Abstract:
A roller cam with pairs of sliding surfaces and wear plates located in an upper plane and with pairs of laterally slanted sliding surfaces and pairs of laterally slanted guiding wear plates located in a lower plane. The guiding wear plates are longitudinally contained between end plates to avoid using screws, which might loosen under stress, to secure the wear plates. Adjusting setscrews are used to laterally adjust the guiding wear plates, and positive return members are used to provide a tool retracting force in addition to that provided by a retracting spring.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The invention relates generally to aerial and die-mount cams and more particularly to improvements in die-mount roller cams having wear plates configured and disposed to facilitate assembly with increased precision and to provide an increased load-bearing capacity and a prolonged useful life.  
         [0003]     2. Background Art  
         [0004]     Since many large presses are capable of exerting force in only a vertical direction, mechanisms have been developed to make efficient use of components of the vertical force to provide useful forces in other directions. These are used to operate tools for such manufacturing operations as punching, trimming, stamping and bending.  
         [0005]     Common among the mechanisms used are aerial and die-mount cams. Each of these typically includes three basic portions. An upper portion is connected to an upper shoe of a press, and a lower portion is connected to a lower shoe. A central portion, or slide, to which a tool can be secured, slidably resides between the upper and lower portions. If the upper portion is a cam adapter and the lower portion is a driver, the mechanism is commonly referred to as an aerial cam. If the upper portion is a driver and the lower portion is a cam adapter, the mechanism is referred to as a die-mount cam.  
         [0006]     The slide, with its attached tool, is driven in a nonvertical direction when the upper portion is forced vertically toward the lower portion by the press. If the tool is, for example, a punch, it will be driven through a workpiece, for example, a metal panel, under urging of the press. The punch is typically withdrawn from the metal panel as the slide is retracted under a stripping force provided by a return spring. Return springs are subject to failure, however, and such failures can damage the roller cam and workpieces. At best, failed return springs need replacement, resulting in press downtime.  
         [0007]     Wear plates are used between sliding surfaces that contact one another to reduce friction and increase element longevity. The wear plates must be capable of bearing the rated cam unit force supplied by the press and of dissipating thermal energy resulting from friction. Wear plates are typically secured in place with screws, and there is a danger that screws can become loose when brought under stress as a sliding surface is repeatedly forced against a wear plate and repeatedly forced to slide along it. Such an event could result in press downtime and damage to the roller cam and workpiece. Also, as their name implies, wear plates wear out with use and must be periodically replaced, which often requires disassembly and reassembly time.  
         [0008]     Many aerial and die-mount cams have wear plates that are mounted so that their working surfaces are laterally horizontal. These wear plates provide support for the slide but provide little resistance to lateral yawing or vertical pitching of the slide. Any amount of pitching or yawing of the slide is likely to result in a proportional amount of inaccuracy in directing a tool to its desired target.  
         [0009]     Commonly, present aerial and die-mount cams have profiles that are high enough to prevent their use in small presses. Many also have no provision for retracting their slides if the return springs used for this purpose jams or breaks.  
       SUMMARY OF THE INVENTION  
       [0010]     An object of the present invention is to provide an improved roller cam including components to initially adjust and thereafter maintain proportional wear plate load distribution. The present roller cam has a slide having a parallel pair of spaced apart lower sliding surfaces disposed in a first plane and a parallel pair of spaced apart upper sliding surfaces disposed in a second plane parallel to and above the first plane. The roller cam also includes a cam adapter having a pair of guiding lower wear plates slidably supporting the pair of lower sliding surfaces and a pair of upper wear plates slidably supporting the upper sliding surfaces. The lower sliding surfaces are laterally canted downwardly toward each other and the guiding lower wear plates have laterally canted surfaces that parallel and guide the lower sliding surfaces. A cam roller is rotatably supported by the slide and responds to a downward motion of the driver by advancing the slide along the cam adapter. A pair of adjusting setscrews are supported by the cam adapter such that, when the setscrews are advanced, one of the pair of guiding lower wear plates is forced laterally toward the other and into contact with one of the pair of lower sliding surfaces to initially adjust, and thereafter maintain, proportional wear plate load distribution.  
         [0011]     The roller cam further includes a driver having a linear cam surface angled relative to the vertical to force, in response to a downward motion of the driver, the slide along the cam adapter. A resilient member acting between the slide and the cam adapter biases the slide back toward its initial position. Additionally, positive return members are mounted on the driver to engage linear surfaces on keeper plates also mounted on the slide to ensure slide retraction.  
