IMPROVEMENTS IN SCREW PROPELLERS
Year: 1882

page_text: LETTERS PATENT to Anthony John Davison of Sunderland, in the County of
Durham, Engineer for an invention of IMPROVEMENTS IN SCREW PROPELLERS
PROVISIONAL SPECIFICATION left by the said Anthony John Davison
at the Office of the Commissioners of Patents on the 3rd May 1882.
ANTHONY JOHN DAVISON of Sunderland in the County of Durham Engineer
"IMPROVEMENTS IN SCREW PROPELLERS AND IN APPLIANCES CONNECTED THEREWITH
"
The first part of my invention relates to improvements in screw propellers and
consists in forming the blades (whether cast solid with, or fitted loose to, the boss)
with corrugated surfaces; the corrugations formning sectors of concentric circles at
suitable intervals over the whole surface of the blade (from the boss to the
periphery) or over such portion of the blade as may be found most efficient. The
corrugations may form grooves with sides of equal or unequal angles and these sides
may be formed with convex, concave, or flat surfaces, preferably hollowed at the
bottom of the grooves.
The second part of my invention relates to improvements in the construction of
stern pipes or tubes for propeller shafts and consists in making the pipe or tube
with openings along its upper portion, fitted with removeable doors or covers, so
that the condition of the propeller shaft can be examined between the inner and
outer bushes at any time without unshipping the propeller or withdrawing the
shaft.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said Anthony John Davison in the Great Seal Patent Office on the
3rd November 1882.
ANTHONY JOHN DAVISON of Sunderland in the County of Durham, Engineer
IMPROVEMENTS IN SCREW PROPELLERS AND IN APPLIANCES CONNECTED THEREWITH
The first part of my invention relates to improvements in screw propellers and
consists in forming the blades (whether cast solid with, or fitted loose to, the boss)
with corrugated surfaces; the corrugations forming sectors of concentric circles at
suitable intervals over the whole surface of the blade (from the boss of the
periphery) or over such portion of the blade as may be found most efficient. The
corrugations on the driving face may form grooves with sides of equal or unequal
angles but I prefer generally to make them forming a series of steps the interval
between each on the surface of the blade being considerably greater than the
depth of the step (as shewn in the drawing) both having flat surfaces preferably
alightly hollowed at the bottom of the step or groove. The back surface of the
blade follows the corrugations of the driving face but the angles are rounded as
shewn on the drawing.
The second part of my invention relates to improvements in the construction of
stern pipes or tubes for propeller shafts and consists in making the pipe or tube
with openings along its upper portion fitted with removeable doors or covers so
that the condition of the propeller shaft can be examined between the inner and
outer bushes at any time without unshipping the propeller or withdrawing the
ahoft
The accompanying sheets of drawings illustrate my Invention as I propose to
carry it into practical operation but I do not confine myself to the exact details of
construction
On sheet 1. Figure 1. Shews an end view looking on the driving face of a solid
right hand four bladed propeller and Figure 2 shews a side elevation of the same.
The dotted shaded portion of Figure 2 shews a section of one of the blades on the
radial centre line from boss to point. The corrugations or grooves are in this
instance extended over the whole of the surface of the blade and present the
steps S of the grooves toward the periphery (or facing outward) but in some cases
I propose to form the grooves so that the steps S are presented toward the centre
(or facing inward) the object being, in either case to obtain a firm hold of the
water and to drive the column from the propeller in a direct line aft. The
corrugations may extend over the whole of the blades or over any portion of them,
they may be spaced at any distance apart and their flat sides may form right angles
acute or obtuse angles.
On sheet 2, Figure 1 shews a longitudinal section, Figure 2 a transverse section
and Figure 3 a plan of a stern pipe constructed according to the second part of
my Invention A is the Bulkhead B the stern post C the inner bush or bearing for
the propeller shaft D the outer bush or bearing for the same fitted as usual with
strips of hard wood-The whole of that portion of the shaft between these two
bushes is accessible for examination by removing the water tight doors E. E (at
suitable opportunities) and turning the shaft round by hand.--Thus the removal of
the propeller and uncoupling the line of shafting to draw in the propeller shaft
for examination, involving great expense and loss of time, are avoided.
Having now described my Invention and illustrated the mode in which I propose

page_text: to carry it into practical application I declare that what I consider novel and
therefore claim as secured to me by Letters Patent are.
First. The construction of screw propellers the blades of which are corrugated or
grooved, to form steps in the manner described by the foregoing specification and
illustrated in one form of application, by the accompanying drawings.
Second. The construction of stern pipes for propeller shafts with openings
between the inner and outer" bushes" or bearings closed by water tight doors to
enable an examination of the shaft to be made, substantially as described and
illustrated.
In witness whereof I the said Anthony John Davison have hereunto set my
hand and seal this second day of November in the year of our Lord one
thousand eight hundred and eighty two.
Witness;
T. J. DANSON F. Inst. P. A.
Consulting Engineer & Patent Agent
Newcastle on Tyne
A. J. DAVISON (L.S.)