Abstract:
A system, method and apparatus for handling and moving a layer of articles, such as cased products. The system and apparatus comprise a hood enclosure having four side panels, and four interconnected corner member. The side walls and corner members interoperate to form an adjustable enclosure to pick the layer of articles. A vacuum generate is utilized to evacuate air from the hood enclosure to assist in lifting the layer of articles. The hood enclosure may utilize an array of vacuum cups to assist in the lifting of articles into the hood enclosure. The method is directed towards utilizing the hood layer end effector to move and hand articles.

Description:
This application claims priority to U.S. Provisional Patent application Ser. No. 60/661,697, entitled “Layer Picking End Effector System, Apparatus, and Method,” filed Mar. 15, 2005, which is incorporated herein by reference in its entirety. 

   TECHNICAL FIELD 
   The present invention is directed to a system, method, and apparatus for handling and moving a collection of articles, and more particularly is directed toward a system, method, and apparatus of a hood enclosure end effector for lifting and moving articles. 
   BACKGROUND OF THE INVENTION 
   An end effector is a tool on the action arm of a robot used to handle materials, perform procedures, or control activities. End effectors have sensors that give them information and communicate to the robot controller that items are in place, missing, or available; that procedures have been completed or a fault or collision occurred. In the following references, which are incorporated herein for all purposes, layer picking end effectors are described and have been in use for many years. 
   U.S. Pat. No. 3,387,718, titled “Pallet Loading and Unloading Apparatus,” to Roth et al., relates to an apparatus for loading and unloading pallets that support multiple layers or tiers of articles, such as packages, boxes, cases for beverages, and other articles to be handled in rigid or semi-rigid containers of wood, paperboard or fiber materials. Conveyor means bring or take away articles from the apparatus. When the conveyor means brings articles to the apparatus, the articles are formed into layers having a desired pattern. After the layers are formed the layers are moved onto a belt. When the conveyor means takes articles away the entire layer is moved off the belt and dispersed by the conveyor means. As part of the apparatus, members seal off the periphery of the layer, and concurrently, push the articles into a compact arrangement to substantially reduce air flow past the article. 
   U.S. Pat. No. 3,404,787, titled “Suction Lift for Article Distribution and Storage System,” to Hayford, et al. is directed to a suction lift for article distribution. The suction lift includes a hollow, moveable head; an open grate movable vertically with respect to the hollow, moveable head; and a flexible curtain depending from the rigid top of the hollow. The open grate is pervious to the movement of air so that suction is readily applied through the grate. The grate is moved vertically downward from the rigid top of the head when a single tier of units is to be lifted and is moved upward toward the rigid top of the head when more than one tier of units is to be lifted. Lifting of a plurality of tiers is improved if the depending curtain is held away from all but the lowermost of the tiers when suction is applied. The Hayford apparatus utilizes a vacuum to lift tiers of units. 
   U.S. Pat. No. 3,556,579, titled “Suction Pads,” to Seymour-Walker et al., describes a suction pad having side portions depending downwardly from a top portion and adapted to be brought into a gripping relationship with the side faces of an article to be lifted by the pad. In one embodiment, the pad presents a lifting surface to the top surface of the article. The Seymour-Walker apparatus utilizes suction with a suction pad to lift an article. 
   U.S. Pat. No. 4,850,627, titled “Packaging Handling Method and Apparatus,” to Franklin, addresses the transfer of a collation of flexible packages from a first location to a second location by employing a loading head. The loading head includes an enclosure having an opening and a permeable barrier extending across the opening. The opening and the collation of flexible packages are brought together at the first location. Suction is applied to the enclosure drawing air into the enclosure through the permeable barrier. Packages are drawn against the barrier by the air drawn through the permeable barrier and thus upper regions of the packages are expanded towards one another by sub-atmospheric air pressure created by the suction. The packages tend to seal against one another and to prevent flow of air through the collation, so that the collation is held by suction against the barrier. The enclosure is transferred to the second location and the suction is removed to release the collation from the enclosure. Apparatus for carrying out this process incorporates a motor-driven radial flow fan without an external shroud mounted on the enclosure to generate the suction. The Franklin apparatus utilizes a vacuum to lift a tray. 
