| 摘要 |
1526477 Seaming non-metallic sheet material; making bags FMC CORP 24 Sept 1976 [19 Nov 1975] 39664/76 Headings B5K and B5D A sealing head assembly 10 for a bag-making machine 12 comprises two opposed sealing heads 60, 62 movable relatively towards and away from one another to form a seal in a web W passing through the assembly and means operable on completion of a seal in the web W to move the head 62 generally in the direction of movement of the web. As shown, draw rolls 14, 16 intermittently feed the web W of flattened tubular thermosealable material through the machine 12. The roll 16 is driven from a main shaft 18 through a crank arm 19, an oscillating gear segment and pinion drive assembly 20, a clutch-brake assembly 22 and a chain drive 24. The assembly 22 is timed such that the web W is advanced only during 180 degrees of rotation of the shaft 18 and during the other 180 degrees. The web is clamped between the rolls 14, 16. Upper and lower series of fingers 26 disposed in annular grooves 28 in the rolls 14, 16 guide the web to a sealing and severing station 30 downstream of which pick-off rolls 32, 34 are provided. The roll 34 is driven from the shaft 18 by a chain or belt drive 38 and the roll 32 is mounted on levers 40 pivoted on a shaft 42 having secured thereto an arm 48 carrying a follower 46 urged by a spring 51 into contact with a cam 44 on a shaft 49 driven from the shaft 18 by a chain or belt drive 50. After each movement of the web W, the roll 32 is moved downwardly from the broken line position to the full line position to tension the web during severance thereof. At the station 30, the head 60 comprises a sealing surface (64), Fig. 2 (not shown), upstream of a knife (66), the surface and the knife being heated by electrical elements 68, Fig. 1. The head 60 is vertically reciprocable by the engagement of followers 74 on rods 72 secured to the head 60 with cams 70 on the shaft 18. The head 62 comprises a seal bar 76 heated electrically by elements 68 and supported on a body 82 rockable about a shaft 84 to which is connected a lever 86 connected by a link 98 to a push rod 94 carrying a follower 100 urged against a cam 90 on the shaft 49 by a spring 102. After a sealing operation, immediately prior to the start of a fresh bag advancing cycle, a lobe 104 rocks the head 62 in the web feed direction, while the web W is still clamped between the rolls 14, 16, to strip the web from the head 62. Although there is an arcuate component of movement, the sealing surface of the head 62 moves substantially parallel to the path of the web W. Strips of polytetrafluoroethylene impregnated glass cloth may be disposed over the sealing surfaces of both heads 60, 62. |
