Improvements in Reversible Screw Propellers.
Year: 1892

page_text: Date of Application, 10th Mar., 1892
Complete Specification Left, 12th Dec., 1892-Accepted; 21st Jan., 1893
PROVISIONAL SPECIFICATION.
Improvements in Reversible Screw Propellers.
I HENRY GRAFTON of Wardrobe Chambers Queen Victoria Street in the City
of London Engineer do hereby declare the nature of this invention to be as
follows:-
My invention relates to an improvement in reversible screw propellers whose
blades are capable of being altered or reversed in pitch whilst the shaft is
revolving for the purpose of regulating or reversing the direction of propulsion
without reversing the engines, and has for its object to strengthen the connection'
of the blades with the shaft by making the diameter of the base of the blade as.
nearly as possible the full diameter of the boss, and to avoid friction by means of"
mechanism whereby the blades are rotated about their axes without putting any
strain upon the supporting bearings of their bases.
Each blade is made in one with a base as nearly as possible, but not quite hemi-
spherical or equal to half the boss, so that the two bases, together with the
intervening frustum together constitute the boss of the propeller.
The intervening frustum is a flat forging in one with or connected to the
propeller shaft, to whose diameter it is about equal in thickness, or it may be a
boss with flats upon it. It has circumferential clips which embrace the bases of
the blades and hold them in firm connection with the middle frustum, whilst
permitting the bases to rotate within said clips.
Within an aperture in this frustum is located the reversing mechanism consisting
of two crossheads whose ends are respectively coupled by links to diametrically-
opposite crank pins, one on the base of each blade. Each crosshead therefore
works both blades, and the two crossheads are simultaneously moved in opposite
directions by power applied thereto through thrust rods passing axially through the
propeller shaft, the one connected to the foremost crosshead being tubular and
the one connected to the aftermost crosshead passing axially through it. At their
inner ends, these thrust rods are provided with means whereby they may be
simultaneously acted on in opposite directions by the same cam or other
mechanical movement, so that the thrust of the one is resisted by that of the
other.
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COMPLETE SPECIFICATION.
Improvements in Reversible Screw Propellers.
I, HENRY GRAFTON of Wardrobe Chambers, Queen Victoria 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 :-
My invention relates to an improvement in screw-propellers whose blades are
capable of being altered or reversed in pitch whilst the shaft is revolving for the
purpose of reversing the direction of propulsion without reversing the engines,
and has for its object to provide mechanism whereby the blades may be rotated
about their axes for the purpose of reversing the direction of propulsion without
thereby putting any strain upon the supporting bearings of their bases. It has

page_text: also for object to strengthen the connection of the blades with the boss by
making the diameter of the bases of the blades as large as possible.
The mechanism for reversing the pitch of the blades consists essentially of two
crossheads movable, simultaneously and,.oppositely in the fore and aft directions
each coupled to two crank, pins, one on the base of each, blade. Each crosshead
therefore works both blades and the crossheads are inoved simultaneously and
oppositely by power applied through concentric rods passing through the propeller
shaft, and operated manually or by power through any suitable mechanism such
that the strains on the two rods mutually resist each other. The connection of
the blades with the boss is made by providing the blades with flanged bases of
short, beight and large diameter, the latter dimension equalling or exceeding
the former as distinguished from shanks, depending on their length for rigidly.
supporting the blade, these, bases being fitted to turn within circumferential clips..
embracing their flanges and bolted to a frame formning the intervening frustum of
the boss within which work the crank pins which project from the opposite inner
faces of the bases, and by which the blades are operated as.above mentioned.
Reference is to be had to the accompanying drawings, forming part of, this
Specification, wherein
T:
Figure: 1 is a longitudinal section, Figure 2 a sectional plan, and Figure 3 a
transverse sectional elevation (looking aft) of the propeller boss. Figures 4 and 5 2
are an end elevation (looking forward) and plan partly in section. Figures 6
and 7 are a sectional elevation and plan, and Figure 8 a transverse section of an
arrangement of mechanism for actuating the blade reversing gear.
The same letters of reference denote like parts in all the figures.
Each blade has a circular flanged base A secured to an intervening frame B by 2
clip-rings C embracing their flanges and bolted to the frame B, the bases, of the
blades being of such form that they, together with the clip-rings and intervening
frame, form a boss of substantially spherical form. The intervening frame B is in
one with, or connected to, the propeller shaft. Its thickness is reduced as much as,
possible consistent with strength, in order that the diameter of the bases of the 3
blades may approach as nearly as possible the diameter of the boss. D, E, are, the
two crossheads, of which the one D is coupled directly by die blocks working in
its slotted ends with two, crank pins F, F, fixed one to the base of each blade at.
opposite sides of the plane common to the axes of the two blades and of the
propeller shaft. The other crosshead E is coupled by links G to two, other crank 3
pins H, H', also fixed one to the base of each blade at diametrically opposite, points
to the pins F, F. By thus moving each blade about its axis by the opposite,
motion of two crossheads acting on it at diametrically opposite points, the act of
revolving the blade in its seat causes no strain thereon and no friction from this
cause as would be the case were one of the crossheads and its adjuncts 4
omitted, since the.. strain. caused by moving the one crosshead is opposed and
balanced by that caused by moving the other. crosshead the forces on the
crank pins of each blade acting as what is known in mechanics as a couple."
To enable the crossheads to, be, thus connected crosswise, to the cranks, and allow
of the crank pins of the one blade passing those of the other, the two ends of 4
each crosshead work in different planes as shewn. The crosshead E is external of
the frame B and the, links G. pass through slots in the end thereof, the crosshead
being enclosed by a cap, I bolted to the frame, B and within which the crosshead
slides in guides il'. The crosshead D works in guides B₁ within the, frame B, the
die block and slot form of connection with the crank pins being adopted to reduce 5
the end wise dimensions of the screw-boss, but for which this crosshead might be
coupled to the blade cranks by links in the same way as the other one E. The
crosshead D is fixed upon a tubular rod K passing through the tubular propeller
shaft and the crosshead E is fixed to a rod L passing through K and projecting
therefrom at both ends. At the inboard end of the rod K is coupled a collar M by 5
means, of cotters passing through. longitudinal slots N, in the propeller. shaft,,
another collar Mihoine
66

page_text: collars M, M, are slid along the shaft in opposite directions by any suitable
mechanism of which I will describe one example without in any way limiting
myself thereto. Each collar is held between a pair of plates 0, 0, forming a
crosshead and between whose ends are fixed nuts P, the nuts of the one crosshead
being in alignment with those of the other and receiving right and left handed
screw-rods parallel with the propeller shaft and coupled together so as to be
operated simultaneously by any suitable worm, toothed, or chain gear, a chain R
being shewn in the present example.
It will be evident that the duplex oppositely moving crossheads and crank pin
gear is not limited to blades having large flat bases with crank pins projecting
from their inner faces as herein described but might be applied to blades having
long pivots and crank arms at the sides thereof as in the well known Bevis screw
although without the advantage of the increased strength derived from the
construction herein described.
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed, I declare that what I
claim is :-
1. In a reversible screw propeller, the combination, with the two blades fitted
to rotate on a common axis in the boss and each having two diametrically opposite
crank pins, of two crossheads or equivalent movable parts, each coupled to pins of
both blades so that each blade is moved by both crossheads moving oppositely and
acting conjointly, as specified.
2. The herein described reversible screw propeller whereof the blades are formed
with flanged bases of large diameter and relatively little height and are held by
circumferential clips to an intermediate flat frame, the bases clips and frame
together constituting the boss, the blade bases having each two diametrically
opposite crank pins, working within the intermediate frame, and the cranks of
each blade being coupled to two crossheads or equivalent oppositely movable parts,
substantially as specified.
3. In the herein described reversible screw propeller wherein each blade is
adjusted by two oppositely movable parts, each coupled to crank pins on both
blades as described, the arrangement of the one crosshead to work between the
bases of the two blades and the coupling of it to a crank pin of each blade
situated at opposite sides of the plane common to the axes of the blades and of
the shaft, substantially as specified.
4. The combination with a reversible propeller wherein each blade is adjusted
by the conjoint action of two oppositely moving crossheads or their equivalents,
each coupled to a crank pin of both blades as described, of mechanism operating
both crossheads simultaneously whereby the thrust on the one is resisted by the
pull on the other as described.
Babed buis
of December 1800.
H. GRAFTON,
By A. M. & Wm. Clark,
53, Chancery Lane, London, Chartered Patent Agents.
on PT Sa na