JPH06115896A - Overloading alarming device for elevated place working vehicle - Google Patents

Abstract

PURPOSE:To perform accurate sounding of an overloading alarm through correction of a pressure during elevation by a method wherein, in the nature of a scissors link mechanism, when a work platform is started to rise and is raised to a highest position, an elevating cylinder pressure is high and a pressure is low in the vicinity of an intermediate part of a rise position, in a device to alarm overloading when weight loaded on the working platform of an elevated place working vehicle exceeds a set value. CONSTITUTION:An output P1 from a pressure sensor PS1 is caused to produce an output P2 to a scissors link mechanism S through a variable resistor 16 interlocked with a link mechanism 17 and compared with an overloading set value Pk by a controller 14 to sound an alarm. A switch link 20 and a correction link 21 are located between the output shaft 19 of a pressure sensor PS2 and the scissors link mechanism S to form an overloading alarming device to sound an alarm by pressing a microswitch MS by means of the link device output end 20a of the switch link 20.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an overload warning device for an aerial work vehicle in which a workbench is mounted to be movable up and down for work at a high place such as indoor piping of a building.

[0002]

2. Description of the Related Art Conventionally, there has been known an aerial work vehicle having a structure in which a workbench is placed on a traveling carriage via a scissor link mechanism and the scissor link mechanism is moved up and down by expanding and contracting a hydraulic cylinder. . In such an aerial work vehicle, if there is an excessive amount of luggage (including the driver) loaded on the workbench, the hydraulic cylinder and the scissor link mechanism will be overloaded, which will be extremely dangerous. It is equipped with an overload warning device. To detect overload, conventionally, a pressure sensor for detecting the pressure of a hydraulic cylinder for moving up and down the scissor link mechanism is attached, an overload set pressure Pk is set, and the cylinder pressure of the cylinder detected by the pressure sensor is detected. The detected value P is the set pressure Pk.
If it is larger than this, an overload warning is issued and the workbench cannot be raised. FIG. 10 is a diagram showing a transition of the detected pressure value P with respect to the workbench height in the conventional overload alarm device by detecting the hydraulic cylinder pressure.

However, even if the weight of the load on the workbench is constant, the pressure value in the hydraulic cylinder will not be constant due to the link ratio of the scissor link mechanism when moving up and down. That is, as shown in FIG. 10, first, a high pressure (initial maximum pressure) Pa is applied at the moment when the hydraulic cylinder is operated when the workbench is stored, and then, the pressure is reduced for a while, and the work crawls on the workbench. The pressure is gradually increased with increasing. In this case, if the initial maximum pressure Pa is equal to or higher than the overload setting pressure Pk, an alarm will be issued as soon as the workbench is raised. This initial maximum pressure Pa
Is instantaneous at the start of the ascent, and as the cylinder pressure drops as soon as it continues to rise, it is very likely that an alarm will be issued frequently at this point and the platform will not be able to be raised. It causes inconvenience. Therefore, conventionally, an alarm is issued when the cylinder pressure P exceeds the overload set pressure Pk for a certain period of time T or more, and the alarm is prevented from being issued near the initial maximum pressure Pa more than necessary. I am doing it. When the workbench reaches the highest position, the cylinder is relieved to stop rising, so the cylinder pressure will be kept very high and an alarm will be issued.To avoid this, At the highest position, lower the workbench slightly to reduce the cylinder pressure and set the overload pressure Pk.
The holding pressure Pb is as follows.

[0004]

In the conventional overload alarm device, when the overload is not detected near the initial maximum pressure Pa (C position), the workbench is further raised and the cylinder pressure P is increased. The pressure rises and the overload setting pressure Pk is reached, and the overload alarm is issued after T time (D position).
That is, the alarm is issued only when the workbench starts to rise, or when the workbench is considerably high and reaches the vicinity of the highest lift position. However, there are cases where luggage is loaded from a high place onto the workbench when the workbench is raised to the middle, and in this case, despite being overloaded,
Since the cylinder pressure is low, the pressure value may not reach the overload setting pressure Pk. In other words, when the workbench is in the middle of the rising position, the error between the cylinder pressure and the actual load on the scissor link mechanism is large, so even if the work load is overloaded, the overload warning will not be issued and the ascent will continue. Continuing with or loading luggage is very dangerous.

