GB2273006A

GB2273006A - Electrical plug insulator and protective cap arrangement

Info

Publication number: GB2273006A
Application number: GB9323503A
Authority: GB
Inventors: Thomas Waible
Original assignee: Taller GmbH
Current assignee: Taller GmbH
Priority date: 1992-11-26
Filing date: 1993-11-15
Publication date: 1994-06-01
Anticipated expiration: 2013-11-15
Also published as: DE4239721A1; GB9323503D0; TW232756B; GB2273006B; DE4239721C2

Abstract

The plug comprises a generally plate-shaped insulator 200 for receiving and holding both an electrical fuse in a hat-shaped cover 202 and the electrical connecting pins and has a protective cap 100 which covers the connexions between the wires and the pins. The cap 100 is a one-piece moulded part and projects over the entire base area of the insulator 200. An inner continuous edge of the cap 100 rests against the outer contour of the insulator 200 and corresponds to the thickness thereof. The cap 100 and the insulator 200 may have a plurality of complementary catch fastenings (groove 107, catch stud 212) in the area of peripheral overlap. In another embodiment the cap and the insulator are ultrasonically welded in the area of peripheral overlap. <IMAGE>

Description

2273006 1 "Plug bridge comprising an insulator and a protective cap for an

electrical plug" The present invention relates to a plug bridge for an electrical plug for connecting an electrical appliance to a mains socket.

Electrical plugs (and plug bridges to be incorporated therein) are known (cf. GB 1 581 661, GB 1 581 662, and GB 1 581 663) in which the so-called earth pin acts in the manner of a mechanical release when the appliance plug is inserted in the socket the power or voltage supply system. The earth pin projects ahead of the two other pins or contact pins, and only when the leading end of the earth pin is inserted is it possible for the contact pins to be inserted in accordance with their function.

In addition to this quasi-mechanical safeguard, electrical safety of the plug itself obviously plays a dominant r61e. For this reason, electrical appliances are today more frequently sold with plugs which consist of a cast or injection-moulded body encasing a plug bridge in which the electrical connexions between the connecting cable for the appliance, on the one hand, and 2 the connecting pins or contact pins for the socket, on the other hand, are enclosed. In general, therefore, the electrical appliance and the connecting cable form one unit; the connecting cable can in any case generally be separated by cutting.

The above-mentioned electrical safety is entirely dependent on the connexions in the interior of the plug being completely sealed from the outside, i.e. it is necessary to ensure that no individual wires of the conductor terminals of the connecting cable project outside beyond the contour of the plug or are situated so close to the surface of the plug that when the plug is inserted into the socket the person inserting the plug into the socket suffers damage to his health or even death.

In the case of the known contact plugs the connexion points between the insulated conductor terminals of the connecting cable and the connecting pins securely connected to the plug bridge are covered or screened by a one-piece protective cap.

The known protective caps are provided with a plurality of projecting studs distributed over the periphery on the edge thereof projecting towards the insulator, which are inserted into complementary openings in the W 1 3 insulator during assembly and which have catch hooks which engage in the openings. Apart from the fact that in unfavourable cases individual wires of the cable can become pinched at the interface between the protective cap and the insulator so as to project laterally, there is also the risk that the studs of the protective cap may break off and so only an inadequate catch fastening will be achieved.

It would be desirable to be able to provide a plug bridge in which the connexion between the protective cap and the insulator is made substantially simpler structurally and absolutely safe functionally.

The present invention provides a plug bridge for an electrical plug, comprising: an insulator having a substantially plate-shaped base with through-holes for the passage of contact pins, and a protective cap for covering the upper ends of the contact pins and conductors connected to them, the cap being a one-piece moulding and having a peripheral wall with an inner peripheral surface which rests against the outer peripheral surface of the base of the insulator, the cap and the insulator being fastened together in the region of overlap of the said peripheral surfaces.

4 Such a plug bridge makes it easy to ensure that bare wires are securely enclosed within the confines of the protective cap and the insulator.

In one embodiment the invention provides a plug bridge comprising: a nonconductive, substantially plate-shaped insulator for receiving and holding both an electrical fuse in a hat-shaped cover and the electrically conductive pins (contact pins, earth pin), which at one end project sufficiently to be inserted into hte mains socket and which at the other end are connected to the insulated end cores of an electrical connecting cable, in particular by being pinched in, by way of hollow cylindrical sleeves; and a protective cap which covers the connexion points between the cores and the connecting pins, wherein the protective cap is formed by a one-piece cap-like mo,61ded part which projects over the entire base area of the insulator and the inner continuous edge of which rests agains the outer contour of the insulator while corresponding to the thickness thereof, and the protective cap and the insulator have a plurality of complementary catch fastenings in the area of the peripheral overlap.

