US3872919A

US3872919A - Controllable-profile roll

Info

Publication number: US3872919A
Application number: US353856A
Authority: US
Inventors: Gustav A Maag
Original assignee: Procter and Gamble Co
Current assignee: Procter and Gamble Co
Priority date: 1973-04-23
Filing date: 1973-04-23
Publication date: 1975-03-25
Anticipated expiration: 1992-03-25
Also published as: FR2226633B1; JPS5727327B2; NL7405410A; CA1027314A; DE2419172A1; GB1456740A; FR2226633A1; BE814001A; JPS5048064A; IT1011315B

Abstract

An improved, substantially solid core roll such as a mill roll having means for circulating heat transfer medium therethrough in close proximity to its working surface for effecting temperature control of the working surface. The improved roll includes means for independently controlling the temperature profile of the core so that the physical profile of the roll, including crowning of the roll surface, can be controlled independently from controlling the temperature of the working surface of the roll. Such improved rolls, when incorporated into an apparatus as one or both of a pair of rolls forming a nip, enable maintaining predetermined nip profiles under variable operating conditions. Such a predetermined nip profile is, for example, a nip having substantially uniform clearance throughout the length of the nip formed in the region where the working surfaces of the rolls are closest together.

Description

limited ttes atet Maag Mar. 25, 1975 CONTROLLABLE-PROFILE ROLL [75] Inventor: Gustav A. Maag, Fort MitchelLKy.

[73] Assignee: The Proctor & Gamble Company, Cincinnati, Ohio [22] Filed: Apr. 23, 1973 [21] Appl. N0.: 353,856

[52] U.S. Cl. 165/30, 165/89 [51] int. Cl. F25b 29/00 [58] Field of Search 165/89, 90, 3O

[56] References Cited UNITED STATES PATENTS 2,692,118 /1954 Holloway 165/90 Primary Examiner-Charles Sukalo Almrney, Agent, or Firm-Thomas J. Slone; John V. Gorman; Richard C. Witte [57] ABSTRACT An improved, substantially solid core roll such as a mill roll having means for circulating heat transfer medium therethrough in close proximity to its working surface for effecting temperature control of the working surface. The improved roll includes means for independently controlling the temperature profile of the core so that the physical profile of the roll, including crowning of the roll surface, can be controlled independently from controlling the temperature of the working surface of the roll. Such improved rolls, when incorporated into an apparatus as one or both of a pair of rolls forming a nip, enable maintaining predetermined nip profiles under variable operating conditions. Such a predetermined nip profile is, for example, a nip having substantially uniform clearance throughout the length of the nip formed in the region where the working surfaces of the rolls are closest together.

5 Claims, 4 Drawing Figures 49 6| 23 re k w 42 4| 1 K 38 52 52 39 /2 33 k, *2 2h 2* uc 33 K so 2% I t I I I 34 V 29l ELECTRICAL POWER PATENTEB AR 2 5 I975 sum 2 or 3 Fig. 4

DISTANCE FROM END OF ROLL, INCHES FIELD OF THE INVENTION This invention relates generally to providing appara tus such as mills for producing ribbons of rolled sheets of coherent doughs, millable plastics, or other materials of the same or similar rheology, which apparatus includes nip-forming rolls having their working surfaces cooled or heated by having flowable heat transfer media circulated through the rolls. Specifically, the present invention relates to controlling the physical profile of substantially solid core rolls, substantially independently from the circulation of such flowable heat transfer media for controlling the surface temperature of the working surface of the roll. Such profile control is effected by independently controlling the temperature profile of the core of the roll. By such independent temperature control of the core and the working surface of at least one roll, a predetermined nip profile such as one providing uniform clearance between the working surfaces of spaced rolls can be maintained despite variations in process variables such as pounds per lineal inch loading on the rolls. For instance, without the roll profile control afforded by the present invention, the nip clearance would vary along the length of the nip as a function ofload induced bending of the mill rolls.

BACKGROUND OF THE INVENTION Ideally, a pair of nip-forming rolls used for rolling or milling sheet or web type products such as paper, metals, plastics or dough are configured so that, when op erated, the nip clearance between such rolls is uniform throughout the axial length of the working surfaces of the rolls. To the degree that such nip clearance is uniform, the products issuing from them are of uniform thickness throughout their entire widths. Such nips having uniform clearances are ideal also for milling, grinding, or comminuting and similar physical treatments induced by passage between closely spaced roll surfaces because of the resulting uniformity of action on materials being milled by the mill rolls throughout the lengths of such nips.

