Stroke volume limiter for collapsible wall blood pump system

Claim 1

A blood circulatory assist device operated by pneumatic pulses comprising: a flexible bladder enclosed in a rigid housing, said bladder forming inlet and outlet means for intermittently admitting and discharging blood to and from the interior of said bladder, said bladder being expandable to its fully distended position under the influence of the blood pressure; a cylindrical pneumatic chamber; wall means dividing said chamber into the opposing compartments pneumatically sealed from each other, said wall means being mounted for reciprocal displacement between the opposing compartments of said chamber in response to pressure differential thereacross; means forming a port from a first of said compartments for receiving pneumatic pulses; a closed pneumatic system including as a part thereof the interface between said bladder and the interior of said housing and the second of said compartments, said closed pneumatic system providing a path of pneumatic communication between said second compartment and said interface for transmitting pneumatic pulses from said second compartment to said interface to collapse said bladder; reciprocally mounted stop means engagable with said wall means for variably limiting reciprocal movement of said wall means to thereby limit the magnitude of the pneumatic pulses transmitted to said closed system independently of the magnitude of the pneumatic pulses received at said port; a hood threadedly engaging the cylindrical wall of said chamber external thereof; means connecting said hood and said stop means whereby rotary movement of said hood advances or retracts said stop means with respect to said wall means, and means permitting said hood to rotate relative to said stop means for preventing transmission of rotational forces to said wall means.