Abstract:
A cam mechanism incorporating a highly precise bearing structure that improves the dynamic stability of the cam mechanism&#39;s rotating output component. Relevant structures consist of a worm gear driven rotating shaft driving a rotating output shaft supported by a cross roller bearing assembly incorporating V-shaped inner and outer bearing races that sandwich and ride over a set of rollers. Of particular note is that the outer or inner bearing race may be formed as a groove machined directly into the circumferential surface of the output shaft. Because the outer bearing race is a ring-shaped structure that concentrically surrounds the rotating output shaft, the output shaft and bearing races can be machined simultaneously as a single workpiece to assure a high degree of concentricity between the shaft and bearing races.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The invention relates to a cam mechanism that incorporates a highly precise bearing assembly capable of significantly improving the dynamic and static positional stability of the cam mechanism&#39;s output shaft.  
           [0003]    2. Description of the Current Art  
           [0004]    Various types of intermittent indexing-type cam mechanisms are currently known in the art. These cam mechanisms incorporate input and output shafts as means of transferring torque into and out of the cam mechanism, and two bearings, axially aligned with and located at each of the input and output shafts as means of supporting both thrust and radial loads applied during operation of the cam mechanism. Tapered roller bearings are generally used in cases where the input and output shaft s must operate with a high degree of precision.  
           [0005]    [0005]FIGS. 20 and 21 show cam mechanism  1   a  in which input shaft  4  is rotatably supported at both ends by tapered roller bearings  3  mounted in housing  2 . Globoid cam  5  is axially formed on input shaft  4 . Output shaft  7 , whose rotating axis is offset 90-degrees in relation to that of input shaft  4 , is rotatably supported by tapered roller bearings  6  mounted at both ends of the shaft and supported by housing  2 . Turret  9  is installed to or integrally formed as part of output shaft  7  and incorporates cam followers  8  installed in a radial pattern on the axial perimeter of shaft  7 . Turret  9  and cam followers  8  are dimensioned so as to allow cam followers  8  to mesh with spiral channel  10  of globoid cam  5 . The rotation of input shaft  4  results in the rotation of output shaft  7  by means of cam followers  8  following the transverse movement of globoid cam valley  10 .  
           [0006]    [0006]FIGS. 22 and 23 illustrate the structure of cam mechanism  1   b  which, similar to cam mechanism  1   a,  incorporates input shaft  4  and output shaft  7 . In cam mechanism  1   b , output shaft  7  is formed as a ring-type structure that radially encompasses hollow cylindrical part  11  integrally formed at the center of housing  2 . Radial and thrust loads applied to output shaft  7  are born by housing  2  as will be explained. Multiple first cam followers  12  are installed in a radial pattern on the perimeter of the inwardly facing radial surface of input shaft  7 . First cam followers  12  slide along cylindrical surface  13  provided by housing  2  as means of bearing radial loads applied to input shaft  7 . Second cam followers  8  are installed to the outwardly facing perimeter of output shaft  7  and are located so as to mesh with cam valley  10  of globoid cam  5 . Support piece  15 , structured so as not to interfere with the rotation of globoid cam  5 , is installed within housing  2 , and ring flange  16 , formed as part of housing  2 , is located radially opposite to support piece  15 . Second cam followers  8  pass through the space provided between support piece  15  and ring flange  16 , thus forming a structure whereby support piece  15  and ring flange  15  are able to bear the thrust loads applied to output shaft  7 . Torque applied to input shaft  4  is transferred to output shaft  7  through the rotation of globoid cam  5  driving cam followers  8 , thus providing a mechanism through which the desired rotational position of output shaft  7  is controlled through the rotation of input shaft  4 .  
           [0007]    Modern industry is being called upon to produce various types of components that must be made smaller and to more precise dimensions. This requirement has resulted in a demand for cam mechanisms that are able to operate with an extremely high degree of precision. It is proving difficult to make conventional cam mechanism structures operate with the degree of precision now required by many industrial applications. Even with the use of precision tapered roller bearings, conventional cam mechanisms cannot provide the high degree of operating precision called for in certain applications. This problem is the result of using standard commercial grade bearings in the construction of the cam mechanism, the difficulty of machining the housing, turret, and output shaft flanges to extremely tight tolerances, the difficulty of maintaining the required dimensions during assembly, and a general fall-off in dimensional accuracy that results from a combination of problems encountered during the manufacturing process. As a result, manufacturers often need to disassemble cam mechanisms that don&#39;t perform to specification, check and re-machine components, and re-assemble the cam mechanism to ascertain if the required operational specifications have been met.  
