Patent Publication Number: US-6216759-B1

Title: Method and apparatus for gluing frames, mirrors, glass sheets and the like to panels, in particular furniture panels

Description:
BACKGROUND OF THE INVENTION 
     The present invention concerns a method and an apparatus for application of frames or mirrors of different shapes and dimensions to furniture panels in general. The method and the apparatus herein disclosed allows a quicker and more precise application of the frame or mirror to each panel. 
     DESCRIPTION OF THE PRIOR ART 
     In the furniture industry ornamental frames, mirrors or glasses are often to be applied to furniture panels. 
     Once the mirrors were applied to e.g. wardrobe doors by means of peripheral frames screwed to the panels used to make the doors. 
     However, fixing frames required long time to be mounted and the result was not always aesthetically acceptable. 
     To decrease the time necessary to set the mirrors and improve the aesthetic result, adhesive means are now used, which grip the mirrors at the back. This allows to apply also ornamental frames without any need to make holes in the panels for the screws or nails. 
     Up to now, ornamental frames or mirrors have been usually applied by means of double-adhesive sided tape, which was applied manually, in pieces, that obviously causes a considerable waste of time. 
     Another drawback of the double-adhesive sided tape is that the grip between the mirror and the panel is too rigid along the whole extension of the mirror. 
     The panels are often subjected to bending, e.g. during transport, or may fall down or have to support considerable weight, e.g. because of piling, and these facts taken alone or in combination often result in breaking of the mirror. Document DD-A5-286,321, to WEB MOBELWERKE EISENBERG, discloses a method for applying mirrors or glass sheets to panels by depositing at least one strip of hot glue onto the mirror or glass sheet, and then applying the panel to said mirror or glass sheet. This is made automatically, by using a single glue sprayer moving along guide rails, while the mirror or glass sheet is carried by a movable carriage. This method is not very efficient, particularly when high production rates or high accuracy are required. 
     Another problem arisen with the use of the known techniques derives from the fact that the panel to which a frame or a mirror has to be applied is often slightly curved. 
     When a frame is applied the bending of the panel provokes misalignment of its sides, which therefore must be kept in the correct position while the frame. is placed on the panel, that is not always a simple operation, in particular if long frames are processed. 
     The adhesive tape is first applied to the backside of the frame, and a wrong positioning of the frame on the panel requires detachment therefrom and reapplying of the frame. Obviously, this could damage the surface of the panel and increases the time required for the operation. 
     Moreover, times imposed by the industrial processing do not allow to strengthen those parts which are most subjected to breaking, because of e.g. through holes for handle screws or the like. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to facilitate the application of frames, mirrors, glass and the like on wardrobe doors or furniture panels in general, no matter of the condition, i.e. perfectly flat or slightly curved, of the panels. 
     Another object of the present invention is to make quicker and more precise the application of frames or mirror of different shapes and dimensions to furniture panels in general. 
     Yet another object of the present invention is to improve the breaking resistance of the fixed glass sheets, by optimal application of adhesive means, so that the two joined parts are less rigid and the most critical parts are reinforced. 
     A further object is to reduce the quantity of adhesive means to the just necessary quantity, with suitable adhesive means distribution, so as to reinforce the most stressed areas and avoid an excessive rigidity between the parts, which could provoke sheets breaking during bending. 
     Finally, it is another object of the invention to improve and make more durable the grip between the joined parts and guarantee a high level of finishing, aesthetically perfect. The above mentioned objects are obtained by means of a method for gluing mirrors, frames or glass sheets and the like to panels, in particular furniture panels, which includes depositing at least one strip of hot glue onto a panel, along a pre-determined path and then applying the mirror, frame or glass sheet to the panel. 
     To carry out the method, it is proposed an apparatus for gluing mirrors, frames or glass sheets and the like to panels, in particular furniture panels, which includes: 
     at least one table for receiving a panel thereon; 
     at least one horizontal cross bar extending over said table and connected to motor means for sliding over said table; 
     at least one slide running along said cross bar and equipped with at least one sprayer pistol for depositing at least one strip of glue on predetermined areas of said panel; 
     motor means for moving said slide along said cross bar. 
     Preferably the apparatus is equipped with an articulated place and press element which can rotate from an inclined position, in which the frame or mirror is loaded, to the horizontal working position, where actuator means push the place and press element downward on said panel, to apply the frame or mirror, and then pull the place and press element upward leaving the frame or mirror attached to said panel. 
     The place and press element is supported by a support bar extending over said table, with rotary actuator means interposed between said support bar and a plurality of uprights which connect said support bar to corresponding ends of said table. 
     The place and press element carries a frame receiving template of a shape corresponding to the frame shape and made of material having such elasticity that allows to compensate for possible working tolerances and deformations of the frame and the panel. 
     The machine, according to the present invention, is equipped with one or more movable cross bars, sliding over the panels supporting table, along which carriages carrying pistols or nozzles distributing hot glue can translate. 
     The cross bar and the carriages are moved in such a way as to deposit the glue along the desired path, corresponding to the frame shape, according to a program prepared in a numerical control station. 
     Moreover, the apparatus is equipped with a particular articulated pressing element supporting the frame, aimed at maintaining the frame in the correct position and pressing it in a uniform way, so as to compensate for deformations and inevitable working tolerance. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Now a more detailed description of the invention will follow, with reference to the enclosed drawings, which illustrate, only as possible examples, different embodiments. 
     FIG. 1 is a schematic view of the apparatus; 
     FIG.  2  and FIG. 3 show corresponding front and lateral views of the apparatus; 
     FIG. 4 shows a lateral view of the apparatus with the placing element in a raised position for mirror loading; 
     FIGS. 5,  6 ,  7  and  8  show schematically the sequence of movements of an articulated frame and pistols for glue distribution on a rectangular path; 
     FIGS. 9 and 10 show transversal section views of the placing element supporting a frame inserted in a template, and after application of the frame to the panel, respectively; 
     FIGS. 11 a  to  11   c  show the way to make a template used in connection with the apparatus; 
     FIG. 12 is a schematic, plan view of the apparatus in a simplified embodiment 
     FIG. 13 is a front view of the embodiment shown in FIG.  12 . 
    
    
     BEST MODES OF CARRYING OUT THE INVENTION 
     With reference to the above described figures, numeral  1  indicates a support table, on which a panel  2  is placed, maintained in the correct position by means of adjustable ledges  3  and adjustable pressing elements  4 . 
     Attached to the upper surface of the table  1  there are stripe elements  32 , made of rubber or another anti-scratch material, on which the panels  2  will be put. 
     According to the invention, the method includes depositing one or more strips  35  of hot glue onto the panel  2 , along a path corresponding to the frame or to the outer border of the mirror to be applied. 
     Then, before the glue becomes cold and hard the frame or mirror or glass sheet is applied to the panel, either manually or by means of an automatic device connected to the apparatus. 
     The strips of glue can be continuous or discontinuous. In the drawings, FIGS. 5 to  9 , two strips  35  have been shown, but this is only an example and there can be only one strip or three and even more parallel strips  35 . 
     Moreover, other path can be followed or other lines can be added to the path shown in FIG. 8, e.g. a longitudinal middle line or transversal middle line, that are not shown since they are obvious to those skilled in the art. 
     Preferably, the method just described should be carried out by means of an automatic apparatus, because manual application cannot give strips as precise as they must be, and moreover manual application is too slow, so that when the strips of glue have been completed the glue applied first is already cold and hard. 
     However, it is to be understood that the method can be carried out by manual application of the strips of glue, by means of a brush or a sprayer pistol. 
     According to the invention, the apparatus to carry out the method includes a carriage  7 , moved by a ratiomotor  8  along a longitudinal guide rail  5  fastened to a side border of the table  1 , as shown in FIG.  1 . 
     The motion can be obtained by means of a pinion, not shown in the figures, keyed to the ratiomotor  8  with a toothed wheel meshing with a rack  6  fastened guide rail  5 . 
     It should be understood that other means can be used instead of the ratiomotor  8 , the toothed wheel and the rack  6  to move the carriage, such as a screw set parallel to the guide rail and in mesh engagement with a nut thread made in the carriage, or an endless belt extending parallel to the guide rail  5  and fastened in a point to the carriage. A wire can be used in place of the belt. 
     In any case, the carriage  7  has a cantilevered cross bar  9  protruding therefrom towards the side border of the table opposite to the guide rail  5  and over the panel  2 . 
