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Bespoke springs solve seat manoeuvrability problem

25 November 2010

With some 200 years of spring making to its credit, problem solving has become a bit of a speciality for Dorset-based William Hughes. The company’s expertise was recently brought to bear on a particularly urgent auto seat adjustment problem, which was quickly and successfully resolved

Spring maker, William Hughes is no stranger to the demanding automotive sector. Earlier this year, the company developed a special spring for a re-designed seat adjustment mechanism on a model already in production (see DPA June 2010 page 11). Notably, Hughes came up with the solution to this particular problem well within the seat supplier’s timeframe and the efforts of this 200 year-old spring maker were duly noted. So, when the customer needed to make further refinements to the mechanism, William Hughes’ expertise was called upon once more.

The seats in question are fitted to a two-door model, and in order to assist back-seat passenger access, they need to slide forward and the squab (seat back) fold down easily and in an appropriate sequence. The car manufacturer had discovered that its existing seat mechanism was a little too heavy to operate, especially for children and elderly people, and while the first solution from William Hughes worked perfectly, further problems were subsequently identified and the seat maker needed to consider an additional modification.

The challenge was far from straightforward as there were a number of stringent specifications to fulfil. For instance, the special spring has to be out of sight, quiet and smooth in operation, and avoid catch points. Moreover, as the seats could not be modified in themselves, William Hughes’ engineers were limited to the existing holes and edges available within the seat structure.

William Hughes’ team arrived at the seat maker’s European manufacturing site to discover that the latter had already come up with an initial proposal. However, it soon became apparent that this proposed mechanism was not going to overcome the problem. Even though it had been designed on the customer’s CAD system, little consideration had been given to performance measures such as force and movement. Time was now of the essence.

Fortunately, William Hughes was quickly able to assess parameters such as torsion force, track length, fitting space and mounting points, and offer some timely technical advice to its client. As a result of this effort, Hughes was able to modify the design and produce a set of prototype springs overnight. After in-situ testing, further modifications led to a second set of rapidly-manufactured prototypes that provided the perfect solution.

Each spring requires a total of six bends, four at one end and two at the other. Concurrent engineering ensured that the special tooling required to manufacture the prototypes was delivered in a matter of days; they have since successfully completed endurance testing and William Hughes is currently ramping up production.

The actual configuration takes the form of a set of springs that includes right- and left-hand versions. Once assembled, this bespoke spring pair ensures a much improved sliding and folding motion when the seat release lever is activated. These springs enhance, rather than replace, the existing mechanism, and while it does introduce extra material, the solution proved far more economical than the customer’s original proposal.

Manufactured from hard drawn spring steel, the special torsion springs have been designed to fit with minimum effort to the car seat structure without any modification to existing parts, thus ensuring continuity of production.

From its facility at Stalbridge in Dorset, William Hughes is able to liaise closely with customers and develop and manufacture bespoke springs from wire diameters between 0.1 and 5.0mm. The combination of design effort and rapid response is a factor that helps differentiate the company. William Hughes only manufactures proprietary springs – compression, tension and torsion – it has no catalogue and does not make for stock.
 
The company can also offer a range of additional services that includes shot-peening (for extended fatigue life) and the application of corrosion-resistant inorganic coatings. Also on offer are heat treatment services, precipitation hardening, assembly, ultrasonic cleaning and full quality control and inspection of finished parts.


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