Thermoplastic Shielded Glass Bottle

Abstract

A container comprising an inner glass receptacle and a closely adhereing exterior protective sheath substantially covering said receptacle. The exterior protective is comprised of a shape-retaining, preferably thermoplastic resin adapted to restrain and retain glass fragments should the glass receptacle be broken. The sheath is further provided with a plurality of outwardly protruding nodular means that lend a roughened appearance to the sheath surface and which produce a surface elevation variance from the mean thickness of the sheath by between about 6 and 60 percent. This surface characteristic minimizes the container surface frictional resistance, increases shock resistance and provides maximum non-slip characteristics to the sheath when the container is hand-held.

Parent Case Text

CROSS REFERENCES TO RELATED APPLICATIONS

This is a continuation in part of my earlier application Ser. No. 162,103 filed July 13, 1971.

Description

This invention concerns protectively sheathed glassware containers and, more particularly, concerns glass receptacles which are so protected by an outer plastic envelope that substantially covers the exterior surface thereof.

As is well known in the trade, glassware is readily susceptable to breakage during handling and use. Further, the consequences of such breakage may be significantly aggravated if the contained product is carbonated or the container thereof is otherwise internally pressurized. Therefore, it has long been an objective of glassware manufacturers and users to minimize the hazards of breakage by treating the exterior surface in numerous ways and by even adding protective overcoatings of various sorts thereto. These prior art approaches have, in fact, improved glassware standards and quality quite significantly since such have tended to effectively reduce the quantity of surface scratches and flaws in the ware and, of course, this reduction in the points of stress concentration enable the ware to retain its characteristic strength.

Such prior art surface treatments, for example, have included metal oxide, and combinations of thin film polyethylene coatings which provide good scratch and abrasion resistance to glassware thereby decreasing the surface flaws spoken of and likewise reducing the likelihood of breakage. Similarly, protective coatings having substantial thicknesses have been known for use on glass products. These, however, have been applicable only to specialized containers, for example, those employed in aerosol spray-type applications. Increased costs, production inefficiencies in capably coating ware in the quantities required, providing a coating of the quality capable of restraining and retaining glass upon fragmentation under pressure, and employment of such ware in conventional filling and handling equipment have theretofore been thought to make impossible the fruitful addition to the market of composite glass, plastic-protected ware.

Specific problems presented and overcome by this invention have been to provide the ware with a protective sheath or outer envelope of a sufficient thickness and resiliency to adequately restrain and retain the glass receptacle portion of a pressurized container against fragmentation. To economically accomplish this end, the volume of coating material must be minimized, yet the effective thickness thereof must be maximized to render the needed protection. Similarly, a consistantly uniform, proper and good adhesion should be maintained between the glass receptacle portion and sheath portion of the container to provide the proper restraining effects. Additionally, in order for plastic coated ware to be easily processed in conventional equipment, exterior surface coefficients of friction must be minimized, yet that same surface should effectively produce a high coefficient when the coated container is hand held. Both of these diametrically opposed propositions (i.e., minimum material yet maximum protection and low yet high coefficients of friction) are satisfied by the novel construction of this invention.

In accordance with this invention, a novel container capable of internal pressurization is provided which has an inner glass receptacle or envelope and a closely adhering outer sheath or envelope which substantially covers the inner glass receptacle. The exterior protective sheath comprises a shape-retaining, flexible resin which is able to restrain and retain fragments of the glass receptacle if the receptacle breaks.

The exterior sheath is further provided with a plurality of outwardly protruding nodular means, nodal areas or nodes that minimize the surface frictional characteristics between abuting bottles and in mechanical handling, are shock absorbent, and due to its stippled effect, provide maximum non-slip characteristics when hand-held.

However, the nodal areas provide the noted increased shock protection while employing a minimum of resin material. Such result is obtained due to an increase in thickness at the nodular areas which will bear the brunt of any physical abuse to which the container is subjected. Similarly, substantial portions of the coating are of a reduced thickness thus providing a material saving and creating voids into which portions of the material forming the nodes may flow upon impact. Thus, the effective thickness of the resin sheath is that of the nodal areas and the necessity of providing a uniform overall coating thickness which would employ substantially more resin is avoided.

The nodes likewise reduce the area of contact exposed for example, between container surface to surface contact or contact between containers and equipment since, in general, only the nodular surface areas will be in contact, thus, the frictional resistance therebetween will be reduced. At the same time, the nodes characteristicly provide a maximum non-slip effect when the container is hand-held, since the flexible supple surface of the human fingers conforms to the nodular or stippled, knurled-like surface of the container and contacts both the surface of the nodes and the surface of the depressions, effectively increasing the contacted surface area in such instances.

To produce these desirable end results, it is preferred that the exterior surface of the outer envelope or sheath deviate from the mean sheath thickness by about between 8 and 20 percent. This, in effect, further defines the respective dimensions of the nodular protrusions and voids therebetween. The novel plastic or resin covering or sheath also restrains and retains fragments of the glass receptacle should such receptacle be broken even when the container is pressurized to conditions approximating sixty pounds per square inch. This effect is produced in accordance with the invention, by providing the plastic covering or sheath of a flexible, resilient resin which will stretch and expand rather than itself fragment in the event of receptacle failure. Such expansion of the covering before its own failure enables glass fragments to be restrained until the pressure within the receptacle escapes through initially formed, relatively small openings or fissures which may appear in the covering or sheath as it fails or until the pressure is otherwise relieved.

