Abstract:
A component feeder including a lift for elevating a selection of components from a bulk storage, and a pick surface adjacent to the lift for receiving the selection of components. A spreader gives the selection of components a push for spreading the selection of components from the lift on the pick surface. The combination of a vertical lift and a separate pick surface adjacent to the lift enables the bulk storage being positioned right below the pick surface. The area of the pick surface is large in relation to the total footprint of the component feeder.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to a device for feeding components from a bulk storage. 
       BACKGROUND OF THE INVENTION 
       [0002]    Feeding individual components from a disordered bulk storage is a common task in automated industrial systems. Feeding devices using many different principles and in different embodiments are known for specific feeding tasks. One common type of component feeder is a vibratory bowl feeder which uses a vibratory movement to advance, orient and sort the components. Typical for vibratory bowl feeders and for many other types of feeders is that they need to be customized for a specific component. At the feeder outlet the components are arranged in a well-defined position and orientation for further processing. A feeder using a rotating disc for advancing components to pass an orientation filter is disclosed in WO89/02865. The feeder according to WO89/02865 further discloses a lift for selecting a number of components from a bulk storage. An upper surface of the lift is inclined such that gravity causes the components to glide on the rotating disc. 
         [0003]    Flexible feeders exist which are not limited to a certain component but can handle a variety of different components. Such feeders typically use a vision system for recognizing the components, and a robot for picking up the recognized components. One such flexible feeder is known from U.S. Pat. No. 5,687,831 wherein a set of conveyors is used to spread the components appropriately on a pick surface from where a gripper can pick them up after being recognized by a vision system. The feeder according to U.S. Pat. No. 5,687,831 is complicated especially because specific transport means are required for returning the remaining components back to the bulk storage. Moreover, as the bulk storage needs to be horizontally displaced in relation to the pick surface, the pick surface area is small in comparison to the total footprint of the feeder. U.S. Pat. No. 7,028,829 provides a similar solution with similar problems. 
         [0004]    DE10126188 discloses another type of flexible feeder which uses a lift to select a number of components from a bulk storage. A lift platform on which the components are resting is then vibrated or rotated to spread the components such that they can be easily recognized by a vision system and picked by a manipulator. The area of the lift platform needs to be relatively small in relation to the total footprint of the feeder, and consequently the pick surface area is also small. In order for the components to be well-spread many of them need to be returned back to the bulk storage, which leads to an undesired wear of the components to be fed. 
       SUMMARY OF THE INVENTION 
       [0005]    One object of the invention is to provide an improved flexible feeder which mitigates the shortcomings of the flexible feeders known in the art i.e. large footprint and wear of the components to be fed. 
         [0006]    A further object of the invention is to provide an improved method for feeding components. 
         [0007]    These objects are achieved by the device for elevating a selection of components from a bulk storage and the method for feeding components. 
         [0008]    According to a first aspect of the invention, there is provided a component feeder comprising a lift for elevating a selection of components from a bulk storage, and a pick surface adjacent to the lift for receiving the selection of components. The component feeder comprises a spreader configured to give the selection of components a push for spreading the selection of components from the lift on the pick surface. 
         [0009]    The combination of a vertical lift and a separate pick surface adjacent to the lift enables the bulk storage being positioned directly below the pick surface. Consequently, the area of the pick surface becomes large in relation to the total footprint of the component feeder. All the lifted components can be spread out without returning any of them to the bulk storage, and the remaining components may be returned to the bulk storage simply by retracting or inclining the pick surface. 
         [0010]    According to one embodiment of the invention the component feeder further comprises retracting means for retracting the pick surface and returning any components lying on it back to the bulk storage. A retractable pick surface provides a simple means for returning components remaining on the pick surface back to the bulk storage. 
         [0011]    According to one embodiment of the invention the retracting means comprises a capstan for furling the pick surface. A capstan provides a simple means for retracting the pick surface. 
         [0012]    According to one embodiment of the invention the lift comprises a lift platform for supporting the selection of components, and the component feeder further comprises a lift adjuster for adjusting the lift platform area. An adjustable lift platform area enables an appropriate number of well-spread components to be achieved with variable component sizes. 
         [0013]    According to one embodiment of the invention the component feeder further comprises vibration means for causing the pick surface to vibrate and reorient the selection of components. A vibrating pick surface further contributes on the spreading of the components. 
         [0014]    According to a second aspect of the invention, there is provided a component feeder system comprising two component feeders according to any of the embodiments described hereinbefore, wherein a single camera is configured to monitor the two pick surfaces. By this measure, an outlay on the vision system used in tandem with the component feeders is minimized. 
         [0015]    According to a third aspect of the invention, there is provided a method for feeding components, the method comprising the steps of: lifting a selection of components from a bulk storage by means of a lift; and giving the selection of components a push to spread the same from the lift on a pick surface adjacent to the lift. 
         [0016]    The combination of lifting and spreading on a separate pick surface enables all the lifted components to be well-spread without returning any of them to the bulk storage. 
         [0017]    Further advantageous embodiments of the method are the subject of the dependent claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]    The invention will be explained in greater detail with reference to the accompanying drawings, wherein 
           [0019]      FIG. 1  shows a component feeder according to one embodiment of the invention in isometric view; 
           [0020]      FIG. 2  shows a cross-section of a component feeder according to one embodiment of the invention; 
           [0021]      FIGS. 3A-I  illustrate a work cycle of a component feeder according to one embodiment of the invention; 
           [0022]      FIG. 4  illustrates emptying of a component feeder according to one embodiment of the invention; and 
           [0023]      FIG. 5  shows a component feeder system according to one embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0024]    Referring to  FIGS. 1 and 2 , one embodiment of a component feeder  10  according to the invention comprises a triangular hopper  20  for receiving a bulk storage of components  30  to be fed. The side walls  40  of the hopper  20  are transparent. At the rear of the hopper  20  there is provided a vertically acting lift  50  with a horizontal lift platform  60  for supporting the components  30 . The lift  50  is operated by a first pneumatically operated piston  70  mounted under the lift platform  60 . In the upper rear corner of the component feeder  10  there is provided a horizontally acting spreader in the form of a pusher plate  80  which is driven by a second pneumatically operated piston  90 . A retractable pick surface  100  covers the bulk storage completely in its unfurled state shown in  FIG. 1 . In a furled state shown in  FIG. 2  the pick surface  100  is stored coiled around a spring driven capstan  110  in a pick surface compartment  120  in the upper front region of the component feeder  10 . Unfurling is effected by a third pneumatically operated piston  130  whose movement is transmitted by a flexible cord  140  passing over pullies  150 . During furling and unfurling the pick surface  100  glides in grooves  160  provided at the side walls  40  of the hopper  20 . 
         [0025]    Situated in the oblique surface of the triangular hopper  20  there is a sliding door  170  which is opened and closed manually. The sliding door  170  opens and closes an emptying aperture which leads onto a chute  180  that guides the components  30  running out when the hopper  20  is emptied. In a compartment under the chute  180  there are located solenoid valves  190 , a control electronics housing  200  and a bank of flow control valves  210 . At the lower rear region of the component feeder  10  there are situated electrical  220  and pneumatic  230  connections. 
         [0026]    The construction of the pick surface  100  is now described with reference to  FIG. 2 , detail “E”. The pick surface  100  is white in colour to provide good contrast for the vision system, and is provided with a flocked coating  240  consisting of short, densely packed vertically oriented fibres. The purpose of this is to reduce the time taken for the parts to settle by damping out rolling and bouncing motions. To the underside of the pick surface  100  there are bonded transverse beams  250  of semicircular cross-section. These beams  250  may be made from carbon fibre or another rigid material and serve to stiffen the pick surface  100  over its width to prevent the weight of parts causing it to bulge inwards. A small gap  260  is left between adjacent beams to provide the flexibility necessary for furling and unfurling. 
         [0027]    The operation of the component feeder  10  is explained with reference to  FIGS. 3   a - 3   i.  At starting position according to  FIG. 3   a , all the pistons  70 ,  90 ,  130  assume fully extracted positions. Components  30  are introduced from above through a filling aperture at the top of the hopper  20 . Upon receiving a command from a robot which the component feeder  10  is intended to serve, the sequence of actions is as follows: At step one according to  FIG. 3   b  the lift  50  is drawn down to its lowermost position and simultaneously the pusher plate  80  is withdrawn to its rearmost position flush with the rear wall of the hopper  20 . At step two according to  FIG. 3   c  the lift  50  moves back to the top, bringing with it a first selection of components  30  which settle on the lift platform  60 . At step three according to  FIG. 3   d  a lift adjuster in the form of the pusher plate  80  advances slowly to a predetermined position partway along its stroke, thereby reducing the lift platform area and pushing some components  30  back to the bulk storage such that a second selection of components  30  remains on the lift platform  60 . At step four according to  FIG. 3   e  the pusher plate  80  retreats once more to its rearward end position. 
         [0028]    The steps three and four are optional and can be omitted if the amount of components  30  in the first selection of components  30  is appropriate. The avoidance of steps three and four is desirable since it shortens the cycle time of the component feeder  10  and contributes to reduced wear of the components  30 . The lift adjuster therefore preferably comprises means to adjust the lift platform area before step two, for example by making the lift platform  60  interchangeable for different types of components  30 . 
         [0029]    At step five according to  FIG. 3   f  the third piston  130  retracts causing the pick surface  100  to unfurl and cover completely the filling aperture. At step six according to  FIG. 3   g  the pusher plate  80  gives the selection of components  30  a push to thereby spread the components  30  out on the pick surface  100 . The push is effected by the second piston  90  which extracts at a high speed. That is, in the present embodiment the pusher plate  80  functions both as a lift adjuster and as a spreader. However, other types of spreaders can be adopted, such as a blow gun blowing compressed air at the selection of components  30 . 
         [0030]    Once the selection of components  30  is at rest on the pick surface  100 , a camera  270  (see  FIG. 5 ) mounted directly above the pick surface  100  takes a picture of the selection of components  30 . Image processing software identifies the silhouettes of any components  30  that happen to lie in a desired orientation, and at step seven according to  FIG. 3   h  a robot gripper  280  picks up all the respective components  30 . At step eight according to  FIG. 3   i  the third piston  130  extracts, whereupon the pick surface  100  is coiled back around its capstan  110 . Any parts eventually remaining on the pick surface  100  after step seven fall back to the bulk storage once the pick surface  100  is fully withdrawn into the pick surface compartment  120 . 
         [0031]    After step eight the state of the component feeder  10  corresponds to the starting position and the cycle may be repeated starting from step one. A typical cycle duration is of the order of 2-5 seconds. The cycle described hereinbefore can be modified in many ways to improve the feeding performance. For example, the steps one and two may be taken already while the robot gripper  280  picks the components  30  at step seven in order to shorten the cycle time. 
         [0032]    The cycle according to steps one to eight may continue until the level of components  30  in the hopper  20  falls below a minimum threshold, as determined by e.g. a level sensor (not shown). At this point, the cycle is paused until the hopper  20  is re-filled and the operation can be resumed. Referring to  FIG. 4 , should it be necessary to empty the hopper  20  e.g. for component changeover, the sliding door  170  can be opened and the entire contents of the hopper  20  fall by gravity through the emptying aperture into a waiting receptacle  290 . To ensure no components  30  are left behind, a sensor (not shown) detects the opening of the sliding door  170  and triggers all the pistons  70 ,  90 ,  130  to extract such that the component feeder  10  assumes the state corresponding to the starting position according to  FIG. 3   a.    
         [0033]    Component changeover requires only two manual adjustments: the partial stroke of the pusher plate  80  at step three and the speed of the pusher plate  80  at step six must be adjusted such that an appropriate number of well-spread components  30  land within the view area of the vision system. 
         [0034]    In the description of the component feeder  10  thus far presented, if no components  30  are lying in the correct orientation, the component feeder  10  simply tries again, repeating the cycle until a pickable component arises. However, depending upon the type of component and its friction coefficient against the pick surface  100 , the component feeder  10  may also be capable of reorienting components  30  to a limited degree. This may be achieved by a vibrating movement of the pick surface  100 . 
         [0035]    To minimize outlay on the vision system used in tandem with the component feeder  10 , it is desirable to use as few cameras  270  as possible. Here, the presently invented component feeder  10  offers another advantage over existing solutions. Referring to  FIG. 5 , a small waste footprint in lateral direction allows the pick surfaces  100  of two component feeders  10  arranged side-by-side to be separated by only 10 mm, which in its turn allows a single camera  270  to monitor two pick surfaces  100 . A single camera  270  equipped with a 25 mm lens and positioned 630 mm overhead can cover around 18000 mm 2  of pick surface area or 94% of the area encompassed by the view area. 
         [0036]    The invention is not limited to the embodiments shown above, but the person skilled in the art may, of course, modify them in a plurality of ways within the scope of the invention as defined by the claims.