JP3167192B2 - Overload warning device for aerial work vehicles - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a work table which can be moved up and down for work at high places such as indoor piping of a building.
The present invention relates to an overload warning device for an aerial work vehicle.

[0002]

2. Description of the Related Art Hitherto, there has been known an aerial work vehicle having a structure in which a working table is connected to a traveling vehicle via a scissor link mechanism, and the scissor link mechanism is moved up and down by expansion and contraction of a hydraulic cylinder. In such a high-altitude working vehicle, if the load (including the driver) loaded on the workbench is excessive, a high pressure is applied to the hydraulic cylinder, which may cause excessive work, resulting in a very dangerous state. The overload warning device is attached. Conventionally, overloading is detected by installing a pressure sensor for detecting the pressure of a hydraulic cylinder for raising and lowering the scissor link mechanism, setting an overloading set pressure Pk, and detecting the cylinder pressure detected by the pressure sensor. The detected value P is equal to the set pressure Pk.
If it is larger than this, an overload warning was issued. In addition, when an overload warning is issued, the workbench is not allowed to ascend.

[0003] However, even when the weight of the load on the work table is constant, the pressure value in the hydraulic cylinder is not constant at the time of ascending and descending due to the link ratio of the scissors link mechanism. That is, as shown in FIG. 11, first, a high pressure (initial maximum pressure) Pa is applied at the moment when the hydraulic cylinder is operated when the worktable is stored, and then the pressure is reduced for a while, and after the worktable has been leveled off, the worktable is eventually released. The pressure gradually increases as the pressure rises. In this case, if the initial maximum pressure Pa is equal to or higher than the overload set pressure Pk, an alarm is issued as soon as the workbench is raised. This initial maximum pressure Pa
Was instantaneous at the start of the ascent, and as the cylinder continued to ascend, the cylinder pressure immediately dropped.Therefore, an alarm was issued frequently at this point, and no alarm was issued if the ascent was raised from that position. .

[0004]

In the conventional overload warning device, the overload set pressure Pk is set to a constant value. If no overload is detected near the initial maximum pressure Pa, the workbench is further raised to raise the cylinder pressure P, and an overload alarm is issued when the overload set pressure Pk is reached. Becomes The problem here is the overload setting pressure P
This is the set value of k, and if the set value is high, the workbench will be quite high and will not rise to near the highest position (Y in FIG. 11).
(Position) No alarm is issued, which is dangerous. On the other hand, if the set value is lowered, the time when the initial maximum pressure Pa exceeds the overload set pressure Pk becomes longer at the start of the ascent of the workbench. At the X position), the workbench cannot be raised.

[0005] As another problem, as shown in FIG. 11, when the work table is raised, the cylinder pressure P reaches an initial maximum pressure Pa, and then becomes wavy and decreases. . Accordingly, the cylinder pressure P that has reached the initial maximum pressure Pa immediately decreases in the form of a wave trough, so that even if the initial maximum pressure Pa is equal to or higher than the overload set pressure Pk, it immediately falls below it. In this state, if the pressure value near the initial maximum pressure Pa exceeds the overload set pressure Pk for a certain time T or more, an overload alarm is issued. In the meantime, the work platform is slightly raised, and during the rise, the pressure suddenly drops in a wave valley, so that the pressure immediately falls below the overload set pressure Pk, and thus the alarm once issued is released. It can happen. In this case, the alarm is canceled in spite of the fact that the alarm has to be issued.

[0006]

Means for Solving the Problems The present invention has the following structure in order to solve the above problems. A scissors link mechanism is interposed between the traveling trolley and the work platform, and the work platform slightly rises from the stowed state in an aerial work vehicle that can be moved up and down by expansion and contraction of a hydraulic cylinder for lifting. A workbench storage detection switch that is turned on at the time, a workbench 1/2 rise detection switch that is turned on when the workbench rises to approximately half the height, and a pressure sensor that detects the pressure of the lifting hydraulic cylinder When the workbench storage detection switch is turned on ,
When the detection value of the pressure sensor exceeds the overload set pressure set for each position when the workbench 1/2 rise detection switch is turned on, an overload warning is issued, and the workbench cannot be lifted. Once an overload alert is issued
Operates the down switch that lowers the workbench to the ON side.
And the pressure detected by the pressure sensor is
Only when it falls, cancel the alarm and work again
The platform can be raised .

