Abstract:
A gripping head for a loading robot or manipulator of a cartoning machine capable of nesting articles arranged on two substantially parallel rows, the gripping head comprising a row of gripping members, wherein each of the gripping members comprises a gripping section adapted to receive two adjacent articles and on opposite sides with respect to a centerline plane, and wherein at least the gripping members having even index position or odd index position in the row rotate by about 180 degrees around an axis.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to European Patent Application No. 11157856.3 filed on 11 Mar. 2011, the contents of which are incorporated herein, in their entirety, by this reference. 
     TECHNICAL FIELD 
     Embodiments of the present invention relate to the field of cartoning machines. Embodiments of the invention relate to a gripping head for a robot or manipulator suitable for use in a cartoning machine. 
     BACKGROUND 
     The handling of articles having a substantially tapered shape for example in form of a cup or a small pot is known in the field of cartoning machines. Examples of such articles are yogurt pots, small cups for food or non-food products, coffee capsules. These articles are well known both in the food and non-food industry; their use has considerably increased over the last years having been boosted especially by the continuously growing use of coffee capsules. 
     A machine for secondary packaging of said articles according to the prior art comprises one or several robots or manipulators which load the articles into carton boxes or cases according to a predefined pattern. The robot or manipulator works with a preset cycle between a station for the arrival of the articles and a delivery station. The articles are supplied to the arrival station for example on one or more tracks or conveyors. The delivery station may coincide with the insertion of the articles into boxes or cases. 
     Tapered articles are generally arranged alternating an upright article with an article overturned by 180 degrees to save space. Such arrangement is known as nesting of the articles and allows optimal use of space within the box and hence reduced costs for transport and logistics. Adjoining articles in a nested arrangement have a complementary shape, i.e. the head of an article is adjacent to the bottom of another article and vice versa. 
     However, a nested arrangement is not easy to obtain especially with large production volumes. There are efficient known transport systems capable of forming two parallel rows of articles in which the articles of a row are turned by 180 degrees with respect to articles of the adjacent row, delivering batches of articles that are substantially arranged in a 2×N matrix, formed by a row of upright articles and a row of overturned articles. However, such systems are not able to operate the nesting within the single rows. 
     As of date, the nested arrangement is costly and difficult to obtain. The known systems in particular are not satisfactory in fields such as that of coffee capsules where the cartoning machine should handle a large number of articles of small dimensions, with a high speed and the need of high flexibility to operate with different formats. Another problem lies in the need of producing boxes with layers (also referred to as levels) of articles in which the articles are alternated in a complementary manner between one layer and the other. For example in the coffee capsules packaging industry it is desirable that the sealing of a capsule always be in contact with the sealing of a capsule of an overlaying layer to avoid damage of the sealing itself. Thus, formats with several levels of capsule require the creation of complementary layers or levels of capsules. 
     SUMMARY 
     The problem underlying one or more embodiments of the present invention is to provide the nesting of articles which are supplied on two substantially parallel rows or tracks, where nesting the articles of a row or track with articles of the adjacent row is required. Furthermore, one or more embodiments of the invention aim at providing complementary arrangements of articles of the first and respectively second row, starting from the same input arrangement. 
     The idea on which one or more embodiments of the present invention is based is to provide the nesting with a robot or manipulator equipped with inverting gripping members, i.e. rotating around a given axis. Thus, the problem is solved by means of a gripping head for a loading robot or manipulator of a cartoning machine, the gripping head comprising a plurality of gripping members, and in which the gripping members are arranged in at least one row according to a longitudinal direction of the gripping head, characterised in that each of the gripping members comprises a gripping section adapted to receive two articles adjacent and on opposite sides with respect to a centerline plane of the gripping section, and in that at least one subset of the gripping members are rotatable by at least 180 degrees around an axis substantially parallel to the plane, the subset comprising at least the gripping members in even index positions or in odd index positions in the longitudinal row of gripping members. 
