Plastic clip

Information

  • Patent Grant
  • 6457218
  • Patent Number
    6,457,218
  • Date Filed
    Tuesday, September 12, 2000
    24 years ago
  • Date Issued
    Tuesday, October 1, 2002
    22 years ago
  • Inventors
  • Examiners
    • Sakran; Victor
    Agents
    • Pizarro; Ramon L.
    • Crabtree; Edwin H.
Abstract
A plastic clip of unitary, one piece construction, and a method for making the same is disclosed. The clip includes a first leg of a first thickness, a second leg of a second thickness, and a bridging section joining the first leg and the second leg, the bridging section being of a dimension that upon cooling or curing of the plastic material, the bridging section biases the first leg against the second leg.
Description




BACKGROUND OF THE INVENTION




(a) Field of the Invention




This invention generally relates to a resilient plastic clip and method for making the clip. More particularly, but not by way of limitation, to a plastic clip having legs or arms that are preloaded or biased directly against one another when the clip is not in use.




(b) Discussion of Known Art




The advantaged of a clip made from spring materials have long been recognized for their simplicity and ease of use. Most known clips consist of a pair of legs or arms that are biased against one another by a spring. Many metal clips take advantage of the modulus of elasticity of sections of metal ribbon to produce an integral clip, having both legs and the spring biasing the legs towards one another made from a single, continuous, section of metal ribbon. Examples of this kind of device can be found in U.S. Pat. No. 609,486 to Wilson shows the use of metal ribbon to create a metal spring. The Wilson device also illustrates the use of legs of uneven length, the shorter leg having a sharp edge to allow the insertion of the short leg between spirals of coiled material, such as ribbon or paper.




Other examples of metal clips can be found in U.S. Pat. Nos. 1,675,286 to Van Valkenburg and 1,621,008 to Fricker. These devices take advantage of the elasticity of metal to provide a clip from a bent section of sheet-metal or metal ribbon. The advantages of sheet-metal or metal ribbon for the manufacture of clips have been difficult to overcome. An important factor that has made metal such an ideal choice for the making of spring clips is that sheet-metal is highly amenable to various cold-working processes that allow the clip to accept a bias, such that the legs of the clip are biased against one another.




While the mechanical properties of many metals lend themselves for the creation of highly effective clips, there remains a need for clips made from materials such as polymers, plastics that provide important mechanical properties that are not inherent in metals. For example, plastics are typically non-abrasive and non-conductive, and are thus innocuous to delicate surfaces or surfaces that must be insulated from electrical currents or protected from galvanic or stress corrosion. Unfortunately, however, it is difficult to take advantage of polymers, and particularly thermoplastics, in the making of spring loaded or biased devices such as clips due to the fact that the polymer must be molded into the shape of the clip. The molding of the material into the shape of the clip makes it difficult to arrive at a clip with legs that retain internal stresses that bias the legs against one another.




Additionally, there remains a need for a plastic, or polymer, clip that can be used for retaining large sections of material together without scarring or scraping the sections of material.




SUMMARY




It has been discovered that the problems left unanswered by known art can be solved by providing a plastic clip of unitary, one piece construction, the clip including at least the following components:




a first leg that is of a first thickness, and a second leg that is of a second thickness, the first leg being biased against the second leg by an bridging section that is greater than the thickness of the first leg or the second leg.




According to a highly preferred embodiment of the invention, the legs of the clip may be of the same or different thickness. The bridging section, is of greater thickness to provide a stiff support for the legs.




The bias of the legs against one another is introduced into the disclosed clip by the molding process used to create the disclosed clip. This process uses a mold that has the legs spaced apart from one another. The mold accepts the thermoplastic material that will be used to form the disclosed clip, and allows the molten thermoplastic material to fill the cavity of the mold, defining the main components of the disclosed clip. Then, a portion of the bridging section is cooled at a faster rate than the remaining portions of the bridging section. This differential cooling introduces internal stresses into the bridging section to introduce a bias forcing the legs against one another.




