Abstract:
The problem of the lag time in picking and dropping mixed load products during a palletization process is solved by using a tool having i) a gripping member that can be partially closed in a first fast movement while it is moved by a robot towards a product and then closed onto the product in a second shorter movement and ii) a product abutting plate that is movable in unison with the tool in opposite direction thereof as the tool is moved by a robot towards and away the mixed load pallet.

Description:
FIELD 
       [0001]    The present disclosure relates to palletizing, and more specifically to palletizing of mixed load products. 
       BACKGROUND 
       [0002]    Warehouses, distribution centers and fulfillment centers typically receive full pallets of uniform products. In many cases, the products are depalettized and stored individually in a storage area. When specific orders need to be prepared, the products are transported to a palletizing cells, which can be either manual, automated or robotized. 
         [0003]    Because of the wide variety of products, a special and versatile end of arm tool is required when the robotized approach is taken. 
         [0004]    Typical tools to grip products are equipped with vacuum cups or pads. Such tools are economical and easy to use. While they can be used with closed boxes or cartons, they show limitations to grip trays, stretch wrapped products or the like. Problems may also occur if the top flaps of the boxes are not glued or tapped adequately. Because of the multiplication of product sizes and formats found in warehouses and distribution centers, a more robust and versatile tool is required. 
         [0005]    The use of a fork-type tool allows solving the above-mentioned drawback. Traditionally, the bottom forks of such tools can be extended or retracted. Therefore, when a product is gripped, the bottom forks are extended to go underneath the product, while they are retracted when the product is dropped in place. This type of tool is popular, considering that it can handle virtually any type of product in a reliable fashion. 
         [0006]    However, a first drawback of typical fork-type gripping tool relates to the width of the bottom forks. Ideally, it should be wide enough to be able to pick and handle products of various dimensions, but when it is too large, it limits the capacity to drop narrow products on the pallet considering that the wide forks might interfere with products already in place on the pallet. A second drawback is the cycle time required for a conventional fork tool to pick and place products. 
         [0007]    U.S. Pat. No. 8,235,436 B2, issued on Aug. 7, 2012, to Ryf and being titled “Bundle Gripper for a Palletizing Machine and Method for the Palletizing of Bundles” describes a bundle gripper for a palletizing machine handling bundles, wherein a bundle is fed from a feeding device to the bundle gripper, the bundle resting against an end stop. Ryf tool has at least two gripper units, and gripper fingers that are extendable. A drawback of the tool by Ryf is that providing movable fingers renders the tool heavier and more complex, therefore requiring additional maintenance. 
         [0008]    U.S. Pat. No. 6,579,053 B1, issued on Jun. 17, 2003 to Grams et al. and being titled “Robotic Containerization and Palletizing System” describes a robotic system using an end effector comprising a plurality of rotatable fingers designed specifically to handle trays, pallets or tubs. 
         [0009]    The approach taken by Grams et al is dedicated to handle objects with geometry similar to trays and the like, and is therefore not suitable for palletizing mixed load products in a warehouse. 
         [0010]    U.S. Pat. No. 8,807,912 B2, issued on Aug. 19, 2014 to Liebheit and being titled “Infeed Station and Stack Gripper of a Palletizing System and Method for Transferring Stacks from an Infeed Station to a Stack Gripper” describes a tool and method for transferring stacks. 
         [0011]    The approach taken by Liebheit is specific to stack handling where a stack conveyor and at least two stack chambers are used. Liebheit uses the gripper described in details in U.S. Pat. No. 8,235,436 B2 discussed above. 
         [0012]    United States Publication No 2010/0218464 A1, published on Sep. 2, 2010 to Baumann and being titled “Gripper for an Automated Manipulator and Method for Operation of the Gripper” describes a tool including bottom forks to secure the product from underneath, and a stop and a counter-stop to firmly hold the product on two opposite sides. This tool is designed to firmly hold a variety of products, but is not suitable for palletizing at high rates because of its multi-step sequence. Once the tool is positioned close to the product to be picked, a first motor moves the bottom forks underneath the product. The counter-stop is then lowered and finally the stop is moved forward to positively hold the product on two opposite sides. The reverse sequence is performed when placing the product on the pallet. It results that the manipulator is in a waiting position for too long and is not suitable for applications where high throughput is required. 
         [0013]    Baumann&#39;s gripper illustrates a problem common to most known grippers, which are designed in such a way that the robot has to completely stop to enable the bottom forks to go underneath the product and then to lower the top pad to securely hold the product before the robot can start its retrieving movement to bring the picked product to the pallet. 
