Abstract:
A rollup barrier is provided for a robotic station. The barrier includes a track having a tapered portion at its lower end. A switch is mounted at the extreme lower end of the track. The switch prevents actuation of the robotic equipment unless the barrier is moved to its extreme lowermost position. Extensible cylinders are used for connection to a chain trained around a sprocket in order to roll the roller.

Description:
BACKGROUND OF THE INVENTION 
   The present invention relates to a safety barrier and method for using same. Rollup barriers have been utilized in the past. 
     FIG. 6  shows a typical prior art rollup barrier. This barrier is designated by the numeral  10  and includes a work piece holder  12  which is adapted to hold a work piece (not shown). The work piece holder  12  is surrounded by fixed side barriers  14  and an inner barrier  16 . A roller  18  is mounted above and forwardly of the work piece holder and includes a flexible barrier  20  which is rolled thereon. The barrier  20  moves from the uppermost position shown in  FIG. 6  to a lowermost position wherein the free end  22  is positioned adjacent the supporting surface. A pair of tracks  24  guide the flexible barrier as it moves to its lowermost position. The prior art work station  10  operates the roller  18  by use of a electric motor  29 . 
   A plurality of cells  28  project a plurality of light beams creating a light sheet  26 . The purpose of this light sheet  26  is to detect when an operator is positioned between the barrier  20  and the work station  12  after the barrier  20  has been lowered to its lowermost position. If the light shield detects a worker in this area, the light shield causes any robotic equipment to be deactuated so that it cannot be actuated until the worker is removed from the area designated by the light shield  26 . It would be desirable to devise a flexible barrier which does not rely upon the light shield  26  for detecting an operator positioned between the barrier  20  and the work station  12 . 
   Therefore, a primary object of the present invention is the provision of an improved safety barrier and method for using same. 
   A further object of the present invention is the provision of an improved safety barrier which eliminates the need for a light sheet at the lower end of the device for detecting an operator located in a dangerous position. 
   A further object of the present invention is the provision of an improved safety barrier and method for using same which includes a track that guides the safety barrier inwardly towards the work piece holder to a position wherein the lower end of the barrier is sufficiently close to the work piece holder to prevent an operator from being located therebetween. 
   A further object of the present invention is the provision of a safety barrier and method for using same which utilizes a mechanical switch located at the lower end of the barrier which can only be activated to activate the robotic equipment for working on the work piece when the barrier has been moved to its lowermost position. 
   A further object of the present invention is the provision of a safety barrier and method for using same which uses pneumatic cylinders for moving the barrier and unrolling the roller. 
   A further object of the present invention is the provision of an improved safety barrier and method for using same which is economical to manufacture, durable in use, and efficient in operation. 
   SUMMARY OF THE INVENTION 
   The foregoing objects can be achieved by a safety barrier for a work station having a support surface, a work piece holder on the support surface having a front and a rear end, a work piece being held by the work piece holder, and a tool adapted to engage and perform tasks on the work piece. The barrier comprises a first frame member and a second frame member mounted on the supporting surface on the opposite sides of the work piece. An elongated roller extends between the first and second frames and is mounted for rotation about a longitudinal roller axis located in spaced relation above the supporting surface. A flexible safety barrier is rolled upon the roller and includes an upper barrier end attached to the roller and a free barrier end adapted to move from a rolled up position adjacent the roller to a rolled down position adjacent the supporting surface in response to rotation of the roller about the roller axis. Each of the first and second frame members includes a guide for guiding the flexible barrier as the free end of the barrier moves from the rolled up position to the rolled down position. The guides of the first and second frame members guide the lower barrier sufficiently close to the work piece holder to avoid space therebetween sufficient for a human being standing on the support surface. A switch is electrically connected to the tool and has an inoperative position preventing actuation of the tool and an operative position permitting actuation of the tool. The switch is biased to the inoperative position and is located so as to be responsive to engagement by the free end of the flexible barrier to move from the inoperative position to the operative position only when the free end of the flexible barrier is in the rolled down position. 
