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BACKGROUND OF THE INVENTION 
     In general, the present invention relates to a door tensioning device or tensioner. Such devices are commonly used to maintain and adjust the tension of a spring used to counterbalance the weight of an upwardly opening door. One type of upward opening door is a rolling door, which uses a curtain made of flexible material or a plurality of panels that is coiled up around itself as the door is opened. One end of the curtain is attached to steel wheels that are welded or otherwise affixed to a support axle. This support axle, often referred to as a live axle because it rotates as the door is opened, is supported and journaled at its ends by brackets attached to the header or jambs of the door. To provide a counterbalancing force for the weight of the door, a spring is attached at one end to one or more of the wheels and at its other end to a tensioning assembly. In the past, the door&#39;s support bracket would act as the tensioning assembly. In this instance, the door typically would arrive at the place of installation in its open position i.e., the curtain being completely coiled around the axle. Once the curtain and axle were mounted on the support brackets, the free end of the spring would be attached to one support bracket and the door would be rotated through one or more rotations to charge the spring. At this point, a bottom bar of the door would be inserted into vertical guides to prevent the door from rotating. Optimally, the counterbalance spring would have sufficient tension such that the door would fully close and only a small amount of force would be necessary to raise the door from the closed position. If the door is not in the optimal position, the installer would adjust the spring tension by removing the bottom bar from the guides and repositioning the end of the spring and the support bracket. After which, the installer would reassemble these components and repeat the pre-tensioning procedure to charge the spring. 
     To avoid repositioning of the spring on the bracket, alternative tensioning assemblies have been developed. In one such assembly, an axle tube is provided with a spring attaching plate and a tensioning plate. The tube is fitted over the axle such that these plates may move independently of the axle. The plates are located on either side of the tensioning bracket and an end of the counterbalance spring passes through the spring attaching plate to eventually attach to the bracket. With the spring so attached, the axle tube may be rotated to increase or decrease tension on the spring. All of the plates are provided with a plurality of holes located radially equidistant from the center of the axle. To maintain the tension on the spring, a pin is passed through the holes in each plate to fix the plates relative to each other and the bracket preventing rotation of the axle tube. Adjustment may be made by removing the pin and rotating the axle tube toward the next appropriate hole. 
     As will be appreciated, this tensioning assembly may be difficult to use. The user must rotate the axle tube with a suitable tool in one hand to align the holes in the spring attaching plate, tensioning bracket, and tension plate, and with the other hand attempt to insert a pin through these holes while maintaining the alignment. As a result, once the installer has the holes aligned, he must maintain the exact tension on the axle tube to preclude relative rotation while inserting the pin. 
     A further disadvantage of this system is that the slidable pin may become disengaged by efforts to tamper with the door or other accidental contact with the pin. Essentially, the pin is not axially held, but for the frictional forces created by the plates and bracket. Therefore, a person could possibly remove the pin without tools or extensive effort causing unintentional release of the spring&#39;s tension. It will be appreciated that such a release could make it difficult or impossible to operate the door and, in more dire instances, cause serious injury. 
     SUMMARY OF THE INVENTION 
     It is, therefore, an aspect of the present invention to provide a door tensioner that automatically prevents rotation of the axle tube as the installer rotates the tube to a desired position. A further aspect of the present invention is to provide a tensioning assembly that includes a gear and spring-loaded pawl to hold the axle tube at the desired position. 
     It is another aspect of the present invention to provide a locking assembly that locks either of the gear or pawl to the support bracket, where the locking assembly cannot be removed without extensive effort or the aid of tools. It is a further aspect of the present invention to provide a fastener supported on the pawl that may be driven into the support bracket to lock the tensioner in place. 
     The present invention generally provides a tensioner in a rolling door system, the rolling door system having a door attached to at least one wheel supported on an axle, the axle being rotatably supported on a pair of support brackets, the support brackets each defining a bore through which the axle is received and a counterbalance assembly that generates a counterbalancing force, the counterbalance assembly having a first end attached to the tensioner and a second end attached to the axle, the tensioner including a sleeve that fits over an end of the axle and is rotatably supported in the bore of the support bracket; a spring holder and a gear wheel attached to the sleeve, wherein the second end of the counterbalance assembly attaches to the spring holder; the gear having a plurality of teeth defining a plurality of notches therebetween; a pawl movable between a disengaged position and an engaged position, the pawl retaining the gear in a position when in the engaged position; the pawl being biased toward the engaged position, whereby the pawl automatically engages the gear to retain the counterbalancing force generated by the counterbalance assembly to balance the weight of the door. 