         [0012]     The slide moves along a channel in the cam adapter. The upper wear plates are fastened to the cam adapter atop respective rims of the channel. The guiding lower wear plates are contained along respective sides at the bottom of the channel by end plates secured within slots in the cam adapter and the upper wear plates. Locating the pairs of wear plates in two planes allows an increase in their total surface area, thus increasing their load-bearing capacity and their longevity. The canted guiding lower wear plates also allows an increase in their total surface area and further contributes increased lateral stability to the slide. Mounting the wear plates in separate planes also facilitates the fabrication of narrower roller cams having the same load-bearing capacity.  
         [0013]     The configuration of the roller cam provides convenient methods for its assembly and especially for assembling and adjusting the guiding lower wear plates. The use of slot-mounted end plates that contain the guiding lower wear plates requires no direct use of fastening devices such as screws, thus minimizing any possibility of a fastener loosening under stress. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]      FIG. 1  is a perspective view of a roller cam and illustrates a combination of a driver, a cam roller, a slide and a cam adapter;  
         [0015]      FIG. 2  is an exploded view, shown from an opposite perspective and including adjusting setscrews and a gas spring, of the roller cam of  FIG. 1 ;  
         [0016]      FIG. 3  is a side view, shown partially by hidden lines, of the roller cam of  FIG. 1 ;  
         [0017]      FIG. 4  is the side view, shown partially by hidden lines and partially broken away, of the roller cam of  FIG. 3 ;  
         [0018]      FIG. 5  is a cross-sectional view, taken on the line  5 - 5 , of  FIG. 4 ;  
         [0019]      FIG. 6  is a side view of an upwardly inclined cam adapter and slide of the roller cam of  FIG. 3 ; and  
         [0020]      FIG. 7  is a side view of the downwardly inclined cam adapter and slide of the roller cam of  FIG. 3 . 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0021]      FIG. 1  shows a perspective view of a representative die-mount roller cam, generally indicated by the reference numeral  10 , that includes a cam driving member, or cam adapter,  12 , a tool holding member, or slide,  14 , and a driver  16 . The cam adapter  12  is secured, typically by bolts passing through bolt holes  20 , to a lower die shoe  19  of a press (not shown). The driver  16  is similarly secured to an upper die shoe  21  of the press (not shown).  
         [0022]     The slide  14 , which has a front end, generally indicated by the reference numeral  26 , and a rear end, generally indicated by the reference numeral  28 , is sandwiched between the cam adapter  12  and the driver  16 . The slide  14  is configured to move, in response to a component of a vertically downward force provided by the press, in a linear path along supporting surfaces of the cam adapter  12  at a desired angle to the vertical path of the upper die shoe  21  of the press. Mounted to the front end  26  of the slide  14  is a representative tool holder  30  capable of holding any of a number of well-known tools such as punches or trimmers (none of which is shown).  
         [0023]     As illustrated in additional detail by  FIG. 2 , which is an exploded, reverse view of the die-mount roller cam  10  of  FIG. 1 , the driver  16  has first and second sides,  32  ( FIG. 1 ) and  34  ( FIG. 2 ) respectively, and a linear cam surface  36  ( FIG. 1 ), which is disposed at an acute angle α ( FIG. 1 ) relative to the vertical. First and second positive return members  38  and  40  are mounted on the respective sides of the slide  14  with fasteners such as screws  42 . At ends distal from the screws  42  securing the positive return members  38  and  40  are respective return flanges  44  and  45  that extend laterally away from the respective sides of the driver  16 .  
         [0024]     As best illustrated by  FIG. 5 , which is a cross-sectional view, taken on the line  5 - 5 , of  FIG. 4 , the slide  14  includes an upper portion, generally indicated by the reference numeral  46 , a central portion, generally indicated by the reference numeral  48 , and a lower portion, generally indicated by the reference numeral  50 . As shown by  FIGS. 1 and 2 , and additionally by  FIG. 5 , the upper portion  46  of the slide  14  houses an elongate, open cavity, generally indicated by the reference numeral  52 . The cavity  52  is defined between parallel, vertical, first and second parallel side walls,  54  and  56  respectively. A laterally extending cam roller shaft  58  ( FIG. 2 ) is supported between the first and second side walls  54  and  56 , and a cam roller  60  is axially supported for rotation about the cam roller shaft  58 .  
         [0025]      FIGS. 1 through 4  show elongate first and second keeper plates,  62  and  64  respectively, mounted on outer surfaces of the respective first and second side walls  54  and  56  of the slide  14  with fasteners such as screws  66 . As illustrated best by  FIGS. 3 and 4 , the first keeper plate  62  extends beyond the cam roller  60  to engage the first positive return member  38 . As shown by  FIGS. 2 and 3 , in the partially blocked view of the first keeper plate  62 , the inner side of the first keeper plate  62  has a relieved portion that leaves a linear surface  65 . The linear surface  65  is substantially parallel to the first return flange  44  of the first positive return member  38  to engage the first return flange  44  when the driver  16  moves upwardly. Although this feature is not shown, the second keeper plate  64  is configured in reverse of the first keeper plate  62  to engage the return flange  45  of the second positive return member  40 .  
         [0026]     As shown by  FIGS. 2 and 5 , the lower portion  50  of the slide  14  has first and second parallel sides,  68  and  70  respectively, that depend vertically from the central portion  48 . The lateral thicknesses of the upper portion  46  and of the lower portion  50  of the slide  14  are less than the width of the central portion  48 , over a rearward portion of the slide  14 , leaving first and second flange-like projections,  72  and  74  respectively, extending laterally in opposite directions above the lower portion  50 . Lower surfaces of the flange-like projections  72  and  74  form first and second upper sliding surfaces,  76  and  78  respectively. The lower portion  50  of the slide  14  also has a lower central slide surface  80  and further has first and second lower sliding surfaces,  82  and  84  respectively, that each angle laterally upwardly from an edge proximate the lower central slide surface  80  to an edge at a respective first and second parallel side  68  and  70  at an acute angle β ( FIG. 2 ) relative to the lower central slide surface  80 .  
         [0027]     As shown by  FIG. 2 , a resilient member, preferably a gas spring  86 , is mounted within a longitudinal bore  88  ( FIG. 5 ) in the front end  26  of the lower portion  50  of the slide  14 . The gas spring  86  extends from the bore  88 .  
         [0028]     The cam adapter  12  has a general configuration of a right prism having a longitudinal, open channel, generally indicated by the reference numeral  90 , extending through an upper portion from a front end, generally indicated by the reference numeral  92 , to a rear end, generally indicated by the reference numeral  94 , of the cam adapter  12 . The channel  90  is defined between vertical, first and second parallel side walls,  96  and  98  respectively, and a lower central channel surface  100  extending between the side walls.  
         [0029]     First and second upper wear plates, preferably self-lubricating wear plates,  102  and  104  respectively (the second upper wear plate not being shown in  FIG. 2 ), each having a generally rectangular cross-section, are secured atop the first and second side walls,  96  and  98  respectively, with any of a number of well-known fastening devices such as bolts  106 . First and second guiding lower wear plates, preferably self-lubricating wear plates,  108  and  110  respectively ( FIG. 5 ), each having a generally wedge-shaped cross-section, are supported by the lower central channel surface  100  and longitudinally extend respectively along the side walls  96  and  98 . The first and second guiding lower wear plates  108  and  110  have upper surfaces  112  and  114  that slope downwardly toward of each other.  
         [0030]     The sliding surfaces are formed of harder material than the wear plates. The sliding surfaces are typically formed of hardened steel and the wear plates, of self-lubricating bronze. Preferably, the wear plates each contain a plurality of lubricating plugs.  
         [0031]     The first and second guiding lower wear plates  108  and  110  are not retained in position by fasteners such as bolts, for example, that extend through the wear plates and into the cam adapter  12 . Rather, they are contained laterally between the side walls  96  and  98 , vertically between the lower central channel surface  100  and the slide  14 , and longitudinally between a cam adapter front plate  116  and first and second cam adapter rear end plates,  118  and  120  respectively. The cam adapter front plate  116  is retained within a lateral slot  122  in the front end  92  of the cam adapter  12  and within lateral slots,  123  and  125  respectively, in the upper wear plates  102  and  104 , the plate being secured to the cam adapter  12  by through-plate fasteners such as bolts  128  that extend through the front plate  116 . The first and second cam adapter rear end plates  118  and  120  are retained within lateral slots  124  and  126  in the rear end  94  of the cam adapter  12  and in lateral slots,  127  and  129  respectively, in the upper wear plates  102  and  104 , the plates being retained within the slots by through-plate fasteners such as bolts  128  that extend through the first and second rear end plates  118  and  120 . With this configuration, the slots absorb forces that might loosen the fasteners.  
         [0032]     The laterally sloping upper surfaces of the first and second guiding lower wear plates,  108  and  110  respectively, preferably do not extend sufficiently toward each other to terminate in sharp edges but rather form blunt surfaces  130  and  132  ( FIGS. 2 and 5 ) extending generally vertically between the lower central channel surface  100  of the cam adapter  12  and the sloping wear plate surfaces  112  and  114 . A pair of setscrews  134  extend laterally through the second side wall  98  to contact the second guiding lower wear plate  110 . Advancing the setscrews  134  forces the second guiding lower wear plate  110  toward the first guiding lower wear plate  108 .  
