Design and development of Multi-Purpose Wheeled Stretcher

XXXX1,a, XXXX1,b, XXXX1,c, XXXXXXX1,d, XXXXXXX1,e, XXXXXXX1,f, XXXXXX1,g, XXXXXX1,h, XXXXXX1,i XXXXXX1,j

1Faculty of Mechanical and Manufacturing Engineering, Universiti Tun Hussein Onn Malaysia,86400 Parit Raja, Batu Pahat, Johor, Malaysia

aA, bB, cC, dD, eE, fF, gG, hH, iI, jJ

ABSTRACT

The acute care, movement and out-of-hospital patients transportation are the integral component in every hospitals. Thus, an ambulance stretcher plays an essential role and it is also the primary apparatus to rescue patients who require medical care. However, the vibration caused by the fast accelerating ambulance may worsen the patient’s injuries. In order to prevent or limit this occasion from happening, a proper design of a multi-purpose wheeled stretcher should be proposed accordance to its capability to be utilized in a Search and Rescue (SAR) operation via helicopter. Besides, the process of mapping a design for a customized structure and joints of a stretcher is constructed in order to improve its efficiency during rescue purposes. Hence, the aim of this study is to in selecting suitable design parameters to improve the stability, comfortability, and capability of a stretcher. The findings suggested that the improved stability, comfortability, and capability could be achieved by using the Face and Finger Hinge Joint and special design of the stretcher able to fit the Search and Rescue (SAR) operation by using helicopter. This study has provided a new perspective in designing a Multi-Structure wheeled stretcher that fullfill the requirements of the project.

Keywords: wheeled stretcher, Search and Rescue (SAR), Face & Finger Hinge Joint,

1. Introduction

Generally, an ambulance stretcher is an integral part of the patient transport system for ambulance services or known as wheeled mobility device designed especially for disabled individuals. It must not only be light in weight while bearing a substantial load, but must optimize the delivery of pre-hospital care and withstand outdoor elements. For seriously injured patients, the ambulance transport is often very dangerous. It may be dangerous trauma to the patient with the accelerations due to a fast ambulance and long road journey. Researchs show that, during about 10% of journeys some patient deterioration occurs. The most harmful vibrations to patients lying down are between about 2 and 8 Hz, close to the natural frequency of the human body and the vibrations caused by the road unevenness and transmitted through the vehicle suspensions are quite strong in this frequency range. In order to avoid this risk, a Multi-Structure wheeled stretcher with ordinary wheeled stretcher features as well as capable to fit the specifications of Save and Rescue (SAR) operation using helicopter should be designed to provide more convenience transport system for patient. In this research, design of Multi-Structure wheeled stretcher was utilized in selecting some suitable design parameters to improve the stability, comfortability, and capability of the stretcher.

The picture shown has two types of stretchers : Ambulance stretcher (left) SAR stretcher (right).

2. Work flow for the design & development of the structure and joints for the stretcher

The multi-structure and joints is one of the most critical components in our project. To design the customized structure and joints for the stretcher, the process mapping was prepared as shown in figure 1 which illustrates the framework or work flow mapping of the design and development scheme. Process mapping is a technique used to identify the steps to be performed for the project purpose. It acts like a tool through which the things are properly documented to get the high efficiency for the work to be performed. Due to unaffordable budget and lack of knowledge on the full scale development of the designed stretcher, a stretcher with 1:2 scale is constructed for illustr

ation

purpose that only specific on the significant parts of the stretcher which is the structure and joints.

FIGURE 1: Work flow mapping for the design & development of the structure and joints for the stretcher

Designing of structure and joints

of a stretcher

Documented the functional

requirements for the stretcher

Identifying the design parameters

of a stretcher

Proposing an idealogy of the design by doing

a rough sketch

Reviewed the existing

stretchers and support designs

Geometrically modeled the feasible and

suitable concepts

Load analysis of the design with suitable

materials and processes

Choosing a design

Selection for better design

Rejected designs are documented

for future reference

Prototyping, actual load testing, and finalization

of the components

Reviewed the existing structure and joint designs

Production, fabrication and assembly processes for the final structure and joints

for the stretcher

Input and output of the process

Decision

Activity

performed in the process

Rejected Design

Approved Design

Concept meeting the entire requirements

Rejected Design

3. Results and Discussion

In order to achieve the highest stability and comfortability, four choosen joints design have been analyzed, that are: Strip Hinge Joint, U-Channel hinge Joint, Flat Face Hinge Joint and Face & Finger Hinge Joint. The analysis was performed using ANASIS software and Table 1 summarizes the design parameters and shows the overall rating results. Besides, FIGURE 2 shows how the Save and Rescue operation by using helicopter is done.

Strip Hinge

Joint

U-Channel

hinge joint

Flat Face

Hinge

Joint

Face &Finger

Hinge Joint

Technical Descriptors

Load Bearing Capacity

(Average Stress MPa at 90 kg UDL)

3 4 7 9

Hinge Joint Weight 9 7 7 3

Compactness/ Folded size(mm) 200 290 90 90

Safety 3 3 5 9

Easy and Quick to Deploy 3 3 5 9

Durability 3 3 5 9

Cost 7 6 5 4

Absolute Weight(g) 190.8 199.0 233.4 300.9

Rating: Low=3, medium =5 and high= 7 Very high=9

TABLE 1: Overall rating results of the choosen joints

Referring to the table, face and finger hinge joint was refined to make it more robust by modifying geometry and becoming the most suitable design configuration material and manufacturing process for our joint on stretcher due to its load bearing capacity is more 90 kg in dynamic load condition, high strength low weight material, easy to fold or unfold, safe to use, high in durability and cost effective.

4. Conclusion

In developing a Multi-Structure wheeled stretcher, proper selection of design parameters of the joints and structure is critical in improving the stability, comfortability and capability. Our findings suggested that using the Face & Finger Hinge Joint result in best performance for each requirements that we consider due to its outstanding properties which is: (i) high in load bearing capacity, (ii) high strength and low weight, (iii) easy assemble-dismantle, (iv) safe to use, (v) high in durability and (vi) low in development cost. In this study, we also provide a new ideology on the design of the stretcher that capable to fit the Save and Rescue (SAR) operation by using helicopter.

5. References

[1] NFO Evbuomwan, S. Sivaloganathan and A Jebb, (1996): A survey of design philosophies, Models, Methods and Systems Proceedings Institute Mechanical Engineers Vol. 210 Part B : Journal of Engineering Manufacture

[2] L.-K. Chan, M.-L. Wu, Quality function deployment (2002): A literature review / European Journal of Operational Research 143 (2002) 463–497, www.elsevier.com/locate/dsw

[3] Ming-Chyuan Lin a, Chieh-Yuan Tsai b, Chao-Chun Cheng c, and C. Alec Chang, (2004) : QFD For Design of Low-End Digital Camera, International Journal of Applied Science and Engineering 2004. 2, 3: 222-233)

[4] Katoch S. (2005) : Introduction of Modern Stretcher in Armed Forces for Improving Casualty Evacuation, Medical Journal Armed Forces India, :Vol. 61, no 2 pp157-162

[5] Knight B.F.,(2000) : Deployable antenna kinematics using tensegrity structure design, a dissertation of doctor of philosophy, university of Florida

[6] Commercial hinge joints source: • www.gutenberg.org • www.impulse-based.de/manual.html • www.support4less.com • www.mdl.co.uk/accesories/cabled-bore track-.html • www.thomasnet.com/knucklehinge.html