EP0494901A1 - Surge protector for telecommunications equipment - Google Patents
Surge protector for telecommunications equipmentInfo
- Publication number
- EP0494901A1 EP0494901A1 EP19900914491 EP90914491A EP0494901A1 EP 0494901 A1 EP0494901 A1 EP 0494901A1 EP 19900914491 EP19900914491 EP 19900914491 EP 90914491 A EP90914491 A EP 90914491A EP 0494901 A1 EP0494901 A1 EP 0494901A1
- Authority
- EP
- European Patent Office
- Prior art keywords
- protector
- spacer
- contact
- protection device
- contacts
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Withdrawn
Links
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Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01C—RESISTORS
- H01C7/00—Non-adjustable resistors formed as one or more layers or coatings; Non-adjustable resistors made from powdered conducting material or powdered semi-conducting material with or without insulating material
- H01C7/10—Non-adjustable resistors formed as one or more layers or coatings; Non-adjustable resistors made from powdered conducting material or powdered semi-conducting material with or without insulating material voltage responsive, i.e. varistors
- H01C7/12—Overvoltage protection resistors
- H01C7/126—Means for protecting against excessive pressure or for disconnecting in case of failure
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01T—SPARK GAPS; OVERVOLTAGE ARRESTERS USING SPARK GAPS; SPARKING PLUGS; CORONA DEVICES; GENERATING IONS TO BE INTRODUCED INTO NON-ENCLOSED GASES
- H01T1/00—Details of spark gaps
- H01T1/14—Means structurally associated with spark gap for protecting it against overload or for disconnecting it in case of failure
Definitions
- This invention relates to protectors for protecting equipment against high voltages and/or currents such as are caused by lightning in the vicinity of the equipment or the cables to which it is connected.
- Embodiments of the invention are especially, but not exclusively, applicable to overvoltage protectors used for protecting telephone equipment.
- overvoltage protectors usually comprise a pair of gas tubes mounted coaxially within a housing. Fusible elements, typically discs of solder, are associated one with each of the gas tubes. The arrangement is such that, when an overload condition persists, for example when a power line contacts the telephone line, the heat generated in the gas tube will cause the fusible element to melt and short-circuit the gas tube, either directly or by releasing a spring-loaded plunger.
- P.S. Lundsgaard et a l disclose such a protector having coaxial gas tubes with a fusible dielectric pellet mounted directly upon each gas tube. Melting of the dielectric pellet allows a resilient conductive member to short-circuit the gas tube.
- Napiorkowski discloses a protector having a sleeve of fluoroplastics material around the gas tube and a clip of spring metal surrounding the sleeve. When a sustained fault occurs, the heat generated causes the fluoroplastics material to melt, allowing the metal clip to contact the gas tube and effect the desired short circuit.
- the plastics material should also preferably exhibit a clearly defined and abrupt transition between its solid and molten states.
- the range of plastics materials which exhibit these characteristics and are capable of withstanding the relatively high temperatures associated with direct contact with the gas tube or other protection device is limited.
- a protector for protecting telephone equipment against excessive voltages comprises:
- a protection device supported by said support member; electrode means for coupling said protection device to the equipment to be protected;
- interconnecting means connecting one terminal of said protection device to the electrode means and to the first contact
- a contact member connecting the second contact to a second terminal of the protection device and comprising a ground contact for connecti ng to a ground el ectrode ext en d in g adjacent the protector when the protector i s i nstal l ed i n the equi pment ; a spacer of thermoplastics material preventing electrical connection between the first contact and the second contact, there being a heat transfer path between the spacer and the protection device;
- the spacer comprises a high density, high molecular weight polyolefin, for example polyethylene.
- the spacer may comprise a film.
- the spacer may comprise a limb and at least one lateral projection abutting a heat-conductive element for transmitting heat from the resistance element, one of the pair of contacts acting against the limb to urge it towards the heat-conductive element, the arrangement being such that heat generated by an excessive current melts the spacer at the junction between the lateral projection and the limb and the limb is displaced until the contacts make contact.
