Abstract: A piston arrangement comprising a piston movable within a cylinder and having a stroke with a first end and a second end, wherein the piston is coupled to a crankshaft by a linkage mechanism including a toggle link which is pivotally coupled to the piston and pivotally coupled to a con-rod, wherein the toggle link has a first position corresponding to the first end of the piston stroke, a second position different to the first position also corresponding to the first end of the piston stroke, and an intermediate position between the first and second positions corresponding to the second end of the piston stroke such that the piston completes four strokes for every one revolution of the crankshaft.

Abstract: A piston arrangement comprising a piston movable within a cylinder and having a stroke with a first end and a second end, wherein the piston is coupled to a crankshaft by a linkage mechanism including a toggle link which is pivotally coupled to the piston and pivotally coupled to a con-rod, wherein the toggle link has a first position corresponding to the first end of the piston stroke, a second position different to the first position also corresponding to the first end of the piston stroke, and an intermediate position between the first and second positions corresponding to the second end of the piston stroke such that the piston completes four strokes for every one revolution of the crankshaft.

Abstract: A blind rivet and a method of assembly comprising a tubular shell and mandrel in combination. The mandrel comprises a stem and a radially-enlarged head which in use forms a blind head to the shell to set the rivet, in which either the head of the mandrel or the bore of the shell is formed with a plurality of depressions the bases of which lie on a notional circle having a diameter which, where the depressions are formed in the head of the mandrel, is less than the bore of the shell or, where the depressions are formed in the bore of the shell, is greater than the diameter of the head of the mandrel. The depressions, which are preferably generally longitudinally disposed, define ribs, ridges or other protusions therebetween which in use and on pulling the mandrel into the shell bore extend radially beyond the bore of the shell, so that material of the shell becomes displaced by contact with the ridges and occupies the depressions. The invention may be applied either to pull-through, or self-plugging rivets.