Expandable Insert for Belling Plastic Tubes

to create an annular groove on heat-softened end of a tube.
The insert ring consists of orange and blue inserts.
Each insert belongs to a parallelogram mechanism, the base of which (yellow or green sliders) can move axially. Springs that tend to turn violet bars forwards are not shown.
When the sliders move backwards, the inserts move inwards under the spring action.
When the sliders move forwards, the front violet bars collide with the front disk (in white) and move the inserts outwards, to set the inserts into a complete ring.
To hide the insert ring, the yellow slider moves backwards before the green one.
To expand the insert ring, the green slider moves forwards before the yellow one.

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