Patent Publication Number: US-7913870-B2

Title: Tamper evident container

Description:
CROSS REFERENCE 
     Applicant claims priority from U.S. Provisional patent application Ser. No. 60/679,321 filed May 10, 2005. 
    
    
     BACKGROUND OF THE INVENTION 
     Food is often placed in a transparent plastic container that includes a base with a large volume cavity that holds the food and with a cover that closes the cavity. Buyers want to be assured that, after the food has been placed in the container, as by a clerk wearing plastic gloves at the food store, that the container has not been opened. There is a possibility that a customer will secretly open the container enough to taste a bit of the food before closing it (and possibly leave his/her germs in the food), and potential buyers want to know whether this has happened. A device that could be installed by the manufacturer of the containers, which could be almost automatically activated by a clerk at the food store when the container was filled and initially closed, and which indicated to customers when a container has been opened, would be of value. Food containers are sold at low costs so any such device should be of low cost and be easily activated by a store clerk. 
     SUMMARY OF THE INVENTION 
     In accordance with one embodiment of the present invention, a container, especially a food container, is provided with a low cost and easily activated means that indicates when the container has been opened after goods such as food was loaded into the container. The container is of the type that includes a base and lid that are each constructed of deformed plastic sheet, with at least the lid being of transparent material. At least first sides of the base and lid form flaps that lie parallel and adjacent to one another. The indicating means includes a character sheet having cuts that form holes and forming characters within the holes. The character sheet portion other than the characters that lie in the holes, forms a carrier that lies outside the holes. The indicator sheet is usually an elongated strip that is placed between the base and lid flaps. When the indicator sheet is activated and the lid is closed, the carrier of the indicator sheet is adhesively bonded to the base flap, while the characters are adhesively bonded to the lid flap. When the container is next opened, the characters stick to the lid flap and pull out of holes in the carrier, and when the lid is closed again the characters will not fit precisely into the holes in the carrier that they were pulled out of. The misalignment is highly noticeable, and shows that the container was opened after the food was loaded. 
     The base and lid flap are latched together by a latch mechanism that causes the lid flap to shift rearward as it is being pushed down to close the container. As a result, the characters on the lid flap are shifted rearward before the lid is fully closed, causing misalignment. 
     The character sheet can be formed of an adhesive sheet that has sticky surfaces on both of its faces and that has front and rear edge sections. The characters lie between the front and rear edge sections of the adhesive sheet. Highly adhesive strips can be attached to the bottom of the front and rear edges of the adhesive sheet to cover only the carrier. The highly adhesive strips hold the carrier down to the base flap, while the tacky upper surface of the adhesive sheet pulls at least some of the characters our of the adhesive sheet as the lid flap is pulled up. 
     The novel features of the invention are set forth with particularity in the appended claims. The invention will be best understood from the following description when read in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a top isometric view of a container of the present invention, shown in the initially closed position. 
         FIG. 2  is an isometric view of a portion of the container of  FIG. 1  after food has been loaded into the container and the lid was closed, and the container has been again opened and closed. 
         FIG. 3  is a sectional view taken on line  3 - 3  of  FIG. 1 , and showing in phantom lines the lid being raised during opening of the container. 
         FIG. 4  is an enlarged sectional view of  FIG. 3 . 
         FIG. 5  is a plan view of a portion of  FIG. 2 , after the container has been opened and closed following the loading of goods  14  into the container. 
         FIG. 6  is an enlarged view of  FIG. 3  showing the upper flap being initially lifted to open the container following the loading of goods into the container. 
         FIG. 7  is a view similar to  FIG. 6 , showing in phantom lines a portion of the lid flap in the course of closing, and showing in solid lines the lid flap pressed down fully to close the container, all following the opening step of  FIG. 6 . 
         FIG. 8  is a sectional view of an indicator sheet prior to its mounting on flaps of the container, and with peel-off protective sheets on its top and bottom faces. 
         FIG. 9  is a sectional view similar to  FIG. 8 , after the lower protective sheet has been removed and the indicator sheet has been pressed against the base flap. 
         FIG. 10  is a sectional view similar to  FIG. 9 , after the upper protective sheet has been removed from the indicator sheet, and the lid flap has been pressed down against the indicator sheet that lies on the base flap. 
