Patent Description:
A bubble detector of generally known type includes a first ultrasonic element disposed on a first support member, a second ultrasonic element disposed on a second support member to face the first ultrasonic element with a tube intervening therebetween, and a first distance adjuster for adjusting the distance between the first support member and the second support member so that the distance between the first ultrasonic element and the second ultrasonic element is adjusted in accordance with the diameter of the tube. Ultrasonic waves transmitted from one of the first ultrasonic element and the second ultrasonic element are received by the other ultrasonic element so that existence of bubbles in a liquid flowing through the tube can be detected (patent literature <NUM>).

The transmission efficiency of the ultrasonic waves in the liquid is different from that of the ultrasonic waves in the bubble. In the presence of bubbles in the liquid, the ultrasonic waves are blocked by the bubbles, which weakens receiving intensity. The bubbles can be detected using this feature. It is necessary to bring the first and the second ultrasonic elements into tight contact with the tube to accurately detect the bubbles. When a small-diameter tube is used along with other tubes each having a different diameter, the first and the second ultrasonic elements cannot be brought into tight contact with such a tube appropriately unless the distance between the first and the second ultrasonic elements is made adjustable. This may result in deteriorated detection accuracy.

The above-described bubble detector is configured to allow the first distance adjuster to adjust the distance between the first and the second ultrasonic elements. Even when tubes of different types are used, the first and the second ultrasonic elements can be constantly brought into tight contact with the tubes appropriately. This makes it possible to prevent the deterioration of detection accuracy.

Patent Literature <NUM> discloses a universal air bubble detector for use with a variety of sizes and types of tubing. The detector maintains proper alignment of a sensor emitter and receiver with different sizes of tubing, by means of pivot arms or sliding mounts for adjusting the distance between a support carrying the emitter and a support carrying the receiver, as well as of guiding structures of said supports, disposed on either side of the emitter and receiver, respectively. The detector may be mounted on existing equipment or may be used to monitor a tubing at any position along the tubing and may operate in a stand-alone mode or in combination with existing equipment.

Patent Literature <NUM> discloses a conduit clamped within a clamping hole formed by a main body, left and right side plates and a top plate. The clamping hole is maintained by a locking mechanism and the conduit is deformed to have a substantially square cross section. Ultrasonic signal transmission and reception elements are arranged in the main body such that an ultrasonic beam emitted from one of the elements is received by the other element after the beam is reflected by the top plate.

Patent Literature <NUM> discloses an apparatus for determining a characteristic such as sound speed for a fluid such as blood in a tube, the apparatus comprising means for applying a force to cause a change in a transverse dimension of a segment of the tube, wherein the change in the transverse dimension is reversible, and means for launching and receiving ultrasonic signals. The applied force may cause the transverse dimension to change continuously or in discrete steps. The characteristic is determined based on information comprising the path length differences and the transit times for each of the ultrasonic signals.

The first distance adjuster of the generally employed bubble detector (patent literature <NUM>) allows the first and the second ultrasonic elements to press the tube in the radial direction. Accordingly, the tube is elliptically pressed to reduce the flow passage area inside the tube. This may cause the risk of failing to secure a required flow rate.

In light of the circumstances, it is an object of the present invention to provide the bubble detector which allows the first and the second ultrasonic elements to be in tight contact with the tube appropriately, and prevents the tube from being pressed elliptically to secure a required flow rate.

According to the present invention there is provided a bubble detector as specified in claim <NUM>.

With the invention according to claim <NUM>, since the distance between the first and the second ultrasonic elements can be adjusted by the first distance adjuster, even if the diameter of the tube is changed, the first and the second ultrasonic elements can be brought into tight contact with the tube appropriately like the generally employed case. This makes it possible to secure detection of bubbles.

At the same time, a pair of side guides facing with each other with the tube intervening therebetween are arranged in the direction intersecting the arrangement direction of the first and the second ultrasonic elements. Further, the second distance adjuster adjusts the distance between those side guides in accordance with the diameter of the tube. This prevents the tube from being elliptically pressed by the first and the second ultrasonic elements and allows the tube to be deformed rectangularly. It is therefore possible to secure a required flow rate by preventing reduction in the flow passage area of the inside of the tube.

