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RE 66 125-B2/08.07
Hitch control valves EHR5 and
EHR23 for mobile applications
Product-specific Instructions
2/28 Bosch Rexroth AG Product-spezific Instructions RE 66 125-B2/08.07
What you need to know about these Operating Instructions
These Operating Instructions apply to Rexroth directional control and hitch control valves for mobile control units
and consist of the following three parts.
Part I General Information RE 64 020-B1
Part II Product-specific Instructions RE 66 125-B2
Part III Technical Data Sheet RE 66 125/09.04
Important: The illustrations on the cover only represent a few of the possible valve options.
To assist your understanding of these Operating Instructions
Cross-references are printed in italics.
! DANGER This symbol of danger indicates high risk, danger of loss of life or of serious injury.
! WARNING This symbol of danger indicates medium risk, injury and serious damage to property.
! CAUTION This symbol of danger indicates slight risk and possible damage.
Important This symbol indicates additional information.
Bosch Rexroth AG
RE 66 125-B2/08.07 Product-spezific Instructions 3/28
Contents
1 Scope of delivery .........................................................4
2 Validity of these Operating Instructions .....................................4
3 Supplementary basic safety advice .........................................5
3.1 Information on the nameplate .........................................5
3.2 Additional nameplates on the product ..................................5
3.3 Special ancillary dangers and protective measures . . . . . . . . . . . . . . . . . . . . . . . 6
4 Assembly and (initial) start-up .............................................7
4.1 Safety advice for assembly and initial start-up ...........................7
4.2 Assembly hitch control valve EHR5 ....................................7
4.3 Assembly hitch control valve EHR23 ...................................8
4.4 Making the hydraulic connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
4.5 Making the electrical connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
4.6 Actuation of electrical hitch control valves EHR .........................12
4.7 Bringing into (first) use, subsequent bringing into use ....................13
4.8 Retrofitting and conversion ..........................................13
4.9 Disassembly hitch control valve EHR5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
4.10 Disassembly hitch control valve EHR23 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
5 Operation ..............................................................18
5.1 Hydraulic symbols .................................................18
5.2 Hitch control valves for electro-magnetic actuation . . . . . . . . . . . . . . . . . . . . . . 20
5.3 2-way pressure balance (individual pressure balance) ....................20
5.4 Check valve .......................................................20
5.5 Load safety valve (LSV) .............................................20
6 Trouble-shooting ........................................................21
6.1 Procedure for function test in the field .................................25
7 Maintenance ............................................................27
7.1 Repairing .........................................................27
8 Accessories and replacement parts ........................................27
8.1 Accessories ......................................................27
8.2 Replacement parts .................................................27
8.3 Contact for ordering accessories and replacement parts . . . . . . . . . . . . . . . . . 27
4/28 Bosch Rexroth AG Product-spezific Instructions RE 66 125-B2/08.07
Scope of delivery1
For details regarding the scope of delivery applicable to your valve model, please generally
refer to the Technical Data Sheet for this valve (Part III of these Operating Instructions).
As an OEM customer, you will find the exact scope of delivery in the quotation drawing of
this valve, in individual cases, Bosch Rexroth will provide further information.
Validity of these Operating Instructions2
These product-specific instructions apply to all hitch control valves types EHR5 and EHR23,
independently of their date of production, until a new version of this document is issued.
Bosch Rexroth AG
RE 66 125-B2/08.07 Product-spezific Instructions 5/28
Supplementary basic safety advice3
Information on the nameplate 3.1
Important The details on the nameplate apply to the valve in its delivery condition. If conversions have
been made to the valve that effect its delivery condition, the details stated on the nameplate
may possibly no longer apply to your valve.
By comparing the material number of the valve stated on the nameplate and the details on
the quotation drawing, make sure that these operating instructions apply to your product.
In
case of doubt please contact Bosch Rexroth AG.
Apart from the manufacturer’s brand (Bosch or Rexroth), the 10 digit material number
(0 52. ... ... or R 917 ... ...) and the country of origin, only details required for internal purposes
of Bosch Rexroth AG are on the nameplate of the Bosch or Rexroth hitch control valves EHR
manufactured before April 2005. For hitch control valves EHR manufactured after April 2005
the year and week of manufacture are stated on the nameplate as follows:
YYwXX
YY = year of manufacture, XX = calendar week
Example:
05w15 = year of manufacture 2005, calendar week 15
015
Made in Germany
Made in Germany
7920
05wXX
MNR: R917XXXXX
Made in
Germany
7920
Additional nameplates on the product3.2
Other labelling on the product is solely intended for internal purposes of Bosch Rexroth AG.
