Working with a leading agricultural machinery manufacturer,Busak+Shamban (Trelleborg ?Polypac) engineers were faced withdesigning a seal for a tractor flexure bar that gave betterperformance than an established competitor?s product, to a specifictarget price. Sealing in such equipment presents difficultchallenges.
Not only must the seal function within a rotating shaft, but itis also required to withstand high frequency oscillating movements- up to three degrees. This is combined with a necessity tooperate in harsh conditions, over a broad temperature range (-20°Cto +115°C) and to be compatible with gearbox oil. With space beinglimited, it needed to be compact and easy to assemble in roddiameters of 25, 30 and 35 mm.
Pictures show: TPU P2IR polyurethane material, bonded in ametal cage
Their solution was an innovative design of seal with integratedwiper lips, manufactured in the Busak+Shamban proprietary TPU P2IRpolyurethane material, bonded in a metal cage. A spiral steelspring ensures the wiper lips remain in contact with the rodthroughout the varied bar movements and stops the ingress of dirtand abrasive media into the housing.
Its optimised flexible profile and abrasion resistance, meantthat in long-term testing (over two million life cycles, usingArizona sand, the most abrasive of all test media) the life of theseal was validated at triple that of the customer?s existingproduct. With less components, it was also easier to assemble andmet the cost criteria given.
The seal, known as the Busak+Shamban Tractor Flexure Bar Seal,can also be used in many other off-road and mobile plantapplications, where extended performance life, compact design andeconomy are prerequisites.