DE10207770B4 - Cannula with facet cut - Google Patents

Abstract

Cannula with facet cut, the facet cut comprising a flat pre-cut (1) with a first angle of inclination (α1) between the pre-cut (1) and the cannula longitudinal axis and also two side facets (2, 3) with a second inclination angle (α2) at the cannula tip wherein the side facets (2, 3) relative to the rough cut (1) are each arranged at a cannula rotation angle (Th1, Th2), the second angle of inclination (α2) being greater than the first angle of inclination (α1 ), characterized in that the cannula has an additional rear bevel (10) with a third angle of inclination (α3) which forms a coherent surface in the area of the cannula-side outlet of the pre-cut (1), the rear cut (10) at the same angle of rotation of the needle how the rough cut (1) is arranged and wherein the third angle of inclination (? 3) is smaller than the first angle of inclination (? 1).

Description

The present invention relates to a cannula with facet grinding according to the preamble of claim 1.

State of the art

For good puncture and low pain sensation in the patient cannula tubes are pointed and sharply made at the front end.

By far the most common cut on cannulas is the facet cut. It is described in international standards such as ISO 7864 for disposable sterile cannulas. It is manufactured in three grinding operations. First, the preliminary grinding under the inclination angle α1 of the cannula tube to the grinding wheel and then the facets under the rotation angles θ1 and θ2 and a larger inclination angle α2 of the cannula tube to the grinding wheel are ground.

Depending on the application and individual experience, the angle and length sizes are given on the cut. The production takes place with the possible precision on precision grinding machines and appropriate technique for the deburring and finishing of the cut.

From the US 3,308,822 Subcutaneous needles are known. In the EP 0 739 640 A1 For example, medical hollow needles and methods of making same are described. Other subcutaneous needles with bevelled tip geometry are in the US 5,752,942 as well as in the US 6,009,933 disclosed.

Criticism of the state of the art

Facet grinding is the simplest technological solution for giving a cannula good piercing and cutting properties and good control in mass production.

However, depending on the cut geometry specification and manufacturing technology, the use of particles from the skin and rubber or plastic parts is regularly observed during application. The reason for this lies in manufacturing tolerances during grinding and subsequent operations. Punching particles always occur when tissue or material parts reach the interior of the cannula opening during the piercing process and are cut by the inner edges of the cut until the cannula eye shears off the particles. For this reason, the inner edge of the Kanülenauges (preferably in großkalibrigen cannulas) rounded with an additional blasting operation. With thick-walled cannula tubes, the cut edges of the tissue and other material slide on the cut surfaces. The inner edge of the cannula eye remains as a risk for punching.

task

The invention has for its object to provide an improved facet grinding, which offers increased Einstechkomfort by the piercing resistance caused by the cannula eye and the punching of particles of skin, tissue and other materials is avoided.

solution

The object is achieved in a cannula with facet grinding according to the invention by the features of the characterizing part of claim 1.

Further preferred embodiments of the invention are defined by the subclaims.

In the production of a standard facet grinding, an additional grinding process takes place in the same rotational position of the pipe as in the rough grinding, by which the cannula eye is reset in the ground contour. The subsequent further treatment of the cannula is carried out according to existing technologies under the special aspect of ensuring the jet treatment of the inner edge of the eye to the beginning of the facet surfaces.

Description of an embodiment

The invention is illustrated in two embodiments.

Show it:

1 to 4 Standard facet cut

5 and 7 V-Bevel cut in side view

6 and 8th V-Bevel cut in top view

9 Piercing force diagrams

1 to 4: cannula with standard facet cut

After grinding the rough grinding (area 1 ) become in turned tube position the facet surfaces 2 and 3 grinded. The tip is created at the front end 4 with the central cutting edge to the point 5 , At the transition from the facet surfaces to the pre-grinding surface, the corner points are created 6 and 7 , The sharp inside edge of the points 6 to the eye 8th is rounded by an additional blasting operation.

Fig. 5 and Fig. 6: V Bevel ground with a flat additional surface

From the standard facet cut to the 1 to 4 is with an additional operation in the same rotational position of the tube as the pre-sharpening at a smaller angle α3 the area 10 grinded. The area 10 is formed from the rear end of the grinding so far that the cannula eye is set back in the ground contour. It ends in pre-sanding at the edges 12 , transverse to the tube axis. This design is characterized by particular value for money, because the additional grinding surface can be produced without additional effort in producing the grinding.

Fig. 7 and Fig. 8: V-Bevel ground with concave additional surface

From the standard facet cut to the 1 to 4 is with an additional operation in the same rotational position of the tube as the pre-grinding the additional surface 11 ground in concave form. The area 11 is formed from the rear end of the cut value so that the cannula eye is set back in the ground contour. It ends in pre-sanding at the edges 12 , transverse to the tube axis. This design is technologically sophisticated and more costly because the additional (concave) facet is made in a separate operation. However, due to the duller angle at the cannula eye, the fragmentation tendency is even further reduced.

The aspect ratios of the cut are preferably:
1/3 of the loop length is facet length,
1/3 of the loop length is the remaining pre-loop length,
1/3 of the loop length is additional area (V-Bevel)

Fig. 9: Einstechkraftdiagramme

The plunge force diagram for the deburring cut (characteristic curve with F ₀ , F ₁ , F ₂ ', F ₂ "and F ₃ ) shows reduced values in comparison to the standard facet cut (characteristic curve with F ₀ , F ₁ , F ₂ and F ₃ ) in the area of the eye (F ₂ ). The punching behavior of the ground edge is significantly reduced.

Achievable benefits

With the V-Bevel cut after the 5 to 8th the incision comfort in clinical use is significantly increased and reduces the traumatic burden on patients. Wound healing is much better.

The modern thin-walled cannulas are prone to punching out of particles due to manufacturing tolerances in the ground geometry and in the deburring technique. With the V-Bevel cut these dangers are reduced or completely excluded.

For technical applications (piercing of rubber or plastic membranes), the V-Bevel cut is advantageous because of the significantly reduced fragmentation tendency. Especially for thick-walled cannulas, the V-Bevel cut is a suitable solution for using a facet cut with a tip instead of the blunt single cut without provoking fragmentation.

Claims (4)

Cannula with facet cut, the facet cut comprising a flat pre-sharpening ( 1 ) with a first inclination angle (α ₁ ) between rough grinding ( 1 ) and cannula longitudinal axis and also at the cannula tip two side facets ( 2 . 3 ) with a second inclination angle (α ₂ ), wherein the side facets ( 2 . 3 ) relative to the preliminary grinding ( 1 ) are each arranged at a cannula rotation angle (Θ ₁ , Θ ₂ ), wherein the second angle of inclination (α ₂ ) is greater than the first angle of inclination (α ₁ ), characterized in that the cannula is located in the area of the cannula-side outlet of the rough grinding ( 1 ) an additional rear ground joint forming a continuous surface ( 10 ) having a third angle of inclination (α ₃ ), the rear section ( 10 ) at the same cannula rotation angle as the pre-grinding ( 1 ) and wherein the third inclination angle (α ₃ ) is smaller than the first inclination angle (α ₁ ). Cannula according to claim 1, characterized in that the additional grinding ( 10 ) is formed. Cannula according to claim 1, characterized in that the additional grinding ( 10 ) is concave. Cannula according to claim 1, characterized in that the total grinding length related to the longitudinal axis of the cannula is substantially facet-shaped ( 2 . 3 ), Rough grinding ( 1 ) and additional cut ( 10 ).

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