US2895686A

US2895686A - Spray gun

Info

Publication number: US2895686A
Application number: US572000A
Authority: US
Inventors: Donald J Peeps
Original assignee: DeVilbiss Co
Current assignee: DeVilbiss Co
Priority date: 1956-03-16
Filing date: 1956-03-16
Publication date: 1959-07-21
Anticipated expiration: 1976-07-21

Description

D. J. PEEPS SPRAY GUN July 2l, 19.59

2 Sheets-Sheet 1 Filed March 16, 1956 mm E m D n m L E, .A l Nn U U.

D. J. PEEPS July 21, 1959 SPRAY GUN 2 Sheets-Sheet 2 Filed March 16, 1956 JNVENTOR.' J PHP5. a @am .UMA/:17

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United States Patent SPRAY GUN Donald J. Peeps, Rossford, Ohio, assignor to The De Vilbiss Company, Toledo, Ohio, a corporation of Ohio Application March 16, 1956, Serial No. 572,000 6 Claims. (Cl. 239-412) This invention relates to an automatic spray gun, and particularly to such a spray gun utilizing compressed air for atomization and for controlling the operation of the device.

The situation in the coating ield is in accord with the general trend in modern industry of more and more operations formerly manually performed being handled by self-functioning mechanisms.

There has been a recent expanding development of the use of automatic spray equipment in the application of lubricants in sheet metal forming and stamping presses. Lubrication is needed principally to facilitate the movement of the metal into its formed shape. It is of further benefit in easing the removal of the punch or die from the finishedr work.

The spray method has proved superior in several important aspects to the wiping, brushing, and dripping devices previously utilized. Alt is not wasteful of lubricant, directing only enough for the purpose to the area under treatment. The distribution by spray is more uniform and selective and is therefore more effective.

Other advantages include labor saving, not only in the application, but in reducing or eliminating the time of cleaning `up excess lubricant collecting on the machines and on the floor which occur with other methods.

Further, as thelubricant is kept in a closed system inv spray equipment it remains clean and unadulterated, and no foreign substances injurious to the work or dies are applied with it. 'Y

Spray equipment for this iield should be as simple Vin design and operation as possible. It further should function rapidly and in proper timing with the cycles of the press. As spiace is frequently limited, a compact spray gun is necessary and one that will not be adversely affected by its proximity to the heat, dirt, and oil accompanying the operation of the press.

.The object of this invention is the provision of a spray gun to meet the requirements referred to above as well as others which will be apparent upon reading the following description and referring to the drawings in which: Figure 1 is a longitudinal vertical section, taken on the line 1 1 of Figure 2, of a spray gun embodying my invention;

n Figure 2 is a yview of the under side of the spray gun of Figure 1 with parts broken away and the inlet connections removed;

Figure 3 is a cross section taken on the line 3-3 of Figure l;

Figure 4 is a similar section taken on the line 4-4 of Figure l;

Figure 5 is a front elevation of the spray gun with the air cap and uid tip removed; and

Figure 6 is an enlarged lengthwise section of the air valve and associated parts within the spray gun.

Referring to the drawings in more detail, the spray gun has a main body member 1, fastened by a series of six bolts 2 to rear body section 3. Opposed

cavities

4 and 5 in the adjoining surfaces of the body member 1 Patented July 21, 1959 and body section 3 form a diaphragm chamber 6. Di. aphragm 7 is held in place therein having its periphery clamped between the two parts of the body.

Coating material enters the spray gun by way of inlet 9 to which it may be fed under pressure from a supply tank through a hose 10 and connection 11. Passage 14 to which inlet 9 communicates has a rearwardly inclined extension 15 leading to the diaphragm chamber 6 on the forward side of the diaphram 7.

An axially located port 16 in the front wall of the chamber provides a path for the coating material to the fluid tip 17 from which the coating material is discharged to the atmosphere through outlet 18. A fluid needle valve 20 governs the flo/w of coating material from outlet 18. The Ineedle valve 20 extends rearwardly through a tubular member 21 fixed to the diaphragm 7 by the nut 22.

Clamped on opposite sides of the diaphragm 7 by the nut 22 and a shoulder on member 21 are two similar discs 23 and 24 which strengthen the diaphragm and prevent undue distortion of it. Disc 24 also serves as a stop in rearward movement of the diaphragm. A spring 25 bearing against disc 23 inclines the diaphragm to its rearward position indicated in dotted lines in Figure 1.

The valve 20 has a snug but slidable iit within the bore of member 21. Threaded into the rear end of member 21 is a hollow extension 26 with its inner chamber 27 closed by plug 28. Within chamber 27 is a spring 29 thrust against the enlargement 30 on the end of the fluid needle valve 20 extending into the chamber. The spring 29 inclines the valve 20 to its seatei-n-fluid tip 17 when the valve is not drawn from its closed position by rearward abutting movement of member 21 against enlargement 20, such movement accompanying like rearward travel of diaphragm 7.

