US3783768A

US3783768A - Damper assembly

Info

Publication number: US3783768A
Application number: US00189085A
Authority: US
Inventors: L Caming; F Fromwiller
Original assignee: IMP DAMPER CO Inc
Current assignee: IMP DAMPER CO Inc
Priority date: 1971-10-14
Filing date: 1971-10-14
Publication date: 1974-01-08
Anticipated expiration: 1991-01-08

Abstract

A damper assembly is provided in a rectangular frame with streamlined blades rotatable on parallel shafts. The shafts may be square in section and ride in square orifices extending through hubs of the extruded blades. Air, smoke or other gaseous leakage is immeasurably reduced between the ends of the blades and the frame by a unique composite seal disposed between the end of the blades and the damper frame.

Description

Waited States Gaming et a1.

DAMPER ASSEMBLY Inventors: Lionel-P. Calming, New York City;

Frank J. Fromwilller, New City, both of N.Y.

Imperial Damper Co., Inc., Bronx, N.Y.

Filed: Oct. 14, 1971 Appl. No.: 189,085

Assignee:

us. ca. 98/110, 98/121 Int. Cl F24f 113/08 Field of Search 98/40 V, 40 VM, 40 R, 98/41R, 110,121

References Cited UNITED STATES PATENTS 4/1963 Scharres 98/110 X Jan. 8, 1974 3,123,098 3/1964 Bishop 98/110 X 3,180,246 4/1965 Johnson.... 98/110 3,547,152 12/1970 Hess 137/601 3,606,245 9/ 1971 Reichow 137/601 Primary ExaminerMeyer Perlin Assistant ExaminerR. Capossela Att0rneyLilling & Siege] [5 7] ABSTRACT A damper assembly is provided in a rectangular frame with streamlined blades rotaable oii'pariila sh ai tsi The shafts may be square in section and ride in square orifices extending through hubs of the extruded blades. Air, smoke or other gaseous leakage is immeasurably reduced between the ends of the blades and the frame by a unique composite seal disposed between the end of the blades and the damper frame.

13 Claims, 18 Drawing Figures PATENTEDJAH 8 m4 3.783.768

INVENTORS. LIONEL P. CAMING FRANK J. FROMWILLER ATTORNEYS PATENTEDJAN 8 I974 SHEET 2 BF 5 INVENTORS.

LIONEL P CAMiNG RY FRANK J. FROMWILLER A TTOR N 4 S PAIENTEUM 8 I974 3783768 sun-:1 3 or 5 INVENTORS. LIONEL P CAMING FRANK J FROMWILLER 2 ATTORN Y5 PATENTEDJAH 8 I974 SHEET IUF 5 FIG. 9

agvaakrss PATENTEDJAH 8 I974 SHEET 5 0F 5 INVENTORS. LIONEL R CAMING [y FRANK J. FROMWILLER ATTO ZNEYS DAMPER ASSEMBLY BACKGROUND OF THE INVENTION The present invention relates to improvements in the design and construction of flow control devices, generally known in the art as dampers or louvers.

In many instances, largely associated with the flow of gaseous fluids in various temperature control systems, such as heating, ventilating and air-conditioning; it is required to regulate the flow of a fluid across an aperture or through a duct continuously from substantially complete cessation of such flow to the maximum rate possible under the available pressure differentials.

It is known in the art to supply a damper, or louver assembly in such instances with a number of parallel, planar blades pivoted near their aerodynamic centers of pressure and provided with mechanisms to rotate them around their respective pivots. These blades may cooperate in forming a complete block to flow through them, or alternately, may be positioned to expose their thickness, rather than their chord, to the flow and thus provide the least possible interference with it.

It is also known that the practical construction of such damper assemblies is attended by many difficulties, notably in securing the best possible seal against leakage when closed, the least impedance to flow when open, and the provision of operating linkages or mechanisms requiring the least possible actuating force and which provides extremely long life of operation substantially free of any malfunctions, such as binding of blades or need of job-site servicing.

For commercial success it is also necessary that the design chosen be adaptable to many differing conditions having wide temperature ranges, varied gases, pressures'and sizes, and that the operating mechanism be readily arranged for both parallel blade rotation and counter-rotation of adjacent blades, such motions being preferred alternately in the several applications of such dampers.

