Abstract:
An HVAC (heating, ventilating and air conditioning) damper includes a series of pivotal damper blades that are opened by an air pressure differential across opposite sides of the damper. In some embodiments, a fan discharging against the damper blades provides the necessary air pressure to open the damper. To control how far the damper opens, an actuator moves a variable position abutment that obstructs the damper blades to limit how far they can pivot in the open direction. The position of the abutment is infinitely adjustable to provide the damper with infinite adjustment over a range of open positions. In some embodiments, the abutment applies a unidirectional torque to the damper blades regardless of whether the damper is opening or closing.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The subject invention generally pertains to heating, ventilating and air conditioning (HVAC) dampers and more specifically to an actuator for such a damper. 
         [0003]    2. Description of Related Art 
         [0004]    HVAC systems often include various dampers for controlling airflow through the system. The dampers typically comprise a series of interconnected damper blades driven by an actuator that tilts the blades in unison between open and closed positions. A coupling or linkage that connects the drive actuator to the damper blades can transmit significant torque from the actuator to the blades, thus the blades need to be sufficiently strong to withstand such torque. Increasing a blade&#39;s strength and stiffness, however, can increase the blade&#39;s cost. Moreover, stronger, thicker blades can increase the damper&#39;s airflow resistance and thus reduce its efficiency when fully open. 
         [0005]    A second problem pertains to a drive actuator having to drive or tilt the blades both clockwise and counterclockwise to selectively open and close the damper. Reversing the torque direction can involve backlash or play between the actuator and the damper blades, which can cause inaccurate blade positioning. Also, repeated torque reversal can cause fatigue that can weaken various parts of the damper. 
         [0006]    Consequently, there is a need for a damper/actuator system that is more efficient, accurate and cost effective. 
       SUMMARY OF THE INVENTION 
       [0007]    It is an object of some embodiments of the invention to provide a damper actuator that applies a torque in only one direction regardless of whether the damper is opening or closing. 
         [0008]    Another object of some embodiments is to provide a damper that under the impetus of a given air pressure differential can open to infinite select open positions. 
         [0009]    Another object of some embodiments is to provide a connection between an actuator and a plurality of damper blades without using a roller that travels along a slot. 
         [0010]    Another object of some embodiments is allow an actuator to separate from a bar or blade-connecting member that interconnects a plurality of damper blades, whereby the damper blades can quickly move to a closed position without the actuator having to respond as quickly. 
         [0011]    One or more of these and/or other objects of the invention are provided by a damper that includes a housing, a plurality of damper blades pivotally coupled to the housing, and an abutment. An air pressure differential urges the damper blades to pivot from a less-open position to a more-open position while the abutment is controllably movable to limit how far the damper opens. 
         [0012]    The present invention provides a damper for controlling air having an air pressure differential. The damper comprises a housing defining an opening across which the air pressure differential exists. A plurality of damper blades are pivotally mounted to the housing in proximity with the opening. The plurality of damper blades are movable over a range of pivotal positions between a more-open position and a less-open position. The air is more free to flow through the opening when the plurality of damper blades are in the more-open position than when the plurality of damper blades are in the less-open position. The air pressure differential urges the plurality of damper blades toward the more-open position. An abutment is coupled to the housing such that the abutment is movable relative to the housing and is movable relative to the plurality of damper blades. The abutment is movable over a range of blocking positions between a first position and a second position. The abutment in the first position holds the plurality of damper blades at the less-open position in opposition to the air pressure differential. The abutment in the second position allows the air to move the plurality of damper blades toward the more-open position. 
         [0013]    The present invention also provides a damper for controlling air, wherein the damper comprises a housing defining an opening. The damper also comprises a plurality of damper blades pivotally mounted to the housing in proximity with the opening. The plurality of damper blades are movable over a range of pivotal positions between a more-open position and a less-open position, wherein the air is more free to flow through the opening when the plurality of damper blades are in the more-open position than when the plurality of damper blades are in the less-open position. The damper also comprises a fan selectively energized and de-energized such that the fan when energized urges the air to flow through the opening such that the air urges the plurality of damper blades to the more-open position. The damper further comprises an abutment being coupled to the housing such that the abutment is movable relative to the housing and is movable relative to the plurality of damper blades. The abutment is movable over a range of blocking positions between a first position and a second position, wherein the abutment in the first position holds the plurality of damper blades at the less-open position regardless of whether the fan is energized, and the abutment in the second position allows the air to move the plurality of damper blades toward the more-open position when the fan is energized. 
