Bearing arrangement in an actuator of a forest machine

A bearing arrangement in an actuator of a forest machine comprising a frame of the actuator, which frame defines a first opening. The bearing arrangement also comprises a bushing, at least part of the bushing arranged in the first opening, the bushing defining a second opening, at least part of an axle and/or a bearing being arranged in the second opening, the axle or bearing being arranged stationary or movable in relation to the bushing, and the bushing being removable from the frame of the actuator. Further, a method for maintaining an actuator of a forest machine, the actuator comprising a bearing arrangement of the described type. In the method, a second, corresponding bushing is provided, which is fitted for said first opening; said bushing is removed from the frame of the actuator, wherein said first opening is exposed; and said second bushing is installed in said first opening.

FIELD OF THE DISCLOSURE

The invention relates to bearings. The invention relates to bearings of work equipment. In particular, the invention relates to bearings in actuators of work equipment, such as forest machines.

BACKGROUND

Various bearings are used in machines. By means of a bearing, a machine part, such as an axle and/or a tool, is arranged to rotate or swivel with respect to another part of the machine, such as the body. In long-term use, the bearings and the body of the machine are worn. Particularly in work equipment, bearings are subject to relatively strong forces, whereby the wear of the bearings and the body is intense compared with some other uses, in which the effective forces are weaker. Due to the wear of the bearings, the machine has to be maintained at times. In solutions of prior art, clearance caused by wear of the body of the machine is difficult to correct, if it can be corrected at all.

SUMMARY

In this description, a bearing solution will be presented for, or in, an actuator of a forest machine, whereby the maintenance of the machine is facilitated to a significant extent. Furthermore, the maintenance interval is increased, thanks to the material choices and/or lubrication and/or shielding. Furthermore, the requirements on the quality and/or precision and/or alignment precision of the machining of the actuator at the manufacturing stage are decreased, whereby the manufacture will be faster and less expensive.

In an embodiment, the bearing arrangement in an actuator of a forest machine comprisesa frame for the actuator of the forest machine, defining a first opening,a bushing, at least part of which is arranged in the first opening,the bushing defining a second opening, in which at least part of an axle and/or a bearing is arranged, which axle or bearing is arranged stationary or movable in relation to the bushing, andthe bushing being removable from the frame of the actuator of the forest machine.

Furthermore, a method is presented for maintaining an actuator of a forest machine. In an embodiment of the method, the actuator of the forest machine to be maintained comprisesa frame of the actuator of the forest machine, which defines a first opening, anda bushing, at least part of which is arranged in the first opening,the bushing defining a second opening, in which at least part of an axle and/or a bearing is arranged, which axle or bearing is arranged stationary or movable in relation to the bushing. In the method,a second, corresponding bushing is arranged available, which bushing is fitted for said first opening,said bushing is removed from the frame of the actuator of the forest machine, wherein said first opening is exposed, andsaid second bushing is installed in said first opening.

InFIGS. 1ato5b, corresponding numbers or symbols are used for corresponding parts.

DETAILED DESCRIPTION

FIG. 1ashows a forest machine200. The forest machine200comprises a base machine210. The forest machine200also comprises a traverser and a crane220mounted on the traverser. The crane220comprises booms, for example a hoist boom, a stick boom, and an extension boom. A rotating device, i.e. a rotator, is provided at the head of the crane220. Furthermore, a tilting device, i.e. a tilter, is provided at the head of the crane. An actuator100is provided at the head of the crane, for example connected to the rotator and/or the tilter. The work equipment200ofFIG. 1is of the forest machine type, more precisely a harvester, for felling, delimbing and cross-cutting trees in a forest into logs of desired length. In the work equipment200shown in the figure, the actuator100is a harvester head. The harvester can be used for implementing the harvesting steps from felling to stacking. Another commonly used forest machine is a forwarder (not shown in the figure), which refers to a forest machine designed for transporting timber. Harvesters are also known which can be used for harvesting timber in a forest as well as for transporting the timber away from the forest. Such a harvester can also be called a combined machine, because properties of a harvester and a forwarder are combined in it.

FIG. 1bshows another forest machine200. The forest machine200ofFIG. 1bis an excavator which can be used not only for excavating but also, for example, for hoisting stumps.

FIG. 1cshows an actuator100of a forest machine in more detail. The actuator100comprises various tools150,150a-150e. Typically, such tools comprise a part that can be swivelled or rotated with respect to the frame of the actuator, whereby the arrangement comprises, in a corresponding way, at least a bearing and in many cases also an axle. Reference numeral152indicates the blade of a tool. In addition or alternatively, the actuator100can also be called an actuator arrangement or an actuator assembly.

The actuator100of the forest machine200typically comprises parts configured to be swivelled with respect to each other, such as the frame110of the actuator and the axle130of the tool, or the tool150and its axle130. The swivelling of the parts with respect to each other is implemented by means of a bearing140or bearings.

In the use of the actuator of the forest machine, it is typical that said swivelling is slow and/or the swivel angles are relatively small. For example, in some cases the swivel angle can be not larger than 360 degrees, in some cases not larger than 180 degrees, and in some cases not larger than 90 degrees. For example, for swivelling the blade of a saw, it may be sufficient to swivel the blade about 90 degrees. Furthermore, the swivelling of the parts of a tool is typically relatively slow, for example not more than 60 rotations per minute (60 rpm), not more than 30 rpm, or not more than 10 rpm. Moreover, the actuator should preferably be compact and light-weight within permissible strength limits. For these reasons, the bearing solution for the present actuator is advantageously a sliding bearing solution, although in principle it would be possible to apply rolling bearings as well.

