WO1997010859A2

WO1997010859A2 - Testing device for a pressure infusion apparatus

Info

Publication number: WO1997010859A2
Application number: PCT/DE1996/001827
Authority: WO
Inventors: Andreas Rex; Frank Discher
Original assignee: Rex Mess-Und Simulationstechnik Gmbh
Priority date: 1995-09-20
Filing date: 1996-09-20
Publication date: 1997-03-27
Also published as: DE19536823C1; AU1854797A; WO1997010859A3

Abstract

The invention relates to a testing device (50) for detecting operational parameters of the drive of a dosing pump, in particular an injection pump (1), with a measuring device for a path-related measured variable and counter-force means which opposes the force produced by the delivery pressure of the pump and is provided with evaluation and display means. The counter-force means (3) is a controllable source of power.

Description

TEST DEVICE FOR A PRESSURE INFUSION APPARATUS

B e s c h r e i b u n

The invention relates to a test device of the type specified in the preamble of claim 1.

So-called pressure infusion devices are used for the continuous supply of liquid medicinal products, - 4th

It is also disadvantageous that different, calibrated measuring springs have to be used for different types of pumps to be tested, and therefore a complex process for the preparation of the measurement is required. It is also disadvantageous that the measuring options for the large number of different syringe pumps are relatively severely limited due to the measuring springs which are only staggered in size.

Based on the shortcomings of the prior art, the object of the invention is to provide a test device of the type mentioned at the beginning with which a simplified test can be carried out with greater accuracy for a large number of different types of syringe pumps and with a pump-specific delivery pressure / delivery rate characteristic a selectable delivery pressure setpoint profile can be determined.

This object is achieved with the characterizing features of claim 1.

The invention includes the knowledge that checking the delivery rate of a syringe pump by checking the speed of the transmission element of the force transmission device under the action of a predetermined or predeterminable variable counterforce advantageously allows a substantially more extensive test of syringe pumps. The desired counterforce is not determined by mechanical components, for example calibrated spring elements, but by a time or path-dependent delivery pressure setpoint profile. nically acting force transmission device, which converts the delivery volume of the pump into a corresponding distance and the delivery pressure of the pump into a corresponding force, and the use of a spring device with at least one calibrated measuring spring, which counteracts the movement of the transmission device. With a mechanical-electrical converter, either a distance measurement or a measurement of the spring force is carried out.

The known solutions have the disadvantage that no constant counterforces can be achieved with a spring device due to the spring characteristic present in each case if the spring length is changed during a measuring or testing process. As a result, the test device cannot provide a defined counterforce that is constant for a specific measuring period.

On the one hand, this has the disadvantage that it cannot be checked whether the element of the mechanically acting transmission device moved by the syringe pump to be examined runs at the same distance within a predetermined tolerance range at constant counterforce in the same time periods, ie is moved at a substantially constant speed (checking the constancy of the delivery volume of the syringe pump with different back pressure) and that, on the other hand, it cannot be determined in which section of the syringe pump to be examined, for example, there is particularly high mechanical wear. - 6 -

The movement of the power transmission means takes place deviating from a predetermined target behavior of the speed (corresponding to the delivery rate as delivery volume / time).

The behavior of the syringe pump drive can be determined precisely over the entire distance to be traveled, so that drive errors can be precisely localized by comparing the advancing feed rate with the respectively given counterforce. By varying the counterforce present for a certain waypoint, a working diagram of the drive can be determined with precise location in the form of a family of characteristic curves. The switch-off behavior of the drive with a correspondingly programmed increase in the counterforce can be determined precisely for all points on the way to work. This is in contrast to the prior art, in which in each case the behavior of the drive could only be averaged over longer processing paths.

The electronic control unit is assigned an input unit designed as a keyboard, by means of which the controller can call up the delivery rate setpoint profile, which can be freely selected in relation to the syringe pump type to be tested, using the memory before starting a measurement.

