Solenoid Valve Assembly

Abstract

A high pressure solenoid valve and spraying head unit including a housing defining a fluid chamber therein with an inlet thereto and an outlet therefrom. An armature is slidably received in the chamber for movement toward and away from the outlet and is spring urged toward the outlet. A pilot adapted to close the outlet is carried by the armature but is freely movable with respect thereto for a prescribed distance. A magnetic coil is provided about the housing to selectively urge the armature and pilot away from the outlet to allow fluid to pass from the chamber.

Description

BACKGROUND OF THE INVENTION

While there are numerous solenoid valves on the market today, air-less paint spraying operations frequently require the high pressure type solenoid valve. Such presently available valves generally operate on the impact principle with a movable magnetically operated armature. The armature movably carries a pilot which actually closes an orifice to stop the flow of fluid and which is spring urged toward its closed position. When the pilot closes the orifice, there is sufficient clearance between the pilot and the abutment on the armature to allow the armature to accelerate before contacting the pilot to lift it from the orifice.

In order for this type valve to operate, it must be oriented so that gravity causes the clearance between the abutment and the pilot in order to achieve operation on the impact principle. Moreover, because the valve must be separate from the spraying head and because these valves do not open at sufficient speed, dripping of large droplets of paint are encountered. Also, since these valves use a non-metallic valve seat for the pilot, a high wear rate is encountered along with the resulting leakage caused thereby.

SUMMARY OF THE INVENTION

These and other problems and disadvantages associated with the prior art are overcome by the invention disclosed herein by providing a combination solenoid valve and spraying head which will operate regardless or orientation in a virtually drip-free manner. Moreover, the invention is lightweight, inexpensive to manufacture, and easy to maintain.

The apparatus of the invention includes a housing which defines a fluid chamber therein. An outlet orifice from the chamber is provided which serves as the spray nozzle and an inlet orifice is provided to introduce fluid into the chamber. An armature is positioned in the chamber and movable therein toward and away from the outlet orifice with a spring urging the armature toward the orifice.

A pilot is carried in that end of the armature facing the outlet orifice and is adapted to fit within a seat at the orifice to close same. The pilot is freely movable within the armature for a prescribed distance along a path aligned with the orifice so as to achieve an operation on the impact principle.

A magnetic coil is provided about the housing for urging the armature away from the orifice and withdrawing the pilot therewith to allow fluid to be sprayed from the orifice. Since both the pilot seat and pilot are metal, very little wear is encountered.

These and other features and advantages of the invention disclosed herein will become more apparent upon consideration of the following specification and accompanying drawings wherein like characters of reference designate corresponding parts throughout the several views and in which:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective exploded view of the invention;

FIG. 2 is a longitudinal cross-sectional view of FIG. 1 showing the valve closed;

FIG. 3 is a view similar to FIG. 2 showing the valve open and the armature rotated 90.degree. about its axis; and,

FIG. 4 is an enlarged view of the outlet orifice and pilot.

These figures and the following detailed description discloses specific embodiments of the invention, however, it is understood that the inventive concept is not limited thereto since it may be embodied in other forms.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

Referring to the drawings, it will be seen that the combination valve and spraying head unit 10 includes a housing 11, a movable valve assembly 12, and a magnetic coil 14. The unit 10 is illustrated as a high pressure airless paint sprayer, however, it is to be understood that the valve mechanism may be used in other applications.

The housing 11 is made up of a spraying head 15 and tube body 16 as best seen in FIGS. 2 and 3. The spraying head and tube body threadedly engage each other at 18 to form a common cylindrical fluid chamber 19 in housing 11 about the common centerline CL. An O-ring 20 is positioned between spraying head 15 and tube body 16 to seal same.

The fluid chamber 19 includes a reduced diameter portion 21 with a shoulder 22 at the junction of the major portion of the chamber 19 and reduced diameter portion 21. The shoulder 22 is used to arrest movement of the valve assembly 12 as it moves into the reduced diameter portion 21 as will be explained.

Spraying head 15 defines an outlet passage 24 which extends from chamber 19 out through head 15 along the centerline CL. The passage 24 has a first portion 25 adjacent the chamber 19 and a reduced diameter orifice portion 26 at the exit end of passage 24. A tapered portion 28 joins the first and reduced diameter portions and serves as a valve seat for the valve assembly as will be explained.

Tube body 16 defines a reduced diameter inlet passage 29 in that end most remote from head 15 which communicates with fluid chamber 19 and lies along centerline CL. An abutment 30 is formed by tube body 16 at the juncture of passage 29 and chamber 19 to support a spring of the valve assembly 12 as will be explained. The outside of the tube body 16 is threaded at 31 for use in securing the magnetic coil 14.

