Abstract:
Bale measuring method for a rectangular baler includes the steps of: measuring a movement of a binding material that is being tied around a bale; using the measured movement of the binding material to calibrate a measurement and calculation tool for measuring a movement of the bale in the baler and for calculating a length of the bale based on said measurement; determining the length of the bale using the calibrated measurement and calculation tool as the bale moves backward in the baler.

Description:
[0001]    This application is the US National Stage filing of International Application Serial No. PCT/EP2014/056238 filed on Mar. 27, 2014 which claims priority to Belgian Application BE2013/0224 filed Apr. 2, 2013, each of which is incorporated herein by reference in its entirety. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates to a bale measuring method and system for a rectangular baler. 
       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 double knotter system for a baler is disclosed in US 2006/0012176 and in BE 2012/0697 in the name of the Applicant. 
         [0004]    At present bale length measurements are performed using a star wheel engaging the crop material. However, the parameters of the crop material, such as density, humidity, crop type, etc, may influence the amount of slip occurring as the star wheel rotates. This may lead to inaccurate measurement results. 
         [0005]    U.S. Pat. No. 5,988,053 in the name of the Applicant discloses a system for measuring the movement of the twines to detect a wide range of mistie conditions, such as broken or jammed strands. 
       SUMMARY OF THE INVENTION 
       [0006]    The object of the present invention is to improve existing bale length measurement systems and methods, and in particular to provide a bale length measurement system and method which is well adapted to work with different crop material parameters. 
         [0007]    According to an embodiment of the invention the bale measuring method for a rectangular baler comprises the following steps. A movement of a binding material that is being tied around a bale is measured. The measured movement of the binding material is used to calibrate a measurement and calculation tool, said measurement and calculation tool being adapted for measuring a movement of the bale in the baler and for calculating a length of the bale based on said measurement. The length of the bale is determined using the calibrated measurement and calculation tool as the bale moves backward in the baler. 
         [0008]    Such an embodiment has the following advantages. The measurement of the movement of the binding material will give an accurate indication of the movement of the crop material and can be used to calibrate a tool which measures the movement of the bale itself. This measurement of the movement of the bale itself may be influenced by crop material parameters, but by performing first a calibration using a measurement of the movement of the binding material, an accurate result can be obtained. For completeness it is noted that a measurement of the binding material over the full length of the bale to get an indication of the bale length is usually not possible because of the knotting cycles, and other disturbing factors. However, according to embodiments of the invention, the measured movement of the binding material is merely used to calibrate the tool which measures the movement of the bale itself, so that the measurement of the binding material can be done during any suitable period and does not need to be performed over the full length of the bale. 
         [0009]    According to a preferred embodiment the measurement and calculation tool comprises a measuring wheel which engages in the crop material and rotates as crop material is being moved in the baler. The calibrating may then comprise determining at least one calibration parameter. For determining the length of the bale, the number of rotations of the measuring wheel is counted as the bale moves backward in the baler and the length of the bale is determined based on said number of rotations and said at least one calibration parameter. 
         [0010]    According to a preferred embodiment of the invention, the binding material is tied around the bale by performing a first knot at a first end of the bale and a second knot at a second end of the bale. The movement of the binding material may then be measured after performing the first knot and before performing the second knot. In that way an accurate measurement of the movement of the binding material may be obtained for calibrating the measurement and calculation tool, avoiding zones surrounding the knotting activity. The measuring of the length of the binding material may be started e.g. a predetermined time after performing the first knot and may be stopped e.g. when a predetermined value for the length of the movement is reached. 
         [0011]    According to another embodiment, the movement of the binding material is measured between a first time corresponding with a first number of plunger strokes performed by the baler since the beginning of the formation of the bale, and a second time corresponding with a second larger number of plunger strokes performed by the baler since the beginning of the formation of the bale. 
         [0012]    According to a preferred embodiment of the invention calibrating the measurement and calculation tool consists in determining a correction factor based on a comparison of the measured movement of the binding material with the measured movement of the bale, said movements of the binding material and the bale being measured at the same time. 
         [0013]    According to a preferred embodiment of the invention the method further comprises triggering a tying mechanism of the baler when the determined length of the bale reaches a predetermined value. Because the length of the bale can be determined in an accurate way, also the triggering of the tying mechanism can be done in an improved way. 
         [0014]    According to a further developed embodiment of the invention the binding material that is being tied around the bale is tensioned using tensioning means, e.g. slacker arms, and the position of the tensioning means is measured. The measured positions may then be used together with the measured movement of the binding material to calibrate the measurement and calculation tool. Typically the position is measured at least at the beginning and at the end of the measured movement of the binding material. In that way any buffering of the binding material can be taken into account, improving the accurateness of the calibration. 
         [0015]    According to another aspect of the invention, there is provided a bale measuring system for a rectangular baler comprising a binding material measurement system and a measurement and calculation tool. The binding material measurement system is adapted for measuring a movement of a binding material that is being tied around a bale. The measurement and calculation tool is adapted for measuring a movement of the bale in the baler; for determining at least one calibration factor using the movement of the binding material as measured by the binding material measurement system and the measured movement of the bale; and for determining the length of the bale using the at least one calibration factor and the measured movement of the bale. 
         [0016]    According to a preferred embodiment of the invention the measurement and calculation tool comprises a measuring wheel which is adapted to engage in the crop material and to rotate as crop material is being moved in the baler; a sensor adapted for measuring the rotation of the measuring wheel; and a processor adapted for determining the length of the bale based on the measured rotation and the at least one calibration parameter. The sensor can be any suitable sensor, e.g. a rotary encoder, a hall effect sensor, an optical sensor, a mechanical or electrical counter, etc. 
         [0017]    According to a preferred embodiment of the invention the bale length measurement system is for use in a baler with a knotter adapted to perform a first knot at a first end of the bale and a second knot at a second end of the bale. The binding material measurement system may then be adapted to measure the movement of the binding material after performing the first knot and before performing the second knot. The binding material measurement system may be adapted to start the measurement at a predetermined time after performing the first knot and to stop measuring when a predetermined value for the movement of the binding material is reached. 
         [0018]    According to a preferred embodiment of the invention the measurement and calculation tool is adapted to determine the at least one calibration factor based on a comparison of the measured movement of the binding material with the measured movement of the bale, said movements of the binding material and the bale being measured at the same time. 
         [0019]    According to a preferred embodiment of the invention the bale measuring system is for use in a baler with a tying mechanism, and further comprises a triggering means adapted for triggering the tying mechanism of the baler when the determined length of the bale reaches a predetermined value. 
         [0020]    Finally according to another embodiment of the invention, there is provided a baler including an embodiment of a bale measuring system as disclosed above. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0021]    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: 
           [0022]      FIG. 1A  is a schematic view of a baler having a double knotter tying mechanism and comprising an embodiment of a bale measuring system of the invention; 
           [0023]      FIGS. 1B and 1C  are detailed schematic views of an embodiment of upper and lower binding material guiding and tensioning means, respectively; 
           [0024]      FIGS. 2A-2C  illustrate three consecutive steps in the baler of  FIG. 1 , as a bale is moving backward in the bale chamber; 
           [0025]      FIG. 3  is a flow chart illustrating an embodiment of the method of the invention; and 
           [0026]      FIG. 4  is a detailed schematic side view of a top door of a bale chamber including elements of an embodiment of a bale measuring system of the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0027]    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 any type of binding material (twine, string, etc.) and twisted junctions of binding material. 
         [0028]    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. 
         [0029]    The baler illustrated in  FIG. 1  has a rectangular bale case  1  that is supported by ground wheels (not shown). The bale case  1  defines a bale chamber  2  wherein material M is pushed in through a curved duct  3 . A plunger  10  reciprocates within the bale case  1  to intermittently pack fresh charges of material from the duct  3  rearward in the chamber  2  in the direction of the arrow P. When the bale reaches a predetermined size, a tying mechanism with a set of needles  5  is activated. As will be appreciated, the tying mechanism  4  comprises a set of individual knotters  4  provided crosswise on top of the bale case  1  at intervals. Each knotter  4  has an associated needle  5  for assisting in forming an individual loop around a finished bale B 0 , B 1 . When the bale B 0 , B 1  needs tying, the knotters  4  and their needles  5  are driven to initiate the tying operation. The knotter  4  may be similar in many respects to the knotter disclosed in US 2006/0012176 in the name of the Applicant or in BE 2012/0697, the disclosure of which is herein incorporated by reference. 
