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FIELD OF THE INVENTION  
       [0001]     The disclosed invention is directed generally to front end loader vehicles with a bucket, particularly a bucket apparatus for snow clearing and more particularly apparatus for protecting the vehicle, loader framework, and driver when the bucket strikes an immovable object when the bucket is sliding along the ground.  
       BACKGROUND  
       [0002]     Both commercial snow plows and front end loaders have a long history of use in removing snow from streets and highways. Over the past several decades the use of snow plows on light and medium duty trucks has become commonplace. Snow plows work well for clearing snow from roadways, particularly in open places and in areas where yearly snowfall totals are such that the snow can be readily pushed off the roadway. However, in densely populated urban areas, where real estate is at a premium, and in areas with large annual snowfalls, there is a need to be able to lift snow over snowbanks for deposit into large piles. Alternately, the snow is often lifted into dump trucks to be hauled and deposited elsewhere, or dumped into snow melting machines. To address this need, front end loader attachments have been developed. One of the issues related to the use of these loaders is that a great deal of stress is imparted to the structural components when plowing in areas such as those prone to frost heaving where manhole covers, and other relatively fixed objects, are struck by the moving plow. Not only do such encounters with immovable objects greatly shorten the life of the loaders, but they are also quite jarring to the vehicle driver and pose an enhanced risk of injury to the driver as well as others in the vicinity of the loader.  
         [0003]     Several devices have been developed for use with snow plows whereby either the whole plow blade, or just a portion of it, pivots back up to about 90 degrees upon encountering a fixed object in the road (see for example U.S. Pat. Nos. 6,701,646 and 5,697,172, respectively). Such devices, while effective for snow plow blades, are not compatible with a loader bucket due to the bucket&#39;s different geometry. In particular, the rigid bucket&#39;s longitudinal depth combined with the required rear pivotal connections for lifting and dumping, prevent such a pivoting back since such pivoting generally requires a pivot point on an angle greater than 45 degrees up from the leading edge. Furthermore, since such buckets typically have a leading edge attached to the horizontal structure of the bucket bottom, as opposed to a sufficiently vertical structure as is the case with snow plow blades, the obvious tilting back solutions applied to snow plow blades are impractical because this would require tilting the whole bucket backwards by around 180 degrees. Consequently, there is a need for a device which allows loader buckets to ride up over fixed objects upon impacting them, which thereby reduces the wear and tear on front end loader vehicles while also enhancing the safety of the vehicle operator and the public at large.  
       BRIEF SUMMARY  
       [0004]     The disclosed invention is directed to front end loader apparatus for attachment to a vehicle. In this context, “vehicle” includes a structure comprising a body, wheels, and a means for self propulsion. An example of the type of vehicles to which the invention may be attached includes all-terrain vehicles (ATVs), farm tractors, skid loaders, automobiles, and trucks. The front end loader apparatus has a frame assembly attachable at one end to a vehicle at a first pivot axis and at another end to a bucket. There is a second pivot axis at the attachment of the bucket to the frame assembly. In one embodiment, the present invention has a sensor and control mechanism for determining when the distance between the first and second pivot axes contracts thereby signaling that the bucket has met an immovable object. When a threshold level is reached, a control mechanism causes the bucket to pivot at the second pivot axis, tilt up, and slide over the immovable object. The bucket and framework are thereby spared from bending and breaking, and the vehicle operator is less likely to be injured.  
         [0005]     In another set of embodiments, the frame assembly has a pair of downwardly projecting legs which at an end attach to the bucket at the second pivot axis. A member, preferably in the form of a hydraulic cylinder attaches between the frame assembly and the bucket at a location forwardly of the downwardly projecting legs. The hydraulic cylinder is pivotally attached to the bucket to form a third pivot axis. There are hinged joints in each of the projecting legs, and a biasing mechanism in the form of a spring or elastomeric member, or a hydraulic or pneumatic cylinder, or a flexible fluid-filled container which provide a biasing force which maintains the bucket edge along the ground. When the bucket strikes an immovable object and generates a force sufficient to overcome the biasing force, the hinged joints allow the bucket to pivot at the second and third pivot axes so that the bucket can tilt and ride over the immovable object. Once past the object, the biasing mechanism causes the hinged joint to close so that the bucket pivots back to its original scraping position.  
