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Millwright 4th yr. RTS > Roller and Pneumatic conveyors > Flashcards

Roller and Pneumatic conveyors Flashcards

1
Q

Roller Conveyor

Roller conveyor require materials being handled to have one solid surface that rides on the roll. With few exceptions, this surface should also be reasonably flat

2 General Types

  1. gravity roller conveyor
  2. live roller conveyor
A

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2
Q

Type of Roller Conveyor

Gravity roller conveyors - can move material in any horizontal direction. When they are tilted down, the force of gravity on the package causes the materials to turn the rollers.

A

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3
Q

Standard gravity roller conveyors - used cylindrical rollers that are usually supported with ball bearings

A

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4
Q

Skate wheel conveyors - consist of a frame with axles spaced evenly along its length. Wheels are installed on the axles and generally staggered on every other axle.

A

Advantages of skate wheel conveyors over roller conveyors:

  • they are less costly
  • they are lighter (portable)
  • they are less angle (pitch) to transport load
  • they maintain package orientation on the conveyor when going around curves
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5
Q

Conveyor Frame and support

The frame that support the rollers is called the “ROLL CASE”
When a wheel conveyor has wheels along the outside frame or rail only, the frame is called a WHEEL RAIL SECTION or SKID assembly

A

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6
Q

Roller or Wheel Spacing

  • for roller conveyors, the smallest number of rollers under the smallest container at any time should be 3
  • for skate wheel conveyors, the smallest number of wheels under the smallest package the conveyor is expected to handle should be 5
A

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7
Q

Bearings

  • in gravity roller conveyors, the outer race of the bearing revolves around the fixed inner race. This means the bearing will most likely have a slight interference fit on the outer race to roller
A

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8
Q

Bearings - Plain bearings

Plain bearings are suitable for clean environments with relatively low amounts of moisture, dust and abrasives. they should be used only for slower speed applications.

A

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9
Q

Conveyor Pitch

  • a typical conveyor pitch’s that vary from 1/4” per foot to 1/2” per foot
A

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10
Q

Curves in Gravity Roller Conveyors

  • curves are used in roller conveyors to change direction horizontally
  • the hand of a curve is named using the direction of flow as reference. If the conveyor turn to the left, it is a left hand curve. If it turns to the right, it is a right hand curve.
A
  • the outside edge of a curve can be banked to prevent packages from falling off
  • the contact surface (top) of tapered rollers is parallel with the top of the frame
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11
Q

Straight Roller (curves arrangement)

  • is the simplest and least expensive
  • disadvantages, packages tend to want to continue to travel in a straight line
A

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12
Q

Tapered Roller (curves arrangement)

  • the outside of the tapered roller moves more lineal inches per revolution than the inside due to its larger circumference. This turns the package as it goes around the curve, thereby keeping the package aligned with the direction of travel.
  • taper of rollers matches radius of turn (advantage)
A

Advantage:

-it requires less pitch for load movement

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13
Q

Double Lane (curves arrangement)

  • also called differential roller curves.
  • the rollers in the outside lane of the conveyor are free to turn at a different rate than those on the inside. This provides some differential action and turns the package as it travels around the curve.
  • used for wider radius turns than are tapered roller curves
A
  • if a centre rail is used, its alignment must be accurate to keep the rollers level to prevent troughing
  • double lane roller curves can maintain the minimum required roller spacing at the outside of the curve
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14
Q

Double lane In- line Curves Arrangement Characteristics:

  • it has both inside and outside roller on a common shaft
  • it has more spacing on the outside of the curve
  • easier to provide the spacing over tapered rollers
  • easy to manufacture
  • it may or not use a center rail
A

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15
Q

Double Lane Staggered Roller Curve Arrangement
Features:

  • each roller is on a separate shaft
    the curve has a center rail for shaft support
    -the spacing at the outside curve can be closer (maintaining the conveyor load rating)
A

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16
Q 
Live Roller Conveyors
Drive types:
- belt-driven roller can be driven by flat belts, v-belts or round belts.  Used for..
- light loads
- application where loads accumulate
- loads fairly smooth and hard bottoms
A

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17
Q

Belt driven - v-belt

  • are used only for short lengths of conveyor and for light loads. They often used to drive straight and tapered roller curved conveyor section.
  • when driving around curves, 3 standard sheaves are used:
    1. the drive sheave
    2. the take-up sheave
    3. the tail sheave
A
  • tension sheaves are used on tapered roller curved conveyor sections to guide the belt and drive the roller
  • the shaft axis of the drive and tail sheaves are at an angle to each other
18
Q

Belt driven Flat belts

  • use as a flat belt under the package carrying rollers

Advantage:
- because the rolls can stop if the package being carried is stopped and the belt continues to run, this drive arrangement is called - NON- POSITIVE

A

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19
Q

Chain drive Rollers

Have some important differences from belt drive rollers conveyors.