Using such a force profile, the delivery rate characteristic and the location of mechanical defects can be determined for the respective pump type, since all deviations that exceed a predetermined tolerance limit which can be specified via an electronic control unit in the form of a controllable power source. The delivery rate corresponds essentially to the existing delivery pressure, which in turn is determined by the counterforce.

According to the preferred embodiment of the invention, the test device for a syringe pump has a speed measuring device which has a force transmission means and converts the delivery volume of the pump into a distance or the delivery pressure of the pump into a force, a force measuring device, a counterforce device, which a generates the counteracting force corresponding to the delivery pressure of the pump, an electronic control unit and an evaluation and display device. The counterforce device is designed according to the invention as a controllable power source, preferably as a constant power source. The counterforce device is part of a control circuit provided in the test device according to the invention, in which the force measuring device is used as a measuring element, the electro-mechanical converter system in connection with the counterforce device as an actuator and the electronic control unit as a controller. A certain force which counteracts the movement of the force transmission means of the speed measuring device is generated and constantly controlled by the control loop. For this purpose, a selectable delivery pressure setpoint profile can be transmitted from the electronic control unit to the controlled system, which is formed by the force transmission means of the speed measuring device. With a faultless syringe pump - 8th

In accordance with a favorable further development of the invention, the display has two display units in order to display both the current measured values (direct display) and any deviations from the prescribed tolerances of the characteristic values of the respective syringe pump (alarm display). In order to indicate that a predetermined tolerance has been exceeded, a comparator unit is provided in the display, the inputs of which are connected via adaptation stages to an output of the input unit and the measured value output of the electronic control unit.

A particular advantage of the test device according to the invention is that by specifying a steep increase in the counterforce and taking into account the previously determined delivery rate, conditions are created in order to determine the correct switch-off behavior of the syringe pump drive on the one hand and on the other hand by an adequate syringe feed during the measurement of the Switch-off pressure in connection with the measurement resolution of the speed measuring device to detect the exact volume of the drug (bolus) dispensed by the syringe.

The possibility of reducing the measuring time for determining the delivery rate is equally favorable. This results from the fact that - as is generally the case with other measuring or testing devices - a specification of the measuring time is not provided, but the measuring accuracy is specified.

The measuring accuracy can be specified differently depending on the test program. For repairs of The speed of the force transmission means of the speed measuring device can be assigned a constant speed by ascertaining the distance in the syringe pump to be checked, which distance has previously been covered by the force transmission device.

The power transmission means of the speed measuring device, designed as a push rod, is influenced in its displacement movement by the counterforce device driven by the electromechanical transducer system in such a way that the force transmission means moves at a constant speed if the syringe pump has no technical defects and the counterforce is constant in accordance with the selected delivery rate setpoint profile is regulated. A constant speed means a constant volume delivery through the syringe pump. All deviations from this equilibrium state of the control circuit, which occur due to technical defects in the syringe pump to be tested and which lie outside the permissible tolerance ranges, lead to a change in speed and are shown by a display assigned to the electronic control unit. The location of a technical defect can be precisely located within the syringe pump from the distance values determined via the measured values of the speed measuring device and made available via an analog / digital converter, at which the speed change occurred, which advantageously results in repair time and - Significantly reduce the effort required for a syringe pump. - 10 -

The measurement of the delivery rate in connection with an essentially freely selectable delivery pressure profile permits a considerably more extensive test of a syringe pump, so that existing or impending defects can be reliably recognized.

By changing the software components of the electronic control unit, the test conditions for a wide variety of syringe pumps can also be conveniently adapted to the requirements of the manufacturers and / or users and can be updated at short notice if necessary.

According to a favorable development of the invention, the push rod of the speed measuring device is designed as a toothed rack and is connected to the electromechanical converter system via a worm wheel.

