Data processing: generic control systems or specific application – Generic control system – apparatus or process – Having protection or reliability feature
Reexamination Certificate
2000-02-25
2003-05-06
Gordon, Paul P. (Department: 2121)
Data processing: generic control systems or specific application
Generic control system, apparatus or process
Having protection or reliability feature
C701S050000, C307S326000
Reexamination Certificate
active
06560495
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a locking method for forcibly halting operation of a work machine and a locking device used for such a method.
BACKGROUND OF THE INVENTION
FIG. 4
shows a hydraulic shovel as a work machine. The hydraulic shovel has a lower structure
13
including a pair of crawler belts
12
that are disposed at the two lateral sides of the lower structure
13
and driven by a pair of laterally arranged travel motors
11
respectively. An upper structure
16
is attached to the lower structure
13
with a rotating portion
15
therebetween. The rotating portion
15
is so designed as to be driven by a swing motor
14
. A cab
17
, in which a driving seat for an operator is installed, and a front attachment
18
for performing excavation are mounted on the upper structure
16
.
The front attachment
18
includes a boom
20
, a stick
22
and an attachment
29
, which may be a bucket
24
, a breaker or the like. The boom
20
is supported by the upper structure
16
by means of a pin
19
, which attaches the boom
20
to a shaft of the upper structure
16
so that the boom
20
is capable of rotating around the shaft. A pin
21
attaches the stick
22
to a shaft disposed at the end of the boom
20
so that the stick
22
is rotatably supported by the boom
20
. A pin
23
attaches the attachment
29
to a shaft disposed at the end of the stick
22
so that the attachment
29
is rotatably supported by the stick
22
. The boom
20
and the stick
22
are adapted to be rotated by a boom cylinder
25
and a stick cylinder
26
respectively, while the bucket
24
or the attachment
29
is adapted to be rotated by a bucket cylinder
27
and a link mechanism
28
.
A work machine having a structure described above is provided with a hydraulic system locking mechanism for locking the supply of oil pressure to various hydraulic actuators, such as the laterally arranged travel motors
11
, the swing motor
14
, the boom cylinder
25
, the stick cylinder
26
and the bucket cylinder
27
.
A conventional hydraulic system locking mechanism is directly operated by turning on or off a lock operation switch. Therefore, when an operator releases the hydraulic system from the locked state, the hydraulic system is unlocked regardless of the condition of the machine. In other words, should the hydraulic system lock be released in a situation where signals have been input to one or a number of the operation levers, the work machine suddenly starts running in response to the signals input to the operation lever(s).
In case the lock of the hydraulic system is released when an operation lever is in an unusual, unexpected state, such that, for example, a part of the clothes of the operator is caught by the operation lever, the work machine will move in a way the operator is not aware of. Such an event is not desirable. One of the worst possible cases will be a situation where a worker is near the work machine while signals to command swinging have been input to the operation levers. In such a case, it is absolutely imperative to prevent releasing of the lock of the hydraulic system.
As described above, a work machine equipped with an electronically controlled hydraulic system that functions according to a conventional method is not always safe, because, depending on an outstanding command input to the corresponding operation lever, releasing the lock of the hydraulic system by the operator may undesirably actuate a hydraulic actuator.
OBJECTS AND SUMMARY OF THE INVENTION
In order to solve the above problem, an object of the present invention is to ensure the safety of a work machine by requiring the operator to check the safety before releasing the work machine from the locked state.
Once a work machine becomes locked so that its operation is forcibly halted, a work machine locking method according to the present invention maintains the work machine locked until a safety check is performed.
Therefore, once the work machine becomes locked, even if release of the lock of the work machine is commanded thereafter, the work machine is kept locked and cannot be released from the locked state regardless of whether the operator of the work machine operates the work machine. The locking continues until the operator of the work machine performs a safety check. The invention thus prevents an accident that may otherwise be caused by inadvertent actuation of the work machine due to carelessness of the operator.
Furthermore, in case unlocking of the work machine is commanded in the situation where there is an outstanding actuation command input to the work machine, the aforementioned method calls for maintaining the work machine locked until a safety check is performed.
Therefore, when the work machine is in the state where an actuation command has been input, even if the operator commands unlocking, the work machine is prevented from being actuated until a safety check is performed. The invention thus prevents an accident that may otherwise be caused by the operator's careless operation to actuate the work machine or release the lock of the work machine.
In case there is an outstanding command for unlocking of the work machine while there is no outstanding actuation command input to the work machine, the aforementioned method calls for maintaining the work machine locked.
When there is no outstanding actuation command input to the work machine, it is often impossible to judge whether the work machine is locked or unlocked. Therefore, even if there is no outstanding actuation command input to the work machine, the invention ensures complete safety by maintaining the work machine locked and calling attention of the operator when unlocking of the work machine has been commanded.
In the method described above, the work machine can be released from the locked state by commanding locking in the state where there is no outstanding actuation command input to the work machine and, thereafter, commanding release of the lock of the work machine.
According to the above method, the work machine is released from the locked state and made ready to be actuated by commanding locking so as to perform a safety check in the state where there is no outstanding actuation command input to the work machine and, thereafter, commanding release of the lock of the work machine. Thus, the invention facilitates a safety check operation.
A work machine locking device according to the present invention includes operating devices for inputting actuation commands to a work machine, a lock commanding means adapted to command locking for halting the work machine or unlocking for enabling the work machine to resume working, an electronic circuit adapted to compute the method of locking said work machine based on signals that have been input from the operating devices and the lock commanding means, and a lock executing means adapted to be controlled by signals output from said electronic circuit so as to maintain or release the work machine at or from the locked state.
As described above, the lock executing means is controlled by signals that have been output from said electronic circuit based on signals input from the operating devices and the lock commanding means. Therefore, locking and unlocking of the work machine can easily be controlled according to signals input from the operating devices and the lock commanding means. For example, in case the operator commands to release the work machine from the locked state in the situation where there is an outstanding actuation command from an operating device, the work machine is maintained locked by the lock executing means, which is controlled based on arithmetic signals from the electronic circuit. In case there is no actuation command from the operating devices, the lock commanding means commands locking and then commands unlocking so that the lock by the lock executing means is released, thereby enabling the actuation of the work machine.
According to another feature of the invention, the aforementioned lock executing means is an electromagnetic selector valve
Furuta Hideto
Moriya Naoyuki
Darby & Darby
Gordon Paul P.
Shin Caterpillar Mitsubishi Ltd.
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