| 摘要 |
In an apparatus useful for sealing layers of a web comprised of plastic film lay ers to one another in a bag-making machine, a sealing drum having a cylindrical surf ace is employed. A sealing blanket is deployed about plural blanket rolls and about the sealing drum so that a substantial portion of the cylindrical surface of the sea ling drum is wrapped by the sealing blanket with the wrapping surface facing the cylindric al surface while the remaining portion of the cylindrical surface is not wrapped th ereby at any given time. A nip roll acts together with one of the blanket rolls so as to define a nip. An idle roll is located near the nip. The sealing apparatus is ope rable so that the sealing blanket is drawn through the nip with the wrapping surface f acing the nip roll, so that the web is drawn through the nip, between the nip roll and the wrapping surface of the sealing blanket, then around the idle roll, and then aro und the sealing drum, between the wrapping surface of the sealing blanket and the cylind rical surface of the sealing drum. The nip roll is pressed pneumatically with an adjus table pressure toward the blanket roll acting together with the nip roll, whereby the nip roll controls the tension on the web being drawn through the nip. |
