US2200724A

US2200724A - Means for producing gyratory motion

Info

Publication number: US2200724A
Application number: US121077A
Authority: US
Inventors: Samuel D Robins
Original assignee: Individual
Current assignee: Individual
Priority date: 1937-01-18
Filing date: 1937-01-18
Publication date: 1940-05-14
Anticipated expiration: 1957-05-14

Description

May 14; 1940. s. D. ROBINS MEANS FOR PRODUCING GYRATORY MOTION Filed Jan. 18, 1937 3 Sheets-Sheet 1 INVENTOR SAMUEL 0. ROB/N5 y 1940- s. D. ROBINS 2.200.724

MEANS FOR PRODUCING GYRATORY MOTION Filed Jan. 18, 1937 SShetS-Sheet 2 FIG. 4.

INVENTO BY :2 a

ATTORNEY R l SAMUEL 0. ROB/NS y 1940- I s. D. ROBINS 2.200.724

MEANS FOR PRQDUCING GYRATORY MOTION Filed Jan. 18, 1937 3 Sheets-Sheet 3 ,INVENTOR SAMUEL 0. ROB/N8 Y'ATTORNEY Patented May 1 9 UNITED STATES PATENT OFFICE MEANS FOR PRODUCING GYBATOBY MOTION This invention relates to an improved means of imparting a gyratory movement to a freely suspended body or a body otherwise supported for movement in a gyratory path. A particular application ofthe invention is the production, by the improved means, of a gyratory motion in a screen used for screening coal, stone and the like.

An important feature of the invention is the 10 production of a gyratory motion through a noncircular orbit. This is especially useful in connection with screens.

Heretofore screens have ordinarily been given .either a so-called straight line, reciprocatory motion or a circular, gyratory motion. Each of these has certain advantages over the other. A 'reciprocatory screen has the advantage of more rapidly advancing the material along its surface. However, in doing this there is the danger that material of a size that should pass through the openings of the screen will not do so because it is not presented to any of the openings in quite 'the right way. A gyratory screen having a circular motion has the advantage of causing the lumps of material, particularly the larger ones, to turn or roll over as they progress and thus they are presented in a variety of different positions to the successive openings. This effects a very good separation of themateri'al into the'desired classifications. However, a gyratory screen of this type willadvance the material only very slowly unless it is disposed at a fairly steep angle to the horizontal. not always available to bring about a'desired feeding action.

By imparting a non-circular, substantially elliptical, gyratory motion to a screen the combined advantages of a reciprocatory and circular. motion are obtained. A very rapid feeding action is obtained with the screen surface arranged horizontally and at the same time the gyratory motion tends to turn or rotate the lumps so that a very good separation between the different sizes iseffected. For uniform and most satisfactory results the motion of the entire screen should be uniform, i. .e., all portions of the screen should describe the same path. A special object of the invention has been to provide particularly simple but effective means for producing a smooth, uniform, non-circular or elliptical, gyratory motion of a screen or other body. This, I accomplish by freely supporting the screen for movement in all directions and imparting to it the effect of aresultant force which is constantly changing in direction and Suflicient head room is magnitude applied at its center of gravity. If the resultant force applied at the center of gravity of the screen were indicated as vectors radiating from a point, representing the-center of gravity, a line connecting the ends of the 5 vectors would indicate the path or orbit traced by every point on the screen, and this, according to the present invention, would be substantially in the form of an ellipse. Such a resultant of constantly changing direction and magnitude w may conveniently be produced by imparting to the screen a rotating force of constant magnitude and at the same time imparting to the screen another force designed to work against and partially counteract or modify the rotating force as m the latter passes through its cycle. This may be accomplished in avariety of different waysI .The constant rotating force may most easily be created by the rotation of .a mass about a point removed from its center, the mass being carried 2% in a suitable way by the body to be gyrated. The modifying force may be created in a simple way, by a non-rotating inertia mass arranged to increase the inertia of the body or its resistance to movement to a greater extent in certain 26 directions than in others. Or the modifying force may be imparted byianother rotating massof appropriate magnitude and in suitable relation to the first rotating mass to-provide the desired resultant effect at the center of gravity 30 of the body. In the preferred arrangement the desired gyratory motion is brought about through the rotation, in opposite directions, of masses of different magnitude or otherwise capable of establishing centrifugal forces of different magnitude. The masses may be arranged to apply their centrifugal forces to the screen or other body directly at the center of gravity of the latter or at points removed from such center but so se- 40 lected that no moments will be set up about said center. The two masses should be rotated at the same speed to insure a desired synchronous relation between them and their relation should be such that their centrifugal forces at certain in- 45 stants are created along the same or parallel lines so as to be directly combined in their effects at a chosen angle to the horizontal. For exampic, I have found that a very desirable screening ,action is produced by a substantially elliptical so motion, the major axis of which is disposed at an angle of about 40 to the horizontal. This may be accomplished by a pair of counterrotating forces if the forces are coincident or parallel and combined along the desired 40 line 66 and are coincident or parallel and opposed along -the forces, their sums determining the major axis and their differences the minor axis of the elliptical path or orbit. However, it is not generally convenient to apply the centrifugal forces to a screen directly at the center of gravity or directly in line with such center at opposite sides of the screen. This is for the reason that a shaft extending through the screen at this point will ordinarily fall in or near the path of travel of the -material to be screened; Accordingly, a special feature of the invention is the provision of an arrangement by which rotating forces of unequal magnitude may be applied to the screen, or other body, at points removed from its center of gravity and in such a way that a uniform motion will be imparted to all parts of the screen. This I preferably accomplish by establishing certain definite relationships between a pair of revolving masses and the center of .gravity of the body to be gyrated. The masses are mounted on the body and impart their centrifugal forces to the body at their centers of rotation, these being spacedfrom the center of gravity of the body at distances inversely proportional to the magnitude of the centrifugal forces. The unequal centrifugal forces created by the revolving masses are at times directly .combined and at other times directly opposed while between these two conditions they have components that combine and components that oppose each other,

