Abstract
An injection needle assembly (50) for an injection device, comprising: a) a needle cannula (3) attached to a needle hub (4) and defining a pointed tip at a free end (3a, 3b), and b) a needle cover (10, 10a, 10b) forming an axially extending elongated flexible enclosure accommodating the needle cannula (3). The needle cover (10, 10a, 10b) is configured to axially collapse and become penetrated by the needle cannula (3) when a penetration force is applied to the needle cover. The needle cover (10, 10a, 10b) defines a shaft section (11a) and a bulb section (11b). The shaft section (11a) encircles the needle cannula (3) and extends axially from the needle hub (4) to the bulb section (11b). The shaft section (11a) comprises a collapsible wall area (15) having wall thickness t.sub.1 less than a predefined wall thickness t.sub.1,lim to provide radial deformability for abutting contact with the needle cannula (3). The bulb section (11b) comprises a wall area (17a, 17b) having a wall thickness t.sub.2 being greater than said predefined wall thickness t.sub.1,lim, and further defines a central end wall area (20) having a wall thickness t.sub.3 smaller than the wall thickness t.sub.2. In an initial non-penet-rated state, the needle cover (10, 10a, 10b) assumes a first configuration wherein the wall areas of the bulb section (11b) and the wall areas of the shaft section (11a) are spaced apart from the needle cannula (3).
Claims
1. An injection needle assembly for an injection device, comprising: a needle cannula attached to a needle hub, the needle cannula extending along an axis from the needle hub towards a free end, and a flexible needle cover forming an axially extending elongated enclosure accommodating the needle cannula, wherein the needle cover has a needle hub end mounted relative to the needle hub and a free end extending beyond the free end of the needle cannula, the needle cover being configured to axially collapse for being penetrated by the needle cannula when an axially directed penetration force is applied on the free end of the needle cover towards the needle hub, the needle cover defining: an elongated shaft section encircling the needle cannula and having a first axial end at the needle hub and a second axial end located axially between the needle hub and the free end of the needle cannula, the shaft section comprising a collapsible wall area that is radially deformable for abutting contact with the needle cannula, the collapsible area comprising an area having wall thickness t.sub.1 less than a predefined wall thickness t.sub.1,lim, and a bulb section connected to the second axial end of the shaft section and extending to a closed end surface at the free end of the needle cover, wherein the bulb section defines a bulb wall area axially overlapping and encircling the free end of the needle cannula wherein the bulb wall area comprises a wall area having wall thickness of at least t.sub.2, wherein t.sub.2 is greater than said predefined wall thickness t.sub.i,lim, and wherein the bulb section defines a central end wall area having a wall thickness t.sub.3 smaller than the wall thickness t.sub.2, wherein the needle cover, in an initial non-penetrated state, assumes a first configuration wherein the wall areas of the bulb section and the wall areas of the shaft section are spaced apart from the needle cannula.
2. An injection needle assembly as defined in claim 1, wherein the free end of the needle cannula is provided with a beveled portion that defines a pointed tip and a heel and wherein said bulb wall area of the bulb section having wall thickness of at least t.sub.2 comprises an annular bulb region that axially overlaps the heel of the bevel when the needle cover assumes the first configuration.
3. An injection needle assembly as defined in claim 2, wherein, when the needle cover assumes the first configuration, the second axial end of the shaft section is located between 0.2 to 2.0 mm from the heel, and wherein said annular bulb region having wall thickness at least t.sub.2 extends axially from the second axial end of the shaft section and axially overlaps the heel of the bevel.
4. An injection needle assembly as defined in claim 2, wherein the wall area of the shaft section having wall thickness t.sub.1 less than the predefined wall thickness t.sub.1,lim connects to said annular bulb region.
5. An injection needle assembly as defined in claim 1 4, wherein t.sub.2 defines a wall thickness greater than 0.4 mm.
6. An injection needle assembly as defined in claim 1, wherein the bulb wall area defines a first annular bulb region and a second annular bulb region, the first and the second bulb regions comprising wall areas having wall thicknesses of at least t.sub.2, and wherein an annular region of reduced wall thickness between 0.15 to 0.35 mm separates the first annular bulb region and second annular bulb region.
