A. V-Belt Driven
B. Flat Belt Driven
C. Zero-Pressure
D. Single strand roller chain driven
E. Roller to roller chain drive
F. Roller Slat Conveyor
Applications
Live roller conveyors, because of the relatively low coefficient
of friction between the bed rollers and the items conveyed, are
used in preference to belt conveyor where:
1. Temporary utilization of the items being conveyed is a
requirement.
2. Items are stopped momentarily such as traffic control points.
3. Items must be turned, say 90° on the conveyor.
4. An air operated or manual stop is injected into the line so
that the item may be inspected or some operation performed while
the conveyor remains in motion.
5. Side loading or unloading is required involving a sliding
motion across the bed rollers.
Belt driven live roller using regular friction surface rubber
filled belting is not recommended for use in high environmental
temperature extremes. Rubber can become sticky and soft at
temperatures exceeding 150°F, and this belting can stiffen
considerably and crack in the minus zero range. PVC or cotton
belting is a considerable improvement in the range described
above. Check with your Master Hytrol Distributor for special cold
room applications.
Keep in mind, that the belt travels in a direction opposite to the
items being conveyed. This is unlike a belt conveyor where the
items are being carried directly upon the belt, so they both go in
the same direction.
V-Belt driven live roller conveyor is that type where a
single strand of V-belt is under the roller bed, on one side of
the rollers, adjacent to the side-frame and is powered in a
direction opposite to that of the items being conveyed. We
recommend this type of conveyor for light and medium duty loads.
This type of conveyor is not recommended for use where moisture or
oily conditions may exist. A very light contact with the underside
of the bed rollers is all that is required to keep the items being
conveyed in motion. This type of conveyor may also be reversible.
Belt driven tapered roller curves generally give good
package conveying action. The tapered roller presents a true
conveying surface on a curve giving the correct radial speed along
the full length of each roller. The curve radius along with the
taper on the roller which comes to a common focal point causes the
package to leave the curve in much the same position in which it
entered. For best results, there should be live rollers, a minimum
of 2/3 of package length at the entry and at the discharge ends of
the curve.
Two rail curves with straight rollers are not normally
recommended for use as a live roller curve because both rows of
rollers must be powered separately and with a different speed in
order to obtain some semblance of differential action. Under some
conditions, the center rail may be move off center, closer to the
outer rail with the longer rollers powered.
Flat Belt driven live roller conveyor is that type where a
flat width of belt is under the roller bed, generally in the
center of the conveyor, but can be mounted off-of-center adjacent
to the side frame if required. Because of the greater contact
surface at the underside of the roller bed, this type of conveyor
is recommended for handling medium to heavy duty loads, where
moisture, hot, dirty or oily conditions do not exist. Again, the
pressure rollers which snub the driving belt to the underside of
the bed rollers are set to a minimum, just enough to convey the
load, yet allow belt slip without undue wear or stress on the gear
motor when the loads are momentarily blocked.
The above described conveyor design cannot be incorporated into a
roller bed curve, and another type of live roller curve must be
utilized where a curve is necessary.
Ripple Belt conveyor is one utilizing a belt, which varies
in thickness at regular intervals along the full length of the
belt. It is set so that the thicker portions of the belt make
contact with the underside of the bed rollers. If the ripples are
relatively far apart, only a few are in contact with the bed
rollers. This makes for a fairly inexpensive live roller with
reduced line pressure under blocked load conditions.
Controlled gravity live roller is similar, in construction,
to flat belt or V-belt driven live roller conveyor, except that
the conveyor is sloped at a grade just sufficient to allow the
items to convey by gravity. On the flat belt conveyor the snubbing
rollers are spaced further apart than the standard horizontal live
roller. Since gravity is the driving force of the items being
conveyed, the snubbing pressure is light enough to simply prevent
the rollers from turning at excessive speeds particularly when
trains of items coming one after another are being conveyed.
