CN112548285B - an electric welding device - Google Patents

Abstract

The invention relates to the technical field of welding fixtures, in particular to an electric welding device. This electric welding device includes: the clamping assembly comprises a mounting seat, a plurality of clamping bodies and a rotating body, and the mounting seat is provided with an axially-penetrating through hole; the mounting seat is also provided with a plurality of inclined moving channels, and the plurality of clamping bodies penetrate through the corresponding inclined moving channels and do reciprocating movement along the extending direction of the inclined moving channels; one side that the cramping body is in opposite directions is provided with the clamping face, and one side that a plurality of cramping bodies dorsad is provided with first screw thread portion, is provided with second screw thread portion in the rotor, and when the rotor rotated around self axis, a plurality of cramping bodies moved along slant migration channel in opposite directions or dorsad. In the embodiment of the invention, the welding rod is arranged among the plurality of clamping bodies, and the plurality of clamping bodies are driven to move along the oblique moving channel by rotating the rotating body, so that automatic centering and clamping are realized, the welding rod is prevented from being skewed during welding, the welding quality is ensured, and the working efficiency is improved.

Description

an electric welding device

technical field

The invention relates to the technical field of welding fixtures, in particular to an electric welding device.

Background technique

The electric welding device is used to hold the electrode for arc welding. The function is to hold the electrode and conduct the welding current during welding. , and a hand-held insulating device that guarantees electrical connection with the electrode.

A conventional electric welding device is generally an electric welding pliers, and the electric welding pliers are tools for electric welding, which have two handles and are shaped like pliers. Electric welding pliers have main technical indicators such as shell protection, protection against electric shock, temperature rise, resistance to welding spatter, and resistance to drop. However, when the conventional electric welding tongs perform manual arc welding, the electrode is often skewed due to the high temperature deformation of the spring, which affects the welding quality, brings inconvenience to the operator, and reduces the production efficiency.

Therefore, it is necessary to design an electric welding device which is convenient for clamping the electrode.

SUMMARY OF THE INVENTION

In view of the above-mentioned technical problems in the prior art, the present invention provides an electric welding device. The welding rod is installed between a plurality of clamping bodies, and the rotating rotating body drives the plurality of clamping bodies in an oblique direction under the action of the screw principle. The movement of the moving channel solves the technical problem of the skew of the clamping electrode in the prior art.

In order to achieve the above technical purpose, an embodiment of the present invention provides an electric welding device, comprising a sleeve body and a clamping assembly connected with the sleeve body, wherein: the clamping assembly includes a mounting seat, a plurality of clamping bodies and a rotating body, the mounting seat is provided with an axially penetrating through hole; the mounting seat is also provided with a plurality of oblique directions corresponding to the clamping bodies and extending to the outer end surface of the mounting seat a moving channel, a plurality of the clamping bodies are penetrated in the corresponding oblique moving channel and can reciprocate along the extending direction of the oblique moving channel; the opposite sides of the plurality of the clamping bodies are arranged There is a clamping surface for clamping the workpiece, a plurality of the clamping bodies are provided with a first threaded portion on the side facing away, and the rotating body is provided with a second threaded portion matched with the first threaded portion, The rotating body and the mounting seat are coaxially arranged, and when the rotating body rotates around its own axis, a plurality of the clamping bodies move toward or away from each other along the oblique movement channel;

The mounting seat includes a first seat body, a second seat body and a third seat body that are connected in sequence, the second seat body is tapered, and the diameter of the connection between the second seat body and the first seat body is The diameter is smaller than the diameter of the connection between the second seat and the third seat, the first threaded portion protrudes from the outer wall surface of the second seat; the rotating body is sleeved on the second seat The second threaded portion on the body and the rotating body is a tapered thread;

The oblique moving channel is inclined toward the inside of the through hole, and the inclination angle between the oblique movement channel and the central axis of the through hole is 10°-15°.

Further, the electric welding device further includes a bridging device and a connecting body, the bridging device includes a thin-walled sleeve, the thin-walled sleeve is sleeved on the clamping component, and the first end of the connecting body is connected to the sleeve. The barrel is threadedly connected, and the second end is rotatably connected to the bridge device.

Further, the clamping assembly further includes a casing, the casing is connected with the rotating body by interference, and the thin-walled sleeve is sleeved on the casing and locked by a first fastener.

