Patent Application
20080271726
The present disclosure is directed to a new wall interface device, commonly known as a “wall thimble,” which is useful for venting combustion by-products from a heating appliance and for providing combustion air to the heating appliance.
Fuel-burning appliances, including wood stoves and pellet stoves, require an exhaust system in order to vent combustion by-products, such as noxious gases, fine ash, and water vapor, to the outside of the structure containing the appliance. In addition, combustion air must be supplied to the appliance to properly fuel the fire. In a typical installation, the appliance includes a mechanical fan to both blow the combustion by-products out through the exhaust pipe and to draw combustion air in through a separate air inlet pipe. However, it is also typical to create two different openings in the wall adjacent to the heating appliance, one for routing the exhaust outlet, and one for routing the combustion air inlet.
It would be desirable to have a single component that provides two paths—one for the exhaust outflow, and one for the combustion air inflow, such that only a single opening in the exterior wall is required.
The present disclosure describes a wall thimble that is adapted for use in a wall opening as part of a venting apparatus for a direct vent heating appliance, such as a pellet stove. Advantageously, the new thimble provides dual functionality in a single device by having a vent path for exhausting combustion by-products, and a separate air inlet path to draw in outside combustion air for use by the heating appliance.
In one embodiment, the wall thimble includes an outside mounting plate and an inside mounting plate. The mounting plates have circular openings that are substantially the same size, and a hollow cylinder of similar size is affixed to the mounting plates coaxially with the mounting plate openings such that an outside portion of the cylinder extends outside of the outside mounting plate. An outside air vent is formed on the outside portion of the cylinder.
In one embodiment, an annular region is formed when a double-walled pipe is coupled to the cylinder at the inside mounting plate and an exhaust pipe is coupled through the cylinder. The outer wall of the double-walled pipe has a diameter slightly less than the cylinder diameter, and may be inserted into and joined with the cylinder. The inner wall of the double-walled pipe has a diameter smaller than the outer wall such that the exhaust pipe may be coupled to the inner wall of the double-walled pipe. The annular region is thus formed between the cylinder and the exhaust pipe. Combustion air is drawn into the annular region through the outside air vent and forced out of the annular region through the inside air vent.
In one embodiment, the thimble includes a pair of cover plates affixed to each end of the cylinder. The cover plates have respective openings that are smaller than the mounting plate openings such that an annular region is formed between an exhaust pipe routed through the cover plate openings and the cylinder wall. An inside air vent is formed on the surface of the cylinder at a location inside of the inside mounting plate, and a coupling for a combustion air pipe is formed on the inside mounting plate proximate to the inside air vent. When an air inlet pipe is coupled to the combustion air pipe coupling, combustion air is drawn into the annular region through the outside air vent then out through the inside air vent to the coupling for the combustion air pipe.
In one embodiment, the wall thimble is advantageously formed in two parts that mate with each other, namely an inner housing and an outer housing, to facilitate field installation. The inner housing includes a first cylinder portion, a first mounting plate, a first cover plate, and a first air vent. The first mounting plate is mounted on the outside of the wall opening and includes an opening. The first cylinder portion has a diameter similar to the first mounting plate opening and is affixed to the first mounting plate opening such that a distal end of the first cylinder portion extends outside of the first mounting plate. The first air vent is formed near the distal end of the first cylinder portion. The first cover plate is affixed to the distal end of the first cylinder portion and includes an opening.
The outer housing includes a second cylinder portion, a second mounting plate, a second cover plate, and a second air vent. The second mounting plate is mounted on the inside of the wall opening and includes an opening corresponding to the first mounting plate opening, and a smaller combustion air opening. The second cylinder portion has a diameter similar to the first cylinder portion and is affixed to the second mounting plate opening. The second air vent is formed near a distal end of the second cylinder portion inside of the second mounting plate. The second cover plate is affixed to the distal end of the second cylinder portion and has an opening corresponding to the first cover plate.
An annular region is formed between an exhaust pipe routed through the cover plate openings and the cylinder portions. When an air inlet pipe is coupled to the combustion air opening, combustion air is drawn into the annular region through the first air vent then out through the second air vent to the combustion air opening.
These and other objects and advantages will appear more clearly from the following description in which several embodiments are described in conjunction with the drawings.
The present disclosure is directed to a new wall interface device for a direct vent heating appliance, commonly referred to as a “thimble,” and a method of using the same. Advantageously, the new thimble provides dual functionality in a single device by having a vent path for exhausting combustion by-products, and a separate air inlet path to draw in outside combustion air for use by the heating appliance. While the thimble is described as part of a pellet stove installation, it should be recognized that the description is not intended to be limiting with respect to the features of the dual function thimble, which are readily applicable to all types of direct vent heating appliances.
Referring now to
The illustrated exhaust/intake system 30 provides direct horizontal venting through an opening in exterior wall 22, although alternative venting techniques could be used and will be readily apparent to workers in this field. The exhaust/intake system 30 may be fabricated using standard sheet metal materials with conventional bending and fastening techniques.
