Abstract:
Knotter system comprising a bill hook, a twine receiver, a cutting arm and drive components and/or means. 
     The twine receiver is adapted to let the twines slip during a second full rotation of the bill hook so that cutting of the twines is avoided when forming the second knot. 
     The drive components and/or means can maintain the cutting arm in the extended position after the second rotation of the bill hook for a predetermined period which is sufficient to allow removal of the second knot from the bill hook.

Description:
[0001]    This application is the US National Stage filing of International Application Serial No. PCT/EP2013/070929 filed on Oct. 8, 2013 which claims priority to Belgian Application BE2012/0697 filed Oct. 16, 2012, each of which is incorporated herein by reference in its entirety. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates to a knotter system, and in particular to a knotter system for a baler for forming two consecutive knots during a single operation cycle. 
       BACKGROUND OF THE INVENTION 
       [0003]    Rectangular bales are able to maintain their shape by means of a series of parallel extending twine loops, provided lengthwise around the bales. Balers typically use automatic knotters by which e.g. two knots are made on every loop for binding a bale. An example of such a knotter system for a baler is disclosed in EP 1.584.227 in the name of the Applicant, the disclosure of which is included herein by reference. The knotter system disclosed in EP 1.584.227 has the advantage that two consecutive knots can be formed during one operation cycle, without the formation of twine tails. 
         [0004]    EP 1 645 509 relates to the holding device which is used in the knotter of a baler to grip hold twines as they are being knotted and cut. To establish a correct gripping and releasing, it is important to align all components to each other. EP 1 645 509 discloses that adjustment of the form of the curved edge of the holding device has a positive effect on the twines when being knotted and cut. 
         [0005]    The object of the present invention is to further improve the knotter system of EP 1.584.227, and more in particular to realize a better and easier removal of the second knot from the bill hook at the end of an operation cycle. 
       SUMMARY OF THE INVENTION 
       [0006]    According to an embodiment of the invention, the knotter system comprises a bill hook, a twine receiver for holding twines, a cutting arm adapted for cutting twines between the bill hook and the twine receiver and for sweeping a formed knot from the bill hook whilst moving between a rest position and an extended position. Further, the knotter system comprises a first drive means adapted to make the bill hook perform at least a first full rotation and a second full rotation and to move the cutting arm at least two times from the rest position to the extended position and back during a full operation cycle, to form respectively a first and second knot. The twine receiver is adapted to let the twines slip during the second full rotation of the bill hook so that cutting of the twines is avoided when forming the second knot. The first drive means are adapted to maintain the cutting arm in the extended position after the second rotation of the bill hook for a predetermined period which is such that the second knot is allowed to be removed from the bill hook without being hindered by the cutting arm moving back from the extended position to the rest position. 
         [0007]    By allowing the twines to slip during the second full rotation of the bill hook, the cutting of the twines is avoided. 
         [0008]    However, in that way, the end parts of the twines extending out of the second knot, are longer and more difficult to remove from the bill hook. In order to make the removal from the bill hook, the cutting arm is maintained for a predetermined period in the extended position after the second rotation of the bill hook, so that the second knot can be removed without being hindered by the cutting arm moving back to the rest position. 
         [0009]    According to a preferred embodiment, the bill hook comprises a lower lip, an upper lip and a positioning means for positioning the upper lip with respect to the lower lip. The positioning means are preferably adapted to move the upper lip away from the lower lip during the predetermined period. By moving the upper lip away from the lower lip during the predetermined period, the removal of the second knot from the bill hook is further ensured. 
         [0010]    According to a preferred embodiment, the first drive means are adapted to make the bill hook perform a third full rotation during the operation cycle, and to maintain the cutting arm in the extended position during at least a first part of said third rotation. More preferably, the positioning means are adapted to move the upper lip away from the lower lip during at least said first part of the third rotation, so that it is guaranteed that the second knot is removed from the bill hook during the first part of the third full rotation of the bill hook. 
         [0011]    According to a possible embodiment, the first drive means comprise a pinion and a first, second and third gear stretch provided along the circumference of a rotating disc. The pinion is adapted to cooperate with the first, second and third gear stretch for making the bill hook perform the first, second and third full rotation, respectively, when the disc is rotated. 
