Abstract:
The present invention is directed to a magnetic duct cleaning hose clamp for attaching an airflow hose to a HVAC duct to be cleaned. The improved duct cleaning hose clamp includes: a planar clamp base; a plurality of magnets arranged around the periphery of the back surface of the clamp base; a compressible sealing member located between the magnetic attachment pads on the back surface of the clamp base; at least one handle portion extending from the front surface of the clamp base; a duct cleaning hose mounting portion protruding from the front surface of the clamp base; and a duct cleaning hose mounting portion defining an airflow aperture which is in fluid communication with a remote HVAC duct cleaning base unit. The present invention further includes magnetic duct access door of similar construction to the clamp. The magnetic access door provides for frequent access to a variety of different kinds of duct. The design of the improved clamp and the improved access door allow for creation of an efficient magnetic attraction seal with a metallic duct and easy manual removal of the clamps or access doors of the invention by tilting the clamp or access door via the handles on its front surface.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention is directed to an improved clamp for attaching a Heating, Ventilation and Air-Conditioning (HVAC) duct cleaning hose to an HVAC duct to be cleaned. More particularly, the invention is directed to a novel duct cleaning clamp that is inexpensive to manufacture, provides a strong sealing connection between hose and duct, and is more efficiently mounted to and removed from the duct. The invention is also directed to methods of manufacture and use of such improved duct cleaning clamps. Invention is still further directed to an improved duct access door for permanent, or semi-permanent installation on a duct for which frequent access for inspection or cleaning is required. 
         [0003]    2. Description of the Prior Art 
         [0004]    During operation of forced air HVAC systems, dust and other particulates including allergens, such as, mold spores, pollen, and pet dander can accumulate in the duct work over time. In order to ensure that the air circulated by the HVAC system is clean and promotes good health, the system duct work should be periodically cleaned so that such particulates, particularly any allergens, are removed from the ducts. In order to clean an HVAC duct, a duct cleaning technician typically creates a hole in the side of a duct and then clamps an airflow hose to the duct around the periphery of the hole. The hose is typically connected on its other end to a HVAC duct cleaning base unit. The function of the duct cleaning base unit is to create rapid airflow (using either negative or positive air pressure) within the duct in order to blow or suck the dust and other particulates from the interior of the duct. In many cases, two HVAC duct cleaning base units are used to clean a single duct run; one unit that blows air into the duct at an upstream location (near a return vent) and another that sucks air from the duct at a downstream location (nearer the HVAC unit air inlet). In order to efficiently clean the duct, the duct cleaning hose(s) must be sealed against the duct around the periphery of the hole so that the airflow provided by the hose(s) is directed entirely within the duct. In order to create that peripheral seal with the duct, the duct cleaning hose(s) typically attaches to a flange on a clamping device, which clamping device is in turn designed to create a seal with the duct peripheral to the hole. 
         [0005]    One commonly used prior art duct clamp is a “hinge clamp” which includes a plurality of mechanical hinges mechanisms located on the inner peripheral edge of flange portion of the clamp. The use of “hinge clamps” typically requires that the technician create a precisely dimensioned circular hole in the duct so that the hinging mechanisms are properly positioned to swing into an engagement position in which they grasp the interior wall of the duct adjacent to the hole. If the dimensions of the hole are inaccurate, one or more of the hinging mechanisms may fail to grasp the interior wall of the duct so that the clamp improperly seals, or in the worst case scenario, may even fall off during the cleaning operation. The creation of such a precisely dimensioned circular hole takes the technician a considerable amount of time. Also, patching circular holes after completion of the cleaning operation is more difficult and time consuming for the technician than patching square or rectangular holes. An alternate prior art clamp device is a “screw mount clamp” which utilizes a number of screws passing through a base portion of the clamp and then passing through to the interior of the duct. The mounting and removal of such “screwed mount clamps” typically require the technician to hold the clamp and hose with one hand while using a hand tool to mount the screws. The screws also create additional holes in the duct that need to be patched after the completion of the duct cleaning operation. Applicant has determined that the processes of installation and removal of both these styles of prior art clamps take longer than is desirable. Moreover, the “hinge style” duct clamping mechanisms of the prior art required a number of precision dimension tolerance metal parts and therefore were relatively expensive to manufacture. Although the “screw mount” prior art clamps were typically less expensive than the “hinge type” to manufacture, they usually where significantly more time consuming to install and remove from the duct. Despite these shortcomings of prior art clamps, past attempts to design and manufacture an inexpensive clamping device which can be efficiently installed and removed from the duct have failed. 
