Abstract:
Chain conveyors in an agricultural harvesting machine can be tensioned by means of a tension adjusting device including an adjusting unit which is coupled to a displaceable shaft via a linkage means or connector members. The adjusting units are advantageously hydraulic cylinders controlled in synchronism. The hydraulic cylinders can be mutually independently pressurized via bypass lines incorporating control valves.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This is a divisional application of prior application Ser. No. 09/586,210, filed Jun. 2, 2000, and now U.S. Pat. No. 6,516,941 which claimed priority of German Application No. 199 25 691.8 filed on Jun. 4, 1999. 
    
    
     TECHNICAL FIELD OF THE INVENTION 
     The present invention relates generally to agricultural machinery and, more particularly, to a tension adjusting device for chain conveyors in agricultural harvesting machinery. 
     BACKGROUND OF THE INVENTION 
     Agricultural harvesting machines are commonly equipped with chain conveyors to transport crops from one part of the machine to another. In particular, standard combine harvesters are equipped with three chain conveyors. The first chain conveyor, the feed conveyor, transports crops from the cutting table to the threshing mechanism. The second conveyor, sometimes referred to as the tailings or returns conveyor, returns any unthreshed material from the sieve device to the threshing mechanism, while the third conveyor transports the grain to the grain tank. The width of the conveyors determines the number of conveyor chains used. For example, the feed conveyor is normally equipped with two conveyor chains whereas the second and third conveyors are each equipped with only one conveyor chain. The second and third conveyors are also equipped with partition walls which are located centrally between two parallel walls of closed housings surrounding the conveyors. The conveying span of the chain is separated from the empty span by the partition wall. 
     It is generally known that each chain in a chain conveyor must be pre-tensioned. This pre-tensioning must be regularly checked before starting work and adjusted if necessary. The tension on the conveyor chains must also be relieved when the machine remains unused for long periods of time. For these reasons, each chain conveyor is normally furnished with a mechanical tensioning device. These devices are equipped with pre-tensioned springs in order to absorb overloading on the chain and to prevent the chain from breaking. 
     A disadvantage of these mechanical tensioning devices is that two people are required to install and operate the system. The tensioning and detensioning of the chains is laborious and time consuming. Moreover, the tensioning device as a whole is relatively expensive. In addition, the tension of each single chain has to be checked during the daily inspection of the harvesting machine prior to starting work. 
     SUMMARY OF THE INVENTION 
     In accordance with the present invention a tension adjusting device includes a displaceable shaft associated with each chain conveyor. The displaceable shaft may be moved to adjust the tension on the conveyor chain. An adjusting unit contains an adjusting member that is connected with the displaceable shaft by a linkage means. Movement of the adjusting member by the adjusting unit induces movement in the displaceable shaft through the linkage means, thereby adjusting the tension in the conveyor chain. 
     In one embodiment, the adjusting unit is a hydraulic cylinder, and the piston rod of the cylinder is the adjusting member. 
     In another embodiment, the linkage means includes a plurality of swing levers supporting the displaceable shaft; a coupling rod is connected to one end of each of the swing levers; and a transverse member connects the ends of the coupling rods opposite their connection with the swing levers with the adjusting member. 
     In another embodiment, a connector member in the form of a U-shaped yoke is carried by the adjusting member and connects the adjusting member with and rotatably supports the displaceable shaft. 
     An object of the invention is to propose a simple and particularly installation- and service-friendly arrangement which will permit the tensioning and detensioning processes to be accomplished in the least amount of time. 
     This and other objects, aspects, features and advantages of the present invention will become apparent from the following detailed description when taken in conjunction with the reference drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Reference is now made more particularly to the drawings which illustrate the best presently known mode of carrying out the invention and wherein similar reference characters indicate the same parts throughout the views. 
     FIG. 1 is the frontal region of an agricultural harvesting machine in the form of a combine harvester incorporating three chain conveyors. 
     FIG. 2 is a side view of the tension adjusting device in a first embodiment. 
     FIG. 3 is a frontal view of the tension adjusting device of FIG.  2 . 
     FIG. 4 is a side view of the tension adjusting device in a second embodiment. 
     FIG. 5 is a frontal view of the tension adjusting device of FIG.  4 . 
     FIG. 6 is a block circuit diagram of the control system for the hydraulic cylinders. 
