Abstract:
A side-by-side robot workcell includes two tables each of which is movable from a work position to a load position. Linkages are connected to the tables and cause the tables to have a slow speed at the time the tables approach either the load or the work position, and a faster speed in the middle of the movement between the work and load positions.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to a side-by-side robot workcell. 
     Workcells are often used with robotic systems. The workcells usually include a work piece holder which moves from a load position adjacent the operator to a work position adjacent the robot. 
     There is a need for a low cost robotic weld station which maintains the safety and functionality of the workcell, but which minimizes the cost. 
     Therefore, a primary object of the present invention is the provision of an improved side-by-side robot workcell. 
     A further object of the present invention is the provision of an improved side-by-side robot workcell which is simple in construction and low in cost. 
     A further object of the present invention is the provision of a side-by-side robot workcell which includes two tables that move quickly to their load and work positions, but which slow down as they approach either the load or the work position. 
     A further objection of the present invention is the provision of a side-by-side robot workcell which minimizes the need for the operator to move and which maximizes the safety of the operator. 
     A further object of the present invention is the provision of an improved side-by-side robot workcell which moves the tables to load positions which substantially wrap around the operator so that the operator does not have to walk or move distances to load the work piece on the work piece tables. 
     A further object of the present invention is the provision of a side-by-side robot workcell which is efficient in operation, economical in manufacture and durable in use. 
     SUMMARY OF THE INVENTION 
     The foregoing objects may be achieved by a work piece cell having a frame and a work piece table adapted to hold a work piece. A hinge mechanism connects the work piece table to the frame for movement about a pivot axis from a load position to a work position. A link member is connected to the hinge mechanism and is movable back and forth between a first position and a second position for causing the work piece table to move about the pivot access between the load and the work positions respectively. A power member is connected to the frame and to the link member for causing movement of the link member between its first and second positions. A counterbiasing member is connected to the frame and to the link member and exerts a counterbiasing force on the link in a direction opposite to the force exerted by the power member during at least a portion of the time that the power member moves the link member between the first and second positions. 
     According to one feature of the invention the link member moves to an intermediate position between its first and second positions and the counterbiasing member exerts a large counterbiasing force on the link member when the link member is in its first or second positions. The counterbiasing member also exerts a lesser biasing force on the link member when the link member is in its intermediate position. 
     Another feature of the present invention includes two work piece tables constructed in the manner described above each being movable between a load position and a work position. When in the work position the two tables are positioned side-by-side with respect to each other and are positioned adjacent the robot. When in the load position the two tables are positioned closely adjacent the operator so that the operator is not required to move far distances to place a work piece on the work piece table. 
    
    
     BRIEF DESCRIPTION OF THE FIGURES OF THE DRAWINGS 
     FIG. 1 is a pictorial view of the side-by-side robot workcell of the present invention. 
     FIG. 2 is a plan view of the linkage, cylinder, and shock absorber construction of the present invention and showing the vertical hinges in section. 
     FIGS. 3A,  3 B, and  3 C are schematic views showing the arrangements of the cylinder, link, and shock absorber during movement of the table between its load and work positions. 
     FIG. 4 is a schematic view showing the side-by-side arrangement of the two worktables in both their work position and their loading position. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to the drawings the numeral  10  generally designates the side-by-side workcell of the present invention. Cell  10  is mounted upon a base  8  and includes a first table  12  and a second table  14  (FIG. 4) which are mounted to first and second hinge mechanisms  16 ,  18  respectively for pivotal movement between a side-by-side work position (shown in solid lines in FIG. 4) and a loading position (shown in shadow lines in FIG.  4 ), 
     The mechanism for moving the tables between their load and work positions include first and second links  20 ,  22 , first and second cylinders  24 ,  26 , and first and second shock absorbers  28 ,  30 . 
     The base  8  includes a front frame member  32 , a rear frame member  34 , and a plurality of cross frame members  36  which extend therebetween. Extending upwardly from the base  8  are first and second vertical frame members  38 ,  40  which support a stationary shield plate  42  at their upper ends. A control panel  44  is also mounted to the first and second vertical frame members  38 ,  40 . 
     Extending across the front of vertical frame members  38 ,  40  is a stop plate  46  which has opposite angled ends  48 . 
