DESCRIPTION

The present invention relates to a welding apparatus and a method for joining together two ends of a strap, a strap dispensing station and a process for supplying the strap to a binding system, and a coiling machine provided with a binding system and a strap dispensing station.

It is known in the technical sector of winding pipes in the form of shanks, coils and the like, that these are obtained by winding the pipes using coiling machines provided with a rotating reel:

Also known in the art are different models of coilers for automatically coiling pipes made of plastic and other materials, which operate with a completely automatic cycle substantially comprising the following steps:

-) automatically taking up the pipe to be wound on the reel by means of a corresponding mechanical device;

-) automatically starting the winding step, during which a pipe-guiding device distributes the pipe on the rotating reel;

-) automatically cutting the pipe when the set winding length is reached;

-) binding the finished coil ready for packaging;

-) automatically unloading the wound and bound coil.

It is also known that the packaging operation is performed by means of an operation of strapping the wound coil, during which the wound coil is bound using a strap in such a way that the pipe wound up in the form of a coil does not come apart, remaining stably assembled in a compact form suitable for being handled during subsequent packaging and/or unloading and/or storage and/or transportation.

In the context of the present description, "strap" is understood as meaning a substantially flat strip of plastic material, usually polypropylene (PP strap) or polyester (PET strap) which is unwound from a store and fed to a binding system of a coiling machine in order to tie coils of wound pipe.

As is known, the strapping operation (binding with a strap) is generally performed by means of strapping apparatus comprising channels for receiving and guiding the strap, inside which the said strap is fed, made to pass around the formed coil and guided back into a strapping head which forms a loop and then pulls and cuts the strap. These receiving and guide channels must generally be designed with dimensions having a width corresponding to the thickness of the strap, in order to prevent the strap from bunching up, being deviated or getting jammed.

The strapping operation is repeated by rotating the coil into different angular positions in order to obtain a plurality of strapped zones of the coiled pipe.

The strapping machine retrieves as required the strap needed for binding from a dispenser which is situated inside the coiling machine. The dispenser has, mounted inside it, a store, for example a reel, for the strap which is gradually fed to the strapping device.

The strap store (reel) is therefore a consumable source which must be replaced when used up, during the pipe coiling procedures.

An example of a coiling machine with two half-reels which can be joined together to form a winding reel, provided with a strapping apparatus, is known from EP2810909A1. Similar solutions are known for reels which are formed as a single rotating body.

In the known coiling machines, strapping machine and dispenser with the strap store are situated inside a safety perimeter of the coiling machine, defined by protective guards of the coiling machine, forming part of a safety system generally configured to stop operation of the machine if the guards are opened or crossed; the strapping machine and dispenser therefore cannot be accessed when the plant is in operation.

The procedure for replacing the strap store is therefore an operation which must be performed with the coiling machine stopped, which operation may take a minimum time of about 3 minutes when carried out by an expert user.

In the case of high-speed pipe production and coiling, e.g. 100 m/min, such a stoppage of the coiling machine produces about 300 m of waste pipe, since although the coiling machine can be stopped and then quickly restarted after replacing the strap, the upstream pipe production line must still continue operating; in fact, in the event of the latter stopping, restarting is much longer and more complicated, resulting in an even greater production loss than that which is instead caused by continuing to produce pipe, said pipe having to be discarded since it cannot be coiled owing to the stoppage of the coiling machine during replacement of the strap reel.

The technical problem which is posed therefore is that of providing apparatus, machines and processes which are able to eliminate or at least limit the aforementioned drawbacks of the prior art associated with feeding of the strap for binding pipes wound in the form of a coil.

One particular aim of the present invention is to reduce or eliminate the downtime and/or wasted material due to the need to replace a strap store required for the binding of coiled pipe.

A further aim of the present invention is to make the strap feeding operations and/or replacement of the strap store safer.

A further aim of the present invention is to provide an apparatus and a process for joining together several strap sections.

In connection with this problem it is particularly desirable that this apparatus and machine should have small dimensions and be able to be easily installed and used.

