Automated dryer control system

• US 4,713,894 A
• Filed: 08/07/1984
• Issued: 12/22/1987
• Est. Priority Date: 08/07/1984
• Status: Expired due to Fees

• Current Assignee: Intraspec Incorporated
• Original Assignee: Intraspec Incorporated
• Inventors: Roth, Philip M., Sussman, Arthur, Itskovitch, Nathan M.
• Primary Examiner(s): Schwartz, Larry I.
• Assistant Examiner(s): NOT, DEFINED
• Application Number:
  US06/638,416
• Time in Patent Office: 1,232 Days
• Field of Search: 34/30, 34/48, 34/53, 34/55
• US Class Current: 34/486
• CPC Class Codes: D06F 2103/12 Temperature
• CPC Class Codes: D06F 2103/38 Time, e.g. duration
• CPC Class Codes: D06F 2105/28 Electric heating
• CPC Class Codes: D06F 2105/62 Stopping or disabling machine operation
• CPC Class Codes: D06F 34/08 Control circuits or arrangements thereof
• CPC Class Codes: D06F 58/263 Gas heating equipment
• CPC Class Codes: D06F 58/38 of drying, e.g. to achieve the target humidity

Abstract

A system for automatically controlling the operation of a dryer, periodically produces signals representative of the present temperature of a load to be dried. Heat is applied to the load in response to the signals representative of the present temperature of the load. A circuit determines a time interval for the load to reach one predetermined temperature from another predetermined temperature. That time interval is representative of the present condition of the load. The dryer is shut off when the present condition of the load reaches a predetermined desired condition.

Claims

1. A system for automatically controlling the operation of a dryer, comprising:

means for cyclically applying heat to the load to be dried so that the temperature of the load varies cyclically in a series of cycles including a learn cycle and one or more conditioning cycles subsequent to said learn cycle;

means for determining the time interval for the load to be dried to reach one predetermined temperature from another predetermined temperature during said learn cycle and during each said conditioning cycle;

a source of adjustable frequency clock pulses;

means for adjusting the frequency of said clock pulses so that a predetermined number of clock pulses are produced during a time equal to said time interval determined during said learn cycle;

means for totalizing said clock pulses during the time interval determined during each of said conditioning cycles;

means for comparing said totalized number of clock pulses for each of said conditioning cycles to said predetermined number of clock pulses; and

control means for ending the application of heat in response to the occurrence of a predetermined relationship between said totalized number of clock pulses for one of said conditioning cycles and said predetermined number of clock pulses whereby application of heat is ended when the thermal response exhibited by the load in said conditioning cycles bears a predetermined relationship to the thermal response exhibited by the load during said learn cycle.

2. A system according to claim 1, additionally comprising means for periodically producing signals representative of the present temperature of the load to be dried, said means for periodically determining a time interval being responsive to said signals representative of the present temperature of the load.

3. A system according to claim 2, additionally comprising means for providing a plurality of temperature reference signals each being representative of a selected temperature, and second means for comparing said signals representative of the present temperature of the load to be dried to first and second ones of said plurality of temperature reference signals, said means for cyclically applying heat being responsive to said second means for comparing to begin the application of heat to the load when said present temperature is below the selected temperature represented by said first reference temperature signal and to end said application when said present temperature is above the selected temperature represented by said second reference temperature signal.

4. A system according to claim 3, wherein said means for cyclically applying heat includes a large gas jet and a small gas jet, said large gas jet being turned on when said present temperature is below the selected temperature represented by said first reference temperature signal and being turned off when said present temperature is above the selected temperature represented by said second reference temperature signal.

5. A system according to claim 3, additionally comprising means for timing out a predetermined period, said means for cyclically applying heat being responsive to said timing means.

6. A system according to claim 5, wherein a third one of said plurality of temperature reference signals represents a selected temperature greater than said selected temperature represented by said second reference temperature signal, said second means for comparing acting to compare said signals representative of the present temperature of the load to said third temperature reference signal such that said means for applying heat begins the application of heat to the load to be dried when said present temperature is below said selected temperature represented by said second reference temperature signal and ends said application when said present temperature is above said selected temperature represented by said third reference temperature signal while said timing means times out said predetermined period.

