Abstract:
A suction gripper for lifting, transporting and depositing items, includes a basic suction body having an inner surface; a first opening for coupling the basic suction body to a suction source; and a second opening through which an item is introduced into the basic suction body by suction. An abutment member is positioned within the basic suction body between the first and second openings such that a clearance is defined between the abutment member and the inner surface of the basic suction body for allowing a suction stream to pass from the second opening through the clearance into the first opening. A storage chamber is defined between the inner surface of basic suction body, the second opening and the abutment member for accommodating an item drawn thereinto and held against the abutment member by suction.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims the priority of Swiss Application No. 2000 1132/00 filed Jun. 8, 2000, which is incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     This invention relates to a gripper apparatus for grasping articles and is of the type which includes a basic suction body to which vacuum is applied and which is provided with a suction opening to be aligned with a surface of the article to be grasped and further includes a vacuum source coupled to the basic suction body. 
     A gripper of the above-outlined type, as described, for example, in German patent document 39 06 634, can simultaneously pick up a plurality of items with a plurality of suction heads. This apparatus, however, is not capable of picking up with one suction head simultaneously or consecutively several items for forming an item group. 
     European Patent No. 0 532 774, to which corresponds U.S. Pat. No. 5,263,753, describes a further gripping apparatus in which the suction opening has four circumferentially arranged gripping arms and which, by exposing a diaphragm coupled thereto with vacuum, swing towards the item to be grasped and capture the same in a centered manner. A plurality of items cannot be simultaneously grasped with such a gripper. 
     U.S. Pat. No. 5,457,933 describes a gripping apparatus for grasping fruit. The apparatus includes a matrix of suction grippers which simultaneously grasp fruits arranged in a pattern and deposit the same at another location. The items are arranged side-by-side in rows and are grasped by a plurality of grippers. 
     Further, U.S. Pat. No. 3,368,324 describes a gripping apparatus for baked goods. The apparatus is particularly designed for handling items having a delicate upper, not necessarily planar, product surface to be grasped by the suction gripper. 
     SUMMARY OF THE INVENTION 
     It is an object of the invention to provide an improved gripper apparatus of the above-outlined type which grasps the articles in a gentler manner while permitting an accelerated packing rate. In particular, it is an object of the invention to form a group of articles such as edible wafers (for example, flat confectionary items) and to increase the packing speed in this manner without relinquishing a gentle handling of the items. 
     This object and others to become apparent as the specification progresses, are accomplished by the invention, according to which, briefly stated, the suction gripper for lifting, transporting and depositing items includes a basic suction body having an inner surface; a first opening for coupling the basic suction body to a suction source; and a second opening through which an item is introduced into the basic suction body by suction. An abutment member is positioned within the basic suction body between the first and second openings such that a clearance is defined between the abutment member and the inner surface of the basic suction body for allowing a suction stream to pass from the second opening through the clearance into the first opening. A storage chamber is defined between the inner surface of the basic suction body, the second opening and the abutment member for accommodating an item drawn thereinto and held against the abutment member by suction. 
     By providing that the basic suction body has a height which is greater than the article to be grasped, an item group may be directly formed in the storage chamber. 
     A method for using a gripping apparatus of the above-outlined construction according to the invention includes the steps of picking up sequentially a plurality of items by the gripper apparatus and while vacuum is continuously applied in the basic suction body of the gripping apparatus, the items are intermediately stored. The temporarily stored item groups are subsequently deposited onto or into a device which moves away the grouped items. 
     Thus, since first a number of items are picked up from the supply conveyor and are then deposited as a group on the removing conveyor or in a package, the displacement paths are significantly reduced, and consequently the apparatus may operate more rapidly and more efficiently. 
     The items handled by the gripper apparatus according to the invention may be, in particular, wafer-shaped items, such as baked products like biscuits, frozen dough pieces, muffins, madeleines or similar products. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic perspective view of a gripper apparatus according to the invention. 
     FIG. 2 is a sectional elevational view of the suction device forming part of the gripper apparatus according to the invention. 
     FIG. 2 a  is a schematic perspective view of a variant of the structure shown in FIG. 1 
     FIG. 3 is a sectional view taken along line III—III of FIG.  2 . 
     FIG. 4 is a view similar to FIG. 3, illustrating a variant. 
     FIG. 5 is a schematic perspective view of the suction device including the component shown in FIG.  4 . 
     FIGS. 6 and 7 and are schematic perspective views of two further preferred embodiments of the suction device according to the invention. 
     FIG. 8 is a schematic sectional side elevational view similar to FIG. 2, showing three drawn-in items stored in the suction device. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 schematically shows a gripper apparatus for forming groups, including a frame  1  and a pickup device  2  mounted thereon. The pickup device  2  has three arms, at the lower end of which a suction device  10  is secured and coupled to a vacuum hose  3 . The suction device includes an outer cylinder jacket  11  shown in more detail in FIG.  2  and also referred to below as a basic suction body. 
     FIG. 1 further shows two conveyor belts  5  and  6  which move leftward as viewed in FIG.  1 . On the first conveyor belt  5  items  7 , such as edible wafers are arranged in an organized or random manner and are advanced into the zone of the frame  1  and thus arrive in the grasping range of the pickup device  2 , 
     In the illustrated embodiment the items are randomly arranged edible waters  7 , for example, circular crackers. The suction device  10  to be described below may also be utilized for other types of items, for example, oval edible wafers  7 , baked goods of irregular shape such as muffins or madeleines or items other than food products. The suction device  10  is capable of handling glazed items, or food products having adhering fragments such as almond slivers or hard, soft, or irregular surfaces. 
     The second conveyor belt  6  moves away the items  7 , deposited by the suction device  10  individually or as item stacks, from the region of the stand  1  and may be subsequently placed into packaging containers. 
     FIG. 2 shows that the suction device  10  has a cylindrical storage chamber  12  defined by the basic suction body  11  which may be of plastic, particularly a food-compatible plastic The items  7  are drawn into the chamber  12  by suction. The cylindrical chamber  12  is adapted to accommodate cylindrical edible wafers  7 , particularly baked products and other items which have a volume that may be surrounded by basic suction body  11 . 
     Also referring to FIG. 3, a septum  13  is disposed perpendicularly to the longitudinal axis  14  of the suction device  10 . The septum  13  is a circular disk whose diameter is slightly less than the inner diameter of the basic suction body  11 , whereby a narrow annular clearance  15  is formed. Given a diameter of 10 cm for the basic suction body  11 , the clearance  15  may be, for example, between 2 and 5 mm. The septum  13  is secured to the jacket  11  by four supports  16  circumferentially spaced at 90° from one another. 
     The cylindrical jacket  11  terminates in a coupling nipple  18  with a tapered portion  17  which defines a suction chamber  22  adjoining the storage chamber  12 . By means of the tapered portion  17 , optionally in conjunction with a cone, a laminar gas flow may run through the clearance  15  and into the coupling nipple  18  through the suction chamber  22  defined by the tapered jacket portion  17 . 
     The four supports  16  are integrated into wedge-shaped ribs  26  which taper at their lower end and merge smoothly into the lower portion and terminal edge  21  of the basic suction body  11 . The ribs  26  serve as centering means for the items  7  to be drawn in by suction to ensure that the air gap  15  is securely preserved about the items  7 . 
     Referring to FIG. 2 a , instead of the septum disk  13  a cone  33  is provided whose point  34  is located in the suction chamber  22 , in the vicinity of the coupling nipple  18 , The cone  33  has a base  35  oriented toward the storage chamber  12  and serving as a counter support for the items  7  drawn into the storage chamber  12 . 
     FIGS. 4 and 5 show a second embodiment which has a sieve or grid  23  instead of a septum  13 . Thus, in case the suction device  10  is empty, the open suction passage cross section is significantly larger in the embodiment according to FIG. 4 than in the embodiment according to FIG.  3 . 
     In the suction device shown in FIG. 6 the basic suction body is formed by a quadratic jacket  31  for receiving flat, square items. The suction device shown in FIG. 7 has a heart-shaped jacket  41  for receiving flat, heart-shaped items. 
     FIGS. 6 and 7 illustrate two exemplary configurations of the cross-sectional outlines of the jackets  31  and  41  of the suction device By means of the identically structured respective coupling nipple  18  a rapid exchange of the pick-up device is possible for products of any desired shape. 
     The suction devices structured according to the invention, particularly according to one of the above-described embodiments, operate identically. In particular, the diameter of the septum  13  or the screen  23  is of the same size as the diameter of the item to be handled so that the suction surface is greater than the item surface engaging the septum  13  or the screen  23 , When the lower, terminal edge  21  of the jacket  11  is moved over an item  7  and a vacuum prevails in the storage chamber  12  by virtue of an air stream flowing from the chamber  12  through the annular clearance  15  and the nipple  18 , the vacuum force lifts the item  7  off the conveyor belt  5  and subsequently the item  7  moves between the walls of the jacket  11  in a centered manner guided by the ribs  26  in the direction of the septum  13 . After the first item is drawn in by suction, it rests against the face of the septum  13  and is, by the continuing suction, held in that position. The septum  13  serves an abutment member for the item  7  and may be provided with an adherence-repellent coating. The vacuum prevailing at the annular clearance  15  continues to be maintained through the annular space formed between the jacket  11  or  31  or  41  on the one hand and the item  7  on the other hand and draws a further item  7  into the storage chamber  12 . Such a second item and additional items (for example, up to four items) are held in a stacked relationship in the jacket  11  or  31  or  41  (the basic suction body) which thus has a height that is a multiple of the item thickness. This arrangement results in a superior efficiency, since the product groups in the suction device are formed within the basic suction body and may be subsequently deposited as a unit. Further, for each group the displacement path which the suction head of the pickup device has to travel is shortened compared to conventional pickup devices. This is so because during group formation the suction head has to travel only short distances above the conveyor belt  5  to consecutively gather the items  7  to form a group within the storage chamber  12 , and after the item group is formed, the suction head has to travel only once the back-and-forth distance to deposit the item group on the conveyor  6 . 
     In using the suction device  10  for such a process, the lower edge of the jacket  11  representing the basic suction body) is moved according to a predetermined pattern at a constant distance above the items  7  to be picked up from the conveyor belt  5 . In the simplest case such a movement is a back-and-forth displacement in a direction transversely to the advancing direction of the conveyor belt  5 . Such a motion may also be effected by a control, based on signals emitted by a camera capturing the position of the items  7  carried by the conveyor belt  5 . Thus, according to a predetermined pattern the suction device  10  is always moved to that item which is nearest to the end of the gripping zone in the direction of movement of the conveyor  5 . Further according to such a pattern, the control device operating the suction device  10 , knowing the quantity X of items which the storage chamber  12  of the suction device  10  can accommodate, calculates the minimum distance to grasp the quantity X of items which are nearest to the end of the gripping zone in the direction of movement of the conveyor  5 . By counting the drawn-in items  7  through transparent walls of the jacket  11  or by other means it may be determined that the group is complete and then the group may be moved to the second conveyor belt  6  to be deposited thereon, Such a deposition of the items may be, for example, at uniform distances as shown in FIG.  1 . 
     The items  7  may be delicate food products, such as confectionery items with almond sliver topping or decorative, sugar based coatings, such as glaze. In general, these products may be characterized as having a particle topping. During the suction process the upper item surface abuts the suitably coated and/or yielding underside of the septum  13 . The coating of the septum  13  may be, for example, Teflon or a microcellular rubber layer or the septum  13  may be resiliently suspended, preferable in combination with motion damping. 
     FIG. 8 shows a suction device according to FIG. 2, containing three superposed, drawn-in items  7  which rest against the underside of the septum  13 . The height of the jacket  11  permits the admission of a fourth item  7 . During the entire suction process and transport of the grouped items  7  to the second conveyor belt  6  vacuum is continuously applied to the coupling nipple  18  so that by virtue of the continuous air flow at the edges of the items  7  and through the annular clearance  15 , the items  7  are held in their position shown in FIG.  8 . 
     Apart from the above-described possibility of grouping of a plurality of food items, it is also feasible to move by suction an individual delicate product. Such product may be, for example, a muffin or a madeleine in which case the septum  13  has to be of arcuate configuration to conform to the surface of the item. Further, the described suction gripper according to the invention is capable of grasping and lifting a previously formed item group as a whole. 
     It will be understood that the above description of the present invention is susceptible to various modifications, changes and adaptations, and the same are intended to be comprehended within the meaning and range of equivalents of the appended claims.