Coaxial cable connector with retractable bushing that grips...

Electrical connectors – Including or for use with coaxial cable – Having screw-threaded or screw-thread operated cable grip

Reexamination Certificate

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Reexamination Certificate

active

06261126

ABSTRACT:

FIELD OF THE INVENTION
This invention relates generally to a connector for coaxial cable, such as the type used for cable TV transmission.
BACKGROUND OF THE INVENTION
Coaxial cable connectors that require crimping are associated with certain disadvantages. Crimping tools tend to wear out with repeated use, and crimping does not provide a satisfactory seal. A number of crimpless connectors have been developed which attempt to overcome these problems.
One type of crimpless connector receives a compression sleeve, which is first broken away from a plastic ring mounted on the connector, and then slid over the cable and finally inserted into the annular cavity between the inner wall of the connector and the jacket of the cable. A tool is used to push the compression sleeve fully into the connector with a snap engagement.
A problem with this connector is that it can be awkward to break the compression sleeve away from the connector and then thread it onto the cable, particularly when used in field installations where there may be adverse weather conditions. The compression sleeve can as well be inadvertently threaded onto the cable backwards, and it can also be dropped and lost.
An alternative crimpless connector has more recently been provided, which permits the cable to be secured to it simply by pushing the cable into the connector and subsequently pulling it back. The body of this “push-pull” connector has a bushing mounted within it near the cable receiving end having a diameter to closely receive the cable. The body of the connector also has within it an annular mandril having a bore to receive the stripped core of the cable, and having a sleeve adapted to engage the cable beneath the jacket by pushing the cable and the mandril together. This stretches the jacket of the cable to a diameter greater than the internal diameter of the bushing.
The mandril is moveable from a position in which the sleeve is surrounded by the bushing in which the sleeve may be engaged to the cable, to a position in which the sleeve is at least partially within the bushing in which the jacket is frictionally engaged by the bushing by pulling the cable away from the connector after it has been pushed onto the mandril sleeve.
While the push-pull cable connector has many advantages, it does not lend itself to all applications. In some publicly accessible installations, for example, it is the usual practice to cover the threaded posts to which the cables are connected by a security ring, making the threaded portion of an installed cable connector inaccessible to finger manipulation or common wrenches or pliers. Unauthorized removal of the cable is thereby discouraged as a special tool is needed to fit within the security ring.
Due to the close tolerances of the standard security ring, the dimensional limitations of the push-pull connector present a significant obstacle. The internal bushing and mandril of the push-pull connector require a larger body diameter than can be accommodated in the standard sized security ring. While a larger security ring could be substituted, doing so would present additional costs.
It has also been found that the push-pull connector can be awkward to use with coaxial cable having multiple layers of braided shielding. Because of the limited travel of the mandril and bushing, the inserted cable must be trimmed to expose only a short distance of braided shielding. Folding back one layer of braided shielding presents little difficulty. However, manipulating multiple layers of braided shielding that are as short as required can be awkward. While a push-pull connector could be made with a longer travel for the mandril and bushing, thus allowing a longer trimmed section for the cable, this would require a longer overall connector length which would increase material costs.
BRIEF SUMMARY OF THE INVENTION
The purpose of the present invention is to obviate or mitigate the disadvantages of known connectors for coaxial cable.
In accordance with the invention, a connector is provided for use with a coaxial cable of the type having a central conductor, a dielectric insulator with a foil cover encasing the central conductor, at least one braided shield surrounding the foil covered dielectric insulator, and a plastic jacket covering the braided shield.
The connector comprises an internal body, means for interconnecting the connector to an electrical device, and an external body, assembled together so as to resist subsequent disassembly. The connector is adapted to receive a coaxial cable and to tightly hold the cable and form a seal with it by moving the external body relative to the internal body without disassembling the external body from the internal body.
The internal body is preferably in the form of a mandril that has a bore of a diameter to receive the dielectric insulator of the coaxial cable. The mandril has a sleeve with an end adapted to engage the cable beneath the braided shield and jacket.
The interconnecting means comprises threaded nut means which is rotatably mounted to the internal body at the end thereof remote from the sleeve end adapted to engage the cable.
The external body is preferably in the form of a gripping bushing that is mounted to the connector partially surrounding the mandril and concentric to it. At its free end it has a bore of a diameter to receive the jacket of the cable. The bushing is moveable from a first position in which the bore of the bushing and the sleeve of the mandril define an annular gap to receive the braided shield and the jacket of the cable, to a second position in which the annular gap between the bushing and the sleeve of the mandril is reduced, thereby squeezing the braided shield and the jacket of the cable.
Preferably the nut means is rotatably mounted to the mandril and retained thereto by a flange on the mandril. More preferably, the sleeve of the mandril is tapered and barbed.
Advantageously the gripping bushing is assembled with the mandril by close frictional contact and is moveable slidingly from its first position to its second position by means of a squeezing tool.
The connector also includes an O-ring retained upon the internal body close to the nut means, and the external body slides over the O-ring when it is moved into its second position.
It has been found that the connector of the present invention provides an effective solution to the problems presented by known prior art coaxial cables, as described above.
The connector of the present invention is preassembled. No separate pieces are involved that must be threaded onto the cable, and which can be misoriented or lost. The dimensional tolerances of the connector of the present invention, moreover, enable it to be used with the standard sized security ring. In addition, the connector of the present invention easily accepts coaxial cable having multiple layers of braided shielding with longer trimmed sections that facilitate folding of the braided shielding back over the cable jacket.


REFERENCES:
patent: 4834675 (1989-05-01), Samchisen
patent: 4902246 (1990-02-01), Samchisen
patent: 4952174 (1990-08-01), Sucht et al.
patent: 5007861 (1991-04-01), Stirling
patent: 5011432 (1991-04-01), Sucht et al.
patent: 5470257 (1995-11-01), Szegda
patent: 5667405 (1997-09-01), Holliday
patent: 0 459 825 (1991-12-01), None
patent: 1087228 (1967-10-01), None
patent: WO 90/15454 (1990-12-01), None

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