Patent Description:
For example, PTL <NUM> describes a filter with a lug. The filter with a lug prevents occurrence of air leak caused by the gap between the filter and the filter frame. In the filter with a lug, the lug parts bonded to both ends of the filter are held and fixed between the filter frame and the prefilter frame. According to the configuration, no gap is formed between the filter and the filter frame, so as to prevent the occurrence of air leak.

The filter with a lug of PTL <NUM> has a lug part in the direction along the folding lines of the filter. Therefore, the occurrence of gaps on the left and right side surfaces on the upstream side of the filter frame can be prevented, but it is difficult to prevent air leak occurring at the corner part, which is the seam part of the upper or lower frame and the left or right frame of the filter frame.

The present invention has been made in consideration of the circumstances, and an object thereof is to provide an air filter that is capable of preventing air leak occurring at the corner part of the filter frame.

To solve the above problem, the air filter according to the present invention includes: a pleated filter material folded into a zig-zag form at folding lines along a first direction to have peak parts and valley parts arising alternately in a second direction perpendicular to the first direction, trapping fine particles in a gaseous matter flowing in a gas flow direction perpendicular to the first direction and the second direction; a filter frame being a rectangular filter frame including one pair of first frame materials facing each other in the second direction having end parts in the first direction, and one pair of second frame materials facing each other in the first direction having end parts in the second direction, opening in the gas flow direction and housing the pleated filter material, each of the first frame materials and each of the second frame materials being combined to provide an overlap part where each of the end parts of each of the first frame materials and each of the end parts of each of the second frame materials overlap each other; and a buffer material disposed between at least each of the second frame materials of the filter frame and the pleated filter material, held with the overlap part.

The problem is solved by an air filter with the features of claim <NUM>. The claims depending from claim <NUM> comprise further developments.

<CIT> discloses an air filter unit of the HEPA type having a filter core of zig-zag folded media enclosed by a four-sided frame having two side casings and two end casings. Each end casing includes a recess extending into the inwardly facing surface thereof and bounded on all four sides by marginal edge portions of the end casing. This document further discloses that the end flaps of the folded media are adhesively secured to the inwardly facing surfaces of the side casings and the recesses in the end casings are filled with an adhesive, initially in a flowable state and hardenable to a solid state.

<CIT> discloses a dust collection filter equipped with a filter element formed by folding a cloth-like filter medium in a zigzag state, a shape retaining peripheral frame body housing the filter element and the spaces interposed between the mutually opposed filtering surfaces of the filter element held to the folded state. In this regard, the filter element is constituted of a synthetic resin material and the peripheral frame body surrounding the outer periphery of the filter element and the spacers are constituted of the synthetic resin material of the same kind.

The air filter according to the present invention can prevent air leak occurring at the corner part of the filter frame.

A first embodiment of the air filter according to the present invention will be described with reference to the drawings.

<FIG> is a perspective view of an air filter <NUM> according to the present embodiment.

<FIG> is a partial cross sectional view of the air filter <NUM>.

<FIG> is a cross sectional view on the line III-III in <FIG>.

In the following description, the X direction in <FIG> is designated as a gas flow direction. The Z direction is designated as a vertically downward direction, and the inverse direction to the Z direction is designated as a vertically upward direction. The Y direction is designated as a horizontally leftward direction, and the inverse direction to the Y direction is designated as a horizontally rightward direction.

The air filter <NUM> has a performance, for example, of a HEPA (high efficiency particulate air) filter. A HEPA filter is a filter that has a trapping efficiency of <NUM>% or more at a rated air capacity to particles having a particle diameter of <NUM>, and an initial pressure loss of <NUM> Pa or less. The air filter <NUM> can be applied to various purposes of cleaning a gas at a high temperature. The air filter <NUM> is applied, for example, to cleaning of an exhaust gas discharged from an incinerator and cleaning of air in a drying furnace for drying components used in a semiconductor production process and a sterilization furnace for sterilizing medical devices. The air filter <NUM> is installed, for example, in midstream of a flow channel for a gas flow connected to the aforementioned furnace in incineration facilities, semiconductor production facilities, hospitals, research facilities, and the like.

The air filter <NUM> includes a filter frame <NUM>, a pleated filter material <NUM>, a reinforcing plate <NUM>, a separator <NUM>, a seal material <NUM>, and a buffer material <NUM>.

The filter frame <NUM> is a rectangular frame member that opens in the gas flow direction and houses the pleated filter material <NUM>. The filter frame <NUM> is constituted by combining one pair of first frame materials <NUM> and one pair of second frame materials <NUM>. The first frame materials <NUM> face each other in the horizontal direction (second direction) and have end parts <NUM> in the vertical direction (first direction). The second frame materials <NUM> face each other in the vertical direction and have end parts <NUM> in the horizontal direction. The filter frame <NUM> has four overlap parts <NUM> where each of the end parts <NUM> of each of the first frame materials <NUM> and each of the end parts <NUM> of each of the second frame materials <NUM> overlap each other, so as to combine the first frame material <NUM> and the second frame material <NUM>. The first frame material <NUM> and the second frame material <NUM> are in contact directly or indirectly with each other in each of the overlap parts <NUM>.

The first frame material <NUM> and the second frame material <NUM> are connected and fixed with a connecting means, such as a bolt, in each of the overlap parts <NUM>, so as to constitute the filter frame <NUM>.

