JPS5832462Y2 - safety retainer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a safety keeper, and more particularly to a safety keeper configured to be detachable with a connector.

A safety keeper is inserted into a signal line between a hazardous area at a site and a control room in a non-hazardous area in order to make the instrumentation of a chemical plant or the like an intrinsically safe explosion-proof system.

The intrinsic safety of the system depends on the reliability of the safety barrier.

For this reason, explosion-proof standards require redundant design in which elements that constitute the circuit of the safety barrier and are directly related to safety maintenance, such as Zener diodes for voltage limitation, are duplicated.

At the same time, circuit redundancy is also checked at the start of operation and during periodic inspections.

For this reason, in recent safety barriers, the electric circuit containing the safety maintenance element is made into a rear unit, and the terminal portions of the externally connected non-bonded side terminals and the safe side terminals are separated as a terminal unit.
The barrier unit and the terminal unit are configured to be detachable using a connector to facilitate maintenance and inspection.

At this time, the fuse is usually integrally molded with an insulating resin or the like inside the barrier unit together with the safety maintaining element, so if the fuse blows out, the entire barrier unit must be replaced, which is not economical.

In order to eliminate such drawbacks, conventionally, as shown in FIG.
is installed on the top surface of the barrier unit) BU, and the barrier unit) B
It is designed so that the fuse unit (FU) can be attached and detached without removing the fuse unit (FU) from the terminal unit (TU), and when a fuse blows out, it is possible to replace only the fuse unit (FU).
There are some that have improved economic efficiency.

By the way, when a fuse blows, it means that some kind of overvoltage has been applied to the safety barrier, and it does not mean that you can use the fuse by just replacing the fuse. The fuse should be replaced.

Therefore, in the case where the fuse unit (FU) is provided on the top surface of the barrier unit (BU) as in the past, the barrier unit (BU) is
There is a risk of replacing the fuse without inspecting the BU.

An object of the present invention is to provide a safety retainer in which only the fuse can be replaced and the barrier unit is not forgotten to be inspected when replacing the fuse.

As shown in the perspective view of FIG. 2 and the electrical connection diagram of FIG. a barrier unit BU including a resistor r for
Terminal unit (including Hoan side terminal A and non-Hoan side terminal B) TU
A FU including fuse F is provided between the fuse unit BU and the terminal unit TU via the fuse unit FU.

That is, the barrier unit BU is connected to the connector c1. c2 connects to fuse unit) FU, terminal unit) TU
is connected to the fuse unit (FU) by connectors atb and g.

The barrier unit) BU and the fuse unit FU are fixed to the terminal unit TU by screws N.

Screw N//i. The grounding terminal of the barrier unit) BU is connected to the busbar BB to which the terminal unit TU is fixed, and together with the connector g, the grounding is redundant, forming a safety barrier for circuit connection as shown in FIG.

In this way, the barrier unit (BU) and the terminal unit (TU) are connected via the fuse unit (FU), so the fuse F cannot be replaced without removing the barrier unit (BU). ) You can reduce the number of times you forget to check the BU.

In the above-mentioned embodiment, the case where the inspection resistor r was included as the barrier unit BU was exemplified, but as shown in FIG. 4, two current-limiting resistors R1 and R2 and the connector c2.
If c3 is used, the inspection resistor r can be omitted and the problem of voltage drop due to r is eliminated, and the Zener diode D
1. D2 can be inspected under the same operating conditions.

Moreover, since two current limiting resistors R1 and R2 are used and connected in parallel, the value of each resistor can be doubled compared to when there is only one current limiting resistor.

Therefore, if a contact failure occurs in either one of the connectors C2ye3, the current flowing to the Hoan side will be halved.

That is, connector c2. The contact failure of c3 is safe, and the contact failure can be detected in the operating state.
2. The use of c3 has no effect on intrinsic safety.

Furthermore, as shown in FIG. 5, a Zener diode D1. D2
between the cathodes of connector c4. If the connection is made through c5, the current limiting resistor is only R1, and the inspection resistor r
can be omitted, and connector c4. Poor contact at c5 is in the safe direction.

Furthermore, the safety maintaining elements are not limited to Zener diodes and current limiting resistors, but voltage limiting circuits and current limiting circuits may be used as necessary.

FIG. 6 is an electrical connection diagram when the safety barrier of the present invention is used in a resistance thermometer circuit.

In the figure, a three-wire resistance temperature detector Rt is placed in a dangerous area of the site, and a resistor Rb1. Rb2
Together with Rb3, it forms a resistor bridge circuit B.

The safety barrier consists of fuses F 1 , F 2 t F 3 and current limiting resistors Rl p R2, R3, the series circuit of F □ and R1 is connected to the conductor 10 of Rt, and the series circuit of F2 and R2 is connected to the conductor 10 of Rt. 12, the series circuit of F3 and R3 is Rt
are connected to conductive wires 13, respectively.

The fuse F1. which constitutes the safety barrier in this way. F2.
F3 is connected in series with the temperature measuring resistor Rt, and any variation in their resistance values will cause a measurement error.

For this reason, fuses F1 to F3 with uniform characteristics are selected and used.

By the way, if a fuse is blown and replaced individually, errors will occur due to variations in characteristics, but with the safety barrier of the present invention, each fuse unit FU consisting of fuses F1 to F3 with uniform characteristics can be replaced. This has the advantage of reducing errors due to variations in characteristics.

As explained above, according to the present invention, it is possible to obtain a safety retainer in which only the fuse can be replaced and there is less need to forget to inspect the barrier unit when replacing the fuse.

[Brief explanation of the drawing]

Figure 1 is a perspective view showing an example of a conventional safety barrier, Figure 2 is a perspective view of an embodiment of the safety barrier of the present invention, and Figure 3 is an electrical diagram of an embodiment of the safety barrier of the present invention. Connection diagrams, Figures 4 and 5 are electrical connection diagrams showing other embodiments of the safety barrier of the present invention, and Figure 6 is an electrical connection diagram when the safety barrier of the present invention is used in a resistance thermometer. It is. BU...Barrier unit, TU...Terminal unit, FU...Fuse unit, F.
...Science, DI, D2...Zener diode, R1, R2...Current limiting resistor, r
...Resistance for inspection, a, b. C1, C22C5, C4°°°°°° Connector, B B
°−−−−−Bus・ノ□−、N・・・9・Fixing screw.

Claims (1)

[Scope of utility model registration request] a barrier unit including a safety retaining element other than a fuse;
It has a terminal unit including external connection terminals on the support side and the non-service side, and a fuse unit including a fuse. Between each unit is a safety retainer configured to be removable with a connector, and the fuse unit is a barrier unit. A safety retainer characterized in that it is arranged between terminal units so that the fuse cannot be replaced without removing the barrier unit.