GB2596619A

GB2596619A - Machine for welding plastic profiled elements

Info

Publication number: GB2596619A
Application number: GB2100476.7A
Authority: GB
Inventors: Vaccari Andrea
Original assignee: Graf Synergy SRL
Current assignee: Graf Synergy SRL
Priority date: 2020-01-17
Filing date: 2021-01-14
Publication date: 2022-01-05
Anticipated expiration: 2041-01-14
Also published as: WO2021144731A1; EP4090518A1; GB202100476D0; IT202000000889A1; GB2596619B; CN114945457A

Abstract

A machine for welding plastic profiled elements 5 (such as for PVC window or door frames) comprises:- one supporting base extending along a first direction (X); at least one lateral welding device (3, fig 2) provided with one lateral heating plate (13, fig 2) adapted to heat a main profiled element and a respective lateral profiled element (6, fig 2); at least one intermediate welding device (4, fig 3) provided with an intermediate heating plate (18, fig 3) shaped in a “V” pattern and adapted to heat the main profiled element and a respective transverse profiled element, in which the main profiled element comprises one pair of intermediate areas to be welded 19, contiguous to each other to form a “V”-shaped concavity 20, and the transverse profiled element comprises, at the point where at least one end is located, a pair of transverse areas to be welded, contiguous to each other to form a “V”-shaped convexity substantially complementary to the concavity; and detection means 33 of the concavity for the positioning of the intermediate welding device along the first direction (X) with respect to the concavity. The detection means preferably comprises a light emitter 34, which may be a laser spacer device with means for sensing the distance of a portion of the concavity illuminated by a beam of the light.

Description

MACHINE FOR WELDING PLASTIC PROFILED ELEMENTS DESCRIPTION

The present invention relates to a machine for welding plastic profiled elements.

More in detail, the present invention relates to a welding machine provided with three or more in-line welding devices for the realization of windows/doors made of plastic material, in particular PVC.

These windows/doors consist of a series of profiled elements made of plastic material, usually formed by extrusion or similar techniques, which 10 are welded together in order to create a frame-shaped framework, within which a central panel made of glass or other material can be positioned.

For some types of windows/doors, especially if of considerable size and/or for design and aesthetics reasons, it may be necessary to build a frame-shaped framework provided with one or more crosspieces, better described below, which aim to make the finished window/door more stable and robust and/or to obtain a different door/window design and/or to divide the door/window into fixed/closed portions and movable/openable portions.

In order to optimize the processing times of these windows/doors, machines are known for welding plastic profiled elements provided with three or more welding devices arranged in line, able to weld a main profiled element with three or more secondary profiled elements at the same time.

The secondary profiled elements are divided into two lateral profiled elements, intended to define a peripheral frame of the window/door 25 together with the main profiled element, and one or more transverse profiled elements, intended to create an internal frame of the window/door itself.

For this purpose, then, the main profiled element is cut at each end to define a respective area to be welded, preferably inclined at 450 with respect to the longitudinal direction of the profiled element itself, and, similarly, the lateral profiled elements are cut at the respective ends to define a corresponding area to be welded at 45°.

The main profiled element is further shaped, e.g. by means of a cutting operation, in an intermediate position so as to define two areas to be welded which are inclined with respect to the longitudinal direction of the profiled element itself and contiguous to each other, to form a concavity; the transverse profiled element, on the contrary, is cut at the ends so as to define two areas to be welded contiguous to each other to form a convexity, complementary to the aforementioned concavity.

The welding machines of known type are provided with lateral welding devices, responsible for welding the lateral profiled elements to the main profiled element, and with intermediate welding devices, responsible for welding the transverse profiled elements to the main profiled element.

In particular, the machines of known type have a supporting base on which 20 the welding devices are movable according to the dimensions of the main profiled element and to the position of the areas to be welded defined thereon.

The welding devices are placed side by side and are connected to each other in line and define a working area that extends along a longitudinal 25 direction along which they can be moved with respect to each other.

In particular, the lateral welding devices and the intermediate welding device are movable in mutual close/away movement to position themselves at the point where the respective areas to be welded of the main profiled element are located.

In addition, the welding devices are provided with retaining members of the profiled elements, movable in mutual approach to bring the respective areas to be welded into contact.

The welding of the main profiled element to the secondary profiled elements is carried out by heating and melting the areas to be welded by 10 means of suitable electric resistance plates and then pressing the areas to be welded against each other to form welding areas.

For this purpose, the intermediate welding device is conveniently provided with "V"-shaped heating plates, so as to simultaneously heat both the concavity of the main profiled element and the convexity of the transverse 15 profiled element.

The machines for welding the profiled elements described above can be used both for the simple construction of a peripheral frame and for the construction of a frame with crosspieces.

For the construction of a peripheral frame, only the lateral welding devices are used or, alternatively, one of either the lateral welding devices or the intermediate welding device conveniently adapted so as to allow welding the ends cut at 450 of the profiled elements; for the construction of a frame with crosspieces, instead, both lateral welding devices and also the intermediate welding device are used.

The welding machines of known type do have, however, some drawbacks.

In fact, for the construction of a peripheral frame, one of the welding devices is not used and can clutter the working area by interfering with the movement of the profiled elements.

In addition, especially in the case where the main profiled element is small, 5 the intermediate welding device may be an obstacle to the approach of the lateral welding devices, thus preventing the correct machining of the window/door.

A further drawback of the machines for welding profiled elements of known type occurs in the construction of a frame with crosspieces, wherein 10 it is necessary to correctly position the intermediate welding device with respect to the concavity made on the main profiled element.

It is in fact essential to position the intermediate welding device extremely precisely with respect to the concavity of the main profiled element and, at the same time, the transverse profiled element with respect thereto to 15 ensure that the welding is effective and robust.

Wrong positioning can lead to important defects in the welding of the transverse profiled element, thus affecting the entire machining of the win dow/door.

Finally, the machines of known type must be unconveniently combined 20 with finishing machines which are adapted to remove the welding bead that is formed during the fusion of the profiled elements.

In fact, at the welding area of the profiled elements, the portion of excess molten material escapes and forms a bead protruding _from the visible surface of the profiled elements.

For this reason, in order to give the finished window/door an appreciable aesthetic appearance, the profiled elements, after being welded, must be transferred onto the finishing machines to undergo a welding bead removal operation.

