US2563266A - Grinding roll mill - Google Patents

Description

' L. A. M. PENIGAULT Aug. 7, 1951 l GRINDING ROLL MILL Filed Sept. 20, 1948 v.ru d www n n f pr f w ,an l.. www ..l

Patented Aug. 7, 1951 'E'A'EES @NT OFFICE Application September 20, 1948, Serial No. 50,172 In France October 9, 1947 2 Claims. 1

The grinding roll mills used for manufacturing paints, chocolate and, in general, for the dispersion of powdery solids in uid or plastic mediums, or for making homogeneous similar matters, have, all conditions being equal, an efficiency so much the greater as the distance existing between the working rolls is smaller.

In practice, for a given machine, and whatever be the importance of the forces which can be applied on roll trunnions by tightening devices, this distance cannot be brought down below the total of the deflections shown by the rolls under the pressures exerted by the handled products.

For the purpose of reducing said deflections roll mill builders have:

(a) Increased the moment of inertia of the roll section;

(b) Decreased the roll length;

(c) Shaped the rolls, giving them a curved surface;

(d) Sloped the axles with reference to the common meridian plane of the rolls;

(e) Increased the number of the rolls in order that the bending stresses therein are added together, the roll axes being arranged in the same plane;

(f) Decreased the pressures by lowering the feed of material to be ground to the roll nip.

Notwithstanding building, machining and operating difficulties which are often very important, these means provide only approximate solutions of the problem, because it is almost impossible to reduce the distance below a few hundredths of a millimeter while the requirements for certain grindings would necessitate still smaller distances. Besides, these means frequently involve conditions diiiicult to meet, such as the necessity of Working with a constant pressure between rolls having a given convexity, in

order to obtain a constant distance along opposite generatrices.

Finally with means as above described, reactions from bearings on roll trunnions are not prevented, or may even be increased. These reactions which reach very important figures, likely in certain cases to exceed tons per bearing, leaving aside the building diiiiculties they involve, make the running of the machines the more delicate as the machining accuracy of the bearings and the thickness of lubricant lms are of the same magnitude as the distance between rolls which it is desirable to obtain and maintain. They also involve power consumptions which are entirely lost since they are produced in bearings 2 which have no action upon the matters during grinding.

It is an object of my invention to provide an improved grinding roll mill wherein the roll deflection is reduced and consequently the grinding effect is better than in mills as above mentioned, another object being to do away with the diniculties above set forth Without providing a particular shape for the rolls and Vcausing excessive loads on the roll bearings.

According to this improvement, strong thrust members are located on both sides of the grinding machine, parallelly with the axis of the roll or rolls, in the plane or near the plane in which are developed the resultants of pressures on the rolls from the products being ground and are associated with intermediary members transmitting said resultants to and along said thrust members.

These intermediary members are adjustable so that it is possible to control the reactions developed along the rolls and thus compensate for the deections which the roll or rolls would assume if they were held by the bearings alone. Between said intermediate members and the roll or rolls,

bars may be interposed for rubbing contact with the said roll or rolls. Thus, instead of having the bearings of the roll or rolls supporting the squeezing stress exerted on the products being ground,

this squeezing stress is transferred on the thrust members and distributed along their length.

A particularly advantageous arrangement is the one according to which the material to be ground is caused to pass between the generatrices of the rolls and the reaction rubbing surfaces. In that way, not only a self lubrication by the material, but also a dissipation through the material of almost the whole mechanical power delivered to the machine are obtained and consequently the eiciency of the said machine is improved.

The invention may be adopted to grinding machines or mills including any number of rolls. However it is particularly desirable to provide an even number of rolls, greater than two. In that case, the machine may be entirely symmetrical, the material supply being located between the two central rolls, and an outlet doctor being combined with each external roll, which gives a symmetrical Working in satisfactory conditions.

The following description, with reference to attached drawing given as a non limiting example, will help to Well understand how the invention may be carried into effect, the features resulting as Well from the drawing as Vfrom the text being, of course, part of said invention.

Fig. V1 is a plan-view of an improved machine constructed according to the invention and including four rolls.