The bearings in an actuator of a forest machine are wherein they are subjected to great forces when used. As a result, the bearings and the parts in contact with them are subjected to significant wear. Therefore, the actuator has to be maintained at times. The bearing is typically replaceable. However, in addition to the bearing, the frame of the actuator may be subjected to wear when the actuator is in use. Installing a new bearing in the worn-out frame of the actuator will not repair the actuator, because the worn-out frame will be too loose for the new bearing. As a repair operation, replacing the frame of the actuator corresponds to the replacement of the whole actuator, in terms of difficulty.

By means of the solution to be presented, the operations for maintaining the actuator become significantly simpler. In addition, the solution to be presented allows a larger variety of materials for the actuator. For example, the frame of the actuator may be made of weldable steel, but the bushing may be made of a steel grade that is more resistant to wear. Furthermore, the solution to be presented provides a greater alignment tolerance for the opening of the frame of the actuator, as will be presented in more detail hereinbelow. Moreover, the solution to be presented provides a lower quality requirement for the machining of the frame of the actuator, as will be presented in more detail hereinbelow. Consequently, the solution to be presented not only makes the maintenance easier but also increases the service life and reduces the manufacturing costs.

FIGS. 2aand2bshow a bearing arrangement104in an actuator100of a forest machine200. With reference to theFIGS. 2aand2b, the bearing arrangement104comprisesa frame110of the actuator100of the forest machine, delimiting a first opening112, anda bushing120, at least part of which is arranged in the first opening112.

The bushing120delimits a second opening122in which at least part of an axle130and/or at least part of a bearing140is arranged. If at least part of the axle130is arranged in the second opening122, as shown inFIG. 2a, the axle130is arranged stationary or movable, such as swivellable or rotatable, with respect to the bushing120. If at least part of the bearing140is arranged in the second opening122, as shown in e.g.FIG. 3b, the bearing140is arranged stationary or movable, such as swivellable or rotatable, with respect to the bushing120. In addition, the bushing120is removable from the frame110of the actuator of the forest machine.

Consequently, the bushing120is replaceable. In this context, the term “axle” refers to a solid or hollow shaft which can be used for supporting pieces to each other, which pieces are swivellable or rotatable with respect to each other.

The bushing120can be installed in the first opening112of the frame110of the actuator, for example, by inserting, pressing and/or lightly knocking. The bushing120is fitted in the frame110of the actuator in such a way that the bushing120does not rotate with respect to the frame110in the normal use of the actuator. Thus, the outer dimension of the cross-section of the bushing120, particularly the frame124of the bushing, is slightly larger than the cross-section of the first opening112of the frame110. The cross-section of the first opening112can be circular or have another shape. However, it is simpler to machine a circular opening than an opening with a different shape in the frame110. As described above, the bushing120is fitted in the first opening. Thus, the shape of the bushing120corresponds to the shape of the first opening.

In addition, the arrangement comprises at least one of the following: an axle130and a bearing140. In the bearing arrangement104ofFIG. 2a, the axle130is fixed with respect to the bushing120in such a way that the axle130does not rotate with respect to the bushing120in the normal use of the actuator. As will be presented in connection withFIG. 3ahereinbelow, in another embodiment the axle130is arranged rotatable with respect to the bushing120. If the axle130and the bearing140are integrated, they can be considered to constitute a single unit which could be called an axle or a bearing. As will be presented in connection withFIG. 3bhereinbelow, in an embodiment the bearing140is arranged rotatable with respect to the bushing120, and a tool150is fastened to the bearing140without a separate axle130. In this case, the frame144of the bearing140constitutes the axle needed.

InFIG. 2a, part of the axle130is arranged in the opening122of the bushing120, i.e. in said second opening122. As will be presented hereinbelow, in an embodiment at least part of the bearing can also be arranged in the second opening122. InFIG. 2a, the second opening122has a circular cross-section. In particular, this is the case even if the axle were arranged to be swivellable with respect to the bushing. Also, the axle130can have a circular cross-section. This is not necessarily the case, whereby a bearing whose shape is fitted to the shape of the axle can be applied in the arrangement.

The first opening112can extend through the frame110. Alternatively, the first opening112can be a blind hole. Advantageously, the depth of the first opening112is at least the length lbof the tubular frame124of the bushing120(seeFIG. 4b).

The above presented bearing arrangement104in the actuator100of the forest machine200represents, first of all, a bearing arrangement104that is suitable for use in the actuator of the forest machine, or, on the other hand, an actuator100of a forest machine200, comprising said bearing arrangement104.

In a bearing arrangement104, the bushing120can be removed in one piece from the first opening112of the frame110. After such a removal, another corresponding bushing can be installed in said first opening112after the bushing120has been removed from the frame110of the actuator110. When the bushing120is removed, said first opening112is exposed. The new bushing is fitted to the shape and the size of the exposed opening112. The new bushing can be installed in the exposed opening112.

