Frictional Drop Resistance for Sash Counterbalanced by Curl Springs
AssigneeCaldwell Manufacturing Company
InventorJeffrey Tuller
Life of this patent
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Abstract
Window sash counterbalances using curl springs and holders can increase resistance to sash drop without causing sash hop by using a high coefficient of friction bearing surfaces against which curled up coils of curl springs slide when uncurling or re-curling. The higher friction bearing material produces more frictional resistance to spring uncurling than to spring re-curling and thus resists drop without causing hop. This allows a wider range of sash weights to be counterbalanced by a fewer number of counterbalance forces, saves manufacturing cost.
Claims16
A combination of a curl spring and a holder used in a window sash counterbalance system, the combination comprising:
- the holder being molded of resin material to hold curled coils of the curl spring and permit uncurled lengths of the curl spring to pass out of the holder;
- a bearing surface of the holder engaged by the curled coils of the curl spring being formed of a frictional resin material having a higher coefficient of friction than the resin material forming the holder so that the bearing surface offers frictional resistance to uncoiling of the curl spring and thereby resists sash drop.
A curl spring holder formed of resin and adapted to serve in a window sash balance system, the curl spring holder comprising:
- a bearing surface of the holder engaging curled coils of the curl spring to support the curl spring against force tending to uncurl the curl spring;
- the bearing surface being formed of a frictional resin material having a higher coefficient of friction than the holder resin to offer frictional resistance to uncurling of the curl spring, which thereby resists sash drop.
A method of reducing the tendency of a counterbalanced sash to drop when the sash is counterbalanced by a curl spring, the method comprising:
- forming a resin holder for the curl spring with a bearing surface engaging curled coils of the curl spring, the bearing surface being formed of a frictional resin having a higher coefficient of friction than the holder resin, and the engagement of curled coils of the curl spring with the frictional resin of the bearing surface providing frictional resistance against uncurling of the curl spring, which thereby resists sash drop.
A method of counterbalancing window sash in a range of sash weights with a curl spring assembly having a single counterbalancing force, the method comprising:
- engaging curled coils of the curl springs of the assembly with a high coefficient of friction bearing surface disposed to resist uncoiling of the curl springs so that the curl spring assembly avoids drop of heavier sash without causing hop of lighter sash.
A combination of a curl spring and holder used in a window sash counterbalance system, the combination comprising:
- a holder bearing surface engaging curled coils of the curl spring to provide frictional resistance to uncurling of the curl spring;
- and
- the frictional resistance being chosen by selecting a high coefficient of friction for the bearing surface.
Dependencies are inferred from the claim text.