WO2009064116A2

WO2009064116A2 - Edm filter

Info

Publication number: WO2009064116A2
Application number: PCT/KR2008/006675
Authority: WO
Inventors: Byung Ryul Jeun
Original assignee: Byung Ryul Jeun
Priority date: 2007-11-15
Filing date: 2008-11-12
Publication date: 2009-05-22
Also published as: KR100850196B1; WO2009064116A3

Abstract

The present invention provides an EDM filter which enhances coupling force between components. The EDM filter includes an inner perforated casing (20) which supports an inner filter unit, an outer perforated casing (24) which supports an outer filter unit, and upper and lower covers (30) and (32) which are adhered to the inner and outer filter units. Bent ends and support ring parts are formed in the upper and lower covers. The EDM filter further includes outer coupling parts (40) which integrally couple the upper and lower covers to the outer perforated casing. Each outer coupling part includes a first coupling end (42) which extends from each of the opposite open ends of the outer perforated casing, and a second coupling end (44) which is bent from the corresponding bent end of the upper and lower covers. The first and second coupling ends are integrally coupled to each other.

Description

Description EDM FILTER

Technical Field

[1] The present invention relates, in general, to EDM (electrical discharge machine) filters which are used in wire-cut EDM machines to filter cooling water and, more particularly, to an EDM filter which improves a coupling structure between upper and lower covers and perforated casings for supporting filter units so as to increase coupling force therebetween, so that even if excessive pressure is applied to the filter units when supplying cooling water thereinto, the upper or lower cover can be prevented from becoming separated from the filter units, thus enhancing filtration efficiency, ensuring reliable coupling force between components of products, and extending the lifetime of the products, thereby enhancing the reliability of the products. Background Art

[2] Generally, wire-cut EDM machines form workpieces in desired shapes in such a way that a taut thin wire having a diameter ranging from 0.25mm to 0.3mm is inserted into a workpiece and cuts the workpiece while discharging electricity. In such a wire-cut EDM machine, while the workpiece is machined, cooling water is continuously jetted between the wire and the workpiece to reduce heat generated therebetween. Here, cooling water which has been used to cool the wire and the workpiece contains foreign substances such as chips generated during the electrical discharge machining process. Therefore, preferably, cooling water which has been used is collected and is filtered by a separate filter before being used again. A representative example of conventional filters for filtrating cooling water was proposed in Korean Utility Model Registration No. 191313.

[3] As shown in FIGS. 1 through 3, an EDM filter 1 according to the conventional technique includes an inner perforated casing 2 which is made of metal and supports an inner filter unit 3 on the outer surface thereof, and an outer perforated casing 4 which is made of metal and supports therein an outer filter unit 5 which is disposed around the inner filter unit 3 at a position spaced apart from the inner filter unit 3 by a predetermined distance. The EDM filter 1 further includes upper and lower covers 6 and 7 which are adhered to the corresponding opposite ends of the inner and outer perforated casings 2 and 4 and the inner and outer filter units 3 and 5 by adhesive 8. A cooling water supply port 6c through which cooling water is supplied into the EDM filter 1 is formed in the upper cover 6. An appropriate amount of adhesive 8 can be evenly applied to the relevant components owing to bent ends 6a and 7a which are formed on the respective outer edges of the upper and lower covers 6 and 7 and have prede- termined heights. The cooling water supply port 6c and support ring parts 6b and 7b of the upper and lower covers 6 and 7 also have almost the same heights as that of the bent ends 6a and 7a, so that the adhesive 8 can be evenly applied to the relevant components.

[4] In the conventional EDM filter 1 having the above-mentioned construction, cooling water which is supplied into the EDM filter 1 through the cooling water supply port 6c at a predetermined pressure is filtrated by the filter units 3 and 5 which are longitudinally supported by the inner and outer perforated casings 2 and 4. The filtrated cooling water is thereafter discharged to outside of the EDM filter 1 through the inner and outer perforated casings 2 and 4. During this process, fine foreign substances, for example, metal chips, which have been contained in cooling water, are removed from the cooling water. Typically, cooling water which has been filtrated is collected in a separate tank and is used again by virtue of a circulation supply system.

[5] However, various kinds of foreign substances are collected by the filter units 3 and 5 during the cooling water filtration process. With the passage of time, many foreign substances accumulate because of the general structure of the filters. Therefore, even though cooling water is supplied into the EDM filter at a constant appropriate pressure (typically, about 3 kg/cm³), as filtration ability deteriorates due to accumulation of foreign substances collected by the filter units 3 and 5 and also the efficiency with which cooling water is discharged becomes reduced, filtration pressure becomes higher than the appropriate pressure at which cooling water is supplied and applied to the interior of the EDM filter. The pressure overload applied to the EDM filter results in deformation of the EDM filter and markedly deteriorates the filtration ability. Furthermore, the pressure overload may induce a serious problem in that the upper or lower cover 6 or 7 becomes separated from the inner and outer perforated casings 2 and 4 and the filter units 3 and 5. Particularly, in the case where the upper or lower cover is separated from the inner and outer perforated casings and the filter units, cooling water leaks out of the EDM filter and contaminates the area around the EDM filter. In addition, the EDM filter loses filtration ability and the lifespan thereof is terminated. As a result, a lack of faith in products may result or the reliability of products may be markedly reduced.

[6] The above problems of the conventional EDM filter 1 are serious in that the upper or lower cover 6 or 7 frequently separates from the EDM filter as a result of the excessive filtration pressure during the process of filtering cooling water because there is a problem in a method of constructing the EDM filter, as described below. As shown in FIGS. 1 through 3, the conventional EDM filter 1 is constructed such that the inner and outer perforated casings 2 and 4 and the filter units 3 and 5 are integrally coupled to the upper and lower covers 6 and 7 only by the adhesive 8 applied to the bottoms of the upper and lower covers 6 and 7. In detail, for example, the upper and lower covers 6 and 7 are adhered in consecutive order to the inner and outer perforated casings 2 and 4 and the filter units 3 and 5 using the adhesive 8 in such a way as to slowly heat and harden the adhesive 8 over a predetermined time (about 40 minutes). Here, if required working conditions cannot be provided and are unsuitable, for example, if a temperature at which the adhesive 8 is heated or hardened is unsuitable during the process of heating or hardening the adhesive 8, the adhesive layer may undesirably peel off the bottom 6-1 or 7-1 of the upper or lower cover 6 or 7. However, it is very difficult for a worker to determine whether the necessary working conditions are satisfied during the process of assembling a product. Therefore, even if the adhesive state is defective, the product has no choice but to be marketed as it is.

