GB1568879A

GB1568879A - Infusion device

Info

Publication number: GB1568879A
Application number: GB2785677A
Authority: GB
Original assignee: Philips Gloeilampenfabrieken NV
Current assignee: Koninklijke Philips NV
Priority date: 1976-07-07
Filing date: 1977-07-04
Publication date: 1980-06-11
Also published as: FR2357259B1; FR2357259A1; SE7707696L; JPS536269A; DE2727714A1; SE448276B; NL7607474A; JPS5530413B2; ES460406A1; DE2727714C3; DE2727714B2; NL166404C; IT1114112B

Description

(54) INFUSION DEVICE (71) We, N.V. PHILLIPS' GLOEILAM PENFABRIEKBN, a limited liability Company, organised and established under the laws of the Kingdom of the Netherlands, of Emmasingel 29, Eindhoven, the Netherlands, do hereby declare the invention for which we pray that a patent may be granted to us, and the mthod by which it is to be performed, to be particularly described in and by the following statent: The invention relates to an infusion device, comprising a duct for a liquid which is to be connected to a supply vessel and which is sub-divided into an upper duct portion and a lower duct portion wherebetween a dosing device is included which comprises a chamber which communicates, via an upper aperture and a lower aperture, with the upper duct portion and the lower duct portion, respectively, said chamber accommodating a vertically movable body which consists at least partly of a ferro magnetic material and which closes the lower aperture in the rest condition, there being provided an electromagnet which, when current is applied thereto, generates a magnetic field in the chamber which exerts an upwards directed force on the body.

A device of the aforesaid kind is known from United States Patent Specification No.

2,254,833. When the electromagnet is excited, the body is lifted, so that per unit of time a quantity of liquid can flow, via the chamber, to the lower duct portion. This quantity is inter alia dependent of the liquid pressure in the upper duct portion, which in its turn is dependent of the location of the supply vessel and the filling degree of this vessel. Consequently, the liquid dosing cannot always be realized with the desired accuracy.

One object of the present invention is to provide an infusion device in which the quantity of liquid conducted per unit of time is substantially independent of the pressure in the upper duct portion.

According to the present invention there is provided an infusion device, comprising a duct for a liquid which is to be connected to a supply vessel and which is sub-divided into an upper duct portion and a lower duct portion wherebetween a dosing device is included which comprises a chamber which communicates, via an upper aperture and a lower aperture, with the upper duct portion and the lower duct portion, respectively, said chamber accommodating a vertically movable body which consists at least partly of a ferromognetic material and which closes the lower aperture in the rest condition, there being provided an electromagnet which, when current is applied thereto, generates a magnetic field in the chamber which exerts an upwards directed force on the body and is characterised in that the body has a spherical shape, the distance over which it is displaceable in the vertical direction not being larger than one tenth of its diameter, there being provided a current source which is adapted to supply delta current pulses as hereinafter defined for the excitation of the electromagnet.

The expression, "delta current pulses" is defined for the purpose of the present invention as the wave form of the excitation current the pulses of which are sufficient to displace the aforesaid body in the vertical direction said wave form of each current pulse being substantially triangular in shape and having a leading edge and a trailing edge and a maximum current value which exceeds the excitation current for a given time and wherein there is a time interval between successive delta current pulses.

In order to enable checking of the proper operation of the device, detection means may be provided for detecting the passage of a liquid pulse through the dosing device.

The detection means may be adapted to detect an abrupt pressure increase in the upper portion which is caused by the abrupt stopping of the liquid flow when the dosing device is closed. The detection means may consist of a space which is connected to the upper duct portion and which is closed on one side by a diaphragm, the deformation of which can be detected by means of a detector which is sensitive to pressure or deformation. The space may also communicate with the lower duct portion, it also being possible to interrupt this connection by exerting external pressure on the diaphragm.

Two embodiments of the invention will now be described by way of example with refrence to the accompanying drawings.