A further preferred aspect is that such an apparatus should be compatible with the pre-existing strapping systems, in particular with regard to the dimensions of the strap receiving and guiding channels and/or should not result in jamming of the said strap.

These results are obtained according to the present invention by a welding apparatus according to the features of Claim 1, by a dispensing machine according to Claim 20 and by a method for joining together strap ends according to Claim 16. The present invention relates furthermore to a coiling machine according to Claim 23 and a process for supplying strap according to Claim 25.

Further details may be obtained from the following description of non-limiting examples of embodiment of the subject of the present invention, provided with reference to the accompanying drawings, in which:

Figure 1: shows a schematic top plan view of a coiling machine according to the present invention;

Figure 2: shows a simplified side view of the machine according to Figure 1, from a side on which a strap dispensing station is arranged;

Figure 3: shows a simplified perspective front view of the machine according to Figure 1 on the side provided with strap dispensing station;

Figure 4: shows a more detailed view of a strap dispensing station according to the present invention;

Figure 5: shows a perspective view of a strap welding apparatus according to the present invention; Figure 6: shows a top plan view of the strap welding apparatus according to Fig. 5;

Figure 7: shows a partial section view, along a vertical plane passing along the line VIII shown in Figure 6, of the welding apparatus according to Figure 5;

Figure 8: shows a schematic perspective view of a front block with strap positioning slider of the apparatus according to Fig. 5, on a side, directed during use, towards the presser unit;

Figures 9-14: show schematic detailed views of a sequence of operations for welding strap ends by means of a welding apparatus of the present invention according to Fig. 5.

As shown in Figs. 1-4 and assuming solely for the purposes of easier description and without a limiting meaning a set of three reference axes, in the longitudinal direction X-X, parallel to a direction of feeding of the pipe to be coiled to a winding reel of the machine, transverse direction Y-Y, parallel to an axis of rotation of the reel, and vertical heightwise direction Z-Z of the machine, perpendicular to the other two preceding directions, an example of embodiment of a machine for coiling pipes 100 according to the present invention comprises:

- a unit (110) for winding pipes in coil form, comprising at least one rotating reel (111 ;112) for winding a pipe in coil form;

- a system 120 for binding the coil of wound pipe by means of a strap;

- a station (130) for dispensing the strap (1);

- a safety system.

As shown, the safety system forms a safety perimeter P which delimits a limited-access safety zone Z.

The safety system may for example comprise a plurality of structures 141 (barriers, doors, etc.) and devices (sensors, alarms, etc.) which overall form and monitor the safety perimeter P, preferably coordinated by a processing unit of the machine in a manner conventional per se.

In general terms, in the context of the present invention it is understood that the limited-access safety zone Z is a zone inside the safety perimeter and such that access by a foreign body, such as an operator O, inside the safety zone is permitted only in the presence of a predefined safety condition and/or produces a safety reaction by the safety system. The safety condition may for example be the fact that one or more units of the machine are not operative and preferably that the machine is completely stopped without winding operations in progress.

A safety reaction may for example comprise the activation of one or more alarms and/or safety countermeasures, such as in particular that the movement of one or more parts of the machine should not be allowed until the said coiling machine is in a safe completely stopped condition, which is the safety condition generally preferred and stipulated by the relevant standards.

As can be seen, the winding unit 110 and the unit 120 for performing binding of the coils of wound pipe by means of a strap 1 are arranged in the safety zone, whereby said units may be per se conventional.

The binding unit 120 is arranged and configured to retrieve the binding strap 1 from a strap dispensing station 130.

According to a first advantageous aspect of the present invention, the strap dispensing station 130 is arranged outside of the safety perimeter P and therefore of the limited-access safety zone Z. As will become clearer below, this allows the replacement of the strap store without the need for access by the operator inside the safety zone Z, with a consequent reduction in the downtime and the waste pipe which affected the machines of the prior art.

