FIELD OF THE INVENTION

The present invention relates to O-rings and particularly to O-rings having superior sealing and vibration dampening qualities, to methods of manufacturing the same and to articles of manufacture including the O-ring of the present invention.

BACKGROUND OF THE INVENTION

Much attention has been paid to providing consistent sealing performance for various articles of manufacture, including packages, valves, bearings, pistons, covers and other articles of manufacture- Current sealing techniques including gaskets and liners have experienced problems in obtaining a proper seal and providing the consumer with product protection and/or long service life.

There is also a ^* need for improved methods and designs for dampening vibration of machines, instruments and 'other articles of manufacture.

It is therefore an object of the invention to provide new and novel seals and means for dampening vibration for a variety of products and to methods of manufacturing and using the same.

SUMMARY OF THE INVENTION

In accordance with the present invention there is provided new and unique methods and functional shapes to produce articles with superior sealing and vibration dampening qualities. The functional shape is a curled hollow substantially O-shaped ring having an inner and an outer free end. The term "substantially O-shaped ring" includes rings wherein the free ends are joined or overlap to provide a cross-section having a true circular shape and rings in which the free ends are merely proximate to each other wherein the cross-section of the ring is a partially opened circle.

Because of the curled O-ring's design it has

enhanced properties of compressibility, stress distribution and vibration dampening characteristics. Under compression its hollow coiled cross section can compress by further coiling as well as by ovaling. Its shape also distributes compressive strain and absorbs vibration.

The O-ring of the invention can be used as a sealing liner or element in a wide range of applications including packaging.

In another embodiment of the invention the O-ring may be used as a vibration dampening element for instruments and machines as mounts, for bearing support or other uses.

In addition the O-ring of the present invention can be used as a sealing and/or vibration dampening element in combination with and as an integral portion of other functional components or articles used in various apparatus, machinery, etc.

The curled O-ring can be made of various plastics or other materials for use under a wide range of conditions of heat, stress and other use and environmental factors. It may also be produced using a combination of materials, in laminar or disbursed reinforcing constructions.

The curling method of the invention includes producing a preform which in a preferred embodiment has a generally cylindrical wall. The curled O-ring is formed by a curling tool which engages the lower free end of the cylindrical preform, and turns it outwardly toward or inwardly from the preform wall and then upwardly channeling and altering the direction of such movement over its working surfaces. Preferably the initiation of the curling action is facilitated by providing a taper to a free end of the cylindrical preform. The curling action at this point produces a

"J" or "U" shape in such free end. To produce an "0" or coil shape, after leaving the working surface of the tool, the free end takes an upward and inward or outward direction relative to itself, which results from the continuing compression and the stresses imposed by its plastic memory, to complete the formation of a hollow "0" ring. Also, the compression of the cylindrical portion can proceed beyond this point and produce a more fully coiled ring. The working surfaces of the curling tool are preferably curved but optionally a plurality of flat surfaces may be employed.

To facilitate the curling operation or to alter the dimension, shape or character of the resultant O-ring, the curling tool can be heated and can be used in straight compression with or without spinning, or rolled along the free end of the cylindrical portion during its shaping. The free end of the cylindrical portion may be curled simultaneously or sequentially.

In another embodiment, the curled free end, where it contacts the wall after formation of the O-ring shape, can be welded to said wall to form a sealed hollow space resulting in a seal having pneumatic sealing qualities.

In yet other embodiments the curled O-ring may have slits or corrugations to alter and enhance its resilience and function.

The O-ring produced by the curling method of the present invention can include a relatively soft and conformable plastic sealing surface and a substrate or supporting portion of the same plastic which is relatively stronger, more resilient and creep resistant. This is achieved by producing and controlling strain within the plastic of the curled O-ring itself. Preferably the outer sealing surface of the O-ring is in a state of tension while the inner or supporting

substrate is in a state of compression. Additionally the O-ring may be made from a multiphase plastic of the invention so that the stretched sealing surface also includes residual microscopic voids which soften it.

BRIEF DESCRIPTION OF THE DRAWINGS The following drawings in which like reference characters indicate like parts are illustrative embodiments of the present invention and are not meant to limit the scope of the invention as set forth in the claims forming part of the application.

