Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
`3
A FLUID TRANSFER MEMBER AND ASSEMBLY
WHICH INCLUDE A RADIANT ENERGY
ABSORBING WALL HAVING OPTIMAL
MELT CHARACTERISTICS
5 FIELD OF THE INVENTION
This invention generally relates to fluid
transfer devices. In particular, this invention
relates to fluid transfer devices which include
meltable portions.
BACKGROUND OF THE INVENTION
~ , , . __
Granzow et al U.S. Patent 4,157,723 concerns
a fluid transfer device which uses a meltable,
radiant energy absorbing wall to normally seal a
conduit from communication with the atmosphere. The
wall is melked in response to exposure to radiant
~, ..,~
' :'
~'b~ 2
- ~ -
energy to open a fluid path through the device. By
coupling two of these devices together and then
applying radiant energy to melt the walls, a sterile,
hermetically sealed fluid pathway can be formed
between the assembled devices.
Other fluid transfer devices and assemblies
which use meltable, radiant energy absorbing walls
are disclosed in the following U.S. Patents:
Ammann et al 4,265,280
Boggs et al 4,325,417
Ammann et al 4,340,097
This general type of fluid transfer device
lends itself to use in systems in which fluids are
transferred in a sterile, or aseptic, manner; for
example, in blood component collection and processing
systems; in chemical compounding and parenteral
solution formation systems: and in fluid systems
associated with peritoneal dialysis.
Because these system~ involve ~he transfer
of human blood and sterile parenteral solutions, it
is desirable that the performance characteristics of
transfer devices and assemblies be optimized to the
greatest extent possible.
Conventionally, it is believed that the
per~ormance characteristics of a meltable, radiant
energy abQorbing wall can be best optimi~ed by
maximizing the density, or opacity, of the meltable
wall to the applied radiant energy. For example,
when the radiant energy applied is infrared energy
--3--
and/or visible light, the meltable wall
conventionally includes a relatively large percentage
by weight of a carbon filler to maximize its opacity
to these types of radiant energy.
Surprisingly, however, in accordance with
this invention, it has been discovered that the
performance characteristics of a meltable, radiant
energy absorbing wall are not optimized at these
maximum opacity levels.
SUM~RY OF THE I~VENTION
A fluid trans~er member is provided
comprising means which defines a meltable wall made
of a radiant energy absorbing material. The wall
normally seals the member from communication with the
atmosphere. In response to the application of
radiant energy, the wall melts, and an opening is
formed in the wall.
In accordance with the invention, the
meltable wall has density, or opacity, to the applied
radiant energy which lies within a specially defined
range of density values~ Density values falling
within this defined range do not maximi~e the opacity
of the meltable wall to the applied radiant energy.
Nevertheless, within this range, the desirable melt
characteristics of the wall are significantly better
than in a wall having an opacity which falls above or
below the range.
--4--
More particularly, the invention provides a
meltable wall which has a density, or opacity, to the
applied radiant energy (hereafter referred to simply
as the "D-value") which lies within the range of
about 3 < D-value < about 12. The D-value is
dimensionless and is directly indicative of the
degree of opacity of the wall. The D-value is
determined by the formula:
D-value = p L.
In this formula, ~ represents the radiant
energy absorbance of the wall. p is itself
determined by the formula and is expressed in units
per centimeter:
~ ln[I ~o]
L
In the above-identified formulas:
(1) "ln" represents the natural
logarithm of the bracketed ratio;
(2~ "Io" represents the intensity of
the applied radiant energy as it enters the meltable
wall, expressed in watts per square centimeter, or
any derivative thereof;
(3) "I" represents the intensity of
the applied radiant energy as it exits the meltable
wall, expressed in the same terms as Io; and
(4) "L" represents the thickness of
the meltable wall in centimeters along the path of
the applied radiant energy.
,
_5_
Preferably, in acc~rdance with ~he
invention, the D-value of the meltable wall, as above
defined, lies within the range of about 4
D-value < about 6.
Most pre~erably, in accordance with the
invention, the D-value of the meltable wall, as above
defined, lies within the range of about 5.5 < D-value <
about 6Ø
In one embodiment, the meltable wall is
interposed between two fluid conduits to normally
bl~ck communication therebetween. In this
arrangement, an opening is formed the meltable wall
in response to the application of radiant energy~
thereby opening flow communication between the
conduits.
Various aspects of the invention are as follows:
A member attachable to a conduit and comprising means
defining a meltable wall made of material which absorbs a type
of electromagnetic radiant energy for normally sealing the
conduit from communication with the atmosphere and for forming,
in response to the application of the type of radiant energy to
melt said wall, an opening in said wall, said wall having an
Opacity to the applied radiant energy which lies within the
range about 3 < Opacity < about 12,
25 wherein Opacity = ~ L;
and wherein ~ represents said wall's absorbance of the
applied radiant energy, expressed in units per centimeter, as
determined by the formula:
~ = -ln[I/Io]
'
. , .
5a
and in which ln represents the natural logarithm of the
bracketed ratio [I/Io];
Io represents the intensity of the applied radiant
energy as it enters said wall, expressed in watts per square
centimeter or any derivative thereof;
I represents the intensity of the applied radiant energy
as it exits said wall, expressed in the same term as Io; and
L represents the thickness of said wall in centimeters.
An assembly for sealing and connecting the end portions of
a pair of conduits, said assembly comprising
housing means having walls enclosing d hollow interior,
said housing means further including spaced first and second
passage means each communicating with said hollow interior and
each adapted for communication with a respective conduit end
portion,
meltable wall means extending across said hollow interior
in the interval between said spaced first and second passage
means, said meltable wall means being made of a material having
an Opacity to a type of electromagnetic radiant energy which
lies in the range of about 3 < Opacity < about 12, said wall
means being operative for normally blocking flow communication
between said rirst and second passage means through said hollow
interior and for forming, in response to the application of the
type of radiant energy through said housing means ~alls to melt
said meltable wall means, an opening establishing flow
communication between said first and second passage means
through said hollow interior,
wherein said Opacity = p L;
5b
and wherein ~ represents the absorbance of said wall
means of the applied radiant energy, expressed in units p~r
centimeter, as determined as follows:
~ = -ln[I/Io]
and in ~Jhich ln represents the natural logarithm of the
bracketed ratio [I/lo];
Io represents the intensity of the applied radiant
energy as it enters said wall, expressed in watts per square
centimeter or any derivative thereof;
I represents the intensity of the applied radiant energy
as it exits said wall, expressed in the same term as lo; and
L represents the thickness of said wall means in
centimeters.
Other features and advantages of the
invention will be pointed out in~ or will be apparent
from, the specification and claims, as will obvious
modification of the embodiments shown in the drawings.
DESCRIPTION OF THE DRAWINGS
Fig. 1 is a perspective view of a fluid
transfer system which employs a pair of fluid
transfer members, each of which embodies the features
of the invention;
Fig. 2 is an enlarged side view, with a
portion broken away and in section, of the fluid
transfer members shown in Fig. 1 in an uncoupled
relationship;
' - .
--6--
Fig. 3 is an enlarged side view, with
portions broken away and in section, of the fluid
~ransfer members shown in Fig. 1 in a coupled
relationship as radiant energy is being applied;
Fig. 4 is an enlarged side view, similar to
Fig. 3, but after the application of radiant energy
and the formation of a fluid path between the members;
Fig. 5 is a graph which plots the absorbance
(~) of a meltable radiant energy absorbing wall
against the charcoal content of the wall;
Fig. 6 is a graph which plots the diameter
of the hole formed in the wall against the associatPd
D-value;
Fig. 7 is a graph which plots the
temperature distribution across the wall against the
associatad absorbance (~);
Fig. 8 is a graph which plots the melt
efficiency of the wall against the associated
D-value; and
Fig. 9 is a graph which plots the
temperature uniformity across the wall against the
associated D value.
Before explaining the embodiments of the
invention in detail, it is to be understood that the
invention is not limited in its application to the
details of construction and the arrangement of
components as set forth in the following description
or as illustrated in the accompanying drawings. The
invention is capable of other embodiments and of
being practiced or carried out in various ways.
2~
--7--
Furthermore, it is to be understood that the
phraseology and terminology employed herein is for
the purpose of description and should not be regarded
as limiting.
DESCRIPTION OF THE PREFERRED EMBODIMENT
A member 10 which is attachable to a conduit
12 is shown in Figs. 1 through 4. As can best be
seen in Fig. 2, the member 10 comprises means which
defines a meltable wall 14.
When the member 10 is attached to the
conduit 12, the meltable wall 14 normally seals the
conduit 12 from communication with the atmosphere.
In accordance with the invention, the
meltable wall 14 is made of a radiant energy
absorbing material. By applying radiant energy, the
wall 14 is melted, and an opening is formed in the
wall 14. Fluid communication is thereby opened with
the associated conduit 12.
As used herein, the term "radiant energy"
broadly refers to energy which is in the form of
electromagnetic waves, such as radio waves, infrared
waves, visible light, ultraviolet waves, x-rays, and
the like. Because the transfer of radiant energy
requires no intervening medium, the transfer can be
faster and more efficient than in conductive or
convective heat transfer, both of which require an
intervening medium.
The member 10 may be variously constructed.
In the illustrated embodiment, the member 10 includes
body means 18 which is attachable to the end portion
20 of the conduit 12. In this arrangement, the
meltable wall 14 is sealingly disposed on the body
means 18 (see, in particular, Fig. 2). In response
to the application of radiant energy, the wall 14
melts, and an opening is formed in the body means 18.
In the illustrated embodiment, the body
means 18 includes a housing 22 which defines a hollow
interior 24 which co~municates with the interior of
th~ attached conduit 12. As is best shown in Fig. 2,
the meltable wall 14 normally seals or closes the
housing interior 24 from communication with the
atmosphere.
The housing 22 further includes a tubular
conduit portion 26 which communicates with the
interior 24 and which serves to interconnect the
housing 22 with the conduit end portion 20.
Whila ~he housing 22 may be ~ariously
attached to the end 20 of the conduit 12g in the
illustrated embodiment, a hermetic, friction-fit
between the end 20 and conduit portion 26 is
envisioned. An elastic band 28, such as made from a
latex material, preferably encircles the outer
periphery of the junction to as~ure a fluid tight,
hermetic fit.
As shown in Fig. 1, the conduit 12 to which
the member 20 is attached can itself be integrally
connected with a container 30, such as a plastic
-~9 -
bag. The container 30 can contain a fluid and be
used to dispense fluids, or it can be empty and be
used to receive fluids.
In this arrangement, a manually operated
inline valve member 32 (shown in phantom lines in
Fig. 1) is preferably provided to normally prevent
fluid communication between the container 30 and the
housing interior 24. While the valve member 32 may
be variously constructed, in the illustrated
embodiment, it takes the form of a manually frangible
valve member, such as that disclosed in Carter et al,
U,S. Patent 4,294,247.
Alternately, the valve member 32 may form an
integr-al part of the member housing 22, such as
disclosed in Ammann et al U.S. Patent 4,340,097.
The material from which the meltable wall 14
is cons~ructed is preferably sele~ted to melt only at
temperatures which result in the destruction of
bacterial contaminants on the surface of the material
(i.e., over 200C). I~ this preferred arrangement,
the wall 14 can be opened only in conjunction with an
active sterilization step which serves to sterilize
the regions adjacent to the fluid path as the fluid
path is formed~
Also preferably, the housing 22 is made o a
material which absorbs the applied radiant energy in
lesser amounts than the wall 14. Most preferably,
the housing 22 is relatively nonabsorbant of the
particular type of radiant energy applied.
--10--
By virtue of this construction, ac radiant
energy is applied to melt the wall 14, the housing 22
itself is not heated to any great extent. Rather,
the housing 22 serves to pass the radiant energy
directly to the wall 14. The transfer of radiant
energy is fast and efficient.
The particular material selected for the
member 10 depends largely upon the type of radiant
energy which is to be applied. Conventionally,
radiant energy which includes infrared and/or visible
light is used.
In this arrangement, the member 10 is
conventionally made of a material fabricated from
poly~4-methyl-1-pentene), which is sold under the
trademark TPX by Mitsui Chemical Company. This
material has a crystalline melting point of
approximately 235~C and i9 further discussed in Boggs
et al, ~.S. Patent 4,325,417O
The meltable wall 14 conventionally contains
large amounts by weight of a carbon filler so as ~o
absorb radiant energy in the infrared and visible
light band. The houqing 22 is conventionally free of
the filler and i5 thus relatively transparent to
(i.e., generally nonabsorbant of~ this band of
radiant energy.
The member 10 as heretofore described can
~erve by it&elf to seal the end portion 20 of thP
conduit 12 from communication with the atmospherP
until time of use. The application of radiant energy
opens the wall 14 at the time 1uid flow through the
conduit 12 is desired.
Alterna~ely, a pair of the members 10 may
also be used to form a fluid transfer assembly 40 to
form a connection between two fluid containers 30 and
31.
More particularly, in the transfer assembly
40, the member 10 includes coupling means 34 for
bringing the meltable wall 14 of one member 10 into
facing contact with a corresponding meltable wall 14
of a second member, The second member is preferably
constructed identically to the member 10 heretofore
described. Because of this, the second member is
also designated by the numeral 10 in Figs. 1 through
4. Other structural elements common to the first and
second members 10 are likewise identified with the
same reference numerals heretofore assigned.
The coupling means 34 may be variously
constructed. In the illustrated embodiment, the
coupling means 34 takes the form of mating
bayonet-type coupling mechanisms 36 which interlock
the members 10 together with their radiant energy
absorbing walls 14 in facing contact (see~ in
parti~ular, Fig. 3). When exposed to a source 38 of
radiant energy spaced from the assembly 40, the
radiant energy absorbing walls 14 jointly melt and
fuse together, as can be seen in Fig. 4. A fusion
bond between the walls 14 is ther~by formed.
In the process of melting, the walls form an
opening 16 which establishes through the members 10 a
fluid path which is at once sterile and hermetically
sealed about its periphery to communication with the
atmosphere.
-12-
Certain characteristics are desirable for
each of the members lO to optimize the perf~rmanca of
the assembly 40. These desirable characteristics
include:
(1) The opening 16 which is formed should
be large enough to allow unimpeded fluid flow through
and between the members lO. In this r~spect, it is
believed that the diameter of the formed hole should
approximate the interior diameter o~ the associated
conduit 12. For example, in the case of conventional
blood flow tubing, the de~ired minimum hole diameter
is about .lO inch;
(2) The fusion bond which is formed between
the walls 14 during the melting process should be
strong enough to protect against an accidental
separation of the members lO. The fusion bond will
thus protect the system 40 against an inadvertant
breach in sterility.
(3) As radiant energy is being absorbed by
the walls 14, the resulting increase in temperatures
should be distributed uniformly through each of the
meltable walls 14. This uniform temperature
distribution minimizes the likelihood that the
localized areas of high temperatures, or "hot ~pots",
develop during the melting proces~. A uniform
temperature distribution reduces the potential of
volatile production and a "splattering" or "bubbling"
of either meltable wall 14 during the melting
process; and
-13-
(4) A favorable melt efficiency should be
P provided, so that relatively low power sourcPs of
radiant energy can be used. A favorable melt
efficiency also minimizes the time involved in
melting each of the walls 14.
Conventionally, it has been believed that
the performance characteristics of the members 10
could be optimized only by maximizing the opacity of
the meltable walls 14 to the particular type of
radiant energy applied.
For example~ a source of radiant energy
which has been used is a incandescen~ quartz lamp
which has a tungsten filament operating at about
3150~K. This lamp emits radiant energy which lies in
a continuous band encompassing mostly infrared and
visible energy, although some ultraviolet radiation
is included.
When this source of radiant energy i8
utilized, the TPX material of the wall 14
conventionally contains about one percent (1%)
activated charcoal by weight to maximize, to the
fullest po3sible extent, the wall's density to the
radiation band emitted by the tungsten lamp.
However, in accordance with the invention,
it has been discovered that, in order to optimize the
melt characteristics of the radiant energy absorbing
wall 14, the wall 14 must have a density, or opacity,
to the applied radiant eneryy which lies only within
a specifically de~ined range.
-14-
More particularly, it has been discovered
that tha melt characteristics of the radiant energy
absorbing wall 14 are optimized only when th~ radiant
energy density of the wall (referred to as the
"D-value") lies within the range of between about 3
D-value -~ about 12. The D-value is a dimensionless
quantity and is a function of the thickness of the
wall and the ability of the wall to absorb the
applied radiant energy per unit of thickness.
More particularly, the D-value is determined
by the formula:
D-value = ~ L
In this formula, ~ represents the radiant
energy absorbance of the wall per unit of thickness
and is itself determined by the following formula:
~ = -ln C I /I O]
In the above the formulas, "Io" represents
the intensity of the applied radiant energy as it
enters the wall 14 and is expressed in terms of watts
per square centimeter or any other derivative
thereof, Quch as amps, volts, lamberts, lumens, etcO
"I" represents the intensity of the applied radiant
energy as it exits the wall 14 and is expressed in
the ~ame term selected for Io. The numerator of
the formula by which ~ is determined is the natural
log (ln) of the ratio between I and Io and is
itself negatively signed, because the ratio is a
fraction. A negative sign is therefore provided
before "ln" in the above formula to convert ~ to a
positive number.
2~
-15-
In both formulas, "L" repxesents the
thickness of the area to be melted measured ~long the
path of radiant energy. L is expressed in
centimeters.
