Automating Bricklaying

The invention relates to methods and apparatus for automating bricklaying.

Automated bricklaying machinery was proposed in U.S. Pat. No. 4,060,955, granted on Dec. 6, 1977 to Lachnit. The machinery includes a main carriage that rolls on horizontal tracks. The main carriage supports a bricklaying machine and a pallet bearing a large supply of stacked bricks. The bricklaying machine has a frame that displaces vertically on uprights fixed to the main carriage. The frame supports a magazine that contains a single vertical stack of bricks, and also supports a pair of horizontal rails. The horizontal rails in turn support a secondary carriage to which a brick-gripping mechanism and a mortar injector are mounted. In operation, the secondary carriage is first positioned beside the brick magazine. A hydraulically-operated lever mechanism transfers a single brick from the magazine to the brick gripper. The secondary carriage then travels along the horizontal rails until the mortar injector and the brick gripper are appropriately positioned to apply mortar and place the gripped brick beside the current flight. When the magazine is empty, another hydraulically-operated mechanism grips a row of bricks on the pallet and reorients the row as a vertical stack in the magazine.

There are several shortcomings to the proposed machinery. Dispensing mortar under pressure is not reliable in an automated process, as mortar has a tendency to clog pumps and conduits. Also, vertical joints between bricks cannot be readily filled. The machinery also requires excessive brick handling. Bricks must be stacked on a pallet, then re-stacked in a magazine, and finally transferred to a brick gripper. The apparatus is also very dependent on precise leveling and positioning of the rails supporting the main carriage.

A variety of robotic mechanisms for placing concrete blocks are canvassed in an article by Slocum and Shena entitled "Blockbot: A Robot To Automate Construction Of Cement Block Walls", published in Robotics & Automation Systems, v. 4, No. 2, June, 1988. One robotic mechanism described in the article includes an arm assembly somewhat similar to that proposed in the present specification. It has an upper arm and a forearm together with appropriate shoulder, elbow and wrist joints that pivot about parallel horizontal axes. The wrist joint supports a block-gripping mechanism. Such an arm assembly is dismissed as having insufficient stiffness and load-bearing capacity and as requiring excessively complex control.

The article suggests use of a robotic arm with a single horizontal arm member. The arm member swings about a vertical axis at a shoulder joint, and the shoulder joint can itself be raised and lowered on a vertical track. A wrist joint between the arm and a block gripping mechanism allows only pivoting of the gripping mechanism about a vertical axis. The robotic arm is mounted on a horizontal track fixed to a wheeled carriage. The carriage has a platform on which a store of individual blocks is rested. In operation, the carriage is moved to a desired location and kept stationary. The arm assembly displaces horizontally along the track in increments correspond to successive block positions in the masonry being constructed. The arm swings horizontally over the platform and lowers to receive a block. The arm then raises, swings horizontally to locate the block over the masonry, and lowers to seat the block on the masonry.

The article proposes that blocks be stacked dry. It suggests that a bonding layer be formed over the exterior of the resulting masonry. There are several shortcomings, however. Precision blocks may be required as there is no bonding composition between blocks to accommodate variations in size. Also, bricks are preferred to blocks largely for esthetic reasons, and placing a bonding layer over brick masonry defeats the basic purpose for using bricks. A number of issues are not adequately addressed, such as how to align the carriage when moved to successive positions along the masonry, and how to supply blocks to the block laying machinery.

The present specification addresses several problems relating to automation of bricklaying. These relate to mortar application, appropriate construction of a robotic arm assembly, how to conveniently supply mortar and bricks to automated bricklaying equipment, and reducing sensitivity of such equipment to variations in the orientation of a guideway or track.

In one aspect, the invention provides a machine for use in laying bricks on brick masonry. The machine has a support frame which preferably displaces along a guideway beside the masonry being erected. The machine has a tool assembly with a controllable mechanism for gripping a brick and a mechanism for dispensing mortar. The mortar-dispensing mechanism includes a form for receiving and shaping a charge of mortar. A closure mechanism is operable to release the shaped mortar charge through a discharge opening in the form. Controllable displacing means move the tool assembly relative to the frame, permitting bricks and mortar charges to be repeatedly received and placed on the brick masonry. The displacing means preferably comprise a pivoting robotic arm.

The mortar-dispensing mechanism preferably comprises a gate mounted for sliding movement relative to the form's discharge opening. Means are provided for sliding the gate between a closed orientation supporting the mortar charge and an open orientation releasing the mortar charge. The form preferably has an elongate circumferential sidewall with a pair of end walls, corresponding generally to the peripheral shape of a brick. The form may be shaped to accumulate the mortar change to a greater depth proximate to one end wall. This permits the contained mortar to be deposited to a greater depth proximate to the last brick laid in the current flight. The next brick can then be appropriately manipulated to force the deposited mortar to fill the vertical gap otherwise occurring between the two bricks, as explained more fully in the description of preferred embodiments.

