A pre-filled pen syringe

Abstract

The present invention is applicable to the technical field of syringes, and provides a prefilled pen-type syringe, comprising an injection pen body; a fixed tube is provided through and in communication with the inner bottom surface of the injection pen body, and a partition is fixed inside the fixed tube; a plurality of hemispherical seats are evenly fixed on the circumferential side surfaces of the fixed tube inside a working chamber; a spherical elastic reset airbag is provided inside the hemispherical seat; an air delivery pipe that passes through the hemispherical seat is provided between the spherical elastic reset airbag and the fixed tube; an extrusion portion is slidably provided in a slide groove; a sliding hole is provided on the surface of the partition; a piston portion is slidably provided in the sliding hole; an injection portion is sealed and clamped inside the fixed tube, and the device presses the gas in the spherical elastic reset airbag into the fixed tube by holding and pressing the ball head, thereby driving the piston to slide and descend along the fixed tube, and then injecting the drug solution in the injection tube into the patient's body through the injection needle, replacing the traditional screw piston pressing injection method, reducing the use length of the pen-type syringe, and making it easy to carry.

Description

Technical Field

[0001] The present invention relates to the technical field of syringes, and more particularly to a prefilled pen-type syringe. Background Art

[0002] Pen syringes / injection pens are products that combine injection liquid preparations and syringes. They are characterized by accurate dosage setting, simple operation, easy to carry, suitable for home use, and avoid the danger of accidentally breaking the syringe when injecting with a glass syringe. Compared with traditional glass syringes, they are safer, more convenient, and more precise in controlling dosage. Injection pens are divided into multiple-use pen syringes and single-use pen syringes (i.e. prefilled injection pens) according to whether the refill can be replaced. The difference between the two is that the former can be used for a long time (as long as the injection "pen refill" is replaced frequently); the latter can only be discarded after use and is a disposable product.

[0003] The push-type injection pen in the prior art includes a medicine tube, a spiral tube, a clutch tube, a screw and a nut tube. A piston is arranged at one end of the screw, and the piston is arranged in the medicine tube. In the initial state, the medicine is placed in the medicine tube ("pen core"), and the piston is far away from the injection needle, so that the screw at the end of the piston extends outward, which increases the length of the pen-type syringe and is not convenient to carry; at the same time, each time the medicine tube is replaced, the pen body needs to be disassembled and assembled, which reduces the convenience of use. Summary of the invention

[0004] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a prefilled pen-type syringe, which can press the gas in the spherical elastic reset airbag into the fixed tube by squeezing the ball head, thereby driving the piston to slide down along the fixed tube, and then inject the medicine in the injection tube into the patient's body through the injection needle, replacing the traditional screw piston pressing injection method, reducing the use length of the pen-type syringe and making it easier to carry.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] A prefilled pen-type syringe comprises an injection pen body; a fixed tube is provided through and connected to the bottom surface of the injection pen body, and a partition is fixed inside the fixed tube; the partition divides the inside of the injection pen body into a working chamber and a liquid storage chamber; a plurality of liquid extraction tubes connected to the liquid storage chamber are provided near the bottom of the fixed tube peripheral side surface; a one-way valve is provided on the liquid extraction tube; a plurality of hemispherical seats are evenly fixed on the peripheral side surface of the fixed tube inside the working chamber; a spherical elastic reset airbag is provided inside the hemispherical seat; an air supply pipe that passes through the hemispherical seat is connected between the spherical elastic reset airbag and the fixed tube; sliding grooves are symmetrically provided on both sides of the inner wall of the working chamber; an extrusion part is slidably provided on the sliding groove; a sliding hole is provided on the surface of the partition; a piston part is slidably provided on the sliding hole; an injection part is sealed and clamped inside the fixed tube.

[0007] The present invention is further configured as follows: the extrusion portion includes a slide plate slidably matched with the slide groove; a pressure plate is fixed to one end of the slide plate, and a ball head is fixed to the other end thereof; a return spring is symmetrically fixed between the pressure plate and the inner wall of the working chamber.

