A Project Report ON “DESIGN AND MODEL OF BUCKET ELEVATOR” Under The Guidance Of Prof. Y.D. Patel Assistant Professor, A. D. Patel Institute of Technology In partial Fulfillment for the award of the degree Of Bachelor of Engineering In Mechanical Engineering Prepared By UTKARSH AMARAVAT (080010119001) Submitted to A.D. Patel Institute of Technology, New V.V. Nagar May, 2012
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
A
Project Report
ON
“DESIGN AND MODEL OF BUCKET ELEVATOR”
Under The Guidance Of
Prof. Y.D. Patel
Assistant Professor, A. D. Patel Institute of Technology
In partial Fulfillment for the award of the degree
Of
Bachelor of Engineering
In
Mechanical Engineering
Prepared By
UTKARSH AMARAVAT
(080010119001)
Submitted to
A.D. Patel Institute of Technology, New V.V. Nagar
May, 2012
i
DECLARATION
I, UTKARSH AMARAVAT hereby declare that the report on entitled “Design and Model of
Bucket Elevator” is a result of my own work and my indebtedness to other work Publications,
if any, have been duly acknowledgment.
Place: - Anand, Gujarat, India
Date: - 6th May, 2012
Utkarsh Amaravat
ii
ACKNOWLEDGEMENT
I deem it a privilege to have been the student of Mechanical Engineering stream in A. D.
Patel Institute of Technology, New V. V. Nagar. My heartfelt thanks to Prof. Y. D. Patel, my
project guide who helped me to bring out this project in good manner with his precious
suggestion and rich experience. I gratefully acknowledge my sincere thanks to my friend
Nirav Sathwara for working as Co-partner and all other friends who help me in this project in
such critical situations and make my project memorable.
I hardly thank to my principle sir Dr. R. K. Jain who grant us permission for economic help
for model making also Mr. Karimbhai, Mr. Samirbhai, Mr. Anandbhai, Mr. Sureshbhai, Mr.
Manishbhai, Mr. Harshadbhai, Mr. Mineshbhai, Mr. Yogeshbhai, Mr. Bharatbhai, Mr.
Birenbhai and Mr. Aashishbhai the staff’s members of ADIT workshop, without help of them
this work is not possible.
iii
ABSTRACT
In this modern competitive industrial world one can get a step ahead of his competitor by
selection of proper material handling equipment. Material handling process is overhead for
the production but it is heart of any process plant. Still people prefer most advanced material
handling equipment even though they are costly. But cost can be justified after prolonged
usage of that equipment.
Bucket elevator has evolved as advanced material handling equipment in mechanized bulk
material handling industry. The effective use of different type of bucket elevators are
completely depends on its design and type of bulk material. In this report different types of
bucket elevator are discussed along their different parts and the design of centrifugal
discharge bucket elevator with simultaneous buckets for lifting wheat at a certain height is
reported for a particular output rate. Detailed design, CAD parts, coding for the design
procedure of bucket elevator, fabrication related data and future scope of work and at last
satisfactory conclusion is worked out in successive chapters.
iv
LIST OF TABLE
Table No.
Table Description Page No.
2.1 Recommendation for selecting bucket elevators 23
2.2 Main characteristics of buckets 26
2.3 Recommendation for selecting bucket Dimension by Maxi-lift 34
3.1 Bill of material for bucket elevator 45
4.1 Design inputs for prototype model 49
4.2 Design outputs for prototype model 49
4.3 Fabrication processes for bucket elevator 51
5.1 Observation table for 10.00 kg of wheat 63
5.2 Observation table for 24.75 kg of wheat 63
v
LIST OF FIGURE
Figure No.
Figure Description Page No.
