Patent Publication Number: US-6987928-B2

Title: Recirculating air snow melting pad system

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to snow and ice melting equipment. More particularly, the present invention relates to equipment for maintaining sidewalks, driveways, and roofs free of ice and snow. 
   2. Description of the Related Art 
   The use of heating coils or the like to maintain surfaces such as sidewalks, driveways, and roofs free from buildup of ice and snow is known. Commonly used devices include steam or hot water heated coils within or underneath the surface material such as concrete or the like. Also known is the use of electrical resistance heating systems including mats for placement over the surface to be cleared having resistance heating elements therein. In some applications resistance electrical heating mats are uneconomical. It would be desirable to provide an alternative mat type system which may use recirculated heated air and which may be placed on the surface to be kept clear of snow, such as a driveway, and is sufficiently sturdy to walk or drive a car over without damage. 
   U.S. Pat. No. 223,784, issued Jan. 20, 1880, to Watson, describes a sidewalk having a fluid circuit of tubes under the surface for conveying steam for heating the sidewalk to prevent snow and ice from accumulating on the surface. 
   U.S. Pat. No. 3,818,892, issued Jun. 25, 1974, to Von Kohorn, describes a system for removing snow and ice from an athletic playing surface where heated air is circulated beneath the surface and up through the porous playing surface. 
   U.S. Pat. No. 4,270,596, issued Jun. 2, 1981, to Zinn et al., describes a heat exchanger for use in embedded radiant heating systems including a plurality of webbed tube mats and associated manifolds. 
   U.S. Pat. No. 4,646,818, issued Mar. 3, 1987, to Ervin, Jr., describes heated mats for melting snow and ice from walkways, driveways, and sidewalks employing tubing carrying a heated mixture of water and antifreeze. 
   U.S. Pat. No. 5,003,157, issued Mar. 26, 1991, to Hargrove, describes a snow melting pathway mat apparatus which is electrically heated and includes hollowed channels extending longitudinally along the mat, allowing melted snow to flow off the mat. 
   U.S. Pat. No. 5,591,365, issued Jan. 7, 1997, to Shields, describes a lattice-like heating mat having electrical resistance heating wire extending through the lattice, the lattice configuration allowing flexibility in conforming to uneven surfaces and for rolling up for storage. 
   None of the above inventions and patents, taken either singly or in combination, is seen to describe the instant invention as claimed. Thus a mat system using recirculated heated air to melt snow solving the aforementioned problems is desired. 
   SUMMARY OF THE INVENTION 
   The mat system of the present invention employs recirculated heated air to melt snow and ice from walkways, driveways or roofs, preventing its accumulation on these surfaces or the like. In the driveway configuration, a mat is provided of appropriate size having upper and lower walls made of tough, pliable rubber, plastic, or the like which is sufficiently resistant to tearing and abrasion to withstand walking or driving a car over the mat. A recirculating air electric heater provides heated air to the interior of the mat. The mat contains baffles to form heated air paths to direct the heated air sinuously through the substantial portion of the mat, and an internal wall forms a cooled air return path along the upper end for recirculating the air to the heater. 
   For a two-car garage, two pads are provided. The second pad may be identical to the first pad. Heated air is directed between the first and second mats for sinuous flow therethrough and returned through the cooled air return path by providing separate removable ducts between heating air paths and cooled air return paths. The mat system in a preferred form is modular, being assembled from identical mats and ducts so as to provide any desired number of melting mats to cover a driveway for two or more cars or a flat roof. A large single mat for a roof is provided employing an industrial-sized electrical recirculating air heater employing commercial electrical power. 
   It is an aspect of the invention to provide improved elements and arrangements thereof for the purposes described which is inexpensive, dependable and fully effective in accomplishing its intended purposes. 
   These and other aspects of the present invention will become readily apparent upon further review of the following specification and drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is an environmental, perspective view of the heated air snow-melting mat of present invention. 
       FIG. 2A  is a plan view of the snow melting mat of  FIG. 1 . 
