GB2328804A

GB2328804A - Plug with removable contact sleeve

Info

Publication number: GB2328804A
Application number: GB9810988A
Authority: GB
Inventors: Alexander W Manninger
Original assignee: In Akustik & Co KG GmbH
Current assignee: In Akustik & Co KG GmbH
Priority date: 1997-08-26
Filing date: 1998-05-19
Publication date: 1999-03-03
Anticipated expiration: 2018-05-19
Also published as: DE19737098C1; GB2328804B; GB9810988D0

Abstract

A plug 1 comprises a resilient hollow contact 5 with a zig-zag slot 6, and a removable insulating sleeve 7. The sleeve may be attached to the plug body or the contact by a screw thread 11 and is provided with means for retaining the sleeve on the contact which require more that unscrewing of the sleeve to remove the sleeve. The means may comprise a screw 10, figure 1, a projection (13) and corresponding recess (14), figure 2, not shown, or and interdigitating ratchet arrangement 19, figure 5. A sleeve 20 containing one part of the ratchet engages with ratchet teeth 21 of the sleeve 7. Alternatively the means may comprise a cotter pin which may be driven out of place or broken before the sleeve can be released. The means may comprise a desired-rupture location to break before release. The rupture force may be so great as to require a tool to remove the sleeve.

Description

Contact Do up The invention concerns a contact plug comprising a pin element which has a contact portion and a stranded wire-receiving portion. an insulation sheathing surrounding the stranded wire-receiving portion and a protective sleeve surrounding the contact portion at a radial spacing.

A contact plug of that kind is known from the applicants' monitor general catalogue 1995/96 under the designation "Savety Banana". and a public use. The previously known contact plug which is intended for use in the audio sector has a pin element which is provided with a contact portion and a stranded wire-receiving portion. At least one stranded wire can be fixed for example by way of wire fixing screws in the stranded wirereceiving portion which is surrounded by an insulation sheathing. The contact portion is of a pin-like configuration and has a number of peripherally disposed, axially outwardly curved contact bars or strips.

The previously known contact plug also has a protective sleeve which surrounds the contact portion at a spacing. The protective sleeve is axially displaceable and in its forwardly displaced position completely surrounds the contact portion. The protective sleeve can be moved against a spring force from the forwardly displaced position into a retracted position in which it completely exposes the contact portion. Admittedly, in the case of the previously known contact plug the contact portion is safeguarded against unintentional contact therewith when the protective sleeve is In the forwardly displaced position. but there is the ready possibility of the contact plug for example being introduced into a plug socket carrying mains voltage, with the protective sleeve being pushed back.

The so-called homepage of the British Federation of Audio, to be found on the Internet at "http://www.british-audio.org.uk" disclosed on 19th August 1997 under the so-called hyperlink "The BFA Audio Connector" a contact plug comprising a pin element having a contact portion and a stranded wire-receiving portion, an insulation sheathing surrounding the stranded wire-receiving portion. and a protective sleeve surrounding the contact portion which is in the form of a hollow plug sleeve. wherein the protective sleeve surrounds the contact portion in directly touching relationship with an increase in its diameter. That contact plug can admittedly not be inserted into a plug socket carrying mains voltage, by virtue of its enlarged outside diameter. but it also cannot be readily used in connection with conventional loudspeaker sockets of an inside diameter of typically 4 millimetres. The contact plug proposed by the British Federation of Audio is however intended solely for use with a mating connector which is also proposed by that organisation, the so-called BFA mating connector.

Prospectus MC-LAB-DOC-5000-4/88 from Multi-Contact AG of Basle.

Switzerland, discloses contact plugs bearing the designations LK2-F, LK2,3 F, having a pin element which is surrounded in a stranded wire-receiving portion by an insulation sheathing. A contact portion of that pin element is in the form of a hollow plug sleeve and can be both fitted into a mating socket and also fitted onto a mating plug connector. That contact plug however suffers from the disadvantage that the contact portion is completely exposed, without any safeguard against being touched, and can be readily inserted into a plug socket carrying mains voltage.

