EP3152445B1

EP3152445B1 - Hydraulic cylinder

Info

Publication number: EP3152445B1
Application number: EP15807025.0A
Authority: EP
Inventors: Roger Gustavsson
Original assignee: Thordab Industri Innovation AB
Current assignee: Thordab Industri Innovation AB
Priority date: 2014-06-09
Filing date: 2015-06-08
Publication date: 2021-02-17
Anticipated expiration: 2035-06-08
Also published as: EP3152445A4; SE538615C2; EP3152445A1; SE1400288A1; WO2015190972A1

Description

Technical Field

The present invention concerns a hydraulic cylinder in accordance with the claims.

Background of the Invention and Prior Art

In connection with lifting loads by various types of lifting equipment such as cranes, construction equipment (machinery) and the like, a large amount of energy is used to change both the position of the lifting device's mass and the position of the mass of the lifted load. The energy consumed to lift for example the own weight of a crane arm or similar is not reused but is lost as heat generation and the like. There exists a need for a more energy efficient system in cranes and construction equipment to raise and lower loads.
Many types of devices have been developed in order to reduce energy losses associated with vertical position changes of loads and the like. For example, different types of hydraulic cylinders and similar have been developed which are designed to reduce energy losses when lifting devices perform positional changes. One example of such a hydraulic cylinder, for use in lifting and lowering a component, is described in patent application SE461391 by the applicant BT Industries. The cylinder described in the application is of a double-acting type. The uniqueness of hydraulic cylinders, which are of a double-acting type, is that they include a piston rod which is hollow that forms an inner pumping chamber in the piston rod. The design includes a variant of a second piston which in its one end is connected to the working cylinder and in its other end is movably arranged relative to the inner chamber of the piston rod. This design differs greatly from the design of the present invention. For example, the second piston is not movably arranged in relation to both the working cylinder and the piston rod.
One problem associated with existing hydraulic systems is that spikes in pressure may cause malfunctions in certain components such as hoses and other hydraulic components.
Furthermore, a hydraulic cylinder which includes an inner chamber in the piston rod is known via US7478489 . In US7478489 is described a variant of a working cylinder with a piston rod that includes an inner chamber in which a fluid is compressed. This design differs substantially from the present invention. For example, it does not include a moveable second piston in accordance with the design according to the present patent application.
A working cylinder which includes an inner chamber in the piston rod in which a liquid is arranged to be compressed is also described in US7441405 . Even this design differs substantially from the present invention. For example, it does not include a moveably arranged second piston in accordance with the present invention.
DE102007061294 describes a variant of a hydraulic cylinder including three lifting chambers. The design includes a working cylinder in the piston rod. Even this design differs substantially from the design in accordance with the present invention. For example, it does not include a moveably arranged second piston in accordance with the present invention. US5219152 describes a variant of a shock-absorber which includes a first piston with a first piston rod that is hollow. The first piston rod has a second rod placed in the first hollow piston rod. This design differs substantially from the design in accordance with the present invention. For example, the design in accordance with its description describes a shock-absorber which lacks a load carrying function in accordance with the design according to the present invention.
US4526088 describes a variant of a shock-absorber which includes a variant of a floating piston with which the piston's movement in the cylinder may be affected. This design differs substantially from the design in accordance with the present patent application. For example, the design in accordance with its description describes a shock-absorber which lacks a load carrying function in accordance with the present invention.
Further relevant prior art is disclosed in US-A-2 624 318 .
One problem with existing energy efficient hydraulic cylinders with a movable piston in a second piston rod's inner chamber is that they are dampening which means that they can start to oscillate. This problem entails for example that these cylinders are unsuited for use in for example cranes and the like. Furthermore, no know design exists whose characteristics may be altered during operation in a similar manner between a dampening and non-dampening function.

Brief Description of the Invention Concept

The main purpose of the present invention is to create a device which eliminates or lessens at least one of the above mentioned problems. This purpose is achieved with the aid of a device in accordance with the claims.

Detailed Description of the Invention

The invention will be described in greater detail below with reference to the accompanying schematic drawings that in an exemplifying purpose show the current preferred embodiments of the invention.

Fig. 1 shows a first embodiment of the present hydraulic cylinder.
Fig. 2 shows a cross-sectional view of the hydraulic cylinder in accordance with Fig. 1.
Fig. 3 shows in a hydraulic diagram an example of use of the hydraulic cylinder.
Fig. 4 shows in a second hydraulic diagram a second example of an application for the present hydraulic cylinder.
Fig. 5 shows in a third hydraulic diagram a third example of an application for a hydraulic cylinder.
Figs.6A and 6B show a first alternative embodiment of the present hydraulic cylinder.
Figs.7A and 7B show a second alternative embodiment of the present hydraulic cylinder.
Fig. 8 shows an alternative embodiment of the embodiments in accordance with Figs.6A and 6B.
Fig. 9 shows schematically a hydraulic cylinder which is connected to a hydraulic unit.
Figs. 10A and 10B show an embodiment of the present hydraulic cylinder according to the invention.
Figs.11A and 11B show enlarged sections of Figs.10A and 10B.
Figs.12A and 12B show a further alternative embodiment of the present hydraulic cylinder.
Fig. 13 shows in a hydraulic diagram an exemplifying system for controlling pressure in a space and the flow to and from the inner space.

With reference to figure 1, an exemplifying version of a hydraulic cylinder 1 is schematically shown. The exemplifying hydraulic cylinder's design is only one of the possible embodiments for how a hydraulic cylinder may be designed.
The hydraulic cylinder 1 is, in its fundamental design, based upon some previously known hydraulic cylinder. The hydraulic cylinder (working cylinder) 1 includes a cylinder housing 2 and in it one movable piston 3. Preferably, the cylinder housing 2 includes a cylinder 4, a first end 5 and a second end 6. The piston 3 includes a piston head 7 (or similar) and at least one piston rod 8. The piston rod 8 runs through a hole (lead-through) in the second end 6 in accordance with previously know technology. The first end 5 and the cylinder 4 may either be separate or integrated with one another. Furthermore, the second end 6 and the cylinder 4 may either be separate or integrated with one another.
The piston head 7 separates the inner space of the cylinder housing into at least one first chamber 9 and at least one second chamber 10. The first chamber 9 is provided with at least one first connection 11 to which the first chamber in the hydraulic cylinder may be connected to a hydraulic circuit system. The second chamber 10 is provided with at least one second connection 12 such as a coupling or the like with which the hydraulic cylinder's second chamber 10 may be connected to a hydraulic circuit (hydraulic system, hydraulic circuit system). Connection of the hydraulic cylinder 1 to the hydraulic system and pressurization of each respective chamber 9 and 10 is done in accordance with previously known technology and this is why this technology is not described in more detail in this patent application. The piston 3 will however move in a direction relative to the cylinder where a lesser force (surface times pressure) works against the piston surface. Preferably, the cylinder housing 2 further includes at least one mounting attachment 13 or the like with which the cylinder housing may be attached (connected) to an object or the like. In the shown embodiment the mounting attachment 13 and the first end 5 consist of an integrated unit. The piston rod 8 includes in its free end at least one mounting attachment 14 or similar with which the piston rod may be attached (connected) to an object in a for the purpose suitable manner. The mounting attachment 13 in the cylinder housing and the mounting attachment 14 in the piston rod consist preferably of a variant of previously known types of mounting attachments which are suitable for the purpose. For example, the mounting attachment 13 and the mounting attachment 14 may consist of an ear or other previously known for the purpose suitable type of mounting attachment.
The piston rod 8 in its axial direction is provided with an inner space 15 which forms a chamber in which a liquid such as hydraulic fluid (oil) or similar may be compressed by at least one second piston 16. The inner space 15 is preferably cylindrical with an axial center essentially parallel with the piston rod's 8 axial center. The inner cylindrical space's 15 axial center essentially coincides with the piston rod's axial center. The piston 16 is movably arranged in relation to the inner space 15. During movement of the piston 16 in the direction into the inner space 15, a compression of the fluid in the inner space will occur.
The second piston 16 is arranged to be moveable in the inner space 15. Further, the piston 16 is free to move relative the cylinder 4 and in relation to the first end 5. The piston 16 runs freely in the essentially cylindrical inner space 15 in the piston rod 8 and the piston 16 is moveably arranged relative the cylinder housing and the cylinder's first end 5. The length and form of the piston 16 may vary greatly. Fig. 2 shows a piston 16 which has the same or essentially the same diameter in its longitudinal direction. In alternative embodiments it is conceivable that the second piston's 16 diameter varies along its longitudinal direction. The inner cylindrical space 15 is via at least one connection 17 attached to a hydraulic circuit, hydraulic system or the like. The connection 17 consists of previously known attachment devices such as for example a hydraulic coupling.
The hydraulic cylinder 1 includes the necessary seals so that satisfactory seals between the piston head and the cylinder housing 2 and between the second piston 16 and the walls in the inner space 15 are achieved. These consist of previously known technology and this is why this technology is not described in more detail in this patent application.
During the pressurization of fluid in the hydraulic cylinder's 1 first chamber 9, the first piston 3 strives to move itself so that the chamber 9 lengthens in the hydraulic cylinder's longitudinal direction. During the pressurization of fluid in the hydraulic cylinder's 1 first chamber 9, the second piston 16 strives to move by the force pressing against the second piston's 16 surface 18. The second piston 16 will through force of pressure in the hydraulic cylinder's 1 first chamber 9, pressing against the surface 18 strive to compress the fluid in the inner cylindrical space 15 via the piston's second surface 19. Movement of the second piston 16 into the inner space 15 will occur under the condition that an outflow of fluid (hydraulic oil) can take place via connection 17. If surface 18 and surface 19 are the same the piston will move in the direction into the space (the inner cylindrical space 15 or the first chamber 9) where a lesser pressure prevails (under the condition that an amount of fluid moves out via the connection 11 or 17).
The present hydraulic cylinder's design allows for the entire or essentially the entire surface 20 on the piston head in the direction towards the chamber 9 and the second piston's surface 18 to be exposed to the pressure in chamber 9. This leads to the hydraulic cylinder's diameter (dimension) being smaller than previously known designs. In previously known designs the corresponding surface 18 is not presented because it is permanently attached to the cylinder housing's end in these designs.
In Fig. 3 is shown, in a hydraulic diagram, a first application where a hydraulic cylinder 1 is suitable to be utilized. In this application the hydraulic cylinder 1 is used in a crane or similar. The hydraulic cylinder 1 is for example used to maneuver the crane arm's (boom's) upward and downward movements. The diagram shows a hydraulic pump and accompanying tank for hydraulic fluid (oil). In the exemplifying embodiment the hydraulic cylinder 1 consists of a hydraulic cylinder of a double-acting type which is equipped with a piston rod 8 with an inner cylindrical space 15, in which a freely running piston 16 is moveably arranged. During pressurization of the first chamber 9 (the plus side) in the hydraulic cylinder 1, overpressure will be created in the accumulator tank and the inner space in the piston rod. The overpressure in the piston rod allows for the second piston 16 to move in the direction of the first end 5 until it presses against the first end 5. When the second piston 16 moves in into the inner space 15 in the piston rod 8, a compression of the fluid in the inner space 15 occurs.
Fig. 3 shows schematically a conceivable application in a crane arm or other application where a load is lifted or balanced with at least one hydraulic cylinder. In the application, at least one hydraulic cylinder is attached to a crane arm or other component in a vehicle (construction equipment) or similar.
The inner space 15 is, via at least one connection such as a hydraulic coupling or similar, connected via at least one hose (tube, line) or similar to a first pressure accumulator 21. In the application, the hydraulic cylinder's plus side is connected via a check valve to a first pressure accumulator 21 and the inner space in the hydraulic piston. During operation of the hydraulic cylinder, the pump piston's overpressure in the hydraulic cylinder's plus side will create an overpressure in the inner space of the piston rod. A restraining force, alternatively a load bearing force, will be created in, alternatively with, the hydraulic cylinder by way of this overpressure. This restraining force will reduce the amount of energy used for the operation of the crane arm. The pressure in pressure accumulator 21 will normally during normal use be between 250 to 300 bar. In alternative embodiments, another for the purpose suitable pressure that deviates from the mentioned pressures may be used.
With reference to Fig. 4, an alternative use of the hydraulic cylinder 1 is shown. The inner space 15 is via at least one connection, such as a hydraulic coupling or similar, connected via at least one hose (tube, line) or similar to a first pressure accumulator 21. The inner space 15 may even via at least one hose (tube, line) or similar be connected to at least one second pressure accumulator 22. The pressure accumulator 21 and/or the pressure accumulator 22 may in alternative embodiments be directly connected to the hydraulic cylinder but are preferably connected to the hydraulic cylinder via at least one check valve. The pressure in pressure accumulator 21 is during normal use between 250 to 300 bar. The pressure in pressure accumulator 22 is normally between 50 to 80 bar. The hydraulic diagram also shows a control valve, a second pressure tank and other hydraulic components such as check valves. Through repeated piston strokes a pressurization of the accumulator tank is created whereby a pressurization of the inner space of the hydraulic piston will occur. When pressure by way of pressure spikes and the like arise in the hydraulic system, the pressure in the inner space 15 will cause the check valves to stop flow out from the inner space 15. A resisting upwardly directed force (in relation to the crane arm) will thereby be achieved via the hydraulic cylinder. If pressure in the inner space rises above a certain predetermined level, a flow will be allowed via a valve to a tank valve. The resisting force is dimensioned (balanced) according to the force that is necessary to hold up the crane arm. The higher pressure from pressure accumulator 21 is used for back pressure during the strain of load (back pressure for both the crane arm's weight and for the lifted load). The lower pressure from pressure accumulator 22 is used as back pressure during minimal load strain (back pressure for the crane arm's weight). Thanks to this design less energy will be used for maneuvering (operating) the crane.
Fig. 5 shows, in a hydraulic diagram, a third conceivable application for a hydraulic cylinder in accordance with the present invention. In this application the hydraulic cylinder is connected between two vehicle parts such as between the chassis and the superstructure of a vehicle. In the hydraulic diagram is shown a second cylinder 23 which is connected between the chassis and the superstructure (alternatively a counterweight or similar). During start the cylinder is pressurized by the counterweight. The counterweight creates an overpressure in the inner space in the hydraulic cylinder which in turn is used to lessen energy consumption when maneuvering a crane arm, boom or the like. The superstructure of a vehicle or another attached part of a vehicle pressurizes the fluid in chamber 24 in the second cylinder 23, which in turn pressurizes the fluid in the inner space 15.
With reference to Fig. 6, a first alternative embodiment of the present hydraulic cylinder is shown. It has unexpectedly been realized that the accumulator according to the previous figures may be integrated in the hydraulic cylinder's piston rod. In the embodiment according to Fig. 6, the inner space 15 in the piston rod 8 is suitable for being filled with gas or a mixture of gasses. For example, the piston rod 8 may be filled with nitrogen gas or another for the purpose suitable gas or combination of gases. In the piston rod's free end, it includes at least one refilling device 25 which may be opened and closed in conjunction with gas being filled to the inner space 15 in the piston rod 8.
With reference to Fig. 6B, an alternative embodiment is shown where the piston 16 is hollow or essentially hollow along its entire length or partial part of its length. The piston rod 8 thereby forms a space 26 which in its one end is connected with the entire or part of the inner space 15. The second piston 16 includes at least one end side 27 or other material layer which will prevent a flow (leakage) of gas or fluids occurring from space 15 to the first chamber 9. This design allows for an increased volume of gas that may be compressed in relation to the case with a massive piston.
With reference to Figs. 7A and 7B, an alternative embodiment of the present hydraulic cylinder is shown. In this embodiment, the hydraulic cylinder includes at least one third piston 28 which is preferably arranged to be moveable inside the inner space 15 in the piston rod 8. In the exemplifying embodiment, the reason for this is to partition the inner space 15 into one first chamber (space) 29 and one second chamber (space) 30. The first chamber 29 is the partitioning part of the inner space 15 which lies closer to the piston rod's free end than the second chamber 30 which lies further from the free end. The technical effect of partitioning the inner space 15 into at least one first inner chamber 29 and at least one second inner chamber 30 is that it allows the hydraulic cylinder's back pressure to be increased and decreased. Fig. 7A shows a piston 16 which is massively (solidly) designed. Fig. 7B shows a piston 16 which includes an inner space 26.
With reference to Fig. 8, an alternative embodiment is shown where it includes one inner third piston 28 in the inner space 15 in the piston rod. The piston's 28 position is permanent or adjustably arranged with at least one adjusting device 31 in the inner space's longitudinal direction. The volume of chamber 30 may be adjusted by moving the inner third piston 28.
With reference to Fig. 9, it is shown how the present hydraulic cylinder 1 allows for control of the pressure in chamber 30. By way of this design, the hydraulic cylinder's 1 characteristics in relation to another component, device or similar may be automatically controlled. It is for example conceivable that the present design allows for the pressure in the first chamber 29 to be pressurized from a load strained hydraulic unit 32. The hydraulic unit may for example consist of a hydraulic cylinder or another hydraulic component in for example a loader (fork lift) or other for the purpose suitable equipment (vehicle, machine). Fig. 9 also shows that the piston is provided with at least one seal 33.
With reference to Figs. 10A and 10B, a hydraulic cylinder 1 according to the invention is shown which includes a function and a device with which the second piston's 16 ability to move is temporarily limited. Thus the hydraulic cylinder includes at least one second inner space 34, preferably a cylindrical space 34, in which the end 35 on piston 16 may be inserted in and out from.
This design includes at least one seal 36 which creates a seal between the piston (piston rod) 16 when the piston 16 is inserted into the inner space 34. When the piston 16 is inserted into the inner space 34 and the inner space is sealed in relation to chamber 9 with seal 36, a limited pressure against surface 18 on the end 35 on the piston 16 is asserted. The second piston 16 will thus remain in the inserted position.
In the exemplifying embodiment, the present invention includes at least one conduit (channel) 37 which connects chamber 9 with the second inner space 34. The conduit in the exemplifying embodiment is provided with a valve 38. The valve 38 in the exemplifying embodiment consists of a valve which limits the flow between chamber 9 and the inner space 34 when the pressure drops below a certain predetermined level. When the pressure rises above a predetermined level, the valve opens and a pressurization of the second inner space 34 may occur by the pressure in chamber 9 being conveyed via the conduit to the inner space 34. When the pressure in chamber 9 is greater than in the inner space 15 in the piston rod that will cause the valve 38 to open, the higher pressure against the surface 18 than the pressure in the inner space 15 (against the second piston's end in the space) will cause the second piston 16 to move out from the inner space 34.
The valve 38 may even include a function such as a check valve which prevents a flow in one direction but allows a flow in the other direction. The valve and the check valve may be integrated into one and the same unit (valve) or consist of separate units. In the case of separate units, an additional conduit (not shown in the figures) is preferably used to connect chamber 9 and the inner space.
In alternative embodiments, it is conceivable that valve 38 may consist of controlled valve which may be operated to open and close the flow in conduit 37. The valve is controlled by a control system. Control may occur independent of the pressure present in chamber 9 and the inner space 15, alternatively with the sensing of the pressure in these. Control may for example be accomplished by electrical means or by another for the purpose suitable technology.
In alternative embodiments of the hydraulic cylinder 1, the conduit 37 includes at least one restrictor (not shown in the figures) with which a delay of the valve's function may be achieved. Restriction prolongs the time before the valve 38 is activated thereby delaying the piston, piston rod being moved out from the inner space.
In alternative embodiments, it is conceivable that the design includes at least one locking device with which the piston is locked into the inserted position. The locking device may consist of any locking device that is suitable for the purpose.
With a design in accordance with the embodiment, it achieves a function with a built-in choke valve which limits spikes in pressure in the hydraulic cylinder.
Figs. 12A and 12B show how the design in accordance with the first embodiment shown in Figs. 1 and 2 and 6A and 6B is provided with a space 34 with a corresponding function that has been described in Figs. 10A and 10B. The piston 16 may be hollow as shown in the figure or be of a solid variant.
With reference to Fig. 13, a hydraulic diagram shows an exemplifying embodiment of a system where the pressure in space 15 is arranged to be controllable. The control system even controls the flow to and from space 15. The system includes at least one control system 39 that includes at least one control unit which controls valve 38. The system includes preferably at least one pressure valve 40, pressure transmitter 41 and at least one pressure source 42. The pressure source 42 may consist of a hydraulic motor or another for the purpose suitable pressure source. Fig. 13 also shows a subsystem for the operation of the hydraulic cylinder's normal function that is to say to control the flow to and from chamber 9 and chamber 10. With a control system and pressure/flow valves it is possible to determine at which pressure dampening should take place and even have the ability to control the properties of the dampening effect. The system even allows for the back pressure (pressure) in space 15 to be controlled. This may be accomplished by controlling the flow of fluid (oil) in and out of space 15. The control system even allows for the possibility to control when the piston 16 is to leave its position in the space and when it should be repositioned in the space. By way of this design, the system may be controlled to operate with a dampening or without a dampening function. The speed of the function as a choke valve may be controlled by this design.
With the present design it is possible to vary the hydraulic cylinder's characteristics depending on if the second piston's end is inserted into the inner space or not. With this design it is possible to choose whether the design should have a dampening function or a non-dampening function.
In the detailed description of the present invention, design details may have been omitted which are apparent to persons skilled in the art. Such obvious design details are included to the extent necessary so that the proper and full performance of the present invention is achieved. For example, components such as seals (washers, rings), hydraulic couplings, hydraulic hoses and several more types of components are included to the extent necessary so that the intended function is obtained.

Advantages of the Invention

The present invention achieves several advantages. The most important advantage is that at least one of the above mentioned disadvantages is eliminated or at least lessened.

Claims

Hydraulic cylinder (1) comprised of a cylinder housing (2), with at least one cylindrical inner space, and in this at least one movably arranged first piston (3) which partitions the hydraulic cylinder into at least one first chamber (9) and at least one second chamber (10), said first piston (3) comprised of at least one piston head (7) and at least one piston rod (8), said piston rod (8), in the piston rod's (8) axial direction, being provided with at least one inner space (15) in which at least one second piston (16) runs, and that the hydraulic cylinder (1) is comprised of at least one third piston (28) which is movably arranged in the inner space (15) in the piston rod (8) which partitions the inner space (15) in at least one first chamber (29) and at least one second chamber (30) wherein the hydraulic cylinder is comprised of at least one second inner space (34) in which an end of the second piston (16) is suitable to be inserted and that the second piston (16) in the inserted position seals against at least one seal (36) whereby the second inner space (34) is separated from the first chamber (9) by the seal (36) and that at least one conduit (37) which may be closed and opened by at least one valve (38) connects the first chamber (9) and the second inner space (34), wherein the movable second piston (16) makes it possible that the hydraulic cylinder may be controlled to not have, or essentially not have, dampening properties when the end of the second piston (16) is inserted in the second inner space (34) and to have dampening properties when the end of the second piston (16) is not inserted in the second inner space (34).
Hydraulic cylinder (1) in accordance with claim 1 characterized in that the hydraulic cylinder includes a check valve which allows flow out from the inner space (34) via the conduit (37), alternatively another conduit but blocks flow in the opposite direction.
Hydraulic cylinder (1) in accordance with claim 2 characterized in that the valve (38) and the check valve are integrated into one unit.
Hydraulic cylinder (1) in accordance with one of the previous claims characterized in that the valve (38) consists of a controlled valve which is controlled by at least one control system.
Hydraulic cylinder (1) in accordance with at least one of the previous claims characterized in that the first chamber (29) includes a gas or a combination of gases.
Hydraulic cylinder (1) in accordance with at least one of the previous claims characterized in that the second chamber (30) includes a gas or a combination of gases.
Hydraulic cylinder (1) in accordance with at least one of the previous claims characterized in that the first chamber (29) includes an adjustable volume of fluid.
Hydraulic cylinder (1) in accordance with at least one of the previous claims characterized in that the first chamber (29) includes an adjustable volume of grease.
Hydraulic cylinder (1) in accordance with at least one of the previous claims characterized in that the conduit includes at least one restrictor.
Hydraulic cylinder (1) in accordance with at least one of the previous claims characterized in that the first chamber (29) is arranged to be connectable to at least one second hydraulic unit (32) comprised of at least one pressurized space, said hydraulic unit's (32) pressurized space being connected to the chamber (29).