Patent Document

BACKGROUND OF THE INVENTION 
     The invention relates to a syringe, and more particularly a syringe for medical applications. 
     The invention also relates to a syringe that can be used for operations of human adipose tissue liposuction. 
     DESCRIPTION OF THE RELATED ART 
     The syringes have been used in medicine, either for sampling operations (blood, tissues, etc. . . . ) or for injection purposes (vaccines, tissues, etc. . . . ). 
     The syringes are used in particular in plastic surgery in techniques of adipose tissue sampling and reinjection, for example to fill losses of sub-cutaneous substance of a patient. Different techniques of adipose tissue sampling are used today, for example excision or liposuction, the latter being able to be practiced by means of a mechanical suction system or performed manually by means of a syringe. 
     The latter technique using a syringe as a suction means has been widely engineered, developed and codified by S. R. Coleman, in order to perform a reinjection (graft) of adipose tissue which is lasting (see in particular the article “Hand rejuvenation with structural fat grafting” in Plastic and Reconstructive Surgery, Vol. 110, No. 7, pp. 1731-1744, December 2002 or the article “Structural Fat Grafting: more than a permanent filler” in Plastic and Reconstructive Surgery, Vol. 118, No. 3S, pp. 108S-120S, September 2006). 
     According to this technique, it is recommended to perform a sampling of adipose tissue on a patient in such a manner to traumatize the less possible the fat cells sampled. For that purpose, it is required to control accurately the vacuum exerted by the syringe on the adipose tissues so that this vacuum is neither too great nor too brutal. 
     In practice, the surgeon using this technique samples a first volume of adipose tissue with the syringe, and, with the syringe still in the body of the patient at the sampling site, creates a vacuum in the syringe by pulling the plunger in the body of the syringe. The surgeon then waits for the pressures in the syringe and the body of the patient, at the sampling site, to balance each other, thereby removing the vacuum inside the syringe. The surgeon can then sample a second volume of tissue, and wait, and repeat these operations as many times as necessary, until sampling the required quantity of adipose tissue. 
     Besides, it has been suggested that, if the vacuum applied by the syringe on the adipose tissue, during the upward movement of the syringe plunger in the syringe body, is too high, then the quality of the sampling is lower, which compromises the success of the operations following the liposuction, in particular the survival at mean and long term of the adipose tissue after reinjection of the latter in the sampled patient. 
     Hence, it has been shown (cf. MD Thesis of M. Ould Ali Djaffar, entitled “ Facteurs mécaniques influençant la qualité des transplants adipocytaires ”, delivered by the University of Aix-Marseille in 2010) that the vacuum created by the syringe should remain lower than 0.4 atmosphere (atm) in absolute value, which corresponds for example to a vacuum volume of about 2 cubic centimeter (cc). 
     The document U.S. Pat. No. 5,047,015 teaches a medical syringe with a plunger provided with a thread on its outer part and a disengagement mechanism allowing to operate the plunger according to two modes. In the first mode, when the mechanism is not activated, the thread of the plunger is engaged and cooperates with another thread present on the inner part of the syringe body, such that the plunger can slide in the syringe body by rotation of the plunger in the syringe body. In the second mode, when the mechanism is activated, the thread of the plunger is disengaged from the other thread, such that the plunger can slide freely in the syringe body. 
     The document U.S. Pat. No. 5,215,536 describes a medical syringe having a locking system allowing to hold the plunger of a syringe in the syringe body, but to squeeze the syringe body to release the plunger, the latter being then able to slide freely in the syringe body. 
     The document GB 958636 teaches a syringe intended to deliver a calibrated dose of a substance, this syringe comprising a syringe body having an axis and a spring held in the syringe body, which exhibits elasticity in a plane perpendicular to the axis of the syringe body, a plunger comprising a cruciform operating rod with four arms at 90° relative to each other and stops arranged on the axial faces of the adjacent arms of the cross of the operating rod. 
     The stops are distributed along the axial faces of the arms of the operating rod so that the stops on the faces of the two arms located in a same plane are aligned between each other and longitudinally offset relative to the stops of the two other arms at 90°. 
     The stops are adapted to allow, in cooperation with the spring, an upward movement, and a downward movement, “tooth by tooth”, of the plunger along the syringe body. 
