Pumps/Actuators A Flashcards Preview

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Flashcards in Pumps/Actuators A Deck (21)
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1
Q

Controlling the output of a piston pump

A

-output can be varied by controlling the length of the stroke

2
Q

Internal leakage

A

-thinner oil could cause it

3
Q

Changing the output of a pump

A
  • use of flow control
  • change the speed of the driver by using a frequency drive
  • use a variable displacement pump (adjusting the swash plate)
4
Q

Positive displacement pump vs. Dynamic

A

-positive displacement has a positive seal between the inlet and outlet

5
Q

Load compensator pump

A

-less pressure when extension, more on retraction
-no flow on extension or retraction after pressure “required” (plus moving the check valve spring) is achieved
-

6
Q

Pressure compensator pump

A

-no flow after reaching max pressure needed to move load or

7
Q

In-line axial piston pump

A
  • swash plate controls flow by changing its angle

- has the bias piston

8
Q

Type of positive displacement pumps

A
  • piston
  • vane
  • gear
9
Q

Difference between rotary and radial

A
  • radial uses a stationary block instead of rotating block like the rotary
  • rotary has the pintle that injects fluid and the radial fluid is ported by check valves in the Pistons
10
Q

Rotary piston pump

A
  • cylinder rotates around stationary pintle
  • the housing is eccentric so when the cylinder is in the middle there is no stroke and no flow, as it moves out of the centre the flow increases.
11
Q

Bent axis piston pump

A
  • controlling the stroke by adjusting the angle between the cylinder and the drive shaft
  • can handle high vacuum so it can be mounted above fluid level
12
Q

Bias piston

A
  • holds swash plate at max angle when needed

- when pressure builds it overcomes bias piston and lowers angle of swash plate

13
Q

Unbalanced vane pump

A
  • hydraulic forces not balanced
  • circular cam is off centre with respect to the rotor
  • advantages: able to give you variable displacement by rotating the cam ring
    disadvantage: very large to support the large radial force
14
Q

Balanced vane

A
  • much more compact because it has two pumping chambers that are 180 apart so the forces at one outlet act against the forces on the opposing outlet.
  • high performance balanced vane pumps have intra-vane
15
Q

Intra vane

A
  • slotted rotor with intra vane passage have outlet pressure constantly applied to small intra vane area of vane
  • pressure on the intra vane along with centrifugal pressure force vanes to maintain constant with cam ring.
  • more stable, less noise, less maintenance than regular vanes
  • found on cartridge style balanced vane pumps
16
Q

Cam ring (unbalanced Vane)

A
  • thickness of the cam ring determines the amount of fluid displaced on each revolution
  • vanes are held against the cam ring by centrifugal force and hydraulic pressure
17
Q

Pintle (Rotary piston)

A

-a stationary shaft that shoots the fluid in and out of the cylinder

21
Q

Gear pumps

A
  • use gear meshing for pumping action
  • two styles: external and internal
  • cannot have adjustable displacement (without fluid bypass or VFD)
  • less efficient (85%) than piston pumps (95%) because of internal leakage
21
Q

External gear pumps

A
  • unbalanced forces
  • spur, helical, or Herrington
  • simple design
  • most dirt tolerant
21
Q

Internal gears

A
21
Q

Gerotor internal

A
  • no crescent seal and is star shaped rotor with one less tooth than the lobes on the outer gear
  • less dirt tolerant