BACKGROUND OF THE PRESENT INVENTION
The present invention is directed to a pull cap having a textured grip surface.
Pull caps have been used commercially for many years. These caps have many uses, such as sealing the ends of tubes, pipes, or other articles of manufacture that may have an open end which needs to be temporarily sealed during manufacturing, storage, transportation, etc.
By way of example, U.S. Pat. Nos. 3,574,312 and 6,520,212 disclose several embodiments of protective plastic end caps for use in protecting the open end of a tube, etc. As shown by U.S. Pat. No. 3,574,312, such end caps can easily be made by means of a vinyl dip molding process.
Current commercially-produced vinyl end caps have an inherently slippery surface due to the lubricity properties of the vinyl material, the inherently smooth surface of the vinyl material, as well as the presence of plasticizers (oily softeners) that tend to leach from the surface of the vinyl material over time.
- OBJECTS AND SUMMARY OF INVENTION
As protective end caps generally are not provided with ergonomically-friendly configurations which might serve to assist in gripping of the end cap, it is sometimes difficult to remove the end cap from engagement with an article to be protected if the respective fit between the end cap and the article is snug or tight. As the degree of protection is enhanced by a snug or tight fit, this problem tends to occur with some frequency. Also, over time the surface of the end cap tends to adhere to the surface to be protected more aggressively, thus further hindering removal of the end cap from engagement.
It is thus an object of the present invention to provide a protective end cap which has the capability to both effectively serve a sealing or capping function, as well as to be more easily removed from engagement with the object to be sealed or capped.
BRIEF DESCRIPTION OF THE DRAWINGS
In accordance with the present invention, there is thus provided a protective vinyl end cap for use in sealing the end of a tube or pipe or other article of manufacture in need of a protective end cap. The end cap has a grip surface which includes a textured grip surface generally different from the surface of the remaining portion of the end cap. The grip surface in association with the textured surface assists in enhancing the ease of installation and/or removal of the end cap from engagement with the article to be capped.
FIG. 1 is a side view of an end cap of the present invention.
FIG. 2 is an oblique view of the end cap of FIG. 1.
FIG. 3 is a side view of another end cap of the present invention.
FIG. 4 is an oblique view of the end cap of FIG. 3.
FIGS. 5 and 6 are side views of another end cap of the present invention.
DETAILED DESCRIPTION OF THE PRESENT INVENTION
FIG. 7 is an oblique view of the end cap of FIGS. 5 and 6.
The invention will be described in connection with FIGS. 1-7.
The end cap 1 of the present invention is made by dip molding. Dip molding processes are well known in the art, and have been used for decades to produce vinyl-based plastic articles.
In a dip molding process, a heated mold form or mandrel is dipped into a plastisol bath whereupon a layer of gelled (fused)_plastisol forms about the mandrel. The coated mandrel is removed from the plastisol dipping tank and the coated layer cured, resulting in a molded article corresponding in configuration to the configuration of the mandrel employed. For instance, when a cylindrical mandrel (or pin) is employed, a tubular article with a closed bottom can be produced. Beverage containers, bicycle handles, gloves and tubular hose bend restrictors are but a few of the products that are presently produced by dip molding by use of a variety of mandrel configurations.
The mandrel may be comprised of any suitable metal such as aluminum, steel, cast iron, brass, copper, titanium, and other ferrous metal combinations. The mandrel may also be coated with a non-ferrous metal. The mandrel is attached to suitable supporting means during the molding process which causes the mandrel to be dipped into and subsequently removed from the plastisol bath, and also permits the coated mandrel to be moved along the molding line to other manufacturing stations.
The mandrel is preheated to a temperature sufficient to cause the plastisol in the bath to gel/fuse and to form a layer on the heated mandrel upon the mandrel being dipped into the plastisol bath. The mandrel is generally preheated to a temperature ranging from about 350 degrees F. +/−50 degrees F. by means such as being passed through an oven, placed into a heated liquid bath, heated by internal heating element, etc. The particular heating means is not critical as long as the temperature of the mandrel is sufficiently high to cause the required gelling of the plastisol on the outer circumferential surface of the mandrel once the mandrel is placed into the plastisol bath.
