PTFE bushings for seat frames

Smart Design Engineered Benefits for Seat Frames

Saint-Gobain engineers use the power of finite element analysis (FEA) to understand system level problems by fully understanding component level performance and its impact on the complete seat structure. Figure 6 shows a pressure analysis performed on both a NORGLIDE® bushing and a competing solution, which in this case is a plastic part. Seat linkages are often made using stamping techniques which often mean a breakout region in the bearing housing cross section that causes line contact on the bearing. So as a person sits on the seat, a force is exerted through the seat height adjuster pivot points which could cause permanent deformation on the bearing through high loads, leading to a possible failure mode. However, with our unique NORGLIDE® bushing, comprising a strong metal backing layer and a thick PTFE layer, the external forces are spread out, reducing the pressure exerted onto the sliding surface of the seat bushing.

Figure 2: Finite element analysis shows that the NORLGLIDE® bushing can be used to spread the external loads much better than can be achieved with an injection-moulded plastic bushing.

Perfect Fit Engineered Benefits for Seat Frames

There can be a trade-off between having a low-effort seat height adjustment mechanism that rattles due to free play and a quiet mechanism that requires high forces to adjust due to interference. However, the thick PTFE layer exhibited by the unique NORGLIDE® bushing allows for a level of tolerance compensation through-out which our seat bushing solutions perform consistently when compared to competing options. This can be seen in Figure 5 where the torque required to turn a shaft within different bushings was examined for several different shaft diameters.

Figure 3: The unique NORGLIDE® bearings perform consistently over a wide range of dimensions when compared to competing solutions. The thick layer of PTFE can compensate for manufacturing tolerances of the mating components, ensuring a consistently smooth adjustment feel

Noise Free Engineered Benefits for Seat Frames

NORGLIDE® PTFE bushings comprise a unique composite (seen in Figure 2) that offers superior vibration damping properties, as can be seen in Figure 3, reducing the level of vibration induced discomfort. With many pivot points located in each seat, manufacturers need to ensure they do all they can to damp vibration and reduce noise inside the cabin at high speeds or on bumpy roads. 

Figure 4: Cross-section through the unique NORGLIDE® materials (left - SMTL-type, right - T-type) that will perform consistently throughout the lifetime of the part due to the thick PTFE layer.

 

Figure 5: The damping ratios as a percentage for two PTFE-based competing solutions and also for the NORGLIDE® T and NORGLIDE® SM Bearings.

Long Life Engineered Benefits for Seat Frames

With car sharing becoming increasingly popular, the seat frame is going to be adjusted more and more to the needs of the driver, sometimes on a daily basis. This creates potential for additional wear on the parts in the seating system and Saint-Gobain engineers place great importance on the parts providing great performance, drive after drive. Figure 4 shows that due to our unique NORGLIDE® materials we are able to maintain the low friction performance for much longer than a competing PTFE bushing.

Figure 4: The relation between the coefficient of friction and radial wear depth of the bearing material for a sintered bronze and PTFE competitor bushing and a NORGLIDE® seat bushing.