 can be used. For example, the structure could be designed such that sealing surface 106 sealed with housing flange 48 rather than pre- screen frame 101. As another example, support structure frame 105 could be removed, support structure 75 could be incorporated into pre-screen frame 101, and flanged end 35 could align directly with pre-screen frame 101. In this embodiment, jack screw 107 could be received by position pin receptacle 114 to ensure alignment, or another position pin receptacle (not shown) on pre-screen frame 101 could be used to ensure alignment between pre-screen frame 101 and flanged end 35. However, it will be appreciated that use of the embodiment described above and shown in Figure 11 , accommodates a water tight seal even if circumferential housing flange 48 is not perfectly circular. The present inventors have found that, because housing flange 48 is welded to housing wall 19, flange 48 will not form a true circle if housing wall 19 is not perfectly cylindrical, if the welding process induces any distortion, or if the water loads during operation induce any distortion.

The invention may further comprise a runner 119, shown in Figure 13. Runner 119 preferably has a runner groove 121, which is suitable for receiving guide rod 92 of Figure 10. Runner 119 facilitates the installation and removal of filter elements 33 by bearing some of the weight of the filter elements and by acting as a guide for aligning guide projection 131 with guide rod receptacle 113, thus assisting the installation, removal, and support of filter elements 33.

Returning to Figures 1 and 2, an inlet zone 60 is defined within the housing 12 from the first end 14 to the first filter element 33. The inlet 21 extends through the wall 19 of the housing 12 into the inlet zone 60. The first end 14 has a flange 62 to which the door 15 seals with the aid of an O-ring and a plurality of swing bolts 64 spaced around the circumference of the flange 62. The door 15 has hinges 65 (best shown in Figure 3) to swing completely away from the opening of the first end 14, thus allowing for ready access to the interior of the housing 12.

Thus, in use, as shown by the arrows in Figures 1 and 2, unfiltered water enters the filter housing 12 through the inlet 21, into the pre-filtration zone 85 where the pressure of the system forces a flow through the filter mesh of the filter elements 33 to provide a flow of filtered water into the filtration zone 40. The water passes perpendicularly through the filter element 33 and into filtration zone. From here filtered water passes from the filtration zone 40 through the outlet 22 and on to its intended purpose. After a period of use, the filter elements 33 will become partially clogged with particulate matter, and a pressure drop will occur at the outlet 22. In response to this problem, the invention can include a vacuum filter cleaning system.

As seen in Figure 2, a hollow shaft 70 extends from the second end 17 of the housing

12 longitudinally through the center of the partition 25 and the filter elements 33. The shaft 70 has a first end 72 which is supported by a bearing 73 in a cross-shaped support structure 75 attached to the filter guide rods 56 by the nuts 57. Shaft 70 is closed at first end 72. The second end 76 of the shaft 70 is attached to rotation means, such as a gear box 79, shown in Figure 1. Gear box 79 is actuated by motor 77, both of which are located at the second end 17 of the housing 12. Gear box 79 may contain a means for selecting various gears relating to various rotational velocities of shaft 70. Alternately, gear box 79 can be designed with a preselected optimal gear ratio to achieve an optimal rotational velocity for shaft 70. The optimal velocity will depend on operating conditions of the system for which the filter is designed, for example, the flow rate required, the pressure differential between the prefiltration zone 85 and the discharge chamber 28, and the size and quantity of impurities flowing into the filter.

In another alternative, rather than using a motor, the filter could be designed to harness the power of the flow of the water through the system for use in rotating the shaft 70, for example, by means of fins secured, directly or indirectly, to said shaft 70.

The shaft 70 has a plurality of hollow filter cleaning heads 80 which extend radially outward from the shaft 70 to a position proximal to the inner surface of each filter element 33. A portion of the shaft 70 near its second end 76 in the discharge chamber 28 has a plurality of holes 81, 82, 83 and 84 (only 82 shown in Figure 2). Thus there is provided flow communication from the inner surfaces of the filter elements 33, through the cleaning heads 80, through the hollow shaft 70 to the discharge chamber 28.

