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TECHNICAL FIELD 
       [0001]    This disclosure relates to operational improvements in work machines utilized in excavation processes such as mining operations. More particularly, the disclosure relates to an improved clam operating control feature adapted to reduce operator fatigue during routine manipulations of a mining shovel. 
       BACKGROUND 
       [0002]    Mining shovels are generally employed on worksites to excavate such materials as iron ore, bauxite, limestone, precious metals, and numerous other substances, including dirt. The shovels may be mounted to various work machines, such as so-called excavators, for example. Mining shovels are generally powered by hydraulic fluid pressure, but may alternatively be powered by pneumatic pressure sources. In any event, a generally high-pressure fluid may be utilized for cyclically moving the shovel for repetitively loading and unloading the shovel. The excavated material may generally be transferred to another work machine, for example to an adjacent dump truck for removal from the worksite. 
         [0003]    The operation of a mining shovel general involves at least five repetitive actions and/or functions, all directed to the cyclic loading and emptying of the shovel. Once a work machine is optimally situated; i.e., positioned to initiate a mining excavation process, the operator must use at least two separately moveable levers, called joysticks, to successfully carry out the excavation process. One directional movement of a first lever may be employed to horizontally rotate the superstructure of the work machine, including the cab and boom, about the tracks of the work machine, so as to angularly position the boom to initiate shoveling of the material to be excavated. A second directional movement of the first lever may be employed to raise and/or lower the boom so as to move the stick to a position to begin an excavation cycle. A second lever may be employed to accommodate a third directional movement resulting in fore and aft movements of the stick, for example to force the shovel into the excavation material. A fourth directional movement of the second lever may be employed to rotate the shovel relative to the end of the stick. As such, the shovel may be raised to directly engage and capture the material, and/or lowered in a vertical plane to unload the material into another work machine, typically a receiving vehicle, for example, a dump truck. 
         [0004]    In combination with the above described joystick movements, a two-way switch must be typically pressed and held to vertically open or close a shovel clam attached to an upper portion of the shovel for unloading or retaining excavated material within the shovel between excavation cycles, as will be appreciated by those skilled in the art. To the extent that such repetitive tasks are associated with work machines generally, not just mining shovels, constant efforts have been made to improve and/or enhance various work machine functions. 
         [0005]    For example, U.S. Pat. No. 6,981,833 discloses a first work machine i.e., a harvesting machine, adapted for moving an agricultural product through a conveyor tube for its transfer to a second work machine, such as a vehicle having a receiving bin. The tube may be swung back and forth, from a retracted or stored position, to a position over the bin of the second work machine for enabling the bin to be “topped off” under precise operator control. The vehicle includes a control system having an extend switch and a retract switch, which operates in a both a latched first mode whenever the product conveyor device is inactive, and in an unlatched second mode whenever the conveyor is powered up to transfer grain. In the unlatched mode, if the operator presses the extend or retract switch, the corresponding swinging motion commences upon such contact. However, in the latter mode, the extend or retract motion ceases whenever the operator ceases tactile contact with, i.e. continuous pressing of, the corresponding switch. 
         [0006]    It may thus be beneficial to utilize a more easily executed switch control function to accommodate movements of a shovel clam in light of an operator&#39;s repetitive manipulations associated with use of a mining shovel, particularly where multiple joy-stick may be involved. A simplified operation may facilitate the operator&#39;s ability to better handle repetitive cyclic movements of the shovel apparatus, and thus to reduce operator fatigue during an excavation process. 
       SUMMARY OF THE DISCLOSURE 
       [0007]    In one aspect of the disclosure, a work machine including a shovel may be configured for excavating material. The work machine may include a main body and a base including tracks, with the main body adapted to swivel about the base. The main body may include an operator cab, and may have a boom moveably secured to the main body at one end. The second end of the boom may be vertically movable relative to the main body. A stick may have a first end attached to the second end of the boom, while a second end of the stick may be aftwardly and rearwardly rotatably movable with respect to the boom. A shovel may be rotatably secured to the second end of the stick. 
         [0008]    In another aspect of the disclosure, the main body may include a movable clam secured to the shovel; the clam may be positioned above the shovel, and adapted to swivel above the shovel between open and closed positions. 
         [0009]    In yet another aspect of the disclosure, the work machine may include a control system configured for loading and unloading the shovel, and the control system may include several moveable levers or joysticks for manipulating the shovel and associated components during an excavation process. 
         [0010]    In yet another aspect of the disclosure, a first directional joystick movement may be adapted for angularly positioning the main body relative to the tracks, a second directional joystick movement adapted for raising and lowering the boom, a third directional joystick movement adapted for controlling forward and aft movements of the stick, and a fourth directional joystick movement may be adapted for controlling vertically oriented, angular rotation of the shovel. 
         [0011]    In a still further aspect of the disclosure, the control system may include a simple rocker switch configured for quick touch actuation, wherein the clam will automatically fully open or fully close whenever the appropriate (open or close) rocker switch end is quickly pressed and released. 
         [0012]    In accordance with a final aspect of the disclosure, whenever the switch may be pressed again, or at any time during either an automatic opening or closing cycle of the clam, any otherwise continued movement of the clam may be immediately halted. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]      FIG. 1  is a perspective view of an excavating machine that may incorporate the disclosed clam control system, shown unloading excavated material contents into an adjacent receiving machine. 
           [0014]      FIG. 2  is one schematic representation of the disclosed joystick and clam control system. 
           [0015]      FIG. 3  is a flowchart of one exemplary operation of the disclosed clam switch control system. 
       
    
    
     DETAILED DESCRIPTION 
       [0016]    Referring initially to  FIG. 1 , a work machine, such as an excavating machine  10 , of a type used for mining, and adapted for digging and removing iron ore, bauxite, limestone, precious metals, and other substances, including dirt, from a construction worksite, is shown. The excavating machine  10  may incorporate an operator cab  12  (shown only fragmentarily and in phantom) secured to, and constituting a part of, a base  16 . The base  16  may include an engine, a hydraulic pump unit, and operating controls (none shown). The base  16  may be supported by, and may be transportable on, tracks  14 . An extensible and/or rotatable boom  20  may be movably anchored to the base  16 , and an articulating stick  22 , also variously called a lift arm, may be secured to and supported for movement on the boom  20 . 
         [0017]    The excavating machine  10  may incorporate a shovel  24  at one end of the stick  22 . Joysticks or operating levers (not shown) may be adapted to be controlled by hydraulic cylinder actuators  26  to move the boom  20  relative to the base  16 , the stick  22  relative to the boom  20 , and to move the shovel  24  relative to the stick  22 . 
         [0018]    Continuing reference to  FIG. 1 , a shovel clam  30  may be rotatably secured to the shovel  24 . The shovel clam  30  may be raised upwardly from the shovel  24  in the direction of arrow R, as shown, and may include a plurality of teeth  32  adapted to facilitate removal of excavation material from a worksite, such as a mine. The shovel clam  30  may be movable via a dedicated pair of hydraulic cylinder actuators  26 , and may be adapted to retain excavation material until time for its release, such as into the refuse bin  34  of an awaiting dump truck  38 , as shown. 
         [0019]    Referring now to  FIG. 2 , an operating control system  40  is shown schematically. The control system  40  may include an electronic central processing unit, or CPU  42 , and a display unit  44 , both situated within the cab  12 . The control system  40  may also include a hydraulic pump  46 , physically situated apart from the cab  12  but within the base  16  of the work machine  10 . The CPU  42  may communicate electronically with a joystick signal interface unit  48  as well as a clam switch signal interface unit  50 . The interface units  48  and  50  may function as electronic buses, capable of facilitating electronic data transfers between clam switches  52 ,  54  and various signal-generating directional joystick movements  60 ,  62 ,  64 , and  66 , the latter triggered by unidirectional movements of a pair of joysticks (not show) positioned within the cab  12  for manipulation by a cab operator. 
