AGRICULTURAL BALERS

Abstract: A round baler for forming bales up to a maximum diame­ ter comprises bale-forming means defining a bale chamber (11) the bale-forming means comprising at least one expand­ able endless flexible member (17, 48) provided with drive and guide members (18, 19, 21, 49, 51, 52) all disposed within the envelope defined by the or each endless member, the arrangement being such that, in use, at least when a bale has reached substantially said maximum diameter, the run of the or each endless member (17, 48) defining the bale chamber (11′) is in contact with all of the associated drive and guide members so as to be supported thereby.

Description: AGRICULTURAL BALERS This invention relates to agricultural balers and move particularly to so-called round balers which produce cylindrical bales or rolls of crop material. In general, round balers are of two types: the expanding chamber type which produces balers with a relatively hard core and a generally high and relatively constant density throughout; and the fixed chamber type which produces bales with a relatively soft core but a relatively compacted or hard outer layer or shell. The advantages of hard core balers are that they pack more crop material into a bale compared with a similarly sized soft core bale, and they can produce bales of any size up to the maximum which a given machine is capable of producing, with all sizes of bales being in generally good order from the standpoint of being subjected to handling without falling apart. The advantages of soft core balers are that they produce bales with a reduced tendency to moulding if the crop material is baled wet; the bale core presents no problems to cattle when feeding from the bale (whereas hard cores can be difficult to tear apart); they produce bales with good weathering characteristics due to the hard shell, and the latter ensures a good looking,11clean11 bale which is very stable when being handled; the balers are of relatively simple design; and the balers normally have no difficulty in forming a bale core which can sometimes be a problem with hard core balers when handling short lengths of crop material. It is an object of the present invention to provide a round baler which affords some of the advantages of both a hard core balers when handling short lengths of crop material. It is an object of the present invention to provide a round baler which affords some of the advantages of both a hard core baler and a soft core baler. One of the problems with achieving this objective is that the bale-forming elements have to be both expandable, to give effect to the high flexibility characteristics of the core forming, and yet exert a relatively large force on the bale at completion thereof to produce the hard outer shell. In the case of round balers employing expandable bale-forming members in the form of a pair of endless flexible members, such as chains#-#r# - belts, the flexible members are 'visually tensioned by sprlng means and irrespective of the tension produced thereby, the flexible member will still be capable of flexing to some extent because it is not positively supported on the major portion of its length. Thus there is a limit to the pressure which is exertable by these flexible members to produce the outer shell of the bale which is why, prior to the present invention, sufficiently hard shells have only been achieved by the fixed bale-forming members of soft core balers. According to the present invention there is provided a round baler for forming bales up to a maximum diameter comprising bale-forming means defining a bale-chamber, the bale-forming means comprising at least one expandable endless flexible member provided with drive and guide members all disposed within the envelope defined by the or each endless member, the arrangement being such that, in use, at least when a bale has reached substantially said maximum diameter, the run of the or each endless member defining the bale chamber is in contact with all of the associated drive and guide members so as to be supported thereby. Preferably, the bale chamber is defined by two endless, flexible members, one or both of which forms part of expandable bale-forming means. Conveniently the or each expandable member comprises a pair of spaced endless chains interconnected by a plurality of slats extending transversely of the machine. When two expandable members are provided1 one such member may be tensioned by tensioning means comprising at least one arm pivotably mounted intermediate its ends¯on the machine the machine and carrying at respective ends rotatable -members around which the expandable member passes, the arm being-urged about its pivot by a torsion spring acting between a stop on the arm and a stop on the machine, whereby the expandable member is tensioned. The pivot of each arm may be offset from the centre thereof. The other expandable member may be tensioned by tensioning means comprising at least one upper and lower tensioning device each in the form of a T-shaped member with the crosspiece thereof carrying a rotatable member at each end, and the stem thereof being pivotally mounted on one end of a support arm pivotally attached to the machine tension spring being connected between said stem and the machine and operable to pivot the T-shaped support such that only one rotatable member thereof is in engagement with the expandable member when the machine is empty. Round balers in accordance with the present invention r will now be described in greater detail, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a schematic side view of a first embodiment of round baler showing tlie machine empty, Figure 2 is a view similar to that of Figure 1 but showing the machine with a completed bale, Figure 3 is an enlarged view of a portion of Figure 1, Figure 4 is a side view of Figure 3, Figure 5 is a schematic view of a component of Figure 1, Figure ó is a partial sectional view, on the line VI-VI of Figure 5, Figure 7 is plan view of Figure 6, Figure 8 is a sectional view on the line VIII-VIII of Figure 7, Figure 9 is an enlarged view of a still further component of Figure 1, Figure 10 is a partial sectional view on the line X-X of Figure 9, Figure 11 is an enlarged view of yet another position of Figure 1, Figure 12 is a partial longitudinal section of the component of Figure 11, Figure 13 is a view of an alternative component for the first embodiment, figures 14 and 15 are'views similar to those ol Figures 1 and 2, respectively, but showing a second embodiment, and Figures 16 and 17 are views similar to that of figure 2 but showing third and fourth embodiments, respectively. Referring first to Figures 1 and 2, the first embodiment is in the form of a pull-type round baler comprising a base frame 1 carrying a pair of ground-engaging wheels 2 and having attached thereto a drawbar 3 for connection to a tractor (not shown) or other towing vehicle. A drive shaft 4 extends above the drawbar 3 and is connected at one end to an input shaft 5 of a gearbox 6, and connectable at the other end to g power-take-off shaft (also not shown) of the towing vehicle. Side walls 7 of the machine are attached to the base frame 1, the side walls partially defining a bale forming chamber by way of providing the sides therefor. The front and rear of the bale forming chamber are defined by portions of respective expandable members 8 and 9 which, when the machine is empty (Figure 1), form together with the side walls 7 a generally vertically oriented, wedge-shaped (as seen in side view) start chamber 11, and which expand on the formation of a bale to form a cylindrical bale chamber 11 (Figure 2). Each side wall 7 is split, with the expandable member 8 forming a front portion of the bale chamber in conjunction with one portion each side wall, and the expandable member 9 forming a rear portion of the bale chamber in conjunction with the other portion of each side wall. As seen in Figures 1 and 2, the rear portion of the bale chamber is larger than the front portion and in fact forms a tailgate 12 for the machine which is pivotable upwardly in order to effect discharge of a completed bale 13 (Figure 2) from the