Although the strap dispensing station 130 is arranged in a lateral position on a longitudinal side of the coiling machine 100 and a point P1 for entry of the strap 1 into the safety zone is arranged on a rear lateral side of the safety perimeter P, it is understood that this arrangement constitutes only a preferred example and other arrangements are within the competence of the person skilled in the art.

With reference to Figs. 2-5, the preferred embodiment of the strap dispensing station 130 comprises:

- at least two strap dispenser units 131, 132, each designed to supply a strap from a respective store 131a; 132a, in particular in the form of a reel of wound strap which is unwound by means of rotation;

- an apparatus 150 for joining together two strap ends, in particular by welding one end together with the other end.

In greater detail, the first dispensing unit 131 is connected to the coiling machine so that the strap of the store 131a is supplied to the binding unit via the point P1 for entry into the safety perimeter P. A second strap dispensing unit 132 is ready to be connected to the binding system 120, in order to replace the first dispensing unit with its strap store 132a, when the strap store of the first unit is nearly depleted.

According to a further particularly advantageous aspect of the present invention, the dispensing station with joining apparatus 150 therefore allows the joining together, in particular hot-welding, of a rear end of the strap supplied from the store (reel) 131a of the first dispensing unit 131 to a front end of the strap supplied from the store (reel) 132a of the second dispensing unit 132, allowing in this way the strap 1 to be supplied in a substantially continuous manner to the coiling machine 100 without the need for access inside the limited-access safety zone Z and therefore without interrupting the pipe coiling and wound coil binding operations.

The two dispensing units 131, 132 are preferably arranged alongside each other in a direction parallel to the axis of the coils 131 a, 132a of strap. The apparatus 150 for joining together the strap ends may be arranged between the two dispensing units, for example arranged in a position situated at the top thereof in the vertical direction, as shown in Fig. 5.

Each strap dispensing unit 131 , 132 is able to allow the continuous unwinding of a strap 1 from the respective reel 131 a; 132a which for this purpose is mounted so as to be able to rotate about a respective axis relative to a fixed frame of the respective dispensing unit.

Each strap dispensing unit 131,132 may preferably comprise a plurality of jockey rollers 133 or alternative transmission means which act as a flywheel for more efficient continuous feeding of the strap to the access point P1 and to the unit 120 for binding the wound coil.

According to a particularly preferred embodiment, the apparatus for joining together the strap ends is a welding apparatus 150 according to the present invention which will be described in greater detail below.

The winding unit 110 may be of any known type designed to wind up pipes in coil form and cooperate with a binding unit for performing binding of the wound coil by means of a strap.

According to conventional technology, the winding unit 110 may for example comprise two winding reels 111 ;112 arranged alongside each other along a same transverse winding axis Y-Y and each designed to wind up in a coil a respective section of pipe (not shown) input by a pipe-guiding device. The two reels 111,112 are only schematically shown in Fig. 1 and not shown in Figs. 2-3.

The component parts of the winding unit are conventional and within the competence of the person skilled in the art and are therefore not illustrated nor described in detail.

The preferred machine according to the invention has a binding system 120 for binding by means of a strap (or "strapping") the wound coil, associated with one or more winding reels 111;112 and coordinated with the movements thereof.

The binding system, which is only schematically shown in Figs. 1-4, may comprise in particular a binding unit (not shown in full detail) which is activated, once winding has ended, in order to perform a plurality of operations for binding the coil in its heightwise direction (axis Y-Y); each binding operation is performed using a continuous strap which is unwound from the strap store 131a of the dispenser unit 131 connected to the binding system 120, made to pass across the jockey rollers 133 which act as a flywheel, fed inside the safety zone X via the entry point P1 and conveyed through a set of guide channels inside which it slides, for example being driven by motor-driven external rollers. For the binding operation, the strap rotates around the coil, forming a loop, which at this point is still loose and the free end of which returns to the starting point, entering into a clamping, welding and cutting device; at the same time, the binding unit advances, causing pulling of the strap and then closing of the loop around the coil; during the advancing movement, the excess strap of the free end of the loop is again taken up by the jockey rollers which assume again the initial position, thereby resetting everything for a new binding operation in a different position, defined by a suitable rotation of the reel.

