Folding filter element

Abstract

The utility model provides a folding filter element which comprises a pleated filter medium, a central rod, an outer support and two end covers, the pleated filter medium is inserted between the central rod and the outer support, and the two end covers are respectively fixed at two axial ends of the pleated filter medium, the central rod and the outer support in a sealing manner; the pleated filter medium comprises a filter membrane and flow guide layers stacked on the two sides of the filter membrane, the filter membrane and the flow guide layers are folded at the same time to form a plurality of first pleats, the pleated filter medium further comprises second pleats formed through hot melting welding, a sealing area is formed in a hot melting welding area, the second pleats are clamped between the two first pleats, and the first pleats and the second pleats are sealed. The pleat height of the second pleat is not greater than that of the first pleat adjacent to the second pleat. By reducing the height of the second pleat formed by the edge sealing, the pleat peak of the second pleat does not protrude relative to the pleat peak of the adjacent first pleat any more, so that the pleat peak of the second pleat is not radially extruded by the outer bracket any more, the gap between the sealing area of the second pleat and the adjacent first pleat is reduced, and the bending of the filter membrane in the first pleat adjacent to the second pleat is inhibited.

Description

Technical Field

[0001] The utility model belongs to the technical field of filtration, and particularly relates to a folded filter element. Background Art

[0002] In the existing folded filter element, as Figures 1-3 shown, the filter medium composed of the filter membrane 10 and the diversion layer 11 is folded together to form a pleated filter medium 1, which includes a plurality of pleats. After the starting section and the ending section of the filter medium are sealed by hot melt welding, they are inserted between the perforated central rod 2 and the outer bracket 3, and then end caps are hermetically fixed at the axial two ends of the central rod, the pleated filter medium and the outer bracket. Among them, the process of forming a seal by hot melt welding in a section of the starting section and the ending section of the filter medium is often simply referred to as side sealing, and the starting section and the ending section of the filter medium respectively constitute two legs of the pleats corresponding to the side sealing. The process of hermetically fixing the end caps at the axial two ends of the central rod, the filter medium and the outer bracket is as follows: the axial two ends of the central rod, the filter medium and the outer bracket and the corresponding end faces of the end caps are softened by hot melt to a certain degree, and then each end cap is axially pressed onto the axial ends of the central rod, the filter medium and the outer bracket to form a hermetic fixation, and this process is usually called end sealing.

[0003] Generally, it is considered that during the process of forming a seal by hot melt welding in a section of the starting section and the ending section of the filter medium, since hot melt welding requires heating the welding area of the filter medium to a relatively high temperature, the high temperature will cause damage to the area where the filter membrane is welded and its adjacent areas, resulting in that during the subsequent end sealing operation or when the filter element is performing the filtering function, compared with other pleats, the filter membrane in the pleat corresponding to the side sealing is more likely to rupture.

[0004] However, actual detection finds that usually, it is the filter membrane in the pleat (designated by the number 12 in Figure 4 and Figure 5 ) adjacent to the pleat corresponding to the side sealing (designated by the number 13 in Figure 4 and Figure 5 ) that ruptures. Further research finds that the filter elements with the filter membrane in the pleat adjacent to the pleat corresponding to the side sealing rupturing all have the following characteristics: after the side sealing is completed, the pleat height of the pleat corresponding to the side sealing is greater than the pleat height of the adjacent pleat.

[0005] Generally, during the manufacturing process of some filter elements, for the convenience of folding, the pleat height of the pleats corresponding to the side seal is equal to that of other pleats, that is, the same pleat height is used for folding. Then, before the side seal, the pleat height of the pleats corresponding to the side seal is the same as that of the adjacent pleats. During the side seal process, the filter membrane and the flow guiding layer are heat-melted and stretched. After the side seal is completed, the pleat height of the pleats corresponding to the side seal will increase, resulting in the pleat peaks of the pleats corresponding to the side seal protruding from the pleat peaks of the adjacent pleats. Moreover, the thickness of the heat-melted welding area will be greatly reduced, and a certain gap will be formed between this area and the legs of the adjacent pleats. After the side-sealed pleated filter medium is installed between the central rod and the outer support, as Figures 2-3 shown, in the cross-section near the end seal area, the pleat peaks of the pleats corresponding to the side seal are radially inwardly pressed by the outer support, further increasing the gap between the heat-melted welding area of the pleats corresponding to the side seal and the legs of the adjacent pleats, that is Figure 3 the maximum value of L in

[0006] can reach more than 1 mm. Figure 3 In addition, before the side seal operation, the starting section and the ending section of the filter medium need to be straightened and aligned before being fed into the welding equipment for heat-melted welding. During the process of straightening the starting section and the ending section of the filter medium, the filter membrane in the pleats adjacent to the starting section and the ending section will be separated from the flow guiding layers on both sides of it. As

