JPS6364394B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an overload prevention device for jib work on a crane.

Cranes equipped with booms, such as vehicle-mounted cranes, use an additional attachment called a jib, which allows the crane to lift a load to a higher location. Generally, the safety limits of this type of crane are regulated from the standpoint of overturning when only a boom is used without using a jib, and from the standpoint of the strength of the jib itself when a jib is used. While the boom is designed to have sufficient mechanical strength, the jib needs to be designed to be as long as possible for its intended use, so it has a lightweight structure. This is due to the fact that the attachment to the tip of the boom relies on a pin connection. Especially when the boom angle is small (close to horizontal), the mechanical strength of the jib (strength against buckling and bending) will be low regardless of the boom length, and the safety limit will be regulated by this strength. However, even in the case of jib work, when the boom is extended beyond a certain length, the moment in the overturning direction becomes considerably large, so safety limits are regulated in terms of overturning. In this way, when the boom angle is small, safety is ensured from the standpoint of mechanical strength regardless of the amount of boom extension, and when the boom is extended beyond a certain length, safety is ensured from the standpoint of preventing falls. Conventionally, the following overload prevention device has been used in jib work, which has a unique property of requiring monitoring of First of all, the weight of the suspended load is detected by a load meter, and the detection result is compared with a preset rated load. An increase in directional moment cannot be detected and there is a risk of falling.

Next, for monitoring during boom work, among the boom rated moment values stored for each boom number, use the value for the boom with the lowest number of stages, and compare this with the actual moment measured during jib work. There are some configurations, but this has the drawback that it is impossible to set appropriate limit values, and it lacks safety, or conversely, it is not possible to make the jib fully demonstrate its performance because it anticipates excessive safety. There is.

Furthermore, as mentioned above, in view of the uniqueness of jib work, some devices are configured to store the rated moment for many combinations of boom length and luffing angle, and compare this with the measured moment. In order to obtain sufficient accuracy, a huge amount of memory capacity is required, which is impractical, and if the number of combinations of boom length and luffing angle is reduced in order to reduce the amount of memory, the lifting limit must be set low. The problem is that you don't get it.

The present invention has been made in order to overcome the drawbacks of such conventional devices, and it is an object of the present invention to provide an overload prevention device for jib work that is highly accurate and has a high safety monitoring ability.

The present invention will be described in detail below based on drawings showing embodiments thereof. FIG. 1 is a schematic side view of a vehicle-mounted crane according to the present invention, in which 1 is a boom, 2 is a jib,
3 is a hoisting cylinder for hoisting the boom 1; 4 is a swivel base; in the illustrated crane, the jib 2 is a two-stage telescoping type; Axis and jib 2
The intersection angle with the axis can be changed in two steps. Therefore, in jib work using this crane, there are four types of lifting load ratings depending on the combination of extension, contraction, shallow angle, and deep angle of the jib 2. That is, the rated lifting load W as a function of the boom lifting angle θ is conceptually expressed as shown in FIG. 2, for example, using the above combination as a parameter. That is, elongation,
The combination with a shallow angle has the lowest value, and conversely, the combination with a shallow angle has a high value.

A winch drum 5 is disposed on the swivel base 4, and a rope 6 wound around the winch drum 5 is passed through a pulley 7 at the tip of the jib on the most distal side and then wrapped around a pulley 8a of a hanging tool 8. A hydraulic motor (not shown) rotates the winch drum 5 to wind up or unwind the rope 6, so that the suspended load 9 moored to the hanging tool 8 can be raised or lowered. The pulley 8a functions as a movable pulley, and the number of ropes 6 to hang (the apparent number of ropes stretched between the pulleys 7 and 8a) is selected depending on the hanging load.

In the vicinity of the pivot point of the boom 1 there are a moment detector 10 and a heave angle detector 11, which are known per se.
The former detects the actual moment (moment in the overturning direction) around the pivot support point at the base of the boom, and the latter detects the heave angle θ, and the detected data is processed by a data processing device that will be described later. 20. Further, a boom length detector 13 is provided which detects the boom length L by converting the winding amount or the feeding amount of the cord 12 stretched between the proximal end boom and the distal end boom into the number of revolutions. Yes, this detected data is also processed by the data processing device 20.
It is configured to be input to .

FIG. 3 shows a data processing device 20 into which data M, θ, and L from the moment detector 10, the heave angle detector 11, and the boom length detector 13 are input.
FIG. This data processing device 20 is installed in a crane operator's cab, etc., and includes various arithmetic units, function generators, changeover switches, digital switches, etc., which will be described later.

21 is a function generator 211, 212, 213, 2
A group of 14 function generators, each function generator corresponding to each of the four types of jib work modes,
The rated load W corresponding to various undulation angles θ is stored, and the rated load W according to the input undulation angle θ is stored.
is now output. Reference numeral 22 denotes a function generator group consisting of function generators 221, 222, 223, and 224, each of which generates a jib according to the boom length L, corresponding to each of the four types of jib work modes. Total dead weight moment of 2 and boom 1
Mb is memorized, and the total dead weight moment Mb corresponding to the input boom length L is output. Note that this total dead weight moment Mb corresponds to the length L of the boom from the most contracted state to the most extended state at the heave angle θ=0°.

