Hydraulic circuit for a hydraulic cylinder

Abstract

 A hydraulic circuit (10) for operating a dual acting hydraulic cylinder (20) is disclosed. The hydraulic circuit reduces the extraction and retraction times of the hydraulic cylinder. The hydraulic circuit comprises a speed component (14) comprising a regeneration valve (18) arranged to return a hydraulic fluid from a rod-side chamber (24) to a piston-side chamber (22) of the cylinder (50) at a start phase of cylinder extraction, and a booster component (12) comprising first pressure intensifier (16) and a second pressure intensifier (17) arranged in parallel to increase flow of fluid at an end phase of cylinder extraction.

Description

Technical Field

[0001] This disclosure relates to a hydraulic apparatus for operation of a piston/cylinder assembly such as a dual acting hydraulic cylinder and to a method of cyclically operating a dual acting hydraulic cylinder. More particularly, this disclosure relates to cyclic operation of a dual acting hydraulic cylinder in a demolition machine.

Background

[0002] A hydraulic cylinder is a mechanical actuator which may be used to give a linear force. The hydraulic cylinder may have varied applications and may be used in vehicles and machines for example a demolition tool, which comprises of a jaw set that may be opened and closed by actuation of a hydraulic cylinder.

[0003] Hydraulic pressure from a pressurised fluid, such as oil, acts on the piston to perform linear work. Pressurised fluid may flow between a reservoir and the piston side or rod side chambers of the hydraulic cylinder for cyclic operation thereof. Generally, flow of pressurised oil into the piston side chamber may effect an extraction of the piston rod while flow of pressurised oil into the rod side chamber may effect retraction of the piston rod. Cycle time to extract or retract the piston rod may be dependent on multiple factors such as size of the cylinder. In certain engineering activities a reduction of the cycle time may be desired.

[0004] The cycle time of a hydraulic cylinder may be reduced by use of a speed valve or a regeneration valve.

[0005] US Patent No. 5996465 describes an oil-pressure cylinder in a crushing device connected to a crushing jaw to actuate the crushing jaw. Cylinder extension may cause the crushing jaw to close and crush an object. During a jaw closing stroke as the crushing jaw starts to close, to the point the crushing jaw comes into contact with the object, an acceleration (speed or regeneration valve) valve may make a continuous communication between a base-side port and a rod-side port in the cylinder. Oil from the rod-side port may be made to flow to the base-side port which may increase the movement-speed of the rod in the jaw closing stroke during the unloaded interval. When the crushing jaw comes into contact with the object, communication of the base-side port to the rod-side port is interrupted.

[0006] US Patent No. 7540231 describes a control valve device for the control of a dual-action consumer. A regeneration function allows the return side of the consumer to be connected with the admission side of the consumer. For the regeneration function, the connection of an additional pressure fluid line that forms the return side of the consumer with the reservoir can be blocked by a shutoff valve device located between the consumer and the control valve. The regeneration function may be overridden by an actuation of the shutoff valve device toward the open position as a function of the admission pressure at the admission side of the consumer. Under operating conditions wherein a high admission pressure is necessary to achieve high output power or increased performance, the regeneration function may be deactivated by the overriding of the regeneration function to ensure that the regeneration function is active only to achieve an increased speed of movement of the consumer.

[0007] Although the time to extract the piston rod may be increased, the aforementioned speed valves have a disadvantage in that the time to retract the piston rod is relatively long.

[0008] US Patent No. 5542180 describes a heavy duty shear comprising a fixed lower jaw and a movable upper jaw driven by a hydraulic cylinder. To overcome jams, the hydraulic cylinder is provided with an intensifier which pressurises a portion of hydraulic fluid above the maximum pressure of the machine hydraulic system. The hydraulic fluid at a higher pressure is provided to the cylinder to facilitate opening of the jaws. The output pressure of the intensifier is selected to overcome the difference in the area at the rod side of the piston and area at the piston side of the piston. The high pressure to open the jaw may be present only when a jam is to be cleared.

[0009] US 5415076 describes fluid regeneration circuits which may be useful for filling expanding sides of a hydraulic cylinder with fluid being exhausted from the other side. A flow regeneration valve and a pressure boost valve may be used in combination with a meter-out valve for providing flow regeneration from the head end chamber to a rod end chamber when fluid pressure in the head end chamber is less than the pressure level of fluid in a passage as determined by a spring of the pressure boost valve. The pressure boost valve may be disposed within the passage and may be oriented to block fluid flow from the exhaust conduit to the inlet of the meter-out valve. The boost valve is biased to the closed position by the spring to block fluid flow from the inlet to the exhaust conduit until the fluid pressure in the inlet exceeds a predetermined level.

[0010] The pressure boost valve may be involved with control of fluid flowing to the tank and may not be involved in improving cycle time of the hydraulic cylinder.

