Fluid power, Hydraulic & penumatic

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Fluid power, Hydraulic & penumatic

  1. 1. Chapter 9 Actuators Workhorses of the System
  2. 2. Objectives Describe the construction and operation of basic hydraulic cylinders, limited-rotation actuators, and motors. Compare the design and operation of various types of hydraulic cylinders. Select appropriate cylinder design options available for mounting hydraulic cylinders and reducing hydraulic shock. Compare the design and operation of various types of hydraulic motors.© Goodheart-Willcox Co., Inc. 3 Permission granted to reproduce for educational use only.
  3. 3. Objectives Contrast the operation of fixed- and variable- speed hydraulic motors. Describe the construction and operation of a basic hydrostatic transmission. Size hydraulic cylinders and motors to correctly meet system force and speed requirements. Interpret manufacturer specifications for hydraulic cylinders.© Goodheart-Willcox Co., Inc. 4 Permission granted to reproduce for educational use only.
  4. 4. Hydraulic Cylinders Actuators are the components used in a hydraulic system to provide power to a required work location Cylinders are the hydraulic system components that convert fluid pressure and flow into linear mechanical force and movement© Goodheart-Willcox Co., Inc. 5 Permission granted to reproduce for educational use only.
  5. 5. Hydraulic Cylinders A basic cylinder consists of: – Piston – Piston rod – Barrel© Goodheart-Willcox Co., Inc. 6 Permission granted to reproduce for educational use only.
  6. 6. Hydraulic Cylinders Parts of a typical cylinder© Goodheart-Willcox Co., Inc. 7 Permission granted to reproduce for educational use only.
  7. 7. Hydraulic Cylinders The piston forms sealed, variable-volume chambers in the cylinder System fluid forced into the chambers drives the piston and rod assembly Linear movement is produced© Goodheart-Willcox Co., Inc. 8 Permission granted to reproduce for educational use only.
  8. 8. Hydraulic Cylinders Seals prevent leakage between: – Piston and cylinder barrel – Piston rod and head – Barrel and its endpieces Wiper seal, or scraper, prevents dirt and water from entering the cylinder during rod retraction© Goodheart-Willcox Co., Inc. 9 Permission granted to reproduce for educational use only.
  9. 9. Hydraulic Cylinders Various seals are used in a cylinder© Goodheart-Willcox Co., Inc. 10 Permission granted to reproduce for educational use only.
  10. 10. Hydraulic Cylinders Rod wipers prevent contamination from entering on rod retraction IMI Norgren, Inc.© Goodheart-Willcox Co., Inc. 11 Permission granted to reproduce for educational use only.
  11. 11. Hydraulic Cylinders Cylinders are typically classified by operating principle or by construction type – Single-acting or double-acting – Tie rod, mill, threaded end, or one piece© Goodheart-Willcox Co., Inc. 12 Permission granted to reproduce for educational use only.
  12. 12. Hydraulic Cylinders Single- and double-acting cylinders Single-acting Double-acting© Goodheart-Willcox Co., Inc. 13 Permission granted to reproduce for educational use only.
  13. 13. Hydraulic Cylinders Single-acting cylinders exert force either on extension or retraction They require an outside force to complete the second motion© Goodheart-Willcox Co., Inc. 14 Permission granted to reproduce for educational use only.
  14. 14. Hydraulic Cylinders Double-acting cylinders generate force during both extension and retraction – Directional control valve alternately directs fluid to opposite sides of the piston – Force output varies between extension and retraction© Goodheart-Willcox Co., Inc. 15 Permission granted to reproduce for educational use only.
  15. 15. Hydraulic Cylinders Effective piston area is reduced on retraction due to the rod cross section© Goodheart-Willcox Co., Inc. 16 Permission granted to reproduce for educational use only.
  16. 16. Hydraulic Cylinders Volume is reduced on retraction© Goodheart-Willcox Co., Inc. 17 Permission granted to reproduce for educational use only.
  17. 17. Hydraulic Cylinders External tie rod bolts are used to secure the ends on the tie-rod cylinder design – Commonly found on heavy industrial machines – External tie rods increase chance of damage and promote accumulation of dirt© Goodheart-Willcox Co., Inc. 18 Permission granted to reproduce for educational use only.
