referring to the drawings , it is possible to observe the major elements and general operation of the present invention . left and right references are used as a matter of convenience and are determined by standing at the rear of the forage harvester and facing the forward end in the normal direction of travel . likewise , forward and rearward are determined by normal direction of travel of the tractor or round baler . upward or downward orientations are relative to the ground or operating surface . horizontal or vertical planes are also relative to ground . in fig1 is shown the feeder device ( 1 ) of a forage harvester with a chopping device ( 2 ) arranged on it in a perspective view from the front and the right , on which the spring system in accordance with the invention is implemented . fig2 conveys a direct side view of its left side without the chopping device ( 2 ). the feeder device ( 1 ) has two upper feeder rollers , which according to the direction of flow of the crop are designated as the prepressing roller ( 3 ) and pressing roller ( 4 ). these are arranged opposite the front lower feeder roller ( 6 ), which is in bearing points at a fixed position in the casing ( 5 ) of the feeder device ( 1 ), and the rear lower feeder roller ( 7 ) in such a way that their distance from these can be varied . for this the pressing roller ( 4 ) with its bearing points ( 8 ) is held in the front ends of oscillating cranks ( 9 ), which with their rear ends carried in bearings on pivot bolts ( 10 ) fixed in the casing ( 5 ) of the feeder device ( 1 ) so that they can pivot . on both sides on the shaft ( 11 ) of the pressing roller ( 4 ) a connecting rod ( 12 ) engages with its rear end in bearings , in the front ends of which there are bearing points ( 13 ) located for the prepressing roller ( 3 ). a short formed part ( 14 ) attached to the oscillating crank ( 9 ) engages with a longer recess ( 15 ) incorporated into the connecting rod ( 12 ), which is depicted in the sectional view of fig7 as a detail . fig3 shows , how the prepressing roller ( 3 ) is raised up maximally by the crop and how through the location of the formed part ( 14 ) on one side of the recess ( 15 ) the pressing roller ( 4 ) is raised a bit without the influence of the crop . on the right side viewed in the direction of travel the connecting rod ( 12 ) is formed as a spur gear box ( 16 ), the central spur wheel of which is connected with a cardan shaft ( 17 ) so that it can be driven . the spring system for the upper feeder rollers is so constructed that on the bearing points ( 13 ) of the prepressing roller ( 3 ) a compression spring ( 18 ) formed as an external spring engages , into which a second compression spring ( 19 ) formed as an internal spring projects . both compression springs ( 18 ; 19 ) have an opposite direction of coiling and abut with their lower ends on a spring base ( 20 ), which is arranged so that it can swivel about a bolt ( 22 ) attached to the connecting rod ( 12 ) by means of a holding bracket ( 21 ). to the spring base ( 20 ) a guide rod ( 23 ) pointing essentially in a vertical direction is rigidly joined , on which the compression springs ( 18 ; 19 ) are located in a concentric arrangement . at the same time the longitudinal axis of the guide rod ( 23 ) lies very close to the central axis of the shaft ( 24 ) of the prepressing roller ( 3 ) or runs directly through it . the lengths of the external springs and of the internal springs are so chosen that the external spring in the lowest position of the prepressing roller ( 3 ) already abuts with its upper end on the upper edge of the casing ( 5 ) of the feeder device ( 1 ), whereas the upper end of the internal spring until then has still some free space . in order to explain the upper abutment refer to fig5 and 6 . here can be seen that first the external spring in fig5 and later also the internal spring as in fig6 abuts from below on a centering disc ( 25 ), which is welded onto the upper edge of the casing ( 5 ) and is surrounded by a sleeve ( 26 ) open below . the centering disc ( 25 ) has a central drilled hole , into which the upper end of the guide rod ( 23 ) is slid . the spring system applying the rolling force to the pressing roller ( 4 ) is in principle constructed the same as that for the prepressing roller ( 3 ), only with the difference that around the guide rod ( 27 ) there is only one single compression spring ( 28 ) analogous to the compression spring ( 18 ) functioning as an external spring for the prepressing roller ( 3 ), the rolling force of which in comparison with the spring package on the prepressing roller ( 3 ) amounts to only 15 to 35 percent . the lower stops for the position of the prepressing roller ( 3 ) and of the pressing roller ( 4 ) in their lowest position are formed from stop plates ( 29 ) fixed to the guide rods ( 23 ; 27 ), which fit closely with the interposition of rubber buffers ( 30 ) from above on the upper edge of the casing ( 5 ) of the feeder device ( 1 ). their position can be adjusted by changing the lower positions of the upper feeder rollers by means of lock nuts ( 31 ). the stop shoulders ( 32 ) fixed to the guide rods ( 23 ; 27 ) serve as upper stops for limiting the lift path of the prepressing roller ( 3 ) and of the pressing roller ( 4 ) in their uppermost position and fit closely from below on the centering disc ( 25 ) under the upper edge of the casing ( 5 ) of the feeder device ( 1 ). the development of the compression spring as an external spring which is already under a certain prestress in the lowest position of the prepressing roller , it is ensured that the second compression spring sticking into it lies protected from dirt and that as a result it also requires no additional space . the opposite direction of the coiling of the outer spring to that of the inner spring it is ensured that they cannot get hooked up in each other in any position . the placing of the lower support of the outer spring and the inner spring as close as possible to the central axis of the shaft of the prepressing roller , in that through it the common roll force presses directly and exclusively on the prepressing roller . through the shorter inner spring it is in addition to be noted , that with smaller layer thicknesses also only a small roll force is exerted only by the outer spring on the crop , which is completely sufficient and as a result the crop is not damaged in any way . with higher layer thicknesses on the other hand , then very high common roll forces are available , which are urgently needed in this region of the lifting path . the lower stops for limiting the position of the prepressing roller and of the pressing roller are located in their lower positions above the upper edge the casing of the feeder device , as a result of which both rollers hang on their guide rods and the lower stops themselves lie in a relatively dirt - free space . rubber buffers cushion any possible impacts from a rapid upward motion of the upper feeder rollers . the invention has proved itself to implement the upper stops for limiting the position of the prepressing roller and the pressing roller in their uppermost positions through the guide rods themselves , in that each one is equipped with stop collar , which bears from below upon centering discs beneath the upper edge of the casing of the feeder device . it is seen in that for a pressing roller with its bearing point points in oscillating cranks and on it connecting rods connected forwards for the bearings of the prepressing roller a facility is installed , which restricts somewhat the freely movable angular area between the oscillating crank and the connecting rod for the avoidance of blockages . in this way it is ensured that the pressing roller cannot remain in its lowest position , if the prepressing roller is in its uppermost position and vice versa . for this a short - formed part is attached which engages in a longer recess in the connecting rod , which forms an upper and a lower stop . it will be obvious to those skilled in the art that various changes may be made without departing from the scope of the invention and the invention is not to be considered limited to what is illustrated in the drawings and described in the specification .
the apparatus is a spring system on forage harvester feedrolls . the upper forward feedroll has two concentric springs on each side . the outer spring is operative over the whole range of displacement . the inner spring exerts tensioning force on the feedroll only as of a certain minimal lifting of the feedroll . the rear upper feedroll has one spring on each side . this one spring has a substantially smaller spring force than the forward spring package . the feedroll supporting linkages are arranged with complementary and cooperating cam surfaces which are disposed so that , when the forward feedroll is lifted above a predetermined minimum value , the rearward feedroll is also lifted thereby without even any lifting force from the crop material passing therebelow .