Note: Descriptions are shown in the official language in which they were submitted.
MARINE PROPULSION DEVICE 203743S
BACKGROUND OF THE INVENTION
The invention relates generally to marine propulsion
devices, and more specifically to marine propulsion devices
having a thrust washer on the propeller shaft.
The use of thrust washers in marine propulsion devices
to position a propeller on a propeller shaft and to transmit
thrust from the propeller to the propeller shaft is known. In
general, prior art thrust washers are machined with a
frustoconical or tapered inner surface and are designed to be
placed over the propeller shaft to engage a portion of the
propeller shaft having a frustoconical or tapered outer
surface. When the thrust washer is placed on the shaft, the
tapered surface of the thrust washer engages the tapered
surface of the propeller shaft. The engaged tapered surfaces
form a contact zone. Both thrust loads developed by rotation
of the propeller and any bending loads caused by hydrodynamic
effects on the propeller are transferred from the propeller to
the propeller shaft through the contact zone.
Prior art thrust washer designs present difficulty
when the tapered surfaces of the propeller shaft and the thrust
washer do not match. Poor manufscture or ~ssembly of the
thrust washer or the propeller shaft can result in mismatched
tapered surfaces. Mi~matched thrust washers and propeller
-2- 2~37435
shafts can result in a highly loaded contact zone which, in the
worst case, is a line contact between the thrust washer and the
shaft around the tapered portion of the propeller shaft. The
smaller the contact zone, the greater the concentration of
stress, and the greater the risk of failure du~ to fatigue.
Accordingly, prior art designs require the expensive machining
of the frustoconical mating surfaces on the thrust washer and
the propeller shaft to narrow tolerance dimensions. Also,
additional measures may have to be taken to assure that an
assembled thrust washer and propeller shaft are properly
matched.
Prior art thrust washer designs present additional
difficulty, because the thrust washer acts on a tapered
surface. Loads from the propeller are concentrated by the
thrust washer on the reduced diameter portion of the shaft
instead of on the larger diameter of the shaft. Bending loads
on a reduced diameter also concentrate stress.
Attention is directed to the thrust washers disclosed
in the following U.S. Patents: U.S. Patent No. 4,793,773
issued to Kinouchi, et al on December 27, 1988; U.S. Patent No.
4,566,855 issued to Costabile, et al on January 28, 1986; U.S.
Patent No. 4,545,771 issued to Iio on October 8, 1985; U.S.
Patent No. 3,876,332 issued to Kashmerick on April 8, 1975;
U.S. Patent No. 3,759,076 issued to Reese on September 18,
1973; U.S. Patent No. 3,444,932 issued to Wlezien on May 20,
1969; U.S. Patent No. 3,389,558 issued to Hall on June 25,
1968; and U.S. Patent No. 3,335,803 issued to Van Ranst on
August 15, 1967.
20374:~S
--3--
SUMMARY OF THE INVENTION
The invention provides a marine propulsion device
including a lower unit, a propeller shaft rotatably supported
by the lower unit and adapted to be driven by an engine and to
support a propeller, the shaft including a longitudinal axis
and a first surface defining a plane which is substantially
normal to the axis, and thrust washer means for transmitting
thrusting force from the propeller to the surface.
In one embodiment, the shaft includes a generally
cylindrical second surface, ~nd a generally cylindrical third
surface, and the first surface is located intermediate the
second and third surfaces.
The invention also provides a marine propulsion device
including a lower unit, a propeller shaft rotatably supported
by the lower unit and adapted to be driven by an engine and to
support a propeller, the shaft including a longitudinal axis, a
first generally cylindrical surface having a first diameter, a
second generally cylindrical surface having a second diameter,
and a transition surface located intermediate the first and
second cylindrical surfaces, the transition surface defining a
plane which is substantially normal to the axis, and thrust
washer means for transmitting thrusting force from the
propeller to the transition surface, for transmitting bending
forces from the propeller to the first cylindrical surface and
for isolating the second cylindrical surface from bending
forces from the propeller.
The invention also provides a marine propulsion device
including a lower unit, a prope~ler shaft rotatably supported
20:~74:~5
--4--
by the lower unit and adapted to be driven by an engine and to
support a propeller, the shaft including a first generally
cylindrical surface and a second generally cylindrical surface,
and means for transmitting bending force from the propeller to
the first surface and for isolating the second surface from
bending force from the propeller.
A principal feature of the invention is the provision
of a propeller shaft having a relatively large diameter for
carrying the bending loads caused by hydrodynamic forces acting
on the propeller, and a surface defining a plane normal to the
axis of the propeller shaft for carrying the thrust loads
developed by rotation of the propeller.
Another feature of the invention is the provision of a
thruqt washer and propeller shaft which afford the transfer of
thrust and bending forcec between the thrust washer and the
propeller shaft through mating surfaces which are perpendicular
to the components of force transmitted therethrough, thus
eliminating expensive machining of frustoconical portions of
the thrust washer and the propeller shaft.
