US2202032A - Apparatus for vibrating paper making machines - Google Patents

Description

May 28, 1940.

E. w. $MITH 2,202,032 APPARATUS FOR VIBRATING PAPER MAKING MACHINES Filed y 20. 1938 fl 1 i i 2 IE 1 1 v 4: 8

i ll 3 O l A l l; E 1 MW 1!: 3; 1: 1 10 E 1 6 j: g /6 i 3E ly a J M W Figure 1 I 5 7am? Z- INVENTOR.

Patented May 28, 1940 UNITED STATES APPARATUS FOR VIBRATING PAPER MAKING MACHINES Edward W. Smith, Melrosc, Mass., assignor to Submarine Signal Company, Boston, Mass, a

corporation of Maine Application May 20, 1938, Serial No. 209,037

10 Claims.

The present invention relates to apparatus for vibrating the wire of a Fourdrinier paper-making machine. More particularly the invention relates to such apparatus in which a compensating mass 5 is elastically connected to the vibrating portions of the Fourdrinier machine to make a vibratory system which is resonant at the desired frequency of vibration. I

In the applicant's prior United States Patents Nos. 2,070,757 and 2,070,929, both granted February 16, 1937, such resonant vibratory systems were disclosed. The latter patent relates particularly to an arrangement wherein the entire Fourdrinier section of the machine is vibrated as a whole. Here a plurality of rolls. over which the wire screen passes are journaled in a pair of so-called shake rails pivoted at the ends nearer the couch roll so that they canbe vibrated horizontally about the pivot.

In Patent No. 2,070,929 it is also pointed out that it is desirable to couple the compensating mass (through the elastic member) to one of the shake rails at the center of percussion of the machine. \With this position of the compensating mass, the stress on the pivots of the shake rails is a minimum.

On the other hand, I have found that if the compensating mass be coupled to the shake rail at the breast roll, the size of compensating mass necessary to produce resonance at the desired frequency of shake is a minimum. I

In the design of new Fourdrinier machines for vibration at relatively high speeds in accordance with my resonant systems, it is readily possible to take advantage of the above facts in order to obtain minimum size of compensating mass. I have found, however, that when attempting to apply my resonant system to a Fourdrinier machine which is already built and in service, it frequently 40 happens that the shake rails or the pivot pins or both are insuflicient in size to withstand the stresses to which they will be subjected during high frequency vibration, if the compensating weight is located at one or the other of the above location. Under these conditions, it is, of course, quite possible to rebuild the Fourdrinier machine in order to provide the necessary strength. However, such rebuilding is not only expensive in itself, but it also may mean that the machine must remain out of service for a considerable period of time. 1

As I have previously pointed out, the stress on the pivots is a minimum when the compensating mass is positioned at the center of percussion of the machine. However, the fibre stress in the shake rails can only be made a minimum by distributing the compensating mass along the rail in the same manner in which the vibrated masses are distributed in the machine proper. This is obviously an uneconomical expedient.

By means of the present invention it is possible to bring about high speed shaking of a Fourdrinier machine without incurring excessive stresses in either the rails or 'the pivots and without unduly increasing the weight of compensating weight required, while at the same time retaining all the. advantages of the resonant system.

My invention will best be understood by reference to the accompanying drawing in which Fig. 1 represents a plan view showing the arrange.- ment of the compensating weights in accordance with this mvention and Fig. 2 is a diagram of the forces applied to one of the shake rails of the machine by two compensating weights and the pivot -pin.

Fig. 1 shows a plan View of the shake section of a Fourdrinier paper-making machine incorporating the present invention. The machine consists essentially in a pair of shake rails l, 2 pivoted at 3 and 3, respectively, for horizontal vibrating motion. The rails are supported on the floor of the building or special foundation by leaf springs or the like in any suitable manner.

At the lower end of the rails as shown in Fig. 1, the breast roll 5 is journaled in suitable bearings. The breast roll is followed by a series of table rolls 6, also journaled in the rails. The wire screen 7 on which the paper is made moves over the breast roll and table rolls, as well known in the art.

This invention is concerned with the problem of vibrating or shaking the whole shake section about the pivots 3; 4 in a horizontal plane. In my Patent No. 2,070,929 I showed a single compensating weight coupled like the weight element 8 through elastic members to the shake rail preferably atthe center of percussion of the Fourdrinier. The weight and its elastic coupling member were of sufficient size to establish with the machine a vibratory system resonant at the desiredfrequency of shake. According to the present invention, however, the compensating weight is divided into at least two separate portions 8 and 9 each of proper size and coupled to the shake rail through suitably proportioned spring elements l and II, respectively.

Vibratory energy is applied to the system at the resonant frequency in any suitable manner, for example, by the shake motor I2 through the eccentric l3 and connecting rod I4 coupled to the shake rail at l at the breast roll. If desired, the

' shake motor may be placed on the same side of the machine as the compensating weights. It is usually desirable to introduce between the shake motor and the machine a device whereby the amplitude of shake, or the stroke, can readily be varied, while the shake motor is running.

