Method and apparatus for making elongated articles having sheathed foam insulation
TECHNICAL FIELD 
     This invention relates to elongated foam insulation and foam insulated articles, the insulation being seamlessly sheathed. The invention has application in various fields, one being providing insulated bundles of flexible tubes which conduct refrigerated liquids used for mixing drinks (for example, soda and water) from storage sources to bars at which they are disposed. 
     BACKGROUND ART 
     Elongated articles of various types are commonly covered with foam insulation, which may be pre-foamed or foamed-in-place. For some uses, it is important to sheath the foam from external effects, for example, to prevent absorption of water, deterioration or abrasion. One example is in the insulation of bundles of flexible tubes utilized to conduct liquids such as soda and water from remote refrigerated storage sources to be dispensed at bars. Such bundles of tubing, which must be flexible, sometimes have been bound by spiral wrappings, then insulated with preformed foam insulation, and then covered with an outer spiral wrap. However, such spiral wrapping may not protect reliably, especially because of flexing of the bundle. 
     Rigid pipes have also been covered with foam sealed by an outer sheathing of plastic film. For example, in U.S. Pat. No. 4,134,782 to Straughan, a foam generator supplies foaming plastic material to the exterior of a pipe which is then covered by a wrapping of plastic film applied in a longitudinal ribbon with an overlapped longitudinal seam. A somewhat similar process is shown in U.S. Pat. No. 3,754,064 to Snelling, in which both the interior and exterior longitudinal sheathing is applied, each with an overlapped longitudinal seam. Likewise, for insulating pipe, spiral wraps of sheathing have been applied, as in U.S. Pat. No. 4,094,715  to Henderson and U.S. Pat. No. 3,941,531 to 
     While each of these utilizations involves covering an elongated article, a need exists also for providing elongated hollow foam sections, as for ducts to conserve heat energy; and in this instance, both the inner and outer surfaces of such ducts may require sheathings. 
     DISCLOSURE OF THE INVENTION 
     In the method of the present invention, at least an outer seamless tubular flexible sheathing is stored on the upstream or loading portion of the outer surface of a tubular sleeve, supported at its downstream end on a longitudinal axis along which the sleeve is positionable relative to a work support guide or core. The upstream end of the sheathing is attached to a slide member, mounted concentric with the guide or core, when the sleeve is positioned downstream relative to it. Drawing the slide downstream relative to the mouth of the sleeve (or in most applications, initially moving the sleeve upstream relative to the core) reverses the upstream end of the sheathing and draws it downstream into the mouth of the sleeve. Thereafter as foam is introduced into the mouth of the sleeve, the foam presses against the sleeve inner surface now covered by the reversed sheathing, which slides readily against the inner surface of the sleeve. When the article so formed with foam and exterior sheathing leaves the downstream end of the sleeve, the pressure within the foam extends the seamless sheathing to its full extent, providing a smooth covering for the foam. The operation continues until a desired length of material has been formed. 
     In those preferred applications of the present invention where a seamless inner sheathing is also used, this is likewise stored bunched, in this instance on the portion of the outer surface of the guiding core which extends cantilever downstream from its upstream end. The slide member, which slides along the core, in this instance slides atop the inner sheathing, which is reversed and brought back over the forward end of the slide and there clamped to the upstream end of the outer sheathing. In the typical case where the sheathed insulation is to be provided about a pre-formed article, such as a bundle of tubing, this tubing is inserted into the upstream end of the hollow core, to be drawn through its interior as the inner sheathing is drawn along the exterior surface of the core; an inner-connected cable harness arrangement may be used to do this. The plastic foam material, expanding as it emerges from the downstream end of the tubular core, then presses the inner sheathing inward against the tubing bundle, filling the spaces between the tubes along the outer side of the bundle. 
     In the preferred embodiment, the foam is provided between the core and the sleeve by a conventional generator of foaming plastic material. However, a pre-foamed insulating ribbon, of sufficient width to wrap around the core, may instead be applied, clamped at its downstream end between such inner and outer sheathings and drawn into the mouth or upstream end of the sleeve simultaneously withdrawing a bundle of tubes through the core. 