In another embodiment the invention provides a plug bridge comprising: a non-conductive, substantially plate-shaped insulator for receiving and holding both an electrical fuse in hat-shaped cover and the electrically conductive pins, which at one end project sufficiently to be inserted into the mains socket and which at the other end are connected to the insulated end cores of an electrical connecting cable, in particular by being pinched in, by way of hollow cylindrical sleeves; and a protective cap which covers the connexion points between the cores and the connecting pins, wherein the protective cap is formed by a one-piece cap-like moulded part which projects over the entire base area of the insulator and the inner continuous edge of which rests against the outer contour of the insulator while corresponding to the thickness thereof, and the protective cap and the insulator have a mutually complementary step in the area of the peripheral overlap, and the protective cap and the insulator are joined together by means of ultrasonic welding processes.

Preferred and optional features of the invention are set forth in the subsidiary claims.

The invention will be described further, by way of example, with reference to the accompanying drawings, which:

6 Figure 1 is a bottom plan view of a protective cap for a plug brige; Figure 2 is a section on line II-II in Figure 1; Figure 3 is an end view of the cap; Figure 4 is a plan view of the cap; Figure 5 is a section on line V-V in Figure 1; Figure 6 is an enlargement of the detail VI-VI in Figure 5; Figure 7 is a bottom plan view of an insulator, with conductive pins, for a plug bridge; Figure 8 is a section on line VIII-VIII in Figure 7; Figure 9 is an enlargement of the detail IX-IX in Figure 8; Figure 10 is a section on line X-X in Figure 7; Figure 11 is a section on line XI-XI in Figure 7; Figure 12 is a plan view of the insulator; T 7 Figure 13 is an enlargement of the detail XIII-XIII in Figure 12; Figure 14 is a view on line XIV-XIV in Figure 13; Figure 15 is a bottom plan view of a plug bridge comprising the protective cap and the insulator with conductive pins; Figure 16 is an end view of the plug bridge Figure 17 is a section on line XVII-XVII in Figure 15; Figure 18 is a section in line XVII1-XVIII in Figure 15; Figure 19 is an enlargement of the detail XIX in Figure 18; Figure 20 is a bottom plan view of a second embodiment of the plug bridge; Figure 21 is an end view of the second embodiment; Figure 22 is a section on line MI-MI in Figure 20; Figure 23 is a section on line MI-MI in Figure 20; and 8 Figure 24 is an enlargement of the detail XXIV in Figure 23.

Figures 15 to 19 show an insulated assembly which comprises a protective cap 100 and an insulator 200, this assembly or so-called plug bridge 1 being supplied as a semi-finished article to the manufacturers of electrical appliances, in particular electrical domestic appliances.

The protective cap 100, the basic form of which is determined by a caplike moulded part 101, will first be explained with reference to Figures 1 to 6. Inside the cross-sectional profile a free space 102 is formed which is closed on one side by the cap base 103 of the moulded part 101 and is open on the other side 104. The space 102 communicates with a semimonocoque attachment 105 which is reinforced by a continuous bead 106 and which is used as an insertion channel for a connecting cable of an electrical appliance. The above-described features of the protective cap 100 can in principle be regarded as being already known.

In addition the protective cap 100 has a plurality of grooves 107 (which may be joined to constitute one continuous groove) behind the surrounding wall of the free side 104 of the moulded part 101 - this may be seen 9 in particular from Figure 6. In the preferred embodiment illustrated - for cooperation with catch studs on the insulator to be described below with reference to Figures 7 to 14 - a pair of spacer webs 108 with freely projecting studs 1081 are integrally moulded distributed over the periphery so that each is adjacent to a groove 107, the purpose of the studs 1081 being to give the moulded part 101 a high degree of stability and to secure the clipped-in insulator with both non-positive locking and positive locking in the assembled state, which will be explained below. In the assembly of a plug bridge 1, the insulator is pressed on from below, until its catch studs are clipped in and the insulator itself rests against the spacer webs.

The insulator 200 will now be explained in greater detail with reference to Figures 7 to 14. It is made of hard-elastic plastics material, and the design, i.e. the external shape, is defined by a flat plate part 201 and a rectangular hat-shaped cover 202. The cover 202 is arranged approximately centrally on the plate part 201 and defines a receiving recess or chamber for an electrical fuse, in the base of the insulator 200.

