Abstract:
Disclosed is an exemplary abrasive surface preparation device for use with a rotary device having a rotatable housing and a support member extending obliquely from the housing. The exemplary abrasive hard surface preparation device includes a substantially planar substrate layer having a first end connectable to the support member and an opposite second end. An abrasive material is attached to at least the second end of the substrate layer.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. Ser. No. 11/655,742, filed on Jan. 19, 2007, now U.S. Pat. No. 7,690,970, issued on Apr. 6, 2010, which application is incorporated herein by reference in its entirety. 
    
    
     TECHNICAL FIELD 
     The field of this invention relates to a reinforced abrasive abrading and grinding device for sanding hard floors and surfaces, for example cement, stone or imitation stone. 
     BACKGROUND OF THE DISCLOSURE 
     While concrete or cement is a very popular material for use in floors and construction materials because of its strength, durability and low costs, if the concrete or cement is left unfinished, the concrete floor will inherently produce dust by the constant scuffing it undergoes whether by foot traffic or wheeled traffic and be susceptible to staining due to porosity. 
     One is thus faced with a dilemma of cleaning a concrete floor with its no gloss utilitarian appearance and with the disadvantage of the inevitable dust that emanates from an unfinished concrete floor or spending considerable money for a protective and decorative covering surface. Vast improvements in coatings for concrete floors have taken place in the recent past and one may also desire to remove an older worn or failed coating and replace it with one of the newer type coatings. Part of the expense to obtain a decorative and protective covering is due to the preparation of the concrete floor to accept the new covering surface. The preparation often includes aggressive sanding to rough up the concrete surface and to remove any previously applied top coating, oil, or grease stains to assure proper adhesion of the new covering. Aggressive sanding of the concrete surface with conventional sand paper on sanding machines is a time consuming effort requiring frequent replacement of the sand paper as the sand particles become worn. 
     Attempts for more aggressive sanding and grinding pads have incorporated hardened particles such as diamonds or silicon carbide. While these pads performed well when new, it has been found that only a small percentage of the particles actually touch the surface at a given time. The cutting edges of these few engaging particles become rounded out through wear and the sanding performance substantially diminishes. In the trade, this is sometimes referred to as a ball bearing effect because the few now rounded diamond particles glide over the surface and no longer effectively cut into the surface. 
     Other problems are known that also prevent or limit the application of hardened particles. The present application of an abrasive bristle made from today&#39;s known higher temperature plastic materials when combined with the aforementioned hard abrasive materials generate much heat when used on a high speed power sander. The generated heat is sufficient to melt the plastic material and fuses the abrasive bristles together rendering the bristle pad useless. 
     The high heat and slow grinding rates pose particular problems for preparation of concrete surfaces that have mastic or older plastic and paints previously coated thereon. The heat melts the old coating materials as it is removed and the coating then adheres to and gums up the bristles which then quickly lose most of their sanding and grinding effectiveness. 
     Previous attempts to produce metal bristles also encountered problems. Attempts have been made to provide hard particles such as silicon carbide or diamond secured onto a bristle strip, blade or plate. The hard particles may be diamond particles brazed onto spring steel or other metal substrate. If the metal substrate is fully brazed with particles, the substrate becomes too brittle and breaks off during high speed application. Even spring steel loses its resilient spring nature after it undergoes brazing. Attempts to limit the diamond particles only to the extreme ends or tips of the bristles to maintain the flexibility of the metal dramatically shorten the workable life of the bristle. 
     What is needed is an abrasive device for concrete sanding that has an improved performance profile by incorporating hardened particles only along a front face of a distal section of a substrate layer and which expose new particle edges as the substrate layer wears down. What is also needed is a flexible metal abrasive element with hardened particles secured thereon with the brazed section only on a front facing distal section of a substrate layer. What is also needed is a metal substrate layer with particles brazed thereon and further reinforced and supported by a resilient backing element to maintain sufficient flexibility and support of the metal substrate layer. 
     What is also needed is a durable abrasion element assembly for mounting to a cleaning or sanding machine that is suitable for preparing cement floors for coating. What is also needed is an expedient method to prepare a polished concrete floor to cut away plastic, mastic and the other heat sensitive materials by an aggressive cutting which forms enough concrete dust to coat the removed waste product before it can stick or adhere to the surfaces of the abrasion element assembly. What is also needed is an abrasion element assembly that has abrasive particles securely affixed to a substrate layer that is reinforced and supported by a resilient backing layer. What is also needed is an efficient sanding element that can be used with decreased horsepower most commonly available on consumer oriented sanding and cleaning machines. 
     SUMMARY OF THE DISCLOSURE 
     In accordance with one aspect of the invention, an abrasive surface preparation device for hard surfaces has a housing, for example a rotatable pad that rotates about its center, for moving over a hard work surface, for example cement, stone, tile or synthetic materials. The housing has a plurality of downwardly extending abrasive elements having a forward facing respective abrasive face with a width and length. Each abrasive element has a substrate layer and an abrasive material secured to the front surface of the substrate layer. Each substrate layer is reinforced by a backing element. The backing element is affixed to the housing such that the forward facing abrasive face generally faces the normal direction of motion of the housing. In another embodiment, the substrate layer is adhered to the backing element with an adhesive bond. 
     Preferably, the substrate layer and the backing element depend downwardly from the housing and are canted between 5° and 75° and most desirably between 25° to 60° from the perpendicular such that the distal lower ends of the substrate layer and backing element are positioned rearwardly of the proximate mounted section at the housing during normal motion of the housing. The abrasive material faces generally forward toward the motion of the housing. 
     It is also desirable that the substrate layer and the backing element are in abutting relationship with each other and both are affixed to a mounting bracket. The mounting bracket in turn is affixed to the housing. 
     Preferably, the abrasive elements are circumferentially spaced on the rotatable pad in proximity to its periphery. In one embodiment, the abrasive elements have their respective front abrasive faces substantially radially aligned with the rotational center of the rotatable pad. 
     The abrasive material is desirable diamond particles. The diamond particles may have varying sizes between 3.4 millimeters diameter and 0.5 microns, i.e., between 5 mesh and 120 mesh. The abrasive particles are desirably secured via brazing with a brazing material on a distal section of the front surface of the substrate layer. The proximate front section and rear surface of the substrate layer are substantially devoid of the brazing material and diamond particles. The substrate layer is preferably made from a low carbon steel and the backing element is preferably made from a spring steel. 
     According to another aspect of the invention, an abrasive element assembly has a substrate layer with abrasive particles brazed with brazing material to a distal front section thereof A backing element is affixed against and provides flex support and reinforcement for the substrate layer. A supporting bracket is affixed to the backing plate. The supporting bracket is constructed for being mounted to a movable housing of a powered abrading device for example a sander or cleaning machine. 
     The abrasive element assembly preferably has the upper section of the mounting bracket constructed for mounting to the housing and an incline depending section for mounting the backing plate and the substrate layer at an angle from a perpendicular. It is desirable that abrasive material made from diamond particles is secured with a brazing material only at a front distal section of the substrate layer. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Reference now is made to the accompanying drawings in which: 
         FIG. 1  is a bottom perspective view of an abrasive pad incorporating one embodiment of the invention; 
         FIG. 2  is a top perspective view of the pad shown in  FIG. 1 ; 
         FIG. 3  is an enlarged side elevational view illustrating one abrasion element assembly shown in  FIG. 1 ; 
         FIG. 4  is an enlarge front elevational view of the abrasion element assembly shown in  FIG. 3 ; 
         FIG. 5  is an enlarged rear elevational view of the abrasion element assembly shown in  FIG. 3 ; 
         FIG. 6  is a side exploded view of the abrasion element assembly shown in  FIG. 3 ; 
         FIG. 7  is a view similar to  FIG. 3  illustrating the abrasion element assembly in a working and flexed position on a concrete surface; 
         FIG. 8  is a method of attaching the bristle shown in  FIG. 7  to a side elevational view illustrating a second embodiment of an abrasion element assembly; 
         FIG. 9  is a side elevational view illustrating a third embodiment of an abrasion element assembly; and 
         FIG. 10  is a side elevational view illustrating a fourth embodiment of an abrasion element assembly. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to  FIG. 1 , a rotatable abrasive preparation device  10  includes a housing, for example in the form of a pad or disc  12  as illustrated that has a plurality of abrasive element assemblies  14  circumferentially mounted near the periphery  16  of disc  12 . The rotatable disc  12  as shown in  FIG. 2  has a mounting aperture  20  in its upper face  18  and conventional snap lock  22  for operably connecting to a drive spindle of a conventionally powered abrading machine for example, a cleaning machine, buffing machine, or sanding machine. The disc  12  is constructed to normally rotate about its center axis  24  in a direction as indicated by arrow  26 . 