FIGS. 2aand2balso show a bearing140. In the case of these figures, the bearing140is arranged stationary with respect to the tool150. The tool is thus swivellable on the bearing140and the axle130, in relation to the frame110of the actuator100. InFIGS. 2aand2b, said swivelling takes place when the bearing140slides in relation to the bushing120.

The swivelling of the above described kind wears the surface on which the tool150is arranged to be swivellable. Without the bushing120, the bearing140would wear the frame110of the actuator directly at the corresponding location. In the arrangement shown inFIGS. 2aand2b, the wearing takes place not only in the bearing140but also in the bushing120, yet not in the frame110of the actuator. Because the bushing120is replaceable, the actuator100is significantly easier to maintain than before.

Also, the material for the bushing120can be selected more freely than the material for the frame110of the actuator. In an example, the bushing120comprises a different material than the frame110of the actuator of the forest machine. In an example, the bushing120comprises steel. In an example, the bushing120comprises wear-resistant steel. The wear-resistant steel can be, for example, hard. The hardness of the wear-resistant steel can be, for example, 180 or more on the Vickers scale (Vickers Hardness). In an example, the bushing120comprises steel whose hardness is at least 190 on the Vickers scale. The wear-resistant steel may comprise, for example, carbon (C), silicon (Si), manganese (Mn), chromium (Cr), and molybdenum (Mo). The wear-resistant steel may comprise, for example 1 to 2% chromium (Cr) and 0.2 to 0.3% molybdenum (Mo). The bushing120may comprise, for example, austenitic steel. The bushing120may comprise, for example, martensitic steel.

For example, the frame of the actuator may comprise weldable material. In an example, the frame110of the actuator comprises a material, such as a metal, with a first hardness; and the bushing120comprises a material, such as a metal, with a second hardness. In the example, the second hardness is higher than the first hardness.

In addition or alternatively, in some embodiments the frame110of the actuator comprises a first material; the bushing comprises a second material; and the wear resistance of the second material is higher than the wear resistance of the first material.

Alternatively or in addition, the bushing120may comprise another hard metal, such as titanium. Alternatively or in addition, the bushing120may comprise another hard material, such as ceramics. In particular, that surface of the bushing which is in contact with the bearing, for example the surface of a flange126of the bushing to be presented further below, may comprise such hard material.

The bushing120is shown in more detail inFIGS. 4aand4b. With further reference toFIG. 2a, in a bearing arrangement,a wall124of the bushing remains between said axle130and said frame110of the actuator of the forest machine, andthe thickness T1of the wall124of said bushing (FIG. 4b) is at least 2 mm With reference toFIG. 3b, in a bearing arrangement,a wall124of the bushing remains between said bearing140and said frame110of the actuator of the forest machine, andthe thickness T1of the wall124of said bushing (FIG. 4b) is at least 2 mm.

Said wall124can remain between both the axle130and the frame110and between the bearing140and the frame110(FIG. 3a).

Such a thickness guarantees that the strength of the bushing is sufficient for actuator applications in a forest machine. In some other examples, the thickness of the wall of the bushing can be, for example, at least 3 mm or at least 4 mm. In some other examples, the thickness of the wall of the bushing can be, for example, not greater than 15 mm or not greater than 8 mm. In an example, the thickness of the wall124of the bushing is between 4.5 mm and 5.5 mm, that is, about 5 mm.

Some bearing arrangements104comprise an axle130. With reference toFIGS. 2aand4b, the inner diameter (d1,FIG. 4b) of the bushing120in an example corresponds to the outer diameter (da,FIG. 2a) of the axle130. With reference toFIG. 3a, in an example at least part of the bearing140also remains between the axle130and the bushing120. The width of the axle130should be selected so that the strength requirements for the actuator of the forest machine are met. In this description, the term “width” refers to the largest longitudinal dimension in the cross-section. If the cross-section is circular, i.e. has the shape of a circle, the width is equal to the diameter of said circle.

In an example, the width daof the axle130(FIG. 2a) is at least 30 mm. In some examples, the width of the axle130is at least 40 mm or at least 50 mm. However, the actuator100should not be too heavy. In some examples, the width of the axle130is not greater than 70 mm, not greater than 80 mm or not greater than 100 mm. In an example, the width of the axle is between 40 mm and 60 mm.

The bushing120should be arranged sufficiently deep in the frame110of the actuator so that the bushing120is resistant to torsional forces as well. For this reason, the walls of the bushing120should be sufficiently long. With reference toFIGS. 4band2a, in a bearing arrangement,a wall124of the bushing remains between said axle130and said frame110of the actuator of the forest machine, andthe length lbof the wall124of the bushing in the longitudinal direction of the axle130(FIG. 4b) is at least 75% of the width da(FIG. 4b), such as the diameter, of the axle.

The ratio between the length lbof the wall of the bushing and the width daof the axle, lb/da, can be, for example, between 0.75 and 2, between 0.8 and 1.5, or about 1, such as 0.9 to 1.2. Also in these examples, the width of the axle130may vary within the above described ranges. The length lbof the wall124of the bushing in the direction of the axle130(FIG. 4b) can be, for example, between 30 mm and 100 mm, such as about 40 mm, about 50 mm or about 60 mm, these figures being given at the accuracy of one digit only.