In order to avoid such inconvenience and to make the overload warning device operate even when the workbench is raised near the middle of the entire lifting height, it is necessary to deal with the weight of the load on the workbench. It is desirable to correct the output value for detecting the overload warning to a constant value regardless of the raised position of the workbench. The present invention is configured in consideration of such points.

[0006]

The present invention has the following constitution in order to solve the above problems. That is, a scissor link mechanism S is provided between the traveling carriage X and the workbench Y, and the scissor link mechanism S can be moved up and down by expanding and contracting the lifting hydraulic cylinder 7. A pressure sensor PS1 that senses the pressure of 7 and outputs an electrical output P1 proportional to the pressure is provided in the hydraulic circuit. Further, the variable resistor 16 and the scissor link mechanism S are linked by a link mechanism 17, and the scissor When the link mechanism S is in the low position and the high position, the resistance value R is high, and when the link mechanism S is in the intermediate position, the resistance value R is low, and when the load weight on the workbench is constant, the pressure sensor PS1 Output P1 of the variable resistor 16
Output value P2 output through the scissor link mechanism S
Is configured to be constant irrespective of the ascending position, and an overload alarm device for an aerial work vehicle that issues an overload alarm when the output value P2 is equal to or greater than the overload set value is configured.

Alternatively, in an aerial work vehicle having the same structure, a pressure sensor PS2 for expanding and contracting the output shaft 19 in proportion to the pressure of the hydraulic cylinder 7 is provided, and the output shaft 19 of the pressure sensor and the scissor link mechanism S are connected to each other. A link device including a switch link 20 and a correction link 21 is interposed between
The anti-correction link side of the switch link 20 is used as the link device output end 20a, and when the load weight on the workbench is constant, the link device output end 20a is in a constant position regardless of the raised position of the scissors link mechanism S. Configured to
Furthermore, a micro switch MS is provided which is turned on when the link device output end 20a operates for a constant stroke,
An overload alarm device for an aerial work vehicle that issues an alarm when the microswitch MS is turned on is configured.

[0008]

In an aerial work vehicle equipped with the overloading device A, the electric output P1 proportional to the cylinder pressure generated by the pressure sensor PS1 for detecting the pressure of the lifting hydraulic cylinders 7a and 7b is variable resistance. It is converted to the output P2 through the converter 16. The output P1 is high when the scissor link mechanism S is in the low position L or the high position H, and is low when it is near the intermediate position M. On the other hand, the resistance value R of the variable resistor 16 is large due to the function of the link mechanism 17 at the low position L and the high position H of the scissor link mechanism S, and becomes small when the scissor link mechanism S is near the intermediate position M. . Therefore, the output P2 is almost constant regardless of the raised position of the scissor link mechanism S, and even when the scissor link mechanism S is near the intermediate position, an alarm is issued when overloaded.

Further, in an aerial work vehicle equipped with the overload warning device B, the output shaft 19 of the pressure sensor PS2 expands and contracts in proportion to the pressure of the lifting hydraulic cylinders 7a and 7b. The mechanism S extends when it is in the low position L or the high position H, and contracts when it is in the vicinity of the intermediate position M. However, due to the correction link 21 interposed between the switch link 20 and the scissor link mechanism S, The position of the link device output end 20a of the switch link 20 becomes almost constant regardless of the raised position of the scissor link mechanism S, that is, the position of the link device output end 20a with respect to the microswitch MS does not change. When the scissors link mechanism S is overloaded even near the intermediate position, the link device output end 20a pushes the micro switch MS. And ON and one in which overload alarm is issued.

[0010]

The problems and configurations to be solved by the present invention are as described above, and the embodiments of the present invention shown in the accompanying drawings will be described below. 1 is an overall side view of an aerial work vehicle using the present invention, FIG. 2 is a perspective view when the workbench Y is raised, FIG. 3 is a circuit diagram of an overload alarm device A, and FIG. 4 is overload. FIG. 5 is a graph showing changes in the electrical output value P1 of the pressure sensor PS1 with respect to the workbench height in the alarm device A, and FIG. 5 is a graph showing changes in the resistance value R of the variable resistor with respect to the workbench height in the overload warning device A. 6 is a graph showing the transition of the output value P2 for detecting an overload alarm in the overload alarm device A with respect to the workbench height, and FIG. 7 is a circuit diagram of the overload alarm device B,
8 is a perspective view showing the operation surface of the upper operation panel K1, FIG.
FIG. 6 is a front view showing an operation surface of a lower operation panel K2.