     Obviously, a second guide rail can be fastened also to the other side of the table with a second carriage sliding thereon. The cross bar  9  is then connected to both the carriages. 
     A slide  10 , supporting with possibility of adjustment, a sprayer pistol  11  for hot glue distribution, is moved along the cross bar  9 , e.g. driven by a ratiomotor  12  and a screw  13  engaging a nut thread made in the slide  10 . 
     It should be understood that other means can be used instead of the screw parallel to the cross bar  9  and the nut thread made in the slide  10 , such as a ratiomotor  8  connected to a toothed wheel and a rack fastened to the cross bar. Also an endless belt extending parallel to the cross bar  9  and fastened in a point to the slide  10  can be used. A wire can be used in place of the belt. 
     As shown in FIGS. 1 and 2, the cross bar  9  supports also a non motorised slide  14 , which can be placed in any position along the cross bar and fixed thereto by means of locking means, not shown. 
     A second sprayer pistol  15 , for hot glue distribution, is applied to the stationary slide  14  with possibility of adjustment. 
     In this particular embodiment, two sprayer pistols are used, of which one is movable and one is stationary with reference to the cross bar  9 . However, this is only one of the possible embodiments of the invention. A variation is possible according to which only one sprayer pistol is used, preferably the movable one. 
     According to another possible variation, also the second sprayer pistol  15  is carried by a slide moved along the cross bar  9  by means of a ratiomotor and a screw as shown with a dashed line in FIG.  1 . Other means can be use to move the slide as in the previous case. 
     Another possible feature of the apparatus includes means for raising and lowering the cross bar  9 , that is shown in a raised position with a dashed line in FIG.  4 . However, these raising and lowering means are not shown since they are obvious to those skilled in the art. 
     The glue is delivered to the pistols or nozzles through ducts  39  which are connected to a hot glue supply station  50 , as seen in FIG.  2 . 
     Lastly, a process control unit, schematically indicated at  40  in FIG. 2 and 13, is connected to the ratiomotors  8  and  12  for cross bar  9  and slide  14  motion control. 
     FIGS. 5,  6 ,  7  and  8  show the movements sequences of the cross bar  9  and motorised slide  10  in order to deposit the glue strips  35  onto the panel  2 , e.g. following a rectangular path, as it will be better described in the following. 
     With reference to FIGS. 1 to  4 , over the table  1  there is also a flat place and press element  16  which is supported by a longitudinal support bar  20 , extending over the table  1  and held by vertical uprights  22  situated at both ends of the table  1 . 
     The longitudinal support bar  20  can be rotated by rotating actuators  21  located at the connecting points between the bar  20  and the uprights  22 , while the place and press element  16  can be lowered, and raised after lowering, by pneumatic cylinders  19  fixed to the longitudinal bar  20 . 
     The result is a possibility for the place and press element  16  to rotate about the longitudinal bar  20  and move up and down. 
     Generally, other means can be used to move the place and press element up and down. 
     The place and press element  16  is equipped with suction cups  23  connected via suitable spiral ducts  24 , shown only in part in FIGS. 9 and 10, to a vacuum system not shown in the figures. 
     The mirror  25  is held by the suction cups  23  as shown in FIG. 2, before the glue strips are deposited and then applied by lowering of the place and press element  16 . If a frame  17  is to be applied to the panel  2 , a template  18  should be used. 
     As shown in fugues  11   a , 11   b , 11   c , the template is obtained by pouring a liquid resin into a mould  30 , FIG. 11 a , together with a catalyst liquid. The mould  30  is made of angle section bars suitably fixed to a plate  26 . Then, a panel  2  with a frame  18  already attached thereto is placed over the mould  30  in such a way that the frame  18  is dipped into the resin (see FIG. 11 b ). 
     After the resin has become hard, about twelve hours later, the panel  2  is raised and the angle section bars are removed (see FIG. 11 c ). 
     The template  18  thus obtained has a groove which receives the frame as a tight fit. To improve frame retention and frame ejection, a plurality of through holes  27  are made in the bottom of the groove and in the plate  26 . With reference to FIG. 2, the holes  27  are connected via hoses  28  to a suction/pressure source not shown. 
     In this way a template is obtained in a very quick and easy way and can be mounted without centring operation, as it will be described in the following. 
     At the beginning of the operation, the stationary slide  14  is positioned so as to run over one side of the path and then fixed to the cross bar. 
     The movable slide  10  is controlled by the process control unit. In case that also the slide  14  is movable, both the slide are controlled by the process control unit. A suitable programme is loaded in the process control unit, e.g. via a disk drive unit. Obviously, other means can be used to input data, such as a keyboard or a net connection, etc. 
     Operation description will now consider a case in which a frame  17  is to be applied to the panel. 
     A sample panel with a frame already attached thereto is set on the table  1 . Positioning of the panels is facilitated by peripheral adjustable ledges  3  and adjustable pressing elements  4 . 
     The panel is blocked by pneumatic pressure means  45  which are adjustable along the guide rail  5 . The pressure means  45  are better shown in FIG.  12 . 
     The support plate  26  with the template  18  is positioned onto the sample panel with the frame  17  inserted into the groove of the template. 
     The place and press element  16  is then lowered until the suction cups  23  touch the upper surface of the support plate  26 , and then they are activated. Connection of the plate and template assembly is immediate with very high precision. The place and press element  16  is raised and the sample panel removed. 
     To change the template for another one, e.g. for another panel, the same operation can be carried out in a very short time. 
     Obviously, other means can be used to fix the template to the place and press element  16 , with or without the support plate  26 , such as screws or clamp means, without going out of the scope of the invention. 
     The first panel  2  is set on the table  1  and the place and press element  16  is rotated as shown in FIG.  4 . The operator inserts a frame into the groove of the template and then the place and press element  16  is rotated and brought to the position shown in FIG.  3 . 
     Suction is applied to the through holes  27  to safely keep the frame  17  inside the template  18  (see FIG.  9 ). 
     At this point, the programmable process control unit  40  makes the slide  10  move along the cross bar  9  and the pistol  11  delivers the glue thus forming transversal strips  35  of glue, as shown with broken line in FIG. 6, corresponding to one side of the path. 
     Subsequently, the cross bar  9  is moved, and simultaneously, the glue is delivered by the pistols or nozzles  11  and  15 , so as to form longitudinal strips  35  on the two longitudinal sides of the path, as shown with broken line in FIG.  7 . 
     After having reached the final position, the cross bar  9  is stopped, the fixed pistol  15  stops delivering glue and the slide  10  is operated again so as to complete, with the pistol  11  still active, the last side of the path, as shown in FIG.  8 . 
     In case that only one movable sprayer pistol is used, only the longitudinal side of the path is made in the forward stroke of the cross bar  9 , while the other longitudinal side of the squared path formed by glue strips is made in the return stroke of the cross bar  9 . 
     If two movable sprayer pistols or nozzles are used, the path will start from a corner with one transversal side of the path deposited by the first movable sprayer pistol, then the two longitudinal side of the path are deposited by both pistols in the forward stroke, and lastly the second transversal side of the path is deposited by the second sprayer pistol. Other paths can be easily followed, such as with longitudinal sides which are not straight lines but curved inwards or outwards. 
     According to the example shown in the figures, the frame is squared as well as the path followed by the strips  35  of glue. 
     With other shapes of the frame the strips of glue will follow a corresponding path. 
     Afterwards, the cross bar  9  is brought again to the rest position of FIG. 1, in order to allow the place and press element  16  to go down to apply the frame and then go up (see FIG. 10) leaving the frame on the panel. 
     To facilitate extraction of the frame from the template, pressure is applied to the through holes  27  of the template  18 . 
     The panel  2  with the frame  17  attached thereto is removed from the table  1  and a new panel is set thereonto. 
     Operation description will now consider a case in which a mirror  25  is to be applied to the panel  2 . 
     The first panel  2  is set on the table  1 . 
     The place and press element  16  is rotated as shown in FIG. 4 and a mirror  25  is positioned on the element  16 , where suitably located stops  29  determine the precise collocation thereof. In other case, the place and press element  16  can pick up the mirror from a supply line, not shown. 
     Afterwards the place and press element  16  is rotated and brought to the position shown in FIG.  3 . 
     At this point, the programmable process control unit makes the slide  10  and the cross bar  9  move as already explained before, while the pistols  11  and  35  deliver the glue forming transversal and longitudinal strips  35  of glue, as shown in FIGS. 6 to  9 . 
     Also in this case if only one pistol or two movable pistols or nozzles are provided, operation of the device will proceed as explained hereinabove for the frame application apparatus. 
     At the end, the cross bar  9  is brought again to the rest position of FIG. 1, in order to allow the place and press element  16  to go down and apply the mirror  25 . 
     The panel  2  is replaced with a new panel without mirror. 
     It is also possible to apply the mirror manually, that means without using the place and press element  16 . 
     When mirrors or glass sheets are applied manually, the apparatus preferably, but not necessarily, does not include the place and press element  16  with the uprights  22  and the longitudinal bar  20 . 
     In fact, also with apparatus equipped with the place and press element  16  mirrors, frames or glass sheets can be applied manually by setting the place and press element  16  out of operation. 
     Application of the mirrors, frames or glass sheets in determined position with respect to the panel edges is facilitated by double peripheral adjustable ledges  3 , of different height and which project inwards over the panel  2 . It is understood that other means can be used to position the mirrors, frames or glass sheets with respect to the panel; the apparatus could be, for instance, equipped with automatic devices which pick the panels, frames or glass sheets from a supply line and place them to the panel without any need of ledges or stops. 
     An example of this configuration can be seen in FIGS. 12 and 13. 
     After the strips  35  of glue have been positioned by the sprayer pistols  11 , 15  the mirror is manually placed on the panel  2 . 
     According to another embodiment shown in FIGS. 12 and 13, the apparatus includes substantially two supporting tables, arranged end to end. 
     A double support table allows to apply the mirror, or the frame, to one panel, placed on one table, and to load a second panel on the other table  1 ′ meanwhile the first panel is spread with glue. 
     It is possible to use only one cross bar  9 , that slides over one table  1  first and then over the other table  1 ′. As an alternative configuration, two cross bars  9  can be mounted, with each cross bar sliding over a related table  1 , 1 ′. 
     With reference to FIGS. 12 and 13, numerals  1  and  1 ′ indicate the two end to end support tables, equipped with adjustable ledges  4  and  4 ′ provided for precise and quick positioning of the panels. 
     As an alternative advantageous solution, substitution of the panels laying on the support tables, arranged side by side, can be performed by a conveying band, with connected thereto manipulators for mirrors and panels. 
     According to the above description, the apparatus of the invention achieves all the objects stated hereinabove. 
     After having deposited the glue onto the panel, either at pre-established intervals or continuously, the mirror or the frame can be applied before the glue becomes cold and hard, and therefore the gripping action is always satisfactory. 
     The glue can be more concentrated in possible points which are more subject to breaking, and anyway it does not produce a rigid connection, so that the panels can be subjected to bending, loads (e.g. when piled) and shock with no mirrors broken or frame detached. 
     The glue distribution could begin at the side opposite to the one shown in the FIGS. 5 and 6, so as to finish near the cross bar rest position, thus reducing the break between the glue distribution and the frame application, which must occur with the glue still hot. 
     The articulated pressing, frame supporting element  16  is first made to rotate from the working position of FIGS. 1,  2  and  3  to the position of FIG. 4, in order to allow an easy loading of the frame  17  to the corresponding housing, as seen in FIG.  9 . 
     This housing is a groove having a shape corresponding to the frame shape and made of a synthetic resin or another material of such elasticity that allows to distribute the pressure uniformly on all the parts, so as to compensate for inevitable tolerances and deformations of the frame and the panel. 
     The carriage  7  could be equipped with another cross bar, or even more, with different pistols or nozzles for hot glue delivery, either motorised or not motorised but adjustable, to be used for gluing mirrors or glass sheets of big dimensions, when it is suitable to add glue distributing units so as to avoid its getting cold too early before the mirror or glass sheet application. 
     In this case, the place and press element  16  could also be equipped with heating means, aimed at delaying the distributed glue getting cold, or other means improving the apparatus operation and the operator&#39;s security. The actuating devices can be of any type suitable for this purpose. 
     Not essential constructive details can differ from the illustrated ones, which are given as a pure example, remaining within the protective limits of the present invention as defined by claims.