Field of the Invention The invention relates to a rotator for a jig-carried tool in accordance with the preamble of claim 1.

Background of the Invention

A problem experienced with rotators for a jig-carried

tool/working implement at an external end of a crane arm or jib resides in the ability to i.a. orientate hoses and

possibly also cables in a rotational manner in respect of the driver of a vehicle provided with said crane arm or jib. The driver must constantly be on his/her guard with regard to the choice of tool rotation, so as to avoid hose breakages.

Externally disposed hose loops are vulnerable to damage and consequently discrete or protected hose orientation is

desirable .

It is known to provide a rotator with means for determining the relative position of rotation between rotor and stator. Said means include a pulse emitter and a number of pulse generating elements such as grooves or teeth. However, by said means it is only possible to determine the relative position of rotation between the rotor and the stator, and it is also sensitive to debris.

Due to increased automatization in forestry there is a demand for forwarders having automatically guided tools/working implements, such as grips, and also for wood harvesters having automatically guided harvesting units, so that the position of rotation of the tool can be determined, preferably the

absolute position. This enables repeating movements, for instance, of the tool can be programmed and thus the work of the driver much simplified. By such programming, also less skilled drivers will increase their performance.

Moreover, by such automatically guided tools the precision of positioning the tools will be much improved, and it will also be possible to reduce the linear velocity of pistons of hydraulic cylinders at its end positions so as to reduce impacts .

Furthermore, by such automatization it will be possible to detect when the rotator approaches the set target angle of rotation and thereby start a decelerating of the rotation of the rotator and thus the load carried by the rotator so as to be able to avoid over-rotation of the rotator.

One object of the present invention is to provide a rotator, which will significantly simplify the work required from the driver of the vehicle and enable a high degree of

automatization to be achieved.

Furthermore, by the inventive rotator it is also possible to prevent hose breakages and cable breakages as a result of wrong rotation of the tool.

Moreover, by absolute position is meant that the each position is unique. This means that a control system for the rotator does not need any reference position and that it is not necessary, at upstart, to rotate the rotator to find the reference position. During maintenance of the tool/working implement, for instance, said tool/working implement may be rotated by hand which means that the position of rotation is different from the position of rotation when the work was stopped. This is a very important safety aspect, particularly when the rotator carries a harvesting unit. Summary of the Invention

The object of the invention is to eliminate wholly or partly the above-identified drawbacks of the prior art. According to the invention this object is achieved by a rotator for a jib-carried tool, said rotator comprising a stator and a rotor, characterized in that said rotator

comprises a device for determining an absolute position of rotation between the stator and the rotor, that said device for determining the absolute position of rotation comprises an encoder in the form of a ring shaped magnetic means

surrounding the rotor, and further comprises a sensor, that said sensor being able to determine the absolute position of rotation between the stator and the rotor, and that said encoder being arranged rotationally fixed relative to the stator and the sensor being arranged rotationally fixed relative to the rotor, or vice versa.

Embodiments of the invention are defined in the appended dependent claims. Brief Description of the Drawings

The invention is described in more detail below in the form of a non-limiting example, reference being made to the

accompanying drawing, in which

- Fig. 1 is a schematic side view of a so-called single grip harvesting unit connected to a crane arm or jib through the medium of the inventive rotator,

- Fig. 2 is a sectional side view of the rotator according to the invention in a first embodiment,

- Fig. 3 is an exploded view of the rotator shown in Fig.2 in its normal working position, - Fig. 4 shows the same view as in Fig. 3 but upside-down,

- Fig. 5 is a sectional view of the rotator according to the invention in a second embodiment taken along section A-A in Fig. 6,

- Fig.6 is a view from below of the rotator shown in Fig. 5

- Fig. 7 is an exploded view of the rotator shown in Fig.5 in its normal working position, and

- Fig. 8 shows the same view as in Fig. 7 but upside-down. Detailed Description of Preferred Embodiments

Regarding expressions such as upper and lower wall these are to be understood as seen in relation to Fig. 1 of the rotator.

Fig. 1 shows a working implement/ tool 1 in the form of a so- called single-grip harvesting unit 1 which is suspended from the tip 2 of a machine-carried jib/crane arm 3 through the medium of a rotator 10 according to the invention. The rotator 10 is connected via a link arrangement or a swing damper 4, for instance, to the tip 2 of the jib/crane arm 3 and allows the tool to swing relative to the tip 2 of the jib/crane arm

3. The rotator 10 enables the tool 1 to be rotated relative to the tip 2 of the jib/crane arm 3. Hydraulic medium (oil) is supplied to the rotator 10 and to the tool 1 through hoses 5, 6, and possible electrical cables 7 for the device for

determining the absolute position of rotation and the tool are provided. The connection of the hoses 5 to a vehicle-carried source of hydraulic medium is not shown.

Figs. 2-4 illustrate a first embodiment of the rotator 10 according to the invention, said rotator 10 includes a stator 20 and a rotor 30. The stator comprises i.a. an upper stator wall 21 provided, at an upper side, with attachment means 22, preferably in the form of two attachment lugs 22a, 22b arranged in pairs, for swiningly attachment to the tip 2 of the

machine-carried jib/crane arm 3, a stator ring 23 and a lower wall 24, which is connected, via the stator ring 23, to the upper stator wall 21 preferably by bolts 25. The rotor 30 being rotationally contained within the stator 20 by said upper and lower wall 21,24 and said stator ring 23.

As seen in Fig. 2, a device 40,50 for determining the absolute position of rotation between the stator 20 and the rotor 30 is arranged at the lower wall 24 of the rotator 10, and signals from the device 40,50 being transmitted to a processor means (not shown) either by wired or wireless communication for further processing.

Hence, according to an embodiment of the present invention, the processor means receives sensor signals from the sensor and process said signals for determining the absolute position of rotation between the stator 20 and the rotor 30. The processor means may e.g. be a CPU configured to execute suitable detection or determining algorithms in this respect. The CPU may be a dedicated processor unit or a processor unit also configured to perform other processing. The processor means may also use the determination of the absolute position in one or more control algorithms for controlling the rotator, the jib-carried tool or any associated cranes, machines, motor vehicles, etc. Therefore, the processor means may also output one or more control signals for controlling the rotator, the jib-carried tool or any associated cranes, machines, or motor vehicles .

From Figs. 2 to 4 it can be seen that said device 40,50 for determining the absolute position of rotation comprises an encoder 40 in the form of a ring shaped magnetic means surrounding the rotor 30, as seen in radial direction of said rotor, and a sensor 50. In the embodiment shown, said encoder 40 is arranged rotationally fixed relative to the stator 20, and said sensor 50 is arranged rotationally fixed relative to the rotor 30. In a second embodiment, to be described below, said encoder 40 and said sensor 50 is arranged vice verse relative the stator 20 and the rotor 30, respectively.

In a preferred embodiment, as seen in Figs. 2 and 4, the encoder 40 has a groove 41 into which a protruding tip 51 of said sensor 50 protrudes so as to enabling determination of the absolute position of rotation between the stator 20 and the rotor 30. Thus, upon rotation of the rotor 30 the

protruding tip 51 is adapted to run in said groove 41 and detect the changes in the magnetic field. To protect the groove 41 from the harsh environment

experienced by the rotator 10, such as debris from processed timbers, water, sand, etc. a groove enclosing means 60 is arranged for enclosing said groove 41. Said groove enclosing means 60 has the form of a flat ring of sheet metal or

plastic, for instance. More particularly, the encoder 40 is preferably shaped as a U and the groove enclosing means 60 is adapted to abut the ends of the legs of the U via at least one intermediate sealing. In one embodiment the encoder 40 is provided with at least one sealing means 42 extending in the circumferential direction of the groove and arranged on each leg/side 43 of said groove 41 and at the end of each leg/side 43. The sealing means can be in the form of an O-ring arranged in a recess formed at the external end of each leg/side 43.

More particular, said groove enclosing means 60 and said encoder 40 are enclosed between the lower wall 24 of the stator 20 and an upper wall 71 of an attachment 70 (Fig. 2) for the jib-carried tool. Said attachment 70 is detachably connected to the rotor 20.

As shown in Figs. 2-4 said tip 51 of said sensor 50 protrudes through a hole 61 in said groove enclosing means 60 and into said groove 41. Possibly a sealing (not shown) is provided between the sensor 50 and the groove enclosing means 60, and the sensor 40 is fixedly attached to the groove enclosing means 60.

Said encoder 40 and said groove enclosing means 60 are

arranged to rotate relative to each other during operation of said rotator 1.

More particular, in the embodiment shown in Fig. 2-4, which preferably is used in the case the jib-carried tool is a harvesting unit, the groove enclosing means 60 with attached sensor 50 is rotationally fixed relative to the attachment 70 which is arranged to rotate (by the rotor) relatively to the encoder 40 which is rotationally fixed relative to said lower wall 24 of the stator 20. Preferably the sensor 50 is arranged within a socket 55. To improve the sealing between the sealing means 42 and the groove enclosing means 60 at least one elastic means 80 is provided between the upper wall 71 of the attachment 70 and a lower wall 62 of said groove enclosing means 60 so as to bias said groove enclosing means against the sealing means 42. In a preferred embodiment said at least one elastic means 80 consists of a plurality of spring means 80, preferably

compression springs.

In Figs.5-8 a second embodiment of the inventive rotator 10' is shown. In the second embodiment the same technical means are denoted by the same reference characters as in the first embodiment with the exception of

The main difference between the first and second embodiment is that, in the second embodiment, the device 40', 50' for

determining the absolute position of rotation between the stator 20' and the rotor 30' has been arranged reversed, that is to say that the encoder 40' is arranged rotationally fixed relative to the rotor 30' , and the sensor 50' is arranged rotationally fixed relative to the stator 30' . This means that the orientation of the encoder 40' and sensor 50' is upside- down as compared to the orientation of the encoder 40 and sensor 50 in the first embodiment.

As shown in Figs. 5, 7 and 8 a seat 90 is arranged which supports the encoder 40' . More particularly, the seat 90 has two ridges 92 enclosing a recess 91 in which the encoder 40' is confined. The seat 90 together with the encoder 40' is biased towards the groove enclosing means 60' by said at least one elastic means 80' as in the first embodiment so as to seal the groove 41 from the environment. In an embodiment not shown each ridge 92 of the seat 90 can be provided with a sealing means possibly instead of the sealing means 42' or in combination with the sealing means 42' of the encoder 40' .

The second embodiment of the rotator 10' is preferably used in the case the jib-carried tool is a grip.

In a third embodiment of the inventive rotator (not shown) the groove enclosing means may be formed of either the upper wall 71 of the attachment 70 for the jib-carried tool or the lower wall 24 of the stator 20. In such a case at least one sealing is formed at least between said stator and said attachment for the jib-carried tool preferably at the periphery of a parting line between said stator and said attachment for the ib- carried tool. The sealing is arranged radially externally of the device 40,50; 40', 50' for determining the absolute

position of rotation. In such case the encoder 40,40' may or may not be provided with the sealing means 42, 42' .

Although, not shown on the drawings, it should be noted that the inventive rotator 10,10' is able to perform two- or three- dimensional movements, i.e. in case of three-dimensional movements the rotator being a so called tiltrotator.

The device 40,50; 40', 50' for determining the absolute

position of rotation comprises in a preferred embodiment a magnetic field sensor 50; 50' and an encoder 40; 40' in the form of a ring shaped encoder body 40; 40' having multiple magnetic regions producing characteristics for magnetic fields, where each magnetic field comprises a radial and axial magnetic field component. The magnetic field components are combined to a magnetic field vector. The magnetic field vector is inclined at a certain angle against the ring plane, where the angle changes along a periphery of the encoder body. This enables the magnetic field sensor 50; 50' to determine a specific point along the periphery of the encoder body 40; 40', i.e. an absolute position along the periphery of the encoder body without having to refer to a zero point. Thereby, the absolute position of rotation between the stator 20;20' and the rotor 30; 30' can be provided. A device of this type if known by EP 2 568 259 Al .

Furthermore, by using a magnetic device for determining the absolute position of rotation there are no mechanical means that can be worn out. The invention is thus not limited to what is described and shown, since modifications and variations are naturally possible within the scope of the accompanying claims.