APPARATUS FOR SENSING CHEMICAL EXHAUSTION

Technical Field

The present invention relates to an apparatus for sensing chemical exhaustion, and more particularly, to an apparatus for sensing chemical exhaustion that detects chemical exhaustion during administering a dose of chemical and emits an alarm sound upon detection of chemical exhaustion.

Background Art Every medical clinic or the like administers Ringer's injection (Ringer's solution) contained in a bottle or a vinyl bag to a patient through a thin tube. FIG. 1 shows a device for injecting Ringer's solution, which is used to administer a chemical contained in a bottle to a patient for a long period of time.

The device for injecting Ringer's solution includes, as shown in FIG. 1, a bottle 10, a connection tube 20, and a transport vinyl tube 30.

The bottle 10 that provides a space for storing the Ringer's solution is delivered from the manufacturer in a sealed condition as filled with the solution. Instead of the bottle, which is more common in use, a vinyl bag may be used to provide a space for containing the Ringer's solution. The connection tube 20 and the transport vinyl tube 30 are provided in an integral structure. At the end of the transport vinyl tube 30 is provided an injection needle for injecting the solution into the blood vessel of a patient.

The connection tube 20 has a Ringer's injection needle for injecting the Ringer's solution into the bottle 10, and the transport vinyl tube 30 has a flow rate controller for

adjusting the width of the transport vinyl tube 30 to control the flow rate of the solution. The Ringer's solution is administered from the bottle 10 to the patient through the connection tube 20 and the transport vinyl tube 30. Only a defined amount of the chemical supplied from the bottle 10 remains in the connection tube 20 and flows into the patient through the transport vinyl tube 30.

The device for injecting Ringer's solution is well known in its structure and operation to those skilled in the art and will not be described below.

In the above-described device for injecting Ringer's solution, the bottle 10 should be removed or replaced with a new one after the solution is used up. Without removal or replacement of the bottle 10 for a long period of time (for more than 10 minutes) after exhaustion of the solution, backflow of blood or inflow of air takes place to cause a medical accident. Just standing the bottle for a long period of time (for more than 10 minutes) after exhaustion of the solution may cause a serious medical accident due to blood backflow or air inflow and become an obstacle to the treatment of the patient, such as insufficient supply of medicine to the patient.

Once the chemical is used up from the bottle 10, a portion of the chemical remaining in the connection tube 20 is also consumed after a predetermined period of time, and then a portion of the chemical remaining in the transport vinyl tube 30 is fed up into the patient. It takes about 5 to 6 minutes to cause a blood backflow after the chemical exhaustion. Hence, the chemical should be refilled within 5 to 6 minutes after its exhaustion from the connection tube 20.

Although expensive equipment for sensing chemical exhaustion is used for serious patients, it is inconveniently needed for guardians or nurses of normal patients to keep eyes on the bottle or the connection tube of Ringer's solution all the time so as to

recognize the chemical exhaustion.

Disclosure of Invention

It is therefore an object of the present invention to provide an apparatus for sensing chemical exhaustion that solves the problems with the prior art.

It is another object of the present invention to provide an apparatus for sensing chemical exhaustion that senses exhaustion of chemical.

It is still another object of the present invention to provide an apparatus for sensing chemical exhaustion that senses exhaustion of chemical at a low cost. It is still further another object of the present invention to provide an apparatus for sensing chemical exhaustion that reduces energy consumption.

To achieve the objects of the present invention, there is provided an apparatus for sensing chemical exhaustion that is for sensing exhaustion of chemical held in a defined container while the chemical is supplied through a defined passage, the apparatus including at least one condenser having electrode plates arranged opposite or adjacent to each other and adhered to the outside of the passage for the chemical to flow along. The apparatus senses exhaustion of the chemical by a change in capacitance of the at least one condenser.

When the passage for the chemical to flow along is a round tube, the electrode plates constituting the condenser are semi-circular tubes, surrounding and adhered to the outside of the round tube, the electrode plates being separated from and opposite to each other to form one condenser.

