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Mill


Mill
The first tool to grind grain into flour were stone mortar and pestle. Some step forward compared to them was the method of grinding the grain instead of pounding. People very soon convinced that the chafing meal turns out much better. However, it was also very tedious job. The big improvement was the transition from the movement of float back and forth to the rotation. Pestle was replaced by a flat stone which moved on a flat stone dish. From the stone, which frays the grain, it was easy to go to the grindstone, that is, to make one stone to slide in rotation on the other. Grain gradually slipped into a hole in the middle of the upper stone millstones, enters the space between the upper and lower stone and rub into the flour. This hand-mill received the most widespread in ancient Greece and Rome. The design of it is very simple. The grounds of the mill served as a stone, bulging in the middle. iron pin is located on the top of it. Second rotating stone had a bell-shaped recess two interconnected hole. Outwardly, he looked like an hourglass was empty inside. This stone is placed on the base. The hole inserted steel strip. By rotating the mill grain, falling between the stones grind. Flour gathered at the lower stone base. These mills have a wide variety of sizes, from small, like a modern coffee grinders, to large, which resulted in the two rotation or slave ass. With the invention of hand-grinding corn mill process eased but was still time-consuming and difficult task. Not coincidentally, it is in fact the milling emerged first in the history of the car, who worked without the use of muscular force of a human or animal. It is a water mill. But first, the ancient masters were to invent a water engine.

The ancient water-car engines are developed, apparently from a watering machine chadufonov by which rises from the river water for irrigation shores. Chadufon represented a number of buckets, which is placed on a large wheel rim with a horizontal axis. By turning the wheel lower dipper submerged river, then climbed to the highest point of the wheel, and turned over to the chute. First, such a wheel rotated by hand, but where water is scarce, and it runs along a steep river bed quickly, the wheel began to supply special blades. Under the pressure of the flow wheel rotates and drawers of water itself. I get a simple pump machine that does not require for its work of human presence. The invention of the water wheel was of great importance for the history of technology. For the first time a person has at its disposal a reliable, versatile and very simple in its manufacture of the engine. It soon became apparent that the movement generated by the water wheel can be used not only for water swing, but also for other needs, such as for grinding grain. In flat areas the rate of flow of the rivers is low in order to rotate the wheel force jet strike. To create the desired pressure began damming the river artificially raise the water level and to direct a jet of the chute on the rotor blades.

However, the invention of the engine immediately gave rise to another problem: how to transfer motion from the water wheel to the device, which must perform useful work for a man? For this purpose, it was a special gear is required, which could not only transmit but also to convert rotational movement. Solving this problem, ancient mechanics turned back to the idea of ​​the wheel. The simplest wheel gear operates as follows. Imagine two wheels with parallel axes of rotation, which is in contact with their rims. Now, if one of the wheels starts to spin (called leading), then due to friction between the rim starts to rotate and the other (slave). Moreover, the path traveled by the points lying on their rims are equal. This is true for all wheel sizes.

Consequently, a larger wheel will do compared with an associated smaller by the same factor less speed, how many times its diameter exceeds the diameter of the latter. If we divide the diameter of the wheels on the diameter of the other, we get a number that is called the gear ratio of the transmission wheel. Imagine two transfer wheels in which one wheel diameter two times greater than the second diameter. If the driven wheel is greater, we can use this transmission double the speed, but the twice reduced torque. This combination is useful in the wheel when it is important to get the output speed greater than the input. If, on the other hand, the driven wheel is smaller, we will lose the output speed, but the torque of the transmission will be doubled. This transfer is useful where you want to "strengthen the movement" (for example, when lifting weights). Thus, by using a system of two wheels of different diameters, it is possible not only to transmit but also to convert motion. In actual practice, the gear wheel with a smooth rim hardly used because insufficient adhesion between the hard and the wheels are slipping. This disadvantage can be eliminated by using jagged instead of smooth wheels. The first wheel gears appeared about two thousand years ago, but widespread, they have received much later. The fact that the cutting teeth requires great accuracy. To when one wheel of uniform rotation of the second rotating too evenly, without jerks and stops, the teeth should be given a special shape, in which the relative motion of the wheels was done to as if they move against each other without sliding, while the teeth of one wheel will fall into another depression. If the gap between the teeth of the wheels will be too large, they will bump into each other and quickly broken off. If the gap is too small - the teeth crash into each other and crumble. Calculation and manufacturing of gears is a challenge for the ancient mechanics, but they appreciated their friendliness. Indeed, various combinations of gears, as well as their connection with some other transmissions given a tremendous opportunity for the motion conversion. For example, after the connection with the screw gear, the worm gear was obtained, which transmits the rotation from one plane to another. By using bevel gears, rotation can be transmitted at any angle to the plane of the drive wheel. By connecting the toothed wheel with a ruler, it is possible to convert rotational movement into translational and vice versa and attaching the connecting rod to the wheel is obtained reciprocates. To calculate the gearing ratio does not usually take the wheel diameter, and the ratio of the driving and driven wheels teeth. Often used in transferring some of the wheels. In this case, the whole transmission gear ratio is equal to the product of the ratios of individual pairs.

When all the difficulties associated with obtaining and transformation of movement, were successfully overcome, there was a water mill. It was first described in detail the device as a mechanic and a Roman architect Vitruvius. Windmill in antiquity had three major components, interconnected in a single device: 1) a motor gear wheel with vertical blades rotating water; 2) transmission or transmission in a second vertical gear; the second gear rotates the third horizontal gear - gear; 3) an actuator in the form of millstones, the upper and lower, the upper millstone was planted on a vertical shaft gears, and by means of which was set in motion. Grain funnel pour out of the bucket above the upper millstone.

Creating a water mill is considered a milestone in the history of technology. It was the first machine, which received the application in the production of a kind of apex, which reached the antique mechanics, and the starting point for technical searches Renaissance mechanics. Its invention was the first tentative step towards machine production.

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