EP4677235A1 - Improved regenerative valve to control the opening and closing movements of the jaws of a clamp, in particular a clamp for forklifts, and a clamp for forklifts comprising such a regenerative valve - Google Patents

Improved regenerative valve to control the opening and closing movements of the jaws of a clamp, in particular a clamp for forklifts, and a clamp for forklifts comprising such a regenerative valve

Info

Publication number
EP4677235A1
EP4677235A1 EP24715679.7A EP24715679A EP4677235A1 EP 4677235 A1 EP4677235 A1 EP 4677235A1 EP 24715679 A EP24715679 A EP 24715679A EP 4677235 A1 EP4677235 A1 EP 4677235A1
Authority
EP
European Patent Office
Prior art keywords
branch
clamp
hydraulic
flow
linear actuator
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.)
Pending
Application number
EP24715679.7A
Other languages
German (de)
French (fr)
Inventor
Pietro Foroni
Nicola Bovo
Davide VENEZIANI
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.)
Bolzoni SpA
Original Assignee
Bolzoni 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 Bolzoni SpA filed Critical Bolzoni SpA
Publication of EP4677235A1 publication Critical patent/EP4677235A1/en
Pending legal-status Critical Current

Links

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
    • F15B11/02—Systems essentially incorporating special features for controlling the speed or actuating force of an output member
    • F15B11/024—Systems essentially incorporating special features for controlling the speed or actuating force of an output member by means of differential connection of the servomotor lines, e.g. regenerative circuits
    • 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
    • B66F9/00—Devices for lifting or lowering bulky or heavy goods for loading or unloading purposes
    • B66F9/06—Devices for lifting or lowering bulky or heavy goods for loading or unloading purposes movable, with their loads, on wheels or the like, e.g. fork-lift trucks
    • B66F9/075—Constructional features or details
    • B66F9/12—Platforms; Forks; Other load supporting or gripping members
    • B66F9/18—Load gripping or retaining means
    • B66F9/183—Coplanar side clamps
    • 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
    • B66F9/00—Devices for lifting or lowering bulky or heavy goods for loading or unloading purposes
    • B66F9/06—Devices for lifting or lowering bulky or heavy goods for loading or unloading purposes movable, with their loads, on wheels or the like, e.g. fork-lift trucks
    • B66F9/075—Constructional features or details
    • B66F9/20—Means for actuating or controlling masts, platforms, or forks
    • B66F9/22—Hydraulic devices or systems
    • 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
    • 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
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/30—Directional control
    • F15B2211/305—Directional control characterised by the type of valves
    • F15B2211/30505—Non-return valves, i.e. check valves
    • 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
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/30—Directional control
    • F15B2211/305—Directional control characterised by the type of valves
    • F15B2211/3056—Assemblies of multiple valves
    • F15B2211/30565—Assemblies of multiple valves having multiple valves for a single output member, e.g. for creating higher valve function by use of multiple valves like two 2/2-valves replacing a 5/3-valve
    • F15B2211/3058—Assemblies of multiple valves having multiple valves for a single output member, e.g. for creating higher valve function by use of multiple valves like two 2/2-valves replacing a 5/3-valve having additional valves for interconnecting the fluid chambers of a double-acting actuator, e.g. for regeneration mode or for floating mode
    • 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
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/30—Directional control
    • F15B2211/32—Directional control characterised by the type of actuation
    • F15B2211/329—Directional control characterised by the type of actuation actuated by fluid pressure
    • 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
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/40—Flow control
    • F15B2211/405—Flow control characterised by the type of flow control means or valve
    • F15B2211/40523—Flow control characterised by the type of flow control means or valve with flow dividers
    • F15B2211/4053—Flow control characterised by the type of flow control means or valve with flow dividers using valves
    • 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
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/40—Flow control
    • F15B2211/415—Flow control characterised by the connections of the flow control means in the circuit
    • F15B2211/41527—Flow control characterised by the connections of the flow control means in the circuit being connected to an output member and a directional control valve
    • F15B2211/41536—Flow control characterised by the connections of the flow control means in the circuit being connected to an output member and a directional control valve being connected to multiple ports of an output member
    • 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
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/70—Output members, e.g. hydraulic motors or cylinders or control therefor
    • F15B2211/705—Output members, e.g. hydraulic motors or cylinders or control therefor characterised by the type of output members or actuators
    • F15B2211/7051—Linear output members
    • F15B2211/7053—Double-acting output members
    • 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
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/70—Output members, e.g. hydraulic motors or cylinders or control therefor
    • F15B2211/78—Control of multiple output members
    • F15B2211/782—Concurrent control, e.g. synchronisation of two or more actuators

