The disc on the left is connected to the left end of the outer shaft. The right disc is connected to the tooth wheel as well as to the outer shaft.
The curtain is glued to the outer shaft while the inner shaft is connected to the shutter wind-and-release mechanics and the other end to the bearing in the camera housing.
Turning the inner shaft with the slotted end turns the middle disc and thus both springs. Tension increases on both sides of the spring and thus on the tooth wheel which is controlled by the camera release mechanism.
The inner shaft should be brought under tension (some 8 turns) before connecting it to the wind/release mechanism of the camera.
When winding the shutter, the tension between the outer and inner shaft will be more and more increased by each turn of this action.
The more the shutter will be wound up, the higher the tension will be in order to draw back the outer shaft and thus tearing the curtain with the slit back in numbered start position.
Since both springs are connected in the same way to inner and outer shaft, both are working together towards the same direction!
