U.S. patent application number 10/140303 was filed with the patent office on 2002-09-12 for watercraft with steer-responsive throttle.
Invention is credited to Michel, Camille, Rheault, Alain.
Application Number | 20020127926 10/140303 |
Document ID | / |
Family ID | 27409607 |
Filed Date | 2002-09-12 |
United States Patent
Application |
20020127926 |
Kind Code |
A1 |
Michel, Camille ; et
al. |
September 12, 2002 |
WATERCRAFT WITH STEER-RESPONSIVE THROTTLE
Abstract
A watercraft with a steer-responsive throttle generates thrust
when the steerable propulsion unit is turned beyond a predetermined
angular threshold. The turning of the steering wheel beyond the
threshold causes the throttle to be opened so that the steerable
propulsion unit produces a thrust at least equal to the minimal
propulsive force needed to effectively steer the watercraft. A
watercraft equipped with a steerresponsive throttle ensures that
there is always sufficient thrust for steering the watercraft even
when the operator fails to open the throttle manually. This
steerresponsive throttle is applicable to single-engine personal
watercraft, twin-engine jet boats or motorboats equipped with
swivel-mounted outboard motors. In a first embodiment of the
steer-responsive throttle, rotation of the steering wheel beyond
the angular threshold causes an actuating cable to open the
throttle. In a second embodiment, an electronic control system
regulates the throttle by calculating the optimal throttle setting
based on measurements derived from a speed sensor, a steering angle
sensor and, optionally, a throttle position sensor.
Inventors: |
Michel, Camille; (Ste-Fuy,
CA) ; Rheault, Alain; (Longusuit, CA) |
Correspondence
Address: |
PILLSBURY WINTHROP
1600 Tysons Boulevard
McLean
VA
22102
US
|
Family ID: |
27409607 |
Appl. No.: |
10/140303 |
Filed: |
May 8, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10140303 |
May 8, 2002 |
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09961387 |
Sep 25, 2001 |
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09961387 |
Sep 25, 2001 |
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09383073 |
Aug 26, 1999 |
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6336833 |
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09383073 |
Aug 26, 1999 |
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08782490 |
Jan 10, 1997 |
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Current U.S.
Class: |
440/38 |
Current CPC
Class: |
G05G 11/00 20130101;
B63H 21/21 20130101; F02D 11/02 20130101; B63H 21/22 20130101; F02B
61/045 20130101 |
Class at
Publication: |
440/38 |
International
Class: |
B63H 011/00 |
Claims
What is claimed is:
1. A watercraft, comprising: a hull; a steering assembly supported
by the hull; an engine mounted within the hull; a manually actuated
throttle control operatively connected to the engine for manually
changing engine speed; a jet propulsion assembly supported by the
hull having an inlet that draws in water and an outlet which expels
water, wherein the jet propulsion assembly is operatively connected
to the engine so that the engine drives the jet propulsion assembly
to generate thrust and expel a pressurized stream of water that
propels the watercraft; a steering nozzle disposed at the outlet of
the jet propulsion assembly and operatively connected to the
steering assembly, wherein the steering assembly transmits steering
signals to the steering nozzle to direct the pressurized stream of
water in a desired direction to steer the watercraft; and an
actuator operatively connected to the engine and the steering
assembly that controls engine speed so that a minimum thrust is
generated by the jet propulsion assembly when the steering assembly
is turned beyond an angular threshold to effectively steer the
watercraft.
Description
[0001] The present application claims priority to and is a
continuation of U.S. application Ser. No. 09/961,387, filed Sep.
25, 2001, which is a continuation of U.S. application Ser. No.
09/383,073, filed Aug. 26, 1999, and issued as U.S. Pat. No.
6,336,833, which is a continuation-in-part of U.S. application Ser.
No. 08/782,490, filed Jan. 10, 1997, now abandoned. This
application relates to co-pending U.S. application Ser. No.
09/904,742, which is also a continuation of U.S. application Ser.
No. 08/782,490. The entirety of each of the above identified
applications are hereby incorporated into the present application
by reference.
FIELD OF THE INVENTION
[0002] The present invention relates to watercraft with steerable
propulsion units and, more particularly, to a steering system for
such a watercraft.
BACKGROUND OF THE INVENTION
[0003] A watercraft equipped with a steerable propulsion unit can
only be steered effectively when the propulsion unit is generating
thrust. Examples of watercraft with a steerable propulsion unit are
jet boats, personal watercraft, jet skis, and motorboats having
swivel-mounted outboard motors. With any of these types of
watercraft, the operator who releases the throttle loses the
ability to effectively steer the watercraft. At low speeds, this
typically makes docking difficult because it becomes necessary to
open the throttle to maneuver the boat. Similarly, if the throttle
is suddenly cut while running the watercraft at high speeds, the
ability to steer can only be regained by reopening the
throttle.
SUMMARY OF THE RELEVANT PRIOR ART
[0004] U.S. Pat. No. 3,183,379 (Heidner) discloses a speed control
device for use primarily on an outboard motor. When a motorboat
that is either at rest or traveling at low speed is steered sharply
(i.e. beyond a predetermined angle), a limiting rod interferes with
the rotation of a throttle control member thereby limiting the RPM
of the motor. The throttle control has a cam with a lobe that
catches the limiting rod when the limiting rod is pressed against
the cam. This prevents the boat from capsizing when the throttle is
suddenly advanced and the motor is already set for a sharp turn.
Since the danger of capsizing is significantly less when the boat
is already traveling above a predetermined speed, the speed control
device allows the motor to be swiveled through a full extent
without actuating the limiting rod and interfering with the
throttle control member. The predetermined speed (or RPM) above
which the throttle control member becomes unconstrained by the
limiting rod corresponds to an angular position of the cam at which
the leading edge of the lobe has been rotated at least slightly
beyond the line of action of the limiting rod.
[0005] U.S. Pat. No. 4,230,646 (Ghizzoni) discloses a carburetor
device having a compensating membrane and a fuel accumulating
chamber which is connected through conventional idling and
high-speed jets to a Venturi upstream from which there is provided
an air intake manifold. Externally of the compensating membrane is
a sealed chamber which communicates via a flexible tube with a
compensating chamber which is maintained naturally or artificially
at atmospheric pressure.
[0006] U.S. Pat. Nos. 5,368,510 and 5,538,449 (Richard) disclose a
trolling valve safety device that locks or limits actuation of a
boat engine throttle from its idle position.
[0007] U.S. Pat. No. 5,423,277 (Gai) discloses a safety device for
helm, throttle and directional controls of watercraft which
prevents a boat from perilously spiraling into a man thrown
overboard by ensuring that the rudder does not flop to one side
under normal water flow pressure.
[0008] U.S. Pat. No. 5,256,092 (Jones) discloses a
carburetor-adjusting accessory harness for personal jet-propelled
watercraft. This removably mounted harness enables one to finely
tune the carburetor while the watercraft is operating unanchored
and afloat without having to remove the hood.
[0009] U.S. Pat. No. 5,253,604 (Bohlin) discloses an
electromechanical steering device, especially for boats, that
comprises an electronic control unit capable of comparing an actual
position signal generated by the steering wheel to a predetermined
position signal and thus actuating a servo motor in accordance with
the difference between said signals.
[0010] U.S. Pat. No. 5,090,929 (Rieben) discloses a paired motor
system for small boat propulsion and steerage. Two spaced-apart
electrically driven motors, which are variable, reversible and
separately controllable by a joystick-type controller, provide
differential propulsion for improved steering and
maneuverability.
[0011] French Patent 2 687 364 (Cany et al) discloses an ergonomic,
simplified control device for operating an outboard motor. A
plurality of control cables links the outboard motor with a single,
centrally mounted control stick.
[0012] U.S. Pat. No. 5,016,553 (Spencer) discloses a vector
steering control system that features at least one thruster mounted
transversely (perpendicular) to the stem drive propeller shaft.
Turning of the steering wheel activates one of the thrusters whose
thrust accelerates the stem of the boat in a direction
perpendicular to the stem drive shaft.
[0013] U.S. Pat. No. 4,962,717 (Tsumiyama) discloses a control
stick that allows a boat to be both steered and accelerated with a
single hand.
[0014] European Patent Application 388 228 (Glen) discloses a
control apparatus for controlling a plurality of outboard motors
with a single tiller. The tiller has a twist grip that winds the
control cables around a drum so that the throttle of each motor can
be controlled by a positive pull-pull action.
[0015] U.S. Pat. No. 4,854,902 (Havins) discloses a boat speed and
direction control system for controlling trolling motors which is
operable in a hands-free manner so that a lone fisherman operating
a craft equipped with such a system would not have to relinquish
control of his rod and reel.
[0016] U.S. Pat. No. 4,739,236 (Burkenpas) discloses a portable
helm that comprises a hand-held controller that can be plugged into
multipin connector-sockets wired at various locations on the ship.
The hand-held controller is able to control the angle of the
rudders, the engine RPM and the direction of the power train (i.e.
forward, neutral or reverse).
[0017] U.S. Pat. No. 3,976,026 (Eastling) discloses a slow-speed
steering control for jetpowered watercraft having a steering plate
(similar to a rudder) mounted parallel to, but beneath, the
deflector plates that vector the thrust of the water exiting the
exhaust port of the jet propulsion unit. The steering plate is
mounted to, and moveable with, the deflector plates such that when
the deflector plates are angled (by turning the steering wheel or
handlebars) the steering plate moves as well. The steering plate is
submerged so that it assists the steering of the boat when the
deflector plates are turned. Even when no flow of water is exiting
the jet propulsion unit, the submerged steering plate still
produces a steering effect when the steering wheel or handlebars
are turned. The steering plate is resiliently mounted to the
deflector plates so that if the underside of the steering plate
collides with land, the steering plate will rise.
[0018] U.S. Pat. No. 3,874,321 (Smith) discloses a boat steering
and reversing system. This system provides a mechanism for rotating
the propulsion unit about a vertical axis by means of a steering
mechanism for normal steering and combining with this arrangement a
reversing changeover control capable of rotating the propulsion
unit by 180 degrees. The mechanism uses a throttle idler or clutch
control to effect the changeover.
[0019] As evinced by the foregoing survey of related prior art, the
closest prior art appears to be a watercraft adapted to carry a
rudder on the underside of its hull. Such a rudder allows the
watercraft to be maneuverable even when the steerable propulsion
unit is not generating any thrust. However, such a rudder is
unsuitable for many jet boats, personal watercraft, jet skis and
motorboats because they preclude these watercraft from operating in
shallow waters which is where these watercraft are commonly used.
The rudder also precludes such a watercraft from being "beached"
without risking damage to the rudder.
[0020] Thus, there is a need in the industry for an improved
steering system for a watercraft equipped with a steerable
propulsion unit.
SUMMARY OF THE INVENTION
[0021] It is thus an object of the present invention to provide an
improved steering system for a watercraft equipped with a steerable
propulsion unit.
[0022] It is another object of the present invention to provide a
watercraft that can be steered effectively when the manual throttle
control is off.
[0023] It is another object of the present invention to provide a
watercraft whose throttle is coupled to the steering of the
watercraft so that the throttle is opened when the watercraft is
steered.
[0024] It is another object of the present invention to provide a
watercraft with steer responsive throttle.
[0025] As embodied and broadly described herein, the present
invention seeks to provide a watercraft comprising:
[0026] (A) a hull
[0027] (B) a steerable propulsion unit driven by an internal
combustion engine, said unit capable of generating thrust and
capable of steering said watercraft by directing said thrust in a
desired direction;
[0028] (C) a manual throttle control for controlling a throttle of
said internal combustion engine;
[0029] (D) a manual steering control for steering said watercraft;
and
[0030] (E) a throttle actuator responsive to said manual steering
control for causing said steerable propulsion unit to generate a
propulsive force at least equal to the minimum propulsive force
necessary to effectively steer said watercraft when said manual
steering control is turned in either direction beyond a
predetermined angular threshold, whereby to cause said watercraft
to remain maneuverable independently of the manual throttle control
setting.
[0031] When the manual steering control is turned beyond a certain,
predetermined angular threshold, the throttle actuator opens the
throttle such that the propulsive force generated by the steerable
propulsion unit is increased to a level corresponding to the
minimal propulsive force needed to effectively steer the
watercraft. This augmentation of propulsive force only occurs if
the manual throttle control is set to produce a propulsive force
less than the minimal propulsive force required for effectively
steering the watercraft. Otherwise, if the manual throttle control
is set to produce a thrust exceeding the minimal propulsive force
required to effectively steer the watercraft, the steer-responsive
throttle will remain open at the level set by the manual throttle
control. Of course, if the manual throttle control is then reduced
to below the threshold setting, the steer-responsive throttle will
remain open so as to produce the minimal propulsive force necessary
to effectively steer the watercraft. Thus, whenever the manual
steering control is turned beyond the angular threshold, the
steer-responsive throttle automatically ensures that the steerable
propulsion unit generates the minimal propulsive force necessary
for effectively steering the watercraft. Thus, the watercraft is
maneuvered more easily since a turning thrust is automatically
generated.
[0032] It is another object of the present invention to provide a
watercraft with a steerresponsive throttle controlled by an
electronic control system.
[0033] As embodied and broadly described herein, the present
invention seeks to provide a watercraft comprising:
[0034] (A) a hull;
[0035] (B) a steerable propulsion unit driven by an internal
combustion engine, said unit capable of generating thrust and
capable of steering said watercraft by directing said thrust in a
desired direction;
[0036] (C) a manual throttle control for controlling said internal
combustion engine;
[0037] (D) a manual steering control for steering said
watercraft;
[0038] (E) a throttle actuator responsive to a signal for causing
the steerable propulsion unit to generate a propulsive force at
least equal to the minimum propulsive force necessary to
effectively steer said watercraft for a given speed when said
manual steering control is turned in either direction beyond a
predetermined angular threshold, whereby to cause said watercraft
to remain maneuverable independently of the manual throttle control
setting;
[0039] (F) a steer angle measuring device for generating a steer
angle signal representative of the steer angle of said steerable
propulsion unit;
[0040] (G) a speed measuring device for generating a speed signal
representative of the speed of the watercraft;
[0041] (H) a throttle actuator control circuit for generating an
output signal for controlling said throttle actuator; said throttle
actuator control circuit having:
[0042] a first input for receiving said steer angle signal;
[0043] a second input for receiving said speed signal; and
[0044] an output signal generator for generating an output signal
in response to signals received at said first and second inputs;
said output signal being applied to said throttle actuator for
controlling said throttle actuator.
[0045] This steer-responsive throttle further incorporates an
electronic control system that senses the steer angle of the manual
steering control as well as the speed of the watercraft and then
computes a throttle setting that corresponds to a propulsive force
appropriate for steering the watercraft.
[0046] Other objects and features of the invention will become
apparent by reference to the following description and the
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0047] A detailed description of the preferred embodiments of the
present invention is provided below, by way of example only, with
reference to the accompanying drawings, in which:
[0048] FIG. 1 is an isometric view of a watercraft's steerable
propulsion system with a typical jet-propelled watercraft depicted
in stippled lines;
[0049] FIG. 2 is an exploded view of a steerable propulsion unit of
a jet-propelled watercraft;
[0050] FIG. 3 is a schematic depicting the operation of a
steer-responsive throttle on a watercraft equipped with a single
steerable propulsion unit;
[0051] FIG. 4 is a schematic depicting the operation of a
steer-responsive throttle on a watercraft equipped with a pair of
steerable propulsion units;
[0052] FIG. 5 is a schematic depicting a manual throttle control
and throttle cables which merge with cables from the steering
assembly for controlling the throttle;
[0053] FIG. 6 is an exploded view of the basic components of a
steer-responsive throttle in accordance with a first embodiment of
the present invention;
[0054] FIG. 7 is an exploded view of the connection of the throttle
actuator cables to the steering assembly in accordance with the
first embodiment of the invention;
[0055] FIG. 8 is a plan view of the cable-supporting bracket shown
in FIG. 7;
[0056] FIG. 9 is an exploded view of a steering system with a
single throttle actuator cable linked to a steer-responsive
throttle in accordance with the first embodiment of the
invention;
[0057] FIG. 10 is an enlarged view of the connection between the
steering nozzle cable and the steering assembly of FIG. 9;
[0058] FIG. 11 is an enlarged view of the connection between the
throttle actuator cable and the bracket of FIG. 8;
[0059] FIG. 12 is an exploded view of a variant of the steering
system of FIG. 9 with a pair of throttle actuator cables linked to
their respective steer-responsive throttles;
[0060] FIG. 13 is an enlarged view of the connection between the
throttle actuator cables and the bracket of FIG. 8;
[0061] FIG. 14 is a schematic depicting a second embodiment of the
steer-responsive throttle in accordance with the present invention,
the throttle being controlled by a control system; and
[0062] FIG. 15 is a schematic depicting a variant of the embodiment
shown in FIG. 14.
[0063] In the drawings, preferred embodiments of the invention are
illustrated by way of examples. It is to be expressly understood
that the description and drawings are only for the purpose of
illustration and are an aid for understanding. They are not
intended to be a definition of the limits of the invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0064] FIG. 1 illustrates in stippled lines a watercraft generally
designated by the reference numeral 2. The watercraft 2 has a pair
of steerable propulsion units 4. It should be noted that the
watercraft could be a jet boat, a personal watercraft, a jet ski or
a motorboat equipped with a swivel-mounted outboard motor. In fact,
the present invention is applicable to any watercraft whose
propulsion unit can be turned for steering the watercraft. The
watercraft can have a single steerable propulsion unit, twin
steerable propulsion units (as shown in FIG. 1) or a plurality of
steerable propulsion units. When the watercraft has more than one
steerable propulsion unit, there is usually a coupling link 5 that
rigidly couples the steerable propulsion units together. In the
case of a motorboat, there can be a single outboard motor or a
plurality of outboard motors (which are usually coupled by a
coupling link).
[0065] As shown in FIG. 1, by way of example only, the steerable
propulsion units 4 are steerable jet propulsion units. Each
propulsion unit has an internal combustion engine 6 which is
typically a two-stroke engine. An example of a suitable engine for
this application is a Rotax 787. This invention is, of course,
equally applicable to watercraft having four-stroke engines or to
watercraft having a single engine as opposed to two engines (as
illustrated as the preferred embodiment). Each internal combustion
engine 6 has a carburetor 7 for regulating the air-fuel mixture in
the engine. A suitable carburetor for this application is a Mikuni
BN40-38-16, although it should be obvious that virtually any
carburetor can be adapted to make use of the present invention. It
should be furthermore noted that this invention could be applied to
watercraft that use electronic fuel injection systems rather than
carburetors.
[0066] As illustrated in FIG. 2, the internal combustion engine 6
drives a stainless steel impeller 8, which draws water through an
intake grating 10, and then discharges a jet of the water through a
venturi 12. A steering nozzle 14 is pivotally mounted aft of the
venturi for deflecting the jet of water exiting the venturi.
[0067] Referring back to FIG. 1, the steering angle of the steering
nozzle 14 is controlled by a manual steering control such as a
steering wheel 16 which actuates the steering nozzle 14 via a
steering assembly 18 and a steering nozzle cable 19. (In the case
of a personal watercraft, the manual steering control would be a
pair of handlebars. In the case of a motorboat, the manual steering
control would be either a steering wheel or tiller.)
[0068] The throttle of each carburetor 7 is controlled by a manual
throttle control 20. This manual throttle control can be operated
by hand or by foot. In the example provided herein, the manual
throttle control has three hand-operated levers (which will be
described in greater detail hereafter) for controlling the engine
and the direction of travel. By activating the manual throttle
control, the operator of the watercraft causes the throttle control
cables 24, 28 to open and close the throttles of each
carburetor.
