Abstract:
A fixture exchange rail system is provided having first and second fixture assemblies movably mounted with respect to respective first and second stationary rails. A movable rail is disposed substantially adjacent to, and movable between, the first and second stationary rails. The movable rail is sufficiently configured to selectively receive the first and second fixture assemblies thereon. A method of operating a workstation having a fixture exchange rail system operable to enable work on a workpiece is also provided including the steps of: A) determining the style of workpiece present at the workstation; B) aligning a movable rail with one of a first and second stationary rail having a respective first and second fixture assembly mounted thereto corresponding to the style of workpiece; and C) moving the fixture assembly corresponding to the style of workpiece from the stationary rail to the movable rail.

Description:
TECHNICAL FIELD 
     The present invention relates to overhead tool or fixture rail systems for workstations and a method of using same. 
     BACKGROUND OF THE INVENTION 
     Overhead tool or fixture rail systems are frequently utilized in manufacturing plants having assembly lines. The overhead fixture rail systems are typically arranged in parallel with the assembly line. These overhead fixture rail systems are utilized for hanging tools or fixtures that are required at a given workstation for the use of the production line workers in assembling a workpiece. Modern assembly line designs typically require provisions for the assembly of more than one type of workpiece on the same assembly line. As such, many different types of tools or fixtures are typically hung from a single overhead fixture rail system. This may lead to operator confusion over which tool to use for a given style of workpiece. Additionally, the operator will be required to move the additional tools or fixtures along the rail system in order to position the tool or fixture required for the particular style of workpiece. 
     SUMMARY OF THE INVENTION 
     A fixture exchange rail system is provided having a first fixture assembly movably mounted with respect to a first stationary rail and a second fixture assembly movably mounted with respect to a second stationary rail. A movable rail is disposable substantially adjacent to the first and second stationary rails. The movable rail is movable between the first and second stationary rails and is sufficiently configured to selectively receive the first and second fixture assemblies thereon. 
     A method of operating the fixture exchange rail system of the present invention is also provided. The method includes the steps of: A) determining the style of workpiece present at the workstation; B) aligning a movable rail, either manually or automatically, with one of a first and second stationary rail having a respective first and second fixture assembly mounted thereto corresponding to the style of workpiece; and C) moving one of the respective first and second fixture assembly corresponding to the style of workpiece from the first and second stationary rail to the movable rail. 
     The above features and advantages and other features and advantages of the present invention are readily apparent from the following detailed description of the best modes for carrying out the invention when taken in connection with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic plan view of a portion of an assembly line illustrating a workstation incorporating a fixture exchange rail system of the present invention; and 
         FIG. 2  is an illustration, in flowchart form, of a method of operating the fixture exchange rail system of  FIG. 1 . 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to  FIG. 1 , there is shown a portion of a production or assembly line  10 . The assembly line  10  includes a workstation  12  incorporating a fixture exchange rail system  14  of the present invention. The workstation  12  is sufficiently configured to receive a workpiece  16 , such as a partially assembled vehicle, as shown in  FIG. 1 . The workpiece  16  is guided along the assembly line  10  by a plurality of tracks  18 . 
     The fixture exchange rail system  14  includes a first, second and third stationary rail  20 A,  20 B, and  20 C, respectively, and a movable rail  22 . The movable rail  22  is disposed adjacent and movable with respect to the first, second, and third stationary rails  20 A,  20 B, and  20 C in the direction of arrow  24 , i.e. substantially parallel to the workpiece  16 . The movable rail  22  is suspended by a plurality of tracks  26 , while the first, second, and third stationary rails  20 A,  20 B, and  20 C are suspended by a plurality of support members  28 . 