Once the filtrate trapped on the filter element becomes dense enough to cause a predetermined drop in pressure, for example, 5 psi (350 kg/cm²), the vacuum cycle may be initiated to remove the filtrate. When the vacuum cycle commences, the motor 77 starts to rotate the gears inside of gear box 79, and the gears rotate the shaft 70 inside of the filter elements 33. Motor 77 may be powered by any means known in the art, for example, electricity or water turbine.

The cleaning heads 80 on the shaft are located with apertures close to the inner face 31 of the filter elements. Since there is water pressure inside the filter body during normal operation, a suction pressure is created once the valve 30 is opened to the atmosphere. As seen by the arrows in Figures 1, 2, 5 and 6, the opening of the valve 30 to the atmosphere creates a suction which draws water through the holes 81, 82, 83, and 84 in the shaft 70 which in turn provides a suction at the ends of the cleaning heads 80 (83 not shown; located opposite hole 81 on shaft 70). By rotating the shaft 70 during the vacuum cycle, the cleaning heads 80 are able to remove entrapped particulate matter so that the filter elements 33 are returned to their former efficiency. While the frequency and duration of the vacuum cycle is adjustable to suit particular circumstances, in one embodiment, the cycle is initiated when the pressure drops by about 5 psi at the outlet 22, and is maintained for 8-10 seconds. In other embodiments, the vacuum cycle could run continuously during filtration, so long as the rate of water flowing through the shaft 70 is less than the rate of water flowing through the inlet 21. In another embodiment, during the cleaning cycle the flow rate through the filter can be reduced or even eliminated, for example, by use of a valve (not shown) at inlet 21.

In the embodiment shown in Figure 15, the cleaning heads are fin nozzle cleaning heads 123. The fin nozzle design increases the efficiency and effective force of the vacuum to better clean the filter elements. The fin nozzle design also decreases the outer surface area of the cleaning heads, thus decreasing the resistance to rotation encountered by the cleaning heads during rotation, thus requiring less energy to rotate the cleaning heads. Also in the embodiment shown in Figure 15, the cleaning heads are offset such that the distribution of weight of the cleaning heads is distributed more evenly from the centerline of shaft 70.

Structural strength is added to nozzle cleaning heads 123 by joining cleaning heads 123 in pairs at two locations. First, cleaning heads 123 are joined in pairs at their distal ends, i.e., their intakes 120. Second, cleaning heads are joined in pairs by means of a support bar 124, which connects to cleaning heads 123 at a position approximately halfway between their intakes 120 and the connector tubes 141, 142, 143 and 144. Also in the embodiment shown in Figure 15, the invention further comprises connector tubes 141, 142, 143 and 144 which are in flow communication between their corresponding cleaning heads 123 and the hollow of shaft 70. Connector tube 141 is the closest of the four connector tubes to first end 72 of shaft 70. Connector tube 142 is the second closest of the four connector tubes to first end 72 of shaft 70. Connector tube 143 is the third closest of the four connector tubes to first end 72 of shaft 70. Connector tube 144 is closest of the four connector tubes to second end 76 of shaft 70.

Stem 129 of cleaning head 123 adjustably inserts into connector tubes 141, 142, 143 and 144 to form a substantially water tight seal. Adjuster screw 127 provides a means for adjusting the outward projection of cleaning head 123 from shaft 70. By adjusting adjuster screw 127, the intake 120 of cleaning head 123 can be positioned a preferred distance from inner face 31. The preferred clearance between inner face 31 and the intake 120 of cleaning head 123 will depend on the size of the impurities which are to be suctioned from filter element 33. This preferred clearance is often between l/8th to 1/16th of an inch (1.59 mm to

3.17 mm).