         [0012]    The disc is rotated around an axis which makes an angle with the axis of rotation of the bill hook. In that way, the existing knotter system can be easily adapted to make the third full rotation of the bill hook possible. 
         [0013]    According to a possible embodiment, the first drive means further comprise a cam track and a cam follower. The cam follower is connected with the cutter arm. The cam track is preferably provided in the disc or in a member mounted for rotating synchronously with the disc. Preferably, the cam track is adapted for moving the cutting arm a first time from the rest position to the extended position and back, and a second from the rest position to the extended position and back during a full operation cycle. When moving the cutting arm for the second time from the rest position to the extended position, the cutting arm is held in the extended position during the predetermined period of time, in order to allow for the removal of the second knot. 
         [0014]    According to a preferred embodiment, the twine receiver comprises a twine disc and a twine holder. The twine holder is adapted to clamp twines against the twine disc. The knotter system may further comprise second drive means adapted for rotating the twine disc during a first turn whilst clamping twines for forming the first knot, and for rotating the twine disc during a second turn whilst letting twines slip for the forming of the second knot. 
         [0015]    According to a preferred embodiment, the twine disc is provided with at least a first and a second notch for receiving the twines. The twines are typically in the first notch during the first turn and in the second notch during the second turn. Note however that during the beginning of the second turn, end parts of the twines may still be in the first notch. However, during the forming of the second knot, the end parts will slip first out of the first notch and then out of the second notch. 
         [0016]    According to a possible embodiment, the second notch is shaped in such a way that the twines are allowed to slip out of the second notch during forming of the second knot. According to another possible embodiment, the twine receiver is provided with biasing means for setting a bias for the clamping action by the twine holder. The biasing means may then be adapted to set a first bias during the first turn, and a second bias during the second turn. The first bias is chosen such that the twines are firmly clamped, while the second bias is chosen such that the twines are allowed to slip out of the twine receiver. 
         [0017]    According to a preferred embodiment, the cutting arm is provided with a cutter and a removal means. The cutter is adapted for cutting twines between the bill hook and the twine receiver, whilst moving from the rest position to the extended position, and the removal means are adapted for sweeping twines from the bill hook whilst moving from the rest position to the extended position. Typically, the removal means have a shape which is complementary to the shape of the bill hook in order to facilitate the removal of the twines. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]    The advantages of this invention will be apparent upon consideration of the following detailed disclosure of exemplary non-limiting embodiments of the invention, especially when taken in conjunction with the accompanying drawings wherein: 
           [0019]      FIG. 1  is a fragmentary, side elevational view of a baler having a double knotter tying mechanism; 
           [0020]      FIG. 2  is a diagrammatic view of a complete and a partial double-knotted loop without the forming of twine tails; 
           [0021]      FIG. 3A  is an exploded perspective view of an embodiment of the double knotter system of the invention; 
           [0022]      FIG. 3B  is an assembled perspective view of the embodiment of the double knotter system of  FIG. 3A ; 
           [0023]      FIG. 3C  a detailed view of the knotter disc of the embodiment of  FIG. 3A ; 
           [0024]      FIG. 3D  a schematic view of an embodiment of a twine disc according to the invention; 
           [0025]      FIG. 4  is an enlarged, fragmentary, side elevational view of the knotter, needle and associated mechanism in mid cycle; 
           [0026]      FIG. 5  is a fragmentary, plan view taken substantially along line  4 - 4  of  FIG. 4 ; 
           [0027]      FIG. 6  is a fragmentary, front perspective view of the knotter with strands of twine draped across the bill hook and held by retaining discs in readiness of preparing a knot; 
           [0028]      FIG. 7  is a fragmentary, elevational view of cams on a drive shaft of the knotter for operating a slack take-up arm and a twine finger; 
           [0029]      FIGS. 8 to 17  are fragmentary, schematic views illustrating the successive steps of a double-knotting operation; 
           [0030]      FIG. 18  is an enlarged, front elevational view of the tip of a needle which presents the strands to the knotter, illustrating details of the construction thereof; and 
           [0031]      FIG. 19  is an enlarged view of the bill hook which forms the knot by turning around its lengthways axis, illustrating details of construction thereof. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0032]    In the description which follows and in certain passages already set forth, the principles of the present invention will be described in terms of “twine” and “knots” formed in such twine. However, it is to be recognized that such principles extend to wire and twisted junctions of wire as well as twine and knots. 
