6. Просмотрите раздел « Operating speeds».Определите основную проблему.
7. Найдите 3-4 предложения , которые передают основную идею раздела.
8. Выпишите из раздела ( 5, 6, 7, 8) ключевые слова , несущие основную смысловую нагрузку.
9. Воспроизведите текст на русский язык.
I0. Переведите 9 абз. без словаря , разберите все глагольные формы.
11. Переведите письменно I0, II абз. за 30 мин. Какая грамматическая структура присутствует в подчёркнутых предложениях.
I2. Переведите следующие словосочетания, взятые из текста: wide range of application, major developments operating speeds, as a results of, increased user demand, ever-widening range of application down-stroke press, long – stroking operation, fast-acting logic valve, automatic feed gear, manual loading, automated handling, reducing down time.
I3. Прочитайте текст В, дайте обоснование заголовков
VARIABLE PRESSING SPEED
I. The slide on an hydraulic press is normally set no slow down to the pressing speed from its fast approach speed just prior to contacting the work-piece. Throughout the empire length of draw, the work is then done at constant speed and power .This eliminates any tearing of the parts as well as damage to dies no problems of midstroke velocity or learning on impact with an hydraulic press the slide of which can be stopped any point and reversed. In a work-stroke, the press slide can either be reversed by closing the dies and building to a desired pressure, or on depth of draw on a die. Additional controls can often be added to change the basic nature of the work being done since the hydraulic force is developed through pumps and valves.
2. It is in the simplicity of die setting where the hydraulic press has the advantage over its mechanical rival. When no fixed stroke or shut height the hydraulic press adapts itself to the job. The work-pies is subjected to a uniform pressure regardless of stock-material variation and without need for shimming the die.
3. Comparison with tool-setting practice ob a mechanical press clearly demonstrated the superiority of the hydraulic machine in the respect. This is especially evident in double-action hydraulic press where, additionally, pressure in each corner of the blankholder can be independently set and can be adjusted even the press is in motion.
4. The principal historical drawback of the hydraulic press was the slow operating speed. Continuous development is now being directed towards removing the few remaining defects.
5,6. Development in both hydraulic pumps and the design and layout of the pumping unit have gone a considerable way to relieving the problem of noise. Pumps can be mounted on anti-vibration mouth and flexible used to prevent noise and vibration being transmitted along pipework to the press frame ..The starting recent advances that have been made in pumping group layout and design are clearly illustrated by the case of two I600ton horizontal extrusion presses .The latest press, a Fielding machine, employs a 3-pump power pack mounted on flexible footings at floor level. The other, a German press 7 to 8 years old, has the pumps mounted in the classical manner over the press on top of hydraulic oil tank .Noise levels at the operating desk were 83dBA for the new Fielding press and 95 to I00dBA on the German machine.
7. A further trend is for a series of hydraulic presses to be powered from a ring main red by a remote power pack. Apart from reducing noise and improving layout of the working area this also permits the installation pf standby pumps.
8. Great strides have been made in resent years in overcoming some of the main problems traditionally associated with operating hydraulic press (fig.4).
Design improvements in hydraulic components have contributed to greater reliability and improved plant availability. The press designers for their part, have successfully eliminated a great deal of the oil loss and contamination.
9. As previously suggested, a modern hydraulic press, correctly maintained, will offer constant trouble-free service. The hydraulic press is essentially self-lubricating, the only added lubrication being required for the slide gibs. In many respects an hydraulic press is simpler than an mechanical press, rams and cylinders replacing gears, shafts, bearings and eccentrics etc .Valves are simple to maintain and reliable in operation provided filters are correctly cleaned. Valves are mounted on manifold blocks, up to nine of each, considerably reducing the number of pipe connection and leakage points.
I0. Standby pumps can be fitted to guarantee continuity of operation in the event of a pump, breakdown or while routine maintenance its being carried out.
Notes: I. ring main – кольцевой магистральный трубопровод
2. apart from – кроме
3.Hydraulic maintenance – обеспечение условий для нормальной работы гидравлического пресса
I5. Дайте сравнительную характеристику двух прессов (a Fielding machine and German press).