and the net effect is the resultant of the'two moments are created about this center.

. away to show in Other objects, features and advantages of the invention will appear from the detailed description of an illustrative form of the same, as applied to a screen structure, which will now be given' in conjunction with the accompanying drawings, in which:

Figure 1 is a side elevation of a screen embodying the invention, a portion being broken section certain of the operating devices.

Figure 2 is a front elevation of the screen with a portion broken away to disclose the operating devices.

Figure 3 is a diagram illustrating the relationship between certain forces created by the operating devices at one instant in the operation of the screen. I

Figure 4 is a diagram resolving the forces of Figure 3 and showing the resultant thereof.

Figure5 is a view similar 'to Figure 3, showing the forces existing at a different instant in the operation of the screen.

Figure 6 is a similar force diagram indicating the relationship of the .forces after they have passed through 90 from the position indicated in Figure-5.

Figuresf to 11, inclusive; are schematic views indicating a variety of different. arrangements -applying counter-rotating forces to a freely,

views showing mcansfor. imparting an elliptic motion to a screen through the usof one or more inertia masses, and

Figure 16 is a diagram illustrating the orbital path of ,each and .every point on a screen operated. in accordance with Figures 7 to' 15, inclusive.

Referring now to the drawings, and more particularly Figs. 1 and 2, there is shown a screen structure including a frame I0 adapted to receive a gyratory motion of the improved type.

This frame maybe of any suitable construction,

and, by, way of example, may be provided with a pair of screening surfaces H and I2 extending horizontally across the same throughout the length of the frame. The screen elements If and 12 may be of any suitable construction and may be secured to the frame in any convenient manner.

Adjacent each of the four corners of the frame there is provided a supporting spring l3 which at its upper end is engaged by a bracket l4 bolted or otherwise secured to the side of the frame. At its lower end each spring engages the top of a suitable support I 5 secured to an appropriate foundation, the members l5 and the foundation constituting a main supporting .frame. The springs l3 are preferably quite soft and readily compressible so that the natural period of vibration of the springs and supported mass will be low. This will preventany danger of undue ina good insulation against the transmission of vibrations from the live frame to thesupporting structure. As indicated, each spring, if desired, may be ,formed in two sectionshaving a thin plate inserted between their abutting ends.

The devices for impartinga gyratory movement to the screen frame arecarried by a housing l6 which extends across the top of the frame and is supported by the latter. It may be secured to the frame in any suitable way, as by means of brackets ll extending I inwardly from the .slde walls of the frame and plates I8 extending upwardly from the outer faces of these walls. Housings l9 and 20, at the opposite ends of the housing l6, provide bearings I90 and 200 for a pair of shafts 2| and 22, which extend across the top of the frame If] within the housing l6. These housings l9 and 20, which are firmly secured to the frame l0, furthermore, enclose inter-meshing gears 23 and 24 secured to. the opposite ends of the shafts 2f and-22. A pulley 25 secured to an extension of the shaft 22 is connected by a belt 26 with apulley 21 carried by the shaft of a motor 28, or is otherwise connected with a suitable source of power.

