23,564. Chaddock, G. A. Oct. 28. Bulkhead doors.-Relates to bulkhead doors of the kind described in Specifications Nos. 3403 and 21,740, A.D. 1902. Fig. 3 shows a door A, which is mounted to slide vertically and turn on a central shaft D, and is supported on ball or other bearings carried by a sleeve L. Pins m, Fig. 10, of the door slide in vertical grooves k in a fixed guide-sleeve K when the sleeve L, with the door, is raised clear of the sill E by a lever and pinions gearing with racks and slide down inclined grooves n in the sleeve when the door is released, thus causing the door to swivel through an angle of 90‹ into an open position, and back again. The pins n are moved from the vertical grooves k into the inclined grooves n by inclined projections l of the sleeve L, or by inclined projectionsp of the door coming in contact with projections o of the frame. Pins of the door move in grooves in the frame to prevent the pins m from re-entering the grooves n when the door is raised again. The door is partially balanced by weighted arms fixed to the operating pinions, and can be secured in an open position by an eccentric or projection u engaging with a stud v projecting from the shaft D. The door can be released by a handle U of the catch, or by rotating the shaft by a handle H, or from a distance by a worm-shaft Y and worm-wheel X. A number of doors and shutters B may be operated simultaneously by an officer on the bridge, or from a central station, by the worm gearing X, Y, and screwed shafts D working through threaded blocks F, which are fixed to the shutters and move vertically to a limited extent in recesses q in the doors. The edges of the shutter and door are formed with interlocking tongues and grooves, the inside faces of the shutter panels and the bottom edge of the door are recessed and grooved to receive packing- material, and the door is wedged against the frame to make a tight joint by inclined projections of the door and frame coming in contact with one another. The lower edges of the doors are slotted to engage with hooked studs of the sill. To facilitate this connection, the shaft may be made of two parts connected by a square pin and socket, and a portion of the socket J is detachable. In a modification, shown in Fig. 14, the door A is pivoted at one side on a vertical shaft D, and is raised and lowered by a lever S and seating L, or by the handle H, or worm gearing X, Y, bevel gearing 8, 6, a threaded sleeve F, and a central screw which is provided with a flange f adapted to engage with a forked angle-plate 2 fixed to the centre of the upper rail of the door. The lower hinge 14 of the door is arranged to slide on a slotted weighted sleeve 15 mounted to slide on pins 16 of the shaft D, and an inclined upper edge 17 of the hinge bears against a pin 18 of the sleeve. This arrangement allows the edge 17 to slide past the pin when the door is held open by a person passing through it. The cam-sleeve K is fixed near the top of the door, which may be balanced by weighted levers under the floor or in a casing above the door. Projections I, I<1> of the door engage with wedging recesses and projections i of the frame E when the door is closed.