Abstract:
A device for controlling the movement of a damper mounted in a housing includes a shaft rotatably secured to the damper for pivoting the damper between an open position and a closed position. A lever arm is mounted on the shaft for rotation therewith and a spring is connected between the housing and the lever arm for normally urging the damper towards the open position. A motor is mounted on the housing and is actuable to overcome the force of the spring to move the damper to the closed position. A force translation arrangement is disposed between the motor and the lever arm for translating the driving force of the motor when the motor is energized to move the damper to the closed position, and for gradually braking the motor when the motor is de-energized and the spring returns the damper to the open position.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     Not applicable. 
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Not applicable. 
     FIELD OF THE INVENTION 
     This invention relates to a heating and cooling system including a damper blade assembly rotatably mounted within a duct to deliver conditioned air to an enclosure, and in particular, to an arrangement for controlling the position of the damper blade assembly within the duct in accordance with the sensed temperature of the air in the enclosure. 
     BACKGROUND OF THE INVENTION 
     Many multi-room structures, such as office buildings and schools as well as residential buildings constructed during the past several years, include heating and cooling systems to deliver either relatively warm or cool conditioned air from a central source thereof to each of the enclosures or rooms in the building. Typically, one or more ducts are employed to deliver the air to each enclosure. Very often, an automatically operated damper blade assembly or similar mechanism is installed in the duct to regulate the flow of air to one or more discharge outlets located in the enclosure being conditioned by the discharge of air thereinto. The movement of the damper blade assembly may be responsive to changes in the temperature of the enclosure. 
     Many of these automatically operated damper blade assemblies use a spring to open the damper and an opposing electric motor and gear train assembly to close the damper and hold it in the closed position when conditioned air is not needed in the enclosure. The damper, the spring, the motor and its gear train assembly are interconnected such that as the motor closes the damper it also acts against the spring. When the motor is de-energized, the spring reacts to open the damper and in doing so rotates the motor shaft in the direction opposite its drive direction until the damper reaches an end stop defining its open position. 
     Certain problems, however, arise when the exact requirements of the damper blade assembly are examined. On the one hand, a relatively strong opening force for the spring is required to ensure that any friction or binding forces on the moving parts of the damper blade assembly will be overcome. On the other hand, the gear train associated with the motor is relatively fragile and will not withstand much in the way of an impact such as can be caused when a moving gear train is stopped suddenly. As a strong spring force drives the damper to an open position, it is subjecting the gear train to a substantial amount of torque. In currently used damper blade assemblies, when the damper reaches the end of its travel towards the open position and contacts an end stop, this torque is transferred to the gear train as an impact force with the result that the gear train may be damaged. Similarly, the gear train can easily be damaged if the damper blade assembly is turned by hand with too much force. This sometimes occurs during the packaging and installation of the system. While some vendors include a shock absorbing spring and add play to the assembly to reduce the chance of over-stress damage, wear of the gears continues to limit the life of the damper blade assembly. The cost of the damper blade assembly is high due to the number of parts and tolerances required. 
     Accordingly, it remains a challenge to construct a mechanism that can maintain the narrow balance between too powerful a spring which will damage the gear train and too weak a spring which will not be able to overcome the friction and drag that will generally increase as the damper becomes worn during its service life. In addition, it remains desirable to prevent over-stress damage to the damper blade assembly by permitting the gear train and the motor to slowly decelerate instead of causing the impact that occurs in the conventional mechanisms when they suddenly stop and the damper hits its end stop in the open position. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention advantageously provides a damper blade control employing a management arrangement which is reliant on a strong spring force for opening yet prevents the torque applied from being transferred to the gear train in a damaging manner. With such construction, an automatically operated damper blade control is provided which ensures positive opening and closing of the damper without exceedingly high manufacturing, installation and servicing costs. 
     It is an object of the present invention to effectively regulate the flow of conditioned air through a supply duct to a discharge outlet located in an enclosure. 
