GROUP 6 RCV PEDAL

1. STRUCTURE
The casing has the oil inlet port P (primary pressure), and the oil outlet port T (tank). In addition the
secondary pressure is taken out through ports 1,2, 3 and 4 provided at the bottom face.

12.4 12.4

40.8
Secondary pressure(kgf/cm 2 )

30.6
30
LH
2 1 20.5+1.5
20.4
4 3
RH
10.2
5+1

0
0 1 2 3 4
0.7 3.4
VIEW "A"
Push rod stroke(mm)

R35Z72RCP01

LH RH
Port Port name Port size
P Pilot oil inlet port
T T Pilot oil return port
P
1 Travel (LH, Backward)
PF 1/4
2 14 3 2 Travel (LH, Forward)
3 Travel (RH, Backward)
4 Travel (RH, Forward)

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CROSS SECTION
The construction of the RCV pedal is shown in the below drawing. The casing has vertical holes in
which reducing valves are assembled.
The pressure reducing section is composed of the spool (19), spring (22) for setting secondary
pressure, return spring (23), spring seat (20) and washer (21). The spring for setting the secondary
pressure has been generally so preset that the secondary pressure is 5 to 19 kgf/cm2 (depending on
the type). The spool is pushed against the push rod (10) by the return spring.
When the push rod is pushed down by tilting pedal, the spring seat comes down simultaneously and
changes setting of the secondary pressure spring.

29
30
25 26
28
27
10
5
6
4
18
3
8
13 9
24
12 2
20 14
7 16

11 22
21 23
15
17
19

1 R35Z72RCP02

1 Casing (1) 11 Shim 21 Washer

2 Casing (2) 12 Spring seat 22 Spring
3 Cover 13 Piston 23 Spring
4 Plug 14 Steel ball 24 Spring
5 Grease cap 15 Plug 25 Cam shaft
6 Packing 16 Plug 26 Bushing
7 O-ring 17 O-ring 27 Cam
8 O-ring 18 Hex soc head screw 28 Steel ball
9 O-ring 19 Spool 29 Set screw
10 Push rod 20 Spring seat 30 Bellows

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2. FUNCTION
1) FUNDAMENTAL FUNCTIONS
The pilot valve is a valve controls the spool stroke, direction, etc of a main control valve. This
function is carried out by providing the spring at one end of the main control valve spool and
applying the output pressure (secondary pressure) of the pilot valve to the other end.
For this function to be carried out satisfactorily, the pilot valve is composed of the following
elements.
(1) Inlet port (P) where oil is supplied from hydraulic pump.
(2) Output port (1, 2, 3 & 4) to apply pressure supplied from inlet port to ends of control valve spools.
(3) Tank port (T) necessary to control the above output pressure.
(4) Spool to connect output port to inlet port tank port.
(5) Mechanical means to control output pressure, including springs that work on the above spools.
2) FUNCTIONS OF MAJOR SECTIONS
The functions of the spool (19) are to receive the supply oil pressure from the hydraulic pump at its
port P, and to change over oil paths to determine whether the pressure oil of port P is led to output
ports 1, 2, 3 & 4 or the output spool to determine the output pressure.
The spring (22) works on this spool to determine the output pressure.
The change the deflection of this spring, the push rod (10) is inserted and can slide in the plug (4).
For the purpose of changing th displacement of the push rod through the cam (27) and steel ball
(28) are provided the pedal that can be tilted in any direction around the fulcrum of the cam (27)
center.
The spring (23) works on the casing (1) and washer (21) and tries to return the push rod (10) to the
zero-displacement position irrespective of the output pressure, securing its resetting to the center
position.
This also has the effect of a reaction spring to give appropriate control feeling to the operator.

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3) OPERATION
The operation of the pilot valve will be described on the basis of the hydraulic circuit diagram shown
below ant the attached operation explanation drawing.
The diagram shown below is the typical application example of the pilot valve.

5 6

3
1
2

2 4

140LC-7 기타2-76

1 Pilot valve 3 Main pump 5 Hydraulic motor

2 Pilot pump 4 Main control valve 6 Hydraulic cylinder

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(1) Case where pedal is in neutral position

22
T 19
23
P

R35Z72RCP04

The force of the spring (22) that determines the output pressure of the pilot valve is not applied to
the spool (19). Therefore, the spool is pushed up by the spring (23) to the position of port 2 in
the operation explanation drawing. Then, since the output port is connected to tank port T only,
the output port pressure becomes equal to tank pressure.

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(2) Case where pedal is tilted

10

19

Port 1

R35Z72RCP05

When the push rod (10) is stroked, the spool (19) moves downwards.
Then port P is connected with port 1, and the oil supplied from the pilot pump flows through port
1 to generate the pressure.
When the pressure at port 1 increases to the value corresponding to the spring force set by tilting
the handle, the hydraulic pressure force balances with the spring force. If the pressure at port 1
increases higher than the set pressure, port P is disconnected from port 1 and port T is
connected with port 1. If it decreases lower than the set pressure, port P is connected with port
1 and port T is disconnected from port 1.
In this manner the secondary pressure is kept at the constant value.

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3. BOOM
BOOM SWING P
PEDAL
EDAL
1) STRUCTURE
TRUCTURE
The casing has the oil inlet P (primary pressure) and the oil return port (tank).
In addition the secondary pressure is taken out through port 1 and port 2 provided at the housing
bottom face.

40

Secondary pressure(kgf/cm 2 )
20+1.5

5+1

0
24 0 3.5
0.7 2.7

Push rod stroke(mm)

1 2
R35Z72RSP01

Port Port name Port size

P Pilot oil inlet port
T Pilot oil return port
PF 1/4
1 Boom swing (LH)
2 Boom swing (RH)
1 T P 2
Hydraulic circuit

2-73
2) COMPONENT
OMPONENT

19

16
17

20 18
15

13,14 12

11

7 10
6 9

3, 4

1
8

R35Z72RSP02

1 Body 8 Stopper 15 DU bush

2 Plug 9 Spring 16 Wrench bolt
3 O-ring 10 Plug 17 Cam
4 Spool 11 O-ring 18 Pin
5 Spring seat 12 Rod seal 19 Adjust screw
6 Spring 13 Push rod 20 Socket bolt
7 Spring seat 14 Cover 21 Bellows

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4. DOZER
DOZER LEVER
1) STRUCTURE
TRUCTURE
The casing has the oil inlet P (primary pressure) and the oil return port (tank).
In addition the secondary pressure is taken out through port 1 and port 2 provided at the housing
bottom face.

22 22

Secondary pressure(kgf/cm 2 )
22 +30

5+1

0
0 2 4 6 7
1+0.5

Push rod stroke(mm)

T T

P P

1 2

1 2

R35Z72DL01

Port Port Port size

P Pilot oil inlet port PF 1/4

T Pilot oil return port PF 1/4

1 Dozer blade up port PF 1/4
1 T P 2 2 Dozer blade down port PF 1/4
Hydraulic circuit

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2) COMPONENT
OMPONENT

23

22
16
21
14
19
13
15
11
18
9
17 , 20
5
8 10

7 12

6 4

3 2
1

R35Z72DL02

1 Body 9 Stopper 17 Pin

2 Plug 10 Plug 18 Socket bolt
3 O-ring 11 Rod seal 19 Nut
4 Spring 12 O-ring 20 Snap ring
5 Spring seat 13 Push rod 21 Spring pin
6 Spool 14 Cover 22 Bellows
7 Spring seat 15 Wrench bolt 23 Lever
8 Spring 16 Guide

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