LAMP GP 9W0051 - Caterpillar

Lockdown (Earlier Machines)
SCHEMATIC OF CUSHION-HITCH HYDRAULIC SYSTEM (LOCKDOWN) (Earlier Machines) 1. Selector valve.2. Oil passage.3. Oil passage.4. Oil passage.5. Pilot valve section.9. Oil line.10. Oil line.12. Accumulators (two).13. Hydraulic cylinder.18. Oil line.19. Centering valve stem.20. Oil line.21. Spring on hitch link.22. Oil pump.B. Pilot valve stem.G. Lockdown check valve.When the lever on selector valve (1) is moved from CUSHION RIDE position to LOCKDOWN position, the pump oil in line (9) is stopped at the selector valve. With no pressure in line (10), the spring over pilot valve stem (B) moves the valve stem to a position, in pilot valve section (5), where passage (3) connects with the passage in the pilot valve section from oil line (20). The position of pilot valve stem (B) opens passage (2) to pump oil. It also opens passage (4) to the top of lockdown check valve (G), passage (3) and oil line (20). The closed circuit oil on top of check valve (G) moves the valve and closes it. Now there is a closed hydraulic circuit from accumulators (12) and head end