DE102004040969A1 - Piston for a syringe and syringe - Google Patents

Abstract

The invention relates to a piston for a syringe having a syringe barrel. The piston has a core element (8) with a peripheral surface (20). The piston has a ring member (11) with an outer circumferential surface (21) surrounding the core member (8) at a distance. The ring member (11) is coated on its outer circumferential surface (21) with a sliding material (22). The core element (8) and the ring element (11) are interconnected by webs (19).

Description

The The present invention relates to a plunger / plug for a syringe and on a syringe into which such a piston is inserted.

One Piston for a syringe and a syringe into which such a piston is inserted, are known, for example, from WO 98/17339 A1, which is incorporated herein by reference Reference is made.

It a common problem with spraying is that the frictional force between the piston and an inner wall of a cylinder of a syringe is large. traditionally, Therefore, at least the cylinder inner wall of the syringe was coated with silicone oil. However, it is uncertain whether in the application of the syringe contents to a patient the silicone oil mitappliziert. Therefore, WO 98/17339 A1 proposes on the silicone oil to dispense with and friction by suitable material of the piston to reduce. It is proposed the piston of polytetrafluoroethylene (PTFE). PTFE is u.a. known under the trade name "Teflon". PTFE has however, the disadvantage that it is not by pouring can be shaped. It has to go to be turned "full". Since PTFE is relatively expensive, leads this too high cost in the production of the piston. Furthermore are the waste when turning from the solid big. For PTFE you have to as hazardous waste be disposed of, which also increases costs.

In the German patent DE 3346 351 with publication date on April 9, 1992, a piston is described, which is at least partially provided with a Teflon coating. Such a piston contacts the cylinder inner wall with beads which exert on the cylinder inner wall a specific pressure, whereby the sealing effect should be ensured. The beads are formed so that the pointing away from the piston perpendicular to the bead surface facing the wall of the Spriztenzylinders. The patent uses Teflon to provide a protective surface between the medium and the rubber part of the piston. It is therefore in this case only an insulating function, the excellent sliding properties of Teflon have not been taken into account. In this publication, the term siliconizing has not been mentioned. Thus, it is to be assumed that in this case, the expert reads this text to the effect that it is an otherwise the general expertise (eg DIN standard 13 098, Part 1, point 4.4) corresponding syringe, which also on the inside of the Cylinder is siliconized. Autoclaving is not mentioned.

In DE-GM 19 73 042 of 23.11.1967 is a plastic syringe made of synthetic resin described, which consists of a plastic cylinder with needle opening and Plunger opening, a piston and a stamp exists. The syringe has as essential feature of a cup or cup-shaped piston, the from commercial Material exists. However, such a sealing lip is only in combination with a lubricant, in particular with silicone oil, executable. Is not silicone before, would the sealing lips change due to the high friction and they would evasive of force. In this publication is the Term siliconizing also has not been mentioned. Thus, too here to assume that the Professional reads this text to the effect that it is an otherwise the general technical knowledge (for example DIN standard 13 098, part 1, point 4.4) corresponding syringe is, which also on the inside of the cylinder is siliconized. Autoclaving is not mentioned.

In Patent AT-E 68 979 is a filled, terminally sterilized Syringe described. The syringe is made of plastic. The syringe has a cylinder with a distal end with a syringe outlet. The syringe outlet is through sealed a closure. Before filling is the inner wall of the syringe coated with silicone oil. The syringe will after filling closed with a flexible rubber piston, which is in the cylinder also because of the silicone oil lubricious is.

The Process for producing a filled, terminally sterilized Syringe starts with waste particles or other contaminants are removed from the closure and the piston. Microbial contaminants on the cap and piston are destroyed. Of the Cylinder is washed with a variety of water jets to To remove pyrogens and waste particles. Subsequently, will silicone oil applied to the inner wall of the syringe. The shutter will then attached to the syringe outlet. Through the proximal end of the syringe, the contrast agent in filled the syringe. The syringe will follow closed with the piston. This composite and filled syringe is sterilized in an autoclave. It is next to the usual Autoclave pressure is still an additional support pressure produced in the autoclave.

From the publication by Venten and Hoppert (E. VENTEN and J. HOPPERT (1978) Pharm. Ind. Vol. 40, No. 6, pages 665 to 671) prefilled, terminally sterilized spray ampoules are known, which on the inner wall with a silicone oil layer are provided. The syringe vials, which have a piston at the proximal end, are filled distally by the rolling rim. The rolled edge is then sealed by a gasket, a Bör delkappe the sealing washer fixed on the rolled edge. (M. JUNGA (1973) Pharm. Ind. Vol. 35, No. 11a, pp. 824 to 829). The pre-filled syringes are then transferred to an autoclave. This autoclave is adjustable in temperature and pressure.