     The present invention further provides a rolling door including an axle supported by end brackets, a plurality of drum wheels mounted on the axle, a multi-section door adapted to be selectively rolled and unrolled about the drum wheels, a gear wheel mounted on the axle proximate to one of the end brackets, a spring retainer associated with the gear wheel, a torsion spring having a first end operatively attached to the multi-section door and a second end attached to the spring retainer, a pivotally mounted pawl selectively engaging the gear wheel to maintain a selected counterbalance force setting and disengaging the gear wheel to permit adjustment of the counterbalance force setting, and a locking assembly carried on the pawl selectively engageable with the support bracket to lock the pawl in an engaged position. 
     A rolling door including, an axle supported by end brackets, a plurality of drum wheels mounted on the axle, a multi-section door adapted to be selectively rolled and unrolled about the drum wheels, a sleeve rotatable on the axle, a gear wheel attached to the sleeve, a spring retainer associated with the gear wheel, a torsion spring having a first end attached to the multi-section door and a second end attached to the spring retainer, a pivotally mounted pawl selectively engaging the gear wheel to maintain a selected counterbalance force setting and disengaging the gear wheel to permit adjustment of the counterbalance force setting, and a locking assembly carried on the pawl selectively engageable with the support bracket to lock the pawl in an engaged position. 
     The present invention further provides a rolling door assembly including an axle supported by end brackets, a plurality of drum wheels mounted on the axle, and a multi-section door adapted to be selectively rolled and unrolled about the drum wheels, a tensioner associated with the axle, a torsion spring having a first end operatively attached to the multi-section door and a second end operatively attached to the tensioner, the tensioner including a gear wheel having a plurality of teeth, the teeth having an undercut stop face, and a pivotally mounted pawl selectively engaging the stop face to maintain a selected counterbalance force setting. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a rear perspective view of a rolling door located within an opening defined in a building and having a counterbalance system operative to provide a balancing force for the weight of the door and a tensioner according to the concepts of the present invention attached to one end of the counterbalance system to adjust and retain the force applied to the door by the counterbalance assembly. 
     FIG. 2 is an enlarged perspective view depicting the support bracket and tensioner to the left of the door as seen in FIG. 1 depicting details of the tensioner including a spring holder and a gear supported on an axle tube on either side of a support bracket, and a pawl pivotally attached to the support bracket, and biased into locking engagement with the gear by a biasing member to prevent rotation of the spring holder; 
     FIG. 3 is a top plan view of the tensioner with the axle removed as seen in FIG. 2 depicting a spacing assembly having a plurality of tabs that provide a clearance for rotation of a spring holder; 
     FIG. 4 is a left side elevational view of the tensioner seen in FIG. 2 depicting the tensioner supported on a support bracket where the tensioner includes a gear supported on a sleeve and a pawl biased into locking engagement with the gear, the engaged position of the pawl, which prevents the gear from rotating, being shown in solid lines with a disengaged position of the pawl, allowing free rotation of the gear, being shown in chain lines; 
     FIG. 5 is a front elevational view of the tensioning assembly seen in FIG. 2 depicting the spatial relationship of the spring holder and gear with the support bracket; and 
     FIG. 6 is an exploded view of the tensioning assembly seen in FIG. 1 depicting the interrelationship of the tensioner components and the support bracket. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     A door tensioner according to the concepts of the present invention is shown in the accompanying figures, and generally referred to by the numeral  50 . The tensioner  50  is used in connection with a door assembly, generally referred to by the numeral  10 , that includes a framework  11  made up of a header  12  and a pair of jambs  13 ,  14 , having vertical guides  16 ,  17 , which receive door D, mounted thereon. This framework  11  defines an opening in which the door D is selectively moved from a closed position depicted in FIG. 1 to an open position (not shown) where the door D is fully retracted and coiled about a plurality of drum wheels  15  located adjacent the header  12  of door D. The drum wheels  15  are attached to an axle  20  rotatably supported adjacent header  12  in a position above the opening. 
