Counter-rotation drive
The mechanical counter-rotation drive according to the present invention is based on the laws of relative motion of an eccentric part of one of at least two shafts, which are constitutive parts of this drive, with respect to the plates of a determined shape whose motion is confined by pins arranged in a determined arrangement, is illustrated in FIG. 1, where in the housing 10 which supports the mechanical counter-rotation drive are accommodated the first (driving) plate 30 and the second (driven) plate 40 in such a manner that they are approximately or completely parallel to one another. In the housing 10 are embedded a plurality of pins 20 of which each one represents a shaft which bears and around which rotates at least one cylinder 35 which is in operational contact with the perimeter 135 of the first plate 30 which is in rigid contact with the first shaft 50 (which shaft is not visible in FIG. 1). In the first plate 30 are embedded a plurality of second pins 80 of which each one represents a shaft which bears and around which rotates at least one cylinder 85 which is in operational contact with the perimeter 145 of the second plate 40. Ball bearings 90 function as a sliding support for the second shaft 60 in the part 10a of the housing, which part is in this case removed in order to allow the view of the design of the counter-rotational drive according to the invention inside the housing 10. In the preferred embodiment of the invention the sliding support of the first shaft 50 in the housing 10 and/or of the second shaft 60 in the part of the housing 10a is realized by ball bearings, but the sliding support can be realized by using other sliding elements and/or sliding surfaces. The axis of rotation of the first shaft 50, which is not visible in FIG. 1, belongs approximately or exactly to the same line as the axis of rotation of the second shaft 60, and the angular direction of rotation of the first shaft 50 is the first direction 55, while the angular direction of rotation of the second 60 shaft is 65, such that the angular directions of rotation 55 and 65 are opposite to each other.
This application is a continuing application of U.S. patent application Ser. No. 11/337,519, filed on Jan. 24, 2006, which claims the priority of provisional patent application No. 60/648,281 filed on Jan. 31, 2005, and claims priority therefrom, both of which are incorporated in their entirety.
FIELD OF THE INVENTIONThe present invention relates generally to transmission systems, and more particularly to transmission systems with rotating plates capable of producing counter-rotation between two inline shafts.
BACKGROUND OF THE INVENTIONCounter-rotation is used in mechanisms which require reversing the angular direction of rotation, in cases in which it is necessary for the driving shaft to rotate in one angular direction, and the other shaft, which is driven by the driving shaft, to rotate in the opposite angular direction. Such forms of transmission are used in helicopter drives, differential transmissions in vehicles, propeller driven marine vessels, turbine engines, turbogenerators, and compressors, to name a few.
Solving the problem of mechanical counter-rotation with a transmission ratio of 1 to 1 and shafts aligned along a common rotational axis is exclusively confined to types of planetary gear transmissions and transmission of torque via gears. The transmission ratio 1 to 1 (1:1) means that an angular displacement at one end of a device is transmitted by the device so that exactly the same angular displacement is produced at the other end of the same device. For example, a solution with a double propeller helicopter with a common axis by S. P. Vaughn (U.S. Pat. No. 2,037,745) where counter-rotation of two propeller systems is used to provide a more stable flight and facilitate the control of the helicopter. A solution with a counter-rotating double propeller system (U.S. Pat. No. 4,642,059) is used for a marine drive, in which case an inner shaft is at one end directly coupled to an outer hollow drive shaft. Another patent (U.S. Pat. No. 4,963,108) describes a system for counter-rotation comprising a propeller with a large gear driven by an engine, with which gear a plurality of smaller gears are in operational contact at its perimeter, so that counter-rotation of the second, driven, shaft is obtained. The known solutions which use planetary geared transmission are cumbersome, with significant losses to friction, accompanied by common problems of wear and low efficiency, due to gaps that cannot be avoided in such solutions. These solutions are also known to produce clattering and loud noise resulting from the existence of the gaps. Such transmission systems also have a low degree of safety of operation, and are known to lack a constant torque at each point. Also, in solutions with planetary gears, the load is unevenly distributed; in most cases concentrated at one point (the point of immediate contact of the driving and driven parts of the assembly). This uneven load distribution creates critical elements in the assembly and requires excessively large parts to provide the necessary safety margins.
