Etesia HYDRO 124D, Technical Training Manual

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2.1.2) The external gear pump
The disengagement of the pinion teeth liberates a volume that fills with oil. This is suction.
The oil is transferred from the suction chamber to the discharge chamber.
The engagement of pinions leads to a reduction in the volume causing the oil to be expelled.
This is discharge.
In our application, we have opted for a unit including two pumps coupled together with shared
suction and activated by the same power take-off on the diesel engine. This is called a
tandem pump.
One with a cubic capacity of 16cc, is reserved for the Power onto which the different
accessories (scarifier, sweeper…) are connected.
The other, with a cubic capacity of 4cc, is reserved for all the other hydraulic functions of the
machine (except the drive), namely :
- the assisted steering.
- the lifting of the grassbox.
- the opening of the grassbox
- the activating of the grassbox flap
- the activating of the accessory-holder triangle
N.B. : the accessory-holder triangle can bear a load of 100kg at a distance of 50cm from
triangle (or 200kg on the triangle), that is to say that the max. acceptable torque is 100
m.kg (100 daN.m). Beyond that, the cylinder which activates this triangle is unable to lift the
load and the modification of the distribution of the masses on the axles may lead to the
machine becoming unbalanced and chassis fatigue.
- The activating of a cylinder mounted on the accessories (depending on the accessory).