Sprayer thermal protection

Information

  • Patent Grant
  • 9027849
  • Patent Number
    9,027,849
  • Date Filed
    Wednesday, December 29, 2004
    19 years ago
  • Date Issued
    Tuesday, May 12, 2015
    9 years ago
Abstract
In an electric airless sprayer (16), as the motor (14) temperature approaches allowable limits, several performance cutbacks can be used to prevent overheating. The preferred method is to gradually reduce the controlled pressure. If the temperature continues to rise, the control (20) switches to on/off or deadband control. If the temperature continues to rise in spite of these measures, the control (20) shuts the unit down.
Description
BACKGROUND ART

Electric airless paint sprayers are popular for applying architectural coatings to various structures. Such sprayers typically utilize either on/off (deadband) or variable speed control to maintain a set pressure. Such sprayers are typically provided with thermal protection which shuts off the sprayer when motor temperature exceeds a predetermined level.


DISCLOSURE OF THE INVENTION

It is therefore an object of this invention to provide a thermal protection system which provides enhanced performance to the painter. It is also an object of this invention to provide protection which allows use of a smaller and/or lighter motor while maintaining an acceptable level of performance.


Towards that end a 100 Kohm NTC thermistor is placed in the brush holder of the electric motor in the sprayer to monitor the temperature of the sprayer. The processor on the control board monitors the thermistor output. At temperatures well below the limits of the motor, the sprayer operates at the full selected pressure and variable speed for optimum performance.


As the temperature approaches allowable limits, several performance cutbacks can be used to prevent overheating. The preferred method is to gradually reduce the controlled pressure. If the temperature continues to rise, the control switches to on/off or deadband control. This mode cools better with small spray tips because the fan speed is higher and there is a considerable amount of off time. If the temperature continues to rise in spite of these measures, the control shuts the unit down.


An additional enhancement to the system is to include a requirement in the control logic that control pursuant to the various trip temperatures takes place on while the motor is running. For instance, if the trip point for on/off operation is 140° C., the control would only change to on/off mode after that temperature had been exceeded for 1 minute of motor on time. This helps to compensate for the fact that motor temperature as seen by the thermistor will continue to rise for a bit after the motor has stopped.


These and other objects and advantages of the invention will appear more fully from the following description made in conjunction with the accompanying drawings wherein like reference characters refer to the same or similar parts throughout the several views.





BRIEF DESCRIPTION OF DRAWINGS


FIG. 1 is a schlematic diagram showing the instant invention.





BEST MODE FOR CARRYING OUT THE INVENTION

As shown in FIG. 1, a 100 Kohm NTC thermistor 10 is placed in the brush holder 12 of the electric motor 14 in the sprayer 16 to monitor the temperature of the sprayer 16. The processor 18 on the control board 20 monitors the thermistor 10 output. At temperatures well below the limits of the motor 14, the sprayer 16 operates at the full selected pressure and variable speed for optimum performance.


As the temperature approaches allowable limits, several performance cutbacks can be used to prevent overheating. The preferred method is to gradually reduce the controlled pressure. If the temperature continues to rise, the control 20 switches to on/off or deadband control. This mode cools better with small spray tips because the fan speed (in the motor) is higher and there is a considerable amount of off time. If the temperature continues to rise in spite of these measures, the control 20 shuts the unit down.


An additional enhancement to the system is to include a requirement in the control logic that control pursuant to the various trip temperatures takes place on while the motor 14 is running. For instance, if the trip point for on/off operation is 140° C., the control 20 would only change to on/off mode after that temperature had been exceeded for 1 minute of motor on time. This helps to compensate for the fact that motor temperature as seen by the thermistor will continue to rise for a bit after the motor has stopped.


It is contemplated that various changes and modifications may be made to the thermal protection system without departing from the spirit and scope of the invention as defined by the following claims.

Claims
  • 1. A method for thermally protecting a variable speed electric paint sprayer having an electric motor, a control and a temperature, and which operates to maintain a user-selected controlled pressure, the method comprising: monitoring the temperature of said electric motor; andreducing said controlled pressure from said user-selected controlled pressure and continuing to continuously spray at a reduced consistent non-zero pressure when said electric motor temperature exceeds a predetermined level.
  • 2. The method of claim 1 wherein said change occurs only after said motor temperature has exceeded said predetermined level for a predetermined length of time of motor operation.
  • 3. A method for thermally protecting a variable speed electric paint sprayer having an electric motor, a control and a temperature, and which operates to maintain a user-selected controlled pressure, the method comprising: monitoring the temperature of said motor; andchanging the control of said motor from variable speed control to on/off control when said motor temperature exceeds a predetermined level to enable continued continuous spraying at said user-selected pressure.
  • 4. The method of claim 3 wherein said change occurs only after said motor temperature has exceeded said predetermined level for a predetermined length of time of motor operation.
  • 5. A method for thermally protecting a variable speed electric paint sprayer having an electric motor, a control and a temperature, and which operates to maintain a user-selected controlled pressure, the method comprising: monitoring the temperature of said motor;reducing the controlled pressure from said user-selected controlled pressure and continuing to continuously spray at a reduced consistent non-zero pressure when said motor temperature exceeds a first predetermined level; andchanging the control of said motor from variable speed control to on/off control when said motor temperature exceeds a second predetermined level to enable continued spraying at a reduced non-zero pressure.
  • 6. The method of claim 5 wherein said second predetermined level is higher than said first predetermined level.
  • 7. The method of claim 5 wherein said change occurs only after said motor temperature has exceeded said predetermined level for a predetermined length of time of motor operation.
TECHNICAL FIELD

This application claims the benefit of U.S. Application Ser. No. 60/534,180, filed Jan. 2, 2004.

PCT Information
Filing Document Filing Date Country Kind 371c Date
PCT/US2004/043580 12/29/2004 WO 00 4/13/2006
Publishing Document Publishing Date Country Kind
WO2005/067697 7/28/2005 WO A
US Referenced Citations (14)
Number Name Date Kind
3555355 Pfister et al. Jan 1971 A
3569781 Strachan Mar 1971 A
3697863 Kilner Oct 1972 A
4335342 Tholome Jun 1982 A
5010264 Yamada et al. Apr 1991 A
5027841 Breunsbach et al. Jul 1991 A
5109881 Baker May 1992 A
5533671 Baer Jul 1996 A
5546262 Baurand et al. Aug 1996 A
5772403 Allison et al. Jun 1998 A
5808441 Nehring Sep 1998 A
5868320 Laabs et al. Feb 1999 A
6020702 Farr Feb 2000 A
6167965 Bearden et al. Jan 2001 B1
Related Publications (1)
Number Date Country
20070132416 A1 Jun 2007 US
Provisional Applications (1)
Number Date Country
60534180 Jan 2004 US