Description:Description

Planters are agricultural equipment which are pulled by attaching to tractor by means of three point linkage system. Precision planters are used for sowing of seeds in agricultural land with precise maintenance of seed spacing and row spacing. Pneumatic planters are precision planters that uses vacuum pressure to meter seed. It comprises of number of identical row units attached to a single frame. Each row unit have separate seed metering units. These seed metering unit have static vacuum chamber with cut off, on which the metering disc rotates. A central shaft transfers rotational motion to the seed metering plate. The orifice size of seed metering plate are designed as per seed shape and size. The vacuum pressure created by a common or individual aspirator for each row unit supplies negative air pressure to vacuum chamber. Vacuum chamber has a cut off section at which air pressure is cut off. The seed metering plate with orifices picks seed from seed chamber and drops at release point as the vacuum pressure is cut off.
The seed metering plate used in pneumatic precision planters are rigid plates. Details of the literature avaialble on different type of developed seed metering plate are given in Annexure V. Achieving high seed singulation using these meters is a tough task. Many time laboratory optimizations are carried out to know best possible orifice size, vacuum pressure, seed metering plate rpm to minimize seed missing, multiples and increase precision. Seed singulator or cut-off devices with sensors and actuators are used, which increases complexity, cost and needs more time in adjustment, maintenance etc. Timely seed release does not occur each time and hence it is assisted by positive air pressure or mechanical seed knock out devices. Successful seed picking at higher speed is not achievable in rigid seed metering plates. High vacuum pressure is required in these seed metering plates to withstand impact force at seed-seed metering plate contact. Possibility of seed damage increases at high vacuum pressure and with use of mechanical seed cut-off and knock out devices. A large gap between laboratory and field performance is observed in these rigid seed metering plates because of field vibration. A flexible orifice metering plate for pneumatic metering of seeds was invented to address the above discussed issues with a low cost solution.
Many types of planters have been emerged to satisfy the requirements using different component arrangements and mechanisms. Pneumatic planter uses negative air pressure to meter seed. The planter seed metering unit as shown in Fig 1 has parts like vacuum chamber as shown in 10 of Fig 2 with pressure cut off region 13 of Fig 1, seed metering plate as shown in 8 of Fig 7 and seed chamber 14 of Fig 1. The vacuum chamber is connected to either central PTO operated aspirator or individual motor operated aspirator to supply vacuum pressure. The seed metering plate as shown in 8 of Fig 7 is a thin metal sheet made, round plate having a slot at the center and small orifices near periphery. The central slot 2 in Fig 7 is engaged with a shaft 17 of Fig 2 mounted on bearings 18 of Fig 2 at center of vacuum chamber. The shaft is powered by ground wheel or motor to rotate the seed metering plate. Small orifices near periphery are used for seed picking and dropping. The seed metering plate has steps before and after the orifice around the center of the plate at backside as shown in 3 and 4 of Fig 7. These steps engage with the round slot made in the vacuum chamber face and seal the negative air pressure to direct the airflow through orifices. Seed chamber remains on one side of the unit, exposing seeds in it to seed metering plate. The seed from hopper flow to seed chamber through seed tube 16 of Fig 1 and hold by the seed metering unit frame 9 of Fig 2 and cover 11 of Fig 2. Multiple seed picking, unsuccessful seed picking by seed metering plate leads to uneven seeding in the field. Even when single seed is picked, uneven release of seed at cut off occurs. The seed size, mass, orientation in which it is engaged to seed metering plate varies and hence different seed falls at different point under action of gravity after vacuum cut off. These parameter affects precision of seed spacing in a row.
The invented metering plate as depicted in Fig 3-7 has flexible orifice. The flexible orifice is made by layering a thin elastomeric rubber layer 7 in Fig 7 above rigid metal seed metering plate 8 in Fig 7. The orifice size in rigid metal seed metering plate 5 in Fig 7 is larger and orifice made in rubber layer 1 in Fig 5 is smaller. The larger orifice is 100% of GMD of largest seed for which seed metering plate is designed whereas the smaller orifice is 60% of GMD of smallest seed for which the seed metering plate is designed. The effect of seed metering plate rpm on seed picking in the invented seed metering plate is negligible. The seed in zero kinetic energy is picked while the metering plate has high kinetic energy at high rpm. The flexible orifice elongates and compresses till the seed achieves the kinetic energy same as of seed metering plate. Thus, the flexible orifice holds the seed in the transition period of the seed kinetic energy. This unique characteristic of flexible orifice metering plate for pneumatic metering of seeds enables it to run equally efficient at high speed. Multiple seed picking is reduced as orifice is completely sealed after seed picking at first attempt. Thus, higher seed singulation is achieved with this invented seed metering plate. Seed strikes and an impact reaction is generated against seed at seed- seed metering plate contact. A higher vacuum pressure is required in conventional rigid seed metering plates to hold the seed against this impact. Invented flexible orifice seed metering unit overcomes this problem as rubber has low coefficient of restitution and rubber deflects using the energy at seed striking. The inward deflected rubber comes back to position at vacuum pressure cut off. This action helps in positive seed release. The rubber force of deflection drops each seed at same point regardless of variability in seed characteristics and degree of engagement of seed to seed metering plate. The seed is released at a certain angle to vertical axis. This angle is dependent on vacuum pressure cut off angle. A greater cut off angle make seed fall at a greater angle w.r.t vertical axis. Seed falling with higher angle to vertical axis are prone to rolling and bouncing post ground contact. The invented flexible orifice seed metering plate has a quick seed releasing characteristic due to reposition of deflected rubber after pressure cut off. This seed metering plate is able to work with a very low cut off angle (about 50% of that required in rigid seed metering plates). The seed rolling and bouncing action at seed-soil contact is minimized with provision of such a low cut off angle. The system works energy efficiently as the additional energy required to hold seed against impact from rigid seed metering plate is not required in flexible orifice metering plate for pneumatic metering of seeds. The kinetic energy of striking seed is rather used in inward deflection of flexible orifice. This saved energy in terms of deflected orifice is later utilized in positive seed release at vacuum pressure cut off. The energy required for positive dropping of seed is saved. The seed is picked and dropped by flexible orifice which does not causes any type of mechanical damage to seed. The invented flexible orifice metering plate for pneumatic metering of seeds damps field vibrations and reduces its effect on seed. This increases the quality of field performance of pneumatic planter. The invented seed metering plate achieves similar results as of laboratory evaluation in the field. It successfully overcomes field vibrations caused by undulated land and vertical movement of depth control system where provided, transmitted vibration by mechanical engagement to tractor, ground wheel, aspirator fan, frame. The seed metering plate performs equally good in zero tillage conditions, due to its vibration damping capabilities. , Claims:Claims

