JPH0217953Y2 - - Google Patents

Description

[Detailed description of the invention] [Technical field to which the invention pertains] This invention relates to an improvement of an earth chuck for preventing fires and other accidents caused by static electricity generated when loading oil into tanker trucks, etc. . In particular, check the electrical ground signal,
The present invention also relates to an earth chuck having a structure that does not generate naked sparks such as sparks in hazardous locations.

[Description of Prior Art] A conventional earth chuck electrically detects the conduction state between the earthed body and the earth wire, sends out a ground confirmation signal, and uses this signal as a signal to start loading liquid. For example, a conventional example shown in Japanese Utility Model Publication No. 47-15694 will be explained. In FIG. 3, reference numeral 1 denotes a base made of a conductive material attached to a part of the body of a tank truck or the like, and a convex contact portion is formed in the center of the base 1. 3 is a spring case made of conductive material with a hollow inside.
A spring 4 with one end fixed is housed in the hollow portion of the spring case 3, and a contact 5 is fixedly provided at the tip of the spring 4.

6 is a cylindrical bush made of an insulating material that is screwed onto the outside of the spring case 3; 7 is a magnet that has a predetermined attractive force and is fitted onto the outside of the bush 6; 8; is a conductive electrode material screwed onto the magnet 7.

Reference numerals 9 and 10 are ground wires, one of which is connected to the spring case 3 by a screw 11, and the other ground wire 10 is connected to the electrode material 8 by a screw 12. 13 is a protective cover provided to protect each component, and 14 is a pull-out cable 15.
This joint is fixed to the protective cover 13 in order to completely clamp the protective cover 13. The pull-out cable 15 has one end grounded at a predetermined position. In this conventional device, a contact portion is formed between a conductor integrally connected to a ground wire and a vehicle body, and the conductive state of the contact portion is maintained by the attraction action of a magnet.

By the way, in this conventional device, sparks are generated between the convex contact portion 2 and the contact point 5 when connecting the ground wire to the vehicle body, and sparks are generated in a place filled with flammable fluid. It was dangerous.

[Purpose of the invention] The object of the invention is to provide an earth chuck having a structure that detects electrical grounding and prevents sparks from becoming naked sparks even if they occur in a hazardous area.

[Explanation based on Examples] FIG. 1 is a sectional view of a main part of an earth chuck according to the present invention. FIG. 2 is a view taken along the AA arrow in FIG.

In FIG. 1, reference numeral 16 is an electrically conductive hollow body having a hollow interior and made of metal such as aluminum. 17 is a lid of the hollow body,
It is made of electrically insulating material such as acrylic. 1
8 is an O fitted into a groove 19 formed in the side wall of the lid 17.
It's a ring. 20 is a screw for fixing the hollow body 16 and the lid 17. Reference numeral 21 indicates a mounting hole formed in the lid 17. The magnet 7 is mounted and fixed in the mounting hole 17. 22 is a through hole opened in the lid 17. The through hole 22 is formed in accordance with the shape of the earthed body to be grounded or the number of convex contact portions as in the above embodiment. A bearing 23 is fitted into the through hole 22 and is made of an electrically insulating material such as Delrin. 24 is a push rod slidably inserted into the bearing 23. The push rods 24 are inserted in a number corresponding to the number of through holes 22 of the push rods 24. An enlarged locking portion 25 is formed at one end of the push rod 24, and a male thread 26 is formed at the other end. A compression spring 27 is stretched between the enlarged locking portion 25 and the bearing 23. 28 is male thread 2
It is a nut screwed into 6. 29 is a recessed portion for housing the magnet 7. 30 connects the magnet 7 to the lid 17
This is a screw for fixing to the mounting hole 21 of. 31
is a contact portion of a micro switch, etc., and is fixed at a predetermined position within the chamber 32 formed by the hollow body 16 and the lid 17. A necessary number of micro switches are also provided corresponding to the push rods 24. 33 is a switch operating lever of the micro switch 31. Reference numeral 34 denotes an actuation lever with an L-shaped cross section, which is integrally fixed to the push rod 24 by the nut 28, and when the push rod 24 moves in the axial direction, the actuation lever 33 of the micro switch opens and closes the contact. It's fixed like that. Reference numeral 35 denotes a signal line (for example, an intrinsically safe signal line) connected to an earth confirmation signal receiving circuit (not shown). 36 is another signal line (for example, a ground side signal line). Signal lines 35 and 36 are connected to normally open contact terminals of microswitches 31 and 31', respectively. Micro switch 3
The common terminals of 1 and 31' are connected to signal lines 37 and 3, respectively.
8 to one end of the push rods 24, 24'. 40 is a cap tire cord connected to the signal line 3.
5, 36 have been transmitted to non-hazardous areas. Signal line 3
5 is grounded on the ground confirmation signal receiving circuit side installed in a non-hazardous location. The signal line 36 is also grounded on the non-hazardous area side. 39 is the hollow body 16 and the lid 1
7 and is made of, for example, neoprene rubber.

When the earthing chuck of the present invention constructed in this way is brought into contact with a predetermined position of the earthed object, the push rod 2
4, 24' move and micro switch 31, 3
1' normally open contacts are closed and signal lines 35, 36
A contact signal is sent to. grounded at the same time.

In the above description, if the sealed hollow chamber 32 formed by the hollow body 16 and the lid 17 is made of a pressure-resistant and explosion-proof structure, it will be safe even if the micro switches 31, 31' are damaged. Furthermore, if the contacts of the micro switches 31, 31' are made of pressure-resistant and explosion-proof construction, double safety can be achieved.

[Explanation of Effects] When the earth chuck according to the present invention explained above is attached to the earth plate, the push rod moves,
Since the contacts connected to the intrinsically safe side signal line and the ground side signal line are closed at the same time, the ground confirmation signal can be detected reliably while being safe. In addition, even if a spark is generated when the contact is closed, the contact of the microswitch 31, 31' is housed in a sealed hollow chamber with a flameproof explosion-proof structure, so even if it is used in a hazardous location, naked sparks will not be generated by the earth spark. It is safe because it will not leak outside.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a main part of an earth chuck according to an embodiment of the present invention. FIG. 2 is a view taken along the AA arrow in FIG. FIG. 3 is a sectional view of a main part of a conventional earth chuck. 16...Hollow body, 17...Mounting hole, 22...Through hole, 23...Bearing, 24...Push rod, 25...Enlarged locking part, 26...Male thread, 27...Compression spring,
32... Sealed hollow chamber, 31... Contact portion, 34...
Actuation lever.

Claims (1)

[Claims for Utility Model Registration] (1) A sealed hollow chamber formed by a hollow body made of an electrically conductive material and a lid made of an electrically insulating material that seals the hollow body, and an insertion hole formed in the lid; In an earth chuck comprising a bearing made of electrically insulating material fitted into the insertion hole and a push rod slidably inserted into the bearing, one end of the push rod has a locking portion that engages with a protrusion of an earthed object. and an operating lever for opening and closing a contact portion having a normally open contact mounted in the sealed chamber is fixed at the other end, a compression spring is stretched between the locking portion and the bearing, and The terminal of the normally open contact of the contact portion is connected to the ground wire side signal line and the intrinsically safe side signal line, and when the rod moves in the axial direction against the spring force of the compression spring, the contact portion opens into the sealed hollow. An earth chuck that is characterized by configuring a closed circuit indoors at the same time. (2) The earth chuck according to claim 1, wherein the sealed hollow chamber has a pressure-resistant and explosion-proof structure. (3) The earth chuck according to claim 1 or 2 of the utility model registration, characterized in that the contact portion is a micro switch.