Abstract:
An apparatus ( 20 ) for measuring angles, typically a bevel square, having a first arm ( 27 ), a second arm ( 21 ) pivotally attached to the first arm, a transducer ( 62, 63 ) for detecting changes in the angular position of the second arm ( 21 ) relative to the first arm ( 27 ), a controller ( 66 ) communicating with the transducer ( 62, 63 ) for calculating an angular position value of the second arm ( 21 ) relative to the first arm ( 27 ) and an output device ( 67 ) communicating with the controller ( 66 ) which outputs the angular position value.

Description:
TECHNICAL FIELD  
         [0001]    The present invention relates generally to an apparatus for measuring angles and, in a particular aspect, to a bevel square capable of measuring and displaying angles.  
           [0002]    The invention has been developed primarily for measuring angles and will be described hereinafter with reference to this application. However, it will be appreciated that the invention is not limited to this particular use.  
         BACKGROUND ART  
         [0003]    A bevel square is an apparatus that enables a user to mark lines at specific angles on a workpiece. A bevel square consists of a ruler or slide that is pivotally attached to a body. The ruler typically has a slot that is used in conjunction with a shaft to attach the ruler to the body. The shaft can slide along the slot so that the ruler can be translated as well as rotated relative to the body. The body typically has a slot in which the ruler or a portion of the ruler can be accommodated.  
           [0004]    In order to mark a line at a desired angle on a workpiece using a bevel square the angle of the ruler relative to the body must first be adjusted. This is accomplished by using a protractor (or similar) to measure the angle of the ruler relative to the body as the position of the ruler is adjusted. Once the ruler is correctly positioned relative to the body the bevel square can be used to mark the line on the workpiece.  
           [0005]    A bevel square can also be used in conjunction with a protractor to measure angles. This is accomplished by placing the bevel square on the workpiece containing the angle to be measured and adjusting the ruler relative to the body until the angle between the ruler and the body corresponds to the angle being measured. The protractor can then be used to measure the relative angle between the ruler and the body.  
           [0006]    A problem with using a bevel square in the above described manner is that the bevel square must be used in conjunction with a protractor or similar device in order to measure the relative angle of the ruler and the body. This has the effect of complicating the tasks of drawing lines at specific angles on a workpiece and measuring angles contained in a workpiece. As a result of this additional complexity the time taken to perform the tasks is increased.  
           [0007]    It is an object of the present invention to substantially overcome, or at least ameliorate, one or more of the deficiencies of the prior art.  
         SUMMARY OF THE INVENTION  
         [0008]    According to a first aspect of the present invention there is provided an apparatus for measuring angles, the apparatus having:  
           [0009]    a first arm;  
           [0010]    a second arm;  
           [0011]    means pivotally connecting said second arm to said first arm;  
           [0012]    a transducer for detecting changes in the angular position of the second arm relative to the first arm;  
           [0013]    a controller communicating with the transducer, wherein the controller calculates an angular position value of the second arm relative to the first arm; and  
           [0014]    an output device communicating with the controller, wherein the output device outputs the angular position value.  
           [0015]    In a more particular form of the invention the apparatus is a bevel square in which the first arm is a body of the bevel square and the second arm is a ruler or slide of the bevel square.  
           [0016]    Preferably, the connecting means comprises pivot means mounted for rotation relative to the first arm. Preferably the pivot means is rotatable with the second arm. Preferably, the second arm has an aperture that engages with the pivot means so that the second arm and the pivot means are rotationally locked together. Preferably, the pivot means is slidable longitudinally of the second arm. The aperture may be in the form of a slot so that the pivot means may slide longitudinally within the slot. The pivot means may include a pair of opposite substantially parallel sides which are spaced apart substantially the same distance as the width of the slot so as to be receivable in the slot for longitudinal slidable movement. Preferably, the first arm carries a shaft and the pivot means is mounted coaxially on the shaft for free rotation relative thereto. Suitably, the pivot means is in the form of a collar or bush mounted on the shaft.  
           [0017]    The first arm preferably houses the transducer, the controller and the output device. An electrical power source for powering the controller, transducer and output device is preferably housed within the first arm.  
           [0018]    Preferably, the transducer includes:  
           [0019]    a sensor wheel that is driven by the pivot means; and  
           [0020]    at least one sensor that can detect rotational movement of the sensor wheel.  
           [0021]    Preferably, the sensor wheel includes a plurality of spokes which are uniformly positioned around the circumference of the sensor wheel. The sensor wheel may have 10 spokes uniformly positioned around its perimeter. The at least one sensor may output an electrical signal as each spoke passes the at least one sensor. The at least one sensor preferably has a light source and a light detector that can respectively transmit and receive infrared light. Preferably, the transducer has two sensors positioned adjacent each other.  
           [0022]    Preferably, the pivot means drives the sensor wheel through a transmission gearing. The transmission gearing suitably comprises a series of intermeshing gears, suitably spur gears, the gears translating rotatable movement of the pivot means relative to the first arm into a multiplied rotational movement of the sensor wheel. Preferably, the gears are arranged longitudinally along the first arm between the pivot means and sensor wheel. The series of gears suitably include a gear mounted for rotation with the pivot means and a gear mounted for rotation with the sensor wheel.  
           [0023]    In one preferred form, the transmission gearing may consist of:  
           [0024]    a first gear coaxially mounted for rotational movement with the pivot means;  
           [0025]    a second shaft;  
           [0026]    a second gear coaxially mounted with the second shaft, wherein the second gear meshes with the first gear;  
           [0027]    a third gear coaxially mounted with the second shaft and rotatable with the second gear;  
           [0028]    a third shaft;  
           [0029]    a fourth gear coaxially mounted with the third shaft, wherein the fourth gear meshes with the third gear;  
           [0030]    a fourth shaft;  
           [0031]    a fifth gear coaxially mounted with the fourth shaft, wherein the fifth gear meshes with the fourth gear;  
           [0032]    a sixth gear coaxially mounted with the fourth shaft and rotatable with the fifth gear;  
           [0033]    a fifth shaft;  
           [0034]    a seventh gear coaxially mounted with the fifth shaft, wherein the seventh gear meshes with the sixth gear;  
           [0035]    an eighth gear coaxially mounted with the fifth shaft and rotatable with the seventh gear;  
           [0036]    a sixth shaft;  
           [0037]    a ninth gear coaxially mounted with the sixth shaft, wherein the ninth gear meshes with the eighth gear;  
           [0038]    a tenth gear coaxially mounted with the sixth shaft and rotatable with the ninth gear;  
           [0039]    a seventh shaft, wherein the sensor wheel is coaxially mounted with the seventh shaft;  
           [0040]    an eleventh gear coaxially mounted with the seventh shaft and wherein the eleventh gear meshes with the tenth gear, the sensor wheel being rotatable with the eleventh gear.  
           [0041]    Preferably, the sensor wheel rotates 180 times for each rotation of the first shaft. Preferably, the gear ratio of the second gear to the first gear is 1:3. Preferably, the gear ratio of the fourth gear to the third gear is 1:2. Preferably, the gear ratio of the fifth gear to the fourth gear is 2:3. Preferably, the gear ratio of the seventh gear to the sixth gear is 1:4. Preferably, the gear ratio of the ninth gear to the eight gear is 1:2. Preferably, the gear ratio of the eleventh gear to the tenth gear is 1:2.5.  
           [0042]    Whilst the above described one configuration of gear train between the pivot means and sensor wheel, it will be appreciated that the gear train may be in many different configurations.  
           [0043]    The apparatus may include one or more adjustment knobs mounted for rotational movement with one gear for manually rotating the gear to effect through the transmission gearing pivotal adjustment of the first arm relative to the second arm.  
           [0044]    A first adjustment knob may be coaxially mounted with and fixed to the fifth shaft, wherein the first adjustment knob can be used to rotate the fifth shaft and thus the sixth gear to effect “course” adjustment of the rotational position of the first arm relative to the second arm. A second adjustment knob may be coaxially mounted with and fixed to the seventh shaft, wherein the second adjustment knob can be used to rotate the seventh shaft and thus the eleventh gear to effect “fine” adjustment of the rotational position of the first arm relative to the second arm.  
           [0045]    Preferably, the controller communicates with at least one button or switch. The at least one button or switch may be used to turn the output device on and off, change the format of the angular position value that is output by the output device or calibrate the apparatus. The controller may calculate the angular position value in degrees, radians or as a gradient. The controller may vary an angular position count depending on the output of the transducer. Preferably, the controller uses the angular position count to calculate the angular position value.  