FIGURE 1 is a prespective view of an O-ring seal of the present invention.

FIGURE 2 is a cross-sectional view of an O-ring seal.

FIGURE 3 is a longitudinal sectional view of a curling tool and a preform to be curled.

FIGUE 3A is an exploded sectional view of a portion of a holder used to position the free end of the preform prior to curling.

FIGURE 4 is a cross-sectional view of the preform having its free end curled by a curling tool.

FIGURE 5 is a cross-sectional view of an O-ring having a central opening.

FIGURE 6 is an exploded sectional view of a curling tool and preform to produce the O-ring shown in FIGURE 5.

FIGURE 7 is a cross-sectional view of the curling tool forming the curled end of the O-ring shown in FIGURE 5.

FIGURE 8 is a enlarged sectional view of the O-ring of FIGURE 5 schematically illustrating the stress in the O-ring in the direction of curl.

FIGURE 9 is a graph schematically illustrating the balance of stresses illustrated in FIGURE 8.

FIGURE 10 is a longitudinal sectional view of a portion of the preform for the O-ring prior to curling.

FIGURE 11 is the same as FIGURE 10 except that

the annular band has been curled with the resultant production of microscopic voids.

FIGURE 12 is the same as FIGURE 11 except that the curled free end is in sealing engagement between the cap and neck of a container with the elimination of some of the microscopic voids in the sealing area.

FIGURE 13 is a longitudinal section view of a portion of a preform for the O-ring seal of the invention in early engagement with a curling tool forming groove which has been modified to heat and melt the preform rim.

FIGURE 14 generally is the same as FIGURE 13 except that the tool curling engagement has been completed and the preform rim has fused and been welded to an upper portion of the preform wall.

FIGURE 15 is a longitudinal cross section of a portion of the O-ring seal of the invention which has been modified to have a plurality or slits to increase its resiliency during compressive sealing engagement.

FIGURE 16 is a plan view of a slitting tool.

FIGURE 17 is a longitudinal sectional view of the slitting tool of FIGURE 16.

FIGURE 18 is a cross section view of a portion of the O-ring seal of FIGURE 15, schematically illustrating the slitting by the blades of the slitting tool of FIGURES 16 and 17.

FIGURE 19 is a cross-sectional view of a laminar composite preform used to make an O-ring having a laminar construction.

FIGURE 20 is a cross-sectional view of an O-ring formed from the preform shown in FIGURE 19.

FIGURE 21 is a cross-sectional view of an O-ring of the present invention formed integrally with an article of manufacture.

FIGURE 22 is a cross-sectional view of another

embodiment of an O-ring formed integrally with an article of manufacture.

FIGURE 23 is a cross-sectional view of an O-ring used as a dampening element of the present invention.

FIGURE 24 is a cross-sectional view of another O-ring of the present invention used as a dampening element.

DETAILED DESCRIPTION OF THE DRAWINGS

Referring now to FIGURES 1 and 2 there is illustrated a hollow O-ring of the invention which is made from plastic, has a curled wall 24, an inner free end 20 and outer free end 22 which are free to move relative to the wall 24 and to each other when subjected to a compressive load and in so doing are able to respond to said compressive load by further curling. This function as well as the hollow shape which allows the O-ring 10 to ovalize in response to compressive loads, imparts a high degree of stress distribution throughout the curled wall 24 to minimize the tendency of plastic materials to cold flow under a compressive load. The design and method of manufacture of the O-ring 10 also permits the use of relatively stronger and more rigid materials in such structures to perform sealirig and vibration dampening functions. Also, the O-ring 10 may be made of suitable heat-resistant plastics for high temperature use.

Referring to FIGURES 3, 3a and 4 there is illustrated a method for producing the O-ring 10 of the invention. In FIGURE 3 a cylindrical tube 18 produced by extrusion molding is shown positioned between a curling tool 26 and a holder 27 ready for curling by the tool 26. The curling tool 26 includes an annular groove 28 of a concave cross section suitable for shaping and dimensioning the curled wall 24. The holder 27 has a smaller annular groove 48 adapted to hold the free end 22 as shown in FIGURE 3a.