[7] As such, in the conventional EDM filter 1, the coupling force of the upper and lower covers 6 and 7 to the inner and outer perforated casings 2 and 4 and the filter units 3 and 5 depends on only the adhesive 8. Hence, if excessive pressure is applied to the interior of the EDM filter when supplying cooling water thereinto, the adhesive layer may not be able to withstand the excessive pressure and thus peel off the bottom 6-1 or 7- 1 of the upper or lower cover 6 or 7, with the result that the upper or lower cover 6 or 7 is separated from the inner and outer perforated casings 2 and 4 and the filter units 3 and 5. At present, those skilled in this art are making a lot of efforts to overcome the above problems. Disclosure of Invention

Technical Problem

[8] Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and an object of the present invention is to provide an EDM filter which improves a coupling structure between components of filters according to the conventional techniques, so that even if excessive pressure is applied to the interior of the filter when filtering cooling water, an upper or lower cover can be prevented from becoming separated from inner and outer perforated casings and filter units, thus ensuring the safety of products, enhancing the reliability of the products, and extending the lifetime of the products. Technical Solution

[9] In an aspect to accomplish the above object, the present invention provides an EDM

(electrical discharge machine) filter, including: an inner perforated casing to support an inner filter unit, the inner perforated casing being made of metal; an outer perforated casing to support an outer filter unit disposed around the inner filter unit at a position spaced apart from the inner filter unit by a predetermined distance, the outer perforated casing being made of metal; upper and lower covers adhered to respective opposite ends of the inner and outer filter units by adhesive, with a bent end and a support ring part formed in each of the upper and lower covers by bending so as to define an adhesive space into which the adhesive is applied, the upper cover having a cooling water supply port therein; and outer coupling parts integrally coupling the upper and lower covers to the outer perforated casing, each of the outer coupling parts having: a first coupling end extended and bent outwards from each of opposite open ends of the outer perforated casing; and a second coupling end bent from the corresponding bent end of the upper and lower covers in a shape overlapping the first coupling end, such that a depression is formed by the bent end and the second coupling end along an outer circumference of the bent end, wherein the first and second coupling ends are integrally coupled to each other.

[10] Preferably, the first and second coupling ends of each of the outer coupling parts may be integrally coupled to each other by a curling, seaming or welding method. Here, the welding method may comprise one selected from between a seam welding method and a spot welding method.

[11] The EDM filter may further include an inner coupling part which integrally couples the upper and lower covers to the inner perforated casing.

[12] Preferably, the inner coupling part may include depressed support parts integrally extended and bent from the respective support ring parts of the upper and lower covers, with a discharge hole formed through each of the depressed support parts, and an insert hole formed through a central portion of each of the depressed support parts; a longitudinal bolt inserted into the insert holes of the depressed support parts; and a nut tightened over the longitudinal bolt.

[13] In another aspect to accomplish the above object, the present invention provides an

EDM filter, including: an inner perforated casing to support an inner filter unit, the inner perforated casing being made of metal; an outer perforated casing to support an outer filter unit disposed around the inner filter unit at a position spaced apart from the inner filter unit by a predetermined distance, the outer perforated casing being made of metal; upper and lower covers adhered to respective opposite ends of the inner and outer filter units by adhesive, with a bent end and a support ring part formed in each of the upper and lower covers by bending so as to define an adhesive space into which the adhesive is applied, the upper cover having a cooling water supply port therein; an inner coupling part integrally coupling central portions of the upper and outer covers to the inner perforated casing, the inner coupling part having horizontal extensions extending from the respective support ring parts of the upper and lower covers inwards such that a through hole is defined by each of the horizontal extensions, support plates seated onto and supported by the respective horizontal extensions, with a plurality of discharge holes and an insert hole formed through each of the support plates, a Ion- gitudinal bolt inserted into the insert holes of the support plates, and a nut tightened over the longitudinal bolt; and outer coupling parts integrally coupling perimeters of the upper and lower covers to the outer perforated casing such that the upper and lower covers and the outer perforated casing are prevented from separating from each other.

[14] Preferably, each of the outer coupling parts may include: a second coupling end bent from the corresponding bent end in vertical and horizontal directions such that the second coupling end extends from the bent end to a position higher than an upper surface of the upper cover or to a position lower than a lower surface of the lower cover; and a first coupling end bent from one of opposite open ends of the outer perforated casing in vertical and horizontal directions such that one surface of the first coupling end is in surface contact with a corresponding surface of the second coupling end. The first and second coupling ends are integrally coupled to each other by a curling or seaming method.

[15] Alternatively, each of the outer coupling parts may include a coupling end extending from one of opposite open ends of the outer perforated casing in a vertical direction to a position higher than an upper surface of the upper cover or to a position lower than a lower surface of the lower cover such that a portion of the coupling end is in surface contact with an outer surface of the corresponding bent end of the upper and lower covers. The coupling end may be bent inwards such that the coupling end is brought into close contact with the upper or lower surface of the corresponding upper or lower cover, thus integrally coupling the corresponding upper or lower cover to the outer perforated casing.

[16] As a further alternative, each of the outer coupling parts may include: a second coupling end bent from the corresponding bent end in a vertical direction such that the second coupling end extends from the bent end to a position higher than an upper surface of the upper cover or to a position lower than a lower surface of the lower cover; and a first coupling end bent from one of opposite open ends of the outer perforated casing in a vertical direction such that one surface of the first coupling end is in surface contact with a corresponding surface of the second coupling end. The first and second coupling ends may be integrally coupled to each other by a seam or spot welding method such that the first and second coupling ends are prevented from separating from each other.

