Fire Damper Blade Latch

Abstract

A pivotally mounted latch for a fire damper blade which is mounted to swing on a horizontal axis between an open position and a closed position. The damper is adapted to be mounted across either a horizontal or a vertical duct. The blade is normally held open by a fire responsive release and is weighted to swing by gravity to closed position across the duct when released. The latch is mounted on the outer side of the blade on a pivot axis parallel to that of the blade and extends through a slot in the blade. The latch has a plate with a generally arcuate edge which is eccentric to its pivot and which strikes a catch as the blade closes. The eccentricity of the latch plate weighs the plate to swing it into locked position behind the catch when the damper blade reaches closed position. The latch operates effectively whether the fire damper is mounted in a horizontal or a vertical position.

Parent Case Text

This application is a continuation-in-part of my copending application Ser. No. 30,225, filed Apr. 20, 1970 now abandoned.

Description

BACKGROUND OF THE INVENTION

This invention relates to a fire damper having a pivoted blade latch.

Heretofore, if latches were employed with fire damper blades, they utilized springs, either in the form of spring catches or spring-actuated latches. Such devices required a substantial amount of force to operate properly. In the event of a fire, the resiliency of the spring also could be destroyed by the heat, causing the latch to fail.

The fire damper in accordance with the instant invention employs a pivoted, gravity-operated latch requiring no springs whatsoever. The latch thereby requires little force to operate and is reliable in operation. Further, the fire damper employing this latch operates effectively in either a horizontal or vertical installation.

It is, therefore, a principal object of the invention to provide a fire damper with an improved latch having the advantages outlined above.

Numerous other objects and advantages of the invention will be apparent from the following detailed description of a preferred embodiment thereof, reference being made to the accompanying drawings, in which:

FIG. 1 is a fragmentary view in perspective of two fire dampers comprising latches embodying the invention, and located side by side in a horizontal duct, one damper blade being shown in open position and the other being shown in closed position;

FIG. 2 is a vertical sectional view taken along the line 2--2 of FIG. 1;

FIG. 3 is a view similar to FIG. 2 but taken along the line 3-3 of FIG. 1;

FIG. 4 is a fragmentary, enlarged sectional view of a latch and catch of the fire damper, in a partially closed position;

FIG. 5 is a view similar to FIG. 1 but showing two fire dampers comprising latches embodying the invention and located side by side in a vertical duct;

FIG. 6 is a vertical sectional view taken along the line 6--6 of FIG. 5; and

FIG. 7 is a view similar to FIG. 6 but taken along the line 6--7 of FIG. 5.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring particularly to FIG. 1, two substantially identical fire dampers generally indicated by the reference number 10 are located in side-by-side relationship, in this instance, in a horizontal duct 12. The fire dampers 10 can be made in several standard sizes and employed singularly, side by side, stacked, or both, to extend completely across a duct or other opening which is to be blocked in the event of fire. The fire dampers are normally held in an open position as shown by the left hand damper in FIG. 1, in which position they provide substantially no resistance to air passing thereby. In the event of fire or heated gases from a fire flowing through the duct, the dampers will close and assume the position illustrated by the right hand damper in FIG. 1, in which instance the flow through the duct or opening is substantially stopped. Each of the fire dampers 10 perfectly is a unit in itself and is installed in the duct or opening as a complete assembly. When two or more dampers are used as an assembly, one can be affixed to the other by suitable fasteners or by welding.

Each of the dampers 10 includes an upper or first frame member 14, a lower or second frame member 16, and two side frame members 18 and 20. As shown, these members are of channel-shaped configuration and are welded together to produce an integral frame. The first frame member 14 has a stop strip 22 extending longitudinally and suitably affixed to a central portion thereof. The second frame member has a catch strip 24 also extending longitudinally and suitably affixed centrally thereof. The stop 22 and the catch 24 can function effectively without extending completely across the damper, but by so extending, they also serve as seals at opposite edges of the damper frame and thereby more effectively prevent passage of gases when the damper is closed.