A bar 29 of appropriately chosen mass extends full distance between the shaft bearings. This bar may be secured to the shaft in any suitable way, as by means of bolts 30. Similarly, a bar 3| extending'longitudinally of the shaft 22jmay be secured thereto by means of bolts 32. As best indicated in Figure 1, the

bars

29 and 3| are of different sizes in cross-section, 'so as to provide longitudinally of the shaft 2| substantially the masses of different magnitude-adapted to be revolved, respectively, about -the axes of the'shaf'ts 2| and 22. The gearing 23, '24 is such that the two shafts-will rotate at the same angular speed but in opposite directions. they'are rotated, I

axis of rotation., Thus, if Bdesignates the centrifugal forces will be developedwhich for of the shaft 22 and E designates the center of the mass 3|, the centrifugal force will always be radially outward along the line BE, the direction of which is, of course, constantly changing. Similarly, if C designates the axis of the shaft 2| and G designates the center of the mass 29, an outward, radial force will be created along the line CG in the course of rotating the shaft 2|. For reasons to be presently explained, .a definite, angular relationship should exist between the lines BE and CG. Assuming that the center of gravity of the frame l together with'the superposed operating mechanism, all of which constitutes what may be designated thedive frame, is

located at the point designated A in Fig. 1, the

masses

29 and 3! should be so located that when a straight line may be drawn through the points A, B and E, a straight line may similarly be drawn through the points A, C and G. This 9 means that when the centrifugal force created by one of the. masses passes directly through the center of gravity, the centrifugal force created by the other mass will do likewise. Another relationship which should exist between the parts is 5 that the distance from A to B should be to the distance from A to C as the centrifugal force produced by the bar 29 is to the centrifugal force produced by the bar 3|. In other Words, these centrifugal forces should be inversely proportional (I to the distances of the centers of rotation of the massesproducing them from the center of gravity of the frame structure. In the construction illustrated, the centers of the two masses are equally distant from their axes of rotation, i. e., the distances BE and CG are the same. Accordingly, the masses themselves are inversely proportional to the distances of their axes of rotation from the center of gravityof the frame. In lieu of selecting masses of different magnitude, the

0 distance from B to E might be made greater than the distance from C to G so that the centrifugal forces created by masses of equal magnitude and rotated at the same speed would be inversely proportional to the distances from the points of aps plication of these forces to the center of gravityof the frame.

. As a specific example of a construction which I have found to be quite satisfactory, the

masses

29 and 3| may be in the ratio of 3 to 4 and the an distances AB and AC should then also be in the ratio of 3 to 4. Assuming now that the masses are being rotated in opposite directions at an appropriate speed, say 1100 R. P. M., the forces existing at an instant when the points A, B and 55 E are aligned are illustrated in Figure 3. Here the force created by the mass 3! is indicated by arrow Fb while the force created by the mass 29 is indicated by the arrow Fc. Since these forces pass directly through the center of gravity of m the frame, it will be apparent that no turning moment will be applied to the frame and the effect will be merely to impart a translational movement to the entire frame. This movement will be in proportion to the resultant of the two 15 forces. Referring to Figure 4. wherein the forces are indicated on a larger scale, the resultant is designated by the arrow Fr. Its magnitude is nearly but not quite the maximum that is applied to the screen. I Fig e 5 indicates diagrammatically the direction a magnitude of the forces when their resultant is greatest. This is whenthe two forces are acting in the same direction along parallel lines. Considering the typical construction mentloned above, in which the two forces Fit and Fe arms of the forces Fb and Fe with respect to the center of gravity A are in the ratio of three to four and, therefore, the product ofone force 'times its moment arm will be the same as the product of the, other force times its moment arm, and there will be no turning moment created about the center of gravity of the body. The resultant force tending to impart bodily movement to the screen will be at its maximum, 1. e., the

, sum of the two forces or seven units. In arriving at the positions indicated by Fig. 5 the centers E and G of the masses 3| and 29 will have turned from the positions indicated in Figs. 1 and 3 through half of the angle BAC. Accordingly, this maximum force created under the conditions indicated in Fig. 5'will be in a direction parallel with the line AD (Figs. 1 and 3) which bisects the angle BAC. Very good screening results will be obtained if this line is disposed at an angle of about 40 to the horizontal, although this may be varied considerably'to suit particular requirements.

The relation of the forces after a rotation of' the

masses

29 and 3| through an angle of 90 from the position indicated in Fig. 5 is shown diagrammatically in Fig. 6. Inasmuch as the masses are rotating at the same angular velocity, the magnitude of the forces will remain the same, i. e., force-Fb will continually remain at four units and the force Fc. will remain at three units, Moreover, the moment arm of the two forces will remain in the same relation and the forces will tend to create turning moments of I equal magnitude in opposite directions about the center of gravity of the .frame. Accordingly,

,there will be no tendency for the frame to rotate i have a magnitude equal to the difference between the two. forces. In the typical example illustrated, this resultant will be one unit.