machine. With this differential sizing of the two portions of the bale chamber, the centre of gravity of a completed bale lies within the rear portion of the bale chamber, whereby there is a natural tendency for a completed bale to roll from the machine once the tailgate 12 has been raised, which tendency greatly facilitates bale discharge. Pivotally mounted at the front of the machine is a conventional crop pick-up unit 14 which, in use, Picks up crop material from the ground and delivers it to a combined crop feeder and bale support device 15 located at the mouth of the bale start chamber 11. located within the rear portion of the bale chamber and disposed at the front bottom corner adjacent the feeder and support device 15 is a rotor 16 which extends across the full width of the bale chamber, i.e. extends between the side walls 7. The rotor 16 also serves to support a bale during its formation. Having described the overall machine in general, certain components will now be described in greater detail with reference to Figures 3 to 12, in addition to Figures 1 and 2, of the drawings. Looking first at the bale chamber, the expandable member 8 partially defining the front surface of the chamber comprises two transversely spaced apart endless chains 17 each extending around, a driven sprocket 18, an idler sprocket, 19 and a non-toothed guide roller 21 disposed at respective apices of a triangle, as seen in side view in Figures 1 and 2. The chains 17 are disposed towards, but inset from, respective sides of the machine and are interconnected by a plurality of slats 22 which extend transversely of the machine, with each end ot each slat extending past the associated chain and terminating just short of the side walls 7 as seen in Figure 5. The construction of each slat 22 will be described hereinafter. With specific reference to Figures 3 and -4, the sprocket 19 and guide roller 21 associated with each chain 17 are mounted for rotation on an arm 23 which itwturn is pivotally mounted on the frame via a pivot shaft 24 (common to both arms 23) offset from the centre of the arm and carried in a bush 25. It will be seen from Figure 4 that each arm 23 comprises a pair of spaced members between which extend two spigots 26 on which the sprocket 19 and guide roller 21 are respectively mounted via bearings 27, only the sprocket being shown in Figure 4. The pivot shaft 24 has, at each end, a first portion of reduced diameter around which is disposed a torsion spring 28, and a second portion of further reduced diameter which is received by the associated bush 25. Each spring 28 serves to bias the associated arm 23 in a clockwise direction as seen in Figures 1 and 2, whereby tension in the chain 17 is maintained and any slack resulting from wear is automatically taken up. The pivotal mounting of the arms 23 allows the orientation of the latter to change as a bale is being formed as will be described. This tensioning of each chain 17 is achieved by locating one end 29 of each spring 28 against a stop 31 fixed to the related arm 23, and locating the other end 32 against a stop 33 fixed to one end of an arm 34 located os the outside of the associated side wall 7, the stop 33 extending through an arcuate slot 35 in the latter. Each arm 34 is pivotally mounted on the pivot shaft 24 via the associated bush 25 and has a reinforcing flange 36 extending around its periphery and away from the side wall 7. A bracket in the form of two spaced plates 37 is attached to the end of each arm 34 opposite to that of which the stop 33 is secured, a pivot pin 38 extending between the plates 37 and being attached to one end of a threaded rod 39, the other end of which is received by a flange 41 provided on the related side wall 7. Nuts 42 adjustably secure each rod 39 to the related flange 41, whereby the arms 34 can be adjusted about the pivot shaft so as to move the stops 33, thereby to set the required torsion in the springs 28 and hence initial tension in the chains 17. The arms 23 and pivot shaft 24 are vertically adjustably mounted with respect to the related side wall 7 by virtue of the ends of the pivot shaft 24 and the bushes 25 being carried by respective plates 43 bolted by bolts 40 to the side wall 7 via slots 44 provided in the latter to permit relative sliding movement. Each plate 43 is formed with a flange 45 to which is attached one end of a threaded rod 46, the other end of which is adjustably attached to the related side wall flange 41 by nuts 47. Adjustment of the nuts 47 after 1loosening the bolts 40 either raises or lowers the plates 43 relative to the side walls 7 so as to move the pivot shaft 24, and hence the arms 23, to the desired position. After adjustment, the pivot shaft 24 and the arms 23 coupled thereto are firmly held in the selected vertical position, on the one hand, by the nuts 47 and the threaded rod 46, and on the other hand, by the bolts 40 firmly tightened to the side walls 7 through the elongate slots 44 therein. It will be noted that by this adjustment, the vertical position of the sprockets 19 relative to fixed upper sprockets 49 of the rear expandable member 9, When the baler is in its empty condition, can be changed. It will also be noted that, as a bale is being formed in the bale chamber, the sprockets 19 move upwardly and away from the fixed upper sprockets 49 of the rear expandable member 9 by virtue of the arms 23 supporting the sprockets 19 pivoting in an anticlo:ckwise direction as seen in Figures 1 and 2. This displacement, however, has been kept to an acceptable minimum by providing the pivot shaft 24 substantially offset relative to the centre of ¯ the arms 23, and such that the sprockets 19 are positioned closer to the pivot shaft 24 than the guide rollers 21. Using the adjustability of the pivot shaft 24 in a generally vertical directions provided by the adjustable plates 43, the forward expandable member 8 is set so that, in the empty condition of the baler, the sprockets 19 are positioned slightly below the fixed sprockets 49 of the rear expandable member 9 and as close as possible to the forward, generally vertical run of the rear expandable member 9 without however the forward and rearward expandable members 8, 9 fouling each other during operation.. Zt will also be noted that, as a bale Is being formed in the bale chamber, the arms 23 pivot anticlockwise, as seen in Figures 1 and 2, until the guide rollers 21 engage the opposed runs of the endless chains 17 forming part of the expandable member 8. At this moment, further pivoting of the arms 23 in the anticlockwise directions and hence further "expansion" of the expandable lumber 8, becomes impossible, whereby the inner run of the expandable member 8 assumes a virtually fixed position which is very much the same as the fixed positfon-assumed by# the bale forming members in a so-called soft core baler or a baler with a fixed bale chamber. Turning now to the expandable member 9, this also comprises a pair of spaced endless chains 48 located adjacent, but inset from, the respective side walls 7 and interconnected by a plurality of slats 22, the construction of which has yet to be described. Again, the slats 22 extend beyond the chains 48 and terminate just short of the side walls 7 as shown in Figure 5. Each chain 48 extends around an upper fixed sprocket 49, a lower fixed sprocket 51 associated with the rotor 16, and one or both movable guide rollers 52 of each of an upper and #ower pair thereof. When the machine is empty (Figure 1), only one roller 52 of each pair is in engagement with the chains 48, but when a bale nears completion, both rollers of each pair are in engagement vith the chains 48. Also, under this condition as a bale nears completion in the bale chamber 11', both the inner and outer runs (as seen with respect to the bale chamber) of the chains 48 engage the rollers 52. The rollers 52 of each pair are rotatably mounted on respective ends of a crosspiece 53 of a generally T-shaped support, the stem 54 of which is provided with a pivot 55 intermediate its ends. Each pivot 55 extends from the stem 54 through an arcuate slot 56 in the associated side wall 7 and is attached to a support arm 57 pivotally