This binding operation is made possible by the channel assembly, known per se, which comprises (Fig. 1) a plurality of internal half-channels distributed in various angular positions of each rotating reel 11, so that they remain always effectively inside the reel which, rotating, brings in succession each internal channel opposite external half-channels 120b which are instead arranged in a fixed angular position with respect to the two reels, so as to form the closed ring for guiding the strap during each binding operation. With reference to Figs. 5-8, a preferred example of embodiment of an apparatus 150 for joining together, by means of welding, strap ends 1a, 1b according to the present invention will now be described.

For the sake of easier description and without a limiting meaning, the following is assumed: a longitudinal direction of the apparatus, parallel to the direction of extension of the strap ends 1a, 1b to be welded, inserted inside the welding apparatus 150, a transverse direction Y-Y parallel to the thickness of the said strap ends 1a, 1b, and a vertical heightwise direction, parallel to the width of the strap; for the sake of easier illustration, these directions are assumed as corresponding to the directions X-X, Y-Y, Z-Z of the coiling machine shown in Figures 1-3, although, as already mentioned, the relative orientation of the dispensing station 130 and the welding apparatus 150 relative to the winding and binding units may be different.

Furthermore, a front side, provided with strap positioning means, and a rear side situated opposite each other in the transverse direction Y-Y, are defined.

This apparatus allows the welding together of the rear tail end 1a of the strap 1 of the reel 131a mounted in the first dispenser 131 and connected to the binding system, and the front end 1b of the strap 132a of the storage reel mounted in the second dispenser 132.

The welding apparatus 150 comprises:

- positioning means 151, 152, 153 configured for positioning of the strap ends parallel to each other, aligned in the vertical direction and superimposed in the transverse thickness direction Y-Y over a predefined length. The positioning means are also configured to allow insertion of the heating means between the superimposed strap ends;

-- strap-retaining means arranged to retain the strap ends 1a, 1b in position for joining by means of welding;

-- a heating unit 160 provided with heating means for heating the strap ends 1a, 1b designed to heat said ends, in particular to a temperature close to the strap melting temperature;

- a pressing unit 170, provided with a presser 173 movable in the transverse direction Y-Y between a position of non-interference and a pressing position where it presses against the strap ends 1a, 1b so as to press the superimposed and heated strap ends 1a, 1b against each other in order to join them together by means of welding. The positioning means comprise in particular a positioning slider 153 and strap-guiding channels 151 , 152, extending parallel to the longitudinal direction X-X on opposite sides of the positioning slider 153 and each configured to receive a respective one of the strap ends 1a, 1b to be joined together.

In greater detail, the welding apparatus 150 may for example comprise a fixed base 154 designed to be fixed to a strap dispensing station and preferably comprising two longitudinal/transverse planes 154a, 154b superimposed in the transverse direction with an interspace 154c between them.

The strap-guiding channels 151 ,152 are fixed to a front longitudinal side of the base 154, in particular to the top surface of the base 154. The strapguiding channels 151 ,152 are arranged on opposite sides of a central transverse axis VIII of the apparatus, so as to leave a space between them in the longitudinal direction.

A front block 157 (Fig. 10) which carries the positioning slider 153 and optionally an associated actuating unit (not shown) is fixed to the front longitudinal side of the base 154.

As can be seen, the positioning slider 153 may be arranged in the space situated in the longitudinal direction X-X between the two strap-guiding channels 151,152.

A vertical surface 157a of the front block 157 directed towards the presser 173 forms a fixed bearing surface for the movement of the said presser in the transverse direction Y-Y and is preferably arranged flush with an inner vertical surface on the front side of the strap-guiding channels 151,152.

The positioning slider 153 is movable in both senses of the vertical direction between a (raised) position for engagement with the strap ends 1a, 1b, where it keeps the strap ends in an aligned and superimposed position, and a (lowered) position for disengagement from the strap ends.