Further, the first fastener is a fastening screw, and the thin-walled sleeve is provided with a threaded hole extending radially of the thin-walled sleeve and matched with the fastening screw.

Further, the connecting body is provided with earrings, the bridging device further comprises an earring seat connected with the thin-walled sleeve, the earring seat includes two oppositely arranged earrings, and the earrings are arranged on the two between the ear pieces and connected by a second fastener.

Further, the earring is provided with a first connection hole, the ear piece is provided with a second connection hole matched with the first connection hole, and the second fastener includes a hole through the first connection hole. The connection hole and the bolt on the second connection hole and the wing nut threaded on the bolt.

Further, the electric welding device further comprises a connecting rod connected to the first end of the connecting body, the diameter of the connecting rod is smaller than the diameter of the sleeve body; the first end of the connecting rod is connected to the connecting rod The first end of the body is threadedly connected, and the second end is provided with a wire inlet for passing through the welding wire, and is locked by a third fastener.

Further, the sleeve body includes a first sleeve and a second sleeve that are connected to each other, the first sleeve and the second sleeve are threadedly connected, and the length of the first sleeve is smaller than the connection The length from the first end of the rod to the third fastener, the length of the sleeve body is slightly larger than the length of the connecting rod.

Further, the connecting rod, the connecting body, the clamping assembly and the bridging device are all conductive materials.

One or more technical solutions provided in the embodiments of the present invention have at least the following technical effects or advantages:

1. In the embodiment of the present invention, the welding rod is installed between a plurality of clamping bodies, and the plurality of clamping bodies are driven to move along the oblique moving channel by the rotation of the rotating body under the action of the screw principle, so as to realize automatic centering and clamping. Compared with the traditional spring and pressure handle, it can effectively prevent the skew of the electrode during welding in conventional manual arc welding, ensure the welding quality and improve the work efficiency.

2. In the embodiment of the present invention, the electric welding device is changed from the traditional clamp-type pressing handle to a smooth straight type, which prolongs the part held by the operator, and is suitable for various narrow or internal welding scenarios, and the electric welding device is relatively increased. scope of application.

3. In the embodiment of the present invention, the bridging device and the connecting body are rotatably connected, and the angle between the clamping bridging device and the connecting body can be adjusted according to the needs, that is, the clamping angle can be adjusted, which is suitable for the needs of electric welding in various occasions; It is easy to disassemble and assemble while welding.

4. In the embodiment of the present invention, the first end of the connecting rod, that is, the top end, is connected and fixed with the connecting body through threads, and the second end, that is, the bottom end, is prefabricated with a wire inlet and a compression screw, which is safe, convenient and fast.

5. In the embodiment of the present invention, the first sleeve and the second sleeve are connected by internal and external threads, which can effectively insulate and protect. The first end of the first sleeve is a prefabricated hexagon, which is convenient for installation, such as when using a wrench and pliers to facilitate clamping.

Description of drawings

1 is a schematic three-dimensional structure diagram of an electric welding device in an embodiment of the present invention;

2 is a schematic three-dimensional structure diagram of a clamping assembly in an embodiment of the present invention;

3 is a front view of the clamping assembly in the embodiment of the present invention;

Fig. 4 is A-A sectional view in Fig. 3;

5 is a schematic diagram of the connection structure of the bridge device and the connector in the embodiment of the present invention;

6 is a schematic structural diagram of a bridge device in an embodiment of the present invention;

7 is a schematic structural diagram of a connector in an embodiment of the present invention;

8 is a schematic diagram of a connection structure of a connecting body and a connecting rod in an embodiment of the present invention;

9 is a schematic structural diagram of a connecting rod in an embodiment of the present invention;

10 is a schematic structural diagram of a first sleeve in an embodiment of the present invention;

FIG. 11 is a schematic structural diagram of the second sleeve in the embodiment of the present invention.

Description of reference numerals

10-sleeve body, 101-first sleeve, 102-second sleeve, 103-first internal thread, 104-second internal thread, 105-first external thread;

20-Clamping assembly, 201-Mounting base, 2011-Through hole, 2012-First base body, 2013-Second base body, 2014-Third base body, 2015-Oblique moving channel, 202-Clamping body, 2021-first threaded part, 203-rotating body, 2031-second threaded part, 204-housing;

30-bridge device, 301-thin-wall sleeve, 302-lug, 3021-second connection hole, 303-fastening screw, 304-bolt, 305-wing nut, 306-protrusion;

40-connecting body, 401-earring, 4011-first connecting hole, 402-transition part, 403-connecting part, 404-second external thread, 405-third internal thread;

50-connecting rod, 501-wire inlet, 502-third external thread, 503-square, 504-compression screw, 505-top screw hole.

