Note: Descriptions are shown in the official language in which they were submitted.
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RFID ENABLED DRAWER REFRIGERATION SYSTEM
INCORPORATED MATERIAL
This application incorporates U.S. Application No. 61/419,762, filed on
December 3,
2010, and U.S. Application No. 12/631,861, filed on December 7,2009, and also
incorporates U.S. Application No. 61/302,912, filed on February 9, 2010, all
of which are
incorporated herein by reference.
BACKGROUND
The invention relates generally to the field of medication administration, and
more
particularly, to a medication administration system and associated method that
provide
identification, tracking, and temperature control over medications.
Medication dispensing systems have been in use for many years. The initial
purpose
of such systems was to reduce medication errors associated with manual
distribution and the
high cost of maintaining a large amount of inventory. Current systems present
many
advantages, including lower costs associated with pharmaceutical distribution,
improved
inventory control, substance control, automated documentation, further
reduction of errors,
and relieving professional pharmacists and nursing personnel of many tasks.
In large medical facilities, the main inventories of pharmaceutical items are
held in
storage locations which are often far removed from the patients who use them.
To facilitate
secure and accurate delivery of the pharmaceutical items from these storage
locations to the
patient, a variety of systems have been proposed and put into use. In earlier
systems, referred
to as a "cart exchange" system, medication carts are distributed at nursing
stations in the
medical facility, remote from the central pharmacy, and are periodically
exchanged with fully
supplied carts. Typically these carts contain a twenty-four hour supply of
medications sorted
by patient into specific drawers. The "used" cart is returned to a central
pharmacy of supply
area where the next twenty-four hours of medications are replenished.
Narcotics, are stored
in locked boxes on the floor, requiring two nurses with separate keys and a
written log.
While the cart exchange system is still in use for some medications, the
activities of
bringing up many new orders from the central pharmacy during the day, and
having a large
amount of unused medication being returned results in a large amount of labor.
The re-
stocking of these medications needs to be done accurately, and is very time
consuming. As a
result there has been an increasing use of automated, processor-based,
medication cabinets on
the nursing floors. The processor on each cabinet monitors the access to the
pharmaceutical
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items in these fixed cabinets, allowing the current on-hand inventory and the
need for
replenishment to be communicated to a central processor at the central
pharmacy location.
These processor-based dispensing cabinets were initially used for the more
convenient
management of narcotics, and for the ability to have a "floor stock" of common
medications
from which a nurse could issue the first dose of a needed new prescription,
while waiting for
the twenty-four hours supply to be delivered from the pharmacy in the exchange
cart, or on a
special order basis.
Referring now to FIG. 23 the medication cabinet 300 typically comprises an
integrated touch screen 304 coupled to a control unit 306, a communication
link 308 for
linking to a central server 310, and a communication link 314 for linking to
one or more carts
316. Such communication links 308 and 314 are schematically shown as
connections for
wired communication, but could also be transmitters and receivers (e.g., RF,
IR, acoustical)
for wireless communication as would be recognized by one of ordinary skill in
communication technologies. In addition to the data that is input via the
communication
links 308 and 314, data is input manually via a virtual keyboard included in
the touch screen
304. The communication link 308 is a connection to the server 310 and allows
the
medication cabinet 300 to interface with the data base 320 to which the server
310 has access
for real-time updates, as needed. It also provides necessary information to
guide the pre-
authorized healthcare attendant in the preparation of patient medications,
intravenous
solutions, and the like. In an alternative embodiment shown in FIG. 24, an
actual keyboard
322 or keypad, or similar device, may replace or augment the functions of the
touch screen
304.
These processor-based medication cabinets 300 offer the possibility of storing
the
majority of medications that the patients on the floor might need during the
day and night. In
many cases, these medications are stored in pockets within locked drawers. A
nurse, upon
entering his or her own personal ID, and the ID of a specific patient, will
see the medications
that are approved overall for that selected patient and will also see what
medications are due
at that particular time, referred to generally as "Due Medications." The task
for the central
pharmacy then is to monitor the on-hand stock of the medications stored in the
cabinets, and
restock those levels at regular intervals. A significant advantage of this
process is not having
unused doses of medications returned to the central pharmacy. It also means
that first doses
(as well as subsequent doses) are immediately available.
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There are still many situations that continue to require medications to be
brought from
the central pharmacy. For example, to avoid medication errors, intravenous
fluids (IVs) that
contain medication may be mixed in the pharmacy and brought up to the floor
for safety
reasons, rather than being prepared by nurses by attaching a so-called piggy-
back medication
bag to a standard diluent bag. There are also specialized, or infrequently-
used medications,
or those with short life, or requiring refrigeration, or that need special
handling from the
pharmacy. Many medicines and vaccines are temperature sensitive and have
precise storage
requirements. Some medical compositions having low stability need to be
maintained under
low temperature, perhaps within the range of 2 to 6 degrees Celsius. Typically
where cooling
is required, a separate medication cabinet is used that includes a
refrigeration unit.
Present medication cabinets are either entirely refrigerated or non-
refrigerated. Every
drawer in these cabinets experiences the same refrigeration, or lack thereof,
depending on the
cabinet. Refrigeration is relatively expensive due to the power requirements
and the
refrigeration devices needed. Medication cabinets as a whole are expensive and
relatively
large, each having its own computer equipment, power equipment, communication
equipment, and each taking up valuable floor space. In many cases in the prior
art where
some patients require medications that must be refrigerated prior to
administration, as well as
medications that should not be refrigerated, two cabinets are required, one of
which is
refrigerated and the other of which is non-refrigerated. In some cases, only a
small portion of
a refrigerated cabinet is needed yet refrigeration is provided to the entire
cabinet, a large
portion of which is empty. This is an inefficient approach. While the current
systems
provide working methods for issuing refrigerated medications, it would be
desirable to reduce
the cost of the cabinet drawers, allowing more items to be kept in a single
cabinet that has
both refrigerated and non-refrigerated drawers. It would therefore be
beneficial from both a
cost standpoint and a space standpoint to have both refrigerated and non-
refrigerated drawers
in a single cabinet.
It is also desirable to be able to track the temperature of the refrigerator
or other
temperature-controlled cabinet or drawer and record the tracked temperature
over time in a
log. Such tracking and record keeping may be strongly recommended or required
by some
healthcare organizations, such as the Joint Commission on Accreditation of
Healthcare
Organizations (JCAHO). It is also desirable to be able to automatically
provide an alert if the
temperature (or relative humidity) is outside an acceptable range for the
medications
requiring temperature control.
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The handling of temperature controlled medications has also been a manual
process in
determining which medication requires temperature control and under what
conditions it
must be stored. Such manual handling, examination, and research is time
consuming. It
would be desirable to provide a system and method that can automate at least
some of these
requirements so that efficiency is increased.
Hence, those skilled in the art have recognized a need for and automated
system and
method for recognizing which medications require refrigeration, determining
what level of
refrigeration is required, and effecting such refrigeration. Those of skill in
the art have also
recognized the need to track the temperature of the refrigerator or other
temperature-
controlled cabinet or drawer in which temperature-controlled medications are
kept and record
the tracked temperature over time in a log. Those of skill in the art have
further recognized
the need for having both refrigerated and non-refrigerated drawers in a single
cabinet so that
expense and requirements for space are both reduced. The present invention
fulfills these
needs and others.
Radio-frequency identification ("RFID") is the use of electromagnetic energy
("EM
energy") to stimulate a responsive device (known as an RFID "tag" or
transponder) to
identify itself and in some cases, provide additionally stored data. RFID tags
typically
include a semiconductor device having a memory, circuitry, and one or more
conductive
traces that form an antenna. Typically, RFID tags act as transponders,
providing information
stored in the semiconductor device memory in response to an RF interrogation
signal
received from a reader, also referred to as an interrogator. Some RFID tags
include security
measures, such as passwords and/or encryption. Many RFID tags also permit
information to
be written or stored in the semiconductor memory via an RF signal.
RFID tags may be incorporated into or attached to articles to be tracked. In
some
cases, the tag may be attached to the outside of an article with adhesive,
tape, or other means
and in other cases, the tag may be inserted within the article, such as being
included in the
packaging, located within the container of the article, or sewn into a
garment. The RFID tags
are manufactured with a unique identification number which is typically a
simple serial
number of a few bytes with a check digit attached. This identification number
is incorporated
into the tag during manufacture. The user cannot alter this
serial/identification number and
manufacturers guarantee that each serial number is used only once. This
configuration
represents the low cost end of the technology in that the RFID tag is read-
only and it
responds to an interrogation signal only with its identification number.
Typically, the tag
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continuously responds with its identification number. Data transmission to the
tag is not
possible. These tags are very low cost and are produced in enormous
quantities.
