Abstract: This invention relates to a spring balance, and in particular to a spring balance for use with a sliding sash window. The invention provides a spring balance comprising a top assembly which is securable to a frame member, a bottom assembly which is securable to a sliding sash, a tension spring connected to the top assembly and to the bottom assembly, a torsion spring, a spiral rod, and a follower bush interconnecting the spiral rod and the torsion spring. The spring balance is adjustable at the top assembly, and includes a limit mechanism for limiting the range of adjustment, the limit mechanism preventing over-adjustment of the spring balance.

Abstract: A self-locking window operator has a reversible rotary drive shaft connectable in sequence to separate linkages respectively controlling movement of a casement relative to a surrounding frame and actuation of a fastening mechanism for releasably securing the casement when closed. The drive shaft is coupled by a worm gear to a drive input member rotatable about a drive axis and each linkage has a drive output member rotatable about separate axes offset from the drive axis. The input member has a drive pin co-operable with a respective pin receiving recess of each output member for sequentially operating the linkages.