one end 15 of a shaft 16 having its opposite end 17 journaled in a hole 18 in a wall portion 19 of the housing 14 fixed to shaft end 17 adjacent wall 19 is a first connecting link 20 concentrically surrounding shaft 16 inwardly of end 15 is a tubular second shaft 21 which is journaled on shaft 16 by suitable needle bearings 22 and 23 lever 12 is fixedly connected to shaft 21 at one end 24 thereof and a second connecting link 25 is connected to the other end 26 of the shaft 21 by suitable clamping means including nut 27 and clamping stud 28 a third tubular shaft 29 is concentrically mounted about shaft 21 by means of needle bearings 30 and 31 to extend inwardly from adjacent lever 12 third operating lever 13 is secured to one end 32 of shaft 29 and a third connecting link 33 is secured to the other end 34 of the shaft 29 third tubular shaft 29 is journaled by means of needle bearings 35 in a portion 36 of housing 14 thus shaft 16 is effectively journaled through bearings 22 and 23 shaft 21 bearings 30 and 31 shaft 29 and.