In another aspect, the invention addresses the problem of supplying bricks and mortar to a bricklaying machine. As mentioned above, the frame of the bricklaying machine is preferably displaceable along a guideway. A brick carrier is mounted to the guideway for travel to and from a brick-transferring position relative to the bricklaying machine. A mortar carrier may be mounted to the guideway for travel to and from a mortar-transferring position relative to the bricklaying machine. The brick and mortar carriers may travel to a predetermined location where bricks and mortar are stored and workers can manually load the carriers.

In another aspect, the bricklaying apparatus is made responsive to a horizontal datum located above the masonry, such as a conventional mason's line. The horizontal distance of the tool assembly components from the frame may be determined with first sensing means responsive to operation of the displacing means, such as optical associated with drive motors. Second sensing means, preferably an ultrasonic detector, sense the horizontal distance from the frame to the datum. Controls operate the displacing means in response to the first and second sensing means to position tool assembly components for deposition of mortar or laying of bricks. This reduces the need for precise positioning of the guideway horizontally and parallel to the masonry. Sensing means may also be provided that displace with the tool assembly and sense the vertical distance from tool assembly components to the datum, and the controls may position tool assembly components in response to the sensed vertical distance. This reduces the need for precise leveling of the guideway.

In another aspect, the displacing means comprise a robotic arm assembly. The arm assembly includes a support, which is preferably mounted to the frame for vertical displacement and horizontal swinging. It also includes first and second arm members. A first pivot joint permits the first arm member to pivot relative to the support about a first horizontal pivot axis, and motor means can be operated to produce such pivoting. A second pivot joint permits the second arm member to pivot about a second pivot axis substantially parallel to the first pivot axis. A third pivot joint permits the tool assembly to pivot about a third axis substantially parallel to the first and second axes. Linkage means couple the arm members such that the third pivot joint is constrained to displace substantially along a predetermined axis extending transversely through the first pivot axis.

The arm assembly effectively defines a shoulder, an upper arm and a forearm together with shoulder, elbow, and wrist joints that permit components to pivot about parallel horizontal axes. In typical use, the linkage means constrain the wrist joint and the tool assembly to displace horizontally as the upper arm pivots about the shoulder. Control is greatly simplified and only a single motor is required for extension or retraction. The linkage means may also couple the pivot joints to maintain the tool assembly in a fixed angular relationship relative to vertical as the arm assembly extends or retracts, further simplifying control. The arm assembly can also be stiffened by using flexible straps of relatively non-extensible material to pivot the forearm, as described more fully below.

Other aspects of the invention will be apparent from a description of preferred embodiments below and will be more specifically defined in the appended claims.

The invention will be better understood with reference to drawings in which:

FIG. 1 is a perspective view of a bricklaying machine and a brick train which supplies brick to the machine;

FIG. 2 is a plan view of the bricklaying machine, the brick train and also a mortar carrier;

FIG. 3 is a partially fragmented side elevation of the bricklaying machine and the brick train;

FIG. 4 diagrammatically illustrates how an arm assembly associated with the bricklaying machine displaces;

FIG. 5 is a diagrammatic perspective view of certain components contained within the arm assembly;

FIG. 6 is a diagrammatic plan view of various components within the arm assembly;

FIG. 7 is a perspective view of a tool assembly located at a wrist joint of the arm assembly;

FIG. 8 corresponds to FIG. 7 fragmented to show further details of a brick-gripping mechanism and a mortar-dispensing mechanism;

FIG. 9 is a fragmented perspective view showing the arm assembly oriented to receive a brick from the brick train;

FIG. 10 is a fragmented perspective view showing the arm assembly oriented to receive a charge of mortar from the mortar carrier;

FIGS. 11-13 are fragmented perspective views showing distinct stages in the depositing of a mortar charge and placement of a brick on brick masonry;

FIGS. 14 and 15 show alternative ways of placing a brick at corners of masonry to spread a deposited mortar charge to fill vertical spaces between bricks;

FIG. 16 diagrammatically illustrates a construction site at which a guideway has been installed for the bricklaying machine, the brick train and the mortar carrier;

FIG. 17 diagrammatically illustrates how signals from attitude sensors mounted on the carriage of the bricklaying machine can be used to adjust sensed horizontal distance to a mason's line during horizontal positioning of bricks in a direction perpendicular to the brick masonry; and,

FIG. 18 diagrammatically illustrates how signals from the attitude sensors can be used to adjust the sensed position of the carriage of the bricklaying machine on its guideway during horizontal positioning of bricks in a direction along the brick masonry.

An overview of equipment for automating bricklaying will be provided with reference primarily to FIGS. 1 and 2. The equipment includes a horizontal guideway 10, which may extend fully about brick masonry 12 that is to be erected (as illustrated in FIG. 16). A bricklaying machine 14 travels along the guideway 10. It has an arm assembly 16 that supports a tool assembly 18. The tool assembly 18 includes a brick-gripping mechanism 20 and a mortar-dispensing mechanism 22. The bricklaying machine 14 is guided in part by a mason's line 24. It repeatedly retrieves a single mortar charge and a single brick, depositing the mortar charge on the brick masonry 12 and then placing the brick onto the mortar. A brick train 26 and a mortar carrier 28 travel along guideway 10. These transfer bricks and mortar from a predetermined storage location 30 to the bricklaying machine 14. The guideway 10 is adapted to supply electricity, cooperate in sensing the position of each machine, and to permit transfer of control signals among the bricklaying machine 14, the brick train 26 and mortar carrier 28. A controller 32 associated with the bricklaying machine 14 may be programmed to continuously lay bricks to construct a predefined structure and also to control the operation of the brick train 26 and mortar carrier 28 to supply bricks and mortar as required. Operations may be monitored and replenishment of the brick train 26 and mortar carrier 28 may may be controlled in whole or in part at a control station 33.

The guideway 10 has a track-supporting structure with a ladder-like construction. The supporting structure has upper and lower horizontal pipes 34, 36 joined by vertical pipes, such as the pipe 38 apparent in FIGS. 1 and 3. The horizontal pipes 34, 36 may be secured with conventional clamps (such as the clamps 40) to uprights of a scaffold 37. A first pair of upper and lower rails 42, 44 are used to support the bricklaying machine 14 and the mortar carrier 28. A second pair of upper and lower rails 46, 48 are used to support the brick train 26. The upper rails 42, 46 are attached by triangular brackets 50 to the upper horizontal pipe 34. The lower rail 48 associated with the brick train 26 is secured to the vertical pipes. The other lower rail 44 is connected in spaced relationship to the lower horizontal pipe. The overall arrangement is such that the brick train 26 can pass between the guideway 10 and either the bricklaying machine 14 or the mortar carrier 28, despite mounting of all components to one lateral side of the guideway 10. The guideway 10 may have a modular construction allowing sections to be joined end-to-end.

The guideway 10 carries a plastic casing 51 that defines separate channels in which communication and power bars are located. Two power bars 52, 54 supply electric power to the bricklaying machine 14 and to the mortar carrier 28. Another pair of power bars 56, 58 supply power to the brick train 26. The power 52 bar is magnetically encoded to serve as a distance indicator for the bricklaying machine 14 and mortar carrier 28. It is encoded at one-eighth inch intervals, allowing for sensing of incremental changes in position. The power bar 56 is similarly configured to serve as a distance indicator for the brick train 26. Two conductors 60, 62 are used for communications, one for the bricklaying machine 14 and mortar carrier 28, and another for the brick train 26. These conductors 60, 62 are in separate channels, but are electrically connected for transfer of signals. Separate power and communication conductors are used to allow the brick train 26 to pass between the guideway 10 and either the bricklaying machine 14 or the mortar carrier 28. The power bars and communication conductors are contacted with sliding, spring-biased shoe assemblies attached to the respective machines. One such assembly is diagrammatically illustrated in association with the brick train 26 in FIG. 3 and indicated generally with the reference numeral 64. One of the shoes on each machine includes a transducer for sensing the magnetic encoding of a contacted power bar. Such components are conventional and have been used, for example, in the operation of gantry cranes. They will consequently not be described further.

The bricklaying machine 14 has a steel support frame or carriage 70 displaceable along the guideway 10. The carriage 70 is mounted with upper rollers 72, 74 to the upper rail 42 of the guideway 10. One such roller 72 is vertically oriented and driven by an electric motor 75 to propel the carriage 70 along the guideway 10. The other roller 74 is horizontally oriented and bears horizontally against the upper rail 42 to maintain the carriage 70 on the guideway 10. The carriage 70 is mounted to the lower rail 44 by another horizontally oriented roller (not illustrated). Additional rollers of similar orientation are present, but are not apparent in the drawings.

The arm assembly 16 includes a clevis-like support 78. The support 78 is mounted to a frame 80 for rotation about a vertical axis. A motor 82 attached to the frame 80 is operable to rotate the support 78. The frame 80 is in turn mounted with linear bearings 84 to two parallel vertical shafts 86. An endless toothed belt 88 (internal teeth not indicated) is located between the two shafts 86. The belt 88 is supported by upper and lower sprockets 90, 92. The upper sprocket 90 is fixed to an axle 94 supported for rotation between the tops of the two vertical shafts 86. The lower sprocket 92 is similarly fixed to an axle 96 that extends between the bottoms of the two shafts 86. The frame 80 is attached to the endless belt 88, and a motor 98 rotates the lower sprocket 92, effectively causing the frame 80 to be raised or lowered. The manner in which the support 78 is secured to the carriage 70 permits two degrees of freedom of movement of the arm assembly 16 and consequently the tool assembly 18: displacement vertically along a predetermined axis and horizontal swinging about that axis. Conventional optical encoders (not illustrated) associated with the motors 82, 98 provide signals indicating, after conventional processing, the vertical position and angular orientation of the arm assembly 16.

The arm assembly 16 is further detailed in the views of FIGS. 4-6 where dimensions and spacing between components have been somewhat exaggerated for purposes of illustration. To make the following description of the arm assembly 16 more meaningful, it will be described by analogy to the human arm in its normal lowered orientation relative to the human body. The terms "upper" and "lower" should be understood accordingly, rather than with reference to any particular orientation seen in the drawings.

The arm assembly 16 comprises an upper arm 100 and a forearm 102 in side-by-side relationship in parallel vertical planes. These components are essentially hollow casings. A first pivot joint 104, effectively a shoulder joint, is formed between the support 78 and an upper end 106 of the upper arm 100. It allows the upper arm 100 to pivot about a first horizontal axis 108. A second pivot joint 110, effectively an elbow joint, is formed between a lower end 112 of the upper arm 100 and an upper end 114 of the forearm 102. The elbow joint 110 allows the forearm 102 to pivot about a second horizontal pivot axis 116 substantially parallel to the first pivot axis 108. A third pivot joint 118, effectively a wrist joint, is formed between a lower end 120 of the forearm 102 and the frame 122 of the tool assembly 18. The wrist joint 118 includes a wrist shaft 124 mounted with a pair of bearings 125 for rotation within the lower end 120 of the forearm 102. This permits the tool assembly 18 to pivot about a third horizontal pivot axis 126 substantially parallel to the first and second pivot axes 108, 116.

The arm assembly 16 is extended and retracted with a single motor 128 at the shoulder joint 104. Linkage described more fully below constrains movement of the arm members so that the pivot axis 126 at the wrist joint 118 always remains substantially level with and parallel to the pivot axis 108 at the shoulder joint. Another linkage, also described more fully below, ensures that the tool assembly 18 remains in a fixed angular orientation relative to vertical at the wrist joint 118. This greatly simplifies control of the arm assembly 16. One advantage of the arm assembly 16 is that it can reach rearwardly, as indicated in phantom outline in FIG. 4. This permits a brick to be retrieved from the brick train 26 when the latter is positioned behind the bricklaying machine 14.

The linkage coupling the shoulder and elbow joints 104, 110 is apparent in FIGS. 5 and 6. The shoulder joint 104 includes a shoulder shaft 130 fixed to the support 78 in alignment with the first pivot axis 108. The upper end 106 of upper arm 100 is mounted with a pair of bearings 131 to the shoulder shaft 130. The motor 128 is stationary relative to the shoulder shaft 130 and connected to the upper arm end 106 to pivot the upper arm 100 about the first pivot axis 108. A pulley assembly comprising an identical pair of shoulder pulleys 132, 134 is fixed to the shoulder shaft 130 and effectively non-rotating. An elbow shaft 136 is aligned with the second pivot axis 116. The elbow shaft 136 is mounted with a pair of bearings 138 to the lower end 112 of the upper arm 100 (fixing of one of the bearings 138 in FIG. 6 to the arm 100 not being shown) for rotation about the second pivot axis 116. The elbow shaft 136 is also fixed to the upper end 114 of the forearm 102 at a location indicated with numeral 139 so that the two rotate together. Another pulley assembly comprises an identical pair of elbow pulleys 140, 141, fixed to the elbow shaft 136 for rotation therewith. They are coupled to the shoulder pulleys 132, 134 by a pair of flexible straps 142, 143 formed of high carbon spring steel, a material which strongly resists lengthwise-extension. Each strap 142 or 143 has one end fixed to the cylindrical surface defined by one of the shoulder pulleys 132, 134 and another end fixed to the cylindrical surface defined by one of the elbow pulley 140, 141, extending in a taut state. Each is positioned to a different side of a hypothetical plane (not illustrated) containing the first and second pivot axes 108, 116 associated with the shoulder and elbow joints 104, 110. Basically, as the motor 128 pivots the upper arm 100, the straps 142, 143 effectively rotate the elbow pulleys 140, 141 thereby rotating the elbow shaft 136 and pivoting the forearm 102. A toothed belt or chain might be used, but the straps 142, 143 considerably enhance the stiffness of the arm assembly 16.

The rest position of the arm assembly 16 may be considered a position in which the upper arm 100 and forearm 102 are vertically oriented in side-by-side relationship. The shoulder pulleys 132, 134 have a diameter which is twice that of the elbow pulleys 140, 141. Accordingly, when the upper arm 100 is pivoted about the shoulder joint 104 through a positive angular increment .phi., counter-clockwise in the view of FIG. 4, the forearm 102 is pivoted in response through a corresponding negative (clockwise) angular increment of 2.phi. relative to the upper arm 100. The distance between the first and second pivot axes is substantially equal to the distance between the second and third pivot axes 116, 126. The net result is that the wrist joint 118 (more specifically the pivot axis 126 of the wrist joint 118) is constrained to displace along the horizontal axis 144 indicated in FIG. 4, which extends perpendicularly through the first pivot axis 108 of the shoulder joint 104. The horizontal position of the tool assembly 18 relative to the carriage 70 is a function of .phi., and a conventional optical encoder 145 associated with the shoulder motor 128 is used effectively to sense the current value of .phi..

