REAR MOUNT COUNTERBALANCE SYSTEM FOR SECTIONAL DOORS

Abstract: An overhead door system (210) for moving a sectional door (D') having top, bottom and intermediate hinged panels (221, 222, 223, 224) between a closed vertical position proximate a door frame (212) and an open horizontal position including a substantially vertical track section (251) for engaging a plurality of rollers (237) attached to and spaced from the bottom and intermediate panels, a curved transition track section (253) commencing at the upper extremity of the vertical track section for changing the direction of travel of the plurality of rollers, a first horizontal track section (255) extending from the transition track section for receiving the plurality of rollers to support the door in the open horizontal position, a second horizontal track section (260) for guiding a top panel roller (232) positioned proximate the top (231) of the top panel from the open position to the closed position of the door, and a rear counterbalancing system (280) mounted proximate the ends (264) of the horizontal track sections remote from the door frame and operatively interrelated with the door.

Description: RBAH MOUNT COUNTERBALANCE SYSTEM FOR SECTIONAL DOORS TECHNICAL FIE P The present invention relates generally to a counterbalancing system for sectional doors. More particularly, the present invention relates to a counterbalancing system for sectional doors which move in and out of position relative to a vertical opening. More specifically, the present invention relates to a compact counterbalancing system for use in conjunction with multi-section doors which are movable from a horizontal position to a vertical position in proximity to a door frame, particularly in circumstances where there is minimal clearance between a door frame and the overhead or suspended elements in the area where the door reposes in its storage position. BACKGROUND ART Counterbalancing systems for sectional doors have been employed for many years. Common examples of such sectional doors are the type employed as garage doors in homes, commercial and utility buildings, and similar applications. Counterbalancing systems originally solved the need for providing mechanical assistance in the instance of very large doors for commercial installations and smaller garage doors for residential use, which were normally constructed of heavy, relatively thick wood or metal components. More recently, counterbalancing systems have been increasingly used to permit opening and closing operations by a single person and to facilitate the use of electric motors, preferably of limited size, to power the opening and closing of such doors. Most such counterbalancing systems utilize drums which carry cables attached to the garage door. Commonly the drums are mounted above the frame defining the door opening, with a drum positioned at each end of the door such that the cables may be conveniently connected proximate the lower lateral corners of the garage door. Basically, the door is moved toward the closed position, blocking the door opening due to gravity acting on the door as it moves from a substantially horizontal, open position above and inwardly of the door frame to a closed position. The path of the door in opening and closing is commonly defined by a track arrangement which interacts with rollers attached to the various sections of the door. The cable drums are classically interconnected with springs in a wide variety of ways so that they are progressively loaded as the door is lowered to prevent uncontrolled descent of the door and employ stored energy to assist in raising the door during subsequent opening operation. The prevailing type of counterbalancing system for garage doors for homes normally having a seven-foot high door involves the utilization of torsion springs mounted on a shaft which is coaxial with or mounts the drums. In such systems, it is established practice to utilize cable drums having a diameter of approximately 3V. inches to 4 inches. A torsion spring or springs mounted outwardly of the shaft has a diameter normally in excess of 1V_ inches to maintain an appropriate spring index. The drums and spring are normally mounted on a tubular shaft having a diameter of approximately 1 inch, which holds the springs and transmits torque from the springs to the drums which are attached to the tubing. These conventional torsion counterbalancing systems require that the tube mounting the drums be positioned above the horizontal track of the door to permit raising the door as high in the door opening as possible to accommodate higher vehicles and to otherwise make optimum use of the door opening. With a counterbalancing system thus positioned and employing conventional 3V_ to 4-inch cable drums, there is a requirement that there be a minimum of 13 to 14 inches above the door opening as overhead clearance to permit the mounting of these counterbalancing systems. However, a disadvantage of these conventional systems is the increasing requirement for a counterbalancing system which can be installed in a structure having a lesser overhead clearance. Frequently, construction parameters dictate a lower ceiling within a garage or the use of beams, supports, or other objects which do not provide the necessary headroom clearance of 13 to 14 inches required for the utilization of these conventional counterbalancing systems. In an attempt to accommodate the requirements for decreased overhead clearance, efforts have been made to modify these conventional counterbalancing systems. If the drums and tube with the mounted springs are merely moved downwardly, one or more of these elements interfere with the door during its opening and closing motion. One alternative which has been employed to solve reduced headroom requirements is to move the drums outboard or laterally of the tracks and lowered to a point that the springs and center bracket supporting the tube normally substantially medially thereof will just permit door clearance. This configuration, however, has serious limitations in that the cable binds the door to some extent due to the outward force applied during operation, and such is only effective to minimally reduce headroom clearance to a distance on the order of 12 inches. A more drastic alternative to obtain additional headroom contemplates the movement of the entire counterbalance system to the rear of the horizontal track, /'._., inwardly of the garage to a position proximate the extremities of the horizontal track where the top of the door reposes when it is in the open position. In systems of this nature, it is necessary to route the cable by pulleys from the counterbalance system to the door frame and then to the door. Systems of this type have proven to be both inefficient and costly, while introducing a relatively large, unsightly mechanism centrally of a garage. In addition, such systems often result in a geometry such that the lower portion of the bottom panel of the door does not reach the lower edge of the header but rather hangs down a substantial distance into the door opening when in the horizontal, open position. If a conventional counterbalance system is rear-mounted in a low headroom environment, a substantial portion of the system normally extends a distance below the horizontal track section. This configuration produces dangerous and thus undesirable