Mechanical device converting rotary input to linear compression or stretching output with a high mechanical advantage

In a rotary to linear device, a screw member and a pair of jaw assemblies, said screw member having multiple-lead threads, each of said jaw assemblies comprising an outer member and a independent plurality of roller members equal in number to the number of thread starts on said screw member, each of said roller members having a plurality of annular teeth of substantially equal axial pitch and substantially matching configuration to the teeth of said screw member, each outer member of said jaw assemblies having a bore therethrough including a plurality of internal annular grooves of substantially equal pitch and complementary shape to the annular teeth of said roller members, the number of annular grooves in each of said outer members being substantially equal to the number of annular teeth on each of said roller members, the roller members of each of said jaw assemblies mounted in substantially equally spaced-apart positions orbit about the periphery of said screw member with said annular teeth thereof in rolling contact with the threads of said screw member and the grooves in said outer members, and the pitch diameters of the roller members and the annular grooves of the outer member of one of said jaw assemblies being greater than the corresponding pitch diameters of the other of said jaw assemblies.