In the embodiment shown in Figures 15-25, shaft 70 comprises four vacuum chambers 161, 162, 163, 164 within the shaft. Each of the four vacuum chambers is of a different length. Shaft 70 has a first vacuum chamber 161 which extends between and is in flow communication with connector tube 141 and hole 81. Second vacuum chamber 162 extends between and is in flow communication with connector tube 142 and hole 82. Third vacuum chamber 163 extends between and is in flow communication with connector tube 143 and hole 83 (not shown). Fourth vacuum chamber 164 extends between and is in flow communication with connector tube 144 and hole 84. By use of the separate vacuum chambers, the vacuum at holes 81, 82, 83 and 84 is more evenly distributed to each connector tube 141, 142, 143 and 144, and hence more evenly distributed to each stem 129 and cleaning head 123. Without separate vacuum chambers, vacuum in shaft 70 might be primarily draw from the closest cleaning heads - e.g. those extending from connector tubes 143 and 144 - at the expense of decreased vacuum available to the cleaning heads extending from connector tubes 141 and

142. Vacuum chambers 161, 162, 163 and 164 may be created by securing various plates and end walls within shaft 70, as follows.

As shown in Figures 15 and 17 to 25, a bisecting plate 151 extends lengthwise along the interior of shaft 70, from connector tube 141 to second end 76 of shaft 70, bisecting the interior of the shaft. As shown in Figure 17, a first end wall 181 seals the end of vacuum chamber 161 which is proximal to first end 72 of shaft 70 such that a portion of the interior of the bisected shaft 70 is in flow communication with connector tube 141 and hole 81 to form first vacuum chamber 161.

As shown in Figures 15 and 19 to 25, a first quartering plate 153 extends lengthwise within shaft 70, from connector tube 142 to second end 76 of shaft 70, bisecting the interior of vacuum chamber 161 along that length, to divide out second vacuum chamber 162 from first vacuum chamber 161 which continues along the interior of shaft 70, reduced in cross-sectional area by half. As shown in Figure 19, a second end wall 182 seals the end of vacuum chamber

162 which is proximal to first end 72 of shaft 70 such that a dedicated portion of the interior of the shaft 70 is in flow communication with connector tube 142 and hole 82 to form second vacuum chamber 162.

As shown in Figures 15 and 21 to 25, a third end wall 183 seals the end of vacuum chamber 163 at connector tube 143 such that the interior of the shaft 70 is in flow communication with connector tube 143 and hole 83 (not shown) to form third vacuum chamber 163.

As shown in Figures 15 and 23 to 25, a second quartering plate 154 extends lengthwise within shaft 70, from connector tube 144 to second end 76 of shaft 70, bisecting the interior of vacuum chamber 163 along that length, to divide out fourth vacuum chamber 164 such that third vacuum chamber 163 continues along the interior of shaft 70, reduced in cross-sectional area by half. As shown in Figures 23 and 25, a fourth end wall 184 seals the end of vacuum chamber 164 which is proximal to first end 72 of shaft 70. The interior of the shaft 70 is thus in flow communication with connector tube 144 and hole 84 to form fourth vacuum chamber Because shaft 70 is closed at first end 72, the interior of shaft 70 which does not comprise one of vacuum chambers 161, 162, 163 or 164 remains essentially water-tight and free from water. This avoids the creation of a "dead zone" within the shaft 70 which contains water not subjected to flow. By avoiding such a "dead zone" the likelihood of buildup of debris or organic growth, such as zebra mussels, is decreased.

As shown in Figure 15, holes 81, 82, 83 and 84 (83 not shown; located opposite hole 81 on shaft 70) are positioned such that the holes collectively do not significantly compromise the structural strength of end 76 of shaft 70. In order to maximize the distance between the four holes, and hence maximize the area of structural shaft 70 between each hole, each of the holes 81, 82, 83 and 84 are stagged 90 degrees rotationally around shaft 70, and holes 81 and 83 are staggered lengthwise on shaft 70 in relation to holes 82 and 84 (83 not shown; located opposite hole 81 on shaft 70).