In the European patent application EP 0553 926 (Filing date: Jan. 26, 1993) describes a method for terminally sterilizing a prefilled plastic syringe or glass syringe, the syringe containing a contrast agent. The inner wall of the disposable syringes is coated with silicone oil. The syringe consists of a syringe barrel having a syringe outlet at the distal end. In addition, disposable syringe ampoules are listed in the form previously described by Venten and Hoppert. The disposable syringes have an open proximal end which is closable by a piston slidable in the disposable syringe. The piston is connected with a stamp.

The WO 95/12482 describes a process for producing prefilled plastic syringes which filled with a contrast agent are. The inner wall of the syringe is coated with silicone oil. The Syringes consist of a cylinder, a syringe outlet on the distal End, which one for one cannula hub is prepared. Furthermore included the syringe has a piston that can slide in the cylinder. He writes the proximal end of the syringe off. The syringe is after a procedure produced, which leads to pyrogen-free objects. As well there are no particles left. The syringe will pass through the proximal Filled at the end, this is the syringe outlet with a Closure sealed. The filled Syringe is closed with the piston.

After this the syringe parts come out of the mold, they are blown off with gas to remove particles. The syringe will follow washed and lubricated. The syringe will be after that sterilized, so that the Syringe optionally further processed, stored or transported can be.

adversely in the known syringes is that silicone oil must be used to the To reduce friction between the piston and syringe inner wall. So useful rubber piston with respect to elastic forces is so problematic is the behavior with respect to the sliding friction. First quite the stiction is even less favorable. Especially with a long one Prolonged storage of the syringe with inserted piston plays the stiction a very important role. Furthermore, with rubber pistons whatsoever the cold flow behavior to be observed. Since this is a not negligible size, rubber pistons with a considerable preload can be used. This is all the more important when the filled Syringes with inserted rubber piston are then autoclaved. The Cold flow the rubber piston is a function of temperature. A high preload is in this case when inserting of the piston necessary. The friction is the same in all cases large, that without silicone oil Handling of the syringes is not possible.

Also When rubber sealing lips are used, they are static State insufficient sealing or suffer from the cold flow behavior, especially during autoclaving. Also in this case is with a considerable Preload to work, so that silicone oil also in This case is indispensable.

One solid Teflon piston has a considerable disadvantage in syringes, which are exposed to thermal stress. Here are enough Temperature variations from -10 ° C to + 40 ° C off to the plastics of the syringe wall against the very strong Teflon material to be stretched. More than anything, autoclaving is one thing Burden for the piston or the syringe, that one from both a cold flow behavior shows that after cooling the syringe leaks result. To seal the piston well, is because of the low elastic Behavior of the massive Teflon piston high preload necessary thereby a big one Friction has to follow. In plastic syringes is such a Teflon piston not to be used, since the cold flow behavior of the syringe wall plastic the inside diameter of the syringe at the level of the piston magnified during autoclaving. hereby gaps are formed through the liquid can get out of the syringe uncontrolled. Also, by doing so uncontrolled air can be sucked. Glass syringes, such a Cold flow do not need to show still with silicone oil on coated on the inner wall to reduce friction, the caused by the very high bias voltage. When autoclaving Such a syringe gives way to the Teflon piston due to the cold flow behavior across from the harder Glass off. Here, too, gaps and gaps are the result after cooling which make the syringe leaking.

It thus sets itself the task, a prefilled, sterile, medical To offer syringe, on the addition of a lubricant in Form of, for example, silicone oil is omitted without thereby the lubricity the piston, which is made of plastic, is compromised in the syringe and at the same time a sufficient sealing of the contents of the syringe by opposite the piston the splash outside area guaranteed becomes.

These Task is solved by a piston according to claim 1.

preferred Embodiments of the piston are in the dependent claims 2 to 16 indicated.

The Task is also solved by a syringe according to claim 17.

A advantageous embodiment of the syringe is specified in claim 18.

The syringe according to the invention can be well filled with contrast agent be sterilized and terminal. Preferred examples of the contrast agent are amidotrizoic, Gadopenic acid, Gadobunol, gadolinium, iopamidol, iopromide, iotrolan, iotroxinic acid.

Of the piston according to the invention has a core element. A ring element surrounds the core element at a distance. The two elements are connected by webs.

This Procedure has the advantage that the piston not massive. Conventional materials such as thermoplastic, from which the pistons are produced, have a large coefficient of thermal expansion on. Therefore, if a syringe with a solid piston of thermoplastic in an autoclave at 121 ° terminal sterilized, the piston deformed because of thermoplastic of the big one thermal expansion coefficient so strong that it is destroyed.