[0011] EP 09178089.0, in the name of Caterpillar Work Tools B.V., discloses a hydraulic device for operating a dual acting hydraulic cylinder comprising a speed component arranged to return a hydraulic fluid from a rod-side chamber to a piston-side chamber of the cylinder at a start phase of cylinder extraction and a booster component arranged to increase the pressure of the fluid at an end phase of cylinder extraction.

[0012] The present disclosure is directed, at least in part, to improving or overcoming one or more aspects of the prior art system.

Brief Summary of the Invention

[0013] In a first aspect, the present disclosure describes a hydraulic circuit for operating a dual acting hydraulic cylinder comprising a speed component comprising a regeneration valve arranged to return a hydraulic fluid from a rod-side chamber to a piston-side chamber of the cylinder at a start phase of cylinder extraction; and a booster component comprising a first pressure intensifier and a second pressure intensifier arranged in parallel to increase flow of fluid at an end phase of cylinder extraction.

[0014] In a second aspect, the present disclosure describes a method of operating a dual acting hydraulic cylinder, the method comprising the steps of: returning a hydraulic fluid from a rod-side chamber to a piston-side chamber of the cylinder during a start phase of cylinder extraction with a speed component; and increasing flow of fluid during end phase of cylinder extraction with a booster component comprising a first pressure intensifier and a second pressure intensifier arranged in parallel.

Brief Description of the Drawings

[0015] The foregoing and other features and advantages of the present disclosure will be more fully understood from the following description of various embodiments, when read together with the accompanying drawings, in which:

Fig. 1 is a schematic representation of a first embodiment of a hydraulic circuit according to the present disclosure coupled to a hydraulic cylinder;

Fig. 2 is a schematic representation of a second embodiment of the hydraulic circuit according to the present disclosure coupled to a hydraulic cylinder; and

Fig. 3 is a comparative graph of operation cycle times of jaw sets of demolition tools during a demolition application including the operation cycle time of a jaw set actuated by a hydraulic cylinder coupled to the hydraulic circuit according to the present disclosure.

Detailed Description

[0016] This disclosure generally relates to a hydraulic device 10 for operating a piston/cylinder assembly such as a hydraulic cylinder, in particular a dual acting hydraulic cylinder.

[0017] Figure 1 shows a schematic representation of hydraulic connections between the hydraulic device 10 and a hydraulic cylinder 20 in a first embodiment. The hydraulic connections may be suitably provided for operation and control of the hydraulic device 10 and the hydraulic cylinder 20. Operation of the hydraulic device 10 and the hydraulic cylinder 20 may be effected through pressurisation of the hydraulic fluid.

[0018] The hydraulic cylinder 20 may comprise of a piston-side chamber 22, a rod-side chamber 24, a rod 26, a piston 28 and a cylinder body 30. The hydraulic cylinder 20 may go through cylinder extraction or extraction stroke when the rod 26 moves out from cylinder body 30. Cylinder retraction or retraction stroke may occur when the rod 26 moves into cylinder body 30.

[0019] Hydraulic lines may be connected to the cylinder body 30 for passage of fluid into the piston-side chamber 22 and the rod-side chamber 24. Line 44 may be connected to piston-side chamber 22. Line 44 may permit flow of fluid to and from piston-side chamber 22. Line 42 may be connected to the rod-side chamber 24. Line 42 may permit flow of fluid to and from rod-side chamber 24.

[0020] For cylinder retraction, the hydraulic fluid from a fluid reservoir 76 may be pumped to rod-side chamber 24 through line 43 and line 42 while fluid from the piston-side chamber 22 may be allowed to return to a fluid source 74 through the line 44 and line 45.

[0021] In an embodiment, fluid reservoir 76 and fluid reservoir 74 may be the same.

[0022] For cylinder extraction, the hydraulic fluid may be pumped from the fluid source 74 to piston-side chamber 22 through line 45 and line 44 while fluid from the rod-side chamber 24 may be allowed to return to the fluid reservoir 76 through the line 42 and line43.

[0023] In an embodiment, at initiation of an operation cycle of the hydraulic circuit 10 the hydraulic cylinder 20 may be fully extracted. The jaws of a demolition device may be completely closed. The hydraulic cylinder 20 may be fully retracted at mid-cycle with the jaws of the demolition device being completely open. At the end of an operation cycle of the hydraulic circuit 10 the hydraulic cylinder 20 may be returned to the fully extracted position so that the jaws of the demolition device are returned to the completely closed position.

[0024] The hydraulic device 10 may comprise of a booster component 12, a speed component 14 and a main valve 40.

[0025] Main valve 40 may permit flow of fluid from the fluid source 74 and/ or the reservoir 76 to the hydraulic cylinder 20. Main valve 40 may be connected to hydraulic cylinder 20 through lines 44 and 42. Main valve 40 may permit fluid to flow between the hydraulic cylinder 20 and the fluid source 74 and/ or the reservoir 76 through lines 44 and 42.