SUMMARY Accordingly, it is therefore, the principle object of the present invention to provide a novel sealing device for reducing the leakage past the ends of the blades of a louver assembly by providing a composite seal between the frame and the blades comprising a unique seal having an arcuate, outer, elastic member of metal or plastic and a resilient inner backing element secured thereto.

It is another object of the' invention to describe novel constructions for the individual louver blades, readily adapted to the provision of many different widths and lengths from prefabricated components.

It is yet another object of the invention to teach the use of a novel pivot-shaft, square in cross-section, for increasing the rigidity of the louver blades and preventing the slippage of the latter in their shafts.

It is a further object of the invention to describe methods for joining a number of complete louver as-' ments and repair; thereby leading to assured commercial success.

These and other objects, features and advantages of the present invention will become more apparent from the detailed description herewith considered in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a damper of the invention shown in an open position;

FIG. la is an enlarged fragmentary view of the sideseal for the damper of the invention;

FIG. 2 is a side elevational view ofa damper assembly with counter-rotating blades;

FIG. 3 illustrates the embodiment of FIG. 2 with all blades rotating in the same sense;

FIG. 4 is a sectional view of the damper assembly il- Iustrating construction of tip-seals;

FIG. 5 is an exploded, perspective view of an actuat ing arm for a damper blade;

FIG. 6 is a detail exploded view of a connector link employed in the embodiment of FIG. 2;

FIG. 7 illustrates a portion of the frame of a multiple damper assembly;

FIGS. 8 and 9 are sectioned views of the jointed frame along the lines 88 and 99 of FIG. 7;

FIG. 10 is a detailed sectional view-of the pivotbearing assembly;

FIG. 10a is an end view or sectional view of the bearing assembly along the lines of l0a-10a of FIG. 10;

FIG. 11 illustrates an alternate embodiment of the louver vane;

FIG. '12 shows a section of another embodiment of the louver or damper blade;

FIGS. 13 and 14 indicate the method of construction of built-up damper blades;

FIG. 15 is a sectional view of the side-seal assembly of FIG. la as may be employed for sealing the top and or bottom rails; and

FIG. 16 is another sectional view indicating the manner of providing a dust-seal cover for the actuating mechanism of the damper assembly.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to FIG. 1, there is shown and illustrated a damper assembly with three

streamlined blades

5a, 5b and 5c. The blades are mounted on parallel pivot shafts, typically 6a, subdividing the aperture of a rectangular frame composed of

siderails

1 and 2, bottom-- rail 4 and top-rail 3. The blades 5 are in the fully open position, with their chords perpendicular to the plane of the aperture and pose little resistance to the flow of a fluid there through. The shaft 6a is preferably square in section so as to provide instant and positive (no slip) blade control and it extends beyond side-frame 1 to receive lever arm 7a, to be further described with reference to FIG. 5. The several lever-arms 7 are connected by push-rod 8; a regulating mechanism suitably of a manual or mechanised design, acts on an extension of the push-rod 8 to open and close the blades 5 by rotating their pivot-shafts 6. These mechanisms have been omitted for clarity; their designs are well extablished in the art and form no part ofthe present invention disclosure.

A small enlarged fragmentary sectional view of the siderail2 is shown in FIG. 1a. The unique seal 9 is formed of an outer flexible, spring-like member 11 and an inner compressible, resilient backing member 10. The inner member 10 may be of any suitable elastomeric material, such as polyvinylchloride, a sponge-like material or a soft neoprene rubber. The outer flexible member 11 may be of a thin, deformable metal, such as copper, bronze, stainless steel, or even of a plastic material, such as teflon, nylon, etc. The inner element 10 is suitably affixed to the outer member as by an adhesive. The seal 9 is disposed in the gap between the end of blades and the

side frame members

1 and 2 and is so dimensioned that it is slightly compressible at all points contacting the blades, as the blades move from an open to a closed position. The seal 9 prevents the flow or passage of gases past the gap between the frame and the blades thus providing the damper assembly with positive scaling properties. The inner member serves to keep any gas or air, etc. from leaking past the side seals 9 and they also prevent gas or air leakage around the shafts passing from the blades through the sides of the frame. Such member is also particularly effective, as will be described hereinafter, about the area around the shaft bearings, which heretofore have been areas where gas or air leakage has been extensive and difficult to overcome.

The inner member 10 also insures and aids in providing proper rigidity to retain correct tension of the outer member or side seal against the ends of the blades. Thus, the ends of the blades force the inner members of the side seals against the side rail frames 1 and 2 and the inherent resiliency of the outer member maintains the side seal in a compressible state when the blades are in an open position. The outer member is therefor when not compressed by the blade ends in its original uncompressed condition.

