100 research outputs found
HidrauliÄki simboli - deo i: opÅ”ti simboli i oznake mernih instrumenata i indikatora
Hydraulic power transfer and management systems are widely used in modern agriculture, especially in agricultural engineering and the associated processing industry. They can be very simple, but also extremely complex, when precise matching of the interaction of their components in real time is very difficult to controll and achieve. In addition, the designs of a number of hydraulic components is sufficiently complicated for detailed representation on the corresponding hydraulic installation. In all cases, analyzing the performance characteristics of components and the entire hydraulic system, as well as understanding the structure of the hydraulic system, is of great importance. One of the generally accepted ways to facilitate and speed up these processes is the application of schematic diagrams of hydraulic systems and their subcircuits. Officially, hydraulic symbols are defined by ISO industry standards. Therefore, ideally, all hydraulic schemes should be configured using universal graphic symbols. Unfortunately, this is not always the case in technical practice. Depending on the manufacturer and/or dealer of the hydraulic equipment, the symbols of the associated schemes vary in a smaller or a greater extent. The real reasons for the existence of these differences can only be assumed. According to some authors, companies want their drawings to differ from the hydraulic schema of competitors. Therefore, the most commonly used hydraulic symbols are presented in this paper.HidrauliÄki sistemi prenosa snage i upravljanja Å”iroko su zastupljeni u savremenoj poljoprivredi, a posebno u poljoprivrednoj tehnici i prateÄoj preraÄivaÄkoj industriji. Mogu biti veoma jednostavni, ali i izuzetno složeni, kada je precizno usklaÄivanje meÄusobnih interakcija njihovih komponenata u realnom vremenu veoma otežano. Pored toga, konstrukcija velikog broja hidrauliÄkih komponenata je dovoljno komplikovana za detaljno predstavljanje u sklopu pripadajuÄe hidrauliÄke instalacije. U svim sluÄajevima, analizanje radnih karakteristika komponenata i celokupnog hidra-uliÄkog sistema, kao i razumevanje strukture hidrauliÄkog sistema, od neprocenjivog je znaÄaja. Jedan od opÅ”te prihvaÄenih naÄina za olakÅ”avanje i ubrzavanje ovih procesa je izrada i koriÅ”Äenje Å”ematskih dijagrama hidrauliÄkih sistema, kao i strujnih kola (podsistema) od kojih su sastavljeni. ZvaniÄno, simboli hidraulike definisani su ISO industrijskim standardima. Stoga, u idealnom sluÄaju, sve hidrauliÄke Å”eme bi trebale sadržati univerzalne simboliÄke oznake. To ipak nije uvek sluÄaj u tehniÄkoj praksi. U zavisnosti od proizvoÄaÄa i/ili prodavca hidrauliÄke opreme, simboli pripadajuÄih Å”ema se nekada mogu razlikovati u izvesnoj meri. Stvarne razloge postojanja ovih razlika je moguÄe samo pretpostaviti. Prema nekim autorima, proizvoÄaÄi i/ili prodavci žele da se njihovi crteži razlikuju od hidrauliÄkih Å”ema konkurenata. Prema drugima, simboli su dizajnirani da predstave veÄinu raspoloživih komponenata, ali ipak ne mogu pokriti sve postojeÄe te se zato formiraju dodatni nestandardni simboli u nekim posebnim situacijama
HidrauliÄki simboli - Deo II: pumpe i izvrÅ”ni organi
At the current level of technological development, it is widely accepted that survival and progress of modern agricultural technology (among other things) is based on the widespread application of electronically controlled hydraulic systems, supported by mechanical elements of power transmission and control. This paper is a logical continuation of the first part, entitled "Hydraulic symbols - part I: general symbols and designations of measuring instruments and indicators". Therefore, the current second part of the paper is devoted to the presentation and description of hydraulic symbols of pumps and various types of actuators: linear, rotary and oscillatory. Symbols of the combined-function devices, which can optionally function in two different operating modes, such as pumps or motors, are also shown. Standard symbols of all groups of hydraulic components, which are in the focus of this paper, are standardized and defined by ISO industry standards.Na