FR2517566A1 - Compressed air paint spray pistol - has free space between nozzle and cap into which air jets are discharged to shape spray - Google Patents

Abstract

The paint spray pistol has a nozzle with a cone tip discharging a central paint jet in a flat fan shape, also a head emitting two compressed-air jets slightly upstream from the tip and of flat fan shape enclosing the paint jet in a sandwich pattern. The nozzle (9) is enclosed by a cap (13) to leave a free annular space (19) between them of truncated-cone shape, aimed towards the flat paint jet. The compressed air jets are discharged into this space. The annular space can be sealed off at the rear end, and the cap can be formed by the air head. The amount of taper of the external face of the nozzle can be different from that of the internal face of the cap.

Description

Hydrostatic spray paint spray guns

  have many advantages over

  spray guns for tire spray paint

  matic; on the other hand, they offer the disadvantage of requiring very high pressures for the spray paint which, until recent years, was 100 atmospheres and even more. It is known in fact that if one seeks to lower the paint pressure of a hydrostatic spray paint spray gun, the flat spray of paint emitted through the slot in the nozzle specially provided for this purpose.

  tends to divide into a central part, which remains general-

  fairly well pulverized, and two lateral parts which more or less separate from the central part, which is generally designated by the name of horns, and which are only very

coarsely sprayed.

  To overcome this drawback, it has been proposed in an American patent COWAN 3,843,052 to converge on the central part of such a flat paint spray two air jets

  symmetrical tablet with respect to the flat paint spray -in

  Venteur had thought that these jets of compressed air converging on the central part of the flat spray of paint would tend to flatten it and, consequently, to push back the edges towards the outside and thus prevent it from separating from its side parts; some results could be obtained in this way

  but they were still far from entirely satisfactory.

  In a completely different vein, the Applicant thought that it would no doubt be possible to avoid the formation of these horns, when the pressure of the paint was lowered

  a spray paint spray gun

  static, by enclosing this flat spray of paint in a veil of compressed air intended to maintain its consistency, and it has

  registered a first French patent N O 73/17011, followed by more

  others, to describe and protect his invention.

  She had first considered using for this purpose

  an annular jet of compressed air, coaxial with the flat paint spray

  re; however, this annular spray tended to narrow the width of the flat paint spray, which was not without presenting

  disadvantages She then found that, much simpler-

  much more effectively, the desired result could be obtained by directing, towards a surface of suitable shape of the spray head of the paint spray gun, for example of more or less frustoconical shape, jets of 'compressed air symmetrical with respect to the jet of paint and situated in a plane passing through

  the axis of this flat jet and perpendicular to said jet, or symmetrical

  ques with respect to this plane, which are deflected by said surface of the spray head and transformed into two sails of compressed air which enclose the flat paint spray to form with it a kind of sandwich The paint spray guns to hydrostatic spraying thus arranged gave full satisfaction; the spraying pressure could be lowered to 30 bars, and even less, while ensuring excellent spraying, with

  great flexibility of operation.

  Since then, the Applicant has found, according to the present invention, that the consumption of compressed air of such paint spray guns could be reduced, and

  also further improve the quality of the projection, in -

  surrounding the nozzle with a cap creating between its inner surface

  upper and the outer surface of the nozzle a free annular space, more or less frustoconical, directed towards the flat spray of paint, into which the symmetrical jets of compressed air penetrate; this annular space can be very flat, of the order

2 mm for example.

  This cap can advantageously be arranged to prevent any backflow of the compressed air so that it is entirely directed towards the flat spray of paint; it can in particular be carried out in the air head in which the vents are pierced through which the jets arrive

compressed air.

  The Applicant has in fact found that this cap preventing any reversal of the compressed air ensured that all of it was used for the formation of the compressed air sails without any loss, and that it effectively protected from any contamination of the paint the outlets of the vents emitting jets of compressed air; it also found that, while such an embodiment of a paint spray gun gave very favorable results in the case of hydrostatic spraying of the paint, it could also be used with success in other types of

  paint spray guns, emitting a spray of paint

  designed to be sandwiched between two sails of compressed air

  fan-shaped, originating on the anterior end

  nozzle and forming a sandwich with it; so

  in particular that it is thus possible to produce spray guns.

  partially hydrostatic and partially pneumatic spray paint, and even fully pneumatic paint.

  The present invention therefore relates to a pistol.

  spraying of paint, the projection head of which comprises a nozzle, the front part of which is more or less shaped

  conical, emitting a central spray of paint intended to develop

  lopper into a flat fan-shaped jet and an air head emitting at least two compressed air jets, symmetrical with respect to the central paint spray, deflected by the

  projection to form two sails of compressed air develops

  fan-shaped pant, each from a point on the nozzle slightly upstream of its anterior end, and enclosing

  the flat spray of paint they sandwich, characteristic

  in that the nozzle is surrounded by a cap leaving in-

  be its inner surface and the outer surface of the nozzle a free annular space, more or less frustoconical, directed

  towards the flat spray of paint, into which symmetrically penetrate

  the aforementioned compressed air jets.