In an embodiment, the width daof the axle is fitted to the width d1of the second opening122. This is illustrated, for example, inFIG. 2a. In another embodiment, the width d1of the second opening122is larger by the thickness of the walls of the frame144of the bearing140than the width daof the axle130. This is illustrated, for example, inFIG. 3a.

The embodiment ofFIG. 3bdoes not comprise a separate axle130, but the axle130consists of the frame144of the bearing140. In this case, as well as in the above mentioned cases, the above mentioned dimensions can be alternatively proportioned to the diameter d1of the second opening122of the bushing120. Thus, the length lbof the wall124of the bushing in the direction of the axle130(FIG. 4b) is at least 75% of the width d1, such as the diameter, of the second opening122of the bushing120(FIG. 4b). The ratio between the length lbof the wall of the bushing and the diameter d1of the second opening122, lb/d1, can be, for example, between 0.75 and 2, between 0.8 and 1.5, or about 1, such as 0.9 to 1.2.

With reference toFIG. 4b, in an advantageous embodiment the bushing120comprisesa tubular frame124, whose shape defines the direction Sx of the longitudinal axis of the bushing120, anda flange126which protrudes from the frame124of the bushing, at its one end in the direction of the longitudinal axis, radially and perpendicularly to the direction Sx of the longitudinal axis of the bushing.

Thus, the bushing120and its flange126are configured to sustain forces in the direction of the longitudinal axis of the bushing. Thus, the bushing120and its flange126are configured to sustain forces in the direction of the longitudinal axis of the axle130.

With reference toFIGS. 2aand3aas well as the above described swivelling of the tool150with respect to the bushing120, the flange126of the bushing forms a considerably larger surface than the end of a bushing without a flange126. Thus, the surface pressure exerted on the flange126is significantly lower than the pressure which would be exerted on the bushing without the flange. InFIG. 4b, the outer diameter of the flange is indicated with the symbol dcand the diameter of the opening of the bushing with the symbol d1. Thus, the width of the flange126is (dc−d1)/2. The ratio between the width of the flange and the thickness of the wall of the bushing, (dc−d1)/(2×T1), is in some examples between 2 and 20, between 3 and 15, or between 4 and 10. Such dimensions are used to secure a sufficient reduction in the surface pressure between the bushing120and the bearing140.

Furthermore, the flange126may be configured to carry relatively high forces in the direction of the axle130(almost) without bending. Thus, the flange is rigid. This gives the advantage that the wear of the bearing140, corresponding to the flange, is relatively even. In practice, a thin flange might bend, whereby the wear of the corresponding bearing would be significantly more intense in the vicinity of the axle than at the outer edge of the flange126. In an example,the frame124of the bushing120has a first thickness T1,the flange126of the bushing120has a second thickness T2, andthe second thickness T2is at least one and a half times the first thickness T1.

In some examples, the ratio T2/T1is between 1.5 and 5, or between 2 and 4, or between 2.2 and 3.

With reference toFIGS. 2a,2b,3a, and3b, some bearing arrangements104comprise a bearing140. The bearing140refers to an element which is configured to be swivellable or rotatable with respect to the bushing120. The bearing140may comprise an antifriction bearing or elements of an antifriction bearing, such as balls or rollers. As mentioned above, the bearing140is advantageously of a sliding bearing type. The sliding bearing comprises a surface that is configured slidable. The surface arranged to be slidable may comprise, for example, bronze. The bearing140may thus comprise bronze. The bearing140may be made of bronze. The surface arranged to be slidable may comprise, for example, ceramics. The bearing140may thus comprise ceramics. The bearing140may be made of ceramics.

In an embodiment (not shown in the figures), the bearing140comprisesa tubular frame144which defines the longitudinal direction of the bearing, whereinthe end of the frame144of the bearing constitutes the motion surface142of the bearing.

In this context, the motion surface142refers to the surface of the bearing140that is arranged to move, such as to slide, in relation to the bushing120. InFIGS. 2band3, the motion surface is formed on the flange146of the bearing140, but in some other embodiments the end of the tubular bearing may act as the motion surface142.

Furthermore, in the bearing arrangement104shown inFIGS. 2a,2band3a,the bearing arrangement comprises an axle130, andsaid axle130is arranged through the frame of the bearing140in said longitudinal direction of the bearing.

With reference to theFIGS. 2aand2b, in a bearing arrangement104the frame144of the bearing140extends in a first direction −Sx from the motion surface142of the bearing140,the bearing140is in contact with the bushing120, andthe bushing120extends in a second direction +Sx from the point of contact between the bearing140and the bushing120,the second direction +Sx being opposite to the first direction −Sx.

The directions +Sx and −Sx refer, for example, to the upper bearing140shown inFIG. 2b. In the lower bearing140b, the directions are the opposite. With reference to theFIGS. 2band4b, the above-mentioned second direction +Sx is the same as the previously mentioned direction Sx of the longitudinal axis of the bushing120. In particular, if the bearing did not comprise a flange, the bearing140and the bushing120could extend in opposite directions in the above described way.

As stated above, for reasons of weight and size, sliding bearings are preferably used in an actuator of a forest machine. Thus, the sliding bearing is constituted by the bushing120and the motion surface142of the bearing.

