RU2111018C1 - Peristaltic apparatus with continuously adjustable medication feeding system - Google Patents

Abstract

FIELD: medical equipment, in particular, dosed parenteral injection of liquid medication. SUBSTANCE: peristaltic drive has five pressure pins with punches at their working ends. Punch section in plane extending in parallel with longitudinal axis of pipe is made in the form of semicircle with radius making 1.5-2.0 of pipe outer diameter. Punch spacing is 2.5-3.0 of pipe outer diameter. First three pins downstream of liquid flow are forcing. Fourth and fifth pins serve both to force and damp pulsed liquid flow feeding speed, which is due to the fact that fourth and fifth pins move only half the full working stroke. Fourth pin may cover pipe section to the extent ranging between half and full pipe working section and fifth pin may cover pipe section to the extent ranging between 0.55-0.7 of pipe inner diameter and half the working section. Stems are reciprocated by cams which are divided into four sectors, each of 90 deg. Two main opposite sectors of each cam have radii whose difference is equal to required pin stroke. Two other sectors are made in the form of Archimedes' spiral. Cams on shaft are turned one with respect to another for an angle of 90 deg. Maximum radius of first four cams is selected to provide minimum moment on working shaft during the initial full pinching of pipe, i.e. it requires minimum cam radius. Maximum radius of fifth cam is less than maximum radius of first four cams by value equal to half the working stroke of first three cams. Working stroke of cams in working part of pipe ranges between 0.55 and 0.7 of pipe inner diameter before pipe section is overlapped. EFFECT: increased efficiency by reduced pulsation of liquid at apparatus output end without increasing the moment on shaft of actuating engine and provision for employment of polyvinyl chloride pipes without usage of special silicone inserts. 5 dwg

Description

 The invention relates to medical equipment and can be used for metered parenteral infusion of liquid drugs both in a hospital and during transportation of the patient.

 The invention relates to the class of medical equipment used for infusion therapy and clinical nutrition, in which the infusion of drugs does not occur under the influence of gravity of the liquid, but using a special peristaltic mechanism that creates the necessary pressure. Such devices allow for a long, strictly dosed administration of drugs, while ensuring automatic control of the infusion process.

 Despite the rather high cost of these devices and their complexity, such areas of medicine as oncology, intensive care, cabustiology, pediatric surgery, have a great need for such technical means.

 A number of devices are known that ensure the infusion process due to a peristaltic power drive (for example, US patent N 4867744, class A 61 M 5/00, 1989; application EPO N 0411543, class A 61 M 5/142, 1991; application Japan N 1-57584, class A 61 M 5/00, 1989; EPO application N 0374618, class A 61 M 5/142, G 01 B 21/14, 1990; Japanese application N 1-16507, class A 61 M 5/00, 1989; German patent N 3912405, class A 61 M 1/00, 1990).

 These devices use two different principles of fluid supply through the deformation of a flexible tube.

 The first (application EPO N 0374618) is the so-called "roller pump" in which the ejection of the liquid is ensured by "rolling" around the circumference of the flexible tube with a roller mechanism containing from one to four rollers.

 Such devices are not economical, since they require a significant increase in the power of the drive motor and, therefore, the dimensions of the entire device due to the fact that in such a pump a continuous (rolling) deformation is performed until it is clamped along the entire working length of the tube in several places simultaneously.

 The use of such pumps is justified for large specific volumes of pumped fluids (> 1000 ml / h). In most cases, with volumes from 1 to 400 ml / h, pumps are used with reciprocating multi-pin or screw principle of peristaltic clamping of a flexible tube with extrusion of liquid.

 Such devices have significantly lower power consumption, dimensions, however, they require a special silicone insert (working section of the tube) and are characterized by significant irregularity (pulsations) of the output fluid flow as a sinusoid, which worsens the medical-therapeutic effect, especially when highly toxic drugs are introduced to the patient.

 Closest to the invention is a device according to the application EPO N 0411543, containing a peristaltic drive, consisting of 11-12 cams, closely spaced to each other and mounted on a single shaft, which lead to reciprocating motion pins pinching the tube according to the type of "traveling wave "and initiating the movement of the fluid forward, promoting it in a sinusoidal manner.

 The purpose of the invention is the improvement of operational characteristics, consisting in a significant reduction in pulsations of the liquid at the pump outlet and the possibility of using flexible pipes based on PVC without a special silicone insert on the working part.

The goal is achieved in that a device containing a container with medicinal fluid connected to a flexible deformable tube, a pump control unit and a peristaltic mechanism containing cams mounted on a shaft and connected to pins, at the working ends of which punches are located, and a clamping device that prevents displacement tube in the direction of pressure, adapted to a peristaltic mechanism consisting of five cams unfolded from each other by 90 ^o and connected with the pins, two of which yavl are damping, and each cam is divided into four equal sectors, and two opposite sectors of the first three cams are made with radii, the difference of which is necessary for the working stroke of the pins, ensuring full clamping and opening of the tube to a value of 0.55-0.7 from its inner diameter and two cams with radii, the difference of which is necessary to ensure half the working stroke of the other two pins, and two other sectors of all cams are made with a profile in the form of an Archimedes spiral connecting sectors with different radii. The maximum radius of the first four cams is the same and is selected from the condition of ensuring the minimum torque on the motor shaft with the maximum displaced fluid volume, and the maximum radius of the fifth cam is reduced by an amount equal to half the working stroke of the first three cams, providing a pin travel that covers the tube from 0.55- 0.7 internal diameter to half of its working part. The punches are made with profiles in the plane parallel to the longitudinal axis of the tube in the form of semicircles, the radii of which are equal to 1.5-2 of the outer diameter of the tube, and the distance between them is 2.5-3 of the outer diameter of the tube.

 In FIG. 1 shows a block diagram of a device; in FIG. 2 is a diagram of the operating modes of the pins; in FIG. 3 is an experimental curve of the displacement fluid volume versus pin displacement for a selected punch profile; in FIG. 4 - cam profile; in FIG. 5 - the design of the peristaltic mechanism.

 The proposed device (Fig. 1) contains a container 1 with a liquid and a deformable polymer tube 2 attached to it with a needle at the end. Any part of the tube is refilled in the peristaltic mechanism 3, in which it is cyclic clamping, leading to forced movement of the fluid. The choice of mode and the operation of the peristaltic mechanism is carried out using the control unit 4 connected to it by the transmission line 5. The peristaltic mechanism 3 consists of cams 6 mounted on the shaft 7 and actuating the pins 9 pressed against the cams by the spring 8 by means of the engine 10. At the ends pins 8 are profile punches 11, which make direct contact with the tube 2 in the process of clamping it relative to the clamping device 12 with an elastic gasket 13 that prevents movement tube 2 in the direction of pressure.

The profile of the punches significantly affects the pressing force and depends on the diameter of the polymer tube 2. In table. 1 shows the results of experimental studies on the selection of the optimal cam profile according to the criterion: "minimum pressing force at the maximum possible ejected volume of fluid" for a widespread polymer tube designed for transfusion of infusion solutions with an outer diameter of D _n = 4.6 mm and an inner diameter D _in = 3.3 mm.

 From experimental studies it was found that the optimal cross section of the punch profile should be in the form of a semicircle with a radius equal to 1.5-2 of the outer diameter of the tube. To ensure a smooth fluid supply as the rod moves forward, it is necessary to ensure a linear dependence of the displacement fluid volume V on the displacement value X, i.e., this dependence should be as close as possible to the form V = KX, where K = const.

 With the selected profile of the punch in the form of a cylinder, the experimental dependence V = f (x) represents a curve (Fig. 2), on which the linear section is clearly visible, within which the movement of the punches deforming the tube should be carried out. This circumstance makes it possible to use tubes with a wide range of outer diameters in the apparatus while maintaining a constant flow rate of the displaced volume of liquid. To maintain this linearity when two adjacent punches are used, the distance between them in the vertical plane should not be less than at least one diameter of their profile.