     Each of the two first and second work tables  12 ,  14  include first and second vertical shield plates  50 ,  52  respectively. The tables  12 ,  14  are welded to the vertical hinge mechanisms  16 ,  18  respectively at a weld joint indicated by the numeral  54 . In addition a gusset member  56  is welded at its lower end to one of the first or second hinge mechanisms  16 ,  18  and extends at an angle upwardly to be welded to the under surface of one of tables  12 ,  14  so as to provide further support thereof. 
     Each of the first and second hinge mechanisms  16 ,  18  include a rotatable sleeve  58  which rotates about a vertical shaft  60  (FIG.  2 ). 
     Referring to FIG. 2, each of the first and second cylinders  24 ,  26  are hinged to a cylinder frame member  62  for pivotal movement about a clevis  64 . Each of the cylinders  24 ,  26  include a cylinder rod  66  which is pivotally connected at a pivot connection  68  to one of the links  20 ,  22 . 
     The first and second shock absorbers  28 ,  30  each include a shock absorber clevis  70  pivotally connecting the shock absorbers  28 ,  30  to frame  8 . Extending from each of the shock absorbers  28 ,  30  is a shock absorber rod  72 . The outer end of rod  72  is pivotally mounted to one of the links  20 ,  22  at a pivot connection  74 . 
     Referring now to the schematic diagrams of FIGS. 3A,  3 B and  3 C, the work piece table  14  is shown in its load position in FIG. 3A, its intermediate position in FIG. 3B, and its work position in FIG.  3 C. The cylinder  26  is in its fully extended position when the table  14  is in its load position shown in FIG.  3 A. It is partially extended in the intermediate position shown in FIG. 3B, and it is retracted in the work position shown in FIG.  3 C. 
     The shock absorber  30  has the rod  72  fully extended in the load position of FIG.  3 A and in the work position of FIG.  3 C. However, in the intermediate position shown in FIG. 3B the shock absorber is fully or at least partially retracted. 
     The geometry is chosen so that the counterbalancing force of the shock absorber  30  is at its maximum force in the load and work positions of FIGS. 3A and 3C, and it is at a minimum in the over center or intermediate position shown in FIG.  3 B. This results in the table moving more slowly at its work and load positions, but moving more quickly as it approaches and leaves the intermediate position. This insures that the table moves quickly as it approaches and leaves the intermediate position, but slows down immediately prior to reaching its load and work positions. 
     In the preferred embodiment cylinder  26  is a pneumatic cylinder. However, other types of cylinders could be used and other types of prime movers could be used such as electric motors, servo motors, or hydraulic motors. 
     Shock absorber  30  is preferably an automotive type of shock absorber. The mounting point geometry of the cylinder  26  and the shock absorber  30  is such that the cylinder has the smallest lever arm at the beginning and at the end of the table motion, and the shock absorber has the greatest lever arm at the beginning and end of the table motion. Conversely the air cylinder  26  has the greatest lever arm at mid stroke while the shock absorber  30  is hardly moving when the table is in this range. This makes the table move more slowly at the beginning and end of the motion, and more quickly through the center of the motion. This is referred to as a ramp up/ramp down velocity during the table movement, and is good for both safety and quick movement. 
     To permit a faster ramp up speed without affecting the ramp down speed, a split valve shock absorber may be used as shock absorber  30 . This type of shock absorber has more resistance while being extended than it does when being compressed. 
     The operator can initiate movement of the tables  12 ,  14  from their load positions to their work positions respectively by pressing the buttons  76  or  78  respectively on control panel  44 . However, for safety, the robot is used for initiating movement from the work position to the load position. This is done by programming the robot to press a button (not shown) when the robot has completed its work on the work piece. This procedure insures that the tables do not leave their work positions before the robot has completed its work. 
     In the work position the ends  48  of stop bar  46  engage the gussets  56  of work tables  12 ,  14  to prevent the tables from moving past their work positions. 
     The side-by-side work cell of the present invention minimizes the amount of walking for the operator, while not requiring the operator to be in a position where he or she may be in harms way of the robot or any welding arc flash. To accomplish this the two tables  12 ,  14  partially wrap around the operator&#39;s position. A panels  50 ,  52  and panel  42  also provide flash protection during welding operations and establish a barrier between the robot and the operator. 
     In the drawings and specification there has been set forth a preferred embodiment of the invention, and although specific terms are employed, these are used in a generic and descriptive sense only and not for purposes of limitation. Changes in the form and the proportion of parts as well as in the substitution of equivalents are contemplated as circumstances may suggest or render expedient without departing from the spirit or scope of the invention as further defined in the following claims.