The linkage which maintains the tool assembly 18 in a constant angular orientation relative to vertical will now be described. A third elbow pulley 146 is fixed to a sleeve 148. The sleeve 148 is mounted with a pair of bearings 149 (shown in phantom outline in FIG. 6) on the elbow shaft 136 (extending centrally through the interior of the sleeve 148) for relative rotation. Another shoulder pulley 150 is fixed to the shoulder shaft 130, and an endless toothed belt 152 couples the shoulder pulley 150 to the third elbow pulley 146. A pulley 154 in the upper end 114 of the forearm 102 is fixed to the sleeve 148 for rotation therewith, and a wrist pulley 156 is fixed to the wrist shaft 124. Another endless toothed belt 158 couples the pulleys 154, 156. The four pulleys 146, 150, 154, 156 have a common diameter. Thus, as the upper arm 100 is pivoted through the positive angular increment .phi., as in FIG. 4, about the first pivot axis 108 of the shoulder joint 104, the tool assembly 18 is pivoted by substantially the same positive angular increment .phi. about the third pivot axis 126 of the wrist joint 118. This maintains the orientation of the tool assembly 18 without reliance on any special control. The tool assembly 18 is actually connected to the wrist shaft 124 through a mounting assembly 160 (conventional for robotic mechanisms) that permits rotation of the tool assembly 18 about a vertical axis 162 centered relative to the brick-gripping mechanism 20. The mounting assembly 160 includes an internal motor 164 (indicated in phantom outline in FIG. 7) that can be operated to produce such rotation, and an appropriate optical encoder (not illustrated) to sense angular orientation relative to the vertical axis 162.

Pulley assemblies comprising paired shoulder pulleys 132, 134 and paired elbow pulleys 140, 141 are shown mounting the straps 142, 143. Pulley assemblies each consisting of a single pulley might be used. However, paired pulleys are desirable to facilitate installation and tightening of the straps 142, 143, whose ends are apt to be fastened to respective pulleys prior to installation.

The brick train 26 will be described primarily with reference to FIGS. 1 and 3. It includes a tractor unit 166 and a towed unit 168 which are articulated with a conventional joint 169. The tractor unit 166 comprises a steel carriage 170 which is mounted to the guideway 10 in substantially the same manner as the carriage 70 of the bricklaying machine 14, except rolling on upper and lower rails 46, 48. It has an upper vertical wheel 172 driven by a motor 174 to propel the carriage 170 along the guideway 10 and an upper horizontal wheel 176 bearing horizontally against the upper rail 46 for support. A lower horizontal wheel 178 bears against the lower rail 48. A brick retainer 180 is mounted to the carriage 170 and shaped to store up to five bricks 182 in a vertical stack. The towed unit 168 is similarly constructed, including another brick retainer 184, and mounted to the guideway 10, but relies on the tractor unit 166 to move along the guideway 10. The tractor unit 166 is currently shown in FIG. 1 in a brick-transferring position relative to the bricklaying machine 14. It may be so positioned in response to position signals from both the tractor unit 166 and the bricklaying machine 14, derived from the magnetically encoded power bars of the guideway 10, and to control signals derived from the conductors 60, 62. When the tractor unit 166 is empty, it may be moved along the guideway 10 to position the towed unit 168 for brick transfer.

The mortar carrier 28 will be described with reference to FIGS. 2, 3 and 10. It comprises a steel carriage 186 mounted to the guideway 10. The mounting is identical to that of the carriage 70 of the bricklaying machine 14 and consequently will not be described further. A motor 188 mounted on the carriage 186 propels the mortar carrier along the guideway 10. The carriage 186 also supports a shoe assembly (not illustrated) similar to that diagrammatically shown in association with the brick train 26, coupling the mortar carrier 28 to the power and communication bars of the guideway 10 for power supply, communication and position sensing. The position sensing permits the mortar carrier 28 to be positioned in a predetermined mortar-transferring orientation relative to the bricklaying machine 14, as in FIGS. 2 and 10.

The mortar carrier 28 has a container 190 for storing mortar. The container 190 has a discharge opening 192 in its bottom. A gate 194 is located within the container 190. The gate 194 is connected to a vertical shaft 196 extending centrally through the interior of the container 190. A motor 198 supported from the top of the container 190 is connected to the shaft 196, and can be actuated to rotate the shaft 196, displacing the gate 194 between a closed orientation (as in FIG. 2) and an open orientation allowing the stored mortar to discharge. A vane assembly 200 comprises three vanes that extend radially from the shaft 196, within the container 190. When the gate 194 is in its open orientation, the vanes 200 are positioned over the discharge opening 192. During discharging of mortar, the shaft 196 and vanes 200 are rotated in opposing angular directions about the central vertical axis of the shaft 196. The rotation may be through about 10 degrees and at a frequency of about 10 cycles per second. This agitates the stored mortar sufficiently to encourage a flow of mortar under gravity from the discharge opening 192. Excessive agitation should be avoided as the constituent components of the mortar will tend to separate.

