Abstract:
The present invention relates to a locking system for a rotating joint. In the device, the locking system (L) comprises a rigid locking means ( 12 ) movable in the axial direction (X 1 ), provided with a first cogging ( 13 ) which can be moved for locking with the locking means ( 12 ) in a contact with a second cogging ( 14 ), to transmit the rotational movement, wherein said coggings ( 13, 14 ) are, for releasing the cogging, designed in such a way that a force effect releasing the locking is formed between them, and a third cogging ( 16 ) which is, during the locking, in a contact with a fourth cogging, to transmit the rotational motion, as well as a sealing element ( 21 ) for forming at least one closed hydraulic space ( 24 ) with a varying volume between the locking means ( 12 ) and the sealing element ( 21 ), wherein the locking means ( 12 ) is arranged to be moved for the locking and to be kept in the locking by the effect of a pressurized medium.

Description:
BACKGROUND OF THE INVENTION 
     The invention relates to a locking system for a rotating joint according to the preamble of the appended claim 1. 
     For harvesting, working machines are known which move on a terrain by means of wheels. These include a harvester in which a harvesting device is provided at the end of a boom assembly, a so-called harvester head for cutting and felling a tree stem and sawing it to pieces of desired length. The sawn tree stems are collected with a loading apparatus, or a forwarder equipped with a grapple, and are transported in its load space. For example, a harvester working machine with articulated steering comprises two frame parts which are arranged, by means of a joint, to swivel in relation to each other around a vertical axis. A swivel base is mounted on the first frame part to swivel around a vertical axis and is equipped with a cabin and a boom assembly, a harvester head being mounted at the end of the boom assembly. The boom assembly can also be mounted on a separate swivel base, and the cabin can be stationary. The second frame is equipped with a power source and a pair of wheels. The first frame part normally comprises one or two pairs of wheels. 
     Another known forwarder, movable by means of wheels, is disclosed in Swedish patent publication 509 907 and comprises two frame parts connected to each other by means of a joint. One of the frame parts is equipped with a load space where the tree stems are collected from the ground by means of a loader, its boom assembly being normally also mounted to the front part of the second frame part. The first frame part is equipped with a cabin and a power source for the working machine. For improving movability on a terrain, the frame parts are arranged to be articulated by means of a rotating joint with respect to each other around an axis in the longitudinal direction of the frame. The turning movement is normally limited. In addition to this, the working machine is controlled by steering the frame parts around a vertical axis by means of cylinders. 
     At present, so-called combined machines are also known, combining the functions of a harvester and a forwarder. In one example, the working machine comprises two frame parts which can be swivelled around a longitudinal and vertical axis. Thus, the first frame part is equipped with a boom assembly and a cabin, for example on a joint swivel base, as well as a power source, and the second frame part is equipped with a space for the load. The second frame part is normally supported by two separate wheel shafts. 
     To maintain stability of the working machine, it must be possible to lock the rotating joint to prevent swivelling of the frame parts. Particularly when the boom assembly is used, for example upon loading, cutting and delimbing, the position is locked, wherein the weight of the second frame part is also utilized as a counterweight. The presented rotating joint normally comprises a circumferential bearing which is a single-row filling slot type bearing. The outer race and the inner race of the bearing are coupled to different frame parts. The frame part may also be equipped with a transverse joint, by means of which the rotating joint and the frame part swivel. 
     As known, the rotating joint is also equipped with separate brake plates which are locked by means of brake cylinders. The brake plates and the brake cylinders become large, and they must be placed outside the rotating joint, which considerably increases the size and weight of the rotating joint. Because of the mounting and size of the brake plate, rotation is often possible within allowed limits only, which restricts the movement of the frame parts. The joint can be equipped with e.g. an arch-like cogging where the cogs extend in the axial direction. The rotation movement is locked with a locking means movable in the radial movement and set in the cogging. For example, a separate cylinder structure for moving the locking means, operated by a pressurized medium, is often also large in size. However, particularly the locking force of a single locking means also causes an unnecessary and uneven torque between the outer and inner races of the circumferential bearing, stressing the circumferential bearing. Consequently, prior art lockings increase the size of joints and the stresses. 
