Plunger for a medical syringe

Abstract

A plunger for a medical syringe includes a plunger body having a longitudinal axis, a lateral surface, a front side and a rear side, wherein a first sealing bead is associated with the front side of the plunger, the rear side is used for connecting to a plunger rod and, in addition, a front part of the plunger including the front side is covered with a film-like cover layer for otherwise separating the plunger from the medical substance in the use position. In addition, the cover layer be configured with different thicknesses, wherein the thickness is greatest in the region of the longitudinal axis and decreases radially outwards from the longitudinal axis.

Claims

1. A plunger (3) for a medical syringe (1), wherein the plunger (3) has a plunger body with a longitudinal axis (x), a lateral surface, a front side, a rear side, and a plurality of sealing beads, wherein a first sealing bead (15) of the plurality of sealing beads is associated with the front side of the plunger (3) and wherein the rear side serves for connecting to a plunger rod (8), wherein further a front part of the plunger (3) including the front side is covered with a film-like cover layer (18) for otherwise separating the plunger (3) from a medical substance in the use position, wherein the cover layer (18) is configured with different thicknesses, wherein the thickness is greatest in the region of the longitudinal axis (x) and decreased radially outwards from the longitudinal axis (x), wherein a difference between a largest radial dimension (a) of the cover layer (18) and a radial dimension (u) of the cover layer corresponds to a radial dimension (b) that is one fifth or less of the largest radial dimension (a), wherein the radial dimension (u) is the dimension where the thickness of the cover layer becomes less than three times greater than a smallest thickness of the cover layer (18).

2. The plunger (3) according to claim 1, wherein the smallest thickness of the cover layer is from 0.4 to 1 μm.

3. The plunger (3) according to claim 1, wherein the smallest thickness of the cover layer is 0.5 μm.

4. The plunger (3) according to claim 1, wherein the thickness of the cover layer (18) decreases radially outwardly continuously or in steps.

5. The plunger (3) according to claim 1, wherein the smallest thickness of the cover layer (18) is associated with the radially outermost region of the plunger (3) in the region of the first sealing bead (15).

6. The plunger (3) according to claim 1, wherein the cover layer (18) is applied to the plunger (3) in a spray process.

7. The plunger (3) according to claim 1, wherein the cover layer (18) is designed as a separate part (20) and attached to the plunger (3).

8. The plunger (3) according to claim 1, wherein the side of the cover layer (18) facing the plunger (3) has one or more protrusions (21) for form-fitting engagement in corresponding recesses (22) in the front side of the plunger (3).

9. The plunger (3) according to claim 1, wherein a protrusion (21) and an associated recess (22) are arranged symmetrically relative to a longitudinal cross section through the plunger (3) or the longitudinal axis (x) passes through the middle of the protrusion and the associated recess.

10. The plunger (3) according to claim 1, wherein the cover layer (18) has a constant thickness over its entire lateral surface (19) and a different thickness in the region of the first sealing bead (15).

11. The plunger (3) according to claim 10, wherein the constant thickness has a dimension from 0.3 to 3 μm.

12. A plunger (3) for a medical syringe (1), wherein the plunger (3) has a plunger body with a longitudinal axis (x), a lateral surface, a front side, a rear side, and a plurality of sealing beads, wherein a first sealing bead (15) of the plurality of sealing beads is associated with the front side of the plunger (3) and wherein the rear side serves for connecting to a plunger rod (8), wherein further a front part of the plunger (3) including the front side is covered with a film-like cover layer (18) for otherwise separating the plunger (3) from a medical substance in the use position, wherein the cover layer (18) is configured with different thicknesses, wherein the thickness is greatest in the region of the longitudinal axis (x) and decreased radially outwards from the longitudinal axis (x), wherein a side of the cover layer (18) facing the plunger (3) has one or more protrusions (21) for form-fitting engagement in corresponding recesses (22) in the front side of the plunger (3).

13. The plunger (3) according to claim 12, wherein a smallest thickness of the cover layer is from 0.4 to 1 μm.

14. The plunger (3) according to claim 12, wherein a smallest thickness of the cover layer is 0.5 μm.

15. The plunger (3) according to claim 12, wherein the thickness of the cover layer (18) decreases radially outwardly continuously or in steps.

16. The plunger (3) according to claim 12, wherein a smallest thickness of the cover layer (18) is associated with the radially outermost region of the plunger (3) in the region of the first sealing bead (15).

17. The plunger (3) according to claim 12, wherein the cover layer (18) is applied to the plunger (3) in a spray process.

18. The plunger (3) according to claim 12, wherein the cover layer (18) is designed as a separate part (20) and attached to the plunger (3).

