The invention concerns a hoop-casing device for hooping an object with a heat-sealable plastic strip placed around it.
Hoop-casing devices of the type mentioned above are multiply known, for instance from EP-0744342. They comprise a tool part and a counter-bearing part, the counter-bearing surfaces of which face each other and match each other and have a structure similar to a toothing to be able to grip the plastic strip as efficiently as possible during tensioning and friction-sealing.
In this context it is a drawback that it is work-expensive and costly to manufacture the desired structure similar to a toothing on the concave counter-bearing surface of the counter-bearing part.
The object of the invention is to provide a hoop-casing device of the relevant generic type that does not have the above mentioned drawback.
According to the invention said object is attained in a hoop-casing device of the relevant generic type by providing a hoop-casing device for hooping an object with a heat-sealable plastic strip placed around the object; the hoop-casing device comprising a unit for tensioning the strip and for friction-sealing two overlapping strip parts of the tensioned strip; the unit comprising a tool part that can be rotatably driven about a rotation axis and having a generally cylindrical tool mantle surface, the unit further comprising a counter-bearing part having a counter-bearing surface facing the tool part and extending over a sector of the tool mantle surface and generally enclosing said sector; at least the counter-bearing surface of the counter-bearing part having a structure similar to toothing; the tool part and the counter-bearing part being mutually pivotable about a swivel axis that is parallel to the rotation axis to grip or release the overlapping strip parts between the counter-bearing surface and the tool mantle surface, characterized in that: the counter-bearing part comprises a multipart shoe made up of holding blocks arranged side by side in angular sequence about the rotation axis; and, the holding blocks having respective outer faces which taken together form an outer face of the shoe as well as the counter-bearing surface of the counter-bearing part.
In this embodiment according to the invention the concave counter-bearing surface of the counter-bearing part is composed of several portions of parts that are arranged side by side, namely, composed of the plurality of outer faces of the holding blocks, which in contrast with the prior art allows rather small areas of the concave counter-bearing surface to be machined individually and the machining costs to be correspondingly reduced.
Advantageous embodiments of the hoop-casing device according to the invention include making the outer faces of the holding blocks essentially planar and rectangular with edges parallel to the rotation axis and swivel axis.
More particularly, it is advantageous to provide that the holding blocks each are provided with an essentially planar and rectangular outer face, the edges of this outer face being parallel to the rotation axis and the swivel axis. Such holding blocks can then be machined economically and at the same time structured with an optimal toothing on one planar outer face. Moreover, when being mounted they are adapted to be arranged side by side and fixed on the shoe in such a way that they end up all located on the mantle surface of a prism having edges essentially parallel to the rotation axis and the swivel axis. Taken together, the holding blocks thus manufactured and mounted make up a counter-bearing surface of the counter-bearing part that approximately matches the generally cylindrical tool mantle surface of the tool part, which, in combination with the optimal toothing, allows the overlapping strip parts inserted therebetween to be well gripped and hold and to be applied high tensioning forces.