FILTER ELEMENT

Abstract: The filter element of the present has a plurality of wavy portions which are so arranged that a plurality of wavy por­ tions make a generally ring like structure. In order to reduce the pressure drop when the fluid flows through the filter element, the present filter element has a special shaped radial gaps. Namely, the width of a first radial gaps, which is formed within adjacent wavy por­ tions and which connects with an inner space formed at the center of the generally ring like structure, increases from the outer end thereof to the inner end thereof. The width of a second radial gap, which is connected with outer atmosphe­ re, decreases from the outer end thereof to the inner end thereof. Both axial ends of the wavy portions are covered with the adhesive sheet on which adhesive layer is cladded.

Description: The invention relates fo a filter element according to the preamble of claim 1. Such a filter element is known from AU-A-34143/84. In this known filter element the fluid is introduced into the second radial gaps and passes through the wavy portions toward the first radial gaps which are connected with the inner space, so that the fluid introduced into the second radial gaps flows toward the inner space through the first radial gaps. This known filter element causes a large pressure drop which reduces the efficiency of filtering as well as the life of the filter element. In a filter element known from DE-B-1 204 629 the width of the first radial gaps opening to the inner space through the inner end thereof decreases from the outer end to the inner end so that the inner end of these gaps is very narrow. The fluid passing through the filter element flows through the narrow inner end of these gaps so that also in this case a serious pressure drop occures. It is the object of the present invention to provide a filter element according to the preamble of claim 1 in such a way that the pressure drop of the fluid flow passing through the filter element is reduced. This is achieved by the features in the characterizing part of claim 1. Since the inner width of the first radial gaps is large, the fluid passing through the filter element can easily flow toward the inner space through the first radial gaps. Fig. 1 is a top view of the filter element according to the first embodiment of this invention, a part of the sheet in Fig. 1 is eliminated, Fig. 2 is an enlarged view of a part of the filter element shown in Fig. 1, Fig. 3 is a perspective view of the filter element shown in Fig. 1, Fig. 4 is a perspective view of a part of the filter element shown in Fig. 1, Fig. 5 is a sectional view taken along with V-V line of Fig. 4, Fig. 6 is a front view of the filter member of Fig. 1, before the filter member is bent, Fig. 7 is an enlarged view of Fig. 6, Fig. 8 is a graph showing the relativeship between the opening angle ϑ and the pressure drop of the fluid flow, Fig. 9 is a front view of the adhesive sheet shown in Fig. 1, Fig. 10 is a perspective view of a part of the filter member, Fig. 11 is a partially sectional view of the filter in which the filter element is employed, Fig. 12 is a perspective view of the adhesive sheet according to the other embodiment of the present invention, Figs. 13 (a) - (d) are diagrams showing the shape of the radial gaps according to the other embodiment of this invention. As shown in Fig. 1 - 3 , a single filter member 5 is bent for forming a plurality of wavy portions 1 which are so arranged to make generally ring like structure. Therefore, a plurality of radial gaps 2 and 3 are formed within the adjacent wavy portions, and an inner space 4 is also formed at a center of the generally ring like structure. Since a plurality of wavy portions are made of the single filter member, which is described more detailedly later, both ends of the single filter member are combined together as indicated by the point A. Half of a plurality of the radial gaps 2 and 3 are the first radial gaps 2 which are connected with the inner space at the inner end thereof as shown in Fig. 1. The wavy portions are bent to be zigzag so that the wavy portion 1 has a number of bent portion 1a, and each edge of the bent portions 1a spaces from the opposed edge of the bent portion 1a. Therefore, the first radial gap 2 is made between the bent portions 1a, the inner end of the first radial gap 2 opens to the inner space 4. The second radial gaps 3, on the other hand, are closed at their inner end by the filter member in order to apart the inside of the radial gaps 3 from the inner space 4, as shown in Figs. 1 and 3. As clearly shown in Fig. 2, the width of a each of the first radial gaps 2 increases from the outer end to the inner end so that the first radial gaps 2 is a taper shape. The second radial gap 3, on the other hand, reduces the width thereof from the outer end to the inner end so that the second radial gap 3 also is a taper shape. Both upper and lower sides of the first radial gap 2 are closed by the resin adhesive sheet 6 which is made of hot melt type material such as polyamide, for example. The shape of the second radial gap 3 is a taper shape which is the same shape as that of opening area within the adjacent bent portions 1a. There are six opening 7 equally apart from each other along with the circumferential direction of the ring like structure. The second radial gap is connected with the opening 7 at both radial and axial end Z of which (shown in Fig. 3). As shown in Figs. 4 and 5 a couple of the resin adhesive sheet 6 make a closed chamber there-between. A single filter member belt which is shown in Figs. 6 and 7, makes a plurality of wavy portions 1. The filter member 5 is bent at the predetermined line b, the length between adjacent predetermined lines b is continuously varied as shown in Fig. 7 so that the trapezoid wavy portion 1 is made after the