The switches 23a, 23b, 23c, and 23d are all four-point switches that are linked to operate in conjunction with each other, and are selectively operated according to the working mode of the four types of jibs.

The number of function generators constituting each of the function generator groups 21 and 22 is determined depending on the number of working modes of the jib, and the same applies to the number of switching points such as the switch 23a.

The output of the undulation angle detector 11, that is, data regarding the undulation angle θ, is supplied to a common terminal of the switch 23a and to function generators 24 and 25. From the common terminal of the switch 23a, it is applied to the function generator 211, 212, 213 or 214 via the selected switching terminal a ₁ , a ₂ , a ₃ or a ₄ , and the W corresponding to the input θ is applied to the function generator 211 , 212 , 213 or 214 . Data is output from this function generator and is input to the multipliers 26, 27 via the selected switching terminal b ₁ , b ₂ , b ₃ or b ₄ of the switch 23b.

The function generator 24 outputs cosθ in response to the data input of θ, and this output is sent to the multipliers 28 and 2.
given to 9.

As is clear from the following, the function generator 25 generates a so-called back moment, which is a moment that acts upward around the pivot support point of the boom 1 due to the pulling force of the rope 6 between the winch drum 5 and the pulley 7. It outputs data used in calculations, and in this embodiment, the vertical distance A from the pivot support point of the boom 1 to the portion of the rope 6 between the winch drum 5 and the pulley 7 is stored as a function of the heave angle θ. The undulation angle detector 11 outputs the value of A according to the data of θ output.
Depending on how the rope is routed, it may be a function of the boom length L, or it may be a function of both L and θ.In such cases, the boom length detector 13 or the boom length A function generator may be provided in which the outputs of the angle detector 13 and the undulation angle detector 11 are input, and A is stored as a function of L or L and θ.

Next, the boom length L data output from the boom length detector 13 is applied to the common terminal of the adder 30 and the switch 23c.

In the adder 30, data regarding the length L _j of the jib 2 is preset as an addend by a setting means (not shown), and the output data L of the boom length detector 13 is given as an addend to this, and L+L _j is given as an addend. The value is calculated and output to the multiplier 28. Note that the value of L _j is 2 depending on the extension and contraction of jib 2.
One of the following values is set.

It is applied from the common terminal of the switch 23c to the function generator 221, 222, 223 or 224 via the selected switching terminal c ₁ , c ₂ , c ₃ or c ₄ ,
Total dead weight moment Mb corresponding to the input L
data is output from this function generator, and the output data is input to the multiplier 29 via the selected switching terminal d ₁ , d ₂ , d ₃ or d ₄ of the switch 23d.

31 is a thumbwheel switch for setting the multiplication number N of the rope, and the output, that is, the data regarding N, is input to the divider 32 as well as the output of the function generator 25; A/
N is calculated, outputted, and given to the multiplier 27.

Therefore, each of the multipliers 28, 29, and 27 uses two inputs as a multiplicand and a multiplier, and (L+L _j )×
Cos θ, that is, the working radius R, Mb×cos θ, that is, the total dead weight moment M 0 of the boom and jib when the boom is upright (θ≠ ₀ ), and (A/N)×W, that is, the back moment are calculated and output. Then, R, M ₀ and (A/N)×W are multiplier 26 and adder 33, respectively.
and is input to the subtracter 34. Since W is also input to the multiplier 26 as described above, the multiplier 26 outputs W×R and inputs this to the adder 33. Therefore, the adder 33 calculates WR+M ₀ ,
This is input to the subtractor 34 as the minuend. (A/N)×W is input to this subtracter 34 as a subtractive number, and in the end, the subtracter 34 receives WR+M ₀ −(A/N).
N)・W will be calculated and output. This output is the sum of the downward moment WR that is allowed for lifting the rated load and the total self-weight moment _M0 of the boom and jib that should also be allowed, that is, the data that should be called the allowable moment. Back moment (A/N)・
W is subtracted, and this is the rated moment
It is calculated as Ml.

The back moment is proportional to the value of A. Therefore, when the rope 6 is located away from the pivot support point of the boom 1, that is, when the value of A is large, the back moment becomes large.

Conventional overload prevention devices did not take back moment into account, which caused errors.
Especially when the value of A is large, a large error occurs. However, in the present invention, since this is used for moment calculation, overload monitoring can be performed with extremely high accuracy.

35 is a comparator, and moment detector 10
The two inputs are the actual moment detected by the sensor and the rated moment Ml calculated by the subtracter 34 as described above, and M≧kMl (k is, for example, 0.9,
1) An alarm signal is generated when the condition occurs.

That is, this device is designed to issue an alarm when the actual moment M is sufficiently close to the rated moment Ml or exceeds the rated moment Ml, thereby preventing accidents such as falling and damage.