In addition to ensuring the linearity of the displaced volume of fluid with uniform movement of the punch, a certain operating mode of the pins is necessary for a smooth continuous supply of fluid. In FIG. 2, and conditionally shows the operating modes of each of the pins for one cycle of the working shaft with the cams. This cycle is divided into four equal cycles, each of which corresponds to 90 ^o rotation of the working shaft. The numbering of the pins arranged sequentially in a row along the tube 2 begins with a pin mounted at the pump inlet. The pins overlap the tube alternately. The fifth pin is damping, eliminating the interruption of flow when the fourth pin overlaps the tube. The position of the pins in FIG. 2 corresponds to the size of the cross section through which the fluid is currently passing. The design feature of the peristaltic mechanism is also the fact that the pins four and five move only half the working stroke of the remaining pins, and the four pins overlap the tube from half of its working part to full closure, and the fifth pin from 0.55-0.7 internal diameter tube to half of its working part. The hatching conventionally shows the part of the liquid participating in its working movement, that is, it is pushed out. To implement this mode of movement of the rods, corresponding cam profiles are required, FIG. 4.

Each of the cams is divided into four equal sectors (I, II, III and IV in Fig. 4). Two opposite sectors I and III have a profile in the form of parts of circles with radii R ₁ and R ₂ , and ΔR = R ₁ -R _{2 of} these circles is equal to the required stroke of the pin. The other two sectors II and IV have a profile in the form of an Archimedes spiral connecting these circles, as conventionally shown in FIG. 4. In order to simplify the manufacturing technology, these sections of the spiral with an error of no more than 5% of the linear dependence can be replaced by parts of a circle with radius R ₃ , the center of which is offset from the center of the circles of two other sectors by ΔX and ΔY, where ΔX ≅ ΔY; ΔY = (R ₁ -R ₂ ) / 2. .

For example, for a tube with an inner diameter of D _in = 3.3 mm and an outer D of _n = 4.6 mm, based on the desire for minimum power consumption of the engine and ensuring technological requirements in the manufacture of cams with minimum dimensions, the dimensions indicated in Table 1 are accepted. 2.

где
M_р - момент силы нормальной к поверхности кулачка;
P - сила пережатия трубки;
R - максимальный радиус кулачка (R₁ на фиг. 4);
M_тр - момент силы трения скольжения оси ролика;
μ - коэффициент трения скольжения;
α - угол скоса поверхности кулачка;
M_к - момент силы, передаваемый кулачку валом для пережатия трубки;
tgα = 2h/R , где h - полный ход штифта.The greatest consumed moment on the working shaft takes place during the beginning of the complete clamping of the tube. This occurs at the end of each measure (FIG. 2). The previous (in front of the closing) pin creates pressure on the bearings of the working shaft, transmitted through the cam, rolled around in an unchanged (maximum) circle, that is, the time required for this - overcomes only rolling friction in the shaft bearings and sliding friction in the axes of the rollers pressed against the cams. The moment necessary for clamping the tube with moving punches can be calculated by the formulas
Mp = PRtgα

Where
M _p - moment of force normal to the surface of the cam;
P is the clamping force of the tube;
R is the maximum radius of the cam (R ₁ in Fig. 4);
M _Tr - the moment of friction force of the sliding axis of the roller;
μ is the coefficient of sliding friction;
α is the bevel angle of the cam surface;
M _to - the moment of force transmitted to the cam shaft for clamping the tube;
tgα = 2h / R, where h is the full stroke of the pin.

