Abstract:
A mold for producing a product with internal flutes is provided. The mold includes a mold body that defines a cavity and a shaft in proximity to the cavity. A pin assembly is receivably engaged in the shaft of the mold body. The pin assembly includes a pin with a grooved portion that has at least one helically shaped groove, a sleeve surroundingly disposed about a portion of the pin, and means to allow rotation of the pin. A gap is defined in between a portion of the walls of the shaft of the mold body and the grooved portion of the pin and the gap is partially terminated by a portion of the sleeve. A method of molding is also provided.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
   This application claims the benefit of U.S. Provisional application Ser. No. 60/335,079, filed on Oct. 24, 2001. 

   FIELD OF THE INVENTION 
   The present invention relates to the art of molding polymers. More particularly, the present invention relates to an apparatus for molding a fastener assembly for plastic components. 
   BACKGROUND OF THE INVENTION 
   The molding of fasteners that are made from polymers often involves complex tooling. For example, the intricate shape of many fasteners requires that the molds often include complex cavities with multiple movable sections to allow a fastener to be molded and then removed without damage. This use of multiple sections increases the cost of the molds and the complexity of the molding operation. 
   In copending U.S. patent application Ser. No. 10/279,434, filed on Oct. 24, 2002, a fastener assembly including molded internal flutes is disclosed. Molding such a fastener using an apparatus of the prior art involves significant expense, as a complex mold (as mentioned above) must be utilized. This same problem applies to other plastic products and fasteners that incorporate internal flutes. 
   As a result, there is a need for a molding apparatus that may overcome the disadvantages of the prior art by allowing a polymer component with internal flutes to be molded and extracted without the use of a complex and costly mold. 
   BRIEF SUMMARY OF THE INVENTION 
   In an exemplary embodiment of the present invention, a mold for producing a product with internal flutes is provided. The mold includes a mold body that defines a cavity and a shaft present in proximity to the cavity. A pin assembly is receivably engaged in the shaft of the mold body. The pin assembly includes a pin with a grooved portion that has at least one helically shaped groove, a sleeve surroundingly disposed about a portion of the pin, and means to allow rotation of the pin. A gap is defined in between a portion of the walls of the shaft of the mold body and the grooved portion of the pin and the gap is partially terminated by a portion of the sleeve. 
   The mold may include two halves, i.e., an upper half and a lower half, where the shaft is defined in the lower half. In addition, the angle of the groove with a radial axis of the pin is between about 30 degrees and about 360 degrees, more preferably between about 60 degrees and 180 degrees, and most preferably between about 90 degrees and 120 degrees. Of course, the at least one groove includes a plurality of grooves. 
   It is important to note that the pin rotates independent of the sleeve. The rotation begins when the sleeve moves toward the gap, i.e., in an upward direction. The rotation of the pin continues as the sleeve moves upward until a shoulder of the sleeve reaches a positive stop. The means to allow rotation of the pin includes a bearing. The bearing is located between a shoulder of the pin and a retaining member of the mold, where the retaining member prevents upward movement of the pin. The means to allow rotation may also include a first washer and a second washer, disposed on either side of the bearing. 
   In another exemplary embodiment of the present invention, an apparatus for use in a mold includes a pin with a lower end and an upper end. A pin shoulder is proximate the lower end of the pin and at least one helical groove is located at the upper end of the pin. A sleeve is disposed about a portion of the pin and means for allowing the pin to rotate within and independent of the sleeve are included. 
   The angle of the groove with a radial axis of the pin is in a range of about 30 degrees to 360 degrees, and the at least one helical groove includes a plurality of grooves. The means for allowing the pin to rotate includes a bearing near the pin shoulder, which may be located in between a first washer and a second washer. 
   In yet another exemplary embodiment of the present invention, a method of molding is provided. The method includes the steps of providing a mold that defines a cavity and a shaft proximate the cavity and inserting a pin assembly into the shaft. The pin assembly includes a pin with a grooved portion defining at least one helical groove, a sleeve disposed about a portion of the pin, and means to allow rotation of the pin. A gap is formed between a portion of the walls of the shaft and the grooved portion of the pin and at least a portion of the gap is sealed with a portion of the sleeve. Molten polymer is injected into the cavity and the gap and the polymer is cooled. The sleeve is moved in the direction of the gap, causing the pin to rotate. 