     BRIEF SUMMARY OF THE INVENTION 
     It is an aim of the present invention to eliminate the above-mentioned problems. To attain this purpose, the locking system according to the invention is primarily characterized in what will be presented in the characterizing part of the appended claim 1. 
     Using the invention, a considerably integrated and compact construction is achieved, wherein it can also be applied in various rotating joints which also comprise joints in the transverse direction. The locking system also makes it possible to rotate the frame parts with respect to each other without limits. A particular advantage is achieved in that in the locked position, the circumferential bearing of the rotating joint is not subjected to forces caused by the locking. In a preferred embodiment of the invention, another particular advantage is a large annular hydraulic space for the pressurized medium, wherein the required control pressures for maintaining even great locking forces can be kept reasonable. The number of separate hydraulic spaces can also be easily increased. One advantage is that external energy and the pressurized medium are only used when necessary for locking and for maintaining the locking, and that the locking will be automatically released, thanks to the design of the cogging. Another advantage is that the rest of the cogging can also be arranged in such a way that it will not cause locking or releasing forces, wherein the locking system can be easily moved. The hydraulic space and the cogging can be made annular, wherein a balanced loading and functionality of the rotating joint are achieved in all the rotating positions. Particularly the cylindrical, centrally placed parts of the locking system are easy to manufacture e.g. by lathing. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the following, the invention will be described in more detail by using as an example a locking system according to an advantageous embodiment with reference to the appended drawings, in which 
     FIG. 1 shows a perspective view of a rotating joint in a working machine, applied in connection with a turning joint and its control cylinders, 
     FIG. 2 shows the rotating joint of FIG. 1 in a cross-section seen from the side, to illustrate a locking system according to an advantageous embodiment of the invention, and 
     FIG. 3 shows a perspective view of the locking system of FIG. 2, detached from the rotating joint. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     In FIG. 1, the rotating joint  1  is shown in an application in connection with a turning joint  7  between the frame parts  5  and  6  of a working machine. The rotating joint  1  is arranged between the first frame part, which in this description will also be called front part  5 , and the second frame part, which in this description will also be called rear part  6 , the frame parts being rotatable with respect to each other around an axis X 1 . The frame part  6  is shown in a cut view. The axis X 1  is normally parallel with the longitudinal axis of the working machine, when the frame parts  5  and  6  are mounted one after the other in the working machine, wherein the frame parts are allowed to rotate around the longitudinal axis. The front frame part of the working machine can be either frame part  5  or  6 . The first frame part  5  of the working machine is also provided with a joint  7 , by means of which the joint  1  and the rest of the frame part  5  can be rotated with respect to each other around a vertical axis Z 1 . The joint  7  is utilized in the frame steering of the working machine. For this purpose, the joint  7  comprises two lugs  7   a  and  7   b  provided at a distance from each other for bearing. The lugs are preferably placed on different sides of the axis X 1 . The axis Z 1  preferably intersects the axis X 1 . It is obvious that the joint  7  can also be totally eliminated, wherein the frame parts  5  and  6  rotate with respect to each other only. Alternatively, the frame part  6  can be provided with a joint  7  of the presented type. It is also possible that both of the frame parts are equipped with such a joint. Furthermore, the joint  7  may comprise one cylinder only. 
     Lugs  9   a  and  9   b  are provided symmetrically on different sides of the axis Z 1 , at a distance from each other. The first end of a first rotating cylinder  2  is mounted by means of a joint to the lug  9   a , and the first end of a second rotating cylinder  3  is mounted by means of a joint to the lug  9   b . The second ends of the cylinders  2  and  3  are mounted by means of joints to that part of the first frame part  5  which is mounted to the joint  7 . By controlling the linear movement of the cylinders, the frame parts are rotated with respect to each other around the axis Z 1 , for example for frame steering. The cylinders are rotated at both ends around a substantially vertical axis. 