We claim the following:

I. A pneumatic seed metering plate or alike mechanism made up of rigid material(8) coated with thin elastomeric material(7) at the side of operation where the orifice on rigid(5) and elastomeric material(1) sharing common centers are made with daimeter greater than or equal to maximum geometric mean diameter (GMD) and lower than minimum GMD respectively of seed or fruits or pharmacetical materials or any other materials to be used for metering or sorting or counting or alike operation, thus the radial extension of elastomeric material towards orifice center of rigid metering plate creates flexible orifice that is able to deflect inward or outward or radially on application of forces which inturn enables the metering plate for sealing of orifice at the first attempt of seed picking, lowers the impact reaction force from metering plate and thereby lowers required vacuum pressure, picks seed at higher peripheral speed because of radial deflection capabilities of orifice that allows the seed to remain intact still it achieves required kinetic energy to move with the orifice, quicker release of each seed exactly at vacuum pressure cut off point due to positive force gained from repositioning of inward deflected orifice and this improves field performance, reduces internal or external damage to seed.
II. The seed metering plate claimed in ‘Claim I’ is made up of any rigid material like aluminum or steel or plastic or rigid rubber (vulcanized/ natural/ synthetic) or alike materials coated with any elastomeric material like rubber (vulcanized/ natural/ synthetic) or alike materials at the seed suction side that has a low thickness, such that it deflects at minimum suction pressure used, the metering system may be of any type of pneumatic metering system including plate type or common cylinder type or unit row cylinder type or conical or belt type or any other alike system operated either with vacuum or positive pressure.
III. The orifice drilled on rigid metering plates as claimed in ‘Claim I’ are having diameter larger than or equal to maximum GMD whereas orifice in the coated elastomeric material are having diameter smaller than minimum GMD of seed or alike object and shape, size of orifice in both rigid as well as elastomeric material may vary according to seed or object to be picked.
IV. The radial extension of elastomeric rubber coating towards center of its orifice over rigid material orifice generates flexible orifice which is able to deflect inward, outward and radially on application of forces.
V. The flexible orifice as described in ‘Claim IV’ helps in soft picking and dropping of seed leading to zero internal as well as external damage to seed, adopts shape of picked seed and seals orifice completely.
VI. The flexible orifice radially elongates and compresses when seed is picked at high speed and gradually comes back to position as seed attends the kinetic energy of seed metering plate.
VII. The impact force to seed while picked by flexible orifice is low due to rubber deflection and low coefficient of restitution that leads to lower need of vacuum pressure, this deflected orifice comes back to position at air suction cutoff and helps in immediate release of each seed at exact drop point with a positive additional force which helps in achieving higher precision with reduced missing due to non clogged orifice.