Cylindrical bore 33, within which hollow extension 26 is conned, is closed at its rear end by the threaded adjustable stop 34. Lock nut 35 holds stop 34 in its selected position for setting the opening limit of needle valve 20.

From an air supply hose 37 atomizing air inlet connection 38 communicates with passage 39, leading to bore 33. An O-ring 40 acts to prevent leakage of air from the bore past the threads of adjustable stop 34.

With rearward travel of the diaphragm 7 air valve 41 is moved from its seat 42. Air valve 41 is composed of an O-ring 43 held between adjacent

annular surfaces

44 and 45, respectively located on the tubular member 21 and its hollow extension 26, as shown most clearly in the enlarged view of Figure 6. The surface 44 is forwardly ared to lock the O-ring in place without severely compressing it.

With air valve 41 drawn from its seat 42, the atomizing air ilows into the restricted bore 47 and down drilling 48. Then the air travels forwardly by way of passage 49 leading through the clamped periphery of diaphragm 7 into intermediate chamber 50 in the main body member 1.

In vertical channel 54 rising from chamber 50, the air stream is divided with one portion entering lateral passage 55 under the throttling action of valve 56, and the other portion passing forwardly through

drillings

57 and 58 into the annular chamber 59.

The part of the atomizing air subject to reduction in pressure by valve 56, reaches, by way of borings 61, the ring shaped space 62 from which it iiows through flange ports 63 in fluid tip 17 to arrive at the outlet passage 64 l 3 to be expelled from the annular outlet 69 between the tip-17and air cap 66 for'primary atomizingv actionupon the coating material issuing from tip 17.

Motivating air for control of the operation of the spray gun enters through connection` 70A from hose 71 andA passes from passage 72 intodiaphragm chamber 6' on the rear sidev of the diaphragm 7 i In utilizing the spray gun of this invention it is mounted in position singly orinY sets' in association with the forming press or other machine with-which itis to be employed. The gun is held on a supporting bar or bolt passed through the ported mounting extension 73. The bar may be part of `any suitable bracket 74.

The coating material, atomizing air and motivating air`

supply hoses

10, 71, and 37 are connected respectively to inlets 9, 38, and-70. The coating material is generally under pressure but may be drawn by the suction effect of the air discharge from the spray gun nozzle, from an unpressurized receptacle. Inthe latter situation the spring 25 is utilized to impel the diaphragm 7 rearwardly upon venting of the motivating air.

The atomizing air is fromv a source regulated towhatever pressure is required for the type of atomization desired and valve 56 is adjusted to provide the appropriate widthof the fan spray.

The pressure of the motivating air is set to exceed the pressure of the coating material, that of the spring- 25- or the sum of the two pressures when both are utilized. The motivating air line is equipped with a three-Way valve actuated by movement-of' the press or in synchro'- nism therewith to alternately vent the motivating air from the spray gun and permit the flow of` air thereto according to the number of spray gun operations needed with each cycle of the press operation;

With preparations complete to initiate the operationof' the press and the attached spray gun or set of guns, the needle valve is seated-inthe fluid tip 17 and the atomizing air valve 41 is against its seat 42; The coating material is within diaphragm chamber 6 with its pressure applied against the forward side of the diaphragm 7; and the motivating air pressure greater'than that of the coating mateiial (and of the spring if it is` being used) is on the other side of the diaphragm and'- holding the diaphragm with the parts carried by it in their-most forward position.

The press is then started .with metal stock being usually' fed manually, if the pieces are particularly large, andl likely, automatically, if a continuousA strip or small blanks are involved.

The spray gun may be directed and arranged for actuation in rapid sequence to coat either or both'tlie lower and upper dies, and in addition or insteadl the4 its .seat 42, allowing atomizing air to flow past the valve to air cap 66; and then through abutment With-the enlargement 39, on needle valve2t) moving the needle valve to open position.

The-extent of opening of valve 2i) -is predetermined -byy adjustment-of stop 34.. against which the outer end of extension26 strikes. The opening of'rvalve 20 immediately permits the lubricant'toow from iluid'tip I7 andbe projected in atomized condition to the surface being; coated.

In order to reduce to a min-- The spray discharge is of extremely short duration constituting-a momentary puff. ItV is terminatedby rapid reversal of the three-way valve which closes the atmospheric vent and re-establish the communication of the air supply with the spray gun whereby the diaphragm is forced forwardly letting the iluid needle 20 be seated first through the influence of spring 29 and then seating air valve 41.

The compact and effective, arrangement of working parts and their mode of function results in exceedingly rapidY and accurate operation ofY the spray gun of this invention.

The. motivatingr air ismaintained at a pressure suficiently high to hold the diaphragm forwardly and the atomizing air valve firmly` uponits seat: At the same time the space behind the diaphragm occupied by the motivating air is so small that evacuation and replacement of this air occurs rapidly.

The" pressure ofthe coating material remains at all timesl bearing against the front faceof the diaphragmV ready with no delay to forcefully move the diaphragm rearwardly and, concurrently, open the valves forthe atomizingairand* coating material.

The' movable elements of the spray gun' structure are alignedV and closely coupled'which resultsin a body'ofl short length and of moderate crosswise dimensions. Theenlployment'of` a diaphragm in place-of a piston'elects asavinginspace asV a diaphragm occupies and requires less longitudinal room in its operation.l

Another featurel of the design contributingv to the unusual compactness is the positioning of the diaphragm' chamber, which is necessarily of considerable width,- in4 the middle of the spray gun and the placingy of the atomizing air valve, which is much smaller in width, tothe rear of the diaphragm chamber.

AA supplemental feature of importance is the air'valve construction inwhieh the O-ring 43'l constitutes the main valve element. While easilyv assembled the parts are designed to` confine the O-ringwithout distortingcompression. This is-accomplished by retaining this element between the flared annular surface 44' on-thetubular' member21' and the straight surface 45- on the extension 26i The flared surface 44 extendsjust-beyond and'over the center'ofthe O-ring with a minor sector of' the ring protruding/'forwardly to effect the tight sealing valve action againstthe seat` 42.

It further should be noted that applicants'spray gun has all moving parts internally located withthe body presentirrg a--trim contour whereby dust, oil; and other impurities present in the surrounding industrial atmosphere areprevented from reaching the moving parts andare easily'removed after settling upon the exterior of thel spray gun.

Various changes and modifications may be made-in the embodiment illustrated and described herein without departing from the scope of the invention as delineated by the followingclaims.

Having thusY described my invention what is claimed as new andl desired' to lue-secured by Letters Patent is:

l. In aspray gun of the type described a main body member, a nozzle at the forward end of the body member for discharging air atomized coating material, means providing-a coating material supply inlet adjacent the forward end of the body member and a passage for conveying coating material under pressure from the supply inlet to the nozzle, other means providing a receiving inletfor atomizing air in the body member adjacent the rear end thereof and also providing a passage for carrying atomizing airffrorn the receiving inlet to the nozzle, a coating material valve, a seat forthe coating material valve in the nozzle against which the valve is normally seated and fromwhich it may be Withdrawn by rearward movement, Va second valve and a valve seat therefor against whichv the second'lvalve'normally is forwardly seated, said` carrying atomizing air near the rear end of the body member, a recprocable, pressure responsive, diaphragm mounted in the mid portion of the body member, connections between the diaphragm and the valves for the coating material and the -atomzing air, means for applying pressure against the forward face of the diaphragm to move the diaphragm rearwardly and through said connections to move the valves from their seats and thus allow coating material and atomizing air to reach and be discharged from the nozzle with the air atomizing the coating material, and additional means for applying air Dressure against the rear face of the diaphragm to return the diaphragm forwardly in opposition to the pressure applied to the forward face of the diaphragm.

2. A spray gun according to claim 1 in which the means applying pressure against the forward face of the diaphragm includes 'a chamber within the body in front of the diaphragm and a branch passage leading to the chamber from. the passage conveying coating material under pressure whereby coating material reaches and s thrust against the forward face of the diaphragm.

3. A spray gun according to claim. 1 in which the main body member has a forward section and rearward Section with the coating material inlet in the forward section, the receiving inlet for atomizing air in the rearward section, and the diaphragm peripherally clamped between the two sections.

4. A spray gun according to claim 1 in which an O-ring constitutes the main element of the second valve within the passage for carrying atomizing air and the valve seat therefor provides a at `annular face against which a side of the O-ring has sealing contact when the second valve is in closed position.

5. A spray gun according to claim 1 in which the connections between the diaphragm and the valves comprise a positive connection with the air valve and a lost-motion connection with the material valve.

6. A `spray gun according to claim 1 in which a spring thrust against the rear end of the coating material valve normally retains the valve in closed position against its seat, and the pressure of the atomizing air against the rear side of the second valve inclines the second valve to closed position.

References Cited in the file of this patent UNITED STATES PATENTS 2,266,365 Harrison Dec. 16, 1941 2,398,503 Paasche Apr. 16, 1946 2,479,895 Bahnson Aug. 23, 1949 2,537,051 Grant Jan. 9, 1951 2,645,466 Jones July 14, 1953 2,712,457 Kimbra July 5, 1955