US3870238A

US3870238A - Sand fracturing apparatus and method

Info

Publication number: US3870238A
Application number: US334695A
Authority: US
Inventors: George L Sellars
Original assignee: Dravo Corp
Current assignee: Dravo Corp
Priority date: 1973-02-22
Filing date: 1973-02-22
Publication date: 1975-03-11
Anticipated expiration: 1992-03-11

Abstract

A sand fracturing machine for breaking coarse grain of sand into smaller grains. The machine includes an open topped container having a bottom wall with circular openings therethrough. Rods of steel or other suitably hard material are located in the box and are supported by the bottom wall. Sand containing grains of many different sieve sizes is introduced into the container through its open top which falls on top of the rods. A vibration mechanism connected to the container is operative to vibrate the container in a substantially vertical direction. The sand sifts downwardly between the vibrating rods and out through the openings in the bottom wall of the container. As the larger grains pass between the vibrating rods, however, they are fractured by the rods to create smaller mid-size grains while the smallest grains sift between the rods unaffected. Consequently, the machine is operative to produce a sand aggregate with a different grain size distribution from that of the sand put into it which principally has a greater percentage of mid-size grains than found in the sand placed into the machine.

Description

United States Patent 11 1 1111 3,870,238 Sellars Mar. 11, 1975 SAND FRACTURING APPARATUS AND Primary Examiner-Roy Lake METHOD Assistant E.\'aminerE. F. Desmond [75] Inventor: George L. Sellars, Cincinnati, Ohio Attorney Agent or Fmn w0od Herron & Evans [73] Assignee: Dravo Corporation, Pittsburgh, Pa. [57 ABSTRACT [22] Filed: Feb. 22, 1973 A sand fracturing machine for breaking coarse grain of sand into smaller grains. The machine includes an [211 App! 334695 open topped container having a bottom wall with circular openings therethrough. Rods of steel or other [52] US. Cl 241/27, 241/DIG. 10, 241/175 suitably hard material are located in the box and are [51] Int. Cl. B02c 17/14 supported by the bottom wall. Sand containing grains [58] Field of Search 241/D1G. 10, 27, 63, 175; of many different sieve sizes is introduced into the 106/97 container through its open top which falls on top of the rods. A vibration mechanism connected to the [56] References Cited container is operative to vibrate the container in a n- STATES PATENTS substantially vertical direction. The sand sifts downwardly between the vibrating rods and out through the 'f 2392 openings in the bottom wall of the container. As the larger grains pass between the vibrating 'rods,.how-

FOREIGN PATENTS OR APPLICATIONS ever, they are fractured by the rods to create smaller 485,969 5/1938 Great Britain 241/175 mid-size grains while the smallest grains sift between OTHER PU BLICATIONS Nordberg, Bror, Sand for Wolf Creek Dam, Rock Products, Dec. 1968, p. 102.

the rods unaffected. Consequently, the machine is operative to produce a sand aggregate with a different grain size distribution from that of the sand put into it which principally has a greater percentage of mid-size grains than found in the sand placed into the machine.

9 Claims, 6 Drawing Figures SAND FRACTURING APPARATUS AND METHOD BACKGROUND OF THE INVENTION This invention relates to a sand fracturing machine for producing a sand aggregate having a more uniform grain size distribution than is normally found in sand removed directly from gravel pits and especially including more grains in the mid sieve size range.

In the field of concrete manufacture, it is highly desirable to have a sand aggregate which includes sand grains of varying sizes. Furthermore, it is equally desirable to have a distribution of grain sizes within the aggregate which approximates a uniform distribution whenever a concrete with a very fine finish is desired.

Typically, however, sands removed from most gravel pits contain uneven distributions of grain sizes. Specifically, the percentage of sand grains which are large in size (sieve sizes greater than No. 30) frequently comprises a large proportion of the raw aggregate. Similarly, sand having a grain size which is very small (sieve sizes less than No. 50) also comprises a very large percentage of the raw material removed from such gravel pits. Consequently, the percentage of sand grains in the mid-size range comprises a lower percentage of the aggregate than is desirable in fine finish concrete. As a consequence, the typical raw sand removed from most gravel pits has a very uneven distribution of grain sizes and is especially lacking in mid-sized grains. When such sand aggregates are used in concrete, for example, the lack of mid-sized grains precludes a substantially uniform mixing of the sand aggregate with the sand binder so that the surface of'the concrete after the binder sets is not very smooth. As such, the typical raw sand from such gravel pits is not well suited for use in concrete where a very smooth surface is desired.