[0008] The present invention is further configured as follows: an air supply pipe is provided through the top of the fixed pipe; a liquid supply pipe is provided through the inner wall of the liquid storage cavity; and stop valves are provided on both the air supply pipe and the liquid supply pipe.

[0009] The present invention is further configured as follows: an annular sealing groove coaxial with the sliding hole is opened on the bottom surface of the partition; the piston part includes a piston; an annular sealing plate plug-fitted with the annular sealing groove is fixed on the top of the piston; a tension spring is fixed between the piston and the top of the fixed tube.

[0010] The present invention is further configured as follows: a plurality of internal elastic sealing ribs are evenly fixed on the inner wall of the fixed tube in the liquid storage chamber from top to bottom, and an internal sealing groove connected to the end of each liquid extraction tube is opened on the inner wall; the injection part includes an injection tube that slides with the fixed tube; an external sealing groove that matches the internal elastic sealing rib is evenly opened on the outer peripheral side of the injection tube from top to bottom; an external elastic sealing rib that matches the internal sealing groove is fixed on the outer peripheral side of the fixed tube near its bottom; a plurality of liquid inlet holes that penetrate the external elastic sealing rib and are coaxial with the corresponding liquid extraction tube are evenly opened on the outer peripheral side of the fixed tube.

[0011] The present invention is further configured as follows: a piston sleeve adapted to the piston is slidably provided on the inner wall of the injection tube; a rubber sleeve is connected between the inner circumferential side surface of the injection tube near its top and the piston sleeve; the injection part also includes a needle seat; a threaded groove threadedly connected to the injection tube is provided on the surface of the needle seat; an injection needle coaxially connected to the injection tube is fixed to the bottom of the needle seat; and a needle sleeve is clamped on the bottom of the needle seat.

[0012] The present invention is further configured as follows: the surface of the needle seat is symmetrically provided with concentric annular grooves, and both ends thereof are provided with insertion holes; an L-shaped seat is symmetrically fixed to the bottom of the injection pen body; a plug rod that is slidably provided through the side of the L-shaped seat and is plugged into and matched with the insertion hole; an L-shaped connecting plate is fixed to the end of the plug rod; a connecting spring that is sleeved on the plug rod is fixed between the L-shaped connecting plate and the L-shaped seat; a square column is fixed to the bottom of the injection pen body; an ear seat is fixed to the bottom end of the square column; a pressing portion that is slidably provided on the square column and is rotatably matched with the annular groove.

[0013] The present invention is further configured as follows: a fixing plate is fixed on the side of the injection pen body; an L-shaped lifting plate is slidably arranged inside the fixing plate; an extension plate is fixed to the bottom of the L-shaped lifting plate; an extension rod is symmetrically fixed to the bottom surface of the extension plate; a push rod is fixed to the bottom surface of the extension plate between the two extension rods; a guide ball is fixed to the bottom end of the extension rod; a guide plate is fixed to the side of the L-shaped connecting plate; one side of the guide plate is arranged as an inclined surface; a baffle is symmetrically fixed to the side of the injection pen body; a guide rod that slides with the L-shaped connecting plate is fixed to the side of the baffle; the pressing part includes a positioning ring that rotatably cooperates with the annular groove; a T-shaped plate is fixed to the side surface of the positioning ring; a guide hole that slides with the square column is opened on the surface of the T-shaped plate; a support spring that is sleeved on the square column is fixed between the T-shaped plate and the ear seat.

[0014] The advantages of the present invention are:

[0015] The present invention presses the gas in the spherical elastic reset airbag into the fixed tube by squeezing the ball head, thereby driving the piston to slide down along the fixed tube, and then injecting the medicine in the injection tube into the patient's body through the injection needle, replacing the traditional screw piston pressing injection method, reducing the use length of the pen-type syringe and making it easy to carry.

