Switching device and electric apparatus

A switching device is provided that includes a switching mechanism unit and a switch drive control circuit. In the switching device, an operating member is maintained in an ON position by the sucking force of a permanent magnet and a yoke, despite the pushing force of a biasing unit, when the permanent magnet is in an ON position. The yoke is magnetized in such a manner as to reduce the magnetic force of the permanent magnet, when a coil wound around the yoke is energized by the switch drive control unit. The operating member and a switching member are moved from the ON position to the OFF position by virtue of the pushing force of the biasing unit, thereby shutting a feed line.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a switching device, and, more particularly, to a switching device that is easy to operate and is so small as to be disposed in the housing of an electric apparatus such as a copying machine, a printer, or a personal computer, and can be used for at least either leakage prevention or excess voltage prevention. The present invention also relates to such an electric apparatus.

2. Description of the Related Art

There have been ground-fault interrupters as domestic wiring devices for detecting and shutting off leakage in domestic wirings (see Japanese Laid-Open Patent Application Nos. 2000-261953, 2001-023501, and 2001-006515). The structures and forms of the conventional ground-fault interrupters are standardized in accordance with the JIS (Japanese Industrial Standards), and the necessary components are housed in standardized housings.

For example, the ground-fault interrupter that is disclosed in Japanese Laid-Open Patent Application No. 5-334953 has a housing that is formed with a main casing and a main cover. This housing contains a zero phase current transformer and an overcurrent transformer that detects leakage and overcurrent in the main circuit, an open-close mechanism unit that opens and closes the main circuit, trip coils that drive the open-close mechanism unit, and the like. One of the trip coils is employed to eliminate leakage, while the other one of the trip coils is employed to eliminate overcurrent. Further, a leakage display device that displays each occasion of leakage elimination in conjunction with the trip coil for eliminating leakage is disposed in the housing in such a manner that each occasion of leakage elimination can be recognized through the housing. In this manner, this ground-fault interrupter has a closed structure.

In such a conventional ground-fault interrupter, the open-close mechanism unit that opens and closes the main circuit is opened by the trip coils, and is closed through a handle that is manually operated after leakage or overcurrent is eliminated. However, priority is put on the opening operation with the trip coils, and the open-close mechanism unit is designed to be accommodated in the housing.

Japanese Laid-Open Patent Application No. 11-299082 discloses a ground-fault interrupter device that includes not only a leakage detector and an excess voltage detector, but also a means of releasing a load from the power source based on the output of either of the leakage detector and the excess voltage detector. With this ground-fault interrupter device, a load can be released from the power source not only when there is leakage but also when excess voltage is detected. Thus, load damage due to abnormal voltage or excess voltage can be prevented.

In each of the above conventional ground-fault interrupters, however, all the necessary components are contained in the housing standardized as a domestic wiring device in accordance with the JIS. Therefore, in a case where such a ground-fault interrupter is employed in an electric apparatus such as a copying machine, a printer, or a personal computer, it is difficult to secure a sufficient ground space in the apparatus. If a sufficient ground space is secured, the apparatus becomes large in size.

Also, the ground-fault interrupter disclosed in Japanese Laid-Open Patent Application No. 5-334953 has the function of detecting leakage and the function of detecting overcurrent. The components that execute those functions are accommodated in the JIS housing, and are hermetically closed by the housing. As a result, the inner structure becomes complicated, and the product becomes expensive. In a case where a ground-fault interrupter having such a housing is disposed in an apparatus, there are two housings existing in one structure. Due to heat generation from the inner components, the temperature in the housing of the ground-fault interrupter becomes higher, resulting in a decrease in detection accuracy.

Further, since the open-close mechanism unit has priority on the opening operation with the trip coils and is designed to be contained in a housing, the handle to open the main circuit of the open-close mechanism unit is not lightly moved, resulting in poor operability and usability.

As for the ground-fault interrupter device disclosed in Japanese Laid-Open Patent Application No. 11-299082, the control circuit is not protected, because operating current is supplied to the control circuit even after the load is released from the power source. Even if excess voltage is detected, the excess voltage is supplied to the control circuit. Further, in this structure, a short-circuit relay is constantly used. In a case where the excess voltage is not eliminated when the main power supply is switched back on, a shutoff operation needs to be performed again. The repetitive shutoff operation might have adverse influence on the load.

Also, as a smoothing capacitor is used to monitor excess voltage so as to increase the detection accuracy, there is a decrease in the accuracy of impulse excess voltage detection. Since the operating power is supplied separately to the leakage detector and the excess voltage detector, a large quantity of standby power is required.

SUMMARY OF THE INVENTION

A general object of the present invention is to provide a switching device and an electric apparatus in which the above disadvantages are eliminated.

A more specific object of the present invention is to provide a switching device with which an ON operation can be performed very easily, and an OFF operation can be automatically performed with an electric signal based on a leakage detection signal or the like. With this switching device, excellent operability and workability can be realized, while a stable switching operation is constantly performed. The present invention is also to provide an electric apparatus that is equipped with the switching device.

Other specific objects of the present invention are to protect the control circuit of the switching device by shutting off the power supply to a load when leakage or excess voltage is generated in an electric apparatus, to prevent a repetitive shutting operation of the switching device due to inadvertent resumption of power supply, to increase the accuracy of leakage and excess voltage detection, and to save standby energy.

The above objects of the present invention are achieved by a switching device that includes: a switching mechanism unit that includes: a yoke around which a coil is wound; a permanent magnet that is movable between an ON position that is in contact with or in the vicinity of the yoke and an OFF position that is at a predetermined distance from the yoke; an operating member that moves to an ON position or an OFF position, as the permanent magnet moves to the ON position or the OFF position; a switching member that connects or shuts a predetermined feed line, as the operating member moves to the ON position or the OFF position; and a biasing unit that pushes the operating member toward the OFF position; and a switch drive control unit that controls energization of the coil that is wound around the yoke.