The frame 122 of the tool assembly 18 is a relatively short strap-like member. The brick-gripping mechanism 20 comprises a pair of stationary fingers 202 extending downwardly from the frame 122. It also includes a single movable finger 204, which is displaced toward and away from the stationary fingers 202 by a hydraulic cylinder 206 mounted to the frame 122.

The mortar-dispensing mechanism 22 comprises a form 208 which is fixed to the frame 122. The form 208 has an upper opening 210 through which mortar can be received. It has a lower discharge opening 212 which is closed by a gate 214 conforming in shape to the bottom of the form 208. The form 208 has a circumferential sidewall 216, including a pair of horizontally spaced-apart end walls 218, 220, which shapes a received mortar charge 224 to correspond generally to the peripheral shape of a brick, allowing for spreading when deposited. The form 208 has a greater depth proximate to one end wall 220. The upper surface 221 of the gate 214, which supports the mortar charge, extends downwardly and laterally toward the end wall 220. This permits a mortar charge to be accumulated to a greater depth proximate to the particular end wall 220. A hydraulic cylinder 222 supported from the frame 122 slides the gate 214 between its closed orientation (as apparent in FIGS. 6, 10 and 11) to an open orientation (as apparent in FIG. 12), releasing the contained mortar charge. Although a variety of gate mechanisms with one or more gates might be used, a sliding gate mechanism is preferred. Since the gate 214 slides relative to the form 208, mortar on its upper surface 221 tends to be scraped from the gate 214 by the bottom of the form. This ensure that mortar does not harden onto the gate 214 and eventually affect operation.

A mortar charge 224 may initially be received from the mortar carrier 28 with the form 208 rotated and positioned in the orientation shown in FIG. 10. The arm assembly 16 displaces the tool assembly 18 until the form 208 is over the brick masonry 12, as in FIG. 12, at the position where the next brick 226 is to be placed. The gate 214 is then opened to released the charge 224. The mortar charge 224 as deposited on an upper exposed surface portion of the masonry 12 has only been shown diagrammatically in FIG. 12. What should be noted is that the deposited charge 224 is thicker proximate to the last brick 228 laid, which extends upwardly on one lateral side of the upper surface portion where the mortar charge 224 is deposited. As the next brick 226 is placed, it is rotated back-and-forth about the vertical axis 162 at the wrist joint 118. The arm assembly 16 simultaneously swings the brick 226 horizontally through an arc corresponding to the length of the thicker deposited part of the mortar charge 224. This action spreads the mortar on the subjacent bricks and also presses the thicker deposit against the brick 228 previously laid, completing the vertical joint between the brick 226, 228.

Horizontal positioning of a brick involves a novel sensing arrangement. A conventional ultrasonic distance sensor 230 is mounted to the carriage 70, and the mason's line 24 is arranged to be substantially at the same height as the sensor 230. The sensor 230 produces a signal indicating the distance from its point of attachment on the carriage 70 to the mason's line 24. That signal will indicate the horizontal distance through which the arm assembly 16 must be extended relative to the carriage 70 to position the brick-gripping mechanism 20 above the masonry 12. The horizontal distance of the brick-gripping mechanism 20 relative to the carriage 70 is a direct function of the angle through which the upper arm 100 is pivoted relative to vertical by the shoulder motor 128 (.phi. in FIG. 4). That angle and consequently the horizontal distance is sensed in a conventional manner with the optical encoder 145 associated with the motor 128 as the arm assembly 16 is extended toward the masonry 12. The controller 32 may control extension of the arm assembly 16 by simply comparing the two sensed horizontal distances, to position the brick-gripping mechanism 20 horizontally over the masonry 12. The mortar-dispensing mechanism 22 can be similarly positioned horizontally for depositing of a mortar charge, distance calculations being adjusted to reflect differences in operative positions of the gripping mechanism 20 and mortar-dispensing mechanism 22 on the frame 122. This arrangement accommodates variations in horizontal spacing of the guideway 10 relative to the masonry 12.

Another ultrasonic distance sensor 232 is attached to the mounting assembly 160 and displaces with the tool assembly 18. When the brick-gripping mechanism 20 has been horizontally positioned for brick placement, it produces a signal indicating the vertical distance from the brick-gripping mechanism 20 to the mason's line 24. Technically, downward displacement of the support 78 to position a brick vertically on the masonry 12 can be controlled in response to the optical encoder associated with the motor 98. However, the sensor 232 provides a more precise distance indication for this critical aspect of brick placement. The controller 32 simply controls the motor 98 in a conventional manner in response to the sensor 232 to vertically position a brick on the masonry 12. This arrangement accommodates variations in the vertical position of the guideway 10. The mortar-dispensing mechanism 22 need only be roughly positioned vertically, which can be done entirely in response to the optical encoder associated with the motor 98. Whether the sensor 232 is then properly positioned to detect vertical distance to the mason's line 24 is not critical.