[0007] shown, the filter membrane in the pleats adjacent to the pleats corresponding to the side seal no longer forms a tight fit with the flow guiding layers on both sides of it, but is separated, forming a certain gap. The ability of the filter membrane separated from the flow guiding layer to withstand impacts alone is relatively poor, and it is easily bent when impacted. After the pleated filter medium is installed between the central rod and the outer shell, the outer shell presses the protruding pleat peaks of the pleats corresponding to the side seal, resulting in a further increase in the gap between its heat-melted welding area and the adjacent pleats. Correspondingly, the gap between the flow guiding layer and the filter membrane in the adjacent pleats also further increases, large enough for the filter membrane to be bent, that is, the increased gap provides a bending space for the filter membrane in the adjacent pleats, resulting in the filter membrane being extremely easy to bend when impacted.

[0007] Since during the subsequent end seal process, the end cap needs to be axially pressed, the molten end seal material liquid will impact and squeeze the filter membrane separated from the flow guiding layer. Also due to the existence of the aforementioned bending space, the impacted filter membrane will be bent, and the bending will cause damage to the filter membrane. Also, since the gap between the filter membrane in the pleats adjacent to the starting section and the ending section and the flow guiding layers on both sides of it is very large, a small amount of the end seal material liquid will squeeze into the gap between the separated filter membrane and the flow guiding layer and form with the filter membrane as Figure 4 and Figure 5The so-called point bonding phenomenon actually occurs when a small amount of end-sealing liquid that flows out of the normal end-sealing area adheres to the surface of the filter membrane adjacent to the normal end-sealing area. The area of this point bonding is basically consistent with the bending position. The superposition of these two factors increases the damage to the filter membrane in the pleat adjacent to the pleat corresponding to the side seal. After the filter element is manufactured and then cleaned and dried, the filter membrane will shrink, and the bent and point-bonded parts of the filter membrane become more fragile and may even be ruptured. Alternatively, during the filtration process, when the liquid to be filtered flows between the filter membrane and the flow guide layer, it will impact the filter membrane in the area near the point bonding. The continuous impact causes the filter membrane near the point bonding or bending area to be pulled, which will also cause the filter membrane in the bending area or point bonding area to rupture prematurely.

[0008] In view of this, it is necessary to improve the structure of the pleat corresponding to the side seal to solve the problem that the filter membrane in the pleat adjacent to the pleat corresponding to the side seal is prone to rupture in the area adjacent to the end cap, and to ensure the integrity of the filter element and extend the service life of the filter element. Summary of the Invention

[0009] In order to solve the problem that the filter membrane in the pleat adjacent to the pleat corresponding to the side seal is prone to rupture in the area adjacent to the end cap, and to ensure the integrity of the filter element and extend the service life of the filter element, the present utility model provides the following technical solutions:

[0010] A folded filter element, comprising:

[0011] A pleated filter medium, a central rod, an outer support, and two end caps. The pleated filter medium is inserted between the central rod and the outer support, and the two end caps are respectively sealed and fixed at the axial two ends of the pleated filter medium, the central rod, and the outer support. One of the end caps has an interface communicating with the inside of the central rod;

[0012] The pleated filter medium includes a filter membrane and flow guide layers stacked on both sides thereof. The filter membrane and the flow guide layers are simultaneously folded to form a plurality of first pleats. Each of the first pleats has a pleat valley close to the central rod, a pleat peak close to the outer support, and two legs extending between the pleat valley and the pleat peak;

[0013] The pleated filter medium further includes a second pleat formed by hot melt welding, and a sealing area is formed in the area of the hot melt welding. The second pleat is clamped between the two first pleats, and the pleat height of the second pleat is not greater than the pleat height of the adjacent first pleat.

[0014] In the folded filter element provided by the present application, the pleated filter medium forms a second pleat through hot melt welding, that is, a section of the starting section and the ending section of the filter membrane facing each other is hot melt welded to form the second pleat, that is, the side seal corresponds to the second pleat. The remaining area of the filter membrane directly forms a plurality of first pleats through folding. By reducing the pleat height of the second pleat so that its pleat height is not greater than the pleat height of the adjacent first pleat, the pleat peak of the second pleat no longer protrudes relative to the pleat peak of the first pleat, and the outer support no longer forms a radial extrusion on the second pleat. As a result, the gap between the sealing area of the second pleat and the legs of the two adjacent first pleats on both sides is greatly reduced. Correspondingly, the overall arrangement of the second pleat and the two adjacent first pleats on both sides is closer. To a certain extent, the filter membrane in the first pleat adjacent to the second pleat and the diversion layers on both sides are restored to fit, that is, the gap between the filter membrane in the first pleat adjacent to the second pleat and the diversion layers on both sides is reduced. This gap is so small that it is not enough for the filter membrane in the first pleat adjacent to the second pleat to bend, thereby inhibiting the bending of the area of the filter membrane in the first pleat facing the sealing area of the second pleat;

