SE1400288A1 - Hydraulcylinder - Google Patents

Abstract

Hydraulic cylinder (1) comprising a cylinder housing (2), with a cylindrical inner space, and in it at least one movably arranged first piston (2) which divides the hydraulic cylinder into at least one first chamber (9) and at least one second chamber (10). The piston (2) comprises a piston head (7) and a piston rod (8) whose piston rod (8), in the axial direction of the piston rod (8), is provided with at least one inner space (15). The hydraulic cylinder (1) comprises at least one piston (28) in the inner space (15) of the piston rod (8) which divides the inner space (15) into at least one first chamber (29) and at least one second chamber (30). The end of the hydraulic cylinder comprises an inner space in which the end of the piston rod is intended to be inserted and that the piston rod seals against the least seal and that the construction comprises at least one lock with which the piston can be locked and released relative to the inner space.

Description

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

Technical background and prior art 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 lifting load and also the mass in the lifting device. The energy needed to lift, for example, a crane arm or similar 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.

In order to reduce the energy losses in connection with vertical position changes of loads and the like, a number of types of devices have been developed. For example, various types of dehydraulic cylinders and the like have been developed which are intended to reduce the energy losses during positional changes of lifting devices. An example of such a hydraulic cylinder, intended for use in tilting and lowering a unit, is described in patent specification SE461391, filed by BT Industrier. The cylinder described in the patent specification is of a double-acting type. The unique thing about hydraulic cylinders 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 comprises a single variant of a second piston which at its one end is connected to the working cylinder and at its other end is movably arranged in relation to an inner space in the piston rod. The construction differs to a large extent from the construction of the present invention. For example, the other piston is not movably arranged in relation to both the working cylinder and the piston rod.

A problem with dangerous hydraulic systems is that pressure spikes can cause malfunctions in components such as hoses and other hydraulic components.

A hydraulic cylinder which comprises an inner chamber in the piston rod is further known via the patent specification US7478489. U.S. Pat. No. 7,478,489 describes a variant of a working cylinder whose piston rod comprises an inner space in which fl uid is compressed. The construction differs to a substantial extent from the present invention construction. For example, this does not include a movable second piston in accordance with the construction of the present patent application. Also in the patent specification US7441405 describe a working cylinder whose piston rod comprises an inner space in which a liquid is arranged to be compressed. This construction also differs significantly in scope from the construction of the present invention. For example, this does not include a movably arranged second piston in accordance with the present invention.

Patent specification DE102007061294 describes a variant of a hydraulic cylinder comprising three lifting chambers. The construction comprises a working cylinder in the piston rod. This construction also differs to a significant extent from the construction in accordance with the present invention. For example, this does not include a movably arranged second piston in accordance with the present invention.

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

Patents US20040065144 and US3 970292 describe a variant of a shock absorber which comprises 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 patent application.

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 self-oscillations. These problems mean, for example, that the cylinders are unsuitable for use, for example in cranes and the like. Furthermore, there is no known cylinder in which a piston inside a piston rod can be changed between a movable and a non-movable structure. The objects of the present invention The main object of the present invention is to create a device and a method for using the device which dissolves or reduces at least one of the above mentioned problems. This object is achieved by means of an apparatus and a method according to the claims.

Detailed Description of the Invention In the following, the invention will be described in more detail with reference to the accompanying schematic drawings which, by way of example, show the presently preferred embodiment of the invention.

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 a 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 7A 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 1OB show a third alternative embodiment of the present hydraulic cylinder. Figures 11A and 11B show enlarged sections of the gears 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 as well as the fate to and from the inner chamber.

Referring to Figure 1, an exemplary variant of a hydraulic cylinder1 in accordance with the present invention is shown schematically. The construction of the exemplary hydraulic cylinder constitutes only one of the conceivable embodiments of how a hydraulic cylinder can be designed in accordance with the present invention. The hydraulic cylinder shown is therefore not limiting of the construction of a hydraulic cylinder in accordance with the present invention.

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. Hydraulic cylinder (working cylinder) 1 comprises a cylinder housing 2 and one in this movable piston 3. The cylinder housing 2 preferably comprises a cylinder 4, a first end 5 and a second end 6. The piston 3 comprises a piston head 7 (or similar) and at least one piston rod 8. The piston rod 8 runs through a hole in the end 6 in accordance with the prior art. The first end 5 and cylinder 4 can be separate or integrated with each other. Furthermore, the second end wall 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 one 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, for example a coupling or the like with which the second chamber 10 of the hydraulic cylinder 10 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 the prior art, which is why this technique 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 a minimum bracket 13 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 the end end 5 consist of an integrated unit. The piston rod 8 comprises at its one end at least one bracket 14 or the like with which the piston rod 8 can be mounted (connected) to an object in a manner suitable for the purpose. The bracket 13 in the cylinder housing and the bracket 14 in the piston rod, respectively, preferably consist of a variant of a previously known type of bracket which is suitable for the purpose. For example, the bracket 13 and the bracket 14 may consist of an ear or arm already previously suitable for the purpose of the type of bracket.

The unique feature of the present invention is that the piston rod 8 in the axial direction is provided with an inner space 15 which forms a chamber in which a liquid such as hydraulic oil or the like can be compressed by at least one second piston 16. The inner space 15 is preferably cylindrical with an axial center substantially parallel to the axial center of the piston rod 8.

The axial center of the inner cylindrical space 15 substantially coincides with the axial center of the piston rod. The piston 16 is movably arranged in relation to the inner space 15. When the piston 16 is moved in the direction into the space 15, a compression of the liquid will take place in the inner space 15.

The second piston 16 is movably arranged in the inner space 15. The piston 16 is further freely movable relative to the cylinder 4 and relative to the end 5. The piston 16 runs freely in the substantially cylindrical inner space 15 in the piston rod 8 and that the piston 16 is movably arranged relative to the cylinder housing and cylinder end 5. The length and shape of the piston 16 can vary widely within the scope of the present invention. Figure 2 shows a 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 a hydraulic circuit, hydraulic system or the like. The connection 17 consists of a previously known connection device such as, for example, a hydraulic coupling.

The hydraulic cylinder 1 comprises the necessary seals in order to obtain a sufficient seal between the piston head and the cylinder housing 2 and between the second piston 16 and the walls of the inner space 16, respectively. These consist of previously 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 displaced by the force acting on the surface 18. The second piston 16 will strive to compress the liquid in the first chamber 9 of the hydraulic cylinder 1 first against the surface 18 the inner cylindrical space 15 via the second surface 19. via the piston 16 The displacement of the second piston 16 inside the inner space (chamber) takes place provided that a discharge of liquid (hydraulic oil a) can take place via the connection17. If the surface 18 and the 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 lower pressure prevails (assuming that a large amount of oil is released via the connection 11 or 17). .

The construction of the present hydraulic cylinder allows the entire, or substantially entire, surface 20 of the piston head in the direction of 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 be made smaller than the previously known constructions. In 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 usable. In the application, the hydraulic cylinder 1 is used in a crane or similar. 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 hydraulic oil a. In the exemplary embodiment, the hydraulic cylinder 1 consists of a double-acting type hydraulic cylinder which is provided with a single piston rod 8 with an inner cylindrical space 15 in which a non-running piston 16 is movable. When the first chamber 9 (plus side) is pressurized on the hydraulic cylinder 1, an overpressure will be created in the accumulator tank and the inner space in the carbon rod. The overpressure in the piston rod means that the second piston 16 will move in the direction of the counter-end 5 until it rests. towards the end 5. When the second piston 16 moves into the inner space 15 in the piston rod 8, a compression of the liquid takes place in the inner space 15.

Figure 3 schematically shows a possible application in a crane arm or other application where the 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 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 connected via a non-return valve to a first pressure accumulator 21 and the inner space of the hydraulic piston. When operating a hydraulic cylinder, the overpressure of the pump piston in the positive side of the hydraulic cylinder will create an overpressure in the inner space of the piston rod. Due to the overpressure, a restraining force will be created in the hydraulic cylinder. 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 amounts to between 250 to 300 bar. In alternative embodiments, other pressure suitable for the purpose that deviates from the approximate may 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 be connected via at least one line 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 alternatively 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 is normal use between 250 - 300 bar. The pressure in the pressure accumulator 22 is normally between 50 - 80 bar. The hydraulic diagram also shows a control valve, a second pressure tank and other hydraulic components such as non-return valves. Through repeated piston strokes, entry of the accumulator tank takes place, whereby a pressurization will take place of the inner space in the hydraulic piston. When the pressure through pressure spikes and similar arising in the hydraulic system, a pressure in the inner space 15 will cause the non-return valve obstruction fl out of the inner space 15. A restraining upward force (relative to the clamping arm) will thus be obtained via the hydraulic cylinder. If the pressure in that interior space exceeds a certain predetermined level, a fl fate will be allowed via a valve refueling 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 the 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 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 cylinder is pressurized against the counterweight. The counterweight creates an overpressure in the inner space of the hydraulic cylinder, which in sintering 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. It has unexpectedly been found that the accumulator according to the previous Figures is integrated in the piston rod of the hydraulic cylinder. In the embodiment according to Figure 6, the inner space 15 of 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 the 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.

Referring to Figure 6B, there is shown an embodiment in which the piston 16 is hollow or substantially hollow along all or part 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 leakage (leakage) of gas or liquid. from the chamber 15 to the first chamber 9. The through 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 7A 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 of the piston rod 8. 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, respectively. 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, the volume of the chamber 30 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 the first chamber 29 is 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 is preferably provided with at least one seal 33.

Referring to Figures 10A to 10D, there is shown a variant of the hydraulic cylinder 1 which includes operation 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, in which the end 35 of the piston 16 can be inserted or removed from.

The structure comprises at least one seal 36 which seals 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 relative to the chamber 9 with seal 36, a limited pressure acts 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 duct 37 which connects chamber 9 to the inner space 34. In the exemplary embodiment the duct is provided with a valve 38. In the exemplary embodiment the valve 38 consists of a valve which limits the space 9 between the chamber and the space between the chambers. 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 may be effected 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 in the piston rod and that the pressure in the chamber 9 is higher than the pressure which causes the valve 38 to open. Because the pressure is higher against the surface 18 than the pressure inside space 15 (towards the end of the second piston in the space), the second piston 16 will move out of the inner space.

The valve 38 may also include a function as a non-return valve which prevents fl fate in that one direction but which enables fl fate in the other direction. The valve and the non-return valve can be integrated in one and the same unit (valve) or consist of separate units. In the case of 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 choke (not shown in fi gures) 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 peaks in pressure in the hydraulic cylinder.

Figures 12A and 12B show how the structure according to the first embodiment shown in Figures 1 and 1 and 6A and 6B is provided with a space 34 with a corresponding function as described in Figures 10A to 10D. The piston 16 may be hollow as shown in the figure or be of a solid variant.

With reference to Figure 13, an exemplary embodiment of a system is shown in a hydraulic diagram where the pressure in the space 15 is arranged in a controllable manner. The control system also controls the fate to and from the chamber 15. 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. The visas clock also shows the subsystem for pre-actuation of the normal function of the hydraulic cylinder, ie to control the fate to and from chamber 9 and chamber 10.

With a control system and pressure / des fate valves, you can control at which pressure the spring is to be activated. As well as being able 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 fate 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 lean its position inside the chamber and when it is to be positioned inside the chamber. Through the construction, the system can be controlled to operate 11 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 hydraulic cylinder properties can be varied depending on whether the end of the second piston is inserted into the interior space or not. The co-construction can be selected if the construction has a resilient function or a non-resilient function.

In the detailed description of the present invention, construction details may be learned which are obvious to a person skilled in the art. Such obvious construction details are included to the extent required to achieve a malfunction of the present invention. For example, components such as seals, hydraulic couplings, hydraulic hoses with fl your 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 relates and all of these are considered to fall within the scope of subsequent patent claims. It is conceivable that the present invention consists of a method for using the present hydraulic cylinder.

Advantages of the Invention With the present invention, a number of advantages are achieved. The main advantage is that at least one of the above disadvantages is eliminated or reduced.