Pre-loaded Electrical Connecting Device

Abstract

Electrical connector adapted to be coupled to a complementary connecting means has contact terminals extending from its mating face. The terminals have conductor receiving slots extending from their leading ends towards the mating face so that when conductors are inserted into the slots, electrical contact is established with the conductors. The connector can be used for conventional conductors and has particular advantages when used with co-axial cables.

Description

BACKGROUND OF THE INVENTION

This invention relates to electrical connectors and contact terminals of the type used in electrical connectors. An "electrical connector" or "electrical connector part" can be described in the context of the instant specification as an insulating housing containing one or more metallic electrical contact terminals to which conductors are, or can be, secured. The connector is adapted to be engaged with a complementary connector to form a "connector assembly" or with other connecting means.

A known type of electrical contact terminal which is being used to an increasing extent comprises a plate-like member having a conductor receiving slot extending inwardly from one of its edges, the width of the slot being less than the width of the conductor so that when the conductor is moved laterally of its axis and into the slot, the conductor will be deformed and the edges of the slot will be brought into electrical contact with the conductor. These slotted beam type contact terminals are being used in a variety of types of connectors and under a variety of circumstances, see for example application Ser. No. 147,569 filed May 27, 1971 and now U.S. Pat. 3,760,335 for PRE-LOADED ELECTRICAL CONNECTOR.

The present invention is directed, in accordance with one apsect thereof, to the achievement of an improved pre-loaded electrical connector having slotted beam type contact terminals therein. The term "pre-loaded connector" as used herein is intended to imply that the terminals are mounted in the connector housing by the connector manufacturer. When a pre-loaded connector having slotted beam type contact terminals therein is placed in service, the conductors are attached to the terminals by merely inserting the conductors into the slots of the terminals. The more commonly used type of connector is not preloaded but has cavities which are adapted to receive electrical contact terminals which have previously been crimped onto conductors.

The invention is directed in accordance with a further aspect thereof towards the achievement of an electrical connector having improved impedance characteristics for connecting co-axial cables to each other or to other circuitry. It should be explained in this respect that co-axial cables are manufactured to rigid tolerances in order to provide precisely controlled and uniform impedance characteristics along their lengths. When two co-axial cables are connected to each other, a discontinuity in the impedance characteristics of the transmission line commonly results. Conventional coaxial connectors are carefully designed with regard to their geometry to minimize this discontinuity but such carefully designed connectors are usually relatively expensive and bulky. A co-axial connector in accordance with the instant invention is relatively compact and can be manufactured at a relatively low cost.

It is accordingly an object of the invention to provide an improved pre-loaded electrical connector. A further object is to provide a connector for co-axial cables having improved impedance characteristics. A still further object is to provide a connector for co-axial cables which is easily installed on the end of a cable. A still further object is to provide an improved contact terminal for an electrical connector.

These and other objects of the invention are achieved in a preferred embodiments thereof which are briefly described in the foregoing abstract, which are described in detail below, and which are shown in the accompanying drawings in which:

FIG. 1 is a perspective view of one form of connector assembly in accordance with the invention, the two connector parts being exploded from each other in this view.

FIG. 2 is a perspective view of a section of co-axial cable of a type for which the embodiment of FIG. 1 is intended.

FIG. 3 is a cross-sectional view taken along the lines 3--3 of FIG. 1.

FIG. 4 is a view taken along the lines 4--4 of FIG. 3.

FIG. 5 is a view similar to FIG. 3 but showing the connector parts coupled to each other.

FIG. 6 is a perspective view of a pair of complementary contact terminals which are contained in the connector parts of FIG. 1.

FIG. 7 is a side view of the contact terminals shown in FIG. 6, the terminals being coupled to each other in this view.

FIG. 8 is a perspective exploded view of one of the connector parts of the embodiment of FIG. 1.

FIGS. 9, 10--10 and 11--11 are sectional views taken along the lines 9--9, 10--10 and 11--11 of FIG. 8.

FIG. 12 is a perspective view of a group or stock of connectors in accordance with an alternative embodiment of the invention, one of the connectors being exploded from the stock.

