DE3922686A1 - Control of flow of fluid pumped into patient's body - roller pump with variable position rollers - Google Patents

Abstract

The pump for pumping a fluid through a flexible tube (10) into a patient's body consists of a rotating disc (18) which carries six equally spaced rollers (1 to 6). The rollers press the flexible tube (10) against the concave surface of the support (20) and so pump the liq. through the tube. With this type of pump there is a risk of a transient reversal of the flow as each roller passes the edge of the concave surface. This reversal of flow is prevented by fitting a device which varies the position of each roller (1to 6) as it passes the edge (20') and also varies the motor speed. These variations are controlled by a computer. USE - Kidney dialysis etc. @(12pp Dwg.No. 1,11/6)

Description

The invention relates to a method for controlling a pump, the fluid through a tube into the human body promotes and to adjust the funding rate intermittently so is operated that it promotes in active phases and inactive phases does not promote, being in during pump operation at certain intervals in which the Funding rate is reduced.

Such a method and such a pump are from DE-PS 31 38 267 known.

As a pump in the sense of the invention, each conveyor is closed understand with the liquid through a hose into the human body is fundable and that during a continuous Nuclear pump operation has conditions in which the Delivery rate compared to that otherwise during pump operation prevailing value is reduced.

This applies in particular, but not only, to roller pumps (DE-PS 31 38 267). In roller pumps, the conditions occur with a reduced delivery rate in that the rollers only squeeze the tube between themselves and a thrust bearing over a limited distance, after which the rollers move away from the thrust bearing at one edge. When the rollers are lifted off the hose, the hose opens due to its elasticity and increases its volume. This widening of the hose leads to a reduction in the conveying rate up to a so-called negative conveyance, ie a sucking back of already conveyed material contrary to the intended conveying direction (this is explained in more detail below with reference to FIG. 1).

In the generic DE-PS 31 38 267 it is proposed adjust the delivery rate of the pump in that the active phases and inactive phases of the pump can be optionally controlled, where in the active phases the pump with a be agreed, optimal speed is driven. This will allows the battery to be operated gently. Of this The invention proceeds from the prior art.

When administering liquid in the human body per comes in a variety of applications, particularly when administering medication, on a very precise Adjustment of the delivery rate and on a very even delivery without fluctuations.

DE-OS 32 47 313 is used to improve the uniformity speed of the fluid flow caused by an infusion pump Number of cams arranged and ge along the hose controls that between the fluid inlet (into the pump) and the Fluid outlet (from the pump) be in phase relationship stands. The speed of the motor drive is also selected automatically increases to unwanted To compensate for periods of reduced fluid pressure. These Solution is relatively complex and requires a complicated one Pump structure. Also the energetic efficiency is with this known control methods can be improved because of the engine is driven at different speeds.

The invention has for its object a method for To provide control of a pump of the type mentioned at the outset,  where with simple means a high uniformity of Promotion with economical energy consumption is achieved.

According to a first solution according to the invention, this becomes ensures that the active phases of the pump are set shorter than the distances between states with reduced funding rate, and in the inactive phases the pump in such a position is brought that no in the subsequent active phase Condition with reduced delivery rate occurs.

According to a variant of the invention, this object solved that it is determined whether a during an active phase State with reduced delivery rate is reached, and then, if a reduced state during an active phase Delivery rate occurs, the pump is brought into a position, in which this state is overcome, and then the Active phase is continued until a predetermined end.

An exemplary embodiment of the invention is described below the drawing explained in more detail. It shows:

FIG. 1 shows the operation of a rolling phases I to V;

FIG. 2a shows the pump delivery characteristic of a conventional roll;

Fig. 2b shows the delivery characteristic, as it can be approximated with a roller pump according to the invention, it can be sufficient;

Fig. 3 is a block diagram of the pump drive and the pump control pen;

Fig. 4 details of the drive of the pump and the determination of the position of the pump rollers;

Fig. 5 shows schematically the sequence of a control according to the invention;

Fig. 6 is a flowchart of the control method according to the invention.