   The step of injecting molten polymer into the cavity and the gap may include forming at least one flute in the at least one helical groove. In addition, the rotation of the pin may be caused by the force of the at least one flute acting on the at least one helical groove as the sleeve is moved in the direction of the gap. The rotation of the pin may be facilitated by a bearing. Moreover, the sleeve may include a shoulder, where the method may also include the step of extracting a molded part when the shoulder contacts a positive stop 
   There are other objects and features of the invention, which will be apparent from the following description and claims. 

   
     BRIEF DESCRIPTION OF THE FIGURES 
     The following is a brief description of the drawings, which are presented for the purpose of illustrating the invention and not for the purpose of limiting the same, and wherein: 
       FIG. 1  is a top perspective view of a fastener assembly; 
       FIG. 2  is a side elevational view, partially in section, of the apparatus of the present invention in a mold that is in a molding position; 
       FIG. 3  is a side elevational view, partially in section, of the apparatus of  FIG. 2  in a mold that is in an ejection position; 
       FIG. 4  is a perspective view of a component of the apparatus of the present invention; and 
       FIG. 5  is a perspective view of multiple components of the apparatus of the present invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Referring now to the drawings, wherein the showings are for purposes of illustrating preferred embodiments of the invention and not for the purpose of particularly limiting the same,  FIG. 1  shows a molded plastic product  10  with a fastener assembly such as a cylindrical wall  12 . The cylindrical wall  12  may extend out from the plastic product  10  (as shown) or into the plastic product  10 . The cylindrical wall  12  defines a longitudinal bore  14  in its inner diameter. Extending radially into the bore  14  from the wall  12  in a helical manner is at least one flute or rib  16 . 
   The flute  16  commences at the top of the wall  12  and extends the length of the wall  22 . The angle of the flute  16  with a radial axis of the cylindrical wall  22  is between about 30 degrees and about 360 degrees, more preferably between about 60 degrees and 180 degrees, and most preferably between about 90 degrees and 120 degrees. The flute  16  may be of right-hand, i.e., extending down to the right, or left-hand, i.e., extending down to the left, orientation. Of course, more than one flute  16  may be present, as shown in  FIG. 1 , and in such a case, the flutes  16  extend along a helical path in a spaced parallel manner. 
   Turning now to  FIG. 2 , a mold  22  used to manufacture a fastener such as the cylindrical wall  12  with internal flutes  16  is shown. The mold includes an upper half  22   a  and a lower half  22   b . A pin assembly  24  is inserted into one of the mold halves  22   a  of  22   b , and is shown as an example in the lower mold half  22   b.    
   With additional reference to  FIGS. 4 and 5 , the pin assembly  24  includes a pin  26  with a lower end  28 . At the lower end  28  of the pin  26  is a shoulder  30 . The pin also includes an upper end  32  at which at least one helical groove  34  is defined. There may be multiple helical grooves  34 , as each helical groove  34  forms a corresponding flute  16  (referring back to  FIG. 1 ) on the cylindrical wall  12 , to be described in detail below. As a result, the number of helical grooves  34  equals the number of flutes  16  to be formed. The grooves  34  extend from the upper end  32  of the pin  26  down the pin  26  a distance l that corresponds to the desired distance that the flutes  16  on the cylindrical wall  12  will extend. Each groove  34  is of a depth d that generally corresponds to the height of the flute  16  that it forms. 
   As shown in  FIG. 5 , a sleeve  36  slides over the pin  26  and has an inner diameter that is slightly larger than the outer diameter of the pin  26  in order to allow the sleeve to slide over and rotate about the pin  26  without excessive wobble or lateral movement. The sleeve includes a shoulder  38 , the purpose of which will be described below. 
