WO1996033523A1

WO1996033523A1 - Insulation displacement contact with strain relief

Info

Publication number: WO1996033523A1
Application number: PCT/US1996/005041
Authority: WO
Inventors: John M. Myer
Original assignee: Whitaker LLC
Current assignee: Whitaker LLC
Priority date: 1995-04-21
Filing date: 1996-04-11
Publication date: 1996-10-24
Anticipated expiration: 1997-10-21

Abstract

An electrical contact assembly (80) includes an electrical contact (10) with a contact section (20), IDC section (30) and a relief section (40). The electrical contact (10) is disposed in a dielectric housing (60) having a rotatable stuffer member (70) for pushing a wire (12) into electrical engagement with IDC section (30). Force vector F is a separating force which will cause the strain relief section (40) to deflect and thereby more firmly grip the wire (12) between a retention gripping portion (46) and a retention surface (76) of stuffer (70). Any separating force will cause stop member (27) of contact section (20) to engage a shoulder (62) of housing (60) thereby causing a shearing action as an edge (28b) engages the stop member (27).

Description

INSULATION DISPLACEMENT CONTACT WITH STRAIN RELIEF

The present invention relates to an electrical contact having a termination section for contact with a further electrical contact, and including an insulation displacement type (IDC) termination section for electrical termination with a conductor, whereby the conductor is relieved of strain adjacent the IDC section.

Strain relief features of electrical connectors provide a means of isolating the electrical termination of a conductor with a termination section of a contact from the deleterious effects of forces acting on the conductor which would otherwise tend to reduce the contact normal force between the termination section and the conductor. Such strain relief is particularly useful where an electrical termination is subject to harsh conditions, for example, the conditions associated with use in an automotive environment where vibration and/or tensile forces will be acting on the conductor. Strain relief members are designed to suppress these forces. Moreover, where the electrical termination comprises an IDC-type termination, as compared to a crimp-type terminal, the IDC termination section must be carefully isolated from such forces.

Conventional strain relief techniques employ the use of plastic housing material adjacent to the contact to frictionally engage the conductor and thereby suppress vibration or tensile forces acting on the conductor. Such use of the housing material for strain relief purposes has several disadvantages, for example: relaxation of the material may occur due to temperature cycling, resulting in a loosened strain relief section; strain induced breakage of the housing material; and the amount of material required to perform the strain relieving function consumes a considerable amount of space, thereby making the connector housing bulky.

A prior electrical connector which typifies the foregoing problems is disclosed in US-A-4493523. This conventional device comprises a housing of insulating material adapted to accommodate an electrical terminal, and includes a plastic strain relief member integral with the housing which is adapted to frictionally engage the wire terminated to the terminal. However, the strain relief member is subject to relaxation due to temperature cycling; strain induced breakage of the housing material; and the amount of material required to perform the strain relieving function, and the space required to allow deflection of the strain relief member, consume a considerable amount of space, thereby making the connector housing bulky.

The present invention overcomes the foregoing problems by providing an electrical contact having a termination section for contact with a further electrical contact, an IDC termination section for electrical termination with a conductor, the conductor is relieved of strain adjacent the IDC section, and the contact advantageously includes an integral strain relief section extending therefrom for strain relieving engagement with the conductor. This integral contact section, as compared to the above-mentioned use of the housing material, is not subject to a high degree of temperature relaxation, is mechanically strong, and is compact. More particularly, the integral strain relief section comprises a stamped metal extension of the contact.

To accomplish its strain relieving function, the strain relief section includes a wire gripping portion and a flexible bend, the wire gripping portion is rotatable about the flexible bend for strain relieving engagement with the conductor. However, to prevent overstress, the strain relief section includes an overstress leg for delimiting the rotation of the wire gripping portion. When the contact is mounted in an electrical connector housing according to the present invention, a rotatable portion of the strain relief section, and a portion of the housing, cooperate to trap the conductor therebetween, thereby providing strain relief to the conductor. Moreover, the housing includes ram members for aligning the conductor in the contact, and the ram members are formed on a stuffer conveniently hinged to the housing. For contact retention in the housing, the termination section includes a deflectable stop member which extends generally transversely of an edge of the termination section, and generally transversely of a shoulder of the housing, whereby the edge and the shoulder are advantageously aligned to apply shear forces to the stop member in retaining the contact in the housing.

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

Pig. 1 shows an isometric view of the electrical contact according to the present invention.

