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(11) | EP 0 734 772 A1 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Filter for use in electrostatic type dust collector and method of manufacturing the same |
| (57) A filter for use in an electrostatic type dust collector including a flexible sheet-like
filtering member pleated into a corrugated configuration in such a manner that alternating
crest lines face toward an upstream side of a dust containing gas flow and the remaining
alternating crest lines face a downstream side of the gas flow, a first set of electrically
conductive or insulating spacers provided between successive facets of an upstream
side of the filtering member, and a second set of electrically conductive spacers
provided between successive facets of a downstream side surface of the filtering member.
The electrically insulating and conductive spacers serve to connect successive facets
to each other with keeping a given distance therebetween, and the electrically conductive
spacers also serve as electric conductors for applying an electric field. |
[0001] The present invention relates to a filter for use in an electrostatic type dust collector for cleaning dust containing air or other gases, and also relates to a method of manufacturing such a dust collecting filter. Related Art Statement
[0002] There have been known the following filters for cleaning dust containing gases:
(a) A so-called "electrostatic mini-pleat type filter" described in Japanese Patent Publication No. 2-61302, column 3, lines 19-31. This filter is used in an electrostatic type dust collector.
(b) A filter including a pleated or corrugated electrically insulating sheet-like filtering member, which is formed by applying an electrically insulating adhesive consisting of aqueous emulsion on front and rear surface of the filtering sheet at opposing positions, pleating the filtering sheet, and by drying an assembly of the filtering sheet and adhesive. In this filter, the adhesive serves to maintain a pleated or folded shape of the filtering sheet as well as a spacer for keeping a distance between successive facets of the pleated sheet.
(c) A filter having a pleated electrically insulating filtering sheet, which is manufactured by applying a strand made of natural fibers and having an insulating adhesive impregnated therein on front and rear surfaces of the filtering sheet at opposing positions, drying the adhesive, and pleating the sheet. In this filter, when the filtering sheet is pleated into a corrugated form, portions of the strand provided on opposing facets are adhered to each other so that the pleated shape is maintained. Further, the strand serve as a spacer for keeping a spacing between successive facets to a predetermined distance.
(d) An electrostatically charged type filter disclosed in Japanese Patent Publication No. 6-87994. An electrically conductive thread-like member such as a metal wire and a carbon fiber strand having an adhesive impregnated therein is applied on front and rear surfaces of an electrically insulating filtering sheet at opposing positions, and then the sheet is pleated into a corrugated shape. Also in this filter, the thread-like member serves as the adhesive and spacer.
(e) An electrostatically charged type filter described in Japanese Patent Publication No. 6-87997. An adhesive having electrically conductive powders dispersed therein is applied on front and rear surfaces of an electrically insulating filtering sheet, and then the sheet is pleated.
[0003] In the known filter (a), the conductive spacer or strand is inserted between successive facets of the pleated sheet and is secured to the sheet by means of the adhesive. Therefore, the conductive spacer is not directly brought into contact with the sheet, so that the filtering sheet could not be charged sufficiently. Moreover, an operation of inserting the conductive strand or spacer between successive facets and securing the strand onto the facets by the adhesive is very cumbersome and time consuming. Moreover, in this known filter, when the conductive spacer is provided on at least an upstream side facets of the pleated filtering sheet, there might occur the following problem:
[0004] Upon collecting dust in an air by the filtering sheet, floating dust particles are deposited on the upstream side facets, so that if the dust particles include electrically conductive particle or substances, an isolation between successive upstream side facets might be lost. Therefore, successive upstream side facets might be short-circuited and a sufficiently high electric field could not be applied to the facets, so that a dust collecting efficiency might be decreased. In this manner, this known filter has such a drawback that its dust collecting efficiency is reduced at an early time of usage.
[0005] The known filters (b) and (c), since the electrically conductive spacer is not used, the filtering sheet could not be electrostatically charged. Therefore, they could not be used in the electrostatic type dust collector to which the present invention relates.
