Material or article handling – Elevator or hoist and loading or unloading means therefor – Comprising device on carrier to move or carry load laterally...
Reexamination Certificate
1999-10-06
2002-06-11
Bratlie, Steven A. (Department: 3652)
Material or article handling
Elevator or hoist and loading or unloading means therefor
Comprising device on carrier to move or carry load laterally...
Reexamination Certificate
active
06402454
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a forklift structured such that baggage carried on a fork can be pushed out by a pusher movable forward in synchronization with the backward movement of a vehicle body.
2. Description of the Related Art
Conventionally, as a forklift of this type, there is known a forklift as shown in FIG.
6
. The forklift comprises an electric vehicle body
1
which includes a mast
2
in the front portion thereof and an elevator body
3
so disposed on the mast
2
as to be movable upward and downward; and, there is provided a fork
4
on the elevator body
3
in such a manner as to project forwardly from the elevator body
3
. And, a pusher
6
is mounted on the elevator body
3
through a pantograph-like link mechanism
5
and, between the elevator body
3
and link mechanism
5
, there is interposed a pusher cylinder
7
which expands and compresses the link mechanism
5
to thereby move the pusher
6
forward, that is, in the direction of an arrow line “a” as shown in
FIG. 6
(forward movement “a”) and backward, that is, in the direction of an arrow “b” shown in
FIG. 6
(backward movement “b”) along the upper surface of the fork
4
. Also, on the elevator body
3
, there is disposed a pusher moving amount detector
9
composed of a potentiometer or the like which can detect the moving amount of the pusher
6
from the pull-out length of a cable body
8
connected to the pusher
6
. Further, a vehicle speed detector
1
c
is disposed on a vehicle drive motor
1
b
which is mounted within the vehicle body
1
. Also, as shown in
FIG. 7
, in the controls
1
a
of the vehicle body
1
, there are disposed a steering wheel
10
, a throttle pedal
11
, a pusher lever
12
, a synchronous mode change-over switch
13
, a synchronous mode lamp
13
a,
and a forward/backward moving lever
14
.
Conventionally, as shown in
FIG. 8
, in an oil pressure circuit
16
which connects together the pusher cylinder
7
and an oil pressure pump
15
, there is disposed a proportional electromagnetic control valve
17
having four ports and three positions. Reference character
18
designates a drive motor for driving the oil pressure pump
15
, while
19
stands for an oil pressure tank.
In the above-mentioned structure, as shown by a solid line in
FIG. 6
, while baggage W is carried on the fork
4
, if the synchronous mode change-over switch
13
is depressed, the forward/backward moving lever
14
is switched from the neutral position thereof to the backward moving side thereof, and the throttle pedal
11
held at the neutral position thereof is stepped down, then a synchronous mode is operated; and, at the same time when the vehicle body drive motor
1
b
is driven and the vehicle body
1
is thereby moved backward “b”, the pressure oil supply amount is adjusted by the proportional electromagnetic control valve
17
which has been switched over to a right side expansion position A according to the amount of step-down of the throttle pedal
11
to thereby control the expansion speed of a piston rod
7
a,
whereby the pusher
6
is moved forward a in synchronization with the backward movement b of the vehicle body
1
to thereby push out the baggage W on the fork
4
(see an imaginary line shown in FIG.
6
).
Thereafter, the synchronous mode can be removed by depressing the synchronous mode change-over switch
13
.
However, in the above-mentioned conventional forklift, in order to move forward the pusher
6
in the arrow line a direction in synchronization with the backward movement “b” of the vehicle body
1
, there is used an expensive proportional electromagnetic control valve
17
, which leads to the expensive manufacturing cost of the forklift.
In view of the above, there can be expected a structure in which, instead of the expensive proportional electromagnetic control valve
17
, there is used an inexpensive hand-operated switch valve and the hand-operated switch valve is operated by hand using the pusher lever
12
. However, in this structure, if an operator operates the hand-operated switch valve in a smaller amount than a set operation amount to thereby control or reduce the pressure oil supply amount to the pusher cylinder
7
too much, then the synchronous operation may be performed incorrectly, thereby causing the properly arranged pieces of baggage to collapse or become rearrangred in a state of disorder.
Further, in the above-mentioned conventional forklift, since the synchronous mode change-over switch
13
is distant from the steering wheel
10
and pusher lever
12
, each time the synchronous mode is switched, an operator must release his or her hand from the steering wheel
10
or pusher lever
12
and press down the synchronous mode change-over switch
13
, which results in a poor operation efficiency. Also, to remove the synchronous mode after completion of the operation in the synchronous mode, it is necessary to press down the synchronous mode change-over switch
13
, which takes time and labor.
Furthermore, in the above-mentioned conventional forklift, the moving amount of the pusher
6
is detected by the pusher moving amount detector
9
, the speed of the vehicle body
1
is detected by the vehicle speed detector
1
c
from the number of rotations of the axle shaft or motor shaft, and, in accordance with the detect signals respectively issued from the two detectors
9
and
1
c,
the backward movement “b” of the vehicle body
1
and the forward movement “a” of the pusher
6
are allowed to synchronize with each other. However, when the tire
1
d
is worn due to use for a long period of time, there is produced an error between the actual vehicle speed and the detected vehicle speed.
Also, in the conventional structure, because no means is disposed for correcting the above-mentioned error, the forward movement “a” of the pusher
6
can be faster than the backward movement “b” of the vehicle body
1
, which not only makes it impossible to place the pieces of baggage W at their respective given positions but also may lead to the pieces of baggage W collapsing or becoming rearranged in a state of disorder.
SUMMARY OF THE INVENTION
The object of the present invention is to eliminate the drawbacks found in the above-mentioned conventional forklift and to provide a forklift which can be manufactured at a low cost and is able to carry out a synchronous operation positively to thereby unload the baggage safely therefrom.
It is another object of the invention to provide a forklift which not only allows an operator to press down a synchronous mode change-over switch without releasing his or her hand from a pusher lever, but also allows the synchronous mode to be removed automatically after completion of the operation in the synchronous mode.
It is also an object of the invention to provide a forklift which allows the backward movement of the vehicle body of the forklift and the forward movement of the pusher to synchronize with each other with no error between them.
In attaining the above object, according to a first aspect of the invention, there is provided a forklift structured such that, while baggage is carried on a fork, if a synchronous mode change-over switch is depressed, a forward/backward moving lever is switched over to its backward moving side, and a throttle pedal is stepped down, then a pusher is moved forward by a pusher cylinder in synchronization with the backward movement of the vehicle body of the forklift to thereby push out the baggage on the fork, wherein, in an oil pressure circuit for connecting together the pusher cylinder and an oil pressure pump, there is disposed a hand-operated switch valve, and there is disposed a valve full-open switch for detecting that the hand-operated switch valve is fully opened, and also wherein, on receiving a detect signal form the valve full-open switch, a synchronous mode is operated.
According to the above structure, there is disposed the inexpensive hand-operated change-over valve in the oil pressure circuit connecting together the oil pressure pu
Kakitsubata Haruhiko
Kikuchi Sanpei
Kitao Takahiro
Minami Hiroshi
Tanaka Shinobu
Bratlie Steven A.
Nippon Yusoki Co., Ltd.
Sughrue & Mion, PLLC
LandOfFree
Forklift does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Forklift, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Forklift will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2963472