Abstract An arrangement is provided for forming the longitudinal seal or seam of a packaging tube by inward clamping movement of a heated sealing shoe and a backup shoe with equal and diametrically opposite force on opposite sides of the coaxial internal form or filling tube about which the packaging tube is formed or positioned. The pressing engagement of the sealing shoe against the overlapped edges of the film assures a uniform and secure seam and the backup shoe prevents misalignment of the depending filling tube by counteracting the pressing force. The opposite acting shoes are mounted on pivotal arms with 2:1 mechanical advantage gained by the fluid cylinder actuator that interconnects the free ends of the arms. Each pivot lies in a separate plane contiguous with the respective area of shoe engagement with the film on the filling tube to assure radial or straight-in movement; the two planes thus being substantially parallel. The pivotal mounting arms are biased outwardly away from the tube and adjustable stop means is provided to assure equal withdrawal distance of the shoes. The biasing spring is on the backup arm so as to assure that nominal engagement of the sealing shoe precedes the backup shoe and that the engagement is gradual by virtue of the spring force, whereby the sealing shoe has a firm grip or seat on the overlapped edges of the film before sealing pressure is applied.
The seamer of claim 1 wherein said first and second mounting means for said shoes are carried by pivot means extending parallel to said form means, said pivot means being positioned so as to be spaced from said moving means whereby clamp action is utilized for pressing the film against said form means.
Claim 2
Dependent Claim
83 words
The seamer of claim 2 wherein said first and second mounting means further comprises first and second arms extending from said pivot means and transversely with respect to said tube, said moving means being carried by the free end of one of said arms on the side of said tube opposite said pivot means and the operating member being connected to the adjacent free end of the other of said arms, whereby operating leverage is obtained for pressing said shoes against the film.
Claim 3
Dependent Claim
62 words
The seamer of claim 2 wherein said pivot means comprises first and second pivots spaced from each other, said pivots being positioned so that planes passing through each pivot and contiguous with the film in the area of engagement with the respective shoes are parallel, whereby the movement of said shoes at the point of engagement is substantially radial during pressure application.
Claim 4
Dependent Claim
68 words
The seamer of claim 1 wherein biasing means is provided on said second mounting means to positively urge the attached backup shoe away from said tube, whereby to assure gradual engagement and a firm seat of said sealing shoe by the spring force prior to pressing engagement by said shoes, the spring force of said biasing means in the extended position being insufficient to misalign said form means.
Claim 5
Dependent Claim
43 words
The seamer of claim 5 wherein is further provided an adjustable stop to limit the opening movement of said second mounting means whereby the shoes may be positioned at substantially equal distance from said tubes to assure unimpeded drawing-out movement of said film.