US3671925A

US3671925A - Pressure lock and release terminal for an electrical receptacle

Info

Publication number: US3671925A
Application number: US103991A
Authority: US
Inventors: William Drapkin
Original assignee: Slater Electric Inc
Current assignee: Slater Electric Inc
Priority date: 1971-01-05
Filing date: 1971-01-05
Publication date: 1972-06-20
Anticipated expiration: 1989-06-20

Abstract

A terminal for an electrical receptacle is provided with a pair of parallel tongues adapted to lock and hold a bare wire conductor without requiring the use of a tool. The wire conductor can be released without opening the receptacle by inserting a tool through a tool access notch and engaging a pair of release tabs on the wire gripping tongues.

Description

United States Patent Drapkin June 20, 1972 541 PRESSURE LOCK AND RELEASE 2,952,331 9/1960 Ehrlich .339/95 1) TERMINAL FOR AN ELECTRIC 2,969,518 1/1961 sum ..339/14 R 3,543,221 11/1970 Schmier ..339/95 1) RECEPTACLE William Drapkin, Suffolk, N.Y.

Slater Electric Inc., Glen Cove, N.Y.

Jan. 5, 1971 Inventor:

Assignee:

Filed:

Appl. No.:

References Cited UNITED STATES PATENTS 4/ I955 Benander ..339/95 D Primary Examiner-Marvin A. Champion Assistant E.\'aminer-Lawrence .l, Staab Attorney-George B. Finnegan, Jr., Granville M. Pine, John D. Foley, Jerome G. Lee, Thomas P. Dowling, John A. Diaz, Warren H. Rotert, John C. Vassil', Alfred P. Ewert and Thomas R. MacDonald [57] ABSTRACT 12 Claims, 9 Drawing Figures PATENTEDJUHZO 1972 SHEET 1 HF FIG.

FIG. 1

INVENTOR WILLIAM DRAPKIN 4 {Bi/J ATTORNEYS PATENIEMURZO 1872 SHEET 2 [IF 3 FIG. 4

FIG. 6

N IIIIIIIIM.

FIG. 3

FIG. 5

PRESSURE LOCK AND RELEASE TERMINAL FOR AN ELECTRICAL RECEP'I'ACLE This invention relates to electrical receptacles. More particularly, this invention relates to a pressure lock and release terminal for use with such receptacles.

Electrical receptacles having pressure lock terminals which do not require the use of screws to secure a bare conductor wire are known in the prior art. These terminals grasp a portion of a bare conductor wire and secure it in place by means of a resilient pressure member, and thus do not require the use of a screw terminal. Such pressure lock terminals have enjoyed great popularity as they permit rapid installation of duplex plug receptacles.

The operation of prior art pressure lock terminals has been less than satisfactory in some respects. One particular defect becomes evident when wire conductors of different gauge sizes are employed, or when wire conductors of the same gauge size are inserted beneath a single resilient pressure member. This defect is due to torsional stresses placed upon the single spring member where the first wire conductor is inserted. In effect the spring is bent and distorted such that the second wire conductor is not adequately secured and held by the opposite end of the resilient pressure member. Attempts have been made to remedy this deficiency by employing a single resilient pressure member having a forked tongue designed to hold a single wire conductor beneath each tongue member. This solution has not proved satisfactory as it is difficult to avoid permanently deforming the individual tongue members or the resilient pressure member upon insertion of the wire conductor.

A further problem relates to the inability of such resilient pressure members to provide sufi'rcient gripping force to secure the wire conductors. If the resilient pressure member or the tongue elements are to provide sufficient gripping force, and not be deformed and permanently damaged upon insertion of a wire conductor, a resilient pressure member or tongue of substantial length must be provided. However, compactness of design is an important factor in the manufacture of such terminal strips, and no suitable design incorporating a resilient pressure member having substantial length and resiliency as well as sufiicient gripping force has yet become available in a reasonably economical and compact form.

