Abstract:
A brake apparatus for a two-wheeled vehicle includes a hydraulic brake, which receives a hydraulic force to thereby generate a braking force, and a braking force control unit, which controls the braking force by increasing or decreasing the hydraulic pressure. The two-wheeled vehicle includes an engine disposed between a front wheel and a rear wheel. The engine includes a crankcase disposed downward thereof and a cylinder extending upwardly from a front portion of the crankcase. The braking force control unit is disposed in a space surrounded by the cylinder at a position forward thereof and the crankcase at a position downward thereof, respectively. The brake apparatus for a two-wheeled vehicle is capable of promoting enhanced maneuverability, achieving sufficient durability performance, and improving electric connection performance.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    The present application claims priority under 35 U.S.C. §119 to Japanese Patent Application No. 2006-038604, filed Feb. 15, 2006, the entire contents of which are hereby incorporated by reference. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates generally to brake apparatuses for two-wheeled vehicles and, more particularly, to a brake apparatus for two-wheeled vehicles used in an antilock brake system (ABS) that brakes front and rear wheels without letting the wheels lock up. 
         [0004]    2. Description of Background Art 
         [0005]    An example of a known brake apparatus for two-wheeled vehicles includes a front wheel modulator disposed forward of a handlebar and a rear wheel modulator disposed forward of a rear wheel (see, for example, Japanese Patent Laid-Open No. Hei 5-105174.) 
         [0006]    The known art disclosed in Japanese Patent Laid-Open No. Hei 5-105174, however, has the following problems. 
         [0007]    The first problem is as follows. Relative to a weight of the entire two-wheeled vehicle, the front wheel modulator that is relatively heavy in weight is disposed forward of the handlebar and the rear wheel modulator that is again relatively heavy in weight is disposed forward of the rear wheel. Each of the front and rear wheel modulators is therefore away from the position of a center of gravity of a vehicle body. As a result, maneuverability of the vehicle is degraded because of dispersed heavy items. 
         [0008]    The second problem is as follows. Each of the front and rear wheel modulators has an internal mechanism thereof exposed to an outside. There is therefore a concern over thermal effect of an engine particularly on the front wheel modulator. This makes it necessary to prepare a modulator that offers outstanding heat resistance. 
         [0009]    The third problem is as follows. The two modulators are disposed away from each other at front and rear. A control unit connected electrically to each of these modulators naturally has a long wiring harness. This results in an increased cost and poor maintainability. 
       SUMMARY AND OBJECTS OF THE INVENTION 
       [0010]    The present invention has been made to solve these problems and it is an object of the present invention to provide a brake apparatus for two-wheeled vehicles capable of promoting enhanced maneuverability, achieving sufficient durability performance, and improving electric connection performance. 
         [0011]    To achieve the foregoing objects, a brake apparatus for a two-wheeled vehicle according to a first aspect of the present invention includes a hydraulic brake and a braking force control unit. The hydraulic brake receives a hydraulic force to thereby generate a braking force. The braking force control unit controls the braking force by increasing or decreasing the hydraulic pressure. The two-wheeled vehicle includes an engine disposed between a front wheel and a rear wheel. The engine includes a crankcase disposed downward thereof and a cylinder that extends upwardly from a front portion of the crankcase. Further, the braking force control unit is disposed in a space surrounded by the cylinder at a position forward thereof and the crankcase at a position downward thereof, respectively. 
         [0012]    A brake apparatus for a two-wheeled vehicle according to a second aspect of the present invention includes a hydraulic brake and a braking force control unit. The hydraulic brake receives a hydraulic force to thereby generate a braking force. The braking force control unit controls the braking force by increasing or decreasing the hydraulic pressure. The two-wheeled vehicle includes an engine disposed between a front wheel and a rear wheel. The engine includes a crankcase disposed downward thereof and a cylinder that extends upwardly from a front portion of the crankcase. Further, the braking force control unit is disposed in a space surrounded by the crankcase at a position forward thereof and the rear wheel at a position rearward thereof, respectively. 
         [0013]    According to a third aspect of the present invention, in addition to the arrangements according to the first or second aspect of the present invention, the braking force control unit is accommodated in a box body having a heat insulation property. 
         [0014]    According to a fourth aspect of the present invention, in addition to the arrangements according to any of the first to third aspects of the present invention, the braking force control unit controls the braking force of the hydraulic brake disposed in the front wheel. 
         [0015]    According to a fifth aspect of the present invention, in addition to the arrangements according to any one of the first to third aspects of the present invention, the braking force control unit controls the braking force of the hydraulic brake disposed in the rear wheel. 
         [0016]    According to a sixth aspect of the present invention, in addition to the arrangements according to the third aspect of the present invention, the braking force control unit is supported in the box body via an elastic member included in the box body. 
         [0017]    According to a seventh aspect of the present invention, in addition to the arrangements according to the third aspect of the present invention, the braking force control unit includes the box body supported by a vehicle body via an elastic member. 
       EFFECTS OF THE INVENTION 
       [0018]    In the brake apparatus for the two-wheeled vehicle according to the first aspect of the present invention, the braking force control unit, which controls the braking force by increasing or decreasing the hydraulic pressure, is disposed in the space surrounded by the cylinder of the engine at the position forward thereof and the crankcase of the engine at the position downward thereof. Unlike the arrangement in the known art, therefore, the braking force control unit is not disposed far away from the center of gravity of the vehicle body. An inertia force that is generated during movement of the vehicle body is generated at a point with a small distance from the position of the center of gravity of the vehicle body. This enhances maneuverability. “Maneuverability” as the term is herein used means following. Specifically, if heavy articles are disposed at different parts in a vehicle, the vehicle body develops a motion in a pitch direction during acceleration or deceleration and that motion becomes large. During turning, the vehicle body is brought down to a side or pulled down, but this movement cannot be made at a fast pace. Further, when the vehicle body posture fluctuates because of bumps and indentations on road surfaces, it takes longer to bring the vehicle posture back to its original position. 
         [0019]    In the brake apparatus for the two-wheeled vehicle according to the second aspect of the present invention, the braking force control unit, which controls the braking force by increasing or decreasing the hydraulic pressure, is disposed in the space surrounded by the crankcase of the engine at the position forward thereof and the rear wheel at the position rearward thereof. Unlike the arrangement in the known art, therefore, the braking force control unit is not disposed far away from the center of gravity of the vehicle body. The inertia force that is generated during movement of the vehicle body is generated at a point with a small distance from the position of the center of gravity of the vehicle body. This enhances maneuverability. 
         [0020]    In the brake apparatus for the two-wheeled vehicle according to the third aspect of the present invention, the braking force control unit is accommodated in the modulator box having the heat insulation property. The braking force control unit is not, therefore, susceptible to heat generated in the engine. This eliminates the need for preparing a modulator offering high heat resistance, which contributes to a reduced cost. 
         [0021]    In the brake apparatus for the two-wheeled vehicle according to the fourth aspect of the present invention, the braking force control unit controls the braking force of the hydraulic brake included in the front wheel. This allows the front wheel to be braked while rotating without developing a wheel lockup when the vehicle body is braked. 
         [0022]    In the brake apparatus for the two-wheeled vehicle according to the fifth aspect of the present invention, the braking force control unit controls the braking force of the hydraulic brake included in the rear wheel. This allows the rear wheel to be braked while rotating without developing a wheel lockup when the vehicle body is braked. 
         [0023]    In the brake apparatus for the two-wheeled vehicle according to the sixth aspect of the present invention, the braking force control unit is supported in the box body via the elastic member included in the box body. The elastic member can therefore prevent effect of heat from the engine. 
         [0024]    In the brake apparatus for the two-wheeled vehicle according to the seventh aspect of the present invention, the braking force control unit includes the box body supported by the vehicle body via the elastic member. The elastic member, being disposed outside the box body, can be easily built largely, which facilitates improvement of shock absorbing performance. 
