JPH0647438B2 - lift device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a portable or self-propelled lifting device which is lifted and lowered by a so-called pantograph type or telescopic boom type lifting mechanism.

[0002]

2. Description of the Related Art A so-called aerial work vehicle is used to perform work in a high place. This aerial work vehicle has, as an example, a pantograph type lifting mechanism, that is, a plurality of link mechanisms in which a pair of arms are angularly displaceably connected at the center thereof are vertically arranged on the bed of a truck, and are vertically adjacent to each other. A structure in which a fluid pressure cylinder is mounted is stacked between the link mechanisms, and the elevating table attached to the tip of the elevating mechanism is driven up and down by the expansion and contraction operation of this cylinder.

Conventionally, since the maximum load is detected when the lift is at the lowermost position, the lift is raised or lowered even if the maximum load is exceeded at the upper position of the lift. However, an excessive load is applied to each part of the lifting device, which may damage the lifting device or cause an accident.

Therefore, the present applicant has previously proposed JP-A-62-111896 from the viewpoint of safety measures against the above problems.

In this system, a telescopic type fluid pressure cylinder is used as a drive source for the lifting mechanism, and the fluid pressure at each expansion and contraction stage of a plurality of stages of cylinders is detected by a detection device. Furthermore, when the reference height is set for the lifting height, and when the lift is higher or lower than the reference height, and the fluid pressure exceeds the set value provided for each expansion / contraction stage, the lift is lifted. I'm trying to stop it.

[0006]

The lifting apparatus of the above-mentioned conventional example has a problem that at least two pressure switches are required and the structure becomes complicated. Further, the actual load received by the cylinder changes as the angle between the arm of the lifting mechanism and the horizontal direction changes, even if the weight of the lifting platform is the same. This is due to the moment with respect to the center position of the angular displacement of the arm of the link mechanism forming the lifting mechanism.

In the above-mentioned conventional example, no measure has been taken in this respect. Therefore, for example, when a load is loaded on the lift table at the lifting end position and the load is lowered, even if the load exceeds the load, the cylinder is in the middle of the load. On the other hand, since the fluid pressure is within the set value, it may not be determined that the load has been exceeded, and the load may be excessive, which may cause a problem in safety during use.

[0008]

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned technical problems and to elevate a platform even when the platform is moving up and down, when the load on the platform exceeds the maximum load. Automatically raises or lowers or raises an alarm,
It is an object of the present invention to provide a lifting device having a simple structure and significantly improved safety.

[0009]

SUMMARY OF THE INVENTION The present invention provides a lifting device for lifting an elevator by mounting an elevator on the tip of an arm member supported by a base so as to be angularly displaced, and driving the arm to perform angular displacement. Driving means for angularly driving the arm member, height detecting means for detecting the ascending / descending height of the lifting table, load measuring means for measuring a load at a predetermined portion of the arm member, and the height detecting means for detecting the load. The height of the lifting platform is compared with the load detected by the load detecting means, and the detected height exceeds a predetermined maximum allowable height corresponding to the load within the movable range at the predetermined portion of the arm member. In this case, or when the detected load exceeds the maximum allowable load corresponding to the ascending / descending height of the ascending / descending platform, a first comparing means for outputting a drive stop signal to the driving means is included. Is.

Further, the present invention is the lifting device, wherein the height detecting means is an angle detecting means for detecting an angle formed with the horizontal direction of the arm member.

Further, according to the present invention, the height of the lift detected by the height detecting means is compared with a predetermined reference height, and if the detected height is less than the reference height, the first comparing means is used. Second comparison means for outputting / stopping a drive stop signal to the drive means based on the comparison result according to, and blocking output of the first comparison means when the detected height exceeds a reference height, Third, comparing the load detected by the load detection means with a predetermined maximum dangerous load, and outputting a drive stop signal to the drive means when the detected load exceeds the maximum dangerous load.
An elevating device including a comparison means.

[0012]

[Operation] In the lifting device according to the present invention, an arm member is supported on a base so as to be angularly displaceable, and an elevating base is provided at a tip thereof, and the arm member is angularly displaced and driven by a driving means to elevate the elevating base. At this time, the height detecting means detects the height of the lifting platform, and the load measuring means measures the load at a predetermined portion of the arm member. The height detected by the height detecting means and the load detected by the load detecting means are first.
When the height detected by the comparison means exceeds the predetermined maximum allowable height corresponding to the load within the movable range at the predetermined portion of the arm member, or the detected load is the vertical movement height of the arm member. When the maximum allowable load corresponding to the height is exceeded, a drive stop signal is output to the drive means.

