JPH03114559A - Spray gun - Google Patents

Abstract

PURPOSE: To prevent the clogging of a nozzle by the dry residue of a coating material or other coating material liquid by providing the spray gun with a means for moving a closing cone in an axial direction between a first closed position where the closing cone is sealed by being in contact with a valve seat and a second open position where the closing cone is displaced from the valve seat toward the flow of the discharged coating material. CONSTITUTION: At the time of stopping coating, compressed air is no longer supplied to a port 16. A belleville spring 62 moves a flange 40 and an adjacent piston 22 toward the left. Consequently, the closing cone 80 of a valve needle 20 moves and engages the valve seat 76, by which a clearance 82 is closed and the discharge of the coating material is interrupted. This discharge clearance 82 is closed at the point of an orifice 34 and, therefore, the closed orifice 34 is not held packed with the coating material which cures on the outer side of the nozzle 18.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention This invention relates to an air atomizing paint spray gun, and more particularly, to an air atomizing paint spray gun that minimizes clogging by cured paint and requires less atomizing air than many conventional nozzles. An improved nozzle configuration for an air atomized paint spray gun.

BACKGROUND OF THE INVENTION A typical conventional paint spray gun has a gun body that supports a nozzle assembly. The nozzle assembly has a fluid outlet defining a paint discharge orifice and an air cap defining various compressed air discharge orifices for atomizing the paint and forming a pattern of the sprayed paint. A valve needle within the body cooperates with the nozzle assembly to define a normally closed paint flow control valve. A spring pushes the tip of the valve needle forward in the direction of paint flow against the valve seat and closes the valve. A manual trigger or actuation mechanism, such as a pneumatic piston, moves the needle from the valve seat to open the valve. Due to the different physical properties of the different paints applied with each spray gun, the various fluid outlets must be equipped with orifices of different sizes to accommodate the different paints.

In conventional spray guns, the paint discharge orifice is located downstream of the paint flow control valve.

In the spray gun shown in U.S. Pat. No. 3,746,253, the paint discharge orifice has a relatively large diameter. The end of the valve needle has a conical shape that engages a conical valve seat at the fluid outlet. The axial position of the valve needle can be adjusted to control the paint delivery flow rate for different paints, thus reducing the need for different sized fluid ports. However, in this spray gun and any other spray gun where the valve is upstream of the discharge orifice, paint remains in the discharge orifice when the paint valve is closed. This results in residual paint drying in the orifice and clogging the nozzle.

Also, problems with some conventional spray guns arise because the valve needle is offset from the center of the nozzle. When the valve needle is moved to the open position for spraying, the off-centered valve needle causes uneven flow through the nozzle orifice, causing paint to exit the gun nozzle in an undesirable lateral direction. It will be done.

It is an object of the present invention to provide an air atomization spray gun that is less susceptible to nozzle clogging by dried residues of paint or other coating liquids.

[Means to solve the problem]

The present invention is directed to a spray gun for atomizing liquids such as paint by means of compressed air, which minimizes clogging of the gun nozzle and provides uniform centrifugal delivery of paint.
red disCharge) is achieved.

To this end, the spray gun has a gun body with a valve needle, which has a closing cone arranged opposite the valve seat at the free outer end of the nozzle. The nozzle is opened and closed at its free outer end by movement of the closing cone. The valve needle can be moved axially within the body of the spray gun by a piston, preferably adapted to be actuated by compressed air. The valve needle is
It is moved by the piston in the direction of the paint flow, thereby forming an annular discharge gap between the closing cone and the valve seat. The spray gun has a bearing part by means of which the valve needle can be moved axially relative to the nozzle, particularly in a centered position adjacent to the valve seat. the result,
The paint is delivered from the spray gun in a uniform, concentrated spray. The dispensed paint is in the shape of an annular cone that flares outward in the dispense direction. To atomize the paint, compressed air is directed at the dispensed paint in an inwardly directed, conical, annular passage.

Alternatively, the patterning air can be placed in an envelope of spray paint to form an elliptical spray pattern.
). The stroke of the piston and thus the discharge orifice between the closing cone and the nozzle is infinitely adjustable by means of an axially adjustable stop ring on the spray gun body which limits the movement of the piston. As a result, the spray discharge orifice can be adjusted outwardly in the direction of the dispensed paint.