Detailed ways

Other objects and advantages of the present invention will become apparent by explaining the following preferred embodiments of the present invention.

1 to 11 are schematic structural diagrams of an electric welding device proposed by the present invention. For the convenience of description, the "up", "down", "left" and "right" referred to below are consistent with the up, down, left and right directions of the drawings themselves, but do not limit the structure of the present invention.

As shown in FIGS. 1-11 , an electric welding device includes a sleeve body 10 and a clamping assembly 20 connected to the sleeve body 10 , wherein the clamping assembly 20 includes a mounting seat 201 , a plurality of clamping bodies 202 and In the rotating body 203, the mounting seat 201 is provided with an axial through hole 2011; the mounting seat 201 is also provided with a plurality of oblique moving channels 2015 corresponding to the clamping bodies 202 one-to-one and extending to the outer end surface of the mounting seat 201 , a plurality of clamping bodies 202 are penetrated in the oblique moving channel 2015 and can reciprocate along the extending direction of the inclined moving channel 2015; A first threaded portion 2021 is provided on the side facing away from the plurality of clamping bodies 202, and a second threaded portion 2031 is arranged in the rotating body 203 to match the first threaded portion 2021. The rotating body 203 is the same as the mounting seat 201. The shaft is arranged, and when the rotating body 203 rotates around its own axis, the plurality of clamping bodies 202 move toward or away from each other along the moving channel. Specifically, the through hole 2011 provides a channel for the installation of the welding rod. The oblique movement channel 2015 is inclined toward the interior of the through hole 2011, and the inclination angle with the central axis of the through hole 2011 is 10°-15°, so as to avoid that the angle is too small to affect the installation of the electrode, and the angle is too large to cause the oblique movement channel 2015 to be too long. The clamping surface on the clamping body 202 is generally in the shape of an inclined arc, and the arc-shaped inclination direction of the clamping surface is adapted to the moving direction of the clamping body 202 , which is convenient for clamping the welding rod and avoids damage to the welding rod. When the rotating body 203 rotates, the first threaded portion 2021 and the second threaded portion 2031 cooperate, and the rotating body 203 does not move axially, and drives the plurality of clamping bodies 202 to move along the oblique movement channel 2015. One ends are close to each other, and the welding rod is clamped with the clamping surface for electric welding.

In the embodiment of the present invention, the welding rod is installed between the plurality of clamping bodies 202, and the plurality of clamping bodies 202 are driven to move along the oblique moving channel 2015 by rotating the rotating body 203 under the action of the screw principle, so as to realize automatic centering and clamping , Compared with the traditional spring and pressure handle, it can effectively prevent the skew of the electrode during welding of conventional manual arc welding, ensure the welding quality and improve the work efficiency. In the embodiment of the present invention, the electric welding device is changed from the traditional clamp-type pressing handle to a smooth straight type, which extends the part that the operator holds, and is suitable for various narrow or internal welding scenarios, which relatively increases the application of the electric welding device. scope.

In some embodiments, as shown in FIGS. 2-4 , the mounting base 201 includes a first base body 2012 , a second base body 2013 and a third base body 2014 connected in sequence, the second base body 2013 is tapered, and the first base body 2013 is tapered. The diameter of the connection between the second seat body 2013 and the first seat body 2012 is smaller than the diameter of the connection between the second seat body 2013 and the third seat body 2014 , and the first threaded portions 2021 on the plurality of clamping bodies 202 protrude from the second seat body The outer wall surface of the body 2013; the rotating body 203 is sleeved on the second seat body 2013 and the second thread portion 2031 of the rotating body 203 is a tapered thread. The rotating body 203 may include two semi-rings with identical structures, which are convenient to be installed on the second base body 2013 . After the rotating body 203 is installed, its outer wall surface is flush with the outer wall surface of the largest diameter part of the third base body 2014 . Through the shape matching between the rotating body 203 and the second base body 2013 , the rotating body 203 drives the plurality of clamping bodies 202 to move axially and the ends of the plurality of clamping bodies 202 are automatically centered and clamped.

