US3343239A - Concrete block forming machine with pneumatic vibration - Google Patents

Description

Sept 26, 1967 M. A. DAVIES CONCRETE BLOCK FORMING MACHINE WITH PNEUMATIC VIBRATION Filed Jan. 27, 1965 2 Sheets-Sheet 1 58 IR m m m MilesA; Davies INVENTOR.

' CONCRETE BLOCK FORMING MACHINE WITH PNEUMATIC VIBRATION Filed Jan. 27, 1965 I -DAwEs 2 Sheets-5 2 Sept Miles ADCIVjes INVENTOR H 'Ti United States Patent 3,343,239 CONCRETE BLOCK FORMING MACHINE WITH PNEUMATIC VIBRATION Miles A. Davies, Vancouver, Wash., assignor to Columbia Machine, Inc., Vancouver, Wash., a corporation of Washington Filed Jan. 27, 1965, Ser. No. 428,404 6 Claims. (Cl. 25-41) This invention pertains to concrete block forming machines, in which controlled vibration and compression are used simultaneously to produce concrete blocks of uniform density and having trowled surfaces.

It is a principal object of this invention to provide a machine for making concrete blocks, in which machine the pallet table, the pallet and blocks supported thereby are vibrated under plural and differing degrees of resistance so that a first pressure may be utilized when the block material is being poured and a second degree of pressure utilized when a block is being vibrated thus to create uniform density within the block.

A further object of this invention is to provide a vibrating support, including a table, pallet and block surrounded by a mold, involving columns of air under pressure greater than atmospheric, which elevated pressure may selectively be changed at will to produce different degrees of support, said changes being made under either manual control or under automatic and mechanically activated control.

A further object of this invention is to provide a block forming machine of this character in which the forming molds may be filled to a predetermined degree while the mold, its contents and the pallet supporting it are under vibration, being supported by elastic media the pressure amplitude of which may be varied torespond properly, while said mass is being poured into the mold, and may be supported by more elevated pressure when the material is being vibrated after pouring has been completed.

A further object of my invention is to provide a block forming machine of this character in which the mold, its contents, and the pallet underlying the mold are vibrated at such a rate, frequency and under controlled elasticity so that the material in the mold will more or less float in the mold while the pallet and the mold are vibrating vertically. This permits any entrapped air in the cementitious mass to escape either through the upper surface or the lower surface depending upon its proximity. Permitting escape of entrapped air through the upper surface or through the lower surface, depending upon the path of freedom, permits the separation of the air from the cementitious mass uniformly and quickly. Blocks thus produced contain few voids, are free from stresses generated during their formation, and do not fracture in use due to lack of homogeneity, or due to a deficiency of bonding material, which is usually Portland cement.

. Further and other features of my invention are hereinafter described with reference to the accompanying drawings, in which:

FIG. 1 is an elevation of a concrete block forming machine forwhich my invention is specifically adapted;

FIG. 2 is a'schematic diagram of control units and pneumatic cylinders for supporting the mold enclosing a cementitious mass supported by a free-floating pallet;

FIG. 3 is a plan view of the face of a pallet holder showing pneumatic piston-and-cylinder elements and portions of conduits leading thereto through which air may be forced into the piston-and-cylinder elements or released therefrom under control conditions, and a mold carried thereby;

4 FIG. 4 is a vertical section taken on the line 44 in 3,343,239 Patented Sept. 26, 1967 "ice FIG. 3, and shows an aligned pair of piston-and-cylinder elements with a helical spring arranged between them;

FIGS. 5 and 6 are related schematic views showing the relationship between the pallet holder, pallet, the mold supported thereby, and the cementitious mass from which blocks are to be formed; FIG. 5 shows the arrangement of said parts at a point approaching the upper limit of swing in a vibrational cycle; FIG. 6 illustrates the relationship of the parts shortly thereafter when the said parts are moving downwardly; and

FIG. 7 is also adiagrammatic view showing ancillary helical springs lying between related pairs of piston-andcylinder pneumatic supports, and illustrates the manner in which the springs twist and untwist under compression, to produce lateral shift of the pallet board when the parts are arranged as is shown in FIG. 6.

