Spray Gun

Abstract

A spray gun includes a unitary housing having a nozzle assembly mounted at the front and a vernier adjustment assembly mounted at the rear for controlling the liquid flow from the nozzle.

Description

The present invention generally relates to pneumatically operated spray guns and it relates more particularly to a new and improved spray gun construction including a vernier adjustment for the spray nozzle which enables precise control of the density of the spray from the gun.

BACKGROUND OF THE INVENTION

Spray guns have been used in the past for emitting a predetermined pattern of an atomized liquid such, for example, as paint. Attempts to incorporate means for adjusting the amount of liquid in the spray have not enabled precise control nor have such guns enabled a very fine, low volume, controllable spray. There is, however, a need for a precision spray gun which emits a low velocity, low volume spray pattern which is adjustable with a high degree of precision thereby to accurately control the rate at which liquid is sprayed from the gun. Such a spray gun would find many applications where spray guns have not previously been used. Moreover, the prior art spray guns have been complex in construction thereby being inherently expensive to manufacture and making it difficult to make precision nozzle assemblies on a quantity production basis.

OBJECTS OF THE INVENTION

Therefore, a principal object of the present invention is to provide a new and improved spray gun having a precisely controllable spray pattern.

Another object of this invention is to provide a new and improved spray gun having vernier control means incorporated therein for adjusting the liquid flow rate from the gun.

A further object of this invention is to provide a novel spray nozzle assembly for a spray gun.

SUMMARY OF THE INVENTION

Briefly, the above and further objects may be realized in accordance with the present invention by providing a unitary spray gun housing having a nozzle assembly affixed to the front end and a vernier spray adjustment assembly including a clutch mounted to the rear end of the gun housing in alignment with the nozzle. The conical end portion of the needle valve is axially movable in a frusto-conical valve port in the nozzle assembly by a pneumatically operated piston, the extent of such movement being controlled by the said vernier adjustment assembly.

BRIEF DESCRIPTION OF THE DRAWINGS

Further objects and advantages and a better understanding of the invention may be had from the following detailed description taken in connection with the accompanying drawings, wherein:

FIG 1 is a side view of a spray gun embodying the present invention;

FIG 2 is a rear end view of the gun of FIG. 1;

FIG. 3 is a front end view of the gun of FIG. 1; and

FIG. 4 is an enlarged, longitudinally sectioned view of the gun of FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to the drawings, a spray gun 10 includes a unitary, one-piece body or main housing member 11 to the front end of which is mounted a nozzle assembly 12 and to the rear end of which is mounted a vernier adjustment assembly 13 for precisely controlling the amount of liquid in the spray emitted from the gun. A liquid inlet connector 14 is threaded into a liquid inlet port 15 at the top of the body member 11 and an air inlet connector 16 is threaded into an air inlet port 17 at the bottom of the body member. A hexagonal surface made up of a plurality of flats 18 is provided at the approximate center of the body 11 to facilitate assembly and mounting of the gun 10.

A central bore 20 is provided in the body member 11 and a drilled hole 21 carries liquid from the inlet port 15 to the bore 20. A liquid feed valve tip 22 is threadedly received in a counterbore at the forward end of the bore 20 and has a frustoconical valve seat 23 receiving the conical tip 24 of a needle valve element 25. A nozzle head 26 is removably secured to the front end of the housing member 11 by means of a collar 27 which fits over an external annular flange 28 at the rear end of the head 26 and is threaded over the front end of the housing member 11. A central hole 30 in the head 26 is of frustoconical configuration and surrounds the tubular tip portion 31 of the valve tip 22 in spaced apart relationship therewith to define an annular air orifice surrounding the tip portion 31. A pair of longitudinal, blind holes 32 and 33 are drilled into the head 26 at diametrically opposite locations and two pairs of parrallel air orifices 34 and 35 respectively extend from the holes 32 and 33 to the front end of the nozzle head to determine the pattern of the spray. The head 26 provides a generally ellipitical spry pattern, and the head 26 may be adjustably rotated for angular orientation of the pattern.

The head 26 is generally cup-shaped to define therein a pressure equalization chamber 30 to which pressurized air is supplied from the inlet port through a passageway 37 drilled from the front end of the body 11 into communication with the port 17. A set screw 38 extends through a threaded bore in the body into the passageway 37 for reducing the air pressure to the nozzle. A nut 39 holds the valve screw 38 in the adjusted position. Air thus flows from the chamber 36 to the central annular orifice and to the orifice pairs 34 and 35. With the needle valve element 25 retracted into an open position as shown in FIG. 4, liquid is educted through the needle valve assembly, atomized and mixed with air and directed forwardly of the gun in a pattern determined by the size and location of the air orifices. The extent to which the needle valve element 25 is retracted determines the flow rate of liquid from the nozzle and thus the density of the liquid in the spray.

In order to prevent the liquid entering the gun from flowing rearwardly along the needle valve element 25, a plurality of interfitting, plastic bushings 40, 41, 42 and 43 are sealably disposed in a portion 44 of the bore 20 and slidably and sealably receive the needle 25. The bushings 40-43 are held in intimate, mutual relationship by a coil spring 45 compressed between the rearwardmost bushing 43 and an internal nut 46 threaded into the rearward end of the bore portion 44.

The rear end off the body 11 is provided with a relatively large, cylindrical counterbore 47, and a piston 48 fixedly mounted on the needle 25 is slidably positioned therein. An air passageway 50 is drilled from the bottom wall of the counterbore 47 to the air inlet port 17 so that when air pressure is supplied to the inlet connector 16 the needle valve is pneumatically urged in a rearward valve opening direction. A coil spring 52 is held between the rear end of the piston 48 and the inner end wall 53 of a cap member 54 threaded onto the rear end of the body member 11. The length of the coil spring 52 is such that when the air supply to the inlet port 17 is interrupted, the spring urges the conical valve portion 24 into sealing engagement with the valve seat 23 to prevent liquid leakage from the nozzle.

