Abstract:
A vacuum fresh-keeping cover includes an upper cover, a top of which is connected with an air suction-ventilation device, a lower rim of which is connected with a soft gasket that can be suppressed on any horizontal surface, and an interior of which is formed with a container space. When a barometric value of the container space gets larger, the air suction-ventilation device is activated to expel out air in the container space continuously, to keep the container space at a near vacuum condition for preserving objects or food. When pulling up a touching element of the air suction-ventilation device, the air in the container space is drained out by the air suction-ventilation device to quickly remove the upper cover, to facilitate consumers for use, and to conveniently separate the air suction-ventilation device from the upper cover, for easily washing the upper cover with water.

Description:
BACKGROUND OF THE INVENTION 
     a) Field of the Invention 
     The present invention relates to a vacuum fresh-keeping cover, and more particularly to a cover which can be suppressed on any horizontal surface to suck out air in a container space of the cover by suppression, allowing a barometric value in the container space to be decreased to approach to a vacuum state, so as to keep food or objects fresh in the container space. In addition, as the cover can be separated from an air suction-ventilation device, the cover can be quickly and conveniently washed with water. 
     b) Description of the Prior Art 
     A conventional vacuum fresh-keeping container is disclosed in a typical example of a food container in the US Patent Publication No. US2007/0034628 A1, wherein its cover is connected with a casing, and an air suction pump is located inside the casing; therefore, the casing is not able to be washed effectively with water. Moreover, as the cover and the casing are mantled by one to one fitting, the cover cannot be independently mantled and implemented on any surface in a negative pressure condition. 
     SUMMARY OF THE INVENTION 
     Accordingly, the primary object of the present invention is to provide a vacuum fresh-keeping cover that can be implemented on any horizontal surface by the cover. 
     Another object of the present invention is to provide a vacuum fresh-keeping cover, wherein the cover and an air suction-ventilation device can be screwed together and separated, such that the independent cover can be washed quickly and conveniently with water. 
     Still another object of the present invention is to provide a vacuum fresh-keeping cover, wherein upon implementing a negative pressure condition, a container space of the cover can be kept at the negative pressure and a near vacuum condition for a long time. 
     To enable a further understanding of the said objectives and the technological methods of the invention herein, the brief description of the drawings below is followed by the detailed description of the preferred embodiments. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows an exploded view of an air suction-ventilation device and an upper cover of the present invention. 
         FIG. 2  shows a blow-up view of a region A in  FIG. 1 . 
         FIG. 3  shows another exploded view of an air suction-ventilation device and an upper cover of the present invention. 
         FIG. 4  shows an exploded view of an air suction-ventilation device of the present invention. 
         FIG. 5  shows another exploded view of an air suction-ventilation device of the present invention. 
         FIG. 6  shows still another exploded view of an air suction-ventilation device of the present invention. 
         FIG. 7  shows a cutaway view of an action that an air suction pump is activated by pressing down a touching element in an air suction-ventilation device of the present invention. 
         FIG. 8  shows a cutaway view of an action that an air suction pump stops operating by pulling up a touching element in an air suction-ventilation device of the present invention. 
         FIG. 9  shows a cutaway view of an action that a container space of an upper cover of the present invention is drawn to a negative pressure condition. 
         FIG. 10  shows an exploded view of an upper cover and a casing of the present invention. 
         FIG. 11  shows a perspective view of an upper cover of the present invention that is mantled on a desktop. 
         FIG. 12  shows a local cross sectional view of an upper cover of the present invention that is mantled on a desktop. 
         FIG. 13  shows a local cutaway view and a perspective view of the present invention. 
         FIG. 14  shows a cross sectional view of an action that air is sucked by the present invention. 