The apparatus for sensing chemical exhaustion includes: a amplitude/phase sensing part for changing the amplitude or phase of an input signal depending on the

capacitance of the condenser; a signal comparison part for comparing the gain of an output signal of the amplitude/phase sensing part with a reference gain level to detect exhaustion of the chemical and thereby determining whether to generate an alarm generation signal; and an alarm generation part for generating an alarm in response to the alarm generation signal output from the signal comparison part. The input signal may include any one selected from sinusoidal wave, step form wave, square wave, or triangle wave.

The amplitude/phase sensing part includes a resistor connected between an input node of the input signal and an output node of the output signal; and the condenser connected between the output node and a ground. The signal comparison part includes a peak detector for detecting a amplitude by using the peak value of the output signal of the amplitude/phase sensing part; and a comparator for comparing the amplitude detected by the peak detector with a reference amplitude level and thereby generating the alarm generation signal when the amplitude is equal to or greater than the reference amplitude level. The signal comparison part includes an AD (analog-digital) converter for analog- to-digital converting the output signal of the amplitude/phase sensing part; and a microcontroller for comparing an output of the AD converter with the reference amplitude level and thereby generating the alarm generation signal when the output of the AD converter is equal to or greater than the reference amplitude level. Additionally, the signal comparison part includes: a first comparator for comparing the input signal with a reference comparison level to generate a phase value; a second comparator for comparing the output signal of the amplitude/phase sensing part with the reference comparison level to generate a phase value; and a micro-controller for detecting a phase difference between output signals of the first and second comparators

and thereby generating the alarm generation signal when the phase difference is equal to or less than a reference phase level. The signal comparison part also includes: a first AD converter for analog-to-digital converting the input signal; a second AD converter for analog-to-digital converting the output signal of the amplitude/phase sensing part; and a micro-controller for generating the alarm generation signal when the amplitude of an output signal of the second AD converter is equal to or greater than a reference amplitude level, or when the phase difference between output signals of the first and second AD converters is equal to or less than a reference phase level under the condition that the amplitude of the output signal of the second AD converter is less than the reference amplitude level. The operation of sensing chemical exhaustion with the apparatus may be carried out at predetermined time intervals.

The apparatus may includes at least two electrode plates constituting the condenser, each plate completely surrounding the passage for the chemical or exposing a part of the passage. The electrode plates are adhered to the outside of the passage in a longitude direction and disposed adjacent to each other. When the passage for the chemical is a round tube, the electrode plates of the condenser are formed in shape of "C" or "O" surrounding the tube.

According to the present invention, it is possible to sense chemical exhaustion at a low cost.

Brief Description of Drawings

FIG. 1 is a schematic of a general device for injecting a Ringer solution;

FIGS. 2 and 3 are schematics of a condenser used for an apparatus for sensing chemical exhaustion according to the present invention;

FIGS. 4 to 7 are block diagrams showing the respective embodiments of the apparatus for sensing chemical exhaustion with the condenser of FIGS. 2 and 3; and

FIG. 8 is a schematic of an apparatus for sensing chemical exhaustion according to another embodiment of the present invention.

Best Mode for Carrying out the Invention

Hereinafter, the preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings, which are intended for purpose of illustration only and are not intended to limit the scope of the invention. FIGS. 2 and 3 illustrate the construction of a condenser used for an apparatus for sensing chemical exhaustion according to embodiments of the present invention. FIG. 2 is a front view showing the construction of the condenser and FIG. 3 is a cross-section.

Generally, a condenser consists of two electrode plates and a dielectric material disposed between the two electrode plates. The condenser has a capacitance given by the expression C = εX(s / d), where ε is the permittivity of the dielectric material; s is the cross-sectional area of the electrode plates; and d is the distance between the electrode plates.

As illustrated in FIGS. 2 and 3, two electrode plates 40a and 40b are adhered to the outside of a transport vinyl tube 30 or a connection tube 20 of a device for injecting Ringer's solution to form a condenser C. Here, the two electrode plates 40a and 40b are arranged opposite to each other to surround the outside of the transport vinyl tube 30 or the connection tube 20. The length or width of the electrode plates may be experimentally determined in an appropriate value.

Although an embodiment of the transport vinyl tube 30 is shown in FIGS. 2 and 3,

it is apparent to those skilled in the art that the connection tube 20 may be embodied in the same construction, hi the following description, both the transport vinyl tube 30 and the connection tube 20 are denoted as "tube 30".