This process of removing the welding bead considerably affect the costs and timing of the window/door construction and, moreover, can be extremely complex to carry out, especially in the presence of radiused and/or curved surfaces, with the risk of causing damage and/or aesthetic defects at the point where the welding areas are located.

In this regard, the patent application WO 2013/132406 Al partly solves this drawback and, in fact, it describes a welding device provided with removal means adapted to make a groove on the peripheral edge of the area to be welded so that, following the welding of the profiled elements, the welding bead extends towards the inside of the profiled elements and is therefore not visible on the visible surface of the window/door.

However, this device is applied to the welding of the corners of the peripheral frame and is susceptible to further upgrades aimed at adapting the removal process also to an intermediate welding device for a transverse profiled element.

The main aim of the present invention is to devise a machine for welding plastic profiled elements that is easily adaptable to the shape of the main profiled element and, in particular, to the position of the concavity thereof In this regard, one object of the present invention is also to devise a machine for welding plastic profiled elements in which it is possible to correctly position the transverse profiled element at the point where the concavity defined on the main profiled element is located.

Another object of the present invention is to devise a machine for the welding of plastic profiled elements that is particularly versatile and that 5 allows carrying out the welding operations in a practical and easy way regardless of the length of the main profiled element.

A further object of the present invention is to devise a machine for welding plastic profiled elements that allows eliminating the need to transfer the welded profiled elements to finishing machines adapted to remove the 10 welding bead.

Another object of the present invention is to devise a machine for welding plastic profiled elements that allows overcoming the above mentioned drawbacks of the prior art in a simple, rational, easy, effective to use and affordable solution with compact dim en si on s.

The above mentioned objects are achieved by the present machine for welding plastic profiled elements having the characteristics of claim 1.

Other characteristics and advantages of the present invention will be more evident from the description of a preferred, but not exclusive, embodiment of a machine for welding plastic profiled elements, illustrated by way of an indicative, yet non-limiting example, in the attached tables of drawings in which: Figure 1 is an axonometric view of a machine for welding plastic profiled elements according to the invention; Figure 2 is a detailed axonometric view of a lateral welding device 25 according to the invention; Figure 3 is a detailed axonometric view of an intermediate welding device according to the invention; Figure 4 is a lateral schematic representation of a machine for welding plastic profiled elements according to the invention; Figures 5-13 are axonometric detailed views of an intermediate welding device according to the invention; Figures 14-17 schematically represent the operation phases of an intermediate welding device according to the invention.

With particular reference to these figures, reference numeral I globally 10 indicates a machine for welding plastic profiled elements.

The machine 1 can be used for welding profiled elements 5, 6, 7 made of plastic material, preferably of PVC, for the construction of a window/door. It cannot, however, be ruled out that the profiled elements 5, 6, 7 are made of a heat-sealable plastic material other than PVC and/or of a plastic material loaded with a reinforcement material, e.g. in the form of fibers such as glass fibers or the like. Embodiment solutions cannot also be ruled out wherein the profiled elements 5, 6, 7 are partly made of plastic and partly of a different material, in a similar way to some well-known materials which, e.g., are provided with a canopy, an external covering or an inner core made of metal, wood or the like.

The machine 1 for welding plastic profiled elements comprises at least one supporting base 2 extending along a first direction X, at least one lateral welding device 3 and at least one intermediate welding device 4 associated with the supporting base 2.

In particular, in the embodiment shown in the figures, the machine 1 comprises two lateral welding devices 3.

The lateral welding devices 3 are adapted to weld a main profiled element 5 to the respective lateral profiled elements 6, which form a peripheral frame 5 of the window/door.

The intermediate welding device 4, on the other hand, is adapted to weld the main profiled element 5 to a transverse profiled element 7.

In the embodiment shown in Figure 1, the machine 1 comprises a plurality of intermediate welding devices 4, adapted to weld a corresponding number of transverse profiled elements 7 to the main profiled element 5; the intermediate welding devices 4 are equal to each other and, for the sake of simplicity, in the following of the present discussion we will refer to only one intermediate welding device 4 and to only one transverse profiled element 7, the description of an intermediate welding device 4 and of the relevant transverse profiled element 7 being also valid for the others.

An overall volume is defined between the lateral welding devices 3.

The main profiled element 5 is positioned inside the overall volume, in a working area that extends along the first direction X. For the purposes of the present description, the term "overall volume" 20 means the machining area of the profiled elements 5, 6, 7 and consists of the volume occupied by the lateral welding devices 3 and of the space defined between them.

Each lateral welding device 3 comprises at least one lateral frame 8, associated with the supporting base 2, and one lateral machining assembly 9, associated with the lateral frame 8, for the machining of the main profiled element 5 and of the lateral profiled element 6.

The lateral machining assembly 9 comprises retaining means of the lateral profiled element 10.

The retaining means of the lateral profiled element 10 are of the type of a vice operated by a piston-operated cylinder.

The lateral machining assembly 9 also comprises lateral retaining means 11 of the main profiled element 5.

The lateral retaining means 11 are of the type of a vice operated by means 10 of a piston-operated cylinder.

The lateral welding device 3 comprises lateral displacement means 12 of the lateral retaining means 11 to displace the main profiled element 5 between at least one position away from the lateral profiled element 6 and at least one position closer to the lateral profiled element 6, wherein the main profiled element 5 and the lateral profiled elements 6 are welded together, as better described below.

The lateral displacement means 12 allow precise and accurate movement of the main profiled element 5 with respect to the lateral profiled element 6. The lateral welding devices 3 are provided with at least one lateral heating plate 13 adapted to heat at least the main profiled element 5 and a respective lateral profiled element 6.

The lateral heating plate 13 is mounted on the lateral machining assembly 9 and is of the type of an electric resistance plate, flat shaped.

The lateral heating plate 13 is adapted to melt at least partly the plastic material of the profiled elements 5, 6, which are then joined and pressed together to bring the melted plastic material into contact.

After having cooled down, the plastic material hardens and holds the 5 profiled elements joined together.

For this purpose, the profiled elements 5, 6 are provided with areas to be welded at the respective ends.

In the ambit of the present discussion, the term "area to be welded" refers to a surface of the profiled element obtained by cutting the profiled element 10 itself along a respective oblique direction.

Appropriately, the areas to be welded are inclined by an angle comprised between 100 and 80° with respect to the direction of longitudinal extension of the profiled element.

Preferably, the areas to be welded are substantially inclined by 45°.