Fig. 1 shows on two sheets the operation of a roller pump in different states. Structure and function of a roller pump are known as such and need not be described here in more detail.

A liquid is to be conveyed through the hose 10 to a patient by means of the roller pump. The direction of delivery through the hose 10 is indicated by arrows 12 . The patient side of the pump thus corresponds to arrow 14 , while the position of a storage container, from which the liquid is removed, is indicated by arrow 16 .

The roller pump has a roller plate 18 in a known manner, on which six rollers 1 , 2 , ... 6 are rotatably mounted in the illustrated embodiment at regular intervals. The six rollers are spaced 60 ° apart. The rollers squeeze the hose 10 against a counter-bearing 20 which is formed complementarily to the roller plate. To convey liquid in the direction of arrow 12 , the turntable 18 rotates in the direction of arrow 24 about an axis of rotation 26 . The material is conveyed in the hose 12 , which is located to the left of a roller that squeezes the hose 10 against the counter bearing 20 .

The phase α shown in FIG. 1, phase I is chosen arbitrarily and serves to be able to designate the position of the roller 1 in the course of the movement of the roller plate 18 .

During the movement corresponding to phase I, liquid is conveyed in the direction of arrow 12 . In phase II, the roller I reaches the trailing edge 20 'of the counter bearing 20th The angle of rotation of the roller 1 is now α + 30 °.

In phase III, roller 1 is rotated further by 5 °, ie up to the angle α + 35 °. At this point, roll 1 begins to take off from Ge counter bearing 20 . The hose opens due to its elasticity and there is a sudden increase in volume of the hose. This becomes clear in phase IV, in which roller 1 has reached the angle α + 42 °. The volume enlargement of the hose 10 causes a suction effect back into the hose, ie it is sucked back into the pump in the direction of arrow 28 ( FIG. 1, phase IV) against the actually desired conveying direction 12 . This suction effect occurs only briefly and depends on the Winkelge speed of rotation of the roller plate 18 .

Following the brief return suction, a so-called "zero delivery" follows, in which the pump does not produce any significant delivery in the direction of 12 . This "zero funding" is due to the fact that a positive pressure must build up again after the suckback effect. Measurements have shown that zero delivery can extend over a rotation angle of 16 °. Phase V shows the state after overcoming zero delivery, i.e. the desired normal operation of the pump.

The delivery characteristic of the pump described qualitatively above is shown quantitatively in FIG. 2a. The funding rate is plotted over time. The phases I to V described above correspond to points 1 to 5 of FIG. 2a. At point 4 there is a "negative delivery rate", ie a suction effect. This is followed by a phase 4 'with "zero funding".

FIG. 2b shows a time-constant delivery rate in idealized form, as it is sought with the invention. States in which there is a reduced delivery rate compared to normal operation of the pump (phases I and V according to FIG. 2a) (states 3, 4 and 4 ' , according to FIG. 2a) are to be largely avoided. The invention achieves this without changing the pump itself, but only through a suitable control of your operation.

As explained at the beginning, the pump is in accordance with the teaching of DE-OS 31 38 267 operated intermittently, i.e. change it so-called active phases and inactive phases from each other. The Ak Active phases are set here constantly. To change the Funding rate, the inactive phases are changed accordingly. For example, if the delivery rate is to be relatively low, then the inactive phases are relatively long. At a high funding rate the inactive phases are relatively short.

In the first solution according to the invention, the active phases of the pump are first set to be significantly shorter than the distances between states with a reduced delivery rate. It follows from the above that in the exemplary embodiment of a roller pump according to FIG. 1 the active phase is set much shorter than it corresponds to a rotation of the roller plate 18 by 60 ° (distance between two rollers).

Furthermore, it is hen in the first solution according to the invention that in the inactive phases the pump is brought into such a position that in the subsequent active phase no state occurs with a reduced delivery rate. A non-return valve is closed downstream of the pump, which is arranged, for example, at point 22 according to FIG. 1 and which excludes a suction effect on the patient side 14 .

In the embodiment of the invention described above, the position of the turntable 18 and its rollers 1 , ..., 6 with respect to the edge 20 '( Fig. 1, phase II) is determined (for example by means of a light barrier arrangement as they below with reference to FIGS. 3 and 4 will be described). It turns out that a state is reached at the end of an active phase that is currently running, which would lead to a state according to phases III and IV of FIG. 1 in the subsequent active phase (after an inactive phase set according to the funding rate has elapsed) ( corresponding to the states 3 , 4 and 4 'according to Fig. 2a), this is prevented by the fact that in the following the active phase, the inactive phase (in which no liquid should be supplied to the human body) with the valve closed (not shown ) a "blind rotation" of the turntable 18 in the direction of arrow 24 takes place at such an angle that an unreduced promotion according to phases I and V of FIG. 1 takes place in the subsequent active phase from start to finish.

Fig. 3 shows a block diagram of the drive of the pump and its control. With this control, details of which are also shown in FIG. 4, a control method other than that described above can also be carried out.

In FIGS. 3 and 4 the engine is shown schematically and designated with the reference numeral 30. A shaft 32 of the motor 30 rotates the roller table 18 . Rigidly connected to the shaft 32 (and thus to the roller plate 18 ) is a slotted disc 34 , with each of which the position of the rollers 1 , ..., 6 of the roller plate 18 in relation to the counter bearing 20 and in particular its tapered edge 20 ' is monitored. The position of the slotted disc 34 is determined in a manner known per se by means of a light barrier consisting of a light-emitting diode 36 and a photodetector 38 and a comparator circuit 40 . The position information, which results, for example, from the position of a slot with respect to the edge 20 ', is input by the comparator 40 into two processors 42 , 44 which are connected via a so-called "handshake". It is also possible to provide a disk made of transparent material instead of the slotted disk, which is provided with a coding. A keyboard 46 is used to enter control commands in the processors. The operating state of the device is displayed, for example, by means of an LCD display 48 . The processors 42 , 44 control an amplifier 52 which excites the coils of the electric motor 30 .

Both the processor 42 and the processor 44 can trigger an alarm, for example if the motor 30 is caused to rotate via the motor amplifier 52 , but the circuit 40 determines that the slotted disc 34 does not perform any rotation.

Fig. 4 shows the pump motor 30 and components already described on a larger scale including a housing wall 60 and a gear 62 , which connects the output shaft (not shown ge) of the motor 30 with the slotted disk 34 and the roller plate 18 rotating shaft 32 .

Fig. 5 shows schematically the principle of a further control according to the Invention.

An active phase, in which liquid is conveyed in the direction of arrow 12 ( FIG. 1) to the patient's body, has four steps in each case. The motor 30 is thus designed as a stepper motor in this embodiment. One step means, for example, 15 ° motor revolution. The gear 62 has a ratio of 1:25, so that one motor step corresponds to a rotation of the roller table 18 by 0.6 °.

In FIGS. 5A and B, the individual active phases are each provided with a, b, c, ..., referred to e. The inactive phases in between are designated "pause".

The active phases a, b, ..., e each consist of four rotation steps of the roller table 18 by 0.6 °, thus corresponding to a total rotation of the roller table of 2.4 °.