Nameplate of valves manufactured before January 2004.
Nameplate of valves manufactured after January 2004.
Nameplate of valves manufactured after April 2005 stating the
year and week of manufacture, if necessary with barcode for
internal purposes of Bosch Rexroth AG
6/28 Bosch Rexroth AG Product-spezific Instructions RE 66 125-B2/08.07
Special ancillary dangers and protective measures3.3
! DANGER Danger zone Ancillary danger Protective measure(s),
safety instructions
Sharp edges on the valve
housing, on threads on the
valve, on the valve spoo
Danger of cutting limbs Only touch the valve wearing
safety gloves.
Valve housing Danger of injury due to parts
flung out by spring force dur-
ing removal of screw plugs
on the valve when disassem-
bling.
Carefully remove the screw
plugs.
When loosening screw
plugs, always exert strong
counter-pressure!
Valve housing,
valve solenoid,
plug connector
Danger of burning on hot
surfaces during operation
Only touch the valve wearing
safety gloves.
Before beginning work on
the valve, put it out of oper-
ation and allow it to cool
down.
Advice on use3.3.1
The hitch control valves EHR must be used only for the purpose specified in Part III, Tech-
nical Data Sheet. If you wish to use the valve for purposes other than those specified in the
Technical Data Sheet, please contact Bosch Rexroth AG before doing so.
Bosch Rexroth AG
RE 66 125-B2/08.07 Product-spezific Instructions 7/28
Assembly and (initial) start-up4
Safety advice for assembly and initial start-up4.1
Please observe the safety instructions in Part I, General Information in 6 Assembly and Ini-
tial Start-up.
Assembly hitch control valve EHR54.2
Tools required:
Torque spanner, suitable for a tightening torque of 30 Nm
Cleaning agent: Grindstone or oil stone, oil-soaked cleaning cloth
Required material:
1 seal set, Mat. No. 1 527 010 381
3 fastening bolts, strength class 10.9
Assembly precondition:
The sealing surface and sealing elements must be undamaged, clean and dry, clean with a
cleaning agent if necessary.
Install the hitch control valve EHR5
1. Insert new O-rings into ports R1
and R2, P, Y and A’ if necessary. For
EHR5-LS, additionally insert a back-up
ring into port P.
2. Attach the hitch control valve EHR5
to the flange intended by the vehicle
manufacturer using 3 fastening bolts
of strength class 10.9. Tighten the
fastening bolts with a tightening torque of
25 +6 Nm.
8/28 Bosch Rexroth AG Product-spezific Instructions RE 66 125-B2/08.07
Assembly hitch control valve EHR234.3
Assemble the individual valve modules into a valve manifold4.3.1
Tools required:
Torque spanner, spanner size 13, suitable for a tightening torque of 30 Nm
Cleaning agent: Grindstone or oil stone, oil-soaked cleaning cloth
Material required:
For hitch control valve EHR23-LS (see Technical Data Sheet):
one seal set Mat. No. 1 527 010 442 per hitch control valve module
For hitch control valve EHR23-ZM (see title page illustration):
one seal set Mat. No. 1 527 010 441 per hitch control valve module
Connecting plate (with O-rings and spacing washer 0.04 mm)
Valve modules (with O-rings and spacing washer 0.04 mm)
End plate
Three tie rods with nuts
You will find the specification of the tie rods and their material numbers that are required
for the number of valve modules used in the Block quotation drawing and/or the Tech-
nical Data Sheet. Only specified tie rods of strength class 10.9 may be used!
Assembly precondition:
All sealing surfaces and sealing elements must be undamaged, clean and dry, clean with a
cleaning agent if necessary.
Installing the connecting plate
1. Oil the tie rods and nuts (for later use).
2. Manually screw in the tie rod screws to the bottom of the threaded hole.
3. When re-using an already used connecting-plate, and if adhesive spacer elements were
formerly stuck to this connecting plate:
Push one spacing washer onto each of the tie rod screws (1), (2) and (3).
4. If the flange surface has embossments that have been treated with a grindstone:
Push one spacing washer onto each of the tie rod screws (1), (2) and (3).
5. Insert new O-rings into ports P, Y and R, additionally insert new backup rings into
ports P and Y. In case of electrically actuated directional control valves, also insert new
O-rings into ports X and Rx.
Bosch Rexroth AG
RE 66 125-B2/08.07 Product-spezific Instructions 9/28
Mount the hitch control valve module
EHR23
1. Fit the hitch control valve module
intended for the position correspond-
ing with the specification of the vehicle
manufacturer, onto the tie rods.
2. When re-using a used hitch control
valve module:
If the flange surface has embossments
that have been treated with a grind-
stone:
Push one spacing washer onto each of
the tie rod screws (1), (2) and (3).
3. Insert shuttle valve (6) into port Y
without jamming, dimension X must be
0.5 mm.
4. Insert new O-rings into ports P, Y
and R. In case of electro-hydraulically
actuated EHS valves, also insert new
O-rings into the control oil connections
X and Rx.
5. Install further directional control valve
modules in the same way.
Installing the end plate
1. Push the end plate (EP) onto the tie
rods and twist the nuts onto the tie
rods by hand.
2. Align the valve modules lying horizon-
tally on the work plate.
Tightening the nuts
1. Tighten the tie rod nuts in the order
(1) (2) (3) with the tightening torque
stated in the illustration.
gen Anziehdrehmoment anziehen.
6
X
EP
AP
10/28 Bosch Rexroth AG Product-spezific Instructions RE 66 125-B2/08.07
Attaching the valve manifold4.3.2
To fasten an assembled valve manifold to a supporting surface, the connecting plate (AP) and
end plate (EP) are each equipped with two threaded holes, see Page 10.
Drill holes must be made in the supporting surface, through which the fastening bolts are
passed, see illustration. An oblong hole must be made in X direction, either on the AP or
the EP side, which enables the compensation of the tolerance range stated in the table. In
Y direction the positions of the holes and their diameters must be chosen such that a toler-
ance range of ±0.3 mm can be compensated
Supporting surface for control block with hitch control valve EHR23
1 2 3 4
D
D
Y
Xmax
Xmin
Mounting holes in the supporting surface
For
thread
Ø D Dimension Y
[mm] Ymin [mm] Ymax [mm]
M8 9 +0,2 93,7 94,3
M10 11 +0,2 93,7 94,3
M12 13 +0,2 93,7 94,3
For
thread
Dimension
X
[mm]
Number of directional control valves including hitch control valve
EHR23 in the valve manifold
123456789
M8 Xmin
Xmax
59,6
60,3
99,4
100,4
139,2
140,5
179,0
180,6
218,8
220,7
258,6
260,8
298,4
300,9
338,2
341,0
378,0
3 81,1
M10 Xmin
Xmax
69,6
70,3
109,4
110,4
149,2
150,5
189,0
190,6
228,8
230,7
268,6
270,8
308,4
310,9
348,2
351,0
388,0
3 91,1
M12 Xmin
Xmax
64,1
64,8
103,9
104,9
143,7
145,0
183,5
185,1
223,3
225,2
263,1
265,3
302,9
305,4
342,7
345,5
382,5
385,6
1 Connecting plate (AP)
2
First directional control valve
3
Last directional control valve
4 End plate (EP)
Bosch Rexroth AG
RE 66 125-B2/08.07 Product-spezific Instructions 11/28
Requirements relating to the screw connection and the supporting surface
For thread Strength
class
Tightening
torque
[Nm]
Screw-in depth
in AP/EP
[mm]
Max. roughness
Rz,max of sup-
porting surface
[µm]
Min. levelness of
supporting sur-
face
[mm]
M8
8.8
10.9
20 + 4
30 + 6 min 11 63 0,1
M10 8.8 40 + 8 min 15 63 0,1
M12 8.8 75 + 15 min 18 63 0,1
• Observe requirements relating to the supporting surface.
• Only fasten the valve manifold with the recommended bolts of one of the stated quali-
ties.
• Tighten the fastening bolts with the respective tightening torque stated in the table.
Making the hydraulic connection4.4
Depending on the type the valves are equipped with cylindrical metric (M) or cylindrical Whit-
worth connection thread (G).
Sealing takes place, depending on the type, either by means of a cutting ring connector to
DIN 3852-1 or DIN 3852-2 or O-rings to ISO 6149-1.
For details regarding your valve, please refer to the material number of the valve in the Tech-
nical Data Sheet or the Quotation Drawing.
Always mount the cutting rings according to the manufacturer’s instructions for the cutting
ring connector used in each case.
For tightening torque values please refer to the following tables.
Thread
size
M
10 × 1
M
12 × 1,5
M
14 × 1,5
M
16 × 1,5
M
18 × 1,5
M
20 × 1,5
M
22 × 1,5
M
26 × 1,5
Tight-
ening
torque
[Nm]
18 +2 25 +3 45 +5 55 +6 70 +7 125 +13 125 +13 180 +20
Thread
size
M
27 × 2
M
33 × 2 G 1/8 G 1/4 G 3/8 G 1/2 G 3/4 7/8 -
14 UNF
Tight-
ening
torque
[Nm]
180 +20 310 +30 18 +2 35 +4 70 +7 90 +9 180 +20 125 +13
12/28 Bosch Rexroth AG Product-spezific Instructions RE 66 125-B2/08.07
Making the electrical connection4.5
! CAUTION Possible functional impairment!
For the electrical connection, only those plug connectors stated in the Technical Data
Sheet may be used.
Observe the manufacturer’s assembly instructions for the plug connector!
Before first use, check whether the voltage corresponds with the values stated in the
quotation drawing and whether the total of the expected solenoid currents is less than
or equal to the load rating of the power supply.
The plug connectors may not be connected or disconnected until they have been de-
energised.
Risk of a light electric shock!
Connecting valve solenoids when energised can lead to temporary interruption, induc-
tive voltage peaks and light electric shocks. Therefore, only connect valve solenoids
when de-energised.
For information with regard to the correct assignment of the connections, please refer to the
Quotation Drawing. For information on the prescribed type of connector and its specifica-
tion, please refer to the Technical Data Sheet.
! CAUTION Possible functional impairment!
Danger of injury due to possible unexpected movement of connected hydraulic con-
sumers!
Malfunctions occur in case of interchanged connectors, which may cause unexpected
movement of connected hydraulic consumers.
Therefore, check the correct assignment of the connectors to the respective valve
solenoids after completion of the connecting work.
Actuation of electrical hitch control valves EHR4.6
For information regarding the electrical actuation of the valves and the adjustment of the
operating parameters (parametrising) of electrical valves to the requirements of the system,
please refer to the interface specifications stated in the table.
Valve type Actuation Interface specification with Material No.
EHR5-OBE
EHR23-OBE
SPA/PWM/
CAN-Bus
see Technical Data Sheet RE 66 125.
EHR5
EHR23 12 VDC Interface specification on the switching solenoid see
Technical Data Sheet RE 66 125
Bosch Rexroth AG
RE 66 125-B2/08.07 Product-spezific Instructions 13/28
Bringing into (first) use, subsequent bringing into use4.7
4.7.1 Before bringing into first use
Please observe the general information on the purity of the pressure fluid in Part I, General
Instructions.
Venting the hydraulic system4.7.2
Before bringing into first use, the valve housing must be completely filled with pressure fluid.
! DANGER Danger of material damage, risk of injury
Air enclosed in hydraulic systems can, during operation, lead to the components
being caused to oscillate, resulting in them hitting the stops and being damaged.
Unexpected swinging of actuators can lead to a risk of injury.
Therefore you must make sure that any air has been fully evacuated from the system
before bringing into first use. This can occur by means of allowing a small flow of
pressure fluid Qpump≤ 20 l/min to flow through in all switching positions.
Please be sure to observe the information on venting in the Operating instructions of
the vehicle.
4.7.3 Carrying out the function test
This function test must take place according to the vehicle manufacturer’s instructions, see
Operating instructions of the vehicle.
The following applies in any case: Always increase the pressure slowly, terminate the func-
tion test immediately in case of any leakage!
Retrofitting and conversion4.8
Retrofitting or conversion of the hitch control valve is not permissible.
Disassembly hitch control valve EHR54.9
Safety instructions for disassembly4.9.1
! DANGER Danger of environmental and material damage, risk of injury
For disassembly, the safety instructions in Part I, General Information in 3.4 Ancillary
dangers and protective measures and in 7.2 Safety during maintenance tasks corre-
spondingly apply.
Additionally there is a danger of injury on sharp-edged, mechanically pre-loaded or
pressurised components.
Wear safety gloves and safety goggles!
14/28 Bosch Rexroth AG Product-spezific Instructions RE 66 125-B2/08.07
Removing the hitch control valve EHR5 from the vehicle4.9.2
1. Deactivate the drive motor and switch through all valves to their end position for pres-
sure relief.
2. Place a collecting trough for the collection of discharging pressure fluid underneath the
hitch control valve.
Important There is still pressure fluid in the hitch control valve EHR5!
3. Remove the hitch control valve EHR5 from the vehicle according to the manufacturer’s
instructions.
4. Place the removed hitch control valve EHR5 onto a clean, stable and safe support.
5. Protect open holes and ports of the hitch control valve from dirt entry, for example by
closing off with plastic plugs.
Important Do not under any circumstances clean the hitch control valve in disassembled condition with
a high pressure cleaner.
6. Free the hitch control valve EHR5 from dirt and foreign objects, and do not use clean-
ing agents that
- affect plastics or change their properties
- corrode metals or react to them
- leave residues.
Disassembling the c hitch ontrol valve
1. Remove the O-rings from ports R1 and
R2, P, Y and A’ of the hitch control valve
if necessary.
Cleaning the flange surface
When cleaning the flange surface prevent any dirt from entering the holes.
1. Free the flange surface from contaminants, dirt, paint residues and rust.
2. Strip the flange surface with an oil stone.
3. Check that the sealing surfaces for O-rings on the flange surface and on the undercut
of the flange surface are not damaged. In case of damage the hitch control valve must
be replaced with a new one!
Bosch Rexroth AG
RE 66 125-B2/08.07 Product-spezific Instructions 15/28
Disassembly hitch control valve EHR234.10
4.10.1 Safety instructions for disassembly
! DANGER Danger of environmental and material damage, risk of injury
For disassembly, the safety instructions in Part I, General Information in 3.4 Ancillary
dangers and protective measures and in 7.2 Safety during maintenance tasks correspond-
ingly apply.
Additionally there is a danger of injury on sharp-edged, mechanically pre-loaded or
pressurised components.
Wear safety gloves and safety goggles!
4.10.2 Removing the valve manifold from the vehicle
1. Deactivate the drive motor and switch through all valves to their end position for pres-
sure relief, see Operating instructions of the vehicle.
2. Place a collecting trough for the collection of discharging pressure fluid underneath the
valve manifold.
Important There is still pressure fluid in the valve manifold!
3. Remove the valve manifold from the vehicle according to the manufacturer’s instruc-
tions.
4. Place the removed valve manifold onto a clean, stable and safe support.
5. Protect open holes and ports of the manifold elements from dirt entry, for example by
closing off with plastic plugs.
Important Do not under any circumstances clean the valve manifold in disassembled condition with a
high pressure cleaner.
6. Free the valve manifold from dirt and foreign objects, and do not use cleaning agents
that
- affect plastics or change their properties
- corrode metals or react to them
- leave residues.
16/28 Bosch Rexroth AG Product-spezific Instructions RE 66 125-B2/08.07
4.10.3 Disassembling the valve mani-
fold
Tools required:
Open-ended spanner or ring wrench,
spanner size 13
Cleaning agent: Grindstone or oil
stone, oil-soaked cleaning cloth
Permanent marker to number the valve
modules
Clean collecting trough for the collec-
tion of discharging pressure fluid
Dismantling the manifold
1. Consecutively number all manifold
elements with a permanent marker,
beginning with the connecting plate
(AP).
2. Place the valve manifold in a clean col-
lecting trough to collect any residues of
discharging pressure fluid.
3. Loosen the nuts on the tie rods and
pull the individual modules over the tie rods.
Important Adhesive forces may act between the individual manifold segments.
Dismantling the hitch control valve module
1. Remove the O-rings from ports P, Y and R of the hitch control valve module. In case of
electro-hydraulically actuated valves, also remove the O-rings from X and Rx.
2. Remove the back-up rings from ports P and Y.
3. Remove the shuttle valve from port Y.
Disassembling the connecting plate
1. Remove the O-rings from ports P, Y and R.
2. Remove the back-up rings from ports P and Y.
3. Pull any existing spacing washers from tie rod screws (1), (2) and (3).
4. Manually unscrew the tie rod screws (1), (2) and (3) out of the connecting plate in anti-
clockwise direction.
AP
EP
Bosch Rexroth AG
RE 66 125-B2/08.07 Product-spezific Instructions 17 /28
Cleaning the flange surfaces of the valve modules and connecting plate.
When cleaning the flange surfaces prevent any dirt from entering the holes.
1. Remove any adhesive spacer elements from the flange surfaces.
2. Free all flange surfaces of the connecting plate, end plate and valve modules from con-
taminants, dirt, paint residues and rust.
3. Strip the flange surface with an oil stone.
4. Check that the sealing surfaces for O-rings on the flange surface and on the undercut
of the flange surface are not damaged. In case of damage the respective manifold ele-
ment must be replaced with a new one!
18/28 Bosch Rexroth AG Product-spezific Instructions RE 66 125-B2/08.07
Operation5
Hydraulic symbols5.1
Assignment of the hydraulic symbols to the order number see Technical Data Sheet
RE 66 125.
Hitch 5.1.1 control valves EHR5
EHR5-OC hitch control valves
A
S
H
1
2
3
4
R1
R2P
- Port P in flange
R1
R2
A
P
S
H
1
43
2
- Port P side (thread)
R1
PAR2
S
H
1
2
43
- Port P in flange
- Port A’ in flange
(max. 25 l/min)
EHR5-LS, OBE hitch control valves
R1
YP
A
S
H
1
3
4
2
- Standard version
R1
PAY
A
S
H
1
2
43
- Port A’ in flange
(max. 25 l/min)
1 2-way pressure balance 3 Lowering module
2 Lifting module 4 Check valve
Hitch control valves EHR235.1.2
EHR23-LS hitch control valves
O ring side
R1
A
H
S
1
6
2
H
2
345
PYR
- Standard version
R1
A
H
H
S
1
6
2
34
PYR
- model without PRV
R1
PYR
A
SH
1
3
6
5
2
H
2
4
- Port R1 in flange
Bosch Rexroth AG
RE 66 125-B2/08.07 Product-spezific Instructions 19/28
A
SH
YPR
6
342
SH
425
1
- internal port R
Rx
PYRX
A
SH
6
35
2
A
SH
2
1
4
- internal port R
- with EHS control oil holes
R1
A
H
S
Rx
PYRX
61
5
2
H
23 4
- Standard model
- with EHS control oil holes
R1
A
SH
61
342
SH
25
PYR
- Port R1 in flange
(O-ring side)
Rx
R1
XPR Y
A
SH
61
2
SH
2
35
4
- Port R1 in flange
(O-ring side)
- with EHS control oil holes
1 2-way pressure balance 3 Lowering module 5 Secondary pressure relief valve
2 Lifting module 4 Check valve 6 Shuttle valve
EHR23-ZM hitch control valves
R1
PYR
A
H
S
61
3
54
2
- Standard version
HR1
PYR
A
S3
5
61
2
4
- with EHS control oil holes
HR1
PYR
A
S
61
2
4
5
3
- lateral A-port turned by 90°
- with EHS control oil holes
A1
R1
PYR
A
S
S
61
2
4
5
3
H
- Ports A and A’
- Port R1 in flange
1 2-way pressure balance 3 Lowering module 5 Secondary pressure relief valve
2 Lifting module 4 Check valve 6 Shuttle valve
20/28 Bosch Rexroth AG Product-spezific Instructions RE 66 125-B2/08.07
Hitch control valves for electro-magnetic actuation 5.2
Direct spool actuation via proportional solenoids, 12V5.2.1
Operating principle:
The hydro-pump delivers an oil flow to the hitch control valve, which controls the lifting
mechanism cylinder. These cylinders act on the lifting link, enabling attached devices to be
lifted, held or lowered.
The reference value is determined via the control panel, the actual values are determined via
the sensors and transferred to the electronic control unit.
The control deviation resulting from the reference-actual values comparison is processed
and passed on to the hitch control valve. The lifting and lowering valve is adjusted via 2 pro-
portional solenoids.
2-way pressure balance (individual pressure balance) 5.3
The pressure balance is intended for the load-independent speed control over the entire
adjusting range. This also applies to the simultaneous actuation of several directional control
valves (parallel operation).
Check valve 5.4
The check valve is intended for the minimisation of the leaks between the cylinder connec-
tion and the tank. So that the attached device does not continuously drop in actuated condi-
tion (due to a leak over the spool), a check valve is installed between the cylinder connection
and the spool.
Load safety valve (LSV) 5.5
The LSV is intended for the pressure limitation of the load pressure between the check valve
and the lifting cylinder. An LSV is installed to prevent the load pressure from increasing to
an impermissible level due to external influences such as vibration of the attached device on
uneven roads or pressure increase in the cylinder caused by a temperature rise.
/