This invention is an improvement on the device disclosed and claimed in prior U.S. Pat. No. 4,143,425, issued to Runge on Mar. 13, 1979.
This invention seeks to improve on the reliability, efficiency and smoothness of operation of the pumping mechanism in said prior patent in several important respects. Potentially, the groove rider in the prior patent is subject to a jerky or rough ride over the spiral groove of the spinner in its return toward the motor end of the spinner during diastole. Eventually, this rough ride could damage the engaging parts and cause jamming of the mechanism to create a serious safety hazard. This drawback is completely eliminated in the present invention through the provision of positive camming means on the spinner to displace the groove rider toward engagement with a holding magnet on the surrounding ring follower housing which holds the rider out of contact with the spinner during its travel toward the far end of the spinner during diastole. Another camming means near the far end of the spinner positively separates the groove rider from the holding magnet and positively cams the rider back into engagement with the spinner groove, thus assuring a more reliable operation of the vital parts which drivingly interconnect the spinner and the ring follower housing, which in turn operates the ejection plate in the manner disclosed in the above-referenced patent.
Another important feature of the present invention resides in the fitting of the groove rider with a ball bearing element producing a low friction ride in the shallow spinner groove, again improving the efficiency and reliability of the pump.
Another significant improvement resides in the use of a fluid coupling, namely a hydraulic, vaned, perforated clutch between the pancake motor and the spinner. In addition to providing a smooth drive for the spinner, the latter is able to idle during diastole while the magnetically held groove rider is traveling toward the motor end of the spinner.
A very important aspect of the present invention resides in the spring suspension of the roof of the shell to which the pancake motor is attached. By virtue of this arrangement, the shell roof can slide freely as a function of duration of systole and magnitude of after load, reducing stroke volume in the presence of high after load. Through the simple mechanical feedback means thus provided, the pump automatically adjusts its pumping rate in response to filling pressure, and automatically reduces its stroke volume in response to after load. These physiologic and safety features are not available in state of the art pumps.
While the present device is intended for use outside of the body during cardiac surgery and for longer term cardiac support, as for a day or two after surgery, it is intended not to limit the invention to such usage, and the pump could be used for implantation in the body in the manner disclosed in U.S. Pat. No. 4,143,425 in conjunction with a source of power external to the body.
Other features and advantages of the invention will become apparent during the course of the following detailed description.