mounted at 58 on said side wall at the centre of curvature of the slot 56. The eend of each stem 54 of the T-shaped support remote from the crosspiece 53 is connected to one end of a tension spring 59, the other end of which is attached to the associated side wall 7. The two upper crosspieces 53 and the two lower crosspieces 53 are interconnected by respective transverse tubular beams 61 to ensure that the two upper and two lower supports pivot in unison. The springs 59 serve in the empty condition of the baler, to bias the upper T-shaped supports in a clockwise direction, and the lower supports in an anti-clockwise direction, as viewed in Figure 1, whereby one roller 52 of each pair engages the associated chain 48 to maintain tension therein and again take up any slack in the chain resulting from wear. Also, the support arms 57 are pivoted in a direction towards the bale start chamber 11 until the pivot pins 55 engage the forward ends of the arcuate slots 56, under the action of the springs 59. It will also be noted that in this empty condition the rear expandable member 9 assumes a generally rectangular oonflguration with the run 7 facing the bale start chamber 11 being oriented generally vertAcally. As a bale is being formed in the bale chamber 11' the forward run 70 is moved in a rearward direction against the force of the springs 59 and inbetween the top and bottom sprockets 49 and 51, respectively. As the bale nears completion, both guide rollers 52 of each pairs of guide rollers first engage the rear runs of the respective chains 48 and ultimately, the forward runs of the chains 48 engage the "opposite sides" of the guide rollers 52. Any "stretching" of the chains 48 resulting from wear is compensated by the T-shaped supports 53, 54 with the guide rolltts 52 thereon moving generally radially outwardly, as seen with respect to the completed bale 13 in the bale chamber 11'. Such radially outward movement is made possible by the provision of the support arms 57 carrying the T-shaped supports being mounted for pivotal movement about the pivots 58, whereby the pivot pins 55 extending through the elongate slots 56 are moved away from the inner ends thereof. It will be appreciated that, like the forward expandable member 8, the rear expandable member 9 also cannot expand any further once both runs of the chains 48 engage the "opposite sides" of the guide rollers 52. Thus, again in this condition, the expandable member 9 also acts as the fixed bale forming means of a so-called soft core round baler. It will also be appreciated that as a result of the guide rollers 21, 52 engaging at times the opposed runs of the respective associated chains 17, 48, these guide rollers 21, 52 need to have smooth outer surfaces, otherwise toothed outer surfaces (such as those of sprockets) would interfere with the proper simultaneous guidance of both runs of the chains. Returning now to the slats 22 forming part dt both the front and rear expandable members 8 and 9, 'and referring to Figures 6 to 8, these are formed from tubular stock and, as already mentioned, extend essentially the full width of the machines. The chains 17 and 48 are inset from the ends of the slats 22, as already described with reference to Figure 5, in order to reduce the unsupported length of each slat, whereby to lessen the chance of the slats flexing, andfndeed being permanently- deformed, when a bale is being formed. Also, the offset loading of the chains 17 and 48 is reduced substantially, resulting in an increased life of the chains or, alternatively, enabling lighter, and hence cheaper, chains to be used based on a required life. The use of tubular stock for the slats 22 maximises the inherent strength of the latter but gives rise to a problem in connecting the slats to the respective chains 17, 48. To overcome this problem, each slat 22 is basically flattened, but in a special manner, at each end, the flattened portion 62 extending from the end of the slat to just beyond the point of connection to the chain 17 or 48. As best seen in Figure 8, the flattened portion 62 of eacfr end of each slat 22 comprises a flat rear portion 63 and an opposed front, working portion having a longitudinally-extending central portion 64 extending parallel to, but spaced from, the rear portion 63 and being flanked by two upstanding portions 65. Thus the front surface ,of each flattened slat portion 62 is channelshaped. The flattening of the ends of the slats 22 destroys the inherent strength of the previous tubular configuration and in order to restore this strength, a fillet or insert 66 cut from flat metal strip is disposed inside each flattened portion 62 in the space between the rear portion 63 and the front central portion 64. Two longitudinally- spaced apertures 67 are provided through each flattened portion 62, including the insert 66, for the reception of bolts 68 by which the slat is attached to lugs 69 carried on either side of the associated chain 17, 48, the lugs being provided with holes to receive the bolts and together forming a surface complementary to the adjacent surface of the portion 63. It will be noted from Figure 8 that the upstanding portions 65 of the flattened end portions 62 extend proud of the heads of the bolts 68, whereby the latter are protected from excessive abrasive wear by the crop material, and the likelihood of crop material getting hooked around the bolt heads reduced. It will also be noted that the upstanding portion 65 Ire generally within the outer periphery of the tubular slat as seen in end view. The threaded ends of the bolts 68 and the nuts 50 cooperating therewith are positioned to the side of the chains 17, 48 facing away from the bale to be formed and hence are also protected from abrasive wear by the crop material. The chains 17, 48 with the lugs 69 thereon are standard commercially available chains which means that the cost thereof is considerably lower than tit would if special chains had to be employed. It will be appreciated that the front and rear surfaces 60, 70 of the start chamber 11 are defined by the slats 22 on the runs of the chains 17 on the longest side of the triangle formed by the sprockets 18, 19 and the guide roller 21, and the slats 22 on the runs of the chains 48 between the upper and lower sprockets 49, 51, respectively. These surfaces 60, 70 change shape as a bale is formed, being transformed from linear to arcuate as has already been mentioned and as will be further described in more detail. Turning now to the combined crop feeder and bale support device 15, and referring to Figures 9 and 10, this comprises a hollow rotor 71 having a smooth outer surface and provided with two diametrically opposed rows of apertures 72 each of which receives an insert 73 from within the rotor, the insert being bolted to the rotor. Each insert 73 comprises two hemiapherical shells 74 formed with flanges 75 by which the insert is bolted to the rotor 72, the sphere formed by the two shells containing a bush 76 of elastomeric synthetic plastics material. Each shell 74 is apertured to provide a through aperture 77 for a rod or finger 78 mounted in a radial extension 79 of a bush 81 of an elastomeric synthetic plastics material. Each rod 78 is retained in the extension 79 by a pin :82, and each bush 81 is rotatably mounted on a stationary crankshaft 83 the ends of which are received in bearings 84 provided in end plates 85 for the rotor 71. The rotor body is driven and rotates around the crankshaft 83, whereby the rods 78 are alternately extended (at the side of the rotot adjacent the pick-up unit 14) and retracted Cat the side of the rotor adjacent the other rotor 16) by way of sliding in and out of the apertures 77 and bushes 76, the ends of the rods describing the circle indicated at 80. The combined crop feeder and bale support device 15, together with the facing runs 60, 70 of the expandable members 8, 9 when in the empty condition of the baler define the generally triangular and upright bale starting chambers I with the device 15 being provided at a distance beneath the lower end of the member 8, thus providing therebetween a bale chamber inlet opening. The device 15 is further mounted proximate, .