Abstract:
A damper assembly is provided having at least one damper blade that operates in a normally open position. A fusible link is connected to the damper blade to maintain the damper blade in the open position against a biasing force tending to close the damper blade. The fusible link fails upon an occurrence of a predetermined condition. A damper mechanism is provided including a locking mechanism linked to the damper blade that resists opening of the damper blade when the blade has closed due to failure of the fusible link.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]    This patent application claims priority to U.S. provisional application Serial No. 60/432,421 filed Dec. 11, 2002 and entitled “Latch Assembly for Damper.” 
     
    
     
       STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT  
       BACKGROUND OF THE INVENTION  
         [0002]    The present invention relates generally to damper assemblies, and in particular, relates to a latch usable in combination with a damper that, when installed within the ductwork of a building, strengthens the seal provided by the damper blades when the damper is closed.  
           [0003]    Building and fire codes require that dampers be placed in specified heating, ventilation, and air conditioning ducts. Dampers include a pair of damper blades that operate in a normally open position, which allows air to flow through the ductwork. The blades can close to prevent air flow through the ductwork in response to a predetermined stimulus. The stimulus can be a dramatic increase in temperature, indicating a fire or other hazardous condition, or any other event that causes the damper blades to close.  
           [0004]    Conventional damper blades are biased towards their closed position by a spring member or the like, but held open by a fusible link or other suitable member that prevents the blades from closing under the spring force. When the fusible link fails in a predetermined manner in response to an elevation in temperature, the mechanical interference maintaining the blades in their open position is removed, and the damper closes to form a seal with the duct with respect to airflow. As a result, airflow throughout the building is minimized in response to a fire or other hazardous condition.  
           [0005]    It should be appreciated that the ability for the damper to prevent the hazardous material or fire from spreading throughout the building depends largely on the strength of the seal between the damper blades and the ductwork when the blades are closed. A damper becomes “fire-rated” by Underwriters Laboratories if it is able to withstand the extreme temperatures for a predetermined amount of time without weakening its seal between the blades and the duct. In conventional dampers, prolonged exposure to extreme temperatures associated with heat tend to weaken the damper components and the resulting seal.  
           [0006]    What is therefore needed is a damper assembly capable of providing an enhanced seal between the damper blades and the duct with respect to conventional damper assemblies.  
         BRIEF SUMMARY OF THE INVENTION  
         [0007]    The present invention recognizes that conventional dampers can be modified to increase their strength characteristics when closed, thereby reducing the risk of spreading fire or contaminants throughout a building during a hazardous situation.  
           [0008]    In accordance with one aspect of the invention, a damper assembly is installed in a housing of the type having a pair of side walls connected to a pair of end wells that define a conduit extending therethrough. The damper assembly is movable from an open position to a closed position to control fluid flow through the conduit. The damper assembly includes at least one damper blade operating in a normally open position.  
           [0009]    In accordance with another aspect of the invention, a biasing member applies a force to the damper blade biasing the blade towards the closed position. In one form, the biasing member is a spring member operably connected between the blade and the housing.  
           [0010]    In accordance with still another aspect of the invention, a retaining member is in removable mechanical communication with the damper blade to maintain the damper blade in the open position against the biasing force.  
           [0011]    In accordance with still another aspect of the invention, a latch mechanism is provided that engages to resist counter-movement of the damper blade towards the open position once the damper blade has closed. In one form, the latch mechanism includes a latch member and a corresponding catch member, one of which in mechanical communication with the blade, the other of which in mechanical communication with the housing, wherein an interference is created between latch member and catch member to resist counter-movement of the damper blade towards the open position once the damper blade has closed.  