   U.S. Pat. No. 5,088,878, titled “Apparatus for the Lifting of Tray Packs,” to Focke et al., discusses that the lifting and transportation of sensitive articles incapable of bearing a mechanical load, without manual involvement, presents special difficulties in packaging technology. This applies, above all, to tray packs in which articles are arranged standing on a bottom part of small height, without any additional anchoring. For grasping and lifting articles of this type, the Focke reference describes a raisable and lowerable suction box which, with suitable dimensions, is placed over the article in a manner of a bell. By the generation of a vacuum within the suction box, the article (for example, tray pack) is held carefully and can be lifted by means of the suction box. Side walls of the suction box are arranged pivotably, to make it easier to place the suction box onto the article. 
   Although the above-mentioned devices are useful in their own right, an improved handling of articles is attainable with the present invention. The inventors have invented a hood style end effector which has four sides that are made of a material with limited flexibility, e.g., sheet metal, and can close around the bottom of a layer of cases, conform to whatever rectangular size the specific layer is, and have special corner members that provide air leakage control. Additionally, the present invention can detect the occurrence of slip sheets, and the dropping of lifted product. 
   BRIEF SUMMARY OF THE INVENTION 
   The present invention includes a system, apparatus, and method of a hood enclosure end effector for lifting and moving articles. 
   In one aspect of the invention, there is an apparatus with a suction generator coupled in fluid communication with a hood enclosure. Preferably, the suction generator is a high volume, low pressure air pump configured to provide evacuation of air from the hood enclosure. The hood enclosure may include one or more mounted pressure transducers to monitor suction level in the hood enclosure so that a predetermined suction level is maintained. 
   The hood enclosure has a top member that has a top side and a bottom side. Four side walls having a top end and bottom end are pivotally connected to the top member. The side walls have an exterior side and an interior side. An arm is connected to the interior side of the side wall, and the top member has an actuating device operably coupled with the arm for moving the side panel. This allows the side walls of the hood enclosure to expand and contract for articles of varying size. 
   The four corner members are slideably connected between an adjacent side panel. The corner member has a first and second panel. The first and second panels slide in concert with different side walls. In one embodiment, the first and second side panels are hinged together. 
   A first ceiling member is moveably connected to the bottom side of the top member. The first ceiling member is configured to be positioned on the top of articles to be lifted and has an array of cups. In one embodiment, the first ceiling member is connected to the top member via a moveable scissors frame. The first ceiling member has four separate cups that are used to detect slipsheets. 
   In another embodiment, a second ceiling member is moveably connected to the top member. The second ceiling member is movable separate from the first ceiling member. An array of suction cups is attached to a bottom side of the second ceiling member. In one configuration, the second ceiling member surrounds or partially surrounds the perimeter of the first ceiling member. Additionally, the second ceiling member can be used in conjunction with the first ceiling member (where the first ceiling member has suction cups) to assist in lifting articles. 
   In another embodiment, a set of dropped product detectors are mounted on the bottom end of at least one of the side walls. The dropped product detectors include light emitting devices on the bottom end of at least one of the side walls, and light beam detectors on the bottom end of at least one of the side walls, such that the light beam detectors detect the transmittance of light beams from the light emitting devices. If while lifting an array of articles, an article is dropped while lifting, the article will break a light beam, thus causing a signal or error situation to warn that an article has not been lifted, or has been dropped. 
   In another embodiment, the hood enclosure is connected to a robotic arm, or an overhead frame, for moving the hood enclosure in any of an x, y, or z axis. In certain aspects the robotic arm will allow rotation about a rotational axis (“u axis”). A robot may also include, but is not limited to a 6-axis articulated arm device. 
   In another aspect of the invention, there is a method for lifting and moving articles. The method includes providing a hood enclosure as discussed herein. The hood enclosure is positioned around a group of articles to be lifted. The side walls are clamped about the perimeter of the group of articles. Air is evacuated from the interior of the hood enclosure. The articles are lifted and/or moved from a first location to a second location. 
   In a further embodiment, the vacuum cups are used to lift an article independently of the hood enclosure. If the particular embodiment uses vacuum cups, then a vacuum source is supplied to the vacuum cups, and the vacuum cups are utilized to lift the articles. 
   In still further embodiments, the hood enclosure may be used in conjunction with the vacuum cups. If the particular embodiment uses vacuum cups, then a vacuum source is supplied to the vacuum cups, and the vacuum cups are utilized to assist in lifting the articles. 
   While the articles are being lifted or moved, dropped or non-lifted articles are detected and a signal can be provided to the system or operator of such an occurrence. 