The object of the present invention is to provide a contact plug of the kind set forth in the opening part of this specification. which without manual intervention cannot be inserted into a plug socket of conventional type carrying mains voltage, which is compatible with the so-called BFA mating connector and which in that respect still remains capable of contact with counterpart or mating pins or sockets of conventional earlier type in the audio sector, in which respect for that purpose a user can also employ the contact plug without a protective sleeve at his own risk.

In accordance with the invention, in a contact plug of the kind set forth in the opening part of this specification, that object is attained in that there are provided fixing means with which the protective sleeve can be releasably fitted to the pin element and/or the insulation sheathing, that there are provided securing means which co-operate with the protective sleeve and which permit at least first-time release of the protective sleeve only with an increased amount of manipulation and that the contact portion is in the form of a resilient hollow plug sleeve which can be contacted with a mating pin in a condition of expansion and with a mating socket in a condition of compression.

The fact that the protective sleeve of the contact plug according to the invention can be releasably fitted to the pin element and/or the insulation sheathing and co-operates with securing means which permit the protective sleeve to be at least released for the first time only with an increased amount of manipulation means that the contact portion is permanently surrounded by the protective sleeve, in correct and proper use of the contact plug. The fact that the contact portion is in the form of a resilient hollow plug sleeve means that the contact plug can be contacted with a mating pin of the so-called BFA mating connector, with an expansion of the hollow plug sleeve. and can be contacted with a mating socket of a conventional audio mating connector of earlier type. with compression of the hollow plug sleeve. If a user of the contact plug intends to use it deliberately with mating sockets of earlier type, the protective sleeve can be removed from the contact portion, involving an increased amount of manipulation, in order to overcome the securing means. with the possibility of the manufacturer being cleared of liability in a situation involving improper use.

In an advantageous embodiment of the contact plug according to the invention the fixing means include a screwthread connection provided between the pin element and/or the insulation sheathing and the protective sleeve. In a further embodiment of the contact plug according to the invention the fixing means include a rotary bayonet connection provided between the pin element and/or the insulation sheathing and the protective sleeve. The protective sleeve can be fitted and released a plurality of times by virtue of the fixing means being designed with a screwthread connection or a bayonet connection.

In an embodiment of the securing means they include at least one securing element which. passing through the protective sleeve, can be introduced into a securing opening in the pin element and/or the insulation sheathing. In a development which is advantageous in this respect the securing element is in the form of a screw which can be screwed into a securing screwthreaded opening as the securing opening. Alternatively or in addition to that development. a securing element or a further securing element is in the form of a securing pin which can be inserted in forcelocking relationship and/or positively locking relationship into a securing pin opening as the securing opening. The provision of a securing element which can be inserted into the securing opening means that the protective sleeve can be removed from the contact portion. involving an increased amount of manipulation, only by manual intervention, under some circumstances also using a tool, only after the securing element has been at least partially removed by being unscrewed, pushed out or broken off.

In a further embodiment the securing means include at least one securing projection which co-operates with the protective sleeve at least prior to release on the first occasion. and makes it necessary to apply a relatively high level of torque when releasing the protective sleeve. The securing projection can be provided alternatively or in addition to the above-mentioned securing elements.

In an advantageous development the securing means have a plurality of securing projections which are formed on the insulation sheathing and which face sawtooth-like in the direction of the protective sleeve and which can be brought into engagement with complementary counterpart openings in the protective sleeve. In that respect it is particularly desirable for the securing projections to have steeper flanks in a direction of rotation for release of the protective sleeve, than in an opposite direction of rotation for fitting the protective sleeve.

It Is particularly desirable if the securing means also include a desired-rupture location which can be destroyed at a predetermined level of force when releasing the protective sleeve. That arrangement ensures that on the one hand the protective sleeve can be released only with the application of an increased amount of force, but it can still be used to protect the contact portion.

The relatively involved manipulation measures or steps which are required in connection with the securing means are within the area of responsibility of a user upon removal of the protective sleeve and in general they are effected by the user only in the event of a clearly intended use in connection with conventional counterpart contact elements carrying a weak current such as mating pins or mating sockets in the audio sector.

It is also desirable for the hollow plug sleeve to have a spring slot which extends in a zig-zag-like fashion and which affords particularly good contact and tensile strength properties upon being fitted onto a mating pin or upon being inserted into a mating socket.