[0015] Moreover, since the gap between the filter membrane in the first pleat adjacent to the second pleat and the diversion layers on both sides is reduced, the resistance for the molten end sealant to squeeze into the gap between the filter membrane in the first pleat adjacent to the second pleat and the diversion layers on both sides is increased. Correspondingly, almost no point bonding phenomenon formed by the filter membrane and the squeezed molten end sealant will appear almost on the inner side in the axial direction of the normal end seal area. Therefore, it can also avoid the damage to the filter membrane caused by point bonding and further improve the integrity of the filter membrane.

[0016] In summary, by reducing the pleat height of the second pleat before side sealing and making the pleat height of the second pleat not greater than the pleat height of the adjacent first pleat after side sealing, the pleat peak of the second pleat is no longer radially extruded by the outer support, and the gap between the sealing area of the second pleat and the legs of the two adjacent first pleats on both sides is greatly reduced. Correspondingly, the diversion layer in the first pleat adjacent to the second pleat will recover in the direction close to the filter membrane in the first pleat, and the gap between the filter membrane in the first pleat adjacent to the second pleat and the diversion layers on both sides is greatly reduced and can even fit again. This gap is so small that it is not enough for the filter membrane in the first pleat adjacent to the second pleat to bend, which inhibits the bending of the filter membrane and avoids the bending of the area of the filter membrane in the first pleat adjacent to the second pleat facing the sealing area of the second pleat near the end cap; moreover, the reduction of the gap between the filter membrane in the first pleat adjacent to the second pleat and the diversion layers on both sides can also avoid the problem of point bonding at the position of the filter membrane in the first pleat adjacent to the second pleat near the end cap, and finally achieve a better protection effect on the area of the filter membrane in the first pleat adjacent to the second pleat near the end cap, protect the integrity of the filter element, and extend the service life of the filter element.

[0017] It should be emphasized that in this application, it is relatively difficult to discover the technical problem itself that the filter membrane in the first fold adjacent to the second fold, rather than the filter membrane in the second fold itself, is more likely to rupture, which is contrary to general knowledge.

[0018] Furthermore, on at least one cross-section within the range where the axial distance from each of the said end caps is not greater than 10% of the total axial height of the filter element, the maximum gap between the sealing area of the second fold and the legs of the two adjacent first folds on both sides is not greater than 0.5 mm.

[0019] By controlling the size of the gap between the sealing area of the second fold and the legs of the two adjacent first folds on both sides, when the maximum width of this gap is not greater than 0.5 mm, even if the filter membrane in the first fold adjacent to the second fold is impacted by the molten end-sealing liquid, it cannot be bent, or only a very small bending deformation can be formed, and this very small bending deformation causes extremely little damage to the filter membrane, thereby protecting the area of the filter membrane in the first fold adjacent to the second fold close to the end cap.

[0020] Furthermore, both legs of the second fold have a first area and a second area located inside and outside its sealing area, and both the first area and the second area are in contact with the legs of the two adjacent first folds on both sides.

[0021] Except for the sealing area, the remaining areas of the second fold are in contact with and abutted against the two adjacent first folds on both sides, that is, the second fold fits as closely as possible with the two adjacent first folds on both sides, which can increase to a certain extent the degree of fitting between the filter membrane in the first fold adjacent to the second fold and the diversion layer, and further increase the difficulty of bending at the position close to the end cap in the area of the filter membrane in the first fold facing the sealing area of the second fold.

[0022] Furthermore, the width of the sealing area of the second fold is 2 - 3 mm.

[0023] With such a design, on the one hand, it ensures the sealing reliability of the second fold, controls the radial extension length of the gap between the sealing area and the legs of the two adjacent first folds on both sides, limits the radial length of the area where the filter membrane in the first fold adjacent to the second fold can be bent, and increases the difficulty of its bending; on the other hand, the areas of the two legs of the second fold located inside the sealing area are also pulled by the sealing area to improve the strength and prevent the areas of the second fold itself located inside the sealing area from being bent.

[0024] Furthermore, the two end caps are respectively welded to the axial two ends of the pleated filter medium, the central rod, and the outer support by hot melting, and the axial height of the areas where the multiple first folds and the second fold are respectively welded to the corresponding end caps at the axial two ends is 0.5 - 1.5 mm.