It is further desirable that the wire gripping members, the plug contacting portions, and the terminal elements be permanently connected to each other and ideally be formed integrally from the same conductive metallic sheet or stamping thus, eliminating the necessity of assembling separate components fabricated of separate materials into a pressure lock terminal strip.

It is also desirable that the resilient gripping members of such a pressure locking terminal strip be actuable to release the wire conductors without having to disassemble the electrical receptacle in which it is contained.

A principal object of the present invention is the provision of an improved pressure lock terminal strip for a duplex electrical assembly which satisfies the foregoing criteria.

A more specific object of this invention to provide such a terminal strip having wire gripping tongues of substantial tongue length capable of securing wire conductors of difierent gauge sizes.

A still further object of this invention is to provide such a terminal strip in which the wire gripping tongues provide increased gripping force on the wire conductor to prevent pullout.

It is a further object of this invention to provide a pressure lock terminal strip having wire gripping tongue members which are simultaneously actuable to release a wire conductor from the exterior of the electrical receptacle.

The instant invention provides an integrally formed pressure lock and release terminal strip of compact design having wire gripping tongues capable of securing a wide range of wire gauge sizes. The wire gripping tongues of this invention are simultaneously actuable to release a gripped wire conductor from the exterior of the electrical receptacle and include a wire trap to provide additional gripping force on a wire conductor.

Further details and other objects and advantages of the invention will be better understood in connection with the following descriptions and claims considered with the accompanying drawings wherein:

FIG. 1 is a top plan view of a duplex plug receptacle of the present invention having a portion of its cover broken away;

FIG. 2 is a rear elevation of the receptacle of FIG. 1 showing the means for electrically connecting wire conductors to the pressure lock and release terminal;

FIG. 3 is a transverse cut-away view taken along the line 3- 3 of FIG. 1 and illustrating the tongue engagement section of the terminal strip in inoperative position;

FIG. 4 is a transverse cut-away view taken along the same line as FIG. 3 andshowing the prong engagement section of the terminal strip in operative engagement with a plug prong;

FIG. 5 is a transverse cut-away view of the device taken along the line 5-5 of FIG. 1 and showing a wire gripping tongue in normal inoperative position;

FIG. 6 is a transverse cut-away view similar to FIG. 5 showing wire gripping tongue in operative engagement with a bare wire conductor;

FIG. 7 is a perspective view of the integral pressure lock and release terminal strip of this invention;

FIG. 7a is a fragmentary perspective view of a portion of the integral pressure lock and release terminal strip illustrated in FIG. 7, showing, as an alternative embodiment of the invention, a single, integral release tab spanning adjoining wire gripping tongues;

FIG. 8 is a cross-sectional view taken along the line 8-8 of FIG. 6 and illustrating in detail the wire trap of the invention.

Referring now to the drawings and particularly to FIG. 1 there is shown a duplex electrical receptacle 10 having a cover 11, a hollow base 12, and supporting strap 13 which are fastened together in the standard fashion using rivets or screws.

The cover member 11 includes the usual plug receiving apertures 14 and a grounding prong aperture 15 in each of a pair of

plug receiving units

16 and 16. Plug prongs are inserted into the prong receiving aperture 14 and grounding plug aperture 15 in the standard fashion. The grounding prongs on a standard plug will pass through the grounding plug aperture 15 and contact a portion of grounding strap 13 which is provided with a terminal portion 17 fonned in a notch defined by the side walls of housing 12. Terminal portion 17 includes a screw terminal 18 through which the mounting strap 13 is connected to ground.