Figure 1 is a diagrammatic representation of the infusion device, Figure 2 is a longitudinal sectional view of the first embodiment of a dosing device for the infusion device shown in Figure 1, Figure 3 is a cross-sectional view, taken along the line III-E in Figure 2, of the housing device shown in Figure 2, Figure 4 illustrates the variation of the excitation current preferably used for controlling the dosing device, Figure 5 is a longitudinal sectional view of the second embodiment of the dosing device, and Figure 6 is a diagrammatic plan view at a reduced scale of the dosing device shown in Figure 5.

The infusion device shown in Figure 1 comprises a supply vessel 1 which contains infusion liquid. The supply vessel 1 may be suspended from a stand (not shown). A duct for liquid which is sub-divided in an upper duct portion 3 and a lower duct portion 4 is connected to the supply vessel 1. At the end of this liquid duct there is provided a needle 5 which can be inserted, for example, into a vein of a patient to be treated.

A dosing device 7 which will be described in detail with refrence to Figures 2 and 3 is included between the duct portions 3 and 4.

The dosing device 7 comprises a chamber 9 which communicates with the upper duct portion 3 and the lower duct portion 4 via an upper aperture 11 and a lower aperture 13, respetively. The chamber 9 accommodates a vertically movable body 15 in the form of a steel ball which bears on the edge of the lower aperture 13 and thus closes this aperture under the influence of the liquid pressure P and the force of gravity.

The chamber 9 is enveloped by an electromagnet comprising pole shoes 16 and a coil 17 which is connected, via a lead 19, to a current source 21 (see Figure 1). When the current source 21 applies a suitable current through the coil 17, a magnetic field is produced which exerts an upwards directed force on the ball 15. When the strength of the magnetic field is adequate, the ball 15 is lifted so that it opens the lower aperture 13. The infusion iquid can then flow from the aperture 11 to the aperture 13 via recesses 23 and ducts 25. When the value of the magnetic field decreases below a given value again, the ball 15 quickly drops down again, inter alia due to the liquid flow, so that the lower aperture 13 is again closed.

The quantity of liquid which is conducted during the period during which the dosing device is open may be dependent inter alia of the duration of this period and of the pressure P of the liquid above the ball 15. Because this pressure P is in many cases formed by the hydrostatic pressure of the liquid, determined by the continuously decreasing level of the liquid level above the ball, it is undesirable for the quantity of conducter liquid to be dependent on this pressure. However, it has been found that if the distance h over which the ball is lifted is not larger than one tenth of the ball diameter (in the order of 0.1 to 0.2 mm for a ball diameter of for example, approximately 5 mm), the quantity of liquid conducted can be made substantially independent of the pressure P by a suitable choice of the shape of the current pulses produced by the generator 21. Figure 4 shows an example of a waveform which illustrates favourable results in this respect.

This current consists of delta pulses; the slopes of the leading edge 27 and the trailing edge 29 may be different and may be chosen so that the flow is as little as possible, dependent on the pressure. The ball 15 is lifted when the current i exceeds a given value ie (at the instant tl) and drops again when the current i decreases below ie fat the instant t,). The dosing device is thus opened during the time interval trt, and the length of this interval determines the quantity of liquid conducted per operation. For a given interval t.-tl, the mean quantity of liquid conducted per unit of time is determined by the repetition frequency of the pulses and hence (once the slopes of the edges 27 and 29 and the maximum current im have been chosen) by the interval t-tz between successive pulses.

Once the desired liquid flow has been adjusted, it is important that the device can operate without continuous supervision from the nursing staff. In practice, however, it has been found that sometimes the liquid flow stops, for example, becalse the supply vessel 1 is empty or because the needle 5 is clogged. In that case an alarm is required, so that the nursing staff can intervene. To this end, use can be made of the fact that, when the dosing device is closed i.e. at the instant t2, a pressure surge occurs in the upper duct portion due to the abrupt stopping of the liquid flow. Figure 5 shows an embodiment of the dosing device which includes detection means for detecting this pressure surge. The parts of the dosing device which correspond to parts of the device shown in the Figures 2 and 3 are denoted by the same reference nume rals.

