Abstract:
A random orbital finishing apparatus for finishing the surfaces of solid material including wood, plastic, metal and composites, but most particularly plastic solid surface materials. The apparatus includes a conveyor for transporting such unfinished material pass a uniquely mounted random orbital sander where it is subsequently finished thereby. The random orbitals may be dually mounted and in an offset position. The apparatus may further include a system of proximity sensors and air cylinders which enable the random orbitals to automatically adjust their position onto the surface to be finished when the material is passed thereby and subsequently return back to a starting position after the material passes.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates generally to surface finishing, and more particularly to an apparatus which utilizes random orbitals to finish the surfaces of solid material including wood, plastic, and metal. 
     In many manufacturing processes, it is necessary to sand, grind, and/or polish wood, metal and synthetic material to create a finished surface ready for installation. Such materials may be used to ultimately create products such as shelves, cabinets, furniture, counter-tops and the like. One of the more difficult materials to finish is what is becoming commonly referred to as solid surface materials or as plastic solid surface materials (PSSMs). These are polymer based building materials typically manufactured and sold in sheet form and used to form counter-tops and the like. The most widely recognized of which is the so-called “Corian” material manufactured by DuPont. 
     Although the present invention may be described as it pertains to the finishing of PSSMs, it will be understood that it is not to be construed as limiting thereto. In fact, it has been found that the present invention finishes metal, wood and other plastic materials with an equally superior effectiveness. 
     Various machines have been designed to enable the sanding and/or finishing of materials to be done automatically rather than by hand. The early of these such machines typically used a belt sander of some sort. The material would enter the machine, be passed under this belt sander by some means, and exit the machine with what was hoped to be a finished surface. However, the exiting material typically had sand lines where the edges of the belt sander ran along the material and/or rough areas where the belt sander ran opposite the grain when sanding wood materials. To remove these imperfections, additional finishing often had to be done by hand with a hand-held sander or with steel wool. 
     To alleviate these problems, the next generation of automatic sanders began to orbit the abrasive rather than merely running it back and forth over the material. This, it was hoped, would remove any sanding patterns and eliminate the finish sanding to be done by hand. The most common of such machines includes an elongated abrasive covered platen generally extending the width of the machine. This platen may move in one or two orbits. One created by the rotation of its connecting shafts and the other by the rotation of a brace connecting the shafts. This dual rotation more accurately simulates the motion of sanding by hand. 
     Although this dual rotating platen may help reduce sand lines and rough areas, it is expensive to manufacture and maintain. Additionally, for this type of sander to function properly, the incoming materials have to be of similar tolerances. Thus, PSSMs are still finished by hand held power sanders known as random orbital sanders. 
     The basic construction of random orbital sanders typically comprises a motor for driving a balanced shaft for rotational movement about a first or driven axis, and a bearing device for coupling a sanding pad or disc to the balanced shaft for rotational movement relative thereto about a second axis disposed in an offset or parallel relation to the first axis. During operation of this type of sander, the sanding pad is forced to move along a circular path disposed concentrically of or to orbit relative to the first axis, while being free to rotate relative to the second axis. 
     These random orbital sanders have always been popular in the automotive industry, and, now, they are currently the best way to remove scratches, marks and other imperfections from the relatively hard surfaces of PSSMs. However, these random orbital sanders are hand held sanders and, as such, have certain drawbacks, the most obvious of which is that they are hand held and require a great deal of workmen&#39;s time to adequately run the sander over the subject material. Additionally, the manual guidance of these sanders may produce an uneven finish across the material&#39;s surface or perhaps a mild bevel effect due to disproportionate sanding. 
     In view of the aforementioned needs and the shortcomings of the prior art, it is therefore an object of the present invention to provide an apparatus that overcomes the deficiencies of the current practices whereby an apparatus is provided for finishing solid materials with a minimum amount of labor with maximum efficiency at a minimum cost. 
     It is another object of the present invention to provide an apparatus capable of effectively finishing the relatively hard surfaces of plastic solid surface materials. 
     Still another object of the present invention is to provide an apparatus for automating sanding work currently performed by hand. 
     It is yet another object of the present invention to provide an apparatus for providing a finished product having a relatively proportionately even degree of smoothness throughout its surface. 
     These and other objects, features and advantages of the present invention will be clearly understood through a consideration of the following detailed description. 
     SUMMARY OF THE INVENTION 
     According to the present invention, there is provided an apparatus for finishing the surfaces of solid materials having a frame, a conveyor system and a material engaging surface. The conveyor system extends from the front to the back of the frame. A drive means provides a first axis of rotation to a drive shaft which is coupled to at least two orbital shafts. These orbital shafts are coupled to the discs in an offset from center position which provides disc rotation about the orbital shaft and the center of the disc to rotate about the shaft. The material engaging surface covers the discs to finish the surface of the material. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The features of the present invention which are believed to be novel are set forth with particularity in the appended claims. The invention, together with the further objects and advantages thereof, may best be understood by reference to the following description taken in conjunction with the accompanying drawings, in the several figures of which like reference numerals identify like elements, and in which: 
     FIG. 1 is a side view shown partially in cross-section of the first embodiment of the Random Orbital Finishing Apparatus of the present invention. 
     FIG. 2 is a front view shown partially in cross-section of the Random Orbital Finishing Apparatus of FIG.  1 . 
     FIG. 3 is an enlarged front view shown partially in cross-section of the dually mounted random orbitals of the Random Orbital Finishing Apparatus of FIG.  1 . 
     FIG. 4 is an enlarged side view shown partially in cross-section of the random orbitals of FIG.  3 . 
     FIG. 5 is a front view of the preferred embodiment of the Random Orbital Finishing Apparatus of the present invention. 
     FIG. 6 is an enlarged view of the control panel of FIG.  5 . 
     FIG. 7 is a machine schematic diagram of the preferred embodiment of the Random Orbital Finishing Apparatus of the present invention. 
     FIG. 8 is a side view shown partially in cross-section of an alternate embodiment of the Random Orbital Finishing Apparatus of the present invention. 
     FIG. 9 is a front view shown partially in cross-section of the Random Orbital Finishing Apparatus of FIG.  8 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to the first embodiment, and FIGS. 1-2 in particular, a random orbital finishing apparatus  10 , is illustrated in partial cross-section. The apparatus includes a main conveyor belt  12  which transports the PSSM (not shown), or other material to be finished from its front-end  148 , under a series of uniquely mounted random orbitals  14  to its back and  150 . Conveyor belt  12  is powered by a transport drive motor  16  which drives belt  12  about the rear end roller of the front-end roller  02  drive pulley  18  and tension roller  20 . Transport rollers  22  provide the needed added support for the belt  12  to effectively convey the material when the random orbitals  14  are applying force against the surface of the material during the finishing process. The drive motor and all rollers are mounted within the bottom half  152  of the mainframe  24 . 
     The top half  154  of mainframe  24  provides the support for the mounting of the random orbitals  14  thereon. An adjustable slide mount  26  is used so as to enable the random orbital  14  to adjust their height and thus the finishing pads  28  height relative to the conveyor belt  12 . During operation, the proximity switch  30  of each random orbital  14  detects when the material is passing thereunder and signals the air cylinder  66  of that particular random orbital to lower the orbital  14  to its predetermined operating height. 
     The random orbitals of the present invention are illustrated in partial cross-section in FIGS. 3 and 4. These Figures clearly illustrate the invention&#39;s dual random orbital configuration. In particular, driver motor  32  or other driving means drives shaft  34  about a first rotations axis or drive axis  36 . Drive shaft  34  in turn drives gear belts  38  which rotate gear pulleys  40  and thus orbital shafts  42  about a second rotational axis or orbital shaft axis  44 . Each orbital shaft  42  is supported at one end by, and includes, a top bearing  46  positioned within the mainplate  48  of random orbital  14  configuration. This bearing  46  provides support for each shaft  42  while enabling rotation thereof. 
     The other end of orbital shafts  42  are partially supported by the backplate  50  and are coupled to cam  51 . Thus cam  51  rotates about shaft axis  44 . In the preferred embodiment, cam  51  is then coupled to disc  56  via disc bearings  52  in an offset position. In other words, the center of the disc  56  which provides for a third rotational axis or disc bearing axis  54  do not align with orbital shaft axis  44  but are instead offset and parallel. Thus, as the attached cam  51  is rotating or spinning about orbital shaft axis  44 , the bearing axis  54  and thus the disc  56  may also be rotating about the orbital shaft axis  44 . More particularly, a counterweight  58  is provided atop the disc  56  and opposite the cam  51  to create the necessary momentum to rotate the disc  56  about the disc bearing axis  54 . 