In order to adjustably control the rearward movement of the needle valve element 25 when pressurized air is supplied to the gun, a stop member 55 is threaded through a threaded axial bore 56 in the cap member and has a forward end 57 providing a stop against which the rear end of the needle element 25 abuts. The rear end of the stop member 55 extends into a drive sleeve 60 and is fixed thereto by a screw 61. The sleeve 60 is journaled in a vernier housing 62 and a drive disc 63 is secured to the inner end of the sleeve 60. The veriner housing 62 is mounted in an end recess 64 in a back member 65 which is press-fitted onto the cap member 54. A radially extending lug 66 on the vernier housing fits in a slot 67 in the cap back 65 to prevent rotation of the vernier housing relative to the gun body. The slot 67 extends forwardly of the lug 66 to provide an opening through which a screw driver may be inserted to loosen or tighten the screw 61 to remove the vernier housing from the gun and to provide a port through which air may flow to and from the back side of the piston 48 through aligned holes 68 in the members 54 and 65.

The vernier mechanism is partially carried by the disc 63 and comprises three pairs of drive wheels 70 freely rotatable on respective shafts 71 equally spaced on and fixed to the disc 63. The wheels in each pair of spring wheels are biased together and the wheel pairs 70 drivingly engage opposite sides of a flat ring 72 fixed to the housing 62. The wheel pairs 70 also drivingly engage a central drive wheel 73 fixed on a manually rotatable shaft 74. A knob 75 is attached to the shaft 74 to rotate the drive wheel 73 thereby to rotate the wheel pairs 70 causing them to roll around the ring 72 and thus rotate the disc 63 The wheel pairs 70 and the ring 72 and wheel 73 provide friction clutches which prevent the needle 25 from being forced into the valve tip 22 with consequent damage thereto by rotation of the knob 75. Mounted over the vernier mechanism is a cover plate 76. The plate is provided with equally spaced graduations 77, and a reference mark 78 is provided on a portion of the ring 72 extending into the slot 67 further to facilitate setting of the liquid flow rate from the nozzle. The relative radii of the disc 73, the wheel pairs 70 and the ring 72 determines the step-down ratio between the shaft 74 and the sleeve 60. For example, a step-down ratio of eight-to-one in conjunction with a forty thread per inch thread on the stop member 55 provides an axial movement of the stop surface 57 of 0.000031 inch for each graduation on the scale. Precise adjustment of the liquid flow rate through the nozzle can thus be made.

OPERATION

In use, a reservoir container (not shown) for the liquid to be sprayed is mounted on the inlet connector 14 at the top of the gun and open to the atmosphere so that the liquid flows by gravity into the annular area surrounding the needle element 25 between the sealing bushing 40 and the valve tip 26. In the absence of air pressure to the gun, the spring 52 holds the needle valve in a forward closed condition. The air inlet connector 16 is connected through suitable valve means (not shown) to a suitable source of pressurized air so that when such valve means is opened the piston 48 is forced rearwardly until the rear end 58 of the valve needle 25 engages the stop surface 57. Air is emitted from the nozzle through the side orifice pairs 34 and 35, and through the central annular orifice surrounding the tip 31. Liquid is thus educted from the valve tip, atomized and directed in a controlled pattern toward a workpiece. The amount of liquid in the spray is precisely adjustable by means of the knob 75 at the back of the gun which determines the degree of opening of the needle valve. When the air pressure is interrupted the spring 52 returns the piston 48 and the needle 25 to the closed forward position.

While the present invention has been described in connection with a particular embodiment thereof, it will be understood that those skilled in the art may make many changes and modifications without departing from the true spirit and scope thereof. Accordingly, the appended claims are intended to cover all such changes and modifications as fall within the true spirit and scope of the present invention.

Claims

What is claimed is:

1. An automatic spray gun of the type having a body to the front end of which is mounted a spray nozzle assembly including a liquid feed valve member rearwardly movable against a stop surface in response to supply of air pressure to said gun, the improvement comprising

a threaded member on the forward end of which said stop surface is provided, and

a rotary reduction unit drivingly connected to said threaded member and mounted at the back end of said body for rotating said threaded member to precisely control the open position of said valve member.

2. An automatic spray gun according to claim 2 wherein said threaded member is axially mounted in said body.

3. An automatic spray gun according to claim 2 wherein said rotary reduction unit comprises

a rotatable adjusting member extending rearwardly from said gun.

4. An automatic spray gun according to claim 1 wherein said rotary reduction unit comprises

clutch means for limiting the torque which can be applied by said rotary reduction unit to said threaded member.

5. An automatic spray gun according to claim 3 comprising a shaft on which said adjusting member is mounted, a drive wheel on said shaft,

a plurality of driven wheels frictionally engaging said driving wheel to be rotated thereby,

a circular track non-rotatably fixed to said body and surrounding said driven and driving wheels and being frictionally engaged by said driven wheels,

a carrier member to which said driven wheels are journaled, said carrier member being fixedly connected to said threaded member, and

means rotatably mounting said carrier member to said body.

6. An automatic spray gun according to claim 5 wherein

said valve member is a needle,

a piston secured to said needle intermediate the ends thereof,

a cylinder in which said piston is slidably mounted,

spring means mounted rearwardly of said piston for urging said piston and said needle into a forward position, and

an air inlet passageway in said body opening into said cylinder forwardly of said piston,

whereby air pressure in said passageway urges said needle rearwardly toward said stop surface into a valve open position.