The problem of obtaining counter-rotation of coupled shafts with a transmission ratio of 1:1 and shafts aligned along the same rotational axis in the manner disclosed here has not been observed in any other solution known in prior art.
SUMMARY OF THE INVENTIONThe invention disclosed herein is a mechanical counter-rotation drive, comprising a support structure that remains stationary with respect to the mechanical drive and providing a structural point of attachment for the mechanical drive, a first driving shaft that provides a drive torque having an eccentric portion and rotating in a first angular direction of rotation, a second shaft, having a same axis of rotation as the first shaft, functioning as a driven shaft and rotating in a second angular direction of rotation that is opposite to the first angular direction of rotation, a first plate having a plurality of lobes and operationally connected with the eccentric portion of the first driving shaft and having a center that is not aligned with the axis of rotation of the first and second shafts and rotates eccentrically with respect to the axis of rotation, a plurality of first pins operationally connected to the support structure and arranged such that a portion of a perimeter of the first plate is in rolling contact with the first pins and such that the arrangement causes the first plate to rotate in the second angular direction of rotation, a plurality of second pins that are operationally connected to the first plate or are constitutive parts of the first plate, and a second plate having a plurality of lobes and operationally connected with the first plate in such a way that a portion of a perimeter of the second plate is in rolling contact with the second pins of the first plate producing a rotation of the second plate in the second angular direction of rotation, wherein the second shaft is operationally connected to the second plate or is a constitutive part of the second plate, and is driven by the second plate.
The present invention also relates to a mechanical counter-rotation drive, which provides mechanical counter-rotation of shafts coupled by the invention with a transmission ratio of 1:1 and aligned along a common rotational axis without planetary transmission elements, whereas in alternate embodiments of the invention it is possible to realize transmission ratios other than 1:1. The basic embodiment of the invention is the realization of a mechanism for reversing the angular direction of rotation between two inline shafts such that the two shafts will rotate with angular directions of rotation that are opposite to each other, and the two shafts share a common rotational axis. The present invention can generally be used for reversing of the angular direction of rotation of inline shafts with a common axis, and particularly in combustion gas turbine engines, turbine engines in general, torque transmissions to propellers, helicopter drives, marine drives, differential transmissions, land vehicles, robotics, and the like.
The above-mentioned and other concepts of the present invention will now be described with reference to the accompanying drawings of the preferred embodiment of the present invention. The presented embodiment is intended to illustrate the application, but not to limit the invention. The drawings contain the following figures, in which like numbers refer to like parts throughout the description and drawings and wherein:
The counter-rotating drive described herein employs some basic concepts. For example, in its broadest concept, the counter-rotation drive reverses the direction of rotation of a driven shaft associated with a drive shaft. Another concept relates to a nested counter-rotating drive configuration, having a drive shaft arranged within a driven shaft. Another concept relates to a counter-rotation drive adapted to minimize the vibration experienced during operation via a configuration that is counter-balanced.
The present invention is disclosed in context of use as a counter-rotation drive for use in any combustion turbine engine. For example, the number of rows of rotating airfoil blades and stationary airfoil vanes in the compressor or turbine sections of a typical combustion turbine engine can be reduced by incorporating the counter-rotation drive. However, the principles of the counter-rotation drive are not limited to use in a combustion turbine engine. The counter-rotation drive can be used in any application where reversing the direction of rotation of a driven shaft associated with a drive shaft is applicable. Examples of such applications include marine drives, turbojets, turbofans, turboshafts, helicopter rotor systems, transmission systems, and geared reduction systems just to name a few. Such systems are commonly used in the transportation industry, aerospace industry, petroleum industry, and many household appliances.
While the counter-rotation drive is disclosed in context of use as a drive system, it is not limited to use as a drive system. The counter-rotation drive may be used as a reduction system as well. One skilled in the art may find different applications, processes, configurations, and methods for the counter-rotation drive disclosed herein. Thus, the illustration and description of the present invention in context of use as a counter-rotation drive is merely one possible application of the present invention. However, the present invention has particular applicability for use as a counter-rotation drive in a combustion turbine compressor.
