Patent Publication Number: US-7581598-B2

Title: Blade motion reduction

Description:
This document claims priority based on U.S. provisional application Ser. No. 60/631,562, filed Nov. 29, 2004, and entitled BLADE MOTION REDUCTION, under 35 U.S.C. 119(e). 

   FIELD OF THE INVENTION 
   This applies to an articulated crawler dozer with four independent tracks and a suspension system. In this configuration, the track systems are mounted such that they can move in a way that they can follow the contour of the ground. 
   BACKGROUND OF THE INVENTION 
   Conventional construction vehicles (dozers, loaders, backhoes, skid steers, graders, etc) do not usually have cushioning suspension systems but are, at most, equipped with pneumatic tires. The consequence is that the machine ride can be very harsh dependant upon the operating conditions of the machine. 
   Traditionally blade equipped vehicles such as crawlers or graders are structurally rigid. This is desirable to avoid undesirable vertical blade movements under changing soil conditions. The cutting edge of the blade is, typically, angled back at the top so that it will shave off the material when elevated material is contacted. A consequence of this characteristic is that a vertical force is generated on the blade cutting edge when hard soil conditions are encountered. If the machine is not sufficiently rigid, the blade will lower and dig into the ground under these conditions. When soft soil is encountered and the vertical force reduced, the blade will tend to rise to a higher elevation. 
   An analogy can be made to a plane that is used in woodworking. A rigid plane would tend to shave off high regions without gouging, and move over low regions without any affect to the material. A relatively flexible plane would tend to gouge the high regions of the wood surface. 
   The addition of suspension to construction vehicles such as, for example, crawlers and graders, can create a situation that is counter to the desired operating conditions stated above. 
   SUMMARY OF THE INVENTION 
   The invention includes a front lower frame and a rear lower frame as well as an articulated chassis having a front portion and a rear portion. The front and rear lower frames are pivotally attached to the articulated chassis. A C-frame for the blade is pivotally attached to the first lower frame and operatively attached via hydraulic cylinders to the front portion of the chassis. Additionally, the blade is directly connected to hydraulic cylinders that are attached to the C-frame. Such an arrangement allows the blade to follow the front tracks of a four track vehicle and not be unduly affected by chassis motion enabled by the suspension system. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a side view of a work vehicle in which the invention may be used; 
       FIG. 2  is an elevated oblique view of an articulated chassis and two A-frames of the vehicle illustrated in  FIG. 1 ; 
       FIG. 3  is a front view of a front portion of the chassis and a first A-frame connected by a pan hard rod; 
       FIG. 4  is a rear view of a rear portion of the chassis and a second A-frame connected by a pan hard rod; 
       FIG. 5  is a front view of the front portion of the chassis and the first A-frame connected by two suspension cylinders; 
       FIG. 6  is a rear view of a rear portion of the chassis and a second A-frame connected by two suspension cylinders; 
       FIG. 7  is an exemplary schematic of the cylinders illustrated in  FIG. 5 ; and 
       FIG. 8  is an exemplary schematic of the cylinders illustrated in  FIG. 6 . 
   

