1. Technical Field
The present invention relates generally to electronic filters used in the cable television industry, and relates more particularly to the construction and assembly of such filters.
2. Background Art
Typical electronic filter constructions in the cable television (CATV) industry involve a considerable number of parts, such as, for example, one or more circuit boards, connecting wires or leads, filter circuit components, isolation plates, blocks or chambers, input and output terminals, moisture barrier seals or plugs, connector housings, sub-housings or caps, o-rings, outer housing sleeves, and potting material. This elaborate array of parts constrains efforts to: minimize the size and weight of the filters; reduce material and labor costs associated with assembly of the filters; and simplify and automate the assembly process. Examples of such filter constructions are shown and described in: U.S. Pat. No. 5,278,525 to Palinkas; U.S. Pat. No. 4,901,043 to Palinkas; U.S. Pat. No. 4,701,726 to Holdsworth; U.S. Pat. No. 4,451,803 to Holdsworth et al; U.S. Pat. No. 3,579,156 to Parfitt; and U.S. Pat. No. 3,065,434 to Calderhead.
For such CATV filters as highpass and lowpass filters, diplex filters, windowed highpass filters, and step attenuator (or return path) filters, tunable filter circuits and shielding between filter components and circuits are not normally required. Thus, for these types of filters, an opportunity is presented to simplify filter components, construction and assembly. U.S. Pat. No. 5,745,838 to Tresness et a. discloses (FIGS. 8-10) a filter construction for a return path filter called a “step attenuator.” This construction is also shown in
Many diplex, windowed highpass, and return path filters (See, e.g., embodiments shown in FIGS. 1-5 of U.S. Pat. No. 5,745,838), have dual (or “parallel”) circuit paths. For example,
U.S. Pat. No. 5,278,525 to Palinkas discloses parallel circuit boards for a CATV notch filter (or “trap”), rather than for a dual path filter. The construction includes a considerable number of extra parts, such as an isolation shield, circuit board housings, tuning screw housings, o-rings, and an outer housing sleeve.
In most CATV applications, the filters are installed outdoors. Thus, it is important that the filter construction be moisture resistant. Efforts to make filters moisture resistant have included enclosing the filter in an outer housing sleeve and employing o-rings between the filter and the outer housing sleeve. See, e.g., U.S. Pat. No. 5,745,838 to Tresness et al., U.S. Pat. No. 5,278,525 to Palinkas, U.S. Pat. No. 4,701,726 to Holdsworth, and U.S. Pat. No. 4,451,803 to Holdsworth et al. Such an approach requires the additional parts and expense of o-rings and outer housing sleeves, and may require manual assembly of such parts.
A prime path for moisture penetration into the filter is through the terminal fittings or connectors. While efforts to prevent moisture penetration through filter connectors (such as disclosed in U.S. Pat. No. 5,278,525 to Palinkas) have been satisfactory, there remains a need to improve moisture resistance through these connector paths.
Another consideration in CATV filter construction is to establish a good and reliable electrical ground between the filter circuit or circuits and the filter housing. Electrical ground has been established by soldering or fitting isolation shields or blocks between the circuit boards and the filter housing, or by soldering wires or leads between the circuit board and housing. See, for example, U.S. Pat. No. 4,701,726 to Holdsworth. However, such methods usually require additional components or manual assembly steps.
It is therefore an object of the present invention to provide an electronic filter construction that avoids the limits and problems associated with the prior art.
It is another object of the present invention to provide an electronic filter construction that is more suitable for automated assembly than previous filter constructions.
It is a further object of the present invention to provide an electronic filter construction that requires less parts than previous filter constructions.
It is still another object of the present invention to reduce material and labor costs associated with the assembly of an electronic filter;
It is still a further object of the present invention to reduce the size and weight of an electronic filter; and
It is still yet another object of the present invention to provide an electronic filter construction that has improved moisture resistance.
These and other objects are attained in accordance with the present invention wherein there is provided an electronic filter assembly of the type that includes a female terminal cap and a collet assembly. The female terminal cap has a fitting portion and contains a terminal passage through the fitting portion. The collet assembly is secured in and substantially closes the terminal passage of the female terminal cap. The collet assembly comprises an insulator, a collet terminal, and a seal. The insulator is made from a single piece of insulator material and contains a bore therethrough. The collet terminal extends through the bore of the insulator. The seal is located inside the terminal passage of the female terminal cap, between the collet terminal and the female terminal cap.
In a more specific embodiment, an electronic filter comprises a conductive housing having input and output ends. The housing has a body portion and a female connector. The female connector is located at the input end of the housing and has a diameter less than that of the body portion. A circuit board is located within the body portion of the housing. A collet assembly is located within the female connector to receive electrical signals and conduct them to the circuit board. The collet assembly includes an insulator member, a conductor, and an elastomeric sealing member. The insulator member is located within the female connector. The insulator member contains a generally cylindrical opening through its length. The conductor extends through the opening of the insulator member. The conductor has an input end adjacent the input end of the housing and an output end adjacent the circuit board. The conductor has a hollow interior at its input end. The elastomeric sealing member surrounds the insulator member in compressed engagement with the insulator member and the surrounding female connector, to provide a moisture seal between the insulator member and the female connector.
Further objects of the present invention will become apparent from the following description of the preferred embodiment with reference to the accompanying drawing, in which:
The filter assembly of the present invention is especially suited for dual (or parallel) path filter circuits. As understood in the art, dual path circuits include at least two separate circuit paths. Examples of dual path filters are diplex, windowed highpass, and some step attenuator filters. Referring now to
The conventional filter construction of
The preferred construction will now be described in detail with reference to
Female terminal cap 52 includes a fitting portion 66 containing external threads 67 and a terminal passage 68. Male terminal cap 54 includes a fitting portion 70 containing internal threads 71 and a terminal passage 72. Passages 68 and 72 each establish a passageway between interior volume 60 and the exterior of filter 50.
As shown in
As best shown in
Dual filter circuit 10 (
Circuit boards 74, 76 are mounted directly to male terminal cap 54. As best shown in
Circuits 80, 88 are electrically coupled to terminal cap 54 via the ground contacts, and thus establish a common electrical ground for circuits 80, 88. Ground contacts 82, 82a and 83, 83a are in registration and direct contact with notches 94a and 94b, respectively, and ground contacts 90, 90a and 91, 91a are in registration and direct contact with notches 94c and 94d, respectively. Each of the ground contacts is coated with solder when circuit boards 74, 76 are produced. The solder coating ensures a tight fit between the contacts and the notches.
In fact, during assembly, the some of the solder is sheared off during insertion of boards 74, 76 into notches process 94a, 94b and 94c, 94d. The ground contacts are soldered to the notches by induction soldering (another automated assembly step). This arrangement establishes a good ground connection between the circuit boards and cap 54.
Terminal 92 is a male connector terminal which extends through and is operatively supported inside terminal passage 72. A potting wafer 95, made of low density polyethylene, is inserted into and substantially closes off terminal passage 72. Wafer 95 contains an open bore through which terminal 92 tightly fits. Once installed, wafer 95 seals passage 72, substantially preventing moisture from entering filter 50 through passage 72.
Terminal 84 includes a female terminal assembly 96 which extends through and is operatively supported inside terminal passage 68. Terminal assembly 96 includes a female connector element or collet terminal 96a, a polypropylene insulator 96b containing an external o-ring groove 96c (
As shown in
As shown in
Referring now to
Referring now to
A circular opening 281a is contained in ground plane 281 to allow terminal 284 to be connected to board 274 without shorting to ground. A similar opening is provided in ground plane 289 for terminal 292. Openings are also contained in the ground planes to accommodate jumper wires 293a, 293b. The embodiment of
While the preferred embodiment of the invention has been particularly described in the specification and illustrated in the drawing, it should be understood that the invention is not so limited. Many modifications, equivalents, and adaptations of the invention will become apparent to those skilled in the art without departing from the spirit and scope of the invention.
This application is a continuation of U.S. application Ser. No. 10/721,492, filed Nov. 25, 2003, which is a continuation of U.S. application Ser. No. 09/898,543, filed Jun. 29, 2001, now U.S. Pat. No. 6,674,343, which is a continuation of application Ser. No. 09/382,064, filed Aug. 24, 1999, now U.S. Pat. No. 6,323,743.
Number | Date | Country | |
---|---|---|---|
Parent | 10721492 | Nov 2003 | US |
Child | 10909958 | Aug 2004 | US |
Parent | 09898543 | Jun 2001 | US |
Child | 10721492 | Nov 2003 | US |
Parent | 09382064 | Aug 1999 | US |
Child | 09898543 | Jun 2001 | US |