I'll try to post a sketch in hopes of explaining why the draft gear Mike has pictured (Feb. 4th post) requires only the one coil spring, which always provides its cushioning action by compression, regardless of whether the coupler is pushed or pulled.
The sketch shows three side views of the internal members of the draft gear. Top view: no load on coupler. Middle view: Coupler in tension (pull). Bottom view: Coupler in compression (push).
The dark rectangles are end views of the spring plates that sandwich the coil spring in Mike's second and fourth Feb, 4th photos. Dimension "M" in the top view is the maximum distance the outer surfaces of the spring plates can be separated. It corresponds to the spacing between either pair of cheek irons, one pair on each side of the pocket, showing in Mike's third photo.
A PULL on the coupler causes it and the drawbar and strap to move to the right, compressing the coil spring against the spring plate marked "C." The "C" stands for constraint, because the spring plate is held stationary by its mating cheek iron. So a gap develops between the constrained spring plate and the end of the drawbar, where shown.
A PUSH on the coupler causes a reversal. Now the spring plate at the other end is the one constrained and the gap develops at its end, as shown. But again, compression of the spring is what provides the cushioning.
In Mike's third photo for Feb. 4, you can see steel bars lying on top of the draft gear timbers. In the fully assembled draft gear these plates are fastened to the bottoms of the cheek irons, and the parts of the spring plates that project beyond the strap ride on those bars; thus preventing the drawbar, strap, etc. from dropping down.