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(45) Date of grant: 20/07/1999

(12) PATENT
 
(51) Int.C1.7: H 01H 079/00, H 01R 009/24, H 02H 009/04

(21) Application Number: 1993/ 000097
(22) Filing Date: 07/07/1993
(30) Priority data: P4225484.1 30/07/1992 DE
 
(73) Owner: KRONE GIVIEH of, Beeskowdamm 3-11, D-100 Berlin 37, Germany., Germany
(72) Inventor: WILHELM BRAMKAMP and INGO DOHNKE
(74) Agent/address for correspondence: Kaplan & Stratton Advocates, P.O. Box 40111-00100, Nairobi
 
(54) Title: PROTECTIVE PLUG FOR TERMINAL AND DOSCONNECT BLOCKS OF TELECOMUNICATION & DATA TECHNIQUE.
(57) Abstract:
The invention relates to a protective plug for terminal and disconnected blocks of the telecommunication and data technique. Said plug connector comprises a flat plastic body 1 having recesses 2 for receiving a voltage surge arrester 3, and a cage 5 having several U-shaped holders 6 attached at the plastic body 1, the front legs 11 of said holders pressing against the one electrode 13 of the voltage surge arrester 3 and the rear-side legs 14 of which resting against the rear-side of the plastic body 1. into the protective plug is embedded a plug contact 7 forming the contact member 8. A melt element 4 is disposed between the contact member 8 and the other electrode 16 of the voltage surge arrester 3.
In order to guarantee the permanent short circuit when releasing the fail-safe, there is provided, according to the invention, a contact spring as an extension of the rear-side leg 14 of the U-shaped holder 6, said contact spring projecting into the recess 2 receiving the voltage surge arrester 3.
 
The inventions relate to a protective plug for terminal and disconnect blocks in telecommunication and data technology.
A protective plug of this kind is known from DE 27 38 851 C3. By virtue of the fuse element disposed between the contact member and the voltage surge arrester, the free end of the rear leg of the U-shaped holder is at a distance from the associated electrode of the voltage surge arrester, which will be bridged by melting of said fuse element only after a prolonged existence of a voltage surge driving a current through the voltage surge arrester and heating the latter.
In such protective plugs having a thermal protection (fail-safe), it is known that with short-time voltage surges driving a low current through the voltage surge arrester, no melting of the fuse element will occur. Arresting of the voltage surge is performed by way of the voltage surge arrester and the U-shaped holder to ground. Only a prolonged voltage surge and the dissipation of power in the voltage surge arrester will cause sufficient heat in the arrester to bring the fuse element into the plastic condition. When the fuse element melts, the arrester is displaced towards the contact member. By pressing the voltage surge arrester onto the contact member and the free rear-end of the U-shaped holder, a contact is made which electrically bridges the voltage surge arrester.
By making the contact, a reduction of the dissipated power in the protective plug is effected, with the consequence of a cooling-down and resolidification of the remaining portion of the fuse element. This construction of the fail-safe contact may, due to different material combinations and the different thermal expansions caused thereby, affect the quality of the contact. The consequence is that the short-circuit contact is not assured in each case, but that instead the protective function may again exist. However, this new protective function does not meet the required insulation conditions, i.e. the required distance between the free rear-end (electrode) of the U-shaped holder and the electrode of the arrester associated therewith. As long as this distance prevails, but is smaller than required and than originally prescribed by the non-plasticized fuse element, the protective plug must no longer be used, since the arresters are changed in their characteristics. In principle, after each triggering of the fail-safe (thermal protection), a replacement of the arrester and fuse element should be performed.
A need thus exists to ensure permanent short-circuiting after the first triggering of the fail-safe (thermal protection).
The invention provides that the extension of the rear leg of the U-shaped holder is adapted as a contact spring projecting into the recess of the voltage surge arrester. Thereby, the arrester, after fusion of the fuse element, will come into a position between the two spring members, namely the resilient front leg of the U-shaped holder disposed on the front side of the plastic body, and the contact spring as an extension of the rear leg of the U-shaped holder, which is resiliently moved under the counter-pressure exerted by the contacting electrode of the voltage surge arrester. Resolidification of the fuse element and the possible expansion thereof in the order of microns will have the effect that the voltage surge arrester is moved back by a corresponding amount in the order of microns, but that the contact spring as an extension of the rear leg of the U-shaped holder can nevertheless follow this path, so that a permanent short-circuit is ensured.
In this context the contact spring, as an extension of the rear leg of the U-shaped holder, is so dimensioned that it will be tensioned, when the fuse element melts by the action of the voltage surge arrester, by the oppositely disposed front leg of the U-shaped holder, and thus establishes a reliable contact. The modes of operation of the two spring members, clamping the voltage surge arrester there between in case of voltage surge, are performed almost separately.
Preferably the contact spring takes the form of a blade spring, the inner side of which is closer to the rear electrode of the voltage surge arrester than the inner side of the contact member forming the plug contact, against which the fuse element rests. Thereby, it is ensured that the electrode of the voltage surge arrester already contacts the contact spring in the form of a blade spring and displaces the latter, when the fuse element is not yet fully fused or pressed into the recess of the button-shaped voltage surge arrester.
According to a preferred embodiment the support point of the contact spring is at a distance from the outer periphery of the voltage surge arrester corresponding approximately to the radius thereof. Thus, it is ensured that the support point of the contact spring is upwardly disposed on the rear of the plastic body, in order to form the contact spring from the material of the U-shaped holder and to ensure the support of the spring member in the rear leg.
According to a preferred embodiment comprising several, preferably two parallel rows of offset voltage surge arresters and a holder in the form of a cage, the front legs are cut free by cuts extending into the base of the U-shaped holder. Thus, the individual resilient legs on the front of the U-shaped holder are designed resiliently nearly independently from one another, so that a larger spring travel is gained for supporting the front spring leg.
Preferably the plastic body for each holder comprises a web having a height increasing from the upper edge of the plastic body, on which web, during the fitting of the protective plug with the inserted voltage surge arresters and fuse elements the front legs are guided onto the voltage surge arresters. This serves to provide that the cage formed of a multitude of U-shaped holders is easy to mount, because the front free ends of the individual holders, when sliding the cage onto the plastic body, slide over the respectively associated webs, and are then slid onto the arresters provided directly at the end of the webs.
In the following, the invention will be described in more detail, with reference to
an embodiment of a protective plug for terminal and disconnect blocks in telecommunication and data technology represented in the drawings. There is shown in:-
Fig.1 a cross-section through the protective plug formed of a flat plastic body with plugged on cage of U-shaped holders, of voltage surge arresters and solder rings, on an enlarged scale,
Fig.2 a front view of the cage formed of several U-shaped holders, in its natural size,
Fig.3 a rear view of the cage, on an enlarged scale,
Fig.4 a top view of the cage according to Fig.3,
Fig.5 a section of the cage, on an enlarged scale,
Fig.6 a top view of the flat plastic body, in its natural size,
Fig.7 a section of the plastic body, on an enlarged scale, and
Fig.8 a section through the protective plug according to Fig.1 after fusion and pressing away of the fuse element.
The protective plug for terminal and disconnect blocks in telecommunication and data technology comprises a flat plastic body 1 having ten recesses 2 for receiving one voltage surge arrester 3 each and one fuse element 3 each, and a cage 5 having ten U-shaped holders 6 plugged onto the plastic body 1, said holders being each assigned to a voltage surge arrester 3.
Into the plastic body 1 shown in a front view in Fig.6 and in section in Fig.7, in the lower portion thereof, one contact member 8 forming the plug contact 7 is embedded for each recess 2, the end of which opposite to the plug contact 7 terminates in the region of the recess 2 and forms the bottom of said recess. The upper portion of the flat plastic body 1 shown in Fig.7 is provided, on its front side, with shorter and longer webs 9, 10, which are alternately disposed and are each assigned to a recess 2 (Fig.6).
 
