Improvements in Thrust Blocks for Propeller and similar Shafts.
Year: 1898

page_text: PROVISIONAL SPECIFICATION.
Improvements in Thrust Blocks for Propeller and similar Shafts.
I, THOMAS COOPER, of The Elms, King's Lynn, in the County of Norfolk,
Engineer, do hereby declare the nature of this invention to be as follows::-
The object of the present invention is to facilitate the employment of antifric-
tion rollers in thrust blocks or bearings used in connection with propeller and
similar shafts.
The main difficulty to be surmounted in attaining the above object, arises
from the failure of the rollers to withstand the pressure of the thrust, combined
with the high rate of speed at which they are called upon to run.
It would appear that antifriction rollers which, when carrying a given load,
will last well, when run at a low rate of speed, will fail very quickly under same
load, if run at a high rate of speed, as is necessary when a propeller shaft is
driven at the ordinary full speed.
This being so, I have directed my attention to the production of means which
will relieve the rollers from an undue rate of speed, while the propeller shaft
continues to be driven as fast as, or even faster than, hitherto.
Accordingly, I employ between the collar of the propeller shaft and the fixed
abutment, a series of sets of antifriction rolls, and between the sets I place a disc
or plate of metal capable of turning loosely on the propeller shaft.
These plates turn, or are turned, upon the shaft at different speeds; that
nearest the propeller shaft, collar rotates at the highest speed, but more slowly
than the shaft, and that nearest the fixed abutment at the lowest speed; and
those between, at rates corresponding to their position between the two end plates.
For instance, supposing six sets of rolls to be employed, there will be five inter-
mediate discs dividing the sets. For the sake of example, I will take the speed
of rotation of the propeller shaft collar at 6 units; the disc nearest thereto will
be driven at 5 units; the next at 4; the next at 3; the next at 2; and the last,
nearest the fixed abutment, at 1. It will thus be seen that each set of antifriction
rollers has only to turn at a speed equal to the difference of rotation between the
two adjacent surfaces, either discs, or a disc and the propeller collar, or a disc
and the fixed abutment. In this manner, the speed of rotation of the propeller
is divided up, and distributed amongst the six sets of antifriction rollers, so that
none are subjected to an injuriously high rate. The number of sets of rolls and
discs may be increased or decreased, to suit varying requirements.
The antifriction rollers are, by preference, carried in cages arranged between
the discs, and free to turn with the propeller shaft upon which they are threaded.
The rollers, which may be tapered to suit correspondingly formed paths, in the
discs, are fitted into recesses in the cages, which recesses, according to an improve-

page_text: those between, at rates corresponding to their position between the two end plates.
For instance, supposing six sets of rolls to be employed, there will be 5 inter-
mediate dises dividing the sets. For the sake of example, I will take the speed
of rotation of the propeller shaft collar at 6 units, the disc nearest thereto will
be driven at 5 units, the next at 4; the next at 3; the next at 2; and the last,
nearest the fixed abutment, at 1.
It will thus be seen that each set of antifriction rollers has only to turn at a
speed equal to the difference of rotation between the two adjacent surfaces, either
discs, or a disc and the propeller collar, or a disc and the fixed abutment. In
this manner, the speed of rotation of the propeller is divided up and distributed
amongst the six sets of antifriction rollers, so that none are subjected to an injuri-
ously high rate. The number of sets of rolls and dises may be increased or
decreased to suit varying requirements.
In the accompanying drawings,
Fig. 1 shews, in longitudinal section, a thrust block embodying my invention.
Fig. 2 is a face view of a detail, detached, as hereinafter explained; and
Fig. 3 is a transverse section, on line X-X of Fig. 1.
A is the propeller shaft, and a is a collar fast thereon. B is a fixed abutment,
between which and the collar a is arranged the antifriction device embodying my
invention.
bis another abutment, which may be connected to the abutment B by means
of bolts or otherwise. This abutment is intended to take the back thrust when
the engine is reversed.
e, e, 2, 3, and ct, are the discs above mentioned, each of which is furnished with
annular races, for the antifriction rollers d.
The antifriction rollers d are by preference carried in cages D (shewn at Fig. 2),
arranged between the discs, and free to turn with the propeller shaft, upon which
they are threaded. The rollers, which are tapered, are fitted into recesses in the
cages, which recesses, according to an improvement which forms part of the pre-
sent invention, I prefer to arrange in two or more concentric rings, although this
arrangement is not in every case essential.
This enables me to obtain with, say, two rings of short rollers of any given
diameter, a greater total of roller length than can be procured when rollers of
double the individual length, arranged in a single ring of recesses, are employed;
and, moreover, the lateral thrust incidental to the employment of long tapered
rollers is thus diminished.
The differential driving of the intermediate plates may be obtained in various
ways. One way, which will be found to answer satisfactorily, however, consists
in the employment (as shewn in Fig. 1 of the drawings) of gear teeth upon the
propeller shaft collar a, and upon the periphery of the discs c, c¹, 2, 3, and c,
and of a train of pinions e, el, e², e, e, e, e, e², es, e, engaging therewith, in such a
way as to drive the discs at the required differential speed, when the propeller
shaft rotates. These pinions may conveniently be mounted in pairs upon shafts E
threaded through bearings carried by the roller
cages.
There may be more than one set of pinions arraned at intervals around the
circumference of the discs (two are drawn in Fig. 1, and four are indicated in
Fig. 2), but the number of sets employed will be in accordance with the require-
ments of each case.
The last of the cages, viz., that marked D* in the drawings (see Fig. 3), is
provided with a brake band F, having an adjustable set screw f. The object of
this brake is to prevent the whole series of geared discs & cages from becoming
locked together, and thereby throwing all the work on the last set of rollers only.
Instead of having a brake, the last cage D* may if preferred, be geared to the
disc c', and to the fixed abutment, so as to regulate its speed of rotation to the
requisite extent.
In thrust blocks constructed as above described, it will be found that the rollers
will both work well and wear well, and will ensure, in the case of propeller shafts,