| 摘要 |
1,071,042. Seaming non-metallic sheet material. FMC CORPORATION. Jan. 19, 1965 [Feb. 6, 1964], No. 2259/65. Heading B5K. Two portions 11, 12 of stretch oriented polymeric strap are secured together in overlapping face-to-face relationship by melting at least one of the portions 11, 12 in a zone including and immediately adjacent one of the faces thereof but without softening the extremity of the free end portion whilst maintaining the major part of the strap portion in stretch oriented condition, and pressing the melted zone of this strap portion against the other strap portion. As shown, a strap 10 has a free end portion 11 and a portion 12 which either extends to a supply or may be a free end. The portions 11, 12 are held apart, preferably by guide rollers, to abut against elements 13, 14 through channels in which cooling fluid is circulated. The opposed faces of the portions 11, 12 are heated by radiant heat from a thin heating blade 20 which is projected and retracted by a pneumatic cylinder 21 (not shown). When the blade 20 is in its retracted position the end thereof is located between a pair of heating devices 22, 23, Figs. 2 and 3 (both not shown). After softening of the opposed faces, the melted areas are squeezed together by moving the element 13 toward the element 14 or vice versa or moving both elements 13, 14 towards each other. Preferably the melted portion 24, Fig. 4 (not shown), does not extend to the end of the strap. The cooled elements 13, 14 prevent heat from migrating through the strap whilst the pressure thereof is maintained. The strap may contact the heating blade but preferably such direct contact is avoided. The blade 20 may be heated electrically and may be replaced by an element of substantial thickness. Specified polymeric materials are polyolefines, e.g. polypropylene, polyesters, polyamides and acrylic resins. A polypropylene strap, of 0À5 mm. thickness, which softens at about 107‹ C. and melts at about 155‹ C., is heated at about 1À5 mm. from an element at 593-650‹ C. for a few milliseconds so that the inner faces of the strap are melted to a depth of 0À08-0À10 mm. and softened for an additional 0À05-0À08 mm. |
