Abstract:
An apparatus for handling layers of palletised goods, including a vertically displaceable lift head ( 2 ) with a mainly horizontal suction face which is substantially adjusted in size for a pallet, and which comprises downwardly open suction chambers ( 8 ) which via individual ball valves and an air distribution chamber are connected to a centrifugal blower ( 4 ), which is the vacuum source of the apparatus. The suction face moves downwards against the upper side of an upper layer of goods on a pallet. The ball valves are light, thin-walled spherical valve bodies ( 10 ) which are closed if the associated suction chamber ( 8 ) is not blocked downwardly by contacting the upper side of the goods on the uppermost pallet layer. The lift head ( 2 ) comprises a vertically adjustable skirt with inflatable squeezing pads for exerting an inwardly directed pressure on the outer sides of the goods of the upper pallet layer.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention concerns an apparatus for handling layers of palletized goods. 
     2. Description of the Prior Art 
     In order to make effective inexpesnive and simplified distribution of goods, most goods are sold on pallets, preferably the so-called EU pallets (800×1200 mm). A widespread need has appeared for also dispatching orders comprising lesser amounts of goods in a correspondingly effective way. Statistically it appears that many orders for small shops actually are consignments of goods which most often consist of very few layers or maybe just a single layer of palletized goods. 
     U.S. Pat. Nos. 3,406,938 and 3,229,953 describe a lifting device and an item holder using relatively complicated lifting or holding faces which have a large number of lesser chambers that are open toward the lifting face and the holding face, respectively. For lifting or holding of, by way of example, plate shaped items with different outer shapes or sizes in the printing industry, it is known to use lifting or holding faces with a differentiated vacuum chamber system, having a number of uniform, but individually connected chambers. These chambers by means of a valve system may be connected with one or more vacuum sources in such a way that sheets or plates with individual shape or size may be lifted or held fast with one and the same lifting or holding face. 
     WO-97/45355-A1 discloses an apparatus for lifting and moving of articles, comprising at least one arrangement with a cavity, hereafter called vacuum chamber, which is connected to an arrangement which is capable of producing negative pressure in the vacuum chamber. The underside of the lower plate is provided with an elastic airtight bottom and also is provided with a number of first through-passages to the vacuum chamber. With the invention each first passage is of a cylindrical design with a diameter reduction in the part which is connected to the vacuum chamber, forming a shoulder in the passage. The passage contains a body arranged moveably in the passage. In the body are planes which are at right angles to the center line of the passage which has a greatest diameter which is only slightly smaller than the diameter of the first passage. The first passage is provided with a second passage with a considerably smaller diameter than the first passage. The body is capable of essentially blocking the first passage when a negative pressure is obtained in the vacuum chamber with the exception of a given air flow in the second passage. 
     WO-00/64790-A1 and corresponding U.S. Pat. No. 6,802,688 discloses an apparatus for handling layers of palletized goods. The apparatus comprises a vertically displaceable lift head with a horizontal suction face which in size is adapted to a pallet and has a large number of downwardly opening suction chambers. The suction face is arranged to be moved downwards against the top side of an upper layer of individually or groupwise packed goods on a pallet. The suction chambers via individual valves are connected with a source of vacuum incorporated in the lift head, where the apparatus is intended for interacting with a depalletizing system. The valves between the suction chambers and the source of vacuum are designed as ball valves with very light thin-walled valve bodies that are enclosed in the suction chamber by means of lateral projections or by means of a retainer net, and which interact with upper round valve openings with spherical valve seats at the bottom if the actual suction chamber is not blocked at the bottom by contacting the top side of the goods in an upper pallet layer. Along the outer sides of the suction face, the lift head comprises means for exerting an inwardly pressure at the outer sides of the goods in the uppermost pallet layer. The description of the this invention is incorporated in the present application by reference. 
     SUMMARY OF THE INVENTION 
     The invention is a new and improved apparatus for handling layers of palletized goods, and which enables mechanising layerwise destacking of individual articles from a pallet with greater certainty, even if the individual pallet layers include openings between the articles or include articles that are film-covered in such a way that openings in the pallet layer are formed upwards so that the shut-off valves of the suction face are close to where there is a hole or openings in the pallet layer. openings are forced open when there is contact on the articles. 