     Each abrasive element assembly  14 , as more clearly shown in  FIGS. 3 to 6 , has a substrate layer  30 , support layer  32  and mounting bracket  34  assembled together via threaded fasteners  36  and secured to the disc  12  via threaded fasteners  38 . The substrate layer  30  as shown in  FIG. 4  has a distal section  40  coated with abrasive particles  42  only at the front surface  44 , for example diamond particles that are brazed onto the substrate layer  30  with a brazing, material  46 . The proximate mounting section  41  and the rear surface  48  of substrate layer  30  are substantially devoid of diamond particles  42  and brazing material  46 . The substrate layer  30  may be a piece of strapping steel or other low carbon steel to which the brazing material  46  affixes the diamond particles  42 . The substrate layer can also be any other metal or a high temperature plastic depending on the particular application. 
     The brazing material  46  may be Nicro Braze LM or other commercially available brazing material. The diamond particles  42  may also be plated onto the substrate layer  30 . The grit size of the diamond particles may be widely varied. It is foreseen that particle sizes of about 5 mesh to 500 mesh or even finer particles sizes can be used. It is preferred that the diamond particles  42  are a blend of different mesh size particles ranging from the 5 mesh size to the 120 mesh size with a great weight percentage of the diamond particles being varied between 16 mesh (1.2 mm) and 120 mesh (110 microns). 
     The backing layer  32  is in abutting relationship to the rear surface  48  of substrate layer  30 . The backing layer  32  can be made from any wear resistant material such as metal or a high temperature polymer but a resilient spring quality metal such as spring steel is preferred. The spring steel layer  32  is not brazed in order to retain its spring and resilient ductile quality. The spring steel backing layer  32  abuts a substantial portion of the rear surface  48  of substrate layer  30  as shown in  FIGS. 3 and 5  and provides reinforcement support to the substrate layer  30 . In some applications, a distal end section  60  of substrate layer  30  may extend beyond the end  62  of backing layer  32 , to provide operating edge  49  beyond end  62 . In other applications it may be preferred that distal section  60  does not extend beyond end  62  so that edge  49  is flush with the distal end  62  of the backing layer  32 . 
     The substrate layer  30  and backing layer  32  may be affixed to bracket  34 . The bracket  34  has an upper section  50  that seats flush against the disc  12 . The bracket  34  upper section can be mounted via threaded fasteners  38  that pass through apertures  51  therein and engage threaded apertures  53  in the disc  12 . The bracket  34  also has a depending canted section  52 . The cant is set at an angle to the perpendicular for example between 5 degrees and 75 degrees, but preferably between 25° and 60° with its distal end  54  trailing with respect to the direction of motion of disc  12 . Threaded fasteners  36  extend through apertures  61  and  63  in both layers  30  and  32  and engage threaded apertures  55  in bracket  34  to securely clamp the two layers  30  and  32  together and secure them to the depending canted section  52  such that the layers  30  and  32  extend along the same canted angle of bracket section  52 . 
     The substrate layer  30  has its front surface  44  facing generally forward relative to the normal operating motion of the pad  12 . As shown, the front surface  44 , may be aligned with the radial center of the pad and its radial extending width is substantially transverse to the normal rotating motion of the pad. However, it should also be understood that the radial extending width can be set at other angles relative to the radial direction as long as the front surface  44  faces generally forward to operably expose the diamond particles  42 . 
     The lengths i.e. heights of the layers  30  and  32  are generally substantially greater than the thickness of the layers  30  and  32  to allow flexibility of the layers  30  and  32  during certain sanding applications. A typical flex during certain sanding operation is schematically shown in  FIG. 7  where the flex further increases the angle at which the front surface  44  engages the working floor surface  56 . In other applications, the support backing element  32  and the bracket  34  may be dimensioned to reduce or substantially eliminate the flex depending on the application 
     The width of the layers  30  and  32  as shown in the figures may be greater than its length so that each abrasive element assembly  14  resembles a blade. The relatively large width provides for greater structural integrity and decreases the number of individual assemblies  14  needed to be mounted onto the disc. However, the width can be substantially changed so that the assemblies  14  can appear to resemble more of a strip, needle, or bristle rather than a blade. 
       FIG. 8  illustrates a modified embodiment where the substrate layer  30  is adhesively secured to the backing layer  32  and does not extend up to fasteners  36 . Fasteners  36  clamp only backing layer  32  to the bracket  34 . The substrate layer by being shortened may have its entire front surface  44  brazed with brazing material  46  to secure diamond particles thereon. The rear surface  48  remains devoid of particles  42  and brazing material  46 . 
       FIG. 9  illustrates a third embodiment where the substrate layer  30  and backing layer  32  both have a distal end  60  and  62  ending at the same point such that edge  49  does not initially extend beyond the backing layer  32 . 
       FIG. 10  illustrates a fourth embodiment where the substrate layer  30  is adheredly bonded directly to the distal leg  52  of the bracket  34 . In this embodiment the leg  52  is dimensional to act and function as the support backing layer  32  shown in other embodiments. The bracket  34  is made of spring steel and its thickness and length are both dimensioned to provide the desired amount of resilient flex and backing support to substrate layer  30 . 
     It has been found that the construction of the invention provides for superior and more efficient performance than previous diamond or hard particle brushes. The weight and horsepower needed to effectively abrade with this improved abrasive device are substantially reduced such that the device  10  can be used on a consumer oriented cleaning or sanding machine rather than heavier more powerful industrial power machine. 
     Furthermore, the diamond particles by being brazed onto the substrate layer with the appropriate brazing material are sacrificial. In other words, the diamonds will wear off the brazed area before they become overly worn and rounded to expose other diamond particles with fresh sharp edges. Thus the performance profile of the abrasion element remains high until the entire distal section with the diamond is worn away. The sacrificing of the diamonds prevents what can be termed a ball bearing effect. If the diamonds stay on too long, they become rounded and lose their cutting edge. If the worn diamond particles remain on the substrate layer, only these worn round points remain in contact with the cement working surface and the rounded points merely glide over the surface without any effective cutting. They start to act more like a ball bearing rather than cutting edges with a resulting dramatic decrease of performance. The sacrificial nature of the diamonds prevents this decrease and maintains the performance level at or near when the abrasive element assembly is newly manufactured. 
     Furthermore, the speed at which the abrasion occurs renders sufficient concrete dust as the assembly cuts into both the concrete surface and any top coating such that the top coating as it melts is instantly covered with the dust to provide a dryer outer surface which prevents the melted paint, mastic or plastic from undesirably sticking to the abrasion element assembly. Conventional wisdom states one must slow down the aggression by slowing the machine down to prevent higher heat and melting of the plastic, mastic or paint coatings. However, a more aggressive cut through the melted plastic, paint, or mastic along with the concrete to provide a dust coating prevents the melted coatings from adhering to the abrasive element assembly. 
     Fasteners  36  and  38  provide an expeditious way to removably secure the operating parts  30 ,  32  and  34  to the disc  12 . When the parts  30 ,  32  and  34  need replacing, the parts can be easily removed and replaced as needed. It is foreseen however that other fasteners other than that shown may be used. It is further foreseen that the abrasive element assembly  14  may be replaceable cartridge that may be secured as a whole to the disc  12  via a slot or bayonet fitting. 
     In this fashion an abrasion device with as few as two or three abrasion element assemblies circumferentially spaced at the bottom of the disc pad in proximity to its periphery can provide for an efficient abrading device for preparation of a cement floor before applying a new coat thereon. 
     Other variations and modifications are possible without departing from the scope and spirit of the present invention as defined by the appended claims.