[0007]

When the work platform of the aerial work platform is released from the retracted state and starts ascending, the work platform is slightly raised (15 cm to 2 cm).
0 cm), the workbench storage detection switch LS1 is turned ON, and after a certain time T, the pressure sensor P
The pressure P near the initial maximum pressure Pa of the hydraulic cylinders 7a and 7b detected by S and the overload set pressure Pk
When the overload warning is not issued at this time, if the workbench is raised further, 1 / l of the total head is lifted.
When the work platform 1/2 rise detection switch LS2 is turned on when the position reaches the position No. 2, the cylinder pressure P is compared with the overload set pressure Pk2, and the cylinder pressure P becomes the overload set pressure. If Pk2 is exceeded, an overload warning is issued and the ascent is stopped before the workbench reaches a high position.

Further, once an alarm is issued, the descending switch 15 is turned on to change the detected pressure P to the overload set pressure Pk1.
Even if the pressure falls below (Pk2) or the detected pressure P falls below the overload set pressure Pk1 (Pk2), the alarm will not be released unless the down switch 15 is turned on. Therefore, the cylinder pressure will be wavy near the initial maximum pressure Pa. Although it is descending, the alarm is issued correctly and the alarm will not be released unless a dangerous state (raising the platform while overloading) is avoided (the platform is lowered).

[0009]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an embodiment of the present invention; 1 is an overall side view of an aerial work vehicle using the present invention, FIG. 2 is a perspective view when the workbench B is raised, FIG. 3 is a circuit diagram of an overload alarm device, and FIG. FIG. 5 is a graph showing a change in cylinder pressure associated with the above and a cylinder pressure detection position in the overload alarm of the present invention, FIG. 5 is a perspective view showing an operation surface of an operation panel unit D1, and FIG.
, FIG. 7 is a plan view of the lift switch 9, FIG. 8 is a perspective view of the lift switch 11, FIG. 9 is a plan view of the travel operation lever 8, and FIG. 10 is steering of the crawler travel device 1 by the travel operation lever 8. It is a figure showing an operation.

The overall construction of the aerial work vehicle will be described with reference to FIGS. The traveling vehicle A uses a driving transmission case M to drive the driving force of the DC motor 2 powered by the battery 3.
To drive the crawler traveling device 1. A controller box 4 is provided near the DC motor 2. Steering is performed by connecting and disconnecting clutches by side clutch actuators 5L and 5R, which are provided with a drive transmission case M and are driven by left and right independent electric motors 5a. An electromagnetic parking brake 13 that automatically brakes when the driving lever 8 is set to a neutral position and the driving is stopped is provided outside the driving transmission case M.

A worktable B is connected to a traveling frame 6 of a traveling vehicle A via a scissors link mechanism C. The scissor link mechanism C has a structure in which three stages of scissor links are pivotally connected, and is an upper lifting cylinder 7a which is a hydraulic cylinder.
And the lower lift cylinder 7b is moved up and down by expansion and contraction. The workbench B has an upper operation panel D1
And a joystick-type traveling operation lever 8 for performing both traveling and steering operations is disposed on the operation surface of the upper operation panel section D1. Further, the traveling vehicle A is provided with a lower operation panel section D2.

The operation surface of the operation panel section D1 is as shown in FIG. 5. In addition to the traveling operation lever 8, an elevation lever 9 for extending and retracting the elevation cylinders 7a and 7b is provided. Various alarm lamps 10 such as an alarm lamp 10a are provided. In addition, an alarm buzzer that sounds at the time of an alarm is built in. And the lower operation panel section D2
As shown in FIG. 6, a lift switch 11 having the same function as the lift lever 9 is provided, and a key switch 12 and the like are provided.

Here, the traveling operation lever 8 will be described. As shown in FIG. 9, the travel operation lever 8 is for forward drive when tilted forward F, and for reverse drive when tilted backward R.
The front / rear center position is a driving neutral position, at which the driving of the DC motor 2 is stopped. Note that the range in which the front-back tilt angle of the lever is small is regarded as an erroneous operation, and the traveling is stopped. When the vehicle is turned in the left and right directions, one of the side clutches is disengaged by the side clutch actuators 5L and 5R, the drive of the left or right of the crawler traveling device 1 is stopped, and the vehicle is turned. Immediately when the side clutch is disengaged, the vehicle body turns even if the lever is erroneously tilted right and left, so that both side clutches are not disengaged in a range in which the left-right tilt angle of the lever is small. When the lever is tilted obliquely, as shown in FIG. 10, while the DC motor is driven, one of the side clutches is disengaged and the crawler traveling device 1 is turned to turn the vehicle.

