US3318530A - Material discharge gun - Google Patents

Description

May 9, 1967 O. RHODES MATERIAL DISCHARGE GUN Filed Aug. 24, 1964 0/27er' Rhodes I N VE NTOR.

BY z/wpw v United States Patent 3,318,530 MATERIAL DISCHARGE GUN Omer Rhodes, Houston, Tex., assignor to Clemtex Ltd., Houston, Tex., a limited partnership Filed Aug. 24, 1964, Ser. No. 391,720 1 Claim. (Cl. 239-117) This invention relates to a pneumatic gun for discharging materials of a semi-fluid nature and more particularly to air brushes of the type adapted for spraying coating materials such as metallic coatings of the type such as zinc coatings. These coatings act as sacrificial protective coatings for steel and this process is sometimes referred to as cold galvanizing.

One of the problems associated with the operation of this type of spray gun is that material being sprayed will quite often build up as a residue on the surface of the gun adjacent to the orifice which emits the material to the atmosphere. This build up of material not only distorts the volume of material being emitted or ejected from the gun but can also be of such extent that When it is desired to terminate operation of the gun, the material will continue to flow from the opening causing great economic loss. This is usually caused by the material build up fouling or otherwise rendering inoperable the valve structure which ordinarily closes off the flow of the material. Moreover, the type of material which is contemplated for use with respect to the instant invention will normally cause severe abrading and thereby render some guns inoperable in a very short time.

The prior art is replete with examples of various gun devices which have been developed and which have one or more of the aforesaid deficiencies. Many of the prior art guns have needle valves which are designed to seal and close off the emitting orifice. However, these needle valves are particularly susceptible to the aforesaid fouling. Other prior art devices have utilized certain flexible butt type valves but they are likewise adversely affected by the build up of residue of the spray material on the surfaces and valve seats thereof.

Moreover, the straight hydraulic guns of the prior art are not satisfactory for spraying the metallic coatings such as zinc coatings because the extremely high pressures at which these type of guns operate causes the zinc or other metal to separate out from the carrier.

It is therefore an objective of the instant invention to provide an improved pneumatic spray gun wherein the aforesaid deficiencies are overcome with a minimum of maintenance problems.

Examples of prior art patents which reflect the general state of the an include the following US. Patents: 1,969,- 205, 2,577,437, Re. 19,907, 1,321,014, 2,457,993, 2,105,- 903, 2,584,943, 1,081,102, 1,736,356.

Briefly stated, the instant invention is a pneumatic spray gun for spraying a coating material, which spray gun has what will be described as a gun body. This gun body is provided with a nozzle end and at least one passage through the body for receiving a pressurized gas such as air, and for discharging the gas in a predetermined pattern out the nozzle end.

Inlet means are connected to the gun body for receiving the coating material under pressure, normally in the range of about fifteen pounds to fifty pounds per square inch. A cylinder is connected to this inlet means for receiving the coating material. One end, i.e., the forward end, of the cylinder has a portion with a reduced diameter, which end is mounted for emitting the material to the atmosphere and through the gas pattern. The other end of the cylinder is provided with a frusto conical shaped valve seat. A frusto conical shaped valve of resilient material such as rubber issupported adjacent to the valve seat and adapted for seating therein in a closing relationship. This valve is mounted on a valve stem, which stem is axially aligned with the central axis of the cylinder. There is also provided means for moving the valve and valve stem axially with respect to the valve seat whereby said valve is moved to and from a closed position.

Biasing means are also provided for normally urging the valve and valve stem to a closed position when the gun is not being operated. The fore end or front end of the valve stem is providing with an extension needle which projects forwardly in the cylinder and has a point which is adapted to move in and out of the reduced end of the cylinder in a loose fitting relationship during opening and closing of the valve. Hence, the diameter of the tip of the pin is smaller than the diameter of the reduced end of the cylinder which forms the emitting orifice. The purpose of this needle is to maintain an opening through this emitting orifice despite a certain amount of residual build up of spray material, and also prevents excessive build up in the orifice.

Reference to the drawings will further explain the invention, wherein:

FIG. 1 is a side elevation view generally in central section of one embodiment of the instant invention.

FIG. 2 is an enlarged fragmentary view of a portion of the cylinder and valve arrangement of the instant invention.

FIG. 3 is a view taken at line 3-3 of FIG. 2 showing the mounting of the valve in relation to the valve stem.

Referring to FIG. 1, one embodiment of the instant invention will be explained in detail. There it will be seen that gun body 11 is provided with air inlet means in the form of air inlet nipple 12 connected to air tube 13 which is, of course, connected to a suitable supply of pressurized air, or gas, which will be used for the spraying operation. Nipple 12 communicates with air duct 14 which leads up through the handle of gun body 11 to lower cylinder 15. Cylinder 15 has spring biased air valve 16 mounted therein and which is actuated by the operation of trigger 17 operating against valve rod 18 working through appropriate packing. When valve 16 is unseated air is supplied through appropriate channels communicating with the annular space 19 which surrounds gasket housing 20 which is mounted in middle cylinder 21.