In this switching device, the operating member is maintained in the ON position by virtue of the sucking force of the permanent magnet and the yoke, despite the pushing force of the biasing unit, when the permanent magnet is in the ON position. The yoke is magnetized in such a manner as to reduce the magnetic force of the permanent magnet, when the coil is energized by the switch drive control unit. The operating member and the switching member are moved from the ON position to the OFF position by virtue of the pushing force of the biasing unit, thereby shutting the feed line.

In the switching device, the switch drive control unit may include at least a leakage detecting unit that determines whether there is leakage due to the feed line or a load that is fed via the feed line. When the leakage detecting unit determines that there is leakage, the switch drive control unit energizes the coil so as to shut the feed line.

Alternatively, the switch drive control unit may include an excess voltage determining unit that monitors input voltage of the feed line and determines whether there is excess voltage based on a predetermined criterion. When the excess voltage determining unit determines that there is excess voltage, the switch drive control unit energizes the coil so as to shut the feed line.

More preferably, the switch drive control unit includes both the leakage detecting unit and the excess voltage determining unit. When leakage or excess voltage is detected, the switch drive control unit energizes the coil so as to shut the feed line.

In such a case, the leakage determining circuit of the leakage detecting unit and the excess voltage determining circuit of the excess voltage determining unit may be disposed in a module of an integral control block.

In this switching device, the excess voltage determining unit preferably performs an excess voltage determining operation on a shorter cycle than a ¼ cycle of the input voltage of the feed line, when the input voltage is alternating voltage.

In this switching device, the switching mechanism unit and the switch drive control unit are preferably disposed on the same surface of a predetermined substrate.

More preferably, the switching mechanism unit is detachably attached onto the substrate.

The above objects of the present invention are also achieved by an electric apparatus that includes the above described switching device. In this electric apparatus, an external power supply introducing outlet is formed on the housing of the electric apparatus. A device power supply unit is provided to generate operating power from the power supplied from an external power source, and to supply the operating power to various internal circuits. The power supply line between the external power supply introducing outlet and the device power supply unit serves as the feed line. The switching mechanism unit is disposed on the power supply line. The switch drive control unit includes at least a leakage detecting unit that determines whether there is leakage due to the feed line or a load that is fed via the feed line. The switch drive control unit energizes the coil so as to shut the feed line, when the leakage detecting unit detects leakage.

In the above electric apparatus, the switch drive control unit may include an excess voltage determining unit that monitors input voltage of the feed line and determines whether there is excess voltage based on a predetermined criterion. The switch drive control unit energizes the coil so as to shut the feed line, when the excess voltage determining unit determines that there is excess voltage.

The switch device control unit may include both the leakage detecting unit and the excess voltage determining unit. When leakage or excess voltage is detected, the switch drive control unit energizes the coil so as to shut the feed line.

In such a case, the leakage determining circuit of the leakage detecting unit and the excess voltage determining circuit of the excess voltage determining unit may be disposed in a module of an integral control block.

In the above electric apparatus, the excess voltage determining unit of the switching device preferably performs an excess voltage determining operation on a shorter cycle than a ¼ cycle of the input voltage of the feed line, when the input voltage is alternating voltage.

The operating power of the switch drive control unit of the switching device is preferably supplied through the power supply line on a downstream side of the leakage detecting unit.

The switching mechanism and the switch drive control unit of the switching device are preferably disposed on the same surface of a predetermined substrate.

More preferably, the switching mechanism unit of the switching device is detachably attached onto the substrate.

In a switching device in accordance with the present invention, the operating member that moves the switching member, which connects or shuts the feed line, between the ON position and the OFF position is pushed toward the OFF position by the biasing unit. The permanent magnet that moves the operating member between the ON position and the OFF position is maintained in the ON position by virtue of its magnetic force. In the ON position, the permanent magnet is in tight contact with or in the vicinity of the yoke around which the coil is wound. As the coil wound around the yoke is energized, the magnetic force of the permanent magnet is reduced, and the operating member and the switching member are moved from the ON position to the OFF position by virtue of the pushing force of the biasing unit, so that the feed line is shut off. As the operating member is moved in the ON direction, the suction force works between the permanent magnet and the yoke. Accordingly, the ON operation can be performed with small operating force, and the OFF operation can be surely performed with an electric signal. Thus, higher operability and usability can be achieved, while a stale switching operation is constantly performed.

When leakage from the feed like is detected or excess voltage is detected in input voltage, the coil is energized so as to shut off the feeding circuit automatically. Thus, great safety can be maintained. Also, the shutoff operation is not to be repeated.

In an electric apparatus equipped with the above switching device, such as a printer, a copying machine, or a personal computer, the switching mechanism unit is disposed on the power supply line between the external power introducing outlet of the housing and the power supply unit of the apparatus. The switch drive control unit of the switching device includes the leakage detecting unit or the excess voltage determining unit. Accordingly, at least either leakage or excess voltage (abnormal voltage) in the apparatus is detected, and the power source can be surely shut off. Thus, greater safety can be provided to the apparatus. Furthermore, the ON operation at the time of recovery can be readily performed with small operating force.

The operating power source of the switch drive control unit is supplied from the power supply line on the downstream side of at least the leakage detecting unit. With this arrangement, leakage detection and power supply from the outside can be both controlled. Thus, greater safety can be provided, and higher usability can be achieved.

The switching mechanism unit and the switch drive control unit are disposed on the same surface of the predetermined substrate, so that the switching device can be made smaller and higher productivity can be achieved.