   Returning to  FIG. 2 , the pin assembly  24  also includes means to allow rotation of the pin  26 , such as a bearing  40  that is located on the in  26  between a first hardened washer  42  and a second hardened washer  44 . The second hardened washer  44  may be in contact with the shoulder  30  of the pin  26 . 
   The molding process involves insertion, typically by injection, of a molten polymeric material into a cavity  46  that is defined by the upper mold half  22   a , which will form the molded plastic product  10  (referring back to  FIG. 1 ). The upper mold half  22   a  is in close contact with the lower mold half  22   b , which defines a shaft  48  for insertion of the pin assembly  24  in proximity with the cavity  46 . When the pin assembly  24  is inserted, a gap  50  is present in between the wall of the shaft  48  and the grooved portion  34  of the pin  26 . The gap  50  is terminated by the upper rim of the sleeve  36 , proximate the end of the grooves  34  in the pin  26 . 
   When molten polymer flows into the cavity  46 , it continues to flow into the gap  50 , which forms the cylindrical wall  12  (referring back to  FIG. 1 ). The molten material also flows into the grooves  34  on the pin  26 , thus forming the flutes  16  on the cylindrical wall  12 . 
   With reference to  FIG. 5 , when the molding process is complete, i.e., the polymer is cool enough to hold its shape and may thus be extracted, the upper mold half  22   a  is moved away from the lower mold half  22   b . The formed product  10  is exposed, but the fastener  12  must be forced out of the lower mold half  22  without damage to the helical flutes  16 , as they are surrounded by the grooves  34  in the pin  26 . To accomplish this, the sleeve  36  is caused to move upward, sliding along the pin  26 . As the sleeve  36  moves, the pin  26  is free to rotate separately from the sleeve  38  in a direction A that corresponds to the orientation of the flutes  16 . In this manner, the product  10  and the cylindrical wall  12  move upward and the flutes  16  slide along and up out of the grooves  34 . 
   The rotation of the pin  26  is facilitated by at least a partial vertical securing of the pin  26  by a retaining member  52 . As the sleeve  36  moves upward, the retaining member  52  prevents the pin from moving upward. The force of the flutes  16  pressing against the grooves  34  of the pin  26 , which is caused by the vertical movement of the sleeve  36 , is essentially allowed to be converted to rotational motion by the bearing  40  that is secured between the washers  42  and  44 , which are in turn secured by the retaining member  52  and the shoulder  30  of the pin  26 . The thrust bearing  40  facilitates the rotation of the pin  26 , allowing extraction of the product  10  and the cylindrical wall  12  without damage to the flutes  16 . 
   The extraction is complete when the shoulder  38  of the sleeve  36  contacts a positive stop, such as a portion of the lower half of the mold  22   b . The sleeve  36  is of a length that corresponds to the distance of the shaft  48 , thereby forcing the cylindrical wall  12  substantially out of the lower half of the mold  22   b.    
   It is important to note that the retaining member  52  may be a separate member, or it may be an integral component of the lower half of the mold  22   b . Also, the angle of the flutes  16 , and hence the grooves  34 , causes the force of the sleeve  36  moving upward to generate a lateral force component that gives rise to the rotation of the pin  26  on the thrust bearing  40 . Moreover, the angle of the flutes  16  and the grooves  34  allows the cylindrical wall  12  to move upward as the pin  26  rotates and the flutes  16  slide along the grooves  34 . 
   The use of the bearing  40  and an axially oriented design allow the pin  26  to rotate in either a clockwise or counterclockwise direction, depending on the orientation of the grooves  34  and the corresponding flutes  16 . The compact and uniaxial design of the pin assembly  24  allows the assembly  24  to be easily inserted into a mold  22  and used interchangeably on different molds. The design also allows the use of different pins with alternative groove configurations in one mold  22 , eliminating or reducing the need to construct different molds for each type of fastener. 
   The invention has been described with reference to preferred embodiments. Obviously, modifications and alterations will occur to others upon reading and understanding the preceding detailed description. It is intended that the invention be construed as including all such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof.