The system described herein relates to a strapping machine comprising a strap guide frame having a strap guide channel and a plurality of closing elements which are arranged in a distributed manner over the length of the channel and which can be moved from a position closing the channel into a position opening the channel counter to a return force, wherein the closing elements can be fixed in the position closing the channel via a closing force which is generated by a magnetic closure device. The system described herein also relates to a method for strapping items with such a strapping machine.
Such a strapping machine is known from publication EP 702 844 B1. The magnetic closure device reliably generates a closing force in a wear-free manner, which closing force keeps the strap guide channel closed. After the end of strapping, a retraction drive pulls the strap back out of the strap guide channel, wherein the strap is pulled against the closing elements and opens the closing elements counter to the closing force. In the case of the embodiment described here, the closing elements are fastened in a flap-like and pivotable manner to the strap guide frame in such a manner that they cover the strap guide channel if the closing parts on the strap guide frame and the closing element adjoin one another, wherein the magnetic force of the closing parts fixes the closing element in this closed position. When opening the closing elements by pulling the strap out of the strap guide channel, a force must act which is greater than the magnetic force in order to open the closing elements. This leads to the strap sliding past the edge of the closing element during opening with increased force, as a result of which significant wear arises which leads to an increased service and repair outlay. Publication DE 25 07 717 C3 discloses a strapping machine with a device for keeping the channel flaps closed, which channel flaps are actuated via cables. A pulling force is exerted on the cable by a spring, a weight, a pneumatic or hydraulic piston or electromagnetically.
The strap is furthermore displaced by the undefined opening movement of the flaps. As a result of this, the positioning of the strap on the product cannot be realized in a precise manner.
One further significant disadvantage is that a minimum distance from the product to the frame must be observed to so that the flaps reliably open. The selection of the flap geometry is also very significantly dependent on the dynamic processes when opening the flaps by pulling out the strap. The flap geometries cannot be freely selected with the objective of optimum frame covering, rather must be defined so that reliable opening of the flaps is ensured.
The development of noise of the flaps during opening by pulling out the strap is also very high. The outlay of force to open the flaps subject to the magnetic force also leads to the use of a drive motor with a transmission stage to generate the required retraction force of the strap.
It is desired to create a strapping machine, in the case of which at least some of the above-mentioned disadvantages are overcome. It is desired to reduce the wear of the closing elements (flaps), avoid a displacement of the strap caused by opening the flaps, enable the free selection of the flap geometries, reduce the development of noise and the required retraction force.
In an embodiment of the system described herein, a magnetic closure device has a displacement means for displacement of at least a part of the magnetic closure device, as a result of which the closing force may be cancelled or an opening force directed counter to the closing force may be generated.
By means of the displacement means, the position of at least a part of the magnetic closure device may be changed so that the closing force drops to zero. This may be, for example, the case if a magnetic closing part is displaced from a position in which it is opposite and attracts another magnetic closing part in such a manner that it is opposite a non-magnetic material portion e.g. made of plastic so that no magnetic closing force is generated any more. The closing parts then may open in a resistance-free manner. If the closing parts are arranged pivotably at the bottom on a horizontally running portion of the strap guide frame, the closing parts may pivot into the opening position as a result of their weight in the event of cancelation of the closing force. The cancelation of the closing force may largely avoid the wear of the closing parts during opening caused by the strap.
However, by means of the displacement means, the magnetic closure device also may be configured so that, in an opening position, two magnetic closing parts with opposite polarity are opposite one another, of which one is arranged on the strap guide frame and one on the movable closing element. The two closing parts then may repel one another and generate an opening force which may push the closing element into the opened position. As a result of this, any contact between strap and closing part may be avoided during contraction of the strap loop formed in the strap guide channel.
