Note: Descriptions are shown in the official language in which they were submitted.
7390
Shock Absorbing Propeller
Technical Field
This invention relates to arrangments for mounting a
propeller on a propeller shaft of a marhne propulsion device
and particularly to su~h an arrangement having a shock ab-
sorbing structure.
Backqround Art
Marine propeller mounting arrangements are known which
use resilient hubs to protect the propeller and propeller drive
train from the shock which can result from impact between the
propeller and submerged obstacles or from shifting gears.
Among themt U.S. Patent No. 3,045,763 to Perrott, issued
July 24, 1962, discloses a shock absorbing drive means for use
on a propeller which is also protected by a shear pin. The
Perrott device utilizes ribs on a drive sleeve engaging
. corresponding grooves in the hub of a propeller to
drive the propeller. The ribs are each covered with rubber
to provide some shock absorbtion.
Disclosure of Invention
In one broad aspect, the invention pertains to
a propeller mounting arrangement which includes a sleeve
member having just two radially outwardly extending
projections positioned axially along the sleeve member
and having an inner bore for drivingly engaging a
propeller shaft, and a propeller having an outer hub,
an inner hub, and a plurality of vanes connecting the inner
hub with the outer hub to form an exhaust gas passageway
between the inner and outer hubs. The inner hub has a
central bore therethrough and just two channels in the wall
of the central bore extending radially outward between the
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vanes with the projections on the sleeve extending
radially outward beyond the central bore into the channels
to loosely register with the channels. A cushion member
encircles the sleeve, the cushion member fitting
in telescoping relationship between the sleeve member
and the propeller inner hub, and the cushion member
engaging the walls of the channels and projections.
More particularly the invention as disclosed provides
a propeller mounting arrangement including a sleeve member
for mounting on a propeller shaft, a propeller having a
hub which fits over the sleeve member, and a cushion member
fitting between the sleeve member and the propeller hub
and encircling the sleeve member. The sleeve member in-
cludes radially outwardly extending projections positioned
axially along the sleeve member and loosely registering
with corresponding chnnels in the inner hub of the propeller.
The propeller has an outer hub surrounding the inner hub
to define an exhaust gas passageway with a plurality of
. vanes supporting the outer hub on the inner hub. The
channels in the inner hub have walls defined by the vanes.
The cushion member engages the walls of both the
projections from the sleeve member and the walls
of the channels and includes void spaces
7;~
between the walls to increase the cushioning effect between the
projections and walls of the channels.
The void spaces in the cushion member preferably are aligned
with the axis of the sleeve member and are formed on the surface of
5 of the member to facilitate manufacture.
By providing the cushion member with thicker walls on one side
of the sleeve member to provide the greatest cushioning effect when
the prope~ler is driven in the forward direction, the space required
by the cushioning system can be reduced. Limiting the number of
10 propeller driving ridges to two also tends to increase the space
available for cushioning against impacts while maintaining the required
area for the exhaust gas passageway.
Description of the Drawings
Figure 1 is an exploded view of a shock absorbing propeller
15 assembly incorporating the invention.
Figure 2 is a longitudinal partial sectional view of the propeller
assembly of Figure 1.
Figure 3 is a sectional view of the propeller of Figure 1.
Figure 4 is an end view of an alternate embodiment of the cush-
20 ion member suitable for use in the assembly of Claim 1.
Figure 5 is an end view of a second alternate embodiment of thecushion member.
Best Modes For Carrying Out The Invention
As shown in the drawings a marine propeller 10 is supported on
25 the propeller shaft 11 of an outboard propulsion unit 12. ` The
- outboard propulsion unit 12, such as typically found on an outboard
motor or stern drive, includes an exhaust gas passageway 13 for
directing engine exhaust aft to be discharged through the hub of the
propeller 10.
The propeller 10 is supported on the splined propeller shaft 11
by a sleeve member 14 having female splines 15 mating with those of
the propeller shaft 11. A cushion member 16 fits in telescoping
relationship between the sleeve men~ber 14 and the propeller inner
hub 17 to provide a shock absorbing cushion bètween the propellcr lO
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and the propeller. shaft 11. .A. for.ward thrust,.hub 18 ,is provided to
carry the forward thrust from the propeller 10 to the propeller shaft
11 and assist in centering the forward portion of the propeller
relative to the shaft 11. An-aft, splined washer. l9 has f~male splines
5 20 engaging the propeller shaft splines and a shoulder 21 which
assists in centering the ,aft portion of the propeller 10. The . entire
assembly is retained on the propeller shaft 11 by a nut 22 engaging
the thread~,.23-at lthe .end Qf..the propelle,r~ shaft 11,, with the nut, 22
locked against rotation by a tab washer ~24 having tabs whiçh . engage
lO the splined,washer 19 in a conventional manner.( . .
