Platen pump

Description

The invention relates to a portable infusion pump, primarily for delivering medication from a flexible plastic container. In the treatment of patients, it is often necessary to continuously administer medications. This was previously solved by placing the bag containing the medication above the patient, from where the medication flowed into the patient under the influence of gravity. Although this method could be used successfully in most cases, the following disadvantages occurred: a) the medication flowed unevenly into the patient if the height difference between the intravenous infusion connection point and the medication bag changed; b) it was inconvenient for the patient to constantly remain under the bag containing the medication liquid; and c) the clamping element that regulates the fluid flow had to be adjusted frequently. In order to alleviate the aforementioned difficulties, electromechanical infusion pumps were developed. However, the use of such pumps is hindered by their large size and the need for a constant power source. These disadvantages are particularly unpleasant in ambulatory patients, as they hinder their free movement. In the last five years, a new type of device for controlled drug delivery has appeared on the market, which operates without an electromechanical pump and can therefore be used by outpatients. This device uses a flexible, expandable latex rubber balloon, which is placed in a rigid, transparent plastic housing. When the device is filled with the drug, the balloon expands. A delivery set is connected to the device, which delivers the drug to the patient. When the drug fills the balloon, the balloon itself provides the driving force to deliver the drug from the reservoir to the patient through the delivery set. The desired rate of drug flow is adjusted by placing an orifice of a predetermined diameter in the drug delivery line. These devices operate at a relatively high pressure, approximately 70-100 kPa. A system comprising a latex balloon is described, for example, in US 4769008 and 4915693 and EP 0426319 A2. Although drug delivery using a latex balloon has certain advantages over an electromechanical infusion pump, this method also has disadvantages. One disadvantage is that the balloon expands in all directions, and therefore the balloon is placed in a round housing. This round shape is disadvantageous when the device is carried in the patient's pocket. In addition, some types of latex balloon devices require a special machine to fill the balloon with the drug under pressure. As a result, the pharmacist must use a special machine to fill the device. An alternative drug delivery system or infusion pump is described in WO 93 / 14797. This infusion pump comprises a cylindrical housing and a pressure plate movable therein. The liquid container can be placed between the pressure plate and an opposing first surface of the housing. The pressure plate is biased towards said first surface by a parallelogram mechanism, i.e. it tries to reduce the volume of the liquid container. The spring and the parallelogram mechanism are supported by a single guide rod which passes radially through the central axis of the housing. Due to the single spring and guide rod, the force acting on the pressure plate is not sufficiently uniform, so that the pressure plate can wobble during operation, the pressure acting on the liquid container and the amount of drug delivery can vary. In addition, the shape and dimensions of the pump make it not comfortable to wear. Our goal with this invention is to create a portable infusion pump primarily for administering medication, which is more comfortable to carry due to its more favorable shape and dimensions than previous ones, and which administers medication more accurately and evenly than before. The portable infusion pump of the present invention is used for dispensing fluid from a fluid storage bag, and comprises: a substantially rectangular housing comprising a base and a lid, having a longitudinal central axis and an interior chamber, the base of the housing having a first surface in contact with the fluid storage bag; a pressure plate within said chamber having a second surface in contact with the fluid storage bag opposite the first surface, the pressure plate being movable between a first position and a second position relative to the first surface, the second position being closer to the first surface than the first position;at least one parallelogram mechanism having first and second connecting rods disposed at opposing first and second hinge points, which are connected to the housing and the pressure plate, respectively, and first and second threaded pins disposed at opposing third and fourth hinge points of the parallelogram mechanism, which are connected to a first and a second movable stop block, respectively; a first guide rod guiding the first and second movable stop blocks, respectively;and at least one spring that biases the first and second stop blocks toward each other to move the first and second threaded pins toward each other and the pressure plate toward the second