#and forwardly of the rotor 16 so that, in the empty condition of the baler, the generally vertical run 70 of the ;rear bale forming member 9 is offset to the rear of the device 15, which in part forms the base of the triangular bale starting chamber 11. The device 15 is further also positioned relative to the lower sprockets 18 of the front bale forming member 8 and the rotor 16 (which is part of the rear bale forming member 9J so that, as a bale is nearing completion within the bale chamber, the bale is supported at least in part bythe cylindrical body 71 of the device 15. Hence the cylindrical body 71 is positioned, together with other components on a circumference defining the cylindrical bale chamber 11' when at its maximum diameter. However, the device 15 is also positioned relative to the bale chamber 11' so that, as a bale is being formed in the bale chamber and is nearing completion, its centre of gravity is moved from generally above the device 15 to the side thereof opposite to the side fading the pick-up device 14. The retractable fingers 78 are substantially in the retracted position at the point on the cylindrical body 71 of the device 15 where, when a bale is being completed in the bale chamber 11', the bale is supported on the cylindrical body, thereby avoiding the fingers penetrating into the bale and adversely affecting the surface thereof. The fingers 78 are extended to the maximum at the side of the cylindrical body 71, facing the discharge end of the pick-up device 14 in order to take over crop material therefrom and are retracted gradually from the maximum extension positt#on to said part of contact of the bale on the cylindrical body 71, as the device is rotated. Referring to Figures 11 and 12, the rotor 16 will now be described. T#e function of the rotor 16 is to provide a positive support for a bale during formation, which support does not impart any substantial vibration to the bale which might impair the formation thereof and/or cause unacceptable wear and/or damage to the emachine. As already described, the chains 48 extend around sprockets 51 associated with the rotor 16 and if the rotor were not provided, the slats 22 would continuously pass beneath the bale being formed, thereby raising the bale on each occasion and thus subjecting the bale to vibration in the generally vertical plane. The rotor 16 overcomes this problem by providing pockets for the slats 22 to enter as they pass beneath -the bale,- whereby the rotor, together with the slats received in' the pockets thereof, provide a substantially smooth or continuous surface on which the bale is supported. The rotor 16 comprises a hollow tubular core 36 extending between the two sprockets 51 and closed at each end by a plate 87 formed with a tubular extension 88 of reduced diameter and concentric with the core and formed with an annular recess 89 around its outer end. The recess 89 receives one end of a tube 91 having the same outer diameter as the extension 88 and being closed at its other and outer end by an end plate 92 which is bolted to a flange 93 carried by a stub shaft 94 by which the rotor is mounted for rotation in bearings Cnot shown) provided in the respective side walls 7. Each tube 91 i's surrounded along the majority of its length by a further tube of the same outer diameter as the core 86 and representing an extension 86' of that core. Each core extension 86' is supported by two annular discs 95 carried by the tube 91. On the main core 86 and the two core extensions 86' of the rotor 16 there are mounted. respective out#' rotor surfaces 96 and 96', which are generally star-shaped in cross-section as seen in Figure 11, thus providing four longitudinally extending pockets 97 for the reception of the slats 22 associated with the chains 48. The surfaces 96, 96' are each formed from four identical sections of sheet metal welded together at the "points" of the star and to the respective end plates 87, 95 of the rotor 16. The two sprockets 51 associated with the rotor 16 are annular and each is welded to an annular disc 99 attached to the tube 91. On assembly, the two ends of the rotor 16 are mounted on the main rotor body by sliding the tubes 91 into the recesses 89 in the extension 88 and bolting the sprockets 51 to respective discs 98 secured to the extensions 88 via bolts 90 welded to the sprockets 51. Thus the sprockets 51 are inset from the ends of the rotor to match the insetting of the chains 48 from the ends of the slats 22. As the rotor 16 rotates, the slats 22 move into the pockets 97 as the chains 48 pass around the sprockets 51, whereby a substantially continuous support surface is seen by the bale 13 being formed as presented at any given instant by a slat and a "point" of the star-sbaped rotor. In this respect, 'it will be seen from Figure 11 that when a slat 22 is received in a pocket 97, the radially outer portion of the main body of the slat is located at the circle 101 circumscribed by the "points" of the rotor 16. From the drawings, and more especially from4F,igure 2, it will be appreciated that only part of the weight-of a bale being formd on the bale chamber is supported on the rotor 16 Cand on a slat 22 received in a pocket 97 thereof and on the chains 49), another part of the bale weight being supported, as already mentioned, by the combined, feeder and bale supporting device 15. It should be noted that the number of teeth on each sprocket 51 is N times the number of links in the chains 48 between adjacent slats 22, where N is an integer, Although preferably not one. Also, the number of teeth on each sprocket 51 is a multiple of the number of pockets provided in the rotor. It will be seen from Figure 11 that in the first embodiment, each sprocket has sixteen teeth which is a multiple of the four pockets 97 and which makes N=4 since a slat 22 is attached to every fourth link of the chains 48. The drives for the various driven components of the baler are shown in Figure 2 of the drawings, these being omitted from Figure 1 for clarity. A sprocket 102 on the output shaft 103 of the gearbox 6 dtyes., via a chain 100, one sprocket of a triple sprocket 104 on a shaft 105 on which the sprocket 18 of the front expandable member 8 is mounted, whereby the chains 17 are driven in a clockwise direction as seen in Figures 1 and 2. Both chains 17 are driven since the shaft 105 is common to both sprockets 18. A further chain 106 extends around a second sprocket of the triple sprocket 104 and around a sprocket 107 on a common shaft 108 for the two sprockets #' of the rear expandable member 9, whereby the two chains 48 are also driven in a clockwise direction as seen in Figures 1 and 2. Thus the runs of the chains 17 and 48 partially defining the start chamber 11 move in opposite directions so as to impart a rolling motion to the crop material fed to the start chamber. A chain 109 extends around the third sprocket of the triple sprocket 104 and around a sprocket Ill provided on one end of the cylindrical body 71 of the rotor 15, whereby the latter is driven in a clockwise direction as seen in Figures 1 and 2. A pulley 112 is also coupled to the sprocket 111 and a belt 113 extends from that pulley to a pulley 114 on the pick-up unit 14 so as to drive the latter also in a clockwise direction as seen in Figures 1 and 2. Thus it is seen that the drives to the driven components are effected in a simple manner. In operation of the embodiment of Figures 1 to 12, the machine is hitched to the tractor or other towing vehicle via the drawhar 3, and the driveshaft 4 connected to the tractor PTQ, whereby the chains 17, 48, the rotor 15 and the pPck-up 14 are driven as described above. Thus as the machine fs towed across. A field to previously cut crop material, the latter is picked up by the pick-up 14 and conveyed overcrop and rearwardly towards the rotor 15. The extended fingers or rods 78 of the latter take over the crop material and feed it into the mouth of the start chamber 11 against the rising run of the chains 48 and associated slats 22, the fingers the-n retracting and thus releasing the crop material. It will be appreciated from the foregoing description that the slats 22 are relatively