When only a single wall 14 is to be melted,
L represents the thickness of only the single wall
14. ~owever, in the case of an assembly 40 of two
walls 14, as shown in Fig. 3, L represents the
combined thickness of both walls 14, i.e., generally
twice the thickness of the single wall 14.
The range of D-values, as defined in
accordance with the above formula, applies
universally to any type of meltable radiant energy
absorbing material, as well as to any type of radiant
energy used to melt the absorbant n~aterial.
When the D-value lies within the range of
about 3 to about 12, acceptable hole formation and
fusion bond strengths are encountered at favorable
melt efficiencies and with a generally uniform
distribution of temperatures across the area to be
~elted.
The range of ~-values as above delineated is
believed to be critical. This is because, below
about 3, extremely unfavorable melt efficlencies are
encountered, while above about 12, the distribution
of temperatures across area to be melted becomes
increa~ingly non-uniform and generally higher
localized temp~ratur2s, or "hot spots", can occur.
"Hot spots" can cause decomposition of the wall
material. They can also lead to substantially higher
~16-
gaseous diffusion rates and result in undesirable
"bubbling" or "splattering" on the sur~ace of the
wall 14. However, when the area to be melted has a
D value which lies within the range of about 3 to
about 12, temperatures are distributed relatively
uniformly across the entire area to be melted, and
localized hot spots do not occur.
Furthermore, it has also been surprisingly
discovered that, when the D-value of the facing walls
in an assembly 40 falls within this prescribed range,
the fusion bond between the members 10 of the
assembly 40 is stronger than when conventional walls
having maximum opacity are used.
Preferably, the range of D-values is between
about 4 and about 6. Within this narrower sub-range,
it has been discovered that melt efficiencies are
maximized to the greatest extent possible.
Most pref0rably, the range of D-values is
between about 5.5 and about 6Ø Within this
narrowest sub-range, it has been discovered ~hat both
hole size and melt efficiency are maximized to the
greatest extent possible.
The invention can be further understood by
reference to the following examples.
-17-
EX~MPLE 1 ~Absorbance (~)]
Five separate blends of the TPX material
laden with activated charcoal were fabricated as
follows:
Charcoal Content
Blena Designation% by Weight
V1 .1239
V2 .2481
V3 .3726
V4 .4975
VS .6226
V6 (Conventional~ .99O1
The blends were used in the meltable walls
14 for members lO constructed as shown in Figs. 1
through 4.
A model Number 325H-PC Hughes helium neon
laser was used as the source of radiant energy. The
laser emits radiant energy having a wavelength of
6328 Angstroms. A lO ~m lens was used to broaden the
beam. The diverging beam was aligned to impinge upon
a silicon sensor photo detector which was located
about 3.5 inches from the lO mm lens. The photo
detector was used in the closed loop current mode,
and the current was measured on a Model 3465A Hewlett
Packard Digital Multimeter~
Each wall to be measured was placed in the
beam at a distance of about 2.25 inches from the
lens. The intensity of the radiant energy was
determined both before and after each wall was
~2~
~18-
inserted in the beam path. Mean and standard
deviations were determined. The ratio of the
detected entering and exiting intensities, i.e., Io
and I, respectively, was calculated .
Four samples of each of the six different
blends were used to determine the absorbance (~) of
each of the blends per centimeter of thickness. The
following, heretofore described formula was used:
~ = -ln(I/Io)
o
Table 1 summarizes absorbance (~) obtained.
In Table 1, ~ is expressed in units per centimeter of
wall thickness. Figure 5 is a graphic display of
Table 1.
D~
_ ~ -19-
aJ
~ ~ x
~ ~ ~ G~
.4 h ,C . . . - - -
h O ~ I` OD L~ O u~
O Q~ N tf~ CO N
~ .~
,.~
U~
~ u, u~ u~ ~ ~ In
C ~ cr ~ o o o
~ O O O ~ O O '
.
U
~'3
_~ ~
U~ _I ~ ~ ~ O
~) O In 11- _I O O O
~ . H N O O O O O
_ . H
W E~
~ _~ --.
m ,~ ~ r~
~: _, a ~ o
_l ~ r~ o I
~ .~ ~ _, o o oO I
,,
~_
o ~ CO U~ o ~ O
~ O H Cl~ _I Q O O O
S~
U
O o o o o I
~ Q) _ r~ o ~ _~
P~
O
o a) a) ~ ~
h ~ ~; ~ a) t~ O
al
O ~ _l ~ ~ ~ ~D
t~ . . . . . .
. ._____
a: ~
-20-
As can be seen in Fig. 5, the absorbance (~)
progressively increases as the percent of activated
charcoal by weight in the wall increases.
