US1543368A - Speed controlling means for paper-drying machines - Google Patents

Description

June 23, 1925 W. H. CARRIER SPEED CONTROLLING MEANS'FOR PAPER DRYING MACHINES Filed Sept. 20, 1920 5 Sheets-Sheet 1 mmssais.

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Patented June 23, 1925.

UNITED STATES PATENT OFFICE.

WILLIS H. CARRIER, OF NEW YORK,- N. Y., ASSIGNOR TO CARRIER ENGINEERING COR- PORATION, OF NEW YORK, N. Y.

SPEED CONTROLLING MEANS FOR PAPER-DRYING MACHINES.

Application filed September 20, 1920. Serial No. 411,524.

To all whom it may concern:

Be it known that I, WILLIS H. CARRIER, a citizen of the United States, residing at New York, in the county of New York and State of New York, have invented a new and useful Improvement in Speed Controlling Means for Paper-Drying Machines, of which the following is a specification.

This invention relates to paper drying machines, and particularly to means for use in such machines for automatically regulat ing the speed of the rolls or supporting devices over which the paper web passes and by which it is caused to travel through the machine.

In drying paper in the standard paper machines the initially wet Web of paper.

traveling from the press rolls is held firmly in contact with the successive hot drying rolls or cylinders by a tightly engaging felt in order to insure flatness of the sheet and to prevent cockle, and the web is under rela tively strong tension where it passes from one roll or cylinder to another. This condition continues from the first drying rollsv to the end of the machine where the paper is dry and where its character and strength, in so far as drying affects the same has therefore been determined. In such drying apparatus, therefore, the paper is mechanically held and not allowed to take up its own dimensions in accordance with varying rates of shrinkage of the Web during different portions of the drying process. Paper dried in this manner, where the web is under strong constraint or tension throughout the drying process, has both a bursting and tensile strength much inferior to paper of like character, which, during a certain portion or portions of the drying operation is relieved from severe tension and restraint in such a manner as to prevent the shrinkage a rather well defined stage or phase of the drying process between the commencement and end thereof, and that the drying under strong mechanical constraint during the early stage of the drying process is not detrimental to strength; But the continuance of strong mechanical constraint or ten sion on the damp web beyond such earl; stage, and particularly the continuance of the customary amount of tension, causes a marked progressive decrease of strength which goes on accumulatively as a result of the usual drying procedure through a second phase or stage of the drying process and ceases again somewhat abruptly toward the end of the drying when the paper has become nearly dry. Decided improvements in the strength of the finished paper thus result from preventing harmful strain or tension on the paper during the above mentioned intermediate stage or phase of the drying process. These improved results can be secured by automatically regulating the speed of the hot, drying cylinders or rolls of the standard drying machine over which the web passes during such intermediate phase of the drying operation in accordance with the shrinkage of the web, in such a manner as to prevent the described harmful strain or tension on the web.

Very decided improvements in the strength and character of the finished paper, and it is believed greater improvements than are attainable in the way just mentioned in connection with the customary drying machine, in which the paper travels throughout the drying operation in contact with the hot drying cylinders or rolls, can be secured by first passing the initially wet web of paper while under tension over a few hot drying cylinders, as in the ordinary paper drying machine, and then subjecting the paper to air-drying while it travels, over supporting and propelling rolls or devices, the speed of which is automatically regulated in accordance with the shrinkage of the web to prevent undue strain or tension thereon. It is also desirable after the web has become nearly dry, in the second or air-drying stage, to complete the drying operation by passing the web over a few final hot drying cylinders or rolls.

This invention is applicable to both these types of drying machines, that is to ma chines in which the paper is dried by contact with successive, heated, drying cylinders or rolls, and to machines in which, after a preliminary drying on the heated cylinders or rolls, the paper is dried by air While passing over supporting and propelling rolls or devices and is relieved from harmful strains or tension. In this application the invention is disclosed in connection with the latter sort of machine. In such a machine, where the web is delivered from the air-drying stage or section to final drying rolls or winding mechanism, it is essential to regulate the speed of such final drying rolls or winding mechanism so as not to take the paper away faster or slower than it is delivered from the air-drying section or stage. Otherwise the paper would be broken or injured. Means are therefore disclosed in this application for automatically regulating the speed of the paper-supporting or propelling rolls or devices in the air-drying section and also the final drying rolls or winding mechanism in such a manner as to give the desired minimum tension on the web during the air drying stage and to cause the final drying rolls or winding mechanism to take the web at the proper speed from the air drying stage or section of the machine.