According to another embodiment of the invention, a push rod is likewise advantageous, which consists at least partially of a ferromagnetic material. The electromechanical transducer system for driving the counterforce device is designed as an electromagnet, correspondingly adapted. As a lifting magnet that can be activated by the electronic control device, the converter system generates a force acting on the push rod in the radial direction. The friction component of this force enables the braking effect on the axial movement of the push rod to be controlled.

According to another advantageous development of the invention, it is partially made of a ferromagnetic material Syringe pumps with subsequent rough calibration require low measuring accuracy. However, the frequent repetition of the individual measurements requires a relatively short measurement time. In the case of safety-related controls, the measurement accuracy must be above the tolerance specified by the manufacturer. With even higher measuring accuracy, it is advantageously possible to recognize, locate defects at certain points of the drive spindle within a syringe feed or to make forward-looking statements regarding an expected failure of a syringe pump.

From the preselected measurement accuracy, the electronic control unit of the test device according to the invention calculates the necessary measurement path to achieve the measurement accuracy, which is dependent on the measurement resolution of the speed measurement device used. The principle of the preselected measuring accuracy enables measurements which - in comparison to measurements when the measuring time is specified - can be carried out in a favorable manner independently of the delivery rate set on the respective syringe pump.

It is equally favorable that a measurement can be stopped at any time in order to restart it at any point within the syringe feed with an identical counterforce. This is possible because the relationship between the delivery pressure and delivery path is not determined by mechanical components, for example calibrated spring elements, but rather can be specified by a delivery pressure setpoint profile via the electronic control unit of the test device according to the invention. - 12 -

is connected to a measuring device 2 for measuring the feed speed. This is in the form of an adapter which can be inserted into the syringe receiving trough of the syringe pump 1. The force transmission means 10 of the measuring device 2 is in operative engagement with a counterforce device 3 and can thus be influenced in its displacement movement. An electromechanical converter system 4, which can be activated by an electronic control unit 6, is provided for driving the counterforce device 3. A force measuring device 5 coupled to the force transmission means 10 supplies a measured value resulting from the advancing movement of the measuring device 2 and from the action of the counterforce device 3 to the electronic control unit 6.

The control circuit 30 formed in this way, consisting of force measuring device 5 (measuring element), electronic control unit 6 (controller) and electromechanical transducer system 4 in connection with the counterforce device 3 (actuator), is suitable in a favorable manner, one in the electronic control unit 6 to implement a feed rate setpoint profile which can be input via an input unit 7 and thus to generate defined counterforces acting on the force transmission means 10 of the measuring device 2 for the feed rate measurement. The counterforce device 3 forms a controllable constant force source in the control circuit 30.

The force transmission means of the measuring device 2, designed as a push rod 10, represents the controlled system of the

Control loop 30 and is in its displacement movement existing push rod as the core through a central opening of the electromagnet and its movement is directly influenced by the force of the magnetic field.

According to an advantageous development, a modem is assigned to the electronic control unit. As a result, there is a favorable possibility of being able to carry out a remote transmission of the measurement data and test results via the telecommunications network between the manufacturer of syringe pumps or a service company and the syringe pump user in order to optimize the exchange of defective syringe pumps in terms of time.

Other advantageous developments of the invention are characterized in the subclaims or are shown below together with the description of the preferred embodiment of the invention with reference to the figures. Show it:

1 shows the preferred embodiment of the invention in the form of a block diagram,

Figure 2 shows a delivery pressure profile in the form of a pressure / displacement diagram, and

Figure 3 is a partial sectional view of a transducer used in the preferred embodiment of the invention.

FIG. 1 shows the block diagram of a test device 50 for a syringe pump 1. The syringe pump 1 to be tested - 14

The state of equilibrium of the test device 50 is detected by the adaptation stage 8.2. The signal outputs of the adaptation stages 8.1 and 8.2 are connected to the input of a comparator unit 8.3, the output signal of which may activate the alarm display 8.4.

