Method and device for welding profiled elements made of a plastic material, in particular PVC

The method for welding profiled elements made of a plastic material, in particular PVC, comprises the steps of:

RELATED APPLICATIONS

This application is a National Phase of PCT Patent Application No. PCT/IB2014/058769 having International filing date of Feb. 4, 2014, which claims the benefit of priority of Italian Patent Application No. MO2013A000024 filed on Feb. 5, 2013. The contents of the above applications are all incorporated by reference as if fully set forth herein in their entirety.

TECHNICAL FIELD

The present invention relates to a method and relative device for welding profiled elements made of a plastic material, in particular PVC.

BACKGROUND ART

In the state of the art, the PVC profiled elements, mainly used as window and door frames, are welded together by means of the melting of respective head surfaces in order to make a frame structure fittable to doors or windows.

In particular, the melting is done by heating the portions to be connected using suitable electric heating plates and then pressing the heated portions the one against the other to favour their welding.

Generally, the heated portions are the head extremities of the profiled elements, suitably cut at 45° to define e.g. a right-angled portion of a respective window or door frame.

This method is carried out by welding machines equipped with respective retaining members of the profiled elements, mobile in a reciprocal closer moving direction to bring the heated extremities to be welded into contact.

Other machines are equipped with finishing systems, suitable for removing the bead or welding bead which forms during the melting of the two profiled elements.

In fact, in correspondence to the joining line of the two profiled elements (surfaces cut at 45°), the portion of melted material in excess comes out and goes to form a bead protruding from the visible surface of the profiled elements.

For this reason, in order to give the finished door or window frame an appreciable aesthetic appearance, once welded, the profiled elements undergo a removal operation of the melted bead.

The known welding devices briefly described do however have major drawbacks mainly tied to the formation of the above-mentioned welding bead.

It must in fact be considered that the welding zone of the PVC profiled elements is not perfectly uniform and parallel to the reciprocal profiled element, and consequently, to make the faces even, a lot of material is melted with the consequent formation of an abundant bead, and there is consequently a lot of waste material to be removed.

Furthermore, the finishing jobs for removing the bead and cleaning the welding zone have a strong effect on the total time required to machine the door or window frame. It should be realized in fact that for every door or window frame welding operation, the profiled elements have to be subsequently machined. Furthermore, in the case of spoked profiled elements, the removal of said bead is very complicated.

Furthermore, the machinery used for the above-mentioned finishing operations is cumbersome and particularly expensive.

This results in the need to sustain additional costs and work times because of the presence of further cumbersome equipment and tools.

SUMMARY OF THE INVENTION

In this context, the technical aim underlying the present invention is to propose a method and relative device for welding profiled elements made of a plastic material, in particular PVC, which overcomes the drawbacks of the above-mentioned state of the art.

In particular, the object of the present invention is to provide a method and relative device for welding two profiled elements made of a plastic material, in particular PVC which are able to eliminate all subsequent additional operations suitable for removing the welding bead.

A further object of the present invention is to provide a method for welding profiled elements made of a plastic material, in particular PVC, that is fast and cheap compared to a welding line and subsequent cleaning.

The above objects are substantially achieved by a method and relative device for welding profiled elements made of a plastic material, in particular PVC, comprising the technical specifications stated in any of the enclosed claims.

DESCRIPTION OF SPECIFIC EMBODIMENTS OF THE INVENTION

With particular reference to the figures enclosed, indicated by1is a device for welding profiled elements made of a plastic material, in particular PVC.

Such device implements a method for welding profiled elements made of a plastic material, in particular PVC, wherein are arranged at least two profiled elements3, with respective zones to be welded4facing one another.

As will be better specified below according to the method, a groove19is made in correspondence to each zone to be welded4of the profiled elements3by means of a removal operation (milling, melting, chamfering, etc.).

Subsequently, the zones to be welded4are heated and coupled by pressing the profiled elements3one against the other to keep the zones to be welded4in reciprocal contact. This way, the grooves19of the two profiled elements3define a containing compartment19afor containing a bead or welding bead produced during the melting of the respective profiled elements3.