A mechanical counter-rotation drive (CRD) according to the present invention is illustrated in
Referring to
Referring to
The first plate 30 and the second plate 40 can be constructed and produced by any suitable method known to a person skilled in the art, from any suitable material such as metal, wood, plastic, composites, alloys, ceramics, or any existing material in solid form. Selection of the first plate 30 and second plate 40 material should be commensurate with the particular application. However, it is not required that the material selection for first plate 30 and second plate 40 be commensurate with the particular application, but may be selected based on economic considerations such as cheapest to produce. Furthermore, the first plate 30 and the second plate 40 are not required to be constructed of the same material. Plates may have additional holes, lobes, incisions, notches and any other elements of shape. It is also anticipated, in other embodiments, to add a second first plate and a second eccentric part of the drive shaft 50 in such a way that these two first plates have a different mass distribution and reduce vibrations that are the result of the possibly uneven mass distribution of a single first plate 30.
In
The first (driving) shaft 50 is supported via the bearings 90 in the housing 10, or within some other assembly, and has an axis of rotation 56. If required, more than one set of bearings 90 can be used to support of the shaft 50. The first plate 30 comprises a plurality of second pins 80 whose axes 81 are approximately or exactly parallel to axes 21 of the first pins 20. Although this is not a general requirement, the outer surfaces of the rotating cylinders 35 and 85 may be approximately or exactly parallel to the surfaces of the perimeters 135 and 145. It is advantageous that the first pins 20 and the second pins 80 be fixed by screws 25. However, this is not a general requirement and other solutions are also applicable. The second (driven) shaft 60, whose axis of rotation is axis 66, is operationally coupled to the second plate 40. However, this is not a general requirement, since the second shaft 60 and the second plate 40 can be made out of a single piece of material, for example. The second shaft 60 is supported in the bearings 90 mounted within the housing 10 or within some other assembly. The axis of rotation 56 of the driving shaft 50 and the axis of rotation 66 of the driven shaft 60 are approximately inline and remain so during operation.
The magnitude and direction of the rotational speed of the first plate 30 depend on the shape of its perimeter 135, number of lobes 130, number of pins 20 supported in the housing 10, the eccentric part 70, and is determined by trigonometric functions that cause the cylinders 35 of the first pins 20 to impinge on the lobes 130 of the first plate 30, thereby rotating the first plate 30 in the desired direction. The rotation of the second plate 40 is produced by the transmission of the rotation of the first plate 30 via the second pins 80 to the second plate 40. The angular speed of rotation of the second plate 40 can be different from the angular speed of rotation of the first plate 30. The magnitude and direction of the rotational speed of the second plate 40 is determined by the number of lobes 130 of the first plate 30, the number of lobes 140 of the second plate 40, the shape of the perimeter 135 of the first plate 30 and the shape of the perimeter 145 of the second plate 40. The principle relationships of these elements can be derived from the translational-rotational motion of a cycloid along a hypocycloid or epicycloid with a predetermined eccentric offset and a predetermined diameter of the circle that produces the cycloid, such that using the same eccentric offset for defining the output, a resulting transmission ratio of rotational motion is obtained, which ratio can be 1 to 1 (1:1) or other ratios, depending on the parameters and the housing-pins environment of the cycloid. All the necessary functional relationships are derived from the set of relevant trigonometric functions (1) where the first pair is used for defining the shapes of the plates and the second pair is used for obtaining the pin positions:
X=(Ra+Rb)·cos(α)+Ra·cos(α+β))
Y=(Ra+Rb)·sin(α)+Ra·sin(α+β)
X=(Rb−Ra)·cos(α)+Ra·cos(β−α)
Y=(Rb−Ra)·sin(α)+Ra·sin(β−α)
where α is the angle defining the position of the center of a moving cylinder (Ra) with respect to the center of a fixed cylinder (Rb), and β is the angle defining the angular position of a fixed point on a moving cylinder (Ra) with respect to the center of the moving cylinder and relative to the center of a fixed cylinder (Rb).