         [0014]    The present invention further provides a damper for controlling air, comprising a housing defining an opening. The damper also comprises a plurality of damper blades pivotally mounted to the housing in proximity with the opening. The plurality of damper blades are movable over a range of pivotal positions between a more-open position and a less-open position, wherein the air is more free to flow through the opening when the plurality of damper blades are in the more-open position than when the plurality of damper blades are in the less-open position. The damper also comprises a blade-connecting member that interconnects the plurality of damper blades such that the plurality of damper blades move in unison. The damper further comprises a fan disposed within the housing and being selectively energized and de-energized such that the fan when energized urges the air to flow through the opening such that the air urges the plurality of damper blades to the more-open position. The damper also comprises an abutment being coupled to the housing such that the abutment is movable relative to the housing, movable relative to the blade-connecting member and is movable relative to the plurality of damper blades. The abutment is movable over a range of blocking positions between a first position and a second position, wherein the abutment in the first position holds the plurality of damper blades at the less-open position regardless of whether the fan is energized, and the abutment in the second position allows the air to move the plurality of damper blades toward the more-open position when the fan is energized. The abutment engages the blade-connecting member when the plurality of damper blades are in the more-open position while the abutment is in the second position, and the abutment is spaced apart from the blade-connecting member when the plurality of damper blades are in the less-open position while the abutment is in the second position. The plurality of damper blades experience a closing torque exerted by the abutment against the blade-connecting member not only when the plurality of damper blades are closing but also when the plurality of damper blades are opening. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]      FIG. 1  is a perspective view of an air-operated damper with a controllable abutment. 
           [0016]      FIG. 2  is a cross-sectional view of an air handler that includes the damper of  FIG. 1 . 
           [0017]      FIG. 3  is a cross-sectional view similar to  FIG. 2  but showing the damper in another position. 
           [0018]      FIG. 4  is a cross-sectional view similar to  FIG. 2  but showing the damper in yet another position. 
           [0019]      FIG. 5  is a cross-sectional view similar to  FIGS. 2-4  but showing the abutment spaced apart from a blade-connecting member. 
           [0020]      FIG. 6  is an enlarged view of  FIG. 2 . 
           [0021]      FIG. 6   a  is a cross-sectional view taken along line  6   a - 6   a  of  FIG. 6 . 
           [0022]      FIG. 7  is an enlarged view of  FIG. 4 . 
           [0023]      FIG. 8  is a cross-sectional view showing the damper at an intermediate position between that of  FIGS. 6 and 7 . 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0024]      FIGS. 1-8  illustrate an air damper apparatus  10  that includes a plurality of damper blades  12  actuated by air pressure with the blades&#39; pivotal travel being limited by a variable position abutment  14 . Although damper  10  can be used in a wide variety of applications, damper  10  will be described, for sake of example, as being an exhaust damper for an HVAC air handler  16  such as those used for cooling or heating a comfort zone within a building  18 . 
         [0025]    In this example, air handler  16  comprises a housing  20  (e.g., a sheet metal enclosure), a heat exchanger  22  for heating or cooling air  30 , a blower  24  for moving air  30 , a supply air duct  26  for conveying conditioned air  30   a  to a comfort zone, a return air duct  28  for conveying used air  30   b  back to housing  20 , a return air damper  32  for selectively directing air  30  either outside and/or to heat exchanger  22 , a fresh air damper  34  for conveying outdoor air  30   c  into housing  20 , exhaust air damper  10  for determining the amount of return air  30   b  to be exhausted outdoors, a fan  36  for forcing air  30   b  through damper  10 , and an actuator  38  for controlling damper  10 . 
         [0026]    The plurality of damper blades  12  are installed in proximity with an opening  40  in housing  20 . Although the exact construction of damper  10  may vary, in this example, a plurality of shafts  42  pivotally couple damper blades  12  to a frame  44  of housing  20 . So that blades  12  can pivot in unison, a plurality of connectors  46  couple blades  12  to a common blade-connecting member  48  (e.g., a bar). The plurality of damper blades  12  can pivot over a range of pivotal positions between a more-open position ( FIGS. 4 and 7 ) and a less-open position ( FIGS. 1 ,  2 ,  3 ,  5  and  6 ). The less-open position can be where damper blades  12  are fully closed ( FIGS. 1 ,  2 ,  5  and  6 ) or where blades  12  are just slightly open ( FIG. 3 ).  FIG. 8  shows the plurality of damper blades  12  at an intermediate position between the more-open position ( FIGS. 4 and 7 ) and the less-open position ( FIGS. 1 ,  2 ,  3 ,  5  and  6 ). 