[0006] In the known filter (d), the electrically conductive strands are applied on the front and rear surfaces of the filtering sheet not on opposing positions, but in a zigzag manner. Therefore, a mechanical strength of an assembly of the pleated sheet is rather low. Moreover, the conductive strand has a substantial rigidity, so that upon pleating the sheet, the strand might be broken. Further, since the conductive strand does not have adhesive nature inherently, it is rather difficult to maintain the pleated configuration. Therefore, in order to keep the desired corrugated shape, it is necessary to provide a separate spacer, and thus the filter might be large in size. The electrically conductive strand is covered with the electrically insulating adhesive and is not directly contacted with the filtering sheet, it is difficult to charge the filtering sheet sufficiently.
[0007] Also the known filter of (e), the electrically conductive adhesive is applied on the front and rear surfaces of the filtering sheet in a zigzag fashion at non-opposing positions, a mechanical strength of the pleated sheet is rather low. When use is made of the adhesive having conductive powders dispersed therein, the adhesive stripe might be broken during the pleating process and the electrical connection could not be attained. The same problem might occur after the pleating process.
Summary of the Invention
[0008] The present invention has for its object to provide a novel and useful filter for use in an electrostatic type dust collector, in which the above mentioned problems of the known filers of (a), (b) and (c) can be removed or at least mitigated.
[0009] According to the invention, a filter for use in an electrostatic type dust collector for collecting electrostatically charged floating particles in a dust containing gas flow passing through a charging section under a function of an electric field comprises:
an electrically insulating sheet-like filtering member pleated in a corrugated shape such that alternating crest lines face toward an upstream side of the dust containing gas flow and the remaining alternating crest lines face toward a downstream side of the dust containing gas flow;
a first set of plural electrically conductive spacers having electrically conductive adhesives and provided on an upstream side surface of the pleated sheet-like filtering member, successive facets of the upstream side surface of the filtering member being connected to each other by said electrically conductive spacers; and
a second set of plural electrically conductive spacers having electrically conductive adhesives and provided on a downstream side surface of the sheet-like filtering member at positions opposing to positions at which said first set of spacers are provided on the upstream side surface of the filtering member, successive facets of the downstream side surface of the filtering member being connected to each other by said electrically conductive spacers.
[0010] According to another aspect of the invention, a filter for use in an electrostatic type dust collector for collecting electrostatically charged floating particles in a dust containing gas flow passing through a charging section under a function of an electric field comprises:
an electrically insulating sheet-like filtering member pleated in a corrugated shape such that alternating crest lines face toward an upstream side of the dust containing gas flow and the remaining alternating crest lines face toward a downstream side of the dust containing gas flow;
a first set of plural electrically insulating spacers having electrically insulating adhesives and provided on an upstream side surface of the pleated sheet-like filtering member, successive facets of the upstream side surface of the filtering member being connected to each other by said electrically insulating spacers; and
a second set of plural electrically conductive spacers having electrically conductive adhesives and provided on a downstream side surface of the sheet-like filtering member at positions opposing to positions at which said first set of spacers are provided on the upstream side surface of the filtering member, successive facets of the downstream side surface of the filtering member being connected to each other by said electrically conductive spacers.
[0011] According to the invention, a method of manufacturing a filter for use in an electrostatic type dust collector collecting electrostatically charged floating particles in a dust containing gas flow passing through a charging section under a function of an electric field comprises the steps of:
applying an electrically conductive adhesive onto flexible thread-like members to form electrically conductive spacers each comprising a flexible thread-like member having the electrically conductive adhesive impregnated therein and an electrically conductive adhesive member applied on the flexible thread-like member:
providing said electrically conductive spacers on upstream and downstream side surfaces of a flexible electrically insulating sheet-like filtering member in parallel with each other at such positions that the electrically conductive spacers on the upstream side surface and the electrically conductive spacers on the downstream side surface are opposed to each other;
drying said electrically conductive adhesive members to such an extent that the electrically conductive adhesive members still have an adhesion and the electrically conductive adhesive is impregnated into the filtering member; and
pleating said flexible sheet-like filtering member into a corrugated configuration such that alternating crest lines face toward an upstream side of the dust containing gas flow, the remaining alternating crest lines face toward the downstream side of the dust containing gas flow, successive facets of the pleated filtering member are connected to each other by means of said electrically conductive adhesive members, and said electrically conductive spacers keep a desired constant distance between successive facets of the filtering member.