Here, due to a moment related to the center position of the angular displacement of the arm member of the lifting device, the actual load received by the above-mentioned portion of the arm member is the same even when the weight of the lifting table is the same. It changes as the height of the lifting platform of the lifting device changes. On the other hand, in the present invention, the first comparison means outputs the drive stop signal for stopping the operation of the drive means under the predetermined condition as described above. This prevents a situation in which, for example, when a load is loaded on the lift table at the lifting end position and lifted or lowered, the lifting or lowering operation is not performed and the arm member is damaged by continuing the lifting or lowering operation. It is possible to improve the safety.

Further, the lifting device of the present invention comprises a second comparing means and a third comparing means, and the second comparing means compares the height of the lifting platform detected by the height detecting means with a predetermined reference height. If the detected height is less than or equal to the reference height, a drive stop signal is output / stopped to the drive means based on the comparison result by the first comparing means, and the detected height is the reference height. When it exceeds, the output of the first comparing means is blocked.

The third comparing means compares the load detected by the load detecting means with a predetermined maximum dangerous load and outputs a drive stop signal to the driving means when the detected load exceeds the maximum dangerous load. . As a result, the safety of the lifting device is significantly improved.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a front view of an embodiment of the present invention.
This is a self-propelled lifting device in which a lifting mechanism 3 is loaded on a truck.

The truck body 1 is provided with an outrigger 2 for fixing it to the ground or the like.
A so-called scissor type lifting mechanism 3 is disposed on the upper surface of the. An elevating table 5 for mounting workers and luggage is attached to the upper end of the elevating mechanism 3, and a handrail 6 is provided around the upper surface of the elevating table 5.

In this scissor-type lifting mechanism 3, a pair of arms 7 and 8 are rotatably supported so as to form an X shape at the center thereof, and a link mechanism 9 is provided. Are arranged in parallel on the left and right sides (perpendicular to the plane of FIG. 1) at a predetermined interval, and the arms 7, 7;
They are connected to each other via a connecting shaft 10, and such a structure is vertically stacked in four stages, for example. In addition, vertically adjacent arms 7, 7; 8,
The ends of 8 are rotatably connected to each other by the connecting shaft 10. Further, of the lowermost arms 7 and 8, one arm 7 has an end connected to the vehicle body 1 by a pin 11, and the other arm 8 has a roller 12 attached to the end thereof.

One of the uppermost arms 7 and 8
The end of the arm 8 is connected to the lifting table 5 by the pin 13, and the roller 14 is attached to the end of the other arm 7. Furthermore,
Between the arm 8 of the lowermost link mechanism 9 and the arm 8 of the uppermost link mechanism 9, and between the arm 8 of the uppermost link mechanism 9.
Hydraulic cylinders 15 are respectively arranged between the arms 8 and the arms 8 of the link mechanism 9 below the arms 8.

The upper end of the hydraulic cylinder 15 is arranged between a pair of left and right arms 7, 7 arranged in parallel or between the arms 8, 7.
8 is held by a support rod 16 that is suspended between 8 and the lower end of the hydraulic cylinder 15 has another pair of arms 7 and 7 below.
Alternatively, it is held by a support rod 16 suspended between the arms 8 and 8.

A hydraulic device 17 including a hydraulic pump for generating hydraulic pressure is fixed on the vehicle body 1 and is connected to each hydraulic cylinder 15 via a hydraulic control device which will be described later. By expanding and contracting 15, the elevating mechanism 9 is expanded and contracted in a pan-graph manner, and the elevating table 5 is moved up and down.

In the present embodiment, as an example, a pressure detecting element 18 for converting the magnitude of pressure into an electric signal and outputting the electric signal is provided at the lower end of the piston 15a of the hydraulic cylinder 15 on the lower side. It comprises a potentiometer for detecting the opening angle between the upper and lower arms 7, 8 and outputting it as a voltage value within a predetermined range, and a rotary encoder for outputting a pulse signal at every predetermined angle. An angle detecting element 19 which is height detecting means is provided.