[0069] FIG. 3 is a schematic showing the operation of the
steer-responsive throttle for a watercraft equipped with a single
steerable propulsion unit 12. In this example, the watercraft has a
steering wheel 16 that rotates a steering assembly 18. Connected to
the steering assembly is a steering nozzle cable 19. The steering
nozzle cable is also connected to a lever arm 14a affixed to a
steering nozzle 14. Turning of the steering wheel thus causes the
steering nozzle cable 19 to exert either a pushing or pulling force
on the steering nozzle 14 thereby causing the steering nozzle to
pivot about its pivot axis. A pivoting bracket 80 is mounted to the
steering assembly 18. The bracket 80 is connected in a lost-motion
arrangement to a throttle actuator cable 110. The throttle actuator
cable 110 is connected to the throttle of the carburetor of
powerplant A. (Powerplant A is the unit composed of the carburetor
and engine). The throttle of powerplant A is also controlled by the
manual throttle control 20 via the throttle control cable 24.
Powerplant A drives the impeller 8 which discharges a jet of water
through the venturi 12 and steering nozzle 14.
[0070] In operation, when the steering wheel 16 is turned, the
steering assembly 18 rotates (as indicated by the circular arrows),
exerting either a pulling force or a pushing force on the steering
nozzle cable 19. Specifically, if the steering wheel is turned to
the left, the steering assembly rotates clockwise and the steering
nozzle cable then exerts a pushing force on the lever arm 14a of
the nozzle 14, causing the nozzle to pivot clockwise. Analogously,
if the steering wheel is turned to the right, the steering assembly
rotates counterclockwise and the steering nozzle cable exerts a
pulling force on the lever arm 14a of the nozzle 14, causing the
nozzle to pivot counterclockwise.
[0071] If the steering wheel 16 is turned beyond a predetermined
angular threshold, the bracket 80 (which pivots with the steering
assembly) exerts a force on the throttle actuator cable 110. The
bracket and throttle actuator cable are connected to one another in
a lost-motion arrangement, meaning that the bracket must travel
through a certain angular extent before it engages the throttle
actuator cable.
[0072] If the manual throttle control is set at a throttle setting
that produces a thrust less than what is needed to effectively
steer the watercraft, the throttle actuator cable 110, will then
open the throttle to produce the required thrust (or propulsive
force) needed for proper steering. If the manual throttle control
is already set so as to produce a large enough thrust to
effectively steer the watercraft, then the throttle actuator cable
110 does not alter the throttle setting. Since the throttle
actuator cable 110 is mounted to the bracket 80 in alignment with
the pivot axis 86a of the bracket, the throttle actuator cable is
actuated equally when the steering wheel is turned to the left or
to the right.
[0073] FIG. 4 is a schematic showing the operation of the
steer-responsive throttle for a watercraft equipped with twin
steerable propulsion units 12. The watercraft has a steering wheel
16 that rotates a steering assembly 18. Connected to the steering
assembly is a steering nozzle cable 19. The steering nozzle cable
is also connected to the lever arm 14a affixed to the right
steering nozzle 14. The right and left steering nozzles are rigidly
coupled by a coupling link 5 so as to enable them to move in
unison. Turning of the steering wheel thus causes the steering
nozzle cable 19 to exert either a pushing or pulling force on the
right steering nozzle 14 thereby causing the steering nozzles to
pivot about their pivot axes. A pivoting bracket 80 is mounted to
the steering assembly 18. The bracket 80 is connected in a
lost-motion arrangement to a pair of throttle actuator cables 110,
120, meaning that the bracket must travel through a certain angular
extent before it engages one of the throttle actuator cables. The
throttle actuator cable 110 is connected to the throttle of the
carburetor of powerplant A while the throttle actuator cable 120 is
connected to the throttle of the carburetor of powerplant B.
[0074] The manual throttle control 20 has a lever 22 linked to a
throttle control cable 24 for controlling the throttle of
powerplant B. The manual throttle control 20 also has a lever 26
linked to a throttle control cable 28 for controlling the throttle
of powerplant A. Both powerplants A and B drive their own impeller
8 and discharge a jet of water through their respective venturi 12
and steering nozzle 14.
[0075] In operation, when the steering wheel 16 is turned, the
steering assembly 18 rotates (as indicated by the circular arrows),
exerting either a pulling force or a pushing force on the steering
nozzle cable 19. Specifically, if the steering wheel is turned to
the left, the steering assembly rotates clockwise and the steering
nozzle cable then exerts a pushing force on the lever arm 14a of
the right nozzle 14, causing both nozzles to pivot clockwise.
Analogously, if the steering wheel is turned to the right, the
steering assembly rotates counterclockwise and the steering nozzle
cable exerts a pulling force on the lever arm 14a of the right
nozzle 14, causing both nozzles to pivot counterclockwise due to
the coupling link 5.
[0076] If the steering wheel 16 is turned to the left beyond a
predetermined angular threshold, the bracket 80 (which pivots
clockwise with the steering assembly) exerts a force on the
throttle actuator cable 120. No force is exerted on the throttle
actuator cable 110 (i.e. the cable 110 remains slack). If the lever
22 of the manual throttle control 20 is set so that powerplant B
generates a thrust less than what is needed to effectively steer
the watercraft, the throttle actuator cable 120 will then open the
throttle of powerplant B to produce the thrust needed for effective
steering. If the lever 22 of the manual throttle control is set so
that powerplant B is already producing a large enough thrust to
effectively steer the watercraft, then the throttle actuator cable
120 does not alter the throttle setting.
[0077] Similarly, if the steering wheel 16 is turned to the right
beyond a predetermined angular threshold, the bracket 80 (which
pivots counterclockwise with the steering assembly) exerts a force
on the throttle actuator cable 110. No force is exerted on the
throttle actuator cable 120 (i.e. the cable 120 remains slack). If
the lever 26 of the manual throttle control 20 is set so that
powerplant A generates a thrust less than what is needed to
effectively steer the watercraft, the throttle actuator cable 110
will then open the throttle of powerplant A to produce the thrust
needed for effective steering. If the lever 26 of the manual
throttle control is set so that powerplant A is already producing a
large enough thrust to effectively steer the watercraft, then the
throttle actuator cable 110 does not alter the throttle
setting.
[0078] In the most preferred embodiment, the throttle of only one
of the two powerplants is opened when the steer angle exceeds the
angular threshold. When the steering wheel is turned to the left,
the throttle of the left propulsion unit (i.e. the throttle of
powerplant B) is opened. Similarly, when the steering wheel is
turned to the right, the throttle of the right propulsion unit
(i.e. the throttle of powerplant A) is opened. Though this may at
first seem counterintuitive, the actuation of the throttles of
powerplants A and B by throttle actuator cables 110 and 120,
respectively, is designed to favor the steering of the watercraft
in reverse. This improves the watercraft's maneuverability when
backing toward a dock. When turning left in reverse, the throttle
of powerplant B is opened and the jet of water produced by the left
propulsion unit is deflected rearward by a left-hand reverse gate.
