U.S. patent application number 11/540743 was filed with the patent office on 2007-04-26 for isolation device for shock reduction in a neonatal transport apparatus.
Invention is credited to Michael Bailey-VanKuren, Amit Shukla.
Application Number | 20070089236 11/540743 |
Document ID | / |
Family ID | 37998712 |
Filed Date | 2007-04-26 |
United States Patent
Application |
20070089236 |
Kind Code |
A1 |
Bailey-VanKuren; Michael ;
et al. |
April 26, 2007 |
Isolation device for shock reduction in a neonatal transport
apparatus
Abstract
A device in combination with a neonatal transport cart that
reduces the amount of energy transmitted to the surface upon which
an infant rests during transport. A pair of plates, one of which is
mounted to the incubator and the other of which is mounted to the
stretcher, has a gap between the substantially parallel plates. The
gap contains springs, preferably gas springs, with a spring rate in
a range and a damping effect. The springs reduce the energy
transmission to the infant by the stretcher or other platform.
Inventors: |
Bailey-VanKuren; Michael;
(Hamilton, OH) ; Shukla; Amit; (Oxford,
OH) |
Correspondence
Address: |
KREMBLAS, FOSTER, PHILLIPS & POLLICK
7632 SLATE RIDGE BOULEVARD
REYNOLDSBURG
OH
43068
US
|
Family ID: |
37998712 |
Appl. No.: |
11/540743 |
Filed: |
September 29, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60721630 |
Sep 29, 2005 |
|
|
|
Current U.S.
Class: |
5/1 |
Current CPC
Class: |
A61G 1/02 20130101; A61G
3/006 20130101; F16F 15/0232 20130101; A61G 11/00 20130101; A61G
1/042 20161101 |
Class at
Publication: |
005/001 |
International
Class: |
A47C 31/00 20060101
A47C031/00 |
Claims
1. An apparatus for reducing the transmission of kinetic energy
from a support table to an isolette in which an infant is resting,
the apparatus comprising: (a) a first plate mounted to the support
table; (b) a second plate spaced from the first plate to form a
gap, the second plate being mounted to the isolette; and (c) at
least one spring mounted in the gap between the first and second
plates.
2. The apparatus in accordance with claim 1, wherein the first
plate is substantially parallel to the second plate.
3. The apparatus in accordance with claim 1, wherein said at least
one spring further comprises a plurality of springs mounted in the
gap, each of said springs being mounted to at least one of the
plates.
4. The apparatus in accordance with claim 3, wherein said plurality
of springs further comprises a plurality of gas springs mounted
around a peripheral edge of the first plate and around a peripheral
edge of the second plate.
5. The apparatus in accordance with claim 4, further comprising a
central gas spring mounted to the first and second plates and
positioned centrally of said plurality of gas springs.
6. The apparatus in accordance with claim 5, wherein at least some
of said plurality of gas springs are mounted to the plates in a
reverse configuration to prevent damage to other of said
springs.
7. The apparatus in accordance with claim 1, wherein the stiffness
of said at least one spring is in a range from about 500 lb/in and
about 4,500 lb/in.
8. The apparatus in accordance with claim 7, wherein the stiffness
of said at least one spring is about 800 lb/in.
9. The apparatus in accordance with claim 1, wherein an effective
attenuation of the apparatus is in a range from about 10 Hz to
about 18 Hz.
10. The apparatus in accordance with claim 9, wherein the effective
attenuation of the apparatus is in a range from about 10.25 to
about 17.09 Hz.
11. The apparatus in accordance with claim 1, wherein a damping
rate is up to about 4.0%.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] This invention relates generally to mechanisms for
transporting newborn infants by ground or air transportation.
[0003] 2. Description of the Related Art
[0004] Neonatal transport is the transport of newborn infants to a
medical facility to provide critical care. Transportation is
typically accomplished via ground, such as by ambulance, and air,
such as by airplane or helicopter. The transportation of neonatal
patients by conventional means, such as in neonatal transport
systems attached to medical stretchers in ambulances, exposes the
patients to physical shock and vibration communicated through the
relatively rigid structures, and this shock is often detrimental to
the medical condition of the patient. Current neonatal transport
systems do not include an effective subsystem for shock
suppression.
[0005] Neonatal patients often exhibit extreme sensitivity to
external stimuli including physical manipulation. The result of
external stimuli is often manifested by a change in heart rate or
breathing rate ultimately affecting the oxygenation rate (% oxygen)
in the bloodstream.
