EP0657208A1 - Device for mixing a multicomponent cement and process for performing the mixing - Google Patents

Abstract

The invention demonstrates an apparatus for mixing multicomponent cement (3), such as bone cement with at least one liquid component (3a), the components (3a, 3b) being introduced into an otherwise empty, slender mixing vessel (11). This mixing vessel is attached on its lower side to a positive and/or frictional coupling (4), which itself is connected to a vibrating drive (7), in order to transmit a vibrating motion to the mixing vessel in a vibration plane (5) transversely to the longitudinal axis (6) of the mixing vessel (11). In order to achieve good flow for mixing the components, a volume of gas or air is left in the mixing vessel (11), which permits a displacement of the liquid component against gravity in the case of accelerations transversely to gravity. A circular vibrating motion is particularly advantageous, because this generates constant acceleration and flow for mixing components (3a, 3b). Since the mixing vessel (11) is free of any additional internals, vessels can be used which are directly suitable for spraying out ready mixed cement. <IMAGE>

Description

The invention relates to a device for mixing a multi-component cement, with a mixing container and with a motor-driven mixing drive, the multi-component cement being introduced into the mixing container in the form of two or more components, at least one of which is liquid.

Multi-component cements are mainly used because of their short curing times, which allows processing with little loss of time. Two-component cements have the advantage that only two parts have to be coordinated to achieve a desired reaction. The mixing process is very important for the quality of such a cement when the two or more components are brought together.

A special type of multi-component cement is bone cement, which is used for the fixation of implants and which has to be processed sterile and which also has to be mixed in its preliminary stage under sterile conditions. So far, mixers have been used for this purpose, which, like a kitchen mixer with motor-driven stirrers, stir the components, at least one of which is liquid, in a mixing container.

The danger of such a device is that air is introduced into the liquid component during the mixing, similar to a cream beater, which is neither advantageous for the chemical reaction during mixing nor physically advantageous for producing large surfaces with the air.

Another possibility for mixing is to add propellant gas and to use frits or static mixers. However, the propellant gas itself is undesirable since, depending on the compatibility, it requires additional safety precautions.

The invention is intended to remedy these disadvantages. Its task is to provide the user of multicomponent cement with another mixing process. This object is achieved with the characteristics of the independent claims 1 and 11, in that the mixing container is a slim vessel which acts to carry out the mixing on its underside via a non-positive and / or positive coupling on a shaking plane transverse to the longitudinal axis of the vessel , designed as a shaking drive mixed drive, while the dependent claims 2 to 10 represent advantageous developments of the invention.

The invention has the advantage that, apart from a gas or air cushion, there are no foreign bodies for mixing in the mixing container and that a simply connected surface can form with the air, under which the actual mixing process takes place. This makes it possible to use the mixing container directly for further processing of the freshly prepared cement and to squeeze out the cement if the container is reduced in its filling volume under the action of a mechanical force from outside. Since the relative displacement of the liquid component to the vessel wall is important for the mixture, the mixing container becomes a narrow vessel designed to produce a large wetted surface in relation to the amount filled. The movement of the vessel takes place in that the bottom of the vessel can be placed on a non-positive and / or positive coupling of a shaking drive. Through a shaking movement in a plane transverse to the longitudinal axis of the vessel, the vessel wall is displaced relative to the liquid via the coupling and generates shear stresses and flow. The entire vessel can be anchored to the coupling without any additional support points, or the vessel is held by hand and only deflected by the coupling at one end in accordance with the shaking movement.