The exhaust/intake system 30 includes a vent pipe 32 which is coupled to the exhaust outlet 11 of stove 10 (shown in
In one embodiment of pipe 32, the inner flue is formed using 0.012 inch type 430 stainless steel, and the outer wall is formed using 0.018 inch galvalume steel to provide heat and corrosion resistance. A one-quarter inch annular air space is provided between the inner and outer walls to provide for static air insulation and to ensure safe outer wall temperatures, while also providing a minimum clearance to nearby combustibles. To prevent fly ash leakage, each pipe joint contains a high temperature ceramic rope gasket. In addition, all elbows, tees, and fittings are sealed with a liberal amount of room-temperature-vulcanizing (“RTV”) silicone.
The thimble 40 provides an inside/outside interface and is mounted in an opening specially formed in the exterior wall 22 to accommodate the exhaust/intake system 30. The thimble 40 includes an inside plate 52 that is mounted to the wall 22 on the inside of structure 20, and an outside plate 62 that is mounted to the wall 22 on the outside of structure 20. For example, the inside plate 52 and outside plate 62 may be rigidly affixed to structural members 24 of wall 22.
The side view shown in
As better shown in
The thimble 40 includes a housing having two main portions that mate with each other, namely an inside housing portion 50 and an outside housing portion 60, and that are each formed as a separate, integral assembly. Advantageously, when the thimble 40 is mounted into a suitable opening in wall 22, the outside housing portion 60 fits within inside housing portion 50. More specifically, the inner band 64 is sized to fit within outer band 54. Further, the length of housing portions 50 and 60 is sufficient to allow the total thickness W of the thimble to be adjusted during field installation to accommodate for differences in wall thicknesses. For example, in one construction, the housing portions allow the thimble thickness W to be adjustable between approximately 5.75 to 8.00 inches.
The inside housing portion 50 includes inside plate 52, inlet pipe 53, outer band 54, and inlet cap 56. The inside plate 52 measures approximately 11 inches wide by 11 inches tall, and includes a first opening 52a and a second opening 52b. The first opening 52a is centrally located at approximately 5 inches from the top and 4.5 inches from the sides of plate 52, and measures approximately 6.964 inches in diameter. The second opening 52b is located in one corner of the plate 52, and is centered at approximately 1.985 inches from the bottom of plate and 2.165 inches from the side of the plate, and measures approximately 2.000 inches in diameter. The outside edges 52c of the plate 52 are folded back at a right angle approximately one-half inch or less on all four sides, and a circular flange 52d of similar dimension is formed inside of opening 52a. The inside plate 52 is formed from 0.018 inch galvanized steel plate or other suitable material.
The inlet pipe 53 is formed from 0.018 inch type 304 stainless steel, which provides excellent corrosion resistance, or other suitable material. The length of inlet pipe 53 is approximately 2 inches, and it is cold-rolled into a cylinder measuring approximately 2.000 inches in effective diameter (adequate to fit within opening 52b), then riveted and spot welded to maintain the cylinder shape. A roll bead 53a is formed near one end of the inlet pipe 53, and that end of the inlet pipe after the roll bead is cut into tabs 53b. The inlet pipe 53 is inserted into opening 52b until stopped by the roll bead 53b. At least some of the tabs 53b are then folded over and spot welded to the inside of inside plate 52, for example, with four resistance welds are that applied at 90 degrees spacing.
The outer band 54 is 0.018 inch zinc-plated galvanized steel plate or other suitable material, and is cold-rolled into a generally cylindrical, hollow section then riveted at the seam 54a to maintain the shape. The outer band 54 has an outside diameter of approximately 7.000 inches and a length of approximately 5 inches. A plurality of vent openings 55 are formed approximately three-quarters inch from the end of outer band 54 proximate to inside plate 52. The vent openings 55 are approximately one-half inch square, and cover the entire circumference around band 54, but in some embodiments could cover only a portion of the circumference, for example one-quarter or one-half. Further, the number and size of the vent openings can be changed as desired or based on empirical studies of combustion air flow.
The inlet cap 56 is 0.018 inch zinc-plated galvanized steel plate or other suitable material, and is formed into a circular piece measuring approximately 6.964 inches in diameter, and having an opening 56a measuring approximately 3.750 inches in diameter, and a right angle flange 56b of approximately one-half inch depth.
The inside housing portion 50 is assembled together by coupling the inlet cap 56 and outer band 54 to the inside plate 52. This is done by fitting the flange 56b of inlet cap 56 over the flange 52d of inside plate 52, then fitting the end of outer band 54 over both sets of flanges, then pop riveting these components together, for example, with four rivets spaced at 90 degrees.