conditions. First, the counterbalance springs are totally exposed to a person in the garage rather than being against the header where the door is between the springs and the person during most of the operating sequence. Second, persons of even average height may be exposed to the possibility of head injury and the irritation of interference with objects being carried in a garage having such an installation. Rear-mounted counterbalance systems in low-overhead environments where it is necessary to maintain the horizontal track sections at the lowest possible height above the door header often experience difficulty in seating and locking the top door panel against the header in manually-operated door installations. In particular, linear or slightly curved tracks proximate the header may operate to effect closing and opening; however, in such installations even minimal forces, e.g., wind, applied to the outside of the top panel can result in its unseating and uncontrolled opening. In many instances, prior-art systems have endeavored to solve low-overhead environments by displacing one or more components of the counterbalance system laterally outwardly of the tracks. However, in many instances, there are complexity and performance sacrifices created, and, in some instances, no solution is realized because low-headroom conditions are not infrequently accompanied by minimal side room to one or both sides of a door opening. The aforedescribed conventional torsion spring counterbalancing systems also have the disadvantage that the weight of the spring members is such as to require the use of a support bracket which normally suspends the tubular shaft substantially medially between the drums. The stationary support bracket is also commonly employed as the stationary anchor for the torsion springs. The support bracket is attached to the door header or more commonly a special spring pad located on the garage wall thereabove. Since the stationary anchor associated with the support bracket undergoes torsional loading equal to the weight of the door, there is a constant potential for operational failure or damage and injury to installation and maintenance personnel. The torsional forces can also result in a loosening of the support bracket, loosening of the stationary spring anchor, a failure of a door opening header or spring pad, all of which can result in a quick and violent untensioning of torsion springs, thereby presenting the potential for damage or injury to any proximate objects. In the case of a conventional rear- mount counterbalance system, the tensioning of conventional torsion springs in a low-headroom environment is very difficult because of the lack of clearance to manipulate the tensioning bars. Further, since the center support bracket must be adequately supported in a cantilevered position due to the torsional loading imparted by the springs even at the expense of additional time or material. Another disadvantage of such conventional torsion spring counterbalancing systems is the susceptibility to variations in balance of the door. With a drum diameter of approximately 4 inches, the drums revolve approximately seven times during an opening cycle of a 7-foot high door. As spring tension is lost through aging or extensive use, a highly noticeable variation in balance of the door is produced, as contrasted with systems which might have a lesser drum diameter and, therefore, rotate a greater number of times during opening and closing, such that the loading effect on a door is less for a given variation in spring tension. This same consideration makes it difficult to adjust the conventional 4-inch drum systems, since minute adjustments in spring tension can produce a substantial effect on a door. DISCLOSURE OF THE INVENTION Therefore, an object of the present invention is to provide a counterbalancing system for sectional doors which is highly compact and capable of being installed in relatively confined locations where there is a minimum of space surrounding the frame for a door opening. Another object of the present invention is to provide such a counterbalancing system which may be adapted for use with a variety of conventional sectional garage doors wherein the overhead clearance in the garage above the door opening is restricted. A further object of the present invention is to provide such a counterbalancing system, wherein the major components are substantially downsized in that elements such as the cable drums may be approximately one-half the diameter of the conventional drums normally employed in the industry on comparably sized doors. Another object of the present invention is to provide a counterbalancing system for sectional doors in which the spring is mounted internally of the tubular shaft so as not to be outwardly exposed and subject to the environment and to provide for easier and faster replacement of broken springs. . A further object of the present invention is to provide such a counterbalancing system wherein one extremity of each of the pair of springs employed is attached to gear shafts supported by brackets to either side of a door so that the torque of the springs is transmitted to the jamb structure outside the track and door opening for safety and accessibility. Yet another object of the present invention is to provide such a counterbalancing system wherein the center bracket, which may be mounted either on the top portion of the door jamb or a relatively vulnerable spring pad located on the garage wall, merely supports the weight of the drive tube springs and related components and does not experience torque loading. Another object of the present invention is to provide a counterbalancing system for sectional garage doors wherein a pair of springs are employed, with each having one end thereof attached to spring perches which are axially freely movable within the spring tube and are thus free to adjustably float therein. A further object of the present invention is to provide such a counterbalancing system where the coils of the spring may be formed with a spacing which will accommodate a lengthening of the spring during tensioning while introducing only a minimum of frictional resistance. Still a further object of the present invention is to provide such a counterbalancing system wherein there is no necessity for set screws or drive pins, which can loosen or fail during operation, to transmit rotational forces between the springs and the other components directly or indirectly attached thereto. Still another object of the present invention is to provide such a counterbalancing system wherein the drive tube is mounted between the cable drums, with provision for sufficient clearance such that the drive tube floats to lessen frictional forces which might otherwise occur. Still another object of the present invention is to provide a counterbalancing system for sectional doors wherein the length of the drive tube is equal to or less than the width of the door to be suspended such that the tube may be packaged in the same container as the door panels for ease of shipment and handling. Another object of the present invention is to provide such a counterbalancing system wherein the springs and worm gears are sized and configured such that they may be assembled at the time of manufacture, inserted into the drive tube, and shipped as an assembly. Still another object of the invention is to