Another advantage is that for a vessel with one or more end pieces, the mixing process can be carried out with the end to the atmosphere in order to keep undesired vapors away from the operating personnel. If such an end piece is designed as a funnel with a closure cap and the filling volume of the vessel can be reduced, then the freshly mixed cement can be sprayed directly at its destination without the need to transfer or scrape out cement. With a suitable coupling, the cylinder and piston of a cement syringe can be used directly as a mixing vessel. If the cement is bone cement that has to be processed under sterile conditions or if clean room conditions have to be observed, a separating film or a sterile cloth can be inserted between the coupling and the vessel with a suitable coupling. A bone cement that requires a mixing time of about two minutes can therefore be mixed exactly on site in the sterile area for processing and delivered in an ideal consistency, since there is no uncertainty regarding decanting or transfer from the non-sterile area. It is sufficient to provide so much play between the coupling and the vessel that the separating film between them can be inserted and the shaking movement is transmitted from the coupling to the vessel via the pressed release film.

A typical coupling option is a coupling with an outer or inner cone, on which a suitably designed vessel base can be centered and can absorb forces transversely to its longitudinal axis.

The actual shaking movement of the coupling takes place in a plane transverse to the longitudinal axis of the vessel. A circular movement in the shaking plane has proven to be advantageous if it is carried out with rotational frequencies ν ≧ 40 s⁻¹. A circular movement of the coupling - without making a rotation in the coupling axis - only slightly loads the vessel wall or an intervening separating film. The generation can be carried out with an eccentric on which the coupling is rotatably mounted. Another possibility is to attach the coupling to a circularly oscillating oscillating element of a shaker drive.

The mixture in the vessel requires the liquid to be displaced. This is particularly large if the liquid can move freely against the force of gravity under the pressure of a horizontally accelerated vessel wall. For this reason, so much air is left at the top when the components are filled in that the liquid can move upwards on the wall of the vessel even when the vessel is closed, the air flowing into the resulting empty space without great resistance.

Fig. 1

Schematisch einen Längsschnitt durch eine Mischvorrichtung mit Mischbehälter und Schütteleinrichtung;

Fig. 2

schematisch einen umgekehrten Mischbehälter aus Fig. 1 beim Auspressen von Zement;

Fig. 3

schematisch eine Mischeinrichtung, bei welcher Kolben und Zylinder einer Zementspritze als Mischbehälter verwendet werden; und

Fig. 4a, b

schematisch das herkömmliche und das erfindungsgemässe Mischen von einem Zweikomponenten-Knochenzement innerhalb seiner für die Handhabung vorgesehenen von seiner Temperatur abhängigen Zeiten.

In the following, the invention is explained on the basis of exemplary embodiments. Show it:

Fig. 1

Schematically a longitudinal section through a mixing device with a mixing container and shaking device;

Fig. 2

schematically shows an inverted mixing container from Figure 1 when squeezing cement.

Fig. 3

schematically a mixing device in which the piston and cylinder of a cement syringe are used as a mixing container; and

4a, b

schematically the conventional and the inventive mixing of a two-component bone cement within its intended times depending on its temperature for handling.

The figures show a device for mixing multicomponent cement such as, for example, bone cement with at least one liquid component, the components being introduced into an otherwise empty, slim mixing container. This mixing container is placed on its underside on a non-positive and / or positive coupling, which in turn is connected to a shaking drive in order to transmit a shaking movement to the mixing container in a shaking plane transverse to the longitudinal axis of the mixing container. In order to achieve a good flow for mixing the components, a volume of gas or air is left in the mixing container, which allows the liquid components to be displaced against gravity when accelerating transversely to the force of gravity. A circular shaking movement is particularly advantageous because it creates a constant acceleration and flow for mixing the components. Since the mixing container is free of any additional internals, containers can can be used, which are suitable for spraying the ready mixed cement.

