JPH0794996B2 - Fluid flow rate sensing device - Google Patents

Description

FIELD OF THE INVENTION The present invention relates generally to devices for sensing fluid flow, and more particularly to flowing slow enough to be detected as individual drops. A device for detecting and measuring the flow rate of a fluid by optical means.

BACKGROUND OF THE INVENTION Fluid flow sensing devices that can detect and measure the flow rate of individual drops of a fluid have many applications. One major application for such sensing devices is to measure the fluid flow rate through a drip chamber assembly within an intravenous (“IV”) fluid infusion device. Such IV fluid injection devices generally include a bottle containing the fluid to be administered, a drip chamber assembly, a tube connecting the bottle to the intake at the top of the drip chamber, and the fluid attached to the tube. A valve for controlling the flow rate of the liquid, a second tube connected to the outlet at the bottom of the drip chamber, and an injection means such as a needle or catheter connected to the second tube. And the fluid enters the patient's body through this injection means.

The drip chamber assembly is typically cylindrical and has a transparent chamber surrounding the drip chamber. Fluid enters the assembly through a drop formation at the top of the chamber and one drop at a time,
Fall through the chamber. The flow rate of fluid through the chamber is
While it is possible to monitor the falling drops by visual observation, various flow sensing devices have been developed to automatically detect the drops falling, allowing the observer to do other work. It is designed to be opened.

An example of a fluid flow sensing device capable of monitoring fluid flow through a drip chamber assembly is U.S. Pat. No. 3,596,51.
Some are disclosed in No. 5 and No. 4,397,648. Flow sensing devices of the type disclosed in these US patents include
Generally, a light energy emitter on one side of the drip chamber assembly and a light energy detector on the other side are used. The energy emitters typically emit light energy in the infrared or visible light spectrum (wavelengths between about 300 nanometers and 2 microns). This light energy passes through the transparent wall of the drip chamber assembly and then strikes the detector. As each individual drop falls through the chamber, it blocks the flow of light energy and causes the detector to generate a corresponding output signal. This output signal is then applied to the monitor device for processing. The monitoring device generally sounds an alarm or monitors the flow rate of the fluid when the fluid flow is stopped.

Existing flow sensing devices, such as those disclosed in the above-referenced US patents, have some drawbacks. One of them is
It is necessary to accurately match the energy emitter and detector during manufacturing, and this process adds significantly to the overall manufacturing cost of the flow sensing device.
If this process could be simplified or eliminated, the flow sensing device could be made more economical.

It is also necessary to shield the detector from being affected by ambient light energy, and
It is necessary to keep all components in the optical path clean to prevent desensitization resulting from dust or moisture blocking the passage of light energy. If a sensing device is obtained that is less sensitive to ambient energy than existing sensing devices and is easier to clean, then this device is more reliable and available in the field than existing sensing devices. It's easier.

Also, the transparent wall of the drip chamber assembly refracts light energy as it passes. This refraction prevents the detector from detecting drops of fluid that do not pass near the center of the chamber when falling. If the chamber is held in a substantially vertical orientation, all the drops fall through the central part of the chamber so that the detector can detect the drops without difficulty. However, the chamber is about 15
If tilted more than one degree away, the drop will not fall through the center of the chamber and the detector will not be able to detect it. If there is a flow sensing device that works correctly both with a vertically held drip chamber and with a tilted drip chamber, this is more versatile than existing flow sensing devices. Target, easier to use, and less likely to give false "no flow" alarms.

The use of IV devices as an important instrument of modern medicine continues to grow, and with this expanding use, there is an ever-increasing demand for IV devices that can function with a minimum of human monitoring work. There is. With this demand, it can be manufactured cheaper than existing sensing devices and is less susceptible to ambient light energy or to dust and humidity in the environment, and the drip chamber has its vertical axis. There is a need for a fluid flow sensing device that can detect the flow rate of fluid through the chamber even when tilted far away from.

One approach to this problem is a non-standard drip with walls formed in the shape of a special lens that allows the light beam to pass through the drip chamber and onto a chip of photosensitive material located adjacent to the chamber. It has been proposed to use a chamber assembly. However, such drip chamber assemblies are relatively expensive to manufacture, and fluid flow sensing devices configured for use with them cannot be used with conventional cylindrical drip chamber assemblies. Unlike ordinary cylindrical assemblies, the lens-shaped walls of such non-standard drip chambers are strict and make the sensing device more difficult to service. Also, this method does not address the problems caused by noise, dirt and moisture in the environment.

