Redesigning a Curling Iron
Wendy Sponaugle
DEA 325 - Homework 3
November 24, 1997
Introduction
Every day, as millions of women get ready for a day of work or school, dress
for a social event or prepare for any occasion, thousands of curling irons
are turned on. Each day in beauty salons, thousands more are turned on to
be used on the myriad of clients appearing throughout the day. And while
many changes have been made in the size of the curling rod and the heat
levels that can be achieved, few of these changes, if any, have considered
the ergonomic needs of the users.
In redesigning this hand tool for the hair, I focus on the three major segments
of the curling iron: the handle, the rod and the tip. These segments are
labeled on a traditional curling iron in Appendix
A.
The activity for which the curling iron is most commonly used is curling
pieces of hair. However, curling irons can also be used to straighten hair
or to warm hair for easier styling. Wig makers may use curling irons to
create waves in both natural and synthetic wigs. Most curling iron users
are women, although male hair stylists, wig makers, and perhaps men frustrated
with their own straight hair make up a portion of the user group. Curling
irons are used both by those curling their own hair and those curling the
hair of others.
In this paper I will discuss my redesign from each of the three segments
of the traditional curling iron. The redesign sketches can be seen in Appendices B, C, D, and E.
Handle - Traditional
The traditional curling iron has a handle that is an extension of the rod
in both size and shape. The cylindrical rod flows into a smooth cylindrical
handle. The three commonly found sizes of curling iron rods are 1",
1-1/2" and 2" diameters.
To turn a curling iron on, most have a switch-pad that slides up or down
to be turned on or off, in some cases having different settings such as
low, medium and high (see example in Appendix
A). Often the sliding switch is moved accidentally
when using a curling iron, which can turn off the heat without the user
realizing it until the rod is cold and will take minutes to warm up again.
Some have a separate on/off switch and a rotating knob that controls heat
settings. And the simplistic curling iron turns on when plugged in and off
when unplugged. Perhaps one of the best innovations in curling irons of
late is the automatic off setting, where a curling iron that has been unused
for a certain amount of time automatically shuts itself off, for fire safety
reasons. Most models available today have an indicator light that tells
the user if the rod is on/hot or off.
In order to raise the clasp on the rod, the thumb must be used to press
on a lever. The lever is in reach of the thumb, even when all four fingers
are clasping the handle.
Handle Redesign (Appendices B & C)
Several new features have been added to the newly designed handle (Appendix B). The most noticeable
difference is the angle of the handle from the rod. In this
case, I used Bennett's idea of "bending the tool, not the wrist"
(Emanuel, Mills, and Bennett in Sanders and McCormick, 1993) and Lewis and
Narayan's (1993) recommendation that while working, the handle and the forearm
should be aligned. The new angle of the handle, approximately 100 degrees,
reduces ulnar deviation, which occurs with the traditional straight handle.
Minimizing ulnar deviation reduces the possibility of carpal tunnel syndrome,
tenosynovitis and tennis elbow in frequent users. The handle also reduces
shoulder abduction because the arm will not need to be raised as high when
curling hair as with a traditional handle. This will reduce stresses on
the shoulder joint, which could otherwise lead to increased muscle fatigue
and cumulative trauma disorders (Hedge, 1997; Schoenmarklin & Marras,
1989). The new handle needs little assistance from the upper arm and shoulder
because the lower arm can easily reach the angled handle simply by bending
the elbow. Another benefit of angling the handle is that changing the shape
of the curling iron from a flat shape to a pistol shape shifts the curling
iron's center of gravity. This shift provides a more even weight distribution
for the user and minimizes the possibility of the uneven weight of the curling
iron causing it to twist out of the user's hand (Armstrong, Radwin &
Hansen, 1986; See Appendix F,
Diagram 2).
Another change from the traditional handle is the method for opening
the clasp. In traditional models, the thumb must apply significant
pressure on the clasp lever in order to raise the clasp, leading to increased
fatigue in the thumb muscles and joints. In addition, the thumb is in an
hyperextended position, which can cause pain and inflammation (Sanders and
McCormick, 1993). The redesign has the user holding the handle like a pair
of pliers. This design spreads out the pressure needed to open the clasp
to all the digits by using handles similar to those in a pair of pliers
(See Appendix F,
Diagram 1). Squeezing the two handles together raises the clasp. The grip
strength needed to raise the clasp is very low, approximately 10 pounds,
to accommodate the 5th percentile female. This is assuming the opening of
the grip axis is two inches (Greenberg and Chaffin, 1977 in Sanders and
McCormick, 1993), which is the standard handle diameter size for my redesign,
regardless of the rod size.
This new method for opening the clasp affects the shape. Because
a contoured hand tool decreases slippage (Hedge, 1997; Lewis & Narayan,
1993), the contoured redesign provides a shape more similar to the anatomy.
This correct shape was derived from the redesigned pliers designed by Damon
(1965 in Sanders and McCormick, 1993) and Tichauer (1966 in Sanders and
McCormick, 1993; see Appendix F, Diagram 1). This contoured shape, which
is closer to that of a gun handle, gives the user more control and reduces
wrist deviation (Hedge, 1997). Additionally, the bend in the handle decreases
stress on flexor tendons and the median nerve, and such curves will not
likely affect performance in using the curling iron (Konz, 1986; Schoenmarklin
& Marras, 1989); there is little worry of a decrease in effectiveness
with a curved handle. It is important to note, however, that despite the
change from a cylindrical to a gun handle shape, the edges of the handle
must maintain a rounded shape because sharp edges can cause cuts, bruises,
or abrasions (Lewis & Narayan, 1993).
The length of the handle extends beyond the hand. Not only
does this provide a more even weight distribution of the rod and handle,
it eliminates the possibility of strain on the center of the palm, as handles
shorter than the palm create high forces in the center of it (Lewis &
Narayan, 1993).
The texture of the redesigned handle is not the typical plastic
seen on traditional handles. To avoid slipping, especially as hands may
perspire due to the hot curling iron, the handle is covered with a layer
of thin foam. In addition to minimizing perspiration, people prefer the
soft feel of foam to hard, smooth wood (Fellows and Freivalds, 1991). This
is most likely due to the fact that foam increases the uniformity of force
distribution from the hand, thus improving user comfort. These findings
can be carried over to the curling iron handle, as a foam handle will most
likely not only decrease slippage, but will also provide stronger user satisfaction.
The power switch for the redesign is a push-button at the
end of the handle. The location at the bottom of the handle will eliminate
a user accidentally turning off the heat while in using the curling iron.
And the easy-to-push button will not strain the digit used to press it.
As in some traditional designs, the heat will automatically be turned off
after a few minutes of non-use. Similar to many curling irons today, an
indicator light is used to tell the user if the rod is on/hot or off.
The motor button in the redesign serves to activate the motor
in the rod (see Appendix D).
The button is pressed by the thumb in the thumb support region. The movement
of the thumb from its location for opening the clasp to its location for
activating the motor is minimal, so it will not likely cause undo strain
on the thumb. Additionally, note that the thumb will not be overextended
(as in the traditional curling iron) while pressing the button due to the
contour of the thumb support region (see region in Appendices
B, C
and F, Diagram 1).
To control the heat setting, the bottom portion of the handle
will rotate to the desired setting. This portion is larger than that on
a traditional curling iron, which makes it easier to turn to adjust the
setting. This portion is serrated to assist the grip. A window in this portion
will show the user the heat setting.
Rod Traditional
The traditional rod (Appendix A)
attaches directly to the handle and does not move from that position. It
is made of metal that quickly heats up and becomes very hot when on. The
clasp of the rod is raised in order to slide a lock of hair underneath and
then lowered to hold the end of the lock. As the handle is turned, the hair
wraps around the rod and heats through heat radiation from the metal.
Rod Redesign (Appendices B & D)
The major new function of the redesign is the addition of a motor
to the rod. This motor will serve to turn the rod with the press of a button
on the handle. This eliminates the major ergonomic problem of using a curling
iron, twisting the wrist over and over to wrap a lock of hair around the
rod, which can cause tenosynovitis. The motor is encased in a heat-resistant
case within the rod to prevent melting. As the motor button activates the
rod, it will slowly spin, wrapping the lock of hair around itself. Such
a motor significantly reduces the effort needed by the user.