closely spaced, and they serve to carry the crop material a certain way into the start chamber 11 before the crop tumbles under gravity and falls downwardly, assisted by the generally downwardly moving slats 22 of the front expandable member 8. The relatively gentle tumbling action of the crop material results in a generally soft core for the bale being formed. However, the-rolliag action imparted to the crop material by the rotor 15, and the slats 22 on the facing runs of the chains 17 and 48 results in a smaller core than would otherwise pertain in a conventional soft core baler. Experience has shown that the core usually starts to roll at a distance above the combined feeder and support device 15 and inbetween the facing runs 60, 70 of the bale forming members 8, 9. As the size of the bale core tOcreREe$, the start chamber 11 becomes full, whereupon the core pressed increasinglyf. harder on the slats 22 of the facing runs of the chains 17 and 48 with the result that runs of chains 17 are urged to the left as seen in Figure 1, and the runs of the chains 48 are urged to the right, the former against the action of the springs 28 and the latter against the action of the springs 59. Accordingly, the layers of crop material surrounding the soft core begin to be more consolidated, the density of the bale in fact increasing to the outer shell thereof since the springs 28 and 59 progressively increase the tension in the chains 17 and 48. It will be appreciated that the degree of compaction depends on the forces exerted by the springs 28 and 59. With the illustrated arrangement it is easy and convenient to vary these spring-forces and thus-vary the density of the bale. Therefore, if it is desired to produce softcore bales pretty much as are conventionally produced with soft core balers, it is sufficient to adjust the springs 28 and 59 accordingly. It should be noted that as the runs 60, 70 of the bale forming members 8, 9 are deflected as the bale increases in size, the facing runs of the chains 17 and 48, together with the associated slats 22, form complementary portions of a cylinder as seen in Figure 2 to give rise to the cylindrical bale chamber 11'. As already mentioned, this deXflection is accompanied by pivotal movement of the arias 23 and the T-shaped 5up#rts, 53, 54 to the portions indicated in Figure 2. rt should also be noted ttL#t the arms 23 are pivoted off centre In order to Ipfnhnfse the relative movements between the sprockets 19 and the sprockets 49 so as not to create any sizeable gap therebetween through which crop material may be lost. When the arms 23 and supports 53, 54 are in the positions of Figure 2, the chains 17 are in contact with opposite "sides", as it were, of the sprockets 18 and 19 and the rollers 21, whereby the chains are positively supported in fixed positions with 'no slack therein. tike- wise the chains 48 are positively supported in fixed positions by the sprockets 49, 51 and the rollers 52. Thus when the bale size of Figure 2 is reached the slats 22 are moved along a fixed path around the bale being completed. As further crop material is still being fed into the bale chamber 11' and as the bale chamber cannot expand further a hard shell or outer layer is formed-on-the bale 'with compaction taking place in an inward direction from the outside. The hardness of this outer shell, and hence its weathering characteristics, depends on the amount of crop material fed into the bale chamber after the bale has reached its maximum diameter. This is comparable to the hard shell which can be produced with soft core balers and is totally independantof the initial setting of the springs 28, 59, As the bale is nearing completion in the bale chamber 11', it is supported in p#rt on the cylindrical body 71 of the device 15 and on the motor 16, together with the slats 22 of the rear bale forming member 9 as they pass in the success-ive pockets 79 of the rotor. This occurs without any undue vihration of the bale in the bale chamber, and hence also of the baler. It will also be appreciated, mainly from Figure 2, that the forward bale forming member 8, together with the sprockets 18, and the rearward bale forming member 9, together with the lower pairs of guide rollers 52 on the T-shaped support members 53, 5t, assist in supporting the weight of the bale in the bale chamber. As already mentioned, the particular mounting of the T-shaped support members 53, 54 provides compensation for any "stretching" of the bale forming member 9 as a resuLt of wear. When the bale 13 has been completed, the tail- gate 12 is raised (by means not shown) above the axis 108 of the sprockets 49 and since the centre of gravity of the bale 15 lies within the rear portion of the bale chamber 11', there is a natural tendency for it to roll from the machine on the raising of the tailgate, This tendency is augmented by the action of the rotor 15, which continues to be driven, and thus positive discharge of a completed bale is achieved. As soon as a completed bale 13 is discharged from the machine, the springs 28 and 59 return the arms '23 and supports 53, 54, respectively, to the pasStions of Figure 1, whereby the tapered start chamber 11 is re-formed ready for forming the next bale. It will he appRecLated that the machine is capable of forming halves of less than the maximum drameter Rs bale discharge can be effected at any tD e by raising the tailgate 12. Wht15t any bale 'less than the maximum size will not have the heavily compacted outer layer or shell, the latter nevertheless will be such that the bale will hold together especially when the springs 28, 59 have been set to give an increased density to the bale being formed. Turning now to Figure 13, this shows a modified arrangement of the guide means for guiding the chains 48 when a bale has reached its maximum diameter in the bale chamber 11'. Figure 13 shows one T-shaped support 53, 54 in the position adopted when a completed bale has been formed. In this' arrangement, each support 53, 54 is provided with two- sprockets 115, 9ne in engagement with the front run of the associated chain at a location proximate one guide roller 52 and the other in engagement with the rear run, again at a location proximate to the other guide roller 52. As before, the chains 48 engage both "sides" of the rollers 52 when in the position (bale completes of Figure 13. This arrangement improves the guidance of both 'runs of the chains 48 on the guide rollers 52 when a bale has reached its maximum size within the bale chamber 11' by positively holaing the chains 48 in alignment with the rollers 52. Figures 14 and 15 shown an alternative embodiment of round baler which, in the main, is similar to that of Figures 1 to 12, the differences belong in respect of the chain tengtontag devices associ,ated with the front and rear expandable XR4ber5 -8 and 9. In this embodiment the arms 23 are replaced by arms 116 khtcE carry at one'end the guide rollers 21, with the sprockets 18 and 19 being fixed. Each arm 116 is pivoted intermediate its ends on a pivot 117, with the other end of the arm connected to one end of a tension spring 118 attached at its other end to the machine frame. With this arrangement, the gaps between the sprockets 19 of the front expandable member 8 and the sprockets 49 of the rear expandable member 9 remain constant and small so the likelihood of any loss of crop material therethrough is small. In the embodiment of Figures 1 to 12, the sprockets 19 are movable relative to the sprockets 49 as a bale being formed increases in size so that care has to be taken with the disposition and mounting of the sprockets 19 with the crop loss problem in mind, -as already explained. As regards the rear expandable member 9, tension in the chains 48 is maintained only by the upper member and not the upper and lower members (supports 53, 54) as in the first embodiment. The lower supports 53, 54 are replaced by arms 119 which carry the guide rollers 52, with the lower arms being mounted for limited movement relative to the side walls 7 by virtue of a pair of elongated slots 121 formed in the side walls which slidably receive mounting pins 112 attached to the associated arms 