FIG. 2 is a system diagram of the hydraulic control device 20. A hydraulic pump 22 is immersed in the oil tank 21, and a hydraulic pressure from the hydraulic pump 22 is changed to a direction switching valve 23 for outputting / stopping the hydraulic pressure, and a supply direction of the hydraulic pressure is either an ascending direction or a descending direction of the lift 5. Lift valve 24 to switch,
It is supplied / stopped to each hydraulic cylinder 15 via the flow rate adjusting valve 25 and the safety valves 26 and 27.

The lift valve 24 includes a check valve 28 between the flow rate adjusting valve 25 and the direction switching valve 23, a solenoid switching valve 29 connected in parallel with the check valve 28, and a variable throttle valve 30. Composed. The direction switching valve 23 is normally set in the state shown in FIG. 2 by a spring, and is switched to the operating position on the right side in FIG. 2 by exciting the solenoid. Similarly, the solenoid switching valve 29 is normally set to the state shown in FIG. 2 by a spring, and is switched to the operating position on the right side of FIG. 2 by exciting the solenoid.

When the lift table 5 is raised, the direction switching valve 23 is excited and the hydraulic pressure from the hydraulic pump 22 is applied to the lift valve 2.
4, is supplied to each hydraulic cylinder 15 via the flow rate adjusting valve 25 and the safety valves 26 and 27. When the excitation of the direction switching valve 23 is stopped, the hydraulic cylinder 15 stops at the position at that time.

When the lift table 5 is lowered, the solenoid switching valve 29 is excited. As a result, each hydraulic cylinder 15
It is opened to the oil tank 21 through the safety valve 26.27, the flow rate adjusting valve 25, the variable throttle valve 30 and the solenoid switching valve 29, and the lifting platform 5 descends. When the excitation of the solenoid switching valve 29 is stopped, each hydraulic cylinder 15 stops at the position at that time.

FIG. 3 is a block diagram of the control circuit 31 for controlling the operation of the hydraulic control device 18. The pressure detection element 1
From 8, the load signal S of a level corresponding to the load, for example,
L is output, and the angle detection element 19 outputs an angle signal SA corresponding to the angle θ formed by the arm 7 and the horizontal direction of the arm 7 corresponding to the opening angle of the arms 7 and 8.

The load signal SL is amplified by the amplifier 32 and input to the inverting input terminal of the comparator 33 which is the third comparing means. From the pressure setting unit 34, which sets a predetermined pressure value corresponding to the maximum load that can be loaded on the lift 5 regardless of the opening angle θ of the arms 7 and 8 to the non-inverting input terminal of the comparator 33. The maximum pressure signal S1 of is input.

The angle signal SA from the angle detecting element 19 is amplified by the amplifier 35 and input to the inverting input terminal of the comparator 36 which is the first comparing means, and the pressure signal SL is input to the non-inverting input terminal of the comparator 36. As will be described later, as an example, the angle signal SA is converted into the pressure signal SL and compared with each other.
Further, the angle signal SA is supplied to another comparator 37 which is the second comparing means.
Input to the inverting input terminal of. The non-inverting input terminal of the comparator 37 is set with a predetermined reference opening angle θ0 corresponding to the reference height of the elevating mechanism 3, such as the elevating intermediate position, regardless of the load on the elevating table 5. The reference angle signal S2 is input from the unit 38.

The outputs from the comparators 35 and 37 are 2-input N
The output of the NAND circuit 39 is input to the AND circuit 39, and the output of the NAND circuit 39 is output from the comparator 34 together with the 2-input NAND circuit 4
Input to 0. The high-level output of the NAND circuit 40, which will be described later, is used as the emergency stop signal SS to generate the excitation circuit 41.
The excitation circuit 41 excites or demagnetizes the solenoid for switching the operating position of the solenoid switching valve 29 as described above. When the solenoid of the solenoid switching valve 29 is demagnetized, each cylinder 15 is stopped urgently.

FIG. 4 is a graph for explaining the operation of the lifting device 42 having the mechanical and electrical structure shown in FIGS. The characteristic operation of this embodiment will be described with reference to these drawings. The pressure signal SL and the angle signal SA from the pressure detection element 18 and the angle detection element 19 in FIG. 3 are converted into the maximum pressure signal S1 and the maximum angle signal S2 from the pressure setting unit 34 and the angle setting unit 38 in the comparators 33 and 37, respectively. Be compared.