Definitions

  • the present invention relates to an improved regenerative valve to control the opening and closing movements of the jaws of a clamp, in particular a clamp for forklifts.
  • the present invention further relates to a clamp for forklifts comprising such a regenerative valve.
  • clamps provided with at least one pair of jaws movable towards and away from each other, respectively, in order to pick up and release a load is well known.
  • These jaws are hydraulically actuated in opening and closing by means of respective hydraulic linear actuators (or more simply 'cylinders') connected to each other in parallel by means of a regenerative valve connected to the hydraulic supply and distribution unit with which the forklift is equipped.
  • a regenerative valve or, more generally, a regenerative circuit is configured so that, when the stems exit from the respective cylinders and, therefore, when the jaws open, the volume of pressurised fluid (oil) contained in the stem-side annulus joins the flow of pressurised fluid fed by the hydraulic power unit to the bottom side, instead of being directed to the outlet, thus contributing to increasing the advancement speed of the stems exiting from the respective cylinders. That is, the regeneration is performed during the opening of the jaws and consists of hydraulically connecting the stem side with the bottom side of the cylinders so that the flow of oil from the stem side, instead of being directed to the outlet, is re-associated with that fed to the bottom. This increases the opening speed of the cylinders, as the useful section for the oil flow from the hydraulic power unit becomes that of the stem of the cylinder alone instead of that of the bottom.
  • regenerative valves provided with a flow divider configured and arranged to subdivide the feed flow to the cylinders into equal parts during the jaw opening movement and re-associate it during the jaw closing movement in order to achieve synchronous jaw movements of the jaws themselves is known to be used to control the opening and closing movements of jaws for clamps for forklifts.
  • the flow divider DV1 works with only the flow coming from the bottom side of the two cylinders.
  • the flow divider DV1 works with a higher flow rate than in closing; for example, the opening flow rate can be as much as 4 or 5 times the closing flow rate.
  • the flow divider was instead sized as a function of the opening fluid flow, it would be oversized for the closing fluid flow rate, so that the synchronism of the jaw movements would be compromised during closing.
  • the flow divider error increases as the flow rate of fluid passing through it decreases with respect to the nominal design flow rate.
  • the flow divider in the known regenerative valves is sized according to compromise criteria between the two opposite requirements mentioned above, resulting in a penalisation of functionality during both opening and closing in terms of a reduction in the benefits of regeneration and synchronisation of the jaw movement.
  • an alternative regenerative valve VR' has been proposed, as shown in Figure 5 and the subject of the same applicant's patent IT102016000042043.
  • a second flow divider DV2 is provided inserted in parallel to the first flow divider DV1.
  • the first flow divider DV1 is sized for the closing oil flow rate, thus without regeneration, while the second flow divider DV2 is sized for the regeneration oil flow rate.
  • the oil flow is distributed in input to the two flow dividers DV1 and DV2, obviating the problem of possible blockage which would generate if there were only the first flow divider DV1.
  • the second flow divider DV2 is excluded from the circuit crossed by the oil flow by the check valve VRT2. Therefore, the oil flow only passes through the first flow divider DV1 , which is sized for this flow rate, thus ensuring the synchronisation of the jaw movement.
  • the aim of the present invention is to make an improved regenerative valve to control the opening and closing movements of the jaws of a clamp, in particular a clamp for forklifts, and a clamp for forklifts comprising such a regenerative valve, which overcome the drawbacks of the prior art.
  • the aim of the present invention is to make a regenerative valve to control the opening and closing movements of the jaws of a clamp, in particular a clamp for forklifts, and a clamp for forklifts comprising such a regenerative valve, which allow to ensure the synchronism of the movements of the jaws under all operating conditions and, at the same time, to ensure the benefits of regeneration during the opening movement of the jaws with limited dimensions.
  • Another aim of the present invention is to make a regenerative valve to control the opening and closing movements of the jaws of a clamp, in particular a clamp for forklifts, and a clamp for forklifts comprising such a regenerative valve which is particularly simple and functional, with low costs.
  • aims according to the present invention are achieved by making a regenerative valve to control the opening and closing movements of the jaws of a clamp, in particular a clamp for forklifts, as set out in claim 1 .
  • figure 1 is a schematic view of a forklift provided with a possible embodiment of the clamp according to the present invention
  • figure 2 is an axonometric and partially exploded view of the clamp of figure 1
  • figure 3 is a hydraulic circuit diagram of a clamp for forklifts incorporating an improved regenerative valve according to the present invention in connection with the hydraulic system (hydraulic supply and distribution unit) existing on a forklift
  • figures 4 and 5 show a hydraulic circuit diagram of a clamp for forklifts incorporating two different regenerative valves according to the prior art.
  • an improved regenerative valve 10 to control the opening and closing movements of the jaws of a clamp 100, in particular a clamp 100 for forklifts 200, is shown.
  • the 100 clamp comprises:
  • At least one pair of hydraulic linear actuators 104, 105 respectively a first hydraulic actuator 104 and a second hydraulic actuator 105, which are mounted on the supporting chassis 101 and each of which is connected to a respective jaw 102, 103 to actuate the movement thereof between said at least one opened position and said at least one closed position and vice versa, and
  • valve block 106 incorporating a regenerative valve 10 according to the present invention and which is configured to hydraulically connect the hydraulic linear actuators 104 and 105 to each other in parallel and control the movements thereof.
  • the valve block 106 is in turn hydraulically connectable to the hydraulic system with which the forklift 200 is equipped and, in particular, to the supplying and distributing hydraulic power unit 201 for supplying and distributing hydraulic fluid (pressurised oil) with which the forklift 200 is normally equipped.
  • valve block 106 hydraulic linear actuators 104, 105 and supplying and distributing hydraulic power unit 201 hydraulically connected to each other form a closed circuit.
  • the jaws 102, 103 are of the flat plate type arranged parallel to each other and each of which is fixed to a respective pair of support arms 107, 108 slidingly guided along straight guides 109 fixed to the supporting chassis 101.
  • the hydraulic linear actuators 104, 105 are arranged one above the other and opposite each other in a direction parallel to the straight guides 109.
  • first and the second hydraulic linear actuator 104, 105 - also known in the field simply as 'cylinders' and hereafter also referred to respectively as first cylinder 104 and second cylinder 105 - each comprise a cylindrical shell which is fixed to the supporting chassis 101 and within which a piston sealingly slides connected to a stem the head of which protrudes outside the front head of the shell (through which the stem itself is slidingly guided) and is articulated to a respective jaw 102, 103.
  • a respective attachment is obtained for the inlet and the outlet of the hydraulic fluid from the respective chamber.
  • such inlets are indicated respectively with T1’ and C/' for the first linear actuator 104 and with T2' and C2' for the second linear actuator 105.
  • the outlet stroke of the stem of each first and second cylinder 104, 105 from the respective shell corresponds to an opening movement of the jaws 102, 103 and the return stroke of the stem of each first and second cylinder 104, 105 into the respective shell corresponds to a closing movement of the jaws 102, 103.
  • the embodiment of the clamp 100 could differ from that depicted in the attached figures.
  • the shape of the jaws 102, 103 and their articulation to the supporting chassis 101 could be different as a function of the type of load C to be handled.
  • the jaws could simply be fork-shaped (prongs of a fork) or arched and rotate instead of translate with respect to one another.
  • a regenerative valve or more in general a regenerative circuit means a valve or a circuit configured so that, as the stems exit from the respective cylinders, the volume of pressurised fluid contained in the stemside annulus joins the flow of pressurised fluid fed by the hydraulic power unit to the bottom side instead of being directed to the outlet, thus contributing to increasing the advancement speed of the stems as they exit the respective cylinders.
  • the latter movement which in the application under consideration corresponds to an opening movement of the jaws 102, 103 or a movement of the jaws 102, 103 mutually away from each other.
  • the regenerative valve 10 comprises:
  • first hydraulic line 1 1 which is hydraulically connectable by means of respective first branches 11 a, 1 1 b opening into respective mouths T1 , T2 which can be connected to the stem side T1 ', T2' respectively of the first cylinder 104 and of the second cylinder 105 and which is provided with a first connecting port CO for the hydraulic connection with the supplying and distributing hydraulic power unit 201 for supplying and distributing a hydraulic fluid (oil),
  • a second hydraulic line 12 which is hydraulically connectable by means of respective second branches 12a, 12b ending in respective mouths C1 , C2 which can be connected to the bottom side C1 C2' of the first cylinder 104 and the second cylinder 105, respectively, and which is provided with a second connecting port AO for the hydraulic connection with the supplying and distributing hydraulic power unit 201 for supplying and distributing,
  • FD1 flow divider 13 arranged along the second hydraulic line 12 between the respective second port AO and the second branches 12a, 12b respectively to subdivide the input flow to the second hydraulic line 12 into the second branches 12a, 12b and to gather the flow from the second branches 12a, 12b in output towards and from the second port AO.
