SAFETY LOCK FOR SLIDING SASH WINDOW

A safety lock is disclosed for a sliding sash window. The lock allows a sliding sash window to be locked in a partially open position but prevents illegal access through a window. The safety lock is for a window with an inner sash and an outer sash and comprises a sliding lock pin located in one corner of the inner sliding sash on a surface normal to the direction of movement of the sliding sash, a corner section at the corner of the inner sliding sash, having a passage for the sliding lock pin to move into a locked position with the outer sash, and a a detent located in the outer sash to engage with the sliding lock pin when in the locked position, the detent positioned so that the inner sash may move a predetermined distance relative to the outer sash before the lock pin engages the detent.