FIG. 5 is a more detailed illustration of the lever-arm 7 whose body is pierced or bored by a square hole 77 so dimensioned that a sliding fit is obtained upon the insertion of shaft 6 therein. Provision is made for setscrews 75 to engage the shaft 6 once proper alignment has been obtained. The elongated hub 70 of the leverarm 7 carries two pairs of parallel extensions which, in turn, are pierced by circular openings 71/72 and 73/74, respectively. A wrist-pin 83 fits through

bushings

81 and 82 inserted into bearing

holes

71 and 72; the wristpin 83 being a cylinder whose axis is aligned parallel to, and offset from, the axis of the orifice 77 and whose diameter carries a bore 88 to receive the push-rod 8. The

push-rod 8 and the wrist-pin 83 may be locked together by a set-screw 84 providedalong the axis of the latter. By this construction, the linear motion of the push-rod 8 may be converted into rotational motion of the army depicted in FIG. 1, with the mechanism arranged to v rate drives were to be connected to push-rods 8 and 108, means for synchronizing their motion would be necessary for reliable operation. This function is undertaken by connector 30, linking pivot pins passing through holes 73 and/or holes 74 in adjacent leverarms, typically 7b and 7c.

The connector 30 is further illustrated in FIG. 6; it is comprised of a priamry element 35 and a secondary element 31. The primary element 35 is an elongated, flat member with

tabs

35a and 35b forming a channel along its major axis at one end, and a Z-shaped yoke-piece 38 forming a clevis at the other. The secondary element 31 is similar in shape to the member 35, except for the tabs of the latter which are omitted, and is so dimensioned that its width is a snug fit between the

tabs

35a and 35b. Both

elements

31 and 35 carry elongated holes, 42 and 41 respectively in such a manner that they may be locked together by bolt 36 being passed through these holes in succession and nut 37 tightened upon the bolt. In this manner relative axial motion between the two elements of the assembly 30 is prevented by the bolt 36 and rotation by the tabs 35. The secondary element 31 also carries on its outboard end a clevis formed by a Z- shaped element 32. Both clevises of the connector 30 are bored to receive pins 33 and 39 respectively; these pins being also used to form rotatable joints in cooperation with bearing

holes

73 and 74 in the

extensions

78 and 79 of adjacent lever-arms 7.

When installed, as in FIG. 2 between lever-arms 7b and 7c, the connector 30 provides a rigid, adjustable link for the transmission of rotary motion between the shafts 6b and 60. If the lever-arms are arranged degrees out of phase relative to one another, such rotary motion will be in opposite sense of the two shaft's. Should one connector 30 prove insufficiently rigid for the imposed loads, another, identical assembly is readily mounted between projections 74 of the same leverarms.

The above construction permits a number of alternate arrangements for counter-rotating assemblies; in particular it admits of the use of an unpowered pushrod 108 driven from the powered push-rod 8 of the embodiment of FIG. 2. It is also possible to provide only one push-rod, connected to alternate arms on the shafts 6, with each of the intervening blades being driven through a connector 30 from one of its neighbors.

FIG. 3 is aside-view of another form of the damper assembly, with the blades rotating in the same sense to open and close upon the actuation of the push-rod 8. The arrow B indicates the direction which the push-rod 8 is moved to open the blades, the motion being transmitted through lever-arms 7 to the shafts 6.

It should be noted that all actuating mechanisms in these embodiments have their moving parts mounted in, and partially enclosed by, the side-rail 1, thereby avoiding the use of levers and pivots exposed to the flow of fluids and to the attendant dangers of collecting dust and accelerated corrosion which characterize 'many designs in the prior art.

FIG. 7 indicates the manner in which the unit damper assemblies of the instant invention may be combined to form control elements for extremely large apertures exposed to fluid flow. Common side and

top rails

102 and 103. extend along perpendicular boundaries of the aperture and are securely 'joined'at their intersection by gusset 100. The field defined'by these members, cooperatively with elements 101 and 104,,not illustrated,

which are mirror images of their

counterparts

102 and 103, is subdivided into a number of rectangles of equal dimension defined by

partitions

1a, 4a, 2b, 4b, and so on. To provide a mechanically sound and rigid base for damper blades and their operating mechanism, these are further joined one to another by standardized connectors 50 and 51.

