This invention relates to liquid spray guns of the type comprising a body assembly including a nozzle portion having a liquid passageway with an outlet end opening through an outlet end of the nozzle portion, and a first air passageway having an outlet end around the outlet end of the liquid passageway and shaped to direct high velocity air against liquid flowing out of that outlet end to propel the liquid away from the nozzle portion while shaping it into a generally conical stream about an axis; the body assembly further including an air cap portion mounted on the nozzle portion and having horns projecting past the outlet end of the nozzle portion on opposite sides of the axis, having a second air passageway extending to outlet passageways and apertures along the horns facing opposite sides of the axis to direct high velocity air against opposite sides of the stream of liquid to reshape it into a wide elongate stream, including means mounting the air cap portion on the nozzle portion for rotation of the air cap portion about the axis relative to the nozzle portion between different relative positions, and including means for retaining the air cap portion at any of those positions.
The prior art is replete with liquid spray guns of the type comprising a body assembly including a nozzle portion having a liquid passageway with an outlet end opening through an outlet end of the nozzle portion, and a first air passageway having an outlet end around the outlet end of the liquid passageway and shaped to direct high velocity air against liquid flowing out of that outlet end to propel the liquid away from the nozzle portion while shaping it into a generally conical stream about an axis; the body assembly further including an air cap portion mounted on the nozzle portion and having horns projecting past the outlet end of the nozzle portion on opposite sides of the axis, having a second air passageway extending to outlet passageways and apertures along the horns facing opposite sides of the axis to direct high velocity air against opposite sides of the stream of liquid to reshape it into a wide elongate stream, including means mounting the air cap portion on the nozzle portion for rotation of the air cap portion about the axis relative to the nozzle portion between different relative positions, and including means for retaining the air cap portion at those positions. U.S. Pat. No. 1,751,787 (Binks); U.S. Pat. No. 1,990,823 (Gustopsson); U.S. Pat. No. 3,746,253 (Walberg); U.S. Pat. No. 5,090,623 (Burns et al.); U.S. Pat. No. 5,102,051 (Smith et al); U.S. Pat. No. 5,209,405 (Robinson et al); U.S. Pat. No. 5,322,221 (Anderson); U.S. Pat. No. 5,344,078 (Fritz et al.) and U.S. Pat. No. 5,803,367 (Heard et al.) and U.S. patent application Publication No. U.S. 2002/0148910 A1 published Oct. 17, 2002, provide illustrative examples.
In the most common type of air gun structures the air cap portion is circular and freely rotateable on the nozzle portion between those positions when the means for retaining is not engaged with the air cap portion, and the means for retaining the air cap portion at those positions includes a retaining ring around the periphery of the air cap portion and in threaded engagement with the nozzle portion that can be tightened to secure the air cap portion against the nozzle portion at one of those positions, and can be loosened to allow manual rotation of the air cap portion between those positions. This means provides the disadvantage that tightening the retaining ring can move the air cap portion with the retaining ring as it approaches its fully tightened position, thereby moving the air cap portion away from a position desired by the user. A device that might overcome this problem is described in U.S. patent application Publication No. U.S. 2002/0080207 A1 published May 1, 2003.
U.S. patent application Publication No. 2003/0052190 A1 published Mar. 20, 2003, describes providing interlocking tabs on the air cap portion which mate with corresponding slots on the barrel or nozzle portion of the air gun to restrict movement of the air cap portion when the retaining ring is tightened. The use of such an air cap portion and retaining ring when repositioning the air cap portion, however, requires not only loosening the retaining ring, rotating the air cap and tightening the retaining ring, but also removing the tabs from one set of slots and reengaging them with another set of slots when the retaining ring is loose, which complicates the repositioning process.
The present invention provides a liquid spray gun on which an air cap portion can be more easily and accurately repositioned with respect to a nozzle portion than can the air cap portions on the types of liquid spray guns described above.
