Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
  • B63H—MARINE PROPULSION OR STEERING
  • B63H1/00—Propulsive elements directly acting on water
  • B63H1/02—Propulsive elements directly acting on water of rotary type
  • B63H1/12—Propulsive elements directly acting on water of rotary type with rotation axis substantially in propulsive direction
  • B63H1/14—Propellers
  • B63H1/20—Hubs; Blade connections
  • B63H1/22—Hubs; Blade connections the blades being foldable
  • B63H1/24—Hubs; Blade connections the blades being foldable automatically foldable or unfoldable

Definitions

• the invention relates to a folding propeller to be fitted on a propeller shaft of a vessel and comprising a hub with blades mounted in the hub so as to be pivotal between a folded and an unfolded position, where the blades form an angle to the axis of rotation of approx. 90°, and where the blades at the end in the hub are designed as a toothed wheel having its centre in the axis of oscillation of the blades, and whose teeth mesh with teeth in a toothed bar being axially displaceable inside the hub when the blades fold or unfold.
• Propellers of this type are particularly used in connection with inboard engine installations in sailing boats, a so-called auxiliary engine installation.
• a fixed screw or propeller fitted on such an installation will offer considerable resistance against the propulsion of the boat when the engine is stopped and the boat is under sail, no matter whether the propeller stands still or rotates freely against the water current.
• the centrifugal force When the engine is moved, the centrifugal force will swing out the blades and, depending on speed of rotation, sea and current, the blades will assume a position in relation to the axis of rotation of between 70° and 90°.
• the water pressure will ensure that the blades assume the correct position when sailing forward, whereas only the centrifugal force keeps the blades unfolded when reversing.
• Hitherto known folding propellers are provided with two blades mounted diametrically in the hub.
• a two-bladed propeller has an effective surface of approx. 20% of the area touched by the blades per rotation, and therefore a two-bladed propeller is inefficient at comparatively low speeds of rotation, whereas the efficiency improves in connection with fast engines.
• a folding propeller with three or more blades all being synchronized is hereby obtained in a surprisingly simple manner.
• the propeller surface can be increased by the extra blade or blades whereby efficiency at low speeds of rotation is considerably improved, and the occurrence of vibrations is considerably reduced. This adds up to the best possible operational economy and performance.
• the toothed bar As dealt with in claim 2, as a body of revolution whose tooth profile is shaped as annu ⁇ lar teeth, the production can be simplified considerably, and also the toothed bar may form part of a hub with an arbitrary number of blades.
• fig. 1 shows an end view of a three-bladed folding pro ⁇ peller
• fig. 2 shows a section through the propeller seen in the direction II-II in fig. 1, and
• fig. 3 shows an end view of a second embodiment of a three-bladed propeller.
• the drawing shows an example of two different embodiments of a three-bladed folding propeller.
• Both embodiments comprise a hub 4, vide fig. 2, which at its one end is provided with a tapered bore 5 and at its other end with a cylindrical bore 7 whose diameter is larger than that of the bore 5 for the formation of a re ⁇ cess 6 at the end of the bore 5.
• the hub 4 To the rear the hub 4 is provided with an end piece 11 which is shaped as a ring having a central bore 13 extend ⁇ ing end to end of the bore 7 in the hub 4.
• the end piece 11 is provided with three radially extending grooves or channels 14. These grooves 14 do not extend through the end piece 11, and consequently, the end piece 11 forms a unit which by means of screws 12 can be secured to the hub 4, as shown in the drawing.
• An axially movably toothed bar 8 is inserted in the bore 7, 13, which bar at its rear end is provided with teeth.
• the member is cylindrical for the formation of a sliding piece 9 being displaceable in the bore 7 in the hub 4.
• the member has an internal bore 10 in order to make room for the nut 3 thus permitting the toothed bar 8 to be displaced axially in the hub 4.
• each groove 14 of the end piece 11 there is mounted a propeller blade 18.
• a propeller blade 18 In the shown example there are three propeller blades.
• Each of these blades 18 is at the end provided with an intermediate piece 17 in the form of a flat part provided with a centrally extending transverse hole for a shaft 15 extending across each groove 14, as im- plied by dashed lines in figs. 1 and 3.
• the shafts 15 are locked in the end piece 11 in a generally known manner.
• the intermediate piece 17 forms a stop 20 to ⁇ wards the bottom of the groove 14 in such a manner that the course of motion of the blades 18 is limited to a position where the blades form an angle to the centre axis of about 90", as shown by the fully drawn line in fig. 2.
• resilient shock ab ⁇ sorbers 19 can be arranged in the bottom of the grooves where the stop 20 hits.
• teeth 16 are provided for the formation of a tooth section at the end edge of the intermediate piece 17, which teeth 16 can interact with the cogging on the toothed bar 8 in that the teeth 16 describe a circle having its centre in -the centre axis of the shaft 15. The extent of this tooth section is so that the blades 18 can assume any position from lying folded around the centre axis, as implied by dashed line in fig. 2, to being completely unfolded, as shown in fig. 2.
• the toothed bar 8 can have different cross sectional shapes.
• Fig. 1 shows a toothed bar having a circular cross section where the teeth are shaped as rings. This gives a precise control of the toothed bar in the bore 7, 13 so that the axial movement becomes even and non-backlash. Moreover, wear of the teeth is distributed across a larger tooth width, and the toothed bar can be applied in hubs with a blade number being different from three.
• Fig. 3 shows an example of a second embodiment where the cross section is an equilateral triangle. This means that the teeth consist of even coggings providing a stable per- formance.
• a four-bladed folding propeller will have a square cross section.
• the blades When the propeller shaft 1 stands still, the blades will assume the folded position where the toothed bar 8 is in- serted in the hub 4. When the shaft starts rotating, the centrifugal force will swing the blades 18 outwards and since all the blades are in uniform mesh with the toothed bar 8, the motion of the blades will be synchronous so that they all will assume the same position in relation to the centre line. Depending on flow conditions and the speed of rotation, the blades will assume the positions during operation which give the maximum effect.
• the folding propeller can be made of any suited material such as bronze and stainless steel. It can be embodied in any required dimension and thus be adapted to any engine installation.

Landscapes

• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Combustion & Propulsion (AREA)
• Mechanical Engineering (AREA)
• Ocean & Marine Engineering (AREA)
• Structures Of Non-Positive Displacement Pumps (AREA)

Applications Claiming Priority (2)

Publications (1)

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ID=8143263

Family Applications (1)

Country Status (4)

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• 1989
  • 1989-11-07 DK DK553389A patent/DK553389A/da not_active Application Discontinuation
• 1990
  • 1990-11-07 EP EP19900917034 patent/EP0499617A1/de not_active Withdrawn
  • 1990-11-07 WO PCT/DK1990/000286 patent/WO1991006468A1/en not_active Application Discontinuation
  • 1990-11-07 AU AU67410/90A patent/AU6741090A/en not_active Abandoned

Non-Patent Citations (1)

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