- the support member with the contact member assembled to it, may be housed in a housing having at least one aperture in a side juxtaposed to the support member.
- the ground contact portion may then be resiliently-biased to project through the aperture.
- the support member may comprise a block of insulating material having a deflection temperature greater then the melting point of the spacer.
- the protection device may be disposed in a recess in the block.
- the support member has a pair of mutually-spaced protection devices, third and fourth mutually proximal contacts and a thermoplastics spacer maintaining electrical separation between the third and fourth contacts.
- Second interconnecting means may then connect the third contact to a terminal of the second protection device and to a second electrode means for connection to the equipment.
- a heat transfer path between the second protection device and the second spacer provides for melting of the second spacer by heat generated by excessive current i n the second protection device.
- the contact member may have a second ground contact portion and the housing corresponding second aperture. contact of the contact member.
- each interconnecting means may extend along one side of member to the corresponding electrode means. W ⁇ tere two protection devices are provided, their respective interconnecting means may extend along opposite sides of the support member.
- aspects of the invention also concern protection against excessive or so-called sneak current. ln telecommunications equipment there is a need for protection against relatively low level current purges which are not accompanied by a voltage surge sufficient to operate the usual overvoltage protector but nevertheless can still damage the telecommunications equipment. To satisffy this need, sneak current protectors are used which incorporate a current sensitive element.
- Known sneak current protectors employ a heat coil which fits into a three dimensional space frame.
- the heat coil comprises a resistive wire, in series with a telephone line or the like, and wrapped around a spool.
- a spring loaded plunger is soldered into the spool.
- heat coils are wound around the plunger and melt the same solder discs as the gas tubes.
- protectors embodying the first aspect of the invention may further comprise a substantially planar resistance element, for example a ceramic chip resistor, connected to the electrodes so as to be in series with a line to be protected.
- the resistance element may be disposed in thermal proximity to the spacer of thermoplastics material.
- a protector for protecting equipment against excessive overvoltages and excessive currents comprises:- an overvoltage protection device;
- interconnecting means connecting respective ones of said pair of electrodes to one terminal of said protection device; a contact member for connecting a second terminal of said overvoltage protection device to a ground electrode of the equipment;
- first and second contacts connected to respective terminals of said protection device and biased one towards the other;
- thermoplastics spacer maintaining separation of said first and second contacts
- the interconnecting means serving to conduct heat from both said resistance element and said protection device to said thermoplastics spacer;
- the resistance element is mounted upon a substrate, for example a printed circuit board
- the interconnection means comprises printed circuit elements connecting the resistance element in series with the equipment to be protected.
- the plastics spacer is also mounted upon the printed circuit board or substrate.
- the length and cross-sectioned area of the printed circuit elements may be controlled to compensate for different amounts of heat generated in the protection device and the resistance element respectively.
- a protector for protecting against excessive currents in telecommunications equipment comprises a resistance element and electrodes for connecting the resistance element in series with a line to the equipment which is to be protected, such pair of contacts being mutually proximal and biased one towards the other but maintained apart by an insulating spacer.
- the spacer comprises a central limb and at least one lateral projection or arm, and comprises a fusible material.
- the projection abuts a heat-conductive element connected to the resistance element.
- One of' the pair of contacts acts against the central limb to urge it towards the heat- conductive element.
- a protector for protecting telephone equipment against excessive voltages comprises:
- interconnecting means connecting one terminal of said protection device to said electrode means and having a first contact
- a contact member comprising a ground contact for contacting a ground electrode extending adjacent said protector when the protector is installed in said equipment and a second contact juxtaposed to said first contact, said first contact and said second contact being biased one toward the other;
- a spacer of thermoplastics material separating said first contact and said second contact, said spacer comprising a limb and at least one lateral projection, the projection abutting a heat-conductive element for transmitting heat from the protection device, one of said first and second contacts acting against the limb to urge it towards the heat-conductive element, the arrangement being such that said excessive heating melts the spacer at the junction between the lateral projection and the limb permitting the limb to displace until the first and second contacts make contact.
- FIG. 1 is an exploded isometric view of a protector for use in equipment in a telephone central office and having a thermal shunt;
- Figure 2 is a plan view of a planar spring metal contact member of the protector showing current flow in the contact member after operation of the thermal shunt;
- Figure 3 is a cross-sectional view on the line 3-3 of Figure 2;
- Figure 4 is a fragmentary cross-sectional view on the longitudinal centre line of the protector.
- Figure 5 is a detail view illustrating an embodiment of a second aspect of the invention.
- Figure 6 is a view of a protector according to a third aspect of the invention:
- Figure 7 is a plan view of the protector of Figure 6;
- Figure 8 is a view corresponding to Figure 6 after the protector has operated:
- Figure 9 is an end view of a detail before operation of the protector.
- Figure 10 is a view corresponding to Figure 9 but after operation of the protector!
- Figure 11 is a sectional partial view of the protector after operation; and Figure 12 is a plan view of a printed circuit board assembly of the protector of Figure 6.
- an overvoltage protector for use in protecting equipment in a telephone central office comprises a housing 10 in the form of an elongate box, of square cross-section, closed at one end and open at the other.
- a handle 12 projects from the closed end.
- a lever 14 Adjacent the. same end, a lever 14 extends generally parallel to the, housing 10 and terminates in a lip 16.
- the lever 14 has a depending detent (not shown) which serves to limit withdrawal of the protector from the equipment at a predetermined position until the lever 14 is flexed to disengage the detent.
- a support member 18 of generally parallelepiped, shape has two recesses 20 and 22, respectively, spaced apart along its length, with a shoulder or land 24 between them.
- the housing 10 and support member 18 are made of insulating material, for example a synthetic plastics material such as Valox 420SEO (Trade Mark), a polyester by General Electric Corporation.
- An interconnecting member, in the form of a flat copper strip 26, extends along one side of the support member 18 between the shoulder or land 24 and a U-shaped groove 28 in the side of the support member 18.
- the groove 28 houses a U-shaped electrode 30 such that its limbs 32 and 34 protrude frond the end of the support member 18 that will be adjacent the open end of housing 10 when installed.
- the limbs 32 and 34 serve as electrodes or contact pins to mate with complementary contacts in the equipment cabinet when the protector is installed.
- the interconnecting strip 26 overlaps the U-shaped electrode 30 and is connected to it by crimping or soldering as at 36.
- the interconnecting strip 26 has two tabs 38 and 40, respectively, formed by bending the edge portions of the interconnecting strip 26 at right angles.
- Tab 38 extends along the bottom of recess 20 and tab 40 projects inwardly a short distance across the upper surface of shoulder or land 24.
- Tab 40 serves as a contact, as will become apparent in the ensuing description.
- a solid state overvoltage protection device 42 is accommodated in recess 20 and rests upon contact tab 38.
- the solid state overvoltage protection device 42 comprises two metal discs 42A and 42B, the latter larger than the former, which serve as terminals.
- the actual solid state device typically a voltage-triggered semiconductor device providing bi-directional overvoltage protection, is sandwiched between the metal discs 42A and 42B.
- a second interconnecting strip 44 extends along the opposite side of the support member 18 and is similar to interconnecting strip 26 in that it has a contact tab 46 projecting inwardly a short distance across shoulder or land 24 and is connected to a U-shaped electrode 48 housed in a groove 50.
- the limbs 52 and 54 of the U-shaped electrode 48 project from the end of the support member 18 in a similar manner to limbs 32 and 34.
- the second interconnecting strip 44 differs from the first interconnecting strip 26 in that its second contact tab 56 extends across the bottom of the second recess 22.
- a second solid state overvoltage protection device 58 similar to device 42, rests upon tab 56 in recess 22.
- the dimensioning of the recesses 20 and 22 and the solid state overvoltage protection devices 42 and 58 is such that the upper faces of the devices 42 and 58 are flush with the uppermost surface of the support member 18.
- This spring contact plate 62 is formed, conveniently by stamping and/or chemical milling, from a piece of flat stock beryllium-copper, or other suitable resilient contact material, as illustrated in Figure 2.
