AN APPARATUS TO CONVERT BIDIRECTIONAL LINEAR MOTION TO UNIDIRECTIONAL ROTARY MOTION

FIELD OF THE INVENTION

The present invention relates to an apparatus to convert bidirectional linear motion to unidirectional rotary motion.

BACKGROUND OF THE INVENTION

Devices float on the sea surface and generate a reciprocating motion. The kinetic energy in this reciprocating motion must translate to motion that an electric generator can use to produce electricity. The process should ideally be carried out using a low-cost, low-maintenance device.

Clement et al, "Wave energy in Europe: current status and prospects", Renewable and Sustainable Energy Reviews, 6, (2002), 4005-431, Brooke, J., "Wave energy conversion", Vol. 6, Elsevier, 2005, "Wave Energy Converter PTO Test Bench" RWTH Aachen University report, Falcao, A. F.O., and "Wave Energy Utilization: A Review of the Technologies", Renewable and Sustainable Energy Reviews, 14, (2010), 899-918 describe several mechanisms to obtain power from the wave energy device. One such device is described in Drew et al., "A Review of Wave Energy Converter Technology", Proc. IMechE, Vol. 223 Part A: J. Power and Energy, June 2009. The possible power take off (PTO) systems are assessed and classified as hydraulic, linear electrical generator, or turbine based. A hydraulic PTO system is generally well suited to absorbing energy from a high force, slow oscillatory motion and can facilitate the conversion of reciprocating motion to rotary motion to drive a generator. There are, however, various design challenges such as efficiency and reliability. A linear electrical generator provides an alternative option; however, the technology is less mature as described in US Patent No: 3,973,445. Related systems are also described in US Patent No. 4,225,110, PCT/SG2010/000281, US Patent No. 5,640,881, US Patent Application Publication No. 2006/0107918, US Patent No. 4,400,913, US Patent No. 4,796,514, US Patent No. 5,640,881, and IN 18/KOL/2009.

Through the literature mentioned above, it may be found that the wave motion is random, and the power production from the wave is very low because the wave energy converter (WEC) systems are not efficient. Several countries including India have installed wave energy device on ocean. The existing mechanisms of power take off (PTO) are: direct mechanical conversion, air turbine, water turbine, hydraulic system and the like. All these have a complex mechanism to convert or transfer power from one system to another system and each system has a loss associated with it. The direct electric conversion machines are inefficient, expensive and massive as described in Drew et al., "A Review of Wave Energy Converter Technology", Proc. IMechE Vol. 223 Part A: J. Power and Energy, June 2009. Another design which is provided in PCT/SG2010/000281 has flexible teeth. The teeth are movable and life of the teeth will be less. The other invention described in IN 2107/CHE/2010 has several moving parts which makes the system less reliable.

SUMMARY OF THE INVENTION

The present invention provides a power take off apparatus for a point absorber ocean wave energy converter comprising a rack and pinion mechanism.

The present apparatus has a simple and elegant design for directly converting unpredictable but reciprocating linear motion (induced by wave motion) to unidirectional rotational motion, which can then be further used to generate electrical power. There are several power take off mechanisms as described in the prior art. However, the present invention provides a mechanical system which produces linear motion to unidirectional rotary motion. The apparatus may also be used in the situations where uneven motion is observed such as building vibration or automotive shock absorber and the like.

BRIEF DESCRIPTION OF THE DRAWINGS:

Fig. 1 depicts the apparatus without hanging mass.

Fig. 2 depicts the apparatus with hanging mass.

Fig. 3 depicts the mechanism for converting mechanical energy to electrical energy.

Fig. 4 depicts the engagement-disengagement mechanism to convert vertical motion to horizontal motion via rack and pinion mechanism.

Fig. 5 depicts the support frame.

Fig. 6 depicts the motion converter described in the prior art.

Referring to the drawings, the embodiments of the present invention are further described. The figures are not necessarily represented to scale, and in some instances the drawings have been exaggerated or simplified for illustrative purposes only. One of ordinary skill in the art may appreciate the many possible applications and variations of the present invention based on the following examples of possible embodiments of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

One aspect of the present invention provides an apparatus for converting bidirectional linear motion to unidirectional rotary motion.

