Abstract:
The dog clutch for a square baler is normally retained in a disengaged position as a continuously driven sprocket rotates around it during baling operations. When a retainer for the dog is released, the dog is released by the retainer and flips out to an engaged position so as to be driven through one knotter revolution by a driving lug on the rotating sprocket, whereupon it is reset by the retainer into its disengaged position. An external lobe on the rotating sprocket blocks releasing movement of the retainer if the driving lug of the sprocket is in the immediate vicinity of the dog, which could otherwise cause an insecure engagement of the lug with the dog. The dog-engaging seat on the retainer is spring-loaded to provide yieldable relief in the event binding starts to occur between the retainer and the dog.

Description:
RELATED APPLICATION  
       [0001]    This application is a division of prior co-pending application Ser. No. 09/518,952, filed Mar. 6, 2000. 
     
    
     
       TECHNICAL FIELD  
         [0002]    This invention relates to hay balers and, more particularly, to improvements associated with the clutch that activates the knotter and twine needles in such a baler.  
         BACKGROUND  
         [0003]    U.S. Pat. No. 5,782,175 titled “Knotter Clutch Control for Square Balers” and assigned to the assignee of the present invention is directed to improvements that prevent the driven dog of the dog clutch on a baler from releasing to its actuated position for engagement with the driving lug of the clutch unless the lug is in a position where positive driving engagement between the lug and the dog is assured. The dog is normally maintained in its retracted position as the constantly moving sprocket having the driving lug mounted thereon rotates around the dog without making contact. The dog is held in the retracted position by a retainer that is released in response to the bale reaching a predetermined size, such release of the retainer permitting the dog to move out into its actuated position where it is picked up by the driving lug on the next cycle of revolution of the sprocket. A strategically located external lobe on the sprocket interacts with the retainer to prevent its release in the event the baler attempts to release the retainer when the lug is in the immediate vicinity of the dog, which release might cause the lug to only partially and temporarily catch the dog for driving the knotter through an operating cycle. By preventing the retainer from releasing unless the driving lug is spaced in its cycle from the dog, either on the approaching side or departing side thereof, positive interengagement between the lug and the dog can be achieved.  
           [0004]    The external lobe also has the effect of resetting or tending to reset the retainer if the retainer has been released before the lobe reaches the reset roller. While this is of no particular consequence so long as the dog has been fully tripped and the operating lever associated therewith has moved past the retaining roller on the retainer, in some situations the roller may hang up on the tip of the lever as the external cam lobe tries to move the retainer in a resetting direction. Damage or breakage of components may result as the lobe attempts to swing the retainer inwardly at the same time the dog lever blocks such motion.  
         SUMMARY OF THE INVENTION  
         [0005]    Accordingly, an important object of the present invention is to eliminate the potential for the retainer and dog to become jammed in a knotter clutch control of the type disclosed in the &#39;175 patent. Such jamming problem is avoided in the present invention by providing a degree of spring relief between the dog and the retainer such that, in the event jamming starts to occur, the spring relief permits relative movement between the two components in such a direction that one or the other of the components can continue its movement in the appropriate direction.  
           [0006]    In a preferred embodiment, such relief is provided by having the dog-engaging part of the retainer spring-loaded so that it can yield when untoward binding forces attempt to arise between the retainer and the dog. Preferably, the dog-engaging part of the retainer takes the form of a swingable member having a relatively flat seat for the outer end of the dog lever, such member being yieldably biased by a tension spring into a dog-blocking position on the supporting body of the retainer. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0007]    [0007]FIG. 1 is a fragmentary side elevational view of a square baler incorporating an improved knotter clutch control constructed in accordance with the principles of the present invention;  
         [0008]    [0008]FIG. 2 is an enlarged, fragmentary side elevational view of the prior art knotter clutch control as disclosed in patent  5 , 782 , 175 , such view illustrating the binding problem that can sometimes arise;  
         [0009]    [0009]FIG. 3 is a further enlarged, fragmentary side elevational view of the improved knotter clutch control of the present invention illustrating the condition of components during normal operation when the clutch is in a disengaged condition and the retainer is holding the dog in its unactuated position;  
         [0010]    [0010]FIG. 4 is a side elevational view similar to FIG. 3 but illustrating how the retainer of the present invention has the capability of relieving potential jamming forces between the retainer and the clutch dog;  
         [0011]    [0011]FIG. 5 is an enlarged, exploded isometric view of a retainer constructed in accordance with the principles of the present invention; and  
         [0012]    [0012]FIG. 6 is an isometric assembly view of the retainer. 
