Abstract:
A foam production system for producing a foam suitable for combining with a concrete mix comprises an air actuator for providing pressurized air to an aerator assembly and a water actuator arranged to provide pressurized water. A foaming agent is added to the water in a mixing chamber. The mixture of water and foaming agent is pumped out of the mixing chamber to the aerator, which is arranged to mix pressurized air into the mixture of a water and foaming agent to produce a foam output that is suitable for being combined with concrete mix to produce foamed concrete.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    This invention relates generally to a system for producing a foam suitable for adding to concrete mix. 
         [0002]    The present invention relates generally to a foam producing apparatus and method, and is particularly concerned with such an apparatus usable for entraining air bubbles in concrete to produce various types of lightweight concrete structures such as concrete wall panels having a high density of air voids. 
         [0003]    It has been known for some time that lighter weight concrete structures can be made by entraining air bubbles in the concrete mixture at some point prior to placing the concrete, so that the concrete hardens to leave air voids throughout the structure. This type of lightweight concrete is generally known in the field as cellular concrete. Cellular or foamed concrete may be made by pre-forming a foam and then adding the foam to a slurry of cement, aggregate and water in a mixing device. Another known technique is to add a gas-forming agent to the slurry, causing the mix to swell as gas bubbles are formed. The reduced density of cellular concrete, and thus the reduced weight, reduces transportation and handling costs, and also reduces the dead load imposed on a structure constructed from such concrete. It also has better heat insulation, freeze and thaw resistance, reduced water permeability and sound absorption properties than conventional concrete. 
         [0004]    This invention incorporates an aerator device similar to the aerator described in U.S. Pat. No. 5,900,191, that issued May 4, 1999 to Gray and Masters and that is incorporated by reference into this disclosure. 
       SUMMARY OF THE INVENTION 
       [0005]    A foam production system according to the present invention for producing a foam suitable for combining with a concrete mix, comprises an air actuator for providing pressurized air; an air pressure regulator arranged to receive pressurized air from the air actuator and provide an air output having a selected air pressure; an aerator assembly arranged to be in fluid communication with the air pressure regulator to receive pressurized air therefrom; and a water actuator arranged to provide pressurized water. The foam production system further comprises a mixing chamber arranged to be in fluid communication with the water actuator to receive water therefrom; a foaming agent tank arranged to be in fluid communication with the mixing chamber to provide a foaming agent that is mixed with water in the mixing chamber; a pump arranged to pump a mixture of water and the foaming agent out of the mixing chamber; and a water pressure regulator arranged to receive the mixture of water and foaming agent output from the pump and to provide the mixture in the aerator at a selected liquid pressure. The aerator assembly is arranged to mix pressurized air into the mixture of water and foaming agent to produce a foam output that is suitable for being combined with concrete mix to produce foamed concrete. 
         [0006]    The foam production system according to the present invention preferably further comprises an input air pressure gauge arranged to measure the pressure of air input to the air actuator; an output air pressure gauge arranged to measure the pressure of air output from the air pressure regulator; an input water pressure gauge arranged to measure the water pressure of water input to the mixing chamber; and an output water pressure gauge arranged to measure the pressure of the mixture of water and foaming agent output from the water pressure regulator. 
         [0007]    One embodiment of the invention is a version that is suitable for attachment to a cement mixing/transport truck to dispense foam before, during and/or after transport. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]      FIG. 1  is a functional block diagram of a first embodiment of a foam production system according to the present invention; 
           [0009]      FIG. 2  is a bottom plan view of an aerator assembly that may be included in a foam production system according to the present invention; 
           [0010]      FIG. 3  is a perspective view showing input and output ports of the aerator assembly of  FIG. 2 ; 
           [0011]      FIG. 4  is a perspective view of an atomizer that may be included in the aerator assembly of  FIGS. 2 and 3 ; 
           [0012]      FIG. 5  is a cross sectional view of the showing atomizers that may be included in the atomizer of  FIGS. 2 and 3 ; 
           [0013]      FIG. 6  is a side elevation view of the of the atomizer as shown in  FIGS. 5 ; 
           [0014]      FIG. 7  is and end elevation view of the atomizer of  FIG. 6 ; 
           [0015]      FIG. 8  is a cross sectional view of the aerator showing the atomizer therein and showing air and liquid inputs to the aerator; 
           [0016]      FIG. 9  is a cross sectional view showing liquid flow into the atomizer; 
           [0017]      FIG. 10  is a cross sectional view showing a portion of a mixing chamber that may be included in the aerator; 
           [0018]      FIG. 11  is a side elevation view showing an agitator that may be placed in the mixing chamber of  FIG. 10 ; 
           [0019]      FIG. 12  is a functional block diagram of a second embodiment of a foam production system according to the present invention 
           [0020]      FIG. 13  is a perspective view showing a dual aerator assembly that may be included in the embodiment of the invention shown in  FIG. 12 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0021]    Referring to  FIG. 1 , a foam production system  20  according to the present invention includes an air intake  22  that inputs air to a first electric actuator  24  and a water intake  38  that inputs water to a second electric actuator  40 . The electric actuator  24  provides air to an air regulator  28  that is included in a control box  26 . The air regulator provides pressurized air to an aerator assembly  50 . A first air pressure gauge  34  in the control box  26  measures the pressure of the air input to the first electric actuator  24 , and a second air pressure gauge  36  in the control box measures the pressure of the air that is output from the air regulator  28  to the aerator assembly  50 . 
