Abstract:
A pothole protection mechanism provides additional support for the vehicle in the event a wheel is driven into a hole while the platform is elevated. The mechanism includes an extendible and retractable pothole protection bar. A five-bar mechanism serves to actuate the pothole protection bar based on a position of the vehicle lifting section. The construction of the mechanism serves to prevent a crushing hazard while deploying the bar and tolerates fixed objects on the ground while raising the bar.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS  
       [0001]     (NOT APPLICABLE)  
       STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT  
       [0002]     (NOT APPLICABLE)  
       BACKGROUND OF THE INVENTION  
       [0003]     The present invention relates to a pothole protection mechanism for a vehicle including an aerial work platform (AWP).  
         [0004]     Self-propelled AWPs such as scissor lifts are typically equipped with an apparatus that prevents them from tipping when driven into a pothole or off a curb while the platform is elevated. Such an apparatus works normally by reducing the ground clearance to less than one inch when the platform of the AWP is elevated beyond a certain height.  
         [0005]     One way of achieving this is by means of a bar or a plate that is attached to the chassis of the AWP and can be lowered down and locked in position when the platform is elevated. Subsequently, the bar or plate can be raised up when the platform is lowered.  
         [0006]     The mechanism that performs the lowering, locking and raising tasks is referred to as a pothole protection mechanism. Important requirements of the pothole protection mechanism are to avoid any crushing hazard while deploying the bar and to be able to tolerate fixed objects on the ground while raising the bar.  
         [0007]     Current designs are typically based on one of two concepts. A typical six-bar mechanism and a spring are provided to ensure the locking position. This design, however, suffers from excessive numbers of parts and consequently from cost and reliability. A typical four-bar mechanism incorporates a linear actuator linking two of its links. The actuator is either hydraulic or electrical. Drawbacks of this design, however, include cost, reliability, and potential leakage of hydraulic fluid.  
       BRIEF SUMMARY OF THE INVENTION  
       [0008]     It would be desirable to provide a simpler five-bar mechanism that performs all the required tasks for a pothole protection mechanism while maintaining reliable and efficient operation. The pothole protection mechanism of the invention includes an actuator that is connected to the lifting platform of the vehicle to drive the mechanism. The actuator includes a spring that is constrained to compress or extend along a pin. With this construction, the pothole protection mechanism of the invention allows for manufacturing tolerances, and allows the lowering of the lifting object with the pothole protection bar hung-up against an object fixed to the ground. Moreover, being part of the lifting object (e.g., scissor arms) rather than the chassis enables the mechanism to be tolerant to debris accumulation.  
         [0009]     In an exemplary embodiment of the invention, a pothole protection mechanism is provided for a lift vehicle including a lifting section supported on a vehicle frame. The pothole protection mechanism includes an actuator attached to the lifting section of the lift vehicle, which actuator is displaced between an extended position and a retracted position based on a position of the lifting section. A crank including an engagement member at an upper end is positioned to be engaged by the actuator. The crank includes a slot between the upper end and a lower end. A connector secured to the vehicle frame and engaged with the crank through the slot movably secures the crank to the frame. A coupler link is pivotally secured at a first end to the lower end of the crank, and a pothole protection bar is pivotally secured to a second end of the coupler link and pivotally secured to the vehicle frame. The vehicle frame, the crank, the connector, the coupler link and the pothole protection bar define a five-bar mechanism for actuation of the pothole protection bar.  
         [0010]     The pothole protection bar may be pivoted between a use position and a stowed position via the five-bar mechanism based on the position of the lifting section. The actuator may include a plate member slidably mounted on a pin rigidly secured to the frame, and a spring mounted on the pin between the frame and the plate member. In this context, a spring constant of the spring is preferably about 470 lb/in.  
         [0011]     The connector may be structurally configured only for translation in the slot, where the slot is preferably at a predetermined angle with respect to a longitudinal axis of the crank. Additionally, the slot may be offset with respect to the longitudinal axis of the crank. The connector may alternatively be structurally configured only for translation and rotation in the slot.  
         [0012]     The pothole protection bar is preferably pivoted through an arc substantially limited to 90° between a use position and a stowed position via the five-bar mechanism based on the position of the lifting section.  
         [0013]     The mechanism may additionally include a frame pin coupled to the vehicle frame, serving as a stop for the crank.  
         [0014]     In another exemplary embodiment of the invention, a lift vehicle incorporates the pothole protection mechanism of the invention. The lifting section may be a scissors lift.  
