Abstract:
A baler for making large parallelepiped bales includes a plunger drive and plunger arrangement wherein one or more load pins are located offset vertically from a centerline of a connecting rod or a mid-plane of the baling chamber. Such an arrangement permits load pins having the same range of measuring capacity to be used with balers of different sizes, with the amount of offset being changed for balers of different sizes. In one arrangement, load pins are offset vertically from the mid-plane of the plunger a distance sufficient to make it possible to measure differences in top-to-bottom reaction forces imposed on the plunger.

Description:
FIELD OF THE INVENTION 
   The present invention relates to balers for making large parallelepiped bales, and more specifically, relates to devices for measuring the load imposed by the baler plunger drive on a bale being formed so as to obtain a control signal used in forming uniform density bales. 
   BACKGROUND OF THE INVENTION 
   Balers for forming large parallelepiped bales are often equipped with a pre-compression chamber in the form of a curved chute or duct in which crop material is accumulated until it reaches a predetermined density whereupon a stuffer arrangement is actuated to lift the charge of crop material into the baling chamber at a location just behind the baler plunger. Once the charge of crop material is in the baling chamber, the plunger operates to compact the charge against previously compacted crop material located in the baling chamber and acting against the restriction of adjustable side panels which adjust the cross section of the baler to restrict the movement of the crop material so as to cause a bale having a desired density to be formed. In order to ensure that the formed bale is of a uniform density, it is a known practice to measure the force required to compact the crop material, this force being indicative of the density. Because the density of the charge of crop material placed in the baling chamber may differ from side-to-side, it is known to take force measurements in each of a pair of laterally spaced connecting rods extending between the plunger driver and the plunger. A signal is generated using these measurements to notify an operator of the need to cause the baler to be displaced transversely one way or the other relative to a crop material windrow in order to cause additional crop material to enter the baler on that side which has the lower measurement of compaction force. 
   U.S. Pat. No. 4,627,341, dated 9 Dec., 1986, and U.S. Pat. No. 5,253,570, dated 19 Oct., 1993, disclose respective examples of load sensors incorporated in transversely spaced connecting rods of the baler plunger drive for the purpose of measuring the load imposed on a bale being formed and generating signals used in a control system for aiding an operator in forming uniform density bales. These load sensing devices are located so as to be at a central horizontal plane through the connecting means when the plunger is fully-extended to the rear during compaction of the charge of crop. 
   Large square balers of different sizes experience plunger loads proportional to the lateral cross-sectional area contained between the opposite side walls of the baling chamber or bale case. Data resolution is lost if a more robust load pin is used than is required for the loads that occur. Consequently, a manufacturer that makes various sizes of balers is required to keep an inventory of load pins of various sizes, which increases cost. 
   SUMMARY OF THE INVENTION 
   According to the present invention, there is provided a novel plunger load sensing arrangement. 
   An object of the invention is to provide a plunger load sensing arrangement which makes it possible to use one size of load sensing pin for various baler sizes. 
   A more specific object of the invention is to provide a load sensing pin arrangement including a plunger drive connecting rod having a separable end coupled to the remainder of the connecting rod by a pair of pins, with one of the pins being a load pin offset from a line of centers extending through plain spherical ball bearings provided at opposite ends of the connecting rod. 
   According to a second embodiment of the invention, it is an object to provide a load pin arrangement used to secure a connecting rod mounting plate to each of laterally spaced locations on the plunger wherein the load pin or pins are offset vertically from a central horizontal plane passing through the plunger. 
   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 DRAWING 
       FIG. 1  is a schematic, left side elevational view of a baler for making large parallelepiped bales and with which the present invention is particularly adapted for use. 
       FIG. 2  is a right front perspective view of the plunger and plunger drive arrangement equipped with the load sensing pins arranged according to a first embodiment of the present invention. 
       FIG. 3  is an enlarged perspective view of one of the plunger drive connecting rods shown in FIG.  2 . 
       FIG. 4  is a longitudinal sectional view taken along line  4 — 4  of FIG.  3 . 
       FIG. 5  is a left side elevational view of an alternate embodiment of the invention wherein the plunger includes separate triangular plates each mounted to the remainder of the plunger by a load sensing pin and a coupling pin, and to the rear end of a respective connecting rod by a further pin. 