Another feature of the invention is the provision of a
thrust washer and propeller shaft which, along a portion of the
shaft, are spaced apart to isolate the portion of the propeller
shaft from the bending loads from the propeller.
Other features and advantages of the invention will
become apparent to those skilled in the art upon review of the
following detailed description, claims and drawings.
2037A3S
--5--
DESCRIPTION OF DRAWINGS
Figure l is an elevation view of a marine propulsion
device embodying the invention.
Figure 2 is an enlarged view, in partial section, of a
portion of the marine propulsion device shown in Fig. 1.
Figure 3 is an enlarged view of a portion of Fig. 3.
Figure 4 is an enlarged perspective view in
cross-section of a portion of the marine propulsion device
shown in Fig. 1.
Before one embodiment of the invention is explained in
detail, it is to be understood that the invention is not
limited in its application to the details of construction and
the arrangements of components set forth in the following
description or illustrated in the drawings. The invention is
capable of other embodiments and of being practiced or being
carried out in variouq ways. Also, it is to be understood that
the phraseology and terminology used herein is for the purpose
of description and should not be regarded as limiting.
GENERAL DESCRIPTION
Shown in Figure 1 is a marine propulsion device 10
which is in the form of an outboard motor 10. However, the
invention is applicable to other forms of marine propulsion
devices, such as, for example, stern drive units. The marine
propulsion device 10 shown in Figure 1 includes a transom
bracket 12 fixed to a boat transom and a swivel bracket 14
connected to the transom bracket 12 for pivotal movement
relative thereto about a horizontal axis 16. The marine
-6- 2037435
propulsio~ device 10 also includes a propulsion unit 17
connected to the swivel bracket 14 for pivotal movement
relative thereto about a vertical axis 18 and for common
movement therewith about the horizontal axis 16. The
propulsion unit 17 includes a power head 20 which includes an
internal combustion engine 22 and which is supported on a lower
unit 24. In the illustrated embodiment, the lower unit 24
includes a drive shaft housing 26 and a gear case 28 which is
fixed to the lower end 30 of the drive shaft housing 26.
The marine propulsion device 10 also includes a
propeller ~haft 32 which has a longitudinal axis 33, which is
supported by the gear case 28 for rotation about the axis 33,
and which i~ connected through a reversing transmission 34 to a
drive shaft 36 that extends through the drive shaft housing 26
and that is driven by the engine 22.
A~ ~hown in Figure 2, the propeller shaft 32 includes
a first portion 40 having a first generally cylindrical outer
surface 42. The propeller shaft 32 also includes a transition
surface 44 located rearwardly of the first portion 40. The
tran~ition surface 44 is generally perpendicular to the
longitudinal axis 33 and defines a plane which is generally
normal to the longitudinal axis 33. The propeller shaft 32
also includes a second portion 46 which extends rearwardly from
the tran~ition ~urface 44, which has a second generally
cylindrical outer surface 48 and which has a diameter smaller
than the diameter of the first portion 40. Thus, the
transition surface 44 is located intermediate the first
cylindrical surface 42 and the second cylindrical surface 48.
~7~ 203~43S
The marine propulsion device 10 also includes a
propeller 50. The propeller 50 includes a generaily
cylindrical inner hub 52 having a forward rim 53 and an inner
surface 54 which extends along the longitudinal axis 33 and
which has a diameter sufficiently large to allow the inner hub
52 to house the second portion 46 of the shaft 32. The
propeller S0 also has a generally cylindrical outer hub 56
which is spaced radially and outwardly from the inner hub 52.
A plurality of webs or connecting members 58 (one of which is
shown) extends between the inner hub 52 and the outer hub 56 to
connect the inner hub 52 and outer hub 56. A plurality of
propeller blades 60 extends radially and outwardly from the
outer hub 56.
The marine propulsion device 10 also includes means 62
for mounting the propeller 50 on the propeller shaft 32. While
various other constructions could be employed, in the
illustrated embodiment, the means 62 for mounting the propeller
S0 on the propeller shaft 32 includes a cylindrical sleeve 64
which is mounted on the second portion 46 of the propeller
shaft 32. In order to transmit torque between the second
portion 46 of the shaft 32 and the sleeve 64, in the preferred
embodiment, the second portion 46 of the shaft 32 and the
sleeve 64 are splined together at 66. In order to transmit
torque to the inner hub 52 of the propeller 50 from the sleeve
64, the means 62 for mounting the propeller 50 on the shaft 32
also includes a generally annular resilient member or
elastomeric ring 68 located between the sleeve 64 and the inner
hub 52. The propeller 50 is driven by the propeller shaft 32
-8- 20~74~S
by a friction fit between the sleeve 64 and the elastomeric
ring 68, and between the elastomeric ring 68 and the inner
surface 54 of the inner hub 52. The elastomeric ring 68
transfers torque from the inner sleeve 64 to the propeller so,
but allows the propeller 50 to slip relative to the propeller
shaft 32 in the event the propeller blades 60 hit an
obstruction.
