Abstract:
A system and method of measuring a rotational motion of a code wheel measures a rotational movement of the code wheel including an error component due to a non-rotational movement of the code wheel; measures the non-rotational movement of the code wheel; and produces an error-corrected measurement of the rotational movement of the code wheel by using the measured non-rotational movement of the code wheel to cancel the error component of the measured rotational movement of the code wheel. A signal can be produced indicating a need for maintenance when the non-rotational movement of the code wheel exceeds a threshold.

Description:
BACKGROUND 
     Optical encoders are used in a wide variety of contexts to determine movement and/or a position of an object with respect to some reference. Optical encoding is often used in mechanical systems as an inexpensive and reliable way to measure and track motion among moving components. For instance, printers, scanners, photocopiers, fax machines, plotters, and other imaging systems often use optical encoding to track the movement of an image media, such as paper, as an image is printed on the media or an image is scanned from the media. 
     One common technique for motion encoding uses an optical encoder and an encoder pattern (or encoding media). The optical encoder focuses light on a surface of the encoder pattern. As the encoder pattern (or encoding media) moves with respect to the optical encoder, an optical sensor reads a pattern of light either transmitted through, or reflected by, the encoder pattern to detect the motion. 
     A typical encoder pattern is an alternating series of features. As the encoder pattern moves relative to the optical encoder (or vice versa), transitions from one feature to the next in the pattern are optically detected. For instance, an encoder pattern could be an alternating pattern of holes, or optically transmissive windows, in an opaque material. In that case, an optical sensor can detect transitions from darkness to light passing through the holes or windows. 
       FIG. 1  illustrates a basic motion encoder set  100  comprising: an optical encoder  110  including a light emitter  112  and an optical sensor  114 ; a housing  175  on which optical encoder  110  is mounted; a rotating shaft  150 ; and a code wheel  130  including an encoder pattern  132  disposed between the light emitter  112  and the optical sensor  114 , mounted on the rotating shaft  150 . Code wheel  130  rotates, thereby moving encoder pattern  132  relative to optical encoder  110 . 
     In the embodiment of  FIG. 1 , optical encoder  110  operates in a transmissive mode by detecting light passed through encoder pattern  132  of code wheel  130 . In another embodiment, light emitter  112  and optical sensor  114  could be disposed on the same side of code wheel  130  such that optical encoder  110  operates in a reflective mode by detecting light reflected by encoder pattern  132  of code wheel  130 . 
     In one embodiment, encoder pattern  132  is an A/B pattern having alternating areas of differing optical transmissivity or reflectivity, depending on the design of optical encoder  110 . Optical sensor  114  detects the rate of change between the A and B patterns and thereby ascertains the relative rotational movement between encoder pattern  132  and optical encoder  110 . 
     However, due to wear and tear of code wheel  130  or shaft  150 , or perhaps a bearing of shaft  150 , the edge of code wheel  130  may eventually begin moving eccentrically (waggling and/or wobbling), and/or moving up and down within the encoder housing  175 . If there is a waggling eccentricity in code wheel  150 &#39;s motion, optical encoder  110  will not encode the rotational movement accurately, especially when the movement is less than one full revolution. Also, a wobbling code wheel  130 , or an up/down movement of code wheel  130 , may rub against or collide with housing  175 , producing inaccurate motion detection signal(s) and possibly damaging housing  175  and/or code wheel  130 . 
     In many cases, a motion encoder set is located internal to some host apparatus so that a waggling or wobbling code wheel, or a code wheel moving up and down in the encoder housing, is not easily observed and recognized. So, a user has no way of determining the magnitude of any waggling or up/down movement of the code wheel or shaft. Therefore, the user may not recognize that the motion encoder set is providing inaccurate signals which may impair operation of the host apparatus, or even damage the host apparatus, or that the motion encoder set itself can be damaged. 
     To address this problem, currently it is required that preventive maintenance be performed periodically on the optical encoder set to inspect for eccentric and/or up/down movement, and to make any necessary repairs and parts replacement. In many cases, this requires the host apparatus to be shut down and opened for inspection. As a result, this periodic maintenance is very expensive, and increases the down-time of the host apparatus. Furthermore, in many cases the maintenance is performed unnecessarily when there is no code wheel eccentricity or up/down movement, and the motion encoder set is performing perfectly. 
