Yam, Kit L. (ed.). The Wiley encyclopedia of packaging technology

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Lubrication of these chain types can take the form of

a spray mist on the idle top side of the chain. The spray

mist consists of soft water mixed with minute amounts of

special liquid soaps specially formulated for either plastic

or metal slat top chains.

Glass containers, steel cans, and abrasive-type pro-

ducts are generally conveyed on carbon or stainless-steel

slat-top chains. Sometimes plastic slat-top chains can be

used as an economy measure or noise reduction measure

where its application is suitable.

Hinged slat-top chains or roller-driven slat top chains

come in the following standard widths to ﬁt the needs of

the packaging process. All widths are narrow as compared

to mat or mesh plastic modular chain. Standard widths

are 3

; 4

; 6 (not common) 7.5, 10, or 12 in. (89, 108, 152,

190, 254, and 305 mm) wide, and containers are carried at

medium to high speed in single lane or mass ﬂow. Speeds

over 300 ft (90 m) per minute may be possible for speciﬁc

chain materials and under certain conditions. Generally,

speeds of under 300 fpm are for normal applications.

The chain or hinge runs in a ‘‘channel,’’ which is

specially designed to support the chain or hinge on both

sides and can carry both the loaded and return sections.

The channel is ﬁtted with wear strips to reduce friction

and prevent long-term damage to the channel and slat

top chains. The channel is designed to allow the hinged

section to pull through on top, feed through the drive and

idle sprockets, and return below the channel smoothly

without hesitation. There is always a catenary or return

chain slack at the drive end, and its proﬁle affects

conveyor torque.

Slat-top chains may be either straight-running or side-

ﬂexing. Straight-running chain is simple in design but

requires special devices such as turntables or dead plates

in order to move product through any type of turn. A side-

ﬂexing conveyor is more expensive but provides smooth,

continuous turns and transfer of products. Side-ﬂexing

gives more control and ﬂexibility than straight-running

slat-top chains.

There is a fundamental problem with the use of side-

ﬂexing chain in that side forces are imposed on the chain,

which can cause it to twist and lift out of the channel.

There are four common designs of side-ﬂexing chain: tab,

wedge, magnetic, and super ﬂex (or multi-ﬂex).

Tab. Tab chain uses short lips on the underside of the

links to hold the chain in the channel and keep it

from lifting. Unfortunately, the tabs cause increased

side loading and a longer maintenance time for

chain repair or replacement.

Wedge. The body of the links are tapered, decreasing

in width near the top surface of the chain. The

channel has a mating taper that prevents the chain

from twisting or lifting. Unfortunately, the wedge

causes increased side loading but less than tabs

and a longer maintenance time for chain repair or

replacement.

Magnetic. Magnetic chain has permanent magnets

located in either the chain or the channel. The

magnetic attraction between the channel and the

chain holds the chain into the channel. Plastic chain

can be used in plastic channels with magnetic im-

pregnated materials only if the link pins are of a

ferrite material.

Super ﬂex (Sometimes Called Multi-ﬂex). Very tight

radius side-ﬂexing chain that can usually be easily

lifted out for cleaning and inspection.

Carrying

way

Roller return

way

Suding

return way

broken contact

Travel

Figure 3. Typical straight-running slat-top-

type conveyor design.

338 CONVEYING

Cloth, Rubber, Synthetic, Reinforced, or Composite Belt

Designs (See Figure 5)

This consists of

. Troughed belt conveyor for bulk granular transfers

. Spiral belt conveyors

. Flat straight belt conveyors

. Magnetic ﬂat belt conveyors

. Retracking belt conveyors

. Magnetic spiral belt conveyors

. Flighted belt conveyors

A belt conveyor is deﬁned as an endless fabric, rubber,

plastic, leather, or metal belt operating over a suitable

drive, tail end, and bend terminals. Most modern belts are

reinforced with steel or Kevlar cords to increase strength

and performance. In the case of handling bulk materials,

packages, or objects placed directly on the belt, the belt is

supported by and operates over belt idlers or a slider bed.