Farther is the ring member according to the invention on its outer peripheral surface with a sliding material coated. This sliding material makes it possible that the Piston can easily be moved into the cylinder of a syringe, which would not be possible if the peripheral surface of the piston made of thermoplastics, because thermoplastic has a high coefficient of friction with materials for syringe barrels like glass or plastic. As the peripheral surface of the Ring element is coated with the expensive sliding material, the Costs are kept low.

There the core element and the ring element are separated from each other and there is a distance between the two is less massive Material for the core element and the ring element present. The radial extent the material is smaller, less than the radius. At the same Expansion coefficient is therefore due to thermal expansion of reduced length smaller. Thus, even when the syringe is heated with the piston of the present invention the piston is not destroyed by the thermal expansion.

Of the rigid core, in which a piston rod can be screwed, provides sure that the Piston rod in an injection not deformed the piston and increases the friction between the piston and a cylinder wall.

If the webs extend radially from the core element to the ring element, can the webs absorb the thermal expansion by upsetting.

If the webs are tangentially attached to the core element, run they are not radially from the inside out. In a thermal Expansion of the core element and the ring element become the webs bent at their starting points. Therefore, not even a compression the webs necessary.

If the ring element in one piece is formed, the injection mold can be easily manufactured.

If the ring member in a plurality of circumferentially spaced Ring segments is divided, can the ring segments at a thermal expansion instead of a radial deformation, which could lead to destruction, deform tangentially, so no destruction occurs.

If the ring member radially encircling projections and in particular projections with Having undercut, the sliding material adheres better to the outer peripheral surface of the Ring material.

If the sliding material has a sealing lip, it is possible a to achieve a particularly good seal. In particular, it is possible to have a dynamic To achieve sealing, which occurs when the piston to the distal The end of the syringe is moved. This is particularly beneficial in a sliding material with a low friction value between the Sliding material and the syringe barrel wall.

If the core element, the webs and the ring element of the same material one piece should be formed, is a particularly cost-effective injection molding for this one-piece Component possible.

preferred Materials for the core element, the webs and the ring element are thermoplastics, polypropylene or polycarbonate.

Preferred materials for the sliding element are thermoplastic elastomers. Preferred examples are: Evoprene 968, Cawiton PR 6173 B, Cawiton PR 6173 D, Cawitone PR 6173 E, Cawiton PR 6173 F, Thermoflex 55 1A5 + 900, Uniprene 7010 RS 70 + 801 (SEBS), Santoprene 181-57 W180 (TPV).

The Spraying is common rotationally symmetrical, only the finger holders and device holders and sometimes also the syringe outlet deviate from the symmetry from. Thus, the syringe outlet piece can be eccentric be arranged. Particularly preferred is the Luer-Lock, since he exclusively at the application of contrast agents comes into play when mechanical pumping devices are used. Even with the manual Application avoids the Luer-Lock and the associated hose, that not intended movements of the doctor to be transferred directly to the cannula. Farther Both the simple luer approach and the record approach are known.

It is possible, too, to weld the syringe outlet and thereby seal. It is advantageous then that a syringe outlet a Sollbruchstellte that easily opens the Syringe outlet piece allowed to use.

The proximal and distal ends of the syringe must be closable. The distal end is sealed by a closure which can be placed on the syringe outlet. The syringe outlet piece in this patent covers the ceiling of the syringe barrel. Further, the syringe outlet includes a tube leading to the needle or tube, an end fitting in contact with the needle or tube, and a threaded cylinder on the inside, with the cylinder surrounding the end and a thread for a Example Luer-Lock carries. In this case, the syringe outlet piece may be integral or multi-piece. The ceiling can be curved, flat or pyramidal. Mixed forms are also conceivable. The piston closes the proximal end of the syringe. It must be slidable in the cylinder and must safely retain the medium from the environment. It should be as little as possible permeable to gases and liquids. Even temperature fluctuations must be absorbed without malfunction. Usually, the piston is not provided with the mechanical emptying of the syringes with its own stamp. Rather, a punch, which is part of the pumping device, engages in a closure in the interior of the piston, so that a movement of the piston is easily possible. (see. EP 0 584 531 )

The terms proximal and distal are defined by the treating physician. At the distal end is the syringe outlet, to which, for example, the cannula or tubing leading to a cannula is connected. At the proximal end is the piston which pushes the medium through the distal end during application. The movement of the piston can be done manually or mechanically. The term piston also includes pistons. For manual operation of the syringe, it is helpful for the operator if the syringe carries finger holders at the proximal end. In this case, the finger holders usually have at least one surface as an abutment for the index finger and middle finger, wherein the surface of the finger holder is substantially perpendicular to the axis of the syringe barrel. In mechanical pumping devices, various models are known. A syringe then preferably carries one or more device holders at the preferably proximal end. Especially good is such a mechanical pump in the EP 0 584 531 (Reilly et al., Filing date 21/07/93). Mixed forms of finger holder and device holder are possible.