According to the present invention there is provided a liquid spray gun comprising a body assembly including a nozzle portion having a liquid passageway extending to an outlet end opening through an outlet end of the nozzle portion. The body assembly has a first air passageway extending to an outlet end at the outlet end of the nozzle portion, with the outlet end of the first air passageway extending around the outlet end of the liquid outlet passageway and being shaped to direct air under greater than atmospheric pressure against liquid flowing out of that outlet end to propel the liquid away from the nozzle portion while shaping the liquid into a generally conical stream about an axis. The body assembly also includes an air cap portion having two spaced horns and means mounting the air cap portion on the nozzle portion with the horns projecting past the outlet end of the nozzle portion on opposite sides of the axis; and has a second air passageway extending to outlet passageways having outlet apertures spaced along the horns from the outlet end of the nozzle and facing opposite sides of the axis, the outlet passageways directing air under greater than atmospheric pressure flowing through the second air passageway against opposite sides of a stream of liquid formed by air flowing through the first air passageway to reshape shape that generally conical stream of liquid into a wide elongate stream. The means mounting the air cap portion on the nozzle portion allows rotation of the air cap portion about the axis relative to the nozzle portion, the air cap and nozzle portions include stops limiting relative rotation of the air cap portion relative to the nozzle portion to rotation through a predetermined angle (e.g., 90 degrees) between first and second relative positions, and the means mounting the air cap portion on the nozzle portion includes surfaces in frictional engagement to restrict relative rotation of the air cap and nozzle portions until a predetermined torque is manually applied between the air cap and nozzle portions.
Thus a person wishing to change the relative position of the air cap portion on the nozzle portion need only rotate the air cap portion relative to the nozzle portion to a new relative position, and the air cap portion and nozzle portion will remain in that new relative position until their relative position is again changed by the operator.
The passageways on the horns opening through the outlet apertures that direct high velocity air flowing through the second air passageway against opposite sides of a stream of liquid formed by air flowing through the first air passageway to reshape that generally conical stream of liquid into a wide elongate stream can have a greater width in a direction at a right angle to the axis than depth in a direction parallel to the axis (e.g., the outlet apertures can be generally rectangular) which has been found to form a liquid stream that is very uniform in width and in the amount of liquid delivered per unit time along its length to facilitate uniform application of the liquid to a surface.
The air cap including the horns can be molded of polymeric material, with the non-circular passageways leading to the outlet apertures being formed during the molding process.
The nozzle portion can also be molded of polymeric material, and the liquid spray gun can further include a reusable platform portion (e.g., of metal) having through air distribution passageways including an inlet opening adapted to be connected to a supply of air under greater than atmospheric pressure, first and second air outlet openings, means for separately regulating the flow of air through the first and second air outlet openings of the air distribution passageways, and manually operated means for stopping or allowing flow of air through the outlet openings of the air distribution passageways. The platform portion and the nozzle portion can then have manually operable means (i.e., means manually operable by a person without the use of tools) for releasably mounting the nozzle portion on the platform portion with the first and second air outlet openings of the air distribution passageways communicating with inlet ends of the first and second passageways. The molded air cap and nozzle portions (which are the only parts of the spray gun assembly that contact the liquid being sprayed) can be sufficiently inexpensive that for some applications they can be discarded rather than cleaned.
