Abstract:
A form measuring mechanism  100  which measures a form of an object  102  to be measured by bringing a probe  124  into direct contact with the object  102,  includes a plurality of reference spheres  130   a  and  130   b  for calibrating the form of the probe  124 , a judging means  154  for judging form abnormal values common in position and size to each other and form abnormal values not common to each other obtained by measuring the reference spheres  130   a  and  130   b , and a notifying means  156  for notifying at least anyone of a contamination or dust adhering state of the probe  124  judged from the common form abnormal values and a worn state and contamination or dust adhering states of the reference spheres  130   a  and  130   b  judged from the form abnormal values not common to each other. Accordingly, it becomes possible to identify contamination or dust adhesion of the probe or contamination or deformation due to wearing of the reference sphere, and at least in the case of contamination or dust adhesion of the probe or reference sphere, the location of the contamination or dust adhesion can be identified, and in the case of wearing of the probe or the reference sphere, a situation of the worn region can be identified or necessity of replacement of the probe or the reference sphere can be judged.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    The disclosure of Japanese Patent Application No. 2007-142928 filed on May 30, 2007 including specifications, drawings and claims is incorporated herein by reference in its entirely. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to an abnormality detecting method for a form measuring mechanism and a form measuring mechanism using various probes such as a scanning probe, a touch signal probe, a probe for a surface roughness measuring machine, a probe for an contour measuring machine, etc., and more specifically, to an abnormality detecting method for a form measuring mechanism which is preferably used in a form measuring mechanism that measures changes of a measured object by bringing a probe into direct contact with the object to be measured, and makes it possible to easily judge contamination and wearing when the contamination and wearing occur on the probe and properly clean or replace the probe, and the form measuring mechanism. 
         [0004]    2. Description of the Related Art 
         [0005]    In a measuring mechanism which measures a form of an object to be measured, during repetition of measurements of the objects, the tip end of a contact type probe (hereinafter, simply referred to as a probe,) is gradually contaminated by several-micrometer to 0.1 millimeter orders of dust and oil on the object. Then, the contact sensitivity changes or foreign bodies such as dust are caught between the probe tip end and an object, resulting in a measurement abnormality. To avoid this, objects and the probe are soaked in a cleaning liquid and cleaned. However, only soaking in a cleaning liquid cannot sufficiently remove contamination, and removed contamination may adhere again, so that as shown in Japanese Laid-Open Patent Publication No. 2000-35325 (Patent document 1), it has been proposed that air is blown to the probe tip end to clean it as appropriate. 
         [0006]    Further, the tip end of the probe is worn and deformed through use. Therefore, to enable accurate measurement even if the tip end of the probe is deformed due to wearing, as shown in Japanese Laid-Open Patent Publication No. 2001-280947 (Patent document 2), it has been proposed that a reference sphere for calibrating the probe form is provided and the probe is calibrated. 
         [0007]    However, as shown in  FIG. 13(   a ), assuming that measurement is made by using the reference sphere  30  shown in Patent document 2 in a state that dust  2 , etc., adheres to the reference sphere  30  and/or probe  24 , a form measured in this case is not the form that should be measured as shown in  FIG. 13(   b ) but is the form measured in actuality as shown in  FIG. 13(   c ). Therefore, from only the result of  FIG. 13(   c ), it cannot be judged whether the measurement abnormality was caused by contamination on the tip end of the probe  24  or contamination on the reference sphere  30 . Therefore, this requires extra labor of randomly repeating cleaning and measurement of the tip end of the probe  24  and the reference sphere  30 . 
         [0008]    Even when the contamination can be judged as contamination on the reference sphere  30  or the tip end of the probe  24 , if the location thereof is not sufficiently identified, cleaning must still be repeated a plurality of times. 
         [0009]    Further, when the probe  24  is used over a long period of time, even if it is calibrated by using the reference sphere  30 , desired measurement accuracy cannot be secured when the probe is extremely worn out, so that the probe  24  needs to be replaced. However, due to influence from the contamination, it is difficult to judge whether the probe  24  has been worn out, and the time of replacement of the probe  24  cannot be judged. 