[0012] According to further aspect of the invention, a method of manufacturing a filter for use in an electrostatic type dust collector collecting electrostatically charged floating particles in a dust containing gas flow passing through a charging section under a function of an electric field comprises the steps of:
applying an electrically conductive adhesive onto flexible thread-like members to form electrically conductive spacers each comprising a flexible thread-like member having the electrically conductive adhesive impregnated therein and an electrically conductive adhesive member applied on the thread-like member, said electrically conductive adhesive being impregnated into the thread-like members:
providing said electrically conductive spacers on a downstream side surface of a flexible electrically insulating sheet-like filtering member in parallel with each other;
drying said electrically conductive adhesive members to such an extent that the electrically conductive adhesive members still have an adhesion and the electrically conductive adhesive is impregnated into the filtering member;
applying an electrically insulating adhesive onto flexible thread-like members to form electrically insulating spacers each comprising a flexible thread-like member having the electrically insulating adhesive impregnated therein and an electrically insulating adhesive member applied on the thread-like member, said electrically insulating adhesive being impregnated into the thread-like member:
providing said electrically insulating spacers on an upstream side surface of the flexible electrically insulating sheet-like filtering member in parallel with each other at such positions that the electrically insulating spacers on the upstream side surface and the electrically conductive spacers on the downstream side surface are opposed to each other;
drying said electrically conductive adhesive members and electrically insulating adhesive members to such an extent that the electrically conductive adhesive members and electrically insulating adhesive members still have an adhesion and said electrically insulating adhesive is impregnated into the filtering member such that said impregnated electrically conductive adhesive is covered with said impregnated electrically insulating adhesive; and
pleating said flexible sheet-like filtering member into a corrugated configuration such that alternating crest lines face toward an upstream side of the dust containing gas flow, the remaining alternating crest lines face toward the downstream side of the dust containing gas flow, successive facets of the upstream side surface of the pleated filtering member are connected to each other by means of said electrically insulating adhesive members, successive facets of the downstream side surface of the pleated filtering member are connected to each other by means of said electrically conductive members, and said electrically insulating spacers and electrically conductive spacers keep a desired constant distance between successive facets of the filtering member.
Brief Explanation of the Drawings
[0013]
Fig. 1 is a schematic perspective view showing an electrostatic type dust collector including a first embodiment of the filter according to the invention;
Fig. 2 is a perspective view illustrating the filter shown in Fig. 1;
Fig. 3 is a perspective view depicting a second embodiment of the filter according to the invention;
Fig. 4 is a schematic view showing the method of manufacturing the filter illustrated in Fig. 3; and
Fig. 5 is a perspective view depicting a part of the filter shown in Fig. 3 on an enlarged scale.
Description of the Preferred Embodiments
[0014] Fig. 1 is a schematic perspective view illustrating an electrostatic type dust collector using an embodiment of the filter according to the invention. A dust collector 1 comprises an electrostatically charging section 2 and a duct collecting section 3. In the charging section 2, a plurality of plate electrodes 4 are arranged equidistantly in parallel with a flow F of a dust containing gas to be cleaned. At middles points between successive plate electrodes 4 are arranged discharging wires 5. A high DC voltage source 6A is connected across the plate electrodes 4 and the discharging wires 5 as shown in Fig. 1, so that dust particles contained in the gas are charged. The thus electrostatically charged dust particles are collected in the dust collecting section 2 under a function of an electric field. To this end, the dust collecting section 2 comprises a filter having an electrically insulating sheet-like filtering member 7 which is pleated or folded in a corrugated fashion such that alternating crest lines 8 face toward an upstream side of a gas flow and remaining crest lines 9 face toward a downstream of the gas flow. Between successive facets of the pleated filtering member 7, there are provided electrically conductive spacers 10 (only upstream side spacer is shown in Fig. 1) such that the facets are separated from each other by a predetermined distance. According to the invention, the electrically conductive spacer is formed by a thread-like member having an electrically conductive adhesive applied thereon as well as impregnated therein. A high DC voltage source 6B is connected across successive conductive spacers 10 to produce an electric field along front and rear surfaces of the filtering member 7, said electric field serving to catch the charged dust particles in an electrostatic manner.
