Abstract:
A cable to translate a magnetic field from one end to the other end of the cable. The cable includes a plurality of axially-extending strands of magnetic core, individually surrounded by non-magnetic claddings, the strands being parallel and coherently arranged. The cable can usefully be placed in a passage through a barrier in structural and fluid sealing relationships with its wall to translate the image of a magnetic field from one side of the wall to the other.

Description:
FIELD OF THE INVENTION 
     Remote replication and translation of a magnetic field for such purposes as imaging the field, and/or for translating its energy for utilization elsewhere. 
     BACKGROUND OF THE INVENTION 
     A magnetic field&#39;s local properties are often a matter of interest and are subjected to measurement and observation by devices that are exposed to the field and act as sensors to produce a signal respective to a measured property of the field. Sensors for this purpose are well-known, and operate as magneto-inductive, magneto-resistive, bias magnetic field, and Hall effect devices, for example. Such sensors to detect, measure and analyze magnetic fields, and provide readout means for measurement purposes are well-known and are being continuously improved. 
     Such known devices function well for their intended purposes of detection and measurement. It is known for them to be used as trigger means to respond to abrupt changes in a magnetic field, for example. Their objective is to respond to a circumstance that is respective to a desired or objectionable situation. This invention is not directed toward the sensing or measurement of a magnetic field, nor to devices responsive to the strength of the field nor to a change in the properties of the field. 
     Instead, this invention is directed to the translation and replication of the magnetic field itself (or of a part thereof), which can be utilized remotely at a removed site for observation of its characteristics, and even for the electromechanical properties of magnetic flux drive as though the using device were located in the place where the magnetic field is initially generated. 
     For example, with this invention an image of the field itself can be remotely obtained, as can a wide-area flux field. The flux field is functionally identical to its “parent” but is intended for use in a remote region. Transfer of magnetic flux through a physical barrier and its ultimate utilization beyond the barrier is now attainable. 
     Rather than transmitting mechanical energy by a rotary shaft through a barrier such as a hull to a user device such as a propeller, a magnetic field now can instead be translated through a rigid immobile barrier. It can then be utilized on the outside by an exterior rotary device that could be coupled to a user device such as a propeller that is journaled outside of the hull, or to a rotatable device which can be used to generate electricity. With such an arrangement it is not necessary to provide a rotary seal around a drive shaft that is sealed and journaled in a barrier such as a hull. Instead, this device utilizes a rigid and stationary translation technique that itself seals the passage in which it is fitted, and which resists push-out forces that might dislodge it. With this device, it is only the translated field that rotates. 
     In addition to providing a rotating field for remote use, this invention can also provide for translation of stationary fields for measurement and observation. 
     BRIEF DESCRIPTION OF THE INVENTION 
     This invention includes a cable having a dimension of length, a cross-section, and a first and a second end. The cable comprises an axially extending matrix of a plurality of parallel strands of magnetizable material. These strands are magnetically insulated from one another by non-magnetizable material. 
     The strands have cross-section areas smaller than the total cross-section area of the cable, and are preferably present in a substantial number. The strand arrangement is coherent in the sense that the position of each strand in the cross-section relative to every other strand is consistent from end to end of the cable. Thus, an image captured at the first end of the cable is precisely the same as the image replicated at the second end. This is a common concept in fiber optic cables, and it is used herein in the same sense in the translation of a magnetic image by this cable, rather than an optical image. 
     Thus, the magnetic field presented to the first end of the cable is replicated at the second end, and can be observed and utilized at the second end precisely as it could have been at the first end. The term “translation” is used herein in the sense of displacement as an entirety from one location to another. 
     According to this invention the cable includes a number of strands sufficient to provide such resolution of the field as is required for the intended usage. 
     According to a preferred but optional feature of the invention, the strands comprise a magnetizable metal core and a cladding of non-magnetic metal. 
     According to yet another optional feature of the invention, the magnetic core of each strand can be surrounded by an optically-transmissive cladding simultaneously to convey a coherent visual image. 
     The above and other features of this invention will be fully understood from the following detailed description and the accompanying drawings, in which: 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side view, partly in cutaway cross-section showing a cable passing through a barrier; 
     FIG. 2 is a right hand view of FIG. 1; 
     FIG. 3 is a cross-section of a first embodiment of the invention; 
     FIG. 4 is a cross-section of a second embodiment of this invention; 
     FIG. 5 is a cross-section of a third embodiment of the invention; 
     FIG. 6 is an axial cross-section of a user device; and 
     FIG. 7 is an axial cross-section of yet another user device. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     A cable  10  according to this invention is shown fixed in a passage  11  through a barrier wall  12 . The barrier wall may be part of a vessel enclosing dangerous materials or conditions, or a structurally integral part of the hull of a surface ship or a submarine. In either situation it will pass through the barrier wall from one side to the other. The objective is to translate a magnetic field from one side of the barrier wall to the other so it can be observed or utilized. The cable in the barrier wall is sufficiently strong to resist forces that may tend to press it out, and also is impermeable to water. 