     
    
     DETAILED DESCRIPTION  
       [0013]    The present invention comprises an improvement upon the invention disclosed and claimed in the above mentioned U.S. Pat. No. 5,782,175. Accordingly, for the sake of brevity, certain details disclosed with particularity in the &#39;175 patent will not be repeated herein. Instead, U.S. Pat. No. 5,782,175 is hereby incorporated by reference into the present specification to the extent necessary for a full and complete understanding of the present invention.  
         [0014]    The present invention is illustrated in connection with a large square baler  210  in FIG. 1. Such balers are typically capable of producing bales on the order of 1,500 to 2,000 pounds or more. However, it will be appreciated that the principles of this invention may also be applied to smaller balers, and such balers need not be of the “extrusion” type as illustrated in FIG. 1 in which new bales are progressively forced out the rear end of the baler through a restricted orifice.  
         [0015]    The baler  210  has a series or “stack” of knotters  212  at the top of the baler which cooperate with twine needles  214  from time-to-time to place strands of twine around a finished bale. The knotters form a secure knot in the opposite ends of each twine strand and then cut the twine from the tied bale while retaining the free end of the twine for use in wrapping around the next bale. Generally speaking, a bale length sensor  216  including a star wheel  218  determines when a bale has reached full length, engages a clutch  220  associated with the stack of knotters  212 , and causes the knotters  212  to actuate for one single revolution of a drive shaft  222 . After each single revolution of the drive shaft  222 , the clutch  220  is disengaged until the next bale reaches the proper length. During each knotter cycle, the needles  214  swing across the bale chamber located inside the baler  210  to present the ends of twine strands to the knotters  212 .  
         [0016]    The knotters  212  are supplied operating power through drive means such as a chain drive assembly  224 . A component of the drive means, such as a sprocket  232 , is constantly driven, so long as power is being supplied to the baler  210 . A chain  230  of the drive assembly  224  is entrained around a sprocket  232  so as to drive the sprocket  232  around the axis of the knotter shaft  222 . Although the sprocket  232  is continuously driven, the knotter shaft  222  does not rotate unless the clutch  220  is engaged.  
         [0017]    The clutch  220  includes a dog  238  mounted on the knotter shaft  222 , and a driving lug  240  mounted on the sprocket  232 . The lug  240  is part of a circular cam ring  242  projecting outwardly from and integral with the outer face of the sprocket  232 . The ring  242  is concentrically disposed about the axis of rotation of the knotter shaft  222  and has a radially inner, annular surface  242   a  that is totally concentric with the knotter shaft  222  except for the driving lug  240 , where the surface  242   a  projects radially inwardly and is truncated to present the lug  240 .  
         [0018]    The clutch  220  further includes a crank arm  244  that is fixed intermediate its opposite ends to the knotter shaft  222  and extends entirely across the face of the sprocket  232 . The crank arm  244  has its lower end operably connected with a linkage  246  that actuates the needles  214 , while the opposite, upper end of the crank arm  244  carries the dog  238 . Dog  238  is pivoted to the crank arm  244  by a pivot  248  and is swingable between a fully retracted position as illustrated in FIG. 3 which renders the clutch  220  disengaged and a fully extended position (not shown except with respect to the prior art in FIG. 2) corresponding to an engaged condition of the clutch  220 .  
         [0019]    A coil spring  250  forms an additional part of the clutch  220  and is connected between the crank arm  244  and a tab  252  on the dog  238  to yieldably bias dog  238  toward its engaged position. In such engaged position, a roller  254  at the outer end of the dog  238  rides along the inner annular surface  242   a  of cam ring  242 . When dog  238  is in its engaged position, it is located within the circular path of travel of the moving lug  240 , but when dog  238  is retracted, it clears dog  240  as dog  240  travels around the axis of knotter shaft  222 .  
