| 摘要 |
1525340 Belt; rope and chain gearing HERCULES Inc 17 March 1976 [18 March 1975] 10714/76 Heading F2Q [Also in Division B5] A drive mechanism provides a drive of cyclically varying speed for a vacuum forming apparatus which includes a rotatable drum 12 of polygonal cross-section which may carry vacuum forming moulds upon one or more of its flat faces, and in which a continuous sheet 18 of hot web material, emerging at position A from a film extrusion die 10, is fed on to successive faces of the drum 12, where the vacuum forming operation proceeds. The drive mechanism includes a drive pulley or sprocket 14 rotated at constant speed, a belt or chain 20, tangentially reaching pulley 14 at a point C, and an idler wheel 16 which maintains substantially constant tension in the belt 20 as it is driven in engagement with the polygonal contour of the drum 12. Although a square section is here shown for drum 12, it may be of a shallow rectangular form carrying moulds on two faces alone, or it may comprise a regular polygon of any number of faces, rotatable about an axis F. The belt or chain 20 may alternatively engage a separate polygonal pulley or sprocket coaxial with the drum 12. In use, the polygonal drum accepts web on to points Bat agreatestradius FB, Fig. 1, and on to planes of a least radius FD, Fig. 2, and the drive mechanism cyclically varies the drum rotational speed in such a manner as to take up the web at an effectively constant rate, in spite of these changes of radius, thereby matching the surface speed of the drum to a constant rate of extrusion of the web. Alternative layouts of other relative angular dispositions of belt and web are disclosed. |
