JP2006185676A - Pressure-resistant explosion-proof sheathed heater - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To miniaturize a heat-insulating explosion-proof sheathed heater and to reduce its manufacturing cost by eliminating the use of a connecting terminal box to a power source-side circuit in the use of a pressure-resistant explosion-proof sheathed heater. <P>SOLUTION: This pressure-resistant explosion-proof sheathed heater is composed of: a sheathed heater body 2 composed by incorporating a heating element or the like in a sealed metal protective tube 5 and by extracting respective lead wires 8 of the heating element or the like from the rear end of the metal protective tube 5 to the outside; a connection mechanism 3 comprising a metal tube protection part 9 welded to the rear end of the sheathed heater body 2, a filler 10a made of a synthetic resin filled by inserting the respective lead wires 8 into its tip side, a connecting space 11 formed at its intermediate part for housing connection parts 16 between the respective lead wires 8 and core wires 4a for circuits, and a filler 10b filled between an explosion-proof circuit 4 inserted into its rear end side and the metal tube protection part 9; and the explosion-proof circuit 4 having a predetermined number of the core wires 4 for the circuit having tips airtightly inserted and fixed in the metal tube protection part 9 and a desired length. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a pressure-resistant explosion-proof sheath heater having a structure in which a connection mechanism for connecting one end of an explosion-proof electric circuit for supplying power, for example, an explosion-proof cable, etc. is integrated with a sheath heater, and is mainly used in an explosive atmosphere. It is used for heat generation / humidification of dryers, thermostats, refrigerators and refrigerators.

  Heating elements, humidifiers, heating elements, etc. (hereinafter collectively referred to as heaters) used in dryers and thermostatic chambers used in explosive atmospheres shall have a flameproof structure to ensure safety. In Japan, industrial electrical equipment explosion-proof material (1979, Ministry of Labor, Industrial Safety Research Institute, hereinafter referred to as structural standard) and explosion-proof structural electrical equipment corresponding to the international electrical standard (IEC) are required. Specific structural standards and the like are determined by the machine / equipment type certification guide (Japan Industrial Safety Technology Association, hereinafter referred to as technical standards).

  For example, an explosion-proof sheath heater A that is provided alone in a natural convection space in a room and heats the surrounding air or heats it to perform moisture retention, dehumidification, etc. is generally a nichrome wire as shown in FIG. The surroundings of the heater 20 and the in-pipe connecting body 21 are surrounded by a metal protective tube 22 and the inside of the metal protective tube 22 is filled with a powdered inorganic insulator 23. In FIG. 3, 24 is a bottom plate (sealing plate), 25 is a mouth insulator, and 26 is a connection terminal.

  The sheath heater A is generally fixed to the explosion-proof terminal box B by inserting an airtight sleeve 27 as shown in FIG. 4, for example, and the connection terminal 26 and the electric wire are connected via a terminal block (not shown). A power supply line or the like (or a power supply cable or the like, not shown) inserted through the explosion-proof electric circuit from the tube connection port 28 is connected to each other. In FIG. B, reference numeral 29 denotes a wall body such as a dryer.

  The method of using the pressure-proof explosion-proof sheath heater A and the explosion-proof terminal box B in combination has many practical uses so far, and has excellent practical utility in terms of safety and convenience of maintenance and inspection. It is what you have.

  However, the explosion-proof terminal box B is considerably difficult to reduce in size and weight because it has a terminal block and the like, and in particular, many sheathed heaters A such as an explosion-proof dryer and an explosion-proof thermostat are provided. When used by inserting in parallel in the heating panel, the number of terminal boxes B themselves increases and becomes bulky, reducing the effective internal volume of the dryer or thermostat, or installed outside the machine. In some cases, there is a problem that the aesthetics of the dryer or the like is impaired.

