Medical syringe needle covers

Abstract

The present invention relates to a needle cover (2) for protecting a needle (3) attached to the tip (10) of a medical injection device, the tip (10) comprising a distal bulge (11), the needle cover comprising an inner needle shield (20) made of a material with elastomeric properties, the inner needle shield (20) comprising an inner seal portion (203b) configured to be in sealing contact with an outer surface (110) of the bulge (11), the inner seal portion (203b) comprising one or more ribs (205) extending inwardly along the periphery of the inner seal portion, at least one rib being a continuous rib in the form of a ring configured to provide continuous contact with the outer surface of the bulge.

Description

[Technical Field]

[0001] The present invention relates to a needle cover adapted to be attached to the tip of a medical injection device for covering a needle attached thereto. The present invention also relates to a medical assembly for use in delivering a medical composition to the body of a patient, the medical assembly including a medical injection device and a needle cover for enclosing a needle of the medical injection device. [Background technology]

[0002] Medical injection devices, such as syringes, typically include a container for containing a medical composition having a distal end in the form of a longitudinal tip that defines a fluid path through which the medical solution exits the container and / or reservoir, with a needle attached to the tip for piercing the skin of a patient to effect injection of the composition.

[0003] To prevent injury prior to end use, a needle cover is attached to the tip to surround the needle, preventing physical access to the needle by persons around the device. The needle cover may include an inner needle shield made of a material with elastomeric properties and an outer needle shield made of hard plastic that surrounds the inner needle shield.

[0004] The inner needle shield ensures a tight seal on the medical injection device. To that end, the inner needle shield includes a seal that sealingly contacts the outer surface of the bulge at the syringe tip to provide a tight seal. The inner needle shield prevents contamination of the medical composition from the external environment, thereby ensuring the integrity of the container seal. The inner needle shield also prevents leakage of the composition from the needle exit into the external environment. To that end, the needle preferably penetrates the inner needle shield.

[0005] A problem with known needle covers is that they can be relatively difficult to remove from the tip: to remove, the user must grasp both the injection device and the needle cover and pull on the needle cover with what can be significant effort.

[0006] The force required to remove a needle cover is measured by a physical parameter called "pull-out force" (acronym POF). The pull-out force required to remove known needle covers from injection devices such as syringes can be very high.

[0007] As a result, a user who is weakened and weakened, for example by an illness, may not be able to remove the needle shield and use the injection device for his treatment. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] European Patent Publication No. 1208861 Summary of the Invention

[0009] The present invention aims to provide a needle cover for a medical injection device that allows for reduced withdrawal force while tightly sealing the tip of the medical injection device.

[0010] To this end, one object of the present invention is a needle cover for protecting a needle attached to the tip of a medical injection device, the tip including a distal bulge, the needle cover including an inner needle shield made of a material having elastomeric properties, the inner needle shield including an inner seal portion configured to sealingly contact an outer surface of the bulge, the inner seal portion including one or more ribs extending inwardly along the periphery of the inner seal portion, at least one rib being a continuous rib in the form of a ring configured to make continuous contact with the outer surface of the bulge.

[0011] The one or more ribs on the inner seal portion provide an overall reduction in withdrawal force while maintaining the integrity of the container closure and the sealing ability of the inner needle shield against the tip of the medical injection device.

[0012] Other optional features of the needle cover include: The inner seal portion includes one, two, or three ribs, preferably one or two ribs, and more preferably two ribs. Three or fewer ribs significantly reduce the pull-out force compared to four or more ribs or no ribs. One or two ribs significantly reduce the pull-out force. Two ribs significantly reduce the pull-out force while providing two sealing barriers.

[0013] Each rib preferably has a rounded shape, with the rounded top of the rib flattening against the outer surface of the tip bulge, thereby improving pressure distribution across the surface contact area between the rib and the bulge, thereby further reducing pull-out forces.

[0014] The height of each rib is between 0.1 mm and 0.4 mm. The rib height is the distance between the base of the rib and the top of the rib, which is intended to contact the outer surface of the tip bulge. The above range defining small ribs leads to a minimum pull-out force compared to taller ribs.

[0015] Each rib extends inwardly in a direction perpendicular to the longitudinal axis of the needle shield.