FIG. 2 illustrates the rear portion of housing 12 which is provided with

parallel rows

19 and 20, of conductor apertures, each aperture extending through housing 12. Conductor wires (now shown) are pushed through the respective apertures and into locking engagement with a pressure lock and release terminal strip which will be described. Housing 12 is normally made of a plastic material and divided by a central rib 21 into two individual, mirror image, longitudinal cavities 22 only one of which is visible in FIG. 1. The interior walls of each cavity are shaped to receive a pressure lock and release terminal strip 60. Each row of conductor apertures 19 and 20 is in alignment with a pressure lock and release terminal strip 60 (illustrated in perspective in FIG. 7), which is mounted in the cavity behind the respective row. Slots 23 are formed in the floor and side walls of housing 12 to permit access with a tool, e.g. a screwdriver, to release a wire conductor being held in pressure lock and release terminal 60. These slots 23 are advantageously located for rapid insertion of a tool such as a screwdriver into the interior of the terminal strip 60, even if receptacle 10 cannot be completely removed from its wall mounting box as described in Slater US. Pat. No. 2,795,677 issued June I1, 1957. Additionally, the floor of housing 12 contains a pair of apertures 49 situated on the midline of the floor between the two rows of wire insertion apertures for receiving assembly screws.

The respective interior cavities 22 of housing 12 have internal walls shaped to receive a pressure lock and release terminal 60 and secure it in a fixed position. A central notch 25 is provided in each of the side walls of housing 12 to admit a portion of terminal 60 which protrudes through the side wall of the housing. The interior side walls of the housing formed along rib 21 are indented as indicated at 26 and 27 to accept a portion of the terminal strip and additionally aid in positioning the terminal strip in alignment with a row of conductor apertures 19, as well as prong apertures 14 and plug

receiving units

16 and 16. In addition, each interior side wall of housing 12 contains several indentations 24 which correspond to wire guiding portions of terminal strip 60. Cover member 11 is formed with the usual ridge structure on the lower surface v thereof which serves to position and secure the cover member with respect to the housing and to align the prong apertures 14 with the respective prong engagement section on terminal strip 60. g

Referring now to FIG. 7 a preferred pressure lock and release terminal strip 60 in accordance with this invention is illustrated therein. Tenninal strip 60 may be generally described as a U-shaped metal stamping. A terminal strip is placed within each cavity 22 of housing 12 where it functions to make contact with the prongs of a wiring plug in addition to contacting the bare wire conductors of the electrical circuit. Two basic pressure lock and release

terminal strip units

28 and 29 joined by a break-off tab 30 are illustrated in FIG. 7 and shown inserted in a housing cavity 22 in FIG. 1. The pressure lock and release terminal strips of this invention may be made by progressively forming a flat stamping of a suitable metallic conductive material e.g. phosphor bronze, brass alloy etc. Although two basic

terminal strip units

28 and 29 joined by a break-away tab 30 will be used in most applications,'each basic terminal strip unit can function as an independent pressure lock and release terminal strip.

A basic terminal strip unit is comprised of a prong engagement section 31 and a conductor engaging section 32.

The prong engagement section 31 is designed to engage a standard plug prong when it is inserted between spring finger 33 and spring contact element 34. Both spring finger 33 and spring contact element 34' have generally convex vertical profiles and are integrally formed from a transverse base section 35. The purpose of forming spring finger 33 and spring contactelement 34 with opposed convex shapes is to provide. them with a superior resilient action which serves to positively engage a plug prong as will be described below.

Base section 35 is integrally joined to a body portion 36 an a flat tongue platform 37 which are formed in essentially parallel relationship to one another. Body portion 36 is essentially flat except for two grooves 38 which serve to guide con-' ductor wires inserted through

conductor apertures

19 and 20 into cooperative locking engagement with

wire gripping tongues

39 and 40 as will be next described. Grooves 38 additionally provide increased electrical contact area between body portion 36 and the bare conductor wire.

Wire gripping tongues

39 and 40 are integrally formed with a tongue platform 37 which is parallel to body portion 36. Each wire gripping tongue consists of an elongated stern portion 41, a release tab 42 and a wire trap 43. The stem 41 of each wire gripping tongue is bent backwards beneath tongue platform 37 towards a corresponding groove 38 in body portion 36. Tongue platform 37 is integrally joined to body portion 36 at one end by support arm 44, and at the other end by base section 35. The stem 41 of each wire gripping tongue is long enough to provide substantial resilient action to the tongue when a wire is engaged between the tongue and the corresponding groove.