As will be demonstrated in Example 8, once a
desired absorbance (~) is known, one can refer to
Fig. 5 to readily determine what percent by weight of
activated charcoal is required.
In Fig. 5, the slope of the curve is
believed to be universally applicable to virtually
any type of base material which is laden with
activated charcoal and w~ich has, before the addition
of the activated charcoal, an inherent absorbance
value of zero (i.e., it is virtually nonabsorbant of
radiant energy). The origin of tha curve in Fig. 5
will change, however, if the initial or inherent
absorbance of the particular base material is greater
than zero. For example, if the inherent absorbance
of the base material is 50 per centimeter, the
applicable curve will shift and appear as shown in
phantom lines in Fig. 5.
Similarly, the slope of the curve itself may
change if a material other than activated charcoal is
used to render the base material ab~orbant to the
applied radiant energy. In other words, just as the
origin of the curve represents the inherent
absorbance of the base material, the slope of the
curve represents the inherent absorbance of the
material which is used to render the base material
radiant energy absorbant.
-21-
EXAMPLE 2 (Hole Formation)
A reflectively focused 8 volt, 50 watt Osram
lamp, type 64607, with a focal length of
approximately 1.5 inches was mounted in a lamp holder
located on an optical bench. The lamp was powered by
a fixed voltage power supply.
Twenty each assemblies 40 with wall blends
Vl through ~6 were separately loaded into the fixture
at the focal point of the lamp and exposed to the
focused radiant energy emitted with the power supply
set at about 6.0 volts. In theqe assemblias 40, the
area to be melted consisted to two walls 14 of the
same blend positioned in facing contact.
- The asaemblies 40 were exposed to the
radiant eneryy or various amounts of ~ime, ranging
from about 5 to about 20 seconds.
After the fluid path between each a~sembly
40 was opened, the a~sembly 40 was visually inspected
for "bubbling" and "splattering" on the ~urface of
the joined walls 14. These results are independently
reported in Example 7.
Each assembly 40 was then sectioned to gain
access to the formed hole for measurements of hole
si7e by a pin gauge technique.
Table 2 summarizes the hole formation data
obtained. Except where noted, the statistical
evaluation is based upon a sample size of five ~5).
Figure 6 is a graphic display of the results
summarized in Table 2.
--22--
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a O O O O O ot
oooooo
O U~ O~
E
O ~C~
Z
_ ~ _ ~_
a ~ oD ,q
U ~ ooooo o
O _~ E ~ ~ l o ~D o
W Z ~ 1 10 0
AS - .___ E
¢ ~ ~o~ 0~0
~ a) ~) ~ oooOoo v ~ O,
E~ U _l _ _ ~-SX
zo . I E ~ ~ ~ ~ ~ u~
V ~ Z o~oOo` O '~
O ~ ~ 11~1l SU~
O I I O O I
.~ tJ _ . _ O ~ ~-
O o I_ ~ O 0~ ~ S
~ ~ 8 ~ 2~ o
Z Z 0.~ 0 0 0 0 O ~.U
Z ~ ._ _ ~ Z ~ Z ~ ~ ~
U ~ ~ C ~ ~
~ O ~D ~ ~-rl
DO
~_1 ...... ~ _~
E l ~ ~ ~ N ~ '0~
...
a E
U ~ ~ ~ .Y
Q ~ ~ Q, E .c L ~
O ~ r~
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;~ O ~ ~ 1 0 _ N 11- CO N r~ U~ ~1
"J
~ ~ ~ ~ 1' ~0
-23-
As can be seen in Fig. 6, the dia~eter of
holes ~ormed in assembled walls having D-values of
about 3 to about 12 is substantially equal to or
better than the holes formed in the assembled walls
having higher D-values.
As can be also seen in Fig. 6, surprisingly,
when the D-values lie in the sub-range of abo~t 5.5
to about 6.0, hole formation characteristics are
optimized at all exposure times.
10 EXAMPLE 3 (TENSILE PULL TEST)
The force required to pull apart the fused
assemblies using either the V2 blend (D-value 5.8) or
the conventional V6 blend (D-value 16.0) was
determin~d using ~n Instrom Tensile Test MachineO
15 The results are summarized in Table 3.
TABLE 3
Failure Point
Connector Pounds
V6 16~5
V6 5.5
V6 20.5
V6 22~0
V6 19~5
V2 26~0
V2 26~0
V2 25.0
V2 23.5
V2 25.5
:~2~
24-
As can be seen, surprisingly, the V2 blend,
which has an D-value of only 5.8, has a significantly
higher tensile strength than the conventional blend
V6, having a much higher D-value of 16.~.