     What is needed, therefore is a motion encoder set that overcomes at least the shortcomings of known motion encoder sets. 
     SUMMARY 
     In an example embodiment, a motion encoder set comprises: a code wheel, including, provided thereon, a first encoder pattern, and a second encoder pattern; a first optical encoder, including a first light source adapted to provide light to the first encoder pattern and a first optical sensor adapted to receive the light from the first encoder pattern and in response thereto to output one or more signals indicating a rotational movement of the code wheel; and a second optical encoder, including a second light source adapted to provide light to the second encoder pattern and a second optical sensor adapted to receive the light from the second encoder pattern and in response thereto to output one or more signals indicating a non-rotational movement of the code wheel. 
     In another example embodiment, a method of determining a motion of a code wheel, comprising: providing light to a first encoder pattern provided on the code wheel; receiving the light from the first encoder pattern and in response thereto outputting one or more signals indicating a rotational movement of the code wheel; providing light to a second encoder pattern provided on the code wheel; and receiving the light from the second encoder pattern and in response thereto outputting one or more signals indicating a non-rotational movement of the code wheel. 
     In yet another example embodiment, a method of measuring a rotational motion of a code wheel comprises: measuring a rotational movement of the code wheel including an error component due to a non-rotational movement of the code wheel; measuring the non-rotational movement of the code wheel; and producing an error-corrected measurement of the rotational movement of the code wheel by using the measured non-rotational movement of the code wheel to cancel the error component of the measured rotational movement of the code wheel. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The example embodiments are best understood from the following detailed description when read with the accompanying drawing figures. It is emphasized that the various features are not necessarily drawn to scale. In fact, the dimensions may be arbitrarily increased or decreased for clarity of discussion. Wherever applicable and practical, like reference numerals refer to like elements. 
         FIG. 1  shows a basic motion encoder set; 
         FIG. 2  shows one embodiment of a self duty error correcting motion encoder set; 
         FIG. 3  shows a bottom view of a code wheel of a self duty error correcting motion encoder set; 
         FIG. 4  illustrates a bottom view of a code wheel of a self duty error correcting motion encoder set when the shaft on which the code wheel is mounted is disposed slightly further away than a nominal position with respect to an optical encoder, due to eccentric movement of the code wheel; 
         FIG. 5  illustrates a bottom view of a code wheel of a self duty error correcting motion encoder set when the shaft on which the code wheel is mounted is disposed slightly closer than a nominal position with respect to an optical encoder, due to eccentric movement of the code wheel; 
         FIG. 6  shows one embodiment of a motion encoder set with up/down code wheel movement detection; 
         FIG. 7  shows a bottom view of a code wheel of a motion encoder set with up/down code wheel movement detection; 
         FIG. 8  illustrates a side view of a code wheel of an optical encoder set with up/down code wheel movement detection when the code wheel is in a normal position; 
         FIG. 9  illustrates a side view of a code wheel of an optical encoder set with up/down code wheel movement detection when the code wheel is tilted upward; 
         FIG. 10  illustrates a side view of a code wheel of an optical encoder set with up/down code wheel movement detection when the code wheel is tilted downward; 
         FIG. 11  illustrates up/down movement of a code wheel in an optical encoder set with up/down code wheel movement detection. 
     
    
    
     DETAILED DESCRIPTION 
     In the following detailed description, for purposes of explanation and not limitation, example embodiments disclosing specific details are set forth in order to provide a thorough understanding of an embodiment according to the present teachings. However, it will be apparent to one having ordinary skill in the art having had the benefit of the present disclosure that other embodiments according to the present teachings that depart from the specific details disclosed herein remain within the scope of the appended claims. Moreover, descriptions of well-known apparati and methods may be omitted so as to not obscure the description of the example embodiments. Such methods and apparati are clearly within the scope of the present teachings. 
       FIG. 2  shows an example embodiment of a self duty error correcting motion encoder set  200 , comprising: a first optical encoder  210  including a first light emitter  212  and a first optical sensor  214 ; a second optical encoder  220  including a second light emitter  222  and a second optical sensor  224 ; a housing  275  on which first and second optical encoders  210 ,  220  are mounted; a rotating shaft  250 ; and a code wheel  230  mounted on shaft  250 , the code wheel  230  including a first encoder pattern  232  and a second encoder pattern  234  disposed thereon, such that first encoder pattern  232  is disposed between first light emitter  212  and first optical sensor  214 . Code wheel  230  rotates along with shaft  250 , thereby moving first encoder pattern  232  relative to first optical encoder  210 , and second encoder pattern  234  relative to second optical encoder  220 . 