In FIG. 1, an operator holds a mixing container 1, which consists of an elongated vessel 11, a screwed-on spray lid 9 and an end cap 8, and presses the vessel 11 on its underside against a coupling 4, which centers the vessel 11 with an inner cone 24. The coupling 4 is rotatably mounted with a bearing 19 on a pin 18, the pin 18 rotating with an eccentricity 22 about an axis of rotation 30 on a circular path 26. Perpendicular to the axis of rotation 30 and corresponding to the eccentricity 22 almost perpendicular to the longitudinal axis 6 of the vessel 11, a circular shaking movement occurs on the vessel 11 in a shaking plane 5, which, when the viscosity of the liquid components is not too great and the acceleration to the vessel wall 17 is adjusted accordingly, becomes one Mixing of the components leads. Since the pin 18 can rotate freely in the coupling axis 16 and the bearing friction as torque between the pin 18 and the coupling 4 is so low that it can be picked up by the operator via the mixing container 1, only a pivoting movement but no rotation occurs in the shaking plane 5 performed around its own axis. This pivoting movement leads to the fact that liquids inside the vessel rise to different heights on the vessel wall and shift their highest liquid level in a rotating manner, in that a gas cushion 20 enclosed by the liquid evades the liquid. The liquid component 3a and a solid component 3b, for example in the form of grains or powder, mix evenly when the gas cushion 20 is so large that the liquid 3a can move freely. The circular movement has the advantage that no splashes occur and that the liquid 3a is closed off by a simply connected contact surface to the gas cushion 20. A Volume fraction of 1/4 gas is usually sufficient. The cement is mixed intimately and without the introduction of gas and therefore has particularly good strength properties. This means that this type of mixing is also worthwhile if the cement is not sprayed directly to its final destination, but is refilled beforehand.

In FIG. 2, the cement 3 mixed together in a mixing container 1 according to FIG. 1 is pressed out after the removal of an end cap under the action of deformation forces 10. The vessel 11 is designed in such a way that it can be folded under lateral deformation forces 10 in order to press out the cement 3.

This mixing process has proven itself, for example, for two-component bone cement such as polymethyl methacrylate and additives, which are sold under the brand names "SULFIX" 60 and "SULFIX" 6 by companies of SULZER AG, Switzerland, when the rotational frequency for shaking a hand syringe ν ≧ 40 s⁻¹ is. The actual shaking times are then of the order of two minutes.

3 shows the piston 13 and the cylinder 12 of a cement syringe, which are used as a mixing container 1, the vessel 11 being closed after the components 3a, 3b have been filled in with a spray lid 9 and an end cap 8. In addition to components 3a, 3b, an air cushion 20 remains, which takes up about 1/4 of the vessel volume. The piston 13, which has a threaded connection 23 for a piston rod, forms the bottom of the vessel under lateral tension to the cylinder 12. The cylinder 12 is placed on its lower opening by an operator on a coupling 4 with a conical surface 15 and pressed. The coupling moves on a circular path 26 about a pivot axis 31 and thus produces a circular one Deflection in the shaking plane 5 and causes the components 3a, 3b to mix.

This type of coupling has the advantage that it can be used on cylinders with different internal diameters. In addition, there is only line contact in the shaking plane 5, so that it is easy to insert a separating film 14 between the coupling and the cylinder, which completely separates the mixing drive 2 from the cylinder 12 attached. In the case of bone cement, the separating film 14 is designed as a sterile cloth in order to cover the mixing drive 2 in a sterile manner and to be able to mix the cement in the sterile area. After mixing, the cylinder 12 is lifted and fixed with its collar 21 to a pistol (not shown), from which a piston rod acts on the piston 13 in order to squeeze out the cement.

Suitable as the actual mixing drive 2 is, for example, a model L46 blood shaker from LABINCO B.V., Zinkstraat 64, NL-4823 AC Breda, onto which a coupling 4 with a conical surface 15 is screwed. Such shakers are supplied with drive current electrically via an electric cable 25. One possibility for driving such shakers is to pivot a vibrating element 29 fastened on a rod designed as a bending spring 27 with a magnetic field 28 changing on a stator body 32 in a more or less circular manner.

• I werden die Komponenten in einen Mischbehälter eingebracht und mit einem mechanischen Rührgerät gemischt;
• II wird die Mischung in eine Spritze umgefüllt, (wobei irgendwo in I oder II der Uebergang in den sterilen Bereich stattfindet);
• III wird die Reaktionszeit des Zements abgewartet;
• IV wird Knochenzement ausgespritzt und das Implantat in seine Endlage gebracht;
• V muss der Zement erschütterungsfrei aushärten.