   Additionally, the method may include detecting slip sheets, and moving slip sheets to a third location separate from the first and second location. 
   Cased product, including, but not limited to packages of canned units, and boxes containing products lend themselves to being picked with the present invention, with or without a vacuum cup assist. Such products may be lifted by using the hood only, the vacuum cups only, or a combination of both hood and vacuum cups. 
   In various embodiments, the present invention may pick a partial layer—anything from a single case to a complete layer missing one case—and the partial layer can have cases anywhere on the layer footprint. In a preferred embodiment, one or more vacuum cups are used to lift a partial layer. 
   Another aspect of the present invention is that it is able to pick and remove slip sheets from the top of a layer. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     For a more complete understanding of the present invention, reference is made to the following description in conjunction with the accompanying drawing, in which: 
       FIG. 1  illustrates an embodiment of the present invention; 
       FIG. 2  illustrates the opening and closing of the corner seal; 
       FIG. 3  illustrates a bottom-view of an embodiment of the present invention; 
       FIG. 4  illustrates an embodiment of the present invention with the hood fully open and initially positioned over cased product; 
       FIG. 5  illustrates an embodiment of the present invention with an open hood, down and over packages layers to be picked; 
       FIG. 6  illustrates an embodiment of the present invention with the closed hood holding layer of cases of product; 
       FIG. 7  illustrates an embodiment of the present invention with a vacuum array; 
       FIG. 8  illustrates an embodiment of the present invention with vacuum array engaging a product layer; and 
       FIG. 9  illustrates an embodiment of the present invention lifting a package layer. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Referring now to  FIGS. 1-6 , an embodiment of the hood layer picker end effector of the present invention is shown. As shown in  FIG. 1 , in this embodiment, the hood layer picker end effector comprises four side walls  32  and four corner members  34 . In this view, the front side wall has been removed to show the internal structure of the end effector. In certain aspects of operation, the corner members  34  and the side walls  32  close about a product layer  36  to be handled. The side walls  32  and corner members  34  cooperate together to form an expandable and retractable hood enclosure  16 . The four side walls  32  are connected to a top member referred to herein as the compliance float  24 . The compliance float  24  is generally square or rectangular in shape. The shape of the hood enclosure  16  when the side walls  32  are perpendicular to the floor is generally square or rectangular in shape. The hood end effector has the capability of using a vacuum array or portions of a vacuum array to remove any partial tier from the top of a pallet of stacked articles. Also, the end effector is capable of reliably handling a great variety and high percentage of articles, particularly those articles requiring special handling. 
   Typically, the side walls  32  are attached via hinges  25 , or by other appropriate attachment means, to the compliance float  24  or other platform such that the side walls  32  may pivot inward or outward to retract or expand the hood enclosure  16 . To pivot the side walls  32 , an actuating device including, but not limited to a pneumatic or hydraulic cylinder may be used. The actuating device  33  is connected to an arm  37  extending from the upper inner side of the side walls  32 . The actuating device  33  extends and retracts arm  37 , which in turn extends and retracts the side walls  32 . 
   Each of the side walls  32  may be expanded or retracted individually so that the hood enclosure can accommodate a particular length and width of a layer of product to be handled. The side walls  32  can fold inward to have the lower bottom portion of the inner sides of the side walls  32  press against the perimeter of the layer  36  to be picked. In a preferred embodiment, there are four sides wall, two side walls (e.g., a first and third side wall) oppose each other, with another two side walls (e.g., a second and fourth side wall) opposing each other. The opposing walls of the hood enclosure  16  may be closed and opened with synchronized motion (e.g., if the left wall closes 5 degrees, the right (opposing) wall also closes 5 degrees). If the product layer  36  is not centered between the side walls  32 , a compliance float  24  allows the hood to move as the side walls close  32 , to center the hood enclosure  16  above the product layer  36 . 
   Referring to  FIG. 2 , the corner members  34  are interconnected with the side walls  32 . In one embodiment, the corners members  34  have two panels that are hinged together. Each panel of the corner members are connected in a sliding fashion with an adjacent side wall  32 . The two panels forming the corner members are hinged together. Typically, the corner member is held up by the chain  43  (see  FIG. 3 ) attached to the inner side of the hood enclosure, and guided plates  44  (see  FIG. 4 ) on the sides forming slots for the corner member. As shown in  FIG. 2 , the corner member is operable between a range of positions from  34   a  to  34   b.    
