FI58231B - LINJESKYDD - Google Patents

Description

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Patent ·) A registry board (44) Nlhttvikjlpancm and kuLjulkalaim pvm. -

Patent and registration authorities AmtUcsii utltgd och utl. * Krifwn pubiicend 29.08.80 - (32) (33) (31) Pyr »« tty «uoikuut — priori ** 19.11.73 USA (US) I + I706 If _ (71) Reliable Electric Company, 11333 Addison Street, Franklin Park, Illinois 60131, USA (72) Milton Arthur Klayum, Itasca, Illinois, Richard E. Nelson, Arlington Heights, Illinois, USA (74) Leitzinger Oy (51) +) Line protector - Line break

The invention relates to a line protector comprising a gas tube with three electrodes, which electrodes are electrically isolated from each other and in which an arcuate gap is formed inside the tube between each of the first and second electrodes and the third electrode, the unit comprising three electrically isolated terminals and the unit being releasably supported said three-electrode gas tube in electrical contact with each of said terminals, the shield comprising a contactor member, a resilient member pushing said contactor member from its normal position where the contactor is not in electrical contact with the terminals in contact with said first and second electrodes, the contactor being in electrical contact with said three terminals and a mechanism for preventing said electrical contact of said contactor member with said first and second electrodes except when said gas pipe overheats, the mechanism comprising a fusible member for receiving heat from the gas pipe, and cooperating parts held tightly relative to each other by said fusible member except when said overheating occurs.

58231

It is common for telephone and similar communication lines to be protected from overvoltages that could damage personnel or equipment connected to these lines. One well-known type of shield is a unit using a gas-filled tube with three electrodes, which is installed with two electrodes connected to a pair of lines, respectively, while a third electrode is connected to ground. Short-term overvoltages from either side of the pair cause an arc inside the tube to the third electrode, causing these overvoltages to ground and the unit to be automatically ready to continue operating. However, the overvoltage fault is sometimes so strong or so prolonged that there is an overcurrent that causes the gas pipe to overheat and vanish. In this case, the gas pipe will no longer be able to function as a good enough line protector and this - may result in damage to equipment or personnel.

As a result, shielding units of known type with three electrodes include an arrangement for grounding the lines in the event that the gas pipe overheats. Such arrangements use a grounding rod or contactor which is pressed by the spring towards the grounding position, but which is normally kept out of this position by one or more solder elements in thermal contact with the grounding or third electrode of the gas pipe. When the pipe overheats, the solder element or elements melt, causing the spring to push the ground rod into its ground position, causing both lines of the pair to ground directly and bypass the pipe. Depending on the device itself, the unit is restored to its normal operating condition, eg by installing a new solder element or elements.

In mechanisms of the type described above, the use of solder elements is not entirely satisfactory. After melting, the solder tends to get stuck in the mechanism in small pieces, which may make it impossible to put the unit into operation without significant repairs. In addition, in the overload state, the fusible solder may get stuck in the mechanism so that the ground rod does not ground both pairs of conductors in the line. In addition, the solder may dissipate in the unit as it melts to such an extent that the solder may eventually cause an unwanted short circuit when solidified. If this happens, the solder must be thoroughly cleaned from the device and it may be necessary to replace the device wiring.

The soldering elements also have the problem that they must have a mass of 3,58231 rather large in order to be easy to handle and to be checked and replaced by repair personnel, or at least to be available to repair personnel. Since these solder elements are of a certain shape and composition for use with a particular type of unit, it is considered impractical for repair personnel to handle the manufacture of such a solder element.

In addition, the solder elements have the disadvantage that a rather long time is required for melting, because the melting time is determined not only by the mass of the element but also by the area of the element connected to the gas pipe. This range is limited by the relatively limited contact range that can be achieved in a standard type three-electrode gas tube.

In addition, the problem with soldering elements is that they are prone to cold fluidity. The solder element is usually subjected to compression from the force of the spring, which force of the spring is applied to the ground rod, and this pressure may cause the solder element to cold flow and possibly ground the lines too early when no disturbance occurs.

