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barrier to the product as well as a merchandiser on the

retail shelf.

New Designs

All of the manufacturers of beverage carriers claim that

they can make custom carriers for their clients. Award-

winning designs have recently come from the Mead West-

vaco Packaging. The ‘‘IcePak’’ is a carrier that holds ice

and melted ice in the form of an end load sleeve so that it

could be loaded with automated equipment. The bottom

ﬂap is interconnected to the side and bottom ﬂap to form a

water seal. Top ﬂaps and gusset form a chimney. Cooled

natural Kraft provides wet strength without additional

coating. The ‘‘Bottle Master’’ is a three-bottle carrier with

unique positioning so no glass to glass contact occurs. The

bottle package was designed to run on existing gluers with

minimal make ready. It ships ﬂat and easily pops open,

locks open, and loads bottles. The ‘‘Bottle Master with

Crown Design’’ is a regular carrier with a cut-out crown

image. It was designed for Anheuser-Busch and ensures

zero impact on operations and runs on exisitng equip-

ment. The ‘‘Fridgemaster has duo strap handles added to

the standard 12-can refrigerator pack (2).

BIBLIOGRAPHY

O. Orta, ‘‘Carriers, Beverage’’ in A. J. Brody and K. S. Marsh, eds.,

Wiley Encyclopedia of Packaging Technology, 2nd edition, John

Wiley & Sons, New York, 1997, pp. 168–170.

Cited Publications

1. M. J. Kirwan, ‘‘Folding Cartons’’ in M. J. Kirwan, ed., Paper

and Paperboard Packaging Technology, Blackwell Publishing

Ltd., London, 2005.

2. Paperboard Packaging Council, ww.w.packagedesignmag.com,

2008.

CARTONING MACHINERY, TOP-LOAD

C. R. KUHR

Kliklok Corporation

Decatur, Georgia

Top-load cartoning employs ﬂat paperboard blanks that

have been die cut by a carton manufacturer [see Figure

1(a,b)] to produce speciﬁc shapes and sizes when formed

or folded into ﬁnished trays or hinge-cover packages. This

style generally includes no pregluing by the carton con-

verter, so ﬂat blanks can be stacked directly on a pallet

and shipped without secondary shipping cases. Hence,

top-load cartons are economical. They also allow product

placement through an opening on the largest panel of the

carton, which can greatly simplify the loading operation

(see the Machinery, cartoning, end-load; Cartons, folding

articles).

CARTON FORMING

The heart of any top-load packaging operation is the

carton-forming machine [see Figure 2(a,b)]. Although

various conﬁgurations exist, the most common is a vertical

system that provides overhanging delivery to outfeed

conveyors or packing conveyors. Generally, these forming

systems incorporate an inclined, gravity-advance maga-

zine or powered horizontal hopper from which individual

die-cut blanks are fed. Carton blanks are retained by

small projections or tabs that extend slightly from the

sides of a gate frame at the front of the magazine. Vacuum

cups, mounted on a reciprocating feed bar, pull the

individual carton blanks from the magazine and transport

them in a downward arc. As vacuum is released, they are

deposited in a registered position on top of a forming

Figure 1. Diagrams of typical (a) hinge-cover carton and compo-

nents and (b) dust-ﬂap-style paperboard tray.

228 CARTONING MACHINERY, TOP-LOAD

cavity. The carton blank is rotated from vertical to a

horizontal plane during this feed cycle, with the vacuum

cups contacting its inside surface. As the feed bar moves

upward to feed the next blank, a plunger or mandrel

moves downward to force the blank through the forming

cavity (see Figure 3). The plunger is designed so that the

carton body conforms to its shape. The carton is folded,

guided, and manipulated by a series of metal or composite

plastic ﬁngers and plows installed within the forming

cavity. As the plunger completes each forming stroke

Figure 2. (a) Top-load carton forming machine with dou-

ble-forming head; (b) rear of carton forming machine with

powered carton hopper.

CARTONING MACHINERY, TOP-LOAD 229

and begins moving upward, spring-loaded mechanical

traps retain the carton and strip it or remove it from the

plunger. In some cases, special carton coatings, shapes,

or speeds dictate the use of a timed air blast system to

positively eject the carton onto takeaway conveyors.