In the preferred embodiment each wire gripping tongue is independently joined to tongue platform 37 to minimize twisting and loss of tension in the adjoining wire gripping tongue when wires of different gauge sizes are engaged between the respective rongues and their corresponding grooves. This independent tongue action will be better understood by refercavity 22. Referring to FIG. 6 a bare conductor wire 45 has been inserted through a conductor aperture 19, guided along groove 38 and has deflected wire gripping tongue 39 from its normal unengaged position to a tensioned position. Tongue platform 37 now contacts a portion of wall 41 providing a suitable pivot point for the resilient action of wire gripping tongue 39, and conductor wire 45 is tightly held between the wire trap 43 on the outer edge 48 of wire gripping tongue 39 and groove 38.

Although release tabs 42 are illustrated as separated from one another by channel 58, they can also be joined as a single integral unit 42 spanning adjoining wire gripping tongues 39 and40 as illustrated in FIG. 7a. This embodiment of the invention provides a more positive simultaneous release of bare conductor wires gripped beneath

wire gripping tongues

39 and 40. This more positive release action is obtained by sacrificing a relatively slight degree of twisting and gripping power.

FIG. 8 illustrates in detail the advantages of wire trap 43 which is essentially a radiused cut-out in the outer edge of wire gripping tongue 39 which extends toward groove 38. The radiused cut-out of wire trap 43 hooks and traps bare conductor wire'45 which has been inserted into the terminal 60 via groove 38. The radius cut-out provides an arcuate contact surface between wire gripping tongue 39 and bare conductor wire 45 and also increases the contacting surface between wire gripping tongue 39 and bare conductor wire 45. The latter property provides an excellent gripping action and prevents the wire from being inadvertently pulled out of engagement with terminal 60. Additionally, it provides a superior electrical contact. This radius cut-out shape also avoids the problem inherent in having a circular conductor contacted at only a single point along its circumference in a high current electrical circuit. Such a contacting situation bearing high current densities over a limited surface area is undesirable in elec trical receptacle terminals and is substantially overcome through use of the wire trap design of this invention.

The gripping force exerted by wire gripping tongue 39 in its engaged position is maximized since substantially the entire longitudinal span of the tongue is utilized as a resilient spring member to apply a gripping force to bare conductor wire 45 and hold it in firm locking engagement with groove 38.

Referring again to FIG. 7 it will be seen that each of the parallel

wire gripping tongues

39 and 40 includes a laterally projecting tab 42 which is congruent with a similar tab on the adjacent wire gripping tongue. These tabs are accessible to a release tool inserted through access notch 46 in body portion 36. When it is desired to release the wire conductors 45 held by

wire gripping tongues

39 and 40, a release tool, e.g. a nail or screwdriver, is extended through slot 23 in the floor of housing 12. Slot 23 is in alignment with tool access notch 46 and allows the tool to bear upon and'deflect wire gripping ton gues 39 and 40 thus releasing the grip on the conductor wires held beneath the tongues. Using this construction, release of a conductor wire from engagement between the wire gripping tongues and a corresponding groove is rapidly accomplished without damage to the yieldable' wire gripping tongues.

Referring now to FIG. 3, a cut-away cross-section of a prong engaging section is illustrated in the unengaged position. The spring contact element 34 and the spring finger 33 are shown with their convex faces in opposed parallel relationship. A 7 prong 47 of a plug is normally inserted through prong aperture 14 and cover member 11 and guided between spring contact element 34 and spring finger 33. This action forces the free end of spring contact element 34 against ridge 50, thus ironing the spring contact element fiat against interior housing wall 52 due to the compression of spring finger 33 the free end of which is now in contact with cover member shoulder 57. In this manner, the prongs 47 of a standard plug are tightly held in good electrical contact with the prong engagement section of terminal 60 (FIG. 4).

