Abstract:
A machine and method for producing dimensionally consistent compressed earthen blocks under consistent and uniform pressures is disclosed. The approximately rectangular shaped block is formed in a rectangular parallelepiped shaped chamber having given dimensions. A plate forms one wall of this chamber and has the mobility required to compress the earth within the chamber. At the termination of compression, this plate is located at a predetermined location. A dog is forced into the compressed earthen block after the compression plate has ceased which effectively reduces the internal volume of the chamber. The dog is forced in under a known and consistent pressure. When a block is formed of less material, the terminal point for the dog will be further into the block than when the same-size block is made of more material. Additional aspects include a calibration unit for determining a volume of raw material to load into the compression chamber; and a hydraulic cylinder able to actuate two coaxial rams independently.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application contains disclosure from and claims the benefit under Title 35, United States Code, §119(e) of the following U.S. Provisional Application: U.S. Provisional Application Ser. No. 60/493,512 filed Aug. 8, 2003, entitled BLOCK MAKING APPARATUS. 
     
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT  
       [0002]     Not applicable.  
       REFERENCE TO MICROFICHE APPENDIX  
       [0003]     Not applicable.  
       BACKGROUND OF THE INVENTION  
       [0004]     1. Field of the Invention  
         [0005]     This invention relates to building material. More particularly, the invention relates to a method and apparatus for making building blocks. In particular, the invention relates to an apparatus and method for the manufacture of compressed-earth building blocks. Further, the invention relates particularly to the manufacture of compressed stabilized building blocks of soil or earth that have a good degree of dimensional accuracy and uniformity or density using a primary and secondary compression method.  
         [0006]     2. Background Art  
         [0007]     Many forms of building block are known for use in construction of building structures. One form of such building block comprises particulate earth or soil which is compressed in a mold to form the building block. Such building blocks are sometimes known by the names “soil blocks,” “earthen blocks,” or “Compressed Earth Blocks” (CEB). The raw material for such blocks may comprise earth of varying types, together, optionally, with suitable stabilizers, such as cementitious materials, liquid for hydration of the cementitious material, sealants, waterproofing agents, fillers, and the like. In order to reduce handling costs during construction, such building blocks are generally large in comparison with traditional fired clay bricks.  
         [0008]     Presently, two approaches are used in the manufacture of compressed earthen building blocks: 
        1. consistent final pressure, inconsistent dimensions, or     2. consistent dimensions, inconsistent density. 
 
 Because the raw materials used in the manufacture of the compressed earthen building blocks varies in character, and because the volume of material may vary slightly between blocks, if all the blocks are made to a specified size, the terminal pressures will vary from finished block to finished block, and thus their densities. On the other hand, if a given terminal pressure is consistently reached, due to the varying characteristics and volume of the raw materials, the blocks will vary in at least one of their terminal dimensions. 
       
 
         [0012]     Another problem encountered in the manufacture of compressed earthen building blocks is the achievement of homogeneity throughout the building block. To achieve a homogeneous building block of even density throughout the block, it is necessary to achieve even pressures throughout the raw material of the building block during the manufacturing process. This has proved a challenge. The raw material used in the manufacture of such blocks is of a particulate nature and the transmission of even compressive forces throughout a large volume of such material is difficult to achieve. Traditionally, such building blocks have been manufactured in a compression chamber, or mold, of generally rectangular parallelepiped shape. One side of the mold is displaceable to act as a ram for compression of the raw material within the compression chamber. In such devices, it is found that it is possible to achieve relatively high pressures for compression proximate the ram, but that the pressures within the cavity of the compression chamber drop off towards the distal end of the chamber. In order to achieve acceptable compression at the distal end of the chamber, it is necessary to apply large ram forces to the raw material, thereby necessitating the use of heavy and expensive equipment and the consumption of relatively large amounts of energy. It has also been found that even where the requisite even distribution of pressure is achieved within the raw material in the compression chamber, it is difficult to achieve dimensional consistency of the finished block.  
         [0013]     A machine for the manufacture of compressed earthen building blocks is disclosed by Rose in U.S. Pat. No. 4,563,144. The raw materials used to make the building blocks are loaded into a hopper. A plunger beneath the hopper measures out a given sample of these materials and loads them into a compression chamber where they are compressed into a compressed earthen building block. No provision is made for the varying conditions of the raw materials and the adjustment of the initial volume thereof. According to the specification, the building blocks are formed to a consistent pressure. The implication of this is that the building blocks will vary in terminal size. For the purpose of this document, “terminal size” is defined as the size of the compressed earthen building blocks when they are expelled from the compression chamber. The compressed earthen building blocks will vary somewhat from their terminal size during further curing.  
         [0014]     Another machine for the manufacture of compressed earthen building blocks is disclosed by Lienau in U.S. Pat. No. 5,629,033. In this invention, a feeder box is provided under the hopper. The raw materials drop from the hopper into the feeder box, and are transported over the compression chamber. A wedge is provided at the top cover of the compression chamber, the wedge being forced under a bucking bar that extends entirely across the compression chamber. Thus, the top cover is secured over the compression chamber.  