     It is a further object of the invention to effectively control the position of a damper blade mounted within a duct to control the conditioned air flow through the duct. 
     It is yet another object of the invention to produce a low cost, simplified yet reliable damper blade assembly using non-precision parts. 
     Still yet another object of the invention is to provide a damper blade assembly having a unique force translation arrangement which will operate equally well between the opening and closing positions of the damper. 
     In one aspect of the invention, a device for controlling the movement of a damper mounted in a housing between an open position and a closed position comprises a shaft rotatably secured to the damper for pivoting the damper between the open position and the closed position. A lever arm is mounted on the shaft for rotation therewith, and a spring is connected between the housing and the lever arm for normally urging the damper towards the open position. A motor is mounted on the housing and is actuable to overcome the force of the spring to move the damper to the closed position. A force translation arrangement is disposed between the motor and the lever arm for translating the driving force of the motor when the motor is energized to move the damper to the closed position, and allow gradually braking the motor due to its internal friction when the motor is de-energized and the spring returns the damper to the open position. 
     In yet another aspect of the invention, there is contemplated a drive system for a damper rotatably mounted on a shaft in a housing between an open position and a closed position. The housing includes a rotatable element joined to the shaft for rotation therewith, a biasing element is provided for urging the damper to the open position, and a motor is actuable to overcome the force of the biasing element to move the damper to the closed position. The improvement resides in a wind-up spool mounted on the housing in driving engagement with the motor. A flexible band extends between the spool and the rotatable element, the band being windable upon the spool when the motor is selectively actuated to move the damper to the closed position. The band is unwindable from the spool when the motor is deactivated allowing the biasing element to rotate the shaft, the damper, the rotatable element, the motor and the spool such that the damper returns to the open position. The spool and the band define an over-travel mechanism for preventing damage to the motor as the damper assumes the open position. 
     Still another aspect of the invention contemplates a mechanism for driving at least one damper supported on a housing for motion between an open position and a closed position. The mechanism comprises at least one rotatable shaft secured to at least one damper for pivoting the damper between the open position and the closed position. A lever arm is mounted on the at least one shaft for rotation therewith, the lever arm being equipped with a pair of stop surfaces. A pair of stops are secured to the housing, each of the stops being engageable with one of the stop surfaces so as to define the limits of travel of the damper corresponding to the open position and the closed position. A biasing device is connected between the housing and the lever arm for normally urging the at least one damper towards the open position. A spool is rotatably mounted on the housing, and a flexible band extends between the spool and the lever arm, the band being windable upon the spool. A motor is drivingly connected to the spool wherein selective actuation of the motor enables the band to be wound upon the spool so as to overcome the force of the biasing device, and rotate the at least one shaft, the at least one damper, and the lever arm towards the closed position at which one of the stop surfaces engages one of the stops. Selective deactivation of the motor enables the biasing device to rotate the at least one shaft, at least one damper, the lever arm, the motor and the spool until the open position is reached at which the other of said stop surfaces engages the other of the stops and rotation of the at least one shaft, the at least one damper and the lever arm is terminated. The motor and the spool continue to rotate by their own inertia causing the band to unwind from the spool and enable the gradual slowdown of the motor to prevent damage thereto. 
     Various other objects, features and advantages of the invention will be made apparent from the following description taken together with the drawings. 
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
     The drawings illustrate the best mode presently contemplated of carrying out the invention. Like numerals denote like elements. 
