Abstract:
Apparatus for automatic assembly of universal joints which include a yoke with snap ring grooves in its yoke arms, a trunnion body, bearings, and snap rings to secure the bearings in the yoke, the apparatus comprising: (a) upper and lower parallel spring-separated plate pairs with axially-aligned holes; (b) upper and lower drive members aligned with holes in each plate pair; (c) a base plate; (d) a movable rod plate; (e) upper and lower power sources configured to provide axial movement of an upper driver plate in the upper plate pair and the rod plate, respectively; and (f) a programmed controller controlling the power sources such that automatic sequencing of the upper driver plate and rod plate sequentially urge snap rings into place in grooves within the snap ring grooves.

Description:
RELATED APPLICATION 
     This application claims the benefit of U.S. Provisional Application Ser. No. 61/604,077, filed Feb. 28, 2012. U.S. Provisional Patent Application Ser. No. 61/604,077 is incorporated herein by reference in its entirety to provide continuity of disclosure. 
    
    
     FIELD OF THE INVENTION 
     The present invention is generally related to the field of automated mechanical assembly and more particularly to methods and apparatus for the automated assembly of universal joints. 
     BACKGROUND OF THE INVENTION 
     Universal joints are common mechanical components in many products such as vehicles of all types and many other products which include the transmission of rotational mechanical power. The process of assembling the components of such universal joints is typically a manually-intensive procedure. As such, the procedure can be complex, time-consuming, difficult to maintain quality, and oftentimes can create unsafe production environments for the assembly personnel. There is therefore a need for a simpler, faster, more repeatable and safer method by which to assemble such mechanical components. 
     In the past, there have been some approaches to addressing these needs. U.S. Pat. No. 4,558,502 (Gossman et al.), entitled “Process and Apparatus for Assembling Universal Joints,” discloses a method and the accompanying apparatus for individually assembling a trunnion and its bearing cup in its corresponding yoke arm. Each yoke arm is pretensioned as part of the process disclosed. 
     Notwithstanding some efforts in improvement of assembly methods and related equipment, there remains a need for an accurate, high-speed and safe assembly method and related apparatus for that purpose. 
     OBJECTS OF THE INVENTION 
     It is an object of the automatic universal joint assembly method and apparatus is to speed up the assembly of universal joints. 
     Another object of the automatic universal joint assembly method and apparatus is to improve the repeatability and quality of the assembly of universal joints. 
     Yet another object of the automatic universal joint assembly method and apparatus is to improve the safety of the process of assembling universal joints. 
     Still another object of the automatic universal joint assembly method and apparatus is to lower the complexity of the process of assembling universal joints. 
     These and other objects of the invention will be apparent from the following descriptions and from the drawings. 
     SUMMARY OF THE INVENTION 
     The present invention is apparatus for automatic assembly of universal joints which include a yoke with snap ring grooves in its yoke arms, a trunnion body, bearings, and snap rings to secure the bearings in the yoke. The apparatus comprises: (a) an upper parallel plate pair, including an uppermost driver plate having an upper drive member, an upper tapered-hole plate defining a tapered hole axially aligned with the upper drive member and having its narrow end away from the upper driver plate, and at least one spring between the plates of the upper pair; (2) a lower parallel plate pair, including a lowermost driver plate having a lower drive member, a lower tapered-hole plate defining a tapered hole axially aligned with the upper and lower drive members and having its narrow end away from the lower driver plate, and at least one spring between the plates of the lower pair; (3) a base plate on which the lower driver plate is mounted and a movable rod plate therebelow having driver rods extending through corresponding holes in the lower driver plate; (4) upper and lower power sources configured to provide axial movement of the upper driver plate and the rod plate, respectively; and (5) a programmed controller controlling the power sources. 
     In certain embodiments of the inventive apparatus, the tapered holes have a taper of between 4° and 6°. 
     In some preferred embodiments, the controller is a programmable logic controller. 
     In other preferred embodiments, at least one of the drive members is magnetic, and in some of these embodiments, the magnetic drive member includes a magnet. 
