Method and apparatus for stretching film or fibrous web

An apparatus for stretching a thermoplastic polymer film or fibrous web, comprising:

• (a) means for feeding the film or fibrous web at a first speed along a longitudinal path;
• (b) a first gripping means including
• (I) at least two first pulleys of substantially the same dimensions disposed radially with respect to a central line along which said longitudinal path extends and rotatable at a peripheral second speed in opposite directions, and
• (II) first endless belt means equal in number to said first pulleys, respectively trained around said first pulleys substantially over a quarter of the full circumference of said first pulleys for gripping the film or fibrous web at at least two laterally spaced first longitudinal portions along at least two first arcuate divergent paths between the peripheries of said first pulleys and said first endless belt means, whereby the film or fibrous web is stretched upon rotation of said first pulleys;
• (c) a second gripping means including
• (I) second pulleys of substantially the same dimensions, the second pulleys being equal in number to said first pulleys and respectively disposed downstream of and close to said first pulleys in coplanar relation thereto and rotatable at a peripheral third speed in directions opposite to those of the respective first pulleys;
• (II) second endless belt means equal in number to the second pulleys, respectively trained around said second pulleys substantially over a quarter of their full circumferences for gripping the film or fibrous web at two laterally spaced second longitudinal portions adjacent to said first longitudinal portions along at least two second arcuate divergent paths between the peripheries of said second pulleys and said second endless belt means, said second arcuate divergent paths being contiguous to said first arcuate divergent paths, whereby the film or fibrous web is further stretched upon rotation of said second pulleys and whereby said film or web is stretched while moving only in one direction wherein said first endless belt means are also trained around said second pulleys along said second arcuate divergent paths, said second endless belt means are also trained around said first pulleys along said first arcuate divergent paths, each of said first and second pulleys includes at least two pulley members rotatable independently with respect to one another, each said first endless belt means is trained around one of said pulley members of each of said first and second pulleys, and each said second endless belt means is trained around the other pulley member of each of said first and second pulleys in parallel relation to said first endless belt means,
• (d) means for conditioning the film or fibrous web to a state suitable for stretching during the stretching thereof;
• and
• (e) means for withdrawing the stretched film or fibrous web.

An apparatus for stretching a thermoplastic polymer film or fibrous web, comprising:

• (a) means for feeding the film or fibrous web at a first speed along a longitudinal path;
• (b) a first gripping means including
• (I) at least two first pulleys of substantially the same dimensions disposed radially with respect to a central line along which said longitudinal path extends and rotatable at a peripheral second speed in opposite directions, and
• (II) first endless belt means equal in number to said first pulleys, respectively trained around said first pulleys substantially over a quarter of the full circumference of said first pulleys for gripping the film or fibrous web at at least two laterally spaced first longitudinal portions along at least two first arcuate divergent paths between the peripheries of said first pulleys and said first endless belt means, whereby the film or fibrous web is stretched upon rotation of said first pulleys;
• (c) a second gripping means including
• (I) second pulleys of substantially the same dimensions, the second pulleys being equal in number to said first pulleys and respectively disposed downstream of and close to said first pulleys in coplanar relation thereto and rotatable at a peripheral third speed in directions opposite to those of the respective first pulleys;
• (II) second endless belt means equal in number to the second pulleys, respectively trained around said second pulleys substantially over a quarter of their full circumferences for gripping the film or fibrous web at two laterally spaced second longitudinal portions adjacent to said first longitudinal portions along at least two second arcuate divergent paths between the peripheries of said second pulleys and said second endless belt means, said second arcuate divergent paths being contiguous to said first arcuate divergent paths, whereby the film or fibrous web is further stretched upon rotation of second pulleys and whereby said film or web is stretched while moving only in one direction wherein said first endless belt means are also trained around said second pulleys along said second arcuate divergent paths, said second endless belt means are also trained around said first pulleys along said first arcuate divergent paths, said first and second endless belt means having respective running paths including portions extending contiguous to and downstream of second arcuate divergent paths in parallel relation to said center line.