ABSTRACT
In the early 1970s swivel office chairs with height adjustment for the seat were introduced. The seat was mounted on a central column with a gas-operated, stepless system, to provide up and down movement, controlled by a lever. There were two designs, side-entry levers and top-entry levers for the cylinders, which allowed the vertical movement at a touch. The side-entry cylinder had an actuating lever which passed through the side of the cylinder to operate the central valve. The weakness in the side-entry design was the point at which the integrated adjustment lever was inserted into the cylinder. Accidents occurred when the central column broke and the contents of the cylinder were fired out explosively, as the pressure was suddenly released. In 1982 at a Bonn police station five of eight gas-lift office chairs were 'destroyed' by the explosion of the cylinders in a short period of time.
