the puncture cannula comprises an elongate hollow steel cannula 10 attached to a cannula hub 11 of a plastic material . steel cannula 10 consists of a tube provided with a nonconductive coating 12 . the tip of the cannula 10 ( not shown ) is exposed . seated on a tubular connecting piece 13 of cannula hub 11 is a protective hose 9 which surrounds steel cannula 10 and extends beyond the length of cannula 10 to protect users from accidental injuries which might be caused by the tip of the cannula . the protective hose 9 can be withdrawn from the connecting piece 13 . the distal portion 10 a extends through a cavity or a recess 14 of the hub 11 of the cannula and ends in a cavity 15 which is closed by a hose connector 16 . a hose 17 , starting from hose connector 16 , is provided for the administration of an anesthetic agent which will then be injected into the patient &# 39 ; s body through steel cannula 10 . an introduction channel 18 is arranged to enter the recess 14 of hub 11 and has a cable 19 extending therethrough . introduction channel 18 is formed along a part 18 a of its length as a circumferentially closed bore , while another part 18 b of the length of channel 18 is formed as an open channel . the channel part 18 b terminates at an end wall 20 forming a stop face for the end of cable 19 . cable 19 comprises a cable core 21 made of copper and an insulation 22 . introduction channel 18 is oriented under an acute angle relative to the longitudinal axis of steel cannula 10 . a guideway 23 , formed for movement of a clamping element 24 therein , is arranged in a transverse direction relative to steel cannula 10 and cable 19 . clamping element 24 comprises an elastic plate 25 made from spring steel . as illustrated in fig2 this plate is formed with a first clamping slot 26 for steel cannula 10 and with a second clamping slot 27 for the core 21 of cable 19 . both clamping slots 26 , 27 are arranged behind each other along a common axis and have a widened opening 28 arranged therebetween . each of the clamping slots 26 , 27 has a tapering shape in the direction of insertion , i . e . from top to bottom in fig2 so that a progressing insertion of the clamping element 24 into the cannula hub 11 will cause an increasingly stronger clamping action on the steel cannula 10 and the cable core 21 , respectively . the edges of second clamping slot 27 are cutting edges provided to cut through the insulation 22 of cable 19 , thus generating a safe electrical contact to the core 21 of cable 19 . clamping slot 26 is delimited by wings 29 , 30 which can be bent about bending regions 31 for adaptation to different diameters of steel cannulae 10 . in fig1 one of these wings , 29 , is shown as bent in outward direction . clamping element 24 comprises a plate which , however , does not necessarily have to be flat . the plate is guided in a linear guideway 23 for displacement between a clamping position and a release position . when the steel cannula 10 and the cable 19 are to be mounted , the steel cannula 10 is inserted into the channel of cannula hub 11 which is provided for this purpose , and the cable 19 along with its insulation 22 is introduced into insertion channel 18 . subsequently , clamping element 24 is inserted into guideway 23 and pushed into the same until reaching the end stop , while the clamping slot 26 exerts a clamping grip on steel cannula 10 and the clamping slot 27 cuts through the insulation 22 into the core 21 of cable 19 . the hub 11 of cannula 10 is then positioned in such an orientation that the recess 14 is facing upwards . in this condition , fig3 represents a plan view from above . next , a liquid adhesive 33 is filled into recess 14 . this adhesive will occupy the recess 14 completely . the adhesive enters into the annular gap between steel cannula 10 and cannula hub 11 and into the annular gap between introduction channel 18 and the cannula hub 11 and will after hardening also keep the clamping element 24 fixed in position . thus , a sole adhesion process is sufficient to fix all of the components relative to each other and to close them in a tightly sealed manner . also the entrance orifice 34 of guideway 23 is closed by adhesive and sealed so that the whole clamping element 24 is embedded in adhesive material . thus , no electrically conductive components are accessible from the outside .
a puncture cannula , particularly for nerve stimulation , comprises a steel cannula attached to a cannula hub , and a cable extending through an insertion channel and having its core connected to the steel cannula . the hub of the cannula comprises a metallic clamping element formed with a first clamping slot engaging the steel cannula and with a second clamping slot engaging the core of the cable .