Fig. 2 shows a top view of the electrical contact of Fig. 1. Fig. 3 shows a side cross sectional view of the electrical contact of Fig. 2 taken along line 3-3.

Fig. 4 shows a front elevational view of the electrical contact of Fig. 1.

Fig. 5 shows an isometric view of a second embodiment of the present invention.

Fig. 6 shows a cross sectional view of an electrical connector assembly according to the present invention.

Fig. 7 shows a cross sectional view of a second embodiment of an electrical connector assembly according to the present invention. Detailed Description of the Invention

Fig. 1 shows an electrical contact 10 having a contact section 20, an IDC section 30, and a strain relief section 40. Contact section 20 includes: a base portion 22 with overstress 22a; walls 24 having edges 24a and shoulders 24b with one wall 24 having a hole 21 formed therein; an inner top portion 25 with a locking tab 25a; a resilient leg 26 for engaging a further electrical component (e.g. a tab or pin contact) ; a resiliently deflectable stop member 27 with bends 27a, a stop leg 27b, and a plate 27c; an edge 28b and an outer top portion 28 having a tab aperture 28a for receiving locking tab 25a; and a resilient off-set portion 29 formed on the bottom of contact section 20 for connection to an electrical connector housing. Offset portion 29 is formed adjacent to a platform 29a, which platform advantageously helps to control the contact forces generated between leg 26 and platform 29a when a tab or pin has been inserted into electrical contact 10. Still referring to Fig. 1, IDC section 30 (IDC) includes a base portion 32 with upstanding walls 34 formed thereon, which walls include IDC blades 36 for receiving, stripping the insulation from a portion of, and terminating an electrical conductor. Stiffening gussets 33 are formed between base section 32 and walls 34 for increasing the contact force generated by the walls 34. Additionally, IDC section 30 includes a boot 38 for uplifting and supporting the wire to be terminated to a more centralized and contact force maintaining location between blades 36.

Strain relief section 40 includes a base portion 42 with a bend 44 extending therefrom. Bend 44 is connected to an intermediate portion 45, and intermediate portion 45 is connected to a generally arcuate wire gripping portion 46. The radius of bend 44 is advantageously greater than the radius of bend 46 for flexibility of intermediate portion 45 and portion 46 about bend 44, but it is contemplated that other radii may be used. Wire gripping portion 46 includes serrations 46a for engaging a wire, as will be described below. Strain relief section 40 further includes an overstress leg 48 having an edge 48a for engagement with base portion 42 when and if edge 48a is deflected that far. Strain relief section 40 comprises three angles: angle α, defined by base portion 42 and intermediate portion 45; angle β, defined by intermediate portion 45 and overstress leg 48; and angle γ, defined by base portion 42 and overstress leg 48.

Now referring to Fig. 2, a top view of the electrical contact 10 of Fig. 1 is shown. This view shows locking tab 25a of inner top portion 25 protruding through tab aperture 28a of outer top portion 28 thereby effectively interlocking inner top portion 25 to outer top portion 28. Additionally, boot 38 is shown laterally aligned with blades 36 of IDC section 30 for uplifting a wire to be terminated in the IDC section 30. Referring to Fig. 3, a cross sectional view of the electrical contact of Fig. 1 taken along line 3-3 of Fig. 2 is shown. Fig. 3 provides a good view of overstress stop 23 of contact section 20, which stop is aligned for engagement with resilient leg 26 when a tab or pin contact is inserted into the contact section 20.

Stop 23 will, if necessary, engage the end of resilient leg 26 thereby preventing overstress of the resilient leg 26. Fig. 3 also shows: bends 27a of stop member 27; plate 27c aligned for engagement with edge 28b of outer top portion 28, as will be further described below; offset portion 29 which is formed into base portion 22; edges 24a of wall 24; overstress 22a for preventing overstress of stop member 27; and angles α, β, and γ. Referring to Fig. 4, a front elevational view of the contact 10 is shown depicting the various parts of contact section 20.

Fig. 5 shows a second embodiment 10' of the present invention. Electrical contact 10' includes a contact section 20, an IDC section 30, and a strain relief section 40, which sections are similar or identical to that of electrical contact 10 as described above. However, electrical contact 10' includes a "wrap around" strain relief member 50 comprising gripping tabs 54 and 55. Tabs 54 and 55 are crimpable tabs adapted for crimpable engagement with the insulation of a wire to be terminated in the electrical contact 10' .

