Pressure Change Indicator

Abstract

The disclosed closure device for a hermetically sealable container has a flexible panel which is drawn inward in response to a vacuum within the container, and which pops outward when pressure in the container is restored; the outward movement of the flexible panel is made very dramatic by virtue of a contrasting color appearing on the top of the closure. The color is preferably provided by reflection from the flexible panel. The reflection occurs when visible light strikes the colored undersurface of a disc-like member attached to the flexible panel.

Description

FIELD OF THE INVENTION

This invention relates generally to a sealed container of the type used for keeping foodstuffs or the like in a well preserved condition until the seal on the container is broken by removing a closure over the mouth of the container. Typically, the foodstuff or other perishable product is preserved with the aid of a vacuum within the container. An aspect of this invention relates to a closure device adapted to provide a dramatic visual indication of a loss of vacuum or other pressure change within the container.

DESCRIPTION OF THE PRIOR ART

It is common practice in the food industry to provide a vacuum within food jars or containers and to hermetically seal the container with a closure that has a vacuum indicator feature, permitting shippers, sellers, and users of the container to ascertain any inadvertent loss of vacuum in the container prior to use. It is well known that loss of vacuum in the container can permit the food or other perishable product to become a breeding ground for disease-causing bacteria. Closures have been designed for these food containers which provide an audible clicking or popping sound when the hermetic seal is broken. A further aspect of these prior art closures involves a change of position of a flexible top panel which is integral with the closure. Typically, the panel is deflected or flexed inwardly when the vacuum is still present in the container, but is flexed outwardly upon leakage of air into the container. Several examples of container lids or caps with this loss of vacuum indicating feature appear in the patent literature, e.g.: U.S. Pats. No. 2,040,798 (Schoonmaker), issued May 12, 1936; No. 2,027,430 (Hansen), issued Jan. 14, 1936; No. 2,130,180 (Evans), issued Sept. 13, 1938; No. 2,296,848 (Gueffroy), issued Sept. 29, 1942; No. 2,458,360 (Fay et al.), issued Jan. 4, 1949; No. 3,062,396 (Foss et al.), issued Nov. 6, 1962; No. 3,152,711 (Mumford et al.) issued Oct. 13, 1964; and No. 3,160,302 (Chaplin), issued Dec. 8, 1964.

A problem with all of these prior art devices is that the indication provided by the flexible panel or the like is not sufficiently dramatic to warn an unsophisticated user that the contents of the container may be unsanitary. For example, the clicking or popping sound may not be heard above a high level of background noise, or the user may forget whether or not he has heard the sound. Even more serious, the user may not be aware that the lack of a click or pop indicates that the contents of the container may be subject to contamination or spoilage. The visual indication provided by the prior art closures is perhaps even less dramatic than the aforementioned sound indication. Typically, the center of a prior art closure travels about 40 mils (about 1 mm) when pressure is restored in the container. This small amount of travel, changing the center of the lid from a slightly concave surface to a slightly convex surface, may easily be overlooked. In view of the importance of the loss of vacuum within the container, a more dramatic means for warning of the possibility of unsanitary spoilage is needed.

A more noticeable visible change in response to a relatively drastic pressure increase may occur by virtue of a rupture or disengagement of a pressure-sensitive member, as in the closures described in U.S. Pats. No. 2,126,212 (Richards), issued Aug. 9, 1938, and No. 2,326,771 (Eidson), issued Aug. 17, 1943. However, these closures, unlike the flexible panel type, do not provide a reliable indication of a loss of vacuum inside the container.

Color changes have been used in the packaging art to indicate the temperature or humidity conditions inside the package. These color changes may be provided either by the movement of a color-coded, relatively complicated mechanical device or by a reversible or irreversible chemical reaction. Apparently, no simple means has been devised for providing a color change upon loss of vacuum or other pressure change within a package or container, at least with respect to the types of hermetically sealed food containers illustrated in the aforementioned patent literature.

Accordingly, this invention contemplates an improvement upon the conventional loss-of-vacuum indicating closure whereby the indication is made more dramatic by virtue of a color appearing on the closure. This invention also contemplates an improved closure which also irreversibly indicates the heat history of the contents of the container.

SUMMARY OF THE INVENTION

Briefly, this invention involves providing a closure device for a hermetically sealable container, which closure device has the conventional flexible panel capable of moving outward in response to an increase in pressure within the container and, attached to this flexible panel, a color-concealing and -revealing member, preferably a disc-like element which covers up all or most of the flexible panel when the panel is flexed inward, but provides a gap around the periphery of the panel when it is flexed outward. This gap reveals a highly-visible or contrasting color, which is seen on the flexible panel either by means of a color on the panel itself or a color on the underside of the disc-like member which is reflected from the panel. When the mechanism or revelation involves reflection, the panel should be a reflective surface. A light color, such as white, capable of reflecting at least 50 percent of the visible light falling upon it, is adequate; but a reflectance of at least 65 percent, preferably at least 90 percent, provides the most dramatic color indication.

DESCRIPTION OF THE DRAWING

This invention can be more clearly understood by referring to the accompanying drawing, wherein:

FIG. 1 is an enlarged cross-sectional view of a closure means of this invention in place over the mouth of a container wherein the interior of the container is under vacuum;

FIG. 2 is a cross-sectional view similar to FIG. 1 illustrating the position of the elements in FIG. 1 upon loss of vacuum within the container, the movement of elements being exaggerated for purposes of illustration;

FIG. 3 is an exploded view in perspective of the closure illustrated in FIGS. 1 and 2;

FIG. 4 is a cross-sectional view similar to FIGS. 1 and 2 showing an alternate embodiment of the invention;

FIG. 5 is an exploded view in perspective of the closure illustrated in FIG. 4; and

FIG. 6 is a perspective view of a closure, illustrating another alternative embodiment of this invention.

In FIGS. 1-3, like reference numerals denote like elements. The same is true of FIGS. 4 and 5.

DETAILED DESCRIPTION OF THE INVENTION

In the Drawing, the hermetically sealed container 10 shown in FIGS. 1 and 2 consists essentially of a jar 11 and a closure 13 engaging the mouth of jar 11. Closure 13 has a substantially planar top panel 15 integral with the peripheral skirt engaging the mouth of jar 11. In the center of top panel 15 is a flexible center panel or portion 17 substantially in the plane of top panel 15 but capable of moving or flexing below this plane (i.e. inwardly or toward the interior of jar 11) or above the plane (i.e. outwardly or away from the interior), depending on the pressure exerted upon the flexible or movable portion 17.

As is conventional in the art, the periphery 16 of the flexible portion 17 is designed to permit this upward or downward movement. When the pressure inside jar 11 is atmospheric or grater, flexible portion 17 assumes the substantially dome-shaped or convex configuration shown in FIG. 2. When the interior pressure in jar 11 is subatmospheric (or, in any event, lower than the interior pressure prevailing in FIG. 2), flexible portion 17 assumes a somewhat concave or flat configuration, as in FIG. 1. Top panel 15 and flexible portion 17 preferably consist of a shiny metal such as aluminum, tin plate, steel, or the like. Alternatively, a plastic metallized on its upper surface can be used. In any event, flexible portion 17, particularly periphery 16 preferably is capable of reflecting more than 50 percent of the visible light falling upon it; suitable metals or metallized surfaces reflect at least 65 percent and ordinarily>90 percent of incident visible light. Attached to flexible portion 17 is a thin disc or button 19 which fits tightly over flexible portion 17 (including periphery 16) when flexible portion 17 is flexed inwardly as in FIG. 1. However, since disc 19 is attached to flexible portion 17 only at center area 23 (FIG. 3), and since the configuration of disc 19 does not conform sufficiently to flexible portion 17 when portion 17 is flexed outwardly (FIG. 2), a gap develops at least between periphery 16 of portion 17 and periphery 16' of disc 19 when the outward position illustrated in FIG. 2 occurs.

From FIG. 3, it can be seen that undersurface 21 of disc 19 is a bright color (in this case red), which strongly contrasts with the metal surface of top panel 15. As shown in FIG. 2, light strikes undersurface 21 when flexible portion 17 is in the outward position, and a red reflection is clearly evident all around periphery 16 of portion 17. Thus, a red color warning of loss of vacuum or other pressure change inside jar 11 can easily be seen from almost any angle ranging from 0.degree. relative to the plane of top panel 15 to almost 90.degree. relative to this plane.

Disc 19 can be attached to portion 17 of top panel 15 in any suitable manner including mechanical fastening means such as rivets or, preferably, pressure, heat, or solvent-activated adhesive or other adhesive bonding means. The preferred adhesive bonding means is a coating of heat-activated adhesive on undersurface 21. When disc 19 is placed on portion 17 during manufacture of closure 13, portion 17 is in the position shown in FIG. 2, and only area 23 (FIG. 3) of portion 17 is in contact with disc 19. Heat (and preferably pressure) is then applied to disc 19 which activates the adhesive and bonds the disc 19 and portion 17 together only at area 23. The adhesive provides bonding only in the contact area (area 23) and is an essentially non-tacky material before and after heat activation in the area outside of area 23. The preferred class of heat-activatible adhesives is the thermoplastic epoxide-vinyl-nitrile rubber type described in U.S. Pat. No. 3,516,852 (Janssen et al.), issued June 23, 1970. An example of this class of adhesives comprises an epichlorohydrin-bisphenol A copolymer, a partially hydrolyzed vinyl chloride-vinyl acetate copolymer, and a butadiene-acrylonitrile rubber. This adhesive can provide a strong bond, but just in case the disc 19 becomes detached from portion 17, area 23 is colored red to indicate that the complete closure device, including loss of vacuum indicator, is no longer intact. For convenience of manufacture, undersurface 21 can be color coated and adhesive-coated in one operation by using a heat-activatible adhesive composition containing a red pigment or the like. Alternatively, disc 19 can be made of pigmented plastic (instead of metal as shown in FIGS. 1-3), so that undersurface 21 will be colored. It is preferred, in this case, to metallize the top surface of disc 19 to make the color change more easily visible.

