To save energy, engineers mount pneumatic valves as close as possible to the actuator. This reduces the length of tubing between the valve and actuator, so it takes less compressed air for each actuator cycle. This can cut compressed- air consumption by up to 20% in some applications.
Unfortunately, common pneumatic valves are usually too large and heavy to mount near actuators in handling applications, where cylinders, grippers, or suction cups sit on moving arms or gantries. The added mass of a valve bank could reduce the arm’s speed and load capacity, and possibly affect positioning accuracy. Or it might require more-powerful drives and beefier structures. This would increase energy consumption of the overall machine and negate the benefits of decentralized pneumatics.
Engineers at Bosch Rexroth, Charlotte, N.C., have reportedly overcome these issues with a valve called the AV03. The AV03 offers high flow rates in a package that is lighter and more compact than traditional air valves. This makes it well suited for handling equipment and other applications where the pneumatic hardware moves.
The new valves have about half the weight of conventional valves, and are about 45% smaller thanks to the use of high-performance polymers, fewer parts, and orienting the spool at an angle within the housing, explains Marchelle Forish, a senior product specialist at Bosch Rexroth Pneumatics, Lexington, Ky.
The valve housing is glass-fiberreinforced polyamide, which is substantially lighter than aluminum and other common valve materials. The polymer also improves chemical resistance, compared to aluminum manifolds.
Mounting internal components on a diagonal makes better use of internal space, says Forish. Engineers can, thus, pack more functions into a smaller space. Working ports are only on the side where needed, and the valve has a smaller footprint for base-plate mounting.
The design also uses fewer parts than previous versions. For example, it needs only a single tie rod for manifold assembly, and a single screw for valve mounting. This eliminates one or two tie rods, depending on the series, as well as one fastener for each valve. It also speeds installation and replacement. The AV03’s built-in pilots further reduce the amount of mounting hardware.
Despite the smaller size, the AV03’s flow capacity actually matches or exceeds that of most competing valves. That’s because arranging internal components at an angle let developers streamline the supply and exhaust channels and reduce flow losses.
The angled design enables larger air channels, which permits more flow in less space, explains Forish. “Every return, throttle, and constriction reduces pressure. And the sharper a return, the greater the reduction in working pressure.
“Improved channel geometry helps avoid turbulent flows and pressure losses, as it uses only the pressure needed. As a result, a lower working pressure can be set upstream of the valve,” says Forish. Users get the same cylinder force yet enjoy flow improvements of 40%, letting them substantially lower the supply pressure and boost efficiency, adds Forish.
The AV03 is a zero-overlap spool valve with soft sealing, and the Series includes 2×3/2-way, 5/2-way, and 5/3-way versions. Users can customize the number and type of valves to meet specific requirements. With a 25-pin D-sub connection, manifolds can be configured in increments of one after the second valve and after the fourth valve with 44-pin D-sub and fieldbus connections. The AV03 controls up to 24 coils with a 25-pin D-sub connection, up to 40coils with a 44-pin D-sub, and up to 128 coils with a fieldbus connection. Designers can also opt for different pressure zones within a single valve manifold.
Users can electrically connect the valve blocks using multipole or fieldbus connections, with integrated I/O modules, depending on the configuration. And because sensors can directly connect to the valve electronics, fewer cables have to be fed back to the control cabinet.
Maximum nominal flow is 300lpm, with operating pressure ranging from –0.9 to 10 bar. Medium/ambient temperature is –10° to 60°C, and valves run on standard compressed air filtered to 40m. Protection class rating is IP65.
The AV03, currently available in Europe, will be released in the U.S. in the 3rd quarter of this year.