Belt conveyors use a belt as a carrying medium for

the controlled movement of a great variety of regular

and irregular-shaped commodities, ranging from light

and fragile to heavy and rugged, to granular, and to solid

unit loads. The belt conveyor can be level or angled up or

down. The angle of transfer is limited mainly by the

stability of the commodity and strength of the product

being moved. Belt conveyors are connected together

usually via a butt transfer, or one belt is above or below

the other and the product drops onto the downstream belt

conveyor.

A belt conveyor consists of a ﬂat belt wrapped around

two end rollers (one powered, one idle) and supported

along its length on both the loaded and return sections.

The ‘‘loaded section’’ is the portion of the belt that carries

Straight section

Corner section

Rectangular

carrying way for

bevel or tab chains

Bevel carrying way

for beveled chains

Chain

Carrying

wear strip

Carrying way

Return

way

Sliding

return way

broken contact

Rectangular

return way

Straight section

only

Corner and straight

section

for tab chains onl

Corner section only

for beveled chains

Bevel

return way

Chain

Return

wear strip

Guide rail

Rectangular

carrying way for

tab chain

Figure 4. Typical Side-Flexing Slat-Top-Type Conveyor design.

CONVEYING 339

product (from idler roller to driver roller), while the

return section runs from the driver back to the idler

underneath the top section to form a closed loop. Belt

conveyors can be driven at the drive or discharge end or at

most locations on the return leg, generally near the

discharge end. Common practice is to drive from the

discharge end. Pushing by driving from the idler end is

problematic, but could be used for very short lightly loaded

belt conveyors.

Support for the top section may take the form of a

ﬁxed sheet or metal on which the belt slides or a series of

equally spaced free-turning rollers or slider bars. Support

for the return section takes the form of free-turning

rollers or a stationary metal strip or horn. A special

type of belt conveyor is the trough conveyor, which has

troughing idlers that consist of two or more rollers

arranged to turn up the edges of the belt to form it into

a moving trough for usually granular or aggregate

products.

Belt conveyors run at a variety of speeds and condi-

tions. Belt conveyors can be used as follows:

1. To transport granular bulk, boxes, cartons, confec-

tionery products, or randomly distributed containers.

2. To set the pace of assembly operations.

3. As a timing medium for integrated handling sys-

tems or subsequent machine operation.

4. For controlling and/or spacing products through the

use of top and bottom or side-to-side grip belts.

Lug or bar chain design

This consists of

. Car-type conveyor

. Crossbar conveyor

. Drag chain conveyor

. Flight or bucket conveyor

. Floor chain conveyor

. Overhead trolley conveyor

. Pan or apron conveyors

. Pallet-type conveyor, indexing or continuous

. Pin-type slat conveyor

. Pocket conveyor

. Pusher bar conveyor

. Pusher chain conveyor

. Reciprocating-beam conveyor

. Rope and button conveyor

. Shuttle conveyor

. Sliding-chain conveyors

. Walking-beam conveyor

. Vertical elevator chain conveyor

Lug or bar chain conveyors transport items via hooks,

brackets, or bars attached to the top or bottom sections of

most types of chains at a predetermined pitch, which will

pull or push the input or product with no slippage.

Continuous belt flat horizontal

Flighted belt

continuous

flat inclined

Flighted belt

continuous

flat skirted

multi-angular

Magnetic belt conveyors continuous

flat horizontal/vertical

Straight belt

continuous

flat horizontal

Straight belt

continuous

troughed

horizontal

Figure 5. Belt conveyor types.

340 CONVEYING

Roller Design (See Figure 6)

This consists of

. Nonpowered roller or wheel conveyors or gravity

roller or wheel conveyors

. Chain-driven live roller conveyors

. Roller spiral gravity conveyor

. Belt-driven live roller conveyor

. Line-shaft roller conveyor—straight, curved, and

spiral

. Skate-wheel spiral conveyor—straight, curved, and

spiral

. Skate-wheel conveyor

This type of conveyor system is used mainly for trans-

porting large and/or heavy inputs or components such as

large cartons (empty or full), cases, pallets, or unit loads.