According to Fig. 5A, the photodetector array 36, 38, 40 by means of the slotted disc 34 determines that occurs during the active phases A and B is no reduction in the delivery rate, so no zero flow according to FIG. 2a, Condition 4 'given. An intervention by the control to equalize the funding rate is therefore not necessary. During the subsequent active phase c ₁ , however, the photodetector arrangement detects with the aid of the slotted disc 34 that a roll of the Rollentel lers 18 approaches the critical edge 20 'of the counter bearing 20 , so that a fluctuation in the delivery rate is to be expected. This is the case after two steps, as indicated at c ₁ . The roller plate 18 is then repositioned in such a way that, after the two steps c _1, the roller plate is rotated continuously by 27 further steps. The 27 steps are dimensioned so that they exactly bridge the so-called zero funding ( Fig. 2a, states 3 , 4 and 4 '). In order to exclude the harmful suction effect, a check valve is arranged downstream of the pump. Since the light barrier 36 , 38 can only recognize the slits of the slotted disk 34 when the motor is running, ie during a transition dark / light, the processors 42 , 44 receive the signal for repositioning the roller table 18 during a conveying cycle. The processor adds the 27 steps mentioned to the remaining funding steps of the currently active phase. In Fig. 5a shows the case that the critical position has been detected a roller of the roller conveyor plate after two steps. Therefore, the motor then carries out 27 + 2 = 29 further steps. The 27 steps correspond to the repositioning of the roller table to overcome the zero funding and the two steps correspond to the remaining funding required to complete the currently active phase.

Fig. 5B will be understood by the above off. In this case, the photodetector arrangement determines a reduction in the demand rate after three steps during the active phase e ₁ , after which the zero conveyance is overcome by repositioning by 27 steps and then a step e _{2 is} required in order to complete the active phase.

After the subsequent break there is an "undisturbed" Active phase f.

The steps performed during repositioning (here e.g. 27) be in the calibration of the delivery rate of the device rearranged.

The repositioning of the roller plate 18 takes place at the same speed of the motor as during the conveying. The funding rates are only set by changing the length of the inactive phases (break times).

FIG. 6 shows a flow chart in which the control algorithm described above is shown:

1st case: break time

• - First check whether slot is available - no;
• - Query whether slot detection has been reset;
• - then he resets the time counter (time counter minus time for 4 bars);
• - Check whether time counter <0 (time counter 0 if pause time has expired);
• - Check whether clock counter = 0;
• - Engine off.

It continues through this loop until the pause time expires fen, then follows:

2nd case: funding

• - Check whether slot is available - no;
• - Query whether slot detection has been reset; Time counter <0;
• - Check time counter <0 - no;
• - Time counter is reset = time for 4 cycles + pause time;  
• - clock counter is set to 4;
• - Query clock counter = 0 - no;
• - engine on;
• - Clock counter counts down 1.

He goes through this loop four times, then he goes through the Loop in the 1st case.

3rd case: slot detection

• - Check whether slot is available - yes;
• - Check whether slot is already recognized - no;
• - setting the slot detection;
• - Clock counter is set to 27 (or because the pump is in during the funding phase, the clock counter is set to 27+ Remaining clocks set);
• - since the clock counter is at least 27, the clock runs at least 27 times Loop "engine on".

Then it runs through the loop again in the first case.

Claims (2)

1. A method of controlling a pump that conveys liquid through a hose into the human body and is operated intermittently to adjust the delivery rate in such a way that it conveys in active phases and does not conveys in inactive phases, and it does so at certain intervals during operation of the pump can come in which the production rate is reduced, characterized in that

• - The active phases of the pump ( 18 , 20 ) set shorter who the than the distances between states with a reduced delivery rate, and
• - In the inactive phases, the pump is brought into such a position that in the subsequent active phase there is no state with a reduced delivery rate.

2. A method of controlling a pump that conveys liquid through a hose into the human body and is operated intermittently to adjust the delivery rate in such a way that it conveys in active phases and does not conveys in inactive phases, and it does so at certain intervals during operation of the pump can come in which the production rate is reduced, characterized in that

• - it is determined whether a state with a reduced delivery rate is reached during an active phase,
• - If, during an active phase, a state with reduced delivery rate is reached, the pump is brought into a position in which this state has been overcome, and
• - then the active phase is continued until a predetermined end.