in the drawing , reference numeral 10 denotes only part of a combine harvester having a front driving axle 12 on which support wheels 14 are disposed . for the sake of simplicity , only the right front wheel 14 is shown in the drawings . disposed on the drive axle 12 are a differential transmission 16 and a transmission casing 18 which accommodates a change - speed transmission with which it is possible to set different speed ranges , originating from a shaft 20 which carries a driven belt pulley 22 . the pulley 22 ( see fig1 ) may also be in the form of an adjustable , torque - dependent belt pulley 122 to 126 , which is disposed on a shaft 71 , as shown in fig1 through 14 . in this case , the double pulley 66 &# 39 ; does not need to be in the form of a torque - dependent double pulley . disposed at the forward end of the combine harvester is a crop pick - up arrangement 23 comprising a cutter mechanism 24 , a cutter mechanism floor 26 and an auger 28 by way of which the crop material which has been picked up is passed into an inclined conveyor housing 30 having an elevator conveyor 32 . the elevator conveyor 32 passes the crop material to a threshing cylinder 36 which is mounted rotatably on a shaft 38 . a concave 40 is disposed beneath the threshing cylinder 36 . the shaft 38 of the threshing cylinder 36 is mounted in the side walls 42 of the combine harvester . disposed on the outer end of the shaft 38 is a drive pulley 44 which is drivingly connected by way of a belt 58 to a pulley 54 . the pulley 54 and a pulley 56 which is arranged therebeside are mounted on a shaft 52 of an internal combustion engine 50 . the internal combustion engine 50 is disposed rearwardly of a grain tank 48 which is provided on the combine harvester 10 . the operator station 46 is disposed in front of the grain tank 48 . the drive axle 12 of the combine harvester 10 and therewith the support wheels 14 are driven by a steplessly adjustable belt - type transmission 59 . the transmission 59 ( see fig1 and 2 ) comprises a pulley 56 which is disposed on the shaft 52 , a double pulley 66 arranged on a pivotally mounted support arm 60 and formed from two v - belt pulleys , and the fourth pulley 22 . the pulley 56 is drivingly connected by way of a belt 69 to the one v - belt pulley 62 ( see fig3 ) of the double pulley 66 while the second v - belt pulley 64 is drivingly connected by way of a belt 68 to the pulley 22 . as can be seen from fig2 the double pulley 66 is adjustable by means of a shaft 70 shiftable in a slot 72 provided in the support arm 60 . the shaft 70 is engaged by a belt tensioning device comprising an adjustable tensioning bolt 74 which is connected at one end to the side wall 42 and which at the other end is rotatably accommodated in a tensioning sleeve 76 . the sleeve 76 is fixedly connected to the shaft 70 . by rotating the bolt 74 , the double pulley 66 can be displaced in the slot 72 so that the belt tension required for the transmission 59 can be set . the support arm 60 is pivotally connected to a mounting 78 on the side wall 42 . for the purposes of pivotal movement of the support arm 60 , the arrangement has a hydraulically operable actuating cylinder 80 which is connected at one end thereof to a mounting 82 on the side wall 42 and which at the other end is connected by its piston rod 84 to a lever arm 87 fixedly connected to the support arm 60 . the support arm 60 can be pivoted by retracting and extending the piston rod 84 of the actuating cylinder 80 , whereby the effective diameters of the two v - belt pulleys 62 and 64 are correspondingly altered . as already mentioned , the double pulley comprises the two v - belt pulleys 62 and 64 ( see fig3 ). the v - belt pulley 62 has an outer pulley half 86 which is non - rotatably connected to a hub 90 by way of bolts 88 . the hub 90 is mounted on the shaft 70 by means of right - hand and left - hand roller bearing assemblies 92 . the left - hand v - belt pulley 62 further comprises a central pulley half 94 which is non - rotatably connected to the hub 90 by way of a spline arrangement 97 , while however being axially displaceable on the hub 90 . adjoining the central pulley half 94 is a second central pulley half 96 which is part of the v - belt pulley 64 . the second pulley half 96 is mounted by means of a bushing 98 on a hub 100 which is fixedly connected to the first pulley half 94 . in that way , the second pulley half 96 can be rotated and also displaced in the axial direction relative to the first pulley half 94 . axial displacement of the second pulley half 96 towards the left is restricted by the inward face 102 of the first pulley half 94 and axial displacement towards the right is restricted by a snap ring 104 which is provided on the outer end of the hub 100 . the end face 102 of the left - hand pulley half 94 is at a small spacing from the end face 106 of the right - hand pulley half 96 . the right - hand v - belt pulley 64 is completed by the outer fourth pulley half 108 which is non - rotatably connected to the hub 90 by way of