Improvements in Propeller Dams for Twin Screw Vessels.
Year: 1892

page_text: Date of Application, 26th Apr., 1892
Complete Specification Left, 25th Jan., 1893-Accepted, 4th Mar., 1893
PROVISIONAL SPECIFICATION.
Improvements in Propeller Dams for Twin Screw Vessels.
I, JOHN HAUG of 206 Walnut Place in the City of Philadelphia, State of
Pennsylvania, United States of America, Marine Engineer and Architect do hereby
declare the nature of my invention to be as follows:-
The object of my invention is to so construct a propeller dam for twin screw
vessels that the same can be readily moved into position to enclose the propeller
and can be as readily removed after inspection or repair has been completed, the
dam being also constructed in such manner as to be applicable to either of the
propellers and to be readily kept tight or free from water during the time that
inspection or repair is being carried on.
According to my invention I provide a rectangular box or casing composed of
suitable timbers, secured, by preference to framework of wrought iron or steel bars.
This box or casing is open at top and bottom and to the outer side of the bottom of
this box a similarly constructed semicircular box or casing is connected by means
of a suitable hinge or pivot rod whereby the two parts of the dam can be opened
so as to permit of the application of the dam to and its removal from the
propeller.
Suitable semi-circular openings are formed in the bottoms of the fore and aft
sides of the upper box and in the tops of the fore and aft sides of the lower box for
the reception of the bracket bearing which projects from the hull of the vessel and
carries the propeller shaft.
By forming openings in both the fore and aft sides of the boxes the dam is
rendered applicable to either the starboard or port propeller, the openings in the
forward sides of the boxes always embracing the bracket bearing and the openings
in the after sides of the boxes being then closed by means of a suitable cover plug
or stopper.
Various means may be adopted for opening and closing the lower box of the dam
and for retaining the same in position when closed for example a rod pivoted at its
lower end to the forward side of the lower box and threaded at the upper end for
adaptation to a nut pivoted to a bearing mounted at the top of the upper box, one
of these operating devices being intended to be employed both at the forward and
aft sides of the dam.
At the inner side of the dam hooked catches may be provided for engaging with
a projecting flange on the framework at the inner portion of the lower box and the
pivoted rod may have arms connected by rods to operating levers at the top of the
upper box so that the catches can be readily operated to engage with or release
the flanged frame of the lower box.
By making the dam in the form of two boxes the lower of which is closed except
at the top and the upper closed except at the top and bottom, and by hinging the
lower box to the upper one at the outer side, the dam can be applied to or removed
from the propeller with the greatest facility and can be readily kept tight or free
from water when in use, the only joint being one extending around the dam so that
the length of the joint is less than if it extended vertically from the bottom to the
top of the dam.
Although I prefer the semi-cylindrical form for the lower box of the dam
because of the minimum displacement which results when this form is adopted it
may be triangular rectangular or of any other available shape.
A
1 1005