- the contact plate 62 comprises a medial portion 64 deformed out-of-plane to form two semi-cylindrical thermal shunt springs 66 and 68, respectively, one each side of a central hole 70.
- the side margins 72 and 74 of medial portion 64 of the plate 62 serve as load distributors, extending longitudinally to overlap, and bear against, the underlying portions 72' and 74', respectively, of the plate 62.
- Contact tab 40 forms with contact portions 74' a first pair of contacts.
- Contact tab 46 forms with contact portions 72' a second pair of contacts.
- the edge portions 72' and 74' are biased towards the support member (downwards in the drawing) by the associated thermal shunt springs 66 and 68, respectively.
- the thermal shunt springs 66 and 68 are deformed both elastically and plastically into their final position to obtain maximum and consistent spring travel and force.
- the plastics film 60 is clamped resiliently between contact plate 62, specifically the marginal contact portions 72' and 74', and contact tabs 40 and 46, and the solid state overvoltage protection devices 42 and 58 make good electrical contact with the underside of the contact plate 62 as shown in Figure 4.
- contact pins 32 and 34 will be corinected to the "tip" conductor and contact pins 52' and 54 will be connected to the "ring" conductor of the telephone line.
- the protruding arched limbs 90 and 92 of spring contact plate 62 will make contact with a ground plane 114 (see Figure 4) in the equipment cabinet.
- solid state overvoltage protection device 42 When an overvoltage occurs on the "tip" conductor, solid state overvoltage protection device 42 will operate to short-circuit the "tip" conductor, by way of interconnecting strip 26, to ground plane 114. If the overvoltage condition is sustained, the heat generated in the solid state overvoltage protection device 42 will be transmitted via tab 38 to tab 40 and to contact plate 62, eventually causing the plastics film 60 to melt.
- the way in which the spring contact plate 62 is formed is particularly advantageous.
- the T-shaped ends 82 of limbs 78 can slide along the surface of outer limbs 76 and 80 as the curved portions 90/92 are flexed. This helps to ensure even distribution of the spring pressure and consistent contact with the ground plane. Moreover, this bifurcate contact between limbs 78 and limbs 76 and 80, shares current flow, increasing current carrying capacity as compared with a single contact.
- the marginal portions 72 and 74 of the spring contact plate 62 can slide relative to the underlying edge portions 72' and 74' of the limbs 80 upon which they bear. This ensures that, as screw 84 is tightened, the force is applied evenly and directly above the corresponding tabs 40 and 46 so that there is little risk of an edge penetrating the plastics film 60 as a result of uneven force distribution.
- Two protrusions may be provided on the underside of the spring contact plate 62, each positioned to bear against one of the overvoltage protection devices 42 and 58.
- the protrusions will improve contact and provide a slight clearance, typically about 0.020 inches, between the top of the overvol tage protecti on devi ce and the spri ng contact pl ate 62.
- Figure 5 shows an overvoltage protector with an alternative form of contact member and means for protecting against excessive or "sneak” current
- the overvoltage protector is generally similar in construction to that described with reference to Figures 1 to 4, but with "sneak” current protection means for protecting against excessive currents.
- Components corresponding to those shown in earlier Figures are identified by the same reference numerals but with the suffix "A”.
- spring contact member 62A which is formed by two strips of spring contact material 63 and 65, the medial portions of which are riveted or welded together as at 67 and extend the full width of the support member 18.
- Spring contact strip 65 thus extends between spring contact strip 63 and the plastics material 60 on shoulder 24 of the support member 18.
- Spring contact strip 65 projects both sides of the shourlder 24 to overlie and make electrical contact with the solid state overvoltage protection devices 42A and 58A, respectively.
- Spring contact strip 63 arches away from spring contact strip
- a pair of planar resistance elements in the 'form of ceramic chip resistors 116 are positioned adjacent the medial shoulder or land 24 of support member 18, one such resistor each side of the central fastening screw 84.
- Each ceramic chip resistor 116 is housed in a recess 118 in the side of the support member 18.
- the interconnection for the "tip" conductor is made by conductors 120 and 122, respectively.
