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BACKGROUND OF THE INVENTION 
   1. Field of Invention 
   This invention relates to the re-surfacing of concrete. More particularly, it relates to an apparatus having utility in resurfacing concrete found in vertical walls such as cooling towers. 
   2. Description of the Prior Art 
   Cooling towers are huge structures having concrete walls of hyperbolic shape. The shape creates an upwardly flowing draft of air that cools heated cooling water from steam condenser boxes that convert hot steam back into condensate water that is re-heated and re-used as steam. The concrete walls require refinishing from time to time. The art currently requires the building of scaffolding that carries workers to the top of the tower and which gradually lowers the workers as they remove the concrete with jack hammers and other equipment. 
   There are a number of drawbacks to the known concrete-removal procedure. Scaffolding is inherently dangerous, for example. Moreover, the work is labor intensive and the time required to remove the concrete is substantial. Jack hammers inherently leave micro fractured concrete behind, creating a very poor surface to which repair concrete may adhere. This leads to premature failure of the repaired concrete. 
   There is a need for a procedure that does not require workers to stand on an elevated scaffold. There is also a need for a procedure that performs the work in substantially less time and which does not create poor concrete bonding surfaces. 
   However, in view of the art considered as a whole at the time the invention was made, it was not obvious to those of ordinary skill in this art how the concrete-removing procedure could be improved. The non-obviousness of the invention disclosed below is established by the many years that the art has employed workers on scaffolds to do the job. 
   SUMMARY OF INVENTION 
   The long-standing but heretofore unfulfilled need for an improved concrete-removal procedure is now met by a new, useful, and non-obvious invention. The novel structure provides an apparatus for removing concrete from a substantially vertical wall. It includes a crawler assembly having a frame of predetermined breadth. A nozzle housing is carried by the frame. A reciprocating means causes the nozzle housing to follow a path of travel that reciprocates between a first end of the frame and a second end of the frame. A nozzle is carried by the nozzle housing and is adapted to emit water under high pressure. The water impinges upon and removes concrete from the substantially vertical wall for refurbishing purposes. A lifting and lowering means is provided for lifting the crawler from a bottom of the vertical wall to a top of the vertical wall and for lowering the crawler from a top of the vertical wall to a bottom of the vertical wall. A vertical strip of concrete is thereby removed from the vertical wall by the water under high pressure as the nozzle housing reciprocates and rotates as the crawler is lowered from a top of the vertical wall to a bottom of the vertical wall. The vertical strip has a width substantially equal to the width of the frame. 
   A first support plate and a second support plate are secured to the substantially vertical wall at an upper end thereof in laterally spaced apart relation to one another. A first pulley is rotatably mounted to the first support plate and a second pulley is rotatably mounted to the second support plate. 
   A hydraulic motor is connected in driving relation to a winch having two winch spools connected to one another by a common shaft to provide conjoint movement. A first elongate cable is wrapped about a first pulley and has a proximal end disposed in coiled relation to a first winch spool and a distal end secured to the frame adjacent a first end thereof. A second elongate cable is wrapped about a second pulley and has a proximal end disposed in coiled relation to a second winch spool and a distal end secured to the frame adjacent a second end thereof. Rotation of the two winch spools in a first direction lifts the crawler from the bottom of the vertical wall to the top thereof and rotation of said spools in a second direction opposite to the first direction lowers the crawler from the top of the vertical wall to the bottom thereof. 
   The frame has a substantially rectangular configuration and includes a laterally disposed top member, a laterally disposed bottom member parallel to the top member, and a longitudinally disposed first side member interconnecting respective first ends of the top and bottom members. The frame further includes a longitudinally disposed second side member parallel to the first side member, said second side member interconnecting respective second ends of the top and bottom members. A first set of wheels adapted to rotatably engage the vertical wall is secured to the top member at the first end thereof. A second set of wheels adapted to rotatably engage the vertical wall is secured to the top member at the second end thereof. A third set of wheels adapted to rotatably engage the vertical wall is secured to the bottom member at the first end thereof, and a fourth set of wheels adapted to rotatably engage the vertical wall is secured to the bottom member at the second end thereof. 
   In an embodiment adapted for use with cooling towers having at least a first and a second vertically extending groove formed in the vertical wall, where the first and second grooves are laterally spaced apart from one another by a distance substantially equal to a distance that separates the first and third set of wheels from one another and the second and fourth set of wheels from one another, each of the sets of wheels includes at least two wheels. One large diameter wheel of the at least two wheels in each of the four sets has a diameter larger than other wheels in each set. The large diameter wheel of each set is adapted to travel in the vertically-extending groove formed in the vertical wall. A first jack assembly adapted to push the first end of the frame away from the vertical wall is secured to a first end of the frame. A second jack assembly adapted to push the second end of the frame away from the vertical wall is secured to a second end of the frame. Said first and second jack assemblies lift each large diameter wheel of said four sets of wheels from its associated groove. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     For a fuller understanding of the invention, reference should be made to the following detailed description, taken in connection with the accompanying drawings, in which: 
       FIG. 1  is a front elevational view depicting an illustrative embodiment of the novel apparatus; 
       FIG. 2  is an exploded, perspective view of the mounting plates that support the weight of the crawler and the other parts of the novel apparatus; and 
       FIG. 3  is a front elevational view of the crawler. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Referring now to  FIG. 1 , it will there be seen that an illustrative embodiment of the invention is denoted as a whole by the reference numeral  10 . 
   Apparatus  10  includes crawler  12  that carries a high-pressure water nozzle that performs the concrete removal preparatory to re-surfacing. The motor and common shaft winch system that control crawler  12  are denoted  14  as a whole. The support assembly that is bolted to concrete wall  11  of a cooling tower or other substantially vertical wall is denoted  16  as a whole. 
   As best understood in connection with  FIGS. 1 and 2 , support assembly  16  includes flat plates, collectively denoted  18 , having apertures, collectively denoted  20 , formed therein at the corners thereof. Each flat plate  18  overlies the concrete surface or wall  11  of a cooling tower or other generally vertically disposed wall made of concrete. Each flat plate  18  is secured to concrete surface  11  by a plurality of bolts, collectively denoted  22 , each of which extends through an associated aperture  20  to engage concrete wall  11  and secure its associated flat plate  18  to said concrete wall  11 . Mounting plate  24  is secured to each flat plate  18 , centrally thereof, Clevis  26  has a flat base  28  secured to mounting plate  24  and a clevis pin  30  extends between transversely opposed arms  32  of the clevis and captures pulley  34 . Clevis pin  30  serves as an axle for pulley  34  so that said pulley is free to rotate. 
   As best understood in connection with  FIG. 1 , cables  36 ,  36  respectively wrap about their associated pulley  34 ,  34 . As best depicted in  FIG. 2 , the angle of wrap is one hundred eighty degrees (180°). A plurality of support assemblies  16  is secured to the cooling tower or other concrete structure having a vertical concrete surface in need of resurfacing, with each support assembly  16  being equidistantly spaced from its contiguous assemblies and with each assembly  16  being at, above, or near the top of the concrete surface to be refinished. 
   As best depicted in  FIG. 3 , the distal end of each cable  36  has a loop  38  formed therein, and each loop engages a ring  40 . Each ring captures an apertured lug  42  and each apertured lug  42  is secured to crawler  12 . 
   As best understood in connection with  FIG. 1 , the proximal end of each cable  36  is disposed in coiled relation about a reel or winch, of which there are two interconnected spools  44 ,  44 , both of which are mounted to platform  45 . Each winch spool  44  rotates conjointly with an output shaft of motor  46  so that a cable  36  is reeled in when motor  46  operates in a first direction and is reeled out when said motor operates in a direction opposite to the first direction. Platform  45  is stationary during operation of hydraulic motor  46 . Therefore, operating hydraulic motor  46  in a first direction reels in cable  36  and lifts crawler  12  and operating said motor in a second direction opposite to the first unreels cables  36  and lowers crawler  12 . 
   Hydraulic supply hoses and electrical power conductors, collectively denoted  48 , are connected to a conventional control box for motion control. 
   Cable  36  is initially reeled in to lift crawler  12  to an upper edge of a concrete wall to be re-surfaced, and nozzle housing  70  is then activated so that it begins its alternating left-to-right and right-to-left travel along the extent of frame  50 . Crawler  12  is slowly lowered during such nozzle travel by slowly reeling out cables  36 ,  36 , thereby slowly lowering crawler  12 . 
