Description:
BACKGROUND OF THE INVENTION
The present invention relates to a coaxial cable connector plug of the kind most generally used in connecting a coaxial cable in an amplifier chassis, as in a CATV system. The chassis ordinarily includes a unit involving a pressure different from that of atmosphere, i.e., it is either vacuumized or pressurized. The connector plug includes a pair of mating parts, one of the parts being mounted directly to the amplifier chassis unit and having contacts operatively engaging elements within the unit. The other mating part is a cap fitted on the body, and the two parts receive the coaxial cable, and when the parts are securely interconnected, electrical engagement is made between the conductor of the cable with the elements within the amplifier chassis unit. The cap may be applied to and removed from the body a number of times as in checking the effectiveness of the cable connection. In removing the cap from the body, the amplifier chassis unit is to remain sealed and the cable is to be effectively connected after each disconnection.
OBJECTS AND SUMMARY OF THE INVENTION
A broad object of the invention is to provide a novel connector plug of the foregoing general character capable of producing advantages not possible heretofore.
Another broad object is to provide a connector plug of the foregoing general character having novel construction particularly operative for producing effective electrical connection with the conductors of the cable.
Another object is to provide a connector plug of the foregoing character including mating parts which are turned up into connected position wherein in the turning operation the cable is effectively prevented from twisting, or turning with either of the connector parts.
Another and important object is to provide a connector plug of the foregoing general character in which the mating parts have interengageable stops establishing positive limitation of the turning up movement, and which is so constructed as to prevent damage to the cable if the tolerances of the various parts or elements are such as would otherwise tend to produce overtightening.
Still another object is to provide a connector plug of the foregoing character which is particularly effective in sealing the interior of the amplifier chassis unit to which it is connected, in all conditions of the connector plug, whether the cable is connected therein or removed therefrom.
An additional object is to provide a connector plug of the foregoing character which is of rugged construction and, in addition to providing effective electrical connection as referred to, provides a connection of the cable that is of unusually great mechanical strength resisting forces tending to pull the cable from the connector plug or to pull apart the parts thereof.
More specifically, another object is to provide an electrical connector for connecting a coaxial cable of the type having an outer sheath conductor and a central conductor in an installation in which it is subjected to severe forces tending to displace it, such as occurring in servicing, and from thermal expansions and contractions, as well as weight loading.
A still more specific object is to provide a connector of the foregoing general character including a body and a cap receiving the coaxial cable, and in the use of which the simple movement of tightening of the unit on the body provides good and effective electrical connection of both the central conductor and the outer sheath conductor and secures both conductors, individually against displacement by external forces, and further maintains securement relative to good electrical transmission characteristics.
A still further object is to provide a connector plug of the character referred to, having novel construction wherein, when the cap is removed from the body, all of the internal elements are prevented from accidentally falling out, thereby facilitating the work of the field man in servicing installations.
In the drawings:
FIG. 1 is a semi-diagrammatic view of an amplifier chassis unit and a cable connected thereto, utilizing a connector plug according to the present invention;
FIG. 2 is an expanded view showing interacting main parts of the connector plug unassembled and a cable to be connected therein;
FIG. 3 is a large scale longitudinal, axial, sectional view of the connector plug in connected position, with the parts at the beginning of the assembled and tightening up step;
FIG. 4 is a view similar to FIG. 3 but in a first stage of tightening;
FIG. 5 is a view similar to FIGS. 3 and 4 but with parts in position assumed in a normally tightened and fully assembled condition; and
FIG. 6 is a view similar to FIGS. 3, 4, and 5 with the main parts of the connector plug in tightened position, with the stops in interengagement, but with certain elements in an "overtightened" position.
Referring in detail to the drawings, FIG. 1 shows an amplifier chassis unit 10 of known kind having a number of electronic components 12 therein. The unit 10 includes a casing 14 having one wall element 16 in which is mounted a connector plug 18 embodying the features of the present invention. The interior of the unit 10 normally is of a pressure different from the atmospheric pressure, such as a partial vacuum.
The connector plug 18 includes two main interacting parts, namely, a body 20 and a cap 22 both of which will be described in detail hereinbelow. The connector plug is for use in connecting a coaxial cable 24 with the components 12 in the interior of the unit 10, this cable being of known kind, including a central conductor 26 such as of copper surrounded by a layer of dielectric material 28 preferably of cellular resilient material which is surrounded by an aluminum jacket 30 forming the outer conductor, concentric with the central conductor 26. The end of the dielectric material 28 and the aluminum jacket 30 together form a forwardly facing shoulder 32, and surrounding the jacket or conductor 30 is an outer layer of insulation or dielectric material 34.
The body 20 as shown in FIGS. 3-6 is of tubular shape having a central bore 35, an intermediate enlarged nut-like element 36, and a forward reduced portion 38 exteriorly threaded at 39 serving as the element by which the connector plug is mounted in the wall 16 of the unit 10. The element 36 has a forwardly facing shoulder 40 having an annular groove 42 receiving a gasket 44 for sealing the interior of the unit 10 from the exterior when the connector plug is applied thereto as in FIG. 1. At the opposite or rear end, the body has a reduced diameter portion 46 forming a shoulder 47 and externally threaded at 48 and having an inwardly directed flange 49 of minor radial dimension, forming a forwardly directed shoulder 50. The flange is provided with a forwardly converging generally inwardly directed camming or wedging surface 52. The body has a main forward portion 54 terminating forwardly at an internal shoulder 56. At the forward end is an insert 58 molded in position therein and in which is embedded a contact 60, this contact having a forward finger member 62 which extends into the interior of the unit 10 and a rearwardly extending or interiorly positioned finger member 64 having a tubular portion 66 split or slotted as indicated at 68 forming finger elements 70 which are provided with internal serrations 72, the finger elements 70 serving as a chuck for gripping or seizing the central conductor of the cable, as referred to again hereinbelow. The finger elements 70 are shaped at their rear end to provide a rearwardly converging, external conical camming or wedging surface 74.
Surrounding the rear end of the finger member 64 is a clamping insulator 76 of suitable insulating or dielectric material resistant to cold flow, having a central bore 78 therethrough including a forwardly disposed forwardly diverging conical camming or wedging surface 80 engageable with the surface 74, and preferably a rearwardly diverging entry opening 81. The clamping insulator 76 includes an external peripheral flange 82 engageable with the shoulder 50, and a rearwardly extending reduced central boss 84.
A compression spring 86 is disposed in the bore 35 in surrounding relation to the finger member 64 and compressed between the shoulder 56 and the clamping insulator 76.
The cap 22 is also of tubular form having a central bore indicated in its entirety at 88 and including a rearmost segment 90 leading into an enlarged segment 92 forming a forwardly facing shoulder 94 therebetween. Forwardly of the segment 92 is another segment or counter bore 95 forming a forwardly facing shoulder 96, the segment 95 being provided with a groove 98 in which is a split retaining ring 100. The segment 95 leads into another larger segment 102 having a circumferential groove 104 in which is disposed an "O" ring or gasket 106. Forwardly of the groove 104 are internal threads 108 threadedly engaging the external threads 48 on the body. The end surface 110 and the shoulder 47 on the body form stop means for positively limiting relative movement between the cap and body member in a manner referred to again hereinbelow.
Mounted in the cap is an "O" ring gasket 112 engageable with the shoulder 94, forwardly of and engageable with which is a thrust ring 114 having a rearwardly facing external shoulder 116 engageable with the shoulder 96, and forwardly of that shoulder an annular generally axially extending flange 118, adapted to ride or slide freely in the bore segment 95. The particular shape and proportions of this thrust ring are of importance in the principles of the invention, as will be described hereinbelow. The thrust ring is preferably made separate from the cap proper, to facilitate its fabrication and to facilitate incorporation of the "O" ring 112 in the cap. The flange 118 has a foremost, forwardly diverging, generally inwardly directed conical camming or wedging surface 120 having a small end indicated by a point or line 120a, rearwardly of which is another internal surface 122, also tapered, but of much lesser taper than the surface 120. For example, the surface 120 is preferably in the neighborhood of 45° to the central axis and the surface 122 is on the order of 7° to that axis. These inclinations are not critical and a reasonable latitude is permitted relative thereto.
Contained within the cap is a ferrule 124, split as indicated at 126 and thus capable of radial contraction and expansion. The ferrule is provided with internal circumferential serrations 128 which may be spiral as in the form of threads, or in the form of individual and disconnected teeth. At the rear end of the ferrule is an external, forwardly diverging conical camming or wedging surface 130 having a small end indicated by the point or line 130a, and engageable with the camming surface 120 and preferably of similar inclination, i.e., 45° to the central axis. Forwardly of the surface 130 is a surface 131 which may be cylindrical or tapered to a degree similar to that of the surface 122 and engageable with that surface. The ferrule has an external circumferential groove 132, forming oppositely facing shoulders 134, 136 engageable with the retaining ring 100 for retaining the ferrule in the cap when the cap is removed from the body.
The ferrule at its forward end has an external, forwardly converging conical camming or wedging surface 138 of an inclination similar to the surface 52, and engageable therewith, the inclination of these surfaces being substantially less than the surfaces 130, 120, i.e., substantially less than 45°. The inclination of the surfaces 138, 52 is not critical and may vary within a substantial range, so long as they remain substantially less than the inclination of the surfaces 130, 120. Rearwardly of the surface 138, the external surface of the ferrule, as indicated at 140, may approach the cylindrical. At the forward end of the ferrule is an inturned flange 142 defining an opening 144 which may approach the cylindrical and is dimensioned for freely receiving the boss 84 on the clamping insulator 76.
In the use of the connector plug, the body 20 is mounted to the unit 10 in a known manner. The end of the cable 24 is then stripped as shown in FIG. 2 and inserted forwardly into the cap 22 from left to right, as indicated above in reference to forward, rearward, etc. It is so inserted until the aluminum jacket 30 at the shoulder 32 engages the flange 142, the ferrule 124 at that time being free of the thrust ring 114 and in expanded condition, enabling free movement of the cable thereinto.
The plurality of connector parts, as thus far described, are assembled by applying the cap 22 to the body 20 and turning the cap thereon via the threads 48 and 108. As the cap is moved along the body, the camming surface 120 engages the camming surface 130 (FIG. 3), and moves the ferrule 124 forwardly, and in this movement the camming surface 138 engages the camming surface 52, and because of the lesser inclination of the latter two surfaces, relative to the surfaces 120, 130, the forward end of the ferrule is immediately radially compressed and the teeth 128 at the forward end immediately engage and grip the aluminum jacket and prevent the cable from turning with the cap, the friction between the cap and the ferrule being substantially less than between the ferrule and cable. As the assembling and tightening up operation continues, the camming surface 138 passes through the camming surface 52 (FIG. 4) and the flange 142 engages the clamping insulator 76, and just prior to this last step, the dielectric material 28 of the cable 24 engages the boss 84 and, because of its resilience, it slightly compacts.
It will be understood that in the application of the cap 22 and cable 24 to the body 20, the central conductor 26 of the cable enters freely into the tubular contact finger member 64; continued movement of the ferrule 124, with the cap, forces the clamping insulator 76 forwardly against the action of the spring 86, bringing the internal camming surface 80 into engagement with the external camming surface 74, radially compressing or contracting the finger elements 70 into gripping engagement with the central conductor.
Upon the clamping insulator 76 reaching its limit position pursuant to clamping the central conductor 26, forward movement of the ferrule 124 is of course arrested, and continued movement of the cap causes the thrust ring 114 to similarly move forwardly, and the internal camming surface 120 acting on the external camming surface 130 causes the rearmost portion of the ferrule to contract into gripping relation with the aluminum jacket 30 of the cable. In this position, the plurality of connector parts are substantially fully assembled and the end of the cable 24 is terminated by the connector 18. FIG. 5 shows the limit position as determined by the positive stop means 110-47, i.e., the former engages the latter and provides a positive limitation to the movement of the cap onto a body. In this position of the parts, ideally the point or line 120a of the surface 120 is substantially at the point or line 130a on the surface of 130.
Coaxial cables with which the present device is to be used are made to relatively close tolerances for purposes of signal transmission functions. When the cap and body are in such positive stop position, as through the elements 110, 47, and if the parts and elements of the connector plug are made to average tolerance, the points 120a and 130a will be substantially in register or in engagement when this positive stop position is reached. However, due to such practical tolerances, it occurs on occasion that overtightening on the cable could result. Damage from this possible source is eliminated by the relative shape between the surfaces 120, 122 on the thrust ring 114. If the tolerances are such that the point 130a would ride past the point 120a, the continued camming or wedging action as produced by the surfaces 120, 130 would terminate and the surfaces 122, 131 would interengage, or the point or line 130a would engage the surface 122, but due to the small inclination of the latter surface, any overriding would produce a minimum contraction of the ferrule. Actually the surface 122 may be only slightly inclined from the cylindrical, it being desired that the contraction not be continued to any appreciable extent, and only that sufficient friction be maintained as to prevent possible expansion of the ferrule at that end after the point 130a rides past the point 120a.
The construction provides unusually strong securement of both the central conductor 26 and the outer sheath conductor 30, and each individually of the other, against both mechanical displacement and disruption from electrical transmission effectiveness from outside forces.
The interior of the connector plug is effectively sealed by the "O" ring 106 between the cap and the body and the "O" ring 112 between the cap and the aluminum jacket of the cable.
The retaining ring 100 retains the ferrule 124, thrust ring 114 and "O" ring 112 in the cap when the cap is removed from the body, as in the field when the service man separates those parts. The retaining ring 100 is of inexpensive construction, being a split ring for enabling application to the ferrule and to the cap. This retaining ring also prevents cocking or skewing of the ferrule in the cap, when the cap is separated from the body, facilitating alignment of the ferrule with the body in connecting the parts.
The compression spring 86 is effective for releasing the clamping insulator 76 from clamping engagement with the contact finger elements 64, this being particularly effective in view of the long, low inclined taper or inclination of the conical surfaces 74, 80 so that upon loosening the cap on the body, the central conductor is immediately released permitting quick and easy removal of the cap.
The various elements of the connector plug are dimensioned in proportion to the size of the cable with which it is to be used, and hence the gap between the abutment surfaces 110, 47 as it occurs in FIG. 3 would be somewhat proportional to absolute dimensions encountered, but, as a practical example, the most common sizes of coaxial cable encountered are between 0.412 and 0.750 inch O.D. of the aluminum jacket, and in relation to a cable of this range the gap between the shoulders 110, 47 may be, for example three-eights inch. The tolerance of the elements making up the connector plug are calculated according to average tolerances occurring in practical operations, and it is found that such tolerances seldom accumulate to more than an amount corresponding to a gap of 0.050 inch between the surfaces 110, 47 when the points 120a, 130a are at the desired optimum position. Then when the service man tightens up the cap so that the surfaces 110, 47 do encounter, he is relieved of the requirement for exactness in sensing the degree of tightness on the cable, since the additional movement of the cap on the body of the amount mentioned, namely, 0.050 inch, is insufficient to cause appreciable camming action by the ferrule through the surfaces 122, 132, and damage to the cable.
This safety feature also prevents damage to the ferrule 124, such as by over-contracting. It enables the use of a thinner wall in the ferrule, providing greater resilience than a thicker wall and hence more flexing without failure or damage.
The construction including the safety feature described enables a greater tolerance in dimensions of the parts and accordingly renders the device much less expensive; and the device can be produced more readily by mass production methods.
The spring 86 also may be utilized in a dielectric balance in association with the contact 60 and the wall of the body 20.