Abstract:
A twine tensioner includes upper and lower ribbed rollers biased together so as to engage a length of twine passing between them so as to cause a predetermined tension to be required for advancing the length of twine through the rollers. The upper roller is mounted for movement relative to the lower roller and is guided such that, as it moves away from the lower roller, the twine tension first increases and then does not undergo any appreciable increase or spike as a knot in the length of twine passes through the nip of the rollers. The tensioner is constructed such that the upper roller may be easily manually moved away from the lower roller so as to permit twine to be threaded through the tensioner without requiring any additional tool.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates to baler twine tensioners, and more specifically relates to a tensioner having the ability to operate satisfactorily when a knot securing ends of the supply rolls of twine passes through the tensioner.  
         BACKGROUND OF THE INVENTION  
         [0002]    Balers using twine for wrapping the bales produced by them are normally provided with several supply rolls of twine, with a twine end of one roll being secured to a twine end of another roll by tying the ends together with a knot. The twine routing path normally includes one or more tensioners which aid in the control of the twine as it is pulled from the supply rolls. When the knot travels through current twine tensioners, the knot creates a restriction in the tensioner creating a very high twine tension. Typical twine tensioners do not allow the knot to pass through the system without a tremendous increase in the tension and this can result in possible damage, increased wear and/or twine breakage.  
           [0003]    The tension of the twine passing through tensioners constructed according to the known designs, (see the tensioner disclosed in U.S. Pat. No. 5,988,053, for example), is directly proportional to the force of a spring or springs used to bias a pair of ribbed rollers together for engaging the twine running between the rollers. Thus, the force acting on the twine is directly related to the roller center distance. In other words, any increase in the roller center distance caused by the twine or a knot creates a direct proportional increase in the twine tension.  
           [0004]    Furthermore, due to this increasing force, it is difficult to manually force the ribbed rollers apart in order to thread or route the twine through the tensioner. This procedure is performed by taking a screw driver, pliers or other tool to pry or forcibly spread the rollers apart.  
         SUMMARY OF INVENTION  
         [0005]    According to the present invention there is provided an improved baler twine tensioner comprising ribbed rollers biased towards each other.  
           [0006]    An object of the invention is to provide a twine tensioner including a pair of ribbed tensioning rolls which are biased together and mounted so as to be able to have a knot pass between them without dramatically increasing twine tension.  
           [0007]    A more specific object of the invention is to provide a twine tensioner wherein a cam design is provided which yields a constant run tension over a range of twine sizes, but which operates to permit the center distance of the rollers to increase without resulting in a directly proportional increase of the twine tension. This is accomplished by arranging the cam and spring in such relationship to each other that the cam causes the spring force to remain substantially constant over the majority of the range of movement normally experienced by the moveable roll. It is conceivable that one or both of the rollers could be mounted to eccentric shafts mounted for pivoting against a resilient force offered by an associated torsion spring, the eccentric shape of the shaft or shafts guiding the roller or rollers so as to maintain a substantially constant tension force in a length of twine passing through the nip of the rollers, even during the time that the rollers separate to permit a knot in the twine to pass between them.  
           [0008]    Yet another object of the invention is to provide a tensioner having a design permitting the moveable ribbed roller to be manually separated from the fixed roller with low force and no tools so as to permit threading of the twine through the tensioner. This is accomplished by mounting a handle to inner roller control or slot plates having the moveable roller mounted between them with its axle projecting through cam slots in respective outer fixed mounting plates, the handle being used to overcome the force of the biasing spring and cause the axle of the moveable roller to move along the cam slots so as to cause a relatively large separation of the tensioner rollers for easy threading of twine between them.  
           [0009]    These and other objects of the invention will become apparent from a reading of the ensuing description together with the appended drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]    [0010]FIG. 1 is a left front perspective view showing a large rectangular baling chamber and some of the structure mounted thereto including the tensioner assembly of the present invention.  
         [0011]    [0011]FIG. 2 is an enlarged left front perspective view of the tensioner assembly shown in FIG. 1.  
         [0012]    [0012]FIG. 3 is a left front, enlarged perspective view of one of the twine tensioners of the assembly shown in FIG. 2.  
         [0013]    [0013]FIG. 4 is a right rear perspective view of the tensioner of FIG. 3, but with the left mounting plate removed.  
         [0014]    [0014]FIG. 5 is a view like that of FIG. 4, but being partially exploded.  
         [0015]    [0015]FIG. 6 is a right rear perspective view of the twine tensioner mounting panel and the twine slack take-up arms located there. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0016]    Referring now to FIG. 1, there is shown a baling chamber  10  of a large rectangular baler. The chamber  10  includes a framework  12  supporting a plunger  14  to which is coupled a drive linkage including a pair of connecting arms  16  having first ends pivotally coupled, as at coupling  18 , to one end of a bifurcated crank arm  20  having a second end pivotally coupled to the framework  12  by a pin  22 . An extensible and retractable, hydraulic cylinder  24  is provided for driving the plunger  14  and has a lower end anchored to the framework  12  by a structure including a connecting pin  26  and having an upper end coupled to the crank arm  20  by a pin  28 . A guide structure  30  is provided at each side of the framework  12  and each of the opposite sides of the plunger  14  is provided with a pair of rollers  32  mounted for traveling along a respective guide structure  30 .  
