text: This invention pertains to an operator for a casement-type window and, more particularly, to a torque operator which causes movement of the window sash by application of torque to have a force applied that is maintained most consistently perpendicular to a ray from the center of the driven gear connected to the window sash.
  A casement-type window has the sash mounted adjacent one edge at the top and bottom thereof on slider structure whereby, in the opening and closing movements of the window, said edge of the sash has both combined linear and pivotal movements with the linear movement being controlled by movement of the sliders along associated channel members fixed to the window frame. A constraining link is connected between the sash and the window frame for guiding the sash movement. A window of this general type is shown in Gill U.S. Pat. No. 2,948.027.
  Typically, a casement-type window operator has a manually-operated pivotal operator arm which is either directly or indirectly connected to the window sash for causing opening and closing movement thereof. Such structures require consideration of the various angles at which the operator arm transmits force to the window sash, taking into account the window action as one edge of the window sash is movable linearly by the sliders moving in the guide channels.
  Applying a window opening and/or closing force to a gear directly associated with the window sash avoids the problems encountered with a pivotally-mounted operator arm. Carrier U.S. Pat. No. 1,302,765 shows a casement window with a sector gear associated therewith which is operable by a worm to cause opening and closing movement of the window. In this patent, the sector gear has its effective center coaxial with the pivot mounting for the window sash and the disclosed structure would not operate with a casement-type window wherein the pivotally-mounted edge of the sash has linear movement as well as pivoting movement during opening and closing of the window.