Patent Description:
As is known, a laminated glass sheet is obtained starting from a laminated glass semifinished product consisting of two side glass sheets and an intermediate sheet of thermoplastic material interposed between the two side glass sheets. After its forming, the laminated semifinished product is heated so as to make the sheet of thermoplastic material firmly adhere to the glass sheets.

Furthermore, as is known, the laminated semifinished product is obtained starting from a laminated glass assembly by arranging the sheet of thermoplastic material between two side glass sheets. In order to prevent uncovered peripheral zones or zones devoid of the sheet of thermoplastic material, during the forming, the same sheet of thermoplastic material is allowed to protrude beyond the peripheral edges of the side glass sheets, forming peripheral portions or wings. The laminated assembly is then subjected to a trimming operation in which the peripheral protruding portions of the sheet are cut and removed.

The trimming operation is carried out manually by an operator who uses a common knife or cutting blade which is advanced as much as possible in contact with the peripheral edges of the laminated assembly. Manual trimming requires a lot of time and above all experience so as to make precise trimming and is therefore time-consuming and expensive and often not entirely easy due to the large size of the glass sheets.

Alternatively, trimming is carried out automatically by arranging the laminated glass semifinished product flatly on a supporting surface and moving motorised cutting heads around the laminated semifinished product.

The automatic trimming allows reducing trimming timing, but it is not always satisfactory with regard to the reliability and the accuracy of the trimming.

The foregoing is consequent on several factors. First of all, the glass sheets are practically never geometrically and / or dimensionally equal to each other and often they are not even arranged in positions perfectly overlapping each other, hence one of the glass sheets usually has segments that protrude more or less in a cantilever fashion beyond the other glass sheet. Hence, it is difficult to control the position of the cutting heads in order to prevent the cutting edges of the same cutting heads from sliding in contact with one or the other glass sheet, suddenly wearing out.

In order to obviate such drawback, rollers of reference, generally of plastic material, are associated with the cutting heads, which rollers roll in contact with the sides of both glass sheets, mechanically keeping the cutting edge of the blade spaced from the glass sheets.

The trimming method of the type described above is sufficiently reliable and precise when the glass sheets have a large thickness, since the rollers can rest on relatively extended peripheral surfaces of the glass sheets. The trimming method described above, instead, is not usable or in any case is unsatisfactory in the presence of "thin" glass sheets, i.e. having a thickness of less than a couple of millimetres. In such conditions, it is necessary to use rollers having a very moderate diameter and in any case the side supporting surface of the rollers is minimal. Hence, the laminated glass assemblies having "thin" glass sheets are still manually trimmed.

In addition to this, the automatic trimming method is not usable or in any case is unsatisfactory when the glass sheets are coated glass sheets, for example low-emissivity glass sheets, where the coating layer (low-E) placed on the glass sheet is, by its nature, very delicate and is often damaged by the sliding of the rollers of reference.

<CIT> discloses a method for trimming a coating layer of an extended external surface of a single glass sheet. <CIT> discloses a method for forming a laminated glass semi finished product, wherein a peripheral portion of a sheet of thermoplastic material is allowed to protrude beyond the outer peripheral edges of a glass sheet, and trimming said peripheral portion by means of a cutting tool. The width of the glass plates can be measured beforehand and the cutting tools can be placed in the correct position according to the measured width.

The object of the present invention is to provide a method for forming a laminated glass semifinished product for forming a laminated glass sheet, which allows solving the problems described above in a simple and cost-effective manner and, in particular, a method which allows trimming the intermediate sheet of thermoplastic material regardless of the geometrical and dimensional characteristics of the side glass sheets, of their thickness and of their relative position.

According to the present invention, a method is provided for forming a laminated glass semifinished product for forming a laminated glass sheet; the method comprising the steps of forming an assembly of laminated glass by interposing a sheet of thermoplastic material between two side glass sheets and allowing at least a peripheral portion of said sheet of thermoplastic material to protrude beyond the outer peripheral edges of said glass sheets, and trimming said peripheral portion by means of a cutting tool; the trimming of said peripheral portion comprising the steps of keeping a cutting edge of said cutting tool spaced from both of the outer peripheral edges of said glass sheets; characterised in that keeping the cutting edge in a position spaced from said peripheral edges comprises the steps of advancing said cutting tool by means of a motorised cart movable in a rectilinear direction; detecting by means of at least an optical detector and during said trimming operation, at least a peripheral segment of the peripheral edge of one of the glass sheets that protrudes in a cantilever fashion beyond the other glass sheet and; generating a corresponding segment position signal; said cutting edge being kept spaced from said peripheral edges by a command and control unit acting on a motorised actuator carried by said motorised cart and in response to the segment position signal received from said optical detector.