Given the above and the data table. 1, and also taking μ = 0.04, we have M _k ≅ 300 Gcm. To take into account additional factors (friction in the bearings of the working shaft, the friction of the axes of the rollers of the steel pins, friction when the pins move, etc.), a safety factor K _s = 2 is introduced. From here, the required calculated moment on the working shaft will be M _{slave shaft} = 2M _to = 600 gsm. Such a moment can be created with a sufficiently small-sized electric motor connected directly to the working shaft without reduction. The most suitable types of electric motors for this purpose are stepper motors, which have wide and precise speed control and provide the required torque without using a gearbox.

 The device operates as follows.

 After the location of the container 1 with the medicine and the "run" of the air column through the infusion tube 2, which is inserted into the corresponding guides of the peristaltic mechanism and pressed with the clamping device 12 to the working punches 11 of the pins 9, the required fluid flow rate is set by the control unit 4 and included in operation of the engine 10, driving the peristaltic mechanism 3, which delivers the fluid according to the diagram in FIG. 2 a. In the first stroke, the first pin blocks the fluid flow, and the second pin squeezes out the full volume available underneath, however, the fourth pin opens halfway, that is, it draws in half the fluid volume pushed out by the second pin. Thus, linear ejection of half of the full volume occurs at a constant speed. In the second step, at the moment the tube is completely closed with the second pin, the third pin begins to move, and the fifth pin retracts half, similarly to the work of the second and fourth pins in the previous cycle. In this case, the liquid is continued to be ejected at the same speed as in the first step. In the third step, the fourth pin pushes out, however, since its stroke is half that of the second and third pins, the speed of the pushed fluid does not change. The fifth pin works similarly, continuing to push at the same speed. At the end of the cycle, the position of the pins corresponds to the beginning of the first measure, which allows repeating cycles without interrupting the flow. In addition, in the second, third, and fourth cycles, fluid is simultaneously drawn into the tube from the side of its inlet, filling its non-working part and preparing it for the next cycle, while at the entrance there is an uneven filling speed, for example, in the first cycle, the liquid is not drawn However, this does not affect the linearity of the flow at the pump outlet. The maximum load on the engine will be only at moments of complete clamping by a moving pin, i.e. at moments corresponding to the boundaries between measures, since the previous pin does not move and, therefore, the engine overcomes only the friction moment created in the bearings from the reaction force of the pressed tube.

 The considered operating mode of the pump allows to obtain a continuous and uniform flow of extruded fluid (Fig. 2, b), which compares the proposed device from existing analogues, which in the best case provide a sinusoidal character of fluid movement, which at low flow rates (<50 ml / h) may lead to blockage of the needle at the exit of the infusion tube with a long delay in the movement of fluid due to its uneven supply. The profile of the cams and their operating mode provide an insignificant moment on the motor shaft, which allows you to abandon the special expensive silicone inserts and use serial infusion systems for transfusion of drugs.

 The design of the peristaltic mechanism with the position of the punches corresponding to the initial state of the cycle (0 in FIG. 2) is shown in FIG. 5.

Claims (1)

A peristaltic apparatus with a smooth drug delivery system comprising a container with medicinal fluid connected by a flexible deformable tube with a needle, a control unit and a peristaltic mechanism with cams mounted on a shaft connected to an electric motor, and actuating pins with punches at their working ends as well as a clamping device that prevents the tube from moving in the direction of pressure, characterized in that the peristaltic mechanism contains five cams, are deployed relative to each other at 90 ^o, with the pins, two of which are damped and punches with profiles in a plane parallel to the longitudinal axis of the tube, are designed as semicircles whose radii are equal to 1.5 - 2 external tube diameter and the distance between them is 2.5 - 3 external diameters, each cam divided into four equal sectors, two opposite sectors of the three cams have different radii to ensure the working stroke of the pins with the possibility of clamping the tube to a value of 0.55 - 0.7 of its internal size and kryvaniya remaining two cams each have two opposite sectors with different radii to provide half of the working stroke of pins, and the other two sectors of five cams formed with a profile in the form of a spiral of Archimedes connecting different radii of two opposing sectors.

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