《机床与液压》七七年第三期刊登的“宝鸡石油机械厂”改进B690的经验介绍,可使滑枕换向时的冲击及振动减小。如果再对换向卸荷做一点改进,还可以使滑枕换向时的振动进一步减弱。原系统中,先导阀在滑枕的拨动下,首先到达卸荷位置,将安全阀的控制腔与低压溢流阀联通,以使油泵输出大部分油液以较低压力经安全阀流回油池。因为控制卸荷的球形溢流阀动态指标较差,反应也不灵敏,所以在卸荷瞬间,将产生较大的压力振摆,卸荷压力难维持在额定值(6～8公斤力/厘米~2)。当其它改进工作已完后,(参阅“机床与液压”七七年第三期68页)试车中观察压力表,压力可瞬间降至2～3公斤力/厘米~2 “Machine and Hydraulic” published in the third issue of 1977 “Baoji Petroleum Machinery Factory” to improve the B690 experience introduced, the impact and vibration can be reduced when the ram change. If we do a little improvement to the diverting unloading, you can also make the vibration of the ram to further weaken. The original system, the pilot valve in the ram toggle, the first to reach the unloading position, the safety valve control chamber and low pressure relief valve Unicom, so that most of the oil pump output at a lower pressure through the safety valve back to back Oil pool. Because the unloading spherical relief valve dynamic index is poor, the reaction is not sensitive, so the moment of unloading, will have a greater pressure swing, unloading pressure difficult to maintain the rating (6 ~ 8 kgf / cm ~ 2). When other improvement work is finished, watch the pressure gauge during the trial run (see “Machine Tool & Hydraulics”, Vol. 3, No. 68, p.73), and the pressure can be instantly reduced to 2 ~ 3 kgf / cm ~ 2