     In the drawing: 
     FIG. 1 is a perspective view of a damper housing having a damper control embodying the present invention so as to control the movement of a pair of damper blades; 
     FIG. 2 is an exploded view of a portion of the damper control shown in FIG. 1; 
     FIG. 3 is an exploded view of the entire damper control shown in FIG. 1; 
     FIG. 4 is a sectional view of the damper control shown in the open position as taken on line  4 - 4  of FIG. 1; 
     FIG. 5 is a sectional view of the damper control shown in the open position as taken on line  5 - 5  of FIG. 1; 
     FIGS. 6 and 7 are views similar to FIGS. 4 and 5 but showing the damper control in the closed position; 
     FIG. 8 is a sectional view on line  8 — 8  of FIG. 4; 
     FIG. 9 is a sectional view on line  9 — 9  of FIG. 4 showing the interconnection between a motor shaft and a spool of the present invention; 
     FIG. 10 is a partial sectional view taken on line  10 — 10  of FIG. 9; 
     FIG. 11 is a sectional view taken on line  11 — 11  of FIG. 10; 
     FIG. 12 is a sectional view taken on line  12 — 12  of FIG. 4; 
     FIGS.  12 ( a ) and  12 ( b ) are diagrammatic views of an integral trigger spring; 
     FIGS. 13A and 13B are fragmentary sectional views of the upper lever arm of FIG. 4 in the open and closed positions, respectively; 
     FIGS. 14A and 14B are sectional views similar to FIGS. 13A and 13B taken on line  14 A of FIG. 12 showing the lower lever arm in open and closed positions, respectively; 
     FIG. 15 is a sectional view on line  15 — 15  of FIG. 6; 
     FIG. 16 is an alternative embodiment of the motor shaft and spool of FIG. 9; 
     FIG. 17 is a partial exploded view of a damper control embodying the present invention so as to control the movement of a single damper blade; 
     FIG. 18 is an alternate embodiment of a damper control in the closed position; 
     FIG. 19 is an alternative embodiment of the damper control of FIG. 18 in the open position; and 
     FIG. 20 is a sectional view taken on line  20 — 20  of FIG.  19 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention is particularly well suited for heating and cooling systems utilizing zoned control, the air flow to each zone being controlled by a motorized damper blade assembly  10  embodying the present invention. By strategically locating the motorized damper blade assembly  10  in the heating and cooling systems, each zone can be controlled by its own thermostat set to a different temperature. 
     Referring to FIGS. 1,  2  and  3 , a rotatable damper blade assembly  10  is positioned within a housing  12  interposed within the duct work of a heating and cooling system (not shown). Housing  12  includes a top wall  14 , a bottom wall  16  and a pair of parallel, spaced apart, flanged sidewalls  18 ,  20 . A set of fasteners  22  passes through suitable apertures  24  on sidewalls  18 ,  20 , and is screwed into threaded guideways  26  formed on top wall  14  and bottom wall  16  to hold housing  12  together. A first or upper rotatable damper blade  28  is provided at each end thereof with a stub shaft  30  having an inner end which is fixedly secured in a hollow channel  32  running longitudinally of damper blade  28 . An outer end of stub shaft  30  is disposed for rotation in a circular bearing retainer  34  friction fitted into opening  36  on each sidewall  18 ,  20 . Alternately, bearing retainer  34  can be snap fit into opening  36 . The bearing retainer  34  is integrally formed with a first raised rim or stop  34   a  (FIGS.  13 A— 13 B) defining a damper blade open position and a second raised rim or stop  34   b  spaced from the first stop  34   a  defining a damper blade closed position. A second or lower damper blade  38  is disposed beneath first rotatable damper blade  28 , and also includes stub shafts  40  and circular bearing retainers  42  with stops  42   a ,  42   b  (FIGS. 14 a ,  14   b ) constructed and mounted in openings  44  identically as described above with respect to bearing retainer  34 . As is well understood, first and second damper blades  28 ,  38  are designed to rotate between an open or horizontally disposed position (FIGS. 4 and 5) so as to permit air flow through a particular sector of duct work, and a closed or vertically oriented position (FIGS. 6 and 7) so as to block air flow in a particular sector of the duct work. 
