JPS633433B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method and apparatus for supplying electricity and water to a heating coil.

Heating coils used when induction heating objects to be heated often have to be self-cooled to suppress heat generation caused by current. In addition, the heating coil used when the heated surface of the heated object is immediately quenched and quenched after induction heating of the heated object has a heating ring made of a tubular body, or integrated with the heating ring. In many cases, the quenching cooling liquid is injected onto the heated surface from cooling liquid injection holes provided on the inner peripheral surface or one end surface of the cooling ring.

For self-cooling of the heating coil, conventionally e.g.
As shown in Fig. 1, the lead portion R of the heating coil C extends from the connection portion of the input terminal IT on one side surface toward the ring portion Cr, and then extends along the side surface of the ring portion.
A copper pipe P that goes around the end face of the Cr and extends along the other side of the lead part R toward the connection part.
Connect the cooling water supply hose Hi to one opening of the copper pipe P and the cooling water drainage hose Ho to the other opening of the copper pipe P, and connect the lead part R and the ring part with the cooling water flowing through the copper pipe P. A method for extracting heat generated from Cr. A cooling water circulation path is provided in the ring part, and the lead part R
Copper pipes running along both sides of the pipe are connected to the cooling water circulation path, and a cooling water supply hose and a cooling water discharge hose are connected to the openings at the other end of each copper pipe to supply water, and the leads are connected in the same way as above. The heat generated by the lead part and the ring part Cr is absorbed through the flow path, or the lead part R is brazed with copper pipes that allow cooling water to circulate on both sides, and the opening at one end of each copper pipe is used to supply cooling water. A cooling water discharge hose is connected to the opening at the other end of the hose, and the cooling water passage in the ring part Cr pipe is connected to the end face or outer peripheral surface of the ring part Cr at a position sandwiching the lead part R near the connection part with the lead part R. A cooling water supply hose and a cooling water discharge hose are connected to each of the nipples, and cooling water is passed through each copper pipe to connect the lead part R and the cooling water of the ring part Cr. There are various methods, such as cooling each ring individually by passing cooling water through the passages, and the appropriate method is selected depending on the conditions such as whether or not there is a dedicated cooling ring for quenching, jetting cooling liquid, heat generation state, and other conditions. It is used.

In addition, in order to inject a cooling liquid for quenching (hereinafter referred to as quenching liquid) from the injection hole of the heating ring of the heating coil or the cooling ring that is attached integrally with the heating ring, quenching is performed in the pipe of the heating ring or cooling ring. When supplying the quenching liquid to the liquid inflow path, conventionally, for example, one or more nipples N communicating with the quenching liquid inflow path are provided on the outer periphery of the ring part Cr or on the end face, as shown in FIG. Each of the nipples N was connected to the quenching fluid supply hose HQ.

Therefore, a large number of hoses H are connected to the heating coil C for supplying and discharging cooling water for self-cooling and for supplying cooling liquid for quenching, and for this reason, there are many hoses H around the heating coil. Not only does the hose H hang down and get in the way of heat treatment work, impeding work efficiency, but when replacing the heating coil, it takes time to attach and detach the hose H, and during that time the heat treatment equipment is not operating, resulting in high efficiency equipment operation. There was a drawback that I couldn't do it.

Furthermore, in the conventional heating coil, as shown in Fig. 1, a flat plate-shaped input terminal IT fixed at right angles to the end face of the lead part R opposite to the ring part Cr is used as a power supply side output terminal.
The structure is such that it is electrically connected to the OT by crimping it with bolts, and the bolts mentioned above are attached to the input terminals, which are unthreaded holes or long holes in the screw holes S of the power supply side output terminals OT. Overlap the IT hole h,
A length that passes through the hole h and reaches the screw hole S,
This is done using a bolt that can be screwed into the screw hole S. By the way, when replacing this type of heating coil C, multiple bolts are used, which not only makes the work difficult, but also causes the absolute position of the heating coil attached to the heat treatment equipment to shift each time the heating coil is replaced. If the absolute position is to be always ensured, adjustment is extremely difficult and time consuming, and a solution has been sought.

The present invention has been made for the purpose of solving many of the problems of the conventional heating coils mentioned above all at once, and it is possible to electrically connect the heating coil to the power supply side with a single touch, and to connect the heating coil to the heating coil for self-cooling and/or self-cooling. Alternatively, it is also possible to connect a passageway for hardening.