The reciprocating linear motion generated by a point absorber wave energy device is converted to unidirectional rotary motion. The motion consequently gets transferred to an alternator or generator to produce electricity. A shaft transfers the reciprocating motion to a pinion (gear) via rack and pinion mechanism. As the Fig. 1 shows, two racks (13 and 13 a) meet with a pinion (8). The racks are fitted in frame (7). The racks can slide inside the frame via roller bearing (4). Springs or magnets (11) always push the racks to engage with pinion. The engagement and disengagement pinions (14) help engaging and disengaging the racks (13, 13a) and pinion (8). A pusher rack (9) helps pushing the racks (13, 13a). The pusher racks (9) have sliding surfaces (15). The pusher racks (9) and the engagement-disengagement pinions (14) may be mounted on the frame (7). As the main shaft (17) moves upward, the engagement-disengagement pinions (14) rotates in anticlockwise direction. The pusher racks (9) move towards right direction (shown with arrow symbol in the Fig. 1) and helps engaging the left hand rack (13) and disengaging the right hand rack (13a) with pinion (8). Once the engagement and disengagement is complete, the stop (10) restricts the vertical rack (12) motion relative to the frame (7). Power from rack (13) to pinion (8) gets transferred. The pinion (8) transfers power to a smaller gear (22) so that speed can be increase (Fig 3). The final motion gets transferred to an alternator or gear to get electric power.

Fig. 1 depicts the basic mechanism how the invention works. During upstroke, the floating device (2) and the vertical rack (12) move upwards. The engagement and disengagement pinions (14) rotate in anticlockwise direction. This gives horizontal motion to the horizontal rack (9). The rack 9 pushes the vertical rack (13a) and disengages the rack (13a) from the pinion (8). The left hand rack (13) moves towards pinion (8) and it engages with the pinion (8) because force provided by the spring (11). After moving certain height, the shaft (17) pushes the frame (7) because of stop mechanism (10). The force is transferred from the floating device (2), the main shaft (17), the frame (7), the rack (13) and pinion (8). In order to ensure easy movement of rack 13 and 13 a, roller bearings (4) are attached in between frame and rack. The pinion (8) gets rotated in clockwise direction. During downwards motion of the main shaft (17), opposite phenomenon occurs. The pusher rack (9) moves in opposite direction and it helps to engage the rack 13a and disengage the rack 13. The rack 13a transmits force to the pinion (8) and the pinion rotates in clockwise direction. Hence, in both the up and down motion of the main shaft, the pinion (8) produces clockwise motion. In the case when the wave height varies, the pinion (8) still rotates in the same direction (clockwise direction). If the pinion speed is high and wave height or wave period gets reduced, still the pinion rotates in the clockwise direction. Hence it can run smoothly.

Fig. 2 shows that a mass has been attached via a pulley. As the wave inherently random and it has all degrees of freedom (DOF), restricting the DOF of the floating body (2) is very difficult. The bearing (3) has very high uneven forces. Therefore, a modification has been done to eliminate this problem. The floating body (2) is connected directly to a pulley (19) via a rope (21). A mass (18) is hanged from the rope so that a constant tension in the rope (21) is maintained. Hence the uneven forces coming to the system cannot reach the power take off (PTO) mechanism. The floating body can have sufficient mass so that will be having vertical motion and it may not submerge or hang above the water surface. The mass (18) and weight of floating body (2) is pre-calculated so that the system runs smoothly. The PTO can be submerged in the water with proper sealing mechanism or can be placed on a platform. If the frame and gearing mechanism mass is higher, the any additional mass may not be required.

As depicted in Fig. 3, the teeth profile may match the buttress teeth for easy engagement or disengagement. These types of teeth have other advantages such as the higher pinion (8) motion does not affect the rack (13 or 13a) or other parts of the system (such as 9, 14, 2 etc). If the pinion (8) motion is higher, and wave height or period is lower, the pinion (8) teeth slide over the rack (13 or 13a) teeth. The spring (11) assists to slide the teeth without transferring any power from or to the alternator (26). Fig 3b shows the mechanism to transfer power from pinion (8) to the alternator (26). The pinion (8) is connected to a small gear (22). The gear shaft (25) is connected to the alternator. A flywheel (24) may be used to reduce energy fluctuation. There may be several gears to increase the speed to feed into the alternator (26). The alternator or generator produces power (27).

Fig. 4 shows the pusher mechanism. This mechanism is to convert vertical linear motion to horizontal linear motion. When the vertical rack (12) moves upward, it rotates the small pinion (14a). The small pinion is fixed with anther bigger pinion (14b). Fig 4b shows these pinions are keyed to the same shaft. Hence the bigger pinion (14b) has same speed as the small pinion (14a). Because of larger diameter, the bigger pinion produces longer horizontal motion to the pusher rack (9). Therefore, a small vertical rack (12) motion produces a longer motion to the horizontal pusher rack (9). The pusher rack pushes the rack (13a in Fig 1) and disengages 13a from the pinion (8). The pinions (13a, 13b) may be mounted on the frame (7). The opposite motion of the vertical rack (12) creates opposite pusher rack (9) motion; and therefore, it disengages the left hand rack (13).

A spring or a shock absorber (40) is attached to the stop mechanism. Therefore, sudden direction change may not allow any impact force on the frame (7). During change of motion direction of the main shaft (17), the stop restricts the main shaft (17) motion relative to the frame (7).

Fig. 5 shows that the whole system can move inside a rigid frame (30). The main frame (7) slides inside the rigid or static frame (30) via a guide rail (34). The pinion shaft (31) rotates on a support fixed with the static frame (30). This static structure also guides the other dynamic parts and does not allow sideways movement. The static frame can also be used to hold the small gear axle (22 in Fig 3).

During upward motion, the following steps may occur preferably in a sequential manner. A) The floating device moves up; B) The main shaft moves up; C) The vertical rack moves up; D) The small pinion (14a) rotates in the anticlockwise direction; E) Bigger pinion (14b) rotates in the anticlockwise direction; F) Horizontal rack moves towards right direction; G) Right hand rack moves further right position because the horizontal rack forces to do so. Therefore, the right hand rack gets disengaged from pinion (8); H) Left hand rack moves towards pinion (8) and teeth of these engage themselves; I) Once the engagement and disengagement is complete, the stop (10) restricts the vertical rack movement and the force from main shaft gets transferred to the frame (7); J) As the left rack (13) is engaged, the power from the frame gets transferred to left rack and from left rack to the pinion (8); K) The pinion (8) rotates in the clockwise direction; L) The power from the pinion gets transferred to the other gears to increase the speed. Finally the gears get connected to a generator to get electrical power; M) The frame (7), rack (13 or 13a), vertical rack (12), engagement and disengagement pinions (14), horizontal rack (9) assembly move all together inside the static frame (30) through guide rail (34).

During downward motion, the following steps may occur preferably in a sequential manner. A) Main shaft (17) and vertical rack (12) moves downward; B) The smaller and the bigger pinion (14a, 14b) rotate in clockwise direction; C) The horizontal rack (9) moves to leftward direction; D) The rack (9) pushes left rack (13) and disengages from pinion (8); E) Spring (11) forces the right rack (13a) towards the pinion (8) and engages with 13a; F) Once the engagement and disengagement is complete, the stop (10) restricts the vertical rack (12) movement and the force from main shaft (17) gets transferred to the frame (7); G) The pinion (8) rotates in clockwise direction; H) The power gets transferred to the generator or alternator (26); I) The frame (7), rack (13 or 13a), vertical rack (12), engagement and disengagement pinions (14), horizontal rack (9) assembly moves all together inside the static frame (30) through guide rail (34).

In both the cases described above, the pinion rotates in clockwise direction. The present device works in vertically or any other direction.