The present invention also relates to a trimming machine for forming a laminated glass semifinished product.

According to the present invention, a trimming machine is provided for forming a laminated glass semifinished product, as claimed in claim <NUM>.

The invention will now be described with reference to the accompanying figures, which show a non-limiting embodiment example thereof, wherein:.

In <FIG>, reference numeral <NUM> indicates, as a whole, a trimming machine for trimming a laminated glass assembly <NUM>, illustrated with continuous lines in <FIG>, and forming a laminated glass semifinished product <NUM>, illustrated with a dashed line always in <FIG>.

With reference to <FIG>, the laminated glass assembly <NUM> comprises two side glass sheets <NUM> and <NUM> having respective peripheral edges 4A and 5A, different from each other and a sheet <NUM> of thermoplastic material arranged between the glass sheets <NUM> and <NUM>. The sheet <NUM> has a greater extension than both the glass sheets <NUM> and <NUM> such to have one or more peripheral portions <NUM> which protrude in a cantilever fashion beyond both edges 4A and 5A. In the illustrated example, the portions <NUM> are joined together.

According to a variant, the peripheral portions <NUM> are at least partially separated from each other so as to form peripheral wings which extend in a cantilever fashion beyond one or both peripheral edges 4A and 5A.

Always with reference to <FIG> and, in particular, to <FIG>, the machine <NUM> comprises a motorised inlet conveyor <NUM>, known per se and not described in detail, for example of the type having motorised belts or rollers, which defines a surface <NUM> for supporting and advancing the laminated assembly <NUM> along a rectilinear path P.

The machine <NUM> then comprises an outlet conveyor <NUM>, this also motorised and known per se, arranged along the path P downstream of the conveyor <NUM> in the direction of advancement H of the assembly <NUM> and defining a supporting surface <NUM> for the semifinished product <NUM>. Conveniently, the supporting surface <NUM> is coplanar with the surface <NUM> and is horizontal.

Between the two supporting surfaces <NUM> and <NUM> and astride a separation zone <NUM> of the conveyors <NUM> and <NUM>, the machine <NUM> comprises a portal frame <NUM>, in turn comprising two uprights <NUM> arranged on opposite lateral sides of the supporting surfaces <NUM> and <NUM> and a crosspiece <NUM> extending orthogonally to the path P, parallel to the supporting surfaces <NUM> and <NUM> and in a raised position with respect to the supporting surfaces <NUM> and <NUM>.

The crosspiece <NUM> supports two trimming devices for the intermediate sheet <NUM> arranged side by side and indicated by <NUM> and <NUM>.

The device <NUM> is an orientable device configured to trim the two edges A and B transversal to the path P and the longitudinal edge C of the assembly <NUM>, while the device <NUM> is provided for trimming the longitudinal edge D of the assembly <NUM> (<FIG> and <FIG>).

With reference to <FIG> and <FIG>, the device <NUM> comprises a cart <NUM> actuaed by a motor <NUM> for moving in opposite directions along the crosspiece <NUM> in a rectilinear direction <NUM> parallel to the surfaces <NUM> and <NUM> and orthogonal to the path P.

The device <NUM> also comprises a guide and slide assembly <NUM>, a rectilinear guide <NUM> thereof (<FIG>) is coupled to the cart <NUM> by means of a hinge for rotating around a vertical axis <NUM> orthogonal to the surfaces <NUM> and <NUM> under the thrust of a rotator <NUM> comprising an electric motor <NUM> arranged on board the cart <NUM>.

The guide and slide assembly <NUM> then comprises a slide <NUM> slidingly coupled to the guide <NUM> in a rectilinear direction <NUM> orthogonal to the direction <NUM> and to the direction <NUM> and parallel to the surfaces <NUM> and <NUM> under the thrust of an electric motor <NUM>.

The slide <NUM> carries a firmly connected supporting structure <NUM>, which extends downwards and carries, in turn, a coupled trimming head <NUM>. The trimming head <NUM> is provided with a motorised cutting blade <NUM>, conveniently a disc blade. Each blade <NUM> is rotatable about its own axis of rotation parallel to the direction <NUM> and has a cutting edge for cutting transversely the portion(s) <NUM> of the thermoplastic sheet <NUM>, as will be better described below.

Still with reference to <FIG> and <FIG>, the device <NUM> further comprises a pair of optical detectors, indicated by <NUM> and <NUM> (<FIG>).

