The innovative SXP EVO system for front loaders and other lifting applications will be introduced at bauma 2019. The system can increase both efficiency and productivity thanks to its capacity to switch the logic element, thus combining the features and benefits resulting from two different circuits, Series and Parallel. The very first tests carried out so far highlighted encouraging results, such as a reduction of machine cycle time by over 20%.
by Alessandro Cervi
Walvoil SXP EVO, evolution of the SXP directional valve already awarded as “technical news” at Eima International 2018, is an innovative system developed for front loaders and other lifting applications that will be launched at bauma 2019 in Munich.
The main feature of new Walvoil SXP patented directional valve is the possibility to switch autonomously from Series Circuit to Parallel Circuit only by detecting the pressure of the circuit and managing this parameter together with the information set by the user. The system increases the efficiency and productivity of the machine because the unconventional series circuit drastically reduces the cycle time; thanks to the uninterrupted switch to the parallel configuration, the maximum load capacity is granted and the operator doesn’t perceive any change in the control of the machine.
An integrated solenoid valve to switch the logic element
The switch of the logic element – the core of the SXP EVO system – is possible thanks to an integrated solenoid valve, appropriately managed by the system’s electronics.
The complete system (see Figure 1) is indeed equipped with a sensor to detect the pressure of the hydraulic circuit and an ECU. This layout enriches the solution created on the valve, offering high flexibility to OEMs but also to end users, thanks to the possibility of setting and customizing the work mode appropriately.
The work mode can be simply set by selecting it on the control panel. In the MIXED system, the circuit works as Series circuit until the pressure sensor detects a pressure value that requires the switching to Parallel configuration.
By selecting the appropriate mode, one could even choose to work with fixed configurations, i.e. exclusively in Series or Parallel without switching.
Combining two different circuits in a single system
The idea of combining the characteristics of two constructively different circuits in a single system stems from a careful analysis of these two systems (Figure 2).
The Series circuits make it possible to increase the loaders speed since, in the first stage, the oil is recovered from the return of the boom and not dissipated to tank. Furthermore, the controllability of the machine is improved since the simultaneous boom and bucket movements are completely controlled and guaranteed even with very different pressure loads.
On the other hand, in Series circuits, in case of simultaneous use, the pressure summation limits the maximum load capacity of the machine. For this reason, today some OEMs prefer the Parallel circuits in order to maximize the lifting capacity and to avoid the annoying effect of the Series circuits: if the cylinders of a function reach their stroke end, also the cylinders of the other function stop.
The system enjoys the benefits resulting from both the circuits
Clearly, these circuits are not free from defects: in case of simultaneous use and depending on the movement and the position of the load, a correct controllability of both movements is not granted. Thanks to the new Walvoil SXP patented system, it is possible to overcome the traditional dichotomy between Series circuit valves (which optimize speed and controllability) and Parallel circuit valves (which optimize load capacity), using a system that combine the positive features of both circuits (Figure 3). The innovation is achieved with a simple device which can be inserted as an additional section into Walvoil wide range of valves or it can be totally integrated in a completely new and customized solution with advantages in terms of cost.
The system prototypes have already been manufactured and tested in the field, showing some great advantages: in specific conditions, in fact, the machine cycle time has been reduced by over 20%. Professional users have confirmed ease of use and working comfort.
The electronic joystick
The SXP EVO system is completed by an innovative HJW Heavy Duty Joystick: an electronic joystick, characterized by its “robust design”. Thanks to its characteristic modularity, it can be provided with mechanical or electromagnetic detent, typically used on the Loader application. Particulary robust and performing, it can be equipped with all the handles and options of Walvoil wide range. It has been set up to communicate with Walvoil control units in order to implement the complete system logic in a simple and efficient solution. The Fan Drive modules and the brand-new Group 3 gear pump complete the Walvoil specific solution for wheel loaders. l
(Eng. Alessandro Cervi is Hydraulics Project Manager at Walvoil Spa)