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 A PAINT-SPRAY NOZZLE 
 TCP MAPI INC TPEES 
 
 January 1952 
 
 
 
 HUME LIBRARY 
 
 OCT bl 19?2 
 Mi 
 
 UNITED STATES DEPARTMENT OF AGRICULTURE 
 
 FOREST SERVICE 
 FOREST PRODUCTS LABORATORY 
 Madison 5, Wisconsin 
 
 In Cooperation with the University of Wisconsin 
 
Digitized by the Internet Archive 
 
 in 2013 
 
 http://archive.org/details/nozzleOOfore 
 
■ 
 
 :• 
 
 L. E. DOWNS, Engineer 
 
 Forest Products Laboratory, i. Forest Service 
 U. S. ] r it of Agriculture 
 
 Introduction 
 
 Pressurized paint cans nay be used for marking trees by adding a special nozzle 
 to the spray cap, so that the air can applied in lines narrow enough to 
 form legible numbers or letters. 
 
 These cans usually contain 12. fluid ounces o~" paint pressurized with dichlorc- 
 dif luor one thane, a gas used as a refrigerant or .■• ■ Llant. The pressure 
 forces the eaint throu rtal tube ea rig fro™ near th i ;om of the 
 can to a spring valve at the bop. .'hen this -,alve is opened by depressing a 
 small lever, the paint emer is fine s^ray. 
 
 Cans of this type are intended for painting flat surfaces and, for such pur- 
 poses, a broad spray is suitable. The mark on a tree, however, should not be 
 more than one-half inch wide. Therefore, a special nozzle, long enough to 
 project over the side of the can, was d signed so the tip could be held 
 close to the tree. In addition, b] Loi r bor rhich is v ,ry small in 
 diameter, reduces the flow and prevents heavy paint d .-posits. Thus, the paint 
 reaches the tree before the spray cc I com.- too wide to form 1 . 
 identification marks. 
 
 Paint-sora Nozzle 
 
 :y; e of Can 
 
 A can with a removable s;ra; r cae and a spring valve that will retain res- 
 sure in the can when the cap is unscrewed is best suited for this • se • 
 This type of cap is often held in place by 7/l°~i nc h threads, 2o threads to 
 the inch. Cnce the nozzle is attached to a cap from t r movable type of 
 can, che unit can be used on any pressurized can having the same size threads. 
 
 — intained at liadison, fis., • ■ ration with the University of Wisconsin. 
 Report No. Rljlk -1- - .;• -Madison 
 
Construction of Nozzle 
 
 The nozzle is made of hexagonal brass bar stock, l/U inch across the flats and 
 is approximately 2 inches long, ks most small drills are short, it is diffi- 
 cult to drill an accurate bore of this length. For this reason, the nozzle 
 was made in parts a, b, and c (fig. l). 
 
 The bore of part a was drilled with a No. 60 drill. This part of the nozzle 
 serves merely as a tube to conduct the paint to part b. The bore should be 
 kept small, however, because a larger bore would hold enough paint and Freon 
 to force paint from the tip of the nozzle after the valve lever is released. 
 
 Parts b and c were drilled with a No. 80 drill, .oven with parts as short as 
 these, it was necessary to rotate the part in an accurate lathe and drill 
 halfway from each end with a drill held in a chuck mounted in the tailstock. 
 
 After the bores were drilled, the ends were beveled out slightly with a larger 
 drill to facilitate the insertion of a small wire for cleaning. 
 
 Parts a and b were fitted with both male and female machine-screw threads, 
 size 6-32. Part c was threaded with male threads so that it could be screwed 
 into either part a or part b. Thus, parts a and c, or parts b and c, can be 
 used alone. 
 
 For appearance, the end of part c — actually the tip of the nozzle — was 
 tapered to a conical shape. The hexagonal corners of parts a and b were 
 rounded off to a l/U-inch diameter near the male threads to provide clearance 
 between the nozzle and the spray cap. 
 
 The small hole in the spray cap was drilled out and tapped with 6-32 machine- 
 screw threads, so that the male end of parts a or b could be attached (d, fig. 
 1). The surface was end-milled to fit flat against the nozzle washer. 
 
 Fiber washers were used as gaskets to prevent paint leakage at the joints. 
 These washers were about l/32 inch thick and l/U inch in diameter. They fit 
 snugly over the 6-32 threads. Three such vra.shers are needed for each nozzle. 
 
 V/ashers of suitable size may be obtained at radio or electrical supply houses. 
 They can be made by drilling a l/U-inch fiber rod with a No. 28 drill and 
 slicing off washers of the correct thickness with a narrow parting tool. 
 
 assembly of Nozzle 
 
 Nozzle parts a, b, and c are screwed together with a washer in each joint. 
 The nozzle is then screwed into the tapped -out spray cap. The third washer 
 is used to seal this joint. 
 
 A pair of small, open-end wrenches should be used to tighten or loosen the 
 various parts, but they should be used with discretion because it is easy to 
 strip the threads of the brass parts or of the spray cap. The use of wrenches 
 not over 1 or 1-1/2 inches long may reduce the danger of applying too much 
 torque. 
 
 Report No. R19lii -2- 
 
Use and Care of the Nozzle 
 
 Using the Nozzle 
 
 The can should be held with the nozzle tip close to the tree if a narrow line 
 is desired. vftien the valve is open, the can should be moved fairly rapidly 
 while the marking is being formed, otherwise the paint may be deposited so 
 thickly that it will run. Care should be taken not to toucii the tree, or the 
 nozzle or spray cap may be damaged. 
 
 Cleaning and Storage 
 
 A piece of wire, 0.013 inch in diameter or smaller, is useful to clean the 
 nozzle if it becomes clogged, i/lire this small is not very common, but it can 
 be obtained. Steel spring wire or piano wire with a diameter of approximately 
 0.0095 inch is used at the Laboratory. 
 
 When spraying is discontinued for a few hours or longer, it is advisable to 
 run the wire through the nozzle and leave it there. This keeps the channel 
 open for future use. It is recommended that the end of the wire be twisted 
 into a loop and a string or tag tied to it to avoid losing it. 
 
 Turpentine or other paint thinners or solvents may be used freely to clean 
 the nozzle parts. Turpentine or paint thinner may also be used to clean the 
 spray cap, but other solvents, such as benzene or acetone may soften or destroy 
 the flexible rubber or neoprene diaphragm in the cap. 
 
 The cans should be stored in an inverted position, so that any pigment that 
 settles vail not clog the open end of the internal metal tube. 
 
 Immediately before use the can should be turned over to its normal position 
 and shaken vigorously until the metal agitators usually found in such cans 
 rattle freely. 
 
 Report No, R191U -3- 
 
Figure 1. --Special tree-marking nozzle for pressurized paint cans. 
 A, can with nozzle in place ^ B, parts of nozzle 
 shown in finished and longitudinal section views, are 
 made of hexagonal brass bar stock . Part a was drilled 
 with a No, 60 drill; parts b and £ with a No. 80 
 drill The hole in spray cap d was drilled and tapped 
 out with a 6-32 machine-screw thread. Threads of a, 
 b, and c, are also 6-32. Washers of hard fiber, 
 about l/32 inch thick and l/k inch in diameter and 
 drilled with a No. 28 drill, are inserted between the 
 three nozzle parts and between the nozzle and can. 
 
 ZM 89196 F 
 
 Report No, R1911+ 
 
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