The valve is composed of return spring 2, slide valve 4 and valve body 3. The structure is shown in Figure 2-13. The traveling shuttle valve is installed on the top of the four-way directional valve and is controlled by the left traveling oil circuit. When the traveling and working devices (or rotary) are operated at the same time, the pressure oil from the shuttle valve of the working device (or rotary) pilot control valve (PPC valve) flows to the linear traveling valve through the traveling edge valve. Its working principle is shown in Figure 2-14.
(1) Operate the propel lever only. When the travel control lever is in the "forward" position, the control pressure oil from the left travel forward circuit flows to port P1 and pushes the slide valve to the right. Therefore, ports Pb, P.,, and Po are all connected through the grooves on the slide valve and are all connected with the linear travel valve. Since no pilot pressure oil flows out of the shuttle valve of the PPC valve, the straight travel valve does not work.
When the travel control lever is in the "reverse" position, the control pressure oil flows from the left travel reverse oil circuit to port P, pushing the slide valve to the left. Port P, port P: port, PS port and port P are all connected through the groove on the slide valve and are all connected with the linear travel valve. Because there is no pilot pressure oil from the pilot control valve (PPC valve), the linear travel valve does not work.
(2) Operate the traveling and working (or slewing) devices at the same time. Make the traveling control lever in the "forward" position, operate the stick control lever at the same time, control the pressure oil to flow from the left traveling forward oil circuit to port P, and push the slide valve to the right. The shuttle valve pilot pressure oil from the stick PPC valve flows to port Pb, then to port P through the groove on the slide valve, and then flows to the linear traveling valve.
When the boom (or bucket) and the traveling device are operated at the same time, as above, the shuttle valve pilot pressure oil from the boom (or bucket) PPC valve flows to port P → port PA → port P. port → linear traveling valve.
When the rotary and traveling devices of Komatsu excavator are operated at the same time, the shuttle valve pilot pressure oil from the rotary PPC valve flows to port P → port PA.
