BLOOD EXTRACTION DEVICE WITH A SUPPORT OUE PRESENTS A CANNULA
FIELD OF INVENTION The present invention relates to a blood extraction device with a support having a hollow needle-shaped cannula, configured with a sharp cutting edge, which is wrapped with clearance by means of a rubber tube as a flexible tube , elastic, closed at one end, the support being provided with a section that secures the valve rubber by its outer lateral surface. DESCRIPTION OF THE PREVIOUS TECHNIQUE From US-A 3 585 984 a blood extraction device of this type is known with a support having a hollow needle-shaped cannula configured with a sharp cutting edge. The cannula is enclosed by a flexible rubber tube-like valve, closed at one end, with clearance between the cannula and the valve gum. The support has a dome-like projection towards the front in which a head piece or plug, thickened, integral with the valve rubber penetrates. This head piece thus represents almost a section that fixes the valve rubber by its outer side surface. The valve rubber is mounted specifically in a front area, that is to say with its thickened head part, with positive connection on the cannula, and therefore it is fixed by friction forces in its interior in relation to the cannula and on its exterior with relation to support. In a blood extraction device disclosed in DE-C 18 12 742 an open tube-shaped support is used on one side having a double hollow needle-shaped cannula configured at both ends with a cutting edge sharp, whose rear end penetrates the support that also serves as a guide bushing. While the end of the rear cannula of the hollow cannula with double edge is encircled by the elastic valve rubber with radial clearance, the end of the front cannula protrudes from the front wall of the support and serves for its introduction into a vein of a patient. The extracted blood reaches a blood collection tube that has previously been connected to the support by the open end thereof. When assembling the support and the blood collection tube, the cutting edge of the rear end of the cannula passes through the wall or the bottom, directed to it of the elastic valve rubber, and then a closing plug of the blood collection tube. , so that ultimately the end of the rear cannula penetrates the blood collection tube; the elastic valve rubber is compressed in the manner of an accordion. After the extraction of blood and removal of the blood withdrawal tube from the support, the valve rubber automatically assumes its starting position in which it closes hermetically the rear end of the cannula. The support could alternatively also be reduced only to a disc that has the cannula, that is to say that the guide sleeve is not necessary. The disc of the support could be united in a case of this type with the dome of a cap of the blood collection tube. Another embodiment of a blood extraction device configured during the extraction of blood with a double cannula, has been disclosed by DE-U 80 16 927. The double cannula consists in this case of a cylindrical housing open on one side with an outer cone formed integrally and with a single-ended cannula disposed therein, which forms the rear cannula end in situ. On the outer cone a cone accommodates a support with a cannula or hollow needle sharpened at both ends, so that once these two components are assembled there is a double cannula, as already described above. With this embodiment of the needle, an adaptation is possible which allows a conventional Luer cannula to be connected to the market with a blood extraction tube. The existing elastic valve rubber also lies intimately in the hollow needle of the holder or of the adapter. Within the framework of employment possibilities, comes to attach an adapter of this type with Luer cone through a special connection to a flexible tube filled with blood, for example. In a safety cannula for multiple blood extraction, known from DE-A 2903 167, the elastic valve rubber, which is compressed in the manner of an accordion when it is connected to the blood collection tube, is again arranged with clearance radial with respect to the rear end of the double cannula, that is to say the valve rubber has in its entire length an inner diameter that is greater than the outer diameter of the cannula or what is the same of the hollow needle. The valve rubber, which surrounds or surrounds the rear end of the cannula in the blood extraction devices, makes it possible to fill several blood extraction tubes by means of coupling to the double cannula. In the case of a valve rubber lying intimately on the hollow needle (see DE-U 80 16 927), friction between the needle and the valve rubber inevitably occurs, which results in the valve rubber back slowly to the starting position slack from the grip to accordion mode; when changing the tubes of extraction of blood is therefore in these cases frequent not avoidable that blood drops of the cannula sprout. This is because the valve rubber can not close the rear end of the double sharpened cannula quickly enough. This is avoided when the elastically flexible tube-like rubber band adopts a radial distance up to the needle, that is to say that it surrounds the needle with clearance (see memory DE-A 29 167 and memory DE-C 18 12 742 ). Due to the fact that the valve rubber does not lie intimately on the needle, problems to provide the valve rubber in a safe position in the holder or adapter anyway are still problems. The valve rubber of the blood extraction device known from DE-C 18 12 742 is therefore configured at its open end with a stop collar which is girded against an inner back of the support and is otherwise positioned in this situation solely by virtue of the friction between the outer side surface of the collar and the inner side surface of the support. The valve gland of the double cannula disclosed in DE-A 29 03 167 is configured at its open rear end with an outer collar which is inserted into an annular groove of the front wall of the support. Without taking into account that in this case too, the valve rubber is fixed only with a loose fitting in the support, the assembly of the valve rubber causes difficulties and requires great care when inserting the elastic valve rubber into the annular groove . In addition, numerous other fastening techniques for the valve rubber are known, for example, the sliding assembly with positive connection of the valve rubber on a cylindrical section in the central area of the cannula.
