Marine propulsion – Jet drive – Direction control for fluid jet
Reexamination Certificate
2001-08-31
2003-07-15
Swinehart, Ed (Department: 3617)
Marine propulsion
Jet drive
Direction control for fluid jet
Reexamination Certificate
active
06592413
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a thrust-reversing nozzle assembly for a watercraft and, in particular, for a jet-propelled watercraft such as a sport boat or a personal watercraft.
BACKGROUND OF THE INVENTION
As shown in
FIG. 1
, a personal watercraft
10
has a hull
12
, a seat
14
configured to support up to four riders, and a steering control mechanism
16
(e.g., handlebars) with which the operator steers the watercraft. Typically, a personal watercraft is propelled by a waterjet thrust system, with the thrust-producing jet of water being expelled at relatively high velocity from a nozzle assembly
18
mounted at the rear of the watercraft
10
. A thrust-directing nozzle member
22
is laterally pivotally mounted in the assembly so as to swing left and right (about a vertically oriented axis), which directs the jet of water left or right and causes the watercraft to turn in the same direction. In some cases, the nozzle member
22
may also be mounted so as to pivot vertically slightly up and down (about a horizontally oriented axis), thereby enabling the “attitude” of the watercraft within the water to be adjusted or “trimmed.” When the steering control mechanism
16
is turned, an interconnected steering linkage
24
pushes and pulls on steering armature
26
, which is connected to (e.g., integral with) the nozzle member
22
, thereby effecting lateral pivoting of the nozzle member
22
and hence turning of the watercraft.
As shown in
FIGS. 2A and 2B
, a retractable reverse gate
30
(not shown in
FIG. 1
for clarity) is attached to the rear portion of the hull of the watercraft and swings vertically between 1) a stowed or retracted position, shown in
FIG. 2A
, in which it is “tucked” partially within the “pocket” or “tunnel”
20
formed by the rear portion of the hull (see
FIG. 1
) and in which the nozzle assembly
18
is mounted; and 2) a lowered or extended position, shown in FIG.
2
B. In the stowed or retracted position (FIG.
2
A), the reverse gate is held out of the way of the propulsive jet of water being expelled from the nozzle assembly
18
, and therefore it does not affect the direction of travel of the watercraft. When it is desired to reverse the direction of travel, i.e., to back up, the reverse gate
30
is lowered (e.g., by pulling or pushing a reverse lever (not shown) that is accessible to the operator) by means of reverse gate linkage
31
into position behind the nozzle assembly
18
, as shown in FIG.
2
B. The reverse gate
30
has a “shell” configuration, with generally hemispherical or quarter-spherical inner surfaces over each of the portions
30
a
and
30
b
. Accordingly, when the water jet being expelled from the nozzle assembly strikes the inner surfaces of the reverse gate, it is deflected or turned so as to be expelled forwardly from the reverse gate, thereby effecting reverse movement of the watercraft.
As further illustrated in
FIG. 2B
, the nozzle member
22
typically is mounted (either directly or via a gimbal system to allow vertical, trim pivoting as well as lateral, steering pivoting) over the exit end of a flow-accelerating venturi member
28
having a narrowing, flow-accelerating interior passage that accelerates the jet of water. The venturi member
28
, in turn, is mounted (e.g., bolted) to impeller housing
32
, which is secured (e.g., bolted) to the pump support of the watercraft. A waterjet-producing impeller and the shaft which spins it are housed within and extend through the impeller housing
32
, respectively.
What we have observed, however, is that the operator of the watercraft typically does not have the same level of directional control when travelling in a reverse direction as when travelling in a forward direction. In fact, it has been observed that, depending upon the desired radius of a reverse-direction turn, a “cross-control” situation can arise in which the watercraft actually turns in the direction opposite to that in which it is desired to travel as the jet of water is deflected back not along the axis of the nozzle, but rather at a complementary angle to it. Additionally, we have found that in the prior art, if the nozzle member is vertically pivotable for adjusting the “trim” of the watercraft, acceptable reverse travelling performance has not been obtained because changing the trim angle of the nozzle can cause 1) the reverse gate to be blown back up to the retracted position by the waterjet; 2) the waterjet to pass completely over the top of the reverse gate; 3) the waterjet to strike the reverse gate too far down on the inner surface to be diverted correctly; or otherwise to be misdirected. Accordingly, there exists a need in the art for an improved reversing assembly for use in waterjet-propelled watercraft such as a personal watercraft, particularly in such waterjet-propelled watercraft in which the nozzle member is capable of pivoting vertically as well as laterally for “trimming” the attitude of the watercraft in the water.
SUMMARY OF THE INVENTION
The present invention overcomes the limitations of the prior art described above and therefore meets this need. In particular, the invention features an improved reverse gate assembly in which the reverse gate is linked to the thrust-directing nozzle member so as to pivot laterally with it (i.e., left and right about a vertically oriented axis), particularly while permitting vertical (i.e., up and down about a horizontally oriented axis), trim-adjusting pivoting of the nozzle (which trim-adjusting pivoting causes the axis about which the reverse gate pivots to move in a vertical direction). This ensures that the net effect of the reversed flow of the waterjet is a reversing thrust force that is oriented substantially along the direction of the axis of the nozzle member; as the nozzle member pivots with steering inputs, the reverse gate also pivots so as to maintain that substantial alignment. Thus, steering sensitivity and control when travelling in the reverse direction are significantly improved as compared to the prior art.
In a first aspect, the invention features a nozzle assembly which is capable of reversing the traveling direction of a waterjet-propelled watercraft. The nozzle assembly includes a nozzle member that is configured to be connected to a rear portion of the watercraft, with the nozzle member being both laterally pivotable with respect to the watercraft (for steering control) and vertically pivotable with respect to the watercraft (to adjust the “trim” or the attitude of the watercraft in the body of water in which it sits). The nozzle assembly further includes a laterally pivotable, retractible reverse gate that is linked to the nozzle member so as to pivot laterally with it. The reverse gate is movable between a stowed position and a thrust-reversing position in which it redirects a jet of water expelled from the nozzle member so as to reverse the traveling direction of the watercraft. (The reverse gate can also be held in a “neutral” position (which requires the operator to hold the actuating lever in a mid-position, between a reverse gate-stowed position and a reverse gate-extended position), in which “neutral” position the reverse gate deflects water straight downward so that the watercraft does not move forward or backward, e.g., when idling.) By being linked to the nozzle member so as to pivot laterally with it, the reverse gate always redirects the jet of water in the same direction relative to the nozzle member, i.e., in a direction such that the net thrust acts in a reversing direction.
In preferred embodiments of the nozzle assembly, the reverse gate is pivotally attached directly to the nozzle member and pivots vertically with respect to it. The nozzle assembly may include a flow-accelerating venturi member that is configured to be connected to the rear portion of the watercraft, or the nozzle assembly may be a retrofit assembly that is configured to be attached to a flow-accelerating venturi member that is already connected to the rear portion of the watercraft.
Preferably, the nozzle assembly is gim
Beauregard Normand
M{dot over (e)}nard {dot over (E)}ric
Simard Richard
Bombardier Inc.
Swinehart Ed
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