[0015] Fig. 2 is a perspective view illustrating the filter of the present embodiment. Electrically conductive spacers 11A and 11B are applied in parallel with each other on a upstream side or front surface of a flexible electrically insulating sheet-like filtering member 13 made of inorganic fibers such as glass fibers or synthetic resin fibers, and electrically conductive spacers 12A and 12B are applied on a downstream or rear surface of the filtering member 13 in parallel with each other. It should be noted that the spacers 11A and 12A are provided to be opposed to each other with interposing the filtering member and similarly the spacers 11B and 12A are opposed to each other. The spacers 11A, 11B and 12A, 12B include flexible thread-like members 16 and 17, respectively and electrically conductive adhesives 14 and 15, respectively. The adhesive members 14 and 15 are impregnated into the thread-like members 16 and 17, respectively. Successive facets of the filtering member 13 are cemented to each other by means of the conductive spacers 11A, 11B, 12A, 12B such that the flexible filtering member is kept in a pleated configuration. Further, the spacers 11A, 11B. 12A, 12B can serve as a spacer for keeping a distance of successive facets of the filtering member 13 to a given desired value. The mutually opposing conductive spacers 11A, 12A are connected to one terminal of the high DC voltage source 6B and the mutually opposing conductive spacers 11B, 12B are connected to the other terminal of the voltage source 6B.
[0016] Now a method of manufacturing the filter shown in Fig. 2 will be explained. An adhesive solution having a viscosity of 200-6000 cps is applied to the flexible thread-like members 16 and 17 to form the adhesive members 14 and 15. At the same time, the adhesive is partially impregnated into the thread-like members. The thread-like members 16 and 17 having the thus formed adhesive members 14 and 15 are adhered onto the front and rear surfaces of the filtering member 13 with the aid of rollers. A distance between adjacent spacers 11A, 12A and 11B, 12B should be determined in dependence upon an applied DC voltage.
[0017] If the distance is too small with respect to the applied voltage, electrostatic charges might leak and if the distance is too long width respect to the applied voltage, an amount of electrostatic charges might be small.
[0018] According to the invention, the thread-like member 16, 17 may be formed by a natural material thread such as cotton thread, hemp thread, silk thread and wool thread, and a synthetic resin thread such as polyester thread, vinylon thread, acrylic thread, nylon thread and tetlon thread. It should be noted that according to the invention, the thread-like member may be formed by a strand-like or stripe-like member made of paper, cloth and sponge or may be formed by rolling a paper, cloth or unwoven cloth into a string, in any shape of sectional view.
[0019] In the present embodiment, the electrically conductive adhesive is formed by adding carbon powders to a mixture of ethylene polyvinyl acetate and natural rubber. According to the invention, the electrically conductive adhesive may be formed by adding electrically conductive substances such as carbon black, metals of copper, nickel, stainless steel etc. in the form of powder and fiber to an aqueous emulsion of ethylene polyvinyl acetate, acryl, vinyl acetate, natural rubber and vinyldene chloride. It is possible to further add an incombustible agent.
