Abstract:
A conveyor is powered by a rotating, generally horizontal drive tube or shaft engaged by angularly disposed trolley wheels, in which trolleys support the conveyed products or materials above the drive tube and clear of any parts of the conveyor structure that would interfere with the desired path of travel. Each of the trolleys is provided with load wheels which ride on load rails above the drive tube and associated drive wheels, thereby providing a structure upon which a platform or other support may be mounted for bearing the transported products.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of a prior filed, application Ser. No. 60/879,176, filed Jan. 8, 2007, entitled INVERTED OVERHEAD CONVEYOR. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to conveyors for transporting parts, products or materials in manufacturing, assembly or treatment operations. 
     BACKGROUND OF THE INVENTION 
     Overhead conveyors are utilized in various production, assembly and treatment environments to transport parts or products through various operational stages. Typically, such conveyors employ a rotating, generally horizontal drive tube or shaft that supports trolleys from which the load is suspended. Wheels on the trolleys ride on the upper surface of the rotating drive tube, and each is mounted for rotation about a driven wheel axis that is non-parallel and non-perpendicular to the drive tube axis, preferably at an acute angle to the drive axis. Overhead conveyors utilizing a drive where the load is suspended beneath the drive tube are disclosed, for example, in U.S. Pat. No. 4,203,511, issued May 20, 1980 to Uhing. 
     Overhead conveyors of this type, however, are restricted to applications in which the products being transported may be suspended beneath the drive tube. Accordingly, belt conveyors and similar configurations are typically used when it is desired to transport products or materials along a path that is spaced above the conveyor drive. However, belt conveyors do not provide the advantages of conveyors powered by a rotating drive tube in quiet operation and the safety provided by the friction drive which stops the advancement of the conveyed products if resistance to movement is encountered. 
     SUMMARY OF THE INVENTION 
     In an embodiment of the present invention the aforementioned problem is addressed by providing a conveyor powered by a rotating, generally horizontal drive shaft or tube engaged by angularly disposed trolley drive wheels, wherein trolleys support the conveyed products or materials above the drive tube and clear of any parts of the conveyor structure that would interfere with the desired path of travel. Each of the trolleys is provided with load wheels which ride on load rails above the drive tube and associated drive wheels, thereby providing a structure upon which a platform or other support may be mounted for bearing the transported products. 
     Other advantages of this invention will become apparent from the following description taken in connection with the accompanying drawings, wherein is set forth by way of illustration and example, an embodiment of the present invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side elevational view of a conveyor powered by a drive tube beneath the product support, parts thereof being broken away or shown in broken lines for clarity (driven wheels behind the drive tube are shown in full lines). 
         FIG. 1A  is an enlarged view of a portion of one of the trolleys shown in  FIG. 1 . 
         FIG. 2  is a vertical cross-section through the conveyor at a right angle to the drive tube, showing a trolley of the present invention as viewed in the direction of the transporting path, an upper connecting spring of the trolley being removed for clarity. 
         FIG. 3  is a view similar to  FIG. 2  showing the trolley including the upper connecting spring. 
         FIG. 4  is a side elevational view of one of the trolleys of the present invention removed from the drive tube and associated conveyor structure for clarity. 
         FIG. 5  is a perspective view of the trolley of  FIG. 4 . 
         FIG. 6  is a perspective view similar to  FIG. 5  but viewing the trolley from the opposite side thereof. 
         FIG. 7  is an end view looking essentially along the axis of the transporting path of the conveyor. 
     
    
    
     DETAILED DESCRIPTION 
     Referring to the drawings,  FIG. 1  illustrates a stretch of a horizontally extending conveyor comprising a portion of a horizontal span of a drive beam  10  to which longitudinally spaced bearing units  12  are mounted for the purpose of supporting a drive shaft or tube  14  of the conveyor system, two trolleys  16  thereof being shown. Legs  18  of upright supports (one of which is shown in  FIG. 1 ) elevate the conveyor system in the conventional manner above a floor or other underlying surface (not shown) and also maintain a predetermined spacing between the drive tube  14  a pair of spaced load rails  20  disposed above the drive tube  14 . As shown in  FIG. 2 , an upright frame comprising an inverted, U-shaped hanger assembly  22  supports the load rails  20  above a cross bar  19 . Drive is provided typically by an electric motor  24  coupled via gearbox  26  to a drive pulley  28  connected to drive tube  14  via belt  30 . 