The slider 153 may comprise (Fig. 8) a plate extending in the vertical/longitudinal direction. The longitudinal faces of the plate, situated opposite each other in the transverse direction and respectively facing the presser 173 and the bearing surface 157a, preferably define a respective seat 153c for positioning a respective strap end.

In greater detail, each longitudinal face of the plate 153 may have a respective tooth 153a, 153b arranged at the longitudinal end of the slider opposite the respective strap-guiding channel 151 ; 152 and projecting outwards (namely towards the presser 173 or the surface 157a, respectively) in the transverse direction Y-Y so as to act as a bearing surface for the respective strap end 1a, 1b, forming in this way the respective inset seat 153c for positioning the strap end.

In order to facilitate insertion of the strap end 1b, 1a inside the respective seat 153c, the longitudinal end 153d of each seat 153c, situated opposite to the end provided with a tooth 153a, may preferably be formed as an inclined surface for assisting positioning, inside the respective seat 153c, of the strap end 1a, 1b which is guided by the respective strap-guiding channel 151 ; 152. The slider 153 may be actuated for the movement in the vertical direction by a respective actuating unit, for example comprising a cylinder with piston movable in the vertical direction Z-Z and firmly fixed to a bottom end of the slider.

According to a preferred embodiment, the strap-retaining means comprise a respective strap-retaining gripper (not shown), preferably situated inside a respective strap-guiding channel 151,152, actuated so as to open and close in the transverse direction Y-Y by suitable actuating means 155, for example of the pneumatic or hydraulic type.

Preferably, a pair of blocking springs 156, arranged above the strap-guiding channels on opposite sides in the longitudinal direction of the positioning slider 153, are movable (for example by means of rotation) between: a position for closing at the top a respective strap-guiding channel 151,152, where the associated strap end 1a, 1b is prevented from coming out in the vertical direction; and a position for disengagement from the respective channel, which allows the vertical insertion/extraction of a strap end inside the said channel.

The heating unit 160 comprises preferably a nose 161 with heating blade 161a, designed to be inserted between the aligned and superimposed strap ends. The nose 161 is movable between: a raised position in the vertical direction for disengagement from the strap ends, and a lowered position in which the heating blade 161a is arranged between the two superimposed strap portions.

The heating blade is in particular provided with heating means, in particular an internal resistance, designed to heat the blade and the therefore the strap to a predefined temperature; for example the temperature may be generally higher than 300°C, in particular about 450°C, and/or very close to the strap softening or melting temperature.

The operation for the raising/lowering movement of the nose 161 may be realized for example by means of actuating means, for example comprising a cylinder and piston unit which by means of an arm rotate the nose 161 about a longitudinal pin 164 inserted in supports 164a fixed to the base 154. Preferably the movement of the nose is coordinated with the movement of the positioning slider 153 so that, when the heating blade comes into contact with the positioning slider 153, the latter moves towards the position for disengagement from the aligned and superimposed strap ends, allowing insertion of the heating blade between them. Preferably, the (bottom) surface of the blade and (top) surface of the slider 153 which come in contact are configured with a complementary form so as to allow engagement in the vertical direction Z-Z.

The heating means are preferably activated once the blade and positioning slider are in contact with each other.

The pressing unit it comprises a presser 173 movable in both senses of the transverse direction Y-Y between a position for disengagement from the strap ends and a position for pressing against the strap ends, wherein the presser bears against the bearing surface 157a of the front block 157 and imparts to the heated strap ends, arranged between presser and bearing surface, a force designed to join them together stably.

The presser is displaced by actuating means, which may be conventional and are not shown in detail, for example comprising an actuating unit which operates a lever arm which, by means of the movement transmission means connected to the presser, moves the presser 173 in the transverse direction Y-Y.

Owing to the effect of the force exerted by the presser 173, the two hot strap ends are compressed against the bearing surface 157a with a force suitable for joining them together stably, preferably such as to define a thickness of the welded strap section substantially corresponding to the thickness of the single strap ends 1a, 1b. In particular, a force applied by the presser may be for example greater or equal to 9900 N.