     However, the syringe disclosed in the document GB 958636 does not allow the full disengagement of the stops by a simple rotational movement of the plunger in the syringe body, the stops being always in cooperation with the spring. 
     Moreover, the use of a syringe according to the prior art does not allow to accurately control the sampling volume, and hence the vacuum exerted on the tissue, during the liposuction operation. 
     Indeed, despite the graduations often present on the outer wall of the syringe body, it is difficult for a surgeon during the sampling operation to control accurately this sampling volume so as not to exceed the limit value of vacuum indicated hereinabove. 
     In addition, a surgeon using a syringe according to the prior art must always keep his thumb on the syringe body so as to hold the plunger in position in the syringe body during the pressure balance step described hereinabove. A manual liposuction using a syringe of the prior art is hence a laborious operation, because it is the thumb of the surgeon that, over the whole duration of the intervention, exerts the force for holding the plunger. This induces tiredness that may lead to gesture imprecisions of the surgeon or to handling errors. Moreover, when it becomes painful for the thumb, a risk exists of “renunciation” by the surgeon, who will tend to increase the vacuum exerted each time, so as to shorten the intervention. 
     SUMMARY OF THE INVENTION 
     To remedy the above-mentioned drawback of the prior art, the present invention proposes a syringe allowing to control the vacuum applied by the syringe during the upward movement of the plunger and to hold without effort the plunger in its position inside the syringe body. 
     For that purpose, the invention relates to a syringe including:
         a syringe body extending along a longitudinal axis from a lower end to an upper end, the lower end of the syringe body allowing the fixation of a needle or a cannula and the upper end of the syringe body having an upper opening allowing the introduction of a plunger into the syringe body, the syringe body having an inner wall and including at least one first stop located along the inner wall of the syringe body near the upper opening, the first stop being adapted to leave at least one first blank surface on the inner wall of the syringe body, and   a plunger sliding along the inner wall of the syringe body along the longitudinal axis, the plunger comprising a plunger head and an operating rod connected to the upper end of the plunger head, the upper end of the plunger head being directed towards the upper opening of the syringe body, the operating rod of the plunger including, on its outer surface, at least one first rack arranged longitudinally along the operating rod, the first rack comprising protruding teeth,
 
the first stop and the protruding teeth being shaped and constituted so as, during the upward movement of the plunger in the syringe body from a low position where the plunger head is near the lower end of the syringe body to a high position where the plunger head is near the upper end of the syringe body, when the first stop and the first rack are opposite to each other, to allow a tooth-by-tooth upward movement of the plunger along the syringe body,
 
the syringe being characterized in that:
   the first stop and the protruding teeth are also shaped and constituted so as to prevent any downward movement of the plunger under the effect of a push on the operating rod, but to disengage the first rack by rotation of the plunger in the syringe body about the longitudinal axis to bring the first rack opposite the first blank surface of the inner wall of the syringe body.       

     Hence, the syringe according to the invention allows to perform operations of adipose tissue sampling by liposuction, with accurate control of the plunger position in the syringe and hence of the sampled volume of tissue thanks to the stops and the protruding teeth, and hence to make sure that the vacuum applied by the syringe is lower than the recommended limit. Therefore, the surgeon does not risk to increase or reduce the sampling volume, and hence the vacuum exerted on the adipose tissues. 
     Moreover, the protruding teeth and the stops cooperate so as to hold the plunger in its last position, preventing it to move downwards. 
     By preventing the plunger to move downwards in the syringe body under the effect of a simple push, the syringe according to the invention allows to free the thumb of the surgeon that operates, because the thumb no longer needs to exert a force for holding the plunger in the syringe body. Hence, the thumb is less tired and the gestures of the surgeon are more accurate. 
     On the other hand, this allows to avoid just-sampled adipose tissue to be reinjected by mistake. Indeed, the syringe according to the invention is not adapted for injections but for suctions. 
     According to the invention, it is required to disengage the first rack by rotation of the plunger and to bring voluntarily the first rack opposite the blank surfaces if it is desired that the plunger moves downwards. 
     Moreover, when required, the overpressure created by the downward movement of the plunger has to be the lowest possible so as to traumatize the less possible the fat cells sampled. 
     Finally, the syringe according to the invention, when placed in a centrifuge after the sampling, prevents a downward movement of the plunger in the syringe body under the effect of the centrifugal force, hence avoiding a degradation of the fat cells sampled. 
