Design and Analysis of a Timing Belt Elevator System. Final year report project

Table of content

Chapter 1 Introduction
1.1 Background of the study
1.2 Problem statement
1.3 Objectives
1.4 Scope and limitation of the study
1.5 Working principle of the system
1.6 Outline of the project

Chapter 2 Literature review
2.1 Introduction
2.2 Timing belt elevators
2.3 Project overview
2.4 Design of elevators
2.5 Elevator installation
2.6 Weights and loads
2.7 Basic system for a traction motor elevator
2.8 Common parts of traction motor elevator
2.9 Components of elevator system
2.10 Elevator door
2.11 Elevator traffic calculation
2.12 Variable frequency low-speed high torque
2.13 Optimization of elevator evacuation considering potential overcrowding
2.14 PID control of maglev guiding system for linear elevators
2.15 Seismic performance of an elevator
2.16 Design and behavioural issues associated with building use
2.17 Summary

Chapter 3
3.1 Introduction
3.2 Project flow chart
3.3 Critical overview
3.4 Project cost
3.5 Project work plan
3.6 Components used in the fabrication of the timing belt elevator
3.7 Machines and instruments used in the fabrication process
3.8 The fabrication process
3.19 Materials used in the fabrication
3.10 Design criteria for the original elevator system
3.11 List of parameters
3.12 Test and analysis

Chapter 4
4.1 Analysis
4.2 ANSYS solution
4.3 Total deformation on the elevator car
4.4 Equivalent stress analysis on the elevator car
4.5 Total deformation on Aluminium alloy rod
4.6 Calculation for the elevator force
4.7 Calculation for the torque of the DC motor
4.8 Calculation for round trip time
4.9 Experimentation to know the amount of load the elevator can sustain
4.10 Calculation for impact force
4.11 Results
4.12 Discussions

Chapter 5
5.1 Conclusions
5.2 Limitations
5.3 Recommendations

References

Chapter 1 Introduction

1.1 Background of the study

During the 3rd Century BC, there have been an earliest kind of elevators which has been existing then. Many sources do operate this kind of elevators during those days like human, animals and automated water wheel power. The introduction of the counter weight elevator later became introduced in the year 1743. The counter weighted elevator introduced then was also operated with man power which built for King Luis XV. Another system of usage of this elevator later became introduced during the middle of the 19th century by the elevators builders and the inventors, this usage system introduced is the steam operating system whereby steam is used to operate this elevators. The main importance of this type of elevators is that it was used to transport materials to warehouses, mines and factories. A safety device was later installed in the elevator which helps in safeguarding the elevator from falling off. (Gravis E. Ottis, 1852).

The purpose of this case study is to apply the fundamentals of systems engineering to the operation of an elevator system. The high-technology representation of how this elevator system works will be shown during the process of this final product. The elevator system gives easy understanding when viewed or accessed, its concept is always seen in the product. An elevator also has single vertically movement elevator system which helps in serving individuals that uses it in its simplest form. There is a button which is fixed at the elevator lobby, any individual that wants to operate on the elevator will have to press this button for easy access (Otis, 2008).

This lobby is simply explained as the area in the building which is adjacent to the elevator at a particular level. The operator will have to press any of the button in the elevator where the either button represents the upward and downward direction as the user desires to move on. When this button is been pressed, a particular responds is been given immediately through the path of predetermined travel route or the elevator cycle. If there is an elevator that is idle without user request, the elevator will move immediately to the present floor the user has pressed the button in either ways. The elevator will have to stop if there is another user in the same direction that requested for the elevator. This simply means that if a particular user presses the downward button for the elevator to locate him or her at a particular floor and there are other user that wishes to use the elevator but in a different floor before the first user, the elevator will have to stop first and pick the last user that presses the button because both are in same direction though different floor. Once all the request made by users has been responded by the elevator, the elevator will now have to reverse to the direction according to the users desires initially. If the elevator stays long without any user request, it will just go to the last or bottom floor.

This elevator system is mainly for a light weight operation, there is no essence to consider or work on the hydraulic elevator system. The main product would be considered to be focused on a timing belt or geared elevator system. An example of the elevator system is shown in Figure 1.1.

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Figure 1.1: An example of an elevator in a building (Otis, 2008)

For this project, the main focus would be channeled on a timing belt elevator system because of reduction in cost and time factor during fabrication and project research which is been considered.