position. The invention features that the pump also includes a second guide rod. The first guide rod and the second guide rod are disposed on opposite sides of said central axis and are substantially parallel to the central axis. Each of the first and second movable stop blocks is slidably connected to each of the first and second guide rods.; A preferred embodiment of the pump includes four springs, a first spring being supported by the first guide rod, a second spring being supported by the second guide rod, and the first and second springs being arranged to bias the first movable stop block in a first direction. A third spring being supported by the first guide rod, a fourth spring being supported by the second guide rod, and the third and fourth springs being arranged to bias the second movable stop block in a second direction opposite to the first direction. Preferably, the parallelogram mechanism comprises connecting arms arranged on two opposite outer sides of the first and second guide rods. HU 226 879 B1 In another preferred embodiment, the interior of the housing is configured to receive a standard rectangular medication pouch. The medication pouch has an injection port, an outlet port, and a reservoir portion, and the first surface of the housing base portion and the second surface of the pressure plate are in contact only with the reservoir portion of the medication pouch. Preferably, the housing also includes an inner wall defining at least one compartment of a size and shape suitable for receiving the injection port and the outlet port. The pump according to the invention can provide constant flow drug delivery. The use of two pairs of springs is particularly advantageous in terms of size reduction, since the same force is obtained by using springs and guide rods of half the diameter as with one pair of springs. The smaller spring diameter reduces the height of the pump. In addition, the two springs placed side by side with a lateral distance exert a more uniform force on the pressure plate. Due to the balanced force, the pressure plate can only wobble to a minimum extent while sinking into the base of the pump. Maintaining a constant outlet pressure is particularly desirable when dispensing certain drugs, such as chemotherapy drugs. The pump according to the invention can achieve dosing cycles of up to eight days. A constant outlet pressure is therefore very important in order to maintain a constant drug flow over a long period of time. The invention allows the use of standard rectangular medication bags in the pressure plate pump. By using standard bags, hospitals do not need to keep a large number of different sizes and shapes of medication bags in stock. The invention will be described in more detail below with reference to exemplary embodiments and drawings. In the drawings, Figure 1: a perspective drawing of a preferred embodiment of the infusion pump according to the invention, Figure 2: exploded view of the embodiment according to Figure 1, Figure 3: Exploded view of the parallelogram mechanism shown in Figure 2, Figure 4: longitudinal section of the embodiment according to Figure 1 with a pressure plate in a first position, Figure 5: longitudinal section of the embodiment according to Figure 1 with a pressure plate in a second position, the Figure 6: a perspective drawing of the crank of the embodiment according to Figure 1, and Figure 7: the embodiment according to Figure 1 with scale. A preferred embodiment of the portable infusion pump according to the invention is designed for a rectangular medication bag. The pump 600 shown in Figure 1 has a housing 601, which consists of a cover 602 and a base 604. The cover 602 and the base 604 are preferably formed using one of the techniques used in the manufacture of medical device housings, for example, by injection molding from thermoplastic or thermosetting plastic. Of course, other manufacturing methods can also be used, including production from sheet metal. A recess 608 may be formed in the cover 602 during manufacture to accommodate a crank 610. As will be described below, the crank 610 is used to raise and lower the pressure plate in the pump 600. When the pressure plate exerts force on the medication bag (not shown), the crank 610 is preferably removed from the pump 600 and inserted into the recess 608 provided for this purpose, which provides a convenient means of storing the crank 610 when not in use. The crank 610 is preferably provided with a We create 609 lifting protrusions that facilitate Removing the crank 610 from the recess 608 for storing it. The cover 602 may also be provided with a projection 612. In a preferred embodiment, the projection 612 has an opening 614 in the center for receiving the crank 610. The projection 612 may of course be configured in many other ways. The crank 610 is positioned above the cover 602 in operation at a distance such that it can be easily rotated without striking the cover 602. A carrying handle 613 may be formed on the surface 619 of the base 604. The carrying handle 613 is provided with an opening 615. Since the pump 600 is designed to be carried by the