           [0046]    The output device is preferably a visual display such as a LCD (liquid crystal display).  
           [0047]    In a further aspect, the present invention provides a bevel square having:  
           [0048]    a main body;  
           [0049]    a ruler or slide;  
           [0050]    means pivotally connecting said ruler or slide to said body;  
           [0051]    means for detecting the angular position or changes in angular position of the ruler or slide relative to said body; and  
           [0052]    means associated with said detecting means for calculating and displaying said angular position.  
           [0053]    Preferably, the detecting means includes pivot means rotatable with said ruler or slide, rotatable sensor means and gearing means between said pivot means and said sensor means for transmitting rotational movement of said pivot means into rotational movement of said sensor means. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0054]    In order that the invention may be more fully understood and put into practice, a preferred embodiment thereof will now be described with reference to the accompanying drawings in which  
         [0055]    [0055]FIG. 1 is a schematic longitudinal sectional elevational view of a bevel square according to a first embodiment of the present invention;  
         [0056]    [0056]FIG. 2 is a schematic plan view of the bevel square illustrated in FIG. 1;  
         [0057]    [0057]FIG. 3 is a block diagram of the microprocessor and associated peripheral devices that are incorporated into the bevel square of FIG. 1; and  
         [0058]    [0058]FIG. 4 is a flowchart that illustrates the operation of the bevel square illustrated in FIG. 1. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0059]    Referring firstly to FIGS. 1 and 2, there is illustrated a bevel square  20  according to a preferred form of the invention having a ruler or slide  21  pivotally attached to a body  27 . Ruler  21  is substantially planar and has a generally elongated shape. Ruler  21  has two longitudinal sides  22 ,  23  that are parallel to each other. A first end  24  of the ruler  21  has a diagonal orientation relative to the sides  22 ,  23  while a second end  25  of the ruler  21  is rounded. The ruler  21  includes a slot  26  that is parallel to the sides  22 ,  23 . The slot  26  extends approximately half the length of the ruler  21 .  
         [0060]    Members  28  and  29  (see FIG. 2) form the body  27  which is also elongated. Members  28 ,  29  are attached to each other by an attachment device  30 . The attachment device  30  may be a screw or similar. The body  27  has a generally elongated shape and has two sides  31 ,  32  that are parallel to each other. The distance between the sides  31 ,  32  is the same as the distance between the sides  22 ,  23  of ruler  21 . The body  27  has a flat first end  33  and a rounded second end  34 . A region  35  between the members  28 ,  29  forms a slot  37  (see FIG. 2) that can accommodate a portion of the ruler  21 . Slot  37  extends from a wall  36  to the rounded end  34  of body  27 . Ruler  21  can be inserted into slot  37  so that end  24  of ruler  21  abuts against the wall  36 .  
         [0061]    A shaft  38  extends through and is fixed to the body  27 . The shaft  38  also extends through a collar  39  which is coaxial with and free to rotate about shaft  38 . The collar  39  extends through the slot  26  in the ruler  21 . The collar  39  has a substantially parallel opposite sides which are spaced apart substantially the same distance as the width of the slot  26  so that the ruler  21  and the collar  39  are rotationally locked together however the collar  39  can slide or move along the length of slot  26  in the ruler  21 . The shaft  38  may terminate in a threaded end for engagement with a thumb screw (not shown) as is conventional in bevel squares to enable the ruler or slide  21  to be locked in a particular position relative to the body  27  by tightening of the screw.  
         [0062]    A gear  40  is fixed to collar  39  so that gear  40  can rotate in unison with collar  39 . The gear  40  in this embodiment has 24 teeth extending around its perimeter.  
         [0063]    With reference to FIG. 2 a shaft  41  is attached to member  28  of body  27  so that shaft  41  is free to rotate about its axis. Shaft  41  extends through and is fixed to a gear  42 . Gear  42  has 8 teeth extending around its perimeter. Gear  42  meshes with gear  40  so that rotation of gear  42  causes gear  40  to rotate and vice versa. The gear ratio of gear  42  to gear  40  is 1:3. A gear  43  is mounted coaxially with and is fixed to gear  42  so that gear  43  and gear  42  can rotate in unison. Gear  43  has 24 teeth extending around its perimeter. Gear  43  does not engage with gear  40 .  
         [0064]    A shaft  44  is attached to member  28  of body  27  so that shaft  44  is free to rotate about its axis. Shaft  44  extends through and is fixed to a gear  45 . Gear  45  has 12 teeth extending around its perimeter. Gear  45  meshes with gear  43  so that rotation of gear  45  causes gear  43  to rotate and vice versa. The gear ratio of gear  45  to gear  43  is 1:2.  
         [0065]    A shaft  46  is attached to member  28  of body  27  so that shaft  46  is free to rotate about its axis. Shaft  46  extends through and is fixed to a gear  47 . Gear  47  has 8 teeth extending around its perimeter. Gear  47  meshes with gear  45  so that rotation of gear  47  causes gear  45  to rotate and vice versa. The gear ratio of gear  47  to gear  45  is 2:3. A gear  48  is mounted coaxially with and is fixed to gear  47  so that gear  48  and gear  47  can rotate in unison. Gear  48  has 40 teeth extending around its perimeter. Gear  48  does not engage with gear  45 .  
         [0066]    A shaft  49  is attached to member  28  of body  27  so that shaft  49  is free to rotate about its axis. Shaft  49  extends through and is fixed to a gear  50 . Gear  50  has 10 teeth extending around its perimeter. Gear  50  meshes with gear  48  so that rotation of gear  50  causes gear  48  to rotate and vice versa. The gear ratio of gear  50  to gear  48  is 1:4. A gear  51  is mounted coaxially with and is fixed to gear  50  so that gear  51  and gear  50  can rotate in unison. Gear  51  has 20 teeth extending around its perimeter. Gear  51  does not engage with gear  48 .  
         [0067]    An adjustment knob  52  may be fixed to the shaft  49 . Adjustment knob  52  enables a user to manually rotate shaft  49  and thus the gear  50  and make coarse adjustments to the angular position of ruler  21  relative to body  27 . By turning adjustment knob  52 , 360 degrees ruler  21  is rotated by 10 degrees relative to the body  27 . This is because the gear ratio between gear  50  and gear  40  is 1:36.  
         [0068]    A shaft  53  is attached to member  28  of body  27  so that shaft  53  is free to rotate about its axis. Shaft  53  extends through and is fixed to a gear  54 . Gear  54  has 10 teeth extending around its perimeter. Gear  54  meshes with gear  51  so that rotation of gear  54  causes gear  51  to rotate and vice versa. The gear ratio of gear  54  to gear  51  is 1:2. A gear  55  is mounted coaxially with and is fixed to gear  54  so that gear  55  and gear  54  can rotate in unison. Gear  55  has 30 teeth extending around its perimeter.  
         [0069]    A shaft  56  is attached to member  28  of body  27  so that shaft  56  is free to rotate about its axis. Shaft  56  extends through and is fixed to a gear  57 . Gear  57  has 12 teeth extending around its perimeter. Gear  57  meshes with gear  55  so that rotation of gear  57  causes gear  55  to rotate and vice versa. The gear ratio of gear  57  to gear  55  is 1:2.5. A sensor wheel  58  is mounted coaxially with and is fixed to gear  57  so that sensor wheel  58  and gear  57  can rotate in unison. Sensor wheel  58  has 10 spaces  59  and 10 radially extending spokes  60  extending around its circumference in an alternating manner.  
         [0070]    An adjustment knob  61  may be fixed to the shaft  56 . Adjustment knob  61  enables a user to manually rotate shaft  56  and thus gear  57  and make fine adjustments to the angular position of ruler  21  relative to body  27 . By turning adjustment knob  61 , 360 degrees ruler  21  is rotated by 2 degrees relative to body  27 . This is because the gear ratio between gear  57  and gear  40  is 1:180.  
         [0071]    As illustrated the respective gears are arranged longitudinally along the body  27  at spaced apart positions. The gears however may be arranged in other orientations and rations to transmit rotational movement of the ruler or slide  21  relative to the body  27  to rotational movement of the sensor wheel  58 .  
