Spraying apparatus

Abstract

The needle valve in a spray head is guided by a plurality of bushings spaced apart by a plurality of packing washers for precise alignment with the associated valve seat, and the needle has a conical front end which prevents liquid from collecting thereon.

Description

The present invention relates to apparatus for atomizing and spraying liquid in a controlled predetermined pattern.

BACKGROUND OF THE INVENTION

The use of spraying apparatus for use in marking and in applying glue has presented several problems which have limited the use of such apparatus to special applications. Whether the apparatus is used for applying a liquid dye or liquid glue it is ordinarily important that the spray pattern remain precisely the same for extended periods of time so that the apparatus may operate unattended. Particularly in the case of glue it is extremely important that the glue not collect at the liquid spray orifice since the collected liquid not only alters the spray pattern but in some cases prevents operation of the apparatus after it has been idle for a period in excess of that required for the glue to set, such, for example, as overnight.

We have determined that it is these two problems inherent in the prior art spraying heads, which have deterred the widespread use of spraying apparatus for marking and gluing applications. The present invention as described hereinafter has enabled the application of glue spraying equipment to high speed packaging lines. When so used, the spray head is sequentially operated at high repitition rates over long periods of time and maintains the density of glue in the spray and the pattern itself constant throughout such periods.

SUMMARY OF THE INVENTION

Briefly, the spraying apparatus of the present invention utilizes a reciprocable needle valve having a conical tip adjacent the frusto-conical valve portion, the latter portion sealably engaging a complimentary shaped seat when the needle is in the forward sealing position. When the needle is retracted the glue exits the head through the annular space surrounding the forward end of the needle. The angle of the conical tip at the distal end of the needle is critical if the liquid being sprayed is not to collect thereon. We have found, for example, that if the taper at the tip is the same as that of the frusto-conical valve portion, or if the tip is flat or semispherical, liquid will collect thereon and drastically impair the operation of the unit. Moreover, we have found that the frusto-conical valve portion of the needle and the associated valve seat must be held withiin extremely close tolerances or else irregular patterns and irregular liquid density distributions will result. Nevertheless, simply controlling these tolerances has not solved the problem and we have further found that only by precisely maintaining the needle on the axis of the valve seat with spaced guide bushings will a precise, repetitive spray pattern be provided and will the tip remain free from liquid.

BRIEF DESCRIPTION OF THE DRAWING

Further objects and advantages and a better understanding of the present invention can be had by reference to the following detailed description, wherein:

FIG. 1 is a side view of liquid spray apparatus embodying the present invention;

FIG. 2 is a front view taken from the left side of FIG. 1;

FIG. 3 is a sectional view taken along the line 3--3 of FIG. 1; and

FIG. 4 is a greatly enlarged sectional view of the tip portion of the apparatus of FIG. 1 showing the double tapered tip of the needle valve.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to the drawing and particularly to FIGS. 1 and 2 thereof, there is shown a liquid atomizing and spraying apparatus 10 including a spray head 12, a liquid inlet connector 14, a first fluid inlet connector 16, and a second air inlet connector 18. An electrically operated solenoid control valve 20 is connected between a source of pressurized air or other fluid (not shown), and a manually adjustable needle valve 22 is connected between the same fluid source and the connector 16.

With reference to FIG. 3, the spray and head 12 comprises an integral body member 24 having a longitudinal bore extending therethrough. This bore has a threaded forward portion 26, an intermediate cylindrical portion 28 separated from an enlarged rear portion 30 by a short threaded portion 32. A valve tip 34 is threaded into the forward bore portion 26 and has an intermediate annular flange 36 which abuts the foreward end of the body member 24. The tip member 34 is provided with a longitudinal bore 38 having a frusto-conical foreward portion 40 which forms a valve seat and liquid orifice.

A needle valve 42 is aligned with the longitudinal axis of the seat 40 and has a frusto-conical valve portion 44 near the forward end and an adjacent conical end or tip portion 46. The tapered valve portion 44 is complimentary to the seat 40 and the portions 40 and 44 are held within close dimensional tolerances. A piston 48 is fixedly attached to the rearward portion of the needle 42 and is pneumatically sealed to the bore portion 30 which functions as a cylinder in which the piston reciprocates. The needle 42 is biased into the forward sealing position closing the orifice in the tip by means of a coil spring 50 compressed between the rear end of the piston 48 and a cap 52 threaded onto the rear end of the body member 24. The cap 52 is provided with one or more air relief holes 54 and is provided with an elongated tubular central section 56 which is internally threaded to receive a manually adjustable stop screw 58 whose forward end 60 limits the rearward movement of the needle 42 and thus determines the size of the orifice opening in the tip when the piston is retracted to open the valve. An adjusting knob 62 is fixed to the rear end of the stop screw 58 and a coil spring 64 prevents spurious rotation thereof.

In order to seal the piston chamber from the foreward part of the unit, a plurality of leather packing or sealing washers 66 are fitted over the intermediate portion of the needle 42 and sealably engage both the needle and the bore portion 28. A guide bushing 68 interposed between the washers 66 is formed of a suitable metal such as brass and provides a slip fit to both the needle 42 and to the bore portion 28. A second guide bushing 70 is also formed of a metal such as brass and provides a slip fit to both the needle 42 and the bore portion 28. The bushing 70 includes a rearwardly extending sleeve portion 72. A screw 74 holds the packing washers and the bushings in place and a coil spring 76 compressed between the bushing 70 and the screw 74 holds the packing in compressed sealing relationship against the foreward end of the bore portion 28. As shown, the bushings 68 and 70 are spaced apart by a plurality of the resilient sealing washers 66 and maintain the needle in alignment with the tip member 34 so that when the valve is open the orifice surrounding the forward needle portion is truly annular. The bushing 70 also keeps the spring 76 centered on the axis of the needle and provides a flat annular forward surface for uniformly compressing the packing washers.

