US2309565A - Paper drier temperature control - Google Patents

Description

Jan. 26, 1943 A. E. ARMSTRONG PAPER DRIER TEMPERATURE CONTROL Filed Aug. 19. 1940 INVENiOR. Ada/77 Z. 14/777J/f0/7 ATT Patented Jan. 26, 1943 'PAPER DRIER TEMPERATURE CONTROL Adam E. Armstrong, Three Rivers, Mich, assignor to Armstrong Machine Works, Three Rivers, Mich., a corporation of Michigan Application August 19, 1940, Serial No. 353,269

12 Claims. (01. 34-41) This invention relates to improvements in pa- 1 per drier temperature controls.

The main objects of this invention are:'

First, to provide a control for low temperature paper driers and the like suitable for installation on the individual driers to control the temperature thereof. Second, to provide a control of the type described which enables the driers at the wet end of a paper drying machine to be individually controlled.

Third, to provide a control device which is simple in its parts and automatic in its operation.

Fourth, to provide a novel method of controlling a steam heated drying unit.

Objects relating to details and economies of the inventionwill appear from the description to follow. The invention is defined and pointed out in the claims.

A structure embodying the features of the invention is illustrated in the accompanying drawing, in which Fig. 1 is a diagrammatic view illustrating a drier element of a web drying machine in longitudinal sectionwith the elements of the temperature control in operative relation thereto; and Fig. 2 is an enlarged fragmentary view in vertical section illustrating more particularlythe details of structure and arrangement of the temperature control associated with the drier element.

In paper drying machines, it is desirable that the initial or wet end driers be held at low temperature and that the heat radiated from these driers be maintained approximately constant. If a condition of uniform heat radiation is maintained at the wet end of the machine, it will be apparent that the task of maintaining control of the drying conditions at the subsequent or dry end of the machine is facilitated and the device "of this invention is accordingly intended to serve this purpose. In its preferred embodiment, I contemplate that a control device in accordance with the description to follow shall besupplied for each of the wet end driers so that the temperature of these driers may be individually set and continually maintained at th original setting thereof.

Referring to the drawing, the reference numeral l indicates the cylindrical drying element or cylinder of a paper drying machine, which in accordance with one contemplated adaptation of the invention is located at the wet end or web input end of the machine, although it will appear from the description to follow that the invention is not unduly restricted as to the location of the cylinder or shell to which it is applied in the machine.

The reference numeral 2 designates a pipe supplying steam at constant pressure to the cylinder, in which pipe is inserted a. return check valve 3. At the rear end of this check valve, I.

provide a connection 4 for supplying air at constant pressure to the steam feed line in advance of the cylinder, there being means preferably in theform of an oriflce 5 in this connection for assuring that a relatively small amount of air will be continuously fed in to the drier. is preferably at slightly greater pressure than the steam pressure (which is usually low at the wet end of the machine). A pressure difference of one pound has been found suitable.

The steam and air are fed to the drier shell through an element or fitting 6 serving as a jour- ,nal for the cylinder and accordingly provided with suitable packing 6| The illustration is conventional in this respect. The mixture of steam and air as well as the condensate resulting from the condensation of the steam in the drier is withdrawn from the drier through a siphon type discharge I which also serves as a. journal for the drier and is appropriately packed for that purpose. These parts. are also conventionally illustrated. The discharge 1 communicates through a T-fitting with an adjustable air relief 8 and a steam trap 9, the latter of which serves to remove condensate drawn all by the siphon tube I while preventing the passage of steam.

The adjustable air relief 8 preferably includes a flexible corrugated bellows Ill filled with water and water vapor and from which air has been expelled, which bellows is housed in a chamber v or dome I I into which the steam and air mixture is admitted. In expelling air from bellows i0 so as to prepare the same for its desired functioning the bellows is first partially filled with water, when in an inverted position, through an opening I08 in the bellows support I 09. The bellows is then heated to cause said water to boil, whereby the air is driven out and the steam evolved fills the remainder of the bellows. In this condition a plug H0 is driven into opening 108 so as to seal the interior of the bellows.

