Patent Description:
The invention relates to a machine to weld section bars made of a plastic material, in particular PVC.

The invention especially finds advantageous application in the manufacturing of door and window frames comprising four section bars arranged so as to be perpendicular to one another two by two, to which explicit reference will be made in the description below without because of this loosing in generality.

In the manufacturing of door and window frames, a machine is known, which is designed to weld section bars made of a plastic material, each having an elongated trapezoid shape and delimited by two opposite end faces oriented at respective <NUM>° angles relative to a longitudinal axis of the section bar.

The machine comprises a plurality of holding and welding units, which are as many as the number of section bars and are each arranged in the area of the end faces of two respective section bars, which are adjacent to one another.

Each holding and welding unit comprises two holding devices, which are arranged and configured so as to grab and hold the free ends of the relative section bars and are mounted so as to move the relative section bars in two moving directions, which are transverse to one another and to the section bars.

Each holding and welding unit cooperates with a milling device, which is designed to create a containing channel along a peripheral edge of the end faces of the relative section bars and further cooperates with a welding plate, which is designed to heat the end faces of the section bars.

In use, once the containing channels have been created and the end faces have been heated, the section bars are moved by the relative holding devices in the moving directions and to a welding position, in which the end faces of the section bars come into contact with one another so as to be welded.

When the section bars are arranged in the welding position, each holding and welding unit further cooperates with a pressing device, which is movable from and to an operating position, in which the pressing device is placed into contact with the relative section bars and around at least part of the relative end faces in order to hold the weld bead produced by the coupling between the end faces inside the relative containing channels.

Known machines to weld section bars made of a plastic material of the type described above are affected by some drawbacks, which are mainly due to the fact that the creation of said containing channels generates shavings and/or swarf, which can jeopardize the correct welding of the section bars, and leads to processing cycles of the end faces of the section bars that are relatively long and expensive. <CIT> and <CIT> disclose a hot-gas welding apparatus wherein a weld material is applied and weld section bars are pre-heated by one nozzle.

The object of the invention is to provide a machine to weld section bars made of a plastic material, in particular PVC, which is not affected by the aforementioned drawbacks and is simple and economic to be manufactured.

According to the invention, there is provided a machine to weld section bars made of a plastic material, in particular PVC, according to claims <NUM> to <NUM>.

The invention further relates to a method to weld section bars made of a plastic material, in particular PVC.

According to the invention, there is provided a method to weld section bars made of a plastic material, in particular PVC, according to claims <NUM> to <NUM>.

The invention will now be described with reference to the accompanying drawings, showing a non-limiting embodiment thereof, wherein:.

With reference to <FIG>, <FIG> and <FIG>, number <NUM> indicates, as a whole, a machine to weld section bars <NUM> made of a plastic material, in particular PVC, and to manufacture, in particular, door and window frames comprising four section bars <NUM>, which are perpendicular to one another two by two.

Each section bar <NUM> has an elongated trapezoid shape, is delimited by an upper face <NUM> and by a lower face <NUM>, which are opposite one another, and is further delimited by two end faces <NUM>, which are oriented at respective <NUM>° angles relative to the faces <NUM> and <NUM> (<FIG>).

The machine <NUM> comprises an elongated base <NUM>, which extends in a horizontal direction <NUM> and is provided with two longitudinal guide members <NUM>, which are parallel to the direction <NUM>.

The base <NUM> supports two cross members <NUM>, which extend above the base <NUM> in a horizontal direction <NUM>, which is transverse to the direction <NUM>, and are coupled to the longitudinal members <NUM> in a sliding manner so as to make straight movements along the longitudinal members <NUM> in the direction <NUM>.

A belt conveyor <NUM> is fixed to each cross member <NUM>, extends in the direction <NUM>, is mounted between the two cross members <NUM> and defines, together with the conveyor <NUM> of the other cross member <NUM>, a conveyor device <NUM> to discharge the door or window frame once it has been produced.

Each cross member <NUM> supports a pair of holding and welding units <NUM>, each comprising a slide <NUM>, which is coupled to the cross member <NUM> in a sliding manner so as to be moved, in an initial set-up phase for the set-up of the machine <NUM>, along the cross member <NUM> in the direction <NUM>.

The slide <NUM> is provided with two guide devices <NUM>, <NUM>, which are mounted parallel to the directions <NUM> and <NUM>, respectively, and support respective holding devices <NUM>, <NUM>.

