press


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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 ?
Well, trooping the colors is a very solemn ceremony, and everybody must stand uncovered when the flag goes by, the commandant and all; and once I was there, and ignorantly walked across right in front of the band, which was an awful disgrace: Ah, the Lieutenant-General was so ashamed, and so distressed that I should have done such a thing before all the world, that she couldn't keep the tears back; and then she taught me the salute, so that if I ever did any other unmilitary act through ignorance I could do my salute and she believed everybody would think it was apology enough and would not press the matter.
and the old man bent down and kissed it reverently, then closed his fingers upon it in an affectionate grasp, crying out, "I could never have dared to believe that before quitting this world it would be granted me to press once more the hand of one of those brave comrades, the hand of my good friend Balmat.
I get the subject to pass the fingers of his right through his hair, so as to get a little coating of the natural oil on them, and then press the balls of them on the glass.
The widow's servants kept him clean and neat, combed and brushed, and they bedded him nightly in unsympathetic sheets that had not one little spot or stain which he could press to his heart and know for a friend.
Why, for instance, should it be said that the liberty of the press shall not be restrained, when no power is given by which restrictions may be imposed?
With frenzied insistence I continued to press the little button which should have sent us racing out into space, but still the vessel refused to budge.
It was a clever move, for it put me at the mercy of a dozen men within a chamber from which assistance was locked out, and it gave the red men in the corridor beyond no avenue of escape should their new antagonists press them too closely.
It was the terror and dazzled amazement of the men of the sanctuary, in the presence of the luminous press of Gutenberg.
But the Tree cried to the Nightingale to press closer against the thorn.
To this it was objected, that in this respect he could not possibly be speaking the truth, since the papers had been deposited in a press in which both his hands and his eyes must have been engaged every day.
But Skipper did not awake and a fine spray of rain, almost as thin as mist, made Jerry curl up and press closely into the angle formed by Skipper's head and shoulder.
She felt his shoulder press hers, and a tremor run through him.