The present invention will be described based on an illustrated example. <FIG> is a schematic circuit diagram of a generally known blood purifier. Two bubble detectors <NUM> according to the present invention are incorporated in the blood purifier. Each of the detectors is configured to detect existence of bubbles in the blood flowing through a blood circuit <NUM>.

The blood circuit <NUM> comprises an arterial-side blood circuit 2A and a venous-side blood circuit 2B. A non-illustrated puncture needle disposed at one end of the arterial-side blood circuit 2A is configured to be connected to a patient. The other end of the arterial-side blood circuit 2A is connected to one end of a dialyzer <NUM> via a blood pump <NUM> and an arterial-side chamber <NUM>.

A terminal end of the venous-side blood circuit 2B is connected to the other end of the dialyzer <NUM>. A top end of the venous-side blood circuit 2B is configured to be connected to the patient via a venous-side chamber <NUM> and a non-illustrated puncture needle.

The dialyzer <NUM> is configured to be supplied with fresh dialysis fluid from a dialysis fluid supply circuit <NUM>. The dialysis fluid supplied into the inside of the dialyzer <NUM> is discharged to the outside via a dialysis fluid discharge circuit <NUM> connected to the dialyzer <NUM>.

Although not illustrated, a large number of hollow fibers are provided in the dialyzer <NUM> in which the blood from the arterial-side blood circuit 2A flows to the venous-side blood circuit 2B via the hollow fibers.

Meanwhile, the dialysis fluid supplied into the dialyzer <NUM> circulates therein on the outer side of the hollow fibers so that the blood is separated from the dialysis fluid via the hollow fibers. Wastes in the blood flowing through the hollow fibers are drawn into the dialysis fluid flowing outside the hollow fibers so that the blood is purified.

As the blood purifier of the above-described type is known, further explanation of the blood purifier will be omitted.

One of the two bubble detectors <NUM>, <NUM> according to the present invention is disposed on an inlet side of the arterial-side blood circuit 2A, and the other bubble detector <NUM> is disposed on an outlet side of the venous-side blood circuit 2B so that existence of bubbles in the blood flowing through the respective blood circuits 2A, 2B can be detected.

<FIG> is a perspective view of a detection box <NUM> assembled with the two bubble detectors <NUM>, <NUM>. The detection box <NUM> is detachably attached to a bracket <NUM> fixed to a front panel of a non-illustrated blood purifier. More specifically, the detection box <NUM> has a rectangular box shape, with its rear part detachably fittable with a rectangular recess part 12a formed in a front surface of the bracket <NUM>. It is possible to provide a falling prevention member that prevents the detection box <NUM> from falling from the bracket <NUM> as needed.

The detection box <NUM> includes a rectangular box-like main body 11A and a cover 11B openably attached via a hinge <NUM> disposed on one side of the main body 11A. When the cover 11B is closed, a latch <NUM> disposed on the other side of the cover 11B is engaged with a locking pin <NUM> disposed on the other side of the main body 11A so that the cover 11B is kept closed.

Operating the latch <NUM> from the closed state so as to disengage the latch <NUM> from the locking pin <NUM> allows the cover 11B to be opened from the closed state as shown in <FIG>.

The main body 11A of the detection box <NUM> has two tube grooves <NUM> that run parallel to each other in an up-down direction. A tube <NUM> that constitutes the arterial-side blood circuit 2A is allowed to be fitted with one of the tube grooves <NUM>, and a tube <NUM> that constitutes the venous-side blood circuit 2B is allowed to be fitted with the other tube groove <NUM>.

Each of the two bubble detectors <NUM> is configured to detect bubbles in the blood flowing through the tube <NUM> fitted with each of the tube grooves <NUM>.

As the two bubble detectors <NUM> have the same structure, an explanation will be made only about one of those bubble detectors <NUM> in detail.

<FIG> is an exploded perspective view of the bubble detector <NUM> in a disassembled state. The bubble detector <NUM> includes a tube guide <NUM>. The tube guide <NUM> has a U-like cross section part 21A and two base parts 21B each horizontally extending from the proximal end thereof. Both of the base parts 21B are fixed to a surface side (side that faces the cover 11B) of the main body 11A of the detection box <NUM>. The inner surface of the U-like cross section part 21A constitutes a part of the tube groove <NUM>.

