Various types of door closures are known. Reference is made to U.S. Pat. Nos. 5,630,248; 5,832,562 and 5,842,255 to evidence some of the more recently known types of door closures. 
Generally, the known door closures include a cylinder having reciprocally mounted therein a piston and a connected piston rod which extends through one end of the cylinder. The piston is normally biased toward a door closing position by a compression spring acting on the piston. With the end of the piston rod that protrudes out of one end of the cylinder and the opposite end of the cylinder suitably connected between the door frame and the door, the arrangement is such that upon opening of the door, the spring is compressed. The compression spring, acting on the piston in its compressed state, functions to  return the door toward the closed position as the door is released upon the opening thereof. 
Normally, in the known door closures, the speed at which the door is returned to its closed position was affected by controlling the flow rate of the fluid, i.e. pneumatic or hydraulic, out of the cylinder space opposed to the piston and closed by the piston. 
In the event the operating fluid is air, the most commonly used system for controlling closing speed, was to provide an adjustable metering screw to adjust the rate at which air is permitted to escape from the cylinder through a relief hole metered by the adjusting screw. 
In the event the operating fluid is a liquid, the most commonly used system to adjust the closing speed was effected by turning the piston while the piston rod is essentially maintained in a fixed position, the rotation of the piston being affected by rotating the entire cylinder around its centerline to control the speed closing rate. 
It has been noted that rotating the cylinder about its centerline was not practical for door closures that are provided with other features, e.g. push-button type mechanisms, which require the cylinder to be maintained with a specific orientation at all times. Also, rotation  of the cylinder to control the liquid flow rate may require additional seals for the piston. 