         [0027]    The combined weight of blade-connecting member  48 , connectors  46  and blades  12  urge the plurality of damper blades  12  to pivot down to their closed position ( FIGS. 1 ,  2 ,  5  and  6 ). A positive air pressure differential across opposite faces of damper  10  urges the plurality of damper blades  12  to their more-open position. The expression, “positive pressure differential,” means the air pressure decreases in the direction blades  12  pivot as damper  10  opens. Thus, a positive air pressure differential means that the air pressure on the right side of damper  10  is greater than that of the outdoor ambient air on the left side of damper  10  (“right” and “left” being as viewed in the cross-sectional drawing figures). In other words, a positive pressure differential tends to blow damper  10  open. The positive pressure differential can be created by fan  36  discharging against damper blades  12  and/or by air pressure inside building  18 , a return air chamber  50  or duct  28  being greater than the ambient air pressure outdoors. 
         [0028]    To controllably move damper blades  12  to any select position within a range of infinite pivotal positions, actuator  38  adjusts the position of abutment  14  relative to damper  10 . Abutment  14  engaging blade-connecting member  48  limits how far blades  12  can pivot in the open direction. For instance, moving abutment  14  to a first position, as shown in  FIGS. 1 ,  2  and  6 , holds damper blades  12  completely closed regardless of any reasonable pressure differential across damper  10 . Abutment  14  in a second position, as shown in  FIGS. 4 and 7 , allows a positive pressure differential, such as that created by fan  36  being energized, to blow damper blades  12  to their more-open position (e.g., fully open). Abutment  14  in another “first position,” as shown in  FIG. 3 , allows damper  10  to be slightly open. Abutment  14  in the position of  FIG. 8  allows a positive pressure differential, such as that created by fan  36  being energized, to blow damper blades  12  to some intermediate open position. 
         [0029]    Although the design of abutment  14 , actuator  38  and the interconnection between the two may vary, abutment  14  preferably comprises a roller  52  attached to a pivotal arm  54 . Roller  52  preferably is softer than blade-connecting member  48  so that roller  52  provides shock absorption in the event of an impact between roller  52  and member  48 . Roller  52 , for example, can be made of plastic, and member  48  can be made of aluminum. A link  56  couples arm  54  to a drive arm  58  of actuator  38  so that the rotation of drive arm  58  pivots arm  54  to move roller  52 . Actuator  38 , in this example, is a motor that powers drive arm  58  counterclockwise (as viewed in the cross-sectional drawing figures). When the actuator&#39;s motor is de-energized, a tension spring  60  forces drive arm  58  back in a clockwise direction toward the position shown in  FIGS. 2 and 6 . 
         [0030]    The aforementioned design allows a damper to comprise multiple sets of damper blades  12   a  and  12   b  to be controlled by multiple abutments  14 , as shown in  FIG. 1 . Abutments  14  can be supported by a plurality of pivotal arms  54  each of which are fixed relative to a rotatable shaft  62 . Shaft  62  is supported by a set of lugs  64  mounted underneath an exhaust hood  66  of housing  20 . Shaft  62  being rotatable relative to lugs  64  allows link  56  to pivot arms  54  about a longitudinal axis of shaft  62 . Arms  54  pivot in unison, as each arm  54  is fixed to shaft  62 . This design can be particularly useful in controlling two sets of damper blades  12   a  and  12   b  that are separated by a structural frame member  68  ( FIG. 1 ) because the design does not require interconnecting linkage between the two sets of damper blades  12   a  and  12   b  in order for them to open. 
         [0031]    Return air damper  32  and fresh air damper  34  can be controlled by an equivalent or modified version of actuator  38 , or dampers  32  and  34  can be operated by conventional actuators  70  and  72 . Actuators  70  and  72  are schematically illustrated to represent common actuators that are well known to those of ordinary skill in the art. To control air handler  16  and its dampers, a controller  74  provides outputs  76 ,  78 ,  80 ,  82  and  84  for selectively energizing or otherwise controlling fan  36 , blower  24 , and actuators  38 ,  70  and  72 . Controller  74  might also be used for controlling a refrigerant circuit or some other heating/cooling system associated with heat exchanger  22 . For sake of example, the operation of air handler  16  will be described with reference to heat exchanger  22  functioning as an evaporator of a refrigerant circuit for cooling air  30 . 
