TECHNICAL FIELD

[0001] The invention relates to a hydraulic system for a tiltrotator and an auxiliary tool arranged on a pivot arm or the like. The hydraulic system is of the type comprising a pressure supply for pressurizing a hydraulic fluid to be fed to the tiltrotator and, via the tiltrotator, to the auxiliary tool. Specifically, the invention relates to such a system which is arranged to deliver an important flow of hydraulic fluid to the auxiliary tool, via the tiltrotator. The invention also relates to a method of distributing hydraulic fluid in such system.

BACKGROUND

[0002] In more and more applications of tools arranged on hydraulic arms of e.g. a wheel or crawler mounted loader, such as an excavator, a tractor or the like a hydraulic tool is attached to the pivot arm via a rotating and/or tilting unit, such that the tool, in addition to its main function, may be rotated and/or tilted. A combined rotating and tilting unit is known as a tiltrotator.

[0003] Some tools, such as hydraulic hammers or compactors demand a great amount of hydraulic flow to function. For each tool a pair of conduits comprising a supply conduit and a return line is needed. Conventionally, the provision of pressurized fluid to the auxiliary tool has been solved by arranging separate conduits for the tiltrotator and the auxiliary tool.

These conduits may be fed with individual flows directly from the hydraulic pressure supply of the pivot arm.

[0004] The mounting of these double conduits may cause problems. Conventionally, hydraulic arms are only provided with one pair of hydraulic conduit, such that when an auxiliary tool is to be arranged a new supply conduit needs to be arranged in parallel to the existing supply conduit. Further, on existing pivot arms the possibility of providing a supplementary pressure conduit may be very limited due to space availability and the difficulty of arranging the conduits in a protected manner on an existing pivot arm. Therefore, the installation of supplementary hydraulic lines is both cumbersome and expensive.

[0005] Hence there is a need of hydraulic system that is more flexible than existing systems and that provides the possibility of feeding both a tiltrotator and a high flow demanding auxiliary tool. SUMMARY OF THE INVENTION

[0006] It is an object of the present invention to provide a hydraulic system that has the possibility of feeding both a tiltrotator and a high flow demanding auxiliary tool and that is flexible in that it may be arranged on an existing hydraulic system.

[0007] According to a first aspect the invention relates to a hydraulic system for a tiltrotator and an auxiliary tool arranged on a pivot arm, excavator or the like, the hydraulic system comprising a pressure supply for pressurizing a hydraulic fluid and a common supply line for feeding the pressurized hydraulic fluid to the tiltrotator and, via the tiltrotator, to the auxiliary tool. A diverter valve is arranged at the end of the common supply line close to the tiltrotator, which diverter valve diverts the hydraulic fluid into two separate conduits, a first conduit being provided to the tiltrotator, and a second conduit being arranged through the tiltrotator to the auxiliary tool.

[0008] Such a hydraulic system may be implemented on both older and new hydraulic machines without cumbersome installations, and hence to a lower cost. Further this may be achieved with an improved functionality.

[0009] In one embodiment, the hydraulic system further involves a control unit for controlling the supply of hydraulic fluid, and wherein the control unit is arranged to increase the flow of hydraulic fluid in the common supply line in response to that the demand of hydraulic fluid to the auxiliary tool is increased, and to that the supply to the tiltrotator is throttled in, or downstream of, the diverter valve.

[0010] In this embodiment the functionality of both the tiltrotator and the auxiliary tool is guaranteed and achieved without interference between the different functions.

[001 1] In a specific embodiment, the tiltrotator comprises at least one inherent valve for controlling the functions of the tiltrotator, wherein the control unit is configured to control said at least one inherent valve in the tiltrotator to a decreased level when the flow of hydraulic fluid in the common supply line is increased in response to that the demand of hydraulic fluid to the auxiliary tool is increased.

[0012] In another specific embodiment, the diverter valve comprises a throttle valve leading to an output of the diverter valve to the first conduit to the tiltrotator and wherein the control unit is configured to control said throttle valve to a decreased level when the flow of hydraulic fluid in the common supply line is increased in response to that the demand of hydraulic fluid to the auxiliary tool is increased. The diverter valve may be a separate part of the tiltrotator, arranged close to the tiltrotator but clearly separated therefrom. The control of the diverter valve may however be made by the control unit in consideration with the control of the valve block on the excavator and in consideration of the control of the functions of the tiltrotator and the auxiliary tool.

[0013] In yet another specific embodiment, the tiltrotator is a part of the hydraulic system and includes a hydraulic swivel for providing swivelled hydraulic fluid to the auxiliary tool. The hydraulic swivel be arranged to swivel the high hydrauicl flow needed by the auxiliary tool, which depending on the size of the machine may be as much as about 200 l/min.

[0014] According to a second aspect the invention relates to a method of controlling a hydraulic system for providing hydraulic fluid to a tiltrotator and an auxiliary hydraulic tool via a common supply line. The method involves a step of, at or close to the tiltrotator, diverting the hydraulic fluid into two separate conduits by means of a diverter valve, a first conduit being provided to the tiltrotator, and a second conduit being arranged through the tiltrotator to the auxiliary tool.

[0015] In a specific embodiment, the flow of hydraulic fluid in the common supply line is governed in response to the one of the tiltrotator and the auxiliary hydraulic tool that in a specific instant demands the highest flow, and wherein the flow to the other of the tiltrotator and the auxiliary hydraulic tool is throttled if it is lower than what is provided in the common supply line.

[0016] In another specific embodiment, the flow of hydraulic fluid in the common supply line is governed in response to the demand of the auxiliary hydraulic tool whenever it is in use and wherein the flow to the tiltrotator is throttled if it is lower than what is provided in the common supply line.

[0017] In yet another specific embodiment, the flow of hydraulic fluid to the tiltrotator is throttled by one or more valves that are inherent in the tiltrotator.

[0018] In an alternative embodiment, the flow of hydraulic fluid to the tiltrotator is throttled by the step of throttling an output of the diverter valve to the first conduit leading to the tiltrotator to a decreased level.

[0019] Other embodiments and advantages will be apparent from the detailed description and the appended drawings. BRIEF DESCRIPTION OF DRAWINGS

[0020] An exemplary embodiment related to the invention will now be described with reference to the appended drawings, in which;

Fig. 1 shows a schematic embodiment of a hydraulic system in accordance with the invention, arranged on an excavator;

Fig. 2 shows a part of an embodiment of a hydraulic system in accordance with the invention, at the free end of a pivot arm; and

Fig. 3 shows a diverter valve of the hydraulic system shown in figures 1 and 2.

DETAILED DESCRIPTION OF EMBODIMENTS

[0021] Fig. 1 shows a wheeled excavator 10 with a boom 1 1 a and an arm 1 1 b that is pivotally arranged on the boom 1 1 a. Hydraulic cylinders are arranged to achieve the pivoting movement. At the free end 12 of the arm 1 1 b a tiltrotator 13 is arranged, and an auxiliary tool 14 in the form of a compactor is attached to the tiltrotator 13. A common supply line 15 is arranged to provide the tools arranged at the free end 12 of the pivot arm 1 1 with pressurized hydraulic fluid. The invention is specifically adapted for systems with a tiltrotator carrying an auxiliary tool with a high demand of hydraulic flow to function.

[0022] Typically, the inventive tiltrotator is of the type comprising a hydraulic swivel that allows a flow of hydraulic fluid of about 200 l/min to pass through it. This flow of 200 l/min is hence arranged to be provided to the high flow demanding auxiliary tool.

[0023] The excavator 10 comprises a cabin 24 in which is arranged a display 17 for displaying the mode and position of the tiltrotator 13 and the auxiliary tool 14 attached to the arm 1 1 b, a manoeuvring unit 18 for manoeuvring the tiltrotator 13 and the auxiliary tool 14. A hydraulic block 19 is provided on the excavator to regulate the hydraulic fluid and to provide hydraulic fluid to the functions demanding it. The hydraulic block 19 may be a part of the hydraulic system controlling the excavator functions or it may be a separate system. In the shown embodiment the hydraulic block 19 includes valves that control the cylinders on the boom 1 1 a and on the arm 1 1 b and it includes a valve that opens to the common supply line 15. A hydraulic pump feeds the hydraulic block 19 with pressurized hydraulic fluid that is distributed by the hydraulic block 19.

[0024] A control unit 25 is arranged to govern the hydraulic system of the tiltrotator 13. The control unit may be located in the cabin 24 or outside the cabin, e.g. on the tiltrotator 13 or on the arm 1 1 b. The control unit 25 is arranged to collect information from the manoeuvring unit 18 and to govern the hydraulic valves of the tiltrotator 13 and the hydraulic block 19 based on this information.

[0025] In accordance with the invention a diverter valve 16 is arranged on the arm 1 1 b at the end of the common supply line 15 close to the tiltrotator 13. The diverter valve 16 diverts the hydraulic fluid into two separate conduits, a first conduit 20 being provided to the tiltrotator 13, and a second conduit 21 being arranged through the tiltrotator to the auxiliary tool 14. In the shown embodiment the diverter valve 16 is a separate part positioned close to the tiltrotator. However, the diverter valve may also be arranged as an integrated part of the tiltrotator 13. Often, the space at or close to the tiltrotator is very limited such that a separate diverter valve is preferred. Further, a separate diverter valve may be provided to a system already including a tiltrotator, e.g. when the tiltrotator is complemented by a high flow demanding auxiliary tool.

[0026] A valve control 23, such as spool valve, is provided on the diverter valve 16 to control the output of the second conduit 21 between an open and a closed position. The diverter valve 16 comprises a communication unit arranged to receive commands from the control unit 25 and to control the valve control 23 in response to said commands.

[0027] The control unit 25 is arranged to control the supply of hydraulic fluid in the common supply line 15 by controlling the valve of the hydraulic block 19 of the excavator that opens to the common supply line 15. Further, the control unit 25 is arranged to control the tiltrotator 13 in dependence of the current supply in the common supply line 15. Specifically, the control unit 25 is arranged to control the specific valve of the hydraulic block 19 to increase the flow of hydraulic fluid in the common supply line 15 when the output of the diverter valve 16 to the second conduit 21 is controlled to an open position. As the flow of hydraulic fluid in the common supply line 15 is increased, the flow in the first supply line 20 will also increase. This results in that the tiltrotator, which is calibrated for a specific flow of hydraulic fluid, will race in the sense that it will rotate and/or tilt to a much higher degree in response to a certain input on the manoeuvring unit 18 compared to when it is fed with the normal flow of hydraulic fluid.

[0028] In short, the control unit 25 is arranged to control the supply of hydraulic fluid in the common supply line 15 to the diverter valve 16 in response to the current demand of hydraulic fluid downstream of the diverter valve 16. This may be achieved by controlling the valve of the hydraulic block 19 of the excavator that opens to the common supply line 15. Further, the control unit 25 is arranged to control the supply downstream of the diverter valve 16, by throttling the supply hydraulic fluid at or downstream of diverter valve 16. This may either be done by a physical throttling in, or downstream of, the diverter valve 16, or by controlling the outcome of a control signal in response to the current supply in the common supply line 15. For instance, an increased supply of hydraulic fluid in the common supply line 15 in response to an increased demand of the auxiliary device may be compensated by a more moderate opening of a valve controlling the rotator in response to a specific input.

[0029] In the inventive hydraulic system a racing tiltrotator is avoided in that all valves are controlled by the control unit 25. Specifically, the control unit 25 is configured to compensate the increased supply of hydraulic fluid in the common supply line 15 by achieving a corresponding throttling at another point in the hydraulic system. Such throttling of the supply of hydraulic fluid to the tiltrotator 13 may be achieved in direct response to that the output of the diverter valve 16 to the second conduit 21 is controlled to an open position. It may also be achieved in direct response to that the valve of the hydraulic block 19 is controlled to increase the flow of hydraulic fluid in the common supply line 15.

[0030] The compensative throttling may be achieved in different manners. In one embodiment the control unit 25 is configured to control one or more inherent valves in a valve block 22 of the tiltrotator 13. The inherent valves in a valve block 22 on the tiltrotator are arranged to control one function each of the tiltrotator. All these valves may be arranged to be compensated in response to an increased flow in in the first conduit 20. In another embodiment the control unit 25 is configured to control an output of the diverter valve 16 to the first conduit 20 leading to the tiltrotator 13. In the latter embodiment, the diverter valve 16 may comprise an adjustable throttling that may be set in at least two different positions; a first fully open position, and a second throttled position, having a reduced section with respect to the fully open position. The object of the reduced section is to avoid racing of the tiltrotator, which is achieved by maintaining the flow in the first conduit 20 at the same level as the fully open position would give in a normal flow of hydraulic fluid in the common supply line 15. The reduced section may e.g. be about 50 % the fully open position. In an advantageous embodiment, the throttling may be a flow regulated valve that adapts itself in response to the incoming flow such that a controlled and substantially constant flow is delivered to the tiltrotator regardless of the flow provided to the diverter valve via the common supply line 15.

[0031] Regardless of where the compensative throttling is achieved it may either be set to a set constant throttling or, in a more precision demanding embodiment, the control unit 25 may be arranged to control the valves such that a specific manoeuvring of the manoeuvre unit will result in the same output motion on the tiltrotator 13. This may be achieved in that the rotating and tilting sensors provided on the tiltrotator so as to verify the movements of the tiltrotator and to adapt the inherent valves of the valve block 22 on the tiltrotator so as to achieve a specific motion corresponding to a specific manoeuvring of the manoeuvre unit 18.

[0032] Above, the invention has been described with reference to a specific embodiment. It is obvious to a person skilled in the art that other embodiments are possible within the scope of the following claims.