The main profiled element 5 comprises two extreme areas to be welded 14, obtained by cutting the ends, adapted to be welded to the respective extreme areas to be welded 14 of the lateral profiled elements 6. Conveniently, the lateral welding devices 3 are provided with lateral removal means 15 for making a groove on the peripheral edge of the extreme areas to be welded 14.

The groove, in particular, affects the peripheral edge of the visible faces of the profiled elements 5, 6.

For the pinposes of the present discussion, the term "visible faces" means the surfaces of the profiled elements that are intended to remain visible 25 after the window/door has been assembled.

In actual facts, when the frame is mounted on a wall, the visible faces are the surfaces of the profiled elements facing the inside or the outside of the wall.

The groove has the ftmction of reducing, in part, the length of the visible 5 faces so that, following the welding of the profiled elements, the welding bead extends towards the inside of the profiled elements 5, 6 and, therefore, is not visible on the visible faces of the window/door.

For the purposes of the present discussion, the term "welding bead" means the portion of excess molten plastic material that is compressed during the 10 joining of the profiled elements and may protrude with respect to the visible faces of the profiled elements themselves.

This way, after the profiled elements 5, 6 have been welded, the visible faces of a profiled element perfectly match the corresponding visible faces of the adjacent profiled element The lateral removal means 15 also have the function of removing a thin layer of plastic material sufficient to smooth and even out the extreme areas to be welded 14.

In other words, the lateral removal means 15 are not only used to shape the grooves but are absolutely essential to even out the walls and correct any cutting errors.

In the absence of such levelling, the extreme areas to be welded 14 would be too irregular and therefore not weldable.

It should also be noted that the grooves and the levelling of the extreme areas to be welded 14 are carried out by the lateral removal means 15 of the 25 lateral welding device 3 when the profiled elements 5, 6 are already mounted on the lateral retaining means 11 and on the retaining means of the lateral profiled element 10 respectively; the extreme areas to be welded 14 are coupled and melted together without removing the profiled elements 5, 6 from the respective retaining means 11, 10.

In other words, the tooling of the profiled elements 5, 6 on the respective retaining means 11, 10 takes place only once and the lateral welding device 3 is able to carry out all the steps required for the machining without the need for the profiled elements 5, 6 to be prepared and/or machined on other machines.

This special feature, as well as ensuring considerable speed of execution, allows avoiding welding errors due to the incorrect assembly of the profiled elements 5, 6 on the respective retaining means 11, 10.

In fact, if the extreme areas to be welded 14 were leveled on a different machine and then mounted on the lateral welding device 3 to be welded, there would be the risk of badly welding the profiled elements 5, 6 because the extreme areas to be welded 14 may not be perfectly facing and parallel. The lateral removal means 15 are mounted on the lateral machining assembly 9 and comprise a pair of milling tools 16 arranged on opposite sides of a special supporting element.

In particular, the milling tools 16 are positioned so that the grooves on both profiled elements 5, 6 are made simultaneously.

In more detail, the milling tools 16 are arranged facing the respective extreme areas to be welded 14 and rotate around an axis of operation that is substantially orthogonal thereto.

The axis of operation is substantially horizontal and inclined substantially by 45° with respect to the longitudinal direction of the main profiled element 5 and of the lateral profiled elements 6.

The lateral removal means 15 are conveniently provided with suction 5 means adapted to remove by suction the plastic swarf formed during the removal operation.

At least one of the lateral welding devices 3 is movable on the supporting base 2 along the first direction X to position itself at the point where the respective extreme area to be welded 14 of the main profiled element 5 is located.

Conveniently, the machine 1 comprises at least one first sliding guide 17, which is associated with the supporting base 2, extends along the first direction X and on which at least one of the lateral welding devices 3 is mounted sliding.

The first sliding guide 17 comprises a group of rails and the lateral welding device 3 sliding along the first direction X is associated with it through the lateral frame 8.

Consequently, the overall volume varies according to the mutual position of the lateral welding devices 3 on the supporting base 2.

The movement of one of the lateral welding devices 3 along the first sliding guide 17 allows the correct positioning of the lateral welding devices 3 according to the actual length measurement of the main profiled element 5. The lateral profiled elements 6 are positioned at the point where the respective lateral welding devices 3 are located so that the extreme areas to be welded 14 face the extreme areas to be welded 14 of the main profiled element 5 for subsequent welding.

In the particular embodiment shown in Figure 1, only one of the lateral welding devices 3 is movable along the first direction X, while the other is fixed to the supporting base 2; however, alternative embodiments of the present invention cannot be ruled out wherein both lateral welding devices 3 can slide on the first sliding guide 17.

The intermediate welding device 4 is provided with at least one intermediate heating plate 18 shaped in a "V" pattern and adapted to heat at 10 least the math profiled element 5 and a respective transverse profiled element 7.

The intermediate heating plate 18 is adapted to at least partly melt the plastic material of the profiled elements 5, 7, which are then joined and pressed together to bring the melted plastic material into contact. After having cooled down, the plastic material hardens and holds the profiled elements together.

In fact, the main profiled element 5 comprises at least one pair of intermediate areas to be welded 19, contiguous to each other to form a shaped concavity 20, and the transverse profiled element 7 comprises, at at least one end, a pair of transverse areas to be welded 21, contiguous to each other to form a "V"-shaped convexity 22 substantially complementary to the concavity 20.

The intermediate welding device 4 is movable on the supporting base 2 along the first direction X to position itself at the respective intermediate 25 areas to be welded 19 of the main profiled element 5.

Advantageously, the machine 1 comprises at least one second sliding guide 23, which is associated with the supporting base 2, extends along the first direction X and on which the intermediate welding device 4 is mounted sliding.

The second sliding guide 23 is separate and distinct from the first sliding guide 17.

In particular, the second sliding guide 23 comprises a group of rails, other than the group of rails of the first sliding guide 17.

The second sliding guide 23 allows the intermediate welding device 4 to be moved on the supporting base 2, for the entire longitudinal extension of the supporting base itself so as not to intercept the lateral welding devices 3. The intermediate welding device 4 comprises at least one intermediate frame 24 associated with the supporting base 2 movable sliding along the first direction X. In particular, the intermediate frame 24 is associated movable sliding with the second sliding guide 23.

The intermediate welding device 4 comprises at least one intermediate machining assembly 25 for the machining of the main profiled element 5 and of the transverse profiled element 7, which is associated with the intermediate frame 24 and is provided with the intermediate heating plate 18.

