Electrical connectors – Including or for use with coaxial cable
Reexamination Certificate
2000-06-27
2004-09-07
Bradley, P. Austin (Department: 2833)
Electrical connectors
Including or for use with coaxial cable
Reexamination Certificate
active
06786767
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention is directed generally to a connector for flexible coaxial cable and, in particular, to an electrical connector for terminating the end of flexible coaxial cable that is relatively small in size, that does not require any crimping and which has increased pull strength and improved anti-rotational captivation.
Coaxial connectors have taken many forms in the prior art as exemplified by U.S. Pat. No. 4,408,821 (Forney, Jr.) which is directed to a connector for semi-rigid coaxial cable. The connector for semi-rigid coaxial cable of Forney, Jr. is directed to a connector that does not require crimping. It uses a grip ring having multiple spline fingers extending therefrom and grooves on its inner surface, and a bored tubular shell member having a contoured internal diameter to accept the cable and the grip ring. When the grip ring and cable are inserted into the tubular body, the spline fingers resiliently deflect inwardly along the shell member contour, and embed into the outer semi-rigid cable sheath. The connector system can not provide termination for flexible cables because they do not include a semi-rigid sheath for the spline fingers to embed into.
U.S. Pat. No. 5,186,655 (Glenday, et al.) is directed to an RF connector. This connector locks in place by having a sleeve that is insertable between the outer conductor of a coaxial cable and the inner dielectric, such that the jacket and the outer conductor are deformed. After the sleeve is inserted, a coupling nut is then moved into place and frictionally engages the sleeve. This invention suffers deficiencies in the manner that the jacket electronically connects with the outer conductor, and the way that the coupling nut is coupled to the sleeve. The Glenday, et al. invention can not provide electrical performance for microwave frequencies because the method of deforming the plastic jacket on the outer conductor does not provide sufficient electrical contact at microwave frequencies. Therefore, this connector can not be used for microwave transmission, and is useful only for frequencies up to a few hundred MHz (CATV).
U.S. Pat. No. 5,607,325, incorporated herein by reference, describes an electrical connector for terminating flexible coaxial cable. The flexible cable includes an inner conductor, an intermediate dielectric, an outer flexible braided conductor and an outer insulator. A bored interface body has a first end with a first bore of relatively large inner diameter, a second end with a second bore of relatively smaller inner diameter than the first bore, and a third bore located therebetween of relatively smaller inner diameter than the second bore. A coupling member is located proximate to the interface body. An annular locking member having an inner diameter sized to receive the coaxial cable therein, an outer diameter sized to fit tightly within the first bore of the interface body, a first end having a collar and a second end having a plurality of ribs disposed proximate thereto is provided. This configuration allows for insertion of the second end of the locking member within the first bore of the interface body, so that the ribs of the locking member frictionally engage the inner wall of the first bore to lock the locking member to the interface body.
A typical connector for flexible microwave coaxial cable uses a ferrule to captivate the connector body to the cable jacket by friction. This crimp attachment improves the pull strength and anti-rotational (torque) captivation. Torque creates a potential failure for an coaxial cable assembly. Captivation of the cable jacket to the connector body is critical for many applications. Even highly flexible coaxial cable assemblies cannot withstand a large amount of torque. Pull strength is important for the mechanical integrity of a cable assembly. Additionally, the electrical performance of the cable assembly relies on mechanical captivation, particularly at high frequencies. Axial force applied to the cable can change the connector dimensions in the interface area, i.e., the contact and dielectric positions relative to the reference plane of the connector. This difference is small, usually about one or two millinches. It does not make a significant difference in the electrical performance of connector at the low frequencies; however, at frequencies higher than 18 GHz, the dimensional difference in the connector interface area has a crucial effect on electrical performance. Modern telecommunications systems need extended frequencies due to the high volume of information that is transmitted. Internet, Wireless, Space and Defense systems are growing at an exponential rate, creating great demands for more bandwidth.
The operational frequency limit of today's typical coaxial assemblies is very high compared to the requirements of only a few years ago. Today, millimeter wave components (frequencies higher than 30 GHz) are common in the marketplace. Some manufacturers have 40 GHz coaxial cables in stock. Currently the highest operational frequency of a flexible coaxial assembly is approximately 65 GHz. In the near future, this limit is expected to extend up to 100 GHz.
For high frequency assemblies, the milliinch difference in the interface dimensions is significant, making the pull strength captivation very important. The best mechanical captivation and electrical performance method is a solder/crimp connector attachment, as shown in FIG.
1
. The connector attachment is defined by a connector
210
which includes a connector or interface body
218
and a coaxial cable
232
formed with an outer insulator or jacket
224
, an outer braided conductor
226
, an inner insulator (not shown), and an inner conductor
230
. Connector body
218
is substantially annular and includes a first end
270
and a second end
272
. First end
270
is proximate a first annular body section
274
and second end
272
is located proximate a second annular body section
276
having a longer external diameter than first body section
274
. Connector
210
also includes an annular extending crimped ferrule
278
. As shown, outer conductor
226
is soldered to connector
218
by means of solder material
225
. Outer conductor
226
is crimped, as shown at
279
, in order to capture first body section
274
of connector body
218
.
A connector with a crimp ferrule has fair axial and anti-torque captivation, but the crimp ferrule adds significant length. Soldering the cable outer conductor to the connector body provides a rigid bond between the connector body and the cable, but the solder joint is subject to cracking during vibration, flexure or thermal cycling, which may cause electrical and/or mechanical failure of the cable assembly. The soldering process also subjects the cable dielectric to excessive heat, which may cause the dielectric to expand, requiring retrimming of the interface dimensions. Crimp and solder crimp attachments have approximately the same length. The connector of U.S. Pat. No. 5,607,325, discussed above, is short in length, which is very convenient for customers. However, it cannot handle the high pull force that some customers require (sometimes more than 20 pounds without any electrical degradation) and it has limited anti-rotational captivation (typically only ±15° for one cycle).
Accordingly, it is desirable to provide a connector for flexible coaxial cable that provides improved pull strength and improved anti-rotational captivation.
SUMMARY OF THE INVENTION
Generally speaking, in accordance with the present invention, an electrical connector for terminating flexible coaxial cable is provided. The connector includes a bored interface body having a first end with a first bore of relatively large inner diameter, a second end with a second bore of relatively smaller inner diameter than the first bore, and a third bore located therebetween of relatively smaller inner diameter than the second bore. A coupling member is located proximate the interface body and an annular locking member having an inner diameter sized to recei
Durett Donald P.
Fuks Rudolf
Georghiou George
Toma Stephen J.
Astrolab Inc.
Figueroa Felix O.
Kaden Jeffrey M.
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