       FIG. 2B  is a plan view of a single mat design similar to that of  FIG. 2A . 
       FIG. 3A  is a section view of the mat of  FIG. 2A  with the upper wall removed. 
       FIG. 3B  is a section view of the mat of  FIG. 2B  with the upper wall removed. 
       FIG. 4  is a plan view of two snow melting mats as in  FIG. 1  connected in series, with the upper wall partially broken away. 
       FIG. 5  is a plan view similar to that of  FIG. 4  with three melting mats connected in series. 
       FIG. 6A  is an environmental plan view of a series of mats similar to that of  FIG. 1  located for melting snow from a flat roof. 
       FIG. 6B  is an environmental plan view similar to that of  FIG. 6A  of a single large mat useful for melting snow from a flat roof. 
       FIG. 7A  is a side view of the upper end portion of the snow clearing mat showing air flow covers in closed and open position. 
       FIG. 7B  is an end view of a duct of  FIG. 2 . 
       FIG. 7C  is an end view of the elbow duct of  FIG. 2 . 
   

   Similar reference characters denote corresponding features consistently throughout the attached drawings. The features of the drawings are not necessarily drawn to scale but are for illustration only. 
   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   The present invention is a mat system employing recirculated heated air to melt snow and ice from walkways, driveways or roofs, preventing its accumulation on these surfaces or the like. In the driveway configuration, a mat is provided of appropriate size having upper- and lower walls made of rubber, plastic, or the like which is sufficiently resistant to tearing and abrasion to withstand walking or driving a car over the mat. A recirculating air electric heater and blower provides heated air to the interior of the mat. The mat contains baffles to form heated air paths to direct the heated air sinuously through the substantial portion of the mat, and an internal wall forms a cooled air return path along the upper end for recirculating the air to the electric heater and blower. The mat system may be modular, assembled from identical mats and ducts so as to provide any desired number of melting mats to cover a driveway for two or more cars or a flat roof. Another embodiment provides a single, large heating mat for use on a roof of a commercial building or the like and employs an industrial sized heater and blower which may use commercial electrical power such as 220 or 440 volt power. 
   Referring to the Figures, melting pad system  10  is shown installed on a concrete or asphalt driveway D (see  FIG. 1 ) leading from street S and garage door GD. A sidewalk SW is shown in a typical location and is cleared by the melting mat system  10 . A lawn L is located on each side of the driveway D. The system  10  may be expanded to include multiple pads for melting snow from larger areas (see  FIGS. 3–6 ) to cover multiple car driveways and flat roofs. 
   Referring to  FIGS. 1 and 2  there are shown an environmental perspective and a plan view of the preferred embodiment of the present invention showing the basic arrangement of parts of the melting pad system  10 , including electrically operated recirculating air heater and blower unit  12  of conventional design having a heated air supply conduit  14  connected with an outlet  16  of unit  12  and a cool air return conduit  18  connected with an inlet  19  of unit  12 . Melting mat  20  is generally rectangular in shape and has a mat upper wall  22 , first and second sidewalls  24 , lower wall  26 , upper end wall  30  and lower end wall  34 . Conduits  14  and  18  are preferably connected to the first sidewall  24 . Driveways D are typically sloped upward from the level of street S to the garage door GD to keep rainwater from draining into the garage and the melting mat system  10  is defined relative to this configuration of driveway. Melting mat  20  defines an upper end portion  28  for receiving and returning air from recirculating air heater and blower  12 , which is most conveniently located near the garage or house. A lower end portion  32  is located at the driveway entrance as shown, however the melting mat  20  may be of any desired length. For example, end wall  34  may be located short of the sidewalk SW. 
   Tie-down stakes  36  are conveniently spaced along the sides of driveway D and driven into lawn L and provide for anchoring of mat  20  by means of connecting ties  38 , preferably of elastic material, to sides  22  of anchor mat  20  for securing mat  20  in position during high wind conditions. 