The vector of the thrust generated by powerplant B is offset from
the longitudinal plane of symmetry of the watercraft. The thrust
multiplied by the perpendicular offset distance contributes a
small, additional turning moment to the main turning moment
produced by the water jet exiting the steering nozzle.
[0079] It should be noted that the throttle actuator cable 110
could be routed to actuate powerplant B while throttle actuator
cable 120 could be routed to actuate powerplant A. This arrangement
would improve forward steering at the slight expense of reverse
steering. It would furthermore be possible to have either throttle
actuator cable 110, 120 able to actuate both powerplants
simultaneously. This would necessitate the bifurcation or splitting
of each throttle actuator cable with a Y-connector.
[0080] FIG. 5 illustrates the manual throttle control 20 of a
twin-engine watercraft. The manual throttle control 20 comprises
three levers 22, 26 and 30. A first lever 22 is a left-hand manual
throttle lever which is connected via the throttle control cable 24
to the throttle of the left-hand propulsion unit. A second lever 26
is a right-hand manual throttle lever which is connected via the
throttle control cable 28 to the throttle of the right-hand
propulsion unit. The manual throttle levers 22, 26 are for
independently controlling the two engines of the watercraft and the
thrust of the water exiting each jet propulsion unit. A third lever
30 (also known as a shift lever) is for selecting forward, reverse
and neutral modes of the watercraft. The shift lever is connected
to a shift cable 32 capable of engaging and disengaging the drive
shaft and activating the reverse gates.
[0081] The left and right engines may be controlled independently
by adjusting the lefthand and right-hand throttle levers 22 and 26.
By separately adjusting and controlling the throttle levers 22 and
26, the operator of the watercraft can separately control each of
the engines and manipulate the performance and directional control
of the watercraft. Some twin-engine watercraft comprise separate
manual throttle levers for each of the engines, but only a single
steering cable for the corresponding steering nozzles. In this
specific configuration, the steering nozzles are coupled together.
Furthermore, in a single-engine watercraft, there are normally only
two levers, one shift lever for selecting forward, reverse and
neutral modes and a manual throttle lever for controlling the
engine.
[0082] As illustrated in FIG. 6, the left throttle control cable 24
(extending from the left manual throttle lever 22) is connected to
a left slide coupler 50. Also connected to the left slide coupler
is the throttle actuator cable 120. Displacement of either cable 24
or 120 causes the left slide coupler to actuate a throttle lever 40
on the left carburetor. Similarly, the right throttle cable 28
(extending from the right manual throttle lever 26) is connected to
a right slide coupler 60. Also connected to the right slide coupler
is the throttle actuator cable 110. Displacement of either cable 28
or 110 causes the right slide coupler to actuate a throttle lever
45 on the right carburetor.
[0083] As shown in FIGS. 6 and 7, the left and right throttle
actuator cables 110, 120 have left and right stoppers 116, 126 at
their tips. Each throttle actuator cable is routed through a hole
in a cylinder. The left throttle actuator cable 110 is routed
through a hole in a left cylinder 118 while the right throttle
actuator cable 120 is routed through a hole in a right cylinder
128. Each cylinder has a top and a bottom protuberance. The bottom
protuberances engage holes on the bracket 80 while the top
protuberances engage corresponding holes on a cover bracket 84. The
cylinders are thus sandwiched between the bracket and the cover
bracket.
[0084] The bracket and cover bracket are held together with a
fastener 87. The fastener is fed through a cylindrical spacer 88,
which ensures that the proper gap between the bracket and cover
bracket. The bracket 80 is mounted to the steering assembly by
virtue of a fastener 86. The throttle actuator cables are supported
by a cable support 100, illustrated in FIG. 8. For twin-engine
watercraft, the cables rest in outer grooves 102 and 104. For
single-engine watercraft, the cable rests in a central groove 106.
In operation, the rotation of the steering assembly causes the
bracket 80 to rotate. Depending on the direction of rotation,
either the left or right throttle actuator cable is actuated when
the steering wheel is turned beyond the predetermined angular
threshold. The bracket 80 pivots until one of the cylinders
collides with its stopper. Further rotation of the bracket results
in an actuating tension to be created in the corresponding throttle
actuator cable. It stands to reason that, for the configuration
illustrated, only one of the throttle actuator cables can be
actuated at a time. When one cylinder has collided with its
stopper, the other cylinder has moved farther from its stopper,
meaning that its cable will remain slack.
[0085] FIG. 6 also illustrates the interaction between the throttle
actuator cables and the corresponding throttle control cables. The
throttles may be opened and closed by either the throttle control
cables 24, 28 or the throttle actuator cables 110, 120. If the
operator has opened the throttle manually (via cables 24, 28) to a
level that generates the required minimal propulsive force for
steering, the actuation of the throttle actuator cables (from
turning the steering wheel) has no impact on the throttles.
Similarly, if one of the throttle actuator cables becomes taut (and
is exerting a pulling force on its corresponding slide coupler),
the counterpart control cable is slack unless the corresponding
lever on the manual throttle control is displaced manually beyond
the throttle setting. Thus, the tension in each cable 56, 66 is
equal to the greater of the tension in either the throttle actuator
cables or the throttle control cables. Finally, it should be noted
that a steer-responsive throttle system can operate with or without
a slide coupler. The slide coupler simply merges the throttle
cables so that the throttle is opened by whichever cable exerts the
greater pulling force. The slide coupler can be eliminated, as
shown in the foregoing schematics (FIGS. 3 and 4) by simply routing
the throttle cables directing to the throttle. The throttle lever
(or valve) is opened by the greater of the forces exerted on it by
either the throttle actuator cables or the throttle control
cables.
[0086] As illustrated in FIGS. 6 and 7, the steer-responsive
throttle system comprises a cable support 100 which is attached to
the steering assembly 18. The cable support 100 has an aperture 135
for securing the cable support 100 to the steering nozzle cable 19
adjacent to an end of the support arm 146. In a twin-engine
watercraft, there is a first cable 110 and a second cable 120
extending from each of the left and right slide couplers 50 and 60
to the cable support 100. The first cable 110 is attached to the
left slide coupler 50 and is mounted to a first slot 102 of the
cable support. Similarly, the second cable 120 is attached to the
right slide coupler 60 and is mounted to a third slot 104 of the
cable support 100. In a single-engine watercraft, there is only a
single cable extending from a single slide coupler to the cable
support 100 and the single cable is mounted in the center slot 106
of the cable support 100.
