Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
  • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
  • F15B11/00—Servomotor systems without provision for follow-up action; Circuits therefor
  • F15B11/16—Servomotor systems without provision for follow-up action; Circuits therefor with two or more servomotors
  • F15B11/22—Synchronisation of the movement of two or more servomotors
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B66—HOISTING; LIFTING; HAULING
  • B66F—HOISTING, LIFTING, HAULING OR PUSHING, NOT OTHERWISE PROVIDED FOR, e.g. DEVICES WHICH APPLY A LIFTING OR PUSHING FORCE DIRECTLY TO THE SURFACE OF A LOAD
  • B66F7/00—Lifting frames, e.g. for lifting vehicles; Platform lifts
  • B66F7/10—Lifting frames, e.g. for lifting vehicles; Platform lifts with platforms supported directly by jacks
  • B66F7/16—Lifting frames, e.g. for lifting vehicles; Platform lifts with platforms supported directly by jacks by one or more hydraulic or pneumatic jacks
  • B66F7/20—Lifting frames, e.g. for lifting vehicles; Platform lifts with platforms supported directly by jacks by one or more hydraulic or pneumatic jacks by several jacks with means for maintaining the platforms horizontal during movement

Definitions

• the invention relates to an electrohydraulic lifting device, in particular a heavy load lifting device including two support platforms, wherein raising and lowering of each support platform are controlled independently from the other platform and, when necessary, compensated, e.g. when a dif ⁇ ference occurs in the heights of the two support platforms.
• a compensation electrohydraulic system is controlled by an electronic control unit that oper- ates in real-time.
• Electrohydraulic lifting devices which include support platforms and are adapted to raise and lower a load that has been put onto the platforms.
• This kind of lifting devices basically in ⁇ clude: - two support platforms, which are parallel to each other and supported by related structures indepen ⁇ dent from each other.
• the structures are made in a way so as to define for the support platforms two extreme positions, namely a lowered position and a raised position,- - one, or more than one, hydraulic cylinders for each of the support platforms, the cylinders being independently fed through respective parallel con ⁇ duits (including cutoff solenoid valves) .
• the stems of the cylinders are synchronically moved as a consequence of a rigid mechanical link connected to the means actuated by the same stems,-
• an electrohydraulic control unit connected to the cylinders of each pair via an oil flow splitting valve.
• the task of this last valve, during either the feeding or discharge, is to subdivide the oil volume displaced into smaller equal volumes which are delivered to two pipes each of which splits into two branches connected to the related cylinders of the respective platforms.
• the above mentioned lifting device has a problem in keeping the platforms in alignment with each other, with respect to a horizontal plane, and this problem has never been easy to solve.
• a difference can occur in the flow of hydrau ⁇ lic pressure media delivered to the above mentioned pairs of cylinders through the said conduits, when one of the two conduits presents a hydraulic flow resistance different from the other one.
• This difference in flow resistance is caused either by the load not being regularly distributed on the support platforms, or by small defects in designing and manufacturing the hydraulic circuits and the mechanical-electromechanical components of the lifting device.
• the two platforms locate at different height levels, and the load takes an inclined position in accordance with this differ- ence.
• a further known device includes a transversal link between the two of the support platforms, this link including mechanical means, such as torsional bars.
• the main object of the present invention is to find a solution to these problems, that is to the horizontal nonalignment of one platform in respect of the other one that occurs during the raising and lowering stages in an electrohydraulic lifting de- vice, without providing any mechanical transversal link between the two of the support platforms.
• each platform is checked second by second and any adjustment, necessary to set again the platforms in reciprocal alignment, is immediate ⁇ ly carried out.
• an electrohydraulic lifting device includ ⁇ ing: at least two support platforms set substantially parallel to each other and carried by related struc- tures made in such a way as to define two extreme positions for the platforms, namely a lowered posi ⁇ tion and a raised position respectively; at least two hydraulic cylinders, namely a first cylinder and a second cylinder, each arranged for operating a respective one of the said structures,- a flow splitting valve connected at one side to pipes, namely a first pipe and a second pipe each connected to a related one of the said hydraulic cylinders,- an electro-hydraulic central unit connected, through a main conduit, to the other side of the said flow splitting valve and provided for feeding the said hydraulic cylinders,- a first duct aimed at connecting said first pipe with said main conduit, via a first synchronising solenoid valve,- a second duct aimed at connecting said second pipe with said main .conduit, via a second synchronising solenoid valve,
• reference numeral 1 and 2 indicate two support platforms, generally alike one to the other, that are carried by respective support structures.
• the support structures are not illustrated in the drawing as they are well known, made like the ones cited in the prior art statement.
• the platforms 1, 2 are indirectly moved by related pairs 10, 20 of hydraulic cylinders 3, 4, namely a first pair and a second pair.
• the cylinders 3 of the first pair 10 are connected to related conduits 5 that include respec ⁇ tive cutoff solenoid valves 6 and that converge to a branch point 7 of a first pipe 8.
• the pipes 8 and 13 are connected to a flow splitting valve 14 that is in turn connected to a main duct 15 departing from an electrohydraulic unit 50, of known type.
• the first pipe 8 is also connected to the main duct 15 via a first channel 30.
• This connection is set or removed by means of a first synchronisation solenoid valve 31, and a necking 42.
• the synchronising solenoid valve 31, 41 are controlled by an electronic control unit 100, that is connected to sensor means first 17 and second 18 respectively adapted to detect, second by second, the length of each of the part of the stems 3a and 4a that is outside the respective cylinder.
• these sensor means are positioned near the stems.
• the electronic unit 100 processes the signals delivered by the sensor means 17, 18 in order to estimate how much the stems 3a, 4a have come out of the cylinders.
• This operating style is performed until the difference in the coming out of the stems 4a, 3a take a value less than the tolerance that has been prefixed.
• each of the support platforms can be moved either by only one hydraulic cylinder or by more that two hydraulic cylinders.

Landscapes

• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Fluid Mechanics (AREA)
• General Engineering & Computer Science (AREA)
• Life Sciences & Earth Sciences (AREA)
• Geology (AREA)
• Structural Engineering (AREA)
• Physics & Mathematics (AREA)
• Fluid-Pressure Circuits (AREA)
• Jib Cranes (AREA)
• Conveying And Assembling Of Building Elements In Situ (AREA)
• Cultivation Receptacles Or Flower-Pots, Or Pots For Seedlings (AREA)
• Accommodation For Nursing Or Treatment Tables (AREA)
• Earth Drilling (AREA)
• General Induction Heating (AREA)
• Elevator Control (AREA)
• Warehouses Or Storage Devices (AREA)
• Vehicle Cleaning, Maintenance, Repair, Refitting, And Outriggers (AREA)
• Forklifts And Lifting Vehicles (AREA)

Priority Applications (3)

Applications Claiming Priority (2)

Publications (1)

Family

ID=11339277

Family Applications (1)

Country Status (7)

Cited By (19)

Families Citing this family (2)

Citations (4)

• 1993
  • 1993-10-22 IT IT93BO000420A patent/IT1264249B1/it active IP Right Grant
• 1994
  • 1994-10-11 TW TW083109381A patent/TW267992B/zh active
  • 1994-10-19 AT AT95900254T patent/ATE176452T1/de not_active IP Right Cessation
  • 1994-10-19 DE DE69416422T patent/DE69416422D1/de not_active Expired - Lifetime
  • 1994-10-19 AU AU81145/94A patent/AU8114594A/en not_active Abandoned
  • 1994-10-19 EP EP95900254A patent/EP0724541B1/en not_active Expired - Lifetime
  • 1994-10-19 WO PCT/IT1994/000175 patent/WO1995011189A1/en active IP Right Grant

Patent Citations (4)

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