WO2018191611A1

WO2018191611A1 - Screen filter for microfiltration

Info

Publication number: WO2018191611A1
Application number: PCT/US2018/027478
Authority: WO
Inventors: Michael Richard EKHOLM; Steven Douglas DEHN; Charles H. Flansburg
Original assignee: Aqseptence Group Inc.
Priority date: 2017-04-13
Filing date: 2018-04-13
Publication date: 2018-10-18
Also published as: CN110740797A; EP3609596A1; EP3609596A4

Abstract

A screen filter having a plurality of support rods arranged in longitudinal relationship such that a continuous length of wire can be spirally wrapped about the support rods to define a cylindrical body. Along the length of the cylindrical body, slots are defined between adjacent wires wherein each slot has a slot width that determines an overall filter performance for the screen filter. The screen filter is fabricated such that an average slot width across the length of the cylindrical body is equal to a filter performance rating. The screen filter is fabricated such that the slot width for the cylindrical body has a normal distribution wherein 99.7% of the slot widths are within three standard deviations of the average slot width.

Description

SCREEN FILTER FOR MICROFILTRATION

PRIORITY CLAIM

The present application claims priority to United States Provisional Application Serial

No. 62/485,051, filed April 13, 2017 and entitled "SCREEN FILTER FOR MICROFILRATION", which is herein incorporated by reference in its entirety.

FIELD OF THE DISCLOSURE

The present invention is related to wire-based screen filters for separating solid matter from fluid streams. More particularly, the present invention is directed to reusable wire-based wired screen filters that are manufactured of shaped wire so as to remove particulate matter and other contaminants having a size less than 20 microns. BACKGROUND OF THE DISCLOSURE

The use of screen filters is well known in the industry. For example, wire-based screens manufactured and sold under the Johnson Screens® mark have been used to filter incoming ground and well water over 100 years. Advantages of wire-based screen filters include their robust strength which allow them to be cleaned and reused for extended periods of time. As such, costs associated with plugging, replacement and disposal as are found with conventional bag, cartridge, ceramic, hollow fiber and membrane filters can be avoided.

One drawback experienced with conventional wire-based screen filters has been that they have been limited to the removal of particulate matter having particle sizes of 20 microns or greater. In addition, conventional manufacturing techniques have limited filter effectiveness to a range of variation for the openings of roughly four times the standard deviation of spacing between the wires. Due to their robustness, strength and ability to be cleaned and placed back in use, it would be advantageous to develop wire-based screen filters that can be used to remove particulates having a particle size less than 20 microns and which had a higher level of consistency with wire spacing. SUMMARY OF THE INVENTION

A representative screen filter of the present invention generally comprises a plurality of support rods arranged in longitudinal relationship such that a continuous length of wire can be spirally wrapped about the support rods to define a cylindrical body. Along the length of the cylindrical body, slots are defined between adjacent wires wherein each slot has a slot width that determines an overall filter performance for the screen filter. Particulates larger than the slot width are retained within the slot or on an exterior surface of the cylindrical body while smaller particulates and fluid is allowed to pass through the slots and into an interior portion of the cylindrical body. Generally, the screen filter is fabricated such that an average slot width across the length of the cylindrical body is equal to a filter performance rating. In one representative embodiment, the filter performance rating can be 20 microns such that the average slot width is also 20 microns. The screen filter is fabricated such that the slot width for the cylindrical body has a normal distribution such that 99.7% of the slot widths are within three standard deviations of the average slot width and correspondingly, the filter performance rating.

In one aspect of the present invention, a representative screen filter can be fabricated with shaped wire or Vee wire that is spirally wound about a plurality of longitudinally arranged support rods.

In another aspect of the present invention, a representative screen filter can be fabricated to have a filter performance rating of 20 microns and a standard deviation of 8 microns for slot width such that 99.7% of all slots along a cylindrical body have a slot width of less than 44 microns. The above summary is not intended to describe each illustrated embodiment or every implementation of the subject matter hereof. The figures and the detailed description that follow more particularly exemplify various embodiments.

BRIEF DESCRIPTION OF THE FIGURES

Subject matter hereof may be more completely understood in consideration of the following detailed description of various embodiments in connection with the accompanying figures, in which:

Figure 1 is a perspective, end view of a screen filter according to a representative embodiment of the present invention.