The filter frame <NUM> is preferably formed of a material having heat resistance. The filter frame <NUM> is formed, for example, of a metal, such as stainless, a stainless steel (such as SUS304 and SUS430), aluminum, an aluminum alloy, a steel, and ceramics. The stainless may be plated with zinc or aluminum. The filter frame <NUM> may include a film formed through an alumite treatment, a chromate treatment, or the like.

The pleated filter material <NUM> traps fine particles in a gaseous matter flowing in the gas flow direction. The pleated filter material <NUM> is formed by folding a filter material in a sheet form into a zig-zag form, and has peak parts and valley parts. The pleated filter material <NUM> has folding lines <NUM> along the vertical direction. The folding lines <NUM> form the peak parts and the valley parts appearing alternately in the horizontal direction. The pleated filter material <NUM> is disposed in the filter frame <NUM> in such a manner that the peak parts and the valley parts appear on the upstream side and the downstream side of the gas flow, respectively.

The pleated filter material <NUM> is, for example, a fibrous material formed of glass fibers, silica fibers, or mixed fibers thereof. The pleated filter material <NUM> has, for example, such a form as a nonwoven fabric, paper, a cotton-like material, or a mat. Specifically, the pleated filter material <NUM> may be formed of a glass nonwoven fabric, glass paper, glass wool, or the like formed of glass fibers. The pleated filter material <NUM> may contain a binder for adhering the fibers. The pleated filter material <NUM> may be held and supported between two sheets of breathable supports having heat resistance (such as metal meshes).

The reinforcing plate <NUM> is a flat plate having an approximately rectangular shape. The reinforcing plate <NUM> is inserted between the peak parts adjacent to each other of the pleated filter material <NUM>, i.e., inserted to the valley part thereof. The reinforcing plate <NUM> supports the positions in the vertical direction of the pleated filter material <NUM> and the other members. Specifically, the reinforcing plate <NUM> prevents the pleated filter material <NUM> and the separator <NUM> from being deformed (such as deviation and turnover) due to heat and from being deformed in the case where a physical force is applied thereto. <FIG> is a cross sectional view of the air filter <NUM> along the vertical direction for describing the reinforcing plate <NUM>.

The reinforcing plate <NUM> has one pair of edges <NUM> along the vertical direction and one pair of edges <NUM> along the gas flow direction. The lengths of the one pair of edges <NUM> along the vertical direction are approximately the same as the vertical length of the pleated filter material <NUM>. The reinforcing plate <NUM> is inserted to at least a part of the valley part of the pleated filter material <NUM>. The reinforcing plate <NUM> is disposed at a prescribed position of the air filter <NUM>, and a necessary number of plies of the reinforcing plates <NUM> may be disposed.

The reinforcing plate <NUM> has a thickness, for example, of <NUM> to <NUM>. The reinforcing plate <NUM> is formed, for example, of a metal. The reinforcing plate <NUM> that is formed of a metal supports the weight of the seal material <NUM> positioned upward, and prevents the seal material <NUM> from falling off. The thermal expansion coefficients (linear thermal expansion coefficients or linear expansion coefficients) of the reinforcing plate <NUM> and the filter frame <NUM> are preferably the same as each other. According to the configuration, for example, the breaking of the seal material <NUM> and the air filter <NUM> due to the effect of thermal expansion can be reduced.

In the case where the air filter <NUM> is used in a high temperature range as in a sterilization furnace or the like, the air filter <NUM> is exposed to a severe temperature change between stoppage and operation of the sterilization furnace. Under the repetition of the temperature change, the fibers of the seal material <NUM> are wasted to form a gap between the reinforcing plate <NUM> and the second frame material <NUM>, which may cause leak. For that problem, the air filter <NUM> has cutout parts <NUM> for the purpose of suppressing the occurrence of leak. The cutout parts <NUM> are formed on one pair of edges <NUM> along the gas flow direction, and each have a semicircular shape having an area increasing from both ends toward the center of each of the one pair of edges <NUM> along the gas flow direction. According to the configuration, the one pair of edges <NUM> along the gas flow direction each have contact parts <NUM> and a non-contact part <NUM> with respect to the seal material <NUM>. The contact parts <NUM> are formed on both the sides of the ends of the one pair of edges <NUM>, and each are formed to have a width of <NUM> to <NUM>. The non-contact part <NUM> is the other part than the contact parts <NUM>. The cutout parts <NUM> reduce the part where the reinforcing plate <NUM> comes into contact with the seal material <NUM>.

In the case where the cutout parts <NUM> are not provided, it is considered that the reinforcing plate <NUM> expands in the vertical direction and the gas flow direction through thermal expansion. In a large expansion thereof in the vertical direction, the reinforcing plate <NUM> thrusts the seal material <NUM>, and thereby the seal material <NUM> tends to crack. In the case where the cutout parts <NUM> are provided, however, the elongation direction through thermal expansion of the reinforcing plate <NUM> can be diffused to reduce the elongation in the vertical direction. According to the mechanism, the thrust of the reinforcing plate <NUM> through thermal expansion onto the seal material <NUM> can be reduced to prevent the breaking of the seal material <NUM>. Accordingly, even on repeated application of a high temperature, the reinforcing plate <NUM> suppresses the seal material <NUM> from being cracked, and prevents the leak from occurring.