[0006] Poor rear suspension with a narrow wheel base and high
center of gravity, as well as poor road conditions, can lead to
uncomfortable bouncing of a medical stretcher. This may be
detrimental to some patients, especially those with orthopedic
injuries. Relating to air transport, gravitational forces can lead
to variations in cardiac output, and the shifting of a patient due
to motion or vibration could be disastrous for one who has a
cervical spine injury. Vibration and noise can be disconcerting to
the patient, lead to increased anxiety, and be manifested
physiologically by increased blood pressure, heart rate,
diaphoresis, and combativeness.
[0007] Transportation can increase the stress of the infant. Some
conditions may worsen during transport due to the vibrations and
bumps of the ride, and chest tubes may move and get dislodged with
the movement or vibrations of the ambulance. Noise and vibration
have a greater effect on neonates, and medical equipment can also
be adversely affected.
[0008] Despite the adverse effects of transportation on neonatal
patients, there has been little advancement in this field. The
existing neonatal transport cart is an adult stretcher with
approximately 450 pounds of instrumentation and equipment mounted
on the support platform, as illustrated in FIG. 1. The neonatal
equipment includes an incubator (also referred to as an isolette),
temperature monitoring instruments, and vital sign indicators. In
all, the value of this system is often close to $500,000. Transport
teams utilize these carts for moving critical patients.
Accelerations experienced in a typical transport system can be as
high as 2.5 g.
[0009] The prior art does not contain a suitable solution for the
problem of the transmission of shock and vibration to neonatal
patients. The need exists for a system to reduce the transmission
of kinetic energy to neonatal patients.
BRIEF SUMMARY OF THE INVENTION
[0010] The invention is an apparatus for reducing the transmission
of kinetic energy from a support platform to an incubator upon
which an infant is resting. The apparatus comprises a first plate
mounted to the support table and a second plate spaced from the
first plate to form a gap. In a preferred embodiment, the first
plate is substantially parallel to the second plate and the second
plate is mounted to the incubator. At least one spring is mounted
in the gap between the first and second plates, the spring further
comprises a plurality of gas springs mounted in the gap, and each
of said springs is mounted to the plates.
[0011] In a more preferred embodiment, some gas springs are mounted
to the plates in a reverse configuration to prevent damage to other
of said springs. This reverse configuration prevents the gas
springs from being damaged under tensile force.
[0012] The invention is a shock suppression system designed to fit
between the isolette and the stretcher platform. This location
facilitates the use of an existing quick disconnect mechanism and
minimizes the ergonomic implications on the transport team
personnel.
[0013] An air spring based system is disclosed in which air springs
are mounted between a pair of stiff plates. One plate is for
mounting to the isolette, and the other plate is for mounting to
the support platform, such as a stretcher. The system dynamics show
that effective attenuation of the vibrations can be achieved by the
air springs. The effect of increasing pressure in the air springs
is presented. Furthermore, the pressure in the air springs and the
configuration of the air springs affect the transport cart system
response at low frequencies. Therefore, the dynamic model of the
transport cart is a valuable tool in the process for redesign of
the neonatal transport cart.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
[0014] FIG. 1 is a side view in perspective illustrating a
conventional neonatal transport cart and isolette.
[0015] FIG. 2 is a side view illustrating the preferred embodiment
of the present invention in an operable position on a transport
cart.
[0016] FIG. 3 is a table containing air spring stiffness equation
parameters.
[0017] FIG. 4 is a table containing nominal system parameters.
[0018] FIG. 5 is a schematic illustration of a neonatal transport
cart in combination with the vibration absorber of the present
invention.
[0019] In describing the preferred embodiment of the invention
which is illustrated in the drawings, specific terminology will be
resorted to for the sake of clarity. However, it is not intended
that the invention be limited to the specific term so selected and
it is to be understood that each specific term includes all
technical equivalents which operate in a similar manner to
accomplish a similar purpose. For example, the word connected or
term similar thereto are often used. They are not limited to direct
connection, but include connection through other elements where
such connection is recognized as being equivalent by those skilled
in the art.
DETAILED DESCRIPTION OF THE INVENTION
[0020] U.S. Provisional Application No. 60/721,630 filed Sep. 29,
2005 is incorporated herein by reference.
