Oven for preforms

An oven for blowing or stretch-blowing preforms configured to form containers with an oval section, comprising:

• a path for the preforms;
• a plurality of mandrels slidingly carried along the path, the mandrels configured to temporarily engage with the preforms to conduct the preforms along the path wherein each of said mandrels comprises a toothed wheel configured to rotate with the preforms;
• a first heating module at a first position along the path for the preforms and providing heat to the preforms, and a second heating module at a second position along the path for the preforms and providing heat to the preforms, wherein said first heating module is configured to continuously rotate the preforms and to provide a uniform direct heating of an entire side surface of the preforms;
• a toothed belt located at a half of a length of said second heating module within said second heating module along the path for the preforms, the toothed belt being configured to mesh with said toothed wheel, the toothed belt having a quantity of teeth to cause a 180 degree rotation of the toothed wheel and said second heating module is configured to directly heat two opposite portions of the side surface of the preforms to provide differentiated heating of the side surface of the preforms;
• wherein the path for the preforms comprises, at said second heating module, a sliding guide comprising two sides, the two sides defining a slot, and wherein the slot has a widened portion along the sliding guide, in a median position with respect to said second heating module;
• wherein the mandrel comprises a body inside of which a gripping finger for a preform is slidingly inserted, the finger extending along a vertical axis, and wherein an orientation member extends from the body along said vertical axis, in a direction opposite to the gripping finger, said orientation member being configured for engagement and rotation with said gripping finger;
• wherein the orientation member comprises a rod having a first end, which is aligned in rotation with the gripping finger of the mandrel, and a second end to which said toothed wheel is fastened, and wherein a positioning bearing configured to slide in said slot of said sliding guide is pivotally supported on a surface of the toothed wheel facing upwards, the positioning bearing having a rotation axis, a diameter and a radius;
• wherein the positioning bearing has a diameter which is equal to or less than a width of the slot of the sliding guide, and wherein a distance of an axis of the orientation member from the axis of the positioning bearing added to the radius of the bearing is equal to or less than half of a width of a widened portion of the slot, wherein at the widened portion of the slot, the toothed wheel engages the toothed belt and advancement rotates the preform in the widened portion of the slot;
• and
• wherein the orientation member is freely rotatable up to 180°, and rotationally aligned with the gripping finger, by the toothed belt at said widened portion of the slot, and wherein the orientation member and the gripping finger are configured to rotate together in a fixed position along a remaining portion of the slot.