Multi-nozzle assembly for extrusion of wall and construction method

GOVERNMENT'S INTEREST IN APPLICATION

0001This invention was made with government support under NSF Grant No. 9634962 and NSF Grant No. 9522982 awarded by the United States Government. The government has certain rights in the invention.

BACKGROUND

0002<i>Field</i>

0003This application relates to a multi-nozzle assembly as per the preamble of claim 1 and to a construction method based on extrusion of materials.

0004<i>Related Art</i>

0005Constructing homes, offices, boats and other structures has an ancient heritage. Despite all of the centuries of development, however, there can be difficulties and problems.

0006Construction is usually very labor intensive. Even a modest size structure usually requires the efforts of numerous individuals. This can be very costly. Simultaneously using the time of numerous individuals in an efficient manner can also be challenging.

0007The results of the construction effort can also be inconsistent. The appearance and quality of one structure can vary from another built from the same design. This can be caused by differences in the skills, efforts, supervision and techniques employed by those that world on the structures.

0008Construction may also result in wasted material. For example, when wood is used, standard, off-the-shelf lengths must often be cut to meet design requirements, resulting in waste.

0009Construction using manual labor can also be very time-consuming, requiring months and, in some instances, years to complete. Construction can also be hazardous. Many construction workers are killed or seriously injured at construction sites, include about 500,000 in the United States alone.

0010<patcit id="pcit0001" dnum="AT385550B"><text>AT 385 550 B</text></patcit> discloses a computer controlled apparatus for producing buildings and alike, wherein three nozzles are positioned at the end of a movable material-positioning head. Fluid construction material is transported through flexible tubes and let out through the three nozzles layer by layer and hardened to produce, for example, walls of a building without using formwork or casings.

0011<patcit id="pcit0002" dnum="US5656230A"><text>US 5 656 230 A</text></patcit> discloses an additive fabrication method using a fluid construction material which can be solidified, trowels defining first and second surfaces, and a nozzle for delivering fluid material to a predetermined location, including the steps of moving the trowels and nozzle along a predetermined path defining an enclosed area, delivering fluid material to the nozzle to extrude the material in a layer as the nozzle is moved along the path, with the first and second surfaces moving with the nozzle to produce a wall of the extruded material forming an enclosed area with a shaped outer surface and a shaped top surface, and delivering fluid material to the enclosed area.

SUMMARY

0012A multi-nozzle assembly according to the invention includes a first nozzle configured to extrude a first material through a first outlet; a second nozzle configured to extrude the first material through a second outlet; a third nozzle configured to extrude a second material different from the first material through a third outlet, the third outlet being between the first and second outlets; and a valve controller arrangement configured to regulate the extrusion by the first, second, and third nozzles so as to allow, during a first pass, extrusion of the first material by the first and second nozzles while not allowing any extrusion of the second material by the third nozzle, then, after the extrusion has hardened, to allow, during a second pass, extrusion of the first material by the first and second nozzles as well as extrusion of the second material by the third nozzle.

0013Each outlet may have a substantially rectangular cross-section.

0014The multi-nozzle assembly may include a nozzle position controller configured to controllably vary the height of at least one of the outlets with respect to the height of at least one of the other outlets.

0015The multi-nozzle assembly may include a first and/or second trowel configured to shape material extruded from the first and/or second nozzles, respectively.

0016The width of the first and the second outlet may be less than the width of the third outlet.

0017The multi-nozzle assembly may include an orientation-control mechanism configured to control the orientation of the multi-nozzle assembly. The orientation-control mechanism may be configured to control the orientation of the multi-nozzle assembly in three dimensions. The nozzle may be mounted on a XYZ motion control platform, such as a gantry robot. This may give the outlet 6 degrees of freedom.

0018The multi-nozzle assembly may include a material feed system configured to feed material to each nozzle. The material feed system may be configured to keep the material that is fed to the first and second nozzles separate from the material that is fed to the third nozzle. The material feed system may include a valve system configured to selectably cut off the flow of material to each of the nozzles in a controllable manner.

0019The multi-nozzle assembly may include a controllable gate configured to controllably block material extruded from at least one of the nozzles from flowing in a direction.