         [0006]    Another prior art duct cleaning clamp was designed to cover a HVAC air return grate. This product included a long pole that had a spring member attached to one end of the pole with a duct cleaning grate adapter attached to the other end. The cleaning unit hose attached to the middle of the duct grate adapter and the pole was the wedged between the floor and the location of the duct in an attempt to hold the duct cleaning grate adapter over the return grate. Such prior art spring-loaded duct cleaning grate adapters suffer from a number of difficulties. First, the spring-loaded duct cleaning grate adapters are difficult to install since frequently will push a return grate mounted in a suspension ceiling back up into the suspension area. This can damage the flexible return duct that is frequently used in suspension ceilings and can also damage the great or adjacent suspension tiles. Second, when installing a prior art spring-loaded duct cleaning adapter onto a wall mounted return grate, the pole and spring member were often times wobbly and unstable to the point that the adapter would fall off the grate during the cleaning operation. 
         [0007]    A related problem to those discussed above is providing access to ducts that need to be cleaned or inspected on a more frequent basis. Such frequent access ducts can be HVAC ducts or other ducts. For example, many industrial food processing facilities utilize frequent access ducts for ventilation of food processing areas or for delivery of particular materials to food processing equipment. One way that access is provided for frequent access ducts is to install a permanent or semi-permanent recloseable door on the duct. In a manner similar to the prior art duct cleaning clamping technology, the most commonly used access doors are of a “hinge style,” which requires installation a plurality of mechanical hinges mechanisms located on the inner peripheral edge of a flange portion of the access door. The use of such “hinge style access doors” typically requires that an installation technician create a precisely dimensioned circular hole in the duct so that the hinging mechanisms are properly positioned to engage the interior wall of the duct adjacent to the hole. If the dimensions of the hole are inaccurate, one or more of the peripheral hinging mechanisms may fail to grasp the interior wall of the duct so that the access door will improperly seal, or in the worst case scenario, may even fall off the duct. The creation of such a precisely dimensioned circular hole takes the technician a considerable amount of time. Applicant has perceived a need to provide a recloseable duct access door which is more economical to manufacture and more efficient and economical to install into on a frequent access duct. 
       OBJECTS OF THE INVENTION 
       [0008]    It is one object of the invention to provide a quick installation duct hose clamp that is less expensive to manufacture than prior art “hinge clamp” designs. 
         [0009]    It is a further object of the invention to provide a duct hose clamp that is more easily installed, removed, and allows for more efficient duct hole creation and patching than prior “hinge clamp” designs. 
         [0010]    It is another object of the invention to provide an easy to install and remove duct hose clamp that can accommodate duct holes of a variety of shapes and sizes. 
         [0011]    It is still further object of the invention to provide an inexpensive duct hose clamp that can be both installed and removed in a matter of seconds. 
         [0012]    It is still another object of the invention to provide a faster, more efficient method of cleaning HVAC ducts by use of a more efficiently installed and removed duct hose clamp. 
         [0013]    It is another object of the invention to provide a duct hose clamp that can be installed on certain types of duct work without having to cut any holes in the duct. 
         [0014]    It is still another further object of the invention to provide a method of cleaning a duct utilizing a duct hose clamp that can be efficiently mounted to a duct vent cover of predetermined dimensions thereby avoiding the necessity of cutting a hole in the sidewall of the duct. 
         [0015]    It is a still further object of the invention to provide a stable, easy to install duct grate cleaning adapter. 
         [0016]    It is a further object of the invention to provide a method to inexpensively manufacture a quick installation duct cleaning hose clamp. 
         [0017]    It is another object of the invention to provide a recloseable duct access door which is less costly to manufacture and more efficient and economical to install onto a frequent access duct. 