         [0020]    The switches  52  may provide for respective automated opening and closing operations of the shovel clam  30  ( FIG. 1 ). The switch  54  may operate as an override to immediately halt any movement of the clam  30  whenever the switch  54  may be actuated during any closing or opening operation of the clam  30 . In the disclosed control system  40 , the open and close switches  52  may be embodied as a single rocker switch (not shown), while the switch  54  may be an entirely separate unit, although interfaced with the open and close switches  52 . Alternatively, the switches  52 ,  54  may be embodied as a single unit, with the rocker switch configured to have clam opening and closing functions triggered by pressing opposite ends of the rocker, while the halting function may be configured to be triggered only while either of the opening and closing functions are actually taking place. For example, in the latter instance if either the opening or closing end of a rocker switch  52  is pressed, a quick press of either of those two switch ends could trigger the halting function. 
         [0021]    Continuing reference to  FIG. 2 , the various signal-generating directional joystick movements  60 ,  62 ,  64 , and  66  may be functionally embodied in a pair of joysticks, and may be described as follows. Directional joystick movement  60  may be a side to side motion of a first joystick (not shown). That movement, identified in the schematic as J- 1 , may cause the base  16  to swivel on the tracks  14 . Directional joystick movement  62 , identified in the schematic as J- 2 , may be a forward-aft motion of the same first joystick, producing a vertical movement; i.e. the raising and lowering, of the boom  20 . Directional joystick movement  64 , identified in the schematic as J- 3 , may be a forward-aft motion of a second joystick (not shown), resulting in a forward aft motion of the stick  22 . Finally, directional joystick movement  66 , identified in the schematic as J- 4 , may be a side to side motion of the same second joystick, resulting in a vertical rotation of the shovel  24 . 
         [0022]    The disclosed control system  40  may incorporate additional enhancements. For example, the opening and closing functions of the clam  30  may be associated with a so-called “ramp-down” feature, wherein hydraulic actuating cylinders  26  associated with the clam  30  may utilize a control valve system configured for slowing the flow of hydraulic fluid as the ends of cylinder travel, associated with the opening and closing limits of clam movement, are approached, whether during cylinder extension or retraction. This feature may soften normally otherwise harsh loads associated with “hitting the stops”, and thus may be effective to avoid damage to cylinder end parts and/or to otherwise prolong the actuator cylinder life. As such, the hydraulic cylinder actuators  26  may incorporate position limit or proximity sensors, or may alternatively be configured to slow the flow of hydraulic fluid whenever a limit switch is tripped. 
         [0023]    Although the drawings and description herein may appear to be limited to the specific embodiments disclosed, those skilled in the art may appreciate that numerous variations may fall within the spirit and scope of the appended claims. 
       INDUSTRIAL APPLICABILITY 
       [0024]    In use, the disclosed control system  40  may be adapted for an excavating machine  10 , such as a mining shovel. The control system  40  may be beneficial for reducing operator errors, as well as for potential reductions in damages to a clam  30 , a shovel  24 , and even more generally to the excavating machine  10 . In addition, the control system  40  may offer a general reduction in operator fatigue. Moreover, the improved clam switch control function, utilizing the switch signal interface unit  50 , may support a quicker learning curve for new operators. 
         [0025]    As disclosed, latched mode switches  52 ,  54  may be embodied in a two-way rocker type switch having open and close positions at opposite ends of the rocker. In a latched mode, the switches may be actuated via a quick touch; conversely in a so-called unlatched mode, such switches may require a constant tactile pressure for assuring continued movement of the clam  30  during an opening or closing sequence. The switches  52 ,  54  may thus be configured for being touched briefly at one end, or in a first way, to initiate an automatic fully open clam function, and at an opposite end, or in a second way, for initiating an automatic fully close clam function. A quick touch of a clam control switch  52 ,  54  as defined herein provides that any clam opening and closing sequence will continue after a respective open or close switch has been briefly actuated by a touch, irrespective of any need to press and hold the switch continuously during such opening or closing operation. 
         [0026]    A typical excavation operation associated with a mining shovel may extend over several workdays. Providing a quick touch clam control mechanism for a mining shovel to avoid an operator&#39;s having to continuously press and hold a button numerous times per cycle, particularly while simultaneously manipulating a pair of joysticks, may offer significant operator fatigue relief. 
