Abstract:
An assembly for controlling the angle of an implement on an earth-moving machine. The assembly includes an upper control arm, a lower control configured to mechanically interface with an implement; a rocker arm configured to pivotably couple the lower control arm to the upper control arm.

Description:
TECHNICAL FIELD 
       [0001]    This disclosure relates generally to a linkage connecting a frame of a machine with an implement. 
       BACKGROUND 
       [0002]    Earth-moving machines, such as loaders, have linkages connecting the frame of the machine to an implement such as a bucket. Many different linkage designs exist. For many linkage configurations, when raising or lowering the implement, the angle of the implement relative changes. In some cases, when the implement is sufficiently raised from the ground, the angle of the implement relative to the ground may cause material to spill from the back of the implement, towards the machine frame. To prevent this from occurring, it is desirable to tilt the angle of the implement forward as the implement is raised, to maintain an approximately constant angle of the implement relative to the ground. 
         [0003]    Methods of maintaining the angle of an implement relative to the ground are known. One common method is by means of a hydraulic system, such as described in U.S. Pat. No. 3,563,137 to Graber et. al. As a bucket is raised from the ground, a hydraulic cylinder is actuated to tilt the angle of the bucket forward to maintain a constant angle or, at a minimum, prevent the angle of the bucket from exceeding a threshold. Systems of this type, however, often require sensors, valves, specific cylinders, hosing, and software control systems. 
         [0004]    To address these concerns, some linkages may be characterized as “self-leveling.” That is, as the linkage is raised, the mechanical configuration of the linkage causes the angle of the implement relative to the ground to stay substantially level. While these linkages do not have some of the same drawbacks as more complicated leveling systems, the components of a self-leveling linkage may be expensive to produce, requiring specific manufacturing tolerances and complex component shapes. Further, forces imposed on the linkage may cause wear or failure of one or more linkage components. It is therefore desirable to have a mechanical linkage design that is easy to manufacture and also has a design that allows for longer wear life. 
         [0005]    The present disclosure is directed to overcoming or mitigating one or more of the problems set forth above. 
       SUMMARY 
       [0006]    One aspect of the disclosure provides a linkage for an earth-moving machine. The linkage includes a boom arm pivotably connected to a machine frame at a first pivot, an implement pivotably connected to the boom arm at a second pivot, and an angle control assembly connected to the machine and connected to the implement. The angle control assembly prevents the implement from tilting beyond a threshold when the boom arm is raised. The angle control assembly includes an upper control arm pivotably operably connected to a lower control arm, and a rocker arm pivotally connected to the upper control arm and to the lower control arm. 
         [0007]    In another aspect, an assembly for controlling the angle of an implement on an earth-moving machine is disclosed. The assembly includes an upper control arm, a lower control configured to mechanically interface with the implement, and a rocker arm configured to pivotably couple the lower control arm to the upper control arm. 
         [0008]    In another aspect, an earth-moving machine is disclosed. The machine includes a machine frame, a ground engaging element, a boom arm pivotably connected to a machine frame at a first pivot, a hydraulic cylinder connected to the machine frame and configured to raise or lower the boom arm, and a bucket pivotably connected to the boom arm at a second pivot. The machine also includes an angle control assembly connected to the machine and connected to the bucket. The angle control assembly arm prevents the angle at second pivot from exceeding a threshold when the boom arm is raised. The angle control assembly includes an upper control arm pivotably connected at the first pivot, a lower control arm pivotably connected to the bucket, a rocker arm pivotally connected to the upper control arm and to the lower control arm. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]      FIG. 1  shows an exemplary machine linkage incorporating a system to prevent the angle of an implement from tilting as the linkage is raised. 
           [0010]      FIG. 2  illustrates a block diagram of an implement angle control assembly. 
           [0011]      FIG. 3  illustrates a linkage according to the present disclosure, in several different positions. 
       
    
    