     The door D may be constructed of a plurality of panels  21  including a top panel  22  and a bottom panel  23 . A bottom bar  24  may be attached to the bottom panel  23  to protect the bottom panel  23  against impact with a floor or objects interposed between the door D and the floor. The bottom bar  24  may be formed with a ridge handle, or other member (not shown) that is easily grasped to raise and lower the door D. 
     The door D is suitably attached to the drum wheels  15  such that upon opening the door D, the door panels  21  are sequentially coiled around the drum wheels  15  to store the door D in a compact fashion above the opening. To facilitate raising and lowering of the door D, one or more counterbalance assemblies, generally indicated by the numeral  25 , may be employed to offset the weight of the door D. The counterbalance assembly  25  may include a spring  26  constructed of suitable resilient material such as steel, for applying a torsional force to the door D. As shown, spring  26  may be a coil spring located generally coaxially of and surrounding axle  20 . Spring  26  is attached at its first end  32  to a retainer which may be in the form of an aperture  36  in spring holder  33  and at its second end  31  to one of the drum wheels  15  or axle  20 , directly or by clips or fasteners. Alternatively, the ends  31 ,  32  of spring  26 , spring holder  33  or drum wheel  15  may be rotatable about axle  20  such that one end of spring  26  is attached to the axle  20  and the other attached to the drum wheel  15  or spring holder  33  such that tension is applied to the spring  26  by rotating the one end relative to the end attached to the drum wheel  15  or spring holder  33 , as by turning axle  20 . In this way, relative rotation of the ends  31 ,  32  of spring  26  may be used to develop or release the torsional forces imposed by spring  26 . To allow spring holder  33  to rotate relative to the drum wheel  15 , spring holder  33  is supported on a sleeve  34  having a bore sized to fit over the axle  20 . The sleeve  34  may be of greater dimension than axle  20  to accommodate a bearing  38 , such as an oil-impregnated collar, fitted within sleeve  33  to journal axle  20 , thereby reducing wear or friction. 
     The axle  20  and sleeve  34  are supported by a support bracket, generally indicated by the numeral  40 . Support bracket  40  includes a mounting flange  41  suitably attached to the framework  1 , or other supporting structure as by cap screws, and an axle supporting portion  42  projecting rearwardly of the frame  11 . Axle supporting portion  42  has an opening  43 , receiving sleeve  34  and axle  20 . The opening  43  is sized such that sleeve  34  is free to rotate therein. As best shown in FIG. 1, a portion of sleeve  34  may protrude axially outward of support bracket  40  to receive a tool used to rotate sleeve  34 , as described below. Also, axle  20  may extend beyond sleeve  34  and be axially fixed by a pin  39  that abuts the edge of sleeve  34 . To provide an additional surface against which the pin  39  rests, sleeve  34  may be provided with an annular plate or washer (FIG. 1) adjacent the pin  39 . 
     To provide a clearance  44  between the axle supporting portion  42  of bracket assembly  40  and the spring holder  33  as well as any fastener or portion of the spring protruding beyond the spring holder  33  toward bracket  40 , a spacing assembly, generally indicated by the numeral  45 , may be placed between the spring holder  33  and bracket assembly  40 . As shown in FIG. 5, spacing assembly  45  may include a plurality of tabs  46  that extend axially inward from the axle supporting portion  42  of bracket assembly  40 . As shown, tabs  46  may be placed in circumferentially spaced relation around opening  43 . As best shown in FIG. 6, three tabs  46  may be arranged in a triangular pattern to act as a stop for axial movement of the spring holder  33 . It will be appreciated that one or more members may be used to perform the same function, such as a single annular ridge, or multiple members that extend from support portion  42 . The tabs  46  are preferably radially spaced away from opening  43  to provide radial clearance for the sleeve  34  to avoid interference of tabs  6  with the free rotation of sleeve  34 . Tabs  46  may be punched from the axle supporting portion  42  of bracket assembly  40  and constructed to provide minimal contact with spring holder  33 . As best shown in FIGS. 5 and 6, tabs  46  may be provided with rounded ends  47  to reduce any frictional forces that might develop in the event of contact between the tabs  46  and spring holder  33 . Since the sleeve  34  and attached spring holder  33  may be rotated independently of axle  20 , spring holder  33  may be rotated to adjust the counterbalancing force generated by spring  26 . In this respect, spring holder  33  may be rotated with a wrench or rods in a manner known to those of ordinary skill in the art. To further facilitate rotation of the spring holder  33 , a hex plate  49  or other grippable surface may be attached to the sleeve  34 . 