           [0012]    These and other aspects of the invention are not intended to define the scope of the invention for which purpose claims are provided. In the following description, reference is made to the accompanying drawings, which form a part hereof, and in which there is shown by way of illustration, and not limitation, a preferred embodiment of the invention. Such embodiment also does not define the scope of the invention and reference must therefore be made to the claims for this purpose.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]    Reference is hereby made to the following drawings in which like reference numerals correspond to like elements throughout, and in which:  
         [0014]    [0014]FIG. 1 is a perspective view of a damper assembly constructed in accordance with the preferred embodiment of the invention;  
         [0015]    [0015]FIG. 2 is a perspective view of the damper blades of the damper assembly illustrated in FIG. 1;  
         [0016]    [0016]FIG. 3 is a sectional side elevation view of the lower damper blade illustrated in FIG. 2;  
         [0017]    [0017]FIG. 4 is a sectional side elevation view of the damper assembly illustrated in FIG. 1 with the blades in an open position;  
         [0018]    [0018]FIG. 5 is a sectional side elevation view of the damper assembly illustrated in FIG. 4 but with the damper blades in a partially closed position;  
         [0019]    [0019]FIG. 6 is a sectional side elevation view of the damper assembly illustrated in FIG. 5 but with the damper blades in a further closed position;  
         [0020]    [0020]FIG. 7 is a sectional side elevation view of the damper assembly illustrated in FIG. 6 but with the damper blades in a fully closed position; and  
         [0021]    [0021]FIG. 8 is a sectional side elevation view of the damper assembly similar to that illustrated in FIG. 4, but having a coupling assembly constructed in accordance with an alternate embodiment of the invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0022]    Referring initially to FIG. 1, a damper assembly  20  is installed in a rectangular housing  22 . It should be appreciated that housing  22  can be installed in the ductwork of a building or, alternatively, that housing  22  could be integral with the ductwork. The term “housing” is thus used broadly throughout this description to define a member that supports the damper assembly  20  in the ductwork of a building, regardless of whether the housing is a separate member and fit inside the ductwork, or whether the housing is integral with the ductwork. Unless otherwise stated, the components of damper assembly  20  are preferably formed of steel, though other suitable materials could be used.  
         [0023]    Housing  22  is defined by opposing side walls  23  and  24  that are elongated in the direction of vertical axis V-V and are connected at their upper and lower ends to opposing end walls  26  and  28 , respectively. End wall  26  thus defines the upper end of damper assembly  20  while end wall  28  defines the lower end, such that end wall  26  is said to be disposed “above” end wall  28 . Walls  23 ,  24 ,  26 , and  28  define an internal void  50  that enables air to flow through the housing  22  (and ductwork of a building) along the direction of Arrow A.  
         [0024]    The terms “upstream” and “downstream” are used herein with respect to the direction of airflow through the housing  22  along the direction of Arrow A. The term “longitudinal” is used throughout the description below to define a horizontal direction along axis L-L and parallel to the direction of air flow through damper assembly  20 . The term “transverse” is used to define a horizontal direction along axis T-T that is orthogonal to longitudinal axis L-L and vertical axis V-V.  
         [0025]    Side walls  23  and  24  are connected to upper end wall  26  and lower end wall  28  at corresponding longitudinally extending upper and lower edges  34  and  36 , respectively. Edges  34  and  36  define the transverse boundaries of upper and lower walls  26  and  28 , respectively, and further define the vertical boundaries of side walls  23  and  24 . The longitudinal boundaries of end walls  26  and  28  are defined by transversely extending edges  30  and  32 . The longitudinal boundaries of side walls  23  and  24  are defined by edges  25  and  27 . Edge  25  defines the leading edge of the damper assembly  20  with respect to airflow, and is disposed upstream of edge  27 .  
