Note: Descriptions are shown in the official language in which they were submitted.
75~
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Field of Invention
.
This invention relates to a coaxial cable coupling
assembly and a method of connecting the coupling to a
coaxial cable. More particularly, this invention relates
a mechanical coupling assembly which when assemblies
provides environmental and EM seal for the assemblies
coupling and cable.
Back round of the Invention
q _ .
Mechanical couplings have been used for a variety of
applications. In particular, such couplings have been
connected to (i.e. joined to, united to or linked with)
various substrates including cables which have then been
terminated or connected to other cables and the like. Such
couplings have been used, for example, in connection with
CAT cable. There are various types of CAT cables. It is
particularly advantageous to use two particular types of
cables with this invention. The first type of cable (Type-I)
includes a center conductor surrounded by a dielectric, a
rigid outer conductive wall defining a shielding means
surrounding the dielectric and a protective jacket surrounding
the outer wall. In some of the newer more flexible cables
of this type, the protective jacket is polyethylene and is
bonded to a thin outer wall such that the jacket cannot be
removed or stripped from the outer wall without damaging the
thin wall.
The second more flexible type of cable (Type-II) in-
eludes a center conductor surrounded by a layer of dielectric
material, which is surrounded by an EM foil shield, which
Jo 7531~
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is surrounded by an electrically conducting braid (also for
EM shielding purposes) and which is surrounded by a protective
jacket. Quite often there are multiple layers of foil and
braid.
A presently used typical coupling for Type-I
cable is a threaded coupling having two outer menders
which are threaded to one another and sealed by means of
an O-ring. The coupling also includes two inside members,
each having a tapered inside surface. The inside members
grip the wall deforming it to a smaller diameter such
that a split ring between the inside members grips the
wall at the deformed portion. O-rings are used to seal
the inside and outside members.
A presently used typical coupling for Type-II
cable includes a connector body having one end adapted
for insertion in the cable between the EM foil shield and
the EM braid. A narrow ring is positioned around the
protective jacket adjacent the area of the cable to be
connected to the coupling. A separate crimping tool is then
positioned around the ring and crimped by applying pressure
to the tool. The ring is distorted by the pressure and
clamps down on the cable and connector body.
Certain disadvantages have been noted in using the
typical coupling for Type-I cable. The typical Type-I
coupling for such cable is craftsman-sensitive. Once the
coupling has been installed on the cable, the coupling must
be tightened to a predetermined torque level for good
electrical properties between the coupled cable and a joint
such as a connection with other cable or termination to a
tap box or the like. If the connection between coupling and
~Z~7538
cable is over tightened and there are corrosive substances
present stress cracking may result. Under tightening will
cause poor EM shielding and cable pull out under wind,
ice or thermal loading conditions.
Additionally typical Type-I and Type-II couplings are
craftsman-sensitive because they require a portion of the
protective jacket to be stripped back before connection
with the cable. If the stripping operation is done incorrectly,
portions of the electrical conductor or aluminum foil shield
or braid shield may be lost and the cable's electrical
properties damaged.
The stripping-back operation of both the Type-I and II
cables destroys, inherently, some of each of the cable's
environmental protection, i.e. the protective jacket at a
particular crucial point, namely the connection or termination
point of the cable. The stripping-back operation also slows
down the craftsman. He must not only do the job, but he
must do it with some degree of delicacy, so as not to
destroy the cable's electrical properties or an unnecessary
amount of its environmental protection.
Additionally, Type-II cables are often crimped in-
correctly. The foil and braid are bunched together or de-
stroked, decreasing the EM shielding properties of the
cable.
Such cables are generally exposed to the harshest of
outdoor environments at the connection or termination
point. Such conditions include temperature changes of lûûDF
or more within a 24 hour period. Additionally, the connection
or termination must be able to withstand rain, ice, snow,
12~753~
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extreme heat and cold, ultraviolet radiation, oxidation,
pollution and salt spray without damage.
Additionally, the connection between the coupling,
cable and termination or connection must be secure enough
to prevent the wind from loosening same. The wind will
cause vibration along the cable line and typically loosen
the connection between coupling and cable and between
coupling and the joint, such as termination or connect
lion point.