         [0015]     Lienau discloses a method for producing blocks of consistent dimension and density by varying the starting point of the press ram, and thus the quantity of raw materials entering the compression chamber. According to the specification, the starting position of the press ram is found by trial and error. No provision for achieving homogeneous density in the finished block is disclosed by Lienau.  
         [0016]     There is, therefore, a need for a method and apparatus for producing compressed earthen building blocks of consistent dimension and density, as well as homogeneous density. There is an additional need for a method and apparatus for determining, without trial and error, a quantity of raw material to insert into the compression chamber to produce blocks of consistent dimension and density.  
         [0017]     There is still another need for a method and apparatus for inserting a compression element, or “dog,” into the dimensioned, compressed earthen building block, and an actuator system for effecting this insertion to achieve homogeneity of density throughout the finished block.  
       BRIEF SUMMARY OF THE INVENTION  
       [0018]     It is an object of the invention to provide a block making apparatus and method for making compressed earthen building blocks which will, at least partially, alleviate the abovementioned problems, enabling the manufacture of building blocks of high dimensional accuracy and homogeneity, as well as having dimensional consistency.  
         [0019]     To effect the abovementioned objects, the apparatus for manufacturing the compressed earthen building blocks has a compression chamber in which the compressed earthen building blocks are compressed. One wall is typically movable under force of a hydraulic cylinder or other actuation device.  
         [0020]     In addition, at least one compression element, referred to herein as a “dog,” is forced into the block after the movable wall has reached its desired terminal location. Thus, at least one cavity is produced in the block to compress the block material to its final compression value. The terminal pressure of the ram or rams for inserting the at least one dog is fixed. Therefore, the distance a dog enters the block will vary depending on the initial volume of earth used for the block, and the characteristics of that earth.  
         [0021]     (For the purposes of this specification, “dog” is defined as a compression element, inserted into a compressed earthen building block for the purpose of enhancing the homogeneity of, and achieving the desired density of the compressed earthen building block. The dog may take on any of a variety of shapes. A single dog, or a plurality of dogs may be used in the manufacture of a given compressed earthen building block.)  
         [0022]     The compression chamber may comprise a first pair of generally parallel side walls, intermediate a second pair of generally parallel front and rear walls. Further, a fifth wall of the chamber may comprise a pressure plate which is displaceable with respect to the front, rear and side walls to slide within a rectangular cylinder defined by these walls. An end of the chamber opposed to the compression plate is openable and the apparatus includes a removable cover operable between a first position in which it is clear of the opening of the compression chamber, for filling the compression chamber with raw material, and a second position in which it operates to close the opening of the chamber and provide a sixth wall for the chamber, thus providing a closed chamber for compressing the raw materials into a compressed earthen building block. Hence, the chamber may be generally parallelepiped in shape when all of the walls are in place, although any of the walls may have formations defined thereon to produce complimentary formations in the building block formed in the chamber.  
         [0023]     The at least one dog is generally cylindrical, having any number of suitable cross-sectional shapes, and is received within an aperture of complementary shape in the pressure plate of the compression chamber. Further, the end of the dog away from the ram by which it is inserted into the block is preferably tapered or rounded. Hence, its penetration is facilitated into the raw material from which the building block is manufactured and to distribute the compression forces to the raw material in the compression chamber more evenly. In one embodiment of the invention, there are two such dogs symmetrically spaced with respect to the pressure plate, axes of the dogs being parallel. Then, the dogs may be independently displaceable with respect to the pressure plate. In a second embodiment, a single dog is used, generally having a “dog bone” or “dumbbell” cross-sectional shape—with larger ends and a narrower middle section.  
         [0024]     The pressure plate and the dogs are displaced by means of actuators. In a preferred embodiment, the hydraulic actuator comprises an outer cylinder, a hollow ram inside the outer cylinder, and an inner, solid ram inside the hollow ram. The hollow ram and the solid ram are actuated individually. The outer ram is used to provide the force required to displace the compression plate to reduce the volume of the earth and other raw materials to the block&#39;s terminal size. The inner, solid ram is used to actuate the at least one dog.  
         [0025]     The cover for the pressure chamber may also be operable under control of an actuator, such as a hydraulic cylinder. Operation of the actuators may be controlled by a control means, which may be a computer processor. Thus, operation of the block making apparatus may be automated.  
         [0026]     Further, each dog includes at least one pin, an axis of which is parallel to the direction of travel of the dogs, to define a passageway between the free end of the dog and the cover of the compression chamber, thereby creating a passageway through the building block.  
         [0027]     It will be appreciated that there is an advantage to use such a building block manufacturing apparatus in situ. Thus, the apparatus may be mounted on a vehicle, trailer, or cart to enable it to be transported to and from a building site. Further, a mixer for mixing the raw material of the building blocks may be included in the apparatus on the trailer, as may a suitable reservoir for hydraulic fluid, pumps for driving the hydraulic cylinders, and an electric generator coupled to an internal combustion engine for powering the pumps and for providing electrical power on site. Alternatively, the pumps may be powered directly from the engine.  