    
    
     DETAILED DESCRIPTION 
     The frontal part of a combine harvester C illustrated in FIG. 1 is equipped with three chain conveyors  1 ,  2  and  3 . The chain conveyor  1  conveys the crop transported thereto by a header auger  4  to an indicatively illustrated threshing mechanism  5 . The chain conveyor  1  is located between the header auger  4  and the driven front wheels  6  of the combine harvester. It runs upwardly toward the front wheels  6 . The tailings or return conveyor  2  conveys the incompletely threshed crop back to the threshing mechanism  5 . The chain conveyor  3  conveys the sieved grains to the grain tank  42 . The chain conveyor  1  used for drawing in the crop preferably comprises two conveyor chains  43 , while the other two chain conveyors  2  and  3  are only equipped with one conveyor chain  43 . Moreover, the two chain conveyors  2  and  3  are arranged within closed housings  9  and  10 . The tension adjusting devices, which will be explained in more detail hereinafter, are equipped with controlled hydraulic cylinders  11 ,  12  and  13 . The chain conveyor  1  is equipped with a fixed driveable shaft  14  and a displaceable shaft  15 . In corresponding manner, the conveyor  2  is equipped with a fixed driveable shaft  16  and a displaceable shaft  17 . In similar manner, the chain conveyor  3  is equipped with a fixed driveable shaft  18  and a displaceable shaft  19 . Mutually spaced feed rake slats are fixed to the chain in the conveyor  1  and feed plates  29  are fixed to the chains in the conveyors  2  and  3 . 
     Advantageously the tension adjusting elements in the tension adjusting devices are hydraulic cylinders  11 ,  12  or  13 , although one should not exclude the possibility of using mechanical, motor driven, linear adjusting devices. One benefit of using hydraulic cylinders  11 ,  12 ,  13  is that they can be installed by a single person without any problem. To tension the conveyor chains  1 ,  2 ,  3 , the hydraulic cylinders are supplied with pressurized oil as hereinafter described. Since a hydraulic system is already available in an agricultural harvesting machine C, the extra costs are extremely small. The components associated with the hydraulic cylinder are simple components which can be easily installed and have a long life. The arrangement of the hydraulic cylinder or the hydraulic cylinders and the design of the linkage or the connector members is determined by the size and the positioning of the conveyor  1 ,  2 ,  3 , within the machine C. 
     In FIGS. 2 and 3, the displaceable shaft (i.e.  15 ,  17 , or  19 ) is rotatably mounted in two swing levers  20 ,  21  disposed externally near the walls of the housing  44  for the chain conveyor. The chain conveyor is provided with a partition wall. A pivotal axis  22  at one end of the swing levers is offset from the shaft  15 ,  17  or  19  but is axially parallel therewith. Coupling rods  23  are articulated at  23 A to the end of the swing levers  20 ,  21  opposite the pivotal axis. The opposite ends of the two coupling rods are attached to a transverse member  24  which is engaged centrally by the piston rod  11 ′ of the hydraulic cylinder e.g.  11 . This hydraulic cylinder  11  is attached to the wall of the housing  44  facing the pivotal axis  22 . As shown in FIG. 2, the shaft  15  lies approximately midway between the pivotal axis  22  and the articulation point  23 A for the coupling rod  23 . Favorable transmission of the forces applied by the hydraulic cylinder  11  results when the displaceable shaft  15 ,  17 , or  19  is mounted centrally between the pivot axis  22  and the articulation point  23 A of the swing levers  20 ,  21 . The swing levers  20 ,  21  then operate as a single arm, thereby resulting in a very effective moment on the displaceable shaft  15 ,  17 , or  19 . Hence, as shown in FIG. 1 and 2, when the piston rod of the hydraulic cylinder  11  extends away from the displaceable shaft  15 ,  17 , or  19 , the distance between the shafts  14 ,  15 ;  16 ,  17 ; or  18 ,  19 , respectively, is increased thereby increasing the tension on the chain  43  and when the piston rod of the hydraulic cylinder  11  retracts towards the displaceable shaft, the distance is decreased thereby reducing the tension of the chain  43 . 