filter member has been bent. The passage of the fluid of this filter element is shown hereinafter. When the fluid flows from lower side of the filter element, the fluid is introduced into the second radial gap 3 through a plurality of axial end openings 7 and radial end openings Z. The fluids then passes through the wavy portions 1 from the second radial gap 3 towards the first radial gap 2. The fluid introduced into the first radial gap 2, then, flows toward the inner space 4. The particulates contained in the fluid is trapped within the filter member when the fluid passes through the wavy portions 1. The shape of the second radial gap 3 as well as the opening 7 are taper, namely radially outward portion thereof are wider than the radially inward portion so that the fluid can be introduced into the second radial gap without causing serious pressure drop. The first radial gap 2 which is connected with the inner space 4, on the other hand, increase its width toward inner side ofwhich. Therefore, the filter element of this invention can reduce the pressure loss of the fluid flowing therethrough. Fig. 8 shows the relationship between the opening angle ϑ of the radial gaps 2 and 3 and the pressure loss of the fluid. The opening angle ϑ is the angle between a couple of lines which connects the tangent of the bent portions 1a, as shown in Fig. 2. The pressure loss of the fluids in Fig. 8 is the value detected when the lubricant oil for internal combustion engine is used as the fluids flowing through the element. The testing conditions of the examination shown in Fig. 8 are as follows: The lubricant oil is SAE #30, the amount of the lubricant oil is 30 l/min, and the temperature of the lubricant oil is about 80 °C. It is clearly shown from Fig. 8 that the pressure loss is varied in accordance with the angle ϑ. The filter element becomes effective when the angle ϑ is at least 4°, and becomes more effective when the angle ϑ is at least 5°. As shown in Fig. 9, the shape of the sheet 6 is the same as the end shape of the filter member 1. The functions of the base 6a when the base is set at the axial end face of the ring like structure and when the base is heated by the heat tool such as a hot plate are described hereinafter, 1. to prevent the adhesive from depositing at the heat tool (in order to make the sheet easily detach from the tool). 2. to prevent such defect as pin hole in the adhesive layer which may be generated while the adhesive layer is melt (during the heat operation) 3. to reinforce the adhesive layer. Since the base is heated while the attaching operation, the base 6a should be made such material which is hard to melt, and also since the base should be rolled and be punched, the material of the base 6a must be soft. Therefore, the paper having a predetermined thickness such as 130 µm (kraft paper or masking paper, for example) or steel film or nickel film having the thickness of 10 µm is suitable for the base 6a. The paper is more valuable from the view point of the capital cost, the aluminum film, on the other hand, is more valuable from the view point of the high speed operation. The effect of the high speed operation of the aluminum film is described in table 1. As described in table 1, the required time for melting the adhesive cladded on the base is short when the base is made of aluminum, so that the attaching operation of the sheet 6 can be carried out quickly. The thickness of the base when the base is made of aluminum film is preferred within the suitable range between 10 - 200 µm in order to roll the base. Hot melt adhesive (polyamide hot melt DPXH 610 producted by HENKERU HAKUSUI CO. LTD., MOVAMID 1030 producted by MITSUBISHI KASEI CO. LTD., or polyester hot melt PES-X-412 producted by TOA GOSEI KAGAKU KOGYO CO. LTD., or B stage epoxy resin (NEF-1200 producted by NITTO DENKO CO., LTD., )) can be used for the adhesive layer 6b. The soft point of hot melt type adhesive layer is better to be under 150 °C from the view point of mass production. As described in table 2, the thickness of the adhesive layer is better between 50 - 600 µm. The viscosity of the adhesive layer is better between 5 - 15,000 poise (dPa) in order to keep the adhesive from permeating into the filter member. The base and the adhesive layer do not have to be combined together, the base and the adhesive can be made independently and be attached each other. The detail attaching operation of this invention is described hereinafter. The filter member is bent in order to make the generally ring like structure, then the both ends of the filter member (point A in Fig. 1) are combined together by the adhesive (such as polyamide type hot melt adhesive). Mean while the adhesive sheet 6 is punched out in order to have the same ring like shape as that of the generally ring like structure (shown in Fig. 9) from the rolled adhesive sheet 6 (shown in Fig. 10). The adhesive sheet is then attached on the end face of the filter element in such a manner that the adhesive layer 6b of the sheet 6 faces the filter element. The heat tool such as a hot plate is attached on the base 6a side of the sheet 6 in order to melt the adhesive 6b, and fix the sheet 6 onto the filter element. The closed chamber (shown in Figs. 4 and 5) is formed within the filter member and a couple of the sheets. The operation of the filter element when the filter element is used as the filter for the lubricant oil of the internal combustion engine is described hereinafter. The filter element 8 is contained in a metal container 13 in such a manner that the inner side of the element 8 is fixed with a punch metal 12 and the punch metal is fixed with an end plate 14. The end plate 14 has a screw hall 14a at the center thereof, and a plurality of openings 14b around the screw hole 14a. The end plate 14 is fixed at the opening edge of the metal container 13. A ring