Hydraulic operating table: energy safely guided in the tightest of spaces

• What was needed: Energy chain and control cable in the lifting column
• Requirements: Compact design to fit into the small installation space, high service life of the cables with small bend radii
• Industry: Medical technology
• Success for the customer: The energy chain, installed in a curved S shape, fits into the extremely tight installation space with millimetre precision. It is strong, does not twist or untwist due to the heavy hydraulic cables. The new, highly flexible chainflex control cable is a far more reliable solution than the previously used spiral cables and significantly exceeds the service life of the operating table, which was designed for 10 years.

In contrast to the previous models with electric height adjustment, the lifting movement of the newly developed operating table from Maquet is hydraulic. This means that electrical cables and hydraulic hoses have to be guided in the table base. The design is not only particularly slim, but also concave. On the one hand, the space available is extremely limited. The dimensions of the column are only 300 x 400mm. The operating table can be extended between 600 and 1,050mm, so the stroke is 450mm.

Maquet was looking for suitable control cables that were, above all, mechanically reliable and particularly flexible. Due to the limited installation space, the smallest possible bend radius is required. The designers initially favoured spiral cables, but these had a number of disadvantages. Their service life was limited due to the large number of mechanical movements. In addition, they were always customised solutions that had to be harnessed by hand. This meant that consistently reliable quality could not be guaranteed. The risk of table failure could not be ruled out. As the operating tables are used worldwide, all components must function reliably in order to avoid breakdowns and expensive repairs.

Over the entire service life of the table, which is at least ten years, the cables must be able to withstand around 15,000 double strokes.

Maquet had already had good experiences with cables from igus in other projects, so they contacted us again and found the ideal solution in our chainflex CF5 PVC control cables and compact e-chains of the E2.1 micro series.

Based on the chainflex service life calculation, which was carried out online prior to the structural design, igus guarantees the required service life - despite the extreme sagging. These are 4 and 5.5 x d respectively for the cables, which is well below the nominal bend radius of 6.8 x d. During the service life test of the prototypes on site in Rastatt, between 30,000 and 50,000 double strokes were carried out without any problems and without any failures.

For space reasons, the e-chain is laid in an S shape. To make filling easier, chain links of the E2.10 and E2i.10 series both openable from the outside and inside have been combined so that it can always be opened from one side. Another design advantage is that it can handle high additional loads such as the two hydraulic cables despite its low inner height of 10mm.

The e-chain and the chainflex control cables are individual solutions that are configured together with hydraulic cables and matching connectors as an assembly in a third place and then installed. To save space further and minimise mechanical influences, the hydraulic and control cables are laid in pairs side by side. This not only simplifies the connections, but also avoids collisions caused by unnecessary friction.