Geneva Conveyor

Geneva drive The Geneva drive or Maltese cross is a gear mechanism that translates a continuous rotation into an intermittent rotary motion. The rotating drive wheel has a pin that reaches into a slot of the driven wheel advancing it by one step. The drive wheel also has a raised circular blocking disc that locks the driven wheel in position between steps.

Background The name derives from the device's earliest application in mechanical watches, Switzerland and Geneva being an important center of watchmaking. The geneva drive is also commonly called a Maltese crossmechanism due to the visual resemblance. In the most common arrangement, the driven wheel has four slots and thus advances for each rotation of the drive wheel by one step of 90°. If the driven wheel has n slots, it advances by 360°/n per full rotation of the drive wheel.

Because the mechanism needs to be well lubricated, it is often enclosed in an oil capsule.

Uses and applications One application of the Geneva drive is in movie projectors: the film does not run continuously through the projector. Instead, the film is advanced frame by frame, each frame standing still in front of the lens for 1/24 of a second (and being exposed twice in that time, resulting in a frequency of 48 Hz). This intermittent motion is achieved using a Geneva drive. (Modern film projectors may also use an electronically controlled indexing mechanism or stepper motor, which allows for fast-forwarding the film.) The first uses of the Geneva drive in film projectors go back to 1896 to the projectors of Oskar Messter and Max Gliewe and the Teatrograph of Robert William Paul. Previous projectors, including Thomas Armat's projector, marketed by Edison as the Vitascope, had used a "beater mechanism", invented by Georges Demenÿ in 1893, to achieve intermittent film transport. Geneva wheels having the form of the driven wheel were also used in mechanical watches, but not in a drive, rather to limit the tension of the spring, such that it would operate only in the range where itselastic force is nearly linear. If one of the slots of the driven wheel is occluded, the number of rotations the drive wheel can make is limited. In watches, the "drive" wheel is the one that winds up the spring, and the Geneva wheel with four or five spokes and one closed slot prevents overwinding (and also complete unwinding) of the spring. This socalled Geneva stop or "Geneva stop work" was the invention of 17th or 18th century watchmakers. Other applications of the Geneva drive include the pen change mechanism in plotters, automated sampling devices, indexing tables in assembly lines, tool changers for CNC machines, banknote counting and so on. The Iron Ring Clock uses a Geneva mechanism to provide intermittent motion to one of its rings.

A Geneva drive was used to change filters in the Dawn mission framing camera used to image the asteroid 4 Vesta in 2011. It was selected to ensure that should the mechanism fail at least one filter would be usable.

Internal Geneva drive

Internal Geneva drive. An internal Geneva drive is a variant on the design. The axis of the drive wheel of the internal drive can have a bearing only on one side. The angle by which the drive wheel has to rotate to effect one step rotation of the driven wheel is always smaller than 180° in an external Geneva drive and always greater than 180° in an internal one, where the switch time is therefore greater than the time the driven wheel stands still. The external form is the more common, as it can be built smaller and can withstand higher mechanical stresses.

DC MOTOR:

D.C MOTOR: The d.c generators and d.c motors have the same general construction.

MOTOR PRINCIPLE: An electric motor is a machine which converts an electrical energy to mechanical energy. All D.C machines have five principal components viz

(i)

Field system (II) armature core (iii) armature winding (iv) Commutator (v) brushes

(ii)

Field system: The function of the field system is to produce Uniform field within which the

armature rotates.it consists of a number of salient poles(of course, even number) bolted to the inside of circular frame (generally called yoke).the yoke is usually made of solid cast steel whereas the pole piece are composed of stacked laminations. Field coils are mounted o n the poles and carry the d.c exciting current. The field coils are connected in such a way that adjacent poles have opposite polarity. The m.m.f. developed by the coils produces a magnetic flux that passes through the pole pieces, the air gap, the armature and the frame. Practical d.c machines have air gaps ranging from 0.5mm to 1.5mm.since armature and field systems are composed of materials that have permeability, most of the m.m.f.of field coils is required to set up flux in the air gap. By reducing the length of air gap, we can reduce the size of field coils (number of turns).

(iii)Armature core: The armature core is keyed to the machine shaft and rotates between the field poles. It consists of slotted soft- iron laminations (about 0.4 to 0.6mm thick) that are stacked to form a cylindrical core. The laminations are individually coated with a thin insulating film so that they do not come in electrical contact with each other. The purpose of laminating the core is to reduce the eddy current loss. The laminations are slotted to accommodate and provide mechanical security to the armature winding and to give shorter air gap for the flux to cross between the pole face and the armature “teeth”. (iv)

Armature winding: The slots of the armature core hold conductors that are connected in a suitable

manner.this are known as armature winding. This is the winding in which “working”e.m.f. is induced. The armature conductors are connected inseries-parallel: the conductors being connected in series so as to increase the voltage and in parallel paths so as to increase the current.the armature winding of a d.c.machine is a closed –circuit winding:the conductors being connected in a symmetrical manner forming a closed loop or series of closed loops.

