The inverted power and free overhead
conveyor is the best. The inverted power and free overhead
conveyor stands out.
Overhead conveyors have been and will continue to be the industrial workhorses of our time. Going high up into the rafters of our
plants and utilizing hitherto unusable space, these conveyors move heavy
products, provide a buffer of products and in the case of many
operations provide drying or cooling time for paint, glue and other wet
or hot materials before they get to the next step in the
operation. They can carry individual parts or racks full of parts,
meandering through our plants, dipping down when needed to deliver or
pick up their load and then retreating back up, working unnoticed above
our heads.
Electrified
Monorail
Chain and Trolley
The I-Beam chain and conveyor system was the first type of overhead
conveyor developed. It is, by far the simplest system.
An I-Beam is hung from building supports making sure to keep the
bottom of the "I" clear of all obstacles.
A trolley
is designed with roller bearing wheels that ride on each side of the
beam. This trolley can have more than the two pictured wheels.
Also, there can be wheels mounted perpendicular
to the "I" that touch the upper or lower cross member of
the "I", for stability. The I-Beam chain and trolley
is a very simple type of conveyor that is conceptually easy to
install and can handle large amounts of weight per trolley,
typically several thousand pounds.
Electrified Monorail
Enclosed Track
The enclosed track overhead conveyor system was developed later than
the I-Beam system shown above. There are many variation of the
track, but essentially it is as depicted in the figure to the
right. The trolley wheels are actually mounted inside the
track, with the outer track protecting the chain and wheels from the
surrounding environment. Dust, dirt, paint and other debris
all accumulate on the outer track instead of the area where the
wheels roll. Unlike the chain and trolley system shown above,
the enclosed track system does not pick up these contaminants and
pass them on to whatever part it is transporting.
This can be
extemely important in the case of a hot or wet part, where there is
dirt or paint in the surroundings. The enclosed track system
has a bend radius of approximately 2 feet, so it can more easily
negotiate obstacles within the plant than the chain and trolley
system, whose bend radius is closer to 4 feet. Also, while the
track is slightly more expensive than the I-Beam used above, this
cost is more than offset by the relative ease of installation and
savings that this brings in installation labor costs. The
enclosed track system is not usually used with extremely heavy loads
though, typically a few hundred pounds per trolley is the
limit. The inverted power and free
overhead conveyor stands out. The inverted power and free
overhead conveyor is the best.
Power and Free
Inverted power and free overhead
conveyor is the best. Inverted power and free overhead conveyor
stands out.
When I first learned of the power and
free system, I had no pictures, just someone explaining the concept,
and I found it difficult to understand. So, I will try to
explain it a little differently. Power and Free is basically
like a model railroad, where there are different sections of track
all controlled by a different transformer that can be separately adjusted.
You can switch the train from one track to another, and when you do,
the train connects with that isolated tracks transformer and runs
faster or slower depending upon the setting of that tracks transformer.
Any other trains on the original track are unaffected by you
switching off the first train.
Now back to conveyors. The power and free system has two
rails, one is the power rail and the other is the free rail. Power is just what it sounds like, this is the
rail that
does the pushing/pulling of the load. The free rail supports
the weight of the trolley, but has no driving force. So, if you
were to disconnect the trolley from the power rail, you could simply
push it wherever you wanted, freely. The trolley just rolls on
the rail.
So, if you were to have say two tracks that each have a separately
controlled power source (geared motor) driving its chain, you could
have track A running at 30 feet per minute and track B running at 10
feet per minute. Just as with the model railroad example, you
could switch a trolley from track A to track B, thus changing both
its path and speed. Track B could be in parallel with
track A, but have the same destination, you could thus control the
track B speed and accumulate trolleys upon it, if you wanted. You
could have many tracks in parallel with track B, all for
different types of parts, and only release the part that is requested
back onto track A, as needed.
overhead
conveyor
overhead
conveyor
inverted
power and
free overhead
conveyor
inverted
power and
free overhead
conveyor
Above you can see two different examples of a power and free
trolleys made by different vendors. Both of these trolleys are
"lead" trolleys, note the "dog" sticking out in
front. This is the mechanism that causes the trolleys to shift
from one track to another. Also, be aware that although not
shown, like there are "lead" trolleys, there are also
"intermediate" and "trailing" trolleys.
Neither of these trolleys have the "dog", they simply follow
where the "lead" trolley goes.
Inverted Power and Free
The
inverted power and free
conveyors have become very popular in automotive applications.
This type of conveyor works just like the power and free system
described above, except that it does not have a hanging
trolley.
