Patent Publication Number: US-6702277-B1

Title: Delivery device for the sections of a strip of film

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a national stage of PCT/EP99/06891 filed Sep. 17, 1999 and based upon German national application 19847923.9 filed Oct. 19, 1998 under the International Convention. 
    
    
     FIELD OF THE INVENTION 
     The invention relates to a delivery device for segments of a web fed in a feed direction and composed of film, for example bags, especially in a separating-seam welding machine. Such a machine can have a rotatably driven rotor whose axis lies in the feed plane or parallel thereto and can be equipped with a plurality of contact regions extending radially with respect to the rotation axis, whereby in operation the web sections fed so as to follow one another are gripped, swung out of the feed plane and deposited one above the other at a deposition station. The respective contact region of the rotor can encompasses suction regions which serve to hold the web section on the contact region with an underpressure when the contact region of the rotor travels over a circular segment between a first and a second angular position. 
     BACKGROUND OF THE INVENTION 
     Such a delivery device is known. It comprises a rotor with bar-shaped gripper arms which extend radially and form the respective contact regions. Each gripper arm of the rotor with a respective pressure communication opening sweeps across an opening delivering underpressure (suction) in a part which is stationary in operation, the suction supply opening extending over the aforedescribed circular segment. When the respective pressure communication opening sweeps across the suction supply opening, underpressure (subatmospheric pressure) is applied to the suction openings of the contact regions of the gripper arm. 
     Depending upon the surface characteristics of the web section to be picked up and delivered, it is desirable to maintain an underpressure at the suction region either for as long as possible and thus until the delivery station is just reached or only up to a certain point in time before reaching the delivery station. The smoother the surface of the web segment, the smaller is the friction with which the respective web segment rests against the contact region of the gripper arm and thus the longer should the underpressure remain applied to the respective gripper arm so that the smooth web section does not slip. The rougher the surface of the material web the higher is the friction and thus the better is the adhesion of the material web of the contact region of the gripper arm. As a consequence it is advantageous in these cases to remove the suction from the suction region even before the delivery station is reached so as to prevent the plastic bag for example, which must be deposited on two spike-like projections, from tearing in the region of the spike-like projections because of excessive adhesion or even from separating at weakening lines which may be provided. 
     After an interruption in operation and thus the bringing of the manufacturing process for the web sections to standstill, a stationary part of the conventional apparatus which has an opening supplying the suction and extending in the peripheral direction, may be rotated which can cause the suction region of a gripper arm in the respective circular segment to be subjected to suction prematurely or too late. In the case of a premature elimination of the underpressure, in the first rotation the underpressure may be applied before the gripper arm comes into contact with the web section. This means that the suction region of the gripper arm is already subjected to underpressure at a point in time in which it has not yet come into contact with a web section to be picked up and to be swung away. The volume rate of flow of air in the rotor is then excessive and results in a reduction of the suction within the rotor. Web sections tend to adhere less well to the contact region of the gripper arm. Problems result because there is an insufficient resistance to the air flow by the web sections in the operation of the device. The web sections can slip on the contact regions of the gripper arm and the operation of the delivery device is defective. The down time of the machine which is provided with the delivery device increases. 
     OBJECT OF THE INVENTION 
     The object of the present invention is to improve a delivery device of the type described at the outset so that suction control is possible during the delivery of the web section and simultaneously the danger which arises in operation of the machine is not increased, i.e. a reliable securing of the web section to the contact region of the rotor is ensured. 
     SUMMARY OF THE INVENTION 
     This object is achieved with a delivery device of the type mentioned according to the invention in that the angle of the circular segment, within which the suction region of the contact region is subject to suction pressure is adjustable within limits. 