In some embodiments, as shown in FIG. 1 , FIG. 5 to FIG. 7 , the electric welding device further includes a bridging device 30 and a connecting body 40 , the bridging device 30 includes a thin-walled sleeve 301 , and the thin-walled sleeve 301 is sleeved on the clamping assembly 20 The first end of the connecting body 40 is threadedly connected with the sleeve body 10 , and the second end is rotatably connected with the bridging device 30 . The clamping assembly 20 is installed in the thin-walled sleeve 301 on the bridging device 30, and the bridging device 30 is rotatably connected with the connecting body 40, and the angle between the clamping bridging device 30 and the connecting body 40 can be adjusted according to the needs, that is, the clamping angle can be adjusted. It is suitable for electric welding needs of various occasions. The connecting body 40 is connected with the sleeve body 10 by means of threads, which is convenient for installation and disassembly.

In some embodiments, as shown in FIGS. 1-4 , the clamping assembly 20 further includes a housing 204 , the housing 204 is connected with the rotating body 203 by interference, and the thin-walled sleeve 301 is sleeved on the housing 204 and is fastened by the first Parts locked. The inside of the thin-walled sleeve 301 is formed with a cylindrical hole that matches the shape of the outer shell 204, and the outer shell 204 is connected with the third seat body 2014 by interference. After the casing 204 is installed, the second base body 2013 , the third base body 2014 and the rotating body 203 are just accommodated in the casing 204 for protection and connection.

In some embodiments, as shown in FIG. 6 , the first fastener is a fastening screw 303 , and the thin-walled sleeve 301 is provided with a threaded hole extending radially of the thin-walled sleeve 301 and matched with the fastening screw 303 . The side of the thin-walled sleeve 301 facing away from the earring seat may be provided with a protruding portion 306, which guides the screwing in of the fastening screw 303, and at the same time limits the fastening position of the fastening screw 303, that is, the head of the fastening screw 303 Locking is achieved by contacting the outer end face of the protruding portion 306 with the outer end surface. By loosening the tightening screw 303, the clamping assembly 20 can be accommodated in the thin-walled sleeve 301, and the tightening screw 303 is tightened so that the end of the tightening screw 303 abuts against the outer wall of the housing 204 to complete the installation.

In some embodiments, as shown in FIGS. 5-7 , the connecting body 40 is provided with earrings 401 , the bridging device 30 further includes an earring seat connected to the thin-walled sleeve 301 , and the earring seat includes two oppositely arranged ear pieces 302 , the earring 401 is arranged between the two ear pieces 302 and connected by a second fastener.

In some embodiments, as shown in FIG. 6 and FIG. 7 , the earring 401 is provided with a first connection hole 4011, the ear piece 302 is provided with a second connection hole 3021 matched with the first connection hole 4011, The fastener includes bolts 304 pierced through the first connection hole 4011 and the second connection hole 3021 and a wing nut 305 threaded on the bolts 304 . Specifically, the second connection holes 3021 on the two lugs 302 are relatively connected, and the first connection holes 4011 on the connecting body 40 are communicated with the second connection holes 3021, and the ends of the bolts 304 pass through one lug 302 in sequence. The second connection hole 3021 , the first connection hole 4011 and the second connection hole 3021 on the other ear piece 302 can be installed by tightening the wing nut 305 . When the angle needs to be adjusted, loosen the wing nut 305 to freely rotate the angle to the desired angle, and then tighten the wing nut 305. The connecting body 40 includes a transition portion 402 and a connecting portion 403 . One end of the transition portion 402 is fixedly connected to the earring 401 , and the other end is fixedly connected to the connecting portion 403 . The transition portion 402 is hexagonal, which is convenient for installation, such as when using a wrench and pliers to facilitate clamping. The connecting body 40 may be integrally formed to enhance the stability of the connection. The bridging device 30 and the connecting body 40 are connected by bolts 304 and fixed by wing nuts 305, which not only can satisfy various welding methods, but also facilitate disassembly and assembly.