7. A system according to claim 1, wherein the dryer additionally comprises a tumbler capable of being rotated in one of two directions, said dryer control system additionally comprising means for determining the present direction of tumber rotation, and means for initiating said periodic production of said time intervals in response to said present direction of tumbler rotation such that said periodic production occurs when the tumbler is rotating in a selected one of said two directions.

8. A system according to claim 1, additionally comprising output means responsive to said control means.

9. A system according to claim 8, wherein said output means further includes a bell.

10. A system as claimed in claim 1 in which said one predetermined temperature is greater than said another predetermined temperature, said means for determining the time interval being operative to determine the time interval during a portion of each said cycle in which the temperature of the load is rising, said control means being operative to end the application of heat when the totalized number of clock pulses for one of said conditioning cycles is equal to or less than a predetermined fraction of said predetermined number of clock pulses.

11. A method for automatically controlling the operation of a dryer, comprising:

cyclically applying heat to the load to be dried so that the temperature of the load varies cyclically in a series of cycles including a learn cycle and one or more conditioning cycles subsequent to said learn cycle;

determining the time interval for the load to be dried to reach one predetermined temperature from another predetermined temperature during said learn cycle and during each of said conditioning cycles;

providing adjustable frequency clock pulses;

adjusting the frequency of said clock pulses so that a predetermined number of clock pulses are produced during a time equal to said time interval determined during said learn cycle;

totalizing said clock pulses during the time interval determined during each of said conditioning cycles;

comparing said totalized number of clock pulses for each of said conditioning cycles to said predetermined number of clock pulses; and

ending the application of heat in response to the occurrence of a predetermined relationship between said totalized number of clock pulses for one of said conditioning cycles and said predetermined number of clock pulses, whereby application of heat is ended when the thermal response exhibited by the load in said conditioning cycles bears a predetermined relationship to the thermal response exhibited by the load during said learn cycle.

12. A method according to claim 11, additionally comprising the step of periodically producing signals representative of the present temperature of the load to be dried, said step of periodically determining a time interval being responsive to said signals representative of the present temperature of the load.

13. A method according to claim 12, additionally comprising the step of providing a plurality of temperature reference signals each being representative of a selected temperature, and the second step of comparing said signals representative of the present temperature of the load to be dried to first and second ones of said plurality of temperature reference signals, said application of heat beginning when said present temperature is below the selected temperature represented by said first reference temperature signal and ending when said present temperature is above the selected temperature represented by said second reference temperature signal.

14. A method according to claim 13, additionally comprising the step of timing out a predetermined period, said step of applying heat to the load to be dried being responsive to said predetermined period.

15. A method according to claim 14, wherein a third one of said plurality of temperature reference signals represents a selected temperature greater than said selected temperature represented by said second reference temperature signal, said second step of comparing further including comparing said signal representative of the present temperature of the load to be dried to said third temperature reference signal, said application of heat beginning when said present temperature of the load is below said selected temperature represented by said second reference temperature signal and ending when said present temperature is above said selected temperature represented by said third reference temperature signal while said predetermined period is timed out.

16. A method according to claim 11, additionally comprising the steps of rotating a tumbler in one of two directions, determining the present direction of tumbler rotation, and initiating said periodic production of time intervals in response to said present direction of tumbler rotation such that said periodic production occurs when the tumbler is rotating in a selected one of said two directions.

17. A method as claimed in claim 11 in which said one predetermined temperature is greater than said another predetermined temperature, said time interval is determined during a portion of each said cycle in which heat is applied to the load and the temperature of the load increases, and the application of heat to the load is ended when said totalized number of clock pulses for one of said conditioning cycles is equal to or less than a predetermined fraction of said predetermined number of clock pulses.