Optionally, a protective housing 180 may be mounted on the base 154 and designed to rotate with respect thereto between an open position and a closed position in which it covers the zone of action of the presser and the heating means, preventing the access of foreign bodies during welding.

With this apparatus, a method according to the present invention for joining together strap ends may generally comprise the following steps:

.) positioning the strap ends aligned in the vertical direction and superimposed in the transverse thickness direction Y-Y over a predefined length;

.) retaining the strap ends 1a, 1b in position for joining together by means of welding;

.) inserting heating means between the superimposed strap ends and heating the said ends, in particular to a temperature close to, equal to or greater than the strap melting temperature;

.) pressing against each other in the transverse thickness direction Y-Y the superimposed and heated strap ends 1a, 1b by means of a presser 173 so as to perform joining together thereof by means of welding.

In greater detail and with reference to Figs. 9-14, a preferred example of embodiment of the method for joining together by means of welding a rear end 1a and a front end 1b of straps 1, performed with a welding apparatus 150 according to the present invention, comprises the following steps:

-) after raising and rotating the two retaining springs (Fig.9), a rear strap end 1a and a front strap end 1b are inserted inside a respective channel of the strap-guiding channels 151 ,152, bringing them in particular into abutment against the respective transverse tooth 153a of the positioning slider 153 (Fig. 9) so as to arrange the strap ends 1a1b with the respective end parts parallel, aligned and superimposed in the transverse direction over a suitable length, for example greater than or equal to 20 mm;

-) the retaining means (grippers inside the strap-guiding channels and retaining springs (156) are brought into the position for retaining the strap ends (Fig.10);

- optionally the protective housing 180 is lowered.

-) the heating blade 161 is operated, moving it towards the lowered position (Fig. 10) until the heating blade 161 is brought into contact with the recessed slider 153 (Fig.11);

-) the positioning slider 153 moves completely downwards into the disengaging position, where it releases the strap ends and allows the welding blade 161a to continue its lowering movement and be inserted between the said strap ends (Fig. 12);

-) the blade 161a inserted between the aligned and superimposed strap ends is heated by means of an internal resistance and heats the strap ends 1a, 1 b (Fig.13) to a suitable predefined temperature, in particular greater than or equal to about 300°C, preferably >450°C, close to the strap softening temperature;

-) the heating nose 161 is raised towards the disengaged position, releasing the strap ends which are hot and ready to be joined together by means of welding (Fig.14).

-) the presser 173 is displaced (Fig. 14) in the transverse direction Y-Y by means of the actuating means and advances until it bears against the opposite bearing surface 157a, imparting a force designed to stably join together the two hot strap portions, welding them together and flattening them; in particular, the presser 173 presses the strap ends together with a force which may be for example equal to about 9900 N;

-) the two strap ends 1a, 1b are now joined together by means of welding, the presser 173 is recalled into the disengaged position, freeing the welded strap 1 ;

-) it is now possible to raise the protective housing 180, rotate the retaining springs 156 inwards until they release the now joined strap and disengage the strap-retaining grippers of the strap-guiding channels 151 ,152;

-) the welded strap 1 is now free and may be extracted from the welding apparatus 150, for example vertically. The slider 153 returns into the raised position for positioning new strap ends to be welded.

Experimental tests have shown that the mode of implementation of the method described above may be realized in about 10 seconds.

The sequence of operations of the method for performing joining by means of welding according to the invention may take place while the winding unit is functioning normally. In fact, the method allows the rear end 1a of the old reel 131 to be welded together with the front end 1 b of the new reel 131 b; there is therefore no need to stop the winding unit in order to access the safety zone and insert the strap in the binding system 120. Stoppage of the machine is therefore eliminated.

Owing to the use of the high-temperature heating means and the presser 173, a particularly preferred embodiment of the apparatus or the method according to the invention allows the strap ends to be joined together by means of welding without increasing substantially the thickness of the strap in the region of the weld.