         [0017]    A U-shaped, needle support yoke  34  includes a pair of opposite arms  36  (only one visible) joined to a cross tube  38  that extends transversely beneath the framework  12 . Mounted at spaced locations along the cross tube  38  are a plurality of twine delivery needles (not shown). Respective ends of the arms  36 , that are remote from the cross tube  36 , are respectively pivotally coupled to the opposite sides of the framework  12  for swinging about oppositely projecting stub shafts  40 . Motion of the needle support yoke  34  is caused by a knotter drive cylinder  42  having its rod end coupled to one end of a drive chain  43 , which is engaged with the teeth of a knotter drive gear, not visible, that is coupled to a knotter drive shaft  44  by a one-way drive coupling  46 , the shaft  44  carrying crank arms  48  at its opposite ends which are connected to the yoke arms  36  by motion transfer links  50 . The opposite end of the drive chain  43  is coupled to a tension spring  52  that is anchored to the framework  12 . A number of knotter gears  54 , equal to the number of needles carried by the yoke  34  and of which only one is schematically indicated, are fixed to the knotter drive shaft  44 . Rotation of the shaft  44  causes the knotter gears  54  to drive respective twine knotters (not shown) so as to secure loops of twine about a finished bale located within the chamber  10 .  
         [0018]    Provided in the path of twine being delivered to the needles is a twine tensioner assembly  56  (see also FIG. 2) including a transverse, upright support panel  58  fixed to the top of the framework  12  at a location in front of the knotter drive shaft  44 . Opposite ends of the panel  58  are defined by forwardly projecting plates  60  which are each provided with three vertically spaced holes, with the two lower holes on each side carrying a twine guide  62  in the form of a ring, which may be made of a wear resistant, low friction plastic material, for example. Spaced equally across the front of the panel  58  are four identical twine tensioners  64 .  
         [0019]    Each twine tensioner  64  includes right- and left-hand, transversely spaced, vertical mounting plates  66  and  68 , respectively, a pair of identical, right and left roller control plates  70  and  72 , identical upper and lower ribbed rollers or gears  74  and  76 , a roller biasing spring assembly  78  and a twine guide mounting plate  80 .  
         [0020]    The mounting plates  66  and  68  are spaced transversely from each other and have respective parallel, planar, fore-and-aft extending portions that are joined to respective transverse mounting flanges which are secured to the panel  58  by vertically spaced bolts  82 . The roller control plates  70  and  72  are respectively located against inner surfaces of the mounting plates  66  and  68 . The upper and lower ribbed rollers or gears  74  and  76  are positioned between the control plates  70  and  72 . The upper and lower ribbed rollers  74  and  76 , respectively, are rotatably mounted on upper and lower roller shafts  84  and  86 .  
         [0021]    Referring now also to FIGS.  3 - 5 , it can be seen that right and left end sections of the upper roller shaft  84  are respectively received in circular holes  88  provided in the roller control plates  70  and  72 , and in guide or cam slots  90  provided in the mounting plates  66  and  68 . The guide slots  90  each include a short, substantially vertical forward end section joined to a substantially longer gradually upwardly and rearwardly inclined section. The lower roller shaft  86  has opposite end sections which respectively extend through clearance holes  92  provided in the control plates  70  and  72  at locations centered to the rear of, and below, the circular holes  88 , with end sections of the lower roller shaft  86  being respectively received in circular holes (not shown) provided in the mounting plates  66  and  68 . It is here noted that the clearance holes  92  could be shaped as cam or guide slots for controlling the movement of the plates  70  and  72  relative to the lower roller shaft  86 . Snap rings  94  are located in annular grooves provided in the opposite ends of the roller shaft  86  so as to hold the assembly together prior to mounting the plates  66  and  68  to the panel  58 . Right-hand end sections of the shafts  84  and  86  are each provided with diametrically opposite flats  96  and a grease zerk.  
         [0022]    The biasing spring assembly  78  is provided for resiliently resisting upward movement of the control plates  70  and  72 , and, hence, upward movement of the upper ribbed roller  74 . For this purpose, the spring assembly  78  includes a transverse support shaft  100  having opposite end sections respectively pivotally received in circular holes  102  provided in the mounting plates  66  and  68  at respective locations below bottom edges of the control plates  70  and  72 . The support shaft  100  is axially fixed by snap rings  104  provided in respective grooves at opposite end locations of the support shaft  100  adjacent outer surfaces of the mounting plates  66  and  68 . A T-bolt  106  includes a stem  108 , projecting downwardly through a cross bore provided in the mounting shaft  100 , and a head  110  having opposite ends respectively located within circular holes  112  provided substantially vertically below the hole  88  in a lower area of each of the control plates  70  and  72 . A compression coil spring  114  is received on the T-bolt stem  108  between a flat washer  116  disposed below the support shaft  100  and a flange nut  118  threaded onto a threaded lower end section of the stem  108  so as to establish a desired state of compression or pre-load in the spring  114 .  