The Medium in the filled Syringe is a mixture of a fluid medium and at least one Gas. The gas volume should be as small as possible fail, desirable is a gas volume which is zero. The medium can be one Liquid, a solution, a suspension or an emulsion. These manifestations are in W. SCHRÖTER et al., (1987) Chemistry; Facts and Laws, 14th edition, Leipzig on pages 23 and following.

Prefers is a fluid medium which is a contrast agent. in this connection these are the following contrast agents with the generic ones Name: amidotrizoic acid, gadopentetic, Gadobutrol, gadolinium EOB-DTPA, iopamidol, iopromide, iotrolan and Iotroxic acid.

Advantageous are medical according to the invention Syringes, the piston being complementary to the shape of the distal End of the syringe is designed to a residual volume, which from the syringe despite complete push in of the piston can not be removed, minimize.

Prefers is a medical invention Syringe, wherein the piston convex, planar or concave training or pyramidal, conical, truncated pyramidal, frustoconical or hemispherical Has configurations, depending on the formation of the end of the Syringe the protuberance pointing distally or proximally.

Prefers is a syringe according to the invention, in which the syringe is autoclavable.

More preferred is a syringe according to the invention, when the syringe at a support pressure autoclavable.

meaningful is it that at least the syringe body is poured or sprayed in a sterile room at least 250 ° C.

Advantageous is a syringe according to the invention, in which the sterile syringe can be packed in a sterile container is, which has at least one gas-permeable, but not germ-permeable wall.

A Syringe must from foreign bodies getting cleaned. foreign body are all the particles that are not from the material of the syringe and the medium and the detached fragments the syringe are.

fumed are substances that, as fragments of the bacteria, provide an immune response provoke of man. In particular, they are lipopolysaccharides, i.e. Cell wall components of Gram-negative bacteria.

After this the syringe has been partially assembled, it may be possible, the syringe again from foreign bodies to clean. foreign body are all the particles that are not from the material of the syringe and the medium are and the detached fragments of the Syringe are.

When Sterilization procedures are particularly suitable: radiation sterilization or chemical sterilization procedures.

When chemical sterilization processes are treatment with ethylene oxide, Propan-3-olide and diethyldicarbonate, still hydrogen peroxide and an ozone / vapor mixture known.

As well Sterilization with high-energy radiation is possible. Here are gamma rays and x-rays known.

Possibly The parts of the syringe are in bacteria-proof, but gas-permeable film or aluminum in sterile packaging. The sterilization is done with help of thermal and / or chemical sterilization, with gamma rays or X-rays, neutron beams or beta rays or a mixture of the aforementioned rays. Preference is given to the treatment with hydrogen peroxide or ozone / steam mixture.

Subsequently, will the syringe body filled by the distal or proximal end, either the piston or the closure that Seal opposite ends. Subsequently, the filling opening is through the closure or closed the piston.

The distal end is connected with a closure or by welding the closed at the distal end. When welding, the distal end points a predetermined breaking point proximal to the weld on. This can do that distal end can be opened easily after welding.

in the next Step up the syringe or cartridge in autoclave or sterilizer with hot air or thermally sterilized by microwave.

In order to the piston does not migrate within the cylinder, it is advantageous when the piston while of sterilization is fixed.

Possibly Is it possible, a support pressure in the sterilization room of the autoclave or the sterile chamber build up a gas in the sterilization room, the pressure on the outer surface of the Syringe bigger, same or less than the pressure on the inner surface of the syringe. The support pressure is to be defined as the pressure which is the sum of the partial pressures in the sterilization room minus corresponds to the partial pressure of the vapor.

Advantageous is when the piston is readjusted after sterilization. hereby is guaranteed that the Piston is in an optimal position. Sometimes it is the friction between piston and cylinder is so great that adjusting the piston in the stable position, with no pressure difference between inside and outside the syringe is not self-sufficient.

At At this point, optical control is advantageous. This will guaranteed that particles that are in the syringe, to be found. Spraying with particles are to be rejected.

Especially essential is the packaging of the sterilized syringe in one container and sterilizing the stuffed Container. This process can take place in a sterile room. This step is particularly advantageous because it gives a security alone is to offer the attending physician an injection that is also external is sterile. This can reduce the risk of contamination. Even with the mechanically emptied syringes comes this advantage to the validity, since the doctor also touches the syringe here. Become frequent used the mechanically drained syringes in sterile operating rooms. In these rooms allowed to only sterile or disinfected materials are introduced. Thus, a must To be emptied mechanically syringe externally necessarily sterile.

