AN IMPROVEMENT IN THE SHAPE OF AND IN THE MANNER OF APPLYING THE MARINE SCREW PROPELLER
Year: 1867

page_text: PROVISIONAL SPECIFICATION left by Henry Spink Swift at the Office of
the Commissioners of Patents, with his Petition, on the 30th April
1867.
Í, HENRY SPINK SWIFT, of No. 99, Hill Street, Peckham, in the County of
Surry, Gentleman, do hereby declare the nature of the said Invention for
"AN IMPROVEMENT IN THE SHAPE OF AND IN THE MANNER OF APPLYING THE
MARINE SCREW PROPELLER," to be as follows:-
A cylinder or case of suitable form, size, and strength to be placed around
the screw opening in the stern of the vessel to which this Invention may be
applied, and to be made to project as far as the outer side of the rudder post
that a straightedge laid across would toutch the outer edges of the cylinder or
case and the outer side of the rudder post, leaving the rudder free and full
action outside the cylinder or case. I recommend the cylinder or case to be
made in two halves, and to be securely fixed in its place by bolting or other-
wise; the inner edge of the cylinder of case is to project no further under the
vessel than the screw opening in the stern; from and around the inner
edges of the cylinder or case, and firmly attached at one end thereto at
suitable distances apart and of suitable strength, longitudinal bars or rods of
suitable length, their other ends to be securely fastened to that part of the
vessel; they may reach in a line parallel to the keel, or with so much deflection
only as may be necessary to reach the nearest part of the vessel's bottom in
that direction (see Figure 1 in Diagram). The screw propeller is to be of the
same diameter as the inner side of the cylinder or case, less so much as will

page_text: allow it to revolve without toutching the sides of the cylinder or case, and
to be made and affixed in the following shape and manner to the screw
shaft, the screw to consist of thin blades of the following shape:-A disk of
suitable diameter to be divided from its outer edge towards the centre into
three equal parts (as shewn in Figure 2 of Diagram), each blade to have a
stein projecting from the centre of its narrow end, which stem should be
equal in length to about one-fourth the length of the blade, the end of the
stem to be firmly attached to a longitudinal section of a cylinder of suitable
width (see Figure 3 in Diagram), that when the three blades are arranged
and fitted in their proper places, that portion of the screw shaft in the centre
of the cylinder or case shall be surrounded with a tight fitting cylinder or
collar, which is to be securely attached by screws or otherwise to the same;
this cylinder or collar may be made to bear on the outer surface of the vessel's
stern post, through which the screw shaft passes, thereby relieving the pressure
and consequent friction of the screw shaft bead, or the stems of the screw
blades may be fastened into the ordinary boss of the screw shaft. I recom-
mend the screw blades to be deflected to an angle equal to one-eight of the
circumferance of the diameter of the screw (see Figure 4 in Diagram).
I do not confine myself to the exact shape and dimentions of the screw
blades as aforesaid, or to the exact pitch or deflection of them, though my
experience has proved to me they are the best.
I claim the application of the cylinder or case surrounding the screw, and
the flat surface of the screw blades in every part being on the same plane;
also the open space around the screw shaft at the base of the screw blades.