The closing elements may be flap-shaped and may be fastened pivotably to the strap guide frame. In the closing position, they may cover the strap guide channel. Flap-shaped closing elements may be the most frequent embodiments of closing elements. The closing elements may be formed to be L-shaped, wherein their lateral limbs may be fastened pivotably to the strap guide frame and the limbs facing the center of the strap guide frame may cover the strap guide channel. However, other flap-shaped closing elements are also known, for example, from EP 1 702 844 B1. It may be vital that the portions of the closing elements which cover the strap guide channel may be moved in such a manner that the strap guide channel is released and a strap in the strap guide channel may be pulled out in order to form a loop bearing tightly around a package. A plurality of closing elements may be normally distributed over the length of the strap guide frame. Each of the closing elements may form a flap. In the case of L-shaped closing elements, it is also known to use in each case pairs of closing elements, of which each may cover half of the strap guide channel. These pairs of flap-shaped closing elements then may flap apart like wings when the strap guide channel is opened.
In practice, the magnetic closure device may have two closing parts which interact with one another, of which one is fastened to a closing element and the other is fastened to the strap guide frame. One of the two closing parts should be permanent-magnetic in order to generate the closing force when oriented with respect to the second closing part. The other closing part may be either permanent-magnetic or ferromagnetic and may be magnetically attracted by the first closing part.
As mentioned further above, in practice, the displacement means may displace one of the closing parts which interact with one another. For the plurality of closing elements of the strap guide frame, the magnetic closure device may have a displacement means which brings about a cancelation of the closing force for each closing element, e.g., by displacement of one of the two closing elements which interact with one another. Thus, by means of an activation of the displacement means, e.g. a displacement, all of the closing elements of the strap guide frame may be simultaneously opened or at least rendered force-free.
In practice, the displacement means may displace the displaceable closing part from a closing position, in which it may be located close to the stationary closing part, into an opening position, in which it may be remote from the stationary closing part. In an embodiment, as a result of the greater distance, no effective magnetic force is then generated any more.
Moreover, the magnetic closure device may have an opening part which, in the opening position, lies close to a closing part. If the relevant closing part and the opening part are both permanent-magnetic and identical poles of the closing part and the opening part face one another, a repelling magnetic force which pushes the closing element into the opening position may be generated between this closing part and the opening part. In the opening position of the closing element, the strap guide channel may be completely opened so that the strap may escape from the strap guide channel without contact with the closing element.
As mentioned, the magnetic closure device may have at each closing element a closing part and a second closing part assigned to this closing part and fastened to the strap guide frame. These two closing parts may pull the closing element magnetically into the closed position.
The displacement means may in practice be fastened to the strap guide frame. The displacement means may have an actuating drive which brings about the displacement of the closing parts on the strap guide frame. The actuating drive may bring about a displacement of the displaceable closing part in both directions, i.e., in the closing direction and in the opening direction. The actuating drive also may, however, only act on one side and may generate an opening force with which the displaceable closing part is displaced into the opening position. The closing parts which interact with one another may generate a magnetic closing force acting in the opposite direction and displacing the displaceable closing part into the closing position.
In the case of one particular embodiment of the strapping machine, each of the two opposite and pivotable closing elements may have a limb which projects toward the center of the strap guide frame, wherein two free end faces of these limbs may adjoin one another in the position closing the channel and wherein each of these limbs may have, proceeding from the respective free end face, a gap and the gaps which lie opposite one another jointly may form the strap guide channel. In other words, the short limbs, facing one another, of the L-shaped flaps may form an integrated strap channel because they may have parallel gaps proceeding from their free end faces, which gaps may be flush with one another and in each case may form a half of the strap guide channel. A corner element of the strap guide frame may have similar strap channel halves which may be integrated into the flaps and which may run along a path curved circularly over 90°. These strap channels integrated into the flaps or portions of the strap channels may enable highly precise guide of the strap with a low degree of play.
In an embodiment of the system described herein, a method for strapping items with a strapping machine is provided, where the strapping machine has a strap guide frame having a strap guide channel and a plurality of closing elements which may be arranged in a distributed manner over the length of the channel and which may be moved from a position closing the channel into a position opening the channel counter to a restoring force, wherein the closing elements may be fixed in the position closing the channel via a closing force which may be generated by a magnetic closure device. In order to reduce the wear of the closing elements, by altering the magnetic closure device, the closing force may be canceled or an opening force directed opposite to the closing force may be generated.