     In the embodiment shown in  FIGS. 2-5 , for the sake of simplifying the explanation, code wheel  230  is shown comprising a single disk, with first encoder pattern  232  and second encoder pattern  234  disposed on one or both planar surfaces thereof. However, it should be understood that code wheel set  230  could instead comprise two or more separate disks rotating on the rotating shaft  250 , with first encoder pattern  232  disposed on one disk, and second encoder pattern  234  disposed on a different, separate, disk. 
     Furthermore, in the embodiment shown in  FIGS. 2-5 , for the sake of simplifying the explanation, first and second optical encoders  210 ,  220  are shown mounted on common housing  275 . However, it should be understood that first and second optical encoders  210 ,  220  can be packaged separately, being mounted on two separate housings  275 . 
     Turning again to  FIG. 2 , as will be explained in further detail below, first optical encoder  210  operates in conjunction with first encoder pattern  232  to measure a rotational movement of code wheel  230  and to output one or more signals indicating the rotational movement of code wheel  230 . That is, first motion detector  210  outputs one or more signals having first coding information indicating a rotational speed of shaft  250  on which code wheel  230  is mounted. In contrast, second optical encoder  220  operates in conjunction with second encoder pattern  234  to measure a non-rotational movement of code wheel  230  and to output one or more signals indicating the non-rotational movement of code wheel  230 . In particular, second optical encoder  220  operates in conjunction with second encoder pattern  234  to measure an eccentric movement of code wheel  230 , specifically a waggling movement. 
     In the embodiment of  FIG. 2 , first optical encoder  210  operates in a transmissive mode by detecting light passed through first encoder pattern  232  of code wheel  230 , while second optical encoder  220  operates in a reflective mode by detecting light reflected by second encoder pattern  234 . However, any combination of optical encoders operating in the transmissive and reflective modes is possible. For example, in another embodiment, first light emitter  212  and first optical sensor  214  could be disposed on the same side of code wheel  230  such that first optical encoder  210  operates in a reflective mode by detecting light reflected by first encoder pattern  232  of code wheel  230 . 
       FIG. 3  shows a bottom view of one embodiment of code wheel  230  that may be used in self duty error correcting motion encoder set  200 . As shown in  FIG. 3 , code wheel  230  comprises a single disk and includes on one or both planar surfaces thereof first encoder pattern  232  and second encoder pattern  234 . In the embodiment of  FIG. 3 , first encoder pattern  232  is a transmissive encoder pattern, and second encoder pattern  234  is a reflective pattern. First encoder pattern  232  codes information for rotational motion detection, and second encoder pattern  234  codes information for non-rotational motion detection. 
     In the embodiment of  FIG. 3 , first encoder pattern  232  is an A/B pattern having alternating areas of differing optical transmissivity or reflectivity, depending on the design of first optical encoder  210 . In that case, optical sensor  214  can detect the rate of change between the A and B patterns and thereby ascertain the relative rotational movement between first optical encoder  210  and encoder pattern  232 . 
     Meanwhile, in the embodiment of  FIG. 3 , second encoder pattern  234  is an alternating pattern of annular rings of differing optical reflectivity, depending on the design of second optical encoder  220  with which it us used. Optical sensor  224  follows a different annular ring of second encoder pattern  234  depending upon the relative in-and-out position of code wheel  230  with respect to second optical encoder  220 , for example due to a waggling or eccentric motion of code wheel  230 . 
     An explanation of the operation of self duty error correcting motion encoder set  200  will now be provided with reference to  FIGS. 4 and 5 . 
       FIG. 4  illustrates a bottom view of code wheel  230  of self duty error correcting motion encoder set  200  when shaft  250  is disposed slightly further away than a nominal position with respect to first optical encoder  210 , due to a waggling or eccentric movement of code wheel  230  and shaft  250 . More specifically, in the case illustrated in  FIG. 4  due to waggling of shaft  250 , code wheel  230  is moved eccentrically in such a way that first optical encoder  210  transmits light through an outer edge of first encoder pattern  232  on the planar surface of code wheel  230 , rather than through a nominal position in first encoder pattern  232 . 