[0016] The present invention realizes quantitative extraction of liquid medicine through linkage between various components. Only a disposable injection part needs to be replaced, and the injection part can be quickly installed and disassembled without disassembling the injection pen body, thereby improving the convenience of use. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic structural diagram of a prefilled pen-type syringe of the present invention.

[0018] Figure 2 For the present invention Figure 1 A schematic diagram of the structure from another angle.

[0019] Figure 3 For the present invention Figure 2 A magnified image of area A.

[0020] Figure 4 It is a schematic diagram of the structure of the present invention in the state of liquid medicine extraction.

[0021] Figure 5 For the present invention Figure 4 A magnified view of area B.

[0022] Figure 6 It is a schematic diagram of the structure of the present invention under the state of drug solution injection.

[0023] Figure 7 For the present invention Figure 6 Magnified view of area C.

[0024] Figure 8 It is a schematic structural diagram of the injection pen body of the present invention.

[0025] Fig. 9 It is a schematic structural diagram of the piston part of the present invention.

[0026] Fig.10 It is a schematic structural diagram of the extrusion portion of the present invention.

[0027] Fig.11 It is a schematic structural diagram of the injection part of the present invention.

[0028] Fig.12 It is a structural schematic diagram of the pressing part of the present invention.

[0029] In the figure: 1, injection pen body; 2, fixing tube; 3, partition; 4, working chamber; 5, liquid storage chamber; 6, liquid extraction tube; 7, hemispherical seat; 8, spherical elastic reset airbag; 9, air delivery tube; 10, slide groove; 11, extrusion part; 12, slide hole; 13, piston part; 14, injection part; 15, slide plate; 16, pressure plate; 17, ball head; 18, reset spring; 19, air supply tube; 20, liquid supply tube; 21, annular sealing groove; 22, piston; 23, annular sealing plate; 24, tension spring; 25, inner elastic sealing rib; 26, inner sealing groove; 27, injection tube; 28, outer sealing groove; 29, outer elastic sealing Sealing rib; 30, liquid inlet hole; 31, piston sleeve; 32, rubber sleeve; 33, needle seat; 34, threaded groove; 35, injection needle; 36, needle sleeve; 37, annular groove; 38, socket; 39, L-shaped seat; 40, plug rod; 41, L-shaped connecting plate; 42, connecting spring; 43, square column; 44, ear seat; 45, pressing part; 46, fixing plate; 47, L-shaped lifting plate; 48, extension plate; 49, extension rod; 50, push rod; 51, guide ball; 52, guide plate; 53, guide rod; 54, positioning ring; 55, T-shaped plate; 56, guide hole; 57, support spring; 58, baffle. DETAILED DESCRIPTION

[0030] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application may be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0031] It should be noted that, unless otherwise specified, all technical and scientific terms used in this application have the same meanings as commonly understood by ordinary technicians in the technical field to which this application belongs.

[0032] In the present invention, unless otherwise specified, the directions used, such as "up" and "down", usually refer to the directions shown in the drawings, or to the vertical, perpendicular or gravity directions; similarly, for ease of understanding and description, "left" and "right" usually refer to the left and right shown in the drawings; "inside" and "outside" refer to the inside and outside relative to the outline of each component itself, but the above-mentioned directions are not used to limit the present invention.

[0033] For example, see Figure 1-12 , the present invention provides the following technical solutions:

[0034] A prefilled pen-type syringe, specifically, comprises an injection pen body 1; a fixed tube 2 is provided through and in communication with the inner bottom surface of the injection pen body 1, and a partition 3 is fixed inside the fixed tube 2; the partition 3 divides the inside of the injection pen body 1 into a working chamber 4 and a liquid storage chamber 5; a plurality of liquid extraction tubes 6 connected with the liquid storage chamber 5 are provided near the bottom of the fixed tube 2 on the circumferential side surface; a one-way valve is provided on the liquid extraction tube 6; a plurality of hemispherical seats 7 are evenly fixed on the circumferential side surface of the fixed tube 2 inside the working chamber 4; a spherical elastic reset airbag 8 is provided inside the hemispherical seat 7; an air delivery pipe 9 passing through the hemispherical seat 7 is provided between the spherical elastic reset airbag 8 and the fixed tube 2; sliding grooves 10 are symmetrically provided on both sides of the inner wall of the working chamber 4; an extrusion portion 11 is slidably provided on the sliding groove 10; a sliding hole 12 is provided on the surface of the partition 3; a piston portion 13 is slidably provided on the sliding hole 12; an injection portion 14 is sealed and clamped inside the fixed tube 2.

