179RE 00 207/10.00

System Drives for Large and Medium-Sized Mobile Cranes

System Drives for Large and Medium-Sized Mobile Cranes

Georg Kreissl / VMT7/EBrueninghaus Hydromatik GmbHElchingen plantPhone +49 (0) 73 08 / 82 24 64Fax +49 (0) 73 08 / 53 38E-Mail: georg.kreissl@bru-hyd.com

IntroductionDrive and control technology is a matter of greatimportance in mobile cranes and therefore it is clearthat hydrostatic drive systems have also to be keeppace with market developments. In addition toensuring a favourable basic price for components, itwill consequently also become more and moreimportant to supply drive units with fully integratedauxiliary functions eliminating the need for on-siteinstallation and time-consuming adjustments by thecrane manufacturer. The A8VO series 63 fromBrueninghaus Hydromatik is a new solution whichhas been specially developed with this target fortelescopic cranes with two diesel engines, i.e. with aseparate engine for crane operation, and for thecrawler crane sector (see Fig. 1).

Fig. 1a: Telescopic Crane

Fig. 1b: Crawler Crane

180 RE 00 207/10.00

System Drives for Large and Medium-Sized Mobile Cranes

Fig. 2: A8VO series 63

Nominal size 80 107 140 200Max. rpm (at Vg max) 2240 2150 2100 2100Pressure range 350/400 bar

Basic unit A8VOAmong other things, Brueninghaus Hydromatik isoffering two series, namely the A11VO tandem andA20VO back-to-back pumps in swashplate design,as well as the A8VO series with the robust bentaxis design for use in multi-circuit open loop drives.Since the features specific to these two conceptsare differing, the decision as to which pump is tobe used will ultimately depend upon theapplication in question.The new generation of A8VO pumps of series 63is now available in nominal sizes of 80, 107, 140and 200 (see Fig. 2). These units are replacing theformer series 61 with nominal sizes of 80, 107 and160. The large size 200 rounds off the rangeadditionally.

In addition to high permissible input speeds, thebasic design of these pumps is also including acompact form, direct mounting on the diesel via around flange and optimization of the weight as apoint of particular importance in craneconstruction.A large power take-off with high torque is alsoprovided for mounting additional pumps.

181RE 00 207/10.00

System Drives for Large and Medium-Sized Mobile Cranes

Fig. 3: Gear Pump Supplying Pilot Oil with Pressure Relief Valve

Fig. 4: Electrically Actuated Pressure Reducing Valve

Integrated auxiliary functionsIn mobile cranes, the pilot oil can be supplied viaa valve unit on the main control block (possiblewith LS systems only) or via a separate gear pump.With the new A8VO units, this gear pump can nowbe mounted on the shovel plate with pilot oil intakedirectly from the pump housing of the A8VO. Theassociated pressure relief valve is similarlyintegrated into the A8VO and the control pressureis then transmitted via port A3 (see Fig. 3).An electrically actuated pressure reducing valve isinstalled for the load limiting control requiredfor multi-circuit drives in cranes of this size. Thevalve is mounted directly and supplied with oil viathe pilot oil pump (see Fig. 4).Control is effected via a special load limitingcontroller or via the central electronic crane control.The control pressure built up by the DRE valve ischanging the power setting on the spring controllerof the A8VO pump.If necessary, these pilot oil supply and load limitingcontrol functions can be completely installed byBrueninghaus Hydromatik with all the necessarypiping and settings, thus eliminating the need forthis work by the crane manufacturer.

182 RE 00 207/10.00

System Drives for Large and Medium-Sized Mobile Cranes

Q in l/min

p in bar

pX3

0

50

4

30

100

200

300

pX1

50%

100%

5 bar

28 bar

Fig. 5: Control Concept A8VO/63

Fig. 6: Pump Control (Illustrated for a Crawler Crane)

Propel drive

Main hoist 2

Main hoist 1 Boom hoist Auxiliary hoist

Swing drive

A8VO...LA1H2

3rd pump

Control conceptThe compact principle of a spring-loaded controllerhas been used here. This control concept ispermitting considerable flexibility with view to thecontroller functions required by the market.Classical pump control can be realized in exactlythe same way as, for instance, a load-sensingcontrol. Depending on the drive load, the swivelangle of the pump is decreased by the springpower controller in accordance with thecharacteristic curve of the spring.Load limiting control is likewise superimposed onthe basic function of the controller (pump control,load sensing) and is only needing to take the finecontrol, adjusting the pump to precisely the loadlimit of the diesel engine (see Fig. 5).

In the case of pump controls (see Fig. 6), eachmain movement is assigned to a particular pump.Leaving out the swing drive, this consequentlymeans that a two-circuit system is obtained withthe two A8VO pumps. No more than twomovements can be executed simultaneously. Thehigh speed mode for the hoist, for example, isobtained through a summation circuit. The speedis preset by adjusting the pump swivel angle viahydraulic or electrical manual controls. The maincontrol valves only determine the direction ofmovement of the actuator and therefore switchon/off only. The main advantages of such a systemare to be found in the optimum precision controlrange and excellent energy or power balance.Moreover, is eliminating all reciprocal influence bythe actuators.

183RE 00 207/10.00

System Drives for Large and Medium-Sized Mobile Cranes

Fig. 7: LS Control (Illustrated for a Telescopic Crane)

Fig. 8: Electronic LS System (Illustrated for a Telescopic Crane)

A8VO...EP

Swing drive

Boom cylinder Telescope

Main hoist

JoystickMicro-

controller

A8VO...LA1S

Load sensing line

Swing drive

Boom cylinder Telescope

Main hoist

Joystick

Once again leaving out the swing drive, a classicalLS control (see Fig. 7) is nothing else but a sin-gle-circuit system. The two controllers of the A8VOunit receive a common LS signal, as the two pumpsare treated as a single unit.Two-circuit systems can also be realized for certainapplications so that the pumps can be adapted tothe actuators more effectively. The speed is presetby adjusting the cross-section of the main controlvalve. The load is signalled hydraulically to thepump controllers while p is kept constant at thecontrol valve by the pump. The fact that primarymovements can be freely combined for paralleltravel is advantageous here. Additional actuatorscan be retrofitted without difficulty and little pipingis required around the main valve.

The crane sector is already relatively advancedwhere the use of electronics is concerned. For thisreason, crane manufacturers are increasinglymaking use of electronic LS systems (seeFig. 8). Electro-proportional pump controllers areused for this application, similar to electrical pumpcontrol systems. The LS main control valves arespecifying the required flow via the set cross-section and the pumps are adjusted to that flowvia an electrical control signal. The overall systemcan be optimized more extensively with suchelectronic systems than with the hydraulic versionof the LS control. System stabilization and theelimination of reciprocal influences are twoproblem areas which can be controlled more easilyby means of suitable software. The LUDV functionand priority switching of individual actuators in theevent of a supply shortage are likewiseimplemented electronically.

184 RE 00 207/10.00

System Drives for Large and Medium-Sized Mobile Cranes

Fig. 9: Swing Drive Pump A4VG...DWD

Nominal size 40 56 71 90 125 180Max. rpm (at Vg max) 4000 3600 3300 3050 2850 2500Pressure range 400/450bar

Slew pumps on the powertake-offOpen or closed loop pumps can basically be usedfor the swing drive.Closed loop pumps are predominating in theheavier equipment under consideration here. Anew slew control with the type designation A4VGDWD is now available from BrueninghausHydromatik to supplement the existing typesA4VG/EP (speed control) and A4VG/MS (torquecontrol). At present, the pumps are available innominal sizes of 40, 56, 71, 90, 125 and 180 (seeFig. 9). The DWD version is a pump control basedon direct control of the pump, in which the pumpswivel angle is additionally controlled by thegenerated high pressure via the forces of the rotarygroup. The size 40-71 pumps are supplied withcontrol pressure directly from the manual control,while the larger size 90 to 180 units are controlled

indirectly via a pressure booster. This is resultingin relatively soft control with the DWD and directmanual control of the swing drive. The DWDcontrol is also available with optional adjustablebraking and rapid resetting of the manual controlto zero. A kind of freewheel can even be realizedwith this version in extreme cases, thus permittingthe use of a mechanical slewing brake.

ConclusionTogether with the existing swing drive optionsavailable, the new, optimized generation of A8VOunits, which has been consistently developed withview to producing system drives and reducingweight, is opening up new prospects for the cranemanufacturers. With the integrated pilot oil supplyand load limiting control functions, customers cannow obtain a complete all-round unit reducing theirinstallation and adjustment effort.The compact design is solving the problem ofinstallation and facilitating to mount the pumpunits on the engine. Last but not least, theoptimized weight of these pump units is alsooffering major advantages for cranes in particular,since every kilogram of drive weight saved can nowbe used to reinforce the crane construction, thuspermitting higher crane loads with the same axleloads.

Index