0020A construction method according to the invention includes simultaneously extruding a first layer of two, spaced apart rims. After the first layer of rims has been permitted to cure, a further layer of two, spaced apart rims may be simultaneously extruded, each directly or indirectly on top of the first layer of one of the spaced apart rims, along with a first layer of filler between the first layer of two, spaced apart rims.

0021The height of the first layer of rims and the first layer of filler may all be substantially the same.

0022The material used for the rims may be different than the material used for the filler. The material used for the rims may be plastic and the material used for the filler may be concrete.

0023The construction method may include, after extruding the further layer of rims, extruding a further layer of filler on top of the last extruded layer of filler without also simultaneously extruding a further layer of rims.

0024These as well as still further objects, features and benefits will now become clear from an examination of the detailed description of illustrative embodiments and the accompanying drawings.

BRIEF DESCRIPTION OF DRAWINGS

0025<figref idref="f0001">FIG. 1</figref> illustrates an example useful to understand the invention of a nozzle assembly that includes a single nozzle.

0026<figref idref="f0001">FIG. 2</figref> illustrates the an example useful to understand the invention of the nozzle assembly shown in <figref idref="f0001">FIG. 1</figref> being used to extrude a wall.

0027<figref idref="f0002">FIG. 3</figref> illustrates an embodiment of a nozzle assembly that includes three nozzles.

0028<figref idref="f0003">FIGS. 4(a)-(c)</figref> illustrate the embodiment of the nozzle assembly shown in <figref idref="f0002">FIG. 3</figref> being used to extrude a wall.

0029<figref idref="f0004">FIG. 5</figref> illustrates the embodiment of the nozzle assembly shown in <figref idref="f0002">FIG. 3</figref> being used to extrude a wall in an angled orientation.

0030<figref idref="f0005">FIG. 6</figref> illustrates an example useful to understand the invention of a nozzle assembly having an orientation control mechanism being used to construct an embodiment of a supportless roof.

0031<figref idref="f0005">FIG. 7</figref> illustrates the supportless roof shown in <figref idref="f0005">FIG. 6</figref> in its completed state atop a wall structure.

0032<figref idref="f0006">FIG. 8</figref> illustrates another embodiment of a nozzle assembly that includes a slot in a central nozzle that accommodates reinforcement members.

0033<figref idref="f0007">FIG. 9</figref> illustrates the nozzle assembly shown in <figref idref="f0006">FIG. 8</figref> being used to construct a wall having reinforcement members.

0034<figref idref="f0008">FIG. 10</figref> illustrates another embodiment of a nozzle assembly.

0035<figref idref="f0008">FIG. 11</figref> illustrates certain components of the nozzle assembly shown in <figref idref="f0008">FIG. 10</figref> in an unassembled form having a central nozzle at a height lower than interior and exterior nozzles.

0036<figref idref="f0009">FIG. 12</figref> illustrates a bottom view of a portion of the nozzle assembly shown in <figref idref="f0008">FIG. 10</figref>.

0037<figref idref="f0009">FIG. 13</figref> illustrates an an example useful to understand the invention of a nozzle including a controllable front and rear gate.

0038<figref idref="f0010">FIG. 14</figref> illustrates one embodiment of a nozzle assembly according to the invention, using the type of nozzle shown in <figref idref="f0009">FIG. 13</figref> being used to extrude a wall.

0039<figref idref="f0011">FIG. 15</figref> illustrates the example of the nozzle shown in <figref idref="f0009">FIG. 13</figref> being used to extrude an insulation layer.

0040<figref idref="f0011">FIG. 16</figref> illustrates a nozzle assembly according to the invention using the nozzle shown in <figref idref="f0009">FIG. 13</figref> being used to extrude a wall with a layer of insulation.

0041<figref idref="f0012">FIG. 17</figref> illustrates another an example useful to understand the invention of a nozzle assembly having slots in a gate being used to extrude a wall with interlocked layers.

0042<figref idref="f0013">FIGS. 18 (a) and (b)</figref> illustrate another embodiment of a nozzle assembly having variable width nozzles.

DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

0043<figref idref="f0001">FIG. 1</figref> illustrates an example useful to understand the invention of a nozzle assembly that includes a single nozzle. As shown in <figref idref="f0001">FIG. 1</figref>, a nozzle assembly <b>101</b> may include a nozzle <b>103</b> having an outlet <b>105</b> (not visible in <figref idref="f0001">FIG. 1</figref>), a trowel <b>107,</b> and a trowel positioning controller, including a servo motor <b>109</b> and trowel linkage <b>111</b> and <b>113.</b>

0044Although shown as cylindrical, the shape of the nozzle <b>103</b> may vary. It may include an inlet <b>115</b> for material in a fluid or semi-fluid form.

0045The cross-section of the outlet <b>105</b> may vary. It may be circular, rectangular or of some other shape.

0046<figref idref="f0001">FIG. 2</figref> illustrates the example of the nozzle assembly shown in <figref idref="f0001">FIG. 1</figref> being used to extrude a wall. As shown in <figref idref="f0001">FIG. 2</figref>, the nozzle assembly <b>101</b> is extruding a layer of material <b>203</b> while being moved in a horizontal direction <b>205.</b> The trowel <b>107</b> smoothens the exterior surface of the layer of material <b>203</b> as it is being extruded from the nozzle <b>103.</b> The lower surface <b>205</b> of the member that supports the nozzle <b>103</b> has an opening (not shown) through which the extruded material flows. The lower surface <b>205</b> may also act as a trowel to smoothen the upper surface of the layer of material <b>203</b> that is being extruded. An additional trowel (not shown) may also be included to smoothen the interior surface of the layer <b>203</b> that is being extruded. Alternatively, a sharp blade parallel to the first trowel may cut out excess material on the interior side to create a planar surface.

0047Referring again to <figref idref="f0001">FIG. 1</figref>, the height of the trowel <b>107</b> may be controlled by the trowel position controller which, as explained above, includes the servo motor <b>109</b> and the trowel linkages <b>111</b> and <b>113.</b> The height of the trowel <b>107</b> may be adjusted to correspond to the height of the extruded layer <b>203.</b> By making the height of the trowel <b>107</b> adjustable, layers of different thickness may be extruded.

0048Although the smoothening surface of the trowel <b>107</b> and the underneath surface 205 are illustrated as being flat, other contours may be used instead.

0049Any type of material may be used and delivered into the inlet <b>115,</b> including cement or plastic. The material may be delivered in a liquid or quasi-liquid form and may include or receive additives or may have characteristics that cause the material to harden into a solid after extrusion.

0050As is apparent from an examination of <figref idref="f0001">FIG. 2</figref>, the nozzle assembly <b>101</b> may be moved horizontally in a back-and-forth motion, each time being elevated in height by approximately the thickness of each extruded layer. The collective effect is to create a wall <b>207</b> consisting of a stacked set of separately-extruded layers.

0051The horizontal direction <b>205</b> of the nozzle assembly <b>101</b> at the end <b>209</b> of a pass may be altered by 90 degrees into the direction <b>111.</b> This can produce an extruded wall that has a sharp right angle bend. Obviously, other types of changes in direction may be used to create other wall shapes, including curved walls and walls that join one another at angles other than 90 degrees.

0052<figref idref="f0002">FIG. 3</figref> illustrates an embodiment of a nozzle assembly that includes three nozzles. As shown in <figref idref="f0002">FIG. 3</figref>, a nozzle assembly <b>301</b> includes an exterior nozzle <b>303,</b> an interior nozzle <b>305</b> and a central nozzle <b>307.</b> The exterior nozzle <b>303</b> may include an outlet <b>309,</b> the interior nozzle <b>305</b> may include an outlet <b>311,</b> and the central nozzle <b>307</b> may include an outlet <b>313.</b> Although each outlet is illustrated as having a rectangular cross-section, other cross-sectional shape could be used instead, such as round or oval. The width of the central outlet <b>313</b> may be equal to, greater or less than the width of the exterior outlet <b>309</b> or the interior outlet <b>311.</b> The width of the exterior outlet <b>309</b> may be equal to or different than the width of the interior outlet <b>311</b>

0053A trowel <b>315</b> may be used to smooth the material that is extruded from the exterior outlet <b>309,</b> while a trowel <b>317</b> may be used to smooth the material that is extruded from the interior outlet <b>311.</b> The height of the exterior trowel <b>315</b> and the interior trowel <b>311</b> may, in turn, be controlled by trowel position controllers <b>319</b> and <b>318,</b> respectively.