The separator <NUM> is a member retaining the gap (valley part) between the peak parts adjacent to each other of the pleated filter material <NUM>. The separator <NUM> is formed, for example, of a metal, such as aluminum and a stainless steel. The separator <NUM> is preferably formed of aluminum or an aluminum alloy for weight reduction. The separator <NUM> has a thickness, for example, of <NUM> to <NUM>. The separator <NUM> is formed through corrugation where the material is folded into a wave shape. The separator <NUM> is inserted to each of the other valley parts than the valley part having the reinforcing plate <NUM> inserted thereto among the valley parts of the pleated filter material <NUM>, in such a manner that the folding lines thereof are along the gas flow direction. The separator <NUM> has approximately the same vertical length as the vertical length of the pleated filter material <NUM>.

The seal material <NUM> (first and second seal materials) seals between at least a part of an inner surface <NUM> of the filter frame <NUM> (surface facing inward the air filter <NUM>) and a part of the pleated filter material <NUM> facing that part. In the air filter <NUM> of the present embodiment, the seal material <NUM> seals between each of the second frame materials <NUM> and the pleated filter material <NUM>. The pleated filter material <NUM> can come into surface contact with each of the first frame materials <NUM> through thrust of the separator <NUM>, but comes into line contact with each of the second frame materials <NUM>, failing to achieve surface contact. For preventing the leak between each of the second frame materials <NUM> and the pleated filter material <NUM>, the seal material <NUM> is preferably provided between each of the second frame materials <NUM> and the pleated filter material <NUM>. Due to the seal material <NUM> provided, the air filter <NUM> can exert a higher leak prevention effect than the case where only the buffer material <NUM> is provided between the filter frame <NUM> and the pleated filter material <NUM>.

For suppressing the breaking of the seal material <NUM> due to the difference in thermal expansion amount from the filter frame <NUM> in the case where the air filter <NUM> is used in a high temperature range, it is considered to form the seal material <NUM> with a ceramic material that is regulated to have the same linear thermal expansion coefficient as the linear thermal expansion coefficient of the filter frame <NUM>. However, the degree of freedom in selecting the material of the seal material <NUM> is restricted thereby. Furthermore, there are cases where materials that have the same linear expansion coefficient in a certain temperature range have different linear thermal expansion coefficients in another temperature range, and there is a concern that the difference in thermal expansion amount cannot be suppressed consequently. Moreover, in the case where a ceramic material having a linear expansion coefficient that is different from the linear expansion coefficient of the filter frame <NUM> is used as the seal material <NUM>, there is a concern that in the case where the air filter <NUM> is used at a high temperature, cracks occur on the surface of the seal material <NUM>, and fine particles of the seal material <NUM> are released from the cracks and flow downstream.

The seal material formed of a ceramic material is generally obtained by coating a ceramic material in the form of paste on the filter material, followed by sintering. The present inventors have found that cracks of the seal material are formed in sintering the ceramic material, and dust emission from the ceramic material in use occurs due to the cracks. It has also been found that the dust emission from the seal material can be suppressed by using the following material as the seal material <NUM>.

The seal material <NUM> is formed of a ceramic material that has a ratio of the linear expansion coefficient (JIS R1618:<NUM>) of the seal material <NUM> in a temperature range of <NUM> to <NUM> of <NUM> to <NUM>% with respect to the linear expansion coefficient (JIS Z2285:<NUM>) of the filter frame <NUM> in that temperature range. Examples of the ceramic material include materials containing silica, alumina, and zirconia. It is preferred that the ceramic material does not contain crystalline silica (such as cristobalite) from the standpoint of preventing a carcinogenic material from being contained therein.

The seal material <NUM> is formed, for example, by sintering a ceramic material in the form of paste or liquid. The seal material <NUM> of this type may have thereinside cracks occurring in sintering the ceramic material in some cases. The cracks have an effect of relaxing the stress inside the seal material <NUM> to suppress cracks newly occurring in use. In the case where the cracks do not reach the surface of the seal material <NUM>, dust emission therefrom does not occur in use, and therefore even when the seal material <NUM> has cracks thereinside, the air filter <NUM> can be used.

It is preferred that the ceramic material of the seal material <NUM> does not contain crystalline silica, contains amorphous silica and alumina, and is formed by sintering a ceramic material in the form of paste having a viscosity at room temperature (<NUM>) of <NUM>,<NUM> to <NUM>,<NUM> mPa·s. The crystalline silica is silica having a crystal structure of SiO<NUM>. The amorphous silica is silica having no crystal structure of SiO<NUM>. The ceramic material does not contain crystal silica, but contains amorphous silica or alumina, thereby facilitating the regulation of the thermal expansion coefficient of the seal material <NUM>. The ceramic material has a viscosity at room temperature in the aforementioned range, and thereby is prevented from penetrating to the interior of the buffer material <NUM> before sintering. Accordingly, the function of the buffer material <NUM> described later allowing the seal material <NUM> to expand or contract after sintering can be favorably exhibited.

The ceramic material having a viscosity in the aforementioned range at room temperature can be readily coated to a uniform thickness on the filter frame <NUM>, and thereby the sintered seal material <NUM> can be suppressed from suffering unevenness in thickness and formation of pores. The components of the ceramic material in the form of paste except for water preferably contain amorphous silica and alumina in an amount of <NUM>% by mass or more. The viscosity thereof at room temperature is preferably <NUM>,<NUM> to <NUM>,<NUM> mPa·s.

