Cable system subscriber tap with rotating center conductor seizure apparatus and spiral contact and method for using same

A cable system subscriber tap equipped with a rotating center conductor seizure apparatus for mechanically and electrically seizing the center conductor of a coaxial cable. The improved seizure apparatus provides a rotating clamp held within an insulating structure mounted in the tap adjacent each of the orthogonally arranged pairs of cable access ports, the seizure clamp being rotatable between orthogonal positions within its insulating structure to alternately seize the center conductor of a coaxial cable inserted through either one of the pair of access ports without diassembly of the clamp or seizure apparatus. The improved clamp provides a nonshear seizure of the center conductor that is both quickly and easily changed in the field. It further includes a conductive, spiral spring contact held within a countersunk axial bore in the clamp and rotatable therewith while maintaining mechanical and electrical connection to the contact pin of a printed circuit board. Improved methods for installing and for changing cable installations are also disclosed using the same.

BACKGROUND OF THE INVENTION 
This invention relates generally to the field of electrical cable 
connecting apparata. More specifically, it relates to a center conductor 
seizure apparatus of particular use in a community antenna television 
transmission system, often referred to as a CATV system. 
In communication systems in general, coaxial cables are almost exclusively 
used for handling the radio and ultra-high frequency wave energies 
necessarily encountered. Such cables typically include elongate center and 
outer conductors having a common axis and separated by a dielectric medium 
which can be air, or a synthetic such as polyethylene foam. The center 
conductor carries the high frequency signal and is of single or 
multi-strand wire design, being made of copper, copper-plated aluminum, or 
some other plated conductive metal. The outer conductor is of tubular 
design, is aluminum or some other alloyed conductive metal, and serves to 
shield the center conductor from external forces that may interfere with 
signal transference, as well as to provide an electrical ground for the 
system. The dielectric spacer material holds the two conductors in coaxial 
alignment and also helps to insulate the center conductor from corrosive 
elements. 
These coaxial cables have proved highly effective in handling the 
frequencies experienced with CATV systems. However, problems have arisen 
in the design and construction of suitable connecting means for 
intermediate and terminal connecting with such cable lines. 
As the name implies, a CATV system contemplates the use of a central 
antenna situated as to best receive a number of differing television 
signals emanating from various sources. The antenna is usually remote from 
the ultimate consumers, and the signals must therefore be transmitted to 
the television sets of the individual subscribers by means of coaxial 
cables connected through a series of intermediate devices. Such devices 
include signal amplifiers, line splitters, direction couplers, and other 
active and passive devices which are interposed at various points in a 
given cable to direct signals along various secondary transmission paths. 
It is the mechanical and electrical connection at these various points 
that has caused continual problems for the CATV systems. 
Another of these intermediate devices is a subscriber tap, also known as a 
tap connector box, a multi-tap, a cable substation, a directional device 
and the like. Regardless of its name, this tap forms the interface between 
the cable system and the ultimate customer. In particular, there exist 
secondary, or "feeder", cables which branch from a primary, or "trunk," 
line to service smaller residential areas by transmitting signals to these 
subscriber taps. Each tap in turn connects into the signal path and 
carries the signal directly to the television sets of a small number of 
individual subscribers. 
These subscriber taps generally include a box-like, conductive housing 
having a removable base and a pair of coaxial cable access ports 
orthogonally positioned at each of two corners on the housing structure to 
signify the signal input and output sides of the housing. These 
alternative input and output ports attest to the two common methods of 
CATV installation. First is an aerial installation in which the housing is 
typically suspended from a metal strand with cable access being through 
opposite sides of the housing to minimize bending of the coaxial cable. 
Second is an above- or below-ground installation in which a pedestal 
mounting is used with cable access generally on the same side of the 
housing for convenience. An "L" installation is also possible with the 
pairs of orthogonal ports; but regardless of the particular installation 
used, the unused ports are generally plugged or capped to maintain the 
integrity of the inner housing chamber. 
Electrical circuitry is then provided in the housing connecting to the 
seized center conductors and transmitting the signal to a number of 
individual subscribers through subscriber connectors and cables attached 
to the base cover of the subscriber tap. 