     A protected bearing according to FIG. 2 is arranged between the front part  5  and the rear part  6 , allowing them to rotate separately around the axis X 1 . By means of the bearing, the disconnection of the front part and the frame part from each other in the direction of the axis X 1  is also prevented. The bearing is preferably implemented by means of a circumferential filling slot type bearing, known as such, which is centrally placed on the axis X 1  and whose outer race is connected to the rear part  6  and whose inner race is connected to the front part  5 . A locking system L according to the invention is also arranged inside the rotating joint  1 , wherein the rotation of the front part  5  and the rear part  6  with respect to each other is also prevented, if necessary. In the locked position, the rotational motion is transferred between the frame parts. The rotating joint  1  is normally locked during loading of the working machine and during use of the boom assembly, and is free during driving. 
     FIG. 2 shows the locking system L in a cross-sectional view cut along the axes X 1  and Z 1  of FIG.  1 . Only the necessary parts of the frame parts  5  and  6  are illustrated. In the presented embodiment, the locking system L and the circumferential bearing  11  are rotationally symmetrical pieces which are centrally placed on the axis X 1 . The locking system L is shown in the locked position, wherein a locking means  12  is moved to the left and wherein a first cogging  13  and a second cogging  14  are in contact with each other. The circumferential bearing  11  comprises an outer race  11   a  and an inner race  11   b . The inner race  11   b  is connected, preferably by means of a screw fastening, to the front part  5  which is illustrated with a simple line of dots and dashes. The outer race  11   a  is coupled to the rear part  6  which is illustrated with a simple line of dots and dashes. 
     The locking system L comprises a cogging  14  which is rotatable with the front part  5  around the axis X 1  and comprises a circumferential front surface facing the rear part  6 , having a substantially standard width, and being equipped with radial cogs. The locking system L comprises an inner cogging  15  which is rotatable with the rear part  6  around the axis X 1  and comprises a circumferential front surface facing the axis X 1 , having a substantially standard width, and being equipped with axial cogs. The locking system L also comprises a rigid locking means  12  which is movable in the direction of the axis X 1  and is arranged in functional contact with the coggings  14  and  15 , wherein it transfers the rotational motion between the front part  5  and the rear part  6 , simultaneously rotating with the rear part  6 . 
     The locking means  12  comprises a cogging  13  which is arranged at its first end  12   a  and comprises a circumferential front surface facing the cogging  14 , having a substantially standard width, and being equipped with radial cogs. The coggings  13  and  14 , as a concentric pair of cogged wheels, are interlocked in a contact that transmits rotational motion and power, wherein the rotational motion between the locking means  12  and the front part  5  is prevented. When the locking means  12  is off the contact, the reciprocal rotational motion is possible. 
     The locking means  12  comprises an outer cogging  16  which is arranged at its second end  12   b  and comprises a circumferential front surface extending radially from the axis X 1 , and being equipped with axial cogs formed by e.g. a grooving. The coggings  15  and  16 , as a concentric and cylindrical pair of inner cogged wheels, are arranged to continuously remain in a contact that transfers rotational motion, wherein the rotational motion between the locking means  12  and the rear part  6  is always prevented. The cogging  16  is arranged to slide back and forth in the cogging  15  in the direction of the axis X 1  to allow movement of the locking means  12 . 
     The locking means  12  is preferably formed a tubular, rotationally symmetrical piece, and the coggings are preferably annular, circumferential or circular, wherein the unlimited rotational motion and locking of the frame parts is possible in all the rotational positions. When the rotating joint  1  is locked, the rigid locking means  12  transmits the rotating torque effective between the frame parts of the working machine. 
