Abstract:
Arrangements are taught for decoratively engraving a surface, such as hardened concrete or stone, particularly by engraving stencil-defined swaths into the surface with a tool of the type commonly called a needle scaler. The arrangements include methods of covering portions of the surface with a stencil made of material capable of withstanding a chisel blow, and then engraving exposed swaths by repeated chisel blows from one or more chisels having a restricted stroke. In some cases non-contiguous portions of a stencil are interconnected by bridge-line connectors selected to allow free access to the entire swath by a needle scaler or other chisel driving apparatus. In other cases a space-frame is placed atop a stencil and used to support discrete non-contiguous island portions of the stencil.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     Not Applicable 
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Not Applicable 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to the art of engraving a surface, often for the purpose of providing a decorative design on a previously hardened concrete, asphalt or other workable surface. 
     2. Background Information 
     Many earlier inventors have taught methods of concrete decoration in which a stencil is laid on a concrete surface and wet, colored concrete materials are added to the pre-existing surface through holes in the stencil. Notable among teachings in this area are the following patents: 
     U.S. Pat. No. 5,792,511, wherein Oliver et al. show a stencil that remains embedded in the decorative coating. 
     U.S. Pat. No. 5,735,094, wherein Zember describes a coating process using specific materials and involving pulling a stencil out of the coating before it sets up. 
     U.S. Pat. No. 5,447,752, wherein Cobb describes a similar process using different materials. 
     U.S. Pat. No. 5,243,905, wherein Webber teaches a stencil comprising interlocking segments and used in a coating process. 
     U.S. Pat. No. 5,133,621, wherein Gonzales describes a way of putting isolated decorative figures in a wet concrete slab. 
     U.S. Pat. No. 5,038,714, Dye et al. teach an arrangement for spraying a dye, but not additional concrete, through a stencil having a gasket on the bottom thereof. 
     The inventor, in his U.S. Pat. No. 5,176,426 and U.S. Pat. No. 5,445,437, has taught method and apparatus for engraving decorative figures into a hardened concrete surface by guiding a cutting apparatus across the surface to be decorated. These arrangements have generally employed small wheeled carts carrying abrasive grinding wheels. 
     Apparatus of the sort generally referred to as “flux chippers” or “needle scalers” is also of interest. In these sorts of apparatus one or more impacting tools, retained for translational motion of a limited extent along a predetermined axis, are repeatedly driven into the surface to be engraved by impacts from a hammer that is conventionally pneumatically operated, but that could be electrically or hydraulically driven. A needle scaler typically uses ten to thirty pointed rods, called “needles”, as the impacting tools. Each of these needles may have a diameter of two to three millimeters and commonly has a nail-head end distal from the pointed or beveled work-impacting end that commonly projects outwardly from a nosepiece of the apparatus. A pneumatically driven hammer head strikes the array of needles and is returned to the beginning of its reciprocating stroke by a return spring. This arrangement provides several thousand blows per minute on the array of nail heads and thereby repeatedly drives the needles back and forth over a total stroke distance of some three centimeters. Needle scalers are generally used in a freehand mode and are made with a variety of grips and nose configuration to adapt them to differing applications. The uses for needle scalers include cleaning rust (e.g., mill scale) from iron and steel castings, peening welded joints, removing barnacles from marine apparatus, and chipping stone, concrete and brick. 
     In addition to the use of grinding wheels and of chisels, it is also known to engrave hard surfaces by sandblasting, shot peening and other such techniques in which impacting tools, comprising small particles of a hard material, are expelled from the nose or nozzle of a tool driving or dispensing means and energetically impact a surface being engraved. When used to make deep cuts in hardened concrete or other aggregate materials comprising segregated portions of differing hardness, sandblasting leads to an engraved region having a rough texture because the softer portions of the concrete are removed more easily than harder ones. 