One object of this invention is to provide practical and efficient mechanism whereby the speed of the rolls'or device over which the paper web travels in a paper machine can be regulated so as to vary the motion of the web in different portions of the machine in such a way as to maintain the paper under a desired minimum tension, or prevent an injurious tension or strain on the paper irrespective of the difference in shrinkage of different portions of the web. Another object of the invention is to provide practical and efiicient means for automatically regulating the speed of the heavy drying cylinders or winding mechanism to which the paper passes from a previous drying section of the machine, so as to correspond with the rate of delivery of the web from such drying section, and to do this by a speed changing mechanism or differential gear which is positive and certain in action but is capable of giving any desired speed within the range required with great exactness and without any slip or difficulty of controlling directly at large, cumbersome, driven roll or mechanism. Another object of the invention is to improve paper drying machines in the other respects herein described and set forth in the claims.

In the embodiment of the invention disclosed in this application the travelling web of paper moves past a perforated pipe from which air under pressure escapes against the paper web. This pipe is so disposed bea sesses tween two of the rolls or devices over which the web passes that an increase in the tension on the web or shrinking of the web will draw the same toward the perforated pipe and obstruct more or less the discharge of air therefrom. T he pressure in the pipe thus varies in accordance with changes in tension on the travelling paper web in the vicinity of the pipe and this varying fluid pressure is utilized through a suitable fluidpressure-actuated motor and speed changing mechanism to regulate or vary the speed of one or more of the adjacent rolls or devices which propel the paper. Preferably several of the perforated pipes, each with its associated fluid pressure motor and speed changing mechanism, are located at different points along the line of travel of the web and separately control successive rolls or groups of rolls in the machine so as to vary or regulate the speed of the rolls and the tension of the paper web as may be necessary to secure the desired tension at different points. The speed of the final drying cylinders or winding mechanism is varied by means of a differential gearing which is operated by a fluid pressure motor, the fluid pressure in which is regulated under the control of the travelling web in the manner above indicated.

In the accompanying drawings:

Fig. 1 is a fragmentary plan view, partly in section, of a paper drying machine embodying the invention.

Fig. 2 is a side elevation thereof.

Fig. is an enlarged section of the perforated air eseape pipe.

Fig. 4 1s a sectional plan of the pressure reducing device.

Fig. 5 is a fragmentary elevation of the final drying cylinders and their speed regulating mechanism.

Fig. 6 is an enlarged transverse sectional elevation of the machine on line 66, Fig. 2.

Fig. 7 is an enlarged side elevation of one of the speed regulating mechanisms.

Fig. 8 is an end elevation, partly in section thereof. 7

Fig. 9 is a sectional plan view of the dif ferential gear mechanism for driving the final drying rolls.

Figs. 10 and 11 are transverse sectional elevations thereof on lines 1010 and 1111 respectively, Fig. 9.

A represents one of the preliminary drying rolls or cylinders at the wet end of the machine, B an air drying chamber or en.- closure throughwhich the paper web passes fnom the preliminary drying rolls A. and C the final rolls or cylinders to which the paper .web passes from the drying chamber. In the drying chamber are suitably journalled a series of upper and lower papersupporting or propelling rolls or devices partly in section D and E over and under which the paper passes alternately so as to travel alternately downwardly and upwardly or in a-Zig-zag path through the drying chamber. In so far as this invention is concerned the paper can be dried in the drying chamber B by means of air or other suitable drying medium supplied to or circulated through the chamber in any suitable way. As shown, air is discharged under pressure and at a relatively high velocity horizontally into the upper portion of the chamber above the paper by injector nozzles F, and induces a circulation of air in the chamber through the spaces between the runs of paper, more or less of the air escaping through openings 9 into an exhaust duct G at the lower portion of that side of the chamber at which the supply nozzles are located. As shown, the upper and lower rolls D, E are arranged in several successive groups numbered 1 to 10 and each of the several groups of rolls is separately driven by a belt 11 which passes around pulleys 12 connected to the shafts of the several rolls D and E, around an idler pulley 13 and around a driving pulley 14. The driving pulley 14 for each group of paper rolls Eli is driven separately under the control of a speed regulating mechanism which will now be described. There may be a greater or less number of the groups of rolls, and each group may contain a greater or less number of rolls, depending upon the requirements.