         [0033]    Many of the fastening, connection, processes and other means and components utilized in this invention are widely known and used in the field of the invention described, and their exact nature or type is not necessary for an understanding and use of the invention by a person skilled in the art, and therefore they will not be discussed in significant detail. Also, any reference herein to the terms “left” or “right” are used as a matter of mere convenience, and are determined by standing at the rear of the machine facing in its normal direction of travel. 
         [0034]    The baler  20  illustrated in  FIG. 1  has a rectangular bale case  22  that is supported by ground wheels  24 . The bale case  22  defines a bale chamber  26  wherein material is pushed in through a curved duct  28 . A plunger  30  reciprocates within the bale case  22  to intermittently pack fresh charges of material from the duct  28  rearwardly in the chamber  26  in the direction of the arrow  32 . When the bale reaches a predetermined size, a trigger  34  is pulled by a rod  36 . This rod  36  engages a dog clutch  38 , the clutch  38  in turn being connected to a tying mechanism  40  and a set of needles  42 . As will be appreciated, the tying mechanism comprises a set of individual tying mechanisms or knotters  40  provided crosswise on top of the bale chamber  26  at intervals. Each knotter  40  has an associated needle  42  for assisting in forming an individual loop around a finished bale. When the bale needs tying, the dog clutch  38  connects the knotter  40  and their needles  42  via a drive chain  44  to a source of driving power to initiate the tying operation. As the individual knotters  40  all operate in an identical manner, it suffices to describe the present invention in relation to only one such knotter  40 . 
         [0035]    The needle  42  is swingably mounted on the bale case  22  by a pivot  46  and is swung back and forth across the bale chamber  26  by a linkage  48 , which is activated by the clutch  38 . The needle  42  has an “at-home” or rest position fully below the bale case  22  as illustrated in  FIG. 1  and a “full-throw” position extending completely across the bale case  22  as illustrated, for example, in  FIG. 9 . As illustrated most clearly in  FIGS. 4 and 18 , the tip  50  of needle  42  has an eyelet  52  defined therein by the opposed furcations  54  and  56  of the bifurcated tip  50  in conjunction with a pair of longitudinally spaced, transversely extending rollers  58  and  60 . It will be noted that the roller  58  is positioned inwardly from the outer extremity of the tip  50 , while the roller  60  is positioned outwardly from the roller  58  more closely adjacent this extremity. Even so, the roller  60  is positioned a short distance inwardly from the outer extremity of the tip  50 , and both of the rollers  58  and  60  may be tapered toward their mid points, comparable to a diabolo, so as to provide secure seats for the tying strands. 
         [0036]    With reference to  FIG. 2 , to the left of completed loop  62  is a partial loop  62   a  which is in the process of being formed. The top strand  64   a  emanates from a source of twine supply  72 , while the bottom strand  66   a  emanates from an entirely separate, second source of twine supply  74 . At the particular point in the sequence chosen for illustration, the knot  68   a  is in existence, and the bale is approaching that length where the needle  42  is ready to swing into operation and present the strands  64   a  and  66   a  to the knotter  40  to start an operation cycle in which two consecutive knots are being formed. In a finished bale, the loop  62  is made from two strands of binding material, i.e., one strand  64  along the top side of the bale and a second strand  66  along the bottom side of the bale and its two opposite, vertical ends. The strands  64  and  66  together form the continuous loop  62 . Together, they fully circumscribe the bale. The knot  68  of a bale is typically a so called loop-knot. This means that the ends of the strands  64  and  66  of the knot  68  are released from a retained position so they can be pulled back instead of being cut by a moving knife arm  88  as will be described further to form a small loop on top of the knot. The knot  68  itself, thus holds the ends of the strands  64  and  66 , united with the knot  68 . 