FIG. 13 is an exploded view of a further embodiment intended for forming series connections along groups of contact terminal posts.

FIG. 14 is a sectional sideview of two connectors of the type shown in FIG. 13 and illustrating the manner of forming series connections among terminal posts.

FIG. 15 is a perspective view of a section of co-axial cable which has been stripped intermediate its ends pre-paratory to installation thereon of a connector of the type shown in FIG. 13.

FIG. 16 is a frontal view of the block portion of the connector of FIG. 13.

FIGS. 17-19 are graphs illustrating the impedance characteristics of a co-axial cable transmission line having a co-axial connecting means therein and illustrating the principle of the invention.

As noted above, the instant invention has particular advantages in applications where one co-axial cable is to be disengageably connected to another co-axial cable or to an alternative connecting means, although the invention can be used for forming connections for conventional conductors as will be described below.

The embodiments of the invention shown in the drawing are all particularly intended for use with a co-axial cable of the type as shown at 2 (FIG. 2) which comprises a center conductor 4, an inner layer 6 of insulating material, a relatively thin metallic layer 8 of shielding material which surrounds the insulating layer 6, and an outer layer of insulating material 12. A drain wire 10 is contained between the shielding layer 8 and the outer layer of insulating 12 purely for convenience in forming electrical connections to, and with, the shielding layer 8, the drain wire being in electrical contact with the shielding layer by virtue of the fact that it is held against the shielding material by the outer layer of insulation. The shielding layer 8 may be in the form of a braided metallic layer of a metal coated plastic.

A connector assembly in accordance with the invention as shown in FIG. 1 comprises two complementary, and in many respects similar, electrical connector parts, 14, 14' which are engageable with each other to connect corresponding co-axial cables 2 to cables 2'. Since the electrical connector part 14 is substantially similar to the connector 14', a description of the connector 14 will, to a large extent, suffice for both of the connector parts. Accordingly, the connector part 14 is described in detail below, and the part 14' is described only to the extent that it differs from the part 14. The same reference numerals, differentiated by prime marks, are used for corresponding structural elements in the two connector parts insofar as is practical.

Connector part 14 has mounted therein a plurality of first electrical contact terminals 16 (FIG. 6) each of which has a channel-shaped cross-section comprising a web 18 and sidewalls 20. The lefthand end of the terminal 16 serves as a contact portion 22 and a conductor receiving slot 24 extends from this contact portion inwardly in the web 18. Contact springs 26 are provided in the sidewalls 20 in the form of inwardly directed lances which are adapted to engage the contact terminals 16' when the terminals are mated with each other. A retention lance 25 is struck from the web 18 at the rearward end of the terminal and provides a forwardly facing shoulder 27 which functions to retain the terminal in a housing rack or block 28 as described below.

The complementary or second terminal 16' is a relatively simple blade-like member 18' having its conductor receiving slot 24' extending inwardly from its leading end. The width of this complementary terminal 16' is such that it can be received between the sidewalls 20 of the terminal 16 as illustrated in FIG. 7. The terminal 16' also has a struck out lance 25' for retention purposes. Conductors are connected to the terminals 16, 16' by simply moving them laterally of their axes and into the slots 24, 24'. It will be noted from FIG. 7 that when the terminals are mated with each other, the conductors in the two terminals are close to each other, a relationship which is significant and important in electrical connections between co-axial cables as will be described below.

Referring now to FIG. 8, the contact terminals 16 are mounted in a housing composed of an insulating block or rack 28 having a mating face 30 and a rearward face 32. A plurality of contact receiving cavities 34 extend between the faces 30, 32 and each cavity has a rearwardly facing shoulder 35 (FIG. 11). The terminals are assembled to the block 32 by merely aligning them with the cavities and inserting them into the cavities until the lances 25 lodge against the shoulders 35.