[0016] Each rib is in the form of a continuous ring configured to provide continuous contact with the outer surface of the bulge.

[0017] The inner needle shield is made from any of the following materials with elastomeric properties: thermoplastic elastomers, elastomers, or rubbers.

[0018] When the inner shield portion includes two or three ribs, the distance between adjacent ribs is preferably comprised between 0.4 mm and 2.8 mm, more preferably between 0.4 mm and 1.2 mm.

[0019] At least one rib is in the form of a discontinuous ring configured to provide discontinuous contact with the outer surface of the bulge.

[0020] The continuous rib is rotationally symmetric about the axis of the needle cover.

[0021] The needle cover may include only an inner needle shield, or may further include an outer needle shield that at least partially surrounds the inner needle shield. The outer needle shield is preferably made of hard plastic.

[0022] Another purpose is A medical injection device, comprising: a body defining a container for containing a medical composition; a tip extending distally from the body, the tip defining a fluid path extending therethrough and in fluid communication with the container, the tip including a distal bulge; a needle attached to the distal end and in fluid communication with the fluid pathway; a medical injection device comprising: the needle cover as described above attached to the distal end of a medical injection device, wherein one or more ribs of the sealing portion of the inner needle shield are in sealing contact with the outer surface of the bulge; A medical assembly comprising:

[0023] According to another optional feature of the medical assembly: the tip further includes a proximal cylindrical portion located proximally of the distal bulge portion, the distal bulge portion having a larger diameter than the proximal cylindrical portion; The inner seal contacts the outer surface of the bulge, The tip of the medical injection device is made of glass. [Brief explanation of the drawings]

[0024] Further features and advantages of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings. [Figure 1A]FIG. 1A is a schematic view of an embodiment of an injection device without a needle cover and with a needle cover attached to the tip of the injection device, respectively. [Figure 1B] FIG. 1B is a schematic view of an embodiment of an injection device without a needle cover and with a needle cover attached to the tip of the injection device, respectively. [Figure 2] FIG. 2 is a cross-sectional view of a needle cover according to one embodiment. [Figure 3] 3 is a cross-sectional view of a medical assembly including a medical injection device and the needle cover of FIG. 2, where the needle cover is attached to the tip of the injection device to cover the needle (not shown). [Figure 4] FIG. 4 shows some structures of needle shields obtained by molding, with reference to M1, M2, M3. [Figure 5A] FIG. 5A is a tomographic view of the structure of FIG. 4 assembled into a medical injection device, FIG. 5A corresponding to design M3. [Figure 5B] FIG. 5B is a tomographic view of the structure of FIG. 4 assembled into a medical injection device, FIG. 5B corresponding to design M2. [Figure 5C] FIG. 5C is a tomographic view of the structure of FIG. 4 assembled into a medical injection device, and FIG. 5C corresponds to design M1. [Figure 6] FIG. 6 is a graph showing values ​​of pull-out force to remove the needle shield shown in FIGS. 5A-5C from the tip of a syringe. [Figure 7] FIG. 7 is a graph showing pressure decay when air is injected into a syringe having a needle covered with the needle shield shown in FIGS. 5A-5C. [Figure 8A] FIG. 8A shows various configurations of the shield portion of the needle shield. [Figure 8B] FIG. 8B shows various configurations of the shield portion of the needle shield. [Figure 8C] FIG. 8C shows various configurations of the shield portion of the needle shield. [Figure 8D]FIG. 8D shows various configurations of the shield portion of the needle shield. [Figure 8E] FIG. 8E shows various configurations of the shield portion of the needle shield. [Figure 8F] FIG. 8F shows various configurations of the shield portion of the needle shield. [Figure 8G] FIG. 8G shows various configurations of the shield portion of the needle shield. [Figure 8H] FIG. 8H shows various configurations of the shield portion of the needle shield. [Figure 8I] FIG. 8I shows various configurations of the shield portion of the needle shield. [Figure 8J] FIG. 8J shows various configurations of the shield portion of the needle shield. [Figure 8K] FIG. 8K shows various configurations of the shield portion of the needle shield. [Figure 9] FIG. 9 shows an example of the results obtained when the force required to remove the needle cover was recorded as a function of the displacement of the needle cover. DETAILED DESCRIPTION OF THE INVENTION

[0025] The present invention provides a needle cover that includes an inner needle shield configured to be attached to the tip of a medical injection device equipped with a needle to protect the needle.

