U.S. patent number 3,910,673 [Application Number 05/398,363] was granted by the patent office on 1975-10-07 for coaxial cable connectors.
This patent grant is currently assigned to The United States of America as represented by the United States Energy. Invention is credited to Danny Burton Stokes.
United States Patent |
3,910,673 |
Stokes |
October 7, 1975 |
Coaxial cable connectors
Abstract
A coaxial cable connector of the type wherein one connector is
suitable for a group of cables having the same nominal size and
impedance characteristics. Clamping force is applied on the outer
conductor of the cable in the radially inward direction upon
fastening the backshell to the body of the connector. A subassembly
captivated within the backshell forces a deformable material into
sealing contact with the outer surface of the cable upon fastening
the backshell to the body.
Inventors: |
Stokes; Danny Burton (Las
Vegas, NV) |
Assignee: |
The United States of America as
represented by the United States Energy (Washington,
DC)
|
Family
ID: |
23575099 |
Appl.
No.: |
05/398,363 |
Filed: |
September 18, 1973 |
Current U.S.
Class: |
439/584;
174/88C |
Current CPC
Class: |
H01R
24/564 (20130101); H01R 2103/00 (20130101) |
Current International
Class: |
H01R
13/00 (20060101); H01R 13/646 (20060101); H01R
017/04 () |
Field of
Search: |
;339/177 ;174/75C,88C,89
;339/6C,88C,89C,99C,91P,94C |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
679,410 |
|
Sep 1952 |
|
GB |
|
861,652 |
|
Feb 1961 |
|
GB |
|
1,242,731 |
|
Jun 1967 |
|
DT |
|
1,237,468 |
|
Jun 1960 |
|
FR |
|
1,065,499 |
|
Sep 1959 |
|
DT |
|
Primary Examiner: Frazier; Roy D.
Assistant Examiner: Staab; Lawrence J.
Attorney, Agent or Firm: Carlson; Dean E. Koch; John A.
Government Interests
BACKGROUND OF THE INVENTION
The invention described herein was made in the course of or under
Contract AT(26-1)-473 with the U.S. Atomic Energy Commission.
Claims
What I claim is:
1. In a connector for coaxial cables of the RF type, a combination
which permits one connector to be suitable for use on a group of
cables having the same impedance characteristics and similar
nominal size but different structural details while reducing the
number of loose components thereof in order to facilitate its
connection onto a cable, said combination comprising:
a. a body having an inner conductor and outer conductor and
dielectric therebetween arranged at its forward end for connection
with another connector and at its rear end for receiving any one of
said group of cables, the outer conductor and some of the
dielectric of said cable being removed from a forward portion
thereof and said dielectric of said body extending rearwardly over
said exposed dielectric of said cable to provide a voltage
standoff, and screw threads on the rear end of said outer conductor
for connection to a backshell,
b. a collet and collet clamp pair positioned at the rear end of
said body for applying clamping force upon the outer conductor of
said cable in the radially inward direction, only, upon axially
forward movement of said collet clamp relative to said collet, a
forward portion of said collet extending over said tubular
extension of the dielectric of the body being dimensioned to
provide an annular space between said portion of the collet and
said extension of the dielectric to provide adjustment of the
dielectric value of the space between the outer surface of the
inner conductor and the inner surface of said portion of said
collet, and
c. a subassembly including a backshell having screw threads at its
forward end for connection with said body and a radially inwardly
extending portion at its rear end, a deformable seal, a
longitudinally extending spacer positioned forward of said seal and
means for captivating said seal and said spacer within said
backshell, the dimensions of the captivated members and backshell
being such that upon the connection of said backshell to said body,
said spacer is forced against said seal thereby deforming said seal
against said cable to make sealing contact with said cable.
Description
This invention relates to connectors for coaxial cables of the RF
(radio frequency) type and, more particularly, high-power, low-loss
cables having foam dielectric and components of relatively large
size.
The use of coaxial cables in the transmission of intelligence via
the propagation of electromagnetic energy is well known. It is also
well known that the intelligence transmitting link must be free
from impedance discontinuities if distortion of the intelligence is
to be avoided. Accordingly, the designer of connectors for coaxial
cables for this type of service must work within very severe
constraints.
U.S. Pat. No. 3,678,446 to Hilbert R. Siebelist, assignor to the
U.S. Atomic Energy Commission, assignee of the present application,
described in some detail the difficulties the large user of coaxial
cables experienced with regard to providing satisfactory connectors
for the multitude of coaxial cables available in any particular
nominal size and impedance rating. To briefly summarize the
situation described more fully in the Siebelist patent, prior to
the Siebelist invention, generally speaking, each cable of a group
of cables having the same impedance rating and nominal size had its
own connector -- usually manufactured and sold by the manufacturer
of the cable -- which had a backshell design that made it suitable
for use with that particular cable and essentially none other. The
Siebelist connector overcame these difficulties by a particular
combination of backshell, body and outer conductor clamping
arrangement which was applicable to an entire group of cables of
nominal size and impedance rating even though a considerable
variance was present within that group of cables with respect to
the configuration, dimensions, etc. of their individual
components.