[0035] Working principle of the first embodiment:

[0036] By arranging a one-way valve on the liquid extraction tube 6, the liquid in the liquid storage chamber 5 can only be extracted into the fixed tube 2 through the liquid extraction tube 6, and the gas in the spherical elastic reset airbag 8 is pressed into the fixed tube 2 by the squeezing and squeezing part 11, thereby driving the piston part 13 to slide down along the fixed tube 2, and then injecting the liquid in the injection part 14 into the patient's body, replacing the traditional screw piston pressing injection method, reducing the use length of the pen-type syringe and making it easy to carry; through the linkage between the various components, quantitative extraction of liquid medicine is achieved, and only the disposable injection part 14 needs to be replaced, and the injection part 14 can be quickly installed and disassembled without disassembling the injection pen body 1, thereby improving the convenience of use.

[0037] For example 2, please refer to Figure 1-12 The second embodiment makes the following improvements on the basis of the first embodiment. Specifically, the extrusion portion 11 includes a slide plate 15 that slidably cooperates with the slide groove 10; a pressure plate 16 is fixed to one end of the slide plate 15, and a ball head 17 is fixed to the other end thereof; a return spring 18 is symmetrically fixed between the pressure plate 16 and the inner wall of the working chamber 4.

[0038] An air supply pipe 19 is provided through the top of the fixed pipe 2 ; a liquid supply pipe 20 is provided through the inner wall of the liquid storage chamber 5 ; and stop valves are provided on both the air supply pipe 19 and the liquid supply pipe 20 .

[0039] The liquid storage chamber 5 is replenished with liquid medicine by opening the stop valve on the liquid replenishment tube 20, and the fixed tube 2 is replenished with air by opening the stop valve on the air replenishment tube 19, so as to ensure that the air volume in the spherical elastic reset airbag 8 and the fixed tube 2 remains consistent.

[0040] An annular sealing groove 21 coaxial with the sliding hole 12 is formed on the bottom surface of the partition 3; the piston part 13 includes a piston 22; an annular sealing plate 23 plugged into the annular sealing groove 21 is fixed to the top of the piston 22; a tension spring 24 is fixed between the piston 22 and the top of the fixed tube 2.

[0041] A number of inner elastic sealing ribs 25 are evenly fixed on the inner wall of the fixed tube 2 in the liquid storage chamber 5 from top to bottom, and an inner sealing groove 26 connected to the end of each liquid extraction tube 6 is opened on its inner wall; the injection part 14 includes an injection tube 27 that slides with the fixed tube 2; an outer sealing groove 28 that matches the inner elastic sealing rib 25 is evenly opened on the outer peripheral side of the injection tube 27 from top to bottom; an outer elastic sealing rib 29 that matches the inner sealing groove 26 is fixed on the outer peripheral side of the fixed tube 2 near its bottom; a number of liquid inlet holes 30 that penetrate the outer elastic sealing rib 29 and are coaxial with the corresponding liquid extraction tube 6 are evenly opened on the outer peripheral side of the fixed tube 2.

[0042] A piston sleeve 31 adapted to the piston 22 is slidably provided on the inner wall of the injection tube 27; a rubber sleeve 32 is connected between the inner circumferential side surface of the injection tube 27 near its top and the piston sleeve 31; the injection part 14 also includes a needle seat 33; a threaded groove 34 threadedly connected to the injection tube 27 is provided on the surface of the needle seat 33; an injection needle 35 coaxially connected to the injection tube 27 is fixed at the bottom of the needle seat 33; a needle sleeve 36 is clamped at the bottom of the needle seat 33.

