US3314355A

US3314355A - Chimney cap

Info

Publication number: US3314355A
Application number: US474870A
Authority: US
Inventors: Kenneth S Bassett
Original assignee: Motor Wheel Corp
Current assignee: Motor Wheel Corp
Priority date: 1965-07-26
Filing date: 1965-07-26
Publication date: 1967-04-18
Anticipated expiration: 1984-04-18

Description

April 18, 1967 K. s. BASSETT 3,314,355

CHIMNEY CAP Filed July 26, 1965 INVENTOR. KENNETH SBAS'SETT ATT OENEVQ United States Patent M 3,314,355 CHIMNEY CAP Kenneth S. Bassett, La Grange, lnd., assignor to Motor gheel Corporation, Lansing, Mich., a corporation of bio Filed July 26, 1965, Ser. No. 474,870 Claims. (Cl. 98-66) This invention relates to chimney caps of the type adapted to prevent down draft conditions in a furnace and to limit up draft conditions to an acceptable level.

It is an object of this invention to provide an improved flue cap or chimney cap which is adapted to neutralize the undesirable effects of wind conditions on flue outlet pressure as well as to prevent entrance of rain into the illk.

Another object of the invention is to provide a chimney cap of the above character which consists of a minimum number of parts and hence is economical to manufacture.

In the drawings:

FIG. 1 is a perspective view of a chimney cap in accordance with the invention.

FIG. 2 is a fragmentary view showing the manner in which the chimney capis mounted on the chimney of a furnace over a roof which may be the roof of a mobile home.

FIG. 3 is a vertical section of the chimney cap taken on the line 33 of FIG. 4.

FIG. 4 is a horizontal section taken along line 4-4 of FIG. 3.

The chimney cap of the invention provides a regulated draft in a furnace and is particularly adapted for use with sealed combustion furnaces of the type often provided in mobile homes.

Incomplete combustion takes place in a furnace if there is any substantial down draft or if the up draft becomes excessive due to high winds. Up drafts increase with increasing wind velocities unless the draft is regulated and limited. Although draft regulating devices for installation on the furnaces itself are available, it is still desirable to provide a chimney cap which limits the up draft in the flue to an acceptable level and which prevents or minimizes down drafts.

The chimney cap is of generally cylindrical construction having side openings 12, a closed dome-shaped top 14 and an inlet 16 through which flue gases enter the cap. Cap 10 may be mounted on a chimney in the manner shown in FIG. 2. The inlet 16 of the cap fits over flue 18 which projects above roof 20. Flue 18 vents gases from the furnace 22 which may be the furnace of a mobile home. Although the chimney cap 10 is particularly useful in connection with sealed combustion furnaces for mobile homes, it is not restricted to this particular application.

The details of the construction of chimney cap 10 are best seen in FIGS. 3 and 4. The cap includes a flue pipe 26 having an imperforate cylindrical side wall with open bottom and

top ends

16 and 28, the inlet end -16 being outwardly flared to facilitate telescoping the pipe 26 onto flue 18. A cylindrical side wall 30, also of sheet metal, encircles pipe 26 and is spaced radially from it to provide an annular passageway 32 between pipe 26 and side wall 30. Openings 12 formed in side wall 30 are spaced equidistantly from each other circumferentially of the side wall. In this embodiment there are twelve of these openings.

As shown best in FIG. 3, each opening 12 is located radially outwardly from flue pipe 26 and preferably the upper edge 34 of each opening 12 is flush with or slightly below the upper end 28 of pipe 26, and the lower edge 36 of each opening 12 is well down the length of pipe of FIG. 1

3,314,355 Patented Apr. 18, 1967 26. End 28 of flue pipe 26 could terminate slightly below the upper edge 34 of opening 12 without departing from the principles of the invention, but it is characteristic of the structure of the invention to have the openings 12 wholly or very nearly wholly between the ends of the flue pipe in the axial direction of the cap. With this construction, flue pipe 26 acts as a vertical baffle which isolates the flow of flue gases traveling upwardly therein from the horizontal windstream flowing through passageway 3-2, and which also in cooperation with cover 14 and outer wall 30 tends to prevent the windstream from entering the flue pipe, thus acting in a positive way to minimize down drafts.