JP 2000-261949 A

  Since the present invention requires the above-described problem in the conventional explosion-proof sheath heater A, that is, when the actual explosion-proof sheath heater A is used, a comparatively large explosion-proof terminal box B having a terminal block inside is required. It is intended to solve problems such as difficulty in securing the installation location of the explosion-proof terminal box B, reduction of the effective internal volume of the thermostat, etc., and high cost of the sheath heater itself. By providing a connection mechanism having a structure in which the connection terminal 26 of the sheath heater A and an explosion-proof electric circuit for power supply, for example, one end of an explosion-proof cable, are directly connected to one end of the metal protective tube 22 of the sheath heater A, The main object of the invention is to provide a flameproof explosion-proof sheathed heater A that can eliminate the use of a large flameproof explosion-proof terminal box B.

  According to the first aspect of the present invention, a heating element and a temperature detection sensor are built in a metal protective tube 5 whose front end is sealed, and each lead wire 8 of the heating element and the temperature detection sensor is connected to the rear of the metal protection tube 5. Sheath heater body 2 drawn outward from the end, metal tube protector 9 welded to the rear end of the metal protection tube 5 of the sheath heater body 2, and each lead wire to the tip of the metal tube protector 9 A synthetic resin filling body 10a filled with 8 inserted, and a connecting space 11 for accommodating the connecting portions 16 of the lead wires 8 and the electric wire core wires 4a formed in the intermediate portion of the metal tube protecting portion 9, A connection mechanism portion 3 composed of an explosion-proof electric circuit 4 inserted to the rear end side of the metal tube protection portion 9 and a synthetic resin filling body 10b filled between the metal tube protection portion 9 and the connection mechanism portion 3; Where the tip is inserted and fixed in an airtight manner into the metal tube protection part 9 Explosion proof path 4 with the path for core 4a having a desired length dimension, in which the basic structure of the invention and.

  According to a second aspect of the present invention, in the first aspect of the invention, the rear short tube in which the metal protective portion 9 forming the connection mechanism portion 3 is detachably screwed to the short tube 9a via the screw portion 9c. 9b, and a rotation stopper 14 is provided on the outer peripheral surface of the rear short tube 9b.

  According to a third aspect of the present invention, in the first aspect of the present invention, a retaining member 14 of the explosion-proof electric circuit 4 inserted inward is provided at the rear end of the rear short tube 9b.

  According to a fourth aspect of the present invention, in the first aspect of the invention, a screw portion 9e is provided at the rear end portion of the rear short tube 9b of the metal tube protection portion 9, and an explosion-proof electric circuit is inserted into the screw portion 9e at the rear end portion. Synthetic resin cylinders inserted between the explosion-proof electric circuit 4 inserted into the rear end side of the metal tube protection portion 9 and the metal tube protection portion 9 by screwing the squeezed pressing body 18 into the metal tube protection portion 9. In this configuration, the filler 18 is pressed.

  According to a fifth aspect of the present invention, in the first to fourth aspects of the invention, the explosion-proof electric circuit 4 is a heat-resistant explosion-proof cable.

  In the explosion-proof explosion-proof sheath heater of the present invention, an explosion-proof connection mechanism made of a combination of short metal pipes having a slightly larger diameter than the metal protective tube is connected and fixed to the end of the metal protective tube of the sheath heater main body in an airtight manner. An explosion-proof electric circuit for power supply that can be used in an explosive atmosphere, for example, a heat-resistant explosion-proof cable is inserted inward from the other end of the explosion-proof connection mechanism, and the connection terminal of the sheath heater is connected to the connection mechanism. In addition to directly connecting a power supply core wire and the like, the synthetic resin filler is filled only inside the ends on both sides of the connection mechanism portion, and the intermediate portion (space portion) for conductor connection is hermetically held. . As a result, it is possible to connect the sheath heater main body and an explosion-proof electric circuit for power supply, for example, a heat-resistant explosion-proof cable very easily, and the connection mechanism can be greatly reduced in size. Since the connecting intermediate portion is an airtight space, the connecting portion can be easily inspected as necessary.