In an optional feature of this invention, the color coating on undersurface 21 can be obtained by heat-activating a color-forming chemical composition such as a dithiooxamide derivative and a nickel salt admixed in a fusible wax matrix or a similar chemical composition. See U.S. Pat. No. 3,280,735 (Clark et al.), issued Oct. 25, 1966. Compositions which irreversibly change color with heat are a known means for indicating the heat history of an article, e.g. whether it has been sterilized. See U.S. Pat. No. 2,606,654 (Davis et al.), issued Aug. 12, 1952. Thus, the color coating could be used to indicate both a loss of vacuum and the presence or lack of prior sterilization of the contents of jar 11. The heat history indicator could also be used in addition to (i.e. not combined with) the loss of vacuum color indicator anywhere on jar 11, e.g. on the top surface of disc 19 or top panel 15. The sterilization indicator can be selected so as to change from, for example, red to colorless or grey so that the consumer will know not to use jar 11 if a red color appears in either of two specified places on closure 13.

FIGS. 4 and 5 illustrate an alternative embodiment of the invention wherein a colored undersurface 51 of disc 49 becomes visible in a manner similar to that illustrated in FIG. 2. As shown in FIG. 5, an adhesive is applied to area 55 of flexible portion 47 such that disc 49 pops up at an angle when portion 47 is in the outward position. This angled position of disc 49 further accentuates the visibility of colored under surface 51.

FIG. 6 illustrates a less preferred embodiment of the invention. For convenience of illustration, the disc element (corresponding to disc 49 of FIGS. 4 and 5, or disc 19 of FIGS. 1-3) is not shown. The closure 60 of FIG. 6 has a top panel 65 and a flexible portion 67, as in the previously described embodiments. However, almost the entire area of portion 67 is provided with a color (in this case red) which strongly contrasts with the relatively colorless remainder of top panel 65. When the disc pops up (as in FIGS. 2 or 4 of the other embodiments), the color on portion 67 is revealed.

Surprisingly, the embodiment of FIG. 6, which provides a direct red image upon loss of vacuum in the jar, is considerably less dramatic in its indicating effect as compared to the effect illustrated in FIGS. 2 and 4. The reflection of the red color off of a shiny surface seems to be more noticeable than the color itself. Furthermore, in FIG. 6 the disc (not shown) must be in register with flexible portion 67; otherwise, some of the red color might show even if the contents of the jar (not shown) were still properly under vacuum. In the preferred embodiments, which involve reflection from undersurface 21 or 51, the disc 19 or 49 could be somewhat out of register with portion 17 or 47, respectively, and the invention would still operate in the manner intended. A possible additional reason for the superiority of the preferred embodiments is that virtually all of the periphery 16 or 46 shows the reflected contrasting color when disc 19 or 49 is in the outward position (FIGS. 2 and 4, respectively), but periphery 66 in FIG. 6 can have the contrasting color on only about half of its area in order to insure against a false indication caused by even the most minimal misregister of the disc and the colored area of flexible portion 67.

Throughout this description of the Drawing, it is to be understood that the "color" on undersurface 21 or 51 or portion 67 is a contrasting color; i.e., some form of coloration or pigmentation which contrasts with a background which can be colorless or some color different from the "contrasting color." Thus, against a silvery or colorless background (on the top panel and/or flexible portion) even black or white would be a "contrasting color." Against a white or pale yellow background, even black or brown would still provide a good contrast. Since it is preferred, in all embodiments, that the background (top panel 65 of FIG. 6 or periphery 16 or 46 of FIGS. 1-5) be colorless or silvery or a very light color such as white or pale yellow, it is therefore preferred that portion 67 (FIG. 6) or the undersurface of the disc (FIGS. 1-5) be colored a dark, bright color such as red, blue, green, or the like. Optionally, fluorescent materials can be added to this bright coloration.

It is also permissible to have colored printing (i.e. brand names, instructions, etc.) on the top panel, provided this printing does not interfere with the color indicating effect.