The outside housing portion 60 includes outside plate 62, inner band 64, and outlet cap 66. The outside plate 62 measures approximately 11 inches wide by 11 inches tall, and includes an opening 62a. The opening 62a is centrally located at approximately 5 inches from the top and 4.5 inches from the sides of outside plate 62, and measures approximately 7.000 inches in diameter. The outside edges 62b of outside plate 62 are folded back at a right angle approximately one-half inch or less on all four sides, and a circular flange 62c of similar dimension is formed to the outside of opening 62a. The outside plate 62 is formed from 0.018 inch galvanized steel plate or other suitable material.
The inner band 64 is 0.018 inch zinc-plated galvanized steel plate or other suitable material, and is cold-rolled into a generally cylindrical, hollow section then riveted at the seam 64a to maintain the shape. The inner band 64 has an outside diameter of approximately 6.964 inches and a length of approximately 5 inches. A first plurality of vent openings 65a are formed near one end of inner band 64, and a second plurality of vent openings 65b are formed near the other end of the inner band. The openings 65a, 65b are each approximately one-half inch square, and cover the entire circumference around inner band 64, but in some embodiments could cover only a portion of the circumference. Also, the number and size of the vent openings could be adjusted. A roll bead 64b is formed on inner band 64 approximately 1½ inches from the end nearest outside plate 62.
The outlet cap 66 is 0.018 inch zinc-plated galvanized steel plate or other suitable material, and is formed into a circular piece measuring approximately 6.964 inches in diameter, and having an opening 66a measuring approximately 3.750 inches in diameter, and a right angle flange 66b.
The outside housing portion 60 is assembled together by coupling the outlet cap 66 and inner band 64 to the outside plate 62. The inner band 64 is fit through opening 62a in outside plate 62 until stopped by roll bead 64b, at which point the end of the inner band extends beyond the outside plate 62 by approximately ½ inches such that openings 65a are exposed outside of exterior wall 22. The flange 62c of outside plate 62 is attached to the inner band 64 using 6 resistance welds spaced at 60 degrees. The flange 66b of outlet cap 66 is fit over the end of inner band 64, and corresponding roll beads (not shown) are formed, then resistance welds are applied, for example, at 90 degrees spacing.
The inside housing portion 50 and outside housing portion 60 are pre-assembled, then are fitted together during field installation and securely attached to wall 22. The slight difference in diameters of the outer band 54 and the inner band 64 allows the inner band to be inserted into the outer band, as previously noted. Thus, as shown in
Finally, exhaust pipe 32 is fitted through the openings 56a and 66a in inlet cap 56 and outlet cap 66, respectively, and coupled to exhaust outlet 11 on the stove and to terminus elbow 34 outside the exterior wall. Thus, the exhaust pipe 32 provides an inside passageway in thimble 40 for carrying exhaust by-products to the exterior of the structure, while at the same time creating an annulus or outside passageway between the pipe and the bands 54, 64 for carrying combustion air from the outside to the stove combustion air inlet 14.
Another embodiment is shown in
The vertical pipe section 170 is also a double-walled pipe, such as a standard stovepipe, having an outer wall diameter of approximately 6.625 inches and an inner pipe diameter of approximately 4 inches, although other sizes could be provided, such as 7 inches OD by 4 inches ID; 8 inches OD by 5 inches ID; and 8.625 inches OD by 5 inches ID. Referring to
As shown in
The outside housing portion 160 includes outside plate 162, inner band 164, and outlet cap 166. A roll bead 164a and vent openings 164b are provided on one end of the inner band 164. The outside housing portion 160 is assembled together by coupling the outlet cap 166 and inner band 164 to the outside plate 162. The inner band 164 is fit through opening 162a in outside plate 162 until stopped by roll bead 164a, at which point the end of the inner band extends beyond the outside plate 162 by approximately 1½ inches such that vent openings 164b are exposed on the outside of wall 22. The flange 162c of outside plate 162 is attached to the inner band 164 using 6 resistance welds spaced at 60 degrees. The flange 166b of outlet cap 166 is fit over the end of inner band 164, and corresponding roll beads (not shown) are formed, then resistance welds are applied, for example, at 90 degrees spacing.
The inside housing portion 150 and outside housing portion 160 are pre-assembled as described above, then installed in the field. For example, the elbow 174 is fitted into the opening 152a of inside plate 152 such that the outer wall of the elbow fits snugly within outer band 154. The joint is then sealed with a high temperature ceramic rope gasket and a liberal amount of RTV. As better shown in
The foregoing detailed description has been presented for purposes of illustration and description. It is not intended to be exhaustive or limiting to the precise form disclosed. Many modifications and variations are possible in light of the above teachings. For example, common variations in structures and materials exist, and suitable modifications to accommodate such different structures and materials could readily be made. The described embodiments were chosen in order to best explain the principles of the disclosure and its practical application to thereby enable others skilled in the art to best utilize the disclosure in various embodiments and with various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the claims appended hereto.
