The invention relates to a process for the alignment of a minimum of one packaging container during which the filled container is fed horizontally into the aligning unit so that the packaging container has an infeed side at the front in the direction of movement and a rear side. In addition, the invention relates to a process for the alignment and sealing of a packaging container and a device for the alignment and sealing of a packing container.
A system for the filling and sealing of bags, specifically of woven bags, is known from US 2012/0227363 A1. The system includes a plastic welding unit, a folding device and nip rollers. To seal, a section of the bag is folded over, welded via the welding unit and pressed together using the nip rollers. The seam is then sealed without the use of hot melt adhesives.
A problem in the sealing of plastic packaging containers, such as plastic woven bags, is the lack of stiffness of the material. Usually the filled packaging containers are fed by a conveyor belt or similar equipment to the sealing unit. As a result of the lack of stiffness of the plastic material, the position of the upper edge of the packaging container to be sealed changes between the filling stage and the sealing unit. In order to ensure that each packaging container is correctly sealed the upper edge of each packaging container must be exactly aligned. One possibility for tackling the problem of the varying position of the upper edge of the packaging containers is to select excess material above the desired weld position which is then cut to a differing extent, depending on the position of the upper edge, in order to maintain the exact position of the upper edge. If the amount of excess material were too low, this would lead to the packaging container not being sealed tightly. The excess packaging material selected to compensate the varying positions of the upper edges of the packaging containers is a significant cost factor, as it increases the overall cost of materials. Additionally, such a cutting process is not possible, for example, for packaging containers with a stepped-end cut.
The primary object of the present invention is to propose a process and equipment with which the unused excess packaging material can be minimized when sealing packaging containers, specifically woven bags, and with which the use of the described sealing equipment for the sealing of packaging containers with a stepped-end cut is made possible.
The solution to this task is provided through a process which is in accordance with the features of the patent claim 1, through a process which is in accordance with the features of the patent claim 9, with equipment which is in accordance with the features of the patent claim 10 and equipment which is in accordance with the features of the patent claim 14. Further developments and beneficial features are included in the appropriate sub-claims.
In a process for the alignment of a minimum of one packaging container, specifically a bag, during which the filled packaging container is moved in a horizontal direction in such a way that the packaging container has an infeed side at the front in the direction of movement and a rear side, it is proposed in the invention that the filled packaging containers are fed into a aligning unit, a minimum of one gripper approaches an upper edge of the packaging container, the position of the upper edge is detected by sensors, the gripper is aligned towards the upper edge of the packing container, the packaging container is grasped by the aligned gripper and the packaging container grasped by the gripper is aligned by a movement of the gripper. The packaging containers may include, for example, plastic bags, in particular plastic woven bags with a stepped-end cut, pinch bottom bags or plastic woven bags with a roll bottom. The packaging containers are filled and, after this is completed, they are fed onwards, for example, via a conveyor belt in order to be sealed. During this process, the packaging containers may be filled either from the side which later form the bottom of the packaging, i.e. from below, or from what will later be the upper side. The upper edge of the packaging container is designated as being the remaining open side of the packaging container which faces away from the conveyor belt. To correctly align the packaging containers for sealing, a gripper approaches the upper edge of the relevant packaging container. To that end, the position of the upper edge of the packaging container is detected by sensors and the gripper is aligned parallel to the upper edge of the packaging container. The gripper which is aligned along the upper edge of the packaging container records this upper edge and thus fixes it into place. The upper edge of the packaging container may, for instance, be in a slanting position which makes correct sealing with a sealing unit more difficult. Through the movement of the gripper, and thus of the detected upper edge of the packaging container, into a fixed position the upper edge of the packaging container can be precisely aligned. The packaging container may then, for example, be transferred in an accurate position to onward transporting equipment, e.g. a processing device, in particular a sealing unit, or directly fed to the sealing section.
In a further development of the process the gripper is moved vertically above the upper edge of the packaging container and the gripper is moved horizontally during which the movement speed of the gripper is adjusted to the speed of the transport device which conveys the packaging container. A packaging container may, for example, be fed via a transport device, in particular a conveyor belt, to the equipment or to the sealing section. Along the transport route the gripper can be moved at the same speed as the conveyed packaging container. Thus the gripper can be moved vertically over the upper edge of the packaging container during the horizontal movement of the packaging container and grasp it.