As shown in FIGURE 4, the forming operation is accomplished by pressing the groove 28 of the tool 26 against the rim 30 of the wall 18. In this embodiment the deepest portion 33 of the groove 28 representing the center of its concavity is located outwardly of the cylindrical plane of the wall 18. Also the groove 28

has a slanted portion 39 inwardly and tangent to its concavity to facilitate centering of the tool 26 and the wall 18. As movement of tool 26 relative to the wall 18 continues toward the holder 27, the cylindrical side of the wall 18 is centered within groove 28 by the slanted portion 39 and is then forced outwardly and then upwardly to assume an interim "J" shape, not shown. As this relative movement continues, the rim 30 is forced upwardly out of groove 28, and at the same time is pulled inwardly in response to the stresses developed therein while being shaped by the tool 26, thereby producing the desired "0" ring curl 24 with its outer free end 22 on its ^* inner surface 34 facing upwardly. Alternatively the outer free end 22 may be located on the outer surface 36 by curling the cylindrical wall 18 inwardly by suitably modifying the tools 26 and 27 and the groove 28.

To facilitate the curling operation, in the case of polypropylene, the tool 25 may be operated at a temperature of about ambient to about 300 degrees F for curling cycles of about one-half to ten seconds depending on the dimension and materials used.

After formation of the curl 24 the curling tool 26 is withdrawn from the O-ring 10. The O-ring 10 includes a bottom sealing portion 32, an inside sealing portion 34 and an outside sealing portion 36 and a top sealing portion 38. One or more of these surfaces can be used for a compressive sealing engagement wherein the O-ring 10 is able to respond to said compression with a high degree of distribution of the resultant strain and therefor with a low degree of cold flow or permanent deformation.

The preferred curling method of the invention is accomplished by simple compression of the preform wall 18 simultaneously around its periphery by the tool

26 with its groove 28. In addition, the tool 26 may be rotated or the curling operation can be performed sequentially around the periphery of the preform wall 18 or sequentially at different work stations. Also the tool 26 or the preform may be heated to facilitate curling.

Referring now to FIGURES 5 to 7 there is illustrated another embodiment of the invention whereby the cylindrical preform 18a for the O-ring 10a is produced having a top wall 12 which may be continuous or with a- central opening 13, as shown. When the top wall 12 is continuous there is no top free end 22 to the wall 18. FIGURES 6 and 7 show the method of holding and curling the preform 18a in the manner described in FIGURES 3 and 4 to produce the O-ring 10a with its outer free end 22 on its upper surface 12 facing inwardly (see Figure 5). The O-ring 10a may be of plastic and its preform formed by injection, compressionor other molding techniques. Additionally the preform 18a of the O-ring 10a may be formed by stamping or other techniques. Other materials may be used with preform forming methods suitable to the material.

With the method of the invention the physical properties of the plastic are modified in such a way as to further enhance its sealing characteristics. That is, the plastic at the sealing surface 24 of the seal is made softer and more conformable and the substrate and supporting portion 44 is made stronger, more resilient and creep resistant as a result of the stresses imposed on the plastic during the curling operation.

Referring now to FIGURES 8 and 9, the curling operation, by imposing an alternative shape on the preformed cylindrical wall 18a also imposes balanced residual stresses and stress differentials to the resultant of the seal 10a. That portion 24 of the seal

10a which is stretched is in extension or a state of tension and that portion 44 which is compressed is in a state of compression. The level of stress varies with the degree of extension or compression and, as in any static condition the total amount and direction of each kind of stress balances and maintains the other.

The balanced residual stresses occur in the direction of the curl as a result of the extension and compression of the preform cylindrical wall 18a across its thickness to form the curled sealing portion 10a, as shown in FIGURE 8. At and near the convex exterior sealing surface 24 represented by point Y, the plastic is stretched in the direction of the curl and is in a state of high residual tension. The opposing concave interior surface, represented by point X is compressed in the direction ^* of the curl and is in a state of high residual compression which balances and maintains the state of tension at or near the exterior convex surface. FIGURE 9 shows the direction, sum and approximate distribution of these stresses across the thickness of the plastic including the neutral point 0 and points of maximum compression and tension at or near the inner and outer surfaces. In the normal practice of the invention maximum tensile stress will occur over a finite distance from the surface. The sum of the compressive stress defined by points AOX equals that of the tensile stress defined by the points BOY. The high state of tension at point Y and the remainder of the sealing surface 24 weakens it and makes it softer in that a much lower level of added tension is required to reach and exceed its yield point wherein deformation is easily achieved. In this regard a normally stiffer and stronger plastic behaves like a softer and weaker plastic. In the same manner the high state of compression at point X and supporting portion 44 makes the plastic there stiffer.

stronger and more creep resistant.

