JPH0423584B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an auto-reverse device for a document shredding machine used for shredding discarded documents, etc. of a company.

[Conventional technology and problems]

Document shredding machines have traditionally been widely used when disposing of confidential documents, important documents, etc. of companies, government offices, etc. Such a document shredding machine is equipped with a cutter for shredding documents, an induction motor for rotating the cutter, and an overload condition on the cutter (when hard documents or large amounts of documents are supplied). The cutter is equipped with an auto-reverse device, etc., which detects the cutter's condition) and reverses the cutter.

Auto-reverse in the conventional device as described above is performed as follows. That is, the line current to the motor is constantly monitored, and when this current value exceeds a predetermined value, it is determined that an overload has been applied to the cutter, and the motor is stopped and rotated in reverse. For this reason, conventional devices require a detection unit to detect an increase in current due to overload and a control unit to switch the rotation direction of the motor, resulting in an increase in the number of parts and cost. It was hot. Another drawback was that the device was large and it was difficult to adjust the detection section.

[Purpose of the invention]

The present invention has been made to overcome the above-mentioned drawbacks of the prior art, and it is an object of the present invention to provide an auto-reverse device for a document shredding machine that has a small number of parts, is low cost, and is easy to adjust.

[Summary of the invention]

To achieve the above object, the present invention shreds documents by driving a cutter in forward rotation with a reversible electric motor, and shreds documents that are being overloaded by driving the cutter in reverse rotation. In an auto-reversing device for a document shredding machine that discharges having a first normally closed and normally open contact and a second normally closed and normally open contact that operate after being turned off, the first normally closed contact and the second normally open contact being connected in series; A connection point is connected to one end side of the series connection body, and a common connection point of the second normally closed contact and the first normally open contact connected in series is connected to the other end side of the series connection body. and a timer relay, wherein when starting the induction motor, the induction motor is started by energizing the path of the first normally closed contact, the series connection body, and the second normally closed contact. When the governor switch is turned on due to an overload after the timer relay operates, electricity is supplied to the path of the first normally open contact, the series connection body, and the second normally open contact. The invention is characterized in that the induction motor is reversely rotated.

[Embodiments of the invention]

Hereinafter, one embodiment of the present invention will be described with reference to FIGS. 1 to 3 of the accompanying drawings. In addition, in the following description of the drawings, the same elements are indicated by the same reference numerals.

FIG. 1 is a circuit diagram of the same embodiment, showing the state before starting. A single-phase induction motor 1 has a main winding M, an auxiliary winding S, and a rotor 2 that is rotated forward or backward by these windings. The main winding M is connected to the AC power supply 3 via the contact R1 of the relay R, and the auxiliary winding S is connected in series with the governor switch G to form a series connection.
are the above contact R1, the alternate contacts T1a (first normally closed contact) and T1b (first normally open contact) of the timer relay T, and the alternate contact T2.
c (second normally closed contact), T2d (second normally open contact)
It is connected to the AC power supply 3 via. Relay R is self-holding contact R2 and starting switch PB.
It is connected to an AC power source 3 via two parallel circuits and a stop switch PB1. The timer relay T connected in parallel with the main winding M operates when a predetermined time has elapsed after the relay R operates and the contact R1 closes (after power is applied to the induction motor 1). Note that this predetermined time is set to be slightly longer than the time until the rotation of the rotor 2 of the induction motor 1 reaches a predetermined number of rotations or more (the rotation becomes stable).

Note that, as shown by the dashed line in FIG. 1, the induction motor 1 in this embodiment includes a rotor 2, a main winding M,
The auxiliary winding S and the governor switch G are integrally assembled, and a commonly manufactured model with general versatility can be used as is.

Generally, in the induction motor 1 that is used for general purpose as described above, the rotation direction of the rotor 2 is determined by the direction of voltage application to the auxiliary winding S, that is, the direction of current flow. Then, when the rotation of the rotor 2 reaches a predetermined rotation speed, the governor switch G is turned off, and the rotation speed further increases. In other words, the governor switch G functions not as a means for detecting the number of revolutions, but rather as a means for determining the direction of rotation at the time of starting.

The present invention focuses on the function of the governor switch G in the versatile induction motor 1 as described above, and the governor switch G, which conventionally functioned as a means for determining the rotation direction at the time of startup, is replaced with a document shredding machine. It is also most suitable for use as an overload detection means.

Next, the operation will be explained. Before the start switch PB2 is closed, the state is as shown in FIG. 1. That is, since the contacts R1 and R2 and the starting switch PB2 are open, no power is supplied to the induction motor 1.