Conventional attitude sensors 234 may be mounted on the carriage 70 of the bricklaying machine 14 to produce signals indicating inclination of the carriage 70 relative to vertical in mutually perpendicular planes. To simplify calculations, one plane will normally be oriented perpendicular to the brick masonry 12 and the other, parallel to the brick masonry 12. Use of the sensor signals for adjustment of the horizontal distance through which the arm assembly 16 must displace a brick toward the masonry 12 will be discussed with reference to FIG. 17. In FIG. 17, the carriage 70 of the bricklaying machine 14 has been diagrammatically illustrated in simplified form as a phantom rectangle and the mason's line 24 and ultrasonic sensor 230 as circles. The carriage 70 is shown inclined at an angle .OMEGA. relative to a vertical axis 258, in a vertical plane perpendicular to the masonry 12. The distance sensor 230 indicates a distance d from the carriage 70 to the mason's line 24, but upper and lower bricks 260, 262 (arbitrarily selected) are actually at shorter horizontal distances d.sub.1 and d.sub.2 from the carriage 70. The adjusting factor which must be subtracted from the value d to arrive at the horizontal distance to any particular brick is, to a first approximation, h sin .OMEGA., where h is the vertical distance in the reference frame of the carriage 70 between the sensor 230 and the height at which the brick must be laid. The relevant brick height relative to the carriage 70 is a value which is set by the algorithm operating the machine 14 and which is sensed with optical encoders associated with the motor 98 that raises and lowers the arm assembly 16. The height of the sensor 230 on the carriage is a fixed quantity, which together with the expected brick height, yield the value h. For example, with respect to the lower brick 262, the illustrated geometry will indicate that the horizontal distance d.sub.2 through which the arm assembly must displace the brick 262 relative to the carriage 70 is just the sensed horizontal distance d reduced by h.sub.2 sin .OMEGA., where h.sub.2 is the height of the sensor 230 relative to the required horizontal position of the brick 262.

The manner in which the attitude sensors 234 are used adjust the horizontal position at which a brick is placed by the arm assembly 16 in the plane of the brick masonry is similar and will be discussed with reference to FIG. 18. A horizontal position signal for brick placement (the position of the carriage 70 along the guideway 10) is derived from the magnetically encoded power bars associated with the guideway 10. In FIG. 18, the carriage 70 of the bricklaying machine 14, diagrammatically illustrated and simplified, is shown inclined at an angle .OMEGA. relative to a vertical axis 264, in a plane parallel to the brick masonry 12. The vertical axis 264 may be assumed, for sake of simplicity, to be horizontally positioned at the sensed horizontal position of the carriage 70 along the guideway 10. Two bricks 266, 268 are specifically indicated in the masonry 12. Assuming the same angle of inclination .OMEGA. in the placement of each brick 266 or 268, relying solely on horizontal position derived from the guideway 10, the bricks 266, 268 would be mispositioned by horizontal distances d.sub.1 and d.sub.2. The adjusting factor which must be subtracted from the sensed position of the carriage 70 relative to the track to properly position bricks horizontally in the plane of the masonry 12 corresponds, in a first approximation, to h sin .OMEGA. where h is now the vertical distance in the reference frame of the carriage 70 between the magnetically encoded bars of the guideway 10 and the height at which the brick must be laid. The relevant brick height is once again a value which is set by the algorithm operating the machine 14 and which is sensed with optical encoders associated with the motor 98 that raises and lowers the arm assembly 16. The position of the guideway 10 is fixed, which together with the expected brick height, yields the value h. With respect to the brick 268, for example, the illustrated geometry indicates that the horizontal distance d.sub.2, the required correcting factor, is h.sub.2 sin .OMEGA..

The inclination angles .OMEGA. indicated in FIGS. 17 and 18 have been grossly exaggerated for purposes of illustration. A reasonable effort must be made to orient the guideway 10 so that the carriage 70 is near vertical at all times. Minor variations from a vertical orientation can be compensated with the techniques described above, but the particular arm assembly 16 described above does not have sufficient freedom of movement (particularly at its wrist joint 118) to produce acceptable results with severe inclination.

The controller 32 is microprocessor-based, and operated according to software algorithms appropriate for construction of particular building structures. The art of programming robotic mechanisms to perform sequential operations is well-developed, and how the controller 32 should be programmed will consequently be apparent from the foregoing description of the bricklaying machinery. An exemplary sequence of steps in the operation of the bricklaying machine 14 will be briefly described to assist in such matters.