     BRIEF SUMMARY OF THE INVENTION 
     A preferred embodiment of the invention provides apparatus for engraving a hardened surface of stone, concrete, asphalt, or the like. This apparatus may comprise one or more impacting tools, retained for translational motion of a limited extent along a predetermined axis; as well as an impact-absorbing stencil exposing those regions of the surface to be engraved while protecting adjacent regions from the impacting tools. In some embodiments, the apparatus comprises a plurality of impacting tools protruding outwardly of an aperture having a selectively alterable shape. This allows an operator to select a relatively elongated and narrow aperture when engraving a narrow swath and to select a relatively equi-axial aperture when engraving broader expanses. 
     In some embodiments, the apparatus of the invention comprises a stencil defining one or more relatively narrow swaths of exposed surface. In some cases, a swath is bordered by a stencil frame or by one of a plurality of non-contiguous “islands” covering portions of the surface that are not to be worked by the tool. In other cases, a swath may be exposed by a slit cut into a single sheet of material used for the stencil. In embodiments having islands, and in some embodiments having a plurality of long slits, bridge-like members may be used to connect adjacent portions of the stencil. In some embodiments these bridges allow engraving of the surface immediately beneath them. This is sometimes done by providing a clearance above the center of the respective exposed swath that is greater than the minimum diameter of the nose of a needle scaler, so that the scaler can be used to engrave that portion of the swath beneath the bridge. In other embodiments, stanchion portions of a bridge are hingedly connected to each of two non-contiguous portions of the stencil so that the bridge can be pivoted from side to side in order to provide an operator with access to the entire swath being engraved. In still other embodiments, one or more of the islands are connected to a space frame disposed on and extending outward from that side of the stencil distal from the engraved surface by connecting means preferably selected to allow a chiseling apparatus or needle scaler free access to all portions of the exposed swaths. 
     The invention provides methods for decoratively engraving a surface, such as hardened concrete or stone. In some embodiments the invention provides a method of engraving a surface by cutting stencil-defined swaths into the surface. This method may comprise the steps of covering portions of the surface with stencil material capable of withstanding a chisel blow, the spaces between adjacent stencil portions defining the swaths; and to then engrave the swaths by repeated chisel blows from one or more chisels having a restricted stroke. In some of these embodiments the method further comprises attaching non-contiguous portions of stencil material to each other by connecting means selected to allow free access to the entire swath by a needle scaler or other chisel driving apparatus. 
     Although it is believed that the foregoing recital of features and advantages may be of use to one who is skilled in the art and who wishes to learn how to practice the invention, it will be recognized that the foregoing recital is not intended to list all of the features and advantages of the invention. Moreover, it may be noted that various embodiments of the invention may provide various combinations of the hereinbefore recited features and advantages of the invention, and that less than all of the recited features and advantages may be provided by some embodiments. 
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
     FIG. 1 is a partly cut-away view of a pneumatic needle scaler engraving an exposed concrete swath between two portions of a stencil separately connected to a space frame attached to the side of the stencil distal from the concrete. 
     FIG. 2 is an exploded view of a two-legged stencil bridge of the invention 
     FIG. 3 is a partly sectional side view, similar to one taken along the line  3 — 3  of FIG. 2, of engraving apparatus being used with a bridged stencil. 
     FIG. 4 is a perspective view of a three-legged embodiment of a stencil bridge of the invention. 
     FIG. 5 is a side elevational view of a bridged stencil of the invention used on a curved surface. 
     FIG. 6 is an elevational view of a stencil usable for engraving near a vertical wall. 
     FIG. 7 is a cross sectional view, taken as indicated by  7 — 7  in FIG. 6, of the stencil of FIG.  6 . 
     FIG. 8 is a partial plan view of a stencil comprising means of adjusting a swath width. 
     FIG. 9 is a plan view of a stencil comprising a space frame supporting non-contiguous stencil islands. 
     FIG. 10 is a plan view of a stencil comprising three- and four-legged bridges. 
     FIG. 11 is an elevational view of a flexible nosepiece in a relaxed state. 
     FIG. 12 is an elevational view of the nosepiece of FIG. 11 pinched into a narrow configuration. 
     FIG. 13 is a perspective view of a hinged nosepiece for a needle scaler. 
     FIG. 14 is a cross section taken perpendicular to a surface to be engraved and through a masking connector connecting two portions of a stencil. 
