referring to fig1 - 2 , the spray applicator shown may be generally similar to the spray applicator described in related patent application ser . no . 09 / 302 , 726 filed apr . 30 , 1999 and entitled but has a novel spray nozzle 10 of different construction from spray nozzle 106 disclosed in the related application . accordingly , while spray nozzle 10 is shown in detail , only small portions of the surrounding structure of the spray applicator are shown . spray nozzle 10 comprises a dispensing tube or lumen 12 which terminates downwardly in an exit aperture 14 from which a liquid to be sprayed can be dispensed . the dispensed liquid is pressurized , for example by a manually operated mechanical actuator , but not atomized , and is discharged from exit aperture 14 as a jet , a stream or as droplets , of liquid . because aperture 14 is not intended to generate fine droplets that can be readily airborne ( which would be difficult with a non - newtonian liquid , as explained above ) but is , in a preferred embodiment , designed for direct application of mixed fibrinogen sealant agents to surgical tissues , exit aperture 14 is relatively larger in area than would be an atomizing orifice , and any droplets that may be dispensed under relatively low pressure operation will be larger than spray droplets , their size being determined by the area of exit aperture 14 . while the invention is not limited to any particular aperture shape or size , exit aperture 14 preferably is circular and has a diameter in the range of about 0 . 25 to about 2 . 5 mm ( about 0 . 01 to about 0 . 1 in . ), more preferably about 0 . 5 to about 1 . 5 mm ( about 0 . 02 to about 0 . 6 in . ), with one suitable size being about 0 . 75 mm ( 0 . 03 in .) in diameter . the spray liquid can be any liquid suitable for spraying but is preferably a non - newtonian liquid , for example , fibrinogen or other polymer solution , or other sprayable aqueous or non - aqueous liquid sealant material , or a non - newtonian paint or the like . a spray plate 16 is oriented and disposed under lumen 12 to stop or deflect the dispensed liquid . it will be understood that lumen 12 could be lumen 18 or lumen 124 , as described in related application ser . no . 09 / 302 , 726 . a gas nozzle 18 incorporating spray plate 16 at its distal edge , is disposed beneath lumen 12 and has a cut away mouth 20 defined by set back shoulders 22 , which embrace and support lumen 12 . gas nozzle 18 has a hollowed - out interior 24 with a proximally tapering groove 26 in the floor of interior 24 which leads distally to spray plate 16 . a gas orifice 28 is disposed in gas nozzle 18 , proximally upstream of spray plate 16 , and provides a stream of carrier gas , for example air , which is guided by nozzle interior 24 toward spray plate 16 . the kinetic energy of the air atomizes the stream of liquid such as a fibrin sealant and conveys the spray onto the target work surface , for example surgical tissue . spray nozzle 10 of the invention is shown , for exemplary purposes , mounted in an spray tip assembly such as taught in the ser . no . 09 / 302 , 726 application as suggested by the partial showing of suction nose 100 and cowling 154 . other spray applicators in which spray nozzle 10 may usefully be employed will be apparent to those skilled in the art . spray plate 16 comprises an impact surface 30 to be impacted by liquid discharged from lumen 12 , and is preferably constructed as a shear plate with a proximal face 32 at a relatively large acute angle to impact surface 30 , or approximately perpendicular thereto , and with a sharp shear edge 34 defined where impact surface 30 and face 32 meet . arrows 36 and 38 schematically indicate the flow of liquid dispensed from lumen 12 and of the gas stream emerging from gas orifice 28 , respectively . as shown in fig2 arrow 36 , indicating liquid flow from lumen 12 is directed toward impact surface 30 of spray plate 16 , while arrow 38 suggests the gas stream is deflected downwardly by lumen 12 . in practice , the area of impact on spray plate 16 may vary , depending upon the velocity with which the spray liquid is discharged from lumen 12 and the velocity of the gas stream , but it appears preferable that lumen 12 and spray plate 16 be aligned for most of the liquid from lumen 12 to strike impact surface 30 just behind shear edge 34 . liquid arriving at surface 30 is carried off distally by the gas stream , forming a good spray , even when employing a fibrinogen sealant mixture having the difficult non - newtonian properties described herein . while the invention is not bound by any particular theory , it appears that impact surface 30 acts as a stop for the liquid agent coming out of lumen 12 , deflecting the flow and permitting some of the kinetic energy of the liquid to be used to facilitate dispersion into droplets . impact surface 30 also prevents the liquid passing right through the gas stream , as might occur were no impact surface aligned with lumen 12 . in such a case the user would need to dispense liquid relatively slowly to avoid “ shoot - through ”. as shown in fig2 the provision of spray plate 16 with impact surface 30 , renders the design relatively insensitive to application rate , which is operator - dependent and difficult to control . additionally , it appears that impact surface 30 is valuable in providing a surface on which the intercepted liquid stream can spread out . such thinning of the liquid agent attributable to wetting of surface 30 and the pressure of the fluid hitting the surface , make the liquid easier to atomize . furthermore , as the gas stream draws the liquid off spray plate 16 , the liquid shears off sharp edge 34 aiding atomization . also it appears that with the juxtaposition of lumen 12 and gas nozzle 18 shown in fig2 the airflow pattern under the application lumen probably is such that the air is constricted by the application lumen enhancing entrainment . the cut away configuration of the device provided by set back shoulders 22 is valuable in providing a user with full visibility of the tip 31 of lumen 12 , and also