Tham khảo tài liệu 'mechanical devices sourcebook 3rd ed [mcgraw-hil 2001] episode 11', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | __CHAPTER 11 PNEUMATIC AND hydraulic machine AND mechanism Control DESIGNS AND OPERATING PRINCIPLES OF TYPICAL PUMPS These pumps are used to transfer liquids and supply hydraulic power. 1. WITH BUT TWO MOVING PARTS the rotors that turn in the same direction this rotary pump has reduced friction to a minimum. The rotors rotate against flexible synthetic rubber cushions that allow sand grit and other abrasives to flow freely through the pump without damage. It is a positive displacement pump that develops a constant pressure and will deliver a uniform flow at any given speed. The pump is reversible and can be driven by a gasoline engine or electric motor. The rubber cushions withstand the action of oil kerosene and gasoline and the pump operates at any angle. It has been used in circulating water systems cutting tool coolant oil systems and general applications. 2. PUMPING ACTION is produced by the meshing of the idler and rotor teeth in this rotary pump. The idler is pinmounted to the head and the rotor operates in either direction. This pump will not splash foam churn or cause pounding. Liquids of any viscosity that do not contain grit can be transferred by this pump which is made of iron and bronze. 3. BASED on the swinging vane principle this pump maintains its volumetric efficiency automatically. The action of the buckets fitted loosely into recesses in the rotor compensates for wear. In operation the tip of the bucket is in light contact with the casing wall. Liquids are moved by sucking and pushing actions and are not churned or foamed. 4. HIGH-PRESSURE high-volume pumps of the axial piston constant displacement type are rated at 3 500 psi for continuous duty operation higher pressure is permissible for intermittent operation. A pressure-balanced piston shoe lubricates the cam plate and prevents direct contact between the shoe and cam plate. The use of the pressure balanced system removes the need for thrust bearings. The two-piece shaft absorbs .
