Fluid level sensing apparatus and method for a spray applicator
The present invention relates to a level sensing spray applicator. In one embodiment, the spray applicator includes a gun that receives a liquid and a supply vessel coupled to the gun. The vessel includes a level sensor responsive to the volume retained by the supply vessel. In another aspect, a level-sensing supply vessel includes a level sensor responsive to a volume of liquid retained by the supply vessel, the sensor including a sensor element to detect the volume by sensing a resistance property of the liquid. In still a further aspect, a method of sensing a level of a liquid retained within a storage vessel includes sensing a first liquid volume, removing a portion of the first volume to define a second volume, determining if the second volume is less than a minimum volume, and generating an alarm signal if the second volume is less than the minimum volume.
The present invention relates generally to equipment for applying a liquid to surfaces, and more particularly, to fluid level sensing for a spray applicator device.
BACKGROUND OF THE INVENTIONA wide variety of spray application devices for applying liquids such as paint, varnish, cleaning solvents, or other liquid materials to a surface are known. Typically, such spray applicator devices include a supply vessel that contains a volume of the liquid to be applied to the surface. The liquid is transferred from the supply vessel to a spray gun that atomizes the liquid and projects the atomized liquid towards the surface. In one example of a spray applicator device, the supply vessel is positioned above the spray gun so that the liquid is transferred to the spray gun by a gravity-feed system. In another example of an applicator device, the supply vessel may be positioned below the spray gun and internally pressurized to transfer the liquid upwardly into the gun. In still other examples, the vessel may be positioned remotely relative to the gun so that the liquid is transferred from the vessel to the spray gun through a flexible hose.
In all of these spray applicator devices, determining the volume of the liquid remaining in the supply vessel as the application of the liquid proceeds constitutes a significant problem. If the liquid volume in the supply vessel is reduced to a low value, the gun may be supplied with liquid only intermittently, so that the gun emits the atomized liquid on an interrupted basis. As a consequence, the spray applicator device fails to apply the liquid uniformly to the surface. In particular, when the spray applicator device is used to apply a paint material to a surface, surface imperfections in the paint finish may result when non-atomized paint is projected, or “sputtered” onto the surface, thus necessitating time consuming surface rework and re-painting. Since supply vessels commonly used with spray guns are comprised of materials that are substantially non-transparent, a visual indication of the liquid level in the supply vessel is not generally possible.
Accordingly, there is a need in the art for a level-sensing device for spray applicators to provide a user of the spray applicator with an audible or visual indication when the volume of liquid in the supply vessel has been reduced to a predetermined level.
SUMMARY OF THE INVENTIONThe present invention relates generally to a spray applicator device for applying a liquid to surfaces, and more particularly, to a fluid level sensing apparatus and method for a spray applicator device. In one aspect, a spray applicator apparatus includes a gun configured to receive a liquid and atomize the liquid, and a supply vessel coupled to the gun. The supply vessel retains a volume of the liquid and includes a level sensor responsive to the volume retained by the supply vessel. In another aspect, a level-sensing supply vessel for a spray applicator includes a level sensor responsive to a volume of liquid retained by the supply vessel, the sensor including a sensor element configured to detect the volume by sensing a resistance property of the liquid. In still a further aspect, a method of sensing a level of a liquid retained within a storage vessel of a spray applicator includes sensing a first volume retained within the vessel, removing a portion of the first volume to define a second volume, determining if the second volume is less than a predetermined minimum volume, and generating an alarm signal if the second volume is less than the predetermined minimum volume.
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention is generally directed to equipment for applying liquid coating materials to surfaces, and in particular, to fluid level sensing for a spray applicator. Many of the specific details of certain embodiments of the invention are set forth in the following description and in
Still referring to
A control system 28 is operatively coupled to the sensor element 20. The control system 28 includes circuitry that is configured to measure electrical resistance quantities sensed by the sensor element 20, and to output a control signal when a predetermined resistance quantity is measured. Referring now to
Turning now to
Returning to
The operation of the spray applicator 10 will now be described in detail. Still referring to
From the foregoing it will be appreciated that, although specific embodiments of the invention have been described herein for purposes of illustration, various modifications may be made without deviating from the spirit and scope of the invention. For example, certain features shown in the context of one embodiment of the invention may be incorporated into other embodiments as well. Accordingly, the invention is not limited by the foregoing description of embodiments except as by the following claims.