     First, second, and third fixture assemblies  30 A,  30 B, and  30 C are mounted to a respective one of the first, second, and third stationary rails  20 A,  20 B, and  20 C and are slidable within channels  32  in the direction of arrows  34 . Each of the first, second, and third fixture assemblies  30 A,  30 B, and  30 C include a respective first, second, and third tool or fixture  36 A,  36 B, and  36 C each suspended from their respective stationary rail  30 A,  30 B, and  30 C by balancers  38 . Those skilled in the art will recognize that balancers  38  are operable to reduce the apparent weight of the fixtures  36 A,  36 B, and  36 C, thereby reducing operator fatigue. Additionally, the balancers  38  may be operated by pneumatic force, spring tension, etc., while remaining within the scope of that which is claimed. 
     The first, second, and third fixture assemblies  30 A,  30 B, and  30 C further include a connector member  40 , while a connector member  42  is mounted with respect to the moveable rail  22 . The connector members  40  and  42  taken together form a connector mechanism  44  operable to selectively connect the first, second, and third fixture assemblies  30 A,  30 B, and  30 C with the movable rail  22 . The first, second, and third tool or fixture  36 A,  36 B, and  36 C are actuated pneumatically via an air hose  46 . 
     Clamping members  48  are provided respectively on each of the first, second, and third stationary rails  20 A,  20 B, and  20 C. The clamping members  48  are operable to retain the movable rail  22  with respect to one of the first, second, and third stationary rails  20 A,  20 B, and  20 C during the transfer of the first, second, and third fixture assemblies  30 A,  30 B, and  30 C to and from the movable rail  22 . Those skilled in the art will recognize that the clamping member  48  may be mounted to the movable rail  22 , while remaining within the scope of that which is claimed. The clamping members  48  are controlled by a controller  50 . Additionally, the controller  50  operates to position the movable rail  22  with respect to a selected one of the first, second, and third stationary rails  20 A,  20 B, and  20 C through a selectively actuatable stop mechanism  52 . 
     Position sensors  54  are provided respectively on each of the first, second, and third stationary rails  20 A,  20 B, and  20 C and operate to provide a signal to the controller  50  to communicate the position of the first, second, and third fixture assemblies  30 A,  30 B, and  30 C. It should be noted that  FIG. 1  illustrates the second and third fixture assemblies  30 B and  30 C in the parked position, while the first fixture assembly  30 A is shown in the out of park position. A sensor  56  is preferably mounted with respect to the assembly line  10 . The sensor  56  operates to communicate to the controller  50  the type or style of workpiece  16  currently at the workstation  12 . In the preferred embodiment, the sensor  56  will operate using optical sensing techniques such as, for example, bar code scanning; however, those skilled in the art will recognize other means of sensing the type or style of workpiece  16  while remaining within the scope of that which is claimed. 
     A sensor  58  is mounted on the movable rail  22  and operates to signal when the connector member  40  of one of the first, second, and third fixture assemblies  30 A,  30 B, and  30 C has engaged the connector member  42  mounted on the movable rail  22  thereby completing the connection of the connector mechanism  44 . The sensor  58  may be mounted with respect to the connector member  42 , but need not be. A drive device  60  is controlled by the controller  50  and operates to selectively move the movable rail  22  with respect to the first, second, and third stationary rails  20 A,  20 B, and  20 C. 
     Referring to  FIG. 2 , and with continued reference to  FIG. 1 , an exemplary method of operating the fixture exchange rail system  14  of the present invention is represented in  FIG. 2 , in flowchart form, and is generally indicated at  62 . The method  62  begins at step  64  and proceeds to step  66  where it is determined if each of the first, second, and third fixture assemblies  30 A,  30 B, and  30 C are in the parked position. This condition is sensed by the position sensors  54  and communicated to the controller  50 . If at least one of the first, second, and third fixture assemblies  30 A,  30 B, and  30 C is not in the parked position the method proceeds to step  68  where they are manually parked; the method  62  then proceeds to step  70 . Alternately, if the first, second, and third fixture assemblies  30 A,  30 B, and  30 C are in the parked position, the method  62  proceeds from step  66  to step  70 . 