When SL ≧ S1 in the comparator 33, an excessive weight is being applied to the lift table 5. The maximum pressure signal S1 corresponds to the lifting mechanism 3 in FIG.
May be selected as the signal corresponding to the load at the maximum load point P1 of the line L1 that represents the maximum load that can be operated at each height within the elevating operation range. At this time, the output of the comparator 33 becomes low level, and the output of the NAND circuit 40 is forced to be high level regardless of the output of the NAND circuit 39. As a result, the excitation circuit 41 demagnetizes the solenoid of the solenoid switching valve 29, and the lifting mechanism 3 is stopped or not activated.

As described above, in the lifting mechanism 3, the lifting table 5
Even if the weights of the luggage and the like are the same, the load detected by the pressure detection element 18 increases as the load decreases. This state is shown by the line L1 in FIG. Therefore,
As an example of the lifting range of the lifting mechanism 3, a reference height such as an intermediate point is set. If the height is equal to or higher than the reference height, the lifting mechanism 3 can be arbitrarily moved up and down within a range in which the weight of the lifting platform 5 does not exceed the maximum load in the pressure setting unit 34. In a range less than the reference height, the angle signal SA and the pressure signal SL are converted and compared as will be described later, and if the relationship between them is an excessive load with respect to the line L1 in FIG. 4, the lifting mechanism 3 is stopped, Or do not start it.

That is, when SA ≧ S2 in the comparator 37, the lift 5 is above the reference height, the output of the comparator 37 becomes low level, and the output of the NAND circuit 39 becomes the output of the comparator 36. It is forced to a high level regardless. At this time, the output of the comparator 39 corresponds to the state where the output of the comparator 33 is high level or low level,
A low level or a high level is generated, whereby the excitation circuit 41 excites or demagnetizes the solenoid of the solenoid switching valve 29, and in response to this, the elevating mechanism 3 continues or stops the elevating operation.

On the other hand, when S2 ≧ SA in the comparator 37, the lift 5 is below the reference height, the output of the comparator 37 becomes high level, and the output of the NAND circuit 39 becomes the output of the comparator 36. Changes in response to. Here, in the comparator 36, the pressure signal SL from the pressure detection element 18
To a corresponding load signal on line L1 of FIG.
The magnitude relationship between the converted load signal ST and pressure signal SL is compared.

When SL ≧ ST in the comparator 36, it means that the load more than the allowable load at the height of the lift 5 at that time is applied, and the output of the comparator 36 becomes high level. The output of the NAND circuit 39 changes according to the output of the comparator 37. If the height of the lift 5 is lower than the reference height, the output of the comparator 37 is high level, and the output of the NAND circuit 39 is low level, N.
The output of the AND circuit 40 becomes high level, and the lifting mechanism 3
Will be forcibly stopped.

Table 1 below shows the outputs S33, S36 of the comparators 33, 36, 37 and the NAND circuits 39, 40, respectively.
State of S37, S39, S40 and solenoid switching valve 2
4 shows the state of excitation or demagnetization of the solenoid of No. 4.

[0039]

[Table 1]

As described above, in the present embodiment, the operation as described above can be achieved by using one pressure detecting element 18 and one angle detecting element 19, respectively. As a result, it is possible to realize a safety measure against excessive loading in the lifting device with a significantly simplified structure as compared with the conventional example.

In this embodiment, the angle detection element 19 detects the opening angle of the arms 7, 8 corresponding to the height of the lift 5 and the pressure detection element 18 determines a predetermined portion of the arms 7, 8. The load at is measured. The angle detected by the angle detecting element 19 and the load detected by the pressure detecting element 18 are compared by the comparator 36, and the detected load corresponds to the opening angle of the arms 7 and 8 at the maximum. If the allowable load is exceeded, the comparator 36 causes the NAND circuit 39,
Via 40, the solenoid of the solenoid switching valve 24 is demagnetized and the lifting operation is stopped.

Due to the momentum regarding the angular displacement center positions of the arms 7 and 8 of the link mechanism 9 which forms the lifting mechanism 3, the actual load received by the cylinder 15 is the same as that of the lifting table 5 and the like. Even if there is, it changes as the angle between the arms 7 and 8 of the lifting mechanism 3 and the horizontal direction, that is, the height of the lifting table 5 changes. However, in the present embodiment, for example, when a load is loaded on the lift table 5 at the lift end position and the load is lowered, an excessive load is prevented from being applied to the cylinder 15 in the middle of the load, and the safety in use is significantly improved. Can be improved.

When the comparator 33 detects that the load detected by the pressure detecting element 18 exceeds the maximum dangerous load regardless of the height of the lifting platform 5, the lifting mechanism is also used in this case. The lifting operation of 3 is stopped.