       SUMMARY OF THE INVENTION 
       [0018]    The present invention is directed to an improved duct cleaning hose clamp for attaching an airflow hose to a HVAC duct to be cleaned, the improved duct cleaning hose clamp includes: a planar clamp base; a plurality of magnets arranged around the periphery of the back surface of the clamp base; a compressible sealing member located between the magnetic attachment pads on the back surface of the clamp base; at least one handle portion extending from the front surface of the clamp base; a duct cleaning hose mounting portion protruding from the front surface of the clamp base; a duct cleaning hose mounting portion defining a central aperture which is in fluid communication with a remote HVAC duct cleaning base unit. The design of the improved clamp allows for creation of an efficient magnetic seal with a metallic HVAC duct and easy manual removal of the clamp by tilting the clamp via the handles on its front surface. The improved duct cleaning hose clamp is inexpensive to manufacture because it can be constructed primarily of molded thermoplastic parts, which significantly reduces manufacturing costs. In one preferred embodiment of the invention, the planar clamp base has a rim portion extending from its back surface, which helps to retain the sealing member and the plurality of magnets in place and to ensure a quality seal with the duct. In another preferred embodiment of the invention, the sealing gasket is an enlarged foam pad covering substantially the entire back surface of the clamp base peripheral to the central aperture (except for the portion of the back surface where the plurality of magnets are mounted), which allows for significant variance in the shape and size of the hole cut in the duct to receive the clamp. 
         [0019]    In another aspect of the invention, an improved duct cleaning hose clamp is provided which is designed to efficiently mount to metallic duct grates of predetermined standard sizes. The duct grate mountable cleaning hose clamps includes: a planar clamp base dimensioned to engage flat metallic portions of the duct grate of a metallic duct grate of a predetermined standard size; a plurality of magnets located on the back surface of the clamp base at locations which correspond to substantially planar metallic portions of the duct grate of a predetermined standard size in order to magnetically bond thereto after installation of the clamp thereon; at least one handle portion extending from the front surface of the clamp base; a hose mounting portion protruding from the front surface of the clamp base; a central aperture defined by the hose mounting portion for receipt of an airflow hose in fluid communication with a remote HVAC duct cleaning base unit; and a compressible sealing member located between the plurality of magnetic attachment pads on the back surface of the clamp base to create a seal with portions of the duct grate peripheral to the central aperture. 
         [0020]    In a still further aspect of the invention, an improved method of a cleaning a HVAC duct is provided, which includes the steps of: providing a HVAC duct cleaning base unit for causing high velocity airflow within the duct to be cleaned; attaching a duct cleaning hose to the duct cleaning base unit to transfer the airflow to the duct to be cleaned; providing a magnetically mountable duct cleaning hose clamp having a plurality of magnetics and having a sealing member disposed between the plurality of magnets; attaching the duct cleaning hose to the magnetically mountable duct cleaning hose clamp; placing the magnetically mountable duct cleaning hose clamp onto the duct to be cleaned so that the plurality of magnets attract the metallic duct and thereby compress the sealing member to create a seal between the clamp and duct; activating the HVAC duct cleaning base unit so that airflow is provided to the duct cleaning hose and directed through the mounted magnetically mountable duct cleaning hose clamp into the duct to be cleaned, removing particulates from the duct to be cleaned; and detaching the magnetically mountable duct cleaning hose clamp by first tilting the clamp relative to the now cleaned duct to break the magnetic attachment between at least a portion of the metallic duct and the plurality of magnets and then by pulling the clamp away from the duct. 
         [0021]    In another aspect of the invention, an improved method of a cleaning a HVAC duct having a metallic return grate of predetermined dimensions is provided, which includes the steps of: providing a HVAC duct cleaning base unit for providing airflow within the duct to be cleaned; attaching a duct cleaning hose to the duct cleaning base unit to transfer the airflow to the duct to be cleaned; providing a magnetically mountable duct cleaning hose clamp having a plurality of magnets spaced apart a predetermined distance to correspond to a plurality of flat metallic portions of the return grate and having a compressible sealing member arranged to be compressed by portions of the return grate to create a seal between the clamp and return grate; attaching the duct cleaning hose to the magnetically mountable duct cleaning hose clamp; placing the magnetically mountable duct cleaning hose clamp onto a return grate of predetermined dimensions so that the plurality of magnets attract portions of the return grate and thereby compress the sealing gasket onto portions of the return grate to create a seal between the clamp and return grate; activating the HVAC duct cleaning base unit so that high velocity airflow is provided to the duct cleaning hose, passes through the magnetically mountable duct cleaning hose clamp, the return grate and into the duct to be cleaned; removing particulates from the duct to be cleaned; and detaching the magnetically mountable duct cleaning hose clamp by first tilting the clamp relative to the return grate over the now cleaned duct to break the magnetic attachment between at least a portion of the return grate and the plurality of magnets and then by pulling the remainder of the clamp away from the return grate to brake the magnetic attachment between the remainder of the plurality of magnets and the return grate. 