In general, the object of the invention is to provide a line shield of the above-mentioned general type, by means of which the above-mentioned difficulties of this type of shield are avoided and in particular the shield ground contactor can be returned to the operating position without replacing the fusible member.

These and other objects and advantages of the invention mentioned below are achieved on the basis of the features of the invention set out in the appended claims, and in particular according to claim 1, so that said cooperating parts are arranged to move to a new position relative to each other when said fusible member melts. that these parts can be repositioned after said fusible member has solidified and, without replacing it, return said contactor member to its normal position.

In a preferred embodiment of the invention, the solder is in the form of a film which holds the telescopic parts of the mechanism together and in which these telescopic parts can be repositioned to return the unit to normal operation after a line failure in which the lines are grounded by a ground rod or contactor. Because the solder film is relatively small in mass, the melting time of the solder is shortened, making the unit more sensitive to line disturbance, and other fault grounding caused by cold flow is avoided.

A particular additional advantage of the invention is that the users of the shield do not have to check the solder elements.

In the following, the invention will be explained in more detail with reference to the accompanying drawings, in which:

Figure 1 is a side elevational view of a protection unit constructed in accordance with the invention and comprising the features of the invention;

Figure 2 is an elevational view of the same guard as seen from the left end of Figure 1;

Fig. 3 is a sectional view taken along line 3-3 of Fig. 1, showing certain views in an elevational view;

Fig. 4 is an enlargement of a part of the arrangement according to Fig. 3, in which the parts of the mechanism shown in Fig. 3 are shown in section;

Figure 5 is an exploded perspective view of a portion of a central bracket and a contactor;

Fig. 6 is an enlarged, fragmentary view similar to Fig. 1, partially in section, showing the state of the mechanism after the fusible solder film has melted as a result of overcurrent on one or more lines;

Fig. 7 is a fragmentary sectional view similar to Fig. 3, but showing a modification of the shield; 5,58231

Fig. 8 is a fragmentary perspective view of the center bracket of Fig. 7;

Fig. 9 is a sectional view taken along line 9-9 of Fig. 7.

The drawings are discussed in more detail below. The shield 2 comprises a base 4 made of a suitable insulating material. The base 4 comprises three spaced-apart members extending through the base and forming terminals 6, 8, 10 which are insulated from each other. The terminals 6, 8, 10 may be members with screw threads which act as fastening pins for connecting the wires to them. In a typical embodiment, the terminals 6, 10 are respectively connected to the conductors of the telephone line pair, while the central terminal 8 is connected to ground.

By means of the terminals 6 and 10, flexible L-shaped metal end brackets 12, 12 are attached to the base 4. The end brackets 12, 12 are aligned with each other on the base 4 and each upper end has a V-shaped projection 14. At a distance below the projection 14, each bracket 12 also includes the bottom portions of the brackets 12 are held against the base 4 in a known manner, e.g. by means of the bases of the terminals 6 and 10, whereby the nuts 18 hold the ends themselves rigidly fixed to the base 4. Between the brackets 12, 12 there is a U-shaped, flexible, metal ground or center bracket 20, the base of which is held against the base 4 by the base of the grounding terminal 8. The central bracket 20 includes opposite sides 22, 22 provided with inwardly projecting flanges 24, 24, the free ends of which are located inside the sides 22, 22 for reasons which will become more apparent below. The free ends of the sides 22, 22 have substantially curved portions 26, 26.

A cylindrical, gas-filled tube 28 with three electrodes, the construction of which is known per se, is detachably attached to the end bracket 12, 12 and the central bracket 20. However, it may be mentioned that the gas pipe 28 comprises opposite electrodes 30, 32 (Fig. 6), each coaxial with respect to the gas pipe and each mechanically and electrically connected to respective end caps 38, 38. The end caps 38, 38 remain in firm contact with the end brackets 12, 12. between the respective projections 14 and the fingers 16. It can be seen from Figure 2 that the free end of each end bracket 12, 12 is divided into two arms to provide a gap 40 in which a conventional sealing projection is located, which projection may be part of the tube and extend axially from the second end cap 38.

