Piston and cylinder unit

A piston and cylinder unit comprising a cylinder barrel defining a piston space, a piston with a non-circular cross section able to run axially in said barrel with a support action due to a peripheral bearing surface of the barrel, said piston including at least one annular runner belt arranged on said piston extending along at least part of the length of the piston, said belt being coaxially arranged thereon along part of the length of the piston, said belt having a surface facing radially outwardly which makes contact with the inner bearing surface of the barrel with sliding fit to support the piston, an inwardly directed surface of the belt bearing on an outer peripheral surface of the piston, said outer peripheral surface of the piston being spaced from the bearing surface of the barrel, said belt further having an inwardly directed retainer spur fitting into a groove-like peripheral recess in the piston, said belt being made of a material with resiliently elastic properties and being interrupted at one position on its periphery, said belt being disposed half-way between the ends of said piston defining a first piston portion on one side of the belt and a second piston portion on the other side of the belt, said first and second portions being opposite to and spaced from the bearing surface of the barrel, said first and second portions having surfaces with a sealing ring in sealing contact with the barrel bearing surface, said belt being interrupted by a slot at an angle of approximately 45.degree. with respect to the peripheral direction of the belt, said belt having two grooves therein extending along the full peripheral extent of said belt for receiving lubricant therein, said spur being received in said recess with a clearance allowing axial play of the belt of approximately one/ten mm.