   Upper end portion  28  of melting mat  20  has mat heated air inlet port  40  and mat cool air outlet port  42  along each sidewall  22  for interconnection with conduits  14  and  16 , respectively, and heated air and cold air return connecting ducts  10  and  72 , respectively (see  FIGS. 4–6 ). 
   The melting mat  20  has parallel, spaced traction treads  44  on its upper wall  22  having a rough or ribbed surface extending the substantial length of mat  10  so as to provide traction for vehicle tires as a vehicle is driven into the garage with the garage door GD lifted. Non-skid material such as waterproof grit covered sheet material  45  (see  FIGS. 2A and 2B ) may be applied to the upper wall surface in tracks up to 3 feet wide or more to provide for additional vehicle tire traction or footing, the material conforming to the airflow tube and drain channel features (see discussion below). Non-skid material may also be used to cover the lower surface of the lower wall  26  of mat  20 . The vehicle would not normally be parked on the mat  20  since its weight could block circulation of air through the mat system. 
   Mat  20  incorporates wind relief tubes  46  therethrough opening between upper and lower walls  22  and  26  in surface areas other than the traction treads  44  and which allow wind to pass through the mat  20  when lifted by a cross wind, thereby aiding in maintaining the mat in its location on the driveway D. The relief tubes  46  are preferably spaced in rows parallel with sidewalls  24 , each row being surrounded by raised strips  47  extending along each row rising upward from upper wall  22  to minimize water drainage into tubes  46 . Water drain channels  48  extend along the substantial length of mat  20  and allow water from melted snow to drain off the pad  20 , thus avoiding refreezing of the melted snow and clogging of wind relief tubes  46 . The diameter of relief tubes  46  and width and depth of water drain channels  48  may be selected depending local weather conditions, the thickness of the mat, and the thickness of the upper wall material forming the mat  20 . 
     FIG. 2B  shows an alternative embodiment of the invention where only a single snow melting mat  20  is contemplated. In this embodiment the second sidewall  24  opposite the first sidewall  24  having heated air inlet port  40  and cool air outlet port  42  extends upward to meet upper wall  30 . 
   As best seen in  FIG. 3A , heated air is maintained separate from cool return air by air return wall  60 . Heated air introduced through heated air inlet port  40  is directed sinuously through the substantial portion of mat  20  by alternating upper wall baffles  62  extending lengthwise from air return wall  60  and lower wall baffles  64  extending lengthwise from lower end wall  34 , forming sinuous path  66 . Cooled air is returned for heating and recycling in unit  12  by along cool air return path  68  formed by cool air return wall  60  and upper end wall  30  and the upper and lower walls of mat  20 . Elbow duct  50  connects heated air exit port  52  to cooled air return port  54  for return of the circulating air along cool air return path  68 . Wind relief tubes  46  are preferably located in rows within sinuous path  66 , centered between baffles  62  and  64 , respectively. 
   Referring to  FIG. 3B , there is shown a section view of the embodiment of  FIG. 2B , wherein inner cold air return wall  60  ends at upper wall baffle  62  providing an internal return port  61  for directing cooled air for return to mat cool air outlet port  42  from the opposite mat side wall  24 . 
   As best seen in  FIGS. 3–5 , multiple snow melting mats  20  may be interconnected by cool air return connecting ducts  70  and heated air connecting ducts  72 . Cool air return connecting ducts  70  connect cool air outlet port  42  to cooled air return ports  54 . Heated air connecting ducts  70  connect heated air exit ports  52  with mat heated air inlet ports  0 . 40 . Connecting ducts  70  and  72  may be identical in configuration. The last of the series of mats  20  may be identical to that of the first mat  20 , employing elbow duct  50  for recirculating air through the mat system. Alternatively, the last of the series of mats  20  may be configured as shown in  FIGS. 2B and 3B  and elbow duct  50  is not required for operation of the mat system. 