0054<figref idref="f0003">FIGS. 4(a)-(c)</figref> illustrate the embodiment of the nozzle assembly shown in <figref idref="f0002">FIG. 3</figref> being used to extrude a wall.

0055As shown in <figref idref="f0003">FIG. 4(a)</figref>, a first layer of a wall <b>403</b> may be extruded by moving the nozzle assembly <b>301</b> in a horizontal direction and by extruding material only through the exterior nozzle <b>303</b> and the interior nozzle <b>305.</b> During this pass, no material may be extruded from the central nozzle <b>307.</b>

0056This approach may cause an exterior rim layer <b>405</b> and an interior rim layer <b>407</b> of material to be extruded. Since no material is being extruded during this pass from the central nozzle <b>307,</b> no significant force will be placed on the interior walls of the rim layers <b>405</b> and <b>407.</b>

0057The rim layers may then be left to cure and thus harden. Various approaches such as thermal and chemical may be used to speed up the curing process. For example, a torch, hot air blower, or microwave energy may be attached to the nozzle assembly <b>309</b> (not shown) to treat the extruded material and speed its curing. A judicious choice of material may also be made for the rims, that cures quickly, such as plastic.

0058As shown in <figref idref="f0003">FIG. 4(b)</figref> another rim layer may be extruded on top of the rim layer that has hardened. This may consist of a second exterior rim <b>413</b> being extruded on top of the first exterior rim <b>405</b> and a second interior rim <b>415</b> being extruded on top of the first interior rim <b>407.</b> A first filler layer <b>411</b> may also be extruded between the first rim layers <b>405</b> and <b>407</b> by extruding material from the central nozzle <b>307</b> at the same time that the second rim layers <b>413</b> and <b>415</b> are being extruded. The filler may be of a much stronger material, such as cement. The filler material may or may not dry as quickly as rim material.

0059If the rim layers are able to cure quickly enough, and if their length is long enough, the nozzle assembly <b>301</b> may be able to return to the beginning of a pass to extrude the next layer of rims on top of the previous layer as soon as extrusion of the previous layer is complete. If the curing is fast enough, the nozzle assembly may instead be directed to extrude its next layers of material during the return traverse. Other sequences could also be followed, including a rest between traverses.

0060The process may be repeated until the height of the wall <b>403</b> reaches the needed level. <figref idref="f0003">FIG. 4(c)</figref> illustrates the wall <b>403</b> with six layers. After the last needed rim layers are extruded, the next pass may extrude only a filler layer, thus completing the wall structure.

0061Delaying the extrusion of filler layers helps insure that the rim layers will be strong enough to contain their neighboring filler layers. Of course, the extrusion of each filler layer need not always or even ever be exactly one traverse behind the extrusion of each neighboring rim layer. In other embodiments, the filler layers might be two or more layers behind the neighboring rim layers. Indeed, none of the filler layers might be extruded until after all or at least several of the rim layers have been extruded and hardened. In this embodiment, the entire wall filler or at least a large portion of it could be extruded in a single pass.

0062<figref idref="f0004">FIG. 5</figref> illustrates the embodiment of the nozzle assembly shown in <figref idref="f0002">FIG. 3</figref> being used to extruded a wall at an angled orientation.

0063Material to be extruded may be delivered through outer tubes <b>517, 519, 521</b> and <b>523.</b> Each of these outer tubes may contain within them a set of inner tubes, one channeling material to the exterior outlet <b>309</b> (see <figref idref="f0002">FIG. 3</figref>) and the interior outlet <b>311</b> (see <figref idref="f0002">FIG. 3</figref>), while the other channeling material to the central outlet <b>313</b> (see <figref idref="f0002">FIG. 3</figref>). In this way, the type of material that is delivered to the exterior outlet <b>309</b> and the interior outlet <b>311</b> is different from the material that is delivered to the central outlet <b>313.</b>

0064In another embodiment, each outer tube <b>517, 519, 521</b> and <b>523</b> may include three interior tubes, allowing a different type of material to be delivered to the exterior outlet <b>309</b> and the interior outlet <b>311</b> as well.

