Caps and Closures
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Bottle caps, or closures, are used to seal the openings of bottles of many types. They can be small circular pieces of metal, usually steel, with plastic backings, and for plastic bottles a plastic cap is used instead. A bottle cap is typically colorfully decorated with the logo of the brand of beverage. Caps can also be plastic, sometimes with a pour spout. Flip-Top caps like Flapper closures provide controlled dispensing of dry products. Bottle caps are often made of a different type of plastic than the bottle itself, and are often recyclable.Bottle caps were originally designed to be pressed over and around the top of a glass bottle to grab a small flange on the bottleneck. The Crown Cork was patented by William Painter on 2 February 1892 (U.S. Patent 468,258). It originally had 24 teeth and a cork seal with a paper backing to prevent contact between the contents and the metal cap. The current version has 21 teeth. To open these bottles, a bottle opener is generally advised, although some bottles incorporate a screw cap, eliminating the need for the opener.Individuals have experimented with different ways of opening bottles, including using teeth or snapping them open across another surface. A separate interest to collecting bottle caps is that of interesting ways to open bottles.The height of the crown cap was reduced and specified in the German standard DIN 6099 in the 1960s. This also defined the "twist-off" crown cap, now widely used in the United States, Canada, and Australia. This bottle cap is pressed around screw threads instead of a flange. Such a bottle cap can be taken off merely by twisting the cap.Bottle caps are also a way for bottlers to hold promotions, especially for soda companies. A message is printed on the inside of the cap and people with the right message may win a prize. Since the bottle must be purchased to determine the message and win, people usually purchase more of the drink to increase their chances of winning. The most common prize is a free soda from that company.Some companies, such as Snapple, also print interesting facts on the inside of their caps. Mickey's Malt Liquor as well, prints riddles underneath the 24 and 40 oz. bottle caps. Usually this is done on wide-mouthed bottles that have large caps with enough printing area to put a short sentence.
Purpose of closuresMany containers and packages require a means of closing. It can be a separate device or seal or sometimes a integral latch or lock. Depending on the contents and container, closures have several functions:Keep the container closed and the contents contained for the specified shelf life until time of openingProvide a barrier to dirt, oxygen, moisture, etc. Control of permeation is critical to many types of products: foods, chemicals, etc.Keep the product secure from undesired premature openingProvide a means of reclosing or reusing the containerAssist in dispensing and use of productAllow reasonable ease to open the container by the intended user. Difficult to open containers may cause wrap rage. The force or torque required to open a closure is an important consideration for packaging engineers.Many types of packaging with their closures are regulated for strength, safety, security, communication, recycling, and environmental requirements.Types of closuresClosures need a means of attaching to the container with sufficient security. Threads, lugs, hinges, locks, adhesives, etc. are used.Many closures need to have the ability to adjust to slight manufacturing variation in the container and the closure structure. Some closures are made of flexible material such as cork, rubber, or plastic foam. Often an o-ring or a closure liner (gasket made of pulp or foam cap liner) is used. Linerless closures often use a deformable plastic rim or structure to maintain the seal.Secondary seals are common with sensitive products that may deteriorate or where extra security is needed. Foil or plastic innerseals are used on some bottles, Heat sealed lidding films are used on some tubs. External shrink bands, labels, and tapes are sometimes used outside the primary closure structure.Screw topA screw closure is a mechanical device which is screwed on and off of a threaded "finish" on a container. Either continuous threads (C-T) or lugs are used. Metal caps can be either preformed or in some instances, rolled on after application. Plastic caps may use several types of molded polymer.Some screw tops have multiple pieces. For example, a mason jar often has a lid with a built in rubbery seal and a separate threaded ring or band.Crown capsBeverage bottles are frequently closed with crown beverage caps. These are shallow metal caps that are crimped into locking position around the head of the bottle.Snap onSome closures snap on . For opening , the top is designed to pry off or , break off, or have a built in dispenser.Â
Friction fitSome containers have a loose lid for a closure. Laboratory glassware often has ground glass joints that allow the pieces to be fitted together easily.An Interference fit or friction fit requires some force to close and open, providing additional security. Paint cans often have a friction fit plug.DispensingA wide variety of convenience dispensing features can be built in to closures. Spray bottles and cans with aerosol spray have special closure requirements. Pour spouts, measuring attachments, sifting devices, etc. are common.HistoryEarly pottery and ceramic containers often had lids that fit reasonably snug onto the body of the container. The narrow necks of ancient amphora were closed with a plug of cork, wood, or ceramic and sealed with mortar.[3] Wooden Barrels often had bungholes closed by cork or wood bungs.Some early tinplate cans were made with threaded necks for screw top closures.Beverage bottles started using the Hutter Stopper in 1893. This involved a porcelain plug fitted with a rubber washer, which was then forced down into the lip of the bottle. This technique only works with carbonated beverages. The Hutter Stopper became standard in beer bottling in the late 1890s / early 1900s. Bail closures on bottles were invented by Henry William Putnam in 1859. These involved heavy wire bail attached to a bottle's neck that swung over the cork to hold it in.The world's first modern bottle cap, the crown cork, was invented by William Painter in 1890 in Baltimore. The screw cap using rust resistant aluminum was first used in prescription drug bottling in the 1920s.Molded urea based bottle caps were first introduced in the early 1900s.
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