           [0008]    A major problem encountered with the use of standard roller bearings is that the bearing is unable to deliver adequate performance after being installed as a component of the cam mechanism. The following discussion will explain some of the shortcomings that can be encountered when installing a roller bearing into the cam mechanism.  
           [0009]    1: One problem is that gap can be generated between the axial surface of output shaft (a) and the inner circumference of the bearing race. Although the perimeter of output shaft (a) and the inner diameter of race (c) may be fabricated to perfectly concentric shapes, gap (d) can exist, as illustrated in FIG. 24, after the cam mechanism is assembled as a result of the diameter of inner race (c) being fabricated to a slightly large diameter. The operating precision of the cam mechanism is thus adversely affected due to gap (d) causing the misalignment of centerline (e) of output shaft (a) with centerline (f) of bearing (b). Moreover, variations in the radial load may continually change the position of gap (d), thus creating abrasion between output shaft (a) and inner race (c), a problem that results in a shortened service life for the cam mechanism.  
           [0010]    2: There is also a problem in that the perimeter of output shaft (a) cannot always be made to a perfectly concentric shape. In order to prevent a gap from forming between the output shaft and bearing race (see the preceding paragraph), some cam mechanisms utilize press fit tolerances in the assembly of output shaft (a) to bearing (b). As shown in FIG. 25, an eccentrically shaped cross section of output shaft (a) can be transferred the inner race (c) of bearing (b) as a result of the press fit, thus distorting bearing race surface (h) that was fabricated to the specified shape and tolerances. As a result of the distorted contours of bearing race surface (h), excessive pressure is applied to some rollers (g) while others fail to contact the race surface, thus creating an eccentric roller path that degrades the bearing&#39;s rotating accuracy and makes it difficult for the cam mechanism to operate with a high degree of precision. Moreover, excessive pressure applied between rollers (g) and race surface (h) causes excessive wear that shortens the service life of the cam mechanism.  
           [0011]    3: Another problem that can arise is an eccentric shape of the inner surface of race (c) that results in the inner contour of the race not accurately matching the perimeter contour of output shaft (a). FIG. 26 provides a view of bearing (b) before (Figure a) and after (Figure b) insertion of output shaft (a) into the bearing race. Even though output shaft (a) may be formed to perfect concentricity, inserting the output shaft into the eccentrically shaped internal diameter of race (c) will transfer the eccentric shape to the race surface (h) and thereby distort the race and bearing surface on which the rollers ride (Figure b).  
           [0012]    4: Furthermore, it can prove difficult to maintain an accurate 90-degree angle between output shaft (a) and seating surface (i) of bearing (b). As shown in FIG. 27, radial flange (j) is provided on output shaft (a) as means of locating bearing (b). In cases where the machining process utilized to form flange (j) leaves metal particles or other debris on the flange surface, bearing (b) will not seat completely by becoming slightly cocked on the shaft, a problem that will result in a falloff of the rotating precision of the cam mechanism&#39;s output shaft resulting from the misalignment of center (e) of output shaft (a) and center (f) of bearing (b).  
           [0013]    The preceding discussion explained the problems that can arise when mounting roller bearing (b) to output shaft (a). These problems can occur even when using high grade bearings, thus making it difficult to maintain precision operation of the cam mechanism&#39;s output shaft. In light of these shortcomings, there is a pronounced need in the art for an improved bearing structure that will assure and maintain high precision operation of the cam mechanism.  
         SUMMARY OF THE INVENTION  
         [0014]    The invention puts forth a structure for a cam mechanism whereby an improved bearing structure is utilized as means of obtaining highly precise dynamic rotation and static positioning of the cam mechanism&#39;s output shaft.  
           [0015]    The cam mechanism put forth by the invention is comprised of a cam driven rotating shaft and a cross roller bearing installed to a support structure, the cross roller bearing being provided as means of rotatably supporting the rotating shaft. Said cross roller bearing is comprised of a V-shaped outer race, a V-shaped inner race, multiple rollers located between the race parts, a roller retainer part located between the inner and outer races, and a circumferential groove, existing as the V-shaped groove of the internal or outer race, formed concentric with the rotating axis of the rotating shaft.  
