GB2076598A

GB2076598A - Improvements in Electrical Connectors

Info

Publication number: GB2076598A
Application number: GB8013484A
Authority: GB
Original assignee: Harvey Hubbell Inc
Current assignee: Harvey Hubbell Inc
Priority date: 1978-01-09
Filing date: 1978-12-12
Publication date: 1981-12-02
Also published as: DE2855685A1; DE2855685C2; GB2076598B; AU521978B2; FR2414261A1; GB2019667B; GB2019667A; ZA786796B; CA1103771A; JPS5495394A; SE7900159L; AU4280678A; SE423292B

Abstract

An electrical connector comprises an integrally molded housing having a dead-front base through which electrical contacts extend and a pair of rigid side covers (240, 260) pivotally connected to it by web hinges (210, 211). The side covers fold about the web hinges to: (i) force insulated cord conductors into insulation displacement terminals (206) which form part of the contacts and which are fixed to the base and thus wire the connector: and (ii) safely enclose the wiring area. The side covers are also locked to the dead-front base by the engagement of mating portions of the covers and base to prevent relative motion should the web hinges fail. The connector can have male 202 or female contacts or both. <IMAGE>

Description

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SPECIFICATION

Improvements in Electrical Connectors

The invention relates to electrical connectors and concerns dead-front electrical connectors 5 which are inexpensive to manufacture and safe to use.

There are two broad categories of electrical plug connectors; live-front and dead-front type. In the live-front type, the screws for securing the 10 cord conductors to the terminals are reached through the face or front of the connector. After the screws are tightened the front is usually covered by a removable insulating disc. This type of connector has few parts and is simple and 15 inexpensive. It requires, however, a high level of care in wiring and maintenance to ensure safety. One common danger of such connectors is that the removable insulating disc covering the front may become damaged or lost and the live 20 terminals may thereby be exposed. In connectors of the dead-front type there is a heavy insulating base at the front of the connector and the terminal screws are accessed from behind this base. The wiring area is usually fully enclosed 25 after wiring. Such connectors can accommodate greater vairations in the quality of wiring and maintenance without loss of safety or service. However, prior art electrical connectors of the dead-front type generally have had more parts 30 and have been more costly to produce than connectors of the live-front type.

One of the many ways of connecting insulated conductors to terminals of wiring devices is the so-called insulating displacement technique 35 which typically involves pushing a conductor into a terminal slot by a pair of hand pliers such that the slot cuts through the insulation and makes electrical contact with the conductor wire. This technique typically requires skillful operators and 40 convenient access to the terminal slots permitting the use of hand pliers.

The objects of the invention include providing at least one of the following; a high strength one-piece housing for a dead-front electrical connector; 45 a housing of this type which fully insulate the wiring area of the connector; a dead-front electrical connector which affords great ease of wiring and assembly; a dead-front connector which eliminates the variability of workmanship 50 associated with screw-type terminal wiring and stripping of conductor ends for screw-type terminals; a connector having a housing made up of a dead-front base and web-hinged side covers which lock to the housing when closed so as to 55 remain locked even in the absence of the holding action of the web hinges; and a dead-front connector which is particularly simple and inexpensive to make, assemble and use.

According to the invention there is provided a 60 dead-front connector having a housing for electrical terminals to which conductors of an electrical cord may be wired comprising:

a dead-front base having a front face and at least a pair of openings for passage of electrical

65 contacts through the base, at least one rigid side cover having a front end and a back end and a web hinge connecting the front end of the at least one side cover to the dead-front base for pivoting the at least one side cover about a hinge axis 70 which extends adjacent said front face, said side cover pivoting between a closed position in which its back end is spaced from the front face along a longitudinal axis transverse to the front face and an open position in which its back end is spaced 75 from the base along a lateral axis transverse to said longitudinal axis, said dead-front face and side cover and web hinge being integrally molded as a unitary structure made of an electrically insulating material;