         [0022]    Another embodiment of the invention provides an improved duct access door for providing temporary access to the interior of a duct during a reoccurring access event and for repeatedly sealing the duct after each access event, the improved duct access door comprising: a duct access door base having a front and back surface; a plurality of magnets arranged around the periphery of the back surface of the duct access door base; a compressible sealing member located between the plurality of magnetic attachment pads on the back surface of the duct access door base; and at least one handle portion extending from the front surface of the duct access door. In one preferred embodiment of the invention, the improved duct access door has a substantially planar duct access door base, which is designed for installation on square or rectangular ducts. In another preferred embodiment the invention, the improved access door has a duct access door base, which is substantially curvilinear with a radius of curvature matching the predetermined radius of curvature of the exterior of a duct. The duct access doors with the curvilinear duct access door base are designed for installation on round ducts or other ducts having curved exterior surfaces. Preferably, the duct access door base of the duct access doors of the invention are molded from a thermoplastic resin. It is also preferred that the duct access doors of the invention have a peripheral rim portion extending from their back surface for retaining the sealing member and the plurality of magnets to ensure a quality seal with the duct. The distance that the peripheral rim extends from the back surface of the duct access door base is also preferably less than the thickness of the compressible sealing member. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0023]      FIG. 1  is a front side, exploded perspective, view of a magnetic duct cleaning hose clamp in accordance with one embodiment of the invention. 
           [0024]      FIG. 2  is a front plan view of the magnetic duct cleaning hose clamp in accordance with the embodiment of  FIG. 1 . 
           [0025]      FIG. 3  is a rear plan view of the magnetic duct cleaning hose clamp of  FIG. 1 . 
           [0026]      FIG. 4  is a side plan view of the parts of the magnetic duct cleaning hose clamp in accordance with the embodiment of  FIG. 1 . 
           [0027]      FIG. 5  is a schematic view of the magnetic duct cleaning hose clamp of  FIG. 1  attached a duct cleaning base unit and duct. 
           [0028]      FIG. 6  is a schematic view of a rectangular clamp in accordance with an alternate embodiment of the invention that is attached to a duct cleaning each unit and duct. 
           [0029]      FIG. 7  is a perspective view of a magnetic, curvilinear duct cleaning clamp in accordance with another embodiment of the invention. 
           [0030]      FIG. 8  is a front side, exploded perspective, view of a magnetic duct access door in accordance with still another embodiment of the invention. 
           [0031]      FIG. 9  is a front side, exploded perspective, view of a magnetic curvilinear duct access door in accordance with a further embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0032]    The magnetic cleaning hose clamp  10  in accordance with the embodiment of  FIGS. 1-5  generally includes a planar clamp base  20 ; magnetic attachment pads  30  extending from the back surface  22  of the planar clamp base  20  with the magnetic pads  30  being located at the four corners of the back surface  22 ; a compressible sealing material  40  arranged between the magnetic attachment pads  30  on the periphery of the back surface  22 ; a rim  46  extending outwardly from the periphery of the back surface  22 ; handles  50  extending from the front surface  21  of the planar clamp base  20 ; and a hose mounting ring  60  protruding from the front surface  21  of the planar clamp base  20 , which mounting ring  60  defines a central aperture  62  to allow airflow to a remote HVAC duct cleaning device base unit  80 . The design of magnetic cleaning hose clamp  10  allows for creation of a strong magnetic seal against the metallic HVAC duct that can be installed in a matter of seconds. All that is necessary is to bring the magnetic cleaning hose clamp  10  within several inches of the duct cleaning hole  72  and the magnetic cleaning hose clamp is drawn instantaneously into strong contact with the peripheral area  74  surrounding the duct cleaning hole  72  which causes the compressible sealing gaskets  40  to form a virtually airtight seal with the duct  70 . Moreover, the magnetic cleaning hose clamps of the invention can be quickly and easily manual removal by tilting the clamp via the handles on its front surface until the force of magnetic attraction is broken along one side of the clamp. Further, duct cleaning hole  72  can be any shape or of any size that is smaller than the exterior dimensions of the planar clamp base  20 . This eliminates the need for the cutting of a precisely dimensioned circular duct access holes as was required for the prior art “hinge clamp” quick release duct cleaning hose clamps. 