   Referring back to  FIG. 1 , a suction generator  20  pumps air out of the hood enclosure  16 . This overcomes a constant leakage and creates sufficient negative pressure to lift the product layer, within the time cycles of the application. The product layer  36  is held while lifting and carrying by suction generated by a suction generator  20 , for example an air pump evacuating air from the hood. Preferably, a high volume suction generator capable of drawing 1, 2, 3 psi or more of vacuum inside the hood enclosure while evacuating air leaking through and around the layer of cases with leakage area in the range of 2, 4, 6, 8, or 10 inches square (in 2 )is preferred. Typically, the hood end effector is capable of depalletizing thousands of cased products that may have leakage area up to 10 in 2  per layer. Air should be suctioned out continuously, providing a steady state negative pressure from inside the hood to underneath the cases sufficient to lift the layer weight—typically a net 1.0 psi. 
   The wrist break  22  is a collision sensor detecting when the hood enclosure  16  hits something while moving. Tripping this collision sensor creates a critical fault signal that automatically stops movement of the hood enclosure, and a warning is messaged visually, and/or electronically to an operator of the hood layer picker. 
   The compliance float  24  allows the hood enclosure to move in the horizontal plane, including rotation about a z-axis, to accommodate source pallets that have layers mis-aligned. Typically, the compliance float  24  is clamped when a robot arm brings the hood enclosure over the source pallet with product. Since the actual product can be located off center by rough handling from a supplier, or when the pallet containing the actual product is moved, the hood enclosure  16  is unclamped when it is lowered to the bottom of the layer, so when the sides come in to the layer sides, the hood may “float” to center itself over the actual center of the layer. After it is raised from the balance of the pallet load, it is re-clamped to bring the layer to perfect center and enable accurate placement. 
   Before the suction can be activated, the ceiling  30  is positioned on top of the layer of product  36 . A ceiling platen is mounted so that it is free to be positioned up and down. As shown in  FIG. 1 , an exemplary scissors frame  28  is shown, but rod bearings, linear guide-ways, or other means can accomplish the motion. The selected structure should keep the ceiling  30  flat however. An air cylinder  26  moves the ceiling  30  up and down. Before the hood enclosure  16  is positioned, the cylinder  26  is extended lowering the ceiling  30  to near the bottom of the hood enclosure  16 . A valve is then opened allowing the cylinder to be moved easily. The hood enclosure  16  is lowered and the ceiling  30  contacts the top of the top layer  36  of the product. When the hood enclosure  16  is lowered to its final position, the ceiling  30  rests on top of the layer. The valve is then closed, blocking the ports of the cylinder and locking the ceiling  30  in position. 
   Referring to  FIG. 4 , the hood enclosure  16  itself is composed of four walls, four corner members and the aforementioned ceiling assembly. Each wall  32  is wider at the top than the widest/longest product layer plus a positioning tolerance. The bottom of the side wall is narrower than the smallest product minus the tolerance. The corner members  34 , which are typically connected by a hinge  48 , block substantially all air leakage, and while doing that, conform to all size and tolerance layers. The corner member attached to the inner side of the hood enclosure and articulate with guide plates  44  on the sides that form slots for the corner member  34 . In a preferred embodiment, the walls  32  of the hood enclosure  16  are stiff or have limited flexibility. A stiff wall typically provides added friction to the interaction between the layer and the hood. In certain aspects, the walls provide additional clamping force due to the force of the vacuum over the area of the walls  32 . 
   The above describes an embodiment of a basic hood layer picker. The invention provides a useful apparatus to de-palletize cases with poor integrity, leaky tops, loose bottoms and cases with high density. 
   Referring now to  FIGS. 3 ,  4  and  7 - 9 , the hood layer picker, is shown with a vacuum cup array  29 . The moveable ceiling  30  in the hood enclosure  16  has mounted to it an array  29  of vacuum cups  35 . The vacuum cups  35  are coupled to a vacuum generating source  40 . The vacuum cups  35  can lift or aid in lifting a layer or partial layer of product. Preferably, the vacuum cups  35  are made of a flexible rubber, or plastic. Other materials can be used to form the vacuum cups  35 . However, the vacuum cups  35  preferably are flexible so as not to damage product casing. The vacuum cup array  29  can serve as an internal ceiling for the hood enclosure to prevent light layers and sealed patterns from being sucked inside the hood if excessive suction is applied. 
