fig1 shows a catheter insertion device 1 having a catheter hub 2 which has a two - part form in the embodiment . a distal hub element 3 of the catheter hub has a holding section 3 a in which a catheter 4 is press - fitted . the proximal end of the hub element 3 has an enlarged diameter with regard to the distal end and forms a connecting section with a hub element 5 whose distal end overlaps the proximal end of the hub element 3 and which is provided at its proximal end with a luer thread 6 . between the two hub elements 3 and 5 , a check valve in the form of a valve disc 7 is inserted and is fixed in place by the two hub elements 3 and 5 . in the ready position according to fig1 , there is inserted in the catheter hub 2 a needle hub 8 to which a hollow needle 9 is fixed which extends through the valve disc 7 and the catheter 4 so that the needle tip 9 a is exposed . between needle hub 8 and valve disc 7 there is displaceably arranged in the proximal hub element 5 a valve actuating element 10 which has a truncated cone - shaped locating section 10 a which serves to open the valve disc 7 , as fig3 shows . on the proximal side , a plunger section 10 b adjoins the locating section 10 a and has a hollow space for receiving a needle guard element 13 . in the embodiment shown , the plunger section 10 b is formed by two spaced plungers between which the needle guard element in the form of a spring clip 13 is inserted , as shown in the cross - sectional view in fig4 . on withdrawal of the hollow needle 9 from the catheter hub 2 , an engaging means 9 b ( fig2 ), provided near the needle tip 9 a and having the form of a radial projection on the hollow needle which can be formed by light crimping , engages with the outer circumference of a bore in the rear wall 13 c of the spring clip 13 , so that the spring clip 13 is removed from the catheter hub with the needle 9 , while simultaneously the spring arms 13 a and 13 b of the spring clip cover the needle tip , completely protecting and blocking it . in this separated position shown in fig2 , the valve disc 7 , due to its elasticity , closes the through - hole for the hollow needle 9 so that no blood can flow out through the catheter 4 . as fig6 shows , the valve disc is provided for example with three slits 7 a starting from the middle and extending radially over a short section x , forming elastic flaps 7 b therebetween which can be expanded by the hollow needle . fig3 shows the insertion of a syringe 14 in the catheter hub 2 , wherein the neck portion 14 a of the syringe comes to abut on the plunger section 10 b of the valve actuating element 10 and presses it against the valve disc 7 , so that the truncated cone - shaped locating section 10 a outwardly displaces the flaps 7 b of the valve disc and thereby opens the valve , so that a liquid can be inserted from the syringe 14 into the catheter 4 . the incline of the truncated cone on the locating section 10 a and the displacement path of the actuating element 10 relative to the valve disc 7 are designed such that due to the elasticity of the material of the valve disc 7 , the flaps 7 b displace the locating section 10 a to the right in fig3 when the syringe 14 is removed from the catheter hub 2 . hereby , the valve disc 7 is automatically closed , as the position in fig2 shows . in the hub element 5 , there is formed by a shoulder 5 a a stop for the actuating element 10 , to define the position of the actuating element in the separated position in fig2 . hereby , the truncated cone - shaped locating section 10 a lies near the stop 5 a , while its distal end abuts on the valve disc 7 as shown in fig2 . the radial slits 7 a of the valve disc 7 are designed such that in the ready position in fig1 , the flaps 7 b are bent radially upwards less than in the open position by the locating section 10 a in fig3 . as the cross - sectional view in fig4 shows , the two plungers lob of the valve actuating element 10 are guided in longitudinal grooves 5 e of the hub element 5 and they project radially inwards into the bore 5 c of the hub element 5 , so that they form an abutting surface for the neck portion 14 a of the syringe 14 . the bore 5 c in the hub element 5 is formed slightly conically corresponding to the conical neck portion 14 a of a syringe . on the inner circumference of the bore 5 c of the hub element 5 , a further shoulder 5 b having a smaller diameter is formed , on which the radially outer areas of the spring arms 13 a and 13 b abut in the ready position in fig1 . hereby , the spring clip 13 is fixed in its position in the hub element 5 . when the needle hub 8 with the hollow needle 9 is removed from the catheter hub 2 , first the spring clip 13 is held on the shoulder 5 b by abutting until the radial projection 9 b comes to abut on the rear wall 13 c of the spring clip . in this position , the two spring arms 13 a , 13 b can be released from the shoulder 5 b and spring back inwards to cover the needle tip , as fig2 shows , whereupon the spring clip 13 with the hollow needle 9 can be removed from the catheter hub . in the embodiment according to fig1 to 3 , the distal end section of the hub element 5 is shrunk , welded or bonded onto the proximal end section of the hub element 3 after the valve actuating element 10 and the valve disc 7 are inserted in the hub element 5 . it is also possible to join the two hub elements 3 and 5 to one another , for example by a thread which is secured against loosening after assembly . the spring clip 13 is inserted together with the hollow needle 9 in the bore 5 c of the hub element 5 during assembly , wherein the radially outer areas of the spring arms 13 a , 13 b snap in at the shoulder 5 b under elastic deformation . preferably , in front of the shoulder 5 b a projection 5 b can be formed in the bore 5 c of the hub element , as shown in fig2 . hereby the snap - in and holding effect of the spring clip 13 is increased . fig5 shows a modified embodiment of the