(v)

commutator; A commutator is a mechanical rectifier which converts the alternating voltage

generated in the armature winding into direct voltage across the brushes.the commutator is made of copper segments insulated from each other by mica sheets and mounted on the shaft of the machine. The armature conductors are soldered to the commutator segments in a suitable manner to give rise to the armature winding.depending upon the manner in which the armature conductors are connected to the commutator segments, there are tow types of armature winding in a.d.c. machine viz(a) lap winding (b) wave winding. Great care is taken in building the commutator because any eccentricity will cause the brushes to bounce, producing unacceptable sparking .the sparks may burn the brushes and overheat and carbonize the commutator.

(vi)

Brushes: The purpose of brushes is to ensure electrical connections between the rotating

commutator and stationary external load circuit. The brushes are made of carbon and rest on the commutator,the brush pressure is adjusted by means of adjustable springs. if the brush pressure is Very large, the friction produces heating of the commutator and the bruches.on the other hand, if it is too weak, the imperfect contact with the commutator may produce sparking.

3.2 STATOR: The stator is the stationary part of an electric generator or electric motor. The nonstationary part on an electric motor is the rotor. Depending on the configuration of a spinning electromotive device the stator may act as the field magnet, interacting with the armature to create motion, or it may act as the armature, receiving its influence from moving field coils on the rotor.

The first DC generators (known as dynamos) and DC motors put the field coils on the stator, and the power generation or motive reaction coils are on the rotor. This was necessary because a continuously moving power switch known as the commutator is needed to keep the field correctly aligned across the spinning rotor. The commutator must become larger and more robust as the current increases. The stator of these devices may be either a permanent magnet or an electromagnet. Where the stator is an electromagnet, the coil which energizes it is known as the field coil or field winding.

3.3 ROTOR: The rotor is the non-stationary part of a rotary electric motor or alternator, which rotates because the wires and magnetic field of the motor are arranged so that a torque is developed about the rotor's axis. In some designs, the rotor can act to serve as the motor's armature, across which the input voltage is supplied. BATTERY: Battery is use for storing the energy produced from the solar power. The battery used is a lead-acid type and has a capacity of 12v; 2.5A.the most inexpensive secondary cell is the lead acid cell and is widely used for commercial purposes. A lead acid cell when ready for use contains two plates immersed in a dilute sulphuric acid (H2 SO 4 ) of specific gravity about 1.28.the positive plate (anode) is of Lead –peroxide (PbO 2 ) which has chocolate brown colour and the negative plate (cathode) is lead (Pb) which is of grey colour. When the cell supplies current to a load (discharging), the chemical action that takes place forms lead sulphate (PbSO 4 ) on both the plates with water being formed in the electrolyte. After a certain amount of energy has been withdrawn from the cell,both plates are Transformed into the same material and the specific gravity of the electrolyte (H 2 so4 ) is lowerd.the cell is then said to be discharged.there are several methods to ascertain whether the cell is discharged or not.

To charge the cell, direct current is passed through the cell in the reverse direction to that in which the cell provided current. This reverses the chemical process and again forms a lead peroxide (PbO 2 ) positive plate and a pure lead (Pb) negative plate. At the same time,(H2 so4 ) is formed at the expense of water,restoring the electrolyte (H2 so4 ) to its original condition. The chemical changes that Occur during discharging and recharging of a lead-acid cell .

Conveyor belt History Primitive conveyor belts were used since the 19th century. In 1892, Thomas Robins began a series of inventions which led to the development of a conveyor belt used for carrying coal, ores and other products.[6] In 1901, Sandvik invented and started the production of steel conveyor belts. In 1905 Richard Sutcliffe invented the first conveyor belts for use in coal mines which revolutionized the mining industry. In 1913, Henry Ford introduced conveyor-belt assembly lines at Ford Motor Company's Highland Park, Michigan factory.[7] In 1972, the French society REI created in New Caledonia the then longest straight-belt conveyor in the world, at a length of 13.8 km. Hyacynthe Marcel Bocchetti was the concept designer.[citation needed] In 1957, the B. F. Goodrich Company patented a conveyor belt that it went on to produce as the Turnover Conveyor Belt System. Incorporating a halftwist, it had the advantage over conventional belts of a longer life because it could expose all of its surface area to wear and tear. Möbius strip belts are no longer manufactured because untwisted modern belts can be made more durable by constructing them from several layers of different materials.[8] In 1970, Intralox, a Louisiana based company, registered the first

patent for all plastic, modular belting. In 1963-64, First Indian Small Scale Industrial Unit with Japanese Plant for Rubber Belts for Conveyor / Elevator / Transmission was installed near National Capital Territory of Delhi and its MrBelts Conveyor Belting has been widely used in Steel, Cement, Fertilizer, Thermal Power, Sponge Iron Plants and Coal / Mineral establishments / Mines, Port Trusts and similar material handling applications of Industry for the last over 4 decades;

A conveyor belt (or belt conveyor) consists of two or more pulleys, with a continuous loop of material - the conveyor belt - that rotates about them. One or both of the pulleys are powered, moving the belt and the material on the belt forward. The powered pulley is called the drive pulley while the unpowered pulley is called the idler. There are two main industrial classes of belt conveyors; Those in general material handling such as those moving boxes along inside a factory and bulk material handling such as those used to transport industrial and agricultural materials, such as grain, coal, ores, etc. generally in outdoor locations. Generally companies providing general material handling type belt conveyors do not provide the conveyors for bulk material handling. In addition there are a number of commercial applications of belt conveyors such as those in grocery stores. The belt consists of one or more layers of material. They can be made out of rubber. Many belts in general material handling have two layers. An under layer of material to provide linear strength and shape called a carcass and an over layer called the cover. The carcass is often a cotton or plastic web or mesh. The cover is often various rubber or plastic compounds specified by use of the belt. Covers can be made from more exotic materials for unusual applications such as silicone for heat or gum rubber when traction is essential. Material flowing over the belt may be weighed in transit using a beltweigher. Belts with regularly spaced partitions, known as elevator belts, are used for transporting loose materials up steep inclines. Belt Conveyors are used in self-unloading bulk freighters and in live bottom trucks. Conveyor technology is also used in conveyor transport such asmoving

sidewalks or escalators, as well as on many manufacturing assembly lines. Stores often have conveyor belts at the check-out counter to move shopping items. Ski areas also use conveyor belts to transport skiers up the hill. A wide variety of related conveying machines are available, different as regards principle of operation, means and direction of conveyance, including screw conveyors, vibrating conveyors, pneumatic conveyors, the moving floor system, which uses reciprocating slats to move cargo, and roller conveyor system, which uses a series of powered rollers to convey boxes or pallets. Belt conveyor systems Conveyors are durable and reliable components used in automated distribution and warehousing.[1] In combination with computer controlled pallet handling equipment this allows for more efficient retail,wholesale, and manufacturing distribution. It is considered a labor saving system that allows large volumes to move rapidly through a process, allowing companies to ship or receive higher volumes with smaller storage space and with less labor expense. Rubber conveyor belts are commonly used to convey items with irregular bottom surfaces, small items that would fall in between rollers (e.g. a sushi conveyor bar), or bags of product that would sag between rollers. Belt conveyors are generally fairly similar in construction consisting of a metal frame with rollers at either end of a flat metal bed. The belt is looped around each of the rollers and when one of the rollers is powered (by an electrical motor) the belting slides across the solid metal frame bed, moving the product. In heavy use applications the beds which the belting is pulled over are replaced with rollers. The rollers allow weight to be conveyed as they reduce the amount of friction generated from the heavier loading on the belting. Belt conveyors can now be manufactured with curved sections which use tapered rollers and curved belting to convey products around a corner. These conveyor systems are commonly used in postal sorting offices and airport baggage handling systems. A sandwich belt conveyor uses two conveyor belts, face-to-face, to firmly contain the item being carried, making steep incline and even vertical- lift runs achievable. Belt conveyors are the most commonly used powered conveyors because they are the most versatile and the least expensive. Product is conveyed directly on the belt so both regular and irregular shaped objects, large or small, light and heavy, can be transported successfully. These conveyors should use only the highest quality premium belting products, which

reduces belt stretch and results in less maintenance for tension adjustments. Belt conveyors can be used to transport product in a straight line or through changes in elevation or direction. In certain applications they can also be used for static accumulation or cartons. Long belt conveyors The longest belt conveyor system in the world is in Western Sahara. It is 98 km long, from the phosphate mines of Bu Craa to the coast south of El-Aaiun.[2] The longest conveyor system in an Airport is the Dubai International Airport baggage handling system at 92 km. It was installed by Siemens and commissioned in 2008, and has a combination of traditional belt conveyors and tray conveyors. [citation needed] Boddington Bauxite Mine in western Australian may claim the Record for the worlds longest and second longest single belts with a 31 km long belt feeding a 20 km long belt. This system feeds bauxite through the difficult terain of the Daring Ranges to the Alumina refinery at Worsley. The longest single belt international conveyor runs from Meghalaya in India to Sylhet in Bangladesh.[3][4][5] It is about 17 km long and conveys limestone and shale at 960 tons/hr, from the quarry in India to a cement factory in Bangladesh (7 km long in India and 10 km long in Bangladesh). The conveyor was engineered by AUMUND France and Larsen & Toubro. The conveyor is actuated by 3 synchronized drive units for a total power of about 1.8 MW (2 drives at the head end in Bangladesh and 1 drive at the tail end in India). The conveyor belt was manufactured in 300-meter lengths on the Indian side and 500-meter lengths on the Bangladesh side, and was installed onsite by NILOS India. The idlers, or rollers, of the system are unique in that they are designed to accommodate both horizontal and vertical curves along the terrain. Dedicated vehicles were designed for the maintenance of the conveyor, which is always at a minimum height of 5 meters above the ground to avoid being flooded during monsoon periods.