Improved Means for Joining Screw-propeller Blades.
Year: 1897

page_text: Date of Application, 4th Aug., 1897-Accepted, 11th Sept., 1897
COMPLETE SPECIFICATION.
Improved Means for Joining Screw-propeller Blades.
I, ROBERT RUNEBERG, of Bureau Vega, 57, Liteinij Perspective, St. Petersburg, in
the Empire of Russia, 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:—
This invention relates to jointed propeller blades, its object being to provide a
strong, rigid joint, having a smooth exterior; at the same time affording ready
means for displacing and readjusting the parts without necessarily resorting to dry
docking the vessel.
According to the usual practice propeller blades are commonly fixed by means of
screw-holts at or near the boss, and, owing to the difficulty in sufficiently trimining
the vessel so as to reach the bolts, it is necessary, when renewing the blades, to run
the vessel into a dry dock.
If, however, the joint be made at or about the middle of the length of the blade,
the difficulty in trimming the vessel sufficiently is minimised and the renewal of
the blades facilitated. Comparatively good results have been obtained by riveting
the overlapping edges of the blades; but, when renewing the blades, difficulties
sometimes arise in applying the means at disposal on the vessel. Moreover, it
frequently happens that the joint of the blade when trimming can only be raised to
about the surface of the water; the use of heated rivets in joining the parts of the
blade together being impracticable under such circumstances.
In the accompanying drawings, Fig. 1 is an elevation of a jointed propeller-blade
contructed according to my invention; Fig. 2 being a vertical section and Fig. 3
a plan. Fig. 4 is a section partly on the line - and partly on the line y-y in
Fig. 1; some of the bolts and cotters being removed from one side of the joint.
The joint A is arranged transversely to the length of the blade. A number of
square bolts B are inserted in suitably formed recesses in the two portions of the
blade, the recesses being disposed on each side of the junction line. The portion of
the recess on one part of the blade is extended laterally wherein engage lateral
projections or T-shaped heads b on the bolts. In the other part of the blade and
transversely to the recesses a slot c is made, the bottom of the slot being formed
with a series of curved depressions. The bolts, when in position, form a smooth
surface in common with that of the blade. The lateral projections b on the bolts
are made with inclined bearing surfaces for engaging with correspondingly formed
portions of the recesses. Curved cotters or wedges C are inserted in the slots c and
are driven through holes in the bolts B. By these means the bolts are drawn and
maintained firmly in position, the one end by the cotter and the other by the inclined
surfaces on the bolts and in the recesses. The cotters C are preferably of a curved
form, and narrowed at one end; whereby their application and removal is facilitated.
As will be seen from the drawing, the cotters and the bolts are covered or protected
by the metal of the blade. Set-screws c¹, preferably of gun-inetal are inserted in
the bolts and serve to prevent the displacement of the cotters.
It will be apparent
that a joint constructed as herein described is strong and rigid, and that the parts
are capable of being readily displaced and reassembled. The central portion of the

page_text: blade may be male of any convenient strength, the resistance offered by the water at
that part being comparatively small.
Having now particularly described and ascertained the nature of this and in what
manner the same is to be performed, I claim
1. The improved means for joining propeller blades substantially as herein
described, consisting in providing the junction ends of the blade parts with a number
of recesses and securing therein a corresponding number of suitably formed bolts;
the latter being protected by the metal of the blade.
2. In joining propeller blades, the employment of bolts furnished with laterally
extending portions having inwardly inclined sides in conjunction with recesses formed
in the junction ends of the blade parts and adapted for the reception of the said bolts,
substantially as herein described.
3. In joining propeller blades, the employment of curved cotters, arranged or operat-
ing substantially as herein described, and whereby the bearing surfaces of the bolts
are drawn into close contact with corresponding surfaces in recesses formed in
the blade.