           [0016]    Because the circumferential groove can be formed in either the inner or outer race and concentrically located around the rotating axis of the rotating shaft, it becomes possible to machine the inner or outer race concentrically to the same center as the rotating shaft because the machining of the inner or outer race can be executed together with the machining of the rotating shaft itself with either one of the races attached to the rotating shaft. This structure establishes a high degree of concentricity between the bearing components and rotating shaft and thus eliminates the need to use of standard commercially available roller bearings that often exhibit defects such as imperfectly formed races and eccentrically shaped race surfaces. As the inner or outer race can be machined together in the same process applied to machine the rotating shaft, the difficulty of obtaining the desired performance from a cam mechanism using conventional roller bearings is eliminated, thus allowing the manufacture of a cam mechanism able to operate with a higher degree of precision.  
           [0017]    An important characteristic of the invention is that the circumferential groove can be directly formed on the outer or inner perimeter of the rotating shaft simultaneously with the machining of the rotating shaft itself. During the machining process the radial center of the inner or outer races can be formed in perfect concentricity with the radial center of the rotating shaft, thus creating a bearing and rotating shaft structure capable of operating with an extremely high degree of dynamic and static precision.  
           [0018]    A primary characteristic of the invention is that the rollers, in addition to being located between the inner and outer races, have their axial centers inclined toward the axial center of the rotating shaft, and are arranged in a radial pattern in which the axial center of each roller is inclined toward the axial center of the rotating shaft at an angle 90-degrees different than that of the adjacent roller. This structure thus allows a single cross roller bearing assembly to support both the thrust and radial loads applied to the rotating shaft during the operation of the cam mechanism. Moreover, the relatively simple construction of the cross roller bearing largely eliminates the possibility of assembly errors during manufacture of the cam mechanism. A further benefit is that the roller retainer is securely maintained in position during rotation, without any play or looseness, due to the rollers supporting the retainer through their 90-degree alternating axial centers.  
           [0019]    The invention is characterized by the provision of oil channels formed in the inner and outer races as means of both supplying oil to and discharging oil away from the rollers.  
           [0020]    The invention is characterized by the rotating shaft being made of a highly rigid material that, due to its minimal distortion under load, allows the inner or outer race to be machined to a high degree of concentricity in relation to the rotating shaft because either race is installed to the shaft, or be integrally machined as part of the shaft, during the machining process. This structure and process are thus able to eliminate the bearing distortion that can be encountered when using a commercially available roller bearing assembly with an imperfectly formed inner race.  
           [0021]    The invention is characterized by the rollers being cylindrical shape with both ends being flat and in parallel alignment.  
           [0022]    The invention is characterized by a structure in which the inner and outer races provide means of supporting and guiding the rotation of the rollers through a particular structure wherein one side of the V-shaped race contacts the load bearing surface of the roller and the other side of the race does not contact the roller, but establishes a gap between the race and the end surface of the roller. This type of roller placement provides for a highly precise low-friction rotating bearing action between the rollers and races.  
           [0023]    The invention is further characterized by multiple pocket orifices formed within the bearing retainer part, each pocket orifice providing means of positionally maintaining a roller within the retainer part and thus allowing the rollers to rotate without mutual contact.  
           [0024]    The internally facing edges of the pocket orifices are formed with chamfered lip parts that run along the cylindrical bearing surface of the roller installed in the retainer part. This chamfered lip part establishes a specific path through which the roller can be inserted at the appropriate angle into the retainer part, and also provides a part that positionally supports the roller within the retainer part. Moreover, the lip part eliminates the need for clearance between the internal edges of the roller pocket and the roller, thus reducing play between the rollers and retainer part and providing means whereby the cam mechanism can operate with a greater degree of precision.  
           [0025]    The inwardly facing edge of the pocket orifice is also concave in cross section, the concave part being formed concentrically with the cylindrical bearing surface of the installed roller. The roller may come into contact with the concave edges of the pocket orifice, or else uniform clearances can be established between the roller and concave pocket edges as means of maintaining an adequate oil film for bearing lubrication, thus further enhancing the operating precision of the cam mechanism.  