119, This particular mounting, ltke the prov2=ton of the pivot arms 57 in the embodiment of Figures 1 to 12, provides co#pensation for any "stretching" of the chains 48 as a result of wear. Tie upper supports 53, 54 are replaced by arms 123 which carry the rollers 52 and are each centrally pivoted on one end of a further arm 124 which is pivoted at its other end to the machine frame. One end of a cable 125 is attached to each arm 124 intermediate its ends, the other end of the cable being secured to one end of a tension spring 126 which in turn has its other end attached to the machine frame, the cable passing over a pulley 127 on an extension 128 on the frame. Thus as the bale forming member 9 gets deflected as the bale grows (as already described with respect to the first embodiment), each arm 124 is pulled anticlockgise about its pivot and takes w4Ch it the cable 125 which therefore stretches the spring 126 associated therewith, thereby increasing the tension in the chains. Similarly, the springs 118 increase the tension in the chains 17 as the arms 116 are pivoted anticlockwise and stretch the springs 118. It will be noted that, unlike in the embodiment of Figure 1 to 12, both guide rollers 52 of each pair of guide rollers engage one run of the respective chains 48, when the baler is empty. In all other respects, the operation of the embodiment of Figures 13 and 14 is similar to that described for the embodiment of Figures 1 to 12. Turning now to Figure 16, this shows a still further embodiment in which again the differences with respect to the embodiment of Figures 1 to 12 are concerned with the chain tensioning devices associated with the front and rear expandable members 8 and 9, the machine otherwise being similar to the first described embodiment. The chain tensioning devices of the embodiment óf Figure -16 have been simplifed with respect to those described hereinbefore and associated with the front expandable member 8. The tensioning devices each comprise an arm 131 pivotally mounted at one end on the shaft of the sprocket 19 which is fixed as in the embodiment of Figures 15 and 16. The other end of the arm carries the guide roller 21 which is urged into contact with the outer run of the chain 17 by a spring 132 acting between the base frame 1 and one end of an arm 133 attached to the arm 131, these two arms in fact forming a cranked lever pivoted, as already mentioned, about the shaft of the sprocket 19. When the machine is empty, each spring 132 acts on the roller 21 to tension the associated chain 17 which thus takes up the broken line position of Figure 116 about the shaft of the sprocket 19, thereby always maintaining tension in the chain 17 in accordance with the strength of the spring 132. In the embodiments of Figures 15, 15 and Figure 16 the fixing of the sprockets 19 is an important feature in that the sprockets can be set with respect to the adjacent respective sprockets 49 of the rear expandable means 9 such that there is little or no gap therebetween through which crop material can be carried by the relatively aggressive rear expandable means 9. As regards the chain tensioning devices associated with the rear expandable member, each comprises an upper and lower device as before with the principal difference being that one of the two rollers of the upper and lower devices is essentially fixed. Looking first at the lower devices, each comprises a fixed roller 134 mounted on a common shaft 135 extending the full width of the machine, and a movable roller 136 rotatably mounted on one end of an arm 137 which is pivotally mounted at its other end on the shaft 135. The arm 137 is slightly cranked and has attached to it a further arm 138 (these two arms forming an overall crank lever), the arm 138 being urged clockwise as seen in Figure 16 by a spring 139 acting between the arm and the base frame of the machine. In the empty condition of the machine, the spring 139 urges the arm 137 and the roller 136 to the broken line position of Figure 16, these components progressively moving to the full line position as a bale is formed. Each upper chain tensioning device similar to the lower device in that a slightly cranked arm 141 carries a movable roller142 at one end and is pivotally mounted at the other end on a common shaft 143 on which is rotatably mounted another roller 144. The arm 141 is urged in a clockwise direction (as seen in Figure 16) by a spring 145 acting between a further arm 146 and the base frame 1, the two arms 141 and 146 being connected to one another and again forming an overall crank lever. However, the rollers 144 are not rigidly fixed unlike the rollers 134 because expansion of the chains 48 has to be accommodated, expansion occurring due to wearing of the links which results in chain stretch. The common shaft 143 on which the rollers 144 of the two upper chain tensioning devices are mounted extends through slots 147 in the sidewalls 7 of the machine and is supported at each end in a bearing block 148 carried on one end of a support link 149 which is pivotally attached at 151 to the exterior of the related sidewall. It should be noted that the shaft 143 is not supported in any way by the slots 147 in the sidewalls, the slots merely allowing arcuate movement of the shaft about the pivots 151 when such movement occurs due to chain stretch and under the action of the springs 145. The provision of substantially fixed rollers 144 in the upper devices and the fixed rollers 134 in the lower devices is advantageous in that they are permanently located at the periphery of a bale of maximum diameter, -whereby they assist more positively in the compaction of the outer bale layer to form the desired hard shell. Furthermore, the fixed rollers 134 also serve to support a bale during formation, in conjunction with the rotor 16. With the previously described embodiments in which only the rotor 16 provided bale support, there is a tendency for a bale to tilt or roll rearwardly since its centre of gravity is rearward of the rotor 16. with the provision of the fixed rollers 134 (which are reasonably closely spaced with respect to the rotor 16, but-not too closely spaced), this tendency for a bale to become offset from the centre of the bale chamber is obviated. It will also be seen that the springs 145 of the upper chain tensioning devices provide a component of force rearwardly of the machine which ensures the taking up of chain stretch. Turning now to the still further embodiment of Figure 17, the basic machine is again similar to that of the previous embodiments but in this case the front expandable means 8 have been replaced by a fixed roller arrangement, and the chain tensioning devices of the rear expandable means 9, whilst being similar to those of the embodiment Figure 16, have been further simplified. Looking at the chain tensioning devices first, the lower devices are identical to those of Figure 16 except that the springs 139 act between the respective arms 138 and the ends of links 155 pivotally mounted at the other ends on the base frame 1 at 156. The upper devices are also identical to those of the embodiment of Figure 16 as far as the arms 141, shaft 143 and rollers 142 and 144 are concerned. However, the further arms 146 have been turned through 1800 and instead of being attached to the springs 145 they are connected by respective pull rods 157 to the links 155, whereby the springs 139 are common to both the upper and lower tensioning devices. The pull rods 157 serve to ensure that a component of the spring forces acting on the rollers 142 is directed generally rearwardly of the machine so that the rollers 144 and shaft 143 are always urged in the correct direction to take up any chain slack due to wear. The arrangement of the springs 139, arms 138, 146 and links 155 is such that a greater force is exerted on the rollers 142 of the upper devices than on the rollers 136 of the lower devices because the upper rollers have to support part of the weight of the chains unlike the lower rollers, and also such that the upper and lower devices move progressively and in unison to the completed bale position in order to avoid irregularity in the bale shape during