   DESCRIPTION OF THE ILLUSTRATED EMBODIMENT 
   The exemplary embodiment of the invention described herein is applied to a crawler dozer with 4 independent tracks. In this configuration, the tracks are mounted such that they can move in a way that they can follow the contour of the ground. Each of the tracks pivots about a drive wheel. 
     FIG. 1  illustrate a vehicle in which the invention may be used. The particular vehicle illustrated in  FIG. 1  is a four track articulated dozer  10  having a front portion  20  a rear portion  30 ; an articulation mechanism  40  between the front portion  20  and the rear portion  30 ; first and second track systems  50 ,  60 ; and third and fourth track systems  70 ,  80 . The front portion  20  includes a blade  22  and a blade mounting frame  23  as well as an operator cab  21 . 
   The first and second track systems  50 ,  60  are mounted on an A-frame structure or a first A-frame  200  that is pivotally connected to both the first and second track frames or rocker arms  51 , 61 . The first A-frame  200  is connected to a front chassis portion  100  primarily at the top of the “A”, i.e., a narrower portion of the first A-frame  200 , with a first spherical ball joint  101 . This first spherical ball joint  101  is located forward of the articulation joint  40 . Laterally the first A-frame  200  is connected to the front chassis portion  100  with a first linkage (first pan-hard rod)  300  (see  FIG. 3 ) to keep the position of the first A-frame  200  approximately centered under the front chassis portion  100 . The front chassis portion  100  is vertically connected to the first A-frame by a first suspension cylinder  231  and a second suspension cylinder  232 . The first and second suspension cylinders are, respectively, attached to first and second hydraulic accumulators  251 ,  252 . A mechanism senses the position of the first A-frame  200  relative to the front chassis portion  100  at each cylinder location, and controls the vehicle height, via hydraulic balancing circuit  240  by adding or removing hydraulic fluid from the first and second suspension cylinders on a continuous basis. These cylinders primarily support the vehicle weight. 
   It is also desired to control vehicle roll position at this front axle  203 . To accomplish this, a head end of the first cylinder  231   a  is hydraulically connected to a rod end of the second cylinder  232   b . Conversely a head end of the second cylinder  232   a  is hydraulically connected to a rod end of the first cylinder  231   b . This methodology reduces the effective cylinder area to be equal to the rod area of the cylinder. This creates a higher pressure in the system which is desirous for improved suspension control. 
   As illustrated in  FIG. 2 , the first and second suspension cylinders  231 ,  232  are attached to the first A-frame  200  at a point behind the respective track frame pivots  51 ,  61  so that they operate at an increased pressure level. This helps contribute to the roll stability mentioned above by increasing the pressure proportionally. 
   The third and fourth track systems  71 ,  81  are mounted on a second A-frame structure  210  that is pivotally connected to both the left and right track frames, i.e., rocker arms  71 ,  81 . The second A-frame  210  is connected a rear chassis portion  210  primarily at the top of the “A”, i.e., at a narrower portion of the second A-frame  210 , with a second ball joint  211 . The second ball joint  211  is located rearwards of the articulation joint  40 . Laterally the second A-frame  210  is connected to the rear chassis portion  110  with a linkage (pan-hard rod)  310  to keep the second A-frame  210  approximately centered under the rear chassis portion  110 . The rear chassis portion  110  is vertically connected to the second A-frame  210  by third and fourth suspension cylinders  233 , 234 , one on the left and one the right side of the vehicle. These suspension cylinders  233 , 234  are hydraulically connected together and are attached to respective hydraulic accumulators  253 ,  254 . A mechanism senses the position of the A-frame relative to the vehicle frame at a point midway between the cylinders indicating the average location, and controls the vehicle height, via hydraulic balancing circuit  241 , by adding or removing hydraulic fluid from the cylinder system on a continuous basis. 
   It is desired to have the rear axle oscillate to ensure all 4 tracks maintain ground contact at all times. This is done by connecting the head end of the right and left cylinders together to allow oil to flow from one to the other as needed. The rod ends of the left and right cylinders are, likewise, connected together. 
   The third and fourth cylinders  233 ,  234  are attached to the second A-frame  210  at respective locations behind the rocker arm pivots  71   a ,  81   a  so that they operate at a reduced pressure level. This lowers the pressure of the system for a smoother ride. 
   First and second balancing circuits  240 ,  241  are hydraulic circuits that maintain the nominal distances between: the front chassis portion  100  and the front A-frame  200 ; and the rear chassis portion  110  and the rear A-frame  210 . 
   The blade mounting structure, referred to as the C-Frame  23 , is operatively attached to the first A-Frame  200 . This ensures the blade level (right to left with respect to the operator) will be consistent with the tracks and not affected by vehicle chassis motion enabled by the suspension system motion. 
   The blade mounting cylinders  105   a ,  105   b  are mounted to the front chassis portion  100  and the blade mounting C-Frame  23 . The location and orientation of these cylinders and their attachment points are selected such that blade vertical movement is minimized or eliminated when suspension movement occurs. 
   Mounting the blade C-frame  23  and controlling cylinders  105   a ,  105   b  to the first A-frame  200  solely would produce an amplified blade motion relative to suspension motion. 
   Mounting the blade C-frame  23  and controlling cylinders  105   a ,  105   b  to the front chassis portion  100  solely would likewise produce an amplified blade motion. Additionally any vertical loading at one end of the blade would generate rolling force in the chassis which would need to be reacted by the suspension system. 
   The ball joints  101  and  211  are close to equidistant from the articulation joint  40  which helps to reduce vehicular distortions due to non-equal moments. 
   The combination specified first creates the maximum blade roll rigidity while minimizing undesired blade vertical movement due to suspension motion. 
   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.