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This application is a divisional of U.S. patent application Ser. No. 11/738,353, filed Apr. 20, 2007, which claims priority to U.S. provisional patent application No. 60/745,270, filed Apr. 20, 2006, which is fully incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The field of this invention is quick couplers for coupling two bodies, and in particular the field is quick couplers for engaging implements, such as buckets and pallet forks, to mining and construction machinery, such as wheel loaders, track loaders, or backhoe loaders. 
     BACKGROUND 
     Mining and construction machinery includes wheel loaders, hydraulic excavators, skid steer loaders, multi-terrain loaders, track loaders, and backhoe loaders and the like. Typically implements are mounted to these machines to perform work. One example of such an implement is a bucket. A bucket could be mounted to one of these machines for performing work like digging a trench in the ground, digging material from a pile, or dozing. Another example is a pallet fork. A pallet fork could be mounted for permitting the machine to pickup and carry palletized materials around a building site or at a factory. Still another example is logging forks. Logging forks are specially adapted for picking up and carrying logs. Other non-limiting examples of implements include hammers, blades, brooms, and snow plows. 
     When a particular implement is attached to the machine, it enables the machine to perform a variety of tasks. In order to perform a task which the implement does not enable the machine to do, a different implement can be attached. The ability to attach multiple implements to a machine so it can perform a variety of tasks—multitasking—increases the utility and value of the machine for the owner. 
     On the other hand, the attaching and detaching of implements to a machine can be cumbersome and time consuming. The time spent switching implements instead of working reduces the utility of the machine. 
     Some implements may be mounted to a machine with a simple pin-style joint, which does not facilitate the switching of implements. With this mounting system, a pin is manually inserted into complementary bores in the machine and implement to create a pin joint. Switching implements with this system requires an operator or technician, or multiple technicians, to manually remove the pins that hold the first implement to the machine, remove the first implement, position a second implement on the machine, and manually reinsert the pins. Besides being time consuming, this switching operation can require considerable skill on the part of the operator and technicians. 
     Quick couplers solve many of the problems that pin-style joints present for switching implements. Quick couplers provide an alternative way to mount implements to mining and construction machinery. The quick coupler is interposed at the junction between machine and implement. The implement is attached to the quick coupler, and the quick coupler is attached to the machine. The operator of the machine commands the quick coupler to release an implement from inside the machine&#39;s cab. The machine is then repositioned to a second implement, where the operator may then manipulate the quick coupler and the machine to pickup the second implement. With a quick coupler, changing from one implement to another implement can be done quickly, and typically only requires the involvement of the machine&#39;s operator. 
     Many types and styles of quick couplers for mining and construction machinery have been used and proposed. One example is the coupler disclosed in EP 0 278 571 B1 (hereinafter the &#39;571 coupler). 
     The &#39;571 coupler suffers from several disadvantages. For instance, the &#39;571 coupler may not create the most favorable wedging action between the coupler and the implement to hold the coupler tightly to the implement, even after possible future wear of the coupling surfaces. The coupling surfaces on the &#39;571 coupler may be prone to sticking problems, making removal of the coupler from the implement difficult. In addition, the &#39;571 coupler may be more expensive to manufacture than it need be. 
     SUMMARY OF THE INVENTION 
     A quick coupler for coupling a first body to a second body comprises attachment means for attaching the coupler to a first body, a tube adapted to be received in hooks on a second body, at least two wedges arranged for retraction and extension movement, and adapted to be extended into and retracted from wedge pockets formed on the second body, and wedge coupling surfaces adapted to engage wedge coupling surfaces on the second body, the wedge coupling surfaces on the quick coupler forming an angle of between 60 and 44 degrees measured between a line passing through the center of the tube and through the wedge coupling surface, and a line parallel to the wedge coupling surface. 
     An implement comprises at least two hooks, at least two wedge pockets, and a wedge coupling surface forming an angle of between 60 and 44 degrees measured between a line passing through the center of the hooks and through the wedge coupling surface, and a line parallel to the wedge coupling surface. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1 and 2  are views of the back and front, respectively, of an exemplary embodiment of a quick coupler. 
         FIG. 3  illustrates the quick coupler of  FIG. 1  mounted to the linkage of an exemplary machine. 