Two problems of mechanical and electrical connection are encountered with 
these subscriber taps. 
First, some form of cable connectors means must be used to mechanically and 
electrically connect the outer cable conductor with the housing at its 
point of entry through an access port. Such connector means are known in 
the art. For example, Forney, Jr., U.S. Pat. No. 3,778,535, issued Dec. 
11, 1973, discloses a coaxial connector designed to avoid collapsing the 
outer cable conductor while not altering the characteristic impedance of 
the coaxial cable, determined as a function of its inner dimensions, 
thereby avoiding any reflective loss in the frequency signal being 
transmitted. Hayward et al., U.S. Pat. No. 3,847,463, issued Nov. 12, 
1974, discloses a related connector apparatus designed to withstand the 
various rotational and vibrational forces experienced by the cable through 
wind and otherwise without the eventual fatigue and rupture experienced 
with other connectors. 
The second area of contact involves the mechanical and electrical seizure 
of the center cable conductor within the housing chamber. This seizure is 
typically accomplished by the use of a screw means clamping the center 
conductor is a connector device after its insertion through one of the 
access ports. Problems are also common with these connectors. 
For example, Lankford et al., U.S. Pat. No. 3,675,181, issued July 4, 1972, 
discloses a connector claiming an improved seal means and supposed to 
avoid the normal conductor loosening encountered with prior art devices as 
a consequence of a metallurgical phenomenon known as "cold flow." Other 
related connecting devices have concentrated on the problems of shearing 
and other damage to the center conductor caused by cross screw connectors, 
such as Cauldwell, U.S. Pat. No. 3,989,333, issued Nov. 2, 1976, and 
Nordberg et al., U.S. Pat. No. 4,025,150, issued May 24, 1977. 
Still two further connector apparatus are shown in Vachhani, U.S. Pat. No. 
3,530,425, issued Sept. 22, 1977, and Devendorf, U.S. Pat. No. 3,951,490, 
issued Apr. 20, 1976. Vachhani securely holds the center conductors of 
connecting cables between the serrated contacts of its pressure terminals. 
Devendorf, on the other hand, discloses a substation seizure apparatus 
secured to the housing by a plurality of standing projections claimed to 
distribute the forces exerted by the center conductor throughout the 
assembly frame. 
Still further problems exist unresolved by the subscriber taps known to 
date. 
For example, the majority of seizure mechanisms now marketed continue to 
permit the shear of center conductors during installation. To provide for 
alternatively using the holes in the seizure device for both the seizure 
screw and the center conductor, these manufacturers drill their devices 
completely through from both the pedestal and aerial directions, tapping 
each hole to alternately accommodate either the screw or the center 
conductor. Therefore, when the seizure screw is tightened down against the 
center conductor, directly behind the center conductor is a hole causing 
the clamp to act like a punch and die set with respect to the conductor 
wire. If tightened too far, the screw will shear the center conductor by 
pushing it into the hole. Even if not severed, the conductor is often 
sufficiently damaged by pressing against either the back opening or the 
cutting threads of the tapped hole to fail under temperature cycles as the 
various expansion and contraction forces are exerted by temperature 
changes in the cable system. 
Another problem concerns material selection. For instance, tin-plated brass 
connectors are known for long-term durability and are used in all 
terminators, drop connectors and expensive addressable taps used in the 
CATV industry. However, some manufacturers use aluminum spigots which 
under atmospheric conditions form a highly corrosive galvanic cell 
interface with a tin-plated brass contact thereby becoming welded, stuck, 
or corroded together. 
A still further problem involves the basic understanding of an ideal 
subscriber tap assembly. It must provide a lasting mechanical and 
electrical connection with the center conductor. It must provide an 
impedance match with the coaxial line to minimize signal loss or ghosting 
due to signal reflections. It must be impervious to weather conditions and 
provide a connection as strong as the cable itself. Finally, it must be 
capable of installation and change quickly and easily in the field under 
all anticipated conditions. 