     A tensioner assembly, generally indicated by the numeral  50 , is provided or interrelates with the sleeve  34  and spring holder  33  to adjust and maintain the tension of spring  26 . The tensioner assembly  50  includes a gear wheel  51  supported on sleeve  34  and rotatable therewith. To provide clearance for the free rotation of gear wheel  51  relative to bracket assembly  40 , a suitable spacer  52 , such as a washer, may be located between gear wheel  51  and bracket assembly  40 . Spacer  52  may aid in reducing friction between the bracket assembly  40  and gear wheel  51  and further reduce the likelihood of interference between these two members. 
     Gear wheel  51  includes a plurality of radially projecting teeth  53  that define notches  54  therebetween. Teeth  53  interrelate with a pawl assembly, generally indicated by the numeral  55 , to incrementally lock the position of spring holder  33  against the uncoiling force of spring  26 . While the gear wheel  51  is shown with eight teeth  53 , the number of teeth  53  may be increased or decreased depending on a desired tensioning increment. The tensioning increment, in terms of one revolution of gear  51 , is essentially inversely proportional to the number of teeth  53 . In the embodiment shown, the eight (8) teeth result in a tensioning increment of ⅛ of a revolution. Pawl assembly  55  interacts with the teeth  53  and notches  54  to selectively hold the gear wheel  51  against the uncoiling force of spring  26 . Pawl assembly  55  includes a pawl  56  pivotally mounted to the axle supporting portion  42  of bracket assembly  40 , as by a bolt  57  and nut  57 ′. Pawl  56  may be located on support bracket  40  such that its pivot is offset from a center line of axle  20  and the circumference traced by teeth  53 . In this circumstance, pawl  56  may extend from pivot  57  at an acute angle from a horizontal line passing through the center of the pivot  57 . If pawl  56  is curved, as shown, the angle of pawl  56  would vary with the increasing slope of the interior surface  72  of pawl  56 . In assembling the gear  51  and pawl  56 , suitable spacers  58  such as washers may be used to insure proper axial alignment of the pawl  56  and teeth  53 . The interaction of the pawl  56  with teeth  53  to lock the position of spring holder  33  causes the tensioning increment to act as a lower limit on the amount of adjustment the installer may make in tensioning spring  26 . 
     To automatically lock the tensioning assembly  50 , the pawl  56  may be biased into an engaged position with gear  51 , as shown in solid lines in FIG.  4 . The pawl  56  may be biased by gravity or a biasing assembly, generally indicated by the numeral  60 , which includes a biasing member, such as spring  61 . In the embodiment shown in FIG. 4, spring  61  exerts an upward force on pawl  56  to drive it into an engaged position (solid lines) by means of opposed first and second legs  62 ,  63  extending from a wound vertex  64 . As best shown in FIG. 2, the spring  61  may be axially located by bolt  57 , which forms a pivot for pawl  56 . As best seen in FIGS. 2 and 6, the shank of bolt  57  is sized to fit through wound vertex  64  and into a bore formed in pawl  56 . Bolt  57  may be secured to support bracket  40 , as by the nut  57 ′. Once secured, the head of bolt  57  traps vertex  64  against pawl  56 . The extending legs  62 ,  63  of spring  61  are compressed between a pair of projections  65 ,  66 . Projections  65 ,  66  extend axially outward from pawl  56  and the axle supporting portion  42  of bracket assembly  40 , respectively. Projections  65 ,  66  may be formed on their respective members, fastened thereto, or formed by fasteners, such as caps screws  67 ,  68 . Projections  65 ,  66 , in general, may be of any configuration shape, or size suitable for capturing the ends of biasing member  61 . As shown, cap screws  67 ,  68 , which form projections  65 ,  66 , extend a sufficient distance such that, they may provide fingerholds for manual or tool-assisted actuation of the pawl  56 , as described below. 
