JPS6160038B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides an overload prevention device for a hoisting machine that performs cargo handling work by connecting a load to a wire rope wound around a winding drum, such as an electric hoist. This is related to the improvement of

[Conventional technology]

Figure 3 shows a conventional device shown in, for example, Japanese Unexamined Patent Publication No. 54-36375. In this configuration, when the hoisting operation switch UP is pressed, an overload is applied and the overload prevention function is activated. When the limit switch LS is turned on, the self-holding power relay MS is energized, so its A contact MS-a turns on and its B contact MS-b turns off, thereby cutting off the circuit of the hoisting contact R. This prevents winding in an overload condition, and also prevents the overload prevention limit switch LS from repeatedly turning on and off, that is, flapping phenomenon, at the moment an overload is detected during winding. Also, when the hoisting operation switch UP is pressed and the overload prevention limit switch LS is turned on, the A contact MS-a is turned on and a self-holding circuit of the self-holding power relay MS is formed. Therefore, it is possible to prevent the flapping phenomenon from occurring during the hoisting operation.

In other words, when the limit switch LS lifts an overload, the dynamic load reaches the operating point _P1 of the limit switch LS at time _T1 , as shown in Figure 4.
Limit switch LS operates and the winding contact R circuit is cut off. Here, if the hoisting operation switch UP is kept in the on state, the dynamic load will become lower than the operating point of the limit switch LS after the _T2 point, so the hoisting will try to be driven again, but the B contact Since MS-b is off,
Contact R is deenergized and the electric motor (not shown) remains stopped. At this point, when the operator turns off the hoisting and drying switch UP, the power relay
MS is deenergized, A contact MS-a is turned off, and power relay MS is released from self-holding.

By the way, if an overload is applied when the hoisting operation switch UP is operated, the limit switch
LS is turned on, but the dynamic load has a vibration waveform as shown in Figure 4, so the limit switch LS detects the dynamic load P ₁ at times T ₁ and T ₃ as shown in Figure 4, and turns on. , midway through the process, it becomes off at a point where it drops from P ₁ , for example between T ₂ and T ₃ and after T ₄ . In other words, the limit switch LS is activated at the time when the dynamic load P ₁ is detected, for example, between T ₁ and T ₂ and T ₃ .
It is turned on during each T ₄ , but remains off after T ₄ . Therefore, if the operator turns off the hoisting operation switch UP while the limit switch LS is off, it will return to the operable state, so if the operator should turn off the hoisting operation switch UP while the load remains overloaded. When turned on, the winding operation will start and the limit switch LS will operate again.

[Problem that the invention seeks to solve]

In the conventional overload prevention device of a hoisting machine as described above, if an overload is applied when the hoisting operation switch UP is operated, the overload prevention limit switch LS is turned on and the hoisting contact R is turned on. The circuit will be cut off, but since the limit switch is generally operated by a dynamic load, it will be turned off immediately. At this point, the hoisting operation switch UP
If you turn off the control circuit, the control circuit will return to a state where hoisting operation is possible, and if the operator opens and closes the hoisting operation switch UP several times, overload will be detected each time. As a result, the load will rise little by little and the overload will be lifted,
This poses problems such as wire rope breakage, electric motor burnout, and early damage to the aircraft.

This invention was made to eliminate the above-mentioned drawbacks, and an object thereof is to provide a highly reliable overload prevention device for a hoisting machine.