Mill roll applications commonly require that the working surface of each roll which contacts process stream materials be maintained substantially at a predetermined and constant temperature to avoid detrimental effects on the materials being milled.

In actual practice, however, mill roll surfaces tend to vary in temperature and are commonly distorted from their intended right circular cylindrical shapes while operating. Such temperature variations and distortion are caused by varying heat and mechanical loads on their working surfaces resulting from variations in the materials being milled. For instance, varying the moisture content ofa dough mix greatly affects the amount of heat generated during its milling and the pounds per lineal inch loading on the mill rolls, thus affecting both roll surface temperature control and nip clearance or nip profile control.

The prior art discloses a variety of approaches for achieving predetermined roll or nip profiles by heating or cooling the working surface(s) of the roll(s) and/or by grinding the cylindrical working surfaces of the rolls(s) convex or concave. However, none of the dis covered prior art discloses or teaches how to maintain predetermined roll or nip profiles despite changes in roll deforming variables while maintaining substantially constant or predetermined temperatures on the working surfaces of the rolls. Representative prior art US Pat. Nos. include 530,094 issued Dec. 4, 1894 to Stewart A. Davis, 737,571 issued Sept. 1, 1903 to Charles W. Bray, 2,793,006 issued May 21, 1957 to LeRoy Eaby, 2,933,760 issued Apr. 26, 1960 to Elmer .I. von

der Heide, and 3,529,045 issued Sept. 15, 1970 to Nathan Rosenstein. Also, improved means for providing mill rolls having substantially constant temperature or isothermal working surfaces are disclosed in the two commonly assigned, copending applications of Gustav A. Maag and John E. Callaham entitled IMPROVED MILL ROLL", Ser. No. 316,807 and SELECTIVELY INSULATED MILL ROLL", Ser. No. 316,809 (now US. Pat. No. 3,834,205) which were concurrently filed Dec. 20, 1972. However, none of'these approaches has solved, in the manner nor to the degree of the instant invention, the problems associated with profile control of rolls which are subjected to variable conditions such as variations in pounds per lineal inch loading of the rolls.

SUMMARY OF THE INVENTION The nature and substance of the invention will be more readily appreciated after giving consideration to its major aims and purposes. The principal objects of the invention are recited in the ensuing paragraphs in order to provide a better appreciation of its important aspects prior to describing the dletails of a preferred embodiment in later portions of the present applica tlon.

A major object of the present invention is to provide an apparatus comprising a substantially solid-core roll and core temperature profile control means so that the physical profile of the roll can be controlled substantially independently from the temperature of and the heat load on the working surface of the roll.

Another major object of the present invention is providing an improved, substantially solid core roll having core temperature controlling means for controlling the physical profile of the roll substantially independently from controlling the temperature of the working surface of the roll.

Another object of the present invention is providing an improved, substantially solid core, internally cooled roll having core heating means for maintaining, despite variations in roll loading, a predetermined physical profile of the roll substantially independently from controlling the working surface of the roll at a constant temperature.

Still another object of the present invention is providing an improved apparatus comprised of at least a pair of nip-forming rolls and means for controlling the temperature of the working surface of at least one roll of said pair of rolls, in which apparatus means are provided for compensating for roll distortions substantially independently from controlling the temperature of the working surface of the roll whereby the nip formed between spaced rolls can be maintained at a substantially uniform clearance throughout the length of the nip during operation of the apparatus.

Yet still another object of the present invention is providing an improved apparatus comprising at least a pair of nip-forming rolls and means for controlling the temperature of the working surfaces of the rolls, in

3. which apparatus means are provided for compensating for roll distortions substantially independently from controlling the temperature of the working surfaces of the rolls whereby the longitudinally extending nip defining portions of the rolls can be maintained substantially straight and uniformly spaced throughout the length of the nip during operation of the apparatus.

These and other objects are achieved by providing a substantially solid-core roll and means for controlling the temperature profile of the core of the roll substantially independently from controlling the temperature of the working surface of the roll so that a predetermined physical profile of the roll can be established and maintained substantially independently from control ling the temperature of the working surface of the roll.

BRIEF DESCRIPTION OF THE DRAWINGS While the specification concludes with claims particularly pointing out and distinctly claiming the subject matter regarded as forming the present invention, it is believed the invention will be better understood from the following description taken in connection with the accompanying drawings in which:

FIG. 1 is a fragmentary, partially cut away plan view of a mill assembly embodying the instant invention.

FIG. 2 is an enlarged scale, fragmentary sectional view of the left end of the partially sectioned mill roll assembly of FIG. 1.

FIG. 3 is a fragmentary cross-sectional view of the partially sectioned mill roll assembly of FIG. 1 taken along line 33 thereof.

FIG. 4 is a composite graph of the Two Roll Total Mill Deflection vs. Distance from the end of a mill assembly like that shown in FIG. 1 under various specified conditions of operation.

DESCRIPTION OF THE PREFERRED EMBODIMENT A mill 19, FIG. 1, which is a preferred embodiment of the present invention is shown to include a substantially solid core mill roll having internal passageways 55 for circulating flowable heat transfer medium subjacent its working surface 56 for controlling the temperature of working surface 56, and core temperature profile control means 21. In the preferred embodiment mill 19, core temperature profile control means 21 comprises heater 22, slip ring and brush assembly 23, an electrical power controller 24,

conductors

25, 26, and cable 27. Mill 19 further comprises mill roll 28 which is spaced from mill roll 20 forming nip 29 of length L therebetween having clearance 29 at the center of the mill and clearance 29" at each end.

Mill rolls

20, 28 are rotatably secured to a frame for rotation by suitable drive means, which frame and drive means are not shown in FIG. 1 in order to more clearly show the essential elements of the present invention. Mill roll 28 may also comprise core temperature profile control means, but to avoid redundancy with respect to one and two roll embodiments of the present invention and embodiments wherein the core temperature profile control means 21 comprises cooling means rather than heating means, the following descriptions generally describe core temperature profile control means with respect to roll 20 only.

Briefly, core temperature profile control means 21 is provided to establish and maintain a predetermined physical profile of roll 20 substantially independently from circulating coolant through roll 20 which circulating coolant is used to control the temperature of the working surface 56 of roll 20. For instance, by applying heat to the core 57 of roll 20 from heater 22 disposed centrally of roll 20, the roll can be crowned or made somewhat barrel shape even though, be being internally cooled, it has a substantially isothermal working surface. Such controllable crowning is effective for compensating for roll distortions such as bending induced by milling forces. By such distortion compensation of either roll, a nip formed between adjacent rolls can be maintained so that the nip has a substantially uniform clearance throughout its length despite variations in milling induced bending forces and heating. Further, by such distortion compensation of both rolls of an apparatus comprising at least one pair of nipforming rolls, the longitudinally extending nip defining portions of the rolls can be maintained substantially straight and uniformly spaced throughout the length of the nip during operation of the apparatus despite variations in milling induced distortion of the rolls.

Roll 20, FIG. 1, comprises cylinder 30,

closure collars

31, 32, two each

gaskets

33, 34,

bushings

35, 36, a plurality of rods 37,

coolant couplings

38, 39, tube 40, seal 41, cap 42, and spacer 43.

Cylinder 30, FIGS. 1-3, is substantially solid and includes

integral journals

48, 49, and shoulders 50. Each journal is bored axially to provide a coolant manifold 52. Each end of cylinder 30 is provided with a plurality of radially extending holes 53 intermediate shoulder and manifold 52. Cylinder 30 also is provided with an axially extending cavity 54 through its center for accommodating heater 22 and for enabling installation and removal of heater 22. Cavity 54 is configured, with respect to the configuration of heater 22, to provide intimate contact with heater 22 when installed therein so that there is a good heat transfer path from heater 22 to cylinder 30.

Cylinder 30 of the preferred embodiment of the present invention also is provided, with a plurality of circumferentially spaced, longitudinally extending coolant passageways 55 subjacent its cylindrical working surface 56.

Cylinder 30,

closure collars

31, 32,

gaskets

33, 34,

bushings

35, 36 and rods 37 are assembled to form roll 20 in such a manner that coolant can be circulated through roll 20 by entering journal 48, then passing radially outwardly through one set of holes 53, then passing longitudinally of cylinder 30 through passageways 55 subjacent working surface 56, then passing radially inwardly through the second set of holes 53, and then exiting through journal 49. Alternatively, the flow path could be the reverse of this sequence. In this manner, the core portion 57 (hereafter core 57) of cylinder 30 is virtually enveloped by a sheath of coolant during mill operation. Such a roll assembly is disclosed in the hereinbefore referenced, commonly assigned, copending patent applications, Ser. No. 316,807 now abandoned and Ser. No. 316,809 (now US. Pat. No. 3,834,205).

Tube 40, rotary seal 41, and cap 42 are adapted to seal heater-accommodating cavity 54 from coolant passing through manifolds 52 in

journals

48, 49.