The composition of the plastisol bath is not critical, as a variety of plastisol compositions are conventionally employed. The plastisol (polyvinylchloride) bath may include various colorants (to cause the formation of a molded article of a particular color), additives, fillers, and/or blowing agents (to cause formation of a foamed layer). Once placed in the plastisol bath, the mandrel is permitted to contact the plastisol for a time sufficient to result in formation of a gelled layer on the metallic surface of the mandrel. The time during which the mandrel is caused to remain in contact with the plastisol bath is determined by a number of factors, such as the temperature of the mandrel and the thickness of the gelled plastisol layer which is desired to be formed on the metallic surface of the mandrel. Generally, it has been found that the mandrel may remain in contact with the plastisol bath for a period of time ranging from about 4 seconds to several minutes depending on material gellation properties, tooling geometry, and wall thickness desired.
Once the mandrel contacts the plastisol bath for a period of time sufficient to form a gelled layer of desired thickness, the coated mandrel is removed from the bath. The resulting thickness of the molded article generally ranges from about 0.03 to 0.20 inch. The mandrel is slowly removed from the plastisol bath to enable excess non-gelled plastisol to fall from the mandrel. The mandrel is then cured to solidify the gelled layer on the mandrel. Such curing may occur by heating to a temperature off from about 390° F. to about 600° F. for a period of time ranging from about 0.50 to 3 minutes. Alternatively, the plastisol layer may be cured by dipping the gelled plastisol layer into a heated bath of molten salt or oil. Such curing means are conventional and well known to those skilled in the art. The cured plastisol-coated mandrel is then cooled by conventional means such as by air or water, and the thus-formed dip molded part 1 removed by either mechanical means, air pressure either internal or external to the mandrel, or by other automated methods. The mandrel then typically has a mold released placed over the molding surface and the form is reused to produce additional molded parts.
If multiple layers of the plastisol are desired, the dipping and/or curing steps are repeated. The formation of multiple (double dipped) plastisol layers is also well known to those skilled in the art, as is the use of a blowing agent to form a foamed plastisol layer. See, for example, U.S. Pat. Nos. 3,904,720 and 4,800,116 in this regard.
The end cap 1 of the present invention has a generally cylindrical or tubular open end 7 and a closed end 9 having formed therein a gripping surface 5 suitable for gripping between a thumb and finger. The gripping surface 5 may merely be provided on the exterior of a cylindrical surface, or the gripping surface may be provided on a molded portion which has a different configuration than the rest of the end cap but may be more specially configured for gripping (such as a thinner or flattened portion as shown in FIGS. 3-7).
It has thus been found that at least a portion of the exterior surface of the end cap should be provided with a thin second layer of texturized surface 5 to assist gripping as well as installation and/or removal of the end cap. Such a coating may be provided by the use of a plastisol bath formulated to provide the desired texturized coating.
Texturized vinyl material may be formulated from a conventional polyvinyl chloride plastisol by substituting up to 50% by weight of the vinyl dispersion resin (typically having a particle size of 1 micron or so) with, for example, polyvinyl chloride suspension resin having a particle size of from 50 to 200 microns, or equivalent course grained fillers. Exemplary fillers may be selected from a variety of conventional metal or inorganic fillers having a size and course surface to provide the requisite texturized surface properties.
More specifically, various inorganic fillers may be used such as sand, coarse talc, calcium carbonate, etc. However, in order to suspend the filler particles in the plastisol, it is desirable to keep the filler to as close to the specific gravity as the plastisol as possible. The fillers can be added in an amount of up to about 30% by weight of the total weight of the plastisol composition. Suspension grades of polyvinyl chloride with particle sizes ranging from 50 microns and higher provide a satisfactory textured surface for the dip molded article. Most dispersion grade polyvinyl chloride resins have a particle size of from 1 to 5 microns.
When large vinyl particles are employed, the use of the larger particle size allows the plasticizer(s) to only slightly solvate the larger particle in the plastisol In the case of course non-resinous fillers, the fillers are randomly fused into the solidifying wall during gellation. As a result, when the plastisol forms a coating 3 on the dip molded mandrel, or as a second coating 5 on a previously-formed dip molded part, the coated surface is not smooth but assumes a texturized surface due to the presence of the unsolvated particles dispersed throughout the plastisol.
The resulting end cap 1 having a texturized surface 5 provides many advantages. As protective caps and pull caps are generally not ergonomically friendly and often difficult to remove, it is highly desirable for the cap to have a texturized grip surface that is easily formed yet greatly improves the tactile properties and gripping ability of the cap. This reduces hand and finger fatigue, and reduces repetitive motion disorders which occur when a production worker is required to repetitively remove a protective cap for long periods of time.