  If the explosion-proof electrical circuit for power supply is a heat-resistant explosion-proof cable, select an appropriate length in advance, for example, a length that can be extended to the power supply device, so that the explosion-proof sheath heater can be attached. It is possible to greatly reduce the number of steps required for such as.

  In addition, if the short tube on the heat-resistant explosion-proof cable insertion side of the connection mechanism section is separable, the tip of the heat-resistant explosion-proof cable can be connected by removing the synthetic resin filler that is detachably inserted into the inside. The part can be pulled out and inspected easily. In addition, since a rotation stop mechanism is provided on the short tube on the insertion side of the heat and explosion proof cable, the short tube is completely prevented from being loosened and the safety is greatly improved.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a longitudinal sectional front view of a main part in which one part of a flameproof explosion-proof sheath heater 1 according to the present invention is omitted.
Referring to FIG. 1, the explosion-proof sheathed heater 1 includes a sheath heater body 2, a connection mechanism 3, an explosion-proof cable 4 that forms an explosion-proof electric circuit, and the like.

  The sheath heater body 2 has substantially the same structure as the conventional explosion-proof sheath heater, and includes a metal protective tube 5 made of stainless steel (SUS304), a magnesia tube 6 inserted therein, and a magnesia tube 6. Magnesia support disks 6a, 6a that support the tube in the protective tube 5 concentrically, a resistance wire (not shown) for the heater wound around the magnesia tube 6, and an end plate that seals the tip of the protective tube 5 (Bottom plate) 5a, a mica board 7 for fixing a magnesia tube, two thermocouples (not shown) for temperature measurement, a lead wire 8 for drawing, and the like.

In this embodiment, the protective tube 5 is selected to have an outer diameter of 16.5 mm, an inner diameter of 14.1 mm, and a length of about 600 mm, and the magnesia tube 6 has an outer diameter of 8 mmφ.
Furthermore, as lead wires 8, a total of six lead wires 8 are drawn out, including two heater resistance wires and four sensors (thermocouples) (two sets).

The distance between the inner wall surface of the metal protective tube 5 and the heater resistance wire and the distance between the lead wires 8 for each lead are regulated by the structural standard, etc. Omitted. The metal protective tube 5 and the end plate 5a are fixed by welding, and the radius of curvature of the end plate 5a is also defined in the structural standard.
Further, in this embodiment, the metal protective tube 5 is a pipe having a circular cross-sectional shape, but only the base end portion (lead wire drawing side) of the protective tube 5 is circular, and most of the sheath heater main body 2 is flat or Of course, the cross section may be finished in a square shape.

  The connection structure part 3 includes a metal tube protection part 9, an epoxy resin filler 10 a filled in the heater main body side of the metal protection part 9, and a silicon resin filler filled in the cable connection side of the metal protection part 9. 10b, a connecting space 11 formed between the fillers 10a and 10b, a connecting wire 12 for connecting the lead wire 8 on the sheath heater main body side and the core wire 4a on the explosion-proof cable portion 4 side, the lead wire 8 and the like Are formed from a guide support plate 13a for supporting the filler, a weir plate 13b for the filler 10b, and the like.

The metal tube protection part 9 is a stainless steel (SUS304) front short tube 9a and a rear short tube 9b which are detachably and airtightly connected and fixed via a screw portion 9c, and the total length is about 140 mm, the outer diameter is 27 mm, the inner diameter of the short tube 9 a is 22 mm, and the inner diameter of the rear short tube 9 b is 24 mm.
Moreover, the screw part 9c which connects the front short tube 9a and the rear short tube 9b is regulated by 5-7 or more threads. Further, a stopper 14 is fixed to the outer peripheral surface of the front end of the rear short tube 9a by welding. By tightening a hexagonal screw 14a of the stopper 14, the short tube 9b is prevented from rotating. Yes.