         [0022]    The second electric actuator  40  provides water to a pressure valve  42  that in turn inputs the pressurized water into a mixing chamber  46 . A first water pressure gauge  34  in the control box measures the pressure of water that the pressure valve  42  provides to the mixing chamber  46 . A tank  44  that contains an air entrainment admixture that is provided to the mixing chamber  46  to be mixed with water. A booster pump  48  pumps the water-air entrainment mixture to a pressure regulator  52 . A booster water pressure gauge  32  in the control box  26  is connected to the pressure regulator  52  for monitoring the pressure therein. The water-air entrainment mixture is output from the pressure regulator  52  to the aerator assembly  50  to be mixed with pressurized air from the air regulator  28  to form a foam that is then output from the aerator assembly  50 . 
         [0023]    The bottom plan view of  FIG. 2  and the perspective view of  FIG. 3  show an embodiment of the aerator assembly  50  that is comprised of three straight pipes  52 - 54 . The pipes  52  and  54  are parallel with the pipe  53  connected between the pipes  52  and  54  at their ends  56  and  58  by two 90° pipe elbows  60  and  62 . A pipe fitting  64  is connected to an end  66  of the pipe  52 . An air inlet  68  is connected to the fitting  68  and is arranged to receive pressurized air from the air pressure regulator  28  of the block diagram of  FIG. 1 . The fitting  66  also includes a liquid inlet  70  that is arranged to receive a mixture of water and the foaming agent from the water pressure regulator  52  of  FIG. 1 . The aerator assembly  50  forms air bubbles in the mixture of water and the foaming agent to form a foamed liquid-like composite material that exits the aerator assembly  50  at an outlet  71  formed in an outlet fitting  72 . The foamed liquid is suitable for mixing with concrete or other material that is to be foamed. 
         [0024]      FIGS. 4-8  illustrate an atomizer  80  that may be included in the aerator assembly  50 . The atomizer  80  is formed as an elongate pipe or tube  81  having a plurality of ports  82  therein. As best illustrated in  FIGS. 5 and 8 , the ports  82  preferably are Venturi passages. However, straight-sided orifices or other configurations may be used in other embodiments. The number of ports shown is merely an example of an embodiment of the atomizer  80 , which actually could include a greater or lesser number of ports than the number shown in  FIGS. 4-8 . 
         [0025]    Referring to  FIGS. 5 and 7 , the atomizer  80  is hollow and has an inner wall  84  and an outer wall  86 . Referring to  FIG. 8 , when the aerator assembly  50  is assembled, the atomizer  80  is placed inside the pipe  52  and secured at ends  90  and  92  so that there is a void  94  between the inner wall  88  of the pipe  52  and the outer wall  86  of the atomizer  80 . A bushing  87  may be mounted to the atomizer near the end  90  thereof. So that the end  90  is secured inside the fitting  64 . A bushing  89  may be mounted inside the pipe  52  so that the O-rings  83  and  85  near the end  92  of the atomizer fits closely against the inner wall of the bushing  89 . 
         [0026]    The mixture of water and the foaming agent flows into the void  94  via the input port  70 . Air is input to the atomizer  80  via the air input port  68 . The bushings  87  and  89  and the O-rings  83  and  85  cooperate to seal the void  94  so that the liquid mixture of water and foaming agent cannot flow past the outer wall  86  of the atomizer  80 . The pressure of the mixture of water and foaming agent in the void  94  is greater than the air pressure input to the atomizer  80  via the air inlet  68  so that the mixture of water and foaming agent is forced into the inner chamber  95  in the atomizer  80 . The bushing  89  seals the end of the void  90  so that the mixture of water and foaming agent cannot flow through the void  90  into the pipe  53 . 