provide such a counterbalancing system which, in addition to its reduced size, may be of reduced weight, of reduced component size, of a reduced number of components, and an otherwise lower cost system. Still a further object of the present invention is to provide a counterbalancing system which is safe and easy to install, even without special tools, which is susceptible of adjustment to effect precise adjustments in spring tension operating on the door and is otherwise advantageous in terms of ease of assembly, operation, and repair. Another object of the present invention is to provide an alternative arrangement for mounting a compact counterbalance system to achieve the capability of a door installation which can be installed in locations having a minimum of headroom and side room relative to the opening for a sectional overhead door. Yet another object of the present invention is to provide such a door system which may be installed in an environment where the available headroom from the ceiling or overhead to the top of the sectional door opening and the available side room requirement for clearance from the edge of the sectional door opening to proximate objects is, in both instances, less than three inches. Still a further object of the present invention is to provide such a door system wherein all components of the counterbalance system are accommodated substantially within the height of the horizontal section of the track system. Still another object of the present invention is to provide a door system having a counterbalancing system mounted to the rear of the door in the open horizontal position proximate to the free ends of the horizontal track section, such that the primary components of the counterbalancing system may be located substantially co-planar with the roller at the upper extremity of top panel of the sectional door. A further object of the present invention is to provide such a door system wherein the upper roller at the top panel of the sectional door follows a substantially horizontal track section through the extent of its travel from the open horizontal position to the closed vertical position of the door. Yet a further object of the present invention is to provide such a door system wherein the upper roller of the top panel has a horizontal track section with a short inclined ramp proximate to the door header which seats and locks the top panel of the sectional door in place without the need for a motor-driven operator. Yet another object of the present invention is to provide a door system having a rear-mounted counterbalance system wherein no portion of the counterbalance system extends below the horizontal track section such as to provide a safe environment for persons in proximity despite a low headroom condition. Still a further object of the invention is to provide such a door system wherein the top of the sectional door never extends above the top of the horizontal track sections. Yet another object of the invention is to provide such a door system employing the compact counterbalance system which transmits torque to the tracks in an area proximate to the supported free ends thereof, such that the cantilevered center support for the counterbalance system is not subjected to torque-loading from the springs of the counterbalance system. A still further object of the present invention is to provide a door system which employs a counterbalancing system which when mounted to the rear of the horizontal tracks maintains all of the operational advantages achieved with conventional jamb mounting. A still further object of the present invention is to provide such a door system which achieves a highly compact configuration with the hang-down of the bottom of the lower panel of the door being minimized by judicious placement of the pulley supporting the counterbalance system cables extending between the cable drums and a bracket at the lower extremity of the bottom panel of the door. In general, the present invention contemplates an overhead door system for moving a sectional door having top, bottom, and intermediate hinged panels between a closed vertical position proximate a door frame and an open horizontal position including a substantially vertical track section for engaging a plurality of rollers attached to and spaced from the bottom and intermediate panels, a curved transition track section commencing at the upper extremity of the vertical track section for changing the direction of travel of the plurality of rollers, a first horizontal track section extending from the transition track section for receiving the plurality of rollers to support the door in the open horizontal position, a second horizontal track section for guiding a top panel roller positioned proximate the top of the top panel from the open position to the closed position of the door, and a rear counterbalancing system mounted proximate the ends of the horizontal track sections remote from the door frame and operatively interrelated with the door. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a fragmentary perspective view depicting a frame for a sectional door and showing a counterbalancing system embodying the concepts of the present invention as mounted in operative relationship to the door. Fig. 2 is a fragmentary elevational view of the left-hand portion of the counterbalancing system of Fig. 1 as viewed from the inside of the sectional door. Fig. 3 is a side elevational view of the counterbalancing system taken substantially along the line 3-3 of Fig. 2 and depicting particularly the mounting bracket and its interrelation with the sectional door frame, together with the worm drive assembly for adjusting the tensioning assembly. Fig. 4 is a cross-sectional view taken substantially along the line 4-4 of Fig. 3 and showing particularly details of the spring, the drive tube, the worm gear shaft, and the spring perch. Fig. 5 is a cross-sectional view taken substantially along the line 5-5 of Fig. 4 and showing particularly the interrelation between the drive tube and the cable drum assembly. Fig. 6 is an exploded perspective view showing details of the worm gear shaft, the spring, the spring perch, the drive tube, and the interrelation therebetween. Fig. 7 is a fragmentary, perspective view with portions broken away of an alternative arrangement for mounting the counterbalancing system of Figs. 1-6 at the rear of the horizontal tracks, as viewed in relation to the inside of a sectional door. Fig. 8 is a fragmentary, side-elevational view taken substantially along the line 8-8 of Fig. 7 of one side of the track and counterbalancing system of the alternative arrangement for mounting the counterbalancing system showing details of the dual horizontal tracks and the counterbalancing system. Fig. 9 is a fragmentary, rear-elevational view taken substantially along the line 9-9 of Fig. 8 of one side of the track and counterbalancing system of the alternative arrangement for mounting the counterbalancing system. Fig. 10 is an enlarged, fragmentary, side-elevational view of a portion of Fig. 8 showing details of the upper horizontal track and the interconnected angular ramp. PREFERRED EMBODIMENT FOR CARRYING OUT THE INVENTION A counterbalancing system according to the concepts of the present invention is generally indicated by the numeral 10 in Fig. 1 of the drawings. The counterbalancing system 10 is shown