Proportional solenoids generate a proportional force effect from an electrical input signal. The force is created
between the movable armature and the magnetizable counter-piece. Due to this known physical effect and
inherent to the functional principle, the magnetic force can actuate in one direction only. The return movement is
made by a spring. Based on this principle the realization of well controllable hydraulic and pneumatic valves is
possible. The novel solenoid design developed at MSM enables a bi-directional force effect. For this, particularly
the armature is considerably modified and fitted with permanent magnets. In addition to the influence of the
force direction, the pre-magnetisation of materials causes a considerable improvement of dynamics.

During the last two decades the aspect of functional safety has constantly gained more importance for all
manufactures of mobile hydraulic machines or manufactures of subsystems used therein. Initiated by the IEC
61508 /1/ first issued in 1998 many divisions have deduced their own standards concerning functional safety
with the goal to build control structures that are leading to fewer occurrence of dangerous situations during
normal machine operation as well as in the case of a failing subsystem.
Looking into the failure modes assigned to a Proportional Pressure Reducing Valve (PPRV) within the ISO
standard 13849 /2/ it was possible to integrate an intrinsic safety function into various types of pressure reducing
valves. In the case of a stuck valve spool this fail safe function opens a second flow path from the control port to
tank (Figure 1) resulting in a limited output pressure (Figure 2). For applications where this limited control
pressure is in accordance with a safe situation this fail safe function is lowering the number of failure modes that
are contributing to a dangerous situation and therefore is able to increase the diagnostic coverage of a subsystem
build with such a fail safe valve. Depending on the working principle of the pressure reducing valve different
types of fail safe designs are needed in order to realize this functionality.

Pressure control valves combine both a reducing and a relieving function. Such valves typically are spool type
valves which principally suffer from leakage flow. Additionally, in case of an electrical failure, usual
proportional pressure reducing and relieving valves fully open either the supply port connection or the tank port
connection. In some applications like clamping functions in machine tools, this is a clear disadvantage. For fail
safe operation in machine tools, it is desired to hold the set pressure in case of failure. The article introduces a
new kind of proportional pressure reducing and relieving valve, which is leak-free due to seat valve technology.
Furthermore, the valve is able to keep the set pressure in case of power-off and is therefore well-qualified for
clamping applications.

The trend of intelligent components can be observed in various fields. Intelligent component means components
with highly integrated sensors and control technology. This enables the system manufacturer to design more
complex equipment, and nevertheless decrease in the required integration effort. As a customer-oriented supplier
and development partner WEBER-HYDRAULIK concern itself with the development of highly integrated,
reliable and reasonably priced sensors for hydraulic cylinders. While an optical position transducer is developed
for mass production, this article focuses on the development activities of an in-cylinder integrated force
measurement. Parallel to the further development of the application-specific force measurement system for
supporting cylinders, a universally applicable concept for contactless force measurement was investigated.