Abstract:
A cam powered mechanism which uses two cam forms, a swing arm, and turret to drive an output shaft with a compound radial and axial movement. An arrangement in which a cam follower is positioned opposite each planar surface of the rectangular spline connecting the turret and output shaft acts to increase turret strength and reduces the size of the mechanism.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to a cam driven mechanism in which the rotating torque applied to a roller gear cam is converted to the oscillating rotational movement of a turret and an output shaft by means of a cam follower. 
     2. Description of the Related Art 
     The type of cam mechanism mentioned above, which has been proposed by Japanese utility model publication 7-52444 (Int.Cl.F16H 37/16), operates by means wherein the rotating movement input to a cam mechanism is converted into a oscillating rotational movement of an output shaft on the radial axis, and also a reciprocating movement of the output shaft in the axial direction. This type of mechanism is commonly applied to the tool changing mechanisms of metal processing machines with the purpose of obtaining a fast and precise tool change indexing action. 
     The aforesaid cam mechanism incorporates a roller gear cam fixedly attached to the input shaft, tapered ribs formed on the cam&#39;s periphery, and a cam channel formed on one of the cam&#39;s lateral surfaces. A roller cam follower, which is supported by a turret piece, rides between the aforesaid tapered ribs on the cam&#39;s periphery, and a swing arm rides in the aforesaid cam channel on the cam&#39;s lateral surface by means of a cam follower pin. An output shaft is installed through the turret&#39;s center by means of a sliding spline joint which fixedly connects the shaft to the turret in the radial direction, but allows free axial movement of the shaft through the turret piece in the axial direction. The end of the aforesaid swing arm is installed to the output shaft. 
     As a result of this configuration, the rotating movement of the input shaft is converted to an oscillating rotational movement of the output shaft by means of the aforesaid turret, and further converted to a reciprocating movement of the output shaft in the axial direction by means of the aforesaid swing arm. 
     A conventional cam mechanism of the type delineated above incorporates a turret whose cross section is shown in FIG.  11 . As turret  1  is connected to output shaft  2  by means of a sliding spline joint, spline shaft  2   a  of output shaft  2  is of a square cross section which approximately corresponds to the square cross section of spline orifice  1   a  in turret  1 . Peripheral surface  1   b  of turret  1  is of a round shape in radial cross section, and has installed to it six roller type cam followers  3 . Cam followers  3 , which ride in the area defined between the aforesaid tapered ribs  4  on the periphery of the aforesaid roller gear cam, are disposed around the periphery of turret  1  at regular intervals with their rotational centerlines C radiating from the center of turret  1  and output shaft  2 . 
     As a total of six cam followers  3  are disposed around the periphery of turret  1 , their orientation in relation to rectangular spline orifice  1   a  results in varying amounts of material existing between each cam followers  3  and output shaft  2 . In other words, the volume of material in turret  1  between cam followers  3  and output shaft  2  is greatest in the area at the center and opposite to the flat surfaces of spline orifice  1   a , and smallest in the areas adjacent to the corners of spline orifice  1   a . As all of the six cam followers  3  cannot be oriented directly opposite the planar surfaces of spline orifice  1   a  where the volume of material is greatest, some of the cam followers  3  must be positioned in a way which reduce the amount of material between the cam follower  3  and spline orifice  1   a.    
     As a result of this configuration, turret  1  must be designed so as to provide adequate strength and rigidity around the cam followers  3  which are supported by the smallest volume of material in relation to the splined orifice  1   a , and in doing so there is created a surplus of rigidity and strength in the area where the cam followers  3  are supported by the largest amount of material. The result is that the periphery of turret  1  is made to relatively large dimensions which, in turn, results in the problem of the entire cam mechanism being made to a larger size than is desirable. 
     SUMMARY OF THE INVENTION 
     This invention provides means by which the aforesaid cam followers can be disposed on the turret in the areas where there is maximum material between the cam follower and rectangular spline orifice, thus maintaining adequate turret rigidity and strength, and thus allowing the entire cam mechanism to be made to a smaller size. 
