| 摘要 |
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.
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