CANNULA DEVICE
This invention concerns a cannula device of the kind (hereinafter called "of the kind referred to") comprising a needle extending from a needle hub and a flexible tube connected to the rearward end of the hub and in fluid communication with the needle (e.g. to provide a supply of fluid to the needle).
According to the present invention there is provided a cannula device of the kind referred to characterised in that the needle hub is axially slidable in a shield there being a radially protruding stud on the needle hub slidable along an axially extending slot which extends through the thickness of the wall of the shield and inwardly directed formations at the rearward end of the slot which after resilient deformation of the shield block the stud when the needle is retracted into the shield to prevent redeployment of the needle.
There may be a window in the shield towards its rearward end and through which the needle hub is visible when the needle is fully retracted.
The needle hub and shield may be of contrasting colours.
Wings may extend from opposite sides of the shield capable of being pinched together to form, a grip to facilitate manipulation of the needle when inserting same into a blood vessel.
The needle may extend from the needle hub at an angle inclined from the central axis of the needle hub.
The invention will be further apparent from the following description with reference to the several figures of the accompanying drawings which show by way of example only one form of cannula device embodying same.
Of the drawings :-
Figure 1 shows a perspective view of the device from above;
Figure 2 shows an underneath plan view of the device;
Figure 3 shows a view similar to that of Figure 2 but with the needle retracted into the shield;
Figure 4 shows a cross-section through the device on the line IV-IV of Figure 2; and
Figures 5, 6 and 7 are perspective views showing the assembly of the needle hub with the shield viewed from the underside and also illustrating a locking feature located at the forward end of the shield.
Referring now to the drawings, it will be seen that the cannula device comprises a needle 10 which extends forwardly from a needle hub 11 axially slidable within a generally cylindrical shield 12. A flexible tube 13 for supply of fluid to the needle 10 extends between the rearward end of the needle hub 11 and a Luer connector 14. Wings 15 extend from opposite sides of the shield 12 and may be pinched together to form a grip to facilitate manipulation of the needle 10 when inserting same into a patient. After insertion the wings may be taped to the skin to hold the needle 10 in position.
A stud 16 extends outwardly from the needle hub 11 and is slidable along an axially extending slot 17 on the underside of the shield 12. The slot 17 extends through the thickness of the wall of the shield 12. Inwardly directed barbs 18 are provided at the rearward end of the slot 17 and are arranged after resilient deformation of the shield 12 to close behind the stud 16 when the needle 10 is retracted into the shield 12 after use by pulling on the flexible tube 13. In this way the needle 10 is locked against redeployment after it has been used.
As best seen from Figure 4, the needle 10 may extend from the needle hub 11 at an angle inclined from the central axis of the needle hub. In this way the needle tip is forced into contact with the inner surface of the shield 12 when the needle is retracted - a further precaution against the possibility of any needle-stick injury. If desired, the shield 12 may include a lip or flange at the forward end thereof to block the needle once retracted.
On the topside of the shield 12 is an aperture forming a window 19 at the rearward end of the shield and through which the needle hub 11, which is of a colour which contrasts with that of the shield 12, will be readily visible when the needle 10 is fully retracted to enable an operator to verify that this is so.
Figures 5 to 7 illustrate assembly of the needle hub 11 to the shield 12. The slot 17 tapers in width towards the rearward end and at the forward end is sufficiently wide to allow the needle hub 11 to be inserted with the stud 16 lying between the side edges of the slot 17. Insertion of the hub 11 through the wider section of the slot 17 may involve resilient deformation of the shield so that the hub, after insertion, is then trapped within the shield but slidable axially relative thereto.
The connection between the hub 11 and flexible tube 13 may be made prior to insertion of the hub into the shield. For instance, as illustrated in Figures 5 to 7 this may be effected by threading the tube 13 through the entry aperture 38 and then through the slot 17 so that the forward end of the tube is available externally of the shield for connection to the hub. Once the tube 13 is connected in this way, it is pulled back into the shield through the slot while pushing the hub through the wider section of the slot.
At its forward end, the shield 12 may be provided with a forward locking feature comprising formations 30 such as barbs which project inwardly of the slot to form a neck past which the stud can be displaced, by resilient deformation of the formations, and into the forward end 32 of the slot 17 so that the hub is then trapped within the shield at that location. The arrangement is such that the stud can be released from the forward end 32 by pulling on the tube 13 and/or by manipulation of the stud to displace it rearwardly past the formations 30. Once the hub has been inserted into the shield with the stud trapped axially by the forward locking feature, the needle 10 may be assembled to the forward end 34 of the hub which may project beyond the forward end of the shield.
Needle retraction is effected by pulling on the tube 13 so that the stud is released from the forward locking feature and withdrawing the needle until the stud is rendered captive with the rearward locking feature 18. As shown in Figure 5, the rearward locking feature may be formed by the tapering sides of the slot 17 so as to form steps or barbs 18 which irreversibly block return movement of the stud and hence the hub/needle assembly once the stud has entered the rearward slot section 36. During retraction of the needle, the stud 16 slides between the side edges of the slot and thereby constrains the hub from rotation. This ensures that the cutting bevel at the needle point remains facing in the desired direction at all times, i.e. upwards relative to the wings 15.
It will be appreciated that it is not intended to limit the invention to the above example only, many variations, such as might readily occur to one skilled in the art, being possible, without departing from the scope thereof as defined by the appended claims.