Three versions of such devices are available to cope successfully with a wide spectrum of requirements for hydraulic shears. They offer optimum solutions for decreasing cycle times, reducing machine noise, achieving energy savings and avoiding any necessity for installing cumbersome heat exchangers.

These devices feature an hydraulic accumulator, which offers two major advantages:

- possibility of achieving angle variations without compelling the max pressure valve to pour;
- a soft inversion at the low end of stroke. The accumulator stores kinetic energy and later on it delivers such energy to drive blank holder cylinders at a speed which is higher then that corresponding to max pump flow.

Devices feature also a differential valve which has the purpose of giving way to oil that comes out from the small (rod) side of cylinder. While the tool is cutting, and until cutting pressure has not reached the set pressure of the differential valve (which is normally set up at a value 10% to 12% lower than that of the max pressure valve), such oil is re-cycled back to input port. Within limits of operation of differential valve, such an arrangement allows for an increase of shearing speed ranging from 30% to 50%, which leads to best results also from a technological point of view. After having reached the set-up pressure, the differential valve turns off and oil outcoming from the small (rod) side of cylinder sinks to tank. In this way, absence of back-pressure is assured, so that shearing force corresponds to nominal nameplate power plus the weight of shear assembly.

To summarise:

- down stroke of blank holder driven by accumulator and pump
- shearing phase controlled by differential valve
- fast inversion, at the end of down stroke, through absorption of moving mass energy by means of accumulator
- total installed power is available for shearing process
- optionally, it is possible to get the blade coming down only after the blank holder has reached a back-pressure corresponding to 60% of accumulator pressure. There is also the possibility of further conditioning of the cutting electrovalve, in order to achieve the function of "cutting mark". Furthermore, the up stroke of blade may be controlled in such a way as to be leading or lagging, in comparison with the up stroke of blank holder.

As far as maintenance is concerned, a suitable procedure consists of:

- switch pump off
- with blade in tracing (up) position, by energizing E2 the accumulator will discharge, causing the blade coming down at a speed which can be controlled by the nozzle placed beneath 1M electrovalve.