Self-aligning and end fixity connector for connecting a hydraulic cylinder piston rod to its respective section in a multi-section telescopic boom assembly
This is a continuation of application Ser. No. 511,606, filed Oct. 3, 1974, now abandoned. 
    
    
     In multi-section telescopic boom assemblies, it is conventional to mount the respective hydraulic rams employed for extending and retracting each boom section in such a manner that the ram cylinder is mounted within and connected to one boom section which telescopically supports the next adjacent boom section to which the ram piston rod is connected. Since the cylinder is connected to one boom section and the piston rod is connected to another boom section, in order that there is no binding of the boom sections during the retraction thereof, there is a necessity to maintain a proper alignment between the respective points of connection of the cylinder to its boom section and of the rod to its boom section. 
     Heretofore, when the cylinder and rod components were pinned to their respective boom sections, the center lines of the two pinned connections became out of alignment which resulted in the binding of the boom sections thus preventing full retraction of one boom section within another. To provide the full retraction without binding, manufacturing tolerances had to be kept very small and strictly adhered to, until the industry went to a floating-type rod connection to overcome increased manufacturing costs of adhering to the required small manufacturing tolerances. The floating rod connection included a spring loaded roller bearing mounted on the end of the piston rod, and movable in a slot formed in a block mounted on the boom section. While this floating rod arrangement provided the necessary alignment between the cylinder connection and the rod end connection, the rod end connection was not maintained fixed; thus, the piston rod had a tendency to rotate about the horizontal transverse axis of the roller bearing. 
     It is well known in the stress art that column-loading can be greatly increased in a column when both ends of the column have end fixity. Thus, the column-loading of a multi-section boom has heretofore been somewhat limited due to the non-fixity of the floating rod connection. 
     After considerable research and experimentation, the rod connection of the present invention has been devised to not only provide the proper alignment between the cylinder connection and the rod connection but also to provide a fixity to the rod end whereby the column loading of the boom assembly is substantially enhanced. 
     The self-aligning and end fixity connector of the present invention comprises, essentially, a pair of rectangular plates secured to the free end of the piston rod, the plates being received in retainers secured to a boom section to thereby prevent the piston rod from rotating and thus providing end fixity to the rod. A clearance is provided between the plates and the retainers to allow a slight floating action of the rod in a vertical plane so that the rod connection point is substantially in alignment with the cylinder connection point to allow full retraction without binding of the boom sections. 
    
    
     In the drawings: 
     FIG. 1 is a fragmentary, sectional side elevational view of a multi-section boom assembly employing the self-aligning and end fixity connector of the present invention; 
     FIG. 1a is a fragmentary, sectional, side elevational view of a multi-section boom assembly with the hydraulic rams removed therefrom to show the retainer plates employed in the connector of the present invention; 
     FIG. 2 is a view taken along line 2--2 of FIG. 1; 
     FIG. 3 is a view taken along line 3--3 of FIG. 1; and 
     FIG. 4 is a view taken along line 4--4 of FIG. 2. 
    
    
     Referring to the drawings and more particularly to FIG. 1, multi-section telescopic boom assemblies, such as, four-section assemblies, include a base section 1 slidably receiving an inner mid section 2 which, in turn, slidably receives an outer mid section 3 which slidably receives a fly section 4, the sliding movement between adjacent sections being facilitated by suitable bearing pads 5. The base section 1 is provided with a bracket 6 through which the boom assembly is pivotally connected to a support platform (not shown) for movement in a vertical plane to elevate and lower the boom assembly. Hydraulic rams are usually provided for this movement of the boom assembly in the vertical plane, and additional hydraulic rams are provided for telescopically moving the boom sections with respect to each other. While FIG. 1 shows only rams 7 and 8 for respectively moving the inner mid section 2 relative to the base section 1, and the outer mid section 3 relative to the inner mid section 2, it will be understood by those skilled in the art that another hydraulic ram is connected between the outer mid section 3 and the fly section 4 for sliding the fly section relative to the outer mid section. The rod end 7a of ram 7 is connected to the base section 1 as at 10 and its cylinder 7b is connected to the inner mid section 2 as at 11. The ram 8 is similarly connected to the inner and outer mid sections at 12 and 13, respectively. By this construction and arrangement, when the rams are actuated to either extend or retract the boom sections, the rods 7a and 8a are maintained substantially stationary and the cylinders 7b and 8b are caused to slide relative to their respective rods, the sliding movement of the cylinders with respect to each other and the boom sections being facilitated by suitable skids 14 and 15. 
     The details of the construction of rod end connection 10 are illustrated in FIG. 2, wherein it will be seen that a pair of spaced, parallel plates 10a are positioned between and welded to the bottom wall 1a of boom section 1 and a top wall 1b extending between the side walls of the boom base section. The free end of the piston rod 7a is provided with a block member 7c having depending plate members 7d welded to the side faces thereof and disposed adjacent the inwardly facing sides of the plates 10a. The plate members 7d are positioned within recesses formed by rectangular frame members having integral end and side walls 10b, 10c, FIG. 1a, welded to the inwardly facing sides of the plates 10a, the plate members 7d being retained in the recesses by side walls 10d secured to the side plates 10a by suitable bolts 10e. While the side edges of the rod plates 7d engage the corresponding side walls 10 c and 10d of the rectangular frame members, as seen in FIG. 4, there is a slight clearance between the upper and lower edges of the plates and the end walls 10b as shown in FIG. 2. 
     Referring to FIGS. 1a and 3, the connection 11 through which the ram cylinder 7b is connected to the inner mid section 2 comprises a collar 11a secured to the outer surface of the cylinder 7b and having trunnions 11b mounted within circular apertures formed in plates 11c. The plates 11c are secured by bolts 11d to the inwardly facing sides of spaced, parallel plates 11e positioned between and welded to the bottom wall 2a and top wall 2b of boom section 2. 
     The connections for securing ram 8 to its respective boom sections are identical to those described above with regard to the connections for ram 7; suffice it to say that the depending rectangular plates 8d are received within the recesses formed by the frame members 12c, 12d, FIG. 1a, secured to the inwardly facing side walls of plates 11e, and the ram cylinder 8b is trunnioned to boom section 3 through apertured plates 13c secured to the side walls of the outer mid section 3. In the rod connection shown at 12, since the frame member 12c is located adjacent the bottom wall of the inner mid-section 2 the bottom wall of the boom section 2 functions as one end wall portion of the frame member 12c so that this frame member is L-shaped rather than C-shaped according to frame member 10b, 10c. With this arrangement, removable frame member 12d is also shorter in length than comparable frame member 10d of connection 10, but the recesses formed for the plate members 7d and 8d within the respective frame members are of the same size such that these plate members 7d and 8d are free to slide, very slightly, up and down in the vertical direction relative to the side walls of the frame members 10c, 10d and 12c, 12d, respectively, to allow slight floating action of the rod ends in vertical plane so that the rod connection is maintained in substantial alignment with the cylinder connection point without binding during operation of boom. 
     From the above description, it will be readily apparent to those skilled in the art that the rod end connections 10 and 12 provide an end fixity to their respective piston rods 7a and 8a since the plate members 7d and 8d are retained within their respective recesses and since the piston on the rods extend somewhat inside the cylinder, the piston rods are prevented from rotating. Thus by substantially fixing opposite ends of the ram piston rods in this manner, the column loading of the rods and associated boom sections is greatly increased.