80 locking means which are in addition to said web hinge and comprise base portions molded integrally with said dead-front base and side portions molded integrally with said at least one side cover, said base and side portions engaging 85 each other matingly when the at least one side cover is in its closed position to resist movement of at least the front end of the at least one side cover relative to the dead-front base along said longitudinal axis as well as along any lateral axis; 90 and at least a pair of terminals each made of an electrically conductive material and disposed adjacent a respective one of said openings in the dead-front base, each terminal having an 95 insulation displacement slot which is behind said front face of the base and extends generally transversely of the longitudinal axis and has a lead-in end open toward said at least one side cover, each terminal being fixedly positioned 100 relative to said base, said side cover including a pusher block molded integrally therewtih and extending, when the side cover is in its closed position generally along at least a portion of each of the terminal slots and adjacent thereto, 105 whereby an electrical conductor with intact insulation may be placed at the lead-in end of each terminal slot when the side cover is in its open position and pushed into the slot by the pusher block as the side cover is brought to its 110 closed position to have its insulation broken through by the terminal slot and to make electrical contact therewith.

The invented connector is of the dead-front type and makes use of a particularly convenient 115 and effective combination of pivoted side covers, and insulation-displacement terminals. One embodiment of the connector comprises a housing made up of a dead-front base and a pair of side covers having front end pivotally connected 120 to the base by web hinges. The base and side covers are integrally molded as a one-piece structure made of an electrically insulating material. The base supports terminals, such as a pair of power terminals and a ground terminal, 125 which have wiring ends extending back of the base. The terminals may have male contacts, such as a pair of power blades and a ground pin extending through suitable openings in the dead-front base, or they may have female contacts

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receiving male contacts passing through suitable openings in the dead-front base, or both types of contacts. Locking portions may be molded integrally with the dead-front base and the side 5 covers which engage when the connector is closed and the back ends of the side cover are secured to each other, which locking portions resist relative motion between the side covers and the dead-front base so as to supplement and even 10 replace, if needed, the holding action provided by the web hinges. The electrical cord may be wired to the terminals in the course of folding the side covers to close the connector by having the wiring ends of the terminals in the form of insulation 15 displacement slots opening toward one of the side covers. The intact insulated conductor wires of the cord are laid against the open ends of the terminal slots and the conductors are pushed into the slots, as the side cover facing the open ends 20 of the slots is being closed, by a pusher shelf or shelves integrally formed with that side cover and suitably displaced with respect to the terminal slots. The terminal slots may be curved to be along an arc centered at one of the hinges so as 25 to facilitate the insulation displacement connection. Their open ends may be staggered such that one of the cord conductors would start being pushed into its slot before another. The dead-front base may have barrier walls which 30 surround the wiring parts of the terminals to keep them out of electrical contact with each other and, moreover, to prevent the terminal slots from being undesirably widened when the insulated conductors are being pushed into them. The 35 locking means which resist relative motion between the side covers and the dead-front base when the connector is closed may include integrally formed means for locking, in a permanently closed position, the side cover which 40 does not face the open ends of the terminal slots so as to use the permanently locked side cover as a shelf against which the cord conductors can be laid prior to closing the other cover as as to make the insulation displacement connection. 45 Figure 1 is a side elevational view of an assembled embodiment of an electrical connector made in accordance with the present invention. Figure 2 is a sectional view taken along lines 2—2 of Figure 1,

50 Figure 3 is a top view of an open position of the connector shown in closed position in Figure 1, Figure 4 is a partly side elevational and partly sectional view taken along lines 4—4 of Figure 3, Figure 5 is a sectional view taken along lines 55 5—5 of Figure 4,

Figure 6 is a sectional view taken along lines 6—6 of Figure 4,

Figures 7 and 8 are partly sectional and partly side elevational views of a portion of the 60 connector of Figure 1 illustrating the operation of selected locking means,

Figure 9 is a partial sectional view taken along lines 9—9 of Figure 3,

Figure 10 is a view similar to that shown in 65 Figure 4 but showing a cord and an individually insulated conductor thereof in position for wiring to the connector, and

Figure 11 is a view similar to that in Figure 10 but showing the connector in its closed position and the cord conductor wired to the connector.

Referring now to Figures 1—11, there is shown an embodiment 200 of a dead-front electrical connector according to the invention herein. It generally comprises a connector body or housing 201 and electrical contacts, such as male contacts comprising two power blades 202 and 203 and a ground pin 204. The dead-front electrical connector 200 is adapted to make electrical connection between a cord 213, comprising three individually insulated wire conductors 214, 215 and 216, and a grounded electrical recepticle which is not shown. The body or housing 201 of the dead-front electrical connector 200 is generally comprised of a dead-front member or base 220 and two side covers 240 and 260 which are pivotally connected to the base 220 by web hinges 210 and 211. The entire connector body or housing 201 is integrally formed, as by molding, of an insulating material which may be nylon.

