Note: Descriptions are shown in the official language in which they were submitted.
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MARINE PROPULSION DEVICE
BACKGROUND OF THE INVENTION
This invention relates to marine propulsion devices
and more particularly to the tilt and trim systems for such
devices.
Marine propulsion devices, such as outboard motors,
generally include a hydraulic tilt system for trimming and
tilting the propulsion device upwardly about a transverse axis
to permit the device to be operated in shallow or
vegetation-filled water. Toward this end, the propulsion
device is pivotally mounted on a bracket secured to the transom
of the boat to be driven. The hydraulic tilt system generally
includes a tilt cylinder pivotally connected to the propulsion
device and the bracket for pivoting the propulsion device
upwardly and one or more relativ~ly short trim cylinders
mounted on the bracket and engageable with the motor for
tilting the propulsion device through relatively small angles.
The hydraulic trim and tilt cylinders are generally
pressurized by a single pump. Initially, both the trim and
tilt cylinders are active to trim the propulsion unit through a
relatively small angle. After the trim cylinders have reached
the end of their stroke, further pivotal movement is under the
operation of the tilt cylinder.
When the propulsion device is pivoted upwardly at a
relatively high angle, the engine is normally run at idle or a
relatively slow speed. However, should the throttle be engaged
inadvertently so that the engine begins operating at a high
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speed, considerable torque will be exerted on the propulsion
device, tending to pivot the same downwardly. In order to
prevent damage to the hydraulic system, a relief valve is
provided which permits the propulsion device to pivot
downwardly in the event this thrust-induced pressure exceeds
some predetermined value. Under such circumstances, the
propulsion device may pivot downwardly at such a rapid rate
that the trim cylinders are damaged.
SUMMARY OF THE INVENTION
It is an object of the invention to provide a new and
improved tilt and trim system for marine propulsion devices.
A further object of the invention is to provide a trim
and tilt system for marine propulsion devices which preven,ts
the rapid descent of the device should the device be throttled
up while in a tilted position.
A still further object of the invention is to provide
a marine propulsion device with means for protecting the trim
cylinders from damage which would otherwise occur as the result
of rapid descent from an elevated position.
These and other objects and advantages of the present
invention will become more apparent from the detailed
description thereof taken with the accompanying drawings.
In general terms, the invention comprises a marine
propulsion device including first means adapted to be attached
to a boat hull and a propulsion assembly having a propeller
adapted to be driven by an engine. The propulsion assembly is
connected to the first means for vertical pivotal movement
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relative thereto. A hydraulic tilt cylinder and piston
assembly has one end connected to the first means and a second
end connected to the propulsion assembly, the tilt cylinder
being operative to move the piston toward the other end when
the one end is pressurized to tilt the propulsion assembly
upwardly. Actuation of the propeller while the propulsion
assembly is tilted upwardly is operative to force the
propulsion device against the piston. A valve means is
operable when the piston is forced toward the one end of the
cylinder to vent hydraulic fluid from the one end of the
cylinder and control means are provided for controlling the
flow rate of fluid through the valve means to prevent the rapid
descent of the propulsion assembly.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a side elevational view, partly in
section, of a portion of a marine propulsion device
incorporating the present invention; and
Figure 2 schematically illustrates the hydraulic
system according to the preferred embodiment of the invention
and employed in the marine propulsion device shown in Figure 1.
ETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Figure 1 schematically illustrates a marine propulsion
device in the form of an outboard motor 11 which includes a
mounting bracket 13 adapted to be attached in any suitable
manner to the transom or hull of a boat 15. The motor 11 may
be pivotally connected to the bracket 13 in any suitable
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manner, such as, by means of a sw~vel bracket 19 which is
connected to the motor 11 and which is pivotally connected to
the mounting bracket 13 by a generally horizontally extending
tilt pin 21. A trim and tilt system 22 is operative to pivot
the motor 11 about the pin 21 as will be described in greater
detail below. It will be appreciated by those skilled in the
art that the propulsion device also includes an internal
combustion engine (not shown) which is coupled by a shaft and
drive train (not shown) to a rotatably mounted propeller 23.
The trim and tilt system 22 includes one or more trim
cylinders 31 and one or more tilt cylinders 33. The trim
cylinders 31 are fixedly mounted at one end on the mounting
bracket 13 and each includes a piston 34 movable therein and
connected to a stem 36 having a rounded head 37 for bearing
against the lower end of the swivel bracket 19. It will be
appreciated that when the tilt cylinders 33 are pressurized at
their lower ends 38, the propulsion device 11 will be tilted
upwardly about tilt pin 21.
