BUSHING-ROCKER 5362844 - Caterpillar

General Information
Illustration 1 g00858317
When the machine is equipped with a bulldozer blade, the bulldozer lift control valve is the first valve in the valve stack. The bulldozer lift control valve controls the vertical movement of the bulldozer blade. The control valve includes these components: control valve spool (3), makeup valve (7), resolver (13) and load check valve (17) .The bulldozer lift control valve is a spring centered valve. Control valve spool (3) is a closed center spool and a pilot operated spool with four positions: RAISE, HOLD, LOWER and FLOAT. Spring (1) keeps the spool in HOLD position when the bulldozer circuit is not active. Movement of the spool is controlled by the pilot control system. The pilot control system connects the bulldozer control lever to control valve spool (3) .Resolver (13) is a two-way check valve. The functions of the resolver and of the control valve spool are described in the sections on positions of the control valve. Descriptions for load check valve (17) and makeup valve (7) are in separate sections.Load Check Valve
Load check valve (17) prevents reverse oil flow in the lift cylinders, which can cause cylinder drift or load loss. The load check valve does not open until pump oil pressure in chamber (15) becomes greater than the force of the spring for the load check valve and the cylinder oil pressure in passage (16) .Makeup Valve
Makeup valve (7) is in the head end of the lift circuit. The makeup valve opens when cylinder oil pressure in passage (6) drops 14 kPa (2 psi) below the return oil pressure in outlet passage (5). Makeup valve (7) adds return oil in outlet passage (5) to cylinder oil in passage (6). The additional oil prevents cavitation (vacuum) in the lift cylinders.Basic Valve Operation
Illustration 2 g00858385
Illustration 3 g00858317
When the control valve spools are in the HOLD position, pump oil flows to inlet passage (14). This passage is common to all sections of the valve stack. Since all the valve spools are in the HOLD position, pump oil fills the parallel oil passages of the control valves. The pump maintains oil pressure at 2950 kPa (410 psi). Passage (8), chamber (9), resolver (13), and passage (18) are drained. Passages (4), (6), and (16) are blocked.
Illustration 4 g00858416
Illustration 5 g00858332
When pilot control pressure causes control valve spool (3) to move to the RAISE position, cylinder oil from passage (4) flows through passage (2) to chamber (9). The oil functions as signal oil. The signal oil opens resolver (13) and flows through the inlet manifold to the compensator valve on the pump.The increase of pump oil flow to inlet passage (14) opens load check valve (17). The oil flows through load check valve (17). The oil then flows through passage (16) around control valve spool (3) and out passage (4) to the rod ends of the lift cylinders. The oil flow to the rod end of the lift cylinders raises the bulldozer blade.Return oil from the head end of the lift cylinders flows through passage