  18. 18. Hydraulic Cylinders Tie-rod cylinder© Goodheart-Willcox Co., Inc. 19 Permission granted to reproduce for educational use only.
  19. 19. Hydraulic Cylinders Mill cylinders Yates Industries, Inc.© Goodheart-Willcox Co., Inc. 20 Permission granted to reproduce for educational use only.
  20. 20. Hydraulic Cylinders Threaded-end cylinder Bailey International Corporation© Goodheart-Willcox Co., Inc. 21 Permission granted to reproduce for educational use only.
  21. 21. Hydraulic Cylinders One-piece cylinder has the cylinder barrel welded to the ends Produces a compact actuator – Cost effective to manufacture – Cannot be serviced (throwaway)© Goodheart-Willcox Co., Inc. 22 Permission granted to reproduce for educational use only.
  22. 22. Hydraulic Cylinders Hydraulic ram is commonly used in hand- operated jacks – Rod is basically the same diameter as the inside of the cylinder barrel – Large-diameter rod is more rigid under load, but cylinder can generate force in only one direction© Goodheart-Willcox Co., Inc. 23 Permission granted to reproduce for educational use only.
  23. 23. Hydraulic Cylinders Typical hand-operated jack © Goodheart-Willcox Co., Inc. 24 Permission granted to reproduce for educational use only.
  24. 24. Hydraulic Cylinders Telescoping cylinders are available for applications requiring long extension distances – Rod is made up of several tubes of varying size nested inside of the barrel – Each tube extends, producing a rod longer than the cylinder barrel – Typical example is the actuator that raises the box on a dump truck© Goodheart-Willcox Co., Inc. 25 Permission granted to reproduce for educational use only.
  25. 25. Hydraulic Cylinders Telescoping cylinders Star Hydraulics, Inc.© Goodheart-Willcox Co., Inc. 26 Permission granted to reproduce for educational use only.
  26. 26. Hydraulic Cylinders Cylinders often use hydraulic cushions – Provide a controlled approach to the end of the stroke – Reduces the shock of the impact as the piston contacts the cylinder head© Goodheart-Willcox Co., Inc. 27 Permission granted to reproduce for educational use only.
  27. 27. Hydraulic Cylinders Cylinder cushioning device© Goodheart-Willcox Co., Inc. 28 Permission granted to reproduce for educational use only.
  28. 28. Hydraulic Cylinders A variety of mounting configurations are used to attach the cylinder body and rod end to machinery – Fixed centerline – Fixed noncenterline – Pivoting centerline – Expected cylinder loading is the major factor in the selection of the mounting style© Goodheart-Willcox Co., Inc. 29 Permission granted to reproduce for educational use only.
  29. 29. Hydraulic Cylinders Head-end flange mount© Goodheart-Willcox Co., Inc. 30 Permission granted to reproduce for educational use only.
  30. 30. Hydraulic Cylinders Fixed-noncenterline mount© Goodheart-Willcox Co., Inc. 31 Permission granted to reproduce for educational use only.
  31. 31. Hydraulic Cylinders Pivoting-centerline, clevis mount© Goodheart-Willcox Co., Inc. 32 Permission granted to reproduce for educational use only.
  32. 32. Hydraulic Cylinders Pivoting-centerline, trunnion mount© Goodheart-Willcox Co., Inc. 33 Permission granted to reproduce for educational use only.
  33. 33. Hydraulic Cylinders The force generated by a cylinder is calculated by multiplying the effective area of the piston by the system pressure© Goodheart-Willcox Co., Inc. 34 Permission granted to reproduce for educational use only.
  34. 34. Hydraulic Cylinders Effective cylinder piston area© Goodheart-Willcox Co., Inc. 35 Permission granted to reproduce for educational use only.
  35. 35. Hydraulic Cylinders Force generated during the extension of a double-acting cylinder with a single-ended rod is calculated as: Ef = Sp × Pa where: Ef = extension force Sp = system pressure Pa = piston area (Calculations require consistent units of measure in these formulas)© Goodheart-Willcox Co., Inc. 36 Permission granted to reproduce for educational use only.