[0020] In order to improve a charging property of the filtering member for increasing an amount of charge, it is preferable that the electrically conductive adhesive is impregnated into the thread-like member. Therefore, the viscosity of the adhesive is preferably set to 200-6000 cps. Furthermore, it is particularly preferable that the adhesive is immersed into the filtering member 13 and the opposing conductive adhesive members 14 and 15 are electrically connected to each other. When the carbon blacks and incombustible agent are added to the aqueous emulsion, an adhesive force is somewhat reduced. However, this decrease in an adhesive force can be compensated for by adding a natural rubber and bridging agent.
[0021] As soon as the thread-like members 16 and 17 having the adhesive members 14 and 15 impregnated therein and applied thereon are placed on the filtering member 13, the impregnation of the adhesive into a bulk of the filtering member begins. In this case, it is preferable that the adhesive has been impregnated into the filtering member over a desired depth before the drying process. However, it is sufficient that the adhesive is impregnated into the filtering member over the given depth in a finally assembled filter, so that prior to the drying process it is not always necessary that the adhesive has been impregnated over the given depth.
[0022] After securing the thread-like members 16 and 17 onto the filtering member 13 in parallel with each other, the drying process is carried out for 30-60 seconds at 100-300° C, and the adhesive members 14 and 15 are dried. During the drying process, the adhesive is impregnated into the filtering member 13 and the thread-like members 16 and 17 are firmly adhered onto the front and rear surfaces of the filtering members, respectively. Portions of the adhesive members 14 and 15 which are remote from the surfaces of the filtering member 13 are also dried to such an extent that they still have a desired adhesion. Immediately after the drying process, the filtering member 13 is pleated in to a corrugated configuration such that alternating crest lines of the pleated configuration face toward the upstream side of the gas flow G, and the remaining crest lines face toward the downstream side. During the pleating process, portions of the thread-like members provided on adjacent facets of the filtering member are cemented to each other as shown by a reference numeral 20. Therefore, according to the invention, the thread-like members 16 and 17 having the adhesive members 14 and 15 applied thereto can effectively serve as a binding or coupling member for maintaining the pleated configuration of the filtering member 13 as well as a spacer for keeping successive facets of the pleated filtering member to be separated from each other by a predetermined distance.
[0023] In the first embodiment explained above, it is possible to provide the thin and small filter having a high duct collecting efficiency for use in the electrostatic type dust collector. Further, the adhesive applied to the thread-like members 16 and 17 opposed to each other is impregnated into the bulk of the filtering member 13 in such a manner that a thick conductor region is formed by the mutually opposing conductive adhesive members 14 and 15 together with a portion of the filtering member into which the adhesive has been impregnated. Therefore, a voltage is applied to the bulk portion of the filtering member 13 to produce an electric field for effectively collecting dusts.
[0024] Furthermore, adjacent facets of the filtering member 13 are cemented to each other by means of the opposing adhesive members 14 and 15 applied on the thread-like members 16 and 17, a mechanical strength of the assembled filter is very high, and the filter is hardly deformed even if a rather strong force is applied in a lateral direction. Moreover, viewed at the crest lines of the pleated filtering member 13, there are formed relatively short conduction paths, so that a resistance becomes low and thus a decrease in the dust collecting efficiency due to a voltage drop along the conduction path can be reduced.
[0025] Since each of the spacers 11A, 11B, 12A and 12B is formed by the flexible thread-like member 16, 17 which is easily bent or curved and the adhesive member 14, 15 applied thereon, the spacer can be effectively prevented from being broken during the pleating process as well as during a usage. Further, the adhesive members 14, 15 formed by an aqueous emulsion are much more safe than a solvent type adhesive and also can save energy.