         [0033]    Returning to  FIG. 1  in greater detail, planar clamp base  20 , rim  46  and hose mounting ring  60  are preferably injection molded in a single integral piece from a suitable thermoplastic resin. The preferred resin performing the planar clamp base  20 , rim  46  hose mounting ring  60  is poly carbon, but other strong, lightweight thermoplastic resins such as Poly-propylene may be used. Four pairs of holes are drilled into the planar clamp base  20  at each of its four corners for receipt of pad attachment fasteners  31 , and four handle attachment apertures  54  are also drilled in the planar clamp base  20 . The pad attachment fasteners  31  are preferably pop rivets, but nuts and bolts or machine screws may also be used to fasten the magnetic attachment pads  30  to the planar clamp base  20 . While forming the planar clamp base  20 , rim  46  and hose mounting ring  60  from thermoplastic is preferred for cost reasons, those structures may also be fabricated from sheet metal. 
         [0034]    As best seen in  FIGS. 1 and 2 , magnetic attachment pads  30  include a magnet  32 , the frame portion  33  for holding the magnet  32  and a pair of fastener receipt bores  34 . When the attachment pad fasteners  31  are threaded machine screws, a lock washer is placed between the attachment pad and planar clamp base  20  and the bore  34  of the fastener is internally threaded. The attachment pads fasteners  34  pass through base pad apertures  35  and into the attachment pad frame aperture  36 . Applicant has found that the use of four magnetic pad rated for 25 pounds of force mounted at each of the corners of planar clamp base  20  provide a sufficiently strong bond with the duct  70  that the hose  82  and clamp  20  do not come loose inadvertently during a cleaning operation, but can easily be removed by tilting one side of the planar clamp base  20  off of the duct  70  by means of handles  50 . While the preferred magnetic force rating for the magnet portions  32  is twenty five pounds per magnet, other stronger or weaker magnets can be used depending upon the job contemplated. For example, if it very heavy duty duct cleaning hose is to be used or if the duct to be cleaned contains mold spores or other noxious particulates, magnet portions  32  with ratings in excess of 25 pounds of force may be used in the magnetic hose clamp  10 . The preferred materials for the magnet  32  are the strong, lightweight rare earth types, such as, neodymium magnets (Nd 2 Fe 14 B) and samarium-cobalt magnets, but metal ferrite or ceramic magnets may also be used. Of course, with the use of magnets rated higher than 25 pounds of force, removal of the clamp after completion of the job becomes more difficult. Similarly, while it is preferred that for magnetic attachment pads  30  are placed at the four corners of the square or rectangular shaped magnetic cleaning hose clamps of the invention, additional magnetic attachment pads can be used along the periphery of the back surface  22  of the clamp base to increase the clamping force of the magnetic hose clamp  10 . The magnetic hose clamp  10  can also be used to temporarily attach a cleaning hose to another structure that needs periodic cleaning such as an industrial powder dispensing apparatus, particularly those used in the food industry, which need nearly daily cleansing. For those applications, it may be necessary to use stronger magnets or larger number of magnets to ensure that the clamp does not become dislodged during the equipment cleaning process in order to avoid a risk of contaminating the equipment. 
         [0035]    Compressible sealing material  40  is preferably die cut from a relatively compressible foam material blank such as foam-rubber buana-n/pvc or pvc foam insulation blanks. The die cut shape has four corner cut outs  41  to accommodate the magnetic attachment pads  30  and a center cutout  42  that matches the dimensions of the central aperture  62 . The height and width of the compressible sealing material closely matches the interior height and width dimensions of the planar clamp base  20  between opposing rim inner surfaces  47  on the back surface  22 . The compressible sealing material  40  is cut to a thickness that is greater than the thickness of the magnetic attachment pads  30 , but slightly less than the height of the rim  46 . The tight fit of the compressible sealing material  40  within the confines of the rim  46  assists in forming a nearly airtight seal when the magnetic cleaning hose clamp  10  is mounted to a duct  70 . The compressible sealing material  40  is preferably mounted to the back surface  22  of the planar clamp base  20  by use of an adhesive such as 3M-scotch weld adhesive, but may also be mounted to the planar base portion via fasteners (not shown). Alternately, the sealing material can be cut into four elongated strips (not shown) that that match the distance between each of the magnetic attachment pads  30 . The elongated strips can be glued to the back surface  22  adjacent to the rim  46  between each of the four magnetic attachment pads  30 . 