The cage S formed in one piece of the ten U-shaped holders 6 embraces the free upper end of the plastic body 1, as shown in Figs. I and 8. Each U-shaped holder 6 comprises a front leg 11 terminating in a curved spring member 12, which bears against the front electrode of the button-shaped voltage surge arrester 3, as shown in Figs. 1 and 8. The rear leg 14 of each U-shaped holder 6 bears against the rear of the plastic body 1, as shown in Figs. 1 and 8. Each U-shaped holder 6 forms a narrow contact spring 15 as an extension of its rear leg 14, as shown in particular in Fig.3, said contact spring taking the form of a blade spring and the inner side of which having a smaller distance to the rear-side electrode 16 of the voltage surge arrester 3 than the inner side of the contact member 8 forming the plug contact 7. This results in the aforementioned inner sides being offset in relation to one another. The support point 18 of each front leg 11 is at a distance of approximately the radius of the voltage surge arrester 3 from the recess 2, for which purpose the rear of the plastic body 1 is provided with a recess 17. Each contact spring 15 forms a contact brought about by a spring member. The latter is dimensioned such that it will be tensioned by the spring member 12 when the fuse element 4 is fused by the voltage surge arrester 3, and thus forms a reliable contact. The design of the spring members 12 is such that they will operate nearly independently of the contact spring 15.
Between the inner side of the contact member 8 forming the plug contact 7 and the rear electrode 16 of the voltage surge arrester 3, a horseshoe-shaped fuse element 4, as is shown in Fig. I is provided. It holds the respective electrode 16 at a distance to the contact spring 15 of the associated U-shaped holder 6.
The protective plug described above operates as follows:
From the spring material of the cage 5 of approximately 0.4 mm thickness or the U-shaped holders 6 forming the latter, two spring members are formed for each voltage surge arrester 3, namely on the front side the spring member 12 formed by the front leg 11 and on the rear side the contact spring 15 forming an extension of the rear leg 14. Both spring members are disposed on one component, the U-shaped holder 6 or the cage 5, resp., and operate nearly independently from one another, in their overall design. The front spring member 12, by way of the voltage surge arrester 3, presses against the horseshoe-shaped fuse element 4, which in turn bears against the inner side of the contact member 8. In the event of a voltage surge with relatively high power, heating will occur causing fusion or plasticization of the fuse element 4. The spring force of the fuse element 12 on the front side of the voltage surge arrester 3 causes a displacement of the voltage surge arrester 3 against the contact member 8, and thus a contact of the associated electrode 16 of the voltage surge arrester 3 with the contact spring 15, which by way of the cage 5, is at ground potential. A short-circuit will result.
By establishing the contact connection between the contact member 8 and the contact spring 15 via the associated electrode 16 of the voltage surge arrester 3, a reduction of the power dissipated at the protective plug will result accordingly, with the consequence of a cooling-down and a resolidification of the remaining portion of the fuse element 4. Movements occurring during this will not affect the quality of the contact, due to the provision of the contact spring 15 at the rear leg 14 of the cage 5, so that a safe contact connection is ensured.
For mutual decoupling and for ensuring a small spring constant of the individual spring members 12 of the front legs 11 of each U-shaped holder 6, cuts 20 are provided extending into the base 19 of the U-shaped holder 6, as shown in Fig.4. Fig.5 shows the different lengths of the front legs 11 of the adjacent U-shaped holders 6, alternately a long and a short spring member 12 being each assigned to the voltage surge arrester 3 disposed in two rows and offset against each other.
Each recess 2 for a voltage surge arrester 3 is associated with a web 9, 10 in the plastic body 1, having a height, increasing from the upper edge 21 of the plastic body 1 towards the recess 2, as shown in Fig.7. During the fitting of the protective plug with inserted voltage surge arresters 3 and solder rings 4, these webs 9, 10 allow an easy sliding of the front legs 11 of the U-shaped holders 6 onto the voltage surge arresters 3. Due to the webs 9, 10 thus having an upwardly inclined portion, the spring members 12 formed of the front legs 11 of the U-shaped holders 6 are automatically pretension during assembly.

The claims which follow are to be considered an integral part of the present disclosure. Reference numbers (directed to the drawings) shown in the claims serve to facilitate the correlation of integers of the claims with illustrated features of the preferred embodiment(s), but are not intended to restrict in any way the language of the claims to what is shown in the drawings, unless the contrary is clearly apparent from the context.
 
CLAIMS
1. A protective plug for terminal and disconnect blocks in telecommunication and data technology, comprising a flat plastic body (1) having at least one recess (2) for receiving a voltage surge arrester (3), a U-shaped holder (6) fitted onto the plastic body (1), the front leg (11) of said holder pressing against the one electrode (13) of the voltage surge arrester (3) and the rear leg (14) of which bears against the rear of the plastic body (1) and projects with its end into the recess (2), further comprising a contact member (8) forming the plug contact (7), and a fuse element (4) disposed between the contact member (8) and the other electrode (16) of the voltage surge arrester (3), and wherein the extension of the rear leg (14) of the U-shaped holder (6) is adapted as a contact spring (15) projecting into the recess (2) for receiving the voltage surge arrester (3).
2. A protective plug according to claim I, wherein the contact spring (15) takes the form of a blade spring, the inner side of which is closer to the rear electrode (16) of the voltage surge arrester (3) than the inner side of the contact member (8) forming the plug contact (7).
3. A protective plug according to claim 1 or 2, wherein the support point (18) of the contact spring (15) is at a distance from the outer periphery of the voltage surge arrester (3) corresponding approximately to the radius thereof.
4. A protective plug according to one of claims 1 to 3, comprising several, preferably two parallel rows of offset voltage surge arresters and a holder in the form of a cage, and wherein the front legs (11) are cut free by cuts (20) extending into the base (19) of the U-shaped holder (6).
5. A protective plug according to claim 4, wherein the plastic body (1) for each holder (6) comprises a web (9, 10) having a height increasing from the upper edge (21) of the plastic body (1), on which web, during the fitting of the protective plug with the inserted voltage surge arresters (3) and fuse elements (4), the front legs (11) are guided onto the voltage surge arresters (3).
6.  A protective plug as claimed in claim 1 substantially as hereinbefore described.
7. A protective plug substantially as described with reference to or as illustrated in the accompanying drawings.
DATED AT PRETORIA THIS 29TH DAY OF JULY, 1993
 
                                                                       HAHN & HAHN AGENT FOR APPLICANT

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