         [0027]    The air may be supplied to air inlet  68  at a pressure in the range from 100 psi±10 psi, while the water/foaming agent mixture may be pressurized to a pressure of 175 psi.±25 psi. By varying the geometry or quantity of the water, jet orifices of the mixing tube or the geometry or medium of the mixing chamber, pressures and pressure relationships may vary significantly. The geometry, orifice size, and pressure relationships must be such that the foam solution is atomized into tiny droplets, to ensure formation of very fine bubbles in the foam. Because of the pressure differential, the aqueous foaming agent will be forced inwardly through the ports  82 , and will be atomized into droplets, or a fine spray, due to passage through the ports  82 . The arrows in  FIG. 9  show the flow of the mixture of air and foaming agent into the inner chamber  95  of the atomizer  80 . The atomized droplets are propelled by the pressurized air along the tube  81  and through a plurality of openings  96  in an end plate  97  ( FIG. 8 ) into an agitation chamber  100  that is inside the pipes  53  and  54 . 
         [0028]    The agitation chamber  100  is filled with a suitable agitating medium that may comprise a plurality of eyelets or tubular members  102  that may be formed in three or more different sizes. The agitation chamber  100  is closed at its outer end by a sealing disc or retainer  110  having a plurality of small passages  112  therethrough as shown in  FIG. 10 . 
         [0029]      FIGS. 10 and 11  illustrate one preferred embodiment of the eyelets  102 . As best illustrated in  FIG. 11 , each eyelet  102  has a sharp-edged tubular section  104  with an annular rim  106  at one end and has a through bore or passage  108 . The eyelets  102  may be formed of brass or other materials, and a plurality of different size eyelets may be used to fill chamber  100  if desired. 
         [0030]    In the agitation chamber  100  the droplets are forced through the multiple randomly oriented tubular openings  108  in eyelets  102  with severe changes in direction, compression, expansion and violent agitation. This causes a foam to be produced that comprises fine bubbles, each containing water. The density of the foam, i.e. the amount of water in a unit quantity of foam, can be varied by changing the pressures at inlets  68  and  70 . This allows the foam density to be varied in the range from 6-11 oz. per gallon of foam, or 45-80 gm of water per liter of foam. Generally, lower inlet pressures produce a foam with a higher density of water, so that an air inlet pressure of 90 psi. and a foamable liquid inlet pressure of 150 psi. produce a foam of around 80 gm. water per liter, while an air inlet pressure of 110 psi. and a foamable liquid inlet pressure of 175 psi. produces a foam of around 45 gm. of water per liter. By varying the geometry, quantity of water, jet orifices of the mixing tube, or the geometry of medium of the mixing chamber, pressures and pressure relationships may vary significantly. 
         [0031]    Referring to  FIG. 12 , a foam production system  110  according to the present invention includes a pair of aerator assemblies  50 A and  50 B, which preferably are essentially identical. The aerators  50 A and  50 B each receive air from the air pressure regulator. 
         [0032]      FIG. 13  is a perspective view showing a dual aerator assembly  112  that is suitable for forming the foam production system  110  of  FIG. 12 . Pipe fittings  114 A and  114 B receive liquid inputs from liquid inlets  116 A and  116 B, respectively. The pipe fittings  114   a  and  114 B also receive air inputs from air inlets  118 A and  118 B, respectively. The air and liquid inputs mix together in atomizers  120 A and  120 B that are connected to the pipe fittings  114 A and  114 B, respectively. The atomizers  120  and  120 B both are preferably formed in accordance with the atomizer  80  previously described. The present invention is not limited to having one or two aerator assemblies. Any desired number of aerator assemblies may be included in a foam production system according to the present invention. 
         [0033]    A fine spray of the foaming agent and air is output from the atomizers  120 A and  120 B via pipe fitting  122 A and  122 B, respectively. The atomizer outputs are combined in a pipe fitting  124  and then forced through a pipe elbow  126  into an agitation chamber  128 . The agitation chamber  128  preferably is formed to have the structure and functions of the agitator  100  previously described. The foam output of the agitation chamber  128  passes through an outlet  130 , which preferably has quick connect/disconnect fittings. 
         [0034]    As discussed above, one possible advantageous use for the foam produced by this apparatus is mixing with liquid concrete to produce a foamed concrete material that can be pre-cast in a mold or cast on site, to produce air-entrained, lightweight concrete on drying. Where the foam is to be mixed with concrete, suitable foaming agents for mixing with water to produce the foam in apparatus  10  are and similar surfactants or foaming agents used in the foaming of concrete. The use of such foaming agents with the pressure differentials described above and the apparatus of  FIGS. 1-13  has been found to produce a thick; creamy foam of fine bubbles that are extremely resistant to collapse and are long-lasting, even when mixed with concrete for extended intervals of several hours. Since the bubbles are retained within the concrete material for longer periods of time without collapsing, they will still be present when the concrete is cast or placed. As the concrete hardens, the heat of concrete curing will collapse the bubbles, releasing the trapped water that the concrete will use in order to fully hydrate. Thus, there is less need to wet the concrete during curing, as is normally necessary with conventional, unfoamed concrete.