Problems to be Solved by the Invention As is apparent from the above, it can be used with an ordinary cylindrical drip chamber assembly, and is cheaper to manufacture than existing sensing devices, and to ambient energy. Optical flow rate that is relatively insensitive, easy to keep clean in the field, and capable of detecting fluid flow even when the drip chamber assembly is tilted far from the vertical A sensing device is required. The present invention seeks to meet this need.

(Means for Solving the Problems) In the present invention, a space is formed between them to separate them from each other.
A fluid flow rate sensing device comprising an arm and a support substrate having a second arm substantially parallel to the arm, wherein the energy emitting means is attached to the first arm and the energy detector is attached to the second arm. A first lens fixedly attached to the first arm, having an outer surface that is convex in both horizontal and vertical cross sections, and having a convex inner surface only in the horizontal cross section, the energy from the energy radiating means. And the energy detector is fixedly attached to the second arm relative to the first lens for refracting and transmitting the energy passing through the space of the arm, and both the horizontal section and the vertical section are A second lens having a convex outer surface and an inner surface, the second lens receiving energy transmitted from the first lens, and The energy is a fluid flow sensing apparatus characterized by having the above-described second lens to convey refracts toward the energy detector.

(Operation) As can be seen from the above, the present invention represents a remarkable advance in the optical fluid flow measuring device. Specifically, the present invention is inexpensive to manufacture because the lens blocks are self-aligning, easy to shield against ambient light energy, easy to keep free of dust and moisture, and A fluid flow rate sensing device that responds to drops falling along the vertical axis of the drip chamber and to drops falling off center.

Other aspects and advantages of the invention will become apparent from the following detailed description of the embodiments of the invention with reference to the drawings.

(Effects) Existing optical flow rate sensing devices are characterized by relatively high manufacturing costs, being susceptible to ambient light energy, dust and moisture, and falling far from the vertical axis of the drip chamber assembly. Unable to respond to drops. The present invention uses a unique lens block to overcome these limitations, particularly for drops that fall near the vertical axis of the drip chamber or for drops that fall near the wall of the drip chamber. A flow sensing device adapted to respond.

EXAMPLE An improved fluid flow sensing device according to the present invention having a drip chamber assembly in place is shown in FIG. This sensing device comprises a first arm 13 with a space 17 between them.
And a support substrate 11 having a second arm 15.
An emitter block 19 with a lens 21 is mounted on the arm 13 to orient the lens 21 towards the cavity 17 and the lens 25
An energy detector block 23 having is mounted on the arm 15 with the lens 25 facing the lens 21 across the cavity 17. A drip chamber assembly 27 is located in the cavity 17 between the emitter lens 21 and the detector lens 25.

As shown in FIGS. 2 and 3, an energy emitter chip 19 is mounted in a cavity 31 within the block 19 (the support substrate 11 is omitted from FIGS. 2 and 3 for clarity). There is). Chip 29 is a printed circuit board in block 19
It is mounted on 33 and is located approximately at the focal point of lens 21. A beam of light energy having rays 35, 37, 39, 41, 43 and 45 is emitted from tip 29 and refracted by lens 21, which then passes through drip chamber assembly 27 to lens 25. Lens 25 focuses the beam on detector chip 47. The detector chip 47 is mounted on the circuit board 49 in the cavity 51 of the block 23. The detector chip 47 is located at approximately the focal point of the lens 25.

As shown in FIGS. 1 and 3, the drip chamber assembly 27 is substantially cylindrical. The assembly 27 has a transparent cylindrical wall 53 that forms a drip chamber 55. An intake pipe 57 leads into the top of the chamber 55. The drop former 59 constitutes the end of the tube 57, and when the fluid flows through the tube 57, a discrete drop 61 of fluid is formed in the drop former 59.
Formed, and falls through the chamber 55 as indicated by arrow 63,
The fluid in the lower part of the chamber 55 enters 65. From the reservoir 65, the fluid flows out of the chamber 55 through the delivery tube 67. As a discrete drop 61 of fluid falls through chamber 55, it crosses some of the light energy rays 35, 37, 39, 41, 43 and 45, and the intensity of the energy beam striking the detector tip. Fluctuate.