The overall structure of the aerial work vehicle will be described with reference to FIGS. 1 and 2. The traveling carriage X uses the driving force of the DC motor 2 powered by the battery 3 to drive the mission case 4
Is used to drive the crawler traveling device 1 with a shift. A controller box 14 is arranged near the DC motor 2. Steering is performed by connecting and disconnecting the clutches by side clutch actuators 5L and 5R that are attached to the drive mission case 4 and are driven by independent electric motors 5a on the left and right. Further, an electromagnetic parking brake 13 that is automatically braked when the traveling operation lever 8 described later is set to the neutral position and the driving is stopped is provided outside the drive mission case 4.

A workbench Y is connected to a traveling frame 6 of a traveling carriage X via a scissors link mechanism S. The scissor link mechanism S has a structure in which three stages of scissor links are pivotally connected, and is an upper lift cylinder 7a which is a hydraulic cylinder.
The lower lifting cylinder 7b is expanded and contracted to move up and down. An upper operation panel K1 is provided on the workbench Y, 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 K1. Further, the traveling carriage X is provided with a lower operation panel K2.

The operation surface of the operation panel K1 is as shown in FIG. 8, and in addition to the traveling operation lever 8, the lifting cylinder 7 is also used.
An elevating lever 9 for expanding and contracting a and 7b is provided,
Also, various warning lamps 10 such as an overloaded warning lamp 10a
Is provided. It also has a built-in alarm buzzer that sounds at the time of an alarm. The lower operation panel K2 is as shown in FIG. 9, and in addition to the elevating switch 11 having the same function as the elevating lever 9, the key switch 12 and the like are arranged.

The elevating lever 9 can be tilted back and forth, and the elevating switch 11 is constructed so as to push the upper part or the lower part. Then, the tilting or push button of the lifting lever 9 or the lifting switch 11 operates the electromagnetic valve SV in the hydraulic circuit shown in FIG. 3 or 7 to expand and contract the lifting hydraulic cylinders 7a and 7b. In the hydraulic circuit of the cylinder, the hydraulic pump 15 uses the driving force of the DC motor 2.

The overload alarm is issued when the overload alarm lamp 10a on the upper operation panel K1 is turned on and the alarm buzzer sounds, and when the alarm is issued, the work platform is raised. It becomes impossible and avoids an increase in risk.

Next, the structure of the overload warning device A will be described. As shown in FIG. 3, lifting hydraulic cylinders 7a and 7b
A pressure sensor PS1 that detects the cylinder pressure and emits an electrical output proportional to the pressure is provided in the hydraulic circuit. The electrical output P1 from the pressure sensor PS1 is
As the workbench Y (the scissor link mechanism S) rises,
It changes as shown in FIG. That is, it rises when the workbench starts to rise, lowers and crawls near the middle of the raised position, and rises again when the workbench Y approaches the highest raised position.

The electrical output P1 generated by the pressure sensor PS1 passes through the variable resistor 16 to become the output P2, which is input to the controller 14, and the output value P2 is compared with the overload set value Pk to give an overload warning. The decision is made. Here, the variable resistor 16 is connected to the scissor link mechanism S by a link mechanism 17 as shown in FIG. 3, and the scissor link mechanism S is configured by the structure of the link mechanism 17.
Is in the low position (workbench rising start position) L or in the high position (workbench highest position) H, the resistor lever 16a is in the "large" position and the resistance value becomes large, and the scissor link mechanism S Is close to the intermediate position M, the resistor lever 16a is in the "small" position and the resistance value is small.
That is, from the rotation base of the scissor link mechanism S to the arm 25
And linking the link mechanism 17 between the arm 25 and the resistor lever 16a.
Since the resistor lever 16a is rotated most when the line is linear, the resistance value R of the variable resistor changes as shown in FIG. 5 as the scissor link mechanism S rises.