The skilled technician will readily appreciate that the contents of a hermetically sealed container of this invention can be preserved under superatmospheric pressure provided by a biologically inert gas or other substantially oxygen-free atmosphere (e.g. nitrogen, helium, argon, propane, butane, carbon dioxide, etc.). In this case the invention can be adapted to operate in a converse manner: presence of the proper packing pressure would be indicated by the color on the top panel, while leakage, hence the potential for spoilage, would cause disappearance of the color. For obvious reasons, this pressure-packing concept is less preferred; furthermore, the indication upon loss of the packing pressure would not be so dramatic.

The preferred vacuum packing procedure for foodstuffs is well known in the art and is illustrated in the previously cited Chaplin and Mumford et al patents, but it is also permissible to provide a container with a pressure-change indicator attached to a permanently integral flexible panel rather than to a closure device as described previously.

Claims

What is claimed is:

1. A closure device for a hermetically sealable container, said closure device comprising:

a flexible panel constructed and arranged to move inwardly and outwardly with respect to the interior of the container in response to changes in pressure within the container and to assume a relatively outward position in response to at least atmospheric pressure inside the container and to assume a relatively inward position when the pressure inside the container is relatively lower, and

a color concealing and revealing member exterior to said container having a portion of a major surface thereof attached to said flexible panel, said major surface being sufficiently conformed to the shape of said flexible panel to conceal at least that portion of the flexible panel underlying the outer periphery of said major surface when the flexible panel is in the relatively inward position but not sufficiently conformed to the shape of the flexible panel to conceal said portion of the flexible panel when the flexible panel is in the relatively outward position, thereby revealing a contrasting color visible on said portion of the flexible panel only when the flexible panel is in the outward position.

2. A closure according to claim 1 wherein the contrasting color visible on said portion of the flexible panel is provided by a colored coating on said portion.

3. A closure according to claim 1 wherein said color is provided by a color on said major surface of said color revealing and concealing member, said color becoming visible when the flexible panel is in said relatively outward position by means of a reflection from the said flexible panel.

4. A closure according to claim 3 wherein said portion of said flexible panel is capable of reflecting at least 50 percent of the visible light falling upon it.

5. A closure according to claim 3 wherein said portion of said flexible panel is capable of reflecting at least 65 percent of the visible light falling upon it.

6. A closure according to claim 1 wherein said color concealing and revealing member is attached to said flexible panel with an adhesive.

7. A closure according to claim 3 wherein said color concealing and revealing member is attached to said flexible panel with an adhesive.

8. A closure according to claim 7 wherein said adhesive is heat-activatible and is contained in a pigmented coating on said major surface of said color revealing and concealing member.

9. A closure according to claim 1 wherein said color visible on said portion of the flexible panel results from an irreversible heat-activated color change.

10. A closure for a hermetically sealed container, said closure being adapted to provide at least a visual indication of pressure changes within said container, said closure comprising:

a top panel and an integral peripheral skirt with means on said skirt for engaging said container and holding the undersurface of said closure in sealed relation over the mouth of said container, said top panel comprising a peripheral portion which is in the plane of the top of the closure and a movable center portion capable of flexing in response to changes in pressure, said movable center portion being constructed and arranged to assume a position above the plane of the top of the closure when the pressure inside the container is at least atmospheric and to assume a position below the plane of the top of the closure when said pressure is subatmospheric, at least the movable center portion of said top panel being capable of reflecting at least 50 percent of the light falling upon it, and

a button-like member having a colored undersurface, the color of said colored undersurface contrasting with the color of said movable center portion, a portion of said colored undersurface being attached to the upper surface of said movable center portion, the area of said colored undersurface being substantially coextensive with the area of said movable center portion, the shape of said colored undersurface being substantially conformed to the shape of said movable center portion only when said movable center portion is below the plane of the top of the closure, whereby the color of said colored undersurface becomes visible by reflection from said movable center portion when said movable center portion is above the plane of the top of the closure but is concealed when the movable center portion is below said plane.

11. A hermetically sealed container comprising:

a flexible panel constructed and arranged to move inwardly and outwardly with respect to the interior of the container in response to changes in pressure within the container and to assume a relatively outward position in response to at least atmospheric pressure inside the container and to assume a relatively inward position when the pressure inside the container is relatively lower, and

a color concealing and revealing member exterior to said container having a portion of a major surface thereof attached to said flexible panel, said major surface being sufficiently conformed to the shape of said flexible panel to conceal at least that portion of the flexible panel underlying the outer periphery of said major surface when the flexible panel is in the relatively inward position but not sufficiently conformed to the shape of the flexible panel to conceal said portion of the flexible panel when the flexible panel is in the relatively outward position, thereby revealing a contrasting color visible on said portion of the flexible panel only when the flexible panel is in the outward position.