FIG. 8 indicates a typical side-frame joint, between elements 1a and 2b. These elements are identical extrusions, in aluminum for preference, and carry along their axis a number of integral grooves and channels, notably grooves 21 for receiving sealing members of the damper assembly,

similar grooves

23 and 24 on the outer faces of their U-shaped cross-section for receiving connectors 50 and 51, as required, and partly open circular sockets 24 to serve as anchorages for selftapping bolts for securing elements joined at right angles to one-another. The connectors 50 and 51 are also extrusions, the former L-shaped and provided with an integral dovetail key, fitting the

grooves

23 and 24, along the outer surface of one leg, the other U-shaped.

Typically, grooves 22 in adjoining edges of members la and 2b have short lengths of

connector

50, 50a and 50b for example, inserted into them; the latter being aligned and drawn together by means of a fastener, suitably a rivet or a bolt 52 engaging a nut 53.

Grooves 23 also receive short length of connector, 50c and 50d in FIG. 8, the gap, if any, between them being bridged by a length of connector 51 which is fastened to both

connectors

50c and 50d.

Top and bottom rails of adjacent dampers are joined in a similar fashion, as shown in FIG. 9, by inserting by imposing psi on a Robert Shaw Pneumatic motor. A static pressure of 4 W.G. was then built up directly upstream of the damper, and, at that pressure, the pressure drop was monitored across a "/s knife edged orifice plate installed in the system and the leakage was determined to be 4 CFM per square foot.

lengths of connector 50 into the integral dovetail grooves 23 and drawing the latter together by means of an appropriate fastener.

As noted hereinbefore with the use of more conventional dampers, a considerable amount of fluid generally leaks past the pivot bearings of the blades. The suppression of such leakage is an important feature of the use of the seal 10 in the damper assembly of the present invention. A specific bearing assembly is illustrated in FIGS. 10 and 10a, the shaft 6 protruding through adapter-sleeve 49 and flanged bearing 47. The sleeve 49 is provided with a square internal orifice closely fitting over the shaft 6 and a cylindrical outer surface which is a sliding fit in the'bearing 47, the flange 48 of which rests against the side rail 1. The bearing 47 has a cup-shaped cross-section, the base of which is pierced by a circular hole slightly larger'in diameter than the diagonal dimension of the shaft 6. If desired, keying means or locating lugs (not shown) may be employed in retaining the bearing 47 in place so that same will not rotate along with the sleeve 49 and shaft 6. Of course, the side seals (elements 10 and 11) are suitably bored so as to receive the shafts therethrough; and such side seals also aid in serving to retain the bearing assemblies in place, although same are pressfitted into the apertures provided in the side rails for the bearings 47.

In order to illustrate the effectiveness of the side seals In another test without the unique side seals, a 2 ft. X 1 ft. opposed blade damper, Imperial Damper Co., Type Ill-0 of the same material as above and frame size, the other sides being of 2 X a X a inch size and the damper was actuated with a Powers Regulator, Pneumatic motor, which shut the damper at 18 psi. The duct was 5 X 2 X 1 feet with the damper in the center and a blower capable of 27,000 ft./min. was used to supply the air for this test. A hole was drilled into the piping that is connected to the 5 ft. long duct in order to determine the static pressure using a tube and manometer. A louver type damper was installed into the piping in front of the manometer so that the static pressure is obtained. The damper was then closed using 18 psi of air and readings obtained at the far end were Static Pressure 4 inches, velocity 8,000 ft./min. and Air Flow Leakage of 27 CFM per square feet.

Thus, leakage is significantly reduced when the novel side seals disclosed herein are employed in a conventional damper construction.

FIG. 11 illustrates a vane with a thickened hubportion 101 centrally located in its substantially flat face, the hub 101 being provided with a square orifice 106 for engaging a shaft 6 of the damper assembly. At the outboard extremities of the vane 105 small, planar projections 104 are provided, extending in opposing directions at right angles from the major surface of the vane and carrying, in their acute corners, dovetail grooves 103 which serve to anchor suitable sealing strips 102. The seals 102 of two adjacent vanes in a louver cooperate with the projections 104 of the neighboring vane to form a tight seal upon rotation of the vanes into their closed position, thereby preventing the flow of fluid past the tips of adjacent louver elements.