The switching mechanism unit is detachably mounted onto the substrate, so that the switching mechanism unit can be easily replaced with a new one. Thus, maintenance of the switching device can be readily done.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following is a description of embodiments of the present invention, with reference to the accompanying drawings. As the embodiments described below are preferred embodiments of the present invention, various restrictions are put on them in terms of technical features. However, the scope of the present invention is not limited to those embodiments, unless otherwise mentioned.

First Embodiment

A first embodiment of a switching device and electric equipment in accordance with the present invention is described.FIGS. 1 through 8illustrate the first embodiment of a switching device in accordance with the present invention.FIG. 1is a plan view of the switching device.FIG. 2is a front view of the switching device.FIG. 3is an enlarged right side view of the switching mechanism of the switching device.FIG. 4is a circuit diagram of the switching device.FIGS. 5 through 8are enlarged front views illustrating the operation of the switching device, showing various states of the switching mechanism.FIG. 9is a perspective rear view of a printer that is an example of electric equipment to which the switching device is applied.

As shown inFIGS. 1 and 2, the switching device1of the first embodiment includes a pair of input connecting terminals3, a switching mechanism unit4, a leakage detecting current transformer5, a pair of output connecting terminals6, two electric cable members7that form feed lines, and a switch drive control circuit8. These components are disposed on the same surface of a substrate2. A housing or the like is not employed to house the input connecting terminals3, the switching mechanism unit4, the leakage detecting current transformer5, the output connecting terminals6, the electric cable members7, and the switch drive control circuit8.

This switching device1is provided within a main housing101of a printer as electric equipment as shown inFIG. 9, for example. In the main housing101, the switching device1is not covered with a housing or the like, as described above, but is left open. Although not shown, this printer100operates with a commercial power supply of 100 V that is supplied from the outside via a power supply cable, and records an image on a recording paper sheet based on input image data by an electrophotographic technique. Electric equipment to which a switching device in accordance with the present invention is not limited to a printer, but a switching device in accordance with the present invention may be applied to various types of electric apparatuses including image forming apparatuses such as copying machines and facsimile machines, and information processing devices such as personal computers.

More specifically, the switching device1has the input connecting terminals3provided at one end of the rectangular-shaped substrate2. The input connecting terminals3are connected to an external power supply introducing outlet through which the power supply cable for supplying the commercial external power supply of 100 V is introduced.

The switching mechanism unit4is detachably attached onto the substrate2via fixed terminals10aand10b(seeFIGS. 2 and 3) mounted to the substrate2. A connecting piece11afor connecting the input connecting terminals3to the input-side fixed terminal10aof the switching mechanism unit4is formed on the bottom surface of the substrate2. A connecting piece11bfor connecting the output-side fixed terminal10bof the switching mechanism unit4to the electric cable members7is also formed on the bottom surface of the substrate2.

The two electric cable members7penetrate the inside of the leakage detecting current transformer5, and are connected to the pair of output connecting terminals6via a connecting piece12formed on the bottom surface of the substrate2. The output connecting terminals6are connected to the power source lines connected to the power supply unit (PSU) or the like (not shown) of the printer100.

Accordingly, in this switching device1, the commercial external supply power of 100 V flows in the order of input connecting terminals3, the connecting piece11a, the fixed terminal10a, the switching mechanism unit4, the fixed terminal10b, the connecting piece11b, the electric cable members7penetrating the leakage detecting current transformer5, the connecting piece12, and the output connecting terminals6. The supply power flowing through the switching device1is supplied to the power supply unit of the printer100via the power supply line connected to the output connecting terminals6.

The leakage detecting current transformer5detects unbalanced AC power flowing through the electric cable members7that penetrate the transformer5. As shown inFIG. 4, a secondary coil13is wound around the leakage detecting current transformer5. When leakage of the power flowing through the electric cable members7is caused, unbalanced voltage is induced, and voltage is generated in the secondary coil13due to the unbalanced voltage.

As shown inFIG. 4, the switch drive control circuit8includes an amplifier circuit21, a leakage determining circuit22, a switch control circuit23, and a power supply circuit24. The power supply circuit24is provided with AC power from the power supply line closer to the downstream side of the power supply than to the leakage detecting current transformer5, for example, from the output connecting terminals6. The AC is rectified and the voltage is adjusted, so that the necessary power supply is provided to the amplifier circuit21, the leakage determining circuit22, and the switch control circuit23. Also, the operating power is supplied to the switch mechanism unit4.

The secondary coil13wound around the leakage detecting current transformer5is connected to the amplifier circuit21. When there is leakage, the voltage generated in the secondary coil13is input as leakage detecting voltage. The amplifier circuit21then amplifies the leakage detecting voltage detected by the secondary coil13, and outputs it to the leakage determining circuit22.

The leakage determining circuit22compares the leakage detecting voltage input from the amplifier circuit21with a preset comparative voltage, thereby determining whether the leakage exceeds a predetermined leakage level. If the leakage exceeds the predetermined leakage level, the leakage determining circuit22outputs a leakage detection signal to the switch control circuit23.

Accordingly, the leakage detecting current transformer5that is equipped with the secondary coil13, the amplifier circuit21, and the leakage determining circuit22collectively function as a leakage detecting unit. Also, the leakage detecting current transformer5and the switch drive control circuit8form a switch drive controlling unit.

The switch control circuit23of the switch drive control circuit8normally shuts off the supply of opening power from the power supply circuit24to the switching mechanism unit4, so that the switching mechanism unit4closes the power supply line and the power supply unit of the printer100is provided with power from an external power source. As a leakage detection signal is input from the leakage determining circuit22, the supply of opening power is resumed from the power supply circuit24to the switching mechanism unit4, so that the switching mechanism unit4opens the power supply line and the power supply from an external power source to any component beyond the switching mechanism unit4is cut off.

The structure of the switching mechanism unit4in an ON state is shown inFIGS. 5 and 6, and the structure of the switching mechanism unit4in an OFF state is shown inFIGS. 7 and 8. As shown in these drawings, the switching mechanism unit4includes a swing handle31that is an operating member, a slide arm32, a permanent magnet33, a return spring34that is a biasing member, a yoke35, a coil36that is wound around the yoke35, a switching member37, an input-side fixed contact member38, and an output-side fixed contact member39.

The swing handle31that is an operating member has arms31aand31bthat extend downward from the end portions. A restricting protrusion31cthat protrudes downward is formed at the center of the swing handle31. The swing handle31is movably supported by a shaft40, with the upper middle portion of the restricting protrusion31cbeing the center of the swing movement. As shown inFIG. 5, in an ON state, the swing handle31has the arm31atilting downward. As shown inFIG. 7, in an OFF state, the swing handle31has the arm31btilting downward. In an ON state, the tilting handle31has the top end of the arm31apushes the return string (the biasing means)34. With the spring pressure of the return spring34, the swing handle31swings counterclockwise or swings in the off direction.

In this state, the swing handle31has the top end of the restricting protrusion31cinserted into a concave portion32aformed in the slide arm32. The concave portion32aof the slide arm32is formed on the tilted wall surface that is formed by tilting the right side wall surface by a predetermined angle, as shown inFIGS. 5 and 7. Accordingly, the tilted wall surface of the slide arm32functions to hold the restricting protrusion31cof the swing handle31in the concave portion32ain an ON state. In an OFF state, the tilted wall surface functions to uplift the top end of the restricting protrusion31cof the swing handle31along the tilted wall surfaces in the sliding direction of the slide arm32, thereby swinging the swing handle31.

The slide arm32is fixed onto the upper surface of the permanent magnet33, and the permanent magnet33is disposed slidably to left and right (in the ON direction and OFF direction) inFIGS. 5 and 7.

The left end surface of the permanent magnet33is disposed to face the end surface of the iron yoke35. The coil36is wound around the yoke35.

With this arrangement, the permanent magnet33moves toward the yoke35by virtue of its magnetic force, and is brought into tight contact with the yoke35. By doing so, the permanent magnet33moves the slide arm32in the ON direction, and the swing handle31in the ON direction shown inFIGS. 5 and 6, thereby putting it into an ON state.

When energized, the coil36wound around the yoke35generates such a magnetic field as to magnetize the yoke35in such a direction as to reduce the magnetic force of the permanent magnet33. Accordingly, the magnetic force of the permanent magnet33is reduced, and the swing handle31swings in the OFF direction (counterclockwise) by virtue of the pushing force of the return spring34and moves to the right (the OFF direction) inFIGS. 5 and 7. Here, a predetermined gap X shown inFIG. 7is made between the yoke35and the permanent magnet33.

Meanwhile, as shown inFIGS. 6 and 8, the swing handle31has a swinging movement keeping unit31that holds and interlocks a swing knob portion37aof the switching member37to the swinging movement of the swing handle31. Thus, the switching member37is swung in the opposite direction to the swing direction of the swing handle31.

In short, the switching member37is swingably supported by a supporting end38aof the input-side fixed contact member38that is connected to the input-side fixed terminal10ashown inFIGS. 2 and 3. Thus, the switching member37is electrically connected to the input-side fixed contact member38. Further, the swing knob portion37ais formed above the supporting position supported by the supporting end38a. The swinging movement keeping portion31dof the swing handle31is disposed to hold the swing knob portion37a.

Also, the switching member37has a movable contact37bon the lower surface of its top end on the opposite side from the input-side fixed contact member38. The output-side fixed contact member39has a fixed contact39aat the location facing the movable contact37b.

Accordingly, when the swing handle31swings or tilts clockwise (in the ON direction), the switching member37connected to the input-side fixed contact member38is swung counterclockwise by the swinging movement keeping portion31dof the swing handle31via the swing knob portion37a, as shown inFIG. 6. The movable contact37bof the switching member37is then brought into contact with the fixed contact39aof the output-side fixed contact member39, so that the input-side fixed contact member38is brought into contact with the output-side fixed contact member39.

When the swing handle31swings counterclockwise (in the OFF direction), the switching member37is swung clockwise by the swinging movement keeping portion31dof the swing handle31via the swing knob portion37a, as shown inFIG. 8. The movable contact37bof the switching member37is then separated from the fixed contact39aof the output-side fixed contact member39, so that the connection between the input-side fixed contact member38and the output-side fixed contact member39is shut off.

The switching mechanism unit4has the coil36connected to the switch control circuit23and the power supply circuit24of the switch drive control circuit8shown inFIG. 4, so that energization of the coil36is controlled by the switch control circuit23.

With this arrangement, in the switching mechanism unit4, the slide arm32is held in the ON direction by virtue of the magnetic force of the permanent magnet33, and the swing handle31is swingably held in the ON direction, so as to put it in an ON state. However, when the coil36is energized, a magnetic field is generated to magnetize the yoke35in such a direction as to reduce the magnetic force of the permanent magnet33. As the magnetic force of the permanent magnet33is reduced, the suction force with the yoke35is also weakened. As a result, the swing handle31is swung in the OFF direction (counterclockwise) by virtue of the pushing force of the return spring34. As the swing handle31swings in the OFF direction (counterclockwise), the switching member37swings clockwise. The movable contact37bof the switching member37is then separated from the fixed contact39aof the output-side fixed contact member39, and the connection between the input-side fixed contact member38and the output-side fixed contact member39is shut off.