[0025] The axial height of the end-sealing area is limited to 0.5-1.5 mm, which can control the amount of the molten end-sealing liquid within an appropriate range, ensure reliable end-sealing effect, guarantee the sealing performance, and at the same time avoid excessive generation of the end-sealing liquid, reduce the impact force generated by the molten end-sealing liquid, and further reduce the possibility that the filter membrane separated from the diversion layer in the first fold adjacent to the second fold is bent due to the impact of the end-sealing liquid.

[0026] Furthermore, the pleat height of the second fold is less than that of the adjacent first fold, and the second fold is wrapped by the two adjacent first folds on both sides.

[0027] The second fold is completely wrapped by the two adjacent first folds on both sides, and the peak of the second fold is no longer squeezed by the outer support, which can better control the gap between the sealing area of the second fold and the legs of the two adjacent first folds on both sides.

[0028] Furthermore, the pleat height of the second fold is not less than 70% of that of the adjacent first fold.

[0029] If the pleat height of the second fold is too small, there will be a large gap in a relatively long area near the peaks of the two adjacent first folds on both sides, resulting in too loose arrangement of the two adjacent first folds on both sides, which is also not conducive to reducing the gap between the sealing area of the second fold and the two adjacent first folds on both sides, nor is it conducive to improving the degree of fitting between the filter membrane and the diversion layer in the two adjacent first folds on both sides. When the pleat height of the second fold is not less than 70% of that of the adjacent first fold and not greater than that of the adjacent first fold, the second fold and the two adjacent first folds on both sides can form a relatively tight fit, the gap between the sealing area of the second fold and the legs of the two adjacent first folds on both sides can be controlled within 0.5 mm and below, and the filter membrane in the first fold and the diversion layers on both sides thereof can also form a tight fit, which can better inhibit the bending of the filter membrane in the first fold adjacent to the second fold.

[0030] Furthermore, the diversion layer on either side of the filter membrane includes an inner diversion layer directly adjacent to the filter membrane and an outer diversion layer far from the filter membrane, and the hardness of the inner diversion layer is less than that of the outer diversion layer.

[0031] The inner diversion layer has a low hardness, small friction with the surface of the filter membrane, and can protect the filter membrane. The outer diversion layer is used to improve the overall stiffness of the first fold and the second fold and enhance the overall strength of the filter element.

[0032] Furthermore, the hardness of the filter membrane is less than that of the outer diversion layer and greater than that of the inner diversion layer, and the thickness of the inner diversion layer is less than that of the filter membrane.

[0033] The inner diversion layer is softer and thinner, can form a closer fit with the filter membrane, and also plays a certain role in inhibiting the bending of the filter membrane in the first fold adjacent to the second fold.

[0034] Further, the thickness of the first fold is 1.3 - 2 mm, and the central angle occupied by a single first fold is between 2.5 - 4.5°.

[0035] The first folds are arranged with the above thickness and fold density to ensure appropriate fitting between adjacent first folds and between the first folds and the second folds, which can provide a stable flow channel. Moreover, during the end - sealing process, the filter membranes in all the folds, especially those in the first fold adjacent to the second fold, are not easily bent. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 Showing a cross - sectional schematic view of an existing folded filter element.

[0037] Figure 2 is Figure 1 a partial enlarged view of part A in

[0038] Figure 3 is Figure 2 a partial enlarged view of part B in

[0039] Figure 4 is Figure 1 a schematic view of the end - sealing of the filter element shown.

[0040] Figure 5 is Figure 4 a partial enlarged view of part C in (showing the bending of the filter membrane in the fold adjacent to the edge - seal and the spot - bonding phenomenon).

[0041] Figure 6 Showing a schematic structural view of the folded filter element provided by the present application.

[0042] Figure 7 is Figure 6 a partial structural schematic view of point O of the folded filter element provided.

[0043] Figure 8 is Figure 6 a cross - sectional view of the folded filter element provided.

[0044] Figure 9 is Figure 8 a partial enlarged view of part P in

[0045] Figure 10 Showing a cross - sectional schematic view of the folded filter element provided by one embodiment of the present application.

[0046] Figure 11 Showing Figure 10 a partial enlargement of part D in

[0047] Figure 12 Showing Figure 11 a partial enlargement of part E in

[0048] Figure 13Shows a cross-sectional schematic diagram of a folded filter element provided by another embodiment of the present application.

[0049] Figure 14 Shows Figure 13 A partial enlargement at F in the figure.

[0050] Figure 15 Shows Figure 14 A partial enlargement at G in the figure.