The terminated or connected cable must be sealed
so that it does not leak electromagnetic radiation, also
known as electromagnetic interference (EM) or radio ire-
quench interference (RFI). Such EM causes disruption
of aircraft instruments, radar and the like and has become
a deep concern for certain federal and state government
agencies.
Typical Type-I and Type-II couplings fail to provide
either adequate environmental seal or EM seal. The result
is that the coupling and/or termination and connection must
be replaced quite frequently. Additionally, poor EM
shielding interferes with the electrical performance of
aircraft instruments, radar and the like.
The tolerance limits for typical GATE cable are quite
broad. For example, a typical 1/2" Type-I cable diameter
varies from .493 to .507. A typical Type-II cable diameter
varies from .234 to .250 for a RG59U cable. Typical
couplings cannot presently handle such wide tolerance
ranges.
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A specific example of a typical Type-II coupling is disk
closed in O'Keefe, US. Patent No. 3,551,882 which is a crimp-
type coupling for multiple outer conductor coaxial. A malleable
ferrule is crimped down onto the inner braid to terminate it to
the connector and an outer ferrule is then crimped down onto
the outer braid directly over the inner ferrule to join it to the
coupling. An example of a Type-I coupling is disclosed in
Blanchard, US. Patent No. 4,346,958 which uses O-rings to provide
an environmental seal. Due to the broad tolerances of cable die-
meter, as mentioned above, it is difficult to achieve satisfactory seals with O-rings. Other examples of coaxial cable connectors
are disclosed in Hyslop, US. Patent No. 3,336,563 and in Hayward,
US. Patent No. 4,400,050.
Additionally a heat-recoverable coaxial coupling asset-
by is known for Type-I cable which includes a connector body
having a mating area and a driver member made from heat-recover-
able material surrounding the mating area. The cable jacket is
positioned between the mating area and the driver member. The
driver member is then heated to effect recovery. As the driver
recovers it deforms the cable jacket at the mating area to prevent
pullout of the cable and forms environmental and EM seal. While
quite effective at eliminating many of the above-described
difficulties, such coupling assembly does require the use of
heat. There are circumstances when heat, especially in the form
of a flame, is undesirable.
SUMMERY OF THE INVENTION
The purpose of this invention is to provide a mechanical
2 I 3
coupling assembly for coaxial cable having a center conductor
surrounded by a dielectric layer which dielectric layer is sun-
rounded by a layer or layers of conductive shielding and which
shielding is surrounded by a protective outer jacket which
environmentally seals the connection between coupling and cable.
A further purpose of this invention is to provide a method for
connecting the coupling to the cable for terminating and connect
tying such a cable such that the connection or termination is
environmentally and electrically sealed.
According to one aspect, the present invention provides
a connector in combination with a coaxial cable having a center
conductor and a substantially cylindrical outer layer surrounding
the center conductor, comprising: a deformable compressive member;
a connector body integrally formed of one piece of material and
having a mating area disposed in contact with an outer layer of
the coaxial cable, the connector body including means for focus-
in deformation of the compressive member, the mating area extend-
in within the outer layer, the focusing means outwardly surround-
in the outer layer; and a driver member for compressing the
deformable compressive member against the focusing means so as to
compress at least part of the outer layer against the mating area.
According to another aspect, the present invention pro-
vises a kit of parts for connecting a coaxial cable to a mounting
unit, comprising: a deformable compressive member; a connector
body integrally formed of one piece of material and having a mat-
in area for engaging an outer layer of the coaxial cable, the
7S3~3
connector body including means for focusing deformation of the
compressive member, the focusing means outwardly surrounding the
mating area; and a driver member for compressing the deformable
compressive member against the focusing means.
According to a further aspect, the present invention
provides a method of connecting a coaxial cable having a center
conductor surrounded by a layer of dielectric material surrounded
by conductive shield surrounded by a protective outer jacket, the
coaxial cable being connected to a connector, comprising the steps
of: inserting a connector body onto an end of the cable such that
a mating area of the connector body separates first and second
conductive shielding layers of the coaxial cable and such that
means for focusing deformation of a compressive member outwardly
surrounds the protective outer jacket; disposing the compressive
member within the focusing means; disposing a driver member
adjacent the compressive member; and urging the driver member
towards the connector body and the compressive member whereby
deformation of the compressive member is focused by the connector
body such that it deforms the cable shield against the mating
area of the connector body thereby locking the cable shield in
place and whereby the compressive member deforms to fill voids
between the connector body and the driver member thereby affecting
an electrical and environmental sealed connection.
