The present invention relates to a device for transmitting rotary motion, said device for transmitting rotary motion comprising a motion-transmitting member for transforming a driving body rotatable about an axis of rotation into rotary motion of a body driven about an axis of rotation.
The invention further relates to a use of the invented device, in which the driven body is adapted to operate contacts of a diverter switch or an on-load tap changer in a transformer.
Further, the invention relates to a method of driving a body.
In certain applications, there is a need to achieve a short, powerful rotary motion in a definite direction. In certain cases, this can be quite unproblematic if the available drive source has a corresponding movement characteristic. However, this is not always the case. It may occur that the available drive source is of such a kind that it carries out rotary motion in one direction as well as in the other direction.
There are also situations where the drive source included does not immediately achieve a required powerful torque for the necessary short period. It may also occur that both of these imperfections occur simultaneously as far as the available drive source is concerned.
One example of such a situation is when operating a diverter switch in an on-load tap changer for controlling the voltage of a transformer. In this case, it may be advantageous that the operating movement always occurs in the same direction of rotation, and it should occur for a relatively short period of time. Usually, the drive source for such a diverter switch is in the form of the drive shaft that operates the selector switch, that is, the mechanism that sets the connections to new tap points in the winding of the trans-former when a change of voltage is to take place. The drive shaft of the selector switch rotates in different directions in dependence on whether it is a question of increasing or reducing the voltage of the transformer.
From WO 89/08924, a motion-transmitting mechanism is previously known, which is able to transform a rotary motion in one or the other direction into a unidirectional movement while at the same time concentrating the rotary motion with respect to time. The unidirection of the movement takes place by a special design of the spring, and elements directly cooperating therewith, which accumulate the energy and concentrate the rotary motion.
From WO 2006/004527, a motion-transmitting mechanism is previously known, which transforms a rotary motion in one or the other direction into a unidirectional movement which via, inter alia, a gear-wheel mechanism and shafts, transfers the rotary motion into an energy-storing system in the form of a spring unit. When the spring unit with a locking device is released, motion is transferred to a final shaft. Both the selector and the diverter switch are surrounded by transformer oil.
SE 0501712-5 describes a motion-transmitting mechanism that transforms an alternating rotary motion into a unidirected rotary motion via a linear translatory motion. Also in this motion-transmitting mechanism, the rotary motion is transmitted to an energy-storing system in the form of a spring unit.
According to a first aspect of the present invention, is seeks to provide an improved device for transmitting a rotary motion as well as a mechanical energy-storing system connected thereto.
According to a second aspect the invention seeks to provide a improved use for transmission of a rotary motion.
According to a third aspect, the invention seeks to provide an improved method for transmitting a rotary motion.
According to the first aspect of the invention, there is provided a device as specified in claim 1. Embodiments will be clear from the subsequent subclaims 2-10.
According to the second aspect of invention, a use of the device is there is provided according to claim 11.
The invention is also directed to a method by which the described device operates and including method steps for carrying out every function of the device according to the third aspect of the invention as specified in claim 12 and the associated subclaims 13-16.
Embodiments of the invention will be explained, by way of example only, in greater detail by the following detailed description of advantageous embodiments thereof with reference to the accompanying drawing figures.
a-2d schematically illustrate the mode of operation of the energy accumulation member and the intermediate body connected thereto.
An input drive shaft 1a is connected to a axis of rotation 3a via a motion-transforming member 4. The input drive shaft 1a is of such a nature that, when operated, it may rotate in one or the other direction. The motion-transforming member 4 is designed such that a rotary motion is always imparted to the axis of rotation 3a in one and the same direction irrespective of in which direction the input drive shaft 1a is rotated. The drive source for the input drive shaft 1a is the drive shaft that operates a diverter selector switch (not shown) in a transformer, that is, the mechanism that sets the connections to new tap points in the winding of a transformer when a change of voltage is to take place. The input drive shaft 1a of the diverter selector switch rotates in different directions in dependence on whether it is a question of increasing or reducing the voltage of the transformer. The output axis of rotation 3a is connected to an intermediate body 3 and to an associated energy accumulation member 5 as well as a driven body 2 with a drive shaft 2a. The body 2, in its turn, drives contacts (not shown here) of the diverter switch. These may be of a kind described in greater detail in WO 2006/004527.
The motion-transforming member 4 may, for example, be either of the kind described in the patent application WO 2006/004527 or of the kind described in the patent application WO 2006/050552.
When the axis of rotation 3a is rotated, it feeds energy into the mechanical energy accumulation member 5 via an intermediate body 3. After a definite angular motion of the axis of rotation, the accumulated energy is released to the intermediate body which rotates the drive shaft 2a rapidly and powerfully and thus imparts a rotary motion to the driving body 2, said rotary motion influencing the components of the diverter switch which are described in detail in the above-mentioned WO 2006/004527. A gear change (not shown) may be arranged between the motion-transforming member 4 and the axis of rotation 3a, so that the movement of the 3a is preferably four times as large as the movement of the motion-transforming member.
