JPH024513B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a jib hoisting device for a jib hoisting crane equipped with an inverter-controlled electric hoisting winch.

[Conventional technology]

FIG. 2 shows an example of a crane having a hoisting jib. In the figure, 1 is a revolving body, and on the revolving body 1, a hoisting winch 2, a hoisting winch 3, an A-frame 4, a control panel 11, etc. are installed. A jib 5 is mounted on the front part of the revolving structure 1 so as to be able to rise and fall freely around a jib foot 23. The jib 5 is hung between the sheave block 19 at the top of the A frame and the bridle 18 connected to the top of the jib 5 via the pendant rope 8, and the jib 5 is hoisted by the operation of the hoisting winch 3. I'm starting to do that. In addition, the hoisting rope 6 wound up and let out by the hoisting winch 2 is connected to a jib point sheave 20 at the top of the jib 5 and a sheave 2 at the hook 9.
1. It is wrapped around a different jib point sheave 22 at the top of the jib 5, and the terminal end is connected to the jib 5.

In such a crane, the luffing winch 3
When the undulating rope 7 is wound at a constant speed, the horizontal movement speed of the hook 9, that is, the suspended load, is equal to the jib angle θ.
(See Figure 4) becomes larger as it becomes larger.
Near the upright position of the jib 5, the suspended load rapidly moves to the rotating structure 1.
It is dangerous to get close to In particular, in a crane in which the driver's seat is located in front of the revolving structure 1, there is a risk that the suspended load will collide with the driver's seat. As a means to solve such problems, a pole change motor or a parent-child motor is used as the drive device of the hoisting winch 3,
There is also a configuration in which a limit switch is provided that operates when the jib angle reaches a certain angle, and the rotational speed of the hoisting winch 3 is automatically switched to a low speed side when the jib angle exceeds a certain angle, cannot be selected. Furthermore, if the speed of the motor is controlled by inverter control, the operator can manually adjust the speed to solve the problem, but in this case, manual operation is required, which is inconvenient.

[Problem that the invention seeks to solve]

In view of the above points, the present invention solves the problem that it is not possible to both automatically regulate the jib hoisting speed based on the jib angle and to freely select the hoisting speed within the regulated range. There is a particular thing.

[Means for solving problems]

In order to solve the above problems, the jib hoisting device for a jib crane of the present invention is equipped with an electric motor whose speed is controlled by an inverter device as a drive device for the hoisting winch, and outputs a signal when the jib angle exceeds a preset angle. the inverter device is provided with at least one angle detector that
one circuit that directly transmits the speed control signal of the motor from the frequency setting potentiometer when there is no output of the signal emitted from the angle detector; and one circuit that directly transmits the speed control signal of the motor from the frequency setting potentiometer when there is no output of the signal emitted from the angle detector; The present invention is characterized in that the motor includes at least one circuit that transmits a speed control signal of the motor from a frequency setting potentiometer after reducing it at a constant ratio.

[Effect]

With the above configuration, the crane jib hoisting device of the present invention is controlled by the speed control signal from the frequency setting potentiometer when the jib angle is below a preset angle, and when the jib angle is above the set angle. The output of the frequency setting potentiometer is reduced to regulate the speed of the motor, and the heave speed can be freely selected within the regulated range.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a jib hoisting device for a crane according to the present invention will be described below with reference to FIGS. 1 to 5.

In the present invention, the jib crane shown in FIG. 2 is equipped with a limit switch 1 as an angle detection means.
3 is attached to the center of the jib foot 23, and an electric motor 27 serving as a drive device for the jib hoisting winch 3 is controlled by an inverter device 15.

Here, in a general jib crane, the horizontal movement speed V _H of the suspended load when the jib is raised or lowered is:
It is obtained by solving equations (1) to (5).

V _H = dR/dt…(1) dl/dt=V/n…(2) l ² = (H-Y) ² + (R+X) ² …(3) L ² = H ² + R ² …(4) θ=tan ⁻¹ (H/R) (5) Here, each symbol other than the above in the above formulas (1) to (5) means the following, as shown in FIG. 4.

R: Horizontal distance l from the center of the jib foot 23 of the jib 5 to the center of the jib point sheave 20; Distance V between the center of the guide sheave 17 and the center of the jib point sheave 20; Winding and unwinding speed n of the hoisting rope 7; undulation Length L of rope 7; Length X of jib 5; Horizontal distance Y from the center of jib foot 23 to the center of guide sheave 17 at the top of A frame 4; Vertical distance H from the center of the jib point sheave 20 to the center of the jib foot 23 In this embodiment, as a jib angle detector,
As shown in FIG. 3, a striker 14 is fixed to the end of the jib foot 23.
A limit switch 13 is fixed on the rotating body side close to the rotating body, and when the jib 5 rotates to a certain angle, the switching lever 13a of the limit switch 13 comes into contact with the striker 14, and the limit switch 13
is switched, and it is detected that the jib 5 has reached a certain set angle.

1a and 1b show a control circuit of the electric motor 27 for driving the hoisting winch 3 (generally, a squirrel cage induction motor is used as this motor), and FIG. 1a shows an inverter circuit, FIG. 1b shows a circuit for controlling an inverter circuit. The limit switch 13 turns off when a certain set angle is detected, and the LS
This is a relay that is energized when the is turned on.

Reference numeral 24 indicates operation switches SW ₁ and SW ₂ for instructing the electric motor 27 to rotate in the winding direction and the feeding direction of the hoisting rope 27 (that is, in the ascending direction and descending direction of the tip of the jib, respectively).
and a potentiometer 25 for commanding the rotational speed. When the potentiometer 25 is operated with a single handle, one of the switches SW ₁ and SW ₂ is turned on depending on the rotational direction of the electric motor.
RU and RD are relays for raising and lowering the jib, respectively. In addition, what is shown by the code|symbol which added a or b to the code|symbol of each relay is an a contact or a b contact of each relay.