Screw Design (See Figure 7)

This consists of

. Screw conveyors

. Ribbon ﬂight screw conveyor

. Gravity chutes or spiral cage

Mostly granular or dough-type products are trans-

ported and/or mixed via screws that are fully or partly

contained in a tube or trough.

Cable Design (See Figure 8)

This consists of

. Floor cable conveyors

. Overhead track with powered rollers

. Steel cable conveyors

. Steel-sheathed cable conveyors

. Urethane cable conveyors

Another basic conveyor design employs a cable as the

transporting vehicle. The cable conveyor is used as an

inexpensive method of moving lightweight containers,

primarily empty cans and plastic bottles, in single-ﬁle

mode only, at speeds of r800–1000 containers per minute.

The method is also used in the food industry for handling

full containers (usually cans) generally at speeds under

500 containers per minute. In operation, a

-in. (9.5-mm)-

diameter, nylon-coated steel cable driven by a motor is

supported on small-diameter sheaves along its length. The

containers are seated on top of the cable and held in

position by adjustable side guiderails made of stainless

steel, aluminum, or plastic. The cable provides the drive

and friction to move the container.

This method provides relatively low-cost conveying,

notably for conditions where lengthy distances must be

economically traversed in a plant environment. A capacity

for long pulls and curves can minimize transfer points.

Although about one-third the cost of ﬂat-topped conveyors,

the system can be used effectively for accumulating con-

tainers such as plastic bottles and metal cans.

Standard live roll case

conveyor with pop up

roller stop

Skate wheel gravity feed

case conveyors

Center SAE chain case

conveyor - chain pulls

load

Pallet roller side chain driven

conveyor with SAE chain pop up for

side transfer

Incline/decline case

powered belt conveyor

Figure 6. Case and pallet conveyor

types.

CONVEYING 341

Also, urethane has made it possible to make short

multiple cable transfer and positioning conveyors for a

wide variety of products and inputs, especially cartons,

pouches, and bags.

Air of Vacuum Design (See Figure 9)

This consists of

. Airveyor (air-driven conveyor)

. Vertical or angled air chutes

. Vacuum bulk-transfer tube conveyor

. Vacuum holddown conveyor

. Air-transfer tube conveyor for parts

. Pneumatic conveying

In the last few decades, packaging technology has devel-

oped new methods of stabilizing lightweight and/or some

oddly shaped containers by drawing the product down

onto ﬂat-topped chain or belts through the use of a

vacuum plenum. This permits conveying the containers

at much higher speeds. The same concept can be applied to

the operation of elevators and lowerators, but is not

common. (See also Air conveying.)

Inputs or products can be very effectively moved in

mass or single ﬁle on a thin ﬁlm of air. Pressurized air

is blown into a plenum, and small holes are drilled or

punched out at an angle into a stationary plate. The

containers are then supported by air pressure, with their

motion over the plate induced by air coming out of the

holes’ raked angle. A major advantage of this low-friction

system is the reduction in the number of moving parts and

reduced maintenance. Disadvantages are the large blower

requirements, which cause noise and power consumption

issues as well as plant air contamination and pressures.

Air transfer is effective for inputs or products that have

light weight, low center of gravity, and a difﬁcult shape,

such as cartons, toilet tissue, and bags.

Pneumatic tubes are very common for the transfer of

granular or powder products, and some solid objects can

also be transferred effectively such as caps.

Vibratory Design (See Figure 10)

This consists of

. Vibrating spiral conveyors

. Vibrating straight transfer conveyors

Most vibratory designs are used to convey granular-

type products over short and long distances. Cereal com-

panies are common users of this type of conveyor.

