Switch

A switch includes a first arm that is rotatably supported, a first contact member that is provided at a free end of the first arm, a second arm that is rotatably supported, and a second contact member that is provided at a free end of the second arm and is to come into contact with the first contact member. After the first contact member and the second contact member have come into contact with each other, a point of contact between the first contact member and the second contact member is displaced with rotational motions of the first arm and the second arm.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a switch. More particularly, the present invention relates to a switch to which a pulsed high current is supplied.

2. Description of the Related Art

In a technique such as electromagnetic forming in which a metal material is plastically processed by utilizing an electromagnetic force, various kinds of forming is performed, for example, pipe expansion, flanging, pipe swaging, sheet metal forming, and so forth. In electromagnetic forming, an object of forming is positioned near an inductor, and energy charged in a capacitor is supplied as a pulsed high current to the inductor for an extremely short period of time of several milliseconds or shorter. Thus, magnetic flux is generated, and an induced current flows through the object of forming. Consequently, in accordance with the Fleming's left-hand rule, the object of forming is deformed plastically.

A gap switch as a pulsed current switch used in electromagnetic forming or the like is disclosed by Japanese Unexamined Patent Application Publication No. 2003-311434. In a gap switch, the discharging gap, i.e., the distance between electrodes, needs to be adjusted in accordance with conditions, such as humidity, of an ambient environment. Such circumstances increase the variation in the amount of deformation of the object of forming. Hence, the gap switch is not suitable for mass production.

In addition to the gap switch, Japanese Unexamined Patent Application Publication No. 2007-253182 proposes a thyratron switch, a semiconductor switch, and an ignitron switch as exemplary pulsed current switches. Among these switches, the ignitron switch is considered to be most suitable as a switch used in a mass production process in which discharge, i.e., shot, is caused for a number of times by supplying a pulsed high current to the switch.

Another option is a mechanical switch to which a current is supplied by mechanically bringing contact members into contact with each other. An exemplary mechanical switch applied to a case where a high current is used is disclosed by Japanese Unexamined Patent Application Publication No. 11-73848. In this mechanical switch, the materials of contact members have specific compositions, respectively, so that the adhesion, i.e., fusion, between the contact members is suppressed.

The degree of fusion may be reduced in the mechanical switch disclosed by Japanese Unexamined Patent Application Publication No. 11-73848. However, for example, in a case of a facility intended for mass production of electromagnetically formed products where discharge is caused successively for a number of times, the switch soon becomes unusable unless the occurrence of fusion is completely avoided, resulting in a reduction in the productivity and an increase in the cost.

SUMMARY OF THE INVENTION

The present invention provides a switch in which the occurrence of fusion between contact members is prevented so that a pulsed high current can be supplied to the switch successively for a number of times.

According to an aspect of the present invention, there if provided a switch including a first arm that is rotatably supported, a first contact member that is provided at a free end of the first arm, a second arm that is rotatably supported, and a second contact member that is provided at a free end of the second arm and is to come into contact with the first contact member. After the first contact member and the second contact member have come into contact with each other, a point of contact between the first contact member and the second contact member is displaced with rotational motions of the first arm and the second arm.

The switch according to the above aspect of the present invention may further include a displacing mechanism that displaces the point of contact. Furthermore, the displacing mechanism may displace the point of contact by causing the first arm to rotate in such a manner as to push back the second arm after the first contact member and the second contact member have come into contact with each other.

In the switch according to the above aspect of the present invention, the displacing mechanism may include an elastic member that applies, to the first arm, an elastic force that pushes back the second arm.

In the switch according to the above aspect of the present invention, an axis of rotation of the first arm and an axis of rotation of the second arm may be positioned on opposite sides with respect to the point of contact between the first contact member and the second contact member, or the axis of rotation of the first arm and the axis of rotation of the second arm may be positioned on the same side with respect to the point of contact between the first contact member and the second contact member.

The switch according to the above aspect of the present invention may further include an annular member that surrounds an area where the first contact member and the second contact member are to come into contact with each other.

In the switch according to the above aspect of the present invention, the annular member may be made of a resin material.

The switch according to the above aspect of the present invention may further include a housing that houses the first arm, the second arm, and the annular member.

In the switch according to the above aspect of the present invention, the housing may have a gas inlet.

In the switch according to the above aspect of the present invention, air in the housing may have been replaced with an inert gas or hydrogen gas.

