Abstract: A steam generator gas burner for burning gases of low calorific value comprises a core air tube, a gas tube arranged coaxially around the core air tube to form a gas flow cross section, at least one further tube element arranged coaxially around the gas tube to form a secondary air flow cross section and first swirlers being arranged in the gas flow cross section. The first swirlers are adjustably arranged to allow for the steam generator gas burner to adjust to varying properties of the combustible gas, in particular a fluctuating calorific value, while taking into consideration the respective ignition intensity.

Abstract: A rotary mechanical drive for transmitting rotational movement in either a clockwise or counter-clockwise direction. The drive has first, second and third drive members. Interferring surfaces between the first and second members provide positive drive between those members in a first angular direction. Interferring surfaces between the second and third members provide positive drive in a second angular direction. Spring couplings between the first and second members and the second and third members permit manual override of the drive in a direction which is opposite to the positive drive direction.