         FIG. 11  is an enlarged view of a portion of the apparatus of  FIG. 10 , and with a black release and background strip. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG. 1  illustrates a container  10  that is especially useful to hold food, which includes a base  12  that forms a food-holding cavity  14 , and a cover or lid  16  that covers the cavity and that can be said to form top walls of the cavity. Both base and lid are constructed of vacuum formed transparent plastic sheets. The base and lid are each of generally rectangular shape and have peripheral portions at each of their four sides  24 - 27 , in the form of base flaps  20  and lid flaps  22 . The base flaps  20  and lid flaps  22  at each side of the container, lie in parallel planes, and lie adjacent to each other. The lid has a tab  80  that can be lifted to open the container. As shown in  FIG. 3 , each flap  20 ,  22  has a mounted edge portion  30 ,  31  that merges with the rest of the base or lid, and has a free edge portion  32 ,  33  that is free to be bent up and down. Applicant places an indicator sheet  34  along at least one side of the container, with  FIG. 1  showing a pair of indicator sheets  34 ,  36  at opposite sides of the container, to indicate when the container has been opened, the particular indicator strips being of white colors when viewed from above. 
     When the container has been initially closed after food has been placed in the container, the container appears “normal” with only two continuous (no gaps) white indicator strips  34 ,  36  seen lying at the container opposite sides between the base and lid. However, if the container thereafter has been opened and reclosed, then an anomaly appears as shown in  FIG. 2 , with gaps  42  and pieces of letters easily seen. The container still can be opened and closed, but the fact that it was initially opened is obvious. 
       FIG. 3  shows that the lid flap  22  can be opened by lifting the lid flap free edge portion  33  up away from the base flap free edge portion  32 , with the lid flap at  22  X being bent to have a concave upper surface, until a lid projection  44  snaps out of a base recess  46 . The lid projection  44  and base recess  46  form a releasable latch mechanism  48 . 
       FIG. 4  shows the initially closed container, with an indicator sheet or strip  34  lying between the base and lid flaps. The indicator strip comprises a character sheet or strip (which is not necessarily elongated)  50  into which at least one character is cut. In  FIG. 4 , the character sheet  50  is an adhesive strip or band of “sticky” material with both its top surface  52  and its bottom surface  54  being adhesively held, with only moderate adhesive strength, respectively to the lid flap  22  and to the base flap  24 . The term “adhesive strength” is used here to indicate the force required to pull off a unit area such as 0.5 inch 2  or peel it off. The indicator strip  34  has cuts  56  that form characters  60  such as letters, numbers, or a fanciful image and that form holes  62  in which the characters lie. The indicator strip also forms a carrier  64  in which the holes  62  have been formed.  FIG. 5  shows the cuts  56  forming letter characters  60  that spell “OPENED” in a middle section or region  68  of the indicator strip. The middle region  68  lies between front F and rear R regions  70 ,  72  of the indicator strip. 
     Initially, the characters  60  lie in the openings or holes  62  of the carrier strip middle region, with the characters precisely matching the shape and positions of the holes and being precisely aligned with the holes, as a result of the letters being left in place in the strip after the cuts are made. However, when the lid and base flaps are separated to open the container to gain access to the food-holding cavity, some or all of the characters  60  stick to the lid flap while the carrier portion, or carrier  64  sticks to the base flap. This is because the character upper face is adhesively held to the lid flap by a first holding strength but the lower face of the character is not held to the base flap with the first holding strength. This is, the character lower face is held to the base flap by a lower or zero holding strength. Similarly, the carrier lower face is held to the base flap by a second holding strength, but the carrier upper face is held by a lower or zero holding strength to the lid flap. 
       FIG. 6  shows the lid flap  22 X as the container is being opened, when the lid flap free edge portion  33  is bent upward before the lid projection  44  has pulled out of the base recess  46 . The lid projection and base recess form the latch mechanism  48  that shifts the lid as it is replaced on the base, as described below. A character  60  has been pulled out from of a corresponding hole  62  in the carrier  64  to rise with the lid flap. At the same time, a part of the base flap  20  is usually held down by a person&#39;s finger and may be bent down. The carrier  64  of the indicator sheet remains stuck on the base flap  20 . 
       FIG. 7  shows the lid flap  22  of  FIG. 6  with the character  60  thereon as the lid flap is being closed onto the base flap  20 , after having been previously opened. The lid flap (and to some extent the base flap, also) is bent differently during opening, when the lid flap is initially lifted, compared to bending that occurs during closing when the lid flaps may be simply pushed down. One difference is that the free edge portion  33  of the lid flap is usually pushed down towards the base flap  20 , causing the character  60  to stick to the carrier  64 , as the lid projection at  44 A moves down across a base inner surface  45 . As a result, the position of the character  60  in  FIG. 7  has shifted forward F when the lid flap is closed, and the character  60  will not be fitted precisely into the hole  62  of the carrier  64 . The result is that the character is shifted and/or skewed, with part of the character lying on top of the carrier  64  and part lying in the carrier hole  62  from which the letter was pulled out. The resulting gaps such as shown at  42  in  FIG. 7  and  FIG. 2 , and some of the letters, spell the word “opened” and can be readily seen by a person. Thus, if a person sees some of the letters of “opened” and sees the messy arrangement of letters lying only partially in the corresponding holes, the person is informed that the container has been opened. 