A wide range of carton sizes can be accommodated in

styles ranging from simple rectangular corner-lock trays

to a myriad of special shapes such as triangles, hexagons,

octagons, and complex hollow-wall or shadow-box struc-

tures. The key to top-load carton forming lies in the special

tooling that is designed and manufactured for each carton

size and style. This removable tooling is commonly re-

ferred to as a forming head. It can be a relatively simple

device or a complicated unit requiring various cams and

actuation for ﬂap folding and manipulation of the paper-

board panels. The forming head consists of (a) the forming

cavity, (b) a plunger or mandrel, and (c) various compo-

nents for the hopper or magazine. By interchanging this

tooling on any given forming machine, it can erect differ-

ent carton styles, shapes, and sizes within a speciﬁed size

range. For standard designs such as simple trays or hinge-

cover cartons, the tooling can generally be changed in

10–15 min. In many cases, a multiple-head conﬁguration

is employed to erect several cartons with each forming

stroke and increase the output of cartons per minute.

Depending on the size of the package to be formed,

machines may accommodate double, triple, or even quad-

ruple forming heads. The carton body can be formed using

locks, adhesive, or heat sealing.

LOCK FORMING

Dozens of different lock designs are available for forming

trays and cartons to meet various packaging requirements.

Most often, the lock design consists of a vertical and/or

horizontal slit in the upright panels or walls of the carton

body through which a specially shaped corner post or tab is

inserted during the forming operation (see Figure 4). The

opening of the die-cut slits in the vertical walls and folding

and insertion of the locking tabs are accomplished using

specially designed and fabricated ﬁngers or guides that are

an integral part of the forming cavity. Normally, a mechan-

ical actuation is also incorporated in the plunger to pull in

the locking limb and ensure positive engagement.

GLUE FORMING

Glue forming of ﬂat die-cut paperboard blanks can be

accomplished using either hot-melt or cold-vinyl adhesives

(see the Adhesives article). Hot-melt adhesive is generally

applied in one of two ways. The simplest method employs

open heated reservoirs mounted in the machine directly

below the forming cavity to melt and contain the adhesive.

This is commonly referred to as an ‘‘open pot’’ system.

Applicator blades are mounted on a shaft that runs across

the top of each reservoir. As the carton blank is placed on

top of the forming cavity, the shaft is mechanically actu-

ated and the blades rise upward from within the adhesive.

They apply a series of dots or lines of adhesive to the

underside of a ﬂap or corner post located in each corner of

the carton blank. As the carton is plunged through the

forming cavity, these ﬂaps are folded inside the vertical

walls of the carton. Spring-loaded rollers in the cavity

Figure 3. Lock-style carton forming head.

Figure 4. Common stripper-lock design: (a) assembled; (b)

unfolded.

230 CARTONING MACHINERY, TOP-LOAD

provide compression using the plunger inside the carton

for backup. This technique compresses the adhesive and

dissipates heat to allow quick bonding for reasonably high

forming speeds.

The other commonly used method of hot-melt glue

forming employs an enclosed, pressurized system where

adhesive is supplied through heated hoses to guns or

nozzles that spray a pattern on the inside of the carton’s

vertical body panels. Depending on the size of the carton

and the pattern desired, this may be performed by ﬁrst

feeding cartons onto a short section of horizontal conveyor

and applying adhesive as they are shuttled into position

on top of the forming cavity. This avoids the need to mount

necessary feed hoses and nozzles within the constraints of

the forming cavity. It also allows greater pattern ﬂexibil-

ity, and fewer nozzles can be used to apply glue to opposing

corners of the carton as it travels beneath them. In

other cases, where only simple glue patterns are required,

applicator nozzles may be permanently ﬁxed at each

corner of the carton above the cavity. After adhesive is

applied, the blanks are plunged vertically through the

cavity and compressed in the manner described above.