     FIG. 15 is a perspective view of a stencil of the invention comprising “needle squeeze” members on a narrowing portion thereof. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Turning initially to FIG. 1, one finds preferred engraving apparatus  10  comprising a plurality of impacting tools  12  adapted to be repeatedly driven into a worked surface  14  by a hammer apparatus  16  that reciprocates the impacting tools  12  along a stroke having a predetermined length. The preferred apparatus  10  also comprises a stencil  18  used to define a swath  20  of the surface  14  to be chased or grooved in the engraving operation. The stencil  18  also protects other portions of the surface from being struck by a scaling needle  22 , chisel, or other impacting tool  12 . Particularly when a narrow swath  20  is to be chased, portions (which may be discrete portions, as will hereinafter be disclosed) of the preferred stencil  18  may have a beveled periphery  24  slanted so as to guide a reciprocating needle  22  onto the worked swath  20 . When a wider swath  20  is being cut a beveled edge  24  is less important because an operator can usually tilt the needles or other impacting tool  12  so as to work close to the edge of the stencil  18 . In many embodiments, portions of the stencil  18  adjacent the swath  20  are chosen to be of a material that can sustain repeated blows from a scaling needle  22 , pneumatically driven chisel, and the like. In various embodiments, resilient stencil portions may be cut from sheets of plywood, metal, or recycled plastic. 
     The engraving apparatus  10  may be used for forming surfaces simulative of brick or field stone surfaces by dyeing a concrete surface and then patterning the surface by cutting swaths, simulative of grout lines, to a depth greater than that of the dye penetration, as is indicated with the reference numeral  76  in FIG.  14 . Other methods of preparing such simulative surfaces have previously taught in my patents U.S. Pat. No. 5,176,426 and U.S. Pat. No. 5,445,437, the teachings of which are incorporated by reference herein. Thus, it is expected that in most cases the worked surface  14  will be a flat, most commonly horizontally disposed surface of a hardened concrete slab  26 , such as a driveway into which a brick-like pattern is to be engraved. The invention, however, is not limited to this case, and may also embrace engraving on curbs  28 , other curved surfaces, or on a wall or ceiling. Moreover, the worked surface  14  need not be an exposed surface of a body of pre-hardened concrete, but can be stone, asphalt, glass, or any other material that can be engraved by using an impacting tool to remove a selected portion of the surface thereof. 
     Turning now to FIG. 5, one finds a stencil  18  comprising two adjacent, non-contiguous masking elements  30  connected by a bridge  32 . The bridge  32  of FIG. 5 comprises stanchions  34  fixedly attached to each of the masking elements and a linking member  36  pivotally connecting the stanchions  34  so as to allow the overall stencil  18  to conform to non-planar portions of the worked surface  14 . Although two hinged attachment points are depicted in FIG. 3, it may be noted that a single hinged connection point  33 , as depicted in FIG. 2, may well be adequate. Although most of the bridges illustrated in the drawing have two legs, in some cases one can profitably reduce the number of bridges  32  required for a stencil  18  by using a bridge having three or more legs  47 , as generally depicted in FIGS. 4 and 10. 
     When a brick or tile surface is being simulated by engraving pseudo-grout lines into a concrete surface, it is often desired that swaths be engraved up to a wall abutting the surface. In such cases one can employ a generally ell-shaped inside corner stencil  31 , as depicted in FIGS. 6 and 7. A preferred inside corner stencil  31  has a slot  41  cut through a leg thereof, with the width of the slot  41  selected to match the width of the swath to be engraved. The slot  41  terminates with an undercut beveled edge portion  42  that allows the scaler needles  22  to reach all the way to the wall without marking the wall. It will be understood to those skilled in the art that if one desires to carry a simulated grout line up along the vertical wall one could use an angled stencil (not shown) having two slotted legs and being similar in appearance to a corner bracket. 