[0026] When the needle cover is attached to the injection device, the combination of the needle cover and the injection device forms a medical assembly that prevents a user from coming into contact with the needle enclosed by the needle cover while protecting the needle from external contamination.

[0027] The medical injection device is preferably a syringe.

[0028] 1A, medical injection device 100 comprises a body 1 extending along a longitudinal axis A adapted to contain a medical composition to be injected, and a plunger rod 4 having a stopper 5 at its distal end. Plunger rod 4 is configured to move translationally within the body from a proximal position to a distal position to inject the composition.

[0029] Medical injection device 100 further comprises a distal tip 10 extending from the distal end of body 1 along axis A. Distal tip 10 is partially hollow so as to form a tube in fluid communication with the body.

[0030] A needle 3 is attached to the tip 10 of the injection device.

[0031] When the plunger rod 4 is actuated and moves from a proximal position to a distal position, the stopper 5 pushes the composition from the body 1 to the tip 10, causing the composition to flow through the needle 3 and be expelled from the injection device.

[0032] The medical injection device is preferably made of glass, more preferably a glass syringe. Such glass syringes are primarily used in hospital environments and are easily sterilized. The medical injection device is preferably a pre-filled syringe. The medical injection device is more preferably a syringe with a pre-inserted needle.

[0033] In known manner, the tip 10 of the injection device comprises a proximal cylindrical portion 12 and a distal bulge 11 located distally from the proximal cylindrical portion 12. Such a bulge is shown in Figure 3 and Figures 5A-5C.

[0034] The bulge 11 has a substantially circular cross section and is a radial extension of the generally rounded cylindrical portion 12. The bulge 11 projects radially from the distal proximal cylindrical portion 12 and includes an outer surface 110.

[0035] The bulge 11 is separated from the proximal cylindrical portion 12 by a shoulder 13 which provides a change in diameter along the tip 10, thereby separating the bulge 11 from the proximal cylindrical portion 12 of the tip.

[0036] The bulge is located at the distal end of the tip.

[0037] The needle cover 2 further comprises an inner needle shield 20. The inner needle shield is made of a material with elastomeric properties, such as a thermoplastic elastomer (TPE), elastomer, rubber, etc. A material with elastomeric properties that is sterilizable is preferred.

[0038] Compared to injection molded plastic syringes, the dimensions of glass syringes, particularly the tip dimensions, are less precisely controlled due to the manufacturing process for the syringes.

[0039] Materials with elastomeric properties are particularly suitable for sealing glass tips because they conform to the contours of the tip, a seal that is rarely achieved with hard plastic materials. A rigid inner shield is used to seal plastic tips with controlled outer dimensions.

[0040] The needle shield 20 is configured to be attached to the tip 10 of the medical injection device 100 such that the inner seal portion 203b of the inner needle shield contacts the outer surface 110 of the bulge. Figure 1B shows the syringe of Figure 1A with the needle cover 2 attached to the tip of the syringe, thus forming a medical assembly 300. Figures 2 and 3 also show embodiments of the needle cover 2 separated from the injection device 100 and attached to the tip 10 of the injection device 100, respectively.

[0041] More specifically, the inner sealing portion 203b of the inner needle shield 20 is configured to tightly and sealingly contact the outer surface 110 of the bulge 11. In this way, the inner sealing portion performs two sealing functions: preventing the medical composition contained in the medical injection device from leaking out, and preventing external contaminants from entering the medical injection device to maintain the integrity of the medical injection device.

[0042] In accordance with the present invention, the inner seal portion 203b of the inner needle shield 20 includes one or more ribs 205 extending inwardly around the periphery of the inner seal portion 203b. In other words, the ribs 205 extend radially from the inner surface 204 of the inner seal portion 203b toward the outer surface 110 of the bulge 11 so as to sealingly contact the bulge.

[0043] Thus, contact surface areas are formed between the ribs 205 and the outer surface 110 of the bulge 11. Each contact surface area, for each rib, substantially forms a circle that extends continuously or discontinuously around the bulge.