     In this case, the duty of pulses reported out of first optical encoder  210  in one or more output signals reflects a revolution of more than 180° because first optical encoder  210  is reading information at the outer edge of first encoder pattern  232 . At this time, second optical encoder  220  will report the magnitude of the eccentricity movement of code wheel  230  based on how many annular rings of second encoder pattern  234  it has moved outward from its initial reading. That is, if second optical encoder  220  is initially reading the central annular ring of second encoder pattern  234 , then due to the eccentric movement of shaft  250  and code wheel  230  it will start to read a different angular ring that is outside the central annular ring. In that case, second optical encoder  220  will report an eccentric movement of +1, +2, etc. depending on which annular ring it reads, which in turn depends on the magnitude of the eccentricity of the movement of code wheel  230 . 
     The information from second optical encoder  220  can be used to correct for a duty cycle error of first optical encoder  210 . Correction can be done using a simple interpolation method. For example, if code wheel  230  will give a maximum of +X° duty cycle (before it is out of coding range) at Y counts of eccentricity magnitude, then the self duty error correction would be:
 
Error=( X°− 180°)*( N/Y ),   1)
 
where N is the eccentricity number (+1, +2, etc.) reported out of second encoder  220 .
 
     Meanwhile, when there is no eccentricity in the movement of shaft  250  and code wheel  230 , then there is no change in the annular ring of second encoder pattern  234  which is followed by second optical encoder  220 , and accordingly second optical encoder  234  does not produce any signal indicating any eccentric movement by code wheel  230 . 
       FIG. 5  illustrates a bottom view of code wheel  230  of self duty error correcting motion encoder set  200  when shaft  250  is disposed slightly closer than a nominal position with respect to first optical encoder  210 , due to eccentric (e.g., waggling) movement of code wheel  230  and shaft  250 . More specifically, in the case illustrated in  FIG. 5  due to eccentric movement of shaft  250 , code wheel  230  is moved eccentrically in such a way that first optical encoder  210  transmits light through an inner edge of first encoder pattern  232  on the planar surface of code wheel  230 , rather than through a nominal position in first encoder pattern  232 . 
     In this case, the duty of pulses reported out of first optical encoder  210  in one or more output signals reflects a revolution of less than 180° because it is reading information at an inner edge of first encoder pattern  232 . At this time, second optical encoder  220  will report the magnitude of the eccentricity movement of code wheel  230  based on how many annular rings of second encoder pattern  234  it has moved inward from its initial reading. That is, if second optical encoder  220  is initially reading the central annular ring of second encoder pattern  234 , then due to the eccentric movement of shaft  250  and code wheel  230  it will start to read a different angular ring that is inside the central annular ring. In that case, second optical encoder  220  will report an eccentric movement of −1, −2, etc. depending on which annular ring it reads, which in turn depends on the magnitude of the eccentricity of the movement of code wheel  230 . 
     The information from second optical encoder  220  can be used to correct for a duty cycle error of first optical encoder  210 . Correction can be done using the simple interpolation method described above. 
     In one embodiment, self duty error correcting motion encoder set  200  outputs an alarm or other signal indicating the need for maintenance, whenever the eccentric movement of code wheel  230  detected by second optical encoder  220  exceeds a preset threshold. This reduces the need for scheduled, periodic, preventative maintenance of the motion encoder set which in turn reduces down-time and operating costs for an apparatus or system that incorporates self duty error correcting motion encoder set  200 . 
       FIG. 6  shows one embodiment of a motion encoder set  600  with up/down code wheel movement detection, comprising: a first optical encoder  610  including a first light emitter  612  and a first optical sensor  614 ; a second optical encoder  620  including a second light emitter  622  and a second optical sensor  624 ; a housing  675  on which first and second optical encoders  610 ,  620  are mounted; a rotating shaft  650 ; a code wheel  630  mounted on shaft  650 , the code wheel  630  including a first encoder pattern  632  on a planar surface  636  thereof, disposed between first light emitter  612  and first optical sensor  614 , and a second encoder pattern  634  disposed on an outer peripheral surface  638  (“thickness”) thereof; a motor controller  670  for turning shaft  650 ; a processor  680 ; and an alarm indicator  690 . Code wheel  630  rotates along with shaft  650 , thereby moving first encoder pattern  632  relative to first optical encoder  610 , and second encoder pattern  634  relative to second optical encoder  620 . 
     In the embodiment shown in  FIGS. 6-11 , for the sake of simplifying the explanation, code wheel  630  is shown comprising a single disk, with first encoder pattern  632  and second encoder pattern  634  disposed thereon. However, it should be understood that code wheel  630  could optionally comprise two or more separate disks rotating on the rotating shaft  650 , with first encoder pattern  232  disposed on one disk, and second encoder pattern  234  disposed on a different, separate, disk. 
     Furthermore, in the embodiment shown in  FIGS. 6-11 , for the sake of simplifying the explanation, first and second optical encoders  610 ,  620  are shown mounted on common housing  675 . However, it should be understood that first and second optical encoders  610 ,  620  can be packaged separately, being mounted on two separate housings  675 . 
     In similarity to first motion detector  210  of self duty error correcting motion encoder set  200 , first optical encoder  610  operates in conjunction with first encoder pattern  632  to measure a rotational movement of code wheel  630  and to output one or more signals indicating the rotational movement of code wheel  630 . That is, first motion detector  610  outputs one or more signals having first coding information indicating a rotational speed of shaft  650  on which code wheel  630  is mounted. In contrast, second optical encoder  620  operates in conjunction with second encoder pattern  634  to measure an up/down movement of outer peripheral surface  638  of code wheel  630  and to output one or more signals indicating the up/down movement and/or wobbling movement of code wheel  630 . 
     In the embodiment of  FIG. 6 , first optical encoder  610  operates in a transmissive mode by detecting light passed through first encoder pattern  632  of code wheel  630 . However, in another embodiment, first light emitter  612  and first optical sensor  614  could be disposed on the same side of code wheel  630  as each other, such that first optical encoder  610  operates in a reflective mode by detecting light reflected from first encoder pattern  632  of code wheel  630 . 
       FIG. 7  shows a bottom view of one embodiment of code wheel  630 , and  FIG. 8  illustrates a side view of one embodiment of code wheel  630  of motion encoder set  600  with up/down code wheel movement detection when code wheel  630  is in a nominal position with respect to second optical encoder  620 . As shown in  FIG. 7 , code wheel  630  comprises a single disk and includes first encoder pattern  632  on a planar surface thereof. Meanwhile, as can be more easily seen in  FIG. 8 , code wheel  630  also includes second encoder pattern  634  on outer peripheral surface  638  (“thickness”) thereof. In the embodiment of  FIG. 7 , first encoder pattern  632  is a transmissive encoder pattern, and second encoder pattern  634  is a reflective pattern. First encoder pattern  632  codes information for rotation motion detection, and second encoder pattern  634  codes information for up/down and/or wobbling motion detection. 
     In the embodiment of  FIG. 7 , first encoder pattern  632  is an A/B pattern having alternating areas of differing optical transmissivity or reflectivity, depending on the design of first optical encoder  610 . Optical sensor  614  detects the rate of change between the A and B patterns and thereby ascertains the relative rotational movement between first optical encoder  610  and encoder pattern  632 . 
     Meanwhile, in the embodiment of  FIG. 7 , second encoder pattern  634  is an alternating pattern of annular rings of differing optical reflectivity disposed on the outer peripheral surface  638  of code wheel  630 . Initially, in a nominal position as shown in  FIG. 8 , optical sensor  624  follows a middle or central annular ring of second encoder pattern  634 . Optical sensor  624  follows a different annular ring of second encoder pattern  634  depending upon the relative up-and-down position of outer peripheral surface  638  of code wheel  630  with respect to second optical encoder  620 , for example due to up/down motion and/or wobbling motion of code wheel  630  and shaft  650 . 
     An explanation of the operation of motion encoder set  600  with up/down and/or wobbling code wheel movement detection will now be provided with reference to  FIGS. 9-11 . 