1.2 Problem statement

This elevator has encountered several problem which has resulted to different incidents during operation. Due to the problem in this elevators, complaints from different clients have been gotten and such problems are inability to maintain the elevator properly and overlook of so many problems from the production engineer that seems minor that causes major problems and incident, from the estimation of death caused by the crash of the elevator, 25% of people dies every year due to the crashes caused by the elevator while 65% are the injured ones. As of the calculation estimated, it was also noticed the out of the 10000 engineers and workers that installs the elevator, 244 of them has succumb to death with other tangible number have encountered serious and brutal injury. This simply denotes that almost 30-40 number of people do die each day as a result caused by the bad installment or repair of the elevators which can also be caused by the material used. So many individuals has always been in phobia because of the incidents encountered by the elevators and have chosen to use the stairways instead.

Today, we can see different kinds of elevators in the shopping malls, offices, story buildings, schools and tourist buildings, most of this elevators are installed by different companies and firms, some of this firms employs are not well trained and they will end up installing the elevator in a bad way which causes incidents to the individuals using it. This is why there was an introduction of a well-engineered elevator box and a better elevator structure. (Riichard J. Botting, 2008).

1.3 Objectives

In line with the above motivation, the objective of this study are set as follows.

I. To develop a prototype of a timing belt elevator system.
II. To fabricate an elevator system that will respond to each button call at every floor.
III. To fabricate an efficient elevator door.

1.4 Scope and limitation of the study

This project will be experimentally tested by assigning loads of different weights and the fabrication will be done by merely demonstration of the working operation of the timing belts elevator system mechanism. This work best defines the advantages which has been achieved from a review done using a gearless elevator system machine. In this project, an intermediate gearing is not needed, therefore making the motion of this elevator system to be basically focused with the use of a DC motor whereby a timing belt sheave is been mounted also. This elevators are main characterized by operating on a low speeds and high torques. Due to the low speed operation and high torques of this elevator, a very large diameter shaft is needed in order to support the elevator system and these are generally of a massive proportions which is relative to their output power. Larger sizes needs to be mounted on a substantial bedplate, and their weights and sizes often creates handling problems during installation in confined spaces and access to where they are most commonly used.

1.5 Working principle of the system

The working principle is all about how the object or machine works. In this case the working principle of this elevator is basically on the pulley system. When a user or passenger presses an elevator button in any direction, the elevator button sensor sends a message or a request to the elevator control system, which then replies by identifying the destination floor of the user. When any new request comes, this new request is added to the list of floors to visit. If the elevator is stationary, the system determines in which direction the system should move in order to service the next request. The control system renders commands to the elevator door to close, when user presses the button for the door to be close. When the door has been closed, the system then passes on the request to the motor to start moving the elevator, either in up and down direction, based on its user direction.

When the elevator moves between floors, the arrival sensor indicates that the elevator is approaching a floor and notifies the system to stop the elevator and open the door of the elevator system. Figures 1.4 shows the elevator’s dispatching strategy.

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Figure 1.2: Elevator dispatching strategy

Therefore this elevator is considered as the best working elevator that suits most companies, malls and houses and it is cheap to afford also and will be considered to be more injury free when compared with other existing elevators.

1.6 Outline of the project

This case study contains six chapters which will be discussed in details, each chapter have its own outline as the case study will be. In chapter one of this case study contains the project introduction in line with the background study and the problem statement stating the outcome problem this system had been undergoing in the globe and also the scope and limitation is also included with the objective which this case study is focusing on. The working principle of the elevator system is also explained in details. In chapter two case study explained the different literature review based on the components and the controller of the timing belt elevator system from different author’s perspective. Chapter three of this case study explained the methods applied to achieve the objectives which is been listed in chapter one. Design diagrams and fabrication process of this elevator system is explained in details in this chapter. Chapter four presents analytical calculation and finite element analysis of the timing belt elevator system, Ansys is the software application used to achieve the finite element analysis. The final chapter which is chapter five of this case study entails the conclusion and recommendation of the timing belt elevator system.