Such read-only RFID tags typically are permanently attached to an article to
be
tracked and, once attached, the serial number of the tag is associated with
its host article in a
computer data base. For example, a particular type of medicine may be
contained in
hundreds or thousands of small vials. Upon manufacture, or receipt of the
vials at a health
care institution, an RFID tag is attached to each vial. Each vial with its
permanently attached
RFID tag will be checked into the data base of the health care institution
upon receipt. The
RFID identification number may be associated in the data base with the type of
medicine,
size of the dose in the vial, and perhaps other information such as the
expiration date of the
medicine. Thereafter, when the RFID tag of a vial is interrogated and its
identification
number read, the data base of the health care institution can match that
identification number
with its stored data about the vial. The contents of the vial can then be
determined as well as
any other characteristics that have been stored in the data base. This system
requires that the
institution maintain a comprehensive data base regarding the articles in
inventory rather than
incorporating such data into an RFID tag.
An object of the tag is to associate it with an article throughout the
article's life in a
particular facility, such as a manufacturing facility, a transport vehicle, a
health care facility,
a storage area, or other, so that the article may be located, identified, and
tracked, as it is
moved. For example, knowing where certain medical articles reside at all times
in a health
care facility can greatly facilitate locating needed medical supplies when
emergencies arise.
Similarly, tracking the articles through the facility can assist in generating
more efficient
dispensing and inventory control systems as well as improving work flow in a
facility.
Additionally, expiration dates can be monitored and those articles that are
older and about to
expire can be moved to the front of the line for immediate dispensing. This
results in better
inventory control and lowered costs.
Other RFID tags are writable and information about the article to which the
RFID tag
is attached can be programmed into the individual tag. While this can provide
a distinct
advantage when a facility's computer servers are unavailable, such tags cost
more, depending
on the size of the memory in the tag. Programming each one of the tags with
information
contained in the article to which they are attached involves further expense.
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RFID tags may be applied to containers or articles to be tracked by the
manufacturer,
the receiving party, or others. In some cases where a manufacturer applies the
tags to the
product, the manufacturer will also supply a respective data base file that
links the
identification number of each of the tags to the contents of each respective
article. That
manufacturer supplied data base can be distributed to the customer in the form
of a file that
may easily be imported into the customer's overall data base thereby saving
the customer
from the expense of creating the data base.
Many RFID tags used today are passive in that they do not have a battery or
other
autonomous power supply and instead, must rely on the interrogating energy
provided by an
RFID reader to provide power to activate the tag. Passive RFID tags require an
electromagnetic field of energy of a certain frequency range and certain
minimum intensity in
order to achieve activation of the tag and transmission of its stored data.
Another choice is an
active RFID tag; however, such tags require an accompanying battery to provide
power to
activate the tag, thus increasing the expense of the tag and making them
undesirable for use
in a large number of applications.
Depending on the requirements of the RFID tag application, such as the
physical size
of the articles to be identified, their location, and the ability to reach
them easily, tags may
need to be read from a short distance or a long distance by an RFID reader.
Such distances
may vary from a few centimeters to ten or more meters. Additionally, in the
U.S. and in
other countries, the frequency range within which such tags are permitted to
operate is
limited. As an example, lower frequency bands, such as 125 KHz and 13.56 MHz,
may be
used for RFID tags in some applications. At this frequency range, the
electromagnetic energy
is less affected by liquids and other dielectric materials, but suffers from
the limitation of a
short interrogating distance. At higher frequency bands where RFID use is
permitted, such as
915 MHz and 2.4 GHz, the RFID tags can be interrogated at longer distances,
but they de-
tune more rapidly as the material to which the tag is attached varies. It has
also been found
that at these higher frequencies, closely spaced RFID tags will de-tune each
other as the
spacing between tags is decreased.
There are a number of common situations where the RFID tags may be located
inside
enclosures. Some of these enclosures may have entirely or partially metal or
metallized
surfaces. Examples of enclosures include metal enclosures (e.g., shipping
containers), partial
metal enclosures (e.g., vehicles such as airplanes, buses, trains, and ships
that have a housing
made from a combination of metal and other materials), and non-metal
enclosures (e.g.,
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warehouses and buildings made of wood). Examples of objects with RFID tags
that may be
located in these enclosures include loose articles, packaged articles, parcels
inside
warehouses, inventory items inside buildings, various goods inside retail
stores, and various
portable items (e.g., passenger identification cards and tickets, baggage,
cargo, individual
life-saving equipment such as life jackets and masks) inside vehicles, etc.
The read range (i.e., the range of the interrogation and/or response signals)
of RFID
tags is limited. For example, some types of passive RFID tags have a maximum
range of
about twelve meters, which may be attained only in ideal free space conditions
with favorable
antenna orientation. In a real situation, the observed tag range is often six
meters or less.
Therefore, some of the enclosures described above may have dimensions that far
exceed the
read range of an individual RFID tag. Unless the RFID reader can be placed in
close
proximity to a target RFID tag in such an enclosure, the tag will not be
activated and read.
Additionally, metal surfaces of the enclosures present a serious obstacle for
the RF signals
that need to be exchanged between RFID readers and RFID tags, making RFID tags
located
behind those metal surfaces difficult or impossible to detect.
In addition to the above, the detection range of the RFID systems is typically
limited
by signal strength to short ranges, frequently less than about thirty
centimeters for 13.56 MHz
systems. Therefore, portable reader units may need to be moved past a group of
tagged items
in order to detect all the tagged items, particularly where the tagged items
are stored in a
space significantly greater than the detection range of a stationary or fixed
single reader
antenna. Alternately, a large reader antenna with sufficient power and range
to detect a larger
number of tagged items may be used. However, such an antenna may be unwieldy
and may
increase the range of the radiated power beyond allowable limits. Furthermore,
these reader
antennae are often located in stores or other locations where space is at a
premium and it is
expensive and inconvenient to use such large reader antennae. In another
possible solution,
multiple small antennae may be used but such a configuration may be awkward to
set up
when space is at a premium and when wiring is preferred or required to be
hidden.
In the case of medical supplies and devices, it is desirable to develop
accurate
tracking, inventory control systems, and dispensing systems so that RFID
tagged devices and
articles may be located quickly should the need arise, and may be identified
for other
purposes, such as expiration dates. In the case of medical supply or
dispensing cabinets used
in a health care facility, a large number of medical devices and articles are
located closely
together, such as in a plurality of drawers. Cabinets such as these are
typically made of
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metal, which can make the use of an external RFID system for identification of
the stored
articles difficult. In some cases, such cabinets are locked due to the
presence of narcotics or
other medical articles or apparatus within them that are subject to a high
theft rate. Thus,
manual identification of the cabinet contents is difficult due to the need to
control access.
Providing an internal RFID system in such a cabinet can pose challenges. Where
internal articles can have random placement within the cabinet, the RFID
system must be
such that there are no "dead zones" that the RFID system is unable to reach.
In general, dead
zones are areas in which the level of coupling between an RFID reader antenna
and an RFID
tag is not adequate for the system to perform a successful read of the tag.
The existence of
such dead zones may be caused by orientations in which the tag and the reader
antennae are
in orthogonal planes. Thus, articles placed in dead zones may not be detected
thereby
resulting in inaccurate tracking of tagged articles.
Often in the medical field, there is a need to read a large number of tags
attached to
articles in such an enclosure, and as mentioned above, such enclosures have
limited access
due to security reasons. The physical dimension of the enclosure may need to
vary to
accommodate a large number of articles or articles of different sizes and
shapes. In order to
obtain an accurate identification and count of such closely-located medical
articles or
devices, a robust electromagnetic energy field must be provided at the
appropriate frequency
within the enclosure to surround all such stored articles and devices to be
sure that their tags
are all are activated and read. Such medical devices may have the RFID tags
attached to the
outside of their containers and may be stored in various orientations with the
RFID tag (and
associated antenna) pointed upwards, sideways, downward, or at some other
angle in a
random pattern.
Generating such a robust EM energy field is not an easy task. Where the
enclosure
has a size that is resonant at the frequency of operation, it can be easier to
generate a robust
EM field since a resonant standing wave may be generated within the enclosure.
However, in
the RFID field the usable frequencies of operation are strictly controlled and
are limited. It
has been found that enclosures are desired for the storage of certain articles
that do not have a
resonant frequency that matches one of the allowed RFID frequencies. Thus, a
robust EM
field must be established in another way.
Additionally, where EM energy is introduced to such an enclosure for reading
the
RFID tags within, efficient energy transfer is of importance. Under static
conditions, the
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input or injection of EM energy into an enclosure can be maximized with a
simple impedance
matching circuit positioned between the conductor delivering the energy and
the enclosure.
As is well known to those of skill in the art, such impedance matching
circuits or devices
maximize the power transfer to the enclosure while minimizing the reflections
of power from
the enclosure. Where the enclosure impedance changes due to the introduction
or removal of
articles to or from the enclosure, a static impedance matching circuit may not
provide
optimum energy transfer into the enclosure. If the energy transfer and
resulting RF field
intensity within the enclosure were to fall below a threshold level, some or
many of the tags
on articles within the enclosure would not be activated to identify
themselves, leaving an
ineffective inventory system.