bolts 112 . so that a driving connection can be made between the left - hand v - belt pulley 62 and the right - hand v - belt pulley 64 , the two central pulley halves 94 and 96 are drivingly connected together by numerous cam elements 110 . as shown in fig4 thru 8 , the cam element 110 comprises a segment of a circular arc which with further cam elements 110 forms a circular arc which is arranged coaxially with respect to the shaft 70 . the individual cam elements 110 are releasably connected by way of bolts 112 to the face 102 of the one pulley half 94 and the face 106 of the other pulley half 96 . the cam elements 110 ( see fig6 and 7 ) have inclinedly extending cam surfaces 114 which , with the face 102 of the pulley half 94 and the face 106 of the pulley half 96 respectively form an angle α which is preferably 40 °. it is also possible however for the angle α to be of a value between 35 ° and 45 °. in operational use , the shaft 20 and therewith the wheels 14 are driven by means of the internal combustion engine 50 by way of the transmission 59 . the tension in respect of the two belts 68 and 69 , which is required to provide the drive , may be adjusted by displacement of the double pulley 66 on the support arm 60 . in that way , in normal operational use , the drive moment may be readily transmitted from the one v - belt pulley 62 to the other v - belt pulley 64 by way of the double pulley 66 . if , for example , the torque changes when the combine harvester 10 is climbing a gradient , then the torque also rises so that the two pulley halves 94 and 96 and therewith the corresponding cam elements 110 are displaced relative to each other . in that situation , as shown in fig7 the lower cam element 110 slides along the upper cam element 110 so that the two cam elements are displaced in the axial direction as indicated by the arrow 116 , with slight rotational movement about the shaft 70 . as a result of such displacement , the pulley halves 94 and 96 are moved in the direction of the outward edges of the belts 68 and 69 and thus the contact pressure as between the edges of the belts and the inward surfaces of the pulley halves 94 and 96 is increased . the higher contact pressure means that a torque which occurs at a higher level may now also be readily transmitted . when the level of the torque drops , the two pulley halves 94 and 96 can move towards each other again so that the frictional pressure is reduced , in accordance with the falling value of the torque . in that way , the required belt tension , corresponding to the level of torque occurring , may be automatically adjusted , during operational use , using simple structural means , in particular at the double pulley at which the greatest amount of slip normally occurs . the above - described belt - type transmission with the double pulley 66 of the advantageous configuration in question may also be readily used in all other working machines which are exposed to non - uniform kinds of loadings in order to provide in the optimum fashion the belt tension that is desired or necessary for the transmission of power . that makes it possible to reduce the amount of wear on the belts to a minimum as slippage at the pulleys can be kept at a low level . fig9 similarly to fig3 shows a double pulley 66 &# 39 ; which however differs from the double pulley 66 shown in fig3 in that the two pulley halves 94 and 96 are each connected to the respectively associated pulley half 86 and 108 by way of a spline arrangement 97 and 95 , respectively . in that way , the pulley 62 &# 39 ; which is formed from the two pulley halves 86 and 94 is mounted rotatably on the shaft 70 , relative rotary movement of the two pulley halves 86 and 94 relative to each other being excluded by virtue of the spline arrangement 97 . the same also applies in regard to the pulley 64 &# 39 ; formed from the pulley halves 96 and 108 . in the case of the pulley 64 &# 39 ;, the spline arrangement 95 which non - rotatably connects the pulley half 96 to the pulley half 108 also ensures that there is no relative rotary movement of the two pulley halves with respect to each other . as in the case of the double pulley 66 , disposed between the two pulley halves 94 and 96 are cam elements 110 which , on an increase in torque , cause the two pulley halves 94 and 96 to be urged away from each other . when that occurs , the cam surfaces 114 of the respectively interengaging cam elements 110 slide against each other so that in that way the pulley formed from the pulley halves 96 and 94 rotates relative to the pulley formed from the pulley halves 96 and 108 until the necessary contact pressure between the belt and the pulley , or the necessary belt tension , has been set in dependence on the increased level of torque . the axial displacement of the two pulley halves 94 and 96 therefore ensures that the respective oppositely disposed pulley halves 86 , 94 and 96 , 108 do not rotate relative to each other . in that way , slip and wear can be reduced . that further ensures that the belt is not