Note: Descriptions are shown in the official language in which they were submitted.
Background o E the Invention
The invention relates to marine propellers,
particularly to marine propellers having a plurality of
replaceable blade sections.
Although a variety of replaceable blade propeller
assemblies have been proposed, including those shown in U.S.
Patents 3,764,228, 3,073,395 and 1,010,929, such multiple piece
propeller assemblies have not found widespread acceptance, and
single piece propellers are presently used on the vast majority
of boats. Use of single piece propellers continues despite the
numerous advanti~ges that a practical, reliable, low cost piece
propeller assembly with replaceable blade sections would have.
For example, one piece propellers usually have to be replaced
if they strike heavy, solid objects that severely bend one
blade of the propeller during operation of the boat. One-piece
hub and propeller assemblies are very bulky, and require a
large amount of storage space in a boat. Furthermore,
propeller blades of different pitches are preferable for
various types o:E boat operation. Therefore, it would be
advantageous for a boat owner to be able to easily and
conveniently change blade pitches for different types of
operation, such as pulling skiers or high speed cruising. Many
single piece propeller assemblies include through-the-propeller
exhaust systems having a plurality of passages in the central
portions of the hub through which exhaust gases can escape
without interferring with flow of water around the propeller
blades during normal boat operation. U.S. Patent 3,876,331
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discloses a three-piece marine propeller assembly having
removable blade sections and exhaust gas passages through the
hub portion thereof. However, none of the three-piece
replaceable blade propeller assemblies mentioned above have
found wide-spread acceptance because of their complexity. All
of them have been implemented by means of inherently flimsy
mortise and tenon or collar arrangements for connecting the
opposed flanges of the blade support sections to a main hub.
Besides being inherently rather flimsy, the proposed devices
have been unduly expensive because the main components have
been required to be precisely machined to a grea-t extent to
provide close tolerance required by the type of construction
required by the design of the prior replaceable blade propeller
assemblies.
Despite the variety of proposed replaceable blade
propeller assemblies that have been introduced, there remains a
need for a low cost, highly reliable, easily replaceable
multiple piece replaceable blade propeller assembly that is
substantially more satisfactory to the boating public than in
the device yet proposed.
Accordingly, it is an object of this invention to
provide a low cost, highly durable, easily installable
replaceable blad,e marine propeller system that is significantly
less complex in design than those of the above-mentioned prior
art.
Many commonly used marine propellers utilize rubber
shock absorption devices in their hub assemblies to reduce
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shock transmitted from a propeller blade that strikes an
obstacle to the drive train or motor of the boat to reduce
damage thereto. Provisi.on of such rubber shock absorbing
devices adds to the complexity of its construction and expense
of marine propellers, especially those having through-the-
propeller exhaust passages, which are highly desirable in order
to achieve efficient propeller operation and avoid cavitation
under high performance operating conditions.
Accordingly, it is another object of the invention to
provide a greatly simplified marine propeller that obviates the
need for using rubber devices to prevent transmission of
excessive shock to the drive train and motor of a boat when the
propeller hits a.n obstruction.
Summary of the Invention
Briefly described and in accordance with one
embodiment thereof, the invention provides a marine propeller
including a cent.ral hub for receiving a motor driven shaft, a
plurality of blade support members that are rigidly but
removably attach.ed to the hub, and attaching devices ~or
removably attach.ing the respective blade support members from
the hub, wherein each of the blade support members has a
propeller blade attached thereto, and includes an inner lip and
an outer lip, the outer l.ip of each blade support member
adjoining and overlapping the inner lip of an adjacent blade
support member, the attaching devices pushing the outer lip of
each blade support member tightly toward the hub, thereby so
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forcing the overlapped and adjoined inner lips against the hub
and rigidly attaching each blade support member to the hub.