  It also relates to a paint spraying process in which a flat fan-shaped paint spray is sandwiched between two sails of compressed air sandwiching it, characterized in that the air jets

  fan-shaped tablets are formed on the anterior part

  of a nozzle of more or less conical shape in a hollow annular space, of frustoconical shape, surrounding this nozzle and

directed at the paint spray.

  The accompanying drawing shows by way of example several embodiments of the invention: FIG. 1 is an elevation view, partly in section,

  of such a paint spray gun.

  Figure 2 is a similar view on a larger scale of the nozzle and the air head of a variant, the carbide part of the spray nozzle being alone in elevation. Figure 3 is a cross-sectional view made

  along line III-III of Figure 2.

  Figure 4 is a view similar to that of Figure 3

showing another variant.

  Figures 5 to 7 are views similar to that of

  Figure 2 showing other variants.

  Figure 8 is a view partly in elevation, partly in

  cross section made along line VIII-VIII of the -

  Figure 7 of the spray head shown in Figure 7.

  Figure 9 is a view similar to that of Figure

  2 of another variant, the entire nozzle being shown

  tee in elevation on the left side of the figure.

  Figure 10 is a cross-sectional view made

  along line X-X in Figure 9.

  Figures 11 and 12 are sectional views along the

other variants.

  The hydrostatic spray paint spray gun shown in Figure 1 is a conventional spray gun with its handle 1, its control trigger-2 which

  actuates an air valve 3 and the paint needle 4.

  The gun is supplied with compressed air by the connector 5 and pressurized paint by the connector 6 The trigger 2 also controls the movements of the needle 4 relative to its seat 7 and makes it possible to obtain the flow rate or the paint flow stop The nozzle 9 covers the nozzle through which the flat paint outlet jet is projected The seal is obtained by a seal 11 The nozzle is in two parts: a body referenced 9 and a part 12 in carbide or any other abrasion resistant material The latter has a specially shaped paint outlet orifice, commonly used for spraying a fan-shaped flat jet by hydrostatic pressure. The air tate 13 covers the nozzle 9; the ring 14, screwed onto the body of the gun, applies the head 13 to the nozzle 9, and its carbide part 12 to the end of the nozzle 10 with interposition of the seal 11 The compressed air arrives in the bedroom

through channel 16.

  The air head 13 is positioned on the nozzle 9 by its

  cylindrical part 17 and it presses on the nozzle by the shoulder-

  ment 18 (FIG. 2) This positioning assembly 17-18 is airtight. A conical annular space 19 is formed between the conical external surface of the nozzle 9 and the internal conical surface of the air head 13 This space

  opens to the outside towards the end of the nozzle.

  In this space, the vents 20 and 21 open out.

  compressed air tees through holes 22 and 23 These vents are located in a plane perpendicular to the spray plane

  and are symmetrical with respect to this plane.

  While a single pair of vents feeds the annular conical space 19 of the gun shown in Figure 1 that

  shown in Figures 2 and 3 has two pairs of parallel vents

  lines 20 a, 20 b and 21 a and 21 b In the variant represented in FIG. 4, the pairs of vents 20 c, 20 d and 21 c, 21 d are concurrent instead of being parallel; they make an angle between them e whose vertex is

on the axis of the paint spray.

  The dimensions a, b, c, d that we see in Figures 2 and 3 can be modified according to the shape of the sails

  of air sought and the air pressure used.

  It is also possible to use for the same purpose nozzles and caps whose inner surfaces of one and outside of the other do not have the same taper 1 this is how Figures 5 and 6 show such surfaces forming an angle between them which is open towards the front in the first and towards the rear in the second; we can thus accentuate the importance of the air jets on the flat-jet

  paint or towards the ends (fringes) of it.

  When using low hydrostatic pressures, for example 10 bars, it may be advantageous to improve the spraying by more effective action of the compressed air In this case, it is possible to use auxiliary air vents directed towards the paint jet leaving the the nozzle, either directly or after deflection on the end of the nozzle. Such a head is shown in FIGS. 7 and 8; the third pair of auxiliary vents 20 e, 2-directed in part on the jet of

  paint improves spraying.

  In all the embodiments of the invention described above with reference to FIGS. 1 to 8, the more or less frustoconical surface of the spray head which deflects the jets of compressed air directed onto it and transforms them into two webs d compressed air which encloses the flat jet of

  paint and sandwich it is made up of the surfa-

  this exterior of the spray nozzle-9; in the embodiments described below with reference to FIGS. 9 to 14, this more or less frustoconical surface consists of

  the inner surface of the cap which surrounds the nozzle

  verification by creating between it and the external surface of the nozzle a free annular space, more or less frustoconical,

directed towards the spray of paint -

  In this case the conduits 22, 23 which communicate the chamber-15 in which the compressed air arrives with the vents, 21 opening into the free annular space 19 instead of being arranged radially are arranged longitudinally; they can be obtained very simply by milling

  practiced in the outer surface of the spray base

  sation, or in the inner surface of the cap.