〔Example〕

Referring to the drawings, the body I2 to which the cylinder 14 is screwed is shown.
A spray gun 10 is shown having a. cylinder 1
4 constitutes port 16, and this port 1-16 is
Control source (not shown) of compressed air (indicated by arrow pointing from left to right) for triggering spray gun 1o
is connected to. Furthermore, the spray gun 1o has a nozzle 18 fixed to the body 12. A central bore extends through the nozzle 18 and the body 12, and a valve needle 20 is axially movably disposed in the central bore. Valve needle 20 and nozzle 18 cooperate with each other to create a uniform, controlled paint delivery pattern and to minimize nozzle clogging, as will be discussed in more detail below.

A piston 22 is provided in the cylinder 14 so as to slide in the axial direction. The cylinder 14 is fixed to the gun body 12 by a threaded portion 15. Piston 22 is moved by compressed air supplied to port 16 from an external source (not shown). An annular seal 24 is positioned between the radial collar 26 of the piston 22 and a retaining ring 27 that engages an annular groove 29 in the piston 22.

Collar 26 and retaining ring 27 establish a sliding seal between piston 22 and inner wall 28 of cylinder 14, securing seal 24 therebetween. As a result, seal 24 allows compressed air being supplied to port 16 to act exclusively on piston 22 and not on any other components of spray gun 10. A retaining ring 30 is fixed to the annular groove 32 of the cylinder 14 . This retaining ring 30 retains the piston 22 within the cylinder 14 and limits axial movement of the piston 22 toward a paint discharge orifice 34 at the front of the spray gun 10.

Piston 22 has an inner end surface 36 that engages outer edge 38 of flange 40 . The flange 40 is provided with a centrally located threaded portion 42 to which a bushing 44 is secured. The bushing 44 has a coaxially mounted neck or collar 46, and the valve needle 20 is attached to the neck or collar 46.
extends through. Collar 46 has an end surface 48 that engages shoulder 50 of valve needle 2o. Flange 4
0 has a centrally located axial bore 52 formed therethrough. Valve needle 20 extends through this bore 52 and has a protruding threaded free end 54 . Attach nut 5 to this threaded end 54 of the valve needle.
6 is engaged. A nut 56 tightens the flange 40 and bushing 44 together against the shoulder 50 of the valve needle so that the flange 40 and bushing 44 move axially with the valve needle 20.

An annular disc 58 is connected to the gun body 12 by suitable means, for example at least two screws 6o. A plurality of flat springs 62 are attached between the flange 40 and the disk 58. These springs 6
2 constantly urges the flange 40 to the left in the drawing when air pressure is not supplied to the port 16. The flange 40 transmits this force to the piston 22 and
to the left so that the outer surface 64 of piston 22 is aligned with port 1.
Close 6. Between the disc 58 and the gun body 12,
An O-ring seal 66 and a diaphragm 68 are sandwiched. A retaining ring 69 is engaged with the bushing 44 . This retaining ring 69 abuts against the annular disc 58 when the valve needle 20 is moved, causing the gun body 12 to
The axial end positions of the bushing 44 and the diaphragm 68 relative to each other are limited.

The nozzle 18 is provided with a bearing part 70 which constitutes a sliding bearing for the valve needle 20. This bearing portion 70 allows the needle 20 to reciprocate axially through the center of the nozzle 18. Further, the body 12 includes at least one
Two axial passages 72 are formed therethrough that allow paint 74 or other liquid to be sprayed to flow toward the paint discharge orifice 34 . Bearing portion 70 is adjacent to a valve seat 76 formed in nozzle 18 near a reduced diameter portion 78 of valve needle 20 . This causes the reduced diameter portion 78 of the valve needle 20 to be movably mounted in a centered position within the nozzle 18 proximate the paint discharge orifice 34.

Accordingly, a relatively precisely centered mounting of the valve needle 20 is achieved.

The right free end of the valve needle 20 is provided with a cone 80 , which is arranged to engage the valve seat 76 and close the orifice 34 . According to the invention, the closing cone 80 is arranged outside the valve seat 76 of the nozzle 18 . The valve seat 76 has a conical shape 80
It has a conical shape complementary to that of the paint 74, and flares outward in the direction in which the paint 74 is discharged. When the spray gun 10 is turned on, the closure cone 80 is moved away from the valve seat 76 to create an annular conical gap 82 that delivers paint to the discharge orifice 34 .

