Abstract:
A conveyor roller includes a generally cylindrical roller tube and a pair of stub shafts rotatably mounted in each end thereof. At least one of the stub shafts is mounted for axial movement between an extended position and a retracted position. When in the extended position, the stub shafts on each end of the conveyor engage respective mounting holes in the conveyor frame. To insert the conveyor roller in the conveyor frame, the movable stub shaft is moved to a retracted position while the roller is lowered into the conveyor frame. When the stub shaft aligns with the mounting holes in the conveyor frame, the stub shaft is urged back to the extended position by a biasing member to engage the mounting hole in the conveyor frame.

Description:
This is a Continuation Application of U.S. patent application Ser. No. 09/560,484, filed Apr. 28, 2000, now issued as U.S. Pat. No. 6,209,702, which itself is a continuation of prior U.S. patent application Ser. No. 08/939,966 originally filed Sep. 29, 1997, and now issued as U.S. Pat. No. 6,076,647. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates generally to improvements in rollers for conveyors and, more particularly, to a conveyor roller of the type which is mounted on stub shafts. 
     BACKGROUND OF THE INVENTION 
     Roller conveyors are commonly used in many industries to move packages or materials. In general, a conveyor roller comprises a plurality of individual rollers mounted between two parallel frames. The roller typically comprises a tube having a bearing in each end thereof which is rotatably journaled on a roller shaft that extends longitudinally through the tube. The roller shaft protrudes from each end of the roller tube and engages mounting holes in the frame. 
     Frequently, the roller shaft not only serves to mount the roller, but also functions as a structural element of the conveyor frame. In such cases, the ends of the shaft are drilled and tapped. Bolts extending from the outside of the frame are threaded into the tapped holes in the roller shaft to secure the frame members and rollers together. This approach to the construction of conveyors makes assembly of the conveyor time consuming and difficult. Moreover, this method of constructing conveyors makes it difficult to replace a single roller. 
     Another method to mount rollers in a conveyor frame is to use a roller having a through-shaft which is spring-loaded. In this case, the frame members are held together independently by a series of cross members rather than through the rollers. The rollers generally are installed after the frame is assembled. To install the roller, the shaft is moved axially against the force of the spring and “snaps” into place when the shaft aligns with the mounting hole in the frame member. This method makes assembly of the conveyor much simpler and facilitates the replacement of rollers when they become worn or defective. 
     Several attempts have been made in the past to eliminate through-shafts in the roller, In place of a single thru-shaft, separate stub shafts have been used to support opposing ends of the conveyor roller. Typically, these stub shafts are bolted to the conveyor frame before the frame is assembled. The conveyor roller is then inserted over the stub shaft as the frame is locked together to create a final assembly. This method of mounting rollers in conveyors also makes assembly difficult. Moreover, this method essentially precludes prefabrication of the conveyor frame. 
     Accordingly, there is a need for a new method for mounting conveyor rollers in a frame which does not rely on a through-shaft extending through the roller, allows prefabrication of the conveyor frame, and facilitates ease of assembly. 
     SUMMARY AND OBJECTS OF THE INVENTION 
     The present invention combines the advantages of spring-loaded shafts, which make installation of the roller quick and easy, and a shaftless design which eliminates the need for a longitudinal through-shaft. To achieve these advantages, the present invention utilizes a sliding stub shaft which is spring-biased to an extended position. The stub shaft can be pushed inward against the force of the spring to allow insertion of the roller into a prefabricated frame. When the stub shaft aligns with the mounting holes in the frame, the spring pushes the stub shaft outward to engage the mounting hole. One advantage of the present invention is that it enables quick and easy assembly of a conveyor. The conveyor frame can be prefabricated at the factory while the rollers are installed on site. Further, the present invention allows for easy replacement of a worn or defective roller without the need to disassemble an entire conveyor section. 
     The spring-biasing of the stub shaft also produces advantages not before realized in conveyors. The spring-biasing tends to center the roller after it is installed so that its rotating members do not rub against either frame member. The spring also allows shock absorption to take place when packages or other conveyed materials are moved laterally across the conveyor as they are loaded or unloaded. Furthermore, the constant preload on the springs eliminates vibration and noise which would resonate through the conveyor frame structure. 
     Yet another advantage of the present invention is its reduced weight. By eliminating a through-shaft that extends through the roller tube and replacing it with two smaller stub shafts, the total weight of the conveyor roller is reduced. Since conveyors use many individual rollers, the total weight reduction in a conveyor can be substantial. This weight reduction makes the conveyors more portable in the event that the conveyors need to be moved from one place to another. Also, shipping costs are reduced. 
     Yet another advantage which is beneficial in the food handling industry, is the ability to produce a relatively low cost, non-corrosive conveyor roller. In the food handling and chemical industries, conveyor rollers frequently employ stainless steel through-shafts. Sometimes, the additional cost of stainless steel makes the installation and use of conveyor systems impractical from a cost standpoint. By eliminating the through-shaft in its entirety, the stub shaft can be supplied with sophisticated corrosion resistant materials. Because the parts are so small, it does not negatively impact the overall cost of the system. 