I6. прочитайте последний раздел. Выберите из предложенных словосочетаний ключевые для оценки нормальной работы гидр. пресса : design improvements, fixed stroke, constant trouble-free service, self-lubricating.
1.The benefits of hydraulic power have been more widely appreciated throughout Europe where the incidence of hydraulic presses is higher than in this country. There is in the UK, however, a marked trend towards the more widespread acceptance of hydraulic presses.
2. Due to the increasing complexity and multiplicity of carboy panels, hydraulic presses have been introduce into UK automotive press shops within the last three to fur years. The results have been highly favourable. Apart from the attraction of lower capital cost, the principal benefit has been reduced tool-setting times particularly on initial drawing operations. A more widespread adoption of hydraulic presses in the British car industry is predicted whereby the double-acting load press.
3. The reduced risk of accidental tool damage plus reduced tool-setting times as well as fewer operating problems are all factors which have led to the adoption of the latest fast-acting hydraulic presses on brake and headlamp-manufacturing operations. (1)
4. The use of hydraulic power for such operations can only improve the component accuracy and also helps to reduce vibration and noise at the operating station – an ever-present problem in busy press shop.
5. Further impetus to the use of hydraulic presses has been given by the development of special tooling systems for certain drawing operations. The use of hydraulic presses with systems which involve telescopic punches, and multiring as well as hydraulic dies, has led to the elimination of many multiple drawing operations as well as the interstage annealing operations then required.
6. With the proving of the latest kind of fast-acting presses and a successful outcome of further developments at present, hydraulic presses will be marking significant in-roads(2) into the traditional market for single-acting mechanical presses.
7. Already the widespread introduction of hydraulic presses is seen in the double and triple-action press field for sheet-metal pressing, where the great advantage over mechanical presses is the controllability offered by hydraulic power.
Notes: 1. brake and headlamp-manufacturing operations-операции по производству тормозов и фар.
19. Ответьте на вопросы.
1. What was the principal benefit of hydraulic presses?
2. What can you say about widespread introduction of hydraulic presses?
4. Прочитайте текст А и выполните задание, данные после предъявления текста:
1.In the past hydraulic presses have been looked upon with soma degree of suspicion, due to fears of their leakage, lack of speed, being incapable of blanking operations etc. and therefore a tendency has been to use them for drawing, and assembly operations. This trend, however, is now changing. The use of hydraulic presses on panel lines in pressed steel plants at Cowley, Swidon proved that the factors were in favour of(1) hydraulic machines.
2. Historically the hydraulic press is one of the oldest of the basic machine tools. As a machine it is probably as old as the bicycle. In recent years, hydraulic presses have been attracting greater attention. Automotive manufacturers stamp out fuel pump diaphragms, assemble shock absorbers and form disc brakes. Aircraft companies form tough titan ten housings and forged turbine blades. Not only engineers are interesting in hydraulic press market place – our knowledge extends to the physicist with his varieties of valves, the biologist, the dentist, and even the makers of food products. There and hundreds of other jobs are being done today in industry by hydraulic presses.
WHAT IS AN HYDRAULIC PRESS?
3. First and foremost it is a press. Although the term hydraulic press covers a very wide range of types of presses they all have in common(2) the application of force to accomplish work through the controlled containment of fluids. One hundred years or so ago, the fluid used to be water – hydraulic presses were all water presses. With the development of the petroleum industry, oil was found to be superior fluid since it lubricated the moving parts of the machine while at the same time providing an excellent medium for transferring pressure. Now 100 years later because of the oil crisis, the industry is on a trend back to the use of water, 95% water and 5% soluble oil.
4. Generally, an hydraulic press includes a frame, a bed, one or more hydraulic cylinders, a guide or slide mechanism to control the ram, a control system and a power source. The construction of an hydraulic press and its characteristic will vary depending upon the intended use. Hydraulic presses are built for rubber moulding (3), fording, various types of metalworking, maintenance work, the emphasis will be on metalworking, hydraulic presses since this application is widespread and the characteristics of a metalworking hydraulic press apply to most other types presses.