     In order to resolve the shortcomings mentioned above, the invention proposes a cam mechanism comprised of a roller gear cam solidly and fixedly attached to an input shaft, tapered ribs formed in a geometric curve pattern on the outer periphery of the roller gear cam, and a turret into whose center is formed a rectangular spline orifice. The turret is driven with an oscillating rotational movement by the rotation of roller gear cam through four cam followers which are located directly opposite and adjacent to the planar sides of the spline orifice formed in the turret center. The cam followers ride between the aforesaid tapered ribs on the roller gear cam periphery in a manner whereby the rotating movement of the roller gear cam is converted into an oscillating rotational movement of the turret. 
     Furthermore, the turret may be formed with the cam follower support pins as solid and integral components of the turret. 
     The geometrically curved tapered ribs on the roller gear cam periphery may be widened by increasing the width of the tapered rib in areas where it is desired to obtain more precise positioning movement for the aforesaid output shaft. 
     The invention further proposes a cam mechanism comprised of a roller gear cam solidly and fixedly attached to an input shaft, tapered ribs formed in a geometric curve pattern on the periphery of the roller gear cam, and a turret into whose center is formed a square spline orifice. The turret supports four cam followers located directly opposite and adjacent to the planar sides of the square spline orifice. These cam followers ride between the aforesaid tapered ribs on the roller gear cam periphery in a manner whereby the rotating movement of the roller gear cam is converted into an oscillating rotational movement of the turret. In this version the aforesaid turret is structured in a manner in which the pins supporting the cam followers are formed as a solid and integral part of the turret. 
     The invention further proposes a cam mechanism comprised of a roller gear cam solidly and fixedly attached to an input shaft, tapered ribs formed in a geometric curve pattern on the outer periphery of the roller gear cam, and a turret into whose center is formed a rectangular spline orifice. The turret supports four cam followers which are located directly opposite and adjacent to the planar sides of the rectangular spline orifice formed in the aforesaid turret, said four cam followers riding between the aforesaid tapered ribs on the roller gear cam periphery in a manner whereby the rotating movement of the roller gear cam is converted into a oscillating rotational movement of the turret. An output shaft is connected to the turret by means of a splined part which inserts into the spline orifice in the turret in a manner which allows free axial movement of the output shaft while it is rotatably held in its radial position supported by the turret. A reciprocating mechanism drives the output shaft with a linear reciprocating movement in the axial direction in synchronization with the output shaft&#39;s rotation on its radial axis. The spline in the turret is formed to a square cross section, and each cam follower on the turret&#39;s periphery is radially disposed directly facing one planar surface of the square spline orifice in the turret. 
     Moreover, the pins supporting the cam followers are formed as solid and integral components of the turret itself. 
     Furthermore, the turret&#39;s spline orifice may be formed to a square cross section, and the splined part of the output shaft may also be formed to the same square cross section as the spline orifice in the turret. 
     Moreover, the angular corners of the aforesaid spline orifice, which operate as the points at which drive torque is transmitted from the turret to the output shaft, are positioned at points as far as possible from the aforesaid cam followers. 
     Furthermore, the width of the geometrically curved tapered ribs on the roller gear cam periphery can be increased in specific areas and in specific lengths so as to narrow the adjacent channels which in turn can impart a more precise positioning action to the cam followers and thus to the output shaft. 
     The invention further proposes a cam mechanism comprised of a roller gear cam solidly and fixedly attached to an input shaft, geometrically curved tapered ribs formed on the outer periphery of said roller gear cam, and a turret into whose center is formed a square spline orifice. The turret supports four freely rotating cam followers by means of support pins which are located directly opposite and adjacent to the planar sides of the spline orifice in the aforesaid turret, and which ride between the aforesaid tapered ribs on the roller gear cam periphery in a manner whereby the rotating movement of the roller gear cam is converted into an oscillating rotational movement of the turret. A reciprocating drive mechanism drives the output shaft with a linear reciprocal movement in the axial direction while the output shaft remains fixed to the turret in the radial direction by means of the square spline part of the output shaft forming a joint with the square spline orifice in the turret. The aforesaid four cam follower support pins may be formed as solid and integral parts of the turret and disposed radially on the turret&#39;s periphery directly opposite and facing each planar side of the aforesaid square spline orifice. This arrangement positions the cam follower support pins a far distance from the angular corners of the spline orifice which transfer torque to the angular corners of the spline part of the output shaft. 