My present improvement relates to the type of machine for making concrete blocks illustrated in United States Patent No. 2,589,115 that was issued Mar. 11, 1952, jointly to Russell B. Nelson, Fred Neth and myself. This organization is particularly adapted for the practice of my invention and to have incorporated therein the structural members which will hereinafter be described. The parts shown in FIG. 1 of the drawings herein respond closely to those illustrated in said Patent No. 2,589,115. They are hereinafter described, and are given the same reference characters as were adopted in said patent, to promote ease of understanding. Said machine, in which my invention is to be incorporated, comprises the following:

In the concrete block making machine embodying the features of this invention, the operating parts are mounted upon a rectangular frame 1. Projecting forwardly from the lateral sides of the front panel are two pairs of base members, namely an upper pair 5 and a lower pair 6. Said base members have vertically aligned holes formed therein for receiving tubular sleeves 7 slidably therein. The lower ends of said sleeves are joined together below the lower base member 6 by a horizontal toggle beam 8 which is secured to said sleeves by means of bolts 9. The toggle beam is supported at its center upon the upper end of a piston rod 10 which is secured thereto. The opposite end of the piston rod is connected to a piston which is movable vertically within a double acting hydraulic stripper cylinder 11. The stripper cylinder is secured by means of bolts 12 to an H-shaped bracket 13 which projects from the frame 1.

The bracket 13 is formed with laterally projecting flanges 14 on its upper edge to provide supports for the upstanding pedestals 15 which are secured thereto. A shoulder 16 is formed about each of said pedestals intermediate the ends thereof. Removable bumpers 17 each have a hollowed end 18 which slidably engages the upper end of the pedestals. A shoulder 19 is formed intermediate the ends of said bumpers. Coil springs 20 encircle the engaged portions of said pedestals and bumpers and abut at their ends against the opposing faces of said shoulders. In the relaxed position of said springs, the telescoping ends of the pedestals and bumpers are spaced apart and may be moved together by compressing the coil springs 20. The upper ends of the bumpers are arranged to contact the toggle beam as the latter approaches its lowermostposition.

A pallet beam 21 extends transversely between the sleeves 7 intermediate the upper and lower base members 5 and 6, respectively, and is secured thereto by means of bolts 22. Since the toggle beam 8 and pallet beam 21 are secured firmly to the sleeves 7, the unit so formed is hereinafter referred to as the stripper assembly. A platform 23 projects forwardly and rearwardly from the center of said beam. Adjustment screws 27 are mounted upon the platform 23 for vertical adjustment and are provided with lock nuts 28 for securing said screws in any position desired. The adjustment screws are arranged to contact the pallet table to prevent excessive rocking of the latter during vibration. The pallet table is proportioned and arranged to support a pallet 103 upon which the concrete blocks 108 are carried from the machine after manufacture.

A concrete block mold 31 is held suspended above the pallet table 25 by vibrator means. Said mold comprises a rectangular box open at the top and bottom. The mold is of conventional construction and may be designed to accommodate the production of any type of block desired. The multiple mold illustrated in the drawings is designed for the manufacture of plural hollow building blocks per cycle and is shown merely for purposes of illustration.

A pressure beam 47 extends laterally across the frame above the sleeve 7. The ends of said pressure beam are formed with downwardly extending tubular shields 48 which loosely encompass the upwardly extending ends of the base members 5. Projecting collars 49 extend upwardly from the ends of the pressure beam and holes are formed vertically therethrough for axial alignment with the holes extending through the sleeves 7. Toggle rods 50 extend vertically through said aligned holes and are secured to the pressure beam by means of set screws 51 provided in the collar 49. The upper end of each toggle rod is also provided with a large washer 52 which is held firmly against the top edge of the collar 49 by means of a nut 53 threaded to the end of said rod. Said washer and nut serve to aid the set screw 51 in pulling the pressure head downwardly during compression of the concrete material in the mold 31.

