IMPROVEMENTS IN REMOVING AND REPLACING THE BLADES OF SCREW PROPELLERS OF SHIPS AND OTHER NAVIGABLE VESSELS WHILE AFLOAT, AND IN APPARATUS EMPLOYED THEREFOR
Year: 1874

page_text: PROVISIONAL SPECIFICATION left by John Pinker and Thomas
Alfred Adamson at the Office of the Commissioners of Patents,
with their Petition, on the 9th April 1874.
We, JOHN PINKER and THOMAS ALFRED ADAMSON, both of Liverpool,
in the County of Lancaster, do hereby declare the nature of the said
Invention for "IMPROVEMENTS IN REMOVING AND REPLACING THE BLADES OF
SCREW PROPELLERS OF SHIPS AND OTHER NAVIGABLE VESSELS WHILE AFLOAT, AND IN
APPARATUS EMPLOYED THEREFOR," to be as follows:-
Our Invention relates to removing and replacing the blades of screw
propellers of steam ships while afloat, and when such blades are made
detacheable from the bosses of the propellers. At present in removing
and replacing the blades it is necessary to put the vessel in a dry dock,
or to use other like means of exposing the propeller as far as the boss so
that workmen can get at it, but in many instances dry docks cannot be
had, also other means of exposing the propeller boss, and such processes
are always attendant with considerable cost and delay.
In some instances caissons have been used round the propeller and the
water then pumped out, but this is likewise a costly and difficult

page_text: Our Invention consists in removing the detacheable blades of screw
propellers through an adjustable trunk or pipe, which is so constructed
as to encircle the blade required to be removed, and of such dimensions
as to allow of a workman operating within it, or so arranged that the
workman can operate by means of suitable spanners from the ship's
deck.
In carrying out this Invention into practice the bosses of screw pro-
propellers are provided round the root of each blade with a provision
having a screw thread, which may be on the boss itself or on a ring, by
preference of brass shrunk on and attached to the boss. One of the
couplings of the propeller shaft is fitted with a provision, being a bolt,
stud, or other suitable means for locking and adjusting the propeller boss
in position required for. operation, that is, bringing the screwed pro-
vision on the boss with its centre quite true with the stern post of the
vessel, or at a suitable angle thereto.--
We form the connecting piece of the stern post forging, that is, the
upper part connecting the stern post with the rudder post of screw ships
in the form of a hoop, and we build in the stern of the vessel and
immediately above this hoop or ring a well which opens out through the
deck above. This well is arranged on a true centre with the before-
mentioned screwed provisions on the boss of the propeller, as they
respectively may be uppermost.
An apparatus for removing the detacheable blades of screw propellers
consists of a trunk or pipe of size suitable to pass down the well before-
mentioned in the stern of the ship, and of length sufficient to reach to
the screwed provisions on the propeller boss. The bottom of the trunk or
pipe is formed with a female screwed provision so as to take or screw on
to the uppermost screwed provision on the propeller boss, the blade to be
operated upon thus coming inside the trunk or pipe. The trunk or pipe
being in position, the water is pumped out and workmen can get at the
bolts attaching the propeller blades to the boss in the case of large
vessels direct, and in the case of smaller vessels by box spanners from
above.
It will thus be seen that by the use of this Invention detacheable
blades of screw propellers can be removed while a vessel is afloat or at
sea, and when propeller blades are broken new ones can be substituted,
or any other repairs or alterations effected that may be necessary,

page_text: In the case of old vessels or vessels where it is difficult and undesirable
to build the well directly in the centre of the stern of the ship, the well
can be built at an angle, the locking arrangement in connexion with the
screw shaft being adjusted to suit, or an independent trunk may be
employed without passing through the counter of the vessel or in
connexion therewith.
In practice the trunk or pipe used in carrying out this Invention may
be made of any material, but we prefer steel for lightness.
The trunk may be made in one or more lengths, and may be in some
instances made telescopic in the well at the stern of the vessel, and so
that it will draw down when required for use. It may be turned to
screw on to the screwed provision on the boss by a cross spanner, hand-
spikes, or other suitable means. The bottom may be fitted with a guide
or a taper screw, so as to more readily adjust it to the screwed provision
on the boss.
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