Referring to FIG. 4, side wall 30 has vanes 40 one projecting inwardly from one vertically extending edge of each opening 12 into passageway 32. All the vanes 40 extend at the same angle A (FIG. 4) relative to a radial line R drawn through the axis of cap 10 and the junction of vane 12 with side wall 30. Preferably angle A is about 2125 and when the radial dimension of passageway 32 is three inches, vanes 12 are preferably about two inches in length. Vanes 40 may be inwardly bent portions of side wall 30 and the top and

bottom edge

41 and 42 of each vane 40 are axially spaced from the respectively adjacent horizontal portions of cover 14 and a bottom baflle 54 of the cap.

Vanes 40 direct air currents about flue pipe 26 in one circular direction in passageway 32 so as to allow windstream air currents to enter the passageway on one side of the cap and leave it on the other side of the cap without any excessive pressure drop en route. Such a flow of air is illustrated in FIG. 4 by arrows indicating air currents entering openings '12 on the Windward side of cap 10 flowing in a counterclockwise direction in passageway 32 circ-urnferentially around flue pipe 26, and leaving through openings 12 on the opposite, leeward side of the cap. If the velocity of such air currents is fairly high, air flowing around the outside of the cap tends to create a low pressure region on the leeward side of the cap. Where the air flowing through passageway 3-2 changes directions sharply before exiting through the openings 12 on the leeward side, there is an increased resistance to flow. As a result, most of the pressure drop experienced by the air traveling through cap 10 is concentrated in the zone between the point where the direction of flow changes near the exit openings and the outside region of low pressure on the leeward side of the cap. When wind velocity increases from a zero value, the pressure drop incurred by air flowing through passageway 32 increases very slowly whereas the pressure drop increases more rapidly in said zone. This has the effect of limiting negative pressure inside the cap and thus limiting up drafts to an acceptable value.

Top 14 of cap 10 comprises an imperforate cover having a dome 46 with a flat central portion 47, a brim 48 and a downwardly extending flange 49 which slips over and may be spot welded to the upper end 50 of side wall 30 to thereby completely close end 46 thereof. The annular space between the bottom end 52 of side wall 30 and flue pipe 26 is closed by a horizontal bottom baflle 5 4 which is imperforate except for a few drain holes 56 (FIG. 4) in baflie 54 to allow rain water to escape from the cap. Baflle 54 has down turned

flanges

58 and 60 joined to pipe 26 and wall 30 respectively, as by spot welding.

Cover 14 acts as a batfle which cooperates with the upper end 28 of flue pipe 26 to deflect gases emitted from end 28 downwardly into passageway 32 in a fountain-like path. This constructional feature allows the use of the imperforate flue pipe 26 while still providing a low resistance p-ath via passageway 32 and openings 12 for flue gases to escape from the flue pipe. When air cur-rents are 3 present, the flue gases join the air currents in passageway 32 and flow out the leeward side of the cap. When there are no air cur-rents, flue gases will escape from all of the openings 12.

From the foregoing description it will now be understood that the chimney cap of the invention is inexpensive in construction and yet performs the desired functions in a reliable manner. The cap has only four parts, all of which may be easily formed from sheet metal and joined together by, for example, spot welding, rivets or snap locking engagement.

I claim:

1. A chimney cap comprising a flue pipe adapted to be oriented in operative position with its axis vertical, said pipe being open at the upper and lower ends thereof and being substantially imperforate between said ends thereof, a side wall spaced radially outwardly from and encircling said flue pipe adjacent the upper end thereof to define with said flue pipe an annular passageway radially therebetween, said side Wall being disposed with at least the major portion of its axial dimension extending downwardly from the plane of the upper end of said flue pipe, said side wall having ciroumferentially spaced openings therein establishing communication between said annular passageway and the exterior of said cap, said openings having upper and lower edges disposed generally axially between the ends of said flue pipe, a series of vanes disposed one adjacent each of said openings and projecting from said side wall into said passageway for directing air currents therein in one circular direction about said flue pipe in response to wind currents entering said passageway via the openings in the windward side of the cap and leaving via the openings on the leeward side of the cap, a substantially int-perforate cover spaced above the upper end of said flue pipe and closing the upper end of said side wall to form a substantially imperforate upper baffle over the upper end of said flue pipe for directing gases leaving said flue pipe into said passageway and a substantially imperforate lower baffle extending radially between said side wall and said flue pipe below said vanes to define a bottom wall of said annular passageway.