Referring to <FIG>, the tube groove <NUM> of the tube guide <NUM> is expressed as being laterally directed. In the state where the detection box <NUM> is assembled with the bracket <NUM> of the blood purifier, the tube groove <NUM> of the tube guide <NUM> is disposed in the up-down direction. In other words, the tube groove is disposed so that its left side shown in <FIG> is directed at the upper side.

Two guide pins <NUM> parallel to each other are disposed on the upper surface of the U-like cross section part 21A of the tube guide <NUM> at both ends in its longitudinal direction. Those guide pins <NUM> are engaged with two engagement holes 23a formed in a sensor block <NUM>, respectively, so that the sensor block <NUM> is attached while being movable in the up-down direction relative to the tube guide <NUM> as shown in <FIG>.

A first ultrasonic element <NUM> is attached to the lower surface of the sensor block <NUM>. The lower surface of the first ultrasonic element <NUM> is retractably movable in the tube groove <NUM> of the tube guide <NUM> via a through hole 21a drilled in the upper surface of the U-like cross section part 21A of the tube guide <NUM>.

Meanwhile, a second ultrasonic element <NUM> is attached to the cover 11B as shown in <FIG>. When the cover 11B is closed, the first ultrasonic element <NUM> and the second ultrasonic element <NUM> face with each other with the tube <NUM> fitted with the tube groove <NUM> intervening therebetween.

In the example, the sensor block <NUM> constitutes a first support member for supporting the first ultrasonic element <NUM>. The cover 11B constitutes a second support member for supporting the second ultrasonic element <NUM>. As is described below, in the state where the first ultrasonic element <NUM> and the second ultrasonic element <NUM> face with each other, the sensor block <NUM> having the first ultrasonic element <NUM> attached thereto is moved reciprocably (moved up and down) along the guide pins <NUM> to allow adjustment of the distance between the first ultrasonic element <NUM> and the second ultrasonic element <NUM>.

The ultrasonic waves transmitted from one of the first ultrasonic element <NUM> and the second ultrasonic element <NUM> are received by the other ultrasonic element so that existence of bubbles in the blood flowing through the tube <NUM> can be detected as is well known in the art.

Referring to <FIG>, the bubble detector <NUM> includes a gate-type slide block <NUM> for moving the sensor block <NUM> up and down along the guide pins <NUM>. Each inner surface of both legs 28A of the gate-type slide block <NUM> is in sliding contact with the facing surface of the U-like cross section part 21A of the tube guide <NUM>. Each lower surface of both legs 28A is in sliding contact with the surface of the base part 21B of the tube guide <NUM>. The slide block <NUM> is thus guided by the respective sliding contact surfaces to be reciprocably movable in the axial direction of the tube <NUM>, that is, the longitudinal direction of the U-like cross section part 21A.

As shown in <FIG>, the upper surface of the slide block <NUM> is in sliding contact with the inner surface of a wall 11a constituting the main body 11A of the detection box <NUM>. This prevents the slide block <NUM> from being separated from the tube guide <NUM> upward in <FIG>. When the cover 11B is closed, the wall 11a faces the cover 11B parallel to each other. When the detection box <NUM> is fitted with the recess part 12a of the bracket <NUM>, the wall 11a is positioned on the inner surface side of the recess part 12a.

As shown in <FIG> and <FIG>, two adjustment screws <NUM> are threaded in the respective ends of the slide block <NUM>. Each of the adjustment screws <NUM> penetrates through a long hole 11b formed in the wall 11a of the main body 11A to protrude to the outside. The long hole 11b is formed in the longitudinal direction of the tube <NUM>. When each of the adjustment screws <NUM> is tightened at an appropriate position determined by longitudinally moving the slide block <NUM>, the slide block <NUM> can be fixed to the wall 11a of the main body 11A, that is, the tube guide <NUM>.

As shown in <FIG>, the sensor block <NUM> has an upper surface inclined along a longitudinal direction of the tube <NUM>. A first engagement portion <NUM> with a dovetailing cross section is disposed on the inclined surface. Meanwhile, the lower surface of the gate-type slide block <NUM>, which is positioned between the two legs 28A, is inclined along the inclined surface. A first guide portion <NUM> with a dovetailing cross section, which is engaged with the first engagement portion <NUM>, is disposed in the inclined surface.

The first engagement portion <NUM> and the first guide portion <NUM> have the dovetailing cross sections, by which those portions are engaged to be slidable relative to each other along the longitudinal direction of the inclined surface. However, they cannot be disengaged in the up-down direction.

When the slide block <NUM> is reciprocably moved in the longitudinal direction of the tube <NUM> relative to the fixed tube guide <NUM>, each inclination of the first engagement portion <NUM> and the first guide portion <NUM> allows the sensor block <NUM> to move up and down along the guide pins <NUM>.

The first ultrasonic element <NUM> disposed on the sensor block <NUM> is moved to approach or separate from the second ultrasonic element <NUM> disposed on the cover 11B so that the distance between those elements is adjustable.

In this example, a first distance adjuster for adjusting the distance between the first ultrasonic element <NUM> and the second ultrasonic element <NUM> is constituted by the slide block <NUM>, the first engagement portion <NUM>, the first guide portion <NUM>, the guide pins <NUM> and the engagement holes 23a.

The bubble detector <NUM> includes a pair of side blocks <NUM> which face with each other with the tube <NUM> intervening therebetween, and are disposed in a lateral direction intersecting the direction in which the first ultrasonic element <NUM> and the second ultrasonic element <NUM> are arranged to face with each other vertically with the tube <NUM> intervening therebetween. The distance between the side blocks <NUM> can be adjusted in accordance with the diameter of the tube <NUM>.

Each of the left and right base parts 21B of the tube guide <NUM> includes a guide hole 21b to be engaged with the corresponding side block <NUM>. Each of the side blocks <NUM> is engaged with each of the guide holes 21b, and reciprocably movable diametrally with respect to the tube <NUM> while being protrudable to the inside of the tube groove <NUM>.

Each of the side blocks <NUM> has a second engagement portion <NUM> at an outer end, which is inclined with respect to the longitudinal direction of the tube <NUM>. Each second engagement portion <NUM> includes an outer protrusion 36a and an inner engagement groove 36b. The engagement groove 36b has its depth corresponding to the surface level of the base part 21B.

Meanwhile, each of the legs 28A of the gate-type slide block <NUM> has a second guide portion <NUM> formed in the lower surface on the inner side, which is engaged with the second engagement portion <NUM>. Each of the second guide portions <NUM> is inclined along the inclination of the second engagement portion <NUM>, and has a protrusion 37a to be engaged with the engagement groove 36b of the second engagement portion <NUM>, and an engagement groove 37b to be engaged with the protrusion 36a of the second engagement portion <NUM> (see <FIG>).

When the slide block <NUM> is reciprocably moved relative to the tube guide <NUM> in the longitudinal direction of the tube <NUM>, the inclination of the second engagement portion <NUM> and the second guide portion <NUM> serves to bring the side blocks <NUM> into approach state or separation state. It is therefore possible to adjust the distance between those side blocks.

At this time, the side blocks <NUM> move to approach or separate from the center line of the tube groove <NUM>. This makes it possible to hold the tube <NUM> fitted with the tube groove <NUM> constantly in the center of the tube groove <NUM>.

In the embodiment, the slide block <NUM>, the second engagement portions <NUM>, and the second guide portions <NUM> constitute a second distance adjuster for adjusting the distance between the side blocks <NUM>.

As shown in <FIG>, an arterial-side clamp <NUM> is disposed on the more upstream side than the arterial-side bubble sensor <NUM>. A venous-side clamp <NUM> is disposed on the more downstream side than the venous-side bubble sensor <NUM>.

Those clamps <NUM>, <NUM> are not provided for the detection box <NUM> but for the blood purifier. Although not illustrated, upon attachment of the detection box <NUM> to the bracket <NUM> of the blood purifier, the respective top ends of the clamps <NUM>, <NUM> are positioned while protruding into enlarged diameter portions 18a of the tube grooves <NUM> formed in the main body 11A of the detection box <NUM>.