  36. 36. Hydraulic Cylinders Force generated during the retraction of a double-acting cylinder with a single-ended rod is calculated as: Rf = Sp × (Pa – Ra) where: Rf = retraction force Sp = system pressure Pa = piston area Ra = rod area© Goodheart-Willcox Co., Inc. 37 Permission granted to reproduce for educational use only.
  37. 37. Hydraulic Cylinders Speed at which the cylinder extends or retracts is determined by: – Physical volume per inch of cylinder piston travel – Amount of fluid entering the cylinder Effective area of the piston is used to calculate the volume of the cylinder per inch of piston travel© Goodheart-Willcox Co., Inc. 38 Permission granted to reproduce for educational use only.
  38. 38. Hydraulic Cylinders Extension speed of a double-acting cylinder with a single-ended rod is calculated as: Es = Fr × (Cg ÷ Pa) where: Es = extension speed Fr = flow delivery rate Cg = cubic inches in one gallon Pa = piston area© Goodheart-Willcox Co., Inc. 39 Permission granted to reproduce for educational use only.
  39. 39. Hydraulic Cylinders Calculate retraction speed of a double-acting cylinder with single-ended rod as: Rs = Fr × [Cg ÷ (Pa – Ra)] where: Rs = retraction speed Fr = flow delivery rate Cg = cubic inches in one gallon Pa = piston area Ra = rod area© Goodheart-Willcox Co., Inc. 40 Permission granted to reproduce for educational use only.
  40. 40. Hydraulic Cylinders Flow rate to produce a desired extension or retraction speed is calculated as: Fr = (Ea × Cs) ÷ Cg where: Fr = system flow rate Ea = effective piston area Cs = cylinder speed Cg = cubic inches in one gallon© Goodheart-Willcox Co., Inc. 41 Permission granted to reproduce for educational use only.
  41. 41. Hydraulic Cylinders Hydraulic cylinder manufacturers provide detailed specifications concerning: – Construction – Physical size – Load capacity© Goodheart-Willcox Co., Inc. 42 Permission granted to reproduce for educational use only.
  42. 42. Hydraulic Cylinders This information includes basic factors such as: – Bore – Stroke – Pressure rating – Other details, such as service rating, rod end configurations, and dimensions© Goodheart-Willcox Co., Inc. 43 Permission granted to reproduce for educational use only.
  43. 43. Hydraulic Cylinders Typical manufacturer’s catalog page Bailey International Corporation© Goodheart-Willcox Co., Inc. 44 Permission granted to reproduce for educational use only.
  44. 44. Limited-Rotation Hydraulic Actuators Limited-rotation devices are actuators with an output shaft that typically applies torque through approximately 360° of rotation Models are available that are limited to less than one revolution, while others may produce several revolutions© Goodheart-Willcox Co., Inc. 45 Permission granted to reproduce for educational use only.
  45. 45. Limited-Rotation Hydraulic Actuators Most common designs of limited-rotation actuators are: – Rack-and-pinion – Vane – Helical piston and rod© Goodheart-Willcox Co., Inc. 46 Permission granted to reproduce for educational use only.
  46. 46. Limited-Rotation Hydraulic Actuators  Rack-and-pinion limited rotation actuator IMI Norgren, Inc.© Goodheart-Willcox Co., Inc. 47 Permission granted to reproduce for educational use only.
  47. 47. Limited-Rotation Hydraulic Actuators Vane limited-rotation actuator© Goodheart-Willcox Co., Inc. 48 Permission granted to reproduce for educational use only.
  48. 48. Limited-Rotation Hydraulic Actuators Helical piston and rod limited-rotation actuator© Goodheart-Willcox Co., Inc. 49 Permission granted to reproduce for educational use only.
  49. 49. Limited-Rotation Hydraulic Actuators Limited-rotation actuators are used to perform a number of functions in a variety of industrial situations – Indexing devices on machine tools – Clamping of workpieces – Operation of large valves© Goodheart-Willcox Co., Inc. 50 Permission granted to reproduce for educational use only.
  50. 50. Limited-Rotation Hydraulic Actuators Limited-rotation actuators are used in this robotic arm IMI Norgren, Inc.© Goodheart-Willcox Co., Inc. 51 Permission granted to reproduce for educational use only.
  51. 51. Hydraulic Motors Hydraulic motors are called rotary actuators They convert fluid pressure and flow into torque and rotational movement© Goodheart-Willcox Co., Inc. 52 Permission granted to reproduce for educational use only.