A further advantage is that the filled and terminal-filled syringe is packed in sterile plastic film and / or aluminum foil under optionally aseptic conditions. It is advantageous that the syringe is packed in possibly sterile blisters, optionally aseptic Conditions prevail.

Subsequently, will the syringe in the container lies, outwardly sterilized again by injecting the syringe with ethylene oxide, propan-3-olide and / or diethyldicarbonate.

Farther Hydrogen peroxide and an ozone / vapor mixture are known.

The Packing the sterilized syringe in a container and sterilizing the filled container can be done in a sterile room. This step is special advantageous, because this alone is given a security, the doctor to offer an injection, also externally is sterile. This can reduce the risk of contamination. Even with the mechanically emptied syringes comes this advantage to the validity, since the doctor also touches the syringe here. Become frequent used the mechanically drained syringes in sterile operating rooms. In these rooms may only sterile or disinfected materials are introduced. Consequently must also a syringe which is to be emptied mechanically must be absolutely sterile on the outside.

When chemical sterilization processes are treatment with ethylene oxide, Propan-3-olide and diethyldicarbonate, still hydrogen peroxide and an ozone / vapor mixture known. Such methods are described in:

• G. SPICHER (1990) Possibilities and limits of sterilization with gases and ionizing radiation in comparison with the classical sterilization procedures, pharmaceutical Technology, Vol. 11, No. 4, pp. 50-56;
• H. HÖRATH (1990) Legal Framework for Sterilization with Ethylene Oxide and formaldehyde, Pharma Technologie, Vol. 11, No. 4, pp. 57-64;
• J. SCHUSTER (1990) The Practice of Operational Ethylene Oxide Sterilization and Optimization Experiments, Pharma Technology, Vol. 11, No. 4, pages 65-71;
• M. MARCZINOWSKI (1990) Practical implementation of formaldehyde sterilization, Pharma Technology, Vol. 11, No. 4, pp. 72-76;

As well Sterilization with high-energy radiation is possible. Here are gamma rays and x-rays known. Likewise, neutron beams, beta rays and alpha rays are used.

• a) sterile Herstellung der Spritzenteile oder Reinigen und Sterilisieren der hergestellten Spritzenteile,
• b) Zusammensetzen der Teile, (i) dabei wird das distale Ende bei proximalem Befüllen verschlossen oder (ii) das proximale Ende durch den Kolben beim distalen Befüllen verschlossen,
• c) gegebenenfalls Sterilisieren der zusammengesetzten Spritze,
• d) proximale oder distale Befüllen, je nach noch verbliebener Öffnung,
• e) proximale Verschließen durch den Kolben oder distales Verschließen durch einen Auslaßverschluß oder ein Verschweißen des Auslasses,
• f) Sterilisieren der befüllten und verschlossenen Spritze,
• g) gegebenenfalls Sterilverpacken der Spritze in einem Behälter mit mindestens einer Oberfläche, die gaspermeabel, jedoch nicht keimpermeabel ist.

The invention also includes a method of making a prefilled sterile syringe comprising the following features:

• a) sterile production of the syringe parts or cleaning and sterilizing the syringe parts produced,
• b) assembling the parts, (i) closing the distal end on proximal filling or (ii) closing the proximal end of the piston during distal filling,
• c) optionally sterilizing the composite syringe,
• d) proximal or distal filling, depending on the remaining opening,
• e) proximal closure by the piston or distal closure by an outlet closure or welding of the outlet,
• f) sterilizing the filled and sealed syringe,
• g) optionally sterile packaging of the syringe in a container having at least one surface which is gas permeable but not germ permeable.

Such methods are described in detail in EP 0 227 401 . EP 0 553 926 and the US patent US 5,207,983 described. Reference is also made to the reference E. Venten and J. Hoppert, Pharm. Ind. Vol. 40, No. 6 (1978). This publication, including the literature cited therein, details sterilization methods. The publication of Venten and Hoppert is by quotation part of the application. It is particularly advantageous if a combination of the syringes according to the invention and an applicator device consists of injectomat and outlets, the injectomat being a pumping system and the connections connecting the outlet of the syringe to the patient. Such an injectomat is z. B. in the EP 0 192 786 described.

The invention further comprises a combination of a pre-filled, terminally sterilized syringe according to the invention and an application device of automatic injectors and ports, the injectomat being a pumping system and the ports connecting the outlet of the syringe to the patient. Such a pumping system is in the publication EP 0 584 531 described.