       FIG. 9  illustrates a side view of code wheel  630  of motion encoder set  600  with up/down code wheel movement detection when code wheel  630  is tilted upward, for example due to a wobbling movement of shaft  650  and code wheel  630 . As noted above, second optical encoder  620  initially follows a central or middle annular ring of second encoder pattern  634 . However, as outer peripheral surface  638  of code wheel  630  tilts upward, second optical encoder  620  begins to follow a lower annular ring of second encoder pattern  634  on outer peripheral surface  638 . Since second encoder  620  encounters a change in the position of the annular ring of second encoder pattern  634  that it is following, it will report a changed magnitude accordingly, as +1, +2, etc. depending on the magnitude of the tilt or up-down movement of code wheel  630 , and the resolution of the second encoder pattern  634 . 
     Meanwhile,  FIG. 10  illustrates a side view of code wheel  630  of motion encoder set  600  with up/down code wheel movement detection in an opposite case when code wheel  630  is tilted downward, for example due to a wobbling movement of shaft  650  and code wheel  630 . With outer peripheral surface  638  of code wheel  630  tilted downward, second optical encoder  620  begins to follow a higher, or upper, annular ring of second encoder pattern  634  on outer peripheral surface  638 . Since second optical encoder  620  encounters a change in the position of the annular ring of second encoder pattern  634  that it is following, it will report a changed magnitude. Since the movement is opposite to the direction discussed above with respect to  FIG. 9 , it will report the magnitude with an opposite sign now, e.g., as −1, −2, etc. depending on the magnitude of the tilt or up-down movement of code wheel  630 , and the resolution of the second encoder pattern  634 . 
     Whenever the wobbling movement of code wheel  630  detected by second optical encoder  620  exceeds a preset threshold, second optical encoder  620  outputs one or more signals that indicate a wobbling movement of code wheel  630 , thus monitoring for such a problem. The signal(s) output by second optical encoder  620  are provided to processor  680  where they can be used to generate an alarm or other signal to be sent to alarm  690 , indicating the need for maintenance, whenever the wobbling movement of code wheel  630  detected by second optical encoder  620  exceeds a preset threshold. This reduces the need for scheduled, periodic, preventative maintenance which in turn reduces down-time and operating costs for an apparatus or system that incorporates motion encoder set  600 . 
       FIG. 11  illustrates up/down movement of code wheel  630  of optical encoder set  600  with up/down code wheel movement detection. Here, code wheel  630  is mounted on a worn out shaft  650  which has an undesired up/down movement with housing  675 . Since code wheel  630  is mounted on shaft  650 , code wheel  630  will also be moving up and down within housing  675 . If the up and down movement is too great, code wheel  630  may rub against, or collide with, housing  675 , whereby motion encoder set  600  may provide inaccurate signals which may impair operation of a host apparatus with which motion encoder set  600  is incorporated, or perhaps even damaging the host apparatus, and/or eventually damaging motion encoder set  600  itself. 
     However, second optical encoder  620  outputs one or more signals that indicates an up/down movement of code wheel  630 , thus monitoring for such a problem. The signal(s) output by second optical encoder  620  are provided to processor  680  where they can be used to generate an alarm or other signal to be sent to alarm  690 , indicating the need for maintenance, whenever the up/down movement of code wheel  630  detected by second optical encoder  620  exceeds a preset threshold. This reduces the need for scheduled, periodic, preventative maintenance which in turn reduces down-time and operating costs for an apparatus or system that incorporates motion encoder set  600 . Also, in a case where motor controller  670  includes an up/down movement control, processor  680  may generate an appropriate signal to be applied to motor controller  670  to reduce or minimize the net up/down movement of code wheel  630  and shaft  650 . 
     In another embodiment, a motion encoder set includes first, second, and third optical encoders, where the first optical encoder measures rotational movement of the code wheel, the second optical encoder measures eccentric movement (e.g., waggling) of the code wheel like the optical encoder  220  described above, and the third optical encoder measures up/down movement of the code wheel like the optical encoder  620  described above. In that case, the code wheel includes first, second, and third encoder patterns. Once again, the code wheel may include one or more disks, and the encoder patterns can be conveniently provided on the same disk, or two or three different disks. Where a single disk is used, first and second encoder patterns are provided on one or more planar surfaces thereof, and third encoder pattern is provided on the outer peripheral surface thereof. An alarm signal indicating a need for repair can be generated in response to the outputs of either or both of the second and third optical encoders. 
     While example embodiments are disclosed herein, one of ordinary skill in the art appreciates that many variations that are in accordance with the present teachings are possible and remain within the scope of the appended claims. The embodiments therefore are not to be restricted except within the scope of the appended claims.