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ABE 223 ABE Principles – Machine systems Cylinders Tony Grift

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Presentation on theme: "ABE 223 ABE Principles – Machine systems Cylinders Tony Grift"— Presentation transcript:

1 ABE 223 ABE Principles – Machine systems Cylinders Tony Grift
Dept. of Agricultural & Biological Engineering University of Illinois

2 Units, Pumps, Pressure Relief Valve Cylinders
Agenda Units, Pumps, Pressure Relief Valve Cylinders Double acting/ Single acting Single rod, Double rod Cylinder construction Pressure, Flow, Work and Power in cylinders Cylinder implementations

3 Hydraulic Units (SI) Pascal Newton Watt

4 Control can take place in various ways
Control can take place in various ways. Power is pressure times flow rate Pressure control Pressure relief valve Pressure reducing valve (regulator) Pressure compensation: Only provide the pressure needed to move the load(s). In idle reduce energy loss by providing a open center condition Pressure compensated pump. Make the pressure independent of the flow required to move the load at a preset speed. Deal with multiple cylinders that need to move simultaneously Flow control Throttle (needle valve, very crude, Orifice equation applies) Pressure compensated Flow Control Valve: Assure a preset flow rate independent of the pressure drop across the valve Pressure and Flow control Load sensing systems: combine pressure and flow control to reduce energy losses

5 Video 9: Hydraulic actuators (6:58)
Cylinders convert hydraulic energy into linear motion Motors generate rotary motion Single acting cylinder: One working port Can do work in only one direction (extension) External force retracts the cylinder No perfect seal, over time oil passes on to unpressurized side: need for drain Good for high load single lift (scissor platform) Return stroke through gravity or spring return Plunger (ram) cylinders: Cap end only, very powerful and stiff Double acting cylinder: Two working ports Pressure advances and retracts the cylinder: push and pull Cylinder retracts faster than it extends due to different areas of cap end and rod end side

6 Video 9: Hydraulic actuators (6:58) cont.
Example: ratio of cap and rod end side area is 2:1. Assume During extension rod end pressure =0 During retraction cap end pressure =0

7 Video 9: Hydraulic actuators (6:58) cont.
Example: ratio of cap and rod end side area is 2:1. Linear Power:

8 Hydraulic Cylinder

9 Cylinder construction

10 Tie rod ( keeps cylinder assembly together )
Rod end head ( mounting point ) Rod end port ( fluid entrance/exit point ) Piston seals ( dynamic, seals cap end from rod end pressure) Cap end head ( mounting point) Cap end port ( fluid entrance/exit point ) Rod bearing ( lateral support of the rod ) Rod wiper ( keeps dirt out ) Rod seal (dynamic, seals fluid from environment ) Barrel ( cylinder ) Piston rod ( mechanical force output ) Piston ( pressure to force converter ) Static seal ( seals fluid from environment )

11 Cylinders are perfect for linear motion
Single rod (most common) Dual rod (power steering)

12 Telescopic cylinder

13 Basic Circuit with Double Acting Cylinder
Pressure gage Actuator Overload Protection Electric Motor Reservoir Pump

14 Question: Can the cylinder be moved ?
Double acting, differential area Fluid is incompressible Rod and cap end connected Check in FluidSim

15 Hydraulic Work (rod end pressure = 0)

16 Differential area cylinder: Flow and displacement

17 Differential area cylinder: Force equilibrium

18 Differential area cylinder: Work

19 Differential area cylinder: Power

20 Dual rod cylinder: Power

21 Power if (as in motors and pumps)

22 Question: Will the cylinder extend ?
Check in FluidSim

23 Video 5: Pressure transmission (0:53)
Pressure intensification in hydraulic systems: Differential area cylinders cause this effect Max pressure in the system is NOT PRV setting ! Check in FluidSim

24 Question in ‘Customary Units’
Given PRV Setting 15 MPa pump displacement of cm3/rev the speed of the pump is 1800 rpm Required Torque needed to drive the pump Power needed to drive the pump Neglect friction

25 Answer in ‘Customary Units’

26 Question in ‘Customary Units’
Given PRV Setting pump displacement of the speed of the pump Required Torque needed to drive the pump Power needed to drive the pump . Neglect friction

27 Answer in SI Units

28 ABE 223 ABE Principles – Machine systems Cylinders The End Tony Grift
Dept. of Agricultural & Biological Engineering University of Illinois


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