It is a goal of many health care facilities to keep the use of EM energy to a
minimum,
or at least contained. The use of high-power readers to locate and extract
data from RFID
tags is generally undesirable in health care facilities, although it may be
acceptable in
warehouses that are sparsely populated with workers, or in aircraft cargo
holds. Radiating a
broad beam of EM energy at a large area, where that EM energy may stray into
adjacent,
more sensitive areas, is undesirable. Efficiency in operating a reader to
obtain the needed
identification information from tags is an objective. In many cases where RFID
tags are read,
hand-held readers are used. Such readers transmit a relatively wide beam of
energy to reach
all RFID tags in a particular location. While the end result of activating
each tag and reading
it may be accomplished, the transmission of the energy is not controlled
except by the aim of
the user. Additionally, this is a manual system that will require the services
of one or more
individuals, which can also be undesirable in facilities where staff is
limited
Hence, those of skill in the art have recognized a need for a medication
cabinet that
provides both a refrigerated drawer and a non-refrigerated drawer to reduce
costs and space
requirements and accommodate various types of medications. A need has also
been
recognized for an RFID tag reader system in which the efficient use of energy
is made to
activate and read all RFID tags in an enclosed area. A further need for
establishing a robust
EM field in enclosures to activate and read tags disposed at random
orientations has also been
recognized. A further need has been recognized for an automated system to
identify articles
stored in a metal cabinet without the need to gain access to the cabinet. The
present invention
fulfills these needs and others.
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SUMMARY OF THE INVENTION
Briefly and in general terms, the present invention is directed to a system
for
providing both refrigerated and non-refrigerated drawers in a single
medication cabinet with
the use of RFID to identify and track medical articles. In particular, there
is provided a
cabinet for storing medical articles, comprising a frame having a plurality of
openings for
receiving drawers, the frame providing an electrically conductive cage about a
first opening
to receive a first drawer, the cage having a front locate at the opening and a
rear, a plurality of
drawers, each of which is configured to be received by a respective opening
and is movable
into and out of the respective opening with the first drawer being configured
to be received
by the opening having the cage, a thermoelectric cooling ("TEC") device
configured to
provide cooling for a single drawer, a second opening adjacent the first
opening having no
cooling device, insulation disposed between the first and second openings
configured to
inhibit cooling from the thermoelectric cooling device from reaching the
drawer of the
second opening, and an RFID reader disposed within the cabinet and configured
to read data
from an RFID tag located within the cabinet.
In accordance with more detailed features, the TEC device is mounted to the
frame
such that the respective drawer moves toward it when the drawer is moved to
the closed
position and moves away from it when the drawer is moved to the open position.
The
respective TEC drawer includes a TEC device enclosure formed at a rear portion
of the
drawer, configured to receive the TEC device into the enclosure when the
drawer is in the
closed position, whereby the depth of the cabinet is reduced. The TEC device
enclosure
comprises a cooling diffuser configured to assist in circulating cooling
equally throughout the
drawer from the TEC device. Also, the drawer having the TEC device enclosure
further
includes partitions configured to separate medical articles from one another
when stored in
the drawer, the partitions also configured such that cooling from the TEC
device is not
inhibited from circulating equally throughout the drawer by the partitions.
In other detailed aspects, the RFID reader comprises an antenna that protrudes
into the
drawer, a drawer includes a TEC enclosure for receiving the TEC device when
the drawer is
in the closed position, the enclosure located so as to not interfere with the
operation of the
antenna in reading tagged articles located in the drawer. The first drawer is
slidable into and
out of the first opening of the cabinet, the drawer having a front panel that
is electrically
conductive and that contacts the electrically conductive cage at the first
opening when the
drawer is slid to a predetermined position within the cabinet. A portion of
the first drawer is
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formed of electrically conductive material which is located at a position on
the drawer such it
comes into contact with the electrically conductive cage to thereby close an
electrically
conductive cage about the drawer.
In yet another aspect in accordance with the invention, the RFID reader is
configured
and positioned within the cabinet to force a resonance in a drawer to result
in a robust
electromagnetic field for reading tagged medical articles stored in the
drawer.
Other detailed aspects include the first drawer being non-electrically
conductive
except for the portion of the drawer that contacts the cage to close the cage
about the drawer.
And further, a temperature sensor is disposed so as to measure the temperature
in a drawer.
The features and advantages of the invention will be more readily understood
from
the following detailed description that should be read in conjunction with the
accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic diagram of a drawer that may be positioned within a
medical
dispensing cabinet, showing the storage of a plurality of medical articles
randomly positioned
in the drawer, each of those articles having an integral RFID tag oriented
randomly;
FIG. 2 is a perspective view of a medication dispensing cabinet having five
drawers,
one of which is similar to the schematic view of FIG. 1, the cabinet also
having an integral
computer for controlling access to the cabinet and performing inventory
tracking by
periodically reading any RFID tags placed on articles stored within the
cabinet, and for
reporting the identified articles to a remote computer;
FIG. 3 is a block and flow diagram showing an embodiment in which an RFID
reader
transmits activating EM energy into a drawer containing RFID tags with a
single transmitting
antenna, receives the data output from the activated RFID tags with a single
receiving
antenna, a computer controlling the transmission of activating energy and
receiving the data
from the activated RFID tags for processing;
FIG. 4 is a block and flow diagram similar to FIG. 3 showing an embodiment in
which an RFID reader transmits activating EM energy into a drawer containing
RFID tags
with two transmitting antennae, receives the data output from the activated
RFID tags with
three receiving antennae, and as in FIG. 3, a computer controlling the
transmission of
activating energy and receiving the data from the activated RFID tags for
processing;
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FIG. 5 shows an enclosure with a single probe and a connector, the probe being
configured to inject EM energy into the enclosure and excite a TE mode;
FIG. 6 shows an enclosure with a single probe and a connector, the probe being
configured to inject EM energy into the enclosure and excite a TM mode;
FIG. 7 shows a plot of coupled power in an enclosure as a function of
frequency for a
resonant enclosure where F. is the natural resonance frequency of the
enclosure;
FIG. 8 shows a plot of coupled power (ordinate axis) in an enclosure as a
function of
frequency (abscissa axis), where ff is a forced resonance frequency, or
otherwise referred to
as a frequency that is not equal to the resonant frequency of the enclosure,
and fõ is the
natural resonant frequency of the enclosure, showing the establishment of a
robust field of
coupled power in the enclosure at the ff frequency;
FIG. 9 shows an enclosure with two probes each with a connector for injecting
EM
energy into the enclosure, one probe being a TM probe and the other being a TE
probe;
FIG. 10 shows a probe, a connector, and an attenuator that is used to improve
the
impedance match between the probe and the enclosure;
FIG. 11 shows a probe, a connector, and a passive matching circuit that is
used to
improve the impedance match between the probe and enclosure;
FIG. 12 shows an active matching circuit connected between a probe located in
an
enclosure and a transceiver, the active matching circuit comprising a tunable
capacitor, a
dual-directional coupler, multiple power sensors, and a comparator used to
provide a closed-
loop, variable matching circuit to improve the impedance match between the
probe and the
enclosure;
FIG. 13 provides a side cross-sectional view of the cabinet of FIG. 2 at the
location of
a drawer with the drawer removed for clarity, showing the placement of two
probe antennae
in a "ceiling mount" configuration for establishing a robust EM field in the
drawer when it is
in place in the cabinet in the closed position;
FIG. 14 is a perspective view of the metallic enclosure showing the probe
configuration of FIG. 13 again showing the two probe antennae for establishing
a robust EM
field in a drawer to be inserted;
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FIG. 15 is a cutaway perspective side view of the metallic enclosure or frame
in
which are mounted the dual probe antennae of FIGS. 13 and 14 with the drawer
removed for
clarity;
FIG. 16 is a frontal perspective view of the view of FIG. 14 with a cutaway
plastic
drawer in place in the metallic enclosure and further showing the dual ceiling
mount probe
antennae protected by an electromagnetically inert protective cover, and
further showing
cooling system components mounted at the back of the cabinet near the drawer's
back, the
drawing also showing a partial view of a drawer slide mechanism for ease in
sliding the
drawer between open and closed positions in the cabinet, the drawer front and
rear panels
having been cutaway in this view;
FIG. 17 is a frontal perspective view at the opposite angle from that of FIG.
16 with
the plastic drawer completely removed showing the dual ceiling mount probe
antennae
protected by the EM inert protective cover mounted to the metallic enclosure,
and further
showing the cooling system components of FIG. 16 mounted at the back of the
cabinet as a
spring loading feature to automatically push the drawer to the open position
when the
drawer's latch is released, the figure also showing a mounting rail for
receiving the slid of the
drawer;
FIG. 18 is a schematic view with measurements in inches of the placement of
two
TEm mode probes in the top surface of the enclosure shown in FIGS. 13-15;
FIG. 19 is a schematic view of the size and placement within the drawer of
FIG. 16 of
two microstrip or "patch" antennae and their microstrip conductors disposed
between
respective antennae and the back of the drawer at which they will be connected
to SMA
connectors in one embodiment, for interconnection with other components;
FIG. 20 is diagram of field strength in an embodiment of an enclosure with a
probe
placed in the enclosure at a position in accordance with the diagram of FIG.