A preferred embodiment of the device is particularly
well-suited for Type-I cables and hollow elongate substrates with
inflexible outer walls, generally. The preferred embodiment
121753B
-pa-
includes sizing means on the front end of the connector body for
providing intimate contact between the rigid outer wall and the
connector body over a wide tolerance range of such cables.
Another preferred feature of the coupling in accordance
with the instant invention which is especially well-suited for
Type-I cables is an anti-rotational means. The anti-rotational
means is positioned at the mating area. After interconnection
of the driver member or means and connector body, the rigid wall
of the cables is deformed over the anti-rotational means to pro-
vent the cable from turning relative to the coupling.
The preferred method of connecting a Type-I cable to the
coupling includes removing or coring the dielectric between the
outer wall and the center conductor over the length of the mating
area. This ensures good electrical connection between the outer
wall and the coupling.
A preferred embodiment of the coupling for either Type-I
or Type-II cables includes the coupling having a stop means for
preventing over inter engagement or over-or under-tightening of
the driver means to the connector body. The stop means for Type-I
comprises the driver means having a rear face and the connector
body having a front face. When the driver means is fully inter-
connected with the connector
~2~753~3
I
body, the faces of each are flush, the coupling is fully
sealed and further tightening is discouraged.
The coupling for Type-II cable includes a stop means
wherein the driver means has a rear face which mates fleshly
with the front face of the tap box or other termination
apparatus when the driver means is fully engaged.
It is an object of this invention to provide a mechanical
coupling assembly which environmentally and electrically
seals the connected cable without the need of stripping the
cable's protective jacket.
Other objects and advantages of the instant invention
will be more fully understood in connection with the de-
tailed description of the drawing as follows:
BRIEF DESCRIPTION OF THE DRAWING
Figure 1 is a partial cross-sectional view of the
coupling in accordance with this invention prior to full
interconnection of driver means and connector body.
Figure 2 is a partial cross-sectional view of the
coupling of Figure 1 after full interconnection of driver
means and connector body.
Figure 3 is a full cross-sectional view of a
coupling in accordance with this invention adapted for
use with flexible coaxial cable and especially well-
suited for Type-II cable.
~753B
- 1 0 -
Figure 4 is a full cross-sectional view of the
coupling of Figure 3 after full compression of the
compression means by the driver means and connector body.
DESCRIPTION OF THE PREFERRED EMBODIMENT
The mechanical coupling assembly in accordance with
this invention is especially well-suited for connection
with two different types of electrical cable. A preferred
embodiment, described in detail below, is especially
well-suited for connection with a hollow rigid walled
cable. An example-of such a cable referred to below is
a Type-I cable to which particular reference is made with
respect to Figures 1 and 2 and is meant strictly for
illustrative purposes only. Such a preferred embodiment may
in fact be used for a variety of cables, including Type-II
cable but it is especially well-suited for Type-I cable.
A second preferred embodiment is described in
detail with reference to Figures 3 and 4. This second
embodiment is especially well-suited for flexible cable
particularly Type-II cable. It should be understood that
such a preferred coupling while especially well-suited for
Type-II cables, may be used effectively for Type-I cables
and other cables as well. The Type-II cable used in the
detailed description below is meant for illustrative
purposes only.
While both preferred embodiments of the invention
include certain special features described in detail below,
the basic elements of each are the same, namely (1) a
connector body having a mating area for engaging an outer
layer of a coaxial cable, (2) a driver means, (3) means for
12~7S~8
--1 1--
urging the driver means and connector body toward each
other, (4) a deformable compressive member positioned
between the driver means and connector body which is deformed
when driver means and connector body are urged toward each
other, and (5) means for focusing the deformation of the
compressive member being deformed by the driver means and
connector body. The term "outer layer" of a cable as used
herein is intended to include any layer outside the dielectric
area surrounding the center conductor. The mating area may
be adapted to the positioned between outer layers of
the cable. The mating area will normally engage an outer
layer which is an EM shielding layer of the cable.