         FIGS. 4 and 5  illustrate an exemplary embodiment of a tool, in this case a bucket, which can be attached to the quick coupler of  FIG. 1 . 
         FIG. 6  illustrates another exemplary embodiment of a tool, a pallet fork, which can be attached to the quick coupler of  FIG. 1 . 
         FIG. 7  is view of the quick coupler of  FIG. 1  attached to the bucket of  FIG. 4 . 
         FIG. 8  is a sectioned solid view of a quick coupler and bucket. 
         FIG. 9  is a detail view taken from  FIG. 8 . 
         FIG. 10  is a sectioned solid view of the quick coupler of  FIG. 8 . 
         FIG. 11  is sectional view of the bucket of  FIG. 8 . 
         FIG. 12  is a rear view of a bucket. 
     
    
    
     DETAILED DESCRIPTION 
       FIGS. 1-12  illustrate embodiments of a quick coupler, and several embodiments of tools that may be attached to the quick coupler. The purpose of these figures and the related descriptions is merely to aid in explaining the principles of the invention. Thus, the figures and descriptions should not be considered as limiting the scope of the invention to the embodiment shown herein. Other embodiments of quick couplers and tools may be created which follow the principles of the invention as taught herein, and these other embodiments are intended to be included within the scope of patent protection. 
     One important feature of a quick coupler is the ability to hold the implement tightly in a variety of conditions. Ideally, there should be no or very little movement between the implement and the quick coupler—they should be firmly mounted to one another in a tight fit. Ideally, the quick coupler should also be capable of compensating for wear on mating surfaces, so that a tight fit can be maintained throughout the coupler&#39;s life. Movement between mating surfaces of the implement and the coupler can cause premature wear. Excessive movement can also affect the controllability of the implement. The implement may be difficult to precisely position if there is uncontrolled movement between the implement and the coupler. 
     Another important feature of a quick coupler is visibility. The quick coupler should allow a line of sight from the machine&#39;s cab, through the quick coupler, and to various areas of implements that may be mounted to the coupler. For example, when pallet forks are attached to the quick coupler, the operator should ideally be able to view the ends of the forks so they can be precisely positioned in a pallet. 
     Another important feature of a quick coupler is its effect on the kinematics of the implement. An implement&#39;s performance may depend closely upon the way the machine can move the implement. For example, a wheel loader bucket&#39;s breakout force depends upon the force applied to the bucket by the wheel loaders tilt actuator, the distance between the bucket-tilt actuator link and the bucket-lift arm link, and the geometry of the bucket. If a quick coupler is interposed between the bucket and the machine, these kinematic factors may change, resulting in a degradation of the bucket&#39;s performance. Thus, ideally the quick coupler should minimize its effect on the kinematic performance of the implement. 
     Other important features of quick couplers include the ease of picking up or attaching various implements, cost, and reliability. The quick coupler must also be able to transfer the high forces on the implement to the machine. Fatigue failures can be a problem if stresses on the quick coupler are too high, and should be avoided by appropriate design and construction. 
     With reference first to  FIGS. 1 and 2 , a quick coupler  10  is illustrated.  FIG. 1  shows a back view of the quick coupler  10 .  FIG. 2  shows a front view of the quick coupler  10 . A frame  100  is the structural “backbone” of the quick coupler  10 . The frame  100  serves to position attachment points for attaching the quick coupler  10  to the machine, and to position attachment points for attaching the quick coupler  10  to various implements. The frame  100  provides rigidity between those attachment points, and transfers forces between the machine and the implements. The frame  100  could take many forms. One advantageous form is depicted in the drawing figures. However, other forms could be used. For example, the quick coupler  10  would have a different frame  100  if it was desired to adapt the quick coupler for a different type of machine. The quick coupler illustrated herein is especially adapted for a wheel loader application. A similar quick coupler could be made for excavators or other machinery through applying the principles of the invention. 