connection of the two hub elements 3 and 5 , in which two cylindrical sections 3 b and 5 d engage in one another . a thread can be provided between these two cylindrical sections . however , it is also possible to bond or weld these two sections . in this embodiment , the valve actuating element 10 is also modified in relation to the embodiment of fig1 to 3 . fig7 a shows a side view of the approximately u - shaped actuating element 10 with the spring clip 13 inserted therein . as the side view rotated by 90 degree in fig7 b shows , the locating section 10 a is partly flattened on opposite sides so that the width of the plunger sections 10 b extends into the locating section 10 a . fig7 c is a front view from the left in fig7 b and shows the flattened structure of the locating section 10 a . fig7 d is a sectional view along the central line in fig7 b . fig7 e shows a section through the valve actuating element 10 along the line b - b in fig7 d . fig5 shows the lower half of the valve actuating element 10 corresponding to the view in fig7 a , and the upper half in a sectional view rotated by 90 degree corresponding to fig7 b . the shoulder 5 a for positioning the valve actuating element 10 in the hub element 5 is hereby formed on the ends of the diametrically opposite grooves 5 e ( fig4 ), so that the proximal ends of the plunger sections 10 b abut on the shoulders 5 a . corresponding to the shoulder 5 b in fig1 to 3 in the embodiment in fig5 , there is formed on the hub element 5 a projection 5 f which projects inwards at diametrically opposite positions on the bore 5 c of the hub element 5 and fixes the spring clip 13 in the hub element 5 until the spring arms 13 a , 13 b spring inwards over the needle tip and the spring clip with the hollow needle 9 is removed from the catheter hub . fig8 shows a modified embodiment having a hollow cylindrical valve actuating element 10 on whose inner circumference a projection 10 f is formed for positioning the spring clip 13 inside the valve actuating element 10 . fig9 a shows a front view of the valve actuating element 10 from the right and fig9 b shows a front view from the left in fig8 , wherein for locating the neck portion 14 a of a syringe 14 , in this embodiment radially inwardly projecting ribs 10 e are formed which protrude radially into the bore 5 c of the hub element 5 , as the upper half of the valve actuating element in fig8 shows , in which the sectional view of the lower half of the valve actuating element 10 is shown rotated by 90 degree in relation to the upper half . fig1 shows a modified embodiment wherein between the two hub elements 3 and 5 a check valve 17 is inserted , which has a hollow cylindrical section 17 b starting from a flange section 17 a and abutting on the inner circumference of the hub element 3 . from the inner circumference near the flange section 17 a there start two opposite flaps 17 c , which abut on the outer circumference of the hollow needle 9 in the ready position in fig1 . when the needle 9 is removed from the catheter hub 2 , the elastically deformed flaps 17 c move inwards and close the valve . in this embodiment , an actuating element for opening the valve 17 is not necessary , because the pressure of the fluid from the syringe 14 displaces the flaps 17 c radially outwards so that the liquid can flow out through the valve 17 . in this embodiment of a check valve , a so - called duck - bill valve is concerned , whose construction is in itself known . in fig1 , in order to allow the spring clip 13 to be held in the catheter hub during withdrawal of the hollow needle 9 from the catheter hub 2 until the radial projection 9 b on the hollow needle engages with the rear wall 13 c to cover the needle tip , in this embodiment there is formed on the inner circumference of the proximal hub element 5 a projection 5 f which extends radially inwards and on which the radially outer areas of the spring arms 13 a and 13 b come to abut and hold the spring clip until the spring arms spring back radially inwards to cover the needle tip . the inner diameter of the projection 5 f is designed only slightly smaller than the maximum radial dimension at the spring arms 13 a and 13 b , so that during assembly the spring clip 13 can be inserted by slight pressure into the position in the catheter hub as shown in fig1 . in the embodiment of a catheter insertion device according to fig1 to 9 , in the position of the valve actuating element 10 in fig2 the valve disc 7 can be opened by low pressure produced by the syringe 4 for drawing off liquid from the catheter , wherein the elastic flaps 7 b are bent upward by the low pressure . in the embodiment of fig1 , a drawing - off of liquid from the catheter is not possible , because the duck - bill valve does not open when there is low pressure on the proximal side . it is convenient to fabricate the check valve in the form of a valve disc 7 or of the flap valve 17 from elastic silicon , while a correspondingly rigid plastic material is used for the hub elements 3 and 5 and for the valve actuating element 10 .
embodiments of a catheter insertion device are discussed comprising : an approximately hollow cylindrical catheter sleeve , at whose distal end a catheter is attached ; a needle sleeve with a hollow needle , which is attached thereto and which , when ready for use , extends through the catheter sleeve and the catheter , and ; a needle protective element that is arranged inside the catheter sleeve while being able to move on the needle . said needle protective element has an engaging section that engages with an engaging device , which is formed in the vicinity of the needle tip , when the hollow needle is withdrawn from the catheter sleeve . a check valve is placed inside the catheter sleeve between the catheter and the needle protective element . the hollow needle , when ready for use , extends through said check valve , and the check valve automatically closes once the needle is withdrawn .