The detector chip 47 produces an electrical output signal that changes in response to variations in the intensity of the light energy striking the chip. As each drop 61 of fluid falls through the drip chamber 55 and fluctuates the intensity of the light energy, the tip 47 follows accordingly.
The output signal from changes. Each change of the above output signal is
Thus, it indicates the passage of one drop of fluid through the chamber 55. Light energy from the emitter or tip 29 passes through virtually the entire width of the chamber 55. Therefore, both a drop passing near the edge of the chamber 55 and a drop passing through the center of the chamber 55 are detected.

The output signal is applied to an electronic monitor (not shown). The monitoring device is configured to measure the flow rate of this fluid by measuring the time interval between successive drops, or an alarm if no drops are falling during a predetermined time interval. Is configured to generate.

Suitable holding means (not shown) are provided to hold the drip chamber assembly 27 in a fixed position within the cavity 17.

By increasing the ratio between the width of the fluid drop 61 and the width of the energy beam striking the detector tip 47, the sensitivity of this flow sensing device can be improved. This is because the magnitude of the change in the output signal from the tip 47 caused by the drop of fluid across the light energy beam is proportional to the magnitude of the change in the intensity of the energy beam striking the tip 47, and As the proportion of the total energy beam traversed by a drop of liquid increases, so does the magnitude of the beam intensity variation caused by the falling drop. Since the drop size is determined by other requirements and cannot be changed for the purpose of improving the sensitivity of the flow sensing device, the ratio between the drop width and the beam width is The only way to increase it is to reduce the beam width. The beam width can be reduced by placing an aperture assembly in the detector block 23, as shown in FIG.

The embodiment of the invention shown in FIG. 4 is similar to that shown in FIG. For convenience, components in FIG. 4 that are similar to components in FIG. 2 are given the same reference numbers. Similar but changing components are given the same reference numbers with the letter "a". Different components have different reference numbers.

An aperture assembly 69 having an opaque side wall 71, an opaque front wall 73, and an opaque top and bottom surface (not shown) is disposed within the cavity area 51 in the detector block 23 and the front wall 73 is attached to the lens 25. Adjacent to the inner surface of the. The top, bottom, and sidewalls 71 of the assembly 69 attach the detector chip 47 to the lens 25.
It shields from light energy that may enter the block through the surface of the block other than the surface on which the block is formed. The front wall 73 extends halfway from the side wall 71 across the lens 25 and forms an aperture 74. The aperture 74 is
Receiving light energy represented by rays 39 and 41 that does not pass through the left and right side regions 78 of the drip chamber 55,
Eliminate the light energy represented by rays 35a, 37a, 43a and 45a and passing through the side regions 78 of the chamber 55. aperture
Only the energy passed through 74 hits the detector chip 47, and the front wall 73 blocks other energy and scatters further away.

The width of the energy beam striking the detector chip 47 is narrowed by narrowing the aperture 74 and widened by widening the aperture 74. The narrower beam of energy received by aperture 74 results in a larger drop width to total beam width ratio, thus making tip 47 more sensitive to drops falling through chamber 55. However, drops falling through the side regions 78 of the chamber 55 are not detected. That is, the rays 35A, 37A,
The portion of the beam of energy represented by 43A and 45A that the drop traverses does not reach the tip 47 and the wall
Because it is scattered far by 73. Therefore,
As the aperture 74 becomes narrower, the side regions 78 where falling drops are not detected become wider. Therefore, the trade-off is that when the aperture 74 becomes narrower, the tip 47 becomes more sensitive to the falling drop, but the portion of the drip chamber 55 where the falling drop is not detected becomes narrower.

When the drip chamber assembly 27 is placed in a completely vertical position,
The 61 drops only through the center of the drip chamber 55 and is detected even with the extremely narrow aperture 74. However, as the assembly 27 tilts further from the vertical, the drops 61 will spill into the chamber 55.
When the assembly 27 is tilted far enough to fall toward the edge of the drop and the drop falls through one of the side regions 74, the detector tip 47 becomes unresponsive to the drop.