patient for an extended period of time, the carrying handle 613 provides a convenient means for this. A split ring, cord, or other similar device may be threaded through the opening 615 of the carrying handle 613. This may be used to secure the pump 600 to an infusion stand or to the patient. Of course, the carrying handle 613 may also be formed in one piece with the cover 602. In addition to the aforementioned, other coupling or fastening devices may also be used to facilitate portability of the pump 600. Figure 2 shows an exploded view of the pump 600. The pump 600 includes a cover 602, a crank 610, a spring-loaded parallelogram mechanism 620, a pressure plate 630, a connecting screw 645, and a base 604. A rectangular pouch 640 is inserted into the base 604, which forms the medication container during operation of the pump 600. The lid 602 has an outer rim 606. This outer rim 606 is slidably inserted from the side 657 of the base 604 into a groove 616 formed in the base 604. When the rim 606 of the lid 602 is inserted into the groove 616 of the base 604, the base 604 and the lid 602 form a chamber 647 in which the components of the infusion device and the medication bag 640 are placed. In an alternative embodiment, the base 604 is provided with a rim and the lid 602 is provided with a groove for slidingly engaging the lid 602 and the base 604. In the illustrated embodiment, the spring-loaded parallelogram mechanism 620 is located between the pressure plate 630 and the cover 602. The parallelogram mechanism 620 has connecting rods 624-627. On the upper side 631 of the pressure plate 630, there are holes for the rods HU 226 879 Β1 a pair of sockets 632 and 634 are formed. The connecting rods 624 and 627 fit into the sockets 632 and 634. A pair of sockets (not shown) are also located on the underside of the cover 602. The connecting rods 625 and 626 fit into the sockets formed in the cover 602. This connection ensures the position of the parallelogram mechanism 620 between the pressure plate 630 and the cover 602. As shown in Figure 2, the connecting screw 645 is preferably passed through the opening 636 of the pressure plate 630, the opening 622 of the movable stop blocks 621 and 623, and the opening 614 of the cover 602. The hole 611 of the crank 610 is formed with a thread corresponding to the thread 646 of the connecting screw 645. The thread of the crank 610, when engaged with the thread 646 of the connecting screw 645, allows the pressure plate 630 to be moved through the spring parallelogram mechanism 620 by rotating the crank 610. When the crank 610 is fully engaged with the connecting screw 645, the pump 600 is in the open position. In the open position of the pump 600, the pressure plate 630 is located completely within the cover 602. This allows the cover 602 to be removed from the base 604 without the pressure plate 630 hitting it. When the crank 610 is unscrewed from the connecting screw 645, the spring-loaded parallelogram mechanism 620 presses the pressure plate 630 downward into the base 604. The medication bag 640 is preferably connected to the patient via an outlet tube 648; the outlet tube 648 is passed through an opening 650 in the base 604. The opening 650 may of course have a different shape than that shown, depending on the design of the lid 602 and the base 604. A device (not shown) for controlling the flow of the medication may be inserted into the outlet tube 648. The bags 640 for use with this embodiment of the invention are well-known, standard drug-holding bags. Such standard bags are manufactured, for example, by Abbott Laboratories and Baxter Healthcare. However, based on the description herein, drug bags for use in the pump 600 can be readily prepared. The bags 640 have a reservoir portion 641, an injection port 642, and an outlet port 644. When a medication is dispensed from a pouch 640 to a patient, the pressure plate 630 only presses the reservoir portion 641, not the injection port 642 and the outlet port 644. The pressure plate 630 is approximately the same size as the reservoir portion 641 of the pouch 640. To protect the injection port 642 and the outlet port 644 of the pouch 640, the base portion 604 preferably includes a protective shield 652, Walls 654 and 656 are formed, which are two 653 and They form a compartment 655. The injection port 642 fits inside the compartment 653 and the outlet port 644 fits inside the compartment 655. When the bag 640 is in the pump 600, the injection port 642 and the outlet port 644 are protected by the compartments 653 and 655. Only the outlet tube 648 protrudes from the pump 600. In Figures 3, 4 and 5, the force exerted by the pressure plate 630 on the bag 640 is transmitted by the spring parallelogram mechanism 620. The spring parallelogram mechanism 620 comprises one or more pressure elements whose longitudinal axis is at an angle to the longitudinal axis of the movement of the pressure plate 630. Preferably, the axis of the pressure element is approximately perpendicular to the axis of the movement of the pressure plate 630. The pressure element, as will be described in more detail below, preferably