         [0026]    A pair of vertically elongated flanges  42  and  44  extends slightly transversely outwardly from edges  25  and  27 , respectively, of side wall  23 . A corresponding pair of flanges  46  and  48  extend slightly transversely outwardly from edges  25  and  27 , respectively, of side wall  24 . Flanges  42  and  46  are disposed upstream of flanges  44  and  48 . Flanges  42 ,  44 ,  46 , and  48  extend vertically a distance slightly beyond edges  34  and  36  and are connected at their outer ends to a pair of upper and lower flanges  52  and  54 , respectively, that extend vertically outwardly from edges  30  and  32 , respectively. A corresponding pair of upper and lower flanges  38  and  40 , respectively, extends longitudinally outwardly from flanges  52  and  54 , respectively, and is configured to be mounted to the interior of the ductwork of a building (not shown). Transverse flanges  42 ,  44 ,  46 , and  48 , and vertical flanges  38  and  40  are configured to form a seal against the inner periphery of the ductwork, f  
         [0027]    Referring also to FIG. 2, upper and lower damper blades  56  and  58 , respectively, are disposed within void  50  and extend between the inner surfaces of side walls  23  and  24 . Blades  56  and  58  extend horizontally when the damper assembly  20  is in the open position illustrated in claim  1  to enable air to flow through the damper assembly and circulate throughout the building. Blades  56  and  58  present upper surfaces  57  and  59 , respectively, and lower surfaces  61  and  63 , respectively, it being appreciated that the terms “upper” and “lower” are used herein to describe the blades when they are in the open position. Blades  56  and  58  define leading edges  60  that are disposed upstream of trailing edges  62  when the blades are open. Blades  56  and  58  have a longitudinal thickness that is sufficient to seal the void  50  with respect to airflow when the blades are closed (see FIG. 7). In particular, when the damper assembly  20  is closed, leading edge  60  of upper damper blade  56  is biased downwardly and trailing edge  62  of lower damper blade  58  is biased upwardly such that edges  60  and  62  abut each other to form a seal with respect to each other.  
         [0028]    Referring also to FIG. 3, damper blades  56  and  58  present downwardly facing triangular grooves  67  that extend centrally along the transverse length of the blades. Grooves  67  define the axes of rotation for blades  56  and  58 . A brackets  64  is mounted, preferably via rivets  65 , onto the lower surface of each damper blade  56  and  58  at their corresponding transverse outer ends. Brackets  64  also define triangular grooves  66  that are upwardly facing and aligned with grooves  67  of blades  56  and  58  to define corresponding noncircular, and preferably rectangular, and more preferably square, bores  68 . Bores  68  receive upper and lower noncircular shafts  70  and  70 ′ which, in turn, are rotatably supported by side walls  23  and  24  (via a bearing or the like). Accordingly, both transverse ends of blades  56  and  58  are rotatably mounted to housing  22  to open and close the damper assembly  20 .  
         [0029]    Blades  56  and  58  are connected to a fusible link assembly  72  that includes a first housing  74  mounted onto the upper surface  59  of lower blade  58 , and a second housing  76  mounted onto the lower surface  61  of upper blade  56 . Housings  74  and  76  are mounted onto blades  56  and  58  on both longitudinal sides of grooves  67  via bolts  78 . Housings  74  and  76  include hooks  80  and  82 , respectively, that are, in turn connected to the outer ends  88  of a fusible link  86 . In particular, hook  80  extends upwardly from one outer end  75  of housing  74 , and in particular extends towards the opposite outer end  77  of housing  76 . Hook  82  extends downwardly from outer end  77  of housing  76  towards outer end  75  of housing  74 . Fusible link  86  defines apertures  84  extending through its outer ends  88  that are engaged by hooks  80  and  82 . Fusible link  86  thus extends diagonally with respect to housings  74  and  76 , and prevents blades  56  and  58  from rotating in response to a torsional force F (clockwise as illustrated in FIG. 2 and counterclockwise as illustrated in FIG. 1). It should be appreciated that the orientation of fusible link  86  could be reversed depending on the direction of force F.  
         [0030]    Fusible link assembly  72  thus supports damper blades  56  and  58 , and maintains damper assembly  20  in its open position to permit fluid to pass unobstructed through opening  50 . However, when the fusible link  86  fails in a predetermined manner in response to a predetermined stimulus, damper blades  56  and  58  rotate to the closed position as illustrated in FIG. 7 to prevent fluid from traveling through damper assembly. Fusible link assembly  72  thus provides a removable mechanical connection between damper blades  56  and  58  that interferes with the blades&#39; ability to close during normal operation. The present invention contemplates that fusible link assembly  72  can be heat responsive, or responsive to any other stimulus to fail in a predetermined manner.  
