Air spring pneumatic product rejection system

1. A double-acting cylinder and piston mechanism comprising:

a cylinder ( 1 ) substantially closed at both ends by front ( 5 ) and rear ( 7 ) end walls,

a piston ( 8 ) axially displaceable within the cylinder ( 1 ),

a first region ( 6 ) defined between the piston ( 8 ) and the rear end wall ( 7 ) of the cylinder ( 1 ) and a second region ( 4 ) defined between the piston ( 8 ) and the front end wall ( 5 ) of the cylinder ( 1 ),

a piston rod ( 2 ) extending from the piston ( 8 ) through the front end wall ( 5 ) of the cylinder ( 1 ),

an air inlet port ( 19 ) for communication with said first region ( 6 ) of the cylinder ( 1 ), and

at least one exhaust vent ( 14 ) which is exposed during axial displacement of the piston ( 8 ) for release of air delivered to the first region ( 6 ) of the cylinder ( 1 ) through the air inlet port ( 19 ),

wherein the piston ( 8 ) is of sufficient length to prevent communication between the second region ( 4 ) and the exhaust vent ( 14 ) so that a static air pressure may be maintained in the second region ( 4 ) of the cylinder ( 1 ) to cushion impact between the piston ( 8 ) and the front end wall ( 5 ) of the cylinder ( 1 ).

2. A double-acting cylinder and piston mechanism according to claim 1 , wherein an axial displacement of the piston ( 8 ) is effected by a change in the differential pressure between the air in the first region ( 6 ) and the air in the second region ( 4 ) of the cylinder ( 1 ).

3. A double-acting cylinder and piston mechanism according to claim 1 , wherein the exhaust vent ( 14 ) is defined in the cylinder wall ( 3 ).

4. A double-acting cylinder and piston mechanism according to claim 3 , wherein, in a horizontal disposition of the cylinder ( 1 ), the exhaust vent ( 14 ) is located at a circumferential angular location relative to the lowermost longitudinal extent of the cylinder ( 1 ).

5. A double-acting cylinder and piston mechanism according to claim 1 , wherein the air inlet port ( 19 ) is at a first axial end region of the cylinder ( 1 ).

6. A double-acting cylinder and piston mechanism according to claim 1 , further comprising sealing means ( 10 , 12 ) between the piston ( 8 ) and the cylinder wall ( 3 ).

7. A double-acting cylinder and piston mechanism according to claim 6 , wherein the sealing means ( 10 , 12 ) comprises at least one piston ring ( 10 , 12 ).

8. A pneumatic product rejection system comprising a double-acting cylinder and piston mechanism including:

a cylinder ( 1 ) substantially closed at both ends by front ( 5 ) and rear ( 7 ) end walls,

a piston ( 8 ) axially displaceable within the cylinder ( 1 ),

a first region ( 6 ) defined between the piston ( 8 ) and the rear end wall ( 7 ) of the cylinder ( 1 ) and a second region ( 4 ) defined between the piston ( 8 ) and the front end wall ( 5 ) of the cylinder ( 1 ),

a piston rod ( 2 ) extending from the piston ( 8 ) through the front end wall ( 5 ) of the cylinder ( 1 ),

an air inlet port ( 19 ) for communication with said first region ( 6 ) of the cylinder ( 1 ), and

at least one exhaust vent ( 14 ) which is exposed during axial displacement of the piston ( 8 ) for release of air delivered to the first region ( 6 ) of the cylinder ( 1 ) through the air inlet port ( 19 ),

wherein the piston ( 8 ) is of sufficient length to prevent communication between the second region ( 4 ) and the exhaust vent ( 14 ) so that a static air pressure may be maintained in the second region ( 4 ) of the cylinder ( 1 ) to cushion impact between the piston ( 8 ) and the front end wall ( 5 ) of the cylinder ( 1 ).

9. A pneumatic product rejection system according to claim 8 further comprising:

a high pressure manifold ( 24 ) in communication with the air inlet port ( 19 ),

a low pressure manifold ( 26 ) in communication with the second region ( 4 ) in the cylinder

a control valve ( 22 ) between the high pressure manifold ( 24 ) and the air inlet port ( 19 ), and

a paddle ( 18 ) mounted at the free end of the piston rod ( 2 ) for contacting and displacing from its path a product to be rejected.

10. A pneumatic product rejection system according to claim 9 wherein the paddle ( 18 ) is pivotally mounted at the free end of the piston rod ( 2 ).

11. A pneumatic product rejection system according to claim 9 comprising a multiplicity of paddles ( 18 ).

12. A pneumatic product rejection system according to claim 8 further comprising:

a paddle ( 18 ) mounted for displacement between a first product rejecting position and a clear position for the uninhibited passage of product;

means for displacing the paddle ( 18 ) from the clear position towards the first rejecting position; and

means for selectively curtailing drive movement of the displacing means on completion of a predetermined increment of travel, less than the travel required to displace the paddle ( 18 ) from the clear position to the first rejecting position.

13. A pneumatic product rejection system according to claim 12 comprising a double-acting cylinder and piston mechanism and said means for selectively curtailing drive movement of the displacing means is adapted to control air pressure forward of the piston ( 8 ) in the direction of advance of the piston ( 8 ) in order to achieve at least one alternative product rejecting position of the paddle ( 18 ) located between the first product rejecting and clear positions of the paddle ( 18 ).

14. A pneumatic product rejection system according to claim 12 comprising a multiplicity of paddles ( 18 ).