Advanced open type hydraulic system design, small change impact, low noise. The constant power control, can automatically adjust the displacement, non metal gear, as between the main pump and motor with low noise, long service life, pumping circuit adopts non-contact, automatic control and delay, reversing accuracy, reliable and stable, the key parts imported seal element, long service life, high reliability, with high and low pressure switching device, concrete pump suitable for high pressure and large displacement of small displacement based delivery.