If start switch PB2 is closed in this state,
Power is supplied to relay R via stop switch PB1 and start switch PB2, relay R operates and contacts R1 and R2 are closed. When contact R1 is closed, AC power is supplied to main winding M, and contact T1a, governor switch G and contact T2c are
Since the positive phase voltage is supplied to the auxiliary winding S through the auxiliary winding S, the rotor 2 of the induction motor 1 starts rotating in the positive direction. Furthermore, since the contact R2 is closed at the same time, the relay R is self-held.

On the other hand, when the contact R1 closes, the timer relay T operates after a short time, but this time is longer than the time it takes for the rotation of the induction motor 1 to stabilize (reach a rotation speed of a predetermined value or higher) as described above. . Therefore, before the timer relay T operates (contacts T1a,
(before T2c is opened), the governor switch G is opened and the current to the auxiliary winding S is cut off.

FIG. 2 shows the state of the circuit after the rotation of the induction motor 1 has stabilized and the timer relay T has operated. As shown, since the contacts T1b and T2d are closed, it can be seen that when the governor switch G is closed in this state, a voltage of the opposite phase is applied to the auxiliary winding S. In other words, after the induction motor 1 enters a stable rotation state (after the governor switch G is opened), the timer relay T operates (contact T1
a, T2c are opened, and contacts T1b, T2d are closed), thereby establishing the conditions for the induction motor 1 to rotate in reverse.

If a large amount of documents or hard documents are fed to the cutter in this state, the induction motor 1 will be overloaded and the rotational speed of the rotor 2 will decrease. and,
When the rotation speed drops below a certain predetermined value, the governor switch G closes, and the auxiliary winding S has contacts T1b,
A reverse phase voltage is applied via T2d and governor switch G, and the induction motor 1 rotates in reverse. As a result, the documents being shredded by the cutter are ejected.

FIG. 3 shows the state of the circuit after the overloaded document being shredded has been discharged. In other words, when the paper is ejected, the stop switch PB1 is opened,
Relay R is released and contacts R1 and R2 are opened. As a result, voltage application to induction motor 1 and timer relay T is cut off, and timer relay T
is released and contacts T1a and T2c are closed. In this way, the circuit returns to its pre-start condition.

The amount of documents to be fed is then reduced and the start switch PB2 is closed again, and the above-described operations are repeated. The stop switch PB1 in the above embodiment may be a manual switch, or may be a switch that is automatically activated after a predetermined period of time has elapsed after the motor is reversed.

Note that the above configuration includes contacts T1a, T1b, and T2.
c, T2d are very favorable. That is, contacts T1a, T2c and contact T
1b and T2d is performed after the current supply is stopped by turning off the governor switch G, so that no spark occurs during the switching. Therefore, the lifetime of these contacts can be very long.

〔Effect of the invention〕

As described above, the present invention focuses on the governor switch of an induction motor, which is commonly used, and has a configuration that effectively utilizes this as is, so there is no need to newly provide a component that corresponds to overload detection means. It is small, has a small number of parts, is low cost, and
It is possible to obtain an auto-reverse device for a document shredder that requires no adjustment at all and has high reliability.

Further, since the contacts of the timer relay for reversing the induction motor are configured to be switched after the governor switch is turned off, the life of the contacts is very favorable.

[Brief explanation of drawings]

1 to 3 are circuit diagrams of an embodiment of the present invention. 1...Induction motor, M...Main winding, S...Auxiliary winding,
G...Governor switch, T...Timer relay, T1
a...first normally closed contact, T1b...first normally open contact,
T2c...Second normally closed contact, T2d...Second normally open contact.

Claims (1)

[Claims] 1 Document shredding by driving a cutter in forward rotation using a reversible electric motor, and discharging overloaded documents being shredded by driving the cutter in reverse rotation. In an auto-reversing device for disconnection, an induction motor is used as the reversible motor and has a main winding and a series connection consisting of an auxiliary winding and a governor switch, and the induction motor is operated at least after the governor switch is turned off after the induction motor is started. a first normally closed and normally open contact and a second normally closed and normally open contact, and the first normally closed contact and the second normally closed contact are connected in series.
A common connection point of the normally open contacts of is connected to one end side of the series connection body, and a common connection point of the normally open contacts of
a timer relay in which a common connection point of a normally closed contact and a first normally open contact is connected to the other end side of the series connection body; The induction motor is caused to rotate in the normal direction by energizing the path of the first normally closed contact, the series connection body, and the second normally closed contact, and after the timer relay operates, the governor switch is turned on due to overload. When this occurs, the induction motor is reversed by energizing the path of the first normally open contact, the series connection body, and the second normally open contact. Device.