         [0030]    The needle  5  is swingably mounted on the bale case  1  by a pivot  6  and is swung back and forth across the bale chamber  2 , see  FIGS. 2A-2C , between an “at-home” or rest position fully below the bale case  1  and a “full-throw” position extending completely across the bale case  1 . With reference to  FIGS. 1 and 2 , to the left of loop  41  is a partial loop  42  which is in the process of being formed. The top strand  43  emanates from a source of twine supply  7 , while the bottom strand  44  emanates from a second source of twine supply  8 . In  FIG. 2B , a first knot  45  of bale B 1  is in existence, and the bale B 1  is approaching a length where the needle  5  is swinging into operation and presents the strands  43  and  44  to the knotter  4  to start an operation cycle in which two consecutive knots are being formed. In a finished bale B 0 , B 1 , the loop  41 ,  42  is made from two strands of binding material, i.e. one strand  43  along the top side of the bale and a second strand  44  along the bottom side of the bale and its two opposite, vertical ends. 
         [0031]    In a baler, it is desirable to measure the length of a bale that is formed.  FIG. 1  illustrates a bale measuring system according to an embodiment of the present invention. The bale measuring system comprises a twine measurement system  21 ,  22 , as well as a measurement and calculation tool  11 ,  12 ,  13  for determining the length of the bale. 
         [0032]    The twine measurement system can be any suitable twine measurement system, and typically includes twine sensors  21  and a processing part  22 . The twine sensors can be e.g. rotary encoders, hall effect sensors, optical sensors, mechanical or electrical counters, etc. The signal SL measured by the twine sensors  21  is sent to the processing part  22  which is adapted to determine the length of twine dispensed from twine source  7 . In the example illustrated in  FIG. 1 , the length of the upper twine  43  is measured. The skilled person will understand that it is also possible to measure the length of the lower twine  44 , or to measure both the upper and the lower twines  43 ,  44  using twine length measurement systems. 
         [0033]    Without loss of generality, the twine measurement system may further comprise a sensor  66 ,  67  or other suitable measurement means for determining the position of the twine tensioning means, here the upper and lower slacker arm  61 ,  62 , see  FIGS. 1B and 1C . A parameter representative for the measured position of the upper and lower slacker arm  61 ,  62  is sent to the processing part  22  to further improve the accurateness of the calculation of the length of the twine that has moved along the bale. Typically the position is measured at least at the beginning and at the end of the measured movement of the twine. In that way any buffering of the binding material can be taken into account. For completeness it is noted that in the illustrated embodiment the twine guiding and tensioning means further comprise an upper twine tensioner  63  and a lower twine tensioner  64 , and the upper twine is further guided along the knife finger drive shaft  65 . The skilled person understands that the twine guide and tensioning means can be implemented in a different way, and that for embodiments of the present invention determining the position of any moveable parts along which the twine is guided, may be advantageous. 
         [0034]    The measurement and calculation tool comprises a star wheel  11  which is mounted in such a way that it engages in the crop material M and rotates as crop material M is being moved in the baler. A sensor  12  is adapted for measuring the rotation of the star wheel  11 . The star wheel sensor  12  can be any suitable sensor, and can be e.g. a rotary encoder, a hall effect sensor, an optical sensor, a mechanical or electrical counter, etc. Further, the measurement and calculation tool comprises a processor  13  processing the signals SB received from star wheel sensor  12  and the output LM from processing part  22 . 
         [0035]    The processor  13  is adapted for determining at least one calibration factor using the measured length LM of the twine and the measured signals SB received from the star wheel sensor  12 . A calibration factor C can e.g. be determined using the following equation: 
         [0000]      [ LM]t 1, t 2=[#counted teeth star wheel] t 1, t 2 *C    
         [0036]    The twine length LM is preferably measured during a period [t 1 ,t 2 ] which allows accurate measuring of the twine length. As illustrated in  FIG. 2A , the twine length may be measured between a first time t 1  and a second time t 2  which corresponds with a period somewhere between the first knot  45  and the second knot  46  of a loop that is made around a bale. More preferably, time t 1  corresponds to a moment in time shortly after the moment at which the first knot  45  is made, wherein sufficient time is left in between the forming of the first knot and t 1  Similarly, time t 2  preferably corresponds to a moment in time shortly before forming the second knot but sufficiently before forming the second knot to avoid errors. In that way, the zones surrounding the knotting activity are avoided, hence, avoiding unreliable measurement signals due to interference of the tension compensation mechanism and the rapid movement of the twines during knotting. In other words, the twine length LM is preferably measured in the zone of steady state movement of the twine between two knotting cycles. The number of teeth mentioned in the formula above corresponds with the number of measured teeth during the same time period [t 1 , t 2 ]. 
