Abstract:
A movable counterweight system moves under a material-handling vehicle to provide a safe low center of gravity, and avoid interference to the operator.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     Continuation in part of application Ser. No. 11/756,069 filed May 31, 2007, U.S. Pat. No. 8,007,222. No new matter has been added to this specification. 
    
    
     FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Not applicable. 
     REFERENCE TO SEQUENCE LISTING, A TABLE, OR A COMPUTER LISTING APPENDIX 
     Not applicable. 
     COPYRIGHT NOTICE 
     A portion of the disclosure of this patent document contains material that is subject to copyright protection. The copyright owner has no objection to the facsimile reproduction by anyone of the patent document or patent disclosure as it appears in the Patent and Trademark office, patent file or records, but otherwise reserves all copyright rights whatsoever. 
     BACKGROUND 
     Field of Invention 
     The present invention relates generally to earth moving devices and more specifically to a variable counterweight system for a material handling vehicle, which increases the operational safety of the vehicle. 
     Background of the Invention 
     U.S. Pat. No. 2,926,799 to Granryd discloses a counterweight arrangement for a tractor loader. The Grandryd patent includes a counterweight that is pivoted on the rear of a tractor loader according to a position of a conventional bucket. U.S. Pat. No. 7,128,517 to Kurtz discloses a loader with extending bucket and counterbalance. The Jurtz patent includes a small loader machine of the skid-steered type having a counterweight to balance heavy loads in the loader bucket. The bucket is automatically extended forward as the counterweight is extended in the opposite direction so as to keep the machine always in reasonable balance. 
     There is a clearly felt need in the art for a variable counterweight system for a material handling vehicle, which includes a counterweight that is moved from the front of the material handling vehicle to the rear of the material handling vehicle, depending on a vertical position of an attachment, such as a bucket. Such a counterweight should have as low a center of gravity as possible for stability, have maximum effect, and be free of obstruction or danger points to the operator. 
     SUMMARY OF THE INVENTION 
     The present invention provides a variable counterweight system for a material handling vehicle, which includes a counterweight that is movable between the front and rear of the material handling vehicle. The variable counterweight system includes a counterweight and at least one linear transfer device. The counterweight may include a plurality of individual counterweight members. Horizontally adjacent counterweight members are preferably pivotally engaged with each other. Each linear transfer device preferably includes a moving track and a drive device. The moving track may be a chain or a belt. The drive device is preferably a hydraulic, electric or pneumatic motor. The moving track is retained on rotary axles. The rotary axles are preferably retained by a guide track. The moving track if preferably retained in the guide track. The drive device includes either a sprocket for driving the chain or a cog for driving the belt. A sprocket or cog is mounted to each rotary axle. At least one vertical sensor determines the position of a boom. At least one horizontal sensor determines the position of the counterweight relative to the vehicle. A control unit receives input from the vertical sensor, and human or sensor input as to whether the boom is lifting upward or pushing downward. In the case of lifting, if the boom is in an elevated position, the control unit powers the drive device to move the counterweight to the rear of the vehicle. In the case of pushing downward, for example digging dirt with a bucket or operating a drill or jackhammer or other, the counterweight is moved to the front of the vehicle to maximize downward force to the bucket, drill, or jackhammer. The variable counterweight could also be manually manipulated by an operator. 
     If the boom is in a lowered position, then the control unit powers the drive device to move the counterweight to the front of the vehicle. The drive device is powered until the counterweight reaches the front of the vehicle. A skid steer is one of many types of material handling vehicles. Accordingly, it is an object of the present invention to provide a variable counterweight system, which includes a counterweight that is moved from the front of the vehicle to the rear of the vehicle depending on a vertical position of an attachment such as a boom. 
     These and additional object, advantages, features and benefits of the present invention will become apparent from the following specification. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side view of a material handling vehicle with a variable counterweight system, where a counterweight is position at the front of the vehicle. 
         FIG. 2  is a side view of a material handling vehicle with a variable counterweight system, where a counterweight is position at the rear of the vehicle. 
         FIG. 3   a  is a top view of a variable counterweight system with a counterweight positioned at the front. 
         FIG. 3   b  is a top view of a variable counterweight system with a counterweight positioned at the rear. 