         [0028]     The method of manufacture of compressed earthen building blocks includes an initial pre-compression stage, in which the raw materials for the building block are partially compressed and contained within a space of predetermined, terminal outer dimensions. The pre-compression step is by means of the pressure plate. The pressure plate provides a wall of the compression chamber to define the predetermined, terminal dimensions of the block.  
         [0029]     As a second stage of manufacture, the at least one dog is urged into the block material in the compression chamber under the action of a predetermined force. In this step, the outer dimensions of the block are not altered, but the block material is significantly compressed, enhancing the overall compression of the block, as well as the homogeneity of the compression.  
         [0030]     During the previous two steps, at least one passageway is formed entirely through the raw material in the compression chamber. At least one static pin associated with each dog extends from the free end of the dog to the cover plate of the compression chamber. The dog slides along the pin.  
         [0031]     After the block has reached its terminal dimension and the final compression step has been carried out using the at least one dog, the compressed earthen building block is removed from the compression chamber. The step of removing the building block from the compression chamber is carried out by urging the building block from the chamber by means of the pressure plate until the block is at least significantly removed from the compression chamber. The building block so removed from the compression chamber may be discharged laterally by the action of the feeder box actuated by a hydraulic cylinder.  
         [0032]     Commonly, the compression chamber has a parallelepiped shape. However, other shapes may be envisioned. In fact, mold plates of different profiles can be readily replaced, enabling compressed earthen building blocks of various profiles to be made, including special purpose and interlocking blocks.  
         [0033]     A difficulty arises in determining how much raw material to load into the compression chamber to produce a satisfactory compressed earthen building block. Trial and error is usually required, especially when using a new batch of earth having different characteristics than previous batches. A technique to overcome this difficulty is to utilize a small sample of the earth and other raw materials used to make the compressed earthen building blocks and place the sample under the same pressure as the blocks will experience. The amount of compression of the block material is measured and the result translated to the amount of raw material needed to make a full compressed earthen building block. A special system in the hopper of the compressed earthen building block manufacturing machine provides the appropriate volume of raw material for each block.  
         [0034]     To determine the compressibility of a sample of raw materials, an accurately bored cylinder is used. The cylinder is charged, level full, with the raw materials. This defines the initial volume. A force is applied to the raw materials such that the pressure on the materials is equal to that applied by the compressed earthen building block machine described previously. The predetermined pressure is applied in one embodiment by a weight and lever arrangement. In a second embodiment, springs are used to apply the requisite force. In still another embodiment, the force is applied by a hydraulic jack.  
         [0035]     Regardless of the source of the force used to compress the raw materials, the compression of the sample is measured. The change in volume in the sample divided by the initial volume of the sample will be approximately equal to the expected change in volume of the compressed earthen building block material divided by its initial volume. In this way, the initial volume of the block raw materials may be calculated. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0036]      FIG. 1  is sectional end view of an apparatus, in accordance with the invention, for making a building block;  
         [0037]      FIG. 2  is a sectional side view of the apparatus of  FIG. 1 ;  
         [0038]      FIG. 3  shows a compression element of the apparatus of  FIGS. 1 and 2 , in a first position;  
         [0039]      FIG. 4  shows the compression element of  FIG. 3 , in a second position;  
         [0040]      FIG. 5  is a side view of an alternative embodiment of the compression element of the apparatus;  
         [0041]      FIG. 6  is a plan view of the compression element of  FIG. 5 ;  
         [0042]      FIG. 7  is a schematic view of the apparatus of the invention, in a first stage of operation;  
         [0043]      FIG. 8  is a schematic view of the apparatus of the invention, in a second stage of operation;  
         [0044]      FIG. 9  is a schematic view of the apparatus of the invention, in a third stage of operation;  
         [0045]      FIG. 10  is a schematic view of the apparatus of the invention, in a fourth stage of operation;  
         [0046]      FIG. 11  is a schematic view of the apparatus of the invention, in a fifth stage of operation;  
         [0047]      FIG. 12  is a schematic view of the apparatus of the invention, in a sixth stage of operation;  
         [0048]      FIG. 13  is a schematic view of the apparatus of the invention, in a seventh stage of operation;  
         [0049]      FIG. 14  is a first perspective view of the compressed earthen building block apparatus;  
         [0050]      FIG. 15  is a second perspective view of the compressed earthen building block apparatus;  
         [0051]      FIG. 16  is a first perspective view of the compressed earthen building block apparatus with dust covers removed for clarity and with the cover on the compression chamber;  
         [0052]      FIG. 17  is a second perspective view of the compressed earthen building block apparatus with dust covers removed and an open compression chamber;  
         [0053]      FIG. 18  is a third perspective view of the compressed earthen building block apparatus with dust covers removed and a covered compression chamber;  
         [0054]      FIG. 19  is a third perspective view of the compressed earthen building block apparatus with dust covers removed;  
         [0055]      FIG. 20  is a detail perspective view of a wedge and rollers for sealing the compression chamber;  