POWER TRANSMISSION COMPONENTS

The following analyses are applicable to almost all types of

conveyor designs. Each conveying system must have a

‘‘drive.’’ The term ‘‘drive’’ refers to the apparatus that

supplies motive power to the conveyor or is the energy

source for the motive power. It usually consists of an

electric motor (AC or DC), a gearbox, and possibly a

mechanical drive train (shaft, chain, or belt). The most

common conﬁguration is still an AC electric motor, gear-

box, and chain drive. Note also that the electric motor may

be supplied by a VFO or variable frequency drive, which is

becoming more of the standard method of control.

Elevator screw conveyor

Granular feed screw conveyors

Timing feed screw

for packaging machinery

Streaming, auger, washer & drag conveyors

Auger vertical feed

transfer screw conveyor

Figure 7. Screw transfer designs.

342 CONVEYING

Overhead track with

powered rollers

Overhead steel cable trolley

Overhead steel

cable

trolley

Steel-sheathed cable for can

vertical or horizontal travel

Polyurethane cables for

light product transfers

Disc cable pull

conveyor

Funnel-shaped cable openings

−

Rotary floating trolley action−

Bush-lock buttons permanently swaged to

cable at accurate immovable centers−

Figure 8. Cable and trolley conveyor types.

Air transfer conveyors using

blowers

Vacuum hold down

conveyor system

Uses negative air pressure to secure

products to the moving belt. Ex-

cellent for conveying lightweight

products with large surface areas,

such as plastic bottles and

packages. Increased stability of

flow; easily achieves high speeds

and 90-degree inclines.

Vacuum transfer system

for granules & powders

Figure 9. Vacuum and air transfer systems.

CONVEYING 343

Gearboxes

The purpose of a gearbox is to change the rotational speed

and torque of a rotating shaft. Most gearboxes are ﬁxed-

ratio designs, where the ratio of input speed to output

speed is constant. Fixed-ratio gearboxes are best with an

AC inverter, and mechanically variable gearboxes should

normally not be used with an AC inverter.

Belt-Pulley Power Transmission

A ﬂexible connector (belt) is wrapped around two or more

pulleys mounted on shafts. Power is transmitted from one

pulley to another by a difference in tension in different

sections of the belt.

There are two types of belt drives: positive (sometimes

called timing belts) and nonpositive. In nonpositive belt

arrangements, friction is relied on to transmit the periph-

eral force from the driving pulley to the belt and then to

the driven pulley. This design permits a small amount of

slippage between the belt and the pulleys. In positive belt

drives, the peripheral force is transmitted by positive

locking of ‘‘teeth’’ on the belt and pulleys. There is no

slippage in this design. Examples of positive drives are

gearbelts (standard or HTD). Gearbelts provide minimum

noise levels and smooth operation. Care must be taken

when high impact loading is required.

Chain–Sprocket Power Transmission

Chain drives are similar in concept to positive belt drives

except that the connector is made from a number of rigid

links that are connected by pins. The links rotate about

the pins providing the ﬂexibility necessary to wrap the

chain around the sprocket. The pins engage the spaces

between the teeth of the sprocket. The most common type

of chain used is SAE roller number 40 and 50 steel chain.

TRANSFERS BETWEEN CONVEYORS USING SLAT-TOP

CHAINS (SEE FIGURE 11)

The most common types of transfer as used in slat-top

(also called table-top) hinged or roller chain conveyors and

some special lug, mesh, and mat-top conveyors are

1. Butt end

2. Side transfer

3. S-inline transfer

In a butt-end transfer, two conveyors are literally put

together inline or end to end in such a manner that one

chain is short of touching the other chain by at least

in. A

dead plate or small rollers are placed between the gap to

allow the product to run or be pushed across. Also, the

upstream chain should be slightly higher by about 1/32 to

1/16 in. than the downstream chain. Therefore the inputs

or product will fall or cascade onto the downstream

conveyor. Belt, chain, slat-top chains (also called tabletop),

mat, and mesh-type conveyors can all be butt-ended. Some

mesh-type conveyors have comb transfer plates between

end to end conveyors to reduce dead transfer and improve

product ﬂow stability.