A freewheel 6 is arranged on the drive shaft 2a, the function of said freewheel being to allow rotation of the intermediate body in one direction but to block rotation in the other direction, thus ensuring that the driving motion is not reversed. The freewheel may be of any conventional kind, that is, be in the form of a ratchet gearing that transmits torque in one direction but freewheels in the other direction.
According to an embodiment of the invention, the intermediate body 3 comprises a cam-shaped driving pulley 30 and the mechanical energy accumulation member 5 is designed as a tensile/compressive spring unit 51, which will be described in greater detail with reference to
a to 2d show schematically the mode of operation of the tensile/compressive spring unit 51 in cooperation with the driving pulley 30. The driving pulley is designed with a largest diameter R and a smallest diameter r. The tensile/-compressive spring unit 51 is connected at one end to a fixed yoke 52 and a movable yoke 53. The movable yoke 53 is provided with a rolling device 54 making contact with the periphery of the driving pulley 30. The movable yoke 53 is adapted to run in a radial direction and parallel to the plane of the driving pulley. This will cause the spring forces to be directed perpendicular to the axis of rotation of the driving pulley, which thus substantially absorbs radially directed forces. The movable yoke 53 moves with a length of stroke corresponding to R-r while the driving pulley rotates one turn about its axis. The direction of rotation of the driving pulley is shown by the arrow a.
In
b shows a position where the mechanical energy stored in the spring unit imparts an accelerating motion to the driving pulley via the drive roll 54. From the starting position at radius R, the driving pulley has here been driven approximately 90°.
c shows the position for the driving pulley when the drive roll reaches the smallest radius r of the driving pulley. In this position, the intended part of the mechanical energy stored in the spring unit has been transmitted to the driving pulley. In this position, the driving pulley has moved approximately two-thirds of a turn, or 2400 from the position 2a. In this position, the spring unit also has a certain prestress, thus ensuring the abutment of the drive roll against the driving pulley.
When the driving pulley has passed the position according to
d shows a position where the driving pulley has delivered its kinetic energy to the spring unit and has been braked to a stop position where the speed of the driving pulley is zero. Because of the engagement of the freewheel, the driving pulley cannot change its direction of rotation either.
In this position, the driving pulley assumes a wait state before the next operation. This is initiated when the input shaft 1a, via the motion-transforming member 4 and the axis of rotation 3a, gives the driving pulley a driving motion. While the driving pulley is rotated to its initial position in
When the driving pulley has reached the position according to
It is realized that it is possible, within the scope of the invention, to influence the different processes above, namely, the driving of the driving pulley from the spring unit, the braking of the driving pulley by the transmission of kinetic energy from the driving pulley to the spring unit, and the tensioning of the spring unit to its initial position, by appropriately dimensioning the cam shape. By adapting the shape of the driving pulley, it is thus realized that it is possible to influence both the acceleration and deceleration processes of the driving pulley.
Preferably, the shape of the driving pulley is of such a nature that it is adapted to the load and hence imparts to the driven body 2 a uniform speed after a short acceleration process.
Also, no separate braking devices for the driving pulley need be arranged, since its remaining kinetic energy is automatically returned to the spring unit and the energy balance implies that the driving pulley, due to any friction losses, independently of the original storing of mechanical energy by the spring unit, always rotates less than one turn. This entails considerable advantages, especially when testing and adjusting the drive system, since the process will be automatically controllable also in the event that, for example, the driving body 2 is disengaged from a subsequent diverter switch. Also in a test position, where the driving body is disengaged from the driving pulley, it will exhibit a controlled motion pattern.
When the driving pulley moves between the positions shown in
According to one embodiment, the largest radius of the driving pulley is between 80 mm and 120 mm, preferably 105 mm, and its smallest radius is between 50 mm and 80 mm, preferably 60 mm. The difference between the largest radius R and the smallest radius r may be between 30 mm and 60 mm, preferably 45 mm.
According to one embodiment, the force of the rolling device against the driving pulley is between 1000 N and 1500 N, and the speed of rotation of the driving pulley is adapted to vary from 0 to 25 rad/s. The time from start to stop of the driving pulley may in this case be 0.2 s.
In the figures the rolling device is designed as a ball-bearing roller, which gives low friction and a large contact surface against the periphery of the driving pulley. According to one embodiment, the roller is a needle bearing. Alternatively, the rolling device may be designed as a spherical ball, rotatably arranged in a ball cage. To minimize the surface pressure against the periphery of the driving pulley, it is suitable in this case to give its cross section a corresponding circular cross-section shape.
The device is suitably surrounded by transformer oil, which serves both as lubrication and cooling of the mechanical components included in the device.
The method of transmitting the driving motion may be summarized in the following operating steps:
The scope of the invention must not be limited by the embodiments presented but also contain embodiments obvious to a person skilled in the art. For instance the device can be immersed in dielectric fluid with similar properties as transformer oil.
Number | Date | Country | Kind |
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0600691-0 | Mar 2006 | SE | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/SE07/50187 | 3/27/2007 | WO | 00 | 9/29/2008 |