         [0056]      FIG. 21  is a fourth perspective view of the compressed earthen building block apparatus mounted on a cart for transport;  
         [0057]      FIG. 22  is a schematic showing additional details of the invention;  
         [0058]      FIG. 23   a  is a detail view of a conventional wedge and rollers for sealing the compression chamber;  
         [0059]      FIG. 23   b  is a detail view of a stepped wedge and rollers for sealing the compression chamber;  
         [0060]      FIG. 24  is a detail perspective view of a compression chamber containing a single dog;  
         [0061]      FIG. 25  is a top plan view of a dog;  
         [0062]      FIG. 26  is a side elevation of a hydraulic cylinder assembly able to individually actuate two separate rams;  
         [0063]      FIG. 27  is a side elevation view of a first embodiment of a calibration unit for determining an initial volume of raw material to load into the compression chamber;  
         [0064]      FIG. 28  is side elevation view of three examples of a second embodiment of a calibration unit for determining an initial volume of raw material to load into the compression chamber;  
         [0065]      FIG. 29  is a side elevation view of a disc spring used in the second embodiment of the calibration unit;  
         [0066]      FIG. 30  is a spring characteristics plot showing force versus displacement for a disc spring;  
         [0067]      FIG. 31  is a side elevation view of a third embodiment of a calibration unit for determining an initial volume of raw material to load into the compression chamber;  
         [0068]      FIG. 32   a  is a side elevation view of the hopper showing a first device for varying an amount of charge of raw materials loaded into the hopper;  
         [0069]      FIG. 32   b  is a perspective view of the hopper showing a first device for varying an amount of charge of raw materials loaded into the hopper;  
         [0070]      FIG. 33   a  is a side elevation view of the hopper showing a second device for varying an amount of charge of raw materials loaded into the hopper; and  
         [0071]      FIG. 33   b  is a perspective view of the hopper showing a second device for varying an amount of charge of raw materials loaded into the hopper. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0072]     In the drawings, reference numeral  10  generally refers to an apparatus, in accordance with the invention, for making a compressed earthen building block.  
         [0073]     As shown in  FIGS. 1-13 , the compressed earthen building block manufacturing apparatus  10  has a compression chamber  12  for compressing raw material  14  for the building block to form the block  16 . The raw material  14  is typically earth, of which a large number of suitable compositions are available, together with a stabilizing material, such as cement or other cementitious material, to which is added sufficient water to hydrate the stabilizing material, and, optionally, waterproofing or sealing agents and fillers, such as ash. The building block  16  is thus of the type known as a compressed earthen building block.  
         [0074]     The compression chamber  12  comprises a pair of co-planar spaced apart side walls  18  and a pair of co-planar spaced end walls  20 . Further, a displaceable pressure plate  22  forms a bottom wall of the compression chamber  12 . The pressure plate  22  is displaceable within the side and end walls  18 ,  20  to move slidingly in relation thereto. An operatively upper end  24  of the compression chamber  12  is open and is closed by means of a cover  26  in the form of a plate, comprising the sixth wall of the chamber  12 . The cover plate  26  is moved in a sliding manner along guide rods  1820  (see  FIGS. 18-19 ), from a first position, in which it is clear of the opening  24  to permit loading and unloading of the chamber  12 , as shown in  FIG. 7 , and a second position, as shown in  FIG. 9 , in which it forms the sixth wall of the chamber  12 , sealing it for compression. The pressure plate  22  is mounted on the piston  28  of a hydraulic cylinder assembly  30 , which acts as an actuator for displacing the pressure plate  22 .  
         [0075]     Although a compression chamber  12  having a parallelepiped shape is shown in this disclosure, other shapes may be envisioned. In fact, mold plates of different profiles can be readily replaced, enabling compressed earthen building blocks  16  of various profiles to be made, including special purpose and interlocking blocks.  
         [0076]     Further, the apparatus  10  has a pair of generally circular cylindrical compression elements, or dogs  32  (although the dog or dogs of the present invention are not limited to a specific shape), each of which is mounted at its operatively lower end  34  to a piston  36  of a hydraulic cylinder assembly  38 , thereby enabling the compression element  32  to be displaced axially between a first position, as shown by the compression element  32 . 1  of  FIG. 2 , and second position, as shown on by the compression element  32 . 2  of  FIG. 1 . The compression elements  32  are axially displaceable independently of the pressure plate  22  and are received through circular apertures defined in the pressure plate  22 .  
         [0077]     Still further, each of the compression elements  32  is radiused at its free end  42 , although the present invention is not limited thereto. Each of the compression elements  32  also carries a circular cylindrical pin  44  at its free end. As shown in  FIGS. 3 and 4 , the pin  44  is received in an axial bore  46  defined in the compression element  32  and is spring-loaded to be axially displaceable with respect to its associated compression element  32 . Thus, the pin  44  may move between an extended position, as shown in  FIG. 4 , and a retracted position, as shown in  FIG. 3 . The free ends  48  of the pins  44  are received in locating recesses  50  defined in the cover  26  of the compression chamber  12  so that, in use, when the pins  44  are located in their associated recesses  50 , a pathway is defined through the raw material  14  of the building block  16  in the compression chamber  12 . It will be appreciated that the compression elements  32  may be of a variety of shapes. As an example, it has been found that a compression element having a generally rectangular cross-section with radiused corners, as shown in  FIGS. 5 and 6  of the drawings, provides a good distribution of compressive forces in the building block.  