The temperature range of <NUM> to <NUM> is a temperature range of the atmosphere where the air filter <NUM> can be used. The temperature range is preferably <NUM> to <NUM>. It suffices that the atmospheric temperature in use of the air filter <NUM> has the maximum temperature in the aforementioned temperature range, and for example, may be less than <NUM> at the beginning of use. The ratio of the linear expansion coefficient of the seal material <NUM> with respect to the linear expansion coefficient of the filter frame <NUM> described above is calculated from the linear expansion coefficients of the filter frame <NUM> and the seal material <NUM> at the same temperature within the aforementioned temperature range. In the present embodiment, the ratio is <NUM> to <NUM>%, and thereby the degree of freedom in selecting the combination of the filter frame <NUM> and the seal material <NUM> is enhanced. In the case where the ratio exceeds <NUM>%, the thermal expansion of the seal material <NUM> along the filter frame <NUM> (along the horizontal direction, which is the longitudinal direction of the seal material <NUM>) is restricted by each of the first frame materials <NUM>, and thereby the compression stress is increased to cause a concern of breaking. In the case where the ratio is less than <NUM>%, the seal material <NUM> is pulled due to the too large thermal expansion amount of the filter frame <NUM> even though the buffer material <NUM> is provided, and thereby there is a concern that the cracks formed inside the seal material <NUM> proceed and appear on the surface of the seal material <NUM>. In the case where the cracks exist on the surface of the seal material <NUM>, fine particles of the seal material <NUM> are released from the wall surface in the cracked part of the seal material <NUM> in use of the air filter <NUM>, and contaminate the gaseous matter passing through the air filter <NUM> to the downstream side. The aforementioned ratio is preferably <NUM> to <NUM>%.

The linear expansion coefficient of the seal material <NUM> may be larger than the linear expansion coefficient of the filter frame <NUM>, may be equal to the linear expansion coefficient of the filter frame <NUM>, or may be smaller than the linear expansion coefficient of the filter frame <NUM>. In the case where the linear expansion coefficient of the seal material <NUM> is larger than the linear expansion coefficient of the filter frame <NUM>, the thermal expansion of the seal material <NUM> in the longitudinal direction (horizontal direction) is restricted with an appropriate force of each of the first frame materials <NUM>, which makes it difficult for the cracks of the seal material <NUM> to proceed. Therefore, the linear expansion coefficient of the seal material <NUM> is preferably larger than the linear expansion coefficient of the filter frame <NUM>.

Although the degree of freedom in selecting the combination of the filter frame <NUM> and the seal material <NUM> is enhanced, there are cases where the difference in thermal expansion amount between the filter frame <NUM> and the seal material <NUM> is increased depending on the selected combination thereof. However, the seal material <NUM> can expand or contract relative to the filter frame <NUM>, and thereby the cracks inside the seal material <NUM> can be suppressed from proceeding. Consequently, the dust emission can be effectively suppressed.

The linear expansion coefficient of the seal material <NUM> is also preferably <NUM>% or more and less than <NUM>% of the linear expansion coefficient of the filter frame <NUM> in a temperature range of <NUM> to <NUM>. The case where the linear expansion coefficient of the seal material <NUM> is smaller than the linear expansion coefficient of the filter frame <NUM> is disadvantageous since the aforementioned effect of suppressing the progress of the cracks by appropriately restricting the thermal expansion of the seal material <NUM> in the longitudinal direction with the first frame material <NUM> is difficult to achieve. However, the buffer material <NUM> is disposed to intervene between the seal material <NUM> and the filter frame <NUM> as described above, and therefore the effect of suppressing the progress of the cracks can be obtained even though the thermal expansion of the seal material <NUM> is not restricted by the first frame material <NUM>.

Among the materials of the filter frame <NUM>, for example, stainless has a larger linear expansion coefficient in a high temperature range than that in a low temperature range, and the thermal expansion amount of the filter frame <NUM> in use of the air filter <NUM> is larger than that in sintering. Accordingly, in the case where the seal material <NUM> is in contact with the filter frame <NUM>, the seal material <NUM> is largely pulled by the filter frame <NUM>, and the cracks of the seal material <NUM> readily proceed to cause dust emission. In the present embodiment, however, various ceramic materials having a smaller linear expansion coefficient than the stainless can be selected as the seal material <NUM> while selecting the stainless steel as the material of the filter frame <NUM>, and thus even in this case, the progress of the cracks of the seal material <NUM> can be suppressed to suppress dust emission.

The buffer material <NUM> is disposed between the second frame material <NUM> of the filter frame <NUM> and the seal material <NUM> (pleated filter material <NUM>). In the case where the filter frame <NUM> expands or contracts, the buffer material <NUM> follows the expansion or contraction thereof, so as to retain the sealability between the pleated filter material <NUM> and the filter frame <NUM>. The expansion or contraction of the filter frame <NUM> means the expansion or contraction thereof in the direction in parallel to the surface direction of the filter frame <NUM> facing the seal material <NUM>. With the buffer material <NUM> disposed between the seal material <NUM> and the second frame material <NUM>, the seal material <NUM> can expand or contract in use of the air filter <NUM> without being restricted with the filter frame <NUM> and without being pulled by the filter frame <NUM>.

The buffer material <NUM> has ends <NUM> in the horizontal direction. The ends <NUM> are each extended to the overlap part <NUM> and held with the first frame material <NUM> and the second frame material <NUM>.