In the illustrated example, the optical detectors <NUM> and <NUM> are carried by the structure <NUM> and, in particular, are firmly connected to the free ends of respective cantilevered arms <NUM>, the opposite ends thereof are firmly connected to the structure <NUM>. In this manner, the optical detectors <NUM> and <NUM> precede the trimming head <NUM> in the direction of advancement of the trimming head <NUM> and of the cart <NUM>.

Alternatively, at least one of the arms <NUM>, for example the upper one, is adjustable, i.e. placed at a variable distance from the other arm <NUM> so as to adjust the distance of the relative optical detector <NUM> from the supporting surface <NUM>.

According to a variant, the head <NUM> is slidingly coupled to the structure <NUM> in a direction <NUM> parallel to the axis of rotation of the blade <NUM> under the thrust of a relative linear actuator for moving in opposite directions with respect to the structure itself.

In any case, the optical detectors <NUM> and <NUM> are arranged on opposite sides of the supporting surface <NUM> and, in use, of the sheet <NUM> of thermoplastic material and are arranged facing the supporting surface <NUM> for detecting, always in use, the profile of the sheet <NUM> and of the sheet <NUM>, respectively, and for sending corresponding edge position signals to a control unit <NUM> of the machine <NUM>.

The device <NUM> is constructionally identical to the device <NUM> and the component parts thereof are marked, where possible, by the same reference numerals of the corresponding parts of the device <NUM>. The device <NUM> differs from the device <NUM> in that it is devoid of the rotator <NUM> and in that the relative guide <NUM> is fixed to the relative cart <NUM> in a position orthogonal to the guide <NUM> of the device <NUM>.

According to a variant, the devices <NUM> and <NUM> are constructively identical. This allows manufacturing a single device and detecting assemblies whose edge D is not rectilinear.

Again with reference to <FIG>, the unit <NUM> comprises a receiver block <NUM> adapted to receive the position signals sent by each pair of detectors <NUM>, <NUM>, and for each pair of detectors <NUM>, <NUM> a block <NUM> for comparing and selecting the signals received and a block <NUM> for controlling the relative motors as a function of the selected signal.

The laminated semifinished product <NUM> is formed as follows.

Firstly, the laminated glass assembly <NUM> is formed by interposing the sheet <NUM> between the sheets <NUM> and <NUM>. Thereafter, the laminated assembly <NUM> is arranged on the supporting surface <NUM> and keeping the trimming devices <NUM> and <NUM> at one end of the crosspiece <NUM> and the device <NUM> oriented so as to arrange its own optical detectors <NUM> and <NUM> on the side of the edge A, as illustrated in <FIG> and <FIG>, the laminated assembly <NUM> is advanced along the path P in the direction H until its front edge A is arranged in the zone <NUM>, i.e. in a position such to be detected by the optical detectors <NUM> and <NUM>.

At this point, keeping the laminated glass assembly <NUM> and the device <NUM> stationary, the device <NUM> is advanced by moving the relative cart <NUM> in the direction <NUM> towards the edge C and after setting its blade <NUM> in rotation. Simultaneously or slightly in advance with respect to the movement of the cart <NUM>, the unit <NUM> actuates the detectors <NUM> and <NUM> of the device <NUM>, which begin to detect in a continuous or discrete manner or, also by points the various segments of the front edge of the glass sheet <NUM> and, respectively, the various segments of the front edge of the glass sheet <NUM> and to send corresponding glass sheet edge position signals to the block <NUM> of the unit <NUM>. Conveniently, each detector <NUM>, <NUM> detects the mentioned edges of the glass sheets by emitting and directing an optical beam orthogonally to the glass sheets <NUM>, <NUM>. The unit <NUM> by means of the comparison and selection block <NUM> compares the signals received with each other, identifies the signal corresponding to the segment of the glass sheet that protrudes in a cantilever fashion with respect to the segment of the other glass sheet, in the specific case the segment <NUM> of the sheet <NUM> and controls the electric motor <NUM> so as to keep the blade <NUM> tangent or at a predetermined distance L from the edge of the sheet <NUM> (<FIG>). In this manner, the blade <NUM> progressively cuts the portion 7A of the sheet <NUM> along a cutting line indicated by K.

