DE8335587U1 - Safety device with power failure character for infusion control devices - Google Patents

Description

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Safety device with current-carrying character for infusion devices

In the case of infusion control devices which are equipped with complex electronic controls and sensitive mechanics in accordance with the current state of the art, failure of electronic components or malfunctions in the mechanics can result in overdosing of the medication with consequent harm to the patient.

It is known that infusion therapy is carried out as follows: a solution containing O-active drugs is fed from a higher container (1) through a hose (2) directly into the patient's circulation by means of a cannula (3). This hose usually consists of a drip chamber (4) into which the solution flows drop by drop and a control element, normally a roller clamp (5), which has the task of reducing the lumen of the hose itself by progressively squeezing the plastic hose in order to influence the drip rate and accordingly the flow rate so that an exact dosage of the drug contained in the solvent can be achieved. This arrangement has proven successful for the administration of minor solutions and for short administration times.

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However, if highly effective solutions or long-term infusions are to be administered, this arrangement does not meet the required accuracy. Many factors influence the drip rate accuracy: the drop in hydrostatic pressure due to the emptying of the container, the flowability of the plastic tube (usually soft PVC) at the pinch point in the roller clamp, changes in the position of the patient and the tube routing (kinks), changes in the circulatory state of the patient himself. In order to eliminate these circumstances and to ensure sufficient accuracy during the entire infusion time, electromechanical control devices, which are shown schematically, have been in use for over 10 years.

A photoelectric drop detection device (6) is attached to the drip chamber, which detects the falling drops and determines the actual drip rate. The target drip rate is set using a coding switch (7) or other suitable devices, such as a potentiometer or a keypad. The drip rate can vary within wide limits, normally from 1 - 200 drops/min, or, if the electronics are designed to convert the drops into volume, from 1 to over 1000 drops/hour. Suitable electronics (3) compare the actual value with the target value and issue appropriate control commands to a mechanical control device in order to influence the flow rate. The mechanical part of an infusion control device consists of, for example:

a gear (in this case a plate gear lever) (10)» a cam (11) with a fixed stop (12), an «I-shaped lever (13) to which a sword (14) is attached» which squeezes the infusion tube (2) against a fixed abutment (15) more or less, depending on the position of the cam (11), the

determined by the servomotor (9), a tension spring (16) which supports the application of the lever (13) to the cam (11), a microswitch (17) which reports the front end position of the lever (13) a drum (18) which is solidly mounted on a gear

β shaft (22), the end of a roller spring (20) which is fixed to the periphery of the drum (18), while the rolled-up end is mounted on a freely rotating roller (19)» a relay (21) which is interrupting in the quiescent current and is connected between the servomotor (9) and the electronic circuit (8) which controls the

TOV safety requirements met, switched 1st. IS The function 1st as follows:

Each time the device is switched on or before the start of each infusion process, the actuator (9), usually a stepper motor ₄ , turns the valve (11) from its fixed stop (12) in the "flow open" direction until the microswitch (17), which detects the position of the control lever, in this case the lever (13) plus the blade (14), is activated. It is important that the lever (13) has a sufficient upper stroke to be able to activate the microswitch (17) without a

2.5 Flow begins, which is easy to manage because the soft hose (2) is easy to squeeze. A timer in the circuit (8) monitors that the microswitch (17) is activated within a specified maximum time. If this is not the case, there is certainly a fault in the system, such as a jam in the kinematics or a malfunction in the microswitch (17). In this case, the electronic circuit (8) reports "device faulty", sounds an alarm and prevents the infusion from starting. During the unscrewing process,

the spring (20), which has sufficient pre-tension to turn the cam (11) back to the fixed stop (12), is wound on the drum (18). When the microswitch (17) is actuated, a suitable device, such as a safety relay (21) with closed contacts in the operating current, interrupts the power supply to the actuator (9) so that the spring force can turn the cam (U) back and the lever (13) can actuate the microswitch (17) in the opposite direction. If this does not happen within a specified time, this means that the spring (20) is not performing its function correctly.

and the cam (11£ is turned back by a motor. Analogous to the above description, an alarm is signaled and the start of the infusion is prevented. In this way, all components of the control and safety device such as: smooth operation of the gear, function of the servomotor, freedom from breakage of the return spring, microphone switch and safety release _function are dynamically checked and thus the TOV requirements are met, which require a safety control device that is independent of the power supply at all times.

