Note: Descriptions are shown in the official language in which they were submitted.
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STERILE CONTAINMENT WELDING DEVICE
WITH SELF-MONITORING HEATER UNIT FOR PLASTIC TUBES
Hackcround of the~Invention
Sterile containment welding devices are known for connecting
and disconnecting plastic tubes. Examples of such devices are
found in U.S. Patent Nos. 5,256,229, 5,279,685 and 5,397,425. In
general, such devices include a pair of tube holders which would
be in alignment with each other. Each of the tube holders has a
base with the tube receiving channel into which a plastic tube
would be placed. Each tube holder also includes a clamping jaw
having a ram and anvil located above the channel. Thus, for
example, when a tube is placed in the channel the clamping jaw is
moved into locking engagement with the base and' the anvil presses
against the tube. In one practice of such devices each tube is
placed in its channel in a bent condition by being bent upon
itself with the bend of the tube extending outwardly from the
outer edge of the channel. Thus, in a connect procedure the pair
of bent ends would he disposed toward each other with each bent
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section in alignment with a corresponding bent section of the
opposite tube holder. The connect procedure is achieved by
passing a heated wafer between the two bent tube ends which
causes the tube ends to melt so that a tube section from each
tube can be pressed into contact with a corresponding tube
section.from the other tube and thereby join the two sets of tube
sections together.
It is known to include in such devices a thermocouple which
monitors the temperature of the heater-device so-that there is
assurance that the wafer will be heated to the desired
predetermined temperature. In operation when the device is
actuated the heater operates continuously to raise its
temperature until the desired temperature is reached. The
thermocouple, which is.separate from the heater, monitors the
temperature rise to sense reaching the desired temperature.
Sumanarv of the Invention
An aim of this invention is to provide such a sterile
containment welding device with a self-monitoring heater which
functions not only to heat the wafer but also to monitor the
heating process.
A further aim of this invention is to provide such a
self-monitoring heater unit which functions in a rapid sequence
of alternatingly monitoring the heater and performing its heating
function.
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r
A still further aim of this invention is to use such self-
monitoring heater for devices other than sterile containment
welding devices.
The invention provides in a device for performing a heating
operation including a heat applying tool for heating an object
at a heating location, and a heater for heating said heat
applying tool, the improvement being in that said heater
includes a self-monitoring heater unit in selective contact
with said tool, said self-monitoring heater unit including
structure for alternately in a rapid sequence heating said tool
and then monitoring the temperature of said tool until a
predetermined temperature has been reached, and conveying
structure for moving said tool to said heating location after
said predetermined temperature has been reached.
The invention also provides in a device for performing a
heating operation including a heat applying tool for heating an
object at a heating location, and a heater for heating said
heat applying tool, the improvement being in that said heater
includes a self-monitoring heater unit in selective contact
with said tool, said self-monitoring heater unit including
structure for alternately in a rapid sequence heating said tool
and then monitoring the temperature of said tool until a
predetermined temperature has been reached, said self-
monitoring heater unit comprising a ribbon having an etched
trace to function as a heater and having a thermocouple
junction, said unit including a pair of said ribbons located
adjacent to and parallel to each other and spaced apart a
distance sufficiently close whereby each of said ribbons
contacts a respective side of said tool when said tool is
located between said ribbons, and said sequence being in an
alternating millisecond sequence of longer heating period than
monitoring period.
The invention also provides a heating and temperature
monitoring assembly comprising a support member having a side
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face, a thermocouple ribbon formed by an etched trace on said
side face of said support member, said trace having a
thermocouple junction to permit a temperature monitoring to
take place, a heat applying tool, said heat applying tool being
in direct contact with said etched trace of said thermocouple
ribbon, a source of electrical power connected to said
thermocouple ribbon for causing the temperature of thermocouple
ribbon to rise for a first fixed period of time to cause said
thermocouple ribbon to function as a heater for said heat
applying tool for said first fixed period of time, said source
of electrical power turning said heater off for a second fixed
period of time, said thermocouple junction monitoring the
temperature of said heat applying tool during said second fixed
period of time, and said first period of time being
substantially longer than said second period of time.
The invention further provides in a method for performing a
heating operation including providing a heat applying tool
which heats an object at a heating location and heating the
heat applying tool with a heater, the improvement being in
using a self-monitoring heater unit in the heater, selectively
contacting the tool with the self-monitoring heater unit, using
the same self-monitoring heater unit to rapidly alternately
heat the tool and monitor its temperature, performing the
heating and monitoring in a millisecond sequence of longer
heating period than monitoring period.
The invention additionally provides in a method of heating
a heat applying tool to a predetermined temperature comprising
providing a heater which includes a thermocouple ribbon formed
by an etched trace with a thermocouple junction on the side
face of a support member, placing the heat applying tool in
contact with the etched trace, heating the heat applying tool
by heat application from the etched trace for a first period of
time, ceasing the heating and monitoring the temperature of the
heat applying tool by use of the thermocouple junction for a
second period of time to create an alternating sequence of
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heating and monitoring by the same heater with the first period
of time being longer than the second period of time, and
repeating the sequence until the temperature of the heat
applying tool is raised to the predetermined temperature.
In accordance with the preferred practice of this invention
a sterile containment welding device includes a pair of
alignable tube holders each of which has a tube receiving
channel with the channels being spaced from each other. A wafer
is provided for selective movement into the space to
connect/disconnect the tube or tubes mounted in the channels
and extending into the space. In accordance with this invention
a self-monitoring heater unit is provided upstream from the
space. The wafer is mounted for movement through the heater
unit prior to movement through the space. The unit comprises a
heater for heating the wafer when the wafer is disposed in the
unit and further includes a temperature sensor for monitoring
the temperature created by the unit. As a result, the wafer is
raised to its predetermined temperature before being moved into
the space.
In a preferred practice of the invention the heating and
monitoring functions place in rapid sequence such as being a
millisecond for each function. More preferably the heating
period is substantially longer than the monitoring period.
Preferably, the self-monitoring heater unit is a ribbon etched
with a trace to act as a heater and which includes a
thermocouple junction for the sensor.
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The Drawings:
Figure 1 is a side elevational view~partly broken away
showing a sterile containment welding device in accordance with
this invention
Figure 2 is a side elevational view of the self-monitoring
heater assembly incorporated in the device of Figure l;
Figure 3 is a exploded perspective view of the self-
monitoring heater assembly shown in Figure 2;
Figure 4 is a top plan view of the~self-monitoring heater
unit shown in Figures 2-3;
Figure 5 is an enlarged side elevational view showing the
etching trace for the self-monitoring heater unit of Figures 2-4;
and
Figure 6 is a graph showing the sequence of operation of the
self-monitoring unit of this invention.
The present invention is directed to sterile containment
welding devices for connecting or disconnecting plastic tubes.
Such devices are known in the art: Examples are described in
U. S . Patent Nos . 5, 256, 229, 5, 279, 685, and 5, 397, 525 .
In particular, the later described self-monitoring heater unit is
incorporated in the type of device shown in detail in U.S. Patent
No. 5, 279, 685.
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In general, the sterile containment welding device l0
includes a base member 12 and a pivotally mounted upper member
14. The base member and upper member maybe considered as
comprising a pair of tube holders each of which has a tube
receiving channel 16 into which a tube or tube section 18 would
be located in a known manner. The tube 18 is in a flattened
condition by manipulating the handle 20 which actuates a clamping
jaw 22 having an anvil 24 which is locatable over the channel ~16
for pressing against the tube. The outer end of the channels are
spaced from each other so that a wafer 26 shown in phantom in the
right hand portion of Figure 2 may pass through the space and
heat two tube sections for welding or connect purposes or melt
through a tube extending across the channels for disconnect
purposes. Wafer 26 which is shown in full lines in the center of
Figure 2 is mounted in a holder 28 received a carriage connected
to a drive 30 and moved by reversible motor 32 known manner in a
forward direction as indicated by the arrow 34. The carriage is
then returned to the start position. The wafer is heated prior
to moving to the spacing to effect the connect/disconnect
operation.
In accordance with this invention a self-monitoring heater
unit 36 is provided to form the dual functions of heating the
wafer and monitoring the heating temperature to assure that the
wafer is heated to its desired predetermined temperature.
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As illustrated, the self-monitoring heater unit 36 comprises
a pair of spaced, parallel thermocouple ribbons 38 which are
formed by having an etched trace 90 as best shown in Figures 3
and 5. Each thermocouple ribbon is laminated onto a thick
support member 92 such as a silicone tape. In the preferred
practice of this invention a flat E-type thermocouple ribbon
composed of Cu/Ni and Ni/Cr (Chromel-Constantan) with the
individual legs of the thermocouple sized so that the electrical
resistances equilibrate out to about 5.68 t 10$ ohm resistance.
The thermocouple trace experiences a temperature rise causing a
voltage change that can be measured. In accordance with this
invention utilization is made of the etched trace 40 so that it
also functions as a heater. The trace 40 includes a thermocouple
function 44 to permit the monitoring to take place. In this
manner there is first a heating operation and then a measuring or
monitoring operation. The switching takes place by appropriate
electronics at speeds of milliseconds. For example, there is one
millisecond of the unit 36 functioning as a heater with the next
millisecond functioning as a thermocouple when the unit 36
functions as a heater. The temperature rises then for the next
millisecond. There is then a monitoring of the temperature with
the temperature again rising in the subsequent millisecond until
the desired temperature is reached. when the desired temperature
is reached, the wafer 26 is heated to that temperature by being
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contacted on each side by an etched trace 40. The heated wafer
then moves from unit 36 to the spacing between the tube holding
channels.