       SUMMARY OF THE INVENTION 
       [0010]    The present invention was made to solve the conventional problems described above, and an object thereof is to provide an abnormality detecting method for a form measuring mechanism and a form measuring mechanism which make it possible to judge contamination on the tip end of the probe  24 , deformation due to wearing on the tip end of the probe  24 , or contamination of the reference sphere  30 , deformation due to wearing of the reference sphere  30 , and make it possible to at least identify a location of contamination in the case of contamination on the tip end of the probe  24  or on the reference sphere  30 , judge a state of a worn region in the case of wearing on the tip end of the probe  24  or on the reference sphere  30 , or judge whether the probe  24  or on the reference sphere  30  needs to be replaced. 
         [0011]    According to the present invention, when detecting an abnormality of a form measuring mechanism which brings a probe into direct contact with an object to be measured to measure the form of the object, a plurality of reference spheres for calibrating the form of the probe are measured, and form abnormal values which are common in position and size to each other and form abnormal values which are not common to each other obtained through measurement of the reference spheres, are judged, and at least any one of a worn state and a contamination including dust adhering of the probe judged from the common form abnormal values and worn states and a contamination including dust adhering of the reference spheres judged from the form abnormal values not common to each other are notified, whereby the problems are solved. 
         [0012]    The principle of the solution means of the present invention will be described with reference to  FIG. 1 . A plurality, for example, two of reference spheres  130   a  and  130   b  are prepared and the reference spheres  130   a  and  130   b  are measured with the probe  124 . At this time, assuming that dust  4  adheres to the surface of the probe  124 , dust  6  adheres to the surface of the reference sphere  130 , and dust  8  adheres to the surface of the reference sphere  130   b , the measurement results of the reference spheres  130   a  and  130   b  are as shown in the lower stage of  FIG. 1 . At this time, dust  4  of the probe  124  is measured as form abnormal values with an inclination angle θ common in both measurement results. On the other hand, the dust  6  appears only in the measurement result of the reference sphere  130   a , and the dust  8  appears only in the measurement result of the reference sphere  130   b . Thus, the dust  4  on the probe  124  can be judged from the common form abnormal values of the plurality of reference spheres. 
         [0013]    The present invention solves the above-described problems in a form measuring mechanism which brings a probe into direct contact with a measured object to measure the form of an object to be measured, including: a plurality of reference spheres for calibrating the form of the probe; a judging means for judging form abnormal values common in position and size to each other and form abnormal values not common to each other obtained through measurement of the reference spheres; and a notifying means which notifies any one of a worn state and a contamination including dust adhering of the probe judged from the common form abnormal values and worn states and contamination including dust adhering of the reference spheres judged from the form abnormal values not common to each other. 
         [0014]    The common form abnormal values can be judged as wearing or contamination including dust adhesion of the probe, and the form abnormal values not common to each other can be judged as wearing or contamination including dust adhesion of the reference sphere. 
         [0015]    When the common form abnormal values are concave, they can be judged as wearing of the probe. 
         [0016]    By judging the worn state of the probe from the common form abnormal values, a replacement time of the probe can be notified. 
         [0017]    When the common form abnormal values are convex, they can be judged as contamination including dust adhering to the probe. 
         [0018]    When one of the form abnormal values not common to each other is concave, it can be judged as wearing of the reference sphere. 
         [0019]    By judging the worn state of the reference sphere from the not common form abnormal values, a replacement time of the reference sphere can be notified. 
         [0020]    When one of the form abnormal values not common to each other is convex, it can be judged as contamination including dust adhering to the reference sphere. 
         [0021]    According to the present invention, it can be identified which position on the probe or the reference sphere the contamination including dust adhering to the tip end of the probe or the reference sphere which may cause a measurement error is distributed, so that the tip end of the probe or the reference sphere can be wiped by directly aiming at the locally contaminated portion. 
         [0022]    It can be confirmed whether contamination including dust adheres to the probe or the reference sphere, so that meaningless cleaning of other components can be avoided, and the working efficiency is improved. 
         [0023]    When form changes of the probe or the reference sphere are continuously traced, the lifetime due to wearing of the probe or the reference sphere can be judged, and more reliable measurement can be made. 
