Hydraulic symbols - part four: Directional control valves

Abstract

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, skladištenju i pratećoj prehrambenoj prerađivačkoj industriji teško se može ostvariti bez automatizacije. U najvećem broju slučajeva, proizvodna efikasnost i ekološka održivost zahtevaju, između ostalog, preciznu kontrolu toka energije u okviru primenjenih instalacija, radnih mašina, uređaja i mehanizmima. Sa gledišta teorije automatskog upravljanja, elementi angažovane tehnike, mašine, uređaji i mehanizmi, mogu predstavljati objekte upravljanja. Kontrolisano usmeravanje i optimalno dostavljanje određene količine energije željenim objektima upravljanja po pravilu je veoma retko uniformno, jer mora biti usklađeno sa vremenski nepredvidivim promenama zahteva proizvodnog procesa ili operacije. Potrebna energija može se preneti prema potrošačima u poljoprivredi primenom odgovarajućih mehaničkih, električnih, pneumatskih ili hidrauličkih sistema, kao i njihovim sadejstvom. Svi postojeći tipovi sistema prenosa energije imaju izvesne prednosti i nedostatke, uz zajednicki zahtev za odgovarajućim upravljačkim elementima. U fokusu ovog rada su grafički simboli upravljačkih ventila hidrauličkog prenosa energije (snage) i upravljačkih signala, označeni kao hidraulički razvodni ventili, ili hidraulički razvodnici.