Abstract:
An apparatus and a method to deform a plastic rivet is described herein. The apparatus comprises a generally tubular outer wall configured and sized to enclose the rivet to be deformed and a piston slidably mounted in the generally tubular outer wall for longitudinal movements between a rest position and a pressure applying position. The deformation of the plastic rivet occurs when said piston moves towards the pressure applying position.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates to rivets. More specifically, the present invention is concerned with a method and apparatus to deform plastic rivets.  
         BACKGROUND OF THE INVENTION  
         [0002]    Rivets are well known in the art. They are usually made of metallic material and are inserted in corresponding apertures of two elements to be secured together while hot and then deformed to permanently join the two elements.  
           [0003]    Variations on this theme have been designed over the years. For example, many rivets are now made of thin metallic material that can be deformed while they are at room temperature.  
           [0004]    Plastic rivets are also known in the art. For example, U.S. Pat. No. 4,478,544 issued on Oct. 23, 1984 and entitled “Composite Rivet” describes a composite rivet similar to a conventional blind rivet.  
           [0005]    Tools used to deform plastic rivets may also be found in the art. For example. U.S. Pat. No. 4,736,507 issued on Apr. 12, 1988 and entitled “Tool for setting plastic rivets” describes such a tool.  
         OBJECTS OF THE INVENTION  
         [0006]    An object of the present invention is therefore to provide an improved method and apparatus to deform a plastic rivet.  
         SUMMARY OF THE INVENTION  
         [0007]    More specifically, in accordance with an aspect of the present invention, there is provided an apparatus to deform a plastic rivet; said apparatus comprising:  
           [0008]    a generally tubular outer wall configured and sized to enclose the rivet to be deformed;  
           [0009]    a piston slidably mounted in said generally tubular outer wall for longitudinal movements between a rest position and a pressure applying position;  
           [0010]    wherein deformation of the plastic rivet occurs when said piston moves towards said pressure applying position.  
           [0011]    According to another aspect of the present invention, there is provided a method for deforming a plastic rivet comprising the acts of:  
           [0012]    enclosing a deformable portion of the rivet with a generally cylindrical outer wall;  
           [0013]    applying pressure on an end of the rivet with a piston slidably movably mounted in the outer wall.  
           [0014]    Other objects, advantages and features of the present invention will become more apparent upon reading of the following nonrestrictive description of preferred embodiments thereof, given by way of example only with reference to the accompanying drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]    In the appended drawings:  
         [0016]    [0016]FIG. 1 is a sectional view of a plastic rivet according to a first embodiment of the present invention shown prior to its deformation; FIG. 1 also shows a portion of an apparatus to deform the plastic rivet;  
         [0017]    [0017]FIG. 2 is a sectional view showing the plastic rivet of FIG. 1 during its deformation;  
         [0018]    [0018]FIG. 3 is a sectional view of the rivet of FIG. 1, fully deformed;  
         [0019]    [0019]FIG. 4 is a perspective view of a portion of an apparatus used to deform a plastic rivet;  
         [0020]    [0020]FIG. 5 is a sectional view similar to FIG. 1 but illustrating a plastic rivet according to a second embodiment of the present invention;  
         [0021]    [0021]FIG. 6 is a sectional view showing the plastic rivet of FIG. 5 during its deformation; and  
         [0022]    [0022]FIG. 7 is a sectional view of the rivet of FIG. 5, fully deformed.  
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0023]    Turning now to FIG. 1, a plastic rivet  10  according to a first aspect of the present invention will be described.  
         [0024]    The rivet  10  is part of a plastic plate  12  to which a second plastic plate  14  is to be permanently secured.  
         [0025]    The goal is to permanently deform the rivet  10  to therefore permanently secure the two plates  12  and  14 .  
         [0026]    This is done with an apparatus  16  partly shown in FIG. 1. This apparatus includes a generally tubular outer wall  18 , a deforming piston  20  and, optionally, a compression resistant surface  22  positioned opposite the outer wall  18 . Indeed, as will be understood by one skilled in the art, a compression resistant surface is required but need not be part of the apparatus  16 .  
         [0027]    The outer wall  18  includes a generally rounded shoulder  24  and the deforming surface  26  of the piston  20  is also generally rounded at the same radius as the shoulders to yield a semi-spherical surface once the piston  20  is in its fully compressing position (shown in FIG. 3).  
         [0028]    The surface  22  is generally flat and, if the apparatus  16  is in the form of pliers, may be hingeably mounted thereto. As will be described hereinbelow, the function of the surface  22  is to oppose the pressure generated by the movements of the piston during the deformation of the rivet  10 .  
         [0029]    Indeed, one skilled in the art will easily understand that an interesting form of the apparatus  16  consists in pliers. Advantageously, these pliers (not shown) would be so designed that the movement of the outer wall  18  towards the compression resistant surface  22  would occur before the movement of the piston  20  towards this same surface  22 . Of course, depending on the size of the rivet to be deformed, force multiplication schemes, such as, for example, ratcheting could be used.  
