Binocular field glass with double joint

Claim 1

In a binocular field glass, two small telescopes having parallel optical axes, a pair of laterally projecting arms on each of said telescopes, each said pair of arms being spaced from each other longitudinally of the respective telescope, a cylindrical pivot pin interconnecting each said pair of arms and having its pivot axis parallel with said optical axes of the telescopes, and a bridge having its opposite ends pivotally secured to said pivot pins, said bridge comprising two identical bridge members, substantially flat opposed surfaces on said bridge members parallel with a plane through the longitudinal axes of said pivot pins, a pair of facing precision finished recesses in said opposite surfaces adjacenT each end of said bridge members shaped to accurately fit said pivot pins, the two recesses in each bridge member being precision finished to identical dimensions simultaneously in a single operation, and each of said recesses engaging the respective pivot pin on a surface that is slightly less than semicylindrical whereby said opposed surfaces of the bridge members are spaced a short distance from each other, adjustable clamping means midway between said pivot pins adapted to clamp said bridge members to each other with adjustable force whereby the frictional engagement between waid recesses and pivot pins is automatically balanced, said bridge members each having a centered counterbored aperture to receive said clamping means, said clamping means comprising two elements having identical head portions received in the counterbores and having external and internal threaded portions, respectively, said head portions being concealed by cover plates substantially flush with the outside surface of said bridge members, and said pairs of laterally projecting arms being of substantially triangular shape to enable compact folding of said binocular field glass in Z configuration, with respective side edges of said triangular arms adjacent each other.