- Conductor 120 is connected at one end to an electrode in the form of contact pin 34A and conductor 122 is connected to an electrode in the form of contact pin 32A.
- the contact pins 34A and 32A are separate and replace the single U-shaped electrode 28 shown in Figure 1.
- Conductor 120 has a first tab 38A extending beneath solid state overvoltage protector 42A and a second tab 40A, serving as a contact, extending across shoulder or land 24 beneath the thermoplastics film 60.
- An extension 124 extends from contact portion or tab 40A to overlie and contact one terminal 126 of the ceramic chip resistor 116.
- the other conductor 122 extends longitudinally of the support member 18 to connect to the other terminal 128 of chip resistor 116. Both conductors 120 and 122 may be soldered to the respective underlying terminals 126 and 128 of the chip resistor 116.
- the chip resistor 116 is thus connected between the contact pins 34A and 32A and hence in series with the "tip" conductor of the telephone line. Should a fault occur which is characterized by a sustained abnormally high current in the line, a so-called “sneak current", but not necessarily accompanied by a voltage high enough to operate the overvoltage protectors 42 and 58, the heat generated in the chip resistor 116 will be conducted via extension 124 at the conductor 120, to tab contact 4 ⁇ A, to melt the plastics film 60, and connect the contact tab 40A to the spring contact plate 62, short-circuiting the protector.
- the embodiment disclosed in Figures 6 to 12 addresses this issue.
- the protector comprises a generally parallelepiped support block 218 which has one surface (that shown uppermost in Figure 6) stepped to provide in descending order, four steps 220, 222, 224 and 226 (see also Figure 7), respectively, with an inclined face 228 between step 224 and step 226.
- Two recesses 230 and 232 are provided in steps 220 and 224, respectively.
- the recesses 230 and 232 house overvoltage protectors 234 and 236, respectively.
- the connector pin 254 extends into a terminal post 256 soldered into a printed circuit board 258 which is mounted upon the lowermost step 226 adjacent the end of support block 218.
- a ceramic chip resistor 240 is surface- mounted upon the printed circuit board 258 and has one terminal connected by printed circuit conductor 262 to terminal post 256.
- the other terminal of chip resistor 260 is connected by printed circuit conductor pad 264 to a second terminal post 266 which is mounted upon the printed circuit board 258.
- the chip resistor 260 is connected in series between the contact pins 244 and 246, respectively, and hence in series with the line between the central office and the outside plant once the protector is installed.
- a spring contact member 290 overlies the support block 218 and is fastened to it by a central screw 292.
- the spring contact plate 290 has three finger portions 294, 296 and 298 at one end and three finger portions 300, 302, 304 at the other end.
- Middle fingers 296 and 302, respectively, curve away from the support block 218 to protrude through respective slots 306 and 308 in the housing 210. In use, the curved fingers 296 and 302 will make contact with a ground plate 310 of the equipment into which the protector is instal led.
- a bifurcate contact plate 312 has a bight portion 314 at one end which is clamped between spring contact plate 290 and the step surface 222 of support block 218.
- the limbs 316 and 318 of the bifurcate contact plate 312 extend longitudinally of the protector to a position above the printed circuit board 258. Their distal ends are supported by plastic spacers 320 and 322, respectively, so that limbs 316 and 318 extend adjacent, but not touching, connecting pins 276 and 254, respectively.
- the contact plate 312 is resilient, for example spring metal, and so shaped that the limbs 312 and 318 are urged towards the adjacent ends of connecting pins 276 and 254 but prevented from contacting them by the plastic spacers 320 and 322, respectively.
- Figure 9 is a detail diagrammatic end view of the printed circuit board 258 showing the limbs 316 and 318 of contact plate 312 supported by plastic spacers 320 and 322, respectively, in the normal or "open-circuit" position.
- the plastics spacers 320 and 322 are of cruciform shape, having central limbs or "web” portions 324 and 326, respectively, and lateral arms 328/338 and 330/331, respectively.
- the web portions 324 and 326 support, at one end, the contact plate limbs 316 and 318, respectively. Their opposite ends extend a small distance into corresponding holes 332 and 334, respectively, in the printed circuit board 258.
