Abstract:
A low wire level alarm comprises a signal element and a wire level detection element. The wire level detection element is adapted for detecting the level of welding wire contained in a welding wire bulk pack, and the signal element is adapted for giving an operator a visual and/or acoustic signal on the level of welding wire contained in the bulk pack. In a welding wire bulk pack having a base, side walls and a coil of welding wire placed inside the side walls, a retainer is arranged on top of the welding wire coil so as to descend in the bulk pack when the level of welding wire inside the pack decreases. A low wire level alarm system is used for signaling to an operator that the level of welding wire remaining in the bulk pack has fallen below a predetermined threshold.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The invention relates to bulk packs containing welding wire which is used in welding machines or robots for making weld seams. 
         [0002]    The use of bulk packs containing large quantities of reverse wound welding wire (in some cases up to as much as 1000 kg) is becoming increasingly popular in the industry since it offers the advantage of great savings thanks to a reduced pack changeover downtime and a higher productivity. Being able to avoid unwanted weld interruptions is, for some applications like the production of pressure vessels or pipelines or wind towers, extremely important because stoppages in the middle of a weld can be the cause for cracks, weld defects, or mechanical failures with consequent product liability issues. A sound good weld with no defects or imperfections is absolutely necessary in order to prevent subsequent leaks or failures. The industry today, especially with large size wires, utilizes mostly coils with welding wire content up to 100 kg, but more and more end users are adopting bulk packs or bulk containers with twist-free reverse wound welding wire in combination with high performing low friction guiding liners with rolling elements inside; introducing a welding wire as thick as 4 mm or even more into a long liner with many curvatures up to the welding torch could however result in a very difficult operation and could take as much time as changing smaller coils. 
         [0003]    It is known in the prior art to provide small inspection windows in the outer wall of the welding wire bulk packs which allow to visually inspect the level of welding wire contained in the respective bulk pack. This however requires that an operator approaches the respective bulk pack to be able to determine the wire level in the inspection window. 
         [0004]    It is also known in the prior art to butt-weld the end of the welding wire stored in a first, currently used bulk pack to the beginning of the welding wire stored in a second, new bulk pack, and to allow the welding wire to automatically change from the first to the second bulk pack. Such system is known as a 24/7 welding system as it allows uninterrupted welding. Further, such system eliminates the risk that the welding machine runs short of welding wire when the welding wire of a currently used bulk pack has been entirely consumed so that the welding wire of a new bulk pack must be fed through the entire welding wire guiding system from the wire entry up to the welding torch. If however for some reasons the operator does not use a 24/7 welding system and does not notice in time that the welding wire contained in the currently used bulk pack is completely consumed, then the wire end is being completely pulled through the liner. This would generate two possible situations: The operator is either forced to repeat the process of the initial insertion of the wire, or the welding process has to be suddenly interrupted, with the consequent quality issues and technical problems previously explained. 
         [0005]    The object of the invention is to provide a simple system which reliably provides to an operator an indication that the level of welding wire contained in a bulk pack has reached a low level. 
       BRIEF DESCRIPTION OF THE INVENTION 
       [0006]    The invention provides a low wire level alarm, comprising a signal element and a wire level detection element. The wire level detection element is adapted for detecting the level of welding wire contained in a welding wire bulk pack. The signal element is adapted for giving an operator a visual and/or acoustic signal on the level of welding wire contained in the bulk pack. This alarm system is inexpensive and practical as it can provide a timely warning of the low wire level inside the pack. If promptly and adequately advised by a visual and/or acoustic warning, the operator can let the weld cycle be completed and then stop the welding process at the wanted time and proceed to cut off and discard the residual welding wire loops, joining the wire with the butt welder to the start of a new pack. 
         [0007]    The invention also provides a welding wire bulk pack having a base, side walls and a coil of welding wire placed inside the side walls. A retainer is arranged on top of the welding wire coil so as to descend in the bulk pack when the level of welding wire inside the pack decreases. A low wire level alarm system is provided which is adapted for signaling to an operator that the level of welding wire remaining in the bulk pack has fallen below a predetermined threshold. The present invention discloses a system, applicable to bulk welding wire packs or containers, which activates a low wire level alarm when the bulk pack is close to empty; the alarm informs the operator in advance so that the end of the welding wire from the empty bulk pack can be butt-welded to the start of the new full bulk pack. The system is especially useful in those applications like submerged arc welding where having to completely re-feed the new wire through a liner would be a problematic and time consuming operation. 