     Besides, other advantageous and non-limitative characteristics of the syringe according to the invention are the following:
         the syringe body includes a second stop similar to the first stop, and located along the inner wall of the syringe body, near the upper opening, so that the first and the second stops form between each other a first and a second blank surfaces on the inner wall of the syringe body, and the operating rod includes on its outer surface a second rack similar to the first rack, and arranged longitudinally along the operating rod, so that, when the first rack is opposite the first stop, the second rack is opposite the second stop;   the first and second stops are substantially diametrically opposed to each other, and the first and second racks are also substantially diametrically opposed to each other.       

     Hence, the syringe according to the invention that has at least two stops, preferably diametrically opposed to each other, allows to limit the transverse movements of the plunger inside the syringe body and makes it easier the manipulation thereof during the liposuction operation. Moreover, as the disengagement of the two racks must be simultaneous, the downward movement by mistake of the plunger in the syringe body is made more difficult. 
     Other advantageous and non-limitative characteristics of the syringe according to the invention are the following:
         the plunger head includes a terminal part facing the lower end of the syringe body, the terminal part being such that it prevents any full disengagement of the plunger from the syringe thanks to a locking by the stop(s), and a base, connected to the terminal part comprising at its periphery at least one first notch and at least one first longitudinal groove, the first notch and the first longitudinal groove of the base being shaped and constituted so as to allow the upward movement and the holding of the plunger in the high position when the first notch is opposite the first stop, and to prevent any downward movement of the plunger along the syringe body, but to disengage the plunger head by rotation of the plunger in the syringe body about the longitudinal axis to bring the first longitudinal groove opposite the first stop;   the base comprises at its periphery a second notch similar to the first notch, and a second longitudinal groove similar to the first longitudinal groove, arranged in such a manner that, when the first longitudinal groove is opposite the first stop, the second longitudinal groove is opposite the second stop;   the first and second longitudinal grooves are substantially diametrically opposed to each other;   the operating rod is detachable from the plunger head;   the plunger head includes a receiving recess integral with the base so that, when the plunger is in the high position, the receiving recess is outside the syringe body, and the plunger operating rod includes at one of its ends an element for connection to the plunger head, the connection element having a shape that is complementary of that of the receiving recess of the piston head, so that, when the plunger is in the high position, the connection element can be engaged into or disengaged from the receiving recess and that, when the connection element is engaged into the receiving recess, the operation rod and the plunger head are translationally integral with each other along the longitudinal axis and rotationally integral with each other about the longitudinal axis;   the receiving recess comprises an open lateral face and an upper face having a central opening substantially positioned along the longitudinal axis of the syringe, so that the connection element is engaged into or disengaged from the receiving recess by being slid through the open lateral face, the central opening allowing the passage of the operating rod.       

     The syringe according to the invention is particularly well adapted to the use of this syringe in a centrifuge, after the sampling operation. 
     Indeed, once the sampling ended and the syringed removed from the patient body, it is sometimes required to separate by centrifugation the different cells constituting the adipose tissue sampled. At this stage, the syringe plunger is generally in its high position, so that the whole syringe has a maximal size. However, the space available in a centrifuge is often limited, so that the detachment of the operating rod from the piston head allows to reduce the total size of the syringe to place the latter in the centrifuge. 