[0021] The preferred embodiment of the present invention is shown
in FIG. 2. The invention includes a pair of plates 10 and 12
arranged in a substantially parallel relationship. The plates 10
and 12 are preferably sheet metal, such as stainless steel, but
could be aluminum, wood, composite or any other suitable material
in sheet form. The upper plate 10 mounts, in an operable position,
to the underside of the isolette 8 (see FIG. 1). The lower plate 12
mounts, in an operable position, to the upper surface of the
neonatal transport cart 40, shown in FIG. 2. The plates 10 and 12
can mount to the respective structures using screws, adhesives,
specialized brackets that clamp or any other conventional fastener.
Furthermore, the transport cart 40 is but one of many types of
support platforms upon which the invention can be mounted. Other
conventional supports can be used in combination with the
invention. The conventional structures operate in a conventional
manner, except for the effect of the invention, as will be
described below.
[0022] The plates 10 and 12 are separated by a gap, and at least
one air spring is interposed in that gap, with firm attachment to
each of the plates 10 and 12. It is preferred that multiple air
springs mount to the plates 10 and 12 in the gap, and it is most
preferred that nine air springs are mounted in the gap, with two at
each corner of the rectangular plates 10 and 12, and one in the
center. However, the number of air springs must be at least one,
and there is no theoretical upper limit to the number of air
springs. Of course, because of the cost of air springs, there will
be a practical upper limit to the number.
[0023] The air springs 20, 22, 24, 26 and 28 mount at their upper
ends to the upper plate 10 using a screw-threaded shaft extending
upwardly through an opening in the plate 10 and a nut fastened on
the opposite side of the plate 10. The air springs 20-28 mount at
their lower ends to the lower plate 12 using similar fasteners. The
air springs 20, 22, 26 and 28 are mounted at the four corners of
the rectangular plates 10 and 12, and the spring 24 mounts
centrally of the plates 10 and 12 by fastening to the plates 10 and
12 in a manner similar to the springs positioned at the peripheral
edges of the plates.
[0024] Each of the corner air springs 20, 22, 26 and 28 is a
conventional spring, such as, for example, a Firestone Industrial
model 2M2A Air Mount. The central air spring 24 can be, for
example, a model 16 Air Mount. Of course, substitute air springs
can be used, as will be understood by the person having ordinary
skill. Still further, other springs, whether mechanical, magnetic,
elastomeric or any other type, can be used in place of the air
springs 20-28, as will be understood. For example, it is
contemplated that mechanical springs in combination with dampers,
such as dashpots or friction brakes, can be substituted for the
preferred air springs, with resulting practical effects that will
be understood by the person having ordinary skill in the art.
[0025] The air springs 20-28 are designed to sustain a compressive
load applied by the plates 10 and 12, which tends to bring the
plates closer to one another. Although not shown in FIG. 2, it is
preferred that an additional air spring be mounted at each corner
of the plates 10 and 12 in order to protect the springs 20, 22, 26
and 28 under tensile loads applied by the plates 10 and 12. These
tensile load-protecting springs prevent the springs 20-28 from
being pulled apart or otherwise damaged by movement of the plates
10 and 12 away from one another.
[0026] The air springs 20-28 have both a spring rate and a
measurable degree of damping. Thus, the air springs 20-28 provide
not only a spreading of the application of the force applied
through the cart to the isolette over a greater period of time, but
they also dampen to reduce the transmission of energy through the
invention. Thus, not all of the energy that is applied to the cart,
such as by the floor of the ambulance in which the cart is riding,
is transferred to the isolette. In fact, it is preferred that a
substantial amount of energy is not transferred to the isolette,
and this is accomplished by the invention.
[0027] The vibration isolation is achieved, in the preferred
embodiment described above, using air springs between the stretcher
and the isolette. Air springs are preferred for vibration isolation
due to their low system natural frequencies (less than 5.0 Hz)
which can be reduced by use of a reservoir. Further, the system
natural frequencies do not change significantly with a change in
load.
[0028] The spring rate of an air spring is not constant and is a
function of the change in effective area, volume, and pressure.
This stiffness of the air springs is related to two factors: the
variation in volume, and the variation of effective area. This
overall stiffness is given as: F s = nP 1 .times. V 1 n .times. A V
1 n + 1 d V 1 d h - ( P 1 - P a ) .times. d A d h ##EQU1## where
F.sub.s is the stiffness of the air spring system and the equation
parameters are defined in FIG. 3. It is preferred that the
stiffness of the air spring system range from no less than about
500 lb/in, and no more than about 4,500 lb/in. The preferred range
is about 800 lb/in.
[0029] The 4.5 in. diameter spring 24 is positioned at the center
of the plates 10 and 12 and the four 1.34 in. diameter springs 20,
22, 26 and 28 are placed at the corners of the plates 10 and 12.
The theoretical system model, with reference to the schematic
illustration of FIG. 5 and the equation parameters as defined in
FIG. 4, is: [ M 1 0 0 M 2 ] .function. [ x 1 x 2 ] + [ C 1 + C 2 -
C 2 - C 2 C 2 ] .function. [ x . 1 x . 2 ] + [ K 1 + K 2 - K 2 - K
2 K 2 ] .function. [ x 1 x 2 ] = [ F 0 ] ##EQU2## where K.sub.2 is
the stiffness of the air spring system. The stiffness of the air
spring system is a function of the pressure in the springs as well
as the configuration used. FIG. 5 shows the principle behind the
invention: that the appropriate combination of spring rate and
damping results in a device that greatly reduces the transmission
of energy to the incubator upon which the infant is resting. Other
apparatuses with spring and damping characteristics within the
range described herein can be substituted for the preferred
embodiment. For example, the central air spring can be 11.34 cm in
diameter and the outer air springs can be 3.4 cm diameter.
[0030] The system natural frequency due to the inclusion of air
springs was determined to be close to 3 Hz. Effective attenuation
of the vibrations was achieved by the air springs, and "effective
attenuation" is defined herein to include a range extending from
about 10 Hz to about 18 Hz. Preferably, the system attenuates
vibrations in the range of about 10.25 to about 17.09 Hz. At
frequencies greater than about 10 Hz, the attenuation obtained for
the various configurations was similar. However, at lower
frequencies the response amplitude was considerably affected by the
configuration.
[0031] The spring system is designed for damping in a range
extending from just greater than zero to about 4.0%. Thus, the
invention serves to dampen the oscillatory motion of the incubator
resulting from the shock of the vibratory motion of the transport
and to reduce the amount of energy transmitted to the isolette in
the manner of a shock absorber. Some damping occurs due to
stretching of the bladder in the air springs 20-28, although any
shock absorber mechanism preferably has some measurable
damping.
[0032] Because the stiffness of an air spring is a function of the
pressure, an increase in air pressure results in higher stiffness.
Thus, one contemplated alternative is to vary the pressure in the
springs during use, such as by the conduits 30 and 32 having gas
passages therein in fluid communication with the reservoirs of the
springs 20-28. The gas passages in the conduits 30 and 32 are
connected to a pneumatic ram or other pressure increasing and
decreasing device (not shown). By compressing or expanding the gas
through the conduits 30 and 32, the device thereby increases or
decreases the pressure in the springs 20-28.
[0033] The invention was tested in three configurations at an
increased pressure level to ascertain a suitable configuration. The
test results revealed the effect of increasing pressure for the
three possible configurations. It is expected that as the pressure
in the air springs is increased, the amplification of the input at
the damped natural frequency of the system model increases.
Furthermore, an increase in air spring pressure increases the
stiffness associated with the spring, which increases the natural
frequency. The effective stiffness for each configuration differs
due to the contributions of the individual springs and the
corresponding pressure.
[0034] A configuration that consisted of smaller springs oriented
at the corners of the rectangular plates displayed the greatest
effect from an increase in pressure with a decrease in transmission
at low frequencies. The inventor concluded that the absence of the
large spring in the center explained some of this difference in
response.
[0035] An air spring based system can effectively attenuate the
vibrations experienced by the transport cart. Additionally, the air
spring pressure and the air spring configuration can affect the
system behavior at low frequencies. Still further, increased
insight into the effect of the air spring pressure on the system
response can assist the designer in air spring selection.
[0036] It is noted herein that alternative embodiments of the
invention exist. It would not be possible to describe all such
alternative embodiments herein. However, it will be understood that
circular plates with numerous springs at the periphery could be
substituted for the preferred embodiment shown in FIG. 2.
Additionally, oval or triangular plates could be used with springs
at positions that will be known by the person having ordinary skill
from the description herein. The plates can be virtually any shape
as can the arrangement of the springs between the plates.
[0037] This detailed description in connection with the drawings is
intended principally as a description of the presently preferred
embodiments of the invention, and is not intended to represent the
only form in which the present invention may be constructed or
utilized. The description sets forth the designs, functions, means,
and methods of implementing the invention in connection with the
illustrated embodiments. It is to be understood, however, that the
same or equivalent functions and features may be accomplished by
different embodiments that are also intended to be encompassed
within the spirit and scope of the invention and that various
modifications may be adopted without departing from the invention
or scope of the following claims.
* * * * *