Abstract:
An improved electrostatic generator comprising a pair of contra-rotating disks, each bearing a plurality of conducting sectors, similar to the prior art Wimshurst generator. A plurality of grounding conductors with brushes at each end are associated with each of two counter-rotating disks, each grounding conductor alternately grounding a pair of opposing charge plates on each disk as it rotates. The generator also includes a pair of output terminals each having a brush at one end for electrical connection to the charge plates on one of the disks. Upon counter-rotation of the pair of disks, the grounding conductors induce each charge plate to accumulate a logarithmically-increasing charge until they are discharged to the next output terminal. The accumulating charge makes the device far more efficient than a conventional Wimshurst generator.

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S)  
       [0001]    The present application derives priority from U.S. Provisional Application No. 60/191,064 filed Mar. 21, 2000. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    1. Field of the Invention  
           [0003]    The present invention relates to electrostatic generators and, more particularly, to an improved high-voltage electrostatic generator having a plurality of electrostatic energy collection means around the circumference of the contra-rotating apparatus.  
           [0004]    2. Description of the Background  
           [0005]    Electrostatic generators are well known and have been commercially available for over a century. Their purpose is to convert mechanical energy, such as that delivered through a rotating shaft by an electric motor or a manual crank, into high-voltage, low-current electrical energy. Electrostatic energy is an important constituent of many modern technologies, including high-energy physics and electronic medical diagnostics.  
           [0006]    An early electrostatic generator was invented by J. Wimshurst in England in 1883. The Wimshurst generator consists of two contra-rotating disks mechanically connected around the same shaft and mechanically driven by belts and pulleys. Each of the disks contains an equal number of evenly spaced regions called sectors around its periphery, on which a conducting foil is applied. The contra-rotating disks with conducting foil sectors are closely spaced to induce an electrostatic charge between them.  
           [0007]    Referring now to FIG. 1, a prior art Wimshurst generator is shown with the contra-rotating disks  10 ,  20  presented as concentric and a plurality of foil sectors  12 ,  22  spaced evenly there about. It is to be understood that in this prior art embodiment the disks are of equal diameter with an equal number of evenly spaced conductive foil sectors  12 ,  22 . Two neutralizing bars  31 ,  34  with end contact brushes  32 ,  33  and  35 ,  36 , respectively, ground and neutralize charged foil sectors  12 ,  22  as they come into contact. In operation, when mechanical rotational energy is applied to the shaft from a hand crank, an electric motor, a flywheel, or any other source, two identical functions take place on each contra-rotating disk  10 ,  20 , one producing a positive electrostatic charge and one producing a negative electrostatic charge. A region of positively charged foil sectors on one disk is brought near a region of neutral foil sectors on the other disk. The positive foil sectors induce a negative charge in the nearby neutral foil sectors on the other disk. The positive charged foil sectors pass under the next adjacent contact brush, e.g, brush  35  of the arm of neutralizing bar  34  which discharges the positive surface electrostatic charge. The formerly neutral foil sectors  12  are now negatively charged, and as they move in the opposite direction from the positively charged foil sectors on the other disk and approach neutral foil sectors. Now these negatively charged foil sectors act as the charged surface to induce a positive electrostatic charge in the neutral foil sectors on the first disk when they touch a contact brush of the second neutralizing bar  35 . As the disks turn, the neutralizing bars  34 ,  35  become energy producing systems, one always producing a positive electrostatic charge and one producing a negative electrostatic charge. Given the above-described configuration, the rotating foil sectors on both disks will reach a point where they both carry a positive electrostatic charge in one segment. Likewise, the opposing foil sectors on both disks will both carry a negative electrostatic charge in an opposite segment. Collectors  41 ,  44  with end contact brushes  42 ,  43 ,  45 ,  46  are located in these two segments collect the respective charges. The result is a high-voltage electrostatic differential. The charges derived from collectors  41 ,  44  can be stored in capacitors for discharge of high energy, and in traditional systems the Leyden jar is used as a capacitor that is well known to those of ordinary skill in the relevant art.  
           [0008]    In this manner, mechanical energy is converted to electrostatic energy. In prior applications of the Wimshurst generator, the amount of energy is increased by increasing the size of the disks. The efficiency of the system is also limited by the number of energy producing systems, there being only two in the above-described example. In other words, the induced charges have to remain on the charged sectors for a significant angular extent before they reach the next collector  41 ,  44 . This leads to inefficiency because ionization losses occur during rotation. It would be greatly advantageous to provide a more efficient electrostatic generator with increased efficiency and energy capacity. In so doing, while the amount of mechanical energy required to operate the generator would increase, the physical apparatus could be more compact and robust. A more compact generator and robust unit could find uses where previously electrostatic generators of this type were too large.  