In a further development of the process a minimum of one position of the packaging container which is being moved by the transport device is detected by sensors and the gripper is moved based on the data from these sensors. The sensor for detecting the position of the packaging container which is being transported via a transport device, e.g. on a conveyor belt can, for example, take the form of an optical sensor, specifically a light barrier. This sensor may be located on the transport device. An item such as a light barrier may be arranged on a conveyor belt vertically to the conveying direction in such a way that packaging containers which pass the light barrier are detected by the sensor. Through the detection of a packaging container on the conveyor belt a control signal may be sent to the gripper so that it is moved from its stand-by position to the position of the packaging container on the conveyor belt. The speed of the conveyor belt and the horizontal movement speed of the gripper should preferably be synchronized so that the gripper can grasp the packaging container during its movement.
In a preferred form of the process the gripper has a minimum of two sensors for the sensor-based determination of the upper edge of the packaging container and the gripper is aligned in accordance with the upper edge of the packaging container determined by the sensors. The gripper has a minimum of two sensors with which the upper edge of the packaging container can be detected. These sensors may take the form of optical sensors, specifically light barriers. The sensors are arranged in such a way in relation to the gripper that they detect the position of this upper edge during the vertical movement of the gripper above the upper edge of the packaging container. When the upper edge is detected the gripper should preferably be aligned parallel to the upper edge and closed in such a way that the upper edge of the packaging container is fixed into place.
In a particularly preferred version of the process the minimum of two sensors are spaced apart from one another on the gripper such that a horizontal inclination of the upper edge of the packaging container is detected and the gripper is suitably aligned in relation to the incline. For the sensor-based determination of an inclination of the upper edge of the packaging container two sensors, for example, which may take the form of light barriers, are spaced on the gripper, preferably at a distance smaller than the width of the packaging container. The two sensors are preferably arranged at the same height in relation to the transport device, for example to the surface of a conveyor belt. If the upper edge of a packaging container is inclined, as the gripper moves in a vertical direction above the upper edge the sensor located closest to the highest point of the upper edge will detect the edge first and the second sensor will detect this upper edge later. The incline of the packaging container can be determined through the detection of the upper edge of the packaging container at different points and the gripper can be appropriately aligned to the incline.
In another preferred version of the invention the gripper has a minimum of two contact surfaces which are arranged parallel to each other. The gripper has two contact surfaces for grasping and fixing the upper edge of the packaging container into position and the upper edge of the packaging container is located between the contact surfaces for the purposes of sensor-based detection. In order to fix the packaging container into place the contact surfaces are moved towards each other and pressed together, preferably using pneumatic equipment. Alternatively, one contact surface may remain immobile in a lateral direction in relation to the transport path and the other contact surface may be pressed against it. The contact surfaces are preferably aligned parallel to the transport path of the packaging containers. The two front sides of the contact surfaces are able to be moved vertically in relation to the direction of movement of the packaging containers and independently of the rear sides of the contact surfaces. As a result of the independent mobility of the front side and rear sides of the gripper, the contact surfaces can be brought into an incline which is thus parallel to any inclination of the upper edge of a packaging container. The gripper preferably moves vertically above the upper edge of a packaging container until the upper edge of the packaging container is detected on one side, remains in position on this side and presses the contact surfaces against together as soon as the upper edge of the packaging container is also detected on the other side.
In a further version of the process the aligned packaging container is transferred to a processing device, specifically a sealing unit, as a result of which the packaging container is grasped by the processing device and the packaging container will not be released by the aligning unit until it is grasped by the processing device. The processing device is preferably a sealing unit with a suitable feeder device. The feeder device may, for example, consist of two conveyor belts arranged parallel to each other with vertical conveying surfaces between which the packaging containers are clamped. The packaging container is moved as a result of the rotation of the conveyor belts around vertically rotating shafts. In order to avoid altering the alignment of the aligned upper edge of the packaging container during the transfer, the packaging container will not be released by the gripper until it has been fully grasped by the processing device. For this purpose, the processing device may have a section at the point of transfer where the distance between the conveyor belts is greater, whereby the width of the section is equivalent to at least the maximum width of a packaging container. Once the packaging container has been completely fed into this section with a larger distance between the conveyor belts, the conveyor belts may be pressed towards each other, preferably through the movement of one of the conveyor belts in the receiving section in order to fix the packaging container securely into place. After the processing device has fixed it into place, the gripper releases the packaging container.
In a preferred further development of the process the packaging container is grasped by the processing device below a fold line at which the top side of the packaging container is folded when being sealed. To seal the packaging containers, specifically packaging containers with a roll bottom or stepped-end cut, the top side of the packaging container is folded over at least once and then sealed. In order to enable accurate folding and sealing of the packaging container, the packaging container is transferred to the processing device, precisely aligned and grasped by it below the fold line.