     Preferably each of the gripping members of the head is rotatable around a respective axis. The rotation axis preferably belongs to the mentioned centerline plane and more preferably is an axis of substantial symmetry of the respective gripping member. Preferably all the gripping members of the head are rotatable around a respective axis and more preferably the rotation of the single gripping members is independent. Advantageously each gripping member comprises a respective motor or actuator which controls the axial rotation. 
     The gripping section may comprise two gripping members, such as for example vacuum suction cups, on opposite sides of the centerline plane. In a preferred embodiment, each gripping member comprises vacuum gripping rods or the same gripping member is represented by a rod with a suitable end. More preferably, a gripping member is represented by a rod having an end with two suction cups or equivalent suction-operated gripping members. Suction may be generated through the internally hollow rod. Preferably the gripping members are substantially parallel. 
     Another aspect of the invention includes providing the gripping head with a plurality of tilting gripping members which can be inclined with respect to a main framework of the head. In one of the embodiments, the tilting gripping members are alternated with gripping members which are termed as fixed. The term of fixed gripping member is used to denote a gripping member possibly rotatable around the axis thereof but unable to tilt with respect to the gripping head. A tilting gripping member is inclinable between a first position of a substantial alignment generally parallel with the fixed gripping members (closed position) and a second position spaced from the fixed members and/or from the resting tiltable members (open position). In some embodiments, the gripping head may comprise gripping members which are tiltable on opposite sides with respect to a median plane. 
     The fixed members and/or the tiltable members can be rotatable around an axis as defined above. Preferably all the members both fixed and tiltable are rotatable around a respective axis. Hence, and according to a preferred embodiment, a tilting gripping member is provided with a double degree of freedom comprising axial rotation and inclination with respect to the framework. 
     In a preferred embodiment each tilting gripping member is supported by a respective auxiliary framework which is hinged to the main framework of the gripping head and which is articulated to the main framework for example with a fulcrum. 
     More preferably the gripping head comprises a plurality of motors or actuators which respectively actuate the axial rotation of each gripping member, and another plurality of motors or actuators which actuate the inclination movement of the tilting gripping members. The motors, both for the axial rotation and for the tilting movement, are preferably pneumatic motors or actuators. The motor which controls the axial rotation of a gripping member and relative transmission means are mounted preferably on the auxiliary framework. 
     Preferably the gripping members are in alignment, i.e. axis of substantial symmetry of the gripping members—while tilting gripping members, when provided, are in the closed position—rest in the same plane. 
     An aspect of the invention includes a robot or a manipulator which is preferably provided with the mentioned gripping head. In the present description and in the claims, any reference to a robot shall be intended to a robot or manipulator of the type used in the packaging machines, with any number of degrees of freedom also named axes. 
     One or more embodiments of the invention allow modifying the arrangement of the articles in a quick and efficient manner and, in particular, allow obtaining the nesting of articles. 
     The gripping head is able to transform a 2×N matrix of articles into a matrix of articles having the same 2×N dimensions where the even or respectively odd columns are inverted due to the axial rotation of the corresponding gripping members. The head may rotate the gripping members in the positions having an odd index (first, third, . . . ) or an even index (second, fourth, . . . ) of the row and by doing so the head can nest the articles of the two input rows. Preferably a robot according to an embodiment of the invention has a control system that can selectively rotate the gripping members in the even or odd positions. 
     The degree of freedom of inclination of the tilting gripping members allows increasing a space of distance between adjacent gripping members and allows rotating the gripping members and relative articles even when the pick-up and/or load format, which is generally set by the format according to specification, requires that the gripping members be arranged very close to each other. Thus, the gripping members can arrange in a close set-up for gripping and releasing the product, and in a temporary set-up with open tiltable members during the step of rotating the gripping members and inversion of the respective articles. 
     In a variant, the gripping head comprises means for spacing (i.e., diverging) and nearing (i.e., compacting) the gripping members with respect to each other in the longitudinal direction. Such effect can be obtained through per se known means such as for example a carriage control. Moving away the gripping members, for example rods, allows obtaining the same effect of the tiltable gripping members or rods, i.e. allow the rotation. Such embodiments shall be considered equivalent. 