The gist of the present invention is that one side of an L-shaped conductor is fixed to a power supply side output terminal, and one surface of a lead part of a heating coil can be pressed into contact with and separated from one of the surfaces of the other side. A method for supplying electricity and water to a heating coil, characterized in that when the other side part and the lead part of the heating coil come into contact, electrical connection and fluid passage connection are made simultaneously through the contact surface. and equipment.

The details of the present invention will be explained using FIGS. 2a to 3b.

FIG. 2a shows an embodiment of the invention. 1 in the right block of the figure is a conductor made of two L-shaped conductive materials, such as copper, which are fixed in parallel with an insulating material 2 in the center. The outer surface of one side 1a of the power supply side output terminal OT surface is overlapped and tightened with a plurality of bolts 11. Therefore, the other side portion 1b is in a state of protruding forward approximately at right angles to the power supply side output terminal. On the inner surface of the side portion 1b, there are predetermined grooves extending parallel to each other at a predetermined interval from the protruding end toward the continuous portion with the side portion 1a along both edges in the protruding direction, with the insulating material 2 as the axis of symmetry. Guide bars 3 and 3 made of at least a non-magnetic material having a length, width and thickness are fixed, and both electrical circuit members (hereinafter simply electrical circuit A stopper 31 made of an insulating material is fixed across the entire length.
Therefore, the inner surface of the side portion 1b is defined by guide bars 3, 3 and a stopper 31,
In addition, the insulating material 2 is held in the center to ensure a sufficiently smooth surface portion A with a predetermined area and a sufficiently smooth finish, which has an electric path divided into two and is open only in the direction of the protruding end.

There is a presser 4 above the approximate center of the smooth surface portion A, and the presser 4 has an upper frame 51 and a lower frame 52 that sandwich the conductor 1 from above and below, and an upper frame 51 and a lower frame 52. Multiple columns 53 to be connected
It is fixed to the tip of the rod 42 of the pressing mechanism 41 mounted on the upper frame 51 of the frame body 5 consisting of.
By moving the lever 43 of the pressing mechanism 41 up and down as shown by the arrows, the rod 42 moves backward and forward, thereby displacing the presser 4 upward and downward, and when displaced upward, the lower surface of the presser 4 and the smooth surface The distance between the pusher 4 and the smooth surface section A is sufficiently wide, and when the pusher 4 is displaced downward, a predetermined pressing force can be exerted by using the space between the lower surface of the pusher 4 and the smooth surface section A as the gap. In this case, the lower frame 52 has the role of preventing the pressing force caused by the downward displacement of the presser, which will be described later, from deforming or destroying the conductor, which has relatively low rigidity.

Each of the electric circuits sandwiching the insulating material 2 of the conductor 1 has through holes 6 and 7 with one end opening at a predetermined position 61 and 71 of the smooth surface portion A, respectively, with the insulating material 2 as an axis of symmetry. It is set up. In the embodiment, the through holes 6 in each of the electric circuits are cooling water passages for self-cooling (hereinafter referred to as cooling water passages), and the other end 62 is open at the side end surface of the side portion 1a, and the through holes 6 in each of the electric circuits are formed three times at approximately right angles. The through hole 7 is a cooling liquid passage for quenching (hereinafter referred to as a quenching liquid passage), and the other end 72 is open at the side end surface of the side part 1b, and the through hole 7 is bent at a substantially right angle. It is refracted once and reaches the smooth surface portion A.
The cooling water passage 6 and the quenching liquid passage 7 each have a predetermined cross-sectional area.
O-rings are fitted into each of 71 and 71, and holes 62, 62, 72 and 7 at the other end are fitted.
Nipples 63, 63, 73 and 73 are fitted into each of the two. The other end of a hose (not shown), one end of which connects to a cooling water supply source for self-cooling, is inserted into the nipple 63 fitted in the cooling water passage 6 of one of the electric circuits, and the other end of the hose (not shown) is inserted into the nipple 63 fitted in the cooling water passage 6 of one of the electric circuits. The other end of a hose with one end serving as a discharge port is inserted into the nipple 63 attached to the hose. Also, nipples 73 installed in the quenching fluid passages 7 of both electric circuits,
The other end of a hose (not shown), one end of which is connected to a cooling liquid supply source for quenching, is inserted into each of the hoses 73.