From the duct 25, communicating with the upper duct portion 3 via the chamber 9 and the upper aperture 11, a connection duct 31 extends to a cavity or space 33 which is closed on one side by a diaphragm 35. An abrupt pressure increase occuring in the upper duct portion 3 causes an abrupt deformation of the diaphragm 35. This deformation can be detected by means of a pressure-sensitive detector 37 in the form of a ring of conductive rubber which is pressed against the diaphragm 35, the resistance of the said ring varying strongly in the case of deformation. Obviously, instead of a ring of conductive rubber, use can be made of any suitable transducer, for example, a piezoelectric transducer or a number of strain gauges. The detector forms part of a known circuit (not shown) which processes the signal produced by the deformation of the diaphragm 35 and which generates an alarm signal, for example, if this signal fails for a predetermined period of time.

The ring 37 is mounted on an arm of a fork-shaped support 39 which is arranged around the dosing device 7 in the manner shown in Figure 6. This support also accomodates the electromagnet 16, 17 for lifting the ball 15.

In some cases it may be desirable not to use a dosing device and to have rather a direct connection between the upper duct portion 3 and the lower duct portion 4. The dosing device shown in Figure 5 offers this possibility in that the space 33 is connected, by way of a connection 41, to a passage 43 which interconnects the lower aperture 13 and the lower duct portion. The diaphragm 35 is provided with a thickened portion 45 opposite the connection 41, the said thickened portion being pressed against the mouth of the connection by a projection 47 formed on the support 39, so that the connection is automatically closed when the support is in the position shown. When the support 39 is removed, the diaphragm 35 is deflected slightly to the left, so that the connection 41 is opened and the liquid can flow without obstruction from the upper aperture 11, via the connection duct 31, the space 33, the connection 41 and the passage 43 to the lower duct portion 4. The connection 41 and the passage 43 are provided in an insert 49 which is secured to be watertight in the dosing device by means of rings 51.

In the embodiment shown in Figure 5 the actual dosing device, the detection means for pressure surges and the "bypass" connection are combined to form one compact and comparatively simple unit, which can be made relatively cheaply of a synthetic material so that it may be con sidered a disposable article; this offers the important advantage that sterilisation after use is not necessary. The support 39, accommodating the more expensive parts, is not in contact with the infusion liquid and can be used over and over again.

If desired, obviously, it is also possible to detect the sudden pressure increase in the upper duct portion 3 by means of a separate device, for example, by having a microphone arranged against the duct wall.

The body 15 need not be a solid steel body. A body comprising a ferromagnetic core covered with a synthetic material also offers excellent results.

WHAT WE CLAIM IS: 1. An infusion device, comprising a duct for a liquid which is to be connected to a supply vessel and which is sub-divided into an upper duct portion and a lower duct portion wherebetween a dosing device is included which comprises a chamber which communicates, via an upper aperture and a lower aperture with the upper duct portion and the lower duct portion respectively, said chamber accommodating a vertically movable body which consists at least partly of a ferromagnetic material and which closes the lower aperture in the rest condition, there being provided an electromagnet which when current is applied thereto, generates a magnetic field in the chamber which exerts an upwards directed force on the body, characterized in that the body has a spherical shape, the distance over which it is displaceable in the vertical direction not being larger than one tenth of its diameter, there being provided a current source which is adapted to supply delta current pulses as herein before defined for the excitation of the electromagnet.

2. A device as claimed in Claim 1, characterized in that there are provided detection means for the detection of the passage of a liquid pulse through the dosing device.

3. A device as claimed in Claim 2 characterized in that detection means are adapted to detect an abrupt pressure increase in the upper portion which is caused by the abrupt stopping of the liquid flow when the dosing device is closed.

4. A device as claimed in Claim 3, characterized in that the detection means consist of a space which is connected to the upper duct portion and which is closed on

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **.

closed i.e. at the instant t2, a pressure surge occurs in the upper duct portion due to the abrupt stopping of the liquid flow. Figure

5 shows an embodiment of the dosing device which includes detection means for detecting this pressure surge. The parts of the dosing device which correspond to parts of the device shown in the Figures 2 and 3 are denoted by the same reference nume rals.