In other words, as the aperture 74 becomes narrower, the tip 47
Is more sensitive and the maximum tilt angle of the drip chamber 55, where drops are reliably sensed, is smaller. A useful solution is to make the apertures 74 sufficiently narrow so that each of the side regions 78 is as wide as one drop. This solution provides good sensitivity and allows the sensing device to reliably detect the passage of a drop through a drip chamber assembly that is inclined at an angle of no more than 26 degrees from the vertical. Like

Optionally, a baffle 75 may be provided within aperture assembly 69 between front wall 73 and detector chip 47. The baffle 75 forms a plane parallel to the front wall 73, which forms a second aperture 76 that is narrower than the aperture 74. The baffle 75 reduces the effect of ambient light energy on the tip 47 by scattering a large amount of that energy away. As will be appreciated by those skilled in the art,
The second set of baffles 77 can be added to further increase the insensitivity to ambient energy as described above, and such baffles may be added.

Next, the energy emitter block 19 will be described in more detail. As shown in FIG. 5, the block is formed of a hollow block made of a transparent material. The rear side 79 of the block 19 has an opening 81 leading into the cavity 31 inside the block 19. The lens 21 is formed on the front side 83 of the block 19, and the lens has a convex outer surface 85 and a convex inner surface 87.
Have. The outer surface 85 and the inner surface 87 of the lens 21 are shaped according to the refractive effect of the walls of the drip chamber assembly 27. In this example, the outer lens surface 85 is convex in both the horizontal and vertical cross sections shown in FIGS. 6 and 7, respectively, and the inner lens surface 87 is convex only in the horizontal cross section.

Energy emitting chip 29 is mounted on circuit board 33 and is connected to printed wiring conductor 89. Wire 91
Are connected to the conductor 89 to make a connection between the chip 29 and an external circuit (not shown).

A shoulder 93 is formed along the periphery of the opening 81, said shoulder being recessed within the cavity 31 by a short distance, said distance being slightly greater than the thickness of the circuit board 33. The circuit board 33 has the same width and length as the opening 81, and is arranged in the opening opposite the shoulder 93. Notch 95 in circuit board 33
Engages with the alignment key 97 extending rearward from the shoulder 93,
The circuit board 33 is held in a fixed position with respect to the block 19. The lens 21 is formed so that the chip 27 is approximately in focus of the lens 21 when the circuit board 33 is positioned opposite the shoulder 93 with the notch 95 engaging the alignment key 97. .

When the circuit board 33 is in place in the opening 81 facing the shoulder 93, the circuit board closes only the passage between the cavity 31 and the outside world, and the circuit board is at the inner edge of the opening 81. In combination with 99, a recessed area 101 is formed. The recessed area 101 is filled with potting material (not shown), which seals the block 19 and protects the cavity 31 from dust, moisture or other contaminants that may be present in the atmosphere. To do. Ideally, the assembly and potting of circuit board 33 into block 19 was dried. For example, in an inert atmosphere such as nitrogen.
So, even if this pre-assembled block is washed or exposed to dusty or other harsh atmospheres, the tip 29 can be damaged or the internal lens surface
No condensation occurs at 87.

The structure of the detector block 23 is almost the same as the structure of the emitter block 19, except that the chip attached to the former is different.
47 is a light energy detection device, and the chip 29 attached to the latter is a light energy emitter. Further, the above two lenses have slightly different focal lengths. Also, in this embodiment, the inner surface 88 of the detector lens 25 is convex both in the horizontal cross section and in the vertical cross section shown in FIG. 3, while the inner surface 87 of the emitter lens 21 is
Is convex only in the horizontal section. Therefore, the above description of the structure of the emitter block 19 also applies to the structure of the detector block 23, except for the above differences.

A fluid flow sensing device as described above, with any drip chamber assembly having a transparent wall and a mechanical size that fits within the cavity 17 between the emitter block 19 and the detector block 23. Can be used.

The insensitivity to ambient light energy is good as the lens 25 tends not to focus such light on the detector chip 47. This insensitivity is due to the aperture assembly 69.
Can be improved and, if necessary, to make the energy emitter emitting infrared energy and the detector chip 47 insensitive to light energy not in the above infrared spectrum. Further improvement can be made by using a filter or other means (not shown).

(Effect of the Invention) Assembling the fluid flow rate sensing device of the present invention is simpler than assembling the conventional sensing device. Instead of having to have a small energy emitter and energy detector mechanically aligned to the sensing device substrate and to each other,
The assembly device need only mount the two lens blocks so that the lenses face each other. Also, the fluid flow sensing device of the present invention does not require additional shielding from ambient energy and must be kept free of dust and moisture because its energy detector and emitter chips are hermetically sealed. The only optical component is the outer lens surface of the two blocks. The present invention also provides
Responds to drops that fall far away from the vertical axis of the drip chamber,
Therefore, it works as well for a drip chamber assembly that is inclined at a large angle, such as 26 degrees, as well as for a vertically oriented assembly.

