Abstract:
A boom position detecting device that detects a boom angle on a work vehicle for a boom that rotates about a pivot. The device includes a boom angle follower and positional sensor. The boom angle follower includes a spring and a follower arm arranged such that the spring biases the follower arm against a surface of the boom and keeps the follower arm in contact with the boom throughout a rotational movement of the boom about the pivot. The positional sensor is physically connected to the boom angle follower and detects at least one boom angle.

Description:
FIELD OF THE INVENTION 
   The invention relates to boom operation on work vehicles such as, for example, loaders. It relates to a simple and inexpensive system and method of improving the safety, comfort, accuracy and repeatability/consistency in boom operation. 
   BACKGROUND OF THE INVENTION 
   On many work vehicles such as, for example, loaders and backhoes, the heights and angles of the work tools must be visually estimated and manually adjusted on a somewhat constant basis. This will quickly lead to fatigue for a normal human operator. On other work vehicles, a few positions, i.e., heights and angles, of the work tools are factory preset allowing the work tools to be automatically placed in those positions at the direction of the operator via a simple pushing of a button, a manipulation of a handle or some other simple operation. On still other work vehicles, kickout positions for the work tools may be programmed and modified by the vehicle operators from without or within the cab. However, the adjustment methods and/or mechanisms appear to be complex, cumbersome and/or expensive as they require sensor systems with complex linkages and/or adjustments by vehicle operators outside of the operator cab. 
   SUMMARY OF THE INVENTION 
   The inventors recognize that conventional boom height sensing and adjustment mechanisms are somewhat cumbersome and/or expensive and have determined that such is unnecessary. They have invented a simplified method of tracking the position of a boom for a work vehicle. The method uses a height or angle sensor of very simple design which comprises a spring loaded follower arm biased such to constantly exert pressure against the boom at all boom positions. Thus, the follower arm rotates as the position of the boom changes and causes a change in electrical potential across an electromechanical device such as, for example, a potentiometer. This change in electrical potential is fed to a signal processing device or onboard computer such as, for example, a chassis control unit and the operator. After electronically sensing the boom position, it is possible to set kickout positions, return to dig positions and/or return to carry positions from the cab with a mere push of a button or operation of a switch at desired boom heights. A boom manipulating control lever, used by the operator to manipulate the boom from within the cab normally has at least one detent or locked position. The boom may be automatically set to move to a set/stored position by moving the control lever to the detent position. Once the boom reaches the position associated with the stored signal the chassis control unit sends a signal to release the control lever from the detent position and allows it to return to a neutral position. Thus, the movement of the boom stops upon release of the control lever. 
   The system is extremely simplified and does not require a linkage system between the sensor and the boom as in conventional systems. Thus, the sensor is capable of being attached with a minimum of modifications to the work vehicle as it is merely rigidly affixed to a portion of the vehicle and connected via electrical cable or wirelessly to the height estimating device. Conveying the position data to the chassis control unit may be accomplished through a flexible electrical cable or wirelessly via electromagnetic waves. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Embodiments of the invention will be described in detail, with reference to the following figures, wherein: 
       FIG. 1  is view of a work vehicle in which the invention may be used; 
       FIG. 2  is an oblique view of an exemplary embodiment of the assembled invention showing the boom in a heightened or kickout position; 
       FIG. 3  is a side view of the embodiment illustrated in  FIG. 2 ; 
       FIG. 4  is a side view of an exemplary embodiment of the assembled invention showing the boom in a lowered or return position; 
       FIG. 5  is a rearward view of the sensor; 
       FIG. 6  is a frontal view of the sensor; 
       FIG. 7  is an exploded view of the sensor; and 
       FIG. 8  is an exemplary embodiment of a functional diagram of the invention. 
   

   DETAILED DESCRIPTION 
     FIG. 1  illustrates a work vehicle in which the invention may be used. The particular work vehicle illustrated in  FIG. 1  is an articulated four wheel drive loader having a main vehicle body  10  that includes a front vehicle portion  100  pivotally connected to a rear vehicle portion  200  by vertical pivots  220 , the loader being steered by pivoting of the front vehicle portion  100  relative to the rear vehicle portion  200  in a manner well known in the art. The front and rear vehicle portions  100  and  200  are respectively supported on front drive wheels  101  and rear drive wheels  201 . An operator&#39;s station  210  is provided on the rear vehicle portion  200  and is generally located above the vertical pivots  220 . The front vehicle portion  100  includes a mast  120 . The front and rear drive wheels  101  and  201  propel the vehicle along the ground and are powered in a manner well known in the art. 
   Mounted on the front vehicle portion  100  is a boom  110 . The rear end of the boom  110  is connected to the mast  120  by transverse pivots  125  and a loader bucket  115  is mounted on the forward end of the boom  110  by transverse pivots  116 . The boom  110  is rotated about the transverse pivots  125  by hydraulic lift cylinders (not shown). 