The buffer material <NUM> preferably has cushioning property and heat resistance, and is preferably formed, for example, of a fibrous material. The buffer material <NUM> formed of a fibrous material can readily expand and contact, and thus has a large effect of allowing the seal material <NUM> to expand or contact along the filter frame <NUM> (which may also be referred to as a buffer effect). The buffer material <NUM> formed of a fibrous material does not come into close contact with the filter frame <NUM>, and thus can secure the slipperiness to the filter frame <NUM>. Furthermore, in the case where the buffer material <NUM> in a compressed state is disposed between the seal material <NUM> and the filter frame <NUM>, the sealability between the seal material <NUM> and the filter frame <NUM> can be obtained with the repulsive force of the fibrous material. The fibrous material may be formed, for example, of glass, ceramics, or minerals. In addition, the buffer material <NUM> formed of a fibrous material can contract along with the seal material <NUM> in sintering the seal material <NUM>, and thereby an effect of suppressing the occurrence of cracks of the seal material <NUM> in sintering can also be obtained. In sintering the seal material <NUM>, the seal material <NUM> contracts, whereas the filter frame <NUM> expands. Accordingly, the buffer material <NUM> intervening between the seal material <NUM> and the filter frame <NUM> in sintering is effective therefor.

The ceramics are, for example, a material containing silica, alumina, zirconia, and the like. In the case where a binder is contained in the buffer material <NUM>, there is a concern that the binder is melted or decomposed in use and flows downstream, and therefore, no binder is preferably contained. The average fiber diameter of fibers constituting the fibrous material is, for example, <NUM> to <NUM>. The form of the buffer material <NUM> is, for example, a cotton-like form or a sponge form (porous form). Examples of the preferred buffer material <NUM> include glass wool and rock wool.

It is preferred that no other member is disposed between the buffer material <NUM> and the seal material <NUM>. Examples of the other member include a fibrous material in the form of sheet, such as filter paper and a nonwoven fabric. In the case where the member intervenes between the buffer material <NUM> and the seal material <NUM>, there is a concern that the effect of suppressing the occurrence of cracks in sintering the seal material <NUM> is decreased.

The air filter <NUM> particularly include a step of forming the seal material <NUM> and a step of disposing the buffer material <NUM>. The step of forming the seal material <NUM> and the step of disposing the buffer material <NUM> may be performed, for example, in the manner shown in the items (<NUM>) and (<NUM>) below.

The buffer material <NUM> is preferably disposed, for example, along the entire inner surface <NUM> of the second frame material <NUM>. The seal material <NUM> preferably has such a size that does not protrude from the buffer material <NUM>.

In the step of forming the seal material <NUM>, the seal material <NUM> in the form of paste or liquid may be spontaneously dried, but is preferably sintered at a high temperature. The sintering is performed, for example, in a dry atmosphere at <NUM> to <NUM>. At this time, the temperature is preferably increased to the sintering temperature at a temperature increasing rate of <NUM> to <NUM>/min for suppressing the occurrence of cracks of the seal material <NUM>. It is preferred that the seal material <NUM> in the form of paste does not contain crystalline silica, contains amorphous silica and alumina, and has a viscosity at room temperature (<NUM>) of <NUM>,<NUM> to <NUM>,<NUM> mPa·s, as described above.

In the case where the air filter <NUM> is produced in this manner, the thickness of the seal material <NUM> is preferably <NUM> to <NUM>. The thickness of the seal material <NUM> is preferably <NUM> to <NUM>. The thickness of the seal material <NUM> means the thickness thereof in the dry state (state after sintering). It has been found that the seal material <NUM> more readily causes cracks in sintering with a smaller thickness thereof. While a large internal stress occurs in the seal material <NUM> due to the contraction of the seal material <NUM> at the time when water escapes from the seal material <NUM> in sintering, it is considered that the thin seal material <NUM> cannot withstand the large internal stress. On the other hand, a too large thickness of the seal material <NUM> fails to achieve weight reduction of the air filter <NUM>.

The thickness of the buffer material <NUM> is preferably <NUM> to <NUM>. The thickness of the buffer material <NUM> is particularly preferably <NUM> to <NUM>.

There may be a large difference in expansion amount or contraction amount in the vertical direction between the pleated filter material <NUM> and the separator <NUM> in some cases. In these cases, with a too large thickness of the buffer material <NUM>, the buffer material <NUM> also contracts in the direction (vertical direction) perpendicular to the direction along the filter frame <NUM>. Therefore, in the case where the buffer material <NUM> receives forces from the pleated filter material <NUM> and the separator <NUM>, the cracks inside the seal material <NUM> readily proceed in the vertical direction to reach the surface of the seal material <NUM>. The seal material <NUM> thus readily emits dust thereby. In the case where the thickness of the seal material <NUM> is large, in particular, the number of positions where the dust emission occurs is increased since there are large wall surfaces in the cracked parts of the seal material <NUM>. In the case where the thickness of the buffer material <NUM> is too large, furthermore, the seal material <NUM> moves downward due to the own weight thereof to compress the buffer material <NUM> against the filter frame <NUM>. Accordingly, a gap occurs on the opposite side, i.e., between the buffer material <NUM> facing the second frame material <NUM> on the upper side and the second frame material <NUM> on the upper side, which causes a concern that leak occurs. This problem becomes conspicuous particularly in the case where the thickness of the seal material <NUM> is large. In this standpoint, the ratio of the thickness of the seal material <NUM> with respect to the thickness of the buffer material <NUM> is preferably <NUM> or more, and more preferably <NUM> or more.