The left block in the figure is a heating coil, and in this case, the heating coil C has a cooling water circulation path for self-cooling (hereinafter referred to as cooling water circulation path) 8 in the pipe of the ring portion Cr.
This is a type consisting only of a heating ring with a cooling liquid inflow path for quenching (hereinafter referred to as a quenching liquid inflow path) 9. However, as a feature of the present invention, there is no plate-shaped input terminal (IT seen in FIG. 1) on the end surface of the lead portion R opposite to the ring portion connection, which was always provided in conventional heating coils.

The lead part R has a parallelepiped shape except for the connecting part with the ring part Cr, and at least the lower surface side B is finished sufficiently smooth, and its length is equal to that of the smooth surface part A of the conductor 1. It is formed so that it is sufficiently longer than the depth regulated by the stopper 31 in the direction along the guide bar 3, the width is almost the same as the spacing between the guide bars 3, and the thickness is a predetermined thickness that is thicker than the thickness of the guide bar. has been done. It goes without saying that an insulating material 2 is clamped at the center in the length direction, and the insulating material 2 insulates each electric path of the lead portion R.

Cooling water passages 66, 66 and quenching liquid passages 77, 77 penetrating through the member are provided in each of the electrical circuits of the lead portion R, and have the same cross-sectional area as that of the conductor 1, and cooling water in each electrical circuit is provided. One ends 661, 661 of the water passages 66, 66 open at a predetermined position on the lower surface B of the electric circuit, and the other ends 662, 662 open into the cooling water circulation path 8 of the ring part Cr at the connection part. Quenching liquid passage 7 in each electrical circuit
One ends 771, 771 of 7, 77 are opened at a predetermined position on the lower surface B side of the electric circuit, similar to the above-mentioned cooling water passage, and the other ends 772, 772 are opened into the quenching liquid inlet passage 9 of the ring part Cr in the connection part. There is. O-rings are fitted into each of the holes 661, 661, 771 and 771 on the lower surface B of the electric circuit. Further, the positional relationship and spacing between the holes 661, 661, 771 and 771 on the lower surface B of the electric circuit are the same as the positional relationship and spacing between the holes 61, 61, 71 and 71 on the smooth surface portion A of the conductor 1. As if they were the same,
And the length from the end surface of the lead portion R in the opposite direction to the ring portion to each hole is the same as the length from the side surface of the stopper 31 that partitions the smooth surface portion A to each hole in the smooth surface portion A. Specifications are set.

A case in which the left and right blocks having the above configuration are combined will be described below.

First, the lever 43 of the pressing mechanism 41 fixed to the upper frame 51 of the frame body 5 is rotated upward to displace the presser 4 upward, thereby increasing the distance between the lower surface of the presser 4 and the smooth surface portion A. The thickness should be sufficiently larger than the thickness of the lead portion R of the heating coil C. Next, heating coil C on the left
With the lead portion R at the tip, move it forward according to the thick arrow, and from the end opening side of the smooth surface portion A, using the guide bars 3, 3 as a guide, align it with the lower surface of the presser 4 along the surface of the smooth surface portion A. 3, and advance it sufficiently until the stopper 31 stops its advancement. When forward movement is stopped, press the lever 4 above.
3 downward to displace the presser 4 downward. As a result, a predetermined length portion of the lead portion R is inserted into the entire surface of the smooth surface portion A, and the lead portion R comes into contact with the lower surface of the pusher 4 that has descended, so that the lower surface B of the lead portion R is inserted into the entire surface of the smooth surface portion A. It is pressed onto the surface of the smooth surface portion A by the pressing force. Smooth surface part A
and the lower surface B of the lead portion R are both sufficiently smooth, and each of the conductor 1 and the lead portion R is constituted by an electric path divided into two by sandwiching an insulating material 2,
Since the electric circuits on one side and the electric circuit on the other side are in close contact with each other, electrical connection can be reliably established with one touch.

At the same time, in this state, the holes 61, 61, 71 and 71 on the smooth surface part A are connected to the holes 61 on the bottom surface B.
1,661,771 and 771, respectively, and are in watertight communication with each other. Therefore, the cooling water flowing from the nipple 63 to which the hose connected to the cooling water supply source attached to the hole 62 on the end face of the electric circuit on one side of the conductor 1 is inserted is connected to one point in FIG. 2b. As shown by the chain line, the ring part Cr passes through the cooling water passages 6 and 66 in the electrical circuit.
The nipple 63 is connected to the cooling water circulation path 8, circulates through the cooling water circulation path 8, passes through the cooling water passages 66 and 6 in the other side electric circuit, is glued to the hole opening 62, and has a hose attached thereto connected to the discharge port. flows through to. In addition, the quenching liquid that flows in from the nipples 73 that are attached to the holes 72, 72 on both end faces of the electric circuit in the side portion 1b of the conductor 1 and that are connected to the cooling liquid supply source for quenching, respectively, is 2
As shown by the two-dot chain line in FIG.
1 to the heated surface.

The heating coil C in the above embodiment described with reference to FIG. 2 is of a type consisting only of a heating ring, which is commonly used for movable hardening, which hardens the surface to be heated while moving the heating coil and the object to be heated relative to each other. However, even in the case of a heating coil for moving quenching, there are cases where a dedicated cooling ring that injects the quenching coolant follows the heating coil at a predetermined interval separately from the relatively moving heating coil, or when the object to be heated is heated while being moved relatively. In the case where only heating is performed, or when only stationary heating is performed, the present invention may be configured with only the cooling water flow path shown by the dashed line in FIG. 2b.

In addition, in stationary quenching in which the object to be heated is heated in place and then a cooling liquid is injected, the heat generation of the heating coil is low and the self-cooling of the heating coil is sufficient by the quenching liquid that flows in when the quenching liquid is injected following heating. etc., it is possible to configure the present invention with only the quenching fluid inlet passage shown by the two-dot chain line in FIG. 2b.

If the heating coil is a heating coil in which a copper pipe P through which self-cooling water flows is brazed along one end surface or outer circumferential surface of the ring part Cr of the heating coil C, the electric circuit of each lead part R should be The ends 662 of the penetrating cooling water passage 66 may not be opened into the pipe of the ring portion Cr, but may be connected to each end of the copper pipe P.

There are many other embodiments in addition to those described above, but all of them are based on the basic idea of the present invention.

Further, in the embodiment described in accordance with FIGS. 2a and 2b above, the pressing mechanism 41 is provided on the upper frame 51 of the frame 5 surrounding the conductor 1, but as shown in FIG. It is also possible to provide it in the member 51', and in this case, the other side 1b of the conductor 1, which has relatively low rigidity, is reinforced with the support member 52' so that it is not damaged by the pressing force applied when the heating coil C is attached. There is a need.

Furthermore, in the present invention, the bent outer surface of the other side 1a of the conductor 1 can be used as the smooth surface part A, as shown in FIG. 3b.

Furthermore, in FIG. 3c, the upper surface of the lead portion R is connected to the conductor 1.
The case of joining to the smooth surface part A of is shown. In this case, the presser 4 is displaced upward from below to press the lead part R into contact with the smooth surface part A, and the arrangement of the press mechanism 41 is fixed to the lower frame 51'', and the upper frame 5
2'' prevents damage to the side portion 1b of the conductor 1 due to the pressing force.

Furthermore, in the present invention, the smooth surface portion A of the conductor 1 and the smooth surface B of the lead portion R do not necessarily have to face each other vertically, or may face each other vertically or diagonally. However, since the weight of the heating coil C is quite large, it is most preferable to have the smooth surface portion A facing upward in the horizontal direction and the smooth surface B placed thereon.

The functions and effects obtained by carrying out the present invention are as follows: (1) The conductor is semi-permanently fixed to the power supply side output terminal, and the heating coil consisting of the ring part and the lead part is tightened to the power supply side output terminal with a single touch. (1) The time required to replace the heating coil, which previously took a long time, is reduced to almost zero, allowing the heat treatment equipment to operate at a high rate; (2) Even when the heating coil is replaced, the electrical connection is completed. Since there is no change in the heating coil, that is, the heating position, in the heat treatment equipment, it is easier to position the object to be heated. Furthermore, the input terminal board that was previously required for the heating coil is no longer required, resulting in material savings. (2) A hose for supplying and discharging cooling water for self-cooling and a supply hose for cooling liquid for quenching are semi-permanently connected to the conductor semi-permanently fixed to the output terminal on the power supply side. Since the connection of the fluid passage between the hose and the heating coil is completed with one touch, there is no need to remove and install multiple hoses, which conventionally required a long time when replacing the heating coil. This not only makes it possible to operate the heat treatment equipment at a high rate, but also allows permanent and intensive piping because the hose is semi-permanently connected to the conductor. (3) The heating coil is relatively flat and compact with no unevenness except for the lead. (1) When moving a conventional heating coil for replacement, there is a risk of accidentally hitting the plate-shaped input terminal or horn-shaped nipples against other objects, causing premature damage to the heating coil. (b) The storage space for the replacement coil is very small, which is extremely remarkable, and it is highly practical.

[Brief explanation of the drawing]

Fig. 1 is a perspective view for explaining the drawbacks of the conventional method and device for energizing and watering a heating coil, and Fig. 2a shows an embodiment of the method and device for energizing and watering a heating coil according to the present invention. FIG. 2B is a perspective view for explaining the water flow path in FIG. 2A, and FIGS. 3A to 3C are cross-sectional side views showing other embodiments of the present invention. 1...Conductor, 1a...One side of the conductor, 1b...
...The other side of the conductor, 2...Insulating material, 3...Guide bar, 4...Press element, 31...Stopper, 41
... Pressing mechanism, 6, 7 ... Conductor through hole, 61 and 62 ... One end opening and the other end opening of the through hole 6, 71 and 72 ... One end opening and the other end opening of the through hole 7, 66 , 77... Through hole of lead part, 661 and 662... One end opening and the other end opening of through hole 66, 771 and 772...
...One end opening and the other end opening of the through hole 77,
8, 9... Conduit of ring part, A... Smooth surface part, B...
...Smooth surface, C...Heating coil, Cr...Ring part of heating coil, R...Lead part of heating coil.

Claims (1)

[Scope of Claims] 1 One side of the L-shaped conductor is fixed to a power supply side output terminal, and one surface of a lead part of a heating coil can be pressed into contact with and separated from one of the surfaces of the other side, and the above-mentioned conductor Electrical connection and fluid passage connection are simultaneously made through the contact surface when the other side of the heating coil contacts the lead portion of the heating coil. water method. 2. Fix one side of a conductor that is L-shaped and has an electric path divided into left and right sides by an insulating material clamped in the center to the power supply side output terminal, and fix the conductor to a predetermined surface of either side of the other side. A predetermined surface of one surface of the lead portion of the heating coil can be press-contacted and separated, and each electric path of the conductor has a conductor that penetrates the electric path and has one end in the portion occupied by each electric path within the predetermined surface. One or more fluid passages are provided which are open and whose other ends are opened to a predetermined surface other than the predetermined surface, and each of the electrical circuits of the lead portion is provided with one end which passes through the electrical circuit and which has one end that opens into the predetermined surface and the other. Fluid passages each having a number and inner diameter corresponding to the fluid passages on the conductor side whose ends open into a predetermined flow path of an annular portion of the heating coil are provided, and the predetermined surface of the lead portion is pressed into contact with the predetermined surface of the conductor. When the electrical circuits of the conductors and the electrical circuits of the lead sections are pressed into close contact and are electrically connected, an electrical circuit is formed between the heating ring of the ring section and the power supply side, and each electrical circuit of the conductor The heating coil is energized, characterized in that the holes on the predetermined surface of the respective electric circuits of the lead portion are overlapped with the holes on the predetermined surface of the electric circuit, so that a fluid passage is communicated, and fluid is allowed to flow.・Water flow method. 3. If there is a single fluid path that communicates in each electric circuit, and the fluid flowing through the fluid path is self-cooling water, the flow path of the self-cooling water may be connected to one of the conductors. One of the heating coil lead parts that flows in from the side and communicates with the fluid passage of the electric circuit reaches a predetermined flow path of the ring part through the fluid passage of the electric circuit, flows through the predetermined flow path of the ring part, and then flows through the other lead part of the said lead part. Electricity/water supply to the heating coil according to claim 2, characterized in that the heating coil flows through a fluid passage of an electric circuit and flows out through a fluid passage on the other electric circuit side of the conductor communicating with the fluid passage. Method. 4 A single or multiple predetermined flow path of the heating coil ring through which self-cooling cooling water flows through a good thermally conductive conduit or a heating ring that is closely fixed to the end surface or outer peripheral surface of the heating ring in the circumferential direction. A method for supplying electricity and water to a heating coil according to claims 2 and 3, wherein the heating coil is a circulation path. 5 If there is a single fluid passage that communicates with each electric circuit, and the fluid flowing through the fluid passage is a cooling liquid for quenching, the flow path of the cooling liquid for quenching is connected to each electric circuit side of the conductor. Claim 2, characterized in that the liquid flows into the predetermined flow path of the ring portion through the respective fluid passages of the heating coil lead portions communicating with the fluid passages of the respective electric circuits. How to supply electricity and water to the heating coil. 6 Claims in which the predetermined flow path of the heating coil ring into which the cooling liquid for quenching flows is an inflow path that penetrates the inside of the heating ring in the circumferential direction or a conduit of a quenching cooling ring that is fixed integrally with the heating ring. Sections 2 and 5