A streamlined damper-blade 205 is illustrated in FIG. 12. The blade 205 has two symmetrical curvillinear surfaces with maximum separation at the midsection of its chord, tapering gently towards sharp edges at either extremity of the chord. With respect to the manner of construction, the blade 205 is preferably a hollow extrusion with a square orifice 206 being formed at its midsection by the side-walls and interconnecting partitions 201a and 201b. The orifice 206 accommodates the shaft 6 which modulates the angular position of the blade 205.

Another design of the damper-blade, for use in the preferred embodiment of the instant invention, is illustrated in FIG. 13. A central boss 306 is formed by a square extrusion and is provided with deformable, toothed extensions 307. The internal orifice formed by the walls of the boss 306 fits over the shaft 6 and forms the hub of a blade completed by the addition of

members

304 and 305. The member 305 is a hollow extrusion whose cross-section approximates to one-half of the streamlined blade 205; its base 301a being provided with rigid, toothed extensions 309 which engage the mating projections 307 of the hub 306 in a snap-joint ber 304 is also a hollow extrusion tapering from a thickness equal to that of the hub 306 to a point and continuing therefrom as a flat plate carrying a tip-seal 302 analogous to the similar component 102 of the vane 101 previously described.

Yet another method of constructing a composite blade is illustrated in FIG. 14 which shows a partial blade 405, similar in cross-section to the streamlined blade 205 and incorporating a central orifice 406 for receiving the shaft 6. The orifice 406 is bounded by the side walls of the partial-blade 405 and webs 401a and 401b; the side-walls being terminated at the web 401b from which extend deformable, toothed projections 407 which are dimensioned to fit into mating projections 309 of the member 305 to form a snap-joint 403.

All of the above described components may be thought of as having considerable lengths of constant section and may be cut into arbitrary length blades, as required. The embodiments of FIG. 13 and 14 may be further utilized in applications requiring blades of differing widths by choosing appropriately dimensioned elements 304 and/or 305 in conjunction with a hub 306 or partial-blade 405. In this manner, blades of either the vane or streamline type may be built up in a wide variety of widths and lengths from a small number of stock extrusions, resulting in considerable economy of manufacture and assembly.

FIG. 4 shows a damper assembly in section with upper and lower frame-rails 3 and 4 and built-up blades composed of partial blades 405 and elements 305 mounted on shaft 6. The tips of the blades nearest the frame 3 and 4 are sealed, in the closed position, by sealing strips 24 inserted into dovetail grooves 2. The seals 24 are manufactured from an elastomeric material, have an elongated cross-section and are mounted, along the inner surfaces of frames 3 and 4, by integral tongues fitting into the aforementioned grooves 21. To minimize leakage past the tips of the blades, when closed, dovetail grooves 25 are provided in an outer surface of each of the blades, slightly offset from the blade-tips and sealing beads 26 of an elastomeric material anchored in them.

An alternate method of sealing the gap between the toprail 3 and the blade 5 is shown in FIG. 15, utilizing the sealing strip and shield 11 in the same manner as the side-seal described with reference to FIGS. 1 and 1a.

A vertical section through a segment of a damper assembly is shown in FIG. 16; a side-rail ll of U-section with unequal lengths sides 1 la and 1 1b carries a typical blade 5 and its shaft 6 on which the actuating hardware is mounted. The side walls 111a and lllb terminate in integral beads 113 whichserve as receivers for a dustcover 112 constructed from light sheetmetal or plastic and whose function is to protect the damper operating linkage from accidental damage during storage, transport and installation, and to keep out dust and other foreign matter.

The above disclosure described many applications and embodiments of the composite seal, square shaft, built-up blades and other features of the instant invention. Arrangements, materials of construction other than those described are possible and may be substituted without altering the basic principles of constructions disclosed herein.

What is claimed is:

1. A damper assembly for the control of the flow of fluids through a rectangular aperture, comprising;

a frame with a first pair of sides joined, in parallel spaced relationship, to a second pair of sides, similarly spaced;

pivot means, including at lease one shaft,

bearing means, for pivotally locating said shaft in said frame parallel to said second pair of sides, with a portion of said shaft protruding beyond at least one of said first pair of sides;

linkage means engaging said shaft on said portion protruding beyond said first pair of sides;

louver means, including vanes or blades having hubs containing orifice means defining a square orifice in a vane for keying said vane to said shaft and said vane extending substantially between said first pair of sides;

side-seal means having a thin, outer flexible member and an inner resilient member of an elasto-meric material secured to the inner surface of said outer flexible member; said side seals being pierced for passage of said shafts therethrough;

said hub of said blade forming substantially a onehalf portion of said vane and the other'portion of said vane is secured to said one-half portion adjacent said hub by locking means which interlock said portions together in a substantially immovable position; and

drive means connected to said linkage means for rotating said vane on said shaft into the plane of said frame, thereby resulting in cessation of flow of fluids through said aperture; and alternately for rotating said vane from the plane of said frame and thereby, permitting the flow of fluids through said aperture.