According to the above aspect of the present invention, a switch to which a pulsed high current can be supplied successively for a number of times is provided.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of the present invention will now be described in detail. The present invention is not limited to the following embodiments.

First Embodiment

A switch1according to a first embodiment of the present invention will first be described.FIGS. 1A to 1Care schematic front views of the switch1according to the first embodiment. In the following description, directions are defined as follows with reference to the axes illustrated inFIGS. 1A to 1C: the positive side in the X-axis direction corresponds to the front side, the negative side in the X-axis direction corresponds to the rear side, the positive side in the Y-axis direction corresponds to the right side, the negative side in the Y-axis direction corresponds to the left side, the positive side in the Z-axis direction corresponds to the upper side, and the negative side in the Z-axis direction corresponds to the lower side. In addition, in the following description, the positive and negative X-axis directions are collectively referred to the depth direction, the positive and negative Y-axis directions are collectively referred to as the horizontal direction, and the positive and negative Z-axis directions are collectively referred to as the height direction.

The switch1according to the first embodiment is applicable to a case where accumulated energy is discharged for a short time, and is suitable for a case where a pulsed high current is supplied to the switch. Specifically, as illustrated inFIGS. 1A to 1C, the switch1includes a first arm3, a first contact member4, a second arm5, and a second contact member6.

The first arm3extends from the upper side toward the lower side. The first arm3has, excluding a lower end thereof, a long plate-like shape with a predetermined width in the depth direction. The first arm3is rotatably supported at the lower end thereof. Specifically, the lower end of the first arm3serves as a first supported portion31having a rectangular shape in front view. The first supported portion31is provided with a first supporting shaft311extending therethrough in the depth direction. The first supporting shaft311serves as an axis of rotation of the first arm3.

The first arm3is rotatably supported at the first supported portion31by the first supporting shaft311. The first supporting shaft311is fixed to a position of the switch1that is predetermined for the fixation of the first supporting shaft311.

The first arm3is made of a conducting material. The conducting material is preferably metal from a viewpoint of providing satisfactory conductivity and strength, or more preferably copper, a copper alloy, tungsten, or the like. The copper alloy is preferably brass or the like from viewpoints of cost, easiness of processing, and so forth. The first supporting shaft311is preferably made of an insulating material from a viewpoint of insulation from the first arm3. The insulating material may be fiber reinforced plastic (FRP) or the like. From a viewpoint of allowing the first arm3to rotate smoothly, a lubricator is preferably provided between the first supporting shaft311and the first arm3. The lubricant may be grease or the like.

The first contact member4is provided at a free end, i.e., an upper end, of the first arm3. Specifically, the first contact member4is rotatable together with the first arm3that supports the first contact member4. The first contact member4is provided at the upper end and on a right side face of the first arm3and projects from the first arm3toward the right side.

The shape of the first contact member4is not limited and may be any shape such as a substantially round column-like shape or a substantially rectangular column-like shape. A right side face41of the first contact member4is preferably a flat surface from a viewpoint of smoothly displacing a point of contact P between the first contact member4and the second contact member6, which will be described separately below. The right side face41of the first contact member4preferably has as large an area as possible from a viewpoint of appropriately allowing a current to flow between the two contact members4and6by minimizing the influence of skin effect caused by high-frequency discharge that may occur between the contact members4and6.

The first contact member4is made of a conducting material. The conducting material is preferably metal from a viewpoint of providing satisfactory conductivity and strength, or more preferably copper, a copper alloy, tungsten, or the like. The copper alloy is preferably brass from viewpoints of cost, easiness of processing, unlikeliness of melting of the first contact member4, and so forth.

The second arm5extends from the lower side toward the upper side. The second arm5has, excluding an upper end thereof, a long plate-like shape with a predetermined width in the depth direction. A lower end of the second arm5is on the right side with respect to the upper end of the first arm3. The second arm5is rotatably supported at the upper end thereof. Specifically, the upper end of the second arm5serves as a second supported portion51having a rectangular shape in front view. The second supported portion51is provided with a second supporting shaft511extending therethrough in the depth direction. The second supporting shaft511serves as an axis of rotation of the second arm5.