[0044] A "continuous rib" is a rib that extends continuously around the circumference of the housing to form an uninterrupted ring, thereby providing continuous contact with the outer surface of the bulge.

[0045] In contrast, a "discontinuous rib" is a rib that extends discontinuously around the circumference of the inner seal portion with one or more interruptions to form an open ring or at least two distinct portions of a ring, thereby providing discontinuous contact with the outer surface of the bulge.

[0046] At least one rib 205 is a continuous rib configured to provide continuous contact with the exterior surface 110 of the bulge 11. If present, other ribs 205 may be continuous or discontinuous. The presence of at least one continuous rib ensures the integrity of the container closure while preventing leak paths.

[0047] The continuous rib is preferably rotationally symmetrical about the axis B of the needle cover (which coincides with the axis A of the injection device). In other words, the continuous rib is symmetrical at each point relative to the axis of the needle cover. The bulge is also rotationally symmetrical about the axis of the tip which coincides with the axis B of the needle cover.

[0048] The one or more ribs 205 of the inner seal portion 203 reduce the surface contact area between the needle cover 2 and the tip 10 of the injection device and modify the contact pressure profile along this surface contact. Furthermore, the ribs 205 can locally increase the contact pressure at such surface contact area. This surprisingly results in an overall reduction in withdrawal force while maintaining the integrity of the container closure and the sealing performance of the needle cover against the tip of the medical injection device.

[0049] This result is unexpected, especially since the reduced surface contact between the inner shield portion 203b and the bulge 11 due to the presence of ribs can generally be associated with reduced sealing performance. Contrary to the present invention, conventional needle shields made of materials with elastomeric properties typically present a smooth sealing portion.

[0050] The needle cover 2 further includes an outer needle shield 21 that at least partially surrounds the inner needle shield 20, thereby surrounding and protecting the inner needle shield. To that end, the outer needle shield 21 is preferably made of a rigid material. According to a preferred embodiment, the outer needle shield 21 is made of hard plastic.

[0051] According to the embodiment shown in FIGS. 2 and 3, the inner needle shield 20 includes a closed distal end 202 and an open proximal end 201 .

[0052] Inner needle shield 20 further includes an inner surface 204. Inner surface 204 preferably has a circular cross-section.

[0053] The inner needle shield 20 includes multiple sections that are distinct sections.

[0054] A first portion 203a extends from the open proximal end 201 to a more distal region of the inner needle shield 20. The first portion 203a preferably has a larger diameter than the rest of the inner needle shield.

[0055] The second portion 203b is the inner seal portion described in detail above and preferably has a reduced section compared to the first portion 203a. The inner seal portion extends from the first portion 203a to a more distal region of the inner needle shield.

[0056] A third portion 203 c preferably tapers from the second portion 203 b to the distal end of the inner needle shield 20 .

[0057] The first portion 203a is configured to accommodate the proximal tip portion 12. The second portion 203b, which is the inner seal portion, is configured to make sealing contact with the bulge 11. The third portion 203c is configured to accommodate the needle 3. More specifically, the third portion 203c is configured to allow the needle 3 to penetrate a distal portion of the third portion.

[0058] The inner seal portion 203b includes at least one rib 205, three ribs are shown on the needle shield in Figures 2 and 3, which extend radially inwardly around the periphery of the inner seal portion.

[0059] If the inner sealing portion 203b includes several ribs, the ribs 205 are preferably parallel to one another.

[0060] The three ribs in Figures 2 and 3 are continuous ribs configured to provide continuous contact with the outer surface of the bulge, although it should be noted that only one or two of the three ribs may be continuous.

[0061] At least one rib 205 is configured to sealingly contact the outer surface of the bulge. In a preferred embodiment, two ribs 205 are configured to sealingly contact the outer surface 110 of the bulge 11. In the embodiment shown, three ribs are configured to sealingly contact the outer surface 110 of the bulge 11. As shown in Figure 3, when the needle cover 2 is attached to the tip 10 of the injection device, the bulge 11 is positioned against the second part 203b of the housing and the tops of the ribs 205 contact the outer surface 110 of the bulge.