FIG. 1 is a front elevational view of a container of the preferred embodiment;

FIG. 2 is a partial cross-sectional view of the container shown in FIG. 1 along line A--A thereof which illustrates prior art construction; and,

FIG. 3 is a partial cross-sectional view of the container shown in FIG. 1 along line A--A thereof illustrating the invention.

In the preferred embodiment of the invention, container 10 as shown in FIGS. 1 and 3 comprises an inner glass receptacle or envelope 12 and an exterior outer sheath or envelope 14 comprised of a flexible shape-retaining resin contiguously covering a majority of the exterior surface 16 of receptacle 12. Sheath 14 is provided on its outer exposed surface 18 with a plurality of preferably randomly positioned outwardly extending shock absorbing nodes 20. These nodes are separated by depressions 22 which are believed to permit maximum deflection and expansion of nodes 20 in a direction parallel to surface 16 upon receipt of excessive impacts. Accordingly, this maximized deflection is believed to increase the shock absorbing characteristics of sheath 14 and in addition, reduces the amount of material needed for an effective shock absorbing sheath 14, thus reducing the cost of manufacturing container 10.

In the preferred embodiment, inner glass receptacle or envelope 12 has a wall thickness (Gx) of from about 0.03 to about 0.12 inches and the outer envelope 14 has a thickness of from about 0.004 to about 0.018 inches. This outer envelope preferably also is formed so that specific dimensional qualities are maintained. For example, it is considered ideal to provide a mean envelope thickness value (Px) of about between 0.008 and 0.012 inches. Similarly, it is preferred that the nodes and voids have a mean deviation above and below this base value on the order of 12 to 18 percent and approximately 8 to 12 percent respectively. In other terms, it is found that the preferred maximum nodular elevation above the mean thickness value varies between 6 and 60 percent and that maximum deflection of the voids below the mean thickness value varies between about 20 and 40 percent.

PREFERRED SHEATH OUTER SURFACE CHARACTERISTICS ______________________________________ Px Sheath Mean Thickness (in.) Px1 Mean Deviation above Px (%) Px2 Mean Deviation below Px (%) % Max. Elevation above Px % Max. Deflection below ______________________________________ Px 0.008 to 0.012 12 to 18 8 to 12 6 to 60 20 to 40 ______________________________________

It should be obvious that this surface configuration substantially differentiates from that shown in FIG. 2 where the outer envelope thickness (Pxo) is virtually uniform and accordingly is devoid of surface deviations as are described. Thus, as is indicated above, the coating thickness is not uniform throughout and the maximum such thickness is created at the nodal areas 20; whereas in each instance the thickness at depression 22 will be within the noted range but less than at the nodes.

The material of construction of sheath 14 may be flexible and resilient resin which will stretch and expand rather than crack or fragment if inner receptacle 12 should break whether or not it is under internal pressure. Thermosetting resins such as flexible cross-linked urethane rubbers or others may be used; however, thermoplastic resins are preferred since they can be formed into coatings and films more easily and react in the manner above described and as is important in carrying out the invention.

Thermoplastic polymers of butadiene, acrylates, ethylene, propylene, styrene, vinyl, chloride, vinyl acetate, cellulose acetate, cellulose butyrate and cellulose propionate may be used. In addition, fluoroplastics, methyl pentenes, polyamides, phenoxy resin, polycarbonates, polyamides, polyphenylene oxides and polysulfone may be used.

The preferred plastics are inexpensive, have a relatively high tear strength, have high impact resistance, easily form a contiguous film or coating and are flexible. Of those above mentioned, the preferred plastics are polyethylene, acrylonitrile-butadiene-styrene copolymers and impact polystyrene.

It is, of course, appreciated that a suitable means of application of the coating material or sheath 14 to inner glass receptacle 12 is a necessity and as examples it is suggested that any of the following may be employed depending upon the manufactures desired:

a. By spraying the the thermoplastic material as a powder, optionally by an electrostatic spraying method, onto the hot external surface of the inner receptacle;

b. By dipping the inner receptacle, maintained at an appropriate temperature, into a fluidized bed of the plastic material in powder form;

c. By dipping the inner receptacle, if desired while hot, into a molten both of the plastic material or into a solution or a dispersion of such material, or

d. By any other method of providing a sleeve type coating to an inner glass receptacle known in the art.

Claims

I claim:

1. A shatter-resistant composite bottle having base means, side walls and a neck portion comprising a pressurizable inner glass envelope having a mean side wall thickness of between about 0.030 inches and 0.120 inches and a thermoplastic resin outer envelope of a mean thickness of between about 0.004 inches and 0.018 inches surrounds said inner envelope and extends over substantially the entirety thereof said outer envelope being further characterized in that its exterior surface is randomly nodularly configured and has a mean deviation value of about 12 and 18 percent above that of the outer envelope thickness and a mean deviation value of about between 8 and 12 percent below that of the outer envelope thickness.

2. A shatter-resistant composite bottle comprising an inner glass envelope having a mean sidewall thickness of between about 0.030 inches and 0.120 inches and an outer envelope of a thermoplastic material having a mean thickness of between about 0.004 inches and 0.018 inches extends over substantially the entirety of said inner glass envelope excepting the finish thereof, the exterior surface of said outer envelope being further characterized in that it is nodularly configured and has a maximum elevation above said mean varying between about 6 and 60 percent thereof.

3. A shatter-resistant composite bottle according to claim 2 wherein said outer envelope is additionally characterized in that its maximum deflection below said mean thickness varies between about 20 and 40 percent thereof.