Abstract:
A damper actuator for a ventilation damper serves as both a control device for the ventilation damper and a fire and smoke rated device for the ventilation damper. The damper actuator includes a modulating motor controller, a two-point motor controller, and a thermal switch or switch like device that is operative to switch control of the motor from the modulating motor controller used during normal operation, to the two-point motor controller during a fire and smoke condition. The damper actuator provides an automatic and permanent disabling (by-passing) of the modulating motor controller functions the first time a pre-determined temperature level (switch point) is reached via the thermal switch or switch like device. Once the modulating motor controller is disabled, the actuator no longer supports the advanced motor control functions (i.e. the modulating control). Thereafter, the thermal switch or switch like device enables a two-point motor controller that is operative to put the damper into either a fully open or a fully closed position.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates generally to building control systems, and more particularly, to ventilation and life safety dampers for use in building control systems.  
         BACKGROUND OF THE INVENTION  
         [0002]    Building control systems control various aspects of a building, including comfort, safety, lighting and other aspects. With respect to comfort, one aspect of a building control system includes heating, ventilation and air conditioning (HVAC). An HVAC system involves conditioning of the air within an area, zone or room. Such conditioning includes providing heated air, cooled air, fresh air, circulated air and/or the like to the particular area depending on various factors. The HVAC system includes a system of ducts that terminate in particular areas or zones. The termination points are controlled by ventilation dampers or damper systems. Each ventilation damper/damper system is operative to control the flow of air from the respective termination point.  
           [0003]    Ventilation dampers/damper systems are thus one component of a building control system that are used to help with the aspect of comfort and safety. In summation, ventilation dampers/dampers systems (collectively, dampers) are used for temperature control, pressure regulation, air circulation and/or replacement of stale air.  
           [0004]    Basic dampers are positionable into either a fully opened or a fully closed position. This provides only either full air flow or no air flow. It is better, however, to use intermediate levels of openness in addition to the fully opened and fully closed positions in order to better control ventilation. For example, in order to maintain a particular temperature, the damper may be opened to allow the flow of conditioned air into the room. If only two states (open and closed) are allowed, the system will constantly be cycling on and off to maintain the particular temperature. With intermediate levels of openness, an amount of conditioned air may be gradually modulated into the room/zone until a quasi-steady state level is achieved (in other words, the flow of conditioned air through the damper more or less equals the thermal load variables within the room that are changing the controlled air requirements of the room).  
           [0005]    Modulating control dampers achieve this elevated level of control over damper position and thus provide better control over temperature, pressure regulation and/or air replacement. Modulating control dampers include a modulating control. The modulating control typically receives signals representative of a particular position (percentage open) and then control an actuator to achieve that position in accordance with particular parameters. A modulating control actuator is used to control position of the damper and thus control air flow. The modulating control utilizes digital and/or analog circuits that operate a motor to cause the damper to travel to and stop in the position identified by the received controls.  
           [0006]    It has been recognized that the needs of the ventilation system change in the presence of fire and its attendant smoke. In certain situations, it is advantageous to vent heat away from affected areas unless smoke is present, in which case the area should be sealed. Ventilation dampers may be configured to perform such functions during a fire and smoke event.  
           [0007]    Dampers having modulating control typically cannot be used for fire and smoke events because the circuits that control position of the motor are not resilient enough to tolerate the extensive heat that accompanies such fire and smoke events. Indeed, standards define the conditions under which the above described fire and smoke operation must be able to be carried out. The types of digital and analog circuitry that currently perform modulating control may not meet those standards.  
           [0008]    Accordingly, the prior art has employed separate dampers in the ducts of buildings, i.e. one damper for comfort control and one damper for fire and smoke control. The comfort control damper may employ a modulating actuator control that opens the damper to a select position of large number of positions. The fire and smoke control damper employs a simpler two-state actuator control that is either open or closed. With this system, the comfort control damper and actuator need not operate fully or function in any manner during a fire and smoke event, and may thus employ significant position control circuitry. Meanwhile, the fire control damper requires fewer control elements, and thus can readily be made to withstand the higher temperature operating requirements.  
           [0009]    One problem with the above-described arrangement for providing dampers in a building control system is the cost associated with requiring multiple dampers for multiple functions for the same room or space. There is a need, therefore, for a system that overcomes the shortcomings of the prior art ventilation damper arrangements.  