         [0015]     In still another exemplary embodiment of the invention, a pothole protection mechanism is provided for a lift vehicle including a lifting section supported on a vehicle frame. The pothole protection mechanism includes an extendable and retractable pothole protection bar and a five-bar mechanism for actuation of the pothole protection bar based on a position of the lifting section.  
         [0016]     In yet another exemplary embodiment of the invention, a pothole protection mechanism is provided for a lift vehicle including a lifting section supported on a vehicle frame. The pothole protection mechanism includes an actuator attached to the lifting section of the lift vehicle, where the actuator is displaced between an extended position and a retracted position based on a position of the lifting section. A crank including an engagement member at an upper end is positioned to be engaged by the actuator, which crank further includes a slot between the upper end and a lower end, wherein a connector secured to the vehicle frame is movably secured in the slot. A coupler link is pivotally secured at a first end to the lower end of the crank, and a pothole protection bar is pivotally secured to a second end of the coupler link and pivotally secured to the vehicle frame. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0017]     These and other aspects and advantages of the present invention will be described in detail with reference to the accompanying drawings, in which:  
         [0018]      FIG. 1  is an exemplary perspective view of a scissor lift incorporating the pothole protection mechanism of the present invention;  
         [0019]      FIG. 2  illustrates the pothole protection mechanism pivoted to a use position; and  
         [0020]      FIG. 3  illustrates the pothole protection mechanism pivoted to a stowed position. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0021]      FIG. 1  is a perspective view of a scissor lift  10 , which is exemplary for an aerial work platform vehicle suitable for the pothole protection mechanism of the present invention. The lift vehicle  10  generally includes a vehicle frame or chassis  12  on which a plurality of wheels  14  are mounted. The wheels  14  are typically driven by a suitable driving mechanism via controls positioned in the vicinity of a vehicle platform  16 . The vehicle platform  16  is raised and lowered by a lifting section  18 , shown as a scissor lift in  FIG. 1 , which lifting section  18  is supported on the vehicle frame  12 . A pothole protection mechanism  20  is secured to the frame  12  generally within a perimeter defined by the vehicle wheels  14 .  
         [0022]     As noted above, the pothole protection mechanism  20  serves to reduce the ground clearance typically to less than one inch when the platform  16  is elevated beyond a certain height. In this manner, the pothole protection mechanism  20  prevents the vehicle  10  from tipping when driven into a pothole or off a curb or the like while the platform  16  is elevated.  
         [0023]      FIGS. 2 and 3  illustrate the details of the pothole protection mechanism  20  of the present invention. The pothole protection mechanism  20  includes a pothole protection bar  22  disposed generally between each of the left and right side wheels  14 , respectively. In  FIG. 2 , the pothole protection bar  22  is shown in a use position, while  FIG. 3  illustrates the pothole protection bar  22  in a stowed position. An advantage of the present invention is that the pothole protection bar  22  is pivoted between the use position and the stowed position without the use of a powered actuator. Rather, a non-powered actuator  24  is coupled directly with the lifting section  18  (such as scissor arms) of the lift vehicle.  
         [0024]     The actuator  24  is secured to the lifting section  18  of the lift vehicle via a connector frame  26  by any suitable connection means. As such, the actuator  24  is displaced between a retracted position ( FIG. 2 ) and an extended position ( FIG. 3 ) based on a position of the lifting section  18 . The actuator  24  is constructed of a plate member  28  slidably mounted on a pin  30 . A spring  32  is mounted on the pin  30  between the plate member  28  and the connector frame  26 . The actuator  24  via plate  28  engages a pair of cranks  34 , one for each pothole protection bar  22 , the cranks  34  including rollers  36  at ends thereof to facilitate engagement. Each crank  34  includes a slot  38  therein between an upper end and a lower end of the crank  34  and is engaged to a connector  40 , which is pivoted to the vehicle frame  12 . The crank is movably secured through its translation joint with the connector  40 . Alternatively, the connection assembly  38 ,  40  can be comprised of a half-joint enabling the crank  34  to both translate and rotate with respect to a pin fixed to the frame. The orientation of the slot  38 , disposed at a predetermined angle with respect to a longitudinal axis of the crank  34 , is designed to allow the crank  34  and coupler link  40  to rotate through a straight-line (i.e., collinear) configuration and to secure locking of the mechanism in the deployed position The slot  38  orientation offset with respect to the longitudinal axis of the crank  34  enables the configuration to assume a locked position.  
         [0025]     A coupler link  42  is pivotally secured at a first end to a lower end of the crank  34 . The pothole protection bar  22  is pivotally secured to a second end of the coupler link  42  and pivotally secured to the vehicle frame  12  at a pivot  44 .  