[0062] The ribs 205 are configured to exert radial pressure against the bulge 11. The total pressure exerted by the ribs on the bulge can be controlled by adjusting several parameters, including the cross-section of the inner seal portion 203b relative to the cross-section of the bulge 11, the dimensions of each rib 205, the number of ribs, and the distance between adjacent ribs. Some of these parameters are described in more detail below in light of example tests.

[0063] The ribs 205 are preferably integrally formed with the inner needle shield 20 and are advantageously made from the same material as the inner needle shield.

[0064] According to a preferred embodiment, the ribs 205 have a rounded shape, i.e., their tops are curved and point inward toward the longitudinal axis of the needle cover. As such, when contacting the bulge 11, the rounded tops of the ribs flatten against the outer surface of the tip bulge, thereby improving pressure distribution across the surface contact area between the ribs 205 and the bulge 11, thereby further reducing the withdrawal force. This flattening is made possible by the elastomeric properties of the inner shield and is not obtainable with rigid materials.

[0065] According to one embodiment, the distance between adjacent ribs is between 0.4 mm and 2.8 mm, preferably between 0.4 mm and 1.2 mm. This range of distances provides the most significant reduction in pull-out force. This distance is the spacing between the tops of the ribs, designated "G" in Figures 8A and 8E.

[0066] As with all other dimensions of the inner needle shield, the distance between two adjacent ribs is measured when the inner needle shield is not attached to the syringe tip. In practice, when the inner needle shield is attached to the syringe tip, the ribs will lie flat against the bulge, and the dimensions of the ribs may differ compared to the dimensions of the ribs when the inner needle shield is not inserted into the syringe tip.

[0067] According to one embodiment, the rib height H, which is the distance between the base of the rib and the top of the rib, is between 0.1 mm and 0.4 mm, this height range providing the most significant reduction in pull-out force.

[0068] According to one embodiment, the radius R of the rib at the base of the rib is between 0.1 mm and 0.4 mm to provide the most significant reduction in pull-out force.

[0069] Although the inner needle shield of the present invention has been described with reference to the figures, the present invention is not limited to the embodiments shown in the figures. For example, the needle cover may have a shape different from that described with reference to the figures. Furthermore, the first portion 203a and / or the third portion 203c of the inner needle shield may have a shape different from that shown in the figures.

[0070] For example, according to some embodiments, the first portion 203a of the inner needle shield 20 may further include an anti-jump rib, as disclosed in U.S. Patent No. 5,629,999, to prevent the needle shield from coming off the tip of the injection device during sterilization.

[0071] When present, the anti-ejection rib extends inwardly along the circumference of the inner surface 204 of the first portion 203a of the inner needle shield 20 that is intended to contact the proximal cylindrical portion 12 of the tip 10. Additionally, the anti-ejection rib is positioned proximally relative to the inner seal portion 203b and shoulder 13 and is configured to contact the proximal cylindrical portion 12.

[0072] More specifically, the anti-jump-out rib is configured to abut the shoulder 13 when the needle cover 2 moves distally relative to the tip 10 of the medical injection device, thereby preventing the inner needle shield 20 from disengaging from the tip 10.

[0073] One embodiment of an anti-jump rib is disclosed in U.S. Patent No. 5,623,666. In this document, when the needle cover is attached to the injection device, the anti-jump rib is located proximally from the shoulder between the bulge and the main portion of the tip of the injection device. The rib is intended to hold the needle shield at the tip during sterilization, which can involve significant changes in pressure between the sterilization chamber and the housing.

[0074] The anti-jump ribs in Patent Document 1 are not located on the inner seal portion 203b intended to contact the bulge 11 of the tip 10. In fact, those skilled in the art would not conventionally modify the inner seal portion 203b because the ribs are intended to ensure the sealing of the needle cover 2. As a result, in Patent Document 1, the inner surface of the inner seal portion is smooth, which reflects common knowledge in the art of sealing, as opposed to the ribbed surface of the present invention.

[0075] Example: Examining various needle shield constructions Example 1 Three different constructions of inner needle shields 20, labeled M, are molded from a thermoplastic elastomer. These inner needle shields are shown in Figure 4. The characteristics of these needle shields are described below and in Table 1.