  • regenerative valve 10 further comprises:
  • first check valves 16,17 (AV1 , AV2), one for each of the first branches 1 1 a,11 b and each of which is arranged along the respective first branch 11 a, 11 b and is configured to allow the unidirectional passage of the input flow from the first connecting port CO along the respective first branch 1 1 a, 1 1 b towards the respective mouth T1 , T2 connectable to the stem side T 1 ', T2' of the first and second cylinder 104,105;
  • each pair comprising one of said first branch 11 a,1 1 b and the corresponding said second branch 12a, 12b and each of which is arranged in hydraulic connection between the respective first branch 1 1 a, 11 b and the respective second branch 12a, 12b and is configured to allow the unidirectional flow from the respective first branch 11 a, 1 1 b to the respective second branch 12a, 12b, only during the opening movement, but not during the closing movement.
  • 'Pair' comprising one of said first branch 1 1 a,11 b and the corresponding second branch 12a, 12b is intended as the set of the first branch 1 1 a,1 1 b and the second branch 12a, 12b hydraulically connectable respectively to the stem side T1 ',T2' and to the bottom side C1 ',C2' of the same cylinder, respectively the first cylinder 104 and the second cylinder 105.
  • Each of the two second check valves 18,19 has a node hydraulically connected to the respective first branch 11 a, 11 b between the respective first check valve 16,17 and the connecting mouth T1 ,T2 to the stem side T1 ', T2' of the first linear actuator 104 and the second linear actuator 105, respectively.
  • the other node is hydraulically connected to the respective second branch 12a, 12b between the flow divider 13 and the connecting mouth C1 ,C2 at the bottom side CT, C2' of the first linear actuator 104 and the second linear actuator 105, respectively.
  • Each of the two second check valves 18, 19 is orientated so as to receive a pilot signal, which opens it, from the respective second branch 12a, 12b and block the flow from the respective first branch 11 a, 11 b to the respective second branch 12a, 12b, in the absence of the pilot signal.
  • a respective second check valve 18, 19 is arranged along the first junction branch 14 and along the respective second junction branch 15 and is configured to allow the flow from the respective first branch 11 a, 11 b to the respective second branch 12a, 12b, only during opening and not during closing, i.e., only during the sliding movement of the stem of each linear actuator 104,105 exiting the respective cylinder, but not during the opposite sliding return movement of the stem back into the cylinder of the respective linear actuator 104,105.
  • flow divider 13 is the only flow divider accompanying the regenerative valve 10 according to the present invention.
  • the regenerative valve 10 comprises a single flow divider 13 which, as will become clear in the following, is sized as a function of the closed oil flow rate without regeneration and thus for the lowest flow rate.
  • the first check valves 16, 17 are located on the stem side of each cylinder, thus downstream of the closing branch.
  • Each of the first junction branch 14 and the second junction branch 15 is hydraulically connected to the respective first branch 11 a, 11 b between the respective first check valve 16, 17 (AV1 , AV2) and the connecting mouth T1 , T2 at the stem side T1 ', T2', or at the latter, respectively of the first cylinder 104 and the second cylinder 105.
  • Each of the first junction branch 14 and the second junction branch 15 is hydraulically connected to the respective second branch 12a, 12b between the flow divider 13 and the connecting mouth C1 , C2 at the bottom side C1 ',C2', or at the latter, respectively of the first cylinder 104 and the second cylinder 105.
  • Each of the second check valves 18, 19 (CV3, CV4) is a piloted check valve.
  • Each of the second check valves 18, 19 (CV3, CV4) is piloted open by the pressure of the hydraulic fluid fed through the flow divider 13 along the second branches 12a, 12b to allow the unidirectional regeneration flow from the respective first branch 11a, 11 b in input to the respective second branch 12a, 12b.
  • the pressure of the hydraulic fluid fed through said flow divider 13 along the second branches 12a, 12b generates a pilot signal for the opening of the second check valves 18,19.
  • Each of the second check valves 18, 19 hydraulically connects the stem side T1 ',T2' with the bottom side C1 ',C2' of the respective cylinder 104,105.
  • the section of the respective first branch 1 1 a, 1 1 b comprised between the first check valve 16,17 and the connecting mouth T1 ,T2 at the stem side T1 ',T2' of the respective cylinder 104,105 is hydraulically connected with the section of the second branch 12a, 12b comprised between the flow divider 13 and the connecting mouth C1 ,C2 at the stem side C1 ',C2' of the respective cylinder 104,105.
  • the first hydraulic line 1 1 and the second hydraulic line 12 are alternately the inlet (supply) and outlet (discharge) of the hydraulic fluid:
  • the first hydraulic line 1 1 is inlet/supply and the second hydraulic line 12 is outlet/discharge
  • the second hydraulic line 12 is input/supply (with regeneration) and the first hydraulic line 1 1 is output/discharge.
  • Complementing the regenerative valve are 10 pressure relief valves 20 and 21 in a configuration known to the person skilled in the art and optional auxiliary ports (not shown) for the possible control of the lateral translation of the jaws.
  • the hydraulic diagram depicted in Figure 3 shows the regenerative valve 10 connected to the cylinders 104, 105 on the clamp 100 and the supplying and distributing hydraulic power unit 201 of which the forklift 200 is provided to form a closed circuit.
  • the supplying and distributing hydraulic power unit 201 has a configuration known to the person skilled in the art and, in general and non-limiting terms, it can comprise, for example, a pump 202 driven by a motor not shown, a tank 203, a pressure relief valve 204, a 4/3 type directional valve 205 connected to the pump 202, to the tank 203 to the first port CO and to the second port A0 for controlling the closing and opening movement of the jaws, respectively, and if envisaged, an auxiliary distributor 206 connected to the pump 202, to the tank 203 and to auxiliary ports for controlling the lateral translation movement of the jaws and not shown.
  • the regenerative valve 10 is integrated in the valve block 106 with which the clamp 100 is generally equipped which, in general, is removably mounted on the forklift 200.
  • the regenerative valve 10 in the use configuration in which it is connected to the cylinders 104, 105 on the clamp 100 and to the supplying and distributing hydraulic power unit 201 of the forklift 200, by means of the distributor 205 the pressurised fluid (oil) is selectively supplied to the first port CO or to the second port A0 and discharged from the other as a function of the control of the closing or opening movement of the jaws 102, 103, respectively.
  • Feeding pressurised fluid in input to the first port CO and discharging it from the second port A0 controls the closing movement of the jaws 102, 103.
  • the fluid is supplied by means of the first line 11 with opening of the first check valves 16,17 (AV1 , AV2) at the stem side inlets T1’, T2' o the cylinders 104, 105 with consequent return stroke thereof and closing of the jaws 102, 103.
  • the second check valves 18,19 remain closed.
  • the flow divider 13 by re-associating the flows, ensures the synchronised movement of the jaws and is crossed by the normal flow rate of oil in closing, as occurs with regenerative valves according to the prior art illustrated above.
  • Feeding the pressurised fluid into the second port AO and discharging it from the first port CO controls the opening movement of the jaws 102, 103 with regeneration.
  • the second check valves 18,19 are instead piloted in opening by the pressure in the respective second branch 12a, 12b.
  • the second check valves 18,19 being open, the oil exiting from the stem side T1 ',T2' of each cylinder 104, 105 is sent to its own bottom side C1 ',C2' through the respective second check valve 18,19 (CV3,CV4) located along the junction branch 14, 15 of the respective first branch 11 a,11 b with the respective second branch 12a, 12b.
  • the regenerating oil flow of each cylinder 104,105 instead of being united with that of the other cylinder is kept separate therefrom, the second check valves 18,19 each being dedicated to its own respective cylinder 104,105.
  • each cylinder 104,105 is sent directly to the bottom side C1 ',C2' of the cylinder 104,105 itself, without being sent upstream of the flow divider 13 to ensure the synchronism.
  • the flow divider 13 is not crossed by significantly different flow rates for the opening and closing of the jaws, which would lead to the disadvantages described above, but is crossed by the 'non- regenerative' closing or opening oil flow rate, i.e., the lower flow rate, as a function of which it can be sized.
  • the regenerative valve 10 according to the present invention comprises only one flow divider with obvious advantages in terms of the dimensions of the valve block 106.
  • the regenerative valve which is the subject matter of the present invention, and the clamp comprising the same, have the advantage of ensuring the synchronism of the movements of the jaws during both the opening and the closing movement thereof, and of ensuring regeneration during the opening movement while avoiding the occurrence of flow blockage problems.
  • the flow divider 13 is operational during both the closing movement and during the opening movement with regeneration:
  • the flow divider 13 is crossed by the opening flow rate supplied by the hydraulic supply and distribution unit, but not by the regeneration flow rate; the regeneration flow rate is in fact sent from the connecting mouth T1 ,T2 to the stem side T1 ',T2' of each cylinder 104,105 directly to the connecting mouth C1 ,C2 on the bottom side C1 ',C2' of the same cylinder 104,105 by means of the respective second check valve 18,19 (CV3, CV3) which is piloted in opening.
  • CV3, CV3 second check valve 18,19
  • regenerative valve to control the opening and closing movements of the jaws of a clamp in particular a clamp for forklifts, and a clamp for forklifts comprising such a regenerative valve thus conceived are susceptible to numerous modifications and variations, all of which are within the scope of the invention; moreover, all details can be replaced by technically equivalent elements.
  • the materials used, as well as their dimensions, can be of any type according to the technical requirements.