A plurality of conductor receiving grooves or recesses 38 extend across the block 28 on the upper side 36 thereof, each recess being of a width sufficient to accomodate a cable 2 and each recess having two branches 40, 42 which open onto the mating face 30 of the block. It will be noted that the ends of these branches 40, 42 are in alignment with the slots 24 of two adjacent contact terminals 16. As shown best in FIG. 9, the floor of each recess is slightly humped at 37 and slopes downwardly as viewed in FIG. 9 towards the rearward face 32 in order to provide a strain relief for the cable and to center the cable relative to the rearward side of the connector part as shown in FIG. 3 and as will be described below.

The block 32 is contained between two identical cover parts 44 (FIG. 8) each of which comprises a flat panel-like section 46 having flanges 48 extending from two opposite sides and having a rear or back flange 50. The flanges 48 and the panel section 46 are of reduced thickness at the lefthand side of the cover as shown at 52, 54 and a shallow recess 56 extends transversely across the panel section 46 parallel to the back flange 50. Circular openings 58 are provided on each side of recess 56 for the accomodation of fasteners 60 which are adapted to extend through these openings and through aligned openings 51 in the block 28.

When the connector part 14 is to be installed on the ends of cables 2, the cables are first stripped or prepared by removing a portion of the outer insulation 12 and the shielding material 8 from the end of the cable without disturbing or cutting the drain wire 10 and insulation 6 and center conductor 4. The end of each cable is then positioned in one of the recesses 38 and the drain wire is lead through the branch 42 while the center connector is lead through the branch 40. The drain wire is moved laterally of its axis into the conductor receiving slot 24 of the immediately adjacent contact terminal 16 which is below (as viewed in FIG. 8) the drain wire. The center conductor is similarly moved laterally of its axis into the conductor receiving slot of the next adjacent contact terminal. It is unnecessary to strip the insulation 6 from the center conductor for the reason that this insulation will be penetrated by the edges of the terminal slot and contact will be made with the center conductor. It may be necessary to provide a slot in the terminal which receives the center conductor which is not of the same width as the width of the slot in the associated terminal which receives the drain wire of a cable if the two conductors are of different diameters.

After the cables 2 have been connected to associated pairs of contact terminals 16, the block 28 is positioned between the two cover members 44 and the cover members are clamped to each other and to the block by the fasteners 60. As shown in FIG. 3, a strain relief for each cable is provided by the hump 37 in each recess 38 and the shallow recess 56 in the upper cover part 44. The back flanges 50 of the cover parts 44 bear against the surface of the cable but provide additional strain relief.

The connector part 14' differs from the connector part 14 in that it has contact terminal blades 16' therein and the cover parts 44' are dimensioned to surround the reduced thickness ends 52, 54 of the cover parts 44. In the assembled connector parts, the contact terminals are thus completely surrounded as shown in FIG. 3 and protected against damage when the two connector parts are disengaged from each other. The connector parts are engaged with each other by simply holding them in alignment as shown in FIGS. 3 and 4 and moving them towards each other so that corresponding contact terminals are engaged with each other thereby to connect the center conductors of each cable 2 to the center conductors of the cables 2'and similarly connect the drain wires of corresponding cables 2, 2'.

The benefits achieved for co-axial cable connections by the practice of the invention can be understood and appreciated in the light of the foregoing description of the embodiment of FIG. 1 taken in conjunction with the following discussion of some factors affecting impedance mismatch in co-axial connections.

Co-axial cables having a signal conductor and shielding material in surrounding relationship to the signal conductor are used in order to protect the signal conductor from interference effects which result from adjacent conductors or other sources. If shielding is required, it is often desirable to provide it in a geometrically constant relationship to the signal conductor so that the impedance of the cable is constant throughout the length of the cable particularly if the cable is used in equipment or systems which operate at high frequencies. Co-axial cables of the type shown in FIG. 2 are thus manufactured rigid tolerances and are made highly uniform along their lengths in order to achieve a constant impedance.

When two co-axial cables are connected to each other, the impedance in the zone of the connection will almost invariably be different from that of the cables and while the resulting impedance mismatch (i.e., the impedance of the cable as compared to the impedance of the connection) can be reduced by careful design and manufacture of the connection, it can probably never be eliminated. The expression "zone of the connection" as used above is intended to define the distance between the locations on the two co-axial cables at which there is a change in the geometry of the transmission line. For example, the zone of the connection between the cables 2 and 2' in FIG. 5 extends from the location 3 of the cable 2 to the position 3' of the cable 2'. The impedance in this zone will ordinarily be different than the normal impedance of the cables 2, 2' by reason of the fact that the shielding has been removed from the transmission line in this zone and the geometry of the line is otherwise different from that of the cables.

It is highly desirable to minimize this impedance mismatch in the zone of connection in order to improve the performance of the system of which the cable forms a part and in order to avoid unforeseen effects which may be brought about by the mismatch. The effects of impedance mismatch are explained below with reference to FIGS. 17-19 which schematically illustrate the mismatch which results if little or no effort is made to achieve a low impedance mismatch (FIG. 17), the manner of reducing the effects of mismatch with known types of co-axial cable connecting devices (FIG. 18), and the manner of reducing the effects of mismatch in accordance with the invention (FIG. 19). It is emphasized that FIGS. 17-19 are qualitative and that the curves of these FIGS. do not represent any actual observed data. These curves do not consider, for example, the fact that mismatch computations must be based on the electrical length of two transmission lines rather than the physical length and actual data curves would be irregular rather than straight and symmetrical as in the drawing. The curves do serve, however, to illustrate the advantages of the invention without recourse to a rigorous mathematical analysis of the numerous variables in a transmission line.

Referring to FIG. 17, if it is assumed that the portions 107 of the curve represent the normal and constant impedance of two co-axial cables, a connection between these cables may result in a mismatch 108 in the form of a significant increase in the impedance along the transmission line (the two cables and the connection). The length of this mismatch will be equal to the length of the connection and the ordinate change will depend upon the impedance of the connection as compared to that of the cable. The disruptive impedance effect of the connection between the cables will be represented by the shaded area in FIG. 17 and the greater this area, the greater the effect of the mismatch. An impedance mismatch of this type in a connection between two cables can, and frequently does, cause noise in the form of pulses in the line caused by reflections of the signals passing through the line. Such renegade pulses reduce the amount of energy transmitted and, more importantly, can cause unforeseeable mischief in the system of which the transmission line forms a part. For example, these unwanted renegade pulses may cause undesired circuit triggering which will have an effect contrary to the overall purpose of the system and which may frustrate the functions of the system.

In accordance with conventional engineering practice, impedance mismatch is reduced to an acceptable level by careful design of the co-axial cable connecting device so that the impedance of the connecting device is very nearly the same as that of the cable. As shown in FIG. 18, the area under the portion 110 of the curve is greatly reduced by careful design of the co-axial connecting device although the length of the connecting device is the same as that illustrated in FIG. 17.

In accordance with the practice of the present invention, the effective length of the connecting device and the zone of the connection, as defined above, are substantially reduced by virtue of the fact that the ends of the drain wires 10, 10' and the signal conductors 4, 4' are closely adjacent to each other when a contact terminal 16 is mated with a contact terminal 16'. Also, the location 3' of the cable 2' is relatively close to the location 3 of the cable 2. It follows that the area under the portion 112 of the impedance line (FIG. 19) is substantially reduced to the point of acceptability. The area under the curve portion 112 of FIG. 19 is equal to the area under the portion 110 of the curve of FIG. 18 even though the increase in impedance is substantially greater in the curve of FIG. 19.

The fact that conductors of a cable are closely adjacent to the conductors of the other cable in accordance with the invention can be translated into distinct economic advantages in that it is not necessary to design the connecting device to rigid dimensional (and other) specifications in order to achieve a low or acceptable impedance mismatch. Additionally, connectors in accordance with the invention can be made extremely compact so that little space is required to disengageably connect one group of co-axial cables to another group of cables.

FIG. 12 shows an alternative embodiment of a connector in accordance with the invention adapted for connecting the center and drain wire conductors of a cable 2 to a pair of associated terminal posts 64, 66 mounted in a panel 68 such as a printed circuit board. The connector 61 comprises a block 70 of insulating material having a conductor receiving passageway 80 on on one side thereof which extends from the upper side or face to the mating face 74. This passageway has branches 82, 84 adjacent to the mating face for the accomodation of the drain wire 10 and the center conductor 4, and terminals 76 extend downwardly from the mating face adjacent to the branches 82, 84. The terminals 76 are of the general type shown at 16, FIG. 6, excepting that the terminals 76 have inwardly formed bow springs 78 on their sidewalls for engagement with the terminal posts 64, 66. Flanges 88 extend downwardly on each side of the mating face of protect the terminals as previously described.

The cable 2 is positioned in the passageway 80 and the conductors are connected to the slotted ends of the terminals 76 as previously described. As shown in FIG. 12, a group of connectors 62 can be stacked against each other in order to form connections with a plurality of associated groups of pairs of posts 64, 66. Cover plates 92 are advantageously bonded or otherwise secured against the outwardly facing surfaces of the end connectors 62 to clamp the cable 2 in the lefthand end connector and to provide protection for the terminals in both ends of the stack. A strain relief is provided for each cable 2 in the form of a hump 86 in the passageway of each of the blocks and recesses 90 are provided for the portion of the cable which is displaced by the hump in the passageway.

The stack of connectors 62 as shown in FIG. 12 can be cemented or otherwise secured to each other to form a single connector assembly for a plurality of cables 2 or the individual connectors can be independent of each other so that they are individually disengageable from the terminal posts in the board.

FIGS. 12-16 show a further embodiment of a connector in accordance with the invention for forming connections among separate groups 94, 96 of terminal posts mounted in panels 98. This connector comprises an insulating block 102 having cable receiving passageways 104 on two oppositely facing sides thereof. Contact terminals 76 as previously described extend from the lower or mating face 106 of the block in alignment with the outlets of the branches 105, 107, of the passageways 104. The cable 2a (FIG. 15) is prepared by removing the outer insulation and the shielding material from an intermediate portion of the cable without cutting the center conductor 4 or the drain wire 10. The center conductor and the drain wire are then inserted into the slots of the terminals 76 and the adjacent portions of the cable are located in the passageways 104 as shown in FIG. 14. The block 102 is then slipped into a suitable insulating case 99 which clamps the cable in the passageways 104 and which extends beyond the mating face 106 to protect the terminals as shown in FIG. 14. Any desired number of connectors 100 can be installed on the cable 2a to connect a like number of pairs of posts 94, 96 in series or daisey chain fashion.

While the practice of the invention is particularly advantageous for co-axial cable connections, connectors in accordance with the invention have several advantages under many circumstances for use with conventional conductors which do not have a shielding layer there around. The connector is pre-loaded, as noted previously, and can be installed with relative ease on the end of the conductor when the connector is put in service. Further, a single type of connector in accordance with the invention can be used for both co-axial cable or conventional conductors. Where conventional conductors are being used, two conductors are positioned in each conductor receiving passageway, 38 of FIG. 8, and one conductor is lead through each of the branches 40, 42 to the separate terminals which are associated with each branch.

Changes in construction will occur to those skilled in the art and various apparently different modifications and embodiments may be made without departing from the scope of the invention. The matter set forth in the foregoing description and accompanying drawings is offered by way of illustration only.

Claims

What is claimed is:

1. An electrical connector intended for use with a pair of associated conductors such as a signal conductor and a grounding conductor, said connector being adapted for engagement with complementary connecting means to disengageably connect said associated conductors to further conductors, said connector comprising:

an insulating housing, said housing having a mating face which is proximate, and opposed to, said complementary connecting means when said connector is engaged with said complementary connecting means, said housing having a rearward face on the side thereof which is opposite from said mating face,

a pair of electrical contact terminals in said housing, said terminals having contact portions which extend normally of, and beyond, said mating face, each of said contact portions having a free end, said free ends being generally channel-shaped in cross-section and having a web and sidewalls, each of said free ends having a conductor receiving slot extending inwardly from its web at said free end, and

conductor-receiving passageway means extending through said housing from said rearward face to said mating face whereby upon positioning said conductors in said conductor-receiving passageway means and locating end portions of said conductors in said conductor-receiving slots, said conductors are electrically connected to said contact terminals adjacent to said free ends, and upon engagement of said connector with said complementary connecting means, said end portions of said conductors are located adjacent to said complementary connecting means.