[0076] [Table 1]

[0077] "Radius" (R) refers to the radius (width) of each rib, "height" (H) refers to the height of each rib, "spacing" (G) refers to the distance between two adjacent ribs, and "D" refers to the inner diameter of the inner needle shield at the inner seal portion. For ribbed structures, the diameter is measured at the top of the rib when the inner needle shield is not inserted into the syringe tip, as shown in Figure 4. For all structures M1, M2, and M3, the needle shield is TPE and the injection device is a glass syringe.

[0078] The structures M1, M2, M3 shown in Figure 4 will be described with reference also to Figures 5A-5C, which correspond to cross-sectional views of the structures M1, M2, M3 of Figure 4 assembled into a syringe tip by a compression bench.

[0079] M3 (FIG. 5A) is the current state-of-the-art needle shield. Such needle shield does not include ribs, i.e., the inner sealing portion 203b is a smooth surface.

[0080] M2 (FIG. 5B) is a needle shield according to the present invention, which includes an inner seal portion 203b with four small ribs 205. The surface contact area between the inner seal portion 203b and the bulge 11 is defined by a plurality of small contact zones 6 between the ribs 205 and the bulge 11. The presence of the ribs ensures that the contact pressure in the non-ribbed areas is zero, or at least significantly reduced in the non-ribbed areas if the surfaces remain in contact (and thus the pressure acting on the bulge is negligible). This reduces the withdrawal force.

[0081] M1 (FIG. 5C) is a needle shield according to the present invention, including an inner seal portion 203b with three large ribs 205. The surface contact area between the inner seal portion 203b and the bulge 11 is defined by multiple small contact zones 6 between the ribs 205 and the bulge 11. This is generally similar to M2 (FIG. 5B), except that the ribs are larger, with a larger radius and height. The surface contact area is reduced compared to the standard, known structure M3. The presence of the ribs eliminates or significantly reduces the contact pressure in the non-ribbed areas, reducing the pull-out force. However, the ribs are taller than those of M2, and the ribs are less flattened at the bulge, resulting in a smaller surface contact area than that of M2.

[0082] Needle shields M1 and M2, which have ribs on the inner seal portion 203b, exhibit reduced pull-out forces compared to needle shield M3, which does not have ribs on the inner seal portion 203b.

[0083] 1. Measurement of pull-out force The force required to remove the needle cover from the syringe is measured over 30 tests. The tests are performed using a traction bench. The method involves the following steps: Place the syringe in the holder The needle cover is held in place by the air pressure press, and then The needle cover is removed by pulling it at a constant displacement rate.

[0084] The force required to remove the needle cover is recorded as a function of the needle cover displacement. As shown in Figure 9, the force required to remove the needle cover increases at the beginning of the needle cover movement until it reaches a maximum value, called the "POF value" in Figure 9, which corresponds to the pull-out force.

[0085] The pull-out force measured by this method is shown in Table 2 and is also shown in the graph of FIG.

[0086] [Table 2]

[0087] These results show that the presence of ribs significantly reduces the pull-out force. In fact, the pull-out force of the ribbed structures M1 (large ribs) and M2 (small ribs) is reduced by approximately 6 Newtons (40%) compared to the standard structure M3 (no ribs). Also, the standard deviation StDev tends to be lower for the ribbed structures M1 and M2 compared to the standard structure M3.

[0088] The pull-out force values ​​of ribbed structures M1 (POF=10,6) and M2 (POF=11,5) are very close to each other, so the difference between large and small ribs is not significant.

[0089] The presence of ribs reduces the pull-out force regardless of the shape or size of the ribs.

[0090] 2.Leak test pressure To evaluate the sealing performance of needle shields with ribs on the inner sealing portion, 15 leak tests were conducted.

[0091] The leak test was performed as follows: an empty pre-filled syringe was fitted with the needle covers M1, M2 and M3 shown in Figure 4. Pressure was applied to the empty syringe barrel for a defined time (1.1 bar for 5 seconds). The pressure decay in the cylinder was measured at the same time. If there is a leak at the interface between the needle cover and the syringe tip, a large pressure decay will be measured. The test complies with the pressure conditions specified in standard 11040-4:2015(E).

[0092] The results are shown in the graph of FIG.

[0093] The results show that all designs (including the known reference design M3) provide very low pressure attenuation values ​​between 0 and 2 Pa. Therefore, optimal sealing of the syringe tip is maintained by the presence of the ribs, regardless of the width and height of the ribs. The sealing performance of the needle shield against the tip of the medical injection device is maintained.