The second arm5is rotatably supported by the second supporting shaft511. The second arm5is made of the same conducting material as the first arm3. The second supporting shaft511is preferably made of an insulating material, such as fiber reinforced plastic, from a viewpoint of insulation from the second arm5. From a viewpoint of allowing the second arm5to rotate smoothly, a lubricator, such as grease, is preferably provided between the second supporting shaft511and the second arm5.

The second contact member6is provided at a free end, i.e., the lower end, of the second arm5. Specifically, the second contact member6is rotatable together with the second arm5that supports the second contact member6. The second contact member6is provided at the lower end and on a left side face of the second arm5and projects from the second arm5toward the left side. The second contact member6faces the first contact member4from the right side. The shape of the second contact member6is not limited and may be any shape such as a substantially round column-like shape or a substantially rectangular column-like shape. The second contact member6is made of the same conducting material as the first contact member4.

The second contact member6is to come into contact with the first contact member4. The second contact member6and the first contact member4in combination allow the first arm3and the second arm5to be electrically continuous with each other.

The switch1is configured such that, after the first contact member4and the second contact member6come into contact with each other, the point of contact P between the two contact members4and6is displaced, i.e., moved, with the rotational motions of the first arm3and the second arm5. To displace the point of contact P between the contact members4and6, the speeds and the directions of rotation or the torques of the arms3and5, the angle between the first contact member4and the second contact member6at the contact between the contact members4and6, or the like may be adjusted according to need. Alternatively, a mechanism that displaces the point of contact P between the first contact member4and the second contact member6may be added.

As illustrated inFIG. 1B, the first supporting shaft311and the second supporting shaft511are positioned on opposite sides with respect to the point of contact P between the first contact member4and the second contact member6. The positional relationship between the two supporting shafts311and511that are on the opposite sides with respect to the point of contact P is retained regardless of the displacement of the point of contact P. In such a configuration, the width of the switch1can be reduced, and the size of the switch1as a whole can be reduced.

As illustrated inFIGS. 1A to 1C, a first lead wire17is connected to the lower end of the first arm3, and a second lead wire18is connected to the upper end of the second arm5. The first lead wire17and the second lead wire18are connected to a power supply and a load (both not illustrated). The load may be an inductor intended for electromagnetic forming, or the like. The lead wires17and18may each be a multi-conductor round cable or the like.

Exemplary Operation of Switch1

An exemplary operation of the switch1will now be described. In the initial state illustrated inFIG. 1A, the first contact member4and the second contact member6are out of contact with each other, and no pulsed current flows therebetween.

When, for example, a power is transmitted from a power source (not illustrated) to the first arm3and the second arm5that are in the initial state, the arms3and5rotate. In this step, the first arm3rotates clockwise inFIG. 1Aabout the first supporting shaft311, and the second arm5also rotates clockwise inFIG. 1Aabout the second supporting shaft511. The two broken-line arrows illustrated inFIG. 1Aindicate the directions of rotation of the respective arms3and5.

With such rotational motions of the first arm3and the second arm5, referring now toFIG. 1B, the first contact member4and the second contact member6start to come into contact with each other. In this step, the point of contact P between the contact members4and6is on the left side, i.e., on a side nearer to the first contact member4, with respect to a virtual line L connecting the center of the first supporting shaft311and the center of the second supporting shaft511. In the state illustrated inFIG. 1B, the point of contact P between the contact members4and6is defined by a point near the lower end of the right side face41of the first contact member4and the lower end of a left side face61of the second contact member6. Depending on the sizes of the contact members4and6or other conditions, the lower end of the right side face41of the first contact member4may come into contact with a point near the lower end of the left side face61of the second contact member6.

The point of contact P in the state illustrated inFIG. 1Bwhere the contact members4and6start to come into contact with each other may be established by, for example, making the speed of rotation of the second arm5higher than that of the first arm3. In that case, as illustrated inFIGS. 1A and 1B, it is preferable that the first arm3be rotated in a direction against the gravitational force acting on the first contact member4, i.e., clockwise, and the second arm5be rotated in a direction of the gravitational force acting on the second contact member6, i.e., clockwise. Thus, the gravitational force acting on the first contact member4acts in such a direction as to prevent the rotation of the first arm3, while the gravitational force acting on the second contact member6acts in such a direction as to promote the rotation of the second arm5. Hence, a difference in the speed of rotation between the arms3and5can be produced efficiently.