1.1 Simple belt conveyor 3
1.2 Simple bucket elevator 4
1.3 Parts of simple belt bucket elevator 5
1.4 Belt bucket elevator 6
1.5 Positive discharge bucket elevator 9
1.6 Gravity discharge bucket elevator 10
1.7 Horizontal discharge bucket elevator 11
1.8 Centrifugal discharge bucket elevator 12
1.9 Twin legged discharge bucket elevator 13
1.10 Single and double bucket elevator 14
1.11 High or Super capacity bucket elevator 15
1.12 Bunge Russia – Oilseed bucket elevator 17
1.13 New Zealand - Bins plant bucket elevator 17
1.14 Cimbria (Egypt) - Bins plant bucket elevator 18
1.15 Bahrain-Coke calcining plant bucket elevator 18
1.16 Jordan - Fertilizer plant bucket elevator 19
2.1 Diagram to calculate the pole distance 20
2.2 Forces acting during bucket unloading 21
2.3 Diagram to determine the paths of ejection of material from buckets 21
2.4 Effect of bucket width B on io/tb ratio 25
2.5 Diagram for elevator calculation 28
2.6 Diagram for bucket calculation 34
3.1 Bucket 40
3.2 Ball bearing 40
3.3 Belt 41
3.4 Shaft 42
3.5 Pulley 43
3.6 Bucket elevator assembly 45
vi
3.7 Mechanism of bucket elevator 46
3.8 Mechanism problem-1 of bucket elevator 47
3.9 Mechanism problem-2 of bucket elevator 47
3.10 Mechanism problem in case study 48
4.1 Side part of bucket 53
4.2 Bend part of bucket 53
4.3 Sheet metal planning for all bucket 53
4.4 Loading and bending moment diagram for upper shaft 56
4.5 Fabricated bucket elevator prototype model 58
5.1 Variation based on lifting height 59
5.2 Variation based on pulley diameter 60
5.3 Variation based on capacity 61
5.4 Variation based on efficiency 62
vii
LIST OF SYMBOLS, ABBREVIATIONS AND
NOMENCLATURE
R Resultant
P, F Forces
Rp Pulley radius
hp Pole distance
ra Bucket circle radius
β Bucket angle
Q Capacity
H Lifting height
ρ Wheat density
ν Belt speed
Dp or dp Pulley diameter
N Rotational speed of pulley
B Bucket width
V Volume
Bb Belt width
tb Bucket pitch
Ψ Average coefficient of bucket filling
mrb Linear mass of belt
g Gravitational constant = 9.81
mb Mass of bucket
T Tension
ζ Resistance on take-up pulley
Ksc Scooping resistance
K Safety factor
W Pulley resistance
μ Coefficient of friction
P Power
η Efficiency
Bp Width of pulley
viii
t Pulley rim thickness
L Belt length
C Centre distance
τs Allowable shear stress
w Width of key
h Height of key
rh Hub radius
d Inner diameter of bearing
D Outer diameter of bearing
b Width of bearing, Projection of bucket
Co Static load
C Dynamic load
h1 Depth of bucket
θ Angle of contact
α Angle subtended by each common tangent
п 3.14
ix
TABLE OF CONTENTS
Page No.
Declaration i
Acknowledgement ii
Abstract iii
List of Tables iv
List of Figures v
List of Symbols, Abbreviations and Nomenclature vii
Table of contents
ix
1. Introduction
1.1 Material handling equipments 1
1.2 Bucket elevator 5
1.3 Classification of bucket elevator 8
1.4 Application of bucket elevator 15
1.5 Presently installed bucket elevator in abroad
17
2. Design of bucket Elevator
2.1 Bucket elevator geometry 20
2.2 Design input data for bucket elevator 22
2.3 Flow chart for coding of design
35
3. Modeling of elevator
3.1 Introduction of modeling and its significance 39
3.2 CAD parts of bucket elevator 40
3.3 Assembly of bucket elevator 44
3.4 Bill of material 45
3.5 Mechanism of bucket elevator
45
x
4. Fabrication of prototype
4.1 Selection of prototype dimension 49
4.2 Fabrication of bucket elevator prototype 51
4.3 Selection of power pulley 55
4.4 Bending moment diagram of upper shaft 55
4.5 Problems occurred during fabrication 57
4.6 Fabricated prototype of bucket elevator
58
5. Results analysis
5.1 Effect of operating variables on performance 59
5.2 Result analysis of prototype model
62
6. Scope of further work
64
7. Conclusion
65
Appendix: A
xi
Bibliography xxv
1
Chapter 1: INTRODUCTION
1.1. MATERIAL HANDLING EQUIPMENTS
Expressed in simple language, Material handling equipment is relates to the movement,
storage, control and protection of materials, goods and products throughout the process of
manufacturing, distribution, consumption and disposal. One of the definitions given by the
American Material Handling Society is: “Materials handling is the art and science of moving,
packaging and storing of substance in any form.” To do it safely and economically and
efficiently, different types of tackles, gadgets and equipment are used, when the materials
handling is referred to as mechanical handling of materials.
Material handling also should be considered with in a system context. Rarely, if ever, are
activities performed in a one area or department of a facility without having an impact on
other operations. Example: The efficiency of store room will affect the efficiency with which
the production operations are performed out on the shop floor. The positioning of conveyor
line in plant might improve material flow through the facility or it could present a hindrance
to plant traffic. A significant improvement in the efficiency of one operation, without a
corresponding improvement in a subsequent step in the work sequence, may only result in a
piling up of materials down the line.
These simple examples illustrates the point that to maximize overall productivity of the plant
or warehouse, the material handling steps that supports production, order assembly, and other
operations must be integrated in to a system of activities rather than being viewed as a
number of isolated independent procedure. In addition to considering time and place utility
and system approach, a through definition of material handling must also include the human
aspect. People are always a part of material handling weather the operation is simple one,
involving only a few items of equipment, or a large, complex, automated system.
Maintenance personnel keep the equipment working properly and keep downtime to a
minimum. Foremen and supervisors oversee overall operations, making sure they meet the
objectives of the department or plant. Training in operating procedure, and in safety practice,
is usually required to make handling operation pay off as expected.
2
Finally, the definition of the material handling must contain an economic consideration.
Certainly the delivery of parts and materials to a specific time, it not completely meaningful
unless accomplished at an acceptable cost so that an adequate return is realized. Material
handling is a system or combination of methods, facilities, labour, and equipments for
moving, packaging and storing of materials to meet specific objectives. A materials handling
operation can be simple and small, and involve only few pieces of basic equipments. Or, it
may be large, complex or automated. Material handling equipment is generally separated into
four main categories.
Storage and handling equipment.
Engineered systems.
Industrial trucks.
Bulk material handling.
Bulk material handling is an engineering field that is cantered around the design of equipment
used for the handling of materials such as ores, coal, cereals, wood chips, sand, gravel and
stone in loose bulk form. It can also relate to the handling of mixed wastes. Bulk materials
handling plants and processes quite often require the elevation (lifting) of bulk materials to
other parts of the plant or process. Numerous technologies and equipment are currently
available for this purpose to the designer and practitioner. Generally they are classifying in to
three main categories.
Pneumatic conveyor or air lifter.
Conventional screw conveyor.
Bucket elevator.
Conveyor is almost universal in application. It can travel for miles at speeds up to 5.08 m/s
and handle larger amount of weight in metric tons with the help of belt. It can also operate
over short distances at speeds slow enough for manual picking, with a capacity of only a few
kilograms per hour. Generally they are use in inclined position and not preferable for vertical
transport. However, it is not normally applicable to processing operations, except under
unusual conditions. Belt conveyors inside the plant may have higher initial cost than some
other types of conveyors and, depending on idler design, may or may not require more
maintenance. However, a belt conveyor given good routine maintenance can be expected to
outlast almost any other type of conveyor. Thus, in terms of cost per ton handled, outstanding
3
economy records have been established by belt conveyors. However, these methods of
elevation can experience a range of problems and limitations, such as in case of:
Pneumatic conveying or lifting:
Relatively high operating costs e.g. blower and compressor
Product velocities and wear rates especially for dilute-phase conveying.
Screw conveying:
Relatively high operating speeds due to slippage between the screw flight and
particles and also due to the back-flow of material through the screw flight and
casing clearance,
Increased particle attrition,
Undesirable casing or screw contact.
Figure 1.1: Simple belt conveyor
(Source: www.enviro-abrassion.com)
4
Bucket elevator is a type of vertical or inclined transport equipment that efficiently moves
goods between floors, vessel or other structure. Elevator is generally powered by electrical
motors that either drive traction cables or counterweight system like a hoist or pump
hydraulic fluid to raise a cylindrical piston like jack. Generally it is preferred for short in
distance compared to belt conveyor. It is more preferable to transport the materials vertically.
The detail explanation of bucket elevator is given in next chapter.
Figure 1.2: Simple bucket elevator
(Source: www.swo-conveyors.com)
5
1.2. BUCKET ELEVATOR
Bucket elevators are the simplest and most dependable units for making vertical lifts. They
are available in a wide range of capacities and may operate entirely in the open or be totally
enclosed. The trend is toward highly standardized units, but for special materials and high
capacities it is wise to use specially engineered equipment. Main variations in quality are in
casing thickness, bucket thickness, belt or chain quality, and drive equipment. The main
purposes of bucket elevators are used to lift bulk materials from one height to another. They
are a reliable and well-proven piece of equipment. The various major parts of bucket elevator
are shown in figure.