     A preferred application consists in cartooning machines or systems fed by two tracks with a track supplying first articles and a track supplying second articles. The articles defined as first and as second can be of different nature or they can be identical articles but with different spatial orientation. For example, embodiments of the invention can be applied to machines for handling tapered or frusto-conical articles such as cups, pots, coffee capsules and the like, and in which the second articles are identical to the first articles but are overturned by 180 degrees. 
     For example, a robot or manipulator according to an embodiment of the invention can receive an input of batches of articles substantially arranged as a 2×N matrix in which the articles of one row are turned with respect to the articles of the adjacent row. The robot is capable of selectively inverting the even or odd columns of the matrix, producing as output a 2×N matrix in which the straight and tilted articles are nested with respect to each other. This term is used to indicate that in the two rows of articles generated in output, the first articles are alternated to the second articles. 
     The possibility of selectively rotating the even or odd columns allows generating matrices of articles which are complementary with respect to each other. For example, an aspect of the invention relates to a method for transferring articles by controlling the robot or manipulator as follows:
         generating a first matrix of articles comprising first articles and second articles nested with respect to each other in a first operating cycle;   generating a second matrix of articles complementary to the first matrix, in at least one subsequent operating cycle.       

     The capacity of generating complementary matrices of articles is particularly useful for loading boxes on several layers. 
     The term of matrix “generated” by the gripping head (or by the robot) is used to indicate the matrix of articles that the gripping head can deliver to a downstream device, for example a box or case conveyor. The term complementary matrices is used to indicate that given a position (i, j), if the first matrix comprises a first or respectively second article in the position, the second complementary matrix comprises a second or respectively first article in the same position. 
     A further advantage of one or more embodiments of the invention lies in the fact that the capacity of nesting the articles is located in the robot. Hence, a great flexibility is obtained without modifying the members upstream (conveyor tracks, phasing systems, etc.), which are generally more expensive. Furthermore, the gripping head can be made for example with pneumatic technology which is relatively inexpensive. 
     The advantages shall be more apparent with the help of the following description and figures, which represent non-limiting examples. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a view of a top load robot according to an embodiment of the invention. 
         FIG. 2  is a detail of the gripping head of the robot of  FIG. 1 . 
         FIG. 3  is a detail of the end of the rods of the gripping head of  FIG. 2 . 
         FIG. 4  is a detail of the gripping head of  FIG. 2 . 
         FIG. 5  is a diagram showing the possibility of inclination of the tiltable rods of the head of  FIG. 2 . 
         FIG. 6  exemplifies some arrangements of articles that can be produced by the robot of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  shows a robot  1  provided with: a first arm  2 , a second arm  3  articulated to the first arm  2 , a gripping head  4  mounted on the second arm  3 . The example refers by way of non-limiting example to a top-loading robot with parallel rods. The robot  1  can be part of a cartooning machine and it can be used for example for picking up articles from an input station and transferring them into boxes or cases. 
     The gripping head  4  comprises a plurality of gripping members which in this case are parallel rods and which are generally indicated with reference  400  ( FIG. 2 ). The rods  400  are substantially rectilinear and parallel each other. In the example, the rods are aligned so that the axes of the rods belong to a common plane; an axis Z of one of the rods is shown in  FIG. 2 . The rods  400  are carried by a main framework  403  which is fixed or preferably articulated to the second arm  3 . 
     The rods are arranged in a row from a first rod which can be conventionally at one end or the other end of the head  4 , to a last rod at the opposite end. Thus, rods are identified in positions defined odd and rods in positions defined even. 
     A generic gripping rod  400  ( FIG. 3 ) is provided with a gripping section  420  adapted to receive two articles which are located on opposite sides with respect to a centerline plane passing through the axis Z of the rod  400 . In the example of the figures, a general rod  400  has a substantially T-shaped end and the end carries two gripping suction cups  401 . One of the two suction cups is visible in  FIG. 3 , the other being hidden by the perspective view. It should be observed that such embodiment is provided by way of non-limiting example. 
     In the figure there are shown a first article A 1  and a second article A 2  taken by respective suction cups  401  of the rod. The first and the second article are substantially complementary i.e. a wider part of the first article A 1  corresponds to a narrower portion of the second article A 2 , and vice versa. For example the first article and the second article are identical but turned with respect to each other by 180 degrees. The articles are for example coffee capsules in which the narrower part corresponds to the bottom of the capsule and the wider part corresponds to the head with sealing. 
     At least some of the rods  400  can rotate around the axis Z thereof. The rotation is defined axial rotation. Preferably, each of the rods  400  has an axial rotation freedom independently from the other rods: for example, the head  4  comprises a plurality of motors or pneumatic actuators  402 , each motor  402  being associated to a respective rod  400  for controlling the axial rotation of the rod around the respective axis Z. Some of the motors  402  are indicated in  FIG. 2 . 
     Due to the arrangement of the rods  400  and of the gripping members  401 , the head  4  is capable of handling at each operating cycle a 2×N matrix of articles, in which N is the number of rods  400 . Each rod carries a column (formed by two articles) of the matrix. Furthermore, it can be understood that a rotatable rod is capable of inverting the position of a respective pair of articles (or column of the matrix) such as for example the articles A 1 , A 2  of  FIG. 3 . This inversion may occur during the operating cycle of the robot and precisely during the displacement from a picking up area to a delivery area. 
     The head  4  advantageously comprises a series of tiltable rods which are preferably alternated with non-tiltable rods which are otherwise referred to as fixed rods. The tiltable rods, in the example, have a further degree of freedom beside the axial rotation around Z, being inclinable with respect to the main framework  403 .  FIG. 2  shows two tiltable rods  404  which are alternated with two fixed rods  405 . 
     Each tilting rod  404  has an oscillation fulcrum with respect to the main framework  403 . The tiltable rods  404  are movable between a first position in which they are parallel to the fixed rods  405 , and a second inclined position where they are spaced away from the plane of parallelism of the fixed rods. With reference to the tiltable rods, the term “closed” rods is also used to indicate the rest position aligned to the fixed rods, as shown in  FIG. 2 , and the term of “open” rods is used for indicating the inclined position away from the plane of the fixed rods. 
       FIG. 4  shows an embodiment in which a general tilting rod  404  is supported by a respective framework  412 . The framework  412  essentially comprises a plate  406  which carries the rod  404  and relative motor for the axial rotation  402 , and an arm  407 . 
     The arm  407  has a fulcrum with respect to a fixed wing  408  integral with the main framework  403 , the arm  407  being able of oscillating due to the fulcrum around an axis represented as X. The axis X is substantially parallel to the longitudinal direction of the head  4  and it is parallel to a plane of alignment to which the axes Z of the rods (with tiltable rods closed i.e. resting) are parallel, and preferably belong. 
     The inclination movement of the tilting rod  404  is exemplified in  FIG. 5  which shows the rod  404  in the position of alignment with the fixed rods and in a position inclined by an angle α. The figure also shows with the reference  421  the line of the plane of the rods  400 , i.e. of the plane of the axes Z of the fixed rods as well as of the tiltable rods in the rest condition. The axis X of  FIG. 4  is perpendicular to the plane of  FIG. 5 . 
     The inclination movement of a tilting rod  404  is set by a respective motor or actuator  413  for example through a pinion which meshes a toothed wheel integral with the arm  407  or through a suitable linkage, according to non-essential details and they may be provided for by a man skilled in the art. 
     In  FIG. 4  it is also shown that upper ends of the rods  400  carry a connector  410  for connecting to a vacuum source. Thus, the hollow rod allows creating a suction up to the gripping suctioning elements  401 . It should be observed that in order to allow the opening of the tiltable rods  404  the rods  404  advantageously pass through a slot—instead of a hole—of the upper plate  411  of the framework  403 . 
