Ventilator apparatus

A portable positive displacement respirator comprising:

• a housing,
• a rigid cylinder inside said housing having a normally open end and a normally closed end, said closed end containing means for exhausting air to a patient,
• a piston received in said rigid cylinder adapted for reciprocal movement,
• a piston connecting rod having a first end attached to said piston,
• motive means attached to said piston connecting rod for imparting reciprocal movement to said piston in said cylinder,
• said motive means including means for converting rotary motion into reciprocating motion and means for adjustably varying the length of the reciprocating movement of said piston in said cylinder, said adjusting means being attached to said reciprocating means and being adjustable to establish a predetermined length of stroke of said piston from the exterior of said housing whether or not piston is moved, said adjusting means comprising
• a shaft rotatably mounted in said housing;
• said motive means including means for rotating said shaft through limited reciprocal arc movement,
• a crank mounted at one end to said shaft and responsive to the movement of said shaft,
• a circular gear mounted for rotational movement near the other end of said crank arm, a pivot gear mounted on said shaft but separately rotatable thereabout, said pivot gear engaging the outer periphery of said circular gear, said piston connecting rod having a second end connected to said circular gear at a position other then its center so that reciprocal arc movement of said shaft is imparted to said connecting rod and wherein said adjustment means includes means for selectively rotating said pivot gear to change and maintain the effective location of the connection of said connecting rod with respect to the location of the center of said circular gear, thereby changing the effective length of the reciprocal movement of said connecting rod without a corresponding change in the size of the arc movement of said shaft.