2. The damper assembly according to claim 1, wherein said vanes are defined by convex arcuate surfaces symmetrical about chords thereof encompassing said hubs.

3. The damper assembly according to claim 1, wherein said inner resilient member is of an elastomeric material and said outer member is of flexible metallic material.

4. The damper assembly according to claim 1, wherein said outer member is of a thin flexible plastic material and said inner resilient member is of an elastomeric material.

5. The damper assembly according to claim 1, wherein said linkage means include lever-arms with a central body portion having an orifice to slideably engage said shaft and provided with at least one pair of extensions spaced along axes of said shaft and rigidly affixed tosaid central portion, each of said pairs of extensions lying in a plane including axis of said orifice.

6. The damper assembly according to claim 1, wherein a plurality of shafts are employed and all of said shafts are square in section, and said louver means are keyed to said shafts by square orifices piercing hubs in midsection of said vanes.

7. The damper assembly according to claim 1, wherein said locking means comprises mating resilient extensions extending outwardly from said one-half portion adjacent said hub and from said other portion of said vane and said extensions having cooperative shoulders which grip each other and thereby interlock said portion as a unitary one-piece assembly.

8. The damper assembly according to claim 1, including blade edge sealing means between abutting surfaces of said blades for insuring a seal between leading edges of adjacent blades when said damper is in a closed position.

9. The damper assembly according to claim 8, wherein said blade edge sealing means comprise elongated elastomeric bodies substantially rectangular in section, one edge thereof being keyed to inner surfaces of said second pair of sides.

10. The damper assembly according to claim 1, wherein said hub forms a central element and said vane is secured to said central element by locking means which interlock said elements together in a substantially immovable position.

11. The damper assembly according to claim 10, wherein said locking means comprises mating resilient and cooperative dovetail keys.

Claims

1. A damper assembly for the control of the flow of fluids through a rectangular aperture, comprising; a frame with a first pair of sides joined, in parallel spaced relationship, to a second pair of sides, similarly spaced; pivot means, including at lease one shaft, bearing means, for pivotally locating said shaft in said frame parallel to said second pair of sides, with a portion of said shaft protruding beyond at least one of said first pair of sides; linkage means engaging said shaft on said portion protruding beyond said first pair of sides; louver means, including vanes or blades having hubs containing orifice means defining a square orifice in a vane for keying said vane to said shaft and said vane extending substantially between said first pair of sides; side-seal means having a thin, outer flexible member and an inner resilient member of an elasto-meric material secured to the inner surface of said outer flexible member; said side seals being pierced for passage of said shafts therethrough; said hub of said blade forming substantially a one-half portion of said vane and the other portion of said vane is secured to said one-half portion adjacent said hub by locking means which interlock said portions together in a substantially immovable position; and drive means connected to said linkage means for rotating said vane on said shaft into the plane of said frame, thereby resulting in cessation of flow of fluids through said aperture; and alternately for rotating said vane from the plane of said frame and thereby, permitting the flow of fluids through said aperture.

5. The damper assembly according to claim 1, wherein said linkage means include lever-arms with a central body portion having an orifice to slideably engage said shaft and provided with at least one pair of extensions spaced along axes of said shaft and rigidly affixed to said central portion, each of said pairs of extensions lying in a plane including axis of said orifice.

11. The damper assembly according to claim 10, wherein said locking means comprises mating resilient extensions, extending outwardly from said hub and said vanes and said extensions having cooperative shoulders which grip each other and thereby interlock said elements as a unitary one-piece vane.

12. The damper assembly according to claim 1, wherein said first and second pair of sides of said frame are provided with means for cooperating with associated means provided on connectors which serve to stack a plurality of damper assemblies adjacent any side of said frame.

13. The damper assembly according to claim 12, wherein said means comprises mating dove-tail grooves and cooperative dovetail keys.