Abstract:
An electronic control system for a planing or sanding machine is disclosed. The system uses twin linear measuring devices and twin motor-driven drive-systems, integrated by a computer or other electronic device, to independently monitor and control the position of each end of the planing or sanding head.

Description:
This non-provisional patent application claims benefit of the provisional patent application entitled “Electronic Control System for Planer/Sander”, having Serial No. 60/224,186, and that was filed on Aug. 9, 2000. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to an electronic control system for a planing or sanding machine. More particularly, the invention relates to a control system using independent measurement and control of the position of each end of the planing or sanding head of the machine, so as to produce a machine capable of planing or sanding a board or panel with minimum deviation in thickness across the width of the piece. 
     BACKGROUND OF THE INVENTION 
     Planing or sanding machines are widely used in a number of industries, including the furniture and construction industries. These machines can produce boards or panels of material, most typically wood, with a uniform thickness and a smooth surface, which may then be utilized directly or further processed to produce a wide variety of useful products. In many of these applications, the thickness of the resulting material must be maintained within exacting tolerances over the entire board or panel being machined. 
     In a fully automated or semi-automated manufacturing process, the sanding or planing thickness must be readily and quickly adjustable, so that boards and panels of various dimensions can be accommodated without interrupting the flow of production. While manually adjustable machines have been used in the past, these systems are unsuitable for high-volume applications. The height of the sanding or planing head (corresponding to the thickness of the resulting board or panel) is therefore often adjusted via an electronic system utilizing a computer, microprocessor or similar device to control an electric motor, which can then reposition the head using a system of gears and drive shafts. Instantaneous electronic control over the position of the planing or sanding head is thereby established, and in a multi-step manufacturing process can be integrated into a computer system which monitors and controls the entire process. 
     Unfortunately, mechanical imperfections in the drive train connecting the motor with the planing or sanding head can lead to disparities between the intended position of the sanding or planing head and its actual position. Backlash, slack, and wear in the gear system is a common cause of such problems. Because of the tolerances required in some applications, even minor inaccuracies in head positioning and board thickness are sometimes unacceptable. 
     In an attempt to resolve this problem, planing or sanding machine manufacturers have developed systems designed to monitor and correct the actual position of the planing or sanding head. In the typical system, an electronic linear measuring device is used to track the position of the planing or sanding head with a high degree of precision. This information is fed into a central processing unit, microprocessor, or similar electronic device, which then provides an electric motor with the instructions necessary to maintain the desired head position with respect to the item being processed. 
     In the systems of this type in use to date, however, a problem arises because a single control system is used to control the movement of the planing or sanding head across its entire width. Typically, the linear measuring device and motor are positioned at one end of the head, and the other end is linked to the motor via a connecting shaft and gearing arrangement. Both ends of the planing or sanding head therefore track together. 
     However, in actual operation this system may result in substantial disparities in thickness across the width of the board or panel being machined. These disparities are caused by natural limitations in the accuracy with which the movements prescribed by the control system on one end of the planing or sanding head are conveyed by gears and shafts to the other. The resulting inaccuracies may be substantial enough to cause unacceptable deviations in the thickness of the resulting machined product. 
     What is desired, then, and not found in the prior art, is a planing or sanding machine control system that will take account of these problems, and produce a precise and uniform thickness across the entire width of the board or panel being processed. 
     SUMMARY OF THE INVENTION 
     It is the primary object of the present invention to provide an electronic control system for a planing or sanding machine that is capable of maintaining a uniform thickness across the entire width of the board or panel being processed. In the improved system disclosed herein, dual and independent control of the two ends of the machine&#39;s planing or sanding head is established. A linear measuring device and motor-driven drive unit is positioned at either end of the head, and linked via a computer, microprocessor or similar electronic device to provide separate control of the movement of each end of the head. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     FIG. 1 is a front view of a planing or sanding machine utilizing a control system as described herein; and 
     FIG. 2 is a block diagram of the control system of the planing or sanding machine of the present invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 illustrates a planing or sanding machine  8  of typical design, utilizing a control system  30  is illustrated in FIG.  2  and described herein. As shown, the preferred embodiment of the sanding machine  8  typically utilizes a conveyor system  12  as a support surface for a rough planar material  24 , such as a board or panel. The conveyor system  12  may incorporate a series of chain-driven rollers  13  and a conveyor belt or similar means to move the planar material  24  through the machine  8  at a controlled pace. Suspended above the conveyor system  12  is a planing or sanding head  10 , which acts on the planar material  24  to reduce its thickness and/or smooth its upper surface. In a familiar arrangement, this planing or sanding head  10  may be driven via a belt (not illustrated) which is also arrayed around a belt idler  14  and the main beam  18  of the machine  10 . This arrangement will provide the mechanical action for the planing or sanding head  10  required to plane or sand the planar material  24 . 
     Looking to the block diagram of FIG. 2, the control system  30  of a preferred embodiment is utilized to maintain the position of the head  10  at a uniform and fixed distance from the conveyor  12 , despite any backlash, slack, or wear which may occur. The control system  30  includes two linear measuring devices  6 ,  7  that are used to monitor the vertical position of each end  11   a ,  11   b  of the head  10 . More specifically, referring back to FIG. 1, the first linear measuring device  6  is used to measure the vertical position of the first end  11   a  of the head  10 , and the second linear measuring device  7  is used to measure the vertical position of the second end  11   b  of the head  10 . 
     Looking to FIG. 2, the linear measuring devices  6 ,  7  are additionally connected to a central processing unit  9  or other electronic device. Consequently, the linear measuring devices  6 ,  7  will provide the respective positioning information to the central processing unit  9  as required. The central processing unit  9  can then utilize the feedback from the linear measuring devices  6 ,  7  to independently control the two motor-driven drive units  2 ,  3  that are connected to the first end  11   a  and the second end  11   b  of the sanding head  10  respectively. The motor-driven drive units  2 ,  3  will thereby generate any necessary corrections through connecting shafts  22  to gear boxes  4  and via additional shafts  20  connected to the sanding head  10  itself. Consequently, unlike prior designs for controlling the sanding of the planar material  24 , the complete width of the head  10  in the present invention is maintained at a uniform distance from the conveyor  12  across its entire width. Since the head  10  is uniform, the machine  8  will producing a planed or sanded planar material  24  of uniform thickness. 
     Thus, although there have been described particular embodiments of the present invention of a new and useful ELECTRONIC CONTROL SYSTEM FOR PLANER/SANDER, it is not intended that such references be construed as limitations upon the scope of this invention except as set forth in the following claims.