         [0024]    These and other novel features and advantages of the present invention will become apparent from the following detailed description of preferred embodiments. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0025]    The preferred embodiments will be described with reference to the drawings, wherein like elements have been denoted throughout the figures with like reference numerals, and wherein; 
           [0026]      FIG. 1  is a drawing showing a calibration principle of the present invention; 
           [0027]      FIG. 2  is a construction schematic diagram of a form measuring mechanism of an embodiment; 
           [0028]      FIG. 3  is an entire block diagram of the form measuring mechanism of the same embodiment; 
           [0029]      FIG. 4  is a flowchart showing a method for calibrating a probe by using reference spheres of the same embodiment; 
           [0030]      FIG. 5  are drawings showing an actual measuring method for the reference spheres of the same embodiment; 
           [0031]      FIG. 6  are drawings showing an example of form measured values of the reference spheres one-dimensionally scanned of the same embodiment; 
           [0032]      FIG. 7  is a diagram showing a coordinate reference for identifying positions on the probe of the same embodiment; 
           [0033]      FIG. 8  is a diagram three-dimensionally showing form errors of the same embodiment; 
           [0034]      FIG. 9  is a diagram showing form abnormal values of the two reference spheres at a specific latitude of the same embodiment; 
           [0035]      FIG. 10  is a diagram showing an example of comparison of a worn state of the probe with a worn state at the time of previous calibration at a specific latitude displayed on a display unit of the same embodiment; 
           [0036]      FIG. 11  is a drawing showing an example of a contaminated state of the probe displayed on the display unit of the same embodiment; 
           [0037]      FIG. 12  are drawings showing an actual measuring method for the reference spheres different from the first embodiment; and 
           [0038]      FIG. 13  are drawings showing forms measured when using a conventional reference sphere. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0039]    Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. 
         [0040]    A first embodiment of the present invention will be described with reference to  FIG. 2  through  FIG. 11 .  FIG. 2  is a construction schematic diagram of a form measuring mechanism of this embodiment,  FIG. 3  is an entire block diagram of the form measuring mechanism of this embodiment,  FIG. 4  is a flowchart showing a method for calibrating a probe by using reference spheres,  FIG. 5  are drawings showing an actual measuring method for the reference spheres,  FIG. 6  are drawings showing an example of form measured values of the reference spheres one-dimensionally scanned,  FIG. 7  is a diagram showing a coordinate reference for identifying positions on the probe,  FIG. 8  is a diagram three-dimensionally showing form errors,  FIG. 9  is a diagram showing form abnormal values of the two reference spheres at a specific latitude,  FIG. 10  is a diagram showing an example of comparison of a worn state of the probe with a worn state of previous calibration at a specific latitude displayed on a display unit, and  FIG. 11  is a drawing showing an example of a contaminated state of the probe displayed on the display unit. 
         [0041]    A form measuring mechanism  100  of this embodiment includes, as shown in  FIG. 3 , a form measuring mechanism main body  110  and a control device  150 . First, the form measuring mechanism main body  110  will be described based on  FIG. 2 . 
         [0042]    The form measuring mechanism main body  110  of this embodiment is, for example, a main body of a three-dimensional coordinate measuring machine, and includes a surface plate  114  on a base  112 , and has a head  120  on a gate-formed frame on the surface plate  114 . On the head  120 , a detector  122  is provided, and to its tip end, a probe  124  is attached. The gate-formed frame is formed by a pair of columns  116  rising from the surface plate  114  and a beam  118  laid across the pair of columns  116 . The columns  116  support the beam  118 , and the head  120  is movable in the left and right direction (X direction) in the figure along the beam  118 . The detector  122  attached to the head  120  is movable in the up and down direction (Z direction) in the figure. The columns  116  are movable in the front and rear direction (Y direction) on the surface plate  114 , so that the head  120  is also movable in the Y-axis direction. The detector  122  can detect pressures and displacements via probe  124  in the X, Y, and Z directions. As shown in  FIG. 3 , for these movements, XYZ motors  126  are used, and moving distances in the respective directions are measured by linear encoders  128 . 
         [0043]    As shown in  FIG. 2 , on the surface plate  114 , two reference spheres  130   a  and  130   b  are provided. The reference spheres  130   a  and  130   b  are used as form measurement references for calibration of the probe  124 , so that reference spheres with sufficient sphericity whose form errors are negligible, for example, reference spheres with form errors not more than 1/10 of the measurement accuracy of the form measuring mechanism  100  can be used. In this embodiment, for example, as the reference sphere  130   a , a reference sphere with a radius larger than that of the reference sphere  130   b  can be used. To the surface plate  114 , an object to be measured  102  is fixed. 
         [0044]    Next, the control device  150  will be described with reference to  FIG. 3 . The control device  150  includes a storage  152 , a controller  154 , a display unit  156 , and an operating unit  158 . 
         [0045]    The storage  152  is connected to the controller  154 , and set values and programs necessary for controlling the form measuring mechanism main body  110  are read therein. Programs to be used for calibrating the probe  124  described later and form abnormal values, reference data, and calibration data of the reference spheres  130   a  and  130   b  are also read therein. 
         [0046]    The controller  154  is connected to the detector  122 , the XYZ motors  126 , and the linear encoders  128 . When measuring the object  102 , for example, the XYZ motors  126  are driven so that the pressure or displacement applied to the detector  122  via the probe  124  becomes constant, and from the values of the linear encoders  128  at this time, the form of the object  102  can be obtained. The controller also functions as a judging means for judging form abnormal values described later. 
         [0047]    The display unit  156  is connected to the controller  154 , and includes a monitor screen and a speaker, and constitutes a notifying means for notifying information necessary for an operator by means of images and voice as appropriate. 
         [0048]    The operating unit  158  has input devices such as a keyboard and a mouse, and is connected to the controller  154 . An instruction is inputted by an operator as appropriate, and based on the instruction, processing of the measured values and control are performed. 
         [0049]    Next, calibrating operations as a working effect of this embodiment will be described by using  FIG. 4  through  FIG. 11 . The calibrating operations of this embodiment are executed according to a program read in the controller  154  from the storage  152 . 
         [0050]    When the calibration of the probe  124  by using the reference spheres  130   a  and  130   b  of this embodiment is started, first, the two reference spheres  130   a  and  130   b  are measured (Step S 10  of  FIG. 4 ). At this time, the entire surfaces of the upper hemispheres of the reference spheres  130   a  and  130   b  are, for example, thoroughly luster-scanned with the probe  124 . Specifically, as shown in  FIG. 5(   a ) and  FIG. 5(   b ), in view in the Z direction, the forms of the reference spheres  130   a  and  130   b  are measured at a predetermined interval. At this time, examples of the measured forms of the reference spheres  130   a  and  130   b  when they are one-dimensionally scanned are shown in  FIG. 6 .  FIG. 6(   a ) shows the reference sphere  130   a , and  FIG. 6(   b ) shows the reference sphere  130   b.    
         [0051]    Next, the form measured values of the reference spheres  130   a  and  130   b  are coordinate-converted (Step S 12  of  FIG. 4 ). When the form measurement is a two-dimensional measurement, as shown in  FIG. 6(   a ) and  FIG. 6(   b ), the forms may be expressed by inclination angles θa and θb and radius errors ΔRa and ΔRb. However, by indicating coordinates on a spherical surface by using a latitude and a longitude, reading-in, reading-out, and processing of the measured values become easy regardless of the sizes of the two reference spheres  130   a  and  130   b , so that the coordinates are converted into a latitude and a longitude in this embodiment. Herein, reference data of the reference spheres  130   a  and  130   b  which had been converted into longitudes and latitudes and read-in the storage  152  are read out by the controller  154  and differences are obtained for each reference sphere  130   a ,  130   b.    
         [0052]    The results of this are obtained as form abnormal values of the probe  124  (Step S 14  of  FIG. 4 ). At this time, by determining a position as a reference of the longitude and latitude of the probe  124  in advance as shown in  FIG. 7 , a graph showing the form abnormal values of the probe  124  can be obtained as shown in  FIG. 8 . Herein,  FIG. 8  is a diagram three-dimensionally showing form abnormal values by means of contours when measuring one reference sphere  130   a  on a two-dimensional coordinate system using longitudes and latitudes. As shown in  FIG. 8 , it can be judged at a glance how the convex of A or B and the concave C or D are distributed on the probe  24 . The differences between A and B and between C and D will be described later. Similarly, from the other reference sphere  130   b , form measurement results are also obtained. 