     To save space, it is expedient if the transverse member  24  or the piston rods  11 ′ are guided. Two guide profiles  25  are fixed to the same wall of the housing, these being provided with slots  26  in which the transverse member  24  is guided. Although in this case, the coupling rod would be inclined relative to the direction of conveyance of the chain conveyor, the hydraulic cylinder or the hydraulic cylinders would nevertheless be accessible. The guide profile  25  is arranged on the same wall of the housing as the hydraulic cylinder  11 . This embodiment is particularly recommended when the width of the chain conveyor  1 ,  2 , or  3  is relatively large, for example, in the case of the feed chain conveyor  1 . 
     To increase the tensional force, it is also possible to connect a hydraulic cylinder (e.g.  11 ) to each coupling rod  23 . A suitable arrangement is shown in phantom lines in FIG. 3 where the tension adjusting device incorporates two hydraulic cylinders  11  which are articulated to the associated ends of the two coupling rods  23 . The hydraulic cylinders  11  are then controllable in synchronism. 
     A sprocket  27  is fixed on the shaft  15 ,  17  or  19  so as to rotate therewith and the conveyor chain  28  is entrained thereover. Mutually spaced feed plates  29  (see FIG. 2) are fixed to the conveyor chain  28 . A similar sprocket is mounted on the fixed shaft  14  so as to rotate therewith and thereby drive the conveyor chain  28 . 
     The embodiment shown in FIGS. 4 and 5 is particularly well-adapted for use with the chain conveyors  2  and  3 . This embodiment is particularly suitable for the conveying to the grain tank and for the return of threshed material to the threshing device since these conveyors are relatively narrow. A sprocket  31  is fixed on the shafts  17  and  19  so as to rotate therewith and the conveyor chain  32  is guided thereover. The belts of chain conveyors  2  and  3  are equipped with partition walls  33  which have Y-shaped recesses (see FIG. 5) below the shafts  17 ,  19  into which the hydraulic cylinders  12 ,  13  are inserted. Bifurcated U-shaped yokes  34  are fixed to the piston rods  12 ′,  13 ′ of the hydraulic cylinders  12 ,  13 , the shafts  17 ,  19  being mounted therein. To prevent the displaceable shaft  17 ,  19  from jamming or tilting, provision is made for the shaft to be guided in slots  36  in two parallel housing walls extending at right angles to the shaft  17 ,  19 . Guide disks  35  disposed at the ends of these shafts slide over the exterior of the housing and cover the slots. The slots  36  create a free-space for the displacement of the shafts  17 ,  19 . The lower shafts  16 ,  18  are mounted at fixed points and are driveable. Sprockets of similar construction to the sprockets  31  are mounted thereon. These conveyor chains  32  have feed plates  29  inserted therein. This embodiment is extremely simple since the existing partition wall is used and the mounting for the displaceable shaft is established by means of the yoke. 
     In an advantageous arrangement, the hydraulic cylinders for each of the chain conveyors are controllable in common. The circuit diagram of FIG. 6 shows that two hydraulic cylinders  11  are used for the chain conveyor  1  while just one hydraulic cylinder  12 ,  13  is employed in the respective chain conveyors  2  and  3 . Pressurized oil is supplied from a common pressure source  37  over the pressure lines  38  to each of the hydraulic cylinders  11 ,  12 ,  13 . A non-return valve  39  is installed in each of the respective supply lines to the hydraulic cylinders  11 ,  12 ,  13  in such a manner that the pressurized oil can flow only in the direction in which the piston rods  11 ′,  12 ′,  13 ′ extend from the hydraulic cylinders  11 ,  12 ,  13 . For load relieving purposes, controlled valves  41  are provided in the bypass lines  40  so that the load can be selectively removed from either the two cylinders  11  or the cylinders  2  or  13 . With this design, it is possible to apply pressure simultaneously to all of the hydraulic cylinders and thereby tension each of the chains. The same pressure is thus applied to all of the cylinders. However, if different tensional forces are required, this can be done by using pistons of different diameter. The non-return valve prevents oil from returning, but the bypass line can relieve the load on a hydraulic cylinder when necessary. Whenever the drive motor of the harvesting machine is restarted, each of the chain tension adjusting devices is simultaneously and automatically supplied with the hydraulic pressures associated therewith and the piston-cylinder units are refilled where necessary. The low pressure hydraulic system in the machine is particularly advantageous and fully adequate for this purpose. 
     Other objects, features and advantages of the present invention will be apparent to those skilled in the art. While preferred embodiments of the present invention have illustrated and described, this has been by way of illustration and the invention should not be limited except as required by the scope of the appended claims.