BACKGROUND OF THE INVENTION

This invention relates to devices for using the inherent resistivity of electrically conductive elements of a structure to generate heat within the structure to keep them from becoming inoperable or damaged due to a cold and/or freezing environment.

SUMMARY OF THE INVENTION

This invention presents a device for generating heat in an electrically conductive element of a structure comprising a means for causing an alternating current through said element, the current being sufficient in relation to an inherent resistivity of said element to generate a desired amount of heat. The desired amount of heat will be that amount sufficient to prevent damage or icing under the circumstances. The frequency of the current is preferably high enough to cause at least a majority of the current carriers to travel on and within a skin portion of said element for more efficient surface heating. The alternating current can be induced and a means for inducing the current can be a source of alternating voltage which is transformed into the alternating current, the alternating voltage being applied to a primary winding of a transformer and the element or elements being serially within an electrical current loop of a secondary winding of the transformer. An object of this invention is to provide a means for generating heat within one or more electrically conductive elements of a structure and thereby heat the structure without the use of any dedicated heating elements, that is, elements whose only function is to generate heat such as heating coils and the like.

Further objects of this invention will be discussed and/or will be readily discernable from a reading of the specification and claims herein.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 illustrates two configurations for this invention as applied to disc-braked wheels.

Figure 2 illustrates application of this invention to a block braked wheel.

Figure 3 illustrates application of this invention to linkage between disc brakes applied to the axle of the wheels.

Figure 4 illustrates application of this invention to the fulcrums of disc brakes affixed to the axle of the wheels. Figure 5 illustrates the application of this invention to an engine block, an oil pan, and a carburetor.

Figure 6 illustrates the application of this invention to a conductive casing for a battery.

Figure 7 illustrates the application of this invention to a vehicle's transmission and gear box, and the vehicles's drive train differential.

Figures 8, 9 and 13 illustrate the application of this invention to towers having conductive structural members.

Figure 10 illustrates the application of this invention to an oil drilling platform.

Figures 11 and 14 illustrate application of this invention to a ship's bulwark.

Figure 12 illustrates application of this invention to the wing frames of an aircraft. Figures 15-17 illustrate application of this invention to pipes, such as oil carrying pipes.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to Figure 1, it depicts one type of disc brake and two different ways to connect this invention. A pair of railroad car wheels, 2 and 4, are connected by axle 6. Each wheel is illustrated as having a braking means associated with it comprising a pair of opposing friction pads, 8A and 10A, and 8B and 10B for the left and right wheels, respectively. The friction pads are selectively applied to the wheels by means of metal calipers, 12A and 12B. The calipers each comprise two metal levers, 14A and 16A for the left and 14B and 16B for the

right, pivotally engaged with a metal fulcrum piece, 18A and 18B, to apply the friction pads to their associated wheels in pincer fashion. Typically one of the levers of each caliper (e.g. 14A and 16B respectively) is held in a fixed position while the other lever (e.g. 16A and 14B respectively) is pivoted about its fulcrum by an hydraulic ram 20 (commonly called a "brake cylinder") through first and second metal coupling linkages, 22A and 24A, respectively, for the left and 22B and 24B, respectively, for the right. Referring again to Figure 1, an embodiment of this invention is illustrated to comprise an alternating voltage source 26A with a two lead output that is electrically connected to a primary winding 28A of a stepdown transformer 30A. The voltage source can be one or more generators turned by the wheels themselves, a generator turned by engine, or any alternating voltage source of suitable capacity as suitability is defined in this specification. The secondary winding is illustrated as being a single electrically conductive loop comprising: a first conductive wire 32 connecting the first linkage 24A to a chassis ground; a second conductive wire 34 ensuring that electrical continuity is maintained between the first linkage and the second linkage 22A; a third conductive wire 36 ensuring that electrical continuity is maintained between the second linkage and the un-fixed caliper 16A; a fourth conductive wire 38 ensuring that electrical continuity is maintained between the un-fixed caliper and its fulcrum 18A; and a fifth conductive wire 40 ensuring that electrical continuity is maintained between the fulcrum and the fixed caliper 14A which is electrically connected to chassis ground. The segment of the secondary conductive loop that actually passes through the transformer's core is illustrated to be the second linkage 22A.