19;
FIG. 21 is a lower scale drawing of the field intensity diagram of FIG. 20
showing a
clearer view of the field intensity nearer the front and back walls of the
enclosure;
FIG. 22 is a block electrical and signal diagram for a multiple-drawer medical
cabinet,
such as that shown in FIG. 2, showing the individual multiplexer switches, the
single RFID
scanner, and power control;
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FIG. 23 shows a medication administration cabinet having a control unit, a
plurality
of drawers and connections to a server and data base;
FIG. 24 shows the medication administration cabinet of FIG. 23 with a view of
two
input devices, one of which is a keyboard and the other of which is a pointing
device in the
form of a "mouse;"
FIG. 25 is an exploded view of a drawer removed from the opening and Faraday
cage
of the medication cabinet, showing details of the drawer design including
partitions for
creating pockets to store medical items, a TEC enclosure at the rear of the
drawer, and part of
the Faraday cage created in the cabinet;
FIG. 26, is an enlarged view of the drawer of FIG. 25 looking from behind the
drawer
so that the metallic front of the drawer can be seen, which, when the drawer
is in the closed
position, completes the Faraday cage about the drawer so that the RFID system
will operate
effectively;
FIG. 27 is another view of the drawer of FIG. 25 showing the TEC device
enclosure
in greater detail at the back of the drawer, showing the thermal diffuser
formed into the
enclosure;
FIG. 28 is a more detailed view of the construction of the part of the cabinet
surrounding a refrigerated drawer showing slabs of insulation around the top,
bottom, and
sides of the drawer, and the metallic liner for forming the Faraday cage;
FIG. 29 presets a partial view of the front of the drawer showing the
insertion of
insulation in the front panel of the drawer;
FIG. 30 presents a perspective view of a system in accordance with aspects of
the
invention showing an open refrigerated drawer with a mounted TEC device,
mediations in
pockets of the drawer, three temperature sensors in pockets, and ambient
temperature sensor,
control unit, and connection with a server and data base;
FIG. 31 presents a method in accordance with aspects of the invention
providing an
automatic system for detecting temperature controlled medications, determining
the
temperature requirements for those medications, and controlling the TEC device
to maintain
the required temperature, with the figure also showing a temperature data
logging system to
satisfy requirements imposed by healthcare authorities; and
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FIG. 32 is a block diagram of a system in accordance with aspects of the
invention in
which an RFID detector system detects the presence of temperature controlled
medical items,
notifies a processor which identifies the temperature requirement for the
detected medication,
and controls the TEC device in a drawer to maintain the required temperature,
the processor
also programmed to create a log of temperature events while the medication is
in the cabinet.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring now in more detail to the exemplary drawings for purposes of
illustrating
embodiments of the invention, wherein like reference numerals designate
corresponding or
like elements among the several views, there is shown in FIG. 1 a schematic
representation of
a partial enclosure 20 in which a plurality of medical articles 22 are stored,
each with a
respective RFID tag 24 that has a unique identification number. The partial
enclosure may
comprise a drawer having a front 26, a left side 28, a right side 30, a rear
32, and a bottom 34.
These articles are randomly distributed in the drawer with the RFID tags
facing in various
and random directions.
As used in regard to the embodiments herein, "reader" and "interrogator" refer
to a
device that may read or write/read. The data capture device is always referred
to as a reader
or an interrogator regardless of whether it can only read or is also capable
of writing. A
reader typically contains a radio frequency module (a transmitter and a
receiver, sometimes
referred to as a "transceiver"), a control unit and a coupling element (such
as an antenna or
antennae) to the RFID tag. Additionally, many readers include an interface for
forwarding
data elsewhere, such as an RS-232 interface. The reader, when transmitting,
has an
interrogation zone within which an RFID tag will be activated. When within the
interrogation zone, the RFID tag will draw its power from the
electrical/magnetic field
created in the interrogation zone by the reader. In a sequential RFID system
(SEQ), the
interrogation field is switched off at regular intervals. The RFID tag is
programmed to
recognize these "off' gaps and they are used by the tag to send data, such as
the tag's unique
identification number. In some systems, the tag's data record contains a
unique serial number
that is incorporated when the tag is manufactured and which cannot be changed.
This
number may be associated in a data base with a particular article when the tag
is attached to
that article. Thus, determining the location of the tag will then result in
determining the
location of the article to which it is attached. In other systems, the RFID
tag may contain
more information about the article to which it is attached, such as the name
or identification
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of the article, its expiration date, it dose, the patient name, and other
information. The RFID
tag may also be writable so that it can be updated.
As used in regard to the embodiments herein, "tag" is meant to refer to an
RFID
transponder. Such tags typically have a coupling element, such as an antenna,
and an
electronic microchip. The microchip includes data storage, also referred to as
memory.
FIG. 2 presents a representative medical dispensing cabinet 40 comprising a
plurality
of movable drawers 42. In this embodiment, there are five drawers that slide
outwardly from
the cabinet so that access is provided to the contents of the drawers. FIG. 1
is a schematic
diagram of a representative drawer that may be positioned within the cabinet
of FIG. 2 for
sliding outward to provide access to the drawer's contents and for sliding
inward into the
cabinet to secure the drawer's contents. The cabinet also comprises an
integral computer 44
that may be used to control access to the drawers and to generate data
concerning access and
contents, and to communicate with other systems. In this embodiment, the
computer
generates data concerning the number and type of articles in the drawers, the
names of the
patients for whom they have been prescribed, the prescribed medications and
their prescribed
administration dates and times, as well as other information. In a simpler
system, the
computer may simply receive unique identification numbers from stored articles
and pass
those identification numbers to an inventory control computer that has access
to a data base
for matching the identification numbers to article descriptions.
Such a cabinet may be located at a nursing station on a particular floor of a
health care
institution and may contain the prescriptions for the patients of that floor.
As prescriptions
are prepared for the patients of that floor, they are delivered and placed
into the cabinet 40.
They are logged into the integral computer 44, which may notify the pharmacy
of their
receipt. A drawer may also contain non-prescription medical supplies or
articles for
dispensing to the patients as determined by the nursing staff At the
appropriate time, a nurse
would access the drawer in which the medical articles are stored through the
use of the
computer 44, remove a particular patient's prescriptions and any needed non-
prescription
articles, and then close the drawer so that it is secured. In order to access
the cabinet, the
nurse may need to provide various information and may need a secure access
code. The
drawers 42 may be locked or unlocked as conditions require.
The computer 44 in some cases may be in communication with other facilities of
the
institution. For example, the computer 44 may notify the pharmacy of the
health care
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institution that a patient's prescription has been removed from the cabinet
for administration
at a particular day and time. The computer may also notify the finance
department of the
health care institution of the removal of prescriptions and other medical
articles for
administration to a particular patient. This medication may then be applied to
the patient's
account. Further, the computer 44 may communicate to administration for the
purpose of
updating a patient's Medication Administration Record (MAR), or e-MAR. The
medication
cabinet 40 computer 44 may be wirelessly connected to other computers of the
health care
institution or may have a wired connection. The cabinet may be mounted on
wheels and may
be moved about as needed or may be stationary and unable to move.
Systems that use RFID tags often employ an RFID reader in communication with
one
or more host computing systems that act as depositories to store, process, and
share data
collected by the RFID reader. Turning now to FIGS. 3 and 4, a system and
method 50 for
tracking articles are shown in which a drawer 20 of the cabinet 40 of FIG. 2
is monitored to
obtain data from RFID tags disposed with articles in that drawer. As mentioned
above, a
robust field of EM energy needs to be established in the storage site so that
the RFID tags
mounted to the various stored articles will be activated, regardless of their
orientation.
In FIGS. 3 and 4, the tracking system 50 is shown for identifying articles in
an
enclosure and comprises a transmitter 52 of EM energy as part of an RFID
reader. The
transmitter 52 has a particular frequency, such as 915 MHz, for transmitting
EM energy into
a drawer 20 by means of a transmitting antenna 54. The transmitter 52 is
configured to
transmit the necessary RFID EM energy and any necessary timing pulses and data
into the
enclosure 20 in which the RFID tags are disposed. In this case, the enclosure
is a drawer 20.
The computer 44 of an RFID reader 51 controls the EM transmitter 52 to cycle
between a
transmit period and a non-transmit, or off, period. During the transmit
period, the transmitted
EM energy at or above a threshold intensity level surrounds the RFID tags in
the drawer
thereby activating them. The transmitter 52 is then switched to the off period
during which
the RFID tags respond with their respective stored data.
The embodiment of FIG. 3 comprises a single transmitting probe antenna 54 and
a
single receiving antenna 56 oriented in such a manner so as to optimally read
the data
transmitted by the activated RFID tags located inside the drawer 20. The
single receiving
antenna 56 is communicatively coupled to the computer 44 of the reader 50
located on the
outside of the drawer 20 or on the inner bottom of the drawer. Other mounting
locations are
possible. Coaxial cables 58 or other suitable signal links can be used to
couple the receiving
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antenna 56 to the computer 44. A wireless link may be used in a different
embodiment.
Although not shown in the figures, those skilled in the art will recognize
that various
additional circuits and devices are used to separate the digital data from the
RF energy, for
use by the computer. Such circuits and devices have not been shown in FIGS. 3
and 4 to
avoid unneeded complexity in the drawing.