   According to another feature of the invention, a sprocket is mounted to the roller and a chain is trained around the sprocket. The chain includes a first chain end and a second chain end on opposite sides of the sprocket. First and second prime movers are connected to the first and second chain ends respectively and are adapted to move the chain on the sprocket to cause the roller to rotate and move the flexible barrier between its rolled up and rolled down positions. 
   According to another feature of the present invention, the first and second prime movers each comprise an elongated cylinder and a piston and rod assembly longitudinally extensible relative to the cylinder. 
   According to another feature of the present invention, the guides of the first and second frame members each comprise an elongated track, the flexible barrier having track followers guided within and by the tracks of the first and second frame members. 
   According to another feature of the present invention, the track followers comprise a plurality of wheels mounted for movement in the elongated tracks of the first and second frame members. 
   According to another feature of the present invention, the roller is positioned above or to the rear of the front end of the work piece holder, and a crane includes a support member positioned in front of the roller for lifting the work piece and holding the work piece for attachment to the work piece holder. 
   According to another feature of the present invention, the tracks each include an upper track end positioned above or to the rear of the front end of the work piece holder, an intermediate track positioned in spaced relation in front of the work piece holder, and a lower track extending in a rear direction from the intermediate track. 
   According to the method of the present invention, the work piece is mounted to a work piece holder having a front end and a rear end. A tool is utilized for performing functions on the work piece holder and the tool includes an actuated state and a non-actuated state. A flexible barrier includes an upper end and free end in front of the work piece holder. The flexible barrier is lowered to its lowered position wherein the upper end of the barrier is above the work piece and the free end of the barrier is located below the work piece and sufficiently close to the front end of the work piece holder to prevent a human being from standing on the supporting surface between the work piece holder and the free end of the barrier. 
   The method further comprises preventing the lower end of the flexible barrier from moving to the lowered position if a human being is positioned between the work piece holder and the free end of the barrier. 
   The method further comprises moving a switch from a normal position preventing actuation of a tool to a second position actuating the tool only in response to the movement of the free end of the barrier to its lowered position. The switch remains in the normal position at all other times. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view of the barrier of the present invention. 
       FIG. 2  is a sectional view taken along line  2 — 2  of  FIG. 1 . 
       FIG. 3  is a sectional view taken along line  3 — 3  of  FIG. 1  and showing the relationship of the device to a robotic work station. 
       FIG. 4  is a sectional view similar to  FIG. 3 , but showing an operator positioned between the lower end of the barrier and the work piece holder. 
       FIG. 5  is a sectional view similar to  FIGS. 3 and 4 , but showing a modified form of the invention. 
       FIG. 6  is a perspective view showing a prior art barrier. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Referring to  FIGS. 1–4 , the numeral  30  designates the barrier assembly of the present invention. Barrier assembly  30  includes a first frame member  32  and a second frame member  34  positioned in spaced relation to one another. A roller  36  extends between the first and second frame members and is rotatably mounted thereon for rotation about a roller axis  38 . Rolled upon the roller  36  is a roll up barrier  40 . A pair of guide tracks  42  are provided in each of the first and second frame members  32 ,  34 . And at the lower ends of guide tracks  42  are a pair of guide beams  44  which are angled away from the vertical orientation of the upper portions of the guide tracks  42 . Each guide track  42  includes an upper end  46 , a vertical middle  48 , and an angled lower end provided by the guide beams  44 . Guide beams  44  are C-shape in cross section and include flanges  52 . 
   The barrier  40  includes a plurality of cross bars  54  mounted therein. The cross bars have rollers  56  at their opposite ends which are guided within the guide tracks  42  and the channels provided by the angled lower ends  50  of the guide tracks  42 . The barrier  40  includes a free end  58  which move from its uppermost position adjacent the roller  36  to its lowermost position shown in  FIG. 3 . In its lowermost position, the free end  58  is angled away from the vertical plane of the vertical middle  48  of the guide tracks  42  and toward the front end  82  of the workstation. A switch  60  is mounted at the extreme lower end of the guide track  42  and includes a switch arm  62 . Switch  60  is adapted to normally be in an inoperative position, and is connected to a robotic tool  68 . When in its inoperative position, the switch prevents actuation of the robotic tool  68 . However, the switch arm  62  is movable to an operative position in response to being engaged by the free end  58  of the barrier  40 . When so engaged (as shown in  FIG. 3 ), the switch arm moves and causes the switch to move to its operative position thereby freeing the robotic tool  68  to be actuated for performing a function on a work piece  66  held in a work piece holder  64 . 
     FIGS. 3 and 4  shows the relative position of the guide track  42  and the barrier  40  to the work piece holder  64  and the work piece  66 . The work piece holder  64  includes a front end  82  which is positioned in very close vertical alignment with the free end  58  of the barrier  40  when the free end is in its lowermost position. The closeness of front end  82  and switch  60  should be such that there is insufficient space for a worker to stand between the two. In  FIG. 3  the free end  58  is shown to be slightly beneath the front edge  82  of the work piece holder  64 . While it is not necessary that there be overlapping, it is important that the free end of the barrier  58  be located sufficiently close to the front edge  82  of the work piece holder to prevent an operator from being positioned therebetween.  FIG. 4  shows what happens when an operator is positioned between the baffler and the front edge  82  of the work piece holder  64 . The worker engages the free end  58  of the baffler before the baffler reaches its lowermost position, and before the free end  58  can engage the switch arm  62 . Thus when an operator such as  84  is positioned between the baffler  40  and the front of the work piece holder  82 , the worker prevents the barrier from moving to its lowermost position and therefore prevents the ability of the robotic tool  68  to be actuated. 
     FIG. 2  illustrates the manner for operating the roller  36 . A first cylinder  70  and a second cylinder  72  are attached at their lower ends to the support frame  34 . A sprocket  74  is attached to the roller  36  and rotates about the axis  38 . Sprocket  74  has a chain  76  trained around it and one end of the chain  76  is connected to a first rod and piston assembly  78  and the other end of the chain  76  is connected to the second rod and piston assembly  80 . As can be seen in  FIG. 2 , the second assembly  80  is extended and the first assembly  78  is retracted. Rotation of the sprocket  74  can be accomplished by extending the rod and piston assembly  78  and by retracting the rod and piston assembly  80 . Reverse rotation can also be achieved by reversing this extensible action. Thus it is possible to rotate the roller  36  and cause the barrier to move between its uppermost position and its lowermost position. The free end  58  of the barrier  40  is propelled by gravity only in response to the rotation of the roller  36 . Therefore, as shown in  FIG. 4 , if a person  84  engages the free end  58 , the downward movement of the free end  58  stops and the barrier  40  merely begins folding in response to the rotation of the roller  36 . It has been found that the use of extensible cylinders  70 ,  72  and piston and rod assemblies  78 ,  80  creates a faster and more efficient movement of the roller than has been previously achieved with electric motors. 
     FIG. 5  illustrates an alternative form of the invention designated by the numeral  86 . The barrier  86  shows a frame  88  which includes an upper angled end  90  for the track and an intermediate vertical portion  92  for the track, and a lowered angled end  94  for the track. A crane  96  includes a movable crane support  98  and a cable  100  having a hook  102  on its lower end. The crane  96  is shown mounted on rollers  104  so it can be moved into position. Other numerals correspond to the numerals set forth in  FIGS. 1–4 . 
   The advantage of the modified form shown in  FIG. 5  is that the roller  38  is out of the way of crane  96  so that heavy work objects can be loaded by the crane  96  onto the work support  82  without encountering interference from the roller  36 . The lower end  94  of the track is essentially the same as shown in  FIGS. 1–4 . 
   The invention has been shown and described above with the preferred embodiments, and it is understood that many modifications, substitutions, and additions may be made which are within the intended spirit and scope of the invention. From the foregoing, it can be seen that the present invention accomplishes at least all of its stated objectives.