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A joint is provided that automatically pre-tensions itself during assembly. The joint includes first and second structural members, such as a back upright and a pivot link in a chair. A torsion spring bushing and a pair of threaded anchors pivotally connect the first structural member to the second

A joint is provided that automatically pre-tensions itself during assembly. The joint includes first and second structural members, such as a back upright and a pivot link in a chair. A torsion spring bushing and a pair of threaded anchors pivotally connect the first structural member to the second structural member. The anchor and back upright include mating angled surfaces that inter-engage and rotate the torsion spring bushing during assembly in a manner that pre-tensions the spring bushing while engaging the anchors in a direction parallel an axis of rotation defined by the joint.

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A joint is provided that automatically pre-tensions itself during assembly. The joint includes first and second structural members, such as a back upright and a pivot link in a chair. A torsion spring bushing and a pair of threaded anchors pivotally connect the first structural member to the second

A joint is provided that automatically pre-tensions itself during assembly. The joint includes first and second structural members, such as a back upright and a pivot link in a chair. A torsion spring bushing and a pair of threaded anchors pivotally connect the first structural member to the second structural member. The anchor and back upright include mating angled surfaces that inter-engage and rotate the torsion spring bushing during assembly in a manner that pre-tensions the spring bushing while engaging the anchors in a direction parallel an axis of rotation defined by the joint. ported by said insertion seats. 4. The shrinkage device of claim 3, further comprising: connection pieces arranged on an underside of said turntable, each of said connection pieces being arranged in flow communication with said guiding grooves of a respective one of said insertion seats; a cooling fan for generating a flow of cooling air; and a plate defining cooling air outlets through which cooling air generated by said cooling fan flows into said connection pieces, said cooling air outlets being situated in association with only said connection pieces associated with said insertion seats away from said induction coil. 5. The shrinkage device of claim 3, wherein said insertion seats each include a recessed, offset shoulder, further comprising an adapter ring arranged on each said shoulders, said tension chucks being arranged on said adapter rings. 6. The shrinkage device of claim 5, wherein said turntable includes recesses each surrounding a respective one of said adapter rings, further comprising air guiding sleeves each arranged in a respective one of said recesses, said air guiding sleeves tapering conically in a direction away from said turntable. 7. The shrinkage device of claim 6, wherein said tension chucks each include an annular flange forming a support for said induction coil, said air guiding sleeves being arranged to terminate below a respective one of said annular flanges. 8. The shrinkage device of claim 1, further comprising: a supporting arm for supporting said induction coil; and a vertically oriented guiding column arranged alongside said turntable, said supporting arm being movable vertically along said guiding column. 9. The shrinkage device of claim 8, further comprising: a cable connected at one end to said supporting arm and running along said guiding column; and a roller arranged at an upper end of said guiding column and over which said cable runs whereby a counterweight arranged in said guiding column is connected to an opposite end of said cable. 10. The shrinkage device of claim 9, further comprising: a first bellows arranged above said supporting arm and around said guiding column; and a second bellows arranged below said supporting arm and around said guiding column, said cable being concealed by at least one of said first and second bellows. 11. The shrinkage device of claim 8, further comprising: supporting legs arranged on said supporting arm around said guiding column and in a substantially horizontal plane, said supporting legs being at least partially elastic; rollers, each of said rollers being arranged on a respective one of said supporting legs and in contact with said guiding column; and set screws for adjusting said supporting legs. 12. The shrinkage device of claim 11, further comprising a molded frame part arranged on said supporting arm and defining an aperture surrounding said guiding column, said frame part being integrally molded with said supporting legs to thereby define slots between said supporting legs and said frame part. 13. The shrinkage device of claim 11, wherein said guiding column has a square cross-section in a horizontal plane and said supporting arm defines a square guiding recess for said guiding column, said supporting legs comprising four supporting legs arranged on a top surface of said supporting arm such that said rollers arranged on said four supporting legs are in contact with four sides of said square guiding column and four supporting legs arranged on a bottom surface of said supporting arm such that said rollers arranged on said four supporting legs are in contact with the four sides of said square guiding column. 14. The shrinkage device of claim 8, wherein said supporting arm comprises a head in which said induction coil is arranged and an outer wall surrounding said head, said outer wall including slots whereby a cooling air flow is directed through said supporting arm and said slots around said induction coil. 15. The