CA1127735A - Interlock of blade and housing side - Google Patents

Abstract

INTERLOCK OF BLADE AND HOUSING SIDE

ABSTRACT OF THE DISCLOSURE
A dead front plug is provided having low cost, strong and reliable interlock between a power blade of the plug and the insulating housing. An efficient inter-lock is achieved at low cost by forming a laterally extending part on the interval portion of the power blades of the plug and by forming a slot integrally with the side walls of the insulating housing to receive the laterally extending part. The housing is preferably of a clam shell design so that the side slots can easily and reliably interlock with the blades as the clam shell housing is folded into a closed position.

Description

~lZ7!735 INTERLOCK OF BLADE AND HOUSING SIDE
The present invention relates-to an electrical , connector and more specifically~to a connector which has;a so-cal}ed~"dead front" construction.
, ~ ~ Electrical connectors which have dead front con- ~-struction have no exposed parts to which wires are attached other than the electric blades which are to receive power from a receptacle or the openings to the ~ contacts of a receptacle itself.
,;~ The concept of the use of a dead front type of construction is that~lt increases the safety asuociated ~ with the use of connectors including both plugs for -~ receiving electric power and receptacles for delivering -~ electri:c power to plugs. In prior art devices there was access to the screws to which~wires were connected through the face of the plug having the power blades extending therefrom. For many such prior art plugs there were variou8 forms of covers that were to be placed over the ; face and to have the blades extending through the cover, but these covers were not always employed by the users of the plug so that when the cover was absent the screws to which wires were attached were accessible from the face.
Further, any wire attached to the screws which became loose or unravelled could extend out from the plug to make contaat with a user or with a metal plate into which the plug was inserted.
In recent times the standard making .
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, llZ7735 organizations, particularly the Underwriters Laboratories, have studied this problem and have determined that connectors, and particularly plugs, should have a dead front construction. The mandating of the use of dead front plugs by UL was subject of a standard and this standard is now in force.
One patent which described a dead front plug construction is the Hoffmann U.S. patent 4,010,999 dated March 8, 1977. Such a construction was known piror to the Hoffmann patent and was in fact shown and described in British patent 676,144.
It is one object of the present invention to provide a connector which is economical to manufacture and which is reliable in use.
Another object is to provide a connector having a clam shell type construction and having a reinforcement between the blade and sides of the clam shell.
A further object is to provide a connector having a clam shell type construction with an interlock between the blade and the folding sides of the clam shell type structure.
Other objects and advantages of the invention will be in part apparent and in part pointed out in the description which follows.
The present invention concerns a dead front connector as the term dead front is employed in this art. The dead front connector has an outer housing in the general form of a clam shell structure and has electrical contacts mounted at least partially within the structure. The contacts themselves are oversized in at least some portion thereof and there are internal portions of the clam shell like housing structure which are adapted to receive the oversi2ed blade portions to form an interlock between the blade and housing. The interlock C