formation. These requirements are also met in the other embodiments. As regards the front bale forming means this is, as already mentioned, in the form of a fixed roller arrangement, more specifically in the form of a set of four rollers 161, 162, 163 and 164 each of which is driven although the centre rollers 162 and 163 could be freely rotatable if desired. The rollers 161, 162, 163 and 164 are disposed such that they are disposed around part of the periphery of maximum sized bale. Thus when such a bale has been formed, the addition of a little further crop material causes the bale to press on the rollers which thus compact the outer layer of crop material to help produce the hard outer shell. The rollers 161 to 164 extend across the width of the machine and are mounted in bearings supported on the base frame 1. Each roller 161 to 164 has a smooth exterior surface and is driven in a clockwise direction (as seen in Figure 17) by a chain 165 which engages sprockets 166 on the rollers and also passes around an idler sprocket 167. The lower roller 161 has a further sprocket 168 engaged by a chain 169 which also engages the sprocket 107 of the rear bale forming means and the sprocket 102 on the-output shaft 103 of the gearbox 6, and has a still further sprocket 171 engaged by a chain 172 which drives the combined crop feeder and bale support device 15 via an idler 173. The device 15 drives the pick-up 14 as before via a belt a pulley arrangement. The fixed roller arrangement for the front bale forming means affords two advantages over the expandable front bale forming means 8 of the previously described emb-odiments: firstly, the rollers form solid, immovable bale forming means which give a good, smooth finish to the outer shell of the bale, and secondly, the use of a plain lower roller 161 reduces, if not eliminates, the possibility of crop material being carried therearound and thus taken out of the inlet throat and lost. The pressure exerted on the front bale forming means 8 by a completed bale is relatively large compared with that exerted on the rear bale forming means 9 due to their differing surface areas and unless the shafts of the former are made sufficiently robust, there is a tendency for them to suffer damage. Furthermore, the slats 22 of the embodiments of Figures 1 to 15 act relatively aggressively on the crop material, whereby there is ,a tendency for the slats of the front bale forming means 8 to pull crop material from the outer surface of the bale and carry it out of the crop inlet throat of the machine whereby that material is lost. Also the pulling of crop material from the bale gives the latter a "hairy" appearance which is undesirable. Another tendency of the slats 22 is to dig into the periphery of the bale and thus produce slight corrugations around the bale periphery. When a completed bale is discharged from the machine, these corrugations disappear because the bale expands but this produces "pockets" of less compacted or "fluffy" material which is also undesirable. It is a general requirement that the front bale forming means are not more aggressive than the rear bale forming means and preferably are less aggressive. The use of smooth, plain rollers 161-164 meets this requirement but it may be desirable to make all but the lower roller 161 more aggressive by making the rollers other than plain such as by fitting ribs thereon or by other means. Also, the rollers 164, 163, 162 and 161 can be made progressively less aggressive. It will be seen that the presen¯ invention provides a round baler which can produce bales with a hard outer shell whilst the density of the crop material within the outer shell can be varied greatly at will from a low density comparable to the characteristics of bales produced with conventional soft core bales to a high density as is known from balers having an expandable bale chamber, thus providing greater flexibility to the operator and combining advantages of conventional soft and hard core balers. The slats 22 are of a strength sufficient to exert the required force on the bale as it is being formed and yet are not bulky. Furthermore standard chains can be used. Also, the insetting of the points of connection to the chains from the ends of the slats helps to reduce chain wear as it has been found that chains located at the extreme ends of the slats are subjected to uneven loading and hence relatively fast wear. This insetting also reduces the unsupported length of the slats so that less robust tubing can be used therefor than would otherwise be the case. In the described embodiments, slats of 1.2 metres are employed, with flattened portions of 30cms, and internal and external diameters of 38mm and 42mm. The chains 17 and 48 are inset from the ends of the slats by 21as. As already mentioned, the rotor 15 has a dual function in feeding crop material to the baDe chamber from the pick-up unit 14, and in helping to support the bale as it is being completed. The rotor 15 thus performs an important part in the formation of a bale and without its presence, the pick-up unit 14 would have to be mounted much closer to the mouth of the bale chamber to an extent that it would inevitably have to support each' bale being formed, and conventional pick-up units are not constructed to fulfil this purpose. The function of the rotor 16 is also important in lending further support to each bale as it is formed and in so doing to present, in conjunction with the slats 22 a substantially smooth surface to the bale. To this end the pockets 97 are formed in the surface of the rotor 16 to accommodate the slats 22 as they pass therearound. As already explained, this prevents the slats from imparting generally vertical vibrations to the bale being formed which would impair formation. Although the illustrated embodiments employ two expandable bale-forming members 8 and 9, the member defining the smaller portion of the bale chamber 11' (be it the front or rear member) may be replaced by one or more of a fixed type of bale-forming means employing, for example, fixed rollers (as in the embodiment of Figure 17), or fixed chain or belt conveyors. Alternatively, the bale-forming members 8 and 9 may be augmented by one or more fixed bale-forming means. Also the chain type bale forming means 8, 9 may be replaced by belt type bale forming members. The present invention provides a round baler capable of producing a bale with a hard outer shell (soft core bale characteristics), and wtth either a relatively high density Chord core bale characteris-t## or a #athe'r low density of crop material thin the outer shell, without giving rise to an over coinplicated structure. The machine can produce a maximum sized hale Cm. 2 metres in diameter) in approximately two minutes, provided crop material is fed to the bale chamber at the appropriate rate. Of this bale-forming time, between 1/3 and 1/4 is devoted to forming the hard shell, i;e. this is the period In which the runs of the chains 17 and 48 are positively supported by the "opposed sides" 'of all the sprockets and guide rollers provided within the envelopes formed by the respective chains. This is a very important aspect because it provides the possibility of producing with a baler of the type having an expanding bale chamber, bale with an extra hard outer shell, such as is obtained with known balers of the type having a fixed chamber and commonly referred to as soft core balers. It will be appreciated that the tension initially set in the chains 17 and 48 determines the hardness of the core as well as influencing the overall density of the bale except for the hardness of the outer shell which basically is determined by the amount of crop material fed into the bale chamber after the latter has expanded to its maximum diameter. In general, a baler in accordance with the present invention provides a core which is smaller than that provided by known soft core machines due to the positive rolling action imparted to the core by the bale-forming members. Thus the baler produces a highly satisfactory bale haying qualities of both. soft core and hard core bales without, as already mentioned, being of complicated mechanical construction.