In the rest of the present description, a single welding device1will be illustrated suitable for welding the extremities of the two respective profiled elements. Nevertheless, the present invention can comprise a series of devices1, each of which operating on a respective extremity of a profiled element3. For example, to make a rectangular frame to be used as a door or window frame, four devices1are used, each intended to weld the profiled elements3in correspondence to right angles of the mentioned frame.

With reference toFIG. 1it should be noted that the device1comprises a pair of retaining members2of respective profiled elements3made of PVC, suitable for engaging the profiled elements3themselves with corresponding zones to be welded4facing one another.

In particular, each retaining member2comprises a base portion5on which the profiled element3is positioned, and a mobile portion6arranged above the base portion5. The mobile portion6is suitably moved to shift towards the base portion5and thus retain the profiled element3.

As can be seen on the attached illustrations, each profiled element3is therefore arranged between the base portion5and the mobile portion6, with the respective head extremity protruding. The head extremities of the profiled elements make up the zones to be welded4and for this reason they are facing one another.

It should also be noted that the zones to be welded4are suitably cut at 45° to define a coupling resulting between two right-angled profiled elements.

Moreover, the device1comprises movement means7of the retaining members2, to shift the profiled elements3between a first reciprocal away position and a second reciprocal closer position wherein the zones to be welded4are coupled together.

In particular, for each retaining member2, the movement means7have a sliding guide8, extending parallel to the longitudinal extension of the profiled element3. On the sliding guide is fitted a carriage9integral with the aforementioned base portion5. Furthermore, each carriage9is coupled with a movement system10suitable for moving both the carriages9of the retaining members2reciprocally closer/away.

The device1also comprises heating means11for heating the aforementioned zones to be welded4of the profiled elements3made of PVC. The heating means11are preferably mobile between an active condition wherein they are placed between the profiled elements3, and a non-use condition wherein they are moved away from the profiled elements3.

In particular, it should be noted that when the profiled elements3are arranged by the movement means7in reciprocal away moving direction, they define a transit zone of the heating means11. This way, once the zones to be welded4have been heated, the profiled elements3are moved closer together and pressed with the respective extremity heads against one another.

Advantageously, the heating means11comprise a hot-plate heat-sealing element12, made up e.g. of a substantially plate-shaped electric resistance, fitted on a movement element13. Preferably, the movement element13is composed of a pair of carriages14mounted sliding in respective rails15and each of which arranged on opposite sides of the aforementioned resistance12. This way, the resistance12is fastened to the carriages14and moved by these along the rails15. The carriages14are also operatively connected to a motor16, by means of a connecting rod-crank17. Advantageously, the connecting rod-crank17transforms the rotary motion given by the motor16into a back and forth motion of the carriages14and of the resistance12to fit/remove the electric resistance12between/from the above-mentioned profiled elements3. The device1is also equipped with removing means18to make at least one groove19on the peripheral edge of at least one zone to be welded4.

The removing means18are, e.g., of the milling type and comprise a supporting frame20placed above the retaining members2, and at least a machining tool21, facing a profiled element3to make the above-mentioned groove19on the zone to be welded4.

The tool21is moved in rotation by a motor part22preferably of the electric type and miniaturized, brushless sensorless motor with very high rotation speed. Furthermore, the tool21is moved by a movement member23, between a first idle condition (position in which it is not placed between the profiled elements3) and a second working condition in which it is placed between the profiled elements3made of PVC.

In greater detail, the removing means18by milling preferably comprise a pair of machining tools21, each of which equipped with an active head21aon the peripheral edge of a respective zone to be welded4.

As illustrated in the detail views, the tools21are opposite one another to work at the same time on both the profiled elements3.

In other words, the two tools21rotate around the same rotation axis on opposite sides of the supporting frame20; this way, the movement of the supporting frame20permits controlling the forward movement of the tool21working on a zone to be welded4and of the other tool21working on another zone to be welded4.

