JPS5940752B2 - Hoist overload prevention device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in an overload prevention device for a hoisting machine, such as an electric hoist, which connects a load to a wire rope wound around a winding drum for cargo handling work.

Generally, the starting torque of the electric motor that is the drive source for a hoisting machine is several times the rated torque, so if you make a mistake in estimating the load and hoist or lower a load that exceeds the rated load during cargo handling work. Accidents such as wire rope breakage, electric motor burnout, and early damage to the aircraft could occur.

In order to prevent such accidents from occurring, overload prevention devices have conventionally been installed on hoisting machines such as electric hoists.

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 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;
7 is a winding drum connected to the final rotating body (not shown) of the reduction gear 4; one end of the winding drum 7 is fixed to the winding drum 6 and wound around the winding drum 6; the other end is connected to the support frame 1; A wire rope 8 connected to an equalizer (not shown) is a hook block that is suspended by the wire rope 7 and moves up and down as the wire rope 7 moves, and a load is suspended on the hook 9.

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 a control means such as a microswitch (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 the controller (not shown) in the controller box 10; 13.14 is a pair of side plates connected to the support frame 1 with bolts 15 and Narrows N6 and 17; Reference numeral 18 denotes a traversal deceleration motor screwed to the side plate 13, 19 a pair of drive wheels connected to the deceleration motor 18, 20 a pair of shafts connected to the side plate 14,
21 is a pair of driven wheels rotatably supported by the pair of shafts 20); 22 is a rail made of engineered steel on which the pair of driving wheels 19 and the pair of driven wheels 21 run; 23;
is a push button switch that controls the controller in the controller box 10.

Next, a control circuit of a conventional overload prevention device will be explained with reference to FIG.

In the figure, 24, 25°, 26, 27, 28 are power supply lines connected to a three-phase power supply (not shown), and 2 is the power supply line 24.
, 25 and 26, which is the drive source for hoisting and lowering the load.

Reference numeral 29 denotes a brake coil of the regular electromagnetic brake device 3 connected to the power supply line 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 limit switch of the hook block 8, 30b is the first stage of the hoisting-upper limit limit switch of the hook block 8, and 31.32 is a switch for turning on the electric motor 2. A winding/lowering operation switch consisting of a push button switch with a normally open contact, 33.34 is this operation switch 31
．． The lowering electromagnetic contactor 35 is energized when 32 is closed, and the lowering electromagnetic contactor 35 is an auxiliary relay, 33a1.
〜33a a is the regular royal contact of the above-mentioned hoisting electromagnetic contactor 33, and 34a1 to 34a3 are the above-mentioned lowering electromagnetic contactor 34.
33b is a normally open auxiliary contact of the lowering magnetic contactor 33, 33c is a normally closed auxiliary contact of the lowering magnetic contactor 33, and 34b is a regular auxiliary contact of the lowering magnetic contactor 34. 34c is a normally open auxiliary contact of the lowering magnetic contactor 34, 34d is a normally closed auxiliary contact of the lowering magnetic contactor 34, 35a is a normally open contact of the auxiliary relay 35, and 35b is the auxiliary relay. 35 is a normally closed contact, and 11a is a normally open contact of the dynamic load detection device 11.

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

When the hoisting operation switch 31 is closed after the power is turned on, the hoisting electromagnetic contactor 33 is energized, and the normally open main contacts 33a1 to 33a are energized.
3a3 and the normally open auxiliary contact 33b are closed, the brake coil 29 and the electric motor 2 are energized, and the electric motor 2 rotates in the hoisting direction to hoist the load below the rated load suspended on the hook 9 of the hook block 8.

Now, when a load greater than the rated load is suspended on the hook 9 and the operation switch 31 is closed, the electric motor 2 rotates in the hoisting direction in the same manner as described above, but when the electric motor 2 is started, the control means 11a is activated instantaneously. and close it.

When the control means 11a closes, 24→27→34c→11
A circuit a→35→28 is formed and the auxiliary relay 35 is excited.

When the auxiliary relay 35 is energized, the normally open contact 35a closes, and the auxiliary relay 35 maintains itself, and at the same time, the normally closed contact 35b closes.
is opened, the motor 2 stops, and the load is hoisted up to a very small height and stops.

In this state, to return the auxiliary relay 35 to the de-energized state, close the operation switch 32 and close the lowering electromagnetic contactor 34.
All you have to do is excite it.

That is, when the lowering electromagnetic contactor 34 is energized, the normally closed auxiliary contacts 34c and 34d are opened, and the auxiliary relay 35 is returned to its non-energized state.

Since the conventional overload prevention device is configured as described above, the cable 12 may be disconnected or the auxiliary relay 35 may be disconnected.
If the dynamic load detection device 11 detects an overload, the auxiliary relay 35 is not energized, so the motor 2 does not stop and continues hoisting the overload, which may cause the above-mentioned accident. There was a major drawback in that it led to

This invention was made to solve these drawbacks, and includes a normally closed contact that detects the hoisting load applied to the motor and opens when the hoisting load reaches a predetermined value, and a second magnetic contactor for hoisting. a detection circuit consisting of a series circuit with a third coil of an auxiliary relay on a first normally open contact that closes when the first coil is energized; A self-holding second normally open contact; and a third normally open contact that is connected in series to the hoisting operation switch and opens the hoisting operation circuit when the third coil is deenergized. The present invention provides a highly reliable overload prevention device for a hoisting machine that can perform fail-safe operation in the event of a circuit break or failure of an auxiliary relay.

An embodiment of the present invention will be described with reference to FIG.

In the figure, 11b is a normally closed contact of the dynamic load detection device 11;
34e is a normally open contact of the lowering electromagnetic contactor 34, and is connected in series to the normally closed contact 11b.

35c is a normally open contact of the auxiliary relay 35, which is connected in series to the hoisting operation switch 31.

Note that the normally closed contact 11b is connected to the normally open contact 34e and the auxiliary relay 3.
5 constitutes a detection circuit, the hoisting operation switch 32, the normally closed auxiliary contact 33c, and the hoisting electromagnetic contactor 34 constitute a hoisting operation circuit, and the hoisting operation switch 31 and the hoisting upper limit switch 30b, the normally closed auxiliary contact 34d, and the hoisting electromagnetic contactor 33 constitute a hoisting operation circuit.

The rest of the configuration is the same as that of the conventional device, so the explanation will be omitted.

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

When the lowering operation switch 32 is closed after the power is turned on, the lowering electromagnetic contactor 34 is energized, and the normally open main contacts 34a1 to 34a are energized.
4a3 and the normally open auxiliary contacts 34b and 34e are closed, and the normally closed auxiliary contact 34d is opened, and the brake coil 29
and the electric motor 2 is energized, the electric motor 2 rotates in the lowering direction, and the auxiliary relay 35 is energized and the normally open contact 35 is energized.
a is closed and the auxiliary relay 35 is self-maintained.

When the auxiliary relay 35 self-holds, the normally open contact 35c closes and the hoisting operation becomes possible.

Now, when a load greater than the rated load is suspended on the hook 9 and the operation switch 31 is closed, the electric motor 2 operates in the same manner as the conventional device.
rotates in the winding direction, but the normally closed contact 11b of the dynamic load detection device 11 opens at the moment the electric motor 2 starts.

Therefore, the self-holding of the auxiliary relay 35 is released and the normally open contact 35c, which was previously closed, is opened, the motor 2 is stopped, and the load is stopped in a state where it is hoisted to an extremely small height.

As described above, this invention detects the hoisting load applied to the electric motor, and when the hoisting load reaches a predetermined value, the normally closed contact closes when the first coil of the electromagnetic contactor for lower winding is energized. a detection circuit consisting of a series circuit of a first normally open contact and a third coil of an auxiliary relay; a second normally open contact that is connected in parallel to the first normally open contact and self-holds the third coil; , and a third normally open contact that is connected in series to the hoisting operation switch and opens the hoisting operation circuit when the third coil is de-energized, so that the connection cable between the control means and the controller is connected to the hoisting operation switch. (When the wire is disconnected or the auxiliary relay fails), it becomes impossible to hoist the load, and it has a fail-safe function and can provide a highly reliable overload prevention device for the hoisting machine, which has great practical effects. It is.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing a transverse electric hoist equipped with an overload prevention device, A is a front view, the mouth is a side view, Fig. 2 is a sequence showing a conventional overload insect control control circuit, and Fig. 3 is a sequence showing a control circuit according to an embodiment of the present invention. In the figure, 2 is an electric motor for hoisting and lowering, 6 is a winding drum, 7 is a wire rope, 8 is a hook block, 10 is a controller box, 11
is a dynamic load detection device, 12 is a cable, 23 is a push button switch, 29 is a brake coil, 31 is a hoisting operation switch, 32 is a hoisting/lowering operation switch, 33 is a hoisting electromagnetic contactor, 34 is for hoisting Magnetic contactor, 35 is auxiliary relay, 11b
34e is a normally open contact of a dynamic load detection device, 34e is a normally open contact of a lowering electromagnetic contactor, and 35a and 35c are normally open contacts of an auxiliary relay. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Claims] 1 A hoisting operation circuit consisting of an electric motor that serves as a drive source for the hoisting machine, a series circuit of a hoisting operation switch and a first coil of a hoisting electromagnetic contactor, and a hoisting operation circuit that drives the electric motor to be hoisted downward; A hoisting operation circuit consisting of a series circuit of an operation switch and a second coil of a hoisting electromagnetic contactor, which drives the motor to hoist, detects a hoisting load applied to the motor, and detects the hoisting load to a predetermined value. A detection circuit consisting of a series circuit of a first normally open contact that closes when the first coil is energized and a third coil of an auxiliary relay; a second normally open contact that is connected in parallel to the normally open contact and capable of self-holding the third coil; and a second normally open contact that is connected in series to the hoisting operation switch and is used for hoisting when the third coil is deenergized. A hoisting machine overload protection device with a third normally open contact for opening the operating circuit.