         [0031]    Referring now to FIGS. 1 and 4 in particular, damper assembly  20  further includes a damper latch mechanism  21  that is mounted onto side wall  23 , though it should be easily appreciated that mechanism  21  could be mounted at any suitable location. Latch mechanism  21  supports rotation of damper blades  56  and  58  and locks the damper blades  56  and  58  in position once the blades have been closed, thereby increasing the damper assembly  20  strength, as will now be described.  
         [0032]    Latch mechanism  21  includes an upper rectangular pivot arm  90  that is pivotally mounted at a first outer end  92  to side wall  23 . In particular, outer end  92  receives shaft  70 , and is swaged or otherwise mechanically coupled to shaft  70 , such that upper damper blade  56 , shaft  70 , and arm  90  rotate together. Upper pivot arm  90  extends upwardly and longitudinally forward from outer end  92  when damper blades  56  and  58  are open. Arm  90  is connected at a second outer end  96  to a linking member  98 , which joins upper pivot arm  90  to a lower pivot plate  100 . Linking member  98  extends vertically between arm  90  and pivot plate  100 , and is disposed adjacent flange  42 . Member  98  defines an upper end  97  that is pivotally connected to outer end  96  of upper pivot arm  90 , and a lower end  99  that is pivotally connected to lower pivot plate  100 . Plate  100  is pivotally mounted at its upper, longitudinally rearward, end through side wall  23  via shaft  70 ′. In particular, plate  100  receives shaft  70 ′ in the manner described above with reference to pivot arm  90 .  
         [0033]    Lower pivot plate  100  includes a lip  108  that extends rearwardly from the longitudinally rear edge of pivot plate  100  at a location below shaft  70 ′. Lip  108  is connected to a first lower end  110  of a spring member  112  that extends upwardly and longitudinally rearward, and has an upper end  114  that is connected to flange  44  at a location above shaft  70 ′. It should be appreciated, however, that upper end  114  of spring can be positioned anywhere such that it biases the dampers towards their closed position. In this regard, the upper end  114  of the spring is said to be supported by (or in mechanical communication with) the housing  22 , and the lower end  110  of spring is in mechanical communication with blades  56  and  58 , and further in mechanical communication with plate  100 . Accordingly, spring  112  imparts a torsional force F to lower pivot arm in the counterclockwise direction (with respect to the view taken in FIG. 4). The fusible link assembly  72  resists force F to prevent damper blades  56  and  58  from rotating, as described above.  
         [0034]    Lower pivot plate  100  is connected to a locking member  116  interposed between side wall  23  and plate  100 . In particular, locking member  116  is pivotally connected to the inner surface of the lower end of pivot plate  100  via a pin  118 . Pin  118  is disposed below and upstream of shaft  70 ′. Locking member  116  includes a central body portion  120  and first and second arms  122  and  124 , respectively. When locking member is in its neutral position (i.e., when damper blades  56  and  58  are open), first arm  122  extends upwardly and downstream from body portion  120  and second arm  124  extends downwardly and downstream from body portion  120 . A hook  126  extends downwardly from the distal end of second arm  124 . A vertically elongated groove  127  extends through flange  44  and defines a lower lip  129  that is substantially horizontally disposed with respect to shaft  70 ′. Hook  126  is configured to engage lip  129  when the damper blades  56  and  58  are closed.  
         [0035]    A spring member  128  is connected at one end to the central body portion  120 . The other end of spring  128  is connected to the longitudinal rearward end of lower pivot plate  100  at a location below shaft  70 ′ and above pin  118 . Spring member  128  is compressed, and extends primarily horizontally, and slightly vertically, when blades  56  and  58  are open.  