           [0009]    There have been a few prior efforts to improve the efficiency of the basic Wimshurst generator. These include improvements such as disks rotating on a single shaft in the same direction, multiple stages of disks, and electrical contacts using conducting pulleys and embedded pellets. An example of all of these developments is described in U.S. Pat. No. 4,789,802 to Miyake. However, when produced with multiple stages, the Miyake generator is much larger and more complicated and more expensive than a Wimshurst generator of the same diameter. The Wimshurst generator, as well as another electrostatic generator known as the Van de Graf generator, are most commonly used to demonstrate electrical and physical phenomena to students. The Van de Graf generator is more commonly used because for a given size it generates greater electrostatic voltage. However, the Wimshurst machine is more easily constructed by students and educators and its components are visible, allowing a more thorough exploration of its function. The scientific and educational benefit of the device is only hampered by its complexity. It would be greatly advantageous to inventors, scientists, educators, students, and hobbyists to provide a more efficient Wimshurst-type electrostatic generator that Is smaller and no more complicated or expensive than the traditional Wimshurst generator.  
         SUMMARY OF THE INVENTION  
         [0010]    It is, therefore, an object of the present invention to provide an electrostatic generator that increases the amount of electrostatic charge and electrostatic voltage differential that can be acquired in a compact apparatus.  
           [0011]    It is another object to provide an inexpensive and facile electrostatic generator that can be constructed and operated by inventors to explore applications of electrostatic energy.  
           [0012]    It is a further object to provide an electrostatic generator that readily demonstrates principles of electrostatic energy to students.  
           [0013]    In accordance with the above objects, an improved high-voltage electrostatic generator is disclosed. The generator includes a pair of counter-rotating disks. Each disk has a plurality of charge plates angularly disposed about the periphery on one side, the charge plates on one disk facing those on the other. A plurality of grounding conductors with brushes at each end are associated with each of the disks, each grounding conductor alternately grounding a pair of opposing charge plates on each disk as it rotates. The generator also includes a pair of output terminals each having a brush at one end for electrical connection to the charge plates on one of the disks. Upon counter-rotation of the pair of disks, the grounding conductors induce each charge plate to accumulate a logarithmically-increasing charge until they are discharged to the next output terminal. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]    Other objects, features, and advantages of the present invention will become more apparent from the following detailed description of the preferred embodiment and certain modifications thereof when taken together with the accompanying drawings in which:  
         [0015]    [0015]FIG. 1 is a schematic diagram of a conventional electrostatic generator of the Wimshurst type to explain the principle and operation thereof.  
         [0016]    [0016]FIG. 2 illustrates one preferred embodiment of an improved electrostatic generator according to my invention.  
         [0017]    [0017]FIG. 3 is a schematic representation of the above-described electrostatic generator A shown side-by-side with a conventional Wimshurst generator B for illustration.  
         [0018]    [0018]FIG. 4 is a side perspective view illustrating a completed mechanical assembly for implementing the above described generator of FIG. 2.  
         [0019]    [0019]FIG. 5 is a front detailed illustration of the metallic ring  14  of FIG. 4.  
         [0020]    [0020]FIG. 6 is an example of unacceptable variations on the generator of FIG. 2 in which the number of charge plates  11 ,  12  on each disk produce conflicting polarities. Conflicting polarities means that pairs of opposing charge plates  11 ,  12  have the same polarity.  
         [0021]    [0021]FIG. 7 is an example of acceptable variations on the generator of FIG. 2 in which the number of charge plates  11 ,  12  on each disk do not produce conflicting polarities. Conflicting polarities occur whenever the number of charge plates per disk  10 ,  20  are double an even number. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0022]    Referring now to FIG. 2, a preferred embodiment of an improved electrostatic generator is shown according to my invention. Ten charge plates  30 - 39  are uniformly spaced around a first rotating disk  10 , and ten charge plates  40 - 49  are uniformly spaced around a second counter-rotating disk  20 . The charge plates are conveniently represented by a series of condensers arranged in two circles. As the two disks  10 ,  20  counter-rotate, a pair of opposing charge plates  37 ,  47  on disks  10 ,  20  will contact output connector  160  at the same time that an opposing pair of charge plates  37 ,  47  on disks  10 ,  20  will contact output connector  170 . The contact with the foregoing and all other charge plates  30 - 49  is accomplished via twelve identical contact brushes  130 - 141 . Four grounded neutralizing brushes  131 ,  135 ,  137  and  141  are in operative contact with the respective charge plates  41 ,  44 ,  46 ,  49  on disk  20 . Similarly, four grounded neutralizing brushes  130 ,  134 ,  136  and  140  are in operative contact with the respective charge plates  30 ,  33 ,  35  and  38  on disk  10 . With this configuration, all charge plates on each disk that are not in contact with output connectors  160 ,  170  are alternately either grounded or left open. Thus, as charge plates  37 ,  47  on disks  10 ,  20  are contacting output connector  160  and charge plates  37 ,  47  on disks  10 ,  20  are contacting output connector  170 , charge plates  30 ,  33 ,  35  and  38  around disk  10  are grounded by respective brushes  130 ,  134 ,  136  and  140 . Likewise, charge plates  41 ,  44 ,  46  and  49  around disk  20  are grounded by respective brushes  131 ,  135 ,  137  and  141 .  
         [0023]    In contrast to the dual-energy producing system as shown in FIG. 1 (prior art), the present invention employs multiple energy producing systems. With reference to the top center area of FIG. 2, as the disks  10 ,  20  counter-rotate, opposite charge plates  30 ,  40  pass and a net charge on one will induce an opposite charge in the other, resulting in a net gain in electrical energy (a conversion of mechanical to electrical energy). Ungrounded charge plates  31 ,  43 ,  34 ,  45 ,  36 ,  48 ,  39  and  40  determine the polarity of each sector. Thus, for example, as the charge plate  40  subsequently encounters brush  131 , this permits contact allowing electrons to be transferred to ground to balance the charges and maintain the increased energy of the new position. This subcycle repeats as the disks  10 ,  20  rotate. With each new position there is a net gain of energy, e.g., an increase in the number of electrons within each charge plate  30 ,  40 . Thus, brushes  130 ,  131 ,  134 ,  135 ,  136 ,  137 ,  140  and  141  increase the charge on the contacting plates before the plates reach the collector output connectors  160 ,  170 . The charging cycle continues until the charge plates  30 ,  40  make contact with the next terminal output connectors  170 . Terminal connectors  160 ,  170  receive the same charge polarities from both disks  10 ,  20  as they turn in opposite directions. Both discs  10  and  20  must turn in order to renew charges on all charge plates  30 - 49 . For example, if one disk  10  or  20  ceased to turn, charge plates  30 ,  40  would soon lose their charge and there would be nothing to produce a charge on either disk  10  or  20 .  
         [0024]    It follows that the greater the number of charge plates and brushes, the higher the induced voltage on the collector output connectors  160 ,  170 . Since ungrounded charge plates  31 ,  43 ,  34 ,  45 ,  36 ,  48 ,  39  and  40  determine the polarity of each sector, it also follows that an even number of sectors leaves one positive output connector  170  and one negative  160 .  
         [0025]    It should be apparent from the foregoing that the number of charge plates may vary. However, one important constraint is that the number of charge plates on each disk  10 ,  20  must be twice an odd number. Otherwise, opposing charge plates may have the same polarity, and this tends to kill any increase in voltage. Thus, any multiple of an odd number such as 6, 10, 14, 18 . . . will avoid this problem. In other words (and in terms of sectors), the number of sectors should not equal the double of any even number, whereas the double of any odd number will avoid such problems.  
         [0026]    [0026]FIG. 3A is a schematic representation of a fourteen-sector electrostatic generator A as described above, with a conventional Wimshurst generator shown in FIG. 3B for comparison. If the disks  10 ,  20  are turned mechanical energy is transferred to the system. With reference to FIG. 3A, the mechanical energy is converted to electrical energy as electrons flow toward the  20  grounded charge plates  40 ,  49 , etc. in an attempt to maintain angular position. This is true despite the fact that alternate charge plates  40 ,  49 , etc. have a common ground. As the non-grounded charge plates  30 ,  39  etc. move away from the illustrated position they carry the extra electrons with them, so they gain electrical energy by virtue of being separated from the oppositely charged plate. In this manner, every single charge plate becomes progressively charged and eventually releases its charge to the output terminals  160 ,  170 . The increase of charge on each charge plate  30 ,  40  is a multiple of its previous charge. Hence, the cumulative increase in charge follows a logarithmic pattern rather than linear. Contrasting the conventional Wimshurst generator of FIG. 3B, there is only one pair of grounded brushes  112 , 114  and  132 ,  134  per disk  10 ,  20 , respectively. With fewer charging plates 30 ,  40  to transfer energy, each charge plate  30 ,  40  simply gains an incremental charge and then discharges it during each cycle. There is no logarithmic building of charge, and clearly the conventional Wimshurst generator is less efficient because it does not use all of its energy conversion ability. The key difference is the use of multiple grounding conductors (and associated brushes) per disk with the realization that these conductors may be commonly grounded and still they will allow the charging plates to accumulate charge according to a logarithmic pattern.  
         [0027]    [0027]FIG. 4 is a side perspective view illustrating a completed mechanical assembly for implementing the above described generator of FIG. 2. Horizontal dimensions are enlarged for illustrative purposes. The assembly includes a box frame container  1 . The box frame container  1  supports two rotatable shafts  2 ,  3 . A hand crank  4  turns shaft  3 , and a large drive wheel  5  turns shaft  2 . Drive pulleys  6 ,  7  and  8  are mounted on shaft  2 . The two disks  10 ,  20  containing respective charge plates  12  (not shown) and  22  are mounted on shaft  3 . Charge plates  12 ,  22  are evenly disposed around both disk&#39;s  10  and  20 , and face each other. A central partition  24  passes between disks  10  and  20 . This partition  24  is formed with a hole  13  that encircles shaft  3 . A conductive metallic ring  14  encircles the inner edge of the hole  13 . Conventional bearing collars  18  are used as desired to rotatably support shaft  3  and to roll against the surfaces of disks  10 ,  20 . Preferably, three bearing collars  18  are used, one between the two disks  10 ,  20  and the others on the opposite sides of the disks  10 ,  20 . The middle bearing collar  18  should be thick enough to provide space for disks  10 ,  20  to clear brushes  15 ,  16 . The outer bearing collars  18  hold disks  10 ,  20  in place, and conventional spacers such as spacer  19  may be used to achieve the proper clearances. Spacer  19  abuts box frame  1  and pulley  5 . Legs  20  support frame  1 . Note that belt  21  is crossed in order to counter-rotate disks  10 ,  20  upon operation of hand crank  4 .  
         [0028]    [0028]FIG. 5 is a front detailed illustration of the metallic ring  14  of FIG. 4, which is segmented as shown in order to isolate two output terminals  22  and  23  from a plurality of conductive brushes  15 ,  16 . Brushes  15  are situate on one side of the ring  14 , and brushes  16  are on the opposite side of the ring  14 . The brushes  15 ,  16  may have a common ground, but this is not necessary inasmuch as only the charge plates  11  (see FIG. 4) carry the induced charge. The insulated output terminals  22  and  23  have brushes on both sides of the ring  14  in order to pick up charges from all charge plates  11 ,  12  on disks  10  and  20 , respectively (see FIG. 4). Conductive ring  14  may be formed aluminum foil or otherwise painted with metallic paint (metallic paint is a poor conductor for low voltage, but adequately conducts a high-voltage current). The brushes  15 ,  16  may be attached cylinders of rolled paper covered with an electrically conductive coating of metallic paint or aluminum foil. The two disks  10 ,  20  (FIG. 4) make contact with the brushes  15 ,  16  so that the charge plates  11 ,  12  on respective disks  10 ,  20  can pick up the charge. Alternate charge plates  12  on disk  10  (FIG. 4) are grounded by the brushes  15 , and alternate charge plates  11  are isolated. The isolated charge plates  11  carry a charge which induces electron flow into the brush connected plates  12  on the opposite disk  10  as described above.  
         [0029]    The mechanical configuration of FIGS. 4 and 5 is one simple and efficient way to achieve the progressive charge accumulation described above with reference to FIG. 2.  
         [0030]    In both mechanical configurations, it is critical to have an acceptable number of charge plates  11 ,  12 . The wrong number will cause conflicting polarities which will defeat voltage output.  
         [0031]    [0031]FIG. 6 illustrates two embodiments with an unacceptable number. In FIG. 6A there are  8  sets of charge plates  11 ,  12  on each disk, thereby yielding 8 voltage producing sectors. This would result in two sectors (circled) having opposing polarities. Similarly, in FIG. 6B there are 12 sets of charge plates  11 ,  12  on each disk, thereby yielding 12 voltage producing sectors two of which (circled) having opposing polarities.  
         [0032]    On the other hand, FIG. 7 illustrates two embodiments with an acceptable number. In FIG. 7A there are 10 sets of charge plates  11 ,  12  on each disk, thereby yielding 10 voltage producing sectors and no conflicting polarities. Likewise, in FIG. 7B there are 14 sets of charge plates  11 ,  12  on each disk, thereby yielding 14 voltage producing sectors and no conflicting polarities. As a general rule, the number of charge plates/sectors should not equal the double of any even number as this will cause conflicting polarities, whereas the double of any odd number will avoid such problems and produce no conflicts.  
         [0033]    Having now fully set forth the preferred embodiments and certain modifications of the concept underlying the present invention, various other embodiments as well as certain variations and modifications of the embodiments herein shown and described will obviously occur to those skilled in the art upon becoming familiar with said underlying concept. It is to be understood, therefore, that the invention may be practiced otherwise than as specifically claimed herein.