it should be made clear that , in all the figures , the same reference numerals correspond to the same or equivalent constituent parts or elements of the assembly , in accordance with the example selected for the present explanation of the single - chamber syringe forming the subject of the invention . as may be appreciated from the drawings , the single - chamber syringe having an internal valve - type closure to which the present patent relates belongs to the type of those comprising a main body ( 1 ), which is a circular cylinder of straight axis , having its lower base ( 2 ) completely open , in which is also included the annular flange ( 3 ) which the user uses as a support for actuating the plunger ( 10 ). the upper base ( 4 ) includes the coaxial hollow injection tip ( 5 ), where an internal tube ( 6 ) is defined through which the liquid flows toward the injection needle ( 9 ) protected by the sheath ( 8 ) which is retained removably when inserted , with a close fit , into the annular cavity defined by the face ( 7 ). as is apparent from these three figures , the plunger ( 10 ) possesses an active head ( 11 ) which acts as a sliding closure plug to prevent the escape of liquid from the interior of the main cylindrical body ( 1 ). this is an elastomeric element whose annular flange ( 12 ) bears with friction on the cylindrical surface of the body ( 1 ), providing a seal to said closure to ensure that no undesirable leaks of liquid take place without obstructing the normal displacement of the plunger . as can be seen in fig1 the internal valve assembly used by the syringe according to the invention comprises a peripheral body ( 13 ) which acts to cooperate with an internal body ( 14 ), which assembly is arranged adjacent to the upper base of the main body and within the latter , so that a single internal chamber ( 16 ) is defined between this valve assembly and the active head ( 11 ) of the plunger and is designed to accommodate and keep isolated the liquid product contained therein . the special design of this valve assembly enables the displacements of said plunger to bring about the opening and closure of the passage to the needle . this is done by means of the suction and pressure exerted by the liquid content itself when said displacements of the plunger take place . from a study of the three representative figures , it is possible to understand the special design of this valve assembly and , in particular , how it acts in a single - chamber syringe . the internal valve body ( 14 ) possesses a special projecting central section ( 21 ) which , being arranged coaxially with said tube ( 6 ) communicating with the injection needle ( 9 ), acts as an upper closing plug ensuring the proper isolation of the latter from the chamber ( 16 ). since this is a valve means where relative and combined movements take place , both the body ( 13 ) and the body ( 14 ) and its projecting section ( 21 ) possess respective annular flanges indicated by references ( 17 , 18 , 19 , 20 , 23 , 24 and 25 ), which bear upon corresponding internal cylindrical surfaces upon which they move . fig1 shows the arrangement of all the elements and parts that intervene when the syringe is in the position of rest , containing the liquid medicinal product in said chamber ( 16 ). the seal is absolutely leaktight and secure both toward the lower base and toward the upper base of said syringe . from a study of fig2 it will be understood that when the plunger ( 10 ) is moved in the direction opposite to that of injection , a vacuum is created in said chamber ( 16 ) which produces the relative movement of the body ( 14 ) relative to the peripheral body ( 13 ), so that an upper communication tube ( 22 ) is opened with said tube ( 6 ) which faces the injection needle . as is apparent from the three figures , this tube ( 22 ) is no more than an opening or orifice made in the upper base of the peripheral body ( 13 ), coaxial with the axis of symmetry of the syringe and therefore aligned with said tube ( 6 ) of the tip ( 5 ) through which the liquid circulates . from a study of fig3 it will be understood that when said plunger ( 10 ) moves in the injection action , the fluid advances in the direction opposite to that shown in the previous figure , passing first through the transfer cavities ( 26 ) and then , through said tube ( 22 ) progressing toward the needle ( 9 ). when the active head of said plunger ( 10 ) enters into contact with the body ( 14 ), it can continue advancing and therefore dislodging liquid toward the tube ( 22 ) until the projecting and coaxial section ( 21 ) itself prevents it . it is to be understood that the invention is not limited to the illustrations described and shown herein , which are deemed to be merely illustrative of the best modes of carrying out the invention , and which are susceptible of modification of form , size , arrangement of parts and details of operation . the invention rather is intended to encompass all such modifications which are within its spirit and scope as defined by the claims .
a single chamber disposable syringe containing a medicament includes a valve member positioned in the variable volume chamber adjacent to the medicament outlet for selectively communicating the variable volume chamber with the medicament outlet .