[17] In a further aspect to accomplish the above object, the present invention provides an

EDM filter, including: an inner perforated casing to support an inner filter unit, the inner perforated casing being made of metal; an outer perforated casing to support an outer filter unit disposed around the inner filter unit at a position spaced apart from the inner filter unit by a predetermined distance, the outer perforated casing being made of metal; upper and lower covers adhered to respective opposite ends of the inner and outer filter units by adhesive, with a bent end and a support ring part formed in each of the upper and lower covers by bending so as to define an adhesive space into which the adhesive is applied, the upper cover having a cooling water supply port therein; an inner coupling part integrally coupling central portions of the upper and outer covers to the inner perforated casing, the inner coupling part including extension ends provided on respective opposite ends of the inner perforated casing which is disposed through and supported by the support ring parts of the upper and lower covers, the extension ends respectively extending to a position higher than an upper surface of the upper cover and to a position lower than a lower surface of the lower cover, the extension ends being locked to the corresponding surfaces of the upper and lower covers by bringing the extension ends into contact with the corresponding surfaces of the upper and lower covers; and outer coupling parts integrally coupling perimeters of the upper and lower covers to the outer perforated casing such that the upper and lower covers and the outer perforated casing are prevented from being separated from each other.

Advantageous Effects

[18] The present invention provides an EDM filter which improves a coupling structure between components of filters according to the conventional techniques in such a way that upper and lower covers are primarily coupled to inner and outer filter units and inner and outer perforated casings using adhesive and the central portion and perimeters of the upper and lower covers are integrally coupled to the filter units and the perforated casings by various bending methods. Therefore, the components of the EDM filter can be reliably coupled to each other, so that even if excessive pressure is applied to the interior of the EDM filter when filtering cooling water, the upper or lower cover can be prevented from being separated from the inner and outer perforated casings and filter units, thus ensuring the safety of products, enhancing the reliability of the products, and extending the lifetime of the products. Thereby, the quality and price competitiveness of the products can be enhanced. Brief Description of the Drawings

[19] FIGS. 1 through 3 are views illustrating the structure of a conventional filter, in which FIG. 1 is a view showing a process of manufacturing the conventional filter, FIG. 2 is a side sectional view showing the structure of the filter manufactured through the process of FIG. 1, and FIG. 3 is a plan sectional view taken along the line A-A of FIG. 2;

[20] FIGS. 4 through 6 are views illustrating the structure of an EDM filter, according to a first embodiment of the present invention, in which FIG. 4 is a side sectional view of the EDM filter before outer coupling parts are coupled thereto, FIG. 5 is a side sectional view of the EDM filter after the outer coupling parts are coupled thereto from the state of FIG. 4, and FIG. 6 is a plan view of FIG. 5;

[21] FIGS. 7a, 7b and 7c are partial sectional views illustrating a process of coupling the outer coupling part to the EDM filter through a seaming coupling process according to the present invention;

[22] FIG. 8 is a side sectional view of an assembled EDM filter, according to a second embodiment of the present invention;

[23] FIG. 9 is a side sectional view of an assembled EDM filter, according to a third embodiment of the present invention;

[24] FIG. 10 is a side sectional view of an assembled EDM filter, according to a fourth embodiment of the present invention;

[25] FIG. 11 is a side sectional view of an assembled EDM filter, according to a fifth embodiment of the present invention;

[26] FIG. 12 is a perspective view of a support plate according to the present invention;

[27] FIG. 13 is a side sectional view illustrating the EDM filter according to the fifth embodiment of the present invention, showing a modification of the outer coupling part;

[28] FIGS. 14a, 14b and 14c are partial sectional views illustrating a process of seaming the outer coupling part to the EDM filter outwards according to the present invention;

[29] FIG. 15 is a partial sectional view corresponding to FIG. 14, but showing the outer coupling part seamed to the EDM filter inwards;

[30] FIG. 16 is a side sectional view of an assembled EDM filter, according to a sixth embodiment of the present invention;

[31] FIG. 17 is a side sectional view of an assembled EDM filter, according to a seventh embodiment of the present invention; and

[32] FIGS. 18 and 19 are side sectional views showing assembled EDM filters, according to an eighth embodiment of the present invention. Best Mode for Carrying Out the Invention

[33] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the attached drawings.

[34] FIGS. 4 through 6 are views illustrating an EDM filter 10 according to a first embodiment of the present invention.

[35] Referring to the drawings, the EDM filter 10 according to the first embodiment includes an inner perforated casing 20, which is made of metal and supports an inner filter unit 22 on the outer surface thereof, and an outer perforated casing 24, which is made of metal and supports therein an outer filter unit 26 which is provided around the inner filter unit 22 at a position spaced apart from the inner filter unit 22 by a predetermined distance. The EDM filter 10 further includes upper and lower covers 30 and 32 which are primarily adhered to the respective opposite ends of the inner and outer filter units 22 and 26 by adhesive 28. A bent end 30a, 32a and a support ring part 30b, 32b are formed in each of the upper and lower covers 30 and 32 by bending so as to define an adhesive space into which the adhesive 28 is applied. A cooling water supply port 30c is formed in the upper cover 30.

[36] The outer perforated casing 24 and the outer edges of the upper and lower covers 30 and 32 are integrally coupled to each other by outer coupling parts 40.

[37] In each outer coupling part 40, as shown in FIG. 4, a first coupling end 42 extends outwards from each of the opposite open ends of the outer perforated casing 24 and is bent, and a second coupling end 44 is integrally bent from the corresponding bent end 30a, 32a of the upper and lower covers 30 and 32 in a shape overlapping the corresponding first coupling end 42, such that a depression 43 is formed by the bent end 30a, 32a and the coupling end 44 along the outer circumference of the bent end 30a, 32a. As shown in the enlarged view of FIG. 5, the first and second coupling ends 42 and 44 are integrated with each other by a curling method.

[38] To assemble the EDM filter 10 according to the first embodiment having the above- mentioned construction, the inner filter unit 22 is fitted over the inner perforated casing 20, and the outer filter unit 26 is fitted into the outer perforated casing 24. Thereafter, an appropriate amount of adhesive 28 is applied to the bottom of one of the upper and lower covers 30 and 32 and to the inner surface of the corresponding bent end 30a, 32a. Subsequently, the inner and outer perforated casings 20 and 24 and the inner and outer filter units 22 and 26 are placed on the upper or lower cover 30 or 32, to which the adhesive 28 has been applied. The upper or lower cover 30 or 32 is thereafter placed on a heating plate (not shown) which is being heated at a constant temperature, so that the adhesive 28 is slowly heated and hardened. In the same manner, a remaining one of the upper and lower covers 30 and 32 is attached using adhesive 28 to the inner and outer perforated casings 20 and 24 and the inner and outer filter units 22 and 26. Here, the adhesive 28 permeates the opposite ends of the inner and outer filter units 22 and 26 while it is hardened, so that the inner and outer filter units 22 and 26 are primarily adhered to the upper and lower covers 30 and 32. This filter assembly process is the same as that of the conventional techniques. Meanwhile, in the filter assembly process, the inner perforated casing 20 is stably supported by the support ring parts 30b and 32b of the upper and lower covers 30 and 32, thus being preventing from undesirably moving.