mounted in conjunction with a conventional sectional door D of the type commonly employed in garages for homes. The opening in which the door is positioned for opening and closing movements relative thereto is surrounded by a frame, generally indicated by the numeral 12, which consists of a pair of spaced jamb members 13 and 14 that, as seen in Fig. 1, are generally parallel and extend vertically upwardly from the ground (not shown). The jambs 13, 14 are spaced and joined at their vertically upper extremity by a header 15 to thereby delineate a generally U-shaped frame 12 around the opening for a door D. The frame 12 is normally constructed of lumber, as is well known to persons skilled in the art, for purposes of reinforcement and to facilitate the attachment of elements supporting and controlling a door D, including the counterbalancing system 10. Affixed to the jambs 13, 14 proximate the upper extremities thereof near the header 15 to either side of the door D are flag angles, generally indicated by the numeral 20. The flag angles 20, which may be of differing configurations, generally consist of L-shaped vertical members 21 having a leg 22 attached to an underlying jamb 13, 14 and a projecting leg 23 preferably disposed substantially perpendicular to the leg 22 and therefor perpendicular to the jambs 13, 14. The flag angles 20 also include an angle iron 25 having a vertical leg 26, which may be attached to the projecting legs 23 of the vertical members 21 as by bolts 27. The angle irons 25 have stiffening legs 28. The angle irons 25 are positioned in supporting relation to the tracks T located to either side of a door D. The tracks T, T provide a guide system for rollers attached to the side of a door D, as is well known to persons skilled in the art. The angle irons 25 preferably extend substantially perpendicular to the jambs 13, 14 and may be attached to the transitional portion of tracks T, T between the vertical portion and horizontal portion thereof or in the horizontal portions of tracks T, T. The tracks T, as is well known, thus define the travel of the door D in moving from the open to closed positions and support a portion of the weight of the door D in the vertical and transition sections and substantially the entirety of the weight of the door in the horizontal sections. The counterbalancing system 10 is positioned at or above the header 15. The counterbalancing system 10 includes an elongate drive tube, generally indicated by the numeral 30, extending between a tensioning assembly 31 and a tensioning assembly 32, which are positioned proximate the right side flag angle 20 and the left side flag angle 20, respectively. The drive tube 30 is a hollow tubular member which is non-circular in cross section, as best seen in Figs. 1 and 5. In the preferred form, the tubular member 35 has a circular portion 36 constituting a substantial portion of the circumference of tubular member 35. The remainder of tubular member 35 consists of a radially projecting cam lobe 37 which preferably extends axially the full length of the tubular member 35. The cam lobe 37 is configured such that the radial distance from the center of tubular member 35 to the radially outermost point of the cam lobe 37 is equal to or greater than the distance to the intersection of two sides of a eight or more sided polygon which might be circumscribed about a circle of the size of the circular portion 36 of tubular member 35. Alternatively, the tubular member 35 could be a polygon with less than seven sides. These exemplary configurations provide examples of a non- circular tubular member 35, such that internally or externally mating members cannot rotate relative to tubular member 35, as hereinafter described under the operating conditions encountered in use of the counterbalancing system 10. Depending upon the width of door D, the drive tube 30 may advantageously be supported substantially medially of its length by a center bracket, generally indicated by the numeral 40, as seen in Figs. 1, 2, and 4 of the drawings. The center bracket 40 includes an L-shaped attachment plate 41 which may be provided with slots 42 or bores for receiving screws 43 to anchor the center bracket 40 to the header 15 or, depending upon the installation, a mounting pad affixed to the garage wall above the header 15. The center bracket 40 has an annular journal box 45 which is spaced from and supported by attachment plate 41 by a plurality of struts 46, 47, and 48, which are preferably oriented substantially radially of annular journal box 45 (Fig. 1). The annular journal box 45 has a radial recess 49 positioned preferably substantially axially medially thereof. The recess 49 seats a bushing 50 which is affixed to the tubular member 35 of drive tube 30 (Fig. 4). The bushing 50 is interiorly contoured to the configuration to the tubular member 35, including the lobe 37, and externally circular to freely rotatably move within the recess 49 of the annular journal box 45. The drive tube 30 interconnects at the ends thereof spaced from the center bracket 40 with the tensioning assemblies 31 and 32. Since the tensioning assemblies 31 and 32 are essentially identical, except that most components are symmetrically opposite, and since they function identically, only the tensioning assembly 32 is hereinafter described, as depicted in Figs. 2-6 of the drawings. The tensioning assembly 32 has an end bracket, generally indicated by the numeral 60, to effect attachment to the flag angle 20 and/or the jamb 14 as by bolts 61 which extend through a backing plate 62 of the end bracket 60 (see Fig. 3). The end bracket 60 includes a tubular bearing box 63, a gear housing 64, and a worm shroud 65. As best seen in Figs. 1 and 3, the worm shroud 65 may be a generally U-shaped enclosed member having spaced legs 65 / and 65* (Fig. 3) for a purpose to be hereinafter detailed. The tubular bearing box 63, gear housing 64, and worm shroud 65 are spaced and supported a distance from the plate 62 by a plurality of braces 66 (Fig. 3). The end bracket 60 may conveniently be provided with a slot 67 to receive the projecting leg 23 of flag angle 20. This serves to align and support the assembled counterbalancing system 10 while bolts 61 are installed to effect permanent placement. The tensioning assembly 32 includes a gear shaft, generally indicated by the numeral 70, which interfits with the end bracket 60. The gear shaft 70 has a worm gear 71 formed therein which is positioned within the gear housing 64 of end bracket 60 (Figs. 3 and 4). Extending axially in one direction from the worm gear 71 is a hollow sleeve 72, which is supported within the tubular bearing box 63 of end bracket 60. The sleeve 72 may terminate in one or more snap locks 73, which extend axially outwardly of and have a radially projecting lip 74 that overlies a portion of the axially outward surface of tubular bearing box 63 of end bracket 60. It will thus be appreciated that the end bracket 60 may be readily attached to the gear shaft 70 during installation of counterbalancing system 10 and particularly during the placement and attachment of the end bracket 60 to the jamb 14. Radially inwardly of the worm gear 71 and accessible through the hollow sleeve 72, the gear shaft 70 may have a bore 75 which may be of octagonal configuration to receive a comparably shaped tool to facilitate gripping of the gear shaft 70 