[Means for solving problems]

The overload prevention device for a hoisting machine according to the present invention includes a hoisting operation circuit in which a hoisting operation switch connected between power supply lines and a hoisting electromagnetic contactor are connected in series, and a hoisting operation circuit is connected in parallel with the hoisting operation circuit. A lowering operation circuit in which a lowering operation switch, a lowering electromagnetic contactor, and a normally closed auxiliary contact of the hoisting magnetic contactor are connected in series, and a lowering operation circuit connected in series with the hoisting machine operation switch in the hoisting operation circuit. A normally closed auxiliary contact of the connected lowering electromagnetic contactor is connected in parallel to the above hoisting operation circuit and the above lowering operation circuit, and is connected in parallel to the normally closed contact of the load detection device and this normally closed contact. A first parallel circuit consisting of the normally closed contact of the hoisting magnetic contactor, an auxiliary relay connected in series to this first parallel circuit, the normally open contact of this auxiliary relay and the above hoisting electromagnetic contact. an overload prevention circuit having a second parallel circuit connected in parallel with the normally open contact of the device and connected in series with the auxiliary relay and the first parallel circuit, and connected in series with the hoisting operation switch; It is equipped with the normally open contact of the auxiliary relay mentioned above.

[Effect]

In this invention, when a load greater than the rated load is connected and the hoisting operation switch is closed, the electric motor rotates in the hoisting direction, but the normally closed contact of the dynamic load detection device momentarily opens when the load is cut off. On the other hand, since the normally closed contact connected in parallel with this normally closed contact is already open, the self-holding of the auxiliary relay is released, and the normally open contact of the hoisting operation circuit, which was closed, is opened and the hoisting The electromagnetic contactor deenergizes, the motor stops reliably, and overload is prevented. From now on, hoisting operation is disabled unless the lowering operation switch is closed, ensuring that overloaded hoisting is not possible. It can be prevented.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 and 2.

In the figure, 1 is a support frame, 2 is a hoisting and lowering electric motor screwed to one end of this support frame 1, 3 is a regular electromagnetic brake device connected to this electric motor 2, and 4 is the above-mentioned support frame 1. A speed reduction device is screwed to the other end and is connected to a rotor shaft (not shown) of the electric motor 2 to reduce the rotation of the rotor shaft. 5 is an emergency brake device connected to the speed reduction device 4; 6 is a winding drum connected to the final rotating body (not shown) of the speed reduction device 4; and 7 is fixed at one end to the winding drum 6; A wire rope 8 is wound and connected to an equalizer (not shown) whose other end is connected to the support frame 1, and 8 indicates this wire rope 7.
A load is suspended on the hook 9 by a hook block which is suspended by the wire rope 7 and moves up and down as the wire rope 7 moves. 10 is a controller box screwed to the support frame 1; 11 is a dynamic load detection device installed at an appropriate location between the hook block 8 of the wire rope 7 and the equalizer; is provided with control means such as a micro switch (not shown) which is activated when the tension applied to the wire rope 7 reaches a predetermined value. 12 is a cable connecting the control means and a controller (not shown) in the controller box 10; 13 and 14 are a pair of side plates connected to the support frame 1 with bolts 15 and nuts 16 and 17; Reference numeral 18 denotes a traverse reduction motor screwed to the side plate 13, 19 a pair of drive wheels connected to the reduction motor 18, 20 a pair of shafts connected to the side plate 14, and 21 the pair of shafts. a pair of driven wheels rotatably supported by 20, 22;
2 is a rail made of section steel on which the pair of driving wheels 19 and the pair of driven wheels 21 run; and 23 is a push button switch that controls the controller in the controller box 10.

