BUDA UNIVERSITY Use inside only Dr Ferenc Szlivka

ÓBUDA UNIVERSITY Use inside only! Dr. Ferenc Szlivka

Hydraulic actuators: cylinders Cylinder types: Single acting: work can be done only in one direction Plunger Double acting piston: Work is done in both directions Piston rod on both sides Piston Tandem Telescopic 2005/2006 I. Fast moving Telescopic Fast moving 2

Overview • • • Types of Cylinders Construction and Operation Cylinder Ratings Formulas for Application Cylinder Features Installation and Trouble Shooting

Types of Cylinders • • • Ram Single Acting Telescopic Spring Return Double Acting 4

Ram Cylinders • The simplest single acting cylinder • One fluid chamber • Exerts force in only one direction • Mounted mostly vertically • The cylinder retracts by the force of the load due to gravity

Ram Cylinders • Ram cylinders are most commonly used in elevators, jacks, and automobile hoists. • Can also be used on a scissors lift like the on the loading dock of KL.

Single Acting Cylinders • Acts much like a ram cylinder • Main difference is that the single acting cylinder uses a piston. The leakage flow that goes past the piston is ported the tank.

Single Acting Plunger Cylinders The single-acting cylinders are used where the hydraulic work requires only one direction of motion. Examples Raising of workpieces, pressure, lowering, hydraulic lifts, scissor lift tables, stage platform lifts. 8

Spring Return Cylinders • Considered a single acting cylinder • Pressure applied to the cap end pushes the spring down as the rod is extending • When the pressure is removed the spring force allows the cylinder to retract • The drain is in the spring chamber and allows the leakage flow past the piston seal

Telescopic Cylinders • Mostly a single acting cylinder • Series of rod segments called sleeves, most common to only have 2 or 5 sleeves in each cylinder • The sleeves work together to provide a longer stroke • The maximum force is at the collapsed position • The speed will increase at each stage, but will not allow as much force.

Telescopic Cylinders • Most commonly seen in high reach Fork Lifts

Double Acting Cylinders Types • Basic double acting (differential cylinder) • Double rod cylinder (nondifferential cylinder) • Tandem cylinder

Double Acting Cylinders • Most common type of cylinder • Pressure is applied to both rod end and cap end • The majority of the cylinders are basic. This means that there is unequal areas at either end.

Double Acting Cylinders The double acting cylinder with piston surface can act on both sides of the working fluid. It is therefore possible to work in two ways. 14

Different types Double Acting Cylinders Differential cylinder Surface Ratio 2: 1 Double Acting Cylinders Double Rod Cylinder Cushioning of the end position Telescopic cylinders Pressure transformation Tandem cylinders 15

Double Acting Cylinders • Rod extension is slower because has a larger area, but allows a greater force because of the bigger area. • Retract is faster because of the smaller area, but the force allowed is smaller because of the smaller area.

Basic Double Acting Cylinder

Double Acting Cylinders Double Rod Cylinder • Nondifferential type cylinder • Same areas at both ends of the cylinder if the rods are the same size • Provides equal force, and equal speed in both directions

Double Acting Cylinders Tandem Cylinder • Two pistons in line with a common rod • This allows you to have a greater forces without increasing the size of the cylinder bore • Tandem cylinders are used in places where there is insufficient space to increase the size of the cylinder bore.

Cylinder Construction 2005/2006 I. Hydraulic and Pneumatic Systems 20

Cylinder Construction 21

Cylinder Construction

Cylinder Actuation • Fluid routed to and from cylinder through ports in each of the heads • Cylinder retracts from pressure to rod end port and the other port connected to tank • Cylinder extends from pressure to cap end port and rod end port connected to tank

Cylinder Mounting • Main function to anchor the cylinder • Mounting methods include tie rod, bolt mount, flange, trunnion, side lug and side tapped, and clevis • Tie rod is most common

Cylinder Mounting

Cylinder Mounting

Cylinder Ratings • Ratings include size specifications and pressure capability • Size specifications - piston diameter (bore) - rod diameter - stroke length • Pressure capability - pressure rating established by manufacturer - rating limits maximum force capability

Effects of Cylinder Performance for Changes of Flow, Size, and Pressure

Data for Different Cylinder Sizes 32 28 25 20 14 40 36 32 25 18 50 45 40 32 22 63 56 50 40 28 80 70 63 50 36 90 70 56 40 100 80 63 45 110 86 70 50 125 100 80 55 140 110 90 63 160 125 100 70 200 160 125 90 the piston diameter φ piston ring rate The strokes are free to choose the preferred dimensions: 20; 25; 40; 50; 63; 80; 100; 125; 160; 200; 250; 320; 400; 500; 630; 800; 1000; 1100; 1250; 1400; 1600; 2000; 2500; 2800; 3000; 3550; 4000 mm

