IMPROVEMENTS IN AND CONNECTED WITH WATER-TIGHT DOORS FOR SHIPS
Year: 1880

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PROVISIONAL SPECIFICATION left by Samuel Crawford at the Office of
the Commissioners of Patents on the 4th December 1880.
SAMUEL CRAWFORD, of Clyde Bank, in the County of Dumbarton, North
Britain. "IMPROVEMENTS IN AND CONNECTED WITH WATER-TIGHT DOORS FOR
SHIPS."
This Invention relates to certain improvements in the construction, fitting, and
operating of water-tight or sluice doors for the bulk-heads of ships, and is specially
designed to enable such doors to be rapidly and easily closed, to stop the com-
munication between any one water-tight compartment and that next to it, on the
occurrence of a collision or similar accident to the vessel.
The main improvement of the Invention consists in the application of an
arrangement of new disengaging apparatus for throwing out of or into gear the
screw or worm which is commonly used for raising and lowering water-tight
doors, so that whilst the slow working and powerful screw can be employed in
raising the door it may be simply disengaged at pleasure to enable the door to fall
by its own weight.
The water-tight door is fitted in the usual vertical flanged framing with truly
planed surfaces and slightly bevilled sides, so that the door in its lower position
can be made quite water-tight. A screw rack, preferably segmental, is formed or
fitted to one side of the door, extending its whole length vertically and at the
centre. A worm or screw on a long vertical shaft is fitted to gear into this rack
to raise the door, the vertical shaft being carried in bearings in cross beams or
brackets on the door framing, and at the top end in a bracket fixed to one of the
vessel's deck framings.
Under the present improvements this vertical screw shaft is carried in eccentric
bearing bushes fitted free to revolve in these cross beams. These eccentric bushes
are prolonged through the carrying beams, and have spur pinions formed or cast
on them, into which similar pinions on a second vertical shaft are made to gear.
This second shaft is fitted alongside and parallel to the first, and terminates with
a square end at the bottom within convenient reach from the floor of the com-
partment, so that a wrench or screw key can be applied to turn it; and it also
terminates above in a similar manner close to the end of the screw shaft, where the

page_text: latter is turned to raise the door. The screw shaft turns freely in its eccentric
bushes, and the pinions and second shaft remain inactive during the raising of the
door and hold the bushes in their normal position; but when the door is to be
lowered this second shaft is turned round half a revolution by means of a screw
key or spanner either from the lower compartments of the vessel, or from the
decks above, and thereby the spur pinions and eccentric bearing bushes are
revolved to the same extent, so that the screw shaft and screw or worm are lifted
away in the bearings quite clear of the screw rack, and the door being no longer
supported is free to drop to its lowest closed position.
To prevent too sudden a fall of the door, and also partly to form guides, two
long rods are fitted to the upper edge of the door, and have pistons fitted at their
ends passing into long cylinders or barrels closed at each end, containing air or
water, with stuffing boxes if required at the lower ends where the rods pass
through. The pistons are a tight fit, and when the door is allowed to drop these
compress the air in the lower ends of their barrels, and may also exhaust or rarefy
the air above and thereby form an efficient brake. These cylinders or barrels have
air holes or openings near each end fitted with regulating taps, so that the air can
be gradually admitted and allowed to escape at either end, and afford a ready
means of controlling the lowering or fall of the door.
The door being slightly wedge shaped to fit tightly in its seat is sometimes liable
to vibrate when being raised or lowered. To obviate or remove this objection a
vertical guide groove is formed in the side of the door, into which a friction pulley
carried in bearings in one of the cross beams or brackets fits and prevents lateral
motion of the door. The teeth of the rack and worm are preferably made rounded
at their outer edges to assist the putting of them into gear when turning the
eccentrics, and to prevent jarring or breakage in withdrawing the screw to lower
the door.