     As seen in FIGS. 3-8, a first or upper lever arm  46  having a circular hub  47  with a spherical protrusion  47   a  and a fish-tail shaped portion  47   b  integral therewith is friction fitted via a depending skirt  47   c  (FIG. 8) on the outer end  30   a  of stub shaft  30  for rotation therewith. The hub  47  includes an eccentric finger  47   d  for a purpose to be appreciated hereafter. Lever arm  46  is provided with a pair of spaced apart stop surfaces  48 ,  50 . Stop surface  48  (FIGS. 13A,  13 B) is notched into the bottom of hub  47  and is engageable with the first stop  34   a  on bearing retainer  34  lying beneath lever arm  46 , and corresponding to the fully open position of damper blades  28 ,  38  (FIG.  5 ). The other stop surface  50  extends outwardly from the periphery of hub  47  and is engageable with an adjustable stop post  52  (FIG. 6) extending inwardly from a face plate or motor plate  80  corresponding to the fully closed position of damper blades  28 ,  38  (FIG.  7 ). Stop post  52  is adjustable by removing screw  54  (FIG. 15) threaded into stop post  52 , and moving the stop post  52  along a slot  56  (FIGS. 4,  6 ) formed in motor plate  80  so as to change the closed position as desired. Lever arm  62  has a similar notch  62   a  engageable with stops  42   a  to define the open position (FIG. 14A) An elongated tension member in the form of a link  60  has an upper end formed with a first clearance hole  60   a , the circular wall of which is snap fitted over a first pivot post  59  (FIG. 4) on lever arm  46 . A lower end of link  60  has a second clearance hole  60   b , the circular wall of which is snap fitted over a second pivot post  61  (FIG. 6) of a second or lower lever arm  62  mounted on rotatable stub shaft  40  of lower damper blade  38  by a friction fit. Lever arm  62  is constructed identical to lever arm  46  and enables a modular design in which lever arms may be freely substituted and added according to the damper blades desired, there being one lever arm for each damper blade. Elements  63   a ,  63   b  and  63   d  correspond to elements  47   a ,  47   b  and  47   d , respectively. Link  60  and lower lever arm  62  function to transmit motion from upper damper components to lower damper components so that upper damper blade  28  and lower damper blade  38  will move in unison. In the preferred embodiment, the link  60  is typically a rigid element fabricated from metal or plastic but the invention also contemplates a non-rigid link as will be appreciated hereafter. 
     A torsion spring  64  surrounds stub shaft  40  between sidewall  20  and lever arm  62 , and is nested beneath and within the finger  63   d  of lever arm  62 . One end  66  of spring  64  is held against stop  42   a  and a second end  67  bears against portion  63   b  beneath the finger  63   d . (FIGS. 14A and 14B) Spring  64  is normally disposed in a condition which acts to rotate shafts  30 ,  40 , lever arms  46 ,  62  and damper blades  28 ,  38  in a clockwise rotation to the fully opened position with stop surface  48  contacting stop  34   a . Lever arm  62  has similar notch  62   a  engageable with stops  42   a  to define the open position (FIG.  14 A). In the twin damper blade design, torsion spring  64  is shown positioned around the lower stub shaft  40 . In the non-rigid link embodiment, the spring force acting on the lower lever arm  62  maintains a tensile load on the non-rigid link under all operating conditions. However, it should be understood that the torsion spring  64  may be installed around the upper stub shaft  30  for a single damper blade (as shown in FIG. 17) or around the lower stub shaft  40 . 
     An additional feature of the invention shown in FIGS. 9,  12 ,  12   a  and  12   b  resides in a pair of trigger springs  68 ,  69  integrally formed on the bottom of the lever arms  46 ,  62 . The purpose of the trigger spring  68 ,  69  is to eliminate free play between the damper blades  28 ,  38  caused by the clearance holes  60   a ,  60   b  in the link  60  and other dimensional variations on the elements of the control. The force applied by the trigger springs  68 ,  69  works opposite to the torsion spring  64  located on one of the lever arms  46 ,  62 . The engagement of the closed stop of  42   b  by the lever arm  62  limits the travel of the torsion spring  64 . By adding the trigger springs  68 ,  69 , each lever arm  46 ,  62  will rotate until it contacts one side of the clearance hole  60   a ,  60   b  in the link  60 . The torque produced by the torsion spring  64  is sufficient to overcome the combined torque of the integral springs  68 ,  69 . This allows the damper blades  28 ,  38  to be held in open position while eliminating the free play. 