2. An electrical connector as set forth in claim 1, each of said contact terminals having contact spring means on its sidewalls for electrical contact with complementary contact terminals in said complementary connecting means.

3. An electrical connector as set forth in claim 1 in combination with a pair of associated conductors, one said conductor being in said conductor-receiving slot means of one of said contact terminals and the other one of said conductors being in said conductor-receiving slot means of the other one of said contact terminals.

4. An electrical connector as set forth in claim 1, said housing being generally prismatic, said conductor receiving passageway means comprising groove means extending on a side of said housing between mating face and said rearward face.

5. An electrical connector as set forth in claim 4, said groove means comprising a single groove extending from said rearward face towards said mating face, said single groove having an end which is proximate to said mating face, and two branch grooves extending from said end to said mating face, each of said branch grooves opening onto said mating face at a location proximate to one of said contact terminals.

6. A connector as set forth in claim 5 in combination with a co-axial electrical cable of the type comprising a center conductor and shielding layer in surrounding relationship to said center conductor, said cable being in said groove, said center conductor extending through one of said branch grooves and being in said conductor-receiving slot of one of said contact terminals, and additional conductor means extending from said shielding through the other one of said branch grooves and being in said conductor-receiving slot of the other one of said contact terminals.

7. A connector as set forth in claim 6, said additional conductor means comprising a drain wire.

8. A connector as set forth in claim 5, said housing having said groove means on two opposite sides thereof.

9. A connector as set forth in claim 8 in combination with a co-axial cable of the type comprising a center conductor, shielding material in surrounding relationship to said center conductor, and a drain wire extending along and against said shielding material, said shielding material being removed from an intermediate portion of said conductor, portions of said cable adjacent to said intermediate portion being in said groove means on said two opposite sides of said mating face, said center conductor being in first corresponding branch grooves on said two sides and extending across said mating face and through said conductor-receiving slot of one of said contact terminals, said drain wire being in second corresponding branch grooves on said two sides and extending across said mating face and through said conductor receiving slot of the other one of said contact terminals.

10. A connector as set forth in claim 4, and enclosure means in surrounding relationship to said housing.

11. An electrical connection between two coaxial cables, each of said cables comprising a center conductor, an insulating sheath surrounding said center conductor, and metallic sheilding material in surrounding relationship to said insulating sheath, said connection comprising:

a pair of complementary connectors, each of said connectors comprising an insulating housing, said housing having a mating face which is proximate, and opposed to, the mating face of the other one of said connectors when said connectors are mated,

two electrical contact terminals in each of said housings, each of said terminals having a contact portion which extends forwardly from the mating face of its associated housing and which has a free end, each of said contact terminals having a conductor-receiving slot extending inwardly from its free end,

each of said cables extending to the mating face of one of said housings and having its center conductor extending through the conductor-receiving slot of one of said terminals, and conductor means extending from said shielding material to the other one of said terminals and through the conductor-receiving slot thereof,

said connectors being mated with each other with the free ends of the contact terminals of each connector in overlapping engagement with the free ends of the contact terminals of the other whereby,

the center conductors of said two cables are connected to each other and the shielding material of each cable is connected to the shielding material of the other, said connection having a short zone of connection and a low impedance mismatch by virtue of the fact that said shielding material and said center conductors are connected to said terminals proximate to said free ends thereof, and said shielding material of each of said cables extends to a location which is proximate to said mating faces and proximate to said free ends of said terminals.

12. An electrical connection as set forth in claim 11, each of said cables having a drain wire extending therealong in contact with said shielding material, said drain wire of each cable extending to the said other one of said terminals and constituting said conductor means extending from said shielding means to the other one of said terminals.

13. An electrical connection as set forth in claim 11, said free ends of said terminals in one of said connectors comprising terminal blades.

14. An electrical connection as set forth in claims 13, said free ends of said terminals in the other one of said connectors having a channel shaped cross-section, said terminal blades extending between the sidewalls of said terminals having a channel-shaped cross-section.