[0051] 1 - pleated filter medium, 10 - filter membrane, 11 - flow guiding layer, 111 - inner flow guiding layer, 112 - outer flow guiding layer, 12 - first pleat, 121 - pleat valley, 122 - pleat peak, 123 - leg, 13 - second pleat, 130 - sealing area, 131 - first area, 132 - second area, 2 - central rod, 3 - outer bracket, 4 - end cap, 40 - interface. Detailed implementation manners

[0052] In order to enable those skilled in the art to better understand the solution of the present utility model, the technical solutions in the embodiments of the present utility model will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present utility model. Obviously, the described embodiments are only a part of the embodiments of the present utility model, rather than all of the embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present utility model.

[0053] As Figures 6-9 The shown folded filter element includes a pleated filter medium 1, a central rod 2, an outer bracket 3 and two end caps 4. Among them, the pleated filter medium 1 is inserted between the central rod 2 and the outer bracket 3, and the two end caps 4 are respectively sealed and fixed at the axial two ends of the pleated filter medium 1, the central rod 2 and the outer bracket 3. One of the end caps 4 has an interface 40 communicating with the inside of the central rod 2, and the other end cap 4 is a closed plate-like structure to close one axial end of the pleated filter medium 1, the central rod 2 and the outer bracket 3.

[0054] The pleated filter medium 1 includes a filter membrane 10 and flow guiding layers 11 stacked on both sides thereof. The filter membrane 10 and the flow guiding layers 11 are simultaneously folded to form a plurality of first pleats 12. Each first pleat 12 has a pleat valley 121 close to the central rod 2, a pleat peak 122 close to the outer bracket 3 and two legs 123 extending between the pleat valley 121 and the pleat peak 122; the pleated filter medium 1 further includes a second pleat 13 formed by hot melt welding, and a sealing area 130 is formed in the area of the hot melt welding. The second pleat 13 is clamped between two first pleats 12. Among them, the pleat height of the second pleat 13 is not greater than the pleat height of the adjacent first pleat 12. Both the filter membrane 10 and the flow guiding layers 11 can play a filtering role and are collectively referred to as the filter medium.

[0055] It should be noted that after the corrugated filter medium 1 is installed between the central rod 2 and the outer support 3, the first corrugation 12 and the second corrugation 13 may be bent or inclined to a certain extent, and the corrugation heights of the first corrugation 12 and the second corrugation 13 cannot be accurately measured directly in the filter element. During actual measurement, remove one of the end caps 4, cut out a section of the filter medium including the first corrugation 12 and the second corrugation 13 from between the central rod 2 and the outer support 3. After straightening the two legs 123 of the first corrugation 12, measure the distance between the corrugation valley 121 and the corrugation peak 122 to obtain the corrugation height of the first corrugation 12, that is, the distance between the adjacent inner and outer creases of the first corrugation 12; the corrugation height of the second corrugation 13 is obtained by measuring the distance between the boundary between any leg of the second corrugation 13 and the leg 123 of the adjacent first corrugation 12 on either side and the end of the second corrugation 13. The boundary between any leg of the second corrugation 13 and the leg 123 of the adjacent first corrugation 12 on either side is exactly the crease between any leg of the second corrugation 13 and the leg 123 of the adjacent first corrugation 12 on either side. The end of the second corrugation 13 refers to its end located radially outside the sealing area 130. The corrugation height of the second corrugation 13 is obtained by straightening the filter medium between the boundary and the end of the second corrugation 13. Among them, the corrugation height of the second corrugation 13 includes the length of the part located radially outside the sealing area 130.

[0056] In this folded filter element, the pleated filter medium 1 includes a second pleat 13 formed by hot melt welding, that is, a section of the starting section and the ending section of the filter medium facing each other is hot melt welded to form the second pleat 13, that is, the side seal corresponds to the second pleat 13. The remaining areas of the filter medium are directly formed into a plurality of first pleats 12 by folding. By reducing the pleat height of the second pleat 13 so that its pleat height is not greater than the pleat height of the adjacent first pleat 12, the peak of the second pleat 13 no longer protrudes relative to the peak 122 of the first pleat 12, and the outer support 3 no longer forms a radial extrusion on the second pleat 13. As a result, the gap between the sealing area 130 of the second pleat 13 and the legs 123 of the two adjacent first pleats 12 on both sides is greatly reduced. Correspondingly, the overall arrangement of the second pleat 13 and the two adjacent first pleats 12 on both sides is closer. To a certain extent, the filter membrane 10 and the diversion layers 11 on both sides in the first pleat 12 adjacent to the second pleat 13 are restored to fit, that is, the gap between the filter membrane 10 and the diversion layers 11 on both sides in the first pleat 12 adjacent to the second pleat 13 is reduced. This gap is so small that it is not sufficient for the filter membrane 10 in the first pleat 12 adjacent to the second pleat 13 to be bent, thereby inhibiting the bending of the area of the filter membrane 10 in the first pleat 12 facing the sealing area 130 of the second pleat 13; moreover, since the gap between the filter membrane 10 and the diversion layers 11 on both sides in the first pleat 12 adjacent to the second pleat 13 is reduced, the resistance for the molten end sealant to squeeze into the gap between the filter membrane 10 and the diversion layers 11 on both sides in the first pleat 12 adjacent to the second pleat 13 is increased. Correspondingly, almost no point bonding phenomenon formed by the filter membrane 10 and the squeezed molten end sealant will appear on the axial inner side of the normal end seal area. Therefore, it can also avoid the damage to the filter membrane 10 caused by point bonding and further improve the integrity of the filter membrane 10.