Figs. 2 and 3 are elevation views at right angles with partial cross-sections.

Figs. 4 and 5 are diagrammatic cross-sections of two modications including two and three rolls.

Fig. 6 is a partial diagrammatic cross-section showing a pressure bar with a concave surface.

Fig. 7 is a partial diagrammatic cross-section of another example.

Fig. 8 is another partial diagrammatic crosssection showing a pressure bar slightly shifted with reference to the plane including the roll axis.

The machine shown in Fig. 1 to 3 includes a stationary framing body I which bears, along opposite sides ab, cd, bearings 2 receiving the trunnions 3 of grinding rolls 4. These bearings are supported in frame I on sides ab, -cd for sliding movement along these sides. In the example of the drawing, the mounting is made by a dovetail assembly, as it is shown at 5 in Fig. 3.' Parallelly with the two other sides ac and bd, that is parallelly with the roll axis, are located two strong cross-bars or beams 6, 'l which constitute the thrust members mentioned in the preamble of the present specication. Accommodated in a longitudinal groove 8 in each beam is a bar or strip 9, I0. These bars 9, IIJ are provided to come into contact along a generatrix with outside rolls and to transmit pressure forces to respective beams 6 and 1. A number of screws II distributed along the length of the beams permit to locally adjust the thrust of bars 9, I upon the rolls, when more or less screwing these screws into the beams. The latter are linked or braced together by four ties I2 simply stopped at one end against one of the beams 1 by nuts I3 and provided at the other end with hand-wheel nuts I4 permitting to adjust the tension of these ties, in order to rough down the general adjustment of the distances between rolls and between rolls and bars. This tension balances the grinding pressure which has a tendency to separate the rolls, and consequently the beams. The latter may be mounted in such a manner that they may slide along sides ab, cd, for instance by means of a dovetail joint as already speciiled for the roll bearings.

The rolls are driven by a pulley I5 and gears I6 which, in the shown example, are designed to give the same speed of revolution to both central rolls and higher speed of revolution to both outer rolls, thus generating a rubbing between central and outside rolls which improves the grinding of the thin layer of material carried round by central rolls into the nip between said rolls and the outer rolls.

The material to be ground is put at I1 between both central rolls. It is submitted to a rst grinding between these rolls, smears their surface, is submitted to a second grinding -as athin. layer between central and outer rolls, is partially carried away by the latter outer rolls, passes between outer rolls and bars 9, I0, being submitted to a last grinding, and nally is collected by symmetrical doctors I8.

The bars 9, I0 have a tendency to be deflected due to the pressure exerted by the material to be ground. This tendency is counteracted by increasing the screwing of screws Il, in order to maintain the bars in a rectilinear shape. When operating that way, the central screws should of course be screwed more tightly than outer or ,4 marginal screws. Under the pressure transmitted by the screws, the beams 6 and 1 which constitute the thrust members have their deflection increased. However the moment of inertia of their section is properly calculated in order that the elastic reaction of these beams, when being deflected, is able to support pressure stresses transmitted by the screws, while annulling the deflections of the bars. The generatrices of the roll or rolls being thus maintained rectilinear, the distances between the rolls, as well as the distances between the outer rolls and the bars 9 and l0, may be reduced as much as it is desired, in order to obtain a grinding as ne as it is required.

As the material being processed passes between bars 9 and Ill and the outer rolls, being also submitted at this place to a complementary grinding, they produce a self-lubrication which decreases the rubbing stress between rolls and bars.

It is observed that in the specified machine, instead of having the tightening stresses of the rolls supported by the bearings of the latter, these stresses are transferred to two outer bearings constituted by bars B, I0. The reactions of the bearings upon the. trunnions are reduced to the stresses required for maintaining the revolution or the rolls, and the mechanical power, supplied to the machine by the motor (not shown) driving pulley I5, is almost entirely dissipated through the material to be processed, which improves the efficiency of the machine.

Many modications of the specified device are also possible. For instance, instead of having the bearings of all rolls slidably supported, it is possible to lock the bearings of one of the central rolls (case of the right central roll in Fig. 2, where two locking keys 4a have been shown in dotted line), or of the two central rolls, the bearings of other rolls being slidably supported. It is also possible,instead of both beams 6, 'I being slidably supported, to lock one of them in a stationary position and to support the bearings for all rolls as well as the other beam for sliding movement.