The lower ends of the toggle rods 50 extend slidably through transversely apertured bars 54. Coil springs 55 encircle said rods below the bars 54 and are secured thereon by means of washers 56 and nuts 57. The bars 54 may slide downwardly along the lower ends of the toggle rods by compressing the springs 55, but said bars are prevented from moving upwardly along the toggle rods away from said springs. The coil springs function to prevent sudden and excessive forces from being exerted upon the concrete material being compressed in the mold 31. To the cylindrical ends of bars 54, the lower arms 58 of toggle joints are pivotally secured. The upper arms 59 of said toggle joints are connected pivotally at one of their ends to the lower arms 58, while the opposite ends are secured firmly to a transverse shaft 60. Said shaft is mounted for rotation in bearing flanges 61 projecting from the toggle beam 8.

Mechanism is provided for vibrating the mold 31 in order generally to distribute and compress the concrete material evenly therein and thereby produce concrete blocks of homogeneous and uniform construction. The mechanism illustrated in FIG. 1 includes a pair of vertical vibrator rods 68 secured adjacent their upper ends to the lateral sides of the mold 31 by means of brackets 69.

An eccentric cam (not shown) is mounted for rotation within bearing 78 and is secured firmly in an olfcenter position to a driven shaft 81. Said driven shaft is mounted transversely across the front of the machine for rotation in end bearings 82 mounted on structural members 83 which are secured to the frame adjacent the lower base members 6.

All of the foregoing description is of parts that are old and are disclosed in United States Patent No. 2,859,115, heretofore identified.

Such a block forming machine has certain inherent difiiculties with which my present invention is concerned. One of the principal ones is that when the springs supporting the pallet holder and the pallet carried thereby are set to a given compression, they can not be changed while the machine is in operation. Thus, the springs must be compressed to a predetermined degree and to acquire a given periodicity. That is, this selection must be made in advance of the operation of the machine. The compression of the springs must be sufficiently loose at the time that cementitious material is being poured in the mold to be vibrated, to permit said mass to flow uniformly into the cavities of the mold. The pallet should be held loosely enough against the lower edge of the mold to permit excess moisture to flow therefrom. This requires that the moisture seal upon said lower edge must become lbroken to permit entrapped air in the mold to escape and to pass under the edge of the mold. That is, it should pass through the bottom face of the block as well as through the upper face thereof. Thereafter, when compression is added to the upper surface of the block, in addition to vibration thereof, it is necessary that said springs must be sufficiently stiff to prevent semi-fluid cementitious mass from extruding between the lower edge of the mold and the pallet. I have determined that a spring pressure of a value of approximately 18 to 25 pounds per square inch is sufiicient to obtain compaction of the cementitious material in the initial portion of the molding process where the material is subject to vibration but not to lateral compression. This permits the cementitious matter to be moved differentially in a mold and to fiow uniformly therein and to permit the moisture or water seal to be broken at the lower edge of the mold and to permit any entrapped air to escape. After said initial filling period, it is essential that elastic pressures in the range of to pounds per square inch be developed between the mold and the pallet holder. In the absence of such pressures, the cementitious material will be expressed or extruded from the open bottom of the mold. This will produce loss which will produce blocks of insufficient height. Also, it will produce fins or wire edges on the bottom surface of the concrete blocks where the cementitious matter is extruded below the mold and over the pallet face.

It is also essential that the elastic supports be effective under compression to hold the pallet, the pallet holder and the mold together while vibrating without interruption.

Another factor is that when helical springs are used as the elastic supports, they do not compress proportionately to the pressure exerted against them. This is particularly true under high degrees of compression where the helical coils tend to approach approximation or abutment with adjacent coils. I have discovered that if air columns, such as are provided by a piston-and-cylinder element, are utilized as the elastic supporting media, the compression of the air columns is uniform throughout the length of the stroke of the piston in its cylinder. This is equally true where air pressures are generated that are initially low, as when vibration alone is involved, and may be quickly stepped up to much higher pressures when the compressing stroke is involved.