[39] As such, after the upper and lower covers 30 and 32 have been primarily adhered to the inner and outer filter units 22 and 26 by the adhesive 28, it is held by a jig (not shown) using the depressions 43 that are formed in the perimeters of the upper and lower covers 30 and 32. Thereafter, the first coupling ends 42 of the opposite ends of the outer perforated casing 24 and the second coupling ends 44 of the upper and lower covers 30 and 32 are integrally coupled to each other by curling them, thus forming the outer coupling parts 40. Thereby, the upper and lower covers 30 and 32 are reliably fastened to the outer filter unit 26.

[40] Meanwhile, the coupling of the upper and lower covers 30 and 32 to the outer filter unit 26 is not limited to the curling coupling structure using the outer coupling part 40. As shown in the enlarged views of FIGS. 7a, 7b and 7c, a first coupling end 42 which extends outwards from each end of the outer perforated casing 24 and is bent, and a second coupling end 44 which extends from the upper or lower cover 30 or 32 and is bent in a shape overlapping the first coupling end 42 may be integrally coupled to each other by a seaming method, thus forming an outer coupling part 40-1.

[41] In detail, to couple the first coupling end 42 and the second coupling end 44 to each other using the seaming method, first, as shown in FIG. 7a, the first and second coupling ends 42 and 44 are bent outwards. Subsequently, as shown in FIG. 7b, a curling process is performed. Thereafter, as shown in FIG. 7c, the first and second coupling ends 42 and 44 which have been processed by the curling process are coupled to each other by the seaming method, thus forming the outer coupling part 40-1 having the seaming coupling structure.

[42] As such, in the EDM filter 10 according to the first embodiment, the outer perforated casing 24 and the upper and lower covers 30 and 32 are primarily coupled to each other using the adhesive 28 and, thereafter, they are secondarily coupled to each other by forming the outer coupling parts 40 or 40- 1 in such a way that the opposite ends of the outer perforated casing 24 and the perimeters of upper and lower covers 30 and 32 are integrally coupled to each other by curling or seaming. Thus, compared to the conventional techniques in which the inner and outer filter units and the upper and lower covers are fastened to each other only using adhesive, the EDM filter 10 according to the first embodiment can maintain more reliable coupling force between the components.

[43] Hence, according to the EDM filter 10 of the present invention having the above- mentioned construction, even if pressure is excessively increased in the filter while filtering cooling water supplied through a cooling water supply port 30c of the upper cover 30, the components constituting the filter, that is, the upper and lower cover 30 and 32, the inner and outer filter units 22 and 26 and the inner and outer filter units 20 and 24, can be prevented from being undesirably separated from each other because they are firmly integrally coupled to each other. In particular, even if the adhesive force of the adhesive 28 weakens and the adhesive 28 is thus separated from the bottom of the upper and lower covers 30 and 32, the outer coupling part 40 or 40-1 can reliably prevent the upper and lower covers 30 and 32 from separating from the inner and outer filter units 22 and 26. Furthermore, cooling water, from which foreign substances are removed by the inner and outer filter units 22 and, is discharged to outside of the filter through the inner and outer perforated casings 20 and 24.

[44] With regard to the curling or seaming method of the first and second coupling ends

42 and 44 constituting the outer coupling part 40 or 40-1 of the EDM filter 10 according to the first embodiment of the present invention, in FIGS. 4 through 7, although the outer coupling part has been illustrated as being formed outwards by curling or seaming, the present invention is not limited to this. That is, the outer coupling part may be curled or seamed inwards, of course.

[45] An EDM filter 100 according to a second embodiment of the present invention is illustrated in FIG. 8. The general construction of the EDM filter 100 according to the second embodiment, except for having an inner coupling part 50 on the central portions of the upper and lower covers 30 and 32, remains the same as the EDM filter 10 of the first embodiment of FIGS. 4 through 6. For descriptive purpose, the same reference numerals are used to designate components corresponding to those of the first embodiment, and detailed explanation thereof will be omitted.

[46] In the EDM filter 100 according to the second embodiment, the inner coupling part

50 includes depressed support parts 52, which are integrally extended and bent from the respective support ring parts 30b and 32b of the upper and lower covers 30 and 32. Discharge holes 54 are formed through each depressed support part 52. The inner coupling part 50 further includes a longitudinal bolt 58, which is inserted into insert holes 56 which are formed through the central portions of the depressed support parts 52, and a nut 59 which is tightened over the longitudinal bolt 58 to fasten the depressed support parts 52 to each other.

[47] As such, the EDM filter 100 according to the second embodiment having the above- mentioned construction has not only the primary coupling structure using the adhesive 28 and the secondary coupling structure using the outer coupling part 40 but also the tertiary coupling structure using the inner coupling part 50 that is formed by the nut and bolt coupling method. Therefore, the central portions and perimeters of the upper and lower covers 30 and 32 are integrally coupled to the inner and outer perforated casings 20 and 24. As a result, compared to the EDM filter 10 according to the first embodiment only having the primary coupling structure using the adhesive 28 and the secondary coupling structure using the outer coupling part 40, the EDM filter 100 of the second embodiment exhibits a more stable and reliable coupling force between the components.

[48] Furthermore, in the construction of the EDM filter 100 according to the second embodiment, cooling water which has been filtered by the inner and outer filter units 22 and 26 are discharged outside of the EDM filter 100 through the outer perforated casing 24 and the discharge holes 54 that are formed through the depressed support part 52 of the inner coupling part 50.

[49] An EDM filter 200 according to a third embodiment of the present invention is illustrated in FIG. 9. The general construction of the EDM filter 200 according to the third embodiment, except for having an outer coupling part 40-2 formed by welding but not by curling or seaming, remains the same as the EDM filter 10 of the first embodiment of FIGS. 4 through 6. For descriptive purposes, the same reference numerals are used to designate components corresponding to those of the first embodiment, and detailed explanation thereof will be omitted.