19. The plunger (3) according to claim 12, wherein a protrusion (21) and an associated recess (22) are arranged symmetrically relative to a longitudinal cross section through the plunger (3) or the longitudinal axis (x) passes through the middle of the protrusion and the associated recess.

20. The plunger (3) according to claim 12, wherein the cover layer (18) has a constant thickness over its entire lateral surface (19) and a different thickness in the region of the first sealing bead (15).

Description

BRIEF DESCRIPTION OF THE DRAWING

(1) In the following text, the invention is explained with reference to the accompanying drawing, which however only represents exemplary embodiments. A part which is explained only with reference to one of the exemplary embodiment and which is not replaced in another embodiment due to the particular property revealed there, is thus included as a part which is at any rate possibly present for this other embodiment as well. In the drawing:

(2) FIG. 1 is a partial sectional view of a medical syringe with a plunger;

(3) FIG. 2 shows a first embodiment of a plunger during a spraying process for applying a cover layer;

(4) FIG. 3 shows a full cross-section of the plunger of FIG. 3 furnished with the cover layer;

(5) FIG. 4 shows the enlarged view of inset IV in FIG. 3;

(6) FIG. 5 shows a macroscopic enlargement of region V in FIG. 4;

(7) FIG. 6 is a representation similar to FIG. 2 relating to a second embodiment during application of the cover layer as separate films;

(8) FIG. 7 is a representation corresponding to FIG. 3 relating to the embodiment of FIG. 6;

(9) FIG. 8 shows the enlarged view of inset VIII in FIG. 7;

(10) FIG. 9 is a representation corresponding to FIG. 3 relating to a further embodiment;

(11) FIG. 10 shows the plunger in a further embodiment in a representation similar to that of FIG. 3;

(12) FIG. 11 is an enlarged view of a further embodiment corresponding to FIG. 4;

(13) FIG. 12 is a representation of a further embodiment corresponding to FIG. 4.

DESCRIPTION OF THE EMBODIMENTS

(14) Firstly with reference to FIG. 1, a syringe 1 for medical purposes is represented and described.

(15) The syringe 1 is composed essentially of an elongated cylinder 2 which is open at both ends, particularly a cylindrical body made for example of glass or plastic, and a plunger 3 which is displaceable inside the cylinder 2 in a direction of advance r and in a direction opposite to the direction of advance r.

(16) The cylinder 2 has a distal end 4 and a proximal end 5. In the region of the distal end 4 the cylinder 2 adjoins a tapered needle hub 6.

(17) A radial enlargement in the form of a flange 7 is conformed in the region of the proximal end 5. During use of the syringe 1, this serves as a counterholder enabling support under the flange for preferably the index and middle fingers of the hand operating the syringe 1.

(18) The plunger 3 is connected to a plunger rod 8. The plunger rod passes through an insertion opening 9 of the cylinder 2 provided in the proximal end 5 and forms a plate-like thumbrest 10 aligned transversely to the lengthwise extension of the plunger rod 8 in the region of the free end 2 farthest from the plunger 3.

(19) As represented, the plunger rod 8 may have the form of fins 11 aligned in cross-like manner.

(20) The plunger of the embodiments represented is preferably produced from a rubber material.

(21) The plunger 3 further has a longitudinal axis x which is coincident with the longitudinal axis of the cylinder 2 of the syringe 1 in the use position according to FIG. 1.

(22) A receiving opening 12 with an internal thread 13 for screwed fastening of the facing distal end of the plunger rod 8 is formed on the plunger 3 coaxially with longitudinal axis x and accessible from the rear end relative to the direction of advance x.

(23) The plunger 3 is furnished with a tip section 14 in the region of the front side of the plunger 3 which faces the distal end 4 of the cylinder 2 in the region of the front side of the plunger 3 in the use position. As shown in the exemplary embodiments, this tip section may be conical in shape. With the tip section 14 as shown, fluid can be expressed completely from the interior of the cylinder 2 through the needle hub 6 which is arranged coaxially with the longitudinal axis x in the region of the distal end 4.

(24) The plunger 3 is furnished with at least one sealing bead 15 extending circumferentially relative to the longitudinal axis x. In the exemplary embodiments shown, three such sealing beads 15 to 17 are provided preferably at equal distances from each other in the direction of extension of the longitudinal axis x.

(25) In this context, the sealing bead 15 is associated with the front side of the plunger 3 and in a preferred variant directly adjoins the tip section 14, so that the transition of surface of the tip section 14 in a roof-like formation in the cross-section of FIG. 3 to the surface of the sealing bead 15 is preferably smooth.