subjected to a torsional loading . that is particularly advantageous when using a belt in which chain links or elements are introduced thereinto . that arrangement therefore ensures that the chain links or members in the belt do not take up an inclined position when slip occurs and then , after a relatively short period of operation , cause such damage to the belt that it has to be replaced . fig1 through 14 each show respective belt pulleys 122 through 126 , wherein one pulley half is non - rotatably connected to the respective other pulley half by way of a spline arrangement 95 in such a way that , depending on the kind of loading , it can move towards or away from the other pulley half . as can be seen in fig1 , the left - hand pulley half 128 is also provided at the rear side with a turned recess 132 therein , in which there are disposed a large number of cam elements 110 which are positioned coaxially with respect to the shaft 71 and which are engaged with oppositely disposed cam elements 110 which are arranged on a cam ring 134 and which are in coaxial relationship with respect to the shaft 71 . the cam ring 134 is connected to the shaft 71 by way of a spline arrangement 136 which may be for example in the form of an involute - tooth or spline arrangement , in such a way that the cam ring 134 is displaceable in the axial direction . the pulley half 128 has a bushing 137 which is fixedly connected thereto and which is non - rotatably connected by way of a spline arrangement 95 to the pulley half 130 which is axially displaceable on the bushing 137 . disposed on the rear side of the pulley half 130 and also arranged coaxially with respect to the shaft 71 are cam elements 110 which are secured to a cam ring 138 disposed coaxially on the shaft 71 . if for example the level of torque rises , then the two pulley halves 128 and 130 rotate somewhat relative to the cam ring 138 while the cam surfaces 114 of the cam elements 110 slide against each other . that increases the contact pressure against the belt and further increases the tension thereof . the pulley 123 ( fig1 ) is slightly different from the pulley 122 shown in fig1 , one pulley half 128 being rotatably mounted by way of a thrust bearing 131 on the shaft 71 . the axially displaceable pulley half 130 is drivingly connected to the shaft 71 by way of the cam elements 110 , the cam ring 138 and a v - type spline arrangement 140 . the spline arrangement 140 may comprise involute - type teeth which are arranged on the one hand in the bore in the cam ring 138 and on the other hand on the end of the shaft 70 . the pulley halves in the embodiments shown in fig1 through 14 are secured in position by means of a nut 142 which for that purpose is screwed onto the screwthread 144 at the end of the shaft 71 and thus also restricts the axial movement of the cam ring 138 . as can be seen from fig1 and 13 , a spring 146 may be provided between the inward end face of the cam ring 138 and the outward side of the pulley half 130 , or a spring 148 may be disposed between the outward end face of the cam ring 138 and the nut 142 . the purpose of the respective springs 146 and 148 is to urge the one pulley half 130 towards the outward pulley half 128 and thus , when the transmission 59 is starting up , to produce the necessary belt tension and the necessary rubbing pressure against the belt so that wear and also slip can be kept at a low level when starting up the transmission 59 . fig1 shows a further pulley 126 which is also provided on the rear side thereof with cam elements 110 which are arranged coaxially with respect to the shaft 71 and which are engaged with cam elements 110 provided on a cam ring 138 . the cam ring 138 is non - rotatably connected to the shaft 71 by way of a spline arrangement 140 . the individual cam elements 110 are of a suitable width to permit a long displacement travel in respect of the axially displaceable pulley half 130 . the travel distance of the pulley half 130 may also be so selected that the individual cam elements 110 are disengaged in order in that way to operate as a slip clutch , when loading peaks occur at the pulley , in order in that way to prevent damage from being done to the pulley or the other drive members .
an infinitely variable belt - type transmission for an agricultural machine or the like includes drive and driven pulleys and a pair of inversely variable diameter pulleys mounted on a shaft that is shiftable to vary the diameter of the pulleys and consequently the drive ratio of the transmission . the inner halves of the adjacent variable diameter pulleys are drivingly connected through a cam that exerts a force on the inner pulley halves tending to increase the pulley diameters and thereby increase the belt tension in response to an increase in torque transmitted through the transmission , and the shiftable pulley half on at least one of the pulleys is splined to its mating half so that the shifting movement in response to the torque increase results only in axial motion of the shiftable pulley half .