Any number of force diagrams may be drawn to indicate the relationbetween the two rotating forces at points intermediate those indicated in Figs. 3, 5 and 6. It will be found in all cases that the turning moments about the center of gravity of the body are balanced and if the resultants of the two ,forces with respect to this center are plotted and a line is drawn through the ends of the arrows, it will be found that a substantially elliptical configuration will be produced, the major axis of the ellipse being seven, units in length and the minor axis being one unit. Since the screen frame 10 is supported for relatively free movement in all directions. it will be apparent that the constantly changing resultant, changing not only in direction but in magnitude, will impart a corresponding change in the move ment of the frame- After the frame has been set into motion at the desired speed, it will be found to follow through a smooth, substantially elliptical, gyratory path, Whose major axis is in the direction AD. As previously stated, the motion so produced has been found ideally suited for the screening of coal. stone and the like. It'will 1 and 2', are also maintained. 'll

Accordingly, movement of the screen along this major axi will have little or no effect upon the tension of the belt. At the same time the movement of the screen along the minor axis is so small that it is readily permitted by the belt and I does not appreciably interfere with the drive of the belt.

' A more uniform action of the screen is insured if the upper ends of the springs l3, i, e., the points at which they support the screen frame, are in a plane passing substantially through the center of gravity of the frame.

In a typical unit constructed in accordance with the foregoing, the screen frame together vs 'th v the gyrating mechanism mounted thereon may weigh, say, one ton. The

masses

29 and 3! may suitably be about 75 pounds and 100 pounds, respectively. When these are rotated at a speed of about 1100 R. P. M. an elliptical motion having a major axis slightly under half an inch and a minor axis of about of an inch will be produced. The masses may be rotated in either direction but I have found that most efficient screening will take place if the rotation is such as to produce a motion of the screen frame counter to the movement of the material along its surface. This means that if the material advances from right to left in Figure 1, the mass 29 should be revolved counter-clockwise and the mass 3| clockwise. I have found that the rate of advance of the material along the screen is substantially the same, i. e., about four feet in five seconds, whether the masses are rotated as specified (Sr in the opposite directions. However, the separation of the material is markedly more efficient when the motion of the screen is counter to the movement of the material than when it is in the direction of this movement.

Referring now to Figures '7 to 15, inclusive,

there is illustrated schematically a number of modified constructions for accomplishing substantially the same result, i. e., the production of a uniform, substantially elliptic motion. In 'each of these modifications the arrangement is such as to produce an elliptic motion of the type illustrated in Figure 16, with its major axis inclined at an angle of about 40 to the horizontal in the direction indicated. The ratio of major to minor axis may, however, be .varied in each case tosuit the particular requirements. In Figure 7 there is shown a'slightly different arrangement particularly suited for use at points at which a smaller amount of head room is available. The screen frame 40 in lieu of being supported from below, may be resiliently suspended from above by means of a series of soft springs- 4|, one at each corner of the frame, having a very low natural period. A pair of

shafts

42 and 43, mounted in suitable bearings secured to the under side of the frame, are geared together by means of gears 44 for rotation in synchronism. The shafts may be driven ,in any suitable way, as by 'means of a pulley secured to one of the shafts and a belt connecting it with a source of power in the manner shown in Figures 1 and 2. A mass 45 on the shaft 42 and a mass 46 on the shaft 43 are revolved in opposite directions to create forces of unequal magnitude radially outward from the axes of the respective shafts, these forces being inversely proportional to the distances of the shaft axes from the center of gravity of the frame. The other relationships, explained in connection with the forces in Figures Should it be desired to provide an elliptic motion having a smaller ratio between the major and minor axes, the arrangement shown in Figure 8 may be adopted. The screen 50 may be resiliently supported or suspended by soft springs 5|. A pair of shafts 52 and 53, mounted on the frame, are disposed along the line 54 which extends through the center of gravity of the frame at an angle of 40 to the horizontal or whatever other angle is chosen as the major axis of the elliptic motion. Itis readily possible with this arrangement to produce an ellipse having a five to one ratio betweenthe major and minor axes without incurring too high tooth velocities on gears 55 connecting the shafts. Thus, the axis of shaft 52 may be two units removed from the center of gravity of the frame while the axis of shaft 53 may be three units removed from said center. Masses 56 and 51, secured to the shafts 52 and 53, respectively, will then be in the ratio of three to two and they will be so positioned above or below the frame or one above and one below, as shown. They should of course. be so disposed that the line bisecting the angle formed between lines connecting the axes of the shafts with the center of gravity of the frame will be in the direction desired for the major axis of the elliptic motion. When the shafts are arranged as shown, the shaft 63 will be disposed along the minor axis of the ellipse. As

in the prior constructions, the centrifugal forces produced by the masses 66 and 61 should be inversely proportional to the distances of the axes of the shafts 6| and 62 fromthe center of gravity 68 of the frame. This arrangement might readily be utilized to provide a three to one ellipse by adopting a two to one ratio between the masses.

