Abstract: A rodless pneumatic cylinder includes main exhaust ports defined by the open ends of a pair of fixed tubular members that extend, respectively, into the cylinder body from its opposed ends. The main piston of the rodless cylinder has an axial bore formed in it in which is slidably mounted a small piston that serves mutually to isolate the working chambers of the cylinder. The bore carries seals adjacent to its opposed ends whereby, during motion of the piston, the bore sealingly receives one or other of the tubular members at a predetermined stage during the motion thereby effectively closing the main exhaust port. During further motion of the piston, air can, therefore, exhaust only through a throttled auxiliary exhaust port and such further motion of the piston is thus cushioned. The arrangement provides for a greater extent of cushioning relative to known arrangements in which the working chambers are mutually isolated by a barrier fixedly secured in the bore.

Abstract: A double-acting pneumatic cylinder is characterised by the provision of a pair of sealing elements respectively located on either side of the piston by means of rods slidably mounted in longitudinal bores formed in the piston. At the commencement of the cylinder's in-stroke, the rod and its associated sealing element is in an extended position and serves to seal off the main exhaust port while the piston is still relatively distantly located from the end of its in-stroke. During further in-stroking the piston, air can therefore exhaust only through the auxiliary exhaust port and the motion is thus cushioned. The out-stroke of the cylinder is similarly cushioned over a relatively large distance by virtue of the sealing element adopting an extended position and closing off the main exhaust port, the air exhausting through the auxiliary exhaust port.