The sleeve member 14 has internal splines 15 engaging the
splinés on the propeller shaft 11 and abuts against the thrust hub 18
which in turn abuts against a shoulder 25 on the propeller shaft.11.
The sleeve member 14 is formed of metal and includes two
l 5 diametrically opposed ~i,ages 26 extending radially outward to trar~smi,t
torque.-. 'rhe ridges 2~ are smoothly faired into the body of the
sleeve member :14.:to avoid stress concentrations. The sleeve member
~ ~ has a ,2 taper from its forward end aft to facilitate both casting
and ass,embly. At the aft end of the sleeve member 14 an annular
20 projection 27 is provided to support the propeller 10.
~ . The propeller 10 includes an inner hub 17 and an outer hub 28
with the outer hub 28 supported on the inner hub- 17 by ,vanes 29.
A propeller 10 having three blades 30 on the outer hub 28 is shown
though any suitable number of blades could be used. The inner hub
25 17 is provided with two deep Ghannels 31 extending radially outward
and having walls aeIïnea ~y the vanes ~9 to accommodate the ridges
26 on the sleeve member .14 and . the cushion member 16. Both the
inner bore 32 of the inner hub 17 and the channels 31 have a 2
taper. At the forward end the inner diameter of the inner hub 17 is
30 sized - to mate with the thrust hub 18, with the reduced diumeter
portion of the thrust hub 18 nesting closely inside the inner bore 32
to center the forward end of the propeller 10 on the propeller shaft
11. A.t the aft end of the propeller inner hub 17 the cup defined by
the inner hub 17 and channels 31 is closed by a flange 33 e~ccept for
35 a central circular opening 34. The ~ircular opening 34 nests around
the annular projection 27 at the aft end of the sieeve member and the
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similar projection on the aft splined washer 19 to center the aft end
of the propeller 10 on the propeller shaft 11. Thus the propeller 10
is held coaxial with the propeller shaft 11.
The cushion member 16 is formed of a shock absorbing
5 elastomer, natural rubber in the preferred embodiment, and fits
between the tapered sleeve member I4 and the tapered inner bore 32
of the inner hub 17 of the propeller 10 to absorb shock between the
sleeve member 14 and the propeller 10. The cushion member 16 may
be in either a relaxed or slightly compressed state when the propeller
lO 10 is held in place by the nut 22 and tab washer 24. To increase the
cushioning effect provided by the cushion member 16, grooves 35 are
formed in the cushion member 16 between the walls of the channels 31
and the ridges 26 on the sleeve member 14. The grooves 35 leave
void spaces between the walls, thus allowing greater compression of
l 5 the cushion member 16 when a shock loading is imposed on the
cushion member 16, either by shifting gears or when the propeller 10
collides with an underwater object.
Several forms of the cushion member 16 are shown in Figures 3,
4, and 5, all formed of the same material. The embodiment shown in
20 Figure 3 positions the sleeve member 14 symmetrically in the propeller
10, ~hus providing equal cushioning against impacts from either
direction while those shown in Figures 4 and 5 position the sleeve
member ridges 26 to provide greater cushioning against impacts
occuring when the propeller 10 is rotating in the clockwise direction,
25 as viewed in the figures. The cushion members 16 of Figure 4 and 5
thus allow the greatest shock absorbtion to be provided when the
propeller 10 is rotating in a direction to drive it forward and will
most frequently be operating at its highest speeds.
The grooves 35 in all of the cushion members 16 are formed on
30 the external surfaces of the members 16, thus allowing the members
to be cast with relatively simple permanent die molds. While the
grooves 3S are illustrated as axially aligned with the sleeve member
14, other orientations are possible and could even be formed as holes
rather than grooves. Though the shape and orientation of the void
35 spaces in the cushion member 16 i~ not critical, the void sp~nces
should be arranged to provide an initinl stiffness great enougll to
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preven~ any substantial deformation. of the .cushion member 16 ~uring
normal operation while allowing substantial deflection during shifting
or upon impact.
In operation, the cushion member 16 is ~slightly compressed
5 between the walls of the channels 31 in the propeller 10 and the
ridges 26 on the sleeve member 14 as the propeller 10 is driven by
the propeller shaft 11. Because the cushion member 16 is loaded in
compression. ~uring, ~normal ,operationj. ther,~ is. litt~e chance of ,its
failing in operation. ~ Further even should .the cushion. member ,16, fail,
l O the ridges 26 on the sleeve member 14 exten~. into the channels 31
and would continue to drive the propeller 10. Should the propeller
10 impact with an under water object, ~he voids in the cushion
member 16 will allow some rotation of the propeller shaft 11 and sleeve
member 14 relative to the propeller 10 to cushion the impact. The
15 ~voids in th.e cushion member 16 serye,to fur.the,r the cushion effect by
increasing the. . relative rotation bet~een- the sleeve member 14 and the
propeller 19 under impact loading.