comprises one or more pairs of springs and at least one guide rod. Since the pump 600 is of a portable design, the pump is made as small and thin as possible. In order to reduce the height of the pump 600, it is advantageous to use two pairs of springs 680 as the pressure elements. The use of two pairs of springs 680 has several advantages. First, we get the same force compared to a pair of springs by using springs and guide rods of half the diameter. The smaller spring diameter reduces the height of the 600 pump.Second, the two springs 680 positioned side by side with a lateral spacing provide a more even force on the pressure plate 630. The balanced force causes the pressure plate 630 to wobble only minimally as it descends into the base portion 604. In the illustrated embodiment, a pair of guide rods 664 and 665 are disposed along an axis substantially perpendicular to the direction of travel of the platen 630. The guide rods 664 and 665 are formed of metal rods approximately 75 mm to approximately 127 mm in length and approximately 3 mm to approximately 6 mm in diameter; other sizes are of course possible. In the embodiment in which the guide rods 664 and 665 are single or multi-part rods with continuous threads along their entire length, a tubular sleeve is preferably provided on the portions of the threaded rods that slidably support other movable parts. In an alternative embodiment, the guide rods 664 and 665 are formed as a plain rod with threads for a nut 670 at only the ends. A spring stop 675 is provided at each end of the guide rods 664 and 665. Of course, various means can be used to keep the springs 680 in tension. For example, a nut, or a nut and washer, can be placed on the threaded ends of the guide rods 664 and 665, which is advantageous from a manufacturing point of view and also allows the manufacturer to adjust the spring tension simply by turning the nut. The spring stop 675 can be secured against further rotation on the guide rods 664 and 665, for example, with epoxy resin. In the illustrated embodiment, a spring stop 675 is provided at the lateral ends of the guide rods 664 and 665 to limit the extension of each spring 680. The spring stops 675 include a radially outwardly extending circumferential flange 677 through which an opening 679 is formed to receive the threaded portion of the guide rods 664 and 665. The spring stop 675 is of a cross-section sufficient to retain the spring 680. The spring stop 675 is preferably provided with an axial tubular sleeve 682 which is disposed within the spring 680 along the guide rods 664 and 665 in the assembled pump 600. HU 226 879 Β1 is located. In the illustrated embodiment, the sleeves 682 are provided with an internal thread corresponding to the thread of the guide rods 664 and 665 for screwing the spring stops 675. In an alternative embodiment (not shown), the spring stop 675 is comprised of the flange 677 and the tubular sleeve 682 as in the previous embodiment. However, the spring stop 675 is secured by a separate threaded nut that is directly mounted on the guide rods 664 and 665. This embodiment eliminates the need for internal threads in the opening 679 and on the inner wall of the sleeve 682. Although the use of a separate nut is advantageous from a manufacturing perspective, it does increase the length of the guide rods 664 and 665, which is not always desirable. The springs 680 are positioned in a compressed state between spring stops 675 and two movable stop blocks 621 and 623. In a preferred embodiment, the springs 680 are made of a material suitable for musical instrument strings and have a wire diameter of approximately 2 mm. A smaller wire diameter, such as 1.6 mm, can be used if the spring preload is increased. The spring constant of the springs 680 is preferably 14 kN / m-16 kN / m, in the two-spring arrangement. Each spring 680 is about 41 mm long in the unloaded state and about 23 mm long in the fully compressed state shown in Figure 4, and the spring diameter is about 13 mm. The sum of the axial displacements of the springs 680 is about 23 mm between the compressed state shown in Figure 4, i.e. the start of the dosing cycle, and the state shown in Figure 5, i.e. the end of the dosing cycle. Depending on the spring constant used, the dosing cycle can range from half an hour to eight days. These dimensions are for a pump designed for a 100 cc medication bag. Of course, larger or smaller medication bags can be used with appropriate modifications to the pump dimensions. The movable stop blocks 621 and 623 act as center spring stops and transmit the center movement of the springs 680 to the parallelogram mechanism 620 and the pressure plate 630. In Figure 3, the stop blocks 621 and 623 are essentially rectangular, but a semicircular cutout 661 is formed on their inner side. The cutout 661 may be of a different shape, the main thing is that the connecting screw 645 can still fit between the stop blocks 621 and 623 when they are in contact with each other. In the stop blocks 621 and 623, annular or tubular recesses 662 are formed, which are shorter than their length. The inner ends of the