[50] The construction of the outer coupling part 40-2 will be explained in more detail below. A first coupling end 42 is provided on each of the opposite ends of the outer perforated casing 26. A second coupling end 44 extends from each of the outer edges of the upper and lower covers 30 and 32 in a shape overlapping the first coupling end 42. The overlapped portions of the first and second coupling ends 42 and 44 are integrally coupled to each other by a welding method, in detail, by a seam or spot welding method.

[51] As such, the upper and lower covers 30 and 32 are integrally coupled to the first and second coupling ends 42 and 44 of the outer perforated casing 24 by the outer coupling parts 40-2 using the welding method, so that products can be manufactured more rapidly. Here, although the outer coupling parts 40-2 are formed by welding, because the portions to be welded are spaced apart from the outer filter unit 26 by the depressions 43 which are formed in the upper and lower covers 30 and 32, the outer filter unit 26 can be prevented from being affected by welding heat.

[52] An EDM filter 300 according to a fourth embodiment of the present invention is illustrated in FIG. 10. The EDM filter 300 according to the fourth embodiment is constructed in such a way that outer coupling parts 40-2 are formed by welding in the same manner as that of the EDM filter 200 of the third embodiment of FIG. 9 and an inner coupling part 50 is further provided in the central portions of upper and lower covers 30 and 32 in the same manner as that of the embodiment of FIG. 8.

[53] The construction of the inner coupling part 50 according to the fourth embodiment remains the same as that of the second embodiment of FIG. 8, therefore further explanation is deemed unnecessary. Furthermore, in the description of the fourth embodiment, the same reference numerals will be used to designate components corresponding to those of the prior embodiments.

[54] In the EDM filter 300 according to the fourth embodiment having the above- mentioned construction, the inner and outer filter units 22 and 26 are primarily coupled to the upper and lower covers 30 and 32 by adhesive 28, and the central portions and perimeters of the upper and lower covers 30 and 32 are coupled to the inner and outer perforated casings 20 and 24 by the inner and outer coupling parts 50 and 40-2 which are formed by the nut and bolt coupling method and the welding method. Therefore, the EDM filter 300 can exhibit a more stable and reliable coupling force between the components.

[55] FIGS. 11 through 19 illustrate EDM filters 400, 500, 600 and 700, each of which has an inner coupling part 150 or 250 and an outer coupling part 140, 140-1, 140-2, 140-3 or 240 formed through one of various bending processes, according to fifth through seventh embodiments of the present invention. Hereinafter, these embodiments will be described in detail.

[56] First, the EDM filter 400 according to the fifth embodiment of the present invention will be described with reference to FIG. 11. In the description of the EDM filter 400 according to the fifth embodiment, the same reference numerals are used to designate components corresponding to those of the first through fourth embodiments, and detailed explanation thereof will be omitted.

[57] Referring to FIG. 11, the EDM filter 400 according to the fifth embodiment includes an inner perforated casing 20, which is made of metal and supports an inner filter unit 22 on the outer surface thereof, and an outer perforated casing 24, which is made of metal and supports therein an outer filter unit 26 which is provided around the inner filter unit 22 at a position spaced apart from the inner filter unit 22 by a predetermined distance. The EDM filter 400 further includes upper and lower covers 30 and 32 which are primarily adhered to the respective opposite ends of the inner and outer filter units 22 and 26 by adhesive 28. A bent end 30a, 32a and a support ring part 30b, 32b are formed in each of the upper and lower covers 30 and 32 by bending so as to define an adhesive space into which the adhesive 28 is applied. A cooling water supply port 30c is formed in the upper cover 30. The inner and outer filter units 20 and 24 and the central portions and the perimeters of the upper and lower covers 30 and 32 are integrally coupled to each other by an inner coupling part 150 and outer coupling parts 140, respectively.

[58] The inner coupling part 150 includes horizontal extensions 30b-l and 32b-l, support plates 152, a longitudinal bolt 158 and a nut 159. Each horizontal extension 30b-l, 32b- 1 extends from the corresponding support ring part 30b, 32b inwards such that a through hole is defined by the horizontal extension 30b-l, 32b- 1. Each support plate 152 is seated onto and supported by the corresponding horizontal extension 30b-l, 32b- 1 and has a plurality of discharge holes 154 and an insert hole 156. The longitudinal bolt 158 is inserted into the insert holes 156 of the support plates 152 and is tightened into the nut 159.

[59] Preferably, the discharge holes 154 are formed through each support plate 152, as shown in FIG. 12, but the present invention is not limited to the shape or structure of FIG. 12 and various shapes or structures may be used as long as it can conduct the same function as that of FIG. 12. For example, a net structure having a lot of discharge holes may be used.

[60] Each outer coupling part 140 includes a second coupling end 144 which is bent from the corresponding bent end 30a, 32a in the vertical and horizontal directions such that it extends from the corresponding bent end 30a, 32a to a position higher than the upper surface of the upper cover 30 or to a position lower than the lower surface of the lower cover 32. The outer coupling part 140 further includes a first coupling end 142, which is bent from the corresponding end of the outer perforated casing 24 in the vertical and horizontal directions such that one surface of the first coupling end 142 is in surface contact with the corresponding surface of the second coupling end 144. The first and second coupling ends 142 and 144 are integrally coupled to each other by curling.

[61] With regard to the structure of the outer coupling part 140, the reason for that the first and second coupling ends 142 and 144 extend to a position higher than the upper surface of the upper cover 30 or to a position lower than the lower surface of the lower cover 32 is that it substitutes for the structure of the depression 43 of the first, second, third or fourth embodiments. In other words, working space for a jig for performing a curling process can be ensured by extending each of the first and second coupling ends 142 and 144 to a position higher than the upper surface of the upper cover 30 or to a position lower than the lower surface of the lower cover 32. As such, unlike the first through fourth embodiments, this embodiment is advantageous in that the bending process for forming the depression 43 is not required but the curling coupling process of the first and second coupling ends 142 and 144 can be performed without restriction.

[62] Meanwhile, in the outer coupling parts 140 formed by the above-mentioned curling process, as shown in the enlarged view of FIG. 11, the first and second coupling ends 142 and 144 may be curled outwards or, alternatively, as shown in FIG. 13, they may be curled inwards.