In the state illustrated inFIG. 1B, the first arm3and the second arm5are electrically continuous with each other and are also electrically continuous with the external power supply via the respective lead wires17and18connected thereto. Therefore, a pulsed current flows between the first arm3and the second arm5on the basis of the energy generated by the power supply.

After the step illustrated inFIG. 1B, the first arm3further rotates clockwise, whereby, referring now toFIG. 1C, the first contact member4and the second contact member6move to respective positions where the displacement of the point of contact P therebetween ends. In this state, the point of contact P between the contact members4and6lies on the virtual line L. In this state, the entirety of the right side face41of the first contact member4and the entirety of the left side face61of the second contact member6may be in surface contact with each other.FIG. 1Cillustrates a state where the displacement of the point of contact P has ended and the contact members4and6are in surface contact with each other in the area encircled by the dash-dot line.

The state illustrated inFIG. 1Cwhere the displacement of the point of contact P between the contact members4and6has ended is established in a configuration in which the direction of rotation of the second arm5is reversed, i.e., changed to the counterclockwise direction, at the point of time illustrated inFIG. 1B.

Then, the first arm3and the second arm5that are in the state illustrated inFIG. 1Care rotated counterclockwise by, for example, controlling the power source, whereby the first arm3and the second arm5are returned to the respective initial positions (as illustrated inFIG. 1A). Thereafter, the change to the state illustrated inFIG. 1B, to the state illustrated inFIG. 1C, and to the state illustrated inFIG. 1Ais repeated sequentially.

When the first contact member4and the second contact member6come into contact with each other, a discharge (a spark) may occur in the gap between the contact members4and6because of the potential difference between the contact members4and6, and the discharge may partially melt the contact members4and6. If such melted portions of the contact members4and6are solidified while the contact members4and6are in contact with each other, the contact members4and6are fused to each other.

However, in the switch1according to the first embodiment, as illustrated inFIGS. 2A to 2C, the point of contact P between the first contact member4and the second contact member6continues to be displaced during a period from when the contact members4and6start to come into contact with each other (as illustrated inFIG. 2A) until when the displacement of the point of contact P ends (as illustrated inFIG. 2C). More specifically, in the case illustrated inFIGS. 2A to 2C, the point of contact P is displaced downward with time. The broken-line arrow illustrated inFIG. 2Aindicates the direction of displacement of the point of contact P. Thus, the melted portions of the contact members4and6are prevented from being solidified while being in contact with each other. Therefore, the contact members4and6are not fused to each other. The direction of displacement of the point of contact P between the first contact member4and the second contact member6is not limited to the downward direction as illustrated inFIGS. 2A to 2Cand may be, for example, the depth direction.

As described above, in the switch1according to the first embodiment, the point of contact P between the first contact member4and the second contact member6is displaced with the rotational motions of the first arm3and the second arm5, whereby the contact members4and6are prevented from being fused to each other. Hence, the contact members4and6can be brought into contact with and moved away from each other repeatedly. Accordingly, a pulsed high current can be supplied to the switch1successively for a number of times.

Furthermore, in the switch1according to the first embodiment, the contact members4and6start to come into contact with each other in a state where no axial compressive forces are applied to the contact members4and6, i.e., in a state where the side faces41and61of the contact members4and6are tilted with respect to each other (seeFIG. 1B). Hence, the contact members4and6are more effectively prevented from being fused to each other.

Furthermore, in the switch1according to the first embodiment, as the contact members4and6repeatedly come into contact with each other and thus melt, the shapes of the contact members4and6gradually change. Hence, the point of contact P established when the contact members4and6start to come into contact with each other changes every time the current is supplied to the switch1. Thus, the contact members4and6are prevented from melting away concentratedly in specific portions thereof. Consequently, the life of the switch1is extended.

Second Embodiment

A switch12according to a second embodiment of the present invention will now be described.FIG. 3is a front view of the switch12according to the second embodiment of the present invention.

The switch12according to the second embodiment has a more specific configuration than the switch1according to the first embodiment.

Specifically, as illustrated inFIG. 3, the switch12includes a housing2that houses the elements3to6and17and18described in the first embodiment.FIG. 3illustrates the switch12with a front wall (not illustrated) of the housing2being open. The front wall may be openably and closably supported by opening/closing members200such as hinges.