springs 680 are inserted into the recesses 662 of the stop blocks 621 and 623. The stop blocks 621 and 623 have openings 660 formed therein, which allow the stop blocks 621 and 623 to slide axially on the guide rods 664 and 665. The movable stop blocks 621 and 623 may be made of a durable material such as aluminum, stainless steel, or other metals commonly used in the manufacture of medical devices. However, it is particularly advantageous to use a strong, lightweight plastic for this purpose; such a material is Delrin, manufactured by DuPont. The stop blocks made of or coated with the polymer slide relatively easily on the guide rods 664 and 665 under the force of the springs 680. An opening 686 is formed on opposite sides of the stop blocks 621 and 623. The openings 686 are provided with an internal thread corresponding to the thread of the threaded pins 688. The threaded pins 688 are screwed into the openings 686 of the stop blocks 621 and 623. In the parallelogram mechanism 620, the first ends of two connecting arms 690 and 692 are pivotally mounted on a threaded pin 688. The second ends of the connecting arms 690 are connected to a connecting rod 625 connected to the cover 602. The second ends of the connecting arms 692 are connected to a connecting rod 624 which is connected to the pressure plate 630. The connecting arms 690 and 692 form a scissor arrangement which is a mirror image of the arrangement of the connecting arms 694 and 696. Together, the four connecting arms 690, 692, 694 and 696 form an adjustable parallelogram-shaped arrangement. Preferably, a corresponding arrangement is formed on two opposite outer sides of the first and second guide rods 664, 665, on the opposite vertical walls of the stop blocks 621 and 623, as shown in Figure 3. In Figure 4, the medicine bag 640 is inserted into the base 604, the base 604 and the lid 602 are fitted together, and the springs 680 are in a maximum tension state. As the springs 680 exert a force perpendicular to the direction of movement of the pressure plate 630, the stop blocks 621 and 623 slide towards each other on the guide rods 664 and 665, causing the second ends of the connecting arms 690, 692, 694 and 696 to move away from each other. This mechanism transfers the force exerted by the springs 680 through the connecting arms 690, 692, 694 and 696 and the sockets 632, 634 to the pressure plate 630. The component of spring force transmitted to the pressure plate 630 through the connecting arms 690, 692, 694 and 696 increases during the medication dispensing cycle from the pouch 640, while the tension of the springs 680 decreases, resulting in medication being dispensed at a substantially constant pressure until the pouch 640 is emptied (Figure 5). Increasing the force during the dispensing cycle, as shown in Figures 2 and 3,It has been experimentally shown that this results in a substantially constant output fluid pressure. Maintaining a constant output pressure is particularly desirable for the administration of certain drugs, such as chemotherapy drugs. As mentioned above, the pump of the invention can be used for up to eight-day dosing cycles. In an eight-day dosing cycle, the pump dispenses one drop of drug approximately every twelve minutes. A constant output pressure is therefore essential for maintaining this constant flow of drug over a long period of time. It is important that the pressure exerted by the pressure plate 630 on the bag 640 increases during the dosing cycle, resulting in a constant flow of drug to the patient. During the dosing cycle, it is useful to know how much medication is left in the 640 sachets. HU 226 879 B1 As shown in Figures 6 and 7, the crank 610 has a A liquid level indicator 697 is provided. During the dispensing of the medication, the crank 610 can be inserted into the opening 614. During dispensing, the pressure plate 630 and the connecting screw 645 move inwardly into the chamber 647 of the base part 604. As a result, the end 699 of the connecting screw 645 sinks into the opening 614. The liquid level indicator 697 is calibrated to indicate the amount of medication that can still be dispensed. The position of the end 699 of the connecting screw 645 depends on this amount. Figure 7 shows another solution for indicating the drug level. In this embodiment, a A scale 698 is provided on the surface 619 of the base 604. The scale 698 can be formed in a variety of ways, such as by attaching a label or during injection molding. During the dispensing of the medication in the pouch 640, the pressure plate 630 moves toward the base 604. The level of liquid remaining in the pump is indicated by the position of the bottom 635 of the pressure plate 630 on the scale 698. When using the pump 600, a bag 640 filled with medication is first connected to the patient by catheter or intravenously through the outlet tube 648. To open the lid 602 and the base 604, the pressure plate 630 can be retracted into the lid 602 by rotating the crank 610, and then the lid 602 and the base 604 can be slid apart. The patient can then insert the bag 640 into the base 604, ensuring that the injection port 642 