         [0036]    As best seen in  FIGS. 2 and 3 , the rim  46  preferably has a height of about ⅜ of an inch and a width of about ⅛ of an inch. The rim  46  assists in retaining the magnetic pad attachment pads  30  and the compressible sealing material  40  in place during mounting and dismounting of the magnetic hose clamp from the duct  70 . This is done by ensuring that the outer exterior side wall of the magnetic attachment pads  30  butts up against the rim  46  and by ensuring that the compressible sealing material is cut to be slightly larger size than the interior width and height of between opposing sides of the rim  46 . 
         [0037]    The pair of handles  50  are mounted to the front surface  21  of the planar clamp base  20  via handle fasteners  51 . The handle fasteners  51  are preferably pop rivets, but nuts and bolts or screws may also be used to fasten the handles  50  to the planar clamp base  20 . The handle fasteners  51  pass through handle apertures  52  and into base handle apertures  53 . Alternately, the handle fasteners  51  may also pass through the compressible material  40  (not shown) so that the compressible material is both adhesively bounded and fastened to the back surface  22  of the planar clamp base  20 . The handles  50  are preferably fabricated from lightweight aluminum plate stock and crimped into the desired shape and then the handle apertures  52  are drilled therein. While aluminum alloys are the preferred material for the handles  50  due to its lightweight, other metals such as tin, steel, or nickel alloys may also be used. 
         [0038]    Hose mounting ring  60  is preferably at least two and one half inches in height so that there is adequate room to accept a hose strap clamp  76  for securing the duct cleaning hose  82  to the hose mounting ring  60 . The outer diameter of the hose mounting ring  60  is preferably about 8 inches which corresponds to industry-standard HVAC duct cleaning hose inner diameter dimension specification. The flexible duct cleaning hose  82  is placed around the hose mounting ring  60  and an annular hose strap clamp  76  is tightened around the cleaning hose  82  to secure to the hose mounting ring  60 . In the embodiment of the invention shown in  FIGS. 1-5 , the length and width of the planar clamp base  20  is about 11 inches. These dimensions allow the magnetic cleaning hose clamp  10  to magnetically mount to standard sized HVAC return duct return ceiling grates that are often found where a drop ceiling has been installed in a building. These duct return ceiling grates typically have an outer metallic frame member that has outer dimensions of 11″×11″ square. The magnetic cleaning hose clamp  10  readily mounts to the outer metallic frame portion of the great thereby obviating the need to cut a hole in such a return duct. Moreover, applicant has found that the magnetic cleaning hose clamps of the invention strongly bond to standard 11″×11″ the ceiling return grates and do not dislodge during normal duct cleaning operations and, when dismounted from the return grate, do not disturb the grate or the adjacent ceiling tiles. 
         [0039]      FIG. 5  shows a schematic view of a duct hose cleaning clamp  10  mounted to a HVAC duct  70 . The cleaning technician has cut a square duct cleaning hole  72  (shown in dashed lines) in the side wall of the duct  70 . The duct hose cleaning clamp  10  encloses the duct hole  72  within the confines of rim  46  so that compressible sealing member  40  is pressed tightly against the adjacent peripheral portion  74  surrounding the duct cleaning hole  72 . The compression of the sealing member  40  creates a nearly airtight seal with the peripheral portion  74  surrounding the duct cleaning hole  72 . The duct cleaning hose  82  is mounted to the hose mounting ring  60  and is sealed thereon by hose strap clamp  76 . The duct cleaning base unit  80  creates a rapid airflow (using either negative or positive air pressure) within the  72  duct and blows or sucks the dust and other particulates from the interior of the duct  72 . The duct hose cleaning clamp  10  can be used to seal a duct cleaning hose to a duct whether the clamp and its attendant hose are located in an upstream location (near a return vent) thereby blowing air into the duct  72  or are located at a downstream location thereby sucking air from the duct (nearer the HVAC unit air inlet). 
