New Position Switches Boost Productivity of Hydraulic MachineSystems

A new range of advanced, magnetically-operated position switches has been launched by Parker Hannifin. Called Read.me position switches, the new devices provide a simple and reliable method of

enabling the stroke position of hydraulic cylinders to be determined accurately and consistently, thereby enabling machine performance, functionality and productivity to be enhanced. Read.me switches are being introduced initially for use with Parker’s widely used, high performance HMI and 2H steel cylinders and will offer engineers an effective alternative to traditional and often unreliable position

sensing mechanisms.

The new Parker Read.me switch has been designed as a low profile external device, which can be used on conventional steel bodied cylinders operating at full rated pressures.

Cylinders fitted with Read.me switch technology incorporate powerful magnets mounted around the circumference of the piston. During initial setup, the magnets are used to format the cylinder body, simply by completing a full extension and retraction cycle of the piston, which imparts a residual magnetic field to the steel body.

Read.me switches can then detect the position of the piston magnets as they pass beneath each switch, as the piston magnets create a stronger magnetic field with opposite polarity to that of  the residual magnetism of the cylinder body. Each switch can therefore be located in the exact position required, with external red and yellow LEDs making it quick and simple to determine the precise sensing point before the switch is then locked firmly in place.

In operation, Read.me switches produce high levels of repeatability, to within 0.5mm, and can be used with Parker’s HMI and 2H cylinders at speeds of up to 0.5m/sec and at pressures of 210bar. As the sensing point is at the end of the switch, it enables each device to provide absolute end of stroke positioning when used at the cap end of the cylinder and within a maximum of 3mm of the end of stroke at the head end; this level of performance is equivalent to, or better than, most conventional end of stroke switches.