The dead-front base 220 of the connector housing 201 comprises a base plate 221, the outer surface of which forms a smooth insulating front face 221 a of the connector 200. A pair of parallel grooves or recesses 222 and 223 are formed into the back side of the base plate 221 at opposite sides thereof but do not go through it. A similar pair of grooves or recesses 222a and 223a are formed into the base plate 221 adjacent the recesses 222 and 223. In order to simplify ..forming the housing 201 by a molding process, the recesses 222a and 223a go through the entire thickness of the base plate 221 so that the mold can form each with a lip such as the lip 223a' seen best at Figures 7 and 8. The purpose of these recesses is to engage mating locking portions integrally formed with the side covers 240 and 260, as discussed in greater detail below.

A thicker central portion 224 of the dead-front -base 220 is formed integrally with the base plate 221 thereof and serves as a supporting and mounting block for the contacts which, in this illustrative case, are shown as the power blades 202 and 203 and the ground pin 204. To this end, two rectangular openings 225 and 226, and a U-shaped or an O-shaped opening 227 are formed through the central portion 224 and integral base plate 221 to receive the power blades 202 and 203 and the ground pin 204 respectively. One or more of the openings 225, 226 and 227 may be provided with a sealing sleeve, e.g., sealing sleeve 228 of opening 225, which sleeve extends longitudinally, i.e., along the vertical direction in Figure 1, into the opening 226. The power blades 202 and 203 and the ground pin 204 are pushed down (in the down direction in Figure 1) through the openings 225, 226 and 227, respectively, to the positions illustrated in Figures 1—11.The power blades

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202 and 203 may be retained in their positions by barbs formed integrally therewith, such as barbs 208 of power blade 202. The ground pin 204 may have similar barbs though they are not 5 shown in Figures 1—11.

The power blades 202 and 203 and the ground pin 204 are integrally formed with insulation displacement terminals 205,206 and 207, respectively, which extend above the thickened 10 portion 224 of the base 220 and are for the purpose of making wiring connections with the three wire conductors 214, 215 and 216 of cord 213, as described in greater detail below. An insulation barrier wall 229 is integral with and 15 upstanding from the central thickened portion 224 of the dead-front base 220 and serves to isolate the terminals 205, 206 and 207 from each other.

A pair of dowel pins 230 and 232 protrude 20 laterally from opposite sides (right and left in Figure 3) of the dead-front base 220. More particularly, the dowel pins 230 and 232 flank the ground pin 204 and protrude laterally outwardly in opposite directions. The purpose of the dowel 25 pins 230 and 232 is to engage with mating locking portions of the side covers 240 and 260, respectively, when the side covers are closed to provide a locking connection, as discussed in greater detail below.

30 The first side cover 240 comprises a panel 241, which in the illustrated case is semi-circular in section as best seen in Figure 6. The web hinge 210 which connects the front end of the side cover 240 to the base 220 is integrally formed 35 with both and comprises a thin web of the same material. The periphery of the panel 241 which faces the other side cover 260 is formed with a recess 243' and a flange 243 which, as explained below, engage with a mating lip and recess of the 40 second side cover 260. The back end of the side cover 240 is formed with a semi-circular opening 244 to permit passage of the cord 213 and possibly a surrounding sealing grommet which is not shown. A pair of flanges or lugs 247 and 248 45 protrude from opposite sides of the side cover 240 toward the base 220, to be received into the recesses 222 and 223 of the base 220, respectively, when the side cover 240 is pivoted about the hinge 210 and is brought to its closed 50 position illustrated in Figures 1 and 8, as discussed in greater detail below. A cord clamp 250 extends diagonally between two thickened portions 252a and 2526 of the back panel 241, and a strengthening rib 253 may also be provided 55 in connection with the cord clamp tooth. Two openings 254 and 255 are formed through the side cover 240 and are counter-sunk into the outside surface of the panel 241 as best seen in Figure 2, for use in connection with assembly 60 screws discussed in greater detail below. The first side cover 240 also has a portion formed with a recess 258 which matingly receives the dowel pin 230 as best seen in Figure 11, when the side cover 240 is in its closed position.