     The aforesaid structure provides means whereby the rotating movement of the input shaft on the roller gear cam is converted to an oscillating rotational movement of the turret through cam followers riding between the tapered ribs on the roller gear cam periphery. 
     The maximum volume of turret material is maintained between each cam follower and the output shaft as a result of positioning each cam follower on the periphery of the turret directly opposite and in the center of the each planar surface of the four-sided spline orifice. Because this configuration maintains the strength of each cam follower mounting area at the optimum level, the cam follower can be made larger, an advantage which acts to increase the strength of the cam follower itself while also extending the service life of the entire cam mechanism. Moreover, this design allows the turret itself to be made smaller, and therefore the size of the entire mechanism can also be reduced. 
     Furthermore, the cost of the cam mechanism is reduced due to the number of cam followers being decreased from the conventional six to four. Also, as each cam follower is positioned in the center of and directly opposite each side of the square spline orifice, it becomes easier to assemble the cam followers to the turret, and easier to fabricate the turret as a one-piece structure. 
     Moreover, the use of four cam followers increases the distance between each cam follower and the adjacent two cam followers, thus allowing the width of the aforesaid tapered ribs to be increased. The benefits of this point are numerous. Not only is the attachment of the cam follower to the turret strengthened as mentioned previously, but the strength of the mating surfaces where the cam follower contacts the tapered ribs is also significantly increased, a benefit which allows an overall smaller cam mechanism to withstand higher torque loads during its operation. 
     In addition, as the roller gear cam rotates in unison with the input shaft, the cam followers riding between the tapered ribs on the roller gear cam&#39;s periphery turn the turret with an oscillating rotational action, and thus the output shaft mounted in the turret&#39;s spline orifice also moves with an oscillating rotational action. Furthermore, the previously mentioned reciprocating mechanism drives the output shaft with a reciprocating movement in the axial direction simultaneously with the reciprocating rotational movement of the output shaft, a compound movement made possible by the sliding spline joint formed by the spline part of the output shaft connecting with the spline orifice in the turret. 
     Considering that torque from the turret is transferred to the angular corners of the spline part of the output shaft from the angular corners of the spline orifice in the turret, the strength of the turret in the area around the angular corners is increased because the cam followers are separated from the angular corners of the spline orifice by the farthest possible distance, thus allowing higher torque loads to be applied to a dimensionally smaller turret. 
     As the cam follower support pins can be formed as solid and integral components of the turret, the need to open bores on the turret periphery to accommodate separately assembled support pins is eliminated, thus also eliminating major stress points within the turret around the aforesaid bores. This configuration significantly strengthens the turret and allows both spline orifice and spline shaft to be enlarged with the result that the spline joint is able to withstand higher torque loads. 
     As mentioned previously, because the invention provides means whereby the tapered ribs on the periphery of the roller gear cam can be made wider (and therefore their adjacent channels narrower) at the area where a higher level of indexing positioning is desired, the area where the channel is narrowed applies a greater preload to the cam follower and therefore imparts a correspondingly higher level of indexing accuracy to the output shaft. Conversely, the preload on the cam followers is reduced at areas where the tapered ribs have not been widened, and thus has the effect of lengthening the service life of the cam mechanism. As a further benefit, heat discharge can be adequately controlled and energy losses minimized because only a very small amount of preload need be applied against the cam followers. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     FIG. 1 is a cross section of one embodiment of the turret part of the invention; 
     FIG. 2 is a cross sectional and internal front view of the invention; 
     FIG. 3 is a cross sectional and internal plan view of the invention; 
     FIG. 4 is a cross sectional and internal front view of the invention showing two operating positions; 
     FIG. 5 is a diagram of the invention utilized as a tool changing mechanism; 
     FIG. 6 is a diagram of the geometrically curved tapered ribs on the cam periphery of the invention; 
     FIG. 7 is a line graph showing the relative timing of the rotating and axial positioning modes of the invention; 
     FIG. 8 is a cross sectional plan view of another embodiment of the turret part of the invention; 
     FIG. 9 is a diagram of the geometrically curved tapered ribs on the cam periphery of another embodiment of the invention; 
     FIG. 10 is a enlarged drawing of a tapered rib used by the invention; and 
     FIG. 11 is a cross sectional plan view of a turret used by a conventional cam-driven indexing mechanism. 
