Abstract:
The screen conveyor for root crop harvesters comprises an endless screen belt conveyor, which consists of at least two conveyor belts and transverse conveying rods fastened to the conveyor belts and rotates about deflection rollers, which are rotatably mounted in a housing and of which at least one group can be driven by a driving mechanism by coaxially disposed deflection rollers. For this purpose, at least one adjuster is provided, which can be shifted into position against the working half of the screen conveyor belt and specifies a changing course for the working half of the conveyor belt by forming a step.

Description:
BACKGROUND OF THE INVENTION 
     The invention relates to a screen conveyor for root crop harvesters. 
     It is known that the screening function of the screen conveyor belt can be improved by causing the working half of the screen conveyor belt to oscillate by means of an oscillating, tapping apparatus or by means of the conveyor driving mechanism and that the disintegration of the dam composite can be accelerated by the shaking action. 
     SUMMARY OF THE INVENTION 
     The invention is concerned with the problem of an intensification of the screening action of the screen belt conveyor, adapted to the particular soil conditions of the harvesting, the potatoes on the screen belt conveyor being treated particularly gently. 
     The inventive screen conveyor provides the possibility for developing falling steps, the height of which is adjustable and which spread out and subsequently bring together the dam containing the potatoes passing over the steps and, with that, produce a motion of the dam components relative to one another. This motion appreciably intensifies the removal of soil by screening. Additional relative motions arise out of the elimination of the parallelity of the course of the dam and the belt surface, which favors the removal by screening even more. By means of the infinitely variable adjustment of the step height between zero and the maximum value, the number of steps can be matched to the particular conditions, such matching being controlled and also regulated as a function of a fixed degree of screening. 
     Further details and advantages arise out of the following specification and the drawing, in which several embodiments of the object of the invention are shown in greater detail diagrammatically. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 shows a diagrammatic side view of an inventive screen conveyor with a number of steps constructed in the working half of the screen conveyor belt, 
     FIG. 2 shows a truncated, enlarged view, similar to that of FIG. 1, for illustrating the screen belt conveyor with the step-free course, 
     FIG. 3 shows a truncated, diagrammatic section along the line A--A of FIG. 2, 
     FIG. 4 shows a sectional representation of a finger of a guiding apron along the line B--B of FIG. 2, 
     FIG. 5 shows a truncated side view similar to that of FIG. 2 in a second embodiment of the screen conveyor with the step-shaped course of the screen conveyor, 
     FIG. 6 shows a view similar to that of FIG. 5 to illustrate the conveyor belt of the screen conveyor with the step-free course, 
     FIG. 7 shows a section representation similar to that of FIG. 3 through the construction of FIG. 6, 
     FIG. 8 shows a truncated side view similar to that of FIG. 5 of a third embodiment of a screen conveyor with a step-shaped course of the conveyor belt, 
     FIG. 9 shows a view similar to that of FIG. 8 to illustrate the screen belt conveyor with a step-free course and 
     FIG. 10 shows a sectional representation similar to that of FIGS. 3 and 7 through the embodiment of FIG. 9. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The screen conveyors for root crop harvesters shown in the drawing, particularly for potato harvesters and pick-up loaders have a conveyor belt 1, which revolves endlessly about deflection rollers 3, 4, 5, 6, 7 rotatably mounted in a housing 2, of which the deflection rollers 5, which are disposed coaxially, can be driven by a driving mechanism, the details of which are not shown. The driving mechanism can be formed by a hydraulic motor or derived from a tractor, for example, over drive shafts. 
     In detail, the screen belt conveyor 1 consists of two conveyor belts 8 disposed on the outside and of transverse conveying rods 9, which are disposed on these at equal distance from one another and parallel to one another and are riveted to the conveyor belts 8 in the region of ends that have been pressed flat. A number of adjusters 10, six in the example shown, are assigned to the working half of the screen belt conveyor 1. With the help of the adjusters 10, steps 11 can be formed in the course of the working half of the conveyor belt. The number of adjusters 10 depends on the length of the screen belt conveyor 1 and on the distance between the adjusters 10, which advisably ranges from 250 mm to 750 mm and preferably is equally large between all adjusters 10. 