for providing access thereto , to remove clogs , if necessary . thus , for example , inadvertent discharge of a coagulable material , such as sealant , which sets up in aperture 14 and has an external portion that cannot be removed by retrograde suction , may be removed manually , if desired . in an alternative construction , gas nozzle 18 has a cup - like configuration , similar to spray nozzle 106 of related application , with lumen 12 discharging sealant against an inside wall portion of spray nozzle 106 . however , such alternative construction lacks the advantages of visibility and accessibility provided by the embodiment of fig1 and 2 . while lumen aperture 14 is shown disposed within the gas stream it could be disposed outside the gas stream , and discharge liquid into the gas stream to hit impact surface 30 . similarly , spray plate 16 , or the output from spray plate 16 , could be disposed outside the gas stream , and the gas stream could be disposed to entrain the fluid droplets exiting from spray plate 16 . in summary , the described spray applicator is particularly useful for atomizing macromolecular fluids , for example sealants , including fibrin sealants whose dynamic rheology impedes atomization . significant forces acting at the spray plate acting positively on the cohesive , aligned large molecules of the sealant or other shear - thickening liquid help divide the liquid into fine particles for dispersion . other liquids that may be beneficially sprayed , employing such a gas - driven shear - spray applicator , for example paints , coatings and the like , will be apparent to those skilled in the art . as will be apparent to those skilled in the art , spray nozzle 10 can , with only minor modifications or adaptations , such as may be necessary , be substituted for spray nose 106 in the preferred embodiment of the invention shown and described in related patent application ser . no . 09 / 302 , 726 filed apr . 30 , 1999 the performance of the spray applicator of the invention is determined in a test employing a spray applicator substantially as described and shown in fig8 - 34 of related patent application ser . no . 09 / 302 , 726 filed apr . 30 , 1999 . with the use of a spray nozzle as described with reference to fig1 and 2 ( test 1 ) and with a spray nozzle similar to spray nozzle 106 of the ser . no . 09 / 302 , 726 with a cup - like spray body 172 , except that the lumen 124 is positioned to direct liquid at the bottom inside surface of spray body 172 . the dispensed liquid comprises a mixed fibrin sealant obtained from a fibrinogen agent stored in one syringe of the applicator and a thrombin agent stored in the other syringe of the applicator . in both test and test 2 , good quality sprays are generated , notwithstanding the difficult nature of fibrinogen . the embodiment used in test 1 provides the advantages of visibility and accessibility . comparative tests a and b are conducted employing different relative positions of dispensing lumen 12 and impact surface 30 as shown in fig3 and 4 . in comparative test a , lumen 12 is relatively high , sufficiently far above gas nozzle 18 that liquid dispensed from aperture 14 traveling in the direction of arrow 36 misses impact surface 30 . the test shows that this configuration can generate a good spray at relatively low application rates , which is to say liquid discharge rates , that may be difficult for an operator to set . however , when the application rate is relatively high , as it often is , much of the fibrin liquid passed right through the air stream , and landed on spray nose 100 instead of on the target , impact surface 30 . also , the spray quality is not as fine as in tests 1 and 2 . as the fibrin leaves the application lumen 12 , it shears off the end of the lumen , and some of the droplets are larger than may be desirable . similarly , comparative test b shows that moving the application lumen 12 forward is also unsatisfactory at higher application rates because there is no impact surface under lumen 12 to stop the liquid from passing through the air stream as shown in fig4 . related application ser . no . 09 / 037 , 160 discloses various sealant applicators comprising an applicator body provided with a pair of syringe reservoirs , for two liquid sealant agents , which agents are dispelled from the syringe reservoirs by manual pressure applied to a trigger - like actuator . the body also is fitted with a suction connection and manually operable suction control valve . a range of applicator heads or tips is mountable on to the applicator body to provide selected functionality . a mixing tip ( or head ) enables the two liquid agents to be discharged into a mixing chamber where they are thoroughly mixed , and provides a flow of mixed sealant to lumen 12 of fig1 herewith . a preferred mixing tip also enables the operator to terminate sealant flow and apply suction to the dispensing lumen to clear it of polymerized sealant and debris . the technique may be termed “ retrograde ” clearing . the sealant dispensing pathway can be appropriately configured , with a non - diminishing cross - section in the clearing direction , to facilitate such clearing . such an applicator , provided with a mixing tip and suction clearing , is preferred in the practice of the present invention to deliver sealant to lumen 12 which would be a component of such a sealant applicator . while illustrative embodiments of the invention have been described above , it is , of course , understood that various modifications will be apparent to those of ordinary skill in the art . many such modifications are contemplated as being within the spirit and scope of the invention .
a spray applicator particularly suited to needs of surgeons for dispensing a multi - component fluid , for example fibrin and thrombin components of a tissue adhesive . the spray applicator having a spray nozzle , a liquid dispensing aperture , a spray plate to be impacted by the liquid dispensed and a gas nozzle to provide a stream of carrier gas to carry the dispensed liquid away from the spray plate to form a spray .