  In addition, one end of a cable retainer 15 is even welded to the rear end of the rear short tube 9b, and the heat-resistant explosion-proof cable 4 inserted in the rear short tube 9b in contact with the cable retainer 15 is inserted. The outer peripheral surface is clamped between the cable support 15 and the cable retaining body 15 with bolts and nuts (not shown) to prevent the explosion-proof cable 4 from being pulled out and dropped off.

The end tube 9a of the metal tube protection portion 9 and the rear end portion of the metal protection tube 5 of the sheath body 2 are welded in an airtight manner via a ring-shaped end plate 9b.
Of course, the mutual spacing, wire diameter, etc. of the lead wire 8, the connecting wire 12, and the internal ground wire 17 in the metal tube protection section 9 are finely regulated by the structural standards as described above.

The explosion-proof cable 4 is a so-called heat-resistant explosion-proof armored cable that is permitted to be used in an explosive gas atmosphere. In this embodiment, a seven-core cable (heater) having a predetermined length is used. Two power feeds, four sensors (two thermocouples), and one ground wire are used.
Of course, the cable 4 may be an electric circuit in which an electric wire covered with a heat-resistant insulating material is housed in an explosion-proof metal pipe.

  The connecting wire 8 on the heater body side and the core wire (leader wire) 4a on the explosion-proof cable 4 side are connected to each other in the connection space 11 with a margin for drawing out. The connecting portion 16 of each line is firmly fixed by so-called brazing.

Next, the assembly of the explosion-proof sheathed heater 1 according to the present invention will be described.
First, the end plate 5a is welded to the distal end portion 5 of the metal protective tube 5, and the front short tube 9a of the metal tube protective portion 9 is welded to the base end portion thereof to form the outer protective tube portion of the heat-resistant explosion-proof sheath heater 1. .
Next, the magnesia tube 6 to which the mica board 7, the magnesia support disks 6 a and 6 a, the heater resistance wire (not shown), the sensor (thermocouple) (not shown) and the like are attached is inserted into the metal protective tube 5. In addition, an epoxy resin is provided between the guide support plates 13a and 13a in a state where the ground wire 17, the lead wire 8, the connection wire 12 connected to the lead wire 8 and the like are held at predetermined positions and intervals by the both guide support plates 13a. And the front portion of the front short tube 9a is hermetically sealed with the epoxy resin filler 10a.

  Thereafter, the tip of the explosion-proof cable 4 is inserted into the rear short tube 9b of the metal tube protection unit 9, the core wires are connected to the connection wires 12, the connection portions 16 are brazed and fixed, and the end plate With the end portion of the explosion-proof cable 4 supported by 9d, the rear short tube 9b is screwed and fixed to the front short tube 9a via the screw portion 9c. Further, the hexagonal screw 14a of the stopper 14 is tightened to stop the rear short tube 9b.

  Finally, the gap between the rear short tube 9b and the heat-resistant explosion-proof cable 4 is filled with silicon resin to form a silicon resin filling body 10b, and the inside of the rear short tube 9b is held in a dense manner, and the cable retainer The cable 4 is fixed to the retaining body 15 by pressing the heat-resistant explosion-proof cable 4 with the pressure support 15 a and the pressure support 15 a. Thereby, the dropout of the heat-resistant explosion-proof cable 4 is prevented.

FIG. 2 shows a second embodiment of the connection mechanism section 3. In the second embodiment, there is a screw portion 9e for screwing the ring-shaped pusher 18 into the rear end portion of the rear short tube 9b. Is formed.
Further, in the space between the rear short tube 9b and the explosion-proof cable 4, a cylindrical seal body 19 made of synthetic resin having elasticity through which the cable 4 is inserted is inserted, and the pushing body 18 is connected to the screw portion 9e. By screwing and pressing the cylindrical sealing body 19 inward, the cylindrical sealing body 19 is deformed and the space between the cable 4 and the rear short tube 9b is sealed in a dense manner, and the cable 4 is pulled out. Will be prevented.
In the second embodiment, it goes without saying that the cable retractor 15 may be provided on the rear short tube 9b or the pusher 18.