         [0006]     In further embodiments, the biasing force provided by the biasing mechanism may be adjusted directly through various mechanical, hydraulic, or pneumatic means of control so that the impact-force threshold beyond which tilting of the bucket occurs may be set by the vehicle operator. For instance, the vehicle driver may set the biasing force at one setting for plowing dirt roads, and at another level when plowing city streets having protruding manhole covers. Any bending and breakage of either the bucket or the framework are avoided, and the vehicle operator is less likely to be injured.  
         [0007]     Additionally, an adjustable threshold impact level may be set through the use of sensors incorporated into an electromechanical control circuit, or mechanically through the use of shear pins or a mechanical nipple and détente assembly. For example, when a bucket strikes an immovable object with a force sufficient to cause a nipple and détente assembly to disengage, the hinged joints allow the bucket to pivot at the second and third pivot axes so that the bucket can tilt and ride over the immovable object. The biasing mechanism then causes the hinged joint to close and the nipple and détente assembly to reset, so that the bucket pivots back to its original scrapping position. Again, any bending and breakage of either the bucket or the framework are avoided, and the vehicle operator is less likely to be injured. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]      FIGS. 1A and 1B  illustrate schematically in side view a first embodiment of the present invention, including a sensor and bucket tilt control system.  FIG. 1A  shows the bucket riding over a flat surface;  FIG. 1B  shows the bucket riding up over a fixed object which it initially struck.  
         [0009]      FIG. 2  is a side view of a second embodiment of the present invention.  
         [0010]      FIG. 3  is an enlarged plan view of the lower bucket assembly as shown in  FIG. 2  taken along auxiliary line  3 - 3 .  
         [0011]      FIG. 4A  is a sectional view of the lower bucket assembly of the second embodiment as shown in  FIG. 3 , taken along section line  4 - 4 , showing the assembly in the undeflected position.  
         [0012]      FIG. 4B  is a sectional view of the lower bucket assembly of the second embodiment as shown in  FIG. 3 , taken along section line  4 - 4 , showing the assembly in the deflected position as the bucket rides up over a fixed object.  
         [0013]      FIG. 5A  is a side view of the lower bucket assembly of a further embodiment, which includes a nipple and détente mechanism, showing the assembly in the undeflected position.  
         [0014]      FIG. 5B  is a side view of the lower bucket assembly of a further embodiment, which includes a nipple and détente mechanism, showing the assembly in the deflected position.  
         [0015]      FIG. 6  is a sectional view of the lower bucket assembly of a third embodiment as shown generally in  FIG. 3 , taken along section line  4 - 4 , showing the assembly in the undeflected position.  
         [0016]      FIG. 7  is a side view of the lower bucket assembly of a fourth embodiment of the present invention, showing the assembly in the undeflected position.  
         [0017]      FIG. 8  is an enlarged plan view of the lower bucket assembly of the fourth embodiment as shown in  FIG. 7  taken along auxiliary line  8 - 8 .  
         [0018]      FIG. 9  is a sectional view of the lower bucket assembly of the fourth embodiment as shown generally in  FIG. 8 , taken along section line  9 - 9 , showing the assembly in the undeflected position.  
         [0019]      FIG. 10A  is a sectional view of the lower bucket assembly of the fourth embodiment as shown in  FIG. 8 , taken along section line  10 - 10 , showing the nipple and détente mechanism when the assembly is in the undeflected position.  
         [0020]      FIG. 10B  is a sectional view of the lower bucket assembly of the fourth embodiment as shown in  FIG. 8 , taken along section line  10 - 10 , showing the nipple and détente mechanism when the assembly is in the deflected position. 
     
    
     DETAILED DESCRIPTION  
       [0021]     Referring to the drawings, wherein like reference numerals designate identical or corresponding parts throughout the several views, and more particularly to  FIGS. 1A and 1B , front end loader apparatus in accordance with the present invention is designated generally by the numeral  10 . Designations such as front, back, top, bottom, right side and left side are to be referenced to the vehicle, particularly from the perspective of the vehicle driver. Apparatus  10  includes a frame assembly  12  attached at first pivot points  14  to a vehicle (not shown). Frame assembly  12  includes a pair of downwardly projecting legs  16  which are pivotally attached at second pivot points  18  to bucket  20 . Hydraulic cylinders  22  are pivotally attached at third pivot points  24  to bucket  20  and also to frame assembly  12  near the top of downwardly projecting legs  16  at fourth pivot points  26 . In the first embodiment, the hydraulic cylinders  22  are part of a mechanism  28  controlled by control system  30 , which in conjunction with sensor  32 , causes the bucket  20  to tip back upon striking an immovable object  34  as shown in  FIG. 1 (B). Sensor  32  senses a change in distance between first and second pivot points  14  and  18  or, alternatively, a change in velocity of bucket  20  or an impact deceleration of bucket  20 . That is, when bucket  20  has met immovable object  34 , sensor  32  sends a signal to control system  30  which determines if a threshold value of the parameter measured has been reached. If the threshold value has been met, control system  30  actuates a contraction of hydraulic cylinders  22  so that bucket  20  tips appropriately and rides up and over the immovable object  34 .  