Data for Different Cylinder Sizes

Cylinder Features • Basic size and pressure ratings are not the only things that define a cylinder • Features such as: - seals - cushions - stop tubes - rod spacers - ports - bleed ports -limit switches

Seals • • Cast iron is most common piston seal Long service life is most important characteristic Rubber-like materials are the most common rod seal Rod wiper or scraper keeps foreign material from entering the cylinder and the hydraulic system

Cylinder Cushions • Used to slow down the piston at the end of its stroke • Basic elements include the plunger, adjustable cushion orifice, and a check valve

Cylinder Cushions Double-acting cylinder end position braking adjustable cushion orifice damper Check valve 34

Cylinder Cushions Löketvégi csillapítás If the double-acting cylinder piston end position and operate the high-speed moving mass, it is necessary to use the end position brake design. Otherwise, the kinetic energy of the moving mass significant structural elements involved in collision deformation in the work of pines, which is undesirable. The end position braking many design variants are known. Their common feature is that the brake fluid escaping from the cylinder throttling, or pretension of created (Figure 41). The pre-loading valve ("A"), the brake pressure is constant along the stopping distance. The variant "B“ the stopping distance along the throttling cross section decreasing. Dynamic aspect of this favorable solution, but one drawback is that the throttling cross section can not be changed, so that a given task is difficult to insert. 35

Cylinder Cushions Double-acting cylinder end position braking In the case of variable throttle conditions: The change in kinetic energy is equal to the brake work: Where v 0 - the reduced mass, the velocity before braking. v(x) - the current velocity where vfo - the velocity of the oil throttling cross section -the throttling loss factor 36

Cylinder Cushions Double-acting cylinder end position braking Both sides of the equation direved with respect to x Using the continuity 37

Cylinder Cushions Double-acting cylinder end position braking The variables are separated Let us introduce the 38

Cylinder Cushions Double-acting cylinder end position braking integrated The initial condition 39

Cylinder Cushions Double-acting cylinder end position braking The bigger pressure, deceleration and braking are at the start of braking: 40

Stop Tubes • • Metal collar that fits over piston rod next to piston Used primarily on long stroke cylinders Provides better cylinder rod support Majority of applications do not require a stop tube

Tie Rod Spacers • Tie rod spacers and center supports improve rigidity of long stroke tie rod cylinders • Spacer keeps proper position and prevents excessive deflection • Tie rod center support has side mounting lugs and serves as additional mounting location

Ports • Internal or external opening in a cylinder or a valve • Designed to allow the passing of fluid into or out of the component • Wide variety of port type configurations • Straight thread O-ring fittings are highly recommended for leak-free connections • Poor installation of tubing or hose to port causes leakage

Bleed Ports • Usually cylinders bleed air when ports are vertical on top • Bleed ports are necessary to remove trapped air when the ports are installed on the bottom of the cylinder • Desirable on high speed, high performance, heavy load applications

Limit Switches • Signal rod position to a control circuit or a safety circuit to limit end of travel • Common types -mechanical = mechanical actuation of electrical switch when switch is activated by lead angle on a hardened cylinder cushion - proximity = activated when metal cushion passes close to magnetic pickup of the switch * becoming increasingly popular due to simplicity

Cylinder Installation and Troubleshooting • Cylinder application design » hydraulic engineers • Installation » hydraulic technician • Proper installation and maintenance is crucial to all components to achieve max efficiency • Recognizing and controlling potential problems is purpose of troubleshooting

Types of connection and notes on installation In addition to needed to know the operating pressure , piston and rod diameters, strake length and pulling or pressing forces. it is necessary to know where the cylinder is to be installed. i. e. what type of mounting it requires A number of mountig possibilities for cylinders are shown in fables 1 and 2. Dr. Szlivka Ferenc: Pneumatika 4, Munkahengerek 47

Types of connection and notes on installation In addition to needed to know the operating pressure , piston and rod diameters, strake length and pulling or pressing forces. it is necessary to know where the cylinder is to be installed. i. e. what type of mounting it requires A number of mountig possibilities for cylinders are shown in fables 1 and 2. 48

Types of connection and notes on installation When installing hydraulic cylinders various criteria with respect to the type of mounting must be taken into account. Six of the most commonly used types of Mounting with their installation notes are shown in table 3. 49

Types of connection and notes on installation When installing hydraulic cylinders various criteria with respect to the type of mounting must be taken into account. Six of the most commonly used types of Moonting with their installation notes are shown in tab!e 3. 50

