Vent Cover

Abstract

A vent cover for prevention of infiltration of particulate matter into a t, which is particularly useful for eliminating snow infiltration in cold regions. The vent cover is an airfoil in the form of a plano-convex lens having a diameter larger than that of the vent pipe on which it rests. Air flowing over the convex upper surface of the vent cover increases in velocity and thereby tends to hold any particulate matter in suspension as it passes over an opening centered at the crown of the vent cover. The vent cover is omni-directional in its effect. The increase in velocity of air flowing over the opening also creates an upward draft in the vent. The combination of upward draft and high velocity air flow across the upper surface of the vent cover prevents particulate matter from entering and accumulating in the vent.

Description

The invention described herein may be manufactured, used, and licensed by or for the Government for governmental purposes without the payment to me of any royalty thereon.

BACKGROUND OF THE INVENTION

This invention relates to a vent cover for use in conjunction with a vent to prevent or minimize the accumulation of particulate matter, such as snow, in the vent without interfering with ventilation.

In cold regions, such as the DEW Line Ice Cap Stations in Greenland, certain activities, such as waste water disposal, may be carried out below the surface in tunnels. Such space requires venting to remove stale or contaminated air while fresh air is being brought in to replace the vented air. Some of the vents are 3 to 4 feet in diameter. In the past, such vents have simply terminated as an open pipe above ground and have repeatedly become plugged with snow during storms. Such plugs have become 10 feet or more in length over the course of a single winter. Attempts to prevent snow infiltration using rotating blades, directional cowlings, or other mechanical devices are frequently unsuccessful. Expensive electrical equipment, such as fans and resistance heaters, may be impractical and of questionable reliability.

It is, therefore, an object of the invention to provide a reliable means for simply and inexpensively preventing the infiltration of particulate matter into vents.

A further and more particular object of the invention is to provide a means for preventing the infiltration of snow into vents connected to underground space, especially in cold regions.

Other objects and advantages will be apparent from the following description of several embodiments of the invention, and the novel features will be particularly pointed out hereinafter in connection with the appended claims.

SUMMARY OF THE INVENTION

The invention comprises a vent cover which is disposed above or mounted on top of the open end of a vent pipe connecting with a space from which air is vented to the external atmosphere. The vent cover is in the form of a plano-convex lens, the plane surface being the lower surface and being generally horizontally disposed, the convex surface being the upper surface. It has a cylindrically-shaped opening passing vertically through its center, the diameter of the opening being from about one-third to about one-half that of the vent. The overall diameter of the vent cover is from about 1.5 to about 2.0 times that of the vent pipe, and consequently the vent cover overhangs the outer edge of the vent pipe. When a wind is blowing from any direction, this configuration increases the velocity of air flowing across the opening in the vent cover. As a result of the velocity increase above the opening, any particulate matter in the air is held in suspension there and thus is prevented from accumulating in the vent. The flow of air over the vent cover also produces a pressure reduction in the region just above the convex upper surface of the vent cover. This lowered pressure is transmitted into the vent thereby enhancing the ventilating capabilities of the vent. The overhang of the vent cover over the vent pipe serves the important purpose of minimizing the adverse effects of an eddy on the leeward side of the opening. Snow or other particles swirling about in such an eddy would be carried inside a vent without the overhang. Thus, accumulation of snow or other particulate matter in the vent is essentially prevented and the vent may be used for an indefinite period of time without becoming plugged with such particulate matter.

BRIEF DESCRIPTION OF THE DRAWING

In the drawing:

FIG. 1 is a top plan view of the vent cover of the invention;

FIG. 2 is a vertical cross-section of the vent cover of FIG. 1 taken through the plane represented by line 2--2 in FIG. 1;

FIG. 3 is a top plan view of a modified form of a vent cover of the invention wherein the central cylindrically shaped opening in the vent cover is shielded by a generally circular flat plate somewhat larger in diameter than the opening and adapted to be adjustably positioned at variable heights above the opening in the vent cover; and

FIG. 4 is a vertical cross-section of the modified form of vent cover of FIG. 3 taken through the plane represented by line 4--4 in FIG. 3.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following description of the preferred embodiments of the invention will be in relation to the prevention of accumulation of snow inside of a vent; but it will be understood that the same principles will apply to the prevention of accumulation of other particulate matter inside of a vent.