         [0036]    The operation of damper assembly  20  will now be described with particular reference to FIGS.  4 - 7 . During normal operating conditions illustrated in FIG. 4, fusible link assembly  72  prevents force F from rotating pivot arm  90  and plate  100  and corresponding damper blades  56  and  58  to their closed positions. Accordingly, blades  56  and  58  extend horizontally, thereby allowing the passage of air through opening  50 . However, if the temperature of fusible link  86  becomes elevated beyond a maximum permissible threshold (well known in the art), the fusible link fails, thus removing the impediment to counterclockwise rotation under spring force F.  
         [0037]    Because linking member  98  is pivotally mounted to the transverse outer surfaces of pivot arm  90  and pivot plate  100  at joints  104  and  106 , respectively, rotation of lower pivot plate  100  in the direction of force F translates linking member  98  to correspondingly rotate upper pivot arm  90  which, in turn, rotates damper blades  56  and  58 . Accordingly, referring now to FIG. 5, when fusible link  86  fails, spring force F biases lower pivot plate  100  in the counterclockwise direction, which translates linkage member  98  downwardly, thereby causing upper pivot arm  90  to rotate in the counterclockwise direction along with lower pivot plate  100 . The rotation of pivot arm  90  and plate  100  causes shafts  70  and  70 ′ along with corresponding damper blades  56  and  58  to rotate counterclockwise along the direction of Arrow A towards their closed position. As blades  56  and  58  rotate to their closed positions, pin  118  is translated primarily longitudinally downstream towards flange  44  and slightly downwardly while spring  128  remains compressed.  
         [0038]    Referring to FIG. 6, as pivot plate  100  rotates counterclockwise, the outer edge of hook  126  contacts the transverse inner surface of flange  44 . As pivot arm  100  continues to rotate counterclockwise, spring  128  is extended, and imparts a compressive spring force F 2  that biases locking member  116  clockwise about pin  118 . The interference between hook  126  and flange  44 , however, prevents further clockwise rotation of locking member  116 . However, as lower pivot plate  100  continues to rotate counterclockwise, pin  118  is translated downstream and upwardly, thereby causing arm  118  and hook  126  to correspondingly translate upwardly towards lower lip  129  of groove  127 . It should be appreciated that spring force F 2  continues to increase as lower pivot arm  100  continues to rotate counterclockwise with respect to locking member  116 .  
         [0039]    Referring now to FIG. 7, spring force F continues to rotate arms  100  and  90  along with damper blades  56  and  58  until the leading edge  60  of upper damper blade  56  engages the trailing edge  62  of lower damper blade  58 , thereby closing the damper assembly  20  and preventing fluid from flowing through ductwork. The components of latch mechanism  21  are configured to enable hook  126  to engage groove  127  as blades  54  and  56  close. In particular, hook  126  slips over and catches lower lip  129  under clockwise spring force F 2  which prevents hook  126  from becoming disengaged from the lower lip  129 . If it becomes desirable to disengage hook  126  from lip  129  in order to reset the damper blades  56  and  58  in their open position, a user can manually rotate hook  126  counterclockwise away from lip  129 .  
         [0040]    The components of latch mechanism  21  are sized and configured such that hook  126  and lip  129  become engaged once blades  54  and  56  rotate to their fully closed position under spring force F. The interlock between hook  126  and lip  129  further maintains the closed position of blades  54  and  56  and strengthens the resulting seal. Additionally, spring force F 2  biases locking member  116  clockwise which, in turn, maintains the interlock between hook  126  and lip  129 . Damper assembly  20  thus provides enhanced strengthening features to prevent damper blades  54  and  56  from opening after fusible link  86  fails. The overall reliability of the damper assembly  20  is thus increased over conventional damper assemblies.  