On the other hand, the inverter device 15 of the electric motor 27 once rectifies the three-phase AC input from the input terminals R, S, and T, and outputs variable frequency AC output from the output terminals U,
V and W are outputs to the motor 27, E is a ground terminal, a is a starting signal self-holding relay terminal,
b is a frequency setting signal input terminal, c is a common terminal for the control circuit, d and e are rotation direction command input terminals,
f and g are control power supply terminals, and h is a start signal input terminal. 25 is a frequency setting potentiometer that can set the speed of the electric motor 27.

In this circuit, if the limit switch 13 does not detect that the angle of the jib 5 has reached the predetermined set angle, that is, if the angle θ of the jib 5 is below the predetermined angle, the limit switch 13 13 is in the on state. Therefore, the output from the potentiometer 25 is directly input to the frequency setting signal input terminal b. In this state, operate the handle of the operation switch 24 to open the switch.
When SW ₁ is turned on and turned in the direction of conduction,
Since the coil of the relay RU is energized, each contact RUa of the inverter circuit is closed, and the a terminal, the g terminal, the h terminal, the c terminal, the d terminal, and the f terminal of the inverter 15 are connected.
The terminal and the potentiometer 25 are brought into conduction, and the motor 27 rotates in a fixed direction (hereinafter this direction will be referred to as an upward direction). This rotational speed can be freely selected up to the maximum hoisting speed V ₀ of the electric motor 27 depending on how the handle of the operating switch 24 is turned. Furthermore, when the handle of the operation switch 24 is turned in the opposite direction and the switch SW ₂ is turned on and becomes conductive, the coil of the relay RD is energized, so each contact RDa of the inverter circuit is closed, and the a terminal of the inverter 15 is turned on. , the g terminal and the h terminal, the c terminal and the e terminal, and the f terminal and the potentiometer 25 are in a conductive state, and the motor 27 is switched on.
It rotates in the opposite direction (hereinafter referred to as the downward direction) from when SW ₁ is on. This rotational speed can also be freely selected up to the maximum hoisting (lowering) speed V ₀ of the electric motor 27 depending on how the handle of the operating switch 24 is turned. Note that while the relay RU coil is energized, the b contact RUb connected in series with the relay RD opens.
Operation of relay RD is prohibited, and while the coil of relay RD is energized, the b contact connected in series with relay RU
RDb is opened and relay RU operation is prohibited.

On the other hand, when the jib angle exceeds the predetermined set angle, the limit switch 13 is turned off, the relay LS is no longer energized, and the output from the potentiometer 25 is output from the frequency setting signal input terminal b.
is inputted to via the converter 26. This converter 2
6 reduces the input signal of the frequency setting voltage by a preset constant ratio and outputs the reduced signal. That is, the voltage decreases at a constant rate.

By using this converter 26, as shown in FIG. 5, the horizontal movement speed curve B of the load suspended from the jib tip when the jib hoisting speed is not limited has a short working radius. (i.e., as the jib angle θ increases),
When the jib angle θ exceeds the certain value, the speed is automatically reduced according to the horizontal movement speed curve A,
The speed can be averaged and the speed can be prevented from increasing rapidly. In addition, by operating the potentiometer 25 of the operation switch 24, the operator can freely select the speed within the range where the horizontal movement speed curve A is the maximum speed.

In the above embodiment, the circuit from the potentiometer 25 of the inverter circuit to the frequency setting signal input terminal b is two circuits, one directly connected and the other via the converter. By using two or more limit switches and by changing the mounting angle to the jib and providing the same number of limit switches as the number of converters, the horizontal movement speed of the suspended load can be more averaged for each jib angle.

〔Effect of the invention〕

As described above, in the present invention, at least one angle detector is provided that outputs a signal when a preset angle is reached, and the inverter device has an output of the signal emitted by the angle detector. one circuit that directly transmits the speed control signal of the motor from a potentiometer for setting the frequency when there is no output, and one circuit that transmits the speed control signal of the motor directly from a potentiometer for setting the frequency; By having at least one circuit that transmits the signal from the frequency setting potentiometer, the jib hoisting speed can be regulated and averaged in stages according to the jib angle, and the hoisting speed can be adjusted freely within the regulated range. You can choose.

[Brief explanation of drawings]

The drawings show an embodiment of the jib hoisting device of the jib crane of the present invention, FIG. 1 a and b are control circuit diagrams of the jib hoisting motor, FIG. 2 is a front view showing the entire jib crane, and FIG. 4 is a dimensional diagram of each part of the crane used to explain the principle of the present invention, and FIG. 5 is a conventional view showing the relationship between the jib angle and the horizontal movement speed of the suspended load in one embodiment It is a figure shown in comparison with an example. 3...Luffing winch, 5...Jib, 13...Limit switch, 14...Striker, 15...
Inverter device, 25... Potentiometer, 2
6...Converter.

Claims (1)

[Claims] 1. An electric motor whose speed is controlled by an inverter device is provided as a drive device for the hoisting winch, and at least one angle detector is provided that outputs a signal when the jib angle exceeds a preset angle, and the inverter device includes: one circuit that directly transmits the speed control signal of the motor from the frequency setting potentiometer when there is no output of the signal emitted from the angle detector; and one circuit that directly transmits the speed control signal of the motor from the frequency setting potentiometer when there is no output of the signal emitted from the angle detector; A jib hoisting device for a jib crane, characterized in that the jib hoisting device for a jib crane is equipped with at least one circuit that reduces and transmits a speed control signal of the electric motor from a frequency setting potentiometer at a constant ratio.