[0057] In summary, by reducing the pleat height of the second pleat 13 before edge sealing and ensuring that the pleat height of the second pleat 13 after edge sealing is not greater than that of the adjacent first pleat 12, the second pleat 13 is no longer radially extruded by the outer support 3 at the pleat peak. The gap between the sealing area 130 of the second pleat 13 and the legs 123 of the two adjacent first pleats 12 is significantly reduced. Correspondingly, the diversion layer 11 in the first pleat 12 adjacent to the second pleat 13 will recover towards the filter membrane 11 in the first pleat 12. The gap between the filter membrane 11 in the first pleat 12 adjacent to the second pleat 13 and the diversion layers 11 on both sides is significantly reduced and can even fit together again. This gap is so small that it is not sufficient for the filter membrane 10 in the first pleat 12 adjacent to the second pleat 13 to bend, which inhibits the bending of this filter membrane 10 and avoids the bending of the area of the filter membrane 10 in the first pleat 12 adjacent to the second pleat 13 near the end cap 4 where it faces the sealing area 130 of the second pleat 13. Moreover, the reduction of the gap between the filter membrane 10 in the first pleat 12 adjacent to the second pleat 13 and the diversion layers 11 on both sides can also avoid the problem of point bonding of the filter membrane 10 in the first pleat 12 adjacent to the second pleat 13 near the end cap 4. Finally, a better protection effect on the area of the filter membrane 10 in the first pleat 12 adjacent to the second pleat 13 near the end cap 4 is achieved, protecting the integrity of the filter element and extending the service life of the filter element.

[0058] Since the gap between the sealing area 130 of the second pleat 13 and the legs 123 of the two adjacent first pleats 12 is large enough, which is a prerequisite for the bending of the filter membrane 10 in the first pleat 12 adjacent to the second pleat 13, therefore, by controlling the size of the gap between the sealing area 130 of the second pleat 13 and the legs 123 of the two adjacent first pleats 12 so that the width of this gap is within a certain range, the bending of the filter membrane 10 in the first pleat 12 adjacent to the second pleat 13 during end sealing can be avoided.

[0059] Among them, the pleat height of the second pleat 13 is not greater than that of the adjacent first pleat 12, which specifically includes two situations: (1) The pleat height of the second pleat 13 is equal to that of the adjacent first pleat 12, as Figures 10-12 shown; (2) The pleat height of the second pleat 13 is less than that of the adjacent first pleat 12, as Figures 13-15 shown.

[0060] Furthermore, by comparing different folded filter elements, it is found that on at least one cross-section within the range where the axial distance from each end cap 4 is not greater than 10% of the total axial height of the filter element, as Figure 12 and Figure 15As shown, when the maximum gap between the sealing area 130 of the second fold 13 and the legs 123 of the adjacent first folds 12 on both sides is no more than 0.5 mm, that is, the widths of the maximum gaps L1 and L2 are both no more than 0.5 mm, the filter membrane 10 in the first fold 12 adjacent to the second fold 13 will not bend. Because when the maximum widths of the maximum gaps L1 and L2 are no more than 0.5 mm, that is, the width of the gap between the sealing area 130 of the second fold 13 and the legs 123 of the adjacent first folds 12 on both sides is small enough and not sufficient for the filter membrane 10 in the first fold 12 adjacent to the second fold 13 to bend. Then, even if the filter membrane 10 is impacted by the molten end-sealing liquid, it cannot bend or can only form a very small bending deformation, and this very small bending deformation causes extremely little damage to the filter membrane 10, thus protecting the area of the filter membrane 10 in the first fold 12 adjacent to the second fold 13 close to the end cap 4.