[63] In the EDM filter 400 according to the fifth embodiment of the present invention, the inner and outer filter units 22 and 26 are primarily adhered to the bottoms of the upper and lower covers 30 and 32 by the adhesive 28. Furthermore, the inner and outer perforated casings 20 and 24 are integrally coupled to the support ring parts 30b and 32b and the coupling ends 144 of the upper and lower covers 30 and 32 by the inner and outer coupling parts 150 and 140, respectively. Therefore, the EDM filter 400 can reliably maintain the coupling force between the components. Furthermore, because of the stable coupling force, even if excessive pressure is applied to the interior of the EDM filter 400, the upper or lower cover 30 or 32 can be prevented from being separated from the inner and outer filter units 22 and 26.

[64] In addition, unlike the second or fourth embodiment, the inner coupling part 150 is constructed in such a way that the support plates 152 are seated onto the respective horizontal extensions 3Ob-I and 32b- 1 that are bent from the corresponding support ring parts 30b and 32b of the upper and lower covers 30 and 32 and the longitudinal bolt 158 is inserted into the support plates 152 and tightened into the nut 149. As such, the construction of the inner coupling part 150 is relatively simple, and thus the assembly or disassembly thereof can be rapidly and reliably conducted.

[65] Ultimately, this embodiment has technical advantages in that the productivity can markedly increase and the increase in productivity reduces the production cost, so that the products having high quality despite low production costs can be supplied to consumers. Therefore, the EDM filter 400 according to this embodiment can have high price competitiveness compared to the EDM filters according to the conventional techniques.

[66] Meanwhile, in the fifth embodiment of the present invention, the first and second coupling ends 142 and 144 constituting the outer coupling part 140 may be processed not only by the curling method but also by the seaming method for forming an outer coupling part 140-2 of FIGS. 14a, 14b, 14c and 15. The construction of the outer coupling part 140-2 that is formed by the seaming method has been already illustrated in the description of the first embodiment with reference to FIG. 7, but this will be described again below.

[67] As shown in FIG. 14a, the first and second coupling ends 142 and 144 extend upwards or downwards from the bent end 30a or 32a of the upper or lower cover 30 or 32 in the vertical direction and then are bent in the horizontal direction. Thereafter, as shown in FIG. 14b, the first and second coupling ends 142 and 144 are processed by a curling method. Subsequently, as shown in FIG. 14c, the first and second coupling ends 142 and 144 which have been processed by the curling method are integrally coupled to each other by a seaming method, thus forming the outer coupling part 140-1 having the seaming coupling structure.

[68] Here, as shown in FIG. 14c, the outer coupling part 140-1 may be formed outwards by the seaming method or, alternatively, as shown in FIG. 15, it may be formed inwards.

[69] An EDM filter 500 according to a sixth embodiment of the present invention is illustrated in FIG. 16. Comparing the EDM filter 500 according to the sixth embodiment to the EDM filter 400 of the fifth embodiment, the construction of an inner coupling part 150 of the sixth embodiment is the same as that of the fifth embodiment with the exception of the construction of an outer coupling part 140-2 which differs from that of the fifth embodiment. For descriptive purposes, the same reference numerals are used to designate components corresponding to those of the fifth embodiment, and detailed explanation thereof will be omitted. [70] Referring to FIG. 16, in the EDM filter 500 according to the sixth embodiment, each outer coupling part 140-2 includes a coupling end 142 which extends from a corresponding end of an outer perforated casing 24 in the vertical direction to a position higher than an upper surface of an upper cover 30 or a position lower than a lower surface of a lower cover 32 such that a portion of the coupling end 142 is in surface contact with an outer surface of a corresponding bent end 30a or 32a of the upper or lower cover 30 or 32. The coupling end 142 is bent inwards such that it is brought into close contact with the upper or lower surface of the corresponding upper or lower cover 30 or 32. As such, the upper and lower covers 30 and 32 are integrally coupled to the outer perforated casing 24 by the above-mentioned bending coupling structure.

[71] Therefore, in the same manner as the fifth embodiment, the EDM filter 500 according to the sixth embodiment having the above-mentioned construction can also have reliable coupling force between the components constituting the EDM filter. Furthermore, because the outer coupling part 140-2 is formed by the bending method, the coupling structure of the coupling end 142 can be further simplified.

[72] An EDM filter 600 according to a seventh embodiment of the present invention is illustrated in FIG. 17. Comparing the EDM filter 600 according to the seventh embodiment to the EDM filters 400 and 500 of the fifth and sixth embodiments, the construction of an inner coupling part 150 of the seventh embodiment is the same as that of the fifth or sixth embodiment, but only the construction of an outer coupling part 140-3 differs from that of the fifth or sixth embodiment. Herein, only the construction of the seventh embodiment that differs from that of the fifth or sixth embodiment will be explained.

[73] Referring to FIG. 16, in the EDM filter 600 according to the seventh embodiment, each outer coupling part 140-3 includes a second coupling end 144 which is bent from a corresponding bent end 30a, 32a in the vertical direction such that the second coupling end 144 extends to a position higher than an upper surface of an upper cover 30 or to a position lower than a lower surface of a lower cover 32, and a first coupling end 142 which is bent from a corresponding end of an outer perforated casing 24 in the vertical direction such that the first coupling end 142 is in surface contact with the second coupling end 144. The overlapped portions of the first and second ends 142 and 144 that protrude from the upper or lower surface of the upper or lower cover 30 or 32 are integrally coupled to each other by welding.

[74] The first and second coupling ends 142 and 144 can be welded to each other by various methods, and, more preferably, they may be integrally coupled to each other by a seam or spot welding method. Because of this construction, the upper and lower covers 30 and 32 can be reliably integrated with the outer perforated casing 24 such that they are prevented from being undesirably separated from each other. [75] Therefore, in the same manner as the fifth or sixth embodiment, the EDM filter 600 according to the seventh embodiment having the above-mentioned construction can also have reliable coupling force between the components constituting the EDM filter because of the construction of the inner and outer coupling parts 150 and 140-3. As well, because the outer coupling parts 140-3 are formed by the seam or spot welding method, the process of integrally coupling the first and second coupling ends 142 and 144 to each other can be simply and rapidly performed.