In an attempt to overcome the problem associated with the lack ofmid-sized grains in typical sand, various types of grinding and crushing machines have been used. However, these machines have produced too large a percentage of fines and have not given the uniform distribution of grain sizes desired in the end product. The grinding action has not been selective in the sense that the mid range of grain sizes is preserved. All grains of the sand have been subjected to crushing action. Thus, these grinding machines have not been successful in providing an aggregate with a greater percentage of mid-size grains of sand than is normally found in sand removed directly from a gravel pit.

In view of the foregoing difficulties in providing sand aggregates having the desired grain size distribution, it is a primary objective of this invention to provide a method and apparatus suitable for producing from available sand aggregates a new aggregate which has a grain size distribution suitable for use in fine finish concrete.

It is a further objective of this invention to provide a sand fracturing machine for breaking large sized grains in available aggregates to produce at its output a new aggregate having a significantly higher percentage of grains in the midsize range than in the aggregate introduced into the machine.

It is still a further objective of this invention to provide a sand fracturing machine that breaks the large sized grains in a typical sand aggregate to produce an aggregate at its output having a significantly higher percentage of mid-sized grains without significantly increasing the percentage of small sized grains in the aggregate.

These and other objects of this invention are generally provided by the sand fracturing machine described herein. The machine includes an open topped container which has an apertured bottom wall to permit output sand to pass freely therethrough. The machine includes a plurality of elongated, cylindrical rods which are disposed within the open topped container with at least some of the rods being directly supported from below by the apertured bottom wall. The box itself is supported by a vibrating support which is operative to vibrate the lower portion of the box in a substantially vertical direction. Raw sand from a typical gravel pit is introduced into the machine and the vibrator turned on. As the open topped container is vertically vibrated, the sand sifts downwardly through the vibrating rods and ultimately passes out through the bottom apertured. wall. The vibration of the rods is operative to break large grains of sand between the rods as the sand sifts downwardly therethrough while passing the smaller grains. Since the broken grains have a smaller size than the original grains, the apparatus is operative to produce a large number of mid-sized grains at its output by cracking the larger sized grains of the input aggregate into smaller grains.

To produce a sand aggregate which has a substantially uniform distribution of grain sizes throughout, the output sand from the machine is then combined with a typical raw sand aggregate from a gravel pit to produce a sand aggregate with a greater percentage of sand grains in the mid grain size than in the original gravel pit aggregate without significantly changing the percentage of sand grains in either of the large or small grain size.

These and other objects, advantages and features of this invention will become more clear from the following detailed description of a preferred embodiment taken in connection with the drawings'which form a part of the original disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a partially cut-away perspective view of the sand fracturing machine of this invention;

FIG. 2 is a vertical sectional view along the longitudinal axis of the machine;

FIG. 3 is a vertical sectional view taken along another axis of the machine;

FIG. 4 is a vertical sectional view taken through a segment of the bottom wall of the machine;

FIG. 5 shows schematically the operation of the machine;

FIG. 6 shows schematically various sand aggregate distributions.

DETAILED DESCRIPTION Briefly, the present invention relates to a sand fracturing apparatus which includes an open topped container for receiving sand aggregate from a typical gravel pit. This open topped container includes a bottom apertured wall with openings therethrough to permit output sand to freely pass therethrough. Disposed within the open topped container are a plurality of elongated rods generally made of a very hard material such as steel which are disposed with their longitudinal axis substantially parallel to the bottom wall and with at least some of these rods resting directly on the bottom wall. A vibrator is provided to vibrate the open topped container and the rods disposed therein in a substantially vertical direction to thereby permit the sand which is introduced into the open topped container to sift downwardly through the vibrating rods and eventually fall through the apertures in the bottom wall. By selecting the rate of vibration, the size and number of rods and even the size of the apertures in the bottom wall, the distribution of grain sizes in the sand aggregate leaving the machine can be significantly changed from the distribution of grain sizes in the sand that is introduced.

The sand that falls through the apertured bottom wall of the container may itself be used for certain types of concrete, however, for extremely smoothed surfaced concretes the output sand is combined normally with sand directly from the gravel pit to provide a combined sand aggregate with a more uniform distribution of sand grain sizes.