         [0033]     The first and second upper wear plates  102  and  104  have larger lateral dimensions than the side walls  96  and  98  upon which they are mounted, and portions of each extend laterally above a portion of the channel  90 . Accordingly, the slide  14  has first and second slots,  103  and  105  respectively, the upper surfaces of which form a an additional portion of the first and second upper sliding surfaces,  76  and  78  respectively. The wider wear plates  102  and  104  increase total wear plate surface area, and their disposition within the lateral slots  103  and  105  keeps the slide  14  against the cam adapter  12 . This inhibits the front end of the slide  14  from pitching upwardly and from rolling when the driver  16  applies a downwardly directed component of force to the rear end of the slide  14 , thus improving tool positioning accuracy.  
         [0034]     When a die-mount roller cam  10  is initially assembled, and the first and second upper sliding surfaces,  76  and  78  respectively, and the first lower sliding surface  82  of the slide  14  are resting upon the first and second upper wear plates,  102  and  104  respectively, and the first guiding lower wear plate  108  of the cam adapter  12 , the setscrews  134  are advanced so that the second guiding lower wear plate  110  just makes contact with the second lower sliding surfaces  84 . The foregoing procedure represents a quick and efficient method for accurately adjusting the positions of wear plates at the point of roller cam assembly without resorting to wearing in the wear plates, or to using precision machining, to ensure a proportional load distribution. The procedure and the configuration of the roller cam have also been developed with an intent to provide a quick and efficient method for subsequent replacement and adjustment of the wear plates at a work site.  
         [0035]     It will be understood by those skilled in the art that a second pair of setscrews (not shown) extending laterally through the first side wall  96  could be installed to urge the first guiding lower wear plate  108  toward the second guiding lower wear plate  110 . Such a small amount of lateral displacement is required to position the wear plates, however, that the second pair of setscrews are not likely to be necessary.  
         [0036]     In operation, when the driver  16  is forced vertically downwardly, the cam surface  36  of the driver  16  imparts a downward force against the cam roller  60  of the slide  14 . The cam roller  60  communicates a component of the downward force to the slide  14  in a direction that forces the slide  14 , and a tool (not shown) mounted in the tool holder  30  toward a workpiece (not shown). The first and second upper sliding surfaces,  76  and  78  respectively, of the slide  14  slide along the first and second upper wear plates,  102  and  104  respectively; and the first and second lower sliding surfaces,  82  and  84  respectively, slide along the first and second guiding lower wear plates,  108  and  110  respectively.  
         [0037]     As the driver  16  is forced downwardly and the slide  14  is advanced, the gas spring  86  is compressed against the front plate  116  of the cam adapter  12 . A tool, for example, a punch (not shown), is forced through a workpiece (not shown). When the driver  16  is raised, the gas spring exerts a force to retract the slide  14 . If the slide  14  fails to retract, the first and second positive return members  38  and  40 , being engaged with the linear surfaces  65  of the respective first and second keeper plates,  62  and  64  respectively, apply supplemental forces to ensure that the slide  14  is retracted.  
         [0038]     Providing wider upper wear plates  102  and  104  and guiding lower wear plates  108  and  110  for the cam adapter  12  shown by  FIG. 2  results in loads being distributed between two vertically displaced sets of wear plates. This allows an increase in their total surface area, with its attending increase in load-bearing capacity and longevity. Accordingly, the roller cam does not have to be as wide, therefore finding more applications in restricted operating locations, to manage the same load as a cam unit having the same total wear plate surface area but in the same plane. Conversely, a roller cam of the same width can manage higher loads due to a larger surface area over which to distribute the load. The canted guiding lower wear plates  108  and  110  also provide an increased total surface area relative to that of wear plates of the same width that are not canted. This not only increases their load-bearing capacity and longevity, it further provides increased lateral stability, thus improving tool positioning accuracy.  
         [0039]      FIGS. 6 and 7  illustrate die-mount roller cams  10  having cam adapters  12  that are representatively mounted at respectively upward and downward angles relative to the horizontal. Their operation would be similar to that of the roller cams  10  shown in previous figures; that is, a component of downward force applied by the press would force the slide  14 , and a tool (not shown) mounted in the tool holder  30  in the direction of a workpiece (not shown). The upward and downward angles are representative of those used to orient tools to perform typical operations such as punching, trimming, stamping and bending. To accommodate mounting the cam adapter  12  at different angles to the horizontal, the keeper plates  62  and  64 , positive return members  38  and  40 , and drivers  16  can be replaced with others having appropriate configurations.  
         [0040]     It will be understood by those skilled in the art that an inverted version of the roller cam, that is, with the cam adapter on the top and the driver on the bottom, could be constructed. Such a version would be an aerial cam.  
         [0041]     While embodiments of the invention have been illustrated and described, it is not intended that these embodiments illustrate and describe all possible forms of the invention. Rather, the words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the invention.