Patent Application
20100247404
Most buildings are heated, cooled and ventilated using air forced through ducts and other confined air paths. It is common to filter the air upstream of a heating or cooling mechanism in order to remove particulate and gases from the air. Removal of these contaminants reduces wear and damage to the heating and cooling mechanisms, and it improves the air quality. For example, some contaminants are poisonous or harmful to the building's occupants. Others can damage or reduce the efficiency of the heating and cooling mechanisms, such as by building up to form a layer of insulation on a heat exchanger.
Conventionally, filtration of the air is accomplished by placing a filtration media in the air path so that air forced through the air path passes through the filter media. The filter media then removes contaminants by causing the air to pass through small, tortuous paths that strain particles, by electrostatic attraction and/or by chemical reaction. The filtration media is typically placed in a frame in the side walls of the air path, and that frame keeps the media from being carried along by the moving air. The air filter, which is the combination of the frame and the media, is removably mounted in the air path of the heating, cooling and ventilation system, and is replaced once its life span has been reached.
It is known that filter media can be placed in a planar configuration across the frame so that the plane of the media is perpendicular to the direction of air flow. It is also known that the effective surface area of the filter can be increased by “pleating” the media, which is forming alternating V-shaped bends (when viewed from the end of the media). Pleating media provides an overall thicker filter than with a planar media, but the gain in effective surface area substantially improves the filter's performance.
Conventional pleated filter media can be strong enough to support itself across the filter frame. However, some media are not strong enough to be self-supporting, so that a support structure must be used to prevent the filter from “blowing out”, which is where the force of the air pushes the media from its original position, possibly completely removing the media from the frame. Support structures used on pleated media include perforated material, such as aluminum, plastic, paperboard and steel. The support can be made of slit and expanded aluminum, for example, that is laminated to the downstream face of media that will be pleated and mounted in a frame.
Typically, support material for pleated media is positioned on the downstream face, which is the face of the media that encounters the air last as it flows through the filter. Downstream support for a pleated filter provides strength to the media without concern about the bonding strength of adhesives that attach the support to the media, which can be a problem with an upstream support.
The present invention relates to a pleated filter with a first layer of filtration media, a layer of support material, such as expanded metal, plastic netting or any other stiff, perforated material, and a second layer of filtration media on the opposite side of the support material as the first layer of filter media. All three layers are laminated together, such as by using adhesives, ultrasonic welding or any other known manner of mounting filtration media to support materials. By forming such a pleated filter, the manufacturer can form pleated filters with variations in the characteristics on opposite sides of the support material.
The support material provides the required stiffness and rigidity for the pleating process, which is carried out after the support layer is laminated between the two filtration media layers. The lamination process can include cold adhesives or hot melt lamination, thermal welding, ultrasonic welding or any other type of lamination.
It is also contemplated that there can be more than one upstream layer of filtration media combined with a support layer and one downstream layer of filtration media. Alternatively it is contemplated that there can be one upstream layer of filtration media combined with a support layer and more than one downstream layer of filtration media. Still further it is contemplated that there can be more than one upstream layer of filtration media combined with a support layer and more than one downstream layer of filtration media. Thus, one or more layers of filtration media can be attached on the upstream side of the perforated support layer and combined with one or more layers of filtration media attached to the downstream side of the perforated support layer.
Any combination of characteristics of the different layers is contemplated. For example, an upstream layer is contemplated to have a lower density than a downstream layer so that large particles are retained in the upstream layer and smaller particles are retained in the downstream layer. Alternatively, the upstream layer can have a high density and the downstream layer can have an electrostatic charge to restrain charged particles that pass through the first layer and the support layer. Still further, an upstream layer can have an electrostatic charge and a downstream layer can have activated carbon that reacts with chemicals in the air to remove the chemicals.
In describing the preferred embodiment of the invention which is illustrated in the drawings, specific terminology will be resorted to for the sake of clarity. However, it is not intended that the invention be limited to the specific term so selected and it is to be understood that each specific term includes all technical equivalents which operate in a similar manner to accomplish a similar purpose. For example, the word connected or term similar thereto are often used. They are not limited to direct connection, but include connection through other elements where such connection is recognized as being equivalent by those skilled in the art.
U.S. Provisional Application No. 61/163,589 filed Mar. 26, 2009 is incorporated in this application by reference. One embodiment of the invention is shown in
Any conventional particulate and vapor filtration media can be used to form the layers 10 and 14. Thus, filtration media includes, but is not limited to, slit and expanded paper, non-woven glass fibers and non-woven polymer fibers made by melt blowing, air or wet laying and spin bonding. Furthermore, the media can be further treated, such as by electrostatically charging the media, placing activated carbon or zeolite particles in the media to absorb or adsorb chemical vapors, one side of the media can be treated with titanium dioxide or a photocatalytic material can be used to treat the media. Of course, other treatments of the media can be carried out in order to have effects known by the person of ordinary skill.