     Since the pawl  56  is biased into an engaged position, it will be appreciated that to release the pawl  56 , the installer may squeeze first projection  65  toward second projection  66  to urge the pawl  56  toward a disengaged position, shown in broken lines in FIG. 4, where the pawl has cleared the adjacent tooth  53 . With the pawl  56  disengaged, the gear  51  is free to rotate. With the gear  51  released, the installer may adjust the tension on spring  26  by rotating spring holder  33  in the appropriate direction. Upon reaching the desired tension, the pawl  56  may be released allowing bias assembly  60  to return the pawl  56  to the solid line engaged position. 
     Each tooth  53  of gear  51  is provided with a stop face  70  that engages the pawl  56 . The stop face  70  is disposed such that it interrelates with the pawl  56  in reaching a state of equilibrium, when the pawl  56  is engaged. In addition to manually disengaging pawl  56  by means of the projections  65 ,  66 , rotation of gear  51  in a direction that moves the stop face  70  away from pawl  56 , in this case a clockwise rotation, may be used to periodically displace pawl  56  out of engagement with the passage of each tooth  53 . A run face  71  connects successive stop faces  70  providing a surface along which the pawl  56  rides during rotation of gear wheel  51 . The run face  71  and stop face  70  join each other at a vertex  73 , and, from this point, run face  71  slopes radially outward and away from stop face  70 . Run face  71  reaches a peak  74  corresponding to the radial height of stop face  70 . In this way the interior surface  72  of pawl  56  rides along run surface  71  in a cam-follower fashion. The slope of run face  71  displaces pawl  56  radially outward of its contact position against stop face  70  to remove the pawl  56  from the engaged position and prepare the pawl for the successive locking motion, where the pawl  56 , under the urging of biasing assembly  60 , is driven into the next notch  54 . This locking motion may be characterized by an audible “click”as the pawl  56  is snapped into place, informing the installer that the pawl  56  has attained the engaged position and that the gear wheel  51  has traveled one tensioning increment. 
     In the embodiment shown, to facilitate the cam follower interaction of the gear  51  and pawl  56 , the run face  71  of gear  51  and interior surface  72  of pawl  56  are made nonlinear or arcuate such that pawl  56  extends in an arcuate fashion toward teeth  53 . The profile of interior surface  72  of pawl  56  may generally correspond to the run face  71  to provide smoother interrelation of the pawl  56  and gear wheel  51 . As shown, these surfaces  71 ,  72  may be elongated to gradually move the pawl  56  out of engagement with the stop surface  70  of tooth  53  as the gear wheel  51  is rotated. Relative to the plane S of the stop face  70 , run face  71  may initially extend in a non-linear fashion, which may be exponential, through a varying angle a toward the peak  74  of tooth  53 . Stop face  70  may radially extend inward from peak  74  such that it is disposed generally perpendicular to the pawl  56  upon contact. Alternatively, the stop face  70  may extend inwardly from peak  74  toward a radial line R extending through the vertex  73  to create an acute angle between the adjacent run face  71 . In this fashion, stop face  70  is “undercut”, signifying that stop face  70  is disposed at an acute angle β relative to radial line R. The undercut stop face  70  helps to draw the pawl  56  radially inward as the gear wheel  51  rotates. Further, the angle β of stop face  70  serves to provide positive resistance against unintentional release or outward displacement of pawl which might result from the torsional force of spring  26  acting on gear wheel  51 . To adjust the tension on spring  26 , gear wheel  51  may have a number of teeth  53  that provide separate points of adjustment for the counterbalance assembly  25 . The embodiment depicted has eight teeth  53  allowing the gear wheel  51  or spring holder  33  to be rotated in one-eighth increments of a complete rotation. As will be appreciated, fewer teeth  53  may be used for coarser incrementation and additional teeth  53  may be added to provide finer adjustment of the counterbalancing force. 
