WOB-L piston pumps work by reduction of a volume by a fixed crank driven piston within a cylinder.

	Compact reciprocating design for vacuum, pressure or combined use
	Oilless design for long life and low maintenance
	Single stage and multi-stage models available
	Flow rates up to 300 l/min, Vacuum down to 10 mbar, Pressure up to 30 bar(g)

Technical Overview
The WOB-L principle has a unitary piston and piston rod whereby the piston 'wobbles' inside the cylinder as the crankshaft rotates. Taking its name from its principle of operation, the WOB-L trade mark was patented by engineers working at Rietschle Thomas forty years ago, and provided a piston compressor radically different from any other design on the market at that time, and remains a signification innovation in the field of compressor technology today.

Unlike the more conventional articulated piston pump, the WOB-L has no gudgeon pin (wrist pin) connecting the piston rod to the piston; the piston and piston rod are a single item, usually a single casting. The piston rod is mounted to an eccentric bearing assembly, which in turn is mounted to the motor shaft to convert rotary energy from the motor into linear motion of the piston within the cylinder.

The piston is sealed to the cylinder by a flanged disk cup, which forms both a seal and mechanical guide for the piston and which runs without lubrication in contact with a low friction, surface coated cylinder of high heat conductivity. As the piston is driven up and down, air resistance on the upward stroke expands the disk's seal on the piston against the cylinder wall to increase its efficiency, while compensating for the 'wobble' action.

The oil-free operation make it extremely popular in the medical, automotive and beverage industries, and the pressure vs. flow, and vacuum against flow characteristics are generally superior to those of diaphragm pumps. In use this provides far higher flows at any given pressure or vacuum to ensure a more consistent operation and giving longer life operation, or allowing a physically smaller pump to be used to perform any given task.

As a piston pump, an inherent characteristic of the design is that the failure mode is a gradual wear-out, rather than the catastrophic failure mode that is a characteristic of many other designs.