[0026] Now a second embodiment of the filter according to the invention will be explained with reference to Fig. 3. In Fig. 3, a reference numeral 21 denotes an upstream side electrically insulating spacer, a reference numeral 22 represents a downstream side electrically conductive spacer, and a reference numeral 23 shows an electrically insulating sheet-like filtering member made of inorganic fibers such as glass fibers or synthetic resin fibers. The electrically insulating spacer 21 comprises a thread-like member 28 and an electrically insulating adhesive member 27 applied on the thread-like member 28, and the electrically conductive spacer 22 includes a thread-like member 25 and an electrically conductive adhesive member applied on the thread-like member 25. Like as the previous embodiment, in the thread-like member 28, an electrically insulating adhesive is impregnated and in the thread-like member 25, an electrically conductive adhesive is impregnated. The electrically insulating spacer 21 and electrically conductive spacer 22 are adhered to an upstream side or front surface and a downstream side or rear surface of the filtering member 23, respectively at opposing positions. A high DC voltage is applied across adjacent electrically conductive spacers 22.
[0027] Now a method of manufacturing the filter of the present embodiment will be explained with reference to Figs. 4 and 5. The flexible thread-like members 25 having the electrically conductive adhesive members 24 applied thereon and impregnated therein are provided on the rear surface of the flexible sheet-like filtering member 23 in parallel with each other. Like as the previous embodiment, a distance between successive thread-like members 22 is determined suitably by considering the applied DC voltage. If the distance is too short, charges on the filtering member 23 might be leaked and if the distance is too long, an amount of charges might be reduced. The electrically conductive adhesive is made of an aqueous emulsion having conductive substances such carbon blacks and incombustible agent added thereto. In order to improve the charging property of the filtering member 23 to increase an amount of charges, it is preferable to impregnate the electrically conductive adhesive into a bulk of the filtering member. Therefore, the electrically conductive adhesive preferably has a viscosity of 200-6000 cps.
[0028] Immediately after applying the electrically conductive adhesive onto the thread-like members 25 to form the electrically conductive adhesive members 24, the thread-like members 25 are urged against the rear surface of the filtering member 23 in parallel with each other with the aid of a roller 26. As soon as the thread-like member 25 having the adhesive impregnated therein and applied thereon are placed on the filtering member 23, the impregnation of the adhesive into a bulk of the filtering member begins. In this case, it is preferable that the impregnation of the adhesive into the filtering member is effected over a desired depth before the drying process. However, it is sufficient that the adhesive is impregnated into the filtering member over the given depth in a finally assembled filter, so that prior to the drying process it is not always necessary that the adhesive has been impregnated over the given depth. In order to improve the dust collecting efficiency, the desired depth t1 is preferably set to a value not shorter than a half of a thickness of the filtering member 23. That is to say, t1≥(1/2)t, where t is a thickness of the filtering member 23. A decrease in an adhesive force due an addition of conductive substances such as carbon powders and incombustible agent may be compensated for by adding a natural rubber and bridging substances.
[0029] After the thread-like member 22 has been secured onto the filtering member 23, the drying process is carried out for 30-60 seconds at 100-300°C. Then, the electrically conductive adhesive member 24 is cemented onto the rear surface of the filtering member 23 and at the same time the adhesive members 24 is dried. Portions of the adhesive member 22 which are remote from the rear surface of the filtering member 13 are also dried to such an extent that they still have a desired adhesion. During the drying process, the electrically conductive adhesive is impregnated into a bulk of the filtering member 23.
[0030] Immediately after applying the electrically insulating adhesive onto the thread-like members 28 to form the electrically insulating members 27, the thread-like members 28 are secured onto the front surface of the filtering member 23 by means of a roller 29 at such positions that the thread-like members 28 are opposed to the previously adhered thread-like members 25. As soon as the thread-like members 28 having the electrically insulating adhesive members 27 applied thereon are placed on the filtering member 23, the impregnation of the electrically insulating adhesive into a bulk of the filtering member starts. In this case, it is preferable that the impregnation of the adhesive into the filtering member is effected over a desired depth before a second drying process. However, it is sufficient that the adhesive is impregnated into the filtering member over the given depth in a finally assembled filter, so that prior to the second drying process it is not always necessary that the adhesive has been impregnated over the given depth. This desired depth is preferably set to a value of t-t1, wherein t1 is the impregnation depth of the electrically conductive adhesive into the filtering member 23.