Figure 1.3: Parts of simple belt bucket elevator
(Source: www.BEUMER.com)
Inspection
panel
Boot
pulley
Relief
vent Bridge tree
Take-up
assembly
Head
pulley Motor
Friction
material
Head
section
Hood
Belt
Casing
Boot
section
Boot Discharge
Bucket Boot
bearing
Short trucking Boot inlet
Adjustable
throat plate
6
The detail description of various parts of bucket elevators is discussed bellow. The major
components of belt bucket elevator are
Drive head
Bottom head
Inlet
Outlet
Buckets
Casing
Drive unit
Take up
Figure 1.4: Belt bucket elevator
(Source: www.motridal.com)
Drive head
Bucket
Inlet
Casing
Take-up
Drive unit
Or Motor
Outlet
7
Drive Head and Bottom Head: Drive head section made with high thickness steel sheets
heavily stiffened. Steel split upper cover easily removable for inspection and maintenance of
drive pulley or wheels. Dust or relief vent on top and inspection panel located at some height
of the outlet. Bottom head is made with high thickness steel sheets is equipped with a
removable bolted door for inspection and cleaning.
Inlet and Outlet: Openings prearranged for the connection with other machines; chutes lined
with wear resistant material when required.
Buckets: On the basis of the conveyed material characteristics the buckets are generally
made of:
Carbon steel
Wear resistant steel
Stainless steel
Plastic material
Buckets are made with bent and welded steel plates, properly reinforced with welded plates
in wear resistant material for heavy duty application, drawn or pressed for light materials.
The buckets are also available in various sections, which are listed below.
Square
V
Trapezoidal
Circular
Casing: It is the cover part of elevators which is made of welded and bolted sections,
designed to obtain a self supporting structure of the machine for the vertical loads. The
assembling sections are done by bolted flanges, with seals between each section. There is a
bolted door for easy bucket inspection and mounting.
Drive Unit: This configuration may vary depending on the application. The typical drive unit
for installed power of 22kW or more includes an electric motor, hydraulic coupling and right
angle gearbox with backstop and torque arm directly mounted on the drive shaft. Additional
8
electric motor for creeping can be installed, upon request, on the gearbox. As an alternative,
drive units can be equipped with a belt drive between electric motor and gear unit.
Take-Up: The gravity take-up system of the bucket elevators is equipped with additional
dust-tight seals between the casing and the guide of the idle shaft belt bucket elevators
realised for heavy duty application are equipped with a self aligning system which ensure the
safe parallel guidance of the pulley.
Method of Operation:
Bucket elevators operate by using an endless belt or chain on which rectangular buckets are
mounted. The belt or chain revolves between a top and bottom pulley and the buckets move
with it. At the bottom the buckets pick up product fed into the elevator boot and at the top the
product is discharged as the bucket turns downward over the head pulley.
1.3. CLASSIFICATION OF BUCKET ELEVATOR
Generally bucket elevators are classified in mainly two types.
Belt type bucket elevator.
Chain type bucket elevator.
Now a day there are many types of bucket elevators are available and each one is different
from other according to their feature, application, and design. The major classifications of
bucket elevators are as follows.
bucket elevator
according to
type of
discharge
positive
gravity
horizontal
centifugal
according
to types of
leg
single
twin
according
to types of
bucket use
single
double
depending
on load
low
medium
heavy
depending
on capacity
low
medium
heavy
9
1. Positive Discharge Bucket Elevator
These types of bucket elevators are widely used for elevating light, fluffy, fragile materials
like free flowing powders and granular products in a range of industries in vertical as well as
inclined position. Buckets are mounted at a well spaced interval, are loaded by digging
material from the boot or by feeding the material in to them. After passing over head wheels,
the buckets are inverted over the discharge spout, providing a positive discharge material.
Generally they have higher conveying capacity. Figure shows the typical diagram of positive
discharge bucket elevator.
Figure 1.5: Positive discharge bucket elevator
(Source: www.fmctechnologies.com and www.rexnord.com)
2. Gravity or Continuous Discharge Bucket Elevator:
In these types of elevators head shafts are fixed, the foot shafts takes up are screw type.
Gravity takes are available. This elevator consists of a series of steel made buckets mounted
on spigot pins between two chains or on the belt with the help of special types of screw. Also
some time the buckets are mounted continuously on the normally friction surface belts.
10
Continuous type steel buckets are used leaving minimum clearance between the buckets. The
buckets retain the material being carried and travelled vertically, until they are mechanically
tipped at discharge positions. Gravity discharge elevators supplied as close bucket discharge
type, central discharge type, or Idler wheel discharge. Generally a slow speed design gravity
bucket elevator is primarily installed for elevating large lumpy, free-flowing material,
sluggish material and abrasive material. Our standard units are usually chain driven, either
friction drive or toothed sprocket. These elevators offer reliability with minimum wear & a
positive discharge emptying of the bucket. The figure shows the vertical arrangement of
gravitational discharge bucket elevator.
Figure 1.6: Gravity discharge bucket elevator
(Source: www.integratedbulksystems.com.au and www.swrewconveyor.com)
3. Horizontal Discharge Bucket Elevator
These elevators are designed and engineered to conform to general practice in the handling of
grain. In particular they are found in flour mills and animal feed mills, where whole grain is
being transferred into intake silos. Also these types of bucket elevators are widely used for
11
elevating aggregate, hard rock, coal from mine in vertical horizontal as well as inclined
horizontal position. Head and foot shafts are provided with roller bearings. Buckets are made
of steel and mounted on the belt with special types of screw. Casing of steel are welded and
dust tight. The curve hood is designed for proper discharge of the grain. The boot can be
loaded from the front or back side or both. Generally they have higher conveying capacity.
Figure shows the typical diagram of horizontal discharge bucket elevator.
Figure 1.7: Horizontal discharge bucket elevator
(Source: www.ryson.com)
4. Centrifugal Discharge Bucket Elevator
Centrifugal elevators are the most common type of elevator installed to most industries
supplied in both belt type and chain type depending on material characteristic and the
capacity being elevated and in some case the feeding method of the elevator. Centrifugal
discharge type elevators are offered as boot take up and head take up. In this types of bucket
elevators buckets are mounted on chain or belt and will handle free-flowing materials with
small to medium size lumps. The standard inlet chute and standard curved bottom plate direct
the material into the buckets and reduce the “digging” action. The speed of the elevator is
12
sufficient to discharge the material by centrifugal force. The feed point is lower, loading is
simpler and fewer buckets are required than for the Continuous Type Bucket Elevator.
Buckets on chain or belt travel at speeds high enough to discharge materials by centrifugal
force as they pass around the head pulley or sprocket. Bucket spacing and speed is important
for centrifugal discharge bucket elevators. Usually buckets are made from malleable iron.
Generally these types of bucket elevators are more preferable in grain industries.
Figure 1.8: Centrifugal discharge bucket elevator
(Source: www.screwconveyor.com and www.go4b.com)
13
5. Twin Leg Bucket Elevator
The twin lagged or double trunk legging bucket elevator has been designed and engineered to
provide efficient high capacities for handling various grains, feeds, mill stock and similar free
flowing granular materials. The elevator is self-supporting with extra large heads and boot
pulleys. They are fabricated from heavy gauge steel and are dust and waterproof and with
provision for easy clean out. It is manufactured in many different sizes to suit individual
requirements. It has double trunk legging construction with connecting angles provided on
each 10 foot flange section. Vertical angle supports are included on taller units.
Figure 1.9: Twin legged discharge bucket elevator
(Source: www.screwconveyor.com, www.integratedbulksystems.com.au and www.rexnord.com)
14
6. Single and Double Bucket Elevator
The construction of these types bucket elevators are same as other types accept that the
number and types of buckets are use is different. The capacity of double bucket elevators is
more compare to single bucket elevator and also high capacity motor is required in operation.
The size of double bucket elevator is large compare to single bucket elevator since two
buckets are use in one raw as shown in figure. The double bucket elevators are used lift heavy
materials and also where, the higher output is required. Generally these types of bucket
elevators are used in aggregate plant, hard rock plant, cement plant where the lift of heavy
material is possible.
Figure 1.10: Single and double bucket elevator
(Source: www.screwconveyor.com and www.indiamart.com)
15
7. High or Super Capacity Bucket Elevator
Super capacity bucket elevators are a continuous discharge type with buckets mounted
between two strands of chain or on the belt. This type of elevator is used where higher
capacities, severe service or higher shaft centres are required. The high or super Capacity
Bucket Elevators are designed to provide efficient high capacities for handling various grains,
feeds, mill stock and similar free flowing granular materials. It is manufactured in many
different size stop suit individual requirements. It has double trunk legging construction with
connecting angles provided on regular interval flange section. Vertical angle supports are
included on taller units.
Figure 1.11: High or Super capacity bucket elevator
(Source: www.feedandgrain.com and www.screwconveyor.com)
1.4. APPLICATION OF BUCKET ELEVATOR
For stable work and application widely bucket elevator are used. By using this one should get
high Productivity. This bucket elevator is normally designed and made for metallurgy,
16
chemical industry, building materials, mine, pulp and paper industries, ports and terminal,
grain and vegetable oil, food, fodder, plastic and medicine related application. Bucket
elevator systems are used for the following industrial fields.
Cement factories: For lime, clay gypsum, clinker and cement additives like pyrite,
silicate, oxide etc
Environment and water treatment: Waste for combustion, biomass, sludge, ashes
etc.
Power plant: For coal, lignite and desulphurization product like gypsum, ashes,
sludge.
Fertilizers and Chemical: For raw materials and additives handling, phosphate,
nitrate.
Steelworks and Aluminium smelter: For coke, ashes, blast furnace slag, coke,
alumina, crushed bath, covers material.
Food industry: For sugar, flour, vegetables pulp, slaughterhouse waste etc.
Z type bucket chain material elevator is Suitable for lifting puffed food, fried food, nuts,
sugar, candy, hardware, medicines and so on. It is easy to operate fast transfer speed with low
noise. For grain or Seed application bucket elevator are used. This bucket elevator can be
equipped multi-channel explosion-proof mouth if required which can prevent dust explosion.
The system of speed monitoring, automatic running deviation alarm, anti-blockage alarm also
can be equipped to ensure the good running.
Reliable Quality Chain Bucket Elevator is designed and made for metallurgy, chemical
industry, building materials, mine, grain and vegetable oil, food, fodder, plastic and medicine
application. The life is long, inflow feeding, none excavating with hopper and there is few
extrusion and collision circumstance between materials. There is little materials sprinkling
during feeding and discharging to reduce machinery abrasion.
Structure Simple Bucket elevator is used for perpendicular transport the grain, powder and
disperse materials, and suitable for the oil, animal feed and chemical industry etc. This
Bucket Elevator is a fixed elevator categorized as feeding device of delivering powdery and
granular materials upward vertically. It has simple structure, smaller cover are, short
17
shipping route and low pollution. Wood chips are received from belt conveyor by a double
led centrifugal discharge bucket elevator and delivered to a distributed belt conveyor over
silos.
1.5. PRESENTLY INSTALLED BUCKET ELEVATORS IN ABROAD:
Bunge Russia recently opened a new oilseed extraction facility featuring Brock steel bins.
Figure 1.12: Bunge Russia – Oilseed bucket elevator
(Source: www.World-Grain.com)
Chief Industries installed two bins to increase storage capacity by 16,000 tonnes at this plant
in New Zealand.
Figure 1.13: New Zealand - Bins plant bucket elevator
(Source: www.World-Grain.com)
Bucket elevator
Bucket elevator
18
Cimbria recently installed bins with a combined storage capacity of 333,000 tonnes at seven
facilities in Egypt.
Figure 1.14: Cimbria (Egypt) - Bins plant bucket elevator
(Source: www.World-Grain.com)
Figure 1.15: Bahrain - Coke calcining plant
(Source: www.motridal.com)
Bucket elevator
19
Figure 1.16: Jordan - Fertilizer plant
(Source: www.motridal.com)
20
Chapter 2: DESIGN OF BUCKET ELEVATOR
2.1. BUCKET ELEVATOR GEOMETRY:
Pole Distance:
Figure 2.1: Diagram to calculate the pole distance
(Source: Spivakovsy, A.O. and Dyachkov, V.K. (1985), Conveying Machine, MIR Publication,
Forth Edition)
As a bucket revolve on the pulley, the resultant R of the forces P and F varies in magnitude
and direction. If however, the resultant force vector is prolonged to the vertical line passing
through the pulley centre, it turns out that at any position of the bucket, and vector R
intersects the vertical in one and the same point B to the pulley centre O is called the pole
distance. The pole distance is denoted by hP.
Bucket Unloading:
At lower speed of the pulley, the effect of the gravity force on unloading become stronger
and hP increases. When hP is not larger than rP the pole is inside the pulley circle (figures 2.2a
and 2.2b), the centrifugal force is much higher than the gravity force and hence bucket