         [0078]     Turning now to FIGS.  7  to  13 , the apparatus  10  and method for manufacturing compressed earthen building blocks is illustrated at various stages of operation, schematically. In addition to the compression chamber  12  of the apparatus  10 , as shown in  FIGS. 1 and 2 , the apparatus  10  also includes a raw material hopper  52 , a feeder box  54 , and a horizontally oriented hydraulic actuating cylinder  56  connected to the cover plate  26  of the chamber  12 . Not shown in the drawings but included in the apparatus are a hydraulically driven mixer for mixing the raw material  14  composition, a hydraulic fluid reservoir, and a hydraulic pump which, in the preferred embodiment, is driven by an electric motor under power from an electric generator which is driven by an engine, for actuating the hydraulic cylinders of the apparatus  10 . All of the component parts of the apparatus  10  are secured to a trailer (not shown) and may be towed for use on site. It will be appreciated that the engine may be a gasoline or diesel engine and that the engine may drive the pump directly, rather than via an electric system.  
         [0079]     In  FIG. 7 , the feeder box  54  is located immediately under the hopper  52  and has been filled with raw material  14 . The cover plate  26  of the compression chamber  12  is clear of the compression chamber  12  so that the compression chamber  12  is open and its operatively upper end  24 . The pressure plate  22  of the compression chamber  12  is at its upper limit, having urged a compressed earthen building block  16  out of the chamber  12 , thereby extruding the compressed earthen building block  16  from the chamber  12 . The compressed earthen building block  16  is shown on a conveyor, having been pushed away from the chamber  12  by the horizontal hydraulic cylinder  56 .  
         [0080]     In  FIG. 8 , the feeder box  54  has been moved, under actuation of the horizontal hydraulic cylinder  56 , towards the compression chamber  12 . Simultaneously, the hopper  52  is closed by means of a closing plate  58  which is connected to the feeder box  54 . As the feeder box  54  begins to discharge its load into the compression chamber  12 , the pressure plate  22  begins to drop to its lower limit (as illustrated by the pressure plate reference by reference numeral  22 . 1  in  FIG. 2 ) and the compression elements  32  also return to their lower position.  
         [0081]     In  FIG. 9 , the compression chamber  12  has been charged via the feeder box  54  with a predetermined volume or weight of raw material  14  and, actuated by the horizontal hydraulic cylinder  56 , the feeder box  54  and cover plate  26  have been positioned so that the compression chamber  12  is closed off by the cover plate  26 . The compression chamber  12  is now sealed.  
         [0082]     In  FIG. 10 , a first stage of pre-compression has been completed and the pressure plate  22  has moved to a position where, together with the remaining walls  18 ,  20  and cover plate  26  of the compression chamber  12 , the external dimensions of the block  16  are determined and a degree of pre-compression of the raw material  14  of the building block  16  has been achieved. The position of the pressure plate  22  is indicated by the numeral  22 . 2  in  FIG. 2 . The dogs  32  are still in their retracted position. Thus, the raw material  14  of the building block  16  has been partly compressed and the size of the block  16  is determined.  
         [0083]     In  FIG. 11  the dogs  32  are urged, under operation of their respective hydraulic cylinders  38 , into the raw material  14  within the compression chamber  12  and the pins  44  of each of the compression elements  32  locate in their respective recesses  50  in the cover plate  26  to form the passageways in the block  16 . Each of the dogs  32  is urged into the partially compressed raw material  14  under a predetermined pressure (as shown by the dog  32 . 2  in  FIG. 2 ). Thus, it will be appreciated that depending on the consistency of the raw material  14  in the compression chamber  12  and the characteristics of the raw material  14  in the immediate vicinity of the compression elements  32 , each of the dogs  32  will intrude into the chamber  12  until the resistance offered by the raw material  14  under compression is equal to the force imparted to that compression element  32  by its associated actuator  38 . At this stage, the dogs  32  come to rest and are in equilibrium. The predetermined force applied to the dogs  32  is determined with a view to ensuring adequate compression and even density throughout the building block  16 . It will be appreciated that this pressure may be varied, depending on circumstances relating to the composition of the raw materials  14  in use, its wetness, and other factors. The pressure plate  22  and dogs  32  are then allowed to relax, in order to allow for a certain amount of expansion of the compressed building block  16  and also to break any bond between the building block  16  and these components.  
         [0084]     In  FIG. 12 , the feeder box  54  and the cover  26  of the compression chamber  12  are once again retracted, clearing the opening  24  of the compression chamber  12 . In  FIG. 13 , the pressure plate  22  is once again urged, under operation of its associated hydraulic cylinder  30  to its upper limit (as shown by the pressure plate numbered  22 . 3  in  FIG. 2 ), thereby extracting the completed compressed earthen building block  16  from the chamber  12 . The compressed earthen building block  16  is then ejected laterally off of the pressure plate  22  by the movement of the feeder box  54  under the influence of the actuation of the horizontal hydraulic cylinder  56  as shown in  FIG. 7 , thereby completing the cycle. An elastic bumper  1310  helps protect the compressed earthen building blocks  16  from damage as they are pushed from the opening  24  compression chamber  12 . The cycle is completed automatically by means of a hydraulic valve system (not shown) under the control of an operator or digital processor (not shown), to enable the automated processing of building blocks.  