In a process for the sealing of a minimum of one packaging container during which the filled packaging container is horizontally fed to the aligning unit so that the packaging container has an infeed side at the front in the direction of movement and a rear side and during which the packaging container is sealed on its upper edge, it is proposed in the invention that the packaging container be aligned before sealing by means of a process in accordance with claims 1 to 8. A welding process, specifically a hot-air welding process, is the preferred application for the sealing of the packaging containers. Firstly, the upper edge of the packaging container, such as a plastic woven bag with a stepped-end cut, is folded so that the folded section of the packaging container, e.g. the section with the stepped-end cut, is brought towards the outer wall of the packaging container. A welding unit, specifically a hot air nozzle, is placed between the folded section of the packaging container and the outer wall of the packaging container and the folded edge is sealed with the outer wall through the welding energy generated by the hot air flow. A pair of nip rollers located immediately behind the hot air nozzle in the direction of transport of the packaging containers press together the weld melt produced as a result of the hot air flow. The pressing together of the pairs of nip rollers may be carried out, for example, using a pneumatic mechanism. During the welding process the packaging container continues moving so that the hot air nozzle and the pair of nip rollers can be located in a fixed position.
In a device for the alignment of a minimum of one packaging container, specifically for the carrying out of a process in accordance with one of the claims 1 to 8, with a minimum of two sensors and a minimum of one gripper which can be moved at least horizontally and/or vertically, it is proposed in the invention that the gripper has a minimum of two sensors for the detection of the upper edge of the packaging container, that the gripper has a controllable suspension device for at least horizontal and vertical movement, that the gripper has at least one signal-conducting connection to a control unit, that the control unit has at least one signal-conducting connection to a minimum of two sensors on the gripper so that the gripper can be controlled based on the data registered by the sensors. The gripper is preferably located above a transport device, for example a conveyor belt, which conveys the packaging containers to be aligned. The gripper may be located such that it can be moved vertically above the upper edge of the packaging container. The unit has a suspension device for moving the gripper, which enables horizontal and vertical movement and a rotation in the vertical plane. The gripper may additionally, for example, be connected to a minimum of two control lines which may take the form of levers or connecting rods and which may be able to be moved up and down using control levers. The gripper may be thus suspended on both sides from the control levers so that both sides of the gripper can be moved independently of each other. This enables a precise movement of the gripper. The control levers may, for example, be able to be controlled using a sensor control unit. This unit for vertical height control may in turn also be fixed but capable of being moved along a horizontal sliding rail. Additionally, a controlled movement of the gripper in the horizontal plane may also be made possible using the control levers. Thus, a spatial movement of the gripper is enabled in all directions. The gripper has a minimum of two sensors, preferably optical sensors and specifically light barriers, with which the upper edge of the packaging container can be detected by sensors. The data recorded by the sensors are transmitted through a signal-conducting connection to a control unit for their evaluation. Based on these data the control of the gripper, specifically its alignment, is carried out, for which purpose it is coupled via a signal-conducting connection to the control unit. The device for the alignment of packaging containers may form a single unit, for example with a sealing unit or another packaging unit, or the device may be arranged as a stand-alone unit which can be combined at will with other units and adapted to them. The device can, for example, be arranged in a mobile form as a stand-alone unit.
In a preferred arrangement of the invention the gripper has a minimum of two contact surfaces which are arranged parallel to each other and in total a minimum of two sensors are located on the facing contact surfaces. The gripper has two parallel arranged contact surfaces between which the upper edge of the packaging container to be aligned is positioned. The contact surfaces can be pressed against each other to fix the packaging container into place. This can be achieved using, for example, a hydraulic, pneumatic or similar mechanism. During this, either both contact surfaces can move in relation to each other or only one contact surface is designed in a mobile form to be pressed against the second contact surface. A minimum of two sensors, specifically light barriers, are arranged for the detection of the upper edge of the packaging container on the inside areas of the facing contact surfaces. The sensors can, for example, also be located above the inside facing surfaces. The sensors are preferably arranged in such a way that one sensor is located in the direction of movement of the packaging containers at the front between the contact surfaces and a second at the rear between the contact surfaces. Here the distance between the sensors is preferably only slightly smaller than the maximum width of a packaging container. For alignment purposes the gripper with the two parallel arranged contact surfaces is moved vertically in such a way that the contact surfaces are virtually parallel to the transport device, for example to the surface of a conveyor belt. As soon as the upper edge of the packaging container is registered by one sensor, the vertical movement can be set on the side of the gripper on which the sensor is located. As soon as the other sensor also registers the upper edge of the packaging container, the vertical movement can also be interrupted on this side. Thus, both contact surfaces are aligned parallel to the upper edge of the packaging container. The contact surfaces are pressed against each other and the upper edge of the packaging container is thus fixed into place. The upper edge of the packaging container is correctly aligned through a further movement of the gripper into a position in which the contact surfaces are once more located parallel to the transport device, preferably horizontal. In addition, it is possible that the movement of the gripper when registering the upper edge of the packaging container is not immediately set on the appropriate side but that the gripper is moved forward along, for example, a preset remaining path and the gripper is then closed. This enables a simple setting of the gripper to, for example, the position of the fold line of the packaging container.