As illustrated inFIG. 3, the first arm3is provided at a position in the housing2that is near a bottom wall21of the housing2. The first arm3is rotatably supported by the first supporting shaft311that is fixed to a rear wall22of the housing2.

As illustrated inFIG. 3, the second arm5is provided at a position in the housing2that is near an upper wall23of the housing2. The second arm5is rotatably supported by the second supporting shaft511that is fixed to the rear wall22of the housing2.

As illustrated inFIG. 3, the switch12includes an arm-moving mechanism7that moves the first arm3and the second arm5.

The configuration of the arm-moving mechanism7is not limited and may include, as illustrated inFIG. 3, an arm-moving shaft71, a first arm-connecting member72, a second arm-connecting member73, and three elastic members74ato74c.

The arm-moving mechanism7illustrated as an example inFIG. 3will further be described. As illustrated inFIG. 3, the arm-moving shaft71has a long shape extending in the height direction and is supported in the housing2in such a manner as to be vertically slidable.

The three elastic members74ato74ceach exert an elastic force against a compressive force applied thereto from an external device. The elastic members74ato74cmay each be, but is not limited to, a compression spring, a rubber cushion, an air damper, or the like. The elastic members74ato74care provided at different positions of the arm-moving shaft71in such a manner as to exert their elastic forces in the axial direction of the arm-moving shaft71.

Specifically, the elastic member74a(hereinafter referred to as the first elastic member74a) is provided at an upper end of the arm-moving shaft71in such a manner as to surround the arm-moving shaft71. More specifically, an upper end of the first elastic member74ais connected to a lower end face of a first flange751that is fixed to the outer circumference of the arm-moving shaft71, and a lower end of the first elastic member74ais connected to a right end of the second arm-connecting member73. The right end of the second arm-connecting member73is connected to the first elastic member74awhile surrounding the arm-moving shaft71. The right end of the second arm-connecting member73is also in contact with an upper end face of a second flange752that is fixed to the outer circumference of the arm-moving shaft71.

The elastic member74c(hereinafter referred to as the third elastic member74c) is provided at a lower end of the arm-moving shaft71in such a manner as to surround the arm-moving shaft71. More specifically, an upper end of the third elastic member74cis connected to a lower end face of a fourth flange754that is fixed to the outer circumference of the arm-moving shaft71, and a lower end of the third elastic member74cis connected to the bottom wall21of the housing2.

The elastic member74b(hereinafter referred to as the second elastic member74b) is provided at a position of the arm-moving shaft71that is above and near the third elastic member74cin such a manner as to surround the arm-moving shaft71. More specifically, an upper end of the second elastic member74bis connected to a lower end face of a third flange753that is fixed to the outer circumference of the arm-moving shaft71, and a lower end of the second elastic member74bis connected to a right end of the first arm-connecting member72. The right end of the first arm-connecting member72is connected to the second elastic member74bwhile surrounding the arm-moving shaft71. The right end of the first arm-connecting member72is also in contact with an upper end face of the fourth flange754.

The first elastic member74aand the second elastic member74bin combination function as a displacing mechanism that displaces the point of contact P between the first contact member4and the second contact member6. The displacing mechanism will be described in detail separately below.

When no external force is applied to the arm-moving shaft71, the arm-moving shaft71is retained at the upper extreme end of its slidable range with the elastic force exerted by the third elastic member74c. It is possible to apply to the arm-moving shaft71a downward external force that is greater than the upward elastic force exerted by the third elastic member74c. For example, a magnetically acting unit (not illustrated) including a ferromagnetic member or the like may be provided to the arm-moving shaft71, and a solenoid that generates a magnetic field extending in the axial direction of the arm-moving shaft71may also be provided around the magnetically acting unit, so that the magnetically acting unit can generate a downward magnetic force. In such a configuration, to avoid damaging the solenoid with the leakage of the current from the arms3and5while the current is supplied to the switch12, the arm-moving shaft71is preferably made of an insulating material. The insulating material is preferably fiber reinforced plastic or the like from viewpoints of providing satisfactory strength to the arm-moving shaft71, reducing the weight of the arm-moving shaft71, and so forth.

The first arm-connecting member72connects the first arm3to a position of the arm-moving shaft71that is near the lower end of the arm-moving shaft71. As described above, the first arm-connecting member72and the arm-moving shaft71are connected to each other with the second elastic member74binterposed therebetween. The first arm-connecting member72is preferably made of fiber reinforced plastic or the like from viewpoints of insulation from the first arm3and providing satisfactory strength to the first arm-connecting member72.