[0087] The steering assembly 18 further comprises a bracket 80
mounted on a top surface area of the steering assembly 18, as shown
in FIGS. 6 and 7. The bracket 80 comprises an aperture 82 for
receiving a screw for securing the bracket 80 to the steering
assembly 18. The bracket further comprises a plurality of apertures
for receiving and containing the cylinders 118 and 128. In a
single-engine arrangement, the bracket 80 is adapted to receive and
contain a single cylinder in the central slots of the bracket 80
and the bracket cover 84. As illustrated in FIGS. 6 and 7, the ends
of the first and second cables 110 and 120 each comprise a stopper
116 and 126, respectively. The stoppers 116 and 126 are permanently
affixed to the end of each of the first and second cables 110 and
120 and are received by the respective cylinders lodged between the
bracket and bracket cover. Accordingly, the ends of the first and
second cables are indirectly attached in a lost-motion arrangement
to the bracket 80 by means of the stoppers 116 and 126.
[0088] The cover bracket 84 fits over a top surface of the bracket
80. The cover bracket 84 comprises a plurality of apertures for
receiving screws 86 which secure the cover bracket 84 to the
bracket 80. The steering assembly 18 further comprises a spacer 88
disposed between the bracket 80 and the cover bracket 84, to
provide space (a gap) therebetween for receiving the cylinders
adjacent to the stoppers of the first and second cables 10 and 120.
Each of the cylinders can abut the stoppers 116 and 126 to engage
one of the cables 110, 120. In a single-engine arrangement, the
steering assembly comprises a single cylinder for engaging a
stopper and thus actuating a single cable. The bracket 80, cover
bracket 84 and the cylinders are rotatable with the steering
assembly (when the steering wheel is turned) and allow the first
and second cables 110 and 120 to be actuated when the rotational
movement of the steering wheel exceeds the threshold. When the
steering wheel exceeds the angular threshold, one of the cylinders
abuts its corresponding stopper, thereby causing its actuator cable
to actuate its corresponding throttle. As the steering wheel is
rotated, the steering nozzle cable 19 is pulled or pushed, causing
the exit nozzle to pivot. In addition, the cylinders are adapted to
pull the cables 110 and 120 by means of the corresponding stoppers
116 and 126, depending upon the directional rotation of the
steering wheel 142.
[0089] When the watercraft is at rest, the stoppers 116 and 126 of
each of the respective cables 110 and 120 are not in contact with
their respective cylinders. Accordingly, as the steering wheel is
rotated in a clockwise or counterclockwise direction, the cylinders
rotate together with the bracket 80 and the cover bracket 84.
[0090] At such time as the manual throttle levers 22 and 30 are in
an off position, the steering wheel may be rotated to a given
clockwise position in order to activate the steer-responsive
throttle. When the manual throttle levers are set in an "off"
position, the engine is calibrated to idle. The engine may be shut
off only by activation of a separate kill-switch. Clockwise
rotation of the steering wheel from a center position to the left
causes the cylinder 128 to abut the stopper 126 of the second cable
120. The left slide coupler 50 is pulled, causing the throttle of
the left engine to be opened.
[0091] Similarly, at such time as the manual throttle levers 22 and
30 are in an off position, the steering wheel may be rotated to the
right (i.e. in a counterclockwise direction). The rotation of the
steering wheel causes the cylinder 118 to abut the stopper 116 of
the first cable 110. The right slide coupler 60 is pulled, causing
the throttle of the right engine to be opened. When the steering
wheel is returned to a straight-ahead position from a given
clockwise or counterclockwise rotation, the first and second cables
110 and 120 return to their rest positions.
[0092] The left and right slide couplers 50 and 60 control
activation of the left and right engines of the watercraft via
either the manual throttle control (also known as the "throttle
assembly") 20 or the steering assembly 18. The slide couplers 50
and 60 respond to the manual throttle levers 22 and 26 as well as
the steering wheel. The proximal ends 52, 62 of the slide couplers
50, 60 are adapted to receive both the first and second cables 24,
28 from the first and second manual throttle levers 22, 26 as well
as the first and throttle actuator cables 110, 120 from the cable
support 100 and the steering assembly 18. However, the distal ends
54, 64 of the slide couplers comprise only one cable extending from
each of the slide couplers. A first cable 56 extends from the left
slide coupler 50 to the left carburetor's throttle lever 40, and a
second cable 66 extends from the right slide coupler 60 to the
right carburetor's throttle lever 45. Both the first cable 56 and
the second cable 66 independently control actuation of the
throttles of the carburetors of the respective engines.
[0093] Upon activation of either the first manual throttle lever 22
or the second manual throttle lever 26, the respective cable
extending to the slide coupler actuates the cable extending to the
throttle lever on the respective carburetor. The same action causes
the activated slide couplers to tighten control on the activated
cables and to provide an increased backlash (slack) in the cable
extending from the slide coupler to the steering assembly. The
increased backlash in the cables 110 and 120 extending from the
slide coupler to the steering assembly 18 allows directional
control of the watercraft by the steering assembly 18 through the
steering nozzle cable 19 without adjusting the throttle lever of
the carburetor. Accordingly, this arrangement allows standard
directional control of a watercraft by means of the steering
assembly 18 at such time as the manual throttle lever is activated
to control the thrust of the water exiting the jet propulsion
unit.
[0094] Rotation of the steering wheel in a clockwise direction
causes the right cylinder 118 to abut the stopper 116 thereby
pulling on the first cable 110 attached to the proximal end 62 of
the right slide coupler 60. This rotation of the steering wheel
further causes a backlash in the throttle control cable 28
extending from the right slide coupler 60 to the second manual
throttle lever 26. Furthermore, the clockwise rotational movement
allows the first cable 110 to open the throttle of the right
engine.
[0095] Similarly, rotation of the steering wheel in a
counterclockwise direction causes the left cylinder 128 to abut the
stopper 126 thereby pulling on the second cable 120 attached to the
proximal end 52 of the left slide coupler 50. This rotation of the
steering wheel further causes a backlash in the throttle control
cable 24 extending from the left slide coupler 50 to the first
manual 22. The counterclockwise rotation opens the throttle of the
left engine.
[0096] Actuation of the throttles by turning the steering wheel
beyond the predetermined angular threshold may produce from about 0
to about 50 pounds of thrust exiting the jet propulsion unit and an
engine speed from about 0 to about 3,000 revolutions per minute.
However, the engine speed and thrust generated by rotation of the
steering wheel may be calibrated as required for different types of
watercraft. The amount of thrust produced by turning the steering
wheel beyond the threshold is sufficient to enable control of
directional movement of the watercraft by the operator. The minimal
thrust produced by rotation of the steering wheel assists the
operator in docking procedures as well as other low speed
maneuvers. The necessary degree of rotation of the steering wheel
from a neutral position may be approximately 180 degrees to
generate a maximum thrust and speed. However, the degree of
rotation may be separately calibrated for different watercrafts.