         [0008]    Preferably, the alarm system is easily movable from one bulk pack to the next, and it should be preferably mounted directly at the pack and be battery operated, in order to avoid the use of electrical cables that could represent a hazard and an impediment for an operator that needs to move freely around the welding cell. 
         [0009]    In a mechanically simple embodiment, the wire level detection element is a rod adapted for being placed on top of a retainer arranged inside a welding wire bulk pack. It preferably has a mark as the signal element which is visible for an operator. In order to allow setting the alarm to a desired level of welding wire remaining in the bulk pack, the signal element is arranged on the rod so as to be adjustable to a desired level. 
         [0010]    In an alternative embodiment, the signal element comprises an electric sensor which can issue an optical alarm, an acoustic alarm or a combination of an acoustic and an optical alarm. 
         [0011]    Preferably, the electric sensor is battery powered so that no electric wiring is required. 
         [0012]    The electric sensor can cooperate with a rod acting as the wire level detection element, the rod being placed on top of a retainer arranged inside a welding wire bulk pack and having a mark which can be detected by the electric sensor. The electric sensor preferably uses a proximity sensor for detecting the mark. 
         [0013]    The electric sensor can alternatively cooperate with a cord wound on a reel and associated to the retainer, such that the electric sensor can detect the amount of cord unwound from the reel when the retainer descends in the bulk pack. 
         [0014]    The cord can be provided with a weight at its end associated to the retainer so that the cord simply follows the retainer when it descends in the bulk pack. Alternatively, the cord can comprise one of a magnet and a piece of ferromagnetic metal at its end associated to the retainer, and the retainer can comprise one of a piece of ferromagnetic metal and a magnet. This ensures that the cord is pulled by the retainer during its descending motion in the bulk pack. 
         [0015]    In another alternative, the retainer can comprise an attachment means for mechanically attaching the cord to the retainer. The retainer can for example comprise an attachment eye, and the cord can comprise a hook. In addition, a cushioning spring can provided. 
         [0016]    In an alternative embodiment, the wire level detection element is an acoustic or optical emitter, and the electric sensor has a receiver and an evaluating unit adapted to calculate the wire level based on the propagation time of the acoustic or optical signals from the emitter to the retainer and back to the receiver. This allows detecting the distance between the electric sensor and the retainer in a contact-free manner. In order to save battery energy, the detection of the wire level can be performed in intervals of e.g. 15 minutes only. 
         [0017]    In welding wire installations using a cover on top of the bulk pack, the sensor is arranged on top of the cover, for example in an appropriate recess or mount. In welding wire installations using no cover on top of the bulk pack, the sensor comprises a mount which allows attaching or clipping it to one of the side walls of the bulk pack. In any case, the electric sensor can easily be removed from one bulk pack and be easily installed at the next bulk pack. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]    The invention will now be described with reference to the enclosed drawings. In the drawings, 
           [0019]      FIGS. 1   a  and  1   b  show a first embodiment of the invention, with the bulk pack being in an initial condition in  FIG. 1   a  and in a low wire level condition in  FIG. 1   b;    
           [0020]      FIGS. 2   a  and  2   b  show a second embodiment of the invention, with the bulk pack being in an initial condition in  FIG. 2   a  and in a low wire level condition in  FIG. 2   b;    
           [0021]      FIGS. 3   a  and  3   b  show a third embodiment of the invention, with the bulk pack being in an initial condition in  FIG. 3   a  and in a low wire level condition in  FIG. 3   b;    
           [0022]      FIGS. 4   a  and  4   b  show a fourth embodiment of the invention, with the bulk pack being in an initial condition in  FIG. 4   a  and in a low wire level condition in  FIG. 4   b;    
           [0023]      FIGS. 5   a  and  5   b  show a fifth embodiment of the invention, with the bulk pack being in an initial condition in  FIG. 5   a  and in a low wire level condition in  FIG. 5   b;    
           [0024]      FIGS. 6   a  and  6   b  show a sixth embodiment of the invention, with the bulk pack being in an initial condition in  FIG. 6   a  and in a low wire level condition in  FIG. 6   b ; and 
           [0025]      FIGS. 7   a  and  7   b  show a seventh embodiment of the invention, with the bulk pack being in an initial condition in  FIG. 7   a  and in a low wire level condition in  FIG. 7   b.    