         [0040]      FIG. 6  shows a schematic view of a rectangular duct hose cleaning clamp  110  mounted to a HVAC duct  170  at a rectangular duct grate  178   a.  The duct hose cleaning clamp  110  is similar in all respects to the hose cleaning clamp  10  other than rectangular shape of its planar base  120 . Accordingly, the description of  FIG. 6  utilizes corresponding 100 series reference numbers to the reference numbers utilized in describing  FIGS. 1-5 . The height and width of the planar base  120  are select to closely match the outer dimensions of the solid metal frame portion  179  located along the periphery of the grate. Air flows from the base unit  180  into the HVAC duct cleaning clamp  182 , through the central aperture  162  of the rectangular duct hose cleaning clamp  110 , through the grate openings  184  formed in grate  178 , and finally into the duct  182  to blow particulates through the duct to a downstream collection point out. The magnetic attachment pads  130  adhere to the solid metal frame portion  179  of the grate  178  and the compressible sealing member  140  contacts portions of the frame  179  to create a seal. For the sake of clarity, duct grate  178   b  is shown in  FIG. 6  without a clamp mounted to it to more clearly illustrate the features of the grates  178   a,    178   b.  The rectangular duct hose cleaning clamp  110  preferably encloses the peripheral edge of the grate  178  within the confines of rim  146  to assist in creating a good seal between the compressible sealing member  140  and grate  178 . The duct cleaning hose  182  is mounted to the hose mounting ring  160  and is sealed thereon by hose strap clamp  176 . The planar duct hose cleaning clamps of the invention are to be supplied in a variety of standard sizes including the aforementioned 11×11 size, and 8×8 size, a 11×14 size for residential buildings, a 24 by 24 size, to match industry-standard or commonly used return grate sizes. 
         [0041]      FIG. 7  illustrates curvilinear magnetic duct cleaning clamp  210  in accordance with another embodiment of the invention. The curvilinear version of the magnetic duct cleaning clamp  210  is designed to accommodate cylindrically shaped (circular in cross-section) HVAC duct. Such cylindrically are less common than the rectilinear ducts, but are sufficiently common that the applicant has perceived a need to manufacture a quick release magnetic hose cleaning clamp to accommodate cylindrically shaped ducts. The duct hose cleaning clamp  210  is similar in all respects to the hose cleaning clamp  10  other than rectangular shape of its base  220  and compressible sealing material  240 . Accordingly, the description of  FIG. 7  below utilizes corresponding 200 series reference numbers to the reference numbers utilized in describing  FIGS. 1-5  and for the sake of brevity does not discuss substantially similar corresponding structures in detail below. 
         [0042]    The manufacturer process for the curvilinear magnetic duct cleaning clamp  210  is substantially similar to that of the planar version  10  with the following exceptions. First, both the clamp base portion  220  and compressible sealing material  240  are curvilinear, rather than planar. The clamp base portion  220  is preferably molded in its curved shape. However, the compressible sealing material is preferably diecut from a flat foam blank and then curved upon being adhered to the curvilinear base portion  220 . 
         [0043]    Installation and removal of the curvilinear magnetic duct cleaning clamp  210  is similar in most respects to installation of the magnetic duct leaning clamp  10 . However, when removing the curvilinear magnetic duct cleaning clamp  210  from a cylindrical duct (not shown) the clamp  220  should the tilted along its radius of curvature, rather than lengthwise. 
         [0044]      FIG. 8  illustrates a planar magnetic duct access door clamp  310  in accordance with another embodiment of the invention. The planar version of the magnetic access door clamp  310  is designed to accommodate planar exterior surface ducts (rectangular or square in cross-section), which require frequent access for inspection of the duct or for frequent cleaning. In food processing facilities, frequent access duct doors are often installed on ducts that provide ventilation to equipment that generates fine particulates, which particulate then enter the building ventilation system or an exhaust ventilation system. Frequent access duct doors are also commonly used in particulate supply ducts that transport particulates between different locations in a food processing facility. To maintain a sanitary environment and to comply with government regulations, food facility ducts require frequent inspection and periodic cleaning, which often necessitates installation of access doors. 
         [0045]    The duct access door  310  is similar in most respects to the hose cleaning clamp  10  of  FIGS. 1-5  other than the lack of a neck structure, lack of an airflow aperture in the planar base portion  320 , and that the compressible sealing material  340  covers the entire back surface  321  of the access door base  320 . Accordingly, the description of  FIG. 8  below utilizes 300 series reference numbers corresponding to the reference numbers utilized in describing the structure shown  FIGS. 1-5 , and for the sake of brevity, the description does not discuss substantially similar corresponding structures in detail below. 