         [0020]    Clutch  220  is engaged and disengaged by a control broadly denoted by the numeral  256 . Bale length sensor  216  forms a part of such control and includes, in addition to the star wheel  218 , an inverted, generally L-shaped arm  258  and linkage  270  extending forwardly from the arm  258 . Further details of the construction and nature of operation of the length sensor  216  can be understood by reference to the &#39;175 patent. In addition to bale length sensor  216 , control  256  includes a lever  272  fixed to dog  238  and projecting radially outwardly from pivot  248 . Lever  272  has a downwardly facing notch  274  in its outer end.  
         [0021]    The control  256  further includes a releasable retainer  276  for releasably holding the dog  238  in its disengaged position of FIG. 3. Retainer  276  includes a generally T-shaped, generally flat support  278  having three legs  280 ,  282  and  284  that all project generally radially outwardly from a central hub  286  encircling a transverse pivot pin  288  on the baler. Legs  280  and  282  extend in opposite directions from one another, while leg  284  extends in a transverse direction relative to the legs  280 , 282 . The lowermost end of leg  282  is pivotally connected to the linkage  270 , while leg  284  carries at its outermost end a roller  290  that may be characterized as a “reset roller” for the retainer  256 . Reset roller  290  is adapted to be engaged along its inner periphery by a reset flange  292  on the upper end of crank arm  244  during each knotting cycle.  
         [0022]    The arm  280  pivotally supports a somewhat J-shaped member  294  on a transverse pivot  296  between opposite upper and lower ends of member  294 . As shown in particular detail in FIGS. 5 and 6, member  294  includes a seat  298  adjacent its upper end that is adapted to underlie and releasably engage the lever  272  of dog  238  when retainer  276  is in its retaining position of FIG. 3. Seat  298  engages lever  272  at notch  274  at this time. Preferably seat  298  is shaped to provide an uppermost flat face  298   a  and an outermost edge  298   b . Furthermore, seat  298  is undercut below edge  298   b  so as to present a receding, inclined surface  298   c . A tang  300  at the rear of seat  298  projects above the flat surface  298   a  to define the upper extremity of the member  294 , while a tail  302  projects laterally from the bottom end of the member  294  generally away from the clutch  220 .  
         [0023]    The support  278  has a lower stop  304  disposed for abutting engagement with the tail  302  of member  294  so as to limit clockwise pivoting movement of member  294  about pivot  296 . Stop  304  is so located that when tail  302  is in engagement therewith, seat  298  is in a blocking position with respect to lever  272  of dog  238  when retainer  276  is in its retaining position of FIG. 3. Member  294  is yieldably biased into abutting engagement with stop  304  by a coiled tension spring  306  connected between the tail  302  of member  294  and a generally L-shaped tab  308  projecting rearwardly from the upper end of the arm  280  of support  278 . Tab  308  also serves as a stop disposed for engagement with the tang  300  after a certain amount of counterclockwise rotation of member  294  from the FIG. 3 position such as, for example, approximately thirty degrees. In its capacity as a stop, tab  308  comes into play in the event that spring  306  breaks, in which event it is desirable to keep the lower end of member  294  from rotating counterclockwise to such an extent that it comes into the path of travel of lever  272  of dog  238  as dog  238  rotates through a knotting cycle. Member  294 , pivot  296  and relief spring  306  may collectively be referred to as relief mechanism for allowing seat  298  to yieldably shift out of its blocking position of FIG. 3 should the need arise as discussed below.  
         [0024]    Control  256  for clutch  220  further includes an external cam lobe  310  on the outside surface of ring  242 . The high spot on lobe  310  is located approximately 130° from driving lug  240  in the counterclockwise direction. When driving lug  240  is at pickup point A in the knotting cycle of revolution, lobe  310  is directly under roller  290  so as to preclude release of retainer  256 .  