     As best shown in FIGS. 1 and 2, the cable has a first end  15  and a second end  16 . Between these ends there extends a plurality of strands  17 . 
     The strands are parallel and coherent. By coherent is meant that each strand occupies the same relative position in the cross-section of the cable at both ends. Thus the magnetic image at both ends is the same. The ends of the cable are preferably but not necessarily smoothly finished, planar, and normal to the cable axis. 
     A magnetic field captured by the cable at the first end will exit the carrier at the second end as a precise replica. 
     Respective portions of the image will be transmitted by the individual strands. The image will, of course, be grainy, just as with optical fibers. Reduction of strand diameter and increase in the number of strands per unit area will increase the resolution of the image. However, any plural number of stands will create at least some image, so the invention is not limited to any particular size or number of strands per unit of cross-section area. 
     While strands with a circular cross-section will ordinarily be preferred for convenience in manufacture and availability, other cross-sections are equally useful, and sometimes preferable. For example, rectangular cross-sections will enable a larger packing ratio, i.e., the ratio of the cross-section of the magnetizable material to the total area of the cable. The difference will be in the total cross-section of the cladding non-magnetizable material. Also different cross-sections may be utilized in different areas of larger total cross-sections. 
     Sizes so small as to pack 1,000 clad strands in a one square inch section may be used, especially when the precise nature of the field is of interest. A lesser resolution, i.e. in a cable of perhaps 24 inches diameter may provide a suitable resolution for a large field with strands whose diameter is on the order of ⅛ to {fraction (3/16)} inches diameter. 
     The cladding will be kept as thin as possible. It will be provided in a thickness only sufficient to prevent magnetic “leakage” between strands. Such leakage would compromise the resolution of the image. It should be kept in mind that the objective of this invention is not to magnetize a cable, but rather to convey through the strands of the cable magnetic lines of flux relating to specific locations on a cross-section, thereby to produce a shaped magnetic field useful for all purposes that were attainable by the original field. 
     The presently-preferred embodiment of a strand  17  is shown in FIG.  3 . It has a cylindrical core  18  with a dimension of length and a circular cross-section with a diameter. A cladding  19  (sometimes called a “shield”) surrounds it. The core is made of a magnetizable material, preferably ferritic, such as mu metal. This metal does not retain magnetism unless subjected to a field with greater than saturation strength. Care will be taken not to saturate this material. The cladding is a non-magnetizable metal such as copper, brass, aluminum, or silver for example. 
     An optional type of strand  25  is shown in FIG.  4 . It includes a magnetizable core  26 , a non-conductive shield  27  and a non-magnetizable cladding  28 . Core  26  and cladding  28  are of the same materials as in FIG.  3 . Shield  27  provides a non-conductive barrier between the core and cladding for applications in which such shielding would be desirable. Suitable materials as organic plastics (especially polyvinylchloride and polyethylene), ceramics, and paper are examples. 
     Strand  35 , shown in FIG. 5 provides for image or light transmission along with magnetic field translation should optical transmission be desired. This can be for illumination or for an image, as desired. A magnetizable core  36 , an optional non-conductive shield  37 , a tubular fiber optic  38 , and a non-magnetizable cladding  39  are concentric and in contiguous contact. Core  36 , shield  37  and cladding  39  are of the same materials shown in FIGS. 3 and 4. The material of fiber optic  38  is transparent, and can utilize the same materials as are used in fiber optic devices generally. It may also be used in place of the cladding, because it is not electrically conductive, and can still perform its light transmissive function. Glass will usually not be used, but any of the clear plastics generally used in endoscopes and borescopes will be suitable. When an image is to be transmitted, optic  38  will be a coherent bundle of fibers when the cores are coherently organized. 
     FIG. 1 illustrates the basic utility of the invention. The cable sealingly passes through the wall, exposed to a magnetic field at its first end, and available for observation and use at its second end. It is structurally sufficiently strong to resist external forces that would press it out of the opening. 
     FIG. 6 shows a stationary plate  45  which is transmissive of the magnetic material to which iron filings or the like may be applied to observe the shape of the field. This is, of course, a simplistic application. Much more sophisticated means can be used to learn the specifics of the field at the exposed end. 
     FIG. 7 shows a practical application, where a motor  50  or other motive means drives a generating device  51  that generates a rotating magnetic field. This field is received by cable  52  which translates it through barrier wall  53  to a user device  54 . The user device is mounted by bearings  55  so it can rotate. It includes windings or other means responsive to the rotating magnetic field, and can thereby be driven. Devices (not shown) such a propellers can be mounted to user device  54 . 
     The term “cable” is used herein to denote a structure which has the same cross-section for a substantial length. It may be short with a large diameter, or long with a thin diameter, or any combination in between. 
     This invention is not to be limited by the embodiments shown in the drawings and described in the description, which are given by way of example and not of limitation, but only in accordance with the scope of the appended claims.