From the duct 25, communicating with the upper duct portion 3 via the chamber 9 and the upper aperture 11, a connection duct 31 extends to a cavity or space 33 which is closed on one side by a diaphragm 35. An abrupt pressure increase occuring in the upper duct portion 3 causes an abrupt deformation of the diaphragm 35. This deformation can be detected by means of a pressure-sensitive detector 37 in the form of a ring of conductive rubber which is pressed against the diaphragm 35, the resistance of the said ring varying strongly in the case of deformation. Obviously, instead of a ring of conductive rubber, use can be made of any suitable transducer, for example, a piezoelectric transducer or a number of strain gauges. The detector forms part of a known circuit (not shown) which processes the signal produced by the deformation of the diaphragm 35 and which generates an alarm signal, for example, if this signal fails for a predetermined period of time.

The ring 37 is mounted on an arm of a fork-shaped support 39 which is arranged around the dosing device 7 in the manner shown in Figure 6. This support also accomodates the electromagnet 16, 17 for lifting the ball 15.

In some cases it may be desirable not to use a dosing device and to have rather a direct connection between the upper duct portion 3 and the lower duct portion 4. The dosing device shown in Figure 5 offers this possibility in that the space 33 is connected, by way of a connection 41, to a passage 43 which interconnects the lower aperture 13 and the lower duct portion. The diaphragm 35 is provided with a thickened portion 45 opposite the connection 41, the said thickened portion being pressed against the mouth of the connection by a projection 47 formed on the support 39, so that the connection is automatically closed when the support is in the position shown. When the support 39 is removed, the diaphragm 35 is deflected slightly to the left, so that the connection 41 is opened and the liquid can flow without obstruction from the upper aperture 11, via the connection duct 31, the space 33, the connection 41 and the passage 43 to the lower duct portion 4. The connection 41 and the passage 43 are provided in an insert 49 which is secured to be watertight in the dosing device by means of rings 51.

In the embodiment shown in Figure 5 the actual dosing device, the detection means for pressure surges and the "bypass" connection are combined to form one compact and comparatively simple unit, which can be made relatively cheaply of a synthetic material so that it may be con sidered a disposable article; this offers the important advantage that sterilisation after use is not necessary. The support 39, accommodating the more expensive parts, is not in contact with the infusion liquid and can be used over and over again.

If desired, obviously, it is also possible to detect the sudden pressure increase in the upper duct portion 3 by means of a separate device, for example, by having a microphone arranged against the duct wall.

The body 15 need not be a solid steel body. A body comprising a ferromagnetic core covered with a synthetic material also offers excellent results.

WHAT WE CLAIM IS: 1. An infusion device, comprising a duct for a liquid which is to be connected to a supply vessel and which is sub-divided into an upper duct portion and a lower duct portion wherebetween a dosing device is included which comprises a chamber which communicates, via an upper aperture and a lower aperture with the upper duct portion and the lower duct portion respectively, said chamber accommodating a vertically movable body which consists at least partly of a ferromagnetic material and which closes the lower aperture in the rest condition, there being provided an electromagnet which when current is applied thereto, generates a magnetic field in the chamber which exerts an upwards directed force on the body, characterized in that the body has a spherical shape, the distance over which it is displaceable in the vertical direction not being larger than one tenth of its diameter, there being provided a current source which is adapted to supply delta current pulses as herein before defined for the excitation of the electromagnet.
2. A device as claimed in Claim 1, characterized in that there are provided detection means for the detection of the passage of a liquid pulse through the dosing device.
3. A device as claimed in Claim 2 characterized in that detection means are adapted to detect an abrupt pressure increase in the upper portion which is caused by the abrupt stopping of the liquid flow when the dosing device is closed.
4. A device as claimed in Claim 3, characterized in that the detection means consist of a space which is connected to the upper duct portion and which is closed on

one side by a diaphragm, the deformation of which can be detected by means of a detector which is sensitive to pressure or deformation.
5. A device as claimed in Claim 4, characterized in that the space also communicates with the lower duct portion, it being possible to interrupt this connection by exerting external pressure on the diaphragm.
6. An infusion device substantially as hereinbefore described with reference to Figures 1 to 6 of the accompanying drawings.