Abstract: Balls such as table tennis balls or tennis balls are continuously fed to two pairs of adjacent flanged rollers of a ball-throwing head by a blower and two transfer ducts. Balls hit by the player are collected by a net and a trough, then fed back to the head. The rollers have separately variable speeds of rotation, a gap being provided between each pair of rollers and adapted to the diameter of the balls. The balls are directed alternately into each transfer duct, the opening of which is located opposite to each gap.

Abstract: The device is intended to cut-off the supply of electric power to a motor (4) automatically when this latter is locked rotationally under the action of a mechanical resistance.This device comprises balls (5) coupled for rotation with the motor (4) and displaceable under the action of the centrifugal force generated at the time of rotation of this motor, these balls (5) being in cooperating relation with an electric contact (9) in order to put the electric power supply of the motor (4) in circuit when this centrifugal force attains a certain threshold value and in order to put this supply out of circuit when this centrifugal force drops under the action of the mechanical resistance set up in opposition to the torque exerted by the motor.Utilization in particular in automatic devices for the control of opening and closing of garage doors.

Abstract: The emergency-opening sliding door comprises at least one door-leaf constituted by a panel which is stationarily fixed with respect to a panel frame attached to the door casing and at least one movable panel coupled to the frame by means of a roller track which permits displacement of the movable panel in sliding motion in a direction parallel to the fixed panel. The door is provided with an articulation system for permitting a movement of rotation of at least one of the panels about a vertical axis. The driving means for displacement in sliding motion are secured to the panel frame so as to be driven together with the frame in its movement of rotation.

Abstract: The device for guiding and actuating a vertical air-tight sliding door is suspended from two carriages each provided with a right-angled support bracket which is capable of horizontal displacement in a slideway. A bent plate which carries the door is rotatably mounted on an elbowed shaft fixed on each carriage. The bent plate carries a roller controlled by a fork and plate assembly which is pivotally mounted on the shaft and actuated by a jack. As the roller reaches the end of the track, the fork and plate assembly is permitted to rotate, with the result that the door carries out a compound movement of downward displacement and application against the wall.