Chapter 2 Literature review

2.1 Introduction

Elevators are the most commonly used mode of vertical transportation in modern buildings having more than one story. More than a decade ago, it was estimated that there were more than half a million passenger elevators in the United States transporting people day and night every day of the year (Swerrie, 2009). This elevator is very common to us nowadays. People makes use of it in everyday life to transport goods and themselves from one vertically high building having different floors to another such as shopping centres, offices, hotels and others. This elevator is very useful in the globe because of the fastest movement of people and goods to different floors at a particular given time. In the United States, many of this elevators are been located at the urban areas in highly seismic regions. In the year 1989, close to twenty thousand of elevators were affected by the Loma Prieta earthquake basically in California. The federal buildings and private residence were not included in the above mentioned figures. This simply implies that the elevator can be vulnerable when a mighty storm shakes occurs in the building.

Emphasis would be also laid on the design of elevators, the requirement of elevators which will be design optimization of timing belt elevators and also development stages will be recalled, review on the writers view and understanding about elevators will be also used for more research and know how the elevators is been operated on. Figure 2.1 presents the interface between user and system elevators ((Otis, 2008).

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Figure 2.1: Interface between user and system elevator (Otis, 2008)

Table 2.1 illustrates different previous researches done about the elevator system and various results gotten as used in this chapter.

Table 2.1: List of previous studies on elevators

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Figure 2.2 presents the subjective of the elevator system as used in this chapter.

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Figure 2.2: Elevator system

2.2 Timing belt elevators

This elevator is a transportation machine which pulls the elevator box by cables or timing belt attached to it. The end of the timing belt is been attached to a component in the elevator system. In this elevator system, it has major ends by which one end is been attached to the counter weight while the other end is been attached to the top of the elevator box. A sheave which is a pulley with grooved ridges helps in holding the timing belts in between the elevator box and the timing belts are looped in it. In the elevator system is a motor which is been connected, the motor helps in turning the sheave in clockwise and anti-clockwise direction. The direction of the elevator system is based on the clockwise and anti-clockwise direction, when the sheave rotates in a clockwise direction the elevator rises, and when it rotates in an anti-clockwise direction the elevator lowers. A guide rails is also installed in the elevator which helps it to control the swinging of the elevator when moving in upward or downward direction. The figure 2.3 indicates the view of the timing belt elevator system (Gratis, 2011).

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Figure 2.3: The timing belt elevator system (Gratis, 2011)

2.3 Project overview

The figure 2.4 shows the floor where passengers desire to visit. This elevator system moves in upward direction or downward direction as desires by the passengers. The sensor which is placed in the elevator is the arrival sensor which indicates the arrival the elevator on any floor respectively. A button is used to fix the elevator car in movement to its respective floor which called the floor button. A floor lamp is also indicated in the elevator which helps to detect the elevator floor, the elevator consists of a direction lamp which shows the direction of the elevator movement based on the direction the passenger presses which can either be upward or downward direction. The elevator button is responsible for the movement of the elevator car either in upward or downward direction (Nakamura, 2012).

The direction of the elevator when the elevator button is been pressed is for determining the either direction of upward or downward direction in the elevator. The DC motor in the system helps in moving forward and reversed direction in other to move the elevator in either upward or downward direction. The door of this elevator system is a very essential part in the elevator system.

This elevator door allows passengers to enter and leave the elevator whenever it stops in a particular floor as operated by the passengers. The sensor that indicates arrival indicates immediately the elevator arrives at a particular floor and the elevator will stop for the passengers to enter or exit the elevator car as shown in Figure: 2.4 (Williams S. Pretzer, 2013).

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Figure 2.4: An elevator overview (Williams S. Pretzer, 2013)

The Elevator button is used for moving the elevator car either in upward and downward direction. Based on the direction pressed on elevator switch, the elevator car is moved either in upward and downward direction. The D.C. Motor is another important component of an elevator system. Based on the switch pressed, the D.C. Motor either moves in forward and reverse direction to move the elevator in either upward or downward direction. The door of the elevator system is one of the important factors of elevator system. When elevator car stops in particular floor, the door of the elevator is opened for passenger to exit and enter the elevator car. Arrival sensor is used in every floor, for detecting the elevator car. When a particular car is reached to the particular floor, this arrival sensor detects the elevator car and stops that car.

2.4 Design of elevators

The elevator system consist of a platform which can be pushed or pulled by any mechanical application. The recent type of elevator is designed with a room like box which is known as the elevator car. The car in the elevator room box is fixed on the platform which has an enclosed space known as the shaft or hoist way (Friedland, 2012).