Claims
1. A spray applicator, comprising:
- a gun configured to receive a liquid and atomize the liquid; and
- a supply vessel coupled to the gun that supplies the liquid to the gun, the supply vessel defining a volume for receiving liquid and including a level sensor responsive to an amount of liquid within the supply vessel, the level sensor including a first electrode and a second electrode mounted to insulating material positioned at a perimeter of the volume.
2. The spray applicator of claim 1, wherein the level sensor further includes a sensor element that extends into the supply vessel, the sensor element being configured to detect a liquid volume by sensing a resistance property of the liquid.
3. The spray applicator of claim 1, wherein the level sensor further includes a control system coupled to the supply vessel that generates a signal when a predetermined liquid volume is retained in the supply vessel.
4. The spray applicator of claim 3, wherein the level sensor further includes an alarm device coupled to the control system to receive the signal and generate an alarm indication.
5. The spray applicator of claim 2, wherein the sensor element further comprises:
- a first electrode; and
- a second electrode spaced apart from the first electrode.
6. The spray applicator of claim 5, wherein the first electrode and the second electrode are positioned adjacent to a wall of the supply vessel, the first electrode and the second electrode being spaced apart from the wall of the supply vessel by an insulating layer interposed between the wall and the first and second electrodes.
7. The spray applicator of claim 5, wherein the first electrode and the second electrode are formed on opposing sides of an insulating substrate.
8. The spray applicator of claim 5, wherein the supply vessel further includes a wall that comprises one of the first electrode and the second electrode.
9. The spray applicator of claim 3, wherein the control system includes a current-sensing network coupled to a voltage source.
10. The spray applicator of claim 3, wherein the control system includes a voltage-sensing network coupled to a current source.
11. A level-sensing supply vessel for a spray applicator, comprising:
- a level sensor responsive to a volume of a liquid retained by the supply vessel, the sensor including a sensor element configured to detect the volume by sensing a resistance property of the liquid.
12. The level-sensing supply vessel of claim 11, wherein the level sensor further includes a control system coupled to the supply vessel that generates a signal when a predetermined liquid volume is retained in the supply vessel.
13. The level-sensing supply vessel of claim 12, wherein the level sensor further includes an alarm device coupled to the control system to receive the signal and generate an alarm indication.
14. The level-sensing supply vessel of claim 11, wherein the sensor element further comprises:
- a first electrode; and
- a second electrode spaced apart from the first electrode.
15. The level-sensing supply vessel of claim 14, wherein the first electrode and the second electrode are positioned adjacent to a wall of the supply vessel, the first electrode and the second electrode being spaced apart from the wall of the supply vessel by an insulating layer interposed between the wall and the first and second electrodes.
16. The spray applicator of claim 14, wherein the first electrode and the second electrode are formed on opposing sides of an insulating substrate.
17. The spray applicator of claim 14, wherein the supply vessel further includes a wall that comprises one of the first electrode and the second electrode.
18. The spray applicator of claim 12, wherein the control system includes a current-sensing network coupled to a voltage source.
19. The spray applicator of claim 12, wherein the control system includes a voltage-sensing network coupled to a current source.
20. A method of sensing a level of a liquid retained within a storage vessel of a spray applicator, comprising:
- sensing a first volume of the liquid retained within the vessel by determining a first resistance value of the liquid;
- removing a portion of the first volume to define a second volume within the storage vessel;
- determining if the second volume is less than a predetermined minimum volume by determining a second resistance value of the liquid and comparing the first resistance value to the second resistance value; and
- generating an alarm signal if the second volume is less than the predetermined minimum volume.
21. (canceled)
22. (canceled)
23. The method of claim 20, wherein generating an alarm signal further comprises generating an audible alarm.
24. The method of claim 20, wherein generating an alarm signal further comprises generating a visual alarm.
25. The method of claim 20, wherein removing a portion of the first volume to define a second volume further comprises expelling the portion through a spray gun coupled to the supply vessel.
Type: Application
Filed: Jun 18, 2007
Publication Date: Oct 25, 2007
Inventor: Clifford Turnbull (Kent, WA)
Application Number: 11/820,526
International Classification: B67D 5/38 (20060101);