[76] An EDM filter 700 according to an eighth embodiment of the present invention is illustrated in FIGS. 18 and 19. The general construction of the EDM filter 700 according to the eighth embodiment, except for the construction of an inner coupling part 250, remains the same as that of the EDM filters 400, 500 and 600 of the fifth through seventh embodiments. Furthermore, as shown in FIGS. 18 and 19, each outer coupling part 240 may be formed by an inward or outward curling method. Alternatively, the outer coupling part 240 may be formed by various methods that have been illustrated in the description of the prior embodiments, although this is not shown in the drawings. For example, the outer coupling part 240 may be formed by a seaming, bending or welding method in the same manner as that of the outer coupling part 140-1, 140-2 or 140-3 of the fifth, sixth or seventh embodiment.

[77] In detail, referring to FIGS. 18 and 19, the EDM filter 700 according to the eighth embodiment includes an inner perforated casing 20 which is made of metal and supports an inner filter unit 22, and an outer perforated casing 24, which is made of metal and supports therein an outer filter unit 26 which is provided around the inner filter unit 22 at a position spaced apart from the inner filter unit 22 by a predetermined distance. The EDM filter 700 further includes upper and lower covers 30 and 32 which are primarily adhered to the respective opposite ends of the inner and outer filter units 22 and 26 by adhesive 28. A bent end 30a, 32a and a support ring part 30b, 32b are formed in each of the upper and lower covers 30 and 32 by bending so as to define an adhesive space into which the adhesive 28 is applied. A cooling water supply port 30c is formed in the upper cover 30.

[78] Here, the upper and lower covers 30 and 32 and the inner perforated casing 20 are coupled to each other by an inner coupling part 250. To form the inner coupling part 250, the inner perforated casing 20 is disposed through and supported by the support ring parts 30b and 32b of the upper and lower covers 30 and 32. Extension ends 20a are provided on the respective opposite ends of the inner perforated casing 20. Each extension end 20a extends to a position higher than the upper surface of the upper cover 30 or to a position lower than the lower surface of the lower cover 32. The extension ends 20a are brought into close contact with the corresponding surfaces of the upper and lower covers 30 and 32 by bending the extension ends 20a, thus completing the construction of the inner coupling part 250.

[79] Furthermore, the upper and lower covers 30 and 32 and the outer perforated casing

24 are integrally coupled to each other by the outer coupling parts 240. Each outer coupling part 240 includes a second coupling end 144 which is bent from the corresponding bent end 30a, 32a in the vertical direction such that it extends from the corresponding bent end 30a, 32a to a position higher than the upper surface of the upper cover 30 or to a position lower than the lower surface of the lower cover 32. The outer coupling part 240 further includes a first coupling end 142, which is bent from the corresponding end of the outer perforated casing 24 in the vertical direction such that one surface of the first coupling end 142 is in surface contact with the corresponding surface of the second coupling end 144. The first and second coupling ends 142 and 144 are integrally coupled to each other by various methods.

[80] With regard to the construction of the inner coupling part 250, as shown in FIGS. 18 and 19, although the inner coupling part 250 has been illustrated as being constructed in such a way that the extension ends 20a of the inner perforated casing 20 are brought into close contact with the corresponding surfaces of the upper and lower covers 30 and 32 by the curling method, the inner coupling part 250 may be constructed not only by the curling method but also by various other methods, for example, a seaming or bending method (not shown). These methods are the same as those in the above-stated embodiments.

[81] Furthermore, each outer coupling part 240 according to the eighth embodiment can be formed not only by the inward or outward curling method shown in FIG. 18 or 19 but also by various other methods, for example, the seaming method (140-1), the bending method (140-2) and the welding method (140-3), as illustrated in the description of the fifth through seventh embodiments.

[82] Because of the above-mentioned construction, particularly, because of the construction of the inner and outer coupling parts 250 and 240, the EDM filter 700 according to the eighth embodiment can ensure reliable coupling force between the components constituting the EDM filter in the same manner as the fifth through seventh embodiments.

[83] As described above, in the EDM filter 400, 500, 600, 700 according to each of the fifth through eighth embodiments of the present invention, the opposite ends of the inner and outer filter units 22 and 26 are primarily adhered to the upper and lower covers 30 and 32 by the adhesive 28, and then the inner and outer perforated casings 20 and 24 are integrally coupled to the upper and lower covers 30 and 32 by the inner coupling part 150, 250 and by the outer coupling parts 140, 140-1, 140-2, 140-3, 240. Therefore, the EDM filter 400, 500, 600, 700 can reliably maintain the coupling force between the components. [84] Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.

Claims

[1] An EDM (electrical discharge machine) filter, comprising: an inner perforated casing to support an inner filter unit, the inner perforated casing being made of metal; an outer perforated casing to support an outer filter unit disposed around the inner filter unit at a position spaced apart from the inner filter unit by a predetermined distance, the outer perforated casing being made of metal; upper and lower covers adhered to respective opposite ends of the inner and outer filter units by adhesive, with a bent end and a support ring part formed in each of the upper and lower covers by bending so as to define an adhesive space into which the adhesive is applied, the upper cover having a cooling water supply port therein; and outer coupling parts integrally coupling the upper and lower covers to the outer perforated casing, each of the outer coupling parts comprising: a first coupling end extended and bent outwards from each of opposite open ends of the outer perforated casing; and a second coupling end bent from the corresponding bent end of the upper and lower covers in a shape overlapping the first coupling end, such that a depression is formed by the bent end and the second coupling end along an outer circumference of the bent end, wherein the first and second coupling ends are integrally coupled to each other.

[2] The EDM filter according to claim 1, wherein the first and second coupling ends of each of the outer coupling parts are integrally coupled to each other by a curling method.

[3] The EDM filter according to claim 1, wherein the first and second coupling ends of each of the outer coupling parts are integrally coupled to each other by a seaming method.

[4] The EDM filter according to claim 1, wherein the first and second coupling ends of each of the outer coupling parts are integrally coupled to each other by a welding method, wherein the welding method comprises one selected from between a seam welding method and a spot welding method.

[5] The EDM filter according to any one of claims 1 through 4, further comprising: an inner coupling part.

[6] The EDM filter according to claim 5, wherein the inner coupling part comprises: depressed support parts integrally extended and bent from the respective support ring parts of the upper and lower covers, with a discharge hole formed through each of the depressed support parts, and an insert hole formed through a central portion of each of the depressed support parts; a longitudinal bolt inserted into the insert holes of the depressed support parts; and a nut tightened over the longitudinal bolt.