[0031] The electrically insulating adhesive member 27 is preferably formed by adding an incombustible agent to an aqueous emulsion and having a viscosity of 200-6000 cps. In the present embodiment, use is made of the incombustible adhesive having a viscosity of 3000 cps. In the present embodiment, the electrically insulating spacers 21 are provided after the electrically conductive spacers 22 have been applied on the filtering member 23. This is preferable for avoiding a possible short-circuit due an electrical connection between successive electrically conductive spacers 22 via conductive particles adhered onto the front surface of the filtering member, because the electrically conductive adhesive impregnated into the filtering member 23 is covered with the impregnated electrically insulating adhesive as illustrated in Fig. 5. It should be noted that the electrically insulating adhesive has a superior adhesive property than the electrically conductive adhesive, so that a mechanical strength of an assembled filter can be improved.
[0032] After applying the thread-like members 28 having the electrically insulating adhesive members 27 applied thereon onto the front or upstream side surface of the filtering member 23, a second drying process is carried out at 100-300°C for 30-60 seconds. Then, the electrically insulating adhesive is impregnated into the bulk of the filtering member 23 and the thread-like members 28 are secured to the filtering member. At the same time, the surfaces of the electrically insulating members 27 are also dried, but their adhesion property is not lost. It should be noted that although the electrically conductive adhesive members 24 are subjected to both the first and second drying processes, they do not loose the bonding property.
[0033] Immediately after the second drying process, the filtering member 23 is pleated into a corrugated configuration such that alternating crest lines 29 of the pleated configuration face toward the upstream side of the gas flow F, and the remaining alternating crest lines 30 face toward the downstream side. During the pleating process, portions of the thread-like members provided on adjacent facets of the filtering member are cemented to each other as shown by a reference numeral 31. Therefore, according to the invention, the thread-like members 25 28 having the electrically insulating adhesive members 27 applied thereto and the thread-like members 25 having the electrically conductive adhesive members 24 applied thereto can effectively serve as a binding or coupling member for maintaining the pleated configuration of the filtering member 23 as well as a spacer for keeping successive facets of the pleated filtering member to be separated from each other by a predetermined distance.
[0034] In the second embodiment of the filter according to the invention, the following advantages can be obtained in addition to the advantages of the first embodiment.
[0035] The electrically conductive adhesive is deeply impregnated into the sheet-like filtering member, and thus there are provided relatively thick conductive members. Therefore, a voltage can be applied to a deeper portion of the filtering member, so that a high dust collecting efficiency can be attained.
[0036] Since the electrically conductive adhesive impregnated into the filtering member is covered with the electrically insulating adhesive also impregnated into the filtering member, even when electrically conductive substances are deposited on the front surface of the filtering member, adjacent electrically conductive spacers are not short-circuited via these electrically conductive substances. Therefore, a decrease in an electric field strength hardly occurs and a high dust collecting efficiency can be maintained for a very long time.
[0037] Moreover, the electrically insulating adhesive is superior to the electrically conductive adhesive in the adhesion property, a mechanical strength of the filter of the present embodiment is superior to the first embodiment in which only the electrically conductive adhesive is used.
[0038] As explained above in detail, according to the invention, it is possible to provide the filter for use in the electrostatic type dust collector, in which the superior electrical property of the filter can be maintained for a long time of usage, and at the same time a mechanical strength is so high that the pleated configuration could not be broken easily.
an electrically insulating sheet-like filtering member pleated in a corrugated shape such that alternating crest lines face toward an upstream side of the dust containing gas flow and the remaining alternating crest lines face toward a downstream side of the dust containing gas flow;
a first set of plural electrically conductive spacers having electrically conductive adhesives and provided on an upstream side surface of the pleated sheet-like filtering member, successive facets of the upstream side surface of the filtering member being connected to each other by said electrically conductive spacers; and
a second set of plural electrically conductive spacers having electrically conductive adhesives and provided on a downstream side surface of the sheet-like filtering member at positions opposing to positions at which said first set of spacers are provided on the upstream side surface of the filtering member, successive facets of the downstream side surface of the filtering member being connected to each other by said electrically conductive spacers.
