Electrical connectors – Including or for use with coaxial cable – Having means for interconnecting outer conductors of three...
Reexamination Certificate
2001-02-07
2002-12-17
Bradley, P. Austin (Department: 2833)
Electrical connectors
Including or for use with coaxial cable
Having means for interconnecting outer conductors of three...
C439S369000, C358S473000
Reexamination Certificate
active
06494739
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to the field of coaxial cable connectors for electronic imager assemblies, and more particularly to features for relieving strain on coaxial cables that connect an electronic imager assembly to a signal processor.
BACKGROUND OF THE INVENTION
Coaxial cables have long been used to connect electrical devices to other electrical apparatus. A typical coaxial cable consists of an outer sheath enclosing a center conductor wire. The center conductor wire carries electrical signals, while the outer sheath provides electrical shielding. When such cables are used, it is well-known to provide some type of strain relief mechanism to alleviate stresses caused in the electrical connection between the coaxial cable wires and an interconnected electrical device. It is necessary that the strain relief provides adequate absorption of any pulling or twisting stresses placed on the coaxial cable wires in order to improve the reliability of the connection and prevent cable disconnection problems.
A particular field in which coaxial cables are used is that of medical or industrial imaging in which imaging devices such as endoscopes or borescopes utilize coaxial cables to connect different electrical devices with a miniature electronic imager and its associated circuitry.
For example, as shown in
FIGS. 1
,
2
, and
12
, a known video endoscopic apparatus
10
, partially shown, typically employs a plurality of coaxial cables
12
to interconnect an electronic imager assembly
20
with a signal processor
13
. The signal processor
13
receives the electrical signals produced by the electronic imager assembly
20
and processes the signals into a suitable video output signal. The signal processor
13
is connected to a video monitor
14
, a video recorder
15
, or other video peripheral device capable of handling the output video signal. The electronic imager assembly
20
shown in the FIGS. includes a miniature electronic imager
22
, such as a CCD, having a transparent window
21
disposed over the image recording surface of the imager. A set of fine pitch imager leads
24
extend from between the miniature imager
22
and the window
21
, extending to a pair of proximally located circuit boards
41
,
42
each having a plurality of electronic components
35
disposed thereupon. A transmission cable
33
includes a plurality of coaxial cables
12
which are used to transmit power to the imager assembly
20
and to transmit an electrical signal, as conditioned by some of the components
35
on the circuit boards
41
,
42
from the imager
22
.
Referring more specifically to
FIG. 12
, the imager assembly
20
is mounted in the distal end of an insertion tube or section
17
relative to a lens system which may include one or more lens elements arranged to focus a target image upon the recording surface of the imager
22
. A series of light emitting ends of a fiber bundle
16
are also disposed in proximity to the distal end of the insertion portion
17
.
A problem is that though electronic imager assemblies have been streamlined and improved, particularly in terms of miniaturization and space savings, there has been relatively little development in providing strain relief for the coaxial cables used with such assemblies. For example, and still referring to
FIGS. 1 and 2
, one method of attaching the plurality of coaxial cables
12
to an electronic imager assembly
20
is provided by solder bonding the ends of each of the center conductor wires
19
of each of the coaxial cables
12
of the transmission cable
33
to traces
34
which are provided on facing surfaces of the pair of elongated circuit boards
41
and
42
which are held in spaced relation from one another. However, in this particular arrangement, the only strain relief is provided by the traces
34
, which include only a relatively small surface area for contacting the center conductor wires
19
of the coaxial cables
12
. However, as electronic imager assemblies continue to shrink in size to meet the target demand for such devices, such forms of strain relief mechanisms have proven inadequate for a variety of reasons.
The above known form of strain relief results in a very stiff distal end since the individual conductors of each coaxial cable
12
are forced apart by a block of resin material
45
and then soldered to the traces
34
in a manner that increases the length of the stiff portion of the assembly. The above solution increases the risk of breaking the connections between the coaxial cable and the assembly when the assembly is bent, twisted or pulled. It would be desirable to decrease the length of this stiff portion, and thereby provide improved flexibility.
Another problem with the above cable interconnection technique is that overall down sizing of endoscopes, borescopes, and other medical and non-medical video inspection instruments has caused the wires of the coaxial cables to become relatively thin and tiny, making these wires even more structurally weak. Utilizing an epoxy or resin to hold these wires is ineffective since their fragility tends to either break the wires completely, or cause them to pull out of the resin when twisted or pulled. Thus, it would also be very desirable to increase the strength of the connection between the wires and the assembly.
A further problem is that available space is limited, meaning conventional means of strain relief, such as clips or interconnect arrays, are highly impractical. Simply put, there is insufficient volume, particularly within an endoscope or borescope, to accommodate such designs. Moreover, there is a general need in the field to minimize the overall size of the insertion portion of these instruments so as to provide improved patient comfort and allow access to small spaces. Thus, it would also be desirable to decrease the volume of space occupied by the wire connector and the electronic imager assembly.
Still a further problem is that the structural components of electronic imager assemblies are also relatively thin and weak. This makes the entire assembly extremely difficult to handle, particularly during assembly of the insertion tube. Thus, there is a need to provide additional structural support to the components of the imager assembly. Moreover, during assembly, there is likelihood that the imager assembly may become misaligned at any time. Even slight misalignments of the imager may render the instrument unsuitable for use. Though applying an epoxy resin in the space between the two hybrid circuit boards prevents the circuit boards from moving apart or closer together, the imager itself is still prone to being misaligned. Thus, it would also be highly desirable to prevent misalignment of the imager itself.
Yet another problem is that the connectors, such as previously described in the above referred to '313 patent, require many manufacturing steps to construct and consist of too many parts. For example, the connectors require hybrid boards that are bonded to a tapered block of resin encapsulating material.
In addition, once the endoscope is assembled, it is an extremely labor intensive, time consuming, and costly process to effect any repairs should they become necessary. As a result, a substantial need has arisen for a connector with an improved strain relief mechanism that is simple to construct and instal, and that will prevent coaxial cables from being detached or broken when placed under tension. Such a feature would vastly improve reliability and help ensure proper operation of the device.
SUMMARY OF THE INVENTION
It is therefore a primary object of the present invention to improve the state of the art of electronic imager assemblies.
It is still a further primary object of the present invention to improve the reliability of coaxial connection mechanisms for imaging instruments, such as endoscopes and borescopes.
It is yet another primary object of the subject invention to improve the integrity of the connection between coaxial cable wires and an electronic imager assembly.
According to a preferr
Burdick Kenneth J.
Grecco James Edward
Johnson Edward Arthur
Vivenzio Robert L.
Bradley P. Austin
Hammond Briggitte R.
Wall Marjama & Bilinski LLP
Welch Allyn Inc.
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