Technical area

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

Technical background

In connection with lifting with different types of lifting devices such as cranes, work machines and the like, a large amount of energy is used to change the position of the mass of the lifted load and also the mass in the lifting device. The energy needed to lift, for example, a crane arm or similar's own weight is not recovered but disappears in energy losses such as heat generation and the like. There is a need for a more energy-efficient system for raising and lowering loads with cranes and work machines.

To reduce the energy losses in connection with vertical position changes of loads and the like, several types of devices have been developed. For example, various types of hydraulic cylinders and the like have been developed which are intended to reduce energy losses in the event of changes in the position of lifting devices. An example of such a hydraulic cylinder, intended for use in lifting and lowering a unit, is described in patent specification SE461391 by applicant BT Industrier. The cylinder described in the patent specification is of a double- acting type. The unique thing about the hydraulic cylinder of a double-acting type is that these comprise a piston rod which is hollow and forms an inner pump chamber in the piston rod.

The construction differs greatly from the construction of the present invention. For example, the second piston is not movably arranged in relation to both the working cylinder and the piston rod.

A problem with existing hydraulic systems is the presence of pressure spikes in the hydraulic system. Pressure spikes pose a risk of malfunctions in components such as hoses and other hydraulic components as well as a risk of damage to the hydraulic cylinder attachments and to implements that are directly or indirectly operated with the hydraulic cylinder. One way to solve the problem with pressure spikes in hydraulic systems is to use so-called shock valves. The problem with these is that the shock valves are located at a distance from the hydraulic cylinder, with small hoses or the like, which gives an unsatisfactory shock limiting effect

A problem with existing energy-efficient hydraulic cylinders with a movable piston in the inner space of a second piston rod is that they are resilient, which means that they can enter into self-oscillations. Said problems mean, for example, that the cylinders are unsuitable for use in, for example, cranes and the like. Furthermore, there is no known cylinder where a piston inside a piston rod can be changed between a movable and a non-movable structure.

A more specific problem exists when these have a relatively long piston, alternatively piston rod. The problem is that the piston, or the piston rod, is not guided in the radial direction of the piston, or the piston rod, which entails a risk of malfunction.

When operating equipment which uses at least one hydraulic cylinder, there is also a need to evacuate return oil from a chamber in the hydraulic cylinder more quickly, such as in the case of a shortening of the hydraulic cylinder. If most of the pressure fluid can be passed through the piston, the dimension of hoses, pipes or the like may be smaller than with known constructions of hydraulic cylinders.

Prior art

A hydraulic cylinder which comprises an inner chamber in the piston rod is further known via the patent US7478489. The patent US7478489 describes a variant of a working cylinder whose piston rod comprises an inner space in which fluid is compressed. The construction differs substantially from the construction of the present invention. For example, this does not include a movable second piston in accordance with the construction in accordance with the present invention.

The patent US7441405 also describes a working cylinder whose piston rod comprises an inner space in which a liquid is arranged to be compressed. This construction also differs substantially from the construction of the present invention. For example, the construction does not include a movably arranged second piston in accordance with the present inventions construction.

The document DE102007061294 describes a variant of a hydraulic cylinder comprising three chambers. The construction comprises a working cylinder in the piston rod: this construction also differs to a substantial extent from the construction in accordance with the present invention. For example, it does not include a movable piston in accordance with the present invention.

A further variant of hydraulic cylinder which comprises a piston rod with an inner chamber is known via the patent specification DE102004044962. Also, construction in accordance with DE102004044962 the script differs substantially from the construction in accordance with the present invention. For example, it does not include a movable piston in accordance with the present invention.

Documents US20040065194 and US3970292 describe variants of a shock absorber which comprise a piston rod which comprises an inner cavity in which a second piston is movably arranged. However, the rod is not movably arranged in relation to the end of the cylinder. The construction therefore differs to a substantial extent from the construction in accordance with the present invention.

Patent specification SE538615 describes a variant of a hydraulic cylinder. The construction according to the patent specification comprises a first piston, at least a second piston and at least a third piston. The construction according to the patent specification differs substantially from the construction according to the present invention. For example, this does not include a corresponding control in accordance with the present invention.

An even further problem with components included in hydraulic systems is the risk of hose breakage or the like. To solve this problem, variants of hose break valves and / or safety valves have been developed in many variants. A problem with these constructions is that they consist of separate components, which is not cost-effective.

The objects of the present invention

The main object of the present invention is to create a device which solves or reduces at least one of the above-mentioned problems. This object is achieved with a device according to the claims.

Brief description of figures

In the following detailed description of the hydraulic cylinder, references and references to the following figures will occur. Note that the figures are schematic and that certain parts of the hydraulic cylinder may be omitted which are obvious to a person skilled in the art in the technical field of which the hydraulic cylinder is included.

Figure 1 shows a first embodiment of the present hydraulic cylinder.