     Besides, according to the invention, the piston head may be held at the high position, even after the operating rod has been detached from the plunger head. Hence, during the centrifugation, there is no risk that the plunger moves again into the syringe body down to the low position, nor that the plunger is fully disengaged from the syringe body, which would be extremely damaging for the sampled tissues. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING FIGURES 
       A particular embodiment of the invention will be described hereinafter, with reference to the appended drawings in which: 
         FIG. 1  is an overall view of a syringe according to an embodiment of the invention; 
         FIG. 2  is a longitudinal sectional view of the body of a syringe according to the embodiment of  FIG. 1 ; 
         FIG. 3  is a top view of the body of a syringe according to the embodiment of  FIG. 1 ; 
         FIG. 4  is a perspective view of a ring comprising two stops opposite to each other; 
         FIG. 5  is a longitudinal sectional view of an operating rod of a syringe plunger according to the embodiment of the invention of  FIG. 1 ; 
         FIG. 6  is a transverse sectional view (according to the direction A-A of  FIG. 5 ) of the plunger operating rod such as shown in  FIG. 5 ; 
         FIG. 7  is a longitudinal sectional view of a syringe plunger head according to the embodiment of the invention of  FIG. 1 ; 
         FIG. 8  is a transverse sectional view (according to the direction B-B of  FIG. 7 ) of the plunger head as shown in  FIG. 7 ; 
         FIG. 9  is a perspective view of a receiving recess according to the embodiment of the invention of  FIG. 1 ; 
         FIG. 10  is a sectional view of a syringe according to the embodiment of  FIG. 1 , when the plunger is in the low position; 
         FIG. 11  is a sectional view of a syringe according to the embodiment of  FIG. 1 , when the plunger is in an intermediate position; 
         FIG. 12  is a sectional view of a syringe according to the embodiment of  FIG. 1 , when the plunger is in the high position; 
         FIG. 13  is a sectional view of a syringe according to the embodiment of  FIG. 1 , when the plunger head is locked by the first and second stops. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     As a preamble, let&#39;s precise that, in the following disclosure, the terms “high” or “upper” and “low” or “lower” will be used in relation to the syringe, the lower side being the side fixed to the needle or the cannula and the upper side being the side from which protrudes the syringe plunger. Likewise, it will be considered that the syringe extends along a substantially vertical direction. 
       FIG. 1  shows an overall view of a syringe  10  according to a particular embodiment of the invention, this syringe including a syringe body  20 . 
     As shown in  FIG. 2 , the syringe body  20  has in its lower part an inner wall  21 . 
     The syringe body  20  comprises a lower end  20 A serving for the fixation of a needle or a cannula. This lower end  20 A has herein a truncated shape. The syringe body  20  also comprises an upper end  20 B having a circular opening  20 C and two flat areas  20 D,  20 E. This circular opening  20 C allows the introduction of the plunger  100  as described in details hereinafter. 
     The syringe body  20  is substantially of revolution about a longitudinal axis A 1 , so that the intermediate part of the syringe body, located between the lower end  20 A and the upper end  20 B is cylindrical. 
     The syringe body  20  has herein a total height of the order of 80 millimeters and an inner diameter of the order of 15 millimeters, hence defining a volume of about 14 milliliters. 
     Furthermore, the syringe body  20  has herein a thickness of about 1 millimeter. 
     As a variant, the syringe body may for example have a total height going up to 150 millimeters and a lower diameter of 25 millimeters, hence defining a volume that can go up to about 75 milliliters. 
     According to this embodiment, the syringe body  20  is made of polypropylene by a moulding process. 
     As a variant, the syringe body may be made of another plastic material, as for example polycarbonate, metal or glass. 
     The syringe body  20  is preferably transparent. This allows the surgeon, who performs a sampling with a syringe  10  according to the embodiment of the invention, to see inside the syringe  10  the quantity, and eventually the nature, of the sampled tissues. 
     The syringe body  20  is provided, near its upper end  20 B, with a ring-shape piece  30 . 
     As shown in  FIG. 4 , this ring  30  includes a flat annular part  31  as well as two arms  32 A,  33 A extending downwards from the lower face of the flat annular part  31 , from the lower edge  31 A thereof. According to the embodiment of the invention, the two arms  32 A,  33 A are herein diametrically opposed to each other. 
     The arm  32 A includes a first stop  32  and the arm  33 A includes a second stop  33 , the first and second stops  32 ,  33  thus being diametrically opposed to each other. The first and second stops  32 ,  33  have a triangular prism shape, whose tip is directed downwards, and protrude towards each other. 
     The first and second stops  32 ,  33  have bearing surfaces  32 B and  33 B, which are substantially horizontal and rectangular in shape. 
     The first and second stops  32 ,  33  have herein a height comprised between 2 and 15 millimeters and the bearing surfaces  32 B,  33 B have a width comprised between 1 and 10 millimeters and a depth comprised between 0.5 and 7 millimeters. 
     According to this embodiment, the ring  30  is made of polypropylene, by a moulding process. Preferentially, the ring  30  is consisted of a material whose colour is different from that of the syringe body  20  so as to allow the distinction between them and to rapidly make sure of the presence of the ring  30  in the syringe body  20 . 
