EP0055697B1 - Hydraulic system with a double section telescopic piston for the movement of loads in unstable conditions - Google Patents

Hydraulic system with a double section telescopic piston for the movement of loads in unstable conditions Download PDF

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Publication number
EP0055697B1
EP0055697B1 EP81830251A EP81830251A EP0055697B1 EP 0055697 B1 EP0055697 B1 EP 0055697B1 EP 81830251 A EP81830251 A EP 81830251A EP 81830251 A EP81830251 A EP 81830251A EP 0055697 B1 EP0055697 B1 EP 0055697B1
Authority
EP
European Patent Office
Prior art keywords
passage
load
piston
serving
double
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired
Application number
EP81830251A
Other languages
German (de)
English (en)
French (fr)
Other versions
EP0055697A1 (en
Inventor
Armando Peruzzi
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Leonardo SpA
Original Assignee
Selenia Industrie Elettroniche Associate SpA
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Selenia Industrie Elettroniche Associate SpA filed Critical Selenia Industrie Elettroniche Associate SpA
Publication of EP0055697A1 publication Critical patent/EP0055697A1/en
Application granted granted Critical
Publication of EP0055697B1 publication Critical patent/EP0055697B1/en
Expired legal-status Critical Current

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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
    • F15B15/00—Fluid-actuated devices for displacing a member from one position to another; Gearing associated therewith
    • F15B15/08—Characterised by the construction of the motor unit
    • F15B15/14—Characterised by the construction of the motor unit of the straight-cylinder type
    • F15B15/16—Characterised by the construction of the motor unit of the straight-cylinder type of the telescopic type

Definitions

  • the invention relates to a hydraulic actuating system comprising a telescopic cylinder and piston assembly for displacing a heavy load about a pivot axis, whereby the center of gravity often moves overcenter, and comprising a control apparatus for supplying pressurized fluid to and exhausting fluid from the telescopic assembly; said telescopic assembly including a plurality of stages, the last stage thereof having a double-acting piston carrying an output rod provided with a first passage serving to supply pressurized fluid to the head end of the telescopic assembly for expanding the latter and also serving as an exhaust passage and provided with a second fluid passage serving to supply pressurized fluid to the rod end of the last stage and also serving as an exhaust passage.
  • An operation such as lifting of the movable carriage of a lorry is normally carried out with simple action hydraulic telescopic piston.
  • Said known hydraulic actuating system is provided with a cushioning sleeve slidable positioned in the cylinder and on the piston head.
  • the inner surface of said sleeve is provided with two pairs of diametrically opposed columns of recesses arranged longitudinally of the sleeve. Said recesses decrease in depth and length from one end of the sleeve toward the other end thereof.
  • a valve assembly for decreasing the speed of cylinder contraction is located in the first passage and includes an openended flow control valve slidably mounted in the passage and formed with a plurality of elongated slots.
  • a spring biases the flow control valve whereby the slots are located outside of the associated passage when the cylinder is expanded.
  • pressurized fluid is pumped through both passages and consequently both ends of said piston head are admitted.
  • the present invention is based on the technical task of how to provide a cushioning effect just at the point of unstable equilibrium in a much more simple manner than in the prior art.
  • the double-acting piston may be in a direct sliding contact with the inner surface of the stage next to the last, and no cushioning sleeve or the like is necessary in order to balance the pull of the load just past the point of unstable equilibrium.
  • the system of the invention is very compact and behaves, forthe first half of the movement up to the point just before inversion of the driving force, as a simple-action telescope, whereas in the second half of the movement it behaves as a double-action piston which by generating a controlled counter-pressure, controls the movement of the load by generating a retaining or braking force, just near to the point of unstable equilibrium (PMS).
  • PMS point of unstable equilibrium
  • FIG. 1a an ideal load driven by a piston 1 and fixed at point C by a hinge is illustrated.
  • the force F is such as to oppose the weight force P of the load, in fact it exceeds P and moves the load so as to bring about its displacement.
  • FIG. 1 b illustrates the position when the load has reached the point of unstable equilibrium (PMF).
  • This condition of the weight force P indicated by "X”
  • X passes the fixed point C of the hinge.
  • the drive force F necessary for lifting, and thus for the displacement of the load must be counter balanced by a retaining force R.
  • Figure 1c illustrates the retaining situation by means of the force R which keeps the load in equilibrium. It is necessary to point out that the most delicate part of the displacement is that in which the drive force F is substituted, in a controlled manner, by the retaining force R which avoids sharp movements or whatsmore falling of the load.
  • FIG 2 a typical realisation of the hydraulic system of the present invention is schematically illustrated.
  • the telescopic piston 1 shown has three sliding sections in the last of which is mounted a double-action piston supplied with two chambers 24 and 30 which are in fact necessary to attain the double effect.
  • the simple-action sliding sections make use of the single chamber 21. These chambers are obviously utilised for the letting-in and out the compressed oil fed by means of pipeline 20.
  • Figure 2 illustrates the hydraulic system in its initial position in which the sliding sections are all closed, and the oil is in a rest condition in all the chambers.
  • pipelines 25 and 20 constitute the forward and return of the oil's counterpressure respectively ( Figure 5).
  • Figure 7 illustrates the telescopic piston on returning to its rest position, when the oil in chamber 21 is withdrawn through pipeline 20.

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Fluid Mechanics (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Actuator (AREA)
EP81830251A 1980-12-31 1981-12-22 Hydraulic system with a double section telescopic piston for the movement of loads in unstable conditions Expired EP0055697B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
IT5049380 1980-12-31
IT50493/80A IT1128739B (it) 1980-12-31 1980-12-31 Dispositivo idraulico con pistone telescopico a doppio effetto per il ribaltamento di carichi in condizioni di instabilita'

Publications (2)

Publication Number Publication Date
EP0055697A1 EP0055697A1 (en) 1982-07-07
EP0055697B1 true EP0055697B1 (en) 1987-07-08

Family

ID=11273078

Family Applications (1)

Application Number Title Priority Date Filing Date
EP81830251A Expired EP0055697B1 (en) 1980-12-31 1981-12-22 Hydraulic system with a double section telescopic piston for the movement of loads in unstable conditions

Country Status (3)

Country Link
EP (1) EP0055697B1 (it)
DE (1) DE3176301D1 (it)
IT (1) IT1128739B (it)

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB8815785D0 (en) * 1988-07-02 1988-08-10 British Petroleum Co Plc Soft-landing device
DE102005011630A1 (de) * 2005-03-14 2006-09-21 Franz Xaver Meiller Fahrzeug- Und Maschinenfabrik - Gmbh & Co Kg Hubgerät für Wechselbehälter auf einem Lastentransportfahrzeug, insbesondere auf einem Abrollkipperfahrzeug oder auf einem Absetzkipperfahrzeug

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2897791A (en) * 1957-01-24 1959-08-04 Int Harvester Co Cushioning means for hydraulic actuating means

Family Cites Families (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE929148C (de) * 1942-08-05 1955-06-20 Meiller Fahrzeuge Hydraulisch betaetigte Hub-, Kipp- und Rueckholpresse, insbesondere fuer Kraftfahrzeuge
US2517153A (en) * 1946-08-16 1950-08-01 Gar Wood Ind Inc Telescopic power down hoist
US3415169A (en) * 1966-06-10 1968-12-10 Euclid Hydraulic cylinder
US3603207A (en) * 1969-05-26 1971-09-07 Koehring Co Multiple-cylinder telescopic actuator
FR2129936B1 (it) * 1971-03-17 1976-02-06 Benalu Fr
US3956970A (en) * 1971-11-02 1976-05-18 Montanhydraulik Gmbh & Co. Kg Multiple stage hydraulic telescopic cylinder device
GB1526563A (en) * 1977-06-17 1978-09-27 Davy Loewy Ltd Fluid operable piston-cylinder device

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2897791A (en) * 1957-01-24 1959-08-04 Int Harvester Co Cushioning means for hydraulic actuating means

Also Published As

Publication number Publication date
IT8050493A0 (it) 1980-12-31
IT1128739B (it) 1986-06-04
EP0055697A1 (en) 1982-07-07
DE3176301D1 (en) 1987-08-13

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