     The radial outer surface  18  of the locking means  12  is also provided with a circumferential axial front surface  17 . By means of a force exerted on the front surface  17 , the locking means  12  is moved towards the cogging  14  in the direction of the axis X 1 . The force is produced by means of a pressure effect by the pressurized medium on the area of the surface  17 . By the effect of the force, the rotating joint  1  is locked, and upon releasing the force, the rotating joint  1  is released. On both sides of the front surface  17 , the locking means  12  is provided with cylindrical outer sealing surfaces on the outer surface  18 . Said surfaces are packed towards the cylindrical inner surface  19  which is fitted in a sealing element  21  rotating with the front part  5  and the inner race  11   b.  Grooves formed on the surface  19 , on both sides of the front surfaces  17  and  20 , are provided with sealings  22  and  23 . The groove on the surface  19  is also provided with a bearing  25 , such as a slide bearing, to connect the means  12  and  21  by a bearing. The inner surface  19  of the sealing element  21  is also provided with a circumferential axial front surface  20 . The front surfaces  20  and  17  face each other. The outer surface  18  and the inner surface  19  also face each other. The area of the surface  20  is also subjected to the above-mentioned pressure effect by the pressurized medium. However, the surface  20  and the sealing element  21  are not allowed to move in the direction of the axis X 1  with respect to the inner race  11   b  or the cogging  15 . The surface  20  is thus subjected to a counterforce for the force effective on the surface  17  and moving the locking means  12  in the axial direction. Said counterforce is effective by means of the inner race  11   b  on the front part  5 . Similarly, the force effective in the coggings  13  and  14  is exerted by means of a part  29  on the front part  5 , wherein a considerable advantage is that no loading forces caused by the locking are effective between the inner race  11   b  and the outer race  11   a.    
     The outer surface  18 , the inner surface  19  and the front surfaces  17  and  20  form an annular hydraulic space  24  for a pressurized medium. The volume of the hydraulic space  24  varies when the locking means  12  is moved, wherein the locking means  12  is used as a kind of a piston and a piston rod, and the sealing element  21  is used as a kind of a cylinder. The distance between the surfaces  17  and  20  in the axial direction is greater than the length of the interlocked coggings  13  and  14  in the locked position of the locking means  12 . It is thus possible to release the locking, and the coggings do not keep rubbing each other. At the same time, the length of the cogging  16  is the respective measurement greater than the width of the cogging  15 , to maintain the contact in the different positions of the locking means  12 . The sealing element  21  is provided with at least one channel (not shown in the figures) for conveying pressurized medium to and from the hydraulic space  24 . The pressurized medium is introduced to the channel for example by means of tubes or hoses. 
     The pressurized medium can be controlled by using valve means, known as such, wherein the pressure, volume flow and flowing direction of the pressurized medium can be controlled in a desired manner, for example by means of a hydraulic, electrically controlled control circuit. The control circuit can be arranged e.g. in connection with another control circuit in the working machine, wherein the operation can also be automatically controlled by means of the control system of the working machine. However, the dimensioning of the required pressure and the volume flow, and the control circuit for different situations and loadings will be obvious for anyone skilled in the art on the basis of the above description, wherein a mored detailed description will not be necessary. Similarly, the final dimensioning of the coggings, e.g. the more detailed selection the profiles, spaces, number and other parameters of the cogs and their testing for the operation of the locking system in different loading situations will be obvious for anyone skilled in the art on the basis of the description above. 
     The operation of the locking means  12  is arranged in the following way. When locked and when the front part  5  is being swivelled, the cogging  14  also rotates the cogging  13  and further, via the means  12  and the coggings  15  and  16 , also the rear part  6 . Due to the profile of the coggings  14  and  13 , the locking means  12  is subjected to a force releasing the locking and being effective in the direction of the axis X 1 . This force is compensated by the force of the pressure effective in the hydraulic space  24 . Due to the profile of the coggings  15  and  16 , particularly friction forces are also effective between them, resisting the sliding of the locking means  12  in different directions. According to the invention, however, the profiles of the cogging are dimensioned so that the axial friction force caused is smaller than the above-mentioned releasing force. The cogging is preferably axial, wherein the means  12  is subjected to axial (X 1 ) forces caused by the transmission of the rotational motion which are as small as possible. Thus, when the pressure effect of the hydraulic space  24  is removed (pressurized medium is discharged and the pressure space  24  becomes smaller), the locking means  12  is automatically moved by the effect of the releasing force and the locking is automatically released. The locking is returned by returning the pressure effect of the hydraulic space  24  (pressurized medium is introduced and the hydraulic space  24  is expanded). 