(26) The cross-section(s) of the sealing bead(s) 15 and optionally 16 and 17 are of rounded construction, particularly before the plunger 3 is inserted in the cylinder 2. In this way, sealing zones are formed by correspondingly ring-like beads and connected to each other via preferably completely cylindrical plunger sections.

(27) The sealing beads 15 to 17 serve to provide liquid-tight support of the plungers 3 against the inner wall of the cylinder.

(28) Each sealing bead, but particularly the sealing bead 15 has a largest radial dimension a in a plane extending perpendicularly to the longitudinal axis x, which largest radial dimension a is formed at the apex of the rounded sealing bead 5 in the unmodified plunger 3, i.e. when the plunger 3 is not inserted in the cylinder 2.

(29) The plunger 3 is covered by a cover layer 18 in the region of its front side. This may be a layer which seals the surface of the plunger 3 facing the medical substance when the syringe 1 is used, so that no direct contact takes place between the actual plunger material and the medical substance.

(30) As may be seen in the illustrations, the cover layer 18 extends radially outwardly relative to a cross section, starting from a central tip region of the plunger 3 through which the longitudinal axis x passes until the largest radial dimension a is reached in the region of the first sealing bead 15, as shown in FIG. 3 for example.

(31) According to the embodiment of FIG. 7, the cover layer 18 may extend over a dimension of 2 μm or more up to 3 mm or more beyond the radial dimension a in the region of the sealing bead 15 starting from the front side of the plunger 3, originating from the plane of the largest radial dimension a in the direction of extension of the longitudinal axis x. The figure shows an embodiment in which the cover layer 18 extends as far as the rear side of the first sealing bead 15 farthest from the front side of the plunger 3, and in this case does not extend as far as the following cylindrical section of the plunger 3.

(32) As represented in FIG. 9, the cover layer 18 may also be provided to completely cover the lateral surface 19 of the plunger 3. In this case, the cover layer extends over the tip section 14 and along the sides of the plunger 3 over all sealing beads 15 to 17 and the cylindrical sections of the plunger 3 that connect them as far as the rear and of the plunger 3.

(33) As may further be seen in the illustration, the thickness d of the cover layer 18 is provided which decreases radially outwardly starting from the region through which the longitudinal axis x passes. The decrease in thickness radially outwards from the inside may be provided in continuous fashion, as shown.

(34) The smallest thickness of the cover layer 18 may be provided in the region of the largest radial dimension a, i.e. preferably in the apex region of the sealing bead 15 associated with the front side of the plunger 3. The smallest thickness d of the cover layer 18 may have a dimension of 0.5 μm. for example.

(35) In this way, a cover layer 18 may be created in which a radial dimension b of the cover layer 18 starting from the radial dimension u corresponds to one fifth or less of the largest radial dimension a, wherein the radial dimension u is present the first time the thickness becomes less than three times greater then the smallest thickness d of the cover layer 18 (see FIG. 3).

(36) The cover layer 18 may be applied to the front side of the plunger by spraying (see also FIGS. 2 to 5).

(37) In this context, a decrease in the cover layer thickness d is realised particularly in the curved section of the sealing bead 15, further in the region of the largest radial dimension a.

(38) In this context, the smallest thickness of the cover layer has a dimension which is preferably selected smaller than the peak-to-valley height of the plunger material.

(39) The cover layer 18 may also be embodied as a separate part 20, in particular as a film part (see FIG. 6). This separate part is applied separately to the front side of the plunger 3 and bonded thereto or alternatively joined to the plunger material in the course of the production process of the plunger 3, in an in-mould process for example.

(40) In the course of the associated production process, the film-like cover layer 18 may be furnished with a thickness which decreases radially outwardly until a smallest thickness is reached in the preferably radially outermost region. Upon reaching the preferably predefined smallest thickness, the layer material extends further, maintaining smallest thickness.

(41) Particularly such a separately produced part 20 may be furnished for the purpose of exact alignment with the plunger 3 with a protrusion 21 facing towards the plunger 3, which protrusion is insertable in an associated recess 22 in the plunger 3, for example in the region of the tip section 14 thereof for a form-fitting connection (see FIG. 10).

(42) A combination of spraying on a cover layer and applying a separately produced cover layer may be provided, such as further for example in a possible variant of the plunger 3 according to the representation in FIG. 9, in which the circumferential plunger shell is also furnished with a cover layer 18. This cover layer may be sprayed on with uniform thickness, in such case in the region of the tip section 14 on the plunger side, further optionally covering said tip section completely. Finally, a cover layer film having a thickness that decreases radially outwardly may be applied to the tip section 14, correspondingly on the front side of the plunger 3.