The embodiment of FIG. 4 is similar to the embodiment of FIG. 3 but instead
uses
two transmitting probe antennae 60 and 62 and three receiving antennae 64, 66,
and 68. The
configuration and the number of transmitting probe antennae and receiving
antennae to be
used for a system may vary based at least in part on the size of the enclosure
20, the
frequency of operation, the relationship between the operation frequency and
the natural
resonance frequency of the enclosure, and the expected number of RFID tags to
be placed in
it, so that all of the RFID tags inside the enclosure can be reliably
activated and read. The
location and number of RFID reader components can be dependent on the
particular
application. For example, fewer components may be required for enclosures
having a
relatively small size, while additional components, such as shown in FIG. 4,
may be needed
for larger enclosures. Although shown in block form in FIGS. 3 and 4, it
should be
recognized that each receiving antenna 56, 64, 66, and 68 of the system 50 may
comprise a
sub-array in a different embodiment.
The transmit antennae (54, 60, and 62) and the receive antennae (56, 64, 66,
and 68)
may take different forms. In one embodiment as is discussed in more detail
below, a plurality
of "patch" or microstrip antennae were used as the reader receiving antennae
and were
located at positions adjacent various portions of the bottom of the drawer
while the transmit
antennae were wire probes located at positions adjacent portions of the top of
the drawer. It
should be noted that in the embodiments of FIGS. 3 and 4, the RFID reader 50
may be
permanently mounted in the same cabinet at a strategic position in relation to
the drawer 20.
One solution for reliably interrogating densely packed or randomly oriented
RFID
tags in an enclosure is to treat the enclosure as a resonant cavity.
Establishing a resonance
within the cavity enclosure can result in a robust electromagnetic field
capable of activating
all RFID tags in the enclosure. This can be performed by building an enclosure
out of
electrically conductive walls and exciting the metallic enclosure, or cavity,
using a probe or
probes to excite transverse electric (TE) or transverse magnetic (TM) fields
in the cavity at
the natural frequency of resonance of the cavity. This technique will work if
the cavity
dimensions can be specifically chosen to set up the resonance at the frequency
of operation or
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if the frequency of operation can be chosen for the specific enclosure size.
Since there are
limited frequency bands available for use in RFID applications, varying the
RFID frequency
is not an option for many applications. Conversely, requiring a specific set
of physical
dimensions for the enclosure so that the natural resonant frequency of the
enclosure will
equal the available RFID tag activating frequency will restrict the use of
this technique for
applications where the enclosure needs to be of a specific size. This latter
approach is not
practical in view of the many different sizes, shapes, and quantities of
medical articles that
must be stored.
Referring now to FIG. 5, a rectangular enclosure 80 is provided that may be
formed as
part of a medical cabinet, such as the cabinet shown in FIG. 2. It may be
embodied as a
frame disposed about a non-metallic drawer in such a cabinet. The enclosure 80
is formed of
metallic or metallized walls 82, floor 83, and ceiling 84 surfaces, all of
which are electrically
conductive. All of the walls 82, floor 83, and ceiling 84 may also be referred
to herein as
"walls" of the enclosure. FIG. 5 also shows the use of an energy coupling or
probe 86 located
at he top surface 84 of the enclosure 80. In this embodiment, the probe takes
the form of a
capacitor probe 88 in that the probe 88 has a first portion 94 that proceeds
axially through a
hole 90 in the ceiling 84 of the enclosure. The purpose of the coupling is to
efficiently
transfer the energy from the source 52 (see FIGS. 3 and 4) to the interior 96
of the enclosure
80. The size and the position of the probe are selected for effective coupling
and the probe is
placed in a region of maximum field intensity. In FIG. 5, a TEm mode is
established through
the use of capacitive coupling. The length and distance of the bent portion 94
of the probe 88
affects the potential difference between the probe and the enclosure 80.
Similarly, FIG. 6 presents an inductive coupling 110 of the external energy to
an
enclosure 112. The coupling takes the form of a loop probe 114 mounted through
a side wall
116 of the enclosure. The purpose of this probe is to establish a TMoi mode in
the enclosure.
The rectangular enclosures 80 and 112 shown in FIGS. 5 and 6 each have a
natural
frequency of resonance fn, shown in FIG. 7 and indicated on the abscissa axis
118 of the
graph by fn. This is the frequency at which the coupled power in the enclosure
is the highest,
as shown on the ordinate axis 119 of the graph. If the injected energy to the
enclosure does
not match the fõ frequency, the coupled power will not benefit from the
resonance
phenomenon of the enclosure. In cases where the frequency of operation cannot
be changed,
and is other than fn, and the size of the enclosure cannot be changed to
obtain an fõ that is
equal to the operating frequency, another power coupling apparatus and method
must be
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used. In accordance with aspects of the invention, an apparatus and method are
provided to
result in a forced resonance ff within the enclosure to obtain a standing wave
within the
enclosure with constructive interference. Such a standing wave will establish
a robust energy
field within the enclosure strong enough to activate all RFID tags residing
therein.
When an EM wave that is resonant with the enclosure enters, it bounces back
and
forth within the enclosure with low loss. As more wave energy enters the
enclosure, it
combines with and reinforces the standing wave, increasing its intensity
(constructive
interference). Resonation occurs at a specific frequency because the
dimensions of the cavity
are an integral multiple of the wavelength at the resonance frequency. In the
present case
where the injected energy is not at the natural resonance frequency fn of the
enclosure, a
solution in accordance with aspects of the invention is to set up a "forced
resonance" in an
enclosure. This forced resonance is different from the natural resonance of
the enclosure in
that the physical dimensions of the enclosure are not equal to an integral
multiple of the
wavelength of the excitation energy, as is the case with a resonant cavity. A
forced resonance
can be achieved by determining a probe position, along with the probe length
to allow for
energy to be injected into the cavity such that constructive interference
results and a standing
wave is established. The energy injected into the enclosure in this case will
set up an
oscillatory field region within the cavity, but will be different from a
standing wave that
would be present at the natural resonance frequency fõ of a resonant cavity.
The EM field
excited from this forced resonance will be different than the field structure
found at the
natural resonance of a resonant cavity, but with proper probe placement of a
probe, a robust
EM field can nevertheless be established in an enclosure for RFID tag
interrogation. Such is
shown in FIG. 8 where it will be noted that the curve for the forced resonance
ff coupled
power is close to that of the natural resonance fn.
Turning now to FIG. 9, an enclosure 120 having two energy injection probes is
provided. The first probe 86 is capacitively coupled to the enclosure 120 in
accordance with
FIG. 5 to establish a TEo I mode. The second probe 114 is inductively coupled
to the
enclosure 120 in accordance with FIG. 6 to establish a TMoi mode. These two
probes are
both coupled to the enclosure to inject energy at a frequency ff that is other
than the natural
resonance frequency fõ of the enclosure. The placement of these probes in
relation to the
ceiling 126 and walls 128 of the enclosure will result in a forced resonance
within the
enclosure 120 that optimally couples the energy to the enclosure and
establishes a robust EM
field within the enclosure for reading RFID tags that may be located therein.
The placement
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of these probes in relation to the walls of the enclosure, in accordance with
aspects of the
invention, result in the forced resonance curve ff shown in FIG. 8.
Referring briefly to FIG. 10, an impedance matching circuit 121 is shown that
functions to match the impedance of a source of energy 122 to the enclosure
120. The
impedance matching circuit is located between the coaxial cable 122 that feeds
activating
energy to the enclosure 120 and the capacitively coupled probe 88 through a
hole in the
metallic ceiling 126 of the enclosure. While the hole is not shown in the
drawing of FIG. 10,
the insulator 123 that electrically insulates the probe from the metallic
ceiling is shown. In
this case, the matching circuit 121 consists of only a resistive attenuator
124 used to reduce
reflections of energy by the enclosure 120. However, as will be appreciated by
those of skill
in the art, capacitive and inductive components are likely to exist in the
enclosure and in the
coupling 88. FIG. 11 on the other hand presents an impedance matching circuit
124 having
passive reactive components for use in matching the impedance of the coaxial
cable/energy
source 122 and the enclosure 120. In this exemplary impedance matching circuit
124, an
inductive component 125 and a capacitive component 127 are connected in
series, although
other configurations, including the addition of a resistive component and
other connection
configurations, are possible.
Passive components such as resistors, inductors, and capacitors shown in FIGS.
10
and 11 can be used to form matching circuits to match the impedances of the
energy source
and the enclosure. This will aid in coupling power into the enclosure.
However, the passive
matching circuit will improve the impedance match for a specific enclosure
loading, such as
an empty enclosure, partially loaded, or fully loaded enclosure. But as the
enclosure contents
are varied, the impedance match may not be optimized due to the variation in
contents in the
enclosure causing the impedance properties of the enclosure to change.
This non-optimal impedance match caused by variation in enclosure loading can
be
overcome by the use of an active impedance matching circuit which utilizes a
closed loop
sensing circuit to monitor forward and reflected power. Referring now to FIG.
12, an active
matching circuit 130 is provided that comprises one or several fixed value
passive
components such as inductors 132, capacitors 134, or resistors (not shown). In
addition, one
or several variable reactance devices, such as a tunable capacitor 134, are
incorporated into
the circuit; these tunable devices making this an active impedance matching
circuit. The
tunable capacitor 134 can take the form of a varactor diode, switched
capacitor assembly,
MEMS capacitor, or BST (Barium Strontium Titanate) capacitor. A control
voltage is
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applied to the tunable capacitor 134 and varied to vary the capacitance
provide by the device.
