Hook load pin retention system
BACKGROUND OF THE INVENTION 
     Various attempts have been made to provide the simple and convenient arrangement for removably attaching a hook to a load lift chain. Of these, the simplest form would appear to involve forming the hook with a clevis whose legs are spaced apart sufficiently to receive the end link of a load chain and are through bored to receive a load pin, which is sized to be slip-fitted through the last link and to be end supported within the bore openings. 
     In these prior constructions, the load pins have been normally formed with either a circular or an oval cross-sectional configuration; the latter design serving to maximize shear strength and resistance to bending. Prior constructions of this type are disclosed for instance by U.S. Pat. Nos. 1,393,568 and 1,562,908. 
     SUMMARY OF THE INVENTION 
     The present invention is directed towards an improved hook load pin retention system and more particularly towards an improved clevis construction facilitating load pin assembly/disassembly operations, while minimizing the likelihood of unintentional removal of the load pin from operative engagement with the clevis and load chain during use of the hook. 
    
    
     DRAWINGS 
     The nature and mode of operation of the present invention is now more clearly described in the following detailed description taken with the accompanying drawings wherein: 
     FIG. 1 is a front elevational view showing a hook formed in accordance with the present invention in association with a load chain; 
     FIG. 2 is a side elevational view thereof; 
     FIG. 3 is a sectional view taken generally along the line 3--3 in FIG. 1; and 
     FIG. 4 is a sectional view taken generally along the line 4--4 in FIG. 2. 
    
    
     DETAILED DESCRIPTION 
     Reference is now made particularly to FIG. 1, wherein 10 generally designates a hook characterized as including integrally formed hook body and clevis portions 12 and 14, respectively, wherein clevis first and second leg portions 16 and 18, respectively, are shown as being spaced apart sufficiently to receive the last link 20 of a load chain therebetween. A load pin 22 is adapted to be removably inserted through last link 20 and have its opposite ends supportingly received within first and second aligned openings 24 and 26 of clevis leg portions 16 and 18, respectively, for the purpose of removably interconnecting the hook and load chain. 
     In accordance with the preferred form of the present invention, load pin 22 is of an oval cross-sectional configuration, wherein its widthwise, minimum dimension is slightly less than the width of space within last link 20, whereby to permit slip fitting of the load pin within last link 20, while constraining rotational movements therebetween. On the other hand, the heightwise, maximum dimension of load pin 22, is slightly less than the size of clevis leg portion openings 24 and 26, which are preferably &#34;bore&#34; openings of circular cross-sectional configuration, whereby to permit both rotational and sliding movements of the load pin relative to the clevis. This arrangement is preferable to prior constructions, which prevent rotation of oval load pins relative to the clevis and thereby cause all relative movements to occur between last link 20 and next to last link 28, such that the load chain is subject to nonuniform wear conditions. In the present construction wherein load pin 22 is journaled by the clevis, the problem of nonuniform chain wear is alleviated without substantially shortening the life of the load pin and/or the clevis due to the substantial bearing area therebetween and the ability to choose materials for the load pin and/or clevis having substantially greater resistance to wear than the material from which the chain is conventionally formed. It would be preferable, however, to limit wear to the load pin inasmuch as it may be of relatively inexpensive construction and easily replaced. 
     Further, in accordance with the present invention, a shield portion of abutment &#34;hood&#34; 30 is carried by leg portion 18 for the purpose of partially blocking or extending across the outer end of second bore opening 26, whereby to define an abutment arranged for engagement by the inserted end surface 22a of load pin 22, when the latter is inserted in succession through bore opening 24, link 20 and bore opening 26 during an assembly operation. However, shield portion 30 does not wholly block or cover the outer end of bore opening 26, thereby permitting insertion of a suitable tool, such as a drive punch, not shown, thereinto, for the purpose of forcing or driving load pin 22 from assembled relationship with clevis 14 and the last link 20 whenever the load pin has become worn and/or it is desired to disconnect the hook from the load chain. The illustrated configuration and positioning of shield portion 30 is nonetheless effective in preventing the unintentional engagement of external objects with inserted end surface 22a of load pin 22, during normal use of hook 10. More specifically, shield portion 30 is preferably formed integrally with leg portion 18 and arranged to project outwardly therefrom in a direction away from leg portion 16 and from adjacent its free or upper end in a direction downwardly towards hook body portion 12, as best shown in FIGS. 1 and 4. As best shown in FIG. 2, shield portion 30 is sized to overlie essentially one-half of bore opening 26 and is formed along its free or lower edge 32 with a drive punch receiving recess or notch 34 disposed essentially in alignment with the axis of bore openings 24 and 26. The term &#34;partially blocking&#34;, as applied to shield portion 30, is meant to additionally include a construction, wherein the shield portion completely bridges across bore opening 26 and is formed with an axially extending through opening sized to receive a load pin removing punch. 
     Now referring primarily to FIGS. 1 and 4, it will be understood that the lengthwise dimension of load pin 22 is such that its opposite or outer end surface 22b is disposed within and spaced inwardly from the outer end of bore opening 24, when load pin 22 is fully inserted to position its inserted end surface 22a in abutting engagement with shield portion 30. Load pin 22 may be removably retained in its fully inserted position by forming leg portion 16 with a third bore opening 36, which is arranged to extend in a transversely directed intersecting relationship with bore opening 24, and removably fitting a suitable retaining pin device 38 within bore opening 36 for engagement with load pin end surface 22b. Pin device 38 may be variously defined, as for instance by a roll pin, set screw or the like, but preferably has its opposite ends supported within bore opening 36, such that its mid portion is arranged to engage opposite end surface 22b. Upon removal of retaining pin device 38 by an operator, load pin 22 may be removed from assembled relationship with clevis 14 and last link 20 in the manner described above. 
     The above described construction is economical from the standpoint that load pin 22 may be formed of uniform cross-sectional material and need be only of a length sufficient to provide for proper bearing engagement of its ends with the surfaces of bore openings 24 and 26. Moreover, the present construction has the advantage that one end of load pin 22 is releasably retained within bore openings 24 and 26 by the expedient of forming leg portion 18 with integral shield portion 30, which although serving as a permanent abutment for the load pin and preventing unintentional engagement thereof with external objects during normal use of hook 10, nonetheless permits ready operator access thereto when required to remove same from coupling engagement with clevis 14 and last link 20. Further, the provision and arrangement of pin device 38 serves to shield this additional load pin retainer, as well as the opposite end of the load pin, from engagement with external objects during use of the hook, and does not require the simple construction of the load pin to be modified in any way for the purpose of cooperating with the retaining pin.