Variable-stroke pneumatic cylinder

Abstract

A variable-stroke pneumatic cylinder; the cylinder comprises a tubular casing, having fore and rear heads, defining a chamber for reciprocation of a piston member along a working stroke; at least one of the heads is provided with an air inlet/outlet hole connected to a central cavity in the cylinder head, which facing towards the piston chamber. The rear head is provided with a pneumatic damping device comprising a venting path provided with a control valve. The pneumatic cylinder also comprises head extension members to change the working stroke; the extension members are in the form of disk-shaped member secured to the cylinder head. Each disk member is provided with a central hole axially aligned with the central cavity of the cylinder head, and an air venting hole axially aligned with a venting hole branched off from the air venting path.

What we claim is:  
     
         1 . A pneumatic cylinder, comprising: 
 a tubular casing defining a chamber for a piston member;    a fore and a rear cylinder head at the ends of the piston chamber, at least the rear one of the cylinder heads being provided with an inlet/outlet hole for feeding and discharging pressurized air, said air inlet/outlet hole opening into a central cavity facing a corresponding side end of the piston chamber;    a reciprocable piston member movable along a working stroke inside the piston chamber, said piston member having a piston rod which tightly protrudes from the fore cylinder head;    in which at least the rear cylinder head is provided with a pneumatic damping device comprising a venting path; and    in which the piston member comprises a plug member designed to tightly penetrate into the central cavity of said rear cylinder head; and    head extension means for axial extension of the rear cylinder head inside the piston chamber for varying the working stroke of the piston member, said head extension means comprising at least one disk-shaped member removably fastened to the rear cylinder head, inside the piston chamber,    said disk-shaped member having a central hole axially aligned to the central cavity of the rear cylinder head, and a side hole axially aligned with a venting hole branched off from the air venting path.    
     
     
         2 . Pneumatic cylinder according to  claim 1 , wherein a sealing gasket is provided at the end of the branched off hole of the air venting path, facing the extension disk member fastened to the rear cylinder head.  
     
     
         3 . Pneumatic cylinder according to  claim 1 , wherein each disk-shaped member, in correspondence with the central hole, is provided with an annular gasket to seal against the plug closing member.  
     
     
         4 . Pneumatic cylinder according to  claim 1 , wherein comprising a plurality of disk-shaped extension members removably connected to each other and to the rear cylinder head.  
     
     
         5 . Pneumatic cylinder according to  claim 4 , wherein comprising disk-shaped members of identical thickness.  
     
     
         6 . Pneumatic cylinder according to  claim 4 , wherein comprising disk-shaped members of different thickness.  
     
     
         7 . Pneumatic cylinder according to  claim 1 , wherein the venting path comprises an adjustable venting valve.