In some embodiments, as shown in FIG. 5 , FIG. 8 and FIG. 9 , the electric welding device further includes a connecting rod 50 connected to the first end of the connecting body 40 , and the diameter of the connecting rod 50 is smaller than the diameter of the sleeve body 10 ; The first end of the rod 50 is threadedly connected with the first end of the connecting body 40, and the second end is provided with a wire inlet 501 for passing the welding wire, and is locked by a third fastener. The connecting rod 50 is integrally formed, and the sleeve body 10 is sleeved on the outside of the connecting rod 50 without interfering with each other. The third fastener is the compression screw 504 . The first end, namely the top end, of the connecting rod 50 is connected and fixed with the connecting body 40 through threads, and the second end, namely the bottom end, is prefabricated with a wire inlet 501 and a compression screw 504 for pressing, which is safe, convenient and quick. Specifically, the connecting portion 403 of the connecting body 40 is provided with a third internal thread 405, the first end of the connecting rod 50 is provided with a third external thread 502 matched with the third internal thread 405, the third internal thread 405 and The second external thread 404 cooperates to connect the connecting rod 50 and the connecting body 40 to facilitate installation and disassembly. The connecting rod 50 is provided with a square 503 for easy operation. A plurality of jack screw holes 505 are provided on the connecting rod 50 at the second end, and the welding wire is fixed and locked by pressing screws 504 through the jack screw holes 505 .

In some embodiments, as shown in FIGS. 1 , 10 and 11 , the sleeve body 10 includes a first sleeve 101 and a second sleeve 102 connected to each other, and the first sleeve 101 and the second sleeve 102 are threaded For connection, the length of the first sleeve 101 is less than the length from the first end of the connecting rod 50 to the third fastener, and the length of the sleeve body 10 is slightly greater than the length of the connecting rod 50 . The length of the first sleeve 101 only needs to be set so as not to affect the installation of the pressing screw 504 , and the length of the overall sleeve body 10 is set to increase the safety of personnel operation. The connecting portion 403 is provided with a second external thread 404 , and the first end of the first sleeve 101 is provided with a first internal thread 103 matched with the second external thread 404 , so as to connect the connecting body 40 and the first sleeve 101 . The second end of the first sleeve 101 is provided with a first external thread 105, and the end of the second sleeve 102 is provided with a second internal thread 104 matched with the first external thread 105, so that the first sleeve 101 and the The second sleeve 102 is installed and removed. The first sleeve 101 is an insulating and insulating material, and the second sleeve 102 is an insulating and insulating material. The first sleeve 101 and the second sleeve 102 are connected by internal and external threads, which can effectively insulate and protect. The first end of the first sleeve 101 is a prefabricated hexagon, which is convenient for installation, such as when using a wrench and pliers to facilitate clamping.

In some embodiments, the connecting rod 50 , the connecting body 40 , the clamping assembly 20 and the bridging device 30 are all conductive materials, such as metal materials, to meet the requirements of electric welding.

The installation process of an electric welding device proposed by the present invention is as follows: the clamping assembly 20 is installed into the bridge device 30 and fixed with the fastening screws 303 . The bridging device 30 is connected to the connecting body 40 using bolts 304 and fixed using wing nuts 305 . The third external thread 502 at the top of the connecting rod 50 is assembled with the third internal thread 405 of the connecting body 40 . Connect the first internal thread 103 on the top of the first sleeve 101 to the second external thread 404 of the connecting body 40 , the second internal thread 104 on the second sleeve 102 and the first external thread 105 on the bottom of the first sleeve 101 assembly.

The working principle of an embodiment of the present invention is as follows: when in use, firstly install the welding wire into the wire inlet 501 on the connecting rod 50, and fasten it with a compression screw 504, and then rotate the housing 204 clockwise to make a plurality of clamps A clamping space is formed between the holding bodies 202, the welding rod is installed, the housing 204 is rotated counterclockwise, and the plurality of clamping bodies 202 are driven to move along the oblique moving channel 2015 by the rotating body 203 under the action of the screw principle, so as to realize automatic centering and clamping tight. If multiple welding methods are required, the wing nut 305 can be loosened to change the angle of the bridge device 30 .

The electric welding device of the present invention is described in detail with reference to the preferred technical solutions of the present invention. However, it should be noted that, without departing from the spirit of the present invention, those skilled in the art can make any modifications on the basis of the above disclosure , modifications and changes. The present invention includes the specific embodiments described above and any equivalents thereof.