5. The mechanical press has dominated the thinking of press users for at least the last 60 or 70 years. The term rower press has almost become synonymous with the term mechanical press. The training that tool and die makers and manufacturing engineers receive is almost always orientated towards mechanical presses. The terms used, the approach to tooling, feeding, and part handling are all centered around mechanical presses.
6. However, figures from the USA indicate that in the 20 year period between 1958 and 1978 the percentage change in the number of presses used showed an increase of 94% for hydraulic presses and only 4% for mechanical presses. It is suspected that UK statistics will show the same growth.
7. Part of the reason for the relative growth in the market of hydraulic presses certainly lies with the improved construction and performance of mechanical presses. Because of greater speed and reliability, fewer mechanical presses are needed to accomplish more work, however, hydraulic presses have been improving at the same time and they too have far greater speeds and reliability. Other factors may have affected this growth. The power press regulations could be one, bearing in mind(4) that most operations are still hand fed, and customers claim that the use of modern high speed hydraulic presses, with light curtain guarding(5) which has been monitored for ultimate safety, can result in between 10% and 20% increased productivity.
Notes: 1. were in favour of – быть в пользу…
2. they all have in common – они все имеют общее…
3. rubber moulding – штамповая резина…
4. bearing in mind – имея ввиду…
5. curtain guarding – защитное устройство по технике безопасности…
5. Расшифруйте заглавие текста, переведите его и данное краткое изложение текста.
Full power stroke – the full power of an hydraulic press can be delivered at any point in the stroke, not only at very bottom as is the case with mechanical presses. One of the advantages is that no allowances should be made for reduced tonnage at the top of the stroke. In drawing operations, for example, full power of the press is available at the top of the stroke and it is unnecessary to buy a 200 ton press to get 100 tons throughout the stroke. Other advantages are faster setups and no time consuming job of adjusying the screw on the slide to accommodate different dies.
Built-in overload protection – a 100 ton hydraulic press will exert only 100 tons pressure (less, if set for less) no matter what mistakes are made in set-up. It is unnecessary to worry about overloading or breaking the press or smashing a die (1). When an hydraulic press reaches its pre-set pressure (2), no further pressure is added since the relief valve opens at that limit and the danger of overload is eliminated.
Muchlower original cost and operating costs – hydraulic presses are relatively simple, and there is a significant cost advantage over mechanical presses in comparable sizes. The number of moving parts are few, and there are fully lubricated in a flow of pressurized oil. Breakage when it occurs is usually minor, not, for example, like a broken crankshaft. Solenoid coils, and occasionally a valve are inexpensive and they are easily replaced without taking the machine apart. This means more operating time and lower maintenance costs.
Larger capacity at lower cost – It is easier and less expensive to buy certain kinds of capacity in hydraulic presses. Stroke length of 12, 18 and 24in are common, extra stroke length is easy to provide. In addition, larger table areas and small presses with big bed areas can be provided. Large 200 ton presses with relatively small beds are available; tonnage of the press does not dictate what the bed size will be.
More control flexibility – Hydraulic press power is always under control. The ram force, the direction, the speed, the release of force, the duration of pressure dwell (3), all can be done with the pressure turned down. The ram can be made to approach the work rapidly, then shifted to a slower speed before contacting the work. Tool life is thus prolonged. Timers, feeders, heaters, coolers and a variety of auxiliary accessories can be switched in the circuit to fit the job. Hydraulic presses can do far more than just go up and down, up and down.
Greater versatility – a single hydraulic press can do a wide variety of jobs within its tonnage range, e.g., forming, blank and pierce, punch, straightening, assembly, powered metal forming, abrasive wheel forming (4), bonding, plastic and rubber compression and moulding.
Quiet – Fewer moving parts and the elimination of a flywheel reduce the overall noise level of hydraulic presses, compared to mechanical presses. Properly sized and properly mounted pumping units meet and exceed current US standarts for phase of the ram movement can be controlled, noise levels can also be controlled. An hydraulic ram be controlled to pass through the work slowly and quietly.
