Fluid-pressure rotary actuator for clamping systems

#When using equipment (e.g., a robot) to replace a human operator and automate manufacturing processes (e.g., the operation of a computer numerical control (CNC) milling machine), it may be necessary to develop systems and techniques for clamping and unclamping associated vises or clamping fixtures. Many manufacturing processes present numerous clamping difficulties. For example, a large amount of clamping torque is required in CNC milling machine applications to prevent a workpiece from moving inside the vise. In other automated manufacturing processes, a large vise jaw travel is required to grip and un-grip parts with irregular profiles or dovetail-shaped features. A large vise jaw travel is often required for dual-moving jaw vises in which two parts are gripped simultaneously.

#FIGS. 1A through 1C illustrate a non-limiting example of a rotary actuator and a vise for providing fluid-pressure rotary actuation for clamping systems in automated machining processes.

#FIG. 2 illustrates various views of a non-limiting example of the rotary actuator to provide fluid-pressure rotary actuation for clamping systems in automated machining processes.

#FIG. 3 illustrates an exploded view of the components in a non-limiting example of the rotary actuator.

#As described above, the automation of manufacturing processes generally requires automated or controllable clamping fixtures. Some clamping systems suitable for the automatic operation of CNC milling machines utilize pneumatic pistons that operate on the clamping axis of the vise. Such clamping techniques require a large amount of pneumatic piston surface area to generate sufficient clamping force, often exceeding 2500 pounds. Adequate piston surface area is generally obtained with a single large piston or multiple smaller pistons stacked axially. Either approach disadvantageously requires much space inside a milling machine, which is generally limited.

#Other clamping systems address the need for a large piston surface area by utilizing a high-pressure fluid (e.g., hydraulic or pneumatic pressure) to actuate the clamping fixture. Commonly available air pressure has a maximum pressure of around 180 pounds per square inch (psi). Such systems require a hydraulic pump and control valves to actuate the clamp and unclamping features. A hydraulic pump system, however, is not commonly installed on milling machines, necessitating the purchase of an auxiliary pump and control valves at often a high expense.

#Pneumatic and hydraulic clamping systems must also be double-acting or have a spring return (e.g., spring clamp). For double-acting systems, clamping pressure cannot be maintained in the event of a pneumatic or hydraulic pressure failure, resulting in the workpiece being released from the vise, creating a safety problem, and potentially causing costly damage. For spring clamps where hydraulic or pneumatic pressure is used to release the vise, a loss of system pressure leads to the vise not releasing or unclamping the workpiece. The failure to release a workpiece raises a new problem in which the applied clamping force is difficult to set and control, making it difficult to hold delicate workpieces.