- lateral arms 328 and 329 of spacer 320 rest upon the subjacent printed circuit conductor sections 336 and 338, respectively, and support the spacer 320 against the spring force ⁇ exerted by the contact plate limb 316.
- lateral arms 330 and 331 of spacer 322 rest upon subjacent printed circuit conductor sections 333 and 335, respectively.
- Figure 12 shows the conductor pattern of the printed circuit board 258 in more detail.
- Conductor 262 has at one end a solder pad area 340, to which the terminal post 274 will be soldered, and at its other end a conductor pad 342 to which one terminal of resistor 260 is soldered and which extends to join pad 335 beneath the lateral arm 331 of spacer 322.
- Conductor pad 264, the bonding pad for terminal post 266, is connected to a second bonding pad 346 for the other terminal of resistor 260.
- Portion 333 which extends between the resistor bonding pad 346 and terminal pad area 264 and beneath the arm 330 of spacer 322, is relatively wide as compared with conductor 262.
- Conductor 262 which interconnects the resistor bonding pad 342 and the terminal bonding pad 340, is relatively long and narrow.
- the width of the conductor strip 262 and its length, are selected so that the thermal resistance between the terminal pad 340 and the resistor 260 is much greater than that between the spacer 322 and the resistor 260. This determines the sensitivity of the sneak current protection by controlling heat sink effects due to the thermal mass of ground electrode 114 ( Figure 4) (318 in Figure 7).
- the interconnecting member 240 connects pad 340 to SSOVP 236 which in turn is connected by contact member 290 to ground electrode 310, which is, in effect, a virtually infinite heat sink.
- interconnecting member 238 connects pad 344 to electrode 244 which, in use, is connected to wiring having a relatively low heat sink effect.
- Conductors 272 and 278 associated with resistor 270 and spacer 320 are formed in a similar way to conductors 262 and 264 and so will not be described in detail.
- a through slot 348 extends down the middle of the printed circuit board 258 to provide thermal isolation between the resistors 260 and 270.
- SSOVP device 234 When an overvoltage condition operates SSOVP device 234 heat is conducted via printed circuit conductor 272 to conductor section 338 to heat arm 329 of spacer 320. Heat is also transmitted by way of resistor 270 to conductor section 336 to heat the other arm 328 of the spacer 320. When SSOVP device 236 operates, heat is transmitted in like manner via printed circuit conductor 262 to heat the lateral 330 and 331 of spacer 332.
- the ground electrode 114/318 in the equipment is, in effect, a virtually infinite heat sink and the contact plate 312 is connected to it.
- the height of the central limb of the spacer provides thermal insulation between the contact plate 312 and the resistance element. This ensures that the heat generated by the resistance element is available to melt the lateral projections.
- an overvoltage protector will usually produce more heat, when conducting, than a resistance element conducting a sneak current.
- the chip resistor could be stocked in various values and readily substituted during manufacture to allow economical manufacturing of protection devices with different current ratings. These advantages are not realised by existing protectors which employ heat coils in the form of wire-wound resistors around plunger pins of gas tube protection devices. Of course, being planar itself, the ceramic chip resistor is particularly advantageously employed in a protector which employs generally "planar” or “epitaxial” components as disclosed hereinbefore.
- the plastics film is required to protect the gas tube against failing open circuit.
- Embodiments of the present invention protect the plastics support member 18 and plastics housing 10 against overheating.
- the characteristics of the plastics material used for the spacer are determined according to the operating requirements of the device.
- the material of the support member (18, 218) has a heat deflection temperature of about 200°C, and the typical maximum environmental temperature is about 70°C, the plastics spacer must melt at a temperature in the range 70-200°C. A melting temperature closer to the upper end of the range is preferred since the device would then be less susceptible to early demise due to AC faults.
- SCLAIR WCI 46C is a polyolefinic polymer of the polyethylene class. It has a clearly defined melting point at the required temperature. It also keeps its conformation requirements up to the melting temperatures.