Connection modes The piston rod end load and connect in various ways done 51

Installation example: Lift table (single-acting cylinder) A lift table is moved by a hydraulic cylinder. You need to install a single-acting cylinder (see figure) Described in the table lift for lifting a single acting cylinders are installed. The cylinder can be controlled by a 2/2 or a 3/2 -way valve. To calculate the required output stroke of the cylinder pressure and the load pressure of the hydraulic system resistances (pressure drops) should be considered. The present case, the resistances are negligible, so only necessary to calculate the load pressure. The calculation is done using the following formula: 52

Installation example: Lift table Here, the force F acting on the roller load in the effective piston area A. The hydraulic cylinder load "F" force can be calculated by the specified load and the geometric structure of the data. Mechanical task. "A" is the effective piston area, selecting the appropriate brochure piston. , Assuming a maximum oil pressure. Example development (schematic drawing: 53

Installation example: Lift table After the power supply there is check valve built-in, to protect the pump against possible oil pressure under reflux. (Hydraulic motor operation is not permitted. ) After the power supply built-in adjustable pressure relife valve protects the cylinder against overload. . 54

Installation example: roof tank (double-acting cylinder) Tank must be opened and closed as shown in the figure. The right cover to move a double-acting cylinder is used. The cylinder provides a cover lifting movement. The cylinder valve is controlled 4/2 -way valve. 55

Installation example: roof tank (double-acting cylinder) A double-acting lifting cylinder is applied for the tank. The double acting cylinder has two oil connections one is at the piston the other is on the piston rod side. Thus, the direction of movement reversed. The piston back and forth in controlled by a 4/2 -way valve. A pump delivers the liquid to the cylinder. Need to know to calculate theoretical flow rate of the pump per rotation of the working volume (V) and motor speed (n). Need to know the volume flow rate for the motion. The relevant context: Substituted for the v velocity v = s / t. A surface must be considered that the piston and the piston ring surface is different. Thus, the output piston area, way back when the effective surface area of the ring. 56

Installation example: roof tank (double-acting cylinder) Piston surface ring surface. Outstroke to backstroke opening closing The cylinder outstroke of a higher force, to the backstroke at higher speeds can be achieved. Assuming that Q is constant. 57

Installation example: roof tank (double-acting cylinder) Accordance with the requirements of the task at rest in a definite position of the equipment necessary for the working element, this can be realized by a springreturn valve. All valves are used for the solution spring return. The 4/2 - valve with spring return was used, as this will ensure that the hydraulic power supply is turned on unauthorized cylinder remains in the desired position. It is important to pump flow rate and calculating the return on and velocity, because · In the pipes, the flow velocities (up to approx. 5 m / s) and · The maximum piston speed (up to approx. 12 m / min) not to be exceeded. 58

Installation example: roof tank (double-acting cylinder) We should calculate the diameter of the piston, rod of the cylinder to the district speed. The electric motor speed 1450/min. The supplied force (opening) F = 5000 N, and the maximum system pressure of 40 bar. The piston area - piston ring ratio of 1. 6: 1 The cylinder diameter is calculated (open state): The above table shows (slide 29) the cylinder with a standard diameter. 59

Data for Different Cylinder Sizes 32 28 25 20 14 40 36 32 25 18 50 45 40 32 22 63 56 50 40 28 80 70 63 50 36 90 70 56 40 100 80 63 45 110 86 70 50 125 100 80 55 140 110 90 63 160 125 100 70 200 160 125 90 the piston diameter φ piston ring rate The strokes are free to choose the preferred dimensions: 20; 25; 40; 50; 63; 80; 100; 125; 160; 200; 250; 320; 400; 500; 630; 800; 1000; 1100; 1250; 1400; 1600; 2000; 2500; 2800; 3000; 3550; 4000 mm

Installation example: roof tank (double-acting cylinder) The maximum piston velocity, calculate the flow rate Q: The way back (closing occurs at higher speeds (v 2), which should be no more than 20 m / min. The A 2 interface specified 1. 6: 1 ratio, can be calculated. A 1, we know. The above table shows the piston rod diameter of 32 mm. 61

Installation example: roof tank (double-acting cylinder) Pump working volume, V per one revolution Need to select a pump that delivers less in one revolution. If the for the roof open and closing do not need high speed, a much smaller capacity pump is sufficient, for example: 2 -3 cm 3/ford. 62

Installation example: roof tank (double-acting cylinder) After the power supply unite there is an adjustable pressure relife valve which protects the cylinder against overload.

Properties: The cylinders have to be good quality steel with close tolerances. There have to be good sealing both at the piston rod and at the cylinder. With time dirt may come in and damage the surfaces. This has to be possibly reduced. In this case, the leakage will increase all the time.