   Additionally, the vacuum generating source  20 ,  40 , or both  20  and  40  may be configured to provide evacuation of air from the hood enclosure  16 , the vacuum array  29 , or the hood enclosure  16  and the vacuum array  29 . These various embodiment can create suction about the perimeter of the layer of product, the top surface of the layer of product, or both the perimeter and the top surface of a layer of product. This suction may be controlled by one or more valving arrangements coupled to one or more blowers. 
   An appropriate diameter of each circular cup in the array  29  that will provide adequate hold strength for a particular product case lifted is about ⅓ the width of the smallest case lifted. A staggered array is a preferable arrangement. The cups may be all of the same size, or an array of different sizes. The shape of the cup is preferably round, however, the cups may take other useful shapes such as square, oval, rectangular, triangular or other polygons. 
   In one exemplary embodiment, over a 45″×54″ area, about 670 vacuum cups may be used. On average about half the cups will have a certain amount of leakage. This leakage, however, should be constantly removed by the suction generator  40 . If sealed properly, a vacuum pressure in the cup will result in about 1, 2, 3 or more psi. 
   For example, a suction generator  40  motor is about 15 horsepower and is capable of providing appropriate negative pressure while pumping. In certain aspects, the suction generator provides about 1, 2, 3, 4, 5, or 6 psi or more of negative pressure. The suction generator will typically pump about 100 cubic feet per minute. In certain instances, all or some of the vacuum cups may leak, so all or some of the vacuum cups may have a throttle orifice (small openings in the suction inlet of the cups) to limit the leakage. Throttling reduces the pressure lifting the cases but may be a necessary trade off. One example is a cup with an orifice of about 0.07 inch. 
   Additionally, the area of coverage of the array  29  of vacuum cups  35  should be about as large as the top surface of the largest layer to be handled, plus the tolerance of its mis-position. The array  29  of vacuum cups  35  serves as a ceiling to the product layer  36 . In one embodiment, the vacuum cup array  29  is connected to the ceiling  30 , such that the vacuum cup array  29  is moveable with the ceiling. The vacuum cup array  29  should be configured to come in to contact with the smallest product layer. 
   The hood end effector can be configured to detect slips sheets on top of layers of product so the slip sheets can be placed into a hopper, or some other location, and provide access to the next layer (see below). In one embodiment, dropped cases can be detected; that is, cases that drop product out of the bottom of the case while being lifted, or isolated cases not picked up when the layer of cases is lifted. As shown in  FIGS. 3 ,  7 ,  8  and  9 , the vacuum cup array  29  may have an second array  31  generally surrounding or outside of the vacuum cup array  29 . For example, an inner core (i.e., vacuum cup array  29 ) sized to the smallest layer, with an outer section  31  sized to a maximum layer plus tolerance. This outer section  31  retracts to the upper height of the hood enclosure  16  which can contain it when the inner core vacuum cup array  29  is used to pick slip sheets or serve as a ceiling. The outer section  31  deploys downward with the inner core vacuum cup array  29  when picking a layer. In certain aspects, the outer section  31  may be operatively coupled to a second ceiling member. In a further aspect, a second ceiling member is moveably connected to the top member. The second ceiling member is movable separate from the first ceiling member. An array of suction cups is attached to a bottom side of the second ceiling member. In one configuration, the second ceiling member surrounds or partially surrounds the perimeter of the first ceiling member. Additionally, the second ceiling member can be used in conjunction with the first ceiling member (where the first ceiling member has suction cups) to assist in lifting articles. 
   In one embodiment, one or more pressure transducers are mounted on the hood enclosure to monitor suction in the hood enclosure to maintain a predetermined suction level. Each product layer may have leakage varying from the norm. To provide a constant lifting force under conditions of unpredictable leakage, a pressure transducer, which can be placed any where on the inside of the hood, measures the real-time negative pressure in the hood. With a constant pump volume, the negative pressure will be reduced if the leakage is above normal, and increased if the leakage is less than normal. The air pump motor should be oversized to accommodate evacuation of above normal leakage. A motor speed control on the air pump motor can adjust the air pump volume. The weight per square inch of all product layers is known and that data is used to set a target negative pressure standard for each product to be handled with the hood. For example, if the total product weight is 1000 lbs and the total top surface area is 1000 sq. inches, then the product weight divided by the product would equal 1 pound per square inch of vacuum necessary to lift the product. Actually, slightly more than 1 pound per square inch of vacuum would be required to safely lift and move the products. 