[0026] Main valve 40 may have an extraction flow position 19 and a retraction flow position 21. At the extraction flow position 19 fluid may be permitted to flow from the fluid source 74 to line 44 and fluid may flow from line 42 to the fluid reservoir 76. At the retraction flow position 21 fluid may be permitted to flow from the fluid reservoir 76 to line 42 and fluid may flow from line 44 to the fluid source 74. The hydraulic cylinder 20 may operate under the normal extraction function with the main valve at the extraction flow position 19. The hydraulic cylinder 20 may be under the normal extraction mode when the extraction flow position 19 is selected.

[0027] The booster component 12 and the speed component 14 may also comprise sequence valves 50, 52 for pressure controlled activation or deactivation of the components. In an embodiment, the hydraulic connections may be arranged to activate or deactivate the booster component 12 and the speed component 14 in sequence. The hydraulic cylinder 20 may be under the speed mode when the speed component 14 is activated and may be under the boost mode when the booster component 12 is activated.

[0028] The speed component 14 may comprise of a regeneration valve. In an embodiment, the regeneration valve 18 may be comprised within the main valve 40.

[0029] Main valve 40 may further comprise a regeneration position 23. Main valve 40 may be actuatable between the extraction flow position 19, the retraction flow position 21 and the regeneration position 23.

[0030] The speed component 14 may be arranged to be activated during the extraction stroke of the cylinder 20. The main valve 40 may be at the regeneration position 23. The speed component may be activated upon flow of hydraulic fluid into line 44.

[0031] At the regeneration position 23 the regeneration valve 18 may permit fluid to flow from the fluid source 74 to the piston-side chamber 22 and may divert fluid flowing from the rod-side chamber 24 to the piston-side chamber 22. The regeneration valve 18 may be active at the regeneration position 23. The regeneration function of hydraulic circuit 10 may be enabled at the regeneration position 23.

[0032] The main valve 40 may be actuatable under fluid pressure. Main valve 40 may be controlled through fluid pressure in lines 43 and 44. A position of the main valve 40 may be selected or deselected by the fluid pressures in the lines 43 and 44. A position of the main valve 40 may be selected or deselected by the difference in fluid pressures in the lines 43 and 44.

[0033] In an embodiment, increase in pressure in line 44 may actuate the main valve 40 from the regeneration position 23 to the extraction flow position 19. In an embodiment, increase in pressure in line 43 may actuate the main valve 24 from the extraction flow position 19 to the regeneration position 23. Return springs associated with the main valve 40 may return the main valve to a previous position upon a decrease in fluid pressure.

[0034] The speed component 14 may be arranged to be deactivated during the extraction stroke if the hydraulic pressure acting on a sequence valve 52 exceeds a predetermined pressure. Thereafter, the speed component 14 may be arranged to be re-activated during the extraction stroke if the hydraulic pressure acting on sequence valve 52 falls below a predetermined pressure. In an embodiment, the activation and deactivation pressures of the sequence valve 52 in speed component 14 may be the same.

[0035] The booster component 12 may comprise of a first pressure intensifier 16 and a second pressure intensifier 17. Booster component 12 may be connected to the piston-side chamber 22 of cylinder 20 through hydraulic line 44.

[0036] The hydraulic circuit 10 may further comprise a control valve 32. Booster component 12 may be controlled by a control valve 32. Control valve 32 may control fluid pressures acting on the first pressure intensifier 16 and the second pressure intensifier 17. Control valve 32 may be positioned on line 44. Control valve 32 may control flow of fluid through line 44.

[0037] Control valve 32 may be a two way valve having a first position 35 and a second position 36. At first position 35 fluid may be permitted to flow directly to piston-side chamber 22. At second position 36 fluid may be diverted to flow directly to first pressure intensifier 16 and second pressure intensifier 17 through line 37. Line 37 may be connected though separate lines to first pressure intensifier 16 and second pressure intensifier 17. Fluid from the first pressure intensifier 16 and second pressure intensifier 17 may flow though line 38 to line 44. Line 38 may be connected though separate lines to first pressure intensifier 16 and second pressure intensifier 17. Fluid from line 38 may enter line 44 downstream from the control valve 32.

[0038] First pressure intensifier 16 may comprise a cylinder 80. The cylinder 80 may have a first side piston 81 and a second side piston 83. The first side piston 81 and the second side piston 83 may extend laterally from opposite ends of a central member 82. The cylinder 80 may comprise a first cavity 84 and a second cavity 85. First cavity 84 may accommodate the first side piston 81. Second cavity 85 may accommodate second side piston 83.

[0039] First cavity 84 may be connected to line 37 and second cavity 85 may be connected to line 38.