  Thus, in the embodiment shown in FIGS. 9 and 10, the longitudinal countersinks 22 f, 23 f of the cylindrical surface of the nozzle 9 and the countersinks 20 f, 21 f of its frustoconical surface, having an inclination $ with respect to the latter, the compressed air coming from the chamber towards the free annular space 19 existing between the external surface of the nozzle 9 and the internal surface of the cap

  13; these countersinks have a flat bottom and a width f.

  In this case, it is advantageous to lengthen the annulai-

  re free 19, as shown in FIGS. 11 and 12, its dimension d being notably greater than that of dimension d in FIG. 9; the countersinks 22 ,, 23 g of the nozzle 9 of FIG. 11 concern both the cylindrical part and the conical part of the nozzle 9 by opening directly into the free annular space 19, the positioning of the head 13 on the nozzle 9 is obtained by its cylindrical bore 24 and its bearing on the conical parts 25 of the nozzle which determine the width of the annular space

free 19.

  You can also arrange such a spray head

  tion so that it includes auxiliary vents, such as -

  those 20 e, 21 e in FIG. 7, directing symmetrical compressed air jets directly onto the flat paint spray in order to

improve spraying.

  The embodiment shown in FIG. 12 comprises two longitudinal countersinks 22 h, 23 h, symmetrical in the cylindrical part of the nozzle 9, opening into the countersinks h, 21 h also symmetrical of its conical part, themselves opening into the 'annular space 19 Part of the compressed air arriving in these mills 20 h, 2' 1 h expands in said annular space 19 to form the two air webs

  symmetrical tablet intended to enclose the flat paint spray

  while the remainder of this compressed air is maintained in the front part of these millings and directed by them directly onto the flat spray of paint which they meet and

  which they improve the spraying.

  Longitudinal milling machines can have a bottom

  flat or curved, they can be replaced by flats.

  It is, moreover, understood that the various embodiments of the present invention which have been described above with reference to the appended drawing have been given for information only and are in no way limitative and that numerous modifications can be made without we depart for

  that of the scope of the present invention.

17566 5

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Claims (8)

  1 Paint spray gun, the projection head of which has a nozzle, the front part of which is more or less conical in shape, emitting a central jet of   paint intended to develop into a flat jet in the shape of an   fan and an air head emitting at least two jets of compressed air, symmetrical with respect to the central spray of paint, deflected by the projection head to form two sails of compressed air developing in the shape of a fan, each at from a point on the nozzle slightly upstream from its end   anterior, and enclosing the flat spray of paint they take   sandwich, characterized in that the nozzle (9) is surrounded   ree of a cap (13) leaving between its inner surface and the outer surface of the nozzle a free annular space (19), more or less frustoconical, directed towards the flat spray of paint and into which the air jets symmetrically penetrate aforementioned tablet.   2 paint spray gun according to claim 1, characterized in that this annular space is closed at its rear.   3 Paint spray gun according to one or   the other of claims 1 or 2, characterized in that its   air head is arranged to constitute this cap.   4 Paint spray gun according to one   any one of claims 1 to 3, characterized in that the   taper of the outer surface of the nozzle (9) and the   inner surface of the cap (i 3) are different.   Paint spray gun according to one   any one of claims 1 to 4, characterized in that the   symmetrical compressed air jets emitted by the air head are directed more or less radially towards the outer surface of   the more or less conical nozzle (9) which deflects them.   6 Paint spray gun according to one   any one of claims 1 to 4 characterized in that the   symmetrical compressed air jets emitted by the air head are directed more or less longitudinally towards the free annular space 19 created between the external surface of the nozzle (9) and the   inner surface of the cap (13).   7 Paint spray gun according to one   any one of claims 1 to 6 characterized in that it   has auxiliary compressed air jets 2 D O e, 21 e, symmetrical   triques compared to the flat paint spray and directed at least   partly directly on this flat paint spray.   8 Paint spray gun according to the resale   dication 6 characterized in that the vents (20, 21) making   pass the compressed air from the chamber (15) into the void space   re free (19) provided between the nozzle (9) and the cap are constituted   killed by countersinks in the exterior surface from the nozzle (9).   9 Paint spray gun according to the resale   dication 6 characterized in that the vents (20, 21) making   pass the compressed air from the chamber (15) into the void space   free re (19) provided between the nozzle (9) and the cap are cons-   formed by milling in the interior surface of the cap (13).   Paint spraying method in which a flat fan-shaped paint stream is sandwiched between two compressed air webs sandwiching it, characterized in that the fan-shaped compressed air jets are formed on the anterior part of a nozzle of more or   less conical in a hollow annular space, frusto-shaped   picnic, surrounding this nozzle and directed towards the spray of paint.