sadaÅ”njem nivou tehnoloÅ”kog razvoja, opÅ”te je prihvaÄeno miÅ”ljenje da savremena poljoprivredna tehnika, izmeÄu ostalog, svoj napredak zasniva na Å”irokoj primeni elektronski kontrolisanih hidrauliÄkih sistema, podržanih mehaniÄkim elementima prenosa snage i upravljanja. Ovaj rukopis predstavlja logiÄan nastavak prvog dela rada, pod nazivom āHidrauliÄki simboli - deo I: opÅ”ti simboli i oznake mernih instrumenata i indikatoraā, posveÄenog pripadajuÄoj tematici. Zato je drugi deo rada posveÄen prikazu i opisu hidrauliÄkih simbola pumpi i razliÄitih tipova izvrÅ”nih hidrauliÄkih organa i to: linearnih, rotacionih i oscilatornih. TakoÄe su predstavljeni i simboli ureÄaja kombinovane namene, koji opciono mogu funkcionisati u dva razliÄita radna režima, kao hidrauliÄke pumpe ili hidrauliÄki motori. Simboli svih grupa hidrauliÄkih komponenata, koje su u fokusu ovog rada, standardizovani su i definisani ISO industrijskim standardima
Ventili kao upravljaÄke komponente hidrostatiÄkih sistema
Modern agricultural engineering involves the wide application of hydraulic and pneumatic systems for the transmission of power (energy) and control signals. This paper presents the most commonly used types of valves in hydraulic systems. In the literature, more classification of hydraulic valves is reported, according to their construction, purposes, etc., which, even within the same classification criteria, sometimes stronglu differ one from the another. Therefore, this presentation is organized by principled valve assignment into four basic groups based on purpose, although there are other divisions according to the purpose of the valve. Other classifications, although present in the available literature, have not been commented in detail, due to space constraints. In this manuscript, the basic elements of the construction of the most important types of valves are described and analyzed, their most important characteristics are described, the base functional principles and technical limitations described, and the given guidelines and recommendations for their optimal application.Efikasnu, ekonomiÄnu i samoodrživu savremenu poljoprivrednu tehniku teÅ”ko je, pored niza drugih agroekoloÅ”kih, tehniÄkih ekonomski i drugih zahteva, zamisliti bez Å”irokog ukljuÄivanja manuelnih, mehaniÄkih, hidrauliÄkih, pneumatskih, elektriÄnih, analognih i digitalnih sistema upravljnja, kao i njihovih usklaÄenih meÄusobnih aktivnosti vezanih za prenos snage (energije) i upravljaÄkih signala. U ovom radu su prikazani najÄeÅ”Äe koriÅ”Äeni tipovi ventila u hidrauliÄkim sistemima. Literatura prikazuje viÅ”e klasifikacija ventila, prema konstukciji, nameni itd., pri Äemu se Äak i isti tip ventila nekada svrstava u razliÄite grupe. Zato su nekada i ventili svrstani u okviru istog klasifikacionog kriterijuma, mogu meÄusobno znaÄajno razlikovati. Iz navedenih razloga, ovaj prikaz je organizovan principijelnim svrstavanjem ventila u Äetiri osnovne grupe, prema osnovnim namenama, mada postoje i drugaÄije podele prema nameni ventila. Ostale klasifikacije, prisutne u dostupnoj literaturi, samo su preliminarno komentarisane. U ovom radu su opisani i analizirani osnovni elementi konstrukcije najvažnijih tipova ventila, navedene njihove najbitnije tehniÄko-operativne karakteristike, opisani bazni funkcionalni principi i tehniÄka ograniÄenja, te date smernice i preporuke za njihovu optimalnu primenu u poljoprivrednoj tehnici
HidrauliÄki simboli - deo V: āPriborā
This paper presents the fifth part of the serie, which presents the graphic designations, i.e. symbols, of the most of standard components of hydraulic systems according to current international standards (ISO). This work is focused to the symbols for simplified presentation on the hydraulic diagrams of the associated components intended for the storage and conditioning of hydraulic oil, and for the storage of energy delivered to the oil as working fluid by hydraulic pumps. The function of oil storage is provided by appropriate hydraulic tanks and the hydraulic energy is stored by means of oil-hydraulic accumulators. Symbols of components for maintaining hydraulic oil operating parameters within optimum limits are also shown. The components also included in this