0065As also shown in <figref idref="f0004">FIG. 5</figref> (and partially in <figref idref="f0002">FIG. 3</figref>), the nozzle assembly <b>101</b> may include an orientation control mechanism that can cause the outlets <b>309, 311</b> and <b>313</b> to be pointed in almost any direction. Any type of control mechanism may be used, including a control mechanism that is capable of orienting the outlets in one, two or three degrees of freedom. With respect to the example assembly <b>101</b> shown in the figures, an orientation control mechanism has been selected that allows the outlets to be oriented in three dimensions. The orientation control mechanism may include servo motors <b>501, 503</b> and <b>505,</b> each controlling a separate axis of orientation. Of course, appropriate internal structures may be included to translate the motion of these servo motors into the necessary movement. In certain embodiments, positioning information may be sent back to a servo controller (not shown) and used in one or more feedback loops to maximize the accuracy of the positioning that is obtained. Appropriate material channeling chambers and gaskets may also be included (not shown) to ensure that the material continues to flow without significant leakage in the moving joints, regardless of the angular orientation that is directed. The nozzle assembly may itself be moved around by a XYZ positioning system, thus providing 6 degrees of freedom to the nozzle head.

0066<figref idref="f0005">FIG. 6</figref> illustrates an example useful to understand the invention of a nozzle assembly having an orientation control mechanism being used to construct an embodiment of a supportless roof. <figref idref="f0005">FIG. 7</figref> illustrates the supportless roof shown in <figref idref="f0005">FIG. 6</figref> in its completed state atop a wall structure. Collectively, these figures demonstrate how the positional flexibility of the example nozzle assembly can facilitate the construction of supportless roofs, such as vaults. Although an example of a nozzle assembly having only a single nozzle is illustrated, it is to be understood that the triple nozzle assembly shown in <figref idref="f0002 f0003 f0004">FIGS. 3-5</figref> could be used.

0067<figref idref="f0006">FIG. 8</figref> illustrates another embodiment of a nozzle assembly that includes a slot in a central nozzle that accommodates reinforcement members. <figref idref="f0007">FIG. 9</figref> illustrates the nozzle assembly shown in <figref idref="f0006">FIG. 8</figref> being used to construct a wall having reinforcement members.

0068As shown in <figref idref="f0006">FIG. 8</figref>, a nozzle assembly <b>801</b> includes an exterior nozzle <b>803</b> having an outlet <b>805,</b> an interior nozzle <b>807</b> having an outlet <b>809</b> and a central nozzle set consisting of two nozzles <b>811</b> and <b>813</b> having outlets <b>815</b> and <b>817,</b> respectively, that are separated by an opening <b>818.</b><figref idref="f0007">FIG. 9</figref> illustrates how the opening <b>819</b> ensures that the nozzle assembly <b>801</b> does not collide with reinforcing members <b>821, 823</b> or <b>825</b> during operation.

0069<figref idref="f0008">FIG. 10</figref> illustrates another embodiment of a nozzle assembly. As shown in <figref idref="f0008">FIG. 10</figref>, a nozzle assembly <b>1001</b> may include an exterior nozzle <b>1003</b> and an associated trowel <b>1005,</b> an interior nozzle <b>1007</b> and an associated trowel <b>1009,</b> and a central nozzle <b>1011.</b> An inlet <b>1013</b> may be provided to receive material that is channeled to the central nozzle <b>1011</b> for extrusion, while an inlet <b>1015</b> may be provided to receive material that is channeled to the exterior nozzle <b>1003</b> and to the interior nozzle <b>1007</b> for extrusion. A bevel gear <b>1017</b> may be provided to rotate the nozzles.

0070Servo motors <b>1019</b> and <b>1021</b> may be used to control the height of the trowels <b>1009</b> and <b>1005,</b> respectively. A servo motor <b>1025</b> may be used to control an internal gate valve (not shown) that is used to regulate the flow of material to the exterior nozzle <b>1003.</b> Similarly, a servo motor <b>1023</b> may be used to control an internal gate valve (not shown) that is used to regulate the flow of material to the interior nozzle <b>1007.</b> The flow of material to the central nozzle <b>1011</b> may also be regulated in a similar or different manner.

0071When making a curved wall, the rim material delivery rate may be different for the exterior and interior outlets. This may be effectuated by appropriate settings of the servo motors <b>1023</b> and <b>1025.</b> The valve may be near or away from the nozzle. The gate valves may be configured to controllably adjust the volume of flow, as well as to completely cut the flow off.

