RAPIDLY CLOSING WATERTIGHT DOORS IN SHIPS WHEN SUCH DOORS ARE WORKED VERTICALLY
Year: 1886

page_text: Date of Application, 1st June, 1886.
Complete Left, 25th Jan., 1887.
Complete Accepted, 4th Mar., 1887.
I, CHARLES DAWE H.M.S. Curlew, Channel Fleet, Engineer in Royal Navy, do
hereby declare the nature of my invention for RAPIDLY CLOSING WATERTIGHT DOORS IN
SHIPS WHEN SUCH DOORS ARE WORKED VERTICALLY, to be as follows:-
Such doors are usually raised & lowered by means of a screw and nut, the screw
resting on a bearing on the frame of the door and the nut being fixed to the door.
The raising and lowering of the door is thus accomplished by turning the screw one
way or the other.
I introduce a second screw of about the same diameter and length as the first but
of a coarser pitch. This screw which I call the lowering screw in distinction to the
first which I call the hoisting screw is placed parallel to the first and is geared with
it by a chain of toothed wheels in such a manner that the rates of advance of the nuts
on the two screws are the same.
By means of a system of levers I take the weight of the door off the hoisting screw
and put a pressure on the lowering screw and the door then descends, turning both
screws in its descent.
In the drawing c. d. e. f is the watertight door sliding up and down in the
frame a. b. g. h. BD is the hoisting screw and A. C. the lowering screw. They rest
in fixed bearings at B and A. M the nut of the hoisting screw is fixed to the door,
N the nut of the lowering screw is unable to turn but is capable of vertical motion;
at its lower end it is provided with a stud F. The two screws are geared together
with toothed wheels so that their relative motions shall be in inverse ratio to their
pitches. E and H are studs fixed in the door, the lever E G rests on the nut N at F
and GI is a rod connecting the two levers E G and HK. L is a stop pin screwed
into the door to prevent the lever HK being pushed down too far.
A downward pressure at K produces a greater pressure on the stud F, and when
the pressure is sufficiently increased the weight of the door is wholly removed from
the hoisting screw and put on the lowering screw, The result of this is that the door

page_text: descends similarly to the nut of an Archimedean screw and the hoisting screw is by
the action of the toothed wheels turned so that it shall not jamb in its nut. The
descent of the door is steady and can be stopped at any point by releasing the lever K,
or it may be checked by removing a portion of the pressure on K when a part of the
weight of the door is put on the hoisting screw and a brake is thus formed.
I propose to fit a light casing around both screws to protect them from coal dust,
and if necessary to put spring buffers at the bottoms of the screws to prevent the door
being lowered too forcibly into its place.
Having thus described the nature of my invention I declare that its essential
points are
1st. The introduction of a lowering screw of coarse pitch parallel to the screw
usually fitted, the screws being geared together so that the rates of advance of the
nuts are the same.
2nd. The adoption of a system of levers by which the weight of the door is taken
off the hoisting screw, a pressure put on the lowering screw and this pressure continues
under the control of a man stationed at the door entrance during the whole time of the
descent of the door.

page_text: I CHARLES DAWE Chief Engineer in Royal Navy H.M.S. Curlew, Channel Fleet,
do hereby declare the nature of this invention and in what manner the same is to
be performed, to be particularly described and ascertained in and by the following
statement:
Such doors are usually raised and lowered by means of a screw and nut, the screw
resting on a bearing on the frame of the door and the nut being fixed to the door.
The raising and lowering of the door is thus accomplished by turning the screw one
way or the other.
I introduce a second screw of about the same diameter and length as the first but
of a coarser pitch. This screw which I call the lowering screw in distinction to the
first which I call the hoisting screw is placed parallel to the first and is geared with it
by a chain of toothed wheels in such a manner that the rates of advance of the nuts
on the two screws are the same.
By means of a system of levers I take the weight of the door off the hoisting screw
and put a pressure on the lowering screw and the door then descends turning both
screws in its descent.
In the drawing c d e f is the watertight door sliding up and down in the
frame abgh; BD is the hoisting screw and AC the lowering screw. They rest in
fixed bearings at B and A. M, the nut of the hoisting screw is fixed to the door,
N the nut of the lowering screw is unable to turn but is capable of vertical motion; at
its lower end it is provided with a stud F. The two screws are geared together with
toothed wheels so that their relative motions shall be in inverse ratio to their pitches.
E and H are studs fixed in the door, the lever E G rests on the nut N at F and GI is.
a rod connecting the two levers E G and HK. L is a stop pin screwed into the door
to prevent the lever H K being pushed down too far.
A downward pressure at K produces a greater pressure on the stud F and when the
pressure is sufficiently increased the weight of the door is wholly removed from the
hoisting screw and put on the lowering screw. The result of this is that the door
descends similarly to the nut of an archimedean screw and the hoisting screw is by
the action of the toothed wheels turned so that it shall not jamb in its nut. The
descent of the door. is steady and can be stopped at any point by releasing the lever K
or it may be checked by removing a portion of the pressure on K when a part of the
weight of the door is put on the hoisting screw and a brake is thus formed.
I propose to fit a light casing around both screws to protect them from coal dust
and if necessary to put spring buffers at the bottoms of the screws to prevent the door
being lowered too forcibly into its place.

page_text: Having thus described the nature of my invention I declare that its essential
points are
1st. The introduction of a lowering screw of coarse pitch parallel to the screw
usually fitted, the screws being geared together so that the rates of advance of the
nuts are the same.
2nd. The adoption of a system of levers by which the weight of the door is taken
off the hoisting screw, a pressure put on the lowering screw and this pressure continued
under the control of a man stationed at the door entrance during the whole time of the
descent of the door.
C. DAWE,
Applicant.