Further advantageous configurations and advantages of the invention are set forth In the appendant claims and the following description of advantageous embodiments of the invention with reference to the Figures of the drawing in which: Figure 1 is partly sectional side view of a embodiment of a contact plug according to the invention with a protective sleeve mounted on a pin element.

Figure 2 is a side view of the pin element of the contact plug shown in Figure 1 with the protective sleeve removed.

Figure 3 is a side view of the pin element shown in Figures 1 and 2 with the insulation sheathing removed, Figure 4 is a partly sectional side view of a further embodiment of a contact plug according to the invention with a protective sleeve which is safeguarded against turning with respect to a pin element by way of a securing detent connection, and Figure 5 is a side view of the pin element of the contact plug shown in Figure 4 with the protective sleeve removed.

Figure 1 is a partly sectional side view of an embodiment of a contact plug according to the invention. The contact plug shown in Figure 1 has an electrically conductive pin element 1 of metal which in a gripping portion 2 is surrounded by a gripping insulation sheathing 3 as insulation sheathing comprising a non-conducting material such as for example a flexible plastics material. The gripping insulation sheathing 3 is applied for example by being injected around the pin element 1 in the region of a stranded wire-receiving portion which is aligned with the gripping portion 2 in the axial direction, wherein a gripping rib structure 4 formed for example by peripherally extending raised portions and recesses is provided in the central region of the gripping insulation sheathing 3 to afford a high level of gripping security.

The pin element 1 shown in Figure 1 is further provided with a hollow plug sleeve 5 as a contact portion, which has a spring slot 6 extending in a zig-zag-like configuration. The hollow plug sleeve 5 which is stamped out of a sheet metal strip and bent into a round configuration can be electrically contacted both with a mating pin (not shown in Figure 1) of a mating connector, undergoing expansion in that situation, and also with a mating socket (also not shown in Figure 1) of a mating connector.

when it undergoes compression.

The contact plug shown in Figure 1 has a protective sleeve 7 of an electrically insulating, stiff material which with a casing portion 8 surrounds the hollow plug sleeve 5 at a radial spacing and which in a fixing portion 9 is mechanically connected to the pin element 1. The mechanical connection between the pin element 1 and the protective sleeve 7 is formed for example by a screwthread connection or a rotary bayonet connection.

Securing means of the contact plug as shown in Figure 1 have a securing element in the form of a securing screw 10 which passes through the fixing portion 9 of the protective sleeve 7 and which can be screwed into the gripping insulation sheathing 3 and/or the pin element 1. When the securing screw 10 is screwed into the electrically conductive pin element 1 it is desirable to use a securing screw 10 comprising a nonconducting material such as a plastics material.

The outside diameter of the protective sleeve 7 is larger than the inside diameter of female contact portions of commercially available plug sockets which are connected to a health-endangering mains voltage. By virtue of that arrangement, when the protective sleeve 7 is fitted in position, the pin element 1 cannot be inserted into mains plug sockets of that kind, but in particular connecting elements which are being used in the audio sector in recent times such as the so-called BFA mating connector with a projecting mating pin over which the hollow plug sleeve 5 can be pushed, can still be contacted, with the protective sleeve 7 being accomomodated.

In order to release the connection between the pin element and the protective sleeve 7 the securing screw 10 is to be unscrewed by using a screwdriver involving an increased amount of manipulation work, before the protective sleeve 7 can be removed for example by rotating the screw connection or the rotary bayonet connection to release same from the pin element 1, exposing the contact portion formed by the hollow plug sleeve 5.

It Is only then that it may be possible for the hollow plug sleeve 5 of the contact plug to be brought into contact with a plug socket connected to a health-endangering mains voltage.

When the protective sleeve 7 is removed it is also possible for conventional mating connectors which are designed with mating sockets in the audio sector to be contacted with the contact plug shown in Figure 1.

in which case however the operation which is necessary for that purpose of removing the protective sleeve from the pin element 1 falls into the area of responsibility of the final user by virtue of the increased amount of manipulation involved when releasing the securing screw 10.