This last concern for the speed and ease of tap installation and change is 
of great importance. The majority of taps on the market provide for 
tightening the seizure screw through the unused orthogonal access port in 
the housing corner. To change from aerial to pedestal mounting, or vice 
versa, requires the installer to completely remove the seizure screw, 
insert the center conductor through the new access port, and then reinsert 
the screw through the alternate port in order to secure the proper 
connection. This operation is burdensome and time consuming to the 
installer. It also promotes conductor shear because the conductor is 
pressed against the serrated threads on the inside wall of either seizure 
bore while further being pressed into the back opening. 
The only subscriber taps on the market not using this disassembly procedure 
provide for vertical seizure of the center conductor by placing two 
separate access ports for the seizure screws in the housing wall opposite 
the base or the base itself. Center conductor seizure through alternate 
ports then does not require complete removal and reinsertion of the 
seizure screw. It does, however, require manipulation of another pair of 
access ports and caps. In addition, one such manufacturer bores completely 
through its clamp in the vertical direction thereby providing the same 
shearing problem during use. 
This requirement of speed and ease in subscriber tap installation or change 
also concerns the accessibility of the inner housing chamber for repair of 
replacement of the seizure mechanism or the printed circuitry used to 
connect to the cable center conductor. In this regard, complex disassembly 
procedures must be avoided so that repair or replacement of internal parts 
can be accomplished quickly and easily in the field. 
SUMMARY OF THE INVENTION 
Various aspects of this invention comprise an improved subscriber tap and 
seizure apparatus eliminating the problem of conductor shear while 
providing means for alternately seizing the center conductors of coaxial 
cables of differing orientation to the seizure apparatus. This means is by 
simple rotation of a seizure clamp and screw within an insulated structure 
and without the need for any disassembly thereof. A third aspect comprises 
an improved method for using the same having corresponding advantages over 
existing prior art methods. 
In one embodiment, an improved rod-like seizure clamp has a first radial 
bore therethrough and a second partial radial bore threaded to receive a 
seizure screw and terminating upon intersection with this first bore. The 
clamp is rotatably held within an insulating structure having orthogonal 
openings to the clamp and alternately alignable with the first and second 
bores therein. A channel cut in the insulating structure joins these 
openings to permit orthogonal rotation of the clamp without disassembly of 
the seizure screw, thus providing for quick and easy installation or 
change in the field. An axial bore in the clamp and mating opening in the 
structure accompany means, including a spiral spring contact, for 
electrically connecting the clamp and seized center conductor with 
appropriate electrical circuitry means in the housing for distribution of 
the signal to individual subscribers. 
Related objects and advantages of the present invention will be apparent 
from the following description.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
For the purposes of promoting an understanding of the principles of the 
invention, reference will now be made to the embodiments illustrated in 
the drawings and specific language will be used to describe the same. It 
will nevertheless be understood that no limitation of the scope of the 
invention is thereby intended, such alterations and further modifications 
in the illustrated devices, and such further applications of the 
principles of the invention as illustrated therein being contemplated as 
would normally occur to one skilled in the art to which the invention 
relates. 
Describing first the preferred apparatus of applicant's invention, it 
generally comprises a cable system subscriber tap incorporating 
applicant's improved rotating center conductor seizure apparatus. In FIG. 
1 there is depicted applicant's preferred tap 10 which includes a 
conductive housing 11 having two pairs of coaxial cable access ports 12 
and 13 orthogonally positioned adjacent two corners 14 and 15 of the 
housing body. These ports 12 and 13 correspond respectively to the signal 
input and signal output path orientations through the subscriber tap. The 
ports are internally threaded to aid in establishing an effective 
mechanical and electrical connection with the outer conductor of a coaxial 
cable which has been prepared in accordance with known procedures. By 
"prepared cable," it is meant that the outer cable conductor and 
dielectric medium have been removed from an area adjacent the cable end to 
expose a portion of the center conductor for insertion and seizure inside 
the inner housing chamber 16. To maintain proper shielding and provide a 
strong connection with the subscriber tap, the prepared cable is also 
connected to some known connecting means which provides a male portion for 
connection with the internal threading 17 of the access port. Two examples 
of such known cable connecting means are disclosed in the Forney, Jr. and 
Hayward et al. references described above. 
In field use, coaxial cables carrying the transmitted signal are 
alternately connected to the orthogonally arranged pairs of access ports 
in accordance with the particular installation required. For example, in 
aerial installation it is desirable to employ the two opposing ports 12 
and 13 in order to minimize the required angular deflection of the center 
conductor inside the tap. With pedestal mounting either above or below 
ground level, however, interests of space and convenience often require 
use of the side-by-side ports 12 and 13 on the same side of the housing 
body. With this orthogonal orientation, it is further possible that a "L" 
cable connection could be used if the circumstances so require. In any 
case, the initial tap installation is accomplished by means of a bracket 
structure 18 including a raised portion 21, a plate 22, and a fastening 
screw 23. A groove 24 is formed in this raised portion and the bracket 
structure is readily attachable to any cable or strand (not shown) for 
either aerial, pedestal or "L" installation. 
Referring now to the sectioned view in FIG. 2, preferred tap 10 also 
includes a conductive base cover 26 detachably secured to the housing by 
fastening means including an O-ring weatherproof seal 27 and three screws 
28 (better shown in FIG. 4). Subscriber connectors 31 on the back of cover 
26 then transmit the signal received from the center cable conductor to 
the television sets of individual subscribers of the particular CATV 
system. 
This subscriber transmission first requires both an effective mechanical 
and electrical seizure of the center conductor after its insertion through 
an input port 12 and a proper mechanical and electrical connection of the 
outer conductor with housing 11. This center conductor seizing means in 
preferred tap 10 is accomplished by use of applicant's improved seizure 
apparatus, or mechanism, generally designated by numeral 32 in FIG. 2. 
In applicant's improved center conductor seizing means, seizure apparatus 
32 first includes a rod-like, conductive seizure clamp 33 having a first 
radial bore 34 extending at least part way therethrough and a second 
radial bore 35 tapped and intersecting the first bore. A seizure screw 36 
is threaded to mate with this second bore and to secure the center 
conductor of a coaxial cable inserted in first bore 34. Clamp 33 is 
rotatably held within a supportive, insulating structure 37 which has a 
plurality of outer openings to the clamp and its first and second bores. 
Means are then provided for alternately seizing, with this clamp 33, 
center conductors of differing orientation to insulating structure 37 by 
simple rotation of the clamp therein and without any disassembly thereof. 
In the preferred embodiment, applicant's improved seizing means is 
therefore usable interchangeably with either one of the orthogonal cable 
access ports through simple rotation of the clamp connector and without 
the need for disassembling and reassembling the screw attachment. This is 
accomplished in preferred tap 10 by extending first bore 24 through the 
clamp with second bore 35 located orthogonally thereto and terminating 
upon intersection with the first bore, as better seen in FIG. 7. Preferred 
insulating structure 37 is provided with a pair of openings 38 
orthogonally arranged to alternately align with the first and second bores 
upon rotation of the seizure clamp therein. Retaining means including a 
pair of brackets 41 projecting from the inner walls of housing 11 secure 
the two seizure mechanisms 32 in the housing corners 14 and 15, 
respectively, with their openings 38 properly aligned with the 
corresponding orthogonal access ports (as better shown in FIGS. 3 and 4). 
Insulating structure 37 in the preferred embodiment further includes a 
radial channel 42 joining its pair of orthogonal openings 38 to permit 
rotation of the seizure clamp between these openings without interference 
with or removal of the preferred seizure screw which has an enlarged head 
43. Openings 38 and the opening ends of first bore 34 have a tapered 
surface 44 to simplify insertion of the center conductor of a prepared 
coaxial cable. Structure 37 includes to additional openings 45 opposite 
these tapered openings 38 to permit the inserted center conductor to pass 
completely through the structure during either aerial or pedestal 
installation of the subscriber tap. 
Applicant's preferred seizure apparatus therefore provides a mechanical and 
electrical fitting that can be installed or changed quickly and easily in 
the field. There is no worry of disassembly because the change from aerial 
to pedestal installation, or vice versa, is accomplished by simply 
rotating the seizure clamp within its insulating structure and without 
disassembly or removal of the seizure screw. There is also no need to 
handle a third vertical access port and screw fastener, as with some prior 
art taps previously mentioned. Instead, applicant's seizure screw secures 
the center conductor of a cable inserted in either end of the first radial 
bore 34 depending upon the rotational alignment of the clamp and screw 
with respect to the orthogonal access ports, as better shown in FIG. 4. 
Applicant's preferred seizure apparatus also eliminates any concern of 
shearing the center conductor during installation or through fatigue and 
rupture during use. Applicant's first bore has no serrated threads to cut 
into the center conductor during seizure. By terminating the second bore 
upon intersection, applicant provides a blind, or positive, stop without a 
back opening to shear the center conductor as is true with the majority of 
taps now marketed. In the preferred embodiment, applicant's seizure screw 
36 is further of such a length as to be too short to contact the inner 
wall of the first bore opposite its intersection therewith. It is thus not 
possible for the screw to be tightened so far as to pinch off the center 
conductor, again as experienced with prior art devices. 
The final aspect of applicant's subscriber tap 10 is the provision of means 
for electrically connecting the center conductor and seizure clamp with 
electrical circuitry means in the housing to transmit the television 
signal to the local subscribers. In the preferred embodiment, this means 
includes an axial bore 46 in one end of the clamp and a conductive spiral 
spring contact 47 received within this bore for connection with the 
electrical circuitry means in the housing. This end portion of the clamp 
33 has a reduced outer diameter 48 mating with a correspondingly sized 
cavity, or recess, 51 in the insulating structure 37. The preferred axial 
bore 46 further extends through the clamp intersecting with the first and 
second radial bores, and has an enlarged countersunk portion 52 for 
positioning of the spiral contact therein. 
An opening 53 in the insulating structure exposes this contact 47 for 
insertion of a conductive contact pin 54 connected to a printed circuit 
board 55 which is attached to the base cover 26 by means of several 
fastening screws 56. This spiral spring contact 47 is highly complementary 
to applicant's rotating seizure clamp 33 by permitting continuous 
electrical contact between a seized center conductor and the contact pin 
54 during rotation of the seizure clamp. This is first accomplished, as 
better seen in FIG. 6, by constructing the contact 47 such that its outer 
diameter 61, when relaxed, is greater than the inside diameter of 
counterbore 52 in the seizure clamp. The spring contact is thus held in 
compression against the inner wall of this counterbore when positioned 
therein to maintain good electrical connection with the clamp 33. Second, 
the inner diameter 62 of the spring contact is constructed smaller than 
the outer diameter of contact pin 54 as to also maintain an electrical 
connection with the contact pin even during rotation of the seizure clamp. 
In the preferred embodiment, contact 47 is further provided with an inner 
chamfer 64 surrounding the central opening 63 to help guide the insertion 
of pin 54 therein. 
The preferred tap 10 then has either two or four subscriber connectors 31 
electrically connected to this printed circuit board for transmitting the 
signal to the local subscribers. The electrical circuitry of this printed 
circuit board 55 and its connection with the subscriber connectors 31 are 
not shown in detail since the specified circuitry is of no inventive 
aspect to applicant's invention and can be arranged as any suitable 
circuit and connection presently known or developed in the future. 
Material selection is not an essential feature of applicant's apparatus, 
but is important if a lasting mechanical and electrical connection is to 
be provided with only negligible leakage or interference with the 
transmitted signal. For this reason, it is preferred to use a tin-plated 
brass seizure clamp connector and a matching printed circuit contact pin. 
Applicant's preferred seizure screw is stainless steel and his contact 
spring is of tin-plated beryllium copper composition. The housing and 
cover are of cast 360 alloy aluminum with chromate conversion coating. 
The preferred insulating structure of applicant's clamp holder is mating 
halves of a block-like polystyrene plastic material, although those 
skilled in the art will realize the structure could be simply molded into 
a single insulating member. As the dimensions of the insulating structure 
and the proximity of the center conductor to the housing walls are both a 
function directly related to the capacitance of the system, it is 
important to size the dielectric, insulating structure as to provide a 
impedance match to the cable so as to offer no abnormal resistance to the 
signal passage. This is known to those skilled in the art and can be 
handled accordingly. 
To provide a sealed inner chamber impervious to weather elements, 
applicant's preferred tap also includes two caps, or plugs, 57 equipped 
with O-ring seals 58 to seal the access ports unused in a particular 
installation. 
Describing now the method of applicant's invention, the improved method of 
establishing or changing a particular CATV subscriber installation is 
described hereinbelow in connection with applicant's preferred tap 10. 
In an initial installation, after mounting the tap using its bracket 
structure 18, the installer must select either the opposing or 
side-by-side access ports 12 or 13 for his aerial or pedestal 
installation. Once selected, and the protective caps 57 removed, the 
coaxial cable (not shown) is properly prepared as described above 
including attachment of a cable connector means for mating with the 
internal threading 27 of the access ports. Seizure clamps 33 are then 
positioned with first bore 34 aligned with the selected port and second 
bore 35 and seizure screw 36 exposed through the unused port. The center 
conductor is inserted through the first bore and corresponding openings 38 
and 53 in the insulating structure, and the screw is tightened against the 
center conductor through the unused port. The caps 57 are then placed on 
the unused ports, the base cover is refastened to the housing (if needed), 
and the prepared cables (also not shown) are connected with the subscriber 
connectors 31 on the back of base cover 26 for transmission to the local 
subscribers. 
A lasting mechanical and electrical connection is thereby formed impervious 
to weather elements with proper impedance match and negligible leakage and 
with a strong, nonshear seizure of the center conductor. 
Change of an single installation is accomplished by first removing the cap 
57, releasing the seized center conductor, and disconnecting the outer 
conductor and connecting means from the access port being used. Seizure 
clamp 33 is then rotated without disassembly through a 90.degree. angle 
within its insulating structure to align the second bore and screw with 
the alternate orthogonal port while also aligning the opposite end of 
first radial bore 34 with the port now desired for installation. The bared 
center conductor and connecting means are then connected with this new 
access port with the conductor extending through first bore 34 and 
corresponding openings 38 and 53. The seizure screw is tightened through 
the now unused port to seize the center conductor within the clamp, and 
the plug is attached to this unused port to once again seal the inner 
chamber from outside weather conditions. 
In this way, applicant's improved method of changing a subscriber tap 
installation is accomplished with simple rotation of the seizure clamp 
within its insulating structure and without any disassembly and later 
reassembly thereof. The installer need not grapple with other external 
access ports and screws, and the changed fitting can be thus made quickly 
and easily in the field. Furthermore, the installer need not remove the 
cover and disconnect the printed circuit board from the seizure apparatus 
during the changeover because the spiral spring contact 47 permits 
rotation of the clamp while maintaining a strong mechanical and electrical 
connection with the contact pin 54. 
A further feature of applicant's preferred embodiment concerns the 
preparation of a coaxial cable for connection to subscriber tap 10. In 
particular, when preparing the coaxial center conductor or connector 
stinger for entry into the tap, the first question to answer is how long 
must the center conductor be to permit proper seizure by the clamp 33. To 
resolve this problem, the preferred housing 11 of applicant's tap includes 
a pair of cast-in center conductor trim guides 65 positioned such that the 
outermost extensions 66 define the correct length for the bared center 
conductor to permit proper internal seizure within the tap. There is no 
guesswork or time wasted by the installer in trial and error attempts. 
Instead, he can simply hold the coaxial cable end up to the cut-off guides 
65 and trim the cable to its proper length. 
A still further feature of applicant's preferred method and tap is the ease 
with which base cover 26 is removed to provide access to inner housing 
chamber 16. The operation is completed by simply removing fastening screws 
28 and pulling on the base cover with sufficient force to dislodge contact 
pins 54 from within their spiral spring contacts 47. The installer has 
then gained full access to the inner chamber to permit unhindered repair 
or replacement of the seizure apparata 32 or printed circuit board 55. 
While the invention has been illustrated and described in detail in the 
drawings and foregoing description, the same is to be considered as 
illustrative and not restrictive in character, it being understood that 
only the preferred embodiments have been shown and described and that all 
changes and modifications that come within the spirit of the invention are 
desired to be protected.