to permit assembly and disassembly of the counterbalancing system 10 in a manner described hereinafter. The gear shaft 70 has spaced a distance axially of the worm gear 71 in the direction opposite the sleeve 72 a radially upstanding bearing surface 76. The bearing surface 76 serves a purpose to be described hereinafter. The gear shaft 70 at the end opposite the sleeve 72 terminates in a spring receiver portion 77. The spring receiver portion 77 consists of a plurality of helical grooves 78 which may be formed at substantially the same pitch angle and diameter as the coil spring, generally indicated by the numeral 80, which reposes thereon. If desired, a number of helical grooves 79 may be of a slightly larger diameter in the area displaced from the end of gear shaft 70 to further facilitate the tension of the spring 80 thereon. The coil spring 80 may be of uniform configuration from end to end and have a spacing between the coils of several hundredths of an inch for purposes of accommodating additional coils of the spring 80 which are present in the working area of the spring 80 when it is subjected to torsional loading as hereinafter described. The spring 80 has a spring end 81, which is mounted in the grooves 78, 79 of the spring receiver portion 77 of gear shaft 70. The spring end 81 may be threaded on receiver 77 with an appropriate tool inserted into the bore 75 to prevent rotation of gear shaft 70 during assembly and disassembly operations. A spring liner 82 may be provided radially outwardly of the spring 80 in the working area of the spring 80, as seen in Fig. 4. The spring liner 82 may conveniently be positioned on the interior surface of the tubular member 35 of drive tube 30 and may be shaped to the internal configuration thereof. The spring liner 82 may be of any impact-resistant plastic material for purposes of damping possible spring chatter which may develop during rapid torsional loading or unloading of the spring 80. Spring 80 has a spring end 83 at the opposite axial extremity from spring end 81 which engages a spring perch, generally indicated by the numeral 90. The spring perch 90 has a body portion 91 which, as seen in Figs. 4 and 6, is externally configured for matingly engaging the inner surface of tubular member 35. The spring perch 90 has a spring receiver portion 92 which extends axially from the body 91. The spring receiver 92 may be formed in a manner comparable to spring receiver 77 and having a plurality of helical grooves 93 and a plurality of helical grooves 94, which are of a slightly greater diameter than the grooves 93, to similarly facilitate retention of spring end 83 when positioned thereon, as depicted in Fig. 4. The spring perch 90 may have a bore 95 of octagonal cross section similar to the bore 75 of gear shaft 70, again for the purposes of facilitating non-rotational retention of spring perch 90 during the assembly and disassembly of spring end 83 thereon. It will thus be appreciated that the spring perch 90, due to the configuration of the body 91, remains non-rotatably positioned relative to and within the drive tube 30, while being capable of floating or moving axially within drive tube 30 when the spring 80 is not under torsional loading. This permits the spring perch 90 to self-adjust axially of the drive tube 30 to accommodate the exact length of a coil spring 80. The drive tube 30 carries at the extremity thereof proximate to the end bracket 60 and supported in part by worm shaft 70 a cable drum mechanism, generally indicated by the numeral 100. Referring particularly to Figs. 2, 4, and 5, the cable drum mechanism 100 has an external surface over a substantial portion of its length consisting of a continuous helical grooves 101. The helical grooves are adapted for reeving a suspension cable C thereabout. The cable C is attached at one end to a point on the door at substantially the bottom of the lowermost panel when a door D is in the closed position. The other end C of the cable C is affixed to the cable drum 100 for selective retention and release when a cable C is installed or replaced. In this respect, an angular bore 102 extends into the drum 100 preferably proximate one extremity of the helical grooves 101 and is sized to receive the cable C. A hex screw 103 is positioned in a tapped radial bore (not shown) which intersects with the bore 102. Thus, the hex screw 103 may be tightened to retentively engage end C of cable C and released by loosening the hex screw 103 to move end C of cable C from the bore 102. The end of cable drum 100 axially opposite the hex screw 103 has a projecting sleeve 104 which may be provided with a plurality of circumferentially- spaced reinforcing ribs 105. The cable drum 100 has a central bore 106 extending through the sleeve 104 and preferably a substantial distance into the drum 100, which is configured to matingly engage the exterior surface of the tubular member 35 of drive tube 30. It will thus be appreciated that the cable drum 100 is non-rotatably affixed to, and therefore at all times rotates with, the drive tube 30. The axial end of cable drum 100 opposite the bore 106 has a bore 107 of lesser diameter which is adapted to matingly engage and ride upon the projecting bearing surface 76 of gear shaft 70. An extent of clearance may be provided between a shoulder 108 formed by the juncture of bores 106 and 107 and the extremity of the drive tube 30 at either end thereof, such that the drive tube 30 is capable of an extent of axial movement to avoid possible binding or frictional interference (Fig. 4). The bore 107 of cable drum 100 may be provided with a plurality of circumferentially-spaced radially inwardly projecting teeth 109. The teeth 109 extend inwardly of the bearing surface 76 of gear shaft 70 for purposes of positioning cable drum 100 axially of gear shaft 70 during assembly and installation. It will thus be appreciated by persons skilled in the art that the counterbalancing system 10, as depicted in Figs. 1, 2, and 4, is shown in a position with the door in substantially the closed position and the spring 80 thus fully tensioned to apply counterbalancing forces to a door D. As a door D would be raised manually or by a powered operator (not shown), the spring 80 having one end fixed by the gear shaft 70 would rotate the spring perch 90 and thus the drive tube 30 which rotates the cable drum mechanism 100 to reeve the cable C onto the groove 101. The spring 80 is thus progressively untensioned as the door D moves upwardly into the open position. Subsequent lowering of the door D operates in a reverse fashion to progressively load spring 80 as the door D is lowered, such that the counterbalancing system 10 reaches substantially the configuration depicted in Figs. 1, 2, and 4. The spring 80 is non-rotatably restrained and suitably pretensioned by a tension adjusting mechanism, generally indicated by the numeral 110 in Figs. 3 and 4 of the drawings. The tension adjusting mechanism 110 is enclosed within the worm shroud 65 of end bracket 60 for purposes of protection from dirt or foreign objects, safety, and appearance. The tension adjusting mechanism 110 includes a worm 111 of relatively short axial extent which engages the worm gear 71 of gear shaft 70. The worm 111 is mounted on a worm shaft 112 which extends through the spaced legs 65 ', 65" of the worm shroud 65 of end bracket 60 for positioning the worm 