Figure 2 is a side view of the contact plug shown in Figure 1 with the pin element 1 and with the protective sleeve 7 removed. It will be clear from Figure 2 that the gripping insulation sheathing 3 disposed on the pin element 1 in the gripping portion 2 has between the gripping rib structure 4 and the hollow plug sleeve 5 an external fixing screwthread 11 onto which can be screwed an internal fixing screwthread 12 formed in the fixing portion 9 of the protective sleeve 7. In addition in the region of the internal securing screwthread 12 the protective sleeve 7 has a through opening 13 as part of the securing means. through which the securing screw 10 can be passed.

The securing means in this embodiment have a securing opening in the form of an internal securing screwthread 14 which is provided in the gripping insulation sheathing 3 in the region of the external fixing screwthread 11. The securing screw 10 can be screwed into the internal securing screwthread 14, in which respect it is desirable if in the region of the internal securing screwthread 14 the pin element 1 is still covered by a residual material thickness so that the securing screw 10 can also comprise an electrically conductive material. The opening 13 and the internal securing screwthread 14 are so arranged that when the protective sleeve 7 is screwed on, they come to lie in aligned relationship near the condition of final abutment so that the securing screw 10 can be screwed into the internal securing screwthread 14.

Figure 3 is a side view of the pin element 1 of the contact plug shown in Figures 1 and 2. In the region of the gripping portion 2 the pin element 1 as shown in Figure 3. in the stranded wire-receiving portion which is now exposed. has a stranded wire-receiving chamber 15 into which can be inserted at least one electrically conductive wire. A stranded wire which is inserted into the stranded wire-receiving chamber 15 can be connected to the pin element 1 in such a way as to withstand a tensile force thereon, by means of wire clamping screws 17 co-operating with clamping screw screwthreads 16. At the end of the gripping portion 2 which is towards the hollow plug sleeve 5 the pin element 1 has an injectionmoulded screwthread 18 which as shown in Figure 2 is surrounded by the portion of the gripping insulation sheathing 3, which has the fixing screwthread 11. The hollow plug sleeve 5 is connected to the gripping portion 2 of the pin element 1 by way of a press rivet connection which is capable of withstanding rotational and pulling-out forces.

Figure 4 is a partly sectional side view of a further embodiment of a contact plug according to the invention which except for the securing means is of a structure corresponding to the embodiment described with reference to Figures 1 to 3. Accordingly, in the embodiments shown in Figures 1 to 4. corresponding components are denoted by the same references and are not described in greater detail herein. The securing means in the embodiment of Figure 4 include a securing retaining or detent connection 19 which has tooth-like sheathing securing projections 20 provided on the gripping insulation sheathing 3 and tooth-like sleeve securing projections 21 provided in the fixing portion 9 of the protective sleeve 7. When the protective sleeve 7 is disposed on the pin element 1 the sheathing securing projections 20 are in engagement with sleeve counterpart openings provided between the sleeve securing projections 21 while the sleeve securing projections 21 are in engagement with sheathing counterpart openings provided between the sheathing securing projections 20.

To remove the protective sleeve 7 from the pin element 1, the contact plug shown in Figure 4 requires the application of a comparatively high level of torque between the pin element 1 with mounted gripping insulation sheathing 3 and the protective sleeve 7 in order to overcome the resistance to rotary movement of the securing retaining or detent connection 19, as constituting the increased amount of manipulation involved That torque is applied by the user only when he intentionally wishes to remove the protective sleeve 7 from the pin element 1 with the gripping insulation sheathing 3 mounted thereon. In that case it is possible within the wear limits of the sheathing securing projections 20 and the sleeve securing projections 21 to restore the securing retaining or detent connection 19 when the protective sleeve 7 is screwed onto the pin element 1.

Figure 5 is a side view of the contact plug shown in Figure 4 with a protective sleeve 7 removed from the pin element 1. It is clear from Figure 5 that the sheathing securing projections 20 and the sleeve securing projections 21 are of such a configuration that the tooth flanks are steeper in a direction of rotation for releasing the protective sleeve 7 than in an opposite direction of rotation for fitting the protective sleeve 7. That means that the torque which has to be applied to fit the protective sleeve 7 onto the pin element 1 is lower than the torque which has to be applied to release the protective sleeve 7 from the pin element 1. in order to make it easier for the user to assemble the contact plug shown in Figure 7 than to dismantle it.

In an embodiment of a contact plug according to the invention, which is not illustrated herein. the securing means have a securing element in the form of a securing pin which. passing through the protective sleeve 7.

can be inserted in force-locking relationship and/or positively locking relationship into a securing pin opening. acting as the securing opening.

which is provided in the gripping insulation sheathing 3 and/or the pin element 1. With securing means of a design configuration of that kind. to release the protective sleeve 7 it is necessary for either the securing pin to be driven out of the securing pin opening or for the securing pin to be sheared off. Both steps can only be implemented with the involvement of an increased amount of manipulation so that the unintentional implementation thereof is as good as impossible.

In developments of the embodiments as illustrated and not illustrated, the securing means include a desired-rupture location. for example in the form of a notch in a securing pin or a shear-off projection which is operatively connected to the protective sleeve 7 and which can be destroyed at a predetermined force when releasing the protective sleeve 7 from the pin element 1. In that respect it is desirable for the desiredrupture location to be such that the force required to destroy it is so high that unintentional release of the protective sleeve 7 from the pin element 1 is reliably excluded. The destruction force for example can be so great that release of the protective sleeve 7 from the pin element 1 can be effected only with tools and manual forces which can be applied by users of average physical constitution are not sufficient for that purpose.

Claims

1. A contact plug comprising a pin element which has a contact portion and a stranded wire-receiving portion, an insulation sheathing surrounding the stranded wire-receiving portion and a protective sleeve surrounding the contact portion at a radial spacing. characterised in that there are provided fixing means (11, 12) with which the protective sleeve (7) can be releasably fitted to the pin element (1) and/or the insulation sheathing (3), that there are provided securing means (10, 13, 14, 19. 20, 21) which co-operate with the protective sleeve (7) and which permit at least first-time release of the protective sleeve (7) only with an increased amount of manipulation and that the contact portion is in the form of a resilient hollow plug sleeve (5) which can be contacted with a mating pin in a condition of expansion and with a mating socket in a condition of compression.

2. A contact plug according to claim 1 characterised in that the fixing means include a screwthread connection (11. 12) provided between the pin element (1) and/or the insulation sheathing (3) and the protective sleeve (7).

3. A contact plug according to claim 1 characterised in that the fixing means include a rotary bayonet connection provided between the pin element (1) and/or the insulation sheathing (3) and the protective sleeve (7).

4. A contact plug according to one of claims 1 to 3 characterised in that the securing means include at least one securing element (20) which, passing through the protective sleeve (7), can be inserted into a securing opening (14) provided in the pin element (1) and/or the insulation sheathing (3).

5. A contact plug according to claim 4 characterised in that the securing element is in the form of a screw (10) which can be screwed into a securing screwthreaded opening (14) as the securing opening.

6. A contact plug according to claim 4 or claim 5 characterised in that the securing element is in the form of a securing pin which can be inserted in force-locking and/or positively locking relationship into a securing pin opening as the securing opening.

7. A contact plug according to one of claims 1 to 6 characterised in that the securing means include at least one securing projection (20.

21) which is provided on the insulation sheathing (3) and/or the protective sleeve (7) and which is in engagement with a complementary counterpart opening at least prior to a first-time release of the protective sleeve (17).

8. A contact plug according to claim 7 characterised in that there is provided a plurality of securing projections (20. 21) provided on the insulation sheathing (3) and the protective sleeve (7), wherein the securing projections (20. 21) can be brought into engagement with a plurality of complementary counterpart openings.

9. A contact plug according to claim 8 characterised in that the securing projections (20. 21) have steeper flanks in a direction of rotation for release of the protective sleeve (7) than in an opposite direction of rotation for fitting the protective sleeve (7).

10. A contact plug according to one of claims 1 to 9 characterised in that the hollow plug sleeve (5) has a spring slot (6) extending in a zig-zag-like configuration.

11. A contact plug according to one of claims 1 to 10 characterised in that the securing means include a desired-rupture location which can be destroyed at a predetermine force for releasing the protective sleeve (7).

12. A contact plug substantially as herein before described with reference to the accompanying drawings.