During operation of the marine propulsion device 10,
the propeller 50 is driven by rotation of the propeller shaft
32. Driving rotation of the propeller S0 by the propeller
shaft 32 and hydrodynamic effects created by driving the
propeller 50 through water result in a combination of thrust
loads, the components of force acting along a line parallel to
the axis 33 of the propeller shaft 32, and bending loads, the
components of force acting along a line which is normal to the
axis 33, on the propeller shaft 32.
In order to transmit the loads from the propeller 50,
the marine propulsion device 10 also includes means 69 for
transmitting thrusting force from the propeller 50 to the
transition surface 44, for transmitting bending forces from the
propeller 50 to the first cylindrical surface 42 of the
propeller shaft 32 and for isolating the second cylindrical
~urface 48 of the propeller shaft 32 from bending forces from
the propeller 50. While various other arrangements could be
employed, in the disclosed embodiment, the means 69 includes a
thrust washer 70 mounted on the propeller shaft 32. The thrust
washer 70 has a generally annular disk shape and, as best shown
in Fig. 4, includes a forward face 72, a rearward face 74 and
-9- 2037435
an annular notch 76 in the rearward face extending around the
circumference of the thrust washer 70 and engaging the forward
rim 53 of the inner hub 52. The washer 70 has therethrough a
bore 78 extending parallel to the longitudinal axis 38. The
bore 78 defines a first, generally cylindrical inner surface 79
which surrounds a length of the second portion 46 of the
propeller shaft 32. As best shown in Figure 3, the first inner
surface 79 is spaced from the second portion 46 of the
propeller shaft 32 and provides an annular clearance between
the outer surface 48 of the second portion 46 of the shaft 32
and the first inner surface 79 of the thrust waæher 70. The
thru~t washer 70 also includes a counterbore 80 extending
partially therethrough. The counterbore 80 is coaxial with the
bore 78 and extends through the forward face 72 toward the
rearward face 74 and defines a second, generally cylindrical
inner surface 82 which engages the first cylindrical surface 42
of the propeller æhaft 32. The coun~erbore 80 also defines a
shoulder 84 wh$ch engages the transition surface 44 of the
propeller shaft 32. The shoulder 84 defines a surface which is
generally perpendicular to the longitudinal axis 33 of the
shaft 32. When the shoulder 84 and the transition surface 44
engage, substantially all of the shoulder 84 engages the
transition surface 44 to maximize the area of contact between
the transition surface 44 and the shoulder 84.
In the disclosed marine propulsion device 10, thrust
and bending loadæ are transmitted from the propeller 50 to the
propeller shaft 32 along two paths.
-lo- 2037435
The first or primary path for transmission of loads
from the propeller 50 to the shaft 32 is from the forward rim
53 of the inner hub 52 to the circumferential notch 76 on the
thrust washer 70, and through the thrust washer 70 to the shaft
32. In the preferred embodiment, the mating fit between the
thrust washer 70 and the first portion 40 of the shaft 32, and
the fit between the inner hub 52 and the annular notch 76 are
critical and are to close tolerances, so that a substantial
portion of the forces from the propeller 50 are transmitted
through the thrust washer 70 to the first portion 40 of the
shaft 32.
Transmission of loads along the primary path results
in the shaft 32 being subject to thrust forces transmitted to
the transition surface 44. Because thrust forces from the
propeller 50 are substantially equally distributed around the
annular notch 76 of the thrust washer 70, and because the
thrust washer 70 acts against the transition surface 44, which
is normal to the direction of thrust forces, transmission of
thrust forces through the thrust washer 70 does not subject the
propeller shaft 32 to bending loads. Transmission of bending
forces along the primary path are transmitted as bending forces
to the first portion 40 of the shaft through the second inner
surface 82 of the thrust washer 70. Because the first inner
surface 79 of the thrust washer 70 is spaced from the surface
48 of the shaft 32, the second portion 46 of the propeller
shaft 32 is substantially isolated from the bending forces
transmitted along the primary path.
-11- z0~74:~5
~ he secondary path for transmission of forces from the
propeller 50 to the shaft 32 is from the inner hub 53 of the
propeller 50 to the propeller shaft 32 through the elastomeric
ring 68 and the sleeve 64.
Because the diameter of the first portion 40 of the
propeller shaft 32 is larger than the diameter of the second
portion 46, the first portion 40 of the propeller shaft 32 is
better suited to bear the bending loads from the propeller S0.
Also, because of the normal relationship between the axis 38
and the shoulder 84 on the thrust washer 70 and between the
axis 38 and the transition surface 44 on the propeller shaft
32, the contact zone formed by the mating surfaces 84 and 44
can be maximized more consistently without expensive machining
and Lnspection of tapered surfaces.
Various other features of the invention are set forth
in the following claims: `
