Adhesive dispensing device having optimized reservoir and capacitive level sensor

Patent metadata

Field	Value
Publication number	US-9304028-B2
Application number	US-201313799622-A
Country	US
Kind code	B2
Filing date	Mar 13, 2013
Priority date	Sep 20, 2012
Publication date	Apr 5, 2016
Grant date	Apr 5, 2016

Abstract

An adhesive dispensing device includes a heater unit for melting adhesive, a fill system communicating with a receiving space for feeding the heater unit, and a reservoir for receiving melted adhesive from the heater unit. The dispensing device also includes a capacitive level sensor located along a sidewall of the receiving space such that the level of adhesive in the receiving space can be detected by sensing the difference in dielectric capacitance where the adhesive is located compared to where air acts as the dielectric. The size of the driven electrode produces a broader sensing window capable of generating multiple control signals corresponding to different fill levels of adhesive. The receiving space and reservoir are minimized in size so that adhesive is not held at elevated temperatures long enough to char or degrade.

First claim

What is claimed is:

1. A fluid level sensor for measuring a fill level of a hot melt adhesive within a receiving space that is at least partially defined by a sidewall and configured to receive adhesive to be melted, the fluid level sensor comprising:
a plate element having an electrically driven electrode and a ground electrode operatively connected for measuring a dielectric capacitance of air and adhesive acting as a dielectric between said driven and ground electrodes, said ground electrode adapted to be electrically connected to the sidewall such that the sidewall forms at least a portion of said ground electrode; and
at least one fastener mount connected to said plate element and adapted to receive a fastener for coupling said plate element into adjacent relationship with the sidewall, such that the dielectric capacitance measured by said plate element varies with the fill level of the adhesive.

2. The fluid level sensor of claim 1 , wherein said plate element is a printed circuit board.

3. The fluid level sensor of claim 1 , wherein said plate element is sized to engage a majority of the sidewall such that heat energy conducted through the sidewall is transferred to said plate element to rapidly melt off any adhesive residue on said plate element above the fill level of the adhesive.

4. The fluid level sensor of claim 1 , wherein said driven electrode defines a plate surface area, the sidewall defines a sidewall surface area, and a ratio of the plate surface area to the sidewall surface area is maximized to provide a sensing window capable of generating multiple control signals corresponding to different fill levels of adhesive.

5. The fluid level sensor of claim 4 , wherein the ratio of the plate surface area to the sidewall surface area is higher than 0.4 to 1.

6. The fluid level sensor of claim 1 , wherein said plate element includes a front face adapted to face the adhesive in the receiving space, said front face including an inner portion electrically separated from an outer portion by a barrier, and wherein said inner portion operates as said driven electrode.

7. The fluid level sensor of claim 6 , wherein said outer portion of said front face operates as said ground electrode.

8. The fluid level sensor of claim 6 , wherein the receiving space is also partially defined by an opposite sidewall facing towards said plate element and coupled to said sidewall forming at least a portion of said ground electrode, and wherein said plate element measures the dielectric capacitance of air and adhesive located between said driven electrode and the opposite sidewall of the receiving space.

9. The fluid level sensor of claim 1 , wherein said plate element is mounted flush with the sidewall using the fastener and said at least one fastener mount.

10. The fluid level sensor of claim 9 , further comprising:
a gasket adapted to be located between the sidewall and said plate element to prevent the adhesive from flowing between the sidewall and said plate element.

11. The fluid level sensor of claim 1 , wherein the fluid level sensor is operatively connected to a controller and a fill system that actuates to supply unmelted adhesive to the receiving space, and the fluid level sensor further comprises:
a timer operatively coupled to said plate element and to the controller; and
a control subroutine loaded into the controller so that the controller is operable to execute said control subroutine to automatically compensate the measurement of the dielectric capacitance based on temperature changes at said plate element, and said control subroutine configured to estimate the temperature changes at said plate element based on a time measured by said timer since a most recent actuation of the fill system.

12. The fluid level sensor of claim 2 , wherein said plate element is sized to engage a majority of the sidewall such that heat energy conducted through the sidewall is transferred to said plate element to rapidly melt off any adhesive residue on said plate element above the fill level of the adhesive.

13. The fluid level sensor of claim 2 , wherein said driven electrode defines a plate surface area, the sidewall defines a sidewall surface area, and a ratio of the plate surface area to the sidewall surface area is maximized to provide a sensing window capable of generating multiple control signals corresponding to different fill levels of adhesive.

14. The fluid level sensor of claim 13 , wherein the ratio of the plate surface area to the sidewall surface area is higher than 0.4 to 1.

15. The fluid level sensor of claim 2 , wherein said plate element includes a front face adapted to face the adhesive, said front face including an inner portion electrically separated from an outer portion by a barrier, and wherein said inner portion operates as said driven electrode.

16. The fluid level sensor of claim 15 , wherein said outer portion of said front face operates as said ground electrode.

17. The fluid level sensor of claim 15 , wherein the receiving space is also partially defined by an opposite sidewall facing towards said plate element and coupled to said sidewall forming at least a portion of said ground electrode, and wherein said plate element measures the dielectric capacitance of air and adhesive located between said driven electrode and the opposite sidewall of the receiving space.

18. The fluid level sensor of claim 2 , wherein the fluid level sensor is operatively connected to a controller and a fill system that actuates to supply unmelted adhesive to the receiving space, and the fluid level sensor further comprises:
a timer operatively coupled to said plate element and to the controller; and
a control subroutine loaded into the controller so that the controller is operable to execute said control subroutine to automatically compensate the measurement of the dielectric capacitance based on temperature changes at said plate element, and said control subroutine configured to estimate the temperature changes at said plate element based on a time measured by said timer since a most recent actuation of the fill system.

19. The fluid level sensor of claim 4 , wherein said plate element is sized to engage a majority of the sidewall such that heat energy conducted through the sidewall is transferred to said plate element to rapidly melt off any adhesive residue on said plate element above the level of the adhesive.

20. The fluid level sensor of claim 4 , wherein said plate element includes a front face adapted to face the adhesive, said front face including an inner portion electrically separated from an outer portion by a barrier, and wherein said inner portion operates as said driven electrode.

21. The fluid level sensor of claim 20 , wherein said outer portion of said front face operates as said ground electrode.

22. The fluid level sensor of claim 20 , wherein the receiving space is also partially defined by an opposite sidewall facing towards the plate element and coupled to said sidewall forming at least a portion of said ground electrode, and wherein said plate element measures the dielectric capacitance of air and adhesive located between said driven electrode and the opposite sidewall of the receiving space.

23. The fluid level sensor of claim 4 , wherein the fluid level sensor is operatively connected to a controller and a fill system that actuates to supply unmelted adhesive to the receiving space, and the fluid level sensor further comprises:
a timer operatively

Assignees

• Nordson Corp

Inventors

• Clark Justin A
• Clark Steven
• Estelle Peter W
• Owen Jeffrey E
• Woodlief Robert J
• Jeter David R

Classifications

• A61B1/044

  for absorption imaging · CPC title

• B05C11/1042 Primary

  provided with means for heating or cooling the liquid or other fluent material in the supplying means upstream of the applying apparatus · CPC title

• G01F23/263 Primary

  by measuring variations in capacitance of capacitors · CPC title

• G01F23/268

  mounting arrangements of probes · CPC title

• G01F23/26

  by measuring variations of capacity or inductance of capacitors or inductors arising from the presence of liquid or fluent solid material in the electric or electromagnetic fields · CPC title