EP2058528B1 - Two-step telescopic cylinder - Google Patents

Two-step telescopic cylinder Download PDF

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Publication number
EP2058528B1
EP2058528B1 EP20080167038 EP08167038A EP2058528B1 EP 2058528 B1 EP2058528 B1 EP 2058528B1 EP 20080167038 EP20080167038 EP 20080167038 EP 08167038 A EP08167038 A EP 08167038A EP 2058528 B1 EP2058528 B1 EP 2058528B1
Authority
EP
European Patent Office
Prior art keywords
oil
piston rod
stowage
port
cylinder tube
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.)
Not-in-force
Application number
EP20080167038
Other languages
German (de)
English (en)
French (fr)
Other versions
EP2058528A2 (en
EP2058528A3 (en
Inventor
Taisuke Tsunoo
Takahiro Kobayashi
Joji Terasaka
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.)
Kobelco Cranes Co Ltd
Original Assignee
Kobelco Cranes Co Ltd
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 Kobelco Cranes Co Ltd filed Critical Kobelco Cranes Co Ltd
Publication of EP2058528A2 publication Critical patent/EP2058528A2/en
Publication of EP2058528A3 publication Critical patent/EP2058528A3/en
Application granted granted Critical
Publication of EP2058528B1 publication Critical patent/EP2058528B1/en
Not-in-force legal-status Critical Current
Anticipated expiration legal-status Critical

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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
    • 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
    • F15B15/149—Fluid interconnections, e.g. fluid connectors, passages

Definitions

  • the present invention relates to a two-step telescopic cylinder installed as an actuator for a telescopic boom of a crane vehicle or the like.
  • a two-step telescopic cylinder disclosed in Japanese Patent Laid-Open No. 2002-70809 or EP 0947709 is known as this type of two-step telescopic cylinder.
  • a two-step telescopic cylinder is arranged inside, a piston rod of this cylinder is connected to a first step boom of the telescopic boom, an inner cylinder tube of the cylinder is connected to a second step boom of the telescopic boom, and an outer cylinder tube of the cylinder is connected to a third step boom of the telescopic boom respectively.
  • a two-step telescopic cylinder disclosed in Japanese Patent No. 2618768 is also known.
  • this two-step telescopic cylinder since a mechanical locking mechanism is provided inside a cylinder main body, an outer diameter of the cylinder main body, that is, an outer diameter of the outer cylinder tube is considerably large. Therefore, in the case that this cylinder is installed in a two-step type telescopic boom, there is a need for enlarging the telescopic boom. Thus, there is a problem that size of the telescopic boom has to be increased.
  • a telescopic cylinder of the present invention comprises a piston rod, an inner cylinder tube concentrically, extendably and stowably fitted onto an outer periphery of the piston rod, and an outer cylinder tube concentrically, extendably and stowably fitted onto an outer periphery of the inner cylinder tube.
  • An inner extension oil chamber is formed between a bottom portion of the inner cylinder tube and a front end surface of the piston rod.
  • An outer extension oil chamber is formed between a bottom portion of the outer cylinder tube and a front end surface of the inner cylinder tube.
  • An inner stowage oil chamber is formed between an inner peripheral surface of the inner cylinder tube and an outer peripheral surface of the piston rod.
  • An outer stowage oil chamber is formed between an inner peripheral surface of the outer cylinder tube and an outer peripheral surface of the inner cylinder tube. Then, the inner extension oil chamber and the outer extension oil chamber are provided so as not to communicate with each other. Meanwhile, the inner stowage oil chamber and the outer stowage oil chamber are provided so as to communicate with each other.
  • a first oil path communicating with the inner extension oil chamber, a second oil path communicating with the outer extension oil chamber, and a third oil path communicating with the inner stowage oil chamber are formed independently from each other in the piston rod so as not to communicate with each other.
  • a communication line for communicating the second oil path with the outer extension oil chamber is provided in the bottom portion of the inner cylinder tube. An end of the communication line is inserted into the second oil path. Insertion length of the communication line into the second oil path is changed in accordance with the telescopic action of the piston rod and the inner cylinder tube.
  • an outer extension port of communicating with said second oil path is provided in a base portion of said piston rod and said telescopic cylinder further comprises a first switching valve for shutting off the outer extension port.
  • the pressure oil from the hydraulic source serving as working oil is supplied to the inner extension oil chamber through the first oil path of the piston rod, and at the same time the working oil in the inner stowage oil chamber is returned to a tank through the third oil path of the piston rod so that the inner cylinder tube performs the extension action.
  • the communication line retains a function of communicating the second oil path with the outer extension oil chamber.
  • the working oil is supplied to the outer extension oil chamber through the second oil path of the piston rod, and at the same time the working oil in the outer stowage oil chamber is returned to the tank through the inner stowage oil chamber and the third oil path of the piston rod so that the outer cylinder tube performs the extension action.
  • the working oil is supplied to the inner stowage oil chamber through the third oil path of the piston rod, and at the same time the working oil in the inner extension oil chamber is returned to the tank through the first oil path of the piston rod, so that the inner cylinder tube performs the stowage action.
  • the communication line retains a function of communicating the second oil path with the outer extension oil chamber.
  • the working oil is supplied to the outer stowage oil chamber through the third oil path of the piston rod and the inner stowage oil chamber, and at the same time the working oil in the outer extension oil chamber is returned to the tank through the second oil path of the piston rod, so that the outer cylinder tube performs the stowage action.
  • the present invention is provided with a return oil path for returning working oil discharged from the second oil path through the outer extension port to the tank by means of bypassing the first switching valve of the switching means, when an insertion length of the communication line into the second oil path is elongated in accordance with a stowage action relatively performed by the piston rod and the inner cylinder tube.
  • the first switching valve communicating with the outer extension port of the piston rod and the second oil path shuts off its communication.
  • the piston rod may be formed in a hollow shape
  • an inner pipe and an outer pipe may be provided in a hollow part of the piston rod so as to form a double tube shape of which center axis coincides with the center axis of the piston rod, and an inside space of the inner pipe may function as the second oil path, a clearance between the inner pipe and the outer pipe may function as the first oil path, and a space between the outer pipe and an inner peripheral surface of the piston rod may function as the third oil path.
  • the piston rod while ensuring the symmetry of the piston rod, that is, the entire cylinder, it is possible to form the three oil paths inside the piston rod with a relatively simple configuration.
  • an inner extension port communicating with the first oil path, an outer extension port communicating with the second oil path and a stowage port communicating with the third oil path may be provided in a base portion of the piston rod.
  • a switching means for supplying pressure oil from a hydraulic source to one of the inner extension port, the outer extension port and the stowage port, for communicating one of the remaining two ports with the tank, and for shutting off the other of the remaining two ports may be provided.
  • the pressure oil from the hydraulic source is supplied to one of the three ports of the base portion in the piston rod, that is, one of the inner extension port, the outer extension port and the stowage port, and one of the remaining two ports is communicated with the tank, and the other port is shut off by the switching means. Therefore, it is possible to easily and properly set and change the telescopic action order of the inner cylinder tube and the outer cylinder tube.
  • the switching means may be provided with a second switching valve in addition to said first switching valve.
  • the second switching valve is switchable between a first position for supplying pressure oil from the hydraulic source to the inner extension port or the outer extension port and for communicating the stowage port with the tank, a second position for communicating pressure oil from the hydraulic source with the stowage port and for communicating the inner extension port or the outer extension port with the tank, and a third position for shutting off the ports.
  • the first switching valve supplies pressure oil supplied through this first switching valve from the hydraulic source to one of the inner extension port and the outer extension port, and it shuts off the other port.
  • the switching means is composed by only two switching valves, it is possible to decrease the number of parts so as to contribute to the cost reduction.
  • the inner cylinder tube When the second switching valve is switched to the first position and the first switching valve is switched to the position for supplying the pressure oil to the inner extension port, the inner cylinder tube performs the extension action.
  • the outer cylinder tube When the first switching valve is switched to the position for supplying the pressure oil to the outer extension port while leaving the second switching valve at the first position, the outer cylinder tube performs the extension action.
  • the inner cylinder tube When the second switching valve is switched to the second position and the first switching valve is switched to the position for communicating the inner extension port with the tank, the inner cylinder tube performs the stowage action.
  • the first switching valve When the first switching valve is switched to the position for communicating the outer extension port with the tank while leaving the second switching valve at the second position, the outer cylinder tube performs the stowage action. It should be noted that when the first switching valve is switched to the third position, the ports are shut off and the working oil is not supplied or discharged. Therefore, the telescopic cylinder is stopped.
  • the second switching valve may be switchable between a first position for supplying pressure oil from the hydraulic source to the inner extension port or the outer extension port and for communicating the stowage port with the tank, a second position for communicating pressure oil from the hydraulic source with the stowage port and for communicating the inner extension port or the outer extension port with the tank, and a third position for shutting off the ports.
  • Two first switching valves may be provided so as to supply pressure oil supplied through this second switching valve from the hydraulic source to the inner extension port and the outer extension port respectively or to shut off the ports.
  • Figs. 1 and 2 show a three-step type telescopic boom A in which a two-step telescopic cylinder of the present invention is installed.
  • This telescopic boom A has three step booms, that is, a first step boom 1, a second step boom 2 and a third step boom 3 in descending order.
  • a telescopic boom main body 4 is formed by extendably and stowably fitting these three step booms 1 to 3 in order.
  • the first step boom is also called as a base boom
  • the second step boom is also called as a middle boom
  • the third step boom is also called as a top boom.
  • a telescopic cylinder 6 of a two-step telescopic cylinder 5 (refer to Fig. 3 ) is arranged in this telescopic boom main body 4.
  • This telescopic cylinder 6 is provided with a piston rod 11, an inner cylinder tube 11 concentrically, extendably and stowably fitted onto an outer periphery of this piston rod 11, and an outer cylinder tube 13 concentrically, extendably and stowably fitted onto an outer periphery of this inner cylinder tube 12.
  • the telescopic cylinder 6 is arranged in a state that a base portion of the piston rod 11 faces a base portion of the telescopic boom main body 4.
  • the base portion of the piston rod 11 of this telescopic cylinder 6 is connected to the first step boom 1 of the telescopic boom main body 4 through a connecting pin 14.
  • a rod side end portion of the inner cylinder tube 12 is connected to the second step boom 2 of the telescopic boom main body 4 through a connecting pin 15.
  • a rod side end portion of the outer cylinder tube 13 is connected to the third step boom 3 of the telescopic boom main body 4 through a connecting pin 16.
  • the two-step telescopic cylinder 5 is provided with the telescopic cylinder 6 and a hydraulic circuit portion 7 for supplying and discharging working oil to and from this telescopic cylinder 6 as shown in Fig. 3 .
  • the telescopic cylinder 6 is provided with the piston rod 11, the inner cylinder tube 12 and the outer cylinder tube 13 as mentioned above.
  • the two-step telescopic cylinder 5 is also provided with an inner extension oil chamber 17 formed between a piston portion 12a forming a bottom portion of the inner cylinder tube 12 and a piston portion 11a forming a front end surface of the piston rod 11, an outer extension oil chamber 18 formed between a bottom portion 13a of the outer cylinder tube 13 and a front end surface of the piston portion 12a of the inner cylinder tube 12, an inner stowage oil chamber 19 formed between an inner peripheral surface of the inner cylinder tube 12 and an outer peripheral surface of the piston rod 11, and an outer stowage oil chamber 20 formed between an inner peripheral surface of the outer cylinder tube 13 and an outer peripheral surface of the inner cylinder tube 12.
  • the inner extension oil chamber 17 and the outer extension oil chamber 18 are provided so as not to communicate with each other by oil-tightly shutting off by the piston portion 12a of the inner cylinder tube 12. Meanwhile, the inner stowage oil chamber 19 and the outer stowage oil chamber 20 are provided so as to communicate with each other through a flexible external communication line 23 arranged between a communication port 21 provided in the rod side end portion of the inner cylinder tube 12 and a communication port 22 provided in the rod side end portion of the outer cylinder tube 13 and made of synthetic resin, synthetic rubber or the like.
  • a first oil path 25 communicating with the inner extension oil chamber 17, a second oil path 26 communicating with the outer extension oil chamber 18 and a third oil path 27 communicating with the inner stowage oil chamber 19 are formed independently from each other in the piston rod 11 so as not to communicate with each other.
  • a communication line 28 for communicating the second oil path 26 with the outer extension oil chamber 18 is integrally formed or provided as a separate body in the piston portion 12a of the inner cylinder tube 12. One end of this communication line 28 is inserted into the second oil path 26 through an insertion hole 29 provided so as to pass through the piston portion 11a of the piston rod 11.
  • the piston rod 11 is formed in a hollow cylindrical shape.
  • An inner pipe 31 and an outer pipe 32 are provided in a hollow part of this piston rod 11 so as to form a double tube shape of which center axis coincides with the center axis of the piston rod 11.
  • An inside space of this inner pipe 31 functions as the second oil path 26.
  • a clearance between the inner pipe 31 and the outer pipe 32 functions as the first oil path 25.
  • a space between the outer pipe 32 and an inner peripheral surface of the piston rod 11 functions as the third oil path 27.
  • the first oil path 25 communicates with the inner extension oil chamber 17 through a communication hole 33 formed in the piston portion 11a of the piston rod 11.
  • the third oil path 27 communicates with the inner stowage oil chamber 19 through a communication hole 34 provided in the outer peripheral surface of the piston rod 11 near the piston portion 11a.
  • An inner extension port 36 communicating with the first oil path 25, an outer extension port 37 communicating with the second oil path 26 and a stowage port 38 communicating with the third oil path 27 are provided in the base portion of the piston rod 11.
  • the working oil is supplied and discharged through these three ports 36 to 38 by means of the hydraulic circuit portion 7.
  • This hydraulic circuit portion 7 is provided with a hydraulic pump 41 and a switching means 43 serving as a hydraulic source.
  • the switching means 43 supplies pressure oil from this hydraulic pump 41 to one of the three ports 36 to 38, communicates one of the remaining two ports with a tank 42, and shuts off the other port.
  • the switching means 43 is composed by a first switching valve 45 and a second switching valve 44.
  • the second switching valve 44 is a four-port and three-position switching valve which is switchable between the first position "a" for supplying the pressure oil from the hydraulic pump 41 to the inner extension port 36 or the outer extension port 37 and for communicating the stowage port 38 with the tank 42, the second position "b" for communicating the pressure oil from the hydraulic pump 41 with the stowage port 38 and for communicating the inner extension port 36 or the outer extension port 37 with the tank 42, and the third position "c" for shutting off the ports 36 to 38.
  • the first switching valve 45 is a three-port and two-position switching valve for supplying the pressure oil from the hydraulic pump 41 supplied through the second switching valve 44 to one of the inner extension port 36 and the outer extension port 37 and for shutting off the other port.
  • the hydraulic circuit portion 7 is provided with a return oil path 46 for returning working oil discharged in accordance with this change caused by the stowage action from the second oil path 26 through the outer extension port 37 to the tank 42 by means of bypassing the first switching valve 45 of the switching means 43.
  • a check valve 47 and a throttle means 48 are placed in series in this return oil path 46.
  • a seal 51 is attached to the outer peripheral surface of the piston portion 11a of the piston rod 11 in Fig. 3 .
  • a seal 52 is attached to the outer peripheral surface of the piston portion 12a of the inner cylinder tube 12.
  • a seal 53 is attached to a part where the rod side end portion of the inner cylinder tube 12 is in sliding contact with the outer peripheral surface of the piston rod 11.
  • a seal 54 is attached a part where the rod side end portion of the outer cylinder tube 13 is in sliding contact with the outer peripheral surface of the inner cylinder tube 12.
  • a seal 55 is attached to a part which is circumferential to the insertion hole 29 of the piston portion 11a of the piston rod 11.
  • this three-step type telescopic boom A particularly an operation of the two-step telescopic cylinder 5 serving as an actuator of the three-step type telescopic boom A will be described.
  • the telescopic cylinder 6 is in a stowage state and the second switching valve 44 of the hydraulic circuit portion 7 is at the third position "c" serving as a stop position.
  • the telescopic boom main body 4 of the three-step type telescopic boom A is in the stowage state as shown in Figs. 1A and 2 .
  • the pressure oil from the hydraulic pump 41 is supplied to the inner extension port 36 in the base portion of the piston rod 11 of the telescopic cylinder 6 through the second switching valve 44 and the first switching valve 45, that is, to the inner extension oil chamber 17 through the first oil path 25 of the piston rod 11.
  • the working oil in the inner stowage oil chamber 19 is returned to the tank 42 through the third oil path 27 of the piston rod 11.
  • the inner cylinder tube 12 of the telescopic cylinder 6 performs the extension action relative to the piston rod 11.
  • the second step boom 2 of the telescopic boom main body 4 is extended integrally with the third step boom 3 as shown in Fig. 1C so that the telescopic boom main body 4 is in a two-step extension state.
  • the second switching valve 44 is firstly switched to the second position "b" and the first switching valve 45 is switched to the first position "a" in the hydraulic circuit portion 7 of the two-step telescopic cylinder 5 so that the pressure oil from the hydraulic pump 41 is supplied to the stowage port 38 in the base portion of the piston rod 11 of the telescopic cylinder 6 through the second switching valve 44, that is, to the inner stowage oil chamber 19 through the third oil path 27 of the piston rod 11.
  • the working oil in the inner extension oil chamber 17 is returned to the tank 42 through the first oil path 25 of the piston rod 11, the first switching valve 45 and the like.
  • the inner cylinder tube 12 of the telescopic cylinder 6 performs the stowage action relative to the piston rod 11.
  • the second step boom 2 of the telescopic boom main body 4 is stowed so that the telescopic boom main body 4 is in a one-step extension state (also called as one-step stowage state) shown in Fig. 1B .
  • the pressure oil from the hydraulic pump 41 is supplied to the stowage port 38 in the base portion of the piston rod 11 of the telescopic cylinder 6 through the second switching valve 44, that is, to the outer stowage oil chamber 20 through the third oil path 27 of the piston rod 11, the inner stowage oil chamber 19 and the external communication line 23.
  • the working oil in the outer extension oil chamber 18 is returned to the tank 42 through the communication line 28, the second oil path 26 of the piston rod 11, the first switching valve 45 and the like.
  • the outer cylinder tube 13 of the telescopic cylinder 6 performs the stowage action relative to the inner cylinder tube 12.
  • the third step boom 3 of the telescopic boom main body 4 is stowed so that the telescopic boom main body 4 is in a two-step stowage state shown in Fig. 1A .
  • the telescopic boom main body 4 is in the two-step extension state or the two-step stowage state after the state that only the third step boom 3 is extended. Therefore, a gravity center of the telescopic boom main body 4 can be maintained on the side of the base portion as long as possible.
  • the second step boom 2 can be firstly extended. Therefore, it is possible to enhance usability of the three-step type telescopic boom A.
  • the three oil paths 25 to 27 of the piston rod 11 are formed independently from each other without using a mechanical locking mechanism as in a conventional example for the telescopic cylinder 6 of the two-step telescopic cylinder 5 serving as the actuator arranged in the telescopic boom main body 4. Since the configuration is relatively simple, a diameter of the telescopic cylinder 6 is accordingly decreased. Consequently, it is possible to decrease size of the telescopic boom main body 4.
  • the first oil path 25 communicating with the inner extension oil chamber 17, the second oil path 26 communicating with the outer extension oil chamber 18, and the third oil path 27 communicating with the inner stowage oil chamber 19 are formed independently from each other in the piston rod 11.
  • the piston rod 11 is formed in a hollow cylindrical shape.
  • the inner pipe 31 and the outer pipe 32 are provided in the hollow part of this piston rod 11 so as to form a double tube shape of which center axis coincides with the center axis of the piston rod 11.
  • the inside space of this inner pipe 31 functions as the second oil path 26.
  • the clearance between the inner pipe 31 and the outer pipe 32 functions as the first oil path 25.
  • the space between the outer pipe 32 and the inner peripheral surface of the piston rod 11 functions as the third oil path 27.
  • the hydraulic circuit portion 7 of the two-step telescopic cylinder 5 supplies the working oil to the three oil paths 25 to 27 of the piston rod 11 and returns the working oil from the oil paths 25 to 27 to the tank 42.
  • This hydraulic circuit portion 7 is provided with the switching means 43 and the hydraulic pump 41 serving as the hydraulic source.
  • the switching means 43 supplies the pressure oil from this hydraulic pump 41 to one of the three ports 36 to 38 provided in the base portion of the piston rod 11, communicates one of the remaining two ports with the tank 42, and shuts off the other port.
  • the switching means 43 is formed only by the second switching valve 44 switchable between the first position "a" serving as an extension action position, the second position “b” serving as a stowage action position and the third position “c" serving as the stop position, and the first switching valve 45 switchable between the first position "a” by which the inner cylinder tube 12 performs the telescopic action and the second position "b” by which the outer cylinder tube 13 performs the telescopic action. Therefore, it is possible to decrease the number of parts so as to contribute to the cost reduction.
  • the insertion length of the communication line 28 provided in the piston portion 12a of the inner cylinder tube 12 into the second oil path 26 is changed in accordance with the telescopic action of the inner cylinder tube 12 while the communication line 28 retains a function of communicating the second oil path 26 with the outer extension oil chamber 18. Therefore, oil spillage or the like is not occurred and it is possible to enhance reliability of the operation.
  • the first switching valve 45 of the switching means 43 is positioned at the first position "a" so as to shut off the communication between the second oil path 26 of the piston rod 11 and the outer extension port 37 and the tank 42.
  • the insertion length of the communication line 28 into the second oil path 26 is elongated in accordance with the stowage action of the inner cylinder tube 12 in this state, the working oil discharged from the second oil path 26 through the outer extension port 37 is accordingly returned to the tank 42 through the return oil path 46 bypassing the first switching valve 45. Therefore, pressure of the working oil in the second oil path 26 is never abnormally increased.
  • Fig. 4 shows a modified example of a hydraulic circuit portion of a two-step telescopic cylinder according to the second embodiment of the present invention.
  • the hydraulic circuit portion 7 of the two-step telescopic cylinder 5 is provided with a switching means 61 and the hydraulic pump 41 serving as the hydraulic source as well as the case of the first embodiment.
  • the switching means 61 supplies pressure oil from this hydraulic pump 41 to one of the inner extension port 36, the outer extension port 37 and the stowage port 38 provided in the base portion of the piston rod 11.
  • the switching means 61 also communicates one of the remaining two ports with the tank 42, and shuts off the other port.
  • the configuration of this switching means 61 is different from the configuration in the case of the first embodiment.
  • the switching means 61 comprises a second switching valve 62 and two first switching valves 63 and 64.
  • the second switching valve 62 is a four-port and three-position switching valve which is switchable between the first position "a" for supplying the pressure oil from the hydraulic pump 41 to the inner extension port 36 or the outer extension port 37 and for communicating the stowage port 38 with the tank 42, the second position "b" for communicating the pressure oil from the hydraulic pump 41 with the stowage port 38 and for communicating the inner extension port 36 or the outer extension port 37 with the tank 42, and the third position "c" for shutting off the ports 36 to 38.
  • the two first switching valves 63 and 64 are open-close valves for supplying the pressure oil from the hydraulic pump 41 supplied through this second switching valve 62 to the inner extension port 36 and the outer extension port 37 or for shutting off respectively.
  • the insertion length of the communication line 28 into the second oil path 26 is elongated in accordance with the stowage action.
  • the hydraulic circuit portion 7 is provided with a return oil path 65 for returning the working oil discharged in accordance with this change caused by the stowage action from the second oil path 26 through the outer extension port 37 to the tank 42 by means of bypassing the first switching valve 64 of the switching means 61.
  • a relief valve 66 and a check valve 67 are placed in this return oil path 65.
  • the present invention is not limited to the first and second embodiments but includes various other modifications.
  • the inner stowage oil chamber 19 and the outer stowage oil chamber 20 of the telescopic cylinder 6 are formed so as to communicate with each other through the external communication line 23 arranged outside the telescopic cylinder 6.
  • a stowage communication line may be formed in a peripheral wall part of the inner cylinder tube as shown in Japanese Paten Laid-Open No. 2002-70809 described in the related art, and the inner stowage oil chamber 19 and the outer stowage oil chamber 20 may communicate with each other through this stowage communication line in a peripheral wall.
  • the three oil paths 25 to 27 are formed in the piston rod 11 of the telescopic cylinder 6, and the piston rod 11 is formed in a hollow cylindrical shape, and the inner pipe 31 and the outer pipe 32 are provided in the hollow part of this piston rod 11 so as to form a double tube shape of which center axis coincides with the center axis of the piston rod 11, and the inside space of this inner pipe 31, the clearance between the inner pipe 31 and the outer pipe 32 and the space between the outer pipe 32 and the inner peripheral surface of the piston rod 11 form the oil paths 25 to 27 respectively.
  • the present invention is not limited to this embodiment.
  • one oil path may be formed by a pipe, or three oil paths extending in the axial direction may be formed in a piston rod in a non-hollow shape.
  • the two-step telescopic cylinder of the present invention is not limited to be installed in the telescopic boom main body 4 of the three-step type telescopic boom A as an actuator as shown in the first embodiment, but can be applied to various other uses.
  • a two-step telescopic cylinder 5 of the present invention is provided with a piston rod 11, an inner cylinder tube 12, an outer cylinder tube 13, an inner extension oil chamber 17, an outer extension oil chamber 18, an inner stowage oil chamber 19 and an outer stowage oil chamber 20.
  • the inner extension oil chamber and the outer extension oil chamber do not communicate with each other, and the inner stowage oil chamber and the outer stowage oil chamber communicate with each other.
  • a first oil path 25 communicating with the inner extension oil chamber, a second oil path 26 communicating with the outer extension oil chamber and a third oil path 27 communicating with the inner stowage oil chamber are formed in the piston rod so as not to communicate with each other.
  • a communication line 28 is provided in a bottom portion of the inner cylinder tube.
EP20080167038 2007-11-07 2008-10-20 Two-step telescopic cylinder Not-in-force EP2058528B1 (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP2007289374A JP4821761B2 (ja) 2007-11-07 2007-11-07 ２段伸縮シリンダ装置及び３段式伸縮ブーム

Publications (3)

Publication Number Publication Date
EP2058528A2 EP2058528A2 (en) 2009-05-13
EP2058528A3 EP2058528A3 (en) 2010-04-07
EP2058528B1 true EP2058528B1 (en) 2013-04-24

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EP20080167038 Not-in-force EP2058528B1 (en) 2007-11-07 2008-10-20 Two-step telescopic cylinder

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EP (1) EP2058528B1 (ja)
JP (1) JP4821761B2 (ja)

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JP5176527B2 (ja) * 2007-08-17 2013-04-03 コベルコクレーン株式会社 伸縮ブーム
CN101806315B (zh) * 2010-04-07 2012-03-14 中联重科股份有限公司 复合油缸及其垃圾压缩机
JP5794683B2 (ja) * 2010-08-25 2015-10-14 コベルコクレーン株式会社 多段伸縮シリンダ
CN102562709B (zh) * 2011-12-30 2015-01-21 湖南特力液压有限公司 双作用同步伸缩式多级液压缸以及液压设备
CN102678654A (zh) * 2012-06-02 2012-09-19 山西高行液压股份有限公司 变速油缸系统
CN102852133B (zh) * 2012-09-17 2014-10-08 李理 一种夯土机的气缸式驱动装置
JP6430332B2 (ja) * 2015-05-19 2018-11-28 Ｉｈｉ運搬機械株式会社 スクリューロッドのカバー装置
ITUB20160363A1 (it) * 2016-01-29 2017-07-29 Manitou Italia Srl Braccio telescopico per macchine operatrici semoventi.
CN110296123B (zh) * 2019-07-26 2024-02-27 娄底市中兴液压件有限公司 油缸、串联油缸和工程车辆
CN112503055A (zh) * 2019-09-16 2021-03-16 湖南特力液压有限公司 多级液压缸
CN111017783B (zh) * 2019-11-14 2022-04-15 武汉船舶通信研究所（中国船舶重工集团公司第七二二研究所） 液压升降设备
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JP2009115225A (ja) 2009-05-28
EP2058528A3 (en) 2010-04-07
JP4821761B2 (ja) 2011-11-24

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