         [0053]    Next, from the form measured results obtained from the two reference spheres  130   a  and  130   b , form abnormal portions N are confirmed (Step S 16  of  FIG. 4 ). Then, to judge all form abnormal portions, a counter in a program for counting the form abnormal portions is initialized (Step S 18  of  FIG. 4 ), and judging of the form abnormal portions one by one is started (Step S 20  of  FIG. 4 ). 
         [0054]    Next, it is judged whether the form abnormal values appear commonly on both the reference spheres  130   a  and  130   b  (Step S 22  of  FIG. 4 ). This is performed so that, for example, as shown in  FIG. 9 , by comparing the form abnormal values ΔZa of the reference sphere  130   a  and the form abnormal values ΔZb of the reference sphere  130   b  at a specific latitude, the same form abnormal values at the same longitude are judged as convex A or concave C. 
         [0055]    Next, when a form abnormal value is common between both the two ΔZa and ΔZb, it is judged whether its form is concave (Step S 24  of  FIG. 4 ). Referring to  FIG. 9 , in ΔZa and ΔZb, the values that are both 0 or less are judged as C. When the form abnormal value is concave in both two ΔZa and ΔZb, the concave is judged as being caused by wearing of the probe  124 , and the position thereof and the abnormal value are read in the storage  152  (Step S 26  of  FIG. 4 ). When the form abnormal value is not concave but convex in both two ΔZa and ΔZb, the convex is judged as contamination or dust adhering to the probe  124 , and the position thereof and the abnormal value are read in the storage  152  (Step S 28  of  FIG. 4 ). 
         [0056]    When a form abnormal value is not common between ΔZa and ΔZb, as shown in  FIG. 9 , it is judged as convex B on only one reference sphere or concave D on only one reference sphere, and then it is judged whether the form abnormal value is concave (Step S 30  of  FIG. 4 ). Referring to  FIG. 9 , in ΔZb, when a form abnormal value is not more than 0, it is judged as D. When a form abnormal value is concave in either of ΔZa and ΔZb, it is judged as a concave of the reference sphere  130   a  or  130   b  and a position thereof and the abnormal value are read in the storage  152  (Step S 32  of  FIG. 4 ). When a form abnormal value is convex in either of ΔZa and ΔZb, it is judged as contamination or dust adhering to the reference sphere  130   a  or  130   b  and the position thereof and the abnormal value are read in the storage  152  (Step S 34  of  FIG. 4 ). 
         [0057]    After judging one form abnormal portion, all portions N are judged in order (Step S 36  of  FIG. 4 ). After judging all portions N, it is judged whether the form abnormal values are in a permissible range (Step S 38  of  FIG. 4 ). The judgment as to whether the abnormal values are in a permissible range is made by the controller  154  by reading permissible values of the wear amounts, concaves, and contamination or dust adhering amounts of the reference spheres  130   a  and  130   b  and the probe  124  in the storage  152  in advance. 
         [0058]    When the abnormal values are in the permissible range, correction data is read from the storage  152 , and the situation of the form abnormal values and correction details are displayed (Step S 40  of  FIG. 4 ). The correction data is prepared in advance in the storage  152 . At this time, for example, regarding the wear amount, when the form abnormal value ΔZa at the time of current calibration is larger than the form abnormal value ΔZap at the time of the previous calibration and the wear amount of the probe  124  progresses more, as shown in  FIG. 10 , the worn state is displayed on the display unit  156 , the lifetime and replacement time of the probe  124  are calculated from the number of uses and use time since the previous calibration and displayed on the display unit  156 , and further, the current wear correction amount can also be displayed. The contamination and concaves on the reference spheres  130   a  and  130   b  are also judged and displayed. 
         [0059]    If the abnormal value is not in the permissible range, a warning is issued to an operator and replacement of a corresponding component or a cleaning portion of the component is displayed (Step S 42  of  FIG. 4 ). For example, when the probe  124  is contaminated, as shown in  FIG. 11 , the location, range, and adhesion thickness as information of this contamination can be displayed in a manner enabling visual judgment thereof. The cleaning and replacement of the reference spheres  130   a  and  130   b  and replacement of the probe  124  due to wearing can also be judged and displayed in the same manner. 