     For adjustment purposes, each adjuster 10 comprises movable control elements 12, which can be adjusted infinitely variably or in steps between a starting position above the conveyor belts 8 that has no effect on the course of the working half of the screen conveyor belt 1 and an end position, in which they form a step of maximum height in the working half of the belt conveyor. These movable control elements 12 act in concert with stationary control elements 13, which in turn have an arrangement below the conveyor belts 8, in which they retain a step-free course for the working half of the screen belt conveyor 1 when the movable control elements 12 are in the starting position. 
     Preferably, the control elements 12, 13, are constructed as bodies of revolution, of which each adjuster 10 has two pairs, which act in concert with the upper side and the underside of the two conveyor belts 8. In the embodiment of FIGS. 1 to 3, the bodies of revolution 12, 13 are formed by cylindrical rollers 14, 15, which offer at their periphery an engagement surface 18, 19, which is rotationally symmetrical with their axis of rotation 16, 17. The engagement surface 18, 19 of the bodies of revolution 14, 15 can be formed cylindrically throughout or also have a basic cylindrical shape with profiling, which acts in concert with elevations on the upper side and the underside of the conveyor belts 8. The elevations on the upper side of the belt are formed by ends, pressed flat, of the transverse conveying rods 9 and the elevations on the underside of the belt can be formed by the flat pieces 20, which correspond to and lie opposite the ends, pressed flat, of the transverse conveying rods 9 and through which the connecting rivets 21 pass. 
     In the case of the engagement surfaces 18, 19 profiled to accommodate the elevations, the bodies of revolution 14, 15 are caused to revolve by the advancing screen conveyor belt, the main engagement, however, taking place between the cylindrical part of the engagement surfaces 18, 19 of the bodies of revolution 14, 15 and the surfaces of the conveyor belts 8. In the case of continuous, cylindrical engagement surfaces 18, 19, which engage only elevations on the conveyor belts 8, the engagement surfaces 18, 19 advisably are formed at a noise-damping and impact-damping peripheral layer, which may consist, for example, of rubber. 
     In the case of the embodiments shown, the control elements 12 are mounted at a rectangular lever 22, which can be swiveled about the axis of rotation 17 of the associated second control element 13 of a control element pair assigned to a conveyor belt 8 and receives its swiveling drive from a control rod 23, which can be operated by a pressure medium cylinder 24. This pressure medium cylinder 24 can be acted upon by a controller 25 over the pressure medium pipelines 26, 27. The controller receives its control input from a measuring instrument 28, such as an infrared sensor or a photoelectric barrier, with which the degree of screening is determined near the discharging end of the screen belt conveyor 1. 
     With the help of the control rods 23, one each of which is assigned to the pair of control elements 12, 13 assigned in each case to a conveyor belt 8, the control elements 12 can be deviated on an arc of a circle about the axis 17 of the control elements 13 out of their starting position illustrated in FIGS. 2, 6 and 9 into an end position, in which they act in concert with the control elements 13 to form the steps 11, as illustrated in FIGS. 1, 5 and 8 with, in each case, the maximum step height. 
     In the example shown, all movable control elements 12 are operated jointly and uniformly with the consequence that steps of the same depth are formed in the screen belt conveyor 1. Instead of this particularly simple form of operating the control elements and forming the steps, it is also possible and advantageous in particular cases to operate the movable control elements 12 of an adjuster 10 independently of the control elements 12 of other adjusters 10. With such individual operation or by operating the movable control elements 12 simultaneously in groups, it is possible to construct steps 11 of independently selectable height in the screen belt conveyor 1, for example, advantageously in the manner that the steps 11, formed in the working half of the screen conveyor belt 1, have a decreasing height in the running direction of the working half of the conveyor belt. Furthermore, it is possible to decrease the number of steps, if necessary, below the number of adjusters 10, if the soil conditions, for example, from the very start ensure good screening and an intensification of the screening to the fullest extent possible is not desired. The different possibilities for controlling or regulating step formation in the screen belt conveyor 1 can be assigned to programs and these can optionally be included in the regulating system under the control of a computer. The primary control input for such regulating process is the degree of screening, which should reach its maximum only shortly before the upper end of the working half of the screen conveyor belt, so that the potatoes, remaining behind on the screen belt conveyor 1, do not remain unprotected on the latter for longer distances after the screening has been completed. 