A significant increase in thickness of the strap in the region of the welding point would make the apparatus difficult to use in many known strap-binding systems, which have strap-receiving channels with a width the same as the normal thickness of the strap itself, in order to prevent, during normal operation, the strap from bunching up, being deviated or jamming owing to the excessive width of the strap-guiding channels.

It is therefore particularly preferred that the two strap ends should be heated to nearly the melting temperature and that, by means of the action of the mechanical presser and the force applied, the two ends should be pressed against each other so as to obtain a thickness of the weld corresponding to the normal thickness of the strap.

With the aforementioned configuration the functioning of the coiling machine may be per se conventional as regards the winding and binding operations, however a strap supplying process according to the invention allows strap to be continuously fed to the binding system 120, without having to stop the machine 100 or access the safety zone Z, for example in accordance with the following operating steps:

- supplying the strap to the binding system from the first strap store (131a), in particular a strap coil, by means of the first dispensing unit (131);

- before the first strap store 131a becomes depleted: joining, in particular by means of hot-welding, a rear end 1a of the first strap store 131a together with a front end 1b of a second strap store 132a, in particular a second strap coil, mounted in the second dispensing unit 132;

- after the first strap store has become depleted: continuing to continuously supply strap 1 to the binding system 120 by means of the second dispensing unit 132 which unwinds from the second strap store 132a the strap whose front end 1b is joined to the rear end 1a of the first strap store. At this point it is the second dispensing unit which is connected so as to supply the binding system 120.

The first strap store 131a, once depleted, may be replaced by a new strap store, the front end of which will be joined to a rear end of the second strap store 132a currently performing supplying, before the said second store becomes depleted. The operation may be repeated as many times as needed in order to ensure the continuous supplying of strap to the coiling machine during the cycle for winding pipe into coils.

The joining together of the strap ends is preferably performed by a welding apparatus according to the invention described above.

According to a preferred aspect, for example in order to avoid complex operations involving extraction of the rear strap end of the supplying strap store 131a from the respective dispenser 131 and/or the passage of the front strap end 1b welded to it through the dispenser 131 of the preceding rear end 1a, a free rear end 1a of the strap 1 being supplied to the binding system may be advantageously obtained by cutting the strap 1 itself downstream of the associated dispenser 131 and upstream of entry point P1 into the safety zone Z. This operation may for example be performed when the store 131a for the strap 1 being supplied to the binding system is nearly depleted. Advantageously, a signalling system of the dispenser 131 may signal the imminent depleted condition of the store 131a suitably in advance, so as to allow cutting of the strap 1, resulting in a free rear end 1a, and welding thereof to the front end 1b of the strap provided in the second dispenser 132, during a subsequent step for winding the pipe in coil form, during which the binding system does not require, nor removes, the strap supplied by the strap dispensing unit 130.

Although not described in detail, it is envisaged that all the movements and synchronisms of the coiling machine and the strap-welding apparatus may be programmed and controlled by means of a processing unit, which controls the servomechanisms and the various units, including the safety system, and sends commands upon receiving corresponding signals from various position sensors and timers, with which the machine is equipped in a conventional manner.

It is therefore clear how with the welding apparatus and the method for joining strap ends according to the invention it is possible to join together stably the strap ends of different strap stores, allowing the substantially continuous supplying of binding strap to a binding system.

In addition to this, with a dispensing station or coiling machine according to the present invention it is possible to perform substantially continuous winding and binding cycles, without having to stop the winder in order to replace a strap store. Owing to the preferred embodiments described which are able to ensure a thickness of the welded zone of the strap substantially corresponding to the nominal thickness of the single strap ends, the solutions according to the present invention are adaptable also to existing binding systems where the strap guiding channels have dimensions substantially corresponding to the thickness of the strap itself, thereby avoiding jamming of the strap and the need to modify the existing systems with complicated modifications in order to allow the passage of a strap section with a larger thickness.

Although described in connection with a number of embodiments and a number of preferred examples of implementation of the invention, it is understood that the scope of protection of the present patent is determined solely by the claims below.