Claims: Claims 1. A round baler for forming bales up to a maximum diameter comprising bale-forming means defining a bale chamber (11, 11'); the bale-forming means comprising at least one expandable endless flexible member (8,9) provided with drive and guide members,(18,19,21, 49, 51, 52) all disposed within the envelope defined by the or each endless member (8;9), characterized in that, in use, at least when a bale (13) has reached substantially said maximum diameter, the run (60,70) of the or each endless member (8,9) defining the bale chamber (11') is in contact with all of the associated drive and guide members (18,19,21,49,51,52) so as to be supported thereby. 2. A baler according to claim 1, characterized in - that the run of the or each flexible member (8,9) not defining the bale chamber (11') is also in contact with all of the associated drive and guide members (18, 19, 21, 49, 51, 52), at least when a bale has reached substantially said maximum diameter. 3. A round baler having an expandable bale chamber (11,11') for forming bales up to a maximum diameter and comprising at least one endless flexible bale forming member (8,9) provided with an excess length around a pair of spaced apart rotatable members (18,19,49,51); the endless bale forming member (8,9) defining, at least in part, between the spaced apart rotatable members (18,19, 49,51) , and by means of said excess length, a final bale chamber (11') of cylindrical shape corresponding to said maximum size bale to be formed; characterized in that floating guide members (21,52) are provided within the envelope defined by the opposed runs of the baleforming members (8,9) for engaging and holding apart both said runs to prevent said runs fouling each other during operation and when a bale has reached substantially said maximum diameter within the bale chamber. 4. A baler according to any of claims 1 to 3, characterized in that the bale chamber is defined by two endless, flexible members (8;9) at least one of which is expandable. 5. A baler according to any of claims 1 to 4, characterized in that one expandable member (9) is tensioned by tensioning means comprising at least one upper and lower tensioning device each in the form of a T-shaped member (53,54) with the crosspiece (53) thereof carrying a rotatable guide member (52) at each end, and the stem (54) thereof being pivotally mounted on one end of support arm (57) pivotally attached to the machine, a tension spring (59) being connected between said stem (54) and the machine and operable to pivot the T-shaped member (53,54) such that only one rotatable guide member (52) thereof is in engagement with the expandable member (9) when the machine is empty. 6. A bale according to claim 5, characterized in that the pivot (55) of each T-shaped member (53,54) extends through an arcuate slot (56) in an adjacent side wall (7) of the machine, and the pivot (58) of the associated support arm (52) is located at the centre of curvature of the arcuate slot (56). 7. A baler according to claim 6, characterized in that the or each expandable member (8;9) comprises a pair of spaced endless chains (17,48) interconnected by a plurality of slats (22) extending transversely of the machine, - two upper and two lower T-shaped members (53,54) are provided with the' upper, respectively the lower T-shaped members having a common pivot (55) and with each upper and lower T-shaped member (53,54) being associated with a respective endless chain (17,48), - a transverse beam (61) is provided coupling to each other the upper T-shaped members (53,54) and - a further transverse beam (61) is provided coupling to each other the lower T-shaped members (53,54). 8. A baler according to any of claims 1 to 4, characterized in that one expandable member (9) is tensioned by tensioning means comprising at least one upper and lower tensioning--device of which the or each upper device (1-23,124) comprises a first arm (123) pivotally mounted on one end of a second arm (124) and carrying at each end a rotatable guide member (52) each arranged in engagement with the associated expandable member (9), the second arm (124) being pivotally attached at its other end to the machine and having one end of a cable (125) attached intermediate its ends, the cable (125) extending from the second arm (124), over a pulley (127) to one end of a tension spring (126), the other end of which is attached to the machine. 9. A baler according to claim 8, characterized in that the or each lower tensioning device comprises an arm (119) mounted for sliding movement relative to the machine and carrying at each end a rotatable guide member (52) arranged in engagement with the expandable member (9). 10. A baler according to claim 9, characterized in that the or each lower tensioning arm (119) is provided with two spaced apart pins (122) which are slidably engaged in respective elongate and parallel slots (121) provided in at least one machine side wall (7) whereby the arm is slidable relative to the machine. 11. A baler according to any of claims 1 to 4, characterized in that one expandable member (9) is tensioned by tensioning means comprising upper and lower devices each of which has a fixed rotatable guide member (134,144), an arm (137,141) pivotally montted at one end about the axis of rotation of the associated fixed guide member (134,144) and carrying a further rotatable guide member (136,142) at its other end, a further arm (138,146) angularly offset from, but attached to, the arm (137,141) and a spring (139,145) acting between the further arm (138,146) and the machine to urge the guide member (136,142) into engagement with the expandable member (9) to tension the latter. 12. A baler according to claim 11, characterized in that the fixed guide member (144) of the upper tensioning device is adjustable in order to take up slack in the expandable member (9) occurring due to stretching of the latter. 13. A baler according to claim 11 or 12, characterized in that the fixed guide member (134) of the or each lower tensioning device is located so as to support a bale as it is being formed. 14. A baler according to any of claims 1 to 4, characterized in that one expandable member (9) is tensioned by upper and lower tensioning devices each of which has a fixed rotatable guide member (134,144), an arm (137,141) pivotally mounted at one end about the axis of rotation of the associated fixed guide member and carrying a further rotatable guide member (136,142) at its other end, a further arm (138,146) angularly offset from, but attached to, the arm (137,141), a link (155) pivotally attached to the machine at one end and being connected to one further arm (138,146) of a pair of upper and lower tensioning devices by a spring (139) and connected to the other further arm (146,138) by a pull rod (157), whereby the spring (139) urges the further guide members (136,142) of both the upper and?lower tensioning devices of a pair into engagement with the expandable member (9) to tension the latter. 15. A baler according to claim 14, characterized in that the further arms (138,146) and link (155) of each pair of upper and lower tensioning devices are such that the tensioning force exerted by the-,ppper device is greater than that of the¯lower device. 16. A baler according to any of claims 5 to 15, characterized in that the expandable member (9) extends around an upper rotatable member (49) mounted forwardly of the ppper tensioning device and a lower rotatable member (51) mounted forwardly of the lower tensioning device, the upper and lower rotatable members (49,51) being disposed in a generally vertical plane, whereby the associated run (70) of the expandable member (9) is also generally vertical when the machine is empty. 17. A baler according to any of claims 5 to 16, characterized in that the expandable member (9) comprises two endless chains (48) interconnected by a plurality of slats (22) extending transversely of the machine, upper and lower tensioning devices being associated with each chain (48) and having the rotatable members (52) thereof arranged for engagement with opposed runs of the respective chains (48); the upper and lower tensioning devices each further comprising two guide sprockets (115) disposed within the chain envelope and operable to align the associated chain (48) with the rotatable members (52), one sprocket (115) being arranged to engage one run of the chain (48), and the other sprocket (115) being arranged to engage an opposed run when a bale has reached the maximum size. 18. A baler according to any of the claims 1 to 4, characterized in that one expandable member (8) is tensioned by tensioning means comprising at least one arm (23) pivotally mounted intermediate its ends on the machine and carrying at respective ends rotatable guide members (19,21) around which the expandable member (8) passes, the arm (23) being urged about its pivot (24) by a torsion spring (28) acting between a stop (31) on the arm (23) and a stop (33) on the machine, whereby the expandable member (8) is tensioned, and further also characterized in that the expandable member (8) also extends around a third rotatable member (18), whereby said expandable member (8) follows a triangular path when the machine is empty. 19. A baler according to any of the claims 1 to 4, characterized in that one expandable member (8) is tensioned by tensioning means comprising at least one arm (116) pivotally mounted on the machine intermediate its ends and carrying at one end a rotatable guide member (21) and being connected at the other end to the machine via a tension spring (118), the latter urging the rotatable guide member (21) into engagement with the expandable member (8) to tension the latter. 20. A baler according to any of claims 1 to 4, characterized in that one expandable member (8) is tensioned by tensioning means comprising an arm (131) pivotally mounted at one end on the machine and carrying a rotatable guide member (21) at the other end, a further rotatable guide member (19) mounted on the pivot of the arm (131), a further arm (133) angularly offset from, but attached to, the arm ('131), and a spring (132) acting between the further arm (133) and the machine to urge the rotatable member (21) into engagement with the expandable member (8) to tension the latter. 21. A baler according to any of the preceding claims, characterized in that the bale forming means further comprise one or more fixed bale-forming means (161-164).

Inventors: DE BUSSCHER, CYRIEL R.J., DECOENE, FRANS J.G.C.
Applicants: FORD NEW HOLLAND N.V.
Application year: 1984
Main classification: A01F15
IPC codes: A01F15