Abstract:
A coupler assembly for a material handling device is provided which accommodates convenient interchanging of work implements. The coupler assembly includes first and second latching arrangements which are provided on a frame member which is adapted to be mounted on the lift arm assembly of material handling device. Notably, the second latching arrangement includes an elongated bar having end portions which are deflectable with respect to the central portion of the bar. A pair of overcenter locking cams are provided for urging the respective end portions of the bar into recesses defined by hooks which are mounted on the implement to be mounted, thus facilitating convenient attachment of the implement to the lift arm assembly.

Description:
TECHNICAL FIELD OF THE INVENTION 
     This invention relates to coupler assemblies and more particularly to coupler assemblies for attaching implements to lift arms as found on mechanized equipment. 
     BACKGROUND OF THE INVENTION 
     Mechanized equipment such as backhoes and tractors having lift arms can be used with various work implements such as buckets, blades, and lift forks. The implement is mounted on the lift arm to facilitate operation and use of the implement. Various mechanisms have been proposed to allow quick interchanging of these work implements so the same tractor can be used for different work functions. Generally, the implement and lift arm are modified or provided with attachment members to releasably mount the various implements on the lift arm to permit quick changing. 
     Some of these quick change mechanisms rely on pins which must be inserted into aligned holes in the implement and mounting brackets on the lift arm. Unfortunately, this type of mechanism can require careful and time consuming alignment of the holes. The pins often must be particularly robust to prevent misalignment problems and to carry the load of the implement. Additionally, the pins are exposed to dirt and tend to wear unevenly causing undesirable looseness and misalignment in the coupling. 
     Other mechanisms proposed have relatively large and complicated linkages. These mechanisms consist of a female member mounted on the implement and an expandable male member mounted on the lift arm of the tractor. The male member has a hinge-like structure which is expanded to engage the female member. Such mechanisms often use hydraulic cylinders. 
     Some of these mechanisms are particularly complex and can offset the balance of the tractor by placing an excessive weight on the end of the lift arm. In addition, the hydraulic system can leak causing the inadvertent disengagement of the implement from the tractor. Other devices have complicated locking mechanisms in a relatively inaccessible location making implement changing difficult for the operator. 
     Accordingly, it would be desirable to provide a coupler assembly which avoids the deficiencies of the prior art and is easy to use and provides sure coupling of an implement on a lift arm. The present invention meets that desire. 
     SUMMARY OF THE INVENTION 
     The present invention is a coupler assembly for attaching various work implements such as a bucket to a lift arm assembly. Such lift arm assemblies can be found on tractors, backhoes, and front end loaders. The coupler assembly of the present invention allows for easy and quick removal of one work implement from the lift arm assembly and the mounting of a different work implement on the lift arm assembly. Thus, the same tractor can serve several functions by simply interchanging the work implement. 
     The coupler assembly basically comprises an attachment structure on the work implement defining a first recess and a second recess opening in opposite directions. First and second latching means are provided on a frame member which is adapted to be mounted on the lift arm assembly. The first latching means is received by the first recess and the second latching means engages the second recess to attach the implement on the frame member. 
     The second latching means includes a bar means having a mounting portion mounted on the frame member and an end portion deflectable with respect to the mounting portion. The end portion is adapted to be received by and engage with the second recess. This deflectable motion provides not only ease of operation, but also the certainty of engagement with the second recess. An engaging or camming means can be associated with the bar means for maintaining the end portion engaged with the second recess. In one preferred embodiment the bar means is a resilient bar having a central mounting portion fixed on the frame member and two opposite end portions adapted to be received by the second latching means which can be two hooks each defining a slot. The resiliency of the bar assists in the operation of the coupler assembly. 
     Because of its design requiring relatively few, light components, the present invention does not offset the balance of the tractor and is also less expensive and easier to produce than many previous devices. The second recess defined by the attachment structure also serves as a guide for the end portion of the bar means to assist in the proper alignment of the work implement on the lift arm. The relative simplicity of the present invention also provides for ease and reliability of operation. 
     Numerous advantages and features of the present invention will become readily apparent from the following detailed description of the preferred embodiment of the invention, the drawings and the accompanying claims. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     FIG. 1 is a side elevational view of a tractor having a lift arm assembly adjacent a bucket together showing a coupler assembly embodying the present invention; 
     FIG. 2 is an enlarged side elevational view of the coupler assembly; and 
     FIG. 3 is a rear elevational view taken generally along plane 3--3 of FIG. 2. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     While this invention can be embodied in many different forms, there is shown in the drawing and described in detail, a preferred embodiment of the invention. The present disclosure is to be considered as an exemplification of the principles of the invention and is not intended to limit the invention to the embodiment illustrated. 
     For ease of description, the coupler assembly embodying this invention will be described in a normal upright operating position and such terms as upper, lower, upwardly, downwardly, will be used with reference to this position. It will be understood, however, that the coupler assembly embodying this invention can be used in an orientation other than the position described. 
     Referring to the FIGURES, a tractor having a lift arm assembly 12, and commonly referred to as a skid steer loader, is shown adjacent to a work implement, a bucket 14. The present invention, a coupler assembly, can be used with any piece of mechanized equipment having a lift arm assembly and any type of work implement such as a bucket, blade, or fork assembly. 
