US3801426A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Dryer control and grade change system for a paper machine
Assignee: Westinghouse Electric Corp
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Filing: 1970-08-26
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Granted: 1974-04-02
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Expires: 1990-08-26
Abstract
Abstract A computer system for controlling a paper sheet drying machine characterized in that a feed-forward signal is developed proportional to desired steam temperature in the machine drying drums from a consideration of the empirical relationship between caliper and production rate. This same of caliper to production rate is used to predict the production rate at a new caliper while maintaining the steam temperature constant. By this means, a grade change transfer path can be computed which avoids the need to change drying conditions. The speed at which the grade can be changed is merely a function of the mechanical response of the machine and completely divorced from the much longer thermal responses. After the new caliper is established, the steam temperature can be varied leisurely over a period of time to increase the production rate.
Inventors
- 👤 R Putman
- 👤 J Carleton
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 16:05
CPC Classifications
D; D21; D21G; D21G9/00; D21G9/0009; D21G9/0036; D21G9/0054; Y; Y10; Y10S; Y10S162/00; Y10S162/09; Y10S162/10; Y10S162/11
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
32 words
The method of claim 1 including the step of controlling the temperature of the rolls in both said first and second plurality of rolls in response to variations in said feed-forward signal.
Claim 2
Dependent Claim
19 words
The process of claim 2 including the step of maintaining the temperature at the output of said pre-dryer constant.
Claim 3
Dependent Claim
72 words
The method of claim 1 wherein said feedback signal varies as a function of the temperature of the web at the output of said second plurality of rolls and including the step of comparing said feedback signal with a signal proportional to the desired temperature of the web at the output of said second plurality of rolls to develop a modifying signal for modifying said feedback signal before modifying said feedforward signal.
Claim 4
Dependent Claim
85 words
The method of claim 1 wherein said feedforward signal is proportional to: (CT3 + T2)/(1 - C) where T3 is the temperature of the web at the output of said second plurality of rolls, T2 is the temperature of the web at the output of said pre-dryer, and C is proportional to: (1/F) (k1 - k2 loge t) where F is the production rate of the drying machine, t is the caliper of the web leaving the drying machine and k1 and k2 are constants.
Claim 5
Dependent Claim
131 words
In the method for effecting a change in caliper in a paper drying machine of the type wherein a pulp web is passed through a pre-dryer and thence over a plurality of heated rolls, the steps of running said machine at a first predetermined caliper and production rate, maintaining the temperature of said pre-dryer essentially constant, calculating a transfer constant based upon said first production rate and caliper, thereafter changing the caliper of said web in increments until the caliper matches a new desired caliper which is different than said first caliper, calculating from a consideration of said transfer constant the new production rate after each incremental change in caliper, and varying the speed at which said web passes through said drying machine each time a new production rate is calculated.
Claim 6
Dependent Claim
34 words
The method of claim 6 wherein said transfer constant is proportional to: (1/F) (k1 - k2 loge t) where F is the production rate, t is the caliper and k1 and k2 are constants.
Claim 7
Dependent Claim
78 words
The method of claim 6 wherein said caliper is controlled by the position of a slice in a head box and the speed of a wire onto which pulp issues from a slice gap opening, and including the step of controlling the position of said slice to vary the dimensions of said slice gap opening to change said caliper while controlling the speed of said wire in response to a change in caliper to change said production rate.
Claim 8
Dependent Claim
36 words
The method of claim 6 including the steps of measuring the caliper of paper issuing from said drying machine, and changing the temperature of said drying rolls after the measured caliper matches said new desired caliper.
References Cited (Backward Citations)
No citation records indexed.
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1977-04-01 | 1977-10-01 | 1978-04-02 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-04-01 | 1981-10-01 | 1982-04-02 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-04-01 | 1985-10-01 | 1986-04-02 | $7700.00 | Window Closed / Lapsed |