Couplings

38, 39 are provided with suitable seals to complete the assembly of mill roll 20 so that, when roll 20 is rotatably mounted and driven (by means not shown coolant can enter through coupling 38 as indicated by arrow 60 and exit through coupling 39 as indicated by arrow 61 or the reverse thereof.

Heater 22 of the preferred embodiment of the present invention is about half the length L of the working surface of roll 20. Heater 22 is electrically powered, has a tubular shape and is installed in cavity 54 of cylinder 30 so that it is symmetrically disposed with respect to working surface 56. Spacer 43, which may be an integral part of cap 42, is provided so that heater 22 is properly positioned in cavity 54 when the right end of heater 22 abuts the left end of spacer 43.

Referring to FIGS. 1 and 2, electrical power is applied to heater 22 through power controller 24,

conductors

25, 26, slip ring and brush assembly 23 and cable 27.

Slip ring and brush assembly 23 provides the necessary electrical connections between the stationary elements (i.e., power controller 24, and conductorsv 25, 26) of the core temperature profile control means 21, and cable 27 and heater 22 which rotate with roll 20.

In the preferred embodiment of the present invention, power controller 24, which is amenable to being incorporated in an automatic control scheme, is pro vided to enable adjusting, as necessary, the electrical power delivered to heater 22 in order to maintain a uniform clearance of nip 29 throughout its length L to compensate for changes in the distortion of mill roll 20 precipitated by milling variables.

In operation, coolant is conducted through mill roll 20 at a fast enough rate to maintain working surface 56 substantially isothermally at a predetermined temperature which temperature is dependent on the properties of the material being milled. Then, substantially independently from the rate of coolant flow or the heat flux between working surface 56 and the walls of coolant passageways 55, power controller 24 is adjusted to increase or decrease the heating of core 57 to accentuate or reduce respectively the crown of roll 20 as necessary to compensate for variations in mill roll distortion. In this manner, the clearance ofnip 29 can be maintained substantially uniform throughout its length L despite milling variations.

For instance, if the moisture content of a potato flour dough mix is reduced, such reduction precipitates an increase in the pounds per lineal inch loading on

rolls

20, 28. Such increased loading bends the rolls so that the clearance 29 at the center of nip 29 becomes greater than the clearance 29" at the ends of nip 20. Thus, nip 29 becomes somewhat double convex in longitudinal cross section. To compensate for such distortion of nip 29, power controller 24 is adjusted to increase the power delivered to heater 22 to sufficiently heat core 57 until roll 20 becomes sufficiently crowned to offset the load induced bending of both

rolls

20 and 28 whereupon the clearance of nip 29 is restored to a substantially uniform state.

By also providing core temperature profile control means for roll 28, the amount of compensation required can be divided between

rolls

20 and 28. If core temperature profile control means is provided for both rolls, the nip therebetween can be maintained with a substantially rectangular longitudinal cross section whereas, if core temperature profile control is provided for only one roll of a pair of nip-forming rolls, the nip therebetween may, under some conditions, have an arcuate longitudinal cross section. Although nips having either arcuate or rectangular longitudinal cross sections or clearances are believed suitable for plastic or flexible materials such as ribbons of rolled sheets of coherent dough, it is believed that rectangular longitudinal nip cross sections are more suitable for apparatus for processing, forwarding, or drawing materials such as metals and glass.

Referring now to FIG. 4, the curves, which are discussed below, illustrate the effectiveness of the present invention for controlling the crown of a mill roll so that a sheet of dough issuing therefrom is of substantially uniform thickness across its full width. Such uniform thickness. of a sheet is beneficial because, for instance, it improves the uniformity of articles produced therefrom.

The mill from which the data for the curves of FIG. 4 were obtained comprises two rolls comprising right circular cylinders like cylinder 30 approximately twenty-five inches in diameter having a working surface about forty-one-and-one-half inches long which cylinders are fabricated of AISI-4340I-I (steel) forgings. One of the rolls comprises a centrally disposed heater 22 having a three-quarter inch diameter and a twenty inch length, which heater 22 is rated to dissipate a maximum of thirty-three hundred watts. When the data for FIG. 4 was obtained, the mill was operated to produce a sheet of potato-flour dough having a nominal thickness of ten-thousandths of an inch with four-thousand pounds per lineal inch loading.

Curve 101 shows the theoretical combined deflection of the mill rolls which is the change in the clearance of nip 29 under four-thousand pounds per lineal inch loading. This loading would cause clearance 29' at the center of the nip to be about one-thousandth of an inch greater than clearance 29 at the ends of the nip. Although the absolute magnitude of such deflection is small in a forty-inch mill, the variation in nip clearance is a not insignificant ten percent of a nominal ten mill nip clearance.