Of course, many modifications and variations of the present invention are possible in light of the above teachings. For example, the radius of curvature of the various lens surfaces may be varied to accommodate for different refractive effects of different drip chamber assemblies. Also, while the present invention has been described above with particular reference to an IV fluid flow monitor, this monitor is applicable to all products in which it is desirable to measure fluid flow by optical means or to sense lack of such flow. It Therefore, various modifications and variations other than the above are possible within the scope of the present invention as described in the claims.

[Brief description of drawings]

FIG. 1 is a perspective view of an improved optical flow sensing device having the novel features of the present invention in operative relationship with the drip chamber assembly of an intravenous fluid infusion device, and FIG. 2 of FIG. 2-
2 is a horizontal cross-sectional view showing the emitter block and the detector block and the drip chamber assembly between them, cut along substantially line 2; FIG. 3 is a vertical cross-sectional view substantially along line 3-3 in FIG. Figures 4 and 5 are cross-sectional views similar to Figure 2 except that the aperture assembly has been added within the detector block.
5 is an enlarged exploded perspective view of the lens block, FIG. 6 is a horizontal sectional view taken substantially along line 6-6 of FIG. 5, and FIG. 7 is a horizontal sectional view taken substantially along line 7-7 of FIG. is there. 11 …… Support substrate 13, 15 …… Arm 19 …… Energy emitter block 21, 25 …… Lens 23 …… Energy detector block 27 …… Drip chamber assembly 29 …… Energy emitter chip 33, 49 …… Printed circuit board 47 …… Energy detector chip 53 …… Transparent wall of drip chamber 55 …… Drip chamber 59 …… Drop forming part 69 …… Aperture assembly 75,77 …… Baffle

Claims (5)

[Claims] 1. A space 17 is formed to be separated from each other.
The support substrate 11 having the first arm 13 and the second arm 15 substantially parallel to the first arm 13 is provided, and the energy emitting means 29 is the first arm.
In a fluid flow rate sensing device attached to 13 and an energy detector 47 attached to the second arm 15, fixedly attached to the first arm 13 with respect to the energy emitting means 29, in both horizontal and vertical sections. A first lens (21) having a convex outer surface and a convex inner surface only in a horizontal section, said energy radiating means (29).
Receives energy from the
The first lens 21 for refracting and transmitting the energy that has passed therethrough and the energy detector 47 are fixedly attached to the second arm 15, and an outer surface having a convex horizontal cross section and a vertical cross section. A second lens 25 having an inner surface, which receives the energy transmitted from the first lens 21,
And a second lens 25 for refracting and transporting the energy toward the energy detector 47. 2. The fluid flow sensing device further comprises an aperture assembly 69 having a plurality of opaque side walls 71 and an opaque front wall 73, the aperture assembly 69 being within the second arm 15. Mounted on the aperture 74 and the length of the side wall 71 allows the aperture to be positioned above the energy detector.
The fluid flow sensing device of claim 1, wherein the fluid flow sensing device is selected for positioning in front of 47 to control the beam width dimension of the energy reaching the energy detector 47. 3. The fluid flow sensing device further comprises opaque baffles 75 mounted in front of the energy detectors 47, each baffle having a plurality of opaque walls and reaching the energy detector 47. A fluid flow sensing device according to claim 1 or 2 having a baffle opening for limiting energy. 4. The fluid flow sensing device further comprises: the energy emitting means for attenuating optical energy in which the energy emitted by the energy emitting means 29 is in the infrared wavelength range and not in the infrared wavelength range. 29 and above energy detector
4. The fluid flow rate sensing device according to claim 1, further comprising a filtering means disposed between 47. 5. A first fluid flow sensing device further mounted with said energy emitting means 29 and subsequently mounted within said first arm 13 for sealing said energy emitting means 29 against contamination. A printed circuit board 33 and a second printed circuit board 49 to which the energy detector 47 is mounted and which is subsequently mounted in the second arm 15 to seal the energy detector 47 against contamination. The fluid flow rate sensing device according to any one of claims 1 to 4, wherein: