| 摘要 |
A plastic liner is attached to the jamb of a vertical sliding window and has a continuous "U" channel with the channel opening facing the window opening and a block member slidingly engaged in the channel adapted to be coupled to the window sash and to one end of an elongated coil spring located in the channel which is attached at its other end to the liner. Primary frictional braking force is provided by a wing member inside the channel pushing against the block member so it rubs against a wall of the channel. The block member rides over a "T" shaped rail in the channel and carries a set screw which can be reached through the channel opening to be threaded through the block member into contact with the top surface of the rail member for manually adjusting the frictional braking force on the block member.
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