         [0037]    According to a variant, the movement of the binding material is measured between a first time t 1  corresponding with a first number of plunger strokes performed by the baler since the beginning of the formation of the bale, and a second time t 2  corresponding with a second larger number of plunger strokes performed by the baler since the beginning of the formation of the bale. Further the skilled person understands that it is possible to perform a number of consecutive measurements and to use an average value. Also, it is possible to configure the processor part  22  to warn the operator in case of a significant divergence from the average value. By doing so, the operator can be warned early in case one of the twines is broken or one of the twine sources are finished. When one of the twines is no longer wrapped around the bale, it will have a significant impact on the overall strength of the remaining binding twines. The expansion forces of the formed bale will then be divided on the remaining twines, which will in some case not be sufficient to hold the bale together resulting in the snapping of the twines. So, as soon as a significant divergence is measured form the average value, the operator may decide to stop the baling process and restore the broken twine or place a new twine source. 
         [0038]    After determining the calibration factor, the length of a bale can be determined by counting the number of teeth during a time period [t 0 , t 3 ] which corresponds with the beginning and the end of the formation of a bale: 
         [0000]        LB =[# of counted teeth] t 0, t 3* C    
         [0039]    In practice, after calibration, the movement of crop material in the bale chamber is continuously measured. When a desirable bale length is reached, the tying mechanism is triggered and two consecutive knots are formed. 
         [0040]    The star wheel  11  is rotatably mounted on a shaft extending in a lateral direction of the baler. The teeth of the star wheel  11  impinge the adjacent crop material of a bale. Thus the star wheel is driven by the forward and backward movement of a bale in the bale chamber.  FIG. 4  illustrates an example of a top door of the bale case  1  having a first part  51  and a second part  52 . The lower wall of the first part  51  is inclined under an angle α with respect to the lower wall of the second part  52 . The first part  51  is meant to be located near the plunger  10 . Typically, the top door is mounted pivotally around an axis  53 . Preferably, the star wheel  11  is arranged in the second part  52  but close to the first part  51 . In that way, the star wheel  11  will engage in a more or less stabilized part of the bale. 
         [0041]      FIG. 3  illustrates schematically embodiment of a bale measuring method for a rectangular baler. In a first step  31  the movement of the binding material is sensed, e.g. through signals SL measured by sensor  21 , and the movement of the bale is sensed, e.g. through signals SB measured by sensor  12 , between time t 1  and t 2 . In a second step  32  the total measured movement LM of the binding material and the total measured movement of the crop material is compared to calibrate a measurement and calculation tool for measuring a movement of the bale in the baler. In a third step  33  the calibrated measurement and calculation tool is used to sense signals SB, and in a fourth step  34  the length of the bale (LB) is determined using the calibrated measurement and calculation tool. 
         [0042]    In the examples given above one calibration parameter is determined However the skilled person will understand that other models are possible to relate the measurement of the movement of the binding material (LM) to the measurement of the movement of the crop material (e.g. the number of counted teeth of the star wheel) using more than one calibration factor and/or using a non-linear relationship between the movement of the binding material (LM) and the measurement of the movement of the crop material (e.g. the number of counted teeth of the star wheel). 
         [0043]    Without loss of generality, the calculation of the calibration parameter may be repeated for every new bale that is being formed, or for every two or three bales. Also, the calibration parameter may be recalculated whenever a new twine roll is installed or whenever a new baling session is started. Further, it is possible to allow an operator to request a new calibration. 
         [0044]    For completeness the following is noted. At the beginning of a baling operation, when the baling chamber is empty, or when there is no or insufficient material present at the position of the star wheel, the star wheel will not function. As a consequence, this can lead to long bales that have to be cut. In such a situation, embodiments of the invention allow to use the measurement that is being performed by the binding material measurement system as a basis for deciding to activate the knotting system. In that way it can be decided to trigger the knotting system earlier in time such that a shorter first bale is obtained which can then be cut open. In that way, a normal operation of the baler can be obtained within a shorter time. In other words, according to embodiments of the invention, the measurement performed on the binding material may be used on its own for deciding to knot the first bale, while for the following bales, the measurement of the binding material may be used in combination with the measurement performed by the star wheel to determine the length of the bale and the moment of triggering the knotting system. 
         [0045]    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.