Part III: Advanced Restraint Systems for Improved Safety, Gear Accommodation, and End User Maintenance
By John-Paul McGovern, Ph.D., Chief of Research and Technology, USSC Group, Inc.
This is the third installment in a series of articles discussing recent technology advancements in fire apparatus seat systems. This discussion will focus on advanced restraint systems for improved occupant safety, ergonomics, and end user maintainability. Future topics will include: advanced materials and coatings selection integration and optimization; and advancements in ride comfort and operator-fatigue reduction technology.
Improved seat restraint systems were a major initiative in development of the Valor line of fire apparatus seating by USSC Group, Inc. With the specialized functionality served by self-contained breathing apparatus (SCBA) fire truck seats as well as the packaging challenges faced within rescue vehicles in general, significant room for improvement above available industry standards were identified. The three main areas of improvement identified were:
- Restraint presentation for ease of use by the occupant.
- Available web length for accommodation of occupants and the many elements of their gear.
- End user ease of maintenance and replacement.
In the area of belt presentation, USSC engineers focused on the shoulder belt portion of the three-point system in their All-Belts-to-Seat (ABTS) applications. Applications of traditional three-point belt systems dictate that the shoulder retractor be mounted to the lower rear of the seat, routed up behind the seat, and passed through a D-loop rigidly mounted to the upper portion of the seat frame. In seat configurations with a removable headrest, it is possible to pass the shoulder webbing over the top of the seat frame for presentation to the occupant. However, because of the requirements of shape for SCBA seats and other integrated headrest first responder seat systems, this became impossible. As such, the shoulder belt passing through a standard D-loop would rest beside the shoulder region of a seat and be potentially difficult for an occupant to reach (as shown in the first image, below) Use of a such a belt is especially difficult when the occupant is burdened with significant quantities of gear, as is often the case.
As such, USSC engineers worked with engineers at IMMI to solve this problem. The result of this collaboration was the integration of IMMI’s proprietary Ready Reach system into all Valor seat systems, as shown in the second image, below. This system uses a double D-loop system and presenter stalk to route the belt up the back of the seat system in the traditional way, but also up and over the shoulder portion of the seat so that it is easily accessible by the user. In doing so, the retractor is still able to be packaged behind the seat structure, but belt routing does not suffer from the position of just a single D-loop on the rear surface of the seat frame.
In addition to shoulder belt presentation, another industry shortcoming identified by USSC was the total length of webbing available on first responder seats. With the traditional single-shoulder-retractor, three-point belt configuration, the amount of webbing available to the occupant was essentially limited by commercially available belt components and applicable FVMSS standards. As such, USSC again worked with IMMI to develop and integrate the dual retractor belt system. By using two retractors (one for the shoulder and one for the lap), with webbing connected at the tongue, a significant increase in available webbing was achieved. As such, seat occupants with bulky gear and equipment are able to comfortably buckle their restraints without issue.
Finally, a requirement set forth in the early days of Valor seat development was for an ABTS belt system that was completely external to the seat frame and upholstery. This industry request for such a system arose out of the complexity of systems on the market associated with internally routed restraints. In the event of a webbing tear or retractor failure, a near complete disassembly of the seat would be required with such routing systems. With a completely external routing of the three-point restraint systems (shown below) on all Valor seats, replacement and, perhaps more importantly, inspection of belt systems is a straightforward procedure.