The two electrode plates 40a and 40b, when mounted on the tube 30, electrically operate as a condenser C. That is, the two electrode plates 40a and 40b function as a condenser C of which the capacitance changes depending on the dielectric material disposed between the electrode plates 40a and 40b. When no chemical flows through the tube 30, in which case air exists solely between the electrode plates 40a and 40b, the condenser C has a decreased capacitance. With a chemical flowing through the tube 30, the condenser C has a greater capacitance because the chemical usually has a greater permittivity than air.

For example, permittivity ε is determined by multiplying relative permittivity by dielectric constant (ε _o = 8.854X10 ^"12 C ² /Nm ² ), where the relative permittivity of air is 1 and that of water is 78.5. Any chemical including Ringer's solution, which normally contains different ingredients as well as water, has a greater relative permittivity than water. Thus a change in capacitance of the condenser C, as compared with the relative permittivity of water or a specific relative permittivity between those of air and water as a reference, indicates whether or not the chemical is left in the tube 30.

Some problems may be found as follows in the case where electrode plates are attached to the tube as illustrated in FIGS. 2 and 3, especially when a condenser is formed on the vinyl tube 30 having a relatively small thickness, although there is no problem with the condenser formed on the connection tube 20.

When the hole through which the chemical flows is too small in relation to the total thickness of the tube 30, the construction provides a series connection between a

capacitance formed from the material (e.g., plastics) of the tube 30 and a capacitance formed from the chemical. The change in capacitance depending on the existence of the chemical in this case is too insignificant to matter.

For example, when the capacitance formed from the tube 30 is C _p and the capacitance formed from the chemical is C _g , the total capacitance may be calculated according to a series connection of the two capacitances as given by (C _p XC _g ) / (C _p + C _g ), resulting in a small change in the total capacitance depending on the existence of the chemical.

Another problem is that it is impossible to provide the electrode plates in larger size. The capacitance increases with an increase in the area of the electrode plates, so the condenser with electrode plates of a larger area is more advantageous. With the tube 30 having a small thickness, however, it is difficult not only to form a condenser having a great capacitance but also to attach the electrode plates to the tube, resulting in a demand of a condenser having a novel structure as illustrated in FIG. 3. FIG. 8 shows the structure of a condenser formed with the tube 30 having a small thickness and presents perspective (a) and cross-section (b).

As illustrated in FIG. 8, two electrode plates 50a and 50b are arranged in the longitude direction of the tube 30 and adjacent to each other to form a condenser.

More particularly, the electrode plates 50a and 50b, each of which does not completely surround the tube 30 used as a passage for the chemical to flow along but exposes only a part of the tube, are formed of the same structure, arranged adjacent to each other and adhered to the outside of the tube 30 in the longitude direction of the tube 30. To realize this structure, the electrode plates 50a and 50b may be formed in a shape of "C".

For another structure, if not illustrated in the figure, the electrode plates completely surrounding the tube 30 are arranged adjacent to each other in the longitude direction of the tube 30 to form a condenser, in which case the electrode plates are formed in a shape of "O". The electrode plates may be formed in the shape of ring that surrounds the tube 30.

When the passage for the chemical to flow along is not a round tube but a polygon, the electrode plates are formed in the same shape of the passage. In this case, the electrode plates are adhered to completely surround the passage or expose only a part of the passage.

Preferably, the condenser is formed to be a fixed structure when using O-shaped electrode plates, or a detachable structure with C-shaped electrode plates.

Compared with the condenser structure of FIGS. 2 and 3, the condenser of the above-described electrode structure has a greater change in the capacitance depending on the existence of the chemical, facilitating attachment as well as signal processing.

There may be provided at least two electrode plates 50a and 50b of the same shape. One condenser is constructed with an arrangement of two electrode plates. With three or more electrode plates, the condenser comes in different capacitances and numbers depending on the choice of electrode plates.

The tube 30 may include at least one condenser constructed as described above. Possibly, the connection tube 20 has the condenser of the structure as illustrated in FIGS. 2 and 3 and the vinyl tube 30 has the condenser of the structure of FIG. 8. In addition, a plurality of condensers may be connected in parallel to have a greater capacitance.

FIG. 4 is a block diagram showing an apparatus for sensing chemical exhaustion according to one embodiment of the present invention using the condenser of the structure shown in FIGS. 2, 3 and 8.

