JPH0224757B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field of the Invention] The present invention relates to an over-hoisting prevention device suitable for preventing over-hoisting and over-lowering of hoisting machines such as electric chain blocks and electric hoists.

[Prior art]

BACKGROUND ART Hoisting machines such as electric chain blocks and electric hoists are equipped with over-winding prevention devices that prevent over-lifting or over-lowering. An example of this will be explained using an electric chain block.

FIG. 1 is a diagram showing an electrical chain block. The electric chain block main body 1 is suspended from a suitable ceiling member by an upper hook 2 fixed to the upper part. By pressing the hoisting instruction pushbutton switch and the lowering instruction pushbutton switch of the operation box 3, the electric motor of the electric chain block main body 1 rotates forward or backward to hoist or lower the chain 4 and move the lower hook 5 up or down. let If the chain 4 is wound too much, the overwinding detector 6 detects the overwinding, and the detector 6 opens the normal rotation circuit of the motor to stop the winding. If the winding is lowered too much, the detector 6 detects the overlowering, and the reversing circuit of the motor is opened to stop winding.

[Problems with conventional technology]

In the electric chain block mentioned above, in the case of over-lifting or over-lowering, the detecting section 6 detects this and stops the motor, but even if the hoisting circuit or lowering circuit is opened, the motor will stop immediately. Instead, the motor continues to rotate due to inertia. Therefore, the support portion 5 of the lower hook 5
A or a stopper (not shown) attached to the rear end of the chain 4 may bite into the lever of the detector 6, causing an accident such as damage to the detector 6. Therefore, a buffer spring 7 is provided above the support portion 5a of the lower hook 5 or above the stopper attached to the rear end of the chain 4 so as to wrap around the chain, and the buffer stroke of the spring 7 causes
This would have prevented the above accident from occurring. However, the dimensions of this spring 7 are large, ranging from 75 mm to 100 mm, depending on the winding and lowering speeds, and therefore the minimum distance H between the upper and lower hooks of the electric chain block cannot be reduced, especially when the ceiling of a building is If the load is low and the minimum distance H between the upper and lower hooks cannot be kept small, the load may not be hoisted sufficiently.
The drawback was that it interfered with cargo handling operations.

Note that the above-mentioned problem also applies to a hoisting machine such as an electric hoist to a greater or lesser extent.

[Purpose of the invention]

The present invention has been made in view of the above points, and provides an over-winding prevention device for a hoisting machine such as an electric chain block and an electric hoist, which can reduce the minimum distance between upper and lower hooks. The purpose is to

[Structure of the invention]

a forward rotation circuit comprising a first switch that rotates the electric motor in the forward direction and a second switch that rotates the electric motor in the reverse direction, and operates the first switch to rotate the electric motor in the forward direction by operating a winding instruction switch; In the hoisting machine, the hoist is equipped with a reverse rotation circuit that operates the second switch and reversely rotates the electric motor by operating a lowering instruction switch, and a hook for suspending a load during over-hoisting and a stopper for over-hoisting. An overwinding detection limit switch is provided, which has a rotary lever that is operated by a rotary lever, and a rotary shaft that rotates in conjunction with the shaft of the rotary lever, and detects overwinding up and down by rotation of the rotary shaft. detects overwinding,
The normally closed contact opens the forward rotation circuit to disable the first switch and stop the forward rotation of the motor, and the normally open contact energizes the reverse rotation circuit to operate the second switch. The motor is rotated in reverse direction, and the normally open contact is opened by the reverse rotation operation of the motor to cut off the current supply to the reverse rotation circuit, thereby stopping the reverse rotation of the motor.

[Embodiments of the invention]

Embodiments of the present invention will be described below based on the drawings.

FIG. 2 is a diagram showing an overwinding/up/down detecting mechanism of an electric chain block, in which FIG. 2A is a front view and FIG. Reference numeral 11 denotes a limit lever, and the limit lever 11 consists of two members fixed to both ends of the limit lever shaft 14, and is attached to the electric chain block main body 12 so as to be able to rotate clockwise and counterclockwise around the limit lever shaft 14. It is pivotally attached to the frame 13.
Guide members 16 and 17 guide the chain 15, and the guide members 16 and 17 are each rotatably mounted between the limit levers 11. The guide member 16 is pushed up by a spring 19 mounted on a stopper 18 fixed to the rear end of the chain 15. The guide member 17 is
In order to be able to guide the chain 15 smoothly when winding it up and lowering it by tilting it,
It is pivotally attached to the limit lever 11 with a slight gap. 22 is a limit switch, and the limit switch 22 is provided with a limit switch shaft 23, and the limit switch is operated by rotating the limit switch shaft 23 clockwise and counterclockwise. One end of the limit switch shaft 23 and the limit lever shaft 14 are connected by a connecting member 24.

In the above structure, when over-winding, lower hook 2
0, over-lowering is caused by the stopper 18, spring 21,
19 to guide member 17 or guide member 16
Push up. Therefore, the limit lever 11 rotates around the limit lever shaft 14, and tilts in the direction B-B' when over-winding, and tilts in the C-C' direction when over-lowering. This rotation of the limit lever shaft 14 causes the limit switch shaft 23 to rotate via the connecting member 24, and the limit switch 22 is activated to detect over-winding or over-lowering.

FIG. 3 is a circuit diagram showing the circuit configuration of the overwinding prevention device. M is a drive motor for the electric chain block, which is a three-phase AC motor. MC1 is a forward rotation electromagnetic switch that rotates the drive motor M in the forward direction and winds up the chain 15; MC1a is its normally open contact;
MC2 is a reversing electromagnetic switch that rotates the drive motor M in the reverse direction and lowers the chain 15, and MC2a is its normally open contact. LS1a and LS1b are contacts of the limit switch 22, which are normally open contacts and normally closed contacts that operate when overwinding occurs. LS2b is also a contact of the limit switch 22, and is a normally closed contact that operates when over-lowering. R is a relay, and R1 is its switching contact. PB-U is a push-button switch that instructs the electric chain block to wind.
PB-D is a push button switch that instructs the electric chain block to lower, and Tr is a transformer.

In the above circuit configuration, push button switch PB
When -U is pressed, current flows through the switching contact R1 of the relay R, the normally closed contact LS1b, and the forward rotation electromagnetic switch MC1, and the forward rotation electromagnetic switch MC1 operates, closing its normally open contact MC1a. When the normally open contact MC1a closes, the drive motor M rotates forward and winds up the chain 15. When overwinding occurs, the normally closed contact LS1b of the limit switch 22 opens, and the normally open contact LS1 opens.
a is closed. As a result, the forward rotation electromagnetic switch MC1
becomes inoperable, the normally open contact MC1a is opened,
The power supplied to the drive motor M in the forward rotation direction is cut off. By closing the normally open contact LS1a, the pushbutton switch PB-U and the normally open contact LS1a
Current flows through the relay R, and the relay R operates, switching its switching contact R1 from a to b. By this switching, relay R is self-maintained through pushbutton switch PB-U and contact R1b, and
Current flows through the push button switch PB-U, switching contact R1, normally open contact LS1a, and normally closed contact LS2b to the reverse electromagnetic switch MC2, which operates and closes the normally open contact MC2a. . When the normally open contact MC2a closes, power is supplied to the drive motor M in the reverse direction, causing the drive motor M to rotate slightly, but as soon as the reverse occurs, the normally open contact LS1a of the limit switch 22 opens, and the reverse electromagnetic switch MC2 is disabled. operation, and the drive motor M
stops.

FIG. 4 is a circuit diagram showing the circuit configuration of the overwinding prevention device when a two-speed variable motor is used as the drive motor M. In this figure, parts given the same reference numerals as those in FIG. 3 indicate the same or equivalent parts. MC3 is an electromagnetic switch for low speed switching, and MC3a
is its normally open contact, MC4 is a high-speed switching electromagnetic switch, MC4a is its normally open contact, and MC4b is its normally closed contact. Push button switch PB for winding instructions
-U is a switch that is pressed in two stages; in the first stage, contacts 1, 1 are closed; in the second stage, contacts 1, 1 and 2, 2 are closed; Releases immediately when pressed. The push button switch PB-D for instructing lowering is also a switch having a structure in which it is pressed in two steps, the same as the push button switch PB-U.

In the above circuit configuration, push button switch PB
When -U is pressed, electromagnetic switching for forward rotation is performed through the normally closed contacts 3 and 3 of the pushbutton switch PB-D, the normally open contacts 1 and 1 of the pushbutton switch PB-U, the switching contact R1 of the relay R, and the normally closed contact LS1b. Current flows through the switch MC1, the forward rotation electromagnetic switch MC1 operates, and its normally open contact MC1a is closed. When the normally open contact MC1a closes, the low speed switching electromagnetic switch MC3 is activated,
As the normally open contact MC3a is closed, power is supplied to the drive motor M in the normal rotation direction, and the drive motor M rotates in the normal direction at a low speed to wind up the chain 15. When overwinding occurs, the normally closed contact of limit switch 22
LS1b is opened, the forward rotation electromagnetic switch MC1 becomes inoperable, and the reverse rotation electromagnetic switch MC2 is activated, and power is supplied to the drive motor M in the reverse direction, causing the drive motor M to rotate slightly, but soon becomes normal. open contact
This circuit is exactly the same as the circuit shown in FIG. 3 in that LS1a is opened and drive motor M is stopped.

When pushbutton switch PB-U is pressed to the 2nd stage,
The normally open contacts 1, 1 and 2, 2 are closed, and through the normally closed contacts 3, 3 of the pushbutton switch PB-D, the normally open contacts 2, 2 of the pushbutton switch PB-U, and the switching contact R1 of the relay R, Electromagnetic switch for high-speed switching
Current flows to MC4, and electromagnetic switch MC for high-speed switching
4, the normally open contact MC4a closes and the normally closed contact MC4b opens, causing the drive motor M
Switch to high speed. Normally open contact MC on drive motor M
Power is supplied in the forward direction through 1a, and the drive motor M rotates at high speed to wind up the chain 15. When over-winding occurs, limit switch 22
The normally closed contact LS1b opens and cuts off the power supplied to the drive motor M, and the normally closed contact LS1a
closes, relay R operates, switches its switching contact R1 from a to b, and then the high-speed switching electromagnetic switch
Open the MC4 operating circuit. As a result, the reversing electromagnetic switch MC2 operates, the high-speed switching electromagnetic switch MC4 becomes inoperable, and these normally open contacts MC
2a and normally closed contact MC4b are closed. normally open contact
By closing MC2a and normally closed contact MC4b, the low speed switching electromagnetic switch MC3 is activated, switching the drive motor M to low speed and supplying electric power in the reverse direction to the drive motor M. As a result, the drive motor M rotates slightly in the reverse direction, but the normally closed contact LS1b of the limit switch 22 immediately closes and the normally closed contact LS1a opens, so that the reverse electromagnetic switch
MC2 becomes inactive.

In addition, in the circuits shown in FIGS. 3 and 4, an example is shown in which over-lifting is detected and braking is applied in the reverse direction by supplying electric power in the reverse direction to the drive motor M. If the normally open contact is used to operate the forward rotation electromagnetic switch MC1, supply power to the drive motor M in the forward rotation direction, and apply braking in the forward rotation direction, the circuit configuration will become slightly more complicated. However, it is naturally possible to prevent excessive lowering. Description of this specific circuit will be omitted.

As explained above, according to the above embodiment, overwinding and overwinding are detected by the overwinding detection mechanism including the limit switch 22, etc., and the normally closed contact LS1b of the limit switch 22 disables the forward rotation electromagnetic switch MC1. In operation, the power in the forward rotation direction supplied to the drive motor M is cut off, and the normally open contact
LS1a operates the reverse electromagnetic switch MC2 to supply power in the reverse direction to the drive motor M, and when the limit switch 22 detects lowering, the normally closed contact LS of the limit switch 22 is activated.
2b, disable the reversing electromagnetic switch MC2,
In addition to cutting off the power in the reverse direction supplied to the drive motor M, the normally open contact is used to close the forward rotation electromagnetic switch MC1.
is activated to supply power in the forward rotation direction to the drive motor M, so that the drive motor M quickly stops due to reverse direction braking. and the amount of lowering can be reduced,
Accordingly, the minimum distance between the upper and lower hooks can be reduced. Also, if the ceiling of the building is particularly low, the spring 21
Since the minimum distance between the upper and lower hooks can be reduced by omitting or making them extremely short, cargo handling operations can be carried out smoothly.

In the above embodiments, an electric chain block was shown as an example, but the technology of the present invention is not limited to electric chain blocks, but can also be used in hoisting machines such as electric hoists.

〔Effect of the invention〕

As explained above, according to the present invention, the following excellent effects can be obtained.

(1) When the limit switch for overwinding detects at least overwinding, the first switch is opened and the second switch is closed, so the motor is braked in the opposite direction and the motor rotation stops in a short time. , the hoisting and hoisting strokes of the hoist can be made larger compared to conventional ones.

(2) Also, as an over-winding detection means, it has a rotary lever that is operated by a load hanging hook and an over-lifting stopper when over-holing, and a rotating shaft that rotates in conjunction with the shaft of the rotary lever. Since an overwinding detection limit switch is provided which detects overwinding up and down by the rotation of the rotating shaft, overwinding up and down can be detected with an extremely small stroke, and the winding machine can take even larger winding and lowering strokes. .

(3) Furthermore, since the control means is configured to open the first switch and close the second switch via the contact of the limit switch for overwinding detection, the structure of the control means is simplified.

[Brief explanation of drawings]

Figure 1 shows the electric chain block, Figure 2
In the figures, a and b are diagrams showing an overwinding detection mechanism according to an embodiment of the present invention, FIG. 3 is a circuit diagram of an overwinding prevention device according to an embodiment of the present invention, and FIG. It is a circuit diagram of a winding prevention device. In the figure, 11... Limit lever, 12... Electric chain block body, 13... Frame, 14... Limit lever shaft, 15... Chain, 16, 17... Guide member, 18... Stopper, 19, 21... Spring, 20...
Lower hook, 22... Limit switch, 23... Limit switch shaft, 24... Connecting member, PB-D...
Push button switch for hoisting instructions, PB-D...Push button switch for lowering instructions, MC1...Solenoid switch for forward rotation, MC2...Solenoid switch for reverse rotation, MC3...Solenoid switch for low speed switching, MC4...Solenoid for high speed switching Switch, R... Relay, LS1a... Normally open contact of limit switch, LS1b... Normally open contact of limit switch, LS2a... Normally open contact of limit switch,
LS2b...Normally closed contact of limit switch.

Claims (1)

[Scope of Claims] 1. A first switch that rotates the electric motor in the forward direction and a second switch that rotates the electric motor in the reverse direction, the first switch is operated to rotate the electric motor in the normal direction by operating a winding instruction switch. A hoist comprising a forward rotation circuit for rotating a load and a reverse rotation circuit for operating the second switch and rotating the electric motor in the reverse direction by operating a lowering instruction switch, the hoist is for lifting a load when over-hoisting. It has a rotating lever that is operated by a hook and an overwinding stopper, and a rotating shaft that rotates in conjunction with the axis of the rotating lever, and is provided with an overwinding detection limit switch that detects overwinding up and down by rotation of the rotating shaft. When the overwinding detection limit switch detects overwinding, it opens the forward rotation circuit through its normally closed contact, disables the first switch, stops the forward rotation of the motor, and energizing the reverse rotation circuit with an open contact, operating the second switch, reversing the motor, and opening the normally open contact with the reversal operation of the motor, cutting off the energization of the reverse rotation circuit; An overwinding prevention device for a winding machine, characterized in that it includes a control means for stopping reverse rotation of the electric motor. 2. The overwinding prevention device for a hoisting machine according to claim 1, wherein the electric motor is an electric motor capable of changing speeds in multiple stages.