   The structure of crawler  12  is best depicted in  FIG. 3 . Lugs  42  are secured to rectangular frame  50  as aforesaid and said frame is spaced apart from the vertical concrete surface by four (4) sets of wheels, collectively denoted  52 . In this illustrative embodiment, each set of wheels includes five (5) wheels disposed in lateral relation to one another, equidistantly spaced apart along the extent of a common axle. The number of wheels may change depending upon what the requirements are of a particular application. In this cooling tower application, each set of wheels includes four (4) rubber or hard plastic wheels, collectively denoted  52   a , having a common size that rotatably engage the vertical surface of a cooling tower and one (1) outboard steel wheel  52   b  that has a diameter that exceeds the common diameter of the four (4) rubber or hard plastic wheels. 
   Each of the outboard wheels is preferably formed of steel and is larger in diameter than the other four (4) wheels in this particular embodiment but the wheels may have a common diameter in many applications. The depicted embodiment is adapted for use in treating the concrete surface of a power plant cooling tower. Such cooling towers typically have a plurality of vertically-extending raised ridges formed on them that extend from the top of the tower to the bottom, and said raided ridges converge toward one another from bottom to top, i.e., diverge from one another from top to bottom. Steel outboard wheels  52   b  keep crawler  12  positioned between contiguous ridges. The width of crawler  12  is dictated by the lateral distance between the ridges when crawler  12  is built for treatment of said cooling towers. Where the concrete wall being blasted with high pressure water is not a cooling tower wall, the width of crawler  12  may be changed to any convenient breadth and wheels  52  may have a common diameter. Each enlarged wheel  52   b  in this depicted embodiment is a hard wheel and is adapted to ride between the cooling tower vertical ridges. Wheels  52   a  of smaller diameter rollingly engage the concrete wall contiguous to the ridge. Thus it is understood that each large steel wheel  52   b  serves as a guide means that ensures that crawler  12  remains between contiguous ridges as said crawler is lowered down or raised up the face of the concrete wall. 
   The opposite ends of each axle  54  engage transversely opposed arms of clevis  56  so that the wheels are free to rotate. Elongate adjustment screws, collectively denoted  58 , adjustably interconnect their associated clevis  56  to frame  50 . This enables frame  50  to be positioned a preselected distance from concrete wall  11 . A pair of braces  60  is positioned at opposite ends of frame  50  to enhance the structural integrity of said frame. 
   Lifting wheels, collectively denoted  62 , have a caster wheel construction as illustrated. Each lifting wheel assembly includes a hand crank  64 . When a vertical strip of wall has been treated, an operator in a man-lift cranks hand crank  64  and said cranking jacks the associated lifting wheel assembly so the caster wheels bear against the concrete wall and lift crawler  12  and wheels  52   a ,  52   b  away from said wall. The lifting distance is sufficient to withdraw large wheel  52   b  of each set of wheels  52  from its associated vertical ridge so that crawler  12  may be moved to the left or right to begin another trip up or down the face of the wall. 
   More particularly, the movement of crawler  12  to the left or right is accomplished by providing a pair of relatively short, fixed length cables, not depicted, that respectively have a first end secured to an associated flat plate  18  and a second end releasably engaged to frame  50 . The second ends of said short cables are detached from frame  50  when apparatus  10  is traveling down the face of the concrete wall being treated. When crawler  12  reaches its lowermost position, i.e., when a first vertical strip of the wall has been treated (said vertical strip being substantially the width of the lateral travel of nozzle housing  70 ), crawler  12  is drawn up to the top of the wall as the first step in re-positioning it to the left or right so that a second vertical strip contiguous to the first may be treated. When so lifted, frame  50  is spaced from support plates  18 ,  18  by a distance less than the respective lengths of the short cables. The lower ends of the short cables are therefore easily attached to frame  50  by means of lugs similar to lugs  42  and crawler  12  is lowered until the short support cables support the weight of crawler  12  and motor assembly  14 . This removes the weight from cables  36 . A worker in a man-lift then lifts each cable  36  from its associated pulley  34  and moves each cable  36  to an associated pulley of a contiguous second set of pulleys that are rotatably supported by a second pair of support plates  18 . A plurality of pairs of support plates  18 ,  18  are secured to the wall to be treated along an upper end thereof as aforesaid, with each pair of support plates being positioned so that when crawler  12  is lowered with respect thereto, a vertical strip of the wall is treated and each vertical strip is contiguous to another vertical strip. Where the wall to be treated is the wall of a cooling tower or other structure having annular walls, the entire structure is encircled by cooperatively positioned pairs of support plates  18 ,  18  so that the crawler may be moved from one pair of support plates to another pair of contiguous support plates until the entire structure has been circumnavigated. 
   Although the invention is not limited to cooling towers, it should be observed that wheels  52  may have a common diameter when a surface other than a cooling tower surface is being treated, unless said surface is also provided with raised ridges in the manner of a cooling tower. 
   A highly focused stream of high-pressure water is denoted  66  in  FIG. 3 . Water  66  removes old concrete so that new concrete may be applied. Water  66  is emitted by nozzle  68  that forms a part of nozzle housing  70 . Hose  72  supplies high-pressure water from a remote source to said nozzle housing  70 . Nozzle housing  70  is adapted to travel laterally, i.e., from left to right and from right to left in alternating sequence as crawler  12  is slowly lowered down the face of concrete wall  11  by unreeling cable  36 ,  36 . A hydraulic motor propels the nozzle housing. A pinion gear, not depicted, is secured to the output shaft of the hydraulic motor for conjoint rotation therewith. The pinion gear meshingly engages a stationary elongate rack gear so that nozzle housing  70  moves along the extent of the rack gear in a first direction as the pinion gear rotates in a first direction. 
   A first limit switch is positioned at a first end of the rack gear so that when nozzle housing  70  contacts said first limit switch, said first limit switch generates and sends a signal to the hydraulic motor that reverses the direction of rotation of the output shaft and hence of the pinion gear, thereby causing the nozzle housing to travel in a second direction opposite to said first direction. A second limit switch is positioned at a second, opposite end of the rack gear so that when nozzle housing  70  contacts said second limit switch, said second limit switch generates and sends a signal to the hydraulic motor that reverses the direction of rotation of the output shaft and hence of the pinion gear so that nozzle housing  70  travels in said first direction, and said alternating or reciprocating travel continues as frame  50  is lowered down the face of the concrete surface undergoing treatment. 
   The hydraulic cylinders that provide the means for such traverse adjustment are denoted  71   a ,  71   b  in  FIGS. 1 and 3 . 
   A worker standing on the ground remotely controls the novel apparatus. This eliminates the prior art hazard of one or more workers positioned on a scaffold at dangerous heights. 
   When crawler  12  reaches the bottom of a concrete wall, it is returned to the top edge of said wall, moved to the left or right one frame length by following the procedure disclosed above, and the process is repeated as needed. The crawler is much safer to use than a manned apparatus, and it performs the concrete removal work much faster and with a high level of consistency. 
   The novel structure efficiently removes unsound concrete without introducing micro fractures, thereby providing high quality surface preparation so that the repair of the concrete surface has substantially enhanced longevity relative to the repair methods heretofore known. 
   The rotation speed of the nozzle is critical, as is the nozzle stand off distance, the nozzle attack angle, its transverse speed, and its vertical (up and down) speed. Optimizing these critical parameters creates the desired high quality surface preparation. While these parameters may vary from job to job, a typical nozzle rotation speed is two hundred revolutions per minute (200 rpm), a typical nozzle standoff is two to three inches (2-3″), a typical nozzle attack angle is twelve degrees (12°), a typical transverse speed is eight inches per second (8″/sec), and a typical up and down speed is three inches per minute (3″/min). 
   It will be seen that the advantages set forth above, and those made apparent from the foregoing description, are efficiently attained and since certain changes may be made in the above construction without departing from the scope of the invention, it is intended that all matters contained in the foregoing description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense. 
   It is also to be understood that the following claims are intended to cover all of the generic and specific features of the invention herein described, and all statements of the scope of the invention that, as a matter of language, might be said to fall therebetween. Now that the invention has been described,

Summary:
Concrete on a vertical wall is removed for resurfacing in the substantial absence of microfracturing by a crawler apparatus that is lowered from the top of the wall to the bottom by remote control. The crawler is raised and lowered by cables that are reeled in or out depending upon the direction of rotation of the output shaft of a motor. A rotating nozzle blasts a focused stream of very high-pressure water against the concrete to be removed. The nozzle is carried back and forth along the breadth of the crawler as the crawler descends the face of the concrete wall so that a vertical strip of concrete substantially equal in width to the width of the crawler is removed. The crawler is then returned to the top of the wall and moved laterally to begin removal of the next vertical strip of concrete.