Patent Publication Number: US-7587983-B2

Title: Drive mechanism for a track mounted body

Description:
This invention relates to a drive mechanism for a track mounted body and in particular to a mechanism that enables movement of the body along the tracks without the use of a load bearing drive wheel. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     An example of where the invention will find application are track mounted shelving or cabinet units. Such shelving units are designed to provide compact storage by having the shelving units abut against one another with only one access opening being provided within which the shelves can be accessed. The shelves can be separated by moving them along the track to open up access at different points along the assembled shelves. 
     2. Description of the Related Art 
     In many instances, shelves are moved manually although it is common to provide a manual crank mechanism or electric drive means to move the shelves. This is particularly necessary when each shelving unit carries a heavy load. 
     The conventional means of providing a drive to each of the shelves is to connect the track mounted wheels to some form of drive means. This means that an axle extends across the base of each shelf to which the wheels are mounted. The shaft is then connected to some form of independent drive means which may be a manually rotated handle or an electric motor driven through a reduction gear box. 
     The need to mount a shaft within the base of the shelf unit results in added cost and complexity to the shelving unit. It would be desirable to have a drive mechanism that could be easily fitted to shelving units that were designed to be manually moved. Accordingly, it is an object of this invention to provide such an arrangement that meets this objective and overcomes the above mentioned problems. 
     SUMMARY OF THE INVENTION 
     In one form, the invention is a drive mechanism for a body, wherein said body has a plurality of load bearing track engaging wheels that allow said body to move back and forth along a track, that comprises,
         an actuator attached to said body that is manually or mechanically driven,   a non-load bearing drive wheel that is attached with respect to said body so that it engages a stationary surface adjacent said body, and   a drive coupling means between said actuator and said drive wheel wherein actuation of said actuator means causes rotation of said drive wheel which moves said body along said tracks.       

     The above invention avoids the need to have a drive axle mounted through the base of each shelf unit. In addition, it enables a simple arrangement to be attached to an existing shelf unit to convert it from a shelf unit that needs to be manually pushed along the tracks to a unit that incorporates a drive mechanism. 
     The actuator preferably is a manually rotated capstan wheel or a crank but the drive wheel could equally be driven by an electric motor via a reduction gear box. 
     The drive wheel applies force to move the body by pushing against the surface or ground on which the body is mounted. Preferably, the periphery of the drive wheel comprises a high friction material such as a polyurethane material and surface against which the periphery of the wheel engages may also be roughened or have a high coefficient of friction to avoid slippage of the drive wheel. 
     Preferably, the drive coupling between the actuator and drive wheel includes reduction gearing. The gearing can include many different types of components such as tooth belts, v-belts, meshing gear wheels and the like. One preferred arrangement is the use of a first belt that extends from the drive shaft towards the base of the body. This belt drives a first pulley wheel that in turn drives a second pulley wheel and there is a belt that extends from the second pulley to a pulley wheel that is attached to the drive wheel which in turn rotates the drive wheel. 
     In order to fully understand the invention, a preferred embodiment will be described. However, it should be realised that the invention is not necessarily restricted to the precise details of this embodiment. In particular, the embodiment is described in relation to application of the invention to a shelving system. However, there may be other applications to which the invention could be equally suited. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention is illustrated in the accompanying drawings in which 
         FIG. 1  shows three shelf units, two of which are track mounted, 
         FIG. 2  shows an exploded view of a drive mechanism and covers that are attached to the side of a shelf unit, 
         FIG. 3  shows a perspective view of an assembled drive mechanism attached to the side of a shelf unit, 
         FIG. 4  shows an exploded view of a drive mechanism, and 
         FIG. 5  shows a cross-section of a carriage within which gearing and the drive wheel are mounted. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to  FIG. 1 , there are three shelf units  10 ,  11  and  12  with shelves  13 . Shelf units  11  and  12  are mounted to load bearing tracks  14  via wheels  15 . Tracks  14  provide a longitudinal recess within which the wheels  15  locate. A pair of wheels  15  are used at each side of the shelf units  11  and  12  and are rotatably mounted about a horizontal axis within a housing which is attached at each side of the unit  11  and  12 . 
     The shelf unit  10  is an end shelf unit and therefore is fixed with respect to the tracks  14 . Shelf units  11  and  12  are moved along the tracks  14  to provide access between various pairs of shelves. For example, shelf unit  11  can be moved so as to open up access between shelf unit  11  and  10 . 
       FIGS. 2 ,  3  and  4  show more detailed views of the drive mechanism. It has an actuator that comprises a drive shaft  17  to which a hand operated wheel  18  is attached. The drive shaft  17  is rotatably secured to a column  19  with column  19  attached to the side of the shelf unit. 
     A first drive belt  20  extends from a pulley wheel  18   a  on the wheel  18  downwardly to a carriage  27  that is located towards the base of the shelf unit  11  and  12 . The belt  20  is an internal tooth belt and the pulley wheel  18   a  on the wheel  18  is toothed to engage with the belt  20 . For ease of drafting purposes, the teeth on the belt  20  and pulley wheels are not drawn. 
     The carriage  27  has mounted to it a first pulley wheel set comprising a first pulley wheel  16  and a second pulley wheel  21 . In addition, the drive wheel  24  is also mounted within the carriage  27 . The belt  20  locates around the first pulley wheel  16  which is connected to the second pulley wheel  21 . A second tooth belt  22  locates around the second pulley wheel  21  and drives a third pulley wheel  23  which is connected to the drive wheel  24 . As can be seen from the drawings, the first pulley wheel  16  is a larger diameter than the second pulley wheel  21 . The combination of the pulley wheel  18   a  on the handle  18  and its diameter difference with the first pulley wheel  16  and the diameter difference between the pulley wheel  16  and the second pulley wheel  21  provides the required reduction in gearing. 
     The carriage  27 , having the drive wheel  24  mounted therein, is pivotally attached to the side of the shelf unit via a pivot connection  28  that is located entirely outward of the side or outer wall of the body of the shelving unit (see  FIGS. 3-5 ). In this embodiment the pivot connection  28  is secured to a plate  29  that is attached to the column  19  and the side of the shelving unit  11  and  12 . 
     The carriage  27  is a u-shaped bracket between which the first and second pulley wheels  16  and  21  and the drive wheel  24  and third pulley drive wheel  23  are rotatably mounted. The axle  36  of the drive wheel  24  is rotatably mounted about a horizontal axis to an inner carriage  37 . The inner carriage  37  locates within the carriage  27 . Elongate slots  38  are provided in the carriage  27  through which the ends of the axle  36  locate. Circips  39  are located on each end of the axle  36  and retain the axle  36  within the carriage  37 . This enables the inner carriage  37  to slide with the carriage  27  and this movement is controlled by threaded bolt  40  which locates within a nut  41  in the end of the inner carriage  37 . Rotation of the bolt  40  enables the inner carriage  37  to be moved to enable tightening the belt  22 . 
     The drive wheel  24  and the wheel  15  on a side of the shelf unit  11 , 12  are mounted for rotations about respective horizontal axes separate from the pivot connection  28 . 
     A spring  30  applies a downward force to the carriage  27  so that the carriage  27  is rotated in an anti clockwise direction. This acts to force the drive wheel  24  against the linear strip  26  of the drive wheel track and to tighten belt  20 . A bracket  31  is part of the plate  29  and the carriage  27  has a flange  32  that locates beneath the bracket  31 . The spring  30  is held under compression between the bracket  31  and the flange  32  so that the necessary rotated force is applied to the carriage  27 . The bracket  31  and flange  32  are on one side of the carriage  27 . However, they may be located centrally over the carriage  27  so that no eccentric force is applied to the carriage. This will prevent side loading being applied to the drive wheel  24 . 
     The drive wheel track  25  is preferably co-extruded with the track  14  and extends parallel to and horizontally alongside the track  14 . The linear strip  26  of the drive wheel track  25  is preferably roughened or has an abrasive strip adhered to it. The drive wheel  24  preferably has a polyurethane tyre which, in combination with the linear strip  26 , provides maximum grip. This grip, in combination with the force applied by the spring  30  is sufficient to ensure that the drive wheel  24  does not slip with respect to the linear strip  26 . 
     Although this preferred embodiment uses a track  25 , which is distinct from the load bearing tracks  14 , the invention would equally work without such a track where the drive wheel  24  engages a floor such as a linoleum surface. 
     The advantage of the pivotally mounted carriage  27  is that a perfectly level track is not required. The floor surface or track  25  may have undulations which are accommodated by the spring  30  and movement of the carriage  27 . 
     As seen in  FIG. 2 , a first cover  33  locates over the side of the shelf units  11  and  12  over the column  19  and a second cover  34  locates over the first cover  33  and extends from the handle  18  down to and over the carriage  27 . 
     The gearing ratio gives adequate speed of movement of the shelving unit while at the same time not requiring excessive effort to be applied to the hand operated wheel  18 . 
     It will be clear from the above description that the invention provides a unique means of providing a drive mechanism for track mounted bodies such as shelf units. The drive mechanism does not make use of a load bearing wheel and does not require the installation of an axle through the base of the unit moving along the track. 
     The design is useful in that it can be manufactured so as to fit to units that are designed to be manually moved. However, the design could equally be incorporated into the shelving unit rather than being a bolt on assembly.