Gasket housing 21 supports plunger 22 therein which is normally biased to the left as viewed in FIG. 1 by spring 23. Plunger 22 connects through gasket housing 20 to piston 24 which in turn is connected to valve rod 30. Piston 24 is engaged by trigger 17 when trigger 17 is moved rearwardly.

Air is then supplied upwardly to upper cylinder 31 through appropriate conduits. Mounted inside of upper cylinder 31 is air control sleeve 32 which forms two channels to the nozzle end of the gun as will now 'be explained.

Sleeve 32 is provided with a plurality of small ports 33 which communicate with the internal chamber 36 which extends forward through sleeve 32. The passage of air through chamber 36 is controlled by needle valve 34 which in turn is adjusted by dial 35 mounted on the back side of gun body 11. Air is thus admitted to internal chamber 36 of sleeve 32. The front end of sleeve 32 is threadably connected to spray head 41, the details of which will now be explained.

While spray head 41 will be described as being unitary, it is to be understood that it could be made of a plurality of parts operably connected together. The lower end of spray head 41 is provided with material inlet means in the form of tube 42 which projects downwardly from the gun. Tube 42 communicates with cylinder 43 which is in the form of a sleeve with a cylindrical opening therein which is generally axially aligned with valve rod 30. Valve rod passes through a rearwardly extending portion of spray head 41 which is held in a ring 40, which is attached to and forms a part of gun body 11. This rearwardly extending portion of spray head 41 supports packing 39 and packing nut 38 through which valve rod 30 moves.

The fore end of the cylindrical opening in cylinder 43 has a reduced area formed by fluid tip 44 which is threadably secured to spray head 41 as best seen in FIG. 2. There it will be observed that cylinder 43 is unobstructed and that fluid is emitted out orifice 45 formed in the forward end of fluid tip 44. Hence, it may be said that orifice 45 has a diameter less than the diameter of cylinder 43. The other end, i.e., the rearwardly end, of cylinder 43 is provided with a frusto conical shaped valve seat 46 which is generally concentric with the central axis of cylinder 43. It is an important feature of this invention that valve seat 46 is frusto conical in shape as'will be explained hereinafter.

Mounted on valve rod 30 and held adjacent to valve seat 46 is a frusto conical shaped resilient valve 47 which may be made of rubber or the like. Valve 47 is held in position by valve retainer washer 48 on the back side thereof and lock washer 49 on the front or leading side thereof. One important feature of the present invention is that the frusto conical section of valve 47 is generally of a longer axial length than the axial length of valve seat 46. Hence, valve 47 has a relatively large seating area for contacting and closing with valve seat 46. The beveled surface or frusto conical shape of valve seat 46 also permits the flow of fluid. there past which helps to cleanse the valve seat area and reduces the amount of material residue build up thereon. In addition, since valve 47 is of a resilient material, it will easily conform to the surface of a valve seat 46 even if there is a slight material build up thereon. Further, the fact that the axial length of the frusto conical section of valve 47 is longer than the axial length of valve seat 46 allows both for any wear on valve 47 and any undesirable build up of residual spray material on valve seat 46. These are some of the important features of the invention and which provide a positive closing action under normal operating conditions when spraying metallic base coatings.

Normally, valve 47 will be biased to the closed position and seated against valve seat 46 by operation of spring 23 acting on plunger 22, piston 24 and rod 30 when the tool is not in operation as is shown in FIG. 1.

Spray head 41 has threadably attached around the end thereof retainer ring which is adapted to secure and hold in place air cap 56 having air discharge orifices 57 which are for projecting air therefrom in a predetermined pattern. In addition, fluid tip 44 has an annular flange 58 which secures annular sleeve 59 in position. Sleeve 59 has spaced thereabout annular bafile rings which help to disperse the air to all of the orifices 57. Sleeve 59 also forms on the inside thereof an annular chamber which communicates with upper cylinder 31 and provides pressurized air through an air orifice in air cap 56, which air orifice surrounds the forward end of fluid tip 44 which forms fluid orifice 45.

In operation of the gun, and starting from the closed or inoperative position, material to be sprayed is supplied through tube 42 under the desired pressure, usually in the range of fifteen pounds to fifty pounds per square inch. In addition, pressurized air is applied through air tube 13 to cylinder 15. Upon actuation of trigger 17 air is simultaneously applied upwardly for passage through chamber 36 of sleeve 32 and then out of orifices 57. At the same time air is applied along the surface of upper cylinder 31 to the chamber surrounding fluid tip 44, through axial openings 60 provided in flange 58, and then outwardly around the forward end of fluid tip 44 and past orifice 45, thereby forming another air pattern I for atomizing and dispersing the coating material.

As trigger 17 is moved rearwardly it also moves piston.

24 and valve rod 30 rearwardly thereby unseating valve 47. At this point the pressurized material will flow upwardly through tube 42, past washer 48, and through peripheral notches 61 provided therein. As the material is forced out orifice 45 under pressure, it will contact the air patterns established by the air being discharged from the nozzle end of the gun and thereby projected to the desired spray pattern.