Thus when the steam condenses the bellows is in a substantially air free condition. The heated steam and air admitted to the chamber elevates the temperature of the water vapor inside the bellows to its own temperature, and since the pressure outside the bellows is greater than the true steam pressure inside the same corresponding to the temperature of the steam-air mix- The air] ture, there is an unbalancing of the pressures acting on the bellows. This is because the bellows has only water or water vapor therein. hence the pressure therein is the true steam pressure corresponding to the temperature of the steam-air mixture externally thereof. The result is that the bellows is compressed by the greater external pressure, moving a valve l2 carried thereby away from a valve seat l3 in the dome II. This valve seat may be adjusted vertically so as to exert any desired initial pressure on the valve l2, tothe end that opening of the valve seat will occur when the proportion of air in the steam-air mixture reaches any desired point. When this point is reached, the steam and air will be vented off from the chamber through the valve seat. From the foregoing it willbe apparent that the present system is in reality a temperature sensitive control in which the temperature of the steam-air mixture internally of element I (and accordingly the 'tem perature of the mixture within dome II) is effective to regulate the action of the ventingvalve [2. This action is produced by a difference in the pressures internally and externally of bellows II], which difference in turn arises from the different character of the gases internally and externally of the bellows; i. e., water vapor internally and a steam-air-mixture externally. For any given desired temperature there is a predetermined corresponding pressure difference acting on the bellows and, as stated above, the valve seat [3 may be properly adjusted so that for the desired temperature the pressure differential is sufficient to shift valve l2 away from the valve seat and vent air and steam from the dome.

It follows from the foregoing arrangement of parts that air is continually supplied to the steam entering drier cylinder 1 while the pressure therein is lower than the pressure of'the air supply. When these two pressures equalize, the flow of incoming air as well as steam terminates. Should the percentage of air in the steam be lower than the value for which the valve seat of the relief 8 is set, the system will be sealed. Upon condensation of steam in drying the web and accompanying cooling of the cylinder in doing this work, the percentage of air in the gaseous mixture increases, and when the aforesaid predeterinined point is exceeded, the air relief operates to vent off air, decreasing the pressure in the cylinder and admitting more steam through the check valve, which raises the temperature of the cylinder by increasing the percentage of steam in the mixture. This causes the valve ll of the air relief to close, inasmuch as the pressure externally of the bellows is more nearly like the true steam pressure internally of the bellows corresponding to the temperature externally thereof, so that the pressure differential tending to compress the bellows is decreased.

The control operates continuously, venting air through the air relief 8 when the air component in the cylinder becomes too great, i.,e., when the temperature drops too low. It should be understood that the amount of air continually admitted through o'rifice is very small and that venting of air by the relief together with the condensation of steam in the cylinder results in a sufilcient pressure drop to enable the steam in supply line 2 to pass check valve 3 in suificient quantities to effect a desired elevation of temperature by correction of the proportion of steam in the cylinder. Steam continues to be admitted in this manner until the correct temperature is reached. The setting of valve seat I3 may be adjusted as desired for any individual drier element I.

In my copending application, Serial No. 353,- 267, filed August 19, 1940, I illustrate and describe a control for room temperatures, operating on somewhat the same principle as the present apparatus, i. e., the admixture of air with steam in a heat radiating element to control the temperature thereof, the difference in the two concepts being that in the present device I utilize the steam-air mixture within the heat exchange unit to effect the desired automatic temperature compensation, whereas in the room temperature control in accordance with the aforesaid application, the temperature of the room as it afiects a thermostat controls the air admitted. Further, in the room control, the admission of air is thermostatically controlled and intermittent, and the bleeding of air from the system is continuous, whereas in. the present installation the reverse is true, i. e., the air is continuously supplied and intermittently bled off in accordance with the extent to which it preponderates in the mixture.

So far as I am aware, it is novel with me to effect the control of a drying or radiating element or cylinder by the admixture of air or other medium than the heating medium with the latter. In fact, in hitherto known steam heated web driers, every attempt has been made to prevent the entrance of air into the system and to remove it immediately should it enter.

I have illustrated and described my improvements in an embodiment which is very practical. From the foregoing discussion of the principles involved in the practice of my method it will be evident that the latter may be performed with I desired.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent, is:

1. A temperature control for a paper web drying element connected to a source of steam supply from which it is supplied at constant pressure, comprising a return check valve in the connection .to said element from said source, means for continually supplying a small amount of air at constant pressure to said element, said means communicating with the element between the same and the check valve, means for withdrawing steam, air and condensate from said element, means for-separating condensate .from the steam and air and for discharging the condensate while preventing discharge of the steam, and means adjustably sensitive to and responsive to the pressureof the mixture in the element to vent off said withdrawn steam and air in proportion to the amount of air in the air-steam mixture in the element whereby in the event of excessive air therein and a resultant excessively'low temperature of the element steam is admitted through said check valve to increase the proportion of steam in the element.