FIG. 4 a shows the typical preparations for a two-component bone cement for cementing an implant over time in minutes. In the period

• I the components are placed in a mixing container and mixed with a mechanical stirrer;
• II the mixture is transferred to a syringe (the transition to the sterile area taking place somewhere in I or II);
• III the reaction time of the cement is waited for;
• IV, bone cement is injected and the implant is brought into its end position;
• V the cement must harden without vibration.

In FIG. 4b, operations I and II have been replaced by M, in the period M in the sterile area, the sterile components are poured into a mixing container according to FIG. 3, sealed and mixed, and the mixing container is placed on the handle part of a cement syringe. The cement can thus remain closed until it is sprayed out to the atmosphere. The cement is sprayed out after 5 minutes, for example. I.e. 5 minutes before the planned spraying, the second component can be filled in the sterile area and the vessel closed to carry out the mixing process.

Claims (11)

Device for mixing a multi-component cement, with a mixing container (1) and with a motor-driven mixing drive (2), the multi-component cement (3) being introduced into the mixing container (1) in the form of two or more components, at least one of which is liquid characterized in that the mixing container is a slim vessel (11), which is used to carry out the mixing on its underside via a non-positive and / or positive coupling (4) in a shaking plane (5) transverse to the longitudinal axis (6) of the vessel (11) acting as a shaking drive (7) designed mixing drive (2) can be placed. Device according to claim 1, characterized in that the vessel (11) can be closed by means of one or more end pieces (8, 9) in order to carry out the mixing process with the end to the atmosphere. Device according to claim 1 or 2, characterized in that the volume of the vessel (11) can be reduced from the outside under the action of a mechanical force (10) in order to eject the cement (3) after mixing. Device according to one of claims 1 to 3, characterized in that the vessel (11) is formed from the cylinder (12) and piston (13) of a cement syringe. Device according to one of claims 1 to 4, characterized in that the coupling (4) between the vessel (11) and shaking drive (7) is provided with enough play that a movable separating film (14), preferably a sterile cloth, can be inserted between them. Device according to one of claims 1 to 5, characterized in that the coupling (4) is designed as a conical surface (15), which the vessel (11) under a contact pressure in the direction of its longitudinal axis (6) in the shaking plane (5) - or centered to transmit a shaking motion. Device according to one of claims 1 to 6, characterized in that the coupling axis (16) in the shaking plane (5) moves on a circular path (26), while the coupling half (4) is rotatably mounted on the shaking drive (7) or on a Vibrating element (29) of a shaker drive (7) is attached. Apparatus according to claim 7, characterized in that the rotational frequency for the circular movement in the shaking plane is ν ≧ 40 s⁻¹. Use of a device according to one of claims 1 to 8 for a multi-component cement (3), the liquid components of which have a viscosity of less than 400 [c St] at 20 ° C before mixing. Use of a device according to one of claims 1 to 8 for a multi-component cement (3) which is suitable as a bone cement, for example a two-component version of polymethyl methacrylate. Method for mixing multicomponent cement (3) using a device according to one of claims 1 to 10, characterized in that - In a first step, the components (3a, 3b) are filled into the vessel (11) and preferably closed therein, about 1/4 or more of the volume that can be filled in liquid not being filled in order to move a movable gas cushion, preferably an air cushion (20). to generate which, with its low mass of liquid (30) - in the event that it is continuously accelerated - can evade so that shear stresses and a flow arise in the liquid part (3a), which are used to mix the components (3a, 3b) to lead, - In a second step, the vessel (11) is pressed onto the coupling (4) of a shaker drive (7) for a certain mixing time in order to produce a constant displacement of the liquid (3a) relative to the vessel wall, with a circular shaking movement in the shaking plane (5) is preferred - In a third step, the mixed cement (3) is emptied for further processing or is preferably pressed directly from the vessel (11).

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