During the olden days when elevator was first invented, the elevator system was then powered by the use of steam and water hydraulic pistons or by manually operation using the hand. In a traction type of elevator, the car is been pulled by the application of rolling steel timing belts over a deeply grooved pulley commonly known as the sheave. The counterweight in the elevator helps in balancing the weight of the car. At times, two elevators may be moving simultaneously opposite to each other, and they now act as each other’s counterweight. There is always a friction force which acts in between the timing belts and the pulley, this friction furnishes the traction that made the elevator have its type of name. Basically, the timing belt elevator is the combination of both timing belts and bearing to raise and lower cars. Some components were added in the recent innovation of the elevator which include the geared motors, machine, room less rail mounted gear machines and the microprocessor controls. The technology which was used in this new installation depends on a variety of factors. Basic economics were to be considered by making a multi production of this elevator components, it is been considered that each building has its own style and requires what is been needed like the floors number, measurement of the wall and others (Otis, 2008).

2.5 Elevator installation

According to Jayasuriya and Kurunegala (2010) this installation comprises of a hoist way cross across multiple levels of parking floors. This will form an opening on each portion to provide the access for the hoist way to bring up the carriage. The opening at any floor and elevator platform creates a drive way for the hoisted vehicle to drive in to the desired floor. Moreover, the hoist way consists of a pair of rails apprehended on two structure beams inclination connecting to the building structure. Therefore the elevator platform travels along the rail track lengthen through multiple of parking floors between top and the lowest parking floor.

Jayasuriya and Kurunegala (2010) also describes that the elevator platform is maintained in horizontal position, so that the vehicle from any floor could be driven in and out of the elevator when it reaches the designated floor.

The elevator platform and the floor ledge at all level will be keeping a close tolerance so driven can access to parking spaces when they have reached their parking levels.

Each hoist way has a pair of constructed rails which is parallel to another that keeps the elevator and the counter weight from swaying or twisting during their movement. The safety system will also comprise to stop the elevator whenever there is an emergency. Like any other traction cable elevator system works, the elevator is provided with braking system and safety that grab onto the rail when the platform moves too fast and whenever required stopping. At the bottom shaft of the elevator and counter weight, heavy-duty shock absorber systems will be applied to soften the elevator system landing (Adak, M.R, 2012).

The parking structure may comprise with a stair way, elevator or escalator to allow the driver to return to ground station after loading the vehicle to the parking floor and vice versa. Similarly, such parking conveyance can be adapted to a multipurpose building where in the building structure is a combination of shopping malls, apartment or any other utilities (Thumm, 2012)

2.6 Weights and loads

Janovsky and Horwood (2012) examined the elevator will be driven on the wheels along rails, so that, the weights of the elevator and load will be distributed on the rails. While the elevator is driven due to traction motor connected by the cables secured to the top of the elevator. The traction pulley will drag the cables passing over it and carries the counter weight hanged on to another pulley. The cable end will be a stationary grip at a higher level. The counter weight is located in a vertical hoist-way which situated on a separate rail system. The counter weight will also travel in opposite direction at the half speed of the elevator. As the platform goes up, the counter weight goes down, and vice versa. This way, the weight of the elevator is balanced by the counterweight, which is actually higher than the weight of the elevator platform. This action is powered and controlled by the traction machine which is an electric motor.

2.7 Basic system for a traction motor elevator

The most popular elevator design is the timing belt elevator. In timing belt elevators, the car is raised and lowered by the traction steel belts rather than pushed from below. The timing belts are attached to the elevator car around a sheave. A sheave is just a pulley with a groove around the circumference. The sheave grips the hoist timing belts, so when the sheave is rotating, the timing belts will move too (LU, Y.F, 2011).

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Figure 2.5: Elevator sheave (Schindler, 2010)

The sheave is connected to an electric motor. When the motor turns one way, the sheave raises the elevator. And when the motor turns the other way, the sheave lowers the elevator. In gearless elevators, the motor rotates the sheaves directly. In geared elevators, the motor turns a gear train that rotates the sheave. Typically, the sheave, the motor and the control system are all housed in a machine room above the elevator shaft (Schindler, 2010).

The timing belts that lift the car are also connected to a counterweight, which hangs on the other side of the sheave. The counterweight weighs about the same as the car filled to 40% capacity. In other words, when the car is 40% full, the counterweight and the car are perfectly balanced (Todorov, 2014).

The purpose of this balance is to conserve energy. With equal loads on each side of the sheave, it only takes a little bit of force to tip the balance in one way or the other. Basically, the motor only have to overcome friction; the weight on the other side does most of the work. To put it in another way, the balance maintains a near constant potential energy system as a whole. Using up the potential energy in the elevator car by letting it descend to the ground, builds up the potential energy in the weight, the weight rises to top of the shaft. The same thing happens in reverse when the elevator goes up. The system is just like a see-saw that has an equally heavy load on each end (May, A.M , 2012).

Both the elevator car and the counterweight ride on guide rails along the sides of the elevator shaft. The rails keep the car and the counterweight from swaying back and forth. They also work with the safety system to stop the car in an emergency.

2.8 Common parts of traction motor elevator

2.8.1 Geared traction motor

Hill, R.J (2011) claimed there are two basic types of elevator systems, Traction and Hydraulic. Because they differ in the way they operate, some of their safety systems differ as well.

In traction elevator systems, the car is raised and lowered by the traction steel belts. The timing belts are attached to the elevator car, and looped around a sheave. A sheave is just a pulley with grooves around the circumference. The sheave grips the hoist timing belts, so when the sheave rotates, the timing belts moves too (Kang, P. 2010).

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Figure 2.6: Elevator traction motor (Otis, 2009)

Emadi et al. (2008) described that the sheave is connected to an electric motor or traction motor. Traction motor is an electrical type of motor that runs the main rotational torque of the machine. This traction motor is commonly used in the electrically powered rail vehicles like electric locomotives and electric multiple units in other various vehicles such as conveyors.

In geared elevators, the motor turns a gear train that rotates the sheave. Basically, the sheave, the motor and the control system are all situated in a machine room above the elevator shaft. Geared traction machines are driven by AC or DC electric motor. Geared machines use worm gears to control mechanical movement of the elevators cars by rolling steel hoist timing belts over a driver sheave which is attached to a gearbox driven by a high speed motor (Alulanko et. al 2012)

Figure 2.7: Inclined cable car system used in Gwynedd, Great Britain

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Comparing the traction and the hydraulic system, the traction elevator has a higher speeds and can travel much faster than the hydraulic elevator. It can also be used to hoist to a much higher level and can be installed in any multi-storey buildings. The elevator can also provide much smoother rides comparing to the hydraulics which are slower and uneven when travelling. The efficiency by using the traction motor is much better comparing towards the hydraulic system (Bjorni, O. 2011).

2.8.2 Wire in timing belt elevator system

Range of high carbon wires for elevator timing belt application according to EN-10264-2 or according to customer specification. Mainly bright phosphate wire. (Redrawn galvanize wire available as well). Table 2.2 presents the technological features of the wire used in this timing belt elevator system.

Table 2.2: Technological features

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2.8.3 Counterweight

Essentially, most traction motor for the elevator will have counterweight for balancing purpose. The weight of the counterweight will facilitate the elevator to transport loads from floor to floor. This also plays important roles in transporting a range of loads so that the elevator can be supported in travelling from lowest floor to the highest. Most common counterweight should be a pile of organized metal plates that will travel vertically ascend and descend in its own shaft. Means it is situated separately from railway for the elevator (Hiraoka, 2012).

2.9 Components of elevator system

Elevators consist of complex structural, mechanical, and electrical components. Janovsky’s monograph (2012) gives a description of the engineering detail of elevator systems. The main components of a typical traction elevator are shown in Figure 2.5. The components related to the rail-counterweight system are explained briefly here. The central and most visible component of an elevator is the passenger car. The car frame, consists of the upper crosshead beam, two vertical uprights (stiles) joining upper and lower members, and lower safety plank, provides the supporting structure for the car. The suspension Timing belts are attached to the crosshead beam. The safety plank supports the car platform, on which passengers or other loads rest during travel. A pair of guide rails is placed on two opposite sides of the car, guiding the car during its vertical motion. The weight of the car and part of its load is balanced by the counterweight. The counterweight consists of steel frame and stacked fillers or weights secured by two or more tie-rods. These weights fill up to two-third of the height of the counterweight. Both passenger car and counterweight are connected through traction timing belts that pass through traction system at the top of the hoist way consisting of driving sheaves and electric motor. Similar to the passenger car, the counterweight is also guided by two guide rails along its sides during the vertical motion (Hagura et. al 2013).

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