Pneumatic valves continue to inspire unique applications Safe, precise control for industry
The medical industry alone does not hold the monopoly on unique valve applications. Even though the typical domain of high-powered hydraulics has a pneumatic counterpart, the hydraulic press has long been the poster child of industrial power. But pneumatic presses are common for their rapid cycle rate, and are used for riveting, punching, crimping and swaging, for example. The challenge with presses closing at a rapid velocity is the potential for human interference as parts are loaded in and out of the machine. Also, the press must be safe during tooling changeover or maintenance.
Because of the potential for danger, regulations for press safety are stringent, and all precaution must be made to prevent unintentional movement of the press and its platen. If the press is mechanical, clutches and brakes are used to ensure the press doesn’t cycle when not intended, and often the clutch and brake are pneumatically controlled. The pneumatic circuit to control the movement of pneumatic pressure—or the clutch and brake of mechanical presses—should be inherently safe, but with redundant controls to prevent accidental operation, or prevent operation when there is a problem.
You could use two pneumatic valves in tandem to create a circuit requiring both valves to function simultaneously to allow press operation, but it just so happens ROSS Controls manufactures its Double Valve, itself a press safety valve operating two valve elements in one body.
The double valve contains two unique valve elements with combination shapes of pistons, poppets and spools, mounted abreast in a single valve body. The internal porting plumbs each element in series so that both are required to be energized simultaneously for airflow to occur. Should one valve element fail open or closed, the valve limits work port pressure to a fraction of inlet pressure, preventing the pneumatic press cylinder or clutch from engaging, or prevents the brake from releasing.
The valve works via pressure differential on each valve element, and the function is impossible to defeat since the plumbing is internal. On top of its inherently safe design, the valve is available with dual pressure switches to monitor the pressure at each valve element. When the valve is not actuated, a signal is present at the normally closed output line of each pressure switch. When the valve is actuated, the switch circuits are reversed and a signal is present at the normally open output lines. The redundant electrical safety provides an extra step of security should machine failure be imminent, and with these features, this safety valve has been popular for years.
In short, the realm of pneumatics is more vast, and specialized, than what can be found in off-the-shelf 5/2 valves and FRLs. As long as there is demand for a unique application, manufacturers will create it. As a result, pneumatics will continue to be a top choice for solving difficult applications.