Elevator – industrial lift truck – or stationary lift for vehicle – Having specific load support drive-means or its control – Includes fluid supporting ram in drive-means
Reexamination Certificate
1999-12-14
2002-08-20
Lillis, Eileen D. (Department: 3652)
Elevator, industrial lift truck, or stationary lift for vehicle
Having specific load support drive-means or its control
Includes fluid supporting ram in drive-means
C091S468000, C060S466000, C060S477000
Reexamination Certificate
active
06435310
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a hydraulic elevator system, and in particular to a hydraulic elevator system of an inverter control method directly controlling a flow amount of a pressed oil discharged from a hydraulic pump by a speed control of a motor driving the hydraulic pump, which can improve energy efficiency and stability.
2. Description of the Background Art
As widely known, a hydraulic elevator system lifts or lowers an elevator car by using a hydraulic cylinder operated by a hydraulic pump, instead of winding or releasing a rope connected to the elevator car by using a sheave rotated by a motor.
Here, the hydraulic cylinder is a single acting ram type. The elevator car is lifted by applying an oil pressure to one side portion of the ram, and lowered due to a self weight by taking back the pressed oil from the hydraulic cylinder.
The conventional hydraulic elevator system will now be described in more detail.
In the conventional hydraulic elevator system, the hydraulic pump is driven by the motor, and thus a predetermined amount of pressed oil is discharged. A flow amount control valve is employed to send the discharged pressed oil to the hydraulic cylinder.
A lifting/lowering speed of the elevator car is controlled by a bleed-off system which adjusts a flow amount of the pressed oil supplied to the hydraulic cylinder by bypassing a part of the pressed oil to an oil tank.
In order to reduce energy consumption, there has been suggested an inverter control method of performing an adjustable speed control on the motor driving the hydraulic pump in the hydraulic elevator system.
A conventional technique of the hydraulic elevator system of the inverter control method has been disclosed in the Japanese Patent Publication 5-105341. The constitution of the conventional hydraulic elevator system will now be explained with reference to FIG.
1
.
FIG. 1
is a circuit diagram illustrating the conventional hydraulic elevator system.
As shown therein, reference numeral ‘
1
’ denotes the hydraulic cylinder, ‘
2
’ denotes the elevator car supported by the ram
1
a
of the hydraulic cylinder
1
, ‘
3
’ denotes the hydraulic pump reversibly rotated for pumping the pressed oil to the hydraulic cylinder
1
through a reverse check valve
5
, and ‘
4
’ denotes a motor for driving the hydraulic pump
3
.
Here, a first valve chamber
51
which uses an oil pressure of the pressed oil pumped by the hydraulic pump
3
as a pressure source is formed at a lower portion of the reverse check valve
5
.
A main chamber
52
through which the hydraulic cylinder
1
and the first valve chamber
51
of the reverse check valve
5
are connected by a second hydraulic path
6
b
discussed later is formed at a middle portion of the reverse check valve
5
. A second valve chamber
53
which uses a pilot oil pressure of the hydraulic cylinder
1
as a power source is formed at an upper portion of the reverse check valve
5
.
In addition, a piston-shaped valve body
54
moving to open/close the main chamber due to a pressure difference between the first valve chamber
51
and the second valve chamber
53
is inserted into the reverse check valve
5
. A stopper
56
restricting a lifting operation of the valve body
54
and an adjusting screw
57
externally adjusting a stroke of the stopper
56
are disposed at an upper end portion of the reverse check valve
5
.
In regard to the constitution of the conventional hydraulic circuit, there are provided a hydraulic circuit
6
including a first hydraulic path
6
a
connecting the hydraulic pump
3
to the first valve chamber
51
of the reverse check valve
5
, and a second hydraulic path
6
b
connecting the main chamber
52
of the reverse check valve
5
to the hydraulic cylinder
1
; and a pilot circuit
9
branched from the second hydraulic path
6
b
of the hydraulic circuit
6
, and including a pilot pressed oil inlet pipe
9
a
connecting the reverse check valve
5
to the second valve chamber
53
, and a pilot pressed oil discharge pipe
9
b
connecting the second valve chamber
53
to the oil tank
8
.
In addition, a normal open type solenoid valve
10
is disposed at the inlet pipe
9
a
of the pilot circuit
9
, and a normal close type solenoid valve
11
is disposed at the discharge pipe
9
b.
Variable throttle valves
12
,
13
for controlling a flow amount of the pressed oil passing through the inlet pipe
9
a
and the discharge pipe
9
b
are provided to an entrance side of the inlet pipe
9
a
of the pilot circuit
9
and an exit side of the discharge pipe
9
b
thereof, respectively.
A control unit
14
for controlling the motor
4
and the solenoid valves
10
,
11
is provided in order to control the lifting, lowering and stopping operations and the speed of the elevator car
2
by the operation of the user.
The operation of the conventional hydraulic elevator system having the hydraulic circuit will now be described.
Firstly, when a lifting operation command of the elevator car
2
is outputted from the control unit
14
, at the same time, a solenoid coil (not shown) of the normal open type and closed solenoid valves
10
,
11
is magnetically excited responding to a control signal from the control unit
14
, and a rotor of the motor
4
rotates.
The oil pressure of the pressed oil pumped by the hydraulic pump
3
driven by the motor
4
is applied to the reverse check valve
5
, the normal open type solenoid valve
10
is closed, and the normal close type solenoid valve
11
is opened. Accordingly, a pressure of the first valve chamber
51
is relatively higher than that of the second valve chamber
53
, the valve body
54
is lifted, and thus the first valve chamber
51
is opened to the main chamber
52
.
Therefore, the pressed oil discharged from the hydraulic pump
3
is supplied to the hydraulic cylinder
1
through the first valve chamber
51
and the main chamber
52
of the reverse check valve
5
, and the car
2
is lifted at a speed corresponding to a flow amount of the pressed oil.
During the lifting operation of the elevator car
2
, when it reaches to a destination floor, an excitation current of the solenoid valves
10
,
11
is shut up by a signal from the control unit
14
, the normal open and close type solenoid valves
10
,
11
return to the original open and close states, respectively, and the driving of the motor
4
stops.
Then, the pressed oil is supplied to the second valve chamber
53
of the reverse check valve
5
through the variable throttle valve
12
disposed at the inlet pipe
9
a
of the pilot circuit
9
, the valve body
54
of the reverse check valve
5
is lowered according to a flow amount of the pressed oil supplied into the second valve chamber
53
, and thus an opening of the main chamber
51
is gradually decreased. Accordingly, the lifting speed of the elevator car
2
is gradually reduced.
When the valve body
54
is lowered and the main chamber
52
of the reverse check valve
5
is completely closed, the elevator car
2
stops at the designated floor.
On the other hand, conversely, when a lowering operation command of the elevator car
2
is outputted from the control unit
14
, at the same time, according to the control signal from the control unit
14
, the normal open type solenoid valve
10
is closed, the normal close type solenoid valve
11
is opened, and the motor
4
is temporarily rotated.
The hydraulic pump
3
is temporarily driven by the temporary rotation of the motor
4
. A pressure of the first valve chamber
51
of the reverse check valve
5
becomes higher than that of the second valve chamber
53
thereof by the pressed oil pumped by the driving of the hydraulic pump
3
. Accordingly, the valve body
54
is lifted, and thus the main chamber
52
of the reverse check valve
5
is opened, as in the lifting operation of the elevator car
2
.
When the main chamber
52
of the reverse check valve
5
is opened, the driving of the motor
4
stops, and the pressed oil in the hydraulic cylinder
2
is reversed through the main c
LG Otis Elevator Company
Lillis Eileen D.
Lowe Michael
LandOfFree
Hydraulic elevator system does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Hydraulic elevator system, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Hydraulic elevator system will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2946931