     At step  70 , a determination is made as to the style or type of the workpiece  16 . This information is sensed by the sensor  56  and communicated to the controller  50  as described hereinabove. In the preferred embodiment, the controller  50  will command the drive device  60  to move the movable rail  22  to one of the first, second, and third stationary rails  20 A,  20 B, and  20 C containing the respective first, second, and third fixture assemblies  30 A,  30 B, and  30 C appropriate for work on the type of workpiece  16  currently within the workstation  12 , as indicated at step  72 . The automatic movement of the movable rail  22  does not pose a safety concern since none of the first, second, and third fixture assemblies  30 A,  30 B, and  30 C are mounted thereto. Upon reaching the appropriate one of the first, second, and third stationary rails  20 A,  20 B, and  20 C, for example the first stationary rail  20 A, the controller  50  will command the stop mechanism  52  to lock the movable rail  22  in position. At this point, the method  62  will proceed to step  74  where the controller  50  commands the clamping member  48  to engage, thereby clamping the movable rail  22  with respect to the first stationary rail  20 A. 
     Proceeding to step  76 , the first fixture assembly  30 A is moved from the respective first stationary rail  20 A to the movable rail  22 . Preferably, step  76  is accomplished manually to give the operator full control over the movement of the first fixture assembly  30 A, such that the first fixture assembly  30 A can be safely positioned overhead. The method  62  then proceeds to step  78  where a determination is made as to whether the first fixture assembly  30 A is connected to the movable rail  22  via the connector mechanism  44 . That is, a determination is made as to whether the connector members  40  and  42  are fully engaged. If the connector members  40  and  42  are not engaged, the method  62  moves to step  80  where the first fixture assembly  30 A is moved further into engagement with the movable rail  22 . The method then proceeds to step  82  where the controller  50  commands the clamping member  48  to unclamp the movable rail  22  from the first stationary rail  20 A. At which point the movable rail  22  is free to translate with respect to the first, second, and third stationary rails  20 A,  20 B, and  20 C. The method  62  then proceeds to step  84 . 
     At step  84 , the movable rail  22 , and therefore the first fixture assembly  30 A is positioned substantially adjacent to the workpiece  16  thereby allowing the first fixture assembly  30 A to be operated, at step  86 , to effect work on the workpiece  16 . Upon the completion of work on the workpiece  16 , the movable rail  22  is realigned with the first stationary rail  20 A at step  88 . Preferably, step  88  is performed manually to give the operator control of the first fixture assembly  30 A. Once aligned with the first stationary rail  20 A, the method  62  will proceed to step  90  where the movable rail  22  is clamped in place as a result of a command by the controller  50  to the clamping member  48 . Once the movable rail  22  is clamped in place, the method  62  proceeds to step  92  where the first fixture assembly  30 A is moved from the movable rail  22  to the first stationary rail  20 A such that the first fixture assembly  30 A engages the position sensor  54  to signal to the controller  50  that the first fixture assembly  30 A is in the fully parked position. The method  62  then proceeds to step  94  to begin the cycle again. 
     The fixture exchange rail system  14  of the present invention provides assembly line flexibility by accommodating multiple styles of the workpiece  16 , while maintaining ergonomically advantageous tool organization. Additionally, by automatically determining the style of workpiece  16  and directing the movable rail  22  to the appropriate one of the first, second, and third fixture assembly  30 A,  30 B, and  30 C, improper assembly and damage to the workpiece  16  caused by the use of an improper fixture assembly may be eliminated. 
     Additionally, although the foregoing description illustrates a fixture exchange rail system  14  having first, second, and third stationary rails  20 A,  20 B, and  20 C, those skilled in the art will recognize that additional or fewer stationary rails may be employed for a given workstation  12  while remaining within the scope of that which is claimed. 
     While the best modes for carrying out the invention have been described in detail, those familiar with the art to which this invention relates will recognize various alternative designs and embodiments for practicing the invention within the scope of the appended claims.