Ships – Steering mechanism – Fluid pressure
Reexamination Certificate
2002-03-20
2004-11-23
Basinger, Sherman (Department: 3617)
Ships
Steering mechanism
Fluid pressure
C440S06100B
Reexamination Certificate
active
06820567
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a steering apparatus, and principally to a steering apparatus that can be used preferably as the steering apparatus of a ship.
BACKGROUND ART
(1) A Manual Steering Apparatus that Uses a Helm Pump
By taking reference to
FIG. 28
, a manual steering apparatus of the prior art using a pump that can be rotated either in forward or reverse direction and can discharge a liquid (oil) of a quantity proportional to the rotating angle (hereinafter referred to as a helm pump) will be described below with reference to FIG.
28
. This apparatus has a steering wheel
13
as steering means and a hemp pump
10
provided on the steersman side and a double action cylinder mechanism provided on the rudder side of the ship as means to drive the rudder
27
. The steering means and the double action cylinder mechanism are connected with a hydraulic channel
14
that consists of a pair of hydraulic circuits
14
a
,
14
b
, so as to constitute a hydraulic circuit a fully closed circuit construction as a whole.
When the steersman turns the steering wheel
13
so that a liquid is discharged from a right port
11
of the helm pump
10
, for example, the liquid discharged from a right port
11
of the helm pump
10
enters a right chamber
25
of a cylinder through the hydraulic circuit
14
a
and a right port
23
of a double action cylinder
20
, so as to push a piston
21
to move in a direction depicted as leftward in the drawing. This causes the rudder
27
to be steered via a piston rod
22
, thereby effecting the steering operation.
When the piston
21
is pressed to move to the left in the double action cylinder
20
, accordingly the liquid contained in the left chamber
26
of the cylinder is forced through the left port
24
into the hydraulic circuit
14
b
, so that the liquid in the hydraulic circuit
14
b
passages through the left port
12
of the helm pump
10
and enters the helm pump
10
. The amount of liquid that enters the helm pump
10
is equal to the amount of the liquid that has been discharged.
When the steering wheel
13
is turned in a direction opposite to the above, the liquid flows in a direction opposite to the above thereby to achieve an effect opposite to that described above.
In the manual steering apparatus using the helm pump
10
, a proportional relationship is maintained between the rotating angle of the steering wheel
13
and the moving distance of the piston rod
22
, so that the rotating angle of the steering wheel
13
and the position of the rudder
27
have a particular relation with each other. As a result, the rudder can be steered by turning the steering wheel
13
over a certain angle thereby to turn the rudder
27
to a required angle.
In the case described above, the rudder
27
is caused to move at a speed proportional to the rotating speed of the steering wheel
13
.
However, the manual steering apparatus requires it to rotate the steering wheel
13
manually against the resistance of the rudder
27
. This is not a problem in a small vessel where the rudder
27
poses a relatively small resistive force, although a significant magnitude of force is required to operate the steering wheel
13
in a large vessel where the rudder
27
poses a large resistive force.
(2) A Power-Assisted Steering Apparatus of the Prior Art Using a Metering Device
For the purpose of solving the problem of the manual steering apparatus described above, power-assisted steering apparatuses have been provided that reduce the amount of force required when steering. A latest example of the power-assisted steering apparatus will be described below with reference to FIG.
29
through FIG.
31
.
FIG. 29
shows a rotary switching valve
130
placed at a neutral position (a position where the rudder is not effective).
FIG. 30
shows the rotary switching valve
130
shifted to the left so that a piston rod
22
is moved to the right by hydraulic pressure.
FIG. 31
shows the rotary switching valve
130
shifted to the right so that a piston rod
22
is moved to the left by hydraulic pressure. In the description that follows, the rudder
27
linked to the piston rod
22
is omitted.
The power-assisted steering apparatus comprises a mechanism that consists of a metering device
100
, a hydraulic pump
120
that supplies the liquid and has a tank
110
for holding returned excess liquid, etc.
While making reference to
FIG. 30
, too, operation and construction of the apparatus will be described below.
When the steering wheel
103
is turned away from the neutral position in one direction, a rotary switching valve
130
that is mechanically linked with the steering wheel
103
so as to operate as the steering wheel
103
rotates moves from the state shown in
FIG. 29
to the left into the state shown in FIG.
30
. Under this condition, a pressure switch
123
is turned on by an increasing pressure of the liquid discharged from the metering pump
100
, so that a pump motor
121
that is mechanically linked with the hydraulic pump
120
is started to run. The liquid discharged from a lower port
120
b
of the hydraulic pump
120
flows through a port
132
b
and a port
132
c
of a rotary switching valve right chamber
132
and enters a right-hand port
101
of the metering device
100
. The amount of liquid that enters is limited to the measured quantity that is determined by the rotating speed of the steering wheel
103
. Excess of the liquid passes through a right-hand bypass passage
132
g
provided in the rotary switching valve
130
and returns to the tank
110
via a port
132
a
of the rotary switching valve right chamber
132
. The liquid introduced into the metering device
100
is discharged through the left-hand port
102
of the metering device to be circulated through a port
132
d
and a port
132
f
of the rotary switching valve right chamber
132
of the rotary switching valve
130
and the left-hand port
24
of the cylinder
20
thereby to enter the left-hand chamber
25
of the cylinder so as to drive the piston
21
and the piston rod
22
. The liquid emerging from the cylinder right-hand chamber
25
passes through a port
132
e
and then a port
132
a
of the rotary switching valve right chamber
132
of the rotary switching valve
130
thereby to return to the tank
110
.
In case the steering wheel
103
is turned in a direction opposite to that described above, the liquid passes through the circuit as shown in
FIG. 31
, so that the piston
21
and the piston rod
22
move in a direction opposite to that described above.
In the power-assisted steering apparatus of the prior art described above, the pump motor
121
rotates at a constant speed so that the hydraulic pump
120
always discharges the maximum flow rate required by the rudder
27
. In case the flow rate required by the cylinder
20
is less than the maximum flow rate, excess of the liquid is all returned to the tank
110
through the right-hand bypass passage
132
g
or the left-hand bypass passage
133
g
of the rotary switching valve
130
.
Therefore, the power-assisted steering apparatus of the prior art described above reduces the force required of the steersman, although the hydraulic pump
120
continues to supply the liquid unnecessarily most of the time, resulting in a significant waste of energy. It has also such a drawback as the steersman cannot get the feel of moving the rudder
27
against external force.
An object of the present invention is to provide a power-assisted steering apparatus that gets rid of the drawbacks of the power-assisted steering apparatus of the prior art described above, allows the steersman to easily operate the steering wheel and saves energy consumption with minimized waste of energy.
Another object of the present invention is to provide a power-assisted steering apparatus of better steerability that lets the steersman feel the resistive force exerted on the steering wheel from the outside as in the case of the manual steering apparatus.
DISCLOSURE OF THE INVENTION
In order to achieve objects described above, the steering
Ito Kenji
Kishi Seiichi
Sonoda Kenichi
Takahashi Nobuyasu
Yoshida Tsukasa
Basinger Sherman
Holt William H.
Marol Co., Ltd.
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