     As a variant, the ring may be made of another plastic material, as for example polycarbonate, or also metal. 
     According to the embodiment of the invention described herein, the ring  30  is inserted and fixed in the syringe body  20  by nesting of the ring  30  at the circular opening  20 C, the material of the ring  30  being flexible enough so as to be elastically deformed and introduced by force in the syringe body  20 . 
     As shown in  FIGS. 2 and 3 , the flat annular part  31  then bears on the two flat areas  20 D,  20 E and on the circular edge of the upper end  20 B of the syringe body  20 . Likewise, the dimensions of the ring  30  are adjusted so that the distance between the two arms  32 A,  33 A is very slightly higher than the inner diameter of the syringe body  20 , the arms  32 A,  33 A then bear on the inner wall  21  of the syringe body  20 , so that the nesting of the ring  30  of the syringe body  20  or the rotation thereof inside the syringe body  20  about the longitudinal axis A 1  requires a significant effort. 
     So arranged, the ring  30  and the syringe body  20  leave between the first and second opposite stops  32 ,  33 , a first and a second blank surfaces  22 ,  23  on the inner wall  21  of the syringe body  20 . The first and the second stops  32 ,  33  being herein substantially diametrically opposite to each other, the first and the second blank surfaces  22 ,  23  are hence also substantially diametrically opposite to each other. 
     As shown in  FIG. 1 , the syringe  10  according to this embodiment of the invention also includes a plunger  100 , the plunger  100  comprising a plunger head  110 , an operating rod  120  and a receiving recess  130 . 
     The total length of the operating rod  120  is herein of about 100 millimeters. 
     The operating rod  120  includes an outer surface  121  whose precise structure is described in  FIGS. 5 and 6 . 
     This outer surface  121  comprises a cross pin  121 A with four arms, orthogonal two by two, and two support elements  121 B arranged in two opposite intervals, formed between two consecutive arms of the cross pin  121 A. 
     The two support elements  121 B extend longitudinally along the operating rod  120 . One of the support elements  121 B includes a first rack  122  arranged longitudinally along the operating rod  120 , the first rack  122  comprising protruding teeth  122 A. 
     The other support element  121 B includes a second rack  123  similar to the first rack  122  comprising protruding teeth  123 A and arranged longitudinally along the operating rod  120 . 
     These protruding teeth  122 A,  123 A protrude outwards from the outer surface  121  of the operating rod  121 . As shown in  FIG. 6 , the protruding teeth  122 A,  123 A are more precisely positioned on two opposite arms of the cross-shaped outer surface  121 . 
     The protruding teeth  122 A,  123 A have a triangular prism shape and are oriented in the opposite direction relative to the stops  32 ,  33 . They are made of a flexible plastic material. 
     According to this embodiment, the first and second racks  122 ,  123  are herein diametrically opposed to each other and each comprise seven protruding teeth  122 A,  123 A, preferably equidistant to each other, the protruding teeth  123 A of the second rack  123  being diametrically opposed to the protruding teeth  122 A of the first rack  122 . 
     The operating rod  120  includes in its lower part a connection element  124  including a parallelepipedal part on which is placed a cylindrical part. The operation of this connection element  124  will be described in more details hereinafter, in particular in the description of the receiving recess  130 . 
     Moreover, the operating rod  120  includes in its upper part a flatten area  125  allowing the plunger  100  to be slid in the syringe body  20 , either downwards by pushing on the flatten area  125 , or upwards by pulling on the flatten area  125 . 
     The plunger  100  also includes a plunger head  110  such as described in  FIGS. 7 and 8 . 
     The plunger head  110  includes at its lower end a terminal part  114  that is of revolution about the longitudinal axis A 1 . The terminal part  114  is a conventional terminal part of a syringe plunger head. It has a cylindrical shape in its upper part to be adapted to the cylindrical shape of the intermediate part of the syringe body  20  and a conical shape in its lower part so as to be adapted to the truncated shape of the lower end  20 A of the syringe body  20 . 
     The terminal part  114  includes an O-ring  114 A at its periphery so that the plunger  100  slides sealingly along the inner wall  21  of the syringe body  20 , hence preventing any leakage of the substance sampled or injected with the syringe  10 . 
     The terminal part  114  of the plunger head  110  is made of polypropylene. 
