PISTON 0931559 - Caterpillar

Illustration 1 g00861423
(1) Open grapple arms. (2) Close grapple arms.Pedal operated valves control the travel system and the grapple arm cylinders. Pedal operated valves get pilot oil pressure from the implement pump.When the grapple pedals are operated, the pilot control valves send pilot pressure oil from the implement pump through the pilot lines to the pilot ports at the implement control valve in order to shift the spool for the grapple cylinders.In order to operate the grapple arms, the hydraulic lockout control must be in the UNLOCKED position. When grapple pedal (1) is depressed the grapple arms will open. When grapple pedal (2) is depressed the grapple arms will close. Grapple pedals (1) and (2) move independently of each other. The pedals cannot be simultaneously depressed.Reference: For additional information on the hydraulic lockout control, refer to Operation and Maintenance Manual, "Hydraulic Lockout Control" for the machine that is being serviced.
Illustration 2 g00861428
(3) Pin. (4) Base. (5) Plunger guide. (6) Race. (7) Springs. (8) Hydraulic tank port. (9) Spool valve. (10) Pilot oil supply port. (11) Controller housing. (12) Pilot pressure port.When grapple pedal (2) is depressed, the pedal pushes down on pin (3) and plunger guide (5). Plunger guide (5) is then pushed against springs (7). Springs (7) compress. Springs (7) push down on spool valve (9). Spool valve (9) moves down and pilot pressure oil inside hydraulic port (10) flows through the center of spool valve (9). Oil then flows from the center of spool valve (9) through pilot pressure port (12). Spool valve (9) is a pressure reducing valve. As pressure increases in port (12) the oil pushes up on the bottom spool valve (9) in order to meter the flow into the center of spool valve (9) .When the pedal is released, springs (7) push up on plunger guide (5) and pin (3). Hydraulic oil drains through the center of spool valve (9) to hydraulic tank port (8).