with reference to fig1 - 4 , a tubular body , generically indicated with 1 , is formed by three sectors 1 a of angular width equal to 120 °. from one end of each of the sectors 1 a , a curved arm 2 extends in a substantially tangential manner ; the free end of the curved arm 2 is rotatably engaged with a pin 3 . the three pins are in turn engaged in three equidistant holes 5 formed on a first ring nut 4 , called fixed ring nut , orthogonal to the longitudinal axis of the tubular body 1 and in circumferential slots 6 made along a second ring nut 7 , called moveable ring nut , coaxially arranged on the fixed ring nut 4 . the threaded ends of the pins 3 projecting from the slots 6 of the moveable ring nut 7 are finally engaged in respective threaded knobs 8 , abutting against moveable ring nut 7 opposedly with respect to the fixed ring nut 4 , thereby obtaining the mutual fixing of the various components . the three sectors 1 a of the tubular body 1 form a channel of inner diameter less than or equal to the outer diameter of the cannula of the commercial trocar to be used , while the outer surface of the sectors 1 a has a saw tooth thread , as in the anchorage cannulae of known type , capable of grasping the walls of the body cavity access hole . the three curved arms 2 are housed within the fixed ring nut 4 , coplanar thereto , and may be simultaneously rotated around the respective pins 3 , to transmit an angular movement to the moveable ring nut 7 . following the rotation of the arms 2 , the cylindrical sectors 1 a extending therefrom progressively divaricate from each other , passing from the closed configuration illustrated in fig1 to the open configuration of fig2 . three angularly equidistant closure pins 9 and three thrust pins 10 extend orthogonally from the face of the moveable ring nut 7 turned towards the fixed ring nut 4 . when the tubular body 1 is in its closed position , as shown in fig1 , the closure pins 9 abut on the convex side of the respective curved arms 2 and maintain the three cylindrical sectors 1 a adjacent to each other , tightening them on the cannula of the trocar so as to permit the axial locking of the trocar . in particular , as shown in fig4 , the arms 2 have seats 2 a , within which the closure pins 9 are engaged . on the other hand , when the moveable ring nut 7 is rotated in the direction of the arrow f of fig3 , the thrust pins 10 come into contact with the concave profile of the arms 2 of the sectors 1 a and , sliding along them away from the hinge pins 3 , ensure that the arms progressively extend . the opening of the sectors 1 a first occurs quickly and then slows approaching the end stop ; in this way it is possible to exert a force as constant as possible throughout the opening step , since the resistance of the tissues increases as the divarication of the sectors 1 a increases . at the stop end , the tubular body 1 remains stably open when the thrust pins reach the dead point . if it is necessary to stop the opening in an intermediate position , it is sufficient to tighten at least one of the three threaded knobs 8 . to ensure an adequate sealing of the gas on the patient side , a membrane 11 is foreseen as shown in fig4 and fig7 , while on the surgeon &# 39 ; s side the seal is ensured by a valve system such as that shown in fig5 and 7 . the membrane 11 has a variable thickness , and in particular in correspondence with its minimum and maximum diameter terminates with respective toroidal rings 11 a and 11 b . the maximum diameter ring 11 b is inserted in a perimetrical groove 4 a of the ring nut 4 , as is visible in fig6 , while the minimum diameter ring 11 a is tight at the base of the sectors 1 a . no groove for housing the ring 11 a is foreseen on said sectors , since the correct position is maintained both because it is a rest position and because the membrane is forced by the abdomen of the patient against the ring nut 4 . the radially expandable anchorage guide for trocars according to the present invention is used in the following manner . at the beginning of the operation , during the insertion step of the trocar in the abdomen ( for example ), the anchorage guide according to the present invention is used as if it was a normal anchorage tube of the trocar to the abdominal wall . as shown in fig8 , the three sectors 1 a are closed around the cannula 12 of the trocar and are tightened to it by rotating the moveable ring nut 7 with respect to the fixed ring nut 4 , and tightening at least one of the locking knobs 8 . in the particular case wherein the trocar inserted is calibrated on the inner size of the closed tubular body 1 , tightening the locking knob 8 can be avoided since the system is irreversible when in completely closed position . a valve 13 , of the type illustrated in fig5 and 6 , is closed around the trocar tube to ensure a perfect gas seal . in the case in which the valve is that illustrated in said figures , it is not necessary to tighten the tubular body 1 on the cannula 12 of the trocar , since the same valve can ensure the axial anchorage of the trocar . indeed , when the membrane tightens around the cannula of the trocar , it generates a consistent radial force which , due to the high coefficient of friction between the same membrane and the cannula of the trocar , ensures a strong axial seal . if during the operation it becomes necessary to insert a trocar of greater size , it will suffice to open the valve 13 of fig8 , open the tubular body 1 by unlocking the cannula 12 of the trocar , extract the trocar to be substituted , insert the new trocar and tighten the tubular body 1 and the seal valve 13 on it . if during the operation it becomes necessary to remove an internal mass , the tubular body 1 may be divaricated to its maximum expansion so that , once the trocar and the seal valve is removed , an access channel is generated at the abdomen of sufficient dimensions for the passage of the mass to be removed . to protect the walls of the access hole from possible contaminations ( for example during the extraction of a tumoral mass in the absence of other types of protection ), it is possible to insert within the divaricated sectors 1 a a tube 14 ( see fig9 ) after having overturned the elastic membrane 14 