However, in an ON state in which the restricting protrusion31cof the swing handle31enters the concave portion32aof the slide arm32and the permanent magnet33is in tight contact with the yoke35, the yoke35is sucked by greater magnetic force than the pushing force of the return spring34pushing the arm31aof the swing handle31in the opening direction (OFF direction). Accordingly, even though the arm31ais pushed in the opening direction (OFF direction) by the return spring34in an ON state, the swing handle31stably maintains the ON state in which the restricting protrusion31cof the swing handle31is inserted into the concave portion32aof the slide arm32by virtue of the magnetic force of the permanent magnet33.

Also, when the switching device1is put into an ON state, the upper surface portion of the arm31aof the swing handle31is manually pushed. Here, the magnetic force of the permanent magnet33acts in such a direction as to swing the swing handle31in the ON direction. Accordingly, the switching device1can be readily put into an ON state by lightly handling the swing handle31.

The switching mechanism unit4is detachably attached onto the substrate2shown inFIGS. 1through3. As the switching mechanism unit4is attached onto the substrate2, the input-side fixed contact member38is connected to the input-side fixed terminal10afixed onto the substrate2, and the output-side fixed contact member39is connected to the output-side fixed terminal10bfixed onto the substrate2.

Next, the functions of the first embodiment are described. In the main housing101of the printer100shown inFIG. 9, the switching device1has the input connecting terminals3, the switching mechanism unit4, the leakage detecting current transformer5, the output connecting terminals6, the electric line members7, and the switch drive control circuit8, which are disposed on the same surface of the substrate2in an open state. With this arrangement, heat can be efficiently generated, as the printer100that is an electric apparatus operates and the switching device1operates.

In the following, explanation is made as to an ON state of the switching device1, a transition state from an ON state to an OFF state, and a transition state from an OFF state to an ON state.

The switching device1has the input connecting terminals3connected to a commercial power supply line supplied to the printer100from the outside. Meanwhile, the switching device1has the output connecting terminals6connected to the power supply line that is connected to the power supply unit of the printer100.

In the switching device1in an ON state shown inFIGS. 5 and 6, the movable contact37bof the switching member37connected to the input-side fixed contact member38of the switching mechanism unit4is in contact with the fixed contact39aof the output-side fixed contact member39. The external commercial power of 100 V flows in the order of the input connecting terminals3, the connecting piece11a, the fixed terminal10a, the switching mechanism unit4, the fixed terminal10b, the connecting piece11b, the electric cable members7penetrating the leakage detecting current transformer5, the connecting piece12, and the output connecting terminals6shown inFIG. 2. The electric power flowing through the switching device1is supplied to the power supply unit (the device power supply unit) of the printer100through the power supply lines connected to the output connecting terminals6.

Since the permanent magnet33is in tight contact with the yoke35by virtue of its magnetic force in an ON state, the switching mechanism unit4has the swing handle31swinging and tilting clockwise about the shaft40. The restricting protrusion31cof the swing handle31enters the concave portion32aof the slide arm32fixed onto the permanent magnet33. The arm31aof the swing handle31then pushes the return spring34down.

In the switching device1in the ON state, the power supply circuit24, to which AC power is supplied through the power supply line at least on the downstream side of the leakage detecting current transformer5, rectifies the alternating current and adjusts the voltage, so as to supply necessary power to the amplifier circuit21, the leakage determining circuit22, and the switch control circuit23. Also, operating power is supplied to the switching mechanism unit4to perform leakage detection and control operations.

When leakage is caused in a circuit of the printer100including the switching device1in an ON state, unbalanced voltage is induced in the leakage detecting current transformer5of the switching device1, and voltage is generated in the secondary coil13and is input as leakage detection voltage to the amplifier circuit21.

The amplifier circuit21amplifies the leakage detection voltage detected in the secondary coil13, and outputs the amplified voltage to the leakage determining circuit22. The leakage determining circuit22compares the leakage detection voltage, which is input from the amplifier circuit21, with the predetermined comparative voltage. If the leakage detection voltage exceeds the predetermined leakage level, the leakage determining circuit22outputs a leakage detection signal to the switch control circuit23.

In the ON state, the switch control circuit23shuts off the supply of the opening operation power from the power supply circuit24to the switching mechanism unit4, so that the switching mechanism unit4closes the power supply lines and electric power is supplied from an external power source to the power supply unit of the printer100. As the leakage detection signal is input from the leakage determining circuit22, the opening operation power is supplied from the power supply circuit24to the switching mechanism unit4. The switching mechanism unit4then opens the power supply lines, so that the power supply to the circuits beyond the switching mechanism unit4is shut off.

As the opening operation power is supplied from the power supply circuit24to the coil36in the switching mechanism unit4, the coil36generates a magnetic field in such a direction as to magnetize the yoke35to reduce the magnetic force of the permanent magnet33. As the magnetic force of the permanent magnet33is reduced, the swing handle31is allowed to swing in the OFF direction (counterclockwise) by virtue of the pushing force of the return spring34, as shown inFIG. 7. The permanent magnet33then moves apart from the yoke35, and the predetermined gap X is made between the yoke35and the permanent magnet33.

As the swing handle31swings in the OFF direction, the switching member37is swung clockwise by the swinging movement keeping portion31dof the swing handle31via the swing knob portion37a. As shown inFIG. 8, the movable contact37bof the switching member37then moves apart from the fixed contact39aof the output-side fixed contact member39, and the connection between the input-side fixed contact member38and the output-side fixed contact member39is cut off.