         [0072]    Sensors  62  and  63  are positioned adjacent to a peripheral region of sensor wheel  58 . Sensors  62  and  63  each have a light source  64  positioned over one side of sensor wheel  58  and a corresponding light detector  65  positioned over an opposite side of sensor wheel  58 . Each light source  64  continually emits infrared light towards a corresponding light detector  65 . Each light detector  65  is able to detect infrared light. As sensor wheel  58  rotates spaces  59  and spokes  60  alternately pass between the light source  64  and light detector  65  of sensors  62  and  63 . If a space  59  is positioned between the light source  64  and light detector  65  of either sensor  62  or  63  the infrared light emitted by the light source  64  is detected by the light detector  65  and the associated sensor  62  or  63  outputs an electrical signal that represents a logic 0. If a spoke  60  is positioned between the light source  64  and light detector  65  of either sensor  62  or  63  the infrared light emitted by the light source  64  is blocked by the spoke  60  so that the light detector  65  does not detect the infrared light. If the light detector  65  does not detect infrared light the associated sensor  62  or  63  outputs an electrical signal that represents a logic 1. Sensors  62  and  63  are positioned adjacent each other. The sensors  62 ,  63  are thus capable of detecting rotation and determining the direction of rotation.  
         [0073]    The 10 spaces  59  and 10 spokes  60  of sensor wheel  58  result in sensors  62 ,  63  outputting a total of 20 pulses for each 360 degree rotation of sensor wheel  58 . Therefore, for each 360 degree rotation of gear  40  (i.e. ruler  21  relative to body  27 ) sensors  62 ,  63  output a total of 36×5×200 3,600 pulses. This means that the maximum resolution of bevel square  20  is 0.1 degrees. Of course different resolutions may be obtained by varying the gearing ratios and/or varying the number of spaces  59  and spokes  60 .  
         [0074]    A microprocessor  66  is housed in member  28  of body  27 . The output of sensors  62  and  63  are input to microprocessor  66  for processing. Microprocessor  66  controls a visual display unit  67  that is housed in member  28  of body  27 . A pair of input buttons or switches  70  (see FIG. 3) are also mounted on body  27 . Input buttons or switches  70  interface with microprocessor  66 . A battery  68  provides electrical power to the electronic devices in bevel square  20 .  
         [0075]    With reference to FIG. 3 sensors  62 ,  63 , visual display  67 , battery  68  and input buttons or switches  70  interface with microprocessor  66 . Microprocessor  66  includes a gear position tracking system  71 , an angle conversion unit  72 , a display controller  73 , a power management system  74 , a button or switch monitoring system  75  and an on off/mode management module  76 . Gear position tracking system  71 , angle conversion unit  72 , display controller  73 , power management system  74 , button monitoring system  75  and on off/mode management module  76  are implemented in software that operates microprocessor  66  in an appropriate manner.  
         [0076]    Gear position tracking system  71  processes the outputs of sensors  62 ,  63  and outputs the angular position of ruler  21  relative to body  27 . Gear position tracking system  71  may, for example, output the angular position of ruler  21  relative to body  27  as an angular position count. A suitable algorithm is used by the gear position tracking system  71  to process the outputs of sensors  62 ,  63 .  
         [0077]    Angle conversion unit  72  processes the output (e.g. angular position count) of the gear tracking system  71  and outputs an angular position value of ruler  21  relative to body  27 . The angular position value is output in a selected format such as degrees, radians or a gradient (e.g. millimetres per one thousand millimetres). On/off/mode management module  76  controls the format of the angular position value calculated by angle conversion unit  72 . Display controller  73  receives the angular position value that is output by angle conversion unit  72  and controls visual display  67  to display the angular position value to a user.  
         [0078]    Power management system  74  monitors and controls the power supplied by battery  68  to microprocessor  66 . On/off/mode management module  76  controls power management system  74 .  
         [0079]    Button monitoring system  75  monitors the state of input buttons or switches  70 . Button monitoring system  75  outputs the state of input buttons or switches  70  to on/off/mode management module  76 . On/off/mode management module  76  uses the state of input buttons or switches  70  to control microprocessor  66 .  
         [0080]    [0080]FIG. 4 is a flowchart that illustrates the operation of microprocessor  66 . Microprocessor  66  operates in a continuous loop.  
         [0081]    The flowchart commences at S 1 . At S 1  the visual display  67  may be on so that the angular position value of ruler  21  relative to body  27  is displayed. Alternatively, the visual display  67  may be off so that the angular position value of ruler  21  relative to body  27  is not displayed.  
