The electrically powered radial blower is central to the equipment’s new E-Vent Plus ventilation technology. Reaching speeds of up to 42,000 r/min in less than 200 msec, the blower checks and constantly ventilates the patient.

To achieve this type of acceleration, the moment of inertia and the weight of the blower wheel need to be as low as possible. “The wheel must be strong enough to prevent its fins from bending due to the enormous centrifugal forces that occur at these speeds,” explains Andrew Ragan, Victrex global leader, Industrial. “High seam strength is also essential.”

To meet these requirements, Draeger Medical uses non-reinforced VICTREX PEEK polyaryletherketone from Victrex USA Inc. (Greenville, SC, U.S.) to injection mold the 55-mm wheel, which has a wall thickness of just 0.3mm. The wheel has a tensile strength of approximately 14,500 psi (100 MPa) at a temperature of 23°C. It also has the purity required for clinical use.

From a production point of view, manufacturing the blower presented a number of challenges. The wheel is made in a tool with 23 slide bars in an injection molding process. It must form a homogeneous, partly crystalline structure. Special attention was given to the parting system and the geometric placement of the ejectors to maintain the tight tolerances required for high balancing quality and to minimize warping in the connection between the shaft and the hub. “Because semi-crystalline VICTREX PEEK can achieve maximum flow rates of up to 150 l/min with an excellent response dynamic, it does not require any more working gas,” says Mr. Ragan. “As a result, operating costs are considerably reduced.”