Now referring to Fig. 6, an electrical connector assembly 80 is shown which includes a housing 60, a stuffer 70, and the electrical contact 10 having a wire terminated therein disposed within the housing 60 and stuffer 70. Housing 60 includes a recess for receiving contact 10 and a shoulder 62 disposed adjacent to stop member 27 of contact section 20 when the stop member is disposed within an aperture 68 of housing 60. A recess 64 is formed in a lower portion of housing 60 for accommodating offset portion 29 of contact section 20 when the contact 10 is disposed within the housing 60. As the contact 10 is slid into housing 60 stop member 27 will engage shoulder 62 and will thereby be deflected downwardly until it passes shoulder 62 at which point the stop member 27 will resile upwardly into aperture 68. Stuffer 70 is hingeably attached to housing 60 by hinge 66, but it is contemplated that stuffer 70 can be formed as wholly separate from housing 60. Stuffer 70 includes a front ram 72, a middle ram 73, a rear ram 74 with edge 74a and nose 74b, a frictional retention surface 76, and a wire guide 78. Referring to the embodiment of Fig. 6, assembly of the electrical contact assembly 10 is accomplished by inserting electrical contact 10 into housing 60 so that offset portion 29 of contact section 20 registers with recess 64, and stop leg 27 is located adjacent to shoulder 62. A wire 12 is then placed over the IDC walls 34 in axial alignment with blades 36 of IDC section 30. At this time, cover 70 is rotated about hinge 66, and rams 72-74 pressingly engage wire 12, thereby stuffing wire 12 into electrical engagement with IDC section 30 between walls 34 and blades 36 thereof. It is important to note, however, that front ram 72 engages a front surface of wire 12, middle ram 73 engages a portion of the wire 12 within IDC section 30, and edge 74a of rear ram 74 engages an axially opposing surface of wire 12. Moreover, nose 74b, which downwardly protrudes from rear ram 74, pushes a respective portion of wire 12 into engagement base portion 42. Boot 38 maintains a centerline of wire 12 relatively higher than a centerline of the respective portion of wire 12 adjacent to nose 74b. It is also important to note that wire 12 is poised for frictional engagement with serrations 46a of wire gripping portion 46 and overstress leg 48 of strain relief section 40, and is arranged for frictional engagement with retention surface 76 of stuffer 70. Thus, wire 12 comprises a series of contortious bends, and thereby is conformed to a torturous path within assembly 80.

As shown in the right hand side of Fig. 6 a tensile force vector F, when it is applied to wire 12, will cause strain relief section 40 to deflect, resulting in an increase in angle α (see Fig. 3) , and thereby defining an eccentric arc ω as shown in the drawing. As wire gripping portion 46 of strain relief section 40 is moved along this eccentric arc, the effective distance between wire gripping portion 46 and retention section surface 76 will decrease. The decrease in distance will result in a squeezing effect, i.e. a greater magnitude in gripping force will be applied to the wire 12 by retention surface 76 of stuffer 70 and wire gripping portion 46. Thus the tensile force F acting on the wire terminated in the IDC is converted to use in increasing the frictional retention forces which tend to resist the tensile forces, thereby creating a "Chinese finger" effect, and which conversion prevents the transmission of tensile forces to the contact termination section 30. The tensile force transmitted to wire 12 by force vector F will cause a force to be applied generally to contact 10. However, bend 44 of strain relief section 40 will not abut the housing 60 but, rather, the force transmitted to electrical contact 10 will be borne by edges 24a and shoulders 24b of walls 24 of contact section 20, which edges and shoulders engage a portion of front ram 72 of stuffer 70, and bend 44 may bear against wire guide 78. As wire 12 is more firmly gripped between wire gripping portion 46 and retention surface 76, no forces will be transmitted to the IDC section 30, thereby advantageously preserving the electrical continuity between walls 34 of IDC section 30 and the conductive core inside wire 12.