In Figure 10 there is schematically shown an arrangement in which the unequal masses H and 12 are revolved about the center of gravity of the frame 10. These masses may, if desired,

, both extend longitudinally of their concentric shafts. However, this will necessitate the pro-' vision of a large tube 'as the shaft for the outer mass, suflicient to allow the inner mass to rotate within it. Accordingly, I prefer to mount one of the masses, preferably the smaller mass 12,

at'each of the ends of a shaft 13 and the other or larger mass H either'at the ends of or distributed along the hollow shaft 14. surrounding shaft 13. Any suitable gearing maybe employed to connect the shafts I3 and 14 for synchronous v rotation in opposite directions. For example, as

best shown in Figure 10a, gears 15 and 16 of the same diameter secured to the ends of the shafts l3 and 14, respectively, may be connected by a bevel pinion 11 rotatable in a suitable bracket 18 secured to the side .of the frame 10. Either shaft may be driven through a belt and pulley drive of the type shown in Figures land 2.

This arrangement allows conveniently for any desired form of elliptic motion since the' masses may be of any chosen magnitude. In fact, they may be readily replaceable or interchangeable so thatellipses of different ratios between major and minor axes may be produced.

A variation of the Figure 10 arrangement is shown in Figure 11. Here, one mass M is mounted upon a shaft 82 carried by the frame 80 atits center of gravity. In lieu of a single second mass of different magnitude from mass 8|, a pair of equal masses 83 and 84 are provided, these having acombined mass different from, preferably greater than, the mass 8|. All three of the masses are rotated at the same speed by gearing 85, the masses 83 and 84 being driven in the same direction andmass BI. in the opposite direction; The axes about which the masses 83 and 84 are revolved are at equal distances on opposite sides of the center of gravity of the frame; accordingly they provide equaland opposite moments about the center of gravity and there is no tendency to rotate the frame.

The masses may be of any chosen magnitude to providean elliptic motion of desired proportions. They maybe disposed either along the shafts or simply at the ends, depending upon the need for conserving vertical space. in this type of construction extend along the shafts of a multi-deck screen, it is necessary to increase somewhat the spacing between the decks to allow for the free passage of the material along the lower deck without interference with the revolving masses.

The foregoing are some of the variations that may be made to provide elliptic motion through the use of counter-rotating forces. It will be apparent that a variety of other modifications may be madeinvolving different combinations of the various features disclosed and other variations will suggest themselves to those skilled in the art.

Means not involving counter-rotating forces may also be employed to produce the desired elliptic motion. In the form schematically shown I in Figure 12, for example, no rotating mass whatever is employed. The screen 90, suspended by means of soft springs 9I at the four corners,has a rotating shaft 92 extending transversely of the screen through its center of gravity. An eccentric 93, secured -to the shaft adjacent its end, coacts with a strap portion of an arm 94. Adjacent its free end thearm 94 is secured to an inertia mass 95 which extends across the top of the screen and'is suspended from any suit: able support by means ofa spring96. Arm 94 preferably extends through the center of the end of the mass and this mass, preferably, has a lift magnitude substantially equal to that 'of the frame 90. A second or auxiliary mass 91 of considerably smaller magnitude, say about 10% of the mass 95, is slidable along the arm 94 and may be locked in any adjusted position by a set-- a screw or in some other convenient way. It will be understood that the arrangement of eccentric, arm and auxiliary mass is duplicated at the opposite side of the screen so as to provide balanced forces at the two sides.

Now, as the eccentric 93 is rotated, the screen frame and the inertia mass 95 will be alternately forced apart and drawn together. 91 were omitted, this'would result in a substantially straight-line reciprocation of the screen frame in the direction of the arm 94. However, the mass 91 induces a considerable deviation from a straight-line motion, the ratio of the longitudinal to the-transverse movement varying with the magnitude and position of'the mass 91. If the mass is relatively close to the shaft 92,

When the masses If the massit will be apparent that a considerable relative movement perpendicular to the arm 94 will take place upon the rotation of the eccentric. The portion of this movement that will be taken by the mass itself and the portion that will be taken by the screen will depend upon the relative weights of the nass and screen. As the mass 91 is shifted along the arm 94, further away from the shaft 92, the relative motion between the mass and framein the direction of the minor axis of the ellipse is decreased and hence the part of this motion that is taken up by the frame is correspondingly smaller. Moreover, the portion of the total, relative -movement in the direction of the minor. axis that .is taken by the frame de-- motion produced may be varied to suit the particular requirements, either by changing the I magnitude of the mass 91 in relation to the mass 95 or by changing the position of mass 91 in relation to the axis of rotation of the eccentric and the center of mass 95. Simply by way of illustration, let, us assume that the two masses 91 combined are of half the magnitude of the mass 95 and the combined weight of all of the masses is equal to that of the frame 90. Let us also assume that the masses 91 are arranged substantially at. the eccentric, i. e., atthe center of gravity of the frame. The movement of the frame in a direction along the arm 94 will in that case be equal to the eccentricity of the eccentric since the total, relative movement be-- tween the frame and masses in this direction will be equally divided between them. Ina direction at right angles to this, on the other hand, only the masses 91 will oppose the free movement of the eccentric and since these masses are only onethird the weight of the frame, the movement of the frame in this direction will be only about transversely through thescreen along its center of gravity and is rotated in any convenient way, as by means of the belt and pulley drive shown in Figures 1 and 2. An eccentric I03 is secured to the shaft I02 adjacent each end and cooperates with the strap portion of an arm I04, the upper free end of which is secured to the end of an inertia mass I05. 4 The latter is similar to the mass 95 and is suspended from some fixed support by means of a spring I06. A mass I01 is bolted or otherwise secured to the shaft I02, preferably in the manner of the masses 29 and 3I of Figure 1. If desired,- however, a pair ofseparate masses may be'provided, one at each end of the shaft and secured thereto in any convenient way. In thejoperation of this form of the invention, the eccentric I03 will tend to produce a straight-line movement of the screen in the direction of the arm I04, the extent of this movement depending upon therelative weights of the screen and mass I05 and the throw of the eccentric. If the screen and mass are of equal weight,