Each device <NUM> comprises a lower jaw <NUM>, which is coupled to the device <NUM> in a sliding manner so as to make, relative to the slide <NUM> and due to the thrust of an actuator device <NUM>, straight movements in the direction <NUM>.

The jaw <NUM> is provided with a limit stop element <NUM> extending in the direction <NUM>, in order to allow for a correct positioning of the section bars <NUM>, and cooperates with an upper jaw <NUM> coupled to the jaw <NUM> so as to move, relative to the jaw <NUM>, in a vertical direction <NUM>, which is orthogonal to the directions <NUM> and <NUM>.

The jaw <NUM> is moved in the direction <NUM> between a locking position and a release position to lock and release the section bars <NUM> by an actuator cylinder <NUM>, which is fixed to the jaw <NUM> parallel to the direction <NUM>.

The jaw <NUM> is provided with a limit stop element <NUM> extending in the direction <NUM>, in order to allow for a correct positioning of the section bars <NUM>, and cooperates with an upper jaw <NUM> coupled to the jaw <NUM> so as to move, relative to the jaw <NUM>, in the direction <NUM>.

The unit <NUM> further comprises a welding plate <NUM>, which extends in a containing plane arranged at a <NUM>° angle relative to the directions <NUM> and <NUM> and is movable in a direction <NUM>, which is parallel to the containing plane, between a retracted rest position (<FIG>) and a forward operating position (<FIG>).

The unit <NUM> further comprises a positioning plate <NUM>, which is parallel and alongside the plate <NUM>, is movable in the direction <NUM> between a retracted rest position (<FIG> and <FIG>) and a forward operating position (not shown) and is provided with a shaped free edge <NUM> having a profile that matches the profile of the section bars <NUM>.

The unit <NUM> is further provided with an applying assembly <NUM> comprising a vertical upright <NUM>, which projects upwards from the slide <NUM>, extends in the direction <NUM> and is engaged, in a sliding manner, by a vertical slide <NUM>, which is movable along the upright <NUM> in the direction <NUM> due to the thrust of a known operating device <NUM>.

The assembly <NUM> further comprises a horizontal slide <NUM>, which is coupled to the slide <NUM> in a sliding manner so as to move, relative to the slide <NUM> and due to the thrust of a known operating device <NUM>, in the direction <NUM>.

The slide <NUM> supports two opposite applying devices <NUM>, each associated with the face <NUM> of a relative section bar <NUM>.

According to <FIG> and <FIG>, each device <NUM> is provided with a dispensing nozzle <NUM>, which extends crosswise to the directions <NUM> and <NUM>, is fixed at the end of a sleeve <NUM> and has an orientation which is contrary to the orientation of the nozzle <NUM> of the other device <NUM>.

The sleeve <NUM> has a longitudinal axis <NUM> parallel to the direction <NUM> and is delimited by a side wall <NUM>, which is coaxial to the axis <NUM> and houses, on the inside, an electric resistance <NUM>, which is wound in a spiral around and along said axis <NUM>.

The sleeve <NUM> houses, on the inside, a feeding Archimedes' screw <NUM>, which is coupled to the sleeve <NUM> in a rotary manner so as to rotate around the axis <NUM> due to the thrust of a known operating device <NUM>.

The Archimedes' screw <NUM> receives a thread <NUM> of weld material, in particular PVC, which is unwound from a spool <NUM> mounted on the slide <NUM> in a rotary manner, at first is fed into the sleeve <NUM> through the wall <NUM>, then is fed by the Archimedes' screw <NUM> with a rotation-translation movement along and around said axis <NUM> in order to be heated by the resistance <NUM> and finally is fed to the nozzle <NUM> and onto the face <NUM> of the relative section bar <NUM>.

With reference to <FIG> and <FIG>, the device <NUM> cooperates with a heating device <NUM> comprising a plurality of blower nozzles <NUM> (in this specific case, four nozzles <NUM>), which are distributed around the nozzle <NUM>, face the face <NUM> of the relative section bar <NUM> and are connected to a source of hot air under pressure in order to heat the face <NUM> of the relative section bar <NUM>.

The nozzles <NUM> are selectively controlled so as to activate the nozzle <NUM> that each time is arranged downstream of the nozzle <NUM> in a moving direction of the nozzle <NUM> along the face <NUM> of the relative section bar <NUM>.

According to a variant which is not shown herein and which is not covered by the claims, the nozzles <NUM> are eliminated and replaced by one single blower nozzle, which is movable around the nozzle <NUM> so as to always be arranged downstream of the nozzle <NUM> in a moving direction of the nozzle <NUM> along the face <NUM> of the relative section bar <NUM>.

The operation of the machine <NUM> will now be described with reference to <FIG>, <FIG> and <FIG>, assuming that two section bars <NUM> are welded, taking into account one single holding and welding unit <NUM> and starting from an instant in which:.

The holding devices <NUM>, <NUM> are moved in the relative directions <NUM>, <NUM> so as to disengage the faces <NUM> of the section bars <NUM> from the plate <NUM>; the plate <NUM> is moved to its retracted rest position; and the applying devices <NUM> are moved between the section bars <NUM> so that they each face the face <NUM> of the relative section bar <NUM>.

By combining the movements of the devices <NUM> in the directions <NUM> and <NUM> with the heating of the faces <NUM> by means of the blower nozzles <NUM> of the heating devices <NUM> and with the heating of the threads <NUM> of weld material through the electric resistances <NUM>, the weld material is applied along a peripheral edge of the faces <NUM> so as to create respective weld material beads <NUM>, which are substantially annular.

Subsequently, the devices <NUM> are lifted in the direction <NUM> and are disengaged from the section bars <NUM>; the welding plate <NUM> is placed in its forward operating position; and the devices <NUM>, <NUM> are moved in the relative directions <NUM>, <NUM> so as to place the beads <NUM> in contact with the plate <NUM>.

Once the beads <NUM> have been heated, the plate <NUM> is moved to its retracted rest position; and the welding area between the two section bars <NUM> is delimited in the directions <NUM> and <NUM> by means of a pressing device <NUM>, which is mounted on the slide <NUM> so as to move from and to an operating position, in which the pressing device <NUM> is placed in contact with the section bars <NUM> and around at least part of the faces <NUM> in order to contain the weld material of the beads <NUM>.

In this specific case, the device <NUM> comprises an upper pressing element <NUM>, which is movable in the direction <NUM> between a lowered operating position and a lifted rest position, and a lower pressing element <NUM>, which is movable in the direction <NUM> between a lifted operating position and a lowered rest position, and an outer side pressing element, which is defined by the shaped edge <NUM> of the plate <NUM> (<FIG>).

When the device <NUM> is arranged in its operating position and the faces <NUM> are in contact with one another with the interposition of the beads <NUM>, the beads <NUM> are welded to one another and the weld material of the beads <NUM> is contained by the pressing elements <NUM> and <NUM> and by the edge <NUM> inside the section bars <NUM>.

The machine <NUM> has some advantages, which are mainly due to the fact that the welding of the section bars <NUM> through the weld material of the threads <NUM> does not require any preliminary chipping machining or any final processing to clean the section bars <NUM>.

According to a variant which is not shown herein, each applying device <NUM> is eliminated and replaced by a 3D printer designed to apply the weld material onto the faces <NUM>.

Claim 1:
A machine to weld section bars (<NUM>) made of a plastic material, in particular PVC, the machine comprising a first holding device (<NUM>) to hold a first section bar (<NUM>) delimited by a first end face (<NUM>); a second holding device (<NUM>) to hold a second section bar (<NUM>) delimited by a second end face (<NUM>); one applying assembly (<NUM>) to apply a weld material (<NUM>) on said first and/or second end faces (<NUM>); said holding devices (<NUM>, <NUM>) being movable relative to one another in order to move the section bars (<NUM>) from and to a welding position, in which the end faces (<NUM>) are in contact with one another with the interposition of the weld material (<NUM>); the applying assembly (<NUM>) comprising a first heating device (<NUM>) to heat said first and/or second end faces (<NUM>), a dispensing nozzle (<NUM>) to apply the weld material (<NUM>) on said first and/or second end faces (<NUM>), and a second heating device (<NUM>) to heat the weld material (<NUM>) fed to the dispensing nozzle (<NUM>); the first heating device (<NUM>) comprising at least one blower nozzle (<NUM>) to feed hot air onto said first and/or second end faces (<NUM>); and being characterized in that the first heating device (<NUM>) comprises a plurality of blower nozzles (<NUM>) distributed around the dispensing nozzle (<NUM>) to feed hot air onto said first and/or second end faces (<NUM>).