In the preferred practice of the invention the thermocouple
ribbon is about 0.002 inches thick. The polarity of the
thermocouple is marked by etching a hole on the constantan or
negative side of the thermocouple. Figure 4 also illustrates
the positive conductor wire 47 for the electrical conductor
cables 46. The~cables 46 are mounted to printed circuit board 45
as best shown in Figure 1. The type-E thermocouple ribbon is
preferably laminated onto a 0.001 inch thick silicone tape. The
trace art work is registered with respect to the thermocouple
junction 44. The trace is then etched followed by a covered
lamination of 0.001 inch thick silicone tape.
As shown in Figure 3 each ribbon 38 is connected to a cable
46 at one end thereof. A leaf spring 98 is provided for each
ribbon 38 to urge the two ribbons toward each other. Each leaf
spring 48 is mounted in a spring clamp 50 on an insulator support
52. A pair of screws 49 extend through the holder 28 and press
against each spring 48 to control the spacing between the two
parallel sections of unit 36 particularly the traces 40. Screws
49 thereby assure that the spacing is sufficient to allow wafer
26 to pass between the two traces 90 and yet be close enough to
assure that there rubbing contact by~each side of the wafer 26
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and its respective heater trace 40.
Wafer 26 may be of any suitable construction and preferably
is of the construction shown and described in U.S. Patent Nos.
5, 525,186 and 5, 397, 425 .
In the practice of the invention the wafer 26 would be
mounted,in the holder 28 between the closely spaced trace
portions 40,40 of the self-monitoring heater unit 36. While the
wafer is in this upstream position the_unit 36 begins its rapid
sequence of heating and temperature monitoring in the sequential
steps illustrated in Figure 6 until, for example, a predetermined
temperature such as 300'C is reached. Figure~6 illustrates the
sequence of heating and temperature monitoring to take place
wherein the heating period of time (which might be considered a
first fixed period of time) is nine times longer than the
monitoring period of time (which might be considered a second
fixed period of time). Thus, this rapid sequence permits the
wafer or heat applying tool to reach~a predetermined temperature
in an accurate manner. With this practice of the invention the
alternating sequence is a long fixed period of heating and a
short period of monitoring. Because the wafer 26 in holder 28 is
in the unit 36 with each side of the wafer 26 contacted~by the
heater element or trace 90 of unit 36, the wafer is raised to its
predetermined temperature. The wafer is removed by the carriage
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from holder 28 and then moved downstream in the direction of
arrow 34 away from unit 36 and into the space between the tube
receiving channels 16 in a known manner.
The present invention thus provides a combined heater and
thermocouple which results in a self-monitoring heater which
detects the temperature rise of its own heating elements in a
rapid sequential manner to effectively heat'a wafer for thereby
improving the heater performance of the sterile containment
welding device.
The present invention is unique in that it utilizes the same
structure which heats a device, such as a heat applying tool or
in the preferred practice a wafer, and which alternately monitors
the temperature of tie tool so that there can be a reliable
accurate reaching of that predetermined temperature. The same
structure undergoes a sequence where, for one period of time, the
structure has its heating function (without temperature
monitoring) and then the same structure which had functioned as a
heater no longer has that function, but instead functions as a
temperature monitor. This sequence of heating and temperature
monitoring takes place in a rapid manner during millisecond time
periods.
The invention may be practiced by utilizing the same structure
in an alternate manner for both heating and temperature monitoring.
For example, the invention utilizes a thermocouple ribbon in such
a manner that a continuous thermocouple junction runs down the
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center of the ribbon. A section of the ribbon is laminated onto a
substrate and etched into a heater trace pattern leaving a
thermocouple function in the middle of the heating traces. This
effectively creates a flexible heater that can sense its own
temperature.
Although the invention has been described with particular
reference to the heating of plastic tubes, the invention may have
other applications where a heating sequence is periodically
monitored for temperature determination. The following are some
examples where the invention could be practiced. The
heating/monitoring sequence could be used for the heating of
automobile seats. In such practice the user would press the
seat/heat button to initiate the heating/monitoring sequence until
the desired temperature is reached. Another practice of the
invention could be in the de-icing of aircraft wings. A further
practice could be for instruments of small aircrafts. In such
small aircrafts there is a need to maintain the instruments in a
sufficiently warm condition. The invention could be used for
assuring that the proper temperature is reached. A still further
practice could be to keep seals warm, such as~ in spacecraft
launching.
In the preferred practice of the invention the heat applying
tool is moved to the heating site after the predetermined
temperature has been reached. The invention may also be practiced
where the heat applying tool is located at the heating site during
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the heating/monitoring sequence. The raising of the temperature of
the heat applying tool would be discontinued_once the predetermined
temperature is reached. This could be done by either stopping the
heating function or by simply supplying enough heat to maintain a
generally constant temperature.
As should thus be apparent, the invention has wide application
where the self-monitoring heater is used to assure reaching a
predetermined temperature.
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