the present invention is susceptible of embodiment in many different forms . while the drawings illustrate and the specification describes certain preferred embodiments of the invention , it is to be understood that such disclosure is by way of example only . there is no intent to limit the principles of the present invention to the particular disclosed embodiments . the present invention is preferably incorporated as part of a round baler 10 such as the 900 series round balers manufactured by agco corporation including the hesston 945 , 955 , 956 , 946a , 956a , new idea 6454 , 6464 , 6465 , and challenger rb45 , rb46 and rb56 round balers ; however , the invention may be incorporated as a part of other types of baling equipment such as fixed chamber balers , square balers , etc . referring to fig1 , the preferred baler 10 includes a pair of laterally spaced apart sidewalls 12 ( only one being shown ) carried by ground wheels 14 ( only one being shown ) for advancement across a field in response to pulling force supplied to a generally fore - and - aft extending tongue 16 at the front of the sidewalls . a suitable power transmission device ( not shown ) incorporated as part of baler 10 is normally connected to the power - take off shaft of a tractor or other vehicle towing baler 10 for thereby supplying driving power to the various moving components of baler 10 including a crop pickup 18 thereof which may be of conventional design . because the sidewalls are laterally spaced - apart respective to the normal path of travel of the baler 10 , room is provided therebetween for formation and transport of a bale of crop formed by material which is picked up and loaded into the space between the sidewalls by pickup 18 . hence , the sidewalls cooperate in part to define a baling chamber . the fore - and - aft limitations of the baling chamber are defined by opposed , initially generally vertically disposed stretches of an endless , flexible web means broadly denoted by the numeral 20 and preferably comprising a series of endless , side - by - side , flexible rubber belt elements having their respective longitudinal axes disposed in a plane parallel to the sidewalls . the endless belts 20 are looped around a number of cylindrical rolls spanning the distance between the sidewalls . for example , a roll 22 adjacent the lower front end of baling chamber may be driven by the output of the power transmission mechanism so as to provide motive force for driving the endless belts 20 longitudinally of themselves . the other rolls may be idlers . the bottom of the baling chamber is open to present a crop inlet 24 for the pickup 18 . the round baler 10 also includes a twine dispensing arm which dispenses twine or other wrapping material for wrapping bales formed in the bale forming chamber . the twine dispensing arm preferably has two twine tubes and is pivotally mounted to a pivot point at the front of the baler 10 . the twine dispensing arm is mechanically controlled by a linear actuator coupled to the arm by a drive chain and sprocket . when the actuator retracts , the end of the twine arm moves to the right side of the baler . when the actuator extends , the twine arm moves to the left side of the baler . the baler 10 also includes a bale shape monitor for assisting the operator in forming uniform bales of crop . as best illustrated in fig2 and 3 , the bale shape monitor preferably includes a bale size sensor 28 , a bale shape sensor assembly 30 , and a user interface 32 . the bale size sensor 28 is preferably a rotary hall - effect sensor such as those manufactured by power components in mishawaka , ind . the bale size sensor 28 includes a rotation element which is coaxially mounted to one end of a mounting shaft 34 for belt tensioning arms 36 to produce an output signal corresponding to the rotational position of the shaft 34 , which position is representative of the size of the bale being formed in the baling chamber . the output signal of the bale size sensor 28 preferably has a range of 1 - 4v . the bale shape sensor assembly 30 includes a center reference assembly 38 , a left side sensor assembly 40 , and a right side sensor assembly 42 . the center reference assembly 38 includes a center arm 44 swingably mounted within the baler by a transverse bar 46 . the center arm 44 is welded or otherwise fixed to the bar 46 . the ends of the bar 46 are rotatably supported to the belt tensioning arms 36 by bearing supports . a feeler wheel 48 , formed of rubber or other suitable material , is mounted to one end of the center arm 44 by a nut and bolt assembly . a bearing assembly within the wheel serves to journal the wheel on the nut and bolt assembly . the center arm 44 is positioned so that its feeler wheel 48 rides against the exterior surface of one of the centermost belts 20 a . the wheel 48 is yieldably biased against the belt 20 a by tension springs . the center reference assembly 38 does not include its own active bale size sensor , but instead serves as a reference for the left side and right side sensors as described below . the left side sensor assembly 40 also includes a swingable arm 50 and a rotatable wheel 52 mounted adjacent one end of the arm by a nut - and - bolt assembly for relative rotational movement by a bearing assembly ( not shown ) contained within the wheel . fixed to the opposite end of the arm 50 is a cylindrical collar for supporting the arm 50 on the bar 46 . the collar loosely receives the bar so as to allow relative movement therebetween . the wheel 52 is yieldably pressed against the front stretch of the leftmost belt 20 b by a tension spring . the location of the collar along the length of the bar is maintained so that the wheel presses against the leftmost belt at a point spaced equally between the sides of the belt . the left side sensor assembly 40 also includes a bale shape sensor 54 , including a signal sender mounted to the bar 46 and an actuator rod mounted to the arm 50 . the bale shape sensor 54 senses the relative difference in the bale diameter at the left side of the bale versus the center by sensing differences in the tension of the leftmost belt 20 b versus the center belt 20 a . relative tension can be sensed because the signal sender is mounted to the bar 46 , which moves with the center arm 44 , whereas the actuator rod is mounted to the left arm 50 , which can move independently of the center arm 44 and bar 46 . when the tension on the left 20 b and center 20 a belts is the same , the signal sender and actuator rod rotate together so that the output signal of the signal sender doesn &# 39 ; t change . however , if the tension on the left belt 20 b is more or less than the tension on the center belt 20 a , the actuator rod will rotate one direction or the other relative to the signal sender to cause the signal sender &# 39 ; s output signal to increase or decrease a proportional amount . the signal sender preferably has an output signal range of 4 volts . the signal sender and actuator rod are preferably installed and calibrated so that an output signal of 1v means the leftmost belt 20 b is in its most slackened position relative to the center belt 20 a , an output signal of 2 . 5v means the leftmost belt is under the same tension as the center belt , and an output signal of 4v means the leftmost belt is in its highest tension relative to the center belt . the right side sensor assembly 42 is structurally and functionally similar to the left side sensor assembly 40 , and includes a swingable arm 56 , a rotatable wheel 58 supported on the bar 46 , and a bale shape sensor 60 . the wheel 58 is yieldably pressed against a rightmost belt 20 c . the bale shape sensor 60 includes a signal sender mounted to the bar 46 and an actuator rod mounted to the arm 56 . the bale shape sensor senses the relative difference in the bale diameter at the right side of the bale versus the center by sensing differences in the tension of the rightmost belt 20 c versus the center belt 20 a as described above with respect to the left side sensor assembly . the signal sender for the right side sensor assembly preferably has an output signal range of 4 volts . the bale shape sensor is preferably installed and calibrated so that an output signal of 4v means the rightmost belt 20 c is in its most slackened position relative to the center belt 20 a , an output signal of 2 . 