In the case where the thickness of the buffer material <NUM> is too small, on the other hand, there are cases where the seal material <NUM> locally reaches the filter frame <NUM> and comes into contact with the filter frame <NUM>, in coating the seal material <NUM> in the form of paste. In these cases, the buffer function of the buffer material <NUM> is restricted to cause a concern that the progress of the cracks of the seal material <NUM> cannot be sufficiently suppressed. In the case where the thickness of the buffer material <NUM> is too small, the repulsive force thereof under compression between the seal material <NUM> and the filter frame <NUM> is weak, and a gap occurs between the seal material <NUM> and the filter frame <NUM> to cause leak in some cases. From this standpoint, the aforementioned ratio is preferably <NUM> or less, and more preferably <NUM> or less.

The thickness of the buffer material <NUM> means the average value of the thicknesses measured at plural (three or more) positions along the longitudinal direction (horizontal direction) of the buffer material <NUM> disposed between the seal material <NUM> and the filter frame <NUM>. The thickness of the buffer material <NUM> can be measured, for example, with a vernier caliper.

The filter frame <NUM> has a corner part <NUM> formed in the overlap part <NUM>. The corner part <NUM> is formed on the side of the inner surface <NUM> of the filter frame <NUM>, and is a part where the first frame material <NUM> and the second frame material <NUM> perpendicularly cross each other. On the corner part <NUM>, the pleated filter material <NUM> is disposed gas tightly on the filter frame <NUM> via the buffer material <NUM> and the seal material <NUM>. However, more than a little gap is formed between the corner part <NUM> and the buffer material <NUM> or the seal material <NUM>, resulting in a concern that air leak occurs at the corner part <NUM>. In the case where the filter frame <NUM> is formed of a metal, in particular, there is a concern that air leak occurs.

In the air filter <NUM> of the present embodiment, on the other hand, the buffer material <NUM> is extended to the overlap part <NUM> and held with the first frame material <NUM> and the second frame material <NUM>. According to the configuration, the buffer material <NUM> can favorably prevent the formation of the gap and can suppress the air leak. As a result, the air filter <NUM> can suppress the decrease in trapping efficiency occurring locally at the corner part <NUM>.

Furthermore, only the dimensional change of the buffer material <NUM> provided for buffering is performed without use of another configuration, and therefore the air leak at the corner part <NUM> can be readily prevented without increasing the number of components of the air filter <NUM>.

While some embodiments of the present invention have been described, the embodiments are merely shown as examples, and do not intend to restrict the scope of the invention. These novel embodiments can be practiced by various other modes, and various omissions, substitutions, and changes may be made therein unless they deviate from the substance of the present invention. These embodiments and modifications thereof are encompassed in the scope and the substance of the present invention, and are also encompassed in the inventions described in the claims and the equivalent ranges thereof.

For example, the buffer material <NUM> may be provided between the pleated filter material <NUM> and the first frame material <NUM>, and may be provided between the pleated filter material <NUM> and both the first frame material <NUM> and the second frame material <NUM>. The buffer material <NUM> may also have the function of the seal material <NUM>.

The seal material <NUM> may be constituted, for example, by a geopolymer, glass wool, or urethane, other than the ceramic material.

The air filter <NUM> may include a filling material used in the overlap part <NUM> for further reducing the air leak. <FIG> is a cross sectional view showing an air filter 1a as a modified example corresponding to <FIG>. The configurations and the parts thereof corresponding to the air filter <NUM> are attached with the same symbols, and redundant descriptions therefor are omitted.

The air filter 1a includes a filling material <NUM> that is further disposed in the overlap part <NUM> in addition to the buffer material <NUM>. Specifically, the filling material <NUM> is held between the first frame material <NUM> and the second frame material <NUM> in the overlap part <NUM>, and fills the gap in the overlap part <NUM>. The filling material <NUM> is formed of a material capable of filling the gap in the overlap part <NUM>, and is formed, for example, of the similar filter paper to the pleated filter material <NUM>, a sintered article of long fibers, or a foamed article.

The filling material <NUM> may be disposed between the buffer material <NUM> and the second frame material <NUM>. In alternative, the filling material <NUM> may be disposed between the separator <NUM> and the first frame material <NUM>. The filling material <NUM> is preferably disposed on the buffer material <NUM> in the overlap part <NUM> on the side of the first frame material <NUM> and the bolt for clamping the first frame material <NUM>. In clamping with the bolt, there is a concern that the fibers of the buffer material <NUM> are entangled on the bolt, inhibiting the clamping and releasing of the bolt. The filling material <NUM> is disposed between the bolt and the buffer material <NUM>, thereby preventing the buffer material <NUM> from being entangled on the bolt in inserting the bolt. The filling material <NUM> presses the fibers of the buffer material <NUM> for preventing the fibers of the buffer material <NUM> entangled on the bolt from being taken out along with the bolt in releasing the bolt.

The air filter 1a includes both the filling material <NUM> and the buffer material <NUM> existing in the overlap part <NUM>, and thereby the gap in the overlap part <NUM> is filled more effectively to prevent the air leak than the air filter <NUM>.