         [0046]    The manufacturer process for the duct access door  310  is substantially similar to that of the planar version of the duct cleaning clamp  10  with the following exceptions. As mentioned briefly above, the access door base portion  320  of the duct access door  310  lacks an airflow aperture. This is because the entire duct access door structure  310  is removed from the frequent access duct (not shown) each time that access is required to the interior of the frequent access duct. The duct access door  310  is installed in the same manner as the duct hose cleaning clamp  10  described in detail above, except that no duct cleaning hose is attached to the duct access door  310 . As there is no airflow aperture in the base portion  320  of the duct access door  310 , it is not necessary to have a corresponding aperture in the sealing material  340  of the duct access door base  320 . This greater surface area of the sealing material  340  allows the duct access door  310  to seal a wide variety of shapes and sizes of holes cut into the frequent access duct. The process of removal of the duct access door  310  is similar to that described above with regard to duct cleaning clamp  10  in that the duct access door  320  is removed from a frequent access duct by grasping handles  350  in order to tilt one edge of the duct access door  320  to release the magnetic attraction between the magnets  332  on the back surface  322  of the base  320  along one edge and the frequent access duct. The handles  350  are then pulled simultaneously outwardly from the frequent access duct to overcome the magnetic attraction between the remainder of the magnets  332  and the frequent access duct. 
         [0047]      FIG. 9  illustrates a curvilinear magnetic duct access door  410  in accordance with yet another embodiment of the invention. The curvilinear version of the magnetic duct access door  410  is designed to accommodate frequent access ducts with curved exterior surfaces (round in cross section or elliptical in cross section). Such curved exterior ducts are less common than the rectilinear exterior surface ducts, but are sufficiently common that the applicant has perceived a need to manufacture a duct access door to accommodate curved exterior surface ducts. The duct access door  410  is similar in all respects to the hose cleaning clamp  210  other than other than the lack of a neck structure, lack of an airflow aperture in the curvilinear base portion  420 , and that the compressible sealing material  440  covers the entire back surface  421  of the access door base  420 . Accordingly, the description of  FIG. 9  below utilizes 400 series reference numbers corresponding to the reference numbers utilized in describing  FIGS. 1-5  and  7 . For the sake of brevity, this specification does not describe substantially similar corresponding structures in detail again below. 
         [0048]    The manufacturer process for the curvilinear magnetic access door  410  is substantially similar to that of the curvilinear version  210  with the following exceptions. As mentioned briefly above, the curvilinear access door base portion  420  of the duct access door  410  lack an airflow aperture. This is because the entire curvilinear duct access door structure  410  is removed from the frequent access duct (not shown) each time that access is required to the interior of the frequent access duct. The duct access door  410  is installed in the same manner as the hose cleaning clamp  10  described in detail above, except that no duct cleaning hose is attached to the duct access door  410 . As there is no airflow aperture in the curvilinear base portion  420  of the curvilinear duct access door  410 , it is not necessary to have a corresponding aperture in the sealing material  440  of the duct access curvilinear door base  420 . This greater surface area for the sealing material  440  allows the curvilinear duct access door  410  to seal a wide variety of shapes and sizes of holes cut into the frequent access duct. The process of removal of the duct access door  410  is similar to that described above with regard to duct cleaning clamp  10  and curvilinear duct cleaning clamp  210  in that the duct access door  420  is removed from a frequent access duct by grasping handles  350  in order to pivot the duct access door  320  along the axis of one its straight edges to release the magnetic attraction between the magnets  432  an duct along the opposite straight edge of the rectilinear base  420 . The handles  450  are then pulled simultaneously outwardly from the frequent access duct to overcome the magnetic attraction between the remainder of the magnets  432  on the other straight edge and the frequent access duct. 
         [0049]    In a similar manner to that described for clamp base portion  220 , curvilinear access door base portion  420  is preferably molded from a thermoplastic resin in its curved shape similar to clamp base portion  220 . In contrast, compressible sealing material  420  is preferably die-cut from a flat foam blank and then curved upon being adhered to the curvilinear base portion  420 . 
         [0050]    Other embodiments, combinations and modifications of this invention will occur readily to those of ordinary skill in the art in view of these teachings. Therefore, this invention is to be limited only by the following claims, which include all such embodiment methods, and modifications when viewed in conjunction with the above specification and accompanying drawings.