18. A method of drying a load comprising the steps of:

(a) cyclically supplying heat to the load so that the temperature of the load varies in a series of cycles including a learn cycle and one or more conditioning cycles subsequent to said learn cycle;

(b) determining a reference rate of temperature variation of the load during a predetermined portion of said learn cycle in which the temperature of the load is increasing through a predetermined temperature range between two predetermined temperatures;

(c) determining a present condition rate of temperature variation during a portion of each of said conditioning cycles corresponding to said predetermined portion of said learn cycle, said portion of each said conditioning cycle being a portion of each said conditioning cycle in which the temperature of the load is increasing through said predetermined temperature range between said two predetermined temperatures;

(d) comparing the present condition rate of temperature variation determined on each of said conditioning cycles with said reference rate of temperature variation; and

(e) terminating said heat supplying step when the present condition rate of temperature variation determined on one of said conditioning cycles bears a predetermined relationship to said reference rate of temperature variation, whereby the heat supplying step is terminated when the thermal response of the load exhibited on said conditioning cycles bears a predetermined relationship to the thermal response exhibited by the load during said learn cycle,

said reference rate of temperature increase being determined by determining a reference time interval required for the temperature of the load to increase through said predetermined temperature range during said learn cycle and the present condition rate of temperature increase being determined by determining a present condition time interval required for the temperature of the load to increase through said predetermined temperature range on each of said conditioning cycles, said step of comparing said present condition rate of temperature variation with said reference rate of temperature variation including the step of comparing said present condition time interval for each said conditioning cycle with said reference time interval, the method further comprising the step of providing adjustable frequency clock pulses and adjusting the frequency of said clock pulses so that a predetermined number of said clock pulses are produced during a time interval equal to said reference time interval, said step of comparing said present condition time interval with said reference time interval being performed by totalizing the number of said clock pulses as the temperature of the load increases through said predetermined temperature range on each said conditioning cycle and comparing the totalized number of clock pulses for with said predetermined number of clock pulses.

19. A method as claimed in claim 18 in which said heat supplying step is terminated when the number of said clock pulses totalized on one of said conditioning cycles is less than or equal to a predetermined fraction of said predetermined number of clock pulses.

20. A method of drying a load comprising the steps of:

(a) cyclically supplying heat to the load so that the temperature of the load varies in a series of cycles including a learn cycle and one or more conditioning cycles subsequent to said learn cycle;

(b) determining a reference rate of temperature variation of the load during a predetermined portion of said learn cycle in which the temperature of the load is increasing through a predetermined temperature range between two predetermined temperatures;

(c) determining a present condition rate of temperature variation during a portion of each of said conditioning cycles corresponding to said predetermined portion of said learn cycle, said portion of each said conditioning cycle being a portion of each said conditioning cycle in which the temperature of the load is increasing through said predetermined temperature range between said two predetermined temperatures;

(d) comparing the present condition rate of temperature variation determined on each of said conditioning cycles with said reference rate of temperature variation; and

(e) terminating said heat supplying step when the present condition rate of temperature variation determined on one of said conditioning cycles bears a predetermined relationship to said reference rate of temperature variation, whereby the heat supplying step is terminated when the thermal response of the load exhibited on said conditioning cycles bears a predetermined relationship to the thermal response exhibited by the load during said learn cycle, the method further comprising the step of maintaining the temperature of the load within a modulation range of temperatures above said predetermined temperature range subsequent to said learn cycle but prior to the last one of said conditioning cycles.

21. A method of drying a load comprising the steps of:

(a) cyclically supplying heat to the load so that the temperature of the load varies in a series of cycles including a learn cycle and one or more conditioning cycles subsequent to said learn cycle;

(b) determining a reference rate of temperature variation of the load during a predetermined portion of said learn cycle in which the temperature of the load is increasing through a predetermined temperature range between two predetermined temperatures;

(c) determining a present condition rate of temperature variation during a portion of each of said conditioning cycles corresponding to said predetermined portion of said learn cycle, said portion of each said conditioning cycle being a portion of each said conditioning cycle in which the temperature of the load is increasing through said predetermined temperature range between said two predetermined temperatures;

(d) comparing the present condition rate of temperature variation determined on each of said conditioning cycles with said reference rate of temperature variation; and

(e) terminating said heat supplying step when the present condition rate of temperature variation determined on one of said conditioning cycles bears a predetermined relationship to said reference rate of temperature variation, whereby the heat supplying step is terminated when the thermal response of the load exhibited on said conditioning cycles bears a predetermined relationship to the thermal response exhibited by the load during said learn cycle, the method further comprising the step of maintaining the temperature of said load in a modulation range of temperatures above said predetermined temperature range prior to said learn cycle.

