Valve opening mechanism

The motor drive system has a drive shaft (10) with a disk (12) holding a first pin (18) with a groove (30) near its tip. The first end of a spring (32) engages in this groove. The spring is coiled around a bearing pin (14) and its second end engages on a pin (34) on a drive crank (16). The drive crank has a central aperture (24) accommodating the bearing pin. The first pin protrudes through an arcuate slot (28) allowing up to 70 degrees of relative movement. The end of the crank (20) has a bearing pin (36) engaging the first end of a connecting rod (22). The second end engages a pin (44) on a crank (46) on the valve shaft.