Therefore, the electric output P1 of the pressure sensor PS1 has a high value when the workbench Y is in the low position or the high position (when the scissor link mechanism S is in the low position L or the high position H). However, the variable resistor 1
Since the resistance value R in 6 is large, the output P2 passing through the variable resistor 16 can be suppressed low. On the other hand, the workbench Y
Is near the intermediate position (when the scissor link mechanism S is near the intermediate position M), the output P1 has a low value. At this time, the resistance value R in the variable resistor 16 is Since it is small, the output P through the variable resistor 16
2 cannot be suppressed too small. That is, since the output P1 from the pressure sensor PS1 passes through the high resistance when the value is high and the low resistance when the value is low, the output P2 used for detecting the overload alarm in the controller 14 is generated.
6 shows an almost constant value regardless of the height of the workbench as shown in FIG. 6, and the comparison with the overload set value Pk can be performed accurately regardless of the position of the workbench. Well, traditionally,
When the workbench is near the intermediate position, the cylinder pressure becomes low, which eliminates the problem that the alarm was not issued even when the workbench was overloaded. The alarm can be properly generated.

Next, regarding the structure of the overload warning device B,
This will be described with reference to FIG. The overload alarm device B detects the output value in the controller 14 like the overload alarm device A,
The structure is not such that an alarm is issued by comparison with the overload setting value Pk, but an alarm is issued by turning on the microswitch MS (lighting of the overload alarm lamp 10a and ringing of an alarm buzzer). First, the pressure sensor PS2 is arranged in the middle of the hydraulic circuit of the lifting hydraulic cylinders 7a and 7b. The pressure sensor PS2 is a cylinder type sensor, and has an output shaft 1 provided with a return spring 18.
9 has a structure that expands when the cylinder pressure is high (“high” direction) and contracts when it is low (“low” direction). Then, connect the end of the output shaft 19 to the switch link 20.
Is pivoted to a pivot point 20c in the middle part of the. One end (correction link connecting end 20b) of the switch link 20 is connected to the arm 25 of the scissors link mechanism S by the correction link 21, and the other end serves as a link device output end 20a that is pressed against the microswitch MS. There is.

When the workbench is raised, the pressure sensor PS2 expands the output shaft 19 because the pressure is high as described above at the start of the workbench and in the vicinity of the highest rising position. In the vicinity of the middle, it is contracted. Here, assuming that the correction link 21 is not provided, the switch link 20 outputs the output when the workbench starts to move up and near the highest rising position (the scissor link mechanism S is in the low position L or the high position H). Axis 19
When the workbench is in the intermediate position (the scissors link mechanism S is in the intermediate position M), the output shaft 19 contracts and moves away from the microswitch MS. Therefore, in this state, even if the load is unloaded on the workbench and overloaded at the workbench or the intermediate position, since the link device output end 20a of the switch link 20 is separated from the microswitch MS, the cylinder pressure is not increased. Even if the pressure sensor output shaft 19 rises and extends, the micro switch MS is not pressed,
There is a danger that the overload warning will not be issued, which is dangerous.

Therefore, the scissor link mechanism S is set to the low position L.
And the correction link connecting end 20b of the switch link 20 is pulled by the correction link 21 toward the microswitch MS side when the switch link 20 is in the high position H, and when the scissor link mechanism S is near the intermediate position M, the pressure sensor P
As the output shaft 19 of S2 contracts, the pivot point 20c moves to the side opposite to the micro switch MS, so the correction link connecting end 20b is pushed by the correction link 21 to move. As a result, even when the pressure sensor output shaft 19 contracts, the link device output end 2 of the switch sensor 20.
0a rotates to the microswitch MS side. Therefore,
When the load on the workbench is the same, the link device output end 20a has a substantially constant position regardless of the vertical position of the scissors link mechanism S (height of the workbench Y) due to the function of the correction link 21. It is kept at. As a result, even if the workbench is near the intermediate position, if the load is overloaded, the link device output end 20a of the switch link 20 presses against the micro switch MS, and the overload alarm is issued. It is emitted.

