# US 6,284,397 B1 · Rotary piston blower for supplying an oxidant stream to a fuel cell > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 6,284,397 B1 - Document ID: US6284397B1 - Status: Granted - Kind: B1 - Application number: 09/321,409 - Filed: 1999-05-27 - Granted: 2001-09-04 - Earliest claimed: 1998-05-29 - Assignees: Ballard Power Systems Inc. - Inventors: Russell H. Barton - Web page: https://patentgrep.com/patent/US6284397B1 ## CPC - F04C 18/126: {with radially from the rotor body extending elements, not necessarily co-operating with corresponding recesses in the other rotor, e.g. lobes, Roots type} - F04C 18/086: {Carter} - Y02E 60/50: Fuel cells - F04C: ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS (engines F03C); ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT PUMPS - Y02E: REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION ## Abstract An improved rotary piston blower supplies an oxidant stream to a fuel cell. In one embodiment, the improved rotary piston blower includes cantilevered shafts. The improved rotary piston blower is also able to supply an oil-free oxidant stream to an electrochemical fuel cell. The improved rotary piston blower has fewer components, fewer seals, and is easier to fabricate, in comparison to conventional, prior art rotary piston blowers. ## Claims ### Claim 1 An improved rotary piston blower comprising: an elongated drive shaft having a longitudinal axis; a driven piston mounted on a first end of said drive shaft; a secondary shaft having a longitudinal axis parallel to said longitudinal axis of said drive shaft; a secondary piston mounted on a first end of said secondary shaft; a first timing gear mounted on said drive shaft; a second timing gear mounted on said secondary shaft wherein said first and second timing gears interlock; a piston housing enclosing said driven and secondary pistons, said piston housing comprising a unitary piston cylinder and a first side plate, said piston housing further comprising a second side plate, wherein said first side plate provides a mounting point for attaching a drive shaft bearing assembly for supporting a second end of said drive shaft and a mounting point for attaching a secondary shaft bearing assembly for supporting a second end of said secondary shaft, whereby said drive shaft and said secondary shaft are supported by said second ends only, and said first ends are unsupported. ### Claim 2 (depends on 1) The rotary piston blower of claim 1 wherein said second side plate has a surface facing the interior of said piston housing wherein said surface is devoid of openings. ### Claim 3 (depends on 1) The rotary piston blower of claim 1 wherein said first and second timing gears are located on said second ends of said drive shaft and said secondary shaft, respectively. ### Claim 4 (depends on 1) The rotary piston blower of claim 1 wherein said drive shaft bearing assembly and said secondary shaft bearing assembly each comprise at least two bearings spaced longitudinally along said drive shaft and said secondary shaft respectively. ### Claim 5 (depends on 1) The rotary piston blower of claim 1 wherein said first ends of said drive shaft and said secondary shaft do not extend beyond the end faces of said driven and secondary pistons respectively. ### Claim 6 (depends on 1) The rotary piston blower of claim 1 further comprising shaft seals between said first and second timing gears and the interior of said piston housing. ### Claim 7 (depends on 1) The rotary piston blower of claim 1 further comprising shaft seals between said bearing assemblies and the interior of said piston housing. ### Claim 8 (depends on 1) The rotary piston blower of claim 1 wherein said bearing assemblies comprise sealed bearings adjacent the interior of said piston housing. ### Claim 9 An improved oxidant supply system for an electrochemical fuel cell comprising a rotary piston blower, an electric motor coupled to an elongated drive shaft having a longitudinal axis extending from said blower, and a filter mounted upstream of an intake port of said blower. ### Claim 10 (depends on 9) The oxidant supply system of claim 9 wherein said rotary piston blower further comprises: a driven piston mounted on a first end of said drive shaft; a secondary shaft having a longitudinal axis parallel to said longitudinal axis of said drive shaft; a secondary piston mounted on a first end of said secondary shaft; a first timing gear mounted on said drive shaft; a second timing gear mounted on said secondary shaft wherein said first and second timing gears interlock; a piston housing enclosing said driven and secondary pistons, said piston housing comprising a piston cylinder interposed between a first side plate and a second side plate wherein said first side plate provides a mounting point for attaching a drive shaft bearing assembly for supporting a second end of said drive shaft and a mounting point for attaching a secondary shaft bearing assembly for supporting a second end of said secondary shaft, whereby said drive shaft and said secondary shaft are supported by said second ends only, and said first ends are unsupported. ### Claim 11 (depends on 9) The oxidant supply system of claim 9 wherein said electrochemical fuel cell is a solid polymer electrolyte fuel cell. ### Claim 12 (depends on 11) The oxidant supply system of claim 11 wherein said electrochemical fuel cell is a portable fuel cell which has a power output of less than 20 kilowatts. ### Claim 13 (depends on 11) The oxidant supply system of claim 11 wherein said blower has an intake flow volume of less than 100 standard liters per minute. ### Claim 14 An improved rotary piston blower comprising: an elongated drive shaft having a longitudinal axis; a driven piston mounted on a first end of said drive shaft; a secondary shaft having a longitudinal axis parallel to said longitudinal axis of said drive shaft; a secondary piston mounted on a first end of said secondary shaft; a first timing gear mounted on said drive shaft; a second timing gear mounted on said secondary shaft wherein said first and second timing gears interlock; a piston housing enclosing said driven and secondary pistons, said piston housing comprising a piston cylinder interposed between a first side plate and a second side plate wherein said first side plate provides a mounting point for attaching a drive shaft bearing assembly for supporting a second end of said drive shaft and a mounting point for attaching a secondary shaft bearing assembly for supporting a second end of said secondary shaft, whereby said drive shaft and said secondary shaft are supported by said second ends only, and said first ends are unsupported; and shaft seals between said first and second timing gears and the interior of said piston housing. ### Claim 15 (depends on 14) The rotary piston blower of claim 14 further comprising shaft seals between said bearing assemblies and the interior of said piston housing. ### Claim 16 (depends on 15) The rotary piston blower of claim 15 wherein said bearing assemblies comprise sealed bearings adjacent the interior of said piston housing. ### Claim 17 A method for supplying oxidant to a fuel cell, said fuel cell comprising a rotary piston blower, an electric motor coupled to an elongated drive shaft having a longitudinal axis extending from said rotary piston blower, and a filter mounted upstream of an intake port of said rotary piston blower, said method comprising the step of using said rotary piston blower to supply said oxidant to said fuel cell. ### Claim 18 (depends on 17) The method of claim 17 wherein said rotary piston blower further comprises a driven piston mounted on a first end of said drive shaft; a secondary shaft having a longitudinal axis parallel to said longitudinal axis of said drive shaft; a secondary piston mounted on a first end of said secondary shaft; a first timing gear mounted on said drive shaft; a second timing gear mounted on said secondary shaft wherein said first and second timing gears interlock; and a piston housing enclosing said driven and secondary pistons, said piston housing comprising a piston cylinder interposed between a first side plate and a second side plate wherein said first side plate provides a mount for a drive shaft bearing assembly for supporting a second end of said drive shaft and a mount for a secondary shaft bearing assembly for supporting a second end of said secondary shaft, whereby said drive shaft and said secondary shaft are supported by said second ends only, and said first ends are unsupported. ### Claim 19 (depends on 17) The method of claim 17 wherein said fuel cell is a solid polymer electrolyte fuel cell. ### Claim 20 (depends on 19) The method of claim 19 wherein said fuel cell is a portable fuel cell which has a power output of less than 20 kilowatts. ### Claim 21 (depends on 19) The method of claim 19 wherein said rotary piston blower provides an intake flow volume of less than 100 standard liters per minute.