     As a variant, the terminal part may be made of polyethylene, polytetrafluoroethylene (PTFE), or fluorinated ethylene propylene (FEP). 
     The terminal part  114  is generally black so as to facilitate the reading of the sampled or injected volume on the graduations present on the syringe body  20 . 
     As shown in  FIG. 7 , on the upper face of the terminal part  114  of the plunger head  110  is fixed a base  111 . This base  111  is of truncated shape. 
     The truncated shape that is linked to the terminal part  114  has a diameter comprised between 14 and 25 millimeters according to the syringe model considered. In its upper part, the base  111  has a truncated section having a diameter comprised between 12 and 23 millimeters. 
     The base  111  includes a first notch  112  and a second notch  113 , in recess, each formed at its periphery, such that the first and second notches  112 ,  113  are diametrically opposed to each other, as can be seen in  FIG. 8 . The first and second notches  112 ,  113  are located at about half the height of the base  111 , separating the base into an upper part and a lower part. 
     The first and second notches  112 ,  113  are triangular in shape so as to define a first and a second planar faces  112 A,  113 A, which are substantially horizontal and directed downwards. 
     In the particular embodiment described in  FIGS. 7 and 8 , the first and second notches  112 ,  113  have a depth comprised between 0.5 and 7 millimeters and a width comprised between 1 and 10 millimeters. 
     These dimensions are substantially identical to the dimensions of the first and second stops  32 ,  33 , such that the shape of the first and second stops  32 ,  33  is substantially complementary to that of the first and second notches  112 ,  113 . 
     The base  111  also includes a first groove  115  and a second groove  116 , rectilinear, formed at its periphery, over the whole height of the base  111 . 
     As shown in  FIG. 8 , the first and second rectilinear grooves  115 ,  116  are diametrically opposed to each other and arranged on the periphery of the base  111  such that, on the one hand, the first rectilinear groove  115  is located between the first notch  112  and the second notch  113 , and forms with each of them an angle of 90 degrees, and that, on the other hand, the second rectilinear groove  116  is located between the second notch  113  and the first notch  112 , and also forms with each of them an angle of 90 degrees. 
     As a variant, the first and second notches  112 ,  113  and the first and second rectilinear grooves  115 ,  116  cannot be diametrically opposed to each other. Likewise, the first and second notches  112 ,  113  and the first and second rectilinear grooves  115 ,  116  can be separated by an angle different from 90 degrees. 
     The first and second rectilinear grooves  115 ,  116  have a width comprised between 1 and 11 millimeters and a depth comprised between 0.5 and 8 millimeters. Their width is slightly higher than the width of the first and second stops  32 ,  33 . 
     The base  111  is made of a flexible plastic material of the polyethylene type. 
     As a variant, the base may for example be made of polypropylene, polycarbonate, polytetrafluoroethylene or fluorinated ethylene propylene. 
     The plunger head  110  finally includes at its upper end a receiving recess  130  made by machining. 
     As an alternative, the receiving recess is fixed on the upper part of the base  111 , by adhesive bonding. 
     As illustrated in  FIG. 9 , this receiving recess  130  is parallelepiped in shape. It hence defines a receiving volume. Herein, the receiving recess  130  has a square base: it has an edge comprised between 10 and 30 millimeters and a height comprised between 5 and 15 millimeters according to the size of the syringe considered. 
     The receiving recess  130  comprises an open lateral face  131  and an upper face  132  perpendicular to the longitudinal axis A 1 . 
     This upper face  132  has at its centre a circular opening  133  centred about the longitudinal axis A 1  and a straight groove  134  extending from the open lateral face  131  to the central opening  133 . 
     The receiving recess  130  is hence dimensioned so as to receive the connection element  124  of the operating rod  120 . 
     The operating rod  120  is herein detachable from the plunger head  110  thanks to the removable link between the connection element  124  and the receiving recess  130 . 
     Indeed, the connection element  124  is engaged with or disengaged from the receiving recess  130  by being slid through the open lateral face  131 , the parallelepipedal part of the connection element  124  being nested into or separated from the receiving recess  130 , the straight groove  134  and the central opening  133  allowing the passage of the cylindrical part of the connection element  124  during the nesting or the separation of the parallelepipedal part of the connection element  124 . 