         FIG. 15  shows a cross sectional view of an action that air is ventilated by the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to  FIGS. 1 to 3 , the present invention includes an upper cover  10 , an interior of which is provided with a container space  12 , a top of which is connected to an air suction-ventilation device  20 , and a lower rim of which is provided with a connecting part  14 ; a soft gasket  30 , a side of which is provided with a connecting slot  32  (as shown in  FIG. 2 ), with the connecting slot  32  being air-tightly fitted into the connecting part  14  and the soft gasket  30  flexibly deforming downward in an air-tight condition, so as to be tightly suppressed on a surface  351  (as shown in  FIG. 12 ); the air suction-ventilation device  20  which is connected above the upper cover  10  and is composed of a bottom air suction-ventilation hole  206  being connected with the container space  12 , a top touching element  22  being able to displace up and down, an air suction pump  25 , and a lower spring leaf  261  and an upper spring leaf  262  at a side of the air suction pump  25 ; and a barometric sensing element  28 , a top of which is provided with a projected body  281  being connected at the lower spring leaf  261 , such that when a barometric value P 1  of the container space  12  is detected high by the barometric sensing element  28  (as shown in  FIG. 8 ), the barometric sensing element  28  will be driven by the high barometric value to be flexibly ascended and restored, so as to drive simultaneously the lower spring leaf  261  to ascend to touch the upper spring leaf  261 , thereby conducting an electric circuit to activate the air suction pump  25  for drawing air  90  inside the container space  12  out of the upper cover  10  through the air suction-ventilation hole  206 ; on the other hand, when the barometric value P 1  of the container space  12  decreases, the barometric sensing element  28  can flexibly descend and displace by an operation of a negative pressure in the container space  12 , to drive the lower spring leaf  261  to descend and displace, thereby forming an off-circuit condition by the upper and lower spring leaves  262 ,  261  to stop the air suction pump  25 . 
     When the touching element  22  is pressed down and displacing, it will drive and touch the upper spring leaf  262 , allowing the upper spring leaf  262  to elastically descend to touch the lower spring leaf  261 , so as to manually conduct electricity to the upper and lower spring leaves  262 ,  261  (or enabling an on state), and to activate the air suction pump  25 , such that the air  90  in the container space  12  can be expelled out of the upper cover  10  (as shown in  FIG. 7 ). 
     Referring to  FIG. 13 , a lower end of the air suction-ventilation device  20  is provided with a screw tube  23 , an outer surface of which is disposed with a male thread  231 , with a part of the screw tube  23  above the male thread  231  being mantled and sealed with a soft gasket  232 . 
     Above the upper cover  10  is provided with a through-hole  16  into which the screw tube  23  is transfixed. 
     An interior of a screw sleeve  21  is provided with a female thread  211 , and a bottom of the screw sleeve  21  is provided with a sealing surface which is disposed with the air suction-ventilation hole  206 . The female thread  211  is screwed with the male thread  231 , and the soft gasket  232  is tightly fitted and abutted at a rim of the through-hole  16 , allowing the air suction-ventilation hole  206  to be connected with an interior space of the screw tube  23 . 
     A center on a lower surface of a circular ring body  24  of the air suction-ventilation device  20  is integrally formed with the screw tube  23 . As shown in  FIG. 4 , a top surface in an interior of the screw tube  23  is provided respectively with a first venthole  63 , a second venthole  236  and a third venthole  235 . 
     Along two side surfaces of the screw tube  23  are provided respectively with a left groove  237  and a right groove  238  (as shown in  FIG. 1 ) for connecting and emplacing batteries. 
     Referring to  FIG. 4 , an outer periphery of the circular ring body  24  is provided with a male thread  241 . 
     Referring to  FIG. 6 , an interior of a circular ring inner cap  242  is provided with a central through-hole  243 , and an inner wall of a periphery is provided with a female thread  244 , with the female thread  244  being screwed with the male thread  241 , and the central through-hole  243  being transfixed and tightly fitted with a surface of the soft gasket  232  located at an outer surface of the screw tube  23 . 
     Referring to  FIG. 2 , an inner wall at a bottom of the soft gasket  30  is formed with an inner cone surface  34  which can be tightly fitted on the horizontal surface  351  (as shown in  FIG. 12 ). 
     The surface  351  can be a surface at an outer periphery of a seat  35  (as shown in  FIG. 10 ), or can be a surface of a desktop  35 ′ (as shown in  FIG. 11 ). 
     Referring to  FIG. 4 , the air suction pump  25  is provided with a rectangular seat  251 , an interior of the rectangular seat  251  is provided with a groove  252  into which is provided respectively with two upright air ducts  253 ,  254 , a first round hole  255  and a second round hole  256 ; whereas, a soft air driver  257  is fitted into the second round hole  256 , a projected body  2571  at a an upper end is connected on an off-center shaft  250  of the air suction pump  25 , an interior at a lower end is provided with an air driving chamber  2572  for compression and deformation, and two sides at a front end are provided respectively with a first guide hole  2573  and a second guide hole  2574 , with the first guide hole  2573  being connected with the first air duct  253 , and the second guide hole  2574  being connected with the second air duct  254 . 