Fig. 4 shows another modification of the machine the diierence of which with the examples of Fig. 1 to 3 is the number of rolls reduced to 2 instead of 4. The material to be ground is put at I'I above the gap between one of the bars 9 and one of the rolls. It passes into this gap, smears the adjacent roll, is ground again between the two rolls and partially carried round by the second roll, passes between it and bar I0 where it is ground a third time and is finally scraped off at I8.

In the case of three rolls, the arrangement may be that of Fig. 5 which it is easy to understand according to the explanation given for the above mentioned examples.

The number of rolls may also be 5, 6, etc.

Bars 9 and I0 may have their surface of contact with the rolls either plane as shown in Fig. 1 to 5, or shaped in order to facilitate the passage of the material between them and the rolls or balance, with unitary pressures which would be admissible for a satisfactory working, the imf portant stresses which have a tendency to separate the rolls and to press them upon the bars. For instance Fig. 6 shows a bar Illa which on the face thereof opposite the adjacent roll is concave with a radius proximate equal to the roll radius for increasing the surface of contact and reducing the pressures by surface unit.

The bars may be cooled or heated by passing a duid therethrough or by any other means according to the nature of the material to be processed.

Other devices may be substituted for bars 9 and I il and screws l I, in order to exert a variable pressure along the outer rolls. Instead of screws it is possible to use small hydraulic jacks acting upon the bars. It is even possible (Fig. 7) to form the longitudinal recess S in beam 'l as a iiuid chamber and for this purpose to provide it with a metal wall 25 which has its longitudinal edges embedded as shown in the flanges of beam 'l and is adapted to be moved outwardly by fluid pressure to bear against the periphery of the adjacent outer roll 4.

Fig. 8 shows another modication in which the generatrix of Contact between bar l and adjacent roll is slightly shifted with reference to the plane of the axis of the rolls, in such a manner that, considering the direction of rotation of the outside roll, the resultant R of the rubbing stress F on the bar and of the pressure of the bar upon the roll P is as horizontal as possible in order to annul the vertical component which would have a tendency in operation to pull the axis of the roll out of the plane in which it should stay, and thus attenuate objectionable deformations.

What I claim is:

l. For a grinding mill having at least one grinding roll, a thrust resisting, roll conning frame, which comprises the combination of a pair of parallel, spaced apart rigid beams having parallel, facing, longitudinal recesses and a plurality of longitudinally spaced apart apertures therethrough opening into said recesses; a longitudinally flexible, roll contacting bar arranged in each recess to be supported and guided therein for inward and outward movement; a movable push member in each aperture for contact with the correspon-ding bar; means backed from the corresponding beam for controllably moving each push member through the corresponding aperture, so as separately to control the local extent of inward projection of the corresponding bar from said beam; and means of adjustable length for tying said beams together.

2. In a grinding roll mill, the combination of a set of adj acent, parallel, grinding rolls having end trunnions, one of said rolls being adapted and arranged to be driven; a stationary framing body providing a pair of parallel slideways spaced apart by the distance between the end trunnions of each roll; a pair of bearings for the trunnions of each roll, the pair corresponding to the driven roll being fast with said framing body while the remainder of said pairs are supported for sliding movement in said slideways; a thrust resisting, roll confining frame comprising a pair of parallel rigid beams located on either side of said roll set and supported by said body for sliding movement parallel to said slideways, said beams having parallel, facing, longitudinal recesses and a plurality of longitudinally spaced apart apertures therethrough opening into said recesses; a longitudinally iiexible, roll contacting bar arranged in each recess to be supported and guided therein for inward and outward movement; a movable push member in each aperture for contact with the corresponding bar; means backed from the corresponding beam for controllably moving each push member through the corresponding aperture, so as separately to control the local extent of inward projection of the corresponding bar from said beam; and means of adjustable length for tying said beams together.

LOUIS A. L. M. PENIGAULT.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Netherlands Apr. 1,6, 1938

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