In the redesign, a joint has been created between the rod
and the handle. Because the handle is at an angle, it will not work well
to rotate the handle in order to wrap the hair around the rod. This is an
advantage in that the hand holding the handle will not have to continuously
rotate when using a curling iron, which could lead to tenosynovitis (Sanders
and McCormick, 1993). The joint allows the rod to move separately from the
handle.
The other change in the rod design is the clasp. Traditional
clasps, if not perfectly aligned with the rod down the entire length of
the clasp, often do not grasp hair tightly enough so that the end slips
out when trying to wind the hair around the rod. The new clasp is made up
of two separate pieces of metal encased in fire-resistant fabric. This gives
more stability to the piece of hair being clasped, as it now has twice "holding
power". While not directly ergonomically beneficial, the frustration
eliminated by this design feature will benefit the psychological well-being
of the user.
Tip Traditional
On traditional curling irons, the main purpose of the tip is to provide
a protective cover to the end of the rod when it is hot. It usually consists
of a small piece of plastic.
Tip Redesign (Appendices B & E)
In the redesign, the tip is used as a rod rest. The tip is
shaped like a circle with two flat edges. Each flat side will serve as a
stable rest when the curling iron is laid down on a flat surface. The two
flat sides gives the user more flexibility as to which side to lay the curling
iron down; this flexibility also supports both right- and left-handed users.
The size of the tip extends far enough beyond the rod so as to be sure the
rod does not touch a surface when the curling iron is laid down. Designing
the tip as a rod rest will decrease the possibility of burns and/or fires
caused by this tool.
Another new function of the tip is that of the turn of direction knob.
Each of the flat sides mentioned above will have soft insets. When the user
squeezes these insets, the joint of the rod will loosen. The rod, and thus
the clasp, can then be rotated to whichever clasp location is best for the
user. This choice of direction makes the curling iron accessible to both
right- and left-handers. It also provides the opportunity to switch curl
direction, that is whether the user wants to curl hair under or out.
Conclusion
This redesigned curling iron could lead to increased user comfort and decreased
hand-tool-related injuries and muscle fatigue, not to mention user frustration.
By minimizing ulnar deviation, thumb hyperextension, wrist deviation, slippage,
tenosynovitis, user frustration and single-hand use, the user will be much
healthier and happier with the new product. Both left and right-handers
can use this curling iron equally well. And due to the small amount of force
needed to squeeze the handle and turn the wheel, and the fairly small scale
of the tool, the users are not limited by gender.
Ergonomic design considerations can improve the well being for human beings,
and whether the improvement is significant or slight, design considerations
should be well thought out when creating a product.
Bibliography
Armstrong, T. J., Radwin, R. G., & Hansen,
D. J. (1986). Repetitive trauma disorders: job evaluation and design. Human
Factors. 28 (3), pp. 325-336.
Fellows, G. L. & Freivalds, A. (1991). Ergonomics
evaluation of a foam rubber grip for tool handles. Applied Ergonomics. 22
(4), pp. 225-230.
Hedge, A. (1997). Hand Tool Design. DEA 651 class
notes.
Konz, S. (1986). Bent hammer handles. Human Factors.
28 (3), pp. 317-323.
Lewis, W. G. & Narayan, C. V. (1993). Design
and sizing of ergonomic handles for hand tools. Applied Ergonomics. 24 (5),
pp. 351-356.
Sanders, M. S. & McCormick, E. J. (1993). Human
Factors in Engineering (7th edition). New York: McGraw-Hill, Inc. pp. 383-409.
Schoenmarklin, R. W. & Marras, W. S. (1989).
Effects of handle angle and work orientation on hammering: II. Muschle fatigue
and subjective ratings of body discomfort. Human Factors. 31 (4), pp. 413-420.
Schoenmarklin, R. W. & Marras, W. S. (1989). Effects of handle angle and work orientation on hammering: I. Wrist motion and hammering performance. Human Factors. 31 (4), pp. 397-411.
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