As a result of the distance measurement which is always carried out when testing the syringe pump 1, the location of a possible technical defect which leads to a tolerance limit that can be determined by measurement on the pressure side can be located within the syringe pump. For an exact determination of the displacement of the force transmission means 10, the use of an analog / digital converter when recording the measured values of the measuring device 2 for the feed speed is particularly favorable.

The interface 9 ensures a direct connection to a computer in order to prepare the test results in terms of data technology. A modem provided for remote data transmission via the telephone network is designated by 22.

The pressure / displacement diagram shown in FIG. 2 represents an example of a delivery pressure profile (pressure setpoint profile) 60 that can be implemented with the test device according to the invention for testing syringe pumps. The delivery rate is measured at three different, constant delivery pressures. This part of the measurement provides information as to whether the syringe pump p- ^ even with different back pressures which are below the cut-off pressure _. up to p ₄ generates a delivery rate which is within the permissible tolerances. Allowed influenced by the counterforce device 3 driven by the electromechanical transducer system such that movement of the force transmission means 10 of the measuring device 2 occurs at a constant speed if the syringe pump 1 has no technical defects under the conditions of the selected rate-setpoint profile. The counterforce device 3 forms a controllable constant force source in the control circuit 30. All deviations from this state of equilibrium, which occur due to technical defects in the syringe pump 1 to be tested and which lie outside the permissible tolerance ranges, are recorded by measurement technology and displayed by a display 8 assigned to the electronic control unit 6.

The input unit 7, which is designed as a keyboard, is connected to the syringe pump 1 to be tested via a control line 7.1 in order to be able to activate the syringe pump during the test cycle when the delivery rate setpoint profile is set.

The display 8 provided for the display of the current settings and measurement results has several display means 8.4, 8.5. The direct display 8.5 of the measured values enables the individual steps of the test process to be tracked precisely. The alarm display 8.4 signals a deviation from a permissible tolerance range. This different tolerance range for the different syringe pumps can be entered via the keyboard 7 into an adaptation stage 8.1. A deviation from the expected one at the given pressure setpoint - 16 -

(Compare position 4 in Figure 1) engages fixed gear 19.2. The rotary motion of the motor 20 is transmitted to the threaded sleeve 13 held in the bearings 14 and 15 via the gear 19 formed from the gear wheels 19.1 and 19.2.

The bearings 14 and 15 are attached to the base plate 18 of the transducer 40 and only allow the threaded sleeve 13 to rotate with little axial play. With the aid of a transition piece 16, this slight axial movement is transmitted to a force sensor 17 of the force measuring device (compare position 5 in FIG. 1). The force sensor 17 is attached to a stop 18 connected to the base plate 21.

If the syringe pump feed generates an axially directed driving force on the push rod 10, this is detected by the force sensor 17. This measured value activates the motor 20 via the electronic control unit (compare position 6 in FIG. 1). Due to the rotary movement transmitted by the motor 20, the threaded sleeve 13 screws onto the section of the push rod 10 designed as a threaded rod 12 and can thus be dependent of the speed 20 of the motor 20 of the push rod 10 oppose a greater or lesser mechanical resistance (braking effect). The threaded sleeve 13 and the gear 19 form the counterforce device 3 of the transducer 40 driven by the motor 20.

The size of the force generated by the counterforce device 3 and acting on the push rod can be regulated and the test device generates a constant pressure, a linear or else a non-linear pressure increase that can be predetermined with any function, such as that for the feed speed of the push rod of the measuring device (compare positions 10 and 2 in FIG. 3 ) through the route section s ₃ to s _{4 in which D} i _agrarri m is shown. The shape of the delivery pressure profile 60 is different for each type of syringe pump.

The sensor 40 of the test device for a syringe pump shown in FIG. 3 is designed in the form of an adapter which can be clamped into the syringe receiving trough of the pump. The pump and the control circuit as well as the associated line connections (compare the corresponding positions in FIG. 1) have been omitted for reasons of clarity.

