Improvements in the Manufacture of Screw Propellers.
Year: 1889

page_text: Date of Application, 17th Dec., 1889
Complete Specification Left, 17th Sept., 1890-Accepted, 1st Nov., 1890
PROVISIONAL SPECIFICATION.
Improvements in the Manufacture of Screw Propellers.
We, JOHN LIST, of No. 3 St. John's Park, Blackheath, in the County of Kent,
Engineer, and GEORGE ALEXANDER DICK, of No. 110, Cannon Street, in the City
of London, Engineer, do hereby declare the nature of this invention to be as
follows:-
This invention relates to improvements in the manufacture of screw propellors for
ships, which propellors are formed of bronze, brass, or other copper alloy, the
objects being to increase the strength thereof, and to economise the cost.
When in use, the blades of propellors of the nature above referred to, frequently
become fractured and broken off at a point near the boss, and in order to obviate
this defect, this invention consists in forming each blade with a core or centre of iron
or steel.
For the purposes of this invention, we cast the copper alloy on to the iron or steel
core, which may be solid, or in the form of a frame by running the molten alloy
into a mould in which this core has been previously arranged.
When the whole of the propellor is made in one casting, we, in some cases, provide
the said cores or centres for the several blades in the form of arms, projecting from
one common piece which forms the core of the boss of the solid propellor.
In order that the alloy may adhere firmly to the iron or steel core we cleanse the
surface of the latter, and, in some cases, wo galvanise or otherwise coat it with metal
such as zinc or tin, or, we, in some cases, offect the desired object by drilling or
forming holes in or through the iron or steel core, or by making the surface of the
latter irregular.
Dated this 17th day of December 1889.
VAUGHAN & SON,
Agents for the Applicants.
COMPLETE
SPECIFICATION.
Improvements in the Manufacture of Screw Propellers.
We, JOHN LIST, of No. 3, St. John's Park, Blackheath, in the County of Kent,
Engineer, and GEORGE ALEXANDER DICK, of No. 110, Cannon Street, in the City of
London, Engineer, 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 :-
Hitherto screw propellors or propellor blades which have been cast entirely of
bronze, gun-metal or other copper alloy have been costly, not only on account
of the high price of the alloy, but also because it has been necessary to cast them of
considerable thickness to avoid risk of fracture, while, at the same time, this excess
of thickness has been objectionable because the thicker the metal the lower is the
mean tenacity throughout the section.
The object of the present invention is to manufacture screw propellors which,
whilst possessing all the advantages of those formed entirely of bronze, gun-inetal
or other copper alloy, shall be less costly to produce and shall possess greater
strength.
For this purpose, we form each blade or the blades and boss of the propellor with
a core of iron or steel on to which we cast an outer covering of a suitable copper
alloy.
When the blades are cast separate from the boss, we arrange the iron or steel
core within the mould and then pour the copper alloy in a molten state into the mould
so as to form a covering to the core and at the same time to give the complote
DQ27

page_text: outside form to the blade. In separate blades constructed in accordance with this
invention this iron or steel core usually extends into the flange by which the blade is
attached to the centre boss.
When the whole of the propellor is made in one casting, the iron or steel cores for
the blades are arranged in the form of arms projecting from an iron or steel centre 5
piece which constitutes the core of the finished boss and this iron or steel core with
arms corresponding to the number of blades is arranged within the mould into
which the molten copper alloy is introduced as above described.
As is well known and understood by persons conversant with this class of casting
operation the iron or steel core must be heated to a high temperature and the molten 1
alloy must be brought into contact therewith before the core has fallen in temperature
to any considerable extent.
In order that the copper alloy may adhere firmly to the iron or steel core, we
cleanse the surface of the latter, and, in some cases, we galvanize or otherwise coat it
with zinc, nickel, tin, or other suitable metal, or, we effect the desired object by 1
applying in tho usual manner a suitablo flux to dissolve the oxide from the surface of
the heated iron or steel core. With the same object in view we drill or form holes
in or through the iron or steel core or make the surface of the latter irregular.
The strength of propellor blades constructed in accordance with this invention is
greatly due to the chilling effect of the iron or steel core upon the copper alloy, 2
the temperature of the core being, even when heated, lower than that of the
molten alloy.
DESCRIPTION OF THE DRAWINGS.
We will now refer to the accompanying drawings from which the nature of our
said invention will be more clearly understood.
Figure 1 is a vertical section of a propellor blade which is intended to be bolted to
the centro boss by a flange.
Figure 2 is an expanded or extended view of the face thereof, and
Figure 3 is a series of horizontal sectional views of such a blade.
Figure 4 is a horizontal sectional view of the blade showing more particularly the
flange above referred to.
Figure 5 is an expanded or extended view of a portion of a screw propellor having
its blades in one casting with the boss.
Figure 6 is a vertical sectional view of the same.
The same letters of reference indicate like parts in all the above Figures.
a is the iron or steel core; b is the outer covering of copper alloy; c are binding
holes made in the core of the flange of the propellor blade the same being made of a
tapering form so that the contraction of the copper alloy in cooling will tend to bind
the latter firmly to the core. The metal plugs care placed in the mouths of the
holes c prior to the core being placed in the mould, in order to prevent the molten
alloy running through the said holes and filling up the hollow space on the under
face of the blade flange.
e are holes through which the studs or bolts for securing the blade to the boss
pass. d are a number of holes formed in the blado part of the iron or steel core
which holes are filled up by the molten alloy thus forming ties between the covering
on both faces of the blade.
We are aware that many proposals have been made for constructing propellors of
iron or steel and covering the surface with copper or copper alloy, but all the
proposed methods which have come under our notice have failed to fulfil satisfactorily
the requirements of reasonable cost combined with strength above referred to.
Having now particularly described and ascertained the nature of our said
invention and in what manner the same is to be performed, we declare that wo
claim is :-
1. The manufacture of screw propellors or screw propellor blades by casting a

page_text: covering of any suitable copper alloy on to a core of iron or steel, substantially as
herein shown and described.
2. A screw propellor or screw propellor blade formed of a core of iron or steel
covered with a coating of any suitable copper alloy cast thereon, substantially as herein
5 shown and doscribed.
.
1000
VAUGHAN & SON,
Agents for the Applicants.