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Another special feature of the system is the following:

O 25 Experience has shown that the servomotor (9) does not work continuously but often remains in a fixed position for a long time when the desired oil flow is reached. In order to reduce the power consumption during this time - an important concern especially for battery-operated devices - the motor current is reduced by cycling, providing resistors or other suitable means until the holding torque of the servomotor (9) is just sufficient to counteract the spring force and the system can be kept in balance.

Instead of a roller spring (20), other spring shapes can also be used, such as a spiral spring, leg spring, rolled-up spiral spring or similar, preferably with a flat characteristic curve.

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GUTTA Society for Infusion Technology m.b.H. Heilwigstrasse 33, D-2000 Hamburg 20

Safety device with power failure character for Infusion rule device

O Safety device with power failure characteristics for infusion control devices consisting of a return spring that brings the control element into the "flow interrupted" position immediately after the power supply to the servomotor is interrupted and whose functionality can be dynamically checked.

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Claims (2)

DIPL-INQ. J.RICHTER \j j. j j 'j . J-J P.* T E N T A N W A L E DIPLw" INQ· Ww InHEH*^Tg*BijBf * * * * * * * * * DlfPL·" INQ· &EEgr;· &bgr;&Rgr;&iacgr;&Igr;&Rgr;&Lgr;&Mgr;&Rgr;"»· EUROPEAN PATENT ATTORNEYS EUROPEAN PATENT ATTORNEYS EUROPEAN PATENT REPRESENTATIVES MANDATAIRES EN BREVETS EUROPEENS D-2OOO HAMBURG 36 29.1.1987 NEW WALL 10 ® (0 40) 34 00 45 G 83 35 587.1 340056 TELEX 2163551INTU D Critikon GmbH, TELEGRAMMS: Norderstedt INVENTIUS HAMBURG YOUR SIGN/YOUR RLE OUR SIGN/OUR RLE C.85235-III-2304 Protection claims 1. Safety device with power failure characteristics for infusion control devices which are provided with a drop chamber into which the infusion liquid flows drop by drop, with a hose line connected to the drop chamber with a control element acting on it for changing the hose diameter to control the drop rate and thus the flow rate of the infusion solution, with a photoelectric drop detection device for determining the actual drop rate, which is attached to the drop chamber, with a device for setting the target drop rate and with an electronic switching device comparing the actual value with the target value, which is connected to a mechanical control device controlling the control element for the transmission of control commands, characterized in that the mechanical control device consists of a gear, such as a planetary gear (10), a cam disk (11) which interacts with a fixed stop (12), a U-shaped lever (13) to which a sword (14) is attached which Infusion tube (2) depending on the position of a servomotor DEUTSCHE BANK AQ HAMBURQ (BL^ 2C)O. lQOfflß[Cp& ,, &Rgr;&Rgr; ⁸ &Igr;? ^&ogr; 4&xgr;9&Rgr;^{&Agr;&Mgr;&Tgr;} HAMBURG (BLZ 200100 20) 2620 80-201 «· *<·*· r. f«(· Ii Ml· &bull; » · · t · I I i (9) predetermined position of the cam disk (11) against a fixed abutment (15), a tension spring (16) which presses the lever (13) against the cam disk (11), a microswitch (17) responding to the front end position of the lever (13) and a drum (18) which is fastened to a shaft (22) of the gear (10) of the control device, wherein the end of a pre-tensioned, resilient element (20) is fastened to the periphery of the drum (18), the rolled-up end of which is mounted on a freely rotatable roller (19). 2. Safety device according to claim 1, characterized in that the pre-tensioned, resilient element (20) consists of a windable and unwindable leaf spring, such as a roller or spiral spring. I · I 1 < · &bull; t I « · ·