EXAMPLE 4
(TEMPERATURE DISTRIBUTION)
An accurate math~matical model was developed
to predict the temperature distribution across the
meltable wall as the hole is formed. To develop the
model, the heat transfer equation was solved in
closed form and evaluated at different points in time.
In developing the model, the following
assumption~ were made:
~1) That thermal propertie~, such as heat
conduction and capacity, remain
constant with time, temperature, and
charcoal content;
(2) That there is no heat loss from either
the front surface or back surface of
~0 the walls, i.e., insulated walls;
(3) That the two walls are in intimate
contact in the assembly (as shown in
Fig. 3) with no thermal contact
reqistance existing between them; and
~4) That the radiant energy absorption is
non-specular.
,
-~5-
The model was reduced to a boundary value
problem and was solved using an integral transform
technique that removes the space variable. The
integral transform and its inversion formula u~ed,
along with the general solution for heat conduction
in a single dimension of finite length, is detailed
in Ozisik, M.N.~ Boundary Value Problems of Heat
Conduction, 1968, International Textbook Company.
The absorbed radiant energy enters the solution by
way of the heat generation function.
A definition of the symbols used in the
mathematical model appears in Table 4.
-26-
TABLE 4
Definition of Symbols
Symbol Definition Unit
Cp Specific Heat cal/gm C
5 k Thermal Conductivity Cal cm/sec cm2
p Density gm/cm 3
Thermal Diffusi~ity =
k/p Cp cm2/sec
L Thickness of the Area cm
To Be Melted
I~ Incident Lamp Intensity cal/sec cm2
. Absorptivity l/cm
x Distance Into Membrane cm
t Time sec
15 T Tempera~ure C
g Heat generation term cal/cm3 sec
Thermal time constant -
l/~5~/L)2 sec
pi 3,1~15927
The following briefly summarizes the steps
used in developing the model.
The local intensity was expressed:
I = Io e ~x
The heat generation term, or energy5 deposition rate, was expressed :
g = dI/dx = Io ~e~~X
; ~
-~7-
The resulting boundary value problem of heat
conduction was given by the following system of
equations:
a2T ~ ~x t) = 1 aT in 0 < x < L ; t >0
a 2 k ~ at
- kaT hiT = fl(t) for x = 0, t >0
~x h2T = f2(t) for x = L, t > 0
T = F(x) in 0 < x< L; t - 0
The boundary conditions that apply to the
meltable membrane wall are (1) that, since it is
assumed that there is no heat loss through either the
front or back face of the wall, then fl(t) =
f2(t) = O, and (2) that the initial temperature (T)
is O.
When the boundary conditions and heat
generation term are substituted into the
above-described system, and ~olved by methods
outlined in the foregoing Ozisik reference, the
following solution results:
-~L ~ m -~L M~x) (m~)2t
T(x,tl = IO(l-e~at~Io~ e ~Cos ~
Lk Lk (l+(m~/~L) 2 ) (m~/L) 2
m = 1
where m = 1, 2, 3, . . .
-28-
In the above solution, the factors
e ~ ~(m ~)2t
will hereafter be ref~rred .o as the "transient
function".
The temperature distribution solution is
solved for time periods after the above-identified
transient function has decayed, using the material
properties of TPX (Mitsui Grade RT18) as found in
Table 5:
TABLE 5
Properties of Polymethylpentene
Density = 09833 gm/cm3
Melting Point Tm = 240C
Thermal Conductivity k = 4.x 10 cal cm/sec cmZ
Specific Heat Cp = 0.47 cal/gmC
Thermal Diffusivity (Calculated)
1.0 x 10 cm~/sec
Heat or Fusion hf = 45 cal/gm
Figure 7 plots the temperature distribution
across the meltable wall for several absorbance
values (~), based upon the foregoing solution and
using only a single source of radiant energy. In
Fig. 7, the l'incident face" is the side of th~
meltable wall facing the radiant energy source.
-29-
As can be seen in Fig. 7, the temperature
distribution becomes increa~ingly more uniform (i.e.,
a "flatter" distribution curve) across the wall as
absorbance (~) values decrease. Therefore, with
S decreasing absorbance, the chance of localized "hot
spots" and the attendant undesirable "bubbling" or
"splattering" will diminish significantly. The
conventional formulation (V6) has an absorbance of
about 250 per centimeter, placing its temperature
distribution somewhat between E and F in Fiyure 7.