In other words, the detection box <NUM> can be removed from the bracket <NUM> while the clamps <NUM>, <NUM> are left on the blood purifier side. Meanwhile, in the state where the detection box <NUM> is attached to the bracket <NUM>, the respective top ends of the clamps <NUM>, <NUM> are positioned in the enlarged diameter portions 18a of the tube grooves <NUM>. Accordingly, the tube <NUM> may be engaged with the top ends of the clamps <NUM>, <NUM> upon fitting of the tube <NUM> with the inside of the tube groove <NUM>. Operation of the clamps <NUM>, <NUM> in this state serves to press the tube <NUM> so that blood circulation can be blocked. In this example, the detection box <NUM> is removed from the bracket <NUM> while the clamps <NUM>, <NUM> are left on the blood purifier side. It is possible to make the detection box <NUM> and the bracket <NUM> in an integrated manner, or make the detection box <NUM>, the bracket <NUM>, and a clamp box having the clamps <NUM>, <NUM> in an integrated manner. Such an integrated configuration may be removed from the front panel of the blood purifier so as to allow adjustment of the distance between the first ultrasonic element <NUM> and the second ultrasonic element <NUM>, and the distance between the side blocks <NUM>.

The above-described structure as shown in <FIG> indicates the initial state where the slide block <NUM> is at the uppermost position with respect to the tube guide <NUM> in the drawing. In the initial state, the first ultrasonic element <NUM> provided to the sensor block <NUM> is separated from the second ultrasonic element <NUM> provided to the cover 11B at the farthest position (see <FIG>). Simultaneously, the paired side blocks <NUM> are separated from each other at the farthest positions (see <FIG>).

In the case of using a large-diameter tube <NUM> from the initial state as shown in <FIG>, the detection box <NUM> is removed from the bracket <NUM>, and then the adjustment screws <NUM> are loosened to move the slide block <NUM> downward as shown in <FIG>.

The first guide portion <NUM> of the slide block <NUM> is thus engaged with the first engagement portion <NUM> of the sensor block <NUM> to allow the sensor block <NUM> and the first ultrasonic element <NUM> attached thereto to be pushed leftward as shown in <FIG>. This makes it possible to reduce the distance between the first ultrasonic element <NUM> and the second ultrasonic element <NUM> when the cover 11B is closed.

At the same time, when the slide block <NUM> is moved downward as shown in <FIG>, each of the second guide portions <NUM> of the slide block <NUM> is engaged with each of the second engagement portions <NUM> of the side blocks <NUM> so that the distance between the paired side blocks <NUM> can be reduced.

At a side of the long hole 11b through which the adjustment screw <NUM> penetrates, a non-illustrated appropriate mark is placed at a position adapted to the diameter of the large-diameter tube <NUM> to be used. The adjustment screws <NUM> are moved to the marked position and tightened so that the slide block <NUM> is fixed to the wall 11a of the detection box <NUM>. This makes it possible to fix the first ultrasonic element <NUM> and the paired side blocks <NUM> at positions optimumly adapted to the large-diameter tube <NUM>. Besides placement of the mark, it is possible to provide one end of the long hole at a position adapted to the large-diameter tube <NUM>, and the other end at a position adapted to the small-diameter tube <NUM>, and it is also possible to form holes by the number corresponding to the number of tube sizes, or to bring a jig corresponding to the tube diameter into abutment for adjustment, all of which are by way of example only.

In this way, the position of the slide block <NUM> is adjusted to the optimum one adapted to the large-diameter tube <NUM>. The detection box <NUM> is then fitted with the recess part 12a of the bracket <NUM> of the blood purifier.

Opening the cover 11B of the detection box <NUM> in the above-described state allows the tube <NUM> constituting the arterial-side circuit 2A, and the tube <NUM> constituting the venous-side blood circuit 2B in the blood circuit <NUM> to be fitted with the respective tube grooves <NUM>. The cover 11B can be closed after fitting of the respective tubes <NUM> with the tube grooves <NUM>.

In this state, since the distance between the first ultrasonic element <NUM> and the second ultrasonic element <NUM>, and the distance between the paired side blocks <NUM> are adjusted to take positions optimumly adapted to the large-diameter tube <NUM>, respectively, the large-diameter tube <NUM> is held and pressed rectangularly in the up-down direction and left-right direction with respect to the cross section.

