Claims
- 1. A counterbalance system for an overhead door, such door being adapted for installation in a doorway to be movable from a closed position wherein it is arranged in a generally vertical orientation closing the doorway and an open position wherein it is disposed above the doorway and at least partially horizontally oriented, guide means for acting between the lateral edges of the door and the sides of the doorway to guide the door in its movement between open and closed positions, said counterbalance system comprising:
- a spool adapted to be rotatably mounted on structure surrounding the doorway and a first cable connected between said spool and said door such that rotation of said spool in a direction to wind the cable onto the spool applies through said first cable a force urging the door to move in the opening direction, the weight of the door as it moves away from the closed position being supported initially by said first cable and subsequently to an increasing extent by said guide means as the door moves towards the fully open position;
- a winding drum fixed to rotate with said spool and comprising: a hub defining therein a longitudinal axis and an axial bore extending through said drum, said drum having an outer periphery configured with a pair of adjacent continuous peripheral grooves extending generally helically thereon and progressing from one end of the drum to the other;
- said drum defining successively in the axial direction:
- a first region wherein said pair of grooves defines a plurality of turns about the axis at a constant radius; and
- a second region wherein the radius of said grooves from said axis increases progressively from said constant radius to a maximum radius that is at least about twice said constant radius;
- a pair of elongate flexible load transmitting elements connected to said drum and laid in respective ones of said pair of grooves to unwind from said drum as said spool rotates to wind the cable thereon, and vice versa;
- said load-transmitting elements freely suspending a counterweight such that the mass thereof provides a torque acting on said drum, said spool, and said first cable to urge said door in the opening direction, said torque having a magnitude that is proportional to the radius from said axis of the point on said drum at which said pair of force transmitting elements part from their respective continuous peripheral grooves;
- wherein said counterweight is independently suspended by each of said force transmitting elements such that in the event of failure of one of said force transmitting elements it will remain suspended by the other.
- 2. A counterbalance system as claimed in claim 1 wherein said drum includes a third region wherein said pair of grooves continue at said maximum radius through a plurality of turns about said axis.
- 3. A counterbalance system as claimed in claim 1 wherein said drum has associated therewith winding means comprising a plurality of formations that define locations that are angularly spaced about the axis of said drum, said formations being selectively engageable at each said location by a torquing tool by means of which the drum can be rotated about said axis.
- 4. A counterbalance system as claimed in claim 1 wherein said drum and said spool are carried on a shaft for mounting to rotate at the top of the doorway, said drum being positioned in proximity of one edge of the doorway, said load transmitting elements comprising a pair of cables attached to the drum in said first region and laid side-by-side in said pair of grooves and extending from said drum each in a depending loop that has an opposite side supported on a fixed mounting and the counterweight being suspended from a pulley carried by said loops.
- 5. A counterbalance system as claimed in claim 4 further including a second drum wherein each of said drums is provided at opposite ends of said shaft, each of said drums having an associated pair of cables extending in a depending loop and suspending a respective counterweight.
- 6. A counterbalance system as claimed in claim 1 including a tubular housing vertically positioned to surround and enclose said counterweight during vertical movement thereof.
- 7. For use in a counterbalance system for a vertically movable door, a drum comprising a hub defining therein an axial through bore, said drum having an outer periphery configured with a pair of side-by-side continuous grooves extending generally helically thereon and each progressing from one end of the drum to the other, the drum having a central axis and defining in the axial direction a first region, wherein said pair of grooves define a plurality of turns about said axis at a constant radius, a second region wherein the radius of said pair of grooves from said axis increases progressively from said constant radius to a maximum radius that is of the order of at least twice said constant radius and a third region wherein said pair of grooves continue at said maximum radius through a plurality of turns about said axis, said drum comprising only said first region, said second region and said third region, said drum further being adapted to have laid side-by-side in said pair of grooves a pair of cables, said drum having attachment means thereon for affixing corresponding ends of said pair of cables to the drum in the vicinity of that end of said first region that is furthest from said second region.
- 8. A drum as claimed in claim 7 wherein the length of said pair of grooves at said maximum radius corresponds to the length of said pair of grooves through said second region.
- 9. A drum as claimed in claim 7 wherein said hub carries means for forming a driving engagement with a shaft passed through said axial bore.
- 10. A drum as claimed in claim 9 wherein said means comprises a radially extending clamping screw threadedly engaged in a bore in said hub that a tip of said clamping screw can be extended into said axial bore.
- 11. A drum as claimed in claim 7 including receiving means to accept a torque arm at a plurality of positions angularly spaced about said axis, whereby said drum can be rotated by means of a torquing tool engaged with any of said receiving means.
- 12. A drum as claimed in claim 7 including clamping means for releasably clamping said drum to a shaft passing through said axial bore, and receiving means for cooperation with a torquing tool to effect angular rotation of said drum about such shaft when said clamping means is released.
- 13. A drum as claimed in claim 7 wherein said drum defines a third region wherein said pair of grooves continue at said maximum radius through a plurality of turns about said axis, said hub carrying means for forming a driving engagement with a shaft passed through said axial bore, and receiving means to accept a torque arm at a plurality of positions angularly spaced about said axis, whereby said drum can be rotated by means of a torquing tool engaged with any of said receiving means.
- 14. A drum as claimed in claim 12, wherein said receiving means is formed on a collar that is integral with said drum and comprise a plurality of bores in said collar extending in a radial direction.
- 15. A winding drum for use in a counterbalance system for an overhead door installation of the type that has door sections guided in tracks at their opposite edges to move upwardly from a closed position to an open position, the weight of the door being balanced throughout the opening movement by a counterweight suspended on cable means wound on the drum, wherein said winding drum comprises:
- a body having an axial bore adapted to receive a shaft;
- said body being defined by an outer periphery only having axially adjacent first, second and third regions, said outer periphery configured with a pair of adjacent continuous grooves extending generally helically thereon around the axis of said bore and progressing from one end of the drum to the other through all of said regions;
- said pair of grooves extending side-by-side and in said first region defining a plurality of turns at constant radius about said axis, in said second region defining a plurality of turns the radius of which increases progressively from said constant radius adjacent said first region to a maximum radius that is of the order of at least twice said constant radius, and in said third region in which a said pair of grooves continue at said maximum radius throughout a plurality of turns about said axis;
- whereby in use a pair of cables can be laid side-by-side in said pair of grooves and upon rotation of said drum will wind on or off in unison, the effective torque applied to said drum by the counterweight suspended on said cables varying according to the point at which the cables disengage from the drum.
- 16. A winding drum as claimed in claim 15 wherein the rate of increase of the radius of said pair of grooves is substantially constant throughout the length of said second region.
- 17. A winding drum as claimed in claim 15 including means for releasably clamping said drum to a shaft inserted in said axial bore, and receiving means for cooperation with a torquing tool to effect angular rotation of said drum about said shaft when said clamping means is released, such that in use the pair of cables can be wound onto or unwound from the drum without rotation of the shaft.
- 18. A winding drum as claimed in claim 17 wherein said receiving means is formed on a collar that is integral with said drum and comprises a plurality of angularly spaced sockets extending in radial directions in said collar.
Priority Claims (1)
Number |
Date |
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Kind |
2006373 |
Dec 1989 |
CAX |
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CROSS REFERENCE TO RELATED APPLICATION
This is a Continuation-in-Part of my copending U.S. patent application No. 07/507,754 filed Apr. 12, 1990 now U.S. Pat. No. 5,103,890.
Continuation in Parts (1)
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Number |
Date |
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Parent |
507754 |
Apr 1990 |
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