JPH04127837A - Safety device - Google Patents

Abstract

PURPOSE:To prevent lowering of efficiency due to heat loss during operation by connecting a resistor having resistance variable with the movement of a housing door in series with a safety switch disposed between an electronic load and a power supply while being interlocked with the door. CONSTITUTION:During an interval when a door 10 closes by some angle from open state, no current flows through a wiring 19 from a power supply 1 and a wiring 20 to an electronic load thus effecting the function of a safety switch 3. When the door 10 is closed by some angle, terminals 13, 14 protruding from the opposite ends of a contact 12 begin to contact with resistors 17, 18, respectively. At that time, a high resistor is inserted between the power supply 1 and the electronic load 2. Upon perfect closure of the door 10, the resistance goes zero. According to the constitution, rush current is prevented upon start of operation and deterioration of the contact in an interlock switch or erroneous function of an overcurrent preventive circuit is prevented while furthermore heat loss is eliminated during operation.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electronic device in which an electronic load and a power source for supplying power to the electronic load are housed in a housing, and the interior of the electronic device is inspected and maintained by opening the door of the housing.

In electronic devices such as electrophotographic devices such as electrophotographic copiers, facsimile machines, and laser printers, and various control devices, the electronic load and the power supply that supplies power to it are generally housed within the housing of the device, and their maintenance and inspection is required. When the housing door is opened for parts replacement, jam removal, etc., the power supply circuit from the power supply to the electronic load opens, and when the door is closed, the power supply circuit is closed. (safety switch) is installed to ensure that when the door is opened, the motor will not inadvertently rotate and drive the machine, or the heat source of the fixing device will turn on, causing harm to the inserted hand or arm. equipment is provided.

FIG. 1 is a diagram showing the most basic rotation of a safety device in which an interlock switch 3 is provided between a power source 1 and an electronic load 2 of an electronic device. Electronic loads include many electro-mechanical conversion parts, such as motors and solenoids, and therefore a large current flows when these electronic loads are started. Therefore,
Ripple fluctuations in the supply voltage become large, and in order to suppress ripples so as not to adversely affect other electronic loads, the number 101 is applied.
Usually, a capacitor 4 of LF to several hundred μF is connected in parallel with the electronic load 2.

The interlock switch 3 is opened and closed in conjunction with opening and closing of the door of the housing.

When the operator performs the required work with the door open and closes the door, interlock switch 3 is activated.
changes from open to closed, and the above electronic load 2 and capacitor 4
Since a rush current flows through the interlock switch 3, there is a risk of deterioration of the contacts of the interlock switch 3 and malfunction of the overcurrent protection circuit of the power supply 1, resulting in a power down. Conventionally, as a countermeasure against this problem, a protective resistor 5 was inserted in series with the electronic load 2 to suppress the rush current as shown in Fig. 2, but although it was possible to suppress the rush current at startup, In other cases, it simply causes heat loss and reduces efficiency.

In view of the above-mentioned problems of the safety device of the conventional electronic device having the above-mentioned structure, the present invention aims to prevent the generation of rush current and the malfunction of the overcurrent protection circuit when the door of the housing starts to close. An object of the present invention is to provide a safety device that can prevent a decrease in efficiency due to heat loss during operation.

Means for Solving the Problems The safety device for an electronic device of the present invention uses, as an electronic load, a resistor whose resistance value changes from high resistance to no resistance in conjunction with the movement of the housing door from the start to the end of the closing operation. It is characterized by a safety switch connected in series with the power supply that opens and closes in conjunction with the opening and closing of the door.

With the above configuration, the above-mentioned resistor is in a high resistance state at the start of the closing operation of the housing door, and the rush current that conventionally flows through the capacitor is suppressed by this resistor. Furthermore, as the door is closed, the resistance decreases, and when the door is completely closed, the resistance becomes zero, allowing a normal voltage current to be supplied to the electronic load, eliminating heat loss due to resistance. .

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail based on the drawings.

