Adjustable wear pads for slotting head yoke plates
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to machinery for forming box blanks from corrugated paperboard sheet material. 
     2. Description of the Prior Art 
     Corrugated paperboard box blanks are fabricated from uniform corrugated sheet material by the selective placement of scores, slots and slits in a blank sheet. Such scores, slots and slits are applied by rotary dies or knives as individual sheet units are nip driven along a machine path between respective die or knife sets. 
     At commercial production rates and speeds, this material forming process represents severe service for the production machinery due to the strength, stiffness and abrasiveness of the process material. One consequence of such service severity is a tendency of the mating die and knife sets to laterally misalign under the operational stress. Cutting and scoring edges destructively clash together. 
     To reduce and control such damaging misalignment, these rotary units have been laterally stabilized with a thrust pad mechanism characterized as a &#34;yoke&#34; and &#34;head&#34; set. Each rotary die, knife or scoring wheel is integrally paired with a massive annular groove wheel called a &#34;head.&#34; A cooperative &#34;yoke&#34; includes two finger projections from an integral heel section that is secured to the machine frame. Tips of the finger projections mesh with the head groove space on diametrically opposite sides of the wheel unit. Pads or bearings secured to the stationary yoke tips side in contact with the rotating head groove walls. Lateral stress on the die, knife or scoring wheel is directly transferred to and resisted by the yoke fingers Simultaneously, however, wear loss of the finger pad material increasingly reduces the sliding contact bias against the head groove walls. After sufficient wear, the pads must be either replaced or repaired. Repair constitutes the insertion of a shim between the pad and the finger structure. In either case, repair or replacement, correction is time consuming and expensive due to the consequential loss of production time. 
     In recognition of this maintenance burden against corrugated box making machinery, the Gartech Manufacturing Co. of Litchfield, Ill. has introduced a stabilizer assembly design which includes two roller bearings mounted within each yoke finger in lieu of traditional wear pads. These two roller bearings are transversely positioned across the finger thickness whereby each outer race surface runs against a respective head groove wall. 
     Although the Gartech stabilizer assembly design is an effective solution to the maintenance burdens created by yoke trust pad wear, the design is sufficiently expensive to manufacture as to largely negate the maintenance savings from the design. 
     It is, therefore, an objective of the present invention to provide a corrugated box machine rotational stabilizer assembly that is both inexpensive to manufacture and requires no machine down time to adjust. 
     Another object of the present invention is to provide an adjustable thrust bearing mechanism for corrugated box machine rotational stabilizers that will fit within the dimensional confines of traditional head grooves and yoke fingers. 
     Another object of the present invention is to provide an adjustable thrust bearing mechanism for corrugated box machine rotational stabilizers that may be adjusted in a few minutes rather than several hours. 
     SUMMARY OF THE INVENTION 
     These and other objects of the invention are accomplished by means of expansible yoke pads. A plurality of disc shape pads are positioned on opposite faces of a yoke finger in the area of head groove space penetration. Both pad face sets are confined to laterally outward movement against the head groove walls by receptacle bore walls within a respective yoke finger. Receptacle bores within respective yoke fingers are axially continuous between opposite finger faces transversely of the finger face planes. Axially intersecting each dowel bore along the finger length is an elongated eccentric shaft. Inner ends of opposite pads are engaged by the eccentric shaft surface. 
     As the pad faces wear from sliding contact with the head groove side walls, the resulting clearance space is periodically closed by angular rotation of the eccentric shaft. A shaft rotational drive handle, knob or wheel is conveniently located for manual adjustment to minimize machine downtime. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Relative to the drawings wherein like reference characters designate like or similar elements throughout the several figures of the drawings: 
     FIG. 1 is an elevational view of a cooperative pair of box blank scoring wheels stabilized by the present invention; 
     FIG. 2 is a sectional end elevation viewed along the cutting plane of II--II in FIG. 1; 
     FIG. 3 is an elevational face view of a yoke finger equipped with a first embodiment of the invention; 
     FIG. 4 is an elevational end view of a yoke finger equipped with a first embodiment of the invention; 
     FIG. 5 is a perspective view of the first embodiment of the invention; 
     FIG. 6 is a perspective view of a second embodiment of the invention; 
     FIG. 7 is an elevational face view of a yoke finger equipped with a third embodiment of the invention; 
     FIG. 8 is an elevational end view of a yoke finger equipped with a third embodiment of the invention; 
     FIG. 9 is a perspective view of the third embodiment of the invention; 
     FIG. 10 is a schematic of the disc pad and eccentric relationship with minimum adjustment; 
     FIG. 11 is a schematic of the disc pad and eccentric relationship with moderate adjustment; and, 
     FIG. 12 is a schematic of the disc pad and eccentric relationship with maximum adjustment. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Corrugated box blank forming machines comprise a series of operating stations along a material travel route. Functionally, a blank sheet of corrugated board is cut to final blank size, side walls are segregated by slotting and slitting and fold lines are scored. Each of these operations is executed between a pair of axle shaft carried tool wheels. The tool wheels carry a respective operating tool, be it a die knife meshing with a die anvil or a score ridge meshing with a score groove. Rotation of the wheel carriage axles and placement of one or more operating tools around the wheel circumference is coordinated to apply the desired operation to the box blank as it advances between these wheels along the material travel route. 