Hytrol Zero-Pressure Live Roller Conveyor is very
completely described in the General Catalog under the headings
190-ACO and 190-ACOC. This is a full length drive shaft
arrangement, with each thread roller driven by a urethane o-ring
from a 1.9" diameter longitudinal drive roller. The 190-ACOC
curves, which are slave driven from the adjacent 190-ACO, is
designed for applications that require accumulation of products
without a build-up of line pressure. In addition, Hytrol has
developed the model 190-ACA, a flat belt drive zero-pressure
conveyor. In all zero-pressure live roller, the conveyor length is
divided into zones, the length of each is greater than the maximum
package length. Zero-pressure is achieved since the packages never
touch one another.
Single strand chain driven live roller is a medium duty
live roller conveyor, ideal for conveying hot or oily items, or
items subject to wash down. In this type of live roller,
"Type A" plate sprockets are welded to one end of each
roller. Care must be taken that the dimension form the end of each
roller is identical to keep the roller chain in a straight path.
In this type of conveyor, the roller chain which powers each
roller only makes contact with just one or tow teeth of the
sprocket. The sprockets and the chain are completely enclosed by
the chain guard which sometimes acts as a hold down for the upper
strand of chain. Rack tooth sprockets must be used for this type
of conveyor. If rollers used are a large diameter and would
necessitate a greater roller spacing than desired, then idler
(non-powered) rollers may be spaced between each driven roller.
Because the chain guard on chain driven live roller conveyor forms
a guardrail on the one side of the conveyor, items can only be
transferred to and from the opposite side of the conveyor. Hytrol
has developed a chain crossover, which simply crosses the chain
over to the opposite side on a slave driven arrangement when items
must be transferred to or from the driven side. Access is
available from the one non-powered side only.
Single strand chain driven live roller curves can also be supplied
using a side bow chain, especially designed to bend around a
curve.
Roll to roll chain driven live roller is a heavy-duty live
roller conveyor for use under the same conditions as for single
strand live roller. In this instance, two type "A"
sprockets are welded to one end of each roller. The roller chain
then makes a complete loop around each pair of adjacent roller
sprockets. With a greater number of sprocket teeth in contact with
the roller chain, more power can be transmitted to and through
each roller. Rack tooth sprockets must not be used on this type of
conveyor.
Roll to roll chain driven live roller curves can also be supplied.
A heavier duty roll to roll chain driven live roller conveyor
utilizing two "B" type sprockets attached to the
extended shaft on the outside of one side frame accomplishes the
same as described above and permits the use of smaller drive
sprockets, thus enabling us to keep the rollers to reasonable
closer centers. This type of live roller can also allow access
from either side of the conveyor provided the chain guard which
covers the outboard row of sprockets does not project above the
top of the conveyor side frame.
Roller slat conveyor utilizes extended pitch bushed roller
chain with oversize rollers rolling in tracks adjacent to the
outer rails. Using ball bearing rollers with the hexagon axles
longer than normal; these axle ends pass through the hexagon
broached bushings of the chain and are generally cottered at both
ends on the outside of the chain.
On a blocked load, the conveyor continues to run and the ball
bearing rollers simply roll under the blocked load. The line
pressure thus is kept to a reasonable low level.
This roller slat conveyor is an extremely heavy type of conveyor,
and must be assembled at the job site as the assembled conveyor
rollers in the chain are much too heavy to handle as an assembled
unit. This is also a fairly expensive type of live roller and is
used only under special conditions; such as heavy duty type for
filled oil drums or perhaps for newspaper mail rooms where the
blocked load of newspapers permit the roller slat to run under the
newspapers without damage.
Except for Hytrol's Zero-Pressure 190-ACOC conveyor, under no
circumstances should curves be used for accumulation of square or
rectangular items. Cylindrical items only are permissible. The
very nature of a square or rectangular conveyor would cause the
corner of one container to dig into the corner of another.
Powered curves should not be warped because of the difficulty in
providing power to the individual rollers of a warped curve.
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