The switching mechanism unit4of the switching device1is activated by supplying AC power as its operating power to the power supply circuit24through the power supply lines at least on the downstream side of the leakage detecting current transformer5, for example, through the output connecting terminals6. Therefore, leakage is detected in the entire switching device1. When leakage is detected and the connection with the input connecting terminals3and the output connecting terminals is shut off, the power supply to the switching device1is also shut off.

Even if leakage is caused in the switching device1, the power supply to the switching device1is also shut off, as described above. Thus, trouble due to leakage can be avoided.

After leakage is detected and the power supply is cut off as described above, the leakage is eliminated, and the power supply from an external power source to the switching device1is resumed. Thus, the printer100can be used again. As indicated by the arrow showing the manual operation inFIG. 7, the upper surface of the arm31aof the swing handle31is pushed down, and the slide arm32and the permanent magnet33in tight contact with the slide arm32are moved toward the yoke35. As the permanent magnet33approaches the yoke35, the suction force of the permanent magnet33to the yoke35becomes greater. Even if the pushing force acting on the upper surface of the arm31aof the swing handle31is small, the swing handle31can be readily swung from an OFF state into an ON state.

As the permanent magnet33is brought into tight contact with the yoke35in the ON state shown inFIG. 5, the switching member37swings in the ON direction in conjunction with the swinging movement of the swing handle31, as shown inFIG. 6. The movable contact37bof the switching member37is then brought into contact with the fixed contact39aof the output-side fixed contact member39, and the input-side fixed contact member38is connected to the output-side fixed contact member39.

As described above, the swing handle31of the first embodiment is pushed in toward the OFF position by the return spring34, and the swing handle31moves the switching member37, which connects to or shuts the power supply lines, between the ON position and the OFF position. The permanent magnet33moves the swing handle31between the ON position and the OFF position. The permanent magnet33holds the ON state by virtue of its magnetic force by which the permanent magnet33stays in tight contact with the yoke35around which the coil36is wound. When the coil36is energized, a magnetic field is generated to magnetize the yoke35in such a manner as to reduce the magnetic force of the permanent magnet33. The swing handle31and the switching member37are then moved from the ON position to the OFF position by virtue of the pushing force of the return spring34, so that the power supply lines are shut.

Accordingly, the swing handle31can be moved in the ON direction with small operating force. Thus, usability can be increased, while s stable switching operation is maintained.

Also, in the switching device1of the first embodiment, the switching mechanism unit4is disposed on the power supply line between the external power source introducing outlet of the housing101and the device power supply unit of the printer100as an electric apparatus. When the leakage detecting current transformer5, the secondary coil13, the amplifier circuit21, and the leakage determining circuit22, which function as a leakage detecting unit, detect leakage in an internal circuit of the printer100, the coil36is energized to shut the power supply line, so that the external power supply to the device power supply unit is cut off. As the switching device1is housed as a leakage detection control device in the housing101of the printer100, a simple structure with excellent air flow can be realized. Also, excellent cooling capability can be achieved, and the printer100can be made smaller and less expensive. Further, the swing handle31located in the housing101of the printer100can be moved in the ON direction with small operating force, and accordingly, leakage detection and open/close control on the power supply line can be stably performed. Thus, higher usability can be achieved.

In this switching device1, the operating power is supplied through the power supply line at least on the downstream side of the leakage detecting current transformer5. Accordingly, leakage in the switching device1can be detected, and the external power supply can be controlled. Thus, even greater safety can be achieved.

Also, in the switching device1of this embodiment, the switching mechanism unit4and the switch drive control circuit8are disposed on the same surface of the substrate2. Accordingly, a smaller structure can be realized, and higher productivity can be achieved. Further, higher switching accuracy and greater safety can be achieved.

In the switching device1of this embodiment, the switching mechanism unit4is detachably mounted onto the substrate2. When the switching mechanism unit4deteriorates, it can be readily replaced with a new one. Accordingly, higher reliability can be achieved. Also, higher switching accuracy and greater safety can be achieved.

It should be noted that the operating member is not limited to the swing handle31in the present invention, but a slide or push operator may be employed if the structure of the switching mechanism unit4is modified.

Second Embodiment

Referring now toFIGS. 10 through 16, a second embodiment of a switching device and an electric apparatus in accordance with the present invention is described.FIG. 10is a circuit diagram of the switching device of the second embedment. The switching device30of this embodiment is the same as the switching device1of the first embodiment, except for the component equivalent to the switch drive control circuit8shown inFIG. 4. Accordingly, the structure including the switching mechanism unit4and the leakage detecting current transformer5illustrated inFIGS. 1 through 3andFIGS. 5 through 8is the same as that of the first embodiment. InFIG. 10, the same components as those shown inFIG. 4are denoted by the same reference numerals as those inFIG. 4.

As shown inFIG. 10, the switching device30of the second embodiment includes the switching mechanism unit4, the leakage detecting current transformer5, the amplifier circuit21, and the switch control circuit23that are the same as those of the first embodiment. The switching device30further includes a control block25and a power supply block40that differ from the components of the first embodiment. The control block25has the leakage determining circuit22, a voltage monitoring circuit26, and an excess voltage determining circuit27that are collectively formed in one module. The power supply block40includes a rectifying circuit41, a voltage converting circuit42, and a voltage regulating circuit43.

The switching mechanism unit4opens and closes the connection between the output-side fixed contact member39and the switching member37so as to shut or open the feed line (the power supply line) formed by the two electric cable members7that supply the alternating current input from a commercial power supply line to the input connecting terminals3to the power supply line of an electric apparatus such as the printer100shown inFIG. 9through the output connecting terminals6.