A single damper blade 26 is of a size to close the opening formed by the respective frame members 14-20 of each of the dampers. The blade 26 has axles 28 and 30 extending outwardly from opposite sides thereof and received respectively in openings 32 and 34 in the side frame members 18 and 20. The axles 28 and 30 are positioned above the center of the blade 26 and the holes 32 and 34 are similarly located closer to the upper frame member 14 than the lower frame member 16 in order to weight the blade 26 to swing closed when released.

In this instance, the blade 26 is held in the open position by a linkage connected to the edge of the blade 26 closer to the upper frame member 14. An ear 36 is suitably affixed to the upper edge portion of the blade 26 and has a hook 38 which connects the ear 36 to a fusible link 40. The fusible link 40 is connected by an additional hook 42, a chain 44, and a lower hook 46 to a mounting eye 48 suitably fastened to or through the lower wall of the duct 12. The fusible link 40 fuses when a certain temperature is reached as is known in the art, thereby to release the blade 26 to swing downwardly by gravity to closed position.

When the blade 26 is held in the open position by the fusible link 40 and associated components, the larger portion of the blade 26 on the opposite side of the axles 28 and 30 bears against a stop 50, as shown in FIG. 1, to prevent the possibility of unwanted movement or wavering of the blade as fluids through the duct 12.

When the link 40 fuses, the unbalanced blade 26 swings shut so that the upper edge thereof contacts the stop 22 and the other edge contacts the catch 24. Particularly with a high volume of heated gases, it is desirable that the damper blade be positively held shut when closed. Heretofore, this has been accomplished by various spring catches or spring-actuated latches. These, however, have required a considerable amount of force to be moved properly and also are subject to failure due to heat from the fire.

The latching arrangement embodying the invention overcomes these disadvantages and is also reliable and effective in operation. A latch embodying the invention is indicated at 52 and comprises a latch plate 54 pivotally carried on a bracket 56 which is affixed, as by rivets, to the outer side of the edge portion of the blade 26 which lies adjacent the catch 24 when the blade is closed. The latch plate 54 includes a shank portion 58 which is pivoted by a suitable pin or rivet 60 to the bracket 56 with the shank integrally connected to a heavy cam portion 62. The cam portion 62 has a generally arcuate cam edge 64 which strikes the catch 24 as the blade 26 closes to swing the latch plate 54 upwardly, in a clockwise direction as shown in broken lines. The latch plate 54 thereby is elevated above the catch 24, and, when the edge of the blade 26 strikes the catch 24, the latch plate 54 snaps downwardly, i.e., radially relative to the axles 28 and 30. A latching edge 66 of the cam portion 62 swings downwardly behind and engages the catch 24. The edge 66 preferably diverges outwardly from the plane of the blade 26 somewhat to assure that the latch will engage the catch and will not bounce away from it. As the latch plate 54 snaps downwardly the upper edge of the catch 24 is wedged between the latching edge 66 and the inner side of the blade 26. This assures a maximum sealing effect between the blade 26 and the fire damper frame.

The cam portion 62 of the latch plate 54 is located on the inner side of the damper blade 26 and the shank portion 58 on the opposite side of the blade, extending through a slot 68 which is generally perpendicular to the axis of the axles 28 and 30. The lower edge of the slot 68 is so located as to prevent the latch plate 54 from being swung radially outwardly too far to engage the catch 24 as the blade swings toward the closed position, as shown in FIG. 4. When the latch plate 54 moves over the catch 24 and snaps downwardly, the catch 24 is wedged between the edge 66 and the blade 26 before the latch plate 54 can move to its lowest position against the lower edge of the slot 68. The upper edge of the slot 68 limits the upward movement of the latch plate 54 to prevent the possibility of the latch plate bouncing excessively when cammed upwardly by the catch 24 during closing movement of the blade 26.