     A flexible, reinforced belt or band  70  has a lug  70   a  (FIG. 10) at one end dropped into a retention slot  71  formed in one side of the fish-tailed portion  47   b  of lever arm  46 , and a medial portion  70   b  extends about a peripheral surface  72  thereof. Another end  70   c  of band  70  is snapped into a retention slot  73  formed in take-up spool  74  rotatably disposed in an optional spool bearing  74   a  mounted in sidewall  20 . Spool  74  is drivingly engageable with a shaft  75  (FIG. 9) having a flat  75   b  (FIG. 10) extending from a bearing  75   a  of a gear train  76  and an electric motor  78 , both of which are mounted by fasteners  81  on the outside of motor plate  80  which in turn is secured to sidewall  20  by fasteners  82 . A loose fit between the shaft  75  and the spool  74  compensates for misalignment of the parts during assembly. Motor  78  is preferably a 24 volt A/C synchronous hysteresis motor which can be stalled indefinitely without overheating so as to maintain damper blades  28 ,  38  in their closed position as long as desired. As seen in FIGS. 1 and 2, gear train  76  and motor  78  are protected by an enclosure  83  which is removably secured to motor plate  80  by suitable clips  84  engageable in horizontal slots  86  formed in motor plate  80 . As will be appreciated hereafter, motor  78 , when selectively actuated, acts to rotate lever arms  46 ,  62  shafts  30 ,  40  and damper blades  28 ,  38  to the closed position against the force of spring  64 . 
     Alternatively as shown in FIG. 16, the shaft  75  has a polygonal periphery  75   b ′ for driving the spool  74 ′ and a ball-type head  74   c  freely rotatable in a socket  74   d  fixed in the spool bearing  74   a ′. This version allows for a larger misalignment between cover plate  80 ′ and sidewall  20 ′ to be compensated for. 
     With the heating and cooling system in operation, motor  78  responds to a control arrangement which sends a signal corresponding to the thermostat in a specific zone of the system. Damper blade assembly  10  is designed so that movement of damper blades  28 ,  38  by the spring force to their open position (FIGS.  4  and  5 ), creates slack in band  70  thereby preventing damaging force from being transferred to the motor  78  and its relatively fragile gear train  76 . When motor  78  is energized as dictated by the control arrangement, motor  78  and gear train  76  will rotate spool  74  such that band  70  will be wound thereon, and will transfer a pulling force which overcomes spring  64  to rotate lever arms  46 ,  62 , shafts  30 ,  40  and damper blades  28 ,  38  to their closed position (FIGS. 6 and 7) at which stop surface  50  engages stop post  52 . It should also be seen that the spring  64  is engaged with the underside of hub  47  of lever arm  62  as the damper blades  28 ,  38  move to a closed position. As long as motor  78  continues to be energized, damper blades  28 ,  38  remain closed. 
     When motor  78  is de-energized, the force of spring  64  will rotate the lever arms  46 ,  62  shafts  30 ,  40  and damper blades  28 ,  38 , spool  74 , motor  78  and gear train  76 , which move together until stop surface  48  re-engages stop  34   a . In a damper design without over-stress protection as provided by the present invention, gear train  76  and motor  78  would be subjected to a sudden stop, inflicting almost certain damage to these drive elements. Because of spool  74  and flexible band  70  which begins to unwind upon engagement between stop surface  48  and stop  34   a , motor  78  and gear train  76  continue to rotate by their own inertia and enable a gradual braking or slow-down of motor  78  and gear train  76  due to internal friction to prevent damage thereto. Spool  74  and flexible band  70  thus act as a force translation arrangement in ensuring the positive opening and closing of damper blades  28 ,  38  without harm to the driving mechanism. 