         [0037]    With this short explanation in mind, the details of the embodiments according to the present invention will now be described.  FIGS. 3A ,  3 B,  3 C, and  3 D illustrate a first embodiment according to the invention, and  FIGS. 4 ,  5 ,  6  and  7  illustrate a second embodiment. For convenience the same reference numerals have been used for referring to similar elements in the different embodiments. The knotter  40  is similar in many respects to the knotter disclosed in EP 1.584.227 in the name of the Applicant, the disclosure of which is herein incorporated by reference. 
         [0038]    The knotter  40  of  FIGS. 3A ,  3 B and  4  comprises a generally circular element, also called knotter disc  76  that is secured to a drive shaft  78  for rotation with the latter through one full revolution when the clutch  38  is engaged. The shaft  78  is supported by a forwardly inclined frame  80  attached to the top of the bale case  22 , and the frame  80  also supports the knotter components for forming the knots in response to rotation of the knotter disc  76 . 
         [0039]    Briefly, such components include a rotary bill hook member  82 , supported by the frame  80  for rotation about an inclined axis  84 ; a twine disc  86  rearwardly of and adjacent to the bill hook  82  for holding strands  64   a  and  66   a  in position for engagement by the bill hook  82  during rotation of the latter; and removal means  93  for sweeping the connected strands from the bill hook  82  connected to an arm  88  pivotally attached to the frame  80  by a bolt  90 . The strands  64   a  and  66   a  are held in notches  87   a ,  87   b  in the rotating twine disc  86  by a retainer or twine holder  220 . The tensioning force of this retainer  220  to the twine disc  86  can be adjusted manually by changing the tension of a leaf-spring  200  when a bolt  210  is loosened or tightened. 
         [0040]    The lower end of the arm  88  is shaped in such a way that it opens away from the twine disc  86  beneath the bill hook  82 . The arm  88  further carries a knife  94  between the bill hook  82  and the twine disc  86  for severing the strands  64   a  and  66   a  in response to a swinging movement of the arm  88  in the proper direction. Such movement of the arm  88  to operate the knife  94  also serves to bring the removal means  93  in engagement with a knot formed on the bill hook  82  for stripping such knot off of the bill hook  82 . The removal means  93  preferably have a shape which is substantially complementary to the shape of the bill hook  82  to improve this sweeping of the bill hook. 
         [0041]    In order to transmit driving power to the bill hook  82 , the knotter disc  76  is provided with a pinion  96  which is disposed for meshing engagement with a pair of circumferentially spaced gear stretches  98 ,  100  and  101  on the knotter disc  76 . Similarly, driving power is transmitted to the discs of the twine disc  86  through, a twine disc pinion  103 , a worm gear drive  102  and a bevel gear  104  in position for sequential meshing engagement with a pair of circumferentially spaced gear sections  106 , and  108  on the knotter disc  76 . 
         [0042]    Power to swing the arm  88  about the pivot bolt  90  is obtained through a cam follower  110  at the upper end of the arm  88  beyond the pivot bolt  90  which is disposed within a cam track  112  on the knotter disc  76 . A pair of circumferentially spaced cam shoulders  114  and  116  in the track  112  are positioned to sequentially engage the follower  110  to operate the latter. 
         [0043]    A finger  118  is located below the bill hook  82  and the arm  88  of the knotter  40  and is mounted on an upright pivot  120  for lateral swinging movement between a standby position illustrated in  FIGS. 4 and 5  and a full-throw, laterally extended position somewhat beyond that illustrated in  FIG. 6 . 
         [0044]    An operating link  122  attached at one end to the finger  118  and at the opposite end to a crank  124  serves to effect swinging of the finger  118 . The crank  124  is in turn fixed to a transversely extending shaft  126  that extends to a point behind the knotter disc  76  where it may carry a second crank  128  as illustrated in  FIG. 7 . The crank  128  is biased upwardly in a counter-clockwise direction by a coil spring  130  and carries a cam follower  132  at its outermost end. The follower  132  is in position for operating engagement with a double-lobed cam  134  fixed to the shaft  78  for rotation therewith, its lobes  136  and  138  being circumferentially spaced apart in accordance with the desired timed relationship between the finger  118  and the knot-forming components of the knotter  40 . 
         [0045]    Also mounted on the shaft  78  with the cam  134  is a second cam  140  having a peripheral land stretch  142  over approximately 180 degrees of its circumference and a peripheral valley stretch  144  over the remaining approximately 180 degrees of its circumference. Such stretches  142  and  144  are disposed for operating engagement with a cam roller  146  located at the outer end of a lever  148  that is fixed at its inner end to a transverse shaft  150 . The lever  148 , and hence the shaft  150 , are biased in a counter-clockwise direction viewing  FIG. 7  by a coil spring  152 . The shaft  150  extends back out to the opposite side of the knotter disc  76  parallel with the shafts  78  and  126  to a point substantially in fore-and-aft alignment with the bill hook  82 . At that location, the shaft  150  fixedly carries a rearwardly extending slack take-up device  154 . The device  154  carries a pair of spaced rollers  156  and  158  at its rearmost end around which the strand  64   a  is entrained as illustrated in  FIG. 4 . A length of the strand  64   a  is also looped upwardly around another roller  160  disposed above the device  154 . The strand  64   a  may be clamped between a pair of opposed plates  162  and  164  ( FIG. 4 ) of a tensioning unit  166 . The force with which the plates  162  and  164  clamp the strand  64   a  may be controlled by a wing nut  168  operating against a spring  170  that in turn presses against the movable plate  164 . A tensioning unit similar to unit  166  may also be provided for the strand  66   a , although such additional unit is not illustrated. 
         [0046]    The condition of the partial loop  62   a  in  FIG. 2 , and that of the knotter  40  and the needle  42 , corresponds substantially with conditions illustrated in  FIGS. 4 ,  5  and  8 , with the exception that in  FIG. 2 , the needle  42  is still in its home position. At this point in the bale forming operation, the bale has reached its desired length and it is time to complete the loop around the bale and make the second knot in the loop. It is remarked that at this specific instance, the strand  64   a  stretches along the top of the bale directly beneath the arm  88  but, at least for all effective purposes, is out of contact with the knotter  40 . As illustrated in  FIG. 8 , as the needle  42  swings upwardly toward the knotter  40 , it carries with it the strand  66   a  as the latter is pulled out of source  74 . Note that because the strand  66   a  is threaded through the eyelet  52  of needle  42 , a length of that strand on the twine source side of the needle  42  is also carried upwardly toward the knotter  40 , such extra length being hereinafter denoted  66   b . While the needle  42  approaches the knotter  40 , no additional length of the strand  64   a  is pulled from the source  72 . Even as the tip of the needle  42 , and more particularly, the roller  60 , snares the strand  64   a  as illustrated in  FIG. 9  and presents strands  64   a  and  66   a  in unison to the knotter  40 , still no additional length of the strand  64   a  is pulled from source  72  because the device  154  rocks upwardly in a counter-clockwise direction to provide the slack necessary in the strand  64   a  to accommodate the needle movement. 
         [0047]    While the strands  64   a  and  66   a  are being delivered across the bill hook  82  to the twine disc  86 , the finger  118  is actuated to swing inwardly and engage at least the strand  66   a  as illustrated in  FIGS. 9 and 10  so as to assure that the strands  64   a  and  66   a  are both in proper position across the bill hook  82 . The twine finger will hold the strands  64   a ,  66   a  on the bill hook  82  during the whole first knot process. 
         [0048]    In presenting the strands  64   a  and  66   a , the needle actually drapes the strands across the bill hook  82  and thence into awaiting notches of the twine disc  86 , whereupon rotation of co-operating discs in the latter, in combination with a pressing twine holder  220 , serve to firmly grip the strands and prevent their escape as the bill hook  82  begins its rotation as illustrated in  FIG. 10 . The needle  42  reaches its highest position and starts to go down, see  FIG. 11 . The twine disc  86  rotates a quarter of a turn and clamps the twines  64   b  and  66   b  firmly together. During the down travel of the needles the two twines on the back of the needles are placed in the next notch of the twine disc for the second knot ( FIG. 12 ). While the needle goes down, the bill hook rotates to form the first knot. The knife arm swings out to cut the twines under the twine disc and sweeps the knot from the bill hook. 
