Arrangement for the compensation of inertia forces in the reciprocating driving of a machine element

An apparatus for compensating inertia forces comprising:

• means for driving an element in a predetermined repeated reciprocating motion between substantially fixed first and second end points, said reciprocating motion having a vertical component;
• first spring means for balancing the weight of the element, the first spring means comprises a first piston reciprocable in a first pneumatic cylinder having a first working chamber, the first piston being connected to the element;
• second spring means for aiding movement of the element away from the second end point towards the first end point, the second spring means comprises a second pneumatic cylinder having a second working chamber, the second cylinder being reciprocable about a second piston, said second piston being connected to a fixed frame;
• said working chambers being contained in a continuous cylinder having a wall fixed with respect to the continuous cylinder therebetween;
• and
• the stroke length of the first piston is less than the distance between the first and second end points whereby the second cylinder moves after the first piston has moved within the first cylinder to contact the fixed wall between the first and second working chambers.