Lazy tong

A lazy tong mechanism is a mechanical linkage consisting of interconnected pivoting bars arranged in a scissor-like pattern. The structure can be extended or contracted while maintaining a controlled linear movement. The mechanism distributes movement across multiple joints, allowing compact folding and adjustable extension with relatively little force.

Some American stereoscopes employed metal lazy tongs as part of their focusing and extension system. The earliest known design for a stereoscope using a lazy tong mechanism was patented by E. K. Page in 1870.

Patents and registrations:

Number: 104990
Stereoscope
Filing: 05-07-1870, Applicant(s): E. K. Page. via: worldwide.espacenet.com