<FIG> is a cross sectional view showing an air filter 1b as another modified example corresponding to <FIG>. An air filter 1b includes a buffer material 60b having an end part 61b that is folded along the shape of the inner surface <NUM> of the filter frame <NUM> for further reducing the air leak. Specifically, the buffer material 60b has an angle part <NUM> formed by folding the end part 61b to the downward direction or the upward direction along the gas flow direction. The buffer material 60b is collapsed due to the cushioning property thereof in fabricating to form the overlap part <NUM> with the first frame material <NUM> and the second frame material <NUM>, so that the a part of the angle part <NUM> is held in the overlap part <NUM>. According to the configuration, the buffer material 60b securely covers the corner part <NUM> and the gap between the pleated filter material <NUM> and the seal material <NUM>, and thereby the air leak occurring from the corner part <NUM> can be further suppressed. The filling material <NUM> is disposed in the overlap part <NUM>.

While the embodiment has been described in which the cutout part <NUM> is formed in a semicircular shape, and the contact parts <NUM> are formed on one pair of edges <NUM> along the gas flow direction, the shape of the cutout part <NUM> is not particularly limited. For example, plural cutout parts <NUM> may be provided on one pair of edges <NUM> along the gas flow direction, and the cutout part <NUM> may have a rectangular shape or a polygonal shape, but not a semicircular shape.

<FIG> is a cross sectional view of an air filter 1c along the vertical direction for describing another reinforcing plate 30c corresponding to <FIG>. The configurations and the parts thereof corresponding to the air filter <NUM> are attached with the same symbols, and redundant descriptions therefor are omitted.

The reinforcing plate 30c has cutout parts 35c each having an approximately rectangular shape, so as to form contact parts 36c and a non-contact part 37c on each of one pair of edges <NUM> along the gas flow direction. At the time when the air filter 1c is at a high temperature, it is considered that the expansion of the reinforcing plate 30c at the cutout part 35c occurs in the directions perpendicular to the edges constituting the periphery of the cutout part 35c, i.e., in the vertical direction and the gas flow direction. According to the configuration, the contact parts 36c can be reduced, and the thrust of the reinforcing plate 30c onto the seal material <NUM> can be reduced similarly to the reinforcing plate <NUM>. Consequently, the breaking of the seal material <NUM> in the air filter 1c can be prevented.

It is considered that the linear part constituting the periphery of the cutout part thermally expands in the direction perpendicular to the linear direction thereof, and the curved part thermally expands in the centrifugal directions. In the case where one pair of edges <NUM> along the gas flow direction each are cutout in a semicircular shape, it is considered that the reinforcing plate thermally expands in the centrifugal directions from the cutout part (i.e., in the directions not along the vertical direction), and thereby the force pressing the seal material <NUM> in the vertical direction is dispersed and reduced. According to the configuration, the reinforcing plate can further prevent the breaking of the seal material <NUM> in the case where the cutout part <NUM> having a semicircular shape having no part perpendicular to the vertical direction is provided.

The pleated filter material <NUM> comes into surface contact at end parts in the horizontal direction with each of the first frame materials <NUM> through thrust of the separator <NUM> as described above, and a presser plate may be provided for further sealing the contact surface.

<FIG> is an illustrative view showing an air filter 1d having a presser plate <NUM>. <FIG> is a cross sectional view on the line IX-IX in <FIG>. In <FIG>, for convenience of explanation, the first frame material <NUM> and the second frame material <NUM> are partially omitted from the illustration. The configurations and the parts thereof corresponding to the air filter <NUM> are attached with the same symbols, and redundant descriptions therefor are omitted.

The air filter 1d further includes, as compared with the air filter <NUM>, a right and left side seal material <NUM> and a presser plate <NUM>.

The right and left side seal material <NUM> (third seal material) seals between a part on the inner surface <NUM> of each of the first frame material <NUM> and an end part <NUM> in the horizontal direction of the pleated filter material <NUM> facing the part of the inner surface <NUM>. The right and left side seal material <NUM> is formed of the same material as the seal material <NUM> or glass fibers.

The presser plate <NUM> compresses and holds the end part <NUM> of the pleated filter material <NUM> and the right and left side seal material <NUM>, which are closely in contact with the first frame material <NUM> thereby. The presser plate <NUM> is formed of a thin plate of a metal, such as stainless, that is folded to have an L-shape viewed in the vertical direction. The presser plate <NUM> includes a rise part <NUM> and a press part <NUM>.

The rise part <NUM> is disposed perpendicularly to the inner surface <NUM> of the first frame material <NUM>. The rise part <NUM> is disposed perpendicularly to the gas flow direction to cover the boundary between the right and left side seal material <NUM> and the end part <NUM> viewed from the upstream side. The rise part <NUM> has approximately the same vertical length as the vertical length of the pleated filter material <NUM>. The rise part <NUM> has a smaller horizontal length than the thickness (horizontal length) of the right and left side seal material <NUM> and the pleated filter material <NUM> under no load.

The press part <NUM> is a part that is formed by folding from an end part <NUM>, which is one of end parts in the horizontal direction of the rise part <NUM> that is located separately from the first frame material <NUM>, to the downstream side approximately perpendicularly to the rise part <NUM>. The press part <NUM> is inserted between the end part <NUM> and the separator <NUM> disposed in the valley part formed by the pleated filter material <NUM> including the end part <NUM>.

In the presser plate <NUM>, for example, an end part <NUM>, which is one of end parts in the horizontal direction of the rise part <NUM> that is located on the side of the first frame material <NUM>, is fixed to the inner surface <NUM> of the first frame material <NUM>. The presser plate <NUM> is fixed with various fixing means, such as welding and a screw. The presser plate <NUM> is preferably fixed through welding, for reducing the gap between the inner surface <NUM> and the presser plate <NUM>.