Next, the control circuit of the overload prevention device will be explained with reference to FIG. In the figure, 24, 25, 26,
27 and 28 are power supply lines connected to a three-phase power supply (not shown), and 2 is a hoisting and lowering electric motor connected to the above-mentioned power supply lines 24, 25, and 26, which is a drive source for hoisting and lowering a load. be. 29 is a brake coil of the service electromagnetic brake device 3 connected to the power supply 25, which is excited when the electric motor 2 is energized and energizes a fixed iron core (not shown) of the electromagnetic brake device 3; The brake on the electric motor 2 is released. 30a is the second stage of the hoisting upper limit switch of the hook block 8, 30b is the first stage of the hoisting upper limit switch of the hook block 8, and 31 and 32 are normally open contact push buttons for turning on the power to the motor 2. The operation switches 33 and 34 for winding up and lowering are operated by the operation switch 3.
A hoisting electromagnetic contactor and a hoisting electromagnetic contactor are excited when 1 and 32 are closed, 35 is an auxiliary relay, and 33a ₁ to 33a ₃ are normal parts of the hoisting electromagnetic contactor 33. 34a ₁ to 34a ₃ are normally open main contacts of the lowering electromagnetic contactor 34, 33b is a normally closed auxiliary contact of the hoisting electromagnetic contactor 33, and 33c is the hoisting electromagnetic contactor 33. The normally closed auxiliary contact 33d is a normally closed contact of the hoisting electromagnetic contactor 33, and is connected in parallel to the normally closed contact 11b of the dynamic load detection device 11.

34d is a normally open auxiliary contact of the lowering electromagnetic contactor 34, 34d is a normally closed auxiliary contact of the lowering magnetic contactor 34, 11b is a normally closed contact of the dynamic load detection device 11, and 34e is a normally closed contact of the lowering magnetic contactor 34. The electromagnetic contactor 34 is a normally open contact and is connected in series to the normally closed contact 11b. 35a is a normally open contact of the auxiliary relay 35;
5c is a normally open contact of the auxiliary relay 35, which is connected in series to the operation switch 31.

Note that the first contact consisting of normally closed contacts 11b and 33d
The parallel circuit 50, the second parallel circuit 60 consisting of the normally open contacts 34e and 35a, and the auxiliary relay 35 constitute an overload prevention circuit 70, and the hoisting operation switch 31 and the normally open contact 35c and the first stage 30b of the hoisting upper limit limit switch, and the normally closed auxiliary contact 34d.
The hoisting operation circuit 80 includes the hoisting electromagnetic contactor 33 and the hoisting magnetic contactor 33.
The lowering operation switch 32, the normally closed auxiliary contact 33c, and the lowering electromagnetic contactor 34 constitute a lowering operation circuit 90, respectively.

Next, the operation of the device configured as described above will be explained. Operation switch 32 for lowering after turning on the power
When closed, the lowering electromagnetic contactor 34 is energized,
Normally open main contacts 34a ₁ to 34a ₃ and normally open auxiliary contacts 34
b, 34e are closed and the normally open auxiliary contact 34d
is opened, the brake coil 29 and the electric motor 2 are energized, the electric motor 2 rotates in the lowering direction, and the auxiliary relay 35 is energized, the normally open contact 35a is closed, and the auxiliary relay 35 is self-holding. When the auxiliary relay 35 self-holds, the normally open contact 35c closes and the hoisting operation becomes possible.

In this state, when a load below the rated load is now suspended on the hook 9 and the hoisting operation switch 31 is closed, the hoisting electromagnetic contactor 33 is energized, and the normally open main contacts 33a 1 to 33a 3 and normally open main contacts 33a ₁ to 33a ₃ are The opening auxiliary contact 33b is closed and the brake coil 29 and electric motor 2 are energized,
The electric motor 2 rotates in the hoisting direction to hoist a load below the rated load suspended on the hook 9 of the hook block 8. Note that when the hoisting electromagnetic contactor 33 is excited, the normally closed contact 33d is opened.

Furthermore, when a load greater than the rated load is connected to the hook 9 and the hoisting operation switch 31 is closed, the electric motor 2 rotates in the hoisting direction, but at the time of ground breaking, the normally closed contact 11b of the dynamic load detection device 11 momentarily closes. to develop. In this case, since the normally closed contact 33d is already open, the self-holding of the auxiliary relay 35 is released and the normally open contact 35c, which had been closed, is opened, and the motor 2 is reliably stopped to prevent overload. Note that the dynamic load detection device 11 does not operate at times other than when the vehicle is off the ground, unless it operates when the vehicle is off the ground.

