Industry benchmark lightweight seatbelt retractor pretensioner goes on 2018 Jeep Wrangler

ZF is now delivering its next-generation SPR8 (Snake Pretensioner Retractor) seatbelt system to the Jeep Wrangler. The innovative system uses a plastic piston instead of conventional metal components to transfer tensioning torque through the torsion bar to the spool, resulting in a simpler design, more compact packaging and industry leading system weight.  

The SPR8 design represents a modular retractor family satisfying everything from base technology through to the next generation ACR8 reversible motorized seat belt pretensioner that combines active and passive safety to pretension the seatbelt before a crash. ZF pioneered this system with Daimler in 2002 on the Mercedes S-Class and will introduce new enhancements to the system soon.  

The innovative system uses a plastic piston instead of conventional metal components to transfer tensioning torque through the torsion bar to the spool, resulting in a simpler design, more compact packaging and industry leading system weight.   

Peter Lake, member of the board of management at ZF, responsible for Corporate Market, said: “We are very pleased to launch this next- generation product on the iconic Jeep Wrangler. This will be closely followed by a launch with a European manufacturer in combination with ACR technology as we roll out this exciting new product generation globally.”  

The functionality of the SPR8 is such that when vehicle sensors trigger the seatbelt system, a pyrotechnical gas generator is ignited releasing a gas that expands and builds up pressure in the guiding tube. This pressure acts on the snake-like plastic piston which is forcefully propelled into a pinion instead of the commonly used steel elements. The pinion then transmits a significant torque to the belt retractor spool to pre-tension the seatbelt. The complete pyrotechnical system is sealed meaning no gas will be emitted during the pretensioning process, which altogether takes just ten milliseconds.  

“This unique technology utilizes lighter weight with plastic material allowing the overall system weight to be reduced by up to more than 20 percent,” said Norbert Kagerer, senior vice-president, ZF Occupant Safety Systems. “The system architecture allows great flexibility for packaging and delivering various load limiting options such as switchable, degressive and load limiting with stop to help manage occupant energy.”