     Once nested into the receiving recess  130 , the connection element  124  can no longer rotate in the receiving recess  130 . In this case, the connection element  124  being attached to the connection rod  120 , on the one hand, and the receiving recess  130  being attached to the plunger head  110 , on the other hand, the operating rod  120  is rotationally integral with the plunger head  110  about the longitudinal axis A 1 . 
     Likewise, the operating rod  120  is translationally integral with the plunger head  110  along the longitudinal axis A 1 . 
     When the operating rod  120  is connected to the plunger head  110  at its upper end, the notch  112  and the rack  122  on the one hand, and the notch  113  and the rack  123  on the other hand, are herein aligned with each other. 
     The operation of the syringe  10  according to the particular embodiment described hereinabove will now be described with respect to  FIGS. 10 to 13 . 
     We consider herein a tissue sampling operation performed by an operator, where the initial state of the syringe  10  is that shown in  FIG. 10 . 
     In this initial position, the plunger  100  is in its low position with respect to the syringe body  20 , i.e. the terminal part  114  of the plunger head  110  presses on the lower end  20 A of the syringe body  20 , the respective shapes thereof being complementary of each other. 
     The operating rod  120  is in part inside the syringe body  20 , its upper end and in particular the flatten area  125  being located outside the syringe body, which allows the operator manipulating the syringe  10  to make the plunger  100  slide along the inner wall  21  of the syringe body  20  along the longitudinal axis A 1 , by pulling on the operating rod  120  at the level of the flatten area  125 . 
     In the situation illustrated in  FIG. 10 , the first rack  122  is aligned with the first stop  32 , and the second rack  123  is aligned with the second stop  33 . The width of the operating rod  120  at the outer surface  121  including the first and second racks  122 ,  123  is lower than the inner diameter of the syringe body  20  such that the protruding teeth  122 A,  123 A does not rub against the inner wall  21  of the syringe body  20 , which hence limit the pulling force that the operator has to exert on the operating rod  120  to make the plunger  100  slide in the syringe body  20  along the longitudinal axis A 1 . 
     Starting from the situation illustrated in  FIG. 10 , the operator hence pulls on the operating rod  120  to begin sampling tissue. The plunger  10  then slides in the syringe body  20  along the longitudinal axis A 1 . The first and second racks  122 ,  123 , and more particularly the first two protruding teeth  122 A,  123 A directed towards the upper end of the operating rod  120  move inside the syringe body  20  up to arrive opposite the first and second stops  32 ,  33 . 
     The distance between the first two protruding teeth  122 A,  123 A being higher than the distance between the first and second stops  32 ,  33 , the operator cannot continue to easily pull on the operating rod  120 . 
     The operator must then exert an additional force so as to move the first two protruding teeth  122 A,  123 A past the first and second stops  32 ,  33 , thanks to the elastic deformation of the first two protruding teeth  122 A,  123 A. 
     Once having moved past the first and second stops  32 ,  33 , the first two protruding teeth  122 A,  123 A bear on the bearing surfaces  32 B,  33 B of the first and second stops  32 ,  33  preventing any downward move of the plunger  100  under the effect of a push on the operating rod  120 . 
     In this configuration shown in  FIG. 11 , the terminal part  114  of the plunger head  110  does no longer bear on the lower end  20 A of the syringe body  20  but is moved upwards inside the syringe body  20 , hence defining a first sampling volume  24 . 
     The position of the first two protruding teeth  122 A,  123 A are determined so that this first sampling volume  24  corresponds to such a volume that the corresponding vacuum exerted on the sampled tissue is lower than a threshold value. 
     Here, the syringe body  20  having a total volume of 10 milliliters, the first sampling volume  24  is equal to 2 cubic centimeters, limiting the vacuum exerted to value of 0.4 atmosphere (in absolute value). 
     By repeating several times the preceding step, the operator moves the plunger  100  upwards, “tooth by tooth”, in the syringe body  20 , the additional volume sampled, and hence the vacuum exerted on the sampled tissues, being always the same due to the constant distance determined between the protruding teeth  122 A,  123 A. 
       FIG. 12  shows an intermediate situation where the plunger  100  is located between the above-described low position and the high position described in more details hereinafter. In this configuration, the first and second stops  32 ,  33  and the first and second racks  122 ,  123  are opposite to each other. Two protruding teeth  122 A,  123 A bearing on the two bearing surfaces  32 B,  33 B of the stops  32 ,  33 , the plunger  100  cannot move downwards in the syringe body  20 . 
