REVERSING DEVICE OF A JET PROPULSION ASSEMBLY FOR A SHIP

Abstract: The present invention briefly concerns a reversing device of a jet propulsion assembly for ships. The jet propulsion assembly comprises a steering means (20) connected to the outlet side of a pump (6), for steering the driving water jet, said steering means including two flaps (18, 19) for reversing the driving water jet. An actuator (21) pivots the one flap (18) downwards around a bearing (23) across the water jet, at the same time as link arms (22), which are journalled between the front edges of the first flap (18) and second flap (19), swing the second flap (19) around bearing (24). The rear portion of the second flap (19) is thereby raised towards the water jet and encounters the inner side of the first flap (18) in such a way that both flaps (18, 19) shut off the passage rearwards and divert the water jet obliquely downwards/forwards. The two flap (18, 19) bearing points on the steering means (20) together with the link arm (22) bearing points on the two flap (18, 19) provide an equilibrium of forces between the actuator (21) pressure on the first flap (18) and water jet pressure on both flaps (18, 19), under the condition that a reduction of the pressure on the actuator (21) results in the flap (18) being swung upwards by the water pressure.

Description: Reversing device of a jet propulsion assembly for a ship The present invention relates to a jet propulsion assembly for ships, and in particular to a reversing device of such assemblies. A jet propulsion assembly for ships basically includes a propeller pump, which generally is mounted at the ships stern and has an inlet connected to an inlet opening in the bottom of the ship, forward of the pump. The propeller pump outlet is generally connected to a steering means, which is laterally pivotal around a vertical axle for steering the driving water jet, and connected to a reversing device adapted to be raised and lowered around a horizontal axle for diverting the driving water jet from straight or obliquely rearwards, or straight or obliquely forwards/downwards. The reversing device of the jet propulsion assembly is normally constructed so that one or several shovel-shaped members can be pivoted horizontally into the driving water jet from the pump to gradually divert the jet. The shovel-shaped members and their suspension points in relation to the steering means and pump are normally positioned so that the water jet will lock the shovel-shaped members in their maximally pivoted positions, in which the water jet is directed obliquely forwards/downwards. Such a known reversing device is disclosed by for example the Swedish patent application No. 8200417-7. This has, as do similar reversing devices, the disadvantage that a considerable force is required to return the shovel-shaped members to their original positions, in which the jet can pass freely straight backwards. It is appreciated that this can give rise to certain risks as the ship is being anoeuvered to change from reverse drive to forward drive. The jet is constantly counteracting the opening of the shovel-shaped members, which can lead to that the ship continues to drive backwards, despite the intention to drive the ship forwards. The purpose of the present invention is to overcome the above problems and to provide a reversering device of a jet propul¬ sion assembly for ships , wherein the outgoing jet does not strive to lock the shoveϊ-shaped members in their maximally reset positions, at the same time as it effectively diverts the water jet gradually as required. The object of the invention as well as the characteristic eature thereof appear from the accompanying patent claims . The invention will be further described below, in conjunction with the attached drawings, wherein FIG . la is a schematical longitudinal section of a jet propulsion assembly with a reversing device according to the invention, wherein the reversing device is shown in its inactive state, FIG. lb is a view corresponding to Fig. la, and showing the reversign device in its fully reversing state, FIG. 2 is a schematic, vertical section of the rear portion of a j et propuls ion as sembly, where the revers ing device according to the invention is illustrated by full lines in its inactive state, and by dashed lines in its fully reversing state, and FIG. 3 is a partially sectioned top view of the jet propulsion assembly in Fig. 2. The jet propulsion assembly according to the drawings is s chematically shown in its position at the stern of a ship, of which only the stern 1 and bottom 2 are implied. The jet propulsion assembly includes an inlet canal 3 extending from a water inlet 4 in the ship bottom 2 to a mounting flange 5 for the pumping house 6 of the assembly. The inlet 4 is provided with a grid 7, which prevents objects from being sucked into the jet propulsion assembly. The pump is comprised of a propeller pump having a hub casing 8, which is provided centrally in the flow way through the pumping house 6. The hub casing 8 is supported by articulated vanes 9. The pump wheel 11 is journalled in the hub casing 8 and is driven from a not further shown driving machinery in the ship by a drive shaft 10. The outlet side of the pump housing 6 is connected to an outlet pipe 15, over which a laterally pivotal steering means 20 is mounted. The steering means 20 is journalled in verti¬ cally positioned axle spindles 16 and 17 and is laterally swiveled around these by means of not further represented hydraulic engines. The steering of the ship takes place when the water jet from the pump is diverted to either side of the inner walls of the steering means 20. To reverse the force direction of the assembly, when retardation or backing up of the ship is required, there are provided two flaps 18, 19, which are pivotal into the water jet in such a way that this is gradually diverted from full speed ahead, the jet being directed straight rearwards, to full speed rearwards, the jet being directed obliquely downwards/forwards. Between the above positions can, if so desired, intermediate positions be obtained in which the jet partially travels forwards and partially rearwards. The upper flap 18 also has a function to act as a splash shield, the upper flap 18 overlapping the rear edge and sides of the lower flap 19. By means of this reversing device, steering can be attained also during backing operations, in that the steering means 20 is pivotal so that the jet is diverted in the direction wanted. The upper flap 18 is journalled in the steering means 20 by means of horizontally positioned axle spindles 23 and is through the lower f lap 19 , which is journalled in the horizontally positioned axle spindles 24, connected to the link arm 22 , which in turn is journalled in the front edges of the flaps 18 and 19. By pivoting the upper flap 18 downwards by means of the reversing device 21 , a downward force is transmitted through the link arm 22 to the front edge of the lower flap 19. This lower flap is swiveled around the axle spindles 24 and encounters the inner wall of the upper flap 18 with its rear edge , which results in the water jet being diverted forwards at the same time as the resulting pressure on the inner walls of the flaps 18 and 19 strives to counter¬ act said diversion. The present invention thus provides a reversing device that meets the initially mentioned purpose.

Claims: CLAIMS Reversing device of a jet propulsion assembly for a ship, comprising a steering means (20) connected to the outlet side of a pump (6), for steering the driving water jet, said steering means including two flaps (18, 19) for reversing the driving water jet, said flaps being provided so that an actuator (21) pivots the one flap (18) down and around a bearing (23) across the water jet at the same time as link arms (22), which are journalled between the front edges .of the flap (18) and flap (19), swing the second flap (19) around the bearing (24) whereby the rear portion of the second (19) flap is raised towards the water jet and encounters the inner side of the first flap in such a way that both flaps (18, 19) jointly shut off the passage rearwards, diverting the water jet obliquely downwards/forwards, c h a r a c t e r i z e d in that the flap (18, 19) bearing points on said steering means (20) together with the link arm (22) bearing points on the flaps (18, 19) provide an equilibrium of forces between the actuator (21) pressure on the first flap (18) and the water jet pressure on both flaps (18, 19) under the condition that a reduction of the pressure on the actuator (21) results in the flap (18) being swung upwards by the water pressure.

Inventors: LUNDBERG NILS ERIK, TOERNEMAN GERARD, LUNDBERG, NILS, ERIK, TOERNEMAN, GERARD
Applicants: MARINE JET POWER AB
Application year: 1988
Main classification: B63H11
IPC codes: B63H11