As illustrated in FIG. 4, the apparatus 100 for sensing chemical exhaustion according to one embodiment of the present invention includes a amplitude/phase sensing part 120 and a signal comparison part 130. The apparatus may further include an input signal generation part 110 for generating an input signal to the amplitude/phase sensing part 120, and an alarm sound generation part 140 for generating an alarm sound in response to an alarm generation signal output from the signal comparison part 130.

The amplitude/phase sensing part 120 changes the amplitude or phase of input signal V _s depending on the capacitance of the condenser C. The amplitude/phase sensing part 120 includes a resistor R and the condenser C. The resistor R is formed between the input signal generation part 110 connected to the input signal V _s and the signal comparison part 130. That is, the resistor R is provided between an input node of the input signal V _s and an output node n of the amplitude/phase sensing part 120. The resistance value may be set to an appropriate value.

The condenser C has a construction as illustrated in FIGS. 2 and 3. The amplitude/phase sensing part 120 is formed using electric wires connected to the electrode plates 40a and 40b of FIGS. 2 and 3, where the electric wire connected to the one electrode plate 40a is connected to a ground, the electric wire connected to the other electrode plate 40b being connected to the resistor R. And the input signal V _s generator is connected between the resistor R and the ground. The input signal V _s may be sinusoidal wave or step form wave. The input signal

V ₈ may also be square wave that occurs when the step form wave is periodically applied, or may be triangle wave instead of the sinusoidal wave.

Assuming that the input signal V _s is sinusoidal wave given by "V ₈ (t) = sin(2πX

1000)t", with the resistance "R = 3kω" and the capacitance of the condenser C for air as

given by "C = 100OpF", the output of the amplitude/phase sensing part 120 at both ends of the condenser C is calculated as follows.

The output of the amplitude/phase sensing part 120 is "V ₀ (jω)/V _s (jω) = 1 /(1 + jω RC)". When the dielectric material is air, the output of the amplitude/phase sensing part 120 approximates to " 1 " and the phase is "- arctan (ω RC) = - 1.1 ° " . With water (H ₂ O) for

the dielectric material, the capacitance of the condenser C is given by "C = 78.5XlOOOpF",

which approximates to "0.56", and the phase is "- arctan (ω RC) = -55.9°"

With water for the dielectric material, the output of the amplitude/phase sensing part 120 approximately becomes 50% of the capacitance with air for the dielectric material, and the phase is "55.9 - 1.1 = 54.8°".

When the input signal V _s is a step form wave having a amplitude of "A", the output signal V ₀ at both ends of the condenser C is given by "V ₀ (t) = A(I -e ⁰⁴ ^". The time constant of the output signal V ₀ at both ends of the condenser C is "RC". This may be applied to the detection of chemical exhaustion through a comparison of output signals according to a change in the capacitance of the condenser C.

In another construction of the amplitude/phase sensing part 120, if not illustrated in the figures, the resistor R may switch locations with the condenser C. That is, the condenser C is connected between the input node of the input signal V ₅ and the output node n of the amplitude/phase sensing part 120, while the resistor R is connected between the output node n and a ground. Then the output of the amplitude/phase sensing part 120 becomes "V ₀ Gω)/V _s (j _ω ) = j _ω RC/(1 +jω RC)".

Even in this case, where the output signal of the amplitude/phase sensing part 120 varies depending on a change in capacitance of the condenser C, chemical exhaustion can be detected through a comparison of the output signals according to a change in the

capacitance of the condenser C.

The signal comparison part 130 compares the gain of the output signal V ₀ of the amplitude/phase sensing part 120 with a reference gain level to detect chemical exhaustion and thereby determines whether to generate an alarm. When the dielectric material is water (H ₂ O), as compared with the case where the dielectric material is air, the output of the amplitude/phase sensing part 120 roughly decreases to 50% and the phase difference becomes "55.9 - 1.1 = 54.8°", making it possible to determine exhaustion of a dose of chemical. In case of a chemical existing as the dielectric material, where the chemical is generally known to have a greater permittivity than water, water may be used as a reference material to determine the reference amplitude level and the reference phase level. When water is used as a reference material having a margin of about 50 %, for example, the reference amplitude level is set to "(1 - 0.56 / 2) = 0.72" and the reference phase level is "54.8 / 2 = 27.4°". Accordingly, non-existence of the chemical, in other words, exhaustion of a dose of the chemical is recognized when the output signal V ₀ of the amplitude/phase sensing part is 0.72 or higher and the phase difference is 27.4° or below.

