Electrical connectors – Including or for use with coaxial cable
Reexamination Certificate
1999-06-08
2001-04-17
Sircus, Brian (Department: 2839)
Electrical connectors
Including or for use with coaxial cable
Reexamination Certificate
active
06217380
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to the field of cables and connectors, and, more particularly, to a connector and associated method for joining together different sized coaxial cables, as may be particularly advantageous in a wireless base station.
BACKGROUND OF THE INVENTION
Coaxial cables are widely used to carry high frequency electrical signals. Coaxial cables enjoy a relatively high bandwidth, low signal losses, are mechanically robust, and are relatively low cost. One particularly advantageous use of a coaxial cable is for connecting electronics at a cellular or wireless base station to an antenna mounted at the top of a nearby antenna tower. For example, the transmitter located in an equipment shelter may be connected to a transmit antenna supported by the antenna tower. Similarly, the receiver is also connected to its associated receiver antenna by a coaxial cable path.
A typical installation includes a relatively large diameter cable extending between the equipment shelter and the top of the antenna tower to thereby reduce signal losses. For example, CommScope, Inc. of Hickory, N.C. and the assignee of the present invention offers its CellReach® coaxial cable for such applications. The cable includes a smooth wall outer conductor which provides superior performance to other cable types. The smooth outer wall construction also provides additional ease of attaching connector portions to the cable ends in comparison to other coaxial cable types, such as including corrugated outer conductors, for example.
Each end of the large diameter coaxial cable is connected to a respective smaller diameter, and relatively short, jumper cable. The jumper coaxial cable has a smaller diameter with greater flexibility to thereby facilitate routing at the equipment shelter and also at the top of the antenna tower. More particularly, a relatively large diameter (about 1 and ⅝ inch) main coaxial cable extends from the shelter to the top of the tower, typically about 90 to 300 feet, to reduce attenuation. The main cable may be a CellReach® model 1873 cable, for example. A short smaller diameter (about ½ inch) coaxial jumper cable is connected to each end of the main cable, and may be a CellReach® model 540 cable, for example. The top jumper is typically 3 to 6 feet long, and the bottom jumper is typically 6 to 10 feet long.
At present, and as understood with reference to the prior art arrangement shown in
FIGS. 2 and 3
, first and second connectors
33
,
34
are typically assembled in a back-to-back relation to couple an end of the main coaxial cable
31
to an end of a jumper coaxial cable
32
. The first connector
33
includes a first back-nut assembly
35
and a first body portion
36
which are threadingly engaged together. A rear
0
-ring, not shown, may seal the cable sheath
54
to the first back-nut assembly
35
. Similarly, the second connector
34
includes a second back-nut assembly
41
which threadingly engages a second connector body portion
42
. As shown in the illustrated prior art connector arrangement
30
, the first or main cable
31
includes an elongate central strength member
43
, a surrounding dielectric layer
45
, and a surrounding adhesive layer
46
for attachment to the tubular copper center conductor
47
. A tubular dielectric layer
48
surrounds the center conductor
47
. In the illustrated embodiment, a portion of the dielectric layer
48
has been removed by a coring tool to thereby facilitate assembly. A tubular plastic body
51
is inserted into the cored cable end.
A portion of the outer smooth wall conductor
53
is exposed beyond the end of the cable sheath
54
. A metal clamping ring
56
is urged against the exposed outer conductor
53
as the back-nut outer cylinder
55
is threaded onto the connector body portion
36
. The connector body portion
36
includes a hollow metal member
57
in which is positioned an annular dielectric spacer
61
, which, in turn, supports a center contact
62
. The center contact
62
includes a tubular proximal end which receives and establishes contact with the inner conductor
47
. An annular dielectric body
63
provides a radially compressive force to the tubular end
63
of the center contact
62
as the back-nut
35
and connector body portion
36
are threadingly engaged. A rubber
0
-ring
67
seals the interface between the first back-nut assembly
35
and the connector body portion
36
. A distal end
65
of the center contact
62
is centered within a hollow tubular distal end
66
of the hollow metal member
57
. The distal end
66
includes threads on its outer surface to mate with the second connector body portion
42
. Another
0
-ring
94
is positioned at the distal end
66
for sealing the interface with the hollow metal member
85
.
Turning now to the right-hand portion of
FIG. 3
, the second connector
34
is briefly described. The second connector
34
includes a second back-nut assembly
41
which is connected to the end of the second or jumper cable
32
. The second cable
32
includes a central metallic conductor
71
, surrounded by a dielectric layer
73
, a portion of which is removed to prepare the cable end. A plastic insert
74
is positioned within the cable end to support the outer conductor
75
. A cylindrical member
77
is secured on the cable end and clamps to an exposed portion of the outer conductor
75
which extends outwardly beyond the end of the cable sheath
76
. Additional metal rings
81
,
82
and
83
cooperate with the second connector body portion
42
and cylinder
77
to provide the necessary clamping action on the outer conductor
75
and also on the inner conductor
71
. A rear
0
-ring, not shown, may seal the cable sheath
76
to the second back-nut assembly
41
.
The second connector body portion
42
includes a hollow metal member
85
which mounts an annular dielectric spacer
86
and which, in turn, carries a center contact
87
. The center contact
87
includes a tubular distal end
88
which receives and is clamped against the inner conductor
71
by the annular dielectric body
90
. An
0
-ring
91
seals the interface between the second connector body portion
42
and the second back-nut assembly
41
. A collar
92
including internal threads on its distal end is rotatably connected at its proximal end to a recess in the distal end of the hollow metal member
85
. The collar
92
secures the first connector
33
to the second connector
34
. The distal end
93
of the center contact
87
engages the distal end
65
of the center contact
62
in the region of the collar
92
.
As will readily be appreciated, the back-to-back connector arrangement
30
includes a relatively large number of component parts which is relatively expensive and may be difficult to assemble. Such an arrangement
30
will also typically have more loss per unit length than the coaxial cable. Such a back-to-back connector arrangement
30
can be unreliable, and presents multiple interfaces for water leakage into the cable. The connector arrangement
30
also presents a number of abrupt edge surfaces which may make routing through restricted openings difficult, such as at the tower entry and exit ports, or at collars at spaced heights within a monopole tower.
A number of patents disclose other arrangements of connectors for securing a larger diameter coaxial cable to a smaller diameter coaxial cable. For example, U.S. Pat. No. 4,853,656 to Guilou et al. discloses such a device. The device comprises a central core in the shape of a truncated cone, whose circular bases have sections respectively identical to those of the central cores of the coaxal cables to be connected together, as well as a peripheral sheath, whose internal wall is a truncated cone shaped surface, whose circular bases have sections respectively identical to the internal sections of the peripheral sheaths of the coaxial cables. The small bases of the truncated cones of the central core and the peripheral sheath are two parallels of a first sphere centered on the apex of the truncate
Nelson Larry W.
Vaccaro Ronald A.
Allen Dyer Doppelt Milbrath & Gilchrist, P.A.
CommScope Inc. of North Carolina
Nguyen Son V.
Sircus Brian
LandOfFree
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