To atomize the paint 74, atomizing air is directed through the tapered annular conical passage 84 and onto the paint 74 as the paint exits the orifice 34 along a diverging conical passage. Passage 84 connects air cap 86 and fluid nozzle 18
is formed between. Air cap on gun body 12
In order to fix the nut 90 to the spray gun body 1,
It is screwed onto the front end of 2. Furthermore, the air cap 86
define a passageway leading to patterning air orifice 92 . Air 94 for pattern formation is passed through orifice 9
2 to give the desired shape to the envelope of spray paint discharged from gun orifice 34. For example, when patterning air 94 is not ejected from orifice 92, a rounded envelope results, and when forming air 94 is ejected from orifice 92, an elliptical shape can be imparted to the spray paint envelope.

Spray gun 10 is also provided with an annular passageway 96 formed between gun body 12, nozzle 18, and valve needle 20. This passageway 96 is adapted to receive paint 74 to be sprayed through an inlet port 98 . The annular passage 96 supplies paint 74 to the axial passage 72, which delivers the paint 74 to the annular passage 1 (10).

This passage 1 (10) is formed between the nozzle 18 and the reduced diameter portion 78 of the valve needle 2o. Spray gun 10
When turned on, the paint 74 flows from the annular passage 1 (10) through the gap 82 to the orifice 34 where it is discharged and
Sprayed.

In operation, compressed air is supplied to the outer surface 64 of the piston 22 through the port 16 from an external source (not shown). This air exerts a force sufficient to move piston 22 axially to the right, thereby also moving flange 40, bushing 44, and valve needle 20 a corresponding distance to the right. Movement to the right continues until the radial collar 26 of the piston 22 engages the retaining ring 30. At this point, further movement to the right is prevented. The movement of the flange 40 to the right compresses the counter spring 62.

The needle 20 is moved by the flange 40 and the bushing 44, which are fixed to the flange 40 and the bushing 44 by a nut 56 and a shoulder 50.
4 also results in a corresponding movement of the valve needle 20. Movement of the valve needle 20 to the right opens the spray gun by moving the closing cone 80 away from the valve seat 76 and creating an annular gap 82 . External source (not shown)
The paint delivered from the annular passageway 96 to the artificial port 98
, axial passage 72, annular passage 1 (10 and gap 82
through which it flows to a discharge orifice 34 where it is discharged and atomized. The amount of paint dispensed from the spray gun 10 is determined in part by the gap 82 defined by the open position of the closure cone 80.
and the size of the orifice 34. Gap 82
And the orifice 34 can be enlarged by screwing the cylinder 14 further into the gun body 12 and moving the retaining ring 30 further forward or to the right in the drawing. Alternatively, gap 82 and orifice 34
can be made smaller by rotating the cylinder 14 and moving the retaining ring 30 further to the left in the drawing. Thus, the gap and orifice 34 can be infinitely adjusted to accommodate paints with different characteristics delivered to the spray gun 10 at different pressures.

When trying to stop painting, the compressed air is no longer blown)
16 is not supplied. Salad spring 62 then moves flange 40 and adjacent piston 22 to the left in the drawing. The movement of the flange 4o moves the attached valve needle 20 to the left. As a result, the closing cone 80 of the valve needle 2o moves and engages the valve seat 76,
This closes the gap 82 and interrupts the paint discharge. Since the discharge gap 82 is closed at the orifice 34, the closed orifice 34 does not remain filled with paint that hardens outside the nozzle 18.

In conventional spray guns, paint may harden at the discharge orifice after the gun is turned off. Since the paint remaining in the spray gun 10 is inside the discharge orifice 34 where it is not exposed to drying air, the adverse effects of cured paint in the discharge orifice 34 are minimized.

Positioning the closure cone 80 outside the valve seat 76 not only minimizes clogging of the orifice 34, but also has other advantages. As the spray gun 10 opens outward, the direction of paint flow assists the closing cone 80 away from the valve seat 76. Furthermore, according to the invention, a bearing portion 70 formed in the nozzle 18 advantageously centers and guides the valve needle 20 within the nozzle 18. As a result, the concentrated discharge of paint from the nozzle 18 becomes uniform, thereby promoting more uniform spraying of the paint. Furthermore, the atomization of the paint is optimized due to the tunability of the conical discharge pattern of the paint. This allows for increased paint atomization with a minimum amount of mist under relatively low air pressure and with a relatively small amount of air. Therefore, air can be used to spray paints with high surface tension, such as water-based lacquers, more advantageously and economically.

