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REFERENCE TO CO-PENDING APPLICATIONS 
     This is a divisional of application Ser. No. 09/361,770, filed on Jul. 27, 1999, now U.S. Pat. No. 6,408,925 which is a non-provisional of provisional application Serial No. 60/094,728, filed Jul. 30, 1998. Priority of the prior applications is claimed pursuant to 35 U.S.C. §120. 
    
    
     BACKGROUND OF THE INVENTION 
     This invention relates to torsion spring counter balancing mechanisms for compensating the weight of roll-up doors and a method and structure for accommodating coil torsion spring growth as the door moves up and down between its open and closed positions. 
     Counterbalancing mechanisms of overhead garage doors utilize coil springs that are placed under a rotational or torsion force to apply a lifting force to the door. The springs are concentrically positioned about a shaft rotatably mounted on fixed supports. The shaft carries hubs accommodating cables. The cables arc attached to the door so that when the hubs are rotated, a lifting force will be applied to the door. The lifting force is transmitted to the hubs via the shaft by the torsion springs. The spring must be twisted to load the spring or place the spring under torsion force. Heretofore, long rods have been used to turn the collar attached to the spring to load the spring. This usually requires two men. A limited amount of force can be applied to the spring since twisting the collar is a manual operation. The procedure requires a considerable amount of time and can be dangerous as the spring is loaded with considerable force. A power tool used to apply torsion forces to the counterbalancing spring of a roll-up door is disclosed by E. Dorma in U.S. Pat. No. 3,979,977. One embodiment of this power tool has a power transmission operated with a portable externally located electric motor. Worm gear power transmission units have been incorporated in door counterbalancing mechanisms. Examples of this type of power transmission unit to wind or twist torsion springs are disclosed by L. C. Votroubek and D. H. Nelson in U.S. Pat. No. 3,921,761. Votroubek and Nelson recognize the danger involved in winding and unwinding a garage door torsion spring and attempt to address this problem. Votroubek utilized a tool with a self-locking worm drive gear and worm wheel which can be put into place about the torsion shaft to effect a gripping of an end collar for connecting the spring to the torsion shaft. After the collar is gripped, the end collar is released from the shaft for movement along the rotation about the torsion shaft. In Votroubek, the tool is mounted on the torsion shaft and blocked against rotation about the torsion shaft in a manner to allow the tool to move axially of the torsion shaft, as the spring is wound, to accommodate the growth of the spring during winding. In a double spring configuration using the Votroubek tool, the springs would be wound and unwound separately with the tool being used to wind the outer-end of each spring. 
     While Votroubek&#39;s tool lessens danger, as compared to the conventional use of a lever bar for winding or unwinding a spring, the spring end is still held by a tool which is separate from the hardware of the mechanism and which must be assembled and disassembled to the counterbalancing mechanism for each winding, unwinding or adjustment of a torsion spring. This tool also must be securely blocked against rotation as a whole about the axis of the torsion rod each time a spring end is to be wound or unwound. Further, during the use of the tool, as in the case of using a lever bar, the door being counterbalanced is placed in a locked position until the winding operation has been completed and the freed end cones or members of the spring are re-secured to the torsion shaft. With the door locked, the setting of the proper spring forces in the torsion spring or springs is done with the use of charts and spring characteristic specifications. When working in this manner, it is difficult to achieve the proper counterbalancing forces, as is true of all the present conventional methods known to applicant, for setting the torsion in a torsion counterbalancing mechanism for a garage door. 
     Conventional torsion springs used in door counterbalance mechanisms have adjacent coils that engage or abut one another when the spring is in its normal unwound resting state. There is no gap between adjacent coils. During the winding process of a torsion coil spring friction forces are generated between adjacent coils of the spring. Coil torsion springs having abutting coils that do not provide for growth and contraction of the spring during the initial winding of the spring and of spring unwinding and winding during raising and lowering of the door. Carper et al in U.S. Pat. No. 5,632,063 uses a sliding cone to anchor an end of the torsion spring to the shaft to allow the spring to elongate and contract as the door opens and closes. This requires a modification of the end cone and rod as the cone must axially move on the rod. Conventional shafts and end cones for the torsional coil spring cannot be used in this door counterbalancing system. 
     It is the object of the present invention to eliminate the dangers of prior art mechanisms relating to torsion spring counterbalancing and to simplify the installation and maintenance with an accompanying savings in time and labor, and to improve the system performance and provide an extended life for the parts of the counterbalance mechanism. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention is an apparatus for applying a torsion force to a spring on a shaft, such as for counterbalancing a roll-up door, wherein a first end of the spring is secured to the shaft. The apparatus comprises a housing that contains a transmission to which is coupled a connector. The connector is con figured to be positioned coaxially over the shaft and connected to a second end of the spring. In one embodiment, the transmission comprises a worm gear meshed with a wheel gear. The connector is coupled to the wheel gear, such that rotation of the worm gear causes a rotation of the connector, and hence a winding of the spring when the second end of the spring is connected to the connector. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a fragmentary elevation view, partly sectioned, of a roll-up door equipped with the counterbalancing apparatus of the invention; 
     FIG. 2 is an enlarged vertical sectional view of a counterbalancing apparatus showing the torsion spring and worm gear unit for applying torque tot he torsion spring; 
     FIG. 3 is an enlarged sectional view taken along the line  3 — 3  of FIG. 2; 
     FIG. 4 is a perspective view of a door counterbalancing apparatus including the non-back drive power transmission for twisting the torsion springs 
     FIG. 5 is a sectional view similar to FIG. 2 showing the spring wound to apply torsion force to the counterbalancing shaft; 
     FIG. 6 is a sectional view taken along line  6 — 6  of FIG. 5; 
     FIG. 7 is a sectional view similar to FIG. 2 showing a modification of the spring stretching assembly used to elongate the spring of the counterbalancing apparatus; 
     FIG. 8 is an enlarged sectional view taken along the line  8 — 8  of FIG. 7; 
     FIG. 9 is a front view of a worm gear assembly connected to a spring of the counterbalancing assembly of FIG. 2; 
     FIG. 10 is a sectional view taken along line  10 — 10  of FIG. 9; 
     FIG. 11 is a sectional view taken along line  11 — 11  of FIG. 10; 
     FIG. 12 is a foreshortened front view of a modification of the roll-up door balancing apparatus of the invention; 
     FIG. 13 is a foreshortened sectional view taken along line  13 — 13  of FIG. 12; 
     FIG. 14 is a foreshortened view similar to FIG. 12 showing the spring in the stretched position; and 
     FIG. 15 is a foreshortened view similar to FIG. 12 showing, the spring wound to apply torsion force to the counterbalancing shaft. 
    
    
     DETAILED DESCRIPTION 
     Referring to the drawings, there is shown in FIG. 1 an overhead roll-up door  20  in the closed position movably mounted on a structure  21 , as a garage, warehouse or the like. Conventional tracks  22  and  23  having upright sections and generally horizontal sections are secured to the structure to movably support the door  20 . A plurality of rollers  24  connected to separate portions of door  20  support the door on the tracks  22  and  23 . The overhead door  20  is usually made of metal, plastic or wood panels and has considerable weight. Counterbalance mechanisms, indicated generally at  25  and  26 , are used to facilitate opening the door  20  and return or slow closing the door. 
     Counterbalance mechanism  25  and  26  are located above the top of the door  20  and has a generally transverse shaft  27 . Opposite end portions of shaft  27  are rotatably supported on support blocks  28  and  29 . A plurality of fasteners  32  secure the blocks  28  and  29  to structure  21  located adjacent the top of door  20 . In some installations, the shaft  27  is rotatably supported on the remote ends of the tracks  22  and  23 . A first drum  33  carrying a cable  36  is secured to the left end of shaft  27 . The lower end of cable  36  is connected with a suitable fastener (not shown) to the bottom of door  20 . In a similar manner, a second drum  34  is fixed to the right end of shaft  27 . A cable  37  wrapped around drum  34  extends downwardly and is attached to the lower end of door  20 . 
     Shaft  27  is subjected to rotational or torsion forces by a pair of coils or helical torsion springs  38  and  42 . One end of spring  38  is secured to an anchor  39  attached to shaft  27 . The opposite end of spring  38  is operatively connected to a non-back drive power transmission unit  40 . Unit  40  is attached to a bracket  41  mounted on structure  21 . Unit  40  can be secured directly to support block  28  to anchor unit  40  on structure  21 . 
     The second counterbalancing mechanism  26  has a second torsion spring  42  located over shaft  27  and secured to shaft  27  with an anchor or plug  43 . The free end of spring  42  is attached to a transmission unit  53 . The counterbalancing mechanisms  25  and  26  have the same structures and operate to apply torsion on springs  38  and  42 , thereby subjecting the shaft to torque the counterbalance of the weight of door  20 . The following description is directed to counterbalancing mechanism  26 . In some installations a single torsion spring and non-back drive power transmission unit is used to apply tension bores to shaft  27  to wind spring  42  and adjust the tension of spring  38 . 