By dividing the necessary compensating weight into two portions it is readily possible to remain below the safe limit of fibre stress in the rails and of side thrust on the pivots if the weights are properly proportioned. I prefer to make the compensating weight which is placed at the center of percussion of the machine exclusive of the breast roll just large enough that it will exert on the shake rail at resonance a force sumcient to balance all stress on the rail at that point, i. e., to produce zero deflection of the rail at that point. The other weight is then made of such a size that the sum of its momentum and that of the first weight is equal to the total momentum of the machine.

The size of the compensating weight at the center of percussion to give zero deflection of the rail is readily found from Fig. 2 in which one of the shake rails AB is diagrammatically illustrated as a beam supported at three points and subjected to a uniformly increasing load from A to B. The rail is pivoted at A and the breast roll is located along BC. R1 represents the reactive force exerted by the pivot pin, while R2 and R: are the forces which must be exerted by the two compensating weights we and an. R2 is at the center of percussion of the shake section of the Fourdrinier exclusive of the breast roll and is at a distance a from the pivot and a distance b from the breast roll. R3 is at a distance L from the pivot, i. e., a-l-b; in other words, at the axis of the breast r011 preferably.

The total accelerating force F required to shake the machine exclusive of the breast roll at the desired frequency can readily be found by adding together the accelerating forces required to move the several rolls and ancillary elements.

Thus

Ft EMcuc (1) where M is the mass of a given portion of the machine, e. g., the breast roll or one of the table rolls and that portion of .the rails which moves at substantially the same amplitude, at is the amplitude of the portion in question, i. e., one-half the stroke, and

I being the frequency of shake in cycles per second. At this point it may also be well to note the general equation of a resonant system having two vibrating masses M1 and M2 coupled together by an elastic element of stillness a:

R, Z A3a 10120 7L) (3) The weight of both compensating weights and the strengths of their springs must then be determined. 4

The desiredstroke of the Fourdrinler at the breast roll SP3 will have been decided upon.

The machine's stroke at the center of percussion sp will then be .where a and L are the distances from the pivot R2 2 n force/unit deflection of spring (4) SW the stroke of the compensating weight at the center of percussion, can be arbitrarily selected, as, for example, equal to the stroke of the Fourdrinier at that point or, preferably, equal to the stroke of the compensating weight at the breast roll. The latter is usually more desirable because it leads to' a smaller weight element and therefore is more economical. The stroke of the weight at the breast roll is often conveniently made the same as that of the Fourdrinier at the breast roll.

Having determined the stiffness n, the weight 102 of the element at the center of percussion can be determined from the general resonance Equation 2. In place of a, we must use the value a which we have just determined; and the masses concerned are the mass m2 of the compensating weight w: at the center of percussion and the effective mass MP2 of the Fourdrinier at that point. Thus,

The above equation considers, of course, only a portion of the resonant system, namely the a resonant system must be equal. Therefore e z= P, r or fi V a w 2 02 (120.! Hence Mr,= m2 (6) where an is the maximum amplitude of the compensating weight at the center of percussion and M3 is the corresponding maximum amplitude of the Fourdrinier S (i. e., -5 Substituting the above value of Mp into Equation 5:

E a m 115+ 2) =a w2 (7) 2 2 ar e -#2 frequency of shake, e. g., 400 to 500 shakes per' The weight of the compensating element at the center of percussion is then where g is the acceleration due to gravity.

The weight 103 of the element which is to be coupled to the shake rail at the breast roll and the stiffness 1.3 of the coupling spring remain to be determined.

We now know the mass of the compensating element at the center of percussion and hence its momentum m2oc2w. By subtracting this from the total momentum of the Fourdrinier, we obtain the momentum and hence the weight wa of the element which must be placed at the breast roll to make the entire system resonant at the desired frequency. The total momentum of the Fourdrinier is the summation of themomenta of the individual rolls and other elements of the machine, namely, EMOLOJ where M is in each case the mass of an element and on its maximum amplitude. We have then m a w (EMaw) m a w (9) whence m3=(ZM0l)'mgd2 Where Mp is the effective mass of the Fourdrinier acting in conjunction with the compensating element there. This efiective mass is unknown, but its value in terms of ms is readily found by again making use of the momentum equation:

where as is the amplitude of the compensating element at the breast roll; m3, its mass as determined by Equation 10; and (1P3 is the amplitude of the Fourdrinier at the breast roll.

Substituting this value of Mr intoEquation 12, we find the stiffness of the spring required at the breast roll to be minute. Moreover, since a considerable portion of the compensating mass is located at the center of percussion of the machine, the stress on the pivots will also be below a safe value.

' However, should a machine be found where the rail strength is still too low or should it be desirable to shake the machine at still higher speeds, it is readily possible further to divide the compensating mass and coupling springs. If in this case, for example, a third mass element were to be used, the mass element at the center of percussion should preferably remain as in the present case, that is, to give zero deflection of the rail at that point. The second mass should then be proportioned to give zero deflection of the rail at the point of its application, and the remaining mass necessary to satisfy the momentum equation should be placed at the breast roll.