0072A servo motor <b>1027</b> may be used to control the height of the central nozzle <b>1011</b> with respect to the external nozzle <b>1003</b> and the internal nozzle <b>1007.</b> The heights of the external and/or internal nozzles may also be controlled in a similar or different manner.

0073<figref idref="f0008">FIG. 11</figref> illustrates certain components of the nozzle assembly shown in <figref idref="f0008">FIG. 10</figref> in an unassembled form-with the central nozzle <b>1011</b> at a height lower than the interior nozzle <b>1007</b> and the exterior nozzle <b>1003.</b> Such a height differential may be useful-in embodiments in which each central filler layer is extruded one pass behind each surrounding rim layer. The ability to control the relative heights of the nozzles may also be useful in applications in which there is a need to avoid occasional obstructions.

0074<figref idref="f0009">FIG. 12</figref> illustrates a bottom view of a portion of the nozzle assembly <b>1001</b> shown in <figref idref="f0008">FIG. 10</figref>. It provides more detail on how the servo motor <b>1029</b> may control the height of the central nozzle <b>1011</b> with respect to the exterior nozzle <b>1003</b> and the interior nozzle <b>1007.</b> This detail includes a drive belt <b>1031</b> that causes ball screws <b>1132</b> and <b>1134</b> (see <figref idref="f0008">FIG. 11</figref>) to rotate and to thus cause a corresponding change in the elevation of the central nozzle <b>1011</b> due to interaction with associated threaded sleeves <b>1137</b> and <b>1139</b> (<figref idref="f0008">FIG. 11</figref>), respectively.

0075<figref idref="f0009">FIG. 13</figref> illustrates an example useful to understand the invention of a nozzle including a controllable front and rear gate. As shown in <figref idref="f0009">FIG. 13</figref>, a nozzle <b>1301</b> includes a controllable front gate <b>1303</b> and a controllable rear gate <b>1305.</b> The controllable gate <b>1303</b> may be controlled by a gate controller, such as a servo motor <b>1307</b> and an associated coupling <b>1309.</b> Similarly, the controllable gate <b>1305</b> may be controlled by a gate control mechanism, such as a servo motor 1311 and an associated control mechanism <b>1315.</b>

0076<figref idref="f0010">FIG. 14</figref> illustrates one embodiment of a nozzle assembly with the nozzle shown in <figref idref="f0009">FIG. 13</figref> being used to extrude a wall. This embodiment allows the beginning and end of each extruded layer to be shaped with a sharp vertical surface by appropriate control of the gates.

0077<figref idref="f0011">FIG. 15</figref> illustrates the example shown in <figref idref="f0009">FIG. 13</figref> being used to extrude an insulation layer. In this embodiment, a polystyrene filament may be fed through an electrically heated barrel <b>1501</b> so that molten plastic comes out through a nozzle <b>1503.</b> Compressed air may be mixed in as well to cause a bead of Styrofoam <b>1505</b> to be created. One or more of these layers may serve as insulation. Other types of polymers or other materials may be used instead.

0078<figref idref="f0011">FIG. 16</figref> illustrates a nozzle assembly-using the nozzle-shown in <figref idref="f0009">FIG. 13</figref> to extrude a wall with insulation. As shown in <figref idref="f0011">FIG. 16</figref>, a wall <b>1601</b> is being extruded by a nozzles assembly <b>1603</b> (shown only in part) that includes a stacked set of Styrofoam layers <b>1605, 1607</b> and <b>1609.</b>

0079<figref idref="f0012">FIG. 17</figref> illustrates another an example useful to understand the invention of a nozzle assembly having slots in a gate being used to extrude a wall with interlocked layers. As shown in <figref idref="f0012">FIG. 17</figref>, a gate <b>1701</b> includes slots <b>1703</b> and <b>1705</b> that cause corresponding ribs <b>1707</b> and <b>1709</b> to be created during the extrusion of the layer <b>1711.</b> These create interlocking ribs, such as the interlocking ribs <b>1713, 1715</b> and <b>1717,</b> thus strengthening the wall that is extruded.