Further Features and Practices of Invention will become apparent from the following description of embodiments based on the figures. From the figures show:

1 a syringe as used for the invention;

2 a cross-sectional view of a piston, as used for the invention;

3 an enlargement of the section X in 2 ;

4 an enlargement of the section Y in 2 ;

5 a view of a piston of a first embodiment seen from the distal side of the syringe;

6 a view of the piston of the first embodiment seen from the proximal side;

7 a view of a piston of a second embodiment seen from the proximal side;

8th a view of a piston of a third embodiment seen from the proximal side;

9 a view of a piston of a fourth embodiment seen from the proximal side;

10 a view of a piston of a fifth embodiment seen from the proximal side;

11 a view of a piston of a sixth embodiment seen from the proximal side;

12 a view of a piston of a seventh embodiment seen from the distal side; and

13 a view of the piston of the seventh embodiment seen from the proximal side.

1 shows a syringe as used for the present invention.

As in 1 shown has a syringe 1 a cylinder 2 and a piston 3 on. The cylinder 1 has a cap at a distal end 4 with a central opening and a neck 5 for picking up a needle or a hose. At a proximal end of the cylinder 2 is a flange 6 for holding or inserting into a motor driven actuator (not shown). From the proximal side is a piston rod 7 in the pistons 3 screwed. For further explanation, reference is made to E. Venten and J. Hoppert, 1978, Pharm. Int. Vol. 40, No. 6, pp. 665-671, the contents of which are incorporated herein by reference.

The terms "top", "bottom", "side" used herein refer to the position of the syringe 1 as they are in 1 is shown. That is, "top" refers to the direction to the distal end, "bottom" refers to the direction to the proximal end.

Now the general structure of the piston 3 with reference to 2 described.

The piston 3 has a generally cup-shaped core element 8th open, downwards. On an inner peripheral surface of the core member 8th is an internal thread 9 provided in which the piston rod 7 can be screwed. The core element 8th has a lateral peripheral surface 10 on. The lateral peripheral surface 10 of the core element 8th is at a distance from an annular ring element 11 surround. The ring element 11 extends in height, ie from a proximal end 12 to a distal end 13 essentially the same height as the core element 8th from a proximal end 14 to a distal end 15 extends. The ring element 11 has at its upper, distal portion a circumferential, radially extending projection or flange 16 on. The ring element 11 has at its lower, proximal portion a circumferential projection 17 with an undercut 18 on.

The core element 8th and the ring element 11 are through a plurality of webs 19 connected. The webs extend substantially over the height of the ring element 11 or the core element 8th , After a modification, the bridges extend 19 but only over a smaller height than the core element 8th and the ring element 11 ,

The core element 8th , the ring element 11 and the footbridges 19 are integrally made by injection molding of a thermoplastic. As a thermoplastic are particularly suitable polypropylene.

On an upper outer surface 20 of the core element 8th and on a lateral outer peripheral surface 21 of the ring element 11 is a layer 22 applied from a sliding material. After a modification is the layer 22 made of sliding material only on the lateral peripheral surface 21 of the ring element 11 applied.

The layer 22 From sliding material has at the upper portion of a circumferential sealing lip 23 on. In 2 is a circle labeled X, which is the sealing lip 23 surrounds. The circle X is enlarged in 3 shown. As in 3 can be seen, points the sealing lip 23 a substantially obliquely upwardly and outwardly extending cross-section, wherein the upper tip of the rectangle is chamfered. The sealing lip 23 forms together with the top of the layer 22 of sliding material a V-shaped circumferential recess 24 , The sealing lip 23 is relatively long and has a relatively shallow angle with respect to the axis of the piston 3 on. This fulfills two functions. The dynami Behavior is such that when you press the syringe 1 , ie pushing the piston 3 to the distal end, the sealing lip is pressed against the cylinder inner wall. In the static ratio, ie without movement, the sealing lip 23 pressed by its elasticity against the cylinder inner wall and ensures a seal.

Furthermore, at about half the height of the outer peripheral surface of the layer 22 of sliding material an outwardly projecting circumferential additional sealing lip 25 intended. In 2 is a circle labeled Y, which is the sealing lip 25 surrounds. The circle Y is enlarged in 4 shown. The sealing lip 25 provides extra security in the sealing of the piston 3 opposite the cylinder 2 the syringe.

How out 2 it can be seen, the layer extends 22 made of sliding material in the undercut 18 , Thereby and by the provision of the circumferential projection 16 is a good stop of the shift 22 made of sliding material on the ring element 11 secured. The layer 22 made of sliding material is after the injection molding of the core element 8th , the bridge 19 and the ring element 11 on the still warm mold from the core element 8th and the ring element 11 sprayed. This adds additional a particularly intimate connection of the layer 22 made of sliding material and the core element 8th and the ring element 11 generated.

The layer 22 is formed of a thermoplastic elastomer. This has the consequence that a small friction value of μ between the layer 22 made of sliding material and the inner wall of the cylinder 2 the syringe 1 can be achieved.

In the following, embodiments of the arrangement of the core element 8th , the bridge 19 and the ring element 11 with reference to the 5 to 13 explained.