         [0085]     A perspective view of the compressed earthen building block apparatus  10  is shown in  FIG. 14 . In this view, a hydraulic fluid reservoir  1410  is clearly seen. Mounted on the hydraulic fluid reservoir  1410  are a set of control valves  1420 . The valves  1420  are used to control the movement of the various hydraulic actuators, including those for the feeder box  54 , the pressure plate  22 , and the dogs  32 . In the embodiment shown in  FIGS. 14-21 , the hopper  52  and feeder box  54  are integral, both sliding together.  
         [0086]     A perspective view of the apparatus of the present invention from another direction is shown in  FIG. 15 . The hydraulic cylinder  56  for the horizontal actuation of the feeder box  54  and cover plate  26  is clearly shown near the point of viewing of  FIG. 15 .  
         [0087]     Dust covers  1510  provide protection for the wedges  1610  (see  FIG. 16 ) and roller surfaces  1710  (see  FIG. 17 ).  
         [0088]     An engine  1520  provides shaft power for at least one hydraulic pump for pressurizing hydraulic fluid from the reservoir  1410  to the various hydraulic actuators  56 ,  30 ,  38  (only one hydraulic cylinder  56  shown in  FIG. 15 ). The engine  1520  may also be used to provide electrical power for various operations on site such as running an electric motor for mixing the raw materials  14  used in the manufacture of the compressed earthen building blocks  16 .  
         [0089]     In  FIG. 16 , the same view as  FIG. 15  is shown except that the dust covers  1510  have been removed for clarity. In  FIGS. 16-21 , the dust covers  1510  are not shown. The present invention may be practiced without the dust covers  1510 , however, that is not the preferred embodiment.  
         [0090]     Clearly seen in  FIG. 16 , is the cover plate  26 . Integral with the cover plate are wedges  1610 , with which the cover is secured down. This will be explained further with regard to FIGS.  17 ,  19 - 21 , and  31 - 32 .  
         [0091]     The compression chamber  12  can be seen in  FIG. 17 . Tops of two pins  44  are seen inside the compression chamber  12 .  
         [0092]     A row of rollers  1710  may be seen on one side of the compression chamber  12 . A similar row of rollers  1710  is located on the other side of the compression chamber  12  as well, but are blocked from view by a side plate  1720  closest to the point of viewing. The rollers  1710  are mounted on their respective side plates  1720 .  
         [0093]     When the hydraulic cylinder  56  is actuated, as shown in  FIG. 18 , the sliding assembly  1810 , including the feeder box  54 , the hopper  52 , and the cover plate  26  slides along guide rods  1820  (which are preferably chromed) by means of suitable sliding bushings  2200  (see  FIG. 22 ). The cover plate  26  is located directly over the upper end  24  of the compression chamber  12 .  
         [0094]     A view more from the top is seen in  FIG. 19 . In this figure, the cover plate  26  is located directly over the upper end  24  of the compression chamber  12 . The wedges  1610  have engaged the sets of rollers  1710  (only one full set visible in  FIG. 19 ). As the wedges  1610  are forced under the rollers  1710 , pressure is exerted downward because of the ramped wedge  1610  surfaces. The guide rods  1820  are mounted at each end in elastomer cushions  1910 ,  1911  which are capable of deflecting radially in all directions to accommodate any guide rod  1820  misalignment and to permit the cover plate  26  to be pressed down over the upper end  24  of the compression chamber  12 , thereby sealing the compression chamber while pressure is applied to the raw materials  14  during the compressed earthen building block  16  making process.  
         [0095]     A detail of one of the two wedges  1610  is shown in  FIG. 20  under the associated set of rollers  1710 .  
         [0096]     The compressed earthen building block apparatus  10  of the present invention is shown in  FIG. 21  on a wheeled cart  2110  to make it mobile. Other options are to mount the compressed earthen building block apparatus  10  on a trailer or sled for towing behind a vehicle, or mounting the compressed earthen building block apparatus  10  permanently to a stationary surface.  
         [0097]     Additional features of the present invention are shown in  FIG. 22 . The hopper  52  is shown mounted on elastomer mounts  2205 . A rod  2210 , attached to the motor mounting frame  2215  and the hopper  52 , transmits vibration from the motor to the hopper to enable efficient and reliable feeding of the raw material  14  to the feeder box  54 .  
         [0098]     The guide rods  1820 , on which the sliding assembly  1810  slides, deflect in the elastomer cushions  1910 ,  1911  over the compression chamber under the action of the wedge  1610 . The angle, a, has been selected for this particular mechanism at a particular value to ensure the least friction and minimal energy losses and to minimize wear. The components in contact comprise two easily replaceable wear plates  2220 .  
         [0099]     Compressed earthen building blocks tend to be more compact in their centers than the outer edges. To counter this effect, upper plate supports  2225  replace the rollers  1710  in this embodiment. The upper plate supports  2225  have an arched void so the upward force from the hydraulic cylinder assembly  30  is shifted to the ends of the upper supporting beams  2230 , thereby reducing bending or flexural stresses therein. In this way, compaction may be concentrated toward the edges of the compressed earthen building block  16 , making a more homogeneous compressed earthen building block  16 , even before the dogs  32  are inserted.  
         [0100]     A detail of a wedge  1610  and associated rollers  1710  is shown in  FIG. 23   a . The hydraulic cylinder  56  forces the cover plate  26  and the wedge  1610  to the right in  FIG. 23   a  in order to seal the compression chamber  12 . The action of the wedge  1610  against the rollers  1710 , under the force of the hydraulic cylinder  56 , forces the cover plate  26  down over the upper end  24  of the compression chamber  12 .  
         [0101]     A stepped wedge  2310  shown in  FIG. 23   b  represents an additional embodiment of the sealing system for the compressed earthen building block apparatus  10  of the present invention. An advantage is realized in this design in that different values of the angle, α, may be adopted without changing the height of the wedge  2310  assembly.  
         [0102]     The cover plate assembly, examples of which are shown in  FIGS. 23   a  and  23   b , evidently does not require a strict wedge shape. The profile must be wedge-like, in that a portion of the profile at one end of the assembly must be lower than the portion of the profile at the other end. If the cover plate assembly is to engage more than one roller, the general trend from the lower end to the upper end must be increasing in height.  
         [0103]     The compression elements, or dogs  32 , shown in  FIGS. 1-13  is a first embodiment of this part of the invention. A second embodiment is shown in  FIGS. 24 and 25  wherein a single dog  2400  is used. As is most clearly seen in  FIG. 25 , the dog  2400  has a dog-bone or dumbbell shape that is narrower in the center and broader at the ends. Only one static pin  44  is shown in  FIGS. 24 and 25 . Where the other static pin  44  has been removed, a mounting rod  2410  to which the pin would be attached is visible.  
         [0104]     Another feature shown most clearly in  FIG. 24  is a two-level pressure plate  22 . The hydraulic cylinder assembly  30  connects to the lower plate  2420 . The lower plate  2420  has an aperture in it for passing a portion of the hydraulic cylinder assembly  30 . The lower plate  2420  connects rigidly to an upper plate  2430 , which engages the raw materials  14  to produce a compressed earthen building block  16 . A space between the lower plate  2420  and the upper plate  2430 , as well as the rigid connection, is effected via standoffs  2440 . A compression box lower plate  2450  provides structure and rigidity to the compression box  12 .  
         [0105]     To provide independent action of the lower plate  22  and the dog  2400 , a novel hydraulic cylinder assembly  30  is provided the present invention and is shown in  FIG. 26 . This hydraulic cylinder assembly  30  comprises two (2) rams  2605 ,  2610 . The outer ram  2605  is hollow and actuates the pressure plate  22 . The inner ram  2610  travels inside the hollow, outer ram  2605  and actuates the dog  2400 . Hydraulic fluid enters the hydraulic cylinder under pressure to force the outer ram upward at the outer ram lower port  2615  while hydraulic fluid enters the hydraulic cylinder under pressure to force the outer ram downward at the outer ram upper port  2625 . Similarly, the inner ram  2610  is forced upward by hydraulic fluid entering the inner ram lower port  2620  under pressure, where the hydraulic fluid bears on the entire circular surface of the upper ram piston  2650 . The inner ram  2610  is forced downward by hydraulic fluid entering the inner ram upper port  2630 . The surfaces on which the pressurized hydraulic fluid act on the rams&#39; pistons  2650 ,  2655  are annular in shape, with the previously mentioned exception of the bottom surface of the inner ram&#39;s piston  2650 .  
         [0106]     A seal  2660  isolates the pressurized fluid acting on the two rams  2605 ,  2610 . In this way, the two rams  2605 ,  2610  may be actuated independently, while remaining coaxial.  
         [0107]     An additional aspect of the present invention is a method and apparatus for accurately determining a volume of raw material  14  with which to begin to produce a compressed earthen building block  16  of consistent dimension and density without resorting to the trial and error method of the prior art. In each of the following embodiments, a sample of the raw materials  14  is inserted in a calibration apparatus and compressed under the same pressure as it would experience in the compressed earthen block apparatus  10 . The volume of raw material  14  to be loaded into the compression chamber  12  may be calculated as:  
           –   ⁢   V     1     =           –   ⁢   V     2     ⁢       v   1       v   2         =         –   ⁢   V     2     ⁡     (         Δ   ⁢           ⁢   v       v   2       +   1     )             
 
 where: 
         1  is the initial (uncompressed) volume of raw material  14  loaded into the compression chamber  12 ,      2  is the terminal volume of the finished block  16  based on the terminal volume of the compression chamber  12 ,     v 1  is the initial (uncompressed) volume of raw material  14  loaded into the calibration unit,     v 2  is the final volume (after compression) of the raw material  14  in the calibration unit, and 
 
Δ v=v   1   −v   2 . 