       OPERATION  
       [0025]    As a bale is being formed within the baler  210 , the chain assembly  224  is continuously operating such that sprocket  232  is continuously rotating. Driving lug  240  is thus also continuously moving in a circular path of travel about the axis of knotter shaft  222  in a counterclockwise direction. However, as long as dog  238  remains in its disengaged position of FIG. 3, driving lug  240  misses roller  254  of dog  238  during each revolution and thus maintains clutch  220  in a disengaged condition. Seat  298  of retainer  276  remains securely beneath lever  272  of dog  238  at this time, assuring that dog  238  does not flip out to its engaged position.  
         [0026]    When the bale length sensor  216  trips, and assuming driving lug  240  is spaced from dog  238  rather than in the immediate vicinity, linkage  270  pulls the leg  282  of retainer  276  rightwardly viewing FIGS. 3 and 4 so as to rotate the retainer in a counterclockwise direction, displacing the seat  298  leftwardly out from under lever  272  of dog  238 . This allows spring  250  to snap roller  254  out into contacting engagement with the inner surface  242   a  of cam ring  242  so as to be within the path of travel of driving lug  240 . Therefore, when driving lug  240  reaches pickup point A, it engages roller  254  of lug  238  and pushes the entire knotter shaft  222 , dog  238  and crank arm  244  in a counterclockwise direction through one complete 360° operating cycle. During such cycle, the reset cam flange  292  engages the reset roller  290  and resets retainer  276  in a clockwise direction back into its retaining position so as to be disposed to engage lever  272  of dog  238  when it returns to pickup point A. This causes dog  238  to be rotated about pivot  248  to its disengaged position while driving lug  240  continues along its path of travel.  
         [0027]    In the event that bale length sensor  216  attempts to release retainer  276  when driving lug  240  is in the immediate vicinity of dog  238 , such release is prevented due to the presence of the external cam lug  310  which is directly under the roller  290  of retainer  276  at such time. External lug  310  thus prevents retainer  276  from rocking back in a counterclockwise direction as long as it is under roller  290 . Once external lug  310  has passed by roller  290 , retainer  276  is free to release, thus tripping dog  238  to its engaged position so that driving lug  240  can pick up roller  254  of dog  238  when lug  240  next reaches pickup point A.  
         [0028]    Normally, conditions are such that once dog  238  is engaged, lever  272  thereof is rotated counterclockwise about pivot  248  a sufficient extent that seat  298  will swing in behind lever  272  during any resetting movement of retainer  276  such as might occur if the external lug  310  were to engage the outside edge of the roller  290 . However, if for some reason, such as tolerance build-up, timing of the knotter trip, or other causes, the seat  298  does not clear the lever  272  when external cam  310  tends to swing retainer  276  back toward its retaining position as illustrated in FIG. 4, relief spring  306  will yield to the extent necessary to accommodate that situation. Once driving lug  240  then picks up dog  238  and starts to move it counterclockwise, lever  272  will disengage from seat  298 , allowing relief spring  306  to return seat  298  to its blocking position with tail  302  engaged against stop  304 . Thus, binding between the retainer  276  and dog  38  is avoided, which prevents damage to operating components and assures more uniform bale length.  
         [0029]    [0029]FIG. 2 illustrates the binding problem that could sometimes occur with the prior arrangement in U.S. Pat. No. 5,782,175. As the roller  88  starts to roll up the ramp  92   b  of external lobe  92 , retainer  76  is cammed inwardly. Instead of roller  86  passing to the backside of lever  72 , however, it may directly strike the tip of lever  72 . As roller  88  continues up the ramp  92   b , binding occurs and breakage may result. With the spring relief now provided in the retainer  276  of the present invention, however, this undesirable situation cannot occur.  
         [0030]    The preferred forms of the invention described above are to be used as illustration only, and should not be utilized in a limiting sense in interpreting the scope of the present invention. Obvious modifications to the exemplary embodiments, as hereinabove set forth, could be readily made by those skilled in the art without departing from the spirit of the present invention.  
         [0031]    The inventors hereby state their intent to rely on the Doctrine of Equivalents to determine and assess the reasonably fair scope of the present invention as pertains to any apparatus not materially departing from but outside the literal scope of the invention as set forth in the following claims.