Abstract:
A measuring apparatus is provided comprising: a stage, including three or more pads formed on a surface of the stage, the pads forming an invisible plane and capable of supporting a panel to be measured; a movable measuring stylus, having a tip, the measuring stylus being movable between an initial position, through an insertion region, and a measuring position; a spring, the spring being disposed to apply downward force upon the measuring stylus so that the measuring stylus presses against the panel; a lever, movably mounted on said base, capable of moving the measuring stylus between the initial position, through the insertion region, and the measuring position; and a means for measuring the difference between the height of a tip of the measuring stylus in the measuring position and the height of the invisible plane.

Description:
BACKGROUND OF THE INVENTION 
   Wood has been used as a structural material dating back into prehistoric times, and is still prized as a material today because it has a wide range of desirable material properties including excellent strength and stiffness, pleasing aesthetics, good insulation properties and easy workability. In recent years, however, wood-based alternatives to natural solid wood lumber have been developed that make more efficient use of harvested wood and reduce the amount of wood discarded as scrap. 
   Plywood, particle board and oriented strand board (“OSB”) are some examples of wood-based composite alternatives to natural solid woodlumber that have replaced natural solid wood lumber in many structural applications in the last seventy-five years. These wood-based composites not only use the available supply of timber wood more efficiently, but they can also be formed from lower grade wood species, and even from wood wastes. 
   While the strength and insulation properties of these wood-based composites are comparable or superior to natural solid wood lumber, it is necessary to carefully monitor the edge of some composite materials because some users have complained that in certain high-moisture environments, the edges of these composite material experience swelling and cracking as water penetrates into the edges. Accordingly there is a need for swiftly, and accurately measuring the thickness of wood composite materials to determine whether the wood composite has undergone edge swelling. 
   One instrument that is commonly used for measuring edge thickness is a micrometer, which when used with sufficient care can precisely measure the thickness of a wood composite materials in order to obtain a measure of possible edge swelling. Unfortunately, there are also certain difficulties entailed with a micrometer. For example, the use of micrometers often introduces a degree of subjectivity into the measurements because the user can strongly influence how much pressure is exerted on the micrometer, i.e., whether the micrometer was twisted “hard” against the wood or “light” against the wood, a different thickness measurement might be returned, especially on wet samples (because they are more pliant, and sponge-like). Precision is particularly important because even a small amount of edge swelling can result in a material that is noticeably swelled and unsatisfactory to a customer. Accordingly, instruments for measuring edge thickness should be able to render such measurements with a great deal of analytical precision. 
   Furthermore, micrometers can also be cumbersome and slow during actual usage because the micrometer must repeatedly “spin” and “unspin” the instrument towards and away from the board being measured. The relative speed at which such measurements can be made is important because hundreds or even thousands of measurements are made in a production environment along the edge of the material in order to obtain an accurate measurement of the product being produced. 
   Accordingly, there is a need in the art for a device that can accurately measure the thickness of the material, particularly the thickness of the material at its edge. Furthermore, such an instrument should be able to make these measurements quickly and efficiently so that the thickness of the material can be readily and accurately assessed. Additional advantages, such as portability and ease of use, are also desirable. 
   BRIEF SUMMARY OF THE INVENTION 
   The present invention includes a measuring apparatus including a stage, including three or more pads formed on a surface of the stage, the pads forming an invisible plane and capable of supporting a panel to be measured; a movable measuring stylus, having a tip, the measuring stylus being movable between an initial position, through an insertion region, and a measuring position; a spring, the spring being disposed to apply downward force upon the measuring stylus so that the measuring stylus presses against the panel; a lever, movably mounted on said base, capable of moving the measuring stylus between the initial position, through the insertion region, and the measuring position; and a means for measuring the difference between the height of a tip of the measuring stylus in the measuring position and the height of the invisible plane. 

   
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
     The foregoing summary, as well as the following detailed description of preferred embodiments of the invention, will be better understood when read in conjunction with the appended drawings. For the purpose of illustrating the invention, there is shown in the drawings embodiments which are presently preferred. It should be understood, however, that the invention is not limited to the precise arrangements and instrumentalities shown. In the drawings: 
       FIG. 1  is a perspective view of a measuring device, depicting a preferred embodiment of the present invention. 
       FIG. 2  is a detailed perspective view of the machine illustrated in  FIG. 1 ; 
       FIG. 3  is a rear perspective view of the machine illustrated in  FIG. 1 ; 
       FIG. 4  is a detailed perspective view of the machine illustrated in  FIG. 1 ; and 
       FIG. 5  is a perspective view of a measuring device, depicting a preferred embodiment of the present invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Referring now to the drawing of the apparatus in  FIGS. 1 and 5 , it can be seen that the apparatus includes at least two components, namely a stage  5  and a measuring arm  8 . The stage includes a base  11 , a rear plate  14 , and a raised fence  17 . It is preferable that the base  11 , rear plate  14 , and raised fence  17  are designed to exactly accommodate the size of the sample so that when a sample  20  is inserted into the apparatus, it fits snugly into place against the rear plate  14  of the stage  5  and the raised fence  17  (as shown in  FIG. 5 ), the measuring stylus  23  is positioned to measure the thickness of the sample midway along the one of the four edges of the square sample  20 . When the sample  20  fits snugly against both the rear plate  14  and the raised fence  17 , the measuring stylus  23  rests of the surface of the sample a certain distance (such as 1 inch) from the edge toward the interior of the sample as required by ASTM D1037. The stage is preferably designed to accommodate a six-inch square sample, although different size samples may be used. 
   Another implementation of the present invention is illustrated in  FIG. 2 . As shown in  FIG. 2 , the stage includes a base  11 , a rear plate  14 , and a raised fence  17 . There is a scored line  27  in the stage  11 . When the edge of the sample being measured is positioned away from the rear plate  14  but fit snugly against raised fence  17  such that the opposing edge of the sample is aligned with the scored line  27  in the base  11 , as shown in  FIG. 2 , the measuring stylus  23  is positioned exactly along the edge of the sample  20 . The stage is preferably designed to accommodate a six-inch square sample, although different size samples may be used. 
   As seen in  FIG. 4 , the base  11  has a series of raised pads  26 , upon which the sample rests. The raised pads  26  define an invisible plane. As can be seen in  FIG. 1 , one raised pad is placed right below the measuring stylus  23  and functions to “tare” the measuring stylus  23 , while the other two raised pads act to hold the entire sample at the tare height, with the bottom of the sample  20  being coplanar with the invisible plane. The thickness measurement using the measuring stylus is made relative to this invisible plane. Additionally, these pads perform the additional important function of raising the level of the sample panel to allow clearance for the swollen edges of the sample  20  so that the swollen edges do not interfere with the measurement by resting on the surface of the stage  5  itself. 
   At rest, the measuring stylus  23  bears against the base  11 . When not in use, the measuring stylus  23  is normally actuated to its lowest position with the stylus  23  itself bearing against the base  11  (or as shown in  FIG. 1  bearing against the measuring pad formed on the base) by means of a spring  35  positioned between the top plate  41  of the stage  5  and the measuring stylus  23 , and positioned around a shaft (shaft not illustrated). This spring  35  is disposed around a shaft that extends into the measuring arm  8 . The configuration of the device with the measuring stylus  23  bearing against one of the measuring pads  26  as shown in  FIG. 1  shall be referred to herein as the “initial position”. 
   A lever  32  is fitted in the rear plate  14  of the stage to contact the measuring stylus  23  and move the measuring stylus  23  so as to insert a sample  20  to be measured. The lever  32  is manually operated and pivotally secured to the rear plate  14 . When the lever is depressed by the operator, the lever  32  pivots and pushes upward on the spring  35  pushing it into compression and creating a space (referred to herein as the “insertion region”) between the raised pads  26  and the measuring stylus  23  in which the sample  20  can be inserted and rested on the raised pads  26 .  FIG. 3  is a back view of the apparatus showing the operational part of the apparatus with an operator pressing downward on the lever  32 ; while  FIG. 4  simultaneously shows the lever  32  pivoting and pushing upward on the spring  35  and elevating the measuring stylus  23 , to create the space for sample insertion. 
