Abstract:
A suspension control system includes a load support member, a base member and a moveable element attached to the base member and the load support member. The load support member is moveable relative to the base member through the moveable element. A accumulator is in fluid communication with the moveable element. A locking circuit is disposed between the moveable element and the accumulator and is selectively activatable to sustain said load support member in a fixed position. The locking circuit includes a pressurized fluid supply and a flow blocking mechanism operably engaged with the pressurized fluid supply. The flow blocking mechanism is urged to block fluid communication between the moveable element and the accumulator when the locking circuit is selectively activated.

Description:
TECHNICAL FIELD  
         [0001]    This invention relates generally to a ride control system for a machine and more particularly to a control system for selectively locking a suspension system.  
         BACKGROUND  
         [0002]    In known ride controls systems for machines, cushioning of the ride is controlled by suspension systems employing a damper between the load bearing frame and the ground engaging wheels to absorb the effects of impact as the machine engages the ground. Machines are often provided with attachments such as a bucket, for example, to perform work on external concerns. In preparation for performing work with the attachment, an operator maneuvers the attachment and thereafter performs the desired operation. However, controllability of the attachment is limited by the suspension system which remains reactive when the operator is attempting to position the attachment. For example, the machine may lurch or settle as the attachment is maneuvered resulting in an inefficient performance of the operation or a failed attempt to perform the desired operation.  
           [0003]    It is known to provide suspension override capabilities to stabilize a rebounding wheel, however this instrumentation is typically complicated and consequently expensive to implement. Additionally, this system requires a significant number of fluid transfer components, and accordingly, system leaks are a concern. Even a slight leak may render the system inoperable.  
           [0004]    For example, U.S. Pat. No. 4,971,353 issued to Buma et al. discloses an accumulator in fluid communication with an actuator through a shut-off valve and a flow resistance. An auxiliary accumulator is connected directly to the actuator to serve as an additional spring in the event a wheel experiences a significant and rapid rebound. The suspension control system slows movement of a piston rod of the actuator by controlling a fluid condition at the site of the rod end, while at the same time, the head end of the actuator is in fluid communication with the auxiliary accumulator through a restriction. Since the actuator remains in continuous fluid communication with the accumulator, fluid transfer between the actuator and accumulator is not effectively blocked.  
           [0005]    It is desirable to provide a suspension control system of simple construct to improve the controllability of the attachment. Further, a suspension control system configured to selectively lock-out the suspension system without a significant addition of fluid transfer components which may otherwise leak and render inoperable the lock-out system is desirable.  
           [0006]    The present invention is directed to overcoming one or more of the problems as set forth above.  
         SUMMARY OF THE INVENTION  
         [0007]    In one aspect of the of the present invention a suspension control system is provided and adapted for use in a fluid system of a machine and includes a locking circuit disposed between a moveable element and a accumulator which is selectively activatable to sustain a load support member in a fixed position relative to a base member. The suspension control system includes the load support member, the base member and a moveable element attached to the base member and the load support member. The load support member is moveable relative to the base member through the moveable element. An accumulator is in fluid communication with the moveable element and a locking circuit is disposed between the moveable element and the accumulator and is selectively activatable to sustain the load support member in a fixed position. The locking circuit includes a pressurized fluid supply and a flow blocking mechanism operably engaged with the pressurized fluid supply. The flow blocking mechanism is urged to block fluid communication between the moveable element and the accumulator when the locking circuit is selectively activated.  
           [0008]    In another aspect of the invention a method for stabilizing an implement of a machine subject to an external influence is provided and includes the steps of accumulating pressurized fluid provided by a accumulator in fluid communication with a moveable suspension member in response to the external influence exerted on the machine; directing the pressurized fluid to a lock-out circuit disposed between the accumulator and the moveable suspension member; and causing the accumulator and the moveable element to be fluidly disconnected, wherein cushioning effects of the accumulator are disabled. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]    [0009]FIG. 1 is a schematic representation of a machine including a first embodiment of a suspension control system according to the present invention;  
         [0010]    [0010]FIG. 2 is a sectional view of a flow blocking mechanism of the suspension control system of FIG. 1; and  
         [0011]    [0011]FIG. 3 is a schematic representation of a second embodiment of a suspension control system according to the present invention. 
     
    
     DETAILED DESCRIPTION  
       [0012]    Referring to FIG. 1, machine  10  includes load support member  12  attached to moveable base member  14 . Load support member  12  may be a load bearing frame member and base member  14  may be a suspension member which supports a wheel  16  of a ground-engaging machine, for example. Load support member  12  is connected to base member  14  through moveable element  18  such as an actuator or suspension cylinder, for example.  
         [0013]    Moveable element  18  is hydraulically connected to pump  20  through conduit  24  and ride height adjustment valve  22  is connected to conduit  24 . Valve  22  is provided to allow an operator to select height X for machine  10  through height adjustment lever  28 . In a conventional manner, pump  20  draws system fluid from tank  26  and urges fluid toward moveable element  18  to cause element  18  to expand or contract to set the desired height of the machine. If a lesser height is desired, valve  22  is selectively manipulated and consequently fluid is discharged to tank  26  causing a contraction of the moveable element.  
         [0014]    Machine  10  is adapted with suspension control system  30  having a fluid reservoir or accumulator  32 . Accumulator  32  is fluidly connected to suspension lock-out system  36  through conduit  34   a  and suspension lock-out system  36  is fluidly connected to moveable element  18  through conduit  34   b . Suspension lock-out system  36  includes lock-out circuit  38  provided with flow blocking mechanism  40  which may be a two-position valve, for example. Lockout circuit  38  is also provided with pilot operator  42 , such as a solenoid, for example which is in a positioning relationship with flow blocking mechanism  40  as hereinafter described.  
         [0015]    Flow blocking mechanism  40  includes pilot end  44 , connected to pilot operator  42  and pilot operator  42  is hydraulically connected to accumulator  32  through bypass passageway  46   b . Flow blocking mechanism  40  is provided with return end  48  hydraulically connected to accumulator  32  through passageway  50 . Resilient member or spring  52  is attached to return end  48  of flow blocking mechanism  40  to urge the same into an unblocked position when pilot operator  42  is deactivated. Flow blocking mechanism  40  includes pilot passageway  54  extended between pilot operator  42  and a pressurized fluid supply  60 . In an exemplary embodiment, pressurized fluid supply  60  may be an accumulator, for example, which derives pressurized fluid from moveable element  18  through a pressure regulated check valve.  
         [0016]    Referring to FIG. 2, flow blocking mechanism  40  includes housing  62  attached to solenoid housing  64 , to form a unitary, integrated body  65 . Housing  62  and solenoid housing  64  respectively include bores  66 ,  68  having valve elements or spools  70 ,  72  reciprocally disposed therein. Housing  62  includes accumulator port  74  and suspension cylinder port  76  which are hydraulically connected when valve element  70  is shifted away from solenoid housing  64 , e.g., the spring biased “unlocked” position (as illustrated in FIG. 2).  
         [0017]    Valve element  70  includes axial end  78 , which is in contact with spring  52 , and opposite axial end  80  which is exposed to a control pressure during activation of lock-out circuit  38 . Spring  52  encircles guiding portion  79  of valve element  70  and is located between solenoid housing  64  and annular land portion  81  of valve element  70 . Valve element ends  78 ,  80  accordingly provide effective areas  83 ,  85  which are exposed to fluid pressure from at least one of accumulator  32  or pressurized fluid supply  60 , to cause movement of valve element  70 , as hereinafter described. In the exemplary embodiment, effective areas  83 ,  85  are substantially identical.  
         [0018]    Solenoid housing  64  of flow blocking mechanism  40  includes pressure control port  82  and a pair of ports  84 ,  86  which extend into bore  68  of solenoid housing  64 . Accumulator  32  (FIG. 1) is in fluid communication with port  84  through bypass passageway  46   b  (FIG. 1) and port  86  through return passageway  50  (FIG. 1). Pressurized fluid supply  60  is in fluid communication with pressure control port  82  through pilot passageway  54  (FIG. 1). As best shown in FIG. 2, solenoid spool  72  includes a non-activated position (as illustrated in FIG. 2), which corresponds to hydraulic connection between accumulator  32  and axial ends  78 ,  80  of valve element  70  via ports  84  and  86 . Solenoid spool  72  includes an activated position corresponding to a hydraulic connection between pressurized fluid supply  60  (FIG. 1) and axial end  80  of valve element  70  via control port  82  when the solenoid  42  is activated.  
         [0019]    Activation of solenoid spool  72  allows pressurized fluid from supply  60  to communicate with end  80  of valve element  70  through port  82 , in solenoid housing  64 , and through bypass passageway  46   a  resulting in movement of valve element  70  towards control operator  42 . When valve element  70  has shifted far enough toward control operator  42 , accumulator port  74  is sealably blocked from suspension cylinder port  76 , and consequently, accumulator  32  is fluidly disconnected from moveable element  18 . Conversely, when control operator is non-activated, solenoid spool  72  is biased to close pressure control port  82  such that pressurized fluid supply  60  is blocked from communication with valve element end  80 , and consequently, moveable element  18  is in fluid communication with accumulator  32  as valve element  70  is spring-biased toward the non-activated position.  
         [0020]    Referring again to FIG. 1, suspension lock-out system  36  includes pilot control system  88  having pressurized fluid supply  60  connected to control operator  42  through passageway  54  located in housing  62  (FIG. 2). Pressurized fluid supply  60  receives fluid from moveable element  18  through conduit  34   b  and one-way check valve  90 . Check valve  90  is biased closed to ensure pressure within supply  60  is generally greater than the pressure accumulated within accumulator  32  such that pressurized fluid supply  60  serves as a high pressure fluid reservoir. Notably, pilot control system  88  includes minimal connections to preserve and sustain the high pressure signal within passageway  54  which may otherwise leak and render inoperable the suspension lock-out system.  
