US2964036A - Curtain dampers - Google Patents

Description

Dec. 13, 1960 ERNEST LOWE 2,964,036

FORMERLY LOEWENHEIM CURTAIN DAMPERS Filed Oct. 15, 1956 2 Sheets-Sheet 1 Dec. 13, 1960 ERNEST LowE- FORMERLY LOEWENHEIM CURTAIN DAMPERS 2 Sheets-Sheet 2 Filed 001;. 15, 1956 rk V 3 known, as wcnke uzz/ CURTAIN DAMPERS Ernest Lowe, formerly Loewenheim, London, England, assignor to Amereng Development Corporation, New York, NY.

Filed October 15, 1956, Ser. No. 615,912

Claims priority, application Great Britain Oct. 18, 1955 .1 Claim. (Cl. 126-285) This invention relates to dampers for providing a gastight seal in flues or other ducts through which flow gases.

Various types of dampers have been used for this purpose. Thus a louvre damper is described in British Patent No. 731,252 which has leaf-spring sealing elements. Such a damper, whilst it gives a satisfactory seal for small or medium sized flues for boilers and furnaces, can be used only with rather limited spindle lengths and is therefore unsuitable for fines of large cross-section. Another disadvantage of the louvre damper is that it constitutes a permanent obstruction in the flue and when the gas velocities are high this causes a pressure drop and is also subject to erosion.

For the gas-tight sealing of flues of large cross-section curtain dampers have been used (see for example British Patent No. 453,477) which comprise a frame and a curtain mounted at one side of the frame and adapted to be drawn across the frame to close it. 'Such dampers as hitherto proposed have provided only an aerostatic seal. If the static differential of gas pressure is too small it may then be insuflicient to overcome creases and unevenness in the curtain materials and hence a poor'seal willresult.

Also the aerostatic seal only works for one direction of gas flow and is destroyed "if "the gas flow reverses its direction or is pulsating.

With the type of curtain material hitherto proposed, i.e. asbestos or similar heat-resisting fabric, destruction of the curtain can result either by bagging out of the "material between supporting grid bars if the pressure differential is too great, resulting in permanent distortion of the material; or by vibration caused by a pulsating gas flow.

Furthermore this type of material even in the thickest weaves is permeable and leakages result which in some circumstances may not be tolerable. Increasing the thickness of the material will reduce its flexibility which will adversely affect the seal.

It has been found that substitution of thin sheet metal for heat-resisting fabric in the aerostatic curtain damper is not satisfactory. Thus distortion between the grid bars and corners soon gives a permanent set which spoils the seal.

it is an object of the invention to provide a curtain-type damper which overcomes the above mentioned diflicu-lties.

The invention consists of a curtain damper comprising a frame, a gas-impermeable curtain, means for mounting the curtain to one side of the frame, means for drawing the curtain across the frame to a closed position, and means for effecting a seal between the margins of the curtain extending in the direction of movement and the frame in the closed position comprising strips of sheet material extending along the margins, flexible along their length and resiliently flexible across their width, and arranged to be resiliently flexed across their width in the closed position of the curtain to effect the seal.

The curtain may be rigid and slid bodily across the frame and back out of the frame or it may be flexible and slid bodily or rolled and unrolled.

It may be mounted above the top side below the bottom side, or to one or other lateral sides of the frame.

The marginal strips which may be straight or curved in section, maybe secured to the frame or secured to or integral with the curtain or secured to neither. Two or more sets of marginal strips may be providedto seal the same marginal edge, e.g. two on the curtain, two on the frame, one on-the frame and one on the curtain, and so on.

The marginal strips may be permanently held in their resiliently flexed position or the bending may be effected (or increased) as the curtain is slid or rolled into the closed position.

In the latter case the flexibility along the length of the strips enables them to follow the movement of the curtain, while in general it enables the strips to adapt themselves to any warpage of frame parts in the flue which may occur.

Generally it will be desirable to have the strips resilient- 1y flexible along their length also and to this end the strips may be of heat-resistant sheet metal, such as spring steel and in planar form when non-flexed.

Conveniently, the whole width of the curtain may be of such sheet metal which then provides margins of the desired properties.

Such a curtain may be stiffened with spaced parallel bars secured thereto (at right angles to the direction of movement in the case of a rolled curtain) and these may be supported by spaced parallel bars across the frame at right angles to the curtain bars.

Considering now the arrangement for resiliently flexing or maintaining resiliently flexed the marginal strips in the closed position of'the damper, various possibilities arise.

If one set of marginal strips'is used thenit is possible to have the curtain held against a marginal abutment on the frame at the same time flexing the marginal strips. The strips maybe secured to or integral with the curtain and flexed against a further marginal abutment or abutments-on the frame, or they may be secured to the frame and flexed against the curtain and if desired, against another abutment as well. 7

Alternatively, the strips may be secured to or integral with the curtain and resiliently flexed by means of two sets of marginal abutments integral with or secured to the frame and one on each side of the strips.