plate 18 which is welded with the end plate 14 is fixed with the opening edge of the container 13. Numeral 15 in Fig. 11 shows a check valve made of rubber, numeral 16 shows a spring, numeral 19 shows a metal end plate fixed with the upper end of the punch metal 12, and numeral 17 shows a gasket made of rubber. As shown by the arrow in Fig. 11, the lubricant oil is introduced into the container 13 through the opening 14b, keeping the check valve 15 open. The lubricant oil introduced into the container, then flows into the gap through the opening 7 and Z and passes through the wavy portion, after that the oil flows into the inner space 4 through the punch metal 12. The lubricant oil after passing through the filter, then, returns to the internal combustion engine from the screw hole 14a. By the way, the lubricant oil is introduced into the wavy portion mainly from the slit 7 when the lubricant oil is introduced into the container 13 from the lower side thereof as shown in Fig. 11. The lubricant oil, on the other hand, is introduced into the wavy portion mainly from the slit Z when the lubricant oil is introduced vertically. The filter element of this invention can be modified as follows: (1) Though both the first and second radial gaps 2 and 3 are designed to be taper in the above embodiment, the filter element of this invention can be used effectively even when only one of the first and second radial gaps 2 and 3 is designed to be taper. (2) Though the filter element, shown in Figs. 1 and 3, has axial openings 7 at the both upper and lower ends of the adhesive sheet 6, the position of the openings 7 can be varied, or the openings 7 of this invention can be made at the only one surface of the element, namely, the opening slit 7 can be formed at the one side of the element and the another side of the element can be closed. It is also possible that both sides of openings are cancelled by using the adhesive sheet 6 shown in Fig. 12, so that the fluid is introduced into the filter element from the radial opening Z at the side face of the element. (3) The space between the zigzag portion of the wavy portions connecting to the second radial gap 3 does not have to be covered. (4) Though all wavy portions of the above embodiment shown in Fig. 1 is made of a single filter member, each block B of the wavy portion can be made from each independent filter member, so that the filter element is made from a plurality of separate blocks B. (5) The pitch between the adjacent bent portions of the wavy portion can be varied from each other. (6) The shape of the filter element of this invention can also be changed, the filter element of this invention can be formed as any polygonal shape depending on the number of the blocks B of the wavy portions. (7) A float portion can be provided in the radial gap between opposed bent portions of the wavy portions. (8) The shape of the radial gaps can be varies as such the shapes shown in Figs. 13a -13d. The shapes shown in these figures can also reduce the pressure loss of the fluid as well as that shown the above embodiment. (9) The filter element of this invention can also be used as air filter for internal combustion engine.

Claims: Filter element comprising a filter member (5), said filter member (5) being bent to be zigzag for forming a plurality of wavy portions (1), said wavy portions (1) having a plurality of zigzag pleats provided with circumferential dimensions which are substantially gradually decreased radially inwardly and being so arranged that a plurality of said wavy portions make a generally ring like structure having an inner space (4) substantially at the center thereof, and that a plurality of first and second radial gaps are provided within adjacent portions (1), said first radial gaps (2) being open to said inner space (4) through the inner end thereof and being closed on the outer end thereof, whereas the second radial gaps (3) being closed on the inner end and being open on the outer end to the outer circumference of the filter element, characterized in that the width of the second radial gaps (3) decreases from the outer end to the inner end, and the width of the first radial gaps (2) increases from the outer end to the inner end thereof. Filter element as claimed in claim 1, wherein the angle of the width of the first radial gaps (2) is at least 4°. Filter element as claimed on claims 1, wherein the angle of the width of the second radial gaps (3) is at least 4°. Filter element as claimed in claims 1 to 3, wherein the angle of the width of said first radial gaps (2) is the same as that of said second radial gaps (3). Filter element as claimed in claim 1, further comprising and adhesive sheet (6) having a soft base (6a) made of an anti-heat material and a resin adhesive layer (6b) provided on a surface of said base; said adhesive sheet (6) being attached on an axial end surface of said filter member so that said adhesive sheet and said filter member provides a closed chamber. Filter element as claimed in claim 5; wherein, said base (6a) is made of a material chosen from a group of kraft paper, masking paper, aluminium film, steel film, nickel film and copper film. Filter element as claimed in claim 5; wherein, said adhesive layer (6b) is made of heat melt type resin adhesive chosen from a group of polyamide and polyester. Filter element as claimed in claim 5,; wherein, the thickness of said base (6a) is between 10 - 200 µm. Filter element as claimed in claim 7; wherein, the thickness of said adhesive layer (6b) is between 50 - 600 µm. Filter element as claimed in claim 9; wherein, the viscosity of said adhesive is between 5 - 15,000 dPas.

Inventors: AKADO, HAJIME, HARADA, HITOSHI, INUKAI, SATOSHI, MIYAKAWA, SUSUMU, SAKAIDA, ATSUSHI, TAKI, YOSHIHIRO
Applicants: NIPPONDENSO CO., LTD.
Application year: 1986
Main classification: B01D27
IPC codes: B01D27