Syringe for medicinal purposes

0001The invention pertains to a syringe for medicinal purposes, with a syringe barrel, one end of which is designed as an adapter for a cannula or a closure piece, e.g., in the form of a tip cap, and with a plunger arranged in the syringe barrel and movable via a piston rod.

0002Syringes of this type are increasingly being marketed, especially as ready-to-use syringes in prefilled form, for self-administration by the patient, as has long been the case, especially for regular administration of insulin in diabetics.

0003In the case of unskilled or infirm people, there is a risk that before application the plunger will accidentally be pulled out of the syringe barrel so that, as a rule, the product is no longer usable.

0004The features of the preamble of claim 1 are known from US-A-4 883 471.

0005US-A-4,267,846 discloses a syringe having a piston brake attached to the syringe barrel. The piston brake acts on the piston for controlling the distance in which the piston can move in both inward and outward directions. The syringe barrel has at its proximal end a flange extending perpendicular to the longitudinal axis of the barrel and providing a finger grip for the user of the syringe during its operation. The piston brake has a hook sized and shaped to snap fit over the flange for fastening the piston brake to the barrel. This requires that the barrel has a flange or other protrusion for fastening the piston brake. However, there exist syringes which do not have a flange on the barrel.

0006It is an object of the invention to provide a syringe having a piston brake, wherein the piston brake is capable of being used in connection with barrels that do not have finger rests.

0007The present invention is defined by claim 1. Accordingly, the rest piece housing includes a circularly shaped side wall having an inside surface contacting the outer surface of the open proximal end of the barrel and includes two radially outwardly projecting wings, said wings forming a finger rest for applying axial force to the barrel.

0008In accordance with the invention on the end of the syringe barrel, away from the adapter, a plunger brake is arranged, which is formed by a rest piece surrounding the syringe barrel and attached removably to it, which has a projection extending into the lumen of the barrel, which forms a stop for the side of the plunger away from the adapter. In the plunger rod assembly brake of the present invention the annular piece has two radially extending, diametrically opposite wings that form a finger rest. This is especially advantageous when syringes with very small volumes are used.

0009The advantage achieved with the invention lies, first of all, in the fact that the projection extending into the lumen of the syringe barrel exerts a braking effect on the plunger, so that even in the case of incorrect manipulation of the syringe by the patient during use, so long as excessive force is not applied, the plunger cannot come out of the syringe barrel.

0010Additional advantages arise in the course of manufacturing, since during the post-sterilization of solutions prefilled into the syringe barrel, the plunger is frequently forced out of the barrel by the pressure differences that arise. The use of the plunger brake prevents the plunger from being forced out of the barrel, for example, by an air bubble present in the barrel. In this process, the plunger brake can be sterilized along with the unit, if, for example, this is made of polypropylene. As a result, the pharmaceutical safety of the syringe as a whole is increased. Since the plunger brake is placed removably on the syringe barrel, it can be removed from the syringe after use; disposal is simplified by separation of the different materials.

0011In an advantageous embodiment of the invention, the rest piece is designed as an annular piece, and the projection is designed as fingers extending axially into the barrel, wherein the freely projecting end of the finger forms the stop for the plunger.

0012In a preferred embodiment of the invention, the annular piece has a separation slit on the side opposite the finger. In this way, the annular piece can especially easily be clipped onto the barrel from the side.

0013Advantageously, the annular piece is sleeve-shaped, so that it does not interfere with handling of the syringe.

0014For easier handling, the annular piece can be provided on its outer surface with a riffling travelling in the circumferential direction. This provides additional security when holding or handling the syringe.

0015In order to also be able to screw the piston rod without difficulty into the plunger, the invention also provides that the piston rod is tapered in the area adjacent to the piston rod thread provided for connection to the plunger.

0016In the following, the invention will be explained in greater detail, based on exemplified embodiments shown in the drawings, which show: <dl id="dl0001"><dt>Fig. 1</dt><dd>a syringe in accordance with the invention in a preferred embodiment, in side view, with the plunger brake clipped on, and</dd><dt>Fig. 2</dt><dd>a perspective view of the plunger brake in accordance with Fig. 1.</dd></dl>

0017The syringe for medicinal purposes shown in the drawing consists of a syringe barrel 1, one end of which is designed as an adapter 2 for a cannula or - as shown in Fig. 1 - for a closure piece 3 in the form of a tip cap. In the syringe barrel 1, a plunger 4 is arranged, which can be moved with the aid of a piston rod 5.

0018At the end of the syringe barrel 1 away from the cannula adapter 2, a plunger brake 6 is arranged. The plunger brake 6 consists, in detail, in a first embodiment shown in Figures 1 and 2, of a first annular piece 6.1, surrounding the barrel 1, and a finger 6.2 projecting into the interior of the barrel 1, connected to the annular piece 6.1. Here the free end of the finger 6.2 forms a stop for the plunger 4.

0019The plunger brake 6 prevents the plunger 4 from being accidentally pulled out of the barrel 1 in the case of incorrect use of the syringe, for example by a unskilled patient.

0020Also, during the manufacturing process of prefilled, ready-to-use syringes, the plunger brake 6 prevents, for example, the plunger 4 from being forced out of the barrel 1 due to excess pressure occurring in the interior during the post-sterilization of solutions previously filled into the barrel 1.

0021The annular portion 6.1 of the plunger brake 6, as shown in Fig. 2, consists of a separation slit 7 located on the side opposite the finger 6.2, as a result of which the plunger brake 6 can be clipped especially easily onto the syringe barrel 1 from the side. The annular portion 6.1 itself has an essentially sleeve-like shape, and is thus adapted in shape to the syringe barrel 1.

0022To improve handling, the annular piece 6.1 can be provided, in a way not shown in detail in the drawing, on its outer surface, with a riffling running in the circumferential direction. In addition, or alternatively. As shown in Fig. 2, the annular piece 6.1 is provided with two radially extending, diametrically opposite wings 8, which form a finger rest. This is especially advantageous in the case of barrels with relatively small volume, since these generally do not have finger rests.

0023As Fig. 1 shows, the finger 6.2 lies against the inner wall of the syringe barrel 1, so that the piston rod 5 can be moved freely.

0024The piston rod 5 is tapered in the area 9 adjacent to the piston rod threads, so that the piston rod threads can be screwed into the plunger 4 without further efford, even when the plunger brake 6 is clipped into place.