Abstract:
It has special application for preparing surfaces of two pieces of a composite material (fiber and resin) which have to be glued by means of an adhesive, establishing a perfect mutual contact between them. The preparation of the surface needs to be uniformed and without damaging the piece. 
     It consists of a moving frame ( 1 ) which can be displaced along some longitudinal guides ( 25 - 26; 27 - 28 ) integral with a bench ( 2 ) on which the piece ( 4, 6, 8 ) to grind is kept immobile. It includes a casing ( 14 ) containing a tool-carrier head ( 15 ) which rotates inside the casing adopting a floating arrangement for smoothly and uniformly pressing the piece to grind, advancing along the whole of the piece and following the geometry of its surface. 
     The casing ( 14 ) incorporates a nozzle ( 16 ) for connecting the inside of the casing to a suction hose for the dust and other particles produced. Moreover, said casing ( 14 ) can be displaced laterally in order to grind possible lateral surface extensions.

Description:
OBJECT OF THE INVENTION 
       [0001]    As stated in the title of this descriptive specification, the present invention relates to a surface grinding machine having special application in the preparation of the surfaces of two pieces made of a fiber and resin composite material, which have to be joined by gluing with an adhesive. 
         [0002]    It is an object of the invention to guarantee uniformity of the surface machining or activating of the surface of the pieces, in the zone of union thereof, for a range of abrasion of the activating agent without attacking the piece. 
         [0003]    It permits a process of preparation of the pieces with a notable increase in productivity and can have manual, semi-automatic or automatic actuation. 
         [0004]    It is especially useful for the surface machining of pieces of length very much greater than their dimension in width. 
       PRIOR ART OF THE INVENTION 
       [0005]    There do not currently exist any surface grinding machines that can follow the surface of the piece to grind in a way that is simple, allowing for its possible curvature so that the abrasive element of activating agent of the surface can pass smoothly over it without excessively attacking it in zones having a certain relief. 
         [0006]    All that is known are surface grinding machines such as milling machines or filing machines, etc., in which completely plane surfaces are obtained after the machining, in addition to the fact that these machines are very aggressive since they eliminate any projection from that surface to be ground. 
         [0007]    The preparation of surfaces, both for buffing and for the application of finishing products (paints, varnishes, etc.) is done in a way that is exclusively manual by means of sandpaper and similar products. 
       DESCRIPTION OF THE INVENTION 
       [0008]    In general terms, the surface grinding machine, which the invention proposes, consists of a moving frame or structure which can be displaced along some longitudinal guides provided in the bench of the machine on which the piece to be ground is kept perfectly secured, which piece, as we have said earlier, presents a very elongated configuration with respect to its dimension in width. This frame includes a casing inside which is to be found a tool-carrier head which rotates by means of a conventional pneumatic or electric device, connected to this head being the tool an abrasive tool or abrasive disc suited to the type of surface machining that is wished. 
         [0009]    This frame is duly displaced guided along the bench and the abrasive tool presses smoothly and constantly on the surface to treat, thanks to the fact that it includes a floating head that can be materialized by a sandwich structure assisted by springs coaxial to some guide rods, or it can offer a pneumatic lung structure with which a uniform pressure is also achieved, giving way in zones where the surface is not plane due to having a certain curvature, whether in elevation or depression, adapting itself perfectly to it. 
         [0010]    The casing also incorporates a connection nozzle to a suction hose for absorbing the dust and particles produced during the machining. 
         [0011]    The casing can furthermore be transversely displaced in the frame in order to be able to grind surface extensions that might exist to one side and the other of the basically longitudinal direction presented by the piece to treat. 
         [0012]    As the pieces to grind do not have marks or any kind of signal that could affect the uniformity of their surface, since this would lessen the quality of the piece and it could also be to the detriment of gluing the attached piece to the base piece, the pieces are respectively secured by means of a voiding device which attracts the piece by suction via a set of holes provided in the support zones, these holes, which are vertical, connecting with pertinent pipes and collectors. If the lower part of the piece to grind is not smooth (such as a T-shaped profile which has to be glued via its crosspiece to a base surface) the surface of the bench is formed from some modular elements by way of strips which can be fitted parallel to each other but at the required distance in order to allow for the core of this T-shaped profile, or any other relief that the piece might possess, in such a way that a vacuum is produced on the arms on one or the other side of the core. 
         [0013]    If the piece to grind is not completely plane but instead has a certain curvature and the depression produced by the voiding machine is not sufficient for achieving its immobilization by overcoming its elastic strength, provision is made for some bands of a cushion or similar type to be inserted, thereby optimizing the seating, and provided with holes in order to transmit the suction action. 
         [0014]    Other means of fixing can also be used different from that mentioned, which mechanically secure the piece in zones where it does not have to be ground, since the important thing is that the surface to be treated for the application of adhesive in this case does not become contaminated. 
         [0015]    In order to permit the adaptation of the abrasive tool to a small curvature existing in the surface to be ground, the tool-carrier is secured to the casing by means of a swivel joint or similar which permits a slight roll so that the tool or abrasive disc in particular can fit perfectly. 
         [0016]    So that the dust and particles formed can be eliminated more effectively, the perimetric edge of the casing includes a seal running along it formed from hairs of a certain length, which is applied to the surface of the bench during the advancing movement of the frame along it. 
         [0017]    In order to facilitate an understanding of the characteristics of the invention and forming an integral part of this descriptive specification, some sheets of plans are attached in which figures the following has, on an illustrative rather than limiting basis, been represented: 
     
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         [0018]    FIG.  1 .—Is a schematic view in perspective of the surface grinding machine, the object of the invention. 
           [0019]    FIG.  2 .—Is a view in longitudinal profile of that shown in  FIG. 1 . 
           [0020]    FIG.  3 .—Is a transverse section in profile of  FIG. 1 . 
           [0021]    FIG.  4 .—Is a partial view of some modular elements fixed to the bench and on which rests the piece to grind, provided with connection holes to a vacuum line. 
           [0022]    FIG.  5 .—Is a partial view in profile of a base piece of a composite material, provided with a pair of attachments of different cross-sections, joined by gluing once just the surfaces have been ground or activated that have to remain in contact with the addition of adhesive. 
       
    
    
     DESCRIPTION OF THE PREFERRED FORM OF EMBODIMENT 
       [0023]    Making reference to the numbering adopted in the figures, we can see how the surface grinding machine which the invention proposes consists of a moving frame  1  that can be displaced linearly in the longitudinal direction with respect to a bench  2  on which the pieces to grind are located, so that on a certain essentially longitudinal band or bands thereof the abrasive disc  3  will act which uniformly activates said surface for a range of abrasion that does not reach the point of attacking the piece, as we have said earlier. 
         [0024]    In  FIG. 3  can be seen the machining of a piece  4  with a T-shaped cross-section in which the continual or outside surface of its crosspiece  5  has to be ground in order to then glue this piece  4  on a base piece  6  (see  FIG. 5 ) which also has to be subjected to an identical machining process in the zones which have to receive said pieces  4  or attachments added by gluing. In this  FIG. 5  the adhesive  7  has been highlighted with a thick line which occupies just the zone of mutual contact of the two pieces  4  and  6 , once they have been ground in that same zone of contact. In this  FIG. 5  another piece  8  can furthermore be seen in the form of an “omega” likewise joined to the base piece  6  via its arms  9 , with all the surfaces in contact being subjected to the same abrasion process in order to optimize the gluing. 
         [0025]    Returning to  FIG. 1 , the moving frame  1  is lightweight and has a prismatic shape, schematically formed by four blocks  10  for fastening of the longitudinal  11  and transverse  12  bars which are secured with screws and with the tightening controls  13 . 
         [0026]    Located in this moving frame  1  is the casing  14  which houses the head  15  carrying the abrasive tool which, in this example of embodiment, is materialized in the form of the abrasive disc  3  referred to earlier. 
         [0027]    The casing  14  also have a rear extension with respect to the direction of advance along the bench  2 , where a connection outlet  16  is to be found for a suction system that will eliminate the dust and particles produced by the machining of the composite material of the pieces  4 ,  6  and  8 . 
         [0028]    The tool-carrier head  15  is coupled to an upper extension  17  of the casing  14  via a swivel joint  18  in order to permit small oscillations of the tool (abrasive disc  3 ) when the surface to grind is not a plane parallel to the plane of the support of the moving frame which advances manually following the surface of the T-shaped piece  4  (see  FIG. 3 ) in a single pass. The head  15  is floating so that the abrasive tool can follow the surface without attacking the piece  4 ,  6 ,  8 . This is schematically represented by the sandwich shape shown by the tool-carrier and located between its parallel plates are some springs  19  coaxial to some rods  20  integral with one of the plates. In this way, the abrasive tool gives way when necessary, and at the same time a slightly abrasive pressure is constantly exerted on the surface to grind. 
         [0029]    If wished, a height adjustment device can be incorporated for the head for better adaptability to the thickness of the piece to grind. 
         [0030]    The casing  14  can be displaced laterally to one side or the other when the surface to grind presents lateral deviations. To achieve this, provision has been made so that it can slide in the actual transverse bars  12  in which it is supported. When the machining is linear and there are no lateral deviations, the casing is locked in the desired position by means of the tightening control  21  (see  FIG. 1 ). 
         [0031]    As we have said earlier, the pieces to grind are locked on the bench  2  preferably by means of vacuum action so as not to damage them. In order to be able to be adapted to the different sizes and models of pieces to grind, such as the T-shaped profiles  4  or the omega-shaped one  8  referred to, the bench  2  includes some fixed modular elements  22  by way of strips along the length of the bench  2 , which can be located in the most suitable positions for achieving the seating of the piece and clearing the projections which this piece might have in its face opposite to the one for machining, such as the core of the profile  4  or the body of the omega-shaped profile  8 , since just the outside of the arms are ground. 
         [0032]    In this case, the strips or modular elements  22  possess holes  23  and internal pipes  24  linked together along with collectors, not represented, in order to communicate the vacuum and secure the pieces by means of depression. 
         [0033]    It can also be mentioned that the moving frame  1  advances (in this case manually though the advance can also be automatic) guided on the bench  2  by means of wheels  25  (see  FIG. 2 ) sliding on longitudinal rails  26  or resting on some lower Teflon-coated bands  27  (see  FIG. 3 ) and lateral bands  28 , though other guiding systems are not rejected, such as “air bushings” sliding on bars. 
         [0034]    In order to optimize suction of the dust produced by the machining, which is absorbed via the connection outlet  16  of the casing  14 , the perimetric edge of the walls of the casing  14  has a seal  29  running along the support surface, this seal preferably consisting of flexible vertical hairs.