Landscapes

  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Structural Engineering (AREA)
  • Transportation (AREA)
  • Civil Engineering (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Geology (AREA)
  • Physics & Mathematics (AREA)
  • Fluid Mechanics (AREA)
  • General Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Forklifts And Lifting Vehicles (AREA)
  • Fluid-Pressure Circuits (AREA)

Abstract

An improved regenerative valve (10) to control the opening and closing movements of the jaws (102, 103) of a clamp (100), wherein the clamp (100) comprises at least one pair of jaws (102, 103) movable with respect to each other between at least one opened position and at least one closed position and vice versa by means of a respective hydraulic linear actuator (104, 105), wherein the regenerative valve (10) comprises a first hydraulic line (11), a second hydraulic line (12), a flow divider (13) arranged along the second hydraulic line (12) between a respective second connecting port (A0) and the second branches (12a, 12b) respectively to subdivide the input flow to the second hydraulic line (12) into the second branches (12a, 12b) and to gather the flow from the second branches (12a, 12b) exiting the second connecting port (A0), a pair of first check valves (16,17), one for each of the first branches (11a,11b) of the first hydraulic line and a pair of second check valves (18,19), one for each pair of the first branches (11a,11b) and the corresponding second branch (12a,12b), wherein each of the second check valves (18,19) is arranged in hydraulic connection between the respective first branch (11a,11b) and the respective second branch (12a,12b) and is configured to allow the flow from the respective first branch (11a, 11b) to the respective second branch (12a, 12b) only during the opening movement and not during the closing movement.

Description

IMPROVED REGENERATIVE VALVE TO CONTROL THE OPENING AND CLOSING MOVEMENTS OF THE JAWS OF A CLAMP, IN PARTICULAR A CLAMP FOR FORKLIFTS, AND A CLAMP FOR FORKLIFTS COMPRISING SUCH A REGENERATIVE VALVE
The present invention relates to an improved regenerative valve to control the opening and closing movements of the jaws of a clamp, in particular a clamp for forklifts.
The present invention further relates to a clamp for forklifts comprising such a regenerative valve.
With particular reference to the forklift sector, the use of clamps provided with at least one pair of jaws movable towards and away from each other, respectively, in order to pick up and release a load is well known. These jaws are hydraulically actuated in opening and closing by means of respective hydraulic linear actuators (or more simply 'cylinders') connected to each other in parallel by means of a regenerative valve connected to the hydraulic supply and distribution unit with which the forklift is equipped.
As is well known, a regenerative valve or, more generally, a regenerative circuit is configured so that, when the stems exit from the respective cylinders and, therefore, when the jaws open, the volume of pressurised fluid (oil) contained in the stem-side annulus joins the flow of pressurised fluid fed by the hydraulic power unit to the bottom side, instead of being directed to the outlet, thus contributing to increasing the advancement speed of the stems exiting from the respective cylinders. That is, the regeneration is performed during the opening of the jaws and consists of hydraulically connecting the stem side with the bottom side of the cylinders so that the flow of oil from the stem side, instead of being directed to the outlet, is re-associated with that fed to the bottom. This increases the opening speed of the cylinders, as the useful section for the oil flow from the hydraulic power unit becomes that of the stem of the cylinder alone instead of that of the bottom.
In particular, the use of regenerative valves provided with a flow divider configured and arranged to subdivide the feed flow to the cylinders into equal parts during the jaw opening movement and re-associate it during the jaw closing movement in order to achieve synchronous jaw movements of the jaws themselves is known to be used to control the opening and closing movements of jaws for clamps for forklifts.
In regenerative valves VR with a known type of flow divider, as for example shown in Figure 4, there is only one flow divider DV1 which, therefore, operates with two different flow rates:
- during the jaw opening movement, which occurs with regeneration, it operates with a flow rate equal to the sum of the input flow rate fed by the hydraulic supply and distribution unit (through the connecting port AO) and the regeneration flow rate coming from the stem side of the two cylinders through the check valve VRT, which is piloted in opening and which is associated with and sent upstream to the flow divider DV1 ;
- during the jaw closing movement, which occurs without regeneration, the flow divider DV1 works with only the flow coming from the bottom side of the two cylinders.
In opening, therefore, the flow divider DV1 works with a higher flow rate than in closing; for example, the opening flow rate can be as much as 4 or 5 times the closing flow rate.
There is, therefore, a flow divider sizing problem. If, in fact, the flow divider were sized as a function of the closing fluid flow rate, it would be undersized for the opening fluid flow rate, so that during opening, a fluid blockage effect would be generated which would compromise the benefits of regeneration.
If the flow divider was instead sized as a function of the opening fluid flow, it would be oversized for the closing fluid flow rate, so that the synchronism of the jaw movements would be compromised during closing. As is well known, the flow divider error increases as the flow rate of fluid passing through it decreases with respect to the nominal design flow rate.
At present, therefore, the flow divider in the known regenerative valves, such as the one shown in Figure 4, is sized according to compromise criteria between the two opposite requirements mentioned above, resulting in a penalisation of functionality during both opening and closing in terms of a reduction in the benefits of regeneration and synchronisation of the jaw movement.
To overcome such a drawback, an alternative regenerative valve VR' has been proposed, as shown in Figure 5 and the subject of the same applicant's patent IT102016000042043. In this case, a second flow divider DV2 is provided inserted in parallel to the first flow divider DV1. The first flow divider DV1 is sized for the closing oil flow rate, thus without regeneration, while the second flow divider DV2 is sized for the regeneration oil flow rate. During opening, which occurs with regeneration and thus a higher flow rate, the oil flow is distributed in input to the two flow dividers DV1 and DV2, obviating the problem of possible blockage which would generate if there were only the first flow divider DV1. During closing, which occurs without regeneration and thus with a lower flow rate, the second flow divider DV2 is excluded from the circuit crossed by the oil flow by the check valve VRT2. Therefore, the oil flow only passes through the first flow divider DV1 , which is sized for this flow rate, thus ensuring the synchronisation of the jaw movement.
Such an alternative solution has proven to be effective in overcoming the drawbacks of the known regenerative valves with only one flow divider and as for example illustrated in Figure 4; however, it requires the use of an additional flow divider which must be sized for higher oil flow rates. This leads to an increase in the overall dimensions of the valve block, as well as a complication of the relative circuit.
The aim of the present invention is to make an improved regenerative valve to control the opening and closing movements of the jaws of a clamp, in particular a clamp for forklifts, and a clamp for forklifts comprising such a regenerative valve, which overcome the drawbacks of the prior art.
In particular, the aim of the present invention is to make a regenerative valve to control the opening and closing movements of the jaws of a clamp, in particular a clamp for forklifts, and a clamp for forklifts comprising such a regenerative valve, which allow to ensure the synchronism of the movements of the jaws under all operating conditions and, at the same time, to ensure the benefits of regeneration during the opening movement of the jaws with limited dimensions.
Another aim of the present invention is to make a regenerative valve to control the opening and closing movements of the jaws of a clamp, in particular a clamp for forklifts, and a clamp for forklifts comprising such a regenerative valve which is particularly simple and functional, with low costs.
These aims according to the present invention are achieved by making a regenerative valve to control the opening and closing movements of the jaws of a clamp, in particular a clamp for forklifts, as set out in claim 1 .
These aims according to the present invention are achieved with a clamp for forklifts as set out in claim 9.
Further features are comprised in the dependent claims.
The features and advantages of an improved regenerative valve to control the opening and closing movements of the jaws of a clamp, in particular a clamp for forklifts, according to the present invention and of a clamp for forklifts comprising such a regenerative valve will be more evident from the following description, which is illustrative and not limiting, referring to the attached schematic drawings in which: figure 1 is a schematic view of a forklift provided with a possible embodiment of the clamp according to the present invention; figure 2 is an axonometric and partially exploded view of the clamp of figure 1 ; figure 3 is a hydraulic circuit diagram of a clamp for forklifts incorporating an improved regenerative valve according to the present invention in connection with the hydraulic system (hydraulic supply and distribution unit) existing on a forklift; figures 4 and 5 show a hydraulic circuit diagram of a clamp for forklifts incorporating two different regenerative valves according to the prior art.
With reference to the attached figures, an improved regenerative valve 10 to control the opening and closing movements of the jaws of a clamp 100, in particular a clamp 100 for forklifts 200, is shown.
In general terms, the 100 clamp comprises:
- a supporting chassis 101 which can be coupled to the mobile chassis of a forklift 200,
- a pair of jaws 102, 103, which are mounted on the supporting chassis 101 in a relatively movable manner with respect to each other between at least one opened position, in which they are distanced from each other to receive therebetween or release a load C, and at least one closed position, in which they are approached to grasp the load C, and vice versa,
- at least one pair of hydraulic linear actuators 104, 105, respectively a first hydraulic actuator 104 and a second hydraulic actuator 105, which are mounted on the supporting chassis 101 and each of which is connected to a respective jaw 102, 103 to actuate the movement thereof between said at least one opened position and said at least one closed position and vice versa, and
- a valve block 106 incorporating a regenerative valve 10 according to the present invention and which is configured to hydraulically connect the hydraulic linear actuators 104 and 105 to each other in parallel and control the movements thereof.
The valve block 106 is in turn hydraulically connectable to the hydraulic system with which the forklift 200 is equipped and, in particular, to the supplying and distributing hydraulic power unit 201 for supplying and distributing hydraulic fluid (pressurised oil) with which the forklift 200 is normally equipped.
The valve block 106, hydraulic linear actuators 104, 105 and supplying and distributing hydraulic power unit 201 hydraulically connected to each other form a closed circuit.
With particular reference to the embodiment shown in the attached figures, the jaws 102, 103 are of the flat plate type arranged parallel to each other and each of which is fixed to a respective pair of support arms 107, 108 slidingly guided along straight guides 109 fixed to the supporting chassis 101. The hydraulic linear actuators 104, 105 are arranged one above the other and opposite each other in a direction parallel to the straight guides 109.
The first and the second hydraulic linear actuator 104, 105 - also known in the field simply as 'cylinders' and hereafter also referred to respectively as first cylinder 104 and second cylinder 105 - each comprise a cylindrical shell which is fixed to the supporting chassis 101 and within which a piston sealingly slides connected to a stem the head of which protrudes outside the front head of the shell (through which the stem itself is slidingly guided) and is articulated to a respective jaw 102, 103. At the front head and rear head or bottom of the shell of each cylinder, a respective attachment is obtained for the inlet and the outlet of the hydraulic fluid from the respective chamber. In the diagrams depicted in the attached figures and in particular in Figure 3, such inlets are indicated respectively with T1’ and C/' for the first linear actuator 104 and with T2' and C2' for the second linear actuator 105.
As immediately comprehensible to the person skilled in the art, the outlet stroke of the stem of each first and second cylinder 104, 105 from the respective shell corresponds to an opening movement of the jaws 102, 103 and the return stroke of the stem of each first and second cylinder 104, 105 into the respective shell corresponds to a closing movement of the jaws 102, 103.
It should be noted that the embodiment of the clamp 100 could differ from that depicted in the attached figures. In particular, the shape of the jaws 102, 103 and their articulation to the supporting chassis 101 could be different as a function of the type of load C to be handled. Thus, for example, the jaws could simply be fork-shaped (prongs of a fork) or arched and rotate instead of translate with respect to one another.
With reference to the hydraulic diagram shown in Figure 3, a regenerative valve 10 according to the present invention is now described in detail.
It should first be noted that, as is well known to the person skilled in the art, a regenerative valve or more in general a regenerative circuit means a valve or a circuit configured so that, as the stems exit from the respective cylinders, the volume of pressurised fluid contained in the stemside annulus joins the flow of pressurised fluid fed by the hydraulic power unit to the bottom side instead of being directed to the outlet, thus contributing to increasing the advancement speed of the stems as they exit the respective cylinders. The latter movement, which in the application under consideration corresponds to an opening movement of the jaws 102, 103 or a movement of the jaws 102, 103 mutually away from each other.
The regenerative valve 10 comprises:
- a first hydraulic line 1 1 which is hydraulically connectable by means of respective first branches 11 a, 1 1 b opening into respective mouths T1 , T2 which can be connected to the stem side T1 ', T2' respectively of the first cylinder 104 and of the second cylinder 105 and which is provided with a first connecting port CO for the hydraulic connection with the supplying and distributing hydraulic power unit 201 for supplying and distributing a hydraulic fluid (oil),
- a second hydraulic line 12 which is hydraulically connectable by means of respective second branches 12a, 12b ending in respective mouths C1 , C2 which can be connected to the bottom side C1 C2' of the first cylinder 104 and the second cylinder 105, respectively, and which is provided with a second connecting port AO for the hydraulic connection with the supplying and distributing hydraulic power unit 201 for supplying and distributing,
- a flow divider 13 (FD1 ) arranged along the second hydraulic line 12 between the respective second port AO and the second branches 12a, 12b respectively to subdivide the input flow to the second hydraulic line 12 into the second branches 12a, 12b and to gather the flow from the second branches 12a, 12b in output towards and from the second port AO.
According to the present invention, regenerative valve 10 further comprises:
- a pair of first check valves 16,17 (AV1 , AV2), one for each of the first branches 1 1 a,11 b and each of which is arranged along the respective first branch 11 a, 11 b and is configured to allow the unidirectional passage of the input flow from the first connecting port CO along the respective first branch 1 1 a, 1 1 b towards the respective mouth T1 , T2 connectable to the stem side T 1 ', T2' of the first and second cylinder 104,105;
- a pair of second check valves 18,19 (CV3, CV4), one of each pair comprising one of said first branch 11 a,1 1 b and the corresponding said second branch 12a, 12b and each of which is arranged in hydraulic connection between the respective first branch 1 1 a, 11 b and the respective second branch 12a, 12b and is configured to allow the unidirectional flow from the respective first branch 11 a, 1 1 b to the respective second branch 12a, 12b, only during the opening movement, but not during the closing movement.
'Pair' comprising one of said first branch 1 1 a,11 b and the corresponding second branch 12a, 12b is intended as the set of the first branch 1 1 a,1 1 b and the second branch 12a, 12b hydraulically connectable respectively to the stem side T1 ',T2' and to the bottom side C1 ',C2' of the same cylinder, respectively the first cylinder 104 and the second cylinder 105.
Each of the two second check valves 18,19 has a node hydraulically connected to the respective first branch 11 a, 11 b between the respective first check valve 16,17 and the connecting mouth T1 ,T2 to the stem side T1 ', T2' of the first linear actuator 104 and the second linear actuator 105, respectively.
The other node is hydraulically connected to the respective second branch 12a, 12b between the flow divider 13 and the connecting mouth C1 ,C2 at the bottom side CT, C2' of the first linear actuator 104 and the second linear actuator 105, respectively.
Each of the two second check valves 18, 19 is orientated so as to receive a pilot signal, which opens it, from the respective second branch 12a, 12b and block the flow from the respective first branch 11 a, 11 b to the respective second branch 12a, 12b, in the absence of the pilot signal.
In more detail, the following are present in the regenerative valve 10:
- a first junction branch 14 between the first branch 11 a and the second branch 12a opening into the mouths T1 ,C1 which can be hydraulically connected to the stem side T1 ' and to the bottom side CT, respectively, of the first linear actuator or cylinder 104;
- a second junction branch 15 between the first branch 11 b and the second branch 12b opening into the mouths T2,C2 which can be hydraulically connected to the stem side T2' and to the bottom side C2', respectively, of the second linear actuator or cylinder 105;
- wherein a respective second check valve 18, 19 (CV3, CV4) is arranged along the first junction branch 14 and along the respective second junction branch 15 and is configured to allow the flow from the respective first branch 11 a, 11 b to the respective second branch 12a, 12b, only during opening and not during closing, i.e., only during the sliding movement of the stem of each linear actuator 104,105 exiting the respective cylinder, but not during the opposite sliding return movement of the stem back into the cylinder of the respective linear actuator 104,105.
It should be noted that the flow divider 13 is the only flow divider accompanying the regenerative valve 10 according to the present invention.
That is, the regenerative valve 10 according to the present invention comprises a single flow divider 13 which, as will become clear in the following, is sized as a function of the closed oil flow rate without regeneration and thus for the lowest flow rate.
The first check valves 16, 17 are located on the stem side of each cylinder, thus downstream of the closing branch.
Each of the first junction branch 14 and the second junction branch 15 is hydraulically connected to the respective first branch 11 a, 11 b between the respective first check valve 16, 17 (AV1 , AV2) and the connecting mouth T1 , T2 at the stem side T1 ', T2', or at the latter, respectively of the first cylinder 104 and the second cylinder 105.
Each of the first junction branch 14 and the second junction branch 15 is hydraulically connected to the respective second branch 12a, 12b between the flow divider 13 and the connecting mouth C1 , C2 at the bottom side C1 ',C2', or at the latter, respectively of the first cylinder 104 and the second cylinder 105.
Each of the second check valves 18, 19 (CV3, CV4) is a piloted check valve.
Each of the second check valves 18, 19 (CV3, CV4) is piloted open by the pressure of the hydraulic fluid fed through the flow divider 13 along the second branches 12a, 12b to allow the unidirectional regeneration flow from the respective first branch 11a, 11 b in input to the respective second branch 12a, 12b. The pressure of the hydraulic fluid fed through said flow divider 13 along the second branches 12a, 12b generates a pilot signal for the opening of the second check valves 18,19.
Each of the second check valves 18, 19 (CV3, CV4) hydraulically connects the stem side T1 ',T2' with the bottom side C1 ',C2' of the respective cylinder 104,105.
In particular, the section of the respective first branch 1 1 a, 1 1 b comprised between the first check valve 16,17 and the connecting mouth T1 ,T2 at the stem side T1 ',T2' of the respective cylinder 104,105 is hydraulically connected with the section of the second branch 12a, 12b comprised between the flow divider 13 and the connecting mouth C1 ,C2 at the stem side C1 ',C2' of the respective cylinder 104,105.
The first hydraulic line 1 1 and the second hydraulic line 12 are alternately the inlet (supply) and outlet (discharge) of the hydraulic fluid:
- for controlling the closing movement of the jaws 102, 103, corresponding to a return stroke of the stems in the respective cylinders 104, 105 (without regeneration), the first hydraulic line 1 1 is inlet/supply and the second hydraulic line 12 is outlet/discharge,
- for controlling the opening movement of the jaws 102, 103, corresponding to an exit stroke of the stems from the respective cylinders 104, 105 (with regeneration), the second hydraulic line 12 is input/supply (with regeneration) and the first hydraulic line 1 1 is output/discharge.
Complementing the regenerative valve are 10 pressure relief valves 20 and 21 in a configuration known to the person skilled in the art and optional auxiliary ports (not shown) for the possible control of the lateral translation of the jaws.
The hydraulic diagram depicted in Figure 3 shows the regenerative valve 10 connected to the cylinders 104, 105 on the clamp 100 and the supplying and distributing hydraulic power unit 201 of which the forklift 200 is provided to form a closed circuit.
The supplying and distributing hydraulic power unit 201 has a configuration known to the person skilled in the art and, in general and non-limiting terms, it can comprise, for example, a pump 202 driven by a motor not shown, a tank 203, a pressure relief valve 204, a 4/3 type directional valve 205 connected to the pump 202, to the tank 203 to the first port CO and to the second port A0 for controlling the closing and opening movement of the jaws, respectively, and if envisaged, an auxiliary distributor 206 connected to the pump 202, to the tank 203 and to auxiliary ports for controlling the lateral translation movement of the jaws and not shown.
As shown in Figure 2, the regenerative valve 10 is integrated in the valve block 106 with which the clamp 100 is generally equipped which, in general, is removably mounted on the forklift 200.
The operation of the regenerative valve 10 according to the present invention is immediately comprehensible to the person skilled in the art from the above description and the attached figures.
In brief, considering the regenerative valve 10 in the use configuration in which it is connected to the cylinders 104, 105 on the clamp 100 and to the supplying and distributing hydraulic power unit 201 of the forklift 200, by means of the distributor 205 the pressurised fluid (oil) is selectively supplied to the first port CO or to the second port A0 and discharged from the other as a function of the control of the closing or opening movement of the jaws 102, 103, respectively.
Feeding pressurised fluid in input to the first port CO and discharging it from the second port A0 controls the closing movement of the jaws 102, 103.
In this configuration, the fluid is supplied by means of the first line 11 with opening of the first check valves 16,17 (AV1 , AV2) at the stem side inlets T1’, T2' o the cylinders 104, 105 with consequent return stroke thereof and closing of the jaws 102, 103. The second check valves 18,19 remain closed.
The fluid in output from the bottom side C1’, C2' of the cylinders 104, 105 passes through flow divider 13 (the second piloted check valves 18,19 remaining closed) which rejoins it in discharge through the second port A0.
The flow divider 13, by re-associating the flows, ensures the synchronised movement of the jaws and is crossed by the normal flow rate of oil in closing, as occurs with regenerative valves according to the prior art illustrated above.
Feeding the pressurised fluid into the second port AO and discharging it from the first port CO controls the opening movement of the jaws 102, 103 with regeneration.
During opening, the first check valves 16,17 (AV1 and AV2) remain closed.
The second check valves 18,19 are instead piloted in opening by the pressure in the respective second branch 12a, 12b.
The second check valves 18,19 being open, the oil exiting from the stem side T1 ',T2' of each cylinder 104, 105 is sent to its own bottom side C1 ',C2' through the respective second check valve 18,19 (CV3,CV4) located along the junction branch 14, 15 of the respective first branch 11 a,11 b with the respective second branch 12a, 12b.
Unlike what occurs in the check valves according to the prior art illustrated above, in the regenerative valve 10 according to the present invention the regenerating oil flow of each cylinder 104,105 instead of being united with that of the other cylinder is kept separate therefrom, the second check valves 18,19 each being dedicated to its own respective cylinder 104,105.
Therefore, the regenerating oil flow of each cylinder 104,105 is sent directly to the bottom side C1 ',C2' of the cylinder 104,105 itself, without being sent upstream of the flow divider 13 to ensure the synchronism.
It is therefore evident that during opening, the flow divider 13 is only crossed by the flow of oil arriving from the second mouth A0 and fed by the control unit 201 , but not by the regeneration flow.
In contrast what occurs in the regenerative valves according to the prior art described above, in the regenerative valve 10 according to the present invention, the flow divider 13 is not crossed by significantly different flow rates for the opening and closing of the jaws, which would lead to the disadvantages described above, but is crossed by the 'non- regenerative' closing or opening oil flow rate, i.e., the lower flow rate, as a function of which it can be sized. Furthermore, as mentioned above, the regenerative valve 10 according to the present invention comprises only one flow divider with obvious advantages in terms of the dimensions of the valve block 106.
The regenerative valve which is the subject matter of the present invention, and the clamp comprising the same, have the advantage of ensuring the synchronism of the movements of the jaws during both the opening and the closing movement thereof, and of ensuring regeneration during the opening movement while avoiding the occurrence of flow blockage problems.
The flow divider 13 is operational during both the closing movement and during the opening movement with regeneration:
- During the closing movement, the flow divider 13 is crossed by the closing flow rate;
- During the opening movement with regeneration, the flow divider 13 is crossed by the opening flow rate supplied by the hydraulic supply and distribution unit, but not by the regeneration flow rate; the regeneration flow rate is in fact sent from the connecting mouth T1 ,T2 to the stem side T1 ',T2' of each cylinder 104,105 directly to the connecting mouth C1 ,C2 on the bottom side C1 ',C2' of the same cylinder 104,105 by means of the respective second check valve 18,19 (CV3, CV3) which is piloted in opening.
The regenerative valve to control the opening and closing movements of the jaws of a clamp, in particular a clamp for forklifts, and a clamp for forklifts comprising such a regenerative valve thus conceived are susceptible to numerous modifications and variations, all of which are within the scope of the invention; moreover, all details can be replaced by technically equivalent elements. In practice, the materials used, as well as their dimensions, can be of any type according to the technical requirements.