The braking system of the right wheel as depicted in Figure 1 is heated with a slightly different circuit. An alternating voltage source 26B is in electrical communication serially with the primary windings 28B of a transformer having a core 30B. The caliper levers 14B and 16B are in electrical

communication with their associated fulcrum 18B as in the left side. The first and second metal coupling linkages, 22B and 24B are electrically connected as on the left side. The difference between the left and right side lies in the fact that the linkage 22B does not pass through the core of the transformer, but rather an electrical current conduit 42 comprising of the secondary winding of the transformer, one end being electrically connected to the linkage 24B and the other end being electrically connected to the lever 16B. The basic principle is to provide heat to structures to prevent them from becoming inoperable or destroyed due to temperatures below zero degree Centigrade or due to ice accretion. In the preferred embodiments described herein, alternating electrical energy is applied to the primary of a stepdown transformer in which a secondary winding produces high current and low voltage in a circuit made up of structural elements or sequences of them serially connected. The high current preferably alternates at a frequency high enough to generate heat by the resistive losses close to the surface of the conductive elements due to skin effect, which concentrates the current at or near the surface, i.e. "skin."

Several variations of the application of this invention to braking systems can be used depending on the linkage systems. For example, the brake blocks themselves could be heated separately.

Referring to Figure 2, a metal brake block 52 is illustrated to be a segment of the secondary winding. Other parts of the railroad car could also be heated by means for this principle. In order to have as high over-all efficiency as possible, the low voltage connecting cables, 54 and 56, should be as short as possible.

Referring to Figure 3, the braking system for the wheels operates under the disk brake principle, but is different from the system as depicted in Figure 1. Disks 60A on the left and 60B on the right illustrate braking disks affixed to the axle 62 of the wheels, the disks being near their respective wheels. An alternating electrical energy source 26C energizes the

primary windings 28C of a transformer having a core 30C. Through the core is a conductive linking rod 64 mechanically linked and electrically connected to caliber levers 66A and 66B. The secondary circuit comprises that linkage 64 as one segment, the upper portion of caliper 66B which is mechanically and electrically connected to chassis ground, through chassis ground, through an upper portion of a caliper 68B which is also electrically and mechanically connected to chassis ground, through a second linkage 70 which is mechanically and electrically connected to lever 68B and 68A, through the upper portion of 68A, through the shell of the ram 20, through the upper portion of lever 68A, and to the linkage 64 again. In this fashion, both the first and second linkages, and all of the caliper levers are warmed by the current flowing in that secondary loop induced therein by the primary of a transformer 28C.

Referring to Figure 4, the same type disk system as illustrated in Figure 4 is shown except with two driving rams 21A and 21B. Two sources of electrical energy 26D and 26E, left and right respectively, are utilized. The secondary loops of the transformers associated with said electrical energy sources are mirror images of each other. So the discussion will be provided only for the left braking mechanism. The secondary loop of the transformer on the left comprises a segment of an elbow 72 which mechanically pivots and is electrically connected to chassis ground. An end of the elbow remote from the ram is mechanically connected and electrically connected to a caliper lever 74. Which in turn is pivotally and electrically connected to a fulcrum arm 76 which passes through the core of the transformer and is in effect a secondary winding of the transformer. The opposite end of the fulcrum are is mechanically and electrically connected to the opposing lever of the caliper 78 which in turn is mechanically and electrically connected to the chassis ground, the chassis ground providing the last link in the loop. The configurations in both Figures 3 and 4 do not require any cables if electrical continuity can be maintained through the linkages' interfaces.

Figure 5 illustrates this invention applied as an engine block heater, oil pan heater and carburetor heater. A source of alternating voltage 82 energizes a primary winding 84 of a transformer, generally designated 86. The secondary comprises basically one conductor 88 having one end electrically connected to a first side of an engine block 90 at connection 92. The other end of the conductor is electrically connected to the second and opposite side of engine block at connection 94. The engine block being typically either cast iron or cast aluminum is electrically conductive and so a current induced in the secondary conductor 88 will flow from the first to the second side of the engine block, and if the frequency of the current is sufficiently high, skin effect will take place effectively increasing the inherent resistivity of the engine block. The inherent resistivity will generate heat within the engine block warming it.

Referring again to Figure 5, a source of alternating voltage 96 energizes the primary winding 98 of a second transformer, generally designated 100. The secondary of the transformer is a single conductor 102 which has its opposite ends connected to opposite sides of an oil pan 104 at connection points, 106 and 108. Typically oil pans are made from steel, or other conductive alloy, and are therefore conductive and have an inherent resistivity. Current induced in the secondary conductor 102 will flow from one side of the oil pan to the other and generate heat therein due to the pan's inherent resistivity. One heater could be used for both the block and the oil pan if proper electrical connections are provided between them. Referring again to Figure 5, also illustrated is a carburetor heater, intended to prevent moisture condensation. A source of alternating voltage 110 induces a current in single conductor 112 by means of a transformer, generally designated 114. The ends of the conductor 112 are connected to opposite points of a carburetor 116. Carburetors are typically made from cast iron, steel or aluminum and are therefore conductive, and therefore have inherent resistivity which can be used to

generate heat in the manner previously discussed.

Figure 6 illustrates this invention applied as a battery 118 heater. In this case the battery has an outside insulation case 120 and an inside partial metal case 122 connected across the secondary of a transformer 123. The metal case is heated by resistive losses, particularly in the skin, according to the principles of this invention as explained above.

Figure 7 illustrates this invention applied to heating the casings of a transmission/gear box 124 and a differential 126 via transformers 127A and 127B, respectively, according to the principles of this invention. The secondary connections are made on opposite sides of the casings.

The conductive structural members of an antenna tower 128 is illustrated in Figure 8 as being heated via transformers, 129A and 129B, according to the principles discussed above. Figure 9 illustrates a transmission line tower 130 heated via transformer 131, and oil rig 132 in Figure 10 is illustrated to have structural members being heated via transformers 133A and 133B according to this invention. There are several different variations of these structures and the applications of the heaters must therefore be custom made in each case.

Figure 11 illustrates this invention applied to heat as a bulwark 134 of a boat or ship. Transformers 135A and 135B are used to induce alternating high current in respective sides of the vessel. Similar arrangements can be made for the superstructure of the vessel.

Figure 12 illustrates one configuration for heating the conductive wing frames 136A and 136B of an aircraft via transformers 137A and 137B respectively. In this case struts 138A and 138B have current induced directly into them, and each causes the current to flow through connected frame loops.

Referring to Figure 13, an alternative configuration for heating an antenna tower 128 is illustrated. Contrary to the configuration of Figure 8, only one transformer 140 is used to induce a current in a single conductor 142. The conductor 142 is connected at one end to the apex 144 of the tower, and at an opposite end to all four tower support legs at their base. In

the configuration illustrated in Figure 8, each transformer induced current in conductors connected to diagonally opposite pairs of legs.

Referring to Figures 11 and 14, the configurations in Figure 14 require less current than the configurations illustrated in Figure 11. On one side of a ship's deck 146 a bulwark 148 is heated by having a segment 150 of it have current induced therein by having a core 152 of a transformer enclose the segment by means of holes 154A and 154B defined by the bulwark through which the core extends. An alternating voltage source 156 creates varying magnetic flux in the core which cuts the bulwark segment 150 and thereby induces current therein. This current then heats the conductive bulwark through resistive losses preferably in the skin of the bulwark. Referring again to Figure 14, on the opposite side of the deck 146 is a second bulwark 158 which defines only one hole 160 through which the core 162 of a transformer extends.

Referring to Figures 15-17, illustrated are pipes, such as oil pipes, which can be heated according to this invention. Figure 15 illustrates a conductive pipe 164 having its opposite ends connected via a single conductor 166. This conductor is in the secondary of a transformer 168 whose primary is energized by alternating electrical energy ' source 170. The pipe is a segment in the secondary of the circuit of the transformer and therefore carries current induced into the secondary. The current according to the principles of this invention, as discussed above, generates heat within the pipe length.

Referring to Figure 16, it is the same pipe 164 but in this configuration its opposite ends are connected to a conductive medium such as ground. A core 172 of a transformer surrounds the pipe and when alternating electrical energy source 174 energizes primary windings wrapped around the core, the core will induce a current in the conductive pipe, thereby heating it according to the principles discussed above.

Referring to Figure 17, the pipe 164 is in the secondary circuit of a transformer 172, as previously discussed with

respect to Figure 16, but in this case the opposite ends of the pipe are not connected to a conductive medium but rather to a second conductive pipe 176 which completes the secondary loop. In this way, both pipes are heated by a single transformer according to the principles as discussed above.

It should be realized that the pipes illustrated in Figures 15-17 would necessarily be covered by electrical insulation material. It should further be realized that the conductive medium referenced with respect to Figure 16 can also be a conductive medium such as sea water or any other conductive liquid medium as well as any conductive solid medium.

In operation, a voltage is applied to the primary of the transformer causing current through its primary windings. This induces a current into the secondary circuit, which is a high- current low-voltage circuit, by means of well known transformer induction principles. Since it is a stepdown transformer, a current gain is felt in the secondary. By proper selection of the primary winding count, the core material of the transformer, and the voltage levels, the current gain can be on the order of hundreds of amperes, enough to generate heat when opposed by the inherent resistivity of a structure's element or elements in the circuit of the transformer's secondary winding, preferably one turn. The high alternating current will generate heat by the resistive losses close to the surface of the conductive elements due to the skin effect, which concentrates the current at or near the surface.

For the purpose of system design the electrical impedance of a cylindrical metal bar is calculated by means by Bessel- type differential equations. The electrical impedance of a solid cylindrical bar is as follows:

Z = R + jωL = HI ρ (1 + ) ohm 2πα

0-5 ω μ μ _α

•where H = Q

. = radius ω = 2-τrf (f = frequency in Hz)

1 = length μ = relative permeability ρ = specific resistivity μ_ = 4-τr x 10 ^"7

This formula is valid for large H x .

For comparison the DC resistance is

R ₀ = _1_-ρ ohm

A solid iron bar was theoretically analyzed and tested as follows:

a = 0.9525 cm f = 60 hz

1 = 0.67 m μ = 815 ρ = 0.119 x 10 ^"6 ohm m

which yields: Z = 2.399677 x 10 ^"3 ohm, and R ₀ = 0.02797 x 10 ^"3 ohm.

The measured data was:

I = 250 A (amperes) V = 0.6 V (volts) S = VI = 150 VA (complex power) P = S COS θ = 150(0.707) = 106 W

The bar could maintain an estimated 75° C temperature and

showed a considerable heat capacity.

The alternating voltage sources as described herein can be any alternating voltage source of suitable capacity as "suitable" is defined in this specification. It is necessary to have flexible connections between any moving parts in order to have good electrical contact between the metal parts and to avoid them being welded together. (A few hundred amperes are to be expected.) In order to optimize the operating cost, a control system of conventional design can be used with temperature sensors and switches operating such that heating takes place only below freezing temperatures, or if so desired, only during intermittent periods. The transformers can also be designed such that they have minimum leakage. The foregoing description and drawings were given for illustrative purposes only, it being understood that the invention is not limited to the embodiments disclosed, but is intended to embrace any and all alternatives, equivalents, modifications and rearrangements of elements falling within the scope of the invention as defined by the following claims.