Consequently, the first ultrasonic element <NUM> and the second ultrasonic element <NUM> are brought into tight contact with the outer circumferential surface of the tube <NUM> appropriately, resulting in secure bubble detection. At the same time, as the tube <NUM> is rectangularly pressed, a larger flow passage area is secured compared with the case where the tube <NUM> is elliptically pressed only by the first ultrasonic element <NUM> and the second ultrasonic element <NUM>. This makes it possible to prevent the risk of failing to secure required blood quantity caused by the reduced flow passage area.

If the use of the small-diameter tube <NUM> as indicated by <FIG> is required from the initial state or the state where the large-diameter tube <NUM> has been used, the adjustment screws <NUM> can be loosened to move the slide block <NUM> downward as shown in <FIG> similarly to the case as described above. The adjustment screws <NUM> then can be moved to a non-illustrated marked position placed at the side of the long hole 11b, which is adapted to the small-diameter tube <NUM>, and then tightened.

As shown in <FIG>, this allows the first ultrasonic element <NUM> to be further pushed leftward, and the distance between the paired side blocks <NUM> to be further reduced as shown in <FIG>. This makes it possible to bring the first ultrasonic element <NUM> and the paired side blocks <NUM> to the optimum positions adapted to the small-diameter tube <NUM>, respectively.

Also in this case, the first ultrasonic element <NUM> and the second ultrasonic element <NUM> can also be brought into tight contact with the outer circumferential surface of the small-diameter tube <NUM> appropriately, resulting in secure bubble detection. Furthermore, as the small-diameter tube <NUM> can be rectangularly pressed, it is possible to suppress reduction in the flow passage area of the tube <NUM>.

In the example, the slide block <NUM> is made slidable to allow adjustment of the distance between the first ultrasonic element <NUM> and the second ultrasonic element <NUM>, and the distance between the paired side blocks <NUM> simultaneously. Moreover, those adjustments may be performed individually. More specifically, although not illustrated, the sensor block <NUM> is operated in an interconnected manner with, for example, a position adjustment screw as the first distance adjuster for reciprocably moving the position of the sensor block <NUM>. The position adjustment screw allows adjustment of the distance between the first ultrasonic element <NUM> and the second ultrasonic element <NUM> by moving the position of the sensor block <NUM> reciprocably. Meanwhile, at least one of the paired side blocks <NUM> is also operated in an interconnected manner with a position adjustment screw as the second distance adjuster for reciprocably moving the position of at least one of the paired side blocks <NUM>. The position adjustment screw allows adjustment of the distance between the side blocks <NUM> by moving the position of at least one of the side blocks <NUM> reciprocably.

Claim 1:
A bubble detector (<NUM>) comprising a first ultrasonic element (<NUM>) which is disposed on a first support member (<NUM>), a second ultrasonic element (<NUM>) which is disposed on a second support member (11B) to face the first ultrasonic element (<NUM>) with a tube (<NUM>) intervening therebetween, and a first distance adjuster for adjusting a distance between the first support member (<NUM>) and the second support member (11B) to adjust a distance between the first ultrasonic element (<NUM>) and the second ultrasonic element (<NUM>) in accordance with a diameter of the tube (<NUM>), the bubble detector (<NUM>) allowing one of the first (<NUM>) and the second (<NUM>) ultrasonic elements to transmit ultrasonic waves, and the other to receive the ultrasonic waves for detecting existence of bubbles in a liquid flowing through the tube (<NUM>), wherein
a pair of side guides (<NUM>) which face each other with the tube (<NUM>) intervening therebetween are disposed in a radial direction of the tube (<NUM>) intersecting a direction in which the first (<NUM>) and the second (<NUM>) ultrasonic elements are arranged to face each other with the tube (<NUM>) intervening therebetween, and a second distance adjuster is provided for adjusting a distance between the pair of side guides (<NUM>) in accordance with the diameter of the tube (<NUM>); wherein the first distance adjuster and the second distance adjuster are operable to adjust the distance between the first ultrasonic element (<NUM>) and the second ultrasonic element (<NUM>) and the distance between the pair of side guides (<NUM>) simultaneously, such that the first ultrasonic element (<NUM>) and the second ultrasonic element (<NUM>) are brought into tight contact with the tube (<NUM>) as the tube (<NUM>) is held and pressed rectangularly.