Curve 102 shows the actual total change in nip clearance or deflection, without core heating, of the mill rolls under actual operating conditions with a heat load of about fifty-thousand to about sixty-thousand BTU per hour. The curve reflects the combination of thermal and mechanical distortion.

Curve 103 shows the compensating effect on the clearance of nip 29 resulting from heating the core 57 of one roll with a heater 22 dissipating about fifteenhundred watts.

Curve 104 represents the net effect of

curves

102 and 103 which shows that core heating substantially compensates for the thermally and mechanically induced roll distortions shown by curve 102.

As previously stated, loading on rolls of dough mills is greatly affected by changes in moisture content of the dough mix. Were the moisture content of the dough mix increased above the level prevailing when the data for FIG. 4 were taken, curves 101 and 102 would reflect less distortion which in turn would require less heater power for compensation, and vice versa.

Although it would be theoretically possible to grind a one-half-thousandths of an inch crown in both rolls, or alternatively a one-thousandths of an inch crown in one roll to provide a mill having :a uniform clearance nip under the conditions stated above, such machining is difficult and expensive. Moreover, such an approach would provide a uniform clearance nip at essentially only one constant value of loading and heating. It

would not provide variable and controllable compensation means for maintaining a substantially uniform clearance nip over a range of transient operating conditions as is provided by the present invention.

Although the preferred embodiment of the present invention described herein comprises a mill roll, it is not intended to thereby foreclose calender rolls, and other single or two roll apparatuses from the scope of the present invention. Also, although the preferred embodiment comprises a single cylindrical-shape electrical heater 22 disposed centrally of core 57 and extending axially thereof in order to achieve a variable crown roll profile, other roll or nip profiles are achievable through the use of the present invention as by distribut ing a plurality of controllable heaters or coolers through roll and independently controlling them to establish the required core temperature profile.

While particular embodiments of the present invention have been illustrated and described, it will be obvious to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention. It is intended to cover in the appended claims all such changes and modifications that are within the scope of the invention.

What is claimed is:

1. In an apparatus comprising a rotatably mounted substantially solid-core roll having a cylindrical working surface and means for controlling the temperature of said working surface, the improvement comprising means for controlling the temperature profile of the core of the roll substantially independently from controlling the temperature of said working surface, said means for controlling the temperature profile being dis posed radially inwardly from said working surface and said means for controlling the temperature of said working surface whereby the physical profile of the roll can be controlled substantially independently from the temperature of and the heat load on the working surface of the roll.

2. In an improved, substantially solid-core, roll having passageways for flowable heat transfer media disposed subjacent the working surface of the roll and means for circulating flowable heat transfer media through said passageways to control the temperature of said working surface, the improvement comprising core temperature profile control means disposed radially inwardly from said passageways for establishing and maintaining a predetermined physical profile of said roll substantially independently from circulating flowable heat transfer media through said passageways.

3. In an improved, substantially solid-core roll having passageways for flowable heat transfer media disposed subjacent the working surface of the roll and means for circulating flowable heat transfer media through said passageways to control the temperature of said working surface, the improvement comprising core temperature profile control means for establishing and maintaining a predetermined physical profile of said roll substantially independently from circulating flowable heat transfer media through said pasageways, said core temperature profile control means comprising heating means disposed centrally of said core and means for varying the heat output from said heating means.

4. In an improved, substantially solid-core roll having passageways for flowable heat transfer media disposed subjacent the working surface of the roll and means for circulating flowable heat transfer media through said passageways to control the temperature of said working surface, the improvement comprising core temperature profile control means for establishing and maintaining a predetermined physical profile of said roll substantially independently from circulating flowable heat transfer media through said passageways, said core temperature profile control means comprising a tubular electric heating element extending axially of said roll and means for varying the electrical power dissipated by said element.

5. The improved roll of claim 4 wherein said heating element extends axially about one-half the axial length

Claims

1. In an apparatus comprising a rotatably mounted substantially solid-core roll having a cylindrical working surface and means for controlling the temperature of said working surface, the improvement comprising means for controlling the temperature profile of the core of the roll substantially independently from controlling the temperature of said working surface, said means for controlling the temperature profile being disposed radially inwardly from said working surface and said means for controlling the temperature of said working surface whereby the physical profile of the roll can be controlled substantially independently from the temperature of and the heat load on the working surface of the roll.

5. The improved roll of claim 4 wherein said heating element extends axially about one-half the axial length of said core.