JPS6219679Y2 - - Google Patents

Description

[Detailed description of the invention] The present invention has a cab as a work platform that can be raised and lowered along a mast or support, like a custom pick car, rack truck, high pickup truck, etc. The present invention relates to forklifts that operate the lift or the movement of the vehicle, and more specifically relates to a safety device when the driver's cab is lowered or the vehicle is moved.

Generally, in the above type of forklift, it is difficult for the driver on the cab to check the area below the cab. On the other hand, since such forklifts are used for the easy dispensing of small products in warehouses where there is a relatively high number of people coming and going, there is a possibility that workers may get stuck directly under the elevated cab. . Therefore, if the driver's cab is lowered or the vehicle is driven without being able to confirm the presence of the worker, there is a risk of personal injury.

An object of the present invention is to provide a safety device for a forklift that can eliminate the above-mentioned conventional drawbacks and ensure the safety of workers.

Hereinafter, the present invention will be specifically explained based on the illustrated embodiments. FIG. 1 shows a reach-type pick-up lift, in which 1 is a vehicle body equipped with a mast device 2, 3 is a driver's cab that is integrated with a fork 4 and is attached to the mast device 2 so that it can be raised and lowered; The driver's cab 3 is equipped with an operation section for operating the elevator cab 3 and the driving of the vehicle.

FIG. 2 is a control circuit diagram, and the elevating and lowering control of the driver's cab 3 and the traveling control of the vehicle will be explained below based on this diagram. Solenoid for the lowering solenoid valve that controls the lowering operation of the lift cylinder that raises and lowers the cab 3
SOL is connected to battery B, which is the power source, via the push button switch SWD for lowering, and has a normally closed contact.
When the push button switch SWD is turned ON with X ₁ b ₁ ON, the solenoid valve is switched to the oil path conduction position and the driver's cab 3 is lowered. Also, a hydraulic pump motor for lifting the cab to supply hydraulic oil to the lift cylinder.
DMP is connected to the battery B via the contact MPa of the electromagnetic contactor MP for rising, and the contact MPa
is activated by turning ON, and supplies hydraulic oil to the lift cylinder to raise the driver's cab 3. In addition, the contact point MPa of the electromagnetic contactor MP is a key switch SWky,
Lifting switch SWP and maximum lifting height detection switch
LSHL (a normally closed switch that detects the rising end of cab 3 and turns OFF when detected) is all ON.
By energizing the electromagnetic contactor MP
It is turned ON, and when the cab 3 reaches the rising end, the maximum lift height detection switch LSHL is turned OFF.
OFF and the hydraulic pump motor DMP is automatically stopped.

The rotational direction of the drive motor DMD for vehicle running is controlled by changing the direction of energization to the field coil, and the energization direction is determined by the contact point MFa of the electromagnetic contactor MF for forward movement or the electromagnetic contactor MR for reverse movement. It is determined by which of the contacts MRa is brought into contact with the power supply side terminal. And an electromagnetic contactor for forward or reverse movement.
MF and MR are the travel stop switch LSND (a switch that turns OFF when the driver's cab 3 is lifted at a certain height, e.g. 4 m, and always remains ON below a certain lift height) and the deadman switch LSD (the switch that is turned OFF when the driver's cab 3 is lifted at a certain height, e.g. 4 m.) (switch turned ON by pressing the button) are both
In the ON state, when forward switch LSF or reverse switch LSR is turned ON, the corresponding contact MFa or MRa is brought into contact with the power supply side terminal.

Further, the speed of the drive motor DMD is controlled by an SCR type chopper CH connected in series to the motor, and the SCR type chopper CH is the resistance of a variable resistor VRA that is linked to an accelerator pedal or an accelerator handle. It is controlled by a pulse signal given from the chopper signal oscillator SG in response to the change. Therefore, the speed of the drive motor DMD increases as the amount of depression of the accelerator pedal increases, but when the cab 3 rises to a certain height (for example, 0.4 m) from the ground, the low speed switch LSSL is turned on. The speed is maintained at a constant low speed regardless of the amount of pedal depression, and the driver's cab 3 is further raised and stopped when the stop switch LSND is turned off. In addition, F in the figure
1, F2, and F3 each indicate a fuse, and
DA stands for armature diode and DF stands for wheeling diode.

Next, a description will be given of the safety device of the present invention, which is intended for a forklift that controls the elevation of the driver's cab 3 and the running of the vehicle as described above. This safety device temporarily restricts the lowering of the driver's cab 3 and the running of the vehicle when the driver's cab 3 is at a higher elevation (e.g., 1.5 m) or higher, and issues a warning (advance notice). In addition, it is incorporated as a safety circuit into the above-mentioned lifting and traveling control circuit.

In other words, the lift height detection switch LSH, which is attached to an appropriate location on the mast device 2 and is turned ON when the lift height of the driver's cab 3 is 1.5 m or more, controls the battery B to communicate with the electromagnetic valve operating circuit, drive motor control circuit, etc. The lift height detection switch is connected in parallel.
A first auxiliary relay _X1 , an operation delay timer TR, a warning buzzer BZ, and a fourth auxiliary relay _X4 are connected in parallel to the LSH. In addition, a second auxiliary relay X ₂ is connected in parallel to the operating circuit of the solenoid SOL for the solenoid valve, and a third auxiliary relay X ₃ is connected in parallel to the forward and reverse circuits in the control circuit of the drive motor DMD.
Connected via D ₁ and D ₂ . And the first
One normally closed contact X ₁ b 1 of the auxiliary relay _{X 1} is inserted in series with the solenoid SOL, and the other one normally closed contact
X ₁ b ₂ is inserted in series in the control circuit of the drive motor DMD. Normally open contact of 2nd auxiliary relay X ₂
X ₂ a and _the normally open contact _of the third auxiliary relay X ₃
These three devices are inserted in parallel. In addition, the normally closed contact X ₄ b of the fourth auxiliary relay X ₄ is inserted in series with the first auxiliary relay X ₁ , and the timer TR
The normally open contact TRa of is inserted in series with the buzzer BZ,
In addition, a normally closed contact TRb is inserted in series with the fourth auxiliary relay _X4 .