     The barometric sensing element  28  is made by a flexible material, and is constituted by the projected body  281  and a horizontal rectangular plate  282  at a bottom. An interior of the projected body  281  is provided with a hollow chamber  2811 , the projected body  281  is protruded out of the first round hole  255 , and the rectangular plate  282  is provided respectively with an upper movable valve reed  2821  and a lower movable valve reed  2822 . A lower side of the upper movable valve reed  2821  forms a transversal air access  2825  (as shown in  FIG. 5 ), a tail end of which is formed with a second through-hole  2823  (as shown in  FIG. 5 ). In addition, a first through-hole  2824  is located on the rectangular plate  282 , and is correspondingly connected with the first guide hole  2573  and the first air duct  253 ; whereas, the second through-hole  2823  is correspondingly connected with the second guide hole  2574  and the second air duct  254 . 
     A third hard plate  70  is emplaced in a rectangular recess  60 , and is located on a surface of the rectangular plate  282  of the barometric sensing element  28 . The third plate  70  is provided with following parts including a shallower first groove  72 , an interior of which is dug out with a deeper second groove  74  being provided with a through-hole A ( 741 ) and a through-hole B ( 742 ), with the through-hole A ( 741 ) being mantled and connected on the upper movable valve reed  2821 , and the through-hole B ( 742 ) being mantled and connected on the lower movable valve reed  2822 ; a first air permeable hole  75 , which is located in the first groove  72 , with an upper hole end being connected with the first guide hole  2573  and the first air duct  253 , and a lower hole end being connected with the first through-hole  2824  of the barometric sensing element  28  (as shown in  FIG. 5 ); a second air permeable hole  76 , which is located in the first groove  72 , with an upper hole end being connected with the second guide hole  2574  and the second air duct  254 , and a lower hole end being connected with the second through-hole  2823  of the barometric sensing element  28 ; and a round through-hole  77 , which is located at a side of the first groove  72  and sheathed with the projected body  281  of the barometric sensing element  28 . 
     Referring to  FIG. 6 , a top of the circular ring body  24  of the air suction-ventilation device  20  is connected with an upper cap  201 , a top of the upper cap  201  is provided with an insertion slot  202 , and a bottom of the insertion slot  202  is provided respectively with a first through-hole  203 , a second through-hole  204 , and a connection hole  205 . 
     The touching element  22  can be an elliptical housing, with an interior being provided respectively with a first rod  221  and a long rod  223 . The touching element  22  is loosely inserted into the insertion slot  202  and can displace up and down vertically in the insertion slot  202 . The first rod  221  can be inserted into the first through-hole  203 , and the long rod  223  can be inserted into the connection hole  205 . 
     The circular ring body  24  is provided with an internal chamber  27 , and an interior of the internal chamber  27  is provided respectively with a left projected body  271  and a right projected body  272 . Connection ends of the left and right projected bodies  271 ,  272  are connected respectively with metallic conducting pieces  273 ,  274  to serve as connection of electrodes  258  of the air suction pump  25 . Other ends of the left and right projected bodies  271 ,  272  are connected respectively with the metallic upper spring leaf  262  and lower spring leaf  261 . Two contact ends of the upper and lower spring leaves  262 ,  261  can be contacted and separated properly, to control electric activation and deactivation of the air suction pump  25 . 
     An interior of the internal chamber  27  is further provided with the rectangular recess  60  (as shown in  FIG. 4 ), an interior of the rectangular recess  60  is provided with an inner circular groove  61 , a bottom of the inner circular groove  61  is provided with a connection hole  62 , and along a periphery of the connection hole  62  is provided with at least one first venthole  63 . 
     An upper surface of a flexible membrane element  29  is a circular membrane  293 , a lower end is provided with a cone-shape pillar  291  and a neck part  292 , the cone-shape pillar  291  is transfixed and tightly fitted into the connection hole  62 , the circular membrane  293  is loosely connected into a slot surface of the inner circular groove  61  to close and open the first venthole  63 , a side of the inner circular groove  61  is concaved with a second access  64 , and a tail end of the second access  64  is put up with a post  65 . 
     A side of the inner circular groove  61  is concaved with a first access  66 , and a tail end of the first access  66  is formed with a small circular groove  661 . 
     Referring to  FIG. 4  and  FIG. 5 , an interior of the rectangular recess  60  is emplaced with a first soft plate  40 , and a body of the first plate  40  is provided respectively with a large circular hole  41 , a first through-hole  42 , with a hole wall being linearly disposed with a first trench  421  correspondingly mantled on the first access  66  in the rectangular recess  60  to form an air passage; and a second through-hole  43 , with a hole wall being linearly disposed with a second trench  431  tightly fitted into the post  65  of the rectangular recess  60  to form an air gap  432 . The second trench  431  is correspondingly mantled on the second access  64  to form an air passage, and the large circular hole  41  is sheathed on a side surface of a projected ring  611  of the inner circular groove  61 . 
     Referring to  FIG. 4  and  FIG. 5 , an interior of the rectangular recess  60  is emplaced with a second hard plate  50  which is mantled on a surface of the first plate  40 , and is provided respectively with an inner groove  52  (as shown in  FIG. 5 ), an interior of which being provided with an air permeable hole  521 , and which being correspondingly mantled into the large circular hole  41  of the first plate  40 ; a first air permeable hole  53 , which is correspondingly connected with the first through-hole  42  on the first plate  40 ; a second air permeable hole  54 , which is correspondingly connected with the second through-hole  43  of the first plate  40 ; and a linear trench  55 , which is formed on an upper surface of the second plate  50 , with a tail end of the trench  55  forming a small circular groove  551 . 
     Referring to  FIG. 4 , the second venthole  236  is connected with the first access  66  which is in a linear trench-shape, and with the small circular groove  661 . Above the small circular groove  661  is connected with the first through-hole  42 , wherein the first trench  421  is correspondingly connected with the first access  66 ; the first through-hole  42  is correspondingly connected with the first air permeable hole  53 ; the first air permeable hole  53  is correspondingly connected with the first through-hole  2824 , and the first air permeable hole  75  on the third plate  70 ; the first air permeable hole  75  is correspondingly connected with the first guide hole  2573 ; the first guide hole  2573  is correspondingly connected with the first air duct  253 ; and the top end of the first air duct  253  is connected with the first through-hole  203 . Therefore, when the rod  221  is pressed down, the first through-hole  203  will be closed, and no air will be guided (as shown in  FIG. 6 ). 
     Referring to  FIG. 4  and  FIG. 5 , the third venthole  235  is connected with the second access  64 , which is in a linear trench-shape; the second through-hole  43  on the first soft plate  40  is loosely fitted into the post  65 ; the circular groove  651  below the post  65  forms the air gap  432  into which the air is connected, along with the second through-hole  43 ; and the circular groove  651  is connected with the second access  64 . The linear trench  431  is corresponding to and connected with the second access  64  to form a passage, the air gap  432  is formed between the post  65  and the second through-hole  43 , the second air permeable hole  54  is transfixed with the post  65 , the air gap  432  is formed between the second air permeable hole  54  and the post  65 , and the hollow chamber  2811  of the barometric sensing element  28  is covered into the second air permeable hole  54 . 
     The outer periphery of the inner circular groove  61  is provided with the projected ring  611 , the large circular hole  41  is sheathed with the projected ring  611 , and is mantled and closed by the inner groove  52 . A top of the air permeable hole  521  in the inner groove  52  is correspondingly connected with the lower movable valve reed  2822 , the lower movable valve reed  2822  is corresponding to the through-hole B ( 742 ), and the through-hole B ( 742 ) is correspondingly connected with the air driving chamber  2572 , which is in a sealed condition (as shown in  FIG. 13 ). 
     The linear trench  55  on the surface of the second plate  50  is correspondingly connected with the air access  2825  (as shown in  FIG. 5 ), the second through-hole  2823  is corresponding to the small circular groove  551 , the lower hole end of the through-hole A ( 741 ) is corresponding to the upper movable valve reed  2821 , and the upper hole end of the through-hole A ( 741 ) is correspondingly connected with the air driving chamber  2572 . 
     Referring to  FIG. 12 , when the touching element  22  is pressed down and the upper cover  10  is suppressed on the horizontal surface  351  by human fingers, the soft gasket  30  can flexibly deform downward and be tightly fitted on the surface  351 . At this time, the container space  12  will be diminished a little by this downward deformation of the soft gasket  30 , and the local air  90  in the container space  12  will flow respectively into the first, second, and third venthole  63 ,  236 ,  235 . 
     Referring to  FIG. 14 , when the air  90  flows into the first venthole  63  from the air suction-ventilation hole  206 , the air pressure is sufficient to attack the circular membrane  293  to deform, so as to form an air gap, allowing the air  90  to enter into the inner circular groove  61  and the inner groove  52 , and then, through the air permeable hole  521 , to force the lower movable valve reed  2822  to open upward an air gap for the air to flow into the through-hole B ( 742 ), the first groove  74 , and the air driving chamber  2572 . As the air driving chamber  2572  is a closed type, the return flow of air will suppress the upper movable valve reed  2821  to deform downward, thereby forming an air gap (as shown in  FIG. 4 ). Therefore, the air  90  will flow along the trench  55 , and be driven out of the insertion slot  202  through the second through-hole  2823 , the second air permeable hole  76 , the second guide hole  2574 , the second venthole  254 , and finally the second through-hole  204  (as shown in  FIG. 6 ), which further allows the container space  12  to be diminished due to ventilation. In addition, as shown in  FIG. 4 , the air  90  will flow into the second access  64  and the circular groove  651  from the third venthole  235 , and be expelled upward into the chamber  2811  along the second through-hole  43 , allowing the chamber  2811  to flexibly displace and to be restored upward, thereby lifting up the projected body  281 . On the other hand, the air  90  will flow into a linear air passage constituted by the first trench  421  and the first access  66  from the second venthole  236 , and flow upward through the first through-hole  42 , the first air permeable hole  53 , the first through-hole  2824  (as shown in  FIG. 5 ), the first air permeable hole  75 , the first guide hole  2573 , and the first air duct  253 . At this time, due to that the first air duct  253  is inserted into the first through-hole  203 , an exit of the first through-hole  203  is closed by being inserted with the first rod  221  (as shown in  FIG. 6 ), and therefore, the air  90  can only flow until the first through-hole  203 . 
     Referring to  FIG. 7 , when the touching element  22  is pressed down, a manual ventilation operation is performed, wherein the first rod  221  is inserted to close the first through-hole  203 , the long rod  223  is extended out of the connection hole  205 , and an end part of the long rod  223  abuts at the upper spring leaf  262  to flexibly deform downward. In a mean time, as the chamber  2811  is filled with the air, the projected body  2811  will drive the lower spring leaf  261  to flexibly displace upward. As the projected body  281  is abutted with the lower spring leaf  261 , the contact ends of the upper and lower spring leaves  262 ,  261  are in touch with each other electrically to conduct an electric circuit for activating the air suction pump  25 . Therefore, the off-center shaft  250  will rotate along an arc line to drive the air driver  257  to displace up and down intermittently, allowing a container space of the air driving chamber  2572  to be diminished and enlarged intermittently (as shown in  FIG. 14  and  FIG. 15 ). When the space of the air driving chamber  2572  is diminished, an air driving operation is manifested (as shown in  FIG. 15 ); whereas, when the space of the air driving chamber  2572  is restored (or enlarged), an air suction operation is manifested. The air suction operation is described as follows. 
     Referring to  FIG. 14 , the upper movable valve reed  2821  displaces upward to seal the through-hole A ( 741 ), the lower movable valve reed  2822  deforms upward to form the air gap, and the through-hole B ( 742 ) is opened. Therefore, an edge of the circular membrane  293  will deform upward to form the air gap  432 , and the air  90  in the container space  12  will flow through the air gap  432  from the first venthole  63 , be drained out of the through-hole B ( 742 ) next, and then enter into the second groove  74  and the air driving chamber  2572 . As the air driving chamber  2572  is closed, the air  90  will be returned in the air driving chamber  2572  and the second groove  74 . 
     For the air driving (draining) operation, please refers to  FIG. 15 , wherein the projected body  2571  displaces downward to flexibly compress the air driving chamber  2572 , allowing the air pressure to operate on the surface of the upper movable valve reed  2821 , such that an air gap is opened downward by the upper movable valve reed  2821 . On the other hand, the air permeable hole  521  is closed by the lower movable valve reed  2821  by the operation of air pressure, and the air will flow through the air gap to the air access  2825 , the second through-hole  2823 , the second air permeable hole  76 , and the second air duct  254  (as shown in  FIG. 5 ). As a tube end of the second air duct  254  passes through the second through-hole  204  as shown in  FIG. 6 , and is further connected with the insertion slot  202  of the upper cap  201 , ambient air is connected. Therefore, the air flow in the air driving chamber  2572  and the second groove  74 , as shown in  FIG. 15 , will be expelled out by the second air duct  254 . At this time, as the lower movable valve reed  2821  is closed, the circular membrane  293  will close the first venthole  63 , and the air in the container space  12  will not be conducted into the first venthole  63 . 
     For the displacement operation of the projected body  281  of the barometric sensing element  28 , please refers to  FIG. 10 , wherein when the barometric value P 1  inside the container space  12  decreases continuously, the air will be expelled into the container space  12  through the chamber  2811 , the second air permeable hole  54 , the second through-hole  43 , the circular groove  651 , the second trench  431 , the second access  64 , and further the third venthole  235 , allowing the chamber  2811  to be flexibly shrunk and diminished. In addition, the projected body  281  is descended (as shown in  FIG. 15 ), which further drives the lower spring leaf  261  to descend, allowing the lower spring leaf  261  to be released from the upper spring leaf  262 , and the electric circuit to be at an off state (as shown in  FIG. 9 ). Therefore, the air suction pump  25  will stop working. At this time, the barometric value P 1  of the container space  12  is much lower than the barometric pressure of the ambient air, to form a negative pressure condition. Hence, food or objects (not shown in the drawing) in the container space  12  will be kept fresh. 
     Referring to  FIG. 11 , if the soft gasket  30  leaks, the ambient air will penetrate into the container space  12 , and the barometric pressure P 1  will rise up. As shown in  FIG. 4 , as the air in the container space  12  will first pass through the first venthole  235 , the second access  64 , the circular groove  651 , and the second through-hole  43 , and further enter into the chamber  2811 , allowing the chamber  2811 , which was originally in a diminished state, to be restored gradually, which enables the projected body  281  to displace upward slowly, to simultaneously drive the contact end of the lower spring leaf  261  to displace upward, to touch the contact end of the upper spring leaf  262  (as shown in  FIG. 7 ), thereby energizing the electric circuit (or enabling the electric circuit to be in an on state) and activating the air suction pump  25  to carry out the aforementioned reciprocative operation of air driving and suction, so as to draw the air  90  in the container space  12  out of the upper cover  10 . When the barometric pressure P 1  of the container space  12  decreases again to a certain value, similarly, the lower spring leaf  261  will be released from the upper spring leaf  262 , the electric circuit is put in the off-circuit condition, and the air suction pump  25  stops working. When the container space  12  is in the negative pressure condition, the upper cover  10  will be pulled up from the surface  351 , by the operations as described below. 
     Referring to  FIG. 8 , the touching element  22  is grabbed and pulled upward by the human fingers, allowing the touching element  22  to displace upward in the insertion slot  202 , as shown in  FIG. 6 . The long rod  223  will displace upward from the connection hole  205 , which further enables the upper spring leaf  262  to be restored upward, and the first rod  221  to displace upward in the first through-hole  203 . Therefore, the first through-hole  203  will be connected with the ambient air; the ambient air will enter into the first air duct  253 , the first air permeable hole  75 , the first through-hole  2824 , the first air permeable hole  53 , the first through-hole  42  and the first trench  421 , through the first through-hole  203 ; and the first trench  421  will be connected with the first access  66 . Therefore, the air will be driven into the container space  12  from the second venthole  236 , the barometric value P 1  of the container space  12  will increase, and the negative pressure condition will disappear. Hence, the soft gasket  30  at the lower edge of the upper cover  10  will be flexibly restored upward to easily escape from the surface  351 , such that the upper cover  10  can be easily removed (as shown in  FIG. 10 ). 
     It is of course to be understood that the embodiments described herein is merely illustrative of the principles of the invention and that a wide variety of modifications thereto may be effected by persons skilled in the art without departing from the spirit and scope of the invention as set forth in the following claims.