It is not required that each lobe 130 comprise a second pin 80 placed in the domain of the lobe 130. The embodiment described produces rotation of the first plate 30 in the opposite angular direction of rotation 65 from the angular direction of rotation 55 of the first shaft 50. The location of the first pins 20 and the shape of the perimeter 135 of the first plate 30, particularly of lobes 130, aid in obtaining counter-rotation. In addition, the magnitude of the distance of the center 136 of the first plate 30 from the center of rotation 56 of the first shaft 50, i.e. the length of the eccentric part 70, is the variable that affects the trigonometric function which defines the shape of the perimeter 135 of the first plate 30.
It is important to note that the driving plate can be either the first plate 30 or the second plate 40, but the present description only deals with the case in which the drive plate is the first plate 30, for simplicity. In the same way, the driving shaft can be either shaft 50 or shaft 60. In other words, the part of the assembly which is functionally the driving part in one embodiment can in another embodiment be functionally the driven part and vice versa. This applies to all descriptions and examples in further text.
In yet another embodiment, the same principles provide a solution which effectively comprises two basic embodiments described above joined into one, in such a way that it includes two first plates 30 and two eccentric parts 70, and the second plates 40 are joined into one part, and the counter-rotation is transferred by a connection outside the housing 10 to a disk which rotates in the opposite angular direction 65 with respect to the first shaft 50, which shaft 50 in such an embodiment extends through the assembly. This embodiment is intended to enhance operational balance of the assembly.
In yet another embodiment the same principles provide a solution which effectively comprises two basic embodiments described above joined into one, in such a way that the second shaft 60 has a larger diameter than the first shaft 50 and is hollow, so that the first shaft 50 extends through the assembly and has the same axis of rotation 56 as the second shaft 60, which causes the counter-rotation of the second shaft 60 around the first shaft 50 which in such an embodiment extends through the assembly.
In yet another embodiment, combining and pairing of the plates (driving and driven, i.e. the first plate 30 and the second plate 40) it is also possible to achieve various transmission ratios. For example, if the first plate 30 is made with 6 lobes 130 and the second plate 40 with 4 lobes 140, with the same conditions as in the above described embodiments, a transmission ratio different from 1:1 is achieved. Also, if the same plates are used for achieving the transmission ratio of 1:1, but with different conditions such as the number of first pins 20 in the housing 10 and the length of the eccentric part 70 of the first shaft 50, then a transmission ratio different from 1:1 is achieved. By adding one more first plate 30 and pairing in such a way that a sequence first 30-second 40-first 30 plate is obtained, the transmission ratio of 1:1 is maintained, but the first and the last shaft in this sequence rotate in the same angular direction of rotation.
In yet another embodiment, the present invention is used in the compressor of a combustion gas turbine engine such that the compressor comprises a plurality of stages consisting of stationary and rotating airfoils, such that a rotating row of airfoils rotates in a direction opposite an adjacent rotating row of airfoils. In such an embodiment, it is possible for the adjacent rows of rotating airfoils to rotate at different rates. This application of the CRD according to the present invention will reduce the stage count in the compressor section of a typical combustion turbine engine.
In other embodiments, the CRD can be applied in any design with drive shafts, such as marine propeller drives, helicopter propeller drives, automotive applications, and home appliances, to name a few. In such applications the CRD according to the invention would provide counter-rotation in addition to varying the transmission ratio.
Furthermore, other embodiments of the CRD according to the invention are possible in turbo-propulsion engines, turbo-shaft engines, turbo-fan engines, other turbine engines, in differential transmissions in cars and other land vehicles, submarine and marine drive systems, and robotics to name a few.
Furthermore, while the CRD is disclosed here in the context of application as a drive system, it is not limited to applications as a drive system. The CRD according to the invention can also be used as a reduction system. A person skilled in the art can find other applications, processes, configurations, and methods for the CRD hereby disclosed. Because of that, the illustration and description of the present invention in the context of application as a counter-rotating drive is only one of many possible applications of the present invention.
EXAMPLESThe following examples are provided and serve as illustration of possible embodiments of the present invention and are not intended to limit the scope of the invention in any way.
Example 1An embodiment of the CRD is illustrated in
A physical model was made according to this embodiment, which model is easily driven by hand, and allowed measurement of the transmission, which was 1:1 in this case. The model dimensions are: diameter 350 mm, both shafts diameter 25 mm, eccentric offset of the eccentric part of the shaft 11.25 mm.