The signal comparison part 130 for sensing chemical exhaustion using reference levels as described above may be constructed in different ways.

As illustrated in FIG. 4, the apparatus 100 for sensing chemical exhaustion according to one embodiment of the present invention, which makes the use of amplitude, the signal comparison part 130 includes a peak detector 132 and a comparator 134.

The peak detector 132 detects a amplitude by using the peak value of the output signal V ₀ at the output node n. The peak detector 132 may be replaced with a full- wave rectifier and a low-pass filter.

The comparator 134 compares the amplitude detected by the peak detector 132 with a reference amplitude level (for example, 0.72) and thereby generates the alarm generation signal when the amplitude is equal to or greater than the reference amplitude level. With the alarm generation signal output from the comparator 134, the alarm sound generation part 140 emits an alarm sound.

FIG. 5 is a block diagram of an apparatus 200 for sensing chemical exhaustion according to another embodiment of the present invention using the condenser C.

As illustrated in FIG. 5, the apparatus 200 for sensing chemical exhaustion according to another embodiment of the present invention, which uses the amplitude of the output signal V ₀ , includes a amplitude/phase sensing part 120 and a signal comparison part 230 in the same manner as shown in FIG. 4.

The apparatus 200 may further include an input signal generation part 110 for generating an input signal to the amplitude/phase sensing part 120, and an alarm sound generation part 240 for generating an alarm sound in response to an alarm generation signal output from the signal comparison part 230.

Those components that have the same construction as illustrated in FIG. 4, such as input signal generation part 110, amplitude/phase sensing part 120 and alarm sound generation part 240 are not described any more in the following description.

The signal comparison part 230 may include an AD converter 232 and a micro- controller 234.

The AD converter 232 analog-to-digital converts the output signal V ₀ at the output node n.

The micro-controller 234 compares the output of the AD converter 232 with the reference amplitude level (for example, 0.72) and thereby generates the alarm generation

signal when the output of the AD converter 232 is equal to or greater than the reference amplitude level. With the alarm generation signal, the alarm sound generation part 240 emits an alarm sound, indicating exhaustion of the chemical.

FIG. 6 is a block diagram of an apparatus 300 for sensing chemical exhaustion according to further another embodiment of the present invention using the condenser C.

As illustrated in FIG. 6, the apparatus 300 for sensing chemical exhaustion according to further another embodiment of the present invention, which uses the phase difference of the output signal V ₀ , includes a amplitude/phase sensing part 120 and a signal comparison part 330. The apparatus 300 may further include an input signal generation part 110 for generating an input signal to the amplitude/phase sensing part 120, and an alarm sound generation part 340 for generating an alarm sound in response to an alarm generation signal output from the signal comparison part 330.

Those components that have the same construction as illustrated in FIG. 4, such as input signal generation part 110, amplitude/phase sensing part 120 and alarm sound generation part 340 are not described any more in the following description.

The signal comparison part 330 may include a first comparator 332, a second comparator 334, and a micro-controller 236.

The first comparator 332 compares the input signal V _s with a reference comparison level to generate a phase value. The reference level is OV with the input signal

V _s being a sinusoidal wave, or may be set to a predetermined value (for example, 50% of the amplitude of the input signal V ₈ ) with the input signal V ₈ being a square wave or a step form wave.

The second comparator 334 compares the input signal V ₀ at the output node n

with a reference comparison level to generate a phase value. The reference level is OV with the input signal V _s being a sinusoidal wave, or may be set to a predetermined value (for example, 50% of the amplitude of the input signal V _s ) with the input signal V _s being a square wave or a step form wave. The micro-controller 336 detects a phase difference between output signals of the first and second comparators 332 and 334. There is a time difference between the outputs of the first and second comparators 332 and 334 depending on the capacitance of the condenser C of the amplitude/phase sensing part 120.