presentation are specified for: purification (oil-hydraulic filters), heating (preheaters/heaters) and cooling (oil-hydraulic coolers).Ovaj rad predstavlja peti deo serije u kome su prikazane grafiÄke oznake (simboli) veÄine standardnih komponenata hidrauliÄkih sistema prema važeÄim meÄunarodnim tehniÄkim standardima (ISO). Prikaz je fokusiran na simbole kojima se na hidrauliÄkim Å”emama uproÅ”Äeno predstavljaju pripadajuÄe komponente namenjene skladiÅ”tenju, preÄiÅ”Äavanju i kondicioniranju hidrauliÄkog ulja, te za skladiÅ”tenje energije predate hidrauliÄkom ulju, kao radnoj teÄnosti, od strane izvornih organa (hidrauliÄkih pumpi). Funkciju skladiÅ”tenja ulja obavljaju hidrauliÄki rezervoari, a hidrauliÄka energija se skladiÅ”ti pomoÄu uljno-hidrauliÄkih akumulatora. Simboli komponenata za održavanje radnih parametara hidrauliÄkog ulja u optimalnim granicama su takoÄe prikazani. ObuhvaÄene su komponente namenjene: preÄiÅ”Äavanju (uljno-hidrauliÄki filteri), grejanju (predgrejaÄi/grejaÄi) i hlaÄenju (uljno-hidrauliÄki hladnjaci)
HidrostatiÄki sistemi prenosa snage poljoprivrednih maÅ”ina: zapreminske pumpe
The paper presents and analyzes the hydrostatic transmission of power and motion. The most important elements of this group of systems and the possibilities of their application in agricultural technology are given. Particular attention is paid to the positive-displacement pumps that have the widest application in agricultural machinery: gear pumps with external and internal gears, vane pumps, piston-axial pumps with inclined swash plate and piston-axial pumps with inclined cylinder block. Two hydrostatic power transmission and control systems are also presented. The first is a very simple mechanical- hydraulic system of automatic leveling of self-propelled berry fruits harvester. In contrast, the other hydrostatic system is very sophisticated. It is implemented as a very complex combination of hydrostatic and mechanical power transmission subsystems, with the accompanying control digital electronic system, and is intended for the wheat harvester propulsion and steering.U radu je prikazan i analiziran hidrostatiÄki prenos snage i upravljanja. Navedeni su najvažniji elementi ove grupe sistema i moguÄnosti njihove primene u poljoprivrednoj tehnici. Posebno pažnja je posveÄena zapreminskim pumpama koje nalaze najÅ”iru primenu u poljoprivrednoj mehanizaciji: zupÄastim pumpama sa spoljaÅ”njim i unutraÅ”njim ozubljenjem, krilnim pumpama, klipno-aksijalnim pumpama sa nagnutom kliznom ploÄom i klipno-aksijalnim pumpama sa nagnutim cilindarskim blokom. Prikazana su dva hidrostatiÄka sistema prenosa snage i upravljanja. Prvi predstavlja veoma jednostavan mehaniÄko-hidrauliÄki sistem automatske nivelacije samohodnog beraÄa jagodastog voÄa. Drugi predstavljeni hidrostatiÄki sistem spada u najsavremenije sisteme koji se koriste u poljoprivrednoj mehanizaciji. Izveden je kao veoma složena kombinacija hidrostatiÄkog i mehaniÄkog prenosnika snage sa prateÄim upravljaÄkim digitalnim elektronskim sistemom, a namenjen je pogonu žitnog kombajna
HidrauliÄki simboli - deo IV: razvodni ventili
The mechanization of a wide variety of production processes and operations in modern primary agricultural production, transport, storage and the accompanying food processing industry can hardly be accomplished without automation. In most cases, production efficiency and environmental sustainability require, among other things, accurate control of the flow of energy within the installations, work machines, devices and mechanisms used. From the point of view of the theory of automatic control and regulation, the elements of the engaged technique: machines, devices and mechanisms represent the objects of control. The controlled routing and optimal delivery of energy to desired management facilities is, as a rule, very rarely uniform, as it must have correctlyaligned timing with the current variable requirements of the production or operation process, which often change quite unpredictably over the time.
The required amount of energy can be transferred to consumers in agriculture through the application of appropriate mechanical, electrical, pneumatic or hydraulic systems, as well as with their combinations.