The leakage detecting current transformer5is located so that the electric cable members7penetrate its core. When leakage is caused, voltage is generated in the secondary coil (a detecting coil)13. After amplifying the voltage generated in the secondary coil13, the amplifier circuit21outputs the amplified voltage to the leakage determining circuit22of the control block25.

When the voltage input from the amplifier circuit21exceeds a predetermined leakage determining value, the leakage determining circuit22outputs a pulse signal as a leakage detection signal to the switch control circuit23. Accordingly, the leakage detecting current transformer5, the amplifier circuit21, and the leakage determining circuit22constitute the leakage detecting unit.

The control block25includes the voltage monitoring circuit26and the excess voltage determining circuit27, as well as the leakage determining circuit22. The power supply block40is described below before the control block25is described in detail.

The rectifying circuit41of the power supply block40receives AC power from a commercial power supply line and supplies rectified pulsating voltage to the internal voltage converting circuit42, the voltage regulating circuit43, and the switching mechanism unit4. The voltage regulating circuit43smoothes and regulates the pulsating voltage supplied from the rectifying circuit41. The voltage regulating circuit43then supplies DC constant voltage regulated power to the amplifier circuit21and each circuit in the control block25through a supply line45. The voltage converting circuit42converts the pulsating voltage supplied from the rectifying circuit41into lower voltage, and then outputs the pulsating voltage to the voltage monitoring circuit26of the control block25without the use of a smoothing capacitor.

The voltage monitoring circuit26receives the pulsating voltage from the voltage converting circuit42, and analog-to-digital converts the pulsating voltage into a code. The coded voltage value is output to the excess voltage determining circuit27. In the excess voltage determining circuit27, reference information for determining excess voltage, including a numerical value for determining excess voltage, acceptable values, and a determining timing adjusting value, is preset and written on a ROM, for example. The input voltage value is compared with the reference numerical values for determining excess voltage. If the input voltage value excesses the preset excess voltage value, a pulse signal is output as an excess voltage detection signal to the switch control circuit23.

Receiving a pulse signal from the leakage determining circuit22or the excess voltage determining circuit27, the switch control circuit23energizes the coil36wound around the yoke35of the switching mechanism unit4.

The return line46shown inFIG. 10is to supply a zero potential to each circuit. The arrows attached to the lines of the circuits shown inFIG. 10indicate the flow of operating current, all of which returns to the return line46.

FIGS. 11A and 11Bare timing charts showing the relationship between the full-wave rectified waveform that is output from the rectifying circuit41and the determining timing of the excess voltage determining circuit27.

FIG. 11Ashows the voltage waveform that is input from a commercial power supply line to the rectifying circuit41shown inFIG. 10, is full-wave rectified, and is output to the voltage converting circuit42and the voltage regulating circuit43. In the graph ofFIG. 11A, the ordinate axis indicates the voltage, and the abscissa axis indicates the time. The voltage value is merely an example value, while the graph shows the relationship in the case where the crest value of the output voltage of the rectifying circuit41is 180 V, and the excess voltage setting value set in the excess voltage determining circuit27is 150 V. The time 10 ms indicating the cycle of the pulsating voltage indicates a case where the frequency of the alternating current of the commercial power supply line is 50 Hz.

The reference voltage value for determining excess voltage varies with the type of the power source of the electric apparatus, but the upper limit value may be set at 40% of the tolerable peak value, for example.

Also, in the case of AC input voltage, the timing for determining excess voltage is preferably set so as to perform a determining operation on a shorter cycle than a ¼ cycle of the input voltage. However, as the cycle of the determining operation becomes shorter, the processing speed becomes lower.

The determining timing of the excess voltage determining circuit27is determined by the processing speed of the control block25. In a case where a microprocessor is used for the control block25, the operation shown in the flowchart ofFIG. 16is set as one processing cycle. When the input of the voltage monitoring circuit26exceeds 0V, the operation starts, and the operation is repeated to set the timing for determining excess voltage.FIG. 11Bshows an example of the timing for determining excess voltage. In this example, half a cycle of the input AC voltage is 10 ms (in the case of a 50-cycle AC power supply), and the cycle of the determining timing is set at approximately 1 ms.

The processing time varies depending on the processing contents. An adjustment value may be set so that the processing can be completed within 1 ms. In such a case, the determining operation can be performed ten times in half a cycle of a commercial power supply (10 ms in the case of 50 Hz). The determining timing and the determining method vary with the required type of the power source, and therefore, they are not limited to the above example.

FIG. 12shows an example of the waveform of a pulse signal (a trigger pulse) that is output from the leakage determining circuit22or the excess voltage determining circuit27of the control block25. With this pulse signal, a trigger voltage Vt is output to the switch control circuit23for a predetermined period of time, for example, 100 ms. In this example, the signal is in the form of a pulse signal, but the signal of the trigger voltage Vt may be directly output.

FIG. 13illustrates an example of the switch control circuit23, together with the yoke35around which the coil36is wound. A full-wave rectified voltage that is output from the rectifying circuit41is input to one of the ends of the coil36. The other end of the coil36is connected to the switch control circuit23.

The switch control circuit23has a thyristor23aas a switching element. In this example, a thyristor is used as a switching element, but it is possible to employ another type of switching element, such as a transistor. The anode terminal of the thyristor23ais connected to the other end of the coil36, and the cathode terminal of the thyristor23ais connected to the return line46. Further, the gate terminal of the thyristor23ais connected to the output terminals of the leakage determining circuit22and the excess voltage determining circuit27of the control block25.

A pulse signal is output as a leakage detection signal or an excess voltage detection signal from the leakage determining circuit22or the excess voltage determining circuit27of the control block25. As the pulse signal is input to the gate of the thyristor23a, the thyristor23abecomes conductive. As a result, a current path that runs from the rectifying circuit41to the coil36, to the thyristor23a, and then to the return line46, is formed in the switching mechanism unit4, and the coil36is energized.