         SUMMARY OF THE INVENTION  
         [0010]    The subject invention addresses the above need, as well as others, by providing a damper system that incorporates both modulating control and fire and smoke control. Particularly, the subject invention provides a dual mode actuator for a damper that disengages modulating control circuitry when a detected temperature exceeds a threshold, and engages a simpler temperature resilient control circuitry for the actuator that moves the damper. Thereafter, the subject invention provides automatic closure of the damper upon power interruption.  
           [0011]    The subject invention provides a ventilation damper actuator that serves as both a control device for the ventilation damper and a fire and smoke rated device for the combination ventilation/fire and smoke rated damper. The subject invention provides an automatic and permanent disabling (by-passing) of advanced modulating motor control functions the first time a pre-determined temperature level (switch point) is reached. This is accomplished with a thermal switch, fuse, sensor, and/or the like. Once the advanced circuitry is disabled, the actuator no longer supports the advanced motor control functions (i.e. the modulating control). Thereafter, the thermal switch enables a two-point motor controller that is operative to put the damper into either a fully open or a fully closed position.  
           [0012]    By using this scheme, the electronics of the drive circuitry are simplified. Additionally, motor operation is ensured at elevated temperatures that may not be realized with the advanced circuitry (i.e. modulating circuitry) since the advanced circuitry may be difficult and costly to realize at high temperatures.  
           [0013]    In yet another form, there is provided a damper actuator having a motor adapted to be coupled to a damper, a thermally actuated switch coupled to the motor, modulating motor control circuitry coupled to the switch; and two-point motor control circuitry coupled to the switch. The thermally actuated switch has a first state wherein the modulating motor control circuitry is coupled to the motor for operational control of the motor and the two-point motor control circuitry is decoupled from operational control of the motor, and a second state wherein the two-point motor control circuitry is coupled to the motor for operational control thereof and the modulating motor control circuitry is decoupled from operational control of the motor.  
           [0014]    The above-described features and advantages, as well as others, will become more readily apparent by reference to the following detailed description and accompanying drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]    [0015]FIG. 1 shows a block diagram representation of a building having an HVAC/control system including ventilation damper systems in accordance with the present principles;  
         [0016]    [0016]FIG. 2 shows a block diagram of a ventilation damper system in accordance with the principles of the subject invention;  
         [0017]    [0017]FIG. 3 shows a perspective view of an exemplary damper system;  
         [0018]    [0018]FIG. 4 shows an exploded perspective view of the actuator in accordance with the principles of the subject invention; and  
         [0019]    [0019]FIG. 5 shows a block diagram of an embodiment of a damper actuator in accordance with the principles of the subject invention. 
     
    
     DETAILED DESCRIPTION  
       [0020]    The above-described embodiments are merely exemplary, and those of ordinary skill in the art may readily devise their own implementations and modifications that incorporate the principles of the present invention and fall within the spirit and scope thereof. With reference now to FIG. 1, there is depicted a representation of a building generally designated  10  in which the subject invention may, and typically is, used. It should be appreciated that the building  10  is representative of any structure that has a ventilation system or systems such as a house, multi-story building or the like. The building  10  has a ventilation/ventilation control system such as an HVAC/control system  12  having various HVAC and control components some of which are hereinafter discussed, including the subject invention, and some of which are known in the art. The HVAC/control system  12  includes HVAC and control unit(s)  14  representative of heating, air conditioning, and/or other ventilation sources/components/systems, equipment and/or the like such as are well known in the art, and control sources/components/systems.  
         [0021]    As is typical, the HVAC/control system  12  includes a plurality of air flow/control systems generally designated  16   1 ,  16   2  through  16   N  that direct the flow of air from the HVAC units to various places in the building  10  and which thereafter control the flow of air into the various places. Such places may be rooms, zones, areas or the like. Each air flow/control system  16   1 ,  16   2  through  16   N  is characterized by a series of ducts or ductwork and communication/control lines both of which are concurrently represented by lines  17   1 ,  17   2  through  17   N . Each line  17   1 ,  17   2  through  17   N  terminates in at least one damper system (D.S.). Each damper system (D.S.) provides adjustable control of air flow from the lines  17   1 ,  17   2  through  17   N  into the particular areas or zones of the building  10 , particularly under control of the control system(s). In accordance with the principles of the subject invention, each damper system D.S. also provides fire and smoke protection. The fire and smoke protection is in accordance with industry standards.  
         [0022]    The ducts or ductwork provide passageways for directing air flow from the HVAC units(s)  14  to various places (e.g. rooms, zones or the like) of the building  10 . Shown in FIG. 1 for illustrative purposes, are various exemplary manners in which the ducts may be configured and/or terminated. Particularly, the system  16 , has a single duct  171  that terminates in a single damper system  18   1 . The system  16   2  has a duct system  17   2  that has various branches from a main duct thereof, each of which terminates in a damper system  18   2a ,  18   2b  through  18   2N . The system  16   N  has a variable branch duct system that terminates in damper systems  18   Na ,  18   Nb  and  18   Nc .  
         [0023]    Referring now to FIG. 2, there is depicted a block diagram of an exemplary damper system  18 . The damper system  18  includes an actuator, actuating circuitry, motor, damper interface, control logic or the like  20  (collectively, “actuator”). In a preferred embodiment, the motor  22  is a brushless DC (BLDC) motor. Other types of motors both AC and DC, however, may be used such as a synchronous motor, a brush DC motor, a shaded pole motor and/or the like. The actuator  20  is operative, configured and/or adapted to control the damper  24 . Particularly, the actuator  20  controls the opening, closing and/or various intermediate positions of the damper  24 . This is accomplished through a motor/damper interface  26 . The damper interface  26  translates the rotational motion of the motor  22  into motion that moves the damper  24  and may or may not including gearing.  
         [0024]    The actuator  20  includes an advanced motor controller, control circuitry, logic or the like  28  and a simple motor controller, control circuitry, logic or the like  30 . In a preferred form, the advanced motor controller  28  is what is known as a modulating controller while the simple motor controller  30  is what is known as a two-point controller. While explained more fully below, the advanced motor controller  28  is operative, configured and/or adapted to provide control signals to the motor  22  that allow the motor  22  to provide precise control of the damper  24  through the motor/damper interface. Particularly, the advanced motor controller  28  provides control signals to the motor  22  that, through the motor/damper interface  26 , controls the damper  24  such that the damper  24  provides a fully open condition wherein the flow of air through the damper  24  is unrestricted, a fully closed condition wherein the flow of air through the damper  24  is totally restricted, and a plurality of variable positions between the fully open and fully closed positions wherein the flow of air through the damper is restricted to a degree between the fully open and fully closed positions.  
         [0025]    In one form, position of the motor/damper interface  26  may be accomplished with the aid of motor position feedback represented by the arrow  36  emanating from the motor  22  to the advanced motor controller  28 . The actuator  20  may have encoding or the like that provides the necessary feedback to determine rotational position of the damper interface  26 . This rotational position may then be used by the advanced motor controller  28  to determine damper position. For example, rotation of the motor a certain number of revolutions in one direction may be known to move the damper into 50% of being open relative to a fully open or fully closed position (i.e. halfway between a fully open position and a fully closed position). As another example, each number of revolutions of the motor  22  may be known to move the damper  24  a known amount. This ratio may be dependant on possible gearing internal to the actuator  20 .  
         [0026]    In another form, position of the damper may be accomplished in a time based manner. For example, applying a control signal of a given length from the advanced motor controller  28  may be known to move the damper  24  a given amount. The time that the control signal is applied thus translates into movement of the damper. This may be accomplished in both rotational directions.  
         [0027]    It should be appreciated, that such feedback may be provided from the motor/damper interface  26  as represented by the dashed arrow  37  emanating from the motor/damper interface  26  rather than the motor  22  or in conjunction therewith. In one form, the motor/damper interface  26  may utilize a potentiometer that changes resistance in proportion to rotational movement thereof. This resistance change is provided to one input of a comparator in the advanced motor controller  28 , while another input of the comparator receives a desired position signal. Output of the comparator determines whether the motor is turned on until the desired position is achieved, or is not turned on.  
         [0028]    Another manner of tracking position with respect to time may be accomplished by using a constant speed reverse rotation braking circuit such as is known in the art. In this configuration, the motor  22  is turned at a constant speed in one rotational direction and tracked according to time. A spring return operatively coupled to the motor  22  rotates the motor  22  in the reverse rotational direction according to a controlled and known speed. In this manner, the time it takes to reverse direction may be tracked to know the position of the damper  24 .  
         [0029]    The advanced motor controller  28  is preferably in two-way communication with control units, sensors and/or the like (not shown) of the overall HVAC system as represented by the double-headed arrow in FIG. 2. Such control units, sensors and/or the like may include such components as thermostats and air flow monitors. The advanced motor controller  28  utilizes control signals from the control units, sensors and/or the like to control damper in any modulated position. The advanced motor controller  28  may also provide feedback as necessary.  
         [0030]    Again, while explained more fully below, the simple motor controller  30  is operative, configured and/or adapted to provide control signals to the motor  22  that allow the motor  22  to position the damper  24  into either the fully open position or the fully closed position. Particularly, the simple motor controller  30  provides control signals to the motor  22  that, through the motor/damper interface  26 , controls the position of the damper  24  such that the damper is either in the fully open or the fully closed position.  
         [0031]    The damper actuator  20  preferably, but not necessarily has a power supply, power supply circuitry, logic or the like  34 . The power supply  34  is operative, configured and/or adapted to receive either AC or DC power (AC/DC IN) and provide appropriately conditioned AC or DC power to the advanced motor controller and the simple motor controller.  
         [0032]    The advanced motor controller  28  and the simple motor controller  30  are each connected to a switch or switch like device  32  that is, in turn, connected to the motor  22 . The switch  32  is operative, configured and/or adapted to provide either the control signals from the advanced motor controller to the motor  22  or control signals from the simple motor controller  30  to the motor  22 . In a normal mode, the switch  32  connects the advanced motor controller  28  to the motor  22  for operational control thereof and by-passes connection of the simple motor controller  30 . In a fire and smoke mode, the switch or switch like device  32  disconnects (by-passes) the advanced motor controller  28  from operational control of the motor  22  and couples or connects the simple motor controller  30  to the motor  22  for operational control of the motor  22 . The switch or switch like device  32  thus provides a first or normal state of operation and a second or fire state of operation.  
         [0033]    The switch or switch like device  32  is caused to change states based on a thermal condition. Particularly, the switch or switch like device  32  is a thermal switch that is operative, configured and/or adapted to be actuated when a predetermined temperature is reached. The switch or switch like device  32  itself may incorporate a thermal sensor that operates to cause the switch to change states, or may utilize an outside thermal control signal that may be generated by a thermal sensor and provided to the switch or switch like device  32 . In a preferred form, the switch  32  is a one-way thermostatic switch such as that made by Selco Products of Anaheim, Calif. Once the one-way thermostatic switch changes states, it will not change back. In this manner, the damper actuator  20  is a one-time use fire and smoke emergency type device (i.e. once it is triggered due to thermal conitions, a new damper actuator must be installed). It should be appreciated, however, that other switching devices may be used that provide a change in states based on a thermal condition (i.e. a pre-determined temperature being reached).  
         [0034]    Referring now to FIG. 3, there is depicted an exemplary damper system  18  having an exemplary damper  24  to which is attached a damper actuator module  39 . The damper actuator  20  houses the motor  22 , the motor/damper interface  26 , control electronics, etc. It should be appreciated that the damper  24  is only exemplary of a style or type of damper and that other styles, configurations and/or types of dampers may be utilized. The damper  24  of FIG. 3, however, provides an illustration of the manner in which most dampers control the flow of air therethrough.  
         [0035]    The damper  24  includes a frame  38  that carries a control shaft  40 . The control shaft  40  is coupled to the motor/damper interface  26  such that the motor/damper interface  26  is operative to move the control shaft  40  appropriately. Particularly, the control shaft  40  is coupled to the motor/damper interface  26  such that the motor/damper interface  26  is operative to controllably rotate the control shaft  40  about its longitudinal axis. The control shaft  40  is coupled to an upper shaft  42  and a lower shaft  44  such that rotation of the control shaft  40  also rotates the upper shaft  42  and the lower shaft  44  or any multiple of auxiliary blades.  
         [0036]    The control shaft  40  is coupled to a vane, blade or the like  46  such that rotational movement of the control shaft  40  rotates the vane  46  about the control shaft  40 . The upper shaft  42  is coupled to a vane, blade or the like  48  such that rotational movement of the upper shaft  42  rotates the vane  48  about the upper shaft  42 . The lower shaft  44  is also coupled to a vane, blade or the like  50  such that rotational movement of the lower shaft  44  rotates the vane  50  about the lower shaft  44 . Thus, rotation of the control shaft  42  rotates the vane  46  as well as the upper and lower shafts  42 ,  44  which, in turn, rotate the vanes  48  and  50 . As the vanes  46 ,  48  and  50  rotate, they open up the damper  24  to the flow of air therethrough. The damper  24  is thus able to be controlled to provide a fully open position, a fully closed position, and positions intermediate the fully open and fully closed positions through controlled rotation of the control shaft  40 . Of course, it should be appreciated that rotation of the control shaft  40  is ceased when a particular (desired) air flow position is achieved.  