     When the door  20  is in its closed position, springs  38  and  42  are fully energized by the twisting action of shaft  27 . The shaft  27  rotates as door  20  moves to its closed position, thereby subjecting springs  38  and  42  to twisting forces which store sufficient energy to counterbalance a substantial portion of the weight of door  20 . Springs  38  and  42  have sufficient energy so that a small amount of lifting force applied to door  20  will open the door. Springs  38  and  42  must be subjected to torsion forces when the door is open so that the springs will hold the door in the open position. 
     Roll-up door counterbalancing mechanism  26  operates to apply torque or torsion force to a shaft  27  connected to drums and cables to counterbalance a roll-up door  20 . FIG. 1 shows the shaft and drums accommodating cables connected to the bottom of a roll-up door. A first end cone or plug  43  secured to shaft  27  with set screws  44  is threaded into an end  46  of torsion spring  42 , as shown in FIG. 2. A second end cone or plug  47  is threaded into end  48  of spring  42 . The spring  42  and end cones  43  and  47  are conventional structures. The adjacent coils of spring  42  normally engage each other as shown in FIG.  1 . 
     Referring to FIG. 2, an elongated tubular member  49  surrounding shaft  27  is located within spring  42 . Member  49  has an end  50  that abuts against plug  43 . The opposite end  51  of member  49  stretches or longitudinally elongates spring  42  about 2½ inches (i.e., the length that spring  42  grows when wound). Spring  42  increases in length by the diameter of spring wire for every turn, 360°, of the spring. Adjacent coils of the spring are spaced from each other, as shown in FIG. 2, by the tubular member  49  which pre-stretches the spring. 
     As further shown in FIG. 2, a transmission unit  53  driven with a conventional electric motor drill, as shown in  143  in U.S. Pat. No. 3,979,977, turns end plug  47  to wind spring  42 . Transmission unit  53  retains spring  42  in the wound position as it does not have back or reverse drive. Transmission unit  53  is also used to adjust the tension of spring  42 . Transmission unit  53  has a gear  54  and a worm  56 . Bolts  57  secured gear  54  to plate  52 . Worm  56  has opposite ends rotatably mounted on a housing  58 . Bolts  59  secure housing  58  to a bracket  61  or similar fixed support. The transmission unit  53  can be planetary or epicyclic train of gears that does not have back drive. A worm gear box having planetary gears, shown in FIGS. 9,  10 , and  11  can be used to wind spring  42 . 
     In use an electric drill or wrench is used to turn worm  56  to rotate gear  54  about 6½ and 7½ turns to wind up spring  42 . When spring  42  is would adjacent coils are in close relationship as shown in FIGS. 5 and 6. Spring  42  is not bound when it is fully wound up. Transmission unit  53 , shown as a worm gear box, retains spring  42  in its wound position. 
     A modification of the roll-up door counter balancing assembly  100 , shown in FIGS. 7 and 8, is located around horizontal shaft  101 . Shaft  101  is a door lift shaft similar to shaft  27  shown in FIG. 1. A power transmission unit  102 , such as a worm gear box, telescopes over shaft  101  and is secured to a fixed support with a bracket  105 . Gear box  102  has a power input coupling  103  adapted to accommodate a socket or tool connected to a reversible electric motor, air motor, fluid motor or power means for rotating the input coupling  103  thereby operating gear box  102  to turn output shaft  104 . Gear box  102  has the same operating gears as transmission unit  53  shown in FIG.  4 . Other gear boxes, as shown in U.S. Pat. Nos. 4,882,806 and 4,981,165 can be used to turn coil spring  108  to apply torsion force to shaft  101 . 
     An input end cone  106  secured to shaft  104  with set screws  107  is threaded into the first end  109  of spring  108 . The opposite end  110  of spring  108  is threaded into an end cone  111 . Set screws  112  anchor cone  111  to shaft  101 . Shaft  101  extends axially through spring  108  and gearbox  102 . 
