Improvements in or connected with Screw Propellers.
Year: 1893

page_text: Date of Application, 14th Jan., 1893
Complete Specification Left. 14th Oct.. 1993-Accepted. 18th Nov., 1893
PROVISIONAL SPECIFICATION.
Improvements in or connected with Screw Propellers.
I, JOHANNES CATHARINUS BULL, of No. 18, Bexley Road, Erith, in the
County of Kent, Engineer, do hereby declare the nature of this invention to be as
follows:-
This invention relates to improvements in or connected with screw propellers, and
has for its object, by a simple arrangement of parts, to enable the pitch of the
blades to be varied within certain limits.
Screw propellers are sometimes made by forging the blades separately and
attaching them to the boss by forming the roots of the blades of a tapered or dove-
tailed section and by employing a corresponding groove for each blade in the boss
of the propeller, but these grooves have been perfectly straight from end to end
thereof, and it was thus impossible to vary or regulate the pitch of the blades
except by the employment of some extraneous means.
Now according to my invention, I form each groove in the boss of the shape of
an are of a circle and undercut or dovetailed and I correspondingly form the root
of each propeller blade, by which means the pitch of the blade may be increased or
reduced from a normal pitch by moving the blade more or less to either end of the
curved groove of the boss.
The dovetailed root of the blade should be made to nicely fit the corresponding
groove of the boss, in which case there will be little or no tendency of the blade to
work out when the propeller is in action, but, as a security against a possible
accident of this kind, I provide loose blocks or distance pieces which are arranged
at each end of the groove with capability of sliding, and I form each of these
distance pieces with a long slot therein to admit of the passage therethrough of a
a stud or bolt which screws into the boss and carries a nut or head, so that it can
be screwed down upon the distance piece in order to fix it in the desired position
whilst the slot therein admits of a certain range of adjustment.
In order to avoid the possibility of the blade at its root becoming fixed or set
within the groove of the boss, it is sometimes desirable to fix it in position by
means of a tapered curved key, driven into position, one side of such key fitting the
curve of the root of the blade, and the other side being slightly eccentric or
tapered with regard to the first so as to admit of its being easily knocked out and
the blade thereby released, whilst the shape of the groove or the root must be made
to correspond with the eccentric curve of the key.
In some cases, the key may be fixed in position by means of a screw stud or studs
passing through long slots formed longitudinally in the key in order to admit of the
position of the latter being shifted to correspond with that of the blade in the groove,
or, with the same object, a transverse piece may be removeably fixed to the blade
so as to overlap the broad end of the key.
If desired, a portion of the metal of the boss between the blades may be removed
so as to increase the propelling surface of the blades and to reduce the resistance of
the boss to the water.
By these means, I obtain a screw propeller the pitch of which can be quickly and
easily varied within certain limits, the blades of which have no flange and are
therefore adapted to be readily forged in steel, Bull's metal, manganese bronze or
other malleable metal or alloy, and, inasmuch as no thickening is required at the
root, the blades can receive a perfect shape, thus securing a large driving or
propelling surface with a reduced disturbance of the water.
Dated this 14th day of January 1893.
VAUGHAN & SON,
Agents for the Applicant.

page_text: COMPLETE SPECIFICATION.
Improvements in or connected with Screw Propellers.
I, JOHANNES CATHARINUS BULL, of No. 18, Bexley Road, Erith, in the
County of Kent, 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 :-
My said invention relates to improvements in or connected with screw propellers,
and has for its object, by a simple arrangement of parts, to enable the pitch of the
blades to be varied within certain limits.
Screw propellers are sometimes made by forging the blades separately and
attaching them to the boss by forming the roots of the blades of a tapered or
dovetailed section, and by employing a corresponding groove for each blade in the
boss of the propeller, but these grooves have been perfectly straight from end to
end thereof and it was thus impossible to vary or regulate the pitch of the blades,
except by the employment of some extraneous means.
Now according to my invention, I form each groove in the boss of the shape of
an arc of a circle, and undercut or dove-tailed, and, 1 correspondingly form the
root of each propeller blade, by which means the pitch of the blade may be
increased or reduced from a normal pitch, by moving the blade more or less to
either end of the curved groove of the boss.
The dovetailed root of the blade should be made to nicely fit the corresponding
groove of the boss in which case there will be little or no tendency of the blade to
work out, when the propeller is in action, but, as a security against a possible
accident of this kind, I provide loose blocks or distance pieces, which are arranged at
each end of the groove with capability of sliding, and, I form each of these distance
pieces with a long slot therein to admit of the passage therethrough of a stud or
bolt, which screws into the boss and carries a nut or head so that it can be screwed
down upon the distance piece in order to fix it in the desired position, whilst the
slot therein admits of a certain range of adjustment.
In order to avoid the possibility of the blade at its root becoming fixed or set
within the groove of the boss, it is sometimes desirable to fix it in position by
means of a tapered curved key driven into position, one side of such key fitting the
curve of the root of the blade and the other side being slightly eccentric or
tapered with regard to the first so as to admit of its being easily knocked out and
the blade thereby released, whilst the shape of the groove, or, the root must be
made to correspond with the eccentric curve of the key.
In some cases, the key may be fixed in position by means of a screw stud or
studs, passing through long slots formed longitudinally in the key in order to admit
of the position of the latter being shifted to correspond with that of the blade in the
groove, or, with the same object, a transverse piece may be removeably fixed to the
blade so as to overlap the broad end of the key.
If desired, a portion of the metal of the boss between the blades may be removed
so as to increase the propelling surface of the blades, and to reduce the resistance
of the boss to the water.
And in order that the said invention may be more clearly understood and readily
carried into effect, I will proceed, aided by the accompanying drawings, more fully
to describe the same.
DESCRIPTION OF THE DRAWINGS.
Figure 1. is a side elevation, partly in section, of a screw propeller constructed
according to the present invention.
Figure 2. is an end elevation thereof.
Figure 3. is a transverse section of part, taken on the line 1-1. of Figure 1., and,
Figures 4. and 5. are similar views to Figure 1. but representing slight
modifications.