7. An injection needle assembly as defined in claim 6, wherein said annular region of the bulb section having reduced wall thickness is axially overlapping the pointed tip of the bevel.
8. An injection needle assembly as defined in claim 1, wherein the bulb section comprises an annular region with a radially outwards facing surface that tapers into a larger diameter towards the free end of the needle cover and wherein a generally flat end surface is arranged at the extreme exterior end surface of the free end of the needle cover.
9. An injection needle assembly as defined in claim 1, wherein at least a portion of said needle cover is spark eroded with a VDI less than 15.
10. An injection needle assembly as defined in claim 1, wherein the needle cover, in the first configuration, comprises a radially inwards facing surface with a diameter within the range 1.5 to 4 mm.
11. An injection needle assembly as defined in claim 1, wherein the predefined wall thickness t.sub.1,lim is selected between 0.12 and 0.3 mm.
12. An injection needle assembly as defined in claim 1, wherein the shaft section comprises one or more reinforcing ribs having a wall thickness greater than 1.5 times t.sub.1,lim, such as greater than 0.4 mm.
13. An injection device comprising an injection needle assembly as defined in claim 1, the injection device further comprising a needle shield with a needle opening, the needle shield and the injection needle assembly being arranged axially slidably relative to each other for causing the needle cannula to penetrate the needle cover and protrude through the needle opening of the needle shield.
14. An injection device as defined in claim 13, wherein the injection device is configured as an auto-injector that is triggerable by relative movement between the needle shield and the injection needle assembly and wherein the needle shield is configured to act on the needle cover for causing the needle cover to be penetrated by the needle cannula.
15. An injection device as defined in claim 13, wherein radially outwards facing surfaces of the shaft section and the bulb section of the needle cover is radially spaced apart from the needle shield at least as the needle shield and the injection needle assembly slides relative to each other for causing the needle cannula to penetrate the needle cover.
16. An injection needle assembly as defined in claim 2, wherein, when the needle cover assumes the first configuration, the second axial end of the shaft section is located between 0.4 to 0.8 mm from the heel and wherein said annular bulb region having wall thickness at least t.sub.2 extends axially from the second axial end of the shaft section and axially overlaps the heel of the bevel.
17. An injection needle assembly as defined in claim 1, wherein t.sub.2 defines a wall thickness greater than 0.5 mm.
18. An injection needle assembly as defined in claim 1, wherein t.sub.2 defines a wall thickness greater than 0.6 mm.
19. An injection needle assembly as defined in claim 1, wherein t.sub.2 defines a wall thickness greater than 0.7 mm.
20. An injection needle assembly as defined in claim 1, wherein the bulb wall area defines a first annular bulb region and a second annular bulb region, the first and the second bulb regions comprising wall areas having wall thicknesses of at least t.sub.2, and wherein an annular region of reduced wall thickness between 0.18 to 0.25 mm separates the first annular bulb region and second annular bulb region.
21. An injection needle assembly as defined in claim 1, wherein at least a portion of said needle cover is polished.
22. An injection needle assembly as defined in claim 1, wherein at least a portion of said needle cover is spark eroded with an A3 polishing.
23. An injection needle assembly as defined in claim 1, wherein the needle cover in the first configuration, comprises a radially inwards facing surface with a diameter within the range 2.2 to 3.0 mm.
24. An injection needle assembly as defined in claim 1, wherein the needle cover in the first configuration, comprises a radially inwards facing surface with a diameter within the range 2.4 to 2.6 mm.
25. An injection needle assembly as defined in claim 1, wherein the predefined wall thickness t.sub.1,lim is selected between 0.15 and 0.25 mm, and more.
26. An injection needle assembly as defined in claim 1, wherein the predefined wall thickness t.sub.1,lim is selected between 0.17 and 0.20 mm.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0082] In the following, the invention will be described in greater detail with reference to embodiments shown by the enclosed figures. It should be emphasized that the embodiments shown are used for example purposes only and should not be used to limit the scope of the invention.