It is to be understood that where the center of percussion of the Fourdrinier is referred to herein with respect to the present invention, it is with reference to the pivot and exclusive of the mass of the breast roll. v

Having now described my invention, I claim:

1. A Fourdrinier paper machine having a shake section containing a pair of shake rails pivoted at one end, means for vibrating said section comprising a plurality of separate, independently vibratable mass elements each individually coupled through elastic elements to one of said shake rails at different points, one of said masses being coupled to the shake rail at the center of percussion of the machine, the remaining mass elements being coupled to the shake rail between the center of percussion and the breast roll end of the machine, the several masses and their elastic elements being proportioned to produce with the machine a vibratory system resonant at the desired shake frequency.

2. A Fourdrinier paper machine having a shake section containing a pair of shake rails pivoted at one end, means for vibrating said section com: prising two separate, independently vibratable mass elements each individually coupled through elastic elements to one of said shake rails at different points, one of said masses being coupled to the shake rail at the center of percussion of the machine, the other mass element being coupled to the shake rail at the breast roll, both masses and their elastic elements being proportioned to produce with the machine a vibratory system res- V onant at the desired shake frequency.

3. A Fourdrinier paper machine having a shake section containing a pair of shake rails pivoted at one end, means for vibrating said section comprising two separate, independently vibratable mass elements each individually coupled through elastic elements to onev of said shake rails at different points, one of said masses being coupled to the shake rail at the center of percussion of the machine, and having a mass just large enough to produce substantially zero deflection in the rail at the resonant frequency, the other mass element being coupled through its elastic element to the shake rail between the center of percussion and the breast roll end of the machine, the two elastic elements and the second masselement being proportioned to produce with the machine a vibratory system resonant at the desired shake frequency.

4. A Fou'rdrinier paper machine having a shake section containing a pair of pivoted shake rails, means for vibrating the said section comprising a plurality of separate, independently vibratable mass elements each individually coupled by elastic members to one of said shake rails at difierent points, the sum of the momenta of all of said mass elements, being equal to the total momentum of the vibrating portions of said shake section at the resonant frequency of the system and means for imparting vibratory energy to the system at said resonant frequency.

5. A resonant vibrating system for a Fourdrinier paper machine constructed as a two-mass resonant vibratory system vibrated at its resonant frequency, one mass comprising the vibrating portions of the machine which move in phase with each other, the second mass being a compensating mass elastically coupled to the first mass, said compensating mass comprising a plurality of separated mass elements each individually coupled through an elastic element to the first mass, at

different positions, the sum of the momenta of all of said compensating mass portions being equal to the total momentum of the first mass at the res-' onant frequency of the system.

6. A resonant vibrating system for a Fourdrinier paper machine including a plurality of mass elements vibratable in phase with each other and coupled by elastic means to a plurality of compensating mass elements vibratable in phase with each other, the first group of mass elements including the shake rails pivoted at one end and the breast roll, table rolls and a Fourd'rinier wire carried thereby and the group of compensating mass elements being two in number each coupled by a separate elastic element to one of the shake rails, one mass being coupled to the shake rail at the center of percussion of the first group of mass elements and the other mass being coupled to the shake rail at the breast roll, the weight of the compensating mass at the center of percussion being such that at the resonant vibrating frequency it will exert a force on the shake rail sufficient to produce zero deflection of the rail at the point of coupling and the weight of the compensating mass at the breast roll being such that its momentum at the resonant vibrating frequency is equal to the difference between the total momentum of the vibrating portions of the Fourdrinier machine proper and the momentum of the compensating mass at the center of percussion.

7. A Fourdrinier paper machine having a shake section containing a pair of shake rails pivoted at one end, means for vibrating said section including a plurality of independently vibratable mass elements each individually coupled by elastic members toa shake rail at different points. the weights of the said elements and the strengths of the elastic members being proportioned to produce with the machine a vibratory system resonant at the desired shake frequency.

8. A Fourdrinier paper machine having a shake section containing a pair of shake rails pivoted at one end, means'for vibrating said section including a plurality of independently vibratable mass elements each individually coupled by elastic members to a shake'rail at different points, the weight of at least one of said elements and the strength of its couplingspring being such as tic members to a shake rail at different points, v

the weight of at least one of said elements and the strength of its coupling spring being such as to produce zero deflection in the shake rail at the point of coupling during vibration and further being proportioned together with the weights of the remaining weight elements and the strengths of their respective elastic coupling members to produce with the machine a vibratory system resonant at the desired stroke frequency.

10. In combination with a Fourdrinier paper machine having a shake section containing a pair of shake rails pivoted at one end, means for vibrating said section including two independently vibratable compensating weight elements of masses m2 and ma, respectively, individually elastically coupled to one of said shake rails, one at the center of percussion of the machine and the other at the breast roll through elastic members of stiffnesses 2 and #3, respectively, the said masses and stiifnesses being so proportioned that where ar- =one half maximum stroke of Fourdrinier at center of percussion az=one half maximum stroke of ma. a1= =one half maximum stroke of Fourdrinier at breast roll a3=one half maximum stroke of ma (ZMa)=S11m of momenta of all movable elements of Fourdrinier w=21rf f=one half the number of shakes per second F R (3atlOL a 7L I where

Images