As the coil36is energized, such a magnetic field as to reduce the magnetic force of the permanent magnet33shown inFIG. 5is generated in the yoke35. The swing handle31and the switching member37shown inFIG. 6is moved from the ON position to the OFF position by virtue of the pushing force of the return spring34. The connection between the switching member37and the output-side fixed contact member39is released as shown inFIG. 8, and the connection between the commercial power supply line and the device power supply line formed by the electric cable members7shown inFIG. 10is cut off.

As the power supply line is cut off, the AC power supply from the commercial power supply line to the rectifying circuit41is stopped, and the voltage supply to the coil36is also cut off. The thyristor23aof the switch control circuit23is turned off, accordingly.

Here, the power supply to the power supply block40, the control block25, and the switching mechanism unit4, is also cut off. Thus, the switching device30and the entire electric apparatus to which power is supplied via the switching device30can be protected from leakage and excess voltage.

The switching device30can maintain the above state, unless the swing handle31shown inFIG. 7is pushed by hand. Thus, greater safety can be achieved, compared with a case where a short-circuit relay is constantly used.

FIGS. 14 and 15illustrate examples of the voltage converting circuit42.

FIG. 14shows an example structure that includes a resistance voltage dividing circuit. In this structure, resistances R1and R2are connected in series between the output terminal of the rectifying circuit41and the return line46, and the voltage dividing point d is connected to the input terminal of the voltage monitoring circuit26. If the resistance ratio of the resistance R1to the resistance R2is 1000:1, a monitoring voltage Vd obtained by dividing the pulsating voltage by approximately 1000 is output to the voltage dividing point d, and is then input to the voltage monitoring circuit26. Here, the pulsating voltage is formed by full-wave rectifying the AC power that is supplied through the commercial power supply line and is output from the rectifying circuit41.

With the resistance values of the resistances R1and R2being R1and R2, the monitoring voltage Vd can be obtained from the following equation:
Vd=(full-wave rectified voltage)×{R2/(R1+R2)}

Here, if R1is 1000 KΩ and R2is 1 KΩ, the monitoring voltage Vd is (rectified voltage)×1/(1+1000), which is a value divided by approximately 1000.

Since the full-wave rectified voltage of a commercial power source that is output from the rectifying circuit41is too high to be input to the control block25consisting of electronic circuits, it is desirable to lower the voltage to 1/1000 or so.

FIG. 15illustrates another example structure of the voltage converting circuit42. In this structure, an insulating transformer T that includes a primary coil L1and a secondary coil L2is employed. One of the terminals of the primary coil L1of the insulating transformer T is connected to the output terminal of the rectifying circuit41, and the other terminal of the primary coil L1is connected to the return line46. Meanwhile, one of the terminals of the secondary coil L2is connected to the input terminal of the voltage monitoring circuit26, and the other terminal of the secondary coil L2is connected to the return line46. As the ratio of the winding number N1of the primary coil L1to the winding number N2of the secondary coil L2is set at approximately 1000:1, a pulsating voltage that is approximately 1/1000 of the pulsating voltage applied to the primary coil L1is induced in the secondary coil L2, and that is input as the monitoring voltage to the voltage monitoring circuit26. In this manner, with the insulating transformer T, output voltage that is formed by arbitrarily reducing the input voltage can be obtained, while insulation from the input side is maintained.

Referring now to the flowchart ofFIG. 16, the operation of the control block25illustrated inFIG. 10is described. The control block25may be formed with a microprocessor.

Once power is supplied to the electric apparatus, the control block25starts the operation shown inFIG. 16. In step S1, voltage is input from the voltage converting circuit42to the voltage monitoring circuit26.

In step S2, the voltage monitoring circuit26analog-to-digital converts the input voltage into a code, and sets monitoring timing or determining timing and sends the timing to the excess voltage determining circuit27.

In step S3, the excess voltage determining circuit27reads the voltage value of a predetermined reference voltage, and compares the input voltage with the reference voltage value to determine whether the input voltage exceeds the reference value in step S4. If the input voltage does not exceed the reference voltage value, the operation comes to an end. If the input voltage exceeds the reference voltage value, the excess voltage determining circuit27determines whether the input voltage exceeds an excess voltage tolerance value in step S5. If the input voltage does not exceed the excess voltage tolerance value, the operation comes to an end. If the input voltage exceeds the excess voltage tolerance value, the excess voltage determining circuit27determines whether the monitoring time has passed in step S6.

If the monitoring time has not passed yet, the operation returns to step S4, and the procedures of steps S4through S6are repeated. If the monitoring time has passed, the operation moves on to step S7, in which the excess voltage determining circuit27outputs a pulse signal as an excess voltage determination trigger pulse to the switch control circuit23.

In step S8, the switch control circuit23puts the thyristor23ain a conducted state. By doing so, the coil36of the switching mechanism unit4is energized, and the switching mechanism unit4is put into an OFF state. The power supply line of the electric apparatus is then shut, and the operation comes to an end.

In the second embodiment, the same modification as described in the first embodiment can be made. In the case where the switching device is mounted onto an electric apparatus, the same conditions as in the first embodiment are applied to the second embodiment.

It should be noted that the present invention is not limited to the embodiments specifically disclosed above, but other variations and modifications may be made without departing from the scope of the present invention.

This patent application is based on Japanese Priority Patent Application Nos. 2004-141245, filed on May 11, 2004, and 2005-036998, filed on Feb. 14, 2005, the entire contents of which are hereby incorporated by reference.