The middle electrode 42 is a hollow cylindrical member coaxially surrounding the electrodes 30, 32. The electrodes 30, 32, 42 are separated by the most insulating spacers 44, 45 so that arcuate gaps are formed inside the tube 28 between the opposite electrodes 30, 32 and the middle electrode 42. between. The curved portions 26, 26 on the center brackets 20 engage the center electrode 42 to hold the tube in place and also to provide a metallic path to the ground through the center bracket 20 and the terminal 8. In this case, in the event of a short-term overvoltage on one or both shielded lines, an arc is created between the one or both electrodes 30, 32 and the center electrode 42, which causes a constant current to flow to ground. ~ "

A substantially U-shaped ground rod or contactor 46 is interposed between the sides 22, 22 of the central brackets. The contactor 46 is an elongate strip of metal extending in the immediate vicinity of the end brackets 12, 12, but still spaced therefrom. The compression coil spring 50 presses against the bottom of the center bracket 20 and saunas against the contactor 46 approximately midway at its opposite ends to press the contactor 46 toward the fingers 16, 16 of the end brackets 12, 12. The contactor 46 may include small lugs 47 and 5 on opposite sides of the flanges 24, 24 (Figs. ) to place the contactor halfway between the brackets 12, 12.

In normal use of the shield, the contactor ends 52, 52 are spaced from the fingers 16, 16 as shown in Figure 1 by a mechanism located between the center electrode 42 and the contactor 46. This mechanism, best illustrated in Figures 4 and 6, includes a metal outer sheath 54 provided at its opposite ends with curved flange portions 56, 56. The size of the curved flange portion 56 is such as to provide a sufficiently large surface area against the surface. metallic contact with the center electrode 42 to ensure good heat transfer from the center electrode 42 to the outer sheath 54. A metal inner sheath 58 cooperating with the outer sheath is telescopically disposed within the outer sheath 54. A film of fusible material, e.g., solder 60, holds the outer and inner sheaths 54, 58 together. the film covers the opening of the outer sheath 54 along its entire length as well as its entire inner circumference. For this reason, the solder film also adheres to the outer surface of the inner sheath 58. The solder can be of any suitable type, e.g. a eutectic solder that melts at 145 ° C. Attached to the contactor 46 is a pin 62, the small diameter main portion 64 of which protrudes through the contactor 46 and is secured thereto either through or otherwise permanently. The other end of the pin 62 protrudes axially into the opening of the outer sheath 54 and includes a shoulder 65 in contact with the end of the inner sheath 58. The smaller diameter end 67 of the pin slides into the inner sheath 58. The pin 62 is preferably made of stainless steel or some other material that is not adhered to the solder.

When an overvoltage occurs on either line to be protected which causes the gas tube to heat up, this heat is transferred from the center electrode 42 to the outer sheath 54 and consequently to the solder film 60. As the solder 60 melts, the shear provided by the spring 50 pin 62 and inner sheath 58 the axial movement of the inner jacket 58 within the outer jacket 54 from the position shown in Fig. 4 to the position shown in Fig. 6. As a result, the contactor 46 protrudes from its normal position (Figures 1 and 4) to its line grounding position shown in Figure 6, where the contactor ends 52 are in contact with the fingers 16, 16 of the end brackets 12, 12. This immediately ground both terminals 6 and 10, causing the associated lines to ground. As the overflow now bypasses the gas pipe 28, the latter cools, thus causing the solder film 60 to solidify. In this case, the inner and outer sheaths 58, 54 are firmly attached to the positions shown in Fig. 6.