Figure 2 shows a cross section of the hydraulic cylinder according to figure 1.

Figure 3 shows in a hydraulic diagram an example of the use of the hydraulic cylinder according to the present invention. Figure 4 shows in a second hydraulic diagram a second example of an application for the present hydraulic cylinder.

Figure 5 shows in a hydraulic diagram a third example of an application for a hydraulic cylinder according to the present invention.

Figures 6A and 6B show a first alternative embodiment of the present hydraulic cylinder.

Figures 7 A and 7B show a second alternative embodiment of the present hydraulic cylinder.

Figure 8 shows an alternative embodiment of the embodiments according to Figures 6A to 6B.

Figure 9 schematically shows a hydraulic cylinder which is connected to a hydraulic unit.

Figures 10A and 10B show a third alternative embodiment of the present hydraulic cylinder.

Figures 11A and 11B show enlarged sections of Figures 10A and 10B.

Figures 12A and 12B show a fourth embodiment of the present invention.

Figure 13 shows in a hydraulic diagram an exemplary system for controlling pressure in the chamber and the flow to and from the inner chamber.

Figures 14A to 14D show a variant of the hydraulic cylinder.

Figure 14E shows the piston 28 in accordance with Figures 14 and 14D in more detail.

Figures 15A to 15D show the hydraulic cylinder of Figures 14A to 14D with at least one second guide.

Figures 16A to 16C are shown in a sequence of use of the hydraulic cylinder in an exemplary crane.

Figures 17 A and 17G show an alternative embodiment of the present hydraulic cylinder which comprises at least one additional piston and with the possibility of controlling pressure.

Figures 18A to 18C show a hydraulic cylinder with two back pressures that can be selected during the whole movement or parts of the movement

Figures 19A and 19B show a variant of hydraulic cylinder where the first piston comprises a channel for dumping oil. Figures 20A and 20B show alternative embodiments of the hydraulic cylinder which comprises at least one flow restrictor.

Detailed description of the invention

Referring to Figure 1, there is schematically shown an exemplary variant of a hydraulic cylinder 1 in accordance with the present invention. The exemplary hydraulic cylinder 1 construction constitutes only one of the conceivable embodiments of how an energy efficient hydraulic cylinder 1 in accordance with the present invention can be designed. The energy efficient hydraulic cylinder 1 shown is therefore not limiting of the design of an energy efficient hydraulic cylinder 1 in accordance with the present invention. The energy efficient hydraulic cylinder is hereinafter referred to as hydraulic cylinder 1 only or energy efficient hydraulic cylinder 1.

Hydraulic cylinder 1 consists in its basic construction of some previously known type of hydraulic cylinder which has been modified in accordance with the present invention. The hydraulic cylinder (working cylinder) 1 comprises a cylinder housing 2 and a first piston 3 movable therein. The cylinder housing 2 preferably comprises a cylinder 4, a first gable 5, end piece or the like and a second gable 6, end piece or the like. The piston 3 comprises a first piston head 7 (or similar) and at least one first piston rod 8. The piston rod 8 runs through a hole in the gable 6 in accordance with previously known technology. The first gable 5 and cylinder 4 can be separate or integrated with each other. Furthermore, the second gable 6 and the cylinder 4 can be separate or integrated with each other.

The piston head 7 divides the inner space of the cylinder housing into at least a first chamber 9 and at least a second chamber 10. The first chamber 9 is provided with at least a first connection 11 to which the first chamber of the hydraulic cylinder can be connected to a hydraulic circuit. The second chamber 10 is provided with at least one second connection 12 such as, for example, a coupling or the like with which the second chamber 10 of the hydraulic cylinder can be connected to a hydraulic circuit (hydraulic system). The connections of the hydraulic cylinder 1 to the hydraulic system and the pressurization of the respective chambers 9 and 10 take place in accordance with already known technology, which is why this technology is not described in more detail in this patent application. However, the piston 3 will move in the direction of the cylinder where a smaller force (surface times pressure) acts against the piston surface. The cylinder housing 2 further preferably comprises at least a first bracket 13, cylinder ears, or the like with which the cylinder housing can be mounted (connected) to an object or the like. In the embodiment shown, the bracket 13 and gable 5 of an integrated unit. The piston rod 8 comprises at its free end at least a second bracket 14, cylinder ear, or the like with which the piston rod 8 can be mounted (connected) to an object in a manner suitable for the purpose. The first bracket 13 in the cylinder housing and the second bracket 14 in the piston rod, respectively, are preferably a variant of a previously known type of bracket which is suitable for the purpose. For example, the first bracket 13 and the second bracket 14 may consist of an ear, cylinder ear or another type of bracket already suitable for the purpose.

The piston rod 8 is provided in the axial direction with an inner space 15 which forms a chamber in which a liquid such as hydraulic oil or the like can be pressurized by at least one second piston 16. The inner space 15 is preferably cylindrical with an axial centre substantially parallel to the first piston rod 8 axial centres. The axial centre of the inner cylindrical space 15 substantially coincides with the axial centre of the first piston rod 8. The second piston 16 is movably arranged relative to the inner space 15. When the second piston 16 is moved in the direction into the space 15, a pressurization (compression) of the liquid in the inner space 15 will take place. In alternative embodiments, the space 15 may comprise, or consist of, an external space which is connected to the inner space in the piston rod.

The second piston 16 is movably arranged in the inner space 15. The second piston 16 runs freely in the substantially cylindrical inner space 15 in the piston rod 8 and that the second piston 16 is movably arranged relative to the cylinder housing and the end of the cylinder 5. The length of the second piston 16 and shape may vary' widely within the scope of the present invention. Figure 2 shows a second piston 16 which has the same or substantially the same diameter in its longitudinal direction. In alternative embodiments, it is conceivable that the diameter of the second piston 16 varies according to its longitudinal direction. The inner cylindrical space 16 is connected via at least one connection 17 to at least one hydraulic circuit, hydraulic system or the like. The connection 17 consists of a previously known connection device such as, for example, a hydraulic coupling or other connection suitable for the purpose. The hydraulic cylinder 1 comprises the necessary seals in order to obtain a sufficient seal between the piston head 7 and the cylinder housing 2 and between the second piston 16 and the walls of the inner space 16, respectively. Said seals consist of already known technology, which is why these are not described in more detail in this patent application

When pressurizing the liquid in the first chamber 9 of the hydraulic cylinder 1, the first piston 3 will strive to move so that the chamber (space) 9 is extended in the longitudinal direction of the hydraulic cylinder When pressurizing the liquid in the first chamber 9 of the hydraulic cylinder 1, the second piston 16 will strive to be moved by the force acting on the surface 18, which in the exemplary embodiment is located at one end of the second piston 16. The second piston 16 will of the compressive force in the first chamber 9 of the hydraulic cylinder 1, which acts against the surface 18, to strive to pressurize the liquid in the inner cylindrical space 15 via the second surface 19, alternatively end of the piston. Movement of the second piston 16 into the inner space (chamber) takes place provided that an outflow of liquid (hydraulic oil) can take place via the connection 17 If the areas of the first surface 18 and the second surface 19 are equal, the second the piston 16 to move in the direction into the space, the cylindrical space 15 or the first chamber, where a lower pressure prevails (this presupposes that a quantity of oil is moved out at connection 11 or the connection 17)

The construction of the present hydraulic cylinder allows the entire, or substantially entire, surface 20 of the piston head towards the chamber 9, and the surface 18 of the second piston, to be subjected to the pressure in the chamber 9. This means that the dimension of the hydraulic cylinder can he made smaller than in most previously known constructions. In the majority of previously known constructions, the corresponding surface 18 disappears when it is firmly connected to the end wall of these constructions.

Figure 3 shows in a hydraulic diagram a first application where a hydraulic cylinder 1 in accordance with the present invention is intended to be used, for example. In the application, the hydraulic cylinder 1 is used, for example, in a crane or the like. The hydraulic cylinder 1 is used, for example, to maneuver the upward and downward movements of the crane arm. The diagram shows a hydraulic pump and associated tank for pressure fluid such as so-called hydraulic oil. In the exemplary embodiment, the hydraulic cylinder 1 consists of a hydraulic cylinder of double-acting type which is provided with a piston rod 8 with an inner cylindrical space 15 in which a free-running second piston 16 is movably arranged. When the first chamber 9 (plus side) is pressurized on the hydraulic cylinder 1, an overpressure will be created in the inner space 15 of the piston rod 8 and the accumulator tank. The overpressure in the inner space 15 of the piston rod 8 means that the second piston 16 will move in the direction of the end 5 until it abuts against the end 5. When the second piston 16 moves into the inner space 15 in the piston rod 8, a pressurization (compression) of the liquid in the interior space 15.

Figure 3 schematically shows a possible application in a crane arm or other application where load is lifted or balanced with at least one hydraulic cylinder in accordance with the present invention. In the application, at least one hydraulic cylinder 1 is connected to a crane arm or other component in a vehicle or the like.

The inner space 15 is connected via at least one connection, such as a hydraulic coupling or the like, via at least one line or the like to a first pressure accumulator 21. In the application, the positive side of the hydraulic cylinder is preferably connected via a non-return valve to a first pressure accumulator 21 and the inner space 15 of the first piston rod 8. When operating the hydraulic cylinder, the first piston 3 will create an overpressure in the positive side of the hydraulic cylinder the space of the piston rod 8. Due to the overpressure in the inner space 15, a restraining force, balancing force, will be created in the hydraulic cylinder 1. The restraining force will reduce the energy consumption for the operation of the crane arm. The pressure in the pressure accumulator usually during normal use is between 250 to 300 bar. In alternative embodiments, other pressure suitable for the purpose which deviates from the said can be used.

Referring to Figure 4, an alternative use of the hydraulic cylinder 1 is shown. The inner space 15 is connected via at least one connection, such as a hydraulic coupling or the like, via at least one line or the like to a first pressure accumulator 21. The inner chamber 15 can also by a channel or the like may 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 non-return valve. The pressure in pressure accumulator 21 during normal use is between 250 - 300 bar. The pressure in the pressure accumulator 22 is normally between 50 - 80 bar. In alternative embodiments, the pressure may deviate from said range. The hydraulic diagram in figure 4 also shows a control valve, a second pressure tank and other hydraulic components such as non-return valves. Through repeated piston strokes, strokes with the piston, a pressurization of the accumulator tank takes place, whereby a pressurization will take place of the inner space in the hydraulic piston. When pressure increase through pressure spikes and the like arising in the hydraulic system, a pressure in the inner space 15 will cause the non-retum valves to prevent flow out of the inner space 15. An opposing upward force (relative to the crane arm) will thus be obtained via the hydraulic cylinder. If the pressure in the interior space exceeds a certain predetermined level, a flow will be allowed via a valve to the tank valve. The restraining force is dimensioned (balanced) according to the force required to hold up the crane arm. The higher pressure from the pressure accumulator 21 is used for back pressure at load (back pressure both for the weight of the crane arm and for the lifted load). The lower pressure from pressure accumulator 22 is used as a back pressure at low load (back pressure for the crane weight). Due to the construction, less energy will be needed to operate the crane.

Figure 5 shows in a hydraulic diagram a third possible application for a hydraulic cylinder 1 in accordance with the present invention. In the application, the hydraulic cylinder is, for example, connected between two vehicle parts, such as between the chassis and the superstructure of a vehicle. The hydraulic diagram shows a second cylinder 23 which is connected between the chassis and the superstructure (alternatively a counterweight or the like). At start-up, the hydraulic cylinder is pressurized by pressure fluid created by the counterweight. The counterweight creates an overpressure in the inner space of the hydraulic cylinder, which in turn is used to reduce the energy consumption for the operation of a crane arm, boom or the like. Superstructure of the vehicle, or other connected part of the vehicle, pressurizes the liquid in the chamber 24 in the second cylinder 23 which in turn pressurizes the liquid in the chamber 15.

Referring to Figure 6, a first alternative embodiment of the present hydraulic cylinder 1 is shown. The accumulator according to the previous figures can be integrated in the piston rod of the hydraulic cylinder. In the embodiment according to Figure 6, the inner space 15 in the piston rod 8 is intended to be filled with gas or a mixture of gases. For example, the piston rod 8 can be filled with nitrogen gas or other gas suitable for the purpose or a combination of gases. In the free end of the piston rod 8 this comprises at least one filling means 25 which can be opened and closed in connection with gas being supplied to the inner space 15 in the piston rod 8. The filling means is in some embodiments the same as the connection 17. In other embodiments this constitutes a separate filling means.

Referring to Figure 6B, there is shown an embodiment in which the piston 16 is hollow or substantially hollow after a portion of its length. The piston rod 8 thereby forms a space 26 which at its one end communicates with all or parts of the inner space 15. The second piston 16 comprises at least one end wall 27, or other material layer, which prevents a flow (leakage) of gas or liquid takes place from the chamber 15 to the first chamber 9. The construction increases the volume of the gas which can be compressed in relation to what is the case with a solid piston.

Referring to Figures 7 A to 7B, an alternative embodiment of the present hydraulic cylinder is shown. In the embodiment, the hydraulic cylinder comprises at least one piston 28 which is preferably movably arranged inside the inner space 15 in the piston rod 8. In piston embodiment, the piston 28 constitutes a third piston. In further embodiments, the piston may be a piston with another name. In the exemplary embodiment, the idea is that it should delimit the inner space 15 in a first chamber (space) 29 and a second chamber (space) 30. The first chamber 29 is the delimited part of the inner space 15 which is closer to the free end of the piston rod than the second chamber 30 which is further away from the free end. The technical effect of dividing the inner space 15 into at least a first inner chamber 29 and at least a second inner chamber 30 is that this enables the back pressure of the hydraulic cylinder to be increased or decreased. Figure 7A shows a piston 16 which is of solid design. Figure 7B shows a piston 16 which comprises an inner space 26.

Referring to Figure 8, an alternative embodiment of the present invention is shown in which it comprises an inner piston 28 in the inner space 15 of the piston rod. The position of the piston 24 is fixedly or adjustably arranged with at least one adjusting device 31 in the longitudinal direction of the inner space. By moving the inner piston 28 in the longitudinal direction of the inner space 15, the volume of the second chamber in the piston rod 8 can be adjusted.

With reference to Figure 9, it is shown how the present hydraulic cylinder 1 enables a control of the pressure in the chamber 30. Through the construction, the properties of the hydraulic cylinder 1 in relation to another component, device or the like can be automatically controlled. For example, it is conceivable that the present construction allows the pressure in the first chamber 29 to be pressurized from a weight-loaded hydraulic unit 32. The hydraulic unit may, for example, consist of a hydraulic cylinder or other hydraulic component in, for example, a truck or other machine suitable for the purpose. Figure 9 also shows that the piston 28 is preferably provided with at least one seal 33.

Referring to Figures 10A to 10D, a variant of the hydraulic cylinder 1 is shown which includes a function and a device with which the mobility of the second piston 16 is temporarily restricted. The hydraulic cylinder thus comprises at least one inner space 34, preferably a cylindrical space 34, into which the end 35 of the piston 16 can be inserted or discharged.

The structure comprises at least one seal 36 which seals between the piston (piston rod) 16 when a part of the piston 16 is inserted into the inner space 34. When a part of the piston 16 is inserted into the inner space 34 and that the inner space is sealed relative to the chamber 9 with seal 36 acts a limited pressure against the surface 18 of the end 35 of the piston 16. The second piston 16 will then remain in the inserted position.

In the exemplary embodiment, the present invention comprises at least one channel 37 which connects chamber 9 to the inner space 34. In the exemplary embodiment, the channel is provided with a valve 38. In the exemplary embodiment, the valve 38 is constituted by a valve which limits the flow between chambers 9. and the interior space 34 when the pressure is below a certain predetermined level. When the pressure exceeds the predetermined level, the valve opens and a pressurization of the inner space 34 can take place by passing the pressure in the chamber 9 via the channel to the inner space. When the pressure in the chamber 9 is higher than in the chamber 30, alternatively in chamber 15, in the piston rod and that the pressure in the chamber 9 is higher than in the pressure which causes the valve 38 to open. Because the pressure is higher against the surface 18 than the pressure inside the space 15 (towards the end of the second piston in the space), the second piston 16 will move out of the inner space 34.

The valve 38 may also include a function as a non-retum valve which prevents the flow in one direction, but which enables flow in the other direction. The valve 38 and the non-retum valve can be integrated in one and the same unit (valve) or consist of separate units. In separate units, an additional channel (not shown in figures) is preferably used which connects the chamber 9 and the inner space.

In alternative embodiments, it is conceivable that the valve 38 consists of a controlled valve, which can be controlled to open and close the flow in the channel 37. The valve is controlled by a control system. The control can take place independently of the pressure prevailing in the chamber 9 and chamber 15, respectively, alternatively with sensing the pressure in these. The control can be done, for example, electrically or with another technology suitable for the purpose.

In alternative embodiments of the hydraulic cylinder 1, the channel 36 comprises at least one throttle (not shown in figures) with which a delay of the function of the valve can be achieved. The throttle displaces the time before the valve 38 is activated and that the piston, the piston rod, is thereby moved out of the inner space.

In alternative embodiments, it is conceivable that the construction comprises at least one locking device with which the piston is locked in the inserted position. The locking device may be of any locking device suitable for the purpose.

With the construction in accordance with the embodiment, this has a function with a built-in shock valve which limits spikes in pressure in the hydraulic cylinder.

Referring to Figures 11A and 1 IB, the second piston 16 shows in a position where it is not inserted into the space 34 and in a position where it is partially inserted into the space 34. In Figure 11A, the piston is movable relative to the end of the hydraulic cylinder. In Figure 1 IB, this is inserted into the interior space 34.

Figures 12A and 12B show a hydraulic cylinder 1 which comprises a piston 28, in the construction constituting a third piston. Hydraulic cylinder 1 according to the embodiment of Figures 12A and 12B differs from the embodiment shown in Figures 7 A and 7B in that the chamber 30 extends via at least one channel, conduit, pipe, hose or the like to an external unit in which the piston 28 divides at least one space in the external unit in a first chamber 29 and a second chamber 30. The hydraulic cylinder 1 is provided with a space 34, in which the end 35 of the second piston 16 has a corresponding function as described in Figures 10A to 10D.

Referring to Figure 13, an exemplary embodiment of a system is shown in a hydraulic diagram in which the pressure in the space 15 in the second piston 16 is controllably arranged. The control system also controls the flow to and from the chamber 15 in the second piston 16. The system comprises at least one control system 39 comprising at least one control unit which controls the valve 38. The system preferably comprises at least one pressure valve 40 pressure sensor 41 and at least one pressure source 42. The pressure source 42 may be a hydraulic motor or other suitable source of pressure. The figure also shows the subsystem for operating the normal function of the hydraulic cylinder, i.e. controlling the flow to and from chamber 9 and chamber 10.

With a control system and pressure / flow valves, you can control at which pressure the suspension is to be activated. And have the opportunity to control the characteristics of the suspension. The system also means that the back pressure (pressure) in the chamber 15 can be controlled. This can be done by controlling the flow of the oil in and out of the chamber 15. The control system also gives the possibility to control when the piston 16 is to leave its position inside the chamber and when it is to be positioned inside the chamber. Through the design, the system can be controlled to function with suspension or without the resilient function. Through the design, the speed of the function as a shock valve can be controlled.

With the present construction it is possible that the properties of the hydraulic cylinder 1 can be varied depending on whether the end 35 of the second piston is inserted in the inner space 34 or not. With the construction it is possible to choose whether the hydraulic cylinder 1 is to have a resilient function or a non-resilient function.

Referring to Figures 14A to 14D, an alternative embodiment of the present hydraulic cylinder 1 is shown. This embodiment of the invention also includes a pressure peak limiting function.

Hydraulic cylinder 1, according to the embodiment, comprises an alternative variant of the piston 28 which in the embodiment constitutes the third piston of the hydraulic cylinder 1. Also in this embodiment, the piston 28 divides the inner space 15 into a first chamber (space) 29 and into a second chamber (space) 30. In the exemplary embodiment in Figure 14E, the construction of the piston 28 causes the hydraulic cylinder 1 to function as a load holding valve / safety valve.

In the embodiment shown in Figures 14A to 14D, the hydraulic cylinder 1 comprises a function and a device with which the movement of the second piston 16 is temporarily limited in the axial direction of the second piston 16 in accordance with the embodiment according to Figures 10A and 10B. The hydraulic cylinder 1 thus comprises at least one inner space 34, preferably a space 34, into which the end 35 of the second piston 16 can be inserted or discharged. The function of releasing the end 35 of the second piston 16 is achieved by a pressurization of space 34 so that the pressure therein becomes higher than the pressure in chamber 30, alternatively 15. In the embodiment, the channel 37 constitutes the valve described with reference to Figures 10A and 10B. The function is achieved by at least one flow restrictor in the channel 37. In the embodiment shown in Figures 14A to 14D, the end 35 of the second piston 16 is guided upwards by the wall in the inner space 34 and by the bushing in the piston head 7.

To further improve the control of the second piston 16 relative to the axial direction of the hydraulic cylinder 1, the second piston 16 is provided with at least a first guide 43, alternatively bearing, for controlling the position of the second piston 16 in radial direction relative to the wall 4 of the cylinder. In the exemplary embodiment, the first guide 43 is located near one end 35 of the second piston 16. However, no closer to the end 35 than the guide 43 does not impede the movement of the end 35 into space 34.

Figure 14E shows the exemplary embodiment of the third piston 28, in accordance with the embodiment of 14A and 14D, in more detail. The third piston 28, the valve, causes it to open only when it receives a control pressure in the chamber 29, which moves the third piston 28 between a closed position and an open position. The third piston 28 comprises at least one first end 44 and at least one second end 45. The third piston 28 is movably arranged in a valve housing 46 with at least one first channel 47 (to), at least one second channel 48 (return) and preferably at least one third channel 49 (leakage line). When pressurizing space 29, the third piston 28 is moved between a position where a flow of fluid, such as pressure fluid, can take place between the channels 47 and 48 and a position where a flow of fluid can take place between the channels 48 and 49. The embodiment may comprise at least one spring , not shown in figures, with which a return of the third piston 28 from an activated position and an inactivated position, original position, is facilitated or ensured. The original position can either be a closed position or an open position.

Referring to Figures 15A to 15D, a further embodiment of the hydraulic cylinder 1 is shown. In this embodiment, the second piston 16 is provided with at least a first guide 43 and at least a second guide 50. The second guide 50 controls the position of the second piston 16, in the radial direction of the second piston 16, towards the wall of the inner space 15. The first guide 43 is preferably located in the vicinity of the end 35, or the end 35, of the second piston 16 and the second guide 50 is located in the other end of the second piston 16, or proximity of the end. In an alternative embodiment, the second guide may be defined as a piston as a variant of a third piston.

Referring to Figures 16A to 16C, there is schematically shown a crane 51 with at least one crane arm 52 and at least one vertical crane portion 53. The crane 51 is provided with at least one hydraulic cylinder 1 which in one cylinder ear is connected to the crane arm 52 and the other cylinder ear is connected to the vertical crane portion 53. The force required to operate the crane arm 52 in the upward direction depends on its position in which position the crane arm 52 is to be operated from. In Figure 16 A, more energy is required to rotate the crane arm 52 in the upward direction than is required to rotate the crane arm 52 upward from the position of Figure 16B. In Figure 16B, more energy is required to turn the crane arm in the upward direction than is needed to turn the crane arm upward from the position of Figure 16C. Referring to Figures 17 A to 17G, a further alternative embodiment of the present hydraulic cylinder 1 is shown. The hydraulic cylinder 1 comprises a shifting function for shifting the counterforce in the inner space 15 from at least one relatively higher counterforce to a relatively lower counterforce or alternatively from a relatively lower counterforce to a relatively higher counterforce. The hydraulic cylinder 1, in accordance with the embodiment shown in Figures 17A to 17G, comprises at least one third piston 28. The piston 28 may alternatively be defined as the third piston 28, or alternatively this may be defined as a fourth piston. In the embodiment, at least one channel 54, hole or bushing or the like extends through the third piston 28. The channel 54 creates a connection between chamber 29 and chamber 30.

In the exemplary embodiment of the hydraulic cylinder shown in Figures 17 A to 17D, the third piston 28 extends longitudinally after the second piston 28. Said distance may vary within the scope of the inventive concept of the present hydraulic cylinder 1. The third piston 28 has a shape like a sleeve or the like which comprises at least one bottom 55 and a tubular part 56. The bottom 55 of the sleeve has an outside 57A and an inside 58A. The tubular portion 56 of the sleeve has an outside 57B and an inside 58B. The third piston 28 includes at least one seal 59 between the inside 58B of the third piston 8 and the outside of the second piston 16. The channel 54 preferably extends from the inside 57A to the inside 58A of the bottom 55 of the third piston 28.

Referring to Figures 17E to 17G, there is shown a sequence of operating the hydraulic cylinder 1 in accordance with Figures 17A to 17D. The relative positions of the components of the hydraulic cylinder 1, in Figures 17E to 17G, shall be related to the positions of the hydraulic cylinder 1 in Figures 16A to 16D.

Figure 17E shows the hydraulic cylinder 1 when the hydraulic cylinder 1 provides the most counterforce. In this position, the hydraulic cylinder 1, for example when used in the exemplary crane 51, is shown in Figure 16A. In the position of the crane 51, the position of the crane arm 52, the force required to operate the crane arm 52 is greater than in Figures 16B and 16C, respectively.

In Fig. 17E, the hydraulic cylinder 1 is in the position according to Fig. 16B. In Fig. 17E, the piston head 7 of the first piston 3 is in, or near, one end position of the first piston 3, in which position the length of the hydraulic cylinder 1 is the shortest. The end 18 of the second piston 16 is inserted into the inner space 34. The end 19 of the second piston 16 abuts the inside 58A of the bottom 55 of the third piston 28. The pressure in chamber 9 causes the first piston 3 to move in the direction where the hydraulic cylinder 1 is extended. The back pressure in chamber 15 causes the third piston 28 to abut against the end 18 of the second piston 16. In this position, the counter force from the hydraulic cylinder is at its highest. In this position, the counterforce is the pressure times the area on the outside 57 A of the third piston 16.

In Fig. 17F, the hydraulic cylinder 1 is in a position corresponding to that of the hydraulic cylinder substantially in Fig. 16B. The first piston 3 has reached and come into contact with the third pistons 28 tubular part 56. In the embodiment according to the figure, the piston 3 has reached the third piston 28. When the first piston 3 reaches the third piston 28, the first piston 3 begins to actuate the third piston 28 to move in the same direction as the first piston 3. The end 35 of the second piston 16 is inserted into the inner space 34. When the first piston 3 and the third piston 28 reach each other, a change takes place between a relatively higher counter force (counter-force) to a relatively lower counterforce.

In Fig. 17G, the hydraulic cylinder 1 is in a position corresponding to that of the hydraulic cylinder 1 in Fig. 16C. In this position the first piston 3 has been operated so that the hydraulic cylinder 1 has been further extended. The end 35 of the second piston 16 is inserted into the inner space 34. The first piston 3 has caused the third piston 28 to move in the direction of the second piston 16. A space 29 is formed between the surface 18 on the end of the second piston 16 and the inside 58 A of the bottom 57 of the third piston 28. The pressure in the chamber 30 causes a corresponding pressure in chamber 29 to be created. In this position, the counterforce is the pressure times the area of the surface 19 on the end of the second piston 16.

In further embodiments of the hydraulic cylinder 1 , the hydraulic cylinder 1 may be designed to comprise more changes of counterforce than one according to the stroke of the hydraulic cylinder 1, i.e. when moving between the first end position and the second end position. This can be achieved, for example, by the hydraulic cylinder 1 further comprising at least one piston, not shown in figures, but a corresponding function as exemplified in figures 17 A to 17G.

Figure 18A shows an alternative embodiment of the hydraulic cylinder 1. Also in this embodiment, the hydraulic cylinder (1) comprises a switching function for the counterforce between at least a relatively higher counterforce to a relatively lower counterforce or from a relatively lower counterforce to a relatively higher counterforce. In the embodiment, the piston 16 of the hydraulic cylinder 1 comprises a space 26 in accordance with Figures 7 A and 7B. In the inner space 26, at least one piston rod 60 with at least one through-going channel 61 extends through the third piston 28 to a connection 62 to at least one first pressure accumulator. Between the piston rod 60 and the wall of the inner space 26 there is a channel 63, gap or the like. The hydraulic cylinder further comprises at least one second connection 64 to at least one second pressure accumulator or the like. The passage of the piston rod through the third piston 16 comprises at least one seal which seals between the third piston 28 and the piston rod 60. The seal consists of a previously known seal, which is why this is not described in more detail.

The change of counterforce takes place by pressurization via the first connection 62 or via the second connection 64. The change takes place because different pressures are present in the first connection 62 and the second connection 64, respectively.

Hydraulic cylinder 1 according to the embodiment shown in Figure 18A has the advantage of it being possible to select at least two different levels of opposite force, back pressure, during the whole movement or parts of the movement. This is useful, for example, if the counterforce, the back pressure, must be greater at at least part of the movement than at least another part of the movement as shown in Figures 16A to 16C. It is also possible to vary the counterforce, the back pressure, at full load and without load (empty load).

Figures 19A and 19B show an embodiment of a hydraulic cylinder where it is possible to dump oil through the piston 3. The cylinder has the advantage that it enables the load to be lowered more quickly, for example if necessary. In this embodiment the first pistons 3 piston head 7 comprises at least a first channel 65, pipe, hose or the like which connects chamber 10 with chamber 9. The channel 65 can be regulated via at least one valve 66 whether it is to be open or closed. In the exemplary embodiment, the valve 66 is a pressure-controlled valve. The pressure-controlled valve is controlled via at least one channel 67, pipe, gap, liner, or the like. The valve 66 is opened when it is pressurized via the channel 67. The described function and construction regarding dumping pressure fluid via at least one channel 65 can also be used in ordinary hydraulic cylinders 1 which only comprises one piston 3 or two pistons.

Referring to Figures 20 A and 20B, a further alternative embodiment of the present hydraulic cylinder 1 is shown which includes a shock absorbing function or shock absorbing effect. Referring to Figure 20A, it is shown that channel 17 includes at least one flow restrictor 68. In the exemplary embodiment of Figure 20A, the flow restrictor is fixed. The flow' restrictor 68 includes at least one hole 69 which restricts the flow. The throttle 68 throttles the same amount of flow in and out of the chamber 15, respectively. With the flow restrictor 68, the technical effect is achieved by keeping the maximum speed of the piston down.

Referring to Figures 20C and 20D, a variant of a hydraulic cylinder is shown which includes a shock absorbing function, shock absorbing effect. Referring to Figure 20B, it is shown that channel 17 includes a second flow restrictor 70. The second flow restrictor is a second type of flow restrictor. The flow restrictor has full flow into the chamber 18 or the chamber 29 and / or the chamber 30 but restricts the flow outwards from said chamber. With the flow restrictor 69, this means that the flow through the flow restrictor can be regulated with a high or the like. The flow restrictor 69 may in alternative embodiments be defined as the third piston 28. In the exemplary embodiment, the second type of control 69 of the pressure in the chamber 15 may affect the flow restrictor between a relatively lower degree of flow restrictor and a relatively higher degree of flow restrictor. This is done by moving the second guide 70 in the axial direction from a first position to a lower position. The second flow restrictor 69 includes at least one second hole 71 which restricts the flow through the flow restrictor. The second flow restrictor 69 further comprises at least a third hole 72 which, when the pressure exceeds a specific pressure level, is blocked by the axial movement of the second flow restrictor 70. The second flow restrictor 70 is preferably spring loaded so that it causes the second flow restrictor 70 to return to its original position when the pressure drops below a certain level.

The design changes the flow restrictors level of restriction depending on the pressure.

With the construction in accordance with Figures 17-19, a shock-absorbing effect for the hydraulic cylinder is also achieved this is achieved by the third piston 28 comprising a channel 54, which channel 54 also functions as a flow restrictor.

In the construction according to 14A - 14D, the shock-absorbing effect of at least one flow restrictor is achieved, which in the unfolding form is controlled by the flow can be increased or decreased. The flow restrictor is integrated with the safety valve / hose break valve.

In the detailed description of the present invention, construction details which may be obvious to a person skilled in the art may have been omitted. Such obvious construction details are included to the extent required to achieve a satisfactory function of the present invention. For example, components such as seals, hydraulic couplings, hydraulic hoses with several types of components are included to the extent required to obtain the intended function.

Although certain preferred embodiments have been described in detail, variations and modifications within the scope of the invention may become apparent to those skilled in the art to which the invention pertains, and all of these are considered to fall within the scope of the appended claims.

Advantages of the invention

With the present invention several of advantages are achieved. The main advantage is that at least one of the above disadvantages is eliminated or reduced.