JPS591675B2 - Overload prevention device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides an overload prevention device for a loading machine, such as a hoist or an electric hoist, which connects a load to a wire rope wound around a winding drum to perform cargo handling work. It is about improvement.

In general, the starting torque of the electric motor that is the drive source for hoisting machines, etc. is several times the rated torque, so it is possible to incorrectly estimate the load and hoist or lower a load that exceeds the rated load during cargo handling work. In case of wire rope cutting accident,
Otherwise, premature damage to the aircraft could occur.

In order to prevent such a situation from occurring, overload prevention devices have conventionally been installed on hoisting machines, electric hoists, and the like.

First, an electric hoist equipped with an overload prevention device will be explained with reference to FIG.

In the figure, 1 is a support frame, 2 is a hoisting electric motor connected to this support frame 1, 3 is a push button switch that controls this hoisting electric motor 2, and 4 is a speed reduction device for the hoisting electric motor 2 (see FIG. One end of the winding drum 5 is fixed to the winding drum 4 and is wound around the winding drum 5 (not shown), and the other end is connected to the support frame 1.
a wire rope coupled to an equalizer 6 coupled to
A hook block 7 is suspended by the wire rope 5 and moves up and down as the wire rope 5 moves, and a load is suspended on the hook 8.

9 is a limit switch for preventing swirling coupled to the support frame 1; 10 is an overload prevention device installed at an appropriate location between the hook block 7 of the wire rope 5 and the equalizer 6; 11 is the above-mentioned This alarm device consists of a buzzer, a lamp, etc. connected to the hoisting motor 2, and is driven by the overload prevention device 10.

Next, a conventional overload prevention device used in electric hoists and the like will be explained according to FIGS. 2 and 3.

In the figure, 12 is the first casing of the overload prevention device 10, 12a is a semicircular first support part provided above the first casing 12 in the figure, and 12b is the first casing 12. In the figure, a semicircular second support part is provided below, 12c is a hollow bulge provided in the center of the first casing 12, and 13 is screwed to the first casing 12. The second casing 13a shown in FIG. 1 is a semicircular first support part provided above in the drawing of the second casing 13, and faces the first support part 12a.

Reference numeral 13b denotes a semicircular second support section provided below the second casing 13 in the drawing, and faces the second support section 12b.

Reference numeral 13c denotes a third support portion consisting of a protruding portion provided at the center of the inner circumferential surface of the second casing 13, and is opposed to the hollow bulging portion 12c.

Reference numeral 5 denotes a wire rope whose one end is connected to the equalizer 6 and whose other end is wound around the winding drum 4 and suspends the hook block 7 on which the load is suspended. It is tightly attached to the first support parts 12a and 13a of the casing 13, and is slidably attached to the second support parts 12b and 13b.

Reference numeral 14 denotes a movable member fitted into the hollow bulging portion 12c of the first casing 12, and 15 is an elastic body made of a disk spring inserted into the hollow bulging portion 12c, which is applied to the wire rope 5. When the tension is less than the rated tension, the wire rope 5 is pressed against the end surface of the third support portion 13c with a predetermined pressing force via the movable element 14, as shown in the figure.

Reference numeral 16 denotes a control means consisting of a microswitch installed in the hollow bulging portion 12c, which is attached to the wire rope 5.
When the component force of the temple tension exceeds the rating, the movable element 14
opens when it moves against the elasticity of the elastic body 15,
It is designed to cut off the operation circuit of the hoisting motor 2, or to operate with an alarm device such as a buzzer or lamp.

Note that the first casing 12 and the second casing 13 constitute a cylinder 17.

T is the tension applied to the wire rope 5, A is the first support portion 12a, 13aSB is the push contact point of the mover 14 with the wire rope 5, and C is the second support portion 12.
b, 13b, TI are the tensions applied between the above B and C of the wire rope 5, and T2 is the tension applied between the above A and B of the wire rope 5.
The tension applied between θ is the cylindrical body 1 of the wire rope 5.
7, Fl is the force applied to the elastic body 15,
F2. F3 is the tension T applied to the wire rope 5 that is applied to the first support parts 12a, 13a and the second support parts 12b, 13b; 5 and the second support portions 12b and 13b.

