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DESIGN OF A PORTABLE AND
ATTACHABLE BABY COT
SOWAH BORIS NII-AKO
Department of Biomedical Engineering, Faculty of Engineering Sciences
University of Ghana, Accra, Ghana
E-mail: borissowah@yahoo.co.uk
CLETUS FIIFI ADAMS
Department of Biomedical Engineering, Faculty of Engineering Sciences
University of Ghana, Accra, Ghana
E-mail: cleadams.23@gmail.com
BERNARD OWUSU ASIMENG
Department of Biomedical Engineering
Faculty of Engineering Sciences, University of Ghana, Accra, Ghana
E-mail: boasimeng@ug.edu.gh
ELSIE EFFAH KAUFMANN
Corresponding Author, Department of Biomedical Engineering
Faculty of Engineering Sciences, University of Ghana, Accra, Ghana
E-mail: eek@ug.edu.gh
Abstract:
To solve congestion problems facing many hospitals in developing countries, baby cots are being eliminated and
mothers are made to sleep on the same bed with their new-born babies; a practice known as co-sleeping. The
work presented here seeks to reduce risks of Sudden Infant Death Syndrome (SIDS) and suffocation associated
with co-sleeping by employing the formal engineering design process to develop a portable, safe and cost
effective baby cot. The cot is attachable to the mother’s bed, has four movement restrictors to regulate the
movement of the baby within a given range and a hard surface mattress to ensure the safety of the baby. There
are ventilation ports provided to keep the temperature within the cot comfortable. The design can be modified
to be used by older babies and may be mounted on a collapsible stand where space limitations are not critical.
Keywords: Baby cot; Co-sleeping; SIDS; Suffocation; Engineering design.
1. Introduction
Several hundred years ago, there were no baby beds and babies were made to sleep with their parents. Baby
cots, sometimes known as cribs or cradles, became popular during the 19th century [2] and are small beds
specifically for infants and generally for young children mostly under the age of four (4). They are usually
designed to restrict the baby to the sleeping area by producing very high sides to prevent the baby from
climbing. They also provide no footholds. They were typically designed to be small free standing beds that
could be placed by the parent’s bed for easy accessibility.
The existing baby cots are usually bulky, making it necessary for many hospitals in resource-limited and
congested hospitals, especially in developing countries, including Ghana to eliminate them. Personal visits to
some hospitals in Accra, Ghana, including the Korle-Bu Teaching Hospital and the University of Ghana
Hospital revealed that baby cots are not in use. Healthcare professionals explained that baby cots have been
eliminated in order to save space and promote bonding between mothers and their babies. Many hospitals are
therefore practicing co-sleeping where nursing mothers are made to sleep on the same bed with their babies.
Co-sleeping is defined as an umbrella term that includes the practice of bed sharing with a caretaker or other
family members, proximate sleeping arrangements, and room sharing during sleep [5]. Unfortunately, the
practice of co-sleeping has been associated with the incidence of Sudden Infant Death Syndrome (SIDS) and
suffocation [5]. A need was thus identified for an alternative to the currently available, bulky or expensive baby
cots. Such a cot is expected to occupy little space (portable), while promoting bonding between mothers and
their babies (attachable to the mother’s bed).
2. Methods
The design of this Portable and Attachable baby Cot (PAC) was done in accordance with the formal engineering
design process; an iterative process consisting of several stages including Problem Identification, Background
Search, Functional Analysis, Development of Specifications, Concept Generation, Analysis and Selection of
Components, Component Implementation, Integration and Testing, and finally Product Presentation[19, 21].
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The major objectives of the project were efficiency, competitive cost, aesthetic appearance, safety and
convenience. These major objectives together with other supporting objectives were organized into an objective
tree as shown in Figure 1 below:
Fig. 1. Objective Tree for the Design of PAC
3. Design, Testing and Evaluation
Figure 2 below shows an annotated schematic diagram of the designed baby cot. The various parts of the cot are
subsequently described and other representations of the cot are shown in Figures 3 and 4. The bill of materials
is presented as Table 1.