2. The chimney cap of claim 1 in which said side wall consists of a cylindrical piece of sheet metal and said vanes are portions of said piece bent inwardly thereof from axially extending edges of said openings, the upper and lower edges of said vanes and said openings being axially spaced respectively below and above the upper and lower edges of said side wall such that two imperforate bands of metal remain in said side wall, one above and one below said openings.

3. The chimney cap of claim 1 in which said vanes each extend at substantially the same angle with respect to an imaginary radial line drawn through the axis of said pipe and the junction of the associated vane with said side wall.

4. The chimney cap of claim 1 in which said upper end of said flue pipe and the upper end of each of said openings are flush with one another.

5. The chimney cap as set forth in claim 1 wherein said side wall is cylindrical and concentric with said flue pipe and each said vane extends from said side wall at an angle of about 21 to about 25 with respect to an imaginary radial line drawn through the axis of said flue pipe and the junction of said vane with said side wall.

References Cited by the Examiner UNITED STATES PATENTS 918,962 4/ 1909 Cauchemount 9866 2,717,547 9/1955 Grenzebach et al 9866- FOREIGN PATENTS 894,908 10/ 1953 Germany.

ROBERT A. OLEARY, Primary Examiner.

M. A. ANTONAKAS, Assistant Examiner.

Claims

1. A CHIMNEY CAP COMPRISING A FLUE PIPE ADAPTED TO BE ORIENTED IN OPERATIVE POSITION WITH ITS AXIS VERTICAL, SAID PIPE BEING OPEN AT THE UPPER AND LOWER ENDS THEREOF AND BEING SUBSTANTIALLY IMPERFORATE BETWEEN SAID ENDS THEREOF, A SIDE WALL SPACED RADIALLY OUTWARDLY FROM AND ENCIRCLING SAID FLUE PIPE ADJACENT THE UPPER END THEREOF TO DEFINE WITH SAID FLUE PIPE AN ANNULAR PASSAGEWAY RADIALLY THEREBETWEEN, SAID SIDE WALL BEING DISPOSED WITH AT LEAST THE MAJOR PORTION OF ITS AXIAL DIMENSION EXTENDING DOWNWARDLY FROM THE PLANE OF THE UPPER END OF SAID FLUE PIPE, SAID SIDE WALL HAVING CIRCUMFERENTIALLY SPACED OPENINGS THEREIN ESTABLISHING COMMUNICATION BETWEEN SAID ANNULAR PASSAGEWAY AND THE EXTERIOR OF SAID CAP, SAID OPENINGS HAVING UPPER AND LOWER EDGES DISPOSED GENERALLY AXIALLY BETWEEN THE ENDS OF SAID FLUE PIPE, A SERIES OF VANES DISPOSED ONE ADJACENT EACH OF SAID OPENINGS AND PROJECTING FROM SAID SIDE WALL INTO SAID PASSAGEWAY FOR DIRECTING AIR CURRENTS THEREIN IN ONE CIRCULAR DIRECTION ABOUT SAID FLUE PIPE IN RESPONSE TO WIND CURRENTS ENTERING SAID PASSAGEWAY VIA THE OPENINGS IN THE WINDWARD SIDE OF THE CAP AND LEAVING VIA THE OPENINGS ON THE LEEWARD SIDE OF THE CAP, A SUBSTANTIALLY IMPERFORATE COVER SPACED ABOVE THE UPPER END OF SAID FLUE PIPE AND CLOSING THE UPPER END OF SAID SIDE WALL TO FORM A SUBSTANTIALLY IMPERFORATE UPPER BAFFLE OVER THE UPPER END OF SAID FLUE PIPE FOR DIRECTING GASES LEAVING SAID FLUE PIPE INTO SAID PASSAGEWAY AND A SUBSTANTIALLY IMPERFORATE LOWER BAFFLE EXTENDING RADIALLY BETWEEN SAID SIDE WALL AND SAID FLUE PIPE BELOW SAID VANES TO DEFINE A BOTTOM WALL OF SAID ANNULAR PASSAGEWAY.