What pushes when the cam lever opens

Side cut through the #1 latch: a printed cam lever on a hinged steel bolt, with four disc springs and a TPU 85A rib. Drag the slider to lift the lever and watch where the force goes.

Cam lever latch, side cross-section Box wall with the TPU rib and the lid tab. A steel bolt hinged at the bottom runs up through the lid tab, the disc springs and a steel plate to a fork head that carries the cam lever. Arrows show the spring force and which way it turns the lever. lid TPU rib disc springs steel bolt hinge pin
Lever lifted
0°
Clamp force
350 N
Disc springs squashed
1.60 mm
TPU rib squeezed
0.80 mm
The springs' push on the lever
holds it shut, 3.6 N at the handle

Spring force Springs turning the lever Printed Stainless steel TPU 85A

Clamp force as the lever lifts

Clamp force against lever angle: about 350 N closed, a small peak of 359 N at dead centre near 10 degrees, falling to zero at about 99 degrees.

The springs and the rib share the squeeze: about 1.6 mm in the springs and 0.8 mm in the rib when closed, at 219 N per mm of spring. Past dead centre both give back what they stored until the cam leaves the plate.

  1. Before dead centre

    0–10° lifted · 350 → 359 N

    The squashed springs push the cam up. The cam's thick side sits just past the pin, so that push presses the lever down onto the lid. This is the lock. Your hand lifts the lever over a small bump.

  2. Past dead centre

    10–99° lifted · 359 → 0 N

    The same push now turns the lever open, up to about 10 N at the handle, so it helps your hand. The springs expand and lift the plate after the cam, and the TPU rib pushes the lid tab up its 0.8 mm.

  3. Released

    past 99° · 0 N

    Springs and rib are back at their free height and the cam has left the plate. Nothing pushes up any more. Swing the bolt out of the lid slot and lift the lid by hand.