     The bucket 14 is provided with an attachment structure 16 which defines at least one and preferably a pair of first, downwardly facing, recesses 18 and at least one and preferably a pair of second, upwardly facing, recesses 22. For ease of description the first recess is identified as the upper recess and the second recess is identified as the lower recess. These terms can be interchanged or replaced by other terms as desired. The first and second recess which can be defined by any suitable opening, open in opposite directions, i.e., one faces downwardly and one faces upwardly. Preferably the recesses open toward each other as shown in FIG. 1. 
     The first or downward facing recess 18 is preferably defined by a first or upper hook means such as one or more hooks 24 on the upper portion of the bucket 14. The second or upwardly facing recess 22 is preferably defined by at least one, preferably two second or lower hook means such as spaced apart lower hooks 26 on the lower portion of the bucket 14. Alternatively, the recesses can be defined by any suitable structure and opening including an elongated channel structure. As shown, the attachment structure 16 is defined by the four hooks which are preferably welded on the back of the bucket 14. 
     The coupler assembly also includes a frame member 32 adapted to be mounted on the lift arm assembly 12. The frame member preferably includes two spaced apart upright channel members 34 which mount on the lift arm assembly 12, and a plate 36 mounted, as by welding, on the channel members. The channel members can be defined by two upright bar members fixed on the plate 36. The channel members 34 and connection means 38 facilitate removably mounting the frame member 32 on lift arm 30 and lift motor 40 of the lift arm assembly 12. The channel members 34, together with the plate 36 also provide structural strength and integrity for mounting with the bucket. 
     The coupler assembly also includes first or upper latching means such as two upper latch members 42 on the channel members 34 and second or lower latching means including bar means 44. The upper and lower latching means cooperate with the attachment structure 16 and the recesses 18 and 22 to attach the bucket 14 on the frame member 32. The upper latch members 42 are preferably cylindrical and closely fit into the slots or recesses 18. Alternatively, the bar means 44 can be part of the upper latching means. 
     The bar means 44 includes a central or mounting portion 46 and at least one and preferably two end portions 48 opposite with respect to the central portion. The central or mounting portion is mounted on the frame member 32 as on the central portion of the plate 36. The end portions 48 are adapted to be received by and engage with the lower hooks 26 and the upwardly facing recesses 22. The lower hooks 26 preferably have an elongated slot configuration and a rounded end 28 to guide the bar into the recess. 
     The bar means is preferably a single round resilient spring steel bar 52 having the central portion 46 fixed on the plate as by retaining block 50 or welding. This prevents rotation of the central portion 46 as first one and then the other end of the bar is locked into position. Alternatively, the bar means 44 can be one or more bars pivotably mounted at the mounting portion 46. The bar means is preferably biased out of engagement with the upwardly facing recesses 22 as shown on the left side of FIG. 3. This biasing is preferably accomplished by the resiliency of the bar, but can also be done with appropriate spring means. Alternatively, the resiliency of the bar can be used to maintain the end portions 48 in engagement with the upwardly facing recesses 22. 
     The use of a single resilient bar is particularly advantagous. Unlike other devices which have complicated linkages to lock the bucket on the lift arm, the present invention uses a bar which is deflectable in an arcuate path. The bar can even provide its own biasing means. Thus, the present invention accomplishes with one part the same function for which other devices require several. This not only reduces the cost, but also provides easier and more certain operation with fewer breakdowns. 
     The coupler assembly is preferably provided with engaging means associated with the bar means 44 for maintaining the end portions 48 engaged with the upwardly facing recess 22. This engaging means is preferably a camming means 54 associated with each end portion 48 for driving the end portions into and maintaining the end portions in engagement with the upwardly facing recesses 22. The camming means 54 is preferably a cam 56 rotatably mounted on the frame member plate 36 near the end of the bar 52. This provides the greatest mechanical leverage for the camming means, insuring ease of operation as well as positioning the cam 56 and its handle 58 outside the channel members to provide easy access for the operator. 
     The cams 56 preferably have an over center locking position i.e. lobed to go over center, as shown in the righthand side of FIG. 3 which contacts a stop such as one of the upright channel members 34 to maintain the bar means 44 engaged with the upwardly facing recess 22. The bar means 44 and camming means 54 are preferably mounted on the lift arm assembly side of the plate 36. The frame member plate 36 can define openings 62 through which the lower hooks 26 extend to permit engagement by the bar means. 
     In operation, the skid steer loader is moved forward and the lift arm assembly 12 positioned so that the upper latch members 42 are received in the downwardly facing recesses 18. The bucket 14 is then raised off the ground on the upper latch members 42 and the bucket pivots on the members so it rests against the frame member plate 36. The lower hooks 26 then extend through the plate openings 62. The operator can then grip the handles 58 to rotate the cams 56 forcing the end portions 48 of the bar 44 into the upwardly facing recesses 22 as shown in the righthand section of FIG. 3. The bucket is then firmly attached to the vehicle and properly aligned for use. To remove the bucket, the cams 56 can be rotated to their unlocked positions as shown in the lefthand portion of FIG. 3, the bucket 14 lowered to the ground and the upper latch members 42 disengaged from the downwardly facing recesses 18. 
     The foregoing specification is intended as illustrative and is not to be taken as limiting. Still other variations within the spirit and scope of the invention are possible and will readily present themselves to those skilled in the art.