Another factor that must be observed is that when the parts are air supported, and when they are approaching their upper limits of throw, a weightless condition is produced in the cementitious material contained within the mold. At this point, the pallet falls away from the under surface of the cementitious material forming a brick, and a gap is produced between the lower marginal edge and the pallet. This is illustrated in FIG. 6 of the drawings. As is viewed in practice and as is indicated by a strobescope, there is an unbroken stratum of air between the lower edge of the mold and the upper face of the pallet formed at the point of reversal in direction. A beam of light directed through this area is not interrupted, -although the stratum above the pallet and below the mold varies in gap, as does the stratum below the pallet and above the pallet holder. In either condition, the pallet is bounced back and forth between the pallet holder and the under edge of the mold, and might be said to reach a state of weightlessness. Another way of describing this relationship is to say that the block is not formed with its base stuck tight to the pallet, but is formed above the face of the pallet. In this situation, the pallet once each vibration pats the under surface of the brick being formed, and bounces away under the influence of the elasticity of the air columns. The presence of an air stratum between the lower edge of the mold and the upper face of the pallet also produces troweling as the pallet slides, pats and slides, over the bottom edge of the mold. Also, the cementitious mass, being free to move vertically, flows over the side walls of the cavities in the mold and is troweled as it slides therein. The stratum of air above the pallet breaks the moisture seal at the margins of the mold and permits air to escape from the interstices in the cementitious mass being formed and to flow under the lateral margins of the bottom of the mold to the atmosphere. Thus, the breaking of said liquid seal at the under surface of the mold, and the presence of said stratum of air, provides another path of freedom for air to escape from the cementitious mass. Air trapped in the bottom portion of a block being formed has a path of freedom to escape to the atmosphere through the bottom face of the block, and air entrapped above it may flow upwardly through the top of the block being formed, to the atmosphere. This is important because the cementitious mass is quite dry and stiff, and the percolation of air therethrough and its escape to the atmosphere is in the form of small bubbles that move very slowly. The alternate paths of freedom eliminates eventual voids in the finished product.

The details of my invention, as it relates to the foregoing discussion, is illustrated in the drawings in FIGS. 2 through 7. With reference to FIG. 3, it should be noted that the pallet holder 101 is generally rectangular. It has an upper plane surface 102, as is illustrated in FIG. 4. It is indented in many places, but the margin or rim portions all lie in a common plane. This is likewise true of the under surface 102a. In FIGS. 5 and 6, this is schematically shown.

The pallet 103 lies flatwise upon the upper surface 102 of the pallet holder 101. At the two ends of the upper surface of the pallet holder are a pair of upstanding flanges 104 serving as pallet guide bars. The lateral spacing of said bars from each other is substantially greater than the overall length of the pallet 103 or the upper surface of the pallet holder 101. I have found that one-eighth of an inch lengthwise is sufiicient to permit the pallet to shift endwise when the parts are thus arranged. Movement laterally of approximately one-half inch is permitted. This clearance longitudinally and laterally permits the pallet to shift under the block being formed and to trowel its under surface. As is shown in FIG. 6, at this point the pallet and the cementitious material in the mold are both more or less weightless. Said pallet may shift freely longitudinally within the limits of the spacing of the opposed faces of the guide bars 104, and the cementitious mass, of which the block is to be formed, may move vertically so that the sidewalls of the mold cavities will trowel the peripheral surfaces of said mass.

The mass of the pallet 103 is substantially less than that of the cementitious material 108 within the mold 3'1, and thus the pallet 103 responds more quickly to change of direction of movement than does the cementitious mass 108. Thus, the pallet moves through space xx in FIG. 6, as has been pointed out, and pats the under side of the material 108 once each cycle of vibration. It can thus be said that the block being formed, due to said vibration and said clearance, never rests upon the upper surface of the pallet, and is thus formed above the pallet.