     It should be appreciated that the present invention provides an improved damper drive mechanism which spares damage to driving motor  78  and gear train  76  through the use of a wind-up spool and band over-travel arrangement  74 ,  70  which allows motor  78  and gear train  76  to slowly decelerate. By employing this arrangement, damper blade assembly  10  is simplified by reducing the number of components, and enabling the assembly to use non-precision parts, both of which contribute to a lower production cost. 
     It should be further appreciated that the snap feature which connects the link  60  to the lever arms  46 ,  62  spaces the link  60  at a distance from the motor plate  80  so that no rubbing or dragging will occur. The lever arms  46 ,  62  are specifically manufactured to be assembled in proper orientation only when the torsion spring  64  is correctly installed. Spool bearing  74   a  supports spool  74  reducing side loading of motor  78  and helps improve the life of motor bearing  75   a . In addition, the integral trigger springs  68 ,  69  eliminate wobble or rattle of the damper blades  28 ,  38 . Owing to their modular design, the lever arms  46 ,  62  are both provided with retention slots  71  on the same side thereof so they can interchangeably connect to band  70 . In addition, each of the lever arms  46 ,  62  is formed with the spherical protrusion  47   a  which provides a single low friction point engageable against motor plate  80 . 
     FIG. 17 illustrates a rotatable damper assembly  10 ′ for a single damper blade  28 ′ as described above. In this version, there is no need for counterparts of the lower lever arm  62  and the link  60 . However, the torsion spring  64 ′ is nested in the lever arm  46 ′ and surrounds the stub shaft  30 ′. The band  70 ′ and spool  74 ′ are identical to those elements previously described. 
     FIGS. 18-20 show an alternative embodiment of the invention, wherein the elongated rigid link  60  is replaced by a non-rigid, flexible belt  88 . In this version, the fish-tail shaped portion  47   b ′ of upper lever arm  46  as well as lower lever arm  62 ′ are each formed with a pair of belt retention slots  71 ′,  90 . As best seen in FIG. 20, each pair of slots  71 ′ is vertically offset from the pair of slots  90  to prevent the band  70 ′ from interfering with belt  88 . As previously described, band  70 ′ runs between spool  74 ′ and retention slot  71 ′ on upper lever arm  46 ′. Belt  88  runs between slot  90  on upper lever arm  46 ′ and slot  71 ′ on lower lever arm  62 ′. As the motor  78  wraps the band  70 ′ around the spool  74 ′, the upper lever arm  46 ′ rotates. Since the turning arc is identical for both lever arms  46 ′,  62 ′, the length of belt  88  therebetween remains constant. This keeps the angular velocity and position of both lever arms constant. By placing the torsion spring  64 ′ on the lever arm  62 ′ farthest from the motor  78 , and disposing the open stop  48 ′ on the lever arm  46 ′ closest to the motor  78 , the connecting member is always in tension. This allows a flexible material like the belt  88  to be used in lieu of the rigid link  60  and eliminates all free play (i.e. rattle) from the assembly. 
     An additional advantage of this concept is the maximization of the mechanical advantage. This is accomplished by an increase in the moment arm as measured from the center of rotation to the location of applied force. The radiused lever arm keeps this distance at a maximum throughout the full range of motion. 
     While the invention has been described with reference to a preferred embodiment, those skilled in the art will appreciate that certain substitutions, alterations and omissions may be made without departing from the spirit thereof. For example, although the preferred embodiment of the invention described herein shows flat damper construction, it should be understood that the invention can also be utilized with dampers having circular cross section and particularly those having a large diameter. Accordingly, the foregoing description is meant to be exemplary only, and should not be deemed limitative on the scope of the invention set forth with following claims.