Referring to FIGURES 10 to 12, there is shown a feature of the invention wherein the sealing surface is softened as a result of the production of microscopic voids thereat by employing plastics which form such voids upon stretching. FIGURE 10 shows the wall 18A of FIGURE 6 including free end 20 prior to curling. FIGURE 11 shows the curled sealing portion 10a of FIGURE 5 including microscopic voids 25 at the sealing surface 24 produced during the curling operation which preferably is done at ambient temperature to facilitate the creation of the voids. The size and/or number of the voids 25 are in relationship to the degree to which the plastic has been stretched.

FIGURE 12 shows the seal 10a with its surface 24 employed as a rim seal gasket in a closure 50 in compression against the rim 64 of a container neck 62 with the resultant reduction and elimination of the voids 25 in the seal area at and adjacent the sealing surface.

Thus, it can be seen that the curling process of the invention used to create the desired shape modifies the physical properties of the plastic at the sealing surface from those of a more rigid, unyielding material desired for overall cap strength and integrity to those of a softer, more yielding and conformable material desired for improved sealing characteristics.

Referring now to FIGURES 13 and 14 there is shown another embodiment of the invention wherein a hollow shaped ring 10c is formed and welded to enclose a hollow space thereby creating an article having pneumatic qualities. FIGURE 13 shows a wall 18a with its free end partially curled by a tool 26. The tool 26 includes an annular groove 28 a portion of which is bounded by an annular tool insert 42 for heating at a

high temperature and insulating portions 51 to allow the remainder of tool 26 to be operated at a lower temperature. The free end 20 has a rim 30 which has a reduced thickness which can be heated to a melting temperature more quickly than the remainder of free end 20. The heated tool insert 42 is heated to a temperature sufficiently above the melting point of the plastic to melt the rim 30 of reduced thickness but not high enough to melt the thicker succeeding portions of free end 20 as it passes in contact with it during curling to form an O-shape curl 24 of free end 20. When the melted rim 30 completes its curling it contacts the wall 18a and forms a welded attachment 49 therewith as shown in FIGURE 14. The resultant curled O-ring 10c is thereby prevented from any possibility of being uncurled and is also converted into a pneumatic shape. Optionally the curled O-ring 10a may be welded or otherwise bonded after the O-shape cross section has been formed.

Referring now to FIGURES 15 to 18 there is shown another embodiment wherein a non-sealing portion of the O-ring lOd of the invention is slit to provide enhanced resilience during a compressive sealing engagement. FIGURE 15 shows a cross section of an inwardly curled wall 24a showing a slit 44 on its inner portion 34. The slits serve the purpose of eliminating the hoop strength of inner portion 34 so that resistance to compression occurs primarily in the curl direction providing increase of flexability and resilience. FIGURES 16 and 17 show a slitting tool 60 with slitting elements 59 spaced radially about its upper periphery. To produce the slitted O-ring lOd, the curled free end 24a is first produced by the method described in FIGURES 6 and 7 and then the slitting tool 60 is brought into engagement with it to produce the slits 44 (see FIGURE 18). Optionally the slitted curled free end 24a may be

produced having an outward orientation. Also the slits may be produced to extend to the lip 20 after curling or by slitting the wall 18d prior to curling.

Now referring to FIGURES 19 and 20 there is shown another embodiment of the invention whereby a laminar composite of two materials may be curled to produce O-rings lOe with enhanced functional properties. FIGURE 19 shows an outer preform 18b similar to that illustrated by FIGURE 6 and an inner preform 19. The inner and outer preforms 19 and 18b may be molded or bonded together or simply nested in generally intimate contact with one another prior to curling. The preforms as a unit are then curled as described in FIGURE 3 to 4 and 6 to 7 with the resultant O-ring lOe illustrated in FIGURE 20. The ability to combine Materials in a laminar O-ring lOe shape can enhance the range of its usefulness by enhancing heat resistance, deformation under heavy loads, surface conformability and sealing integrity, resistance to vibratory fatique and other characteristics.