5 shows the piston of a first embodiment from below, before the layer 22 is applied from sliding material, and 6 shows the piston of the first embodiment from above, before the layer 22 is applied from sliding material. The piston 26 has a core element 27 and a ring element 28 on, passing through four footbridges 29a . 29b . 29c and 29d are connected. The core element 27 is in proportion to the entire piston 26 relatively small, its diameter is about 1/8 of the diameter of the piston. On the top (see 6 ) is a groove 30 shown in the layer 22 from slip material in the spraying occurs, so that the layer 22 made of sliding material reliably on top of the piston 26 is held. The bridges 29a to 29d extend radially from the core element 27 to the ring element 28 , When the piston of the first embodiment is heated, the webs are stiffened 29a to 29d in their longitudinal direction and thus absorb the thermal expansion. At the in 5 and 6 shown first embodiment are four webs 29a to 29d intended. According to a modification, however, three or five or more webs may be provided. At the peripheral surface, the layer becomes 22 on the sliding material through the flange 16 and the lead 17 held.

7 shows a piston 31 a second embodiment from above. The piston 31 The second embodiment is substantially the same as the piston 26 The first embodiment gebil det. Therefore, a description of the same features will not be repeated. The piston 31 however, the second embodiment is different from the piston 16 the first embodiment in that webs 32a . 32b . 32c and 32d not radially from the core element 27 to the ring element 28 extend, but that the webs 32a to 32d tangent to the core element 27 are attached. This approach has the advantage that upon expansion of the core element 27 and the ring element 28 when heating the bars 32a to 32d not be upset, but a rotary motion on the core 27 exercise. Therefore, the thermal expansion of the piston 31 be absorbed even better during warming.

8th shows a piston 33 a third embodiment from above. The piston 33 The third embodiment substantially corresponds to the piston 26 the first embodiment. Therefore, the description of the same features will not be repeated. The piston 33 however, the third embodiment is different from the piston 26 the first embodiment in that a ring element 34 is not continuous, but in ring segments 35a . 35b . 35c . 35d . 35e and 35f is divided, which are spaced apart in the circumferential direction. Stege 36a . 36b . 36c . 36d . 36e and 36f extend radially from the core element 27 to the ring segments 35a to 35f , The third embodiment has the advantage that upon thermal expansion of the ring element 34 the gaps between the ring segments 35a to 35f can accommodate the expansion. The force on the piston 33 can be better absorbed by thermal expansion. At the in 8th shown third embodiment are six ring segments 35a to 35f and six bridges 36a to 36f intended. However, according to a modification, three to five or seven or more ring segments and webs may be provided.

9 shows a piston 37 a fourth embodiment. The piston 37 The fourth embodiment substantially corresponds to the piston 33 the third embodiment. Therefore, the Be spelling of the same characteristics not repeated. The piston 37 however, the fourth embodiment is different from the piston 33 the third embodiment in that webs 38a . 38b . 38c . 38d . 38e and 38f not radially on the core element 37 attack, but that the webs 38a to 38f tangent to the core element 27 attack like the piston 31 the second embodiment. Thus, the piston unites 37 In the fourth embodiment, the advantages that the second embodiment and the third embodiment have. A thermal expansion of the core element 27 and the ring element 34 can be absorbed superbly.

10 shows a piston 39 a fifth embodiment from above. The piston 39 corresponds essentially to the piston 26 the first embodiment. Therefore, a description of the same features will not be repeated. The piston 39 however, the fifth embodiment is different from the piston 26 the first embodiment in that a core element 40 compared to the entire piston 39 is formed larger. The diameter of the core element 40 The fifth embodiment corresponds to about 2/3 of the diameter of the piston 39 the fifth embodiment. This allows a great stability for the core element 40 , Stege 41a . 41b . 41c and 41d can be very short. This embodiment is particularly advantageous when no large temperature increases are to be expected, so that the thermal expansion remains limited.

According to a modification of the fifth embodiment, the webs 41a to 41d not radially on the core element 40 attached, but they are provided tangentially as in the second embodiment. Thus, the same advantage can be obtained in the modification as in the second embodiment.

11 shows a piston 42 a sixth embodiment. The piston 42 The sixth embodiment corresponds to the piston 39 the fifth embodiment. Therefore, the description of the same features will not be repeated. The piston 42 however, the sixth embodiment has the ring member 34 on that in ring segments 35a to 35f is divided, as in the piston 37 the fourth embodiment. At the piston 42 the sixth embodiment are webs 43a . 43b . 43c . 43d . 43e and 43f tangent to the ring element 40 appropriate. Unlike the piston 37 However, the fourth embodiment, the webs 43a to 43f not in the middle of the ring segments 35a to 35f attached, but the webs 43a to 43f are each at one end of the ring segments 35a to 35f attached, as in 11 is shown. The procedure with the piston 42 The sixth embodiment therefore additionally has the advantage that the ring segments 35a to 35f can fold in at their free ends. This allows the ring segments 35a to 35f with thermal expansion, it is even better to absorb the thermal expansion.

According to a modification of the sixth embodiment, the ring segments 35a to 35f not uniformly thick, as in 11 is shown, but the ring segments 35a to 35f are beveled at their free ends on the inside. This allows the ring segments 35a to 35f even better turn inwards, with the webs 43a to 43f serve as fulcrums.

This allows the ring segments 35a to 35f even better avoid the thermal expansion.

12 and 13 show a piston 44 a seventh embodiment. The piston 44 The seventh embodiment corresponds to the piston 42 the sixth embodiment. Therefore, the description of the same features will not be repeated. The piston 44 The seventh embodiment is different from the piston 42 However, the sixth embodiment in that webs 45a . 45b . 45c . 45d . 45e and 45f the core element 40 with the ring segments 35a to 35e connect, which are not radially aligned, but which are slightly inclined relative to the radial direction. The bridges 45a to 45f are each in the middle of the ring segments 35a to 35f appropriate. The bridges 45a to 45f are not so strongly inclined that they are tangential to the core element 40 are attached, but they are arranged slightly closer to the radial direction. Also with the piston 44 In the seventh embodiment, the thermal expansion can be absorbed when the piston and the syringe are heated, the thermal expansion.

Claims (17)

Piston ( 3 . 26 . 31 . 33 . 37 . 39 . 42 . 44 ) for a syringe ( 1 ) with a syringe barrel ( 2 ), comprising: a core element ( 8th . 27 . 40 ) having an outer peripheral surface ( 10 ) and a ring element surrounding the core element at a distance ( 11 . 28 . 34 ) having an outer peripheral surface ( 21 ), wherein the ring element on its outer circumferential surface with a sliding material ( 22 ) is coated and the core element and the ring element by webs ( 19 . 29 . 32 . 36 . 38 . 41 . 43 . 45 ) are connected. Piston according to claim 1, in which the webs ( 29 . 36 . 41 ) radially from the core element ( 27 . 40 ) to the ring element ( 28 . 34 ). Piston according to claim 1, wherein the Ste ge ( 32 . 38 . 43 ) tangentially from the peripheral surface ( 20 ) of the core element ( 27 . 40 ) to the ring element ( 28 . 34 ). Piston according to one of claims 1 to 3, in which the ring element ( 28 ) is integrally formed. Piston according to one of claims 1 to 3, in which the ring element ( 34 ) a plurality of circumferentially spaced ring segments (US Pat. 35a . 35b . 35c . 35d . 35e . 35f ) having. Piston according to one of claims 1 to 5, with a lower side, which is a proximal end of the syringe ( 1 ) and with an upper surface facing a distal end of the syringe (FIG. 1 ) is facing. Piston according to claim 6, wherein on the outer surface ( 21 ) of the ring element ( 11 ) radially around the outer surface ( 21 ) of the ring element ( 11 ) extending projection ( 23 ) is provided on a top side facing portion. Piston according to claim 6 or 7, wherein on the outer surface ( 21 ) of the ring element ( 11 ) radially around the outer surface ( 21 ) of the ring element ( 11 ) extending projection ( 17 ) with an undercut ( 18 ) on an underside facing portion of the outer peripheral surface (FIG. 21 ) of the ring element ( 11 ) is provided. Piston according to one of Claims 6 to 8, in which the core element ( 8th ) is open to the bottom and an internal thread ( 9 ) for receiving a piston rod ( 7 ) having. Piston according to one of claims 6 to 9, in which the sliding material ( 22 ) on top of the core element ( 8th ) and the ring element ( 11 ) is formed. Piston according to one of claims 8 to 10, in which the sliding material ( 22 ) into the kerning ( 18 ). Piston according to one of claims 6 to 11, in which the sliding material ( 22 ) an annular sealing lip ( 23 ) on the top side facing portion, wherein the sealing lip ( 23 ) on an inner wall of the syringe barrel ( 2 ) sealingly. Piston according to one of claims 1 to 12, in which the core element ( 8th ), the webs ( 19 ) and the ring element ( 11 ) are integrally formed of the same material. A piston according to claim 13, wherein the material is a Thermoplastic, preferably polypropylene, is. Piston according to one of claims 1 to 14, in which the sliding material ( 22 ) is a thermoplastic elastomer, preferably santoprene. Syringe ( 1 ) with a syringe barrel ( 2 ) made of glass or plastic and one in the syringe barrel ( 2 ) introduced piston ( 3 ) as claimed in any one of claims 1 to 15. A syringe according to claim 16 which is pre-filled.