     DETAILED DESCRIPTION 
       [0012]      FIG. 1  shows an exemplary machine linkage  10  suitable for earth moving machines such as a track loader, wheel loader or backhoe-loader, or a similar machine carrying an implement such as bucket. Machine linkage  10  includes a boom arm  12  operably attached to a frame tower  14 , which is in turn coupled to a machine frame  15 . Boom arm  12  is pivotably connected to machine frame  15  at a pivot  28 . As shown in  FIG. 1 , machine linkage  10  may include a plurality of boom arms  12 , and optionally include other structural components, such as a crossbar  16  and a crossbar  18 . 
         [0013]    In the example shown, boom arm  12  is pivotably connected to a bucket  20  at a pivot  42 . Bucket  20  may be raised or lowered relative to the ground by means of one or more boom cylinders  22 . Boom cylinders  22  are coupled to boom arms  12 , and also coupled to frame tower  14 , machine frame  15 , or some other structural component of the machine. Extension of boom cylinders  22  allows bucket  20  to be raised vertically relative to the ground. 
         [0014]    Bucket  20  is also coupled to an implement control cylinder  34  at implement armature  38 . In addition, implement control cylinder is connected at pivot  40 , with implement armature  36  running from pivot  40  to bucket  20 . Extension of implement control cylinder  34  allows bucket  20  to tilt backward or “rack back.” Retraction of the implement control cylinder  34  allows bucket  20  to rotate forward or “dump.” 
         [0015]    In the absence of any other control mechanism, as boom cylinders  22  extend and boom arm  12  is raised, the angle of bucket  20  relative to the ground changes. Potentially, if the linkage is raised to a sufficient height, material might fall out of bucket  20  backward (i.e., towards the frame of the machine). To mitigate this, bucket  20  is pivotably attached to lower control arm  32  at second pivot  21 , to react against bucket  20  as machine linkage  10  is raised, to maintain a substantially constant angle of bucket  20  relative to the ground. Lower control arm  32  is coupled to a rocker arm  30 , which in turn is pivotably connected to boom arm  12 . Rocker arm  30  is pivotably connected to an upper control arm  26 , which preferably but not necessarily attaches to boom arms  12  at first pivot  28 . 
         [0016]      FIG. 2  illustrates a block diagram of an exemplary implement angle control assembly. As will be described in more detail below, angle control assembly  200  prevents an implement from tilting beyond a threshold angle when a linkage is raised by mechanically transmitting motion to a hydraulic valve, which in turns actuates a hydraulic cylinder to control the angle of the implement. 
         [0017]    Angle control assembly  200  includes lower control arm  32  with end  204  for connecting to an implement such as a bucket. Lower control arm  32  also includes end  206  for coupling to rocker arm  30 . Rocker arm  30  is operably coupled to upper control arm  26 , and includes end  210 , where rocker arm  30  may be coupled to the machine (such as to boom arm  12  in  FIG. 1 ). These pivotable connections may be made by means of pins or any other mechanisms for fastening well known in the art. 
         [0018]      FIG. 2A  shows a closer view of rocker arm  30 . Rocker arm  30  is preferably triangular in shape in one plane, with end  206  of lower control arm  32  preferably attaching near the top of rocker arm  30 , and with end  214  of upper control arm  26  preferably attaching below end  206  on rocker arm  30 . As used herein, the directional terms “above” and “below” refer to height relative to the ground when attached to a machine, and “forward” means in the direction of the implement on the machine, and “backwards” means in the direction away from the implement towards the machine frame. Preferably, rocker arm  30  attaches to the machine at end  210 . 
         [0019]    Angle φ in  FIG. 2A  is convenient to use as a method of measuring the angular distance between lower mechanism  209  and upper mechanisms  211 , where lower mechanism  209  is formed by points  206 ,  210 ,  221  and  204 , and the upper mechanism  211  is formed by the points  216 ,  214 ,  210  and  218 . Lower mechanism  209  and upper mechanism  211  are in essence two four-bar linkages sharing point  210  and separated by angle φ, which can range from a positive angle to a negative angle. The angle φ, as well as the lengths of the lower control arm  32 , upper control arm  26 , rocker arm  30 , the distance from  204  to point  221 , and the distance from  216  to  218 , can be appropriately dimensioned to control the overall action of angle control assembly  200 . The configuration shown allows the movement of lower control arm  32  to be transmitted to upper control arm  26 , through rotation of rocker arm  30 . This movement is not necessarily in a 1 to 1 ratio, and is dependent on the ratio between the lengths  210  to  206  and  218  to  216 . Lower control arm  32  moves in the range of about 1.2 to 2.5 times the distance of movement of upper control arm  26 , as machine linkage  10  is raised, more preferably in the range of about 1.3 to 2.0 times the distance of movement of upper control arm  26 . 
         [0020]    Angle control assembly  200  includes pivot link  216  for rotation about pivot  218 . Angle control assembly  200  also includes a rear assembly  220 . Rear assembly  220  is responsible for transmitting the action of the front mechanism to a valve that controls a hydraulic implement tilt cylinder (e.g., implement control cylinder  34  in  FIG. 1 ), thus completing a mechanical feedback loop which controls the angle of bucket  20 , and keeps it from surpassing a certain angle relative to the ground. More specifically in the example of  FIG. 2 , rotation of pivot link  216  about pivot  218  rotates lever  222 , which contacts lever  224  and causes rotation of lever  224  about pivot  226 . This in turn, causes movement of linkage arms  232 ,  236 ,  242 , and  246 , about pivots  226 ,  230 ,  234 ,  238 ,  240 ,  244 , and  248 . The resulting mechanical motion causes lever  250  to rotate about pivot  248  to actuate a hydraulic valve  252 . Actuation of hydraulic valve  252  causes extension or retraction of a hydraulic cylinder to control the angle of tilt of the implement. Hydraulic valve is preferably a well-known mechanical valve that allows lever  250  to push down or pull up on the valve spool, allowing mechanical motion of lever  250  to be transferred into a change in hydraulic pressure of hydraulic cylinder  34 . 
         [0021]      FIG. 3  shows a linkage consistent with the present disclosure in three different positions. In position A the linkage is not raised and the bucket is the in the dumped position. In positions B and C, however, the linkage is raised at two different heights above the ground, however the angle of the bucket relative to the ground is substantially unchanged. This depicts operation of an angle control assembly such as that described in  FIGS. 1 and 2 . 
       INDUSTRIAL APPLICABILITY 
       [0022]    The present disclosure provides an advantageous linkage system to prevent material from spilling from an implement, such as the bucket on an earth-moving machine. The disclosure provides a mechanical system that avoids the complexities of other types of implement control systems, while providing the necessary control of the angle of a bucket with components that may be easy to manufacture. In addition, due to the arrangement of the components and the nature of forces placed on the components, the components may be relatively more durable over the operating life of the linkage. 
         [0023]    Other embodiments, features, aspects, and principles of the disclosed examples will be apparent to those skilled in the art and may be implemented in various environments and systems.