     The apparatus according to the invention arresting means for actuating valve balls for individual suction chambers. The means are constituted by downwardly extending bluntly designed bodies which are resiliently suspended for yielding to valve balls which are already in closing abutment with the valve seat of the associated suction chamber, and for preventing valve balls from contacting the valve seats of valves that have not been closed. By means of these simple measures, there is hereby achieved a new and improved apparatus that enables handling of many different types of palletized goods in layers with great certainty. 
     Alternatively, the apparatus according to the invention the arresting means includes bodies bluntly designed at the bottom and which are arranged to be vertically displaceable in order to be displaced in height in relation to valve balls which are already in closing abutment with the valve seat of the associated suction chamber, and for preventing valve balls from contacting valve seats of valves that have not been closed. 
     In order to ensure automatic release of the valve balls, the apparatus according to the invention may advantageously be designed so that each of the valves includes a valve seat having an elastic material for releasing the valve balls automatically by venting a vacuum from the air distribution chamber. 
     With an object of achieving easier replacement of valve balls, the apparatus according to the invention may advantageously have the valve balls of each of the valves supported at the bottom on inwards projecting edge parts of elastic material. 
     In addition, the apparatus according to the invention includes a separate blower for operating inflatable squeezing pads. Between the blower and the inflatable squeezing pads is a changeover valve for connecting the inflatable squeezing pads either to the suction side or to the pressure side of the blower which is preferably is a side channel blower. 
     With regard to optimizing the functions of the apparatus according to the invention, the invention may advantageously be designed so that it includes a pressure regulating valve between the changeover valve and the inflatable squeezing pads. 
     In order to achieve an additionally simple and reliable action, the apparatus according to the invention may be designed so that the pressure regulating valve includes an upper venting valve with a valve ball which is actuated by one or more upper lever arms with regulating slides. 
     The apparatus according to the invention is suitably further designed so that the pressure regulating valve includes a cylinder or a bellows arrangement with a piston arranged to lift one or more of the lever arms for opening the venting valve. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention is explained more closely in the following in connection with the drawing, on which: 
         FIG. 1  shows a perspective view of an embodiment of a lift head for an apparatus according to the invention; 
         FIG. 2  shows a perspective view of the lift head shown in  FIG. 1 , seen from another angle and with a partly open side; 
         FIG. 3  shows a side view of a separate side channel blower with a pressure regulating valve for operating the inflatable pads in an apparatus according to the invention; 
         FIG. 4  shows a side view, partly in section, of an embodiment of a pressure regulating valve for an apparatus according to the invention and shown with a setting corresponding to reduced pressure in the inflatable pads; 
         FIG. 5  shows a side view, partly in section, of an embodiment shown in  FIG. 4  of a pressure regulating valve for an apparatus according to the invention and shown with a setting corresponding to high pressure in the inflatable pads; 
         FIG. 6  shows a side view, partly in section, of an embodiment shown in  FIG. 4  of a pressure regulating valve for an apparatus according to the invention and shown with a setting corresponding to emptying the inflatable pads; 
         FIG. 7  shows a perspective view of an embodiment of a side channel blower with associated changeover valve and pressure regulating valve according to the invention for an apparatus according to the invention; 
         FIG. 8  shows a perspective view of a pallet layer for illustrating a pallet layer with holes in the pallet layer which will require forced opening of the suction chambers of the suction sole; 
         FIG. 9  shows a side view of an embodiment of arresting means for an apparatus according to the invention, shown in initial position; 
         FIG. 10  shows a side view of arresting means, shown in  FIG. 9 , for an apparatus according to the invention, shown with activated vacuum; 
         FIG. 11  shows a side view of arresting means, shown in  FIG. 9 , for an apparatus according to the invention, shown with activated vacuum and lowered frame; 
         FIG. 12  shows a side view of arresting means, shown in  FIG. 9 , for an apparatus according to the invention, shown with activated vacuum, lowered frame and locked pins; 
         FIG. 13  shows a side view of arresting means, shown in  FIG. 9 , for an apparatus according to the invention, shown with activated vacuum, lowered frame and actively fixed pins; 
         FIG. 14  shows a side view of a second embodiment of arresting means for an apparatus according to the invention, shown without activity; 
         FIG. 15  shows a side view of arresting means, shown in  FIG. 14 , for an apparatus according to the invention, shown with activated vacuum; 
         FIG. 16  shows a side view of arresting means, shown in  FIG. 14 , for an apparatus according to the invention, shown with activated vacuum and displaced arresting means that yield where valve balls close the valves; 
         FIG. 17  shows a side view of arresting means, shown in  FIG. 14 , for an apparatus according to the invention, shown with activated vacuum and with forced opening of valve balls; 
         FIG. 18  shows a side view of arresting means, shown in  FIG. 14 , for an apparatus according to the invention, shown without vacuum and release of possibly stuck valve balls; 
         FIG. 19  shows a side view of arresting means, shown in  FIG. 14 , for an apparatus according to the invention, shown in initial position; 
         FIG. 20  shows a partial perspective view of an embodiment for a common activation system for arresting means, shown in inactive position; 
         FIG. 21  shows a partial perspective view, of the embodiment shown in  FIG. 20 , of a common activation system for arresting means, shown in active position; 
         FIG. 22  shows a plan view of an embodiment for a common rotary valve between suction face and air distribution chamber by an apparatus according to the invention, shown in open position; 
         FIG. 23  shows a plan view of an embodiment shown in  FIG. 22 , of a common rotary valve between suction face and air distribution chamber in an apparatus according to the invention, shown in closed position; 
         FIG. 24  shows a perspective view of a common rotary valve shown in  FIG. 22 , combined with an embodiment of a vacuum venting system, shown with open rotary valve and closed vacuum venting connection, respectively; and 
         FIG. 25  shows a perspective view of a common rotary valve shown in  FIG. 23 , combined with an embodiment of a vacuum venting system, shown with closed rotary valve and open vacuum venting connection, respectively. 
     
    
    
     Like reference numerals identify like parts throughout the drawings. 
     DETAILED DESCRIPTION OF THE INVENTION 
     The lift head  2  shown in  FIGS. 1-2  is adapted for destacking by layers of articles from a filled pallet that for example is taken from a rollerway. The lift head  2  includes a vacuum source in the form of a strong centrifugal blower  4 , having a central suction opening connected to a rectangular air distribution chamber which via a special rotary valve  6  ( FIGS. 22-25 ) is connected with a large number of suction chambers  8  (FIGS.  10  and  14 - 19 ) that are open at the bottom and together form a suction face. 
     The suction chambers  8  ( FIG. 10  et. seq.) are connected at the top with the front of the rotary valve  6  ( FIGS. 22-25 ) via round valve openings with spherical edges or valve seats at the bottom that fit to the outer spherical surface of rather light, thin-walled, spherical valve bodies  10  ( FIG. 9 , et. seq.) which are enclosed in each their suction chamber  8 . Combined, the suction chambers  8  constitute a rectangular lower suction face  12  ( FIGS. 9-13 ) which in size is adapted to a standard pallet, e.g. an EU pallet or a UK pallet. 
     The lift head  2  includes, in accordance WO-00/64790 and corresponding U.S. Pat. No. 6,802,688, as mentioned in the introduction, a special vertically adjustable, outer squeezing arrangement  44  which at each of the outer sides of the suction face comprises inflatable pads  46 . As shown in FIGS. 4, 5 and 7 of WO-00/64790 and corresponding U.S. Pat. No. 6,802,680, the squeezing arrangement  44  therein is surrounded by an inner skirt  48  and an outer skirt or a casing  50  for absorbing the reaction pressure of the squeezing pads  46  therein such that when the pads are inflated, an inwardly directed squeezing pressure is exerted on the outer sides of the pallet layer. Vertical adjustment is provided by the squeezing arrangement  44  which provides adjustment of the squeezing arrangement in height relative to the actual goods in the pallet layer. Preferably a motor driven winch and lift slings is utilized at each side of the lift head  2 . 
     The squeezing pads  46  of  FIGS. 1 and 2  are generally identified by reference numeral  46  which correspond to WO-00/64790 and U.S. Pat. No. 6,802,680 and are inflated via a pressure regulation valve  18  and a changeover valve  20  by means of air from a side channel blower  22  ( FIGS. 3-7 ) so that the pallet layer is clamped between the squeezing pads simultaneously with activating the suction face  12 . When the squeezing pressure is to be relieved subsequently, this occurs rapidly by shifting the changeover valve  20  so that the side channel blower  22  provides for rapid emptying of the squeezing pads  46 . 
     The pressure regulating valve  18  includes an upper pressure regulating system  24  with two lever arms  26  that actuate a valve ball  28  in a ball valve with a valve seat  30  with a permanent downwards pressure which can be set by means of slides on the lever arms  26 , as the use of one of the lever arms  26  corresponds to low pressure in the squeezing pads. When high pressure is present in the squeezing pads  46  of  FIGS. 1 and 2 , both lever arms  26  are used. 
       FIG. 5  corresponds to high pressure in the tube stud  16  which is connected to the inflatable pads  46  of  FIGS. 1 and 2  as indicated by arrows  17 . The inflatable pads  46  are positioned inside a lower surrounding inner and outer skirt  45  of  FIGS. 1 and 2  The ball valve with the valve seat  30  is then closed. When low pressure is present in the inflatable pads  46 , the ball valve in  FIG. 4  is open, as indicated by arrows  15 . Opening the ball valve  32  with the valve seat  30  in  FIG. 4  by upward movement of the lever arms  26  is effected by means of a piston  34  and a bellows arrangement  36 , as a solenoid valve (not illustrated) is opened and feeds air to the bellows arrangement  36 , as shown by the arrow  35 . 
     In  FIG. 6 , the inflatable pads  46  inside the lower surrounding inner and outer skirt  45  of  FIGS. 1 and 2  are emptied through the tube stud  16  as indicated by arrows  19 . The ball valve with the valve seat  30  is closed while a lower ball valve  32  is open so that air is also sucked in from the surroundings. The object is preventing the side channel blower  22  from being blocked when the squeezing pads are without air. 
     If the actual pallet layer to be lifted by means of the lift head  2  is relatively light and fragile packing items that do not stand up to lateral pressure, and which do not require very great suction pressure either, the overall suction pressure may be lowered by reducing the rotational speed of the centrifugal blower  4 . Whether the valve balls  10  are closing or not is only determined by the combination of actual opening in the pallet layer and the rotational speed of the centrifugal blower  4 . 
     In  FIG. 8  is shown a pallet with an uppermost pallet layer  38  in which there is a hole or opening which is larger than 300 cm 2 . This implies that to achieve a secure and rapid depalletizing, it is necessary to apply forced action downwards on the valve balls  10  in order to avoid that the valve balls  10  close the associated suction chambers  8  due to false air in the pallet layer  38 . The openings which are cross hatched are not blocked. 
       FIGS. 9-13  show an embodiment of an arresting system according to the invention, where a common frame  40  opposite each valve opening in the suction chambers  8  is provided with individually loose pins  42 , which, however, can be locked in relation to the frame  40 . The arrow  45  in  FIGS. 9-11  indicates upward and downward vertical measurement of the common frame  40  which carries the pins  42 . 
     In  FIG. 9 , the suction face  12  has been moved down upon a pallet layer  38  with openings so that the three left suction chambers  8  are placed upon an object that blocks the suction chambers  8  at the bottom, while the three right suction chambers  8  are not blocked at the bottom by an object or an article. 
     In  FIG. 10 , the suction face  12  is also moved down upon the pallet layer  38  ( FIG. 8 ) and vacuum is activated. The situation is changed, as the valve balls  10  to the right, which are cross hatched, are now closed. That is, the three left suction chambers  8  are communicating with the source of vacuum while the three right suction chambers  8  are now closed, because the suction face  12  is not in contact with objects or articles. 
     In  FIG. 11 , the suction face is also moved down upon the pallet layer  38  ( FIG. 38 ) and vacuum is activated. That is, the situation is unchanged, as the three left suction chambers  8 , which are cross hatched, are communicating with the source of vacuum while the three right suction chambers  8  are still closed, because the suction face  12  is not in contact with objects or articles. The frame  40  is now moved down so that three pins  42  to the left are in contact with the valve balls  10  in the open suction chambers  8 , while three pins  42  to the right are in contact with valve balls  10  in the blocked suction chambers  8 . That is, the pins  42  to the left are farther down compared with the other three pins  42  to the right. 
     In  FIG. 12 , the situation is almost unchanged as the pins  42  are here locked in the frame  40  only. 
     In  FIG. 13 , the situation is still unchanged with vacuum being activated. Where the suction face previously had contact with an article or an object, by plucking a film-enveloped product, an airflow  47  occurs due to forced opening by means of the pins  42 , where the airflow would normally make the valve balls close, but due to the forced opening in this area, the suction face will contact the article or the object anyway. 
       FIGS. 14-19  show a second embodiment of an arresting system according to the invention, where a common frame  44  opposite each valve opening in the suction chambers  8  is provided with individually rubber suspended arresting bodies  46 . 
     In  FIG. 14 , the common frame  44  is in its initial position. No vacuum is activated. 
     Vacuum is active in  FIG. 15 . Valve balls  10  close where there is airflow, namely at the two middle suction chambers  8 , while the outermost suction chambers are active because the suction chambers  8  are blocked at the bottom by abutting against article or object. 
     In  FIG. 16 , vacuum is still active. Here the frame  44  is displaced to the right so that the two middle arresting bodies  46  hit the valve balls  10  and are deflected to the left, as the arresting bodies  46  are rubber suspended at  48 . 
     Vacuum is active in  FIG. 17 . While the suction face previously had contacted the product, now by plucking a film enveloped product, there will arise a certain airflow  49  which normally would make the valve balls close, but due to the partitioned suction face there is now achieved a forced opening of the area of the suction face previously having contact with the product. 
       FIG. 18  shows how the frame  44 , after finished plucking, is advanced further and presses possible stuck valve balls  10  free of the valve seat. In  FIG. 19 , the ball valves are again back to their initial position. 
       FIGS. 20-21  show how a common arresting system for the entire suction face can be operated by an electric gear motor  50 , which via a number of eccentric discs  52  and turning arms  54 , may lift and lower a large number of arresting bodies  56  opposite each suction chamber  8 . In  FIG. 20 , the arresting bodies  56  are lifted off the suction chambers  8 , while the arresting bodies  56  in  FIG. 21 , are lowered into each their valve opening. 
     The above-mentioned rotary valve  6 , which is shown in  FIGS. 22-23 , has a circle of mutually separate valve openings  60  which are formed in the lower wall of the air distribution chamber  63 , and a valve plate  62  arranged rotatably in relation thereto with a corresponding circle of valve openings  64 . The valve plate  62  is arranged to be turned for opening and closing the rotary valve  6  by means of arms  66 , an eccentric  68  and an electric motor. 
       FIGS. 24 and 25  additionally show that the rotary valve  6  interacts with a vacuum valve  72 , which is disposed in open air and spaced apart from the rotary valve  6 , namely at the end of a vertical pipe  74 . However, vacuum valve  72  interacts with the rotary valve  6  via an actuation plate  76  and an actuation rod  78  which is connected with the vacuum valve  72 .  FIG. 24  shows the rotary valve  6  in open condition and the vacuum valve  72  in closed condition, while  FIG. 25  shows the rotary valve  6  in closed condition and the vacuum valve  72  in the open condition. In  FIG. 24 , the arrow  79  with an “X” indicates that vacuum is not applied. In  FIG. 25 , the arrow  79 ′ indicates the application of a vacuum. 
     Alternatively, the arresting means may be comprised of a common plate or frame on which opposite the individual valve seats for the suction chambers  8  there are mounted on individually resilient fingers. The fingers by means of the common plate or frame may be displaced across the valve openings in such a way that the resilient fingers, where the valve balls  10  are already in contact with the valve seat and shut off the suction chambers  8 . The suction chambers yield to the valve balls  10  and move down along the top side of the valve balls  10  without pressing the latter downwards. The resilient fingers where the valve balls  10  are not in contact against the valve seat are moved in under the opposite side of the valve seat and prevent the valve balls  10  from subsequently shutting off the suction chambers  8 . The advantage of this alternative arrangement is that there may be attained greater distance between the valve balls  10  and their associated valve seats. That is there may be attained greater airflow by arrested valve balls  10 . 
     Finally, the suction face  12  may advantageously be built up from individual suction chambers of flexible material such as for example in the form of loose suction chambers  8  moulded in plastic. Thereby, a significant reduction in maintenance costs may be achieved. If the suction chambers  8  are made of flexible material with lower inwardly projecting retainer members for the valve balls  10 , it will be much easier to replace damaged valve balls with new valve balls. New balls may just be pressed up into the suction chamber from below through the inwardly projecting flexible retainer members of the valve balls  10 .