Electrical Connector

Abstract

An electrical connector jack having an outer cylindrical housing and a central coaxial conducting member which is slidable along its axis when receiving a plug so as to complete a contact with a second central coaxial conductor and simultaneously open a switch connected to a second central coaxial conductor so as to disconnect a terminating resistance or an alternate circuit path. The second conductor is connected so that there is no unused stub to cause reflections.

Description

BACKGROUND OF THE INVENTION

The field of this invention relates primarily to panel mounted electrical jacks of the type that are in widespread use in the telephone industry and other related arts. These signal carrying jacks have a standardized construction utilizing a cylindrical housing as a first circuit path and a coaxial center conductor as a second circuit path. It has become standard practice in the art to provide a switching arrangement internal to these jacks such that the two circuit paths are connected by a terminating resistance when no plug is inserted in the jack. In this way the end of the line is not allowed to remain in an open state which causes signals to be reflected therefrom interfering with the signal source. In the past terminating resistances have, of necessity, been connected between the outer housing and the central conductor at a position such that they do not interfere with the insertion of a suitable plug in the jack. As a consequence, when the plug is withdrawn and the terminating resistance is connected, a small unconnected portion of the central connecting stub remains beyond the point where the terminating resistance is connected. It is impossible to avoid a certain amount of capacitive coupling between ths dead end stub portion and the outer cylindrical housing and it has been found that this stub reflects energy back down the line. The effect becomes very objectional above about 60 megahertz. Since more and more signal transmission information is taking place at higher frequencies this disadvantage has become quite unacceptable in modern telephone and related equipment.

If a different type of connector could be used that did not have a long central prong this problem would not arise. Unfortunately millions of plugs now in use in the field have been built with this particular construction and it is therefore now impractical to adopt a whole new connector system which would not be compatible with the existing equipment now in use. The present invention overcomes the above disadvantages without departing from the standard configuration plug and provides a connecting jack in which the voltage standing wave ratio (VSWR) is maintained very close to unity so as to virtually eliminate reflection of the signal from the jack structure.

SUMMARY OF THE INVENTION

Briefly, my invention provides a unique mechanism wherein the withdrawal of the plug from the new and novel jack allows the central conductor to slide out of contact with the active circuit. This leaves the terminating resistance connected to the very end of the circuit so that there is no unused stub to cause reflections and impair the VSWR. When a plug is inserted into the jack of my invention it moves the central conductor axially back into contact with the active circuit and simultaneously disconnects, by means of a small switch, the terminating resistance. Despite the fact that two different switching operations are accomplished the structure of my invention still retains the dimensional configurations necessary to hold the VSWR near unity. In the preferred embodiment the VSWR has been measured as low as 1.03 for 70 megahertz. The new jack is compatible with equipment now in the field and fits a standard jack panel without any modification being required. It may therefore be seen that it is an object of my invention to provide an improved electrical connector jack adaptable to standard equipment now in use and having a VSWR very close to unity. Further objects and advantages will become apparent to those skilled in the art upon consideration of the following description and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram showing the basic operation of prior art connectors and demonstrating the disadvantages inherent therein.

FIG. 2 is a sectional view of the connector of my invention in the non-connected position with a terminating resistance in electrical contact with the very end of the circuit.

FIG. 3 is a detail view of a portion of the apparatus of FIG. 2 showing the displaced position of the central conductor caused by inserting the plug in the jack of my invention with the terminating resistor disconnected and the central conductor connected through the jack.

DESCRIPTION OF THE PREFERRED EMBODIMENT

In FIG. 1 the prior art type of jack is depicted in a generalized schematic diagram. The prior art jack comprises a cylindrical housing 10 with a central pin accepting conductor 12 supported by means of an insulator 14. Suitable connections 15 and 16 are made to the housing and the center conductor from a shielded cable 17. In the actual embodiment, of course, the shielding is continuous throughout and the center conductor is carefully maintained in a coaxial position equidistant from the walls according to specifications and design features well known to those skilled in the art.

The prior art plug comprises a cylindrical housing 20 and a central conductor pin 22 supported in an insulator 24. Again the shielded cable 25 is connected, as shown schematically by leads 26 and 27, to the respective circuit paths. When the plug is inserted into the jack, as shown in FIG. 1, the central pin 22 travels into central conductor 12 and maintains a path through the connector which path is coaxial with the outer housing and carefully spaced therefrom. If a signal is present on lines 15 and 16 and no plug is inserted in the jack the signal will be reflected objectionably back down cable 17 causing interference with other equipment unless a terminating resistance 34 is provided inside the jack. In the prior art it is the conventional practice to provide some sort of a switch wherein terminating resistance 34 is connected between the circuit paths so as to present an impedance, for example 75 ohms, when the plug 20 is withdrawn. In the schematic diagram of FIG. 1 this is shown as a slide bar 28 inside of central conductor 12 which slides against the action of a spring 30. A tab 32 is positioned so that as plug 20 and central pin 22 are withdrawn, spring 30 moves slide bar 28 and tab 32 into contact with terminating resistance 34. In this way the line becomes terminated by a suitable resistor and the VSWR is held close to unity.

It has been found that for signals in the range of 60 megahertz and higher this standard approach, as depicted in FIG. 1, is unsuitable. The reason for this is that the portion of central conductor 12 designated 12A extends beyond terminating resistance 34 and coacts capacitively with the housing 10A. It is absolutely essential for higher frequencies that the terminating resistance 34 be positioned at the very end of the circuit in order to avoid reflections. It can be seen however that this is not the case with the prior art. Instead the remaining portion 12A of the central conductor 12 operates as a small reflecting antenna which significantly impairs the operation of the system. My invention overcomes these problems as can be seen in FIG. 2.

In FIG. 2 the connector of the present invention is shown comprising a jack adapted to be mounted in a conventional panel. A cylindrical outer housing 40 encloses the entire jack assembly being secured to the internal components by a set screw 41. A panel mounting bracket 42 is fastened to the outside of housing 40. Housing 40 provides a smooth surface for insertion in the panel and is not a necessary part of the total structure of the invention. A first inner housing 44 is fitted within outer housing 40 and threaded to a second inner housing 46 by means of a set of threads 47. In FIG. 2 both inner housings 44 and 46 are provided with openings at the top of the drawing through which suitable electrical connections may be made. Positioned about the left end of inner housing 44 is a circumferential metal sleeve 48 which is slotted and bent to form contact pins 50. Each pin 50 nests inside a small ridge 51 formed in the interior surface of outer housing 40. Each pin 50 is bent inward as shown at 52 to provide frictional contact with the outer cylindrical housing of the plug which enters from the left in FIG. 2. In the prior art, and in the preferred embodiment of the present invention, the housings are preferrably constructed from brass although other metals would serve as well.

The structure of the inner and outer cylindrical housings 40, 44, 46 and 48 provide a first circuit path. The second circuit path is provided by a central conductor comprising an axially movable portion 68 and a fixed portion 54. Fixed portion 54 is held in place by means of a pair of suitable insulators 56 and 58 which are mounted in housing 46. The construction of these insulators is well known to those skilled in the art and is not further discussed herein. Axial movement of fixed portion 54 is prevented by a pair of annular flanges 61 and 63. A central hole 60 in fixed portion 54 accepts the central conductor of a shielded cable which enters from the right in FIG. 2. The other conductor of the shielded cable is fastened to annular housing 46A. The central conductor is soldered in hole 60 through an opening 62.

Axially movable center conductor 68 is supported for sliding movement in a pair of disc shaped insulators 69 and 71. The right end of center conductor 68 is formed into a hollow cylinder 70 which slides over an insulating guide pin 66 mounted in the cylindrical end 64 of fixed center conductor 54. In the rest position slidable center conductor 68 is held to its leftmost position by means of a spring 72 bearing against the end of insulating guide pin 66. In this position it may be seen that slidable center conductor 68 is not in contact with fixed center conductor 54. When a plug is inserted from the left the central pin of the plug, similar to pin 22 in FIG. 1, enters into the hollow area formed by the cylindrical left end 74 of slidable conductor 68. Cylindrical end 74 is provided with slots 77 and indented at 76 so that a controllable frictional fit is provided between the entering plug center pin and the jack center conductor. A frictional fit is utilized since the difference between the plug outer housing length and the center pin length is not uniform in the industry. Thus, it is not desirable to rely upon the end of the plug center pin for moving the slidable center conductor 68 into contact with the fixed center conductor 54. Instead, a frictional contact between the plug center pin and the indented portions 76 of cylindrical end 74 is relied upon.

With the plug withdrawn it may be seen that a spring 82 held in a hole 86 in an insulating member 84 contacts the cylindrical end 64 of fixed center conductor 54. A terminating resistance 88 of suitable value is connected between spring 82 and the housing 44 through a small hole 90 in insulator 71. A non-conducting insulating sleeve 80 surrounds the end of movable center conductor 68. Sleeve 80 moves spring 82 out of contact with fixed center conductor 54 as the plug is inserted. This may be more clearly seen in FIG. 3.

After the plug is inserted the movable center conductor 68 moves to the right as shown in FIG. 3. spring 72 is compressed and the cylindrical end 70 of movable center conductor 68 slides over and into contact with the cylindrical end 64 of fixed center conductor 54 allowing a complete conduction path through the center of the jack and into the plug pin. At the same time cylindrical insulating sleeve 80 lifts spring 82 out of contact with fixed center conductor 54, thus, disconnecting the terminating resistance 88. It should be noticed that despite the fact that a dual switching function is accomplised the center conductor is still designed to remain within the coaxial center of the outer cylindrical housing and at a predetermined distance therefrom.

It should also be understood that the connector of my invention is adaptable to a dual connector jack configuration commonly referred to in the telephone arts as a "normal through" device. In this arrangement two jacks of the type shown in FIG. 2 are employed and a connection is made from the spring contact 82 of one jack directly to the spring contact 82 of the other jack instead of to a resistor 88. In this design the signal flows from one jack into the other jack and back along its cable unless a plug is inserted to sample the signal. In this embodiment the jack of my invention is doubly effective since two conventional jacks would have two dead end stubs which would interfere seriously with the normal cable impedance. Other variations are also possible in constructing the jack herein described. For example, the specific insulating spacers and arrangements shown are only one possible design and other arrangements will become apparent to those having ordinary skill in the art. Likewise the method of springing the central conductor and the particular form of making contact with the fixed central conductor could be varied widely without departing from the spirit and scope of the invention. I therefore intend to be limited only to the appended claims.

Claims

I claim:

1. An electrical connector especially suitable for higher frequency signals comprising, about a common axis, an outer cylindrical housing forming a first circuit path and a coaxial center conductor having first and second portions, both of said portions mounted in non-conducting spacers inside said housing forming a second circuit path, the first portion of said center conductor having a pin receiving means at one end and being slidable over a limited distance along said axis so as to be movable in and out of contact at its other end with the fixed second portion of said center conductor, an electrical contract means connecting said second portion to said outer cylindrical housing, said first portion of said center conductor including means operable to open the electrical contact means at the contacted end of the second portion of said center conductor upon movement of said first portion into contact with said remaining portion.

2. The connector of claim 1 in which said electrical contact is springable into a rest position against the end of said second portion and said first portion moves said springable contact out of said rest position upon movement of said first portion into contact with said second portion.

3. The connector of claim 2 including resistance means connected between the springable contact and said outer housing.

4. The connector of claim 2 including a non-conducting guide pin means mounted on the end of said second portion of said center conductor sized to fit into a hole in the end of said first portion of said center conductor, said hole being aligned with said axis.

5. The connector of claim 4 in which said end of said first portion is hollow so as to slide over said guide pin means and over the end of said second portion of said center conductor so as to make contact therewith.

6. The connector of claim 4 including a non-conducting circumferential sleeve positioned about said end of said first contacting portion so as to move said springable contact away from the rest position on said second portion upon movement of said first portion toward said second portion.

7. The connector of claim 6 in which said end of said first portion is hollow so as to slide over said guide pin means and over the end of said second portion of said center conductor so as to make contact therewith.

8. The connector of claim 7 including resistance means connected between the springable contact and said outer housing.