(43) The material of the cover layers 18 for covering the lateral surface 19 of the plunger may optionally be the same as or different from the cover layer material of the tip section 14.

(44) As shown in the enlarged insets in FIGS. 11 and 12, the sealing bead 15 may also be embodied as a double bead with two immediately sealing zones located immediately one after the other in the axial direction, wherein the sealing zones 15′ and 15″ may have the same diameter. Alternatively, the diameter of the sealing zone 15″ farthest from the tip region may selected larger than the closer sealing zone 15′. In this case, the cover layer 18 of the tip section 14 preferably only extends behind the first sealing zone 15′ of the sealing bead 15. The second sealing zone 15″ may cooperate directly with the facing interior surface of the cylinder 2 without a cover layer, as is preferred.

(45) The preceding notes serve to explain the totality of the inventions included in the application which advance the related art also individually, at least by the following combinations of features, specifically:

(46) A plunger 3 which is characterized in that the cover layer 18 is constructed with various thicknesses, wherein the thickness d is largest in the region of the longitudinal axis x and decreased radially outwardly starting from the longitudinal axis x.

(47) A plunger 3 which is characterized in that the cover layer 18 has a smallest thickness d from 0.1 to 3 μm.

(48) A plunger 3 which is characterized in that the cover layer 18 has a smallest thickness d from 0.4 to 1 μm.

(49) A plunger 3 which is characterized in that the cover layer 18 has a smallest thickness d of 0.5 μm.

(50) A plunger 3 which is characterized in that the plunger 3 is furnished with one more sealing beads 15-17 extending in a plane perpendicularly to the longitudinal axis x, which a first sealing bead 15 associated with the front side of the plunger 3, wherein one sealing bead 15-17 has a contour which is rounded relative to a longitudinal cross section through the plunger 3 before the plunger 3 is inserted in a syringe, with a largest radial dimension a in a plane extending perpendicularly to the longitudinal axis x.

(51) A plunger 3 which is characterized in that the cover layer 18 extends as far as the radially outermost region of the first sealing bead 15 and in axial direction over 0.1 mm or more up to 3 mm in the direction of the longitudinal axis x starting from the point at which it first reaches the outermost region of the first sealing bead 15.

(52) A plunger 3 which is characterized in that the thickness of the cover layer 18 decreases radially outwardly continuously or in steps.

(53) A plunger 3 which is characterized in that the smallest thickness d of the cover layer 18 is associated with the radially outermost region of the plunger 3 in the region of the first sealing bead 15.

(54) A plunger 3 which is characterized in that a radial dimension a of the cover layer 18 starting from a radial dimension u which is realised the first time the thickness becomes less than 3 times the smallest thickness d, is equivalent to one fifth or less of the largest radial dimension.

(55) A plunger 3 which is characterized in that the cover layer 18 is applied to the plunger 3 in a spray process.

(56) A plunger 3 which is characterized in that the cover layer 18 is designed as a separate part 20 and applied to the plunger 3.

(57) A plunger 3 which is characterized in that the cover layer 18 has one or more protrusions 21 on the side thereof facing the plunger 3 for a form-fitting engagement in corresponding recesses 22 in the front side of the plunger 3.

(58) A plunger 3 which is characterized in that a protrusion 21 and an associated recess 22 are arranged symmetrically with respect to a longitudinal cross section through the plunger 3, or the longitudinal axis x bisects them symmetrically.

(59) A plunger 3 which is characterized in that the plunger 3 has a cover layer 18 of constant thickness d over its entire lateral surface 19, except as far as the region of the first sealing bead 15.

(60) A plunger 3 which is characterized in that the constant thickness d has a dimension up to 3 μm.

(61) All disclosed features are essential to the invention individually but also in combination with each other. The disclosed content of the associated/accompanying priority documents (photocopy of the preliminary application) is herewith also included in its entirety in the disclosure of the present application also for the purpose of incorporating features of those documents in the claims of the present application. The features described in the subclaims characterize independent inventive further developments of the related art, particularly to enable partial applications to be made on the basis of these claims.

REFERENCE LIST

(62) 1 Syringe 2 Cylinder 3 Plunger 4 Distal end 5 Proximal end 6 Needle hub 7 Flange 8 Plunger rod 9 Insertion opening 10 Thumbrest 11 Fin 12 Receiving opening 13 Internal thread 14 Tip section 15 Sealing bead 15′ Sealing zone 15″ Sealing zone 16 Sealing bead 17 Sealing bead 18 Cover layer 19 Lateral surface 20 Part 21 Protrusion 22 Recess a Radial dimension b Radial dimension d Thickness r Direction of advance u Radial dimension x Longitudinal axis