Case studies

The development of a single, flat mounted sliding system for armrests

Many adjustable car armrests have, up until now, been mounted on a pair of ball bearing linear slides to give movement through the X plane (open sections facing sideways), which gave them strength and stability under load. Initially Accuride designed solutions for front row occupant armrest slides, which in main consisted of a pair of “cambered” slides (angled together at approx 30 degrees).

Due to the increased influence of styling and marketing in the end product, the vertical package of armrests was gradually reduced to such an extent that the slide angle was virtually flat (approx 10 degrees).

In an effort to simplify the assembly process and cut assembly tolerances associated with aligning two slides, a single flat mounted slide was proposed. This slide was extremely basic in its construction (inner member, outer member, balls and ball retainer) and fell within Accuride’s standard product range. The issues with using this slide were vertical stability under load and movement effort control. The former was solved with the customer adding “outriggers” or “skids” to the armrest mouldings - which supported the armrest both laterally (side-to-side) and vertically (for end load deflection). The movement effort control was resolved with the customer inserting a silicon oil filled rotary damper and rack into the armrest mouldings, thus giving a controlled motion meeting the OEM’s specification.

After the success of the original project the automotive OEM approached Accuride to be a supplier for their follow-on project. This vehicle was to include a sliding armrest with a single flat mounted slide - but cost was critical. This requirement led Accuride to design a new slide profile.

To maintain lateral stability this new slide needed to be about the size of 2 x 35mm slides side by side (flat mounted). However this would not be favourable for any sort of end loading as the wider slide would deform too much along its centreline and fail at relatively low loads. However, in this orientation, standard slides suffer from a reduced strength when considering vertical cantilever forces, such as from an abuse load applied to the end of the bun, and to loads typically caused in crash situations.

To compensate, Accuride designed a new patented ‘Wide Slide’ profile in which the moving components are prevented from separation by an overlapping flange, significantly increasing its overload and crash performance.

The wide section of this new profile allows increased internal package space for additional features such as a rotary damper. The fact that the slide encapsulates this technology means lower resource requirements and less logistical issues for the Tier 1.

Since its conception, the wide slide has been adopted by a number of major OEMs for current and future production. The current production slides only encompass a method of controlling efforts - be it either a silicon rotary damper or a friction damper. Through the use of the Accuride friction damped system it is possible to control, independently, the movement force and detent (positional locator) force consequently giving additional flexibility to the overall functionality and yet again reducing the customers’ handling and assembly costs.

Accuride has continued to develop the wide slide, independently of customer demands, to include features such as spring return and hinge integrated lock- outs. These features allow increased functionality to the end user while maintaining relatively low piece part effect to the Tier 1 or OEM.

Accuride continues to work closely with car manufacturers, interior suppliers and with design and engineering specialists to develop sliding armrests, under seat storage, seat adjustment, sliding door mechanisms, loading platforms and other storage solutions that meet with the stringent quality requirements of both the manufacturers and drivers.

01 / 03 Side view of an armrest using a single flat mounted sliding system.
02 / 03 view of the single flat mounted system that is used for armrests.
03 / 03 Accuride's single flat mounted system used for armrests, showing inner sections of the system