0080<figref idref="f0013">FIGS. 18 (a) and (b)</figref> illustrate another embodiment of a nozzle assembly having variable width nozzles. As shown in <figref idref="f0013">FIGS. 18(a) and (b)</figref>, a nozzle assembly <b>1801</b> includes an exterior nozzle <b>1803,</b> a central nozzle <b>1805</b> and an interior nozzle <b>1807.</b> The width of the layer that is extruded from the exterior and interior nozzles <b>1803</b> and <b>1807,</b> respectively, may be varied by adjusting the relative separation of these nozzles, either manually or automatically-under servo control. <figref idref="f0013">FIG.18(a)</figref> illustrates the exterior and interior nozzles being widely separated for a wider rim layer, while <figref idref="f0013">FIG.18(b)</figref> illustrates these same nozzles being compressed together for a narrower rim layer. The flow rate of the extruded material may be reduced during a wider setting to insure that a full layer is extruded. The separating distance between the two rim nozzles may be varied during the extrusion of a structure to facilitate the construction of structures such as domes with a progressively thinning wall or to make certain walls, such as interior walls, thinner than other walls, such as exterior walls. Appropriate adjustments could also be made to make one rim layer thinner than the other.

0081A broad variety of construction applications may advantageously utilize one or more of the nozzle assemblies that have now been described.

0082For example, a nozzle assembly may include a roller that follows the extrusion and creates textures on the walls of the layers that are extruded.

0083A nozzle assembly may also be attached to an arm of a robotic system. Under computer or other control, the nozzle assembly may extrude the walls of an entire building, including several rooms. A gantry system may be used to support and position the nozzle assembly as it traverses the need paths. A positioning system may also be used to accurately position the nozzle assembly, such as a system that includes fixed reference points and a laser-guided detector mounted on the nozzle assembly.

0084Instead of one large gantry system and a single nozzle assembly traversing the layers of the entire structure, a plurality of nozzle assemblies may simultaneously be employed. Each may be attached and controlled by the arm of a small mobile robot dedicated to that nozzle assembly. The position and actions of this workforce of robots may be directed wirelessly by a central command station. Each one of these small robots, in turn, may include on-board tanks to contain the necessary materials that are extrude. These small robots may also return to a central filling station to refill their tanks when needed.

0085Rigid horizontal members may be used to facilitate the construction of windows, door openings and ceilings by bridging openings beneath them. To create a window, for example, the controller of a nozzle assembly may turn off the flow of material to all outlets in the nozzle assembly when the nozzle assembly is traversing an area that has been designated as the window opening. After the top of the walls surrounding the window have been extruded, a rigid horizontal member may be placed across the top of these walls to create the header of the window. One or more continuous layers of material may then be extruded on top of the header and the surrounding walls. A similar bridging approach may be used to create door openings. A ceiling may similarly be created by placing a series of neighboring structural members across the top walls of a structure, over which material may be extruded to give strength to the structure.

0086One or more of the robotic systems described above may also be used to place these structural members where needed, i.e., across the tops of window and door openings and across the tops of wall structures to provide a roof.

0087A variety of techniques may also be employed in an automated fashion to reinforce the strength of walls that are extruded. These techniques may include the automated insertion or embedding of clips across or within the rims of the walls periodically along their length. These reinforcement mechanisms may also include the insertion of rigid vertical members within the interior of the wall, including, in certain embodiments, rigid horizontal links between these vertical members. Again, all of this may be accomplished under automated robotic control.

0088Plumbing may also be installed as part of the automated process. Segments of plumbing pipe may be secured to other segments using automated installation and welding techniques.

0089Electrical wiring may similarly be installed as part of the automated process. Electrical wires may be housed in modules that are connected together within the walls, again under robotic control.

0090Sensors may be inserted within the structure to provide feedback regarding construction performance. After the structure is completed, these sensors may continue to be used to report on information about the structure, such as heat, humidity, and deformation.

0091Tiling and even painting may similarly be done under robotic control.

0092A mixer may also be provided in association with a nozzle assembly to allow the components of a fast-curing material to be mixed near the head of the assembly.

0093By combining some or all of these features into a single system, the vast majority of a sound and quality structure may be built according to custom specifications very quickly, efficiently, accurately and with few personnel.

0094Although now having described certain embodiments of nozzle assemblies and construction methods, it is to be understood that the concepts implicit in these embodiments may be used in other embodiments as well. In short, the protection of this application is limited solely to the claims that now follow.