       FIG. 6  is a side view of the triangular plate shown in  FIG. 5 , with the connecting rod input and reactive plunger drive forces being indicated. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Referring now to  FIG. 1 , there is shown a baler  10  for forming large parallelepiped bales and including a main frame  12  supported on a tandem set of ground wheels  14 . A draft tongue  16  projects forwardly from the front of the frame  12  and is adapted for attachment to a towing vehicle, such as an agricultural tractor, not shown. A baling chamber  18  includes parallel top and bottom walls  20  and  22 , respectively and opposite, parallel side walls, which are all arranged so as to have a square or rectangular cross section. The bottom wall  22  is provided with a crop inlet  24  to which is coupled the upper end of a pre-compression chamber  26  in the form of a duct that curves upwardly and rearwardly from a crop pick-up  28 . Located in the region between the pick-up  28  and the pre-compression chamber  26  is a feeder fork arrangement  30  that operates to positively move crop into the forward end of the chamber  26 . Transversely spaced tines  32  of a pivotally mounted crop blocking fork  34  are selectively movable between a crop retaining position, as shown, wherein they extend through over an upper edge of a back wall of the pre-compression chamber  26  at a location adjacent the baling chamber inlet  24 , and a rearwardly pivoted crop release position, for permitting an accumulated charge of crop to be moved into the baling chamber  18  through operation of a stuffing fork  36  having transversely spaced forks that move down through slots provided in a front wall of the pre-compression chamber  26 , and then sweep upwardly through the chamber  26  to move the charge of crop into the baling chamber  18 . Appropriate actuators, not shown, are associated with the blocking fork  34  and stuffing fork  36 , and are associated with controls that are sequenced to effect retraction of the blocking fork  34  and then operation of the stuffer fork  36  once the charge of crop has reached a pre-selected density as determined by a spring loaded, density sensing door  38 . 
   Once the charge of crop has been moved into the baling chamber  18 , it is moved rearwardly by operation of a plunger drive  40  acting on a plunger  42  which compresses the charge of crop against a partially formed bale  44  and a completely formed bale  46  which has already been bound together by several transversely spaced loops of twine that have been placed there by operation of a twine tying arrangement, of which only a needle yoke  48  is shown, which is pivotally mounted for delivering twine through the baling chamber when a forming bale  44  reaches a predetermined length. 
   Referring now also to  FIG. 2 , it can be seen that the plunger drive  40  includes an extensible and retractable hydraulic drive cylinder  50  having its cylinder end anchored to the frame  12  by a coupling pin  52 , and having its rod end pivotally coupled, as at pin  54 , to a crank arm  56 . The crank arm  56  is mounted for oscillating about a horizontal transverse axis defined by a pin  58  coupling the forward end of the crank arm  56  to the frame  12 . The rear end of the crank arm  56  is pivotally coupled, as by a coupling pin  60 , to the forward ends of a parallel pair of transversely spaced connecting rods  62  having their rear ends pivotally coupled to the plunger  42  by respective coupling pins  64 . The hydraulic drive cylinder  50  is shown in its retracted position in  FIG. 2 , this position corresponding to that which it occupies when the plunger  42  is fully extended to the rear within the baling chamber  18 . Movement of the plunger  42  between its fully retracted position, shown in  FIG. 1 , and its fully extended position, is guided by front and rear pairs of rollers  66  and  68 , respectively mounted for rotation about front and rear pairs of pins  70  and  72  fixed to opposite side walls of the plunger  42 . It is significant to note that a line of centers C′ extends between the centers of the pins  60  and  64  of each of the connecting rods  62 . 
   Referring now also to  FIGS. 3 and 4 , it can be seen that front and rear ends of each connecting rod  62  are respectively provided with transverse bores in which are located identical front and rear plain spherical-ball bearings  74  and  76 , with a center line. Each connecting rod  62  includes a separate forward end section  78  defined by a bar of rectangular cross section in which is located the bore containing the front bearing  74 . The connecting rod forward end section  78  includes a reduced-width tongue  80  located between opposite sides of a bifurcated forward end of the remaining portion of the connecting rod  62 . The end section  78  is held in place by a force-sensing load pin  82  and a further pin  84 , with the pins  82  and  84  respectively being located offset above and below the center line C′. 
   Referring to  FIG. 4 , there is shown a force analysis of one of the connecting rods  62 . Since the plain spherical-ball bearings  74  and  76  are located at each end of the connecting rod  62 , the connecting rod  62  will not endure any bending load, but only tension or compression forces F. The load path will always be through the centers of each ball of the bearings  74  and  76 . The distance from the load path to the load pin  82  is L 1 , while the distance between the connecting pin  84  and the load path is L 2 . Consequently, the ratio of distances between the load path and the pins  82  and  84  (L 1 /L 2 ) will determine the amount of force generated in each pin. If L 1 &gt;L 2 , the force through the load pin  82  will be smaller, and if L 1 &lt;L 2 , the force through the load pin  82  will be greater. Accordingly, the connecting rod  62  can be designed to use the full load range of an already existing load pin, thereby maximizing the electronic sensitivity of the load pin. 