         [0014]    Many systems from the prior art include an upper mobile pad or plate to secure the product from the top. One known approach is to use a servo-driven axis to lower the upper pad to the desired height. This approach is fast to modify and adapt the tool&#39;s opening from one product to the other, but does not precisely adapt to the real product&#39;s dimension because the exact dimensions of the cases are rarely their nominal values. If the real dimension is slightly higher that the nominal value, the upper pad can crush the product and possibly damage at least the packing if not the product itself. Similarly, if the product real height is less that its nominal value, the upper pad will not hold the product properly. Another approach from the prior art is to use pneumatic driven axes to move a plate to pick the product. This approach is slower compared to the one previously mentioned because the upper pad returns to the uppermost position between each product. When a small product is picked, the long downward movement increases the picking time, thus the overall cycle time. On the other hand, this approach allows applying a predetermined pressure that enables the tool to firmly hold the product without damaging the packing or the product regardless of its real dimensions. 
       SUMMARY 
       [0015]    Many issues and challenges are encountered when developing a tool for mixed load palletizing. The tool has to be large enough to pick big products but slim enough to place smaller products between two previously placed products. The cycle time is also an important feature and the method used has to limit, or ideally eliminate, the waiting time of the manipulator or robot arm. Similarly, the clamping process has to be as fast as possible for similar reasons. 
         [0016]    The problem of the lag time in picking and dropping mixed load products during a palletization process is solved by using a tool having i) a gripping member that can be partially closed in a first fast movement while it is moved by a robot towards a product and then closed onto the product in a second shorter precise movement and ii) a product abutting plate that is movable along an axis in unison with the tool in opposite direction thereof. 
         [0017]    According to an illustrative embodiment, there is provided a tool for palletizing mixed load products, the tool comprising: 
         [0018]    a frame for mounting the tool to a robot; 
         [0019]    a fork assembly including a plurality of side by side and distanced product-supporting members, each mounted to the frame; 
         [0020]    a gripping assembly having at least one gripping member mounted to the frame in a parallel relationship with the product-supporting members; the at least one gripping member being movable relative to the product-supporting members so as to vary a distance therewith; and 
         [0021]    a pusher assembly including a pusher that is mounted to the frame for longitudinal movement along the product-supporting members. 
         [0022]    According to another illustrative embodiment, there is provided a palletizing cell comprising: 
         [0023]    an infeed conveyor for providing mixed products to be palletized; 
         [0024]    a pallet-receiving station; and 
         [0025]    a robot equipped with the tool as recited hereinabove, that is positioned within reach of both the infeed station and pallet-receiving station; the robot being for sequentially gripping the mixed products and for placing each gripped product on a pallet positioned at the pallet-receiving station. 
         [0026]    According to still another embodiment, there is provided a tool comprising: 
         [0027]    a gripping member that is partially closable in a first fast movement while the tool moves towards a product and then closable onto the product in a second movement; and 
         [0028]    a product abutting member that is movable within the gripping member in unison with the tool in opposite direction thereof. 
         [0029]    According to a further embodiment, there is provided, a method for palletizing mixed load products using a tool mounted to a robot, the method comprising: 
         [0030]    adjusting the width of the tool in response to a width of a selected product among products to be palletized; 
         [0031]    the robot simultaneously moving towards the selected product to be palletized and opening a gripper assembly of the tool to a nominal height of the selected product plus an offset gap; 
         [0032]    when the tool is positioned to start gripping the selected product, closing the gripper a distance sufficient to contact the product; 
         [0033]    contacting the selected product with a pusher within the gripper assembly of the tool; 
         [0034]    moving the pusher backward in synchronicity with moving the tool forward until the selected product is gripped by the tool; 
         [0035]    moving the tool adjacent a mixed load pallet at a position selected to drop the selected product; and 
         [0036]    moving the pusher forward in synchronicity with moving the tool backward until the selected product is dropped by the tool at the selected position while the gripper assembly keeps contact with the product. 
         [0037]    With a tool according to illustrated embodiments, the robot is not required to stop while placing a product. This is done by pushing the product while the robot moves away from the position where the product is being placed. The pushing movement is provided by a servo drive and this movement is synchronized with the robot&#39;s movement. These combined movements produce the overall effect of a product being gently placed on the pallet while the robot starts his movement to pick the next product. The same principle applies in the picking process. 