The groove19obtained by each tool21has a substantially stepped conformation in square, i.e., shaped at 90°, which extends along the entire extension of the zone to be welded4.

The containing compartment19adefined by bringing the grooves19made this way alongside is delimited by a base wall60and by a pair of opposite side walls61.

The base wall60is substantially horizontal while the side walls61are substantially vertical.

Furthermore, the frame20has a supporting bar24arranged above the retaining members2and designed to support the tools21which in this situation are mounted on a lower extremity of the bar24itself.

The bar24is operatively connected to the movement member23to be moved in correspondence to the zones to be welded4.

Advantageously, the tools21are positioned in correspondence to the side edge of the zone to be welded4by means of the movement of the above-mentioned movement member23.

In particular, the member23comprises a pair of supporting guides25on which the bar24is mounted sliding and moved by a known motor not described in detail.

Furthermore, the bar24is moved vertically by means of an axis with wormscrew26arranged in correspondence to the frame20.

Advantageously, both the tools21and the motor part22are supported by the bar24and are mobile with it both horizontally (along the guides25) and vertically (by means of the wormscrew26).

The device1also has a vortex suction system29a,29bconcentric with the tool21which permits removing the shavings which form during the removal operation by milling.

The suction system29a,29b, e.g., consists of a chamber29awhich is arranged around each tool21and which is connected to a suction duct29bwhich moves the shavings away.

For this purpose, furthermore, the tool21consists of a helical-shaped cutter that conveys the removed shavings towards the inside of the chamber29ato make suctioning the shavings easier.

Advantageously, all the shavings in plastic material produced by the removal operation by milling are easily suctioned.

The device1also has pressing means27,28suitable for abutting on the grooves19to define, in collaboration with the grooves themselves, the containing compartment19a.

The pressing means27,28, in fact, are meant to close the side of the containing compartment19aopposite the base wall60and adjacent to the side walls61, so as to prevent any melted material coming out of the compartment itself. The pressing means27,28, in particular, comprise:at least a first work surface62having a protruding portion63; andat least a second work surface64of final finishing.

The pressing means27,28cooperate with the operating means65,66suitable for displacing the pressing means27,28alternately between:an idle position moved away from the profiled elements3;a first work position wherein the first work surface62is abutted on the grooves19with the protruding portion63located at least in part inside the containing compartment19ato deviate the welding bead towards the side walls61of the containing compartment19a; anda second work position wherein the second work surface64is abutted on the grooves19so as to obtain a finished welding bead.

The pressing means27,28comprise at least a containing presser27,28having both the first work surface62and the second work surface64.

Alternative embodiments cannot however be ruled out wherein the first work surface62and the second work surface64are mounted on components distinct the one from the other and separately mobile.

In the embodiment of the device1shown in the illustrations, the pressing means27,28comprise a pair of containing pressers27,28, facing one another on opposite sides (above and below) with respect to the plane on which the profiled elements3lie.

In particular, a first containing presser27is arranged above the profiled elements3and herein after may be called upper containing presser, while a second containing presser28is arranged below the profiled elements3and herein after may be called lower containing presser.

Both the containing pressers27,28are mobile in reciprocal closer moving direction to define, in collaboration with the grooves19, two containing compartments19aobtained on opposite sides of the profiled elements3so as to contain and limit the material coming out of the compartments themselves.

It will in fact be noted that the grooves19are applied for the externally visible portions of the profiled elements3, i.e., the upper and lower edges of the faces cut at 45° which when welded the one to the other determine the formation of a protruding welding bead.

In this situation, the bead does not come out of the containing compartment19abut is contained inside it.

Each containing presser27,28comprises a rod68which extends along a longitudinal direction A substantially parallel to the grooves19.

In particular the longitudinal direction is substantially horizontal.

The rod68is rigid and made, e.g., of steel.

For each containing presser27,28, the rod68comprises a first longitudinal face69in correspondence to which the first work surface62is arranged and a second longitudinal face70in correspondence to which the second work surface64is arranged.