The present invention is mainly used in explosion-proof explosion-proof dryers, temperature-controlled baths, refrigerators / refrigerators (frost-proof heaters), and the like. In addition to being applicable to two classes, it can be applied to equipment used in explosive atmospheres with ignition degrees G ₁ to G ₆ and explosion grades 1 to 3 according to the explosion-proof guidelines.
The explosion-proof explosion-proof sheath heater 1 may be used in any form, and for example, a method of inserting and using it in an insertion hole of a heat sink is often used.

It is the principal part longitudinal section front view which abbreviate | omitted one part of the flameproof explosion-proof sheath heater which concerns on this invention. It is a vertical front view which shows the other Example of a connection mechanism part. It is a longitudinal cross-sectional view which shows an example of the conventional flameproof explosion-proof sheath heater. It is explanatory drawing which shows an example of the attachment method to the flameproof explosion-proof connection box of the conventional flameproof explosion-proof sheath heater.

Explanation of symbols

1 Explosion-proof explosion-proof sheath heater 2 Sheath heater body 3 Connection mechanism 4 Explosion-proof electric circuit (heat-resistant explosion-proof cable)
4a Core wire 5 for electric circuit 5 Metal protective tube 5a End plate 6 Magnesia tube 6a Support disk 7 Mica plate 8 Lead wire 9 Metal tube protective portion 9a Front short tube 9b Rear short tube 9c Screw portion 9d End plate 9e Screw portion 10a Epoxy resin Filler 10b Silicone filler 11 Connection space 12 Connection line 13a Guide support plate 13b Damping plate 14 Stopping body 14a Hexagon screw 15 Cable retainer 15a Pressure support 16 Connection 17 Internal ground wire 18 Push Body 19 Synthetic resin cylindrical filler

Claims (5)

  A heating element and a temperature detection sensor are built in a metal protective tube (5) whose front end is sealed, and each lead wire (8) of the heating element and the temperature detection sensor is connected to the rear end of the metal protection tube (5). A sheath heater main body (2) drawn out outward, a metal tube protection section (9) welded to the rear end of the metal protection tube (5) of the sheath heater main body (2), and a metal tube protection section (9 ) And the lead wire (8) formed in the middle part of the metal tube protection part (9) and the lead wire (8a) for the electric circuit. A connection space (11) for accommodating the connection portion (16) with the core wire (4a), an explosion-proof electric circuit (4) inserted into the rear end side of the metal tube protection portion (9), and a metal tube protection portion (9 And a connecting mechanism portion (3) comprising a synthetic resin filling body (10b) filled between An electrical circuit core (4a) having a predetermined number of electrical circuit cores (4) having a distal end inserted and fixed in an airtight manner into the metal tube protective part (9) of the part (3), and an explosion-proof electrical circuit (4) having a desired length Formed explosion-proof sheathed heater.   The metal protective part (9) forming the connection mechanism part (3) is formed by the short pipe (9a) and the rear short pipe (9b) removably screwed to the short pipe (9a) via the screw part (9c). In addition, the explosion-proof sheathed heater according to claim 1, wherein a rotation stop body (14) is provided on the outer peripheral surface of the rear short tube (9b).   The explosion-proof explosion-proof sheath heater according to claim 1, wherein a retaining body (14) of an explosion-proof electric circuit (4) inserted inward is provided at a rear end portion of the rear short tube (9b).   A pusher (18) provided with a screw portion (9e) at the rear end of the rear short tube (9b) of the metal tube protection portion (9) and having an explosion-proof electric circuit inserted through the screw portion (9e) of the rear end. ), And the push-in body (18) is inserted between the explosion-proof electric circuit (4) inserted into the rear end side of the metal tube protection part (9) and the metal tube protection part (9). The explosion-proof explosion-proof sheath heater according to claim 1, wherein the tubular filler (18) made of resin is pressed.   The explosion-proof explosion-proof sheath heater according to claim 1, wherein the explosion-proof electric circuit (4) is a heat-resistant explosion-proof cable.

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