  • the roller have shaft mounted solidly on the rolls
  • bearings are locked on the roller shaft, the bearing housings are attached to the roll case
  • the inner race of the bearing turns
A

Gravity or belt driven rollers

  • shaft does not turn chain driven rollers
  • shaft turns
20
Q

Chain Driven Rollers - Drive Configurations

Determining Factors:

  • weight of the load
  • frequency of starting and stopping
  • overall length of the conveyor
A

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21
Q

Continuous Chain drive system

  • use a hold down plate to keep the chain in contact with the sprocket
  • chain return is either a channel or uses idler sprockets
  • for medium loads
  • not used for frequent starts and stops
  • positive drive system, cannot be stopped without shutting off the drive unit
A

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22
Q

Roll to Roll Drive Systems

  • have 2 sprockets on each shaft
  • is a positive drive system
  • used for frequent starting, stopping and reversing and heavy loads
  • used when longer packages
  • every roll is driven
A

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23
Q

Eccentic Roll

  • the roller is oblong shape, the highest point on the roller tends to raise the materials conveyed above or to cross the travelling chain.
  • it is a transfer device or transfer in direction
A

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24
Q

Bottle Rolls - also transfer device/direction

  • are frequently used in sawmills and planner mills to end lumber against a straight edge before the lumber enters scanners or trimmers.

Bottle rolls Characteristic:

  • the tapered end of bottle roll faces upstream into the material flow
A

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25
Q

Spiral Rolls - also transfer device/direction

  • are generally used to move objects sideways across the roll reaching an end stop
A

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26
Q

Angled Rolls

  • rolls set at an angle on their roll cases (guided roll cases) are used when the packages or product must lined up against one side.
    ex. bring the product close to or into position for marking/ stamping it.
A

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27
Q

Hourglass Rolls

  • are specially shaped rolls designed to carry cylindrical such as pipe or logs.
  • they are usually chain to chain driven
  • specially designed lifting arms powered by hydraulic or pneumatic cylinders move the log from the rolls onto a deck located beside the roll case.
A

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28
Q

Spurs

  • are roller or wheel conveyors used to transfer load off of or onto belt or roller conveyor
A

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29
Q

Gravity Roller Spurs - are used to transfer packages off of or onto the main conveyor in a system

main driven ___
conveyor ___ 30* / ___ /
system ____max . /___/ . gravity roller spur
____ /___/

A

main driven ___
roller ____
conveyor ___ 90* / ___ /
___ /___/ spur entering a main
____ /___/ . conveyor

30
Q

Live Roller Spurs

  • are used to maintain control over packages being transferred. Automated control systems require accurate package positioning which is usually achieved using live rollers
A

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31
Q

Deflectors - shorting packages, designed to use on live rollers

are moveable arms or plates used to sort packages in a roller conveyor system

A

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32
Q

Jump Rolls - also transfer device/direction

  • if rolls are lowered, the transfer chains carry the package away
  • if the rolls are raised, the rolls carry the package across the chains and onto the next conveyor
A

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33
Q

Two and Three-Way Switches

  • pivot a short moveable section of live roller conveyor to sort packages from a main conveyor to 2 or 3 conveyors downstream of the pivoting section.
    A B C
    _____ /____/
    /___/ _____ /____/
    _____
                         /\_\_\_\_/
                    /\_\_\_\_/
A

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34
Q

Converge Conveyor Section

  • join the package flow on 2 or more conveyors into one conveyor line
A

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35
Q

Diverge Conveyor Section

  • send packages from a single roller conveyor to 2 or more conveyors lines
A

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36
Q

Ball Transfer Table - allow manual movement to or from any of the four conveyors

Rotating turtables transfer product 90* from initial direction of product

A

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37
Q

Vacuum Conveying System
- used primary when material must be conveyed from more than one location to a single location. They rely on the differential pressure between atmospheric ( 14.7 psi) and system pressure ( below atmospheric)

A

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38
Q

Low Pressure - 15 psi

  • use lobe or roots type blower to supply the air pressure in the transport line. The material to be transported is then introduced into the air stream at an angle in the direction of the air blow by means of a rotary feeder.
  • another method of transportation is directly feeding the intake eye of the fan use to generate the pressure. The material then becomes part of the air stream. This method is used to convey wood chips, fibrous material, plastic beads with material coming into direct contact with the fan blades, blade ear becomes a problem. When combustible material is being conveyed, provision for fire protection must be included. Fire protection involves installing spark detectors both before and after the fan.
A

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39
Q

Medium Pressure Conveyor ( 15 - 45 psi)

  • conveyed of fluidized solids. The solids must be dry and a uniform size and shape. The material is usually fed from a hopper into the feed screw or pump and then fed into the mixing chamber where air nozzles aerate and mix the material before transporting it along the feed lines. This system can convey materials over large distances and heights and is commonly used in cement industry to transport both raw mix and finished product.
A

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Millwright 4th yr. RTS (15 decks)

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