     In the delivery device of the invention it is also possible after adjustment or adjustable setting of the first angular position, preferably such that suction is applied to the suction region exactly at the point in time in which the contact region comes into contact with the web section, the second angular position can be adjusted corresponding to the surface characteristics of the web section. Thus according to the invention there is not a fixed circular segment angle which can be rotated as such in the rotation direction or counter to the rotation direction, but a variation in the size of the circular segment and thus the size or the circumferential length of this region over which suction remains applied to the suction region. It has been found to be advantageous and satisfactory when the first angular position is not adjustable and the second angular position is provided so as to be adjustable. In this manner, the first angular position can be set so that the time point of underpressure application coincides with the time point at which the contact region of the rotor contacts the web section. The disadvantage of the known device, that too great a volume flow takes place via the suction region into the interior of the rotor and the underpressure remaining there drops, can be avoided. 
     According to the present invention, respective separately controllable spaces can follow one another for example in the rotation direction and in which respective underpressures are generated and can be swept by the respective pressure communication openings of respective contact regions of the rotor. The size and therefore the angle of the circular segment in which an underpressure application to the suction region of the rotor arises can be achieved by a corresponding adjustment or nonadjustment of the openings. 
     A preferred embodiment of the invention is characterized in that a mouth opening of a passage connected to the suction region of a respective contact region and rotating with the contact region is provided in the region within the circular segments with one or more openings extending in the rotation direction or arranged in the rotation direction and communicating with the contact regions while between the mouth opening of the passage and the suction supplying opening at least one control element defining a control opening is provided which is rotatable relative to the rotor. According to this inventive concept, the size of the angle and thus the angular extent or length of the circular segment within which there is application of suction to the respective suction region is varied by the setting element and such that at least one control opening in the setting element extends or shortens the suction feed opening in the circumferential direction. 
     From a point of view of manufacture, it has been found to be advantageous for the underpressure feed opening to be formed by a part which is stationary relative to a machine frame in operation. In this manner it is possible to exactly define the first angular position relative to the feed plane of the material web sections. Furthermore, any optional passage means, which need not be flexible can be used for pressure communication between the underpressure feed opening and device for generating the underpressure. 
     The aforementioned stationary part can form a hub through which a drive train for the rotor can extend. 
     According to a further preferred embodiment, the stationary part, especially the hub, bounds the compartment feeding the suction and extending in the peripheral direction and which opens via the suction supply opening in a sealing surface against which the setting element lies slidingly with its control opening. The suction supply chamber provides a sufficient suction capacity. As a consequence of the fact that the suction supply chamber is formed directly in the stationary part, it is possible without further passage means between them to have the suction chamber open directly via the suction supply opening in the sealing surface so that the greatest possible flow cross section is available and such that only the size of the mouth opening of the respective duct means of the contact region is limiting. 
     While the sealing surface does not necessarily have to be planar to be useful (it can also have a cone shape), it has been found to be advantageous for the setting element to be disk-shaped or flange-shaped and to be rotatable relative to the suction supply opening about the rotation axis. The system thus does not deal with a linearly shiftable slide or shifting element but rather the setting element is rotatable about the same axis is as the rotor with respect to which the suction supply opening is bounded. 
     The setting element is, in a further feature of the invention, advantageously rotatably limited by a stop element. In an especially advantageous further feature of this inventive concept, the stop element is formed by a projection projecting over the sealing surface into a recess of the setting element. 
     According to still a further inventive concept, the projection bounds the suction supply opening on one side in the peripheral direction and engages as sealing cams in a control opening of the setting element. The projection serves thus at the same time as a stop element and as the means defining the first angular position independently of the instantaneous setting of the setting element. 
     When the delivery device is to reliably release the web section from the contact region following the underpressure application to the contact region, an overpressure application to the contact region should be effective and thus it is especially advantageous for there to be an overpressure energized section following the control opening of the setting element in the direction of rotation of the rotor which is swept over in operation by the mouth opening of the duct means. The invention in a further feature proposes that the section to which overpressure is applied be formed within the setting element. It can, in this case, be formed by a radial and axial opening communicating a compressed air connection. 