         FIG. 4  is an enlarged side view of a material handling vehicle with a variable counterweight system, where a counterweight is positioned at the rear of the vehicle in a guide track. 
         FIG. 5  is an enlarged top view of two weight members pivotally engaged with each other of a variable counterweight system. 
         FIG. 6  is an enlarged top view of two weight members pivotally engaged with each other of a variable counterweight system. 
         FIG. 7  is a rear view of a material handling vehicle with a variable counterweight system. 
         FIG. 8  is a cross sectional of a variable counterweight system mounted to a material handling vehicle. 
         FIG. 9  is a block diagram of a control unit of a variable counterweight system. 
         FIG. 10  shows a device requiring downward pressure rather than lifting. 
         FIG. 11  shows a track creating maximum countereffect. 
         FIG. 12  shows a counterweight which conforms to the shape of the vehicle bottom for maximum weight. 
         FIG. 13  shows a counterweight requiring downward pressure with a drill attachment. 
         FIG. 14  shows a counterweight requiring rearward counterpressure with a forklift attachment. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to  FIG. 1 , there is shown a material handling vehicle or machine  100  with a portion of a variable counterweight system  1 , wheels omitted for visibility. The wheels disclosed are the type which contact the riding surface, typically earth, but the wheels could drive a tread for crawler-type vehicles. “Material handling” is construed to include not only movement of material within a component of the vehicle  100 , but also material outside the vehicle  100 , e.g. dirt which is scooped into the bucket  104 , or material drilled or broken or otherwise transformed by the vehicle  100 . A material handling machine comprising any type of industrial machine, whether or not having attached mobilizers such as wheels or is stationary by design, for purposes of handling material as defined above. A material handling vehicle being more specifically a material handling machine having a mobilizing feature such as wheels or rotating tractor belt. 
     The vehicle  100  may have, although not necessarily in all circumstances, a chassis  150  enclosing the vehicle engine, motors, various electrical, hydraulic or pneumatic connections from external damaging articles such as sticks, rocks or debris. Alternatively, said components may be attached near said chassis, either above or below the chassis, for the purpose of being positioned near the vehicle&#39;s lowest center of gravity. See  FIGS. 13 and 14  depicting the components held within said chassis  170  and  FIG. 1  wherein the components are held externally  150 . 
     The chassis is an operator control location such as a seat  152  with control panel  154 . Control panel  154  may contain on/off, auto/manual, speed, sensitivity, and direction controls adjustable by the operator in seat  152 . A boom  102  raises and lowers a material handling device such as a bucket  104 . Boom  102  is disclosed as a lever, but boom  102  could be a hydraulic mast or any other lifting device. With reference to  FIGS. 2-6 , the vehicle  100  has wheels  156  with axles  158 , the rear wheel omitted for visibility in  FIG. 2 . 
     The variable counterweight system  1  includes a counterweight  10  and at least one linear transfer device  12 . The counterweight  10  preferably includes a plurality of pivoting weight members  14  and a plurality of hanging weight members  16 . A top of each hanging weight members  16  is attached to a bottom of an adjacent pivoting weight member  14  with at least two fasteners. A plurality of link slots  20  and a plurality of link clearance slots  22  are cut into each end of each adjacent pivoting weight members  14 . A plurality of pivoting links  18  are secured to each pivoting weight members  14  by welding or other suitable process. Each linear transfer device  12  preferably includes a moving track  24  and a drive device  26 . However, other types of linear transfer devices may be used, such as a pair of hydraulic cylinders. The moving track  24  could be a chain or a belt. The drive device  26  is preferably a hydraulic, electric or pneumatic motor. The moving track  24  is retained on two rotary axles  28  but may be enabled by at least one rotary axle. 