         [0026]     The described components, including the vehicle frame  12 , the crank  34 , the connector  40 , the coupler link  42  and the pothole protection bar  22  define a five-bar mechanism to effect actuation of the pothole protection bar. When the connector  40  is constructed utilizing a half-joint, enabling translation and rotation of the crank with respect to the chassis  12 , the arrangement is deemed a modified five-bar mechanism. Generally, the half joint (pin in a slot) is the preferred choice for the present application; although for other applications with higher loads, a pinned or pivoted slider would be a preferred design.  
         [0027]     Link one ( 1 ) is the pothole protection bar  22 , which is permitted to rotate a maximum of substantially 90° toward the chassis  12  center. No rotation is permitted in the opposite direction. Link two ( 2 ) is the coupler link  42 , and link three ( 3 ) is the crank  34 . Link four ( 4 ) is represented by the connector  40 , which constrains the crank  34  to slide with respect to the connector  40 . Finally, link five ( 5 ) is the chassis  12 , which provides a ground for the mechanism.  
         [0028]     The construction of the actuator  24  including the plate  28 , pin  30  and spring  32  coupled through the connector frame  26  to the lifting section  18  of the vehicle effects important advantages of the invention, allowing for manufacturing tolerances and additionally enables lowering of the lifting object even with the pothole protection bar  22  hung-up against an object fixed to the ground. That is, if tolerance stack up makes the pothole protection bar  22  reach the limit of its rotation for the stowed position with less than the nominal rotation of the crank  34 , the spring compliance would allow for that without causing any damage to the mechanism components. Additionally, since the actuator forms part of the lifting section  18  rather than the chassis  12 , the device is more tolerant to debris accumulation. That is, if the plunger is attached to the chassis  12 , debris might get into the spring coil  32  preventing it from working properly.  
         [0029]     Deployment and retraction of the pothole protection mechanism will be described with continued reference to  FIGS. 2 and 3 .  FIG. 3  shows the actuator  24  in its extended position with the pothole protection bar  22  pivoted to its stowed position. The pothole protection bar  22  is stowed when the lifting mechanism is in a lowered position. When the lifting section  18  starts to move up in order to lift the platform  16 , the actuator  24  moves with the lifting section  18  away from the rollers  36  of the cranks  34 . This action serves to release the load that keeps the mechanism in its raised or stowed position. Simultaneously, under the effect of gravity, the pothole protection bar  22  starts to pivot about pivot  44  toward its use position. The crank  34  and coupler link  42  go through straight-line configuration and end up with the coupler link  42  near horizontal and the crank  34  jammed against a stop or frame pin  46  on the frame  12 . Due to its weight and constrained movement from the frame pin  46 , the crank  34  rotates counterclockwise around its pivot with the coupler link  42  until it makes contact with the connector  40  at the opposite end of the slot  38 .  
         [0030]     In the use position, the pothole protection bar  22  is locked in place, and the only way to displace the pothole protection bar  22  out of this position is to push downward on the crank  34  at or near the roller  36 . In other words, any force in any direction on the pothole protection bar  22  will not lead to movement out of the locked use position.  
         [0031]     The process of retracting the pothole protection bar  22  to its stowed position is exactly opposite to the process of deploying it. When the lifting section  18  approaches its retracted position, the actuator  24  makes contact with the rollers  36 , gradually pushing them downward, which in turn forces the cranks  34  to slide along the slot  38 . As the actuator  24  continues to push down, the cranks  34  pivot around the slot and connector arrangement  38 ,  40  and rotates upward lifting with it the pothole protection bar  22  to its stowed position.  
         [0032]     The stiffness of the actuator spring  32  is designed to prevent movement of the pothole protection bar  22  during transportation. Additionally, the spring  32  is compliant enough to allow for lowering the lifting mechanism  18  when the pothole protection bar  22  is hung-up against an object fixed to the ground. The spring constant of the spring  32  is generally a function of the weight of the lifting mechanism  18  as well as the force required to displace the pothole protection bar  22 . In one preferred configuration, the spring constant is about 470 lb/in.  
         [0033]     With the pothole protection mechanism of the present invention, a simplified construction facilitates operation, reduces construction costs and reduces maintenance. Additionally, due to the fact that the mechanism locks right after the pothole protection bar is fully lowered to its use position, it prevents crushing hazards, and the use of a spring-loaded actuator enables the mechanism to tolerate fixed objects on the ground while raising the bar.  
         [0034]     While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiments, it is to be understood that the invention is not to be limited to the disclosed embodiments, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.