     The frame  100  includes plate-shaped center members  110   a  and  110   b . Throughout this description, like elements on opposite sides of a structure will be referred to by the same reference number, followed by the suffix “a” or “b.” The frame  100  also includes plate-shaped middle members  120   a  and  120   b , and plate-shaped end members  130   a  and  130   b . Top extension plates  132   a  and  132   b , and bottom extension plates  133   a  and  133   b  attach the end members  130   a  and  130   b  to the middle members  120   a  and  120   b . Top extension plates  132   a  and  132   b  also act as rack stops for an implement. A box structure  140  extends between and ties together the center members  110   a  and  110   b  and the middle members  120   a  and  120   b . The box structure includes box ends  141   a  and  141   b , a top plate  142 , a bottom plate  143 , and a front plate  144 . 
     The quick coupler  10  has attachment means including mounting structure for mounting to a machine. Lift arm bores  131   a ,  131   b ,  145   a , and  145   b  are formed in the end members  130   a  and  103   b , and the box ends  141   a  and  141   b , respectively. The lift arm bores accept pins (not shown) for attaching the quick coupler  10  to the lift arms of a linkage of a machine. Likewise, tilt link bores  111   a  and  111   b  are formed in the center members  110   a  and  110   b  and accept a pin (not shown) for attaching the quick coupler  10  to the tilt link of a linkage of a machine.  FIG. 3  illustrates how the coupler  10  attaches to a machine&#39;s lift arms  1   a  and  1   b  and tilt link  2 . The pin joints permit relative rotation between the lift arms  1   a  and  1   b  and the quick coupler  10 . Likewise, the pin joint at the tilt link  2  permits rotation of the quick coupler  10 . The tilt link  2  may be attached to a tilt lever  3 , as is known in this art, to cause quick coupler to tilt, or rack, backward and forward. The lift arms  1   a  and  1   b  rotate relative to the machine at their ends opposite the quick coupler  10  to raise and lower the coupler. In  FIG. 3 , it can be seen how top extension plates  132   a  and  132   b  will contact lift arms  1   a  and  1   b  and act as a rack stop if the quick coupler  10  is racked back all the way towards the lift arms. 
     Returning to  FIGS. 1 and 2 , the quick coupler  10  includes mounting structure for mounting an implement thereto. The mounting structure includes a tube  210  that extends between the middle members  120   a  and  120   b , and is also attached to center members  110   a  and  110   b . Hydraulic cylinders  220   a  and  220   b  are mounted at one end to the frame  100  by mounting posts  221   a  and  221   b . At the other end of hydraulic cylinders  220   a  and  220   b  are mounted wedges  230   a  and  230   b . The hydraulic cylinders  220   a  and  220   b  are configured to extend and retract wedges  230   a  and  230   b  under power of pressurized hydraulic fluid. The extension and refraction of the wedges  230   a  and  230   b  occurs during the mounting and dismounting of an implement to the quick coupler  10 . Although hydraulic cylinders  220   a  and  220   b  are illustrated, other actuators could be used to move the wedges  230   a  and  230   b , as will be understood by those of ordinary skill in the art. In addition, although two hydraulic cylinders  220   a  and  220   b  are illustrated, a single hydraulic cylinder with a linkage system could be used to extend and retract both wedges  230   a  and  230   b.    
     The relative placement on the coupler  10  of the mounting structure for mounting the coupler to the machine, and the mounting structure for mounting the coupler to the implement, may minimize the impact on the kinematics between machine and implement. 
       FIGS. 4 and 5  illustrate a type of implement, a bucket  30 , that could be mounted to the quick coupler  10 . Bucket  30  includes mounting structure to mount the bucket to the quick coupler  10 . The mounting structure includes a wedge plate  310 . Wedge plate  310  includes wedge pockets  320   a  and  320   b . The mounting structure also includes hook plates  330   a  and  330   b . Hook plates  330   a  and  330   b  define hooks  331   a  and  331   b . Each of hooks  331   a  and  331   b  may be generally circularly defined with a center point along a central axis. As shown in the figures herein, the central axes of the hooks  331   a  and  331   b  may be coaxial. Each of the Hooks  331   a  and  331   b  are configured to mount to the top tube  210  of quick coupler  10 . Wedge pockets  320   a  and  320   b  are configured to accept wedges  230   a  and  230   b , as will be described in more detail hereinafter. The wedge pockets  320   a  and  320   b  may be advantageously formed as rectangularly-shaped cut through holes in the wedge plate  310 , with sides that are parallel to one another and perpendicular to the top of wedge plate  310 . This reduces the manufacturing cost and complexity. 