Two (in particular rectangular) openings for two contact pins 203, 204 are provided parallel to one side of the cover 202 at the specified (standard) distance from each other in the plate part 201. The cross-sections of the contact pins 203, 204 are complementary to the cross-sections of the openings, since ultimately during the injection-moulding of the insulator 200 the contact pins 203, 204 are simultaneously moulded in. An earth pin 205, which likewise has a rectangular shape and is moulded in or fixed respectively during the injection-moulding of the insulator 200, is provided in the opposite side of the cover 202 in a pre-determined relation to the contact pins 203, 204.

The contact pins 203, 204 and the earth pin 205 each project axially parallel to one another from the base of the insulator 200, namely from the side opposite the cover 202; on the inside the contact pins 203, 204 and the earth pin 205 pass into hollow-cylindrical sleeves 206, 207, 208, into which the bared wires of a connecting cable are subsequently inserted. The earth pin 205 is longer than the two contact pins 203, 204, in order to make possible the above-mentioned mechanical unlocking with the leading end. (In the case of shock-proof appliances, i.e. when the earth pin has no electrical function, it can be integrally moulded directly onto the insulator 200).

1 11 11 The mutual arrangement and coordination of the pins of the plug bridge 1 is determined by the socket or the receiving clips thereof, with which the electrical plug is eventually to be used.

On its approximately flat covering side 209 situated parallel to the plate part 201 the cover 202 has two spaced bores 210, 211 into which spring clips are inserted for receiving and holding the electrical fuse. The spring clip adjacent to one contact pin is connected thereto by way of a shorting bar by way of a connecting pin passing through to the outside; the other spring clip is accessible from the top of the cover 202 by way of a connecting pin.

In order to increase the positive locking between the insulator 200 and the contact pins 203, 204 as well as the earth pin 205, the pins are provided with continuous annular grooves in the zone which fits in the plate part 201. During the injection-moulding of the insulator 200, with the pins inserted into the injection mould, the annular grooves are filled so that the pins are firmly secured.

The features of the insulator 200 described above are known in principle; it is also known to provide the connecting pins individually with a conical enlargement 12 so as to be able to introduce the bared wires safely, which is particularly important with respect to automated manufacture. In addition, it is also known in principle to cover the insulator 200 with a protective cap so as to close off the electrical terminals.

The insulator 200 is designed in such a way that a plug bridge 1 joined with both positive and non-positive locking can be produced in conjunction with a protective cap 100 of the type described with reference to Figures 1 to 6. To this end, catch studs 212 are provided on the outer periphery of the insulator 200 to complement the grooves 107 in the inner periphery of the protective cap 100. When the cap 100 is fitted onto the insulator 200 the catch studs 212 engage in the grooves 107 of the cap 100; the cap 100 is securely mounted on the insulator 200 and projects beyond the external contour thereof. Furthermore, the free end face 104 of the cap 100 and the outside of the plate part 201 are flush with each other; on the inside, as mentioned, the insulator rests 200 against the spacer webs 108, with each catch stud 212 being laterally correlated with a pair of webs 108. In order to facilitate the assembly of the insulator 200, the catch studs 212 are designed in such a way that they end in a taper 212, towards the side with the hat-shaped cover 202, cf. Fig. 9.

13 For the sake of completeness it should be further noted that a semimonocoque attachment 213 with a bead 214 is also formed integrally on the insulator 200 in a similar manner to the attachment 105 on the protective cap 100. This attachment 213 is extended towards the hat-shaped cover 202 and is provided with a plurality of ribs 215 which act as a safeguard to prevent an inserted connecting cable from being pulled out.

The assembly or plug bridge 1 comprising the protective cap 100 and the insulator 200 will now be explained with reference to Figures 15 to 19. The starting point is the insulator 200 with its conductive pins (203, 204, 205) projecting outwards; these pins are connected at their second ends, i.e. by way of the cylindrical hat-shaped sleeves (206, 207, 208), to the conductor terminals (bared wires) of a connecting cable which rests securely on the attachment 213 with the ribs 215 at the rear. The protective cap 100 is now mounted on the pre-fabricated unit and is clipped on firmly by way of the catch fastenings each comprising a groove 107 and a catch stud 102. The said catch fastening is clearly shown in Figure 19: the protective cap 100 is pressed over the taper 2121 of the catch studs 212, until the catch studs 212 clip into the grooves 107. At the same time the inside of the insulator 200 then abuts against the cap 100, by way of the spacer webs 108 formed 14 integrally on the cap 100, in such a way that the cap 100 can no longer be raised from the outside, since web 2001 on the insulator 200, complementary to the studs 1081 of the spacer webs 108, engage behind the studs 1081.