Cold-vinyl carton forming was virtually eliminated

with the advent of hot-melt adhesives because of the

extended compression times required for setup. Carton

styles were generally limited to speciﬁc compatible de-

signs, such as outward tapered trays, which could be

nested for extended compression times after the package

was discharged from the forming machine. However,

recent developments in applicator technology and new

end-use markets have created a renewed interest in this

forming method. Today, it is frequently used to produce

paperboard scoops, boats, and clamshells for the fast-food

and food-service industries, as it suits their requirement

for economical, preformed packages with a bonding med-

ium that is not sensitive to heat. This heat resistance

has also led to applications in connection with ‘‘ovenable’’

cartons. In the forming operation, a carton blank is fed

from the magazine and deposited on top of a forming

cavity. Specially designed adhesive application nozzles are

mounted on the forming cavity and are then mechanically

actuated to deposit small dots of cold-vinyl adhesive on the

inside of the carton blank. Adhesive is supplied under

pressure from a single remote tank. A plunger forces the

blank through the forming cavity and, in this case,

deposits the formed trays into a nest or stack to keep

them under pressure until the adhesive has set. This

method allows forming at speeds of up to B80 strokes

per minute or more than 300 cartons per minute with

multiple heads to satisfy the substantial production vo-

lumes required by the fast-food industry.

HEAT-SEAL FORMING

Heat-seal forming uses special coatings or preapplied hot-

melt adhesives on the paperboard as a bonding medium in

the carton-forming operation. Overall board coatings that

can be heat-seal formed include single-side polyethylene,

double-side polyethylene, polyester, and polypropylene.

Special pattern-applied hot-melt adhesive coatings, placed

only in the area to be bonded, can also be used. The heat-

seal system is designed to force air through electrically

heated quartz elements into specially designed nozzles on

the forming cavity. Depending on the carton coating, air

temperatures that range from 400 to 8001F (200–4251C)

are directed over speciﬁc areas of the carton blank, where

the coating on the paperboard stock is melted or activated.

The carton blank is plunged through the forming cavity,

and the board coating serves to bond the appropriate

carton ﬂaps. High speeds—up to a maximum of B90

strokes per minute—can be achieved, depending on vari-

ables such as coating thickness, carton size, and carton

style. Heat-seal forming operations require some degree of

cooling to prevent heat buildup in various parts of the

forming head and to accelerate carton compression times.

Water or special refrigerants are plumbed to various

components within the forming cavity and plunger. The

extent of cooling generally depends on the bonding med-

ium used, but it becomes most extensive when double-

polyethylene coatings are involved. Heat-seal forming is

employed most often in the frozen-food industry, where

thermoplastic coatings are otherwise included for moist-

ure-barrier protection, graphic enhancement, or a degree

of leak resistance necessitated by wet products.

TOP-LOAD FORMING CAPABILITIES

Various carton forming machine models are produced,

each designed for a given size range and speed rating.

The same basic machine chassis can usually be modiﬁed

with special attachments and equipped as a dedicated

lock, glue, or heat-seal system. As indicated, machines can

be equipped with double, triple, or quadruple heads to feed

and form multiple carton blanks simultaneously. Forming

speeds generally range from 20 to 120 strokes per minute,

and with multiple forming heads, a single machine can

produce more than 300 cartons per minute.

CARTON CONVEYING

After forming, the top-load carton is typically carried on a

conveyor for loading either manually or automatically. For

slow- to moderate-speed hand packing, simple ﬂat-belt or

plastic tabletop chain conveyors are frequently employed

and offer the most economical approach. One end of the

conveyor is generally placed below the forming cavity and

is independently driven with no electrical or mechanical

connection

between the conveyor

and the forming ma-

chine. After forming, trays or cartons drop onto the

conveyor and are carried downstream for product loading.

The alternative to this method is a conveyor with chain

ﬂights or lugs (see Figure 5). Generally, ﬂighted conveyors

are either attached to and mechanically driven by the

forming machine or electronically synchronized through

the use of intelligently controlled independent drive mo-

tors. Flighted conveyors offer the advantage of packing the

operators, because they cannot individually retard cartons

for loading as they can on a ﬂat belt. Flighted systems

are required to achieve adequate carton control in any

CARTONING MACHINERY, TOP-LOAD 231

high-speed operation. They also allow the carton cover to

be controlled during the packing operation by either

maintaining a vertical position or folding it back almost

1801 to permit loading from either side of the conveyor.

Packing conveyors should be designed so that the bottom

of the carton is approximately 30–34 in. (76–86 cm) from

the ﬂoor. This helps optimize the efﬁciency of operators

who are placing product into the cartons by hand.