an electrically insulating sheet-like filtering member pleated in a corrugated shape such that alternating crest lines face toward an upstream side of the dust containing gas flow and the remaining alternating crest lines face toward a downstream side of the dust containing gas flow;
a first set of plural electrically insulating spacers having electrically insulating adhesives and provided on an upstream side surface of the pleated sheet-like filtering member, successive facets of the upstream side surface of the filtering member being connected to each other by said electrically insulating spacers; and
a second set of plural electrically conductive spacers having electrically conductive adhesives and provided on a downstream side surface of the sheet-like filtering member at positions opposing to positions at which said first set of spacers are provided on the upstream side surface of the filtering member, successive facets of the downstream side surface of the filtering member being connected to each other by said electrically conductive spacers.
applying an electrically conductive adhesive onto flexible thread-like members to form electrically conductive spacers each comprising a flexible thread-like member having the electrically conductive adhesive impregnated therein and an electrically conductive adhesive member applied on the flexible thread-like member:
providing said electrically conductive spacers on upstream and downstream side surfaces of a flexible electrically insulating sheet-like filtering member in parallel with each other at such positions that the electrically conductive spacers on the upstream side surface and the electrically conductive spacers on the downstream side surface are opposed to each other;
drying said electrically conductive adhesive members to such an extent that the electrically conductive adhesive members still have an adhesion and the electrically conductive adhesive is impregnated into the filtering member; and
pleating said flexible sheet-like filtering member into a corrugated configuration such that alternating crest lines face toward an upstream side of the dust containing gas flow, the remaining alternating crest lines face toward the downstream side of the dust containing gas flow, successive facets of the pleated filtering member are connected to each other by means of said electrically conductive adhesive members, and said electrically conductive spacers keep a desired constant distance between successive facets of the filtering member.
applying an electrically conductive adhesive onto flexible thread-like members to form electrically conductive spacers each comprising a flexible thread-like member having the electrically conductive adhesive impregnated therein and an electrically conductive adhesive member applied on the thread-like member, said electrically conductive adhesive being impregnated into the thread-like members:
providing said electrically conductive spacers on a downstream side surface of a flexible electrically insulating sheet-like filtering member in parallel with each other;
drying said electrically conductive adhesive members to such an extent that the electrically conductive adhesive members still have an adhesion and the electrically conductive adhesive is impregnated into the filtering member;
applying an electrically insulating adhesive onto flexible thread-like members to form electrically insulating spacers each comprising a flexible thread-like member having the electrically insulating adhesive impregnated therein and an electrically insulating adhesive member applied on the thread-like member, said electrically insulating adhesive being impregnated into the thread-like member:
providing said electrically insulating spacers on an upstream side surface of the flexible electrically insulating sheet-like filtering member in parallel with each other at such positions that the electrically insulating spacers on the upstream side surface and the electrically conductive spacers on the downstream side surface are opposed to each other;
drying said electrically conductive adhesive members and electrically insulating adhesive members to such an extent that the electrically conductive adhesive members and electrically insulating adhesive members still have an adhesion and said electrically insulating adhesive is impregnated into the filtering member such that said impregnated electrically conductive adhesive is covered with said impregnated electrically insulating adhesive; and
pleating said flexible sheet-like filtering member into a corrugated configuration such that alternating crest lines face toward an upstream side of the dust containing gas flow, the remaining alternating crest lines face toward the downstream side of the dust containing gas flow, successive facets of the upstream side surface of the pleated filtering member are connected to each other by means of said electrically insulating adhesive members, successive facets of the downstream side surface of the pleated filtering member are connected to each other by means of said electrically conductive members, and said electrically insulating spacers and electrically conductive spacers keep a desired constant distance between successive facets of the filtering member.