In the embodiment according to Figures 20 to 24, the fastening at the peripheral interface of the cap 100 and insulator 200 is produced by ultrasonic welding (cf. Figure 24). The ultrasonic weld is formed between complementary steps 301, 302 moulded integrally in the region of the overlap between the insulator 200 and the protective vap 100. The two parts 100 and 200 rest against each other with positive locking above the transverse surfaces of the steps 301,302 and they are then joined together by ultrasonic welding.

The plug bridge is inserted into an injection mould and has plastics material injected around it to form a finished plug, which therefore appears as an integral plug which is.suspended on the connecting cable and has the three projecting pins for insertion into a socket. The injection moulded material encases the plug bridge without covering the lid of the fuse-receiving recess in the base.

1 Cl ai ms:

1. A plug bridge for an electrical plug, comprising: an insulator having a substantially plate-shaped base with through-holes for the passage of contact pins, and a protective cap for covering the upper ends of the contact pins and conductors connected to them, the cap being a one-piece moulding and having a peripheral wall with an inner peripheral surface which rests against the outer peripheral surface of the base of the insulator, the cap and the insulator being fastened together in the region of overlap of the said peripheral surfaces.

2. A plug bridge as claimed in claim 1, in which the free end of the peripheral wall of the cap is substantially flush with the underside of the insulator.

3. A plug bridge as claimed in claim 1 or 2, in which the insulator includes a cover portion above the base in a region occupied by a recess for receiving a fuse.

4. A plug bridge for an electrical plug, comprising: a generally plateshaped insulator for receiving and holding a fuse and electrical connecting pins which at one end project sufficiently to be inserted into a mains socket and at the other end are connectable to the conductors of an electrical cable, and a protective cap 16 for covering the connexions between the conductors and the pins, the protective cap being constituted by a one-piece cap-like moulded part which projects over the entire base area of the insulator and has an inner continuous edge which rests against the outer contour of the insulator and corresponds to the thickness thereof, the protective cap and the insulator having a plurality of complementary catch fastenings in the area of peripheral overlap.

5. A plug bridge as claimed in claim 4, in which, in the overlap area between the cap and the insulator, the cap has a plurality of grooves distributed over the inner periphery and the insulator has a plurality of catch studs complementary thereto.

6. A plug bridge as claimed in claim 5, in which the plurality of grooves are connected together to constitute a uniform continuous annular groove.

7. A plug bridge as claimed in claim 5 or 6, in which the catch studs taper towards the upper side of the insulator.

8. A plug bridge as claimed in any of claims 5 to 7 in which the protective cap comprises a pair of spacer webs in lateral correlation with each catch stud of the i I? insulator.

9. A plug bridge as claimed in claim 8, in which the spacer webs cooperate with the edge region of the insulator between the catch studs and the grooves in such a manner that clamping occurs by way of webs on the insulator and studs on the spacer webs.

10. A plug bridge as claimed in any of claims 4 to 9, in which the cap and the insulator have respective integrally formed half-shells which together define a conduit for the cable, the half shell of the insulator being extended into the insulator and constructed with ribs to prevent the cable from being pulled out.

11. A plug bridge for an electrical plug, comprising: a plate-shaped insulator for receiving and holding a fuse and electrical connecting pins which at one end project sufficiently to be inserted into a mains socket and which at the other end are connectable to the conductors of an electrical cable, and a protective cap for covering the connexions between the coductors and the pins, the protective cap being constituted by a one-piece cap-like moulded part which projects over the entire base area of the insulator and has an inner continuous edge which rests against the outer contour of the insulator and corresponds to the thickness thereof, 18 the protective cap and the insulator having mutually complementary steps in the area of peripheral overlap, and the protective cap and the insulator being joined together by ultrasonic welding.

12. A plug bridge substantially as described with reference to Figures 1 to 19 or Figures 20 to 24 of the accompanying drawings.

13. An electrical plug comprising a plug bridge according to any preceding claim.

14. An electrical plug as claimed in claim 13, in which the plug bridge is encased in injection-moulded material.

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