111 in operative relation to the worm gear 71. The tension adjusting mechanism 110 and worm gear 71 are designed and configured such that the worm mechanism can be operated only by actuation of the head 113 of non-circular worm shaft 112 which rotates the worm 111. Worm 111 and worm gear 71 are designed in such a fashion that the worm gear 71 cannot rotate the worm 111 in the operating range of the counterbalancing system 10. This is effected in part by employing a lead angle on worm 111 and worm gear 71 to provide increased friction, thus decreasing the operating efficiency thereof. A lead angle of approximately 11 to 14 degrees has been found to be sufficient to meet these operating parameters for systems involving doors in the size range herein contemplated. If desired in particular installations, a fiber washer 114 may be positioned proximate the worm 111 to provide additional friction and increase anti-reversing friction to assure that worm gear 71 does not drive worm 111 under any operating circumstances. It will be appreciated that the rotational position of gear shaft 70 remains fixed at all times during operation of the counterbalancing system 10, except when the head 113 of worm shaft 112 is rotated. It will be further appreciated that tensioning adjustments may be readily made by using a conventional hex socket and drill to rotate the head 113 in the desired direction to effect a selected pretensioning of the spring 80. Thus, it should be evident that the counterbalancing system 10 for a sectional door D disclosed herein carries out various of the objects of the present invention set forth above and otherwise constitutes an advantageous contribution to the art. As will be apparent to persons skilled in the art, modifications can be made to the preferred embodiments disclosed herein without departing from the spirit of the invention. For example, it will be appreciated that only one of the tensioning assemblies 31, 32 might be employed, as with only an end bracket 60, gear shaft 70, and cable drum 100 being provided at one end, to supply the entirety of the torsional forces for the counterbalancing system 10. An alternate arrangement for employing the counterbalance system 10 is shown in the form of the overhead door mounting system, generally indicated by the numeral 210, in Figs. 7 and 8. The door mounting system 210 is shown in relation to a conventional sectional door D ' of the type commonly employed in residential garages, utility buildings, and the like. The opening in relation to which the door is positioned for opening and closing movements is surrounded by a door frame, generally indicated by the numeral 212, which consists of a pair of spaced jamb members 213 and 214 that are generally parallel and extend vertically upwardly from the garage floor or ground G. The jambs 213, 214 are spaced and joined at their vertically upper extremity by a header 215 to thereby form a generally U-shaped frame 212 around the opening for the door D • . A peripheral molding 216 may overlie and extend inwardly of the frame 212 to form a co-planar door engaging surface. The frame 212 may be conventionally constructed, as indicated hereinabove, in conjunction with the frame 12. As seen in Figs. 7 and 8, the sectional door D ' consists of a rectangular arrangement of panels 220, including a top panel 221, an adjacent upper middle panel 222, an adjacent lower middle panel 223, and an adjacent bottom panel 224. The top panel 221 has top brackets 230 positioned at either side near the top edge 231, each of which mounts an upper roller 232 that is offset from door D ' a slight distance. As best seen in Fig. 8, hinge brackets 235 having pivot pins 236 and rollers 237 are positioned proximate the juncture of panels 221 and 222, the juncture of panels 222 and 223, and the juncture of panels 223 and 224 at either side of door D • . The brackets 235 may have vertically progressively greater offsets of the rollers 237 with respect to the door panels to assist in bringing the door downward and progressively into contact with the peripheral molding 216 of jamb brackets 213, 214 in a manner well known in the art. A bottom bracket 240 positions a bottom roller 241 proximate the lower edge of the bottom panel 224, as best seen in Fig. 8. Referring still to Figs. 7 and 8, the door mounting system 210 has the door D ' movably interrelated with the frame 212 by a track system, generally indicated by the numeral 250. The track system 250 has vertical track sections 251 to either side of the door D ' extending from the ground G constituting the floor of a garage or other structure to a position somewhat below the header 215 of the frame 212. The vertical track sections 251 are positioned laterally of and vertically with respect to jambs 213 and 214 as by a plurality of conventional jamb brackets 252 (see Fig. 7). The vertical track sections 251 are connected to curved transition track sections 253, which may be an involute transcending through approximately ninety degrees and terminating in a substantially horizontal orientation at a height substantially in vertical alignment with the top edge 231 of top panel 221 of door D • in the closed vertical position, as best seen in Fig. 8. The transition track sections 253 merge into or are connected to lower horizontal track sections 255 which extend rearwardly from, and are substantially perpendicular to, frame 212. The lower horizontal track sections 255 are supported proximate their rearward extremity by struts 256 which may be attached to the overhead O thereabove in a conventional fashion well known in the art. The track system 250 differs in significant respect from conventional track systems in having upper auxiliary horizontal track sections 260. As shown, the upper auxiliary horizontal track sections 260 are substantially parallel with, are in substantially vertical alignment with, and are preferably in abutting longitudinal engagement with the lower horizontal track sections 255. Optionally, the track sections 255 and 260 may be welded along their entire abutting surfaces to impart additional strength and rigidity thereto. If desired, one or more reinforcing plates 261 may be attached to both of the adjacent track sections 255 and 260 as by welds 262 for further strengthening. The upper auxiliary horizontal track sections 260 have proximate ends 263 in substantial alignment with the bottom of the header 215 as supported by flag angles, generally indicated by the numeral 265. As shown, the flag angles 265 consist of L-shaped vertical members having a leg 266 overlying and attached to the respective jamb brackets 213 and 214 and the header 215. The flag angles 265 have projecting legs 267 which extend substantially perpendicular to the legs 266 and have the proximate ends 263 of upper auxiliary horizontal track section 260 attached thereto as by bolts 268, as seen in Figs. 8 and 10, or other fasteners. If desired, the flag angles 265 may have a second projecting leg 269 to which the vertical track sections 251 and the transition track sections 253 may be attached as by bolts 269 • or other fasteners. The proximate ends 263 of upper auxiliary horizontal track sections 260 transcend into door-seating assemblies, generally indicated by the numeral 270, which, as best seen in Figs. 8 and 10, is a short contoured track section. The door-seating assemblies 270 preferably have