Floating fulcrum for torque wrenches

A torque wrench comprising an elongate manually-engagable lever arm with a cylindrical interior bearing surface and front and rear ends, an elongate work-engaging head at the front end of the arm on an axis normal to the axis of the arm, an elongate lever projecting rearwardly from the head and freely into the arm, a first pivot pin pivotally connecting the front end portion of the lever to the front end portion of the arm on an axis spaced rearward from and parallel with the axis of the head, an elongate link with front and rear ends positioned freely within the arm rearward of the lever, a second pivot pin pivotally connecting the front end of the link to the rear end of the lever on an axis spaced rearward from and parallel with the first pivot pin, a rearwardly-disposed front cam seat at the rear end of the link, an elongate fulcrum block with a cylindrical exterior bearing surface and a central longitudinal opening, said fulcrum block is engaged freely about the link between the ends thereof and is positioned in the arm rearward of the lever with its exterior bearing surface in sliding bearing engagement with said interior bearing surface of the arm, an elongate fulcrum pin carried by the fulcrum block between the ends thereof and engaged through and pivotally coupling the link with the block on an axis spaced rearward from and parallel with the axis of said second pivot pin, an elongate plunger with front and rear ends slidably engaged in the arm rearward of the link, a forwardly disposed rear cam seat at the front end of the plunger, a cam block with forwardly and rearwardly-disposed cam faces normally establishing flat bearing engagement with front and rear cam seats on the link and the plunger, said fulcrum block has radially outwardly annular grooves at its opposite ends and annular sealing and wiping rings are engaged in said grooves and project therefrom into sealing wiping engagement with said interior bearing surface, a spring means in the arm rearward of and yieldingly urging the plunger forward and holding the plunger, cam block and link in pressure engagement with each other, said plunger, link, fulcrum block and lever are normally axially aligned within the arm, said lever and link pivot about said first pivot pin and fulcrum pin and said plunger and fulcrum block move longitudinally in the arm when the wrench is operated.