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press

1
1. any machine that exerts pressure to form, shape, or cut materials or to extract liquids, compress solids, or hold components together while an adhesive joint is formed
2. Weightlifting a lift in which the weight is raised to shoulder level and then above the head

press

2
recruitment into military service by forcible measures, as by a press gang

Press

 

a machine with static (nonimpact) action for working metals by means of pressure. Presses are widely used in various branches of industry for the processing of metals, plastics, rubber, agricultural and food products, and other materials. They are also used for the study of the properties of these materials under high pressures. Presses have their widest range of application in the metalworking industry, where they are used for forging, for stamping solid stock and sheet metal, and for forming extrusions. They are also used for metalworking assembly operations, such as press-fitting of gears, pins, and bearing races, and for mechanical testing.

Historical information. Manually operated screw presses were used as early as the 15th and 16th centuries in such trades as butter-making, viticulture, printing, and bookbinding, which are not connected with metalworking. At the end of the 17th and beginning of the 18th century, screw presses were used for working metals under pressure, specifically for minting coins and medals, and later, for stamping. Hydraulic presses became common in the mid-19th century in the forging and stamping industry. With the development of large-series and mass production, crank presses, which constitute the largest group of forging and stamping machines, came to be widely used, especially after the invention of electric motors.

Design and principles of operation. The basic parts of a press are the slide, a bed with guides for the slide and bolster plate, drive and control mechanisms, mechanization and automation devices, and the tool. The moving part of the tool is attached to the slide, which performs a reciprocating motion, and the stationary part is attached to the bolster plate. The article is shaped by compression of the blank between the moving and the stationary parts of the tool. The principal parameters of the press, which, taken as a whole, determine its technical capacity and construction features, are nominal strength, stroke and velocity of the slide, and dimensions of the bolster plate.

Basic types. According to the drive used, presses are classified as hydraulic, mechanical (crank, screw, and friction types), and hydromechanical. In hydraulic presses, the slide is actuated by the pressure exerted by water, emulsion, or oil, which functions as the carrier of energy. Upon entering the cylinder, the hydraulic fluid displaces a piston that is connected to the slide. A crank press works by using a crank gear to transform the rotary motion of the drive into the reciprocating motion of the slide. The screw press uses a screw mandrel with a non-self-braking thread to impart motion to the slide. The mandrel is rotated either by an electric motor acting through a friction gear (friction press), or by fluid pressure (hydraulic screw press). Depending on the intended use, presses have slides that move either vertically, for example, for stamping, or horizontally, for example, for forming.

Hydraulic presses are the most powerful. Hydraulic stamping presses develop forces of up to 735 meganewtons, (MN), or 75,000 tons-force (tf); hydraulic presses for the production of diamonds develop forces of up to 490 MN, or 50,000 tf. Crank presses produce a maximum force of about 100 MN, and screw presses produce a maximum force of about 125 MN.

REFERENCES

Mikheev, V. A. Gidravlicheskie pressovye ustanovki, 2nd ed. Moscow, 1953.
Zhivov, L. I., and A. G. Ovchinnikov. Kuznechno-shtampovochnoe oborudovanie: Pressy. Kharkov, 1966.
Rovinskii, G. N., and S. L. Zlotnikov. Listoshtampovochnye mekhanicheskie pressy. Moscow, 1968.

I. A. SHUR

press

[pres]
(mechanical engineering)
Any of various machines by which pressure is applied to a workpiece, by which a material is cut or shaped under pressure, by which a substance is compressed, or by which liquid is expressed.
References in classic literature ?
I pressed my thumb upon the button which controls the ray of repulsion, that splendid discovery of the Martians which permits them to navigate the thin atmosphere of their planet in huge ships that dwarf the dreadnoughts of our earthly navies into pitiful significance.
For an instant the blacks pressed close to reach me with their shorter swords, but presently they gave back, and the esteem in which they suddenly had learned to hold my sword arm was writ large upon each countenance.
So the Nightingale pressed closer against the thorn, and the thorn touched her heart, and a fierce pang of pain shot through her.
See, here's an officer jammed in too"- different voices were saying in the crowd, as the men looked at one another, and all pressed toward the exit from the bridge.
Mukhorty, buried up to his belly in snow, with the breeching and drugget hanging down, stood all white, his dead head pressed against his frozen throat: icicles hung from his nostrils, his eyes were covered with hoar-frost as though filled with tears, and he had grown so thin in that one night that he was nothing but skin and bone.
Again he saw himself as he pressed the switch of his electric torch and looked.
Then he felt her body yielding, and once again she was close in his arms and lips were pressed on lips.
I am thinking, my lord," added she "(for this fellow is too mean for your personal resentment), whether it would not be possible for your lordship to contrive some method of having him pressed and sent on board a ship.
She pressed me very much to go and see her," Anna went on; "and I shall be glad to go to see her tomorrow.
I pressed this home to him with so many arguments, and answered all his own passionate objections so effectually that he embraced me, and told me I treated him with such sincerity and affection as overcame him; that he would take my advice, and would strive to submit to his fate in hope of having the comfort of my assistance, and of so faithful a counsellor and such a companion in his misery.
The woman's husband was pressed, their goods seized for some debts of his, and she, with two small children, turned into the streets a-begging.
The horror-stricken witness of this scene pressed his hands upon his ears, and with his eyes closed got up and paced violently to and fro, like one distracted.