  52. 52. Hydraulic Motors Typical hydraulic motor application© Goodheart-Willcox Co., Inc. 53 Permission granted to reproduce for educational use only.
  53. 53. Hydraulic Motors All basic hydraulic motors consist of three component groups: – Housing – Rotating internal parts – Power output shaft© Goodheart-Willcox Co., Inc. 54 Permission granted to reproduce for educational use only.
  54. 54. Hydraulic Motors Parts of a typical hydraulic motor© Goodheart-Willcox Co., Inc. 55 Permission granted to reproduce for educational use only.
  55. 55. Hydraulic Motors System fluid enters the housing and applies pressure to the rotating internal parts This, in turn, moves the power output shaft and applies torque to rotate a load© Goodheart-Willcox Co., Inc. 56 Permission granted to reproduce for educational use only.
  56. 56. Hydraulic Motors Primary parts that produce the rotating motion in most hydraulic motors are either: – Gears – Vanes – Pistons© Goodheart-Willcox Co., Inc. 57 Permission granted to reproduce for educational use only.
  57. 57. Hydraulic Motors Four requirements of a motor© Goodheart-Willcox Co., Inc. 58 Permission granted to reproduce for educational use only.
  58. 58. Hydraulic Motors Displacement of a hydraulic motor indicates the volume of fluid needed to turn the output shaft one revolution – Fixed displacement – Variable displacement© Goodheart-Willcox Co., Inc. 59 Permission granted to reproduce for educational use only.
  59. 59. Hydraulic Motors In a fixed-displacement motor: – Internal geometry cannot be changed – Same volume needed per output shaft revolution© Goodheart-Willcox Co., Inc. 60 Permission granted to reproduce for educational use only.
  60. 60. Hydraulic Motors In a variable-displacement motor: – Internal geometry can be changed – Displacement per shaft revolution can be adjusted – Motor can operate at variable speeds with a constant input flow© Goodheart-Willcox Co., Inc. 61 Permission granted to reproduce for educational use only.
  61. 61. Hydraulic Motors Hydraulic motors may be classified by the type of load applied to the bearings of the output shaft – Unbalanced indicates the output shaft is loaded from one side, side loading the shaft bearings – Balanced indicates the bearing load is balanced by use of two inlet ports arranged opposite of each other and two outlet ports similarly arranged© Goodheart-Willcox Co., Inc. 62 Permission granted to reproduce for educational use only.
  62. 62. Hydraulic Motors The external gear hydraulic motor is the most common and simplest of the basic motor types – Fixed displacement – Unbalanced load on the bearings© Goodheart-Willcox Co., Inc. 63 Permission granted to reproduce for educational use only.
  63. 63. Hydraulic Motors  The most common internal gear motor has a gerotor design Courtesy of Eaton Fluid Power Training© Goodheart-Willcox Co., Inc. 64 Permission granted to reproduce for educational use only.
  64. 64. Hydraulic Motors The specially shaped gear teeth of the gerotor form variable-volume chambers that allow system fluid flow and pressure to turn the motor output shaft Gerotor motors are fixed-displacement units operating with an unbalanced bearing load© Goodheart-Willcox Co., Inc. 65 Permission granted to reproduce for educational use only.
  65. 65. Hydraulic Motors An orbiting gerotor motor is a variation of the basic gerotor design – Uses a fixed outer gerotor gear with internal teeth and an inner gear with external teeth – Center point of the inner gear orbits around the center point of the fixed gear with internal teeth – Motor operates at a slower speed, but has a higher torque output© Goodheart-Willcox Co., Inc. 66 Permission granted to reproduce for educational use only.
  66. 66. Hydraulic Motors Orbiting gerotor motor Courtesy of Eaton Fluid Power Training© Goodheart-Willcox Co., Inc. 67 Permission granted to reproduce for educational use only.
  67. 67. Hydraulic Motors Basic vane motor has a slotted rotor located off center in a circular chamber and fitted with movable vanes – Space between the vanes creates a number of variable-sized chambers – Forcing fluid into the small-size chambers causes the volume of the chambers to increase, turning the motor shaft – Basic vane motor is fixed displacement with an unbalanced bearing load© Goodheart-Willcox Co., Inc. 68 Permission granted to reproduce for educational use only.