     FIG. 2  illustrates an exemplary embodiment of a boom position sensing device  300  of the invention mounted to the mast  120 . In this particular embodiment, the sensing device  300  is mounted to a side wall  121  of the mast  120  via screws  301 . In this particular embodiment, a spring loaded follower arm  312  is biased against the underside of the boom  110  such that the follower arm  312  exerts pressure against the boom  110  at all rotational locations. Thus, as shown in  FIG. 3  and  FIG. 4 , the spring loaded follower arm  312  of this embodiment contacts the underside of the boom  110  at all points of rotation for the boom  110  without the necessity of a physical attachment to the boom  110  and the accompanying complexities associated with such an attachment. 
     FIG. 5  illustrates an exemplary embodiment of the boom position sensing device  300  of the invention. As shown in  FIG. 5 , the boom position sensing device  300  includes a body  309 , a follower assembly  310  and a potentiometer assembly  306 . 
   The body  309  includes a first body portion  302  and a second body portion  303 , the first and second body portions  302  and  303  being rigidly connected to each other via bolts  304   a  and locknuts  304   b . The first body portion  302  includes a L channel portion  302   a  and a C channel portion  302   b . The L channel portion  302   a  contains two holes  301   a  for attaching the entire boom position sensing device  300  to the outer wall  121  of the mast  120  via bolts  301 . It also contains two holes  304   c  for attaching the first body portion  302  to the second body portion  303  via bolts  304   a  and locknuts  304   b . The C channel portion  302   b  contains two holes  307   a  for attaching a potentiometer assembly  306  via locknuts  306   e  and bolts  306   c  and a third hole  306   j  to allow the passage of shaft  316  through the wall of the C channel portion  302   b  and into the potentiometer  306   b . Finally, the C channel portion  302   b  contains an anchor bolt hole  320   a  for attaching a spring anchor bolt subassembly  320 . 
   The second body portion  303  contains two holes  315   e ,  315   f  for attaching the first body portion  302  to the second body portion  303 . The second body portion  303  also contains two additional holes  315   a  and  315   d . Attached to the second body portion at holes  315   a ,  315   d , is a stop assembly  315  to restrict rotational motion on the follower arm  312 . Press fitted into the hole  316   a  and toward a first end of a shaft  316  of the follower assembly  310  is a shaft bushing  310   a  to enhance rotational movement of the shaft and to restrict axial movement of the spring bushing  318 . Washers  317  are placed along the shaft  316  on either side of the spring bushing  318 , a first end of the follower arm  312  is press fitted onto the shaft at a position next to the spring bushing  318 , and a snap ring is assembled to a snap ring groove  316   a  toward a second end of the shaft  316  to hold all of the washers  317  and the spring bushing  318  in place as well as to restrict axial movement of the shaft  316 . A first end of torsional loading spring  314  is anchored to spring anchor  320  while a second end of torsional loading spring  314  constrains and biases the follower arm  312  against the underside of the first boom arm  110   a . Attached to a second end of the follower arm  312  is a roller assembly  313  which includes a roller wheel  313   a  and bushing  313   d  as well as a roller bolt  313   b  and a locknut  313   c  to restrict all motion of the roller wheel  313   a  and the bushing  313   d  relative to the roller bolt  313   b  excepting rotational motion. 
   The follower assembly  310  includes the follower arm  312 , the torsional spring  314 , the shaft  316 , the shaft bushing  310   a , the plurality of spacers  317 , the snap ring  330 , and the spring bushing  318 . 
   Attached to the C channel portion  302   b  is a sensor or potentiometer assembly  306  which includes a bracket portion  306   a  and a sensor portion or potentiometer  306   b . The bracket portion  306   a  and the potentiometer  306   b  are attached to opposite sides of a C channel wall  302   c  via bolts  306   c , washers  306   d  and locknuts  306   e . On assembly of the potentiometer assembly  306 , rubber washers  302   f  are placed between the C channel wall  302   c  and the potentiometer  306   b  as a seal against the environment. On assembly of the entire boom height sensing device  300  the second end of the shaft  316  protrudes through a hole  306   g  in the bracket portion  306   a  and into a hole  306   h  in the potentiometer  306   b  where it is keyed in a well known manner to a conventional rotor in the potentiometer  306   b  such that a change in the angle of the shaft  316  results in a proportional change in the potential across the potentiometer  306   b.    
   As illustrated in  FIG. 8 , the detected signal from the boom position detector  300  is transmitted to the chassis control unit  500  via electrical wire or wirelessly through electromagnetic waves. The first rocker switch  601  and the second rocker switch  602  are activated with a push. Subsequent to activation, the operation of the first rocker switch  601  and/or the second rocker switch  602  sends a momentary signal to the chassis control unit  500  which causes the chassis control unit  500  to record the current signal value from the boom position detector  300 . The chassis control unit  500  then compares the recorded signal to the detected signal from the boom position detector  300  and sends a signal to unlock the control lever  700  from the detent position when the recorded signal is approximately equal to the detected signal. The chassis control unit  500  is capable of storing additional detected signal values, i.e., after storing a value for the first rocker switch  601 , it may store an additional value for the second rocker switch  602 . Thus, boom kickout values and return to carry values may coexist in the chassis control unit increasing the convenience and ease of operation of the work vehicle. 
   Having described the illustrated 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. For example, it is possible for a dial in potentiometer or a digital device with a position readout to be calibrated to the potentiometer  306   b  such that the position could be dialed or typed in by the operator prior to placing the boom in that position.