   Referring to  FIG. 6A , there is shown another application of the recirculating heated air snow melting mat system  10  of the present invention where melting mats  20  are installed on the flat roof R (slightly sloping for drainage) of a commercial building. The building has a cornice C and overlooks a sidewalk SW and a street S for travel of automobile A. The mat system  10  is installed such that water drains from cavities  48  along the slope of the roof R to drains DR in roof R. The ties  38  may be tied to stakes  36  installed in receiving tubes (not shown) or tied to eyelets or other connecting support structures of known type and design. 
   As shown in  FIG. 6B , the mat system  10  may employ a single large mat  90  of greater width relative to length, as desired, the number of heated air baffles being increased (not shown) for distribution of heat over the wide mat. The roof R is shown as that of a commercial building B, the roof being substantially flat or slightly sloped and having drain holes DR. A sidewalk SW surrounds the building B next to which an automobile A is parked on street S. A single large mat substantially covering roof R may be tied securely to two or more walls of cornices C by ties to anchor bolts  92 . Recirculated heated air is provided by an industrial sized electrical unit through heated air supply conduit  14  from cool air return conduit  18  in a manner similar to that of the driveway mat  20 . The mat is oriented such that it drains toward drainpipes DR. 
   The mat  90  may also be installed on a sloping roof (not shown) if properly sized and tied down. A 220-volt AC heater and blower may be useful in this application. In a similar manner, a single mat  90  of having a double or triple width (not shown) may be used for a double or triple car driveway as desired and may include corresponding pairs of traction treads  44  thereon. 
   Referring to  FIG. 7A , there is shown a side view of the upper end portion  28  of the snow clearing mat  20  showing heated air inlet port  40  and cool air outlet port  42  having covers  82  in the uncovered and covered positions, respectively. The covers are useful for storage purposes to prevent the entry of pests, dirt and debris into disassembled and stored system. The covers  82  may be hinged to the sidewall  24  by integral hinge  83  as shown for port  40  or be provided as a separate component of the system  10 . The covers  82  are preferably removably connected to the sidewall  24  by hook and loop material (Velcro). As shown, port  40  is surrounded by hook material  84  and the border of cover  82  covered with loop material  86 . For port  42  the engaged hook material is covered with loop material  86  (hidden lines) of a cover  82 . 
   Referring to  FIG. 7B  there is shown an end view of a connecting duct  70  having ends  88  surrounded by loop material  86  for connection with hook material  84  of heated air inlet port  40  and cool air outlet port  42 . Ducts  70  and  72  have identical ends  88  having loop material  86  for connection with heated air exit port  52  and cooled air return port  54 . 
   Referring to  FIG. 7C  there is shown an end view of elbow duct  50  having elbow air inlet  55  for mating with mat heated air exit port  52  and elbow circulating air outlet  57  for mating with mat cooled air return port  54 , respectively. Elbow air inlet  55  and elbow circulating air outlet  57  each have loop material  86  for connection with corresponding hook material  84  of heated air exit port  52  and cooled air return port  54 , respectively. 
   The hook material  84  and loop material  86  (Velcro) may be interchanged between ducts the  50 ,  70 , and  72  and the heated air inlet and exit ports and the cooled air inlet and exit ports of mat  20  as desired. The configuration of the mat connecting ends of heated air supply conduit  14  (see  FIGS. 1 and 2 ) and cool air return conduit  18  may be identical to that of ducts  70  and  72  employing hook material and mating loop material (not shown) for removable connection therewith in the same manner. 
   The material of the inventive snow-melting mat is preferably a lightweight, tough, pliable plastic or rubber material. The mat is preferably from about 1″ to about 2″ in overall thickness. Each driveway mat  20  is preferably about 10 feet in width and of a length of from about 20 to about 30 feet in length. The single roof type mat may be from about 50 to 100 feet in width and from about 50 to 150 fee in length. The electrically powered heater and blower for the single roof type mat may be powered by 110, 220, or 480 volt electrical current. 
   It is to be understood that the present invention is not limited to the embodiments described above, but encompasses any and all embodiments within the scope of the following claims.