Referring now to FIG. 1, a preferred sand fracturing machine is shown in perspective and partially cut-away. The machine is generally supported on a rigid support frame which typically comprises a number of steel beams welded or otherwise rigidly connected together to form a rigid support for the movable portions of the apparatus. Rigidly mounted on and supported by the support frame 10 is a drive motor 12 which provides the motive power for the vibratory motion of the machine. The motor 12 is typically an electric motor having a rotary drive shaft 14 to which a pulley 16 is affixed. For the preferred embodiment of this invention, the pulley 16 includes two circumferential beltengaging grooves so that the rotary drive power can be transmitted via two drive belts 18 from the pulley 16 to the driven pulley 20. A belt shroud 22 supported by the support frame 10 is provided to protect workers from possible breakage of a drive belt 18 as well as to protect workers from accidentally coming into contact with the rotatingpulleys l6 and or the moving drive belts 18.

In a preferred embodiment of this invention, the motor 12, the pulley l6 and the driven pulley 20 are arranged so that the driven pulley 20 will rotate at approximately 510 revolutions per minute when driven by the motor 12. It will be clear to those of skill in the art, however, that different rotary speeds of the driven pulley 20 may be employed by apparatus of the type characterized by this invention to thereby provide different vibrational frequencies.

The driven pulley 20 is affixed to a drive shaft 24 so that both the driven pulley 20 and the drive shaft 24 have a common axis of rotation 26. The drive shaft 24 is rotatably mounted at one end 25 to the support frame 10 by a bearing 28 and a bearing support 30 which is rigidly affixed to the support frame 10. The other end 32 of the drive shaft 24 engages a second bearing 34 supported by a second bearing support 36 which itself is rigidly affixed to the support frame 10. This end 32 of drive shaft 24 has an axis of rotation 38 which, if extended, coincides with the axis of rotation 26 for the other end 25 of drive shaft 24. Disposed between the

ends

25, 32 of the drive shaft 24 is a support shaft 40 which comprises a solid cylindrical body preferably formed of steel or other hard and strong material and has an axis of rotation 42. The support shaft 40 is rigidly connected to the drive shaft ends 25 and 32 by welding or other suitably strong connection in a manner so that the axis 42 of the support shaft 40 is displaced from though parallel to axis 26 and 28. Consequently, the support shaft 40 is eccentrically connected to the drive shaft ends 25 and 32 so that when the drive shaft 24 is driven in rotary motion about the axes of

rotation

26 and 38, the support shaft 40 rotates eccentri' cally about the drive shaft axes. In the preferred embodiment of this invention, the axis 42 of the support shaft 40 is displaced from the drive shaft axes 26, 38 by approximately one-quarter inch.

Rotatably secured to the shaft 40 is an open topped container which includes two end walls 44 which are disposed in parallel spaced relation and supported on the support shaft 40 by two bearings 46 which are located in the end walls 44 substantially near the uppermost part thereof. The end wall 44 in the preferred embodiment of this invention comprise a rigid planar body of steel or rigid strong material approximately one-half inch thick.

Disposed between the two end walls 44 are two side walls 45 formed of the same material as the end walls 44 and located between the end walls 44 in parallel spaced relation to thereby provide a container whose upper opening and lower opening is substantially rectangular in shape. Removably mounted to the lowermost edges of the end walls 44 and the side walls 45 is an apertured bottom wall 48 which includes a plurality of apertures 50 extending completely through the bottom wall 48. Like the side walls 45 and the end walls 44, the bottom wall 48 is preferably formed of a strong planar material, such as a one-half inch steel plate, through which the apertures 50 have been made. The bottom wall 48 is preferably removably attached to the end walls 44 and the side walls 45 by a plurality of nuts and bolts 52 which secure the bottom walls 48 to the outwardly extending flanges 54 of the end walls 44 and the side walls 45. Since the bottom wall 48 is removably attached to the end walls 44 and the side walls 45, the bottom wall 48 may be readily removed and replaced by another bottom wall having apertures of different size and number from the bottom wall removed from the open topped containers.

Extending downwardly from the apertured bottom wall 48 are a plurality of rib-like bottom wall strengtheners 56 which are preferably made of steel or other suitably strong material, and are welded or otherwise rigidly affixed at their upper end to the lower surface of the apertured bottom wall 48. Disposed at opposite ends of support ribs 56 are supporting end walls 58 which include outwardly extending flanges 60 in juxtaposition to the flanges 54 through which the nuts and bolts 52 also extend to thereby rigidly secure the support walls 58 to the side walls 45 and end walls 44. It will be clear to those of skill in the art that the support ribs 56 and the support end walls 58 may be formed in numerous other ways while still maintaining adequate support for the bottom wall 48.

Referring briefly to FIG. 4, the apertures 50 in the bottom walls 48 are shown in greater detail. Each of these apertures 50 includes an upper opening having a circular diameter 62 and a lower opening having a circular diameter 64. Sloping side walls 66 connect the upper opening with the lower opening. Since the upper opening has a diameter 62 which is preferably smaller than the lower diameter 64, the aperture 50 through the bottom wall 48 is frustoconical in shape and advantageously provides an aperture in the bottom wall 48 through which sand grains will readily pass and. as is well known in the art, the aperture 50 shaped as de scribed will prevent sand grains from becoming wedged therein because the upper opening has a smaller diameter than the lower opening.

Returning now to FIGS. l-3, the apparatus of this invention includes a plurality of elongated rods 68 located at the bottom of the open topped container. The longitudinal axes of each rod is disposed substantially parallel to the bottom wall 48. Additionally, the diameter of these rods 68 is selected so that at least some of the rods 68 are resting on the bottom wall 48 and that some other rods 68 are supported above the bottom wall 48 in resting engagement with other rods 68. In one preferred. embodiment of this invention, the rods 68 are formed of solid steel and preferably Rychrome steel manufactured by the Ryerson Steel Company. Each rod 68 has a length substantially equal to but slightly less than the distance between the end walls 44, thereby providing a layer of rods 68 located at the bottom of the open topped container which, as will become more clear later, is operative to crack larger sand grains into smaller sand grains while permitting smaller grains to flow freely therethrough and ultimately through the apertures 50 in the bottom wall 48.

Rotatably mounted to each end wall 44 at a point generally shown as 70 is the tie rod 72. At the opposite end of each tie rod 72 from the point 70 is a similar rotary connection 74 for joining each tie rod 72 to a support bracket 76 which is rigidly affixed to the support frame 10. The tie rod 72 is provided to restrain the movement of the open topped container in a horizontal or sidewise direction indicated generally by the doubleheaded arrow 78 at the lowermost portion thereof, while permitting substantially vertical movement in the direction indicated by the substantially vertical doubleheaded arrow 80. As such, the lower portion of the open topped container which includes the end walls 44, the side walls 45, and the bottom wall 48, is constrained to substantially vertical movement near the lowermost portions thereof.

In operation mechanically, the apparatus shown in FIGS. l-3 performs in the following manner. The electric motor is operative to rotate the pulley 16 about the drive axis 14. The drive belts 18, being in operative engagement with the pulley l6 and the pulley 20, transmit the rotary motion from the motor 12 to the driven pulley 20. This rotary motion of the driven pulley 20 is transmitted to the connected drive shaft 24 to thereby move the support shaft 40 in an eccentric manner. The support shaft 40 is rotatably mounted to the end walls 44 of the open topped container by the bearings 46. Consequently, when the motor 12 is turned on, the upper portion of the open topped container is eccentrically moved about the axes of

rotation

26, 38. Since the lower portion of the open top container is restrained by the tie rod 72, the lower portion of the open topped container is vibrated substantially in a vertical direction as indicated by the arrow 80 to thereby move up and down the lower portion of the open topped container by an amount approximately equal to one-half inch in the preferred embodiment of this invention.

Referring again to FIGS. l-3, a cylindrical steel support rod protecting shroud 81 is provided to protect the support shaft 40 and is joined at opposite ends to the end walls 44. This shroud 81 is primarily provided to shield the rotary support shaft 40 from excessive wear due to contact with sand as it is introduced into the open topped container which comprises the end walls 44, the side walls 45, and the bottom wall 48'. The shroud 81 also serves to protect the bearings 46 from contact with the sand as well. In addition, an outwardly extending flange 79 is provided along the edges of each end wall 44 to prevent contact with rotary parts as well as to serve as a measure of protection for the bearings 46 from contact with sand.

Since there is an eccentric connection between the drive shaft ends 25 and 32 with the support shaft 42, counterweights 82 are disposed on these

ends

25 and 32 to assure that the vibratory motion imparted to the open topped container is not transmitted through the drive shaft to the frame 10. Again, as a safety measure. protective shrouds 83 are provided to prevent accidental contact with the rotating counterweights 82 as well as to provide some measure of protection of these rotating parts from sand or other foreign objects.

Having described the apparatus and its mechanical operation, the usefulness of this apparatus is best described with reference to FIG. 5. The operator will normally introduce an amount of sand into the open topped container so that the sand covers the rods 68. When the motor 12 is activated, the open topped container, the rods 68 and sand vibrated to thereby permit the sand located above the rods 68 to gradually shift downwardly between the rods 68. This is shown in FIG. 5 wherein a plurality of sand grains are shown diagrammatically at and include small grains 92 and a larger grain 94. As the sand sifts between the vibrating rods 68, the larger grains 94 will become located between the rods 68. As the vibrating rods come together, they will crack larger grains of sand disposed therebetween but will not crack the smaller grains because the larger grains separate the rods 68 preventing contact thereby with smaller grains. Since the larger grains 94 are cracked, however, the number of sand grains in the mid-size range which fall through the apertures in the bottom wall 48 is increased because the cracking process tends to produce from larger grains a large number of grains in the mid-size range.

The usefulness of this sand fracturing machine is best shown in connection with FIG. 6. For various applications, the sand aggregate required for a particular job is often defined according to specifications. Typical specifications for a very fine finish concrete is shown in FIG. 6 in the shaded region. The sand aggregate for this concrete ideally should have a grain size distribution such that, for example, all of the sand in the aggregate will be passed by a /8 inch sieve while from 0 to 4 percent of the aggregate should be passed by a No. 200 sieve. For other sieve sizes, the range in which the aggregate should fall is shown, as indicated earlier, by the shaded area. In addition, it has been found to be highly desirable to have grains of sand in the mid-size range, i.e., those in the No. 30 to No. 50 sieve size fall well within the acceptable range. Experience has shown, however, that normal gravel pit outputs are especially lacking in sand grains in this particular range of grain sizes. This indeed is shown by the curve labeled input. This curve shows a specific sample of a typical gravel pit output and for the No. 30 sieve size, the percentage of aggregate passing through the No. 30 sieve.

size is very close to the lower limit of the specifications and, when the sieve size is decreased to that ofNo. 40,

the percentage passing through the No. 40 sieve is less than called for by the specifications. As a consequence,

the sand from this particular gravel pit does not meet the required specifications for fine finish concrete and something must be done to the gravel aggregate to make it conform.

In the past, one approach to changing the distribution of grain sizes in the aggregate has been to first size the sand using various sift sizes and then combine the separated sands to produce the desired distribution. Obviously, this particular approach is inefficient and costly.

To overcome the prior art deficiencies in producing a sand with an aggregate content which fully meets the specifications, a sand fracturing machine of the type disclosed is very useful. In FIG. 6, for example, a curve labeled output is drawn for the aggregate content at the output of the machine when a sand with the aggregate content shown for the input curve is put into this machine. It should be noted that the curve representing the aggregate content for the sand crusher output falls within the specifications except for the grain sizes between No. 10 and No. 4. However, in the critical midsize range between No. 30 and No. 50, the output of the sand crusher is well within and substantially at the middle of the specification range.

The sand crusher output itself may even be acceptable for use in smooth surfaced concrete because the deviation in the grain size content between No. 10 and No.4 is not very significant and, furthermore, this deviation occurs for a less critical grain size. On the other hand, a sand with an aggregate content fully meeting specifications can very easily be produced by combining on, a one-for-one basis, the sand crusher output with the uncrushed gravel pit sand. By such a combination on a one-for-one basis, the actual aggregate curve would lie midway between the input and the output curves which will lie completely within the specifications. As such, for the particular gravel pit sand aggregate sample shown in FIG. 6, and for the results achieved with the machine, an operator can readily modify the aggregate composition of the sand so that a sand meeting fine finish concrete specifications is available.

It will be clear to those skilled in the art that the foregoing discussion has been made with particular emphasis on using the sand breaking apparatus with a sand having a known aggregate composition and that the method of operation is equally applicable to sands having differing aggregate compositions. For each application, the aggregate composition of the sand before and after crushing must be known so that the proper quantities of each type of sand (treated or untreated) can be combined to form a combined aggregate with the desired distribution of the sand grain sizes.

While the foregoing description has been made with particular emphasis on a preferred sand fracturing machine, it will be clear to those skilled in the art that certain modifications in form only may be made without departing from the spirit and scope of this invention. For example, the apparatus of the present invention might readily be modified to change the vibrating mechanism so that the open topped sand receiving container would be vibrated in vertical direction by other means other than those specifically shown in FIGS. 1-3. Indeed, some form of eccentric drive means might be located beneath the sand receiving container to vibrate the box only in a vertical direction.

While the preferred embodiment of this invention utilizes steel rods of approximately 2 inches in diameter, it will be clear to those of skill in the art that rods of different or even differing diameters may also be used with the same advantageous results achieved by the present invention. By using a different number of rods having either different or differing diameters, the actual results of the operation on a given input sand aggregate is somewhat different from the output with other rods. As such, the operator may, if he so chooses, vary the rod diameter in order to vary the aggregate composition of the sand output, thereby providing a sand aggregate with a grain sized distribution preferably more approximating those of a desired specification. It is equally clear that the bottom aperture wall, being removably attached to the end walls and the side walls, may also be changed to provide some corresponding changes in the aggregate distribution at the output.

A further modification is to vary the vibration frequency to thereby increase or decrease the vibration rate on the rods which has an effect on the overall grain size distribution at the output of the machine.

The foregoing and other modifications in form only may be readily made by those of skill in the art without I departing from the spirit and scope of this invention as defined by the following claims.

What is claimed is:

1. A sand fracturing machine comprising, in combination:

an open topped container with a horizontal bottom wall with apertures therethrough and vertical side walls, said apertures being shaped to prevent sand grains from becoming wedged therein and large enough to pass substantially all the sand aggregate introduced into said container, said container being mounted for movement substantially only in a vertical direction;

a plurality of elongated rods disposed within said container with the longitudinal axis of each rod being disposed substantially parallel to said bottom wall, said rods being unattached to said container and free to move in a vertical direction; and

a vibrator apparatus operably connected to said container to vibrate said container and rods in a generally vertical direction wherein the larger grains of sand in a sand aggregate placed into said open topped container are fractured by the vibrating rods to produce a greater percentage of mid-size sand grains in the output sand aggregate of the machine than is contained in sand aggregate introduced into the machine without substantially increasing the percentage of fine sand grains in the output sand aggregate.

2. The machine according to claim 1 wherein each of said apertures in said bottom wall are frustoconical in shape with its smaller opening being disposed upwardly to communicate with said container.

3. The machine according to claim 1 wherein at least some of said rods are supported from below by said bottom wall and at least some other rods are supported from below by other rods.

4. The machine according to claim 1 wherein said vibrator means includes an eccentric drive connected to said container near the top of said container, said eccentric drive being operative to move the upper portion of said container in eccentric motion.

5. The machine according to claim 4 additionally including a motion restraint member connected to the lower portion of said container to restrain horizontal motion while permitting vertical motion of the lower portion of said container.

6. The machine according to claim 1 wherein said bottom wall is removably attached to said container.

7. A sand fracturing machine comprising, in combination:

an open topped container for receiving sand to be fractured, said container including a horizontal bottom wall with apertures therethrough large enough to permit substantially all the sand aggregate introduced into said container to freely pass therethrough without becoming wedged therein, said container including vertical side walls;

a plurality of elongated rods disposed within said container with the longitudinal axis of each rod being disposed substantially parallel to said bottom wall, at least some of said rods resting on said bottom wall, said rods being unattached to said container and free to move in a vertical direction;

a support shaft rotatably mounted to said container near the upper opening therefor;

a support frame;

a pair of drive shafts with common axes of rotation rotatably mounted to said frame and eccentrically connected a vibrator apparatus operably connected to said container to vibrate said container and rods in a generally vertical direction wherein the larger grains of sand in a sand aggregate placed into said open topped container are fractured by the vibrating rods to produce a greater percentage of mid-size sand grains in the output sand aggregate of the machine than is contained in sand aggregate introduced into the machine without substantially increasing the percentage of fine sand grains in the output sand aggregate.

8. The sand fracturing machine according to claim 7 wherein said open topped container includes two end walls in parallel spaced relation and two side walls also inparallel spaced relation, said side walls and end walls being joined together to form the sides of said container, said container also including said bottom wall which is removably attached to the lower edges of said end and said side walls.

9. A method of modifying the percentage of sand grains in the mid grain size of a sand aggregate contain- ,ing relatively few sand grains in the mid grain size comprising the steps of:

introducing a quantity of raw sand aggregate containsize grains than found in the raw aggregate.

Claims

1. A SAND FRACTURING MACHINE COMPRISING, IN COMBINATION: AN OPEN TOPPED CONTAINER WITH A HORIZONTAL BOTTOM WALL WITH APERTURES THERETHROUGH AND VERTICAL SIDE WALLS, SAID APERTURES BEING SHAPED TO PREVENT SAID GRAINS FROM BECOMING WEDGED THEREIN AND LARGE ENOUGH TO PASS SUBSTANTIALLY ALL THE SAND AGGREGATE INTRODUCED INTO SAID CONTAINER, SAID CONTAINER BEING MOUNTED FOR MOVEMENT SUBSTANTIALLY ONLY IN A VERTICAL DIRECTION; A PLURALITY OF ELONGATED RODS DISPOSED WITHIN SAID CONTAINER WITH THE LONGITUDINAL AXIS OF EACH ROD BEING DISPOSED SUBSTANTIALLY PARRALLEL TO SAID BOTTOM WALL, SAID RODS BEING UNUNATTACHED TO SAID CONTAINER FREE TO MOVE IN A VERTICAL DIRECTION; AND A VIBRATOR APPARATUS OPERABLE CONNECTED TO SAID CONTAINER TO VIBRATE SAID CONTAINER AND RODS IN A GENERALLY VERTICAL DIRECTION WHEREIN THE LARGER GRAINS OF SAND IN A SAND AGGTEGATE PLACED INTO SAID OPEN TOPPED CONTAINER ARE FRACTURED BY THE VIBRATING RODS TO PRODUCED A GREATER PERCENTAGE OF MID-SIZE SAND GRAINS IN THE OUTPUT SAND AGGREGATE OF THE MICHINE THAN CONTAINED IN SAND AGGTEGATE INTRODUCED INTO THE MACHINE WITHOUT SUBSTANTIALLY INCREASING THE PERCENTAGE OF FINE SAND GRAINS IN THE OUTPUT SAND AGGREGATE.

1. A sand fracturing machine comprising, in combination: an open topped container with a horizontal bottom wall with apertures therethrough and vertical side walls, said apertures being shaped to prevent sand grains from becoming wedged therein and large enough to pass substantially all the sand aggregate introduced into said container, said container being mounted for movement substantially only in a vertical direction; a plurality of elongated rods disposed within said container with the longitudinal axis of each rod being disposed subsTantially parallel to said bottom wall, said rods being unattached to said container and free to move in a vertical direction; and a vibrator apparatus operably connected to said container to vibrate said container and rods in a generally vertical direction wherein the larger grains of sand in a sand aggregate placed into said open topped container are fractured by the vibrating rods to produce a greater percentage of mid-size sand grains in the output sand aggregate of the machine than is contained in sand aggregate introduced into the machine without substantially increasing the percentage of fine sand grains in the output sand aggregate.

7. A sand fracturing machine comprising, in combination: an open topped container for receiving sand to be fractured, said container including a horizontal bottom wall with apertures therethrough large enough to permit substantially all the sand aggregate introduced into said container to freely pass therethrough without becoming wedged therein, said container including vertical side walls; a plurality of elongated rods disposed within said container with the longitudinal axis of each rod being disposed substantially parallel to said bottom wall, at least some of said rods resting on said bottom wall, said rods being unattached to said container and free to move in a vertical direction; a support shaft rotatably mounted to said container near the upper opening therefor; a support frame; a pair of drive shafts with common axes of rotation rotatably mounted to said frame and eccentrically connected to said support shaft at opposite ends thereof for providing eccentric motion to said support shaft relative to said support frame when said drive shafts are rotated; means for rotating at least one of said drive shafts; and at least one tie rod pivotally connected at one end to said support frame and pivotally connected at the other end to the lower portion of said container said tie rod being operative to restrain horizontal motion of the lower portion of said container while permitting substantially vertical motion when said drive means is operative to rotate said drive shaft.

8. The sand fracturing machine according to claim 7 wherein said open topped container includes two end walls in parallel spaced relation and two side walls also in parallel spaced relation, said side walls and end walls being joined together to form the sides of said container, said container also including said bottom wall which is removably attached to the lower edges of said end and said side walls.