It will be assumed that a brick has just been placed on the masonry 12, and that the brick tractor unit 166 is the brick-transferring position, as in FIG. 9. The arm assembly 16 is raised vertically to position the tool assembly 18 at a predetermined height appropriate to clear the top of the brick retainer 180. The bricklaying machine 14, the brick train 26 and the mortar carrier 28 may then be displaced along the guideway a distance corresponding to the length of a brick. The tool assembly 18 is rotated through 180 degrees so that the brick-gripping mechanism 20 is facing toward the brick retainer 180, and the upper arm 100 is simultaneously pivoted in a negative angular direction to displace the tool assembly 18 horizontally until the brick-gripping mechanism 20 is a predetermined distance behind the carriage 70. That distance is pre-calculated to place the brick-gripping mechanism 20 immediately above the brick retainer 180 (in the predetermined brick-transferring position). The tool assembly 18 is then lowered until the brick-gripping mechanism 20 engages the uppermost brick in the stack of bricks 182, as in FIG. 9. A conventional limit switch (not illustrated) may be mounted on the frame 122 to detect contact. The movable finger 204 is then displaced to grip the upper brick. The tool assembly 18 is then raised back to the predetermined height required to clear the brick retainer 180. The arm assembly 16 is then pivoted in a positive angular direction about the shoulder axis 108 substantially to its rest position with the upper arm 100 and forearm 102 vertical, and the tool assembly 18 is rotated 90 degrees to align the form 208 with the discharge opening 212 of the mortar carrier's container 190. The tool assembly 18 is then raised to another predetermined height expected to place the form 208 just below the discharge opening 212 of the mortar container 190, as in FIG. 10. The controller 32 of the bricklaying machine 14 then actuates the motor 198 of the mortar carrier 28 to open the gate 194 and to agitate the contents of the container 190, to discharge mortar to the form 208, for a predetermined period of time. The form 208 is preferably dimensioned to hold a quantity of mortar sufficient to lay one brick, when completely filled, and the upper surface of the form 208 is held substantially flush against the bottom of the mortar container 190 to avoid spillage when the form 208 is full. The time period may be empirically determined to ensure that the mortar charge 224 completely fills the form 208. It should be noted that manual finishing of the masonry 12 to remove mortar protruding between bricks is expected.

The arm assembly 16 may then be extended and the tool assembly 18 simultaneously rotated through 90 degrees to position the form 208 above the next brick-placing position in the masonry 12. The tool assembly 18 is then lowered to position the form 208 a short distance above the upper surface of the brick masonry 12, and the gate 214 is opened momentarily to release the mortar charge and then closed. The arm assembly 16 may then be retracted a short distance to clear the tool assembly 18 for rotation, assuming wood framing (not illustrated) is positioned behind the masonry 12. The tool assembly 18 is then rotated through 180 degrees, effectively to interchange the brick-gripping mechanism 20 and the mortar-dispensing mechanism 22. The arm assembly 16 is then extended to position the brick-gripping mechanism 20 above the deposited mortar charge. The arm assembly 16 is then swung horizontally away from the last brick laid to prepare for mortar spreading, and lowered until the gripped brick contacts the deposited mortar. The gripped brick is then swung horizontally toward the last brick laid with appropriate rotation of the brick by means of the motor 164 to ensure even spreading. The various steps can then be repeated or varied according to the shape of the masonry 12.

Bricks can be laid at corners of the masonry 12. FIGS. 14 and 15 show corner configurations in the brick masonry 12, and show the overall direction of brick displacement just before setting, exaggerated and indicated with arrows. One possible corner configuration is shown in FIG. 14. A mortar charge 236 is deposited at right angles to the last brick 238 laid, with the thicker portion 240 of the charge 236 proximate to a lengthwise side 242 of the last brick 238. The next brick 244 is positioned vertically on the thinner region of the mortar charge 236 and then swung horizontally to spread the thicker charge portion 240 against the side 242 of the last brick 238, rotating back and forth horizontally to properly spread the charge 236, all in the manner described above. A more difficult corner configuration is shown in FIG. 15, in which the last brick 246 is offset from the corner 248 by about one-half of a brick length. A mortar charge 250 is deposited once again at right angles to the last brick 246, but with the thicker portion 252 at the end surface 254 of the last brick 246. The next brick 256 cannot simply be swung into place as before. Instead, the arm assembly 16 is manipulated to displace the next brick 256 horizontally at an appropriate height to spread the thicker portion 252 of the mortar charge against the end surface 254 of the last brick 246 and to spread mortar below the brick 256. The ultrasonic distance sensor 232 can be used to ensure proper vertical positioning of the brick 256 for such purposes, despite some horizontal offsetting of the sensor 232 relative to the mason's line 254. Rotation of the brick 256 for purposes of mortar spreading must be stopped as the brick 256 approaches the last brick 246. Subsequent manual finishing may be required.

The invention has been described in the context of forming a brick structure essentially as part of a building. Navigation relative to a mason's line is important in such applications. However, the invention can also be used to construct partitions or other structures that are simply installed at a remote location as pre-assembled units. In such applications, precision tracks can be readily provided for repetitive construction of predetermined structures using the bricklaying machinery described. The carriage 70 can be simplified accordingly. Alternatively, the brick masonry may be displaced horizontally relative to the bricklaying machinery. It is possible to use separate robotic mechanisms to displace the brick-gripping mechanism 20 and mortar-dispensing mechanism 22 in such applications. Manipulating the tool assembly 18 as a single unit with a single robotic arm simplifies control, and is strongly preferred for general construction of buildings on site.

It will be appreciated that particular embodiments of the invention have been described and that modifications may be made therein without departing from the spirit of the invention or necessarily departing from the scope of the appended claims.