The predetermined angular threshold (i.e. the steer angle at which
a stopper engages a cylinder and thus actuates a throttle) depends
upon the calibration of the system. Accordingly, the rotation of
the steering wheel produces sufficient thrust to enable proper
steering of the watercraft.
[0097] In an alternative embodiment, the steer-responsive throttle
may comprise a series of electronic controls and wires. This
embodiment comprises a steering assembly having sensors or switches
for detecting the degree of rotation of the steering wheel. In
addition, the carburetor comprises a separate set of switches for
controlling the air-fuel mixture entering each of the respective
carburetors. At such time as the manual throttle levers 22 and 26
are set to an off or low-thrust position, the steering wheel may be
rotated to a given degree in a clockwise or counterclockwise
direction. When the steering wheel is rotated in a clockwise
direction a first set of sensors or switches adjacent to the
steering wheel causes the throttle of the right carburetor to
open.
[0098] Similarly, as the steering wheel is rotated in a
counterclockwise direction the first set of sensors or switches
adjacent to the steering wheel causes the throttle of the left
carburetor to open. In a preferred embodiment, the carburetor is a
solenoid switch. The switches and sensors adjacent to the steering
wheel are connected to the solenoid switches adjacent to the
corresponding right and left carburetors by means of electronic
wires. In this preferred embodiment, an electric current is sent
through the wires from the steering assembly to the carburetors,
thereby controlling the air-fuel mixture in each of the respective
carburetors and controlling the engine speed and thrust of the
water exiting the jet propulsion unit. When the steering wheel is
returned to a neutral maneuvering position, the sensors and
switches adjacent to the steering assembly cause the throttle
actuators adjust the carburetors so that the watercraft's engines
return to a neutral idling position.
[0099] Shown in FIGS. 9-11 is a steer-responsive throttle system
for a single-engine watercraft, such as a PWC. The steering wheel
16 is connected to the steering assembly 18. The steering assembly
contains either bevel gears or worm gears to convert the rotation
of the steering wheel into a rotation of a portion of the steering
assembly about the pivot axis 86a. By turning the steering wheel,
the steering assembly exerts a pushing or pulling force on the
steering nozzle cable 19 which, in turn, causes the nozzle 14 to
pivot. As the steering wheel is turned, the rotation of the
steering assembly also causes the bracket 80, which is mounted to
the steering assembly, and the bracket cover 84, which is fastened
to the bracket 80, to pivot. Sandwiched between the bracket 80 and
the bracket cover 84 (and thus rotatable therewith) is a single
cylinder 118. The cylinder has top and bottom protuberances that
mate with corresponding holes in the bracket and bracket cover. The
cylinder also has a hole that is normal to the longitudinal axis of
the cylinder through which the throttle actuator cable 110 can
translate. The throttle actuator cable 110 is supported by cable
support 100 and has a stopper 116 at one end. The stopper is sized
so that it cannot pass through the hole in the cylinder. The length
of cable or wire that extends from the cylinder to the stopper
corresponds to the extent of lost motion in the mechanism. The
cylinder 118 is aligned with the pivot axis 86a such that rotation
of the bracket clockwise or counterclockwise will result in
symmetrical actuation of the throttle. If the steering wheel is
turned to the right, the steering assembly pivots counterclockwise
(as seen from above) and the cylinder eventually abuts the stopper.
Similarly, if the steering wheel is turned to the left, the
steering assembly pivots clockwise (as seen from above) and the
cylinder also eventually abuts the stopper. If the steering wheel
is turned far enough to either side, the cylinder will abut the
stopper as the bracket pivots past the threshold. Once the cylinder
has collided with the stopper, the throttle actuator cable 110
becomes taut. Further rotation of the bracket (by further turning
the steering wheel) causes the throttle actuator cable to pull open
the throttle so that the propulsion unit produces a thrust suitable
for steering the watercraft. The throttle can, of course, also be
controlled by the manual throttle control. Thus, only if the manual
throttle control is set to produce a thrust less than what is
needed for steering can the throttle actuator cable 110 actuate the
throttle.
[0100] Shown in FIGS. 12-13 is a steer-responsive throttle system
for a twin-engine watercraft, such as a jet boat. The system
functions similarly to the single-engine configuration except that
there are two throttle actuator cables 110, 120. When the steering
wheel is turned to the right, the bracket pivots counterclockwise
(as seen from above) until the right cylinder collides with the
right stopper. Meanwhile, the left throttle actuator cable 120
remains slack. Similarly, when the steering wheel is turned to the
left, the bracket pivots clockwise (as seen from above) until the
right cylinder collides with the right stopper. The right throttle
actuator cable 110 then pulls open the throttle of the right
engine. Meanwhile, the left throttle actuator cable 120 remains
slack. Similarly, when the steering wheel is turned to the left,
the bracket pivots clockwise (as seen from above) until the left
cylinder collides when the left stopper. The left throttle actuator
cable 120 then pulls open the throttle of the left engine.
Meanwhile, the right throttle actuator cable 110 remains slack.
[0101] As depicted in FIG. 14, a watercraft with a steer-responsive
throttle may comprise, as an alternative, preferred embodiment, an
electronic control system to regulate the thrust of the propulsion
unit as a function of the watercraft's speed and the angle of the
steering nozzle. The schematic shown in FIG. 14 is similar to the
one shown in FIG. 3. Unlike the purely mechanical system shown in
FIG. 3, the electronically controlled system of FIG. 14 does not
employ throttle actuator cables linking the steering assembly to
the throttle. Though not explicitly illustrated, it should be
apparent that this electronically controlled steer-responsive
throttle is equally applicable to single-engine and twin-engine
watercraft.
[0102] The configuration shown in FIG. 14 is for a single-engine
watercraft. A steering wheel 16 connected to a steering assembly
18. A portion of the steering assembly rotates about pivot axis
86a. The rotation of the steering assembly causes the steering
nozzle cable 19 to be pushed or pulled. The steering nozzle cable,
in turn, exerts either a forward or rearward force on the lever arm
14a affixed to the steering nozzle 14. The force pivots the
steering nozzle 14 clockwise for a left turn or counterclockwise
for a right turn. The operator can control the throttle opening and
hence the thrust generated by the impeller 8 of the propulsion unit
12 by manually displacing the manual throttle lever 22 of the
manual throttle control 20. The shift lever 30 is displaced to
select forward, reverse or neutral modes of operation. The manual
throttle lever 22 opens and closes the throttle of powerplant A via
a throttle control wire 24a which conveys an electrical signal to a
throttle control system module 300. The control system module 300
also comprises a processor, an output signal generator and an
actuator for opening and closing the throttle.
[0103] A steering sensor 310 measures the linear displacement of
the steering nozzle cable 19. The steering sensor 310 sends an
electrical signal to the control system module 300. This steering
sensor could be a linear voltage displacement transducer (LVDT).
Equivalently, a steering sensor could be mounted on the steering
nozzle, on the steering wheel or on the steering assembly so long
as the steering sensor yields a signal that is proportional to the
steer angle of the nozzle. The steering sensor will be either a
linear displacement sensor or an angle sensor, depending on the
application. Alternatively, a pair of electric switches can be used
to activate the throttle when the steering wheel has reached either
the left or right angular threshold. With electric switch
actuation, the throttle is opened to a predetermined setting (i.e.,
with such a "step-response", the system is either on or off)
whereas with a steer sensor, the thrust can be gradually increased
as a function of the steer angle.
[0104] A speed sensor 320 measures the forward speed of the
watercraft. In this preferred embodiment, the speed sensor is a
pitot tube for measuring air speed. The pitot tube comprises a
transducer for converting the pressure reading of the pitot tube
into an electrical signal proportional to the speed of the
watercraft. (The differential between the dynamic pressure at the
stagnation point inside the pitot tube and the ambient pressure is
related to the air speed by Bernoulli's Equation.) This pitot tube,
or speed sensor, sends the signal to the electronic control module
300. Equivalently, the pitot tube can be placed under the
watercraft to measure water flow velocity. Alternatively, the speed
sensor can be a submerged rotor or water wheel capable of emitting
an electric pulse per revolution. The frequency of the pulses can
be readily calibrated to the water flow velocity. The air speed
pitot tube is preferred because a device that protrudes from the
hull will detrimentally affect the hydrodynamics of the hull.
[0105] The electronic control module 300 calculates the optimal
throttle opening for effectively steering the watercraft based on
the input signals from the steering sensor 310 and the speed sensor
(pitot tube) 320. A throttle position sensor (TPS) 330 measures the
actual position of the throttle lever, which is essentially a
measurement of how much the throttle is open. The electronic
control module generates an output signal that activates a throttle
actuator only when the measured throttle setting is less than the
desired throttle setting for a given speed and steer angle. In
other words, the output signal is only generated if the signal from
the manual throttle control corresponds to a throttle setting that
will produce a thrust less than what is needed to steer the
watercraft. The throttle actuator opens and closes the throttle so
as to optimize the thrust for steering. In the preferred
embodiment, the control module will increase the opening of the
throttle as the watercraft speed increases in a non-linear fashion.
For the purposes of illustration only, the throttle may be set so
that the engine idles at 2000 RPM for a speed of zero knots. For a
speed of 10 knots, the throttle may be opened so that the engine
runs at 2600 RPM. For a speed of 20 knots, the throttle may be
opened to produce an engine speed of 2900 RPM. The optimal throttle
setting can be determined empirically by measuring the thrust
needed to effectively steer the watercraft and by correlating that
thrust to the impeller's speed of rotation, the engine RPM, and the
throttle setting. of course, the thrust needed to effectively steer
the watercraft depends on the size and type of watercraft.
[0106] For steady-state operation, the throttle opening is readily
correlated with the thrust of the water jet exiting the nozzle.
However, there is a response lag between the opening of the
throttle and the increase in engine speed. There is a further
response lag between the increase in engine speed and the increase
in thrust. Since the parameter that is to be ultimately controlled
is the actual thrust of the water jet, it might appear to be
sensible to replace the TPS with a pitot tube aft of the impeller.
Such a pitot tube measures dynamic water pressure, which is more
directly representative of thrust than a TPS. The pitot tube
measurement would be fed to the control system's processor module
whereupon the throttle would be adjusted accordingly until the
desired thrust is attained. However, a pitot tube aft of the
impeller may obstruct flow unacceptably and thus an alternative
sensor (to replace the TPS) would be an engine speed sensor or an
impeller speed sensor. All of the sensors, it should be noted, are
adequate to provide feedback control of the propulsion unit's
thrust. The use of a TPS is preferred because it is reliable,
inexpensive and easy to mount to existing carburetors. Furthermore,
since the throttle is the object that is being actually controlled,
it makes sense to measure the actual throttle setting to provide a
feedback control system that corrects the throttle setting based on
the differential between the actual and the desired settings.
[0107] In the variant illustrated in FIG. 15, there is no TPS (or
equivalent sensor). The throttle control cable 24 is connected
directly to the throttle, replacing the electrical wire 24a linking
the manual throttle control and the control system module. With a
direct mechanical connection, the throttle control cable 24 can
open the throttle independently of the throttle actuator cable 110
(as previously described with regard to FIG. 3). Since the throttle
actuator cable 110 and throttle control cable 24 can independently
open the throttle, the actual throttle setting is determined by
whichever device (the actuator cable or the control cable) opens
the throttle the most. Whether the throttle is opened by the
displacement of the throttle actuator depends on the current
throttle setting. If the manual throttle lever is set to produce
sufficient thrust for steering, the throttle actuator will have no
effect on the throttle. Only if the manual throttle lever is set to
produce insufficient thrust for steering will the throttle actuator
open the throttle. The throttle actuator will thus ensure that the
throttle is opened to a setting corresponding to the minimum thrust
required for steering regardless of the position of the manual
throttle lever.
[0108] A steer-angle sensor 310 and an airspeed-measuring pitot
tube 320 convey electrical signals to the control module 300 which
calculates the required thrust based on the inputs from the speed
sensor and steering sensor. An output signal is generated (if
additional steering thrust found to be necessary). A rev limiter
receives the output signal. The rev limiter functions to limit the
engine speed by cutting the sparks in the cylinder of the engine.
Alternatively, a rev limiter can delay the sparking in the cylinder
so as to produce a non-optimal power-stroke. In either event, the
rev limiter reduces the engine speed and thus the thrust being
produced by the propulsion unit. For the variant shown in FIG. 15,
the throttle is calibrated to open to the maximum thrust that would
be required for steering. If the manual throttle control is set to
produce a thrust that is insufficient for steering and the steering
wheel is turned beyond the predetermined angular threshold, the
throttle actuator cable 110 opens the throttle to a maximum setting
corresponding uniquely to the steer-angle (i.e., regardless of the
watercraft's speed). When a lesser thrust is required (e.g., if the
control module registers via the pitot tube 320 that the watercraft
is travelling at a lesser speed), the control module activates the
rev limiter. Irrespective of the opening of the throttle, the rev
limiter is capable of limiting the RPM of the engine, thereby
reducing the thrust generated by the propulsion unit.
[0109] The above description of preferred embodiments should not be
interpreted in a limiting manner since other variations,
modification and refinements are possible within the spirit and
scope of the present invention. The scope of the invention is
defined in the appended claims and their equivalents.
[0110] The above description of preferred embodiments should not be
interpreted in a limiting manner since other variations,
modifications and refinements are possible within the spirit and
scope of the present invention. The scope of the invention is
defined in the appended claims and their equivalents.
* * * * *