While the shape of the cam portion 62 is shown as generally arcuate, it can vary substantially, it being only important that the edge 64 is effective to force the latch plate 54 in the direction opposite to the direction it is urged by gravity. Also, the cam portion 62 must be eccentric to the rivet 60 and of sufficient weight to urge the latch plate 54 toward the latching position, in a counterclockwise direction, as shown in the drawing.

While the latch has been disclosed specifically in connection with a single-blade fire damper, it can be used with equal efficacy with fire dampers having more than one mechanically connected blade.

FIGS. 5, 6 and 7 show a pair of dampers 10a positioned across a vertical duct 12a, the dampers 10a being identical in every respect with the dampers 10 illustrated in FIGS. 1-4 and all of their structure and details corresponding to the structure and details of the dampers 10 as described above.

In the arrangement illustrated in FIGS. 5, 6 and 7, however, damper blades 26a extend generally vertically when in open position and lie horizontally when in closed position. It will also be observed in FIG. 5 that the damper blade 26a at the left side of the drawing is not precisely vertical but is inclined forwardly slightly relative to the vertical so as to be weighted to swing downwardly into the closed position illustrated at the right side of FIG. 5 when its fusible link 40a is released in response to fire or heat.

As can best be seen by comparing FIGS. 1 and 5 the damper blade 26a is identical with the damper blade 26 of FIGS. 1-4, inclusive and, in open position, is positioned the same relative to its frame. The blade 26a has a latch 52a identical in every respect with the latch 52 shown in FIGS. 1-4. When its fusible link 40a releases the blade 26a, gravity swings the blade downwardly to the right (in a clockwise direction) and, as in the case when the damper 10 is in the vertical position illustrated in FIGS. 1-4, inclusive, engagement of the generally arcuate cam edge 64a with the edge of its associated catch 24a causes the latch 52a to be snapped sharply in a clockwise direction around its pivot 60a a degree of arcuate movement limited by the inner edge of its slot 68a. As the outer edge of the damper blade 26a strikes the catch 24a, the eccentric weighting of the latch 52a and its inertia cause it to fly radially outwardly relative to the damper blade axles 28a and 30a snapping it sharply outwardly beneath the catch 24a to wedge the catch 24a against the inner (in this case lower) side of the edge portion of the damper blade 26a.

Details of construction, sizes, shapes, function and operation of the damper having a catch embodying the invention are identical whether the damper is arranged in vertical position as shown in FIGS. 1-4, inclusive, or in horizontal position as shown in FIGS. 5-7, inclusive. In either orientation, the eccentric weighted design of the latch 52 or 52a and its positioning at the edge of the blade 26 or 26a results in the latch 52 or 52a functioning automatically, precisely and definitely with no likelihood either that it will bounce open and remain unlatched when the damper blade 26 or 26a reaches closed position or that it will fail to remain in latched position after once having been closed.

Claims

I claim:

1. An automatic fire damper comprising a frame lying generally in a plane and defining an opening for the flow of air therethrough in a direction generally normal to the plane of said frame, a blade fitting such opening for closing the same upon the occurrence of a fire, cooperating axially aligned pivot means on said frame and said blade providing for angular movement of said blade between a closed position across said opening and an open position, said blade being biased toward closed position when in such open position, heat fusible means for holding said blade in open position, a catch on said frame protruding therefrom into such opening generally parallel to the plane of said frame and a latch pivotally mounted on said blade at a position to engage said catch when said blade moves into closed position, said latch having an integral weighted portion offset horizontally relative to its pivot point for swinging said latch into engagement over said catch upon movement of said blade to closed position both when said frame lies in a horizontal plane and when said frame lies in a vertical plane.

2. A fire damper according to claim 1 in which the catch on the frame is a flat bar extending parallel to the pivot line of the pivot means and the latch is pivoted on an axis parallel to such pivot line.

3. A fire damper according to claim 2 in which the latch has a cam portion engageable with said catch as said blade moves to closed position and said cam portion is weighted for causing said latch to fall over said catch when said blade reaches closed position.