Note: Descriptions are shown in the official language in which they were submitted.
2907
D E S C R I P T I O N
Title
DAMPER BLADE SEAL
Technical Field
The sub~ect invention generally pertains to rotatable
damper blades and ~ore specifically to the seals associated with
such blades.
Background of The Invention
Rectangular damper blades generally open and close by
rotating about their longitudinal center line. Such blades are
usually positioned within an appropriate rectangular inlet
opening, and blade geals are often situated between the inlet
opening and the blade's longitudinal edges.
In designing the specific geometry and mounting
configuration of the blade seals, several interrelated factors
need to be taken into account. These factors include sealing
abillty, closing force, friction, blade twist, drive requirement,
and tolerance of misalignment and overshoot. Sealing ability is
generally a function of the closing force of the blade and/or the
radial interference at the seal between the blade and the inlet
opening. Increasing the closing force, however, often requires
the use of relatively large drives and sturdy blades that resist
twisting. Likewise, increasing radial interfereoee increases
` friction which also requires larger drives and sturdier blades.
Overshoot i8 the distance the blade attempts to travel after
reaching its intended closed position. Some seal designs have an
abrupt closing point that provide little or no tolerance to blade
twist or overshoot, making them susceptible to both leakage and
; damage. And light weight blades driven by small drive motors are
usually sensitive to overshoot or allow only the use of light
weight seals th-t provide inadequate ~ealing.
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Previous blade designs typically address some of the
above problems while compromising on others. Consequently a
need exists for a single, well designed damper blade that
addresses all of the above problems.
I provide a pair of damper blade seals whose seal-
ing force increases in response to the pressure differential
across the damper blade.
I also provide a seal whose sealing force is
generally aligned with the damper blade to minimize the
bending moment on the blade.
In addition I provide a seal that offers a sliding
contact as the blade closes, thereby allowing for blade twist
and overshoot.
I further provide a pair of generally inter-
changeable seals, one of which is attached directly to an
edge of the blade and the other being attached to a similar
edge next to the blade.
I also provide a pair of seals that augment the
closing force of the blade in the presence of a pressure dif-
ferential across the blade.
I also provide a direct drive damper blade having
sliding contact blade seals for eliminating the need for
accurate blade alignment and linkage adjustment.
According to one aspect of the present invention
there is provided a damper assembly which comprises a. general-
ly rectangular solid damper blade adapted to divide a current
of air between an upstream and a downstream side, said blade
being rotatable about its longitudinal center line between
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an open and a closed position, said damper blade having
two generally similar flat longitudinal edges that general-
ly describe a cylinder as said blade is rotated, said flat
longitudinal edges extend generally perpendicular to said
generally planar damper blade;
b. a first seal attached to one of said longitudinal
edges and including a flexible lip extending generally
upstream and sealing in sliding contact against a first
adjacent edge to provide a wiping action in a direction
generally tangent to said cylinder as said damper blade
closes and to urge said damper blade to said closed position
under the impetus of a pressure differential between said
upstream and downstream side; and
c. a second seal, substantially similar to said first
seal, attached to a second edge adjacent to an other longi-
tudinal edge of said blade, said second seal including a
flexible lip extending generally upstream and sealing in
sliding contact against said other longitudinal edge of said
blade to provide a wiping action in a direction generally
tangent to said cylinder as said damper blade closes.
Brief Description of the ~rawings
Figure 1 shows the preferred embodiment of the in-
vention with the damper blade in an open position.
Figure 2 is a perspective view of Figure 1.
Figure 3 shows the damper blade of Figure 1 in
the closed position.
Figure 4 is a perspective view of Figure 3.
Figure 5 is an enlarged view of the seal shown in
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Figures 1-4.
Figure 6 shows an embodiment of the invention that
includes multiple blades.
Figure 7 shows the damper assembly of Figure 6 in
the closed position.
