| 摘要 |
557,574. Seaming non-metallic materials: sealing bags. WINGFOOT CORPORATION. June 17, 1942, No. 8303. Convention date, Jan. 14. [Class 42 (i)] [Also in Group XVII] Two or more plies of thermoplastic material are sealed by heat, the seam or seal formed by coalescence between the plies being reduced in thickness during coalescence and the surface thereof sloping gradually into the surface of the unreduced part of the material ; the sealed area may taper off at one or both sides and the sealing may be accomplished by a heated element having a sloping heated surface or by a heated element that is cooler at the edges than at the middle or other edge, or an element combining the sloping surface and the non-uniform temperature may be used. As shown in Fig. 1, the plies are sealed by a jaw 1 pivoted to a support carrying a fixed jaw 2 of resilient material. The jaw 1 comprises an electrically-heated aluminium blade 6 and a block 7 of a material of low heat conductivity, e.g. an asbestos-cement moulded product, the undersurface of the block being shaped so that the bottom of the blade 6 and the portion 8 of the block form a plane parallel to the surface of the jaw 2 when the jaws are brought together while the rest of the bottom of the block slopes away from the portion 8 and terminates in a tip 9 which does not engage the jaw 2. The two plies 10, 11, Fig. 7, placed between the jaws are united by heat and pressure, a depression 13 formed by the block 7 gradually blending at one side into the top surface of the film while an abrupt wall 15 is formed near the edges of the films by the blade 6; in uniting the two plies of a bag the wall 15 would be at the edges of the bag. Since the blade 6 is heated, the temperature of the block 7 is graduated, a notch 18 aiding radiation and lowering the temperature of the tip 9, so that a difference of at least 100‹F. and preferably 250‹F. is obtained between the temperatures of the blade 6 and tip 9 ; consequently the jaws need not slope away from one another. The block 7 may have an extension projecting under the blade so that the latter does not contact with the films, a block may be fixed to each side of the blade, or the heated element may be an aluminium roller flanked on one or both sides by discs of low heat conductivity which have sloping peripheries ; the two latter forms may be used for sealing the centre seam of a bag. |