In a preferred embodiment of the invention one of the legs includes a leading edge that is sloped or rounded towards the opposite leg. This sloping or rounded edge creates a leading edge that provides a smooth transition from a surface that is held between the two legs. It has been discovered that this smooth transition is particularly useful when using the disclosed clip for holding the flaps of containers, such as cardboard boxes, in an open position to allow loading and unloading of the containers. In this application, the tapered leading edge provides an unobtrusive transition between the internal surface of the box and the clip, prevent snagging and inadvertent removal of the clip when removing materials from the container.




Still further, it is contemplated that the leg opposite to the leg with the tapered leading edge will include a flared or bent end that will allow the user to capture materials between the two legs easily.




Thus, as illustrated by this summary, it should be understood that while the above and other advantages and results of the present invention will become apparent to those skilled in the art from the following detailed description and accompanying drawings, showing the contemplated novel construction, combinations and elements as herein described, and more particularly defined by the appended claims. It should also be clearly understood that changes in the precise embodiments of the herein disclosed invention are meant to be included within the scope of the claims, except insofar as they may be precluded by the prior art.











DRAWINGS




The accompanying drawings illustrate preferred embodiments of the present invention according to the best mode presently devised for making and using the instant invention, and in which:





FIG. 1

is a perspective view of an embodiment of the disclosed clip.





FIG. 2

is a side view of the clip illustrated in FIG.


1


.





FIG. 3

is a top, plan view of the embodiment illustrated in FIG.


2


. The view looking down at the leg with the curled end, opposite to the leg with the tapered edge.





FIG. 4

illustrates a mold cavity, together with cooling passages, used to create the bias of the legs of the disclosed clip.











DETAILED DESCRIPTION OF PREFERRED EXEMPLAR EMBODIMENTS




While the invention will be described and disclosed here in connection with certain preferred embodiments, the description is not intended to limit the invention to the specific embodiments shown and described here, but rather the invention is intended to cover all alternative embodiments and modifications that fall within the spirit and scope of the invention as defined by the claims included herein as well as any equivalents of the disclosed and claimed invention.




Turning now to

FIG. 1

where a plastic clip


10


incorporating principles taught herein has been illustrated. As illustrated, a highly preferred embodiment of the plastic clip


10


includes a first leg


12


of a first thickness


14


, and a second leg


16


of a second thickness


18


. The first leg


12


and the second leg


16


are joined by a bridging section


20


, which holds and biases the first leg


12


against the second leg


16


. As will be described in greater detail below, a highly preferred embodiment of the plastic clip


10


will be of unitary, one piece, construction, with the first leg


12


and the second leg


16


being permanently urged against one another by internal stresses incorporated into the bridging section. However, it is important to note that the principles taught herein will allow an individual to make a plastic device that has legs that are joined from separate components and biased against one another though a plastic spring element.




Turning to

FIG. 2

it will be understood that it is also preferred that the bridging section


20


is of a thickness


22


that is greater than the thickness of the first leg


12


, referred to herein as the first thickness


14


. Similarly, it is contemplated that the thickness


22


of the bridging section


20


will be greater than the second thickness


18


of the second leg


16


. The greater thickness of the bridging section


20


will allow the bridging section


20


to achieve greater rigidity than the legs of the clip


10


. This enhanced rigidity will allow the development of a strong bias or force that keeps the first leg


12


pressed against, or urged towards, the second leg


16


. Furthermore, as will be discussed in further detail below, when the bridging section


20


is made by using a molding process that provides differential cooling of different areas of the bridging section


20


, the resulting bridging section


20


will have internal stresses that will bias one leg against the other.




As can be understood from

FIG. 2

, the second leg


16


includes a first end


24


, a second end


26


, and a generally planar section


28


that faces the first leg


12


. Additionally, the second end


26


of the second leg


16


is connected, and preferably as an integral one piece construction, to the bridging section


20


. Similarly, the first leg


12


includes a first end


28


and a second end


30


. The second end


30


being integral with the bridging section


20


. The bridging section


20


also includes an internal portion


32


and an external portion


34


. The internal portion


32


extends between the two legs of the clip


10


.




