DESIGN OF A DEVICE TO CONNECT A WHEEL CHAIR WITH A SHOPPING
CART
A Project
Presented to the faculty of the Department of Mechanical Engineering
California State University, Sacramento
Submitted in the partial satisfaction of
the requirements for the degree of
MASTER OF SCIENCE
in
Mechanical Engineering
by
Parshu Ram Reddy Kontham
SUMMER
2012
DESIGN OF A DEVICE TO CONNECT A WHEEL CHAIR WITH A SHOPPING
CART
A Project
by
Parshu Ram Reddy Kontham
Approved by:
____________________________________, Committee Chair
Akihiko Kumagai
_______________________
Date
ii
Student: Parshu Ram Reddy Kontham
I certify that this student has met the requirements for format contained in the University
format manual, and that this Project is suitable for shelving in the Library and credit is to
be awarded for the Project.
___________________________________, Department Chair
Susan L. Holl
Department of Mechanical Engineering
iii
______________
Date
Abstract
of
DESIGN OF A DEVICE TO CONNECT A WHEEL CHAIR WITH A SHOPPING
CART
by
Parshu Ram Reddy Kontham
People with disability have to face a lot of problems in their day-to-day life due to the
flexibility issues. One such issue is using the shopping cart in the grocery stores. Using
shopping cart becomes very difficult, as they have to control the movement of the wheel
chair and shopping chair at the same time while placing the grocery in the shopping cart,
which is an extra burden on the user. They would have to constantly control the
movement of the cart, as there would be lot of obstacles in the store which becomes a
very big problem for the user.
The aim of my project is to design a device to connect a wheel chair with a
shopping cart. The device would be designed in such a way that the user would be able to
connect the wheel chair with the shopping cart sitting in the wheel chair without anyone’s
help. This would give them that flexibility to do the things on their own instead of
depending on others. This would also help them to place the grocery in the cart easily as
the length of the device is smaller than the length of the average arm. The user does not
have to apply a lot of effort in controlling the movement of the wheel chair and shopping
iv
cart as the shopping cart would act just like an extension of the wheel chair, which makes
it very easy to control. The device is portable and the cost would also be very cheap as
the individual parts used in the device are easily manufactured.
____________________________________, Committee Chair
Akihiko Kumagai
_______________________
Date
v
ACKNOWLEDGEMENTS
I would like to thank Dr.Yong S.Shu and Dr. Akihiko Kumagai for their guidance and
support in completion of my project. My project would never have turned out to be what
it is today if not for their guidance and support. I would like to thank the whole
Mechanical engineering department at California State University, Sacramento for their
support in completing my Master’s in Mechanical Engineering. I would also like to thank
my family for their support.
vi
TABLE OF CONTENTS
Page
Acknowledgements
vi
List of figures
viii
Chapter
1. INTRODUCTION
1
2. DESIGN INTENT
3
2.1 Design Details
3
2.2 Initial Designs
4
2.3 Final Design
20
3. ANALYSIS
30
3.1 Finite Element Analysis of Attachment Device
30
4. CONCLUSION
36
4.1 Conclusion
36
4.2 Future Work
36
Appendix Drawing Set
37
References
42
vii
LIST OF FIGURES
Page
Figures
1. Figure 2.1 Assembly showing the device attached to the shopping cart and
wheel chair
4
2. Figure 2.2 Assembly of the device with specially designed latch and
cylindrical shaft with handle
5
3. Figure 2.3 cylindrical shaft with handle
6
4. Figure 2.4 Different views of cylindrical shaft with handle
7
5. Figure 2.5 specially designed latch with spring
8
6. Figure 2.6 Different parts of the specially designed latch
9
7. Figure 2.7 Different views of inside jaw
10
8. Figure 2.8 Different views of outside jaw
11
9. Figure 2.9 Different views of sliding jaw
12
10. Figure 2.10 Latch connecting the device to the cart
13
11. Figure 2.11 Assembly showing the device connecting the wheel chair and
shopping cart
15
12. Figure 2.12 Assembly of the attachment device 2
16
13. Figure 2.13 Pedal mechanism with clamp at one end and locking
mechanism on the other end
17
14. Figure 2.14 Cylindrical shaft with clamps on either end
18
15. Figure 2.15 clamp connecting the device to the cart
19
viii
16. Figure 2.16 Assembly showing the device connecting the wheel chair and
shopping cart
21
17. Figure 2.17 Assembly of attachment device 3
22
18. Figure 2.18 Cylindrical rotating shaft
23
19. Figure 2.19 Screw Clamp for connecting the device to cart
24
20. Figure 2.20 Different views of clamp with rotating handle
25
21. Figure 2.21 Clamp with rotating handle for connecting the device to the
wheel chair
26
22. Figure 2.22 clamp connecting the device to the cart
27
23. Fig 2.23 clamp with rotating handle connecting the device to the
wheel chair
28
24. Figure 3.1 Stress deformations due 200N force and 40 N-M torque
30
25. Figure 3.2 Strain deformations due 200N force and 40 N-M torque
31
27. Figure 3.3 Displacement deformations due to 200 N force 40 N-M torque
32
28. Figure 3.4 Stress deformations due to 250 N force and 45 N-M torque
33
29. Figure 3.5 strain deformations due to 250 N force 45 N-M torque
34
30. Figure 3.6 Displacement deformations due to 250N force 45 N-M torque
35
ix
1
Chapter 1
INTRODUCTION
1.1 Introduction:
People with disability face a lot of problems in their day-to-day life as they have
to put in double effort to do the things which an abled body person is able to do.
