STANDUP WHEEL CHAIR

BY

            Akshat Sisodia                        Roll No. 06

            Ali Akber Kapadia                  Roll No. 08

Prepared in partial fulfillment of the course

Industrial Engineering Concepts

AT

NATIONAL INSTITUTE OF INDUSTRIAL ENGINEERING, MUMBAI

August, 2012

1.  Introduction

The project aims to design a wheelchair that will enable the user to stand up while remaining supported on the backrest of the chair. The wheel chair comprises of a seat, a backrest and a lifting mechanism mounted on a strong base. The two front and two rear wheels provide the necessary mobility to the structure. A foot rest and hand rest are meant for the ease and usability of the user. The front wheels or the guide wheels can rotate about their own axis which helps in easy movement and in taking turns. A lifting mechanism raises and lowers the invalid from seated position on the seat to a substantially standing position. The mechanism is a particular geometrical arrangement of many links such that a downward force on the footrest rest results in vertical movement of the all the joints including the seat which helps the invalid stand up. In operation the invalid’s hands approximate the level of a hand height of a non handicapped person.

2. Motivation for the Project

Studies have shown that a regular program of repetitive standing can help to prevent many problems associated with wheelchair confinement including: skin breakdown, urinary tract infections, bone demineralization, poor circulation, spasticity, muscle contractures and shoulder pain. This set us thinking for a wheelchair design that would enable its occupant to stand up and sit down with ease without any external help.

A stand-up wheelchair is a great elevator for wheelchair users whose muscles will not support them enough to stand up. It often works best for disabled individuals whose finger and arm control is sufficient at least one side, as often is with paraplegia, quadriplegia, muscular dystrophy, or cerebral palsy.

This wheelchair offer virtually infinite standing positions, and helps improve the patient’s health through increased circulation. There is no jerking motion while raising or lowering the Wheelchair, which reduces stress on sensitive body parts. It does not need a separate standing frame, saves space, decreases dependence on caregiver, and best of all the patient can stand in the wheelchair as often and as short/long as desired.

3. Materials and Components Used

3.1            Mild-Steel Flat Plates:

Two different flat plates were used.

a)      For the lifting mechanism. The dimensions are as follows

Thickness = 1/4”

Width       = 1”

b)      For connecting the guiding wheels to the chassis. Higher strength was needed here as they had to bear the entire load of the chassis along with its occupant. The Dimensions are

Thickness = 1/2"

Width       = 1 ¼”

Mild steel was used because of its good strength and the property of corrosion resistance due to the presence of carbon. Its low cost was an added advantage.

3.2            Mild-Steel L-section:

L sections of two different dimensions have been used :

a)      For the seat , back , legs and the footrest. Its dimensions are

Thickness =   1/4”

Width       = 1 ¼”

b)      The lower portion on which the wheels are mounted has been made with L section having the following specifications:

Thickness = 1/4”

Width =     1 ¾ “

L-Section was preferred over the Flat Plate to make the chassis as it has a higher Moment of Inertia which makes it less vulnerable to failure due to bending.

3.3            Wooden Planks:

Wooden Planks have been used to make hand-rest, foot-rest, back-rest and the seat. The choice is apt due to the fact that wood is easier to machine, cheap and light-weight. Also it has better aesthetic value and usability.

3.4            Bolt and nut:

Two types of Regular Hexagonal Head Bolts have been used.

a)      For wooden planks:

Diameter - ¼”

Length – 1 ¼”

Width of the head – 7/16”

Height of the head – 11/64”.

b)      For guiding wheels

Diameter = 3/8”

Length    = 1”

Width of head = 9/16”

Height of head = 1/4”

3.5            Rivets:

Rivets of the following specifications were used

Length = 1”

Diameter = ¼”

3.6            Rear Tyres:

Standard bicycle tyres of 24” diameter were used.

3.7            Guiding Wheels:

These wheels can rotate 360 degrees about the vertical axis. They guide the wheel chair and enable turning. The diameter of the wheel is 8”.        

4. Sequence of Operations

4.1            Design :

As a first step we proposed a mechanism using by applying the knowledge of links. The following figures show the design developed:

Sitting Position

Standing Position

Fig. 4.1 & 4.2: Proposed Design

4.2            Sawing:

The second step was to cut the desired lengths out of the flat plate or the L section as per the requirements. Three types of saws processes were used for this purpose. These are:

a)      Power saw: This saw was primarily used for cutting thicker L sections            and flat plates.                                                                                                                                                                                                                         

b)      Hacksaw: Hack Saw was used to cut rivets as per their desired length.

c)      DoAll Machine: DoAll Saw Machine was used to cut the thinner components.

4.3            Drilling :

Holes of ¼“diameter were drilled into the cut out lengths at appropriate positions for the purpose of riveting. A centre punch was used to locate the exact position of the hole before drilling.

Fig. 4.3: Drilling

          4.4            Shearing

Shearing was used to cut out sheets of the desired dimensions.

Fig. 4.4: Shearing

4.5            Joining

a) Riveting: Riveting has been done for the revolute joints to facilitate their relative angular motion. The rivets were cut to appropriate length by hand sawing using a vice and grinding. Riveting was then done by mounting the components on anvil and hammering.

b) Welding: Electric Arc Welding was used to make permanent joints between two metal components. The electrode material was mild steel. The weld joints were of various types depending upon the usability of the joint – Fillet Joint, Corner Joint and Lap Joint. No filler material was used.

Fig. 4.5: Arc welding

c)      Bolt and Nut: Bolt and Nut joints were used for joining hand-rest, foot-rest, back-rest, seat and guiding wheels to the chassis. These were also used to make temporary joints which were finally riveted.

4.6            Carpentry :

Carpentry was used to make the seat, back rest and the hand rests.

4.7            Counter Sinking :

This was done for proper seating of the bolt head in the wooden planks.

Fig.4.6:  Counter sinking in wooden plank

4.8            Grinding :

Grinding was used to smoothen the edges of the links and also to improve the quality of the weldments.

4.9            Filing :

This was used to smoothen the sharp edges of the drilled holes as well as to remove the excessive chips.

  

4.10       Finishing :

The wooden parts were polished and paint was applied on the metal parts.

5. Conclusion

An attempt has been made to design a wheelchair that can be made to stand along with its occupant thus providing comfort to the patient and increasing his independence. This idea can immensely improve the quality of life for the elderly and the diseased.

During the course of designing, we learnt how to use our theoretical knowledge to find solutions in real practical situations. Most of all we worked together as a team.