     Another feature of the conveyor roller is increased safety. The retention of the roller in the frame is assured even in the event of bolt failure or vibration which could cause the bolt to fall out. In either instance, the spring-loading bias on the stub shaft acts as a reductive retention system to prevent the roller from falling out of the frame. 
     Other objects and advantages of the present invention will become apparent and obvious from a study of the following description and the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a partial cross section of the conveyor roller of the present invention showing the stub shaft in a normal extended position. 
     FIG. 2 is a cross section of the conveyor roller being inserted into a conveyor frame showing the stub shaft in a retracted position. 
     FIG. 3 is a cross section of the conveyor roller after its insertion into the frame showing the stub shaft in a partially extended position and engaged with the mounting holes in the frame member. 
     FIG. 4 is an end view of the second embodiment of the conveyor roller. 
     FIG. 5 is a partial cross section of the conveyor roller of the second embodiment showing the stub shaft in a normal extended position. 
     FIG. 6 is a cross section of the conveyor roller of the second embodiment being inserted into a conveyor frame showing the stub shaft in a retracted position. 
     FIG. 7 is a cross section of the conveyor roller of the second embodiment after its insertion into the frame showing the stub shaft in a partially extended position and engaged with the mounting holes in the frame member. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to the drawings, and particularly to FIG. 1, the conveyor roller of the present invention is shown therein an indicated generally by the numeral  10 . The roller  10  is adapted for use in conveyors, packaging machinery, linear motion material handling devices, and treadmills, but may also have other applications. The roller  10  is mounted between parallel frame members  12  which support the roller  10  at opposite ends thereof. The frame members  12  form part of a conveyor frame and may be held together, for example, by cross members (not shown). Each frame member  12  has a series of mounting holes  14  formed therein for mounting the roller  10 . The present invention is particularly related to an improved mounting system for mounting the roller  10  in the conveyor frame. 
     The roller  10  comprises a generally cylindrical roller tube  20  which is rotatably journaled on a pair of stub shafts  50 . A bearing housing  22  is inserted into each end of the roller tube  20  and houses a bearing  38  in which the stub shaft  50  is journaled. The bearing  38  is retained by friction in the bearing housing  22 . A bearing shield  40  fits on the outer end of the stub shaft  50 . The stub shaft  50  and bearing shield  40  are biased by a spring  60  to an extended position as shown in FIG.  1 . The stub shaft  50  can be moved to a retracted position by applying a force to the end of the stub shaft  50 . With the stub shaft  50  in a retracted position, it is easy to insert the roller  10  into an already assembled conveyor frame. 
     The bearing housing  22  is typically molded from a plastic material. The bearing housing  22  includes an outer cylindrical wall  24  and an inner cylindrical wall  26  which define an annular cavity  28  therebetween. The outer wall  24  is sized to provide an interference fit with the roller tube  20 . The inner wall  26  frictionally engages and holds the roller bearing  38 . The roller bearing  38  is pressed into the bearing housing  22  until it engages the back wall  30 . Back wall  30  of the bearing housing  22  includes a center opening  31  through which the stub shaft  50  extends. 
     The outer end  32  of the bearing housing  22  includes a seal cavity  34  which, in conjunction with the bearing shield  40 , provides a labyrinth seal to prevent dirt and other contaminants from reaching the bearing  38 . A lip  36  is also formed at the outer end  32  of the end cap  22  which butts against the end of the roller tube  20 , which is bent inward slightly to help hold the bearing housing  22  in place. The inner end of the outer wall  24  is slightly tapered to facilitate insertion of the end cap  22  into the roller tube  20 . 
     As previously mentioned, the bearing housing  22  houses a bearing  38 . The bearing  38  may preferably be a radial ball type bearing as shown in FIG.  1 . However, it should be understood that the present invention will work equally well with molded plastic or bronze bushing designs. The function of the bearing  38  is to reduce friction as the roller tube  20  rotates about the stub shaft  50 . 
     The stub shaft  50  includes an inner portion  52  and an outer portion  54 . The inner portion  52  has a cylindrical configuration and is journaled in the bearing  38 . It should be noted, however, that the inner portion  52  of the stub shaft  50  and the inner race of the bearing  34  could have a polygonal configuration without departing from the spirit of the present invention. The outer portion  54  of the stub shaft  50  preferably has a hexagonal configuration and is adapted to mate with a similarly shaped and sized opening  14  in the mounting frame  12 . 
     A small flange  56  is formed at the inner end of the stub shaft  50 . The purpose of the flange  56  is to act as a stop when the stub shaft  50  reaches an extended position. The flange  56  is designed to butt against the bearing  38  to prevent the further extension of the stub shaft  50 . 