In addition, the first side cover 240 includes a pusher block generally indicated at 188 in Figure 6 which, as explained in greater detail below, serves to make an insulation displacement connection between the wires of the cord 213 and the terminals 205,206, and 207 as the first side cover 240 is brought to its closed position. The pusher block comprises a top shelf 189 and a bottom shelf 190 which are generally parallel to the front face 221 a when the connector is closed or folded but are spaced from each other so as to permit the free ends of the terminals 205,206 and 207 to enter in the space between them. The top pusher shelf 189 is formed with semi-circular recesses 189a, 1896 and 189c which are aligned with the terminals 205, 206 and 207, respectively, and are dimensioned to partly receive the insulated conductors 214, 215 and 216. The bottom pusher shelf 190 is formed with similar semi-circular recesses 190a, 1906 and 190c which are similarly disposed and shaped. In addition, the bottom pusher shelf 190 has a cutout 190^ disposed and dimensioned to receive a portion of the barrier wall 229 which is between the terminals 205 and 207, and a similar cutout 190e similarly shaped and disposed to receive a portion of the barrier wall 229, which is between the terminals 206 and 207. A further recess 191a is disposed and shaped to receive a portion of the barrier wall 229 which is on the outward side of the terminal 205 and another recess 191 b is shaped and disposed to receive a portion of the barrier wall 229 which is on the outward side of the terminal 206. Strengthening ribs 192a, 1926 and 192c connect the two pusher shelves 189 and 190 and are dimensioned and positioned to enter into mating insulation displacement slots 205a, 206a and 207a of the terminals 205,206 and 207, respectively, when the first cover 240 is brought to its closed position.

The second side cover 260 is similar to the first side cover 240 and comprises a similar panel 261. The second side cover 260 is hingedly connected to the dead-front member 220 by web hinge 211. A wall 263 extends around the periphery of the panel 260 which faces the first side cover 240, and the wall 263 is in the form of a flange which protrudes toward the side cover 240 from a surrounding recess 263' such that when the connector is folded or closed to the position shown in Figures 1 and 11, the wall 243 of the first side cover 240 fits in the recess 263' of the second side cover 260 and the wall 263 of the second side cover 260 fits in the recess 243' of the first side cover 240. The wall 263 includes a semi-circular opening 264 which cooperates with the opening 244 in wall 243 to accommodate passage of the cord 213 and of a possible associated grommet, not shown. A pair of flanges or lugs 267 and 268 extend from opposite side of the side cover 260 toward the base 220 and are positiond and dimensioned to be engaged matingly by the recesses 222a and 223a, respectively, of the base 220 when the side cover 260 is brought to its closed position. As

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best seen in Figures 7 and 8, the flange or lug 268 has a locking tooth 268a dimensioned and positioned to snap against a lip 223a' in the recess 223a when the side cover 260 is brought 5 to its closed position so as to permanently retain the side cover 260 in said closed position. A cord clamp tooth 270 extends diagonally between blocks 272 and 273 which are formed integrally with the side cover 260, and may have a 10 strengthening rib 270a. The cord clamp teeth 250 and 270 are oriented such that they criss-cross when the connector is assembled so as to suitably deform the cord 213 and grip it securely. Two openings 274 and 275 are formed partially into 15 the blocks 272 and 273, respectively to receive self tapping assembly screws passed through the openings 254 and 255 of the first side cover 240, as discussed in greater detail below. The second side cover 260 also has a recess 278 20 dimensioned and positioned to matingly receive the dowel pin 232 when the second side cover is in its closed position.