In this way, the safety of the lifting device is greatly improved.

In the present invention, the means for detecting the height of the lifting platform 5 is not limited to the angle detecting element 19 of the above-mentioned embodiment, and for example, the vertical acceleration of the lifting platform 5 and its time are detected to determine the height. May be used, or a means for optically or electromagnetically detecting the distance between the lift 5 and the vehicle body 1 may be used.

The lifting device of the present invention is not limited to the type of being mounted on a truck as in the above-mentioned embodiment, but may be implemented as a portable type that is manually carried. The lifting mechanism is not limited to a pantograph type which is a combination of so-called rhombuses, that is, a scissors type, but may be an X-type or Z-type pantograph type or a straight extension boom or a bending extension boom.

[0047]

As described above, according to the present invention, the height detecting means detects the height of the lifting platform, and the load measuring means measures the load at a predetermined portion of the arm member. The height detected by the height detecting means and the load detected by the load detecting means are compared by the first comparing means, and the detected height corresponds to the load within the movable range in a predetermined portion of the arm member. If the detected maximum load exceeds the maximum allowable load, or if the detected load exceeds the maximum allowable load corresponding to the ascending / descending height of the arm member, a drive stop signal is output to the drive means.

As a result, for example, when loads are overloaded on the lift table at the end position of ascending and ascend or descend, the ascending or descending operation is stopped even if the arm member is overloaded during ascending or descending. It is possible to prevent a situation in which the arm member is damaged and the arm member is damaged, and the safety is remarkably improved.

Further, the lifting device of the present invention comprises the second comparing means and the third comparing means, and the second comparing means compares the height of the lifting platform detected by the height detecting means with a predetermined reference height. If the detected height is less than or equal to the reference height, a drive stop signal is output / stopped to the drive means based on the comparison result by the first comparing means, and the detected height is the reference height. When it exceeds, the output of the first comparing means is blocked.

Thus, the third comparing means compares the load detected by the load detecting means with a predetermined maximum dangerous load, and when the detected load exceeds the maximum dangerous load, a drive stop signal is sent to the driving means. Is output. As a result, the safety of the lifting device is significantly improved.

[Brief description of drawings]

FIG. 1 is a front view of a lifting device according to an embodiment of the present invention.

FIG. 2 is a system diagram showing a hydraulic system of the lifting device of the present embodiment.

FIG. 3 is a block diagram of a control circuit 31 of this embodiment.

FIG. 4 is a graph illustrating the operation of this embodiment.

[Explanation of symbols]

 3 ... Lifting mechanism 5 ... Lifting platform 7,8 ... Arm 9 ... Link mechanism 15 ... Hydraulic cylinder 17 ... Hydraulic device 18 ... Pressure detecting element 19 ... Angle detecting element 20 ... Hydraulic control Device 23 ... Direction switching valve 24 ... Lift valve 29 ... Solenoid switching valve 31 ... Control circuit 33, 36, 37 ... Comparator 34 ... Pressure setting unit 38 ... Angle setting unit 39, 40 ... NAND Circuit SA …… Angle signal SL …… Load signal SS …… Emergency stop signal

Claims (3)

[Claims] Claims: 1. A lifting device provided with an elevating table at the tip of an arm member supported by a base so as to be angularly displaceable, and driving the arm member in an angular displacement to elevate the elevating table. Means, height detecting means for detecting the height of the lifting platform, load measuring means for measuring the load at a predetermined portion of the arm member, height of the lifting platform detected by the height detecting means, and load When the detected height is compared with the load detected by the detection means, and the detected height exceeds a predetermined maximum allowable height corresponding to the load of the ascending / descending range in the predetermined portion of the arm member, or the detected load is An elevating device comprising: first comparing means for outputting a drive stop signal to the driving means when a maximum allowable load corresponding to the ascending / descending height of the elevating table is exceeded. 2. The elevating device according to claim 1, wherein the height detecting means is an angle detecting means for detecting an angle formed with the horizontal direction of the arm member. 3. The height of the lift detected by the height detecting means is compared with a predetermined reference height, and when the detected height is less than the reference height, the comparison result by the first comparing means. And a load detecting means for outputting / stopping a drive stop signal to the driving means and for blocking output of the first comparing means when the detected height exceeds a reference height. And a third comparing means for outputting a drive stop signal to the drive means when the detected load exceeds the maximum dangerous load. The lifting device according to claim 1.