     Spring  108  is a conventional closed metal coil spring having turns of uniform diameter. Adjacent turns normally contact each other. A spring stretching assembly  113  located about spring  108  longitudinally elongates spring  108  to allow for spring growth as it is turned or twisted to apply a torsion force to shaft  101 . Spring stretching assembly  113  has a first tubular member  114  engageable with end cone  106 . Member  116  telescopes into member  114 . Members  114  and  116  have cooperating threads  117  that connect the members and allow longitudinal adjustment of the length of the spring stretching assembly  113 . Tubular member  114  is rotated relative to tubular member  116  to elongate or stretch spring  108 , as shown in FIG.  7 . Set screws  112  are released to allow end cone  111  to slide on shaft  101 . When spring  108  has been elongated, set screws  112  are turned down to anchor end cone  111  on shaft  101  and hold spring  108  in the stretched position. Spring stretching assembly  113  surrounds the entire spring  108  and provide a protective shield in the event of failure of part or parts of the spring. When spring  108  is wound or twisted the axial growth of the spring is compensated by the stretched spring. The gear box  102  functions as a power transmission that operates to twist spring  108  and hold the spring in its twisted position to maintain torsion force on shaft  101 . Gear box  102  is also operated to adjust the tension of torsion force of spring  108 . 
     A modification of the power transmission unit shown as a worm gear box  200 , is represented in FIGS. 9,  10 , and  11 . Gear box  200  operates to wind spring  42  to apply torsion forces on shaft  27 . Gear box  200  fits over shaft  27  and replaces transmission unit  53  (shown in FIG.  4 ). A bracket  201 , such as a bearing plate, secured to the door frame or header is connected to gear box  200  to support and prevent rotation of gear box  200 . An end cone  202  threaded into spring end  48  is connected to the output drive of gear box  200  with bolts  203 . 
     As shown in FIG. 10, gear box  200  has a housing  204  surrounding a chamber  206  closed with an end plate  207 . A worm gear  208  joined to a sleeve  209  is located within chamber  206 . Sleeve  209  is rotatably mounted on shaft  27 . A worm  211  rotatably mounted on housing  204  has teeth that engage the teeth of gear  208 . As seen in FIG. 9, worm  211  has an external hexagonal end  212  for accommodating a socket of a power tool, such as an electric hand drill, used to rotate worm  211 . The rotating worm  211  turns gear  208  and sleeve  209  about the axis of sleeve  209 . Returning to FIGS. 10 and 11, a planetary gear assembly comprising a spur gear  213  secured to sleeve  209  engages planet gears  214 ,  215  and  216 . A fixed ring gear  210  engages the teeth of planet gears  214 ,  215  and  216 . Gear  217  is secured to housing  204 . Planet gears  214 ,  215  and  216  are rotatably mounted on cylindrical bosses  217 ,  218  and  219  joined to a circular output drive disk or plate  221 . Plate  221  has a central hole  222  accommodating sleeve  209 . Bolts  203  connect end cone  202  to plate  221 . Plate  221  is retained in assembled relation with sleeve  209  and gears  214 , 215  and  216  with a bearing  223 . A snap ring  224  cooperating with sleeve  209  hold bearing  223  adjacent plate  221 . 
     In use, sleeve  49  holds spring  42  in the elongated or stretched position. Adjacent coils of the spring  42  are separated from each other to compensate for spring growth during turning or twisting, of spring  49  by operation of gear box  200 . A hand power tool, such as an electric drill or air operated motor equipped with a socket, is used to turn worm  211 . The socket fits on hexagonal end  212  of worm  211  whereby torque can be transferred from the power tool to worm  211 . The planetary gear assembly functions as a speed reducer that applies considerable twisting or torsional force to end cone  202  which winds spring  42 . Relatively large coil springs can be wound with gear box  200  equipped with the planetary gear assembly. Gear box  200  can be used in the door counterbalancing mechanisms  26 ,  100  and  300  herein described. 
     Referring to FIGS. 12 to  15  there is shown another modification of the roll-up door counterbalancing assembly  300  of the invention for applying torsional force on shaft  301 . Shaft  301  corresponds to shaft  27  connected to cable drums  33  and  34 . Assembly  300  has a coil spring  302  having adjacent coils contacting each other. Spring  302  is made from metal rod stock which is helically wound into an elongated cylindrical coil spring. An end cone  303  turned into the distal end of spring  302  is anchored to shaft  301  with set screws  304 . A second end cone  306  is turned into the proximal end of spring  302 . The side of spring  302  is marked with color spots  307 , such as white paint, used to provide a visual image of the number of turns or twists of the spring as shown in FIG.  15 . 