Designing a device which can be easily attached, portable and cheap brought this
project into existence. The main aim of this project is to design a device to attach a wheel
chair with a shopping cart with the user sitting in the wheel chair and without anyone’s
help, should be able to carry it around with them and is affordable. The length of the
device should be less the length of the average arm as the user has to put the grocery into
the shopping cart without and difficulty. The user will be able to control the movement of
the shopping cart with wheel chair itself as the shopping cart acts just like an extension of
the wheel chair once the device is attached. The user will not have to apply lot of
effort to move the cart as it only needs a little push which will be provided by the
movement of the wheel chair. There are several other devices which have be designed
for the same purpose such as
1. Development of a Device for Attaching a Wheelchair to a Shopping Cart or Baby
Stroller [1]. The device consists of two flat aluminum plates, each sitting on three
small swiveling casters and housing one of the rear wheels of the cart [1].These
plates lift the back wheels of the cart which allows the user to control the motion
of the cart. Connecting this device to the cart by the user would be difficult
2
as it would take a lot of effort, so the user will have to take the help of some one
else to attach the device to the cart.
2. Wheelchair attachable shopping cart [2]. Two attachable arms that are moveable
horizontally and vertically attached to the each foot rest support in a low position.
The horizontally and vertically movement of the attachable arms permit the cart to
be attached to different wheelchairs. The attachable arms have ends that are easily
attached and detached from the foot rest supports. In one embodiment, the
attachment arms have a U-shaped end that fits around the foot rest support and is
held in place by a strap [2].
In device 1 connecting the device to the cart by the user is difficult and in
device 2 the device is attached at angle to the cart and is attached by a strap to the
wheel which makes is difficult for the user to control the motion of the cart. In my
design I have taken these two points into consideration and have worked on them
to make the device more efficient and easy to use. The project report starts with
Introduction in chapter one. Design details are discussed in chapter two. FEA analysis
details are discussed in chapter three. Chapter four conclusion.
3
Chapter 2
DESIGN INTENT
2.1 Design details:
1. Model an attachment that helps to connect a wheel chair with a shopping cart.
2. The attachment must be designed such that it would allow the user to connect the
attachment to the wheel chair and shopping cart without any difficulty
3. The attachment consists of a cylindrical shaft and two fasteners.
4. The user will be able to connect the attachment from the wheel chair to the cart
by rotating the shaft and by using a small handle on other side to the wheel chair.
5. Two sets are fasten to the sides and a third parallel to the ground that nullifies the
vector force across the chair to the cart.
6. The material used is AL alloy 6061. AL 6061 is used as it is light in weight ,
corrosion resistant. The material has elongation (stretch before ultimate failure)
of 25–30 % and is also used in making similar parts for automobiles
which makes it the preferred material [3].
7. The size of the device is smaller than an average arm which makes is easier for
the user to drop things into the cart.
8. It is a four part device and all the parts can be machined easily from a bar stock
of AL.
9. The cost of the device would be affordable to the common user.
10.
FEA should be done on the device.
4
2.2 Initial Designs:
Before deciding upon the final design I had to try several design as the design had to
fulfill all the requirements and assumptions that have been taken into consideration
for designing the device.
Attachment device 1: Cylindrical shaft with handle and specially designed clamp
for controlling the movement of the shopping cart.
Figure 2.1 Assembly showing the device attached to the shopping cart and wheel chair.