     In other preferred embodiments of the inventive apparatus, the spring(s) of the lower plate pair have a lower stiffness than the spring(s) of the upper plate pair. 
     The present invention also includes a method for automatic assembly of universal joints which include a yoke with snap ring grooves in its yoke arms, a trunnion body, bearings, and snap rings to secure the bearings in the yoke. The steps of the inventive method comprise: (1) providing an upper parallel plate pair, including an uppermost driver plate having an upper drive member, an upper tapered-hole plate defining a tapered hole axially aligned with the upper drive member and having its narrow end away from the upper driver plate, and at least one spring between the plates of the upper pair; (2) providing a lower parallel plate pair, including a lowermost driver plate having a lower drive member, a lower tapered-hole plate defining a tapered hole axially aligned with the upper and lower drive members and having its narrow end away from the lower driver plate, and at least one spring between the plates of the lower pair, such spring(s) having a lower stiffness than the spring(s) of the upper plate pair; (3) providing a base plate on which the lower driver plate is mounted and a movable rod plate therebelow having driver rods extending through corresponding holes in the lower driver plate; (4) providing upper and lower power sources configured to provide axial movement of the upper driver plate and the rod plate, respectively; (5) providing a programmed controller controlling the power sources; (6) positioning the distal ends of the upper and lower drive members at the wide ends of the upper and lower tapered holes, respectively; (7) placing one of the snap rings in each of the two tapered holes and thereafter placing one of the bearings in each of such tapered holes; (8) placing the yoke and trunnion body such that the trunnions are in alignment with the tapered holes; and (9) automatically sequencing movements of the upper driver plate and the rod plate to sequentially urge each of the snap rings through its corresponding narrowing tapered hole such that the snap ring moves into position for expansion into the corresponding groove. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an exploded view perspective drawing of one type of universal joint assembly which is assembled by the inventive method and apparatus of this invention. 
         FIGS. 2A-2D  are sequential schematic drawings illustrating the steps of the snap ring insertion process of the inventive assembly method and apparatus. 
         FIG. 3A  is a cross-sectional schematic drawing illustrating the step of manually loading the snap rings into the inventive apparatus. 
         FIG. 3B  is a cross-sectional schematic drawing illustrating the step of manually loading the needle bearings into the inventive apparatus. 
         FIG. 3C  is a cross-sectional schematic drawing illustrating the step of manually placing the universal joint yoke and trunnion body the inventive apparatus. 
         FIG. 3D  is a cross-sectional schematic drawing illustrating the step of automatic lower snap ring insertion into its corresponding U-joint yoke arm using the method and apparatus of this invention. 
         FIGS. 3E and 3F  are cross-sectional schematic drawings illustrating the subsequent steps of automatic upper snap ring insertion into its corresponding U-joint yoke arm using the method and apparatus of this invention. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       FIG. 1  illustrates a portion of one type of universal joint assembly  10 , hereinafter referred to as U-joint  10 . U-joint  10  includes a yoke body  12  which is connected to a shaft such as a drive shaft, not shown but connected to yoke body  12  with a connector  36 , and is aligned therein with a yoke body axis  12   a . U-joint  10  also includes a trunnion body  14  with four cylindrical trunnions: a first trunnion  24  and a second trunnion  26  each aligned with a first trunnion axis  14   a  and a third trunnion  42  and a fourth trunnion  44  each aligned with a second trunnion axis  14   b  which is perpendicular to and coplanar with axis  14   a.    
     Yoke body  12  of U-joint  10  includes a first yoke arm  38  and a second yoke arm  40 . First yoke arm  38  is also herein referred to as upper arm  38  and second yoke arm  40  is also herein referred to as lower arm  40 . In similar fashion, first trunnion  24  and second trunnion  26  are also herein referred to as upper trunnion  24  and lower trunnion  26 , respectively. The use of “upper” and “lower” as such descriptors is not intended to limit the orientation of such elements but is used herein as a convenience in describing the assembly of U-joint  10  when referring to the elements of  FIG. 1  and other figures accordingly. 
     Upper and lower arms  38  and  40  include a pair of openings  28  and  32 , respectively. Openings  28  and  32  are configured to receive a pair of needle bearings  16  and  18 , respectively. Needle bearing  16  includes bearing cup  16   c  and needles  16   n , and needle bearing  18  includes bearing cup  18   c  and needles (not shown). 
     In assembled form, upper trunnion  24  is surrounded by needle bearing  16  which is held within opening  28 , and in similar fashion, lower trunnion  26  is surrounded by needle bearing  18  which is held within opening  32 . Needle  16   n  of bearing  16  bear on the outer surface of upper trunnion  24 , and the needles of needle bearing  18  bear on the outer surface of trunnion  26 . Bearing cups  16   c  and  18   c  are retained in openings  28  and  32 , respectively, by a pair of snap rings  20  and  22 . Snap rings  20  and  22  are seated within a pair of grooves  30  and  34  in openings  28  and  32 , respectively. 
     U-joint  10  provides low-friction rotation of trunnion body  14  with respect to yoke body  12  around axis  14   a . In a similar fashion but not shown in  FIG. 1 , third and fourth trunnions may be installed in a second yoke body to provide for rotation of trunnion body  14  with respect to such second yoke body around axis  14   b . The elements to provide such relative movement may be similar to the elements shown in  FIG. 1 . Such a U-joint configuration is well-known and is used provide a flexible connection between a driveshaft connected to yoke body  12  and a second shaft similarly connected to the second yoke body, thereby transmitting rotational mechanical power between the two shafts. 
       FIGS. 2A-2D  show the steps of the snap ring insertion process of the inventive assembly method and apparatus. As described above, the U-joints being assembled by the inventive method and apparatus have snap rings  20  and  22  in each of the two yoke arms  38  and  40 , respectively. The means by which snap rings  20  and  22  are automatically inserted includes the use of two pairs of plates, including upper pair  102  and  104  and lower pair  114  and  116 . See  FIGS. 3A-3F .  FIGS. 2A-2D  illustrate the insertion process by means of a pair of plates  50  and  52  to represent both upper and lower pairs later shown in  FIGS. 3A-3F . 
     Referring to  FIGS. 2A-2D , tapered-hole plate  50  defines a tapered hole  56  configured to receive snap ring  22  manually. At the beginning of the assembly process, snap ring  22  is supported on driver  54  which is mounted on driver plate  52 . During the automatic insertion process, driver  54  drives snap ring  22  into tapered hole  56  and the taper serves to laterally compress snap ring  22  as it approaches the narrow end of tapered hole  56 , at which point snap ring  22  is compressed to a width sufficient to allow snap ring  22  to slide into opening  32  of yoke arm  40  and subsequently into groove  34  of yoke arm  40 . 
     The insertion of snap ring  20  occurs in a similar fashion to the insertion of snap ring  22  illustrated in  FIGS. 2A-2D . 
     The taper of tapered hole  56  is preferably between 4° and 6°. Tapered hole  56  may include an entrance straight section  56   n  and an exit straight section  56   x . Tapered hole  56  in  FIGS. 2A-3F  all have such straight sections. 
       FIGS. 3A-3F  schematically illustrate the apparatus and the steps of the automated assembly method of this invention. Note that each of these schematics may have portions of the illustration done in “transparent” cross-section in order to be able to see the relative positions of each of the components of the apparatus and the U-joint being assembled. 
     Apparatus  100  includes a pair of upper plates (upper driver plate  102  and upper tapered-hole plate  104 ) and a pair of generally similar lower plates (lower driver plate  116  and lower tapered-hold plate  114 ). Lower driver plate  116  is stationary on base plate  124  and is indicated as stationary with dotted line  126 . 