[0094] Example 2: Development of various structures for the sealing surface of the needle cover A finite element analysis was performed to investigate the effect of the size and number of ribs on the pull-out force. This analysis uses the material properties of a thermoplastic elastomer (similar to the material molded in Example 1). The removal of the needle cover was simulated and the pull-out force was calculated.

[0095] The simulated structure of the needle cover seal is shown in Table 3 below.

[0096] [Table 3]

[0097] Trials 1 and 2 correspond to structures M1 and M2, respectively, described above in Example 1.

[0098] Trials 3 and 4 correspond to structure M1, but the radius R of each rib is 0.55 mm in trial 3 and 0.2 mm in trial 4, rather than 0.4 mm. These trials allow the evaluation of the effect of rib width (compared to structure M1) on the pull-out force.

[0099] Trial 5 corresponds to structure M1, but the spacing G between two adjacent ribs is 0.8 mm instead of 1.07 mm, and the contact area consists of four ribs instead of three.

[0100] Trial 6 corresponds to structure M1, but the spacing G between two adjacent ribs is 1.07 mm instead of 0.71 mm, and the contact area consists of two ribs instead of four.

[0101] Trial 7 corresponds to structure M1, but the contact area consists of only one rib instead of four.

[0102] In both trials 6 and 7, the effect of the number of ribs on the pull-out force (compared to structure M1) can be evaluated.

[0103] Trial 8 corresponds to structure M1, but the contact area consists of only one rib instead of four, and this one rib is the rib from Trial 4 (R = 0.2 mm).

[0104] Trial 9 corresponds to design M1, but with each rib having a height of 0.35 mm instead of 0.25 mm. This trial allows for the evaluation of the effect of rib height (compared to structure M1) on the pull-out force.

[0105] Trial 10 corresponds to structure M1, but the inner diameter of each rib is 3.60 mm instead of 3.80 mm.

[0106] Trial 11 corresponds to structure M2, but the contact area is a perfect sinusoidal shape. This trial allows evaluation of the pull-out force when the inner surface of the sinusoidal shape does not contact the syringe tip.

[0107] 1. Effect of rib characteristics on pull-out force The calculated pull-out force values ​​for the 11 trial structures described above are shown in Table 4.

[0108] [Table 4]

[0109] a) Effect of rib width (radius) on pull-out force As shown in Table 4, comparing Trial 1 and Trial 3, when the rib width increases from 0.4 mm in Trial 1 (M1) to 0.55 mm in Trial 3, the pull-out force decreases slightly from 11.3 Newtons to 11.1 Newtons.

[0110] Comparing Trial 1 and Trial 4, when the width is reduced from 0.4 mm in Trial 1 (M1) to 0.2 mm in Trial 4, the pull-out force decreases slightly from 11.3 Newtons to 10.8 Newtons.

[0111] The reduction in pull-out force is very small in trials 3 and 4 and occurs both when the width is increased and decreased relative to M1.

[0112] Therefore, the width of the rib does not significantly affect the pull-out force.

[0113] b) Effect of number of ribs on pull-out force As shown in Table 4, comparing Trial 2 and Trial 6, when the number of ribs is reduced from 4 to 2, the pull-out force decreases from 12.1 Newtons to 7.0 Newtons.

[0114] Comparing trial 2 and trial 7, when the number of ribs is reduced from four to one, the pull-out force decreases from 12.1 Newtons to 7.0 Newtons.

[0115] Therefore, by reducing the number of ribs, the pull-out force is reduced and vice versa.

[0116] A low number of ribs, especially between one and three, and especially one or two ribs, is preferred as it results in low pull-out force values.

[0117] c) Effect of rib height on pull-out force As shown in Table 4, comparing Trial 1 and Trial 9, when the height of each rib increases from 0.25 mm to 0.35 mm, the pull-out force increases from 11.3 Newtons to 15.3 Newtons.

[0118] Therefore, increasing the height of the rib increases the pull-out force.

[0119] Ribs with a low height, especially between 0.1mm and 0.4mm in height, are preferred as they result in low pull-out force values.

[0120] 2. Effect of needle shield material on withdrawal force To investigate the influence of the material properties of the needle shield, the pull-out forces of several materials were simulated by finite element analysis.

[0121] TPE is the material used in section 1 above.

[0122] Next, three rubbers with different properties were simulated: Rubber 1 is styrene butadiene rubber, Rubber 2 is synthetic isoprene rubber, and Rubber 3 is natural rubber.

[0123] Only four structures are evaluated out of the 11 structures in Tables 3 and 4. The pull-out force values ​​for the four structures and four materials are shown in Table 5.

[0124] [Table 5]

[0125] As shown in Table 5, the results previously described in Example 1, Part 1 and Example 2, Parts 1a), 1b), and 1c) are confirmed regardless of the elastomeric properties of the needle shield. Indeed, regardless of whether the inner needle shield material is TPE, Rubber 1, Rubber 2, or Rubber 3, the ribbed structure (Trial 1) (with ribs) exhibits a lower pullout force than the standard structure (without ribs). Regardless of whether the needle shield material is TPE, Rubber 1, Rubber 2, or Rubber 3, the structure (Trial 6) with fewer ribs (M1, with only two ribs) exhibits a lower pullout force than the structure (Trial 1) with more ribs (M1, with three ribs). Regardless of whether the needle shield material is TPE, Rubber 1, Rubber 2, or Rubber 3, the structure (Trial 9) with a higher rib height (M1, with H = 0.35 mm) exhibits a higher pullout force than the structure (Trial 1) with a lower rib height (M1, with H = 0.25 mm).

Claims

1. 1. A needle cover (2) for protecting a needle (3) attached to a tip (10) of a medical injection device (100), the tip (10) of the medical injection device (100) including a distal bulge (11), the needle cover including an inner needle shield (20) made of a material having elastomeric properties, the inner needle shield (20) including an inner seal portion (203b) configured to make sealing contact with an outer surface (110) of the bulge (11), the inner seal portion (203b) including a plurality of ribs (205) extending inwardly along the periphery of the inner seal portion, each rib (205) being a continuous rib in the form of a continuous ring configured to make continuous contact with the outer surface (110) of the bulge (11), and each rib (205) having a height of between 0.1 mm and 0.4 mm.

2. 2. The needle cover (2) according to claim 1, characterized in that the inner sealing portion (203b) comprises two or three ribs (205).

3. Needle cover (2) according to claim 1 or 2, characterized in that each rib (205) has a rounded shape.

4. A needle cover (2) according to any one of claims 1 to 3, characterized in that each rib (205) extends inwards in a direction perpendicular to the longitudinal axis (B) of the inner needle shield.

5. Needle cover (2) according to any of the preceding claims, characterized in that the material with elastomeric properties is a thermoplastic elastomer, an elastomer or a rubber.

6. 6. The needle cover (2) according to any one of claims 1 to 5, characterized in that the inner sealing portion (203b) comprises two or three ribs (205), and the distance (G) between adjacent ribs is comprised between 0.4 mm and 2.8 mm.

7. Needle cover (2) according to any one of the preceding claims, characterized in that the continuous rib is rotationally symmetrical about the axis (B) of the needle cover.

8. A needle cover (2) according to any one of the preceding claims, further comprising an outer needle shield (21) at least partially surrounding the inner needle shield (20).

9. A medical injection device (100), comprising: a body (1) defining a container for containing a medical composition; a tip (10) extending distally from the body, the tip (10) defining a fluid path extending therethrough and in fluid communication with a container, the tip (10) including a distal bulge (11); a needle (3) attached to the tip and in fluid communication with the fluid pathway; a medical injection device (100) comprising:

9. A needle cover (2) according to any one of claims 1 to 8, attached to the tip (10) of the medical injection device, wherein a plurality of ribs (205) of the inner seal portion (203b) of the inner needle shield (20) are in sealing contact with the outer surface (110) of the bulge (11), each rib (205) being a continuous rib in the form of a continuous ring configured to make continuous contact with the outer surface (110) of the bulge (11), each rib (205) having a height between 0.1 mm and 0.4 mm; A medical assembly (300) comprising:

10. 10. The medical assembly (300) of claim 9, wherein the tip (10) of the medical injection device is made of glass.

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