The magnetic closure device may have two closing parts which interact with one another, of which one may be fastened to a closing element and the second may be fastened to the strap guide frame and of which one may be permanent-magnetic and the other may be either permanent-magnetic or ferromagnetic, wherein one of the closing parts may be displaced to alter the magnetic closure device.
The displaceable closing part may be displaced from a closing position close to the stationary closing part into an opening position remote from the stationary closing part.
The magnetic closure device may have an opening part which, in the opening position, lies close to one of the closing parts, wherein this closing part and the opening part may be permanent-magnetic and identical poles of the closing part and the opening part may face one another.
In practice, an actuating drive may generate an opening force with which the displaceable closing part is displaced into the opening position, wherein the closing parts which interact with one another may generate a magnetic closing force with which the displaceable closing part is displaced into the closing position.
Further practical embodiments and advantages of the system described herein are described below in conjunction with the drawings. In the drawings:
The strapping machine 1 represented in
The tensioned loop may be subsequently cut off from the strap supply. The start of the loop may be connected to the end of the loop by means of a closure assembly 10. The closure assembly 10 may comprise in practice, e.g., a welding device which welds the two ends of the formed packing strap loop to one another. The closure assembly 10 may weld the film-like plastic material of which the strap may be composed. The conveyor with which the item 7 may be transported into and out of the strapping zone within the strap guide frame is not represented in
Enlarged views of
The plastic bar may have elongated holes 25 to receive the bearing pins 13 which guide and fasten the plastic bar on the strap guide frame 9. The elongated holes 25, through which the bearing pins 13 project, of the plastic bar 17 are apparent in, e.g.,
The structure of the strap guide frame is apparent in detail in
It is apparent that the flaps 11, 12 may be closed by displacement of the plastic bar 17 from the opening position into the closing position and the flaps 11, 12 may be opened by displacement from the closing position into the opening positions. For this purpose, in the opening position, the plastic bar 17 may lie in relation to the magnetic closing parts 14, 15 of the flaps 11, 12 such that in each case an opening magnet 18 is flush with the magnetic closing parts 14,15, which may be opposite one another and may generate an opening force between the opening magnet 18, which may form the opening part, and the closing parts 14, 15 because one end of a magnetic closing part 14,15 may be opposite each end of the opening magnet 18.
It is apparent for the person skilled in the art that the opening magnet 18 on the plastic bar 17 may be dispensed with. In this case, no opening force may be generated when displacing the plastic bar 17 into the opening position, rather the flap-shaped closing element 11, 12 may be held without force on the strap guide frame 9, because a non-magnetic plastic portion of the plastic bar 17 may be opposite each magnetic closing part 14,15.
In contrast, in the closing position, the ferromagnetic steel bolt 16 may be opposite the magnetic closing parts 14,15 so that the closing parts 14,15 are magnetically attracted.
It is likewise apparent for the person skilled in the art that the displacement of the plastic bars 17 or the displacement of the steel bolts 16 as a ferromagnetic closing part or of the opening magnet 18 as an opening part may be brought about in a different manner than by a drive motor. The displacement may be generated by any other desired actuating drive or linear motor, for example, a solenoid linear motor. It also may be possible to use the magnetic force which prevails between the magnetic closing parts 14,15 at the flaps 11, 12 and the magnetic closing part at the plastic bar 17 to displace the plastic bar 17 into the closing position. In this closing position, the closing parts may attract one another so that this magnetic force brings about the displacement of the movable plastic bar into the closing position.
The features of the system described herein disclosed in the present description, in the drawings and in the claims may be significant both individually and in any desired combinations for the achievement of the system described herein in its various embodiments. The invention is not restricted to the described embodiments. It may be varied in the scope of the claims and taking into account the knowledge of the relevant person skilled in the art. Other embodiments of the invention will be apparent to those skilled in the art from a consideration of the specification and/or an attempt to put into practice the system described herein. It is intended that the specification and examples be considered as illustrative only, with the true scope and spirit of the invention being indicated by the following claims.
Number | Date | Country | Kind |
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10 2018 131 395.0 | Dec 2018 | DE | national |
Filing Document | Filing Date | Country | Kind |
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PCT/EP2019/077235 | 10/8/2019 | WO | 00 |