5v means the rightmost belt is under the same tension as the center belt , and a signal output of 1v means the rightmost belt is in its highest tension relative to the center belt . it will be appreciated that the left and right side sensor assemblies 40 , 42 are not necessarily limited to being associated with the endmost belts of the baler . in some baler constructions , it may be sufficient to associate the sensor assemblies 40 , 42 with a belt that is only proximate to the adjacent baler sidewall . for example , the bale diameter may be sufficiently detected by associating the sensor assemblies with a belt spaced inwardly from one or more of the other belts . furthermore , it is entirely within the scope of the present invention to utilize a pair of left and right side sensors and an intermediate sensor such as described in united states statutory invention registration no . h1 , 819 , hereby incorporated into the present application by reference . the user interface 32 receives inputs from an operator of the tractor . an external control device or other computing device connection to the user interface receives output signals from the bale size sensor 28 and the left and right side bale shape sensors 54 , 60 . the user interface 32 is preferably compatible with iso 11783 standards so that it can be used to control operation of any implement used with the tractor or other towing vehicle . the user interface 32 is programmed with a computer program comprising an ordered listing of executable instructions for implementing logical functions of the user interface 32 . the computer program can be embodied in any computer - readable medium for use by or in connection with an instruction execution system , apparatus , or device , such as a computer - based system , processor - containing system , or other system that can fetch the instructions from the instruction execution system , apparatus , or device , and execute the instructions . in the context of this application , a “ computer - readable medium ” can be any means that can contain , store , communicate , propagate or transport the program for use by or in connection with the instruction execution system , apparatus , or device . the computer - readable medium can be , for example , but not limited to , an electronic , magnetic , optical , electro - magnetic , infrared , or semi - conductor system , apparatus , device , or propagation medium . more specific , although not inclusive , examples of the computer - readable medium would include the following : an electrical connection having one or more wires , a portable computer diskette , a random access memory ( ram ), a read - only memory ( rom ), an erasable , programmable , read - only memory ( eprom or flash memory ), an optical fiber , and a portable compact disk read - only memory ( cdrom ). the computer - readable medium could even be paper or another suitable medium upon which the program is printed , as the program can be electronically captured , via for instance , optical scanning of the paper or other medium , then compiled , interpreted , or otherwise processed in a suitable manner , if necessary , and then stored in a computer memory . as best illustrated in fig3 , a preferred embodiment of the user interface 32 includes a display screen 62 , a control knob 63 , a plurality of function keys 65 or other inputs , and an internal controller , processor or other control device . the user interface 32 is preferably connected to the tractor key switch so that it automatically turns on when the tractor key is used to start the tractor . the control knob 63 allows the operator to scroll through the functions shown on the display screen and select one of the functions when the knob is pressed . the function keys 65 enable a displayed function or cause display of another screen . the particular operation or function of each function key is determined by software and can be changed . other details of round balers which may be used with the present invention are described in u . s . pat . nos . 6 , 477 , 824 ; 6 , 675 , 561 ; 4 , 850 , 271 ; and 4 , 224 , 867 , all incorporated into the present application by reference . to begin a bale - forming operation , an operator pulls the baler 10 across a windrow with a tractor or other vehicle in a conventional manner . as crop material is added to the bale forming chamber , the belts 20 stretch to accommodate the ever - increasing size of the bale . the bale shape monitor monitors the size and shape of the bale as it is being formed and provides important feedback to the operator via the display 62 on the user interface 32 . in a preferred embodiment , the display 62 provides a representation of the bale size and shape with a three bar indicator 64 as illustrated in fig3 - 11 . the middle bar 66 provides an indication of the overall bale size and is driven by the output signal of the bale size sensor 28 . for example , a bale size sensor output of 1v , which corresponds to a bale that has just started to form , results in a relatively short middle bar 66 . a sensor output of 4v , which corresponds to a bale that is fully formed , results in a relatively a tall middle bar 66 . the left bar 68 provides an indication of the size of the left side of the bale and is driven by an algorithm that takes into account the output signal from the left side sensor assembly 40 and a selected bale shape sensitivity variable . in accordance with one important aspect of the present invention , the user interface 32 is programmed to provide a bale shape display that is less sensitive at small bale sizes and relatively more sensitive at larger bale sizes . for example , when the left side sensor assembly 40 determines that the leftmost belt 20 b is slackened relative to the centermost belt 20 a , the left bar 68 of the indicator 64 will be slightly shorter than the middle bar 66 when the bale is small , but may be significantly shorter than the middle bar for the same amount of slack when the bale is almost fully formed . this prevents the indicator from “ jumping around ” when the bale is small ( and a relatively small amount of crop can change its diameter ) and gives the operator a more exaggerated indication of an uneven bale shape when the bale is nearly full ( and the operator needs to quickly make changes before the bale is full size ). similarly , the right bar 70 of the indicator 64 provides an indication of the size of the right side of the bale and is driven by an algorithm that takes into account the output signal from the right side sensor assembly 42 and a selected bale shape sensitivity variable . where : bale size = current size of the bale in the chamber in inches as measured by the bale size sensor . left diff = difference between bale size sensor output and left bale shape sensor output voltages . left limit = lower voltage limit of left bale sensor . emptychamber left shape sensor voltage = the signal output of the left bale shape sensor when the bale chamber is empty . sensfactor = a variable to make shape bar graphs move more ( or less ) than “ normal ” for a given amount of voltage difference . the following are examples of the algorithm results for different bale shape and size scenarios : 1 ) the bale is approximately ¼ formed and the left side is bigger than the center . bale size setting = 72 ″ ¼ formed bale = 18 ″ left shape sensor voltage = 3 . 1v bale size sensor voltage = 2 . 6v empty chamber left shape sensor voltage = 2 . 6v sensfactor = 1 . 0 ( normal sensitivity ) left limit = 0 . 5v leftbarvalue = bale size ×( 1 . 0 +(( 1 . 0 − leftdiff /( emptychamber left shape sensor voltage − left limit )− 1 . 0 )× sensfactor )) = 18 ×( 1 +( 1 −( 2 . 5 − 3 . 1 )/( 2 . 6 − 0 . 5 )− 1 )× 1 )) = 23 inches thus , the left bar 68 indicates a left side size of 23 ″ and the middle bar 66 indicates a bale size of 18 ″. for one embodiment , this may result in the left bar being 37 % filled and the center bar being 29 % filled . 2 ) the bale is ½ formed and the left side is smaller than the center . bale size setting = 72 ″ ½ formed bale = 36 ″ left shape sensor voltage = 2 . 6v bale size sensor voltage = 3 . 1v empty chamber left shape sensor voltage = 2 . 6v sensfactor = 1 . 0 ( normal sensitivity ) left limit = 0 . 5v leftbarvalue = bale size ×( 1 . 0 +(( 1 . 0 − leftdiff /( emptychamber left shape sensor voltage − left limit )− 1 . 0 )× sensfactor )) = 36 ×( 1 +( 1 −( 3 . 1 − 2 . 6 )/( 2 . 6 − 0 . 5 )− 1 )× 1 )) = 27 inches thus , the left bar 68 indicates a left side size of 27 ″ and the middle bar 66 indicates a bale size of 36 ″. for one embodiment , this may result in the left bar being 40 % filled and the center bar being 53 % filled . 3 ) the bale is almost fully formed and the right and / or left sides are smaller than the center . bale size setting = 72 ″ almost formed bale = 68 ″ left shape sensor voltage = 3 . 5v bale size sensor voltage = 4 . 0v empty chamber left shape sensor voltage = 2 . 6v sensfactor = 1 . 0 ( normal sensitivity ) left limit = 0 . 5v leftbarvalue = bale size ×( 1 . 0 +(( 1 . 0 − leftdiff /( emptychamber left shape sensor voltage − left limit )− 1 . 0 )× sensfactor )) = 68 ×( 1 +( 1 −( 4 . 0 − 3 . 5 )/( 2 . 6 − 0 . 5 )− 1 )× 1 )) = 52 inches thus , the left bar 68 indicates a left side size of 52 ″ and the middle bar 66 indicates a bale size of 68 ″. for one embodiment , this may result in the left bar being 73 % filled and the center bar being 96 % filled . 4 ) the bale is almost fully formed and the right and / or left sides are bigger than the center . bale size setting = 72 ″ almost formed bale = 68 ″ left shape sensor voltage = 4 . 