The first longitudinal face69and the second longitudinal face70are substantially opposite and parallel to one another.

The first work surface62is defined by an insert71associable with the first longitudinal face69, e.g., by means of gluing.

The insert71is rigid and made, e.g., of hard plastic.

The first work surface62has a flat portion72from which the protruding portion63extends.

The protruding portion63extends longitudinally along the substantial totality of the rod68.

In the transversal section, instead, the protruding portion63has a pair of cavities73which, in the first work position, are placed substantially facing the side walls61of the containing compartment19a.

The presence of the cavities73, in other words, results in the transversal section of the protruding portion63being in undercut.

More in detail, the protruding portion63has a transversal section substantially shaped like an isosceles trapezium with a projecting longer base.

In this respect, it is underlined that, within the scope of the present treatise, the expression “projecting longer base” means that the lesser base of the trapezium is defined in correspondence to the flat portion72while the isosceles sides of the trapezium extend projecting from the flat portion72and stretch underneath the longer base of the trapezium which, therefore, with respect to the flat portion72, is placed in distal position.

In this embodiment, the cavities73of the transversal section of the protruding portion63are defined between the isosceles sides of the trapezium and the flat portion72.

Alternative embodiments cannot however be ruled out wherein the transversal section of the protruding portion has a different conformation.

TheFIG. 12, e.g., shows an embodiment wherein the transversal section of the protruding portion63is substantially rectangular.

The second work surface64is defined by a sheet-shaped element74suitable for abutting on the grooves19and by a shock-absorbing element75supporting the sheet-shaped element74.

The sheet-shaped element74consists, e.g., of a metal blade of reduced thickness or flexible hard plastic.

The shock-absorbing element75, on the other hand, is a layer made of a yielding material, e.g., rubber, placed between the second longitudinal face70and the sheet-shaped element74.

In the embodiment shown in the illustrations, the second work surface64is substantially flat and permits obtaining a substantially flat finished welding bead.

Alternative embodiments cannot however be ruled out wherein the second work surface64has protrusions and/or recesses to reproduce a particular shape on the hot piece that has just been worked. The still hot material, in fact, is easily pliable.

It is also easy to appreciate that in the presence of profiled elements3with spoked visible surfaces, the first work surface62and the second work surface64are shaped so as to follow the form of the visible surfaces.

In this respect, it is underlined that, usefully, the containing pressers27,28are releasable from the rest of the device1and replaceable with containing pressers27,28having diversified shapes depending on the type of profiled elements3to be welded.

The operating means65,66comprise at least a shift unit65to shift the pressing means27,28along a direction B transversal to the direction of movement of the profiled elements3.

The transversal direction B is substantially at right angles to the plane on which the profiled elements3lie and, therefore, vertical.

TheFIGS. 1aand 1bshow in detail only the shift unit65meant to translate the upper containing presser27.

Such shift unit65is defined by a vertical pneumatic cylinder having a mobile extremity to which a supporting element76is fitted.

Alternative embodiments of the shift unit65are however also possible.

The operating means65,66also comprise at least a rotation unit66suitable for rotating the rod68of the containing pressers27,28around the longitudinal direction A and alternately turning the first work surface62and the second work surface64towards the grooves19.

Considering that the first work surface62and the second work surface64are mounted on opposite faces of the rod68, then the rotation unit66is suitable for rotating the rod68around itself by 180°.

Alternative embodiments cannot however be ruled out wherein the work surfaces62,64are arranged on adjacent and contiguous faces of the rod68, in which case the rotation of the rod68is reduced to just 90°.

TheFIGS. 1aand 1bshow in detail only the rotation unit66meant for the rotation of the upper containing presser27.

Such rotation unit66is defined by a rotary motor positioned between the supporting element76and a grip extremity77of the rod68.

Alternative embodiments are however possible for the rotation unit66such as, e.g., in the event of its consisting of a crank mechanism made by means of an actuator cylinder and a lever.

The device1, described above in prevalently structural terms, implements a welding method which is the subject of the present invention.