The above figure shows the assembly where the attachment device connects the wheel
chair with the shopping cart. The shopping cart and wheel chair models in the assembly
5
are only taken as reference as the FEA analysis has to be done on the device by taking
into consideration the forces acting at different position of the device when it is attached
to the wheel chair and shopping cart.
Figure 2.2 Assembly of the device with specially designed latch and cylindrical shaft
with handle.
The above figure shows the assembly of the attachment device with specially designed
latch mechanisms so that the device can be attached to the shopping cart without and
difficulty.
6
Figure 2.3 cylindrical shaft with handle.
The above fig cylindrical shaft with handle and cylindrical shaft the individual parts
of the attachment device.
7
Figure 2.4 Different views of cylindrical shaft with handle.
8
Figure 2.5 specially designed latch with spring loaded locking mechanism.
The above fig shows the specially designed latch with spring loaded locking mechanism
in the sliding jaw which allows the latch to open and close.
9
Figure 2.6 Different parts of the specially designed latch
The above figure shows individual parts of the specially designed latch. The latch is
designed as the device has be connected to shopping cart at a position where there would
be shopping cart mesh.
10
Figure 2.7 Different views of inside jaw.
11
Figure 2.8 Different views of outside jaw.
12
Figure 2.9 Different views of sliding jaw.
13
Figure 2.10 Latch connecting the device to the cart.
The above figure shows the latch connecting the device to the cart. The latch has two
springs in the sliding jaw which is connected to the outside jaw using these spring . These
springs help the latch to open and close. This helps the latch to hold the cart in place. .
Design Flaws:
1. In this design the user has to control the motion using the cylindrical shafts with
handles.
2. Controlling the motion would be difficult as the length of the device is more than
the length of the average users arm.
3. The fastener used to clamp the shopping cart is a specially designed part as it is
14
positioned at the mesh part of the shopping cart.
4. It would be difficult to machine the specially designed part which in turn would
increase the cost.
5. The device is only attached to the sides which makes it difficult to control the
motion of the shopping cart.
15
Attachment device 2: Pedal mechanism with a rod to lift the shopping cart above the
ground and cylindrical shaft and clamps to attach the device to the wheel chair.
Figure 2.11 Assembly showing the device connecting the wheel chair and shopping cart.
The above figure show the assembly where the devices connects to the wheel chair and
lift the shopping cart to a certain height above the ground. The wheel chair and shopping
cart models are only used as references to do the analysis of the part.
16
Figure 2.12 Assembly of the attachment device 2
The above figure shows the assembly of the attachment device which connects the wheel
chair with the shopping cart.
17
Figure 2.13 Pedal mechanism with clamp at one end and locking mechanism on the other
end.
The above figure shows the Pedal mechanism with clamp at one end to lift the shopping
cart and locking mechanism at other end to lock the pedal mechanism once the cart is
lifted to a certain position.
18
Figure 2.14 Cylindrical shaft with clamps on either end.
The above figure shows two cylindrical shaft and two clamps on either ends which would
be attached to the wheel chair.
19
Figure 2.15 clamp connecting the device to the cart.
The above figure shows the clamp lifting the cart in the air at one end and the locking
mechanism which controls the rod movement that is used to lift the cart above the ground
to a certain height. The clamps on each end of the cylindrical shafts are used to connect
the device with the wheel chair.
20
Design Flaws:
1. In this design the motion is controlled by lifting the back wheels of the shopping
cart above the ground using the device.
2. Lifting the shopping cart would make very difficult for the person sitting in the
wheel chair to control the motion as it is very unstable.
3. The design of the device is very complicated and machining of the parts would be
very difficult.
4. Due to complexity of the design the cost of the device would be considerably be
very high.
5. It is very difficult to control the motion of the shopping cart, moreover the
person sitting in the wheel chair has to apply lot of force on the pedal in order to
lift the shopping cart above the ground.
2.3 Final Design:
Attachment device 3: Cylindrical rotating shaft with two clamps fastened to the
shopping cart by rotating the cylindrical shaft on one side and the other by rotating
the handle on the other side.
21
Figure 2.16 Assembly showing the device connecting the wheel chair and shopping cart.
The above figure shows the assembly where the device connects the wheel chair with the
shopping cart. The device is attached at three different places. One on each side and the
other parallel to the ground.
22
Figure 2.17 Assembly of attachment device 3
The above figure shows the assembly of the device used to connect a wheel chair with
shopping cart.
23
Figure 2.18 Cylindrical rotating shaft.
The above figure shows cylindrical rotating shaft which is used to fasten the clamp which
attaches to the shopping cart.
24
Figure 2.19 Screw Clamp for connecting the device to cart.