[0061] Among them, on at least one cross-section within the range where the axial distance from each end cap 4 is no more than 10% of the total axial height of the filter element, the width condition of the gap between the sealing area 130 of the second fold 13 and the legs 123 of the adjacent first folds 12 on both sides reflects the actual situation of the width of the maximum gap between the junction of the pleated filter medium 1 and the end cap 4 and between the sealing area 130 of the second fold 13 and the legs 123 of the adjacent first folds 12 on both sides. As long as on at least one cross-section within the above axial height range, the width of the maximum gap between the sealing area 130 of the second fold 13 and the legs 123 of the adjacent first folds 12 on both sides is no more than 0.5 mm, the width of the maximum gap between the junction of the pleated filter medium 1 and the end cap 4 and between the sealing area 130 of the second fold 13 and the legs 123 of the adjacent first folds 12 on both sides is small enough, and the bending of the filter membrane 10 in the first fold 12 adjacent to the second fold 13 can be avoided.

[0062] As Figure 6 and Figure 7 shown, the diversion layer 11 on either side of the filter membrane 10 includes an inner diversion layer 111 directly adjacent to the filter membrane 10 and an outer diversion layer 112 far from the filter membrane. The hardness of the inner diversion layer 111 is less than that of the outer diversion layer 112. The low hardness of the inner diversion layer 111 results in small friction with the surface of the filter membrane 10 and can protect the filter membrane 10. The outer diversion layer 112 is used to increase the overall stiffness of the first fold 12 and the second fold 13 and improve the overall strength of the filter element. In other better embodiments, the hardness of the filter membrane 10 is less than that of the outer diversion layer 112 and greater than that of the inner diversion layer 111, and the thickness of the inner diversion layer 111 is less than that of the filter membrane 10. The inner diversion layer 111 is softer and thinner, can form a closer fit with the filter membrane 10, and also plays a certain role in suppressing the bending of the filter membrane 10 in the first fold 12 adjacent to the second fold 13.

[0063] As Figure 11 and 14As shown, both legs of the second fold 13 have a first region 131 and a second region 132 located inside and outside its sealing region 130. The first region 131 and the second region 132 are both in contact with the legs 123 of the first folds 12 adjacent on both sides. Except for the sealing region 130, the remaining regions of the second fold 13, namely the first region 131 and the second region 132, are in contact with and abutted against the first folds 12 adjacent on both sides. That is, the second fold 13 fits as closely as possible to the first folds 12 adjacent on both sides, which can increase to a certain extent the degree of fit between the filter membrane 10 and the flow guiding layer 11 in the first fold 12 adjacent to the second fold 13, and further increase the difficulty of bending at the position near the end cap 4 in the region of the filter membrane 10 in the first fold 12 facing the sealing region 130 of the second fold 13.

[0064] Preferably, as Figure 12 and Figure 15 shown, the length L3 of the sealing region 130 of the second fold 13 is 2 - 3 mm. With such a design, on the one hand, it ensures the sealing reliability of the second fold 13 itself, controls the radial extension length of the gap between the sealing region 130 and the legs 123 of the first folds 12 adjacent on both sides, limits the radial length of the region where the filter membrane 10 in the first fold 12 adjacent to the second fold 13 can be bent, and increases the difficulty of its bending; on the other hand, the regions of the two legs of the second fold 13 located inside the sealing region 130 are also pulled by the sealing region 130 to improve the strength, and prevent the regions of the second fold 13 itself located inside the sealing region 130 from being bent.

[0065] As Figure 9 shown, the two end caps 4 are respectively welded to the axial ends of the pleated filter medium 1, the central rod 2, and the outer support 3 by hot melt welding, and the axial height H of the regions where the multiple first folds 12 and the second fold 13 are respectively welded to the corresponding end caps 4 at the axial ends is 0.5 - 1.5 mm. Limiting the axial height H of the end sealing region to 0.5 - 1.5 mm can control the amount of the molten end sealing liquid within an appropriate range. On the one hand, it ensures a reliable end sealing effect and guarantees the sealing performance; on the other hand, it avoids excessive generation of the end sealing liquid, reduces the impact force generated by the molten end sealing liquid when axially pressing the end cap 4 during the end sealing process, and further reduces the possibility that the filter membrane 10 separated from the flow guiding layer 11 in the first fold 12 adjacent to the second fold 13 is bent due to the impact of the end sealing liquid.