MANUAL PRODUCT LOADING

For hand-pack operations, product can be presented to the

operator in many different ways. These range from tote

bins to product conveyors running up to the carton con-

veyor. The most efﬁcient method involves bringing the

product in on a ﬂat belt or tabletop chain that runs

parallel and adjacent to carton ﬂow. The bottom of the

product should be elevated just slightly above the top of

the carton to allow for simple sweep loading into the

largest opening of the carton. This is the most efﬁcient

and reliable method of hand packing.

AUTOMATIC PRODUCT LOADING

The automatic loading of products into top-load cartons

can be accomplished using many different standard and or

highly customized systems. Free-ﬂowing products, such as

individually quick-frozen vegetables, are often ﬁlled auto-

matically using a volumetric system that is integrated

mechanically or electronically with the carton conveying

system. Where netweight ﬁlling is desirable, a variety of

different systems can be employed. These are normally

interlocked electrically with the carton forming and con-

veying system to sense the presence of a formed carton

and to signal the scales to dump. For net weighing or

automatic loading of some products into top-load cartons,

the carton conveyor must sometimes operate on an inter-

mittent-motion basis. This allows the carton to stop or

dwell momentarily beneath a ﬁlling device, providing

sufﬁcient time to completely load the product charge.

Alternatively, special traveling or reciprocating-funnel

systems can be incorporated at the point of product

loading to allow continuous motion. The top or throat of

the funnel is designed to provide a continuous open target

beneath the ﬁller discharge while the bottom aligns

and travels in synchronization with the carton on the

conveyor.

Many products are loaded into top-load cartons by

count, in a speciﬁc pattern. These range from things

such as spark plugs or hardware items to bare frozen

hamburger or potato patties. Many other products such as

wrapped candy, pouched mixes, boil-in-bag items, over-

wrapped baked goods, healthcare and pharmaceutical

items, ofﬁce supplies, tobacco products, and all types of

frozen foods have been automatically loaded into top-load

cartons. The loading technique depends on the product

and can vary from a simple mechanical shuttle to ad-

vanced units that automatically align, accumulate, group,

and transfer product into the carton. Characteristics and

consistency in the product’s weight, size, shape, texture,

temperature, and surface traits all have signiﬁcant inﬂu-

ence on the method of automatic loading. The transfer

of such products is most frequently accomplished using

a high-volume, low-pressure vacuum pickup system (see

Figure 6). A reciprocating-vacuum manifold transports

items into the carton after they have been previously

organized into required patterns. In some instances, ad-

vanced robotics, incorporating sophisticated vision

Figure 5. Flighted carton packing conveyor, hand packing.

Figure 6. Automatic product loading, vacuum transfer.

232 CARTONING MACHINERY, TOP-LOAD

systems, are used to locate product from a randomly

positioned supply and automatically transfer it into

cartons.

CARTON CLOSING

When hinge-cover or self-cover designs are used in any

topload cartoning application, the method of carton clos-

ing becomes a ﬁnal major consideration. General cate-

gories of carton closers include ﬂighted or lugless models.

On ﬂighted systems, actuation and sealing functions are

timed according to predeﬁned spacing between conveyor

ﬂights. On lugless systems, intelligently controlled motors

and other functions react to the presence and position of a

carton as it is photosensed on conveyor belts. In broad

terms, ﬂighted systems generally provide a higher degree

of carton control, whereas lugless systems offer greater

speed, ﬂexibility, and ease of maintenance. For slow to

moderately high-speed ﬂighted operations, the closing

machine is usually an independent unit with its own drive

motor. It is equipped with a special infeed assembly that

accepts cartons at random from an upstream packing

conveyor and automatically times them into the ﬂights

of the closing machine. When ﬂighted systems are re-

quired to operate at high speeds (W200 cartons per

minute), it is desirable to eliminate the infeed section

and drive the entire packaging line from the carton

forming machine. This ‘‘line-driven’’ method requires the

use of ﬂighted packing conveyor and ensures that positive

carton control is maintained throughout. The need to

retime cartons into the closer at high speeds is eliminated.

Lugless systems are, inherently, independent as op-

posed to line-driven. Cartons are received at random and

conveyed with sequential belts that have special surface

traction characteristics. Both overhead and underlying

conveyor belts may be employed to maximize control.