         [0049]    When the bill hook  82  rotates around its axis  84 , a cam follower  85 , which is connected to the upper lip  83   a , engages an element having a cam shoulder (not shown). When rotating, the cam follower will push the upper lip  83   a  away from the lower lip  83   b , thus enabling the strands  64   a  and  66   a  to enter in between the two lips  83   a  and  83   b  while the bill hook is rotated. 
         [0050]    When the needle  42  delivers the strands  64  and  66  to the twine disc  86 , the twine disc  86  rotates in such a manner that the strands  64  and  66  are retained twice in different notches  87   a ,  87   b  in the twine disc  86 , see  FIG. 12  and the schematic top view of the twine disc  86  shown in  FIG. 12A . By doing so, two knots  70   a  and  68   b  can be formed during one knotting cycle as will be explained further, whereby the knife  94  severs the strands  64   a  and  66   a  from the strands  64   b  and  66   b  after the first knot  70  is formed and the removal part  93  removes the first knot from the bill hook  82 , thus separating the two loops from each other. The adjustable leaf-spring  200  pushes against the twine holder  220 , thus co-operating with the twine disc  86  to retain the strands. 
         [0051]    The foregoing described movement on the part of the bill hook  82  and the twine disc  86  are brought about by operable inter-engagement of the gear stretch  98  and gear section  106  on the knotter disc  76  with their respective gears  96  and  104  on the bill hook  82  and the twine disc  86 . Such driving inter-engagement continues until a knot has been formed on the bill hook  82  as illustrated in  FIGS. 11 and 12 , by which time the needle  42  has begun to withdraw. At this point, the cam shoulder  114  of the knotter disc  76  comes into engagement with the roller  110  of the arm  88  so as to swing the bottom of the latter, and hence the knife  94 , across that portion of the strands between the bill hook  82  and the twine disc  86 , thereby severing the same as illustrated in  FIG. 12  and previously explained. At the moment of cutting, the strands  64   a  and  66   a  extend from in between the lips  83   a  and  83   b  towards the twine disc  86 . Considering that the knife  94  moves very closely alongside the bill hook  82 , the free ends of the cut strands  64   a  and  66   a  extend only over a very short distance out of the lips  83   a  and  83   b . To complete the knot formation, the removal part  93  engages the strands  64   a  and  66   a  which are retained in a twisted manner around the bill hook  82 . In so doing, the strand parts lying on top of the lip  83   a  are pulled over the strand parts laying in between the lips  83   a  and  83   b , thereby forming the knot. As described above, since the free ends of the strands  64   a  and  66   a  are very short, they are pulled completely through the knot during its final formation, resulting in the so-called conventional knot  70   a , as best seen in  FIG. 13 . 
         [0052]    Besides completing the knot, further motion of the arm  88  also strips the finished knot  70   a  completely from the bill hook  82  and drops the completed loop on the bale as illustrated in  FIG. 13 . 
         [0053]    When the knot  70   a  is dropped by the knotter  40  following severance and stripping from the bill hook  82 , the strand  66   b  from source  74 , as well as strand  64   b  from source  72  is still retained in the second notch  87   b  and possibly also in the first notch  87   a  of the twine disc  86 . At this instance, the upper lip  83   a  is open again. Consequently, as the needle  42  continues to retract, the strand  66   b  is draped downwardly across the bale chamber  26  thereby pushing the upper lip  83   a  down because of the pressure of the strands on the upper lip  83   a , while the slack take-up device  154  lowers to its normal position to pull a small amount of additional twine from the source  72 . Upon reaching the condition illustrated in  FIG. 14 , the strands  64   b  and  66   b  are in position for initiating the second tying cycle which is started by the finger  118  swinging inwardly to engage the strands  64   b  and  66   b  and to assure that the strands  64   b  and  66   b  are properly positioned across and in engagement with the bill hook  82 , see  FIG. 15 , whereupon the latter and the twine disc  86  are operated by their second respective gear stretch  100  and gear section  108  on the knotter disc  76 . 