[0043] The surface of the needle seat 33 is symmetrically provided with concentric annular grooves 37, and both ends of the needle seat 33 are provided with insertion holes 38; an L-shaped seat 39 is symmetrically fixed to the bottom of the injection pen body 1; a plug rod 40 that is plugged and matched with the insertion hole 38 is slidably provided through the side of the L-shaped seat 39; an L-shaped connecting plate 41 is fixed to the end of the plug rod 40; a connecting spring 42 that is sleeved on the plug rod 40 is fixed between the L-shaped connecting plate 41 and the L-shaped seat 39; a square column 43 is fixed to the bottom of the injection pen body 1; an ear seat 44 is fixed to the bottom end of the square column 43; a pressing portion 45 that is rotatably matched with the annular groove 37 is slidably provided on the square column 43.

[0044] A fixing plate 46 is fixed to the side of the injection pen body 1; an L-shaped lifting plate 47 is slidably arranged inside the fixing plate 46; an extension plate 48 is fixed to the bottom of the L-shaped lifting plate 47; an extension rod 49 is symmetrically fixed to the bottom surface of the extension plate 48; a push rod 50 is fixed to the bottom surface of the extension plate 48 between the two extension rods 49; a guide ball 51 is fixed to the bottom end of the extension rod 49; a guide plate 52 is fixed to the side of the L-shaped connecting plate 41; one side of the guide plate 52 is arranged as an inclined surface; a baffle plate 58 is symmetrically fixed to the side of the injection pen body 1; a guide rod 53 slidably matched with the L-shaped connecting plate 41 is fixed to the side of the baffle plate 58; the pressing portion 45 includes a positioning ring 54 rotatably matched with the annular groove 37; a T-shaped plate 55 is fixed to the side surface of the positioning ring 54; a guide hole 56 slidably matched with the square column 43 is opened on the surface of the T-shaped plate 55; a support spring 57 sleeved on the square column 43 is fixed between the T-shaped plate 55 and the ear seat 44.

[0045] Working principle of the second embodiment:

[0046] During the injection process, hold the two sets of ball heads 17 and press them inward, so that the reset spring 18 is stretched, thereby driving the two sets of pressure plates 16 to slide together synchronously, pressing the corresponding spherical elastic reset airbags 8 into the corresponding hemispherical seats 7, and the air in the spherical elastic reset airbags 8 enters the fixed tube 2 through the air supply pipe 9, thereby driving the piston 22 and the piston sleeve 31 to slide down along the inner wall of the injection tube 27, and the corresponding rubber sleeve 32 is stretched, so that the liquid medicine in the injection tube 27 is injected into the patient's body through the injection needle 35.

[0047] The L-shaped lifting plate 47 is pressed by the thumb of the hand holding the ball head 17 to make it slide down along the fixed plate 46, so that the guide ball 51 slides down and squeezes the oblique side surface of the corresponding guide plate 52, so that the two groups of guide plates 52 slide away along the corresponding guide rods 53, so that the two insertion rods 40 are pulled out of the corresponding insertion holes 38, and the corresponding connecting springs 42 are compressed to release the fixed limit of the needle seat 33. During the continuous descending process of the L-shaped lifting plate 47, the guide ball 51 always slides on the oblique side surface of the corresponding guide plate 52, so that the push rod 50 gradually presses the T-shaped plate 55, thereby driving the positioning ring 54 to press the needle seat 33, so that the injection part 14 is separated from the fixed tube 2, and the discarded injection part 14 is taken out.

[0048] During the assembly process, the injection tube 27 on the new injection part 14 is inserted into the fixed tube 2. After the connection is completed, the inner elastic sealing ribs 25 of each group are snapped into the corresponding outer sealing grooves 28, and the outer elastic sealing ribs 29 are snapped into the inner sealing grooves 26. During this process, the piston sleeve 31 is sleeved on the piston 22, and the rubber sleeve 32 is stretched. The needle seat 33 is rotated so that the socket 38 and the corresponding insertion rod 40 are coaxially arranged. At this time, the liquid inlet hole 30 is connected to the corresponding liquid extraction tube 6. Release the thumb, and under the elastic reset force of the connecting spring 42, the insertion rod 40 is driven to be inserted into the corresponding socket 38 to complete the sealed connection between the injection part 14 and the fixed tube 2.

[0049] During the disassembly and assembly process of the injection unit 14 , the piston 22 is separated from the drug solution by the piston sleeve 31 and the rubber sleeve 32 , so as to prevent the piston 22 from directly contacting the drug solution and causing cross contamination before and after the injection unit 14 is replaced.

[0050] After the liquid extraction process and the completion of the sealed connection between the new injection part 14 and the fixed tube 2, the arm is turned so that the injection needle 35 is facing downward, so that the medicine in the liquid storage chamber 5 is immersed in each group of liquid extraction tubes 6, and the hand holding the ball head 17 is slowly released. Under the elastic reset force of the reset spring 18, the spherical elastic reset airbag 8 and the rubber sleeve 32, the two groups of extrusion parts 11 are driven to slide outward and reset, and the air in the fixed tube 2 is drawn back into each group of spherical elastic reset airbags 8 through the air supply pipe 9, thereby driving the piston 22 together with the piston sleeve 31 to slide and rise along the inner wall of the injection tube 27, so that the medicine in the liquid storage chamber 5 is drawn into the injection tube 27 through the liquid extraction tube 6, completing the quantitative extraction of the medicine.

[0051] Obviously, the above-described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0052] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0053] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the numbers used in this way can be interchanged where appropriate, so that the embodiments of the present application described herein can be implemented in an order other than those illustrated or described herein.

[0054] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

[0055] The above is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above embodiments. All technical solutions under the concept of the present invention belong to the protection scope of the present invention. It should be pointed out that for ordinary technicians in this technical field, some improvements and modifications without departing from the principle of the present invention should also be regarded as the protection scope of the present invention.

Claims

1. A prefilled pen-type injector, comprising an injection pen body (1); characterized in that: The inner bottom surface of the injection pen body (1) is provided with a fixed tube (2) penetrating and communicating therewith, and a partition (3) is fixed therein; the partition (3) divides the interior of the injection pen body (1) into a working chamber (4) and a liquid storage chamber (5); a plurality of liquid extraction tubes (6) communicating with the liquid storage chamber (5) are provided on the peripheral side surface of the fixed tube (2) near the bottom thereof; and a one-way valve is provided on the liquid extraction tube (6); A plurality of hemispherical seats (7) are evenly fixed on the side surface of the fixed tube (2) inside the working chamber (4); a spherical elastic reset airbag (8) is arranged inside the hemispherical seat (7); and an air supply pipe (9) penetrating the hemispherical seat (7) is arranged between the spherical elastic reset airbag (8) and the fixed tube (2); Slide grooves (10) are symmetrically provided on both sides of the inner wall of the working chamber (4); an extrusion portion (11) is slidably provided on the slide groove (10); a slide hole (12) is provided on the surface of the partition plate (3); a piston portion (13) is slidably provided on the slide hole (12); an injection portion (14) is sealed and clamped inside the fixed tube (2); The injection part (14) comprises an injection tube (27) which is slidably matched with the fixing tube (2); the injection part (14) further comprises a needle seat (33); the surface of the needle seat (33) is symmetrically provided with concentric annular grooves (37), and both ends thereof are provided with insertion holes (38); an L-shaped seat (39) is symmetrically fixed to the bottom of the injection pen body (1); a plug rod (40) which is plugged and matched with the insertion hole (38) is slidably provided through the side of the L-shaped seat (39); an L-shaped connecting plate (41) is fixed to the end of the plug rod (40); a connecting spring (42) which is sleeved on the plug rod (40) is fixed between the L-shaped connecting plate (41) and the L-shaped seat (39); a square column (43) is fixed to the bottom of the injection pen body (1); an ear seat (44) is fixed to the bottom end of the square column (43); a pressing portion (45) which is slidably provided on the square column (43) and is rotatably matched with the annular groove (37); A fixing plate (46) is fixed on the side of the injection pen body (1); an L-shaped lifting plate (47) is slidably provided inside the fixing plate (46); an extension plate (48) is fixed on the bottom of the L-shaped lifting plate (47); an extension rod (49) is symmetrically fixed on the bottom surface of the extension plate (48); a stop rod (50) is fixed on the bottom surface of the extension plate (48) between the two extension rods (49); a guide ball (51) is fixed at the bottom end of the extension rod (49); a guide plate (52) is fixed on the side of the L-shaped connecting plate (41); one side surface of the guide plate (52) is an inclined surface. The device is provided with a baffle (58) symmetrically fixed on the side of the injection pen body (1); a guide rod (53) slidably engaged with the L-shaped connecting plate (41) is fixed on the side of the baffle (58); the pressing portion (45) comprises a positioning ring (54) rotatably engaged with the annular groove (37); a T-shaped plate (55) is fixed on the side of the positioning ring (54); a guide hole (56) slidably engaged with the square column (43) is formed on the surface of the T-shaped plate (55); and a support spring (57) sleeved on the square column (43) is fixed between the T-shaped plate (55) and the ear seat (44).

2. A prefilled pen-type injector according to claim 1, characterized in that: The extrusion portion (11) comprises a slide plate (15) slidably engaged with the slide groove (10); a pressure plate (16) is fixed to one end of the slide plate (15), and a ball head (17) is fixed to the other end; a return spring (18) is symmetrically fixed between the pressure plate (16) and the inner wall of the working chamber (4).

3. A prefilled pen-type injector according to claim 2, characterized in that: An air supply pipe (19) is provided through the top of the fixed pipe (2); a liquid supply pipe (20) is provided through the inner wall of the liquid storage chamber (5); and stop valves are provided on both the air supply pipe (19) and the liquid supply pipe (20).

4. A prefilled pen-type injector according to claim 3, characterized in that: The bottom surface of the partition plate (3) is provided with an annular sealing groove (21) coaxial with the sliding hole (12); the piston portion (13) comprises a piston (22); an annular sealing plate (23) pluggably engaged with the annular sealing groove (21) is fixed to the top of the piston (22); and a tension spring (24) is fixed between the piston (22) and the top of the fixed tube (2).

5. A prefilled pen-type injector according to claim 4, characterized in that: A plurality of internal elastic sealing ribs (25) are evenly fixed on the inner wall of the fixed tube (2) in the liquid storage cavity (5) from top to bottom, and an internal sealing groove (26) communicating with the ends of each liquid extraction tube (6) is formed on the inner wall; The injection tube (27) is provided with an outer sealing groove (28) evenly spaced from top to bottom, which is compatible with the inner elastic sealing rib (25); the fixed tube (2) is provided with an outer elastic sealing rib (29) compatible with the inner sealing groove (26) fixed near its bottom on the outer peripheral side; the fixed tube (2) is provided with a plurality of liquid inlet holes (30) evenly spaced on the outer peripheral side, which penetrate the outer elastic sealing rib (29) and are coaxial with the corresponding liquid extraction tube (6).

6. A prefilled pen-type injector according to claim 5, characterized in that: The inner wall of the injection tube (27) is slidably provided with a piston sleeve (31) adapted to the piston (22); a rubber sleeve (32) is connected between the inner peripheral side surface of the injection tube (27) near the top thereof and the piston sleeve (31); The surface of the needle seat (33) is provided with a threaded groove (34) threadedly connected to the injection tube (27); an injection needle (35) coaxially connected to the injection tube (27) is fixed to the bottom of the needle seat (33); and a needle sleeve (36) is clamped and arranged at the bottom of the needle seat (33).

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