Apparatus for welding sheets (3a,3b) of themoplastic material together along proximate edges including a supporting frame (25), a pair of joining rollers (11,13) mounted on the frame and forming a nip (12) with an axis parallel to the axes of the rollers, a motor (23) to drive at least one of the rollers, a horn (15) having a tip (17), and an ultrasonic transducer (39) to reciprocate the horn (15) and tip (17) in the direction of the longitudinal axis of the horn (15), the horn being so positioned in the nip (12) that the tip reciprocates in a direction transverse to the axis of the nip (12), so that proximate edges of the sheets (3a,3b) may move through the nip (12) with one edge on each side of the tip (17), be uniformly melted on their surfaces by frictional energy created by the reciprocal motion of the tip (17), and then be pressed and welded together in the nip (12). Fault detection circuitry stops the operation if the sheet material is not properly overlapping or if it runs out.

An integral thermoplastic sheet being formed of a plurality of separate sheets welded together in a longitudinal seam along their edges, the seam having been formed by the melting together of the inner surfaces of the separate sheets and being of uniform welded strength in a direction across the seam in a direction transverse to the longitudinal direction of the seam.

Sealing rollers (23, 24, 25) serve for connecting tear-open strips with a film web (10) by applying heat and pressure, the sealing rollers (23, 24, 25) resting against the film web (10) in the region of the tear-open strips. Opposite of the sealing rollers (23, 24, 25) there are positioned counter rollers which make it possible to transfer pressure by means of the sealing rollers (23 to 25). The sealing rollers (23 to 25) are heated, specifically by radiant heat from a heated housing (31), which serves as a carrier for the sealing rollers (23, 24, 25).

The present invention provides a hot air welding apparatus that provides accurate and repeatable control of the drive wheel speed. To afford very precise control of the speed and relative rotation of the drive wheels at all times during the welding process, the present invention is provided with a computer control system and two high torque stepper motors, one for each drive wheel. The computer control system allows the speed and position of the drive wheels to be regulated with a very high accuracy. The computer control system allows the drive wheel settings to be adjusted while the seam is being welded and further includes an automatic ramp capability, a repeat mode, and a test strip mode. Further, the computer control system is capable of controlling the temperature of the air used in the welding process.

The present invention provides a hot air welding apparatus that provides accurate and repeatable control of the drive wheel speed. To afford very precise control of the speed and the relative rotation of the drive wheels at all times during the welding process, the present invention is provided with a computer control system and two high torque stepper motors, one for each drive wheel. The computer control system allows the speed and position of the drive wheels to be regulated with a very high accuracy. The computer control system allows the drive wheel settings to be adjusted while the seam is being welded and further includes an automatic ramp capability, a repeat mode, and a test strip mode. Further, the computer control system is capable of controlling the temperature of the air used in the welding process. The present invention further provides methods of joining pieces of fabric, films and extruded materials without using traditional sewing techniques and further provides products seamed by such methods.