In the overload device B, the overload set pressure value of the lifting hydraulic cylinders 7a and 7b is adjusted by adjusting the mounting position of the microswitch MS.

[0023]

Since the present invention is constructed as described above, it has the following effects. In other words, conventionally, the pressure of the hydraulic cylinder for lifting and lowering was not constant, so it was possible to issue the overload warning only when the workbench started to rise or near the highest rising position. In the overload alarm device A having a structure that issues an alarm in comparison with the set pressure value, by setting the hydraulic cylinder pressure value to a constant value through a variable resistor,
Alternatively, in the overload alarm device B having a structure in which an output end that rotates by hydraulic cylinder pressure is pressed against a microswitch to issue an overload alarm, the distance between the microswitch and the output end should be fixed by a link device. This makes it possible to issue an overload alarm regardless of the raised position of the workbench, and even when the workbench is in the vicinity of the middle position of the ascended range, the workbench can be loaded and unloaded to detect an overload. When this happens, an overload warning will be issued appropriately to avoid a dangerous situation.

[Brief description of drawings]

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

FIG. 2 is a perspective view of the same when the workbench Y is raised.

FIG. 3 is a circuit diagram of an overload warning device A.

4 is a graph showing a transition of an electric output value P1 of a pressure sensor PS1 with respect to a workbench height in the overload alarm device A. FIG.

5 is a graph showing a transition of a resistance value R of the variable resistor with respect to a workbench height in the overload alarm device A. FIG.

6 is a graph showing a transition of an output value P2 for detecting an overload alarm in the overload alarm device A with respect to a workbench height. FIG.

7 is a circuit diagram of an overload warning device B. FIG.

FIG. 8 is a perspective view showing an operation surface of an upper operation panel K1.

FIG. 9 is a front view showing an operation surface of a lower operation panel K2.

FIG. 10 is a detection pressure value P with respect to a workbench height in a conventional overload alarm device based on detection of hydraulic cylinder pressure.
It is a graph which shows the change of.

[Explanation of symbols]

 X Traveling carriage Y Workbench S Lifting link K1 Upper operating box K2 Lower operating box PS1 Pressure sensor PS2 Pressure sensor MS Micro switch 7a Upper hydraulic cylinder 7b Lower hydraulic cylinder 9 Lifting lever 10 Alarm lamp 10a Overload warning lamp 11 Lifting switch 14 Controller 16 Variable Resistor 17 Link Mechanism 19 Output Shaft 20 Switch Link 20a Link Device Output End 21 Correction Link

Claims (2)

[Claims] 1. An aerial work vehicle in which a scissors link mechanism S is interposed between a traveling carriage X and a workbench Y, and the scissors link mechanism S can be raised and lowered by extending and retracting a lifting hydraulic cylinder 7. A pressure sensor PS1 that senses the pressure of the hydraulic cylinder 7 and outputs an electrical output P1 proportional thereto is provided in the hydraulic circuit, and further, the variable resistor 16 and the scissor link mechanism S are linked by the link mechanism 17, When the scissor link mechanism S is in the low position and the high position, the resistance value R
Is high and the resistance value R is low when it is in the intermediate position, and when the load weight on the workbench is constant, the output P1 generated by the pressure sensor PS1 is changed to the variable resistor 1
A high position characterized in that the output value P2 output through 6 is made constant regardless of the raised position of the scissors link mechanism S, and an overload alarm is issued when the output value P2 is equal to or higher than the overload set value. Overload warning device for work vehicles. 2. An aerial work vehicle in which a scissor link mechanism S is interposed between a traveling carriage X and a workbench Y, and the scissor link mechanism S can be raised and lowered by extending and retracting a hydraulic cylinder 7 for raising and lowering. The pressure sensor P detects the pressure of the hydraulic cylinder 7.
A link device is interposed between the output shaft 19 of the pressure sensor and the scissors link mechanism S, and the link device output end 20a is detected regardless of the rising position of the link device and the scissors link mechanism S. Is located at a fixed position when the load weight on the workbench is constant, and a micro switch MS is provided near the link device output end 20a.
An overload warning device for an aerial work vehicle, which issues an alarm when the microswitch MS is turned on.