The second arm-connecting member73connects the second arm5to a position of the arm-moving shaft71that is near the upper end of the arm-moving shaft71. As described above, the second arm-connecting member73and the arm-moving shaft71are connected to each other with the first elastic member74ainterposed therebetween. The second arm-connecting member73is preferably made of fiber reinforced plastic or the like from viewpoints of insulation from the second arm5and providing satisfactory strength to the second arm-connecting member73.

In addition to the above configuration, the housing2may have a gas inlet80as illustrated inFIG. 3. Furthermore, air in the housing2may be replaced with an inert gas or hydrogen gas supplied into the housing2from an external gas supply source through the gas inlet80. The inert gas may be nitrogen gas, argon gas, or the like. In such a configuration, the contact members4and6are prevented from being oxidized, and the generation of a spark at the discharge between the contact members4and6is suppressed. The housing2may also have a gas outlet81.

If the gas supplied into the housing2is heavier than air, the gas inlet80is preferably provided at a position near the bottom of the housing2, and the gas outlet81is preferably provided at a position near the top of the housing2as illustrated inFIG. 3. In such a configuration, after the housing2is fully filled with the gas, an extra amount of gas is exhausted from the housing2. Therefore, the contact members4and6are more effectively prevented from being oxidized, and the generation of a spark at the discharge between the contact members4and6is more effectively suppressed.

The contact members4and6are preferably attachable to and detachable from the respective arms3and5from viewpoints of easiness of maintenance, easiness of assembling, and so forth. In such a configuration, the contact members4and6may be attached to or detached from the arms3and5by a simple work of fastening or loosening female screws provided to the respective arms3and5and male screws provided to the contact members4and6. In such a case, as illustrated inFIG. 3, the outer surface of each of the contact members4and6may include a flat surface4aor6aso that a wrench used in attaching or detaching the contact member4or6can easily catch the contact member4or6.

Furthermore, fins for radiating heat of the contact members4and6may be provided on the arms3and5.

Furthermore, the power source provided for the arm-moving shaft71is not limited to a solenoid and may be any of other various power sources that are capable of vertically moving the arm-moving shaft71.

Exemplary Operation of Switch12

An exemplary operation of the switch12according to the second embodiment will now be described. In the switch12according to the second embodiment, the initial state illustrated inFIG. 1Ais established by the elastic force, i.e., an upward force, exerted by the third elastic member74cand acting on the arm-moving shaft71.

Subsequently, the state illustrated inFIG. 1Bin which the first contact member4and the second contact member6start to come into contact with each other is established by a downward external force acting on the arm-moving shaft71. Specifically, the downward external force acting on the arm-moving shaft71moves the arm-moving shaft71downward against the elastic force exerted by the third elastic member74c. In this step, the third elastic member74cfunctions as a damper and stabilizes downward movement of the arm-moving shaft71. Then, with the downward movement of the arm-moving shaft71, the first arm3connected to the arm-moving shaft71rotates clockwise inFIG. 3about the first supporting shaft311, and the second arm5connected to the arm-moving shaft71rotates clockwise inFIG. 3about the second supporting shaft511. Thus, the contact members4and6come into contact with each other. The downward external force acting on the arm-moving shaft71may be applied repeatedly at regular time intervals by intermittently supplying a current to the solenoid from a power supply device (not illustrated).

Subsequently, the first elastic member74aand the second elastic member74b, which in combination function as an exemplary displacing mechanism, displaces the point of contact P between the first contact member4and the second contact member6as illustrated inFIGS. 2A to 2C. Specifically, when the arm-moving shaft71in the state where the contact members4and6start to come into contact with each other (seeFIG. 1B) is further moved downward, the downward forces applied to the upper ends of the first elastic member74aand the second elastic member74bfrom the respective flanges751and753increase.

Hence, the first elastic member74aand the second elastic member74bare compressed from above. In response to this, the first elastic member74aand the second elastic member74bexert restoring forces, respectively, so as to resist the compression. Specifically, the first elastic member74aexerts a force that pushes down the second arm-connecting member73connected to the lower end of the first elastic member74a. That is, the first elastic member74aexerts an elastic force that causes the second arm5to further rotate clockwise. Meanwhile, the second elastic member74bexerts a force that pushes down the first arm-connecting member72connected to the lower end of the second elastic member74b.That is, the second elastic member74bexerts an elastic force that causes the first arm3to further rotate clockwise.