It should also be noted that when the contactor 46 has moved to contact the fingers 16, 16, the contactor is in firm contact with the flanges 24, 24. This ensures that the ground connection through the contactor 46 passes through the center bracket 20, so that there is no need to rely on the spring 50 to carry current. Therefore, the distance between the flanges 24, 24 is made slightly smaller than the width of the contactor 46 at this point. The flanges 24, 24 can be resilient somewhat outwards, so that they do not in any way significantly impede the movement of the contactor 46.

The contactor can be restored to normal operation by repositioning a unit of inner and outer sheaths 58, 54 in the device. For this purpose, the gas tube 28 may first be pulled out of the inverted pin 62 as a unit and placed back into the pin 62. In this case, the contactor 46 is still in contact with the fingers 16, 16; however, the gas tube 28 is repositioned in the brackets 12, 12, 20. , which applies to the outer sheath 54, the inner sheath 58 and the pin 62 to press down on the spring 50, whereby the contactor 46 disengages from its contact with the fingers 16, 16, whereby the shield is completely restored to the operative position. The holding force exerted by the fasteners 12, 12, 20 on the gas pipe is greater than the force of the spring 50.

In order to ensure that the unit consisting of the inner and outer sheaths 58, 54 functions properly upside down, the length of the inner and outer sheaths and the movement of the contactor 46 should be closely monitored. In this case, the distance from the axial lower end (i.e., shoulder 65) of the inner sheath 58 to the axial lower end of the outer sheath 54 should be the same as the distance between the axial upper end of the inner sheath 58 and the axial upper end of the outer sheath 54 after the shield has grounded as described above.

In this case, the distance of the ends 52, 52 from the fingers 16, 16 remains the same each time the sheath unit 58, 54 is turned upside down to reactivate the guard.

It is also possible to provide a modification of the unit formed by the gas tube of the three electrodes as shown in Figs. 7 to 9, in which the corresponding reference numerals denote corresponding parts as described above. In the arrangement according to Figures 7-9, the length of the gas pipe 28a is smaller than that of the gas pipe 28, and then the end brackets 12a, 12a are correspondingly closer to each other and the contactor 46a is shorter in length. The gas tube 28a may include electrode ends 38a, 38a and a central electrode 42a in the form of a rim. Both curved portions 26a of the central bracket 20a are formed in connection with the curved recess 67a to provide good contact with the central electrode 42a. Likewise, the curved flange portions 56a of the outer sheath 54a include curved grooves 69 for receiving and joining the center electrode 42a. In other respects, the shield of Figures 7-9 operates in the same manner as the shield of Figures 1-6.

Claims (5)

A line cover containing a gas tube (28) having three electrodes (30, 32, 42), the electrodes being electrically insulated from each other, and thus forming within the tube between each first and second and third electrodes (42), the unit being contains three interconnected electrically insulated pipes (6, 8, 10) and the unit is adapted to releasably carry said three-electrode gas tube in electrical contact with each of said terminals, the cover comprising contactor means (46), elastic means (50 ) pushing said contactor means out of its normal position, wherein the contactor is not in electrical contact with said terminals connected to said first and second electrode terminals, said contactor being in electrical contact with said three terminals and a mechanism, preventing said electrical contact of the contactor by terminals connected to said first and second electrodes except when said gas tube becomes overheated, but contains a fusible means (60) for receiving the heat coming from the gas pipe, and cooperating parts (54, 58, 62) which are poured strictly into their mutual positions of said fusible means (60) except where present said superheat, characterized in that the said cooperating parts (54, 58, 62) are arranged, upon melting of the fusible agent due to superheating to move in relation to each other in such a relative position that these parts (54 , 58, 62) can be restored after solidifying the digestible agent and without replacing it, restoring said contactor agent (46) to its normal position. A line guard according to claim 1, characterized in that one of said cooperating parts (58) is telescoped within the other cooperating part (54), said meltable means (60) being radially disposed between said latter parts and the latter. said elastic means (50) provides a cutting force for said meltable means. A line guard according to claim 2, characterized in that the second part (58) is axially slidable within the second part (54) in the event of said melting, said movement taking place so long that said parts can after said rigid-