Additionally, it should be understood that the Type-I
and II cables are merely examples or subsets of a larger set
where the generic cables include a center conductor surrounded
by dielectric, a layer or layers of electrically conducting
shielding surrounding the dielectric and a protective outer
jacket surrounding and environmentally protecting the other
elements of the cable.
With particular reference to the drawing, wherein
like reference characters designate like or corresponding
parts throughout the several views and referring particularly
to Figures 1 and 2, there is seen the coupling of the
instant invention designated generally by the numeral 10.
The coupling includes a connector body 12.
The connector body 12 is generally cylindrical and
hollow. The body 12 has a mating area generally designated
by the numeral 14 for engaging the outer wall 26 of a Type-I
coaxial cable 16. The body 12 includes a front outer
threaded surface 18 which defines one element of the mess
121753~3
for urging the connector body 12 and the driver means 32
toward each other.
The connector body 12 also includes a means 20 for pro-
venting rotation of the cable with respect to the coupling,
which comprises a hexagonal ring 22 having six edges 24
which penetrate the surface, only, of the outer wall or
shielding layer 26 of cable 16. The coupling 10 is thus
resistant to turning with respect to the cable as a result
of wind and other like forces.
he connector body 12 further includes a cable
sizing means 28. The shielding layer 26 is typically made
from aluminum which, while being rigid is malleable
The sizing means 28 comprises an enlarged head 30 having
an outside diameter approximately the same as the largest
anticipated inside diameter of the shielding layer 26 of
cable 16. The connector body 12 with its sizing means
28 accommodates a wide range of cables while assuring
good electrical and physical contact between coupling 10
and cable 16.
Preferably, the connector body 12 is made from the
same material as the outer wall or shielding layer 26 of
cable 16. Thus, in this example, connector body 12 is made
from aluminum. This discourages corrosion and adds to the
environmental and electrical sealing properties of coupling
10. If the shielding layer 26 were made from stainless
sleet, copper or other materials, the connector body 12
could be made to match.
The coupling 10 includes a driver means 32 which air-
cumferentially surrounds and interconnects body 12 through
7538
threads 18 and 34. The driver 32 is hollow and generally
cylindrical and is made from the same material as the body
12 for the same reasons stated above. Threads 18 and 34
comprise the means for urging body 12 and driver 32 toward
each other. Upon initial interconnection as shown in Figure
1, a void or space 36 is created between the driver 32 and
body 12. As seen in Figure 2, the volume of space 36 decreases
as full inter engagement of the driver 32 and body 12 is
reached. The space 36 defines the means for focusing the
deformation of the compressive member 42.
As set forth above, the coupling includes visual means
for determining full engagement of driver 32 and body 12.
The visual means comprises the body 12 having front face 38
and the driver 32 having a rear face 40. The body 12 and
driver 32 are shaped and sized so that upon full interconnect
lion of the body 12 and driver 32, the faces 38 and 40 are
flush against one another. The field craftsman installing
coupling 10 on cable 16 merely tightens the driver 32 to
body 12 until the faces 38 and 40 are flush. If the crafts-
man over tightens the coupling 10, the force will be absorbed
by the body 12 and driver 32 without damaging the cable
16.
The coupling further includes a compressive member
42 which surrounds the body 12 at the mating area 14.
The compressive member contacts the cable 16 at least at
the anti-rotational means after full inter-connection of the
driver 32 and body 12. This secures the cable 16 at the
edges 24 and prevents rotational movement of the cable 16
with respect to the body 12 as earlier described.
~2~L753~
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driver 32 and body 12. This secures the cable 16 at the
edges 24 an prevents rotational movement of the cable 16
with respect to the body 12 as earlier described.
The compressive member 42 is deformable but has
sufficient compressive strength to deform the cable 16
and in particular, the outer wall 26 with its protective
jacket 44 thereon as shown in Figure 2. As measured by
the American Society for Testing and Materials method
ASTM D 695, the compressive member 42 has a compressive
strength of at least owe psi, and preferably between 2000
and 40,000 psi and most preferably 7100 psi. The material
currently used which satisfies these conditions is polyp
tetrafluoroethylene. Additionally, polyvinyl chloride,
polyethylene, fluorinated ethylene-propylene copolymer,
and aluminum 1100-0 are currently known to also possess
the above characteristics.
_ .