3 to 5 show circuit diagrams of the safety device according to the present invention in the door open state, the door closing start point, and the door closing end point, and FIGS. 6(a) and (b).

(c) shows an example of the specific structure of the safety switch and variable resistor when the door is opened, during closing operation, and when the door is closed.

In the configuration of the embodiment shown in FIG. 6, a protrusion 11 is erected inside the opening/closing door 10 of the housing, and a contact 12 made of an electrical conductor is provided at the tip of the protrusion 11 parallel to the surface of the door. It has been extended. Projecting terminals 13.1 are provided at both ends of the contact 12.
4 is provided. A resistor board 16 is fixed to the device body housing 15 at a position corresponding to the projection 11. A pair of resistors 17 and 18 having a certain length perpendicular to the surface of the housing is provided on the board 16, and the +24VIN wiring 19 from the power supply 1 is connected to the resistor 17.
A +24VOUT (7) wiring 20 to an electronic load is connected to the resistor 18 via conductor terminals 21 and 22.

As shown in FIG. 6(a), from the open state of the door 10 to the opening degree at which it begins to close, the terminals 13 and 14 at both ends of the contact 12 on the protrusion 11 of the door are connected to the resistor 17 and 18. Wiring 19 from power supply 1 and wiring 2 to electronic load
0, no current flows between the switch and the safety switch 3. This state is shown in a circuit diagram in FIG. door 10
When the opening angle reaches a certain angle, as shown in Fig. 6(b),
The protruding terminals 13 and 14 at both ends of the contact 12 are connected to resistors 17, respectively.
．． Start contacting 18. As a result, from the wiring 19 to the conductor terminal 21, to the resistor 17. Projection terminal 13, contact 12, projection terminal 14, resistor 17. A current flows to the wiring 20 via the conductor terminal 22. In this case, a high resistance is inserted between the power supply 1 and the electronic load 2 as shown in the circuit diagram in FIG. This suppresses the rush current that conventionally flows through the capacitor 4.

As shown in FIG. 6(c), when the door 10 is completely closed, the protruding terminals 13.14 contact the conductor terminals 21 and 22, and the current from the power source 1 to the electronic load 2 passes through the resistor 17.18. It flows without passing through, and the resistance becomes zero.

This state is shown in a circuit diagram in FIG. Since the resistance becomes zero, it becomes possible to normally supply a current of +24V to the electronic load 2.

Effects As described above, according to the present invention, the resistor is inserted into the current circuit from the power source to the electronic load in conjunction with the movement of the door of the housing from the open state to the closing state until the closing is completed. changes from infinite → high resistance → low resistance → zero, preventing rush current at startup and deteriorating the interlock switch contacts.

Malfunction of the current overcurrent protection circuit can be prevented, and
It is possible to eliminate heat loss during operation and prevent a decrease in efficiency.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram showing a basic circuit of a safety device for an electronic device to which the present invention is applied, Fig. 2 is a circuit diagram of an example of a circuit with conventional rush current suppression measures, and Figs. 3 to 5 The figures are circuit diagrams of the safety device according to the embodiment of the present invention when the door is open, at the initial stage of closing, and when the door is fully closed. Example of door opening and initial closing 1. FIG. 3 is a front view showing the state when the closure is completed. 1...Power supply, 2...Electronic load, 3...Interlock switch (safety switch), 10
...Door, 12...Contact, 13.14...Protruding terminal, 16...Substrate, 17.18...Resistor. 19.20...Wiring, 21.22...Conductor terminal 2 also represented by patent attorney Takehisa Ito's, Ya.

Claims (1)

[Claims] An electronic load and a power supply for supplying power to the electronic load are housed in a device housing, and a safety switch that opens and closes in conjunction with opening and closing of a door of the housing is configured to supply power from the power supply to the electronic load. In a safety device for an electronic device in a supply circuit, a resistor whose resistance value changes from high resistance to no resistance is connected between the electronic load and the power source in conjunction with the movement of the door from the start to the end of the closing operation of the door. A safety device characterized by being connected in series with the above safety switch.