Having thus described a preferred embodiment of the invention, it is contemplated that spray gun 10 may be used without departing from the spirit and scope of the claims.
It will be appreciated that various changes and modifications may be made to the. For example, although the valve needle is shown as being opened by a pneumatic cylinder, it will be appreciated that other known trigger structures may be used to move the valve needle.

[Brief explanation of drawings]

The drawing is an enlarged cross-sectional view of a spray gun according to the invention in an open position for dispensing and spraying paint. 10... Spray gun 12... Body I4... Cylinder 16... Port 18... Nozzle 20... Valve needle 22... Piston 24...
Annular seal 30...Retaining ring 32...
...Annular groove 34 ...Paint discharge orifice 40 ...Flange 44 ...Bushing 56 ...Nut 62 ...Flat spring 68 ...Diaphragm 69 ...Retaining ring 70 ...Bearing part 74 ...Paint 82 ...Gap 8
4... Passage 86... Air cap 88... Atomizing air 92... Pattern forming air orifice 94...
... Pattern-forming air 1 (10... Annular passage

Claims (12)

[Claims] (1) a housing and a nozzle secured to the housing, the nozzle having a forwardly facing conical valve seat and a free outer end defining a passageway opening aligned with the conical valve seat; a valve needle is positioned in the passageway, the valve needle having an end forming a closing cone disposed opposite the valve seat; a first closed position in which the valve seals against the valve seat, and the valve seat in the direction of the flow of paint discharged from an annular conical gap formed between the valve seat and the displaced closing cone; An air atomized paint spray gun comprising means for axially moving the closing cone between a second open position in which the closing cone is displaced from the valve seat. (2) Claim (1) characterized in that the valve needle and the closing cone are coaxial with the axis of the valve seat.
) spray gun. (3) The apparatus according to claim (2), further comprising an adjusting means for adjusting the axial position of the second position, and the discharge gap is adjustable in the direction of paint flow. spray gun. (4) The adjusting means comprises a pneumatic spray gun mounted on a cylinder and means for adjustably fixing the cylinder to an end of the housing, the piston being mounted on one side thereof. Claim 1, characterized in that said valve needle is moved in response to the application of compressed air of
The spray gun described in 3). (5) The spray gun according to claim 4, wherein the cylinder is screwed onto the housing so as to be adjustable in the axial direction of the valve needle. (6) further comprising a stop ring fixed to the cylinder for limiting movement of the piston in the direction of the second position of the valve needle. Spray gun as described. (7) The discharge gap is an outwardly flared annular conical gap and further directs atomizing air through the inwardly directed annular conical gap onto the paint discharged from the discharge gap. Spray gun according to claim 1, characterized in that it is provided with means for. (8) a gun body and a nozzle fixed to the body, the nozzle having a forwardly facing conical valve seat and a center extending through the nozzle and opening coaxially with the conical valve seat; and a free outer end defining a passage, said passage forming a support for axially movably receiving and centering a valve needle, said valve needle being in said valve seat. the ends defining oppositely disposed closing cones, and a first closed position in which the closing cones seal against the valve seat; a second opening position in which the closing cone is displaced from the valve seat in the direction of the flow of paint discharged from an annular conical gap formed between the closing cone and the closing cone; An air atomized paint sprayer, characterized in that it comprises means for axially displacing the cone, thereby minimizing clogging of the nozzle by dry paint when returning the valve needle to said first closed position. gun. (9) The spray gun according to claim (8), further comprising means for adjusting the second open position. (10) a cylinder attached to the gun body;
a piston reciprocally disposed within the cylinder; means for moving the valve needle in response to movement of the piston; and means for moving the valve needle to the second position. further comprising means for supplying compressed air to one side and means for returning said valve needle and said piston to said first position when compressed air is removed from said side of the piston. Spray gun according to claim 9, characterized in that: 11. The spray gun of claim 10, wherein the cylinder is threaded onto the gun body for adjusting the second position of the valve needle. (12) The discharge gap is an outwardly flared annular conical gap and further directs atomizing air through the inwardly directed annular conical gap onto the paint discharged from the discharge gap. Spray gun according to claim 8, characterized in that it is provided with means for.