     For shielding the adjusters 10 from contact with the components of a potato dam transferred to the working half of the screen conveyor belt 1, lateral, supported guiding aprons 29, which run parallel to the running direction of the working half of the screen conveyor belt and are aligned essentially at right angles to its surface, are provided at the housing 2. The lower border edge of the guiding apron 29 in each case is impenetrable on the inside, next to the conveyor belts 8. When the course of the working half of the conveyor belt is step-free, the lower edge region of the guiding aprons 29 can lie on the upper side of the working half of the screen conveyor belt or end impenetrably above the working half of the screen conveyor belt 1. In any case, the lower part of the guiding aprons 29 is elastically deformable and adaptable to the course of the working half of the screen conveyor belt 1, when the latter is constructed in these steps 11. 
     Preferably, the lower part of the guiding aprons 29 is formed by elastically flexible guiding fingers 30 disposed impenetrably in parallel behind one another in the running direction of the working half of the screen conveyor belt 1. Said guiding fingers 30 experience an intensified elastic deviation during the formation of the steps. 
     Because the ends of the guiding fingers slide over the transverse conveying rods 9 of the screen belt conveyor 1, said rods 9 experience a back and forth motion in and counter to the running direction of the working half of the conveyor belt, so that they bring about active shielding. The guiding fingers 30 can all have the same length (FIGS. 2, 6 and 9), in which case they lie on the undeformed working half of the conveyor belt with uniform deformation of their lower ends. However, they can also have a stepped length to correspond to the intended maximum step formation, in which case, when the steps have the maximum height, they are in engagement with the working half of the screen belt conveyor 1 with uniformly deformed lower ends and, when the working half of the conveyor belt has no steps, experience greater or lesser deformations in zones. The guiding fingers 30 can be circular or also oval in cross section, as shown in FIG. 4. Such guiding aprons can also be used for screen conveyors, in which steps are not formed in the conveyor belt. 
     The constructions of FIGS. 5 to 7 on the one hand and of FIGS. 8 to 10 on the other differ from the construction of the screen conveyor of FIGS. 1 to 4 only due to the different configuration of the control elements 12, 13. In the constructions of FIGS. 5 to 7, these are formed by bodies of revolution 31, 32, which basically have a square shape and elevations 33 molded at the periphery. In the construction of FIGS. 8 to 10, they are formed by bodies of revolution 34, 35, which basically have an approximately elliptical shape and elevations 36 molded at the periphery. 
     The bodies of revolution 31, 32 of the construction of the screen conveyor of FIGS. 5 to 7 have an engagement surface 37, 38 at the periphery, which basically offers a square shape, but on which elevations 33 are superimposed, of which one each is provided in the four corners and a further one between the corner elevations. 
     The bodies of revolution 34, 35 of the screen conveyor of FIGS. 8 to 10 have an engagement surface 39, 40 at the periphery, which basically offers an elliptical shape and on which elevations 36 are also superimposed. One each of the elevations is disposed here in an aligned extension of the long or short axis of the ellipse and a further elevation is provided between these. 
     The elevations 33 and 36 provide the engagement surfaces 37, 38 and 39, 40 respectively of the bodies of revolution 31, 32 and 34, 35 respectively with a profiling, by means of which they act in concert, in a driving sense, with the elevations on the upper side and the underside of the conveyor belts 8. The bodies of rotation 31, 32; 34, 35 of the pair of bodies or rotation, acting in concert with a conveyor belt 8 of the screen belt conveyor 1, are aligned with respect to one another in such a manner, that the engagement surfaces 37, 38 and 39, 40 respectively in each case act on the conveyor belts 8 simultaneously with their regions with a maximum axial distance and subsequently correspondingly in each case simultaneously with regions with a minimum axial distance. At the same time, they are revolving synchronously. 