[0083] FIG. 1 shows a sectional side view of one example of an injection device suitable for incorporation of a needle assembly in accordance with the present invention, the needle assembly being in an initial shielded state,
[0084] FIG. 2 shows a sectional side view of the injection device of FIG. 1 in a state where the distal end of the needle fully protrudes from a needle shield,
[0085] FIG. 3 shows a sectional side view of the injection device of FIG. 1 in a state where a cartridge has been connected to the proximal end of the needle for fluid delivery and wherein expelling has been initiated,
[0086] FIG. 4 shows a sectional side view of the injection device of FIG. 1 in a state where the needle shield has returned to its original position to put the needle into a shielded state again,
[0087] FIGS. 5a-5d respectively show a perspective rear view, a perspective front view, a cross sectional side view and a perspective cross sectional view of a first embodiment of a needle cover in accordance with the present invention,
[0088] FIG. 6 shows schematically a cross sectional side view of the tip portion of an injection needle and its needle cover during steam sterilization,
[0089] FIG. 7 shows a cross sectional side view of the front portion of a first embodiment of an injection device incorporating a needle assembly according to the invention,
[0090] FIG. 8 shows a side view of deformation of a rear needle cover as it cooperates with a distal part of a cartridge,
[0091] FIGS. 9a-9d respectively show a perspective rear view, a perspective front view, a cross sectional side view and a perspective cross sectional view of a second embodiment of a needle cover in accordance with the present invention,
[0092] FIGS. 10a-10d respectively show a perspective sectional rear view, a perspective front view, a side view and a cross sectional side view of a third embodiment of a needle cover in accordance with the present invention,
[0093] FIGS. 11a-11d respectively show a perspective sectional rear view, a perspective front view, a side view and a cross sectional side view of a fourth embodiment of a needle cover in accordance with the present invention,
[0094] FIGS. 12a-12d respectively show a perspective rear view, a perspective front view, a cross sectional side view and a perspective cross sectional view of a fifth embodiment of a needle cover in accordance with the present invention, and
[0095] FIGS. 13a-13d respectively show a perspective rear view, a perspective front view, a cross sectional side view and a perspective cross sectional view of a sixth embodiment of a needle cover in accordance with the present invention.
DETAILED DESCRIPTION OF THE EMBODIMENTS
[0096] FIGS. 1 to 4 illustrate operational states for an example injection device which incorporates a needle assembly in accordance with the present invention. The injection device is shown in four different states of operation in order to explain the basic function of the device.
[0097] It is to be noted that the shown injection device forms a non-limiting example and that the needle assembly of the present invention can be used together with other types of injection devices. All the details of the shown injection device will not be described in detail since these details have already been described in other patent specifications of the applicant. Reference is made to these other specifications for additional details.
[0098] FIGS. 1 to 4 show an injection device 1 with a medicament containing cartridge 2, an injection needle provided as a needle cannula 3 having a proximal end 3a and a distal end 3b, a needle hub 4, a needle shield 5, a housing 6 and an expelling assembly 7. The details of the expelling assembly will not be further described in this specification since the needle assembly of the present invention will work with many different types of expelling assemblies.
[0099] In the shown embodiment, in the shielded state as shown in FIG. 1, the distal end of the needle shield 5 is arranged distally to the distal end 3b of the needle. In this way, the needle is completely shielded by the needle shield. It can also be seen that in the current embodiment, the needle shield 5 is a single element which completely encases the needle assembly.
[0100] As can be seen from FIG. 1, the needle 3 is arranged as a needle cannula having two pointed ends, one arranged at the proximal end of the needle cannula and one arranged at the distal end. The needle hub 4 grips the middle portion of the needle cannula 3 so that both the distal and the proximal ends of the needle protrude axially relative to the hub 4, i.e. respectively forming a front needle and a rear needle. In the shown embodiment, the hub 4 is mounted fixedly relative to the housing 6. During use, the proximal end of the needle 3a is arranged to engage with a container 2 containing the medicament which is to be injected while the distal end 3b is arranged to pierce the skin of the user to inject the medicament into the body of the user.
[0101] In the shown embodiment, the container 2 forms a cartridge with a body 2a having a distally arranged outlet covered by a cartridge septum 2b adapted to be pierced by a needle for establishing fluid communication with the cartridge interior. The body of the cartridge accommodates a slidably arranged piston 2c. In the state where a needle has pierced cartridge septum 2b, piston 2c is drivable towards the outlet in order to dispense medicament from the cartridge 2. It should however be noted that the current invention could also be used in embodiments of an injection device where the needle assembly is arranged with only one pointed end having the needle connected to a source of medicament in another manner, without the use of a pierceable container septum as is shown in the appended figures.
[0102] As can also be seen from FIG. 1, the proximal end 3a of the needle is covered by a proximal needle cover 10a forming a flexible pierceable needle cover and the distal end of the needle 3b is covered by a distal needle cover 10b also forming a flexible pierceable needle cover. The needle covers 10a and 10b will also be referred to as a rear cover and front cover, respectively. Likewise, the part of the needle cannula that extends in a proximal direction from the hub will be referred to as the rear needle, whereas the part of the needle cannula extending in a distal direction from the hub will be referred to as the front needle. It is to be noted that in FIGS. 1 to 4 the shape of the needle covers 10a and 10b are only schematically depicted. The rear and front needle covers 10a and 10b are arranged to allow the needle to be sterilized and then ensure that the needle itself is not contaminated by further handling of the needle assembly.
[0103] In FIG. 2, the needle shield 5 has been retracted with respect to the needle hub 4 such that the distal end 3b of the needle now extends distally past the distal end 5b of the needle shield. In this way the distal end of the needle 3b is now exposed and ready for fluid communication with a user. As can also be seen in FIG. 2, the act of retracting the needle shield has caused the distal needle cover 10b to be pulled back. This causes the distal end of the needle to pierce through the needle cover thereby uncovering the distal end of the needle. Due to the flexible nature of the needle cover, the needle cover is easily retracted.
[0104] In the shown embodiment, the act of retracting the needle shield relative to the needle hub activates the expelling assembly which initially provides a force for moving the cartridge 2 relative to the housing 6. In FIG. 3, it can be seen that the expelling assembly 7 has pushed the medicament containing cartridge 2 forward in a distal direction to engage the cartridge with the proximal end of the needle. The proximal end of the needle punctures the septum of the cartridge thereby establishing a fluid path from the cartridge through the needle and to the distal end of the needle whereby the medicament can be injected into the user at the selected injection site. As can also be seen in FIG. 3, the proximal needle cover 10a has also been compressed by the motion of the cartridge towards the needle. This thereby uncovers the proximal end of the needle and allows it to engage with the cartridge.
[0105] In FIG. 4, the expelling assembly has pushed the piston 2c arranged in the cartridge downwards, thereby causing the medicament in the cartridge to be injected through the needle into the injection site. After the medicament has been injected, the needle shield is again pushed forward with respect to the needle hub to shield the distal end of the needle. In the shown embodiment, this occurs as a consequence of the user manually retracting the housing 6 of the injection device relative to the injection site. In the shown embodiment, the needle shield 5 is biased in the distal direction by means of a needle shield spring.
[0106] The description above with respect to FIGS. 1 to 4 has been provided to give a background of the use of an injection device. The injection device described is one of many different available injection devices. It should be noted that the needle assembly of the current invention can be used with different injection devices, not just the one described above with respect to FIGS. 1 to 4. During manufacture of the injection device, the needle assembly will be subjected to a sterilization procedure so that it is ensured that the needle assembly is in a sterile condition.
[0107] FIGS. 5 to 13 show different views of a needle assembly 50 and, in particular, a variety of needle covers for use in such needle assemblies in accordance with the current invention. The needle assembly according to the invention may in different variants include a front needle only, variants including a rear needle only or variants including both a front needle and a rear needle. Flexible needle covers may be arranged to encase respective needle ends.
[0108] FIGS. 5a, 5b, 5c and 5d respectively show a perspective rear view, a perspective front view, a cross sectional side view and a perspective cross sectional view of a first embodiment of a needle cover 10 which may be used for sealing either the front needle or the rear needle of a particular needle assembly. The needle cover 10 is formed as an axially extending elongated enclosure formed for accommodating the part of the needle cannula 3 that extends axially from the first end, i.e. the needle hub 4 end. In the shown embodiment, the interior wall surface has a generally cylindrical shape that is closed off at its free end opposite the needle hub end by a closed central end surface 18. The needle cover is made from a flexible pierceable material. In the shown embodiment, the needle cover is made from a liquid silicon rubber having shore A 70.
[0109] Referring mainly to FIG. 5c, the needle cover 10 is basically formed by two sections, i.e. a shaft section 11a that mounts to the needle hub, and a bulb section 11b that connects to the shaft section at a location axially opposite to the needle hub. The bulb section is formed so as to encircle the free end of the needle cannula and for closing off the end of the needle cover 10.
[0110] The shaft section 11a is formed as a generally thin-walled cylindrical object having a rim portion 12 that is configured for mating and mounting relative to the needle hub 4. A number of circular reinforcing ribs may be formed on the exterior surface of the shaft section 11a. Each reinforcing rib encircles the needle cannula at a particular axial location between the bulb section and the needle hub and thus divides two annular regions that may be referred to as collapse regions 15 of the shaft section 11a. In the shown embodiment, two ribs 16 are distributed along the length of the shaft section. However, other embodiments may include less or more reinforcing ribs 16 distributed along the length of the shaft section 11a, such as one, three, four or five. In other embodiments, the shaft section does not include reinforcing ribs.
[0111] In the shown embodiment, the bulb section 11b is formed as a cylinder with bulb wall areas 17a having a wall thickness t.sub.2 larger than the wall thickness t.sub.1 of the collapse regions 15. The bulb section 11b extends from the free end of the needle cover 10 to the shaft section 11a so that the bulb section 11b axially overlaps the pointed tip of the needle by a particular margin. The end wall located at the free end of the needle cover may exhibit a wall thickness with a wall thickness t.sub.3 smaller than the wall thickness t.sub.2 of wall areas 17a.
[0112] With reference to FIG. 6, which schematically shows a part of the needle assembly 50 during steam sterilization, the varying pressure during pressure cycles of a steam sterilization process tend to sequentially radially collapse and expand the shaft section 11a. At some instances, the thin-walled areas of the needle cover deforms and collapses first and makes the thicker material in the tip form a protective “bulb” around the needle tip. The increased wall thickness of the wall areas 17a effectively stiffens the bulb section 11 b meaning that the bulb section is able to withstand the pressure so that no parts of the bulb section 11b gets into contact with the sharpened parts of the needle cannula. Hence, the risk that the needle cover 10 unintentionally becomes pierced by the needle cannula 3 during steam sterilization will be effectively lowered.
[0113] With reference to FIG. 7, which shows a detailed view of the distal portion of a second embodiment of an injection device 1, the needle assembly 50 comprises a needle hub 4, a rear needle 3a, a front needle 3b, a rear needle cover 10a and a front needle cover 10b. FIG. 7 further depicts a distal portion of the needle shield 5, a distal portion of the housing 6 and a distal portion of the cartridge 2. Each of the rear needle cover 10a and front needle cover 10b may be formed generally as shown in FIGS. 5a-5d. As seen in FIG. 7, respective ones of the needle covers 10a and 10b is mounted relative to the hub 4 so as to snugly fit a cylindrical mounting surface formed on the needle hub. Non-limiting examples for fixation of the needle cover relative to the needle hub may include a press-fit or include further mechanical fastening elements that squeezes and withhold the rim portion 12 of the needle cover, such as by means of a snap action. It is seen that, for the shown embodiment, the needle covers are formed so that when no external forces act to deform the needle covers the internal wall surfaces of the needle covers are spaced apart from their respective parts of the needle cannula without touching it. However, during operation of the device 1, as described in connection with FIGS. 1-4, the relative movement between the needle shield 5 and the housing 6, and subsequently the relative movement between the cartridge 2 and the needle cannula 3, the needle covers 10b and 10a will become axially compressed and ultimately penetrated by the pointed tips of the respective parts of the needle cannula 3.
[0114] FIG. 8 depicts a simulation of deformation of the rear needle cover 10a as it cooperates with the distal part of the cartridge 2 at a particular point in time during operation of the device, i.e. during relative axial movement between the cartridge 2 and the rear needle 3a. Initially, the needle cover 10a is spaced apart from the septum 2b of the cartridge 2. However, during relative axial movement, the closed central end surface 18 of bulb section 11b of the rear needle cover 10a will abut the distal part of cartridge 2. The rear needle cover 10a, in particular the shaft section 11a, will initially start to deform. Due to the reinforcing ribs 16, a controlled deformation will mainly start at the collapse regions 15. Pairs of opposing wall areas in the collapse regions 15 on opposite sides of the needle cannula 3 will either start to deform radially towards each other or radially away from each other. The reinforcing ribs 16 however ensure that the shaft section 11a will not start to tilt with respect to the needle axis. As a consequence, a controlled axial collapse is ensured and the potential risk that the pointed needle tip should penetrate the closed central end surface 18 at a location offset from the intended one is minimized. This means that the risk that the rear needle 3a will become bent during collapsing of the needle cover will be minimized.
[0115] For the shown embodiment of the rear needle cover 10a, for a first annular collapse region 15, two opposing wall areas deform radially towards each other along a first axis that extends normal to the needle axis. Further deformation of the needle cover 10a means that for annular collapse regions 15 adjoining said first annular collapse region two opposing wall areas deform radially away from each other along said first axis.
[0116] The same considerations apply for the front needle cover 10b where reinforcing ribs 16 may be disposed to ensure that the front needle 3b will not be unintentionally bent during movement of the needle shield 5 relative to the front needle 3b.
[0117] As a further means for ensuring a controlled axial collapse of the needle covers 10a and 10b, the shape of the central end surfaces 18, respectively adapted to abut the distal face of the cartridge 2 and the proximal surface of the needle shield 5, may be formed in agreement with the shape of these abutting elements. The abutting surfaces of the central end surface 18 may for example be formed as a substantial flat surface, such as being formed as a circular planar surface.
[0118] The wall thickness of the “thin walled areas” of the needle cover 10, such as the collapse regions 15, is selected to allow steam to penetrate the material in a rate suitable for steam sterilization. In the shown embodiments, a wall thickness t.sub.1 of thin walled areas may be selected in the order of 0.18 mm. As non-limiting examples, in the first embodiment, the collapse regions 15 may be formed with a wall thickness in the range of 0.15-0.22 mm, the reinforcing ribs 16 may have a wall thickness in the range of 0.22-0.25 mm, whereas the wall areas 17 of the bulb section 11b may be selected with a wall thickness in the range of 0.40-0.80 mm. The radially inwards facing surface of needle cover may be formed with an internal diameter about 2.5 mm to provide for safe assembly of the needle cover relative to the cannula. Non-limiting exemplary needle cannulas for the front needle 3b may be selected as a 28 gauge needle having a length between 6-10 mm. Depending on the particular application, the rear needle may typically be selected with an increased lumen to facilitate greater flow velocities.
[0119] FIGS. 9a to 9d show a second embodiment of a needle cover 10 in views corresponding to the views shown in FIGS. 5a to 5d. In the second embodiment, the bulb section 11b has mainly been modified relative to the first embodiment, by introducing an annular band 19 of reduced wall thickness axially dividing relatively thick walled first and second annular bands 17a and 17b. In the shown embodiment, the annular bands 17a and 17b are formed by areas with a wall thickness t.sub.2 that exhibit the same wall thickness throughout the circumferential and axial extension of annular bands 17a and 17b. However, in other embodiments, the annular bands 17a and 17b may be formed with geometries that differ relative to each other. Each annular band 17a and 17b may be formed by areas with a uniform thickness or be defined by sub-areas of varying thickness. The annular band 19 serves to lower the compression force needed when axially deforming the needle cover 10 during operation of the injection device. The bulb section 11b however still effectively aids in minimizing the risk of unintentional piercing of the bulb section 11b during steam sterilization. Further, a ventilation zone 20 located at the central end surface 18 may be introduced with a reduced wall thickness t.sub.3. The annular band 19 and the ventilation zone 20 aid in flow of steam towards the interior of the bulb section 11b during steam sterilization. As indicated in FIG. 6, the radial collapsing of the shaft section 11a of the needle cover 10 may tend to introduce a gasket effect lowering flow of steam towards the tip section of the needle cannula. The ventilation zone and the annular band 19 thus aid in providing steam towards the tip of the needle cannula as well as to the interior lumen of the needle cannula. Further, the reduced thickness of ventilation zone 20 reduces the risk of needle coring as the needle pierces and penetrates through the central end surface 18. The ventilation zone 20 may be formed as a flat surface. However, other shaped surfaces, such as a dome-shaped surface may be selected for the ventilation zone 20.
[0120] FIGS. 10a to 10d show a third embodiment of a needle cover 10 in different views. Compared to the second embodiment, the bulb section 11b has been changed so that the annular band 19 of reduced thickness and the second annular band 17b having a thick wall have been replaced by a tapered section that increases in diameter towards the free end of the needle cover 10. The first annular band 17a of wall thickness t.sub.2 still divides the bulb section 11a from the shaft section 11b. The bulb section 11b still exhibits an annular region 19 with reduced wall thickness whereas the inner circumferential edge at the free end of the needle cover performs as a strengthening zone 17b to provide the necessary rigidity to prevent the bulb from collapsing during steam sterilization. A central end wall area 20 performs as a ventilation zone having a wall thickness (t.sub.3) smaller than wall thickness (t.sub.2), such as between 0.20 and 0.3 mm, such as between 0.23 and 0.28 mm.
[0121] FIGS. 11a to 11d show a fourth embodiment of a needle cover 10 in different views. This embodiment most closely resembles the first embodiment. The differing features mainly involve a central end wall area 20 with reduced wall thickness performing as a ventilation zone and ensuring reduced risk of coring during penetration of the needle cannula 3 through wall area 20. Again, at the free end of the needle cover, the inner circumferential edge is provided with stiffening geometries.
[0122] FIGS. 12a to 12d show a fifth embodiment of a needle cover 10 in views corresponding to the views shown in FIGS. 5a-5d. In the fifth embodiment, the shaft section 11a has mainly been modified relative to the first embodiment in that the circular reinforcing ribs 16 of the first embodiment have been replaced by semi-circular bands 16 that alternatingly have been arranged on either side of the shaft section 11a. Again, the reinforcing ribs 16 divide the remaining parts of the shaft section 11a into collapse regions 15. The action of each reinforcing rib 16 serves to ensure a controlled axial collapse of the shaft section upon application of a penetration force. The reinforcing ribs 16 define predetermined locations where the needle cover 10 will start deformation allowing further ribs 16 to control the progression of the axial collapse. In the shown embodiment, two semi-circular ribs 16 have been shown but in other embodiments a different number of semi-circular ribs may be selected. Also, ribs having a different angular extension than 180 degrees extension can be used.
[0123] FIGS. 13a-13d show a sixth embodiment of a needle cover 10 in views corresponding to the views shown in FIGS. 5a-5d. In the sixth embodiment, the shaft section 11a has been modified relative to the first embodiment in that the circular reinforcing ribs 16 of the first embodiment have been replaced by helical rib 16 that extends around the shaft section 11a in a helical fashion. The thin-walled areas located between segments of the helical rib 16 form collapse regions 15.
[0124] It is to be noted that the figures and the above description have shown and described the example embodiments without describing each individual feature shown in the drawings. Furthermore, many of the details have not been described in detail since the person skilled in the art should be familiar with these details and they would just unnecessarily complicate this description.
[0125] Furthermore, some preferred embodiments have been shown in the foregoing, but it should be stressed that the invention is not limited to these, but may be embodied in other ways within the subject matter defined in the following claims and within the remaining disclosure.