The connector illustrated in Figures 1—11 is assembled as follows. The power blades 202 and 25 203 and the ground pin 204 are forced down into their respective openings 225,226 and 227 to the positions illustrated in Figures 4 and 9. The second side cover 260 is then brought from the open position shown in solid lines in Figure 4 to 30 the closed or folded position shown in broken lines in the same figure. Note that, as best illustrated in Figure 8, when the second side cover 260 is brought to its closed position it is permanently locked in that position by the 35 engagement of the locking teeth 267a, 268a and the lips 222a', 223a'. To wire the terminal, the outer insulation 213a of the cord 213 is stripped for a length short enough to permit the outer insulation 213a to be gripped by the clamp teeth 40 250 and 270 when the connector is assembled and the three wire conductors 214, 215 and 216, with their individual insulations intact, are placed into the respective recesses formed by the barrier walls 229 for the respective terminals 205, 206 45 and 207, as illustrated in Figure 10 for the wire 215. Note that the insulation displacement slots of the terminals have widened lead-ins at their free ends to facilitate alignment of the insulated wires with the respective slots. Moreover, the 50 lead-ins or the slots or both may be thinned out or sharpened to help cut through the insulation of the wires being pushed into the terminal slots. Note also that the width of the slot is no greater than the respective diameters of the conductor 55 wires to be wired thereto and that the barrier walls 229 are closely adjacent to the tines forming the terminal slots so as to constrain the tines and prevent undesirable opening and setting of the slots due to slot spreading forces when the 60 wires are being pushed into them. Not also that the terminal slots are staggered, that is, the slot 207a extends further to the right side of Figure 3 than the other two slots. If desired, the other two terminal slots may also be staggered with respect 65 to each other. This staggering is for the purpose of avoiding having to force all three wires 214, 215 and 216 simultaneously through the respective lead-ins of their terminals, thus avoiding excessive stress and strain.

After the second side cover 260 is brought to its closed position illustrated in Figure 10, and the three wires 214,215 and 216 are placed at the lead-ins of their respective terminals slots 205a, 206a and 207a in the manner illustrated for the wire 215, the first side cover 240 is pivoted about the hinge 210 toward the second side cover 260. ■ The upper and lower pusher shelves 189 and 190 engage the portions of the wires 214, 215 and 216 immediately above and immediately below the lead-ins of the terminals. In particular, since the lead-in of terminal 207 extends furthest toward the side cover 240, the recesses 189c and 190c and the rib 192c engage the wire 216 before the other wires 214 and 215 are similarly engaged. As the first side cover 240 is moved further toward its closed position the wire 216 is formed through the lead-in of terminal 207 into its insulation displacement slot 207a, in the process of which the terminal cuts through the insulation of the wire 216 and makes electrical contact with the electrical conductor thereof.

Note that the rib 192c enters into the terminal slot 207a to push the wire 216 further therein as the first side cover 240 is brought to its fully closed position. The wires 214 and 215 are similarly forced into the slots 205a and 206a, respectively, by the respective recesses 189a and 190a and rib 191 a, and recesses 1896 and 1906 and rib 1926, as the first side cover 240 moves further toward its closed position. When the first side cover 240 reaches its closed position it not only helped make electrical contact between the terminals and the wires but has also helped fully enclose the wiring area and grip the cord 213 between the cord clamp teeth 250 and 270 as illustrated in Figure 11. The fact that the slots • 205a, 206a and 207a extend along curves which are substantially arcs of a circle centered at the hinge 210 helps facilitate breaking through the insulation of the wires 214,215 and 216 as the first side cover 240 is brought to its closed position. The back portions of the two side covers 240 and 260 are secured to each other by assembly screws 286 and 287 which pass through openings 254 and 255, respectively, in the first side cover 240, and are self tapping into partial openings 274 and 275, respectively, of the second side cover 260. The first side cover may be moved by hand toward its closed position until it starts engaging at least the wire 216, and the assembly screws 286 and 287 may be then turned by a screw-driver or otherwise to exert the remainder of the force necessary to assemble the connector completely.

