Pump, a homogenizer comprising said pump and a method for pumping a liquid product

A method for pumping a liquid product in a pump, said pump comprising:

• a hydraulic fluid reservoir,
• a bushing element attached in a passage between a piston cavity and a membrane cavity, said bushing element having a radial opening in fluid connection with the hydraulic fluid reservoir,
• an axle element arranged such that a first axial end thereof is attached to a first membrane provided in the membrane cavity, and such that at least a portion of said axle element is journalled, and adapted for axial movement, in the bushing element,
• said axle element being further provided with a first recess proximate the first axial end and formed as a cut extending axially along an outer surface of the axle element, wherein the method comprises the steps of
• filling a second membrane cavity portion, of the membrane cavity, with the liquid product by moving the first membrane to a first operational turning point,
• emptying the liquid product from the second membrane cavity portion by moving the first membrane to a second operational turning point,
• wherein the method further comprises the step of,
• if the first membrane is displaced beyond the first operational turning point, to a point at, or in close vicinity of, a first extreme point, creating a fluid connection between the hydraulic fluid reservoir and a hydraulic fluid volume of the pump for introducing hydraulic fluid into the pump by letting the first recess of the axle element come into fluid connection with the radial opening of the bushing element and the membrane cavity, whereby the hydraulic fluid reservoir and the membrane cavity are fluidly connected, and
• if the first membrane is displaced beyond a second operational turning point, to a point between the second operational turning point and a second extreme point, creating a fluid connection between the hydraulic fluid reservoir and the hydraulic fluid volume of the pump for discharging hydraulic fluid from the pump by a second axial end of the axle element axially moving away from a blocking position in which the second axial end blocks fluid communication between the radial opening and the piston cavity, and providing fluid connection between the radial opening of the bushing element and the piston cavity, wherein fluid flows between the piston cavity and the hydraulic fluid reservoir past the second axial end.