     It has been found to be advantageous further for the setting element to be rotatably driven with respect to the underpressure feed opening by a motor, which can be pneumatic or hydraulic, or driven in some other way. For this purpose, the setting element can have on its outer periphery coupling means, for example in the form of teeth, an articulation for a reciprocating rod or the like. It is however also possible to provide internal teeth on an appropriate section of the setting element which can mesh with a pinion as long as that section is radially outwardly of the drive train for the rotor. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     Further features, details and advantages of the invention are given with reference to the illustrations and the subsequent description of a preferred embodiment of a delivery device according to the invention which has been shown only fragmentarily in the drawing. In the drawing: 
     FIG. 1 shows a sectional view through a rotor region of a delivery device according to the invention for web segments; 
     FIG. 2 shows a partly broken away elevational view of the rotor region of FIG. 1; 
     FIG. 3 is an elevational view of a stationary hub seen in the direction of the arrows III—III in FIG. 1; 
     FIG. 4 is a plan view of the rotor seen in the direction of the arrows IV—IV in FIG. 1; 
     FIG. 5 is a plan view of a setting element seen in the direction of the arrow V—V in FIG. 1; and 
     FIG. 6 is a plan view of the setting element in the state in which it is mounted on the hub. 
    
    
     SPECIFIC DESCRIPTION 
     FIGS. 1 and 2 are views of the rotor region  2  of a delivery device for a separating-seam welding machine for producing bags from film which are stacked upon one another at the delivery station and are thereby accumulated on mandrel-shaped projections. The rotor  4  of the delivery device encompasses a plurality of gripper arms extending radially to a rotor disk  6 . The gripper arms  8  of rotor  4  pass through a pickup station to which the web segments are fed in succession. In passing through the pickup station, the gripper arms  8  of rotor  4  engage below respective web segments to lift them out of the pickup station and carry them into the previously described delivery station. 
     The gripper arms  8  of the rotor  4  are configured as bar-shaped hollow bodies. 
     As has been indicated in FIG. 4, the gripper arms  8  have a contact region  10  with which they can lie against the web segments to be handled. The arms also have suction regions  12  which are located within a circular segment region  14  (see FIG. 6) between a first angular position  16  and a second angular position  18  of the respective gripper arms  8  and within which suction is applied thereto. 
     Gripper arms  8  are fitted into respective radially directed correspondingly shaped openings  20  (FIG. 1) in the rotor disk  6  at the right-hand end and are secured by means of an axial cover  22  and an axial securing means  24  both in the axial direction and in the radial direction against release from the rotor disk  6 . The cover  22  is bolted to the rotor disk  6  as represented at  26 . 
     Each gripper arm  8  has an axial opening  28  which, within the shaped recess  20  registers with an axial opening  30  in the rotor disk  6 . The axial opening  30  forms a mouth opening  32  of the rotor  4 . The hollow gripper arm  8  forms a duct  34  between the mouth opening  32  and the suction openings  12  of a respective contact region  10 . 
     The rotor  4  is journaled with its rotor disk  6  relative to a stationary part  36  forming a hub  38  (FIG. 3) for the rotation about a rotation axis  40  about which it is driven by a drive shaft  42 . Between the rotor disk  6  and the hub  38  is a positioning and setting device  44  to be described further and which has been illustrated in detail in FIG.  5 . 
     The hub  38  has, as can be seen from FIGS. 1 and 3, a chamber  46  extending in the rotation direction concentrically to the rotation axis  40  and which is connectable with a device for producing suction and which has not been shown, via a suction duct  45  (FIG. 2, not shown in FIG.  3 ). The chamber  46  is in the form of a recess worked into the hub forming part  38  of member  36 . This recess is bounded, toward the setting member  44 , by an opening  47  delivering the underpressure. The axial region of part  36  surrounding the underpressure-delivering opening  47  forms a sealing surface  48  against which the axial side of the setting device  44  lies in a substantially sealing manner. From the sealing surface  48 , projections  50  and  52  protrude, the projection  50  limiting the space  46  in the peripheral direction, the projection  52  is set back from the other peripheral end of the chamber  46  in the peripheral direction. 
     The projections  50 ,  52  engage in recesses  54 ,  56  in the setting device  44  (FIGS. 5,  6 ). Each one side  58 ,  60  of the projections  50 ,  52  forms an abutment element and limits the rotatability of the setting device  44  in the clockwise direction of FIG.  6 . The other side  62  of the projection  52  forms an abutment for the rotation in the counterclockwise direction. 