Next, the lifting lever 9 and the lifting switch 11
Will be described with reference to FIGS. 7 and 8. FIG. The elevating lever 9 can be tilted forward and backward.
Is configured to push the upper or lower part. In the vehicle, a lift switch 14 for extending the lift cylinder 7 to raise the worktable B and a lower switch 15 for contracting the lift cylinder 7 to lower the worktable B are provided.
When the lifting lever 9 is tilted forward or the upper part of the lifting switch 11 is pressed, the lifting switch 14 is turned on, and the lifting lever 9 is tilted forward or the lifting switch When the lower part of the switch 11 is pressed, the lowering switch 15 is turned on. And, as shown in FIG.
ON of the up switch 14 or the down switch 15 is input to the controller 4 to operate the electromagnetic valve SV,
The upper and lower hydraulic cylinders 7a and 7b are extended when the raising switch 14 is turned ON, and the hydraulic cylinders 7a and 7b are contracted when the lowering switch 15 is turned ON. The work table B is raised and lowered by operating the scissors link mechanism C. A hydraulic pump 16 for feeding oil to the hydraulic cylinder
Uses the driving force of the DC motor 2. A pressure sensor PS for detecting a cylinder oil pressure value is provided in an oil passage of the hydraulic cylinders 7a and 7b.

The work frame storage detection switch LS1, which is a limit switch, is provided on the traveling frame 6 at a position slightly raised from the storage position of the work table B (at a height of about 15 to 20 cm). Raise the platform B, and when the height is about 1/2 of the maximum height,
Since the workbench 1/2 ascending detection switch LS2 composed of a limit switch for N is installed near the pivot shaft of the scissors link mechanism C, and is turned on / off when the workbench B moves up and down. is there.

Next, the structure of the overload warning device will be described with reference to FIGS. The overload warning device basically compares the detected pressure value (cylinder pressure) P of the pressure sensor PS for detecting the hydraulic pressure of the hydraulic cylinders 7a and 7b with the overload set pressure, and determines that the detected pressure value is If the pressure is equal to or higher than the set pressure value, an overload warning is issued. What is problematic here is when to perform the pressure comparison while the workbench is being lifted. As described in the prior art, the pressure value of the hydraulic cylinder is not constant during the ascent of the workbench. Therefore, first, as shown in FIG. 4, the overload setting pressure Pk1 is set, and the workbench storage detection switch LS1 is turned on.
Is detected, that is, when the cylinder pressure P reaches the initial maximum pressure Pa, the pressure is detected, and the initial maximum pressure Pa is set for a set time T (T is a very short time, but it is activated by noise in an electric circuit or the like. If the overload set pressure Pk1 is exceeded during this period, an alarm is issued. However, even in the state of overloading, if the workbench storage detection switch LS1 breaks down, or if overloading occurs due to loading of luggage during ascent and descent, no alarm is issued, and the cylinder pressure P is then reduced. Exceeding the overload set pressure Pk1 will occur after the workbench B is raised considerably. Therefore, when the workbench 1/2 rise detection switch LS2 is turned on until the workbench B is raised to a high position, that is, the workbench B has reached a height of about 1/2 of the total head. At the moment, the cylinder pressure P is detected and compared with the overload set pressure Pk2 set separately (to a slightly lower value) from the overload set pressure Pk1. In this position, since the cylinder pressure increases each time the workbench is raised thereafter, the detection is instantaneous, instead of taking a fixed time as in the detection at the initial maximum pressure Pa, and an alarm is issued immediately and the ascent is stopped. Is to be done.

The overload alarm is performed by the overload alarm lamp 1 among the alarm lamps 10 installed in the upper operation box D1.
0a is turned on, and the buzzer BZ sounds. Further, when the alarm is issued, the electromagnetic valve SV is actuated and the driving of the hydraulic cylinders 7a and 7b is stopped, so that the scissors link mechanism C and the worktable B cannot be raised. Normally, when the lowering switch 15 is turned on by the raising / lowering lever 9 or the raising / lowering switch 11, the cylinder pressure is lowered, and the load is further lowered, the cylinder pressure is reduced below the set pressure. It becomes.

