JPH0155524B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an abnormality detection device for a two-handed operating switch, which is frequently used as a safety device for presses.

A press equipped with a two-handed operation switch has the advantage of increasing worker safety since it is necessary to simultaneously operate each operation switch by hand when operating the press.

However, if, for example, a short circuit occurs in the contacts of one of the switches, there is a risk that the press will start operating even if only a normal switch is operated. However, in the past, there was no device to detect switch abnormalities such as short circuits, so even presses equipped with two-handed operation switches could not necessarily be said to be safe.

The present invention has been made in view of the above, and includes:
A control circuit for this relay is used to control a relay such as a clutch relay or clutch auxiliary relay in which a first operating switch operated by one hand and a second operating switch operated by the other hand are connected in series. The same number of contacts as the input terminals are connected to both ends of each contact of both switches connected in series to the
Equipped with an AC/DC converter and a timer that outputs an abnormal signal when the output of the AC/DC converter continues for a predetermined period of time, it is possible to reliably detect short-circuit accidents of the operation switch contacts and eliminate short-circuit accidents and malfunctions. The purpose of this is to solve various problems caused by

The present invention will be explained in detail below based on an illustrated embodiment.

The control circuit voltage lines RC and TC, to which 100V AC voltage stepped down via a transformer is applied from the power supply line that supplies power to the main motor of the press (not shown), are connected to the first operation operated by the left hand. Normally open contact PB1a of switch PB1, normally open contact PB2a of second operating switch PB2 operated with the right hand,
Normally closed contact ry of clutch auxiliary relay RY3 described later
3', Normally closed contact of abnormality detection relay RY4, which will be described later.
Clutch relay RY is connected via a series circuit of ry4' and normally open contact ry5 of a restart prevention relay (not shown).
1. Connect RY2 and switch the first operation switch.
Normally closed contact PB1b of PB1 and second operation switch PB
The clutch auxiliary relay RY3 is connected through a series circuit with normally closed contact PB2b of No. 2, thereby forming a two-handed control circuit.

Also, four AC/DC converters a1, a2, a, the same number as the number of contacts of both switches PB1, PB2,
3, a4 is provided, and the first AC/DC converter a1
input terminal and the normally open contact of the first operation switch PB1
Connect both ends 1 and 2 of PB1a with a signal line, and do the following:
Similarly, the normally open contact PB of the second operation switch PB2
Connect both ends 2 and 3 of 2a to the second AC/DC converter a
Connect both ends 4 and 5 of the normally closed contact PB1b of the first operation switch PB1 to the input terminal of the second operation switch PB1 to the input terminal of the third AC/DC converter a3.
Both ends 5 and 6 of normally closed contact PB2b of No. 2 are connected to the fourth AC/
Each is connected to the input terminal of DC converter a4 via a signal line.

And each of the above AC/DC converters a1 to a4
After connecting the output terminals of the constant voltage circuits b1 to b4 to the input terminals of the constant voltage circuits b1 to b4, respectively,
The output of b4 is supplied to timers c1 to c4, respectively, and signals are supplied to timers c1 to c4 from AC/DC converters a1 to a4 via constant voltage circuits b1 to b4 for a period longer than the time set by timers c1 to c4. Then, the output circuit e is output via the OR gate d.
The abnormality detection relay RY4 is energized. Also, the normally open contact of abnormality detection relay RY4
4, an abnormality indicator lamp PL is connected between the control circuit voltage lines RC and TC. f is a reset switch for stop relay RY4.

In the above configuration, when one of the two contacts connected in series is closed and the other is open, alternating current is applied to the input terminal of the AC/DC converter, so direct current is applied from the converter. is output. This direct current is supplied to the timer after becoming a constant voltage in the constant voltage circuit, and if this input continues for a predetermined period of time or more, an abnormal signal is supplied from the timer to the output circuit via the OR gate. Then, the abnormality detection relay RY4 of the circuit is activated, turning on the normally open contact ry4 and turning off the normally closed contact ry4', so that the abnormality indicator lamp PL lights up to indicate an abnormality, and at the same time clutch relays RY1 and RY2 are activated. Since the energization is stopped and held, the press etc. are held inoperable.