Figure 2 is an end view of the screen filter of Figure 1.

Figure 3 is a section view of a screen filter according to a representative embodiment of the present invention.

Figure 4 is a chart illustrating slot characteristics of a screen filter of the present invention.

While various embodiments are amenable to various modifications and alternative forms, specifics thereof have been shown by way of example in the drawings and will be described in detail. It should be understood, however, that the intention is not to limit the claimed inventions to the particular embodiments described. On the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the subject matter as defined by the claims.

DETAILED DESCRIPTION OF THE INVENTION

A representative screen filter 100 according to the present invention is illustrated generally in Figures 1 and 2. As shown, screen filter 100 can be fabricated to assume a cylindrical body 101. Alternatively, screen filter 100 can be fabricated so as to assume a flat screen, whereby two or more flat screens can be operably coupled to assume other geometric configurations. Screen filter 100 is generally fabricated from suitable metallic materials and alloys including, for example, stainless steel, titanium and the like. Material selection can be dependent on compatibility characteristics with a fluid to be filtered or based upon other process variables. Other non-metal materials including, for example, PVC, that have properties allowing for fabrication with similar geometries having the same opening sizes and precision can also be used in potential embodiments of the invention.

As shown in Figures 1 and 2, screen filter 100 generally comprises a plurality of support rods 102. As shown in Figures 1 and 2, support rods 102 can be evenly spaced and arranged in parallel relation to a longitudinal axis 104 of the screen filter 100. As best seen in Figure 3, each support rod 102 include an interior surface 106 and an exterior surface 108 so as to define a support rod height 110 there between. A continuous length of wire 110 is wound about the support rods 102 such that the wire 110 can be affixed to the exterior surface 108 at each point of contact 112. As the wire 110 is continually wound and spiraled about the support rods 102, the cylindrical body 101 is generally defined for the screen filter 100. Depending upon the overall size of the screen filter 100, for example, the diameter and/or length of the cylindrical body 101, the wire 110 can comprise two or more lengths or spools of wire 110 that have been joined together such that the spiral winding of the wire 110 about the support rods 102 is continuous. In some embodiments, the cylindrical body 101 can be cut, sheared or otherwise reformed into a flat screen or into other alternative screen shapes. In addition, screen filter 100 can include additional attachment or framing elements such as, for example, rings, fittings, bards and other like devices to assist with mounting the screen filter 100 in the desired application.

As best seen in Figure 3, wire 110 preferably possesses a triangular cross-section 120 and is commonly referred to in industry as a Vee-wire. While the Vee-wire style is preferred, other conventional wire profiles known in the art can also be employed without departing from the scope of the present invention. The wire 110 generally has a first vertex 122 that is affixed to the support rod 102 at the point of contact 112. The first vertex 122 is operably coupled to the wire 110 using a suitable technique such as, for example, electric resistance welding. As the weld is completed at each point of contact 112, a penetration depth 123 is defined in the wire 110. Opposite the first vertex 122 is an exposed wire surface 124 having a wire width 125 defined between a second vertex 126 and a third vertex 128. The second vertex 126 and third vertex 128 each define a corner radius 130. A pair of relief surfaces 132a, 132b extend between the first vertex 122 and the second and third vertexes 126, 128 respectively. Relief surface 132a, 132b and the exposed wire surface 124 define a pair of relief angles 134a and 134b. A wire height 136 is defined between the first vertex 122 and the exposed wire surface 124. When the wire 110 is operably coupled to the support rod 102, an overall screen height 138 is generally defined between the interior surface 106 and the exposed wired surface 124. Screen height 138 is generally equivalent to the sum of the wire height 136 and the support rod height 100 minus the penetration depth 125. Spiral wrapping and welding of the wire 110 about the support rods 102 results in a repeating pattern of adjacent wires shown as 110a, 110b. Defined between the corner radius 130 of the adjacent wires 110a, 110b is a slot 140 having a slot width 142. In certain applications, it may be desirable to "reverse" the attachment of the wire 110 to the support rod 102 such that the exposed wire surface 124 is affixed to the support rod 102 such that the slot width 142 is defined proximate the support rod 102 and is inwardly facing toward a center of the cylindrical body 101.