- Other polyethelynes indeed other polyolefines such as polypropylene or polybuteric, can be used providing that the degree of crystallinity, stereospecificity and molecular weight combine to give the required thermal and mechanical properties.
- polystyrene resins might also be suitable.
- a high density, of at least about 0.941, has been found to give a suitably clear and quick transition between the solid and liquid states.
- manufacturing limitations may limit the specific gravity to about 0.965.
- a high molecular weight, at least 250,000, has been found to provide the necessary strength to meet the long term creepage requirements.
- Fluoroplastics such as are disclosed in the cited patent specifications, have a poorer resistance to creep, a broader range of deflection temperatures, and their combustion can produce hydrofluoric acid (in the presence of water), which is undesirable in a central office where hundreds of protectors might operate simultaneously, and in subscriber's premises.
- An advantage of the "planar” or “laminar” form of protector disclosed herein, i.e. wherein the protection devices and contacts are assembled onto top and side faces of the support member, is that it facilitates automatic manufacture. It is anticipated that this Will lead to cost savings compared to known protectors which employ coaxial gas tubes, heat coils, solder discs, and soon. Placing the shunt away from the protection devices (SSOVP) enhances the life expectancy of the device since it avoids early tripping of the protector on low level AC faults that normally can be handled by the SSOVP device. This is in contrast to certain gas tube devices which have a solder pellet mounted directly to the gas tube, and the gas tube device disclosed in the afore-mentioned U.S. patent specification number 4,212,047 which has a fusible plastics sleeve mounted directly upon the gas tube.
- the use of a plastics film which ruptures to allow short-circuiting of the protection devices advantageously reduces the size of the protector and permits an epitaxial form of construction with a generally planar contact plate assembly on one face of a support member.
- a disadvantage of protectors employing gas tubes is that the gas tubes are relatively bulky and assembly of the various components is relatively complicated and hence relatively costly.
- the size of the protector may be reduced by using solid-state devices instead of gas tubes.
- Such a solid state protector is disclosed in U.S. patent number 4,796,150 by Dickey et al, issued January 3, 1989, to which the reader is directed for reference.
- Dickey et al disclose a protector having a plurality of disc-shaped solid state protection devices located in recesses in opposite sides of a support member and contacting a central ground plane. These devices are secured to the support member by means of U-shaped spring clips which also provide a path to ground for the surges.
- the individual surge-prctection devices are relatively small, the arrangement is still relatively bulky and complicated to assemble.
- the overvoltage protection device is a solid-state device. It will be appreciated, however, that an alternative protection device, such as a gas tube, could be used.
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- Engineering & Computer Science (AREA)
- Microelectronics & Electronic Packaging (AREA)
- Physics & Mathematics (AREA)
- Electromagnetism (AREA)
- Emergency Protection Circuit Devices (AREA)
Abstract
L'installation de protection décrite, qui sert à protéger un équipement tel que notamment un équipement téléphonique contre les surcharges transitoires de haute tension et/ou de courant causées par exemple par des éclairs à proximité de l'équipement ou des câbles auxquels l'équipement est connecté, comprend un ou plusieurs dispositifs (42, 58; 234, 236) de protection contre les surtensions qui sont montées sur l'une des faces d'un support isolant (18; 218). Un élément de contact généralement plat (62; 290, 312), monté sur l'élément de support, comporte un élément de contact à la terre (90, 296) servant à établir un contact sur une électrode de terre (114, 310) dans l'équipement à protéger et avec chaque dispositif de protection contre les surtensions. Une pièce d'espacement (60, 320, 322) en matériau plastique fusible, couplée thermiquement au dispositif de protection, fond lorsqu'une condition défectueuse soutenue se produit. En fondant la pièce d'espacement permet une connexion électrique entre l'élément de contact et la ligne à laquelle le dispositif