Patent GB-739668-A (GB)
Title: Method of making reinforced tubing
IPC: B29C53/78
Filed: 1954-03-23
Abstract: 739,668. Reinforced flexible tubing. MEISSNER, W. E. March 23, 1954, No. 8449/54. Class 99 (2). A flexible tube is formed by helically wrapping a plastic strip into a tubular shape with its edges in contiguity contact or overlapping, guiding a preformed helical reinforcing element longitudinally into position along the contiguous or contacting edges or between the overlapping edges of the strip, coalescing the materials of the edges to the element and then setting the tubular assembly of element and strip. A continuous strip is helically wound about a mandrel and the convolutions are simultaneously advanced axially of the mandrel. As shown in Fig. 1 a plastic strip 20 and a preformed reinforcing element 28 (plastic mono-fil having a greater resiliency and stiffness than the plastic material of the strip 20 or a tempered metallic spring) are wound helically on a mandrel 14. Heat is applied either by heating the element 28 by means of an electrical heating coil or a heat transfer coil 33 or by heating the mandrel 14 or by a nozzle or nozzles 37 supplying heated air or by any two or all of these expedients so that the edges of the plastic strip coalesce with the reinforcing element. The mandrel 14 is heated internally by a heat-transfer medium which may be glycerine or molten salt. A heater 12 is provided such as a helical electrical heating element or a hollow tube or coil for conveying a heat-transfer fluid such as steam. It may extend within the mandrel. A thermosensitive device 13 such as a bimetallic switch is provided. The device 13 may be within the vessel 5 or within one of two semi-cylindrical channels in a stationary member 3 within the mandrel 14. It controls the heating in conventional fashion. It may be connected to the electrical heating element 12. The end 15 of the mandrel may comprise a cap of heatinsulating material. As the formed tubing proceeds downwardly a blast of cool or refrigerated air is supplied by one or more nozzles 38. The plastic strip 20 may be supplied by means of an extrusion apparatus 26 which may extrude a molten mass of plastic material or a solution of plastic material in a volatile solvent the strip being set by evaporation of the solvent. The strip may be warm or hot when it reaches the mandrel. The preformed reinforcing element 28 is supplied by a rotatably mounted tubular receptacle 29 which may support a great length of the element in a straight line. The mandrel 14 may be of somewhat greater diameter than the inside diameter of the preformed element. The inner surface of the feeding belt 23 may be shaped to conform to the shape of the strip 20. The tube may comprise two or more layers of plastic strip material with the reinforcing element embedded therein. The angle of helix of the several layers may be the same or opposite. A plurality of reinforcing elements may be employed with their turns in side-by-side relationship either in contact or spaced apart. In Fig. 3b the element may be partially or completely embedded in the adjacent edges of the plastic strip. The preformed plastic reinforcing element may be tempered or annealed. A lubricant such as glycerine may be supplied by the wick 26a.