     In some embodiments the stanchions  34  are selected to be tall enough so the portion of the swath  20  beneath the bridge  32  can be engraved by the impacting tools  12 . In these embodiments the clearance, as measured along a line perpendicular to the worked surface  14 , between the surface  14  and the bridge  32  is greater than a diameter of the nose  38  of the hammer apparatus  16  or other tool. In other embodiments the stanchions  34  are hingedly attached to a base  35  portion of the bridge  32  so that the bridge  32  can be pivoted out of the way of the hammer apparatus  16 , as depicted in FIG.  3 . Moreover, a bridge  32  may comprise stanchions  34  linked by a linking member  36  having a length-extensible portion  37  so as to allow for appropriate selection of the widths of swaths to be engraved. 
     Although the ability to engrave a shadowed portion of a swath disposed along a line running between the ends of by a bridge or other connecting member is important for some applications, this is not universally the case. In some cases it is necessary, or at least convenient, to attach the stencil  18  to a worked surface  14 , such as a vertical wall. When engraving to remove a dyed portion having a limited depth  76 , it is desirable to avoid marring the masked dyed portion. If one were to simply attach a stencil to a surface by making temporary mounting holes in masked regions, after the engraving was completed one would then have to both fill those holes and dye the filler material to match the surrounding surface. This commonly results in visually obvious and undesired marks on the surface. Hence a preferred approach is to attach a stencil  18  to a worked surface  14  by means of a plurality of screws  74  extending through respective throughholes formed in bridges  32  or in flat, shadowing, connecting members  72 . By using this approach, one assures that the subsequent mounting hole patches can be made without having to match dye coloration. In situations where a narrow, grout-line simulative, swath is cut, the resultant patched hole is nearly invisible. 
     The use of temporary mounting screws necessarily obscures part of the surface to be engraved. In some cases, e.g., when an engraved figure is substantially wider than the impacting tool  12  and when a tall enough bridge  32  is used so that only that portion of the surface immediately adjacent the mounting screw  74  is not worked while the bridge is in place, freehand engraving can be used to finish up around the patched mounting hole. When narrow swaths are being engraved, however, a separate single-slotted stencil having a slot width matching the swath width (such as that shown in FIG. 6) can be used to engrave shadowed regions. Alternately, one can provide a set of slots  78  in masking portions  30  of the stencil, where all of the slots  78  are located the same distance from a mounting hole so that after removing the mounting screws, an operator can translate the entire stencil to one side or another to align the slots  78  with the previously shadowed portions of the worked surface 14 . 
     In some embodiments the stencil  18  may comprise a frame portion  40  surrounding a portion of a surface  14 . This frame  40  comprises a large aperture  42  within which are disposed a plurality of non-contiguous masking elements  30 , each of which is separated from the frame  40  and from adjacent masking elements by a swath  20  wherefrom material is to removed from the surface  14  during the engraving operation. Because it is desirable to be able to select a variety of widths a swath  20 , some embodiments of the invention provide a length-adjustable connecting means  44 , such as the elongate metal loop  46  depicted in FIG.  8 . Moreover, because it is also desirable to simulate paving stones having a variety of sizes, some embodiments of the invention provide sets of multiple masking elements  30   a,    30   b,    30   c,    30   d  connected by length-adjustable connecting means  44  and shaped so that they can be drawn together or displaced some distance from each other. When spaced apart, these mask elements may be separated by a unused swath  20   a  that is not to be engraved. 
     A stencil comprising an unbroken outer frame  40  allows one to use a ganged support  48  to hold several non-contiguous masking elements  30  within the frame  40 . A ganged support  48 , as depicted in FIGS. 1 and 9, may comprise stanchions  34  extending outwards of the distal side of the frame (i.e., that side of the frame  40  distal from the worked surface  14 ), and elongate supporting members  50  extending between the stanchions  34 . In some embodiments commercially available plumbing pipes are used for the elongate support members  50  and oversized plumbing tees  52 , retained in selected positions with set screws  54 , are used to suspend individual masking elements  30  on the end of additional short pieces of piping  56 . In other cases, a custom-fabricated screw-clamped fitting  53  may be used. 
     An additional advantage of a framed stencil is that one can select the shape of the aperture  42  so that after engraving a set of exposed swaths, the stencil  18  can be translated along the worked surface  14  and placed in a new position defining a second set of swaths, where the second set is aligned with respect to the first. For example, if one were to use a square aperture, the frame could be translated along orthogonal Cartesian axes so as to cover the worked surface with a square array of swaths. In simulating fieldstone paving, however, it has been found to be esthetically more pleasing to employ a frame  40  having a aperture  42  having four matching arcuate edges  58  that all have the same radius of curvature. 
     Many impacting tools  12  and tool driving means are suitable for engraving or chasing hard surfaces. These include manually and pneumatically driven single chisels, pneumatically driven sets of multiple small pointed rods or chisels of the sort commonly called “needles”, as well as sand or other abrasive material carried to the working surface by air or water. Manually chasing a concrete surface in order to define a decorative pattern is generally too laborious. Sandblasting, which may use some sort of stencil, is less laborious, but tends to create a undesirably rough groove in concrete because the impacting grains of sand preferentially remove softer cement while leaving harder chunks of aggregate material exposed. Grooving a concrete surface with a single pneumatically driven chisel is also known, but tends to leave recognizable tool marks in the grooves. Hence, the preferred embodiments of the invention employ a needle scaler  60  comprising a reciprocating pneumatic hammer apparatus simultaneously reciprocating a plurality of needle-like impacting tools  12  along a predetermined stroke so as to remove many small chips of material from the worked surface without simultaneously creating an undesired texture. 
     Most needle scalers employ a nose  38  having a round aperture, or one in which the range of diameters  62  is relatively small—i.e., in which the aspect ratio of length to width of the aperture is less than 2:1. Although the beveled edges  24  of the stencil  18  are useful for guiding needles into a swath  20 , it is nonetheless also advantageous to provide a means of forcing an array of needles into a nearly linear configuration in which the minimum width of the needle array is substantially narrower than a swath  20 . In one arrangement for controllably varying the minimum width of a nosepiece of a needle scaler between an expanded configuration, in which the minimum width of the nosepiece is greater than the width of a swath, and a contracted configuration in which the minimum width of the nosepiece is less than the width of the swath, a flexible nosepiece  64  provides a means of forming a narrow needle array. In another embodiment, a flap portion  66  of an otherwise conventional steel nosepiece  68  is attached to the balance of the nosepiece by a hinge  70 . With this apparatus, an operator can “pinch” the needle array into a narrow configuration, insert the nearly linear array into the swath between two neighboring masking elements and then begin chipping. 
     Local thickness variations in a stencil  18  are also useful for realigning an array of scaler needles  22  so that all the needles impact the worked surface  26  in a narrow swath  20 . For example, a locally thicker portion configured as a “squeeze chute”  84  can placed on the stencil  18  so that a bifurcating slit in the squeeze chute  84  is aligned over a portion of a swath  20  defined by a stencil  18 . The squeeze chute  84  may have a funnel-like end (as depicted in FIG.  15 ), or may have a portion with beveled edges similar to the beveled stencil edge depicted in FIG.  1 . An operator can use a squeeze chute  84  having a funnel-like opening to get all of a set of needles  22  into the narrow swath by tilting the needle scaler slightly away from a vertical setting (e.g., by 15° or so), moving the array of needles into the chute  84  and then returning the scaler to a vertical setting. Similarly, a squeeze chute having beveled edges can be used to work an array of needles into a narrow swath by lowering the needle scaler through the squeeze chute until the needles contact the surface being worked. Although the squeeze chute  84  depicted in FIG. 15 is clearly meant to be temporarily placed over a portion of the stencil when an operator wishes to work an array of needles into a narrow space, it should be noted that one could also provide squeeze chutes permanently attached to portions of the stencil. This latter approach is commonly less desirable because the increased local thickness of the stencil makes it difficult for the operator to bring the needles to bear on the edges of the swath—i.e., tilting a needle scaler away from the vertical along a line locally perpendicular to the swath is limited by the local height of the stencil. 
     Although the present invention has been described with respect to several preferred embodiments, many modifications and alterations can be made without departing from the invention. Accordingly, it is intended that all such modifications and alterations be considered as within the spirit and scope of the invention as defined in the attached claims.