de protection contre les surtensions est connectée, court-circuitant ainsi de façon efficace la ligne à la terre. La protection contre les surcharges de courant peut être obtenue, au moyen d'une résistance (116) disposée en série avec la ligne et placée proche de la pièce d'espacement en plastique de façon à chauffer cette dernière lorsqu'une surcharge de courant se produit. Dans un premier cas, la pièce d'espacement comprend un film (60) placé directement entre une paire de contacts (40, 74') qui servent à court-circuiter le dispositif de protection. Dans un deuxième cas, la pièce d'espacement comprend une branche (324) présentant des saillies latérales relativement minces (328, 338) qui fondent et se cisaillent. Dans les deux cas, la pièce d'espacement se compose de préférence d'un polyéthylène haute densité et à poids moléculaire élevé.The protection installation described, which serves to protect equipment such as in particular telephone equipment against transient high voltage and / or current overloads caused for example by lightning near the equipment or cables to which the equipment is connected, comprises one or more overvoltage protection devices (42, 58; 234, 236) which are mounted on one side of an insulating support (18; 218). A generally flat contact member (62; 290, 312), mounted on the support member, includes a ground contact member (90, 296) for making contact on a ground electrode (114, 310) in the equipment to be protected and with each overvoltage protection device. A spacer (60, 320, 322) of fusible plastic material, thermally coupled to the protection device, melts when a sustained defective condition occurs. Grounding the spacer allows an electrical connection between the contact element and the line to which the surge protector is connected, effectively shorting the line to ground. Protection against current overloads can be obtained by means of a resistor (116) arranged in series with the line and placed close to the plastic spacer so as to heat the latter when a current overload occurs. product. In a first case, the spacer comprises a film (60) placed directly between a pair of contacts (40, 74 ') which serve to short-circuit the protection device. In a second case, the spacer comprises a branch (324) having relatively thin lateral projections (328, 338) which melt and shear. In both cases, the spacer preferably consists of high density, high molecular weight polyethylene.
Description
Claims
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US41578089A | 1989-10-02 | 1989-10-02 | |
US415780 | 1989-10-02 |
Publications (1)
Publication Number | Publication Date |
---|---|
EP0494901A1 true EP0494901A1 (en) | 1992-07-22 |
Family
ID=23647161
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP19900914491 Withdrawn EP0494901A1 (en) | 1989-10-02 | 1990-10-02 | Surge protector for telecommunications equipment |
Country Status (4)
Country | Link |
---|---|
EP (1) | EP0494901A1 (en) |
JP (1) | JPH04505991A (en) |
CA (1) | CA2066648C (en) |
WO (1) | WO1991005387A1 (en) |
Family Cites Families (7)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4062054A (en) * | 1976-08-31 | 1977-12-06 | Tii Corporation | Multi-function fail-safe arrangements for overvoltage gas tubes |
US4086648A (en) * | 1976-11-01 | 1978-04-25 | Cook Electric Company | Protector module |
US4132915A (en) * | 1977-01-14 | 1979-01-02 | Joslyn Mfg. And Supply Co. | Spark gap protector |
US4233641A (en) * | 1979-04-06 | 1980-11-11 | Reliable Electric Company | Line protector for a communications circuit |
IN170586B (en) * | 1987-01-07 | 1992-04-18 | Samhwa Electric Ind Co | |
US4796150A (en) * | 1987-04-16 | 1989-01-03 | American Telephone And Telegraph Company, At&T Bell Laboratories | Telecommunication protector unit with pivotal surge protector |
US4856060A (en) * | 1988-08-01 | 1989-08-08 | Porta Systems Corp. | Solid state telephone protector module |
-
1990
- 1990-10-02 JP JP51351090A patent/JPH04505991A/en active Pending
- 1990-10-02 EP EP19900914491 patent/EP0494901A1/en not_active Withdrawn
- 1990-10-02 CA CA 2066648 patent/CA2066648C/en not_active Expired - Fee Related
- 1990-10-02 WO PCT/CA1990/000336 patent/WO1991005387A1/en not_active Application Discontinuation
Non-Patent Citations (1)
Title |
---|
See references of WO9105387A1 * |
Also Published As
Publication number | Publication date |
---|---|
CA2066648A1 (en) | 1991-04-03 |
WO1991005387A1 (en) | 1991-04-18 |
JPH04505991A (en) | 1992-10-15 |
CA2066648C (en) | 1997-04-15 |
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