This arrangement affords an eflicient seal for either direction of gas flow.

If two sets of marginal strips are used these may be secured to the frame and resiliently flexed one on each side of the curtain; or they may be secured to or integral with the curtain and flexed, inwardly or outwardly, one on each side of a marginal abutment on the frame (or separate abutments may be provided for each strip).

These arrangements would also provide a seal for either direction of gas flow.

The arrangements for sealing the leading edge of the curtain extending at right angles to the direction of movement as the curtain is closed may be similar in construction to those for sealing the edges of the curtain extending in the direction of movement. Conveniently, one or both edges of the curtain extending at right angles to the direction of movement may be sealed by marginal strips of heat-resistant, spring steel sheet secured to the frame on one side of the curtain and resting against the curtain over a flat portion of the strips.

The curtain may be pushed (it suitably constructed) or pulled to draw it across the frame and various means of operation may be used.

Flue dust ejection arrangements may be provided if desired.

The invention will be further described with reference to the embodiments shown in the accompanying drawings. V

In the drawings:

Figure 1 is a side elevation of a roller curtain damper in accordance with the invention.

Figure 2 is a section on the line A-A of Figure 1.

Figure 2a is an enlarged detail of Figure 2.

Figure 3 is a section on the line BB of Figure l; and

Figures 3a and 3b are enlarged details of Figure 3.

In the embodiment of Figures 1 to 3, the frame 1 is adapted to be closed by a heat-resistant sheet-steel curtain 2 having marginal leaf-spring strips 2a having free edges. The curtain is guided into position by bars 3 across the frame three on one side and two on the other.

In so guiding the curtain these bars 3 bend the strips 2a at lateral free edges thereof against a bracket 1a in the frame and against an abutment 1b having an elongated planar surface (offering two lines or surfaces of contact). The strips 2a have, therefore, inward and outward portions engaging the bracket 1a and the abutment 1b.

This sealing arrangement is suitable for fines in which the gas flow is in one direction only, preferably that which reinforces the sealing action.

To raise and lower the curtain, it is rolled at the top within head gear casing 4 around a roller 5. The roller is operated by a chain drive 6 from an electric motor 7 mounted on the headgear or may be operated by hand by a second chain drive 8 from a handle 9 in an emergency.

At the top the curtain emerges into the frame over a top seal comprising strips 10 of spring steel heat-resistant sheet mounted in the head gear 4, one on each side of the curtain and adapted to bear against the curtain from the respective sides over a flat portion of the steel strip. The strips are bent back at the edges in a permanent set to allow the curtain to slide into the headgear 4 without catching in the edges of the strips.

At the bottom curtain deflecting wedges 11 are provided on the frame and a guide member 2b is provided on the curtain which co-operates with the wedges 11 to flex the bottom marginal spring steel edge of the curtain against an inclined surface portion of abutment bar 12 on the frame.

The guide member 2b acts also as a weight for lowering the curtain.

What I claim is:

A flue sealing arrangement comprising an open frame for installation in a flue, a reciprocable curtain-type damper in said frame, a first cooperable imperforate wall means forming at least part of said damper, a second cooperable imperforate wall means forming part of said frame relative to which said first cooperable means is movable, means operatively connected to said first cooperable means for reciprocably moving the latter relative to the opening of said frame, said second cooperable means including abutment means having an elongated planar surface extending at an acute angle to said frame and supported thereby, said second cooperable means terminating in a marginal edge, said first cooperable means being movable between a first position allowing free passage of flue gases through said open frame and a second position closing said passage through said frame, said first cooper-able means including heat resistant marginal spring strip means extending in planar form when nonfiexed and engaging said marginal edge of said second cooperable means, said strip means terminating in at least one free edge projecting beyond said marginal edge onto said planar surface of said abutment means and in surface contact therewith so that inward and outward portions of said strip means are in contact engagement with said second cooperable means, said spring strip means conforming to the contour of said second cooperable means even in distorted condition and upon said free edge of said strip means being pressed thereagainst in overlapping and surface contact relation due to the inherent resilient force of said strip means in said second position of said first cooperable means, to thereby form a gas-tight seal in said flue.

References Cited in the file of this patent UNITED STATES PATENTS 2,349,368 Myers May 23, 1944 2,489,915. Loewenheim Nov. 29, 1949 FOREIGN PATENTS 18,948 Austria Jan. 25, 1905 364,454 Germany Nov. 24, 1922 656,748 Germany Nov. 7, 1933 524,220 Great Britain .Aug. 1, 1940 536,314 Great Britain May 9, 1941

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