         [0082]    At S 2  microprocessor  66  determines whether a first button of input buttons  70  has been pressed since the previous cycle. If the first button has been pressed microprocessor  66  proceeds to S 3 . If the first button has not been pressed microprocessor  66  proceeds to S 4 .  
         [0083]    At S 3  microprocessor  66  switches the visual display  67  on if the visual display  67  is off. Alternatively, if the visual display  67  is on microprocessor  66  switches it off. After S 3  microprocessor  66  loops back to A to start the processing cycle again.  
         [0084]    At S 4  microprocessor  66  determines whether a second button of input buttons  70  has been pressed since the previous cycle. If the second button has been pressed microprocessor  66  proceeds to S 5 . If the second button has not been pressed microprocessor  66  proceeds to S 8 .  
         [0085]    At S 5  microprocessor  66  determines whether the second button was held down. If the second button was not held down microprocessor  66  proceeds to S 6 . If the second button was held down microprocessor  66  proceeds to S 7 .  
         [0086]    At S 6  microprocessor  66  changes the display mode. For example, if the visual display  67  was displaying the angular position value in degrees microprocessor  66  may control the visual display  67  to display the angular position value as a gradient. As mentioned previously, the angular position value may also be displayed in radians. After S 6  microprocessor  66  loops back to A to start the processing cycle again.  
         [0087]    At S 7  microprocessor  66  resets the angular position count of the gear position tracking system  71  to zero. This is done regardless of the actual angular position of ruler  21  relative to body  27 . Thus, by holding the second button down a user is able to calibrate bevel square  20 . After S 7  microprocessor  66  loops back to A to start the processing cycle again.  
         [0088]    At S 8  microprocessor  66  determines whether sensor wheel  58  has moved since the previous cycle. If sensor wheel  58  has moved microprocessor  66  proceeds to S 9 . If sensor wheel  58  has not moved microprocessor  66  proceeds to S 10 .  
         [0089]    At S 9  microprocessor  66  determines the amount and the direction of movement of sensor wheel  58 . The angular position count of gear position tracking system  71  is then appropriately adjusted. After S 9  microprocessor  66  loops back to A to start the processing cycle again.  
         [0090]    At S 10  microprocessor  66  determines the current display mode of visual display  67 . If visual display  67  is not displaying the angular position value in degrees microprocessor  66  proceeds to S 11 . If visual display  67  is displaying the angular position value in degrees microprocessor  66  proceeds to S 12 .  
         [0091]    At S 11  microprocessor  66  converts the angular position count of gear position tracking system  71  into an angular position value that is in the form of a gradient. Alternatively, microprocessor  66  may convert the angular position count into an angular position value that is measured in radians.  
         [0092]    At S 12  microprocessor  66  converts the angular position count of gear position tracking system  71  into an angular position value that is measured in degrees.  
         [0093]    After S 11  or S 12  microprocessor  66  then proceeds to S 13 . At S 13  the angular position value is converted to Binary Coded Decimal (BCD) format and is displayed on visual display  67 . After S 13  microprocessor  66  loops back to A to start the processing cycle again.  
         [0094]    In order to set the angular position of ruler  21  relative to body  27  to a desired angular position adjustment knob  52  may be rotated in the appropriate direction until the actual angular position value displayed on visual display  67  approximates the desired angular position. Alternatively, ruler  21  may be rotated without using adjustment knob  52 . In the later method of operation, a user merely grasps ruler  21  and manually rotates it relative to body  27 . It can be appreciated that both of the aforementioned methods of operation enable coarse adjustments to be made to the angular position. In order to make fine adjustments to the angular position of 0.1 degrees or more adjustment knob  61  is rotated in the appropriate direction until the actual angular position displayed on visual display  67  is the same as the desired angular position. Fine position adjustment can also be achieved by manually rotating the ruler  21  relative to the body  27 . Thus it is possible to provide the bevel square without adjustment knobs  52  and  61 . In addition to setting the angular position of bevel square  20  to a desired angular position bevel square  20  can also be used to measure angles.  
         [0095]    The foregoing describes only one embodiment of the present invention and modifications, obvious to those skilled in the art, can be made thereto without departing from the scope of the present invention.