Patent Application
20210237917
The present invention relates to a strapping machine according to the preamble of claim 1. The invention also relates to a method according to the preamble of claim 9 for securing a piece of metal strap in a loop around one or more objects.
Automatic strapping machines for applying a metal strap in a loop around an object or a bundle of objects, drawing the strap tightly around the object/bundle and thereafter joining overlapping sections of the strap in order to secure the strap around the object/bundle are known in many different configurations. WO 2017/129679 A1 discloses a strapping machine where a welding device is used for forming a welded joint between overlapping sections of a metal strap to thereby secure the metal strap in a loop around an object or a bundle of objects. This known strapping machine comprises a gripping device for gripping and locking a first strap section at the leading end of the strap after the application of a piece of the strap in a loop around the object/bundle and before the strap is retracted in order to draw it tightly around the object/bundle, wherein the gripping device is configured to grip the strap at an area that will form part of the final strap loop on the object/bundle and that will be subjected to tensile stress when the strap loop has been released from the strapping machine. This is the normal gripping position for a gripping device of a strapping machine to be used for strapping an object or a bundle of objects with a strap of metallic material.
The object of the present invention is to achieve a new and favourable strapping machine of the above-mentioned type.
According to the invention, this object is achieved by means of a strapping machine having the features defined in claim 1.
The strapping machine of the present invention comprises:
According to the invention, the strapping unit comprises a pressing element, which has a shape adapted to the shape of the recess in the support member so as to allow the pressing element to be received in this recess. The strapping unit further comprises an actuating device which is configured to move the pressing element and the support member in relation to each other between a first mutual position, in which the pressing element is positioned at a distance from the recess in the support member, and a second mutual position, in which the pressing element is received in said recess, wherein the pressing element and the support member are configured to form a permanent bulge on the first strap section at a position between the leading end of said strap piece and said welded joint by a press forming action between the pressing element and the support member when the pressing element and the support member are moved in relation to each other by the actuating device from said first mutual position to said second mutual position with a part of the first strap section received in the space between the pressing element and the support member.
The permanent bulge formed on the first strap section will together with the pressing element and the recess in the support member, and as long as the pressing element and the support member are made to remain in the above-mentioned second mutual position, ensure that the first strap section is locked to the strapping unit with a positive locking effect and thereby prevented from slipping in the longitudinal direction of the strap when the feeding device retracts the strap and draws it tightly against the object or bundle of objects to be strapped. Hereby, the leading end of the strap is locked to the strapping unit in an efficient and reliable manner. Furthermore, the bulge formed on the first strap section will be located between the leading end of the strap and the welded joint between the first and second strap sections, i.e. on a part of the strap piece that will not be subjected to any tensile stress when the strap piece has been released from the strapping unit. Thus, the weakening deformation caused by the pressing element and the support member on the strap piece at the area of the bulge will not have any negative effect on the strength of the loop formed by the strap piece, in contrast to the previously mentioned normal case when the strap is gripped and subjected to a weakening deformation on the opposite side of the welded joint, i.e. on a part of the strap piece that will be subjected to tensile stress when the strap piece has been released from the strapping unit. In the latter, previously known case, the weakening deformation on the strap piece caused by the gripping of the first strap section will have a negative effect on the strength of the loop formed by the strap piece.
When the strap piece has been released from the strapping unit, the bulge formed on the strap piece by the pressing element will be pressed against an outer surface on the object/bundle and act as a spacer between the object/bundle and the loop formed by the strap piece. Hereby, the bulge will contribute to an increased tensional force in the loop and thereby an improved strapping effect. The gap formed between the loop and the outer surface of the object/bundle by the bulge will also facilitate a cutting of the loop in connection with a later destrapping operation when the metal strap is to be removed from the object/bundle.
Further advantageous features of the strapping machine according to the present invention will appear from the description following below and the dependent claims.
The invention also relates to a method having the features defined in claim 9.
Further advantageous features of the method according to the present invention will appear from the description following below and the dependent claims.
With reference to the appended drawings, a specific description of embodiments of the invention cited as examples follows below. In the drawings:
Some of the parts included in a strapping machine 1 according to an embodiment of the present invention are very schematically illustrated in
The guide track 2 may for instance have the form of a rail with a longitudinal opening facing said object receiving space 4. As an alternative, the strap may also be feed in a loop around the object or objects to be strapped without using any guide track. This may be accomplished by feeding the strap through a bending device that is configured to bend the strap in such a manner that it will move in free space, without contact with any guide track or the similar, in an essentially circular path around the object or objects 10 to be strapped, wherein a funnel-shaped guiding element may be arranged at the end of said path in order to catch the leading end of the strap and guide it into the strapping unit.
The object or objects 10 to be strapped may be positioned in the object receiving space 4 before, during or after the feeding of the strap 3 in a loop around this space 4.
As an alternative to the use of an accumulator 9, the slackening of the strap 3 when the strap is retracted by the feeding device 5 may be taken up or avoided by rotating the supply coil 6 in a reversed direction.