         [0032]    In the operating mode of  FIG. 2  (also shown in  FIGS. 1 and 6 ), controller  74  commands actuator  70  to open damper  32  and commands actuators  38  and  72  to close dampers  10  and  34 . Damper  10  is closed by controller  74  de-energizing fan  36  and abutment  14  being at a first position obstructing blade-connecting member  48 . Controller  74  energizes blower  24  to force air  30  from a comfort zone via return air duct  28 , through open return damper  32 , through heat exchanger  22  to be cooled, and out through supply air duct  26 , wherein supply air duct  26  conveys the cooled air  30   a  back to the comfort zone. In this operating mode, substantially all of the comfort zone&#39;s air is recirculated through air handler  16 . Substantially no outdoor air is added, and substantially no return air  30   b  is exhausted outside. 
         [0033]    The configuration of  FIG. 3  is similar to that of  FIG. 2 ; however, the illustrated configuration of  FIG. 3  represents various possible operating modes. In  FIG. 3 , actuator  38  positions abutment  14  to another “first position” such that damper  10  can be slightly open or closed tight, depending on the air pressure differential across damper  10 . Fresh air damper  34  can also be closed or slightly open, depending on the need. 
         [0034]    In one operating mode of  FIG. 3 , fan  36  is de-energized, fresh air damper  34  is closed tight, and a positive air pressure in return air chamber  50  (i.e., greater than the outdoor air pressure) forces damper  10  slightly open to release excess air pressure within building  18 . 
         [0035]    In a second operating mode of  FIG. 3 , exhaust fan  36  is energized, fresh air damper  34  is closed tight, and exhaust damper  10  is slightly open to forcibly draw air  30   b  out from with return air chamber  50  and exhaust it outside, thereby further reducing the air pressure within building  18 . 
         [0036]    In a third operating mode of  FIG. 3 , fan  36  is energized, fresh air damper  34  is slightly open, and exhaust air damper  10  is slightly open. This is similar to the operation of  FIG. 2  but with some used return air  30   b  exchanged for some fresh outdoor air. 
         [0037]    In a fourth operating mode of  FIG. 3 , fan  36  is de-energized, fresh air damper  34  is closed tight, and exhaust damper  10  is closed tight due a negative air pressure in return chamber  50 , i.e., the outdoor air pressure is greater than the pressure in return air chamber  50 . With damper  10  closed tight, abutment  14  will be slightly spaced apart from blade-connecting member  48 . This fourth mode can be used to maintain a certain negative pressure in building  18 , if so desired. 
         [0038]    In the operating mode of  FIG. 4  (also shown in  FIG. 7 ), controller  74  commands actuator  38  to close return damper  32  and commands actuator  72  to open fresh air damper  34 . Controller  74  also energizes fan  36  and commands actuator  38  to move abutment  14  to its second position. Controller  74  energizes blower  24  to draw in fresh outdoor air  30   c  and force the air through heat exchanger  22  to be cooled. Supply air duct  26  then conveys the cool fresh air  30  to the comfort zone. The used return air  30   b  is then exhausted outside through damper  10 . In this operating mode, substantially none of the used return air is recirculated back to the comfort zone, but instead fresh outdoor air is used. 
         [0039]      FIGS. 4 and 7  show both dampers  10  and  34  being fully or nearly fully open; however, dampers  10  and  34  can be opened at any intermediate position.  FIG. 8 , for example, shows dampers  10  and  34  partially open with return air damper  32  partially open as well. This provides the comfort zone with a mixture of fresh and recirculated return air, rather than substantially 100% fresh outdoor air ( FIGS. 4 and 7 ) or substantially 100% recirculated return air ( FIGS. 2 and 6 ). In providing such a mixture of fresh air  30   c  and return air  30   b,  actuators  38  and  72  preferably move their respective dampers  10  and  34  in some directly proportional manner. Although dampers  10  and  34  preferably both open together and close together, their relationship of movement is not necessarily linear, so one damper might open farther or faster than the other. 
         [0040]    The open/close travel limits of abutment  14  can be adjusted by various means including, but not limited to, adjusting the mounting position of actuator  38  relative to housing  20 , or adjusting the position of a connecting pin  86  on link  56  as shown in  FIG. 6   a.    
         [0041]      FIG. 5  shows how abutment  14  and blade-connecting member  48  can be spaced apart if actuator  38  moves abutment  14  to an intermediate or open position, and fan  36  is de-energized with a negative or zero pressure differential across damper  10 . 
         [0042]    Although the invention is described with respect to a preferred embodiment, modifications thereto will be apparent to those of ordinary skill in the art. The scope of the invention, therefore, is to be determined by reference to the following claims: