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Title:
HYDRAULIC ROTATOR WITH EXTENDING VANES
Document Type and Number:
WIPO Patent Application WO/2019/233973
Kind Code:
A1
Abstract:
The invention relates to a hydraulic rotator (11) for rotating a tool with respect to a crane arm, the motor of the hydraulic rotator comprising a stator (14) and a rotor (15) rotatably arranged inside the stator (14), wherein the rotor (15) comprises vanes (18) that are biased to extend radially outwards from vane openings (17) in an external surface (16) of said rotor (15). The vanes (18) have a front portion (18a) of a rounded shape and side portions (18b) that are flat, wherein a minimal depth (dmin) between an inner circumferential surface (25) of the stator and the external surface (16) of the rotor (15) is greater than an extension of said front portion (18a) around the full circumferential of stator (14), such that said front portion (18a) will extend outside the vane openings (17) and such that said side portions (18b) are arranged to abut an edge (33) of the corresponding vane opening (17) through which it extends.

Inventors:
HARR JOAKIM (SE)
Application Number:
PCT/EP2019/064402
Publication Date:
December 12, 2019
Filing Date:
June 04, 2019
Export Citation:
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Assignee:
INDEXATOR ROTATOR SYS AB (SE)
International Classes:
B66C1/68; B66C3/00; E02F3/36
Domestic Patent References:
WO2003082725A12003-10-09
Foreign References:
EP2460758A12012-06-06
DE3146695A11983-07-07
Attorney, Agent or Firm:
EHRNER & DELMAR PATENTBYRÅ AB (SE)
Download PDF:
Claims:
CLAIMS

1. A hydraulic rotator (1 1 ) for rotating a tool with respect to a crane arm, the hydraulic rotator comprising a first attachment piece (12) for connection to a crane arm and a second attachment piece (13) for connection to a tool, said first and second attachment piece being rotatably connected to each other via a motor comprising: a stator (14) having an inner circumferential surface (25) and

a rotor (15), rotatably arranged inside the stator (14) to rotate around an axial axis (A), wherein the rotor (15) comprises vanes (18) that are biased to extend radially outwards from vane openings (17) arranged in a mid-portion (16b) of an external surface (16) of said rotor (15), wherein the inner circumferential surface (25) of the stator (14) comprises a circumferential track (32) arranged to receive said vanes (18), and wherein said track (32) includes at least two chambers (19a) having a maximal depth (dmax) between the inner circumferential surface (25) and said external surface (16) of said rotor (15) and two interposed shallow portions (19b) having a corresponding minimal depth (dmin) , said minimal depth (dmin) being substantially smaller than said maximal depth (dmax) but sufficiently deep to allow each vane (18) to partially extend out from the corresponding vane opening (17) of the rotor,

characterised in that the vanes (18) have a front portion (18a) of a rounded shape and that side portions (18b) of said vanes (18) are flat on both sides of each vane (18), wherein the minimal depth (dmin) is greater than an extension of said front portion (18a) such that, around the full circumferential of said track (32), said front portion (18a) is fully received into said track (32) to extend outside the vane openings (17) and such that at least one of said side portions (18b) of said vanes (18) is arranged to abut an edge (33) of the corresponding vane opening (17) through which it extends.

2. The hydraulic rotator (1 1 ) according to claim 1 , wherein the vane openings (17) are slightly wider than the vanes (18) such that a vane gap (31 ) exist between a vane (18) and a corresponding vane opening (17) and such that only one side portion (18b) of each vane (18) may be arranged to abut a corresponding edge (33) of the vane opening (17) through which it extends at a time.

3. The hydraulic rotator (1 1 ) according to claim 1 or 2, wherein each chamber (19a) and each shallow portion (19b) extend over the same or a greater angle than the angle formed between two adjacent vanes (18) such that at least one vane (18) is located in each chamber (19a) and each shallow portion (19b) at all times.

4. The hydraulic rotator (1 1 ) according to claim 3, wherein said minimal depth (dmin) in the shallow portions (19b) is constant for at least an angular portion corresponding to the angle formed between two adjacent vanes (18).

5. The hydraulic rotator (1 1 ) according to anyone of claims 3 or 4, wherein said maximal depth (dmax) in the chambers (19a) is constant for at least an angular portion corresponding to the angle formed between two adjacent vanes (18).

6. The hydraulic rotator (1 1 ) according to anyone of the preceding claims, wherein the inner circumferential surface (25) of the stator (14) is limited in an axial direction by a first circumferential rim (26) arranged to be in contact with a first axial end portion (28) of the vanes, and a second circumferential rim (27) arranged to be in contact with a second axial end portion (29) of the vanes (18), to guide said vanes (18) and to provide a sealing with respect to said vanes (18) along both the first and the second axial end portions (28,29) of the vanes (18).

7. The hydraulic rotator according to claim 6, wherein the stator (14) includes a first stator plate (14a), which is rigidly connected to the first attachment piece (12), a second stator plate (14c), and a stator frame (14b) arranged between said first and second stator plates (14a, 14c), wherein the inner circumferential surface (25) is defined by an inner surface of the stator frame (14b) in the radial direction, and wherein the height of the vanes (18) corresponds to a height of the stator frame (14b), the first circumferential rim (26) being formed by a first surface of the first stator plate (14a), and the second circumferential rim (27) being formed by a first surface of the second stator plate (14c).

8. The hydraulic rotator according to anyone of the claims 6 or 7, wherein the external surface (16) of the rotor (15) has a height (H2) that is greater than a height (Hi) between said first circumferential rim (26) and said second circumferential rim (27).

Description:
HYDRAULIC ROTATOR WITH EXTENDING VANES

TECHNICAL FIELD

[0001] The invention relates to a hydraulic rotator for rotating a tool with respect to a crane arm. Specifically, the invention relates to the configuration of a hydraulic vane motor in such a rotator.

BACKGROUND

[0002] Hydraulic rotators are widely used in foresting, harvesting or the like where a carrier, truck, tractor or the like carries such an apparatus to provide rotatable connection for excavators, timber tools, harvest tools or the like. The hydraulically driven apparatuses are arranged to the free end of a crane arm or the like. A rotator includes a motor, typically a hydraulic vane motor, to provide the rotational movement.

[0003] Such rotator arrangements are exposed to heavy forces both radially and axially. Conventionally, these heavy forces are handled by dimensioning the rotator arrangement and specifically the motor with components adapted to withstand very high efforts. In combination with this high mechanical demands the precision of the components, including the fit between the stator and rotor needs to be very accurate and precise.

[0004] To provide a motor with as small losses as possible the precision between the stator and rotor needs to be very exact, both axially and radially. This is due to the fact that each gap in the active part of the motor, i.e. the part of the motor where pressurised hydraulic fluid is present, will yield a loss in efficiency. The combination of this very high demand on the precision and the equally high demands on strength makes the production very difficult and costly.

[0005] A specific problem related to a vane motor is that the precision of the vanes with respect to the chambers of the stator needs to be very precise in order to minimize internal leakage. Further, in conventional vane motors, the vanes and/or an active part of the rotor will be exposed to axial forces acting on the rotor with respect to the active part of the stator. This may lead to that the motor will seize, unless the precision is very high or that the active parts of the rotor and stator are dimensioned to cope with axial forces to a satisfactory degree. This is more closely described in the first part of the detailed description of this specification, in which reference is made to a prior art hydraulic rotator.

[0006] Therefore, there is a need of a hydraulic rotator that has a good precision and that has a good capacity to carry high loads without stressing active parts of the motor. SUMMARY OF THE INVENTION

[0007] It is an object of the present invention to provide a hydraulic rotator with good precision and with a good tolerance with respect to external loads acting on the hydraulic rotator.

[0008] The invention relates to a hydraulic rotator for rotating a tool with respect to a crane arm, the hydraulic rotator comprising a first attachment piece for connection to a crane arm and a second attachment piece for connection to a tool, said first and second

attachment piece being rotatably connected to each other via a motor comprising;

a stator comprising an inner circumferential surface, and

a rotor, rotatably arranged inside the stator to rotate around an axial axis, wherein the rotor comprises vanes that are biased to extend radially outwards from vane openings arranged in a mid-portion of an external surface of said rotor, wherein the inner circumferential surface of the stator comprises a circumferential track arranged to receive said vanes, and wherein said track includes at least two chambers having a maximal depth between the inner circumferential surface and said external surface of said rotor and two interposed shallow portions having a corresponding minimal depth, said minimal depth being substantially smaller than said maximal depth but sufficient deep to allow each vane to partially extend out from the corresponding vane opening of the rotor. A front portion of the vanes has a rounded shape and side portions of said vanes are flat on both sides, wherein the minimum is greater than an extension of said front portion such that, around the full circumferential of said track, said front portion is fully received into said track to extend outside the vane openings and such that said side portions of said vanes are arranged to abut an edge of the corresponding vane opening through which it extends.

[0009] The construction with a gap between the outer surface of the rotor and the inner circumferential surface of the stator involves several advantages. Firstly, obviously, the outer surface of the rotor need not be exactly adapted to the inner circumferential surface of the stator, such that production costs may be cut. Instead, the rotor may be cylindrical with a constant cross-section and the demand for exactness of the axial bearing is thereby easy to achieve. Further though, this construction will involve less internal leakage than a

conventional hydraulic rotator.

[0010] The abutment between the said side portions of the vanes and the edge of the corresponding vane opening provides an efficient fluid tight sealing in operation.

[001 1] In a specific embodiment the vane openings are slightly wider than the vanes such that a vane gap exist between a vane and a corresponding vane opening and such that only one side portion of each vane may be arranged to abut a corresponding edge of the vane opening through which it extends at a time.

[0012] In a specific embodiment each shallow portion and each chamber extend over the same or a greater angle than the angle formed between two adjacent vanes such that at least one vane is located in each shallow portion and each chamber at all times.

[0013] With this arrangement is achieved that the chambers are separated from each other by the interaction between the shallow portions and the at least one vane that is located at said shallow portion. This interaction replaces the close interaction of partition walls of the stator and the outer surface of the rotor in prior art arrangements.

[0014] Preferably, said minimal depth in the shallow portions is constant for at least an angular portion corresponding to the angle formed between two adjacent vanes.

[0015] Similarly, said maximal depth in the chambers is preferably constant for at least an angular portion corresponding to the angle formed between two adjacent vanes.

[0016] This is advantageous because the pressure inside the motor may be very high, such that a difference in depth between the inner circumferential surface of the stator and the external surface of said rotor would give rise to unwanted variations in the output of the motor.

[0017] In a specific embodiment each chamber and each shallow portion extend over 60° or more, and wherein the rotor comprises at least 6 equidistantly arranged vanes.

[0018] In a specific embodiment the inner circumferential surface of the stator is limited in an axial direction by a first circumferential rim arranged to be in contact with a first axial end portion of the vanes and a second circumferential rim arranged to be in contact with a second axial end portion of the vanes, to guide said vanes and to provide a sealing with respect to said vanes along both the first and the second axial end portions of the vanes.

[0019] The contact between the respective axial end portions of the vanes and the corresponding circumferential rims provides a substantially fluid tight sealing above and below each vane.

[0020] In a specific embodiment the stator includes a first stator plate, which is rigidly connected to the first attachment piece, a second stator plate, and a stator frame arranged between said first and second stator plates, wherein the inner circumferential surface is defined by an inner surface of the stator frame in the radial direction, and wherein the height of the vanes corresponds to a height of the stator frame, the first circumferential rim being formed by a first surface of the first stator plate, and the second circumferential rim being formed by a first surface of the second stator plate.

[0021] In a specific embodiment the external surface of the rotor is substantially cylindrical and has a height that is greater than a height between said first circumferential rim and said second circumferential rim. Thereby, an upper and a lower cylindrical portion of the rotor may function as radial bearings for the rotor inside the stator.

[0022] Preferably the rotor extends both above said first circumferential rim and below said second circumferential rim. This construction implies that the circumferential rim support only the vanes in the axial direction, and not the rotor. The rotor may instead be supported by an axial bearing at the lower end, and by an axial contact between the rotor and the stator at the upper end of the rotor.

[0023] Other embodiments and advantages will be apparent from the detailed description and the appended drawings.

BRIEF DESCRIPTION OF DRAWINGS

[0024] An exemplary embodiment related to the invention will now be described with reference to the appended drawings, in which;

Fig. 1 , 1 a-1 bshow a prior art hydraulic rotator;

Fig. 2 is a side view of a hydraulic rotator according to a specific embodiment of the invention;

Fig. 3 is a sectional view taken along the line Ill-Ill in fig. 2;

Fig. 3a is a detailed view of detail A in fig. 3;

Fig. 4 is a sectional view taken along the line IV-IV in fig. 3;

Fig. 5 is a sectional view taken along the line V-V in fig. 3;

Fig. 6 is a sectional view taken along the line VI-VI in fig. 3;

Fig. 7 is a detailed view of quarter of the sectional view in fig. 3;

Fig. 8 is a perspective view of a rotor according to a specific embodiment of the

invention; Fig. 9 is a perspective view of a hydraulic rotator according to a specific embodiment of the invention with the first stator frame and first attachment piece removed;

Fig. 10 is a sectional view of a vane in rotor according to a specific embodiment of the invention;

Fig. 11 is a detailed sectional view of an outer portion of the vane in Fig. 10.

Fig. 12 is a detailed sectional view of an inclined vane in operation; and

Fig. 13 is a sectional view of an alternative embodiment of the inventive hydraulic

rotator.

DETAILED DESCRIPTION OF DRAWINGS

[0025] In Figs. 1 and 1A-1 C a prior art rotator is shown. This prior art rotator is not part of the invention. The shown prior art rotator 1 has a first attachment piece 2 for connection to a crane arm and a second attachment piece 3 for connection to a tool. The first attachment piece 2 is attached to a stator 4 and the second attachment piece 3 is attached to a rotor 5, the rotor being rotatably arranged inside the stator 4. As is shown in Fig. 1 B the stator is comprised of three parts; a first stator plate 4a which is integrated with the first attachment piece 2, a second stator plate 4c, and a stator frame 4b, which is the active part of the stator and is arranged between the first and second stator plates 4a and 4c.

[0026] The rotor 5 is arranged inside the stator 4, and the second part of the rotor 5 is connected to the second attachment piece 3. The rotor 5 comprises a cylindrical portion 6 that extends radially outside a main body of the rotor. The height of the cylindrical portion 6 corresponds to the height of the stator frame 4b and is arranged to be received between the first and second stator plates 4a and 4c, respectively. In order to make sure that hydraulic fluid will not leak along the edges of the cylindrical portion 6 of the rotor and the first and second stator plates 4a and 4c, respectively, the cylindrical portion 6 shall fit as tightly as possible between the first and second stator plates 4a and 4c. The cylindrical portion 6 is delimited by a first circumferential rim 6a and second circumferential rim 6b arranged to face inner circumferential edge portions of the first and second stator plates 4a and 4c, respectively.

[0027] The rotor 5 is rotatably supported by an axial bearing 10. Normally shims need to be provided between the axial bearing 10 and the rotor 5 in order to make sure that the cylindrical portion 6 of the rotor including the first and second circumferential rims 6a and 6b, respectively, is fylly received between the first and second stator plates 4a and 4c. [0028] The cylindrical portion 6 of the rotor comprises four vane openings 7 that extend along the axial axis of the rotor 5. In each vane opening 7, a spring biased vane 8 is arranged. The hydraulic motor is driven in either direction by providing a pressurised hydraulic fluid at a first side of the vanes and a non-pressurised hydraulic fluid at the opposite second side of the vanes. The height of the vanes 8 may correspond to the height of the cylindrical portion 6 of the rotor 5 such that the edge portions of the vanes 18 are arranged in line with the first and second circumferential rim 6a and 6b, respectively, or the vanes 8 may have a somewhat greater height than said cylindrical portion 6.The height of the vanes 8 should correspond to the height of the stator frame 4b, such that the vanes 8 fit tightly between the first and second stator plates 4a and 4c and are guided by said stator plates.

[0029] In Fig. 1 A a detailed sectional view of the rotor 5 and the stator frame 4b is shown. The rotation of the rotor 5 is achieved in that pressurised hydraulic fluid is provided to a first end of a chamber 9a, arranged in the stator frame 4b. Normally, the stator frame 4b comprises two chambers. Which are separated from each other by partition walls 9b, in which a fluid tight seal is provided between the cylindrical portion 6 of the rotor and the inner surface of the stator. The precision between the partition walls 9b and the cylindrical portion 6 of the rotor 5 needs to be very high in order to make sure that the hydraulic fluid will not leak from one chamber to another. When passing a partition wall 9b the vane 8 is fully received inside a vane opening 7, such that gaps appear on both sides of the rounded tip of the vane with respect to the vane opening 7. These gaps are a source for leakage of hydraulic fluid from one said of the vane 8 to the other, not immediately at the partition walls 9b as the partition provides a fluid tight seal. The leakage may appear close to the partition walls 9b, in a position where the tip of the vane 8 is partly inside the vane opening 7, wherein hydraulic fluid may flow into the vane opening 7 and escape past the vane 8, below and above the same.

[0030] In the inventive rotator, precision is achieved by an alternative construction.

[0031] Fig. 2 shows a specific embodiment of a hydraulic rotator 1 1 for rotating a tool

(not shown) with respect to a crane arm or the like (not shown). The shown hydraulic rotator comprises a first attachment piece 12 and a second attachment piece 13. In the shown embodiment the first attachment piece 12 is arranged for connection to said crane arm and the second attachment piece 13 is arranged for connection to said tool. The rotator 1 1 comprises a stator 14, comprised of a first stator plate 14a that in the shown embodiment is integrated with the first attachment piece 12, a second stator plate 14c, and a stator frame 14b, which is the active part of the stator 14 and is arranged between the first and second stator plates 14a and 14c, respectively. Attachment bolts 14d are arranged to hold the first and second stator plates 14a and 14c together, thereby securing the stator frame 14b between them. Such attachment bolts may be arranged through the stator frame 14b or, as in the shown embodiment, outside the stator frame 14b.

[0032] Fig. 3 is a sectional view taken along the line Ill-Ill in Fig. 2. From Fig. 3 it is apparent that a rotor 15 is rotatably arranged inside the stator 14 to rotate around an axial axis A (see Figs 4-6). The rotor 15 comprises vanes 18 that are biased to extend radially outwards from said rotor. The vanes 18 are arranged in vane openings 17 in an external surface 16 of the rotor 15. The external surface 16 of the rotor 15 is preferably substantially cylindrical. Except for the vane opening 18 the external surface 16 may be perfectly cylindrical. However, in view of that a central portion of the rotor 15, i.e. the portion from which the vanes 18 extend, will not be in contact with the surrounding inner circumferential surface 25 of the stator, said central portion of the rotor 15 need not be perfectly cylindrical.

[0033] The vanes are arranged to fit inside said vane openings 17 in a manner that allows no hydraulic fluid to leak past the vanes 18. A fluid tight seal between a vane 18 and a vane opening 17 is achieved in that the hydraulic pressure acting on a vane 18 will press said vane into close contact with the opposite side of the vane opening 17, thereby preventing any leakage along the length of said vane 18 as further described below.

[0034] Springs 21 are arranged to push the vanes 18 outwards from the vane openings 17 in the external surface 16 of the rotor 15. As is apparent from Fig. 3 the stator frame 14b comprises an inner circumferential surface 25 to receive the vanes 18. The inner circumferential surface 25 comprises at least two chambers 19a arranged to receive each vane 18 to a first extent, and at least two shallow portions 19b arranged to receive each vane of said vanes to a second extent, which is substantially less compared to said first extent. In the shown embodiment, the inner circumferential surface 25 comprises two chambers 19a and two shallow portions 19b, such that one chamber 19a is arranged between two shallow portions 19b, and vice versa.

[0035] The inner circumferential surface 25 of the stator delimits a track 32 arranged to receive at least a tip portion of the vanes 18 throughout the whole periphery of the stator. In contrast to prior art configurations a central portion 16b of the external surface 16 of the rotor 15 does not meet the inner circumferential surface 25 of the stator. In other words, no partition wall where the external surface 16 of the rotor 15 meets the inner surface of the stator 14 is arranged, such that at least a tip portion of the vanes 18 will extend out of the external surface 16 of the rotor 15 at all times. [0036] The track 32 is delimited in the axial direction by circumferential rims 26,27 arranged to be in contact with axial end portions 28,29 of the vanes to guide said vanes and to provide a sealing with respect to said vanes.

[0037] In Fig. 3 a first pair of hydraulic ports 22 are shown. This first pair of hydraulic ports 22 are arranged in the second stator plate 14c. A second pair of hydraulic ports are arranged in the first stator plate 14a (not shown). These second pair of hydraulic ports are arranged diagonally across the chamber 19a with respect to the first pair of hydraulic ports 22. In operation one pair of hydraulic ports at a time is connected to the pressure line and the other pair is connected to tank. When the first pair of hydraulic ports 22 is connected to the pressure line, the rotor 5 will rotate counter clockwise with respect to the view shown in fig. 3, and when the second pair of hydraulic ports is connected to the pressure line, the rotor 5 will rotate clockwise with respect to the view shown in Fig. 3.

[0038] As is apparent in Fig. 3, each shallow portion 19b extends over a greater angle than the angle formed between two adjacent vanes 18 such that at least one vane 18 is located at each shallow portion 19b at all times. Further, at least one vane must be located between the hydraulic ports of one chamber 19a at all times. In the shown embodiment this is achieved in that the rotor 15 comprises 6 equidistantly arranged vanes 18. Further, each shallow portion 19b and each chamber 19a has an angular extension of more than a sixth of a lap, i.e. at least 60°. Other embodiments are also possible. For instance, the stator may include three chambers and the rotor may include 9 vanes in order to guarantee that one vane 18 will be located at each shallow portion 19b at all times and that at least one vane must be located in each chamber 19a, between the respective hydraulic ports at all times.

[0039] As is apparent from Fig. 3 the gap between the inner circumferential surface 25 of the stator 14 and the external surface 16 of the rotor 15 in the shallow portions 19b, which is denoted the minimal depth dmin, is constant throughout each shallow portion 19b.

Preferably, it is constant for at least an angular portion corresponding to the angle formed between two adjacent vanes 18.

[0040] Similarly, the distance between the inner circumferential surface 25 of the stator 14 and the external surface 16 of the rotor 15 in the chamber 19a, which is herein denoted the maximal depth dmax, is constant throughout each chamber 19a. Preferably the maximal depth d max is constant for at least an angular portion corresponding to the angle formed between two adjacent vanes.

[0041] This is advantageous in view of that the pressure inside the motor may be very high, such that a difference in depth between the inner circumferential surface of the stator and the external surface of said rotor would give rise to unwanted variations in the output of the motor. Constant depths will provide a minimal output variation.

[0042] In order to achieve as long portions of constant depths as possible, the transition between the chambers 19a and the shallow portions 19b, e.g. ramps 33, should be held short, i.e. only cover a short angle. This will of course be a trade off with the

smoothness of the motor as these ramps 33 should not include a too steep inclination for the vanes to follow in both directions. In the shown embodiment with two chambers and two shallow portions and 6 vanes the ramps must have an angular extension of less than 30°, in order to allow each chamber and each shallow portion to span over at least 60°. Preferably, the extension of maximum 30° of each ramp should include the extension of a hydraulic port of the adjacent chamber 19a.

[0043] Fig. 3a is a detailed view of detail A in Fig. 3. In this view a vane 18 is shown in a position at a first end of the shallow portion 19b. If it will rotate counter clockwise it will enter the chamber 19a and pass the hydraulic port 22. The spring 21 will act to push the vane 18 outwards to abut the inner circumferential surface 25 of the stator and provide a fluid tight sealing with respect to said surface. As soon as the vane 18 will have passed the hydraulic port 22 it will be pressurized on its trailing side such that the hydraulic fluid will provide a torque forcing the vane 18 and the rotor 15 to rotate further counter clockwise. This will continue as long as the valves (not shown) are connected to provide pressurized hydraulic fluid to the first pair of hydraulic ports 22.

[0044] Figs. 4-6 are longitudinal sections of the hydraulic rotator corresponding to the lines IV-IV, V-V and VI-VI, respectively, in Fig. 3. Hence, Fig. 4 is a longitudinal section of the hydraulic rotator along the line IV-IV, showing a gap between the external surface 16 of the rotor 15 and the surface of the inner circumferential surface 25 of the stator frame 14b. This gap forms the shallow portion 19b. In Fig. 4 it is shown that the external surface 16 of the rotor 15 is cylindrical over the whole of the stator frame 14b, and more.

[0045] In the shown embodiment the external surface 16 of the rotor 15 extends both above and below the inner circumferential surface 25 of the stator 14, i.e. into both the first stator plate 14a and the second stator plate 14c of the shown embodiment. In other words, the external surface 16 of the rotor 15 has a height H 2 that is greater than a height Hi between a first circumferential rim 26 and a second circumferential rim 27. A central portion 16b of the external surface 16 of the rotor 15 is defined by the height of the vanes 18, which are extending out from said central portion. [0046] As illustrated in the drawings the external surface 16 of the rotor 15 is substantially cylindrical with a constant diameter over its axial length, from an upper cylindrical portion 16a, over the central portion 16b and into a lower cylindrical portion 16c. In other words the external surface 16 of the rotor 15 is cylindrical with a circular cross section over its axial length, from the first cylindrical portion 16a over the central portion 16b and into the second cylindrical portion 16c, but irregularities may be provided in the central portion 16b, and that vane openings 17 are provided with an extension from the upper cylindrical portion 16a, over the whole central portion 16b and into the lower cylindrical portion 16c. The upper cylindrical portion 16a and the lower cylindrical portion 16c should, except for the vane openings, preferably be circularly cylindrical so as to provide a fluid tight seal between the external surface 16 of the rotor 15 and the first and the second circumferential rims 26 and 27, respectively, and so as to provide radial bearings for the rotor, above and below track 32.

[0047] An axial bearing 20 is arranged between supporting surfaces of the rotor 5 and the second stator plate 14c. The axial bearing 20 will support forces acting downwards on the rotor 5. The first stator plate 14a comprises an abutment 23 arranged to interact with a shoulder 24 on the first portion of the rotor 5. The interaction between said abutment 23 and said shoulder 24 will handle forces acting upwards on the rotor 5, e.g. when the tool is pushed down into the ground.

[0048] An advantage of the shown embodiment is that the axial forces will not be handled in the interaction between the active parts of the motor, i.e. the rotor 15 and the stator frame 14b. The vanes 18 are preferably arranged in a slidable manner inside the vane openings 17, such that they may be translated in the axial direction. The flexibility with regard to the axial position of the vanes 18 will assure a perfect positioning of the vanes 18 with respect to the stator. The inner circumferential surface 25 of the stator forms a track in which the vanes 18 are received, which track 32 is axially delimited by the two circumferential rims 26 and 27.

[0049] The first circumferential rim 26 is arranged to be in contact with a first axial end portion 28 of each vane 18, and the second circumferential rim 27 is arranged to be in contact with a second axial end portion 29 of each vane 18. The height of the vanes 18 is adapted to fit tightly between the first circumferential rim 26 and the second circumferential rim 27. The contact between the circumferential rims and the vanes is configured both to guide said vanes and to provide a sealing with respect to said vanes along both the first and the second axial end portions 28 and 29 of the vanes 18. [0050] It should be noted that the external surface 16 of the rotor 15 extends both into the first stator plate 14a and into the second stator plate 14c, whereby the external surface 16 of the rotor 15 will provide a fluid tight seal with respect to both the first stator plate 14a and second stator plate 14c. For this reason, the upper and lower parts 16a, 16c of the external surface 16 of the rotor 15 should be cylindrical and fit tightly inside the inner circumferential surfaces of the first stator plate 14a and second stator plate 14c, respectively. In a specific embodiment at least one of the first stator plate 14a and second stator plate 14c is integrated with the stator frame 14b, such that the limit between the stator frame 14b and said stator plate 14a and/or 14c will be defined by the circumferential rim 26 and/or 27.

[0051] In Fig. 5, which is a longitudinal section of the hydraulic rotator along the line V- V in Fig. 3, the vanes 18 are shown in a position where they extend into the shallow portion 19b of the inner circumferential surface 25 of the stator. In this position, only the tips of the vanes 18 including the front portion 18a extend out from the external surface 16 of the rotor 15 and into contact with the inner circumferential surface 25 of the stator 14. The contact between the tips of the vanes 18 and the circumferential rims 26,27 is sufficient to provide guiding of the vanes 18, such that they will not move in the axial direction. Further, said contact will provide a sealing between the vanes and the stator 14. From Fig. 5 it is apparent that the vane openings 17 have a greater height than the vanes 18. A gap is hence available in the vane openings 17 above and below the vane 18. The gap allows the vane to move along the axial direction with respect to the vane opening 17 of the rotor 5.

[0052] Fig. 6 is a longitudinal section of the hydraulic rotator along the line VI-VI in Fig. 3. In this position the shown vanes 18 are located in the middle of the chamber 19a formed in the space between the external surface 16 of the rotor 15 and the inner circumferential surface 25 of the stator 14. As is apparent from Fig. 3, the chambers 19a are formed in that the stator frame 14b comprises two widened portions arranged opposite to each other, both having a maximal depth d max·

[0053] The fact that no partition walls are present in the rotor apparatus 1 1 , and that instead the vanes 18 are arranged to provide the sealing between the chambers will imply that a foremost vane in the shallow portion 19b will act in a direction opposite to the current rotational direction of the rotor. This is illustrated in Fig. 7, which is a close-up representing a quarter of the rotator shown in Fig. 3.

[0054] In Fig. 7 the rotor is rotated counter clockwise. A foremost vane 18’ in the shallow portion will rotate opposite the pressure provided in the chamber 19a. The force F 0 resulting from the pressure acting on this foremost vane 18’ will be neutralised by the force Fo acting in the opposite direction on the innermost portion of the active vane 18” extending into the chamber 19a. The resulting torque that acts to push said active vane 18” in the counter clockwise direction is hence based on the integral of the force Fi over the active surface of the active vane 18”. At least one of the vanes will always be active, i.e. subjected to a high pressure on one side, at a time. In the shown embodiment two vanes, i.e. one vane per chamber will be active, at all times. This is achieved in that the chamber is wider, i.e. spans over a wider angle, than the distance between two adjacent vanes. In this way the foremost vane 18’ will enter the chamber 19a and be put under pressure by the hydraulic fluid before the active vane 18” will have been relieved from pressure. Hence, when the foremost vane 18’ is put under pressure it will become the active vane.

[0055] The depth of the shallow portion 19b will hence not contribute to torque of the hydraulic motor. Therefore, the shallow portion 19b has a minimal depth dmin, which should be kept as shallow as possible. The minimal depth d min of the shallow portion 19b is in the shown embodiment defined by the length of the first circumferential rim 26 and the second circumferential rim 27, and in order for said first and second circumferential rims 26 and 27 to provide a reliable guiding of the vanes, they should preferably be at least some millimetres wide, but since their widths implies a trade-off on the torque, it may be kept smaller. The minimal depth d min is therefore decided in dependence of the intended application of the rotator.

[0056] In Fig. 8, a rotor 15 in accordance with a specific embodiment of the invention is shown. The rotor 15 comprises an external surface 16 in which vane openings 17 that extend in the axial direction of the rotor are arranged. On either end of the external surface 16 a shoulder 24 is arranged to provide a support surface to act against a corresponding surface inside the stator 14, typically the axial bearing 20 arranged at the second stator plate 14c and an abutment arranged in the first stator plate 14a. In the shown embodiment, the rotor is connected to a swivel 30, arranged to provide a swiveled hydraulic fluid to the tool arranged at the second attachment piece.

[0057] In Fig. 9, the rotor is shown at location inside the stator frame 14b. The first stator plate arranged to be provided above the stator frame 14b is removed for illustration purposes in Fig. 9. As is apparent in Fig. 9, the height of the vanes 18 correspond to the height of the stator frame, such that when the first stator plate 14a is arranged it will fit tightly above the vanes and provide a fluid tight sealing with respect to the first axial end portion 28 of the vanes 18. Similarly, the second stator plate 14c will provide a fluid tight sealing with respect to the second axial end portion 29 of the vanes 18. [0058] In Fig. 9, it is illustrated how an upper cylindrical portion 16a of the rotor 15 extends above the stator frame 14b to abut the inner surface of the first stator plate 14a around its whole circumference. Similarly, a lower cylindrical portion 16c of the rotor 15 is arranged to abut the inner circumferential surface 25 of the second stator plate 14c. (see Fig. 5 and 8) The interaction between the respective first and second cylindrical surfaces 16a and 16c, respectively with the first and second stator plate 14a and 14c, respectively, constitute radial bearings adapted to take up radial forces acting on the rotor 15 with respect to the stator 14.

[0059] Fig. 10 is a view of a vane 18 extending into a 19b of the track 32 between the inner circumferential surface 25 of the stator 14 and the external surface 16 of the rotor 15, and Fig. 1 1 is a detailed view of the tip of said vane 18.

[0060] As illustrated in Figs. 10-1 1 each vane 18 has a front portion 18a of a rounded shape, wherein side portions 18b of the same vane 18 are flat on both sides thereof. With respect to prior art vane the inventive vane 18 has a less curved front portion 18a, in order to achieve a small extension of said front portion. Namely, the depth of the shallow portion 19b of the track 32, corresponding to the minimal depth d min between the inner circumferential surface 25 of the stator 14 and the external surface 16 of the rotor 15, needs to be greater than the extension of said front portion 18a such that said front portion 18a is fully received into said track 32 to extend outside the vane openings 17. Thereby, the side portions 18b of said vanes 18, which are substantially flat, are arranged to abut an edge 33 of the

corresponding vane opening 17 through which it extends and provide a fluid tight seal there between. The shallow portions 19b are the shallowest parts of the circumferential track 32. Therefore, said front portion 18a of each vane is fully received into said track 32 so as to extend outside the vane openings 17 around the full circumferential of said track 32.

[0061 ] A transition point 18c may be determined at each side of the vane 18 at the point where the rounded shape of the front portion 18a is has transitioned into the flat side portions 18b. The shallow portions 19b shall hence have a minimal depth d min that exceeds the extension of the curved front portion 18a in the radial direction of the rotor whereby the transition point 18c will be located outside vane opening 17 through out the full lap in the track 32.

[0062] As illustrated in Fig. 1 1 the vane openings 17 are slightly wider than the vanes 18 such that a vane gap 31 exist between a vane 18 and a corresponding vane opening 17. In the drawing, a small vane gap 31 is apparent on both sides of the vane 18. However, in operation, the vane is pressurized such that it will pushed in either direction depending on which side is currently being pressurized.

[0063] As is illustrated in Fig. 12, only one side portion 18b of each vane 18 will abut a corresponding edge 33 of the vane opening 17 through which it extends at a time. This abutment provides a fluid tight sealing line such that no hydraulic fluid will pass this line. A gap 31 will hence be apparent only on one side of the vane 18, between a side portion 18b of the vane 18 and the corresponding side of the vane opening 17. The outer end of the curved front portion 18a will provide a seal with respect to the the inner circumferential surface 25 of the stator 14, and the not shown axial end portions 28,29 of the vane will provide a seal with respect to the circumferential rims 26,27. See e.g. Fig 6.

[0064] As indicated above, the chamber 19a preferably has a constant depth d max between the hydraulic ports, such that the vane 18 will not be forced to move in or out with respect to the vane opening 17 as long as said vane 18 is put under great pressure. This is advantageous as it minimises wear at the contact lines of the vane 18 with respect to the vane opening 17, e.g. at the edge 33 of the vane opening 17 and at an inner end 34 of the vane 18.

[0065] In figure 13, an alternative embodiment of the inventive hydraulic rotator is shown. This alternative embodiment is similar to the embodiments shown in figures 2-12 with respect to all details that are crucial for the invention. Specifically, the height H 2 of the external surface 16 of the rotor 15 is greater than the height Hi of the inner circumferential surface 25 of the stator 14 as defined by the first and second circumferential rims 26 and 27 of the stator 14.

[0066] A major difference of this alternative embodiment is however that the first attachment piece 12 is arranged for connection to a tool and the second attachment piece 13 is arranged for connection to a crane arm. Further, a transmission unit 31 is arranged to transmit the rotational movement between the second attachment piece 13 and the rotor 15. An external axial bearing 20’ is arranged to allow the first and second attachment pieces 12 and 13 and to handle the forces acting on the rotator. In view of that the rotor 15 has a cylindrical external surface 16 without rims or the like, no axial positioning is needed and there is hence no need for shims. The vanes 18 will adapt to the given position thanks to the axial oversize of the vane openings 17.

[0067] Above, the invention has been described with reference to specific

embodiments. The invention is however not limited to this embodiment. It is obvious to a person skilled in the art that other embodiments are possible within the scope of the following claims.