In the illustrated embodiment, the feeding device 5 comprises two rotatable feed rollers 5a, 5b, which are located opposite each other and configured to be in contact with opposite sides of a part of the strap 3 received in the nip between the feed rollers. At least one of the feed rollers 5a, 5b is rotatably driven by an actuator (not shown) in the form of a reversible drive motor in order to move the strap 3 in its longitudinal direction. The drive motor is preferably an electric motor, but it could as an alternative be a hydraulic or pneumatic motor. The feeding device 5 may also comprise any other suitable type of actuator for feeding and retracting the strap 3.
Some of the parts included in the above-mentioned strapping unit 20 are very schematically illustrated in
The welding device 21 may be any suitable type of welding device. In the illustrated embodiment, the welding device 21 is a laser welding device provided with a laser welding head 22, wherein said welded joint 8 between the first and second strap sections 7a, 7b is formed by means of a laser beam 23 (see
The strapping unit 20 further comprises a support member 24 for supporting said overlapping first and second strap sections 7a, 7b during the formation of the welded joint 8. The support member 24 is configured to be located between the first strap section 7a and an outer surface of the object or objects 10 to be strapped during the formation of the welded joint 8. A recess 25 is provided in an upper support surface 26 on the support member 24. When the welded joint 8 has been formed, the support member 24 is moved laterally out of the area between the strapped object/objects 10 and the strap loop 11 (see
In the examples illustrated in
The strapping unit 20 also comprises a pressing element 27, which has a shape adapted to the shape of the recess 25 in the support member 24 so as to allow the pressing element 27 to be received in this recess 25. The pressing element 27 has an upper surface 28 which is flush or at least essentially flush with the upper support surface 26 on the support member 24 when the pressing element 27 is received in the recess 25 in the support member, as illustrated in
An actuating device 29 (very schematically illustrated in
In the embodiment illustrated in
The pressing element 27 is also moveable horizontally by means of the actuating device 29 in order to allow the pressing element to be moved laterally out of the bulge 30 when the first and second strap sections 7a, 7b have been secured to each other by the welding device 21 and the strap loop 11 thereby formed is to be released from the strapping unit 20. According to a first alternative, the pressing element 27 is formed as a single-part element and moveable out of the bulge 30 by a displacement in a horizontal direction. According to another alternative, the pressing element 27 is divided into two parts, which are located opposite each other and moveable out of the bulge 30 by being displaced laterally in opposite directions away from each other.
The support member 24 may comprise first and second support jaws located opposite each other in the manner shown in WO 2017/129679 A1, wherein the support jaws are moveable in relation to each other between an advanced supporting position, in which the support jaws form a support for the first strap section 7a, and a retracted releasing position, in which the support jaws are retracted from each other in order to allow the first and second strap sections 7a, 7b, after having been joined to each other, to pass through a gap between the support jaws. Each support jaw may be fixed to a pivot arm, which in its turn is pivotally mounted to a housing 36 of the strapping unit 20. Thus, in this case, the support jaws are pivotable between the supporting and releasing positions. As an alternative, the support jaws could be linearly moveable between the supporting and releasing positions. The support jaws are moveable between the supporting and releasing positions by means of the actuating device 29. As an alternative, the support member 24 is formed as a single-part member and moveable between the supporting and releasing positions by a displacement in a horizontal direction.
The actuating device 29 may be electrically, pneumatically or hydraulically driven and may comprise one or more electrically, pneumatically or hydraulically driven actuators.
The strapping unit 20 illustrated in
The support member 24, the pressing element 27 and the squeezing device 34 may of course also have any other suitable design in addition to the designs illustrated in
The strapping machine 1 further comprises an electronic control device 60 (very schematically illustrated in
The electronic control device 60 is configured to control the feeding device 5 to stop the feeding of the strap 3 when the leading end 12 of the strap during its second passage over the support member 24 has passed over the recess 25 in the support member from a first end 25a (see
The distance D between the above-mentioned first and second ends 25a, 25b of the recess 25 is at least 10 mm, preferably at least 15 mm. The recess 25 has a depth d of at least 5 mm, preferably at least 6 mm.
In the example illustrated in
There is also a further recess 42 provided in the upper support surface 26 on the support member 24, wherein this further recess 42 is aligned with the passage 37 in the squeezing member 35. The purpose of this further recess 42 is to make sure that there is a gap between the first strap section 7a and the support member 24 below the welding area on the overlapping first and second strap sections 7a, 7b, to thereby prevent that material of the first strap section 7a that is subjected to heating and melting during the welding phase bonds to the material of the support member 24 when the overlapping first and second strap sections 7a, 7b are joined to each other by welding under the effect of a laser beam 23 emitted from the laser welding head 22.