Each sequence of the operation is powered by its own

individual, intelligently controlled drive motor, so speeds

and relationships between various machine functions can

be readily adjusted through program controls. This allows a

much greater degree of ﬂexibility and ﬁnetuning without

the need for physical changeover and tool adjustments.

DUST-FLAP-STYLE CLOSURE

Dust-ﬂap-style cartons require closure of only a single

tuck panel. As such, they can be closed on a straight-line

operation where it is unnecessary to turn or rotate the

carton. A static plow folds down the leading dust ﬂap

while a rotating paddle or wheel assembly, timed to the

carton-conveying chain, serves to ‘‘kick’’ the trailing dust

ﬂap forward. After this has taken place, the cover is

plowed down using guide rods, belts, or rollers. As the

cover is plowed down, the front tuck score is prebroken in

preparation for ﬁnal closure. Dust-ﬂap-style cartons can

be closed either by inserting and locking the front tuck

inside the body of the carton, or, by applying hot-melt

adhesive to the inner surface of the tuck and adhering it to

the outside of the carton’s front panel.

TRIPLE-SEAL-STYLE CLOSURE

The hinge-cover carton design most frequently used is the

triple-seal (‘‘tri-seal’’) style, which is also called the ‘‘three-

ﬂap’’ or ‘‘charlotte’’ style. For this carton style, three

primary closer designs are available: vertical, right angle,

and straight line. For slow-to-moderate-speed operations,

where space is a limiting factor, a compact machine design

consists of an intermittent motion unit with vertical

carton compression. Cartons are indexed by shuttling

them at a right angle into a single hot-melt adhesive

application station. Adhesive is applied to all three carton

cover ﬂaps simultaneously.

This type of closer generally uses an open-reservoir

style of application system, with blades rising from within

the adhesive to apply solid lines or dots of adhesive as

required. It can also be equipped with gun- or nozzle-style

applicators that spray adhesive onto the carton ﬂaps.

After adhesive application, the entire carton is elevated

vertically through a compression tunnel that folds down

all three ﬂaps and discharges ﬁnished cartons at the top of

the machine.

For most applications, tri-seal cartons are closed using

either right-angle or straight-line machine conﬁgurations.

In the right-angle operation (see Figure 7), the carton is

indexed into the closer, the front tuck is sealed to the

carton body, and the carton is shuttled through a 901

change of direction for sealing the charlottes or end ﬂaps.

With the straight-line closer design (see Figure 8), the

carton body is rotated or turned 901 after closure of the

front tuck, as it continues to travel in a straight line. This

positions the charlottes parallel to the line of travel to

facilitate application of adhesive or hot-air sealing and

subsequent compression. To achieve proper registration

between the cover and the carton body, it is best to fold

down and trap the trailing charlotte before front-tuck

closure. This is generally executed with an overhead,

rotating tucker paddle. This paddle is positioned above a

chain transfer area, where a new set of lugs then traps the

trailing charlotte against the rear of the carton and holds

Figure 7. Right-angle top-load carton closer.

CARTONING MACHINERY, TOP-LOAD 233

it in position through the front-tuck closing section. On

lugless systems, the speed of overhead belts can simply be

adjusted in relation to the carton-carrying belts in order to

precisely position the cover.

LOCK CLOSURE

Closure of tri-seal cartons can be accomplished using

locks, adhesive, or heat sealing. Lock closure is effected

by using specially designed plows, guides, and tucking

ﬁngers and is employed most often in the frozen-vegetable

industry for plain-paperboard shells that are later over-

wrapped with printed paper.

ADHESIVE CLOSURE

Adhesive closure can be accomplished with either hotmelt

or cold-vinyl adhesives. Hot melt is most frequently

employed, and the adhesive is commonly applied using

either open-pot or enclosed, pressurized nozzle systems.

Depending on the glue pattern required, a thin wheel or

cluster of wheels can be used to apply adhesive from an

open reservoir to the carton ﬂaps. When special patterns

are desired, intaglio-wheels or nozzle-type applicators

supplied by a remote tank generally offer greater

ﬂexibility.

