Improvements in Propeller Dams for Vessels.
Year: 1889

page_text: Date of Application, 8th Oct., 1889-Accepted, 9th Nov., 1889
COMPLETE SPECIFICATION.
Improvements in Propeller Dams for Vessels.
1, GEORGE CLARKE, of 85, Forrest Street, Jersey City, New Jersey, United
States of America, Engineer, do hereby declare the nature of the said invention and
in what manner the same is to be performed to be particularly described and
ascertained in and by the following statement :-
The object of my invention is to construct a propeller dam for, vessels of the twin
screw type, by which only the propeller to be repaired will be encased and not the
stern of the vessel as in ordinary coffer dams of this class.
Referring to the drawings: Fig. 1, is a sectional elevation of my improved
propeller dam, showing its position in relation to the vessel; Fig. 2, is a section on
the line 1-2, Fig. 1; Fig. 8, is a section on the line 3, 4, Fig. 1. Fig. 4, is a
sectional view of the stern of the vessel with one of the dams attached; and Fig. 5,
is a view of the dam applied to a vessel of the single screw type. A, A, are the
heads of the dam made preferably of wood, and having stay bars, a, of wood or iron,
and connecting these two heads together is a body, B, of the shape shown in Fig. 1.
This body is also made preferably of wood or sheet-iron, and suitably stayed by
angle bars, b.
There is sufficient iron used in the construction of this propeller dam to allow it to
sink a certain depth in the water, so that it can be readily shipped in position around
the propeller shaft.
The head, A, is slotted, as shown in Fig. 1, and adapted to grooves, c, in this head,
is a gate, ; The lower portion of this gate is cut away for the reception of the
bracket, D, of the propeller, and a portion of the head, A, is also cut away to
receive this bracket D.
'
On the top of the gate, C, is a bar, F, through which pass bolts, ", hung to the
head, A, at,, Fig. 1, and adapted to these bolts are handled nuts, f, so that when
the gate is placed in position, the handled nuts are turned, making a tight fit between
the gate and the head, A. Suitable strips of packing may be placed around the gate
to prevent water from gaining access after the propeller dam has been pumped clear
of the water in the first place.
Attached to the side, H', of the vessel is a plate, H, and on each side of the
propeller dam are plates, G, having orifices which correspond with orifices in the
plate, H. Bolts are adapted to these orifices and nuts applied, which will hold
the propeller dam in position with respect to the vessel, as the propeller-dan is secured
to the vessel as well as to the propeller-bracket. To prevent the outer end of the
propeller dam from lifting, I place struts or shores from the dam to the underside of
the vessel, as shown in Fig. 4.
The propeller-dam is of a size sufficient to take in the blades, e, of the vessel, and
is shifted in position, as shown by dotted lines in Figs. 1 and 4, after which it is
turned up, as shown by full lines in Figs. 1 and 4, and secured to the vessel.
After
it has been pumped out, workmen can enter the dam and remove one or more blades
of the propeller for repairs, and can gain access to any portion of the propeller as
circumstances require.
I have shown in the drawing the propeller having three blades, but any number of
blades may be used as circumstances may require. By making the propeller dam in
the shape shown, it can be applied either to the right or left hand propeller without
alteration as shown in Fig. 4.
The opening in the head, A, is made sufficiently large in order to take in the
propeller without enlarging the dam.
In Fig. 5, I have shown the propeller-dam adapted to a vessel of the single screw
type, the dam, in this instance, being placed in the screw-space between the rudder-
post and the stern-post of the vessel.

page_text: Having now particularly described and ascertained the nature of the said Inven-
tion and in what manner the same is to he performed, 1 declare that what I
claim is.
1. A propeller or coffer dam for the propellers of vessels, said dam being of such
shape and size as to encompass the propeller without encompassing the stern of the
vessel.
•
2. The combination of a propeller or cofferdam for vessels, of the heads, A, A',
with the body, B, the head, A, having an opening for the reception of the shank or
bracket of the propeller and a gate for closing said opening, substantially as herein-
before specified.
3. The combination in a propeller or coffer dain for vessels having two heads, one
of which is adapted to receive the shank or bracket of the propeller, said dam having
a body of the form substantially as shown and described, so that the said propeller-
dam will fit over either. the right or left hand propeller, substantially as hereinhefore
described.
4. The combination of the heads, A, A', the body, B, with securing flanges on
each side of the body, said flanges being adapted to be secured to flanges on the
vessel, substantially as hereinbefore described.
5. The combination of the heads, A, A¹, of the body, B, an opening in the head, A,
for the reception of the shank or bracket of the propeller, with a gate, C, adapted to
said opening, a bar, F, secured to the head, with bolts passing through said bars and
nuts for forcing the gate to its seat.
Dated this 27th day of September 1889.
DAY, DAVIES & HUNT,
321, High Holborn, London, W.C., Agents for the Applicant.