   Referring now to  FIG. 5 , there is shown a second embodiment of the invention. Specifically, illustrated is a plunger  42 ′ including right- and left-hand identical, transversely spaced plates, with only the left-hand plate  86  being visible. The plate  86  is here shown in the form of an equilateral triangle, with two corners being disposed in vertical alignment with each other and equally offset vertically on opposite sides of the central plane C, and with the remaining corner being located ahead of the other two corners and centered on the central plane C. The right- and left-hand triangular plates are respectively received between right- and left-hand pairs of plate-like, vertical strengthening ribs of the plunger  42 ′, with only the left-hand pair of ribs  88  being visible. A left-hand load pin  90 L extends through aligned holes provided in the pair of ribs  88  and a bushing  92  forming an upper rear corner of the triangular plate  86 , with it to be understood that a right-hand load pin  90 R (not visible) is similarly provided for securing the upper rear corner of the right-hand triangular plate to the right-hand pair of plate-like strengthening ribs of the plunger  42 ′. Similarly, a left-hand coupling pin  94 L extends through aligned holes in the pair of ribs  88  and in a bushing  96  forming a lower rear corner of the triangular plate  86 . Similarly, a right-hand coupling pin  94 R (not visible) extends through aligned holes in the right-hand pair of strengthening ribs and a bushing defining a lower rear corner of the right-hand triangular plate. The rear ends of a pair of connecting rods  62 ′ are respectively coupled to the forward corners of the right- and left-hand triangular plates, with only the coupling of a left-hand connecting rod  62 ′ to the left-hand plate  86  being shown. Specifically, a front section of the triangular plate  86  is bifurcated so as to define a front corner comprising parallel, transversely spaced sides  98  which are each provided with a bushing  100 , the bushings  100  cooperating to define the forward corner of the plate  86 . The rear end of the left-hand coupling rod  62 ′ is received between the spaced sides  98  of the front section of the plate  86  and secured thereto by a coupling pin  102 , which is centered on the plane C. The connecting rods  62 ′ carry the spherical-ball bearings  74  and  76 , respectively, at their front and rear ends. 
   It is here noted that whether or not the plates coupling the connecting rods to the plunger  42 ′ are triangular is immaterial, but what is material is the locations of the load pins and coupling pins since the load computations are easier if these locations are similar to the triangular pattern shown. Like the connecting rods  62  of the first embodiment, the front ends of the connecting rods  62 ′ are pivotally coupled to the rear end of the crank arm  56  by the pin  60 . 
   Referring now to  FIG. 6 , there is shown the left-hand triangular plate  86  showing the forces imposed thereon during a compaction stroke, with it to be understood that similar forces will be imposed on the right-hand triangular plate. 
   The following calculations, together with the free-body forces illustrated in  FIGS. 5 and 6 , demonstrate a concept to determine both side-to-side and vertical offset loading on the plunger of a baler while using only two load pins. There are four sensors, namely, a crank angle position sensor  104 , which determines the position of the plunger  42  as a function of the angular relationship between the crank arm  56  and the center plane C, a cylinder pressure sensor  106  coupled to the plunger drive cylinder  50 , and the right and left load pins  90 R and  90 L, respectively. The additional top-to-bottom offset loading information may be used to adjust stuffer speed and stroke as well as the pre-compression chamber density. All of these machine settings may be used to make a more uniform flake and thus, a more uniform bale. 
   The following identifies the various terms used in the calculations:
         F=connecting rod force   H=reacting force resisting plunger movement   a=longitudinal distance between load pins and rear plunger roller   b=longitudinal distance between load pins and front plunger roller   c=vertical distance between coupling pins and load pins   d=vertical distance from connecting rod pin to lower plunger pin   e=horizontal distance from pinned connections between triangular plates and plunger   Axl=left hand reaction at point A in the longitudinal direction   Axr=right hand reaction at point A in the longitudinal direction   θ=crank angle   R 2 l=reaction at plunger&#39;s left, front bearing   R 2 r=reaction at plunger&#39;s right, front bearing
 
The equations then are:
       

   H=F (cos θ), with F being known with the pressure sensor  106  coupled to the drive cylinder  50  and with θ being known from the sensor  104 . For the purposes of the below calculation, the case is that where a=0, but it does not have to be. Further, assume the plunger  42 ′ and triangular attaching plates  86  to be infinitely rigid and not experiencing rotational or translational acceleration. As shown in  FIG. 5 , the sum of the moments about point O on the plunger  42 ′ must equal zero. Consequently, Axl(c)+Axr(c)+R 2 l(b)+R 2 r(b)=H(c/ 2 −v), with it being noted that the front and rear pairs of plunger rollers  66  and  68  counter any moment induced on the plunger through an offset in top-to-bottom loading. The goal is to determine the sum of the moments about point O on the attaching plate assemblies  86 . As applied to  FIG. 6 , the equation for doing this is: F(cos θ)(d)−F(sin θ)(e)=Axl(c)+Axr(c) where Axl and Axr are actual load pin readings. Left-to-right, or lateral, offset loading is easily calculated in the following equation: L-to-R offset=Axl−Axr/(Axl+Axr). Top-to-bottom, or vertical, offset loading is the difference between the expected Ax pin load and the actual pin readings. Specifically, Top-to-Bottom Offset=[F(cos θ)−Axl−Axr]/F(cos θ). A positive value indicates the reactive load H resisting plunger movement is below center while a negative value indicates the load H is acting above the center of the plunger. 
   Thus, it will be appreciated that the plunger/connecting rod/connecting plate arrangement of the second embodiment has the same ability to measure side-to-side load differences on the plunger as does the plunger/connecting rod arrangement of the first embodiment, and additionally has the ability to measure top-to-bottom load differences. 
   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.