   After the sample is inserted and rests on the raised pads  26 , the operator gradually removes the pressure applied to the lever  32  allowing the spring  35  to extend into tension thereby pushing downwardly on the lever  32  until the tip  38  of the measuring stylus  23  bears and applies pressure against the top surface of the sample  20 . This may be denoted as the “measuring position”. 
   When the apparatus is in the measuring position, the height difference between the tip  38  of the measuring stylus  23  and the invisible plane (which is the amount that the measuring stylus is deflected from its rest position) is obtained. The measuring stylus  23  is mechanically connected to an electronic indicator through the shaft (not illustrated) in the measuring arm, which measures the amount that the measuring stylus  23  is deflected and converts it to a measure of the sample thickness. A display on the electronic indicator gives the thickness measurement and a cable attached to the electronic indicator sends the thickness measurement to a computer where the values are recorded. This not only saves time, but prevents the operator from inadvertently recording the wrong measurement value. 
   Any suitable commercial electronic measurement tool and indicator is acceptable. Suitable such devices are available from Mitutoyo America Corporation, Aurora, Ill. 
   The measuring stylus  23  itself as can be seen in  FIGS. 2 and 4  has a tip  38 . The tip may be in form of a “foot” or “shoe”. Tip is preferably designed according to one or both of published specifications: (1) the ASTM Standard D1037, and (2) the Voluntary Product Standard PS 2-92 as established under the direction of the Department of Commerce and available in published form from APA/The Engineered Wood Association and the TECO Corporation. Specifically, the tip should have a diameter of between about 10 mm to about 20 mm. Also, the ASTM standard D 1037 specifically states that the diameter of the tip must be sized so that it does not penetrate local indentations on a textured surface; this should also apply to typical surface defects and voids. Additionally, when the apparatus is in the measuring position with the spring pushing downwardly so that the tip  38  of the measuring stylus  23  bears against the top surface of the sample  20 , in this position, the tip  38  should be applying between 35 Kpa (5 psi) to 69 KPa (10 psi). The spring rate will vary with the surface area of the tip/disk/foot and must be chosen so that it applies the right amount of pressure. The spring actuated measuring stylus is a particular advantage of the present invention. Previously such thickness measurements were made using a micrometer. This introduced a degree of subjectivity into the measurements, because depending on how much pressure was exerted on the micrometer, i.e., whether the micrometer was twisted “hard” against the wood or “light” against the wood, a different measured thickness might be returned. In the present case, there is consistency across measured board thicknesses, because the spring always exerts the same exact amount of pressure, and human interference with the measurement is at least reduced, if not completely eliminated. Thus, even more highly refined thickness measurements can be made. 
   Moreover, the use of a measuring base  11  in combination with the measuring stylus  23 , lever  32  and spring has another particular advantage in that the combination of these components speed the process of measurement. A micrometer is more time consuming to “spin” and “unspin” the instrument towards and away from the board being measured. With the present apparatus the process is very simple and less time consuming: the measuring stylus  23  is raised, the sample panel  20  is inserted into the stage  5  under the stylus  23 , and the stylus  23  is brought down upon the sample  20  and the measurement recorded  20 . While such a measurement made using a micrometer might take several seconds, in the present apparatus it can be performed in just a few seconds. 
   As discussed above, this device is envisioned as being used for accurately measuring the thickness of material, particularly the thickness of of wood composite materials such as oriented strand board, which is described in greater detail in U.S. Pat. No. 6,479,127. The thickness of the oriented strand material is typically between about 0.6 cm (about ¼″) to about 5 cm (about 2″). 
   It will be appreciated by those skilled in the art that changes could be made to the embodiments described above without departing from the broad inventive concept thereof. It is understood, therefore, that this invention is not limited to the particular embodiments disclosed, but it is intended to cover modifications within the spirit and scope of the present invention as defined by the appended claims.