The tilt cylinder 33 is pivotally connected at its
lower end to the mounting bracket 13 and at its upper end to
the swivel bracket 19 so that pressurization of the tilt
cylinder will cause the propulsion device 11 to tilt upwardly
and in a counterclockwise direction as viewed in Figure 1. It
will be appreciated that because the stroke of the tilt
cylinder 33 exceeds that of the trim cylinders 31, both the
trim and tilt cylinders will be employed when the propulsion
device is being trimmed. On the other hand, when the trim
cylinders have reached the maximum extent of their stroke,
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further pivotal movement will be under the operation of the
tilt cylinder 33.
The tilt cylinder 33 also includes a piston 39 having
a stem 40 which is pivotally connected at its upper end to the
swivel bracket 19. It will be appreciated that when the lower
end 42 of the cylinder 33 is pressurized, the piston 39 will
move toward the other end 43 of cylinder 33 whereby the
propulsion device 11 will be pivoted in a counterclockwise
direction about swivel bracket 19 as shown in Figure 1 while
pressurization of the other end 43 will pivot the propulsion
device in the opposite direction.
A one-way valve 45 located in the piston 39 prevents
fluid flow from the lower end of cylinder 42 to the upper end
43, but permits flow in the opposite direction. While the
valve 45 may take any conventional form, in the illustrated
embodiment it comprises a spring biased ball check valve.
Valve 45 permits the tilt cylinder 33 to extend rapidly as
fluid flows from the upper end 43 to the lower end 42 in the
event the propulsion device 11 impacts an underwater obstacle.
The bias on the valve 45 is relatively high, for example, about
2500 lbs./sq. in.
Reference is now made to Figure 2, which schematically
illustrates the hydraulic assembly in accordance with the
preferred embodiment of the invention. In particular, the
hydraulic assembly includes pressure fluid supply and control
means for selectively supplying the trim and tilt cylinders 31
and 33 with pressure fluid. While various means may be
employed, in the illustrated embodiment, the fluid pressure
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supply and control means comprises a reservoir or sump 51, a
pump 52, driven by a reversible motor 53 and connected to sump
51, a control cylinder or valve 54 connected to pump 52, and
fluid duct coupling the control valve 54 with the tilt and trim
cylinders 31 and 33 and the pump 52. The pump 52 may be
reversibly driven by motor 53 and includes a first fluid
connection or ducts 55 for supplying pressure fluid when the
pump 52 is rotating in one direction and a second duct 56 for
supplying pressure fluid when pump 52 is rotated in the
opposite direction. The ducts 55 and 56 also are respectively
connected through conduits 57 and 58 with reservoir 51. In
addition, the conduits 57 and 58 include one-way valves 59 and
60, respectively, which permit flow to the pump 52 and prevent
flow from the pump to the reservoir 51. Preferably, the
conduits 58 and 59 communicate with the sump or reservoir 51
through a common filter 61.
The control valve 54 includes a housing or cylinder 62
which has opposing first and second ends 64 and 65 which
respectively communicate with the ducts 58 and 59. Disposed
within the housing 62 is a control piston 66 which is mounted
for movement from a center position toward the end 65 when the
first end of the cylinder 64 is pressurized from conduit 58.
Conversely, when the end 65 of cylinder 62 is pressurized
through conduit 57, piston 69 will move toward the end 64 of
cylinder 62.
Communicating with the first end 64 of cylinder 62 is
a spring biased, normally closed valve 70 which also
communicates through conduits 72 and 73, respectively, with the
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lower ends of the trim cylinders 31 and the end 42 of tilt
cylinder 33. A second spring biased, normally closed valve 75
communicates with the end 65 of cylinder 62 and through conduit
75 to the upper end 43 of tilt cylinder 33. While any suitable
valves may be employed, ball check valves are shown for
purposes of illustration.
Any suitable means, such as stems 78 and 79~ which
extend coaxially from the opposite ends of piston 69, are
provided for respectively opening ball valves 70 and 75 upon
movement of the piston 69 into the ends 64 or 65 of cylinder
62~ In particular, when the first end 64 of cylinder 62 is
pressurized, the piston 69 will move toward the second end 65
whereby stem 79 will move ball valve 75 off of its seat to
communicate conduits 76 and 57~ In addition, the pressure in
cylinder end 64 will move ball valve 70 off of its seat and
against its biasing spring, thereby communicating conduits 58
and 72. Conversely, when the end 65 of cylinder 62 is
pressurized, piston 69 will move to the end 64 of cylinder 62
so that stem 78 will move valve 70 from its seat, while the
pressure will move valve 75 from its seat and against its
biasing spring.
A manual release valve 80 is interposed between
conduits 82 and 83 ~ which aré connected between conduits 76 and
72~ Valve 80 has a closed position, a first open position
which connects conduits 82 and 83 to each other, and a third
position which connects conduits 82 and 83 to sump Sl through
conduit 85 and filter 86 ~ Also connected between conduit 83
and sump 51 is the series combination of a shallow water drive
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valve 88 and an orifice 90.