       FIG. 6  illustrates another type of implement that could be mounted to the quick coupler  10 , a pallet fork  20 . Pallet fork  20  may include the same mounting structure for mounting to quick coupler  10  as bucket  30 . However, instead of a single wedge plate  310 , pallet fork  20  has two wedge plates  310   a  and  310   b . Wedge pockets  320   a  and  320   b  are formed in the wedge plates  310   a  and  310   b , respectively. 
       FIG. 7  illustrates the quick coupler  10  mounted to the bucket  30 . The tube  210  is first positioned in hooks  331   a  and  331   b . The machine operator then lifts the lift arms  1   a  and  1   b , lifting the quick coupler  10  and the bucket  30 . If necessary, the operator can then rack back the quick coupler  10  until the wedges  230   a  and  230   b  are positioned over the wedge pockets  320   a  and  320   b . The operator can then command, from inside the cab via an auxiliary hydraulic circuit, the hydraulic cylinders  220   a  and  220   b  to extend. The cylinders drive the wedges  230   a  and  230   b  into the wedge pockets  320   a  and  320   b  to complete the coupling procedure. The bucket  30  can be released from the quick coupler  10  through reversing the same procedure. 
     The top tube  210  includes ears  211   a  and  211   b . When the quick coupler is mounted to an implement, the ears  211   a  and  211   b  abut the hook plates  330   a  and  330   b . This helps prevent the bucket  30  from twisting relative to the quick coupler  10  and helps prevent relative movement. 
       FIG. 8  is a solid sectioned view of the bucket  30  and quick coupler  10 . This sectioned view is taken through the central axis of hydraulic cylinder  220   b , and parallel to the mid-plane of middle member  120   b .  FIG. 9  is a detail view taken from  FIG. 8 .  FIG. 8  shows the wedge  230   b  refracted from the wedge pocket  320   b  so that quick coupler  10  can be detached from bucket  30 . Wedge  230   b  extends out from the frame  100  through a wedge coupling surface  240   b  which at least partially surrounds wedge  230   b . Likewise, wedge  230   a  extends out from a wedge coupling surface  240   a  which at least partially surrounds wedge  230   a . The bucket  30  also has wedge coupling surfaces  340   a  and  340   b  formed on wedge plate  310 , which each at least partially surround the wedge pockets  320   a  and  320   b , respectively. The surfaces  240   a ,  240   b ,  340   a , and  340   b  are at least approximately parallel when the quick coupler  10  engages the bucket  30 . 
     The wedges  230   a ,  230   b  include a camming surface  231   a ,  231   b . When the quick coupler  10  and the bucket  30  are engaged, the camming surfaces  231   a  and  231   b  are approximately parallel to the side walls of wedge pockets  320   a  and  320   b  of bucket  30 . When the wedges  230   a  and  230   b  are extended, the camming surfaces  231   a  and  231   b  engage and cam, or wedge, against the rear side walls  321   a  and  321   b  of pockets  320   a  and  320   b . Downward force on the wedges  230   a  and  230   b  at this moment converts into a force pushing wedge coupling surfaces  240   a  and  240   b  toward bucket  30 , and into tighter engagement with wedge coupling surfaces  340   a  and  340   b . The wedging action between the wedge coupling surfaces holds the coupler  10  tighter against the bucket  30 . When the wedging action occurs, the quick coupler is rotating slightly relative to the bucket  30  around the center of the hooks  331   a  and  331   b  and the top tube  210 . 
     The wedge coupling surfaces  240   a  and  240   b  on the coupler wedge against the wedge coupling surfaces  340   a  and  340   b  on the bucket, as explained above. These surfaces form an angle α relative to a line passing through the center of the hooks  331   a  and  331   b  and the top tube  210  and through the surfaces themselves. The angle α is important for achieving the right balance of wedging action and the proper functioning of the coupler  10 . If the angle α is too close to 90 degrees, then the surfaces  240   a,b  and  340  can wedge together too tightly, making it difficult to disengage the bucket  30  from the quick coupler  10 . If the angle α is too close to 0 degrees, there will not be adequate wedging action to force the surface tightly together and create a tight fit. An angle α of approximately 60-44 degrees has been found to be an ideal balance, creating adequate wedging action to hold the wedging surfaces together tightly, but not too tightly. Even better is an angle α in the range of 56-48 degrees, and even better would be an angle α of approximately 52 degrees. 