Method of supplying electricity and water to the heating coil as described in section. 7 When there is a plurality of fluid passages communicated in each electrical circuit, the first communicating fluid passage is a heating system that communicates self-cooling water from the fluid passage of the electrical circuit on one side of the conductor to the fluid passage of the electrical circuit. Fluid in the other electrical circuit of the conductor that communicates with the fluid channel of the other electrical circuit in the lead portion of the coil through the fluid passage of one electrical circuit in the lead portion of the coil, a predetermined flow path in the ring portion, and the fluid passage in the other electrical circuit of the lead portion in sequence. a second communicating fluid passageway for communicating the quenching coolant from the fluid passageway of each electrical path of the conductor through the fluidic passageway of each electrical path of the lead portion of the heating coil that communicates with the respective fluidic passageway; Energizing the heating coil according to claim 2, characterized in that the heating coil is made to flow into a predetermined inflow path of the ring portion.
Water flow method. 8 A conductor formed by fixing two L-shaped electrically conductive circuit members in parallel with an insulating material sandwiched between them, one side of the L-shape of the conductor configured to be fixable to the power supply side output terminal, and the other side A smooth surface portion having a predetermined width and a predetermined depth that is symmetrical about the insulating material as a center line is formed on one of the surfaces from the end face direction to the connection portion direction, and each electric circuit of the conductor is The member is provided with one or more through holes having a predetermined cross-sectional area that penetrate through the member and have one end opening at a predetermined position of each portion of the smooth surface portion and the other end opening onto another predetermined surface. A lead part of a heating coil is formed by fixing two electrical circuit members with an insulating material sandwiched between them, one end of the lead part is connected to the ring part, and the other end part is connected to the center line with the above insulating material on the upper or lower surface. It is formed into a parallelogram with a predetermined thickness and has a smooth surface that is bilaterally symmetrical and has a length equivalent to the width and depth that is almost the same as the smooth surface part of the conductor, and each electric circuit of the lead part. The member has a through hole provided in each electric circuit member of the conductor, which penetrates through the member and has one end opening at a predetermined position of each portion on the smooth surface and the other end opening into a predetermined conduit in the ring part. A pressing mechanism is provided with through holes having a number and a predetermined cross-sectional area corresponding to The presser element is configured to be able to be vertically displaced on a perpendicular line with respect to the smooth surface portion, and to be able to generate a predetermined pressing force with the downward displacement, and the smooth surface portion of the conductor and the smooth surface of the lead portion of the heating coil are connected to each other. As the presser of the pressing mechanism is moved downward, the smooth surface is pressed into close contact with the back side of the smooth surface, and as the pusher is displaced upward, it can be separated. One comrade and the other comrades of the electric circuit members are connected at the close contact surface,
An apparatus for supplying electricity and water to a heating coil, characterized in that the through-hole openings of each of the electrical circuit members are set to overlap on the contact surface and conduction is established. 9 A guide bar made of a non-magnetic material fixed on the surface so that the smooth surface of the other side of the conductor is parallel to the end face of the conductor with a predetermined width maintained from the end face direction to the connection part direction, and a predetermined length apart from the end face. 9. The device for supplying electricity and water to a heating coil according to claim 8, wherein the surface is regulated by a stopper made of an insulating material fixed on the surface near the connecting portion.