Example 2According to the embodiment of the present invention with a transmission ratio of 1:1 a physical model was made of metal, with similar basic dimensions as in Example 1. This metal model was used to test the possibility of achieving high rotational speeds. The model reached speeds in excess of 100,000 RPM (one hundred thousand revolutions per minute). The test confirmed that the overall friction in this embodiment originates from the bearings while rolling, and the heat generated is associated with the bearings and their motion.
This model was also tested for mechanical breakdown and proved to be mechanically robust and had a safety factor higher than that of classical gear transmission devices.
While the invention has been described in connection with what is presently considered to be the preferred embodiments, it is to be understood that its modifications, equivalents, and variations will be obvious, without changing the essence of the invention, to persons skilled in the art upon learning the essence of the invention from its description disclosed herein. It is therefore the intention of the author for these possible embodiments to be included within the spirit and scope of the appended patent claims.
Claims
1. A counter-rotation device, comprising:
- a first drive shaft having an eccentric portion and a second drive shaft, both shafts having a same axis of rotation, the first drive shaft rotating in a first angular direction of rotation and the second drive shaft rotating in a second angular direction of rotation;
- a first plate having a plurality of lobes, connected with the eccentric portion of the first drive shaft and having a center that is not aligned with the axis of rotation of the first or second drive shafts, and rotates with respect to the axis of rotation;
- a plurality of first pins connected to a support structure and arranged having a portion of a perimeter of the first plate in rolling contact with the first pins causing the first plate to rotate in the second angular direction of rotation;
- a plurality of second pins connected to the first plate, or are a constitutive part of the first plate; and
- a second plate having a plurality of lobes and connected with the first plate such that a portion of a perimeter of the second plate is in rolling contact with the second pins of the first plate causing a rotation of the second plate in the second angular direction of rotation,
- wherein the second shaft is connected to the second plate or is a constitutive part of the second plate, and is driven by the second plate.
2. A method to counter rotate adjacent shafts, comprising:
- providing a first lobed plate connected to an eccentric portion of a first drive shaft, the first drive shaft rotating in a first angular direction;
- providing a second lobed plate connected to and a second drive shaft, the second drive shaft being driven by the second plate and rotating in a second angular direction, wherein the first and second drive shafts have the same axis of rotation;
- providing a plurality of stationary pins in rolling contact with a periphery of the first lobed plate as to produce a rotation of the first lobed plate in a second angular direction;
- providing a plurality of second pins affixed to the first lobed plate and in rolling contact with the a periphery of the second lobed plate as to produce a rotation of the second lobed plate in the second angular direction,
- wherein the first and second lobed plates rotate with respect to the axis of rotation and the second drive shaft is caused to rotate in a second angular direction.
3. A method of operating a compressor for a gas turbine engine, comprising:
- providing a plurality of stationary compressor blades; and
- providing a plurality of rotating compressor blades, wherein the rotating compressor blades are attached to a counter-rotation device, comprising;
- a first drive shaft having an eccentric portion and a second drive shaft, both shafts having a same axis of rotation, the first drive shaft rotating in a first angular direction of rotation and the second drive shaft rotating in a second angular direction of rotation;
- a first plate having a plurality of lobes, connected with the eccentric portion of the first drive shaft and having a center that is not aligned with the axis of rotation of the first or second drive shafts, and rotates with respect to the axis of rotation;
- a plurality of first pins connected to a support structure and arranged having a portion of a perimeter of the first plate in rolling contact with the first pins causing the first plate to rotate in the second angular direction of rotation;
- a plurality of second pins connected to the first plate, or are a constitutive part of the first plate; and
- a second plate having a plurality of lobes and connected with the first plate such that a portion of a perimeter of the second plate is in rolling contact with the second pins of the first plate causing a rotation of the second plate in the second angular direction of rotation,
- wherein the second shaft is connected to the second plate or is a constitutive part of the second plate, and is driven by the second plate.
Type: Application
Filed: Mar 26, 2008
Publication Date: Oct 16, 2008
Inventor: Marko Ivankovic (Valjevo)
Application Number: 12/079,423
International Classification: F01D 15/12 (20060101);