Patent ID: 8859972

Claim:
An occlusion sensor system comprising: a pumping device; a cassette removably attachable to the pumping device, the cassette comprising a tube; an infra-red reflective sensor comprising an infra-red light emitting diode and an infra-red phototransistor receiver or photo-diode, being positioned to lay side-by-side, the infra-red reflective sensor being positioned so that an infra-red light can be directly transmitted to a respective portion of the tube comprising an infra-red reflective surface and at least a portion of the infra-red light reflected off the portion of the tube can be detected by the infra-red phototransistor receiver or photo-diode; and a processor configured to determine a presence of an occlusion based on the infra-red reflective sensor and to stop pumping in response to the occlusion, and the processor is programmed to use the intensity of the detected infra-red light at various stages of contraction of the sidewall of the portion of the tube to determine an amount of contraction or expansion that is used to determine a strength of the occlusion.