In some embodiments, the bearing140comprises a flange146. In an embodiment of the bearing arrangement104,the bearing140comprises a flange146which protrudes from the frame142of the bearing, at its one end, radially and perpendicularly to the longitudinal direction of the bearing, in which casethe flange146of the bearing comprises a first surface and an opposite second surface, andsaid first or second surface of the flange146of the bearing constitutes the motion surface142of the bearing.

FIGS. 2a,3aand3billustrate bearing arrangements which comprise a bearing140comprising a flange146. Also, a bearing140with a flange can be arranged movable with respect to the bushing120in the way presented above and inFIG. 2a. Thus,the motion surface142of the bearing140is formed on the end surface of the flange146of the bearing, whereby the frame144of the bearing extends in a first direction −Sx from the motion surface142of the bearing, the first direction −Sx being, seen from the motion surface142of the bearing, the same direction in which the surface of the flange of the bearing opposite to the end surface (in this case, the motion surface) is located,the motion surface142of the bearing is in contact with the bushing120, andthe bushing120extends in a second direction +Sx from the point of contact between the bearing140and the bushing120,the second direction +Sx being opposite to the first direction −Sx.

The directions +Sx and −Sx refer, for example, to the upper bearing140shown inFIG. 2b. In the lower bearing, the directions are the opposite.

In this embodiment, as well as in the previously described embodiment comprising a bearing without a flange, the axle130is configured to be stationary with respect to the bushing120. Thus, in normal use, the axle130is not movable in relation to the bushing120. The bearing140is arranged swivellable with respect to the axle. The tool150of the actuator100can be fastened to the bearing140or the frame110. The frame110, in turn, is fastened to the bushing120, as described above.

In this embodiment, as also in the previously described embodiment comprising a bearing without a flange, the contact between the bearing140and the bushing120sustains particularly forces which are parallel to the axle130. The bearing140can be, for example, supported to the bushing120, when the bearing is subjected to a force having a component in the second direction +Sx. The bearing arrangement can also comprise a second bushing120band a second bearing140b, as shown inFIG. 2b. The second bearing140bcan be supported to the second bushing120b, when the second bearing140bis subjected to a force having a component in the first direction −Sx. InFIG. 2b, the first direction −Sx is opposite to the second direction Sx. In this way, by means of the two bearings (140,140b), it is possible to prevent the movement of the tool150in the direction of the axle. In a corresponding way, by means of the two bushings (120,120b), it is possible to facilitate the maintenance of the actuator in two parts. In this embodiment, only the axle130is arranged in the above mentioned second opening122.

Alternatively, the bearing140and the bushing120can be arranged in the way shown inFIG. 3aor3bwith respect to each other. In the bearing arrangement according to this embodiment,the motion surface142of the bearing and the frame144of the bearing are oriented in the same direction with respect to the end surface of the flange146of the bearing (indicated with the direction Sx inFIG. 3a),the motion surface142of the bearing is in contact with the bushing120, andat last part of the frame144of the bearing140is arranged in the second opening122limited by the frame124of the bushing120.

In this embodiment, the axle130is arranged movable, i.e. swivellable or rotatable, with respect to the bushing120. In this embodiment, the axle130is arranged stationary with respect to the bearing140in such a way that in normal use, the bearing140does not move in relation to the axle130. The tool150of the actuator100can be fastened to the bearing140or the frame110. The frame110, in turn, is fastened to the bushing120, as described above.

In this embodiment, the contact between the bearing140and the bushing120sustains not only forces parallel to the axle130but also forces perpendicular to the longitudinal direction of the axle130. On the basis ofFIGS. 3aand3b, it is obvious that the bearing140is supported to the bushing120when the bearing140is subjected to a force having a component perpendicular to the direction of the axle. Furthermore, inFIGS. 3aand3b, the bearing140is supported to the bushing120when the bearing is subjected to a force having a component in the direction +Sx. The bearing arrangement can also comprise a second bushing120band a second bearing140b, in a way corresponding to that shown inFIG. 2b. In this way, by means of the two bearings (140,140b), it is possible to prevent the movement of the tool150in the direction of the axle. In a corresponding way, by means of the two bushings (120,120b), it is possible to facilitate the maintenance of the actuator in two parts.

In this embodiment, not only the axle130but also at least part of the bearing140is arranged in the above mentioned second opening122.

With reference toFIG. 2b, a bearing arrangement104comprisesa frame110of an actuator of a forest machine, delimiting a first opening112,a second first opening delimited by said frame110or another frame; advantageously, said other frame is mounted on said frame110of the actuator of the forest machine for reinforcing the structure,a first bushing120, at least part of which is arranged in the first opening112,the first bushing120delimiting a second opening122, in which is arranged at least part of an axle130and/or a bearing140, the axle130or bearing140being arranged stationary or movable in relation to the bushing, andthe first bushing120being removable from the frame of the actuator of the forest machine, and alsoa second bushing120b, at least part of which being arranged in said second first opening.

The second bushing120bdelimits another second opening. At least part of said axle130can be arranged in said another second opening. Alternatively or in addition, at least part of the second bearing140bcan be arranged in said another second opening.