     A power transmission unit, shown as a worm gear box  308 , mounted on shaft  301  is operable to elongate spring  302 , twist spring  302 , and hold spring  302  in its twisted or torsion position thereby subjecting shaft  301  to a torsion force which counterbalances the roll-up door. Gear box  308  has a housing  309  accommodating end plates  311  and  312 . A bracket  313  attached to end plate  313  with bolts  314  secures gear box  308  to a support, such as a door frame or header. Other structures can be used to attach gear box  308  to a fixed support. End plates  311  and  312  support central bearings  315  that rotatably engage an elongated sleeve  316 . Sleeve  316  extends through gear box  308  and into spring,  302 . The outer section of sleeve  316  has threads  317 . A nut or threaded block  318  cooperatively engages threads  317  whereby upon rotation of sleeve  316  block  318  moves along sleeve  316  to expand or stretch spring  302  as shown in FIG.  14 . Bolts  319  connect block  318  to end cone  306 . An annular stop collar  321  surround sleeve  316  to limit axial movement of block  318 . Set screws  322  anchor collar  321  to sleeve  316  and allow the position of collar  321  to be adjusted relative to sleeve  316 . This adjustment is used to control the amount of stretch of spring  302 . 
     A worm gear  323  within gear box  308  is driveably connected to sleeve  316  with set screws  324 . Splines and keys can be used to connect gear  323  to sleeve  316 . A worm  326  rotatably mounted on housing  309  has threads that cooperate with the threads of gear  323 . Worm  326  has an exterior hexagonal end  327  adapted to receive a socket on a power tool or socket wrench used to operate the worm gear box. 
     Rotation of worm  326  with a power tool, such as a portable electric drill, turns gear  323  and sleeve  316 . As shown in FIG. 12, gear box  308  is attached to a fixed part of the door structure and spring  302  is placed on shaft  301  in its normal closed position. End cones  303  and  306  have been threaded into opposite ends of springs  302  before they are assembled about shaft  301 . Shaft  301  is moved through sleeve  316 . Opposite ends of the shaft  301  are attached to drums, such as drums  33  and  34  accommodating cables which are attached to bottom portions of the roll-up door. The block  318  is turned to move it toward the end of the threaded section  317   b  of sleeve  316 , as shown in FIGS. 12 and 13. End cone  306  is attached with bolts  319  to block  318 . Spring  302  in its normal non-tension condition extends along shaft  301 . End cone  303  is anchored to shaft  301  with set screws  304  to fix the position of end cone  303  on shaft  301 . Stop collar  321  is positioned a selected distance from block  318  and anchored to sleeve  316  with set screws  322 . Spring  302  increases in length by a distance equal to the diameter of the spring coil or wire for each 360 degree turn of the spring. The spacing between block  318  and stop collar is determined by the diameter of the coil and the desired number of turns of the spring. 
     A power tool, such as a portable electric drill, connected to a socket is used to rotate worm  326  which turns gear  323  and sleeve  316 . Block  318  during rotation of sleeve  316  does not turn with sleeve  316  as it is prevented from turning by the resistance of the spring to twist. Block  318  moves toward stop collar  321  until it contacts collar  321 . Further movement of block  318  on sleeve  316  is terminated when block  318  contacts collar  321 . Spring  302 , as shown in FIG. 14, is expanded or stretched. Adjacent spring coils are spaced from each other to provide spaces for growth of the spring as it is twisted. Continual rotation of sleeve  316  by operation of gear box  308  winds spring  302  around shaft  301  which applies torsion force to shaft  301 . As shown in FIG. 15, the coils of spring  302  contact each other when the spring is wound up. The colored spots  307  are helically located around spring  302  and represent the number of 360 degree twists of spring  302 . Gear box  308  retains spring  302  in the wound position as worm gear  323  and worm  326  must be turned to operate gear box  308 . Gear box  308  can be driven in a reverse direction to unwind spring  302  to relieve torsion force on shaft  301  to allow the cables and drums can be adjusted, repaired or replaced when spring torsion has been released. Gear box  308  is also operated to adjust the tension of spring  302 . 
     While several preferred embodiments of the roll-up door counterbalancing assembly has been disclosed, it is to be understood that one skilled in the art to which the invention pertains may make changes in the parts and arrangement of the parts and materials without departing from the invention.

Summary:
An apparatus for winding a spring on a shaft, such as for counterbalancing a roll-up door, includes a housing that carries a transmission which is positionable over the shaft. The transmission is configured to be coupled via a connector to one end of the spring, while the other end of the spring is fixed to the shaft. Rotation of the transmission results in a turning of the connector and a winding and/or elongation of the spring.