     FIG. 12 is a cross sectional plan view showing a rectangular spline. 
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     The preferred embodiments of the invention are directed to the invention as being applied as a tool changing mechanism for a metal processing machine. 
     Rotational torque applied to input shaft  12  allows cam driven tool change mechanism  10 , as shown in FIGS. 2 and 3, to provide the compound movement needed for a tool change cycle. Input shaft  12  is rotatably supported within housing  16  by means of roller bearings  14  and  14   a , and is formed as a single integral structure together with roller gear cam  18 . 
     As shown in FIG. 6, geometrically curved tapered ribs  20  are formed on the periphery of roller gear cam  18 , these tapered ribs  20  being disposed so as to mesh with cam followers  24  on the periphery of turret  22 . The rotational movement of roller gear cam  18  and the placement of tapered ribs  20  on the cam&#39;s periphery imparts an oscillating rotational movement to turret  22  through cam followers  24 , thus also imparting an oscillating rotational movement to output shaft  28  which is installed to turret  22  by means of sliding spline joint  26 . Components (i), (ii), (iii), and (iv) shown in FIG. 6 denote the cam followers  24  and their sequential disposition in relation to the tapered ribs  20  and the resulting oscillating rotational movement imparted to turret  22 . 
     As shown in FIG. 2, cam channel  30  is formed in the lateral surface of roller gear cam  18  as a continuously varying geometric curve. Swing lever  32  is positioned over cam channel  30  with its right end  32   a  being rotatably supported by fixed pivot pin  34  which is solidly attached to housing  16 . Cam follower pin  36  is attached to middle part  32   b  of swing lever  32  and also rides within cam channel  30 . 
     Moreover, pin  38  is installed to left end  32   c  of swing arm  32  and rides within groove  40  which is located on the periphery of output shaft  28 . When roller gear cam  18  rotates, cam channel  30  drives right end  32   c  of swing arm  32  with an upward and downward reciprocating movement by means of cam follower pin  32   b , thus imparting a reciprocating movement to input shaft  28  in the axial direction by means of the connection between pin  38  and groove  40 . Cam channel  30  and swing arm  32  comprise the main components of reciprocating mechanism  33 . 
     Turret  22  is held within support cylinder  42  in a rotatable condition by means of bearings  44  and  44   a  which are positioned at the upper and lower ends of support cylinder  42 . Support cylinder  42  is installed to lower surface  16   a  of housing  16 . Output shaft  28 , which is connected to turret  22  at sliding spline joint  26 , is supported at its upper end by bearing  46 . Bearing  46 , installed to upper surface  16   b  of housing  16 , allows output shaft  28  to move freely both in the axial and radial directions. 
     As shown in FIG. 1, sliding spline joint  26  is comprised of spline orifice  50 , located in the center of turret  22 , and spline shaft  52  of output shaft  28 . This joint  26  allows spline shaft  52  to move freely within turret  22  in the axial direction. The periphery of turret  22  is formed as an intermittently round cross section, and incorporates spline orifice  50  which is a square shape in cross section. Spline shaft  52  inserts into spline orifice  50  with sufficient clearance so that spline shaft  52  can move freely in the axial direction only. 
     Cam followers  24  are positioned at each flat surface  22   b  on the periphery of turret  22  in radial disposition whereby the lower surface of each cam follower  24  directly opposes each flat side  50   a  of square spline orifice  50 , and are supported by cam follower support pins  54  which insert into cam follower attachment bores  22   c  which are in turn formed on each flat surface  22   b.    
     As shown in FIG. 5, the tool change mechanism  10  is mounted in the vicinity of metal processing machine spindle  60  and tool carrier arm  62  is supported by output shaft  28 . FIG. 5 shows the length of output shaft  28  as opposed to its radial cross section which is shown in FIG.  1 . Tool support piece  62   a  is installed to each end of tool carrier arm  62 , and mates with tool  64  when a tool change cycle is executed. 