Raised portions 53 on the floor of housing 12, along with built-up section 54, permits rapid positioning and installation of a terminal strip 60 in cavity 22 and also serve to positively secure the terminal strip 60 in a fixed position after the duplex electrical receptacle is assembled. Additionally, transverse locating rib 56 divides each cavity 22 and also serves to rapidly position terminal strip 60 for installation in the cavity via a corresponding rib notch 57 beneath tab 30 on terminal strip 60. Shoulder member 55 prevents damage to wire

gripping tongues

39 and 40 due to over-travel, by halting the downward movement of the tongues before they are damaged or deformed.

A one-piece pressure lock and release terminal member as illustrated and described can be fabricated in economical fashion from a strip of conductive material. Two mirror image basic

terminal units

28 and 29 are normally fabricated as an integral unit joined by break-off tab 30. If only a single outlet is desired in a particular circuit, break-off tab 30 may be worked back and forth, fatigued and broken, thereby separating pressure lock and release terminal 60 into two basic

terminal units

28 and 29 which can then be wired into two separate circuits in a duplex receptacle, or suitable for use in receptacles having only a single outlet. The pressure lock and release terminals of this invention are easily assembled by placing a terminal strip 60 into the cavity 22 formed on each side of central rib 21 in housing 12. The duplex electrical receptacle containing the terminal strips is easily assembled by fixing the mounting strap and cover member in position. When thus assembled, the terminal strips will receive bare conductor wires inserted through conductor apertures 19 and on the floor of housing 12 and firmly grip such wires providing good electrical contact. The wire gripping tongues of the invention provide maximum gripping force since they have a substantial length available for utilization as a resilient spring member. Further, the wire gripping tongues of this invention minimize or entirely eliminate twisting and diminished gripping power when a bare conductor wire is engaged by an adjoining wire gripping tongue. In addition, the wire traps of this invention provide a firm gripping action thus guarding against inadvertent disengagement of a bare wire conductor. These traps further provide improved electrical contact between the terminal strip and a conductor wire. Yet another advantage of the wire gripping tongues of this invention is the simplified means for releasing the engagement of a wire gripped between the tongue and an opposing groove.

What is claimed is:

1. In a pressure lock and release terminal for an electrical receptacle, the improvement which comprises a conductive metallic terminal strip including a body portion having a pair of transverse grooves and a tool access notch located between said grooves, a base section integrally formed from one end of said body portion and lying in generally transverse relation to said body portion, a prong engagement assembly integrally formed with said base section in generally transverse relationship thereto, a platform integrally formed with said base section and in generally parallel relation with said body portion, and a pair of parallel yieldable wire gripping tongues integrally formed with said platform, each of said tongues including a wire trap, at least one of said pair of wire gripping tongues having a release tab adjoined thereto, said release tab being accessible with a tool through said tool access notch, and said wire gripping tongues extending toward said body portion to locate said wire traps a distance less than the diameter of a bare conductor wire from said grooves.

2. In a pressure lock and release terminal for an electrical receptacle, the improvement as defined in claim I, wherein said prong engagement assembly includes a spring finger and a spring contact element in substantially parallel relationship and integrally formed with said base section in generally transverse relationship thereto.

3. In a pressure lock and release terminal for an electrical receptacle, the improvement as defined in claim 2, including a support arm integrally formed in generally perpendicular relation with said body portion, said platform integrally formed with said support arm and said base section.

4. In a pressure lock and release terminal for an electrical receptacle, the improvement as defined in claim 3, wherein said wire trap is located on an outer edge of each of said wire gripping tongues.

5. In a pressure lock and release terminal for an electrical receptacle, the improvement as defined in claim 4, wherein said wire trap comprises a radiused cut-out in a portion of said outer edge.

6. In a pressure lock and release terminal for an electrical receptacle, the improvement as defined in claim 5, including two release tabs wherein each of said release tabs comprises an independent lateral projection integrally formed on each of said wire gripping tongues, said lateral projection extending toward a congruent independent lateral projection on an adjacent wire gripping tongue.