a inside the tube itself . in particular , the tube 14 is composed of a rigid cylinder of thin thickness buried within an elastic membrane terminating at both ends with two large diameter discs with reinforced edges , one of which is the membrane 14 a . for its insertion inside the divaricated tubular body 1 , the inner disc or membrane 14 a is folded inside the tube 14 and subsequently made to expand inside the abdomen . the membrane 14 a protects from contaminations the inner wall of the abdomen near the access hole . the axial position of the tube 14 is ensured by the tightening of the three sectors 1 a on it . the tube 14 has an outer elastic disc 15 at the other end which may be folded on the moveable ring nut 7 of the anchorage guide so as to protect it from contamination . fig9 has the expandable anchorage guide according to the invention in a configuration suitable for the extraction of an internal mass . to extract the tube 14 , it suffices to further divaricate the sectors 1 a and pull the tube 14 through the outer disc 15 . the valve 13 illustrated in fig5 and 6 is based on the principal of operation of a commercial device named “ lap - disc ”, described in the u . s . pat . nos . 6 , 110 , 154 and 6 , 589 , 167 and used for making an abdomen access for the surgeon &# 39 ; s hand in hand - assisted laparoscopic surgery operations , even if it uses a different method for maintaining the set position . with particular reference to fig5 and 6 , the valve 13 comprises a fixed support 16 which can be connected by bayonet coupling to the outer face of the moveable ring nut 7 . on the latter , in fact , radial expansions 17 are foreseen defining circumferential grooves 18 with the outer face of the moveable ring nut 7 , within which radial tongues 19 are friction engaged , extending from the outer wall of the fixed support 16 . the seal between the fixed support 16 and the moveable ring nut 7 is ensured by a seal ring 20 arranged therebetween . the valve 13 moreover comprises a control ring nut 21 rotatably engaged within the fixed support 16 and maintained in the desired angular position by means of flexible arms 22 axially extending from the fixed support 16 . the arms 22 have inner radial projections 23 which are engaged in axial grooves 24 formed on the outer surface of the control ring nut 21 . the obturator of the valve 13 comprises an elastic membrane 25 having in rest position a toroidal shape with “ omega ” cross section , which is maintained tight on the inner walls of the control ring nut 21 and the fixed support 16 , respectively , by means of expansion rings 26 and 27 of rectangular section , cut sideways to permit the flattening of the membrane against the walls of the control ring nut 21 and the fixed support 16 without gap . rotating the control ring nut 21 with respect to the support 16 , the flexible arms 22 bend , making the projections 23 move from one groove 24 to the other , so that the elastic membrane 25 , due to the torsion to which it is subjected , closes radially like a diaphragm . with an appropriate rotation angle of the control ring nut 21 , it is possible to completely occlude the opening of the valve 13 , or partially occlude it in case the cannula of a trocar must pass through said opening , tightening the membrane 25 around it and ensuring the gas seal and a consistent axial tightening . the expandable anchorage guide according to the invention , in addition to having the diaphragm valve described above , may naturally be employed even in association with valves for trocars of another type , such as that illustrated in fig7 . the valve herein illustrated is of double seal type : i . e . it has a first elastic obturator 26 with flute mouth geometry which in rest is maintained in closed position by the pressure established in the body cavity . if an instrument is inserted , the flute mouth 26 obturator opens in correspondence with the longitudinal cuts , losing however the gas seal . a second obturator 27 is therefore foreseen , upstream of the first and formed by an elastic membrane with calibrated hole to make a seal on a particular instrument diameter . normally , having to insert an instrument with different diameter , the second obturator block 27 fixed with bayonet coupling to the first obturator must be substituted . the double obturator scheme as illustrated allows instruments to be extracted and inserted without losing the seal , while , when the instrument is inserted , the second obturator ensures the seal by forcing radially against the instrument . the valve system described and illustrated in fig7 is among the most commercially widespread , but there exist many others predominantly intended to house instruments with different diameters , without the need to interchange the second obturator . the instrument according to the invention may house , by means of an appropriate adaptor , any commercial sealing system . naturally , the tubular body 1 of the expandable anchorage guide according to the invention can be made in a different number of cylindrical sectors 1 a with respect to that described and illustrated . in this manner , it is possible to better approximate the circular shape of the realized opening , through the cost of the instrument increases . variations and / or modifications can be made to the anchorage guide for trocars according to the present invention without departing from the protective scope of the invention as set forth in the following claims .
an anchor guide for a trocar comprising a tubular body , formed by a plurality of substantially circular sectors , moveable radially toward and away from a longitudinal axis of the tubular body between a first position where they flank one another , according to a first substantially circular arrangement with diameter generally equal to that of the tubular body , and a second position at which they are generally equidistant from one another , according to a second substantially circular arrangement of greater diameter than that of the first arrangement . each sector is rotatably connected to a support element and a manual operation is provided , moveably connected to the support element , for moving the sectors from the first to the second position and vice versa .