Fig. 2. Schematic diagram of the baby cot
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3.1 Sleeping surface
This consists of the mattress and the base of the baby cot. A high density and hard surface mattress made from
polyurethane of thickness up to 15 cm was selected in conformity to standards [6]. Additionally, restrictive
materials to ensure safety against suffocation were provided [20]. The restrictive materials (rectangular
shapedfoams) are fastened to the mattress by Velcro strips.
Fig. 3. Top perspective view showing the sleeping surface of PAC without the mattress.
3.2 Ventilation ports
These are vertical gaps left in the baby cot to aid in ventilation to help prevent suffocation. The collapsible baby
cot is rectangular in shape with one open end to allow for easy access of the baby by the mother; a means of
promoting bonding between the baby and the mother. The baby cot has a total of fifteen (15) ventilation ports,
each having dimensions of 0.055 m by 0.3 m.
3.3 Attachment
There are three points of attachment in this design. Firstly, the attachment of the three (3) vertical sides to the
base (sleeping surface). Secondly, the attachment of the sides together and finally, the attachment of the
assembled baby cot to the bed of the mother. The sides are attached to the sleeping surface by hinges and the
sides are held together by metallic locks. There are two flexible belts attached to the side adjacent the open end.
These flexible belts are fixed to the cot by the help of washers and screws. The free ends of the flexible belts
have two holes perforated on each to be used to attach to the bed using washers and screws.
Fig. 4. A 3-dimensional representation of the PAC
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Table 1. Bill of Materials for the Portable and Attachable Cot
NUMBER PART QUANTITY DESCRIPTION COST
(GH¢)
COST
(US $)
1 Base 1 Plywood of thickness ¾ m, length of 0.75 m
and width of 0.40 m. 10 5
2 Sides 2 Ofram wood of length 0.4 m, width of 0.4 m
and thickness of 0.06 m.
10
5
3 Back 1 Ofram wood of length 0.75 m, width of 0.4 m
and thickness of 0.06 m.
4 Restrictive
materials
and
sleeping
surface
1
A mattress of length 0.74 m, width of 0.48 m
and thickness of 0.07m made of polyurethane
foam.
15.75
7.90
5 Fasteners
to the bed 8 pairs Screws of length 0.05 m and core diameter
0.01 m. A washer of diameter 0.009 m.
1.6
0.80
6 Joint
fasteners 3 Hinges. 9 4.50
7 Fasteners
to the
mattress
4 A Velcro strip of length 0.15 m and width
0.01 m. 1 0.50
8 Attachment
material 2 A strong and flexible belt made of car tyres
(rubber). 2 1
3.4 Mode of operation
Since the baby cot is collapsible, it must be assembled before use. The three sides are first erected by attaching
each side to the sleeping surface using the hinges found on the sleeping surface. These sides are then held
together by means of metallic locks. The flexible belts are then attached to the side adjacent to the open end by
means of screws and washers. The free ends of the flexible belts are finally screwed to the bed by aligning the
washers and perforated holes.
3.5 Mechanical testing
Mechanical testing (stress analysis) was done on a virtual model, which was identical to the real piece in terms
of dimensions, shape and material properties. Stress analysis was performed on the casing of the crib because
the presence of the ventilation ports makes it easily susceptible to shearing as compared to other parts. In Figure
5, the casing is hinged at the face labelled B whilst the force is applied to the face labelled A. Upon applying
forces of varying magnitudes, it was observed that the minimum force that would cause shearing is 2 kN. The
blue coloration in Figure 5 is the pictorial display of distortion relative to the true shape of the crib under the
action of the 2 kN force.
The simulation also indicated that forces between 0.5 kN and 2 kN result in an observable distortion but do
not lead to shearing. This suggests that the fasteners that attach the casing to the base of the crib, at the site of
distortion, may shear or bend even if the crib does not fracture. To this end, forces greater than 0.5 kN may
cause damage to the crib, as shown in Figure 6.