       FIG. 8  shows a strip assembly  90  which includes the original indicator strip  34  as it is supplied to the manufacturer of containers. The strip assembly includes the adhesive sheet, or sheet of “sticky” material  50  and top and bottom peel-off protective sheets or strips, or protectors  92 .  94  lying against the opposite faces  53 ,  55  of the character sheet  50 .  FIG. 8  shows highly adhesive layers  102 ,  104  lying on the bottom surface of the front and rear edge regions  70 ,  72  of the carrier  64 , to securely hold the carrier to the base flap.  FIG. 9  shows the indicator sheet after the bottom protector strip  94  has been removed, so only the upper protector strip  92  remains. As a result, the highly adhesive strips  102 ,  104  adhere to the base flap  20 . The highly adhesive strips can be layers sprayed or brushed on by the manufacturer. Usually it is the manufacturer of the container base and lid who has removed the lower protector strip and pressed the highly adhesive strips against the base flap, and then ships the base and lid to food stores with the top peel-off protective sheet  92  in place. 
       FIG. 10  shows the assembly of  FIG. 9 , after food or other goods have been placed in the base cavity, a store clerk has peeled off the top protective sheet, and the lid flap has been pressed down towards the base flap, with only the indicator sheet  34  between them. The lid flap  22  has been pressed down firmly so the character  60  adheres to the lid flap. When the lid flap begins to be pulled up during a first opening of the container, as in  FIG. 6 , the carrier  64  remains on the base flap at least partially because of the highly adhesive layers  102 ,  104  that hold the front and rear edge regions of the carrier to the base flap. The characters  60  tend to move upward with the lid flap. This can be assured by placing a barrier indicated at  100  in  FIG. 6 , of non-adhesive release material, under the bottom of only the middle region  68  of the character sheet where the characters are located. Some or all of the characters will adhere to the lid flap  22 . It is even possible to place a drop of highly adhesive material on the top of one or a few of the characters to assure that at least one character will stick to the lid flap. 
     When the lid is closed after it has been first opened, the character  60  will be shifted by the bending and displacement of the flaps, especially the lid flap, so the character such as  60  will not fit into the hole  62  in the carrier that it was pulled out of during opening of the container. Instead, as shown in  FIG. 7 , there will be uncovered gaps  42  in the carrier strip  64 . A person looking at the indicator sheet  34  of  FIG. 2  though the transparent lid flap  22  will see a largely white strip with gaps in the white strip where the holes have not been covered. The color seen though the gaps will be easily noticed. A black background strip can be placed under the adhesive sheet or even at the bottom of the base flap to enhance the contrast between the white strip and the gaps in it.  FIG. 11  shows a black background strip  100 A under the middle region  68 , with a lower release surface that does not stick to the base flap and an upper adhesive layer  104  that sticks to the middle region. It is possible to merely paint the bottom of carrier middle region. 
     Where only one side of the container lid can be lifted because the other side is pivotally connected to the base, only one indicator strip is required. Where both sides of the container can be lifted so either one of the container opposite sides can be lifted to open the container, an indicator sheet is preferably placed on the flaps at both opposite sides of the container. Use of the term “strip” does not mean that a sheet is elongated. Such indicator strips can be placed at opposite sides of the container such as at the opposite long sides. Instead of a white strip, other contrasting colors can be used for the character sheet and the backup sheet. Although the indicator strip assemblies were designed for food containers, they can be used to hold containers for other goods. 
     Thus, the invention provides the combination of a container having at least one pair of base and lid flaps, and an indicator sheet or strip which indicates if the lid has been opened after the indicator strip was fully installed, which occurs after goods are loaded into the container. The indicator sheet has at least one cut that forms a hole and a character in the hole, and a carrier that surrounds the hole and the character therein. The hole could extend to the front or rear edge of the indicator sheet. The indicator sheet has a first adhesive surface that holds down the carrier to the base flap, and has another adhesive surface the holds the character to the lid flap when the lid flap is raised away from the base flap. There is zero or a lesser holding strength of the carrier for the lid and of the character for the base. As a result, when the lid flap is raised, the character is lifted out of its hole. When the lid flap is next lowered towards the base flap, the character will be lowered to a position offset from its original position, creating a gap between part of the character and the walls of the hole. The offsetting creates a gap which can be readily seen, to indicate to customers that the container has been opened since it was first closed after goods were loaded into the container. It is possible to adhere the character to the base and adhere the carrier to the lid, although that is not preferred. 
     Although particular embodiments of the invention have been described and illustrated herein, it is recognized that modifications and variations may readily occur to those skilled in the art, and consequently, it is intended that the claims be interpreted to cover such modifications and equivalents.