An assembly for a bay, including: - a frame intended to be mounted in the bay, - a leaf, in particular of the window type, movably mounted on the frame between an open position wherein it releases a passage through the frame and a closed position wherein it seals said passage, the leaf being equipped with a control rod intended to be moved by a control handle between a locking position and an unlocking position, - a track delimiting an aperture having a first portion extending according to a longitudinal axis (X'-X), - at least one hinged arm having a first end freely mounted in rotation on the frame or on the leaf about an axis of rotation (Z'-Z), and an opposite second end slidably mounted in the aperture between a first position wherein the leaf is in the closed position, and a second position wherein the leaf is in a predetermined open position, - the aperture having a second portion extending along an oblique direction (Y'-Y) relative to the longitudinal axis (X'-X), the second portion being shaped to receive the second end of the hinged arm in the second position, - the control rod being arranged for driving in rotation the hinged arm about the axis of rotation (Z'-Z) between: - a locking position wherein the hinged arm and the oblique direction (Y'-Y) of the second portion of the aperture form an angle (β) having a first value adapted so that the second end of the hinged arm is in stable equilibrium in the second portion of the aperture, and - an unlocking position wherein said angle (β) has a second value lower than the first value, the second value being adapted so that the second end of the hinged arm is in unstable equilibrium in the second portion of the aperture, characterized in that the assembly includes means for actuating the second end of the hinged arm arranged to dislodge said second end from the second portion of the aperture when the control rod is in the unlocking position. - a frame intended to be mounted in the bay, - a leaf, in particular of the window type, movably mounted on the frame between an open position wherein it releases a passage through the frame and a closed position wherein it seals said passage, the leaf being equipped with a control rod intended to be moved by a control handle between a locking position and an unlocking position, - a track delimiting an aperture having a first portion extending according to a longitudinal axis (X'-X), - at least one hinged arm having a first end freely mounted in rotation on the frame or on the leaf about an axis of rotation (Z'-Z), and an opposite second end slidably mounted in the aperture between a first position wherein the leaf is in the closed position, and a second position wherein the leaf is in a predetermined open position, - the aperture having a second portion extending along an oblique direction (Y'-Y) relative to the longitudinal axis (X'-X), the second portion being shaped to receive the second end of the hinged arm in the second position, - the control rod being arranged for driving in rotation the hinged arm about the axis of rotation (Z'-Z) between: - a locking position wherein the hinged arm and the oblique direction (Y'-Y) of the second portion of the aperture form an angle (β) having a first value adapted so that the second end of the hinged arm is in stable equilibrium in the second portion of the aperture, and - an unlocking position wherein said angle (β) has a second value lower than the first value, the second value being adapted so that the second end of the hinged arm is in unstable equilibrium in the second portion of the aperture,