All existing kinds of energy transmission systems have certain advantages and disadvantages, with a common requirement for appropriate controls. In the focus of interest of this paper are the graphic symbols of the directional control valves for hydraulic transmission and control, designated as hydraulic directional control valves, or shorter, the hydraulic distributors.Mehanizacija mnogobrojnih proizvodnih procesa i operacija u savremenoj primarnoj poljoprivrednoj proizvodnji, transportu, skladiÅ”tenju i prateÄoj prehrambenoj preraÄivaÄkoj industriji teÅ”ko se može ostvariti bez automatizacije. U najveÄem broju sluÄajeva, proizvodna efikasnost i ekoloÅ”ka održivost zahtevaju, izmeÄu ostalog, preciznu kontrolu toka energije u okviru primenjenih instalacija, radnih maÅ”ina, ureÄaja i mehanizmima. Sa glediÅ”ta teorije automatskog upravljanja, elementi angažovane tehnike, maÅ”ine, ureÄaji i mehanizmi, mogu predstavljati objekte upravljanja. Kontrolisano usmeravanje i optimalno dostavljanje odreÄene koliÄine energije željenim objektima upravljanja po pravilu je veoma retko uniformno, jer mora biti usklaÄeno sa vremenski nepredvidivim promenama zahteva proizvodnog procesa ili operacije. Potrebna energija može se preneti prema potroÅ”aÄima u poljoprivredi primenom odgovarajuÄih mehaniÄkih, elektriÄnih, pneumatskih ili hidrauliÄkih sistema, kao i njihovim sadejstvom. Svi postojeÄi tipovi sistema prenosa energije imaju izvesne prednosti i nedostatke, uz zajednicki zahtev za odgovarajuÄim upravljaÄkim elementima. U fokusu ovog rada su grafiÄki simboli upravljaÄkih ventila hidrauliÄkog prenosa energije (snage) i upravljaÄkih signala, oznaÄeni kao hidrauliÄki razvodni ventili, ili hidrauliÄki razvodnici
HidrauliÄki simboli - deo III: Ventili
Similar to human health, the importance of hydraulics sometimes becomes apparent only in her absence. Images and motives of agricultural workers from the past times and centuries can look attractive only on paintings of arts. In reality, it was a very hard and sometimes quite dangerous job.
The introduction of hydraulics in construction of modern farming machines, agriculture is less demanding for all farm workers, but also more efficient, which is of particular importance for providing enough food for the growing world during the 20-th century. Achieving high efficiency, reliability and long service life of these systems requires sophisticated diagnostics and failure repairment, regular maintenance and careful use of each hydraulic system, and this is only possible with a good knowledge of the functional principles of all elements, their connections and the whole system. However, modern hydraulic systems of agricultural machines are often very complicated, and the construction of their components is too complex for detailed graphic representation within the whole corresponding hydraulic installation. Therefore, instead of detailed representation of the components, schematic diagrams are used. This manuscript represents a logical continuation of the first and second parts of the paper, devoted to the general symbols, labels of measuring instruments and indicators (part one), as well as pumps and actuators (part two). The third) part of the paper presents the hydraulic symbols of the system control elements - hydraulic valves. The graphical symbols of these components are defined by ISO standards.SliÄno ljudskom zdravlju, znaÄaj hidraulike ponekad postaje vidljiv samo u njenom odsustvu. Slike i motivi radnika u poljoprivredi iz proÅ”lih vremena i vekova mogu izgledati privlaÄno samo na umetniÄkim slikama. U stvarnosti, to je bio veoma naporan i ponekad priliÄno opasan posao. UvoÄenje hidraulike u konstrukcije savremenih poljoprivrednih maÅ”ina za poljoprivrednu proizvodnju, uÄinilo je poljoprivredu fiziÄki manje zahtevnom za radnike, ali i efikasnijom, Å”to je od posebne važnosti za obezbeÄenje hrane rastuÄe svetske populacije tokom XX veka. Postizanje visoke efikasnosti, pouzdanosti i dugog radnog veka ovih sistema zahteva naprednu dijagnostika i otklanjanje kvarova, redovno održavanje i pažljivo koriÅ”Äenje svakog hidrauliÄkog sistema, a to je moguÄe samo uz dobro poznavanje funkcionalnih principa svih elemenata, njihovih veza i sistema u celini. MeÄutim, savremeni hidrauliÄki sistemi poljoprivrednih maÅ”ina Äesto su veoma komplikovani, a konstrukcija njihovih komponenata previÅ”e kompeksna za detaljno grafiÄko predstavljanje u sastavu pripadajuÄe hidrauliÄke instalacije. Zato, umesto detaljnog predstavljanja komponenata, koriste se odgovarajuÄi Å”ematski dijagrami. Ovaj tekst predstavlja logiÄan nastavak prvog i drugog dela rada, posveÄenih opÅ”tim simbolima, oznakama mernih instrumenata i indikatora (prvi deo), kao i pumpama i izvrÅ”nim elementima (drugi deo). TreÄi deo rada prikazuje hidrauliÄke simbole elemenata za upravljanje ā hidrauliÄke ventile. GrafiÄke simboliÄke oznake upravljaÄkih komponenata su definisane ISO standardima
