Material or article handling – Elevator or hoist and loading or unloading means therefor – Elevator wherein means comprises guide mounted for relative...
Reexamination Certificate
2002-12-13
2004-07-27
Bidwell, James R. (Department: 3651)
Material or article handling
Elevator or hoist and loading or unloading means therefor
Elevator wherein means comprises guide mounted for relative...
C414S619000, C414S622000
Reexamination Certificate
active
06767175
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a forklift provided with a pallet lock device for locking a pallet lifted by a fork to prevent the pallet from being oscillated or accidentally being displaced while it is being conveyed.
2. Description of the Related Art
FIG. 15
is a side view schematically showing a conventional order picking truck
1
. In the order picking truck
1
, a fork
2
and an operator's stand
3
are integrally elevated so that reloading of a load is conducted at a high position. Reference numeral
4
is a pedestal on which an operator gets in the operator's stand
3
. A pallet
6
into which the fork
2
is inserted is locked by a lock bar
5
provided at the rear of the pedestal
4
, that is, provided on the fork
2
side of the order picking truck
1
. The lock bar
5
is supported by the pedestal
4
and is rotatable upward and downward. Usually, the lock bar
5
is set parallel with the fork
2
. After the lock bar
5
is inserted into a hole of the pallet
6
together with the fork
2
, the lock bar
5
is rotated downward by operation conducted by an operator. In this way, the lock bar
5
pushes a lower deck board of the pallet
6
from above, so that the pallet
6
is locked. In order to release the lock of the lock bar
5
, the operator conducts operation reverse to that conducted in the case of locking. By the reverse operation, the lock bar
5
is rotated upward and returned to the initial horizontal posture, so that the lock is released. The operator manually conducts the locking and unlocking operation by controlling a lever and a pedal arranged in the operator's stand
3
.
When the pallet
6
is oscillated on the fork
2
while the operator conducts reloading at a high place, there is a possibility that the load falls. Thus, the pallet should be locked. The lock is released when the fork is drawn out from the pallet, so that the pallet is placed on a shelf or ground.
As above described, the locking operation is very important. Accordingly, the operator positively executes the locking operation. However, the unlocking operation is not necessarily conducted at an appropriate timing. If unlocking operation is incompletely conducted when the fork is drawn out from the pallet which is set on a shelf, the fork or lock device is brought into contact with the pallet so that the pallet is drawn out together with the fork and falls from the shelf. If the lock is released before the pallet is surely placed on the shelf, the pallet becomes unbalanced and the pallet is oscillated on the fork depending upon a state of the load placed on the pallet, and there is a possibility that the load collapses.
Also, in case where the pallet
6
is locked according to the operator's will, there is a possibility that the operator forgets to conduct the locking operation. In this case, the pallet
6
becomes unstable and the load may collapse.
SUMMARY OF THE INVENTION
The present invention has been accomplished to solve the above problems. An object of the present invention is to provide a forklift capable of positively releasing the lock of a pallet at an appropriate timing.
Another object of the present invention is to provide a forklift capable of positively locking the pallet at an appropriate timing.
According to a first aspect of the present invention, there is provided a forklift comprising: a fork to be inserted into a pallet; a hoisting device for hoisting the fork; and a pallet lock device for locking the pallet, the pallet lock device having a lock bar which is pushable a lower deck board of the pallet to lock the pallet, wherein the pallet lock device releases the lock of the pallet when an intensity of the force given to the lock bar from the lower deck board exceeds a predetermined value.
According to a second aspect of the present invention, the pallet lock device releases the lock of the pallet when the lock bar is displaced upward by the force given from the lower deck board.
According to a third aspect of the present invention, the pallet lock device comprises: a lock bar driver for moving the lock bar upward and downward; and a detector for detecting an upward displacement of the lock bar caused by the force given from the lower deck board, wherein the lock bar driver releases the lock of the pallet when the detector detects the upward displacement of the lock bar.
According to a fourth aspect of the present invention, the pallet lock device releases the lock of the pallet when the fork is operated to a state in which the fork is drawable out from the pallet.
According to the first to fourth aspects of the invention, the lock bar pushing the lower deck board of the pallet is given an upward force from the lower deck board when the fork is lowered and the pallet is placed on a shelf or ground. When an intensity of this upward force given from the lower deck board to the lock bar becomes higher than a predetermined value, it is judged that the pallet is placed, and the lock is automatically released. Therefore, it is unnecessary for an operator to manually conduct an unlocking operation. The lock is appropriately released, and the above problems are not caused. Since the unlocking operation is conducted after the pallet is placed on a shelf etc., the load on the pallet does not become unbalanced and does not collapse. The predetermined value must be set at a value higher than an intensity of the force given from the lower deck board to the lock bar when the forklift runs and the fork is oscillated upward and downward. If the predetermined value is set at an excessively low value, the lock is released each time the forklift runs and the fork is oscillated. Accordingly, the predetermined value must be set based on a value of the upward force given from the lower deck board to the lock bar when the forklift is running, which can be calculated, actually measured or estimated. And the predetermined value must be set at a value higher than the value of the upward force. The detector for detecting the force given from the lower deck board to the lock bar may be a sensor capable of detecting stress acting upward on the lock bar. Alternatively, the detector may be a sensor or switch for detecting an upward displacement of the lock bar which is displacably supported so that it can be displaced upward according to the force given from the lower deck board. Alternatively, the detector may be provided separately from the lock bar for detecting the force. The displacement of the lock bar may be electrically detected. Alternatively, the displacement of the lock bar may be detected by a mechanical means; which is mechanically linked with the displacement. The lock bar may be urged by a spring which pushes the lock bar downward when locking the pallet and pushes the lock bar upward when unlocking the pallet, so that lock bar is rotated.
According to a fifth aspect of the present invention, the lock bar is supported on the pallet lock device via an elastic member for elastically pushing the pallet.
According to the fifth aspect, the pallet is elastically pushed by the elastic member. Therefore, the lock bar can be easily displaced upward by a force given from the lower deck board. Further, dimensional error of the pallet hole in the vertical direction can be is absorbed by the elastic member.
According to a sixth aspect of the present invention, there is provided a forklift comprising: a fork to be inserted into a pallet; a hoisting device for hoisting the fork; a pallet lock device for locking the pallet; a pallet detector for detecting an insertion of the fork into the pallet; and an upward movement detector for detecting an upward movement of the fork, wherein the pallet lock device locks the pallet after the pallet detector detects the insertion of the fork into the pallet and the upward movement detector detects the upward movement of the fork of a predetermined distance.
According to the sixth aspect, after the pallet detector detects the insertion of the fork into the pallet and the upward movement
Fujita Tutomu
Kokura Kazumasa
Tomiyama Yasunobu
Bidwell James R.
Nippon Yusoki Co., Ltd.
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