7. In a pressure lock and release terminal for an electrical receptacle, the improvement as defined in claim 6, including a break-away tab integrally joining said pressure lock and release terminal to a second mirror image pressure and release terminal strip.

8. In a duplex electrical wiring receptacle, the improvement which comprises a housing of insulating material having a pair of cavities formed therein, said cavities being defined on one side by a side wall of said housing and on the other side by a central rib, a pressure lock and release terminal strip disposed in each of said cavities, said terminal strip including a flat body portion having a pair of transverse wire guide grooves and a tool access notch located between said wire guide grooves, a base section integrally formed from one end of said body portion and lying in generally transverse relation to said body portion, a prong engagement assembly integrally formed with said base section in generally transverse relationship thereto, a tongue platform integrally formed with said base section and in generally parallel relation to said body portion, and a pair of parallel yieldable wire gripping tongues integrally formed with said tongue platform and a single laterally projecting release tab integrally joining said tongues, said release tab being accessible with a tool through said tool access notch, extending toward said body portion.

9. In a duplex electrical receptacle, the improvement as defined in claim 8, wherein said prong engagement assembly includes a spring finger and a spring contact element in parallel relationship and integrally formed with said base section.

10. In a duplex electrical receptacle, the improvement as defined in claim 9, wherein each of said tongues includes a wire trap on an outer edge of said wire gripping tongue.

11. In a duplex electrical receptacle, the improvement as defined in claim 10, wherein said wire trap comprises a radiused cut-out in a portion of said outer edge and said wire trap is located less than the diameter of a bare conductor wire from said grooves.

12. In a terminal for an electrical receptacle, the improvement which comprises a conductive metallic terminal strip including a flat body portion having a pair of transverse wire guide grooves and a tool access notch located between said wire guide grooves, a base section integrally formed from one end of said body portion and lying in generally transverse relation to said body portion, a spring finger and a spring contact element in parallel relationship and integrally fonned with said base section in generally transverse relationship thereto, a support arm integrally formed in generally perpendicular relation with said body portion, a tongue platform integrally formed with said support arm and said base section in generally parallel relation to said body portion, and a pair of parallel yieldable wire gripping tongues integrally formed with said tongue platform, each of said tongues bearing a wire trap on an outer edge of said wire gripping tongue opposite said tongue platform and a laterally projecting release tab integrally formed with said wire gripping tongue and said tabs positioned in lateral opposition to each other and being accessible with a tool through said tool access notch, said wire gripping tongues extending toward said body portion to locate said wire traps a distance less than the diameter of a bare conductor wire from said wire guide grooves.

4: k a: a:

Claims

2. In a pressure lock and release terminal for an electrical receptacle, the improvement as defined in claim 1, wherein said prong engagement assembly includes a spring finger and a spring contact element in substantially parallel relationship and integrally formed with said base section in generally transverse relationship thereto.

12. In a terminal for an electrical receptacle, the improvement which comprises a conductive metallic terminal strip including a flat body portion having a pair of transverse wire guide grooves and a tool access notch located between said wire guide grooves, a base section integrally formed from one end of said body portion and lying in generally transverse relation to said body portion, a spring finger and a spring contact element in parallel relationship and integrally formed with said base section in generally transverse relationship thereto, a support arm integrally formed in generally perpendicular relation with said body portion, a tongue platform integrally formed with said support arm and said base section in generally parallel relation to said body portion, and a pair of parallel yieldable wire gripping tongues integrally formed with said tongue platform, each of said tongues bearing a wire trap on an outer edge of said wire gripping tongue opposite said tongue platform and a laterally projecting release tab integrally formed with said wire gripping tongue and said tabs positioned in lateral opposition to each other and being accessible with a tool through said tool access notch, said wire gripping tongues extending toward said body portion to locate said wire traps a distance less than the diameter of a bare conductor wire from said wire guide grooves.