Standard vibratory conveyor

with spring dampeners

Snack food line using bucket elevator &

vibratory conveyor to feed weigh cell units

Vibratory conveyance of tablets,

capsules or small candies

Figure 10. Vibratory feeder conveyors.

344 CONVEYING

It is not advisable to use only a dead plate transfer for:

. Unstable packages with a difﬁcult shape and/or high

center of gravity or product that is open on the top

and could allow spillover of the product bouncing

across the dead plate or being pushed across by the

next product.

. Conveyor speeds are above 150 ft/min.

. Package is shorter than the dead plate or transfer

roller such that the package will hang up and wait for

the next package to push it off.

. Packages have a base with sharp edges.

Twin side-driven belt conveyors can be used to grip most

types of containers (especially with vertical side faces) and

laterally carry them over the dead spot on the butt-end

transfer. High-speed transfers can be accomplished under

speciﬁc conditions.

In a side transfer, two conveyors are placed side by side

so that the package is guided via angled guiderails from

one conveyor onto the other. This ensures that the pack-

age will be controlled and powered from one conveyor onto

the next.

The items one should consider when designing side

transfers are

. The gap between chains should never exceed

in.

(6 mm);

in. is optimum.

. The downstream conveyor should be about

in.

(1 mm) lower than the upstream conveyor for good

transfer.

. The angle of cross transfer should not be greater than

151. For difﬁcult shapes or higher centers of gravity,

less than 10 1 is advisable.

. Guiderail shape can be critical for difﬁcult shapes.

. Conveyor speed differentials can be very critical.

. Because the transfer guiderails are angled to the

conveyor pull direction, rotational forces on the con-

tainer or input can be substantial.

In an S-curve transfer, two conveyors operate parallel

together in an elongated S form so that the guiderails

are straight and the conveyors ﬂex at the transfer. This

ensures that the package will be controlled and powered

from one conveyor onto the next in line with minimal side

forces and maximum control. Although this type of con-

veyor is more expensive than the traditional side transfer,

the control for difﬁcult shapes is superior and guiderail

changeover to other sizes is quicker and more accurate.

The items one should consider when designing S-transfers

are as follows:

1. The gap between chains should never exceed

in.

(6 mm).

2. The downstream conveyor should be about

in.

(1 mm) lower than the upstream conveyor for good

transfer.

3. Conveyor speed differentials are a minor

consideration.

4. The side-ﬂex radii should exceed minimum chain

speciﬁcations. Only side-ﬂex conveyor chains can be

used.

5. The idle and drive ends should be straight sections

for about 12 in.

In general, conveyors are critical elements in any

packaging process and are grossly misunderstood and

poorly manufactured. This is mainly due to nonpackaging

people and some packaging people thinking that con-

veyors are non-value-added items that are as follows:

. Not a major item or consideration.

. The last thing considered in packaging line design

and the last item purchased.

. Cheap units for moving inputs from machine to

machine.

. One conveyor type is as good as another.

This thinking can be disastrous for many inputs and

packages that have difﬁcult or irregular shapes, sizes,

and weights.

DESIGN AND INSTALLATION OF GUIDERAILS AND

HANDLING CONTROL COMPONENTS

In general, guiderails are critical control parts attached to

every conveyor system. They are very important parts in

any packaging process and are grossly misunderstood,

poorly manufactured, poorly set up, and usually not

robust enough. This is mainly because most people think

that guiderails are like the conveyors themselves, non-

value-added items that are as follows:

. Not a major item or consideration.

. The last thing considered in line design and are

poorly speciﬁed.

. Cheap units for just keeping inputs from falling over

the conveyor.

. One guiderail is as good as another.

Butt end

transfer

Parallel side

transfer

S-Curve

transfer

Figure 11. Type of slat-chain conveyor-to-conveyor transfer.

CONVEYING 345

This thinking can be disastrous for many package shapes

and sizes. Today, many packaging engineers require quick

positive position guiderails that are robust in adjustment

features. This is imperative on modern packaging lines

that have multiple changeovers (Figure 12).