- Piston-and-cylinder elements 105 underlie the four corners of the pallet holder, as is shown in FIG. 3. Each thus resists or supports movement of the pallet holder and the pallet, together with the cementitious material lying above it. They are telescopic in form, and the piston 105a is separated from the cylinder by air under pressure, which is supplied through hose connections 106 joined to a common reservoir. Each piston-and-cylinder element is filled with air at pressures exceeding that of the atmosphere, and said air pressure may be varied at will by devices hereinafter described.

Lying intermediate the piston-and-cylinder elements 105, at the left and right hand sides thereof, is a pair of mated helical springs 107, as is illustrated in FIG. 3. These helical springs underlie and engage the pallet holder at their upper ends and seat upon platform 23 at their lower ends. The compression exerted by the springs 107 is only suflicient to support the weight of the pallet holder 101 and the pallet 103 when at rest and not whilesupporting the mass of cementitious material of which a block is formed. This elastic pressure afforded by the springs is of the order of an overall upward pressure of 25 pounds, and is thus quite small compared to that generated by the four piston-and-cylinder elements 105. That is to say, the helical springs merely augment the major pressure supporting the pallet and devices accessory thereto. They do have one particular function, however, that is important. That is, as the springs compress and expand, they rotate in the manner indicated in FIG. 7. The rotation of the springs tends to shift the pallet laterally over the face of the pallet holder. Thus, the pallet moves laterally under the influence of the coiling and uncoiling of the springs to trowel the bottom face of a block held, and being formed, in a mold.

It is to be remembered that the troweling action thus continues during all of the time that the block is being vibrated in the machine, first, while it is being poured into the mold, and, after that, when it is subjected to lateral compression. This continues to a lesser degree while the lateral pressure ejects the finished block downwardly and out of the mold, as is explained in Patent No. 2,589,115.

As is shown, the heads of the pistons in the piston-andcylinder elements 105 bear against the under surface of the pallet 103. The support provided by the air in the piston-and-cylinder elements and constituting air columns reacts sufficiently quickly to hold the heads of said pistons against the pallet holder, but with varying degree. The pallet holder is held by heads 109 of hold-down bolts 27, and these are lodged in cavities 110 in the pallet holders. The cavities provide vertical clearances much. greater than theclearances above the pallet 103 and mold 31 and below the pallet holder, which clearances are identified by the arrows xx and yy, respectively. This produces the result that the pallet, to a greater degree and the pallet holder to a lesser degree, lag behind the vibration developed in the mechanical parts of the machine, which define a lost-motion device and thus the pallet and pallet holder tend to float on air so to speak, while the other mechanical parts are clamped together and vibrate rapidly upwardly and downwardly.

Even though the piston-and-cylinder elements 105 operate from a common reservoir of air under uniform pressure applied equally to each of the pistons, one of the four pistons, or a pair thereof, will respond sometimes more rapidly than will the others, and this causes the pallet or pallet holder to tip slightly, thus permitting one portion of it to rock to a higher elevation than another. This permits the pallet holder and the pallet to slide and shift within the limits of the spacing of the guide bars 104 as well as-laterally to produce the troweling action noted heretofore.

As is shown in FIG. 2, the controls for air include a pressure regulator apparatus 111. Air under pressure is forced in from the left-hand side of said regulator, shown schematically in said figure. Flow is indicated by the use of arrows, and the air flows through conduit 112. It may pass directly upwardly through the conduit 113 that joins with conduit 112, or it may follow along conduit 112 and flow into conduit 114. Said conduits 1 13 and 114 both open to the interior cavity of valve body 115. A doubleheaded valve unit 116 reciprocates longitudinally of the valve body 115 under the influence of air. Air is controlled by the valve action of a solenoid 117, for example. When the valve unit is shifted to the left, as viewed in FIG. 2, it will permit air to flow from conduit 112 through conduit 114 under the influence of pressure regulator element 118 and into the valve body 116, which has plural work chambers. The air, under pressure limited by element 118, then flows downwardly through a central conduit 119 and to the four piston-and-cylinder elements. If the solenoid is actuated to shift the controls for the double-headed valve 116 towards the right, its right-hand end will cut off flow through conduit 114 and will uncover conduit 113. Air flowing through conduit 113 is under the influence of pressure regulator 118a, and air under such pressure will flow into the valve body and from there into the conduit 119 and be distributed to all four piston-and-cylinder elements.