         [0038]    Other objects, advantages and features of the tool and method for palletizing mixed load products will become more apparent upon reading the following non restrictive description of preferred embodiments thereof, given by way of example only with reference to the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0039]    In the appended drawings: 
           [0040]      FIG. 1  is a perspective view of a palletizing cell for mixed load products, including a tool for mixed load palletizing according to a first illustrative embodiment; 
           [0041]      FIG. 2  is a perspective view of the tool from  FIG. 1 , illustrating the tool in its narrower configuration, the gripping members in their upper position, and the pusher bars in their back position; 
           [0042]      FIG. 3   a  is a top perspective view of the tool from  FIG. 2 , illustrating the tool in its wider configuration, the gripping members in their lower position and the pusher bars in a front position; 
           [0043]      FIG. 3   b  is a partial top perspective view similar to  FIG. 3   a , taken from the opposite side thereof; 
           [0044]      FIG. 3   c  is a bottom perspective view of the tool from  FIG. 2 , illustrating the tool in its wider configuration, the gripping members in their lower position and the pusher bars in a front position; 
           [0045]      FIG. 4  is a back elevation of the tool from  FIG. 2 ; the tool being shown in the same configuration of  FIG. 3 ; 
           [0046]      FIG. 5  is a flowchart illustrating a method for palletizing mixed load products according to an illustrative embodiment; 
           [0047]      FIGS. 6   a  to  6   d  are partial side elevations of the tool from  FIG. 2  illustrating the robot withdrawing step (step  222 ) from  FIG. 5 ; 
           [0048]      FIG. 7  is a side elevation of the tool from  FIG. 2 , illustrating the resiliency of the gripping members; 
           [0049]      FIG. 8  is a perspective view of a tool for mixed load palletizing according to a second illustrated embodiment; 
           [0050]      FIG. 9  is a side elevation of the tool from  FIG. 8 ; and 
           [0051]      FIGS. 10 and 11  are back elevations of the tool from  FIG. 8 , respectively showing the forks in their narrow and extended configuration. 
       
    
    
     DETAILED DESCRIPTION 
       [0052]    In the following description, similar features in the drawings have been given similar reference numerals, and in order not to weigh down the figures, some elements are not referred to in some figures if they were already identified in a precedent figure. 
         [0053]    The use of the word “a” or “an” when used in conjunction with the term “comprising” in the claims and/or the specification may mean “one”, but it is also consistent with the meaning of “one or more”, “at least one”, and “one or more than one”. Similarly, the word “another” may mean at least a second or more. 
         [0054]    As used in this specification and claim(s), the words “comprising” (and any form of comprising, such as “comprise” and “comprises”), “having” (and any form of having, such as “have” and “has”), “including” (and any form of including, such as “include” and “includes”) or “containing” (and any form of containing, such as “contain” and “contains”), are inclusive or open-ended and do not exclude additional, unrecited elements. 
         [0055]    A tool  10  for palletizing mixed load products  12  according to a first illustrative embodiment will now be described with reference to  FIGS. 1-3 . 
         [0056]    As shown in  FIG. 1 , the tool  10  according to the first illustrated embodiment is operatively mounted to an industrial robot arm  14  which is positioned adjacent both an infeed conveyor  16  and a pallet receiving station  18 . The ensemble of the robot  14  with tool  10 , infeed conveyor  16  and pallet receiving station  18  will be referred to herein as a palletizing cell. 
         [0057]    As an input, products  12 , that can be of various sizes, arrive from the infeed conveyor  16  and each one is gripped by the tool  10  in such a way as to firmly hold it to enable fast transfer to a pallet  20  without damaging the product  12  and without relative movement between the product  12  and the tool  10 . The product  12  is then released and placed on the pallet  20 . 
         [0058]    The expression “product” should be construed herein as including any type of case, carton, tray, stretch wrapped, etc. 
         [0059]    Generally, the product is of a rectangular shape. The product dimensions may vary greatly between each different types of product. Typical dimensions (W×L×H) are between 4″×6″×2″ (10.16 cm×15.25 cm×5.08 cm) and 20″×25″×24″ (50.8 cm×63.5 cm×61.0 cm). 
         [0060]    It is to be noted that the illustrated products are referred to using the same reference number  12 , while they may vary in configuration and size. 
         [0061]    The infeed conveyor  16  is in the form of a roller type conveyor. According to another embodiment (not shown), the products  12  are brought to a location within reach of the robot  14  via another type of conveyor such as a narrow belt conveyor with a pop-up mechanism between the narrow belts to lift the products. According to still another embodiment, the infeed conveyor  16  is replaced by any other means allowing products  12  to be presented to the tool  10  so as to be gripped thereby. 
         [0062]    The pallet receiving station  18  is in the form of a cleared area within reach of the robot  14 , that is sufficiently large to receive a full mixed load pallet. 
         [0063]    The tool  10  is attached to a standard four-axis or six-axis industrial articulated robot arm  14 . Equipped with the tool  10 , the robot  14  is capable of securely gripping and transfering one or more products  12  from the infeed conveyor  16  to the pallet  20 . A conventional robot arm can be used, such as ABB&#39;s IRB 660 or IRB 6640, FANUC&#39;s R2000 or M410, or any similar robot arm offered by other manufacturers like Kuka or Motoman. 
