jupitersterrain four

contraction and relaxation of muscles which propagates in a wave down the muscular tube. Earthworms use a similar mechanism to drive peri stallein wave pushes the ball contracting behind the chewed material


Catastalsis is similar but is not preceded by a wave of inhibition


smooth muscles contract behind the ball

Once processed and digested by the stomach, the milky chyme is squeezed through the pyloric sphincter



chyle


19.51, 2.12.12.

During vomiting the propulsion of food up the esophagus and out the mouth comes from contraction of the abdominal muscles


As the rotor turns, the part of tube under compression is pinched closed (or "occludes") 

 Additionally, as the tube opens to its natural state after the passing of the cam ("restitution" or "resilience") fluid flow is induced to the pump


 Typically, there will be two or more rollers occluding the tube, trapping between them a body of fluid.
Peristaltic pumps may run continuously, or they may be indexed through partial revolutions to deliver smaller amounts of fluid

Occlusion

The minimum gap between the roller and the housing determines the maximum squeeze applied on the tubing. The amount of squeeze applied to the tubing affects pumping performance and the tube life - more squeezing decreases the tubing life dramatically, while less squeezing can cause the pumped medium to slip back, especially in high pressure pumping, and decreases the efficiency of the pump dramatically and the high velocity of the slip back typically causes premature failure of the hose. Therefore, this amount of squeeze becomes an important design parameter.

The term "occlusion" is used to measure the amount of squeeze. It is either expressed as a percentage of twice the wall thickness, or as an absolute amount of the wall that is squeezed.

Let

y = occlusion

g = minimum gap between the roller and the housing

t = wall thickness of the tubing

Then

y = 2 x t - g (when expressed as the absolute amount of squeeze)

y = (2 x t - g) / (2 x t) x 100 (when expressed as a percentage of twice the wall thickness)

The occlusion is typically 10 to 20%, with a higher occlusion for a softer tube material and a lower occlusion for a harder tube material.

Thus for a given pump, the most critical tubing dimension becomes the wall thickness. An interesting point here is that the inside diameter of the tubing is not an important design parameter for the suitability of the tubing for the pump. Therefore, it is common for more than one ID be used with a pump, as long as the wall thickness remains the same