MXPA06004315A - Filtration element having a variable density sidewall - Google Patents

Abstract

A filtration element formed of overlapping fibrous strands or components. Those fibrous strands at the side of the filtration element which first receives the liqui d flow being of one thickness and those fibrous strands at the side of the filtration element where the liquid flow exits being of a thickness substantially less than the one thickness of the strand s at the opposite sidewall of the element.

Description

FILTER ELEMENT HAVING A VARIABLE DENSITY SIDE WALL FIELD OF THE INVENTION The present invention is concerned with a filtration element for liquids and will have application to bag type filters. In this invention, the filtering element was formed of overlapping strands or fibrous components, the strands varying in diameter or thickness, the largest of which is on the side of the fibers that receives first of the flow of the filtration liquid and the more small of which is on the opposite side of the filter where the liquid comes out after passing through the filtering element. In addition, the side of the filter that first receives the flow of the liquid will generally be stiffer than the opposite side of the filter to provide a substantially incomprehensible surface. Thus, it is an object of this invention to provide a filtration element that is of economic construction that is efficient to operate. Yet another object of this invention is to provide a filtration element that is for liquids and that provides a more uniform distribution of particulate matter filtered throughout the thickness of the element. Other objects of the invention will become apparent upon reading the following description.

BRIEF DESCRIPTION OF THE FIGURES Figure 1 is a fragmentary perspective view showing an example of the apparatus that can be used to manufacture the filtration element of this invention. Figure 2 is a side view of a filter element in the form of a bag having a portion of the side wall of the bag in section to illustrate in cross section the filter strands forming the side wall of the filter bag. Figure 3 is a side view of the filter bag illustratively showing the variable thickness of the filter strands.

DETAILED DESCRIPTION OF THE INVENTION The preferred embodiment described herein is not intended to be exhaustive or to limit the invention to the precise form disclosed. It is chosen and described to explain the principles of the invention and its application and practical use to enable others skilled in the art to make better use of the invention. This invention can be better understood by the following descriptions and the work of the equipment that is used to produce the filter element, seen in the figures as a bag of filters. As illustrated in Figure 1, an amount of material, preferably polypropylene or other thermoplastic materials capable of producing filaments when melted and dried by air, is introduced to an extruder 12 in the hopper 14 and is fed through a nozzle 16. A plurality of ring heaters 18 circumscribe the nozzle 16 and serve to produce sufficient heat to liquefy the thermoplastic material as it flows through the nozzle. The nozzle 16 terminates in a plurality of laterally spaced discharge outlets 22 through which the thermoplastic material in the molten state is driven in fused and fibrous strands 20 by heated air from manifolds 23 to a mandrel 28. The mandrel 28 can be formed from metal, wood or similar material and resembles in its external configuration the proposed shape of the filter bag 10 to be produced. The mandrel 28 is rotated about an axis 35 within the flow path of the fibrous strands 20 from the discharge outlets 22 of the nozzle. Normally, the mandrel 28 is placed between 30 cm to 90 cm (1 to 3 ft) from the outlets 22 and is rotated at a constant speed, such as between 30 to 80 revolutions per minute. The fibrous material or strands are sufficiently cooled as they reach the mandrel 28 to be formed around the layered mandrel. In this invention, the diameters of the strands 20 are varied as the thickness of the side wall 32 of the bag 10 increases. This is best illustrated by looking at Figures 2 and 3 wherein a section of the side wall of the filter bag is cut for illustrative purposes. In figure 2, the strands 20 are shown in cross section, the strands of larger diameter are inside the bag and the smaller diameter of the strands is on the outside of the bag with the flow of the liquid through the bag that is from the bag. inside towards the outside of the bag. In figure 3 the variable thickness of the strands 20 is shown in illustrative form with the strands becoming progressively thinner from the inside to the outside of the bag in the direction of flow of the liquid through the bag. In this way, the outer margin of the side wall of the bag will have its strands more compactly ratified to increase the degree of filtration as it reaches the outer edges of the bag. Thus, the larger particulate matter that is filtered from the liquid will first be dragged into the bag of filters closest to the inside of the bag with the smaller particulate matter that is drawn closer to the outside of the bag. This will produce a more even distribution of the particulate matter filtered through the bag. The thickness of the strands 20 of the bag 10 can fluctuate from 50 to 200 microns toward the inside of the bag and becomes productively smaller in transverse dimension at 0.5 microns on the outer surface of the bag, with the bag being approximately 1" of thickness." The precise thickness or transverse dimension of the strands of the fibrous material and the thickness of the bag may vary depending on the type of material designed to be filtered and the size of the bag of filters. In the production of the bag of the filter 10, the thicker strands are first wound on the mandrel and then as the thickness of the bag increases progressively, the temperature produced by the heaters 18 can be increased to make the thermoplastic material more melted with the air pressure produced in the multiples 23 increased, thus increasing the length of the strands and reducing their transverse dimension. In this way, by selectively increasing the temperature of the molten thermoplastic material and / or increasing the air pressure by which the molten thermoplastic material is propelled through and propelled from the nozzles, the thickness of the strands can be selectively varied as they are wound on the mandrel to produce the side wall of the filter bag or cartridges depending on the type of filter elements that is produced. Also in addition to varying the thickness of the strands, by varying the temperature of the molten thermoplastic material and / or varying the volume of air by which the material is driven through and propelled from the nozzles, the stiffness of the strands can to be increased in such a way that the inner wall section 20a of the filter bag becomes brittle or rigid. Normally, the side walls of the bag are substantially crushed during use due to the pressure of the liquid inside the bag. This reduces the permeability of the bag and filtration capacity of the bag. By rigulating a wall section of the bag on the side where the liquid comes into contact with for the first time, the strands of the bag remain open to provide at intervals or gaps between the strands to trap or entrain filtered particles. The depth of the wall section 20a may vary, as it extends to the entire thickness of the filter bag, depending on the desired filtration characteristics. It is anticipated that for a liquid pressure of 25 pounds / square inch within a sack of filters having a substantially rigid wall section 20a formed of strands having gaps or gaps between the strands of 25 or more microns there will be approximately a reduction of 15% or less in the wall thickness of the bag. Also, it is anticipated that for a liquid section of 15 pounds / square inch inside the filter bag having a substantially rigid wall section 20a with gaps between the strands of 10 or less microns there will be approximately a reduction of 50% or more in the wall thickness of the bag.