Referring to the drawing, wherein like characters designate like parts in all views, 10 designates a vent cover, in accordance with the invention, which is in the form of a plano-convex lens, as shown in FIGS. 2 and 4. The vent cover has a cylindrically-shaped opening 11 passing vertically through its center, forming a passageway for the flow of air through the vent cover from vent 12. Vent 12 is the space confined by vent pipe 13, which is usually cylindrically shaped and connects with the space to be ventilated, not shown. The ground through which the vent pipe passes is represented by numeral 14, although the vent pipe may pass through other media if desired. The overall diameter of the vent cover is greater than the overall diameter of vent pipe 13, providing an overhanging portion 15 of the vent cover overhanging the outer surface 16 of the vent pipe. The diameter of the vent cover is from about 1.5 to about 2.0 times that of the vent pipe. The upper surface 20 of the vent cover is convex upward, which causes the vent cover to function as an airfoil when a wind is blowing toward the vent cover from any direction. Thus, as air flow lines 17 are deflected up and over the vent cover, as shown in FIG. 2, their velocity increases. The increased air flow velocity across the convex upper surface of the vent cover with even the slightest breeze blowing prevents snow from collecting within the vent since the snow is held in suspension as it passes over the opening in the vent cover. The vent cover is disposed in a fixed relationship to the vent pipe above the same and preferably is fastened to the top of the vent pipe by fastening means such as clip angles 18. It is preferred that the lower surface 19 of the vent cover be substantially flat.

The overhanging portion 15 acts as a baffle against the upward swirling of snow caused by eddies created on the leeward side of the vent pipe, further minimizing the chances of snow getting into the vent.

It is preferred that the diameter of opening 11 be from about one-third to about one-half the diameter of the vent, i.e., one-third to one-half the inside diameter of the vent pipe.

It is preferred that the centerline height of the vent cover be from about 10 percent to about 15 percent of the diameter of the vent cover.

FIGS. 3 and 4 represent a modified form of vent cover which is particularly useful in areas where much of the snowfall is not accompanied by an appreciable amount of wind. This modification comprises a flat, generally circularly-shaped plate 21 mounted on the upper end of shaft 22. Shaft 22 is adjustably mounted to slide up or down through bracket 23, which is attached to the inside wall of the vent pipe, and to be clamped in position thereby with plate 21 adjusted to any desired level with respect to vent cover 10 and opening 11 therein. Plate 21 is disposed above the vent cover and substantially parallel to the lower surface of the vent cover, has a diameter from about 30 percent to about 60 percent greater than the diameter of opening 11 in the vent cover, and has its axis substantially coaxial with the axis of vent cover 10 and opening 11 so that snow falling in a quiescent atmosphere will not collect within vent 12, but rather will collect on plate 21 and on the upper surface of the vent cover. Either subsequent winds will remove this snow or it will melt, drip onto the upper surface of the vent cover, and drain to the peripheral edge of the vent cover.

The materials of which the vent cover of the invention is constructed may vary considerably. For example, the vent cover may comprise a metallic skin forming the upper and lower surfaces thereof as well as the walls of the opening 11; and the space between the several portions of the skin may contain a wide variety of supporting and filling materials, including plastic materials, either expanded or not as desired, wood, cork, and other similar materials for the purpose. The vent cover could be molded in one piece from plastic or other material capable of withstanding temperatures to which it would be likely to be exposed without shattering or cracking.

The vent cover of the invention has the advantage of being omnidirectional in its action and is useful for minimizing snow infiltration into vent shafts employed in the ventilation of spaces in cold regions. However, it could also serve to control particulate matter other than snow flowing in either liquids or gases.

It will be understood that various changes in the details, materials, and arrangements of parts, which have been herein described and illustrated in order to explain the nature of the invention, may be made by those skilled in the art, within the principle and scope of the invention as expressed in the appended claims.

Claims

I claim:

1. In combination, a hollow vent pipe defining an air vent, and means for preventing the accumulation of particulate matter within said air vent, said means comprising a vent cover mounted on top of said vent pipe, said vent cover being substantially circular in its horizontal plane and having a diameter from about 1.5 to about 2.0 times that of said vent pipe, said vent cover being of a generally plano-convex form, the lower surface of said vent cover being generally planar, the upper surface of said vent cover being convex, said vent cover having a generally cylindrically shaped opening of lesser diameter than the inside diameter of said vent pipe passing vertically from said lower surface to said upper surface of said vent cover substantially through the center of said vent cover through which air is conducted upwardly from said vent, said vent cover being adapted to increase the velocity of air flowing above the upper surface of said vent cover regardless of the direction of the compass from which wind blows against the edge of said vent cover and to cause the production of a lower pressure than the atmospheric pressure in the region just above the upper surface of said vent cover, whereby particulate matter falling or being transported by wind or being carried upwardly by eddies of air in the vicinity of said vent pipe, vent and vent cover is prevented from accumulating within said vent.

2. The combination according to claim 1, wherein said cylindrically shaped opening has a diameter from about one-third to about one-half the diameter of said vent.

3. The combination according to claim 1, wherein the upper surface of said vent cover is convex upward so that the centerline height of said vent cover is from about 10 percent to about 15 percent of the diameter of said vent cover.

4. The combination according to claim 2, wherein the upper surface of said vent cover is convex upward so that the centerline height of said vent cover is from about 10 percent to about 15 percent of the diameter of said vent cover.