The tunable capacitor 134 provides the capability to actively change the
impedance match
between the probe 140 and the enclosure 142.
To complete the active matching circuit, a dual directional coupler 144 along
with two
power sensors 146 can be incorporated. The dual directional coupler 144 and
the power
sensors 146 provide the ability to sense forward and reflected power between
the RFID
transceiver 148 and the active matching circuit 130 and enclosure 142.
Continuous
monitoring of the ratio of forward and reflected power by a comparator 150
provides a metric
to use to adjust the tunable capacitor 134 to keep the probe 140 impedance
matched to the
enclosure 142. An ability to continuously monitor and improve the impedance
match as the
contents of the enclosure are varied is provided with the active matching
circuit 130.
Referring now to the side cross-sectional view of FIG. 13, two ceiling-mounted
160
probe antennae 162 and 164 are shown mounted within an enclosure, which may
also be
referred to herein as a cavity 166, which in this embodiment, operates as a
Faraday cage. As
shown, the Faraday cage 166 comprises walls (one of which is shown) 168, a
back 170, a
floor 172, a ceiling 160, and a front 161 (only the position of the front wall
is shown). All
surfaces forming the cavity are electrically conductive, are electrically
connected with one
another, and are structurally formed to be able to conduct the frequency of
energy ff injected
by the two probes 162 and 164. In this embodiment, the cavity 166 is
constructed as a metal
frame 167 that may form a part of a medical supply cabinet similar to that
shown in FIG. 2.
Into that metal frame may be mounted a slidable drawer. The slidable drawer in
this
embodiment is formed of electrically inert material, that is, it is not
electrically conductive,
except for the front. When the drawer is slid into the cabinet to a closed
configuration, the
electrically conductive front panel of the drawer comes into electrical
contact with another
part or parts of the metallic frame 167 thereby forming the front wall 161 of
the Faraday cage
167.
The amount of penetration or retention into the cavity by the central
conductor 180 of
each probe is selected so as to achieve optimum coupling. The length of the
bent portion 94
of the probe is selected to result in better impedance matching. The position
of the probe in
relation to the walls of the cavity is selected to create a standing wave in
the cavity. In this
embodiment, the probe antennae 162 and 164 have been located at a particular
distance D1
and D3 from respective front 161 and back 170 walls.. These probe antennae, in
accordance
with one aspect of the invention, are only activated sequentially after the
other probe has
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become inactivated. It has been found that this configuration results in a
standing wave
where the injected energy waves are in phase so that constructive interference
results.
FIG. 14 is a front perspective view of the probe configuration of FIG. 13
again
showing the two probe antennae 162 and 164 located in a Faraday-type enclosure
166 for
establishing a robust EM field in an article storage drawer to be inserted. It
should be noted
again that the Faraday cavity 166 is constructed as a metallic frame 167. In
this figure, the
cavity is incomplete in that the front surface of the "cage" is missing. In
one embodiment,
this front surface is provided by an electrically conductive front panel of a
slidable drawer.
When the drawer is slid into the cabinet, the front panel will make electrical
contact with the
other portions of the metallic frame 167 thereby completing the Faraday cage
166, although
other portions of the drawer are plastic or are otherwise non-electrically
conductive. In the
embodiment discussed and shown herein, the two probe antennae 162 and 164 are
both
located along a centerline between the side walls 166 and 168 of the frame
166. The
enclosure in one embodiment was 19.2 inches wide with the probe antennae
spaced 9.6
inches from each side wall. This centered location between the two side walls
was for
convenience in the case of one embodiment. The probes may be placed elsewhere
in another
embodiment. In this embodiment, the spacing of the probes 162 and 164 from
each other is
of little significance since they are sequentially activated. Although not
shown, two receiving
antennae will also be placed into the Faraday cage 166 to receive response
signals from the
activated RFID tags residing within the cavity 166.
It will also be noted from reference to the figures that the probes each have
a bent
portion used for capacitive coupling with the ceiling 160 of the cavity, as is
shown in FIG.
13. The front probe 162 is bent forward while the back probe 164 is bent
rearward A
purpose for this configuration was to obtain more spatial diversity and obtain
better coverage
by the EM field established in the drawer. Other arrangements may be possible
to achieve a
robust field within the cavity 166. Additionally two probes were used in the
particular
enclosure 166 so that better EM field coverage of the enclosure 166 would
result.
FIG. 15 is a cutaway perspective side view of the dual probe antennae 162 and
164 of
FIGS. 13 and 14, also with the drawer removed for clarity. The front probe 162
is spaced
from the left side wall by 1/2 k of the operating frequency Ff as shown. It
will be noted that
the probes each have a bent portion used for capacitive coupling with the
ceiling 160 of the
enclosure 166 as shown in FIG. 13. The front probe 162 is bent forward for
coupling with
the more forward portion of the enclosure while the back probe 164 is bent
rearward for
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coupling with the more rearward portion of the enclosure 166 to obtain more
spatial diversity
and obtain better coverage by the EM field in the drawer. Other arrangements
may be
possible to achieve a robust field and further spatial diversity and coverage
within the
enclosure.
FIG. 16 is a frontal upward-looking perspective view of the frame 167 forming
a
Faraday cage 166 showing a portion of a drawer 180 that has been slidably
mounted within
the frame 167. The front metallic panel of the drawer has been removed so that
its sliding
operation can be more clearly seen. It will also be noted that the dual
ceiling mount probe
antennae 162 and 164 have been covered and protected by an electromagnetically
inert
protective cover 182. The drawer is formed of a non-metallic material, such as
a plastic or
other electromagnetic inert material having a low RF constant. The back 184 of
the drawer
has also been cut away so that a cooling system 189 comprising coils 186 and a
fan 188
located in the back of the frame 167 can be seen. In this case, the drawer 180
is slidably
mounted to the Faraday cage frame with metallic sliding hardware 190. The
sliding hardware
of the drawer is so near the side of the frame 167 of the enclosure 166 and
may be in
electrical contact with the metallic slide hardware of the side walls 168 of
the enclosure that
these metallic rails will have only a small effect on the EM field established
within the
enclosure.
FIG. 17 is an upward looking, frontal perspective view at the opposite angle
from that
of FIG. 16; however, the drawer has been removed. The frame 167 in this
embodiment
includes a mounting rail 192 for receiving the slide of the drawer 180. In
this embodiment,
the mounting rail is formed of a metallic material; however, it is firmly
attached to a side 168
of the Faraday cage and thus is in electrical continuity with the cage. The
figure also shows a
spring mechanism 194 used to assist in sliding the drawer outward so that
access to the
articles stored in the drawer may be gained. The spring is configured to
automatically push
the drawer outward when the drawer's latch is released.
FIG. 18 is a schematic view showing measurements of the placement of two TEm
mode capacitive coupling probes 162 and 164 in the ceiling 160 of the frame
167 shown in
FIGS. 13-15. In this embodiment, the frequency of operation with the RFID tags
is 915
MHz, which therefore has a wavelength of 0.32764 meters or 1.07494 feet. One-
half
wavelength is therefore 0.16382 meters or 6.4495 inches. The length of the
capacitive
coupling bent portion 200 of each of the probes is 5.08 cm or 2.00 in. The
length of the axial
extension 202 of the probes into the enclosure is 3.81 cm or 1.50 in., as
measured from the
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insulator 204 into the enclosure 166. The probe configuration and placement in
the
embodiment was based on an operation frequency of 915 MHz. In one embodiment,
the
enclosure 166 had a depth of 16.1 inches (40.89 cm), a width of 19.2 inches
(48.77 cm) and a
height of 3 inches (7.62 cm). It was found that the optimum probe placements
for this size
and shape (rectangular) enclosure and for the 915 MHz operating frequency
were: the front
probe was spaced from the front wall by 5.0 inches (12.7 cm) and the rear
probe was spaced
from the back wall by 5.0 inches (12.7 cm). As discuss above, the probes in
this embodiment
would only be activated sequentially.
FIG. 19 is a schematic view of the size and placement within the enclosure 166
of
FIG. 16 of two microstrip or "patch" antennae 210 and 212 and their microstrip
conductors
214 and 216 disposed between the respective antennae and the back of the
enclosure at which
they will be connected to SMA connectors (not shown) in one embodiment. Feed
lines 58
(FIG. 3) may be connected to those SMA connectors and routed to the computer
44 for use in
communicating the RFID signals for further processing. The measurements of the
spacing of
some of the microstrip components are provided in inches. The spacing of 9.7
in. is
equivalent to 24.64 cm. The width of the microstrip line of 0.67 in. is
equivalent to 17.0 mm.
The spacing of 1.4 in. is equivalent to 3.56 cm. Other configurations and
types of receiving
antennae may be used, as well as different numbers of such antennae. In the
present
embodiment, the receiving antennae are mounted on insulation at the bottom
inside surface of
the metallic enclosure frame 167 so that the receiving patch antennae are not
in contact with
the metal surfaces of the Faraday cage.
Referring now to FIG. 20, the field intensity or field strength in the
enclosure
discussed above is shown with the ordinate axis shown in volts/meter and the
abscissa axis
shown in meters. It will be seen from the diagram that the maximum field
intensity occurs at
about 5.0 inches (.127 m) which results from the probe positioned at 5.0
inches (12.7 cm)
from the front wall and at a 915 MHz operating frequency. Referring now to
FIG. 21, the
scale has been reduced although the large rise in field intensity can be seen
at 5.0 inches. It
can also be more clearly seen that the field intensity falls off at the right
wall but remains
strong very close to the left wall. Therefore in an embodiment, a second probe
was used that
was placed 5.0 inches (12.7 cm) from the right wall thereby resulting in a
mirror image field
intensity to that shown in FIG. 21. The two probes 162 and 164 are activated
sequentially
and are not both activated simultaneously. It will be noted that better EM
field coverage of
the enclosure 166 is obtained with the two probes and that RFID tags on
articles positioned
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close to the front wall 161 will be activated by the front probe 162 and that
RFID tags on
articles positioned close to the rear wall 170 will be activated by the rear
probe 164 (see FIG.
13).
Although not intending to be bound by theory, in deriving the probe location
for TE
modes in a square or rectangular non-resonant cavity, the following equation
can be useful:
N =2 x L2 ________ - L1
2g
where: N = positive non-zero integer, for example 1,
2, 3, etc.
L1 = distance between probe and back wall
L2 = distance between probe and front wall
kg = wavelength in the cavity
L1 cannot be zero for TE modes, which implies that the probe for TE mode
excitation
cannot be at the front or back wall. For TM modes, the equation is the same,
but N can equal
zero as well as other positive integers. The probe position cannot be kg/2
from the front or
back wall. An L1 and an L2 are chosen such that N can be a positive integer
that satisfies the
equation. For example, for the enclosure 166 discussed above:
L1 = 4.785 inches
L2 = 11.225 inches
kg = 12.83 inches
Therefore, N = 2 x 11.215 ¨ 4.785 =1.0
12.83
The actual enclosure had the probe located at a slightly different location
(5.0 inches)
than that indicated by the equation (4.785 inches) which was possibly due to
the insertion of a
plastic drawer in the cavity, which introduces a change in the phase from the
reflected
signals. The equation above is set up such that the reflected phase from both
front and back
walls is equal, i.e., they are "in phase" at the probe location.
The wavelength in the enclosure, kg, can be calculated using waveguide
equations.
Equations for a rectangular cavity are shown below. The cutoff frequency is
required for this
calculation. The equations will change for a cylindrical cavity or for other
shapes.
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The cutoff frequency is at the point where g vanishes. Therefore, the cutoff
frequency
in Hertz is:
1 ( \ 2 2
nv-t- ( n21-` , , ,
(le). ______________________________ vi
¨ ¨ + ¨ z)
221-1/Tx a ) b2
The cutoff wavelength in meters is:
(A) 2. = (m)
7 tri2 in 2.
I¨ ¨
\ a j b1
where: a = inside width
b = inside height
m = number of 1/2-wavelength variations of fields in the "a" direction
n = number of 1/2-wavelength variations of fields in the "b" direction
E = permittivity
II = permeability
The mode with the lowest cutoff frequency is called the dominant mode. Since
TEio
mode is the minimum possible mode that gives nonzero field expressions for
rectangular
waveguides, it is the dominant mode of a rectangular waveguide with a > b and
so the
dominant frequency is:
1
(Hz)
2avT16,
The wave impedance is defined as the ratio of the transverse electric and
magnetic
fields. Therefore, impedance is:
E x jw,u jw !I kr/
ZTE ¨
H 7 ill 11
Y
The guide wavelength is defined as the distance between two equal phase planes
along the waveguide and it is equal to:
2,r 2,r ,
2 = ¨ > ¨ = A
g fi k
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iiiM
r. _____________________ \ 2
R"
where lc= ¨ + ¨nrc ; and
\a) b)
/3 = VC ¨ke2
FIG. 22 provides a block electrical and signal diagram for a multiple-drawer
medical
cabinet, such as that shown in FIG. 2. In this case, the cabinet has eight
drawers 220. Each
drawer includes two top antennae, two bottom antennae and a lock with a lock
sensor 222 for
securing the drawer. Signals to and from the antennae of each drawer are fed
through an RF
multiplexer switch 224. Each RF multiplexer switch 224 in this embodiment
handles the
routing of RF signals for two drawers. RFID activation field and RFID received
signals are
fed through the respective RF multiplexer switch 224 to a main RFID scanner
230. The
scanner 230 output is directed to a microprocessor 232 for use in
communicating relevant
information to remote locations, in this case by wired connection 234 and
wireless connection
236. Various support systems are also shown on FIG. 20, such as power
connections, power
distribution, back up battery, interconnection PCBA, USB support, cooling, and
others.
In accordance with one embodiment, drawers are sequentially monitored. Within
each drawer, the antennae are sequentially activated by the associated
multiplexer 224. Other
embodiments for the signal and electrical control systems are possible.
Although RFID tags are used herein as an embodiment, other data carriers that
communicate through electromagnetic energy may also be usable.
REFRIGERATED DRAWER
Referring now to FIG. 25, a generally non-metallic slidable drawer 330 is
configured
to be mounted within a medication cabinet 332. It includes various dividers or
partitions 334
in the drawer that form "pockets" 336 within which are placed medical articles
for storage
and administration. The cabinet within which the drawer is slidably mounted
includes a
metallic frame 338 surrounding the drawer to operate as a Faraday cage. Also
now referring
to FIG. 26, the front portion 340 of the drawer 330 may be formed of metal 342
or include a
metallic portion that contacts the remainder of the metallic frame 338 of the
cabinet 332
when the drawer is in the closed configuration to complete the Faraday cage
around the
drawer. Within that frame is included an RF system for detecting the existence
of RFID
tagged articles placed in the drawer as discussed above in further detail.
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Referring now to FIG. 16, in accordance with another aspect of the invention,
a
thermoelectric cooling ("TEC") device 189 is disposed at the back of the
metallic frame 170.
See also FIG. 30 showing the position of a TEC device 189 that has been
mounted to the
drawer and moves with it to the open and closed positions. In one embodiment
the TEC
device is located at a corner of the back of the drawer as opposed to being
centrally located.
An RFID reader 182 for detecting RFID tagged articles in the drawer 180 is
included in the
frame about the drawer with the probes 162, 164 being centrally placed above
the drawer in
this embodiment. Therefore, there is less room available for a TEC device 189
in the center
of the drawer. Additionally, it was noticed by the inventors that the TEC
device must
actually extend somewhat into the drawer due to a need to keep the medication
cabinets and
drawers at a smaller size. When the TEC device is located at a corner of the
back of the
drawer, it was found that it only interferes with two pockets 336 of the
drawer, as seen in
FIG. 25. However, if it is placed in the center of the drawer, it would
interfere with three
pockets, thereby resulting in less storage room for storing medical articles
in a drawer.
In an embodiment of the invention, a Peltier TEC device 189 was used. Such
units
are available from TE Technology, Inc., having an address of 1590 Keane,
Traverse City, MI,
part number AC-073 (www.tetech.com). In this embodiment, a Peltier-type unit
was used
due its small size, semi-conductor nature, availability, and sufficient
cooling capacity. The
use of such units provides significant advantages, one of which is the lack of
vibration since
no compressor is needed. However, the invention is not limited to only thermo-
cooling type
units, but others that exist now or may become available in the future can be
used.
One of the advantages of the invention is that a cabinet of the present
embodiment has
both cooled and uncooled drawers. In the prior art, cabinets were either
completely
refrigerated or completely non-refrigerated as was discussed in detail above
in the
Background section. This is an undesirable approach since two cabinets are
necessary for the
two different types of medications, one of which requires constant cooling,
and the other of
which needs to be at room temperature for use. Thus, a cabinet that is able to
provide both
refrigerated and non-refrigerated drawers is needed in the art and is provided
here.
Referring again to FIG. 25 and also to FIG. 27, a TEC device enclosure 350 is
shown
at the rear corner of the drawer 330. In FIG. 25, this enclosure 350 is
covered but FIG. 27
shows it more clearly. This enclosure is a part of the "real estate" of the
drawer and is used to
receive the TEC device when the drawer is in the closed position. It will be
noted that holes
352 are formed in the enclosure 350 in the front and side partitions 334 which
operate to
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diffuse the cooling effect of the TEC device. FIG. 16 also shows that the TEC
device 189 of
this embodiment includes a fan 188 that, when combined with the diffuser,
lowers or
eliminates any temperature gradients that may tend to exist in the drawer 330
(FIG. 25). The
size and locations of the partitions 334 also assist in lowering any
temperature gradients as
well as the holes 360 formed in the partitions.
In one embodiment, the TEC device 189 is anchored to the frame of the cabinet
300
and the drawer 330 engages it when closed and is moved away from it when open.
This
configuration is shown in FIG. 16. This permits ambient air to have a greater
effect on the
contents of the drawer when the drawer is in the open position. In another
embodiment as
shown in FIG. 30, the TEC device is anchored to the drawer 330 and moves with
the drawer
when the drawer is opened. This will permit the cooler air from the TEC device
to be
continually present thus lessening the effect of the ambient air on the drawer
contents when
the drawer is open.
Returning again to the drawer 330, an RF drawer as contemplated by the
invention
uses both electrical insulation and thermal insulation. The electrical
insulation is provided by
locating electrically conductive materials about the drawer on all sides to
form the required
Faraday cage, some of which is shown in FIG. 25 as the frame 338 and as shown
in FIG. 28,
which shows a portion of the cabinet with a drawer removed. The thermal
insulation 344 is
provided by the use of standard thermal insulation available widely. In some
cases where
large surface areas are available, slabs of the thermal insulation are cut at
the appropriate
sizes and installed in the framework around the location of the drawer 330 as
shown in FIG.
28. As shown in FIG. 29, the front 340 of the drawer 330 may also have
insulation 344
located within it. In areas such as the back of the drawer where there are
electrical
conductors and other equipment used in conjunction with the drawer, spray-type
insulation
(not shown) may be used after the manufacture of the drawer is completed to
place the
required thermal insulation around the drawer. Use of a high quality thermal
insulation, such
as Semi-Rigid PVC Foam, not only keeps the cool air within the drawer when the
drawer is
in the closed position, but also protects adjacent drawers from cooling
produced by the TEC
device 189 for that particular drawer. It has been found that with the proper
amount of
insulation, adjacent drawers are at room temperature while the refrigerated
drawer may be
held at a range of 3-10 C.
In one embodiment, the TE Technology Peltier thermoelectric cooler module 189
listed above was used and had a capacity of 73 watts at a 00 temperature
difference. The
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medication cabinet 300 in which it was installed for refrigerating a single
drawer 330, held a
total of 5 drawers. It was found that by using a Peltier unit of this capacity
with the
surrounding insulation approach discussed above and shown in the drawings, the
target
drawer was kept at the temperature desired and adjacent drawers were able to
remain at room
temperature. Furthermore, the power requirements and size of the TEC device
are
substantially reduced compared to the traditional compressor-based systems.
In another feature, the TEC devices 189 for the drawers 330 of the cabinet 300
may
be selectively turned off so that the cooling system is not running and the
drawer can be at
ambient temperature. This allows the healthcare facility to lower costs since
the TEC device
189 will not needlessly be consuming electricity.
In a further feature, the drawers 330 include at least one temperature sensor
370. The
temperature data from these sensors are communicated to the control unit 306
for monitoring.
Should the temperature of a refrigerated drawer rise above a selected
threshold, an alarm may
be provided at the display 304. Additionally the control unit 306, server 310,
and data base
320 may cooperate to conduct temperature data logging for historical charting
and analysis.
In the embodiment of FIG. 30, an ambient temperature sensor 372 is provided.
This sensor is
located at a position away from the heat exhaust of the TEC device or devices
so that its
reading is not influenced by those exhausts. Having a single ambient
temperature sensor
obviates the need for a sensor in each of the non-refrigerated drawers. Since
those drawers
have no temperature control devices affecting them, it is presumed that they
are at the
ambient temperature.
This invention utilizes a data base 320 that a healthcare institution can
maintain to list
medications and other medical supplies that require refrigerated conditions.
In addition, there
is an RFID system that determines the need for and controls the environment of
refrigerated
medications within an RFID-enabled dispensing cabinet 300 or mobile cart 318.
The system
will automatically determine via the database what conditions a medication
that has been
loaded into it will require and make the necessary inputs/outputs to insure
the medication's
environmental requirements are maintained as well as recorded on a pre-
determined time
interval basis for history record purposes.
When a medication 378 is placed into the RFID dispensing cabinet 300 or mobile
cart
316, the system recognizes the need for refrigeration, if required. This
recognition may occur
in different ways. In one way, the RFID tag associated with the medication may
be coded to
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indicate that temperature control is required and at what temperature. In
another way, the
control unit 306 receives the identification of the medication in the drawer
330 from the
RFID detection system, accesses the remote server 310 and its data base 320,
and receives the
data about this identified medication indicating that the medication needs
temperature control
and the temperature required.
A "smart" system via the host computer 306 determines the need for
refrigeration and
effects the necessary outputs to provide the correct environmental conditions
for such.
Turning in more detail to FIG. 30 and to FIG. 31, a system and method are
presented for this
"smart" system. In FIG. 30, a cabinet 300 is shown with a drawer 330 open.
Pockets of the
drawer are shown and some of those pockets contain medications 378, each of
which has an
RFID tag. When the drawer is pushed back into the cabinet, the RFID system
automatically
detects the tag of the medication and reads it 400. In one embodiment, the
control unit 306
receives the data from that RFID tag, automatically contacts the remote server
310 and looks
up 402 the medication in the data base 320. The control unit then determines
if the
medication requires temperature control 404. If it does require temperature
control, the
control unit automatically measures the temperature of the ambient air 406
through reference
to the ambient air sensor 372 to determine if a refrigerated drawer is needed
408. If the
ambient air temperature meets the requirement for the temperature controlled
medication 378,
the control unit then continues to monitor the ambient temperature to be sure
that no changes
are occurring.
In another embodiment, the RFID tag placed on each medication 378 includes a
temperature sensor, and part of the data transmitted by the RFID tag for that
medication
includes the temperature of the medication.
If the ambient temperature is not consistent with the temperature requirement
of the
medication, the control unit determines if the drawer in which the medication
has been placed
can be temperature controlled 410. If it cannot, an alert is automatically
provided 412 that
the medication must be moved to a refrigerated drawer. Once the medication is
moved to a
refrigerated drawer, the RFID system once again automatically determines its
presence in that
drawer and the control unit 306 then sets the temperature 414 for the TEC
device to maintain
for the medication.
Another feature in accordance with aspects of the invention is that
temperature
monitoring and logging occur. The control unit 306 determines if a temperature
controlled
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(TC) medication is located in a drawer 420. If so, the temperatures sensors
370 of that
drawer are monitored 422 by the control unit 306 and are periodically logged
424 as required
by the policies of the healthcare institution or other authorities. When
needed, the logs may
be printed or forwarded elsewhere in digital form.
Turning now to FIG. 32, a block diagram of a system 440 in accordance with
aspects
of the invention is shown. An RFID detector system 442 located in a drawer of
a cabinet
detects the existence of a medical item having and RFID tag. The detector
system 442
provides the data read from the RFID tag to the processor 444. The processor
then accesses
the server 446 and the associated data base 448 to determine the
characteristics of the
detected medical item and to determine if it has any temperature control
requirements. Other
data about the medical item may be of importance in tracking the item, and for
other
purposes.
If the medical item requires temperature control, the processor accesses the
ambient
temperature sensor 450 to determine if the ambient temperature satisfies the
medical item's
requirements. If the medical item needs a temperature below the ambient
temperature, the
processor will determine if the medical item is currently in a temperature
controlled drawer of
the medical cabinet. If it is not, the processor will display an ALERT message
on the display
452 to have a user move the medical item to a temperature controlled drawer.
Once this has
been done, the RFID detector system 442 will automatically detect the presence
of the
medical item in a temperature controlled drawer and will inform the processor
444. The
processor will then set the TEC device 454 of that drawer to the correct
temperature to be
maintained. The TEC device will automatically maintain the temperature of that
drawer to
the temperature required for the medical item. The system 440 of FIG. 32 may
have another
one or more temperature controlled drawers with a sensor 460 and TEC device
462.
The same is true of removal of the temperature controlled medication from a
drawer.
The processor monitors all medications delivered to the drawer and removed
from the drawer
and automatically controls the refrigeration device accordingly. If there are
no more
medications left in the drawer that have temperature control requirements, the
processor will
automatically deactivate the refrigeration unit of that drawer and allow the
drawer to return to
ambient temperature, thus conserving energy.
In another feature, the processor monitors the temperature sensor 456 of that
drawer
and creates a log 470 concerning that medical item and the sensed temperature
at which it
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was kept, at intervals as required, for example twice per day. The log may be
kept in a
processor memory, forwarded to a server, or otherwise stored or printed.
Various details may
be included in the log, such as cabinet identification, drawer identification,
temperature
sensor type, calibration date, arrival date and time, removal date and time,
and other data, as
required.
Thus an RFID enabled drawer refrigeration system provides numerous advantages.
Selective cooling of certain drawers may occur while other drawers are at room
temperature.
Because of this feature, only one cabinet is needed for both refrigerated
medical articles and
room temperature medical articles. There is a modular design in that the
drawers are
configuarable and selectable between refrigerated and ambient temperatures.
Unless the context requires otherwise, throughout the specification and claims
that
follow, the word "comprise" and variations thereof, such as, "comprises" and
"comprising"
are to be construed in an open, inclusive sense, which is as "including, but
not limited to."
While the invention has been described in connection with what is presently
considered to be the most practical and preferred embodiments, it is to be
understood that the
invention is not to be limited to the disclosed embodiments and elements, but,
to the contrary,
is intended to cover various modifications, combinations of features,
equivalent
arrangements, and equivalent elements included within the spirit and scope of
the appended
claims.
