Abstract: A system for maintaining a desired sealing force is provided, which incorporates a closed loop control system. The system includes a platen, which has a surface for making contact with one or more items to be sealed, a motor for producing a linear movement, a linkage coupled to the platen and the motor for transferring the linear movement produced by the motor to the platen, and a transducer coupled between the linkage and the platen for measuring the force applied to the platen via the linkage through the linear movement of the motor and producing a signal representative of the force measured. A motor controller produces a motor control signal, which is supplied to the motor for controlling the same. The motor control signal is used to control the linear movement produced by the motor. The motor controller further receives the feedback signal from the transducer, and correspondingly adjusts the value of the control signal used to control the magnitude of the linear movement.

Abstract: A system for maintaining a desired sealing force is provided, which incorporates a closed loop control system. The system includes a platen, which has a surface for making contact with one or more items to be sealed, a motor for producing a linear movement, a linkage coupled to the platen and the motor for transferring the linear movement produced by the motor to the platen, and a transducer coupled between the linkage and the platen for measuring the force applied to the platen via the linkage through the linear movement of the motor and producing a signal representative of the force measured. A motor controller produces a motor control signal, which is supplied to the motor for controlling the same. The motor control signal is used to control the linear movement produced by the motor. The motor controller further receives the feedback signal from the transducer, and correspondingly adjusts the value of the control signal used to control the magnitude of the linear movement.

Abstract: In a bag making machine the longitudinal side edges and adjacent portions of an elongate plastic web, which is folded in half medially of its centerline, pass from a set of inlet rolls over and under, respectively, a pair of vertically spaced separating rolls before merging at a set of outlet rolls. The separating arms extend inwardly between the two separated portions of the web only part way toward the fold line, and are spaced apart exactly twice the depth of the gusset that is to be formed.

Abstract: The two separable elements of a conventional plastic zipper are advanced through a zipper guide slot from the inlet to the outlet end of a machine, simultaneously with two sections of a plastic film or web, one section of which overlies one of the zipper elements, and the other section of which overlies the other zipper element. Intermittently two jaws are advanced toward the web sections to squeeze them against opposite sides of the zipper, at which time a pair of registering hot bars that are resiliently mounted on the jaws adjacent the inlet end of the machine fuse each web section to a different one of the two zipper elements. At the same time, a pair of cold bars carried by the jaws adjacent the outlet end of the machine engage and cool portions of web sections which were previously fused to the two zipper elements. Idler rolls inclined to the zipper guide slot retain the folded web tautly over opposite sides of the zipper guide slot.