         [0025]    Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0026]    The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention, and wherein: 
           [0027]      FIG. 1  is a left side elevational view showing a motorcycle including a brake apparatus for two-wheeled vehicles according to an embodiment of the present invention; 
           [0028]      FIG. 2  is a perspective view showing a braking force control unit and parts surrounding the control unit in the motorcycle shown in  FIG. 1 ; 
           [0029]      FIG. 3  is a partly cutaway perspective view showing a braking force control portion for a front wheel and parts surrounding the control portion in the braking force control unit shown in  FIG. 2 ; and 
           [0030]      FIG. 4  is a partly cutaway perspective view showing a braking force control portion for a rear wheel and parts surrounding the control portion in the braking force control unit shown in  FIG. 2 . 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0031]    A brake apparatus for two-wheeled vehicles according to a specific embodiment to which the present invention is applied will be described in detail below with reference to the accompanying drawings. 
         [0032]      FIGS. 1 through 4  are views showing an embodiment of the present invention.  FIG. 1  is a left side elevational view showing a motorcycle including the brake apparatus for two-wheeled vehicles according to the embodiment of the present invention.  FIG. 2  is a perspective view showing a braking force control unit and parts surrounding the control unit in the motorcycle shown in  FIG. 1 .  FIG. 3  is a partly cutaway perspective view showing a braking force control portion for a front wheel and parts surrounding the control portion in the braking force control unit shown in  FIG. 2 .  FIG. 4  is a partly cutaway perspective view showing a braking force control portion for a rear wheel and parts surrounding the control portion in the braking force control unit shown in  FIG. 2 . In the description that follows hereunder, “front,” “rear,” “right,” and “left” refer to corresponding directions as viewed from a rider riding the motorcycle. 
         [0033]    Referring to  FIGS. 1 and 2 , a motorcycle  10  includes, as main elements thereof, a frame  11 , a front fork  13 , a handlebar  14 , a front wheel  15 , a power unit  16 , a swing arm  19 , a rear wheel  20 , and a tandem seat  22 . The front fork  13  is attached to a head pipe  12  disposed at a front end portion of the frame  11 . The handlebar  14  is connected to an upper portion of the front fork  13 . The front wheel  15  is mounted to a lower portion of the front fork  13 . The power unit  16  includes an engine  17  and a transmission  18  mounted on a front lower portion of the frame  11 . The swing arm  19  is disposed at a rear lower portion of the frame  11 . The rear wheel  20  is attached to a leading end portion of the swing arm  19 . The tandem seat  22  is mounted to an upper portion in the rear of the frame  11  via a seat rail  21 . The motorcycle  10  is a sports type vehicle that uses the power unit  16  to drive the rear wheel  20 . 
         [0034]    The motorcycle  10  further includes a radiator  23 , a front cowl  24 , and an under cowl  25 . The radiator  23  is disposed at a front portion and downward of the frame  11 . The front cowl  24  covers the front portion and both side portions of the frame  11 . The under cowl  25  covers a lower portion of the frame  11  and a lower portion and both side portions of the power unit  16 . The front cowl  24  and the under cowl  25  are formed from a lightweight FRP or other synthetic resin. 
         [0035]    The frame  11  includes a pair of left and right main frame portions  26 . The main frame portions  26 , which are formed, for example, of aluminum alloy castings into substantially an inverted U-shape, extend downwardly toward the rear. The head pipe  12 , of a cylindrical shape, is disposed at a front end of the main frame portions  26 . In addition, the frame  11  also has a center frame portion  27  that protrudes downwardly at a rear end of the main frame portions  26 . 
         [0036]    The handlebar  14  includes a front brake lever  28  disposed on a rightward side thereof. The handlebar  14  further includes a front brake master cylinder  29  mounted thereon and connected to the front brake lever  28 . The front brake master cylinder  29  stores therein brake oil not shown. 
         [0037]    Referring to the power unit  16 , the engine  17  is a water-cooled four-stroke DOHC four-cylinder engine. The transmission  18  is built into a crankcase  30 . The power unit  16  is fixed to the main frame portions  26  and the center frame portion  27  of the frame  11 . A fuel tank  31  is disposed above an air cleaner (not shown) in an upper portion of the power unit  16 . The engine  17  includes a cylinder  32  disposed upward of the crankcase  30 . An electronic fuel supply system (not shown) is connected to an intake port (not shown) in the cylinder  32 . An exhaust pipe  33  connected to an exhaust port (not shown) of the cylinder  32  is connected to a main muffler  34  at a lower portion of the engine  17 . The main muffler  34  is connected to a sub muffler  35 . An output from the transmission  18  is used for, what is called, a chain drive. The output from the transmission  18  is transmitted from a drive sprocket  36  mounted to an output shaft (not shown) of the transmission  18  to a driven sprocket  38  fixed to the rear wheel  20  via a chain  37 . 
         [0038]    The front fork  13  has a front suspension  39  built therein. The front suspension  39  includes a coil spring and a damper. The front fork  13  also has a front caliper  41  assembled thereto. The front caliper  41  applies a braking force to a pair of front disc rotors  40  fixed to the front wheel  15 . A front fender  42  is attached to an upper portion of the front wheel  15 . The front caliper  41  has a twin-port caliper cylinder  43 . A pulsar ring (not shown) is coaxially mounted to the front wheel  15 . A front wheel speed sensor  44  for detecting a rotational speed of the front wheel  15  is assembled to an outer periphery of the pulsar ring in a non-contact fashion. 
         [0039]    The swing arm  19  is swingably connected to the center frame portion  27  of the frame  11 . Shock otherwise applied to the swing arm  19  is absorbed by a rear suspension  45  disposed between the swing arm  19  and the center frame portion  27 . The rear suspension  45  includes a coil spring and a damper. Like the front wheel  15 , rear disc rotors  46  are mounted to the rear wheel  20 . A rear caliper  47 , which applies a braking force to the rear disc rotors  46 , includes a single-port caliper cylinder  48 . A pulsar ring (not shown) is coaxially mounted to the rear wheel  20 . A rear wheel speed sensor  49  for detecting a rotational speed of the rear wheel  20  is assembled to an outer periphery of the pulsar ring in a non-contact fashion. 
         [0040]    A rear brake pedal  50  is depressibly journaled on a right side portion of the center frame portion  27 . A rear brake master cylinder  51  connected to the rear brake pedal  50  is mounted on a side portion. Brake oil not shown is stored in the rear brake master cylinder  51 . 
         [0041]    The motorcycle  10  further includes a front wheel modulator  61  and a rear wheel modulator  62 . The front wheel modulator  61 , which serves as the braking force control unit for the front wheel, is disposed in a space surrounded by the cylinder  32  of the engine  17  at the front and the crankcase  30  of the engine  17  on the bottom. The rear wheel modulator  62 , which serves as the braking force control unit for the rear wheel, is disposed in a space surrounded by the crankcase  30  of the engine  17  at the front and the rear wheel  20  in the rear. 
         [0042]    The front wheel modulator  61  is incorporated in a modulator box  63  of a rectangular box body. The front wheel modulator  61  has an internal mechanism (see  FIG. 3 )  64  built therein. The modulator box  63  is formed from a resin or the like having a heat insulation property. The modulator box  63  is screwed to a modulator fixing portion  52  formed on a left side portion of the main frame portions  26  via a bracket  65  that is assembled so as to surround an outside of the modulator box  63 . The bracket  65  is fixed in position using three bolts  66 . 
         [0043]    The front wheel modulator  61  has an inlet side brake hose  67  and an outlet side brake hose  68  protruding outwardly therefrom. The inlet side brake hose  67  is connected in fluid communication to the front brake master cylinder  29 . The outlet side brake hose  68  is connected in fluid communication to the caliper cylinder  43  for the front wheel. 
         [0044]    The rear wheel modulator  62  is incorporated in a modulator box  71  of a rectangular box body having an open rearward end. The rear wheel modulator  62  has an internal mechanism (see  FIG. 4 )  72  built therein. The modulator box  71  is formed from a resin or the like having a heat insulation property. The modulator box  71  is fixed to a modulator fixing portion  53  formed on a rear portion of the main frame portions  26  via a bracket  73  disposed rearwardly. The bracket  73  is fixed in position using three damper-less bolts  74  and three damper bolts  76  through which damper members  75  are passed. 
         [0045]    The rear wheel modulator  62  has an inlet side brake hose  77  and an outlet side brake hose  78  protruding outwardly therefrom. The inlet side brake hose  77  is connected in fluid communication to the rear brake master cylinder  51 . The outlet side brake hose  78  is connected in fluid communication to the caliper cylinder  48  for the rear wheel. 