           [0026]    A further characteristic of the invention is that the outer race is formed as a ring-shaped structure that surrounds the rotating shaft which is secured to the support structure. In cases where it may be difficult to form the outer race directly into the housing, a ring shaped structure formed separately from the housing may be utilized as an aid in fabricating the outer race to a high degree of dimensional accuracy.  
           [0027]    The separate ring-shaped structure may be formed of multiple overlapping plates that constitute the outer race, thus providing for an assembly process in which the rollers can be easily inserted between the inner and outer races supported by the retainer part there between. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWING  
       [0028]    [0028]FIG. 1 is a cross sectional view of an embodiment of the bearing structure of the invention.  
         [0029]    [0029]FIG. 2 is a plan view of the rollers and roller retainer part of the bearing structure shown in FIG. 1.  
         [0030]    [0030]FIG. 3 is a detailed cross sectional view of an embodiment of the cross roller bearing structure shown in FIG. 1.  
         [0031]    [0031]FIG. 4 is a detailed cross sectional view of an embodiment of the cross roller bearing structure shown in FIG. 1 differing from the embodiment shown in FIG. 3.  
         [0032]    [0032]FIG. 5 shows two types of bearing and retainer assemblies for explanatory purposes.  
         [0033]    [0033]FIG. 6 shows the assembled roller bearing and bearing retainer structure as presented in FIG. 1.  
         [0034]    [0034]FIG. 7 shows two possible embodiments of the assembled roller bearing and bearing retainer structure presented in FIG. 1.  
         [0035]    [0035]FIG. 8 shows one embodiment of the cam mechanism incorporating the bearing structure presented in FIG. 1.  
         [0036]    [0036]FIG. 9 is a cross sectional view of a different embodiment of the cam mechanism incorporated the bearing structure presented in FIG. 1.  
         [0037]    [0037]FIG. 10 is a plan view of a rotating table incorporated in the cam mechanism utilizing the bearing structure shown in FIG. 1.  
         [0038]    [0038]FIG. 11 is a cross sectional view taken from line Z-Z of FIG. 10.  
         [0039]    [0039]FIG. 12 is an explanatory diagram of the assembled bearing structure and output shaft of the cam mechanism shown in FIG. 8.  
         [0040]    [0040]FIG. 13 is a cross sectional view of the assembled bearing structure and output shaft of the cam mechanism shown in FIG. 8.  
         [0041]    [0041]FIG. 14 is an explanatory diagram of another type of assembled bearing structure and output shaft of the cam mechanism shown in FIG. 8.  
         [0042]    [0042]FIG. 15 is a cross sectional view of another type of assembled bearing structure and output shaft that can be incorporated into the cam mechanism shown in FIG. 8.  
         [0043]    [0043]FIG. 16 is a cross sectional view of the assembled bearing structure and output shaft of the cam mechanism shown in FIG. 9.  
         [0044]    [0044]FIG. 17 is a cross sectional view of another type of assembled bearing structure and output shaft that can be incorporated into the cam mechanism shown in FIG. 9.  
         [0045]    [0045]FIG. 18 is a cross sectional view of another type of assembled bearing and output shaft structure that can be incorporated into the cam mechanism shown in FIG. 9.  
         [0046]    [0046]FIG. 19 is a cross sectional view of another type of assembled bearing and output shaft structure that can be incorporated into the cam mechanism shown in FIG. 9.  
         [0047]    [0047]FIG. 20 is a lateral cross section of the output shaft assembly of a cam mechanism of the type currently known in the art.  
         [0048]    [0048]FIG. 21 is a plan cross section of the cam mechanism shown in FIG. 20.  
         [0049]    [0049]FIG. 22 is a lateral cross section of the output shaft assembly of another type of cam mechanism currently known in the art.  
         [0050]    [0050]FIG. 23 is a lateral cross section of the cam mechanism shown in FIG. 22.  
         [0051]    [0051]FIG. 24 is a diagram depicting one of the problems of a conventional bearing structure.  
         [0052]    [0052]FIG. 25 is a diagram depicting another problem of a conventional bearing structure.  
         [0053]    [0053]FIG. 26 is a diagram depicting still another problem of a conventional bearing structure.  
         [0054]    [0054]FIG. 27 is a diagram depicting an additional problem of a conventional bearing structure. 