15 represents a perforated air-escape pipe which extends across the drying chamber adjacent to and parallel with one of the runs of'the paper web extending from one of the upper to one of the lower rolls. There is one of these perforated pipes for each separately driven group of rolls D, E and the several pipes 15 are preferably connected to a main supply pipe 16 to which air or other suitable gas or fluid is supplied under pressure by suitable means, such for instance as an ordinary centrifugal blower (not shown). Each of the, escape pipes 15 is provided in one side thereof with a series of perforations or holes through which the compressed air is adapted to escape against the face of the adjacent run of the paper web. The escape pipe is disposed at one side of a straight line connecting the two rolls between which it is located so that if the paper web shrinks or tightens it will be drawn towards the pipe and more or less obstruct the escape of air from the perforations of the pipe 15. Preferably a diaphragm '17, Fig. 4, having a small orifice 17 is provided in the connection between the main air supply pipe 16 and each perforated pipe 15. This orifice restricts the flow of air to the perforated pipe and determines the minimum pressure which will obtain in this pipe when the perforations are unobstructed. This minimum pressure, which depends upon the size of the orifice, is preferably about one-sixth of the maximum pressure in the main air supply pipe. This occurs when there is no tension on the paper web. The maximum air pressure occurs when the paper is under maximum tension and causes the maximum obstruction to the escape of the air from the perforated pipe. The pressure in the perforated pipe will then be substantially the same as that in the main air supply pipe 16. Each air escape pipe 15 is connected, as by a pipe 18, to a fluid-pressure-actuatcd motor 19 which is adapted to operate in response to changes in pressure in the perforated pipe 15. This motor is preferably of the gasometer type and comprises a stationary reservoir 20 open at its upper end and containing liquid into which the lower end of a movable open-bottomed bell 21 depends. The pipe 18 extends up into the gasometer above the liquid. 22 represents a U-shaped overflow pipe arranged with one leg extending up into the gasometer above the level of the liquid therein and the other leg extending up outside of the same. The motor 19 is preferably operated by the saturated or humidified air which is used for drying the paper, since moisture condensing from this air in the gasometer will replenish that lost by evaporation. If the condensation is greater than the evaporation the surplus will escape through the overflow pipe 22 so that the liquid will be maintained at a constant level in the gasometer and ensure like operation of the motor at all times for a given change in air pressure.

The bell or movable member of the motor operates through suitable mechanism to vary the speed of the drive pulley 14 for one of the groups of paper rolls D and E. In the mechanism shown for this purpose the bell 21 is connected by a rod 23, lever 24 and link 25 to a belt shipper lever 26 which is adapted to shift a belt 27 passing around oppositely arranged driving and driven cone pulleys 28 and 29, the shafts for which are suitably journalled on the frame of the machine. The shaft of the pulley 29 which is driven from the pulley 28 by the belt 27, is connected to the pulley 14 for the paper rolls D, E. Consequently the speed of this pulley 14 and the paper web will be changed by shifting the belt 27 on the cone pulleys. Preferably the lever 24 is provided with a weight 30 for counterbalancing more or less the weight of the gasometer bell and rod 23, and the bell shipper lever 26 is preferably L-shaped and provided with a weight 31 which takes up slack in the connections, and also with a pendant arm 32 provided with an adjustable weight which 0 erates as ti stabilizer for the belt shipper. s shown, the pulley 28 is connected by bevel wheels 33 to a drive shaft 34. This shaft extends along one side of the drying machine and is similarly connected by'bevel wheels to the driving cone pulleys 28 for each speed regu lating mechanism, of which there is one for separately controlling each of the several groups 1 to 10 of the paper rolls D, E.

If the tension on the web of paper increases in the vicinity of any one of the air escape pipes 15 the web will be drawn toward the pipe and obstruct more or less the perforations, thus increasing the pressure in the pipe and in the companion motor 19. The bell 21 of the motor will then be raised and, through the described mechanism, will move the belt shipper and shift the belt 27 so as to reduce the speed of the driven cone pulley 29 and driving pulley 14 for the connected paper propelling roll. The movement of the belt and the reduction in speed of the pulley 14 will depend upon the amount of shrinkage and tension on the paper, When the tension decreases by reason of the reduction in speed of the pulley 14 and the paper rolls the pressure in the perforated pipe and motor will decrease and permit the motor bell and belt shipper to return to the normal position when the normal desired tension is restored,

In this way the speed of each group 1 to 10 of the paper propelling rolls D, E is separately controlled in accordance with the tension. on the paper passing around such group of rolls and the tension on the paper'in the different portions of the drying chamber can be maintained at the desired minimum, which can be either constant throughout the length of the drying chamber or different in different portions thereof, as may be necessary, depending upon the adjustment of the several speed regulating mechanisms. And this is so regardless of the speed or fluctuations in speed of the paper due to irregularities in the motion of the main driving shaft by which the paper-propelling rolls are driven.