In order to ensure that the legs of the plastic clip


10


maintain a bias against one another, the disclosed clip


10


is made from a thermoplastic material that shrinks as it cools, or solidifies from a molten state, during the molding or forming process. Referring to

FIG. 4

, it will be understood that the disclosed clip


10


must be molded with the legs,


12


and


16


, spaced from one another. However, to ensure that the legs assume a configuration that is different from the configuration imposed by the mold


36


, which as illustrated, forms the clip


10


with each leg as separate element, each being spaced from the other. To create a part that has the legs with a bias against one another, the mold


36


provides a cooling system that allows differential cooling rates as experienced by the internal portion


32


compared to the external portion


34


of the clip


10


. The differential cooling is carried out in a manner that achieves solidification of one surface before the opposite surface. The side that solidifies first assumes a fixed dimension or proportion. Then as the opposite side cools, it migrates towards its cooled, solid, dimension or proportion. In this example, the thermoplastic will be of a type that shrinks in dimension as it goes from a molten state to a solid. Thus, by first cooling the external portion


34


to a temperature that solidifies the external portion and sets its dimension or size, while keeping the internal portion


32


in a molten state. Then, the internal portion


32


is cooled until it has solidified, which will also allow the internal portion to shrink as it cools.




Once the clip


10


has cooled enough to be released from the mold


36


, it is then ejected from the mold. The differential cooling, meaning the cooling of different surfaces at different times or at different rates, induces internal stresses into the bridging section, the stresses being induced by the fact that the dimension of one section of the part was fixed before the opposing part was allowed to cool and contract. Thus, as shown on

FIG. 4

, the mold


36


will include a temperature or cooling control mechanism. In the illustrated example this mechanism, or system, is provided by cooling ducts or passages


37


that allow the cooling to be controlled. It is important to note that the passages


37


are provided merely as examples. It is contemplated that instead of passages, the mold


36


may simply include sections of highly conductive metal that provide more efficient heat transfer at desired locations, as well as other systems to carry out the differential cooling taught herein.




Turning now to

FIG. 3

where it has been illustrated that in a preferred embodiment of the invention the first end


24


of the second leg


16


includes a tapered section


38


, the tapered section


38


creating an area of gradually increasing thickness


40


starting in an edge


42


on the planar section


44


of the second leg


16


and increasing to the second thickness


18


of the second leg


16


.




Also illustrated in

FIG. 3

is that in a preferred embodiment of the invention the first leg


12


is of a first length


46


and the second leg


16


is of a second length


48


, the second length


48


being greater than the first length


46


. Furthermore, the first leg


12


includes an end


50


that curls away from the first end


24


of the second leg


16


to allow the clip to grasp or slide easily over material to be retained between the legs. The tapered section


38


of the second leg


16


has been designed to provide a smooth transition between a surface that is caught between the legs. This transition will allow the clip


10


to be used for tasks such as filling a cardboard box, for example, where the flaps need to be held in open position, away from the opening of the box. In this use the second leg


16


would be positioned against the internal surface of the box, with the flaps trapped between the legs and extending away from the box opening. The tapered section


38


would thus allow easy removal of items being placed into or removed from the box, without snagging the leg of the clip as the item is removed or inserted from the box.




Also, as shown on

FIG. 2

, a bead


52


has been incorporated into the clip


10


to provide a pressure point between the legs. The bead


52


provides a section of enhanced pressure and grip between the legs of the clip


10


.




Thus it can be appreciated that the above described embodiments are illustrative of just a few of the numerous variations of arrangements of the disclosed elements used to carry out the disclosed invention. Moreover, while the invention has been particularly shown, described and illustrated in detail with reference to preferred embodiments and modifications thereof, it should be understood that the foregoing and other modifications are exemplary only, and that equivalent changes in form and detail may be made without departing from the true spirit and scope of the invention as claimed, except as precluded by the prior art.



Claims
  • 1. A plastic clip of unitary, one piece construction, the clip comprising:a first leg of a first thickness, the first leg having an internal surface; a second leg of a second thickness, the second leg having an internal surface; and a bridging section joining the first leg and the second leg, the bridging section having an internal portion and an external portion, the internal portion of the bridging section being between and facing the internal surface of the first leg and the internal surface of the second leg, the internal portion of the bridging section having an internal stress produced by cooling of the of the internal surface at a greater rate than the external surface, and so that the bridging section biases the first leg against the second leg.
  • 2. A plastic clip according to claim 1 wherein said bridging section is of a thickness that is greater than the first thickness of the first leg.
  • 3. A plastic clip according to claim 1 wherein said bridging section is of a thickness that is greater than the second thickness of the second leg.
  • 4. A plastic clip according to claim 1 wherein said bridging section is of a thickness that is greater than the first thickness of said first leg and the second thickness of the second leg.
  • 5. A plastic clip according to claim 1 wherein said second leg is of a second length and further comprises a first end and a second end, and a generally planar section facing the first leg, the second end being connected to said bridging section, the first end having a tapered section, the tapered section creating an area of gradually increasing thickness starting in an edge on the planar section of the second leg and increasing to the second thickness of the second section.
  • 6. A plastic clip according to claim 5 wherein said first leg is of a first length, the first length of said first leg being shorter than the second length of the second leg.
  • 7. A plastic clip according to claim 6 wherein said first leg includes an end that curls away from the first end of said second leg.
  • 8. A plastic clip having a first leg of a first thickness, the first leg having an internal surface, a second leg of a second thickness, the second leg having an internal surface and a bridging section joining the first leg and the second leg, the clip being of unitary, one piece construction, the bridging section having an internal portion and an external portion, the internal portion of the bridging section being between and facing the internal surface of the first leg and the internal surface of the second leg, the internal portion of the bridging section having an internal stress that urges the internal surface of the first leg towards the internal surface of the first leg, the internal stress resulting from a thermal shrinkage of the of the internal surface relative to the external surface, and so that the bridging section the first leg and the second leg being permanently urged against one another by the bridging section.
  • 9. A plastic clip according to claim 8 wherein said bridging section is of a thickness that is greater than the first thickness of the first leg.
  • 10. A plastic clip according to claim 8 wherein said bridging section is of a thickness that is greater than the second thickness of the second leg.
  • 11. A plastic clip according to claim 8 wherein said bridging section is of a thickness that is greater than the first thickness of said first leg and the second thickness of the second leg.
  • 12. A plastic clip according to claim 11 wherein said second leg is of a second length and further comprises a first end and a second end, and a generally planar section facing the first leg, the second end being connected to said bridging section, the first end having a tapered section, the tapered section creating an area of gradually increasing thickness starting in an edge on the planar section of the second leg and increasing to the second thickness of the second section.
  • 13. A plastic clip according to claim 12 wherein said first leg is of a first length, the first length of said first leg being shorter than the second length of the second leg.
  • 14. A plastic clip according to claim 13 wherein said first leg includes an end that curls away from the first end of said second leg.
US Referenced Citations (15)
Number Name Date Kind
20364 Pierce May 1858 A
609486 Wilson Aug 1898 A
1621008 Fricker Mar 1927 A
1675286 Van Valkenburg Jun 1928 A
D244907 Link Jul 1977 S
4747496 Rendine May 1988 A
4889380 Pillifant, Jr. Dec 1989 A
4903375 DiFranco Feb 1990 A
D328187 Saurette Jul 1992 S
D363453 Herdt Oct 1995 S
D382592 Maruchi Aug 1997 S
5697131 Hunt et al. Dec 1997 A
D394745 Egelja Jun 1998 S
5913618 Yosha Jun 1999 A
5970777 Hunt et al. Oct 1999 A
Foreign Referenced Citations (1)
Number Date Country
0253453 Apr 1967 AI