         [0030]    Returning to FIG. 1, it is to be noted that the aperture  28  includes a double rectangular shoulder ( 30  and  32 ). It is also to be noted that the portion of the rivet  10  exceeding the plate  14  has a volume that is generally equal to the sum of the volumes of the shoulders  30  and  32 , the rounded shoulders  24  and the concavity of the deforming surface  26 .  
         [0031]    The deformation of the rivet  10  will now be described with reference to FIGS.  1  to  3 .  
         [0032]    The first step in the deformation of the rivet  10  is illustrated in FIG. 1. His first step generally consists in moving the outer wall  18  in the direction of arrow  33  so that it encloses the rivet  10  while being in contact with the plate  14  while the surface  22  is in contact with the plate  12 , thereby firmly pressing the two plates  12  and  14  against each other.  
         [0033]    [0033]FIG. 2 illustrates the second step in the deformation of the rivet  10 . This step consists in physically deforming the rivet. More specifically, FIG. 2 illustrates the beginning of the deformation of the rivet  10  by the downward pressure of the piston  20  (see arrow  34 ). As can be seen in this Figure, the portion of the rivet  10  exceeding the plate  14  is gradually deformed to fill the shoulders  24 ,  30  and  32 . It is to be noted that during this step, the outer wall  18  does not move.  
         [0034]    Once the deformation is complete (see FIG. 3), the apparatus  16  used to deform the rivet  10  may be removed (see arrows  36  and  38 ) to leave the two plates  12  and  14  permanently attached.  
         [0035]    It is to be noted that depending on the type of plastic used to form the rivet  10 , it is possible to design an apparatus  16  where the piston  20  will move a little further than the position illustrated in FIG. 3 so that when the pressure is relieved, the spring back of the head of the rivet will form the spherical shape illustrated in FIG. 3.  
         [0036]    It is to be noted that the shoulders  30  and  32  are not required.  
         [0037]    Turning now briefly to FIGS.  5  to  7  of the appended drawings, a rivet  100  according to another embodiment of the present invention will be described. Since the rivet  100  is very similar to the rivet  10  illustrates in FIGS.  1  to  3  only the differences between these rivets will be described hereinbelow.  
         [0038]    As can be seen from FIG. 6, the main difference between the rivet  100  and the rivet  10  is the size. Indeed, the rivet  100  is not intended to have a semi-spherical head once deformed but is intended to be flat with the surface of the plate  14 .  
         [0039]    To achieve this flat deformation, the apparatus  102  has an outer wall  104  having flat shoulders and the deforming surface  106  of the piston  108  is also flat.  
         [0040]    Again, the deformation of the rivet  100  is done in the same steps as described hereinabove. The pre-deformation step is illustrated in FIG. 5 (see arrow  110 ), the deformation step is illustrated in FIG. 6 (see arrow  112 ) and the post deformation step is illustrated in FIG. 7 (see arrows  114  and  116 ).  
         [0041]    As will easily be understood by one skilled in the art, depending on the kind of plastic used to form the rivets  10  and  100 , the deformation may be done when the rivet is cold or warm.  
         [0042]    Turning now to FIG. 4 of the appended drawings, a pressure-applying portion  200  of an apparatus to deform plastic rivets will briefly be described.  
         [0043]    The portion  200  is designed to be mounted to a press-type machine to rivet three rivets at the same time. Of course, one skilled in the art will understand that more or less than three rivets could be deformed simultaneously.  
         [0044]    This portion includes a front element  208 , three tubular outer walls  214 ,  216  and  218 , three pistons  202 ,  204  and  206  longitudinally slidable in a respective tubular outer wall, and a rear element  210  configured to apply pressure on the protruding ends of the pistons  202 ,  204  and  206 .  
         [0045]    In operation, the front element  208  is positioned against the pieces to be joined (not shown but corresponding to the plate  14  of FIGS.  1  to  3 ) and then the rear element  210  is moved in the direction of arrow  212  to contact the protruding ends of the pistons  202 ,  204  and  206 , that are slidably mounted in respective tubular outer walls  214 ,  216  and  218 , to cause the pressure applying ends of the pistons to contact the rivets (not shown). The deformation of the three rivets is then done as described hereinabove.  
         [0046]    As will easily be understood by one skilled in the art, other apparatuses to deform plastic rivets could be designed.  
         [0047]    One skilled in the art, will understand that by enclosing the rivet to be deformed prior or at the beginning of the pressure applying step of the piston, the final shape of the deformed rivet is more predictable.  
         [0048]    It is to be noted that even though the appended figures all illustrate a plastic rivet that is integral with one of the plates, the above-described apparatus and method are not limited to that kind of rivet but would also be advantageous with rivets that are separate from both plates and where the plates are both provided with apertures.  
         [0049]    Although the present invention has been described hereinabove by way of preferred embodiments thereof, it can be modified, without departing from the spirit and nature of the subject invention as defined in the appended claims.