       
 
         [0113]     The various embodiments illustrated in  FIGS. 27-32  vary only in the manner in which the force is generated to compress the raw materials  14 .  
         [0114]     A first embodiment of a calibration unit is shown in  FIG. 27 . The calibration cylinder  2710  is filled with a known volume of raw material  14 , such as a complete calibration cylinder  2710  full. A weight  2720  has been sized to provide a pressure in the calibration cylinder  2710  equal to that which will be experienced in the compression chamber of the compressed earthen building block apparatus  10 . The weight  2720  apples a force at the end of a lever arm  2730  to which a piston  2740  is operatively, pivotally attached. The lower end of the piston  2740  engages the raw materials  14  in the calibration cylinder  2710 . After the lever arm  2730  and weight  2720  have ceased their descent, the sample has achieved its full compression as it would in the compression chamber  12  of the compressed earthen building block apparatus  10 . The amount of compression may be read off a scale  2750  which may be graduated into units representing either v 2  or Av.  
         [0115]     A second embodiment of a calibration unit is shown in  FIG. 28 . In this embodiment, disc springs  2900  as detailed in  FIG. 29  are used to apply the force to the raw materials  14 . Again, a cylinder  2800  is filled with raw materials  14 , in this case, from the bottom of the cylinder  2810  as shown in  FIG. 28 . A force mechanism  2820  is threaded down over the cylinder  2810  via threads  2830 . The force mechanism  2820  comprises a piston  2840  that engages the raw materials  14 , and a plurality of disc springs  2900 . An example of a force-displacement spring characteristics plot is shown in  FIG. 30 . In this embodiment, an operator must keep track of both the compression amount via a lower scale  2850  that moves with the piston  2840  and an upper scale  2860  that is stationary with respect to a lower knob  2870 . In this way, the compression of the springs  2900  may be calculated by subtracting the length of the lower scale  2850  from that of the upper scale  2860 . Based on the stress-strain relationship shown in  FIG. 30 , the springs  2900  will be compressed a known amount in order to achieve the same pressure as that of the compression chamber  12  of the compressed earthen building block apparatus  10 .  
         [0116]     Another embodiment of the calibration unit is shown in  FIG. 31 . Here again, a cylinder  3110  is filled with a known volume of raw materials  14 . The force, in this embodiment, is produced by a hydraulic bottle jack  3100 . A pressure gage  3120  may be calibrated to provide a reading of the pressure in the cylinder  3110 . Alternatively, the actual pressure in the hydraulic bottle jack  3100  may be converted to the pressure in the cylinder  3110  with a simple scaling constant. The cylinder  3110  is filled with raw materials  14 , and threaded down over threads  3130  on a neck of the hydraulic bottle jack  3100 . Pressure is applied to the raw materials  14  by pumping the handle (not shown) of the hydraulic bottle jack  3100  until the same pressure is reached in the cylinder  3110  as will be realized in the compression chamber  12  of the compressed earthen building block apparatus  10 . The amount of compression is read from the scale  3140 . Again, the scale  3140  may be in terms of v 2  or Δv. The knob  3150  on top may be used to manually press the hydraulic bottle jack&#39;s  3100  piston back to its lowered position.  
         [0117]     Once the appropriate initial volume of raw materials  14  has been calculated using measurements from one of the calibration units, it is prudent to modify the hopper  52  to automatically receive only this volume of raw material. A first embodiment of such a modification is shown in  FIGS. 32   a  and  32   b . A sliding plate  3200  may be adjusted to vary the top opening of the hopper  32 . The result is an empty space, void of raw materials  14  under the sliding plate  3200 , effectively reducing the amount of raw materials  14  loaded into the hopper  52  at each charge.  
         [0118]     A second embodiment of an apparatus for gauging the initial charge of raw materials  14  in the hopper is shown in  FIGS. 33   a  and  33   b . In this embodiment, adjustable wings  3300  pivot at the top at hinges  3310 . Pins or rods passed through appropriate holes  3320  are used to hold the wings  3300  in place.  
         [0119]     By means of the invention, there is provided an apparatus  10  and a method for the production of earth-based building blocks  16  used in construction that enable the production of compressed earthen building blocks  16  having a high degree of homogeneity, consistent density of material throughout the block, and the achievement of compression pressures throughout the block during the course of construction that facilitate the creation of hard-wearing building blocks having a high degree of dimensional precision. Further, the energy required in the compression of blocks  16  is reduced in comparison with existing methods for the production of similar blocks. Since the pressures involved in the manufacture of the building blocks  16  are relatively reduced, the power requirements of the apparatus are similarly reduced and the size of the apparatus is sufficiently small to be readily transported on a road trailer for use on site.  
         [0120]     The above embodiments are the preferred embodiments, but this invention is not limited thereto. It is, therefore, apparent that many modifications and variations of the present invention are possible in light of the above teachings. It is, therefore, to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described.