# US 5,344,345 A · Water vessel propulsion apparatus > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 5,344,345 A - Document ID: US5344345A - Status: Granted - Kind: A - Application number: 08/070,788 - Filed: 1993-06-03 - Granted: 1994-09-06 - Earliest claimed: 1992-06-03 - Assignees: Idc, LLC - Inventors: Fumio Nagata - Web page: https://patentgrep.com/patent/US5344345A ## CPC - B63H 11/08: of rotary type - B63H: MARINE PROPULSION OR STEERING (propulsion of air-cushion vehicles B60V1/14; specially adapted for submarines, other than nuclear propulsion, B63G; specially adapted for torpedoes F42B19/00) ## Abstract A water jet propulsion apparatus creates a high speed water jet rearwardly through a duct in a hull by injecting air and water into the duct from at least one injection port, thereby to impart a thrust to the hull. The need of forming protrusions such as an impeller within the duct thus is eliminated, and the resistance loss of the jet is minimized. Propulsion efficiency is improved remarkably and noise is reduced, while at the same time course stability is improved. ## Claims ### Claim 1 In a water vessel hull having a propulsion apparatus for propelling said hull through the water, the improvement wherein said propulsion apparatus comprises: a duct connected to said hull and depending therefrom at a position to be beneath the water surface, said duct having extending entirely therethrough a rectilinear passage having an inlet and an outlet both to be open to the water; at least one injection port extending into said passage at a position between said inlet and outlet thereof, said at least one injection port being directed toward said outlet; a pressurized water port opening into said injection port in a direction toward said outlet; a compressed air port surrounding said pressurized water port and opening into said injection port in a direction toward said outlet; and said pressurized water port and said compressed air port being connected respectively to pressurized water and compressed air sources in said hull, thereby to inject through said injection port into said passage a water jet and a surrounding air jet directed toward said outlet. ### Claim 2 (depends on 1) The improvement claimed in claim 1, wherein said compressed air source comprises an air compressor located in said hull. ### Claim 3 (depends on 1) The improvement claimed in claim 1, wherein said pressurized water source comprises a high pressure pump located in said hull and drawing water therethrough. ### Claim 4 (depends on 1) The improvement claimed in claim 1, comprising a plurality of said injection ports located at circumferentially spaced positions within said duct and opening into the periphery of said passage. ### Claim 5 (depends on 4) The improvement claimed in claim 4, comprising a plurality of said pressurized water ports located at circumferentially spaced positions within said duct and opening into respective said injection ports. ### Claim 6 (depends on 5) The improvement claimed in claim 5, further comprising an annular pressurized water chamber formed in said duct and opening into said plurality of pressurized water ports. ### Claim 7 (depends on 4) The improvement claimed in claim 4, comprising a plurality of said compressed air ports located at circumferentially spaced positions within said duct and opening into respective said injection ports. ### Claim 8 (depends on 7) The improvement claimed in claim 7, further comprising an annular compressed air chamber formed in said duct and opening into said plurality of compressed air ports. ### Claim 9 (depends on 1) The improvement claimed in claim 1, further comprising a second duct having a larger diameter than said duct and positioned coaxially outwardly of said duct an extending rearwardly beyond a rear end thereof. ### Claim 10 (depends on 9) The improvement claimed in claim 9, wherein said second duct is displaceable relative to said duct in directions axially thereof. ### Claim 11 (depends on 1) The improvement claimed in claim 1, further comprising at least one thrust reverser mounted on said duct adjacent a rear end thereof. ### Claim 12 (depends on 1) The improvement claimed in claim 1, comprising a single said injection port formed in a support extending into said passage from said duct, said single injection port being located on a longitudinal center axis of said passage. ### Claim 13 (depends on 1) The improvement claimed in claim 1, further comprising a guide vane positioned in said injection port at a position confronting said compressed air port and extending in a direction inclined outwardly from the direction of an air jet ejected from said compressed air port. ### Claim 14 (depends on 1) The improvement claimed in claim 1, further comprising a needle valve positioned in said duct for movement toward and away from said pressurized water port, thereby to regulate the degree of opening thereof. ### Claim 15 A propulsion apparatus for propelling a water vessel hull through water, said propulsion apparatus comprising: a duct to be connected to the hull to depend therefrom at a position to be beneath the water surface, said duct having extending entirely therethrough a rectilinear passage having an inlet and an outlet both to be open to the water; at least one injection port extending into said passage at a position between said inlet and outlet thereof, said at least one injection port being directed toward said outlet; a pressurized water port opening into said injection port in a direction toward said outlet; a compressed air port surrounding said pressurized water port and opening into said injection port in a direction toward said outlet; and said pressurized water port and said compressed air port being connected to respective connections through said duct to enable the respective supply thereto of pressurized water and compressed air, thereby to enable the injection through said injection port into said passage of a water jet and a surrounding air jet directed toward said outlet. ### Claim 16 (depends on 15) A propulsion apparatus as claimed in claim 15, comprising a plurality of said injection ports located at circumferentially spaced positions within said duct and opening into the periphery of said passage. ### Claim 17 (depends on 16) A propulsion apparatus as claimed in claim 16, comprising a plurality of said pressurized water ports located at circumferentially spaced positions within said duct and opening into respective said injection ports. ### Claim 18 (depends on 17) A propulsion apparatus as claimed in claim 17, further comprising an annular pressurized water chamber formed in said duct and opening into said plurality of pressurized water ports. ### Claim 19 (depends on 16) A propulsion apparatus as claimed in claim 16, comprising a plurality of said compressed air ports located at circumferentially spaced positions within said duct and opening into respective said injection ports. ### Claim 20 (depends on 19) A propulsion apparatus as claimed in claim 19, further comprising an annular compressed air chamber formed in said duct and opening into said plurality of compressed air ports. ### Claim 21 (depends on 15) A propulsion apparatus as claimed in claim 15, further comprising a second duct having a larger diameter than said duct and positioned coaxially outwardly of said duct and extending rearwardly beyond a rear end thereof. ### Claim 22 (depends on 21) A propulsion apparatus as claimed in claim 21, wherein said second duct is displaceable relative to said duct in directions axially thereof. ### Claim 23 (depends on 15) A propulsion apparatus as claimed in claim 15, further comprising at least one thrust reverser mounted on said duct adjacent a rear end thereof. ### Claim 24 (depends on 15) A propulsion apparatus as claimed in claim 15, comprising a single said injection port formed in a support extending into said passage from said duct, said single injection port being located on a longitudinal center axis of said passage. ### Claim 25 (depends on 15) A propulsion apparatus as claimed in claim 15, further comprising a guide vane positioned in said injection port at a position confronting said compressed air port and extending in a direction inclined outwardly from the direction of an air jet ejected from said compressed air port. ### Claim 26 (depends on 15) A propulsion apparatus as claimed in claim 15, further comprising a needle valve positioned in said duct for movement toward and away from said pressurized water port, thereby to regulate the degree of opening thereof.