Method for producing a link-plate chain

1. A method for producing a strengthened link-plate chain, said method comprising the steps of:

installing a closed link-plate chain about a pair of conical pulleys having parallel axes of rotation that are spaced from each other in a longitudinal direction of the chain, the chain having a plurality of link plates interconnected by rocker pressure pieces, wherein the link plates each have a single link plate opening within which opening two pairs of rocker pressure pieces having the same cross-sectional form are received, each pair of rocker pressure pieces spaced from the other pair in the chain longitudinal direction and each surface of the rocker pressure pieces that extends transversely relative to the longitudinal direction of the chain is convexly curved so that the contacting surfaces of the rocker pressure pieces of each rocker pressure piece pair are convexly curved, and wherein the chain passes around each of the conical pulleys and travels in a direct linear path from one conical pulley to the other conical pulley of the pair of spaced conical pulleys;

applying in a longitudinal direction of the chain as the chain is in a continuous longitudinally straightened condition extending between the conical pulleys a first stretching force to the chain by moving the axes of rotation of the conical pulleys away from each other in a longitudinal direction of the chain while one of the conical pulleys is driven to rotate in a first direction of rotation to provide in the chain first regions of permanent deformation by plasticization of chain material in the first regions of permanent deformation;

applying in a longitudinal direction of the chain as the chain is in a continuous longitudinally straightened condition extending between the conical pulleys a second stretching force to the chain by moving the axes of rotation of the conical pulleys away from each other in a longitudinal direction of the chain while one of the conical pulleys is driven to rotate in a second direction of rotation that is opposite to the first direction of rotation to provide in the chain second regions of permanent deformation by plasticization of chain material in the second regions of permanent deformation;

whereby longitudinally opposed inner, longitudinally spaced end faces of the link plate openings are subjected to the stretching forces to cause permanent plastic deformation of the longitudinally opposed inner end faces of the link openings;

wherein respective first and second regions of permanent deformation are spaced from each other in a longitudinal direction of the chain, are distributed symmetrically in relation to a link plate center axis, and serve to increase the strength of the chain as compared with a chain not having longitudinally spaced first and second regions of permanent deformation.

2. The method according to claim 1 , wherein after a first stretching process in each direction of rotation of the conical pulleys, the link-plate chain is re-stretched once under rotational speed of the conical pulleys in opposite directions of rotation of the conical pulleys.

3. The method according to claim 1 , wherein the link-plate chain is stretched multiple times in opposite directions of rotation of the conical pulleys.

4. The method according to claim 1 , wherein after a stretching process in the first direction of rotation of the conical pulleys the link-plate chain is re-stretched exactly once in the second direction of rotation and under the same stretching parameters as are applied in the first direction of rotation.

5. A link-plate chain having a plurality of link plates and rocker pressure pieces; the link-plate chain having been produced according to the method of claim 1 , wherein respective ones of at least the link plates and the rocker pressure pieces of the link-plate chain have plasticization regions which are distributed evenly within respective ones of at least one of the link plates and the rocker pressure pieces of the link-plate chain, and are distributed symmetrically in relation to a link plate center axis.

6. The link-plate chain according to claim 5 , wherein the link-plate chain has greater strength than a link-plate chain which has been stretched in only one direction of rotation of the conical pulleys.

7. The link-plate chain according to claim 5 , wherein the link-plate chain has at least one link plate having a projection which extends in a longitudinal direction of the link-plate chain.