     If a hollow section of insulation material is to be formed, the foam (in this case preferably generated at the site and applied as a liquid in the annular space between the sleeve and the core) is so supplied between the inner and outer sheathings without any pre-formed elongated article being utilized; the foam will then emerge solidified in a seamlessly sheathed duct-like section. For this use the interior sheathing may be of great importance. At the opposite end of the scale of uses, the inner sheathing is not used if a rigid pipe is to be coated. Such a pipe may be inserted through a mere guide, without any inner sheathing and its downstream end connected directly to the outer sheathing and drawn downstream with it as foam is generated around it. Together they emerge from the downstream end of the sleeve as an insulated seamlessly sheathed rigid article. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side view, partially schematic, of apparatus embodying the present invention, with a mold sleeve shown in a downstream loading position. 
     FIG. 2 is a fragmentary view similar to FIG. 1 showing the mold sleeve moved upstream to a sheath-joining position. 
     FIG. 3 is an enlarged fragmentary view of the center portion of FIG. 2, showing a connection outward of a hollow mandrel or core for connecting the ends of an outer sheathing. Inside the mandrel is shown the connection which clamps the end of a tube to be covered with foam insulation. 
     FIG. 4 is a cross-section taken along line 4--4 of FIG. 3. 
     FIG. 5 is a view similar to FIG. 3 showing the mold sleeve moved to the farthest upstream position for foaming, with a foam nozzle inserted into its upstream end. 
     FIG. 6 is a cross-section taken along line 6--6 of FIG. 5. 
     FIG. 7 is an enlarged view showing a sheathed foamed article emerging from the tubular core and from the downstream end of the mold sleeve. 
     FIG. 8 is a cross-sectional view taken along line 8--8 of FIG. 7, also showing a structural support for sliding the mold sleeve axially. 
     FIG. 9 is a cross-sectional view of the completed foam-insulated article as seen along line 9--9 of FIG. 7. 
    
    
     BEST MODES FOR CARRYING OUT THE INVENTION 
     Prior to describing the preferred process of the present invention the preferred apparatus, shown in the drawings, will be described. 
     Elongated base means generally designated 10 may be of any familiar simple construction such as a simple rigid square frame tube 11, shown in FIG. 8, and cross-braced legs 12. The base means so provided may be any convenient length, say 20 feet. Close to its upstream end is positioned a reel rack 13 illustrated schematically, bearing a plurality of reels 14 carrying the flexible tubing to be insulated; in the embodiment shown seven such reels are to be provided. The tubing 15 drawn from the reels 14 passes through a gathering eye 16 which may be carried by and project upward from the frame tube 11, gathering the tubes 15 together on the longitudinal axis 20 along which the process of the invention is performed. 
     Adjacent to the eye 16, welded on to the frame tube 11, is the support 21 for an elongated tubular mandrel or core 22. The core 22 is of heavy rigid steel tubing, cantilever-supported by the support 21 and projecting downstream concentric with the axis 20 a useful distance, say 15 feet, to its downstream end 23. On an intermediate portion, starting from the support 21 and extending downstream, the outer surface 24 of the core 22 has an uninterrupted cylindrical surface, the portion adjacent to the support 21 being referred to as the core outer loading surface 25. This is used for loading a length of inner flexible seamless sheathing, hereinafter referred to. 
     Extending along the sides of the frame tube 11 upstream from near its downstream end at least to a point near the core outer loading surface 25, and supported by sideward-extending lugs 27, are guide rods or ways 28. On these ways are mounted the longitudinally-bored mold sleeve slide mount blocks 29, which are welded to and support the downstream end 30 of an elongated mold sleeve generally designated 31. From the sleeve downstream end 30, so supported, the mold sleeve 31 extends upstream concentric with the axis 20 and spaced outward of the elongated core 22. This upstream portion of the mold sleeve 31 has a smooth uninterrupted outer cylindrical surface which is referred to as the outer loading surface 32; this terminates in a smoothly rounded edge at the inlet end 33. 
     Positioned a substantial distance, say 40 feet or more, from the downstream end of the frame tube 11 is a support 34 for controlled tension-exerting means, such as an electric winch designated 35 having a cable-like connector 36 which it draws downstream along the machine axis 20. 
     Conventional apparatus for generating an insulating foam is shown in the block marked foam generator 40. When operated in the conventional manner, a foamable plastic such as polyurethane will be generated and distributed through the flexible hose 41 to a nozzle 42 which, for loading, is readily movable out of the way but in operation is inserted in the inlet end 33 of the mold sleeve as shown in FIG. 5. 
     For advancing the tubing 15 through the gathering eye 16 and the core 22, tension of the connector cable 36 is applied through a pair of diagonal connectors 44 to a tube clamp 45. As best seen in FIGS. 4 and 5, the tube clamp 45 is smaller than the inside diameter of the core 22. In order to apply it, the connector cable 36 may be passed through and out the upstream end of the core 22, just downstream of the gathering eye 16 shown in FIG. 1; the clamp 45 is then applied to the ends of the several pieces of tubing 15, drawing them together as shown in FIGS. 4 and 5; after which the winch 35 draws the cable 36 and its attached diagonal connectors 45 downstream to a point within the core 22 a convenient amount, preferably somewhat past the position of the foam nozzle 42 as seen in FIG. 1. 
     It is additionally necessary to load the machine with the material which will serve as inner and outer seamless sheathings for the insulations. With the mold sleeve 31 in its downstream or loading position, as shown in FIG. 1, a length of seamless tubular flexible plastic sheathing material, such as polyethylene, whose tubing diameter is slightly greater than the outer diameter of the sleeve 31, is applied on its upstream end 32. As may be seen, the entire surface of the sleeve 31 upstream of its cantilever support by the mount blocks 29 is available for loading this material; accordingly, 50 feet or so of the material 48, so bunched, may be loaded in place. 
     Likewise, a similar length of seamless tubular inner sheathing material 50 is loaded on the outer loading surface 25 of the core 22, starting at its downstream end for bunching the material upstream adjacent to the welded core support 21. The inner sheathing 50 is sufficiently great to permit it to be bunched on the outer surface of the core 21. 
     The downstream end of the inner sheathing material 50 and the upstream end of the outer sheathing material 48 are then joined to each other in the following manner: the downstream end of the inner sheathing material 50 is drawn smoothly downstream along the outer surface of the core 22 as shown in FIG. 4, and a slide mount 52 is applied over the upper surface of the end portion so drawn, and is then drawn back aft over two forward end mount lugs 53 which penetrate it. The aft portion of the slide mount 52 mounts a foam stop ring 55, whose outer diameter is nearly as great as the inner diameter of the mold sleeve 31, leaving an annular space along the forward portion of the outer surface of the slide mount 52. A pair of slide mount cables 57 are connected to the mount lugs 53; these extend downstream as shown in FIG. 3 and are joined at their forward ends by small ring 60, as seen in FIG. 1, positioned slightly downstream from a stop 62 affixed to the cable connector 36 which passes along the longitudinal axis 20. As a result, drawing the cable connector 36 downstream will present the stop 62 against the ring 60, these portions then serving as means to innerconnect and coordinate downstream movement of the cable connector 36 with the slide mount cables 57. 
     After the slide mount cables 57 are so connected, the upstream end of the outer sheathing 48 is drawn upstream over the slide mount 52, and there clamped to the downstream end of the inner sheathing 50 by a clamp ring 64, having a conventional clamp tightening provision. 
     The mold sleeve 31 is then moved upstream to the foaming position shown in FIG. 5. The movement from the loading position, FIG. 3, to the foaming position, FIG. 5, has the following unusual consequence: the attendant axial change feeds the upstream end of the outer sheathing 48 reversibly around the inlet end surface 33 of the mold sleeve 31 and into its upstream end 32. Hence, as seen in FIG. 5, downstream movement of the cable 36, following contact of the stop 62 with the ring 60, will draw the bundles of tubing 15 downstream inside the core 22 while it draws the outer and inner sheathings 48, 50 simultaneously downstream in the annular space between the outer surface of the core 22 and the inner surface of the sleeve 31, the sheathings 48, 50 being maintained separate from each other by the foam stop ring 55. 
     After these preliminary steps of loading the outer and inner sheathings 48, 50, passing the leading ends of a bundle of tubes 15 into the tubular core, joining the downstream end of the inner sheathing 50 and the upstream end of the outer sheathing 48, and effecting an interconnection with the leading ends of the tubing 15, and then moving the mold sleeve 31 axially relative to the core 22 so that the core projects into the mold sleeve as shown in FIG. 5, the following operative steps are then performed: 
     With the foam nozzle 42 positioned to feed an expanding foaming plastic from the foam generator 40 into the annular space at the inlet end 33 of the mold sleeve 31, between the outer and inner sheathings 48, 50, the foam is generated and supplied as the winch 35 draws the connector cable 36 downstream at a controlled rate coordinated with the rate of foam supply. Foaming plastic material so fed expands behind the annular foam stop 55, which holds the sheathings separate from each other. As the foam expands, it presses the inner and outer sheathings 50, 48 respectively against the outer surface of the core 22 and the inner surface of the mold sleeve 31. The sheathing material slides smoothly against these surfaces, whereas in its absence the foam would adhere to them. The pressure generated in the foam causes it to distribute itself substantially evenly within the annular space between the core 22 and sleeve 31. As the assembly progresses toward the downstream end of the core 22, the arrangement of the tubing 15 within the core 22, the inner sheathing 50 against its outer surface, the outer sheathing 48 within the inner surface of the sleeve 31, and the foamed plastic layer 65 between the two sheathings, is as shown in FIG. 6. 
     With the foam layer 65 still expanding, the article so being foamed is drawn outward from the downstream ends of the core 22 and sleeve 31, as shown in FIG. 7. Assuming the downstream end of the core 22 terminates prior to the termination of the sleeve 31 (which is a matter of designer&#39;s choice), the foaming plastic will then press inward, forcing the inner sheathing 50 into the spaces between the outer surface of the bundle of tubing 15 in the undulated manner shown in the cross-section FIG. 8. This inward expansion may proceed to take up all slack in the inner sheathing 50. As the foam covered article then exits from the downstream end of the sleeve 31, the residual pressure in the foam plastic layer 65 expands the foam to take up the slack in the outer sheathing 48, extending it to its full diameter as shown in FIG. 7 and in the cross-section FIG. 9. 
     If a hollow article such as a section of plastic duct is to be formed, with seamless sheathing on its inner and outer sides, the same apparatus may be utilized. For this purpose there is no need for the tube clamp 45 and cables 44; the core 22 could be solid rather than hollow. 
     Further, for covering a pre-formed pipe or rod with a foam plastic having an outer seamless sheath, the rigidity of the pipe or rod might permit the core 22 to be reduced greatly in length, so that where the article was of sufficient rigidity, a mere guide at the upstream or inlet end 33 of the sleeve 31 may suffice to hold it concentric along the axis 20. The outer sheathing upstream end may be attached directly to the end of the pipe to be so insulated. 
     Should an insulating ribbon of pre-formed elastic foam material be desired to be utilized, instead of the type of chemical plastic which foams in place, this may be done as follows: by wrapping the end of the foam ribbon about the downstream end of the inner sheathing 50 and clamping it, along with the outer sheathing 48, on to the slide mount 52. Then, drawing the clamped ends into the sleeve 31 will itself compress the pre-formed foam without provision of an annular space outwardly of a mandrel or core. For this application, the core itself need not extend into the mouth of the pre-formed foam against the bundle of tubing, and its elastic compression will itself assure substantial concentricity. Hence, for the use of a pre-formed foam ribbon, whose side edges are to be abutted longitudinally around the tubes through the bundle of tubing 15 drawn through the sleeve, it is preferred that the sleeve 31 be positioned axially slightly downstream from the downstream end of the core 22, to permit immediate abutting of the longitudinal edges of the preformed foam ribbon as it is drawn from its source into the upstream end 33 of the sleeve 31. 
     INDUSTRIAL APPLICABILITY 
     The principal uses of the present invention, as now contemplated, are: 
     For the specialized use in supplying inward and outward sheathed insulated bundles of tubing for conducting liquids, as well as other elongated articles having a seamless sheathing on the inner side of the insulated covering, as well as on its outer side, 
     For insulating elongated rigid pipes with foam insulation, either rigid or elastic, the foam being seamlessly sheathed on its outer side; and 
     For hollow articles, such as insulating duct sections, sheathed seamlessly on both inner and outer sides.