The valve assembly 12 includes an armature 40 as best seen in FIGS. 2 and 3 which is slidably carried in chamber 19 for free movement toward and away from the outlet passage 24. Armature 40 has a main body 41 with a reduced diameter projection 42 at that end facing the outlet passage 24. Main body 41 has a diameter larger than the diameter of portion 21 but small enough for free movement within the chamber 19, while the projection 42 has a diameter small enough to be received within the reduced diameter portion 21 of chamber 19. The movement of armature 40 toward outlet passage 24 is arrested when the arresting shoulder 44 between the main body 41 and projection 41 strikes the shoulder 22 in chamber 19.

A coil spring 45 is positioned between that end of armature 40 facing the inlet passage 29 and the abutment 30 which constantly urges armature 40 toward outlet passage 24 and arresting shoulder 44 into engagement with the shoulder 22. The spring constant of spring 45 is such that the magnetic coil 14, when energized, will overcome the force of spring 45 and force armature 40 away from outlet passage 24 toward inlet passage 29.

The armature 40 is made of a magnetic material and defines a plurality of circumferentially spaced, longitudinally extending grooves 46 in the main body portion to facilitate the passage of fluid in chamber 19 from the inlet passage 29 to outlet passage 24. A diametrically extending cross-passage 48 is formed through armature 40 at the juncture of the main body 41 and projection 42. A guide opening 49 smaller in diameter than the cross-passage 48 is defined through the projection 42 along the centerline CL of armature 40. Opening 49 opens into cross-passage 48 at one end thereof and onto that end of the projection 42 facing passage 24 at its other end. A retaining flange 50 extends inwardly about the opening 49 at that end facing passage 24.

A pilot 51 is carried within opening 49 and extends therefrom to selectively engage the spraying head 15 about outlet passage 24 to selectively stop the flow of fluid from chamber 19. Pilot 51 includes an elongate cylindrical body 52 having a diameter freely movable in opening 49 by flange 50. That end of body 52 extending into opening 49 is integral with a head 54 having a diameter just sufficient to be received in the opening 49 yet be retained therein by flange 50. The other end of body 52 is tapered to form a conical valve seat 28 of passage 24 and stop the flow of fluid from chamber 19.

As best seen in FIG. 2 there is a clearance between the underside of head 54 of pilot 51 and flange 50 of armature 40 when pilot 51 is engaging seat 28 of passage 24 and shoulder 44 of armature 40 is engaging shoulder 22 in chamber 19. This clearance is necessary so that armature 40 may be accelerated before flange 50 engages head 54 to achieve an operation on the impact principle as is common with high pressure solenoid valves. It will also be noted that the side of the cross-passage 48 opposite opening 49 serves to limit the movement of the pilot 51 into the armature 40 as will be explained.

Referring particularly to FIG. 4, it will be seen that the valve surface 55 defines a first angle .alpha. with respect to centerline CL and the valve seat 28 forms a second angle .beta. with respect to the centerline CL. In order to obtain the proper sealing of passage 24, it is preferrable that both angles .alpha. and .beta. be small and that angle .alpha. be approximately one-half that of angle .beta.. While several different angles may be used, it has been found that an angle .alpha. of approximately 10.degree. and an angle .beta. of approximately 20.degree. is satisfactory. It will also be noted that the tip 56 of pilot 51 is smoothly rounded to facilitate the seating of pilot 51.

Referring now to FIGS. 2 and 3, the magnetic coil 14 is placed around tube body 16 with a housing 60 thereover. The housing 60 and coil 14 are held in place by a nut 61 engaging the threads 31 on body 16. Wrenching surfaces 62 may be provided on the threaded portion of tube body 16 to assist in tightening nut 61.

The spraying head 15 may be equipped with a standard nozzle assembly N to control the spray pattern from the unit 10.

OPERATION

In operation, the unit 10 is connected to a pressurized fluid source F as seen in FIG. 1 so that fluid is supplied to the fluid chamber 19 through inlet passage 29 and the coil 14 is connected to a d-c power source through switch S-1 to selectively energize coil 14.

When coil 14 is de-energized, the fluid pressure and the force of spring 45 causes the armature 40 to be moved to the position shown in FIG. 2 so that pilot 51 moves into passage 24 to block the flow of fluid from chamber 19.

When switch S-1 is closed to energize coil 14, the magnetic force exerted on armature 40 causes it to move to the position shown in FIG. 3. As the electromagnetic forces overcome the force of spring 45, the armature 40 will be accelerated to the left as seen in FIGS. 2 and 3 for a short distance while the pilot 51 continues stationary to block the flow of fluid through outlet passage 24. This acceleration creates sufficient momentum in armature 40 to retract pilot 51 from seat 28 even though the coil 14 would be unable to do so if the armature was not allowed to accelerate. By leaving pilot 51 free of any forces except those of the fluid, a smaller power requirement than that normally required to operate a high pressure valve can be used.