Historically, cold-vinyl adhesive found little application

in on-line closing operations because of extended compres-

sion times required for setup. Recently, however, interest

has been prompted by the requirement for ovenable paper-

board packaging, where most hot-melts are unsuitable

because they tend to soften and release during cooking. As

a result, systems have been developed for polyester-coated

ovenable board stocks. These systems apply a ﬁnely

atomized spray of cold-vinyl adhesive, which is followed

by the application of electrically generated hot air in a

manner similar to that used for heat sealing. The hot

air accelerates the water evaporation process and allows

use of carton compression sections that are comparable

in length to those of hot-melt systems. Sufﬁciently

high production speeds (B150 cartons per minute) are

achieved. This system has been used with polyester-

coated paperboards for dual-oven applications, where the

product is intended for preparation in either microwave or

conventional ovens. Among the various thermoplastic

polymers used for carton coatings, polyester is generally

the only one considered suitable for dual-oven use because

of its high-temperature compatibility and limited heat

solubility. By the same token, these characteristics neces-

sitate high temperatures and extreme compression when

the coating is used as a heat-sealing medium to bond

the carton. Although the coating can be used for carton

forming, where a plunger inside the carton provides

necessary backup for compression, it is not practical for

conventional heat-seal closure because only limited com-

pression can be applied against the hollow package.

HEAT-SEAL CLOSURE

Heat-seal closure can be used for cartons that include

thermoplastic coatings, heat-sealable wax coatings (see

the Waxes article), or preapplied hot-melt adhesives. Here

again, the board coating or sealing medium is activated

using electrically generated hot air at high temperatures.

The package then proceeds through compression to bond

the ﬂaps as the coating solidiﬁes. For wax-coated cartons,

the compression section must consist of refrigerated bars

to prevent smearing of the wax. This method also results

in quick bonding of the paperboard ﬂaps, within a rela-

tively short compression section.

OPTIONAL FUNCTIONS

Top-load cartoning systems can be equipped with a wide

variety of options, including many types of coding devices,

leaﬂet feeders, labelers, sensors, and computers to facil-

itate effective control and management of the entire

packaging system.

CARTONS, FOLDING

PAUL OBOLEWICZ

Rand Whitney Packaging,

West Chester, Pennsylvania

Updated by Staff

INTRODUCTION

Folding cartons are containers made from sheets of paper-

board (see Paperboard) that have been cut and creased for

forming into a designed shape. They comprise a signiﬁcant

proportion of the packaging found in the retail sector.

Cartons meet packaging needs cost-effectively by provid-

ing product protection and information, visual impact, and

convenience appropriate for the product concerned and its

method of distrbution and consumer use (1).

There is evidence that paper was used by Egyptian

merchants to wrap goods for their customers as early as

Figure 8. Straight-line lugless top-load carton closer.

234 CARTONS, FOLDING

1035 A.D. The modern-day folding-carton industry began in

1839 when Colonel Andrew Dennison began producing

commercial folding cartons to complement and protect

jewelry sold in his retail store. By the mid-1890s, auto-

matic machines were in widespread use for the production

of cartons (2).

Merchandise displays at supermarkets and drug, hard-

ware, automotive, and department stores demonstrate the

extent to which folding cartons are used today. Cereal,

crackers, facial tissue, detergent, dry mixes, frozen food,

ice cream, butter, bacon, bar soap, candy, cosmetics, toys,

cigarettes, canned beverages, carryout foods, and pharma-

ceuticals represent the broad range of products for which

folding cartons are commonly utilized. The use of folding

cartons is widespread because of the ability of this packa-

ging format to satisfy the functions of protection, utility,

and motivation. Protection from crushing, bending, con-

tamination, sifting, grease, moisture, and tampering can

all be built into folding cartons. For the producer, utility is

achieved through high-speed automatic packing (see Car-

toning machinery). For the end-user or consumer, utility is

provided by opening, reclosing, and dispensing features.

In some cases, the carton even serves as the cooking

utensil. High-quality graphic reproduction, excellent bill-

board presentation of the graphics design, and the ability

to take on unique and varied shapes provide the carton

user with the means to motivate the consumer to purchase

products packaged in folding cartons.