The compressive member 42 provides a number of ad van-
taxes, examples of which are the following. During assembly
of the connector the compressive member 42 can grip the
cable jacket and pull the cable into the connector during
the final stage of assembly to assure good electrical
connection. When used in the form of a ring, compressive
member 42 can be split to facilitate fitting the ring over
varying sizes of cables. The split then closes and a good
seal is obtained upon assembly of the connector. Use of an
appropriate material as the compressive member will allow a
smelt portion of the material to extrude, under the pressure
of the final stage of assembly, out between the cable jacket
and the driver 32 to enhance the environmental seal and to
provide visual indicator of proper assembly.
753~
As previously mentioned, when the driver 32 and
body 12 are initially interconnected the space 36 is
defined. The compressive member 42 surrounds the mating
area 14 and is located in the space 36. The volume V1
of compressive member 42, is such that upon full inter-
connection of driver 32 and body 12, that the volume
V2, equals V1. In this example, the means for focusing
the deformation of compressive member 42 is the angled
surface I which focuses the forces from the deformation of
compressive member 42 toward mating area 14 and deforms
cable outer wall 26 and protective jacket 44 to Form the
desired environmental and electrical seals.
In use, the cable 16 is prepared for connection
with coupling 10 by coring the cable 16 of dielectric
material 46. The outer wall 26 is positioned to surround
mating area 14 with the wall 26 intimately engaging
anti-rotational means 20. The cable 16 includes a
center conductor 48 which extends through the hollow
body 12.
After positioning the cable as described above, the
compressive member 42 is positioned over cable 16 to surround
the jacket 44 at the mating area 14 and especially to
surround the jacket 44 at anti-rotational means 20. The
driver 32 is slipped over cable 16 and then interconnected
with the connector body 12 by engaging threads 34 with the
threads 18.
The driver 32 is tightened onto body 12. As the
tonguing operation proceeds, the compressive member 42
deforms and is compressed. The deformation and consequently
the compression is focused by the combination of the body
7S3~
-16-
12 and driver 32. As the volume of the space 36 decreases
more compression is realized and a greater compressive force
is focused against the cable 16. As can be seen clearly
with reference to Figure 2, the compressive force of the
member 42 deformesthe cable 16 and effectively locks
cable 16 into position on the connector body 12.
The combination of the configuration of the come
pressive member 42 and the penetration of the edges 24 into
the surface of the outer wall 26 discourages cable pull
back. If an axial pull back force is exerted on the cable,
for example in the direction of arrow 52, a normal force
will be created against the combination of the driver 32 and
compressive member 42. Since the wall 26 has been deformed
a significant component of the axial force will be exerted
against the normal force of the driver 32 and member 42,
relieving some of the strain of cable 16 and effectively
discouraging cable pull back.
Since no stripping operation was necessary, the pro-
tective jacket 44 of the cable 16 fully covers the cable 16
after connection with coupling 10. The cable 16 retains all
of its environmental protection. After full interconnection,
the volume Al of the compressive member 42 equals the
volume V2 of the space 36. Since no void exists which can
trap corrosive substances, the coupling 10 with connected
cable 16 is also environmentally sealed.
It is especially important to have intimate contact
between the connector body 12 and the outer wall shielding
layer 26 as it discourages EM leakage and effectively
electrically seals the connected cable 16.
~2~7538
-17-
The connector body 12 is provided with threads 50 for
connection with a compatible termination block, junction
box, female connector for joining with another cable, or
other components.
With particular reference to Figure 3 and 4 there is
shown another preferred coupling 110 including the following
elements, which function in the same manner as those desk
cried above except as set forth: a connector body 112
having a mating area 114, a driver means 132 having threads
134 and a rear face 140, and a compressive member 142.
The coupling assembly 110 is connected to a wall
mounting unit 152 e.g., a tap box in Figure 3 through
threads 154 which is typical for Type-II cables illustrated
by 116 in Figure 3 and is commonly referred to as an
"F-connector."
_ .
For this type of cable, it is necessary to separate
the delicate foil shielding and braided layers, 156 and 158,
respectively. The connector body 112 includes a mating area
114 for contacting the braided layer and a distal end 115
which is sharpened to wedge between the delicate foil 156
and braid 158. This sharpened elongated portion 115 of
connector body 112 provides a visual means for the craftsman
to assure that the braided layer is in fact separated from
the foil shield and is being properly positioned on the
exterior of portion 115 of connector body 112, i.e., on
mating area 114, as the connector body 112 is being
positioned on cable 116. This embodiment of the invention
provides another visual inspection opportunity for the
craftsman to assure proper separation of the foil shield 156
and braided layer 158 by extending the dielectric and foil
753~3
-18-
past the end of connector body 112. After visual inspection
to assure the fold shield is undamaged, the dielectric and
foil can be cut Gil flush with the end of the connector
body, leaving the center conductor extended as needed. Some
Type-II cables have the foil shield bonded to the dielectric
in an effort to assure the foil will remain intact during
installation of a connector.
In use, the cable 116 is connected to the coupling
assembly 110 by first connecting the cable 116 to the
mating area 114. By providing appropriate presume, this
operation is done without damaging the cable and it elect
tribally seals the cable.
The driver 132 and compressive member 142 are slipped
over the cable prior to engaging distal end 115 into the
cable. The driver 132 is then connected to wall unit 152 by
threads 134 and 154, respectively, and thereby provides the
means for urging connector body 112 and driver member 132 to-
ward each other to deform compressive member 142. Similar
to that set forth above with respect to Figures 1 and 2, a
space 1~6 is created between the driver member 132 and
connector body 112. The driver member 132 is tightened
until its face 140 engages the face 160 of the wall unit
152. At that point, the volume of space 136 is slightly
less than the volume of compressive member 142 to produce
protuberance 124 in cable protective jacket 144 which also
serves to lock cable 116 to the body 112.
The cable 116 remains environmentally sealed since
stripping of its protective jacket outside the coupling 110
is not required. The coupling 110 is environmentally sealed
through the use of the compressive member 142 and the flush
~2~7538
--1 9
fit of faces 140 and 160. Additionally, the coupling 110 is
provided with a washer 162 which when compressed environment-
ally seals the connection between the coupling assembly 110
to the wall 152.
Additionally, coupling 110 is provided with 2 means for
preventing cable pull-out, such as in response to a force in
the direction of arrow 152. The means comprises protuberance
124 which works in a manner substantially identical to anti-
rotation means 24 sod which, as described above, was. formed
during connection by the volume difference between space 136
and member 142.
Connector body 112 is provided with a shoulder 148 to
assure good electrical contact with wall unit 152 and
provide maximum electrical continuity from the foil shield,
braided layers and connector body 112 to wall unit 152. In
some cases it may also be desirable to enhance the EM
shielding in the mating area 114 and between portion 115 of
connector body 112 and foil shield 156 by providing sufficient
focused force from deformation of compressive memoir 142 to
not only deform the cable protective jacket 144 and braided
layer 158 radially inward but to also deform portion 115 of
connector body radially inward sufficient to maximize the
electrical contact with the foil shield 156. This can be
accomplished by adjusting the volume of compressive member
142 relative to space 136 and/or the shape of the outer part
of the connector body 112 and the interior shape of driver
member 132. Such optimization of this invention will be
apparent to one skilled in the art who practices the various
advantages provided by this invention.
~Z~7S38
-20-
The coupling assemblies of this invention form airtight
connections with the cable. This provides a pressure seal
which further serves to protect the cable and coupling
from environmental damage. This invention is especially
useful since it involves connecting the mechanical coupling
assembly of the type described above without stripping
off the protective outer jacket of the cable. The steps
of the method include providing a coupling assembly of the
type in accordance with the above, inserting the cable onto
the connector body such that the outer conductor contacts
the connector body at the mating area without stripping
off the protective outer jacket, placing the compressive
member to surround the cable at the mating area, placing
the driver means to surround the compressive member, and
urging the driver means and the connector body together
and focusing the deformation of the compressive member
such that it deforms the cable to the connector body
thereby locking it in place and filling voids between
the connector body and the driver means, thereby effect-
in a sealed electrical and environmental connection.
While the instant invention has been described by
reference to what is believed to be the most practical
embodiment, it is understood that the invention may embody
other specific forms not departing from the spirit of the
invention. The present embodiments, therefore, should be
considered in all respects as illustrative and not limited
to the details disclosed herein but are to be accorded the
full scope of the claimed claims so as to embrace any and
all equivalent apparatus, articles and methods.