Advantageously, the first bushing120comprises a flange126. Advantageously, the second bushing120balso comprises a flange. Thus, the bushings120,120bcan be arranged in such a way thatthe first bushing120comprises a frame124and a flange126in such a way that the frame124extends in a direction +Sx from the flange126,the second bushing120bcomprises a frame and a flange in such a way that the frame extends in a second direction −Sx from the flange, andthe second direction is opposite to the first direction.

Such an arrangement can also comprise a bearing140and a second bearing140b. At least one, advantageously both, of said bearings can comprise a flange, as illustrated inFIG. 2b.

In the above described embodiments, the bushing120does not necessarily comprise a flange126. The bearing140can swivel and be supported directly to an end of the frame140of bushing, if the bushing120does not comprise a flange126. As stated above, the motion surface142of the bearing and the bushing120advantageously constitute a sliding bearing.

For the above mentioned reasons, the flange126is advantageous in the bushing120as well. In such an embodiment, the bushing120comprisesa tubular frame124whose shape defines the direction Sx of the longitudinal axis of the bushing, anda flange126which protrudes from the frame124of the bushing, at its one end, radially and perpendicularly to the direction Sx of the longitudinal axis of the bushing120, whereinthe flange126of the bushing120comprises an end surface and another opposite surface.

Furthermore, in this embodiment, said motion surface142of the bearing140is arranged in contact with the end surface of the flange126of the bushing. In this context, the end surface refers to that surface of the flange126of the bushing, seen from which the second surface of the flange126of the bushing and the frame124are left on the same side.

As stated above, for reasons of weight and size, sliding bearings are preferably used in an actuator of a forest machine. Thus, the motion surface142of the bearing and the flange126of the bushing constitute the sliding bearing.

In general, the operation of bearings is secured by sufficient lubrication. In some embodiments, the bearing arrangement comprises means for applying a lubricant, such as oil or grease, between the bearing140and the bushing120, particularly between the motion surface142of the bearing and the bushing120.

For example inFIG. 2a, the axle130, the tool150and the bearing140constitute a channel170, along which a lubricant, such as oil or grease, can be introduced between the bearing140and the bushing120. Thus, the axle130ofFIG. 2acomprises at least part of the channel170. Thus, part of the axle130ofFIG. 2aconstitutes a pipe for introducing lubricant.

The lubricant not only lubricates the bearing arrangement but also prevents the entry of impurities between the bearing140and the bushing120Impurities increase the wear of the bearing arrangement. Thus, the lubrication reduces the wear of the bearing arrangement, i.e. reduces the need for maintenance.

In addition or alternatively, the entry of impurities between the bearing140and the bushing120can be reduced by means of a shield180. A location for the shield180in the bearing arrangement is shown inFIG. 2a. InFIG. 2a, the bushing120of the bearing arrangement comprisesa tubular frame124whose shape defines the longitudinal direction Sx of the bushing, anda flange126, which protrudes from the frame124of the bushing, at its one end, radially and perpendicularly to the longitudinal direction Sx of the bushing.

Furthermore, the bearing arrangement comprisesa shield180, which is attached to the flange126of the bushing,the shield180encircling the flange126of the bushing.

The shield180protects the bearing arrangement104, particularly the bushing120, from impurities and mechanical impacts. Advantageously, the shield180encircles closely the flange126of the bushing.

This solution provides an advantage in view of manufacturing technology. That is to say, the alignment of the first opening112of the frame110is not very accurate in this solution. If the shield were fastened to the frame110, the first opening112of the frame110should be aligned very accurately in the correct position, so that the shield could be installed in the frame in such a way that the shield would protect the bushing120and possibly the bearing140.

In the above presented solution, in which the shield180is fastened particularly to the flange126of the bushing120, there is no such problem of alignment. Completely irrespective of the way in which the first opening112is placed in the frame110, the shield can be connected to the flange126of the bushing in such a way that the shield is placed tightly around the bushing120.

With reference toFIG. 4b, in an embodiment, the flange126of the bushing comprises a collar128. By means of the collar128, the shield180can be fastened to the flange126. With reference toFIG. 5b, the shield can comprise for example a groove183corresponding to the collar128. Thus, the shape of the shield180is fitted to the shape of the flange126of the bushing.

The primary function of the shield is to prevent contamination. Thus, the shield180does not need to be made of a particularly strong material. The shield may comprise, for example, at least one of the following: plastic and metal. A suitable material can be selected on the basis of, for example, costs.

FIGS. 5aand5billustrate an embodiment of the shield180. Advantageously, the shield180is replaceable. Advantageously, the shield180is replaceable in such a way that the rest of the actuator100does not need to be particularly disassembled. In an advantageous embodiment, some parts182of the shield180can be removed from the bearing arrangement104in a direction that is perpendicular to the longitudinal direction of the axle130. However, an axle130is not included in all embodiments, whereby some parts182of the shield180can be removed from the bearing arrangement104in a direction that is perpendicular to the longitudinal direction (Sx,FIG. 4b) of the bushing120. In this embodiment,the shield180(FIG. 5a) comprises at least two open parts182(FIG. 5b) of the shield removably connected to each other, wherein said at least two parts182of the shield180are removable from the bearing arrangement104in a direction perpendicular to the longitudinal direction of said bushing120.