(see DE-A 37 40 269). For the memory EP-A 0
619 096 it has been known to slide the valve rubber in its front area on a cone-shaped flange, whereas on the other hand memory O-A 95/16395 teaches mounting the valve rubber on a collar in the form of surrounding cone with undercuts and stick it there, if necessary. According to the specification EP-A-0 678 279 the valve rubber with a surrounding neck engages in a surrounding edge inside the support and is secured by a plastic insert. SUMMARY OF THE INVENTION The object of the invention is to provide a blood extraction device of the kind mentioned at the outset, which allows a safe adjustment of the valve rubber on the support or adapter with a low assembly cost. This task is solved according to the invention because the section of the support that fixes the valve rubber on its outer side, is a deformable tightening element, in this way it is achieved that the valve rubber is no longer only loose or attached by friction or even glued to the support, but by means of the deformable clamping element according to the invention, it is fixed in a captive manner; this valve rubber can no longer be removed from the cannula and can not be removed by itself from the support at all. In the same way it is guaranteed that between the valve rubber and the needle, or what is the same, the rear end of the double cannula, there is a radial distance along the entire length of the valve rubber, so that between these two parts no friction is produced, and the elasticity of the valve rubber is taken care of by an immediate closure of the rear end of the cannula, when a blood extraction tube is replaced; in this way a leakage of blood in this place is avoided. The manufacture of the valve rubber does not require excessive demands in terms of compliance with contours and tolerance, nor are special seals required on the inner side surface of the valve rubber. DETAILED DESCRIPTION OF THE INVENTION Other characteristics and advantages of the invention result from the following description in which an exemplary embodiment of the object of the invention is explained in detail by means of a support for a blood extraction device, which is configured as a support open on one side with a section in the form of a tube that acts as a guide sleeve, and has a double cannula sharpened at both ends. In the same way, the different embodiments of the supports described at the beginning can alternatively also be used, the support can also be configured integrally with the cannula. From a long-known blood collection device, there is shown in the single figure of the drawing a support 1 open on one side, on the front wall 2 of which, in the exemplary embodiment, a double cannula 3 is fixed by means of, for example , welding or pecjado; therefore, additional ancillary support can be dispensed with. The double cannula 3 is configured in front and behind with a cutting edge 4 and 5 respectively; the rear end of the cannula 6 penetrates the guide sleeve 7 of the support 1, while the end of the forward cannula 8 protrudes from the support 1 and for the extraction of blood is introduced into a vein of a patient. For the extraction of blood the guide sleeve 7 is mounted in a known manner on a corresponding blood extraction tube, the cutting edge 5 of the end of the cannula 6 passing through both the bottom 9 of a valve rubber 11 that surrounds the end of cannula 6 rear with radial distance 10, as well as to an elastic closing plug of the blood collection tube (not shown), until communication with the interior of the blood collection tube is established. The rubber valve 1 elastic, as a flexible tube, is introduced with its open end, opposite the bottom 9, in a clamping element 12 concentric to the guide bush 7 in the support 1, formed on the inner side of the front wall 2. The clamping element 12 can be treated, for example, of a peripherally closed ring, or of a ring that consists of spaced-apart partial segments, which, or their annular segments, once fitted the valve rubber is brought up, or lean against the outer lateral surface 13 of the valve rubber 11, and in doing so is pressed and They deform, or deform, permanently for the tightening of the valve rubber 1, as illustrated in the lower half of the drawing by the reference figure 12 'for the clamping element. The open end of the valve gland 11 therefore only needs to be inserted until it stops on the lower side of the front wall 2 in the annular gap between the clamping elements 12, and is then firmly secured in the support 1 after the deformation of one or more tightening elements. The formation of the tightening element or of individual partial tightening elements can be achieved, for example, by means of a plug having a hole for receiving the rear end of the cannula 6, including the valve rubber 11 that wraps it. When the front section of the bore is conical and has a diameter greater than that of the clamping element 12 in the form of a bushing, or the individual clamping elements provided for tightening it, or the clamping elements, when a axial movement of the male are pressed by the conical part of the bore in the outer lateral surface 13 of the valve rubber 11 (see reference numeral 12 'in the figure). Once the core has been withdrawn, the clamping element 12 remains in this position and tightens the valve rubber 11 firmly and imperceptibly in the support 1. NOVELTY OF THE INVENTION The present invention has been described as a novelty, and therefore , the content of the following claims is claimed as property.