Advanced Patent Search
Home / Patents / Patent Number 06186941


A portable electronic PEMF apparatus comprises a PEMF coil, power supply, and electronic switching means contained therein. The power supply along with the switching means provide periodic electric power to the PEMF coil. The PEMF coil comprises multiple turns of a conductive wire around a core with an elongated cross section. The core comprises a magnetic shield layer of materials such as mu metal or soft iron. The power supply comprises a battery, a regulated voltage source and unregulated voltage source from the battery and electronic switching circuit, powered by the regulated voltage, for electrically connecting the unregulated voltage source to the coil. The electronic switching circuit is tuned to periodically provide power to the coil at a frequency to generate a non-inverting, varying electromagnetic field from the coil.

Inventor: Lyman L. Blackwell
Original Assignee: Orthosoft, LLC


The present invention generally relates to pulsed electromagnetic field (PENW) coils for the treatment of injuries in a patient, and more specifically to methods and apparatuses relating to portable PEMF coils, and PEMF coils with high field strength and field generating efficiency.


Traditional methods for treating certain injuries to a body (e.g., humans, animals) involve setting and immobilize the injured member to allow natural healing of the injury. Often, it is desirable that natural healing will restore damaged structures to their original uninjured condition without significant inconvenience to a patient. Traditional problems in injury treatments have been associated with the inability of the patient's body to heal correctly or rapidly and the inability of the healed part to regain fall strength and freedom of movement. These problems are especially acute in patients with suboptimal health and reduced healing capacity such as elderly, bedridden or patients with multiple disorders.

Attempts to address these problems and to promote more rapid healing have led to the use of pulsed electromagnetic fields. It is generally known that electromagnetic fields applied to a body can produce favorable biological effects. For example, FDA approved pulsed electromagnetic field (PEMF) apparatuses are available for use in bone healing. These apparatuses are used to augment and accelerate the natural healing process. PEMF is also effective in the treatment of severe injuries and fractures which are not otherwise treatable using conventional techniques.

Known methods and apparatuses which have been used to treat injuries using PEMF include the use of Helmholtz and toroidal coils to deliver PEMF. These methods and apparatuses have suffered from various deficiencies. For example, Helmholtz coils suffer from field inhomogeneity and field dropouts (e.g., the field drops to zero near the center of the coil). Toroidal coils are inefficient and have a relatively weak field strength. Further, known methods of PEMF treatment have problems associated with system complexity, large size and weight, long treatment times, weak PEMF strength and low efficiencies in promoting healing. Current devices and methods of PEMF treatment further fail to provide adequate mobility during treatment. Other drawbacks also exist.


It is an object of the present invention to overcome these and other drawbacks of the prior art.

It is another object of the present invention to provide a PEMF apparatus using a coil design that produces a single polarity magnetic field that is relatively homogenous and that maintains its field strength even at distances spaced from the coil.

It is another object of the present invention to provide a PEMF apparatus using a planar coil with a core comprising a magnetic shielding material.

It is another object of the present invention to provide a PEMF apparatus sized to allow PEMF treatment while a patient is mobile and engaged in physical activity.

It is another object of the present invention to provide a PEMF apparatus which can be incorporated as part of a cast or attached to the outside of a cast to augment the natural healing abilities of the body.

It is another object of the present invention to provide an efficient method to energize a coil to produce a single polarity PEMF that eliminates or minimizes ringing without the need for a shunt diode across the coil.

It is another object of the present invention to provide a coil for use in PEMF treatment which is deformable, flexible and pliant and easily adaptable for the application of an electromagnetic field to injuries at any location on a patient's body.

To accomplish these and other objects of the present invention, one preferred embodiment of the invention is directed to a PEMF apparatus having a coil wrapped around a core in a generally rectangular configuration with a magnetic shield located within the core. The coil comprises a plurality of turns of an electrically conductive wire, preferably with each turn having a length to width ratio of at least five. The apparatus may be deformable, flexible and pliant, and may be shaped to conform to portions of a patient's body. Advantageously, both the top and bottom surfaces of the apparatus will produce a substantially homogeneous, unipolar, non-inverting PEMF with little or no field dropout. The top and the bottom surface generate PEMF of opposite polarity. Preferably the surface generating the N polarity of the magnetic field may be positioned proximal to the portion of the patient to be treated.

According to another preferred embodiment, the core comprises a first end portion and a second end portion of a spacer material such as wood, plastic, foam, or other mat which defines a width, height and thickness. The first and second end portions may be separated by a space therebetween. A sheet of magnetic shielding material such as metal is wrapped around the first and second end portions to define a core with an inner surface and a top surface. A plurality of turns of an electrically conductive wire may be wound around the first end portion, the bottom surface, the second end portion and the top surface to form a coil. The components of the core may be attached to each other and to the coil by adhesives such as epoxy.

According to another preferred embodiment, a PEMF treatment apparatus for PEMF treatment of a patient while the patient is engaged in active physical activity is disclosed. The PEMF treatment apparatus preferably comprises a coil wrapped around a flexible core, a power supply and a solid state switching circuit connected between the power supply and the coil to drive the coil with a current at a periodic pulsed frequency to generate a non-inverting PEMF. The power supply is preferably a battery.

Other embodiments and advantages of the invention are set forth in the description taken in conjunction with the drawing figures.