In a further arrangement of the invention the device has a sensor for the detection of a minimum of one position of a packaging container conveyed by a transport device. The sensor can, for example, take the form of an optical sensor, specifically a light barrier. The transport device is preferably a conveyor belt. The sensor is, for example, located above the conveyor belt so that the detection path of the sensor runs vertically to the direction of conveying. If a packaging container is being conveyed on the transport device, it passes through the light barrier from which a signal is able to be transmitted to the gripper. The gripper is moved from its stand-by position so that it can approach the upper edge of the packaging container.
In a further preferred arrangement of the invention the device has a minimum of one synchronization unit, specifically for synchronizing the movement speed of the transport device for the feed of the packaging containers and the gripper. The horizontal movement speed of the gripper and of the transport device must be synchronized so that the gripper, specifically the contact surfaces of the gripper, can be correctly brought into position over the upper edge of the packaging container which is being moved by the transport device. For this purpose, the transport device may have a sensor which passes the relevant movement speed to the gripper. Alternatively, a measuring wheel, specifically a digital measuring wheel, can be located with contact to the surface of the conveyor belt which records the transport speed of the conveyor belt through its speed of rotation and passes this on to the gripper.
In a device for the alignment and sealing of a packaging container, specifically for the carrying out of a process in accordance with claim 9, with a minimum of two sensors, a minimum of one gripper which can be moved at least horizontally and/or vertically and at least one transport device it is proposed that the gripper has a minimum of two sensors for the detection of the upper edge of the packaging container. The upper edge of the packaging container to be aligned can be correctly grasped and aligned by the gripper via the sensors. The aligned packaging container is fed on to a device for further processing, specifically a sealing unit. For this purpose, the device may have a unit for further processing with an appropriate transfer unit. The transfer unit can, for example, take the form of two conveyor belts which are mounted, for example, between vertically rotating shafts. The conveyor belts are in this case arranged in parallel so that they are in contact with each other for at least part of the distance traveled. The speed of rotation of the conveyor belts must be thereby precisely synchronized. Once a packaging container has been clamped, specifically the top part of a bag, it is transported onward between the conveyor belts. To receive a packaging container, the transfer unit has a section whose width is equivalent to at least the maximum width of a packaging container. In this section the conveyor belts have a greater distance from each other than in the subsequent sections. The width of the distance can be adjusted by, for example, traversable, vertically rotating shafts around which one of the two conveyor belts runs and whose position may be moved in the direction of the other conveyor belt. In this section with a larger gap between the conveyor belts the packaging container is transferred from the gripper and both conveyor belts are pressed against each other so that the packaging container is fixed into place. After the transfer unit has fixed the packaging container into place, the gripper releases it again. This ensures that the position of the upper edge of the packaging container does not change during the transfer of the packaging container from the gripper to the transfer unit. The packaging container is transported onward through the rotation of the conveyor belts and fed to a sealing unit. The sealing unit has a folding device in which the upper section of a packaging container is folded. Hot air is fed in via an air flow nozzle between the surface of the packaging container and the folded section of the packaging container. Through the hot air a weld melt is produced on the surface of the plastic material which is pressed together using nip rollers which are located behind the hot air nozzle in the direction of movement of the packaging containers.
The invention is explained in further detail below using a sample design shown in the drawing. The schematic representations are as follows:
In
In
A partial view of a sealing unit is shown in
All of the features mentioned in the above description and in the claims may be freely combined with the features of the independent claim. The disclosure of the invention is thus not restricted to the described or claimed combinations of features but rather all reasonable combinations of features within the terms of the invention may be regarded as being disclosed.
Number | Date | Country | Kind |
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12 2014 001 013.9 | Jan 2014 | DE | national |