[0040] Second pressure intensifier 17 may comprise a cylinder 90. The cylinder 90 may have a first side piston 91 and a second side piston 93. The first side piston 91 and the second side piston 93 may extend laterally from opposite ends of a central member 92. The cylinder 90 may comprise a first cavity 94 and a second cavity 95. First cavity 94 may accommodate the first side piston 91. Second cavity 95 may accommodate second side piston 93.

[0041] First cavity 94 may be connected to line 37 and second cavity 95 may be connected to line 38.

[0042] The booster component 12 and the speed component 14 may be arranged to remain inactive during cylinder retraction regardless of the hydraulic pressure acting on sequence valves 50, 52.

[0043] The booster component 12 may be arranged to be activated during the extraction stroke if pressure acting on sequence valve 50 exceeds a predetermined pressure and may be deactivated if the pressure acting on sequence valve 50 falls below a predetermined pressure.

[0044] In an embodiment the activation and deactivation pressures of the sequence valve 50 in the booster component 12 may be the same.

[0045] The control valve 24 may be actuatable by fluid pressure in line 44. Increasing fluid pressure in line 44 may actuate sequence valve 50 to permit fluid to flow for actuation of the control valve 32 from the first position 35 to the second position 36. As fluid pressure decreases the sequence valve 50 may no longer permit flow of fluid to control valve 32. The decrease of pressure acting on control valve 32 may permit a return spring associated with the control valve 32 to move the control valve 32 from the second position 36 to the first position 35.

[0046] At initiation of the operation cycle of the hydraulic circuit 10 the hydraulic cylinder 20 may be fully extracted and the main valve 40 may be at the retraction position 21 to enable retraction of the hydraulic cylinder 20.

[0047] As the hydraulic cylinder 20 is retracted the operation cycle may reach mid-cycle and the hydraulic cylinder 20 may be fully retracted.

[0048] As the operation cycle moves from mid-cycle to the end of the cycle, the main valve 40 may be actuated from the regeneration position 23 to the extraction position 19 to enable extraction of the cylinder 20. The extraction position 19 may be selected when fluid pressure increases to a predetermined pressure level in line 44.

[0049] As the pressure in line 44 increases further the booster component 12 may be activated through the actuation of the sequence valve 50 and the control valve 32.

[0050] In an embodiment, the regeneration position 23 may be selected only once during an operation cycle. Subsequent to complete retraction of the hydraulic cylinder 20 main valve 40 may be actuated to the regeneration position 23. After the actuation from regeneration position 23 to the extraction position 19 the regeneration position 23 may not be re-selected before end of the operation cycle of the hydraulic circuit 10.

[0051] Figure 2 shows a schematic representation of hydraulic connections between the hydraulic circuit 10 and the hydraulic cylinder 20 in a second embodiment.

[0052] In the second embodiment, the speed component 14 and the main valve 40 may function as described in the first embodiment.

[0053] In the second embodiment, the booster component 12 may comprise the first pressure intensifier 16, the second pressure intensifier 17, the sequence valve 50, a diversion valve 54 and an additional sequence valve 56.

[0054] The first pressure intensifier 16 and the second pressure intensifier 17 may comprise features as described in the first embodiment. Line 37 may connect diversion valve 54 though separate lines to first pressure intensifier 16 and second pressure intensifier 17. Fluid from the first pressure intensifier 16 and second pressure intensifier 17 may flow though line 38 to the diversion valve 54. Line 38 may be connected though separate lines to first pressure intensifier 16 and second pressure intensifier 17.

[0055] The booster component 12 may be arranged for activation and deactivation during both the extraction and the retraction stroke. The hydraulic device 10 may have additional hydraulic connections to the hydraulic cylinder 20. Booster component 12 may be connected through hydraulic lines 42, 44 to both the piston-side chamber 22 and the rod-side chamber 24. The booster component 12 may be connected to the hydraulic lines 42, 44 through a diversion valve 54. The diversion valve 54 may be arranged to divert the flow of hydraulic fluid from either the piston-side chamber 22 or the rod-side chamber 24 of the hydraulic cylinder 20 through the booster component 12 in accordance with an extraction stroke or a retraction stroke.

[0056] The diversion valve 54 may be arranged to divert the flow of hydraulic fluid from the rod-side chamber 24 through the booster component 12 during retraction stroke. The diversion valve 54 may be arranged to divert the flow of hydraulic fluid from the piston-side chamber 22 through the booster component 12 during the extraction stroke.

[0057] For cylinder retraction, the main valve 40 may pump hydraulic fluid from the fluid reservoir 76 to rod-side chamber 24 through lines 42 and 43 while fluid from the piston-side chamber 22 may be allowed to return to the fluid source 74 through the lines 44 and 45. The booster component 12 may be arranged to be activated during the retraction stroke if pressure acting on sequence valve 56 exceeds a predetermined pressure. The booster component 12 may be arranged to be deactivated during the retraction stoke if pressure acting on sequence valve 56 falls below a predetermined pressure. In an embodiment the activation and deactivation pressures of the sequence valve 56 in booster component 12 may be the same.

[0058] For cylinder extraction, the main valve 40 may pump hydraulic fluid from the fluid source 74 to piston-side chamber 22 through lines 44 and 45 while fluid from the rod-side chamber 24 may be allowed to return to the fluid reservoir 76 through the lines 42 and 43. The booster component 12 may be arranged to be activated during the extraction stroke if pressure acting on sequence valve 50 exceeds a predetermined pressure and may be deactivated if the pressure acting on sequence valve 50 falls below a predetermined pressure. In an embodiment the activation and deactivation pressures of the sequence valve 50 in the booster component 12 may be the same.

[0059] The hydraulic circuit 10 may be provided with additional pressure intensifiers. The additional pressure intensifiers may be connected to the hydraulic circuit 10 between lines 37 and 38. The additional pressure intensifiers may be connected so that fluid flow is as described with reference to the first and second pressure intensifiers 16, 17. In an embodiment, the hydraulic circuit 10 may comprise 3 or more booster components.

[0060] The hydraulic circuit 10 may engage the hydraulic cylinder 20 through an operation cycle thereof. A cycle of the hydraulic cylinder 20 may comprise of an extraction stroke and a retraction stroke. The retraction stroke of the hydraulic cylinder 20, coupled to the hydraulic device 10, may have a single phase with a high retraction speed. The speed component 14 and the booster component 12 of the hydraulic device 10 may be inactive during the retraction stroke of the hydraulic cylinder 20.

[0061] The general operation of the hydraulic circuit 10 may proceed as follows. The main valve 40 may be at the regeneration position 23 for the start of the extraction stroke. As the load increases, the main valve 40 may be switched to the extraction flow position 19. The hydraulic circuit 10 may operate under the normal extraction mode and the cylinder 20 may extract at normal speed. As the load further increases, the control valve 32 may be activated so as to activate the booster component 12. The hydraulic circuit 10 may operate under the booster mode. Under the booster mode the pressure in the cylinder 20 may increase above the pressure of the machine. Subsequently, after the work material has been crushed, the pressure may decrease and the control valve 32 may be deactivated. The deactivation of the control valve 32 may permit the hydraulic circuit 10 to return to either the normal extraction mode or the speed mode.

[0062] The operation of hydraulic circuit 10 may effect an operation of the hydraulic cylinder 20. An operation cycle of the hydraulic cylinder 20 may comprise of an extraction stroke and a retraction stroke. The retraction stroke of the hydraulic cylinder 20 may have a single phase with a high retraction speed. The speed component 14 and the booster component 12 of the may not be selected during the retraction stroke of the hydraulic cylinder 20. During the retraction stroke the hydraulic cylinder 20 may not be subject to a load. The main valve may be at the retraction flow position 21.

[0063] In an embodiment, the booster component 12 may be activated during the retraction stroke, if a jam occurs during the stroke. Activation of the booster component 12 may decrease retraction speed.

[0064] In an embodiment, the hydraulic cylinder 20 may have a 3 phase extraction stroke when subjected to a load.

[0065] In the first phase, the regeneration position 23 may be selected and booster component 12 may not be activated. The hydraulic cylinder 20 may be under the regeneration mode and may have a high extraction speed combined with low force output. During the first phase, the hydraulic cylinder 20 may not yet be subjected to the load.

[0066] In the second phase, the extraction flow position 19 may be selected and the booster component 12 may not yet be activated. Hydraulic cylinder 20 may have a medium extraction speed combined with a medium force output. During the second phase hydraulic cylinder 50 may be subjected to the load.

[0067] In the third phase, the booster component 12 may be activated while the main valve is at the extraction flow position 19. The hydraulic cylinder 20 may have a low extraction speed and a high force output. During the third phase hydraulic cylinder 20 may be subjected to a higher load.

[0068] The respective times of each of the phase and sequence of the phases may be dependent on the load of the hydraulic cylinder 20.

[0069] A 3 phase extraction may allow the hydraulic cylinder 20 to adapt suitably to requirements of a work application which may result in a more effective load cycle. Depending on the requirement of the work application the booster component 12 or the speed component 14 may be activated in order to provide sufficient closing speed or crushing force of a jaw set. The speed component 14 may be activated through the selection of the regeneration position 23 during cylinder extraction when no load is present. The booster component 12 may be selected during cylinder extraction when a higher crushing force is required. The switching capability allows for the right amount of force output to be provided as required by the momentary work requirement of the jaw set.

[0070] In certain work applications, the hydraulic circuit 10 may enable a 2 phase extension stroke of the hydraulic cylinder 20, when subjected to a load, wherein the first phase is followed immediately by the third phase. A 2 phase extension stroke of the hydraulic cylinder 20 may occur when the hydraulic cylinder 20 is subjected to a very high load as soon as the jaw set contact the material to be worked.

[0071] The transition between the phases may occur as a function of pressure changes within the hydraulic circuit 10. Hydraulic pressure within the hydraulic circuit 10 may effect activation of the speed component 14 or booster component 12 during the extraction stroke.

[0072] The hydraulic circuit 10 may provide for a short cycle time for a hydraulic cylinder 20 by decreasing the time needed for cylinder extraction. The hydraulic circuit 10 may increase fluid flow to the hydraulic cylinder 20 through the first and second pressure intensifiers 16, 17. The output fluid flow of the first and second pressure intensifiers 16, 17 may reduce decrease the extraction time of hydraulic cylinder 20.

[0073] Fig. 3 is a comparative graph of jaw set operation cycle times of demolition tools during a demolition application. The jaw set of the demolition tool may open to enable material to be introduced therein. To crush, cut, pulverise or otherwise work the material, the jaw set may close with the material contained therein.

[0074] The cycle time of the jaw set actuated by a hydraulic cylinder 20 coupled to an embodiment of the hydraulic circuit 10 is shown as line 306. The cycle time of the jaw set actuated by a hydraulic cylinder coupled to a single booster component and a regeneration component shown as line 300. The cycle time of a jaw set actuated by a hydraulic cylinder coupled to a booster component is shown as 302. The cycle time of a jaw set actuated by a hydraulic cylinder coupled to a regeneration component is shown as line 304.

i. Cylinder retraction

[0075] During cylinder retraction the jaw set of a demolition tool may move from a closed position to an open position. The retraction flow position 21 may be selected in the main valve 40. The booster component 12 and the speed component 14 may be inactive in the hydraulic circuit 10. The hydraulic cylinder 20 may function as a standard dual acting cylinder. Hydraulic fluid may flow to the rod-side chamber 24 of the hydraulic cylinder 20 and pressure may be applied on the piston 28 at the rod-side chamber 24.

[0076] The time for a jaw set of a demolition tool to fully open may be independent of a load presented by the material. The opening time may be dependent on the hydraulic cylinder and the components acting on the hydraulic cylinder. In Fig. 3 line 306 shows that the hydraulic cylinder 20 coupled to the hydraulic circuit 10 may be able to move from being fully closed (denoted by P₁) to fully open (denoted by P₂) in t₀-t₁ sec. Line 300 shows that the hydraulic cylinder coupled to the booster component and regeneration component may be able to move in the same time. Line 302 shows that the hydraulic cylinder coupled to the booster component may be able to move in the same time. Line 304 shows that the hydraulic cylinder coupled to the regeneration may be able to move from P₁ to P₂ in t₀-t₅ sec.

ii. Cylinder extraction (Start Phase)

[0077] During cylinder extraction the jaw set of a demolition tool may move from an open position to a closed position. The regeneration position 23 may be selected through actuation of the main valve 40. The hydraulic cylinder 20 may operate under the regeneration function. Hydraulic fluid may flow to the piston-side chamber 22 of the hydraulic cylinder 20 and pressure may be applied on the piston 28 at the piston-side chamber 22. Return flow of the hydraulic fluid from the rod-side chamber 24 may be redirected to the piston-side chamber 22 to increase velocity of cylinder extraction.

[0078] Return flow of the hydraulic fluid may be redirected as the hydraulic circuit 10 is subjected to a low to medium pressure. During this phase of cylinder extraction the jaw set which may contain the material to be worked, may not yet be subjected to the work load. As both jaws of a jaw set contact the material to be worked, the pressure in the hydraulic circuit 10 may spike (denoted by P₃).

[0079] The time for a jaw set of a demolition tool to move from P₂ to P₃ may be independent of a load of the material. The start phase time may be dependent on the hydraulic cylinder 20 and the components acting on the hydraulic cylinder 20. In Fig. 3 line 306 shows that the hydraulic cylinder 20 coupled to the hydraulic circuit 10 may be able to move from P₂ to P₃ in t₁-t₂ sec.

[0080] Line 300 shows that the hydraulic cylinder coupled to the booster component and regeneration component may be able to move from P₂ to P₃ in the same time. Line 302 shows that the hydraulic cylinder coupled to the booster component may be able to move from P₂ to P₃ in t₁-t₃ sec. Line 304 shows that the hydraulic cylinder coupled to the speed component may be able to move from P₂ to P₃ in about t₅-t₆ sec.

iii. Cylinder extraction (Intermediate Phase)

[0081] The pressure in the hydraulic cylinder 20 may increase as the jaw set contacts the material. The hydraulic cylinder 20 coupled to the hydraulic device 10 may be under the normal extraction function.