Next, the operation of the device configured as described above will be explained.

When a load below the rated load is suspended on the hook 8 of the hook block 7 and the hoisting motor 2 is driven to hoist or lower the load, the tension T applied to the wire rope 5 is below the rated load. , therefore, the component force F of the tension applied to the elastic body 15
1 is also below the rated value, the elastic body 15 is not displaced, and therefore the control means 16 remains closed, the hoisting motor 2 continues to rotate, and the alarm device also does not operate.

When the load ψ exceeds the rating, the tension T applied to the wire rope 5 also exceeds the rating, the component force F1 of the tension T applied to the elastic body 15 also exceeds the rating, and the mover 14 resists the elasticity of the elastic body 15. and is displaced to press the control means 16.

For this reason, the control means 16 is opened to stop the hoisting motor 2 and activate an alarm device to prevent overload on the wire rope 5 and the machine body.

Since the conventional overload prevention device is configured as below, the force applied to the elastic body 15 is F 1 = 2 sin θ・T (
1±2 μ5irlθ), but the wire rope 5 is B
Since it is possible to slide at points B and C, there is a drawback that the detection accuracy of the load due to friction at points B and C is poor.

When the wire rope 5 is bent, the second support portions 12b and 13
The support parts 12 b , 13 b , 13 c, etc. are worn out because they come into sliding contact with the movable member 14 and the third support part 13 c.

Therefore, the bending angle θ of the wire rope 5 within the cylindrical body 17 decreases, resulting in a disadvantage that the load is detected to be small.

Further, the force F1 applied to the elastic body 15 is applied to the second support portion 12b.
, 13b, which is twice as large as the force F3, which requires an elastic body 15 with large elasticity, which has the drawback of increasing the size of the device and increasing the cost.

Moreover, compared to the second support parts 12b and 13b, the third
Since the stroke at the support portion 13c is 1/2, there is a drawback that the load detection accuracy is 1/2.

This invention was made in an attempt to eliminate the drawbacks of the conventional overload prevention device, and includes a central support part that is eccentric, a mover that presses a wire rope against one support part, and a mover that presses the wire rope against one support part. By providing an elastic body that biases and a control means that detects the displacement of the mover and performs a control operation,
The purpose is to provide an overload prevention device that can improve detection accuracy.

An embodiment of the present invention will be described with reference to FIGS. 4 and 5.

In the figure, 12 is the first casing of the overload prevention device 10, 12a is a semicircular first support part provided above the first casing 12 in the figure, and 12b is the first casing 12. A semicircular second support portion 12c provided approximately in the center of the first casing 1
2, 13 is a second casing which is screwed to the first casing 12, and 13a is a half provided above in the figure of the second casing 13. A circular first support part,
The support portion 12a is opposed to the supporting portion 12a.

Reference numeral 13b denotes a semicircular second support part provided approximately at the center of the second casing 13,
It faces 2b.

Reference numeral 13c denotes a third support portion consisting of a protruding portion provided downward in the drawing of the second casing 13, and is substantially opposed to the hollow bulging portion 12c.

5 has one end connected to the equalizer 6 and the other end connected to the winding drum 4.
A wire rope for suspending the hook block, on which the load is suspended, is wound around the first support portions 12a, 1.
3a and the second support portions 12b and 13b, respectively.

14 is a movable element fitted into the hollow bulging part 12c of the first casing 12, and 15 is an elastic body made of a disc spring inserted into the hollow bulging part 12c, which acts on the tension applied to the wire rope 5. If it is below the rated value, the wire rope 5 is not displaced, and the wire rope 5 is pressed against the end surface of the third support portion 13c with a predetermined pressing force via the movable element 14, as shown in the figure.

Note that the wire rope 5 is able to come into sliding contact with the end surface of the third support portion 13c.

Reference numeral 16 denotes a control means consisting of a microswitch installed in the hollow bulging portion 12c, which causes the movable element 14 to respond to the elasticity of the elastic body 15 when the component of the tension applied to the wire rope 5 exceeds the rated value. The movable element 14 moves against the
When pressed, the opening is opened, and the operating circuit of the hoisting motor 2 is cut off, or an alarm device such as a buzzer or a lamp is operated.

Note that the first casing 12 and the second casing 1
3 constitutes a cylindrical body 17.

Other symbols are the same as those in the conventional device, so their explanation will be omitted.

Next, the operation of the device configured as described above will be explained.

Force applied to elastic body 15 F 1 =T 2Sinθ, T2
=T (1±μsinθ) Tonari, mata, wire rope 5
Since the sliding contact points are only the third support portion 13c and the mover 14, the force F1 applied to the elastic body 15 is 1/1 of that of the conventional device.
2, the elastic body 15 can be made small, and the entire device can be made small and inexpensive.

Furthermore, since there are fewer friction points, load detection accuracy is improved.

Other operations are the same as those of the conventional device, so explanations will be omitted.

Although this embodiment describes an overload prevention device for an electric hoist, it goes without saying that the same effect can be achieved if one end of the wire rope 5 is fixed and tension is applied to the other end. It is.

In addition, although the explanation has been made regarding the structure in which the third support part 13c1, the mover 14, and the elastic body 15 are provided below, for example, if the lower part of the wire rope 5 is fixed in FIG. 4 and the tension is applied from above, Of course, the same effect can be obtained even if the first support parts 12a and 13a are provided at the lower side in the figure, and the third support part 13c1, the mover 14, and the elastic body 15 are provided at the upper side in the figure.

As described above, in this invention, the central support part among the three support parts is positioned eccentrically with respect to the line connecting the other two support parts, and the central support part and the other two support parts are arranged eccentrically. The wire rope is bent and tightly attached to one of the support parts of the points, and the other support part is provided so as to be freely displaceable in a direction orthogonal to the wire rope, and is disposed in the eccentric direction of the central support part. is provided with a mover that presses the wire rope in the opposite direction, an elastic body that urges the mover toward the wire rope, and a control means that detects displacement of the mover in the eccentric direction and performs a control operation. Therefore, not only the accuracy of detecting the load applied to the wire rope is improved, but also the force applied to the elastic body is halved compared to the conventional device, making the device smaller and cheaper.

[Brief explanation of the drawing]

Figure 1 is a side view of an electric hoist equipped with an overload prevention device, Figure 2 is a sectional view of a conventional overload prevention device, and Figure 3 is a balance of the forces applied to the wire rope by the conventional overload prevention device. FIG. 4 is a sectional view showing an embodiment of the present invention, and FIG. 5 is a diagram showing a state of balance of the forces applied to the wire rope according to the embodiment of the present invention. In the figure, 1 is a support frame, 2 is a hoisting motor, 3 is a push button switch, 4 is a winding drum, 5 is a wire rope, 6 is an equalizer, and 7
is a hook block, 8 is a hook, 9 is a swirl prevention limit switch, 10 is an overload prevention device, 11 is a warning device, 1
2 is a first casing, 12a and 13a are first support parts, and 12b. 13b is a second support part, 12c is a hollow bulging part, 13 is a second casing, 13c is a third support part, 14 is a movable element, 15 is an elastic body, 16 is a control means, 17 is a cylindrical body, T is the tension applied to the wire rope, θ is the bending angle of the wire rope, and μ is the coefficient of friction. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Claims] 1. A wire rope whose one end is fixed to support tension, and a casing that is connected to this wire rope and has three supporting parts on its inner circumference, and supports the wire rope with these supporting parts. In this case, the central support part among the three support parts is positioned eccentrically with respect to the line connecting the other two support parts, and two of the central support parts and the other two points are located eccentrically. The wire rope is bent and tightly attached to the supporting part, and the other supporting part is provided so as to be freely displaceable in a direction perpendicular to the wire rope, and in a direction opposite to the eccentric direction of the central supporting part. a mover that presses the wire rope; an elastic body that urges the mover toward the wire rope;
An overload prevention device comprising a control means that detects displacement of the movable element in the eccentric direction and performs a control operation.