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
  • F15B13/00—Details of servomotor systems ; Valves for servomotor systems
  • F15B13/01—Locking-valves or other detent i.e. load-holding devices

Definitions

• the present invention relates to a device for holding in position the rod of a hydraulic cylinder. It also relates to the detection of leaks in the return circuit of the motor chamber.
• Hydraulic cylinders are frequently used as drive members in the lifting and lowering assemblies of a support structure. These assemblies are well known and used in the field of transport, but also in the building and other places on which the movements' raising and lowering of a load are daily and require repeated efforts and greater than human force.
• a cylinder is conventionally maintained under load by a non-return valve inserted in the cylinder supply circuit in the direction passing towards the outlet chamber of the rod.
• This function of maintaining under load fulfills its role as long as the sealing of the valve can be preserved. This exists at the start because of the quality controls carried out in the manufacturing workshops.
• the valve may gradually or suddenly exhibit a leakage after a certain period of time, for various reasons linked to operation or aging, or even to a minor fault of origin which has gone unnoticed.
• a cause a geometric defect, for example of sphericity of the ball, a solid impurity present in the oil circuit and coming to rest on the valve seat or any other cause of poor mechanical contact. or local allowance between the valve body and its seat.
• This holding function turns out to be compulsory in all use cases in which the safety of holding in the support position is an important if not essential condition.
• the valve To ensure that a function as important as the safety of maintenance is maintained without fail, the valve must offer a total guarantee of watertightness. This total guarantee cannot exist and, for this reason, when security demands, the lifting cylinders are associated with mechanical blocking-locking devices, for example locking pins or with safety stops.
• the purpose of these mechanical blocking-locking or abutment devices is to ensure the safety of the load-bearing structures being held in position during a prolonged outage. This holding in position represents a safety measure for goods and people that the cylinder and its control circuit cannot ensure alone in an infallible manner due to the always possible leaks at the non-return valve.
• the object of the invention is to dispense with the use of these additional mechanical retaining means, necessary to ensure the safety of the maintenance in the case of a hydraulic cylinder locked in the load retaining position.
• the invention relates to a device for maintaining the position of the rod of an hydraulic cylinder at least with a single effect, comprising a chamber, for example from the output of its rod, and to the at least one non-return valve mounted in the chamber supply circuit, passing towards this chamber, the holding device consisting of a hydraulic isolation block through which this chamber is supplied, characterized in that:
• the non-return valve called the primary valve is completed by a safety check valve separate from the primary valve and mounted upstream in the supply circuit of this chamber, passing in the same direction towards this chamber,
• an airlock presenting at each of its two inlets and outlets a non-return valve including, on the one hand, the primary valve placed closest to this chamber, and the safety valve,. means for deferred closing of the safety valve with respect to that of the primary valve,. a means for controlling the opening of the two valves.
• the invention finds multiple applications in many fields when it comes to lifting-lowering a load with maintenance in the retaining position and more particularly in the extended position of the cylinder rod.
• the hydraulic device according to the invention is inexpensive
• Figure 1 is a general schematic sectional view showing the holding device according to the invention mounted on the supply legs of a cylinder; .
• Figure 2 is a longitudinal sectional view of a first embodiment of the holding device; .
• Figures 3 and 4 are respectively enlarged views in longitudinal section of the central part of the holding device in the case of the two variants, one with conical valve and the other with fully sealed valve, with valves shown in the state closed ;
• Figure 5 is a general schematic sectional view showing the simplified variant of the holding device according to one invention mounted on the supply branches of a cylinder with valves shown in one closed state;
• Figure 6 is a longitudinal sectional view of the simplified variant of the holding device.
• the device for holding in position the rod of a hydraulic cylinder 1 is in the form of an isolation assembly 2 mounted between a branch 3 and another branch 4 for supplying working fluid respectively to a reentry 5 and an outlet chamber 6 of a rod 7 of the hydraulic cylinder
• This isolation assembly 2 forms a hydraulic block 8 containing a chamber-lock 9 called for reasons of convenience simply lock.
• This airlock has a lower orifice 10 provided with a primary non-return valve 11 in hydraulic connection with the outlet chamber 6 of the rod 7 of the jack and opposite, an upper orifice 12 provided with a safety non-return valve 13 in hydraulic communication with a hydraulic inlet 14 extended by a transverse channel 15 for supplying motive fluid to the outlet chamber 6 from the hydraulic inlet 14.
• the primary non-return 11 and safety check valves 13 are physically separate and mounted pass-through in the direction from the top to the bottom of the figures, that is to say in the direction of supply of the outlet chamber 6 of the rod 7 from the hydraulic inlet 14.
• the primary valve 11 is produced in the form of a non-return ball valve 16 forced into a closing reminder against a seat of suitable shape, for example conical 17 traversed in its center by the lower orifice 10.
• the return force is generated by a return spring 18 trapped in a housing 19 at the lower end of the isolation block 2.
• the safety check valve 13 is produced in a first variant in the form of a frustoconical body 20 with an active conical surface in contact in the closed position with a circular rim 21 of an annular shoulder 22 traversed in its center by the 'upper orifice 12.
• the safety valve 13 opens conventionally and automatically by the incident pressure.
• the opening of the safety valve 13 can be controlled by a means external to the isolation block 2, for example by the driving force of the hydraulic fluid under pressure supplying the re-entry chamber of the rod or any other means. It also causes the controlled opening of the primary valve 11 to be cascaded. To do this, the safety valve 13 is extended downwards by a lower control rod 23 which carries, threaded on its lateral surface, a return spring 24 in the closed position.
• This control rod 23 ends with a free end with a straight thrust front which can pass through the lower orifice 10 of the airlock 9 to move by pushing the body of the primary valve 11 when opening, that is to say away from its seat 17 against the elastic return force provided by the spring 18.
• the safety valve 13 is integral with a means of slowing down its stroke in closing reminder so as to delay its closing with respect to that of the primary valve 11. This can thus guarantee 1 * absence of significant dynamic pressure and therefore of flow in the airlock 9 during the closing phase of the safety valve 13.
• This characteristic makes it possible in particular to envisage the use of a seal to perfect the seal and thus increase the efficiency of the safety valve.
• This type of valve with seal will be called a fully sealed valve 26. It constitutes the ideal means of closing the airlock 9 and of enhanced guarantee of the position held under load of the cylinder rod.
• This variant is represented in FIG. 4 in the form of a fully sealed valve 26 with a seal 27, for example an O-ring resting on a groove-shaped seat 28.
• These fully sealed valves are not very resistant to dynamic pressure due to the risks of extrusion of the seal that it can cause.
• the conical surface of the body of the safety valve 13 shown in FIG. 3 is either partially or completely lined with a coating or a seal. sealing which will come to press in sealing contact on one shoulder 22 advantageously chamfer for this purpose.
• One of the merits of one invention relates to the possibility of using a valve with total tightness, for example such as 26 for the second so-called safety valve 13 due to the absence of dynamic pressure at the right of the seat during closing. of the valve.
• the means for slowing down the return stroke of the safety valve 13 takes the form in the example shown in the form of a composite upper mechanical connection 29 constituting a guided moving assembly.
• This composite upper mechanical connection 29 consists of three free moving parts guided relative to one another. We distinguish the upper part formed by a push piston 30 mounted tight by a seal 31, push piston which moves along a chamber 32 open to one atmosphere by a vent 33 opening on one side of the block isolation 2.
• the counterweight 34 of the composite mechanical link 29 comprises a seal 38 in the vicinity of its lower end providing the seal for this segment relative to the chamber 32 in which the push-piston 30 moves.
• the upper moving part consists of a last segment 39 in the form of a rod secured to the body of the valve.
• This rod 39 has an upper cylindrical end upwards, forming an end piston 40 sliding with play along the guide bore 35 formed in the insert 36.
• This insert 36 laterally delimits with the isolation block 2 an annular chamber 41 through which the engine oil arrives which acts on the body of the safety valve 13.
• the opposite ends of the counterweight 34 and the end piston 40 are separated by a space forming with the side wall of the guide bore a reservoir chamber 42 full of oil used as a shock absorbing pad.
• the push-piston 30 actuates the safety valve 13 in opening by a downward movement of the motor from a control means, for example the force generated by the pressure of the working fluid of the reentry chamber 5 of the rod 7 of the jack which is exerted on the upper face of the plunger 30 placed in the supply duct of this reentry chamber.
• a control means for example the force generated by the pressure of the working fluid of the reentry chamber 5 of the rod 7 of the jack which is exerted on the upper face of the plunger 30 placed in the supply duct of this reentry chamber.
• the command to open the safety valve 13 can come from another means or from another driving source.
• the damping effect results from the presence of oil contained in the reservoir chamber 42 forming a buffer and which will be gradually expelled from this reservoir chamber 42 during the return stroke of the safety valve 13 as a closing reminder.
• the oil will be removed from this chamber by rolling along the end piston 40 because of the play existing between the latter and its guide bore 35.
• the damping effect also results from the viscous friction of the valve stem in the oil.
• This damping effect can be used in conjunction with a suitable distribution of the difference in stiffness of the valve return springs or with geometric variations in the hydraulic components. Either of these parameters can be used alone or in combination.
• the airlock 9 communicates hydraulically through a channel 43 with a pressure sensitive sensor or detector 44, for example a pressure switch inserted in an electrical or electronic circuit whose electrical signal is used to signal a leak by a visual, audible or other.
• FIG. 2 shows the mechanical block 45 of the pressure switch 44 and its two output pins 46 and 47 for its electrical connection with the operating circuit.
• the actuation of the safety valve is ensured by any independent means, for example electromechanical, electromagnetic or any other means.
• the holding device according to the invention is perfectly reversible with regard to the supply connections.
• the outlet of the isolation block 2 can be connected to the reentry chamber 5 and conversely, the outlet chamber 6 can be connected directly to a pressure source.
• the control at the output of the rod 7 of the jack is effected by sending, for example, a calibrated pressure to the hydraulic input 14 of the hydraulic block 8.
• This driving pressure will automatically open the two valves one after the other. 13 and 11 against the restoring force of each of the springs 24 and 18 and will then supply the outlet chamber 6 of the rod.
• the pressure will be cut off when the rod 7 of the jack reaches a desired outlet length.
• the pressure is sent to the re-entry chamber 5. This arriving at the push-piston 30 1 'will actuate towards. the bottom, causing by displacement of the moving element the opening in series, one after the other, of the valves 13 then 11 in order to release the fluid out of the outlet chamber 6 through the airlock 9.
• Figures 5 and 6 relate to a simplified variant of the device for holding in position a load according to the invention in which the general functions are preserved and implemented by the same means or equivalent means.
• the device for holding in position applies mainly but not exclusively to a hydraulic cylinder 1 supporting a load carried by a support with a view to lifting and lowering it and keeping it securely in a given position.
• the device for holding in position is a hydraulic isolation assembly 2 in the form of a hydraulic block 8 mounted between two branches 3 and 4 for supplying driving fluid respectively to the reentry chamber 5 and the outlet chamber 6 of its rod 7 in the case of a double-acting cylinder.
• the hydraulic block 8 contains a chamber 9 comprising a lower orifice 10 with a primary non-return valve 11 in connection with the outlet chamber 6 and an upper orifice 12 provided with the non-return safety valve 13 in hydraulic communication with a hydraulic inlet 14 extended by a transverse channel 15.
• the valves 11 and 13 are mounted passing from the top to the bottom of the figures.
• the primary valve 11 has a ball 16 elastically returned to the closed position against its seat by a spring 18.
• the safety valve 13 in the embodiment shown for this variant is of the type with a circular flat body 48 with a shoulder having a diameter less than that of its housing 49.
• This fully sealed valve 13 ensures that the load is kept in position.
• the clearance 25 existing between the lower end of the rod 23 and the ball 16 determines a degree of freedom of movement between the two valves and introduced into the commanded mode the delay in the opening of the primary valve 11 caused by the opening of the safety valve 13.
• the security of holding in position is given by the valve 13.
• the effectiveness of this safety valve depends on the holding of its seal after a large number of operations.
• the slowing down function allowing delayed closure of the two valves can be obtained by different means taken individually or in combination, namely: the different stiffnesses of the two return springs of the valves, the viscous friction of the valve stem 13 in the chamber-airlock 9 and generally the damping of the rod in the oil and the shape and dimensions of the hydraulic components.
• the modifications which result in changes of references are as follows.
• the transverse channel 15 of the hydraulic inlet 14 has a bypass 53 towards a buffer chamber 54 located under the push piston 30.
• this buffer chamber 54 no longer has communication with the outside via a vent. It is connected to inlet 14 and filled with pressurized oil. Consequently, the risk of corrosion which arose from its constant communication with the outside is completely eliminated.
• the ascent of the push-piston 30 is guaranteed by a return spring 56.
• Another advantage of this feature relates to the seal.
• the sealing constraints are less important because the leaks feed the lines of the hydraulic circuit. The consequence is the possibility of removing the seal between the buffer chamber 54 and the arrival of the conduit 3 at the upper part of the push-piston 30 on the one hand and that which existed between the upper rod 40 of the check valve. security 13 and the buffer chamber 54 on the other hand.
• This advantage further increases the reliability of the device.
• the pressurized working fluid enters the hydraulic block 8 through the branches 15 and 53 towards the safety valve 13 and the buffer chamber 54.
• This pressure is sufficient to first open the safety valve 13 and then the primary non-return valve 11 to feed the cylinder through its chamber 6 at the outlet of its rod 7.
• the rod 7 rises with the load which it supports up to the level desired programmed or not. The pressure is then cut and the rod is immobilized in position. Immediately after immobilization, the charge causes an oil return for a short time.
• the rapid oil return participates in the return movement of the ball of the primary valve 11 which comes to rest against its seat under the effect of the elastic restoring force.
• the safety valve 13 then closes in the airlock chamber 9 in the absence of pressure due to the insulation resulting from the prior closure of the primary valve 11. This closure in the absence of dynamic pressure and therefore flow protects the seal of the safety valve and prevents it from coming out of its housing.
• the delivery rate and the restoring force are sufficient for the ball 16 to close the primary valve 11 before the safety valve 13.
• the safety of maintaining the load in position is guaranteed by the two non-return valves.
• the primary ball valve 11 allows by its closure the immediate maintenance of the load.
• Maintaining security is provided by the safety valve 13.
• the seal provided by the safety valve is of high reliability.
• the load will remain in position almost indefinitely.
• the command to lower the rod 7 of the jack under load requires the opening of the two valves.
• the force causing the opening is given by a control pressure. This can be the pressure exerted on the other chamber of the double-acting cylinder or an independent pressure for control or piloting.
• the safety valve stem continues to descend.
• the lower end of its rod 23 comes into thrust contact with the shutter element of the primary valve and by continuing its travel forces it to open.
• the safety valve being in position open, its seal does not risk damage or exit from its housing.
• valve opening control is no longer maintained and a delay in closing the safety valve 13 is caused in the same way as above. to the primary valve 11.
• the retraction of the cylinder rod can also result from an otherwise controlled opening of the valves, that is to say independent of the driving pressure causing the retraction of the rod.
• the device according to the invention can be oriented for mounting in the opposite direction to that shown in the figures or according to any other orientation of its support.

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• Engineering & Computer Science (AREA)
• Physics & Mathematics (AREA)
• Fluid Mechanics (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Actuator (AREA)
• Fluid-Pressure Circuits (AREA)
• Load-Engaging Elements For Cranes (AREA)
• Gripping On Spindles (AREA)
• Gripping Jigs, Holding Jigs, And Positioning Jigs (AREA)
• Jigs For Machine Tools (AREA)
• Fluid-Damping Devices (AREA)

Applications Claiming Priority (3)

Publications (2)

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ID=9497542

Family Applications (1)

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Cited By (1)

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• 1996
  • 1996-11-07 FR FR9613778A patent/FR2755481B1/fr not_active Expired - Fee Related
• 1997
  • 1997-11-06 WO PCT/FR1997/001994 patent/WO1998020260A2/fr active IP Right Grant
  • 1997-11-06 EP EP97913266A patent/EP0935715B1/de not_active Expired - Lifetime
  • 1997-11-06 AT AT97913266T patent/ATE258274T1/de not_active IP Right Cessation
  • 1997-11-06 UA UA99063105A patent/UA46875C2/uk unknown
  • 1997-11-06 CA CA002270579A patent/CA2270579A1/fr not_active Abandoned
  • 1997-11-06 ES ES97913266T patent/ES2216132T3/es not_active Expired - Lifetime
  • 1997-11-06 CN CN97199511A patent/CN1103411C/zh not_active Expired - Lifetime
  • 1997-11-06 RU RU99112128/06A patent/RU2191298C2/ru active
  • 1997-11-06 DE DE1997627307 patent/DE69727307T2/de not_active Expired - Lifetime
  • 1997-11-07 US US08/966,186 patent/US5913810A/en not_active Expired - Lifetime

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