     With reference now to  FIG. 10 , attached to the bottom plate  143 , and forming at least part of the opening for the wedge  230   b , are two horseshoe plates  146   b  and  147   b . Likewise, horse shoe plates  146   a  and  146   b  form at least part of the opening for wedge  230   a . These horseshoe plates are especially adapted to transfer the loads from the wedges  230   a  and  230   b  to the box structure  140 . 
       FIG. 11  is a sectional view of the bucket  30  alone which more clearly shows the measurement of the angle α. The angle α is measured between a line passing through the center of hook  331   b  and through the intersection of the rear side wall  321   b  and the wedge coupling surface  340   b , and a line parallel to the wedge coupling surface  340   b.    
     The only contact between the bucket  30  and the quick coupler  10  occurs between the top tube  210  and the hook plates  330   a  and  330   b , between the wedge coupling surfaces  240   a ,  240   b ,  340   a , and  340   b , and between the wedges  230   a  and  230   b  and the pockets  320   a  and  320   b . The forces from the bucket  30  to the quick coupler  10  are generally transferred between the top tube and hook plates, and between the wedge coupling surfaces. If any of these surfaces should wear during use, the wedging action of the coupler  10  to the bucket  30  will take up the extra play and keep the two tightly engaged. This is facilitated by the stroke of hydraulic cylinders  220   a  and  220   b  being selected such that the cylinders are capable of extending farther than the position where the wedges  230   a  and  230   b  would normally come to rest against the rear side walls  321   a  and  321   b  of the wedge pockets  320   a  and  320   b . This is also facilitated by ample space between the surfaces of the coupler  10  and bucket  30  so those other surfaces do not interfere even after significant wear of the wedge coupling surfaces. The wedge coupling surfaces  240   a  and  240   b  of coupler  10  should be allowed to swing at least 5 mm closer to the bucket  30  to account for future possible wear, and ideally 15 mm, and even more ideally 30 mm. 
       FIG. 12  shows a rear view of the bucket  30 . The hook plate  330   a  is generally in the same vertical plane on the bucket  30  as wedge pocket  320   a . The vertical plane can be defined as a plane parallel to a mid plane of the hook plate  330   a  or  330   b . Likewise, hook plate  330   b  is generally in the same vertical plane on the bucket  30  as wedge pocket  320   b . The distance A between hook plates  330   a  and  330   b  controls the relative placement of hydraulic cylinders  220   a  and  220   b  on coupler  10  because the cylinders must be approximately in line with wedge pockets  320   a  and  320   b . As discussed previously, visibility is an important concern in designing a quick coupler. Ideally, the operator should have lines of sight through the coupler to important areas on the implement. The placement of the hydraulic cylinders  220   a  and  220   b , which also effects the placement of members within frame  100 , has a large impact on visibility. It has been determined that an optimum distance A between hook plates  330   a  and  330   b  for permitting visibility to the important areas on an implement is within the range of 580 mm to 500 mm. More ideally, the distance A is between 560 mm to 520 mm, and most ideally the distance A is approximately 540 mm. This distance A has been also been determined based upon the desire to adapt the coupler  10  to be usable with many different styles of linkages of machines, and also to allow for the adequate strength of all the members of coupler  10  and bucket  30 .

Summary:
A quick coupler includes mounting structure for mounting the coupler to a machine, and for mounting the coupler to an implement. The mounting structure on the coupler includes wedge coupling surfaces and a tube. The mounting structure on the implement includes hooks for engaging the tube, and complementary wedge coupling surfaces. The wedge coupling surfaces wedge together during coupling to produce and tight fit and solid hold between the coupler and implement. The mounting structure is robust, and can accommodate future possible wear. The kinematic impact on the performance of the implement due to the use of the quick coupler is minimized.