When the two side covers 240 and 260 are in their closed positions, as shown in Figure 11, the lugs 230 and 232 are matingly received in the recesses 258 and 278, respectively and resist relative motion between the base 220 and the

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side covers 240 and 260 both in the longitudinal direction (i.e., in the vertical direction in Figure 11) and in a lateral direction parallel to the hinges

210 and 211. The lugs 267 and 268 are received 5 in their respective recesses 222a and 223a as illustrated for the lug 268 in Figure 8 and the respective locking teeth 267a and 268a are locked against the respective lips 222a' and 223a', as illustrated in Figure 8 in the case of the 10 lug 268. This permanent locking arrangement between the lugs 267 and 268 and the respective recesses 222a and 223a resists relative movement between the second side cover 260 and the base 220 in the longitudinal direction as 15 well as in any lateral direction transverse to the longitudinal one. The engagement of the lugs 247 and 248 of the first side cover 240 into the recesses 222 and 223 of the base 220 resists movement of the first side cover 240 relative to 20 the base in any lateral direction transverse to the longitudinal one. These engagements between locking or mating portions integrally formed with the base and side covers, relieve forces which might act on the web hinges 210 and 211 and 25 permit the connector to be assembled or reassembled conveniently and to be used safely even if one or both of the web hinges 210 and

211 are weakened or torn.

The connector illustrated in Figures 1—11 may 30 be used as a plug having male contacts, as illustrated, or as a connector having female contacts, not illustrated, in place of the blades . 202 and 203 and the ground pin 204. Each of such female contacts would be electrically 35 connected as by being integrally formed, with a respective one of the insulation displacement terminals 205, 206 and 207. Alternately, the connector illustrated in Figures 1—11 may have one or more male contacts and one or more 40 female contacts.

Thus, the dead-front electrical connectors illustrated in Figures 1—11 are made up of a single molded housing or body to which only electrical contacts and terminals and perhaps 45 assembly screws need be added, which achieves low manufacturing and assembly cost. No separate parts are likely to be lost during wiring, and the open position of one or both of the side covers allows complete access to the wiring area. 50 In the case of the connector shown in Figures 1— 11, the variability of workmanship associated with screw-type terminals is eliminated both with respect to the quality of stripping conductor ends and with respect to terminal screw tightening 55 torques. The interlocking of the side casings and base of all of the connectors discussed above relieve stresses on the web hinges and provide a strong structure which remains fully insulated and serviceable despite possible weakening or failure 60 of the web hinges.

The above described dead-front connector is also described and features of it claimed in our co-pending Application No. 8013484 which was divided from the present Application.

Claims

65 Claims

1. A dead-front connector having a housing for electrical terminals to which conductors of an electrical cord may be wired comprising:

a dead-front base having a front face and at 70 least a pair of openings for passage of electrical contacts through the base, at least one rigid side cover having a front end and a back end and a web hinge connecting the front end of the at least one side cover to the dead-front base for pivoting 75 the at least one side cover about a hinge axis which extends adjacent said front face, said side cover pivoting between a closed position in which its back end is spaced from the front face along a longitudinal axis transverse to the front face and 80 an open position in which its back end is spaced from the base along a lateral axis transverse to said longitudinal axis, said dead-front face and side cover and web hinge being integrally molded as a unitary structure made of an electrically 85 insulating material;

locking means which are in addition to said web hinge and comprise base portions molded integrally with said dead-front base and side portions molded integrally with said at least one 90 side cover, said base and side portions engaging each other matingly when the at least one side cover is in its closed position to resist movement of at least the front end of the at least one side cover relative to the dead-front base along said 95 longitudinal axis as well as along any lateral axis; and at least a pair of terminals each made of an electrically conductive material and disposed adjacent a respective one of said openings in the 100 dead-front base, each terminal having an insulation displacement slot which is behind said front face of the base and extends generally transversely of the longitudinal axis and has a lead-in end open toward said at least one side cover, each terminal 105 being fixedly positioned relative to said base, said side cover including a pusher block molded integrally therewith and extending, when the side cover is in its closed position generally along at least a portion of each of the terminal slots and 110 adjacent thereto, whereby an electrical conductor with intact insulation may be placed at the lead-in end of each terminal slot when the side cover is in its open position and pushed into the slot by the pusher block as the side cover is brought to its 115 closed position to have its insulation broken through by the terminal slot and to make electrical contact therewith.

2. A dead-front connector as claimed in Claim 1, wherein each terminal is electrically isolated

120 from the one or more other terminals.

3. A dead-front connector substantially as hereinbefore described with reference to and as illustrated in Figs. 1 to 11 of the accompanying drawings.

Printed for Her Majesty's Stationery Office by the Courier Press, Leamington Spa, 1981. Published by the Patent Office, 25 Southampton Buildings, London, WC2A 1 AY, from which copies may be obtained.