When the detectors <NUM> and <NUM> detect the corner (the right one of <FIG>), the unit <NUM> acting on the motor <NUM>, rotates the guide <NUM> counterclockwise in <FIG> and <FIG>, bringing the blade <NUM> in a position parallel to the longitudinal side C of the laminated assembly <NUM>. At this point, the unit <NUM> also actuates the device <NUM>, after which the laminated assembly <NUM> is advanced in the direction H of <FIG>. During the advancement of the assembly <NUM>, the optical detectors <NUM> and <NUM> of both devices <NUM> and <NUM> detect, in a manner analogous to what described above, the segments of the respective longitudinal edges C and D, transmit respective signals to the unit <NUM> which in response controls both motors <NUM> so as to keep both blades <NUM> tangent or at a determined distance M from the edges of the glass sheets that protrude in a cantilever fashion so as to move the blades <NUM> along respective longitudinal paths R and S as illustrated in <FIG>.

When the blades <NUM> reach the rear corners of the assembly <NUM>, the device <NUM> is stopped and the guide <NUM> of the device <NUM> is rotated by a further <NUM>° always counterclockwise, after which also the rear portion 7B is cut by guiding the cutting blade <NUM> as for the cutting of the front edge A along the line K1.

Once the rear edge has been cut, both devices <NUM> and <NUM> are returned to the starting position while the semifinished product <NUM> thus obtained is advanced into a heating station.

From the foregoing, it is to be understood that the use of the optical detectors <NUM>, <NUM> allows detecting, on the one hand, the segments of a glass sheet that protrude in a cantilever fashion with respect to the other glass sheet in a simple, precise manner and regardless of the thickness and of the geometry of the glass sheets <NUM> and <NUM>. On the other hand, the use of the optical detectors <NUM>, <NUM> allows detecting the segments or edges of the glass sheet protruding in total absence of physical contact with the glass sheets <NUM> and <NUM>. This is particularly advantageous especially in the presence of coated glass sheets, where it is indispensable to prevent physical contacts with the coating layer.

Finally, the control of the position of the blades <NUM> as a function of the signals coming from an optical detector allows keeping constant or varying arbitrarily in a simple and fast manner the distance between each blade <NUM> and the edges of the glass sheets <NUM>, <NUM> and therefore the overhang of the thermoplastic material increasing the operating life of the blade <NUM> and the quality of the trimming regardless of the geometry of the edges of the glass sheets.

From the foregoing it is to be understood that modifications and variants can be made to the described machine <NUM> without thereby departing from the scope of protection defined by the independent claim.

In particular, in the machine <NUM>, the trimming device <NUM> could be devoid of the relative optical detectors <NUM> and <NUM>, in the cases wherein along the longitudinal edge D of the assembly the glass sheets <NUM> and <NUM> have peripheral edges perfectly overlapping each other.

In addition to this, one or both trimming devices <NUM>, <NUM> could comprise a single optical detector <NUM>, <NUM> arranged above or below the supporting surface <NUM> but always in a position such to be able to detect the edge of that glass sheet which protrudes in a cantilever fashion beyond the edge of the other glass sheet. Such solution finds advantageous application, for example, in the cases wherein the thermoplastic sheet <NUM> is permeable to the light beam emitted by the optical detector <NUM>, <NUM> since it allows simplifying and reducing the cost of the trimming device(s) <NUM>, <NUM>.

Claim 1:
A method for forming a laminated glass semifinished product for forming a laminated glass sheet; the method comprising the steps of forming an assembly (<NUM>) of laminated glass by interposing a sheet of thermoplastic material (<NUM>) between two side glass sheets (<NUM>) (<NUM>) and allowing at least a peripheral portion (<NUM>) of said sheet of thermoplastic material (<NUM>) to protrude beyond the outer peripheral edges (4A)(5A) of said glass sheets (<NUM>)(<NUM>), and trimming said peripheral portion by means of a cutting tool (<NUM>); the trimming of said peripheral portion (4A)(5A) comprising the steps of keeping a cutting edge of said cutting tool (<NUM>) spaced from both of the outer peripheral edges (4A) (5A) of said glass sheets (<NUM>) (<NUM>); characterised in that keeping the cutting edge in a position spaced from said peripheral edges (4A) (5A) comprises the steps of advancing said cutting tool (<NUM>) by means of a motorised cart (<NUM>) movable in a rectilinear direction (<NUM>); detecting by means of at least an optical detector (<NUM>)(<NUM>) and during said trimming operation, at least a peripheral segment of the peripheral edge of one of the glass sheets (<NUM>) (<NUM>) that protrudes in a cantilever fashion beyond the other glass sheet (<NUM>)(<NUM>) and; generating a corresponding segment position signal; said cutting edge being kept spaced from said peripheral edges (4A) (5A) by a command and control unit (<NUM>) acting on a motorised actuator (<NUM>) carried by said motorised cart (<NUM>) and in response to the segment position signal received from said optical detector (<NUM>) (<NUM>) .