The energy loss to get unidirectional motion from the device of present invention may be found in: A) The transition period, i.e., when the main shaft changes direction (up/down), the engagement and disengagement pinions (14a, 14b) takes some energy to move the pusher rack (9). The energy consumption for this mechanism is negligible as this mechanism is not involved for transmitting power. Another, during this transition period, the energy producing body will produce a very less energy, and that part of energy will be used for this purpose. In fig 1, it can be seen that stop mechanism (10) allows the main shaft motion without producing electrical power during transition period. The length between stops can be very small by selecting a bigger pinion (14b). For example, if the pinions (14a, 14b) diameter ratio is 3 and the length between stops is 5 mm, the pusher rod movement will be 15 mm; B) The loss in the racks (13, 13a) and pinion, i.e., there will be some friction involved. Selecting a low friction material will have negligible loss. C) At a time one rack (13 or 13 a) is engaged with the pinion (8) and the other rack (13a or 13) may not consume any energy by friction etc. as it is separated from the pinion (8); D) The pinion (8) will be engaged with other gear mechanism and finally with the alternator. Substantially low friction material will help for reducing loss; and E) The static frame does not consume any energy as this is only be used for guiding the frame (7).

Therefore, total energy loss may be summed as friction loss in the pinion (8) and rack teeth (13 or 13 a) + Friction in the pinion (8) shaft bearing + Engagement and disengagement mechanism related loss + Guide rail friction (34) + Losses in gears to increase rotational speed from pinion (8) + Loss related to generator power conversion.

During the transition period i.e. when the main shaft (17) motion direction changes, the rack (13 or 13a) engages itself with the pinion (8). Because the stop (10) allows some movement of the rack (13 or 13a) and spring forces engaging the pinion (8), the teeth adjusts to meet each other.

The system is designed in such a way that any small reciprocating movement of main shaft (17) can be captured to produce energy. Randomness of wave will not hamper the present system as this system can be operated in any wave condition.

The wave dragon, oscillating water column and similar wave energy devices use fluid to pass through pump or turbine and finally these generates electrical energy. Therefore, a huge energy loss is observed. The present invention can be used in such systems. The device of present invention has a weight that can be lower if the device is optimized for best material considering weight, strength and friction.

The present invention is useful for the energy industry and the industry needs to convert linear motion to unidirectional rotary motion. This apparatus may be used to harvest energy from alternating motion coming from natural resources such as vibration etc. This apparatus may also be use in motor vehicle where the shock absorber can be replaced by present apparatus and rotary motion can be achieved. The rotary motion may be used to drive the vehicle so that energy can be saved.

It may be appreciated by those skilled in the art having the benefit of this disclosure that this invention provides an apparatus to convert bidirectional linear motion to unidirectional rotary motion. It should be understood that the drawings and detailed description herein are to be regarded in an illustrative rather than a restrictive manner.

We Claim:

1. An apparatus for converting bidirectional linear motion to unidirectional rotary motion.

2. An apparatus as claimed in claim 1, is a motion converter comprising a rack and pinion mechanism.

3. An apparatus as claimed in claim 1, wherein unidirectional rotary motion is transferred to alternator/ generator to produce electricity.

4. An apparatus as claimed in claim 1, consists of a shaft, racks, engagement and disengagement pinions, a vertical rack, pusher rack or horizontal rack, stop, pinion, alternator/gear, floating body.

5. An apparatus as claimed in claim 1, works sequentially depending on the strokes applied during upward and downward motions.

6. An apparatus as claimed in claim 1, wherein in upward motion moves floating device, main shaft and vertical rack upwards, small pinion and bigger pinion rotates in anticlockwise direction, horizontal rack right, left hand rack moves towards pinion and the pinion transfers power to gears which connects to generator resulting in production of electricity.

7. An apparatus as claimed in claim 1, wherein in downward motion moves floating device, main shaft and vertical rack downwards, small pinion and bigger pinion rotates in clockwise direction, horizontal rack left, spring pushes the right rack towards the pinion, pinion rotates in clockwise direction and power is transferred to generator/alternator produces electricity.

8. An apparatus as claimed in claim 1, wherein converts reciprocating linear motion produced by devices floating on sea to unidirectional rotary motion and the motion consequently gets transferred to an alternator or generator to produce electricity.

9. An apparatus as claimed in claim 1, wherein the pinion rotates in clockwise direction. The present device works in vertically or any other direction.

10. An apparatus as claimed in claim 1, wherein the present invention is useful for the energy industry, to harvest energy from alternating motion coming from natural resources such as vibration etc, in motor vehicle where the shock absorber, to drive the vehicle.