Archive for the ‘Breast pump’ Category

Breast pumps.

These are a form of suction pump where the level of suction changes throughout the cycle.
They are used to take milk from the breast of women who have just given birth, this milk can be stored in a refrigerator till the baby needs it or if the mother is producing more milk than her baby needs it can be used for others.
The level of suction can often be altered from a low-level to a maximum.
They suck in a cyclic way at a rate of about 48 cycles per minute. It sort of mimics the way a baby suckles.
One make much used, The EGNELL I have described below.

These are very well made machines that will run for years with little attention.               The electric motor  (on the right in the photo) and worm gear drive make up one integral unit, the gearbox gives the 48 cycles per minute.
There is a cylinder and piston, (on the left in the photo)  the cylinder is flexibly attached to the worm gear housing and the piston has two leather packings.
The excess pressure resulting from the upward travel of the piston is released by a check valve on the cylinder head.
When the suction adjustment is moved to the left an aperture in the suction line is uncovered so the suction level is reduced.
There is a safety bottle which protects the motor from overflows.
As the worm gear drive goes round and round so the piston goes up and down and the cylinder oscillates to and fro and so the suction is created.
This is the working cycle which can be subdivided into three phases:

a. A short suction phase during which the pressure decreases from atmospheric to a negative
Pressure of 240 mm Hg or 31 Kpa.

b. A short relief phase back to atmospheric pressure.

c. A resting phase with a slight positive pressure of 10 mm Hg or 1.3 kPa.
When the suction adjustment lever is turned to the minimum position, the maximum value of the suction phase is reduced to a negative pressure of about 120 mm Hg or 16 kPa.

This should be done once a year.
This includes:

a. A function check.

b. Cleaning and inspection of the various parts subject to wear, replacing parts as required.

c. A function check after any repairs.

d. Electrical safety check.

Take a pressure gauge of the right negative value, remove the cover glass and paint the limits of negative pressure ( maximum and minimum ) on it.
This can then be used as a test gauge during your checks.
Paint the marks at – 56 kPa and – 12 kPa.

Egnell Ameda Limited,
Unit 2,
Belvedere Trading estate,
Somerset TA1 1BH.

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