The shield180ofFIG. 5a, and some of the presented bearing arrangements104, also comprise a clamp184for the shield. By means of the clamp184, the parts182of the shield can be clamped to form a uniform shield180. The clamp184is advantageously totally openable, whereby the clamp184is also removable from the bearing arrangement104in a direction perpendicular to the longitudinal direction of said bushing120(or axle130). It is possible that the clamp can only be opened to such an extent that said at least two parts182are replaceable but the clamp184is not replaceable without dismantling the actuator.

In an embodiment, the bearing arrangement comprisesa bearing140, which is arranged to be in contact with the flange126of the bushing120, whereina seam remains between said flange126of the bushing and the bearing140, andsaid shield180also surrounds said seam.

This seam is thus formed between the motion surface142of the bearing and the bushing120. Shielding the seam will contribute to keeping the bearing arrangement clean and thereby reducing the wear and the need for maintenance.

In an embodiment, the bearing arrangement104comprisesa gasket160(FIG. 2a), such as an O ring for sealing said seam.

The gasket160contributes to keeping the seam clean.

The above presented solution has several technical advantages:1) The maintenance operations become easier. Because the bushing120is replaceable, the need for maintenance of the frame110of the actuator100, due to wear caused by the bearing, is reduced or eliminated.2) The maintenance interval increases as a result of the material selections. Because the bushing120can be worked more easily and is smaller in size (i.e. in the need for material) than the frame110of the actuator, it is possible to use more durable materials in the bearing arrangement in a cost efficient way. Thus, the bushing120is worn less than the frame of a corresponding actuator without a bushing would be worn in corresponding use.3) The maintenance interval increases as a result of lubrication. An embodiment comprises means for introducing oil or grease between the bushing120and the bearing140. This also contributes to the reduction of friction and wear and thereby extends the maintenance interval.4) The maintenance interval is extended as a result of the shielding. In an embodiment, the shield180is arranged to protect the seam between the bushing120and the bearing140from impurities. Impurities would increase the wear of the structure and the need for maintenance. In an embodiment, the seam is also protected by means of a gasket160.5) The quality and/or accuracy required of machining. Because the first opening112of the frame110is not fitted for the bearing140but for the bushing, it is possible to apply less precise tools for machining the first opening, compared with a situation in which a bearing were arranged in the first opening112. The accuracy requirements are reduced in terms of the size tolerance (for example, the diameter of the first opening) as well as the quality of the work (roughness of the surface of the opening).6) Alignment accuracy required of machining Because the shield180is fastened to the bushing120instead of the frame110, the shield180can be placed in just the correct place irrespective of the accuracy of the alignment of the central axis of the first opening112in the frame110.

The presented solution facilitates the maintenance of the actuator100significantly. When maintaining an actuator of the presented type for a forest machine, the actuator for the forest machine comprisesa frame110of the actuator100of the forest machine200, defining a first opening112, anda bushing120, at least part of which is arranged in the first opening112,the bushing120defining a second opening122, in which is arranged at least part of an axle130, which axle130is arranged stationary or movable in relation to the bushing.

In an embodiment of the method, the bushing120is replaced with another, new bushing. In the method,a second, corresponding bushing is arranged available, which bushing is fitted for said first opening112,said bushing120is removed from the frame110of the actuator of the forest machine, wherein said first opening112is exposed, andsaid second bushing is installed in said exposed first opening112.

In the figures the reference numerals refer to the following features:100Actuator of a forest machine104Bearing arrangement, especially in an actuator of a forest machine110Frame of an actuator of a forest machine112First opening (i.e. opening in frame110for bushing120)120(also120b) Bushing122Second opening (i.e. opening in bushing for at least an axle130)124Frame of bushing126Flange of bushing128Collar of flange of bushing130Axle140(also140b) Bearing142Motion surface of bearing144(also144b) Frame of bearing146(also146b) Flange of bearing150(also150a,150b,150c,150d,150e) Tool of actuator100152Blade of tool of actuator160Gasket170Channel for supplying lubricant180Shield182Part of shield183Groove in shield184Clamp for shield200Forest machine210Base machine220Cranedawidth of axle; diameter of axle with a circular cross-section;dcDiameter of flange of bushingdldiameter of first opening112lbLength of frame of bushing in the direction of the axleSx a direction−Sx A second direction, opposite to direction SxT1Thickness of wall of frame of bushingT2Thickness of flange of bushing
Examples of some embodiments

1. A bearing arrangement in an actuator of a forest machine, the bearing arrangement comprisinga frame for the actuator of the forest machine, defining a first opening, the bearing arrangement comprisinga bushing, at least part of the bushing being arranged in the first opening,the bushing defining a second opening, at least part of an axle and/or a bearing being arranged in the second opening, the axle or bearing being arranged stationary or movable in relation to the bushing, andthe bushing being removable from the frame of the actuator of the forest machine.

2. The bearing arrangement according to Example 1, in whichthe bushing is removable in one piece from the first opening of the frame, wherein after the removal of the bushing, a corresponding second bushing can be installed in said first opening.

3. The bearing arrangement according to Example 1 or 2, in whichthe bushing comprises a different material than the frame of the actuator of the forest machine,the bushing comprises steel, orthe frame of the actuator comprises a material, such as a metal, with a first hardness; the bushing comprises a material, such as a metal, with a second hardness; and the second hardness is greater than the first hardness.