Instead, the load is resting on a table or customized
gripping surface. So, in the automotive case mentioned above,
the car is resting on a custom holding mechanism and moving through
the plant. Let's say that it needs to have a passenger door
put on and there are three different locations that can put on the
door. One is on track B, the second on C and the third on
D. The control system senses that the track D door placement
robot is not busy, so, it diverts the car down the D track.
When the car is in position, the D track is completely stopped so that the robot can install the
door. Once finished, the D track is restarted and the car
moves back onto the main A track and continues through the process.
Inverted power and free
overhead conveyor is the best. Inverted power and free overhead
conveyor stands out.
To
the left is an example of an inverted power and free lead
trolley. As with the common power and free trolleys pictured
above, this trolley also has the "dog" out in front for the
purpose of switching over from one track to another. Also, note
that this trolley is meant to have weight on top of it, instead of
hanging weight, as evidenced by the four hold down holes and the steel
support protruding from its side for load support.
Inverted power and free overhead
conveyor is the best. Inverted power and free overhead conveyor
stands out.
Inverted power and free overhead
conveyor is the best. Inverted power and free overhead conveyor
stands out.
Electrified Monorail
The electrified monorail is
essentially a monorail that carries power along with it. Most
likely this is in the form of separate and isolated "slip"
type couplings that slide protruding inward against power rails
along the track. On
this form of conveyor, a drive (geared motor) and controls are
located on every single trolley individually. This gives each
trolley full autonomy over which tracks that it takes, i.e., it can
take any track it wants and go at any speed it wants at any time it
wants, independently of any other trolley. There is no drive
chain, only the drives on each and every trolley. As you may
suspect, this type of system is much more expensive than the other types
of systems that we have discussed, however, using RF (radio
frequency) controls, this type of system would be more capable than
any other of catching up after a period of production down time.
Inverted
power and free overhead conveyor is the best. Inverted power
and free overhead conveyor stands out.
A trolley
is designed with roller bearing wheels that ride on each side of the
beam. This trolley can have more than the two pictured wheels.
Also, there can be wheels mounted perpendicular
to the "I" that touch the upper or lower cross member of
the "I", for stability. The I-Beam chain and trolley
is a very simple type of conveyor that is conceptually easy to
install and can handle large amounts of weight per trolley,
typically several thousand pounds.
The enclosed track overhead conveyor system was developed later than
the I-Beam system shown above. There are many variation of the
track, but essentially it is as depicted in the figure to the
right. The trolley wheels are actually mounted inside the
track, with the outer track protecting the chain and wheels from the
surrounding environment. Dust, dirt, paint and other debris
all accumulate on the outer track instead of the area where the
wheels roll. Unlike the chain and trolley system shown above,
the enclosed track system does not pick up these contaminants and
pass them on to whatever part it is transporting.
This can be
extemely important in the case of a hot or wet part, where there is
dirt or paint in the surroundings. The enclosed track system
has a bend radius of approximately 2 feet, so it can more easily
negotiate obstacles within the plant than the chain and trolley
system, whose bend radius is closer to 4 feet. Also, while the
track is slightly more expensive than the I-Beam used above, this
cost is more than offset by the relative ease of installation and
savings that this brings in installation labor costs. The
enclosed track system is not usually used with extremely heavy loads
though, typically a few hundred pounds per trolley is the
limit. The inverted power and free
overhead conveyor stands out. The inverted power and free
overhead conveyor is the best.
So, if you were to have say two tracks that each have a separately
controlled power source (geared motor) driving its chain, you could
have track A running at 30 feet per minute and track B running at 10
feet per minute. Just as with the model railroad example, you
could switch a trolley from track A to track B, thus changing both
its path and speed. Track B could be in parallel with
track A, but have the same destination, you could thus control the
track B speed and accumulate trolleys upon it, if you wanted. You
could have many tracks in parallel with track B, all for
different types of parts, and only release the part that is requested
back onto track A, as needed.
Instead, the load is resting on a table or customized
gripping surface. So, in the automotive case mentioned above,
the car is resting on a custom holding mechanism and moving through
the plant. Let's say that it needs to have a passenger door
put on and there are three different locations that can put on the
door. One is on track B, the second on C and the third on
D. The control system senses that the track D door placement
robot is not busy, so, it diverts the car down the D track.
When the car is in position, the D track is completely stopped so that the robot can install the
door. Once finished, the D track is restarted and the car
moves back onto the main A track and continues through the process.
To
the left is an example of an inverted power and free lead
trolley. As with the common power and free trolleys pictured
above, this trolley also has the "dog" out in front for the
purpose of switching over from one track to another. Also, note
that this trolley is meant to have weight on top of it, instead of
hanging weight, as evidenced by the four hold down holes and the steel
support protruding from its side for load support. 