Elevator – industrial lift truck – or stationary lift for vehicle – Having specific load support drive-means or its control – Includes linking support cable in drive-means
Reexamination Certificate
2000-01-03
2001-09-18
Lillis, Eileen D (Department: 3652)
Elevator, industrial lift truck, or stationary lift for vehicle
Having specific load support drive-means or its control
Includes linking support cable in drive-means
C187S272000
Reexamination Certificate
active
06290026
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a hydraulic elevator that is raised and lowered by a hydraulic jack unit.
BACKGROUND ART
FIG. 9
is a side elevational view showing a conventional hydraulic elevator disclosed in, for example, Japanese Patent Application Laid-Open No. 7-20827 and
FIG. 10
is a plan view showing the hydraulic elevator shown in FIG.
9
. In these drawings, a pair of guide rails
2
are disposed spaced from each other within a hoistway
1
. A car
3
that is raised and lowered along the guide rails
2
is disposed between the guide rails
2
. A plurality of guide shoes
4
are fixed to the car
3
as guide members which engage with the guide rails
2
, respectively.
First and second hydraulic jacks
5
and
6
are installed on one side of the car
3
within the hoistway
1
. These hydraulic jacks
5
and
6
have jack bases
5
a
and
6
a
fixed on a floor
1
b
of a pit
1
a
of the hoistway
1
, cylinders
5
b
and
6
b
fixed on the jack bases
5
a
and
6
b
, and plungers
5
c
and
6
c
that are reciprocated in a vertical direction inserted into the cylinders
5
b
and
6
b.
Upper end portions of the plungers
5
c
and
6
c
are connected to each other by a support frame
7
. A rotatable suspension sheave
8
is mounted on the support frame
7
. A pair of guide rails
9
a
and
9
b
for guiding the ascending/descending movement of the support frame
7
are fixed to the upper end portions of the cylinders
5
b
and
6
b
, respectively.
A hydraulic power unit
12
having an oil tank
11
is installed within a machine room
10
adjacent to the hoistway
1
. The hydraulic power unit
12
is connected to the first and second hydraulic jacks
5
and
6
through a pipe
13
branched at a midway portion thereof.
A stationary member
14
is fixed to the floor
1
b
of the pit
1
b
. The car
3
is suspended within the hoistway
1
by a suspension rope
15
wound around the suspension sheave
8
. The suspension rope
15
has a hoistway side fastening end
15
a
fastened to the stationary member
14
and a car side fastening end
15
b
fastened to the car
3
. The car side fastening end
15
b
is fastened to a rope support beam
17
of the car
3
through a spring
16
.
The operation will now be described. A pressurized oil is fed into the cylinders
5
b
and
6
b
of the first and second hydraulic jacks
5
and
6
from the hydraulic power unit
12
so that the plungers
5
c
and
6
c
are raised and the car
3
is raised along the guide rails
2
. In this case, the elevating velocity of the car
3
is twice as fast as the elevating velocity of the plungers
5
c
and
6
c
. Also, the hydraulic oil within the cylinders
5
b
and
6
b
is fed back to the hydraulic power unit
12
by the weight of the car
3
, allowing the car
3
to descend.
In this case, it should be noted that there is a predetermined upper limit of working pressure for respective hydraulic equipment such as the hydraulic pump (not shown), the hydraulic valve (not shown), the pipe
13
, the hydraulic jacks
5
and
6
and the like within the hydraulic power unit
12
. The upper limit of the working pressure is set to be greater than a value obtained by dividing twice the sum of the respective weights such as the tare weight (dead weight) of the car
3
, the load, the weight of the suspension sheave
8
and the like by the cross-sectional area of the plungers
5
c
and
6
c.
In the thus constructed conventional hydraulic elevator, a coupling force (the pair of forces that are the same in magnitude, but opposite in direction) about a fixed point of the suspension rope
15
in the car
3
is received by the guide shoes
4
. The load (guide shoe reactive force) applied to the guide shoes
4
is given by the equation: F=Wc×Ex/H, where F is the guide shoe reactive force, Wc is the weight of the car
3
, Ex is the distance, in the opening direction of the doors, from the gravitational center of the car
3
to the suspension point thereof, and H is the interval between the upper and lower guide shoes
4
of the car
3
, as shown in FIG.
11
.
As described in the equation, the guide shoe reactive force is proportional to the distance Ex from the gravitational center of the car
3
to the suspension point in the opening direction of the doors. Accordingly, in a hydraulic elevator having a larger dimension in the opening direction of the doors of the car
3
, there are certain instances where the car
3
can not be guided by the guide shoes
4
.
For example, the guide shoe reactive force in a hydraulic elevator (car dimensions: opening direction of the doors dimension of 1,400 mm×depth dimension of 1,350 mm×door opening height of 2,100 mm) with a load of 750 kg, 11 persons standardized in accordance with Japanese Elevator Association is given as follows:
Namely, since the weight of the car is about 1.2 times the load, the relationship, Wc=750×1.2=900 kg, is established. Normally, the position of the center of gravity is substantially at the center of the car in the opening direction of the doors, and the dimension from an end of the car in the opening direction of the doors to the suspension point is about 150 mm. Accordingly, the distance from the gravitational center of the car to the suspension point in the opening direction of the doors is Ex=1,400/2+150=850 mm. Also, the interval H between the upper and lower guide shoes is normally about 3,000 mm.
If such conditions are substituted in the above-described equation, the relationship of the guide shoe reactive force, F=900×850/3,000=255 kg, is established. When the guide shoe reactive force becomes large, the cost is increased since it is necessary to enlarge the size of members such as the guide shoes, the guide rails and the car frame which are subjected to the guide shoe reactive force, resulting in a less economical elevator.
Also, in the above-described hydraulic elevator, since the fastening force of the plungers
5
c
and
6
c
on the packing (not shown) for preventing oil leakage from the sliding portions between the cylinders
5
b
and
6
b
and the plungers
5
c
and
6
c
, respectively, varies, the travel resistance of the plungers
5
c
and
6
c
also fluctuates. Accordingly, even if the hydraulic jacks
5
and
6
are controlled in the same manner, the extension speeds of the plungers
5
c
and
6
c
become different from each other, resulting in abnormal wear of the packing due to the slant of the plungers
5
c
and
6
c
and the application of an overly large force to the support frame
7
. These factors cause the hydraulic elevator to breakdown.
Also, Japanese Patent Application Laid-Open No. 62-264186 and Japanese Patent Application Laid-Open No. 8-268664 show a hydraulic elevator in which a car is raised and lowered by using a plurality of hydraulic jacks. However, since there is a single suspension point for the suspension rope, a large reactive force is applied to the guide members for guiding the movement of the car in the vertical direction.
DISCLOSURE OF THE INVENTION
The present invention has been made in order to solve the above-noted problems, and therefore an object of the present invention is to provide a hydraulic elevator in which the reactive force applied to guide members can be reduced, and the car can be raised and lowered stably.
According to the present invention, there is provided a hydraulic elevator comprising: a pair of guide rails spaced from each other within a hoistway; a car which is interposed between the pair of guide rails and which is raised and lowered along the pair of guide rails; a plurality of hydraulic jack units spaced from each other within the hoistway so as to straddle at least a section of a vertically projected area of the car; a plurality of rotatable suspension sheaves each moved up and down by the hydraulic jack units; a stationary member located below the suspension sheaves within the hoistway; a flexible suspension means wound around the suspension sheaves with a hoistway side fastening end fas
Leydig , Voit & Mayer, Ltd.
Lillis Eileen D
Mitsubishi Denki & Kabushiki Kaisha
Tran Thuy V.
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