     To secure the releasing of the locking and to move the coggings  13  and  14  farther from each other, a pressure spring  26  is used. The spring  26  produces an axial force which moves the locking means  12 . The spring  26  can be light in its structure, e.g. a coil spring, because it must only compensate the friction forces caused by the sealings  22 ,  23  and the bearing  25  as well as the friction force between the coggings  15  and  16 . At its first end, the spring  26  is effective on a circumferential end part  27  which is fixed, preferably by screw fastening, to the locking means  12 . At its second end, the spring  26  is supported to an annular spring suspension part  28  which is set around the locking means  12  and is also equipped with an inner cogging  15 , e.g. by means of a grooving. The spring suspension part  28  is further mounted to the rear part  6 , preferably by screw fastening. The cogging  14  is formed on an annular end part  29  which is further mounted to the rear part  5 , preferably by screw fastening. To the end part  29  is mounted, preferably by a screw fastening, an annular collar part  30  extending inside the locking means  12  and packed against the same, to support the locking means  12 . The sealing element  21  is placed around the locking means  12  and centrally inside the circumferential bearing  11 . The sealing element  21  is mounted to the inner race  11   b,  preferably by screw fastening. The sealing element  21  and the inner race  11   b  can also be integrated in one part. In the same way, for example the parts  29  and  30  as well as the parts  12  and  27  can be integrated in one part, but in the presented embodiment, they are separate, particularly to facilitate the manufacture of the coggings. The parts  27  and  28  form a preferably annular packed space for the springs  26 . 
     A protective hollow space  31  is left in the centre of the locking system L, through which it is possible to lead tubes, hoses and wires for electricity and pressurized medium from one frame part to the other in the working machine. The sealing element  21  is not moved in the axial direction, and in the presented advantageous embodiment, it is rotated with the front part  5 . The sealing element  21  can also be mounted to the rear part  6 , wherein it is rotated with the rear part  6  together with the locking means  12 . Thus, the above-described counterforce is exerted by means of the rear part  6  to the outer race  11   a , wherein the bearing  11  is subjected to a loading between the inner race  11   b  and the outer race  11   a , caused by the locking. Thus, the cogging  15  can be formed in the sealing element  21  or, for example, the operations of the spring suspension part  28  and the sealing element  21  can be combined at least partly. 
     It is also obvious that the coggings  13  and  14  can also be tilted in the direction of the longitudinal axis X 1 , wherein they become conical. Furthermore, it is obvious that the coggings  15  and  16  can also be tilted in the direction of the longitudinal axis X 1 , wherein the contact between them can be released when the locking means  12  is moved, and wherein they become conical. Thus, also the coggings  15  and  16  are arranged in such a way that they are placed in a contact transmitting the rotational motion at least when the locking means  12  is locked. However, the forces releasing the locking, caused by the profiles of the coggings, can thus be increased, wherein also the required pressure effect must be greater. At the same time, the connecting may take more time and the wear of the coggings is increased. Furthermore, the outer race  11   a  and the inner race  11   b  are subjected to a loading caused by diagonal or upright coggings  15  and  16 , if the locking means  12  is fastened to the inner race  11   b.  It is also possible to provide several separate hydraulic spaces  24  between the means  12  and  21 , to achieve a sufficient force effect. 
     FIG. 3 shows the locking system L detached from the rotating joint  1  to illustrate the circumferential and rotationally symmetrical structure of the system. The figure also shows the coggings  13 ,  14  and  16 . The system L is shown in its locked position. The references of FIG. 3 correspond to the references of FIG. 2, and for example the end part  29  is also visible in FIG.  1 . It is obvious that the coggings can also consist of one or several arch-like parts of different lengths which only cover a part of the circumference, particularly when the rotational motion of the rotating joint is limited. In the embodiment of FIG. 2, the coggings  15  and  16  can be arch-like. For balanced loading, the separate arch-like parts must be placed symmetrically with respect to the axis X 1 . 
     The invention is not limited solely to the above-presented embodiment, but it can be modified within the scope of the appended claims.