Claims (7)

1. An electric welding device, comprising a sleeve body (10) and a clamping assembly (20) connected to the sleeve body (10), wherein:

the clamping assembly (20) comprises an installation seat (201), a plurality of clamping bodies (202) and a rotating body (203), and a through hole (2011) which penetrates in the axial direction is formed in the installation seat (201);

the mounting base (201) is further provided with a plurality of inclined moving channels (2015) which correspond to the clamping bodies (202) in a one-to-one mode and extend to the outer end face of the mounting base (201), and the plurality of clamping bodies (202) penetrate through the corresponding inclined moving channels (2015) and can reciprocate along the extending direction of the inclined moving channels (2015); a clamping surface for clamping a workpiece is arranged on one opposite side of the clamping bodies (202), a first threaded part (2021) is arranged on one opposite side of the clamping bodies (202), a second threaded part (2031) matched with the first threaded part (2021) is arranged in the rotating body (203), the rotating body (203) and the mounting seat (201) are coaxially arranged, and when the rotating body (203) rotates around the axis of the rotating body, the clamping bodies (202) move oppositely or reversely along the oblique moving channel (2015);

the mounting seat (201) comprises a first seat body (2012), a second seat body (2013) and a third seat body (2014) which are sequentially connected, the second seat body (2013) is conical, the diameter of the joint of the second seat body (2013) and the first seat body (2012) is smaller than the diameter of the joint of the second seat body (2013) and the third seat body (2014), and the first threaded part (2021) protrudes out of the outer wall surface of the second seat body (2013); the rotating body (203) is sleeved on the second seat body (2013), and a second threaded part (2031) of the rotating body (203) is a conical thread;

the inclined moving channel (2015) inclines towards the inside of the through hole (2011), and the inclination angle of the inclined moving channel and the central axis of the through hole (2011) is 10-15 degrees;

the electric welding device further comprises a bridging device (30) and a connecting body (40), wherein the bridging device (30) comprises a thin-wall sleeve (301), the thin-wall sleeve (301) is sleeved on the clamping component (20), the first end of the connecting body (40) is in threaded connection with the sleeve body (10), and the second end of the connecting body is rotatably connected with the bridging device (30);

the clamping assembly (20) further comprises a shell (204), the shell (204) is in interference connection with the rotating body (203), and the thin-wall sleeve (301) is sleeved on the shell (204) and locked through a first fastener.

2. The electric welding device according to claim 1, characterized in that said first fastening member is a fastening screw (303), and said thin-walled sleeve (301) is provided with a threaded hole extending radially along said thin-walled sleeve (301) and cooperating with said fastening screw (303).

3. The electric welding device according to claim 1, characterized in that an ear ring (401) is arranged on said connecting body (40), said bridging device (30) further comprises an ear ring seat connected with said thin-walled sleeve (301), said ear ring seat comprises two oppositely arranged ear plates (302), said ear ring (401) is arranged between two of said ear plates (302) and is connected by a second fastening member.

4. The electric welding device according to claim 3, characterized in that a first connecting hole (4011) is arranged on the ear ring (401), a second connecting hole (3021) matched with the first connecting hole (4011) is arranged on the ear piece (302), and the second fastener comprises a bolt (304) penetrating through the first connecting hole (4011) and the second connecting hole (3021) and a butterfly nut (305) threaded on the bolt (304).

5. The electric welding device according to claim 1, characterized in that it further comprises a connecting rod (50) connected to a first end of said connecting body (40), said connecting rod (50) having a diameter smaller than the diameter of said sleeve body (10); the first end of the connecting rod (50) is in threaded connection with the first end of the connecting body (40), the second end of the connecting rod is provided with a wire inlet (501) for penetrating a welding wire, and the connecting rod is locked by a third fastener.

6. The electric welding device according to claim 5, characterized in that said sleeve body (10) comprises a first sleeve (101) and a second sleeve (102) connected to each other, said first sleeve (101) and said second sleeve (102) being screwed, said first sleeve (101) having a length smaller than the length of said connecting rod (50) from the first end to said third fastening, said sleeve body (10) having a length slightly greater than the length of said connecting rod (50).

7. The electric welding device according to claim 5, characterized in that said connecting rod (50), said connecting body (40), said clamping assembly (20) and said bridging device (30) are all of electrically conductive material.

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