  68. 68. Hydraulic Motors Basic vane motor© Goodheart-Willcox Co., Inc. 69 Permission granted to reproduce for educational use only.
  69. 69. Hydraulic Motors Balanced vane motors evenly distribute the load on the bearings – Achieved by operating the rotor and vanes in a slightly oblong chamber – Allows two inlet ports and two outlets ports to be used in the motor – Placing ports opposite each other balances bearing loading© Goodheart-Willcox Co., Inc. 70 Permission granted to reproduce for educational use only.
  70. 70. Hydraulic Motors A basic, balanced vane motor© Goodheart-Willcox Co., Inc. 71 Permission granted to reproduce for educational use only.
  71. 71. Hydraulic Motors Vane motors are available as either fixed or variable displacement The variable-displacement feature allows an operator to change the speed of a motor without changing the system flow rate© Goodheart-Willcox Co., Inc. 72 Permission granted to reproduce for educational use only.
  72. 72. Hydraulic Motors In variable-displacement designs, the chamber in which the rotor and vanes operate is contained in a moveable ring – When the center point of the rotor and ring are concentric, the displacement is zero – Moving the ring so the center points are not concentric increases the motor displacement and changes motor speed© Goodheart-Willcox Co., Inc. 73 Permission granted to reproduce for educational use only.
  73. 73. Hydraulic Motors Piston motors are available having either fixed or variable displacements In variable-displacement designs, the length of the piston stroke is changed to vary the volume of fluid needed to rotate the motor one revolution© Goodheart-Willcox Co., Inc. 74 Permission granted to reproduce for educational use only.
  74. 74. Hydraulic Motors Two basic classifications of piston motors are axial piston and radial piston – An axial piston motor has pistons with centerlines parallel to the axis of the output shaft – A radial piston motor has pistons with centerlines perpendicular to the axis of the output shaft© Goodheart-Willcox Co., Inc. 75 Permission granted to reproduce for educational use only.
  75. 75. Hydraulic Motors Axial piston motor The Oilgear Company© Goodheart-Willcox Co., Inc. 76 Permission granted to reproduce for educational use only.
  76. 76. Hydraulic Motors Axial piston motors are available in two configurations: – Inline – Bent axis© Goodheart-Willcox Co., Inc. 77 Permission granted to reproduce for educational use only.
  77. 77. Hydraulic Motors In an inline piston motor: – Centerline of the barrel is concentric with the centerline of the power output shaft – A swash plate transmits force from the pistons to the shaft© Goodheart-Willcox Co., Inc. 78 Permission granted to reproduce for educational use only.
  78. 78. Hydraulic Motors Inline piston motor The Oilgear Company© Goodheart-Willcox Co., Inc. 79 Permission granted to reproduce for educational use only.
  79. 79. Hydraulic Motors In a bent-axis piston motor: – Centerline of the barrel is at an angle to the centerline of the output shaft – A universal joint and other fittings are used to transmit force between the barrel and the output shaft© Goodheart-Willcox Co., Inc. 80 Permission granted to reproduce for educational use only.
  80. 80. Hydraulic Motors Bent-axis piston motor Courtesy of Eaton Fluid Power Training© Goodheart-Willcox Co., Inc. 81 Permission granted to reproduce for educational use only.
  81. 81. Hydraulic Motors A number of alternate motor designs are used in specialized hydraulic applications – Screw motor designs for quiet, continuous operation – Special piston-motor designs allowing the direct mounting and drive of wheels for off-road, heavy- transport vehicles© Goodheart-Willcox Co., Inc. 82 Permission granted to reproduce for educational use only.
  82. 82. Hydraulic Motors Hydraulic motors may be incorporated into circuits using series or parallel connections – Series circuits: total system pressure is determined by adding the loads placed on each unit – Parallel circuits: each motor receives full system pressure; loads must be matched or equal flow supplied to each motor if constant speed is desired from each unit© Goodheart-Willcox Co., Inc. 83 Permission granted to reproduce for educational use only.
  83. 83. Hydraulic Motors Motors in series© Goodheart-Willcox Co., Inc. 84 Permission granted to reproduce for educational use only.