The present invention is directed to solution of the same problems
to which the Siebelist connector was directed. However, I have
found a combination of components in a cable connector backshell
and cable outer conductor clamping arrangement which provides
certain important advantages over the Siebelist connector.
The connector in accordance with the present invention does not
require that the outer conductor of a cable be flared in
preparation to assembling the connector onto the cable as does the
Siebelist connector. Flaring the outer conductor required a number
of hand operations by workmen in the field including the
compression of the end of the outer conductor in a specially
designed hand operated die set in order to obtain the appropriate
flare angle. Moreover, my connector involves a lesser number of
loose parts with which the workman in the field must contend and
requires fewer steps and utilization of fewer specialized tools in
connection with its installation. Accordingly, the connector in
accordance with the present invention facilitates and simplifies
the connection of cables in the field while retaining the
advantages of the Siebelist connector.
SUMMARY OF THE INVENTION
Accordingly, it is an object of this invention to provide a cable
connector of the type which permits one connector to be suitable
for use on a group of coaxial cables which have the same impedance
characteristics and the same or similar nominal size but have
different structural details. It is a further object of the
invention to provide a connector of this general type which is more
easily connected to cables in the field than the connectors
previously known.
Briefly summarized, this and additional objects and advantages of
the invention are accomplished by a connector having a backshell
which admits a number of cables of the same nominal size and
employs a radially compressible collet, the configuration of the
radially inward surface of which grips the outer conductor of the
cable. Means are provided which compress the collet, thereby
clamping it onto the outer conductor, upon longitudiinal movement
of the backshell with respect to the body of the connector. An
environmental seal is forced into engagement with the outer surface
of the cable in response to the same longitudinal movement of the
backshell that actuates the collet.
The means for compressing the collet include a collet clamp and a
longitudinally extending spacer positioned within the backshell.
The radially outer perimeter of the collet and the radially inward
perimeter of the collet clamp have complementary surfaces which
expand radially outwardly in the forward direction. The forward end
of the spacer engages the collet clamp. A deformable material is
positioned between the rear end of the spacer and the rear end of
the backshell. Accordingly, relative longitudinal movement between
the backshell and the body of the connector upon fastening the two
together causes the collet clamp to be forced forward thereby
applying a radially inward force to the collet which clamps the
collet onto the cable outer conductor. Simultaneously, the
deformable material is carried forward by the rear end of the
backshell into forceable contact with the rear end of the spacer.
The deformable material is thereby forced to expand in the radially
inward direction into contact with the outer surface of the cable
to provide a seal.
Captivation of the spacer and environmental seal within the
backshell reduces the number of loose parts with which the workman
in the field must contend. Since the interface between the collet
and collet clamp can be standardized for the entire group of cables
for which the connector is applicable, the collet is the only
component of the connector that needs to be specialized for
particular cables of the group.
Additional objects and advantages and a better understanding of the
invention will be apparent after consideration of the following
description of preferred embodiments thereof.
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 of the drawing is a longitudinal view, primarily in
cross-section, of a preferred embodiment of the invention,
FIG. 2 is a longitudinal view of another connector according to the
invention partially in section to illustrate an alternative to FIG.
1 with respect to the collet and dielectric arrangement, and
FIG. 3 shows the backshell subcombination of FIG. 1.
DESCRIPTION OF PREFERRED EMBODIMENT
Referring now to FIG. 1 of the drawing, the components of cable
connector 10 are shown in the positions they assume when connection
with cable 12 has been accomplished. Cable 12 is a typical coaxial
cable having a central inner conductor 14, concentric outer
conductor 16, dielectric material 18 between the two conductors and
an outer protective covering 22.
The forward portion of connector 10 also has an outer conductor,
inner conductor and mass of dielectric therebetween. While the
invention is not limited to connectors having any particular
arrangement or configuration of parts in their forward portions, a
typical arrangement is illustrated in FIG. 1. The outer conductor
takes the form of body 24 which may or may not be fabricated from
two components as shown in the drawing. Rearward portion 26 of
connector inner conductor 28 accommodates entry therein of inner
conductor 14 of the cable and forward portion 32 the entry of the
inner conductor 33 of a standard interface 34. Forward end 35 of
connector dielectric 36 is of a configuration to receive the
complementary configuration of dielectric of standard interface 34
in any usual manner which provides the necessary voltage withstand.
Nut 38 is utilized to fasten connector 10 to another connection
device, which may or may not be identical to connector 10, in the
usual manner.
The manner in which cable 12 is clamped within connector 10 to
provide the required mechanical strength of the union and the
transition of the outer conductor from the cable to the outer
conductor (body 24) of the connector will now be described. As will
be noted in FIG. 1, the preparation of outer conductor 16 and
dielectric 18 of the cable requires only that they be cut flush and
the annulus 40 be cut out of the dielectric by a hand tool to
accommodate tubular extension 42 of the dielectric 36 to provide
satisfactory voltage withstand. Further preparation is unnecessary
since securing cable 12 to the connector is effected through the
application of a radial force on outer conductor 16. This is
accomplished through the combined action of slotted collet 44,
collet clamp 46 and backshell 52 in the following manner.
The complementary outer surface 54 of slotted collet 44 and inner
surface 56 of collet clamp 46 are frustoconical and expand
radiallyoutwardly in the forward direction. Accordingly, relative
movement of clamp 46 in the forward direction exerts a radially
inward force upon slotted collet 44 which causes the collet to be
compressed inwardly upon the cable. The forward movement of clamp
46 is brought about in conjunction with the relative forward
longitudinal movement of backshell 52 with respect to body 24 which
accompanies the fastening of the backshell to the body through
suitable means such as complementary screw threads 58. The forward
thrust on clamp 46 is initially imparted through spacer 60
successively from seal 62, washer 64 and rear end 66 of the
backshell. However, that final forward thrust on clamp 46 which
locks collet 44 onto outer conductor 16 is applied to the clamp
through radially inwardly extending, forward facing shoulder 68 of
backshell 52.
Seal 62, made from a deformable material such as rubber, spacer 60,
washer 64 and end 66 cooperate to seal the connection from the
environment in those applications where an environmental seal is
necessary or desirable. The forceable engagement of the seal
between spacer 60 and washer 64 causes it to expand radially
inwardly into sealing contact with outer covering 22 of the cable.
Washer 64 provides a metal to metal contact with end 66 to
facilitate the rotation of backshell 52 in connection with securing
the backshell to the body such as through screw threads 58. The
dimensions of backshell 52, spacer 60, washer 64 and seal 62 are
selected to insure that sealing contact between the seal and outer
covering 22 is effected with that cable of the group of cables with
which one connector configuration will be used which has the
smallest O.D. The inner diameter of spacer 60 is sufficiently large
to accommodate the deformation of excess seal material into the
annular space between the spacer and outer covering 22 when
connector 10 is utilized with cables of larger O.D.
FIG. 2 illustrates an alternative arrangement for providing a
voltage withstand that provides advantages in making connections of
certain types of cables. It is normal practice when making a
connection between coaxial components to provide a protrusion of
the dielectric of one component into the dielectric of the other
component. This increases the air gap spark path between inner and
outer conductors to provide a satisfactory voltage withstand.
Foamed polyolefin is quite often the dielectric used in coaxial
cables whereas polytetrafluoroethylene (TFE) is commonly used in
connectors. Since the dielectric constant of TFE is significantly
higher than that of the foamed polyolefin, there will be instances
when the change in impedance caused by the arrangement of FIG. 1
will be unacceptable as, for instance, when the dielectric of a
cable is sufficiently thin that the thinnest practicable protrusion
from the connector dielectric too greatly affects the actual
dielectric value of the combination.
Accordingly, the embodiment of FIG. 2 provides an arrangement by
which the adjustment of the dielectric value can be readily
accomplished for particular cables. As shown, outer cable conductor
16' and an outer portion of the cable dielectric 18' are trimmed to
accommodate tubular extension 42' of connector dielectric 36'. The
compensation of the dielectric value is effected by providing an
air gap 72 of sufficient thickness by undercutting the inner side
of an extended portion of collet 44' at 74. Since air has a lower
dielectric value then foamed polyolefin (or other dielectric used
in cables), the thickness of the air gap can be selected to
compensate for the higher dielectric value of the TFE and provide
in combination with the thicknesses of the polyolefin and the TFE
an effective dielectric value, which closely approximates that of
the thickness of the polyolefin in the cable. The remaining
components of the connector of FIG. 2 are similar in structure and
function to corresponding components of the connector of FIG.
1.
It has been found that the assembly of connectors onto cables in
the field is facilitated by minimizing the number of components
with which the workman must contend. This is accommodated by
providing a subassembly of spacer 60, seal 62, washer 64 and
backshell 52, which is shown in FIG. 3. The interior parts are
captivated within backshell 52 by some suitable means such as
stakes 76 which may be formed by use of a punch and hammer. The
outer diameter of spacer 60 is relieved at 78 to provide clearance
for the stakes.
It will be appreciated from the foregoing that the inner radial,
dimensions of backshell end 66, washer 64, seal 62, spacer 60 and
collet clamp 46 would be made sufficiently large as to admit the
largest cable of the group of cables to which the connector is
applied and, in the case of the spacer, to provide space within
which excess seal material would be accommodated. It will also be
appreciated that the only component that would not be
interchangeable among particular cables of the group is collet 44.
The inner surface of the collet would be specially formed to
sufficiently conform to or to provide adequate gripping of the
outer surface of the outer conductor of a particular cable, or
sub-group of the group of cables, as to obtain the required
mechanical strength and electrical continuity in the union.
While the foregoing describes the fundamental novel features of the
invention as applied to preferred embodiments, it will be
understood that various omissions, substitutions and/or changes may
be made by those skilled in the art within the principle and scope
of the invention as expressed in the appended claims.
* * * * *