4. The bearing arrangement according to any of the Examples 1 to 3, in whicha wall of the bushing is left between said axle and said frame of the actuator of the forest machine, and/or a wall of the bushing is left between said bearing and said frame of the actuator of the forest machine; andthe thickness of said wall of the bushing is at least 2 mm

5. The bearing arrangement according to any of the Examples 1 to 4,the bearing arrangement comprising an axle, andthe width of said axle being at least 30 mm.

6. The bearing arrangement according to any of the Examples 1 to 5, in whicha wall of the bushing is left between said axle and said frame of the actuator of the forest machine, and/or a wall of the bushing is left between said bearing and said frame of the actuator of the forest machine; andthe length of the wall of the bushing in the direction of the axle is at least 75% of the width of the second opening of the bushing.

7. The bearing arrangement according to any of the Examples 1 to 6, in whichthe bushing comprisesa tubular frame whose shape defines the longitudinal direction of the bushing, anda flange protruding from the frame of the bushing, at its one end, radially and perpendicularly to the longitudinal direction of the bushing,

wherein the bushing and its flange are arranged to sustain forces in the longitudinal direction of the bushing.

8. The bearing arrangement according to Example 7, in whichthe frame of the bushing has a first thickness,the flange of the bushing has a second thickness, andthe second thickness is at least one and a half times the first thickness.

9. The bearing arrangement according to any of the Examples 1 to 8, comprisingan axle anda bearing which comprisesa tubular frame which defines the longitudinal direction of the bearing, whereinthe end of the frame of the bearing forms a motion surface of the bearing; andsaid axle is arranged through the frame of the bearing in said longitudinal direction of the bearing.

10. The bearing arrangement according to Example 9, in whichthe frame of the bearing extends in a first direction from the motion surface of the bearing,the bearing is in contact with the bushing, andthe bushing extends in a second direction from the point of contact between the bearing and the bushing,the second direction being opposite to the first direction.

11. The bearing arrangement according to Example 9, in whichthe bearing comprises a flange protruding from the frame of the bearing, at its one end, radially and perpendicularly to the longitudinal direction of the bearing, whereinthe flange of the bearing comprises a first surface and an opposite second surface, andsaid first or second surface of the flange of the bearing forms a motion surface of the bearing.

12. The bearing arrangement according to Example 11, in which

(a)a motion surface of the bearing is formed on the end surface of the flange of the bearing, wherein the frame of the bearing extends in a first direction from the motion surface of the bearing, the first direction being, seen from the motion surface of the bearing, the same direction in which the surface of the flange of the bearing opposite to the end surface is located;the motion surface of the bearing is in contact with the bushing, andthe bushing extends in a second direction from the point of contact between the bearing and the bushing,the second direction being opposite to the first direction, or

(b)a motion surface of the bearing and the frame of the bearing are oriented in the same direction, seen from the end surface of the flange of the bearing,the motion surface of the bearing is in contact with the bushing, andat least a part of the frame of the bearing is arranged in the second opening delimited by the frame of the bushing.

13. The bearing arrangement according to any of the Examples 9 to 12, whereinthe bushing comprisesa tubular frame whose shape defines the longitudinal direction of the bushing, anda flange protruding from the frame of the bushing, at its one end, radially and perpendicularly to the longitudinal direction of the bushing, whereinthe flange of the bushing comprises an end surface and another opposite surface,said motion surface of the bearing is arranged in contact with the end surface of the flange of the bushing.

14. The bearing arrangement according to Example 13, in whicha motion surface of the bearing and the flange of the bushing constitute a sliding bearing.

15. The bearing arrangement according to any of the Examples 9 to 14, comprisingmeans for applying a lubricant, such as oil or grease, between the motion surface of the bearing and the bushing.

16. The bearing arrangement according to any of the Examples 1 to 15, whereinthe bushing comprisesa tubular frame whose shape defines the longitudinal direction of the bushing, anda flange protruding from the frame of the bushing, at its one end, radially and perpendicularly to the longitudinal direction of the bushing; and the bearing arrangement comprisesa shield which is attached to the flange of the bushing, and whichshield encircles the flange of the bushing.

17. The bearing arrangement according to Example 16, in whichthe shield comprises at least two open parts removably connected to each other, wherein said at least two parts of the shield are removable from the bearing arrangement in a direction perpendicular to the longitudinal direction of said bushing.

18. The bearing arrangement according to Example 16 or 17, comprisinga bearing arranged in contact with the flange of the bushing, whereina seam is left between said flange of the bushing and the bearing, andsaid shield also surrounds said seam.

19. The bearing arrangement according to Example 18, comprisinga gasket, such as an O ring, for sealing said seam.

20. A method for maintaining an actuator of a forest machine, in which method the actuator of the forest machine comprisesa frame of the actuator of the forest machine, the frame delimiting a first opening, anda bushing, at least part of the bushing being arranged in the first opening,the bushing delimiting a second opening, at least part of an axle and/or a bearing being arranged in the second opening, said axle or bearing being arranged stationary or movable in relation to the bushing, and the method comprisingarranging a second, corresponding bushing available, which bushing is fitted for said first opening,removing said bushing from the frame of the actuator of the forest machine, wherein said first opening is exposed, andinstalling said second bushing in said first opening.