     FIG. 1 illustrates a typical scoring station whereat a box blank portion B receives a score line 10 between a circular, tool wheel carried ridge 11 and a circular, tool wheel carried groove 12. It will be understood by those with skill in the art that in lieu of the scoring ridge and groove, the tool carrier wheels may just as well carry a die knife or die anvil. 
     Tool carriage wheels 13 and 14 are respectively driven rotatively by parallel axles 15 and 16. Each tool carriage wheel is provided with a grooved head wheel 17 and 18, respectively, and the two are rigidly unitized and secured to a respective axle. The grooves 19 and 20 respective to each head wheel 17 and 18 are formed between oppositely facing parallel groove walls 21 and 22. 
     For each head wheel, a yoke plate 30 and 31 is rigidly secured to a frame member 40 in planar alignment with corresponding head grooves 19 and 20. Each yoke plate 30 and 31 includes a pair of finger projections 32 and 33 from a heel base aligned within respective head grooves 20 and 19. Projecting from the opposite finger side faces are disc shaped pads 50 as shown clearly by the FIG. 2 section and the details of the remaining Figures. 
     Standard industry dimensions for this assembly include a head groove width of about 0.875 inch and a depth of about 1.25 inches. The yoke plate is about 0.625 inch thick to leave a 0.125 inch space between each yoke face and the adjacent groove wall. This 0.125 inch space is spanned by the pads. 
     The first embodiment of the invention shown in FIG. 5 provides a slot 34 along the finger projection length from the terminal end 35 to a transverse notch 36 between opposite face plates 38. This longitudinal slot 34 opens from the outside finger edge 37 opposite from the head wheel. Receptacle bores 39 are cut into the face plate 38 material along an axis that is transverse to the parallel outer planes of the face plates. 
     Within the longitudinal slot 34 is secured an eccentric rod assembly comprising an end bearing block 60, a mid-bearing block 61 and an eccentric shaft 62. A journal socket 63 in the end bearing block 60 receives one distal end 64 of the shaft 62 whereas journal socket 65 in the mid-bearing block 61 receives the other distal end 66 of the shaft 62. A transverse roll pin 67 confines the end bearing block 60 within the slot 34. 
     Mid-bearing block 61 is secured to the yoke structure by means of a cap screw 68. Cap screw 69 cooperates with slot 70 to clamp the eccentric shaft 62 in the desired angular position. The space represented by slot 70 intersects with the space represented by journal socket 65. Adjustment rod 71 penetrates eccentric shaft 62 to facilitate angular rotation and setting of the unit. 
     Dimensioned to a sliding fit within each receptacle bore space 39 is a disc shaped pad 50. The present embodiment of the invention provides four such pads 50 projecting from each yoke face. 
     Axially, each pad 50 is confined within its respective receptacle bore 39 by the adjacent head groove wall 21 or 22 and a longitudinal perimeter element of eccentric 62. With specific reference to the sequential schematics of FIGS. 10, 11 and 12, new, maximum thickness pads 50 are shown in FIG. 10 to be coordinated with a minimum eccentric diameter 72. Similarly, FIG. 11 shows moderately worn pads 50 to be biased apart by an intermediate eccentric diameter 73. FIG. 12 illustrates the eccentric 62 to be rotated to the maximum eccentric diameter alignment 74 between opposing pads 50. 
     A second embodiment of the invention, represented by FIG. 6, differs from the first embodiment by location of the eccentric adjustment means. As in the first embodiment, a longitudinal slot 34 is provided along the yoke finger projection length between opposite face plates 38. Pads 50 slide through respective receptacle bores 39 into contact with an eccentric rod 39. Midbearing block 42 seats one distal end of the eccentric rod whereas end-bearing block 44 rotatably confines the other rod end. Roll pins 43 secure the position of both bearing blocks within the slot 34. 
     This FIG. 6 invention embodiment locates the manual adjustment wheel 45 at the outer or distal end of the yoke finger 32. A split journal clamp 46 closed by a cap screw 47 secures the desired angular position of the eccentric 62. 
     The invention embodiment of FIGS. 7, 8 and 9 aligns a yoke finger slot 52 to open along one face of the finger assembly. The longitudinal slot 52 extends from the distal end of the finger 32 into a transverse through-slot 53. Disc pad receptacle bores 54 are of greater diameter than the slot 52 width thereby providing axial guideways for the pads 50 transverse of the yoke finger face. Along the slot 52 walls, these guideways take the form of fly cut channels. 
     Similar to the other embodiments, the pad adjustment eccentric 62 is unitized with an end bearing block 55 and a mid-bearing block 56. A manual adjustment wheel 57 secured to the end of the eccentric rod 62 is caged within the transverse slot 53 while the end-bearing block 55 is roll-pinned into finger slot 52. Cap screws 58 secure the mid-bearing block 56 to the yoke face and lock screw 59 clamps the desired angular position of the eccentric 62. 
     It will be noted that the pads 50 in all embodiments of the invention are provided with diametric slots 75 across the outer, head wheel groove engaging face thereof. Upon new installation, a temporary binder such as a band of rubber is passed around the yoke finger assembly and through the slots 75 for the purpose of retaining the bushing pads in the receptacle bores during the installation procedure. Once in place, the bushing pads 50 are externally confined by the head wheel groove walls 21 or 22. A retainer material such as rubber requires no specific removal step since operational heat of the machine will clear the retainer by ablation. 
     Having fully disclosed my invention, others of ordinary skill in the art may devise obvious mechanical equivalents to these specifically described preferred embodiments. As my invention, however,