The present invention will be further described with reference to the accompanying drawings wherein like reference numerals refer to like or corresponding parts throughout the several views, and wherein:
Referring now to the drawing there is illustrated a liquid spraying device or spray gun 10 according to the present invention. Generally, the liquid spray gun 10 comprises a body assembly 12 including a nozzle portion 14 with an outlet end 15. The nozzle portion 14 has a liquid passageway 16 extending from an inlet end 17 to an outlet end 18 opening through the outlet end 15 of the nozzle portion 14. The body assembly 12 also has a first air passageway 20 extending from an inlet end 21 to an outlet end 22 at the outlet end 15 of the nozzle portion 14. The outlet end 22 of the first air passageway 20 extends around the outlet end 18 of the liquid passageway 16 and is shaped to direct air under greater than atmospheric pressure against liquid flowing out of the outlet end 18 of the liquid passageway 16 to propel liquid flowing out of the liquid passageway 16 away from the outlet end 15 of the nozzle portion 14 while shaping the liquid into a generally conical stream about an axis 23. The body assembly 12 includes horns 24 projecting past the outlet end 15 of the nozzle portion 14 on opposite sides of that axis 23, and the body assembly 12 has a second air passageway 26 extending from an inlet end 27 through portions of the horns 24 to outlet passageways 28 having outlet apertures spaced along the horns 24 from the outlet end 15 of the nozzle portion 14 and facing opposite sides of the axis 23. The outlet passageways 28 and apertures are non-circular and are shaped to direct air under greater than atmospheric pressure flowing through the second air passageway 26 against opposite sides of a generally conical stream of liquid formed by air flowing through the first air passageway 20 to reshape that generally conical stream of liquid into a wide elongate stream. The outlet passageways 28 and apertures are generally rectangular and have a greater width in a direction at a right angle to the axis 23 than depth in a direction parallel to the axis.
As a non-limiting example, as illustrated the outlet passageways 28 and apertures can comprise first and second pairs 28a and 28b of opposed outlet passageways 28 and apertures on the horns 24, the first pair of outlet passageways 28a and apertures each having a width in a direction at a right angle to the axis 23 of about 0.154 inch or 0.39 cm, a depth in a direction parallel to the axis 23 of about 0.35 inch or 0.89 cm, and being spaced about 0.25 inch or 0.64 cm from the outlet end 15 of the nozzle portion 14, with the outlet passageways 28a being disposed at an angle of about 66 degrees with respect to the axis; and the second pair of outlet passageways 28b and apertures each having a width in a direction at a right angle to the axis 23 of about 0.165 inch or 0.42 cm, a depth in a direction parallel to the axis of about 0.050 inch or 0.13 cm, and being spaced about 0.35 inch or 0.89 cm from the outlet end 15 of the nozzle portion 14 with the outlet passageways 28b being disposed at an angle of about 75 degrees with respect to the axis 23.
The body assembly 12 includes an air cap portion 30 including the horns 24 that is preferably molded of a polymeric material (e.g., polypropylene, polyethylene, or glass filled nylon), with the outlet passageways 28 and apertures being formed by the molding process. The body assembly 12 also includes means for mounting the air cap portion 30 on the nozzle portion 14 so that adjacent surfaces of the air cap portion 30 and the nozzle portion 14 form parts of the first and second air passageways 20 and 26. The means mounting the air cap portion 30 on the nozzle portion 14 includes a radially outwardly projecting annular ring 32 around the outlet end 15 of the nozzle portion 14 co-axial with the axis 23, and a generally cylindrical collar 33 on the air cap portion 30 having an annular recess 34 from its inner surface adapted to receive the annular ring 32 of the nozzle portion 14. The collar 33 on the air cap portion 30 is sufficiently resiliently flexible that the inner surface of the collar 33 can be pressed over the annular ring 32 to position the ring 32 in the recess 34. A cylindrical part 35 of the inner surface of the air cap portion has a close sliding fit around an outer surface of a cylindrical portion 37 of the nozzle portion 14 to separate the first and second air passageways 20 and 26. This means for mounting the air cap portion 30 on the nozzle portion allows rotation of the air cap portion 30 about the axis 23 relative to the nozzle portion 14. The air cap and nozzle portions 30 and 14 include stops 36 and 38 respectively that limit relative rotation of the air cap and nozzle portions 30 and 14 to rotation through a predetermined angle (90 degrees as illustrated) between first and second relative positions. This means mounting the air cap portion 30 on the nozzle portion 14 also includes surfaces on the air cap and nozzle portions 30 and 14 in frictional engagement (i.e., such engagement can be with each other as illustrated or, alternatively, could be with a frictional layer, not shown, between the air cap and nozzle portions 30 and 14) to restrict relative rotation of the air cap and nozzle portions 30 and 14 until a predetermined torque is manually applied between the air cap and nozzle portions 30 and 14. That predetermined torque should be enough to restrict rotation of the air cap portion 30 on the nozzle portion 14 by slight contact with the air cap portion, but not so much that it is difficult to manually rotate the nozzle portion 14 on the air cap portion 30. Such torque should thus be in the range of 5 to 40 inch pounds, and more preferably in the range of 10 to 20 inch pounds. An O-ring 39 is positioned between the air cap and nozzle portions 30 and 14 to restrict leakage between the collar 33 and the nozzle portion 14.
