Biological safety cabinet with window counterbalance

Claim 1

A laboratory cabinet comprising: back and side walls defining a work area interiorly of the cabinet; a front opening extending between the side walls and allowing, access to said work area; a sliding window including a pair of side edges operable for sliding movement in a vertical direction to selectively open and close said front opening of said cabinet; at least one constant rate force pneumatic spring including a cylinder member having two ends and a cavity defined therein, a piston reciprocal in said cavity of said cylinder and defining two working chambers within said cavity, a pressurized fluid in said two working chambers, and a piston rod connected at one end to said piston and having an opposite end; a pulley mounted at said opposite end of said piston rod for sliding movement with movement of said piston rod; and cable means attached at one end to said cabinet and at its other end to the side edges of said window, said cable means passing over said pulley thereby being operatively connected to said pneumatic spring in turn operatively connecting said window to said pneumatic spring such that said pneumatic spring provides a substantially constant rate spring force to assist in raising and lowering of said window with the application of a substantially equal operator force.