page_text: In the several figures, like parts are indicated by similar letters of reference.
Referring to Figures 1., 2., and 3. a. represents the propeller shaft, b. represents
the propeller boss, and a' represents the usual nut which jams the boss b. upon the
shaft a.
Around the circumference of the boss b., are formed several grooves
one to
each blade c. of the propeller and each of these grooves b', is formed of the shape
of an arc of a circle, as represented more particularly at Figure 1.
Each of the grooves & in cross section is formed undercut and dovetailed and the
root c' of each propeller blade c. is correspondingly formed by which means the
pitch of the blade c. may be increased or reduced from a normal pitch by moving
the root of the blade more or less to either end of the curved groove of the
boss b.
The dovetailed root c¹ of the blade c. should be made to nicely fit the corre-
sponding groove of the boss b. in which case there will be little or no tendency
for the blade c. to work out when the propeller is in action, but, as a security
against a possible accident of the kind, loose blocks or distance pieces d. are
provided and are arranged at each end of the groove b¹ with capability of sliding
therein and each of these distance pieces d. is formed with a long slot d therein to
admit of the passage therethrough of a stud or bolt d³ which screws into a tapped
hole formed in the boss b., and carries a nut or head so that it can be screwed.
down upon the distance piece d. in order to fix the latter in the desired position
whilst the slot d' admits of a certain range of adjustment thereof.
In the example given at Figure 4., a device is shown for preventing the possibility
of the blade c. at its root c¹ becoming fixed or set within the groove b' of the boss.b.
or of working loose.
For this purpose; the distance pieces d. referred to in the arrangement lastly
hereinbefore described are dispensed with and the blade c. is fixed in position by
means of a tapered curved wedge or key e. driven into position between one side of
the root of the blade e, and one of the undercut walls of the groove b¹.
One side of the wedge or key e. is formed to fit the curve of the root c² of the
blade and the other side is formed slightly eccentric or tapered with regard to the
first side so as to admit of its being easily knocked out and the blade c. thereby
released, whilst the shape of the groove 6' in the boss b. or the root c¹ of the blade c.
must be made to correspond with the eccentric curve of the wedge or key e., as will
be readily understood, the key and root c¹ being normally fixed against independent
movement by means of a transverse piece which is, by a screw stud e¹, removeably
fixed to the root c¹ of the blade c. so as to overlap the broad end of the wedge or
key e. and thereby prevent accidental movement of the parts, whilst at the same
time admitting of the necessary adjustment.
In the example given at Figure 5., the groove b¹ in the boss b., instead of being
formed open from end to end, is formed with closed ends and the root c¹ of the
blade c. is first inserted into such groove and the wedge or key e. is afterwards
dropped therein and driven home by any suitable means and is retained in position
by an adjusting screw e¹ which screws through a tapped hole in the end wall of the
groove, and impinges directly upon the broad end of the wedge or key e., whilst,
in order to retain the root c¹ of the blade c. in the required position in the groove b¹
of the boss b., several packing pieces f. are employed at each end of such groove,
those at one end being capable of being forced up against the root c¹ of the blade c.
by means of a set screw, the number of the packing pieces f. at either end of the
groove being varied according to the position that it is desired the blade shall
occupy.
If desired, a portion of the metal of the boss b., between the blades c. may be
removed so as to increase the propelling surface. of the blades and to reduce the
resistance of the boss to the water.
By the means herein before described, a screw propeller is obtained the pitch of
the blades of which can be equally and easily varied within certain limits, the
blades of which have no flange and are therefore adapted to be easily forged in

page_text: steel, Bull's metal, manganese bronze, or other suitable malleable metal or alloy,
and, inasmuch as no thickening is required at the root c', the blades c. can receive a
perfect shape thus securing an increased driving or propelling surface with a
reduced disturbance of the water..
Having now particularly described, and ascertained the nature of my said
invention and in what manner the same is to be performed, I declare that what f
claim is;-
1. In a screw propeller, the combination of a groove in the boss formed in the
arc of a circle, a blade having its root correspondingly shaped and adapted to
traverse such groove and means of fixing the blade in the required position,
substantially as herein shown and described and for the purpose stated.
2. In a screw propeller, the combination of an undercut groove in the boss formed
in the arc of a circle, a blade having its root correspondingly shaped and adapted
to traverse such groove and means of fixing the blade in the required position, sub-
stantially as herein shown and described and for the purpose stated.
3. In combination with a screw propeller of the character hereinbefore referred
to, an eccentrically shaped key or wedge for fixing the blade in the required position
and means for preventing endway movement of such key, substantially as herein
shown and described and for the purpose stated.
Dated this 14th day of October 1893.
VAUGHAN & SON,
Agents for the Applicant.