Freshman Engineering Design Lab
“One-Handed
Food Cutting Device”
Final Project
Design Report
Date
Submitted: June 6, 2013
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Submitted
to:
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Rahamim Seliktar, seliktr@drexel.edu
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Group
Members:
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Luyando Chibwe, lc626@drexel.edu
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Neil Llona , nal54@drexel.edu
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Tom Mazza, tam338@drexel.edu
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Peter Esslinger, pce32@drexel.edu
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Abstract:
A
problem that occurs in people that have lost use of an arm due to some sort of
medical condition was chosen to be addressed for this design project. The issue
comes in the process of cutting tough food such as steak. With only the use of
one hand, one cannot effectively hold the food in place while cutting. The most
popular existing design solutions include the rocker knife, the knuckle-T
rocker knife, and a fork/knife combination device. The design uses a modified
fork design to hold the food in place, with a mechanism to slide a straight
edge knife down, using the force applied by the user, to cut the food. A spring
is then used to retract the knife so the food can be properly handled without a
knife near the user’s face. The design can be implemented in the everyday lives
of those with the use of only one hand and especially in a public setting, such
as at a restaurant.
1
Introduction
1.1 Problem
Overview
The design project is aimed at helping people who have only one
functional arm, such as unilateral amputees or hemiplegics. For these people, a
simple task like cutting and eating food in a restaurant can be a large
obstacle. They may need assistance in handling their food which can be
frustrating for them and their helper. If the person does not have someone
there to assist them in cutting their food, they may be forced to resort to
attempting to cut a particularly tough food, such as steak, on their own. The
problem with that is that the task would be very difficult with the use of only
one hand and it would be even more difficult to do so in a civilized manner
that does not attract a lot of attention such as in a restaurant setting. The
design must be small and somewhat discreet so that it doesn’t attract a lot of
attention to the user. It cannot be much larger than a standard 6” fork and it
must also be lightweight. The design must also be cost effective and durable.
1.2 Existing
Solutions
The rocker knife (Figure 1) is one of the
more popular designs that is out there as a solution. This design has a curved
blade with prongs on its backside. The blade is on the curved front-side of the
device and the prongs and located at the end of the curve and face the opposite
direction of the blade. The design allows for users to cut their food with a
rocking motion and then eat food with the fork end which can also be used as a
pick [1]. This has shown to be an effective solution for cutting large foods.
The problem with this design comes into play when trying to cut bite-sized
pieces of food. It also depends on the kind of food that is being cut. It is
more difficult to cut small foods that tend to slide around a lot. There is no
way to keep the food in place while cutting it.
Another
solution that is available is the knuckle T version of the rocker knife (Figure
2). This design features and small handle with a curved knife branched off from
it. The user clenches a fist to grip the handle and presses their fist straight
downward onto their food. Users then make a rocking motion with their hand to
cut through the food [2]. This knife is better equipped for cutting bite-sized
pieces of food, but it does not keep the food in place while cutting and since
there is no fork attached. Additionally, users must constantly switch back and
forth from the knife to the fork to alternate cutting and eating their food
which is of great inconvenience to the user. Also, it is not very practical
because it is aesthetically displeasing and attracts a lot of attention to the
user. This is the kind of device that may be functional but one that people may
choose to not use.
The knife and fork combination one hand model (Figure 3) is another pre-existing solution. This device is a fork that is surrounded by straight knives on three different sides of it which creates a box shape with an opening on one end. The way that it works is that when pushed down onto food the fork retracts up inside the three-sided box knife using a spring mechanism within the handle. The knife then cuts a bite-sized piece of food. When pressure is released the spring-mounted fork with the cut food extends past the knife [3]. The problem with this design is that it is very limited in its use. It can easily cut soft foods but if would have trouble cutting tough foods like steak because it relies on a completely vertical motion of the blades. It is also not very cost effective and costs about $140.
Figure 1. Rocker knife Figure 2. Knuckle T rocker knife Figure
3. Fork-knife combination
1.3 Project
Objectives
The
goal of this project is to create a device that will allow people with use of
one arm to cut their food in a civilized manner. The design to solve this
problem is a variation of the Fork-knife combination design (Figure 3). The
design features a knife that it directly in front of the fork and is operated
by a button. There is a spring in the handle which is what drives the button
mechanism which extends and retracts the knife. Allowing for the knife to be easily
retracted is unique to the design of group 6 and it ensures the safety of the
user. Users will be able to cut their food and eat it without having a blade
uncomfortably close to their face since the knife is retractable. The food will
also be able to be held in place while cutting because the user can use the
fork to hold it and then extend the knife out to cut the food. The deliverables
for the design include a functional prototype of the design.
2
Technical Activities
2.1
Project Timeline
The timeline of events
during this term changed dramatically from what was originally expected. An
overhaul was necessary before the midpoint of the term, and the project was
more or less restarted. There was still enough time to complete the new design,
though. Here is the series of major events throughout the past ten weeks:
Table 1: This timeline shows the how the term has progressed so far and
should progress in the future.
Week
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||||||||||
Task
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1
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2
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3
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4
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5
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6
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7
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8
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9
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10
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Introductory Brainstorming
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x
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x
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||||||||
CAD Design
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x
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x
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x
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|||||||
Reevaluation of Project
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x
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x
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||||||||
Research and Dimensions
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x
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x
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||||||||
Design and Construction of Prototype
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x
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x
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x
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|||||||
Testing
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x
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x
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||||||||
Final report preparation
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x
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x
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During
the first few weeks of the term, the initial design was created to allow people
to cut their food with one hand but without the use of a knife. The initial
design consisted of a pie server with an opening in it (Figure 4), where
high-grade scissors could be fixed in and they would cut the food (Figure 5). A
few designs of this concept were modeled in Creo Parametric.