         [0054]    Thus, the second knot  68   b  becomes formed as illustrated in  FIG. 16 , whereupon the arm  88  is once again actuated, but this time by the second cam shoulder  116 . Preferably the pressure of the twine holder  220  on the twine disc  86  and/or the shape of those elements should be such that a controlled slipping of the strands  64   b  and  66   b  is obtained during the formation of the second knot  68   b . This may be reached by a suitable form of the twine disc  86 , and in particular by a suitable shape of the recess in which the strands  64   b  and  66   b  are taken up.  FIG. 3D  illustrates an example of a possible twine disc having a first type of recess  87   a  in which the twines can be firmly clamped and a second type of recess  87   b  in which the twines are allowed to slip. The skilled person will understand that other shapes are possible and that it may be possible to provide more or less recesses in the twine disc. The twine disc could e.g. be provided with two notches spaced along the circumference at an angle which is larger than 90 degrees, in which case the rotation of the twine disc will have to be adapted accordingly. 
         [0055]    According to an alternative variant the pressure exerted by the leaf spring  200  could be regulated using a setting means  302  adapted to decrease this pressure when the gear  96  engages gear section  100 . According to yet another possibility the twine holder  220  could be pushed away against the force of the leaf spring  200  during the formation of the second knot  68   b . The skilled person understands that this regulating of the pressure/pushing away of the twine holder can be reached using any suitable mechanical or hydraulic transfer, e.g. by mechanically coupling the rotation of the knotter disc  76  and the setting means  302  for setting the pressure exerted on the twine holder  220 . Also, instead of providing the spring means  200 , there could be provided a different actuator  304  for biasing the twine holder  220 , which actuator could be regulated e.g. by means of a control device for exerting a lower biasing during the second tying cycle. The operator would then be able to adjust the pressure exerted by the twine holder on the twine disk and the twines which are placed in the twine disk, such that the proper tension can be chosen, depending on e.g. the crops which is being baled, the speed of travel of the machine, the weather conditions, the quality of the twine, . . . . Finally the skilled person understands that an adaption of shape of the recesses  87   a ,  87   b  and the use of a biasing means such as  302  or  304  may be combined. 
         [0056]    Because the free ends of the strands  64   b  and  66   b  are considerably longer than the free ends obtained during the first knot formation, upon finalizing the knot, free ends  64   b  and  66   b  no longer are pulled completely out of the knot, resulting in a so-called loop-knot  68   b , as best seen in  FIG. 17 . 
         [0057]    The cam shoulder  116  extends over a part of the circumference, see also reference numeral  117  so as to create a large shoulder which keeps the knife  94  in its furthest extended position after removal of the knot  68   b  of the bill hook  82 . This position of the cutter arm  88  is best illustrated in  FIG. 3B . Pinion  96  will now engage gear stretch  101  and continue to rotate while the upper lip  83   a  opens a little. By keeping the cutter arm  88  in its furthest position and continuing to rotate the bill hook  82 , it is made sure that the strands can be properly removed and do not remain attached to the bill hook. 
         [0058]    As illustrated in  FIG. 4 , there may be provided a supplementary gear section  109  providing a prolonged operation of the twine disc  86 . In that way the strands  64   b  and  66   b  will no longer be retained between the twine disc  86  and the twine holder  220 , causing a further slipping of the twines during the forming of the second knot. Indeed, even though the knife  94  is very sharp, it will not be able to cut the strands because instead of holding the strands, the twine disc  86  is releasing them on account of the continued rotation of the twine disc  86  and the low pressure of the twine holder  220  on the twine disc  86 , while the arm  88  continues moving and stripping of the almost completed knot from the bill hook  82 , thus pulling the strands out of the twine disc  86 . The skilled person understands that the supplementary gear section  109  is not necessary, and that substantially the same effect can be reached when the tensioning force of the leaf spring  200  to the twine holder  220  is sufficiently decreased. 
         [0059]    This knot  68   b  is the start of a new bight for the next bale. Such bight is in position to receive new material that is packed into the bale chamber  26  by the plunger  30 , and the bight grows in length as additional lengths of the strands  64   b  and  66   b  are simultaneously pulled from their sources  72  and  74 . Finally, when the bale has reached its desired size, the sequence returns to its starting point, whereupon the bight is closed by operation of the needle  42  to complete the loop around the bale and form the other knot. 
         [0060]    While the principles of the invention have been set out above in connection with specific embodiments, it is to be understood that this description is merely made by way of example and not as a limitation of the scope of protection, which is determined by the appended claims.