is in the compartment 653 and the outlet port 644 is in the compartment 655. The outlet tube 648 is led out of the base 604 through the opening 650. Since the pressure plate 630 is completely contained within the cover 602, the cover 602 and the base 604 can be slid together. The patient then rotates the crank 610 until it is unscrewed from the connecting screw 645. The end 699 of the connecting screw 645 is then located in the opening 614. The crank 610 can be stored in the recess 608.After the crank 610 is removed, the parallelogram mechanism 620 and the pressure plate 630 exert a steadily increasing force on the medication-retaining bag 640 during the dispensing cycle, as previously described. This force presses the pressure plate 630 against the medication-retaining bag 640, thereby providing a substantially constant flow of fluid through the outlet tube 648. After all medication has been dispensed, the patient removes the crank 610 from the recess 608 and inserts it into the slot 614. The crank 610 is screwed onto the connecting screw 645, thereby compressing the parallelogram mechanism 620 and retracting the pressure plate 630 into the cover 602. When the pressure plate 630 is fully seated in the cover 602, the cover 602 and the base 604 can be slid apart. The empty pouch 640 can then be removed from the base 604 and the pump 600 is once again ready for another dosing cycle. The invention has been described above based on exemplary embodiments; in addition to those described, of course, numerous further variations and modifications are possible within the scope of protection defined in the claims.

Claims

PATENT CLAIMS 1. A portable infusion pump (600) for dispensing fluid from a fluid storage bag (640), the pump (600) comprising: a substantially rectangular housing (601) comprising a base (604) and a cover (602) and having a longitudinal central axis and an interior chamber (647), the base (604) of the housing (601) having a first surface in contact with the fluid storage bag (640); a pressure plate (630) within said chamber (647) having a second surface in contact with the fluid storage bag (640) opposite the first surface, the pressure plate (630) being movable between a first position and a second position relative to the first surface, the second position being closer to the first surface than the first position;at least one parallelogram mechanism (620) having first and second connecting rods (624, 625) disposed at first and second hinge points opposite to each other, which are connected to the housing (601) and the pressure plate (630), respectively, and first and second threaded pins (688) disposed at third and fourth hinge points opposite to each other of the parallelogram mechanism (620) which are connected to a first and a second movable stop block (621, 623), respectively; a first guide rod (664) guiding the first and second movable stop blocks (621, 623), respectively;and at least one spring (680) for biasing the first and second stop blocks (621, 623) toward each other to move the first and second threaded pins (688) toward each other and the pressure plate (630) toward the second position, characterized in that it also includes a second guide rod (665), the first guide rod (664) and the second guide rod (665) being disposed on opposite sides of said central axis substantially parallel to the central axis, and each of the first and second movable stop blocks (621, 623) being slidably connected to each of the first and second guide rods (664, 665); 2. The infusion pump (600) of claim 1, characterized in that it comprises four springs (680), a first spring of the four springs (680) is supported by the first guide rod (664), a second spring is supported by the second guide rod (665), and the first and second springs are arranged to bias the first movable stop block (621) in a first direction, and a third spring of the four springs (680) is supported by the first guide rod (664), a fourth spring is supported by the second guide rod (665), and the third and fourth springs are arranged to bias the second movable stop block (623) in a second direction opposite to the first direction.

3. The infusion pump (600) of claim 1, wherein the parallelogram mechanism (620) comprises connecting arms (690, 692, 694, 696) disposed on two opposite outer sides of the first and second guide rods (664, 665).

4. The infusion pump (600) of claim 1, wherein the interior of the housing (601) is configured to receive a standard rectangular medication bag (640).

5. The infusion pump (600) according to claim 4, characterized in that the medicine bag (640) has an injection opening (642), an outlet opening (644) and a reservoir portion (641), and further the first surface of the base portion (604) of the housing (601) and the second surface of the pressure plate (630) are in contact only with the reservoir portion (641) of the medicine bag (640).

6. The infusion pump (600) of claim 5, wherein the housing (601) further comprises an inner wall (652, 654, 656) defining at least one compartment (653, 655) sized and shaped to receive the injection port (642) and the outlet port (644).