     So as to disengage the first and second racks  122 ,  123 , the operator bring the first rack  122 , respectively the second rack  123 , opposite the first blank surface  22 , respectively the second blank surface  23 , of the inner wall  21  of the syringe body  20  by rotation of the plunger  100  in the syringe body  20  about the longitudinal axis A 1 . 
     Hence, the width of the outer surface  121  of the operating rod  120  being lower that the distance between the first and the second stops  32 ,  33 , the plunger  100  can slide without hindrance along the inner wall  21  of the syringe body  20 . 
     The operator may then either bring the plunger  10  down to its low position, such as shown in  FIG. 10 , or lock again the plunger  100  in the intermediate position by reengaging the first and second racks  122 ,  123  into the first and second stops  32 ,  33  by rotation of the operating rod  120 . 
     If, starting from the situation shown in  FIG. 12 , the operator continues to move the plunger  100  upwards, tooth by tooth, by making the plunger slide along the syringe body  20 , the movement will end in the passage of all the protruding teeth  122 A,  123 A of the first and second rack  122 ,  123  as shown in  FIG. 13 . Then, only the plunger head  110  remains inside the syringe body  20 , and in particular the receiving recess  130 , which then forbids any detachment of the operating rod  120  from the plunger head  110  by sliding of the connection element  124  outside the receiving recess  130 . 
     By continuing to exert a pulling force on the operating rod  120 , the operator brings the upper part of the base  111  between the first and second stops  32 ,  33 , the base  111  being deformed thanks to its elasticity, as the protruding teeth  122 A,  123 A. The first and second stops  32 ,  33  are then opposite the first and second notches  112 ,  113 , and the first and second planar faces  112 A,  113 A of the first and second notches  112 ,  113  bear on the first and second bearing surfaces  32 B,  33 B of the first and second stops  32 ,  33 . 
     As hereinabove, the passage of the first base part  111  increases the sampling volume by such a value that the corresponding vacuum exerted on the sampled tissues is lower than the above-defined threshold value, and preferably similar to the moving tooth by tooth. 
     When the first and second notches  112 ,  113  are opposite the first and second bearing surfaces  32 B,  33 B of the first and second stops  32 ,  33 , the plunger  100  is held in the high position and cannot move downwards along the syringe body  20 . 
     So as to disengage the plunger head  110 , the operator brings the first longitudinal groove  115  opposite the first stop  32  by rotation of the plunger  100  in the syringe body  20  by means of the operating rod  120 . The second stop  33  and the second longitudinal groove  116  being diametrically opposed to the first stop  32  and to the first longitudinal groove  115 , respectively, the second stop  33  and the second longitudinal groove  116  are then also opposite to each other. 
     Moreover, the first and second racks  122 ,  123  being aligned with the first and second notches  112 ,  113 , they are located above and in the alignment with the first and second blank surfaces  22 ,  23 . 
     Hence, the operator can then slide the plunger  100  downwards inside the syringe body  20  by exerting a pushing force on the operating rod  120 . 
     Besides, as shown in  FIG. 13 , when the plunger  100  is in the high position, the terminal part  114  prevents any full disengagement of the plunger  100  from the syringe body  20  thanks to the locking of the plunger head  110  by the first and second stops  32 ,  33 . 
     Indeed, the terminal part  114  being made of a rigid material, the operator cannot fully disengage the plunger  100  from the syringe body  20 , but to exert voluntarily a very high pulling force on the operating rod  120 . This avoids that involuntary errors of manipulation fully disengage the plunger head  110  from the syringe body  20  and possibly compromise the quality of the sampling. 
     Furthermore, the longitudinal position of the first and second notches  112 ,  113  on the base  111  is such that, in the high position shown in  FIG. 13 , the upper end of the plunger end, and more particularly the receiving recess  130 , protrudes enough from the upper end  20 B of the syringe body  20  to allow the disengagement of the connection element  124  by its sliding out of the receiving recess  130 . 
     The operating rod  120  may then be detached from the piston head  110 , which reduces the total length of the syringe  10  when the plunger head  110  is in the high position and hence facilitating the manipulation of the syringe  10 .

Technology Category: 1