Patent ID: 11885162
Assignee: NAKANISHI INDUSTRIAL CO., LTD.
Field: Civil engineering (Other fields)
Classification: CPC E | IPC E

Claim 4:
5. A counter balance device for a sash window, comprising
a pipe extending vertically along a window frame;
a spiral rod extending axially inside the pipe, the spiral rod having an upper end portion disposed in the pipe, a lower end portion protruding from a lower end of the pipe, and a screw portion extending axially between the upper and lower end portions;
a coupling rotatably disposed near the lower end of the pipe and having a slot through which extends the screw portion of the spiral rod;
a torsion spring extending axially inside the pipe and having a lower end fixed to the coupling to rotate therewith and an upper end fixed near an upper end of the pipe and to which an initial spring force corresponding to the window's weight is applied by winding the spiral rod in a direction to wind the torsion spring;
a slide block disposed to slide vertically along the window frame and connected to move with the window;
a rotation shaft rotatably mounted on the slide block and connected to the lower end of the spiral rod protruding from the pipe; and
a buffer spring interposed between the rotation shaft and the slide block and having a spring force larger than the initial spring force of the torsion spring for urging the rotation shaft in a direction reverse to the winding direction of the spiral rod.