US2276613A - Apparatus for compacting materials by vibration - Google Patents

Description

G. M. GORDON APPARATUS FOR COMPACTING MATERIALS BY vIBRATIoN March 17, 1942.

Filed May 24, 1932 INVENTOR.

ATTORNEY.

Patented Mar. 17, 1.942

APPARATUS EGR CDMPACTING MIATERHALS BY VTBRATION Graham M.. Gordon, Los Angeles, Calif., assigner,

by mesne assignment Angeles, Calif., a corp s, to Viber Company,V Los eration of California Application May 24, 1932, Serial No. 613,227

5' Claims.

My invention relates to an improvedy method for compacting granular and plastic materials by imparting regulated and controlled vibration thereto, and to an improved'mechanism for accomplishing this.

In the art'of vibrating granular and plastic materials, in order to compact said masses,v there have been developed in general three classes of vibratory means, Which classes are not Wholly distinct, but overlap to some extent as will be noted in the examples given.

In the first class, methods and means of Vibration have been developed in Which not only is the granular or plastic mass` vibrated, but also the container or conning structure. In most cases, the mass of material constituting these conning structures is greater than, or at least a large part of ther total mass to be. vibrated, and the overcoming of the inertia,l and thel frictional re.-

sistances, of such large bodies results inv a most ineiicient transmission of the vibratory energy to the plastic or granular material which is desired to be compacted. In practice, the net result has usually been that only a relatively small amount of energy is exerted in vibrating the plastic or granular materials, the balance of the applied energy being dissipated as useless Work on the conning structure. As examples of this class of vibrators may be mentioned the apparatus of Priest in U. S. Patent 1,072,495 of September 9, 1913; of Price in U. S. Patent` 1,387,175 of August 9, 1921; of Pelton in U. S. Patent 1,800,401 of April 14, 1931; of Jackson in U. S. Patents 1,787,529 and 1,787,449 of January 6, 1931, No.

1,774,977 of September 2, 1930, and No. 1,751,087 i of March 18, 1930. In practice, particularly With cementitious mixtures such as concrete, the use of this method and type of vibrating mechanism has resulted in the segregation of the different materials in the mixture, particularly the Water and fine cement, i. e. the grout, which tends to move to the place of maximum vibration, (which obviously in this class is to the outside of the body or form) thus robbing the concrete in the interior of its binding agent, and weakening the nal strength of the concrete body. The use of this type of vibrating device is also restricted by the fact that since the larger partv of ther vibrational energy is absorbed by the forms or the containing structure, these forms, unlessy heavily built or reinforced are soon distorted and Weakened, entailing expensive replacements, and sometimes resulting in disastrous collapsingV of unset concrete and forms during the vibration period. The amount of vibrational energy which can be appliedl depends upon the strength, rigidity and elasticityA of the confining walls and forms, and this fact greatly decreases or restricts the amount of energy which may safely and practically be used on the cementitious mass itself. Since the energy is applied so inelliciently a, large motive unit must be employed to attain even a moderate vibrating action in the material itself, and the vibrating unit becomes heavy and unwieldy', and lacks portability.

In the second class of vibratory means are those in which a relatively small amount of energy is applied to a large mass of plastic or granula-r material in an effort to settle the particles to positions of maximum packing. The energy thus imparted is usually not great. enough to overcome the internal resistance to displacement of the particles, constituting the. mass, and hence the, action is entirely localized, and; of little avail in the accomplishment of the compaction ofthe Whole mass to be compacted. Typical of this class are those described in Pelton, U. S. Patent No. 1,747,555 0f February 18, 1930; Peltcn in U. S.

Patent No. 1,784,385 of December 9, 1930; of Atterbury in U. S. Patent No. 1,293,662 of February 11, 191-9; and of Priest in U. S. Patent No. 1,072,495 of September 9, 1913. In these devices the action consists in rapidly repeated tappings or impacts, and relatively little energy is applied; they construction is such that a substantial portion of the energy is absorbed or dissipated as heat at the points of impact. There is no tendv ency in the device itself to vibrate, and it merely moves. in response to the repeated application of a small disturbing force. In practice this method of compacting concrete and similar masses has been demonstrated to be ineffectual, Whether the device is applied within the mass or by means of tapping` the container, for the very obvious reason that only a small localized action on the particlesr of the concrete mass is realized, and the energy put to the useful Work of settling the particles to maximum density packing is extremely small.