     Once suitable counterbalancing force has been achieved in the counterbalance assembly, to prevent tampering which could cause unintentional release of the counterbalancing force, a locking assembly, generally indicated by the numeral  65 , may be used to prevent the spring holder  33  from rotating. To that end, either of the gear wheel  51  or pawl  56  maybe locked in place by locking assembly  65 , such that gear wheel  51  and connected spring holder  33  are not free to rotate. Locking assembly  65  may include a lock member that is not easily removed to guard against a user from pulling the member out by hand or having the member come free when jarred or under the influence of vibration within the structure. Suitable lock members might include a Zip-tie or similar device or a fastener, such as a cap screw  67  may be inserted through pawl  56  and into bracket assembly  40  to prevent the pawl  56  from moving out of the engaged position. In that way, the installer may secure the cap screw  67  into a threaded bore  68  in support bracket  40  or a nut, such that an average person would not be able to accidentally remove the cap screw  67  or otherwise release gear  51 . This helps eliminate accidental release of the counterbalance assembly  25  and discourages tampering with the tensioning assembly  50 . In operation, tensioner  50  automatically retains the position of spring holder  33  and accordingly tension on counterbalance assembly  25  by biasing pawl assembly  55  into locking engagement with gear wheel  51 . The device  50  may be assembled as shown in FIG. 6 with the gear wheel  51  and spring holder  33  located on opposite sides of support bracket  40 . The counterbalance spring  26  of door assembly  10  is attached to the spring holder  33 , as by a nut and bolt. In the embodiment shown, to increase force upon the counterbalance assembly  25 , the user would apply a force to hex plate  49  or sleeve  34  using pliers, a pipe wrench, or rods, which may be inserted through sleeve  34  or other tools known in the art. Once the force of counterbalance assembly  25  is overcome, the gear wheel  51  of tensioner assembly  50  would rotate past pawl assembly  55 . Pawl  56  of pawl assembly  55  would follow the contour of gear wheel  51  in a cam follower-type fashion. As each tooth  53  passes pawl  56 , the pawl  56  “clicks” down to the next gear tooth  53 . Once the user stops applying a tensioning force, the force of the counterbalance assembly  25  would cause the gear wheel  51  to rotate in the opposite direction. Under the force of biasing assembly  60 , pawl  56  continues to follow the contour of the gear wheel  51  until the pawl  56  encounters the stop surface  70  of tooth  53 , at which point the counterbalancing force of the counterbalance assembly  25  is held relative to the support bracket  40  by pawl  56 . To reduce the counterbalancing force within counterbalance assembly  25 , the user would release pawl  56 , as by squeezing cap screws  67 ,  68  together. Once the pawl  56  is released, the user slowly reduces the applied force until the gear wheel  51  of tensioner  50  begins to turn in the direction appropriate to reduce the counterbalancing force. Once sufficiently reduced, the installer would return the pawl  56  to the engaged position, as by simply releasing cap screw  67  to allow the pawl  56  to engage an adjacent notch  54  as urged by biasing assembly  60 . Once the appropriate counterbalancing force is achieved within the counterbalance assembly  25 , the installer may lock tensioner  50  with a locking assembly, such as by driving cap screw  67  into support bracket  40  to lock the pawl  56  in place to prevent tampering with the tensioner  50 . 
     In light of the foregoing, it should be apparent that the invention as described and shown provides a new and useful improvement in the art. It should further be noted that various modifications and substitutions may be made in the present invention without deviating from the spirit thereof. Thus, for an appreciation of the scope of the present invention, reference should be made to the following claims.

Summary:
A rolling door including an axle supported by end brackets, a plurality of drum wheels mounted on the axle, a multi-section door adapted to be selectively rolled and unrolled about the drum wheels, a gear wheel mounted on the axle proximate to one of the end brackets, a spring retainer associated with the gear wheel, a torsion spring having a first end operatively attached to the multi-section door and a second end attached to the spring retainer, a pivotally mounted pawl selectively engaging the gear wheel to maintain a selected counterbalance force setting and disengaging the gear wheel to permit adjustment of the counterbalance force setting, and a locking assembly carried on the pawl selectively engageable with the support bracket to lock the pawl in an engaged position.