Pristupi ispitivanju statiÄke stabilnosti traktora toÄkaÅ”a
The analysis of the factors that show decisive influence on the tractors stability and the possible overturning, should preventively indicate the possible improvements of the tractor construction, in order to increase the tractorās and operatorās safety. The purpose of this paper is to check the static angles of the longitudinal and lateral tractor stability, using the different methods that check the tractor stability up to the to the turnover limit. The process is based on the tractor longitudinal and lateral tilting and measurement of the reference values of the wheels heights with respect to the base. The same angles can be obtained by various analytical and numerical methoids methods based on the Theoretical mechanics. This paper suggests on the importance of empirical data, because they are the basis for further stability analysis of the tractors, other selfpropelled agricultural machines.Analiza faktora koji pokazuju odluÄujuÄe uticaje na stabilnost i moguÄa prevrtanja traktora treba preventivno da ukaže na podruÄja njihove efiksne i sigurne primene, kao i na glavne pravce poboljÅ”anja konstrukcije traktora radi poveÄanja bezbednosti traktora i rukovaoca. Cilj ovog rada predstavlja provera statiÄkih uglova podužne i popreÄne stabilnosti traktora, primenom razliÄitih pristupa, tako Å”to se isti dovodi do granice prevrtanja. Sam proces se zasniva na podužnom i boÄnom podizanju traktora, uz stalno merenje referentnih vrednosti kota oslonih taÄaka toÄkova u odnosu na podlogu. Isti uglovi se mogu proceniti i primenom analitiÄkih i numeriÄkih metoda, zasnovanih na principima teorijske mehanike. Rad ukazuje i na znaÄaj empirijskih podataka, jer su oni osnova za sve dalje analize stabilnosti traktora I drugih samohodnih poljoprivrednih maÅ”ina
Pregled lekovitih biljnih taksona razdela Magnoliophyta na lokalitetu KoŔutnjak
This work provides a description off collected herbal types that according to their taxonomy belong to the Magnoliophyta division on the locality of KoÅ”utnjak (Belgrade). It is determined a significant diverse flora of medicinal herbs. A biological material is collected in a herbarium and it is determined by the keys for plant identification. A treatment effect of medicinal herbs is based on pharmacological active components that mostly belong to a group of secondary metabolites.U ovom radu, dat je prikaz sakupljenih biljnih vrsta, koje taksonomski pripadaju razdelu Magnoliophyta, na lokalitetu KoÅ”utnjak (Beograd). PrimeÄen je znaÄajan diverzitet flore lekovitih biljaka. BioloÅ”ki materijal je herbarizovan i determinisan pomoÄu kljuÄeva za determinaciju biljaka. Terapijsko dejstvo lekovitog bilja, zasniva se na farmakoloÅ”ki aktivnim sastojcima, koji uglavnom pripadaju grupi sekundarnih metabolita
Brojnost i znaÄaj aktinomiceta u zemljiÅ”tu u fazi fizioloÅ”ke zrelosti zrna kukuruza (Zea mays L.)
In this work, it is determined the number of actinomycetes, a very diverse order of microorganisms, which take part in the transformation of the soil organic matter depending on the soil type, the quantity of applied N and the way of the soil treating. The stage of physiological corn kernel maturity shows the higher number of actinomycetes in "cernozem" under the sown maize as well as a stimulating effect of nitrogen.U ovom radu, odreÄena je brojnost aktinomiceta, veoma raznovrsne grupe mikroorganizama, koja uÄestvuje u transformaciji zemljiÅ”ne organske materije, u zavisnosti od tipa zemljiÅ”ta, koliÄine primenjenog azotnog (N) Äubriva i naÄina obrade zemljiÅ”ta. U fazi fizioloÅ”ke zrelosti zrna kukuruza, utvrÄena je veÄa brojnost aktinomiceta u Äernozemu, pod usevom kukuruza, kao i stimulativni efekat azota
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