From the foregoing it will be appreciated that the present invention provides a number of advantages over prior devices. Stainless steel wire mesh filter units are expensive components, particularly those large units required for high throughput devices. Previously, filter units have been designed to serve a particular purpose, and thus, one design has usually been found not to be suitable for either scaled up or scaled down applications. In contrast, the present invention provides a combination of components which can readily be sized and configured to serve a wide variety of applications. The present invention is a modular system which allows the use of a plurality of smaller filter units which are nested together using metal to metal water seals. The releasable securing mechanism for the filter elements of the present invention is particularly useful in that it allows for a plurality of filter elements of a smaller size, as opposed to a single filter element of a larger size to be used. This facilitates construction, maintenance, removal and replacement of the filter elements. These filter units are lighter and easier to manufacture, hence, cheaper than larger units. Because they are smaller and lighter, the filter units of the invention are easy to install and remove.

The guide rods of the present device ensure an accurate alignment of the filter units and provide means for ensuring that the filter elements and their respective seals are aligned and centered properly, and to generally assist in securing them in place. These rods allow the design of the invention to be scaled up to handle very large flows. The rods, together with the use of the sealing surfaces and the support structure enable one to compress the filter elements together to form the proper sealing required for the function of the filter. Also, the use of the cross shaped support structure 75 allows the shaft 70 to be centered and solidly supported.

The large water-tight door at one end of the present device allows a worker to more readily observe the filter operation, including the rotation of the shaft, while the device is empty of water, thus enabling a quicker determination of a malfunction than is possible with prior devices. Removal and replacement of the filter elements is likewise facilitated by the use of the door.

Removal and replacement of the filter elements are further facilitated by the sealing mechanism of the present invention. Whereas the prior art teaches methods of sealing using, for example, a lower O-ring in conjunction with a locking slit, the use of the sealing surfaces of the present invention, in conjunction with the compression from the rods allows for removal and replacement of filter elements without rotating or otherwise unlocking the filter elements.

This allows for the handling of larger filter elements than would be practical with conventional methods of sealing in the art.

Thus there are several aspects of the present invention that counter size and mass concerns of industrial filters. The present invention is particularly suited to industrial uses requiring high throughput, large volume filters. The sealing mechanism of the present invention has been found to be useful for filters where the pressure differential from one side of the filter element must be kept at a low level, for example, less than approximately 5 psi (350 kg/cm²), in order to maintain the required flow of water.

The present invention also provides a low maintenance filter system, thus increasing cost efficiency. By employing a minimum of moving parts, and by providing for a self- cleaning system, the filters of the invention can operate for months, and possibly years without requiring maintenance apart from standard maintenance for the movement means, which is conveniently located outside the filter housing. Unlike self-cleaning filters of the prior art, motor or gearbox maintenance may be readily performed without opening or draining the filter housing. The filter of the present invention may be particularly suited for water intake ports, such as those found at power plants. The filter of the present invention is also useful for other applications, for example, in the food industry, pulp and paper industry, and for fish hatcheries. The filter is also useful for non-water applications, for example, for filtering machine cuttings out of an oil emulsion.

Although preferred embodiments of the invention have been disclosed for illustrative purposes, it will be appreciated that variations or modifications of the disclosed apparatus lie within the scope of the present embodiments.