22. A method of drying a load to substantially complete dryness comprising the steps of:

(a) cyclically supplying heat to said load so that the temperature of said load varies cyclically;

(b) determining the rate of temperature variation of the load during a predetermined portion of each cycle by providing clock pulses and totalizing the number of clock pulses occurring while the temperature of the load increases through a predetermined range of temperatures;

(c) comparing the rates determined on successive ones of said cycles by comparing the number of said clock pulses totalized on said successive cycles; and

(d) adding one to a value stored in a counter when the numbers of said clock pulses totalized on consecutive ones of said cycles differ from one another by less than a predetermined repeat parameter and resetting said value to zero whenever the numbers of clock pulses totalized on consecutive ones of said cycles differ from one another by more than said repeat parameter; and

(e) terminating said heat supplying step when the value stored in said counter reaches a predetermined value, whereby said heat supplying step is terminated when the rates of temperature variation determined measured during consecutive ones of said cycles differ from one another by less than a predetermined amount.

23. A method as claimed in claim 22 in which said predetermined value is two or more.

24. A control system for controlling operation of a dryer having a heat source comprising:

(a) means for cyclically actuating said heat source so that the temperature of the load to be dried varies in a series of cycles including a learn cycle and one or more conditioning cycles subsequent to said learn cycle;

(b) rate-determining means for determining a reference rate of temperature variation of the load during a predetermined portion of said learn cycle and determining a present condition rate of temperature variation during a portion of each of said conditioning cycles corresponding to said predetermined portion of said learn cycle;

(c) comparison means for comparing said present condition rate of temperature variation determined on each of said conditioning cycles with said reference rate of temperature variation; and

(d) control means for terminating operation of said heat source when the present condition rate of temperature variation determined on one of said conditioning cycles bears a predetermined relationship to said reference rate of temperature variation, whereby operation of said heat source is terminated when the thermal response of the load exhibited on said conditioning cycles bears a predetermined relationship to the thermal response exhibited by the load during said learn cycle,

said rate-determining means including means for determining a reference time interval required for the temperature of the load to increase through a predetermined temperature range between two predetermined temperatures during said learn cycle and means for determining a present condition time interval required for the temperature of the load to increase through said predetermined temperature range between said two predetermined temperatures on each of said conditioning cycles, said comparison means including time-comparing means for comparing the present condition time interval for each conditioning cycle with said reference time interval,

said time-comparing means including means for providing adjustable frequency clock pulses and means for adjusting the frequency of said clock pulses so that a predetermined number of said clock pulses are produced during a time interval equal to said reference time interval, means for totalizing the number of said clock pulses as the temperature of the load increases through said predetermined temperature range on each said conditioning cycle and means for comparing the totalized number of clock pulses for with said predetermined number of clock pulses.

25. A control system as claimed in claim 24 in which said control means is operative to terminate operation of said heat source when the number of said clock pulses totalized on one of said conditioning cycles is less than or equal to a predetermined fraction of said predetermined number of clock pulses.

26. A control system for controlling a dryer having a heat source to dry a load to substantially complete dryness comprising:

(a) means for cyclically actuating said heat source so that the temperature of said load varies cyclically;

(b) rate-determining means for determining the rate of temperature variation of the load during a predetermined portion of each said cycle;

(c) comparison means for comparing the rates determined on consecutive ones of said cycles; and

(d) control means terminating of said heat source when the rates measured during consecutive ones of said cycles differ from one another by less than a predetermined amount,

said rate determining means including a source of clock pulses, said comparision means including means for totalizing the number of clock pulses occurring while the temperature of the load increases through a predetermined range of temperatures and comparing the number of said clock pulses totalized on consecutive ones of said cycles,

said control means including a counter, incrementing means for adding one to a value stored in said counter when the numbers of clock pulses totalized on consecutive ones of said cycles differ from one another by less than a predetermined repeat parameter, reset means for resetting said value to zero whenever the numbers of clock pulses totalized on consecutive ones of said cycles differ from one another by more than said predetermined repeat parameter, and means for terminating operation of said heat source when said value reaches a predetermined value.

27. A control system as claimed in claim 26 in which said predetermined value is two or more.