         [0022]     In a second embodiment, the preferred embodiment, as shown in FIGS.  2 - 5 (B), there are two downwardly projecting legs  16 ′ which have hinged joints  36  which allow bucket  20  to tip relative to frame assembly  12 ′. Each downwardly projecting leg  16 ′ has upper and lower portions  38 ,  40  separated at a break location  42 . The two upper portions  38  are rigidly connected by a first cross member  60  as shown in  FIG. 3 . The two lower portions  40  are rigidly connected by a second cross member  41 . The upper portions  38  and lower portions  40  of each of the downwardly projecting legs  16 ′ are rotatably fastened together at a pivot point  44 . Pivot points  44  have axes lying parallel and located rearwardly of the axes of hinged joints  24  and rearward of break locations  42 . A lever arm  46  is fixedly attached to the lower portion  40  of each of the downwardly projecting legs  16 ′. Alternatively, lever arm  46  could be a unitary part of the lower portion  40  of the downwardly projecting leg  16 ′. A mating leg  48  extends rearwardly from each of the upper portions  38  of downwardly projecting legs  16 ′ so that the rearward end of lever arm  46  and mating leg  48  are pivotally attached together at a fifth pivot point  44 . The lower portions  40  of the downwardly projecting legs  16 ′ are attached to bucket  20  at second pivot points  18 .  
         [0023]     Working in conjunction with hinged joints  36  are hinged joint closing devices  50 . With respect to  FIGS. 4A and 4B , a hinged joint closing device  50  includes a coil spring  52 . One end  54  of the spring  52  is attached to a forwardly extending portion  56  of lever arm  46 . The other end  58  of the spring  52  is attached to the first cross member  60  which rigidly connects the upper portions  38  of the downwardly projecting legs  16 ′. As shown in  FIG. 3 , there are similar hinged joint closing devices  50  associated with each of the downwardly projecting legs  16 ′.  
         [0024]     In use, apparatus  10  is positioned so that the bottom  62  of bucket  20  is flat on the ground so that the front edge  64  scrapes snow and ice appropriately along the ground. When front edge  64  strikes an immovable object  34  as shown in  FIG. 4B , the lower portions  40  of the downwardly projecting legs  16 ′ pivot backward about fifth pivot points  44 . As the lower portion of the downwardly projecting legs  40  pivot backward the bucket  20  pivots about the third pivot points  24  and second pivot points  18  thereby allowing the front edge  64  of the bucket  20  to lift up and over the immovable object  34 . Hydraulic cylinder  22  maintains a constant length during these operations. The impact force of the immovable object  34  is counteracted by the hinged joint closing device  50 , or more particularly, springs  52 . When the impact force of the immovable object  34  overcomes the counteracting spring force, which is determined by the spring constant, as well as the length of the lever arm  46  relative to fifth pivot points  44 , the front edge  64  of the bucket  20  will lift up and over the immovable object  34  as shown in  FIG. 4B . Once the immovable object  34  has been cleared, the springs  52  will pivot the lower portion  40  of the downwardly projecting legs  16 ′ about the fifth pivot points  44  so that the upper portions  38  and the lower portions  40  lie directly adjacent one another in the area of break locations  42 , thereby resetting the hinged joint closing device  50 .  
         [0025]     In a further embodiment of apparatus  10  as shown in  FIGS. 5A and 5B , a sensor in the form of a mechanical nipple/détente assembly  82  is disclosed. Nipple/détente assembly  82  includes a détente member  84  pivotally attached to both the right and left sides of the lower portion  40  of each downwardly projecting leg  16 ′at pivot point  86 . The detent member  84  additionally provides a stop which prevents the over-rotation of the lower portion  40  of the downwardly projecting leg  16 ′. A nipple sub-assembly  88  is pivotally attached to the inside of the upper portion  38  of each downwardly projecting leg  16 ′. Nipple sub-assembly  88  includes a pair of plates  94 , on either side of détente member  84 , held together with a bolt  96  and nut  98 . A coil spring  100  is provided on bolt  96  between nut  98  and one of plates  94 . The combination of nut and bolt  98 ,  96  and spring  100  provides a force adjustment for nipple/détente assembly  82 . That is, if nut  98  is tightened against spring  100 , it takes more force to separate plates  94  and allow détente member to pull away and further allow hinged joints  36  to open. Protuberance nipples  102  are provided on each of the plates  94 , while indention détentes  104  are located to receive nipples  102  when hinged joints  36  are closed. It is preferred that nipple/détente assembly  82  be a part of embodiments 2, 3 and 4.  
         [0026]     In use, when an immovable object  34  is struck, if a force is generated above the preset threshold to which spring  100  is adjusted, détente member  84  overcomes the force of the compression spring  100  thereby releasing détente member  84  which allows lower portion  40  to rotate so that the hinge joints  36  open as depicted in  FIG. 5B . Once the hinged joints  36  close, nipple/détente assembly  82  resets as in  FIG. 5A .  
         [0027]     The use of nipple/détente assembly  82  is readily tailored to snowplowing conditions, and may even provide a mechanism for locking out the bucket tilting function during activities such as excavating soil and the like for the front-end loader vehicle.  
         [0028]     In a third embodiment as shown in  FIG. 6 , springs  52  of the second embodiment are replaced by fluid-filled (pneumatic or hydraulic) cylinders  66 . The rest of the apparatus is as disclosed with respect to the second embodiment. As shown in broken lines, a fluid-filled cylinder  66  includes a piston  68  having first and second chambers  70 ,  72  on either side of piston  68 . When bottom  62  of bucket  20  is sliding along the ground at a level orientation, the first chambers  70  are maintained at a greater pressure than the pressure in the second chambers  72  such that the fluid-filled cylinders  66  provide a biasing force to the end of the lever arms  46 .  
         [0029]     When front edge  64  strikes an immovable object  34 , as similarly shown in  FIG. 5B , the lower portions  40  of the downwardly projecting legs  16 ′ pivot backward about fifth pivot points  44 . As the lower portion of the downwardly projecting legs  40  pivot backward, the bucket  20  pivots about the third pivot points  24  and second pivot points  18  thereby allowing the front edge  64  of the bucket  20  to lift up and over the immovable object  34 . Hydraulic cylinder  22  maintains a constant length during these operations. The impact force of the immovable object  34  is counteracted by the hinged joint closing device  50 , or more particularly fluid-filled cylinders  66 . When the impact force of the immovable object  34  overcomes the counteracting force provided by the fluid-filled cylinders, the front edge  64  of the bucket  20  will lift up and over the immovable object  34 . Once the immovable object  34  has been cleared, the fluid-filled cylinders  66  will pivot the lower portion  40  of the downwardly projecting legs  16 ′ about the fifth pivot points  44  so that the upper portions  38  and the lower portions  40  lie directly adjacent to one another in the area of break locations  42 , thereby resetting the hinged joint closing device  50 .  
         [0030]     In a fourth embodiment as shown in  FIGS. 7-10B , a different type of fluid-filled or elastomeric device is used. A lever arm  74  is solidly attached to the second cross member  41 ′ near its midpoint. The top end portion  76  of lever arm  74  includes a bumper member  78  comprising a volume-constrained fluid-filled bag, or an elastomeric member, which presses against a bumper coupler member  106  which is attached to a first cross member  60 ′ near its midpoint. When bucket  20  strikes an immovable object  34  causing hinged joint  36  to open, lever arm  74  presses the bumper member  78  against the bumper coupler member  106  thereby causing it to deform. This deformation stores energy in the bumper member  78  as either increased fluid pressure in the case of the volume-constrained bag, or as stored elastic energy in the case of an elastomeric member. The deformation of the bumper member  78  opposes the opening of hinged joints  36  and urges them closed. As this occurs, bucket  20  rides over immovable object  34  as discussed earlier.  
         [0031]     Thus, preferred embodiments of front-end loader apparatus, in accordance with the present invention have been described in detail. It is understood, however, that equivalents to the disclosed invention are possible. Therefore, it is further understood that changes made, especially in matter of shape, size and arrangement to the full extent extended by the general meaning of the terms in which the appended claims are expressed, are within the principle of the invention.

Summary:
A mounting apparatus for a bucket of a front end loader vehicle. The mounting system allows the bucket to pivot up and over fixed objects when the leading edge of the bucket strikes an immovable object for the purpose of protecting the loader assembly, vehicle, and operator.