         [0064]    The robot arm  14  includes other well-known systems and components that allow its operation. Since these systems and components are believed to be well-known in the art, they will not be described herein in more detail for concision purposes. 
         [0065]    In the description and in the claim, the expressions ‘robot’ and ‘robot arm’ will be used interchangeably to mean a programmable system including articulated and/or movable members that can receive, control and move a tool. 
         [0066]    The robot arm  14  is conventionally coupled to a controller  22  that controls the operation of the robot arm  14  and tool  10 . 
         [0067]    The expression “controller” should be construed broadly as including one or more electronic devices, including for example one or more computers that are configured with components and/or programmed with instructions that produce one or more functionalities, including communicating data and instructions with an electronic or electro-mechanical machine or device. 
         [0068]    With reference to  FIGS. 2 ,  3  and  4 , the tool  10  will now be described in more detail. 
         [0069]    The tool  10  comprises a frame  24 , a gripping mechanism  26  and a pusher assembly  28 , both mounted to the frame  24 , and a width-adjusting assembly  29 . 
         [0070]    The frame  24  receives a robot-mounting bracket  30  that allows the tool  10  to be conventionally attached to the robot  14 . 
         [0071]    The gripping mechanism  26  includes two parallel first track assemblies  32 - 32 ′, each extending from the frame  24  between a proximate end  34  to a distal end  36 , two forks  38 - 38 ′, each fixedly mounted to a respective track assembly  32 - 32 ′ at the distal end  36  thereof, and two side by side gripping members  40 - 40 ′, each one being mounted to a respective one of the two track assemblies  32 - 32 ′ so as to extend generally perpendicularly therefrom and for movement in unison therealong. The gripping members  40 - 40 ′ are maintained in parallel relationship with the fork assemblies  38 - 38 ′. 
         [0072]    As will become more apparent upon reading the following description, parts that are referred to with a prime (′) is identical to the other part identified with the same but unprimed numeral reference, the only difference is that the primed reference refers to a movable part. 
         [0073]    Each track assembly  32 - 32 ′ is in the form of a hollow rectangular post  41 - 41 ′ including tracks  42 - 42 ′ secured on both lateral sides thereof. The track assemblies  32 - 32 ′ are not limited to hollow rectangular posts and can take any other rigid form that can receive and position an elongated track and forks  38 - 38 ′. 
         [0074]    Each fork  38 ,  38 ′ is defined by two parallel fingers  44 . Each pair of fingers  44  is secured to a respective post  41 - 41 ′ via a mounting bracket  43  that is fixedly mounted to the post  41 - 41 ′ at the distal end  36  thereof. The fingers  44  of the two forks  38 - 38 ′ extend from a respective post  32 - 32 ′ so as to generally lie within a same plane that is generally perpendicular to the posts  41 - 41 ′. 
         [0075]    The fingers  44  are beveled to ease their insertion under a product  12  as will be described furtherin. 
         [0076]    According to another embodiment (not shown), the forks  38 - 38 ′ include another number of fingers  44  than two (2), the fingers  44  have another shape than the one shown in the Figures, and/or a fork assembly is provided that includes another number of forks than two (all not shown). 
         [0077]    Each gripping member  40 ,  40 ′ includes a belt  46  that is endlessly mounted between two shoe-shaped side plates  48 ,  48 ′, secured therebetween. 
         [0078]    Each gripping member  40 ,  40 ′ is slidably mounted to a respective post  41 ,  41 ′. More specifically, rail-engaging elements  50  are secured to both shoe-shaped side plates  48  and  48 ′ near the proximate enlarged ends thereof. The distance between the facing plates  48 - 48 ′ is such that the gripping members  40  and  40 ′ remain mounted to its respective tracks  42 - 42 ′ when the gripping members  40  and  40 ′ are moved therealong. 
         [0079]    The distance between the bottom portions of the gripping members  40 - 40 ′ and the top portion of the respective forks  38 - 38 ′ defines the opening of the gripping mechanism  26  and can be adjusted for the height of a given product  12 . For that purpose, the position and movement of the gripping members  40 - 40 ′ are servo-driven and pneumatically actuated by a first drive assembly  54 . 
         [0080]    The first drive assembly  54  includes a first drive  56  having an output shaft provided with a first pulley  58  that operatively receive an endless belt  60 , that is further mounted on a second pulley  62 . A roll  59 , that is rotatably mounted to the frame, is provided to tension the belt  60 . The pulley  62  is mounted to a first end of a shaft, and a driven gear  64  is provided at its other end. The driven gear  64  is rotatably mounted to the frame  24  and receives an endless timing belt  65 . 
