MAGNETIC FIELD GENERATOR FOR THERAPEUTIC PURPOSES

Abstract: A magnetic field generator generates a magnetic field with an extremely low frequency, for therapeutic purposes. The generator produces simultaneously both a delta wave frequency and a second frequency which will be determined for each patient. The generator is housed in a small casing (64) which can be carried on the person, and the electromagnetic field is produced by a coil (62) which surrounds a core (60). The core is provided by the battery which acts as the power source for the generator.

Description: MAGNETIC FIELD GENERATOR FOR THERAPEUTIC PURPOSES This invention relates to a magnetic field generator for generating a therapeutically-useful magnetic field. The invention is particularly, but not exclusively, concerned with a portable, self-contained generator which can be easily attached to or worn on the human body. There have been many instances in recent years where the exposure of a patient to a magnetic field has been shown to have a therapeutic effect. The reasons for this are not clearly known, but it is apparent that a magnetic field can have a beneficial effect. Examples of such effects are described in, inter alia, US patents 4 501 265, 4 550 714, 4 574 809 and 4 616 629. British patent 2 156 679 describes such a generator which has a first oscillator for generating a delta-wave frequency, a second oscillator for generating a second frequency which corresponds to a brain wave frequency, mean for mixing the generator frequencies, and an electromagnet adapted to be powered by the pulses produced by the oscillators. The extremely low frequency electric currents produced by activity of the human brain are conventionally classified into the following frequency bands: It is known that the inductance and thus the field strength produced by an electromagnet is substantially enhanced if a soft iron or other magnetically susceptible core is placed within the coil. The use of such a core is associated with a certain volume and additional weight which are disadvantageous when attempting to produce a generator in a small package. According to the present invention there is provided a battery-powered magnetic field generator having a first oscillator for generating a delta-wave frequency, a second oscillator for generating a second frequency which corresponds to a brain-wave frequency, both oscillators being arranged to operate at extremely low frequencies (ELF) below 200 Hz, means for mixing the generated frequencies, a coil adapted to receive the pulses produced by the oscillators and a battery, wherein the coil is arranged around the battery so that the coil and the battery between them form an electromagnet of which the battery is the core. The battery may be a disc-shaped battery of the type commonly sold for use in electronic wrist watches, and in a preferred embodiment the battery is a lithium battery. We have surprisingly found that such batteries, which are contained within a steel casing, have a very much better effect in enhancing the inductance of the core than does a plain steel core. A lithium battery is noticeably superior in this respect to a silver oxide battery which in turn is noticeably superior to a steel core. The coil is preferably circular and the battery and the coil are arranged coaxially. The generator is preferably controlled by a microcomputer which may be contained on a single chip. The microcomputer includes an oscillator which generates regular accurate pulses using an external crystal as the accurate reference. The oscillator controls a counter/timer, and a central processing unit uses the counter/timer to generate pulses at the correct frequency for the delta wave and for the second frequency output. The CPU preferably has a user controlled input through which the second frequency can be set. The input can be in the form of push buttons, and at least one of the push buttons necessary to set the second frequency can be mounted inside the generator casing so that it is not normally accessible to the user. In one convenient embodiment, the microcomputer which controls the generation of the necessary frequencies also has a real time clock function, so that the unit functions as a conventional watch, in addition to its function as a generator. The generator can be of a size such that it can be worn on a strap on the wrist or on a chain hanging around the neck or clipped to clothing. In this case, the oscillator, counter/timer and central processing unit with associated random access memory and read only memory are all common to the watch and generator functions of the unit. The unit preferably has a liquid crystal display screen on which the time is normally displayed. However when the second frequency is to be set, then the LCD can display the frequency setting. The invention will now be further described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a circuit diagram of a magnetic field generator according to the prior art; Figure 2 is a block diagram showing a particular embodiment of generator in accordance with the invention; Figure 3 shows the exterior of the generator of Figure 0 2; Figure 4 is an underneath plan view of the generator of Figures 2 and 3, partly in section; 15 Figure 5 is a side view of the generator of Figures 2, 3 and 4; and Figure 6 illustrates the electro magnetic field produced by the generator of Figures 2 to 5. 20 In Figure 1, a first oscillator circuit 10 and a second oscillator circuit 12 are supplied with power from a battery along the line 14. The oscillator 10 is set to provide output pulses along the line 16 at a frequency of 1.15 Hz, 25. ie at a delta wave frequency. The second oscillator 12 includes three parallel switches 18, 20 and 22. The closure of any one of these switches will produce a pulse output in the line 24 at a frequency of 4.4, 9.7 or 14.2 Hz respectively, equivalent to a brain wave frequency. The two 30 pulsed signals are each passed through a resistor 26, 28 and a capacitor 30, 32 to a transistor 34 which feeds an electro magnetic coil 36. The transistor has the function of mixing the pulsed signals from the oscillators 10 and 12 and 35 switches the coil 36 on and off in accordance with the frequency of the pulsed signal. Suitably the electro¬ magnetic coil 36 can comprise 600 turns of 0.2mm diameter wire wound around a steel bolt 6mm in diameter and 40mm long. This prior art generator is relatively bulky and also has the disadvantage that the second frequency has only three possible settings. Figure 2 shows a generator to be housed in a wrist watch-sized casing or housing. That part of the generator shown within the dotted line 11 will be provided on a single chip four bit micro computer. Externally of the chip there will be an LCD 7-segment display 13, a quartz crystal 15, a three volt lithium battery 17, a set of four pushbuttons 19 through which the computer can be set, and a coil 21 with an associated driver transistor 23. On the chip, an oscillator 25 is connected to the crystal 15. The oscillator generates regular accurate pulses for a counter/timer 27 using the crystal 15 as the accurate reference. A central processing unit (CPU) 29 uses the counter/timer 27 to generate pulses at the correct frequency. In this respect, three sets of frequencies are necessary a) a delta wave frequency b) a "second frequency" which will be set for each particular patient, and c) a clock frequency for a real time clock. The software which the CPU 29 needs to operate is contained in a read only memory 31, and a random access memory 33 is used to store information that is temporary and/or is changed during operation, eg the current time of day required by the real time clock. An LCD driver circuit 35 is connected to the CPU. The chip also has an input port 37 and an output port 39. When first being set up, the time of day displayed on the LCD display 13 is adjusted using a time set button 41 to place the unit in the correct mode, and then using a step up button 43 or a step down button 45. The CPU can read the input from these buttons via the input port 37. If the step down button 45 is pressed on its own, the display 13 changes from showing the time of day to showing the value of the second frequency. This frequency can be changed by pressing the step up and step down buttons 43 and 45 in conjunction with a frequency set button 47. The frequency set button 47 is actually located apart from the buttons 41, 43 and 45 and is inside the back of the casing to prevent the user from altering this setting. In practice this frequency setting will be set by the qualified person who prescribes the generator, in accordance with brain wave data collected from that particular patient. The complex wave form output from the CPU 29 is fed from the output port 39 to the transistor 23 which drives the coil 21. Diodes 49 in the driver circuit protect both the chip and the transistor from damage caused by back EMF produced by the coil. Figure 4 shows the physical form of the generator which is contained within a casing 64. The LCD display 13 appears on one face of the casing, and the time set button 41 together with the step up and step down buttons 43, 45 are accessible on the outside of the casing. The frequency set button 47 is however arranged inside the housing behind a removeable back panel 65. The entire unit can be mounted on a wrist strap 67, as is conventional for digital electronic wrist watches. Figure 5 and 6 show more details of the physical construction. The battery 60 which is a circular three volt lithium type battery is mounted centrally within the coil 62 and forms the core for the coil as well as providing the power source for the generator. Figure 6 shows how the circuit is constructed on a double-sided circuit board 66 populated on one side with the surface mounted chip 11. On the reverse side is mounted the coil which is self-formed and then bonded to the board. The coil uses the battery as a core which sits in the centre of the coil with the battery negative contact face down on a contact on the board. The positive terminal of the battery is electrically connected to the board through a phosphor- bronze spring 70. One end of the spring is fixed to the board, and the other end extends over the top of the battery and has a free end which is pressed into the battery terminal when the casing 64 is closed. The spring also holds the battery in place. By using the battery as a core for the coil, sufficient field strength can be produced to maintain effectiveness. Typically the diameter C of the battery 60 will be 20mm, the internal diameter B of the coil will be 22 mm and the external diameter 25mm. This will allow for a 2mm air gap 72 between the battery and the coil. Figure 6 shows the configuration and extent of the magnetic field produced by this generator. Where the field strength amounts to 400 micro amps per metre, the dimensions D which refer to the boundaries 74 of the useable magnetic field, have been found to extend to 35mm each, and the dimension Ξ to 60mm. A three volt lithium battery used in this application has been found to have a useable life of about three months before needing replacement. Replacement of the battery will be signalled by the LCD display (which will normally be showing the time of day) beginning to fade. This will therefore indicate to the user that the magnetic field produced by the generator is beginning to fade and that the battery should be replaced. Tests have been carried out to determine the inductance of the coil using various different cores, but the same coil each time. The results were as follows: Core Material Inductance Air 26.5 millihenrys Steel 26.7 millihenrys Silver Oxide battery 28.0 millihenrys Lithium battery 30.5 millihenrys Soft Iron 31.0 millihenrys Lithium batteries from three different manufacturers (Duracell, Sanyo, Varta) were tested and all gave the same result. The selection of the second frequency will be set by the qualified person who is prescribing the device after having taken electroencephalograph (or other equivalent instrument) readings for that particular patient. The actual frequency chosen for the second frequency for that patient will depend on the results achieved and the ailment which the device is intended to treat. Tests have shown that a generator of the kind described can be effective in particular for the treatment of migraine. There are however positive indications that the generator can be helpful to lower back pain, to other disorders of the sciatic nerve, to osteoarthritis and in cases of hypertension in lowering blood pressure. It is thought that the reproduction of brain wave frequencies in the generator may stimulate production of those same frequencies by the brain itself. It has been established by other work that alpha- and beta- brain waves cause the blood capillares in the body to contract, thus slowing down blood flow. Delta- and theta- wave frequencies have an opposite effect. Thus it may be that the generator of the present invention enhances those effects which result from particular brain wave frequencies.

Claims: CLAIMS : 1. A battery-powered magnetic field generator having a first oscillator for generating a delta-wave frequency, a second oscillator for generating a second frequency which corresponds to a brain-wave frequency, both oscillators being arranged to operate at extremely low frequencies (ELF) below 200 Hz, means for mixing the generated frequencies, a coil adapted to receive the pulses produced by the oscillators and a battery, wherein the coil is arranged around the battery so that the coil and the battery between them form an electromagnet of which the battery is the core. 2. A generator as claimed in Claim 1, wherein the battery is a disc-shaped battery of the type used in wristwatches. 3. A generator as claimed in Claim 2, wherein the battery is a lithium battery. 4. A generator as claimed in any preceding claim, wherein the coil is circular and the battery and the coil are arranged coaxially. 5. A generator as claimed in any preceding claim, which includes a microcomputer, and the microcomputer includes an oscillator and a central processing unit which generates pulses at the correct frequency for the delta wave and for the second frequency output. 6. A generator as claimed in Claim 5, wherein the CPU has a user controlled input through which the second frequency can be set. 7. A generator as claimed in Claim 6, wherein the input is in the form of pushbuttons and at least one of the pushbuttons necessary to set the second frequency is mounted inside the generator casing so that it is not normally accessible to the user. 8. A generator as claimed in any one of Claims 5 to 7, wherein the microcomputer also has a real time clock function. 9. A generator as claimed in any one of Claims 5 to 8, including a visual display and where the value of the second frequency can be displayed on the visual display. 10. A generator as claimed in any preceding claim, mounted on a wrist strap so that it can be worn on the wrist. 11. A generator as claimed in any one of Claims 1 to 9, provided with a clip by which it can be attached to clothing. 12. A generator as claimed in any one of Claims 1 to 9, attached to a chain by which it can be hung around the neck.

Inventors: WALPOLE STEPHEN JOHN, WALPOLE, STEPHEN, JOHN
Applicants: ELECTROMAGNETIC THERAPIES LIMI, ELECTROMAGNETIC THERAPIES LIMITED
Application year: 1988
Main classification: A61N1
IPC codes: A61N2