When switch S-1 is opened to de-energize coil 14, spring 45 causes armature 40 to be accelerated to the right as seen in FIGS. 2 and 3. The inertia of pilot 51 causes it to be accelerated slower until the head 54 thereof strikes the opposite wall of cross-passage 48. The pilot 51 then moves with armature 40 until the arresting shoulder 44 of the armature engages shoulder 22 in chamber 19. This stops the movement of armature 40, however, the momentum of pilot 51 causes it to continue to move toward seat 28 and, in combination with the force of the fluid on pilot 51, causes the surface 55 to engage seat 28 and stop the flow of fluid from chamber 19.

Because the angles .alpha. and .beta. are small, both the pilot 51 and seat 28 can be made of wear resistance metals such as stainless steel. This greatly increases the useful life of these components thus reducing the maintenance cost of the unit 10. Also, the use of wear resistance metals allows the use of the unit 10 with very high pressures.

Also very little lift-off of the pilot 51 is necessary for successful operation of the unit giving it a very high speed operation. While different amounts of lift-off may be used, it has been found that a lift-off distance of approximately 0.020 inch is satisfactory.

The unit 10 is especially suited for high pressure operations where the static pressure is in the 2500-3000p.s.i. range and the operating pressure is about 1500 p.s.i. This unit does not produce any significant dripping either during opening or closing.

While specific embodiments of the invention have been disclosed herein, it is to be understood that full use may be made of modifications, substitutions and equivalents without departing from the scope of the inventive concept.

Claims

I claim:

1. A solenoid spraying unit for connection to a pressurized fluid source and an electric power source to selectively spray fluid therefrom, said unit including:

a housing comprising a spraying head and a tube body connected together and defining a fluid chamber therein, said spraying head defining an outlet passage therethrough communicating with said fluid chamber and lying along the centerline of said chamber for discharging fluid from said chamber, said spraying head further defining an arresting shoulder projecting into said fluid chamber and defining an abutting surface facing away from said outlet passage a prescribed distance from said outlet passage, said spraying head defining a valve seat about said outlet passage, and said housing defining an inlet passage therein communicating with said fluid chamber and connectable to the fluid source for introducing fluid under pressure into said chamber;

an armature slidably carried within said fluid chamber for movement toward and away from said outlet passage, said armature including a main body portion of a first diameter and a projection having a smaller diameter connected to that end of said main body portion facing said outlet passage, said armature further defining an abutting shoulder at the juncture of said main body portion and said projection facing said outlet passage adapted to engage said abutting surface of said arresting shoulder as said armature moves toward said outlet passage to arrest the movement of said armature toward said outlet passage, said projection defining an axially extending cavity therein opening onto that end of said projection facing said outlet passage and defining a retaining lip projecting into said cavity at that end of said cavity facing said outlet passage, said armature further defining a fluid passage connecting that end of said cavity opposite said outlet opening with said fluid chamber defined in said housing and pilot arresting means spaced from said retaining lip a predetermined distance opposite to said outlet passage;

a spring carried within said cavity and engaging said armature for constantly urging said armature toward said outlet passage;

a magnetic coil carried by said tube body for urging said armature away from said outlet passage when said coil is energized;

switch means selectively connecting said magnetic coil to said electric power source to selectively energize said coil; and,

a pilot comprising a head and an elongate valve body extending from said head, said valve body defining a valve on the projecting free end thereof adapted to engage said valve seat to selectively close said outlet passage, said head of a size freely movable within said cavity but retained by said retaining lip and said arresting means, said valve body of a size freely movable by said retaining lip so that said valve body projects from said projection toward said outlet passage,

said prescribed distance between said outlet passage and said arresting shoulder, said predetermined distance between said arresting means and said retaining lip, and the length of said valve body being such that as said armature moves toward said outlet passage under the influence of said spring, said arresting means engages said head of said pilot and moves said pilot therewith so that said arresting shoulder engages said abutting shoulder to arrest movement of said armature before said valve is seated on said valve seat and said valve is in the vicinity of said valve seat to cause the fluid issuing from said outlet passage to force said valve against said valve seat in combination with the force of the fluid on said head of said pilot through said fluid passage in said armature to close said outlet passage, said length of said valve body further being such that said head of said pilot is spaced away from said retaining lip in a direction away from said outlet passage when valve engages said valve seat to close said outlet passage.

2. A solenoid spraying unit as set forth in claim 1 wherein said valve seat defines a first angle with respect to the centerline of said passage, and wherein said valve of said valve body defines a tapered surface which defines a second angle with respect to the centerline of said valve body and the centerline of said outlet passage which is less than said first angle.

3. A solenoid spraying unit as set forth in claim 2 wherein said first and second angles are both acute and said first angle is approximately twice as great as said second angle.

4. A solenoid spraying unit as set forth in claim 3 wherein said first angle is approximately 20.degree. and said second angle is approximately 10.degree..

5. A solenoid spraying unit as set forth in claim 4 wherein said spraying head and said pilot are made of stainless steel.

6. A solenoid spraying unit as set forth in claim 1 wherein said spraying head further includes a nozzle assembly operatively associated with said outlet passage.