SPEEDS, FEEDS, DYNAMICS, AND LOADS FOR

INTERCONNECTING MACHINERY

The common thread throughout all the operations de-

scribed above is the use of conveyors to transport inputs

from machine to machine, and ﬁnally to storage facilities

or shipping positions. In general, each machine or staging

point will have different requirements in terms of con-

tainer spacing, linear infeed and outfeed speeds, method of

infeed and input, or package or case orientation. For the

packaging line to function smoothly, the conveying system

must provide the required changes in pitch and speed and

must also serve at times as a reservoir of inputs to help

level out ﬂuctuations in machine operation. In addition,

the conveying system may also have to convert from single

to multilane or mass ﬂow and vice versa. All of these

requirements must be met without tipping, spilling, jam-

ming, or damaging the inputs, packages, cases, or pallet

loads.

In the past, packages or case transfer rates were

relatively low (e.g., r300 ppm or o20 cases per minute)

and the packages were geometrically simple with low

centers of gravity (e.g., short, round bottles). Recently,

however, higher speed and performance requirements and

more sophisticated machines have resulted in increased

line rates (r2000 bottles per minute in the case of

breweries). Also, the aesthetic appeal of complex shapes

and the use of lightweight materials and thin walling have

resulted in a new generation of stability and quality

problems associated with conveyance systems.

Traditionally, line speeds have been dictated by the

operating capacity of the critical machine in the line such

as the ﬁlling station. As a result of these changes, however,

the performance of today’s lines are limited not by the

capabilities of the machinery employed but by the convey-

ing systems used for package transport and manipulation.

CONVEYOR DESIGN

A packaging line should try to balance its machinery and

conveyors with compatible function type. Function type

means the method of operation, which can be either

continuous or intermittent. Most low-speed lines gener-

ally have intermittent-motion machinery. High-speed

lines usually have all continuous motion machinery. Med-

ium-speed lines could be a mix of both. There usually are

tremendous problems when a intermittent machine is

coupled to a continuous-motion machine. The best way

to solve the mix is to place a buffer between the two

elements. These two motions are almost impossible to

line-shaft mechanically but could be electronically line-

shafted, but with great difﬁculty. It is possible to effec-

tively run an intermittent motion on top of or within a

continuous-motion machine or vice versa. These types of

new high-technology machines require the correct selec-

tion of conveyor system for optimal results.

All packaging machines and equipment require some

form of conveyance system to transport product or inputs

from one machine to the next. Conveyors are therefore an

integral part of the packaging process and are critical to

the function of the packaging process.

The primary objective in the design or selection of the

conveyor is that it function as efﬁciently and with as little

maintenance as possible. Factors to consider are materi-

als, load capacity, type of drive, speed range, and capabil-

ity of the conveyor, not only with the objects being

transported but also with the other equipment in the

production line.

Many industries have developed specialized conveyors

to suit particular needs. Often they travel at very slow

Figure 12. Typical guiderail conﬁgurations.

346 CONVEYING

speeds. Overhead trolley conveyors, for example, are used

in heavy industrial applications, such as in automative

plants and in other heavy manufacturing facilities. Drag-

type chain conveyors connect under an automobile’s chas-

sis and intermittently and very slowly pull the vehicle

along its manufacturing and assembly cycle.

Interfacing with feedscrews (feedscrews are sometimes

called scolls, timing screws, worms) can be very critical.

Normally, conveyors should run about 10% faster than the

discharge feedscrew pitch.

CONVEYOR TECHNOLOGY RELATED TO SPEED

The beer–beverage industry is a prime example of reliance

on advanced conveying and packaging technology to meet

steadily increasing demands for greater speeds, produc-

tion efﬁciencies, and marketing innovations. The develop-

ments in current high-speed conveyor systems are a

response to this need. Today’s state-of-the-art high-pro-

duction conveyor systems can achieve smooth, damage-

free travel of containers from delivery to ﬁnal packaging.