When the transducer 40 is clamped in the syringe pump, the toggle provided for driving the syringe plunger is pivoted onto the pressure plate 11 of the measuring device 2 for the feed rate. The pressure plate 11 is arranged at one end of a push rod 10, which is axially displaceably mounted as a force transmission means in the cylindrical measuring device 2. The end of the push rod 10 opposite the pressure plate 11 is designed as a threaded rod 12 and carries a threaded sleeve 13. On the periphery of the threaded sleeve 13, a gear 19.1 is provided on one side, which is in another, on the output shaft of an electromechanical converter designed as a motor 20 - 18 -

Expectations

l. Test device (50) for determining operating characteristics of the drive of a metering pump, in particular a syringe pump (1), with a measuring device for a path-related measured variable and a counterforce device which counteracts the force caused by the delivery pressure of the pump and with an evaluation and display - facility is provided,

characterized ,

that the counterforce device (3) is designed as a controllable power source.

2. Test device according to claim 1, d a d u r c h g e ¬ k e n n z e i c h n e t that the controllable power source is designed as a constant power source.

3. Test device according to claim 1 or 2, ie, that the measuring device (2) is designed for a path-related measured variable, in particular for the feed rate.

4. Test device according to one of the preceding claims, that a d u r c h g e k e n n z e i c h n e t that the

Counterforce device (3) with an electromechanical, permits in the equilibrium state of the control circuit (compare position 30 in FIG. 1) and in the case of a technically fault-free syringe pump by the defined delivery pressure of the syringe pump acting in the direction of the longitudinal axis of the threaded sleeve 13 (compare the pressure setpoint profile 60 in FIG. 2) generating force a rotary movement of the push rod 10 at a constant speed in the direction of the longitudinal axis.

The embodiment of the invention is not limited to the preferred embodiment described above. Rather, a number of variants are conceivable which make use of the solution shown, even in the case of fundamentally different types. * * * * *

Claims

- 20 -

8. Test device according to claim 7, d a d u r c h g e k e n n z e i c h n e t that the gear (19) is designed as a gear transmission.

9. Test device according to claim 7 or 8, so that the push rod (10) is at least partially designed as a toothed rack and is connected to the electromechanical transducer system (4, 20) via a worm wheel.

10. Test device according to one of claims 7 to 9, d a d u r c h g e k e n n e e c h n e t that the push rod (10) at least partially consists of a ferromagnetic material.

11. Test device according to one of the preceding claims, ie that a linear, non-linear or non-continuous pressure profile is provided without changing mechanical devices of the test device (50).

12. Test device according to one of the preceding claims, characterized in that several test cycles with identical delivery pressure profiles can be carried out within one syringe feed movement of the syringe pump (1). In particular as an electromotive drive converter system (4, 20), with a force measuring device (5) and an electronic control unit (6) forms a control loop (30), with a fixed setpoint or a selectable time or path-dependent delivery pressure setpoint profile via the electronic control unit (6) can be predetermined.

5. Test device according to claim 4, that the electronic control unit (6) is designed to be programmable and has a memory for the pressure setpoint profiles that can be used for the test.

6. Test device according to claim 4 or 5, d a ¬ d u r c h g e k e n n z e i c h n e t that the electro-mechanical transducer system (4, 20) is designed as an electric motor or as an electromagnet.

7. Testing device according to one of the preceding claims, characterized in that the counter-force device (3) has a rotatable threaded sleeve (13) which can be screwed onto the force transmission means (10) and which is designed as a push rod, which is connected via a gear (19) to the Electromechanical transducer system (4, 20) is connected. 13. Test device according to one of the preceding claims, characterized in that a duration of the measuring time can be set by specifying the measuring accuracy of the conveying rate as a function of the measuring accuracy or the measuring resolution of the measuring device (2) and the size of the conveying rate.

14. A test device according to one of the preceding claims, a modem (22) connected to the electronic control device (6) for the remote transmission of measurement and test data.

* * * * *