     As can be deduced from FIG. 1, the setting device  44  is disk-shaped and has a flange segment  64  with which it extends in a central opening of the hub  38 . Within the flange segment  64 , a roller bearing  66  is provided which is journaled on a radially inward shoulder sleeve  68  rotationally fixed to the drive shaft  42  and which is rotationally fixed to the rotor disk  6  by screws  70 . 
     The setting element  44  is disposed opposite the hub  38  in the axial direction so that it rests against the sealing surface  48  of the hub  38 , whereby the projections  50 ,  52  of the hub  38  engage in the recesses  54 ,  56  of the setting element  44 . Between the setting element  44  and the hub  38  an O-ring  72  of elastomeric material is provided relatively far outwardly. This O-ring effects a sealing action radially outwardly on the one half and on the other half generates a prestress and renders a relative rotation of the setting element  44  and the hub  38  more difficult. In this manner the play for the adjustment setting device  74  to be described in the setting element is quasi abolished. 
     This setting device is described as a whole by the reference character  74  and encompasses a radially projecting region  76  of the setting element  44  and on which a gear toothing  78  is provided for engagement with measuring pinion  80  of an electric motor drive  82 . It can also be seen from FIG. 1 that the electric motor drive  82  and the hub  38  are mounted on a machine frame  83  which is stationary in operation. 
     The suction application via the suction openings  12  of the contact region of each respective gripper arm  8  is effected via the suction delivery chamber  46  connected by a suction duct  47  with a device for producing the underpressure. From chamber  46  the suction is applied from the underpressure supply passage  47  via control openings  84  in the setting element  44  to the respective openings  32  in the rotor disk  6  and to the duct  34  to the suction openings  12 . This occurs in a circular segment region  14  by rotation of the setting element  44  so that the control opening  84  in the setting element  44  and the respective mouth opening  32  in the rotor disk  6  overlap one another. As is apparent from FIG. 6 (in which however the rotor disk  6  has been omitted) this circular segment region  14  begins at the first angular position  16 . As soon as the opening  32  of the rotor disk  6  has passed this angular position  16  suction is applied to the associated suction openings  12  of the respective gripper arm  8 . This suction communication remains until the mouth opening  32  has been completely passed to the second angular position  18 . By rotation of the setting element  44  in the counterclockwise direction of FIG. 6, the control opening  84  can overlap the illustrated boundary  86  of the space  46  and in this manner achieve a lengthening or enlargement of the circular segment region  14  until the side  60  of the projection  52  is engaged as a stop element in the setting element  44 . In any case, the second angular position  18  can be advanced to the indicated position  18 ′. By rotation of the setting element  44  in the counterclockwise direction, the control opening  84  effects a shortening of the circular segment over which suction can be communicated to the arms. 
     When the delivery device is so mounted on the machine frame  83  (which also can be achieved by a preadjustment) that underpressure preferably is applied to the suction region  12  when the gripper arm  8  swings through the displacement plane of the web segment, the point in time or the position of the gripper arm  8  can be established at which the underpressure application ends. This can be set by an electric motor adjustment of the setting element  44  in the desired manner as a function of the surface characteristics of the web segments to be handled. 
     To keep the friction loss as low as possible, the rotor disk  6  to and the setting element  44  have the smallest possible axial spacing from one another. This can be achieved by matching the radial ball bearing  66  and conventional setting means. So that at the same time a sufficient seal is achieved, on the sealing element  44  and the rotor disk  6 , labyrinth-like mutually interdigitating ring segment sections  88  are provided. 
     As can be seen from FIGS. 5 and 6, a section  90 , which has superatmospheric pressure overpressure applied thereto is provided in the setting element  44  and is arranged after the peripheral boundary of the control opening  84  in the direction of rotation of the rotor. This section encompasses a radial opening  92  to which a compressed air fitting not shown is connectable and an axial opening  94  which is overlapped by a respective opening  32  of the rotor  4  at the instant of overlapping, the mouth opening  32  and the passages  34  to the suction region  12  of the respective gripper arm are subjected to air pressure which ensures a reliable release of a web segment.