         [0081]    The coupling assembly  70  operatively couples the timing belt  65  to the track  42  of the fixed post  41 . Another coupling assembly  71  operatively couples the distal end  69  of the pneumatic actuator  68  to side plate  48 . The horizontal bar  74  is coupled to the gripping assembly  40 - 40 ′ as can be better seen from  FIG. 3   a.    
         [0082]    A horizontal bar  74 , that is secured to the gripping member  40  on the side of the fixed post  41  and that is slidably received by the other gripping member  40 , forces both gripping members  40 - 40 ′ to slide along the track assemblies  42 - 42 ′ in unison when the drive assembly  54  is actuated. 
         [0083]    The width-adjusting assembly  29  allows moving the tool  10  between two specific width configurations, a narrow and a wide configuration, depending on the size of each product  12  to pick. More specifically, the width-adjusting assembly  29  allows moving and maintaining the distance between the movable post  41 ′ and the fixed post  41 , and therefore between the gripping members  40  and  40 ′ and between the forks  38  and  38 ′. 
         [0084]    The width-adjusting assembly  29  includes top and bottom cursors  76  and  78  that receive respective horizontal tracks  80  and  75 . The track  75  is fastened to the horizontal bar  74 . The top horizontal tracks  80  is fixedly mounted to the frame  24  thereunder and the top cursor  76  is slidably mounted to the tracks  80  and fixedly mounted to the movable post  41 ′. The bottom track  75  is fixedly mounted to the gripping member  40  and the bottom cursor  78  is fixedly mounted to the other gripping member  40 ′ and slidably mounted to the track  75 . A slot  82  is provided in the exterior side plate  48  of this other gripping member  40 ′ to allow passage for the horizontal bar  74  and bottom track  75  when the movable gripping member  40 ′ is moved towards the other gripping member  40 . 
         [0085]    The width-adjusting assembly  29  further includes a pneumatic cylinder  84  mounted to the frame near the fixed post  41 . Extending or retracting the cylinder rod  86  allows modifying the width of the tool  10 . 
         [0086]    The pusher assembly  28  will now be described in more detail. As will become apparent upon reading the following description, the pusher assembly  28  defines a product abutment, that extends generally perpendicularly to both the forks  38 - 38 ′ and the gripping members  40 - 40 ′ therebetween, and whose longitudinal position along the forks  38 - 38 ′ is movable in unison with the displacement of the tool  10  in opposite direction thereof. 
         [0087]    The pusher assembly  28  includes a third track assembly  90 , including tracks  96  that extend generally parallel to the forks  38 - 38 ′, two pusher bars  94 - 94 ′ that are mounted to the tracks  96  via a pusher bar holder  92 , and a second drive assembly  88  for moving the pusher bar holder  92  in the tracks  96  therealong. 
         [0088]    The pusher bar holder  92  is slidably mounted to the tracks  96  via a cursor  102  fixed to the pusher bar holder  92 . The holder  92  includes tracks  98  that are oriented perpendicular to the gripping members  40 - 40 ′. 
         [0089]    The proximate end  87  of the pusher bar  94  is fixedly mounted to the pusher bar holder  92 . The proximate end  87 ′ of the pusher bar  94 ′ is slidably mounted in the tracks  98  via a cursor  104  for movement therealong. The pusher bars  94  are further slidably mounted to the inner side plate  48  of the gripping member  40  via hollow brackets  91  for free movement along the gripping members  40 - 40 ′ and also so as to allow transversal movement of the gripping members  40 - 40 ′ along the pusher bars  94 - 94 ′. The brackets  91  are slidably mounted to the inner side plates  48 . 
         [0090]    The distal ends  89  of the pusher bars  94  are provided with fingers  93  that extend laterally from the pusher bars  94 - 94 ′, perpendicularly therefrom in opposite directions. The length of these two fingers  93  are such that they do not extend beyond the forks  38  and gripping members  40  when the gripping member  40 ′ and fork  38 ′ are positioned closer to the other corresponding assembly  40  and fork  38 . 
         [0091]    The second drive assembly  88  includes a drive  106  having an output shaft provided with a pulley  107  that is operatively coupled to an endless belt  109 . The endless belt  109  is coupled to the pulley  111 . A roller  108 , that is secured to the frame  24 , is provided to tension the belt  109 . The pulley  111  is coupled to the pulley  113  via the coupling shaft  112 , who is coupled to the timing belt  115 . The other end of the endless belt  115  is mounted to a pulley  114  that is rotatably mounted to the frame  24  via a mounting bracket  116 . The cursor  102  is attached to the belt  115  via a clipping assembly  118  for movement of the holder  92  in unison with the belt  115 . 
         [0092]    In operation of the pusher assembly  28 , the longitudinal position of both pusher bars  94 - 94 ′ along the gripping members  40 - 40 ′ is controlled by the drive  106 , the bar  94 ′ moves laterally in unison with the gripping member  40 ′ when the width of the tool  10  is adjusted for the width or length of the product  12  to pick, and the gripping members  40  and  40 ′ are free to move along the pusher bars  94 - 94 ′ to adjust for the height of the product  12 . 
         [0093]    When the pusher assembly  28  is moved by the second drive assembly  88 , the belts  46  follow the movement of the pusher assembly  28  in unison. The pusher bars  94  and  94 ′ are attached to the belts  46  with clipping assemblies  119  and  119 ′ (see on  FIG. 3   c ). 
         [0094]    The operation of the robotic cell of  FIG. 1  will now be described with  FIGS. 1-4  and  6   a - 6   d  and with reference to  FIG. 5  that describes a depalletizing method  200  according to an illustrative embodiment. 
         [0095]    In step  202 , the robot  14  receives instructions to pick a product  12  on the infeed conveyor  16 , and nominal dimensions of the product  12  is received by the robot controller  22  (step  204 ). 
         [0096]    The nominal dimensions of the product  12  can be received by the controller  22  as the product  12  arrives on the conveyor  16  or it can be sent thereto in batch for a given number of products  12  that are known to sequentially arrived on the conveyor  16 . Also, the nominal dimensions can be provided for example by the manufacturer of the product or measured using a vision system or else (not shown). 
         [0097]    The controller  22  activates the width-adjusting assembly  29  so that the width of the tool  10  is slightly less than the nominal width or length of the product  12  (step  206 ). More specifically, when the product dimensions are less than a predetermined value, the tool  10  is configured to its narrow configuration, and, when the product dimensions are more than a predetermined value, the tool  10  is configured to its wide configuration. After step  206  or at the same time, the pneumatic actuator  68  is extended to lower the two gripping member  40 - 40 ′ along the vertical track assemblies  32 - 32 ′ as the robot  14  approaches the infeed conveyor  16  (step  208 ). 
         [0098]    The first drive  56  lowers the gripping members  40 - 40 ′ along the vertical track assemblies  32 - 32 ′ to yield a distance between the forks  38 - 38 ′ and the belts  46  equivalent to the product&#39;s  12  nominal height plus an offset (step  210 ). 
         [0099]    Steps  206 - 210  can be performed at the same time the robot  14  positions the tool  10  to start the gripping process (step  212 ). 
         [0100]    As the forks  38 - 38 ′ begin their insertion underneath the product  12  by the movement of the robot arm  14 , the first drive  56  again lowers the gripping members  40 - 40 ′ along the vertical track assemblies  32 - 32 ′ to have a positive contact between the belts  46  and the product  12  (step  214 ). 
         [0101]    Then, (in step  216 ) as the robot arm  14  moves the forks  38 - 38 ′ underneath the product  12 , the second drive  106  moves the pusher bar holder  92  along the horizontal track  96  in a synchronous movement. By this action, the pusher bars  94  move backward as the tool  10  moves forward. Since the pusher bars  94  are mechanically attached to the belts  46  with the clipping assemblies  119 - 119 ′, the later move in unison with the pusher bars  94 , therefore keeping a positive contact between the belts  46  and the product  12 . When the forks  38 - 38 ′ are properly positioned under the product  12 , the first drive  56  lowers the gripping members  40 - 40 ′ to firmly hold the product  12 . At the end of this step, the product is gripped by the tool  10  (step  218 ). 
         [0102]    The robot controller  22  then instructs the robot  14  to position the gripped product  12  in a predetermined location on the mixed load pallet  20  (step  220 ). 
         [0103]    When this location is reached by the tool  10 , the robot controller  22  instructs the second drive  106  to move outwardly in order to push the product  12  with the pusher bars  94 - 94 ′ while the robot  14  starts its retracting movement in a synchronous fashion to prepare itself for the next product  12  to be picked. Since the pusher bars  94 - 94 ′ are mechanically attached to the belts  46  with the clipping assemblies  119 - 119 ′, the later move in a synchronous fashion with the movement of the tool  10 , therefore keeping a positive contact between the belt  46  and the product  12  (step  222 ). 
         [0104]      FIGS. 6   a - 6   d  illustrate in more details step  222 . It is to be noted that  FIGS. 6   a - 6   d  show the tool  10  gripping another product than the box from  FIG. 1 . 
         [0105]    When the tool  10  is positioning the product  12  in the proper position on the pallet  22 , the drive  106  starts moving the pusher bar holder  92  along the horizontal track  96  (see arrow  120  in  FIG. 6   a ) as the robot  14  starts its withdrawing movement (see arrow  122 ) in a synchronous fashion. As previously mentioned, the belts  46  also moves in a synchronous movement with the product  12  being placed (see arrow  124 ). It is to be noted that the belts  46  are not motorized and are caused to move in unison with the pusher bars  94 - 94 ′ because of the clipping assemblies  119 - 119 ′. These synchronous movements causes the product  12  to stay at the same location on the pallet  20 , while the tool  10  withdraws (see  FIG. 6   b ). 
         [0106]    As we can see in more details in  FIG. 6   c , the gripping members  40 - 40 ′ are slightly longer that the forks  38 . Therefore, when the pusher bars  94  are at the end of their travel, the product  12  is no longer supported from underneath by the forks  38 . At this moment, because of the previously activation of the actuator  68 , the gripping members  40 - 40 ′ push down the product  12 , (see arrow  126  in  FIG. 6   d ), forcing it to sit properly on the pallet  20  or on previously palletized products  12 . It is to be noted that this step is performed in a very short period of time as the above-mentioned withdrawal of the robot  14  corresponds to the beginning of its movement to pick the next product  12 . 
         [0107]    When the palletizing process is completed, the gripping members  40 - 40 ′ are moved upward (step  224 ) and the robot arm  14  can immediately move to get the next product  12  to be picked (step  202 ). The process  200  is then repeated for each new product  12  on the infeed conveyor  16 . 
         [0108]      FIGS. 3 and 4  illustrate the tool  10  while the actuator  86  is in the extended position, while  FIG. 2  illustrates the tool  10  while the actuator  86  is in the retracted position. For example, when a product  12  to be picked is less than a predetermined dimension, the tool is in the retracted position of  FIG. 2 . Since the fork  38 ′ and the movable gripping member  40 ′ are coupled, both move together in unison with the actuator  86 . 
         [0109]    Similarly, since the pusher bar  94 ′ is associated with the gripping member  40 ′, both move in unison with the actuator  86 . 
         [0110]      FIG. 7  illustrates the resiliency of the belts  46  which allows irregular shaped products such as bottles  130  to be safely gripped while keeping its functionality described above because of the presence of a foam material supporting the belts  46 . 
         [0111]    According to another embodiment, the foam material is replaced by rubber, or another material. According to still another embodiment, the foam material is omitted. 
         [0112]    In most application, the infeed conveyor  16  is in the form of a roller type conveyor. Providing forks  38  as the bottom support of the tool  10  allows inserting the bottom support underneath the product  12  and between the rollers  17  of the infeed conveyor  16 . 
         [0113]    The widths of the product  12  coming on the infeed conveyor  16  may vary greatly. As the mixed load pallet  20  is being built, products  12  of different sizes and geometries are positioned on the pallet  20 . Adjusting the width of the tool  10  so that it is narrower than the product  12  that is being palletized. allows avoiding collisions between the tool  10  and already positioned products  12  on the pallet  20 . 
         [0114]    Providing the tool  10  with pusher bars  94  that are movable in unison with the tool  10  but in opposite direction thereof enables picking the product  12  and then placing the product  12  on the pallet  20  without stopping the robot&#39;s movement. This allows maximizing throughput. 
         [0115]    Providing gripping members including belts  46  that move in unison with the pusher bars  94  enables a better control of the product gripping and dropping processes, minimizing the possibility of product tipping. 
         [0116]    Using a combined servo driven and pneumatic actuated gripping members  40 - 40 ′ allows adapting the tool  10  to the product&#39;s height without imposing any delay in the picking process or damaging the products  12 . The drive assembly  54  allows maximizing speed by using the servo drive  56  to position the gripping members  40 - 40 ′ close to their clamping position and then using the compliance feature obtained with the pneumatic actuator  68  to actually clamp a product  12 . 
         [0117]    The tool  10  allows simultaneously picking two products  12 . When two products  12  are picked, each one is clamped between one fork  38 ,  38 ′ and one gripping member  40 ,  40 ′ enabling secure holding of both products  12 . The tool  10  can also pick two or more products in a perpendicular fashion, the products&#39; length being perpendicular to the main axis of the gripping members  40 - 40 ′ and the forks  38 - 38 ′. 
         [0118]    The drive assemblies are not limited to the illustrated embodiment and can be modified in any way allowing to yield the same functionalities. As one example of a possible modification, the pneumatic actuators can be replaced by other actuating means. Also the belt assembly can be replaced by other mechanical movement transmission assemblies. 
         [0119]    Any one of the illustrated tracks can be substituted with any type of linear guided slide or bearing. 
         [0120]    The number and configuration of the gripping members  40  and  40 ′ can also differ to those illustrated. For example, the belts  46  can be replaced by a low friction material for the gripping members  40 . 
         [0121]    With reference to  FIGS. 8 and 9 , a tool  140  for palletizing mixed load products according to a second illustrating embodiment will now be described in more detail. Since the tool  140  is similar to the tool  10 , only the differences therebetween will be described hereinbelow in more detail for concision purposes. 
         [0122]    The tool  140  comprises a fork  142  having three fingers  144  and  145  mounted to the frame  146  via tapered beams  148  and  150  so as to extend perpendicularly therefrom. The center beam  150  is fixedly mounted to the frame  146  and the two side beams  148  are mounted to the frame  146  for lateral movement relative to the center beam  150 . 
         [0123]    More specifically, the beams  148  are mounted to tracks  152  and their lateral distance from the center beam  150  can be modified via the actuators  154 . 
         [0124]    The tool  140  further comprises a pusher assembly  156  of fixed dimensions. The pusher assembly  156  is mounted to the frame  146  via a track  158  for slidable movement along the center finger  145 . The displacement of the pusher assembly  156  is driven by a first drive assembly  162  that includes first drive  164 , first endless belt assembly  166  and associated pulleys. 
         [0125]    A pad  176 , that forms a gripping element with the fork  142 , is mounted to the pusher assembly  156  via a track  171  for slidable movement therealong. The longitudinal movement of the pad  176  in the track  171  is driven by a second drive assembly  168  that includes a second drive  170 , a spline shaft  160 , an endless belt assembly  172  and actuator  174 . 
         [0126]    As the robot  14  is instructed to pick a product  12 , the robot controller  22  activates the first actuator  154  to position the outer forks  144  to yield the proper width for the tool  140  to the retracted or extended position, depending of the product&#39;s dimension. The robot controller  22  activates the second actuator  174  to lower the top pad  176 . Also, the second drive  170  positions the pad  176  to a specific distance between the forks  144 - 145  and the pad  176  equivalent to the product&#39;s nominal height added to an offset. As the robot  14  inserts the forks  144  underneath the product  12 , the pusher assembly  156  is moved backwards by the first drive  164  in unison with the robot&#39;s movement and the pad  176  is lowered to be in contact with the top surface of the product. When the forks  144  are properly positioned under the product  12 , the first drive  164  lowers the pad  176  to firmly hold the product  12 . 
         [0127]    When the robot  14  is instructed by the controller  22  to position the product  12  on the mixed pallet  20 , the following sequence is performed. The robot controller  22  instructs the robot  14  to position the product  12  to be placed in a predetermined location on the mixed load pallet  20 . When this location is reached, the robot controller  22  instructs the first drive  164  to move outwardly the pusher assembly  156  in order to push the product  12  out of the tool  140  while the robot  14  starts its retracting movement to prepare itself for the next product  12  to be picked. The pad  176  maintains its pressure on the product  12  and is activated upward only when the product  12  is completely out of the tool  140 . 
         [0128]    As the robot  14  moves to approach the next product  12  to be picked, the palletizing process is repeated. 
         [0129]      FIGS. 10 and 11  illustrate the two positions of the forks  144 . When the product  12  to be picked is less that a predetermined dimension, the outer forks  144  are in the retracted position shown in  FIG. 10 . Consequently, when the products  12  widths (or lengths) to be picked are equal or greater than a predetermined dimension, the outer forks  144  are in the extended position shown in  FIG. 11 . 
         [0130]    As it can be appreciated by reading the above description of illustrated embodiments, the method  200  for picking and then placing a product enables a product to be picked without putting the robot  14  in a waiting mode, therefore reducing the cycle time, as the tool&#39;s pusher bars or pusher assembly move backward as the tool  10  or  140  inserts the forks underneath the product. Similarly, the present method  200  and tools  10 ,  140  enable the product  12  to be placed on the mixed pallet without putting the robot  14  in a waiting mode, also reducing the cycle time, since the tool&#39;s pusher bars or pusher assembly move forward as the robot  14  retrieves the forks. 
         [0131]    It is to be noted that many other modifications could be made to the tools  10  and  140  for palletizing mixed load products described hereinabove and illustrated in the appended drawings. For example:
       the robot arm  14  can be replaced by a gantry type equipment or any other similar means;   the product to palletize can be placed on an output conveyor, a table, a platform, an AGV (automated guided vehicle) or any other means that can accepts the product;   the tool is not limited to include three or four forks. According to another embodiment, the tool includes another number of forks, bars, or any other to shaped bottom support allowing picking a product on a roller conveyor or on another type thereof.       
 
         [0135]    It is to be understood that embodiments of the tool and method for palletizing mixed load products are not limited in their application to the details of construction and parts illustrated in the accompanying drawings and described hereinabove. Other embodiments can be foreseen and practiced in various ways. It is also to be understood that the phraseology or terminology used herein is for the purpose of description and not limitation.