5v bale size sensor voltage = 4 . 0v empty chamber left shape sensor voltage = 2 . 6v sensfactor = 1 . 0 ( normal sensitivity ) left limit = 0 . 5v leftbarvalue = bale size ×( 1 . 0 +(( 1 . 0 − leftdiff /( emptychamber left shape sensor voltage − left limit )− 1 . 0 )× sensfactor )) = 68 ×( 1 +( 1 −( 4 . 0 − 4 . 5 )/( 2 . 6 − 0 . 5 )− 1 )× 1 )) = 84 inches thus , the left bar 68 indicates a left side size of 84 ″ and the middle bar 66 indicates a bale size of 68 ″. for one embodiment , this may result in the left bar being 100 % filled and the center bar being 96 % filled . as illustrated by the above examples , at an 18 ″ bale size , a 0 . 5v difference between bale size sensor voltage and left side bale shape sensor voltage results in a difference of 5 inches in representative size of the center and left bars , 66 , 68 . at a 36 ″ bale size a 0 . 5v difference results in a difference of 9 inches . at a 68 ″ bale size , a 0 . 5v difference results in a difference of 16 inches . so as the bale size grows , the same voltage difference produces more bar graph difference between bars 66 and 68 . the effect is a more sensitive bar graph display as the bale gets closer to full size . the above examples include a sensitivity of “ normal ” in all cases . for a “ high ” sensitivity setting , the values could be scaled up by 25 % or some other amount to further increase the sensitivity of the bar indicator to shape problems . for a “ low ” sensitivity setting , the values could be scaled down by 25 % or some other amount to decrease the sensitivity of the bar indicator to shape problems . in accordance with another important aspect of the present invention , the color of one or more of the bars 66 , 68 , 70 on the display changes when the bale shape falls outside of certain shape limits . for example , the right bar 70 may turn yellow as depicted in fig8 if the controller determines the right side of the bale is a percentage smaller than the center of the bale . similarly , the left bar may turn red and the right bar yellow as depicted in fig7 if the left side is a percentage bigger than the center and the right side is a percentage smaller than the center . the left and right bars may also simultaneously turn yellow or red as depicted in fig1 and 11 if both the left and right sides deviate from the center . the user interface 32 may also provide certain text messages to assist the operator in forming uniformly shaped bales . for example , “ fill left ” may be displayed as depicted in fig9 when the left bar 68 is lower than the right bar 70 . “ fill left ” may also be displayed when the right bar is higher than both the middle bar and the left bar . “ fill right ” may be displayed when the right bar 70 is lower than either the left bar 68 or the middle bar 66 as depicted in fig7 and 8 . “ fill edges ” may be displayed as depicted in fig1 when both the left and right bars 68 , 70 are lower than the middle bar 66 . “ fill center ” may be displayed as depicted in fig1 when both the left and right bars 68 , 70 are higher than the middle bar 66 . “ near full ” may be displayed for 2 seconds when the bale nearly reaches the full bale size limit . “ near full ” display takes priority over bale shape texts for 2 seconds . “ full bale ” may be displayed as depicted in fig6 when the bale reaches the full bale size limit . “ full bale ” text takes priority over all other texts on the general text object . although the invention has been described with reference to the preferred embodiment illustrated in the attached drawing figures , it is noted that equivalents may be employed and substitutions made herein without departing from the scope of the invention as recited in the claims . for example , although the bale size and shape indicator of the present invention is particularly suited for use with round balers , it may also be used with other baling equipment .
a bale shape monitor for assisting an operator of a round baler . the bale shape monitor has an indicator with variable sensitivity . the indicator is less sensitive for small bales and more sensitive for larger bales so that the indicator de - emphasizes bale shape problems at the beginning of bale formation and emphasizes bale shape problems when the bale is almost fully formed . the indicator also changes colors according to the degree the bale is misshapen and provides textual driving instructions .