PREFERRED EMBODIMENT FOR CARRYING OUT THE INVENTION

[0017] A counterbalance system according to the concepts of the present invention is generally indicated by the numeral 10 in FIGS. 1 and 2 of the drawings. The counterbalance system 10 is shown mounted in conjunction with a sectional door, generally indicated by the letter D, and may include an operator system, generally indicated by the numeral 11 , which may be a type of jack shaft operator and may be employed particularly in garages for residential housing. The opening in which the door D is positioned for moving between a closed vertical position and an open horizontal position is defined by a frame, generally indicated by the numeral 12 . The frame 12 consists of a pair of spaced jambs 13 and 14 that, as seen in FIG. 1 , are generally parallel and extend vertically upwardly from the ground or a floor (not shown). The jambs 13 , 14 are spaced and joined at their vertical upward extremity by a header 15 to thereby delineate a generally inverted U-shaped frame 12 around the opening for the door D. The frame 12 is normally constructed of wood for purposes of reinforcement and facilitating the attachment of elements for supporting and controlling the door D, including the operator system 11 . The door D has a top section 16 , a bottom section 17 , and one or more intermediate sections 18 which are interconnected by horizontally spaced hinges 19 in a manner well known to persons skilled in the art.

[0018] Affixed to the jambs 13 , 14 proximate the upper extremities thereof and the lateral extremities of the header 15 to either side of the door D are flag angles, generally indicated by the numeral 20 . The flag angles 20 generally consist of L-shaped vertical members 21 having a leg 22 attached to an underlying jamb 13 , 14 by lag bolts 23 , or the like, and a projecting leg 24 preferably disposed substantially perpendicular to the leg 22 and, therefore, perpendicular to the jambs 13 , 14 . Associated with flag angles 20 is a horizontal angle iron 25 extending from the projecting leg 24 and supporting roller tracks T, T located to either side of door D. Tracks T, T provide a guide system for rollers R attached to either side of the door D, in a manner well known to persons skilled in the art. The horizontal angle irons 25 normally extend substantially perpendicular to the jambs 13 , 14 and may be attached to the transition portion of tracks T, T between the vertical section and the horizontal section thereof or at the beginning of the horizontal section of tracks T, T closest to the jambs 13 , 14 . The tracks T, T define the travel of the door D in moving between the closed vertical position and the open horizontal position of the door D.

[0019] The operator system 11 interrelates with the door D through counterbalance system 10 including cable drum mechanisms, generally indicated by the numeral 30 . As shown, the cable drum mechanisms 30 are positioned on a drive tube 31 which extends a substantial portion of the distance between the flag angles 20 , 20 to either side of the door D. If desired, the drive tube 31 could be constructed of two or more telescoping members to facilitate packaging, assembly, and/or adjustment. As shown, the cable drum mechanisms 30 are positioned on the drive tube 31 at the ends thereof and are in all instances nonrotatably affixed to the drive tube 31 . As seen in FIG. 1 , the operator system 11 may have an operator housing 32 which encloses a length of drive tube 31 that interacts with the operator drive elements (not shown) in a manner known to persons skilled in the art to selectively effect rotational drive of the drive tube 31 in both rotational directions to supply the power required for driving the door D between the closed vertical position and the open horizontal position. While drive tube 31 is depicted as a hollow tubular member that is noncircular in cross-section (see FIGS. 3 and 4 ), it is to be appreciated that circular drive tubes, solid shafts and other types of driving elements capable of rotating the cable drum mechanisms 30 may be employed and are encompassed within this terminology in the context of this specification.

[0020] The cable drum mechanisms 30 each include a cable drum 35 which is of a generally cylindrical configuration. The cable drum 35 has at its inboard end an axially projecting drum sleeve 36 which receives drive tube 31 and may be provided with a plurality of circumferentially spaced reinforcing ribs 37 . As can be see in FIGS. 2 and 4 , the drum sleeve 36 is noncircular in the manner of the drive tube 31 and is sized to telescopically receive drive tube 31 , whereby cable drums 35 at all times rotate with the drive tube 31 .

[0021] As best seen in FIG. 4 , the cable drums 35 are positioned for rotation with the drive tube 31 by cylindrical drum supports 38 which have radially indented bearing surfaces 39 . The bearing surfaces 39 are sized to fit within notches 40 located in the projecting leg 24 of the flag angles 20 . The drum support 38 is maintained seated in the notches 40 by a drum keeper bracket 41 seen in FIG. 4 . The drum keeper bracket 41 has an attachment leg 42 and a U-shaped retainer leg 43 . The retainer leg 43 overlies the end of drum support 38 and may reside in part in the notch 40 when assembled. The drum keeper bracket 41 is maintained with the retainer leg 43 positioned over drum support 38 by a bolt 44 and nut 45 which secures the attachment leg 42 of drum keeper bracket 41 against the projecting leg 24 of flag angles 20 . Thus, the cable drums 35 are supported and retained after assembly in the position depicted in the drawing figures.

[0022] As can be seen in FIGS. 2 - 4 of the drawings, the cable drums 35 have a cylindrical or tapered cylindrical surface 50 over a substantial portion of the axial length thereof. The cable drums 35 have the cylindrical surface 50 thereof provided with continuous helical grooves 51 having a minor diameter 52 located as best seen in FIG. 3 of the drawings. The cylindrical surface 50 has an outboard array 53 of a plurality of helical grooves 51 which may all have substantially the same minor diameter 52 . As shown, the cylindrical surface 50 of cable drums 35 also has an inboard array 54 of a plurality of helical grooves 51 having substantially the same minor diameters 52 . As can be appreciated from FIG. 3 , the helical grooves of the inboard array 54 have a minor diameter which is less than the minor diameter 52 of the helical grooves 51 of the outboard array 53 . An intermediate array 55 of the grooves 51 is interposed between the outboard array 53 and the inboard array 54 . The minor diameter 52 of helical grooves 51 in the intermediate array 55 is less than the minor diameter 52 of grooves 51 of the outboard array 53 and greater than the minor diameter 52 of helical grooves 51 of the inboard array 54 . In the preferred embodiment of the invention depicted in the drawings, the minor diameter 52 of grooves 51 of the intermediate array 55 varies substantially linearly from the minor diameter 52 of helical grooves 51 of outboard array 53 to the minor diameter 52 of helical grooves 51 of the inboard array 54 . It is to be appreciated that other variations may be introduced in the profile of the cable drums 35 in instances where the door sections 16 - 18 may have different weights so that the effective weight of the door varies nonlinearly as the door moves between the closed vertical position and the open horizontal position. Thus, the cable drums 35 are designed so that the diameter 52 of the helical grooves 51 along the axial extent of the cable drums 35 takes into account the weight of the door D in the vertical position being acted upon by gravity as a function of the position of the door D.

[0023] The counterbalance system 10 in the preferred embodiment disclosed herein has an extension spring assembly, generally indicated by the numeral 60 , associated with each of the cable drum mechanisms 30 . Inasmuch as the extension spring assemblies associated with each of the cable drums 35 are identical, only the extension spring assembly 60 seen in FIG. 2 as taken from the right side of FIG. 1 is described in detail. As best seen in FIG. 1 , the extension spring assembly 60 is generally aligned between a cable drum 35 and a rear ceiling support 61 which also supports the track T. The extension spring assembly 60 uses a conventional extension spring 62 of the type commonly employed in the industry. Attached to one end of extension spring 62 is an eye bolt 63 which is in turn attached to the rear ceiling support 61 by nut 64 which threads on the eye bolt 63 . This secures the extension spring 62 at its rear end to the rear ceiling support 61 . The front end of extension spring 62 opposite the eye bolt 64 has a sheave fork 65 permanently attached thereto. The sheave fork 65 mounts a sheave 66 on a pivot axis in the form of a bolt 67 .

[0024] To prevent possible damage to person or property in the event of failure of the extension spring 62 or components to which it is attached when extension spring 62 is tensioned, a conventional snubber assembly, generally indicated by the numeral 70 , is provided. The snubber assembly 70 consists of a snubber cable 71 which is threaded through the extension spring 62 and secured to the rear ceiling support 61 at one end and to the frame 12 at the other end at a position generally aligned with the axis of the extension spring 62 . The snubber cable 71 may be attached to the frame 12 by a clip 72 and a lag screw 73 extending through the clip 72 into the frame 12 .

[0025] The extension spring assembly 60 is interconnected with the door D by a counterbalance cable 75 . The counterbalance cable 75 may be of a construction commonly employed in the industry and has one extremity secured to a bottom bracket 76 on the bottom section 17 of the door according to conventional practice. The second end of the cable 75 is secured to a clip 77 which receives an S-hook 78 which may be attached to a horizontal angle iron 25 as best seen in FIG. 2 . The counterbalance cable 75 proceeds rearward of the door D from the clip 77 where it is threaded around the sheave 66 attached to the extension spring 62 which redirects the cable toward the door D. In particular, the cable proceeds forwardly from the sheave 66 where it engages the cable drum 35 , rather than a conventional sheave, prior to being directed downwardly to its attachment point at the bottom bracket 76 on the door D, as seen in FIGS. 2 and 3 .

[0026] As can be appreciated from FIGS. 2 and 3 , the counterbalance cable 75 extends from the sheave 66 and engages the top of the cable drum 35 where it is looped or reeved one full turn around the cable drum 35 and through an additional, approximately ninety degree, interval before the cable departs tangentially downwardly to where it is anchored to the bottom bracket 76 with the door in the closed position seen in the drawings. In the filly open position of the door D, the counterbalance cable 75 may engage the cable drum 35 through a slightly greater circumferential extent, e.g., on the order of approximately 135 degrees beyond one full turn. It is significant to operation of the door D that the tension supplied by extension spring 62 and the diameter of the helical grooves 51 be related to the effective weight of the door D at any point in moving between the open horizontal position and the closed vertical position so that the counterbalance cable 75 does not slip on the cable drum 35 at any time during the operating cycle of the door D. If necessary to insure adequate friction between the helical grooves 51 of cable drum 35 and counterbalance cable 75 to preclude slippage, the counterbalance cable 75 may be looped a second full turn or more around the cable drum 35 between the entry location of counterbalance cable 75 from sheave 66 and the departure location to the door D.

[0027] Once assembled and adjusted with appropriate extension springs 62 and configuration of the cable drums 35 , the door D enjoys improved operating parameters. As will be appreciated, the large minor diameter 52 of helical grooves 51 in the outboard array 53 reduces the linear tensioning effect of extension spring 62 to allow the door D to increasingly control door movement during the last 18 to 24 inches from closure so that the door D fully closes and maintains the closed vertical position. The diameter of the helical grooves 51 of inboard array 54 is selected so that in the final 12 to 18 inches of door movement prior to reaching the open horizontal position, the remaining weight of the door operating against the spring 62 is minimized to permit immediate stable positioning of the door D upon reaching the fully open position. The minor diameter 52 of helical grooves 51 in the intermediate array 55 , in varying normally substantially linearly between the helical grooves 51 of the outboard and inboard arrays 53 , 54 , provides a substantially uniform transition area accommodating the linear change in tension of extension spring 62 to provide smooth intermediate movement of the door D. The three arrays 53 , 54 and 55 of the helical grooves 51 allow the use of springs having an increased spring tension which assists in moving the door D upwardly out of the opening established by frame 12 and prevents slippage of the counterbalance cable 75 on the helical grooves 51 of the cable drums 35 .

[0028] Thus, it should be evident that the counterbalance system disclosed herein carries out one or more 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 embodiment disclosed herein without departing from the spirit of the invention, the scope of the invention herein being limited solely by the scope of the attached claims.