page_text: COMPLETE SPECIFICATION.
Improvements in Propeller Dams for Twin Screw Vessels.
I, JOHN HAUG of 206 Walnut Place, in the City of Philadelphia, State of
Pennsylvania, United States of America, Marine Engineer and Architect 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:-
The object of my invention is to so construct a propeller dam for twin screw
vessels that the same can be readily moved into position to enclose the propeller,
and can be as readily removed after inspection or repair has been completed, the
dam being also constructed in such manner as to be applicable to either of the
propellers and to be readily kept tight or free from water during the time that
inspection or repair is being carried on.
In the accompanying drawing:-
Figure 1 is a transverse sectional view of my improved propeller dam for twin
screw vessels showing the same applied to the starboard screw;
Figure 2 is a longitudinal section on the line 1-2 Figure 1;
Figure 3 is a rear elevation illustrating the manner of applying the dam to or
removing it from the propeller; and
Figure 4 is a transverse sectional view of a modified form of the dam.
In Figures 1, and 3 A represents a rectangular box or casing composed of
suitable timbers secured, by preference, to a framework of wrought iron or steel
bars, and open at the top and bottom. B is a semicylindrical box likewise similarly
constructed of wood and metal, the said box B being hung to the outer side of the
bottom of the box A by means of a suitable hinge or pivot rod a, whereby the two
parts of the dam can be permitted to swing open, as shown in Figure 3, to permit
of the application of the dam to, and its removal from the propeller, and of being
closed, as shown in Figures 1 and 2, after the dam has been applied to the
propeller.
Suitable semicircular openings 6 are formed in the bottoms of the fore and aft
sides of the box A and in the tops of the fore and aft sides of the box B for the
reception of the bracket bearing d which projects from the hull of the vessel and
carries the propeller shaft.
By forming openings in both the fore and aft sides of the boxes A and B the
dam is rendered applicable to either the starboard or port propeller, the openings
in the forward sides of the boxes always embracing the bracket bearing, and the
openings in the after sides of the boxes being then closed by means of a suitable
plug or stopper D, as shown in Figure 2.
Various means may be adopted for opening and closing the lower box B of the
dam and for retaining the same in position when closed.
2
In the drawing I have shown a rod f pivoted at its lower end to the forward side
of the box B and threaded at the upper end for adaptation to a nut 9 pivoted to a
bearing / mounted at the top of the box A, one of these operating devices being
intended to be employed both at the forward and aft sides of the dam.
At the inner side of the dam I have shown a rod i having hooked catches m for
engaging with a projecting flange on the frame-work at the inner portion of the
box B, as shown in Figure 1, the said rod i having arms n connected by rods p to
operating levers s at the top of the box A so that the catches m can be readily
operated to engage with or release the flanged frame of the box B.
By making the dam in the form of two boxes the lower of which is closed, except
at the top, and the upper closed except at the top and bottom, and by hinging the
lower box to the upper one at the outer side, the dam can be applied to or removed
from the propeller with the greatest facility and can be readily kept tight or free
from water when in use, the only joint being one extending around the dam so that

page_text: the length of the joint is less than if it extended vertically from the bottom to the
top of the dam.
Although I prefer the semi-cylindrical form for the lower box B of the dam
because of the minimum displacement which results when this form is adopted, it
will be evident that the said lower box might be triangular, rectangular, or of any
other available shape, without departing from the main feature of my invention.
The shape of the upper box A may also be varied, for instance in Figure 4, I
have shown a dam in which the said upper box is contracted in width from the
bottom towards the top, so that it can be applied to either the starboard or port
propeller without the necessity for reversing it end for end, the lower box B in this
case having hinges a at each side, the hinge pins being removed from that side of
the dam which is to be opened.
In this case also the openings 6 need be formed only in the forward ends of the
boxes, suitable projecting boxes or casings on the after ends being, by preference,
provided in order to permit of the removal of the hub of the propeller from the end
of the shaft after the blades have been detached.
To the bottom of the box B is secured a transverse beam B¹ one end of which is
adapted to project under the keel of the vessel, as shown, so as to transmit to the
latter a portion of the strain due to the upward pressure of water upon
the dam.
Special dams, one for each propeller, might also be designed without departing
from the essential principle of my invention although, it is preferable to construct
the dam in the manner set forth herein, so that it is applicable to either
propeller.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed, I declare that what I
claim is :-
1. A propeller dam for twin screw vessels, consisting of upper and lower boxes
hinged together at their outer sides, whereby the inner portion of the lower box
can be dropped so as to permit the dam to pass over the propeller, substantially as
hereinbefore described.
2nd. A propeller dam for twin screw vessels, consisting of upper and lower boxes
hinged together at their outer sides, and constructed, so that the dam can be applied
to either the starboard or port propeller, as required substantially as herein before
described.
3rd. A propeller dam for twin screw vessels, consisting of an upper box and a
lower semi-cylindrical box, the said boxes being pivoted together at their outer
sides, substantially as herein before described.
4th. In a propeller dam for twin screw vessels, the combination of the upper and
lower boxes pivoted together at their outer sides, and operating screws and nuts
whereby the movement of the lower section of the dam in respect to the upper
section may be controlled, substantially as hereinbefore described.
5th. In a propeller dam for twin screw vessels, the combination of the upper and
lower boxes pivoted together at their outer sides, retaining catches for locking
together the inner portions of the two boxes when the dam is closed, and rods and
levers for operating the said catches, substantially as hereinbefore described.
Dated this 25th day of January 1893.
J. H. JOHNSON & Co.
Agents.