However, in the vicinity of the initial maximum pressure Pa, if the excess load set pressure Pk1 is exceeded for more than the set time T at which the alarm is issued, an alarm is issued and the rise of the scissor link mechanism C is stopped. , The scissors link mechanism C slightly rises before the stop,
There was a problem that the pressure suddenly dropped in a wave-like manner, immediately fell below the overload set pressure Pk1, was released even though it was necessary to issue an alarm, and the workbench B could be raised. . Therefore, in the present invention, once the alarm is issued, the detected pressure value P becomes equal to the overload set pressure value Pk1.
(Or Pk2), and the down switch 15 is
If N is not set, the alarm is not released and the scissors link mechanism C (workbench B) cannot be raised. That is, in the case of the above-described problem, even if the detected pressure value P falls below the overload set pressure value Pk1, the alarm is not released because the descending switch 15 is not turned on. On the other hand, even when the descending switch 15 is turned on, the alarm will not be released unless the detected pressure P falls below the overload set pressure PK1 (Pk2). In this way, it is possible to prevent the danger that the alarm will be canceled even if the alarm is necessary.

[0019]

As described above, the present invention has the following advantages. First, the overload set pressure is increased when the workbench starts to rise and when the workbench is about half of the total lift.
Is set in two stages, when it reaches the height of
In the case of an overloaded state, even if the alarm is not issued at the start of the ascent of the workbench, an alarm is issued at the height of the workbench and the workbench is raised to a high position before being raised. As the climb stops, safety is assured. Second , the detection at both points is based on the ON of the workbench storage detection switch LS1 and the workbench 1/2 rise detection switch LS2. An alarm is issued by the operation of one of the switches, so that safety can be ensured. Third,
Once the alarm is issued, the alarm will not be released and the platform cannot be raised unless the lowering switch is turned on and the cylinder pressure becomes less than the overload set pressure. Even at the point where the pressure is reduced in a wavy manner, the safety is maintained without unduly releasing the alarm. As described above, the present invention
An object of the present invention is to provide an overload alarm device that operates safely and properly.

[Brief description of the drawings]

FIG. 1 is an overall side view of an aerial work vehicle using the present invention.

FIG. 2 is a perspective view when the work table B is raised.

FIG. 3 is a circuit diagram of the overload alarm device.

FIG. 4 is a graph showing a transition of cylinder pressure as the workbench rises and a cylinder pressure detection position in an overload alarm according to the present invention.

FIG. 5 is a perspective view showing an operation surface of the operation panel unit D1.

FIG. 6 is a front view of an operation panel unit D2.

FIG. 7 is a plan view of a lifting lever 9;

FIG. 8 is a perspective view of a lifting switch 11;

9 is a plan view of the traveling operation lever 8. FIG.

10 is a crawler traveling device 1 using a traveling operation lever 8. FIG.
It is a figure which shows the steering operation.

FIG. 11 is a graph showing a cylinder pressure detection method in a conventional overloading device.

[Explanation of symbols]

 Reference Signs List A traveling cart B platform C lifting link D1 upper operation box D2 lower operation box PS pressure sensor LS1 platform storage detection switch LS2 platform 1/2 elevation detection switch P hydraulic cylinder pressure (detected pressure value) Pk1 overload setting pressure Pk2 Overload setting pressure 1 Crawler traveling device 2 DC motor 4 Controller 7a Upper hydraulic cylinder 7b Lower hydraulic cylinder 9 Elevating lever 10 Alarm lamp 10a Overload alarm lamp 11 Elevating switch 14 Up switch 15 Down switch

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yukinori Kimura 428 Enami, Okayama City Inside of Seirei Kogyo Co., Ltd. (56) References Hikaru 4-130296 (JP, U) (58) Field surveyed (Int. Cl. ⁷ , DB name) B66F 9/06, 9/24

Claims (1)

(57) [Claims] A scissors link mechanism is interposed between a traveling vehicle and a work table, and the scissor link mechanism can be moved up and down by expansion and contraction of a lifting hydraulic cylinder. The workbench storage detection switch that turns on when the workbench rises slightly, the workbench 1/2 rise detection switch that turns on when the workbench rises to approximately half the height, and the pressure of the lifting hydraulic cylinder A pressure sensor is provided to detect
When turned ON, and work table 1/2 rise detection switch is ON
When the detection value of the pressure sensor exceeds the overload set pressure set for each position, an overload alarm is issued, the workbench cannot be raised, and an overload alarm is issued once.
The lower switch that lowers the workbench.
Side, and the pressure detected by the pressure sensor is overloaded.
Only when the pressure falls below the constant pressure, the alarm is released, and
An overload warning device for aerial work vehicles, wherein the worktable can be raised again .