[0066] As Figure 13 and 14As shown, the height of the second pleat 13 is less than that of the adjacent first pleat 12, and the second pleat 13 is wrapped by the first pleats 12 adjacent on both sides. The second pleat 13 is completely wrapped by the first pleats 12 adjacent on both sides, and the peak of the second pleat 13, i.e., the end on its radial outer side, is no longer squeezed by the outer bracket 3, which can better control the width of the gap between the sealing area 130 of the second pleat 13 and the legs 123 of the first pleats 12 adjacent on both sides. Preferably, the height of the second pleat 13 is not less than 70% of the height of the adjacent first pleat 12. When the height of the second pleat 13 is too small, a relatively large gap will be formed between the peaks 122 of the first pleats 12 adjacent on both sides, resulting in an overly loose arrangement of the first pleats 12 adjacent on both sides, which is not conducive to reducing the gap between the sealing area 130 of the second pleat 13 and the first pleats 12 adjacent on both sides, nor to improving the degree of adhesion between the filter membrane 10 and the diversion layer 11 in the first pleats 12 adjacent on both sides. When the height of the second pleat 13 is not less than 70% of the height of the adjacent first pleat 12 and not greater than the height of the adjacent first pleat 12, the second pleat 13 and the first pleats 12 adjacent on both sides can form a relatively tight fit. The gap between the sealing area 130 of the second pleat 13 and the legs of the first pleats adjacent on both sides can be controlled within 0.5 mm or less, and the filter membrane 10 in the first pleat 12 can also form a tight fit with the diversion layers 11 on both sides, which can better inhibit the bending of the filter membrane 10 in the first pleat 12 adjacent to the second pleat 13.

[0067] In another embodiment, the thickness of the first pleat 12 is 1.3 - 2 mm, and the central angle occupied by a single first pleat 12 is between 2.5 - 4.5°. With the above thickness and pleat density arrangement of the first pleat 12, it is ensured that the degree of adhesion between adjacent first pleats 12 and between the first pleat 12 and the second pleat 13 is appropriate, which can provide a stable flow channel, and during the end sealing process, the filter membrane 10 in all the pleats, especially the filter membrane 10 in the first pleat 12 adjacent to the second pleat 13, is not easily bent.

Claims

1. A folded filter element, comprising: A pleated filter medium, a center rod, an outer bracket and two end caps, wherein the pleated filter medium is inserted between the center rod and the outer bracket, and the two end caps are respectively sealed and fixed to the axial ends of the pleated filter medium, the center rod and the outer bracket, and one of the end caps has an interface communicating with the inside of the center rod; The pleated filter medium comprises a filter membrane and a guide layer stacked on both sides thereof, wherein the filter membrane and the guide layer are folded simultaneously to form a plurality of first pleats, each of the first pleats having a pleat valley close to the central rod and a pleat peak close to the outer support and two legs extending between the pleat valley and the pleat peak; characterized in that: The pleated filter medium further comprises a second pleat formed by heat-fusion welding, and a sealing area is formed in the heat-fusion welding area, the second pleat is sandwiched between two first pleats, and the pleat height of the second pleat is not greater than the pleat height of the first pleat adjacent thereto.

2. The pleated filter element according to claim 1, characterized in that: In at least one cross section within the range where the axial distance from each end cap is not greater than 10% of the total axial height of the filter element, the maximum gap between the sealing area of ​​the second pleat and the legs of the adjacent first pleats on both sides is not greater than 0.5 mm.

3. The pleated filter element according to claim 1 or 2, characterized in that: Both legs of the second pleat have a first area and a second area located inside and outside the sealing area thereof, and both the first area and the second area are in contact with the legs of the first pleats adjacent to both sides.

4. The pleated filter element according to claim 1, characterized in that: The length of the sealing area of ​​the second pleat is 2-3 mm.

5. The pleated filter element according to claim 1 or 2, characterized in that: The two end caps are respectively welded to the axial ends of the pleated filter medium, the center rod, and the outer bracket by hot melt welding, and the axial height of the areas where the multiple first pleats and the second pleats are welded with the corresponding end caps at the axial ends is 0.5-1.5mm.

6. The pleated filter element according to claim 1, characterized in that: The pleat height of the second pleat is smaller than the pleat height of the first pleat adjacent thereto, and the second pleat is wrapped by the first pleats adjacent thereto on both sides.

7. The pleated filter element according to claim 1, characterized in that: The pleat height of the second pleat is not less than 70% of the pleat height of the first pleat adjacent thereto.

8. The pleated filter element according to claim 1, characterized in that: The guide layers on either side of the filter membrane include an inner guide layer directly adjacent to the filter membrane and an outer guide layer away from the filter membrane, and the hardness of the inner guide layer is less than that of the outer guide layer.

9. The pleated filter element according to claim 8, characterized in that: The hardness of the filter membrane is less than that of the outer guide layer and greater than that of the inner guide layer, and the thickness of the inner guide layer is less than that of the filter membrane.

10. The pleated filter element according to claim 1, characterized in that: The thickness of the first pleat is 1.3-2 mm, and the central angle of a single first pleat is between 2.5-4.5°.

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