  84. 84. Hydraulic Motors Motors in parallel© Goodheart-Willcox Co., Inc. 85 Permission granted to reproduce for educational use only.
  85. 85. Hydraulic Motors Motors in parallel with flow control© Goodheart-Willcox Co., Inc. 86 Permission granted to reproduce for educational use only.
  86. 86. Hydraulic Motors Braking circuits are used to slow hydraulic motors to a stop – Inertia of a heavy rotating load can continue to turn the motor shaft – Braking occurs when fluid discharged from the motor outlet port is forced to pass through an adjustable pressure control valve before returning to the reservoir© Goodheart-Willcox Co., Inc. 87 Permission granted to reproduce for educational use only.
  87. 87. Hydraulic Motors Braking circuit© Goodheart-Willcox Co., Inc. 88 Permission granted to reproduce for educational use only.
  88. 88. Hydraulic Motors An open-loop hydraulic motor system uses a layout typical of a basic hydraulic system – Pump moves fluid from a reservoir, through a directional control valve, to the motor – Fluid is then returned from the motor to the reservoir through the same control valve© Goodheart-Willcox Co., Inc. 89 Permission granted to reproduce for educational use only.
  89. 89. Hydraulic Motors Closed-loop hydraulic motor systems continuously circulate fluid between the pump and the motor without returning it to a system reservoir These systems use a replenishment circuit to replace fluid lost through leakage© Goodheart-Willcox Co., Inc. 90 Permission granted to reproduce for educational use only.
  90. 90. Hydraulic Motors Replenishment circuit© Goodheart-Willcox Co., Inc. 91 Permission granted to reproduce for educational use only.
  91. 91. Hydrostatic Drives Hydrostatic drive systems consist of the basic components typically found in other hydraulic motor circuits MDMA Equipment—Menomonie© Goodheart-Willcox Co., Inc. 92 Permission granted to reproduce for educational use only.
  92. 92. Hydrostatic Drives Hydrostatic drives provide effective transmission of power and allow easy adjustment and control of: – Output shaft speed – Torque – Horsepower – Direction of rotation© Goodheart-Willcox Co., Inc. 93 Permission granted to reproduce for educational use only.
  93. 93. Hydrostatic Drives When compared to conventional transmissions, hydrostatic drives: – Have a high power output–to–size ratio – May be stalled under full load with no internal damage – Accurately maintain speed under varying load conditions – Provide an almost infinite number of input/output speed ratios© Goodheart-Willcox Co., Inc. 94 Permission granted to reproduce for educational use only.
  94. 94. Hydrostatic Drives Hydrostatic drives may be open or closed circuits – Open circuit has the layout of a basic hydraulic motor circuit – Closed circuit has the outlet of the pump directly connected to the inlet of the motor and the outlet of the motor directly connected to the inlet of the pump© Goodheart-Willcox Co., Inc. 95 Permission granted to reproduce for educational use only.
  95. 95. Hydrostatic Drives Open circuit design© Goodheart-Willcox Co., Inc. 96 Permission granted to reproduce for educational use only.
  96. 96. Hydrostatic Drives Closed circuit design Sauer-Danfoss, Ames, IA© Goodheart-Willcox Co., Inc. 97 Permission granted to reproduce for educational use only.
  97. 97. Hydrostatic Drives Four combinations of pump/motor arrangements can be used – Fixed-displacement pump and motor – Fixed-displacement pump and variable- displacement motor – Variable-displacement pump and fixed- displacement motor – Variable-displacement pump and motor© Goodheart-Willcox Co., Inc. 98 Permission granted to reproduce for educational use only.
  98. 98. Hydrostatic Drives Fixed-displacement pump and motor: – Maximum horsepower, torque, and output shaft speed are fixed – Pump and motor have fixed displacement, so these characteristics cannot be changed© Goodheart-Willcox Co., Inc. 99 Permission granted to reproduce for educational use only.
  99. 99. Hydrostatic Drives Fixed-displacement pump and variable- displacement motor: – Maximum horsepower is fixed – Torque and speed are variable – Due to use of a relief valve, efficiency is lowered – Output shaft rotation may be reversed if the pump is reversible© Goodheart-Willcox Co., Inc. 100 Permission granted to reproduce for educational use only.