The outlet end 22 of the first air passageway 20 is shaped to direct a peripheral portion of air exiting the first air passageway 20 in a converging conical pattern (e.g., converging at an angle in the range of about 30 to 45 degrees with respect to the axis 23 against liquid exiting the outlet end 18 of the liquid passageway 16. This converging conical pattern better atomizes the liquid leaving the outlet end 18 of the liquid passageway 16 than would air flowing out of the outlet end 22 of the first air passageway 20 in a direction parallel to the stream of fluid leaving the outlet end 18 of the liquid passageway 16.
The liquid spray gun 10 further includes a platform portion 40 including a frame 41 having through air distribution passageways including an inlet passageway 42 (see
The platform portion 40 can be made by modifying a metal spray gun that is commercial available under the trade designation “HVLP Gravity feed spray gun” from Graco, Minneapolis, Minn., by adding to the frame 41 a portion 41a for mounting the latch member 55 described above and by adding to the frame 41 a plate 58 which provides the outer surface 50 shaped for sealing engagement with the contact surface 53 on the nozzle portion 14, and in which the first and second air outlet openings 43 and 44 are formed. The second air outlet openings 44 are defined by sockets adapted to closely receive projecting tubular portions 59 that are at the inlet ends 27 of the second air passageways 26 in the nozzle portion 14. The plate 55 has an opening 71 adapted to closely receive a projection 57 on the nozzle portion 14 to help locate the nozzle portion 14 on the plate 58, and has a groove 69 around its periphery adapted to receive in sealing engagement a projecting lip 68 around the periphery of the nozzle portion 14.
The manually operated valve means 46 (see
Liquid can be gravity fed to the outlet end 15 of the liquid passageway 16 from a suitable container at its inlet end 17, which container could be the container described in U.S. Pat. No. 6,588,681 that includes a portion of a connector adapted for manually releasable engagement with a connector portion 80 illustrated about the inlet end 17 of the liquid passageway 16. Alternatively, smaller volume liquid containers such as those described in U.S. patent application Ser. No. 10/112,182 (Schwartz), filed Mar. 28, 2002 could be used.
Optionally, a pressure tap 77 (see
The content of the aforementioned U.S. Pat. No. 6,588,681 and U.S. Applications Nos. 10/112,182 and 10/279,518 are hereby incorporated herein by reference.
The body assembly 12 including both the nozzle portion 14 and the air cap portion 30 can be molded of a suitable polymeric material (e.g., polypropylene, polyethylene, or glass filled nylon). The body assembly 12, and particularly its nozzle portion 14 will make most of the contact with a liquid (e.g., paint) being sprayed (i.e., only the needle 70 on the platform portion 40 will contact that liquid), and the molded body assembly 12 can be sufficiently inexpensive that it can be discarded rather than being cleaned for some applications.
The present invention has now been described with reference to one embodiment and possible modifications thereof. It will be apparent to those skilled in the art that many changes can be made in the embodiments described without departing from the scope of the present invention. For example, the outlet passageways 28 and apertures in the air horns 24 that have a greater width in a direction at a right angle to the axis 23 than depth in a direction parallel to the axis 23 could have shapes other than rectangular, such as, but not limited to, oval shapes 28a and 28b illustrated in