In use, a fluid to be filtered is introduced at an exterior to the cylindrical body configuration 114. The fluid preferably passes through the slots 140, past the relief surface 132a, 132b and support rod 102 and into a screen interior 150 of the screen filter 100. Particulate matter within the fluid is physically prevented from proceeding past the slots 140 and can become lodged within the slots 140 or against the exposed wire surface 124. As particulates accumulated against the exterior of the cylindrical body configuration 114, it may become necessary to backwash the screen filter 100 by introducing a fluid into the screen interior 150, whereby the fluid can flow past the support rods 102, the relief surfaces 132a, 132b and out the slots 140 to dislodge and remove the accumulated particulates. With respect to filtration performance, the slot width 142 generally defines the filtration limits for the screen filter 100. For example, particulates having a size that exceed the slot width 142 will be physically prevented from pasting through the slots 140 and into the screen interior 150.

Screen filter 100 of the present invention is generally fabricated such that slot width 142 is uniform and consistently defined between each of the adjacent wires 1 10a, 1 10b along a length of the cylindrical body configuration 1 14. Screen filter 100 is fabricated such the uniformity of the slot width 142 is represented by a bell curve having a normal distribution as contained in Figure 4. As illustrated, 68% of all the slots 142 along the length of the cylindrical body configuration 1 14 are within one standard deviation of the slot average for screen filter 100, 95.5% of all the slots 142 are within two standard deviations of the slot average for the screen filter 100 (27.5% of the slots 142 between 1 and 2 standard deviations of the slot average) and 99.7%) of the slots 142 are within three standard deviations of the slot average for the screen filter (4.2%) of the slots 142 between 2 and 3 standard deviations of the slot average).

Example: Screen Filter Rated for 20 Micron Particulate Removal

Target Filter Rating: 20 Micron

• Average Slot Width: 20 Microns

• Standard Deviation: 8 Microns

• 68% of Slots between 12 and 28 Microns

• 95.5%) of Slots between 4 and 36 Microns

• 99.7% of Slots less than 44 Microns In certain filtering applications, it may be desirable to form screen filter 100 such that the slot width 142 is intentionally variable, i.e. smaller or larger, at specific locations of the screen filter 100. In those instances, the slot width 142 can be controlled at those specified locations such that the uniformity at the specified location has a normal distribution profile.

Various embodiments of systems, devices, and methods have been described herein. These embodiments are given only by way of example and are not intended to limit the scope of the claimed inventions. It should be appreciated, moreover, that the various features of the embodiments that have been described may be combined in various ways to produce numerous additional embodiments. Moreover, while various materials, dimensions, shapes, configurations and locations, etc. have been described for use with disclosed embodiments, others besides those disclosed may be utilized without exceeding the scope of the claimed inventions.

Claims

1. A screen filter, comprising:

a plurality of support rods arranged in longitudinal relation; and

a continuous length of wire that is continually and spirally wrapped about the plurality of support rods to define a cylindrical body, said cylindrical body defined by adjacent wires along a length of the cylindrical body,

wherein adjacent wires define a slot there between, each slot having a slot width with said slot width having a normal distribution across the length of the cylindrical body.

2. The screen filter of claim 1, wherein the continuous length of wire comprises a Vee-wire.

3. The screen filter of claim 2, wherein the slot width is defined between a corner radius of adjacent Vee wires.

4. The screen filter of claim 3, wherein the screen filter has a target filter rating and wherein an average of the slot widths across the length of the cylindrical body equals the target filter rating.

5. The screen filter of claim 4, wherein the target filter rating is less than 20 microns.

6. The screen filter of claim 5, wherein the standard deviation is equal to or less than 8 microns.

7. The screen filter of claims 1-6, wherein the slot width is intentionally varied across the length of the cylindrical body, and wherein the slot width is within the normal distribution.

8. The screen filter of claims 1-7, wherein a surface of retention of the wire faces inwards toward an interior of the cylindrical body.

9. The screen filter of claims 1-8, further comprising one or more attachment or framing devices selected from rings, fittings, bars and other like devices known to one of ordinary skill in the art.

10. The screen filter of claim 1, wherein the wire comprises a profile known to one of skill in the art other than a Vee-Wire.

11. The screen filter of claim 1, wherein the cylindrical body can be cut or reformed into a flat or shaped filter screen surface having slot widths with the normal distribution.