     To summarize, drive shaft  34  rotates about drive axis  36  to drive gear belts  38  to rotate gear pulleys  40 . Gear pulleys  40  then rotate orbital shafts  42  and thus cam  51  about orbital shaft axis  44 . Now, if the pressure exerted against the disc  56  is less than the inherent disc bearing  52  threshold, the counterweight  58  creates the necessary momentum to rotate the disc  56  about the bearing axis  54  via disc bearing  52 . In other words, the speed of rotation of the disc  56 , if at all, about bearing axis  54  depends upon the amount of pressure exerted against the disc  56 . Thus, the random orbital motion of the present invention includes the rotation of cam  51  about shaft axis  44  and the random rotation of disc  56  about bearing axis  54 . 
     This random orbital movement of the discs  56  provides for a unique finishing area when the abrasive finishing cover  156  is applied to the pads  28  and the dually mounted orbitals of the preferred embodiment are operating to finish the material. More particularly, the two orbital shafts  42  of each random orbital  14  are not squarely mounted with respect to the direction of the conveyor. In fact, and as shown in FIG. 4, one shaft is mounted near the front portion  59  of the orbital housing  60 , while the other shaft is mounted near the rear portion  62 . 
     Additionally, because each disc bearing axis  54  rotates about its respective shaft axis  44 , the finishing cover is able to finish a wider area then if it was only rotating about its shaft axis. For example, if the pad  28  has a diameter of 20 cm and the shaft axis  44  and disc bearing axis  54  are offset by 2 cm, then the finishing cover will be able to finish 24 cm of the width of the material passed under it. In the illustrated embodiment, the distance  64  between the shaft axis is such that the finishing width of the respective finishing covers overlap. To continue the above example, if this amount of overlap is 3 cm, then the total finishing width of the dually mounted random orbital  14  will be 42 cm. This overlap diminishes any sanding lines which may otherwise appear on the surface of the material due to a side-by-side arrangement of the finishing covers. It will be understood that the present invention may utilize only a single dually mounted random orbital, adjacent dually mounted random orbitals and/or a series of dually mounted random orbitals. 
     FIG. 4 also illustrates the basic mechanisms for the control of the operating height of the random orbital. The operating height being that position of the random orbital in which the finishing cover will be able to adequately finish the surface of the material. In the first embodiment, this height is set before the material is placed upon the conveyor by manually adjusting the cylinder stops (not shown). These stops prevent the air cylinder  66  from lowering the finishing covers below the predetermined operating height. However, this operating height may be automatically set without the use of the stops, but rather by sensing the thickness of the material and setting the appropriate maximum extension of the air cylinder. 
     In any event, when the proximity switch  30  senses the material, the air cylinder  66  (through the flow control  68 ), adjusts the random orbital to its predetermined operating height to enable the finishing covers to finish the surface of the material. Once the material passes the proximity switch  30 , the air cylinder returns the random orbital to its starting position. The air cylinder of each random orbital is mounted to slide bracket  70 . This slide bracket is adjustably engaged to slide mount  26  so as to enable the bracket and thus the random orbital to slide and adjust its height. 
     FIG. 5 is illustrative of the front view of the preferred embodiment of the random orbital finishing apparatus  10  of the present invention. The mainframe  24  is supported by feet  72  which can be adjusted to level the apparatus. Side covers  74  are provided to protect the user from any debris which may be created when the apparatus is turned on and a piece of unfinished material is placed upon belt  12 . The entire operational process is controlled via control panel  76 . 
     The control panel  76  of the preferred embodiment is shown in FIG.  6 . The pressure supplied to the air cylinders  66  is turned on by the pressure buttons  78  and monitored by pressure gauges  80 . The conveyor and orbital power are controlled by buttons  82  and  84  respectively, while their speed is controlled by dials  86  and  88  respectively. The remaining controls on panel  76  of the preferred embodiment include an automatic/hand button  90 , a reset button  92  and an emergency stop button  94 . 
     The operation and control of the present invention may best be described with respect to and in association with the machine schematic diagram of FIG.  7 . Turning thereto, the apparatus is shown to be powered by 120 VAC which is supplied through transformer  96  by which 240 VAC was originally provided. When powered up, the main contactor relay  98  will be closed thereby allowing current to flow through the left side of the schematic  100 , and generally from the left side to the right side  102 . If the emergency stop button  94  is pressed at any time after power up, the main contactor relay  98  will open and stop the current flow through  100 . In that case, the reset button  92  may be depressed to close the main contactor relay and restore current flow. 
     When the sanders are switched on through buttons  84 , relays  104 ,  106 ,  108  and  110  will be closed. Note that relay  110  and its associated switch  84  are shown as optional in the Figure. It will be understood that although the embodiment of FIGS. 1-6 illustrated a three sander apparatus, and FIG. 7 illustrates a possible forth, the number of sanders and/or buffers used will depend upon the workload of the machine and other individual design parameters. In any event, if one of the sander buttons  84  is not activated, its associated relay will be held in the open position. 
     When the conveyor button  82  is activated, inhibit relay  112  will be closed thereby allowing current to flow to the lower half of the circuit, however, if the auto/hand button  90  is activated (i.e. shutting off the conveyor), then inhibit relay  112  will open. In any event, whether transported by conveyor  12  or by hand, when the material to be finished activates the proximity sensor  30 , auto relay  114  will close. With auto relay  114  closed and in conjunction with the previously discussed buttons and relays, the appropriate solenoids will be triggered to lower and raise the random orbitals at the appropriate time to finish the surface of the material. 
     With the foregoing discussion of the internal operation of the apparatus, the typical use thereof will be readily understood. First, if the apparatus is not capable of automatically setting the predetermined operating height, the user must adjust the stops accordingly. The apparatus is then powered up and depending upon how many sanders and/or buffers are to be used, the appropriate buttons  84  are activated. The material may then enter the apparatus via the conveyor belt, if activated ( 82 ), or by hand if button  90  is activated. In any event, when the material gets close enough to the random orbitals, the proximity switch  30  senses such and lowers the orbital to finish the surface of the material. The speed of the conveyor and random orbitals may be adjusted to the desired levels via dials  86  and  88  respectively. 
     An alternative embodiment of the present invention is now discussed with respect to FIGS. 8 and 9. Generally, this alternate embodiment differs from that as previously discussed in that the orbitals will be mounted on the lower half of the frame and positioned so that they are below the plane of travel of the material to be finished. In other words, as the first embodiment finished the top surface of the infeed material, this alternate embodiment will finish at the bottom surface of the infeed material. 
     More particularly, and referring to FIGS. 8 and 9, a random orbital finishing apparatus  120 , is illustrated in partial cross-section. This apparatus includes a more sophisticated conveying system than that illustrated in the first embodiment. In particular, this embodiment includes an infeed conveyor belt  122  powered by an infeed drive pulley  124 , an outfeed conveyor belt  126  powered by an outfeed drive pulley  128  and intermediate drive support rollers  130  positioned in between the random orbitals  132 . These components of the conveying system as well as the random orbitals are mounted within the bottom half  156  of the mainframe  134 . 
     The top half  160  of mainframe  134  provides the support for the mounting of the hold down conveyors  136 . These conveyors  136  provide the support against the material when it is acted upon by the random orbitals. As this apparatus  120  is capable of accommodating material of various thicknesses and widths, the hold down conveyors  136  are horizontally and vertically adjustable. Referring to FIG. 9, hold down conveyors  136  are raised and lowered by hold down motor  138 . Additionally, hold down conveyors  136  may be adjusted from side to side by either manually or automatically sliding the slide plates  140  through channel  142 . With the capacity of these hold down conveyors to be moved up and down as well as sideways, this embodiment need not compensate for the thickness of the material. In other words, the material need not be flat or of a particular thickness, in fact, this embodiment is capable of finishing material of virtually any dimension, for example, a counter-top with a bowl mounted thereon is easily passed through and finished by this apparatus. 
     FIGS. 8 and 9 illustrate an apparatus with six (6) dually mounted random orbitals  132 , which consists of 12 discs. However, it will be understood that any amount of random orbitals  132  may be mounted adjacent each other as well as in series depending upon the particular design parameters. During operation, this embodiment may include proximity switch  144  on each random orbital  132  to detect when the material is passing thereover and signal the air cylinder  146  of that particular random orbital to raise the orbital to its predetermined operating height. Or, this sensing may preferably be controlled by a capacitor switch (not shown) mounted on the infeed table to sense the material and send pulses which will then control the air solenoid to activate the air cylinder  146  to move up and down. Now, glide plates  140  may be positioned and motors  138  may be adjusted to accommodate the particular position needed for each material to be finished. 
     It will be understood that the random orbital design of the alternate embodiment is the same as the previously discussed embodiment. In particular, the random orbitals of the present invention are of a dually mounted design which may be positioned either above or below the flow of the material to be finished. The positioning as well as the number of random orbitals depending upon the workload and particular design parameters of each apparatus. 
     While particular embodiments of the invention has been shown and described, it will be obvious to those skilled in the art that changes and modifications may be made therein without departing from the invention in its broader aspects and, therefore, the aim in the appended claims is to cover all such changes and modifications as fall within the true spirit and scope of the invention.