Claims

CLAIMSWe claim:

1. A filter ( 10) for filtering liquids comprising a housing ( 12) having an inlet (21 ), an outlet (22) and an inner surface, said housing having:

(i) at least one filter element (33) having an inner face (31), an outer face (32) and first and second ends (35,36), each end having a sealing face (50);

(ii) a first sealing face (43) on said inner surface of said housing, said first sealing face being sealable with said sealing face on the first end of the filter element;

(iii) a second sealing face (49) on said inner surface of the housing, said second sealing face being sealable with said sealing face on the second end of the filter element, said sealing faces sealable to define a liquid flowpath through said inlet, through said inner face of said filter element to said outer face of said filter element and out said outlet; and (iv) a cleaning member configured for cleaning said inner face of said filter element, said cleaning member having: a plurality of cleaning heads (129) positioned adjacent said inner face; a discharge aperture (82) extending through said housing; a plurality of conduits (70), each said conduit in flow communication respectively with one of the cleaning heads from said one of the cleaning heads to the discharge aperture; and a vacuum connected to and arranged for providing suction to the conduits and the cleaning heads to suction material from the inner face of said filter element, through the conduits and out the discharge aperture.

2. A filter as claimed in claim 1 , having four of the cleaning heads and four of the conduits.

3. A filter as claimed in claim 2, wherein each of said conduits is located in a quarter of a hollow shaft quartered lengthwise.

4. A filter as claimed in claim 3, wherein said quarters of said hollow shaft are sealed at an end which is opposite said discharge aperture and proximal to said conduit's respective cleaning head.

5. A filter as claimed in claims 2, 3 or 4 wherein said cleaning heads are arranged in a first and second pair each with first and second cleaning heads, and each said first and second cleaning heads extends from said shaft in parallel, and said first pair extends from said shaft in a direction opposite said second pair.

6. A filter as claimed in any one of claims 1-5, further comprising a plurality of cleaning heads arranged in pairs, each said pair having first and second cleaning heads, and said first cleaning head is structurally secured to said second cleaning head.

7. A filter ( 10) for filtering liquids comprising a housing ( 12) having an inlet (21 ), an outlet (22) and an inner surface, said housing having:

(i) a filter element (33) having an inner face (31), an outer face (32) and first and second ends (35, 36), each of the ends having a sealing face (50); (ii) a first sealing face (43) on said inner surface of the housing, said first sealing face being sealable with said sealing face of the first end of the filter element;

(iii) a second sealing face (49) on said inner surface of the housing, said second sealing face being sealable with said sealing face of the second end of the filter element; said sealing faces sealable to define a liquid flowpath through said inlet, through said inner face of said filter element to said outer face of said filter element and out said outlet; and

8. A filter as claimed in claim 7, wherein said deflector plate has a shape similar to a cross section of said outlet perpendicular to said flowpath through said outlet.

9. A filter as claimed in claim 7, wherein said deflector plate has a surface area similar to a cross section of an area of said outlet perpendicular to said flowpath through said outlet.

10. A filter as claimed in claim 7, wherein said deflector plate has a surface area which is about 1.5 times an area of a cross section of the outlet perpendicular to said flowpath through said outlet.

11. A filter as claimed in any one of claims 1-10, wherein said filter element is cylindrical.

12. A filter as claimed in any one of claims 1-11, further comprising a pre-screen positioned in the flowpath between said inlet and said filter element, and a pre-screen drain positioned in the flowpath between said pre-screen and said inlet.

13. A filter as claimed in any one of claims 1-6, wherein said filter further comprises a motor (77) connected to said cleaning member, and said motor moves said cleaning head parallel to said inner face of said filter element.

14. A filter as claimed in claim 13, wherein said filter element is cylindrical and said cleaning member moves rotationally.

15. A filter as claimed in any one of claims 1-6 or 13-14, wherein said cleaning head does not contact said inner face.

16. A filter as claimed in claim 13, wherein said cleaning member passes through said housing and said motor is located outside of said housing.

17. A filter as claimed in any one of claims 1-6 or 13, wherein said cleaning member further comprises a plurality of cleaning heads in communication with said conduit, said cleaning heads positioned along said cleaning member such that substantially all of said inner face is subjected to vacuum from said cleaning heads when said motor is operated.

18. A filter as claimed in any one of claims 1-6 or 13-17, wherein said cleaning head is a triangular fin nozzle.

19. A filter as claimed in any one of claims 1-18, wherein said housing is oriented vertically.