11~7q35 between blade and housing prevents a separation of the contacts from the portion of the housing constituting the sides of the clam shell even in the event that the sides are severed from the bottom of the clam shell.
The present invention will be better understood by reference to the accompanying drawings in which:
Figure 1 is a perspective view of a plug and power supply wire as provided pursuant to the present invention.
Figure 2 is a perspective side view of the housing of the plug of Figure 1 shown in an opened position with power blades posed for entry into the housing.
Figure 3 is a partial plan view of the exterior of the housing of the plug of Figure 1 also shown in an opened position.
Figure 4 is a sectional view taken along the line Figure 4-4 of Figure 3.
Figure 5 is a sectional view taken along the line Figure 5-5 of Figure 3.
Figure 6 is an end elevation of the insulating housing of the plug as illustrated in Figure 1 in part broken away and portraying the housing in a partially opened position.
Figure 7 is an end elevational view similar to that of Figure 6 with the housing shown in the closed position and with the housing partially broken away to show a portion of the interior thereof.
Figure 8 is a side elevational view of the plug of Figure 1 with portions broken away to illustrate the relationship of the parts therein.
Figure 9 is a perspective view of a power blade as used pursuant to the present invention.
Figure 10 is a top plan view of the insulating housing of the plug of Figure 1 showing the housing in a fully opened position to view the interior thereof.
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, 112'~ 5 With reference co che Figures structural details and features of the present invention are pointed out.
In Figure 1 a plug as provided pursuant to the present invention is illustrated in perspective view.
The plug 10 is provided with a power supply conductor 12.
The conductor has an outer insulation 14 covering two inner wires 16 and 18, each of which is provided with insulating sheaths 20 and 22. For essentially all con-nectors of the present invention, provision is made for receiving and retaining a conductor, such as 12, in the mechanism of the connector and for making electrical connection within the device between the conductors 16 and 18 and the electrical contacts of the device. In the case of plug 10 the contacts have the external power blades 24 and 26 which are connected respectively with the conductors 16 and 18.
The insulating housing into which the blades 24 and 26 as well as the wire 12 enters is a plastlc insulating housing made up of three portions, two of which are side portions 30 and 32, and the other of which is a base portion 34. The side and base portions are connected by thin sections of the material which serve as webs or hinges 36 and 38. The two side portions 30 and 32 are held together by a screw member, the head of which 40 is shown in place in side 30 of housing 10. The screw head 40 is shown in phantom as 40', which with its shank 42', is poised directly above the hole in housing 10 where screw 40 is positioned to close sides 30 and 32 of the housing 10.
Referring next to Figure 2, the insulating housing 11 of plug 10 is shown in an opened position with a perspective view of the interior thereof, and with che power blades 24 and 26 of the contacts 60 and 62 shown poised for insertion into receiving openings in the base 34 of the housing 11. The side portions 30 and 112'~735 32 of the housing ll are made up of cord re~training portions 44 and 46 near the point where the cord enters housing ll and contact retaining portions 48 and 50 adjacent to the respective cord retaining portions.
The base 34 is also adjacent to the contact retaining portions 48 and 50.
This base 34 receives. the two contacts 60 and 62 as the blades 24 and 26 respectively are inserted through the base to occupy the position illustrated in Figure l.
The base 34 is illustrated from the bottom in Figure 3 with the webs 36 and 38 extending QUt from the base 34 to portions of the side structures 30 and 32. The blade ports 52 and 54 are the ports through which the blades 24 and 26 are inserted during assembly of the connector 10. The two latch wells 56 and 58 adjacent to the blade ports 52 and 54 respectively receive and hold a latch element to hold the blades in place once they are inserted. The portion of the housing illustrated in Figure 3 is shown in section in Figures 4 and 5.
The Figure 4 is a transverse sectional view taken along the lines 4-4 of Figure 3 and showing the base 34 in vertical section. Figure 5 is a longitudinal sectional view taken along the line 5-5 of Figure 3 and showing the base 34 and adjoining portions in section.
It will be noted particularly from contact 60 of Figure 2 that a latch is formed by stamping the tab 64 out of a portion of contact 60 which portion is immediately above the elongated blade portion 24.
The blade 24 is inserted through the blade port 52 in the manner illustrated in Figure 2 and as is evident from Figure 4 such insertion will bring the tab 64 into the latch well 56 after the tab has been compressed and squeezed by the well wall 66.

1127~73.5 - 6 - .
As is also evident from Figure 4, the base 34 is also provided with internal wells 70 and 72. The contact 62 has an offset arm 74 which holds the bladed end 76 of the contact 62. The offset arm 74 extends from the main axis of the contact 62 by a cross arm 78. The cross arm 78 seats within the internal well 70 on the platform 80 at the bottom of well 70.
The offset arm 74 may rest against the internal side wall 82 of well 70. Similarly, the contact 60 is situated in the port 54, latchwell 58 and internal well 72 of base 34 in essentially a mirror image fashion to the situation of contact 60 in the base 34. It is evident from consideration of the configuration of the contacts 60 and 62 as well as the internal and external wells of the body 34 that when the contact is inserted in place in the base, the blade will extend out of the base for its normal purpose of insertion into a receptacle. Accordingly the contact itself will be precisely located within and held within the base 34 in a position which cannot be easily altered independently of whether or not a wire has been assembled to the device and whether or not the device has been assembled as illustrated in Figure 1.
For example, the tendency of the blade to be forced out of the base 34 as the blades are inserted into a receptacle is resisted by the tab 64 pressing against the upper wall of the well 56 and 58. Conversely where the tension is applied to the outwardly extending blade portions 24 and 26 the blade cannot be moved out of its place in the base 34 due to the cross arm 78 of the contact abutting against the platform 80 at the bottom of the internal well 70 of base 34.
The firm securing of the blade in the base is accomplished prior to any assembly of the sides of the housing 11. Accordin~ly,the combination of the con-figuration of the contacts. taken together with the : . ,:

112'-~!735 configuration of the base 34 provides a result which permits the connector to be assembled and contact to be made with conductors positioned therein with great ease of manufacture and assèmbly and with great reliability of operation and performance. The illustration of the contacts fully assembled into the base 34 iæ
given in Figure 10 which is a top plan view of the fully opened connector with the contacts pressed into place and held firmly in place in the base 34 of the connector.
Turning now to Figure 6, there is illustrated a side elevational view in part broken away and in section of a fold up housing 11 being folded in clam shell fashion to close the two sides of the housing 30 and 32 together above the base 34. The folding action takes place based on the high flexibility of the web or hinge portions 36 and 38.
In Figure 7 the side elevational view of the folded connector and blade combination of the present invention, in part broken away, is illustrated with the power blades in place. In this illustration the blade 26 extends downward from the base 34 of the closed housing 10. Once the housing is closed the blade is anchored in place extending from housing 10 by the upper tab 108.
It will be noted accordingly that a very important aspect of the present device is the provision of means by which a wiring device may operate in the opened condition, and prior to the assembly or full assembly of the device into the final closed condition as illustrated in Figure 1.
In Figure 2 the contacts 60 and 62 are illus-trated in their position poised for entry into the base 34. Once the contacts are inserted in place they are firmly retained as part of the base and independent of the support and assistance of the two side portions 30 :` ,, :
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llZ,7 735 and 32 of the clam shell-like structure of the housing 11 of the connector. Accordingly, while the sides 30 and 32 of the clam shell do lend substantial assistance and support to the contacts, the base is able to operate and the combination of the housing 11 and the contacts 60 and 62 serve as a functioning unit for attachment of a wire such as 12 thereto in a manner to be described below. However, as furnished to the public, the unit comprises the insulating body 11 with the contacts 60 and 62 mounted therein and with an assembly screw 40 provided for the assembly of the unit to a wire. The unit is self-sufficient in carrying with it all of its essential ingredients and in enabling the potential user to take advantage of the novel features thereof without any equipment beyond a conventional screwdriver which is employed conventionally in the assembly of most such structures.
- Pursuant to the present invention, an inter-lock is provided between the contacts employed within the structure and the inner side walls of the structure.
By inner side walls is meant the side wall portion visible in Figures 2, 8 and 10 in particular, and to a more limited degree in the other Figures. For example, in Figure 7 the mode of interlock is evident through the broken away portion of the lower part of the housing of the connector shown therein.
With regard to the interlock, this interlock is accomplished principally between the upper or inner ends 90 and 92 respectively of the contacts 60 and 62 as illustrated in Figure 2, for example. More specifi-cally,the interlock occurs between the edges 88 and 94 of upper end 90 and conforming slots in the portions 48 and 50 of the housing 11 and between the edges 96 and 98 of the upper end 92 and other conforming slots in the portions 48 and 50 of the housing 11. Still more specifically, the edge 94 interlocks with slot 100 and ~7 735 _ g _ edge 88 interlocks with slot 102. Similarly, edge 98 interlocks with slot 104 end edge 96 interlocks with slot 106.
The actual slots are provided with a ramp surface on one side as best seen perhaps in Figure 7.
Thus the slot 100 has ramp surface 108 and slot 102 has ramp surface 110. These ramp surfaces permit the easy entry of the edges 94 and'88 of the upper end 90 of the contact element'60.
It is noteworthy that the structure of the present invention is one which permits a rapid, easy, automatic interIocking between the contacts mounted within the connector and the side walls of the connector.
In this regard, the specially provided transverse portion at the upper ends of the contacts are adapted for entry in a transverse fashion into the set of slots provided specifically therefor in the sides of the housing.
Accordingly, if the webs 36 and 38,,which are formed inte;grally with the housing as the housing itself is formed, are slit or otherwise separated to permit the side portions 30 and 32 to be separated from the base portion 34, the assembled connector will not suffer any separation of portions thereof inasmuch as the blades through their upper portions 90 and 92 provide an effective interlock with the slots 100, 102, 104 and 106. A longitudinal pull exerted either on the blades 24 and 26, or on the wire 12, of Figure 1, will not result in a separation of the base 34 from the sides 30 and 32 due at least in part to the strong interlock formed between the ends of the contacts as set forth above and the slots into which they are automatically positioned as the connector is assembled. This assembly of the sides 30 and 32 of the connector up and about the ends 90 and 92 of the blades is accom-plished as is indicated above as the sides 30 and32 are folded up in clam shell fashion above the base 34 C

to enclose the contents of the connector 10 including the exposed portions of the wire and the inner ends of the blade from contact with the hands of the user or with instruments or tools which the user may be employing S in working with the connector. Accordingly, the present invention provides a very effective means of accomplishing an interlocking of portions of the structure, and particularly a lateral interlocking of portions of the sides of the housing with upper or inner portions of the contacts.

Claims (5)

The embodiments of the invention in which an exclusive property or privilege is claime are defiend as follows:

1. A dead front plug comprising an insulating housing formed in three sections jointed by two living hinges disposed between adjacent sections, the center section forming the dead front end of said plug, a first end section forming the side housing of said plug and a second end section forming the opposite side housing of said plug, means for joining the first and second end sections, a pair of power blades extending through the center section of said housing, said power blades having enlarged portions in said housing adapted to engage the interior surfaces of said housing sides, conforming recesses in the housing sides adapted to interlock with the enlarged inner portion of the power blades to minimize longitudinal movement of said blades when the housing sides are folded together.

2. The dead front plug of claim 1 in which the enlarged portions of the power blades are at the inner ends thereof.

3. The dead front plug of claim 2 in which the inner blade ends are folded.

4. The dead front plug of claim 1 in which the conforming recesses of the housing sides are adapted to receive a blade portion positioned generally normal to the longitudinal axis of the blade.

5. The dead front plug of claim 1 in which one inner blade end is longer than the blade shank and is folded approximately normal to the longitudinal axis of the blade shank.