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The filtration media layers on the upstream and downstream sides of the support layer can be laminated together and to the support layer using adhesives such as cold glue or hot melt. Current lamination technology, which is designed to laminate one layer of media to one side of a support layer, must be modified to allow for lamination of two layers on opposing faces of a support layer, such as a support layer made of expanded metal. When plastic netting is used as the support layer, other lamination techniques can be utilized such as thermal bonding or ultrasonic bonding.
The support layer preferably exhibits low resistance to airflow passing through the media while providing the stiffness needed to retain a shape after deformation of the filtration media to form pleats therein. The support layer material can be slit and expanded metal, netting or any conventional open support material. The support layer can be a bi-component netting in which one set of strands is made of one material and another set of strands is made of another material (e.g., one set is made of polyester and the other set is made of polyethylene).
The preferred thickness of plastic netting, such as PET, nylon or other polymers, used as a support layer is between about 0.010 inches and about 0.100 inches and more preferably between about 0.020 inches and about 0.040 inches. The preferred thickness of an expanded metal support layer, which can be made of steel or aluminum, is between about 0.004 inches and about 0.015 inches and more preferably between about 0.006 inches and about 0.010 inches.
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The present invention provides a filter manufacturer with a greater degree of freedom in selecting media for a given filter application, such as by combining media from different suppliers. Currently manufacturers are limited in their designs of composite filters, because if they purchase multiple layered media, they have to accept the media as it comes and generally they cannot alter its properties. With the present invention, a manufacturer can design a composite filter to fit virtually any application, because it can purchase filter media with specific performance characteristics and, because the manufacturer attaches the media to the support layer, it can modify the media prior to attaching to the support layer and other filtration media layers.
Upstream and downstream layers can be made of different materials or the same materials with different treatments. For example, synthetic nonwoven materials (wet laid, dry laid, meltblown, spunbond), cellulose and glass fiber paper and metal fibers with a different function are all contemplated. As an example, an upstream layer can be made of a material to provide filtration against particulate matter, and it can also be electrostatically enhanced. Alternatively, the upstream layer can be a membrane or wetlaid paper.
A downstream layer can be made of a more efficient filtration material than the upstream layer to create a gradient density filter material with increased dust-holding capacity. The downstream layer can also have a different function than the upstream layer, such as odor and VOC removal (gas phase filtration), antimicrobial properties (treated with antimicrobial agents) and/or photocatalytic properties (treated with catalyst such as TiO2).
For example, one upstream layer can be made of thicker material with a more open structure and a downstream layer can be made of a thinner material that is more dense. The upstream layer can be treated to have adsorption properties based on activated carbon, zeolite or a material treated with an antimicrobial agent. A downstream and/or an upstream layer can be made of electrostatically enhanced materials or filter media based on mechanical filtration such as glass fibers or nanofibers.
The technology of the present invention can be utilized in residential and commercial heating, ventilation and air conditioning (HVAC) applications, and it can be used in portable air cleaners. The invention works with essentially any type of filtration media used for flowing a gas through, with some limitations on mass/weight and thickness of the material to retain the ability to be pleated.
It is preferred that the total thickness of the composite material formed in accordance with this invention (including all filtration media layers and the interposed support layer) be within a range from about 0.015 inches to about 0.500 inches and more preferably a range from about 0.025 inches to about 0.300 inches. Of course, the final thickness may vary with the requirements of the filter application.
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One contemplated filtration media has an upstream filtration media layer that provides particulate removal and a downstream filtration media layer that removes a gas phase, including a catalyst and an antimicrobial agent.
It should be noted that the filtration media layers and the support layer of each filter have lateral edges that define the outer boundaries of the respective layers. When laminated together, the lateral edges of each layer of filtration media are aligned with one another in each filter. The lateral edges of the support layer are aligned on the ends of the filter, but the sides can be withdrawn slightly, such as by about one-quarter to about one-half inch, from the sides of the filtration media. This substantial alignment of all layers of each filter provides a sufficient seal where the lateral edges of the filter are fixed, such as by adhesive, in a frame. The fact that the support layer can be up to about one-half inch inside of the filtration media does not substantially alter the function of the filter.
This detailed description in connection with the drawings is intended principally as a description of the presently preferred embodiments of the invention, and is not intended to represent the only form in which the present invention may be constructed or utilized. The description sets forth the designs, functions, means, and methods of implementing the invention in connection with the illustrated embodiments. It is to be understood, however, that the same or equivalent functions and features may be accomplished by different embodiments that are also intended to be encompassed within the spirit and scope of the invention and that various modifications may be adopted without departing from the invention or scope of the following claims.
| Number | Date | Country | |
|---|---|---|---|
| 61163589 | Mar 2009 | US |