     A threaded hole  58  is located through the center of the stub shaft formed at the end of the outer portion  54 . The threaded hole  58  is adapted to receive a bolt  62  which extends from the outside of the frame  12  into the threaded hole  58 . The purpose of the bolt  62  is to secure the roller  10  in place after it has been inserted into the frame  12 . 
     The bearing shield  40  is press fit onto the outer portion  54  of the stub shaft  50 . The bearing shield  40  includes a hub  42  and a cover portion  44 . The hub  42  includes a hexagonal bore  45  which is sized to provide a tight, frictional fit with the outer portion  54  of the stub shaft  50 . The cover portion  44  extends radially outward from the hub  42  to provide a cover for the bearing  34 . Two cylindrical walls  46  and  48  project inwardly from the back side of the cover portion  44 . The outer wall  46  is disposed at the periphery of the cover portion  44 . The inner wall  46  is spaced slightly inward from the outer wall  44  and is concentric with the outer wall  46 . The walls  46  and  48 , along with the previously mentioned seal cavity  34 , forms a labyrinth seal. 
     The spring  60  is disposed around the hub  42  of the bearing shield  40 . One end of the spring  60  presses against the bearing  38  while the opposite end presses against the bearing shield  40 . Thus, the spring  36  biases the stub shaft  50  to an extended position. 
     To install the roller  10  between parallel frame members  12 , the roller  10  is held in a tilted position while the stub shaft  50  at one end is inserted into its mating mounting hole  14 . After the first end of the roller is inserted into the mounting hole  14 , the stub shaft  50  on the opposing end is pressed inward to move the stub shaft  50  to a retracted position (see FIG.  2 ). The second end is then lowered between the frame members  12  until the stub shaft  50  is aligned with its mating mounting hole  14  in the frame member  12 . When the stub shaft  50  is aligned with the mounting hole  14 , the spring  36  urges the stub shaft  50  to an extended position so that it engages the mounting hole  14  (see FIG.  3 ). The bolt  62  is then inserted through the mounting hole  14  in the frame member  12  and threaded into the threaded hole  58  in the stub shaft  50  to secure the roller  10  in place. 
     FIGS. 4-6 illustrate an alternate embodiment of the roller  10 . This embodiment uses the same roller  10  and bearing housing  22  as previously described. The description of these elements, therefore, will not be repeated. However, it should be noted that the reference numbers in FIGS. 4-6 which are the same as the reference numbers in FIGS. 1-3 indicate the same parts. 
     The second embodiment, shown in FIGS. 4-6, eliminates the stub shaft  50 . Instead, a bearing shaft  70  is integrally formed with the bearing shield  40 . The bearing shaft  70  is journalled in the bearing  38 . The bearing shaft  70  is hollow and internally threaded. The inner end  72  of the bearing shaft is designed to retain the bearing shaft  70  in place. Two diametrically opposed relief slots  74  are formed in the inner end  72  of the bearing shaft  70 . The purpose of the relief slots  74  is to facilitate insertion of the bearing shaft  70  through the bearing  38 . When the bearing shaft  70  is pressed into the bearing  38 , the inner end  72  collapses inwardly to allow the bearing shaft  70  to pass through the bearing  38 . When the bearing shaft  70  passes through the bearing  38 , the inner end  72  expands back to its original form due to the inherent resiliency of the material. 
     An insert  80  is adapted to fit into a recess formed in the outer surface of the bearing shield  40 . The insert  80  includes a hexagonal stub member  82  and a base portion  84 . The hexagonal stub member  82  mates with the hole  14  in the frame member  12 . The base portion  84  of the insert  80  fits into a recess or socket formed in the outer surface of the bearing shield  40 . The base  84  of the insert  80  and the recess both have a square configuration to prevent rotation of the insert  80  relative to the bearing shield  40 . 
     A hole  86  extends through the insert  80 . The bolt  62 , which secures the roller  10  to the frame member  12 , passes through the insert  80  and engages the threads on the inner surface of the bearing shaft  70 . Consequently, the insert  80  gets captured between the bearing shield  40  and the frame member  12  so that it cannot be dislodged. 
     One advantage of using insert  80  is that it can be easily interchanged in the field. For example, if the frame member  12  has square mounting holes  14  rather than hexagonal mounting holes  14 , an insert  80  with a square stub  82  can be inserted into the shield  40 . Without the replaceable insert  80 , it would be considerably more difficult to modify the roller to fit a square mounting hole  14 . 
     Based on the foregoing, it will be apparent that the conveyor roller  10  of the present invention can be easily installed and removed from a pre-fabricated conveyor frame. Moreover, the present invention employs a “shaftless” design which substantially reduces the weight of the roller. 
     The present invention may, of course, be carried out in other specific ways than those herein set forth without departing from the spirit and essential characteristics of the invention. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive, and all changes coming within the meaning and equivalency range of the appended claims are intended to be embraced therein.