         [0037]    It should be appreciated that the damper  24  in FIG. 3 is depicted in the fully closed position. In this position, the vanes  46 ,  48  and  50  are perpendicular to the flow of air through the damper  24  and thus prevents same. A fully open position has the vanes  46 ,  48  and  50  parallel to the flow of air through the damper  24 . The intermediate positions have the vanes  46 ,  48  and  50  at a rotational angle between perpendicular and parallel.  
         [0038]    As indicated above, the control shaft  40  is coupled to the motor/damper interface  26 . The motor  22 , under control by either the advanced motor controller  28  or the simple motor controller  30 , depending on whether there is a normal mode or a fire/smoke mode, actuates the motor/damper interface  26  which, in turn, rotates the control shaft  40 .  
         [0039]    Referring to FIG. 4, there is depicted an exploded view of an example actuator  20 . The actuator  20  includes a housing  60  that encloses the motor  22 , a printed circuit assembly  52  that contains the modulating motor control/controller circuitry  28  and the two-point motor control/controller circuitry  30  (both of which are not specifically delineated thereon), a gear train  54  that is operatively connected to the motor  22 , and a control shaft coupling  56  that is operatively connected to the gear train  54 . The control shaft coupling  56  is operative, configured and/or adapted to receive the control shaft  40  and rotate same. Moreover, the actuator  20  may include a mechanical spring return  58  that is operative to control the control shaft coupling  56  when power to the actuator  20  ceases. Other means of returning the actuator  20  to it&#39;s zero position may also be employed.  
         [0040]    Particularly, when the power to the actuator  20  is cut off because of a smoke controller or sensor (not shown) detects smoke because of a fire condition or any other emergency situation, and thus the modulating controller  28  and the two-point controller  30  are inoperative due to power loss, the mechanical spring return  58 , or any other fail to zero position mechanism, causes the control shaft coupling  56  to position the control shaft  40 , and thus the vanes of the damper  24 , to close thereby putting the damper  24  into a fully closed or fully open position. During the time that either the modulating controller  28  and the two-point controller  30  are operative, the spring tension on the mechanical spring return  58  ,or any other fail to zero position mechanism, is overcome or overridden by the motor  22  or other means.  
         [0041]    Referring now to FIG. 5, there is depicted a block diagram of the electronics of actuator  20 . The electronics shown in FIG. 5 particularly depicts a manner of connecting the modulating controller  28  and the two-point controller  30  to the thermal switch  32 , the internal switching thereof, and the connection of the switch  32  to the motor  22 . Moreover, the switch  32  is shown coupled to a thermal sensor  64  that provides a control signal to the switch or switch like device  32  when a pre-determined temperature is reached. The control signal is operative to cause the switch  32  to change states (i.e. switch over the control from the modulating controller  28  to the two-point controller  30 ). While the sensor  64  is shown external to the switch  32 , it should be appreciated that the sensor  64  may be internal to the switch  32  or external to the actuator  20 . Further depicted is a feedback line  66  from the motor  22  that may be used by the two-point controller  30  for control of the motor  22 .  
         [0042]    The subject damper actuator  20  thus provides adjustable control of the damper  24  via the modulating controller  28  during normal operation, on/off (fully open/fully closed) control of the damper  24  via the two-point controller  30  during a sensed fire and smoke/heat/emergency condition, and a return to a predetermined zero position control of the damper  24  via a biased spring or the like during a fire and smoke condition when power to the damper actuator has been cut off.  
         [0043]    Moreover, the subject invention provides a ventilation damper that acts in a two point mode which fulfills all U/L 555(S) (i.e. a U/L specification that covers the requirements for approving a fire and smoke rating of an actuator and damper assembly) requirements for fire and smoke operation. The present ventilation damper would never be required to resume operation in the modulating mode because it will be disposed of after a smoke/fire emergency. Thus, the permanent switch-over from the modulating mode to the on/off mode provides clear evidence that a ventilation damper system needs replacement. In this manner, no further means for indicating an exposure to high temperature levels are necessary.