Abstract:
An expansion coupling and method of use for joining the ends of a pair of first and second conduits along a longitudinal axis. Each of the conduits is a tubular member of circular cross-section having an outside threaded leading end and an outside threaded trailing end. The coupling comprises an inner and outer sleeve. Both sleeves are elongated tubular members having a first end in the form of an internally threaded throat adapted to threadedly receive a respective threaded end of a respective conduit. The inner sleeve has a second end of a square outer periphery. The outer sleeve also has a second end of a square outer periphery. The second end of the inner sleeve is arranged for disposition within the second end of the outer sleeve to readily slide with respect thereto along the longitudinal axis, with the contiguous surfaces of the second ends of both sleeves preventing the rotation of the sleeves with respect to each other about the longitudinal axis.

Description:
This application is a continuation-in-part of my earlier filed U.S. patent application Ser. No. 07/495,655 filed on Mar. 19, 1990, entitled Expansion Joint For Conduit For Cables, whose disclosure is incorporated by reference herein, and the invention hereof relates generally to expansion joints and more particularly to expansion joints for conduits carrying cables. Basically the invention comprises an expansion joint which is used to connect adjacent ends of conduits carrying cables, such as fiber optic cables. 
    
    
     BACKGROUND OF THE INVENTION 
     In the prior art conduits for carrying cables, e.g., fiber optic, electrical, etc., have been connected by an expansion joint (coupling) to accommodate changing temperatures. Such expansion joints basically comprise two members, namely a collar and a cap, which are threadedly secured together. The collar is a cylindrical member having one end at which there is disposed a female threaded opening. That threaded opening is arranged to receive the trailing end of one conduit, e.g., a leading conduit. The cap is threadedly secured onto the collar and includes a smooth, i.e., non-threaded, opening for receiving the leading end of the next, e.g., trailing, conduit. Since the leading end of the trailing conduit is not threadedly engaged by any portion of the coupling it can thus slide longitudinally through the opening in the coupling&#39;s cap. 
     It has been found that when such couplings are used in application wherein the conduits are supported above the ground, e.g., where they cross bridges, overpasses, etc., the conduits have a tendency to become disconnected. Such disconnections typically result from vibrations which are transmitted to the structure supporting the conduits and expansion joint coupling. In particular, where the conduits are supported by rollers or some other means to enable the conduits to move longitudinally, loosening, if not total disconnection, commonly occurs. In this regard since the trailing conduit can slide longitudinally within the cap of the coupling (it is not threaded in that cap) it is free to rotate about its longitudinal axis, whereupon it may become unthreaded from the threaded collar of the trailing coupling. 
     OBJECTS OF THE INVENTION 
     Accordingly, it is a general object of this invention to provide a coupling forming an expansion joint for conduits which overcomes the disadvantages of the prior art. 
     It is a further object of this invention to provide a coupling forming an expansion joint for conduits which can be used for new construction to connect conduits together so that a cable may extend therethrough. 
     It is still a further object of this invention to provide a coupling forming an expansion joint to retrofit prior art couplings for existing cable systems. 
     It is yet a further object of this invention to provide a coupling forming an expansion joint for conduits which is simple in construction, relatively low in cost, and effective in operation. 
     SUMMARY OF THE INVENTION 
     These and other objects of this invention are achieved by providing an expansion coupling and method of use for joining the ends of a pair of first and second conduits along a longitudinal axis. Each of the conduits is a tubular member having an outside threaded leading end and an outside threaded trailing end. The coupling comprises inner sleeve means and outer sleeve means. The inner sleeve means is a short length tubular member having a first end in the form of an internally threaded throat adapted to threadedly receive the trailing end of the first conduit. The outer sleeve means is a tubular member of substantially longer length than the inner sleeve means and having a first end in the form of an internally threaded throat adapted to threadedly receive the leading end of the second conduit. The inner sleeve means has a second end of a predetermined shaped outer periphery having at least one first predetermined shape, e.g., flat, surface. The outer sleeve means has a second end of a predetermined shaped inner periphery having at least one second predetermined shape, e.g., flat, surface. The second end of the inner sleeve means is arranged for disposition within the second end of the outer sleeve means and with their respective first and second surfaces contiguous with each other. The inner and outer sleeve means are arranged to readily slide with respect to each other along the longitudinal axis, with the contiguous first and second surfaces preventing the rotation of the inner sleeve means with respect to the outer sleeve means about the longitudinal axis. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     Other objects and many attendant features of this invention will become readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein: 
     FIG. 1 is an isometric view of one embodiment of an expansion joint coupling constructed in accordance with this invention; 
     FIG. 2 is an enlarged sectional view taken along line 2--2 of FIG. 1; 
     FIG. 3 is an enlarged sectional view taken along line 3--3 of FIG. 2; 
     FIG. 4 is an isometric view of another embodiment of an expansion joint coupling constructed in accordance with this invention; 
     FIG. 5 is an enlarged sectional view taken along line 5--5 of FIG. 5; 
     FIG. 6 is an enlarged sectional view taken along line 6--6 of FIG. 5; 
     FIG. 7 is an isometric view of yet another embodiment of an expansion joint coupling constructed in accordance with this invention; and 
     FIG. 8 is an enlarged sectional view taken transversely to the longitudinal axis of the embodiment of the coupling of FIG. 7 shown assembled. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to various figures of the drawing where like reference numerals refer to like parts there is shown at 20 in FIG. 1 an expansion coupling constructed in accordance with this invention. The coupling 20 is arranged for new construction, that is to connect the ends of a pair of conduits 22 and 24 (FIG. 2) before a cable 26 (FIG. 2) is extended therethrough. In FIGS. 4-6 there is shown another embodiment of a coupling 100 constructed in accordance with this invention. In FIGS. 7 and 8 there is shown yet another embodiment of a coupling 400 constructed in accordance with this invention. 
     The couplings 100 and 400 are each arranged for use in existing cable systems to replace prior art expansion couplings without requiring the disconnection of or interfering with the cable(s) extending therethrough. The details of retrofit couplings 100 and 400 will be described later. 
     As can be seen in FIGS. 1-3 the coupling 20 basically comprises two sleeve members 28 and 30. Each of the members is an elongated tube having one end of circular cross-section and another end of square cross-section. In particular, the sleeve member 28, hereinafter referred to as the inner sleeve member, has a circular cross-sectional end 28A and a square cross-sectional end 28B. Similarly, the sleeve member 30, hereinafter referred to as the outer sleeve member, has a circular cross-sectional end 30A and a square cross-sectional end 30B. 
     The interior or throat of the free end 28A of the inner sleeve 28 is threaded at 28C to provide means for connecting the trailing end 22B of the conduit 22 to it. Thus, as can be seen in FIG. 2 the conduit&#39;s trailing end 22B is externally threaded with threads to mate with the internal threads 28C of the inner sleeve 28. In a similar manner the interior or throat of the free end 30A of the outer sleeve 30 is threaded at 30C to provide means for connecting the leading end 24A of the conduit 24 to it. That conduit&#39;s leading end 24A is externally threaded with threads to mate with the internal threads 30C of the outer sleeve 30. 
     In accordance with the teachings of this invention the inner sleeve is arranged to be coupled to the outer sleeve to connect the conduits to each other and with the sleeves being freely slidable with respect to each other to take up any expansion or contraction of the connected conduits 22 and 24. To that end the square cross-section portion 28B of the inner sleeve is configured to closely fit within the outer sleeve portion 30B so that the two members 28 and 30 can slide with respect to each other along their longitudinal, central axis. 
     As will be appreciated by those skilled in the art inasmuch as the engaging portions 28B and 30B are each of square cross section each includes one flat surface disposed contiguous with the other. Thus, the two sleeves 28 and 30 cannot rotate about the longitudinal axis of the coupling. Accordingly, the conduits 22 and 24 when connected (screwed) to their respective coupling sleeves are unable to rotate about their longitudinal axis and cannot become disconnected (unscrewed). The resulting joint, however, can expand or contract (as the case may be) by the longitudinal sliding of the inner sleeve 28 with respect to the outer sleeve 30. 
     In one exemplary embodiment this invention for use with two inch (5.1 cm) GIP conduits, each of the sleeves 28 and 30 is fourteen inches (35.6 cm) long, with their circular cross-sectional portions being two inches (5.1 cm) long. The outer sleeve portion 30B is three inches (7.6 cm) in width and height, while the inner sleeve portion 28B is two and a half inches (6.4 cm) in width and height. The space provided inside of the foregoing sized coupling 20 allows for at least eight inches of longitudinal expansion, but such an arrangement is merely exemplary. Thus, other couplers constructed in accordance with this invention can be designed to accommodate other longitudinal expansions. Also, it should be understood that couplers in accordance with this invention can be designed to accommodate conduits of various diameters. 
     It must be pointed out at this juncture that the engaging portions 28B and 30B of the sleeves 28 and 30, respectively, need not be of square cross section so long as they each include one flat surface to prevent relative rotation with respect to each other about their longitudinal central axis. 
     The retrofit embodiment coupling 100 is made up of an inner sleeve 102 and an outer sleeve 104. The sleeves 102 and 104 are basically constructed in the same manner as described heretofore with reference to sleeves 28 and 30, except that each sleeve is bisected (split) horizontally so that each includes an upper section and a lower section, which are arranged to be clamped together. Thus, the inner sleeve 102 comprises an upper section 106 and an lower section 108, while the outer sleeve 104 comprises an upper section 110 and a lower section 112. When the upper section 106 of the inner sleeve 102 is disposed over its lower section 108 the resulting body is virtually identical to the inner sleeve 28 described heretofore. So too, when the upper section 110 of the outer sleeve 104 is disposed over its lower section 112 the resulting body is virtually identical to the inner sleeve 30 described heretofore. Hence the common structural features of the sleeves will not be reiterated hereinafter. 
     The securement of the inner sleeve sections 106 and 108 is accomplished by the use of a clamp 200. The clamp 200 basically comprises a U-shaped member 202 and a yoke member 204. The member 202 has a pair of legs 206 each terminating in a respective threaded end 208. Each leg is arranged to extend through a respective opening 210 in the yoke member 204. The yoke member 204 includes a curved surface 214 whose radius is the same as that of the circular cross sectional portion of the sleeve 102. Once the legs 206 are extended through the openings 210 respective nuts 212 are screwed onto the respective threads 208 on the legs to hold the yoke member 204 in place on the U-shaped member 202. The circular cross-sectional portion of the inner sleeve 102 is disposed within the space between the U-shaped member and the curved surface 214 of the yoke member 204, and the nuts are tightened to firmly secure the sections 106 and 108 together. 
     The circular cross-sectional portion of the outer sleeve 104 is secured together in the same manner by use of another clamp 200. 
     The square cross-sectional portions of the two sections 110 and 112 of the outer sleeve 104 are secured together by use of another type of clamp 300. As can be seen in FIG. 6 the clamp 300 basically comprises a U-shaped member 300 and a linear bridging member 304. The member 302 has a pair of legs 306 each terminating in a respective threaded end 308. Each leg is arranged to extend through a respective opening (not shown) in the bridging member 304. Once the legs are extended through those openings respective nuts 312 are screwed onto the respective threads 308 on the legs 306 to hold the bridging member 304 in place on the U-shaped member 302. The square cross-sectional portion of the outer sleeve 104 is disposed within the square space between the U-shaped member 302 and the bridging member 304, and the nuts are tightened to firmly secure the sections 110 and 112 together. 
     The retrofit coupling 100 is used as follows: the existing (e.g., prior art) coupling (not shown) serving to connect the two conduits 22 and 24 is cut off or otherwise removed from the two adjacent ends 24A and 22B without disconnecting or interfering with the cable 26 passing therethrough. This action exposes the adjacent threaded ends of the two conduits. The lower section 108 of the inner sleeve 102 is then disposed under the leading conduit 22 so that it&#39;s threads 102C receive the threads 22B of the conduit 22. In a similar manner the lower section 112 of the outer sleeve 104 is positioned under the conduit 24 and with respect to section 108 so that its threads 104C receive the threads 24A end of the trailing conduit 24. The upper section 106 of the inner sleeve 102 is then put in place in the same manner as the lower section 108 of that sleeve and the upper section 110 of the outer sleeve 104 is then put in place of the same manner as the lower section 112 of the outer sleeve. The upper and lower sections of the inner sleeve 102 are then clamped together by the clamp 200 extending about the circular end of that sleeve. Another clamp 200 clamps the circular end of two sections of the outer sleeve, while the intermediate clamp 300 is placed about the square section of the outer sleeve to complete the assembly. 
     The second retrofit embodiment of this invention, namely, coupling 400, is designed for use in more confined spaces than coupling 100. Moreover, it is somewhat simpler in construction than coupling 100. As can be seen in FIGS. 7 and 8 the coupling 400 basically comprises an inner sleeve 402 and an outer sleeve 404. The outer sleeve 404 is constructed in the same manner as described heretofore with reference to the outer sleeve 104 of coupling 100 and thus the same reference numerals as given with respect to sleeve 104 will be given with respect to sleeve 404 of coupling 100 and its details will not be reiterated herein. The inner sleeve 402 basically comprises a circular, cylindrical tubular member of short longitudinal length. The outer periphery of the sleeve 402 includes four flatted surfaces 406 extending longitudinally therealong. The surfaces 406 are disposed at equidistantly spaced locations on the periphery of the sleeve and perpendicular to each other so that the periphery of the sleeve is a square having rounded corners (the corners being made up of the circular portion of the sleeve&#39;s periphery between immediately adjacent flatted surfaces 406). 
     As can be seen clearly in FIG. 8 the spacing between opposed flatted surfaces 406 is slightly less than the spacing between the opposed inner surfaces of the outer sleeve 404 so that the inner sleeve can readily fit within the outer sleeve. Like the outer sleeve 404 the inner sleeve 402 is bisected (split) horizontally so that it includes an upper section 408 and a lower section 410. These sections are arranged to be held together when the inner sleeve 402 is disposed within the outer sleeve 404. 
     The circular inner surface of the each of the inner sleeve sections 408 and 410 includes helical threads 412. When the sections 408 and 410 are assembled as shown in FIG. 7 the helical threads of each section conjoin with each other to form a cylindrical threaded throat arranged to receive and mate with the helical threads 22B on the conduit 22. While the threads 412 are shown extending the length of the sleeve 402, such a construction is not required. All that is required is that the threads extend for a sufficient distance from the leading face 414 of the sleeve 402 to securely receive the threads of the trailing end 22B of conduit 22. 
     The securement of the outer sleeve sections 110 and 112 together is accomplished via the clamps 200 and 300 as described heretofore, and hence will not be reiterated herein. No separate clamping means are used to hold the inner sleeve sections 408 and 410 together when the coupling 400 is assembled and connected to the conduits 22 and 24 Instead, it is the assembled outer sleeve 404 (which is held together by the clamps 200 and 300) which holds the inner sleeve sections together. 
     The retrofit coupling 400 is used as follows: the existing (e.g., prior art) coupling (not shown) serving to connect the two conduits 22 and 24 is cut off or otherwise removed from the two adjacent ends 24A and 22B without disconnecting or interfering with the cable 26 passing therethrough. This action exposes the adjacent threaded ends of the two conduits. The lower section 410 of the inner sleeve 402 is then disposed under the leading conduit 22 so that its threads 412 receive the threads 22B of the conduit 22. In a similar manner the lower section 112 of the outer sleeve 104 is positioned under the conduit 24 and with respect to section 108 so that its threads 104C receive the threads 24A end of the trailing conduit 24. The upper section 408 of the inner sleeve 402 is then put in place in the same manner as the lower section 410 of that sleeve and the upper section 110 of the outer sleeve 104 is then put in place of the same manner as the lower section 112 of the outer sleeve. The upper and lower sections of the outer sleeve 404 are then clamped together by the clamps 200 and 300. This action clamps the inner sleeve sections together, completing the expansion joint between the conduits. 
     Without further elaboration the foregoing will so fully illustrate my invention that others may, by applying current or future knowledge, adopt the same for use under various conditions of service.