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Description of The Preferred Embodiment
Figures 1-4 illustrate the preferred embodiment of the
invention with Figures 1 and 2 showing a rotatable damper blade
10 in an open position, and Figures 3 and 4 showing blade 10 in a
closed position. Damper blade 10 moves between an open and
closed position by rotating about ~ts longitudinal axis 14. In
the preferred embodiment, axis 14 happens to be the blade's
longitudinal center line. As an alternative, however, any other
rotational axis of the blade could also be used.
In the closed position, damper blade 10 substantially
blocks the airflow of a current of air 16 through enclosure inlet-
18. Flexible polymeric seals 20 and 22 further assist in
blocW ng the airflow by preventing air from leaking past the
damper between an outer longitudinal etge 24 of blate 10 ant an
at~acent inlet edge 26, ant also between another longitutinal
edge 30 and another ad~acent inlet edge 28. Seal 22 extends from
blsde etge 30, ant seal 20 extents from an inlet etge 26 of
enclosure 32. Although in the preferret embodiment edge 26
partially tefines an inlet opening through enclosure 32, in other
variations of the invention, edge 26 could be a part of any air
handling device such as a discharge air tuct or even another
damper bIade which will be further descrlbed below. $n addition,
seals 20 and 22 could be made of any flexible material, such as
thin sheet metal, and coult even be an integral part of the blade
itself or an integral part of edge 26.
Referring to Figure 5, a ba~e portion 34 of seals 20
and 22 have a U-shape profile which makes them readily mountable
by using any one of a variety of fasteners, by gluing, or even by
means of an interference or snap-on fit. The similarity of edges
26 and 30 allows seal~ 20 and 22 to have simllar cross-sections,
making them mountable on either blade edge 30 or inlet edge 26,
i.e., they are generally interchangeable except in some cases
their length and fastening means may differ somewhat.
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Seals 20 and 22 include a flexible llp 36 that is in
sllding contact to provide a wiping action with an ad~acent edge
such as edge 24 or 28. In the closed position, the lips flex to
extend generally perpendicular to blade 10 and tangent to
5 cylinder 38 which i9 an imaginary cylinder generated by edges 24
and 30 as blade lO rotates about its axis 14. The generally
tangent configuration of the lips reduces the wiping friction
along edges 24 and 28 which minimizes the blade's tendency to
twist. The tangential configuration of the lips in addition to
10 its flexibility allows for variation in radial clearance 40
without exerting undue radial compressive forces agalnst blade
10. Radial clearance 40 is made possible by the distance between
edge9 24 and 30 being less than the distance between edges 26 and
28. The reduced friction and tolerance of misalignment
15 facilitate the use of a direct drive tor 44 (8ee figure 2)
which ellminate~ the need for ad~ustable drive linkages and
careful alignment procedures.
When tamper blade 10 is closed, as shown in FLgure 3,
the flexible lips 36 both point generally upstresm 46. This
20 allows an air pressure differential (upstream 46 minus downstream
48) acros6 blade 10 to increase both the sealing force 50 and
closing moment 52. The ~ealing force 50 is the force applied by
the seal~ against their sealing edges 24 and 28 under the
influence of the pressure differential. The sealing force 50
25 approxlmately equals the product of the pressure tifferential
times half the seal width 54 times the seal length 55. Closing
moment 52 i8 what urges the da1nper to close in re6ponse to the
pressure differential acros6 the blade. In the closed position,
the closing mo~Dent approximately equals a closing force 58 times
30 a moment arm 56, with the closing force 58 being equal to the
radial clearance 40 times the seal length 55 times the pressure
differential, and the moment arm 56 being the perpendicular
distance between closing force 58 and axis 14.
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Flgures 7 and 8 illustrate a multiple blade
configuration that employs the basic principles of the preferred
embodiment. Each blade 10 is associated with two seals, one
being attached to the lower edge 30 of the blade, and the other
being attached to an edge that is ad~acent to upper edge 24 when
the blade is closed, i.e., attached to edge 2~ or edge 30 of an
ad~acent blade. These and other modifications to the preferred
embodiment, as disclosed hereinabove, will be readily apparent to
those skilled in the art, and it should be understood that while
the present invention has been described with respect to the
preferred embodiment, such modifications lie within the scope of
the present invention as defined in the clalms which follow:
I claim:
