Patent Application
20240030795
At the present time, certain industries have benefited from a strong and sustained rise in the price of the products they sell as a result of their activity. An example of the above is the case of mining, which for some time has experienced an increase in the price of minerals that are extracted as a result of exploitation. As a consequence of this phenomenon, the focus of the operation has lately been on increasing production to take advantage of the good price of these products. Such is the case of the exploitation of various minerals such as iron, copper, aluminum, silver, gold, etc.
To increase production and take advantage of high mineral prices, the effectiveness of critical equipment and its energy efficiency are of vital importance. This is a reality in every machinery-intensive industry and in the case of Mining, an important part of operational efficiency can be achieved in the first part of the process, called “Mine Operations”. This set of operations includes, among other stages: (i) “drilling”, in which certain specialized machines drill into the rock; (ii) “burning” (or explosion), in which each of the perforations is charged with explosives. Once these explosives are detonated, the rock is reduced to adequate sizes to be processed in later stages; (iii) and finally the “loading”, in which the rock is mounted on large trucks thanks to the operation of the loading shovel.
In a mining operation, the critical equipment that carries out the “Mine Operations” are rock drills, loading shovels and large trucks. The proportions in which this equipment is in the field are approximately one loading shovel and two drills for every 5 to 10 trucks. Therefore, one of the critical pieces of equipment in the operation of a mining company are rock drills, in which the critical variables for their operation are their reliability, the speed at which they drill the rock and the energy efficiency with which they carry it out.
In this way, any improvement that makes the operation of this type of equipment more effective and efficient can be translated into operational efficiencies of the mining operation seen as a whole.
In underground mining, the operations are the same, although the models of the equipment are different, mainly due to their height and the limited space available.
This type of equipment, such as the loading shovel and some drilling rigs, are fed with medium voltage triphasic electrical energy (8 kV or 15 kV). Therefore, the power supply that allows the proper functioning of this equipment is also critical.
There are different techniques for drilling rock, depending on: (i) the application (oil wells, construction, mining production, etc.); (ii) the hardness of the surface to be drilled; (iii) the drilling diameter; (iv) the desired depth, etc. However, they all seek the same goal: to increase the drilling speed (penetration rate), consuming the least amount of energy. That is why the industry is constantly looking for different alternatives to improve speed and efficiency.
Rock Drilling Methods.
There are many methods of rock drilling. Ordered from most to least used, they are: (i) mechanical (percussion, rotation, rotary percussion); (ii) thermal (thermal lance, plasma, hot fluid, freezing); (iii) hydraulic (water jet, erosion, cavitation); (iv) sonic (high frequency vibration); (v) chemicals (micro blasting, dissolution); (vi) electrical (electric arc, magnetic induction); (vii) seismic (laser beams); (viii) nuclear (fusion and fission).
Despite the great variety of possible rock penetration systems, in mining and construction, drilling is currently carried out mainly using mechanical energy.
In this way, there are basically two types of perforation. Pure rotary drilling and rotary percussion drilling. The type of drilling chosen will basically depend on the type of ground and its hardness, the diameter of the hole and the desired depth, in order to always achieve the same objective: increase the drilling speed (known as penetration rate), with the lowest possible energy consumption.
In general it is used for large diameters, up to 300 mm and soft soils (low compressive strength, measured in MPa). It consists of applying energy to the rock, making a tool rotate, together with the action of a vertical thrust force that presses the rock. It originates from oil wells, limited to soft rocks. At the beginning of the 1950s, it began to be applied to drilling for blasting. Usual diameters are between 50 mm and 300 mm.
Rotary Percussion Drilling.
In general, it is used for small and medium diameters, up to 200 mm and hard soils (medium to high compressive strength, measured in MPa). It consists of applying energy to the rock, through the impact of a piece of steel (piston) on a tool (chisel) that transmits the energy to the bottom of the hole. Especially suitable for hard rocks and small drilling diameters (50 mm to 200 mm). Depending on the place where the hammer is installed, it can be distinguished:
Percussion with Top Hammer (TOH, Top of Hole).
Top hammers are pneumatic or hydraulic actuators. Both rotation and percussion take place outside the borehole. The percussion is transmitted by the bars to the mouth of the perforation. Given this, for drilling deeper than 30 meters, these types of hammers are not effective. Top hammer drilling diameters range from (38 mm to 127 mm). For pneumatic drills the piston stroke is between 35 mm and 95 mm. Hit frequency is between 25 Hz and 55 Hz. There are also hydraulic drills, whose impact power is between 6 kW and 20 kW and a blow frequency between 30 Hz and 80 Hz.
Down the Hole Hammer Percussion (DTH, Down the Hole).
Down-the-hole hammers are pneumatic actuators. The drive of the piston is through compressed air and the percussion takes place inside the perforation mouth. Rotation takes place outside of the borehole. Its penetration rate is quite homogeneous with increasing depth and depths greater than 100 m can be achieved.
Down-the-hole hammer drilling diameters range from (85 mm to 200 mm). Drilling speeds are between 0.5 and 0.6 m/min for diameters between 105 mm and 165 mm. The beat frequency is between 10 Hz and 26 Hz (blows per second). Piston strokes are in the order of 100 mm and compete with hydraulic top hammer drilling for ranges from 76 mm to 125 mm. Regarding the efficiency of the tool, it is about 10%. That is, to deliver 30 kW to the rock, the air compressor consumes around 300 kW.
The widely used rotary percussion techniques (pneumatic and hydraulic) use a fluid (air or oil, respectively) to transmit energy to the percussion tool. This fluid is centrally pressurized through a compressor or an hydraulic pump, respectively, in such a way that the flow transmitted to the tool is driven by this pressurized fluid. Then, the power delivered to the tool is the product of pressure times flow, with flow being a pressure-dependent variable. If there is need to increase the power transmitted to the tool through the fluid, the pressure with which the fluid is driven needs to be increased. The resultant higher pressure increases the flow. In other words, both variables are tied together.
Now, from the point of view of the tool, the power received by the pressurized fluid is transformed into power delivered to the rock, which is the product of the kinetic energy of the piston when striking the chisel, times the impact frequency of the piston when hitting the chisel. To achieve more drilling speed, the impact frequency must be increased, ensuring minimal impact to break the rock. However, with current tools (pneumatic and hydraulic), to increase the impact frequency, the power to the tool must be increased and the final result is that the impact frequency and the energy with which the tool is impacted are increased at the same time.
This is not the most efficient, since in theory it would not be necessary to increase the impact energy, because the rock is already breaking. The desirable thing would be to transform the installed power into frequency, keeping the impact energy at a minimum to break the rock.
On the other hand, experience in the industry shows that, for an installed power on the drilling rig, a higher drilling speed can be achieved if it is distributed independently the energy delivered to the surface and on the other hand the impact frequency.
Given the above, there are several attempts to develop devices that are more flexible in terms of controlling their operating parameters (energy and frequency). In this sense, electrical devices allow to control voltages, currents, frequencies, etc. and on the other hand, the energization is already available in the mining operation.
Then the motivations to study electric hammers are clear: electric traction systems are characterized by high efficiency, and they can be controlled remotely. Then, the percussion frequency could eventually be controlled, independently of the impact, while keeping a high energy efficiency of the cycle.
In other words, a device is sought that it is capable of delivering high power to the rock and at the same time is it flexible so it can modify its operating conditions, keeping its efficiency within acceptable ranges.
The reason that justifies the development of an electric hammer is based precisely on the properties that electrical systems present: high efficiency and remote parameter control. It is interesting then, to combine the properties of the various electrical systems with the requirements and characteristics of rock drilling.
Specifically, the possibility of varying the parameters of an electromechanical system makes it possible to vary the percussion frequencies while maintaining a high efficiency of the cycle. By adjusting the parameters for different rocks, a higher penetration rate could be achieved.
The massive use of any drilling equipment that uses electrical energy directly to generate percussion on the rock is not seen in the market. However, the specification of the rock drilling technique, and the new applications that currently require the use of hammers, motivate the study of new possibilities that make the rock drilling process faster and more efficient.
There are a variety of patents and scientific publications for electric drilling tools. The vast majority of them contemplate the use of solenoids that move ferromagnetic masses in combination with springs to generate an oscillatory movement. Such is the case of U.S. Pat. No. 6,201,362 B1, which proposes a ferrous mass located inside electrical coils and which is driven by one or two coils. Together, the ferrous mass and a coil form a solenoid. The coils drive the ferrous mass against a chisel and after impact, the coils lift the mass again, generating a reciprocating motion. When the coils are excited with electrical energy coming from outside the device (it can be alternating or continuous), the ferrous mass is attracted to the center of the coil, since in this way the energy of the system is at a minimum and the ferrous mass finds a balance inside the coil, in its center. The reciprocating movement is achieved by changing the position of the ferrous mass from one coil to another and the patent proposes a power system that extends the life of the coils through the use of an inertia wheel that stores energy externally to the device.
Another case of an electric rock drilling tool is U.S. Pat. No. 5,168,939A, which proposes an electromagnetic gun system for accelerating a ferrous mass that passes through the center of successive coils that accelerate it. The coils are excited sequentially in a feedback way according to the position of the ferrous mass. This tool is designed to hit very hard, but with a very low frequency. That is, a high kinetic energy (½*mv{circumflex over ( )}2) of impact (measured in Joules) in combination with a low frequency (measured in Hz=1/second). The product of impact energy by impact frequency, results in the power delivered to the rock (measured in Watts=Joules/second). So if the frequency is too low, the power delivered to the rock is low and as can be assumed the penetration rate will be low.
Both power tools, like those proposed in U.S. Pat. Nos. 6,520,269, 4,215,297, 4,015,671, 2,861,778, 1,941,655, 1,725,504, CN 205,317,438 U, CN 1,061,922 A, disclose similar systems in terms of driving coils to generate a reciprocating movement of a ferrous mass using coils that attract the ferrous mass to the center of the coil.
However, the configuration in all these patents considers the use of open magnetic circuits (1505) at some point in the iron, giving spaces for air gaps (1504). In the configurations proposed in the cited patents, the air gaps are present to allow the movement of the ferrous mass. These air gaps (1504) are air gaps (1509) with a very low magnetic permeability compared to the iron zone (1510) which has a magnetic permeability several orders of magnitude higher. Depending on the material, it can be of the order of 100 to 1000 times. The effect of this air gap (1504) is that the magnetic circuit (1505) finds it difficult to generate a high field density inside the iron, generating a border effect (1502), in which the field becomes less dense (fewer lines field (1501) per unit area). As in electrical circuits, in which a high resistance prevents the passage of current, in the case of magnetic circuits, a high reluctance (due to the air gaps) prevents the passage of magnetic flux. This generates that for the same excitation (magnetomotive force N*I, given by the product of the winding of N turns (1507) and the current circulating in the winding (1508)), a lower field density is obtained (magnetic field lines (1501) divided by the cross section of the iron core (1503)) in the magnetic core. In other words, in order to generate a magnetic field density that is good enough to generate high power, it is necessary to consume a lot of electrical energy.
In this way, those proposals that include air gaps (1504) either consume a lot of energy or generate little mechanical movement.
Other patents talk about linear stepper motors, like the 1926 U.S. Pat. No. 1,720,854, but also consider air gaps to allow mechanical movement. This patent considers a complex configuration since the forces of attraction between the iron elements are high and for this reason it contemplates the use of linear bearings or systems that ensure a very precise centering of the mobile element. On the other hand, the use of windings that must be powered electrically in the mobile zone implies the need for mobile electrical contacts (brushes, carbons, etc.) that generate many maintenance needs that make the operation of the device very expensive or decidedly so unreliable.
Other alternatives proposed in scientific publications (Tao, Bekken and Zhang et al) correspond to permanent magnet synchronous linear motors to generate translational and reciprocating motion. In these alternatives, the stator contains the permanent magnets and the element that generates the movement has only coils. However, the use of permanent magnets in applications with high temperatures, high vibration and high shock is not desirable, especially given the structure of modern permanent magnets, manufactured by sintering. This manufacturing process consists of compacting at high pressure the metallic and/or ceramic powders of certain particular materials, homogeneously mixed and, once compacted, carrying out a heat treatment at a temperature below the melting temperature of the mixture, obtaining a consolidated and compact piece.
Technical Problems Solved by this Development.
An electric drilling device is proposed that includes a linear reciprocating induction motor, confined inside an electric transformer (101), and that through an air chamber (1704) delivers power to the percussion piston (1705). This one hits the chisel (1706) which is what finally destroys the rock. The characteristics of this device are: (i) its energy efficiency (electric power consumed versus power delivered to the rock); (ii) flexibility to control operating parameters, such as impact frequency, stroke, and impact energy; (iii) low capital cost because, unlike hydraulic and pneumatic drills, the entire tool is self-contained. That is, hydraulic and pneumatic drills require a hydraulic pump and an air compressor, respectively, to drive the fluid to the tool. These hydraulic pumps and air compressors are equipment with a high capital cost due to the number of parts and pieces that make up the equipment. However, in the case of the proposed development, the same transformer (101) generates the movement of the electrically conductive ring (201) and the quantity and interaction of the parts of an electrical transformer is much lower than that of a pneumatic pump or an air compressor; (iv) low maintenance cost because, unlike hydraulic and pneumatic drills that require intensive maintenance, the entire tool of the present development is self-contained. The maintenance of electrical equipment, specifically transformers, is much lower due to the lower labor force and robustness of the equipment, than hydraulic and pneumatic equipment, especially when the latter depend on internal combustion engines to generate movement. In this way, hydraulic and pneumatic drills require a hydraulic pump or an air compressor, respectively, to push the fluid to the tool, requiring two elements to generate the desired effect: the fluid drive element and the drilling tool. As we mentioned earlier, hydraulic pumps and air compressors are maintenance-intensive equipment. However, in the case of the proposed development, the same transformer generates the movement of the electrically conductive ring and this is maintenance free.
The widely used rotary percussion techniques (pneumatic and hydraulic) use a fluid (air or oil, respectively) to transmit energy to the percussion tool. This fluid is centrally pressurized through a compressor or a hydraulic pump, respectively, in such a way that the flow transmitted to the tool is driven by this pressurized fluid. Then, the power delivered to the tool is the product of pressure times flow, with flow being a pressure-dependent variable. If it is needed more power transmitted to the tool through the fluid, it will be necessary to increase the pressure with which the fluid is driven and that higher pressure increases the flow of the fluid. In other words, both variables are tied.
Now, from the point of view of the tool, the power received by the pressurized fluid is transformed into power delivered to the rock, which is the product of the kinetic energy of the piston when striking the chisel, times the impact frequency of the piston when hitting the chisel. To achieve more drilling speed, the impact frequency must be increased, ensuring minimal impact to break the rock. However, with current tools (pneumatic and hydraulic), to increase the impact frequency, the power to the tool must be increased and the final result is that the impact frequency and the energy with which the tool is impacted are increased at the same time.
This is not the most efficient, since in theory it would not be necessary to increase the impact energy because the rock is already breaking. The desirable thing would be to transform the installed power into frequency, keeping the impact energy at a minimum to break the rock.
On the other hand, experience in the industry shows that, for an installed power on the drilling rig, a higher drilling speed can be achieved if it is distributed independently the energy delivered to the surface and on the other hand the impact frequency.
Then the motivations to study electric hammers are clear: electric traction systems are characterized by high efficiency, and they can be controlled remotely. Then, the percussion frequency could eventually be controlled, independently of the impact, while keeping a high energy efficiency of the cycle.
In other words, a small size device is sought (which does not depend on the size of its installed power and delivered to the rock) that it is capable of delivering high power to the rock and at the same time is it flexible so it can modify its operating conditions, keeping its efficiency within acceptable ranges.
The reason that justifies the development of an electric hammer is based precisely on the properties that electrical systems present: high efficiency and remote parameter control. It is interesting then, to combine the properties of the various electrical systems with the requirements and characteristics of rock drilling.
Specifically, the possibility of varying the parameters of an electromechanical system makes it possible to vary the percussion frequencies while maintaining a high efficiency of the cycle. By adjusting the parameters for different rocks, a higher penetration rate can be achieved.
The present development proposes an electric drilling device that comprises a linear reciprocating induction motor, confined inside an electric transformer (101), and that through an air chamber (1704) delivers power to the percussion piston (1705). This one hits the chisel (1706) which is what finally destroys the rock. The characteristics of this device are its efficiency and flexibility to control the operating parameters, such as impact frequency, stroke and impact energy and a small size, independent of power requirements compared to known hydraulic and pneumatic systems.
In this way, with respect to rotary percussive tools, both hydraulic and pneumatic, a configuration such as the one proposed, solves the technical problems of: (i) energy efficiency, in the sense that a significant proportion of the power consumed by the equipment can be converted into mechanical power and this delivered to the rock; (ii) a size of the equipment independent of the power required in comparison with the hydraulic and pneumatic systems, and (iii) control of the parameters that allow to exchange impact energy in impact frequency. For this, the proposed device has two degrees of freedom:
With these possibilities of externally changing the frequency of the electrically conductive ring (201), the device can better face the possible scenarios:
I. Hard Rock.
In this scenario, the tool must hit with a strong impact to break the rock. In this way, the primary windings (104) must be separated ensuring a greater stroke of the electrically conductive ring (201). In such a way, the electrically conductive ring (201) will experiment a greater travel with thrust from the coils combined with the gravity accelerating the electrically conductive ring (201). This will result in a greater speed of the electrically conductive ring (201) at the moment of impact and, therefore, greater impact energy delivered to the rock. Once the minimum impact to break the rock has been achieved, all the installed power can be transformed into a higher oscillation frequency of the electrically conductive ring (201) which in turn will cause a higher impact frequency. In this way it will be possible to increase the drilling speed as much as possible. This increase in oscillation frequency is achieved by increasing the frequency of the enveloping curves (801, 803, 901, 903, 1001, 1003, 1101, 1103).
II. Medium Rock.
In this scenario, the tool must hit with a minor impact to break the rock. In this way, the distance between the primary windings (104) must be shortened and with it, shorten the stroke of the electrically conductive ring (201), accelerating it just enough to deliver the minimum impact energy to the rock to break it. The great advantage of shortening the stroke is that it allows to further increase the frequency with which the upper and lower primary windings (104) alternate. Once the minimum impact to break the rock has been achieved, all the installed power can be transformed into a higher oscillation frequency of the electrically conductive ring (201) which in turn will cause a higher impact frequency. In this way it will be possible to increase the drilling speed as much as possible. This increase in oscillation frequency is achieved by increasing the frequency of the enveloping curves (801, 803, 901, 903, 1001, 1003, 1101, 1103).
Regarding percussion power tools, the solution presented in this document differs strongly in:
In addition to the above, the axial perforations (1401) help to substantially improve the efficiency of the system, since they cool the ring and reduce air resistance.
It should be understood that the present development is not limited to the particular methodology, compounds, materials, manufacturing techniques, uses and applications described herein, as these may vary. It should also be understood that the terminology employed herein is used for the sole purpose of describing a particular representation and is not intended to limit the scope and potential of the present development.
It should be noted that the device, system, procedure, use and method, here, in the specification and throughout the text that the singular does not exclude the plural, unless the context clearly implies it. So, for example, a reference to a “device or system” is a reference to one or more devices or systems and includes equivalents known to those knowledgeable in the art. Similarly, as another example, a reference to “a step”, “a stage” or a “mode” is a reference to one or more steps, stages or modes and may include implicit and sub-steps, stages or modes or supervening.
All the conjunctions used must be understood in their least restrictive and most inclusive sense possible. Thus, for example, the conjunction “or” must be understood in its orthodox logical sense, and not as an exclusive “or”, unless the context or the text expressly requires or indicates it. The structures, materials and/or elements described must also be understood to refer to functionally equivalent ones and thus avoid endless exhaustive enumerations.
The expressions used to indicate approximations or conceptualizations must be understood in this way unless the context mandates a different interpretation.
All names and technical and/or scientific terms used herein have the common meaning given by a common person, qualified in these matters, unless otherwise expressly indicated.
The methods, techniques, elements, devices and systems are described, although methods, techniques, elements, devices and systems similar and/or equivalent to those described may be used or preferred in the practice and/or tests of the present development.
All patents and other publications are incorporated as references, with the purpose of describing and/or informing, for example, the methodologies described in said publications, which may be useful in relation to the present development.
These publications are included only for their information prior to the filing date of this patent application.
In this regard, nothing should be considered as an admission or acceptance, rejection, or exclusion, that the authors and/or inventors are not legitimated to be so, or that said publications are pre-dated by virtue of previous ones, or for any other reason.
To provide clarity to this development, the following concepts will be defined:
The linear reciprocating induction motor device for percussion applications that is proposed in the present development, comprises an electrically conductive ring (201) that oscillates inside a single-phase transformer (101), with a closed ferrous core (annealed iron wire or ferrite or preferably laminated silicon iron) with two primary windings (104) of enameled annealed wire, which can be copper or aluminum. The primary windings (104) can also be made of annealed copper tubing, internally cooled with soft water, as is normally done in induction heating appliances. If this is the case, the pipe must be externally insulated with tape or enamel and then wound to form the coil. This wire or pipe is wound on a plastic spool, this being a dry transformer (not submerged in oil). The primary windings (104) are energized alternately with direct or alternating current, and in a complementary way, implying that while one of the primary windings is energized, the other is not, and vice versa. The oscillation of the electrically conductive ring (201) is produced by the interaction between the magnetic field (301) and the current (501) of the primary winding (104).
In this way, the current (501) from the primary winding (104) produces an alternating magnetic field (102) within the laminated silicon iron (101) of the transformer. The ferrous material of the transformer can also be annealed iron wire or ferrite or any other material that concentrates the magnetic field, preferably laminated silicon iron with the greatest number of field lines prior to saturation. By Faraday's law and Lenz's law, this alternating magnetic field (102) induces an alternating current (401) inside the electrically conducting ring (201) in the opposite direction to the current (501) of the primary winding (104). The induced current (401) within the electrically conductive ring (201) generates an alternating magnetic field (301) that opposes the original magnetic field (102).
Since the alternating magnetic field (301) is a vector field, each field line has a vertical component (503A) and a horizontal component (503B).
In this way, the horizontal component (503B) of the magnetic (301) and the current (501) of the primary winding (104) interact with each other and their vector product (F=I×B) generates a vertical repulsive force (601) between the electrically conductive ring (201) and the primary winding (104). This vertical repulsive force (601) is what allows the electrically conductive ring (201) to oscillate in the central column of the closed-core transformer.
Likewise, the vertical component (503A) of the magnetic field (301) and the current (501) of the primary winding (104) interact with each other and their vector product (F=I×B) generates a radial horizontal force (602) between the electrically conductive ring (201) and the primary winding (104). This radial horizontal force (602) has a resultant equal to zero, since it cancels (vectorial sum equal to zero). This radial horizontal force (602) allows the electrically conducting ring (201) to be centered and to move practically without friction along the vertical column of the transformer (101).
The oscillating movement of the electrically conducting ring (201) is generated by alternately energizing the lower primary winding (104) and the upper primary winding (104). Then the vertical force of repulsion (601) is upwards when the lower primary winding (104) is energized, and the electrically conductive ring (201) moves upwards. When the electrically conductive ring (201) is close to the upper primary winding (104), it is energized and the vertical repulsion force (601) is downwards, generating a displacement of the ring towards the lower primary winding (104). And so on.
The excitation of the upper and lower primary windings (104, 702) can be done directly from the electrical network (103), with frequencies of 50 Hz or 60 Hz, as the case may be, or through a special source, such as an H bridge (701). There must be one H-bridge for each primary winding (104, 702).
If it is desired to excite the primary windings (104, 702) directly from the electrical network (103), the excitation frequency that generates induction in the electrically conductive ring (201) is the frequency of the network (902, 904, 1102, 1104). And each primary winding (104, 702) must be alternately energized through some switching device, such as a relay (using Normal Open and Normal Close states), two solid state relays, or transistors. The alternation with which the lower primary winding (104, 702) is energized and later the upper primary winding (104, 702) and so on, will be the oscillation frequency of the electrically conductive ring (201) inside the transformer (101), which corresponds to the enveloping curves (901, 903) for a duty cycle of 50% and to the enveloping curves (1101, 1103) for a duty cycle of less than 50%.
If it is desired to drive the primary windings (104, 702) with an H-bridge (701), the same H-bridge (701) allows voltage and current to be delivered to the primary windings (104, 702) to achieve high (induction) frequency. and additionally, the low frequency, (alternating between them) to oscillate the electrically conductive ring (201).
The H bridge (701) allows the primary windings (104, 702) to be energized to achieve a current in one direction (positive to the right) with the activation of the transistors 703 (MOSFET, IGBT, BJT, among others). An instant later in time (half an induction cycle) the transistors 703 are no longer powered and the transistors 704 are powered to generate a current flow in the reverse direction (positive to the left).
For a 50% duty cycle, the drive signals of the H bridge (701) of the primary windings (104, 702) must be 180° out of phase, in such a way as to achieve the oscillation of the electrically conductive ring (201). In this way, for a 50% duty cycle, the drive signal of the H-bridge (701) for the upper primary winding (104, 702) is the induction signal (802) and also the enveloping curve (801) that generates the oscillation of the electrically conductive ring (201). Likewise, the drive signal of the H bridge (701) for the lower primary winding (104, 702) is the induction signal (804) and also the enveloping curve (803) that generates the oscillation of the electrically conductive ring (201).
For a duty cycle of less than 50%, the drive signal of the H bridge (701) for the upper primary winding (104, 702) is the induction signal (1002) and also the enveloping curve (1001) that generates the oscillation of the electrically conductive ring (201). Likewise, the drive signal of the H-bridge (701) for the lower primary winding (104, 702) is the induction signal (1004) and also the enveloping curve (1003) that generates the oscillation of the electrically conductive ring (201).
With the use of modern sources such as an H-bridge, as a current or voltage source, one can have a lot of flexibility in the oscillation frequency parameters (801, 803, 901, 903, 1001, 1003, 1101, 1103) of the electrically conductive ring (201). Externally to the device, the excitation frequency of the coils (enveloping curve) (801, 803, 901, 903, 1001, 1003, 1101, 1103) can be varied.
It is advisable to use modern sources such as the H bridge as a voltage or current source, since for this device to be competitive, the electrically conductive ring (201) must be able to oscillate at more than 30 Hz. For this, the induction frequencies must be substantially higher (of the order of 10 times more), so that with each oscillation the ring has at least one complete induction cycle and thus ensure that the currents inside it are effectively very high.
In addition to the above, the path of the electrically conductive ring (201) inside the transformer (stroke) can be varied. The stroke that the electrically conductive ring travels is determined by the distance between the upper and lower primary windings (104). As can be understood, at a greater distance, the frequency of the electrically conductive ring (201) will be lower and vice versa.
The proposed configuration is that of a closed-core single-phase transformer comprising:
The combination between a closed magnetic circuit (101), without an air gap, with a great capacity to concentrate the magnetic field (102) and a primary winding (104) that generates that magnetic field, inducing gigantic currents in the electrically conductive ring (201), it causes a very efficient system in the sense that it does not generate losses for its operation.
To assure the effectiveness (movement) and efficiency (ratio between electrical energy consumed and energy transformed into mechanical movement) of the system and reduce operating losses, cooling of the electrically conductive ring (201) must be ensured, which is achieved preferentially, by the surrounding air generated by the movement of the ring, without ruling out, but being only an option, the use of inert or dielectric gases such as nitrogen, argon, SF6, among others. This is due to the fact that if the induced current (401) in the electrically conductive ring (201) is hundreds of thousands of amperes and the current density is of the order of hundreds of amperes per square millimeter, the electrically conductive ring (201) will tend to heat up and this will generate on the one hand: (i) losses in the system since part of the power consumed by the reciprocating linear motor device will be converted into heat, but on the other hand (ii) less movement of the electrically conductive ring (201). This lesser movement is due to the fact that when the electrically conductive ring (201) heats up, its electrical resistance will increase, and the induced current (401) will decrease. As the induced current (401) decreases, the intensity of the magnetic field (301) associated with the induced currents (401) in the electrically conductive ring (201) will decrease.
That is why the electrically conductive ring (201) considers axial perforations (1401) parallel to its direction of movement. In this way, by forced convection and thanks to the good thermal conductivity of aluminum, the heat generated in the electrically conductive ring (201) is displaced by the high current density in it.
The axial perforations (1401) that cool the electrically conductive ring (201), also decrease the resistance of the air to the displacement of the ring. Since the average speed of the electrically conductive ring (201) is of the order of tens of meters per second, and the resistance with the air increases quadratically with the speed, decreasing this aerodynamic resistance increases the efficiency of the system. That is why the electrically conductive ring (201) considers axial perforations (1401).
The mobile element is simply an electrically conductive ring (201), preferably made of aluminum or its alloys, without ruling out other materials, in which currents (401) are induced without electrical contact of any kind. That is, the active component of the conductive ring (201) that generates reciprocating movement, are induced currents. Unlike those solutions that propose permanent magnets or electrical loops in the mobile element that must make contact with the stator, the electrically conductive ring (201) is capable of handling hundreds or thousands of amperes without making electrical contact with the rest of the equipment.
The reciprocating vertical linear movement is achieved from a slip fit between the inside diameter of the electrically conductive ring (201) and the central column of the transformer (101). That is, linear bearings to restrict radial movements are not required, given by the resulting radial forces between the transformer (101) and the electrically conductive ring (201). This is because there are no attractive forces between the laminated silicon iron of the transformer (101) and the electrically conductive ring (201). In fact, the radial forces (602) that exist between the vertical component (503A) of the magnetic field (301) generated by the electrically conductive ring (201) and the current of the coil (104), cancel around the entire perimeter of the electrically conductive ring (201).
The manufacturing method of the reciprocating induction linear motor device has variations, depending on the format of the ferrous core that is used. It basically depends on: (i) the core can be opened and closed during the manufacturing process, or, (ii) that once the core is manufactured, it can no longer be opened again.
The application example of the present development of the linear induction motor device corresponds to:
With the above configuration, without optimization of any kind, oscillation frequencies of the aluminum electrically conductive ring (201) are achieved above 10 Hz, with a stroke of 500 mm, theoretical currents within the aluminum electrically conductive ring (201) around at 180 kA, a current density of 115 A/mm2 and an average speed of more than 5 m/s.
As can be seen, for this application example, the frequencies developed by the aluminum electrically conductive ring (201) are comparable to the tools used in the industry with a much higher stroke. However, the application example did not consider hitting a rock, but when removing the springs and making an impact, the frequency managed to stay above 7 Hz.
Number 101 is the laminated silicon iron core.
Number 102 corresponds to the magnetic field lines.
Number 103 is the excitation source of the primary windings (104). It can be alternating current or direct current. If it is direct current, the inductive effect on the electrically conducting ring (201) will be only in the transient period.
Number 104 corresponds to the primary winding.
Number 201 is the electrically conductive ring.
Number 301 is the magnetic field generated by the induced current in the electrically conductive ring (201), due to the alternating magnetic field (102) in the laminated silicon iron (101).
Number 201A is a sectional view of the electrically conductive ring (201).
Number 201B is a top view of the electrically conductive ring (201).
Number 401 is the induced current for each of the views.
Number 401A is the induced current in the electrically conductive ring (201), entering the sheet.
Number 401B is the current induced in the electrically conductive ring (201), exiting the sheet.
Number 301 is the vector magnetic field generated by the induced current 401.
The magnetic field (102) in the laminated iron (101) of the transformer has a downward direction (502) in the central column of the transformer given the right-hand rule. This magnetic field in the iron (101) induces a current (401) in the electrically conductive ring (201) in the opposite direction to the original current (501). The induced current (401) generates a second magnetic field (301), whose vector field is represented by the arrows (503). As can be seen, in the center of the ring, the prevailing component is the vertical, with an upward direction, but the magnetic field, being vectorial, always has an horizontal component (503B) and a vertical component (503A).
Number 501 is the current in the primary winding (104).
Number 502 is the direction of the magnetic field (102) in the laminated iron (101) of the transformer.
Number 503 is the direction and sense of the vector magnetic field (301), in the center of the electrically conductive ring (201).
Number 503A is the vertical component of the vector magnetic field (301).
Number 503B is the horizontal component of the vector magnetic field (301).
Since the alternating magnetic field (301) is a vector field, each field line has a vertical component (503A) and a horizontal component (503B). In this way, the horizontal component (503B) of the vector magnetic (301) and the current (501) of the primary winding (104) interact with each other and their vector product (F=I×B) generates a vertical repulsive force (601) between the electrically conductive ring (201) and the primary winding (104).
Likewise, the vertical component (503A) of the vector magnetic field (301) and the current (501) of the primary winding (104) interact with each other and their vector product (F=I×B) generates a radial horizontal force (602) between the electrically conductive ring (201) and the primary winding (104). This radial horizontal force (602) has a resultant equal to zero since it cancels (vectorial sum equal to zero).
Number 601 corresponds to a vertical repulsive force between the electrically conductive ring (201) and the primary winding (104).
Number 602 corresponds to a radial horizontal force between the electrically conductive ring (201) and the primary winding (104).
The H bridge (701) allows the primary windings (104, 702) to be excited to achieve a current in one direction (from positive to negative) with the activation of the transistors 703 (MOSFET, IGBT, BJT, etc). A later time instant (half an induction cycle) the transistors 703 are no longer powered and the transistors 704 are powered to generate a current flow in the reverse direction (from negative to positive).
Number 701 corresponds to the H bridge.
Number 702 corresponds to the load that feeds the H bridge, which, in this case, corresponds to the primary windings (104).
Number 703 corresponds to the group of transistors that allows the flow of current in a positive direction to the right.
Number 704 corresponds to the group of transistors that allows the flow of current in a positive direction to the left.
Number 801 is the signal (input) of the H bridge (701) that feeds the upper primary winding (104). This signal is a low frequency enveloping curve that drives the transistors (703, 704) that allow current output from the H bridge to the upper primary winding (104, 702) and ensures the oscillation of the electrically conductive ring (201). As can be seen in the figure, the duty cycle is 50%.
Number 802 is the signal (input) of the H bridge (701) that feeds the upper primary winding (104). This is the high frequency excitation signal that drives the transistors (703, 704) and allows current output from the H bridge to the upper primary winding (104, 702), which ensures the induction of currents in the ring. electrical conductor (201). As can be seen in the figure, the duty cycle is 50%.
Number 803 is the signal (input) of the H bridge (701) that feeds the lower primary winding (104). This signal is a low frequency enveloping curve that drives the transistors (703, 704) and allows current output from the H bridge to the lower primary winding (104, 702) and ensures the oscillation of the electrically conductive ring (201). As can be seen in the figure, the duty cycle is 50%.
Number 804 is the signal (input) of the H bridge (701) that feeds the lower primary winding (104). This is the high-frequency excitation signal that drives the transistors (703, 704) and allows current output from the H-bridge to the lower primary winding (104, 702), which ensures the induction of currents in the ring. electrical conductor (201). As can be seen in the figure, the duty cycle is 50%.
These voltages or currents are 180° out of phase, in such a way as to achieve the oscillation of the electrically conductive ring (201). In this way, for a 50% duty cycle, the output current of the H-bridge (701) for the upper primary winding (104, 702) is the high-frequency current that generates induction (902) and also the enveloping current curve of low frequency (901) that generates the oscillation of the electrically conductive ring (201). Likewise, the output current of the H-bridge for the lower primary winding (104, 702) is the high-frequency current that generates induction (904) and also the low-frequency enveloping current curve (903) that generates the oscillation of the electrically conductive ring (201).
Number 901 is the voltage that from the H bridge (701) feeds the upper primary winding (104). This voltage is low frequency and generates the H-bridge current to the upper primary winding (104, 702). It is this current that ensures the oscillation of the electrically conductive ring (201). As can be seen in the figure, the duty cycle is 50%.
Number 902 is the voltage that feeds the upper primary winding (104) from the H bridge (701). This voltage is the high frequency excitation that allows current output from the H bridge towards the upper primary winding (104, 702), which ensures the induction of currents in the electrically conductive ring (201). As can be seen in the figure, the duty cycle is 50%.
Number 903 is the voltage that feeds the lower primary winding (104) from the H bridge (701). This voltage is low frequency and generates the current output from the H-bridge to the lower primary winding (104, 702). This current ensures the oscillation of the electrically conductive ring (201). As can be seen in the figure, the duty cycle is 50%.
The number 904 is the voltage from the H bridge (701) that feeds the lower primary winding (104). This voltage is the high-frequency excitation and generates the current output from the H-bridge towards the lower primary winding (104, 702), which ensures the induction of currents in the electrically conducting ring (201). As can be seen in the figure, the duty cycle is 50%.
Number 1001 is the signal (input) of the H bridge (701) that feeds the upper primary winding (104). This signal is a low frequency enveloping curve that drives the transistors (703, 704) that allow current output from the H bridge to the upper primary winding (104, 702) and ensures the oscillation of the electrically conductive ring (201). As can be seen in the figure, the duty cycle is less than 50%.
Number 1002 is the signal (input) of the H bridge (701) that feeds the upper primary winding (104). This is the high frequency excitation signal that drives the transistors (703, 704) and allows current output from the H bridge to the upper primary winding (104, 702), which ensures the induction of currents in the aluminum ring (201). As can be seen in the figure, the duty cycle is less than 50%.
Number 1003 is the signal (input) of the H bridge (701) that feeds the lower primary winding (104). This signal is a low frequency enveloping curve that drives the transistors (703, 704) and allows current output from the H bridge to the lower primary winding (104, 702) and ensures the oscillation of the electrically conductive ring (201). As can be seen in the figure, the duty cycle is less than 50%.
Number 1004 is the signal (input) of the H bridge (701) that feeds the lower primary winding (104). This is the high-frequency excitation signal that drives the transistors (703, 704) and allows current output from the H-bridge to the lower primary winding (104, 702), which ensures the induction of currents in the aluminum ring (201). As can be seen in the figure, the duty cycle is less than 50%.
These voltages or currents are 180° out of phase, in such a way as to achieve the oscillation of the electrically conductive ring (201). In this way, for a duty cycle of less than 50%, the output current of the H-bridge (701) for the upper primary winding (104, 702) is the high-frequency current that generates induction (1102) and also the current low frequency enveloping curve (1101) that generates the oscillation of the electrically conductive ring (201). Likewise, the output current of the H-bridge for the lower primary winding (104, 702) is the high-frequency current that generates induction (1104) and also the low-frequency enveloping current curve (1103) that generates the oscillation of the electrically conductive ring (201).
The number 1101 is the voltage that feeds the upper primary winding (104) from the H bridge (701). This voltage is low frequency and generates the H-bridge current to the upper primary winding (104, 702). It is this current that ensures the oscillation of the electrically conductive ring (201). As can be seen in the figure, the duty cycle is less than 50%.
The number 1102 is the voltage that feeds the upper primary winding (104) from the H bridge (701). This voltage is the high frequency excitation that allows current output from the H bridge towards the upper primary winding (104, 702), which ensures the induction of currents in the electrically conductive ring (201). As can be seen in the figure, the duty cycle is less than 50%.
The number 1103 is the voltage that feeds the lower primary winding (104) from the H bridge (701). This voltage is low frequency and generates the current output from the H-bridge to the lower primary winding (104, 702). This current ensures the oscillation of the electrically conductive ring (201). As can be seen in the figure, the duty cycle is less than 50%.
The number 1104 is the voltage from the H bridge (701) that feeds the lower primary winding (104). This voltage is the high-frequency excitation and generates the current output from the H-bridge towards the lower primary winding (104, 702), which ensures the induction of currents in the electrically conducting ring (201). As can be seen in the figure, the duty cycle is less than 50%.
In the elevation view, the vertical-axial force (601) exerted on the electrically conductive ring (201) can be observed, which is responsible for its oscillation within the electrical transformer (101).
Since the alternating magnetic field (301) is a vector field, each field line has a vertical component (503A) and an horizontal component (503B). In this way, the horizontal component (503B) of the vector magnetic (301) and the current (501) circulating in the primary winding (104) interact with each other. Its cross product (F=I×B) generates a vertical repulsive force (601) between the electrically conducting ring (201) and the primary winding (104).
In the top view, the horizontal-radial force (602) exerted on the electrically conductive ring (201) can be observed, which is responsible for the electrically conductive ring (201) self-centering in the central column of the electrical transformer. (101).
Likewise, the vertical component (503A) of the vector magnetic field (301) and the current (501) of the primary winding (104) interact with each other and their vector product (F=I×B) generates a radial horizontal force (602) between the electrically conductive ring (201) and the primary winding (104). This radial horizontal force (602) has a resultant equal to zero, since it cancels (vectorial sum equal to zero). This allows the electrically conductive ring (201) to self-center on the central column of the electrical transformer (101).
Number 1401 corresponds to the axial through-holes in the electrically conductive ring (201).
The air gap (1504) generates a high reluctance in the magnetic circuit (1505). As in electrical circuits, where a high resistance prevents the passage of current, in the case of magnetic circuits a high reluctance (due to air gaps) prevents the passage of magnetic flux. This generates that for the same excitation (magnetomotive force N*I, given by the product of the winding of N turns (1507) and the current circulating in the winding (1508)), a lower field density is obtained (magnetic field lines (1501) divided by the cross section of the iron core (1503)) in the magnetic core.
Number 1501 corresponds to the magnetic field lines in the air gap.
Number 1502 plots the boundary effect on the air gap.
Number 1503 is the cross section of the iron core.
Number 1504 is the air gap.
Number 1505 corresponds to the magnetic field lines.
Number 1506 is the length of the iron core.
Number 1507 is the winding with N turns.
Number 1508 is the current circulating in the winding.
Number 1509 is the zone with magnetic permeability equal to that of air.
Number 1510 is the area with magnetic permeability equal to that of iron.
The reciprocating vertical movement of the electrically conductive ring (201) generates a volume change in the air chamber (1704) which drives the piston (1705), which in turn strikes the chisel (1706), which in turn strikes the rock.
Number 1701A corresponds to the superior ideal spring.
Number 1701B corresponds to the lower ideal spring.
Number 1702 corresponds to two dampers that make the action of the springs (1701A, 1701 B) real, according to the dynamic model of
Number 1703 corresponds to the larger plunger in the air chamber (1704).
Number 1704 is the air chamber that transmits the movement of the electrically conductive ring to the piston (1705).
Number 1705 is the piston which in turn strikes the chisel (1706) which in turn strikes the rock.
Number 1706 is the chisel that hits the rock.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/CL2020/050100 | 9/3/2020 | WO |