PAPERBOARD SELECTION

Successfully meeting the needs of a folding-carton user

begins with choosing the paperboard best suited for the

job. In general, this means selecting the grade with the

lowest cost per unit area that is capable of satisfying

the performance requirements of the speciﬁc application.

Economics and performance dictate careful selection of

paperboard grades for each use.

Selection Criteria

A variety of criteria are commonly used in the selection of

paperboard grades. The Technical Association of the Pulp

and Paper Industry (TAPPI) has published standardized

test methods for many of these criteria (3) (see Testing,

packaging materials). TAPPI Standard Methods are widely

used and accepted by the industry. The most important and

widely used criteria are shown below.

FDA/USDA Compliance. This is a nondiscretionary cri-

terion for food products and is dependent on the type of

food and the type of contact anticipated between the food

and the paperboard or coatings on the paperboard.

Color. Color is typically chosen for marketing reasons.

The side of the paperboard that becomes the outside of the

carton is generally white, but the degree of whiteness

varies among grades. Depending on the materials-selec-

tion and processing strategies of suppliers, outside board

color can be blue-white or cream-white. These shades are

noticeably different and can limit substitution of grades.

Board color on the inside of cartons varies from white to

gray to brown.

Physical Characteristics. It is possible to establish mini-

mum levels for each carton application that allow the

package to satisfactorily withstand the rigors of packaging

machinery, shipping, distribution, and use by the consu-

mer. Physical properties commonly used to predict

suitability of board for a given use include stiffness, tear

strength, compressive strength, plybond strength, burst

strength, tensile strength, elongation, and tensile energy

absorption. Physical criteria normally deﬁne the basis

weight and thickness of paperboard that is used to pro-

duce a carton.

Printing Characteristics. Following the selection of a

speciﬁc graphic design and printing method for the carton,

a paperboard is selected based on these criteria: smooth-

ness; coating strength; ink and varnish gloss; mottle

resistance; and ink receptivity. Not all criteria are impor-

tant for every printing technique.

Barrier. The most common barrier requirements are for

cartons to provide protection against moisture and grease.

The choice of a barrier material and application method

inﬂuences board choice. For example, if polyethylene (PE)

is to be applied to the carton, a board with a treatment

that holds the PE on the board surface can have economic

and processing advantages over an untreated board.

Materials and application methods are described below.

Paperboard Types

In the United States, the three most widely used types of

paperboard are identiﬁed as follows:

Coated Solid Bleached Sulfate (SBS). 100% virgin,

bleached, chemical furnish, clay-coated for print-

ability.

Coated Solid Unbleached Sulfate (SUS). 100% virgin,

unbleached, chemical furnish, clay-coated for

printability.

Coated Recycled. Multiple layers of recycled ﬁbers from

a variety of sources, clay-coated for printability.

Coated recycled boards are the most widely used. Other

types include folding box

board (FBB) and white lined

chipboard (WCC).

Overall treatments or coatings are applied to webs of

paperboard to provide speciﬁc functions. Clay-based coat-

ings to provide high-quality printing surfaces are the most

common treatment applied on the paperboard machine.

Grease-resistant ﬂuorochemicals are applied on board

machines as well, either as furnish additives, surface

treatments, additives to clay coatings, or in combination.

Mold-inhibiting chemicals are also applied to boards de-

signed for bar-soap packaging, to prevent moisture in the

product from initiating mold growth. Surface treatments

applied on other-than-board production equipment are

discussed below under Carton Manufacturing Processes.

CARTONS, FOLDING 235

Paperboard is the overwhelming choice as the sub-

strate for folding cartons. However, a segment has devel-

oped that utilizes plastic sheet as a substrate. These

cartons are normally produced from clear, impact grades

of PVC sheet (see Film, rigid PVC) using specialized

heated-scoring techniques to achieve acceptable folding

characteristics. Unique product visibility is the primary

reason for the use of this more costly substrate for speci-

alty folding-carton applications, such as cosmetics and soft

goods (see Boxes, rigid plastic).

Another segment making an impact on the folding

carton market is E-ﬂute, and the newer F-ﬂute is corru-

gated. E-ﬂute is a transitional medium between corru-

gated and folding cartons. While E-ﬂute height, depending

on the proﬁle of the manufacturing ranges within 43/1000

and 5/1000 in. F-ﬂute, is typically B30/1000 in. The ﬂuted

material has positive attributes for its stacking strength,

low weight, and stiffness, as well as for its insulating and

shock-absorbing properties. It is used typically in cartons

for products such as perfumes, glassware, household

products, candies, fast foods, and countertop displays.