a cross-sectional configuration substantially the same as the track sections 260 and are adjustably positioned in relation thereto by selective attachment to the legs 267 of flag angles 265 as by bolts 271 or other fasteners. The door-seating assemblies 270 have curved surfaces 272 for engaging the running surface of upper roller 232, which is relatively sharply downwardly directed and merges into a linear ramp 273 that is downwardly and outwardly inclined toward header 215 preferably at an angle in the range of approximately twenty degrees to sixty degrees with respect to horizontal track sections 260. It will thus be appreciated that the upper rollers 232 at the top edge 231 of top panel 221 are maintained within upper auxiliary horizontal track sections 260 or door seating assemblies 270 at all times during travel of the door D ' . When the sectional door D ' is moved from the open horizontal position to the closed vertical position, the rollers 232 enter door-seating assemblies 270 just prior to reaching the closed position. At that time, the rollers 232 pass over the curved surfaces 272 and embark upon the ramps 273, which facilitates seating of top panel 221 against the peripheral molding 216 of header 215 to securely close the top panel 221 in vertical alignment with the remainder of the panels 224, 225, and 226. The inclined ramps 273 maintain the top panel 221 in its seated position until sufficient vertical opening forces are applied to the door D » , such that the rollers 232 can transcend the inclined ramps 273 and curved sections 272 to commence horizontal traverse in the upper auxiliary horizontal track sections 260. The upper auxiliary horizontal track sections 260 have rear ends 264 at the opposite extremity from the proximate ends 263. Each of the rear ends 264 of upper auxiliary track sections 260 carry a rear mounting bracket, generally indicated by the numeral 275, in Figs. 8 and 9. The rear mounting bracket 275, as shown particularly in Fig. 9, may be of a general angle iron configuration, including a vertical leg 276 and a horizontal leg 277. The vertical leg 276 is preferably attached proximate the rear end 264 of upper auxiliary horizontal track sections 260 and may be advantageously attached thereto and to lower horizontal track sections 255 as by welds 278 to interconnect the track sections 255 and 260 and to provide a rigid mounting for the rear mounting bracket 275. As shown, the rear mounting bracket 275 supports a counterbalancing system, generally indicated by the numeral 280, as seen in Figs. 8 and 9. In view of the highly compact dimensions of the components, the relative placement of the structural elements, and other features described hereinabove, the counterbalancing system 280 may, as best seen in Fig. 9, employ the elongate drive tube 30 and tensioning assemblies 31 and 32, all as detailed hereinabove in conjunction with the counterbalancing system 10. As shown, the tensioning assemblies 31, 32 may be attached to the rear mounting brackets 275 by affixing backing plates 62 of the end brackets 60 to the horizontal leg 277 of rear mounting bracket 275 as by bolts and nuts 279 or other similar fasteners. A center bracket 40 may support drive tube 30 from the overhead O at a position substantially medially thereof. As best seen in Fig. 9, with the counterbalancing assemblies 280 thus mounted, such are essentially in alignment with the upper auxiliary horizontal track sections 260 and extend only a slight distance laterally outwardly thereof and thereabove such as to be substantially within the confines of the track sections 260, 260. The counterbalance systems 280 include cable drum mechanisms 100 which have the upper extremity of the grooved surface 101 positioned slightly above and axially within the upper auxiliary horizontal track sections 260. The helical grooves 101 direct the cable C of the counterbalance assemblies 280 forwardly toward the header 215 and minimally above the door D « . The cables C are engaged at a position spaced from the door header 215 by direction change pulley mechanisms, generally indicated by the numeral 285. The direction change pulley mechanisms 285 divert the direction of the cable C from the horizontal position slightly above the door D ' when in the open horizontal position downwardly to the bottom panel 224 of the door D • for attachment as described hereinafter. As best seen in Fig. 8, each of the direction change pulley mechanisms consist of a sheave 286 which is grooved in conventional fashion to receive the cable C and a shaft 287 upon which the sheave 286 freely rotates. The shaft 287 and thus the sheave 286 are supported on mounting brackets 288 which may be attached to one or both of the tracks 260, 253 as by welds 289, which may secondarily interconnect and rigidify the track sections 253, 260. The end of the cables C opposite to that attached to cable drum mechanisms 100 is anchored to brackets 290, which are preferably affixed proximate the bottom edge of the bottom panel 224 of the door D ' . As shown particularly in Figs. 7 and 8, the bottom door bracket 290 extends outwardly a short distance from the inner surface of the panel 224 and may be of essentially conventional configuration in carrying a pin 291 to which the end of cable C may be affixed as by a cable clamp (not shown) or other conventional fastening elements. The positioning of the direction change pulley assembly 285 is effectively controlled by the balancing of a plurality of factors which are to some extent conflicting. Initially, it will be appreciated that the further the bottom edge of bottom panel 224 moves upwardly and to the right, as viewed in Fig. 8, as sheave 286 is offset a greater distance from header 215, the greater the clearance below the door D • for a given height of header 215. This is because the door D ' cannot proceed further to the right or toward an open position than when cable C, shown in chain lines in the extreme position C • in Fig. 8, is directly vertically suspended from the sheave 286. However, the further the bottom door panel 224 is displaced inwardly from frame 212 in the horizontal open position depicted in chain lines as 224 ' , the longer the tracks 255 and tracks 260 must be to accommodate the door D ' and the more material required. In addition, as the direction change pulley assembly 285 is moved inwardly from the header 215, the greater the angle at which cable C exerts force on bracket 290 and thus the bottom of door panel 224. It will be appreciated by persons skilled in the art that increasingly greater angles between the cable C and the vertical track section 251, the less the vertical lifting force component exerted on the door D • , such that stronger forces must be generated by tensioning assemblies 31 and 32. A balancing of these factors thus depends on the geometry and requirements of a particular system. Thus, it should be evident that the rear mount counterbalance system for sectional doors disclosed herein carries out various of the objects of the present invention set forth above and otherwise constitutes an advantageous contribution to the art. As will be apparent to persons skilled in the art, modifications can be made to the preferred embodiments disclosed herein without departing from the spirit of the invention, the scope of the invention being limited solely by the scope of the attached claims.

Claims: CLAIMS 1. An overhead door system for moving a sectional door having top, bottom, and intermediate hinged panels between a closed vertical position proximate a door frame and an open horizontal position comprising, substantially vertical track means for engaging a plurality of rollers attached to and spaced from the bottom and intermediate panels, transition track means commencing at the upper extremity of said vertical track means curving through an angle of approximately ninety degrees for directing the travel of said plurality of rollers, first horizontal track means extending from said transition track means for receiving said plurality of rollers to support the door in the open horizontal position, second horizontal track means for guiding top panel roller means positioned proximate the top of the top panel in a substantially horizontal path from the open position to the closed position of the door, and door seating means interposed between said second horizontal track means and the door frame for positioning and maintaining the door against the door frame when the door is in the closed position. 2. An overhead door system according to claim 1, wherein said first horizontal track means and said second horizontal track means are substantially parallel. 3. An overhead door system according to claim 2, wherein said first horizontal track means and said second horizontal track means are in abutting longitudinal engagement. 4. An overhead door system according to claim 2, wherein said first horizontal track means and said second horizontal track means are substantially vertically aligned. 5. An overhead door system according to claim 1, wherein said door seating means includes a short contoured track section which is adjustably mounted relative to said second horizontal track means and the door frame. 6. An overhead door system according to claim 1, wherein said door seating means includes a ramp for guiding said top panel roller means downwardly and outwardly toward the frame. 7. An overhead door system according to claim 6, wherein said ramp is linear and said door seating means includes a downwardly curved surface interposed between said second horizontal track means and said ramp. 8. An overhead door system according to claim 6, wherein said ramp is positioned at an angle of approximately twenty degrees to sixty degrees with respect to said second horizontal track means. 9. An overhead door system according to claim 1 further comprising counterbalancing means mounted proximate the ends of said first and second horizontal track means displaced from the frame, cable means interconnecting said counterbalancing means and the bottom panel of the door, and pulley means on said horizontal track means offset from the frame for engaging and directing said cable means. 10. An overhead door system for moving a sectional door having top, bottom, and intermediate hinged panels between a closed vertical position proximate a door frame and an open horizontal position comprising, substantially vertical track means for engaging a plurality of rollers attached to and spaced from the bottom and intermediate panels, curved transition track means commencing at the upper extremity of said vertical track means for changing the direction of travel of said plurality of rollers, first horizontal track means extending from said transition track means for receiving said plurality of rollers to support the door in the open horizontal position, second horizontal track means for guiding top panel roller means positioned proximate the top of the top panel from the open position to the closed position of the door, and rear counterbalancing means mounted proximate the ends of said horizontal track means remote from the door frame substantially within the confines of said second horizontal track means and operatively interrelated with the door. 11. An overhead door system according to claim 10, wherein said counterbalancing means includes cable drum mechanisms mounted axially within said second horizontal track means. 12. An overhead door system according to claim 10, wherein said rear counterbalancing means is attached to a mounting bracket positioned at the end of said second horizontal track means remote from the door frame. 13. An overhead door system according to claim 10, wherein said rear counterbalancing means is operatively interrelated with the door through cable means having one end attached to drum means of the tensioning means of the counterbalancing means and the other end attached to the bottom panel of the door. 14. An overhead door system according to claim 13, wherein bottom brackets positioned proximate the bottom edge of the door have said other end of said cable means attached thereto. 15. An overhead door system according to claim 13, wherein pulley mechanisms mounted on said horizontal track means are offset a distance from the frame and engage said cable means between said drum means and the bottom panel of the door. 16. An overhead door system according to claim 15, wherein said drum means and said pulley mechanisms extend a slight distance above said second horizontal track means, whereby said cable means extending therebetween is positioned minimally above the door in the open position. 17. An overhead door system according to claim 15, wherein said pulley mechanisms include sheaves having grooves for receiving and angularly redirecting said cable means. 18. An overhead door system according to claim 17, wherein said sheaves are mounted on shafts carried by mounting brackets attached to said horizontal track means.

Inventors: ALLIS DAVID C, DRAPER THOMAS F III, MULLET WILLIS, ALLIS, DAVID, C., DRAPER, THOMAS, F., III, MULLET, WILLIS
Applicants: WAYNE DALTON CORP, WAYNE-DALTON CORP.
Application year: 1996
Main classification: E05D15
IPC codes: E05D15