a vacuum - compression injector 11 of the invention is illustrated in fig1 . therein , an exterior cylindrical housing 13 contains a vacuum chamber 15 and an interior cylindrical chamber 17 . the interior cylindrical chamber 17 contains a movable piston 19 with an o - ring 21 providing an air - tight seal between the piston 19 and the interior of cylindrical chamber 17 . the piston 19 has a piston rod or plunger 23 extending forwardly in the interior chamber 17 and maintained in an axial position by a guide bushing 25 which is held in position by a retaining ring 27 at the right end of the interior chamber 17 in fig1 . the other end of the interior cylindrical chamber 17 contains a port 29 through which air under pressure enters and impinges upon a face 31 of the piston 19 . the right end of the interior cylindrical chamber 17 adjacent to the piston rod guide bushing 25 has a plurality of vents 33 opening through the cylindrical housing 13 to the atmosphere . the air supply port 29 is connected by an air supply line 35 to a two - phase pneumatic switch 37 which , in turn , is connected through an air pressure regulator valve 34 to an air supply source ( not shown ). the air pressure regulator valve 34 has a dial with a central handle 36 to regulate the air pressure to the switch 37 and the supply line 35 . the right end of the cylindrical housing 13 in fig1 has interior threads 38 for threadably joining the tapered base 39 of a generally cylindrical nozzle housing 41 . the cylindrical nozzle housing 41 contains a hollow concentric cylindrical medicament - insert - holder 43 which is spaced from the interior of the cylindrical housing 41 leaving an annular passageway 45 extending from a forward end 47 of the housing 41 back through a plurality of vacuum ports 49 to the vacuum chamber 15 . the vacuum chamber 15 is connected to a second annular passageway 51 contained within the cylindrical housing 13 . this second passageway 51 extends to the end of the housing 13 where it joins a vacuum line 53 . the vacuum line 53 is connected through the two phase pneumatic switch 37 and a vacuum pressure regulator valve 52 to a source of vacuum ( not shown ). the vacuum pressure regulator valve 52 has a dial with a control handle 54 to regulate the vacuum pressure to the switch 37 and the vacuum line 53 . a cylindrical medicament insert 55 ( fig2 ) has an interior cavity 57 for storing a supply of medicament . the medicament insert 55 has an orifice 59 at its forward end 61 and is sealed at its other end by a plunger - plug 63 . as can be seen in fig3 the forward end 47 of the nozzle housing 41 is spaced from the medicament insert holder 43 by a plurality of spacers 65 defining the annular vacuum passageway 45 . the forward end 61 of the medicament insert 55 protrudes through the forward end wall of the insert holder 43 , as shown in fig1 and 3 . the medicament orifice 59 in the insert 55 is centrally located in the forward end 61 of the insert 55 to form a nozzle as can be seen in fig2 and 3 . in an alternative embodiment , not shown , the nozzle is formed integrally with the holder 43 and the insert 55 located therebehind but ; of course , in communication with the passageway leading to orifice 59 . in still another alternative embodiment , the insert is essentially stationary with medicament being supplied thereto from an outside source as required . in another embodiment as illustrated in fig4 , and 6 , a disposable medicament insert 71 has a plurality of nodules 73 positioned about the periphery of its outer surface . the nodules 73 hold the medicament insert 71 in position inside the nozzle housing 41 and a removable forward - end section 75 which is slidably or threadably engaged in the housing 41 . the nodules 73 provide spacing between the medicament insert 71 and the nozzle housing 41 and its forward end section 75 for an annular vacuum passageway 77 . a forward end 79 of the medicament insert 71 contains an orifice 81 and protrudes beyond a cylindrical end 83 of the removable forward end section 75 of the nozzle housing 41 . in still another embodiment as illustrated in fig7 and 8 , the removable forward - end section 75 of the nozzle housing 41 has an oval - shaped end 85 or the like to permit access to somewhat elongated surface areas in an oral cavity , for example . other end - shapes are used to accommodate confined or other areas into which medicament is to be injected . the medicament inserts shown in fig4 through 8 may be constructed from a plastic , or a metal or the like and are preferably disposable . in operation , with a medicament insert 55 in position within the holder 43 of the nozzle housing 41 , the two phase pneumatic switch 37 is initially depressed halfway to open the vacuum source through line 53 and intervening passageway 51 , chamber 15 , and passageway 45 to the forward end 47 of the nozzle housing 41 to draw a patient &# 39 ; s tissue firmly over the forward end 61 of the medicament insert 55 and its orifice 59 . in this manner the tissue is immobilized . the two phase pneumatic switch 37 is then fully depressed to release a charge of compressed air through line 35 to impinge upon the piston face 31 driving the piston 19 forward in the interior chamber 17 . at the same time the piston rod 23 drives the plunger - plug 63 forward in the medicament insert 55 forcing the medicament out through the passageway leading to orifice 59 ( and orifice 59 itself ) with sufficient force to penetrate the soft tissue of the patient . as this occurs air trapped forward of the piston 19 is exhausted from the chamber 17 through the vents 33 to the atmosphere . the depth of penetration of the medicament into the tissue of the patient is controlled by adjusting the control handle 36 of the air pressure regulator valve 34 . this adjustment is made by reference to the dial on the regulator 34 prior to actuation of the switch 37 . in this respect , it has been found that in one embodiment the depth of penetration was limited to only 1 / 4 centimeter at a pressure of 20 psi but extended to 8 . 9 centimeters at a pressure of 110 psi , with different depths of penetration , of course , resulting from different pressures in between . after the injection has been completed , the nozzle housing 41 is unscrewed from the cylindrical housing 13 and the cylindrical medicament insert 55 is removed from the insert holder 43 and disposed of . a new medicament insert 55 containing a medicament charge is then inserted into the holder 43 . pressure is then exerted against the piston rod 23 to return the piston 19 to its aft position in the cylindrical housing 13 and then the housing 41 is again threaded into the cylindrical housing 13 . as has been illustrated , the patient &# 39 ; s tissue is immobilized by using an annular ring of vacuum to draw the patient &# 39 ; s tissue tightly over the orifice of a pressure injector prior to discharging it through the dermis or mucosa so as to prevent the trauma of tearing the tissue and the related post - operative pain . in addition , the replaceable medicament insert 55 with its forward end 61 and orifice 59 provide a completely sanitary and safe means for using the injector on a series of patients or for interchanging the medicaments between injections . in the alternate embodiments of fig4 - 8 forward - end sections 75 may be removed from the nozzle housing 41 after use on one patient and either disposed of and replaced by a new end section 75 or sterilized before treating a second patient . similarly , the medicament insert 71 may also be disposed of after use on one patient . the amount of vacuum employed to draw a patient &# 39 ; s tissue over the forward end section of the medicament insert 55 is controlled by adjusting the control handle 54 of the vacuum pressure regulator valve 52 with reference to the dial on the regulator 52 . while the invention has been particuarly shown and described with reference to preferred embodiments thereof , it will be understood by those skilled in the art that various alterations in form and detail may be made therein without departing from the spirit and scope of the invention .
a needleless vacuum - compression injector applies a continuous vacuum between a medicament holder and an outwardly extending member spaced therefrom . the continuous vacuum holds tissue taut and immobilizes the tissue over a nozzle without puncturing the tissue . pressurized gas then injects the medicament into the tissue to a predetermined depth determined by the pressure of the gas . the outwardly extending member can be a removable sleeve . particularly for oral applications , the tissue - engaging surface of the outwardly extending member can be oval or otherwise non - circular in shape to accommodate the shape of the tissue to be injected .