Figure
4. This is a model of the pie server. It has an opening for the scissors and a
spot where they could possibly be fastened in.
Figure
5. This is one half of the average pair of scissors that was used to try to
better visualize the design.
After
plenty of consideration and visualization of this design, it was decided that
it would be scrapped in favor of a new, better design. This new design was to
consist of both a fork and a knife for the convenience of the user. These two
would be encased in separate compartments of a 3D-printed casing (Figure 6),
and at least one would be able extend and retract so that not only would they
not get in the way of each other, but also the knife would be less dangerous.
It was considered very undesirable to have a knife which is required to be very
sharp to be too close to the face of the user. Careful thought was put into the
details of this design, and eventually it was decided that the fork would
remain in place, the fork would also be flat in order to give the knife room to
cut (Figure 7), the knife would use a sliding mechanism in which the user’s
thumb would push down a lockable tab in order for the knife to extend and
retract, and also the knife would use a rocking motion in order to cut the food
(Figure 8). Here are some of the Creo models for these concepts:
Figure
6. This is the idea for the casing of the two. At the bottom, the openings for
both the fork and the knife can be seen, and the opening on the side is for the
sliding mechanism.
Figure
7. This is the fork, showing how it is flat as opposed to the curves of a
normal fork. 
Figure
8. This is the knife. It can be seen how the knife would rock in order to cut.
The tab at the top would be for locking it into place while allowing to move up
and down when needed.
This
design, however, required further revisions. The casing was far too bulky, the
sliding mechanism as it was modeled was too impractical, and the rocking motion
for the knife was rejected. The bulky casing was remedied by changing the shape
to a semicircle (Figure 9). The fork was attached to the flat backside of the
semicircle to attempt to minimize the material used. The knife’s design was
changed so that it was not shaped like a semicircle but was instead flat and
sharp. The tab at the top would be pressed down with the user’s thumb, which
would compress the spring that is keeping the knife in its compartment, and moved
to the other side of the J, providing a way to extend and retract the knife as
desired (Figure 10). The fork was cut from stainless steel so that its prongs
can stay sharp. The knife was made out of aluminum in order to make it
lightweight and the casing was 3D-printed.
Figure
9. This is the finalized casing, showing the J opening and the opening for the
knife.
Figure
10. This is the final knife, which includes the new straight edge and the tab
to extend and retract it.
2.2 Project Budget
The
table below shows what items needed to be obtained in order to complete the
project. It also compares the price that one might pay if they were to attempt
to recreate this design process to how much money group six actually spent
utilizing resources.
Table 2.
This table compares the cost of the project to group six against someone
replicating the design.
Item
|
Cost
to someone else
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Cost
to group six
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12” x 12” of 0.3” thick plate of aluminum
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$62.01
|
$0
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12” x 12” of 0.03” thick sheet of
stainless steel
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$15.39
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$0
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4 pack of 5/16” x 1-1/2” x 0.020” springs
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$2.68
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$2.68
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3D print of casing
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$10.10
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$0
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Total
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$90.18
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$2.68
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The only item that was purchased was the
pack of springs for $2.68 from Lowes. Relatively small plates of different
metals were available at Drexel’s machine shop. This was taken advantage of
since the design was so small and the required plates of metal did not need to
be very thick and that is how the aluminum plate and stainless steel sheet were
obtained without any cost. Drexel also offers usage of 3D printing services and
that was taken advantage of in order to print the casing at no cost.
3
Results
It can be concluded from the final model of the
single handed cutting device that although the device is flawed, it can
efficiently extrude and retract the knife. Given enough pressure from the user,
the device can make a sufficient slice into tough foods. With the knife
retracted, the fork can successfully pick up the cut food and deliver to the
user all with the user only using on hand. Though the design is functional it
does not run as smoothly as intended. These issues can be related to the lack
of desired materials and this pertains especially to the knife. The knife used in
the current prototype is constructed out of aluminum, in order to make it
lighter, and therefore cannot hold a very sharp edge and will dull more quickly.
Along with this, the J-shaped spring slider mechanism is functional but is
prone to getting stuck due to a slight rotation in the shaft of the knife and
this makes it a bit more difficult to use.
4 Future Work
The next step in the design would be to simplify it in such
a way that it could be mass produced. The cutter would not be very useful or
helpful to people if it could not be produced in large quantities because if
not, the cost may be too high for people to afford. The design may also need to
be simplified a bit in order to allow it to be mass produced. A more simplified
design would also make the cutter more lightweight and user-friendly.
The design, as it currently stands, does not seem like it
needs any additional elements. It could possibly be fine-tuned with better
materials so that it will last longer, but this may have an adverse effect by
increasing the cost to produce it. The knife would be made of high strength
stainless steel preferably so that it was keep a razor sharp edge longer. Also,
the casing would ideally be made of a high grade plastic. The sliding mechanism
could also be tweaked in order to make a smoother transition from the resting
position to the cutting position of the knife. An alternative to the sliding
mechanism that was used would be some sort of button mechanism that would make
the knife extend, lock into place, and then retract at the press of a button.
5 References
[1] Elder Store. Rocker Knife Fork
Combination. [Online]. Available:
http://www.elderstore.com/rocker-knife-fork-combination.aspx
[2] Access Technologies, Inc. Cutlery -
Rocking T-Knife. [Online]. Available:
http://www.accesstechnologiesinc.org/product_sales_and_rentals/deviceloan_categories.aspx?RentalCatID=95b2b7db-aaab-4719-8978-32528eced1ad&Page=4
[3] Boca Medical Supply. Knife and Fork
Combination One-Hand Model. [Online].
Available:http://bocamedicalsupply.com/onlinestore/product.php?catId=4&prodId=7#
More.
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