Abstract:
An extendible flexible electrical conduit with a telescoping section connected between two spiral gooseneck sections and having insulated electrical conductors extending through the conduit. The conductors are helically wound inside the inner tube of the telescoping section so as to allow them to extend and contract to accommodate extension and contraction of the telescoping section. The outer tube of the telescoping section is oval along most of its length and the sliding end of the inner tube is also oval. The length of the telescoping section may be locked by rotating the inner tube with respect to the outer tube.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     Flexible spiral wound conduits are well known for carrying and protecting electrical conductors, sometimes referred to as “goosenecks”. Such flexible conduits have recently become miniaturized and used to carry internal wiring for communications purposes such as microphone holders. Also well known are telescoping coaxially sliding tubes used as conduits to extend or contract the conduit. These are used with swivel table lamps and also to hold microphones. Each of these two different types of conduits has utility for specific applications. For example, spiral wound flexible casings may be bent universally in different directions and hold the bent position, but are non-extendible. On the other hand, telescoping tubes will extend and contract in a single direction, but are not bendable or flexible, and require universal joints or pivots at their ends to change their orientation.  
         [0002]     U.S. Pat. No. 5,065,299 issued Nov. 12, 1991 to Cohen discloses a power extendible lamp, wherein short telescopic sections of non-circular cross section appear to give limited flexibility to a lamp holder. Limited curvature is apparently achieved by utilizing many very short telescopic sections.  
         [0003]     U.S. Pat. No. 3,324,254 issued Jun. 6, 1967 to Shaw et al. discloses a microphone holder with a rigid telescoping section containing microphone wires which collapse into the space between the ends of the telescoping tubes when the unit is contracted. A jam nut is required to hold a desired position, and provision for vibration reduction is also added. A pivot pin and a swivel mounting allow for movement of the microphone in different directions.  
         [0004]     U.S. Pat. No. 2,209,912 issued Jul. 30, 1940 to Deems illustrates a telescoping underground protective conduit for armored electrical cable, which is helically wound inside the inner telescoping tube to permit raising the upper end of the assembly.  
         [0005]     There is a need for a flexible extendible conduit which will accommodate a number of conductors, which allows full freedom of direction at one or both ends of the conduit as well as the ability to extend and contract in length. All of this should be suitable for ease of manufacture in miniaturized form, so that it could be used for applications such as microphone holders, small lamps and the like. In addition, it would be desirable to lock the telescoping section in a desired place without the need for a jam nut which is commonly employed today in microphone holders. Also there is a need for an extendible flexible conduit which reduces vibration or shocks due to impact.  
         [0006]     Accordingly, one object of the present invention is to provide an improved extendible flexible electrical conduit with conductors therein.  
         [0007]     Another object is to provide such an extendible flexible electrical conduit with means to lock the extendible section in place.  
         [0008]     Another object is to provide such an extendible flexible electrical conduit which reduces shocks and vibration along the conduit.  
       SUMMARY OF THE INVENTION  
       [0009]     Briefly stated, the invention comprises an extendible flexible electrical conduit with conductors therein comprising at least one spiral wound flexible casing, a rigid telescoping section connected thereto and having insulated electrical conductors extending through the conduit. The conductors are arranged inside the telescoping section, preferably by bunching up or helically winding the conductors so as to allow them to extend and contract to accommodate extension and contraction of the telescoping section. The telescoping section comprises inner and outer tubes that are slidably and coaxially disposed to allow the telescoping section to extend and contract. In order to limit rotation of the inner tube with respect to the outer tube, the outer tube is preferably oval along most of its length and the sliding end of the inner tube is also oval. By rotating the inner tube with respect to the outer tube, the length of the telescoping section may be locked without the use of a jam nut. Preferably there are spiral wound flexible casings on either end of the telescoping section. 
     
    
     DRAWING  
       [0010]     The invention will be better understood by reference to the following description, taken in connection with the accompanying drawings, in which:  
         [0011]      FIG. 1  is an elevation view of the extendible flexible electrical conduit in accordance with the present invention,  
         [0012]      FIG. 2  is a partial view in cross section, illustrating the construction at the interfaces of the telescoping middle section with the flexible casing sections attached thereto,  
         [0013]      FIG. 3  is an enlarged plan view in cross section taken along lines III-III of  FIG. 2 ,  
         [0014]      FIG. 4  is an enlarged plan view in cross section, taken along lines IV-IV of  FIG. 2 ,  
         [0015]      FIG. 5  is an enlarged plan view in cross section, taken along the same plane as  FIG. 4 , but with inner and outer tubes rotated with respect to one another,  
         [0016]      FIG. 6  is an enlarged elevation view of four helically wound conductors interspersed with one another, and  
         [0017]      FIG. 7  is an enlarged elevation view of five conductors spirally wound into a single multi-strand conductor in the form of a helix. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0018]     Referring now to  FIG. 1  of the drawing, an extendible flexible electrical conduit is shown generally at  10 , which comprises a first spiral wound flexible casing  12 , a second spiral wound flexible casing  14 , and a rigid telescoping middle section  16  connected between flexible casings  12  and  14 . The flexible casings  12  and  14  are of a construction well known in the art, consisting of a spirally wound spring with formed metal wire separating the coils of the spring creating friction between spring and formed wire, so that the casing may be bent in any direction and will retain its bent shape as illustrated in the drawing.  
         [0019]     The telescoping middle section  16  comprises an inner tube  18  and an outer tube  20 . The outer tube  20  has an expanded (swaged) attachment end  22  and an expanded free end  24 . The inner tube  18  has an expanded attachment end  26  and a free end (not shown in  FIG. 1 ) that slides in close contact within outer tube  20  so that the middle section  16  can extend and contract.  
         [0020]     For reasons later to be explained, the invention may include an indicia line  28  inscribed on the inner tube and a pointer  30  inscribed on the outer tube. A group of insulated electrical conductors  32  extend through flexible casing  12 , telescoping middle section  16 , and flexible casing  14 .  
         [0021]     Referring to  FIG. 2  of the drawing, portions of the conduit are illustrated in enlarged cross sectional views at the connection between the first (upper) flexible casing  12  and inner tube  18 , and also between the second (lower) flexible casing  14  and the outer tube  20 .  
         [0022]     The arrangement of electrical conductors may take several forms. In  FIG. 2 , there are two insulated conductors  32   a ,  32   b  running through the upper flexible casing  12  and held within a plastic retaining ring  34 . Conductors  32   a ,  32   b  are interleaved with one another and formed into a helical coil  36 , which extends most of the length of the telescoping middle section  16 . The conductors are attached to another retaining ring  38 , and from there pass through the lower flexible casing  14 . Retaining rings  34 ,  38  are dimensioned to fit tightly within the expanded sections  26 ,  22  of the inner and outer tubes  18 ,  20  respectively. A bushing  40  of plastic material is disposed in the expanded section  24  of outer tube  20 , to receive the inner tube  18 , so that tubes  18 ,  20  will slide easily within one another.  
         [0023]     In accordance with one aspect of the present invention, portions of the inner and outer tubes are made to be non-circular so as to limit rotation about their axes relative to one another. Although the non-circularity may take several forms, the preferred embodiment makes the cross section of the outer tube  20  oval along the major length thereof between attachment end  22  and free end  24 . In addition, a relatively short portion of the free end of inner tube  18  (designated by reference number  42  in  FIG. 2 ) is also made oval with the same outline as outer tube  20  but forming close clearance therewith.  
         [0024]     Reference to  FIGS. 3 and 4  of the drawings illustrate the preferred form of the invention. In  FIG. 3 , a conductor  32   a  of helix  36  is seen inside the circular cross section of inner tube designated at  18   a . The cross section of the outer tube designated at  20   a  has a slightly oval or elliptical cross section with major axis  44  and minor axis  46 .  
         [0025]     Referring to  FIG. 4  of the drawings, taken through the free end  42  of the inner tube as shown in  FIG. 2 , a conductor  32   a  of the helix  36  is disposed inside free end  42 , which is oval or elliptical in cross section as indicated at reference number  18   b . The outer tube  20  is also elliptical in cross section as indicated at reference  20   b . Both the ellipses of  18   b  and  20   b  have the same major axis  44  and minor axis  46 . When the major and minor axes  44 ,  46  are aligned, the inscribed line  28  and pointer  30  ( FIG. 1 ) appear as shown, and the middle telescoping assembly will freely extend and contract while the helix  36  of conductors  32   a ,  32   b  will also extend and contract to accommodate the movement.  
         [0026]     Reference to  FIG. 5  illustrates the same cross section as  FIG. 4 , but with inner and outer tubes  18 ,  20  rotated about their longitudinal axis with respect to one another, so that the major axis of elliptical inner tube free end, designated  44   a  is rotated with respect to the major axis of elliptical outer tube  20   b , as indicated at  44   b . In this position there is interference between the walls of inner and outer tubes and they will not slide longitudinally with respect to one another. Thus rotation will lock the tubes so that the middle section cannot extend or contract until the indices  28 ,  30  are again aligned. This is a useful feature for a microphone holder, lamp or other device and obviates the need for a jam nut as in prior art devices.  
         [0027]     The arrangement of the conductors inside the telescoping middle section  16  can take several forms without departing from the scope of the present invention. In its simplest form, the conductors may simply be wadded or jumbled up inside the inner tube in a random fashion, or they may be arranged in a zig-zag or helical fashion. The preferred embodiment utilizes a helical arrangement to prevent possibility of entanglement.  
         [0028]      FIG. 6  of the drawing shows one arrangement wherein the conductors are separately insulated and interleaved with one another in a helical arrangement. These are shown as conductors  48   a ,  48   b ,  48   c ,  48   d  which are interleaved into a single interleaved helix  48 .  
         [0029]     Referring to  FIG. 7  of the drawing, individual conductive strands  50   a - 50   e  are spirally wound into a single multi-strand conductor  50  which is again shaped as a helix in a preferred form of the invention.  
         [heading-0030]     Operation  
         [0031]     The components are assembled as described and indicated in  FIGS. 1 and 2 . The free ends of the flexible casings  12 ,  14  may be attached to the desired components and the conductors  32  connected in a conventional fashion. For example, flexible casing  14  might be connected to a support for a microphone podium, while a microphone would be attached to the free end of casing  12 . The spiral construction of the flexible casings serves to dampen and reduce any shocks or vibration between the podium and the microphone.  
         [0032]     The telescoping middle section  16  may be extended or contracted to provide the proper length, while the flexible casings  12 ,  14  are bent manually to conform to a desired shape, which they will retain. The inner tube  18  may then be rotated with respect to outer tube  20  to lock the telescoping mid-section in the desired position. Thus the invention provides an improved functionality and is adaptable to a great many devices requiring an extendible flexible electrical conduit with conductors therein.  
         [0033]     While the invention is shown in its preferred form with flexible casings attached on either end of a telescoping middle section, it is within the scope and purview of the present invention to utilize only one such flexible casing to obtain universal bending action in combination with length extension. Thus, a single spiral casing might be used on the lower end to attach to a support, while a lamp or microphone might be attached to the upper end, either with or without a pivot connection. Conversely a pivot or swivel connection could directly connect the telescoping section to a support, and a spiral casing used at the upper end to obtain directional placement of a microphone or lamp.  
         [0034]     Other modifications will occur to those skilled in the art, and it is desired to secure in the appended claims all such modifications as fall within the true spirit and scope of the invention.