Accordingly, in the present invention, when calculating the rated moment Ml, the back moment is subtracted. This is because the moment detector 10 detects the load acting on the jib due to the suspended load as a downward moment around the pivot support point of the boom. This is because the value detected as ) appears smaller by (A/N) x W, just as the suspended load becomes lighter. Therefore, as a reference value for comparison, the value obtained by subtracting this back moment is set as the rated moment Ml. As can be understood from this, the data processing device may be configured to add back moment (A/N) x W to the actual moment and compare this added value with the allowable moment WR + M ₀ . Of course.

The device of the present invention configured as described above has settings of L _j , N, etc., and switches 23a to 23a according to the working mode of the jib.
When the switching operation 23d is performed, the above-mentioned calculations are performed, M and Ml are compared, and safety monitoring is automatically carried out. The device of the present invention captures the load acting on the jib due to the suspended load as the actual moment around the boom pivot support point, and compares this with the rated moment, so that the direction of overturning due to swinging of the suspended load can be determined. It is also possible to accurately capture the increase in moment and compare it with the rated moment. Therefore, with conventional equipment that detects the weight of the suspended load using a load cell and compares it with the rated load, the amount of suspended load does not change even if load swing occurs.
In contrast, the device of the present invention significantly increases safety, whereas it has been impossible to detect or predict danger.

In addition, in consideration of the performance characteristics of the jib as described above, the device of the present invention is based on the total dead weight moment of the boom and jib and the rated load memory value of the jib, and the rated moment corresponding to the boom length and boom heave angle that change every moment during work. Since this configuration calculates the moment and compares it with the actual moment, it is possible to perform safety monitoring with higher precision than with a configuration that uses data for boom work. Since the back moment is also used to calculate the rated moment, the monitoring accuracy is extremely high, and the jib performance can be improved to the point where it is determined by its essential mechanical strength.

Furthermore, the device of the present invention does not store the rated moment for all combinations of factors that determine it, but stores the rated load W that depends only on the undulation angle θ, as well as the vertical distance A, etc. Since it is configured to calculate based on these stored values, the capacity of the storage device is also small and it is highly practical.

As described above, the overload prevention device for jib work according to the present invention has a jib attached to the tip of a telescoping boom,
This is an overload prevention device for jib work on cranes that suspends loads with a winch rope that hangs around the jib from a winch mounted on a base that pivots the base end of the boom. Equipped with an angle detector and a boom length detector, it emits a predetermined output according to the result of comparing the allowable moment determined by the boom's heave angle and boom length with the actual moment generated around the boom's pivot point. means for generating a jib rated load signal corresponding to the boom heave angle detected by the heave angle detector, and a winch rope acting around the boom pivot point based on this rated load signal. means for calculating a backing moment; means for generating a total self-weight moment signal of the boom and jib corresponding to the boom length detected by the boom length detector; means for generating a radial direction;
means for calculating an allowable moment during jib work based on the rated load signal, working radius signal, and total self-weight moment signal of the boom and jib;
Substantially, it is characterized by having a means for comparing the value obtained by subtracting the back moment from the allowable moment and the actual moment value during jib work, which improves monitoring accuracy, jib performance, and economical efficiency. In either case, it is possible to realize an excellent overload prevention device.

In the above-described embodiment, the rope hook number N was configured to be manually set, but it may be configured to be automatically set by a method such as using a known rope hook number detector. It goes without saying that the data processing device 20 may be constructed using a small electronic calculator such as a microcomputer.

[Brief explanation of drawings]

The drawings show embodiments of the present invention, in which Fig. 1 is a schematic side view of a vehicle-mounted crane according to the present invention, Fig. 2 is a conceptual diagram of rated load memory values, and Fig. 3 is an illustration of the device of the present invention. It is a block diagram of the main part. 1...Boom, 2...Jib, 5...Winch drum, 6...Rope, 10...Moment detector, 11...Luffing angle detector, 13...Boom length detector, 20...Data processing Device.

Claims (1)

[Claims] 1. A jib is attached to the tip of a telescoping boom, and a load is lifted by a winch rope that hangs around the jib from a winch mounted on a base that pivots the base end of the boom. This is an overload prevention device for jib work on cranes that operate, and is equipped with a boom heave angle detector and a boom length detector, and measures the allowable moment determined by the boom heave angle and boom length, and the actual moment that occurs around the boom pivot point. means for generating a jib rated load signal corresponding to the boom heave angle detected by the heave angle detector; means for calculating the back moment applied by the winch rope around the pivot point of the boom based on the rated load signal; and a combined dead weight moment signal of the boom and jib corresponding to the boom length detected by the boom length detector. means for generating a working radius signal based on the heave angle and boom length of the boom; An overload for jib work, characterized by comprising means for calculating an allowable moment, and means for comparing a value obtained by subtracting a back moment from the allowable moment with an actual moment value during jib work. Prevention device.