In the third class of vibratory devices are those partly included also in one or the other of the preceding classes, in which the vibrations act in a direction essentially parallel to the earths gravitational torce, i. e. vertically. Such devices- I have discovered by practical. trials the futility ofv trying tol compact such materials as moist con-l crete by vibration in a direction essentially vertical, and believe that the small practical success of all devices restricted to this type of vibration is due to this fundamental defect. A consideration of the internal movements which must take place when a granular or plastic body is settled to the most compact form-that is when each particle is packed in the least possible space, and the interstices between the larger particles are most completely lled by properly sized and placed smaller particlesindicates clearly that a lateral movement is essential to the distribution required for maximum density; and if lateral movement is supplied by vibratory motion, the force of gravity will automatically function to displace the particles in the vertical direction as required for maximum compaction. Y

The particular objects then of my invention are to overcome the defects of the Previous means, and particularly first, to provide portable means of creating high frequency vibrations; second, to provide a method for transferring a relatively large amount of properly directed energy to a mass of granular plastic material to compact it; third, to provide a method and means for regulating and controlling the nodes, amplitudes, frequencies, and direction of vibration so that the maximum amount of energy may be imparted to the granular plastic mass to be compacted; fourth, to provide shaped tools suitably connected to the mechanism so that the vibrational energy may be concentrated at selected points within the plastic or granular masses; and

for further objects which will be apparent from the accompanying drawing and description.

In the drawing, Fig. 1 is a perspective view of one form of my vibrator; Fig. 2 is a vertical cross-section of the vibrator of Fig. 1, but with a different terminal shape; Fig. 3 is an elevation of still another form indicating an elongated flexible shaft between the vibratory member proper and the means of rotation, Fig. 4 is a horizontal section of Fig. 3 taken substantially at the line 4-4 to better show the terminal tool shape. l

Referring more specifically to the drawing, the apparatus consists of an electric motor l0, comprising a rotor II and stators I2 connected to a source of electrical energy by the lead wires i3 connected to the control or rheostat switch I4. The motor is supported and enclosed by the housing I5, to which are attached handles I5 for inserting and withdrawing the vibrator. The shaft I'I of the motor IU, is connected to the elongated shaft I9 of the unbalanced mechanism thru the flexible coupling I8. In the type of apparatus shown in Fig. 3, this flexible coupling takes the form of a long enclosed flexible shaft within a metal sheathing, I3a, which transmits the rotation of the motor to the unbalanced mechanism within the vibrator casing 20. The elongated shaft I9 is supported by bearings, preferably ball bearings, 2|, 22, 23, which are supported in place by the outer tubular casing 20. Mounted on the shaft I9 between the bearings 22 and 23 is a delicately adjusted out-of-balance weight 24 xed to the shaft by the pins 25. This weight is so designed that substantially all of its mass when at rest, is on one side of the shaft. When set in rotation, this weight gives a dynamically unbalanced condition which sets up the vibrations. The shaft I9 is held in longitudinal position by the collars 26 and 21. The tubular outer casing 20 is flexibly attached to the motor housing l5 by the flange 23, which is held flexibly by the compressible gaskets 29 placed on either side of the flange, the assembly being held in place by bolts 3| securing the plate 30 to the motor housing I5. The elongated housing 20 is terminated by a tamping tool 32, which is particularly shaped for the space in which it is to be operated. A blunt rounded form is shown in Fig. l; a toothed rake-like form is shown in Fig. 2, vmth teeth at 34; and a cross-bladed spadelke tool is shown in Fig. 3, with a cross-section shown in Fig. 4. Any desired shaped tool may be used, the attachment to the tubular housing 20 being indicated by the inside fitting sleeve 36 held in place by the pin 31.

Referring to Fig. 2, the cooperative action of the separate parts in developing vibrational energy is believed to be somewhat as follows: the motor III revolving at highl speed, acts upon the vibrator shaft I9 thru the flexible coupling I8 to revolve the eccentric weight 24. As the bearings 2l, 22, and 23 are xed to the casing 20 which is itself exibly attached to the motor housing I5, not only does the revolving shaft and weight vibrate, but another vibration is induced or set up in the outer casing 20. If the elongated housing is xed rigidly to the motor housing I5, I have found that the whole apparatus vibrates strongly. In my experimenting, I have discovered that by adjusting the size of the eccentric weight 24 with the speed of rotation, coupled with a given length of outer casing and inner shafting, and location of eccentric weight on the shaft, lengthwise, that it is possible to produce a node, or point of neutral vibrations in the complex system which is set up in my vibrator, which may be directed and localized to practically eliminate vibration in the motor I0 and/or the handles I5 of the portable machine; and may in a like manner and at the same time be adjusted to produce a maximum vibration at the tool shaped end 32 of the device, which is the portion inserted within the mass to be compacted. The motor continuously supplies energy to set up the forced vibrations in the shaft, which act upon the elastic body of the casing tube, setting up other vibrations therein. By adjusting the length of the outer casing in suitable relation to the speed of rotation, the eccentricity and location of the weight and the inertia, elasticity, friction and other forces entering into the kind of vibration of the complex system, it is possible to produce a'region of maximum vibration in the shaped end of the apparatus, and also to produce a node, or region of minimum vibration in the motor, or at the opposite end from the shaped tool.

It is believed that complex harmonic vibration is set up in the apparatus; that due to the high speed and the eccentric weight the phenomena of whirling of the shaft takes place, which sets up a vibration, thru the bearings to the outer casing and by the outer casing to the mass of granular plastic material; superimposed upon this vibration is another vibration related to the natural period of vibration of the tubular system;the sum total of all the vibrations being damped by the inertia of the surrounding mass of material being compacted. This is given as a suggestion of the explanation of the vibratory action in my device, but this attempt at anV explanation is not to be considered as a limitation of my invention, as the whole eld of vibration is none too well understood at this time.

As one example of the dimensions whichl have been found to give the type of vibration required, I may refer to Figure 2 in which the length of the steel shaft from the motor shaft is thirtysix inches; its diameter is five-sixteenths inch; the overall housing length is forty-four inches and one and three-quarters inches in diameter in the small section with wall thickness of fivethirty-seconds inch; the eccentric weight weighs two pounds; the motor is one-half horsepower and operates at five to six thousand revolutions per minute under load (i. e. in concrete mixture). The overall weight is thirty-six pounds.

Other combinations of dimensions, speeds, etc. have been found experimentally to give the desired vibrational results as above described. The actual speed of rotation may be controlled by repeatedly switching the motor off and on, or by the use of Well known electrical speed regulating devices.

The importance of superimposing the several vibrations one upon the other to provide a node at the motor end, and a maximum at the tool end, is emphasized, lbecause this device permits the use of a light weight fully portable mechanism whereas with a simple vibratory system, heavy weight in the motor or handling end would be required, in order that vibrational energy in large amount would be transferred to the tool end, and also so that the machine could be kept in control by the ope-rator.

The method of using the device is simple. After the granular plastic material has been placed Within the space to be filled, as in a form, the shaped tool end of the vibrator is inserted within the material, the motor set in rotation, lateral vibrations are produced which are transmitted to the mass in a substantially horizontal direction, causing the 'particles to vibrate and settle to maximum density, eliminating water pockets and air pockets. In the case of concrete mixes, this mechanism permits the placing in intricate forms or around intricate reenforcing metal structures, of concrete of a drier consistency than can be placed by hand operation, with a resulting greater strength in the set concrete; it being well understood in the art of making concrete, that the strength of the set concrete rises rapidly as the water content is decrease-d at the time of placing and initial setting. I have found that I may place or compact a concrete mix with my vibrator which has such low water cement ratio that the resulting set concrete is double the strength of the driest concrete mixture which can be properly placed by hand tamping.

The insert end of theapparatus, in which the vibrations are concentrated, by alterations of design and operating characteristics, may be suitably shaped for use in large masses, as shown in Fig. 1; or for long narrow spaces between confining walls as in Fig. 2; or for surfacing of shallow depths of material as in Fig. 3 and Fig. 4; or in other shapes for particular purposes, it being necessary to change slightly the dimensions and operating characteristics to focus the point of maximum vibration in the tools.

Iclaim:

1. A vib-ratory compacting device comprising a motor housing provided with handles, a motor in the housing, a dynamically eccentric weight carried by a shaft, flexible means connecting said shaft to the shaft of the motor, a ri-gid tubular housing for said weight and its shaft, said tubular housing providing bearings for the weighted shaft and being vibrated by said unbalanced weight upon rotation thereof by the motor, said tubular housing provided with an outwardly extending flange on the end adjacent the motor, compressible gaskets on each side of said flange, and clamping means carried by the motor housing for flexibly securing the tubular housing to the motor housing by clamping said flange and gaskets thereto, whereby vibrations of said shaft and its housing are absorbed by the icompressible gaskets and flexible means without being transmitted to the motor and handles.

2. A vibratory compacting device comprising a housing provi-ded with handles; a motor in the housing; a watertight tubular casing; a shaft in said casing; iiexible means connecting said shaft to the motor shaft; an eccentric weight mounted on said shaft; bearings for the ends of the weight supported in the casing whereby said casing will be vibrated upon rotation ofthe shaft; means for flexibly securing the casing to the housing; the relative'length of the casing, speed of the motor shaft, and size and location of the weight being such as to set up a complex vibration in the` tubular system consisting of that produced by the inertia of the Aweight having superimposed thereon that of the natural period of vibration of the entire tubular system to produce a node in the `casing localized adjacent the handle end, whereby vibrations of the shaft and casing are absorbed Without being transmitted to the motor and handles.

3. In a vibrator of the class described, a vibrator housing adapted to be at least partially immersed in a mass of vibratable material, vibratory means in said housing, a casing with a connection to said housing, said connection formed to maintain the axis of said housing in substantial alignment with the axis of said casing, .power operated means in said casing, power transmission means connecting said power operated means and said vibratory means within said connection, said connection damping the transmission of destructive vibrations from said housing to said casing.

4. Vibratory mechanism comprising a housing adapted to be at least partially immersed in a mass to be vibrated, a rotor having its centre of mass disposed eccentrically to itsaxis of rotation and located within said housing, a motor therefor also located within said housing, a flexible driving connection between said motor and said rotor and a flexible connection adapted to deaden vibratory motion interposed between a vibratory portion of said housing and 'said motor.

5. Vibratory mechanism comprising in combination, a housing adapt-ed to be immersed at least partially in a mass to be vibrated, means for vibrating said housing, a motor flexibly associated with said housing, a exible coupling between said motor and the means for vibrating said housing and a handle for manipulating said motor and said vibrating means.

GRAHAM M. GORDGN.

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