         [0023]    The twine guide mounting plate  80  is rectangular or square and is disposed transversely across the front of the twine tensioner  64  with a slot being provided in a lower left corner region of the plate  80  and receiving a tab  120  that is welded within the slot. A pair of partial circular openings  122  that are joined at their inner sides are provided in an upper location of the plate  80 , with a circular twine guide  124 , having a smooth-walled, low friction interior surface, being mounted in one of the openings  122 , the other opening being available for use with a baler for making different sized bales where a different number of twine loops are tied about a formed bale. The twine guide  124  includes a forward end that is too large to fit through the opening  122 , and a snap ring  126  is received in a groove provided in the guide  124  at a location just to the rear of the mounting plate  80 . The twine guide  124  is located so as to be just forward of the nip defined between the upper and lower ribbed rollers  74  and  76 , respectively.  
         [0024]    To aid in manually separating the rollers  74  and  76  so as to thread a length of twine between the rollers, a rear end section of an upwardly and forwardly inclined handle  128  is located between and secured to an upper forward location of the roller control plates  70  and  72 , as by bolts  130 . Thus, by manually applying a lifting force to the handle  128 , the force of the spring  114  is overcome and the control plates  70  and  72  are caused to carry the upper roller shaft  84  along the guide or cam slot  90  such as to move the upper roller  74  away from the lower roller  76 . A length of twine can then be threaded through the guide  124 , between the rollers  74  and  76  and then through a further guide  132  (FIG. 6) located in the panel  58 . The handle  128  can then be released and the twine end extending through the guide  132  can be pulled to advance a necessary length of the twine through the rollers  74  and  76 .  
         [0025]    Referring now also to FIG. 6, it can be seen that behind the panel  58 , and associated one each with one of the tensioners  64 , are a plurality of fore-and-aft extending twine slack take-up arms  134 . Each arm  134  is generally T-shaped with the stem of the T having its forward end mounted to a bracket  136  for pivoting vertically about a horizontal transverse axis defined by pivot mounts  138 . A twine guide roller  140  is mounted to a lower end of the head of the T and is normally engaged by the length of twine emanating from the adjacent twine guide  132 . A coil tension spring  142  has hooks formed in its opposite ends that are respectively engaged in a hole provided at the upper end of the head of the T of the arm  134  and in an upper end of the bracket  136 . A stop  144  is mounted to the bracket  136  at a location where it engages an upper surface of the stem of the T-shaped arm so as to limit upward pivoting movement of the arm  134 . Thus, downward pivotal movement of each arm  134  is resisted by the coil tension spring  142 . During the process of tying loops of twine about a bale, the springs  142  cause any excess slack in the loops of twine to be taken up so that a tying malfunction due to such excess slack does not occur.  
         [0026]    In operation, assume that a knot, which is tied to join two supply rolls of twine together, is in a length of twine passing through one of the twine tensioners  64  at a location just upstream of the tensioner. Then, if the tying process requires more twine, a pulling force will be exerted on the twine length to cause it to be pulled through the nip of the upper and lower ribbed rollers  74  and  76 . When the knot reaches the nip, it will exert a force on the upper roller  74  so as to cause it to be lifted against the bias of the spring  114 . Because the roller shaft  84  is constrained by the guide or cam slots  90 , the roller will be moved along a path having a corresponding shape, this shape being such that the spring force resisting movement of the roller  74  away from the roller  72  initially increases a small amount during the upward movement of the roller  74 , noting that the shaft  84  is close to the top of the vertical leg of the slot  90 , and then remains substantially constant as the roller  74  moves substantially horizontally to the rear in the gradually sloped part of the cam slots  90  resulting in the amount of tension force exerted on the twine remaining substantially constant as the knot is advanced through the nip of the rollers  72  and  74 . It is also noted that the direction of the gradually sloped part of the cam slots  90  is favorable since a majority of the tension force tending to separate the rollers  72  and  74  is directed parallel to the gradually sloped part of the cam slots  90 .  
         [0027]    When it is necessary to load the system with a new length of twine, this may easily be done manually by exerting a lifting force on the handle  128  of the respective tensioner  64  with one hand while using the other hand to thread the twine through the twine guide  124 , the gap between the rollers  74  and  76  and the twine guide  132 . The handle  128  may then be released and the twine end grasped and pulled to advance sufficient twine through the rollers  74  and  76  for permitting the twine to be threaded over the slack arm roller  140  and then on to other components of the tying assembly, as is well known.  
         [0028]    Having described the preferred embodiment, it will become apparent that various modifications can be made without departing from the scope of the invention as defined in the accompanying claims.