     The motor  402  controls the rotation around the axis Z of the rod  404  through a gear  409  which is partly visible in  FIG. 4  and which essentially comprises a pinion actuated by the motor  402  and a toothed wheel keyed on the rod. Such details are preferably identical for all the rods both fixed and tiltable. In the case of the tiltable rods, the group of motor  402  and gear  409  is integral with the framework  412 . The motors  402  can be offset as shown in the figure in order to reduce the overall dimensions. 
     Preferably the motors  402  that impart the axial rotation and the motors  413  that actuate the tiltable rods are pneumatic motors. The pneumatic connections are not shown in the figures. The motors are controlled by opening and closing a series of solenoid valves according to a technique per se known in the pneumatic industry and which is thus not described in detail. In any case, reference to pneumatic motors should be deemed not to be restrictive and pneumatic or any other type of actuators can be used according to other embodiments of the invention. 
     The opening movement takes the rods  404  outside the plane of alignment  421  and hence allows the axial rotation and the inversion of the articles A 1  and A 2  even when the rods are very close and/or the overall dimension of the articles would cause interference as observable for example in the detail of  FIG. 3 . In another embodiment (not illustrated), a device is provided for moving away and compacting the rods in the longitudinal direction and/or grouping the rods in subsets according to the required format, for example to allow the head to load several boxes for each work travel. The moving away and compacting can be obtained with a carriage system actuated by a template according to per se known technique. 
     The system for controlling the robot  1  operates consequently. For example a work cycle of the robot  1  comprises the steps of:
         a) gripping the product with the all rods  400  aligned namely with the tiltable rods  404  in “closed” position;   b) opening of the tiltable rods  404 ;   c) axial rotation around Z of the rods  404  while they are open, or axial rotation of the fixed rods  405  while the tiltable rods  404  are open;   d) closing of the tiltable rods  404  bringing all the rods back in alignment;   e) release of the product;   f) possible reverse rotation of the rods rotated at point c).       

     In the step c) the head may equally rotate the fixed rods or the open tiltable rods, due to the increase of the distance between centres between the rods. The optional step f) may be required if the end of the rods is asymmetric and/or if the gripping members  401  are configured in a specific manner at one of the rows of the input matrix. In this case, the step f) returns the rods in the original configuration. If required, also the step f) can be combined with the inclination of the tiltable rods  404 , even though in the absence of the overall dimension caused by the product this may not be required, i.e. in absence of the product the distance between centres is sufficient to allow the axial rotation of the rods. Steps b) to d) are carried out while the robot moves from the arrival station  5  to a delivery station  6  (shown in  FIG. 1 ). 
     The operation is further exemplified by  FIG. 6  showing examples of arrangement of the input and output articles. An example of 2×N input matrix is shown in  FIG. 6  (A). Such matrix may be produced for example by a conveying system with two tracks (such as tracks  5   a ,  5   b , shown in  FIG. 1 ) provided with devices capable of overturning (capsizing) the articles of a track. The matrix hence has a row of first articles A 1  “straight” and a row of articles A 2  overturned. The columns of the matrix are indicated from C 1  to CS; each column is formed by a straight article and an overturned article. 
       FIG. 6  B) shows a matrix of the articles produced in output by the gripping head  4 . In the example, the gripping head has swapped the positions of the articles in the even columns C 2 , C 4 , . . . by rotating the respective rods  400 , obtaining a nested arrangement of the articles, in which straight articles A 1  and overturned A 2  are alternated in each row.  FIG. 6  C) shows a matrix of articles complementary to that of  FIG. 6  B), which can be obtained from the same input matrix by rotating the rods corresponding to the odd columns C 1 , C 3 , . . . . The complementary arrangements of  FIG. 6  B) and  FIG. 6  C) can for example be applied to provide formats on multiple levels. Such complementary arrangement can for example be desirable to obtain contact between homologous surfaces of the articles, for example while handling coffee pods, to guarantee bottom to bottom and sealing to sealing contact.