         [0021]    Suspension control system  30  includes input device  98  such as a lock-out lever provided in a cab portion of machine  10 , for example, and may be engaged by an operator when suspension lock-out is desired. Alternatively, other input devices known by those having ordinary skill in the art may be used. Further, as an alternative to input device  98  being manually controlled, it is envisioned that the pilot control system may be automatically or remotely controlled, for example.  
         [0022]    Referring to FIG. 3, a second embodiment of a suspension control system is shown and differs from suspension control system  36  (FIG. 1) in several aspects. One aspect may include a suspension control system  36 ′ provided with a pressure relief valve arrangement  92  adapted to be variably adjusted through an external setting, for example, by an operator. One mode of operation of the relief valve arrangement  92  may include pressure within the pressurized fluid supply  60  being relieved or dumped to the accumulator  32  when the relief valve arrangement  92  is exposed to a predetermined, high pressure. By providing a relief valve between the pressurized fluid supply and the accumulator, overpressure fluid may be directed to the accumulator, rather than the tank so as to decrease the risk of system leakage. Moreover, since the accumulator  32  is significantly larger in volume than the pressurized fluid supply  60 , overpressure fluid passed from the pressurized fluid supply to the accumulator is not likely to significantly influence pressure conditions within the accumulator.  
         [0023]    Suspension control system  30 ′ includes an additional moveable element  18  which may be associated with a second wheel (not shown) rotatably attached to the load support member  12  (FIG. 1). Suspension control system  30 ′ also includes a lock-out circuit  38 ′ which differs from lock out circuit  38  of FIG. 1, by isolating return passageway  50 ′ such that end  94  of the control operator  42 ′ does not fluidly communicate with return passageway  50 ′.  
         [0024]    Industrial Applicability  
         [0025]    In operation, pressurized fluid supply  60  is initially pressurized by having been stored from prior use or is quickly brought to pressure as the moveable element is displaced by an external influence (i.e., the wheel strikes a pot-hole or traverses uneven ground). In turn, a piston within the moveable element causes an amount of fluid to be pressurized. When it is desirable to lock the suspension control system, the operator manipulates the input device  98  causing an electrical signal to be either established or diminished through instrument line  100  to accordingly, activate lock-out circuit  38 . As an alternative to employing an electrically activated control operator, control operator  42  may be hydraulically activated wherein activation of input device  98  causes activation of pilot operator  42  through instrument line  100 , which may be a hydraulic conduit, for example. Consequently, valve element  72  within control operator  42  is shifted away from solenoid  42  and pressurized fluid supply  60  is deployed to end  80  of valve element  70 .  
         [0026]    Referring to FIG. 2, as flow blocking mechanism  40  is urged toward an activated condition, corresponding to a suspension lock-out mode, the force on end  80  of valve element  70  exceeds the force acting on end  78  since the control pressure exceeds accumulator pressure. Consequently, the valve element  70  is shifted towards the solenoid  42  to compress spring  52 . As a result, fluid communication between moveable member  18  (FIG. 1) and accumulator  32  (FIG. 1) is disconnected since valve element  70  sealably blocks accumulator port  74  from suspension cylinder port  76  and the suspension system is effectively “locked-out”.  
         [0027]    During normal operation of suspension control system  30 , moveable element  18  is displaced in response to an external influence on base member  14  and fluid is directed to accumulator  32  to provide a cushioned ride for machine  10 . As a result, machine  10  absorbs external influences such as impacts and the operator experiences a cushioned ride. When it is desirable to accurately position an implement attached to machine  10 , the operator manipulates input device  98  which causes disabling of the cushioning effects provided by the suspension system.  
         [0028]    For example, when positioning a cutting edge of a grading attachment during a digging or grading operation, the suspension system which normally responds to external influences, is locked-out to provide increased accuracy of operator placement of the implement. Notably, since suspension lock-out system  36  may be adapted directly between the moveable element and the accumulator, few additional parts are required and the potential for leakage is not significantly increased.  
         [0029]    Suspension control system  30 ′ operates similar to that of suspension control system  30  in accordance with operation of machine  10 . However, the pressure relief valve arrangement  92  of suspension control system  30  provides protection for lock-out circuit  38 ′ from an overpressure condition caused by an impact experienced by moveable element  18 , for example. Since the relief valve arrangement  92  is positioned between the pilot passageway  54  and the moveable elements  18  the pilot passageway  54  is protected from an overpressure condition.  
         [0030]    From the foregoing, it is readily apparent that the subject hydraulic suspension control systems  30 ,  30 ′ provide a cushion ride arrangement for a machine and such suspension may be selectively disabled in the event precise and accurate control of an attachment is warranted.  
         [0031]    Other aspects, objects and advantages of the invention can be obtained from a study of the drawings, the disclosure and the appended claims.