The above figure shows the clamps which is used to connect the device to the shopping
cart.
25
Figure 2.20 Different views of clamp with rotating handle.
26
Figure 2.21 Screw type Clamp with rotating handle for connecting the device to the
wheel chair.
The above figure shows the clamp with rotating handle which connects the device with
the wheel chair by fastening the clamp.
27
Figure 2.22 clamp connecting the device to the cart.
The above figure shows the clamp connected to the cart using the cylindrical shaft which
acts like a fastener and allows the user to fasten the device to the cart sitting in the wheel
chair.
28
Figure 2.23 clamp with rotating handle connecting the device to the wheel chair.
The above figure shows the clamp with the rotating handle connecting the device to the
cart. The device is connect to the cart by rotating the handle which fasten the clamp to the
cart.
29
Design advantages:
1. Length of the attachment device is less than the average length of the arm which
helps the user to easily control the motion.
2. The parts of the attachment device can be easily machined without any difficulty.
3. The cost of the device would be very less compared to my initial designs.
4. The device can be easily attached to the wheelchair and shopping cart by the user
without anyone's help.
HOW THE MOTION IS CONTROLLED WHEN THE DEVICE IS ATTACHED:
1. Device is attached to the wheel chair and shopping cart , one on each side and
another parallel to the ground.
2. The device and shopping cart act just like an extension of the wheel chair which
allows the user to control the motion of the shopping cart using wheel chair.
3. An example of this would be a stack of shopping carts at a walmart or safeway
when the stack is moved the whole stack acts as a single shopping cart which
allows the person to control the motion of the whole stack.
30
Chapter 3
ANALYSIS
3.1 Finite element analysis of the attachment device:
Figure 3.1 Stress deformation due 200N force and 40 N-M torque (color showing the
extent of deformation).
FEA analysis showing force and torque acting at different position on the device which
is similar to the force and torque when it is attached to wheel chair and the deformation
due to stress when force applied is 200N and torque applied is 40 N-M.
31
Figure 3.2 Strain deformation due 200N force and 40 N-M torque
FEA analysis showing force and torque acting at different position on the device which
is similar to the force and torque when it is attached to wheel chair and the deformation
due to strain when force applied is 200N and torque applied is 40 N-M.
32
Figure 3.3 Displacement deformations due to 200 N force 40 N-M torque.
FEA analysis showing force and torque acting at different position on the device which is
similar to the force and torque when it is attached to wheel chair and the deformation due
to displacement when the force applied is 200N and torque applied is 40 N-M.
33
Figure 3.4 Stress deformation due to 250 N force and 45 N-M torque.
FEA analysis showing force and torque acting at different position on the device which is
similar to the force and torque when it is attached to wheel chair and the deformation due
to stress when force applied is 250N and torque applied is 45 N-M.
34
Figure 3.5 strain deformation due to 250 N force 45 N-M torque .
FEA analysis showing force and torque acting at different position on the device which is
similar to the force and torque when it is attached to wheel chair and the deformation due
to strain when force applied is 250N and torque applied is 45 N-M.
35
Figure 3.6 Displacement deformation due to 250N force 45 N-M torque.
FEA analysis showing force and torque acting at different position on the device which
is similar to the force and torque when it is attached to wheel chair and the deformation
due to displacement when the force applied is 250N and torque applied is 45 N-M.
36
Chapter 4
CONCLUSION
4.1 Conclusion:
A new device for connecting a wheel chair with a shopping cart has been
designed according to the needs of the people with disability. The new device is
light in weight, portable and affordable by common user. The initial designs
helped a lot to learn from the mistakes and design the device according to the
needs of the people with disability. The new device helps the user to connect the
wheel chair with the shopping cart sitting in the wheel chair itself.
4.2 Future Work:
Even more analysis need to be done in order to make the device as efficient as
possible taking into consideration the different factors that affect the wheel chair
and the shopping cart. Standard dimensions of the wheel chair and shopping cart
need to be used in the modeling to do the analysis.
37
DRAWING SET
38
39
40
41
42
REFERENCES
[1] Development of a Device for Attaching a Wheelchair to a Shopping Cart or
Baby Stroller [online]
Available:
<http://web.resna.org/conference/proceedings/2007/Practice/Mobility/Forney.html>
[2] Wheelchair attachable shopping [online]
Available:
< http://www.freepatentsonline.com/6702313.html >
[3] Material used Al ALLOY 6061
Available:
<http://www.fergusonperf.com/the-perforating-process/material-information/
aluminum-alloy_6061.asp >