         [0046]    The front wheel modulator  61  has a controller (not shown) built therein, in addition to the internal mechanism  64 . The front wheel controller incorporates electronic devices of various types and is electrically connected to a power source (not shown), the front wheel speed sensor  44 , the rear wheel speed sensor  49 , and the front wheel modulator  61 . Constantly monitoring a front wheel speed signal (electric signal) provided by the front wheel speed sensor  44  and a rear wheel speed signal (electric signal) provided by the rear wheel speed sensor  49 , the front wheel controller applies a drive signal to the front wheel modulator  61 . Being integrally built into the front wheel modulator  61 , the front wheel controller allows a wiring harness  70  to have a short routing length. A rear wheel controller is also built into the rear wheel modulator  62 . The front wheel controller and the rear wheel controller are electrically connected to each other. 
         [0047]    In the motorcycle  10 , the front brake lever  28 , the front brake master cylinder  29 , the front wheel speed sensor  44 , the rear brake pedal  50 , the rear brake master cylinder  51 , the rear wheel speed sensor  49 , the front wheel modulator  61 , and the rear wheel modulator  62  constitute a brake apparatus for two-wheeled vehicles  100 . 
         [0048]    Referring to  FIG. 3 , the front wheel modulator  61  has the internal mechanism  64 , which is built into the modulator box  63 , assembled on a damper member  79  formed of an elastic rubber. Accordingly, despite the arrangement, in which the front wheel modulator  61  is fixed to the modulator fixing portion  52  on the main frame portions  26  using the three bolts  66  via the bracket  65 , the internal mechanism  64  is supported without being directly subject to vibration of the vehicle body. It goes without saying that the internal mechanism  64  is not directly subject to heat from the engine  17 , either, since the modulator box  63  has a heat insulation property. Further, the front wheel modulator  61  is fixed to the modulator fixing portion  52  that is surrounded by the cylinder  32  of the engine  17  at the front and the crankcase  30  of the engine  17  on the bottom, so that the front wheel modulator  61  is disposed at a position near a center of gravity of the motorcycle  10 . 
         [0049]    Referring to  FIG. 4 , the rear wheel modulator  62  has the internal mechanism  72  built into the modulator box  71  having an opening  80  in the rear. The rear wheel modulator  62  is fixed to the modulator fixing portion  53  at the rear portion of the center frame portion  27  via the bracket  73 . It is to be noted herein that the bracket  73  is fixed in position as detailed in the following. Specifically, the three damper-less bolts  74  are directly screwed into the modulator fixing portion  53 . Two of the three damper bolts  76 , through which the damper members  75  are passed, are screwed into a metal plate  81  fixed to the modulator box  71 . The remaining one damper bolt  76  is screwed into the modulator box  71 . 
         [0050]    Accordingly, the arrangement, in which the rear wheel modulator  62  is fixed with the damper bolts  76  to the modulator fixing portion  53  of the center frame portion  27  via the bracket  73 , allows the internal mechanism  72  to be supported without being directly subject to the vibration of the vehicle body. It goes without saying that the internal mechanism  72  is not directly subject to heat from the engine  17 , since the modulator box  71  has a heat insulation property. Further, the rear wheel modulator  62  is fixed to the modulator fixing portion  53  that is surrounded by the crankcase  30  of the engine  17  at the front and the rear wheel in the rear, so that the rear wheel modulator  62  is disposed at a position near the center of gravity of the motorcycle  10 . 
         [0051]    In the motorcycle  10  having the arrangements as described in the foregoing, the front brake lever  28  is gripped or the rear brake pedal  50  is depressed during ordinary braking. Then a pressurized brake oil is supplied to the caliper cylinder  43  on the side of the front wheel  15  from the front brake master cylinder  29 . Alternatively, a pressurized brake oil is supplied to the caliper cylinder  48  on the side of the rear wheel  20  from the rear brake master cylinder  51 . This applies a braking force to the front disc rotors  40 , or to the rear disc rotors  46 . At this time, neither the front wheel modulator  61  nor the rear wheel modulator  62  is energized. 
         [0052]    Unlike the foregoing situation, when the front brake lever  28  is gripped in the same manner as above while the motorcycle  10  is running, the value of a front wheel speed signal given by the front wheel speed sensor  44  may become extremely small, resulting in the speed of the front wheel  15  decreasing excessively relative to the speed of the vehicle body. At this time, the front wheel controller, which constantly monitors the above electric signal, applies a drive signal to the internal mechanism  64  of the front wheel modulator  61 . This causes the front wheel modulator  61  to decrease the pressure of the brake oil in the outlet side brake hose  68  instantaneously and thereafter increase the pressure of the brake oil again. The front wheel modulator  61  executes this sequence of operations repeatedly, for example, a plurality of number of times per one second. This ensures that the front wheel  15  is braked while rotating without developing a wheel lockup. 
         [0053]    Similarly, when the rear brake pedal  50  is depressed in the same manner as above while the motorcycle  10  is running, the value of a rear wheel speed signal given by the rear wheel speed sensor  49  may become extremely small, resulting in the speed of the rear wheel  20  decreasing excessively relative to the speed of the vehicle body. At this time, the rear wheel controller applies a drive signal to the internal mechanism  72  of the rear wheel modulator  62 . This causes the rear wheel modulator  62  to decrease the pressure of the brake oil in the outlet side brake hose  78  instantaneously and thereafter increase the pressure of the brake oil again. The rear wheel modulator  62  executes this sequence of operations repeatedly, for example, a plurality of number of times per 1 second. This ensures the rear wheel  20  is braked while rotating without developing a wheel lockup. 
         [0054]    In accordance with the brake apparatus for two-wheeled vehicles  100  as described in the foregoing, the front wheel modulator  61 , which controls the braking force by increasing or decreasing the brake oil pressure, is disposed in the space surrounded by the cylinder  32  of the engine  17  at the front and the crankcase  30  of the engine  17  on the bottom. Specifically, the front wheel modulator  61  is disposed in a position near the center of gravity of the vehicle body surrounding the engine. Unlike the arrangement in the known art, therefore, the front wheel modulator  61  is not disposed far away from the center of gravity of the vehicle body. An inertia force that is generated during movement of the vehicle body is generated at a point with a small distance from the position of the center of gravity of the vehicle body. This enhances maneuverability. 
         [0055]    In addition, in the brake apparatus for two-wheeled vehicles  100 , the rear wheel modulator  62 , which controls the braking force by increasing or decreasing the brake oil pressure, is disposed in the space surrounded by the crankcase  30  of the engine  17  at the front and the rear wheel  20  in the rear. Specifically, the rear wheel modulator  62  is disposed in a position near the center of gravity of the vehicle body surrounding the engine  17 . Unlike the arrangement in the known art, therefore, the rear wheel modulator  62  is not disposed far away from the center of gravity of the vehicle body. The inertia force that is generated during movement of the vehicle body is generated at a point with a small distance from the position of the center of gravity of the vehicle body. This enhances maneuverability. 
         [0056]    In the brake apparatus for two-wheeled vehicles  100  according to the embodiment of the present invention, the front wheel modulator  61  and the rear wheel modulator  62  are accommodated in the modulator boxes  63 ,  71  having the heat insulation property, respectively. The modulators  61 ,  62  are not, therefore, susceptible to heat generated in the engine  17 . This eliminates the need for preparing a modulator offering high heat resistance, which contributes to a reduced cost. Further, performance can be ensured even if a modulator having low heat resistance is used. 
         [0057]    In the brake apparatus for two-wheeled vehicles  100  according to the embodiment of the present invention, the front wheel modulator  61  controls the braking force of the caliper cylinder  43  included in the front wheel  15 . This allows the front wheel  15  to be braked while rotating without developing a wheel lockup when the vehicle body is braked. 
         [0058]    In the brake apparatus for two-wheeled vehicles  100  according to the embodiment of the present invention, the rear wheel modulator  62  controls the braking force of the caliper cylinder  48  included in the rear wheel  20 . This allows the rear wheel  20  to be braked while rotating without developing a wheel lockup when the vehicle body is braked. 
         [0059]    The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.