The mechanism shown for controlling the speed of the final. drying cylinders C or other mechanism which takes the paper web from the drying chamber or section B of the machine is constructed as follows:

85 represents a differential gear mechanism which can be of any suitable construction That shown is of the planetary type comprising a driving sun. gear 36 and a plurality of planet gears 37 meshing therewith and with an internal driven gear 38 The driving gear 36 is suitably connected to the main drive mechanism for the paper web and is driven thereby, Preferably is keyed on the main drive shaft 39 of the drying machine while the driven gear is adapted to turn loosely on said shaft, and the planet gears are journaled on a worm wheel or carrier 40 also adapted to turn loosely on the shaft 39. Tn accordance with the well known operation of difierential gears the driven gear 38 can be caused to rotate at the same speed as the driving gear or at different desired speeds relatively thereto by rotating the planet gear carrier 40 at the same or different speeds from the driving gear 36. The driven gear 38 drives the final drying cylinders 0 through suitable drive connections, such for example as bevel gears 41, 42, connecting said driven gear to a shaft 43 which is provided with a pinion 44 meshing with gears 45 which are secured to the shafts of the two lower drying cylinders G, and each of which, in turn, meshes with a similar gear 46 on one of the upper cylinders C. :The differential gearing and bevel gears connecting it to the cylinder drive shaft 43 are preferably enclosed in a suitable oil case or housing 47.

48 and 49 represent two cone pulleys arranged oppositely with their adjacent sides parallel and close together. The shaft of one of these pulleys is geared, as by gear wheels 50, 51 to the cylinder drive shaft 43 and the shaft of the other cone pulley 49 is provided with a worm 52 which meshes with the worm wheel or gear carrier 40 of the differential gearing. A belt 53 passes between and frictionally engages the adjacent surfaces of the two cone pulleys so that the pulley 49 is driven by the belt from the pulley 48 and at the same or a difierent speed, depending upon the position of the belt endwise of the pulleys. The speed of the cone pulley 49 and the connected gear carrier 40 can therefore be changed to vary the speed of rotation of the driven gear 38 of the differential gearing and the drying cylinders which it drives by shifting the belt to different positions between the cone pulleys 48 and 49. The belt is shifted for this purpose by a belt shipper 54 operated by a fluid-pressure actuated motor 55, which is preferably similar to the motors 19 for the paper-propelling rolls 1), E. This belt shipper can be of any suitable construction and operatively connected to the movable member of the motor by any suitable mechanism 56. As in the case of the motors 19, air or other fluid under pressure is supplied to the motor 55 through aperforated air escape pipe 57 This pipe is located so that the escape of air from the same is controlled by the paper web whereit passes from the drying chamber B to the final drying cylinders G. The arrangement is such that if the tension on the paper at this point increases or decreases the paper will more or less obstruct or allow the escape of air from the pipe, thereby varying the fluid pressure in the motor and causing, through the described speed. controlling mechanism a decrease or increase in the speed of the drying cylinders, so they will take the paper at the same speed that it is delivered from the drying section B and thus prevent undue tension on or injury to the paper.

While the described speed controlling mechanism enables the speed of the final drying cylinders to change as required, the cylinders are nevertheless gear-driven and the action of the mechanism is positive, the very minute changes in speed of the heavy, cumbersome cylinders can be made with great accuracy and without any slip. Furthermore, very little power is required for effecting the change in speed, since the Worm can be designed so as to have a greater or less holding or braking effect on the worm wheel or planet gear carrier and the power required for driving the worm tochange the speed of the gear carrier need only be suflicient to overcome the friction of the parts. The speed changing belt can therefore be shifted by a very slight change in pressure in the operating motor 55.

This speed controlling mechanism has been described herein as for the purpose of regulating the speed of final drying cylinders C by which the paper web is further dried after leaving the air-drying section B of the machine. Manifestly, however, the controlling mechanism could be utilized in the same way to regulate the speed of a winding or other mechanism which takes the paper from the air drying section of the machine, and it is not intended. to limit the application of the controlling mechanism to drying cylinders.