   If the steady state negative pressure is under target for a given layer, the air pump motor is set to a higher speed. If the hood negative pressure is much higher than target, the air pump motor speed is reduced. In one embodiment, one or more pressure transducers can be mounted on the hood enclosure to monitor suction in the enclosure for maintenance of a predetermined suction level. 
   Referring now to  FIGS. 4 ,  5 , and  6 , an example of the hood layer picker of the present invention is shown with a lost case detector. It is important to detect a case that either falls from the hood enclosure  16  or was never suctioned at all. The hood enclosure  16  has a set of light emitting devices  42  that generate light beams that cut the layer pick up plane at the bottom of the long sides of the hood enclosure  16 . The light emitting devices  42  are typically in communication with the controls of the end effector via cabling  45 . As shown in  FIG. 9 , the product layer  36 ″ is exposed when layer  36 ′ is lifted. In certain aspects, multiple layers may be lifted at a time depending on the size and weight of the layer. 
   When cases are picked by vacuum cups  35 , the ceiling and cases in layer  36 ′ are retracted up inside the hood enclosure  16 . This allows the light beams to pass under the layer  36 ′ of cases held. If after picking the layer of cases  36 ′ and retracting them into the hood, the light beams are not all cleared, the apparatus can determine that at least one case has not been picked. If all the layer of cases  36 ′ have been picked, but the beam is broken during movement, it will conclude that a case has fallen out, or that material/product has fallen out the bottom of a case. A light sensor on the opposite side of the light emitting device may be used to determine if the light beam is broken or not. 
   At various positions in vacuum cup array  29 , preferably the corners or in proximity of the corners, there may be at least 1, 2, 3, 4 or more cups (slip sheet vacuum cups)  41 , preferably at least four, that may be individually plumbed with very low pressure vacuum generators and sensors to detect this low vacuum. The level of vacuum is sufficient to lift a slip sheet but not a product case. Every time a layer is picked up, the ceiling with vacuum cups contacts the top surface of the layer, only the four special cups are turned on and the hood is raised only about an inch or two. If the cups maintain vacuum, a slip sheet is detected. If the cups have no negative pressure after the hood is raised, a slip sheet is not present. 
   The sequence of operation depends on which end effector type has been selected for the specific product, hood, vacuum array, or a combination of hood and vacuum array. The first steps are common for both. In a common sequence, the open hood enclosure  16  with core vacuum cup array  29  comes down over the product layer  36 ′ until the cup array touches the top. The slip sheet vacuum cups  41  are activated and then the vacuum array  29  is raised an inch or two. If the cups have vacuum sensed, the slip sheet held and moved by the core vacuum array  29  and deposited into a slip sheet receptacle, such as a bin. 
   With a hood enclosure used without a vacuum cup array  29 , the hood enclosure  16  then moves down over the product layer  36 ′ with the core vacuum array  29  or a ceiling down but relaxed and capable of being pushed up easily. The hood enclosure  16  comes down until the bottom of the side walls are within about an inch above the bottom of the tier. 
   In certain aspects the compliant clamps are released, the side walls  32  are brought in against the layer, the hood floats to center above the product layer  36 ′, the suction is turned on and when the target vacuum is achieved, the product layer  36 ′ is lifted and the compliance clamps engaged. 
   With a hood enclosure having the vacuum cup array  29 , hood enclosure  16  then descends over the tier  36 ′ with both the vacuum array  29  section and core down and relaxed. On approach, the vacuum is turned on. When vacuum is sensed the hood enclosure  16  stops descending. The ceiling and the suctioned cases  36 ′ are retracted into the hood enclosure  16 , and the hood enclosure  16  is raised enough to have the light beams just above the remaining tiers of product  36 ″. If all light beams are correct, all cases of the picked layer  36 ′ are confirmed captured and they are then moved. Typically, the pressure transducers indicate that a layer has been engaged by the hood and light beams monitor the integrity of lifting using the vacuum array. 
   Although the present invention and its advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the invention as defined by the appended claims. Moreover, the scope of the present application is not intended to be limited to the particular embodiments of the process, machine, manufacture, compositions of matter, means, methods and steps described in the specification. As one will readily appreciate from the disclosure, processes, machines, manufacture, compositions of matter, means, methods, or steps, presently existing or later to be developed that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein may be utilized. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, or steps.