To obtain two different degrees of air pressure, it is essential that there be two pressure regulator elements. If it is desired that the piston-and-cylinder elements i105 be operated under three or four different and successive oper ating pressures, this may be accomplished by providing a corresponding number of pressure regulators and heads in the valve element to cause the generated pressure to act upon the said elements 105.

The solenoids may be operated manually, or may be operated automatically or manually by a time clock, but preferably the solenoid is actuated by movement of its parts of the machine as they complete successive operations necessary to produce a finished block.

It has been my observation in the use of pneumatic columns, in lieu of mechanical springs or other expedients with which I am familiar, has increased the quality of blocks produced and has decreased the time cycle for forming and finishing a block made in a machine such as is illustrated and described.

Blocks formed by the use of this development now disclosed are more uniform in quality. There is little stratification between the bottom of the block and the top portion thereof as it stands in a mold. There are few voids produced by air entrapped in the block, and thus the blocks are uniformly dense. No structural flaws appear, and there is no sloughing of the material or extrusion thereof. The increase in elastic pressure against the die and mold operation also causes the granules of aggregate to become rearranged and compacted in a shorter period of time.

I claim:

1. In a machine for making concrete blocks, a frame, a mold suspended in said frame, a laterally spaced pair of sleeves movable vertically on said frame, a pallet beam below said mold and lying intermediate said pair of sleeves, a pallet holder mounted upon said pallet beam, said pallet holder having a pallet loosely lying upon the upper face of said pallet holder, plural air operated pistonand-cylinder elements lying operatively between the pallet beam and said pallet holder, a driven member mounted on said frame, eccentrically mounted vibrator means operatively joined to the driven member and to the pallet beam for vibrating said mold vertically, the improvement comprising a plural stage, air pressure control element for supplying air to the plural piston-and-cylinder elements and maintaining them at one of plural selected pressures, whereby the pallet and a block being formed and carried by the pallet can vibrate to a different amplitude than that of the mold box mounted thereon.

2. In a machine for making concrete blocks, a frame, a mold suspended in said frame, a laterally spaced pair of sleeves movable vertically on said frame, a pallet beam below said mold and lying intermediate said pair of sleeves, a pallet holder mounted upon said pallet beam, said pallet holder having a pallet loosely lying upon the upper face of said pallet holder, plural air operated piston-and-cylinder elements lying operatively between the pallet beam and said pallet holder, a driven member mounted on said frame, eccentrically mounted vibrator means operatively joined to the driven member and to the pallet beam for vibrating said mold vertically, the improvement comprising a plural stage, air pressure control element for supplying air to the plural piston-andcylinder elements and maintaining them at one of plural selected pressures, and a lostamotion device joining the vibrator means and the pallet holder to permit the pallet holder to vibrate vertically independently of the vibrator means but responsive thereto, whereby the pallet and a block being formed and carried by the pallet can vibrate to a different amplitude than that of the mold box mounted thereon.

3. In a machine for making concrete blocks, a frame, a mold suspended in said frame, a laterally spaced pair of sleeves, a pallet holder mounted upon said pallet beam, said pallet holder having a pallet loosely lying upon the upper face of said pallet holder, plural air operated piston-and-cylinder elements lying operatively between the pallet beam and said pallet holder, a driven member mounted on said frame, eccentrically mounted vibrator means operatively joined to the driven member and to the pallet beam for vibrating said mold vertically, the improvement comprising a plural stage, air pressure control element for supplying air to the plural piston-andcylinder elements and maintaining them at one of plural selected pressures, whereby the pallet and a block being formed and carried by the pallet can vibrate to a different amplitude than that of the mold box mounted thereon, said plural air operated piston-and-cylinder elements being grouped in spaced but related pairs, a helical spring arranged between said group and lying laterally centrally of the pallet holder, whereby the pallet holder can tip laterally and the pallet supported thereby can shift and trowel the under surface of the concrete block being formed.