The presser plate <NUM> forms a housing space with the inner surface <NUM> of the first frame material <NUM>, the rise part <NUM>, and the press part <NUM>. The horizontal length of the rise part <NUM> is set to a smaller value than the thickness of the right and left side seal material <NUM> and the pleated filter material <NUM>, as described above. According to the configuration, the presser plate <NUM> houses in the housing space thereof the pleated filter material <NUM> and the right and left side seal material <NUM> under compression with the press part <NUM> in the direction toward the inner surface <NUM>. The right and left side seal material <NUM> and the pleated filter material <NUM> are pressed onto the inner surface <NUM> of the first frame material <NUM>. According to the configuration, sealability can be obtained in the gaps among the inner surface <NUM> of the first frame material <NUM>, the right and left side seal material <NUM>, and the pleated filter material <NUM>, and dust can be suppressed from entering into the gap between the first frame material <NUM> and the right and left side seal material <NUM>. The voids in the fibers of the right and left side seal material <NUM> formed of a fibrous material can be reduced by compressing the right and left side seal material <NUM>, thereby increasing the sealability.

In the case where the end part <NUM> of the pleated filter material <NUM> is extended from the upstream side to the downstream side toward the tip thereof, it suffices that the presser plate <NUM> is disposed in such a manner that the rise part <NUM> covers the boundary between the right and left side seal material <NUM> and the end part <NUM> viewed from the downstream side. The vertical length of the presser plate <NUM> may be shorter than the vertical length of the pleated filter material <NUM>, and the presser plate <NUM> may be disposed by dividing along the vertical direction.

The shape of the presser plate <NUM> is not limited to the above, and another shape may be used as far as sealability can be imparted to gaps among the inner surface <NUM> of the first frame material <NUM>, the right and left side seal material <NUM>, and the pleated filter material <NUM>.

For example, <FIG> is a cross sectional view of an air filter 1e having another presser plate 90e corresponding to <FIG>. The configurations and the parts thereof corresponding to the air filter <NUM> are attached with the same symbols, and redundant descriptions therefor are omitted.

The presser plate 90e includes a rise part 91e and a press part 95e. The rise part 91e is disposed perpendicularly to the inner surface <NUM> of the first frame material <NUM>. The rise part 91e is disposed perpendicularly to the gas flow direction to cover the boundary between the right and left side seal material <NUM> and the end part <NUM> viewed from the upstream side, along with the press part 95e. The rise part 91e has approximately the same vertical length as the vertical length of the pleated filter material <NUM>.

The press part 95e is a part that is formed by folding from an end part 93e, which is one of end parts in the horizontal direction of the rise part 91e that is located on the side of the first frame material <NUM>, to the downstream side. The press part 95e is folded in such a manner that it gradually opens in the direction away from the inner surface <NUM> of the first frame material <NUM>. According to the configuration, the press part 95e functions as a leaf spring pressing the end part <NUM> and the right and left side seal material <NUM> onto the inner surface <NUM>.

The presser plate 90e forms a housing space with the inner surface <NUM> of the first frame material <NUM> and the press part 95e. The horizontal length of the housing space (distance from the inner surface <NUM>) is gradually increased along the gas flow direction. The presser plate 90e has a larger force pressing the right and left side seal material <NUM> and the pleated filter material <NUM> onto the inner surface <NUM> than the presser plate <NUM> due to the spring property thereof, and thus can further enhance the sealability.

For further enhancing the sealability in the air filter 1e, the right and left side seal material <NUM> may be disposed between the presser plate <NUM> and the pleated filter material <NUM>. For example, <FIG> is a cross sectional view of an air filter 1f having another right and left side seal material 80f corresponding to <FIG>.

Claim 1:
An air filter (<NUM>) comprising:
a pleated filter material (<NUM>) folded into a zig-zag form at folding lines (<NUM>) along a first direction to have peak parts and valley parts arising alternately in a second direction perpendicular to the first direction, trapping fine particles in a gaseous matter flowing in a gas flow direction perpendicular to the first direction and the second direction;
a filter frame (<NUM>) being a rectangular filter frame including one pair of first frame materials (<NUM>) facing each other in the second direction having end parts (<NUM>) in the first direction, and one pair of second frame materials (<NUM>) facing each other in the first direction having end parts (<NUM>) in the second direction, opening in the gas flow direction and housing the pleated filter material (<NUM>), each of the first frame materials (<NUM>) and each of the second frame materials (<NUM>) being combined to provide an overlap part (<NUM>) where each of the end parts (<NUM>) of each of the first frame materials (<NUM>) and each of the end parts (<NUM>) of each of the second frame materials (<NUM>) overlap each other;
a buffer material (<NUM>) disposed between at least each of the second frame materials (<NUM>) of the filter frame (<NUM>) and the pleated filter material (<NUM>), held with the overlap part (<NUM>); and
a seal material (<NUM>) sealing between at least a part of an inner surface (<NUM>) of the filter frame (<NUM>) and a part of the pleated filter material (<NUM>) facing the part of the inner surface (<NUM>),
wherein the buffer material (<NUM>) is disposed to intervene between the seal material (<NUM>) and the filter frame (<NUM>), and allows the seal material (<NUM>) to expand or contract along the filter frame (<NUM>).