[7] An EDM filter, comprising: an inner perforated casing to support an inner filter unit, the inner perforated casing being made of metal; an outer perforated casing to support an outer filter unit disposed around the inner filter unit at a position spaced apart from the inner filter unit by a predetermined distance, the outer perforated casing being made of metal; upper and lower covers adhered to respective opposite ends of the inner and outer filter units by adhesive, with a bent end and a support ring part formed in each of the upper and lower covers by bending so as to define an adhesive space into which the adhesive is applied, the upper cover having a cooling water supply port therein; an inner coupling part integrally coupling central portions of the upper and outer covers to the inner perforated casing, the inner coupling part including: horizontal extensions extending from the respective support ring parts of the upper and lower covers inwards such that a through hole is defined by each of the horizontal extensions; support plates seated onto and supported by the respective horizontal extensions, with a plurality of discharge holes and an insert hole formed through each of the support plates; a longitudinal bolt inserted into the insert holes of the support plates; and a nut tightened over the longitudinal bolt; and outer coupling parts integrally coupling perimeters of the upper and lower covers to the outer perforated casing such that the upper and lower covers and the outer perforated casing are prevented from separating from each other.

[8] The EDM filter according to claim 7, wherein each of the outer coupling parts comprises: a second coupling end bent from the corresponding bent end in vertical and horizontal directions such that the second coupling end extends from the bent end to a position higher than an upper surface of the upper cover or to a position lower than a lower surface of the lower cover; and a first coupling end bent from one of opposite open ends of the outer perforated casing in vertical and horizontal directions such that one surface of the first coupling end is in surface contact with a corresponding surface of the second coupling end, wherein the first and second coupling ends are integrally coupled to each other by a curling method.

[9] The EDM filter according to claim 7, wherein each of the outer coupling parts comprises: a second coupling end bent from the corresponding bent end in vertical and horizontal directions such that the second coupling end extends from the bent end to a position higher than an upper surface of the upper cover or to a position lower than a lower surface of the lower cover; and a first coupling end bent from one of opposite open ends of the outer perforated casing in vertical and horizontal directions such that one surface of the first coupling end is in surface contact with a corresponding surface of the second coupling end, wherein the first and second coupling ends are integrally coupled to each other by a seaming method.

[10] The EDM filter according to claim 7, wherein each of the outer coupling parts comprises: a coupling end extending from one of opposite open ends of the outer perforated casing in a vertical direction to a position higher than an upper surface of the upper cover or to a position lower than a lower surface of the lower cover such that a portion of the coupling end is in surface contact with an outer surface of the corresponding bent end of the upper and lower covers, the coupling end being bent inwards such that the coupling end is brought into close contact with the upper or lower surface of the corresponding upper or lower cover, thus integrally coupling the corresponding upper or lower cover to the outer perforated casing.

[11] The EDM filter according to claim 7, wherein each of the outer coupling parts comprises: a second coupling end bent from the corresponding bent end in a vertical direction such that the second coupling end extends from the bent end to a position higher than an upper surface of the upper cover or to a position lower than a lower surface of the lower cover; and a first coupling end bent from one of opposite open ends of the outer perforated casing in a vertical direction such that one surface of the first coupling end is in surface contact with a corresponding surface of the second coupling end, wherein the first and second coupling ends are integrally coupled to each other by a seam or spot welding method such that the first and second coupling ends are prevented from separating from each other.

[12] An EDM filter, comprising: an inner perforated casing to support an inner filter unit, the inner perforated casing being made of metal; an outer perforated casing to support an outer filter unit disposed around the inner filter unit at a position spaced apart from the inner filter unit by a predetermined distance, the outer perforated casing being made of metal; upper and lower covers adhered to respective opposite ends of the inner and outer filter units by adhesive, with a bent end and a support ring part formed in each of the upper and lower covers by bending so as to define an adhesive space into which the adhesive is applied, the upper cover having a cooling water supply port therein; an inner coupling part integrally coupling central portions of the upper and outer covers to the inner perforated casing, the inner coupling part including extension ends provided on respective opposite ends of the inner perforated casing which is disposed through and supported by the support ring parts of the upper and lower covers, the extension ends respectively extending to a position higher than an upper surface of the upper cover and to a position lower than a lower surface of the lower cover, the extension ends being locked to the corresponding surfaces of the upper and lower covers by bringing the extension ends into contact with the corresponding surfaces of the upper and lower covers; and outer coupling parts integrally coupling perimeters of the upper and lower covers to the outer perforated casing such that the upper and lower covers and the outer perforated casing are prevented from being separated from each other.

[13] The EDM filter according to claim 12, wherein each of the outer coupling parts comprises: a second coupling end bent from the corresponding bent end in vertical and horizontal directions such that the second coupling end extends from the bent end to a position higher than an upper surface of the upper cover or to a position lower than a lower surface of the lower cover; and a first coupling end bent from one of opposite open ends of the outer perforated casing in vertical and horizontal directions such that one surface of the first coupling end is in surface contact with a corresponding surface of the second coupling end, wherein the first and second coupling ends are integrally coupled to each other by a curling or seaming method.

[14] The EDM filter according to claim 12, wherein each of the outer coupling parts comprises: a second coupling end bent from the corresponding bent end in a vertical direction such that the second coupling end extends from the bent end to a position higher than an upper surface of the upper cover or to a position lower than a lower surface of the lower cover; and a first coupling end bent from one of opposite open ends of the outer perforated casing in a vertical direction such that one surface of the first coupling end is in surface contact with a corresponding surface of the second coupling end, wherein overlapping portions of the first and second coupling ends are integrally coupled to each other by a seam or spot welding method such that the first and second coupling ends are prevented from being separated from each other.

[15] The EDM filter according to claim 12, wherein each of the outer coupling parts comprises: a coupling end extending from one of opposite open ends of the outer perforated casing in a vertical direction to a position higher than an upper surface of the upper cover or to a position lower than a lower surface of the lower cover such that a portion of the coupling end is in surface contact with an outer surface of the corresponding bent end of the upper and lower covers, the coupling end being bent inwards such that the coupling end is brought into close contact with the upper or lower surface of the corresponding upper or lower cover, thus integrally coupling the corresponding upper or lower cover to the outer perforated casing.