     Referring particularly to  FIGS. 3-6 , each of the trolleys  16  of the present invention is inverted as compared with trolleys of prior overhead conveyors where products are carried by the conveyor beneath the trolleys. A yoke plate member  32  carries four driven wheels  34  as is clear in  FIGS. 3 and 5 , all of which contact the surface of the drive tube  14 . The axes of the four driven wheels  34  are at an acute angle with respect to the axis of the drive tube  14  as is typical in conveyor systems in order to propel the trolley  16  in an axial direction with respect to the drive tube  14  when the latter is driven by the motor  24 . The wheels  34  are pressed into contact with the drive tube  14  by a vertically oriented coil spring component  36  that is coaxial with and surrounds a depending stem  38  ( FIG. 3 ) to which the yoke plate  32  is mounted. It will be appreciated that two spaced stems  38  and associated coaxial springs are employed at the front and rear of the trolley  16 , one of which is seen in the figures. As will be further appreciated hereinbelow, the trolley  16  comprises two vertically spaced parts (spaced upper and lower sections  39  and  41 ) each elongated in the direction of travel and having an inverted, U-shaped transverse configuration. The sections  39  and  41  are maintained in operative interrelationship by a pair of coil springs  40 , both of which can be seen in the side view of  FIG. 4 . Lateral displacement is prevented by two pairs of guide wheels  37  on lower section  41  which rotate about vertical axes and contact the respective inner faces of load rails  20 . 
     A pair of upstanding trolley tabs  42  (see particularly  FIG. 2 ) each secured by two vertically spaced bolts  43  to the center portion of the lower trolley section  41  are received in respective spaced slots  44  ( FIGS. 4 and 6 ) in an elongated, inverted U-shaped top plate  46  of the upper section  39  of the trolley and thus permit the upper and lower trolley sections to be united and held by the springs  40 , upper section  39  being movable vertically on tabs  42  against the bias of springs  40  to conform to any irregularities in the load rails  20 . A channel-shaped load bar  48  atop the trolley  16  ( FIG. 2 ) has an opening in its base receiving a load bar pin  53  and is seated on a thrust bearing  50  and secured by a snap ring  52 . The pin  53  is secured by an upright retaining screw  51 . It should be understood that in  FIGS. 4-6  the thrust bearing  50  is directly beneath the snap ring  52  as the trolley is shown separately removed from the conveyor for clarity. Installed and in operation as illustrated in  FIGS. 1 and 2  supported by two spaced trolleys  16 , the load bar  48  is interposed between the thrust bearing  50  of each trolley and the associated snap ring  52 . 
     A horizontal product platform  54  or other support as desired is welded to the load bar  48  and thus may receive parts, products or other items as required (not shown) for movement along the conveyor line. It should be noted in this respect that platform  54  and the load items to be placed thereon are entirely clear of the underlying conveyor apparatus throughout the desired path of travel of the conveyed items along the conveyor line. 
     The lower, inverted U-shaped section  41  of the trolley body extends fore and aft and has four load wheels  56  comprising a front and rear pair thereof as is clear in  FIGS. 5 and 6 . Similarly, the upper, inverted U-shaped section  39  has front and rear pairs of load wheels  58 , the load wheels  58  and  56  cooperating to embrace the two laterally spaced load rails  20  and run on the upper and lower surfaces thereof as shown in  FIGS. 1-3 . Therefore, in operation the four load wheels  56  of the lower trolley section bear against and ride on the parallel, elongated lower surfaces of the two load rails  20 , and the four load wheels  58  of the upper trolley section ride on the parallel, elongated upper surfaces of the two load rails  20 . Accordingly, under the action of the two springs  40  that unite the upper and lower trolley sections, the load wheels  58  and  56  embrace the load rails  20  and run on the top and bottom surfaces thereof and thus are confined to the path defined by the load rails  20 , while the four drive wheels  34  are maintained in contact with the drive tube  14  by the action of springs  36 . A transported load on platform  54  of each conveyor unit of the system is thus carried and maintained above the underlying conveyor apparatus and clear of all of the drive components. 
     It should be understood that while certain forms of this invention have been illustrated and described, it is not limited thereto except insofar as such limitations are included in the following claims.