Adjustable knuckle joint device for folding ladders

Claim 1

An adjustable knuckle joint device for folding ladders comprising in combination: a first coupling means having a first circular junction portion with an aperture in the center and a bottom surface and a first elongate joint portion formed at an angle with said first circular junction portion; a second coupling means having a second circular junction portion with a flat top surface and an aperture in the center, said top surface corresponding to and being in bearing engagement with said bottom surface of the first circular junction portion of the first coupling means and a second elongate joint portion formed at an angle with said second circular portion with a plurality of screw holes provided therein; a straight axle fitting movably connecting the bottom surface of said first circular junction portion to the top surface of said second circular junction portion through the apertures thereof; and a snap catch position means fixed on said second elongate joint portion through said screw holes in conjunction with the first circular junction portion of said first coupling means; whereby, said first coupling means and said second coupling means can be conveniently adjusted and safely secured in position through said catch position means, said snap catch position means comprising a coupling bracket fixed on said second elongate joint portion through said screw holes and having two side supporting walls uprightly extending at the opposite ends thereof with a guide opening separately formed therein, a plurality of orifices provided in the horizontal surface thereof for use in securing the bracket on the top surface of said second elongate joint portion of said second coupling means through said screw holes, a damper having a protection on the upper edge horizontally formed on one of the side supporting walls and extending at a right angle therefrom, an elastic member placed on the horizontal surface of said coupling bracket with its front end free and its rear end held in position on the horizontal surface of said coupling bracket, a positioning means adjustably disposed in said coupling bracket through said guide openings and said elastic member with respect to said first circular junction portion of said first coupling means so as to effect the desired adjustment therewith, said positioning means including a crank rod movable between a forward and rearward position having a stem portion at one end with a notch at the front and a groove at the rear respectively formed therein and an operating portion at the other end at a right angle with said stem portion, said crank rod being inserted into said guide openings of said coupling bracket through said elastic member with said notch closing the inner surface of said first support wall, a catch member having a check portion at one end with an opening formed therein, and an arcuate portion at another end with an open section in the middle thereof, said catch member being firmly connected to the notch of said crank rod through the open section with said check portion fixed to the front end of said elastic member through the opening thereof, said projection of said damper retaining said check portion when the rod is moved into its rearward position, a C-shaped retaining ring fixedly coupled with the stem portion of said crank rod through said groove thereof providing a stop for said crank rod within the bracket when the crank rod is moved to its rearward position; thereby, said crank rod can be effectively operated for making the required adjustment.