  100. 100. Hydrostatic Drives Variable-displacement pump and fixed- displacement motor: – Torque output is fixed – Horsepower and output shaft speed are variable – Output shaft rotation may be reversed if pump is reversible© Goodheart-Willcox Co., Inc. 101 Permission granted to reproduce for educational use only.
  101. 101. Hydrostatic Drives Variable-displacement pump and motor: – Horsepower, torque, output shaft speed are variable – Output shaft direction is reversible – Most versatile of the four pump/motor combinations© Goodheart-Willcox Co., Inc. 102 Permission granted to reproduce for educational use only.
  102. 102. Hydrostatic Drives Hydrostatic drives are typically considered hydrostatic transmissions when both the pump and motor have variable displacement This combination allows manual or automatic control of torque, speed, and power output© Goodheart-Willcox Co., Inc. 103 Permission granted to reproduce for educational use only.
  103. 103. Hydrostatic Drives  Two different general techniques are used in the construction of hydrostatic transmissions – Integral – Nonintegral© Goodheart-Willcox Co., Inc. 104 Permission granted to reproduce for educational use only.
  104. 104. Hydrostatic Drives Integral construction combines all of the transmission parts into a single housing Nonintegral construction involves separate pump, motor, and accessories connected by hoses or tube assemblies© Goodheart-Willcox Co., Inc. 105 Permission granted to reproduce for educational use only.
  105. 105. Review Question A(n) _____ cylinder can exert force during both the extension and retraction strokes. double-acting© Goodheart-Willcox Co., Inc. 106 Permission granted to reproduce for educational use only.
  106. 106. Review Question A(n) _____ is the system component that converts fluid pressure and flow into linear force and movement. hydraulic cylinder© Goodheart-Willcox Co., Inc. 107 Permission granted to reproduce for educational use only.
  107. 107. Review Question List the three basic configurations used to mount cylinders to equipment. A. Fixed centerline, B. fixed non-centerline, and C. pivoting centerline.© Goodheart-Willcox Co., Inc. 108 Permission granted to reproduce for educational use only.
  108. 108. Review Question The three conceptual component groups that make up any hydraulic motor are: A. Rotor, vanes, and eccentric. B. Housing, rotating internal parts, and power output shaft. C. Housing, reciprocating internal parts, and power input shaft. D. Rotating internal parts, power input shaft, and power output shaft. B. Housing, rotating internal parts, and power output shaft.© Goodheart-Willcox Co., Inc. 109 Permission granted to reproduce for educational use only.
  109. 109. Review Question To vary the displacement of a vane motor, a movable _____ is used to change the size of the pumping chambers. cam ring© Goodheart-Willcox Co., Inc. 110 Permission granted to reproduce for educational use only.
  110. 110. Review Question List the four possible pump/motor arrangements that may be used with a hydrostatic system. A. Both pump and motor have fixed displacements, B. pump has a fixed displacement and the motor a variable displacement, C. pump has a variable displacement and the motor a fixed displacement, and D. both pump and motor have variable displacement.© Goodheart-Willcox Co., Inc. 111 Permission granted to reproduce for educational use only.
  111. 111. Review Question During retraction, what is the effective area of the piston of a double-acting cylinder? The cross-sectional area of the piston minus the cross-sectional area of the rod.© Goodheart-Willcox Co., Inc. 112 Permission granted to reproduce for educational use only.
  112. 112. Review Question A cylinder that has externally mounted metal rods holding the ends on the barrel is called a(n) _____ cylinder. tie-rod© Goodheart-Willcox Co., Inc. 113 Permission granted to reproduce for educational use only.
  113. 113. Glossary Barrel – The component containing the cylinders of an axial piston hydraulic pump. Clevis mount – A cylinder rod and cap mounting configuration involving a C-shaped casting and a mounting pin that allows the cylinder to pivot during extension and retraction.© Goodheart-Willcox Co., Inc. 114 Permission granted to reproduce for educational use only.
  114. 114. Glossary Closed circuit – A hydraulic circuit design in which pump output is returned directly to the pump inlet after passing through a hydraulic motor. The design is commonly used with hydrostatic drive systems.© Goodheart-Willcox Co., Inc. 115 Permission granted to reproduce for educational use only.