2. A temperature control for a paper web drying element connected to a source of steam supply from which it is supplied at constant presthe element.

the element to vent of! air from sure, comprising means for supplying air at constant pressure to said element, means for withdrawing air and condensate from said element, means for separating condensate from the air and for discharging the condensate while preventing discharge of the air, and means adjustably sensitive to and responsive to the pressure of the mixture in the element to vent ofi said withdrawn air in proportion to the amount of air in the element whereby in the event of excessive 'air therein and a resultant excessively low temperature of the element steam is admitted to increase the 3. A temperature control for a heat radiating element, comprising means for supplying steam at constant pressure to said element, means for continually supplying a small amount of air at constant pressure to said element, means for withdrawing steam, air and condensate from said element, means for separating condensate from the steam and air and for discharging the condensate, and means adjustably sensitive to and responsive to the pressure of the mixture in the element to vent oif steam and air from the element in proportion to the amount of air in the air-steam mixture in the element whereby, in the event excessive air is present therein and a resultant excessively low temperature of the element, the pressure in the element is reduced and further steam is supplied by said first named means to increase the element.

4. A temperature control for a heat radiatingelement, comprising means for supplying steam at constant pressure to said element, means for supplying air at constant pressure to said element, means adjustably sensitive to and responsive to the pressure of the mixture in the element to vent ofi air from the element in proportion to the amount of air in the air-steam mixture in the element whereby, in the event excessive air is present therein and a resultant excessively low temperature of the element, the pressure in the element is reduced and further steam is supplied by said first named means to increase the proportion of steam in the element 5. A temperature control fora heat radiating element, comprising means for supplying steam at constant pressure to said element, means for continually supplying a small amount of air at constant pressure to said element, means for withdrawing steam, air and condensate from said element, and means adjustably sensitive to and responsive to the pressure of the mixture in the element to vent ofi steam and mentin the event excessive air whereby the pressure in the element is reduced and further steam is supplied by said first named means to increase the proportion of steam' in the element.

- 6. A temperature control for valve closed to preventadmission of steam to the element, and means adjustably sensitive to and responsive to the pressure of the mixture in proportion of steam in air from the ele-, is present therein a heat radiating steam heated element, comprising means for sup- I plying steam at constant pressure to the eleproportion of steam in the the element, and controlling the element to (5 reduce the pressure therein when the proportion of air in the air-steam mixturein the element is excessive, with a resultant excessively low temperature of the element, said first named means then supplying steam to the element through said check valve to increase the proportion of steam therein. a v

'7. A temperature control for a heat radiating steam heated element, comprising means for supplying steam at constant pressure to the element, means for supplying air at constant pressure to said element, and means adjustably sensitive to and responsive to the pressure of the mixture in the element to vent off air from the element to reduce the pressure therein when the proportion of air in the air-steam mixture in the element is from the element in accordance with the percentage of air in the steam-air mixture in the element, separating and discharging condensate from the steam and air in the element, and controlling the supply of steam to the element in accordance with the pressure therein, said pressure being governed by said intermittent venting and by the amount of condensation occur- 4 ring in operation of the element.

9. The method of controlling the temperature of a steam heated heat exchange element, comprising supplying steam at constant pressure to the element, adding air at constant pressure to the steam in the element, venting air from the element in response to the proportion of 'air in,

the element and only when said proportion exceeds a predetermined value, and, separating and discharging condensate from the steam and air in the element, said venting controlling the supply of steam to the element in accordance with temperature thereof, said temperature being governed by the relative proportion of air in the steam-air mixture in the element and by the amount of condensation occurring in operation of the element.

10. The method of controlling the temperature of a steam heated heat exchange element,'comprising supplying steam at constant pressure to the element, adding air at constant pressure to the steam in the element, and venting air from the element in response .to the proportion of air in the element and only'when said proportion exceeds a predetermined value, said venting controlling the supply of steam to the element in accordance with the temperature thereof, said temperature being governed by the relative proportion of air in the steam-air mixture in the element and by the amount of condensation occurring in operation of the element.

11. The method of controlling the temperature ofa heat exchange element, comprising supplying steam at constant pressure to the element, continually adding a small amount of air at con,- stant pressure to the steam in the element, venting air from the element in accordance with the percentage of air in the steam-air mixture in the supply of steam to the element in accordance with the pressure therein, said pressure being governed by said element in response to the proportion of air in the element and only when said proportion exceeds a predetermined value, and, separating and discharging condensate from the steam and air in the element, said venting controlling the supply of steam to the element in accordance with the pressure therein, said pressure being governed by said intermittent venting and by the amount of condensation occurring in operation of the element.

ADAM E. ARMSTRONG.

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