         [0060]    Then, the calibration using the reference spheres  130   a  and  130   b  in this embodiment is finished, however, if the form abnormal values are not in the permissible range, for confirmation, the calibration using the reference spheres  130   a  and  130   b  of this embodiment can be performed after cleaning. 
         [0061]    Thus, according to this embodiment, contamination or dust adhesion on the tip end of the probe  124 , deformation due to wearing of the tip end of the probe  124 , contamination or dust adhesion of the reference spheres  130   a  and  130   b , and concaves including deformation due to wearing of the reference spheres  130   a  and  130   b  can be judged. Therefore, when cleaning the contamination or dust, only the corresponding component can be cleaned, and it is not necessary to wastefully clean other components, so that the working efficiency is improved. 
         [0062]    In the case of contamination or dust adhesion on the tip end of the probe  124 , it can be identified what position and how much the contamination or dust adhesion is distributed on the probe  124 , so that the locally contaminated or dust adhesion portion on the tip end of the probe  124  can be directly wiped off. 
         [0063]    In the case of deformation due to wearing of the tip end of the probe  124 , the situation of the worn region can be grasped, and correction can be made in a correctable range and accurate form measurement can be made. If it cannot be corrected, the probe can be quickly replaced. By comparing the wear amounts of the previous calibration time and this calibration time, form changes of the probe  124  can be continuously traced, so that the lifetime due to wearing of the probe  124  can be judged in advance, and the effect of the correction enables measurement with higher reliability until the end of the lifetime. 
         [0064]    In the case of contamination or dust adhesion of the reference sphere  130   a  or  130   b , it can be identified what position and how much the contamination or dust adhesion is distributed on the reference sphere  130   a  or  130   b , so that the locally contaminated or dust adhesion portion of the reference sphere  130   a  or  130   b  can be directly wiped off. 
         [0065]    In the case of a concave of the reference sphere  130   a  or  130   b , when it is in the permissible range, it can be reflected on the correction data and accurate form measurement can be made. If it is out of the permissible range, the reference sphere  130   a  or  130   b  can be quickly replaced. 
         [0066]    Even when the reference sphere  130   a  ( 130   b ) and the probe  124  are contaminated or dust adhesion at the same longitude and the same latitude, by measuring the form at the same longitude and the same latitude of the reference sphere  130   b  ( 130   a ), it can be judged whether the contamination or dust adhesion is of the probe  124  or of the reference sphere  130   a  ( 130   b ). 
         [0067]    In the embodiment described above, the two reference spheres  130   a  and  130   b  have different radiuses, however, they may have the same radius. When the reference spheres  130   a  and  130   b  are sufficiently high in accuracy for calibrating the probe  124 , reference data is not always necessary. 
         [0068]    The number of reference spheres is not limited to two, and three or more may be arranged on the surface plate  114 . In this case, when contamination, etc., are at the same latitude and the same longitude on the probe  124  and two reference spheres, an effect of making it easy to distinguish the contamination is obtained. 
         [0069]    The method for scanning the reference spheres  130   a  and  130   b  was luster scanning, however, the present invention is not limited to this, and spiral scanning shown in  FIG. 12  can be performed. 
         [0070]    The X direction and Y direction are used for convenience, and the X axis and Y axis may be set vice versa. 
         [0071]    In this embodiment, it is judged first whether form abnormal values obtained by using two reference spheres  130   a  and  130   b  are common to each other, however, a method in which it is judged first whether the form abnormal values are concave or convex is also included in the present invention. 
         [0072]    In this embodiment, the permissible range of the form abnormal values and correction data are read in the storage  152  and used, however, the present invention is not limited to this, and input values from the operating unit  158  may be used. 
         [0073]    Those to be displayed on the monitor of the display unit  156  are not limited to  FIG. 10  or  FIG. 11 , and to notify an operator of information as to where contamination, etc., adheres to from the measurement results,  FIG. 4  through  FIG. 9  themselves or a part or a combination of these maybe displayed at each step of the flowchart of  FIG. 4 , or voice guidance may be given. 
         [0074]    It should be apparent to those skilled in the art that the above-described exemplary embodiments are merely illustrative which represent the application of the principles of the present invention. Numerous and various other arrangements can be readily devised by those skilled in the art without departing from the spirit and the scope of the present invention.