         [0027]    Referring now to  FIG. 3 , an exemplary operation of the clam switch controls, utilizing the disclosed functional open and close switches  52  and the clam halt override switch  54 , may now be described as follows. 
         [0028]    In the following description, the meanings of “no” and “not” are synonymous. Upon initialization via an operator in the cab  12 , the CPU  42  may initially make inquiry as to whether the above-described joystick and switch controls are active. If the controls are not active, the CPU may reroute the same inquiry, per the loop shown, until the controls become active. 
         [0029]    If and when the controls are or have become active, the CPU may next inquire whether the clam is fully open. If not, the CPU may ask whether the open switch has been pressed. If not, the CPU may again reroute the inquiry to determine whether the controls are active, per the loop shown. If yes, the CPU may command the clam to fully open. Once the clam begins to open, the CPU may inquire as to whether the close or open switch has been pressed while the clam is opening. 
         [0030]    If not, the CPU will continue to command the clam to fully open. If either the close or open switches have been pressed while the clam is opening, the CPU will command the clam to immediately halt any further motion. Once the clam has been halted, the CPU will reroute the inquiry back to whether or not the controls are active, as per the loop shown. 
         [0031]    On the other hand, if the response to whether the claim is fully open is yes, the CPU may next inquire whether the close switch has been pressed. If not, the CPU may reroute the inquiry to determine whether the controls are active, per the loop shown. If yes, the CPU may command the clam to fully close. While closing, the CPU may inquire as to whether either of the close or open switches has been pressed while the claim is closing. 
         [0032]    If not, the CPU will continue to command the clam to fully close. On the other hand if yes, the CPU will command the clam to halt. Once the clam has halted, the CPU will once again reroute the inquiry back to whether or not the controls are active, as per the loop shown. 
         [0033]    A method of providing a quick touch clam control for a work machine having a mining shovel clam  30  may include: 
         [0034]    providing a CPU, a plurality of joysticks, and a plurality of switches, and configuring the CPU to interface with the joysticks and switches through respective joystick and clam switch bus signal interface units; 
         [0035]    providing a system of signals to be generated from the joysticks in accordance with a set of predetermined directional joystick movements, and having the signals read by the CPU through the joystick bus signal interface unit; 
         [0036]    providing a system of signals to be generated from predetermined switch positions in accordance with selective switch movements, and having the signals read by the CPU through the switch bus signal interface unit; 
         [0037]    configuring the switches to control a shovel clam, such that the shovel clam may be either automatically fully opened or fully closed by briefly touching a respective open or a close switch; and 
         [0038]    providing a halt switch override function, such that any automatic movement of the shovel clam is immediately halted by briefly touching either the open or close switch during any open or close movement of the shovel clam. 
         [0039]    Although only one generally described method of forming a quick touch clam switch control system has been disclosed herein, numerous other variations may fall within the spirit and scope of this disclosure. For example, a separate control apparatus may be included and configured to change the timing of fully open and fully closed automatic clam sequences, as for example to offer a range of opening and closing speeds of clam movement between clam position limits 
         [0040]    As another example, the described latched switch functionality may be an adjunct to, rather than a replacement of, an unlatched clam switch arrangement, the latter requiring the pressing and holding of the clam switch for continuous movement of the clam between respective open and close position limits In the unlatched arrangement, clam movement would be automatically halted upon an operator&#39;s physical release of the switch.

Summary:
An improved clam control mechanism for a mining shovel may offer reduced operator fatigue during excavation operations involving the simultaneous and repetitive manipulation of joysticks and switches. The control mechanism may be configured for the loading and unloading of a shovel having a clam rotatable above the shovel, and may include at least two joysticks adapted for a variety of tasks including fore and aft movements, and angular rotation of the shovel. At least one switch may be adapted for moving the clam automatically between fully open and fully closed positions, such that when the switch is briefly pressed a first way, the clam automatically fully opens, and when a switch is briefly pressed a second way, the clam automatically fully closes. On the other hand, if the switch is briefly pressed during either automatic opening or closing of the clam, any movement of the clam may be immediately halted.