Expandable type press plunge (4) comprising two plunge parts, named formation part (8) and expansion part (9), which are axially movable in relation to each other, and in which the expansion part (9) is adapted to provide an expansion of some part of the plunge (4) when said two parts are moved together, and in which the expansion part (9) comprises an expansion disc (19) made of an elastic or deformable material which is cup-formed in its non-operated condition, and in that the formation part (8) is formed with a bottom plate (16) having an upper surface supporting and guiding at least a part of the bottom surface of the expansion disc (19), and in which the outer peripheral surface of the bottom plate (16) is of the same shape and at least the same size as the outer peripheral edge of the expansion disc (19) in its non-operated condition, and whereby the cup-formed expansion disc (19) is more or less flattened and the outer peripheral edge thereof is widened outside the bottom plate (19) when the formation part (8) and the expansion part (9) are moved axially in a direction towards each other.Get more news about Shrinkless Expanding Machine,you can vist our website!
The present invention rebates to an expandable type press . plunge comprising two plunge parts, named formation part and expansion part, which are axially movable in relation to each other, and in which the expansion part is adapted, while moving the parts together, to provide an expansion of some part of the plunge (4).

Said expandable type press plunge is in the first place intended for pressing a lid having upwardly projecting rims to the inner surface of a tubular container while joining, for instance welding together, the lid and the container. The invention is useful for many other purposes whereby it is desired to provide a temporary radial expansion of a plunge, for instance when glue-pressing an inner lid or a similar means in a container tube, when press-forming a part of a tube etc.

The invention has been made especially in connection to high frequence welding of an inner lid in a tubular container, especially a tube having a body of a material which does not absorb high frequence energy, like cardboard, plastic or a similar material, and in which the inner surface of the tube or the outer surface of the lid rim, or both, are formed with a layer of a high frequence receivable material, for instance aluminum, and on said layer a heat weldable layer of material like a suitable plastic, and in which the high frequence receivable layer of material, when being subjected to high frequence currents, is heated so that the outer layer of said weldable material melts and the container parts are welded together.

Although it is stated that the invention is useful in many technical fields and for many different purposes, the invention will in the following mainly be described with reference to weld joining of a lid in a tubular container.

For providing such a pressing together of the lid rim and the inner surface of the container that the container becomes liquid proof, and even gas proof, it is known to use a radially expandable plunge, which is expanded when the high frequence current is connected, so that the two parts of material are pressed together with a predetermined pressure until the high frequence current is disconnected or the weldable layer or layers of material have solidified and become cool enough to give a sealed joint. In many cases the lid is shaped from a plane lid blank which is pressed through a formation ring provided just above the container tube and is moved directly down in the open end of the container tube, preferably by means of the same expandable press plunge as mentioned above.
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In similar connections a plunge of the type shown in the US patent 2,423,965 (J. Coyle) or in applicant's Swedish patent 8302841-5 (= US 4,640,733) has been used.