[0082] During this phase of cylinder extraction the jaw set which may contain the material to be worked, may be subjected to the work load as the jaw set initiates work on the material.

[0083] The time for a jaw set of a demolition tool to move from P₃ (i.e. position of jaw at deselection of speed component 12) to P₄ may be dependent on the load of the material, on the hydraulic cylinder 20 and the components acting on the hydraulic cylinder 20. In Fig. 3 line 306 shows that the hydraulic cylinder 50 coupled to the hydraulic circuit 10 may be able to move from P₃ to P₄ in t₂-t₄ sec.

[0084] Line 300 shows that the hydraulic cylinder coupled to the booster component and regeneration component may be able to move from P₃ to P₄ in the same time. Line 302 and line 304 respectively show that the hydraulic cylinder coupled to the booster component and the hydraulic cylinder coupled to the speed component do not exhibit a phase 2 during cylinder extraction and instead transition directly from the start phase to the end phase.

iv. Cylinder extraction (End Phase)

[0085] The pressure in the hydraulic cylinder 20 may increase as the jaw set continues work on the material. At a predetermined pressure value, the booster component 12 may be activated. The hydraulic cylinder 20 coupled to the hydraulic circuit 10 may transition from operating under the normal extraction function to operating under the booster function.

[0086] Hydraulic fluid from the first and second pressure intensifiers 16, 17 may flow to the piston-side chamber 22 of the hydraulic cylinder 20 may be applied on the piston 28 at the piston-side chamber 22. Return flow from the rod-side chamber 24 may be redirected to the fluid reservoir 76.

[0087] During this phase of cylinder extraction the jaw set which may contain the material to be worked, may be subjected to the work load as the jaw set continues work on the material resulting in a further increase of pressure in the hydraulic circuit 10. The pressure intensifiers 16, 17 may increase the closing force of the jaw set to a maximum level by increasing the pressure of the fluid flowing to the piston-side chamber 22.

[0088] The time for a jaw set of a demolition tool to move from P₄ (i.e. position of jaw set at activation of pressure intensifiers 16, 17) to P₁ (i.e. fully closed position of jaw set) may be dependent on the load of the material, on the hydraulic cylinder 20 and the components acting on the hydraulic cylinder 20. In Fig. 3 line 306 shows that the hydraulic cylinder 10 coupled to the hydraulic circuit 10 may be able to move from P₄ to P₁ in t₄-t₇ sec.

[0089] Line 300 shows that the hydraulic cylinder coupled to a single booster component and regeneration component may be able to move from P₄ to P₁ in t₄-t₈ sec. Line 302 and line 304 respectively show that the hydraulic cylinder coupled to the booster valve and the hydraulic cylinder coupled to the speed valve transition directly from the start phase to the end phase. Line 302 shows that the hydraulic cylinder coupled to the booster valve may be able to move from P₃ to P₁ in t₃-t₁₀ sec. Line 304 shows that the hydraulic cylinder coupled to the speed valve may be able to move from P₃ to P₁ in about t₆-t₉ sec.

[0090] Fig. 3 indicates that the overall cycle time of line 306 is shorter than the respective cycle times of lines 300, 302 and 304. Hence, the jaw set actuated by a hydraulic cylinder 20 coupled to the hydraulic circuit 10 may be able to open and close faster than jaws actuated by hydraulic cylinders coupled to a booster component or a speed component; or both a booster component and a speed component. The hydraulic cylinder 20 coupled to the hydraulic circuit 10 may require about half the time to open and close the jaw set compared to a hydraulic cylinder coupled to a single booster component and regeneration component. The time taken by hydraulic cylinder 20 coupled to the hydraulic circuit 10 may decrease to one third with three pressure intensifiers compared to a hydraulic cylinder coupled to a single booster component and regeneration component.

[0091] The skilled person would appreciate that foregoing embodiments may be modified or combined to obtain the hydraulic circuit 10 of the present disclosure.

Industrial Applicability

[0092] This disclosure describes a hydraulic circuit 10 for cyclically operating a dual acting hydraulic cylinder 20.

[0093] In the operation of the hydraulic circuit 10 may be used to operate a dual acting hydraulic cylinder 20 that actuates a demolition tool. The hydraulic circuit 10 may be disposed within the demolition tool which incorporates the hydraulic cylinder 20. The demolition tool may have a jaw set and may be used for crushing, cutting or pulverising material. The hydraulic circuit 10 may improve the opening and closing times of the jaw set.

[0094] The hydraulic circuit 10 may enable the jaws to open rapidly in the retraction stroke of the hydraulic cylinder 20. Closing the jaw set in the extraction stroke of the hydraulic cylinder, the hydraulic circuit 10 may be actuated to the speed mode to enable the jaws to close at a faster rate, up to the point the jaws come into contact with material present in the jaws. Contact of the jaws with the material may result in a pressure spike in the hydraulic circuit 10 effecting a switch to the booster mode. In the boost mode a high pressure may be sent to the hydraulic cylinder 20 to increase the crushing, cutting or pulverising force of the jaw.

[0095] Switching of modes in the hydraulic circuit 10 may be dependent on the material to be worked. As an example of concrete as a material. The hydraulic circuit 10 may be initially in the speed mode upon contact with the concrete the hydraulic circuit 10 may be actuated immediately from the speed mode to the boost mode. In an alternative example with steel as a material, the hydraulic circuit 10 may be initially in the speed mode upon contact with the steel the hydraulic circuit 10 may remain in the speed mode. As the jaws of the demolition tool closes further the hydraulic circuit 10 may be actuated to the boost mode.

[0096] The hydraulic circuit 10 may comprise a booster component 14 having a first pressure intensifier 16 and a second pressure intensifier 17 in combination with a regeneration valve 18. The pressure intensifiers may be arranged in parallel so that the maximum output pressure will not be higher than a circuit having a single pressure intensifier. The output flow may be doubled in comparison to a circuit having a single intensifier. Although the output is doubled, the material stress levels are not increased on the individual components. The output flow of each individual pressure intensifier may be collected through a hydraulic manifold and directed into the hydraulic cylinder 20.

[0097] The hydraulic circuit 10 with the first and second pressure intensifiers 16, 17 may decrease the cycle time of a jaw set during normal operation. An advantage of the plurality of pressure intensifiers 16, 17 may be that each of pressure intensifier may have a smaller diameter cylinder rather than a single pressure intensifier having a large diameter cylinder which is required to have the same amount of fluid flow. Additionally, the working pressure of the jaw set with the plurality of pressure intensifiers 16, 17 may be substantially similar to the pressure of a single larger diameter cylinder.

[0098] Additionally, even with a failure of one pressure intensifier 16, 17 work operations may still continue with the remaining pressure intensifier 16, 17.

[0099] Accordingly, this disclosure includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the disclosure unless otherwise indicated herein.

[0100] Where technical features mentioned in any claim are followed by references signs, the reference signs have been included for the sole purpose of increasing the intelligibility of the claims and accordingly, neither the reference signs nor their absence have any limiting effect on the technical features as described above or on the scope of any claim elements.

[0101] One skilled in the art will realise the disclosure may be embodied in other specific forms without departing from the disclosure or essential characteristics thereof. The foregoing embodiments are therefore to be considered in all respects illustrative rather than limiting of the disclosure described herein. Scope of the invention is thus indicated by the appended claims, rather than the foregoing description, and all changes that come within the meaning and range of equivalence of the claims are therefore intended to be embraced therein.

Claims

1. A hydraulic circuit (10) for operating a dual acting hydraulic cylinder (20) comprising:

a speed component (14) comprising a regeneration valve (18) arranged to return a hydraulic fluid from a rod-side chamber (24) to a piston-side chamber (22) of the cylinder (50) at a start phase of cylinder extraction; and

a booster component (12) comprising a first pressure intensifier (16) and a second pressure intensifier (17) arranged in parallel to increase flow of fluid at an end phase of cylinder extraction.

2. The hydraulic circuit (10) of claim 2 further comprising a main valve (40) for control of fluid flow to the first pressure intensifier (16) and a second pressure intensifier (17) and the hydraulic cylinder (50).

3. The hydraulic circuit (10) of any one of preceding claims wherein the speed component (14), the first pressure intensifier (16) and the second pressure intensifier (17) are arranged to be inactive at an intermediate phase of cylinder extraction.

4. The hydraulic circuit (10) of any one of preceding claims comprising three pressure intensifiers.

5. The hydraulic circuit (10) of any one of preceding claims comprising a pressure actuated control valve (32) to divert fluid flow through the booster component (12).

6. A demolition tool comprising a hydraulic circuit (10) of any one of preceding claims.

7. A method of operating a dual acting hydraulic cylinder (20), the method comprising the steps of:

returning a hydraulic fluid from a rod-side chamber (24) to a piston-side chamber (22) of the cylinder (20) during a start phase of cylinder extraction with a speed component (14) comprising a regeneration valve (18); and

increasing flow of fluid during end phase of cylinder extraction with a booster component (12) comprising a first pressure intensifier (16) and a second pressure intensifier (17) arranged in parallel.

8. The method of claim 7 wherein the fluid pressure is increased at the rod-side chamber (24).

9. The method of claim 7 or 8 wherein step of increasing pressure of the fluid during end phase of cylinder extraction comprises increasing the fluid pressure at the piston-side chamber (22).

10. The method of claim 9 further comprising a step of returning fluid from the rod-side chamber (24) to a fluid reservoir (76) during an intermediate phase of cylinder extraction.

Drawing