     
    
     DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0055]    The following discussion will explain various embodiments of the invention with reference to the attached figures. FIGS. 1 through 4 depict the cross roller bearing structure invention utilized by the cam mechanism  
         [0056]    Generally, a cross roller bearing utilizes multiple cylindrical rollers arranged in alternating axial positions to form a radial pattern. The rollers are uniformly spaced and located between a rotating part and a supporting part with the rotating part maintaining the supporting part, thus forming a structure in which a radial gap is established between the aforesaid rotating part and supporting part. The rollers, for example, may rotate against an inner race formed on an internal ring installed to an internally located rotating part, and against an outer race formed on an external ring installed to an externally located supporting part. In cases where the rotating part radially encompasses the supporting part, the inner ring may be installed to the supporting part, and the outer ring to the externally located rotating part. In a cross roller bearing assembly, the axial centerlines of the rollers are inclined at a specific angle in relation to the rotating part with the axial centerline of each roller being inclined at a different angle in relation to that of the adjacent rollers. A roller bearing retainer is used to locate and support the rollers between the internal and external races. The type of cross roller bearing structure explained above is well known in the art.  
         [0057]    [0057]FIGS. 1 through 4 provide a graphic illustration of the specific type of cross bearing structure utilized by the invention. Each of multiple rollers  23  incorporate cylindrical bearing surface  21  and parallel end faces  22  located at both ends of cylindrical surface  21 . In this embodiment the rotating part is comprised of turret  9  to which cam followers  8  are installed circumferentially on the radial axis. Rollers  23  are located between turret  9  and space  24  of housing  2  in a radial pattern with uniform spaces provided there between. Inner race  25  is formed on the radial circumference of turret  9 . Ring plate assembly  26 , which incorporates outer race  27 , is fixedly attached to housing  2  within space  24  and surrounds the radial circumference of inner race  25 . Rollers  23  are in contact with and rotate between inner race  25  and outer race  27 . Furthermore, as shown in FIGS. 3 and 4, axial centerline x 1  of roller  23  is inclined toward axial centerline x 2  of turret  9 , and axial centerline x 1  of the adjacent roller  23  is inclined in the opposite direction toward axial centerline x 2  of turret  9 , thus forming a pattern in which the axial centerline of each roller is inclined in the opposite direction in relation to the adjacent rollers. A space is provided between the circumference of turret  9  and ring plate assembly  26  as means of providing clearance for the installation of thin cylindrical shaped retainer  28  that supports rollers  23 . Multiple uniformly spaced pocket orifices  29  are formed within retainer  28  as means of locating each of rollers  23 .  
         [0058]    Although not completely shown in FIGS. 1 through 4, cam followers  8  are installed to the circumference of turret  9  in a radial pattern at mutual uniform intervals, and are located so as to mesh with a roller gear cam part of the cam mechanism. Ring boss  30  is fixedly installed to the exposed face of turret  9 , its radial perimeter located diametrically inward of the turret perimeter as means of providing a sealing surface for ring-shaped oil seal  31  which resides between perimeter ring  30  and ring plate assembly  26 . Ring plate assembly  26  is comprised of outer ring plate  32  and inner ring plate  33 , plate  33  being concentrically located and installed beneath outer ring plate  32 . Inner ring plate  33  is concentrically aligned within outer ring plate  32 , and a gap is maintained between the facing surfaces of the two plates. Radial flange  34  extends from the perimeter of outer ring plate  32  to provide means by which clamp bolts  35  can be used to fixedly secure ring plate  32  to housing  2 . Ring-shaped oil seal  31  is in contact with the inner perimeter of outer ring  32  and the outer perimeter of flange  34 . Inner ring plate  33  is secured to outer ring plate  32  through bolts  36 .  
         [0059]    Outer race  27  is formed by the juxtaposition of the chamfered inner edge of outer ring plate  32  and chamfered outer edge of inner ring plate  33 , the chamfered surfaces forming a V-shape in cross section. Outer race  27  is inclined toward axial center x 2  of turret  9  to provide a contact face for the cylindrical surface of axially inclined roller  23 , while race surface  22  maintains a clearance from the radial end surface of roller  23 . Race  27  is thus able to provide an external support path for the rotation of roller  23 .  