     With reference to  FIGS. 7-8 , the rotary axles  28  (in  FIGS. 3   a - eb ) may be retained by a guide track  30  or alternatively positioned external and adjacently to said guide track in direct contact with said moving track for purposes of driving said moving track. The moving track  24  is preferably retained in the guide track  30 . The guide track  30  is mounted to a bottom of the vehicle  100 , or inside the chassis  150 . The drive device  26  includes either a sprocket or cog  35  for driving the chain or belt. A pair of idler shafts  37  may be located adjacent the sprocket or cog  35  to guide the moving track  24 . The guide track  30  includes a moving track portion  32  and a counterweight portion  34 . The moving track portion  32  supports the counterweight  10 . A folding bearing  36  may be pivotally retained on each end of at least some of the pivoting weight members  14 . The rolling bearing  36  includes a diameter that is greater than a thickness of each pivoting weight bearing  14 . The folding bearing  36  rolls within the counterweight  34 . 
     With reference to  FIGS. 9 ,  13  and  14 , a lower vertical sensor  38  and an upper vertical sensor  40  determine the position of an attachment or a boom  102  of the material handling vehicle  100  according to the position of its weight or pressure load. The attachment could be a bucket  104 , a fork lift  172 , a grapple, a drill  171 , a jackhammer, or other types of attachment. A front horizontal sensor  42  and a rear horizontal sensor  44  determine the position of the counterweight  10  relative to the front and rear of the vehicle  100 . A control unit  46  receives input from the upper and lower vertical sensors. Control unit  46  may also control drive devices  26  based on tilt meter  43 , which could utilize a gravitometer. The tilt meter is yet another manner of measuring the load position of the machine&#39;s functioning pieces relative to its overall position or the counterweight. 
     If the bucket  104  or the boom  102  are in either an elevated position  173  or a lowered position, then the control unit  46  activates a power control device  48 . The power control device  48  could be a hydraulic valve, a relay or any other suitable device. The power control device  48  allows power to flow from a power source  50 . The power source  50  could be pressurized hydraulic fluid electricity, or any suitable source of power. Power flows from the power source  50  to the drive device  26 , when the power control device  48  is activated. The drive device  26  moves the counterweight  10  to a front of the vehicle  100 , if the boom  102  is placed in a lowered position. The drive device  26  is powered, until the front horizontal sensor  42  senses that the counterweight  10  reaches the front of the vehicle  100 . The control unit  46  deactivates the power control device  48  to stop the flow of power to the drive device  26 . The counterweight  10  located at the front of the vehicle  100  increases pressure on the bucket  104  or other attachment. 
     The drive device  26  moves the counterweight  10  to the rear of the vehicle  100 ,  177 , if the boom  102  is placed in an elevated position. The drive device  26  is powered, until the rear horizontal sensor  44  senses that the counterweight  10  reaches a rear of the vehicle  100 . The control unit  46  deactivates the power control device  48  to stop the flow of power to the drive device  26 . 
     Referring to  FIG. 10 , the counterweight system  1  may consist of a single counterweight  10 , rather than multiple counterweights. Also referring to  FIG. 10 , the operator may be operating a jackhammer or drill  105 ,  171  at height, requiring more downward force in what will be termed pushdown mode. Either manually by switching the control panel, or by sensing vehicle tilt by a tilt-meter  43 , gravitometer or other means, in pushdown mode, the counterweights are moved forward  174  with the boom upward  175 , to counter the force causing the backward tilt from the jackhammer or drill. 
     Referring to  FIG. 11 , to maximize the leverage of the counterweight, the track  30  guiding the weight members  14  may wrap around the rear of the vehicle  100 ,  176 , allowing more of the weights to be at a maximum distance from the front wheels. The track at the rear of the vehicle  100  has an angle of preferably within thirty degrees, and more preferably five degree of vertical when the vehicle  100  is parked on a flat surface. Referring to  FIG. 12 , to maximize the weight of the counterweight, the lateral top profile  162  of the counterweight may be contoured to the lateral contour  160  of the bottom of the vehicle chassis. For instance, the clearance between the lateral top profile  162  and the lateral bottom profile  160  would conform to within less than an inch. Weight and counteraction is thereby maximized for the allowable space. The invention is not limited to the preferred mode illustrated. For instance, the invention is disclosed as being exterior to the chassis of the vehicle, but could be in the interior of the chassis  170 , resulting in less snagging. An additional chassis or cover may enclose the counterweight system  10 , alternatively resulting in less snagging. The counterweight system  10  may be comprised of a single weight or multiple weights. These and other variants are within the spirit and scope of the claims below.