PDF Service Manual New Holland LB75.B LB90.B LB95.B LB110.B LB115.B 4WS Backhoe Loader - 8 MB

This comprehensive service manual covers a wide range of New Holland backhoe loaders, including the LB75.B, LB90.B, LB95.B, LB110.B, and LB115.B models.

It provides detailed instructions for every aspect of repair and maintenance, from the engine to the hydraulic system.

This is the ultimate guide for technicians working on these versatile machines.

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--- Page 1 ---
SERVICE
MANUAL
LB75.B
LB90.B
LB95.B
LB110.B
LB115.B 4WS
BACKHOE LOADERS


                  CONSTRUCTION

6036702103

--- Page 49 ---
36                 SECTION 35 -- HYDRAULIC SYSTEMS -- CHAPTER 1


                                         Unload Valve Operation


                                                                                          52
                                    Oil Flow When Backhoe is in use


                                                                                          53
                                  Oil Flow when Loader only is in use

            Front Pump Flow                                           Transfer Pressure

            Rear Pump Flow                                            Return to Tank

D. Flow From Front Pump                               E. Flow From Rear Pump
1. Unload Valve                                       3. System Pressure Relief Valve
2. Combined Pump Flow Load Check Valve                4. Unload Spool


 12/2004

--- Page 52 ---
56                     SECTION 35 -- HYDRAULIC SYSTEMS -- CHAPTER 1


                                                                                                                   89
                                        Operation of Regenerative Check Valve
               Pump Pressure Oil                                           Trapped Oil

               Cylinder Exhaust Oil                                        Return to Reservoir
               @ Higher than Pump Pressure
Port H -- Pump Flow from Loader Valve                        Port J -- Return to Reservoir
1. Clamp System Dump Solenoid                                7. Parallel Gallery
2. Clamp System Check Valve                                  8. Regenerative Check Valve
3. Boom Cylinder Control Valve                               9. Back Pressure Valve
4. Swing Cylinder Control Valve                              10. Control Valve Exhaust Gallery
5. Bucket Cylinder Control Valve                             11. Staggered Open Centre Gallery
6. Dipper Cylinder Control Valve


Regenerative Check Valve Operation                           When cylinder exhaust pressure is higher than pump
When a digging element is rapidly operated, for              pressure, the flow of oil from the exhausting cylinder
example the boom is quickly lowered into a trench,           lifts the check valve of its seat allowing exhaust oil to
the situation can arise where, if engine speed is too        flow past the check valve into the parallel gallery and
low, pump output is insufficient to meet demand of           supplement the insufficient flow from the pump to op-
the cylinder and the cylinder will cavitate.                 erate the cylinder and prevent the void from occur-
                                                             ring.
This will result in a hydraulic void occurring in the pis-
ton (extending) side of the cylinder.                        The back pressure valve will remain closed in this
                                                             operation.
To overcome this situation the regenerative check
valve is installed.


 05/2003

--- Page 59 ---
26                     SECTION 35 - HYDRAULIC SYSTEMS - CHAPTER 3


                          Load sensing flow sharing - two spools operating
           1st spool operating pressure                         Trapped oil
           2nd spool operating pressure                         Return to reservoir

 1 Load check valve                                   3 Pressure compensating valve
 2 Load sensing line                                  4 Spool


11/2003

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