〔Effect of the invention〕

As described above, the present invention includes a hoisting operation circuit in which a hoisting operation switch and a hoisting electromagnetic contactor connected between power supply lines are connected in series; and a lowering operation circuit in which a lowering electromagnetic contactor and a normally closed auxiliary contact of the hoisting magnetic contactor are connected in series, and a lowering operation circuit connected in series with the hoisting operation switch in the hoisting operation circuit. A normally closed auxiliary contact of the electromagnetic contactor is connected in parallel to the hoisting operation circuit and the hoisting operation circuit, and a normally closed contact for load detection operation and this prevention contact are connected in parallel to the hoisting electromagnetic contactor. A first parallel circuit consisting of a normally closed contact, an auxiliary relay connected in series to this first parallel circuit, and a normally open contact of this auxiliary relay and a normally open contact of the lowering magnetic contactor connected in parallel. an overload prevention circuit having a second parallel circuit connected in series to the auxiliary relay and the first parallel circuit; Since it is equipped with a contact point, once the load detection device detects an overload, the hoisting operation will remain stopped even if the hoisting operation switch is closed, unless the hoisting operation switch is operated. This means that overload hoisting can be prevented.Firstly, when the load detection device detects an overload, the hoisting operation is stopped.Secondly, once the hoisting operation is stopped, the hoisting operation will not continue unless the hoisting operation switch is operated. Since the operation is maintained in a stopped state, there is double protection against overload, and since the lowering operation is always performed as the next operation after overload is detected,
The overload that has been lifted slightly is grounded again to the ground, which reliably prevents wire rope breakage, motor burnout, and early damage to the aircraft, greatly improving safety.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing an electric transverse type electric hoist equipped with an overload prevention device of the present invention, in which A is a front view, B is a side view, and Fig. 2 is a circuit diagram showing an embodiment of the present invention. FIG. 3 is a circuit diagram of the conventional device, and FIG. 4 is its operating waveform diagram. In the figure, 2 is a hoisting and lowering electric motor, 11 is a dynamic load detection device, 11d and 33d are normally closed contacts, 30 is a hoisting operation switch, 32 is a hoisting and lowering operation switch, 3
3 is an electromagnetic contactor for hoisting, 34 is an electromagnetic contactor for hoisting, 33c, 34d are normally closed auxiliary contacts, 35 is an auxiliary relay, 35a, 34e, 35c are normally open contacts, 5
0 is the first parallel circuit, 60 is the second parallel circuit, 7
0 is an overload prevention circuit, 80 is a hoisting operation circuit, 90
is the lowering operation circuit. Note that the same reference numerals in each figure indicate the same or corresponding parts.

Claims (1)

[Claims] 1. A hoisting operation circuit in which a hoisting operation switch and a hoisting electromagnetic contactor are connected in series between power supply lines,
A lowering operation circuit connected in parallel with this hoisting operation circuit and having a lowering operation switch, a lowering electromagnetic contactor, and a normally closed auxiliary contact of the hoisting magnetic contactor connected in series;
In the hoisting operation circuit, a normally closed auxiliary contact of the lowering electromagnetic contactor is connected in series with the hoisting operation switch, and a normally closed auxiliary contact of the lowering electromagnetic contactor is connected in parallel with the hoisting operation circuit and the lowering operation circuit, and is connected in parallel to the hoisting operation circuit and the lowering operation circuit. a first parallel circuit consisting of a normally closed contact and a normally closed contact of the hoisting magnetic contactor connected in parallel to this normally closed contact; an auxiliary relay connected in series to this first parallel circuit; A normally open contact of the auxiliary relay and a normally open contact of the lowering magnetic contactor are connected in parallel, and a second parallel circuit is connected in series to the auxiliary relay and the first parallel circuit. An overload prevention device for a hoisting machine, comprising a load prevention circuit and a normally open contact of the auxiliary relay connected in series with the hoisting operation switch.