An air cap 77 is positioned over the tip member 34 and is held in place against the front end of the body member 24 by a collar 78 threaded over the front end thereon. An air chamber 90 is located in the cap 77 surrounding the tip member 34 and is supplied with air from a port 90. A plurality of orifices 82 in the cap 76 control the shape of the spray pattern in the known manner. Also, an annular orifice 84 surrounds the foreward end or nose of the tip member 34 for educting liquid therefrom when the needle valve is open.

The body member 24 is provided with a port and associated passageway 86 to which the connector 18 is connected for controllably operating the piston 48 to open the needle valve. A port 88 and associated passageway supply liquid from the connector 14 to the foreward side of the packing and thus to the passageway through the tip member 34. The port 90 and associated passageway receive air or other fluid from the connector 16 and couple it to the chamber 80 at the front of the unit.

In use, the liquid to be sprayed is supplied from a gravity head or other pressure source via the connector 14, and air at a pressure of about 50 psi is supplied to the valves 20 and 22. Air thus constantly flows from the orifices 82 and 84 across the nose of the tip member. When the solenoid is to be actuated to open the valve 20, air pressure is supplied to the foreward side of the piston 48 forcing it back against the stop screw 58 to open the liquid orifice at the front a preset amount. Liquid thus exits from the tip and is sprayed in a controlled pattern determined by the angle and location of the orifices 82. The density of the pattern is adjustable by means of the knob 62 and also by the control valve 22. The size of the pattern depends on the distance between the unit and the surface to be sprayed.

A problem which has heretofore remained unsolved in spray equipment is the collection of liquid at the front end of the spray device and particularly on the foreward or distal end of the needle. We have found that by selecting the proper angle of taper of the tip portion 46 this problem is solved even with highly viscous and tenacious liquids such as glue. In FIG. 4, the angle of taper of the valve portion 44 is indicated to be b and the angle of taper of the nose portion 46 is indicated to be .alpha.. The angle b is about 10.degree. to provide a tip and needle assembly having a long life. The angle .alpha. is extremely critical and must be between 47.degree. and 58.degree. to prevent adherence of the liquid thereon. We have found the preferred angle to be about 54.degree.. The included apex angle of the tip must, therefore, be in the range of 94.degree. to 116.degree.. Moreover, the tip portion 46 must be adjacent the front end of the seat 40 as shown in FIG. 4 so that when the needle is in the retracted position the nose portion of the needle is within the tip member.

While the present invention has been described in connection with particular embodiments thereof, it will be understood by those skilled in the art that many changes and modifications may be made without departing from the true spirit and scope of the present invention. Therefore, it is intended by the appended claims to cover all such changes and modifications which come within the true spirit and scope of the invention.

Claims

What is claimed is:

1. Apparatus for atomizing and spraying a liquid, comprising

a body member having a bore therein,

a tubular tip member mounted in one end of said bore and having a forewardly disposed liquid orifice defined by a conical valve seat,

a needle valve having a frusto-conical valve portion reciprocably mounted in said bore for movement of said valve portion into and out of sealing engagement with said valve seat,

spring means mounted in said bore urging said needle valve into sealing engagement with said valve seat,

fluid operated means mounted in said bore for moving said needle out of sealing engagement with said valve seat,

a plurality of sealing gaskets interposed between an intermediate portion of said needle and said bore for preventing fluid from traveling across said intermediate portion of said needle,

a plurality of bushings slidably disposed on said needle and spaced apart by a plurality of said gaskets for guiding said needle for movement along the central longitudinal axis of said valve seat, and

passageway means for supplying said liquid to said bore forwardly of said sealing gaskets.

2. Apparatus according to claim 1 wherein

the distal end portion of said needle adjacent said valve portion is conical and has an included apex angle within the range of 94.degree. and 116.degree.,

said distal end portion being external of and adjacent to said orifice tip when said needle is in the foreward valve sealing position.

3. Apparatus according to claim 2 wherein

said angle is about 108.degree..

4. Apparatus according to claim 2 comprising

a nose piece mounted to said body member over said tip,

said nose piece having a plurality of orifices for directing a fluid in a predetermined pattern across the outer end of said tip to draw liquid therethrough when said needle valve is open, and

passageway means in said body member for supplying said fluid to said nose piece.

5. Apparatus according to claim 4 comprising

control means mounted to said body member for adjusting the rate of flow of said fluid to said nose piece.

6. Apparatus for atomizing and spraying a liquid, comprising

a body,

a tubular spray tip disposed at the front end of said body and having a frusto-conical valve seat,

a needle reciprocably mounted in said body and having a frusto-conical intermediate portion adapted to seat against said valve seat when said needle is in a foreward position,

the distal end of said needle adjacent said frusto-conical intermediate portion being conical and having an apex angle within the range of 94.degree. and 116.degree.,

said distal end extending forewardly of said seat when said needle is in said forward position,

means for directing an annular stream of air across said tip, and

means for supplying said liquid to said seat interiorly of said tip.

7. Apparatus according to claim 6 wherein

said frusto-conical intermediate portion has an angle of taper of about 10.degree..