the throw of the screen, as a result of the ro-- tation of the eccentric alone, would be, equal to the eccentricity of the'member I03. However,

. the'actual movment of the screen will .be modified by the rotating mass I01 to an extent de-, pending upon the centrifugal force created by this mass. Its effect will be added to that of the eccentric in the direction of the arm I04 so,

that the extent of movement along this-line will be greater than if the mass were omitted. At

the same time,however,' the rotating mass will I "impart to the screen a motion transverse to the length of the arm I04.

Accordingly, it will be seen that an elliptical motion will be produced and the ratio of the major to the minor axis of the ellipse will depend upon the magnitude of the centrifugal force created by mass I01 and by the magnitude of the inertia mass I05. An ellipse of substantially any desired proportions may be produced in this way. In a typical unit in which the frame I weighs a ton, the mass I may be, say, l000pounds and the mass I01 may be acting against the inertia mass I05, the direction of the major axis of the ellipse will be at right angles to the arm I04 rather than along this arm. This condition is illustratedin Figure 14,

in which the mass 17a is indicated as of considerable magnitude. In this construction the mass 905 and the eccentric tend to restrict the movement of the screen in the direction along the armto an amount less than the movement which the rotating mass would of itself tend to impart to the screen. For this purpose the typical. unit specified above for Figure 13 might be modified to provide a somewhat smaller inertia mass M511 and to employ a rotating mass of, say, 200 pounds.

A still further modification is illustrated in Figure 15. Here the desired motion of the screen is derived from the use of a single rotating mass and one or more inertia masses having pivotal connection with the live frame. The screen or other body 0, as before, is supported or suspended by means of soft springs III, one arranged at each of the four corners of the frame.

A shaft IIZ extending transversely of the screen passes through the center of gravity. A mass H3 is secured to this shaft and develops a suitable centrifugal force for gyrating the screen upon revolution of the shaft at an appropriate speed. At each side of thescreen there is provided a pair of arms H4 connected pivotally with the screen at points H5, arranged in the same plane as the center of gravity of the screen and spaced equal distances from the center of gravity. At-their upper ends the arms II4 are secured to inertia masses H6 suspended from any suitable support by means of springs I". It

will be apparent that as the mass I I3 rotates,-

it will impart substantially its full effect to the screen along the'line H8 whereas in a direction transverse to this, i. e., parallel with the arms N4, the centrifugal force of mass H3 will be opposed by the inertia of the masses 6. N0 turning moments will be applied to the screen due to the fact that the mass 3 acts upon the screen directly at its center of gravity while the inertia masses impart their retarding effects along parallel lines. and in the same direction at ints equally spaced from the center of grav-v rty and on opposite sides thereof. It is assumed, of course, that the inertia masses H6 will be of equal magnitude so that the retarding forces will be equal.

It will be clear from the foregoing that the path of movement of the screen II 0 will be elliptical and the ratio-of the major to the minor axis of the ellipse. will depend upon the relation between the Weight of the live frame and the sum of the Weights II6.' The larger the masses H6 in proportion to the weight of the frame, the greater will be the ratio between the major and minor axes of the ellipse. In lieu of providdepends, of course, upon the magnitude of the inertia force produced by the mass H3.

The term primary force as used herein and in the appended claims is defined as a force applied through, or in conjunction with, an external source of power as distinguished from mere reactive forces. For example, the rotating masses and the inertia masses in conjunction with positively driven eccentrics apply primary forces to the suspended body. The suspending means apply merely reactive forces.

In connection with all of the forms of the in-' vention which have been merely schematically illustrated, it will be understood that the various devices shown will be duplicated at the two sides of the screen frame wherever required or desirable to provide a well balanced structure.

tating masses provided adjacent the ends of a shaft, eccentrics, and the various arms-connecting the inertia masses with the screen frames.

While a variety of diiferentconstructions, ca-

screen -or similar body along an elliptical path, have been described in considerable detail, it will be understood that numerous other modifications than those specifically suggested may be made without departing from the general principles and scope of the invention. The terms and expressions employed herein have been used stantially elliptical motion to all portions of said body, said means'comprising eccentrically mountnitude mounted onsaid body.

3." In apparatus of the class described a main ed oppositely rotating masses of unequal magframe, a body supported by said frame, and means for imparting a uniform substantially This applies, for example, to the supporting springs,

the gearing between counter-rotating shafts, ro-

.pable of imparting a gyratory movement to a elliptical motion to all portions of said body,

said means comprising eccentrically mounted,

oppositely rotating masses of unequal magnitude carriedby said body, the axis of rotation of said masses being substantiallyat the center of gravity of said body.

4. In apparatus of the class described a main frame, a body, resilient means for supporting said body from said frame, and means for imparting a uniform substantially elliptical mo tion to all portions of said body, said means comprising a plurality of masses mounted on said body to revolve in opposite directions, said masses being of different magnitude and revolving about difierent axes eccentric to the centers of gravity of the masses.

5. In apparatus of the class described a main.

frame, a body, resilient means for supporting said body from said frame, and means for imparting a uniform substantially elliptical motion to all portions of said body, said means comprising a plurality of masses mounted on said body to revolve in opposite, directions, said masses being of different magnitude and revolving about different axes eccentric to the centers of gravity of the masses and to the center of gravity of said body.

6. In apparatus of the class described a main frame, a body, resilient means for supporting said body from said frame, and means for imparting a uniform substantially elliptical motion to all portions of saidbody, said means compris-' ing a plurality of masses revolving in opposite directions, said masses being of diiferent magnitude and revolving about different axes eccentrio to the centers of gravity of the masses and to the center of gravity of said body the mag nitude of said masses being inversely proportional'to the distances between their axes of rotation and the center of gravity of the body.

'7. In apparatus of the .class described a main frame, a body, resilient means for supporting said body from said frame, and means for im-' parting a uniform substantially elliptical motion to all portions of said body, said means comprising 'a plurality of masses revolving in opposite directions, said masses being of different magnitude and revolving about different axes eccentric to the centers of gravity of the masses and to the center'of gravity of said body, the magnitude of said masses being inversely proportional to the distances between their axes of rotation and the center of gravity of the body,

said masses being rotated at the same speeds and each having its axis-of rotation at the same distance from its center of gravity asthe other. 8. In apparatus of the class described a main frame, a body, resilient means for supporting said body from said frame, and means for imparting auniform substantially elliptical motion to all portions of saidbody, said means comprising a plurality of masses revolving in opposite directions, said masses being of different magnitude and revolving about different'axes eccentric to the centers of gravity of the masses and to the center of gravity of said body, the magnitude of said masses being inversely proportional to the distances between their axes of rotation and the center of gravity of the body, said masses being rotated at the same speedsand each having its axis of rotation at the same distance from its center of gravity as the other, the arrangement of said masses being such that when a straight line passing through the axis of rotation and the center of gravity of one mass tive to apply resultant forces at the center of gravity of said body such as to produce a uniform, substantially elliptical motion at all points of said body.

10. In apparatus of the class described a gymtory body, means for resiliently supporting said body, means'for imparting a constantrotating force to said body about a substantially horizontal axis, and means for imparting a second force to said body to modify the effect of said first mentioned force, said two force imparting means. being constructed and arranged to apply a resultant force to said body of constantly changing direction and magnitude.

11. In apparatus of the class described a gymtory body, means for resiliently supporting said body, and a plurality of means for imparting I constantrotating forces of different magnitude to said body at different points, the forces rotating about substantiallyhorizontal axes, said force imparting means being constructed and arranged to apply a resultant force to said body of constantly changing direction-and magnitude.

12. In apparatus of the class described a gymtory body, means for resiliently supporting said body, and means for imparting a plurality of forces to said body substantially at the center of gravity thereof, the forces rotating about substantially horizontal axes, the resultant of said forces being of constantly changing magnitude and direction; 13. In apparatus of the class described a gymtory body, means for resiliently supporting said body, rotating means for imparting a force to said body, and'inertia means connected with said body, said rotating means and said inertia means being so constructed and arranged as to impart to said body the effect of aforce constantly changing in direction and magnitude applied at the center of gravity of the body. V

14. In apparatus of the class described a gymtory body, means for=supporting said body for gyratory movement, and means for imparting to said body at a pair of points spaced different distances fromthe center of gravity thereof rotating forces of constant magnitude, said forces being of unequal magnitude and inversely proportional to the distances of the points of application from the center of gravity of said body.

15. In apparatus of the class described a 'gyra-' 'torybody, .means for supporting said body for gyratory movement, and means for imparting to said body at a pair of points spaced different distances from the center of gravity thereof rotating forces of'constant magnitude said forces being of unequalmagnitude and inversely proportional to the distances of the points of application from the center of gravity of said body, and said forces being rotated in synchronism in opposite directions and being alined with said said body at a pair of points spaced different distances from the center of gravity thereof rotating forces of constant magnitude, said forces being of. unequal magnitude and inversely proportional to the distances of the points of application from the center of gravity of said body, and said forces being rotated in synchronism in opposite directions and, being alined with said center of gravity at the same' instant, a line bisecting the angle between said forces when alined with the centerof gravity of said "body being disposed at an angle of about 40 to the horizontal.

17. In apparatus of the class described a gyratory body, means for supporting said body for gyratory movement, means for imparting to said body at substantially the center of gravity thereof a force of constant magnitude but continually changing in direction through a,predetermined cycle, and means for imposing a greater inertia force in opposition to said force in certain directions than in others.

18. In apparatus of the class described a gyra-.

tory body,- means for supporting said body for gyratory movement, means for imparting to said body at substantially the center of gravity thereof a force of constant magnitude but continually plurality of points for a free gyratory motion,

means for imparting a constantly rotating force of invariable magnitude to said body, and means for imparting a modifying force to said body at a point removed from said plurality of points to produce a uniform, substantially elliptical motion at all points of said body.

20. In apparatus of the class described a gymtory body, means for supporting said body for gyratory movement, a shaft extending through said body at its center of gravity, an eccentric mounted on said shaft, an inertia mass freely suspended adjacent saidbody, an arm connected with said mass and having a strap surrounding said eccentric, meansfor rotating said shaft and eccentric to produce relative movement between said body and massin the direction of said arm, and means for inducing movement ofsaid body in a direction transverse to said arm.

21. In apparatus of the class described a gyratory body, means for supporting said body for gyratory movement, a shaft extending through said body at its center of gravity, an. eccentric mounted on said shaft, an inertia mass freely suspended adjacent said body, an arm connected with saidmass and having a strap surrounding said eccentric, means for rotating saidsh'aft and eccentric to produce relative movement between said body and mass in the direction of said arm,

and an auxiliary mass adjustably mountedon said arm.

22. In apparatus of the class described a gyratory body, means for supporting said body for gyratory movement, a shaft extending through said body at its center of gravity, an eccentric mounted on said shaft, an inertia mass freely suspended ,adjacent said body, an arm connected with said mass and having a strap surrounding said eccentric, means for rotating said shaft and eccentric to produce. relative movement between body throughout.

' gyratory movement, a shaft extending through said body at its center of gravity, a mass secured to said shaft for rotation therewith, inertia mass means suspended for free movement adjacent said body, and means connecting said body with said inertia mass means.

24. In apparatus of the class described a gyratory body, means for supporting said body for gyratory movement, a shaft extending through said body at its center of gravity, a pair of shafts parallel with said first mentioned shaft extending through said body on opposite sides of said first mentioned shaft and spaced equally therefrom, means for rotating said shafts at the same speed, the shafts of said pair rotating in the same direction and opposite to the rotation of said first mentioned shaft, and a mass secured to each of said shafts for rotation therewith, the masses secured to the shafts of said pair being of equal magnitude.

25. In apparatus of the class described a gyratory body, means for supporting said body for gyratory movement, and means for imparting a uniform, substantially elliptical movement to all portions of said body, said last mentioned means comprising a plurality 'of parallel shafts mounted on said body in a plane passing through-the centerv of gravity thereof, means for rotating said shafts, and a mass secured to each of said shafts for rotation therewith.

26. In apparatus of the class described a gyratory body, means for supportingsaid body for gyratory movement, and means for imparting a uniform, substantially elliptical movement to all portions of said body, said last mentioned means comprising a plurality of parallel shafts mounted onsaid body in a plane passing through the center of gravity thereof, means for rotating said.

shafts, and a mass secured to each of said shafts for rotation therewith, said shafts being rotated in opposite directions and said masses being of unequal magnitude.

27. In apparatus of the class described, a gym tory body, softly resilient means for supporting said body for free gyratory motion, and means separate from saidsupportingmeans comprising moving masses connected to said body whose dynamic effect imparts resultant force to said body in such changing direction and magnitude as to produce a substantially uniform and substantially elliptical motion of the body throughout.

8. In apparatus of the class described a gyratory body, instrumentalities for supporting said' body for gyratory motion, and mechanism separate from said instrumentalities connected with said body for producing a substantially uniform and substantially elliptical motion of the body throughout.

29. In apparatus of the class described a gymtory body, instrumentalities for supporting said body for gyratory motion, and mechanism separate from said instrumentalities including a rotating member and a moving mass and connected with said body for producing a substantially uni- I form and substantially elliptical motion of the SAMUEL D. ROBINS.,