Patent ID: 6846386

Claim:
A headbox for delivering a jet of stock to a forming zone in a former for wet forming of a fiber web, comprising: a slice having a chamber; a turbulence generator comprising turbulence channels opening into the slice chamber, and at least one anchoring element that separates the turbulence channels, at least one vane arranged in the slice chamber; and an arrangement for detachable mounting of the vane to said anchoring element, said mounting arrangement comprising a plurality of engagement members that are connected to the vane at an upstream end portion thereof, and an elongate structural element having a longitudinal groove for receiving the engagement members of the vane, said groove having inner, parallel, downstream and upstream support walls that face towards said engagement members for cooperation therewith, wherein said plurality of engagement members comprise at least one outer engagement member in the proximity of each side edge of the vane such that an inner area of the upstream end portion of the vane is defined between said outer engagement members, said outer engagement members being arranged during operation for at least one specific period of time as the only engagement members to contact the downstream support wall, such that said inner area of the upstream end portion is arranged to move freely in the machine direction in relation to said downstream support wall during said period of time or part thereof.