     Upper plates  102  and  104  have springs  108  therebetween (two shown). Upper driver plate  102  includes driver  106  which is a cylindrical member sized to pass through the narrow end of tapered hole  112  and into opening  28  of yoke  12 . Likewise, lower plates  116  and  114  have springs  120  therebetween (two shown). Lower driver plate  116  includes driver  118  which is a cylindrical member sized to pass through the narrow end of tapered hole  123  and into opening  32  of yoke  12 . 
     Lower driver plate  116  and base plate  124  include holes  132  through which driver rods  130  (two shown) may be driven to engage lower tapered hole plate  114 . Rods  130  are mounted on rod plate  128  which is driven by power source  122  (not shown in any detail). Upper driver plate  102  is similarly driven by power source  110  (also not shown in any detail). Power sources  110  and  122  may be hydraulic, pneumatic or electrically driven to provide linear motion and are programmably controlled by a controller (not shown) such as a PLC (programmable logic controller) or other logic controller such as, but not limited to, a fluidic controller or a computer. The controller may include one or more limit switches which serve to indicate when the distance between a pair of plates has reached a predetermined value. Such use of limit switches, not shown in the figures, is well-known to those skilled in the art of controllers for mechanical systems. 
       FIGS. 3A-3C  illustrate the manual set-up steps prior to the automated steps of the inventive assembly method.  FIG. 3A  shows snap rings  20  and  22  in loaded positions in the inventive apparatus. Upper snap ring  20  is held in place by virtue of driver  106  being magnetic or including a separate magnet  106   m . (Magnet  106   m  is illustrated only in  FIG. 3A ). Lower snap ring  22  rests on driver  118  by gravity. Snap rings  20  and  22  are not fully circular and thus can be manually loaded through the narrow ends of tapered holes  112  and  123 , respectively.  FIG. 3B  shows needle bearings  16  and  18  placed in position for automated assembly. Finally,  FIG. 3C  shows U-joint yoke  12  and trunnion body  14  manually positioned in apparatus  100 . In such position, trunnions  24  and  26  and yoke arm openings  28  and  32  are all in alignment with needle bearings  16  and  18  and tapered holes  112  and  123 . In this position, all of the components U-joint  10  are ready for automated assembly. 
       FIG. 3D  illustrates the result of movement provided by power source  110  driving upper driver  106  through upper driver plate  102  which in turn moves a number of elements of apparatus  100  and U-joint  10 . Springs  108  are stiffer than springs  120 ; consequently, movement of the lower plate pair  114 ,  116  relative to one another is greater than movement of the upper plate pair  102 ,  104  relative to one another. This serves to drive lower snap ring  22  (via driver  118 ) along tapered hole  123 , into opening  32  and into groove  34 , as illustrated in  FIGS. 2A-2D  and described above. As a result, needle bearing  18 , on trunnion  26 , is positioned against lower snap ring  22 . 
       FIG. 3E  illustrates the resulting positions of the components of apparatus  100  and U-joint  10  after upper driver  106  is partially backed away through the action of power source  110 . Since springs  108  are stiffer than springs  120 , the spacing between plates  102  and  104  is larger than the spacing between plates  114  and  116 . Apparatus  100  is now ready for the final automatic assembly step as shown in  FIG. 3F . 
     In the step illustrated in  FIG. 3F , power source  122  provides linear movement of rod plate  128 , thereby extending rods  130  through holes  132  to engage and raise lower tapered hole plate  114  which in turn raises yoke  12  and decreases the spacing between upper plates  102  and  104  until snap ring  20  seats in groove  30 . At this point, power sources  110  and  122  provide linear movement to open apparatus  100  to permit removal of fully-assembled U-joint  10  and prepare apparatus  100  for subsequent manual loading and automatic assembly of additional U-joints. 
     The steps illustrated in  FIGS. 3D-3F  are fully-automatic, hands-free, timed movements which quickly, safely and repeatably assemble U-joints of the type shown in  FIG. 1 . 
     While the principles of this invention have been described in connection with specific embodiments, it should be understood clearly that these descriptions are made only by way of example and are not intended to limit the scope of the invention.