     The pairs of asymmetric bodies of revolution 31, 32 and 34, 35 respectively, which act in concert, are disposed in their starting position of FIGS. 6 and 9, in which they permit the working half of the screen conveyor belt 1 to have a step-free course, so that their engagement surfaces 37, 38 and 39, 40 respectively are in engagement with the upper side and the underside respectively of the conveyor belts 8 and revolve synchronously. As a result, flat steps are formed temporarily in the screen belt conveyor 1 whenever the regions of the engagement surfaces 37, 38 and 39, 40 respectively engage the conveyor belts 8 with a maximum axial distance. On the other hand, in between times, when the regions of the engagement surfaces 37, 38 and 39, 40 respectively act on the conveyor belts 8 with a minimum axial distance, the working half of the screen conveyor belt 1 once again assumes its step-free course. 
     Since the bodies or rotation 31, 32 have four regions of engagement surfaces 37, 38 with a maximum axial distance, the working half of the screen conveyor belt 1 experiences four step formations during its advance during each full revolution of the bodies of rotation 31, 32. Due to this rapid, consecutive formation of flat steps, the working half of the screen conveyor belt 1 is set, as it were, into pulsating oscillations and exerts shaking motions in conjunction with changes in the course of the surface on the upper side of the potato dam. The screening action is favored appreciably by these shaking motions. 
     The screening action is intensified even significantly more, if the control elements 12, 13 bring about a permanent formation of steps, as shown in FIGS. 5 and 8 with, by way of example, a maximum step depth. In addition to the forces, which intensify the screening action and which are transferred to the potato dam by the steps formed and by the asymmetry of the bodies of rotation 31, 32 and 34, 35 respectively, further forces, increasing the screening effect, are exerted on the potato dam owing to the fact that the regions of the working half of the conveyor belt between two consecutive adjusters 10 with asymmetric bodies of rotation experience accelerations and decelerations in and counter to the running direction of the working half of the screen conveyor belt 1 and agreeing in frequency with the changes in the engagement with regions of the engagement surfaces 37, 38; 39, 40 with a maximum distance and with regions with a minimum axial distance. 
     In the case of bodies of rotation 31, 32 with basically a square shape, the frequency of the step shape-intensifying and step shape-attenuating deformations is twice as high as in the case of bodies of rotation 34, 35. On the other hand, in the case of the elliptical or oval bodies of rotation 34, 35, the deformation amplitude can be made more pronounced in relation to the total dimensions of the bodies of rotation 34, 35. 
     Instead of a constant engagement of the profiled pairs of bodies of rotation 31, 32 and 34, 35 respectively with the conveyor belts 8, provisions can also be made that these, in the starting position for a step-free course of the working half of the screen conveyor belt 1, are disengaged from the elevations on the conveyor belt 8 and engage the conveyor belts 8 only when permanent steps are formed. Constructively, this can be realized, for example, owing to the fact that the rectangular lever 22 additionally can be pivoted clockwise about a swivel pin, which is placed centrally between the axes of rotation 16 and 17, beyond the position in FIG. 6 and 9, until the two bodies of rotation 31, 32 and 34, 35 respectively are raised from the conveyor belts 8. In the case of such a construction, the lower body of rotation 32, 35 is to be mounted at the lower end of the angle rectangular lever 22 and in a bearing of the housing 2, the bearing in the housing 2 being guided in an arc-shaped slot restricted about the central swivel pin of the rectangular lever 22. For the central swivel pin of the rectangular lever, the mounting must be pivotable about the axis of rotation 17 of the bodies of rotation 32, 35 in a limited fashion in an arc-shaped slot, the ends of the slot, as stops, in each case defining the pivoting ranges. 
     A synchronizing gear can be assigned to each pair of bodies of rotation acting in concert, in order to ensure synchronous running when the engagement between the bodies of rotation 31, 32 and 34, 35 respectively and the conveyor belts 8 is terminated completely.