Sizing cylinder for pressure load inertial forces maximum load Outward: friction forces slow motion, can be often neglected A 2 A 1 p 2 Backward: p 1 Q v. B v 0

Sizing cylinder for pressure load Resize the cylinder!

Sizing cylinder for pressure load

Sizing cylinder for pressure load Speed and direction of movement to be carried out during the session: Movement velocities [mm/s] H+ H- Quick V 11=80 Slow V 12=20 Work V 13=5 Back V 21=100

Sizing cylinder for pressure load

Sizing cylinder for pressure load The cylinder connection

Sizing cylinder for pressure load

Calculation of a telescopic cylinder Determine the pressure of each telescopes! Calculate the speed of each telescopes, if the flow rate is constant 60 dm 3/min!

Checking for buckling Leonhard Euler in 1757 determined the size of the critical breaking force for the case when the compressive stress caused by the breaking strength of the case is less than the yield stress of the material stick, in other words, if elastic buckling is taking place. In this case, the elastic fiber can be written as differential equations: where the x axis is taken up in the rod axis, the origin of the rod is hinged at the end point (which will probably hinge moment can not wake up), and the y axis is perpendicular to M of the rod load an arbitrary point bending moment, I is the rod cross-section of minimum moment of inertia, E is the modulus of elasticity of the bar material. The bending moment M equal the produckt of the breaking force Ft and the y. Dr. Szlivka Ferenc: Pneumatika 4, Munkahengerek 73

Checking for buckling Finally, if we introduce the nomination, the differential equation of this form will be: This equation has the general solution: wherein A and B depends on the boundary conditions. As the rod length l at both ends hinged clamping, The latter is not trivial from solutions practically interesting case where. Substituting the values obtained value of the critical breaking force: 74

Checking for buckling value of the critical breaking force : If the hinge has not depressed the rod end of the differential equation will be the same, only the boundary conditions will be different and they affect the size of the breaking strength. Cases in the figure below can be summarized in the following equation: where μ depending on the type of capture factor is shown. Two ends One end free pivoted and One end fixed guided Or trunnion at end One end guided and pivoted, other end fixed Two ends fixed and guided 75

Checking for buckling Euler’s cases 1. Case 2. Case 3. Case 4. Case One end free One end fixed Or trunnion at end Two ends pivoted and guided One end guided and pivoted, other end fixed Two ends fixed and guided Picture Free buckling length Manner of end fixing mounting style Note 2005/2006 I. Hydraulic and Pneumatic Systems 76

Checking for buckling Critical force Safety factor Young modulus Free buckling length The cylinder rod second order torque 77

Checking for buckling 78

Checking for buckling of a telescopic cylinder Three cylinder jack is the force. Data of the cylinders: Questions: a. / How big is the pressure for lifting the F? b. / Check for buckling the jack ? Solution: a. / The smallest cylinder should lift the load force, so the equation of equilibrium: We can get the maximum pressure: 79

Checking for buckling of a telescopic cylinder We should choose from the cases in the figure below can be summarized in the following equation: The third case is ours One end guided and pivoted, other end fixed We calculate with bigger safe if we select the minimum diameter for the whole length. We can calculate with a safety factor ”n”, in usually 3 -5 is the magnitude. The piston rod is made of steel the Young modulus E The cylinder rod second order torque 80

Checking for buckling of a telescopic cylinder The breaking force is two orders of magnitude greater than the loading force, so the cylinder is proper. 81

03 Hydraulics problem Data: The efficiency of the pump A hydraulic system drives a cylinder and a motor. The hydraulic pump has a control, which, makes a pressure drop Δp = 16 bar. We ignore the drop in the pipes now. Determine the pump needed ' P ' power, as well as the efficiency of the whole system.

03 Hydraulics problem Calculate first the cylinder volume flow ! Then theoretical volume flow rate for the hydro motor The real volume flow rate of hydro motor: All of the volume flow rate:

03 Hydraulics problem Calculate the pressure of the cylinder Calculate the pressure drop in the hydro motor, we know that The pump pressure rise

03 Hydraulics problem The necessary total power for the hydraulic pump can be calculated by the total effscience of the pump: To calculate the whole system total efficiency we should calculate first the useful power The whole system total efficiency

04 Hydraulics problem Determine the pressure as a function of the way for the telescopic cylinder along the motion! Determine the power to drive the pump during the motion of cylinder! Calculate the working piston surfaces:

04 Hydraulics problem Calculate the pressure of each cylinder part! The pump pressure

04 Hydraulics problem Calculate the necessary volume flow rate for each section! Számítsuk ki a teljesítményeket: