Abstract: A back-up pad is provided over an anvil surface of a back-up plate, and between the anvil surface and a sealing surface of a sealing die, in an apparatus for forming seals between layers of film material. The back-up pad has a slip surface on one side thereof and a spring surface on an opposite side thereof, the slip surface opposing the sealing face of the die so that the layers of film material pass between the sealing die and the back-up pad during seal formation. The spring surface is comprised of a plurality of outwardly extending resilient spring loops that act against the back-up plate during seal formation, the spring loops resiliently urging the layers of film material against the sealing face to effect seal formation between the film layers while cushioning the film layers to prevent damage to the film layers due to drag between layers and the die face.

Abstract: An improved apparatus and method for providing uniform fin-type back seals with flexible packaging material for use in conjunction with form-fill-and-seal machines is disclosed which utilizes a moveable tucker plate disposed between the mated edges of the flexible packaging material and the body of the packaging material. When sealing, the tucker plate moves against the body of the packaging material and prevents lateral movement of such material during the sealing operation. The tucker plate is joined to a sealing platen in a manner which maintains a fixed distance between the tucker plate and the sealing platen until a threshold sealing pressure is exceeded.