Conventional devices for ultrasonic sealing normally consist of a converter, a booster and a horn. In the converter, an electric oscillation is converted into a mechanical oscillation, and the booster is employed to fix the system mechanically and boost the amplitude. In the horn, further amplitude boosting takes place, at the same time as the horn provides the desired sealing surface. These conventional, thoroughly well-tested ultrasonic sealing devices suffer, however, from the disadvantage of being relatively bulky. For certain practical applications, it is desirable to realize an ultrasonic sealing device which requires considerably less space.
Within the packaging industry which deals with packages of the single-use disposable type, it is common to seal laminates with thermoplastic or pure thermoplastic material. These seals are normally carried out using heat or, when the laminate includes an aluminium foil, using induction heat. However, it is desirable to be able to employ ultrasonic sealing, since this method does not require a laminate which includes a metal foil. The conventional ultrasonic sealing devices have, however, proved to be far too bulky.
Small-scale ultrasonic sealing equipment has already been produced. However, these are rotation-symmetric and can only carry out spot-sealing. In the above-outlined application within the packaging industry, it is desirable to carry out transverse sealings of a certain length, i.e. a long and narrow seal.