  115. 115. Glossary Cushioning – A design feature in fluid power cylinders that reduces fluid flow near the end of the extension or retraction stroke to decelerate piston movement, which avoids both noise and component damage. Double-acting cylinder – Cylinders that may be powered both on the extension and retraction strokes.© Goodheart-Willcox Co., Inc. 116 Permission granted to reproduce for educational use only.
  116. 116. Glossary Effective piston area – The area of a piston that contributes to the force generated by system pressure. For example, the effective area of a cylinder piston during retraction is the area of the piston minus the cross-sectional area of the piston rod.© Goodheart-Willcox Co., Inc. 117 Permission granted to reproduce for educational use only.
  117. 117. Glossary Fixed-centerline mount – A cylinder-mounting design in which the load carried by the cylinder rod and piston is supported at the centerline of the cylinder barrel, which is fixed to a machine member.© Goodheart-Willcox Co., Inc. 118 Permission granted to reproduce for educational use only.
  118. 118. Glossary Head – The height of a column of water or other liquid necessary to develop a stated pressure. Hydrostatic drive – A fluid power drive system using a hydraulic pump and motor to transmit the power of a prime mover to the input of a machine. Available in either open- or closed-circuit designs.© Goodheart-Willcox Co., Inc. 119 Permission granted to reproduce for educational use only.
  119. 119. Glossary Limited-rotation actuator – An actuator design that primarily produces rotational movement of one revolution or less. Various designs are available using a rack and pinion, vane, or helical shaft. Mill cylinder – A hydraulic cylinder constructed of heavy steel for use in industries such as foundries and steel mills.© Goodheart-Willcox Co., Inc. 120 Permission granted to reproduce for educational use only.
  120. 120. Glossary Open circuit – A hydraulic circuit that uses the layout of a basic hydraulic motor circuit with a directional control valve to control motor direction and a reservoir to hold surplus fluid.© Goodheart-Willcox Co., Inc. 121 Permission granted to reproduce for educational use only.
  121. 121. Glossary Orbiting gerotor motor – A variation of the gerotor motor that uses the internal-toothed gear of the gerotor set as a fixed gear. The external-toothed gear orbits following the internal-toothed gear. This produces higher torque/lower speed output.© Goodheart-Willcox Co., Inc. 122 Permission granted to reproduce for educational use only.
  122. 122. Glossary Parallel circuit – An electrical or fluid power circuit that simultaneously provides multiple paths for the current or fluid to follow as it moves through a circuit.© Goodheart-Willcox Co., Inc. 123 Permission granted to reproduce for educational use only.
  123. 123. Glossary Pivoting-centerline mount – A clevis or trunnion mounting that allows the cylinder to follow an arc as it powers a machine member. The load remains concentrated on the centerline of the cylinder.© Goodheart-Willcox Co., Inc. 124 Permission granted to reproduce for educational use only.
  124. 124. Glossary Replenishment circuit – A circuit used with closed-loop hydraulic systems that provides makeup fluid to replace any fluid lost from leakage during system operation. Series circuit – An electrical or fluid power circuit that provides only one path for the current or fluid to follow as it moves through the circuit.© Goodheart-Willcox Co., Inc. 125 Permission granted to reproduce for educational use only.
  125. 125. Glossary Single-acting cylinder – A cylinder design that exerts force only on extension or retraction and depends on some outside force to complete the second movement.© Goodheart-Willcox Co., Inc. 126 Permission granted to reproduce for educational use only.
  126. 126. Glossary Telescoping cylinder – A linear actuator constructed of several nested tubes that can extend a distance equal to several times the actuator’s retracted length. Threaded-end cylinder – A linear actuator design in which the cap and head are attached to the barrel of the cylinder by threads.© Goodheart-Willcox Co., Inc. 127 Permission granted to reproduce for educational use only.
  127. 127. Glossary Tie-rod cylinder – A linear actuator design in which the cap and head components are secured to the barrel of the cylinder by external tie rods that run between those components.© Goodheart-Willcox Co., Inc. 128 Permission granted to reproduce for educational use only.
  128. 128. Glossary Trunnion mount – A cylinder mounting method that places fittings on the sides of cylinders, allowing the cylinder to pivot as it extends and retracts to move a machine member.© Goodheart-Willcox Co., Inc. 129 Permission granted to reproduce for educational use only.

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