Railways – Magnetically suspended car – Propulsion means employed to suspend car
Reexamination Certificate
2000-02-18
2002-03-19
Morano, S. Joseph (Department: 3617)
Railways
Magnetically suspended car
Propulsion means employed to suspend car
C104S281000, C104S282000, C104S286000, C104S283000, C104S284000, C310S012060, C310S255000
Reexamination Certificate
active
06357359
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to the complete construction and design of a high or low speed MAGLEV (Magnetic Levitated Vehicle) system. Of central concern is the means by which propulsion, levitation and stabilization forces are provided to the vehicle.
Design Requirements of a MAGLEV System
Unlike the design of many conventional electric motors, a MAGLEV system must be sensitive to the fact that one side of the motor, either the rotor or the stator, is nearly infinite in length. Thus, the components, and the cost of the track in particular, is a much greater concern than is usually the case with a conventional motor, in which both the rotor and stator are comparatively small and of finite length.
Most high speed MAGLEV vehicles are projected to run at speeds of about 150-300 mph. Not only is the aerodynamic drag a key factor in the design of the vehicle, but magnetic drag is as well. The term magnetic drag refers to the forces exerted on the vehicle by eddy currents induced in the track acting against vehicle-based magnets. At low speeds in the neighborhood of 30 mph, this drag can constitute up to 200 to 300 per cent of the total drag, while at 300 mph it might constitute 5 per cent of the total drag. Magnetic drag should be minimized, whenever possible.
Of equal importance to the design of a MAGLEV vehicle is the issue of how levitation and stabilization will be achieved. By way of comparison, all commercial aircraft land at speeds less than 170 mph since the landing wheels can not withstand impact at higher speeds. Whatever mechanism is used to achieve the levitation and stabilization of a MAGLEV vehicle, it must be guaranteed to be fail-safe when a local power substation goes down. Similarly, it cannot depend on one or two superconducting magnets which have the possibility of quenching at any time. Lastly, there must a mechanism for transferring both propulsion power and service power (lighting, heating, air-conditioning, etc.) to the vehicle.
In summary, the targeted objectives for an efficient and viable MAGLEV system are as follows:
1. A low cost track. This is the element of the system which will constitute the greatest component of its costs.
2. Means for reducing unwanted eddy currents with their commensurate heating loss and magnetic drag.
3. Means for realizing efficient levitation and stabilization in a fail-safe mode. This means should be able to realize such levitation and stabilization at both high and low speeds—preferably without incurring undue additional cost to the system.
4. Means for delivering propulsion and service power to the vehicle.
Background Work
The background work in this area is quite extensive. Among the earliest patents proposed for a MAGLEV system is that by Maurice F. Jones and Lee A. Kilgore, U.S. Pat. No. 2,412,512 (1946). Their proposed system consisted of a laminated polyphased wound core in the vehicle which acted against a squirrel cage current rail extending the length of the track. This patent shares some features with that of Millard Smith and Marion Roberts, U.S. Pat. No. 3,233,559 (1966), which also proposed a linear electric induction motor as a means of propelling a vehicle down the track. Both suggestions suffer the problem of getting a large amount of power into the vehicle; this task might be possible at present using state of the art brushes. With the proposed squirrel cage arrangement, operation would not be possible without considerable magnetic drag loss. Frank Godsey and Maraca Jones, U.S. Pat. No. 2,666,879 (1954), suggest a similar configuration, but mount the windings along the length of the track; the vehicle need only carry a conducting sheet which would be sandwiched between these windings. The cost of such a MAGLEV configuration might be astronomical.
More recently, additional systems have been suggested which attempt to realize propulsion using linear synchronous motors. More notable among this group is the patent by Naoki Maki, et al, U.S. Pat. No. 3,913,493 (October 1975). Their system uses a linear synchronous motor in which track-based three phase coils interact with a vehicle-based magnetic coil group to realize the propulsion. Again, the cost of such a system could be extremely high.
Among the first groups to suggest an integrated system yielding levitational guidance and propulsion was that by Richard Thornton, U.S. Pat. No. 3,850,109 (November 1974). The vehicle was constructed with a number of long, thin superconducting coils which, when energized, would interact with “I” strips along the guideway to effect levitation. Propulsion was accomplished by interaction with other vehicle coils reacting with an armature based winding in the track. Although such a system would indeed realize levitation at very low speeds, along with propulsion, the cost could be very large. Moreover, if either of the two lift coils suffered a superconducting quench, catastrophic results would no doubt ensue.
In what might be summed up as possibly the most expensive MAGLEV system ever proposed, Ushio Kawabe and Hiroshi Kimura (U.S. Pat. No. 3,662,689 (May 1972)) suggest the use of a hard superconductor which is laid out along the length of the track and flooded with superconducting fluid. The superconductor would react against a vehicle-based magnet to induce eddy currents realizing both the levitation and stabilization. The superconductor was arranged in a box-like configuration underneath the vehicle. Also laid along the length of the track was a ladder structure. Current would be impressed from one side of the ladder, laid horizontally along the ground, to the other side of the ladder. A propulsion force would then be generated as a consequence of the interaction of the vehicle-based magnetic field with the current in this ladder using conventional Lorentz forces, i.e. {right arrow over (J)}×{right arrow over (B)}. If one examines
FIG. 5
of that patent more closely, it will become apparent that the superconducting magnet in the track underneath the solenoidal magnet is used to generate the propulsion/lift field in the vehicle. The interaction of the two fields will actually cause the magnetic field to be horizontally directed in the plane of the ladder. The {right arrow over (J)}×{right arrow over (B)} forces realized would be very small indeed. This parenthetical note is important because the propulsion forces realized by the present system are not unlike those which Kawabe was attempting to realize, but had failed to. In any event, the cost of his levitation system seems hopelessly unrealistic.
Kazumi Matsui, et al., in U.S. Pat. No. 3,771,033 (November 1973), and U.S. Pat. No. 3,904,941, (September 1975), outline a means for generating propulsion forces for a MAGLEV system using current conductors in a picket fence type arrangement in the presence of a homogenous field. These patents deserve mention because the propulsion system used in the present invention also incorporates currents passing through a picket fence arrangement of conductors lying within a homogenous field. The arrangement proposed however by Matsui is quite inefficient. Over the span of a single permanent magnet field, multiply directed currents are injected into these conductors in both directions to yield {right arrow over (J)}×{right arrow over (B)} forces which are counterproductive. The proposed system overcomes this drawback and maintains a higher efficiency by allowing currents of like direction only to contribute over a common pole face of a vehicle-based magnet.
The last patent that will be mentioned in reference to mechanisms for generating propulsion forces is that of Osamu Shibuka, et al, U.S. Pat. No. 4,641,065 (February 1987). Their track consists of a rail of north-south magnets directing their flux in a predominately horizontal direction with the ground. A conducting rail of U-shaped cross-section fits around the magnets and is provided with a set of brushes for changing the direction of the current within a moving U-shaped coil. The brushes pick up current from the stationary feed line; the curren
Davey Kent R.
Morris Tony J.
Jules Frantz F.
Levisohn, Lerner, Berger and Langsam
Morano S. Joseph
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