In this described embodiment of the invention, the
hub includes a cylindrical central portion for receiving the
motor driven shaft and three uniformly spaced spoke members
extending radia:Lly outward from the cylindrical central
portion. The inner lips of the respective blade support
sections adjoin the respective outer end portions of the three
spoke members. A plurality of cap screws extend through
aligned holes in the adjoining outer and inner lips and engage
threaded holes in the outer end portions of the respective
spoke members. The spaces between the radial spoke members
form passages for exhaust gases, which pass from the front of
the propeller out the rear of the propeller during boat
operation. In one described embodiment of the invention, a
propeller blade is integrally formed with each of the blade
support sections,, and the inner and outer lips and also an
outwardly flared! skirt flange are also integrally formed with
each blade suppc~rt section. ~1hen the three blade support
sections are rigidly attached to the hub, the three blade
support sections form a cylindrical sleeve about the hub.
In one! embodiment of the invention, the weakened
portion having a groove therein is provided in the base portion
of each propelle!r blade to provide a break-away blade that will
break free of the blade support sections if that propeller
blade strikes an obstacle during boat operation, thereby
avoiding excessive shock from being transmitted to the drive
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train or motor of the boat and preventing damage thereto.
In another embodiment of the invention, each
propeller blade includes separate base and main portions that
have respective;ly adjoining and mating overlapping tongue and
groove sections, and are held together by a plurality of cap
screws. Propel:Ler blades can then be removed and replaced by
removing those cap screws and fastening new propeller blades
onto the original bases.
Brief Description of the Drawings
Fig. 1 is a partial exploded view of one embodiment
of the invention.
Fig. 2 is a perspective view of the hub of the
replaceable blacle propeller of Fig. 1.
Fig. 3 is a partial sectional view of the replaceable
blade propeller shown in Fig. 1.
Fig. 4 i9 a partial top view of the propeller of
Fig. 1 with one blade support section moved aside.
Fig. 5 is a sectional view of an alternate embodiment
of the inventiorll.
Fig. ~ is an enlarged view of detail 6 of Fig. 5.
Fig. 7 is a side view of an embodiment of the
invention shown in Fi.g. 5.
Description of the Invention
Referring now to the drawings, particularly
Figs. 1-~, replaceable blade propeller assembly 1 includes a
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hub 3 and three replaceable blade sections 5, 11 and 15 that
support propeller blades 7, 13, and 17, respectively.
Referring particularly to Figs. 1 and 2, hub 3 (which
is shown reversed end to end in Fig. 2) includes a cylindrical
center portion 3B having an axial hole 3A therein for receiving
a motor driven shaft. The rear end of hole 3A has a plurality
of spline teeth 3A' for engaging mating teeth of a typical
motor driven shaft. Three spoke members 3C, 3E, and 3F extend
radially outward from cylindrical portion 3B of hub 3. Each of
spoke members 3C, 3E, and 3F is integral with hub section 3B,
is rectangular in configuration, and includes a rounded outer
surface such as 3D having a radius of curvature that extends to
the center axis of cylindrical portion 3B.
Each of replaceable blade sections 5, 11, and 15 are
identical, and only blade section 5 will be described in
detail.
Replaceable blade section 5 includes a blade support
section 5A that has the general configuration of a third of a
cylinder. Its leading edge has a shoulder 43 which, in
combination with the similar shoulders of the remaining two
replaceable blade sections forms a cylindrical band of reduced
diameter for cor~municating with a recess in the housing of a
typical propeller shaft for preventing escape of exhaust gases
around the leadin~ of the propeller and causing exhaust gases
to flow through the passages formed by the spaces between spoke
members 3C, 3E, and 3F.
The left edge of blade support section 5A includes an
inner lip 21 having three holes 37 therein. The right-hand
edge of blade support 5A includes an outer lip 23 having a
plurality of holes 35 therein, each of holes 35 having an outer
5 increased diameter shoulder 33 for retaining the head of a cap
screw 39.
Similarly, blade support section 15 has an outer lip
25 and an inner lip 31. Blade support section 11 has an outer
lip 29 and an inner lip 27.
Each outer lip ad~oins and overlaps the inner lip of
an adjacent one of the blade support sections. The holes 37 of
each inner lip are aligned with the spaced holes 19 located
across the outer surface of a respective one of the spoke
members 3C, 3E, or 3F against which that lip member is
15 adjoined. The holes 37 of each lip are also aligned with the
holes 35 of the overlapping outer lip of an adjacent blade
support section.
Each of cap screws 39 passes through one of holes 35
of an outer lip, an aligned hole 37 of an inner lip, and
20 engages the threads of a hole 19 in one of spoke members 3C,
3E, or 3F. The head of each cap screw 39 is retained by the
corresponding shoulder 33.
Thus, it can be seen that when all of the cap screws
39 are in place, the three replaceable blade sections 5, 11 and
25 15 form a contirluous cylinder attached to hub 3 supporting the
three propeller blades 7, 13 and 17, respectively, to provide a
single marine propeller unit.
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Note that the edges such as 45 and 47 of hub 3 are
rounded to prov:ide smooth and efficient flow of pressurized
exhaust gases around spoke members 3C, 3E, etc. and through the
above-mentioned passages to the rear of propeller 1.
Preferably, hub 3 is formed of hard, high ~uality
stainless steel~ Replaceable blade sections 7 can be unitary
devices cast from suitable aluminum or aluminum alloy
materials, plast:ic or stainless steel materials, or the like.
Referring now to Fig. 5, in an alternate embodiment
of the invention, each of the propeller blades, such as 7,
include a base portion 7' attached to the outer surface of
blade support section, such as 5A. As best shown in Fig. 6,
which is an enlarged view of detail 6 of Fig. 5, base section
7' includes a lip section 51 that has an interior narrowed
upper end 51A. Upper section of blade 7 includes a groove 60
that receives narrowed portion 51A of lip 51. The upper
portion of blade 7 includes a lip 55 that has an interior
narrowed portion 55A that fits snugly in a slot 62 of base
portion 7'. The surfaces of lips 51 and 55 are precisely flat,
so that the corresponding lip and groove portions of base
section 7' and the upper portion of blade 7 fits snugly in a
tongue-and-groove relationship. A hole 57 through lip section
51 and a hole 5~ through lip section 55 are aligned when the
upper section of blade 7 is snugly mated with base section 7'
thereof. A cap screw 61 extends through clearance hole 59 and
engages threads of hole 57, and is flush with the left surface
of lip 51 when cap screw 61 is tightened.
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In this embodiment of the invention, a groove 49
disposed above the connecting means shown in Fig. 6 is provided
along the width of each propeller blade, such as 7, as better
seen in Fig. 7. This groove results in a weakened section near
the base of blade 7, so that the main portion of blade 7 will
break away from the base portion 7' thereof if the main portion
hits an obstruction during operation of the boat. This will
prevent excessive shock from being transmitted through the
propeller shaft to the drive train or motor of the boat, and
thereby will prevent damage to the drive train or motor. The
broken main blade section 7 can then be removed and replaced by
removing the cap screws 61 and reinstalling a spare blade. Of
course, different pitched blades can be easily installed.
In Fig. 7, the arrangement of Fig. 5 is shown on a
conventional single piece hub and blade support section,
wherein the base support sections ar~o separately removable.
The described embodiments of the invention provide a
low cost, highly rigid and durable, and greatly simplified
replaceable blade marine propeller that overcomes the
previously mentioned disadvantages of prior art replaceable
blade marine propellers. In the embodiments of the invention
shown in Figs. 5 through 7, spare main blade portions of
different pitches may be stored in a boat without requiring a
significant amount of storage space. The embodiment of the
invention shown in Figs. 1-4 provides an extremely rugged
arrangement that allows quick replacement of an entire blade
section if one blade is damaged, or if a propeller of different
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pitch is required without the necessity of removing the hub
from the propeller shaft. The replaceable blade sections of
Fig. 1 are much more easily stored than an entire spare
propeller. The cost of each of replaceable blade sections such
as 5, 11, etc. is far less than the cost of a replacement
single piece marine propeller of comparable performance
capability.
~ Ihile the invention has been described with reference
to a particular embodiment thereof, those skilled in the art
will be able to make various obvious modifications to the
described embodiments of the invention without departing from
the true spirit and scope thereof.