That is, for example, if the normally open contact PB1a of the first operation switch PB1 has caused a short-circuit accident, a potential difference will occur between both ends 2 and 3 of the normally open contact PB2a of the second operation switch PB2, so that the second AC/ An alternating current is supplied to the DC converter a2, and a direct current is supplied to the second constant voltage circuit b2. The DC signal thus supplied becomes a constant voltage DC signal and is supplied to the timer c2, and when the timer c2 is charged with a predetermined charge, that is, it continues for the time set in the timer or more. When DC is output from the AC/DC converter, an abnormal signal is output from timer c2. Also, when the normally open contact PB2a of the second operation switch PB2 is short-circuited, the first AC/
AC is supplied to DC converter a1. Similarly,
If the normally closed contact PB1b of the first operation switch PB1 remains short-circuited when operation switches PB1 and PB2 are operated, alternating current is supplied to the fourth AC/DC converter a4, and the normally closed contact PB of the second operation switch PB2 is
When 2b is short-circuited, alternating current is supplied to the third AC/DC converter a3.

Therefore, even when any contact is short-circuited, an abnormality signal is supplied to the output circuit e via the OR gate d, and the abnormality indicator lamp PL lights up to indicate that the operation switch is abnormal. display,
At the same time, clutch relays RY1 and RY2 are held in a state where electricity cannot be applied, so the press is not operated.

In addition, during normal operation, the left and right operation switches are
Since PB1 and PB2 are operated at least within the time set by the timer, there is no malfunction due to a lag in the timing of operation. For example, if only one operation switch is operated, an error signal will be output in the same way as in the case of a short circuit, so you can tell from the lighting status of the error indicator lamp PL that it has been an erroneous operation, and the error detection relay RY4 will be reset. It can be reset only by switch f.

On the other hand, under normal conditions, there is no potential difference between both ends of the contact, so there is no possibility that an abnormal signal will be output.
In addition, if the contacts connected in series are short-circuited at the same time, the above-mentioned abnormality detection will not be performed, but in this case, the operation will start at the same time as the power switch (not shown) is turned on, so there will be no abnormality. You can know.

In the embodiment, the normally closed contact ry3' of the clutch auxiliary relay RY3 is interposed between the series circuit of the normally open contacts PB1a and PB2a and the clutch relays RY1 and RY2, and the normally closed contact ry3' of the clutch auxiliary relay RY3
is connected to the series circuit of normally closed contacts PB1b and PB2b, but in short, the 2 contacts are operated with one hand at a time.
The configuration of the operating circuit is arbitrary as long as the contacts of the operating switches are connected in series. In addition, although the example uses the same number of timers as the number of AC/DC converters, there is a gap between the converters and the timers.
It is also possible to use one timer by interposing an OR gate, and when the timer is made independent as in the embodiment, the short circuit location can be indicated by the abnormal signal. It is needless to mention in detail that the timer setting time may be variable, and
Of course, the abnormality signal can be used for purposes other than the abnormality display and operation stop trigger signal shown in the embodiment.

As explained above, according to the present invention, short circuits in the contacts of the operation switch can be detected by simply adding simple devices such as an AC/DC converter and a timer while using the conventional operation switch as is. The reliability of the two-handed operation switch can be improved, and the safety of presses and the like equipped with the switch can be improved.

[Brief explanation of drawings]

The figure is an electrical circuit diagram of one embodiment of the present invention. PB1...First operation switch, PB2...Second operation switch, PB1a, PB1b, PB2a, PB2
b...Contact, a1, a2, a3, a4...AC/
DC converter, c1, c2, c3, c4...timer, d...OR gate, e...output circuit, RY
1, RY2...Clutch relay, RY3...Clutch auxiliary relay, RY4...Abnormality detection relay, PL
...Error indicator lamp.

Claims (1)

[Claims] 1. In a two-handed operation switch in which a first operation switch operated with one hand and a second operation switch operated with the other hand are connected in series, both switches are connected in series to a control circuit of a relay. The same number of contacts as the input terminals are connected to both ends of each contact.
An abnormality detection device for a two-handed operation switch comprising an AC/DC converter and a timer that outputs an abnormal signal when the output of the AC/DC converter continues for a predetermined period of time or more.