Large tyre building mandrel - with positive mechanical radial extensibility for carcass support at any intermediate level of distension

摘要

Tyre building mandrel comprises a drum made of several parallel strips with arcuate surfaces which are each mounted on radial supports engaged by a conic cam. A lead screw can shift the conic cam coaxially relative to the mandre. The lead screw can be stopped to hold the strips at any required position between max. and min. extension. The mandrel surface is covered with a tubular sheath of elastic material to mask the slight discontinuities in between adjacent strips (the discontinuities may be radial, in partially deployed positions, or circumferential, in fully extended position). Esp. suitable for machines for building large tyres, esp. for all-surface use where the tyre construction involves structural and protective bandages at various levels and where the quantities of prodn. of individual tyres of similar but different dias. or forms are relatively small. The positive, mechanical action of the mechanism is more reproducible and more stable than use of hydraulically distended elastic envelopes or pistons. The mandrel dia. may be adjusted to different values as most appropriate during lay-up of individual tyres, to optimise reproducibility of tyre build-up.