I claim as my invention:

1. The combination of propelling devices for a web, variable speed driving means for said propelling devices, and means im-' mediately responsive to all variations in the tension of the travelling web and operating automatically to regulate said driving means to change the speed of one or more of said propelling devices in accordance with changes in tension on the web.

2. The combination of-successive propelling devices for a web, variable speed driving means for said propelling devices constructed to independently regulate the speed of successive, propelling devices, and means independently responsive to all variations in the tension of the travelling web at different points and operating automatically to regulate said driving means to independently change the speed of successive propelling devices in accordance with changes in the tension of the web at such different points.

3. In a paper drying machine, the combination of propelling devices for the paper web, driving means for said propelling devices including a change speed mechanism, a fluid-pressure-actuated motor, for operating said change speed mechanism, and means controlled by the tension of the travelling web and controlling the operation of said motor to change the speed of one or more of said propelling devices in accordance with changes in tension on the paper web.

4. In a paper drying machine, the combination of propelling devices for the paper Web, driving means for said propelling devices including a change speed mechanism, a fluid-pressure-actuated motor for operating said change speed mechanism, and means for varying the fluid pressure in said motor under the control of the tension of the travelling web to change the speed of one or more of said propelling devices in accordance with changes in tension on the paper web.

5. In a paper drying machine, the combination of means for propelling the paper web, fluid-pressure-actuated means for regulating the speed of said propelling means, and means for varying the fluid pressure in said pressure-actuated means under the control of the tension of the travelling paper web to change the speed of said propelling means in accordance with changes in tension on the paper web.

6. In a paper drying machine, the combination of means for propelling the paper web, a pipe for fluid under pressure having a fluid escape opening arranged to be obstructed more or less by the travelling paper web depending upon the tension thereon, and means controlled by the variable fluid pressure in said pipe for regulating the speed of said paper propelling means.

7. In a paper drying machine, the combination of means for propelling the paper web, a pipe for fluid under pressure having a fluid escape opening arranged to be obstructed more or less by the travelling paper web. depending upon the tension thereon, a fluid-pressure-actuated motor controlled by the variable fluid-pressure in said pipe, and mechanism actuated by said motor for regulating the speed of said paper propelling means. v

8. In a aper drying machine, the combination o propelling devices for the paper web, driving means for said propelling devices including a change speed mechanism, a pipe for fluid under pressure having a fluid escape opening arranged to be obstructed more or less by the travelling paper web depending upon the tension thereon, and means controlled by the variable fluid pressure in said pipe for actuating sald t change speed mechanism to regulate the speed of said paper propelling means.

9. In a paper drying machine, the combination of successive propelling devices for the paper web, a plurality of pipes for fluid under pressure arranged adjacent to successive portions of the travelling paper web and having fluid escape openings adapted to be more orless obstructed by the web depending upon the tension on such successive portions thereof, and means controlled by the variable fluid pressure in said pipes for separately regulating the speed of said successive propelling devices.

10. In a paper drying machine, the combination of a preliminary heated drying cylinder, an air drying chamber to which the paper web is delivered from said drying cylinder, variable speed means for propelling the paper web in said drying chamber, and means immediately responsive to all variations in the tension. of the travelling web in said drying chamber and operating automatically to change the speed of said propelling means in accordance with changes in tension on the paper web in the drying chamber,

11. In a paper drying machine, the com bination of a preliminary heated drying cylinder, an air drying chamber to which the paper web is delivered from said drying cylinder, successive driven devices for propelling the paper web in said drying chamber, and means immediately responsive to all variations in the tension of successive portions of the travelling web in the drying chamber and operating automatically to change the speed of said successive propelling devices in accordance with changes in tension on such successive portions of the paper web.

12, In a paper drying machine, the combination of a preliminary heated drying cylinder, an air drying chamber to which the paper web is delivered from said drying cylinder, means for propelling the paper web in said drying chamber, means controlled by the tension of the travelling web n said drying chamber and operating automatically to change the speed of said propelling means in accordance with changes in tension on the paper web in the drying chamber, and a final heated drying cylinder to which. the paper web is delivered from the drying chamber and by which it is further dried,

13. In a paper drying machine, the com bination of a preliminary heated drying cylinder, an air drying chamber to which the paper web is delivered from said drying cylinder, means for propelling the paper web in said drying chamber, means controlled by the tension of the travelling web in said drying chamber and operating automatically to change the speed of said propolling means in accordance with changes in tension on the paper web in the drying chamber, a final heated drying cylinder to which the paper web is delivered from the drying chamber and by which it is further dried and means controlled by the tension of the paper web between said drying chamber and said final drying cylinder and operating automatically to change the speed or said neeaaee final drying cylinder in accordance with changes in such tension on the paper web.

14. In a paper drying machine, the combination of a preliminary heated drying cylinder, an air drying chamber to which the paper web is delivered from said drying cylinder, means for propelling the paper web in said drying chamber, means controlled by the tension on the travelling web in said drying chamber and operating automatically to change the speed of said propelling means in accordance with changes in tension on the paper web in the drying chamber, a driven device which takes the paper web from the drying chamber, and means controlled by the tension of the paper web between said drying chamber and said driven device and operating automatically to change the speed of said device in accordance with changes in such tension on the paper web.

15. In a paper drying machine, the combination of a preliminary heated drying cylinder, an air drying chamber to which the paper web is delivered from said drying cylinder, means for propelling the paper web in said drying chamber, means controlled by the tension of the travelling web in said drying chamber and operating automatically to change the speed of said propelling means in accordance with changes in tension on the paper web in the drying chamber, a driven device which takes the paper web from the drying chamber, a differential gear for driving said device, and means controlled by the tension of the paper web between said drying chamber and said driven device and controlling said diilerential gear to change the speed of said device in accordance with changes in such tension on the paper web,

16, In a paper drying machine, the combination of means for propelling the paper web, means for drying the travelling paper web, means for regulating the speed of said propelling means to give a desired tension on the paper web, a device which takes the paper from said propelling means, drive means for said device including a difierential gearing for changing the speed of said device, and means controlled by the tension of the paper web between said propelling means and said device and controlling said diilerential gear to regulate the speed of said device in accordance with changes in such tension on the paper web,

17. In a paper drying machine, the combination of means for propelling the paper web, means for drying the travelling aper web, means for regulating the speed 0 said propelling means to give a desired tension on the paper web a device which takes the paper from said propelling means, drive means for said device including a differential gearing for changing the speed of said gear of said differential gearing, a shiftable member for transmitting motion from said pulley to the other pulley, said other pulley being connected with said differential gearing for changing the speed of the driven gear thereof, and means controlled by the tension of the paper web between said propelling means and said device for shifting said shiftable member on said cone pulleys to regulate the speed of said device,

18. In a paper drying machine, the combination of a device for propelling the paper web, means for drying the travelhng web, drive means for said propelling device including a differential gearing for changing the speed of said device, a variable speed controlling mechanism driven by the driven gear of said differential gearing and operatively connected to the'difl'erential gear for regulating the speed of the driven gear thereof, and means controlled by the ten- I sion of the paper .weband controlling the action of said variable speed mechanism on the diflerential gearing.

19. In a paper drying machine, the combination of a device for propelling the paper web, means for drying the travelling web, drive means for said propelling deviceincluding a difl'erential gearing for changing the speed of said device, a pair of oppositely arranged cone pulleys, one of which is driven by the driven gear of said differential gearing,a shiftable member for transmitting motion from said pulley to the other pulley, said other pulley being connected with said differential gearing for changing the speed of the driven gear thereof, and means controlled by the tension'of the paper web for shifting the shiftable member on said cone pulleys to regulate the speed of said device.

20. In a paper dryin machine, the combination of driven varia le speed propelling devices forthe paper web, and means immediately' responsive to all changes in the tension of the travelling web and operating au-, tomatically to change the speed at which said propelling devices are driven in ac cordance with changes in tension on the paper web.

21. In a paper drying machine, the combination of driven variable speed propelling devices for the paper web, and means immediately, responsive to all changes in the tension of the travelling web at different points inits length and operating automatically to vary the speed at which said propelling devices are driven at different points in the length of the web in accordance with changes in tension onthe paper web at said o1n P 22. In a paper machine, the combination of a driven member which acts on the paper web, driving mechanism for said member ineluding a differential gearingfor changing thespeed of said member, a variable speed controllin mechanismdriven by the driven gear of said diflerential gearing and operatively connected to the differential gearing for regulating the speed of the driven gear thereof, and means controlling the action of said variable speed mechanism on the differential gearing for varying the speed of said member.

Witness my hand this 7th day of August,

WILLIS H. CARRIER.

Witnesses:

K. BERENSMANN, J. I. LYLE.

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