The design challenge is to sustain high production rates

through the proper integration of the various conveyor

types despite any temporary interruptions in container

ﬂow that may occur at any points.

High-speed can–bottle conveyor technology is a combi-

nation of up-to-date mechanical, electromechanical, and

electrical/electronic techniques, resulting in production

capabilities of up to 2000 cpm and plastic bottle rates of

200–1000 bottles per minute (bpm). The high production

derives from container transport and accumulation tech-

niques combined with microcircuit-controlled, start–stop,

and speed modulation that compensates for intermittent

container-ﬂow variations.

Most high-speed container packaging lines have one

or more critical machines in the line, such as the ﬁlling

machine, which dictates the ﬂow parameters for the

remainder of the system. For smooth continuous produc-

tion, all functions upstream and downstream of the

critical machine(s) must be designed to assure an unin-

terrupted supply of inputs in and out of the critical

machine(s). The conveyor system then must isolate

discontinuities in input ﬂow so that the critical machine(s)

will be neither short of inputs from the upstream

side nor slowed or shut down because of inputs that are

backed up downstream. Continuous movement of the

inputs in and out of the critical machine(s) is the best

indication that the conveyor system is functioning prop-

erly, barring unreliability in upstream and downstream

machines.

Backpressure is a multiple of the product weight times

the coefﬁcient of friction between the chain and product.

Factors affecting chain pulls include the type of chain,

container weight, and whether the process is dry or wet,

depending on the product being handled. Smooth side

transfers to and from the buffer areas and coordination

of conveyor speeds with the number of lanes also

are critical to the maintenance of the high production

rates.

HANDLING LIGHTWEIGHT CONTAINERS

For delicate inputs or packages such as lightweight alu-

minum cans and thin-walled plastic bottles, confectionery

goods, bakery goods, and medical and high-cost quality

products, conveyors must handle the inputs gently, with

as little contact and pressure as possible. This is accom-

plished by combining the buffer techniques and container

trafﬁc patterns with sensing and interlock devices that

prevent jamming of containers and assure smooth, shock-

free ﬂow and minimal surging (which is critical for some

types of plastic containers). Conveyor surfaces that reduce

friction, techniques that maintain container-separation

gaps, dimensional precision in fabrication of conveyor

components to minimize binding and jerking, and inter-

locked motion controls are also a requirement for handling

lightweight containers.

The container material, type, and shape are equally

important factors in the design of a conveyor. Flow paths

and buffer areas must be sensitive to the increased jam-

ming potential of nonround shapes. Lightweight plastic

bottles, particularly without base cups, are more likely to

tip over. Usually nonround lightweight plastic container

designs might function best with vacuum conveyors

that stabilize the packages by pulling them and holding

them onto conveyor surface for optimum control. Another

method more commonly used is to use airveyors and

convey plastic bottles via a designed in bottle neck ring.

STAGES IN CONVEYING

Today most production packaging lines receive a contin-

uous supply of containers from single or multiple feed

lines. The latest designs use a programmable controller

that contains the electronic logic for operation of the

solenoids, motors, clutches, brakes, and other control

components to monitor the supply lines and determine

the routing of inputs into and through the packaging

line and the routing of ﬁnished goods to the truck or

warehouse.

Sometimes, to prevent impact shocks downstream,

notably at the critical machine, a comparatively slow,

usually double or triple 7

-in. (19-cm)-wide mass conveyor

is used to spread the large volume of inputs, such as round

stable containers, over a wider surface area. The high

production rate can then be maintained, and the conveyor

velocity is limited to up to 50 ft/min (15 m/min). Experi-

ence has shown this rate to be the maximum manageable

at this stage of the production line to minimize package

damage.

SINGLE FILING FROM MASS FLOW

Conventional methods of single ﬁling containers have

been limited to round units, with the volume of containers

from multiple lanes or mass ﬂow being directed into a

single lane with the aid of converging guiderails (which

have a shaker bar or use small plastic roller chain in the

vertical position to facilitate merging and reducing friction

CONVEYING 347