Novel u-turn actuator has a halfway option

Dean Palmer reports on a compact, robust pneumatic swivel unit that boasts a continuously adjustable angle of rotation and an option to stop the device at its mid position A pneumatic oscillating swivel device has been developed with the objective of replacing ageing rotary actuators in a diverse range of machine building and parts handling applications. Italian company Gimatic's novel 'RT series' units, launched in December 2005, boast a patented single piston and 'pin-made' pinion actuator, making the device compact, robust and powerful. The unit also has a mid-position (90 degrees) stopper option. UK distributor for the RT Series is FS Engineering (Automation Systems) based in North Yorkshire. MD at the company Felix Stockmann, told Eureka: "Many of our machine builder customers have been overloading their conventional rack-and-pinion devices and so we can now offer them a powerful, robust but compact swivel unit, particularly if they have large loads to decelerate." According to Stockmann, the RT series units have better shock resistance and 50% less parts than conventional rack-and-pinion drives. This, he said, ensures improved reliability, durability and longer service lives (10 million cycles), compactness for installation in tight spaces, lower manufacturing and final product costs. The units have a hard, anodised aluminium housing, with distinctive red end plates, which houses a single pneumatic piston, including a rack to rotate the table via its pinned shaft. In other words, it is fitted with dowel pins rather than a typical geared pinion. The round teeth match the pins' diameter and provide a smooth translation of energy from linear to rotary motion. A robust, well-guided rack moves along in the opposite direction and its stroke is freely adjustable from both end caps to obtain any angle of rotation within the maximum of 190 degrees. Settings are made with either optional rubber capped screws for 'soft' stopping or with hydraulic shock absorbers to achieve an impressive repeatability of ±0.02°. There's also an optional intermediate stopping unit (RTD). This consists of a single acting cylinder with a bore larger than the chosen swivel unit. Operated by a separate solenoid valve, it can be actuated when the table is required to rotate to the mid-position at 90°. There are two large ball bearings on the drive shaft which provide high load capacity on a robust-looking table, which itself features threaded mounting holes and precision locations for custom tooling. The hollow rotary shaft enables air pipes and sensor leads to be routed internally to the table top. The top and bottom flat body, with threaded and through-holes, provides machine designers with a number of installation possibilities and optional flush-fitting stroke sensors can be fitted into the grooves on one side of the body to provide cycle signals to a PLC. The devices come in six sizes with bores from 10mm up to 63mm, giving torque ratings at 6 bar of 28Ncm up to 3,926Ncm. The RT series units are supplied with a manufacturer's warranty of 10 million cycles lubrication- and maintenance-free operation. Pointers: * The swivel units have a single piston rack and pin-made pinion patented movement for long service life * Optional intermediate stopper for mid-position * Optional proximity magnetic sensors for motion control * Continuously adjustable angle of rotation for flexibility