The electronic control device 60 may be configured to control the welding device 21 to direct a laser beam 23 (see
The laser welding head 22 may comprise one or more computer-controlled scanning mirrors for controlling the direction and movement of the laser beam 23 emitted from the laser welding head. As an alternative, the direction and movement of the laser beam 23 may be controlled by computer-controlled movements of the entire laser welding head 22. The laser welding head 22 is provided with a focusing lens 38, through which the laser beam 23 leaves the laser welding head.
In the illustrated embodiment, the welding device 21 further comprises a laser source 39 (see
The electronic control device 60 may be configured to control the welding device 21 to reduce the tensile strength of the strap 3 at the trailing end of the second strap section 7b by heating the above-mentioned area 14 at the trailing end of the second strap section 7b under the effect of said laser beam 23 and without cutting or penetrating into the strap 3. In order to heat the area 14 at the trailing end of the second strap section 7b, the welding device 21 is made to sweep the laser beam 23 over the area 14 (schematically illustrated with dotted lines in
As an alternative, the electronic control device 60 may be configured to control the welding device 21 to reduce the tensile strength of the strap 3 at the trailing end of the second strap section 7b by forming one or more depressions 18, 18′ (see
The electronic control device 60 may be implemented by one single electronic control unit or by two or more mutually co-operating electronic control units.
An operating sequence for securing a strap 3 in the form of a strap in a loop around a bundle of objects 10 by means of the above-described strapping machine 1 will now be described with reference to
In a first step, a motor of the feeding device 5 is operated in a first direction in order to feed the strap 3 forwards from the supply coil 6, through the strapping unit 20, in a loop around the object receiving space 4 of the strapping machine 1 and then back into the strapping unit 20. The leading end 12 of the strap is first moved over the support member 24 and the pressing element 27, thereafter in a loop around the object receiving space 4 and then into a space between the pressing element 27 and the recess 25 in the support surface 26 on the support member 24, wherein the feeding of the strap 3 is stopped when the leading end 12 of the strap has passed over said recess 25 from the first end 25a thereof to the opposite second end 25b thereof and has reached a final position beyond the second end 25b of the recess.
During the feeding of the strap 3, the squeezing member 35 is in its retracted first position.
In the illustrated example, the pressing element 27 is positioned in the recess 25 in the support member 24 before the initial feeding of the leading end 12 of the strap through the strapping unit 20 and maintained in the recess 25 until the leading end 12 of the strap has passed over the upper surface 28 of pressing element 27 and the upper support surface 26 on the support member 24, as illustrated in
When the strap 3 has been fed through the guide track 2 in a loop around the object receiving space 4, the leading end 12 of the strap 3 will leave the guide track 2 and pass through the gap between the pressing element 27 and the support member 24 (see
When the strap 3 has been drawn tightly around the objects 10, the motor of the feeding device 5 is stopped and the squeezing member 35 is moved to its advanced second position in order to squeeze together the first and second strap sections 7a, 7b between the squeezing member 35 and the support member 24 (see
The intended welding area on the first and second strap sections 7a, 7b is with advantage preheated by means of a laser beam emitted from the laser welding head 22 of the welding device 21 before the formation of the welded joint 8. The welding area is preferably preheated to such a temperature that possible layers of paint and/or wax on the first and second strap sections 7a, 7b are removed by vaporization at the intended welding area. The pre-heating temperature is preferably also so adapted that the metallic material of the first and second strap sections 7a, 7b is subjected to metallurgical changes which result in improved welding conditions.
The welding area on the first and second strap sections 7a, 7b is with advantage also postheated by means of a laser beam emitted from the laser welding head 22 of the welding device 21 after the formation of the welded joint 8, wherein the post-heating temperature is so adapted that the metallic material of the first and second strap sections 7a, 7b is subjected to metallurgical changes which influence the strength of the welded joint 8 in a favourable manner.
In order to make sure that the laser beam will heat the welding area without cutting into the strap 3 in connection with the pre-heating and post-heating, the focal point of the laser beam is adjusted, for instance by means of the above-mentioned focusing optics of the optical connector 41, in such a manner that the laser beam is out of focus when hitting the second strap section 7b during the pre-heating step and the post-heating step. The pre-heating and post-heating laser beam is directed onto an outer surface of the second strap section 7b, wherein heat energy is transmitted from the second strap section 7b to the first strap section 7a by thermal conduction.
The invention is of course not in any way restricted to the embodiments described above. On the contrary, many possibilities to modifications thereof will be apparent to a person with ordinary skill in the art without departing from the basic idea of the invention such as defined in the appended claims. The strapping machine according to the present invention may for instance be design for co-operation with a compacting machine in order to strap a coil of wire compacted by the compacting machine. In the latter case, several strapping units are mounted to the compacting machine and used simultaneously in order to apply strap loops at different positions around the compacted coil of wire, wherein each strap loop extends along the inside of the coil through a central axial opening therein and along the outside of the coil.
| Number | Date | Country | Kind |
|---|---|---|---|
| 18171768.7 | May 2018 | EP | regional |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2019/061920 | 5/9/2019 | WO | 00 |
