General Guidelines

• Seatback should provide full contact from: Top of Pelvis to Shoulder  [4]

  • Headrest will provide contact for Head and/or Neck

• Beyond the 325mm line that is above the H Point (will be shown in diagrams further below) the geometry should be fairly flat  [4]

  • Ergonomics of this will be described in Pressure Distribution Section

Lumbar Support

• Preferred apex of lumbar support (i.e. where it protrudes out the most): 152mm above the H Point  [4]

  • Or 150mm above the H Point [6]   (only a 2mm difference, doesn’t really matter which one is used)

• Preferred prominence of a fixed, non-movable lumbar support (i.e. how much it protrudes): 20mm  [6]

• Preferred prominence of a movable lumbar support: 30mm  [6]

• Range of motion for a movable lumbar support: 100mm - 200mm above the H Point  [6]

• Lumbar Support Cushioning should not compress more than 80%  [6]

  • Greater than 80% compression leads to decrease in water vapor diffusion, leading to increase in local humidity

Depressed Seatback Cushion Contour  [4]

• Assumed this was approximately 99th Percentile Male, thus H Point is 135mm away from Depressed Seatback Cushion Contour

• Depressed Cushion Contour is the bolded black line that is pointed at by the red arrow in the image below

  • 

    • Steps to recreate this Depressed Cushion Contour in CAD

      • Draw torso line (a line emanating from the H Point, at the angle that you have determined the occupant will be sitting at)

      • Draw three perpendicular lines to the torso line

        • At 115mm, 160mm and 325mm from the H Point

        • Each of these lines (in this case) are 135mm long though depending on the occupant it may be a different length for you

      • Draw a line connecting the endpoints of the 325mm and 115mm line

      • At the endpoint of the 115mm line, construct an arc with 100mm radius that will stop at the stiffer/base layer foam below it

Undepressed Seatback Cushion Contour [4] & [6]

• Still under assumption we are using a 99th Percentile Male as the occupant - H Point is 135mm away from the depressed seatback cushion contour

  • Source 4 undepressed seatback cushion contour 

    • 

      • NOTE: For MSXIV a fixed lumbar support was used, thus to have a 20mm prominence all Y-values above were multiplied by 0.4

• Source 6 undepressed seatback cushion contour

  • Due to manufacturing concerns, source 4’s undepressed seatback cushion contour may be too complicated to make, source 6’s is merely an arc - which makes manufacturing much easier

  • Radius for fixed lumbar support: 300mm

  • Radius for lumbar support of this type that can adjust its radius (separate from adjusting the height of the apex): 240mm - 400mm

  • Note: Guidelines for the prominence of the lumbar support still apply with this type of undepressed seatback cushion contour