         [0060]    Similarly, V-shaped inner race  25 , formed on the radial surface of turret  9  facing outer race  27 , provides both race surface  21  on which axially inclined roller  23  rotates, and surface  22  that maintains a clearance from the radial end face of roller  23 , thus providing an internal support path for the rotation of roller  23 . Internal race  25  is structured as a circular channel, V-shaped in cross section, formed directly into the circumferential surface of turret  9 .  
         [0061]    Narrow circular channel  37  is provided at the bottom of outer race  27  and inner race  25  as means of supplying and discharging lubricating oil to and from roller  23 .  
         [0062]    Pocket orifices  29  are provided in bearing retainer  28 , each pocket orifice incorporating a tapered lip  38  that extends over cylindrical surface  21  of roller  23  as means of partially supporting and locating roller  23 . When roller  23  is installed to retainer  28 , cylindrical bearing surface  21  is maintained in contact with tapered lip  38  while radial end surface  22  is inclined toward orifice  29 . Moreover, as tapered lip  38  is oriented in an alternate direction for each adjacent orifice  29 , rollers  23  are only able to be inserted in the direction prescribed by the orientation of the tapered lip, thus allowing insertion of each roller  23  in only one specified and correct orientation. In other words, the structure of the bearing retainer establishes the correct orientation for the insertion and positioning of each roller, and maintains each roller in the appropriate axial orientation for assembly to the cam mechanism.  
         [0063]    In a cam mechanism of the type that utilizes cross roller bearing assembly  20 , it is desirable that inner race  25  be machining directly into the circumference of turret  9  at the same time that turret  9  itself is being machined. This method assures that the axial center of inner race  25  will be concentric with rotating center x 2  of turret  9 . In other words, inner race  25  is machined to the same center as turret  9  the same time that the turret  9  itself is machined.  
         [0064]    Moreover, as turret  9  is fabricated from rigid high-strength steel, inner race  25  can be formed to a perfect circular shape with minimal process-induced distortion. This fabrication method eliminates the imperfections and dimensional imprecision commonly found in the inner races of standard commercially available roller bearing assemblies.  
         [0065]    This type of cross roller bearing assembly put forth by the invention eliminates many of the deficiencies that have been responsible for the imprecise operation of conventional roller bearing assemblies, and allows the fabrication of a cam mechanism able to operate with an extremely high degree of precision.  
         [0066]    Furthermore, because roller rotating axis x 1  is inclined in relation to rotating axis x 2  of turret  9 , and because rotating axis x 1  is inclined in an alternating direction for each successive roller, a single cross roller bearing assembly is able to support both radial and thrust loads applied to the turret, thus providing for a simplified cam mechanism structure that can be fabricated with fewer manufacturing errors.  
         [0067]    Moreover, in regard to the structure of the pocket orifice  29 , FIG. 5 a  shows a bearing retainer pocket orifice formed larger than roller  23 . This structure allows the roller to reside in the pocket in non-specific orientation, so the roller is able to move within the pocket orifice, thus resulting in a certain amount of bearing play. Moreover, bearing play is also generated because the pocket orifice is unable to restrain the position of the roller. Furthermore, as shown in FIG. 5 b,  the lubricating oil film can be easily broken as a result of the narrow line of contact between roller  23  and orifice  29 .  
         [0068]    [0068]FIG. 6 a  illustrates the bearing retainer structure put forth by the invention in which tapered lip  38  largely eliminates the gap between the roller and retainer, thus better stabilizing the rotational movement of the roller. Moreover, as shown in FIG. 7, each tapered lip in the retainer locates the roller on an axis different to that of the adjacent roller, thus preventing both unnecessary movement of bearing retainer  28  and the possibility of retainer  28  coming into contact with turret  9  or ring plate assembly  26 . Furthermore, as shown in FIG. 6 b,  the end surface of lip  38  may be formed to a concave shape in cross section, a shape that may closely follow the round contour of the cylindrical bearing surface of roller  23 . This concave contour, which can be formed so as to either contact the roller or establish a small clearance around it, provides means by which the lubricating oil film around the roller can be more effectively maintained. To summarize, the structures provide means by which unnecessary movement of roller  23  and retainer  28  can be reduced while simultaneously maintaining an adequate lubricating oil film around roller  23 , thus allowing for the construction of a cam mechanism able to operate with a higher degree of precision compared to conventional types.  
         [0069]    [0069]FIGS. 8 through 11 show cam mechanisms  1   c  and  1   d  that incorporate the cross roller bearing structure  20  put forth by the invention, and cam mechanism  61  that incorporates a rotating table.  
         [0070]    [0070]FIG. 8 illustrates cam mechanism  1   c  that incorporates cross roller bearing assembly  20  instead of the conventional roller bearings used in cam mechanism  1   a  shown in FIG. 20 and  21 . As a result of the cross roller bearing&#39;s ability to withstand both radial and thrust loads, turret  9  can be adequately supported on one side by a single cross bearing assembly. An additional advantage is that turret  9  can be installed to housing  2  as part of an output shaft assembly consisting of turret  9 , cross roller bearing  20 , and ring assembly  26 . The output shaft assembly can be quickly and easily installed through bolts  35  that secure outer ring plate  32  to housing  2 .  
         [0071]    [0071]FIG. 9 illustrates cam mechanism  1 d that incorporates a cross roller bearing type of output shaft support structure instead of the support structure consisting of cam followers  8  and  12  of cam mechanism  1   a  (shown in FIGS. 22 and 23). The use of a cross roller bearing makes it possible to adequately support output shaft assembly  39  at a single location at the axial center of the shaft&#39;s radial perimeter. Component  40  is an oil seal.  
         [0072]    [0072]FIGS. 10 and 11 depict an embodiment of the invention incorporating rotating table unit  61 . Drive shaft  62 , which incorporates roller gear cam  64 , is rotatably supported in housing  63  by tapered roller bearings  60 .  
         [0073]    Revolving table  65 , comprised of cross roller bearing  20 , outer ring plate  32 , inner ring plate  33 , rollers  23 , and inner race  25  formed as an integral part of table  65 , is rotatably supported within housing  63  by cross roller bearing assembly  20 . Bolts are utilized to fixedly secure outer ring plate  32  to housing  63 , and inner ring plate  33  to outer ring plate  32 . Multiple cam followers  67  are installed to the circumference of rotating table  65  in a radial pattern, and are oriented so as to fit between the spiral flanges of roller gear cam  64  on drive shaft  62 . Space  95  is provided within housing  63  as means of holding lubricating oil for the lubrication of roller gear cam  64  and cam followers  67 . Seal  90  and O-ring  80  are provided to prevent oil from leaking out of the cam mechanism.  
         [0074]    Although not shown in the figures, a motor or like drive means is utilized to rotate drive shaft  62  and roller gear cam  64 . The traversing action of the cam flanges is converted to a rotating movement of revolving table  65  through the following movement of cam followers  67 , thus resulting in the rotation of table  65  around axial centerline  66 .  
         [0075]    Various embodiments of the turret attachment structure are shown in FIGS. 12 through 22. FIGS. 12 through 15 illustrate variations of the turret attachment structure that can be applied to cam mechanism  1   c  shown in FIG. 8. FIGS. 16 through 19 illustrate variations of the turret attachment structure that can be applied to cam mechanism  1   d  shown in FIG. 9.  
         [0076]    [0076]FIG. 12 a  depicts the same attachment structure previously shown in FIG. 1, a structure in which bolts  36 , inserted through outer ring plate  32 , are used to secure inner ring plate  33  to the outer ring plate. After output shaft assembly  39  is installed to housing  2  by bolts  35 , bolts  36  can be tightened to their final torque specification to complete the assembly of cross bearing unit  20  by establishing an adjustable gap between the inner and outer ring plates.  
         [0077]    [0077]FIG. 12 b  depicts the same attachment structure shown previously in FIG. 8, a structure in which bolts  36 , inserted up through inner ring plate  33 , are threaded into outer ring plate  32  as means of securing inner ring plate  33  to plate  32 . In this case, inner ring plate  33  is completely assembled to outer ring plate  32  before the bearing assembly is installed to housing  2 .  
         [0078]    [0078]FIG. 13 depicts an output shaft assembly mounting structure in which outer ring plate  32  and housing  2  are formed with inclined cone shaped contact surfaces as means of aligning output shaft assembly  39  with the mounting  24  bore of housing  2 .  
         [0079]    [0079]FIG. 14 a  illustrates an output shaft assembly mounting structure in which both outer ring plate  32  and inner ring plate  33  are secured to housing  2  through bolts  35  installed through aligned holes provided in the outer and inner plates, and threaded into tapped bores in housing  2 . This structure allows outer and inner ring plates  32  and  33  and output shaft assembly  39  to be assembled and installed to housing  2  simultaneously. Radial flanges  42  and  43  are provided on ring plates  32  and  33  respectively as means of providing a surface through which bolts  35  can be installed. Ring-shaped spacer  44  can be installed between flanges  42  and  43  (FIG. 14 b ) as means of adjusting the width of gap  37 .  
         [0080]    [0080]FIG. 15 illustrates an output shaft assembly in which inner ring plate  33  is a cylindrical structure that resides within the output shaft mounting bore provided in housing  2 . Ring-shaped collar  45 , formed as part of outer ring plate  32 , is located above the internal radial surface of inner ring plate  33 . Outer ring plate  32  is formed with a large diameter circumferential male thread that allows plate  32  to be screwed into a corresponding female thread formed within inner ring plate  33 , thus providing a threaded means of connecting the two ring plates. Output shaft assembly  39  is installed to housing  2  by means of radial flange  47 , formed as an extension of the perimeter of inner ring plate  33 , being fixedly secured to housing  2  by bolts  35 . The large diameter threaded connection between plate  32  and  33  allows the cross bearing assembly to be installed or removed by simply screwing in or unscrewing collar  45 .  
         [0081]    [0081]FIGS. 16 through 19 depict various output shaft structures that can be applied to the cam mechanism shown in FIG. 9 in which cross roller bearing  20  is attached to and sealed within housing  2 .  
         [0082]    [0082]FIG. 16 depicts a structure in which multiple bolts  36  secure ring plate assembly  26  to housing  2  by clamping assembly  26  to housing  2  through tapped holes provided in housing  2 , and in which bolts  36  also fasten ring plate  32  to ring plate  33  by means of tapped holes provided in plate  33 , thus forming a structure whereby ring plates  32  and  33  can be mutually assembled at the same time that output shaft assembly  39  is installed to housing  2 .  
         [0083]    In the structure shown in FIG. 17, output shaft assembly  39  is formed by ring plate  33  being clamped to ring plate  32  by bolts  36  that insert inwardly toward the axial center of output shaft  9  through ring plate  33  and thread into tapped holes provided in ring plate  32 . Output shaft assembly  39  is attached to housing  2  by means of bolts  35  that pass through ring plate assembly  26 , in the opposite direction to bolts  36 , and screw into tapped holes provided in housing  2 . In this structure, ring plates  32  and  33  are joined together with bolts  36  before ring assembly  26  is installed to housing  2 .  
         [0084]    In the structure shown in FIG. 18, ring plate  32  is clamped to ring plate  33  by bolts  36  that run through ring plate  32  and into threaded bores formed in ring plate  33 , thus forming output shaft assembly  39  which is secured to housing  2  through bolts  35  that clamp radial flange  48  of ring plate  33  to housing  2  by anchoring to tapped bores provided in housing  2 . In this structure, a gap is provided between the facing surfaces of ring plates  32  and  33 , thereby providing means of adjusting the size of the gap through the amount of torque applied by bolts  36 .  
         [0085]    [0085]FIG. 19 illustrates a modified version of the structure shown in FIG. 18. Ring plate  33  incorporates conical surface  49  that mates with a corresponding conical surface  49  formed on housing  2 , thus providing means of accurately positioning output shaft unit  39  within housing  2 .  
         [0086]    While the various embodiments of the cam mechanism put forth in this specification explain a design in which ring plate assembly  26  is structured so as to radially encompass the perimeter of turret  9  with race  27  provided as the outer race, this structure by no means limits the scope of the invention. The output shaft may also take the form of housing  2  itself, and turret  9  may be structured so as to radially surround the rotating output shaft. The inner race  25  may be provided on housing  2 , and the outer race  27  may be machined directly into turret  9 .  
         [0087]    The cross bearing assembly explained in this specification provides a particular benefit when installed to a cam mechanism in that the operating qualities of the cross bearing structure allow the output shaft of the cam mechanism to maintain its positional stability while moving with an extremely high degree of dynamic precision. More specifically, the cross bearing assembly can provide a significant increase in the operational stability and precision of cam mechanisms of the type that utilize a roller gear cam input shaft.