Claims

1. Improved regenerative valve (10) to control the opening and closing movements of the jaws (102, 103) of a clamp (100), in particular a clamp for forklifts (200), wherein the clamp (100) comprises at least one pair of jaws (102, 103) movable with respect to each other between at least one opened position and at least one closed position and vice versa by means of at least one corresponding hydraulic linear actuator (104, 105), respectively at least one first linear actuator (104) and at least one second linear actuator (105), wherein said regenerative valve (10) comprises:
- a first hydraulic line (11 ) which is hydraulically connectable by means of respective first branches (11 a, 11 b) to the stem side (T1 ’, T2’) of each of said first and second linear actuators (104, 105) and which is provided with a first connecting port (CO) for the hydraulic connection with a supplying and distributing hydraulic power unit (201 ) for supplying and distributing a hydraulic fluid,
- a second hydraulic line (12) which is hydraulically connectable by means of respective second branches (12a, 12b) to the bottom side (C1 ’, C2’) of each of said first and second linear actuators (104, 105) and which is provided with a second connecting port (A0) for the hydraulic connection with said supplying and distributing hydraulic power unit (201 ),
- a flow divider (13) arranged along said second hydraulic line (12) between said respective second connecting port (A0) and said second branches (12a, 12b) respectively to subdivide the input flow to said second hydraulic line (12) into said second branches (12a, 12b) and to gather the flow from said second branches (12a, 12b) towards the exit from said second connecting port (A0), characterized by comprising:
- a pair of first check valves (16, 17), one for each of said first branches (11 a, 11 b) and each of which is arranged along the respective first branch (11 a, 11 b) and is configured to allow the unidirectional passage of the input flow from said first connecting port (CO) along said respective first branch (11 a, 11 b); and
- a pair of second check valves (18, 19), one for each pair of said first branches (11 a, 11 b) and the corresponding said second branch (12a, 12b), wherein the first branch (11 a, 11 b) and the second branch (12a, 12b) of each of said pairs are hydraulically connectable respectively to the stem side (T1 ’, T2’) and the bottom side (C1 ’, C2’) of the same respective first and second linear actuator (104, 105), wherein each of said second check valves (18, 19) is arranged in hydraulic connection between the respective first branch (11 a, 11 b) and the respective second branch (12a, 12b) and is configured to allow the flow from said respective first branch (11 a, 11 b) to said respective second branch (12a, 12b) only during the opening movement and not during the closing movement.
2. Regenerative valve (10) according to claim 1 , wherein each of said second check valves (18, 19) is hydraulically connected to the respective first branch (11 a, 11 b) between the respective said first check valve (16, 17) and the connecting mouth (T1 , T2) to the stem side (T1 ’, T2’) respectively of said first linear actuator (104) and said second linear actuator (105).
3. Regenerative valve (10) according to claim 1 or 2, wherein each of said second check valves (18, 19) is hydraulically connected to the respective second branch (12a, 12b) between said flow divider (13) and the connecting mouth (C1 , C2) to the bottom side (C1 ’, C2’) respectively of said first linear actuator (104) and said second linear actuator (105).
4. Regenerative valve (10) according to any one of the preceding claims, wherein each of said second check valves (18, 19) is a pilot-operated check valve which is driven in the opening state by the pressure of the hydraulic fluid supplied through said flow divider (13) along said second branches (12a, 12b) to allow the unidirectional regeneration flow from the respective said first branch (11 a, 11 b) entering the respective said second branch (12a, 12b), wherein in the absence of pilot signal each of said second check valves (18, 19) is configured to block the flow from said respective first branch (11 a, 11 b) to said respective second branch (12a, 12b).
5. Regenerative valve (10) according to any one of the preceding claims, characterized by comprising:
- a first junction branch (14) between the first branch (11a) and the second branch (12a) hydraulically connectable to said first linear actuator (104);
- a second junction branch (15) between the first branch (11 b) and the second branch (12b) hydraulically connectable to said second linear actuator (105);
- wherein a respective said second check valve (18, 19), configured to allow the flow from the respective said first branch (11 a, 11 b) to the respective said second branch (12a, 12b) only during the opening movement and not during the closing movement, is arranged along each of said first junction branch (14) and said second junction branch (15).
6. Regenerative valve (10) according to claim 5, wherein each of said first junction branch (14) and said second junction branch (15) is hydraulically connected to the respective first branch (11a, 11 b) between the respective said first check valve (16, 17) and the connecting mouth (T1 , T2) to the stem side (T1 ’, T2’) respectively of said first linear actuator (104) and said second linear actuator (105).
7. Regenerative valve (10) according to claim 5 or 6, wherein each of said first junction branch (14) and said second junction branch (15) is hydraulically connected to the respective second branch (12a, 12b) between said flow divider (13) and the connecting mouth (C1 , C2) to the bottom side (C1 ’, C2’) respectively of said first linear actuator (104) and said second linear actuator (105).
8. Regenerative valve (10) according to any one of the preceding claims, wherein said flow divider (13) is the only flow divider equipping said regenerative valve (10).
9. Clamp (100) for forklifts (200) comprising a supporting chassis (101 ) which is couplable to a forklift, at least one pair of jaws (102, 103) being mounted on said supporting chassis (101 ) in a movable manner with respect to each other between at least one opening position and at least one closing position and vice versa, at least one pair of hydraulic linear actuators (104, 105) each of which is mounted on said supporting chassis (101 ) and is connected to a respective jaw of said at least one pair of jaws (102, 103), characterized by comprising a regenerative valve (10) according to one or more of the preceding claims whose first branches (11 a, 11 b) and second branches (12a, 12b) are hydraulically connected to the stem side (T1 ’, T2’) and to the bottom side (C1 ’, C2’) respectively of said hydraulic linear actuators (104, 105) thus connected in parallel to control the shift of said jaws (102, 103) between said at least one opened position and said at least one closed position and vice versa, wherein said first connecting port (CO) and said second connecting port (A0) are connectable to the supplying and distributing hydraulic power unit (201 ) for supplying and distributing the hydraulic fluid of which said forklift is provided with.
10. Forklift (200) comprising a clamp according to claim 9.
EP24715679.7A 2023-03-06 2024-03-05 Improved regenerative valve to control the opening and closing movements of the jaws of a clamp, in particular a clamp for forklifts, and a clamp for forklifts comprising such a regenerative valve Pending EP4677235A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
IT102023000004011A IT202300004011A1 (en) 2023-03-06 2023-03-06 IMPROVED REGENERATIVE VALVE FOR CONTROLLING THE OPENING AND CLOSING MOVEMENTS OF THE JAWS OF A CLAMP, IN PARTICULAR A FORKLIFT CLAMP, AND A FORKLIFT CLAMP INCLUDING SUCH REGENERATIVE VALVE.
PCT/IB2024/052099 WO2024184799A1 (en) 2023-03-06 2024-03-05 Improved regenerative valve to control the opening and closing movements of the jaws of a clamp, in particular a clamp for forklifts, and a clamp for forklifts comprising such a regenerative valve

Publications (1)

Publication Number Publication Date
EP4677235A1 true EP4677235A1 (en) 2026-01-14

Family

ID=86469001

Family Applications (1)

Application Number Title Priority Date Filing Date
EP24715679.7A Pending EP4677235A1 (en) 2023-03-06 2024-03-05 Improved regenerative valve to control the opening and closing movements of the jaws of a clamp, in particular a clamp for forklifts, and a clamp for forklifts comprising such a regenerative valve

Country Status (3)

Country Link
EP (1) EP4677235A1 (en)
IT (1) IT202300004011A1 (en)
WO (1) WO2024184799A1 (en)

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1293033B (en) * 1964-04-09 1969-04-17 Crede & Co Gmbh Geb Hydraulic clamp, particularly for use on forklift trucks
US10494241B2 (en) * 2016-09-16 2019-12-03 Cascade Corporation Hydraulic clamping systems having load side-shifting variably responsive to load weight

Also Published As

Publication number Publication date
IT202300004011A1 (en) 2024-09-06
WO2024184799A1 (en) 2024-09-12

Similar Documents

Publication Publication Date Title
US8671824B2 (en) Hydraulic control system
CN101003977B (en) Hydraulic control device for working machine
CN101253335B (en) Oil circuit for controlling double-acting hydraulic drive cylinders
KR100636863B1 (en) Hydraulic circuit
CN111033056B (en) Hydraulic circuit
US6701823B2 (en) Method and device for controlling a lift cylinder, especially of working machines
US10473125B2 (en) Hydraulic actuator control circuit
US11692332B2 (en) Hydraulic control system
US8281583B2 (en) Hydraulic control assembly
JP7633823B2 (en) Hydraulic Control System
US6976418B2 (en) Hydraulic system with an actuator having independent meter-in meter-out control
JP2016223590A5 (en)
CZ63897A3 (en) Apparatus for recovery of energy
EP1760325B1 (en) Hydraulic load sensing system for agricultural tractors
US5261232A (en) Valve system for supplying fluid from a pair of fluid pressure sources to a load
EP4677235A1 (en) Improved regenerative valve to control the opening and closing movements of the jaws of a clamp, in particular a clamp for forklifts, and a clamp for forklifts comprising such a regenerative valve
US20060266029A1 (en) Working machine
JP2013249954A (en) Hydraulic control block, hydraulic system, and construction machine equipped with hydraulic control block
US20110232787A1 (en) Stack valve
JPH06505081A (en) Load sensing hydraulic control system
GB2499111A (en) A hydraulic control arrangement
KR20170009758A (en) Hydraulic circuit for construction machine and construction machine
KR101718604B1 (en) Hydraulic circuit for construction machine
US7320272B2 (en) Hydraulic system
JPH01320303A (en) Hydraulic circuit and hydraulic change-over valve for hydraulic shovel

Legal Events

Date Code Title Description
STAA Information on the status of an ep patent application or granted ep patent

Free format text: STATUS: UNKNOWN

STAA Information on the status of an ep patent application or granted ep patent

Free format text: STATUS: THE INTERNATIONAL PUBLICATION HAS BEEN MADE

PUAI Public reference made under article 153(3) epc to a published international application that has entered the european phase

Free format text: ORIGINAL CODE: 0009012

STAA Information on the status of an ep patent application or granted ep patent

Free format text: STATUS: REQUEST FOR EXAMINATION WAS MADE

17P Request for examination filed

Effective date: 20250903

AK Designated contracting states

Kind code of ref document: A1

Designated state(s): AL AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LI LT LU LV MC ME MK MT NL NO PL PT RO RS SE SI SK SM TR