Referring to FIGURE 21 there is shown another embodiment of the invention wherein the curled O-ring lOf is a sealing element integral with another functional component or article 6 having a recess 16 which cooperates with the curling tool 26 to form and retain the curl 24. Adjacent the recess is a bearing surface 40 which also serves to limit the amount that the curl 24 can be axially compressed so that it can only be used within prescribed limits of deflection or compression thereby creating a predetermined amount of sealing force which can be exerted by the curl 24 and an assurance of a consistent level of resilient use. Optionally the bearing surface 40 which limits the compression of curl 24 can be in a removed location. As shown the article 6 has a central opening 13.

Referring to FIGURE 22 there is shown an article 6a similar to the article 6 of FIGURE 21 except that the bearing surface 40 is located to limit the deflection of the curl 24 in a radial direction. The O-rings lOf and lOg can be used in this and other manners with articles 6, 6a and the like which are sleeves, pistons, rotors, stators, covers, containers, valves, bearings and other articles or components which require a seal.

Referring to FIGURE 23 and 24 there is an illustrated the use of the invention to provide a mounting 54 which dampens vibration. FIGURE 23 shows a rotor 56 and a bearing mount 54a having an integral O-ring portion lOh through which the Bearing 58 is attached to its housing or other adjacent components. The O-ring lOh has an integral wall 56 extending from its outer free end 22 to engage the bearing 58. Optionally the O-ring lOh may be integral with the bearing 58. FIGURE 24 shows a mounting foot 54b having an integral O-ring portion lOi employed in a similar fashion. The O-ring shape distributes and absorbs vibratory stress to serve as an effective vibration dampening mechanism. In such applications the O-ring portion may be integral or attached to the bearing or foot and may be made from materials, including plastic which provide superior resilience, vibratory fatigue resistance or vibration absorption characteristics. Acetal polymers, nylon and other semi-rigid and rigid plastics are exemplary. The dimensions for the O-ring 10 for such mounting application will vary greatly with the loading, the character of the vibration and the material selected for its construction.

In the case of a polypropylene O-ring gasket or liner of the invention for a cap, typical dimensions of the "0" ring curl 24 for a 28mm size cap are about

0.040 to 0.150 inches for the curl diameter and about 0.0007 to 0.030 inches in wall thickness.

Cap sizes for such O-ring liners typically range from under 20mm to 120mm and bottle and/or jar sizes range from under 2 ounce to 128 ounce capacity. Larger capacity containers such as drums or kegs are also suitable for the practice of the invention as are smaller vials and other containers.

Useful plastics which can be used for forming the O-rings 10 of the invention include polypropylene, high density polyethylene, polystyrene, acrylonitrile - styrene - butadiene polymers, acetal polymers, nylons, polyesters, polycarbonates, polysulfones and many other semi-rigid to rigid plastic materials including reinforced or laminar composites.

Other useful plastic which produce voids and resultant softening which can be used for the O-ring seals of the invention are chosen from the group of plastics which have in common the fact that when strethed beyond their tensile yield point they develop microscopic voids or fissures within the plastic which serve to soften it and make it more compressible. The group of plastics manifesting this behavior includes essentially all polymer classes (e.g., polystyrene, polyvinyl chloride, polyolefins, polycarbonates, polysulfones, polyesters, nylons, etc.) and preferably are selected from the group of plastics known as alloys, blends, multipolymers, multiphase polymers or other nomenclature, many of which are listed in Modern Plastics Encyclopedia, 1986-1987, pages 105 to 111, the entire disclosure of which is incorporated herein by references. Examples of such polymers are ethylene-propylene copolymers (e.g., Himont SB781) and rubber modified polystyrene (e.g., Monsanto Lustrex 4300). Typically a useful plastic is a propylene

copolymer, Shell 7522, which upon stretching produces microscopic voids in the range of about 0.25 to about 3.0 microns.

The invention in its broader aspects is not limited to the specific described embodiments and departures may be made therefrom within the scope of the accompanying claims without departing from the principles of the invention and without sacrificing its chief advantages.