     When this embodiment of the invention is utilized as tool change mechanism  10 , rotating torque applied to input shaft  12  turns roller gear cam  18 , thereby driving cam followers  24  through the rotating and simultaneous lateral movement of tapered ribs  20 . Tapered ribs  20  are made to specific geometric curves which are designed to impart a timed oscillating rotational movement to turret  22  as shown by line “a” in the graph in FIG.  7 . As turret  22  is connected to output shaft  28  through sliding spline joint  26 , tool carrier arm  62  installed on the tip of output shaft  28  is also driven with an oscillating rotational movement. 
     At the same time, when roller gear cam  18  revolves, cam follower pin  36  rides within and follows cam channel  30 , thus imparting an oscillating axial movement to swing arm  32 . As pin  38  is both attached to end part  32   c  of swing arm  32  and inserted within the channel on collar  40  of output shaft  28 , output shaft  28  is reciprocally driven in the axial direction as allowed by sliding spline joint  26  in turret  22 . This movement is shown as line “b” in the graph in FIG.  7 . 
     Because output shaft  28  rotates on its radial axis while simultaneously reciprocating in the axial direction, a compound tool change action can be imparted to both ends of tool carrier arm  62 . In other words, as shown by line “c” in FIG. 7, timing can be established whereby the rotational movement of tool carrier arm  62  stops in synchronization with the clamp and unclamp operations applied to tool  64 . 
     In regard to the structure of turret  22 , as spline orifice  50  is formed with a square cross section, and as cam follower  24  faces directly opposite side and also in the center of surface  50   a , the maximum amount of turret material (shown as “t”) is used to support each cam follower  24  around spline orifice  50 . 
     As a result of this design, the attachment area of cam follower  24  to turret  22  is strengthened, thus allowing cam follower  24  to be made larger, and thus increasing its strength, thereby extending the service life of tool change mechanism  10 . Also, this design allows turret  22  itself to be made to smaller dimensions, thus allowing tool change mechanism  10  to be also made to smaller dimensions without any sacrifice in strength. 
     Moreover, as the number of cam followers  24  has been reduced from that used in the conventional mechanism, the cost of constructing tool change mechanism  10  is reduced. The positions of cam follower pins  24  in relation to spline orifice  50  also make it easier to assemble the turret  22 . 
     Furthermore, the use of four cam followers  24  provides more space adjacent to each cam follower  24  and thus allows width “w” of tapered ribs  20  to be made to a wider dimension (see FIGS.  3  and  6 ). Also, the use of four cam followers  24  not only strengthens bore  22   c  into which cam follower support pin  54  is pressure inserted, but also strengthens the attachment of the cam follower  24  to the turret  22 . This increase in strength can allow roller gear cam  18  to apply higher loads to turret  22 , and thus in turn allow tool change mechanism  10  to be made to smaller dimensions while maintaining adequate torque handling capability. 
     When output shaft  28  is rotationally driven by turret  22 , the result is that pressure is applied to angular corners  50   b  of spline orifice  50  as well as angular corners  52   a  of spline shaft  52 . As cam followers  24  are attached to turret  22  at locations far from angular corners  50   b  of spline orifice  50 , corners  50   b  are strengthened, thus allowing turret  22  to be made to smaller dimensions without sacrificing strength. 
     FIG. 8 depicts another embodiment of the invention in which four cam follower support pins  54   a  are formed at 90-degree angles on the periphery of turret  22  as solid and integral parts of turret  22 . 
     Ring washer  70  is inserted over cam follower support pin  54   a  as a base for needle bearing unit  72 , said needle bearing unit  72  being installed over and around support pin  54   a . Cam follower  24  rides over needle bearing unit  72 , and retainer plate  74  is installed to the end of support pin  54 , by means of threaded fasteners, as means of securing cam follower  24 . 
     As support pins  54   a  are formed as an integral part of turret  22  in this embodiment, the need to bore holes on the turret periphery to accommodate separate support pins is eliminated, thus also eliminating major stress accumulation points within the turret  22 . This design has the effect of not only significantly strengthening turret  22 , but also allows both spline orifice  50  and spline shaft  52  to be enlarged in order to withstand higher torque loads. 
     FIGS. 9 and 10 show a further embodiment of the invention in which thickness “W”, said thickness being in the width direction of the tapered ribs  20  on periphery  18   a  of roller gear cam  18 , is widened within the area along the cam periphery shown as X (zone X) with the purpose of increasing the precision of the indexing movement within zone X. Consequently, the width W 1  of the tapered rib within zone X is larger than its width W 2  in zone Y. For example, zone X can be established as the position at which a highly precise indexing action is desired for tool carrier arm  62 , such as the position at which tool carrier arm  62  must be in perfect alignment with spindle  60  (FIG.  5 ), or in perfect alignment with a specific tool magazine position. (This position is shown as length “X” on line “a” in FIG. 7.) Therefore, cam follower  24  is able to ride between tapered ribs  20  with little or no preload in zone Y where the distance between the tapered ribs  20  is larger. Upon entering zone X, however, the narrower channel formed by the increases in the width of the tapered rib  20  will increase the preload against cam follower  24 , and thus increase the precision of the indexing movement applied to output shaft  28 . 
     Conversely, as cam follower  24  is subjected to less preload when riding between the tapered ribs  20  in zone Y, the service life of tool change mechanism  10  can be extended. Also, by placing a minimum preload on cam follower  24 , thermal discharge can be better controlled and energy losses reduced. 
     The three embodiments discussed here make reference to the invention as applied to tool change mechanism  10 . The invention, however, is not limited solely to this application, and may be further applied to any mechanisms making use of a cam-driven turret. 
     Because the invention provides means whereby the turret incorporates four cam followers installed on its periphery, each cam follower being positioned directly opposite each planar side of the rectangular spline orifice located in the center of the turret, the maximum amount of material can be maintained around the turret&#39;s spline orifice. Accordingly, the attachment strength of the cam follower to the turret can be significantly increased, the cam followers themselves can be made with greater strength, and the service life of the entire cam mechanism can be extended. Also, the turret can be made to smaller dimensions, thus allowing the entire mechanism to be made to a smaller size. 
     Moreover, as the number of cam followers is decreased as compared to the conventional mechanism, the cost of the cam mechanism can be lowered. Furthermore, the placement of the four cam followers directly opposite the planar sides of the spline orifice allows for easier assembly as well as easier fabrication of the turret as a one-piece assembly. 
     Furthermore, the use of only four cam followers increases the space adjacent to each cam follower, thus allowing the tapered ribs on the cam periphery to be made wider and stronger. Moreover, the use of only four cam followers not only allows a stronger joint to be formed between the turret and cam follower, but also forms a significantly stronger power transfer connection between the tapered ribs and turret, thus allowing higher operating loads to be placed on the turret which in turn allows the mechanism to be made smaller without sacrificing strength. 
     Moreover, considering that torque from the turret is transferred to the angular corners of the spline part of the output shaft from the angular corners of the spline orifice in the turret, the strength of the turret in the area around the angular corners can be increased due to the cam followers being separated from the angular corners of the spline orifice by the farthest possible distance, thus allowing the application of higher torque loads to a dimensionally smaller turret. 
     Furthermore, as the cam follower support pins can be formed as a solid and integral part of the turret, the need to bore holes on the turret periphery to accommodate separate support pins is eliminated, thus also eliminating major stress points within the turret around the bores. This configuration significantly strengthens the turret and allows both the spline orifice and spline part of the output shaft to be enlarged with a resulting increase in strength of the entire spline joint. 
     Moreover, the width of the geometrically curved tapered ribs on the periphery of the roller gear cam can be widened, and the adjacent channels correspondingly narrowed, along a specific length of the tapered rib where an especially precision indexing action is desired. A higher preload is applied to the cam follower when it enters the narrower channel, thus increasing indexing precision at the outputs haft. Conversely, a lower preload is applied to the cam follower when it is riding in the wider channel adjacent to the area where the tapered rib is narrower, thus aiding in extending the service life of the mechanism. Because a minimum preload can be maintained along much of the roller gear cam&#39;s rotational traverse, thermal discharge can be controlled and energy losses reduced.