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Fig. 5. Result of mechanical test on a virtual model. The direction of force applied is indicated by the arrows. The blue colour shows
distortion relative to the true shape of the crib under the action of a 2 kN force
Fig. 6. Fracture due to a 4 kN force
3.6 Advantages of the design
The portable and attachable baby cot is:
Stable and robust
Very safe to use
Well-ventilated
Light in weight, occupies little space and is collapsible for easy portability
Affordable and has low maintenance cost as it is fabricated from readily available local materials
Easy to fix/assemble and use
Attachable to the maternity bed to allow mothers to easily access their babies, thus promoting bonding
and easy breast-feeding
To determine whether the design performs its specified functions effectively and efficiently, a prototype was
fabricated and the attributes of the prototype were evaluated against the design objectives and specifications that
were originally defined.
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Further testing on the prototype showed that the product can be folded making it easier to be carried around.
The means of attachment to the bed was very strong making it safe to attach to the bed. Additionally
mechanical tests performed on the prototype indicated that the design would be able to support various weights
and stresses above the specified values without failing. The mattress used had a hard surface which helps
reduce the possibility of suffocation. The end facing the mother is opened to ensure that the mother can easily
access the baby to promote bonding.
Table 2. Product Evaluation
OBJECTIVE SPECIFICATION EVALUATION ACHIEVED?
ALLOW FOR
VENTILATION -Number of ventilation ports ≤
50
-Sizes of ventilation ports ≤
0.06*0.4 m
The number of ventilation ports
was 15 and the size of each port
was 0.055 m by 0.3 m
Yes
ATTACHED TO
THE BED -Number of joints < 10
-Detachment time < 20 minutes The number of joints was 6 and the
detachment time was
approximately 5 minutes
Yes
EASY TO FIX AND
USE -Steps to fix PAC <10
-Steps to use PAC <10 The number of steps to fix and use
PAC was less than 10 each
Yes
SAFE AND
DURABLE
-Number of sharp edges 0
-Yield strength of the material ≥
1.74 kPa
-Comfortable temperature within
the cot
-Effective restrictions
The design has no sharp edges.
The yield strength of the wood
used was greater than the specified
value
The temperature within the cot was
identical to ambient temperature.
There were 4 restrictive materials
to regulate the movement of the
baby but these materials are not so
strongly attached to the sleeping
surface.
Yes
PORTABLE
(Occupies less
space)
-Length (0.75 m)
-Height (0.40 m)
-Width (0.40 m)
The design conformed to the
specified dimensions and also to
further ensure that moving it is
much easier, the product can be
collapsed when not in use
Yes
ATTACHABLE
-Flexible belt
The flexible belt used was very
strong and can easily be bent
without failing to ensure that PAC
is strongly attached to the bed
Yes
AFFORDABILITY
- Total cost <GH¢ 250.00
-Selling price < GH¢ 300.00
-Total cost = GH¢ 84.65
[Approximately US$ 43]
-Selling price = GH¢ 105.81
[Approximately US$ 53]
Yes
4. Conclusion
Testing and evaluation show that the designed system met the requirements for an efficient, portable and
attachable baby cot. This cot addresses some of the problems posed by existing designs. Additionally, it
ameliorates the sleeping restrictions mothers face when they are made to sleep on the same bed with their
babies. It may also help to address the problem of high suffocation and SIDS risks encountered as a result of
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co-sleeping. The mechanical tests performed on the prototype indicate that the design would be able to support
various weights and stresses above the specified values without failing.
To add value to the product and improve its aesthetic appeal a bag can be designed to carry the cot. The cot
can be modified to be used by older babies outside the maternity wards. A collapsible stand can also be
fabricated for use in venues where space availability does not pose a problem and there is a preference to keep
the cot off the mother’s bed.
Acknowledgment
Mr. Kwabena Kan-Dapaah is gratefully acknowledged for academic guidance during the initial stages of the
project.
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