The intermediate welding device 4 also comprises transverse profiled element retaining means 26 which are associated with the intermediate frame 24.

The characteristics of the intermediate machining assembly 25 and of the transverse profiled element retaining means 26 will be described in detail later in the present description.

Advantageously, the intermediate machining assembly 25 and the 5 transverse profiled element retaining means 26 are arranged on opposite sides of the first sliding guide 17.

The intermediate frame 24 comprises at least one connecting portion 24a between the intermediate machining assembly 25 and the transverse profiled element retaining means 26 which is located below the first sliding guide 17.

The connecting portion 24a is used to hold the intermediate machining assembly 25 and the transverse profiled element retaining means 26 together when the intermediate frame 24 moves along the second sliding guide 23, so that they can be positioned simultaneously with respect to the supporting base 2.

The machine 1 comprises movement means 27, 31 of the intermediate welding device 4 between an operating position, wherein the intermediate welding device 4 is placed between the lateral welding devices 3 inside the overall volume, and a home position, wherein the intermediate welding device 4 is placed outside the overall volume. (Figure 4) The machine 1, in fact, can also be used for the simple realization of a window/door without crosspieces In actual facts, when it is not necessary to weld a transverse profiled element 7 to the main profiled element 5, the intermediate welding device 4 can be moved away from the working area to avoid interfering with the lateral welding devices 3 during the respective welding operations.

This is particularly advantageous, especially when the main profiled element 5 is small, so that the intermediate welding device 4 is an obstacle 5 to the correct positioning of the lateral welding devices 3.

In the home position, the intermediate welding device 4 is movable along the first direction X for the entire extension of the second sliding guide 23. On the contrary, in the operating position, the intermediate welding device 4 is movable along the second sliding guide 23 between the lateral welding devices 3.

In the configuration shown in Figure 1, for example, two intermediate welding devices 4 are positioned between the lateral welding devices 3 in the proximity of one end of the sliding guides 17 and 23, while another intermediate welding device 4 is parked in the proximity of the opposite end of the sliding guides 17 and 23 to make a window/door with only two crosspieces; however, it is easy to understand that, thanks to the movement means 27, 31, the machine 1 can take on other configurations wherein, for example: all three intermediate welding devices 4 are arranged between the lateral welding devices 3 in the operating position so as to create windows/doors with three crosspieces; an intermediate welding device 4 is arranged between the lateral welding devices 3 in the operating position and two intermediate welding devices 4 are parked in the proximity of one end of the sliding guides 17 and 23. This way it is possible to create windows/doors with two crosspieces; -all three intermediate welding devices 4 are parked in the proximity of one end of the sliding guides 17 and 23 to create windows/doors without crosspieces.

The movement means 27, 31 comprise a first movement assembly 27 of the intermediate machining assembly 25 with respect to the intermediate frame 24.

The first movement assembly 27 allows the movement of the intermediate 10 machining assembly 25 along a second direction Y substantially perpendicular to the first direction X, between the operating position and the home position.

In more detail, the second direction Y is substantially horizontal. Conveniently, the first movement assembly 27 comprises horizontal sliding 15 means 29, 30 for the movement of the intermediate machining assembly 25 along the second direction Y. The horizontal sliding means 29, 30 allow the intermediate machining assembly 25 to shift to the front, towards the overall volume, or to the rear, away from the overall volume, to position itself in the operating position or 20 in the home position, respectively.

In particular, the intermediate machining assembly 25 comprises a supporting structure 28 associated with the intermediate frame 24.

The supporting structure 28 is associated sliding with the intermediate frame 24 by means of the horizontal sliding means 29, 30.

The horizontal sliding means 29, 30 comprise a motor unit 29 provided with a worm gear drive shaft 30.

In addition, the movement means 27, 31 comprise a second movement assembly 31 of the transverse profiled element retaining means 26 with 5 respect to the intermediate frame 24.

The second movement assembly 31 allows moving the transverse profiled element retaining means 26 along a third direction Z substantially perpendicular to the first direction X, between the operating position and the home position.

In more detail, the third direction Z is substantially vertical.

Substantially, the first direction X, the second direction Y and the third direction Z are orthogonal to each other and define a Cartesian space.

The second movement assembly 31 comprises vertical sliding means 32 for the movement of the transverse profiled element retaining means 26 along the third direction Z. The vertical sliding means 32 comprise at least one linear actuator with pneumatic cylinder.

The transverse profiled element retaining means 26 are then able to shift upwards or downwards to be positioned in the operating position or in the 20 home position, respectively.

In order to carry out the welding operations of the transverse profiled element 7, the intermediate welding device 4 is positioned so as to be arranged inside the overall volume.

The intermediate machining assembly 25 is then moved horizontally 25 towards the working area, while the transverse profiled element retaining means 26 slide vertically upwards.

In the operating position, the intermediate welding device 4 can be moved further along the first direction X to position itself at the point where the pair of intermediate areas to be welded 19 of the main profiled element 5 is located.

Advantageously, the machine 1 comprises detection means 33 of the concavity 20 for the positioning of the intermediate welding device 4 along the first direction X with respect to the concavity 20.

The detection means 33 allow the intermediate welding device 4 to be positioned correctly and extremely precisely so that the machining of the profiled elements 5, 7 and the subsequent welding is accurate and effective. The detection means 33 conveniently comprise at least one light emitter 34 mounted on the intemiediate welding device 4 and adapted to project a beam of light 35 onto the concavity 20, illuminating the surface thereof.

The light emitter 34 can be associated with the intermediate machining assembly 25.

In this case, the light emitter 34 can, e.g., be arranged above the main profiled element 5 and direct the beam of light 35 towards the visible face of the main profiled element itself, from top to bottom.

Alternatively, the light emitter 34 can be associated with the transverse profiled element retaining means 26.

In this case, the light emitter 34 can, e.g., be placed next to the main profiled element 5 and direct the beam of light 35 substantially horizontally towards a lateral face of the main profiled element itself For the purposes of the present discussion, the term "lateral face" means the surface of the transverse profiled element with respect to the visible faces.

In particular, in this specific case, the lateral face is the transverse surface 5 involved in the cut during the realization of the intermediate areas to be welded 19, and therefore it is provided with the concavity 20.

The beam of light 35 is selected from the list comprising: point beam, line beam.

In the case of a point beam, the light emitter 34 projects a single ray of light into the space that hits the main profiled element 5 at a single point.

In the case of a line beam, the light emitter 34 projects a series of rays of light into the space that hit the main profiled element 5 along a line.

The light emitter 34 is configured to emit the beam of light 35 inside a vertical projection plane P substantially orthogonal to the first direction X. In other words, the light emitter 34 is arranged and oriented to emit the beam of light 35 so as to intercept the main profiled element 5 and project on its surface a luminous mark 35a (punctifonn or linear) indicating the position of the intermediate welding device 4 with respect to the main profiled element 5.

This way, by moving the intermediate welding device 4 along the first direction X, a sort of "scanning" of the main profiled element 5 and of the concavity 20 is carried out. (Figure 7) In an embodiment of the present invention, the light emitter 34 is a laser pointer device.

The correct positioning of the intermediate welding device 4, therefore, is based on the visual detection by an operator of the luminous mark 35a that is formed when the beam of light 35 intercepts the main profiled element 5. In actual facts, the operator makes the intermediate welding device 4 slide along the first direction X until the beam of light 35 hits exactly the vertex of the concavity 20; in this position, the intermediate welding device 4 is aligned to the concavity 20 and the sliding thereof along the first direction X is blocked by the operator using a parking brake, not shown in the figures.

Alternatively, the light emitter 34 is a laser distance measuring device provided with means for sensing the distance of a portion of the concavity 20 illuminated by the beam of light 35.

The distance sensing means are able to determine the distance of the faces of the main profiled element 5 with respect to a reference system on board the intermediate welding device 4 and, consequently, to determine in which position the intermediate welding device 4 is located with respect to the concavity 20.

The laser distance measuring device is operationally connected to the display means of the detected distance.

The distance display means, through a graphic interface, signal to an operator a numerical value which is representative of the measured distance.

In more detail, the laser distance measuring device can detect and communicate to the display means an approximate value for a width 25 measurement of the visible face of the main profiled element 5 or for a depth measurement of the lateral face of the main profiled element 5 depending on whether the laser distance measuring device is mounted on the intermediate machining assembly 25 or on the transverse profiled element retaining means 26 respectively.

Substantially, if the beam of light 35 is emitted towards the visible face of the main profiled element 5, the distance sensing means detect a decreasing numerical value as the portion of the concavity 20 moves closer, in which the intermediate areas to be welded 19 join (i.e. the vertex of the concavity 20).

Conversely, if the beam of light 35 is emitted towards the lateral face of the main profiled element 5, the distance sensing means detect an increasing numerical value as the portion of the concavity 20 moves closer, in which the intermediate areas to be welded 19 join.

After the portion of the concavity 20 has been detected in which the 15 intermediate areas to be welded 19 join, the movement of the intermediate welding device 4 along the first direction X is interrupted once again by a parking brake not shown in the figures.

During the "scanning" of the main profiled element 5 and the intervention of the detection means 33, the main profiled element 5 is kept stationary by means of the lateral retaining means 11 of the lateral welding devices 3. Conveniently, the intermediate welding device 4 is also provided with means which allow blocking the main profiled element 5 and which consist of intermediate retaining means 36.

The intermediate retaining means 36 are mounted on the supporting 25 structure 28 of the intermediate machining assembly 25.

The intermediate retaining means 36 are of the type of a vice operated vertically by means of a piston-operated cylinder.

The intermediate welding device 4 also comprises intermediate displacement means 37 of the intermediate retaining means 36 to displace 5 the main profiled element 5 between at least one position of moving away from the transverse profiled element 7 and at least one position of moving close to the transverse profiled element 7, wherein the intermediate areas to be welded 19 and the transverse areas to be welded 21 are joined together. The intermediate displacement means 37 allow precise and accurate 10 movement of the main profiled element 5 with respect to the transverse profiled element 7.

The intermediate displacement means 37 coincide with the first movement assembly 27 of the movement means 27, 31 described above.

In other words, the first movement assembly 27, which displaces hidden the intermediate machining assembly 25 between the operating position and the home position, also makes it possible, in use, to move the main profiled element 5 closer to and further away from the transverse profiled element 7.

The intermediate displacement means 37 are operationally connected to the 20 lateral displacement means 12 to allow a coordinated movement of the main profiled element 5.

For this purpose, the machine 1 comprises connecting means between the intermediate displacement means 37 and the lateral displacement means 12, which are not shown in detail in the figures. In particular, the connecting means are of the electrical type. It cannot however be ruled out that the connecting means are of a different type.

During the operation of the machine 1, in fact, the transverse profiled element 7 and the lateral profiled elements 6 are kept stationary while the 5 main profiled element 5 is displaced to bring the areas to be welded 14, 19, 21 closer or further away from each other.

The transverse profiled element 7 is positioned on the intermediate welding device 4 so that the convexity 22 faces the concavity 20.

In particular, the transverse profiled element 7 is kept in position by the 10 transverse profiled element retaining means 26.

The transverse profiled element retaining means 26 comprise a vice with two jaws 38 mutually movable to intercept the transverse profiled element 7.

Conveniently, the opening and closing movement of the jaws 38 is made along a horizontal direction parallel to the first direction X. Advantageously, the transverse profiled element retaining means 26 comprise at least one centering device 39 of the transverse profiled element 7 with respect to a vertical reference plane R of the intermediate welding device 4.

The vertical reference plane R coincides with the vertical projection plane P of the light emitter 34.

In this case, the centering device 39 comprises a self-centering double rack system associated with the jaws 38.

Substantially, each of the two jaws 38 is associated with a rack 40 and the two racks 40 are arranged so that their respective teeth are facing each other.

The two racks 40 are connected and moved by a gear wheel 41 positioned 5 between the two and associated with both of them.

When the gear wheel 41 is set in rotation, the racks 40 are shifted in opposite directions and the jaws 38 move away from or approach the vertical reference plane R simultaneously.

The self-centering vice allows positioning and retaining the transverse profiled element 7 so that the vertex of the convexity 22 lies on the vertical reference plane R: since the vertical reference plane R coincides with the vertical projection plane P of the light emitter, to align the beam of light 35 to the vertex of the concavity 20 also means to align the concavity 20 of the main profiled element 5 and the convexity 22 of the transverse profiled element 7 to each other.

The intermediate machining assembly 25 comprise intermediate removal means 42 to make at least one groove 43 on at least one peripheral edge of the intermediate areas to be welded 19 and/or of the transverse areas to be welded 21.

The groove 43, in particular, affects the peripheral edge of the visible faces of the profiled elements 5, 7.

The groove 43 aims at reducing, in part, the extension of the visible faces so that, as a result of the welding of the profiled elements 5, 7, the welding bead extends towards the inside of the profiled elements 5, 7 and, therefore, 25 is not visible on the visible faces of the window/door.

As with the lateral removal means 15, the intermediate removal means 42 has also the ft.mction of removing a thin layer of plastic material which is sufficient to level and even out the areas to be welded 19 and 21 of the respective profiled elements 5, 7.

In addition, it should be noted that the groove 43 and the levelling of the areas to be welded 19, 21 are carried out by the intermediate removal means 42 of the intermediate welding device 4 when the profiled elements 5, 7 are already mounted on the intermediate retaining means 36 and on the transverse profiled element retaining means 26, respectively; the areas to be welded 19, 21 are coupled and melted together without disassembling the profiled elements 5, 7 from the respective retaining means 36, 26.

In other words, the tooling of the profiled elements 5, 7 on the respective retaining means 36, 26 takes place only once and the intermediate welding device 4 is able to carry out all the steps required for machining without the need for the profiled elements 5, 7 to be prepared and/or machined on other machines.

This special feature, as well as ensuring considerable speed of execution, allows avoiding welding errors due to an incorrect assembly of the profiled elements 5, 7 on the respective retaining means 36, 26.

In fact, if the areas to be welded 19,21 were leveled on a different machine and then mounted on the intermediate welding device 4 to be welded, there would be the risk of badly welding the profiled elements 5, 7 because the areas to be welded 19, 21 may not be perfectly facing and parallel.

Alternative embodiments of the present invention cannot however be ruled 25 out wherein the machine 1 is not provided with lateral removal means 15 and/or with the intermediate removal means 42 and grooves making and/or profiled element levelling are carried out on separate milling machines before the profiled elements are placed on the machine 1.

The intermediate removal means 42 comprise at least one milling tool 16 5 that can be rotated around a working axis A substantially parallel to the intermediate areas to be welded 19 and/or to the transverse areas to be welded 21.

The working axis A is substantially orthogonal to a lying plane of the profiled elements 5, 7.

Advantageously, the working axis A is substantially vertical.

In contrast to the intermediate removal means 42, the vertical arrangement of the milling tools 16 is in fact more favorable because the intermediate areas to be welded 19 and the transverse areas to be welded 21 define a narrow working space and wherein it is difficult to insert and move a machining tool which is able to remove correctly the plastic material.

Therefore, the arrangement of the milling tool 16 along a vertical working axis A allows creating a groove 43 precisely and easily.

Further embodiments cannot however be ruled out wherein the working axis A is horizontal but parallel to the areas to be welded A, or that it is 20 oblique but parallel to the areas to be welded 19, 21 or again that it is transverse with respect to the areas to be welded 19, 21.

The intermediate removal means 42 comprise at least one holding frame 44 associated movable with the supporting structure 28 and at least one tool set 45 associated with the holding frame 44.

The tool set 45 comprises the above-mentioned milling tool 16 and is facing at least one face of at least one of either the main profiled element 5 or the transverse profiled element 7 to make the groove 43.

The tool set 45 also comprises a suction unit 46 adapted to suck up the residues of plastic material generated during the making of the groove 43. The suction unit 46 comprises a suction opening 46a defined at the point where the milling tool 16 is located through which the plastic residues are conveyed to a recovery container.

In more detail, the milling tool 16 is arranged through the suction opening 10 46a towards the areas to be welded 19, 21.

The suction unit 46 comprises a series of brush elements 47 arranged radially around the suction opening 46a and adapted to facilitate the collection of chips and remove the residues of plastic material more effectively.

Advantageously, the intermediate removal means 42 comprise a pair of tool sets 45, each of which can be placed facing a respective visible face of at least one of either the main profiled element 5 or the transverse profiled element 7.

The tool sets 45 are arranged above and below with respect to the lying 20 plane of the profiled elements 5, 7 so that the upper visible faces and the lower visible faces are machined respectively.

Each of the tool sets 45 comprises a milling tool 16.

The milling tools 16 are aligned along the same working axis A and are arranged on opposite sides of the lying plane of the profiled elements 5, 7.

It cannot, however, be ruled out that the milling tools 16 can be mounted on the intermediate machining assembly 25 differently.

The intermediate removal means 42 also comprise a movement system 48 of the holding frame 44 compared to the supporting structure 28.

The movement system 48 allows the movement of the tool sets 45 with respect to the visible faces of the profiled elements 5, 7 for making the grooves 43.

The movement system 48 comprises at least one set of controlled axes 49 mounted on the supporting structure 28.

For the purposes of the present discussion, the term "controlled axes" means a numerical control system that allows the movement of the tool set 45 along predefined axes with controlled millimetric or micrometric displacements.

The set of controlled axes 49 is movable along a first axis X' substantially 15 parallel to the first direction X, a second axis Y' substantially orthogonal to the first axis X' and a third axis Z' substantially orthogonal to the first axis X' and to the second axis Y'.

In particular, the second axis Y' is substantially horizontal and parallel to the second direction Y and the third axis Z' is substantially vertical and 20 parallel to the third direction Z. The movement system 48 allows the movement of the holding frame 44 and, therefore, of the tool set 45 in space to displace the milling tool 16 along the visible faces of the profiled elements 5, 7.

As mentioned above, the intermediate welding device 4 comprises an 25 intermediate heating plate 18 in a "V" pattern and intended to melt and heat at least the main profiled element 5 and a respective transverse profiled element 7.

The intermediate heating plate 18 is of the type of an electric resistance plate and is made in a single body piece.

It cannot, however, be ruled out that the intermediate heating plate 18 may consist of several heating elements associated with each other to define a "V-pattern.

The intermediate heating plate 18 is mounted on the holding frame 44 of the intermediate removal means 42 and is movable with respect thereto to 10 position itself between the intermediate areas to be welded 19 and the transverse areas to be welded 21.

The intermediate heating plate 18 is movable between: an active condition, wherein it is positioned between the main profiled element 5 and the transverse profiled element 7 to heat and melt at least partly the intermediate areas to be welded 19 and the transverse areas to be welded 21; and a home condition, wherein it is moved away from the main profiled element 5 and from the transverse profiled element 7.

The intermediate heating plate 18 is movable with respect to the holding frame 44 between the active condition and the home condition by means of a pneumatic cylinder. Further embodiments cannot however be ruled out wherein the intermediate heating plate 18 is moved by means of different type.

In the active condition, the intermediate heating plate 18 is movable to 25 approach the transverse profiled element 7 and to move closer to the transverse areas to be welded 21 of the transverse profiled element 7 blocked on the transverse profiled element retaining means 26.

At the same time, the main profiled element 5 is in turn approached to the intermediate heating plate 18 by means of the lateral displacement means 12 and the intermediate displacement means 37, with a forward movement rate substantially twice as fast as the speed at which the intermediate heating plate 18 approaches the transverse profiled element 7.

For this purpose, since the intermediate retaining means 36 and the intermediate heating plate 18 are mounted on the same supporting structure 28, the intermediate retaining means 36 are moved along the second direction Y by means of the intermediate displacement means 37, approaching the transverse profiled element retaining means 26, while the intermediate heating plate 18 is moved along the second axis Y' by means of the movement system 48, away from the transverse profiled element retaining means 26.

This way, the concavity 20 and the convexity 22 come into contact at the same time with the opposite faces of the intermediate heating plate 18.

After the plastic material has been melted, the intermediate heating plate 18 is brought to the home condition to allow the union of the main profiled 20 element 5 to the transverse profiled element 7.

The intermediate welding device 4 also comprises at least one containment element 50, 51 which is shaped in a -V" pattern and can abut against the grooves 43 to define therewith a containment compartment 52 of a welding bead.

The containment element 50, 51 comprises two containment portions arranged substantially at 90° to overlap the grooves 43.

The containment element 50, 51 is intended to be positioned on the visible face of the profiled elements 5, 7, at the point where the grooves 43 are 5 located, in order to prevent the molten plastic material from escaping from the containment compartment 52.

The containment element 50, 51 is associated with the holding frame 44.

In particular, the containment element 50, 51 is associated with the holding frame 44 by the interposition of a displacement assembly 53 adapted to displace the containment element 50, 51 along a direction of close/away movement D between an operating position, wherein it is approached to the grooves 43, and a spaced away position, wherein it is moved away from the grooves 43.

The direction of close/away movement D is substantially vertical; it cannot 15 however be ruled out that the direction of close/away movement D is oriented according to different axes, but always in such a way that the containment element 50, 51 is overlapped on the grooves 43.

Advantageously, the intermediate welding device 4 comprises at least one pair of containment elements 50, 51, which are arranged on opposite sides to the lying plane of the profiled elements 5, 7 and each of which faces a respective visible face of the main profiled element 5 and of the transverse profiled element 7.

The containment elements 50, 51 are aligned and movable along the same vertical direction of close/away movement D. This way, the containment elements 50, 51 are able to contain the welding bead inside the containment compartment 52 on both visible surfaces of the window/door.

Conveniently, the intermediate welding device 4 comprises a plurality of 5 containment elements 50, 51 arranged on the same side to a lying plane of the profiled elements 5, 7 and facing only one visible side of the main profiled element 5 and of the transverse profiled element 7.

The containment elements 50, 51 are side by side and movable along separate vertical directions of close/away movement D. In particular, the containment elements 50, 51 comprise a first containment element 50 provided with a first contact surface 50a.

The first contact surface 50a comprises a protruding portion 54 adapted to fit at least partly inside the containment compartment 52.

The containment elements 50, 51 also comprise a second containment 15 element 51 provided with a second contact surface 51a.

The second contact surface 51a is adapted to allow a final finish of the welding operation and is substantially flat or differently shaped.

In the embodiment of the present invention, shown in detail in Figure 13, the intermediate welding device 4 comprises a pair of first containment elements 50, arranged one above and one below the lying plane of the profiled elements 5, 7, and a pair of second containment elements 51, arranged one above and one below the lying plane of the profiled elements 5, 7.

The operation of the present invention is as follows.

Initially, one of the lateral welding devices 3 is moved on the supporting base 2 along the first sliding guide 17, based on the actual length dimensions of the main profiled element 5, thus defining the overall volume.

The intermediate welding devices 4 of the machine I are positioned outside the overall volume defined by the lateral welding devices 3.

Depending on the type of machining to be carried out, a number of intermediate welding devices 4, equal to the number of transverse profiled elements 7 to be welded to the main profiled element 5, is brought inside 10 the overall volume.

For sake of simplicity, the operation of the machine 1 will be described for the case in which there is only one transverse profiled element 7 to be welded to the main profiled element 5.

In this case, only one intermediate welding device 4 is brought within the 15 overall volume, while the others remain parked and unused.

For this purpose, the intermediate machining assembly 25 of the intermediate welding device 4 to be used is displaced to the home position by means of the horizontal sliding means 29, 30 along the second direction Y. At the same time, the transverse profiled element retaining means 26 are brought to the home position by means of the vertical sliding means 32 along the third direction Z. (Figures 4 and 5) The intermediate welding device 4 can now be moved on the supporting base 2 along the first direction X for the entire extension of the second 25 sliding guide 23.

The intermediate welding device 4 is positioned on the supporting base 2 so that the intermediate frame 24 is in the position between the lateral welding devices 3.

The intermediate machining assembly 25 and the transverse profiled 5 element retaining means 26 are then moved to the operating position inside the overall volume.

The main profiled element 5 is positioned in the operating area so as to position the extreme areas to be welded 14 at the point where the lateral welding devices 3 are located.

The intermediate welding device 4 is moved again along the first direction X on the second sliding guide 23 to position itself at the point where the intermediate areas to be welded 19 are located. (Figure 6) Thanks to the light emitter 34, a scan of the main profiled element 5 is carried out to detect the portion of concavity 20 wherein the intermediate 15 areas to be welded 19 join. (Figure 7) After the intermediate welding device 4 has been correctly positioned, its parking brake is activated to block further slides along the second sliding guide 23 and the intermediate retaining means 36 are activated to keep the main profiled element 5 stationary with respect to the intermediate welding device 4.

The lateral profiled elements 6 and the transverse profiled element 7 are positioned on the corresponding welding devices 3, 4 and kept stationary by the respective retaining means 10, 26.

In particular, the transverse profiled element 7 is held by the centering 25 device 39 so that the transverse areas to be welded 21 face the intermediate areas to be welded 19. (Figure 8) At this point the removal means 15, 42 make a groove 43 at the point where the visible faces of the respective profiled elements 5, 6, 7 are located.

In more detail, the lateral removal means 15 operate simultaneously on the visible faces of the main profiled element 5 and of the respective lateral profiled element 6 to define the groove 43, above and below the lying plane of the profiled elements 5, 6.

The intermediate removal means 42, on the other hand, are moved by the set of controlled axes 49 in such a way that one of the tool sets 45 first operates on a visible face of the main profiled element 5 and on a visible face of the transverse profiled element 7, above the lying plane. Then the other of the tool sets 45 operates on the respective visible faces, below the lying plane of the profiled elements 5,7. (Figures 10 and 11) Subsequently, the lateral heating plates 13 and the intermediate heating plate 18 are moved in the active condition to the respective areas to be welded 14, 19, 21 to position themselves between the profiled elements 5, 6, 7.

The heating plates 13, 18 are moved towards the lateral profiled elements 6 20 and towards the transverse profiled element 7 to come into contact with the areas to be welded 14, 19,21.

At the same time, the lateral displacement means 12 and the intermediate displacement means 37 move the main profiled element 5 towards the lateral profiled elements 6 and towards the transverse profiled element 7 to 25 approach and come into contact with the heating plates 13, 18. (Figure 12).

After the plastic material has been melted, the heating plates 13, 18 are moved away, in the home condition, to allow the approach of the main profiled element 5 to the lateral profiled elements 6 and to the transverse profiled element 7.

The profiled elements 5, 6, 7 are joined and the containment elements 50, 51 are moved to abut against the grooves 43 and define the containment compartment 52 of the welding bead. (Figure 13) In this regard, at first, the first containment elements 50 abut against the grooves 43, both above and below the lying surface of the profiled 10 elements 5, 7, with the protruding portion 54 inside the relevant containment compartment 52 (Figure 14).

The welding bead resulting from the relevant approach of the profiled elements 5, 7 extends at the center of the containment compartment 52 and comes into contact with the protruding portion 54, which diverts it towards 15 the lateral walls of the containment compartment 52 (Figure 15).

Subsequently, the first containment elements 50 are spaced apart from the profiled elements 5, 7 (Figure 16).

At this point, the second containment elements 51 are moved to bring the second contact surface 51a in contact with the visible faces of the profiled 20 elements 5, 7, at the point where the grooves 43 are located In this position, the second contact surface 51a flattens the visible faces of the profiled elements 5, 7 and contains any pressure towards the visible faces by the welding bead.

At this stage, in fact, the profiled elements 5, 7 continue to be brought 25 closer together and the molten plastic material continues to form until the containment compartment 52 is completely filled (Figure 17).

The possibility of using only one of either the first containment elements 50 or the second containment elements 51 cannot however be ruled out.

All the sub-phases shown in Figures 14 to 17 are carried out quickly and in such a way as to prevent the molten material from solidifying before the containment compartment 52 is completely filled.

It has in practice been ascertained that the described invention achieves the intended objects and in particular the fact is underlined that the machine for welding plastic profiled elements is easily adaptable according to the shape of the main profiled element and, in particular, it can be easily positioned at its concavity.

The machine for welding plastic profiled elements allows the profiled element to be precisely positioned at the concavity defined on the main profiled element.

Claims

CLAIMS1) Machine (1) for welding plastic profiled elements, characterized by the fact that it comprises: - at least one supporting base (2) extending along a first direction (X); -at least one lateral welding device (3) associated with said supporting base (2) and provided with at least one lateral heating plate (13) adapted to heat at least one main profiled element (5) and at least one respective lateral profiled element (6); - at least one intermediate welding device (4) associated with said supporting base (2) and provided with at least one intermediate heating plate (18) shaped in a "V" pattern and adapted to heat at least the main profiled element (5) and a respective transverse profiled element (7), in which said main profiled element (5) comprises at least one pair of intermediate areas to be welded (19), contiguous to each other to form a "V--shaped concavity (20), and said transverse profiled element (7) comprises at at least one end at least a pair of transverse areas to be welded (21), contiguous to each other to form a "V--shaped convexity (22) substantially complementary to said concavity (20), wherein said intermediate welding device (4) comprises: at least one intermediate frame (24) associated with said supporting base (2) movable sliding along said first direction (X); - at least one intermediate machining assembly (25) for the machining of said main profiled element (5) and of said transverse profiled element (7), which is associated with said intermediate frame (24) and is provided with said intermediate heating plate (18) and; - transverse profiled element retaining means (26) associated with said intermediate frame (24); - detection means (33) of said concavity (20) for the positioning of said intermediate welding device (4) along said first direction (X) with respect to said concavity (20).
2) Machine (1) according to claim 1, characterized by the fact that said detection means (33) comprise at least one light emitter (34) mounted on 10 said intermediate welding device (4) and adapted to project a beam of light (35) onto said concavity (20).
3) Machine (1) according to one or more of the preceding claims, characterized by the fact that said light emitter (34) is configured to emit 15 said beam of light (35) inside a vertical projection plane (P) substantially orthogonal to said first direction (X).
4) Machine (1) according to one or more of the preceding claims, characterized by the fact that said beam of light (35) is selected from the 20 list comprising: point beam, line beam.
5) Machine (1) according to one or more of the preceding claims, characterized by the fact that said light emitter (34) is a laser spacer device provided with means for sensing the distance of a portion of said concavity (20) illuminated by said beam of light (35).
6) Machine (1) according to one or more of the preceding claims, characterized by the fact that said light emitter (34) is a laser pointer device.
7) Machine (I) according to one or more of the preceding claims, characterized by the fact that said light emitter (34) is associated with said intermediate machining assembly (25).
8) Machine (1) according to one or more of claims 1 to 6, characterized by the fact that said light emitter (34) is associated with said transverse profiled element retaining means (26).
9) Machine (1) according to one or more of the preceding claims, characterized by the fact that said transverse profiled element retaining means (26) comprise at least one centering device (39) of said transverse profiled element (7) with respect to a vertical reference plane (R) of said intermediate welding device (4).
10) Machine (1) according to one or more of the preceding claims, 20 characterized by the fact that said vertical reference plane (R) coincides with said vertical projection plane (P).
11) Machine (1) according to one or more of the preceding claims, characterized by the fact that said centering device (39) comprises a self-25 centering double rack system.