Depending on the capacitance difference of the condenser C, for example, the time delay of the output of the second comparator 334 after the output of the first comparator 332 is changed, thereby causing a time difference between the outputs of the first and second comparators 332 and 334.

Normally, the time difference (phase difference) increases with an increase in the capacitance of the condenser C. The micro-controller 336 compares the time difference with the reference phase level (for example, 27.4°) and thereby generates the alarm generation signal when the time difference is equal to or less than the reference phase level. With the alarm generation signal, the alarm sound generation part 340 emits an alarm sound, indicating exhaustion of the chemical.

FIG. 7 is a block diagram of an apparatus 400 for sensing chemical exhaustion according to still further another embodiment of the present invention using the condenser C.

As illustrated in FIG. 7, the apparatus 400 for sensing chemical exhaustion according to still further another embodiment of the present invention, which uses the phase difference and magnitude of the output signal V ₀ , includes a amplitude/phase

sensing part 120 and a signal comparison part 430.

The apparatus 400 may further include an input signal generation part 110 for generating an input signal to the amplitude/phase sensing part 120, and an alarm sound generation part 440 for generating an alarm sound in response to an alarm generation signal output from the signal comparison part 430.

Those components that have the same construction as illustrated in FIG. 4, such as input signal generation part 110, amplitude/phase sensing part 120 and alarm sound generation part 440 are not described any more in the following description.

The signal comparison part 430 may include a first AD converter 432, a second AD converter 434, and a micro-controller 436

The first AD converter 432 analog-to-digital converts the input signal V ₈ .

The second AD converter 434 analog-to-digital converts the output signal V ₀ at the output node n.

When the chemical exists in the tube, as compared with the case of chemical exhaustion, the condenser has a greater capacitance, as well as less amplitude and greater phase difference as already described above.

The micro-controller 436 detects chemical exhaustion to generate the alarm generation signal, when the amplitude of the output signal of the second AD converter 434 is equal to or greater than the reference amplitude level (for example, 0.72). Otherwise, when the amplitude of the output signal of the second AD converter

434 is less than the reference amplitude level (for example, 0.72), the micro-controller 436 calculates the time difference between the maximum or minimum output signals of the first and second AD converters 432 and 434. The time difference between the two signals corresponds to the phase difference. The micro-controller 436 detects chemical exhaustion

to generate the alarm generation signal, when the phase difference is equal to or less than the reference phase difference (for example, 27.4°). Of course, there is no alarm generation signal when the phase difference is above the reference phase difference (for example, 27.4°). With the alarm generation signal, the alarm sound generation part 440 emits an alarm sound, indicating exhaustion of the chemical.

The above-described apparatuses 100, 200, 300 and 400 for sensing chemical exhaustion may be designed to operate at predetermined time intervals. As for a device for injecting Ringer's solution, for example, a little more of the solution still remains in the transport vinyl tube 30 to be administered for more about 5 to 6 minutes even after the solution in the connection tube 20 is used up. Thus operating the apparatuses 100, 200, 300 and 400 at predetermined time intervals of less than 5 minutes may lead to a reduction of energy consumption.

As described above, the apparatus for sensing chemical exhaustion according to the embodiments of the present invention makes it easier to detect chemical exhaustion, allowing its realization in a simple way at a lower cost and consuming less electric energy.

The apparatus for sensing chemical exhaustion is applicable to any device or means for supplying chemical through a thin tube, that is, all the chemical supply devices in need of a function of sensing chemical exhaustion, as well as a device for injecting Ringer's solution used in medical clinics. In supplying or circulating a fluid such as blood, oil or water into a specific place through a tube, for example, the apparatus for sensing chemical exhaustion may be used as an air detector for detecting existence of air inside the tube.

The condenser in this construction may be provided inside the tube. The condenser may be fixed on a specific area of the tube or movable along the tube. Using the

condenser of a movable structure makes it possible to detect existence of air in a specific area of the tube where a portion of water or oil is left.

While this invention has been described in connection with the embodiments, it is to be understood to those skilled in the art that the description is not intended to be exhaustive or to limit the scope of the invention. Many modifications and variations are possible in light of the above teaching without departing from the scope of the following claims.

Industrial availability As described above, the present invention makes it easier to detect chemical exhaustion, allows simple realization at a lower cost and reduces energy consumption.