The invention is not limited to the details given above being that it can be modified within the scope of the appended claims.

Claims (7)

1. CLAIMS 1.- A filtering element characterized in that it comprises a side wall part, the side wall part has a first side which the flow of the liquid through the element comes into contact for the first time and a second side of which the flow of the liquid leaves the element, the side wall part includes overlapping fibrous strands, those strands on the first side of the side wall part are of a thickness and those strands on the second side of the side wall part are of a thickness. thickness substantially less than the thickness of the first side of the side wall portion.
2. 2. The filtering element according to claim 1, characterized in that the strands vary productively in transverse dimension from the first side of the side wall part to the second side of the side wall part.
3. 3. - The filter element according to claim 1 or 2, characterized in that the strands vary regressively in stiffness from the first side of the side wall portion to the second side of the side wall portion to form a wall part laterally rigid on the first side.
4. 4. A method for forming a filter element characterized in that it comprises the steps of: (a) ejecting thermoplastic material through a nozzle by gas pressure to form strands of fibrous material; (b) heat the material before it is ejected from the nozzle; (c) forming the strands of fibrous material to a side wall of the filter element and (d) varying the thickness of the strands, the thicker strands being on the side of the filter element where the flow of the liquid through the element flows for the first time.
5. 5. The method according to claim 4, characterized in that step (a) includes varying the pressure of the gas through the nozzle to vary the thickness of the strands.
6. 6. The method according to claim 4, characterized in that step (b) includes changing the temperature of the material before it is ejected from the nozzle to vary the thickness of the strands.
7. 7. The method according to claim 4, characterized in that step (d) includes varying the rigidity of the strands on the side of the filtration element where the flow of the liquid through the element flows for the first time.