The method comprises the steps of preparing at least two profiled elements3, arranged with the respective zones to be welded4facing one another, in correspondence to the retaining members2.

Then, the grooves19are made in correspondence to each zone to be welded4of the profiled elements3.

The step of making the grooves19is performed by means of a removal operation of material on the peripheral edges defined by the head extremities of each profiled element3.

This removal is done by milling by means of the tools21.

During the removal step, a retention step is performed of the shavings by means of the tool21with helical shape and the axial suction which conveys the removed shavings towards the inside of the chamber29a.

The zones to be welded4are subsequently heated, by pressing them on the opposite sides of the hot-plate heat-sealing element12, and coupled together by pressing the profiled elements3one against the other.

The coupling of the zones to be welded4occurs keeping them in reciprocal contact to melt them together and define the welding bead.

During the coupling of the zones to be welded4, the sub-step is performed which consists in arranging the pressing means27,28in correspondence to the grooves19to define, in collaboration with the grooves themselves, the containing compartments19aof the welding bead.

Such sub-step occurs by means of the operating means65,66, which alternately move the pressing means27,28among the idle position, the first work position and the second work position.

In such sub-step, both the containing pressers27,28operate, and are arranged on opposite sides, above and below the profiled elements3.

TheFIGS. 8, 9, 10 and 11show the operation of only the upper containing presser27, but it is easy to appreciate by analogy also that of the lower containing presser28.

Once the zones to be welded4have been brought closer together, the containing pressers27,28are moved from the idle position to the first work position thanks to the operation of the shift units65which move the pressing means along the transversal direction B.

This way, the first work surface62of each containing presser27,28abuts on the grooves19with the protruding portion63inside the relative containing compartment19a(FIG. 8).

The welding bead created by the relative closer moving of the profiled elements3stands up at the centre of the containing compartment19auntil it comes into contact with the protruding portion63, which deviates it towards the side walls61until the cavities73have been filled (FIG. 9).

The presence of the protruding portion63is crucial for the purpose of completely and correctly filling the entire containing compartment19awith the melted plastic material forming the welding bead.

In this respect, it is underlined that in the absence of the protruding portion63the welding bead tends to remain at the centre of the containing compartment19aand reach the side walls61much later, when the material has already started to solidify, determining a filling of the containing compartment19awhich is not always optimal and, in any case, in a non-functional way.

Subsequently, the containing pressers27,28are moved away from the profiled elements3along a transversal direction B.

The undercut defined by the trapezoid shape of the protruding portion63determines a slight lifting of the two lips78of the plastic material which had previously occupied the cavities73and which, being still in a softened state, is easily deformable (FIG. 10).

At this point, the containing pressers27,28are moved and made to rotate around the longitudinal direction A to turn the second work surface64towards the grooves19instead of the first work surface62, and moved closer to the profiled elements3until they are arranged in the second work position.

In this position, the sheet-shaped element74pushes downwards and evens out the lips78which had previously lifted up and curbs any outward thrusts by the welding bead.

In this step in fact, the zones to be welded4of the profiled elements3continue to move closer and the melted plastic material continues to form until the containing compartment19ais completely full and the lips78are alongside (FIG. 11).

All the sub-steps shown in theFIGS. 8, 9, 10 and 11are performed quickly and within times such as to prevent the solidification of the melted material before the containing compartment19ais completely full.

In this respect it is underlined that in the second work position the presence of the shock-absorbing element75permits distributing, in a uniform and homogeneous way along the entire containing compartment19a, any internal pressure produced inside the grooves19during the operation.

The present invention achieves the proposed objects.

In particular, the possibility of maintaining the welding bead inside the containing compartment defined by the two grooves prevents excess material coming out.

Consequently, all the surface finishing jobs suitable for removing excess material are eliminated, with the consequent advantages in terms of time, energy and saving relating to the use of further machinery.

To this must be added that, thanks to the alternate intervention of the first work surface with protruding portion and of the second work surface of final finishing, the end result on the profiled elements is aesthetically excellent and far superior to any welding method and device of known type.