In this step, the elastic force exerted by the second elastic member74bis larger than the elastic force exerted by the first elastic member74abecause of the difference between the elastic moduli of the respective elastic members74aand74b,and so forth. Hence, the clockwise rotation of the first arm3overrides the clockwise rotation of the second arm5. Hence, the second arm5is pushed back by the first arm3at the point of contact P between the contact members4and6and rotates counterclockwise. Thus, the point of contact P between the contact members4and6is displaced downward, whereby the state illustrated inFIG. 1Cis established. The mechanism of causing the first arm3to push back the second arm5is not limited to the above mechanism.

After the state illustrated inFIG. 1Cis established, the application of the downward external force to the arm-moving shaft71is stopped, whereby the arm-moving shaft71is moved upward by the elastic force exerted by the third elastic member74c. With the upward movement of the arm-moving shaft71, the first arm3and the second arm5return to their initial positions (as illustrated inFIG. 1A).

In the switch12according to the second embodiment, the displacing mechanism (the elastic members74aand74b) causes the first arm3to rotate in such a manner as to push back the second arm5at the contact between the contact members4and6, whereby the point of contact P between the contact members4and6is displaced simply and assuredly. Furthermore, the displacing mechanism (the elastic members74aand74b) includes the second elastic member74bthat applies to the first arm3an elastic force that pushes back the second arm5. Therefore, the point of contact P is displaced with a simple mechanism and at a low cost. Furthermore, since the displacing mechanism (the elastic members74aand74b) is included in the arm-moving mechanism7, the configuration of the switch12is more simplified. Furthermore, since the first supporting shaft311and the second supporting shaft511are positioned on the opposite sides with respect to the point of contact P between the contact members4and6, one arm-moving shaft71included in the arm-moving mechanism7is used for moving both the first arm3and the second arm5. Accordingly, the number of components is reduced.

Third Embodiment

A switch13according to a third embodiment of the present invention will now be described.FIG. 4illustrates a configuration of the switch13according to the third embodiment of the present invention.

The switch13according to the third embodiment differs from the switch1according to the first embodiment in the relative positions of the first supporting shaft311and the second supporting shaft511with respect to the point of contact P between the first contact member4and the second contact member6. Specifically, as illustrated inFIG. 4, the third embodiment concerns a case where the first supporting shaft311and the second supporting shaft511are provided on the same side, more specifically, on the upper side inFIG. 4, with respect to the point of contact P.

Furthermore, as illustrated inFIG. 4, the right side face41of the first contact member4slopes with respect to the longitudinal direction of the first arm3, and the left side face61of the second contact member6slopes with respect to the longitudinal direction of the second arm5.

In the switch13according to the third embodiment, the first arm3and the second arm5rotate in the opposite directions so as to bring the first contact member4and the second contact member6into contact with each other. Specifically, the first arm3rotates counterclockwise inFIG. 4while the second arm5rotates clockwise inFIG. 4, whereby the first contact member4and the second contact member6come into contact with each other.

The switch13according to the third embodiment is suitable for a case where the height of the switch needs to be reduced.

Fourth Embodiment

A switch14according to a fourth embodiment of the present invention will now be described.FIG. 5illustrates a configuration of the switch14according to the fourth embodiment of the present invention.

The switch14according to the fourth embodiment differs from the switch12according to the second embodiment only in, as illustrated inFIG. 5, further including an annular member20that surrounds an area where the first contact member4and the second contact member6are to come into contact with each other. The annular member20, together with the first arm3and the second arm5, is housed by the housing2(seeFIG. 3).

The annular member20is preferably made of an insulating material from a viewpoint of providing a satisfactory insulating characteristic, or more preferably made of a fluorocarbon resin from a viewpoint of providing satisfactory resistance to heat and impact. The fluorocarbon resin may be polytetrafluoroethylene or the like.

In the switch14according to the fourth embodiment, the annular member20protects the housing2from a jet stream produced at the contact between the first contact member4and the second contact member6. Furthermore, even if some melted metal composing the contact members4and6is scattered by the jet stream, the scattering is suppressed within the annular member20.

The annular member20may also be applied to the switch13according to the third embodiment.