4. In a machine for making concrete blocks, a frame, a mold suspended in said frame, a laterally spaced pair of sleeves movable vertically on said frame, a pallet beam below said beam mold and lying intermediate said pair of sleeves, a pallet holder mounted upon said pallet beam, said pallet holder having a pallet loosely lying upon the upper face of said pallet holder, plural air operated piston-and-cylinder elements lying operatively between the pallet beam and said pallet holder, a driven member mounted on said frame, eccentrically mounted vibrator means operatively joined to the driven member and to the pallet beam for vibrating said mold vertically, the improvement comprising a plural stage, air pressure control element for supplying air to the plural piston-andcylinder elements and maintaining them at one of plural selected pressures, whereby the pallet and a block being formed and carried by the pallet can vibrate to a different amplitude than that of the mold box mounted thereon, said plural air operated piston-and-cylinder elements being grouped in spaced but related pairs, a pair of helical springs arranged between said groups and lying laterally centrally of the pallet holder, whereby the pallet holder can tip laterally and the pallet supported thereby can shift and trowel the under surface of the concrete block being formed.

5. In a machine for making concrete blocks, a vertically disposed frame, a mold suspended in said frame, means for vibrating said mold vertically, a pallet holder mounted below said mold, a pallet lying loosely upon the upper face of the pallet holder, means for moving the pallet holder and the pallet lying thereon against the underside of the mold, elastic means underlying the pallet holder and overlying and bearing upon the means for vibrating said mold vertically, the improvement comprising air filled cushion elements constituting the elastic means lying intermediate the pallet holder and vibrating means, and means for varying the effective pressure of air in said cushion element while the machine is under vibration, whereby the pallet and a block formed there- 9 on can vibrate to a different amplitude than that of the mold box.

6. In a machine for making concrete blocks, a vertically disposed frame, a mold suspended in said frame, means for vibrating said mold vertically, a pallet holder mounted below said mold, a pallet lying loosely upon the upper face of the pallet holder, means for moving the pallet holder and the pallet lying thereon against the under side of the mold, elastic means underlying the pallet holder and overlying and bearing upon the means for vibrating said mold vertically, the improvement comprising air filled cushion elements constituting the elastic means lying intermediate the pallet holder and the vibrating means, means for varying the eifective pressure References Cited UNITED STATES PATENTS 2,147,836 2/1939 Gaskell 2541 2,589,115 3/1952 Nelson et al. 2541 2,636,719 4/1953 OConner 25-41 X 3,153,834 10/1964 Boyer et al.

J. SPENCER OVERHOLSER, Primary Examiner.

of air in said cushion element while the machine is under [5 E. MAR, Examiner.

Claims (1)

1. 5. IN A MACHINE FOR MAKING CONCRETE BLOCKS, A VERTICALLY DISPOSED FRAME, A MOLD SUSPENDED IN SAID FRAME, MEANS FOR VIBRATING SDAID MOLD VERTICALLY, A PALLET HOLDER MOUNTED BELOW SAID MOLD, A PALLET LYING LOOSELY UPON THE UPPER FACE OF THE PALLET HOLDER, MEANS FOR MOVING THE PALLET HOLDER AND THE PALLET LYING THEREON AGAINST THE UNDERSIDE OF THE MOLD, ELASTIC MEANS UNDERLYING THE PALLET HOLDER AND OVERLYING AND BEARING UPON THE MEANS FOR VIBRATING SAID MOLD VERTICALLY, THE IMPROVEMENT COMPRISING AIR FILLED CUSHION ELEMENTS CONSTITUTING THE ELASTIC MEANS LYING INTERMEDIATE THE PALLET HOLDER AND VIBRATING MEANS, AND MEANS FOR VARYING THE EFFECTIVE PRESSURE OF AIR IN SAID CUSHION ELEMENT WHILE THE MACHINE IS UNDER VIBRATION, WHEREBY THE PALLET AND A BLOCK FORMED THERE-

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