           [0026]      FIGS. 8   a  and  8   b  show an eights embodiment of the invention, with the bulk pack being in an initial condition in  FIG. 8   a  and in a low wire level condition in  FIG. 8   b.    
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0027]    In  FIG. 1 , a welding wire bulk pack  10  is shown, which has a base  12  and side walls  14 . Base  12  can be a wooden pallet, and side walls  12  can be formed from cardboard. In a top view, the bulk pack can have a circular or a polygonal shape. Side walls  14  can be formed from a single piece of cardboard which extends around the entire circumference of the bulk pack. 
         [0028]    In the interior of the bulk pack, a welding wire coil  16  is arranged. Welding wire coil  16  is formed from a continuous length of welding wire wound into the bulk pack so that the welding wire can be withdrawn from the upper end face of the coil. In order to prevent that welding wire prematurely lifts from the coil, a retainer  18  is arranged on top of welding wire coil  16 , which mechanically holds the welding wire at its place until it is being withdrawn. Withdrawal of the welding wire takes place through an opening in a cover  20  which is placed on side walls  14  so as to close the upper side of the bulk pack. 
         [0029]    A rod  22  is provided which extends vertically through an opening in cover  20  so as to rest on top of retainer  18 . A small depression or similar accommodation for the lower end of rod  22  can be provided at the retainer in order to make sure that rod  22  is kept in a vertical orientation. In order to improve the stability, a holding bracket  23  can be arranged on top of cover  20 , the holding bracket being placed in a suitable depression or mount which is formed in cover  20 . 
         [0030]    Associated with rod  22  is a mark  24  which can be connected to rod  22  at a desired level. To this end, a small adjustment screw  26  is provided within mark  24 . As can be seen by comparing  FIGS. 1   a  and  1   b , retainer  18  descends within bulk pack  10  when the welding wire forming welding wire coil  16  is being increasingly consumed. Rod  22  then acts as a wire level detection element which descends into the bulk pack as a result of the retainer  18  descending. Mark  24 , which is preferably coated with a signal color such as red, acts as a signal element which very conveniently allows an operator to see from a distance how much wire is left inside the bulk pack. As soon as mark  24  sits on top of cover  20 , the operator is informed that the predetermined level of welding wire remaining in the bulk pack has been reached. By adjusting the mark to a desired position on rod  22 , this level of welding wire at which the mark reaches the cover  20  can be adjusted by the operator according to the requirements. 
         [0031]    In  FIG. 2 , a second embodiment is described. For those elements already known from the first embodiment, the same reference numerals are used, and reference is made to the above comments. 
         [0032]    The second embodiment distinguishes over the first embodiment in that an electric sensor  30  is provided which is able to detect the position of mark  24 . In particular, electric sensor  30  can comprise a proximity sensor  32  which is able to detect the presence of mark  24 . As soon as the welding wire has been withdrawn from the bulk pack to an extent that retainer  18  has descended to the level shown in  FIG. 2   b , mark  24  has reached a position in front of proximity sensor  32  so that electric sensor  30  is activated. Electric sensor  30  can issue an optical signal such as a flash light, can issue an acoustic signal such as a warning tone, or can issue a combination of an acoustic and an optical alarm. Thereby, an operator is immediately notified that the welding wire remaining in the particular bulk pack has reached a certain low level. Here again, the level at which the alarm is given can be set to a desired value by simply changing the position of mark  24  on rod  22 . 
         [0033]    Electric sensor  30  is preferably powered by a battery so that no electric cables and no wiring is required. The entire alarm system can be simply transferred from one emptied bulk pack to a new bulk pack by simply transferring cover  20  with rod  22 , holding bracket  23  and electric sensor  30  to the new pack. 
         [0034]    In  FIG. 3 , a third embodiment of the invention is shown. For those components which are already known from the previous embodiments, the same reference numerals are used, and reference is made to the above comments. 
         [0035]    The difference between the third and the second embodiment is that in the third embodiment, rod  22  is formed from telescopic retractable tubes, the lowest of the tubes having a weight  34  which rests on the upper surface of retainer  18 . In the initial condition shown in  FIG. 3   a , mark  24  is maintained spaced from proximity sensor  32  so that no alarm is issued. When retainer  18  has descended to a level which does not allow the telescopic rod  22  to be extended any further, mark  24  is pulled downwards so as to lie opposite proximity sensor  32 . Then, the alarm is issued. 