CARTON STYLES

As the demand for cartons grew, so did demands for

additional features. These demands catalyzed the devel-

opment of new and unique ways to cut and fold sheets of

paperboard to produce cartons. The records of the U.S.

Patent and Trademark Ofﬁce contain many thousands of

patents granted to protect folding-carton structures.

Three broad classiﬁcations are commonly used to cate-

gorize folding-carton styles: tube (end load); tray (top

load); and special construction. Figure 1 describes ac-

cepted terminology for the various parts of tube (a) and

tray (b) cartons (4), as well as the order in which dimen-

sions are listed in carton speciﬁcations. Compliance with

these standards prevents confusion.

Tube Style

Tube (shell) constructions are the most common style in

use today. Figure 2 shows a typical sealed-end carton in

various stages of production and ﬁlling. These cartons are

characterized by a ﬁfth panel glue seam in the depth

direction, yielding a side-seamed shell that folds ﬂat for

transportation. The cross section of the carton opening is

normally rectangular, and product may be loaded either

horizontally or vertically (see Cartoning machinery).

Tube-style cartons are well-suited for very high speed

automated ﬁlling lines, but they are also used for manual

ﬁlling applications.

Figure 3 shows the treatment of end ﬂaps on a tuck-end

carton. Other end treatments are in common use, includ-

ing zippers and similar opening features for sealed-end

cartons. Internal shelves and panels are often included to

secure and protect the product. This is particularly done

when the product is irregular in shape or the carton is

much larger than the product for improved graphic pre-

sentation or shoplifting deterrence. When heavy granular

products are packaged, bulging of main panels can be a

problem. The use of bridges connecting the two main

panels increases the carton’s integrity required to resist

bulbing. These bridges can be made from paperboard and

attached during the gluing operation.

Tube-style cartons are commonly used for granular or

pourable solid products such as detergent, cereal, and dry

mixes. Dispensing features are often designed by special

cuts and creases in the paperboard. End opening is pre-

ferred when inner bags are employed (see Bag-in-box, dry

product). Large products packed one to a carton, such as

pizzas, frozen dinners, pot pies, cosmetics, and pharma-

ceuticals, are packed in end-opening tube-style cartons.

End-loaded cartons are also designed for opening and

product removal through the main panel; a cream cheese

carton is a good example of this approach. Gabletop milk

cartons also fall into the tube or shell category (see

Cartons, gabletop). They incorporate liquid-tight sealing

Figure 1. Terminology.

236 CARTONS, FOLDING

and a reclosable pour spout. From ice cream to lipstick,

tube-style cartons satisfy many diverse packaging needs.

Tray Style

Tray or top-load cartons are characterized by a solid bottom

panel opposite the product-loading opening. As shown in

Figure 1b, panels are connected to each edge of that bottom

panel. Tray cartons are especially useful for manual or

automatic loading of multiple products. Figure 4 contains

schematic drawings of a tray carton blank, the carton setup

for loading, and the completely closed and sealed carton. In

this example, the front and back panels are connected to

the end panels using mechanical locks. Panels are also

commonly connected using adhesives or heat sealing (see

Adhesives; Sealing, heat).

Where additional resistance to leakage is desired, web

corners are employed. Figure 5 shows a web-corner tray

with folded double sidewalls that provide ﬁnished sidewall

edges. A similar, slightly larger tray could be used to cover

the tray following product loading, yielding an extremely

crush-resistant package. Figure 6 shows a six-corner

Figure 2. Sealed-end carton: (a) blank; (b) side-seamed shell; (c)

carton erected for loading; (d) ﬁlled and sealed carton.

Figure 3. Tuck-end carton: (a) blank; (b) erected carton for

Figure 4. Locked corner hinge cover carton: (a) blank; (b) car-

ton; (c) tuck-end carton.

Figure 5. Web-corner tray: (a) blank; (b) sidewalls glued; (c)

ﬁnal panel folding.

CARTONS, FOLDING 237