Методические указания по обучению чтению технической литературы на английском языке по специальности «прессы»
Скачать 193.91 Kb.
|
| Глава 2. MARKET PENETRATION BY HYDRAULIC PRESSES Предтекстовые задания. 1.Повторите лексику, значение незнакомых слов найдите в словаре. adjust, as far as, by means of, improvement, introduction, flexibility, level, loading, manual, maintenance, operating speed, stroke, suit, to be contrary to. 2.Восстановите словарную форму выделенных слов. Переведите предложение. In this traditional regards, the principle arguments against winder applications for hydraulic presses were their slow stroking, oil leakage and other maintenance problems as well as the noise made by the hydraulic power packs. 3.Переведите следующие слова как глаголы и как существительные: point, speed, range, design, demand, use, slide, cycle, desire. Задание к тексту. 1.Прочитайте текст А и выполните задания, данные после предъявления текста. TEXT A 1. The performance of hydraulic presses has developed to a point where they now complete successfully against mechanical presses over a wide range of applications and major developments in recent years have raised operating speeds to levels which allow these machines to compete even against single-acting mechanical presses. As a result of continued design improvements, both in the press and in hydraulic presses have been realized and have been reflected in increased user demand for an everwidening range of applications. CHANGE IN EMPHASIS 2. For the majority of cold-forming operations, the single-acting mechanical downstroke press has been traditionally regarded as the “workhouse” of the industry and for shallow draw work the custom has been to use the double-acting mechanical press. Hydraulic presses have been considered to be applicable only to long-stroking operations such as deep drawing, where the controllability of hydraulic power is of prime importance. 3. In traditional regard, the principle arguments against wider applications for hydraulic presses were their slow stroking speed, old leakage and other maintenance problems, as well as the noise made by the hydraulic power packs. 4. As a result of the design improvements, major developments are taking place which have been already led to a new type of fast-acting presses which are arousing considerable interest in what usually was a predominantly mechanical press field. 5. Operating speeds Central to new developments to improve operating speeds of hydraulic presses has been the introduction of the fast-acting logic valve. A 300 ton hydraulic press with a 200mm working stroke and a 3mm pressure stroke can now cycle, for example, in 2.4 sec when applied to coining, planishing and sizing operations,(fig 1). 6. It should be stressed, however, that while the high stroking speeds of mechanical presses can be utilized in conjunction with automatic feed gear, as in the case of blanking, the majority of medium-to-large press work in this country involves manual loading and in many cases manual unloading as well. Although the mechanical press in capable of stroking in around 2 sec, floor-to-floor time for this type of work, however, are typically of the order of 15 to 30 sec. 7. While emphasis is often laid on the operating speed of the press with regard to the overall cycle time (3), we have to consider the time for transportation by the development of automated handing and the introduction of more efficient guarding. Arising from the ability to lock the side on every stroke and at any position on an hydraulic press it has proved possible to adopt photocell guarding while conforming to the majority of applied safety regulations. Arranged automatically to cycle the press, the introduction of photocell guarding has, in itself, made a major contribution towards reducing overall cycling time. 8. It must be born in mind, however, that continuity of production is often more significant than speed of production and attention will continue to be focused on reducing downtime. 9. WHY HYDRAULIC? It is the desire to realize the operating benefits of hydraulic presses which has stimulated press builders to break the hydraulic speed barrier. These benefits include the operating flexibility of an hydraulic press, the reduced down-time for tool setting, and the minimized risk of accidental tool damage. The key, of course, is provided by the controllability of hydraulic power. 10. CONTROLED PRESSURE. The pressure on an hydraulic press depends on the setting of an adjustable relief valve which is regulated automatically from the operator’s console. This pressure is continually controllable from maximum down to approximately 20 per cent of its maximum value and is available throughout the work-stroke. 11. Through the complete work-stroke, the pressure of the system, therefore, is built up only to that required to overcome the resistance of the work-piece, and will increase only as far as the relief-valve pressure setting. As a consequence, it is almost impossible to overload an hydraulic press due, for example, to double-blanking or inaccurate die setting. Also, the length of stroke of the slide can be adjusted by means of limit switches to suits any depth of draw, any desired stroke being set in a matter of seconds. This is contrary to the mechanical press where the stroke cannot be altered, the full stroke of the crank having to take place regardless of the actual depth of draw. In addition, the pressure in a mechanical press builds up to an increasing and uncontrolled rate after midstroke to maximum power only at the end of the stroke. 12. For example, it can be said that to obtain 1000 tons at say 5in from stroke bottom the mechanical press would have to be up-rated to 3000 tons power, where as in the case of the hydraulic press the maximum power of 1000 tons is available through out the whole of the stroke. Notes: 1. power pack – узел привода 2. floor – to – floor time – время перемещения от места к месту 3. overall cycle time – время полного цикла 2. Переведите I абзац текста , догадайтесь по смыслу о значении слов : complete, benefit , inherent . Проверьте правильность по словарю. 3. Переведите 2 , 3 абзацы .Что определяется словосочетанием « workhorse in the industry»? 4. Прочитайте подчёркнутое предложение 2 абз., какая синтаксическая конструкция используется для характеристики работы гидравлического пресса. 5. Прочитайте 4 абз., разберитесь в структуре предложения , найдите главные члены, переведите. 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 TEXT B. 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. DIE SETTING. 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. REDUCING NOISE. 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. HYDRAULIC MAINTENANCE. 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 I4. Найдите в каждом разделе предложения, подчёркивающие основную мысль. 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. I7. Прочитайте текст C,найдите аргументы, касающиеся преодоления основных проблем, связанных с работой гидравлических прессов. TEXT C APPLICATIONS 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. CONCLUSION 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. 2. in-roads-вторжение 19. Ответьте на вопросы. 1. What was the principal benefit of hydraulic presses? 2. What can you say about widespread introduction of hydraulic presses? 20. Слова для активизации: Cold-forming operation, coining, deep drawing, extrusion press, feed gear, gear, guard, handling, impact, long-stroke operation, manual unloading, planishing, reverse (v), relief valve, stock-material, single-acting mechanical press, sizing, shallow draw work, shaft. Глава №3 MECHANICAL PRESSES – A DYING BREED? Предтекстовые задания 1.Повторите лексику, значения незнакомых слов найдите в словаре: advantage, accomplish, approach, at least, to be in favour of, capacity, cost, conventional, cover (v), compress, compact, depend upon, due to, protection, transfer, range, repair, reason, relative, vary (v). 2.Определите по суффиксам, к каким частям речи относятся следующие слова; переведите: compactness, containment, flexibility, historically, incapable, limitation, maintenance, manufacturer, medium, probably, regulation, reliability. 3. |
Похожие:
 |  | ||
| Методическое пособие предназначено для студентов заочного факультета технических специальностей. Цели методического пособия развитие... | | Учебно-методическое пособие по обучению профессионально-ориентированному чтению студентов специальности «Автоматика, телемеханика... |
| Рекомендовано к изданию научно-методическим советом Псковского государственного политехнического института | | Материалы промежуточной аттестации по дисциплине «Фразеология радиообмена на английском языке» для студентов заочной формы обучения... |
| Методические указания для студентов по выполнению самостоятельной работы по мдк 01. 03. «Детская литература с практикумом по выразительному... | | «Ростовский государственный университет путей сообщения Министерства путей сообщения Российской Федерации» |
| «Ростовский государственный университет путей сообщения Министерства путей сообщения Российской Федерации» | | Учебное пособие предназначено для студентов, обучающихся по дисциплине «Иностранный язык (английский)», по всем специальностям факультета... |