Moreover, any force vector F which tends to separate the contact 10 from housing 60 will result in a shearing force being applied to stop member 27. Force vector F will tend to shift electrical contact 10 relatively to the right as shown in Fig. 6 (with the housing 60 remaining stationery) . Stop leg 27b of stop member 27 will thus engage shoulder 62 of housing 60. As this occurs, stop member 27 will be resiliently deflected towards and will forcibly engage edge 28b of outer top portion 28 of contact section 20. Thus a shearing force is imparted to stop member 27 by engagement of edge 28b with stop member 27 on a lower side, and the shoulder 62 of housing 60 engaging stop member 27 on an upper side. Since this shearing force is resisted by generally the full thickness of stop member 27, electrical contact 10 is capable of withstanding a great deal of force tending to separate it from housing 60. Referring now to Fig. 7, electrical connector assembly 80' will be described. Assembly 80' essentially incorporates electrical contact 10' into housing 60 with a stuffer 70 similar to the embodiment of Fig. 6. However, the rear ram 74 has been modified to a rear ram 74' with a truncated lower surface.

Truncating the lower surf ce of rear ram 74' creates space for wrap around strain relief member 50 with gripping tabs 54 and 55 for firmly capturing the wire 12 thereby obviating the need for a further gripping portion such as, for example, the nose 74b of rear ram 74 of the embodiment of Fig. 6.

Thus, while preferred embodiments of the invention have been disclosed, it is to be understood that the invention is not to be strictly limited to such embodiments but may be otherwise variously embodied and practiced within the scope of the appended claims. For example, although stuffer 70 is shown hinged to housing 60 by a hinge 66, it is contemplated that stuffer 70 can be a wholly separate member. Moreover, although receptacle contacts 10 and 10' have been disclosed, it is contemplated that the present invention can be adapted for use with any IDC contact including pin, tab, or other interconnection systems. Additionally, it is contemplated that boot 38 can take the form of a mere tab. It is also contemplated that the housing 60 and stuffer 70 can be modified to include a plurality of electrical contacts 10 and/or 10' for mass termination of a plurality of wires 12. It is also contemplated that the stuffer 70 can be modified to eliminate the middle ram 73 and still satisfactorily perform its wire stuffing function. The ideal engineering materials for the electrical contacts disclosed above will comprise metals having high strength, high conductivity, and a low cost. For example, such metals as copper, brass, bronze, beryllium copper, copper alloys, steel, nickel, aluminum, and zinc. Additionally, it is preferred that the above described contacts comprise a stamped and formed contact. However, other methods may be used to form the contact as well. It is further desired that the electrical contacts will be coated or plated for corrosion resistance. For example, a coating comprising tin, tin low lead, tin lead, nickel, gold, silver, copper, zinc, or palladium. It is further contemplated that the electrical contacts will be plated by, for example, an electro-deposition process. The housing 60 and stuffer 70 can be formed of any suitable dielectric plastic or other dielectric material.

Claims

CLAIMS :

1. An electrical contact (10) having a termination section (20) for contact with a further electrical contact, an IDC termination section (30) for electrical termination with a conductor (12) , said conductor is relieved of strain adjacent said IDC section, and said contact (10) is characterized in that: said contact includes an integral strain relief section (40) extending therefrom for strain relieving engagement with the conductor.

2. The contact (10) of claim 1, wherein the strain relief section includes a wire gripping portion (46) and a flexible bend (44) , the wire gripping portion is rotatable about the flexible bend for strain relieving engagement with the conductor.

3. The contact (10) of claim 2, wherein the strain relief section includes an overstress leg (48) for delimiting the rotation of the wire gripping portion.

4. The contact (10) of claim 1, wherein said strain relief section (40) comprises a stamped metal extension of said contact (10) .

5. The contact (10) of claim 1, wherein when said contact (10) is mounted in an electrical connector housing (60,70) , a rotatable portion (46) of the strain relief section, and a portion (76) of the housing, cooperate to trap said conductor (12) , thereby providing strain relief to the conductor.

6. The contact (10) of claim 1, wherein the termination section (30) includes a deflectable stop member (27) for retaining the contact (10) in an electrical connector housing (60) .

7. The contact (10) of claim 6, wherein the stop member extends generally transversely of an edge (28b) of the termination section, and generally transversely of a shoulder (62) of the housing (60) , whereby said edge (28b) and said shoulder (62) are generally aligned to apply shear forces to said stop member (27) in retaining the contact in the housing.

8. The contact (10) of claim 1, wherein said contact is disposed in a housing (60,70), and said housing includes ram members (72,73,74) for aligning the conductor (12) in the contact (10).

9. The contact (10) of claim 8, wherein the ram members are formed on a stuffer (70) hinged to the housing (60) .

10. The contact (10) of claim 9, wherein the stuffer includes a wire engaging surface (72) for cooperating with the strain relief section in trapping said conductor (12) therebetween, for strain relieving the conductor.