More compact – a typical 20 ton hydraulic press is 8ft high, 6ft deep, and 2ft wide. A 200 ton press is only 10ft high, 9ft deep, and a little over 3ft wide. At 10 times the capacity (5), the 200 ton press only takes up 50% more floor space, consequently hydraulic presses become less and less expensive compared to mechanical presses.
Lower tool costs – The built-in overload protection applies to the tools also. If they are built to withstand a certain load, there is no danger of damaging them because of overloading. The pressure of the press can be regulated to suit the job and the lack of impact, shock, and vibration promotes longer tool life.
Safety – No manufacturer will (or should) claim that hydraulic presses are safer than mechanical presses. Both types of machines are designed and built to be safe if the controls and safety features built in are used properly. Improperly used, all machines are potentially dangerous, but the factor of control of the ram movements makes hydraulic presses easy to make safe. The interlocking of guards, as well as other safety devices, is relatively easy because of the nature of an hydraulic press control system.
Notes: 1. smashing a die – разрушение штампа
2. pre-set pressure – заранее установленное давление
16. Просмотрите текст С. Вам нужно извлечь только определенную информацию. Сделайте это, выполнив задание к тексту.
SELECTION OF HYRDRAULIC PRESS
The tonnage required to do a job is the same for an hydraulic press as it is for a mechanical press and therefore the same formulae(1) are used to determine capacity. There may be certain applications such as deep drawing where the full power stroke characteristic of hydraulic presses tend to reduce the tonnage but there are no known instances where using an hydraulic press required more tonnage. The most misleading practice is to assume that because a job is now successfully done on a 100 ton mechanical press that the pressure required is 100 tons. It may be that less, possibly 80 tons or even 50 tons, is adequate. With an hydraulic press the precise tonnage required to a job can be determined by observing the pressure gauge and the successful completion of a part. From this the proper tonnage of the press can be set.
Even though the tonnage question might be settled, considering the action of the machine, the question of the effect of the stroke on the work is often asked. Is it the same as with a mechanical press? The answer is yes in most cases, at though there are some specific limitations: drop hammers and some mechanical presses seem to do a better job on soft jewellery pieces(2) and impact jobs; the coining action seem sharper if impact is there; in deep drawling the full power stroke may produce different results ( usually better ). Otherwise there are very few example where the application of 100 tons of hydraulic force produces any significant difference in the character of the part given the same tooling(3). Some investigators claimed that tool life was increased using hydraulic presses. Shear in the dies will reduce blacking tonnage in the same way.
When considering type of press selection, the following should be taken into account. Open gap presses provide easy pressure distribution and straight side presses offer the rigidity required for off-centre loading(4) in progressive die applications. The more critical the work and demanding the tolerances the more reserve capacity(5) is recommended. That is, if the work requires 42 tons to do the job, a 75 ton or even a 100 tom press should be considered.
Most hydraulic press builders offer a lot of accessories. These commonly include such items as: distance reversal switches(6); automatic (continuous) cycling; sliding bolsters, rotary index tables, and hydraulic clamping; die cushions; ejection cylinders; electronic light curtains and other devices; damping facilities for shock loads as in blacking.
The industry offers various levels of quality. There are light duty presses that are capable of hitting the work momentarily and reversing. The are heavy duty machines designed for general purpose metalworking applications. A few construction points that will provide a basis for comparison of one machine with another are first the frame weights. The character of frame construction eg plate sizes, bolster thickness, stress relieving and other factors should also be determined. Second the cylinder and piston rod diameters.
Finally the maximum system pressures should be compared, die the pressures at witch presses develop full tonnage. Some companies like to keep this figure to 1000 lb\in2 maximum but most press manufactures today are operating in the 1000 to 3000 lb\in2 zone. Although vales and equipment available in the 1000 to 3000 lb\in2 range are prevalent, current developments indicate that during the 80s, increasing efforts will be towards higher pressures in hydraulic systems up to 5000 lb\in2 and, of course, the development of pumps capable of generating them. Notes: 1. formulae – мн.ч. от сущ. formula 2. jewellery pieces – ювелирные изделия 3. given the same tooling- при той же оснастке