When the motor 53 is at rest and the pump 52 is not
operating, the piston 69 is locked in a position intermediate
the ends of cylinder 62 and the valves 70 and 75 are biased
into a closed position by their respective springs. Assuming
that the manual release valve 80 is also closed, fluid flow in
either direction is prevented and the trim cylinders 31 and the
tilt cylinder 33 are maintained in position.
Assume for purposes of illustration that the trim
cylinders 31 and the tilt cylinder 33 are in their retracted
conditions and the marine propulsion device 11 is untilted. If
it is desired to upwardly tilt the marine propulsion device 11,
the motor 53 is actuated to drive pump 52 in a forward
direction thereby providing fluid under pressure through
conduits 55 and 58 to the end 64 of cylinder 62. This moves
the valve 70 from its seat thereby providing fluid under
pressure to conduit 72, which is connected to the lower ends of
the trim cylinders 31 and the lower end 42 of tilt cylinder
33. As a result, each of the trim cylinders 31 and the tilt
cylinder 33 are extended so that the marine propulsion device
11 begins to pivot counterclockwise as shown in Figure 1.
Pressurization of the end 64 of cylinder 62 will also cause
piston 69 to move toward the end 65 of cylinder 62 so that stem
79 moves valve 75 from its seat. This permits return fluid
flow from the end 43 of tilt cylinder 33 to the intake of pump
52 through conduits 75 and 56. Fluid flow from the upper end
of trim cylinders 31 flows to sump 51 through conduit 92 and
filter 93.
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If it is desired to trim the propulsion device 11, the
motor and pump are stopped before the trim cylinders 31 reach
the end of their stroke. This causes a decrease in fluid
pressure within the end 64 of cylinder 62 which permits the
piston 69 to return to its neutral position and the valves 70
and 75 to close under the influence of their respective biasing
springs. The propulsion device 11 will be supported in its
trim position by the trim cylinders 31 and the tilt cylinder 33.
On the other hand, if it is desired to move the
propulsion device ll into a tilt position beyond the stroke of
the trim cylinders 31, operation of the pump 52 is continued so
that the trim cylinders 31 reach the end of their stroke and
continued movement of the piston 39 will tilt the propulsion
device ll into a higher tilt angle. After the piston 39
reaches the end of its stroke, a pressure relief valve 97
connected between conduit 55 and sump 51 will open to connect
the pump 52 to the sump 51 and thereby prevent damage to the
cylinder 33 or the hydraulic system. The pump 52 is then
deactivated so that the valves 70 and 75 close and the piston
69 returns to its neutral position. The cylinder 33 will then
support the propulsion device 11 in its tilted position.
When it is desired to lower the propulsion device 11
from its tilted position, the motor 53 and the pump 52 are
operated in the reverse direction, thereby pressurizing the end
65 of cylinder 62. This moves the valve 75 from its seat so
that hydraulic fluid under pressure is provided to the upper
end 43 of tilt cylinder 33 through conduits 57 and 76. In
addition, piston 69 moves toward the end 64 of cylinder 62,
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thereby moving valve 70 from its seat so that hydraulic fluid
can flow from the lower end 42 of tilt cylinder 33 to the
opposite side of the pump 52. When the piston 39 reaches the
end of its stroke, a second pressure relief valve 94, which is
connected between conduit 57 and sump 51, will open to prevent
damage to the system as the pump 40 continues to operate.
Normally, when the propulsion device 11 is in its
tilted position, the engine is idled or operated at a very low
speed. However, should the throttle be moved, causing the
engine to operate at a much higher speed, the action of the
propeller 33 will tend to pivot the propulsion device
downwardly and in the clockwise direction as viewed in
Figure 1. Fluid flows from the lower end 42 of tilt cylinder
33 through pressure relief valve 88. In prior art systems,
this descent occurred quite rapidly and tended to damage the
trim cylinders 31. A flow restricting orifice 90 according to
the invention limits the rate of descent in the event the
engine throttle is actuated, so that the trim cylinders 33 are
not damaged.
Because the pump is not operating when the piston 39
descends as a result of the engine being operated, fluid is
drawn to the upper end of the cylinder from sump 51 through
filter 95, check valve 96, and conduit 98.
While only a single embodiment of the invention has
been illustrated and described, those skilled in the art will
appreciate that the invention is not limited to the details set
forth in the description of the preferred embodiment and
illustrated in the drawings and that the invention may be
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practiced by the use of other embodiments as well.
Accordingly, it is not intended that the invention be limited
to the embodiment illustrated and described, but only by the
scope of the appended claims.