It will be observed that the forward end of rod 30 has attached thereto needle 62, the tip of which is of a smaller diameter than orifice 45, and hence fits therein in a loose fitting arrangement. When the spray gun is not in operation, valve 47 is seated in valve seat 46. Upon actuation of trigger -17, needle 62 is withdrawn from orifice 45 at the same time that valve 47 is unseated. The purpose of needle 62 is to prevent stop-up of orifice 45 by residual spray material during close down or non-' operation of the tool. Needle 62 is supported on rod 30 such that cylinder 43 is maintained in an unobstructed condition so that spray material may easily flow therethrough.

The instant invention provides many advantages over the prior art. For example, a spray gun constructed according to the present invention has operated for a long period of time with few maintenanceproblems, whereas a prior art gun heretofore used for this purpose without the novel elements of the present invention was susceptible to malfunctioning after a short period of operation. For example, the gun of the instant invention has sprayed in excess of 800 gallons of a coatingmateria-l, such as zinc spray coating, without failure or malfunctioning, whereas the use of a similar gun without the novel elements of this invention sprayed only five gallons before shut down, disassembly, and cleaning of the gun was required. .In the case of this prior art gun, the build up of residue material in the valve structure prevented the cut off of the flow of the spray material during non-operation. Hence, there was great loss of material from the gun when not spraying. In addition, there was much loss of time in disassembling the gun to correct this malfunctioning.

One advantage of the instant invention is that the novel shape and arrangement of resilient valve 47 in relation to valve seat 46 provides a very positive closing of the fluid material flow. In addition, the resiliency of valve 47 accommodates any slight build up which may occur on valve seat 46. Moreover, build up of residual spray material on valve seat 46 is reduced because of the tapered or frusto conical shape of seat 46. It is thought that the fluid flow through, along, and past the beveled surface of valve seat 46 assists in cleaning therefrom the material that may build thereon. In addition, needle 62 projects into orifice 45 during non-operation of the tool to prevent the hardening of any residue of spray material therein. Hence, when operations are resumed with the gun, an immediate opening is provided through orifice 45. This is more than a cleaning action on the part of needle 62 in that it also provides a continuous opening through orifice 45 upon removal of needle 62 therefrom. Depending upon the particular material being sprayed, orifice 45 will generally have a diameter of at least of an inch or larger.

For purposes of convenience, gun body 11 and spray head 41, together will sometimes be referred to as a gun body generally.

Further, for purposes of convenience cylinder 43 and fluid tip 44 may sometimes be referred to together as a cylinder for receiving the coating material to be sprayed.

In this connection, and as explained above, spray head 41 and associated elements may be unitary or a plurality of parts which when assembled, assume the form of the invention described. Hence, in some instances,-prior art guns may be converted to guns which embody the instant in ention by use of a conversion kit having the necessary elements and adaptors for the spray gun of this invention.

Further modifications may be made in the invention as particularly described without departing from the scope of the invention. Accordingly, the foregoing description is to be construed illustratively only and is not to be construed as a limitation upon the invention as defined in the following claim. 1

What is claimed is:

A pneumatic spray gun for spraying a metallic coating material, the combination comprising:

a gun body having a nozzle end and at least one passage therethrough for receiving pressurized air and for discharging said air in a predetermined air pattern out said nozzle end,

inlet means connected to said gun body for receiving said coating material under pressure,

a cylinder forming an unobstructed chamber connected at a generally right angle to said inlet means for receiving said coating material, one end of said cylinder having a reduced diameter forming a discharge opening and mounted for emitting said material through said air pattern and the other end of said cylinder having a frusto conical shaped valve seat concentric with central axis of said cylinder and positioned substantially rearward of said discharge opening and adjacent said inlet means with the smallest diameter of said valve seat being at least twice the diameter of said discharge opening, whereby a given quantity of spray material will pass therethrough in the open position at a substantially lower velocity than through said discharge opening,

a frusto conical shaped valve of resilient material supported adjacent to said valve seat and for seating therein in a closing relationship, the axial length of the frusto conical portion of said valve being of a greater length than the axial length of said valve seat,

said valve being mounted on a valve stem axially aligned with said cylinder,

means for moving said valve and valve stem axially with respect to said valve seat, whereby said valve is thereby opened and closed,

resilient biasing means for normally urging said valve and valve stem to a closed position when said gun is not being operated, and

an extension needle connected to the front end of said valve stem and projecting into said discharge opening in loose fitting relationship when said valve is in the closed position, whereby an opening is maintained through said discharge opening even during times when coating material residue tends to build up therein.

References Cited by the Examiner UNITED STATES PATENTS 1,661,150 2/1928 Birkenmaier 239-117 2,172,193 9/1939 Downs 239-597 2,236,551 4/1941 Striegel 239407 2,705,663 4/1955 Gilbreath 239590.3 3,111,271 11/1963 Lofgren 239117 3,198,435 8/1965 Ullrnan 239117 M. HENSON WOOD, JR., Primary Examiner.

R. S. STROBEL, Assistant Examiner.

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