         [0036]    The main advantage of the third embodiment over the first and second embodiment is that rod  22  does not significantly protrude upwardly over the bulk back in the initial condition, thereby preventing any entanglement of the welding wire with rod  22 . It must be noted that in view of the capacity and the dimensions of large bulk packs, rod  22  used in the first and second embodiment can protrude up to 30 inches above cover  20  when the bulk pack is completely filled. 
         [0037]    In  FIG. 4 , a fourth embodiment of the invention is shown. For the elements already known from one of the preceding embodiments, the same reference numerals are used, and reference is made to the above comments. 
         [0038]    The main difference between the fourth embodiment and the first three embodiments is that in the fourth embodiment, a cord  36  is used as the wire level detection element. Cord  36  is connected to a reel  38  rotatably mounted at electric sensor  30 . At its free end, cord  36  is provided with a weight  34  which rests on top of retainer  18 . When retainer  18  descends inside bulk pack  10  as a result of welding wire being withdrawn, an increasing amount of cord  36  is withdrawn from reel  38 . Electric sensor  30  is adapted for counting the number of revolutions made by reel  38 , e.g. by means of a microswitch. As soon as a predetermined number has been reached, the alarm is given. Here again, the level at which the alarm is given can be individually defined by the operator according to the requirements. 
         [0039]    In  FIG. 5 , an embodiment is shown which is an alternative to the embodiment shown in  FIG. 4 . The difference over the embodiment shown in  FIG. 4  is that cord  36  in the embodiment of  FIG. 5  is provided with a small magnet  40 , and retainer  18  is provided with a small piece  42  of ferromagnetic metal. Of course, the magnet could also be provided in the retainer while the piece of ferromagnetic metal could be attached to cord  36 . In any case, the magnetic attraction ensures that cord  36  is reliably wound from reel  38  when retainer  18  descends downwardly in the bulk pack  10 . 
         [0040]    In  FIG. 6 , another alternative is shown. Here, cord  36  is provided with a hook  44  which engages into an attachment eye  46  arranged at retainer  18 . In addition, a cushioning spring  48  can be provided between hook  44  and cord  36 . The mechanical connection between cord  36  and retainer  18  ensures that cord  36  is reliably unwound from reel  38  when retainer  18  descends downwardly in the bulk pack. 
         [0041]    In  FIG. 6   c , a simplified embodiment is shown in which no cushioning spring  48  is used. 
         [0042]    In  FIG. 7 , a seventh embodiment is shown which largely corresponds to the sixth embodiment. The difference between the sixth and the seventh embodiment is that in the seventh embodiment, no cover  20  is placed on top of the bulk pack  10  for guiding the welding wire during withdrawal from the bulk pack. Rather, a rotatable boom  50  is used to which a liner  52  is connected. Inside liner  52 , a plurality of small rolling elements are provided which ensure a smooth, low-friction displacement of the welding wire from the bulk pack towards the welding machine. This system is particularly suitable for sub-arc welding applications where welding wires having a diameter of 4 mm and above are used. 
         [0043]    As no cover  20  is provided, electric sensor  30  is provided with a mount  54  which allows to clip it onto the upper end of one of the side walls  14  of the bulk pack. Here again, this kind of attachment allows to very conveniently transfer the electric sensor  30  from one bulk pack to the next one. 
         [0044]    In  FIG. 8 , an alternative embodiment is shown. Here, electric sensor  30  is provided with an emitter  60  and a receiver  62 . Emitter  60  sends out a signal which can be an acoustic signals, in particular in a frequency range which cannot be heard by humans, or optical signals such as a laser beam. These signals are reflected on the upper surface of retainer  18  and are then detected by receiver  62 . Electric sensor  30  is able to calculate the distance between the electric sensor  30  and the retainer based on the propagation time of the signals from the emitter to the receiver. In order to maintain a longer battery life, the detection of the wire level can be performed in intervals only, e.g. every 15 minutes. 
         [0045]    For all embodiments using the electric sensor  30 , it can be provided that the electric sensor is connected to the welding robot where additional alarms can be given on a screen or in an acoustic manner.