         [0041]    Advantageously, damper latch mechanism  21  is constructed to be installed integrally with damper assembly  20 . In particular, referring to FIGS. 1 and 4, locking member  116  is attached to the lower pivot plate which is conventionally used during normal operation of a damper assembly. Spring  128  may then be connected from lower pivot arm  100  to locking member, and notch  127  may be formed in flange  44 . Accordingly, the present invention includes the construction of damper assembly  20  along with the modification of a conventional damper assembly by installing damper latch mechanism  21  to maintain the damper blades  56  and  58  in their closed position upon failure of the fusible link. Furthermore, because locking member  116  is installed at a location transversely inwardly of lower pivot plate  100 , damper latch mechanism  21  adds only minimal size to conventional damper assemblies.  
         [0042]    It should be appreciated, however, that latch mechanism  21  as described above is only one possible configuration, and that the present invention is not intended to be limited to the latch mechanism described above. Rather, the present invention is intended to broadly cover any mechanism that prevents the damper blades from inadvertently opening once they have closed. For instance, referring now to FIG. 8, damper assembly  20  is illustrated similar to the assembly described above. However, the latch mechanism  21  is constructed in accordance with an alternate embodiment.  
         [0043]    In particular, lower plate  100  defines a lower edge  113  that extends generally longitudinally when damper blades  56  and  58  are in the open position. A flange  115  extends outwardly from edge  113  that provides a catch for plate  100 . Flange  115  connects to an outer edge  117  that provides the outer edge of lip  108 . A plate  119 , formed from steel or any other suitable material, includes a base  121  and a bent section  123  extending upwardly and upstream from the base. Base  121  is connected to flange  44  via rivets  125 , or the like. A handle  131  extends generally downstream, and slightly upwardly, from bent section  123 . Handle  131  extends through an opening (not shown) in flange  44 , and thus extends outside the housing so as to be accessible to a user. Bent section  123  defines an outer edge  133  that provides a follower over outer edge  117 , which provides a cam surface as will now be described.  
         [0044]    During operation, when blades  56  and  58  are biased closed in the manner described above, plate  100  rotates counterclockwise under force F. As plate  100  rotates, lip  108  engages plate  119 , thereby causing edge  133  to follow over cam surface  117 . Lip  108  and plate  119  are sized and shaped such that, as blades  56  and  58  become fully closed, edge  133  snaps over flange  115 . The interference between edge  133  and flange  115  locks plate  100  and blades  56  and  58  with respect to clockwise rotation. If it becomes desirable to reset damper blades  56  and  58  to their open position, a user can apply a downwards force to the exposed end of handle  131 , thereby rotating edge  133  clockwise and removing edge  133  from engagement with flange  115 .  
         [0045]    The latch mechanisms  21  described above are only examples of a number of designs that are intended to fall within the scope of the present invention. For example, the present invention contemplates that a damper blade itself could provide a latch that catches on a member protruding from within the housing when the blade closes to prevent the blade from opening. Accordingly, unless otherwise noted, the present invention is intended to include any latch mechanism that engages to resist counter-movement of the damper blade towards the open position once the damper blade has closed. More specifically, the latch mechanism can include a latching member that is in mechanical communication with the housing or the damper blade, and a corresponding catch that is in mechanical communication with the damper blade or the housing, respectively, that creates a mechanical interference to resist counter-movement of the damper blade(s) towards the open position once the damper blade has closed.  
         [0046]    One skilled in the art will appreciate that damper assemblies are available having a pair of damper blades, as described above, or alternatively with one damper blade that opens and closes to block the ductwork, or alternatively still with more than two damper blades that rotate in concert. The present invention recognizes that all such damper assemblies would benefit by the strengthening features of the present invention. The present invention is thus intended to encompass any damper assembly that can benefit by a locking member that becomes engaged when the damper blade(s) are closed to support the closed position of the damper assembly and resist the blades from opening.  
         [0047]    The invention has been described in connection with what are presently considered to be the most practical and preferred embodiments. However, the present invention has been presented by way of illustration and is not intended to be limited to the disclosed embodiments. Accordingly, those skilled in the art will realize that the invention is intended to encompass all modifications and alternative arrangements included within the spirit and scope of the invention, as set forth by the appended claims.