Therefore, when the cab 3 is elevated to a height of 1.5 m or more, the lift height detection switch LSH is ON, and at this time, the first auxiliary relay X ₁ is energized and its normally closed contact X ₁ b ₁ and X ₁ b ₂ are respectively
OFF, and as a result the solenoid for the solenoid valve SOL
and operation of the drive motor DMD is prohibited.
In addition, the hydraulic pump motor DMD for raising the cab can be operated, and the driver can press the lift switch.
The driver's cab 3 can be raised by turning on the SWP.

Now, when the above-mentioned lifting height detection switch LSH is in the ON state, when the lowering push button switch SWD is turned on, the normally open contact X ₂ a is turned ON by the excitation of the second auxiliary relay X ₂ , so the timer When TR operates, its normally closed contact TRb turns OFF, and its normally open contact
TRa turns ON. Therefore, the buzzer BZ is activated to forewarn the descent of the driver's cab 3. Then, after a preset period of time has elapsed, that is, when the timer TR times up, the normally closed contact TRb turns on and the normally open contact
Since TRa turns OFF, the buzzer BZ stops and the 4th auxiliary relay X ₄ is energized and its normally closed contact
Turn off X ₄ b. As a result, the first auxiliary relay X ₁ is de-energized and the normally closed contact X ₁ b ₁ for the solenoid circuit is opened.
In order to turn ON, the lowering electromagnetic valve solenoid SOL is energized and the lift cylinder oil passage is switched to the lowering side, and thus the cab 3 is lowered.

Also, when the forward switch LSF or reverse switch LSR is turned on to drive the vehicle, the third
The normally open contact X _{3 a} is turned ON by the energization of the auxiliary relay X 3 and the timer TR is activated, so the buzzer BZ gives a warning in the same way as during the lowering described above, and the first auxiliary relay is activated based on the time up of the timer TR. When the relay X ₁ is de-energized, the normally closed contact X ₁ b ₂ inserted in the control circuit of the drive motor DMD is turned on. Therefore, the forward or reverse electromagnetic contactors MF and MR are energized and their contacts MFa or MRa are brought into contact with the power supply side terminals, so the drive motor DMD is driven in the forward or reverse direction, causing the vehicle to move forward or backward. The vehicle will be moved backwards, but in this case the vehicle will be driven at a distance of 0.4m or more from the driver's cab 3.
The vehicle is running at low speed because the low speed switch LSSL is in the ON state.

Note that in this example, the conditions for limiting descent and traveling were the same, but it is also possible to separate the lifting height detection switch LSH for setting conditions for descending and traveling and set the limiting conditions separately. do not have. In that case, regarding the descent, it is set to turn ON only at a certain specific position, for example, when the cab 3 is lifted to a height of 2 m, and when descending below 2 m, the above-mentioned safety circuit is activated only at the 2 m position. It is possible to configure it so that it can be freely raised and lowered within a range exceeding 2 m.

In addition, when the forklift is a reach type as shown in the figure, a photoelectric device is provided on the reach leg 5 for detecting workers, etc., and the normally open contact X ₅ a of the photoelectric device is connected to the first contact point as shown in FIG. If _the circuit of auxiliary relay X ₁ is inserted in parallel with _the normally closed contact X ₄ b of the fourth auxiliary relay Since the first auxiliary relay _X1 maintains the energized state even if time-up occurs, it is possible to prohibit descent or running, further improving safety.

As described in detail above, the present invention is a forklift in which the driver's cab moves up and down, and when the driver's cab is lowered or the vehicle is moved while the cab is in the raised state, a buzzer etc. is activated. The system is designed so that the operation is activated after a warning (advance notice) is given, and therefore, for example, when dispensing work in a warehouse rack, there is a possibility that a worker may get under the cab and work in a dangerous situation. It is also effective in reducing the mental fatigue of drivers.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention; Fig. 1 is a perspective view of a reach-type pick-up lift; Fig. 2 is a control circuit for lifting and traveling incorporating a safety circuit, which is the main part of the invention; FIG. 3 is a circuit diagram showing another embodiment. 3... Driver's cab, SOL... Solenoid, B...
Battery, DMD... Drive motor, SWD...
Lowering push button switch, SWP... Ascent switch, LSF... Forward switch, LSR... Reverse switch, LSH... Lifting height detection switch, TR... Timer, BZ... Buzzer, X ₁ to X ₄ ... ...1st to 4th
Auxiliary relay.

Claims (1)

[Scope of utility model registration request] A lift height for detecting a lift height of the driver's cab above a certain level in a forklift in which a driver's cab is provided so as to be movable up and down, and the driver's cab is equipped with an operation unit for controlling the raising and lowering of the driver's cab and the traveling of the vehicle. A circuit includes a detection switch, and when the switch is activated, the solenoid of the lowering solenoid valve and the drive motor for driving are cut off from electricity, and in this cut-off state, the operating section operates the solenoid or the drive motor. A safety device for a forklift, comprising a circuit that issues an alarm when a drive operation is performed, and restores energization to the solenoid or drive motor after a certain period of time after the alarm is issued.