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Parker Hannifin has launched advanced, magnetically operated position switches that boost the productivity of hydraulic machine systems.

The position switches are said to provide a simple and reliable method of enabling the stroke position of hydraulic cylinders to be determined accurately and consistently, thereby enhancing machine performance, functionality and productivity.

The switches are being introduced initially for use with the company’s high-performance HMI and 2H steel cylinders and will offer engineers an effective alternative to traditional and often unreliable position-sensing mechanisms.

To date, the stroke position of hydraulic cylinders has generally been measured using external end stroke limit switches, which are vulnerable to damage and cannot be used to indicate the midpoint positions of the piston.

Alternatively, double-rodded cylinders that trip mechanical switches, or external sensors activated by magnetic pistons inside aluminium or non-ferrous cylinders, can be used.

These methods can, however, increase overall cylinder dimensions or be located in exposed positions where they can become misaligned, resulting in a loss of accuracy; in addition, aluminium or non-ferrous cylinders have a relatively low pressure rating, which limits their potential application.

By comparison, the new Parker switch has been designed as a low-profile external device that can be used on conventional steel-bodied cylinders operating at full-rated pressures.

Cylinders fitted with switch technology incorporate powerful magnets mounted around the circumference of the piston.

During initial setup, the magnets are used to format the cylinder body by completing a full extension and retraction cycle of the piston, which imparts a residual magnetic field to the steel body. 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 light-emitting diodes (LEDs) making it quick and simple to determine the precise sensing point before the switch is then locked firmly in place, according to Parker.

In operation, switches produce high levels of repeatability, to within 0.5mm, and can be used with the company’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.

Unlike traditional methods of position sensing, single or multiple switches can be placed anywhere along the stroke length and do not affect the overall dimensions of the cylinder.

In addition, the non-contact design has no moving parts, ensuring a long operating life, while setup, operation and, if required, reconfiguration, are straightforward, with electrical output taking place via standard switch connectors.

Parker Hannifin — Parker Sales UK

With annual sales exceeding $10bn, Parker Hannifin is the world's leading manufacturer of motion and control technologies and systems, providing precision-engineered solutions for a wide variety of commercial, mobile, industrial and aerospace markets.

To meet its customers' needs in motion and control, Parker provides the broadest range of products available from any single supplier. This is supported by expertise in nine major technologies:

  • Hydraulics
  • Pneumatics
  • Electromechanical
  • Filtration
  • Process control
  • Fluid and gas handling
  • Sealing and shielding
  • Climate control
  • Aerospace

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