EXAMPLE 5 (Theoretical Melt Efficiency)
Using the mathematical model heretofore
described, the energy required bring the far side of
the wall (i.e., the side opposite to the incident
face) up to a given temperature can be calculated as
; a function of D-value. This relationship is directly
indicative of the melt efficiency of the wall 14.
This plot is shown on Figure 8, and has been
normalized to the energy requirements at infinite
absorbance.
Fig. 8 clearly shows that m~ximum me~t
efficiencies occur at D-values of between about 3 and
about 6~ At D-values below about 3, melt
efficiencies significantly deteriorate.
It is significant to recall that, as shown
in Fig. 6, hole formation is also optimized within
the same range of D-values at which optimal melt
efficiency is achieved (i.e., between about 3 and
about 6).
,,.. ~ .
-30-
EXAMPLE 6 (Theoretical Temperature Uniformity)
Using the model, the temperature
differential between the incident face and the far
side face can be plotted as a function of D-value.
The results are shown in Figure 90
Fig. 9 clearly shows that, as the D-values
are successively reduced from about 12 toward 3, the
distribution of heat across the wall becomes
increasingly more uniform. Thus, thP formation of
localized "hot spots" is avoided.
Actual data confirms the validity of the
foregoing theoretical model in generally assessing
the melt characteristics of a radiant energy
absorbing wall.
For example, the model indicates that the
principal effect of lowering the D~value is to reduce
the range of temperature existent within the wall
during the melting phase (qee, in particular, FigsO 7
and 9). The model also indicates that the energy
requirements are optimized in D-values falling within
the range of about 3 to 6 (see, in particular, Fig.
8).
Actual data confirms these indications. For
example, the tensile pull tests (Example 3) confirm
that increased fusion strengths occur at lower
D-values. This is becaus~, at lower D-values, the
heat penetrates deeper into the wall as a result of
the more uniform temperature dis ribution indicated
by the model, and thP melt ~one does become, in fact,
more uniform. Furthermore, as Example 7 confirms,
: ~ ... .
-31-
"hot spots" and attendant "splattering" and
"bubbling" are in fact eliminated at lower D-values.
This confirms that more uniform distributions of
temperatures do in fact occur at lower D-values, as
again indicated by the model.
EXAMPLE 7 ~"Splattering")
The "splattering" characteristic of
conventional walls (V6 blend) is demonstrably avoi~ed
with materials of lesser D-values.
More particularly, during the test conducted
in the foregoing Example 2, the splattering phenomona
was noted for all of the walls of the conventional ~J6
blend for both the 15 and 20 ~econd exposures.
Splattering was most serious at the 20 second
eXposure-
On the other hand, there was no detectablesplattering of any of the five blends Vl through V5
having lesser D-values at any of the exposure level~.
From the foregoing Examples 1 through 7, it
can be seen that, at D-values of between about 3 and
about 12, qignificant improvements in the overall
performance characteristics of a meltable, radiant
energy absorbing wall can be achieved. These
improv~ments are more apparent at D-values of between
about 4 and about 6, and most apparent at D-values of
between about 5.5 and about 6Ø
The following Example 8 is provided to
illustrate how the invention can be used in selecting
a meltable radiant energy absorbing wall having
optimal melt characteristics.
... .
:
-32-
EXAMPLE 8 (Hypotheticals~
(13 Assume that one requires a meltable
wall having a overall thicknes~ (L) of about .06 cm.
To o~tain the most preferred D-value of about 6, the
absorbance (~ must be about 100 per centimeter;
i.e., if D-value = ~ L, then ~ = D-value
L
By referring to FigO 5, one ~an see that
appro~imately .35% by weight of ac~ivated charcoal i~
required to achieve thi~ absorbance level.
(2) Assume tha~ one has a thermoplastic
blend containing about .5% by weight of ~ctiva~ed
charcoal. By fir~t referred to Fig~ 5, one ~an
determine ~hat thiR blend ha~ an absorban~e ~) of
about 150 per centimeter. If one wants to use thi~
blend a~ a meltable radiant energy absorbing wall
having optimi~ed melt characteristic~ (i.e~, a
D-value of about 6 . O ), the thi~kne~ of the meltabla
wall should be about .04 cm
i~e., L = D-value
It ~hould be apprsciated hat, in either of
the foregoing hypothetical e~ample~, the absorbance
(~) could be determined e~perimentally, withou~ ~he
use o~ FigO 50
Variou~ of the feature3 of the invention are
set forth in ~he following claims.
' ' '
- ~
