US2191144A - Press roll - Google Patents

Description

Feb. 20, 1940. L, HoRNBosTEL PRESS ROLL Filed Dec. 31. 1937 2 lShetS--Sheet 1 Pelo/e r Feb. 20,'1940.

L. HoRNBQsTr-:L

PRESS ROLL Filed Deve. 31, 195? 2 sheets-sheet 2 Lorb Me/vaosre-L.

` Patented Feb.V 20, 19401 l UNITED STATES PATENT OFFICE PRESS ROLL consin Application December 31, 1937-, Serial No. 182,926

4 Claims.

tain uniform contact or nip pressure ,between the rolls, it has been the practice to put most 1,5 of the crown in one of the rolls to offset against this sagging. However, since the crowning of a roll varies the diameter of the roll along its length, and since the uncrowned roll has a uniform. diameter along its length, if these two rolls Contact uniformly after sagging, as is desired, a portion of the'crowned roll at the line of contact must slip or slide relative to the uncrowned roll. Thus, if twoV rolls of a two roll press have the same diameter at their ends and one of the rolls isv crowned, the diameter of the crowned portion of the roll is greater than the diameter of the uncrowned cooperating roll. Now, if in operation, the rolls sag into full line contact with each other to give a desired nip pressure therebetween, the peripheral or lineal speed of the uncrowned roll at the nip will be uniform along its length and will correspond with the peripheral or lineal speed at the ends of, the crowned roll where the diameter is equal to the diameter of the uncrowned roll. However, the crowned portion of the crowned roll, due to its increased diameter, has a greater lineal or peripheral speed and this portion must slip relative to its cooperating portionv of the uncrowned roll. Such slippage will, of course, damage the paper web and/or felt passed between the rolls.

` In rubber covered suction press roll assemblies where only the rubber cover for the'suction roll was provided with a crown, while the top press roll was uncrowned, the rubber cover has frequently been torn loose from the suction roll at'the center of the roll. This has been due to slippage between the rolls caused by diierences in peripheral speeds between the ends and center of the crowned roll.

According to this invention, uniform nip pressure between press rolls and identical peripheral or lineal speeds along cooperating increments of the press rolls are obtained by crowning all of the rolls of an assembly to odset against deflection or sagging of the rolls, the crowning being directly proportional to the respective diameters of the rolls.

It is then an object of this invention to eliminate slippage between press rolls caused by 5 crowning onefof the rolls to offset against deflection of the assembly.

Another object of this invention is to obtain uniform nip pressures .and identical peripheral or lineal speeds at the nips between cooperat- 10 ing press rolls.

A further object of this invention is to crown cooperating rolls in peripheral pressure relation t obtain'a uniform nip pressure between the rol s and identical peripheral or lineal speeds 15 along cooperating increments of the rolls.

Other and further objects of this invention will become apparent to those skilled in the art from the following detailed description of the annexed sheet/soly drawings which disclose prel0 ferred embodiments of the invention and compare the invention with-the prior art practice.

The invention will be hereinafter specifically described in connection with *wo roll suction presses wherein the suction roll has a cooperat- 25 ing top roll. It should be understood, however, that the invention is not limited to such assemblies since it is applicable to any type ofv roll assembly irrespective of the relative positions ofy the rolls or the number of rolls in the $0 assembly.

On the drawings:

Figure l is a diagrammatic side elevational view' of a two-roll rubber covered suction press illustrating the rolls in an unsagged condition. 35

Figure 2 is a vertical cross-sectional view taken along the line II-II of Figure l.

Figure 3 is a diagrammatic side elevational view of the `suction press shown in Figure 1, illustrating the manner in which the rolls sag orv 40 deflect between their ends.

Figure 4 is a diagrammatic side elevational view, with a part broken away and shown in cross section, of a two roll suction press according to vthis invention, showing the rolls in an 45 unsagged condition.

Figure 5 is a diagrammatic side elevational view of the suction press shown in Figure 4, but with the rolls in a sagged or deflected condition.

Figure 6 is a diagrammatic side elevational 50 view of a two roll suction press according to this invention, showing the rolls in an unsagged condition and illustrating a suction roll that has only. half the diameter of the press roll.

lvFigure 7 is a diagrammatic` `side elevational 55 view of the assembly shown mmgure s but inus- `trating the rolls in a sagged condition.

form nip pressures between the rolls.

As shown on the drawings: v In Figures 1 to 3, the reference numeral I0 designates generally a suction roll having trunnions or journals I I extending from the ends thereoffor rotatably mounting the roll I in bearing supports (not shown).

As best shown in Figure 2 the suction roll III comprises a perforated metal shell I2, a-perforated rubber cover or sleeve I3 covering the shell I2 and a suction head I4 within the shell I2 and communicating through the perforations in the shell vand rubber cover I3 to define a suction area on the outside of the roll.

The rubber cover I3 is provided with a crown C as is customary to offset against deflection of the rolls of the assembly between their ends. The crown C is greatest at the center of the roll and slopes from the center toward each end of the roll to give the roll a somewhat barrel-shaped contour.

In Figures 1 to 3, the reference numeral I5 designates a metal top press roll for the suction roll III. The roll I5is uncrowned or very slightly 4 crowned, as is customary, and has trunnions or.

journals I6 extending from the ends thereof to rotatably mount the roll in bearing supports l(not shown).

v As shown in Figure 1, the roll I5 has an almost uniform diameter D across its entire length.

The suction roll Ill has the same diameter D only at the ends thereof -and due to the crowning of the cover I3, the diameter of the suction .roll I 0 at the middle of the roll will be D plus 2C or D as indicated. Assuming for the purpose of illustration that the rolls do not sag, it is obvious, as shown in Figure 1, that the rollV I5 will only contact the roll I0 at the middle of the roll I0, while the ends of the rolls will be spaced from each other.

However, as shown in Figure 3, the rolls I0 and I5 both sag or deflect between their ends due to their own weight and pressure applied to the ends of the top roll for urging the rolls together. In some special cases only the bottom roll may sag and its crown is then just suilicient to keep the axis of the top roll straight, but the effect is the same. The crown C is of such a nature to offset, against -this sagging or deflection`so that, upon sagging, the rolls will come into full line contact along their entire lengths as shown at I1 in Figure 3. This produces a desired uniform nip pressure between the rolls along the entire lengths of the rolls.

However, since the middle of the suction roll IIJ has the diameter D', or greater than the diameter D of the middle of the press roll I5 due to the crown C, the peripheral or lineal speed of the roll I0 at the middle thereof will be greater than the peripheral or lineal speed lat the middle of the roll I5. At the same time the ends of the rolls IIJ and I5 will have the same peripheral or lineal speed since theyare of equal diameter. Under these circumstances those increments of `the crowned suction roll traveling at greater speeds than theircooperating increments of the press roll I5 must slide relative'to the roll I5. It is because of such slippage, due to unequal peripheral or lineal speeds at the nip between the rolls, that the crowned rubber cover I3 for the suction roll IIlwill tear loose from the shell I2.

Further, if a web of paper is passed through the 5 nip between the rolls and one side of the web contacts a roll traveling at the same lineal or peripheral speed across its entire length while the other side of the web contacts a roll having a greater lineal speed at least along portions of the width of the web, the web will, of course, be damaged. If, in addition, a felt is passed through the nip between the rolls for supporting or carrying the web of paper as is customary in some suction presses, the felt will likewise be damaged or moved relative to the web, thereby causing a wnkling or other damage of the paper.

Thus, while `the prior art practice of placing all or practically all of the crown in one of the rolls of a press roll assembly to offset against deflection due to sagging of the rolls may give a desired uniform nip pressure between the rolls, the desired advantages of uniform nip pressures effect disadvantages because of diierences in lineal ,or peripheral speeds at the nip causing slippage between the rolls.

As shown in Figures 4 and 5 a suction roll 20 has trunnions or journals 2I at the ends thereof to rotatably support the suction roll from bearing supports (not shown). erates with the suction roll to provide a suction press assembly. The top roll 22 has trunnions or journals -23 extending from the ends thereof to rotatably support the rolls from bearing supports (not shown) al As shown in Figure 4, according to this invention both the rolls and 22 have the same diameters D at the ends thereof and are provided with the same crowns C so that the rolls have diameters D at the middle thereof intermediate their ends. Figure 4 shows the theoretical position of the rolls if no sagging occurs. As shown, the rolls only contact at the middle thereof and are spaced from each other at the ends. However, due to the sagging of the rolls between their ends, the same deect into the position shown in Figure 5 to have a uniform line contact indicated at 24, therebetween. l

As shown in Figure-4 the suction roll 20 may have a perforated rubber cover 25 on its perforated metal shell 26 and the rubber cover need only be provided with a crown.

The crowns C offset against the deflection of the rolls to produce the uniform line contact between the rolls along their entire lengths.`

Since the ends of lboth rolls have the same diameters D and since the rolls have the samel crowns C all cooperating increments of the rolls have the same diameters. For example, the diameter of the middle portions of the rolls is D as shown in Figure 5. Therefore, since all cooperating increments of the rolls have the same diameters, the peripheral or lineal speed of each roll at these increments is equal and a paper web and/or felt passing through the nip between the rolls is not only subjected to uniform nip pressure across its entire width, but is also subjected to the sainespeed of travel on both sides thereof.

As a lresult, the paper and/or felt passing through the nips of rolls crowned according to this invention will not be damaged, since no slippage occurs between the rolls. If the suction roll is` rubber covered, the rubber cover is not torn loose `from the metal shell of the roll as 'n A top press roll 22 coopme:

is thecase in the structure dened in `Figures 1 to 3.

When the rolls of the assembly are not initially of uniform diameter such as when the diameter of the suction roll is only half the diameter of the top press roll, according to this invention,

the crown on the suction roll is only half the crown on the top press roll. This embodiment of the invention is shown in Figures 6 and 7.

As shown in Figure 6, a suction roll 3l) is provided with the usual trunnions or journals 3| projecting from the ends of the roll Ato rotatably mount the roll in bearing supports (not shown). A top press roll 32 cooperates with the suction roll 30 and has the usual trunnions or journals 33 extending from the ends thereof for rotatably mounting the roll in bearing supports (not shown).

The roll 32 has a diameter D at the ends thereof and is provided with a crown C to offset against vertical deflection of the roll. The diameter of the middle portion of the roll intermediate the ends will therefore be l) plus 2C or D".

The suction roll 30 has only half the diameter of the top press roll 32. The suction roll 3l! therefore has a diameter of one-half D at the ends thereof as shown in Figure 6. The roll 3@ is provided` with a crown to offset against deflection of the roll and this crown is only one-half the size of the crown for the roll 32. The roll 30 thus has a crown one-`half C as shown in- Figure 6 and a diameter at the .middle of the roll intermediate its ends oi one-half D plus one-half 2C or one-half D' as shown.

In the assembly shown in Figure 6 illustrating the theoretical positions of the rolls if the saine did not sag, it is obvious that the rolls will only contact at the middles thereof intermediate their ends. However, since the rolls sag due to their own weights and/or pressure applied to the ends of the rolls urging the same together, the crowns C and one-half C provide for a full line contact indicated at -34 between the rolls. The crowns thus provide for anveven nip pressure along the entire length of the nip. However, since the crowns of each roll are directly proportional to the respective diameters of the rolls it follows that the peripheral or lineal speed of each cooperating incrementv of the rolls will be the same although the smaller suction roll will have an angular speed of twice the speed of the top press roll.

'Ihe suction rolls and/or top press rolls shown in Figures 4 to 7 can be plain or rubber covered. If the Arolls are rubber covered, the covers only need be crowned as shown in Figure 4.

From the above description it should be understood that this invention provides for the crown-n ing of each cooperating roll of roll assemblies wherein the rolls are in peripheral pressure relan tion with each other to oiset against deflection or sagging or the mus due to their own weights and/or pressure applied to the ends of the rolls for urging the same together.

According tothis invention the amount voi! the crown is directly proportional to the respective diameters oi the rolls. In this manner slippage between the rolls is avoided and all cooperating increments of the rolls travel at the same peripheral speed.

I am aware that many changes may be made and numerous details of construction may be varied through a wide range without departing from the principles of this invention, and I, therefore, do not propose limiting the patent granted hereon otherwise than necessitated by the prior art.

I claim as my invention:

1. A press roll assembly for paper making machines comprising a plurality of rolls in peripheral pressure relation, each roll'of said assem bly being crowned to offset against defiection and the crowning of said rolls being directly proportional to. the respective diameters of the rolls.

2. A press roll. assembly for paper making machines comprising a pair of rolls in peripheral pressure relation one of said rolls having twice the diameter of the other roll at the ends thereof, said rolls being crowned to offset against deflectionand said smaller roll being provided with haii the crown of the large roll whereby the sagging oi `the rolls in operation will bring the same into liull line contact with each other and each of the cooperating increments of the rolls will have the same peripheral speed due to the proportional crowning of the rolls.

3. A suction press comprising a rubber covered suction roll and a cooperating press roll, said rubber cover for the suction roll being crowned to offset against sagging of the suction roll and said press roll being crowned to odset against sagging of the press roll, said crowns being directly proportional to the respective dia-meters of said rolls.

4. A suction press roll assembly having uniform nip pressure and peripheral speed at the nip, comprising a perforated cylindrical suction roll, a perforated rubber cover around said roll, said cover increasing in thickness from the ends thereof to provide a crown on the roll and a crowned press roll cooperating with the rubber covered suction roll to provide a pressure nip, the amount of said crown on therespective rolls being directly proportional to the respective diameters of the rolls whereby a sagging of the rolls due to their own weight and pressures applied thereto will eifect an even pressure nip along the entire length of the rolls with each of the cooperating increments of the rolls at the nip having the w same peripheral speed.

Hmm HORNBOSTEL.

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