US2921635A

US2921635A - Reversible propeller

Info

Publication number: US2921635A
Application number: US649391A
Authority: US
Inventors: Arthur W Wanzer
Original assignee: Murray & Tregurtha Inc
Current assignee: Murray & Tregurtha Inc
Priority date: 1957-03-29
Filing date: 1957-03-29
Publication date: 1960-01-19
Anticipated expiration: 1977-01-19

Description

Jan. 19, 1960 A. w. WANZER REVERSIBLE PROPELLER Filed March 29, 1957 jaw/22%? i I I J United States Patent 2,921,635 REVERSIBLE PROPELLER Application March 29, 1957, Serial No. 649,391

1 Claim. (Cl. 170-165) "This invention relates to an improved reversible pro- 'peller. 7

It is a principal object of the invention to provide a novel and improved dual propeller unit which is well :adapted to operate with a maximum efiiciency for either direction of rotation of the propeller unit. 7

More specifically it is an object of the invention to ,provide dual propellers rotatable as a unit in either direction having blades with oppositely disposed propelling surfaces constructed and arranged so that for either direction of rotation the leading propeller will ope'rate efiiciently to produce a maximum thrust, and the trailing propeller operating in the quick water produced by the leading propeller will produce a substantial additional increment of thrust in the same direction. In carrying out the invention the blades of one propeller are of the same hand and are constructed each with two substantially flat oppositely disposed propelling surfaces which are inclined with relation to one another so that the blade tapers from a relatively thick section at one edge to a thin section at theother edge of the blade. The second propeller spaced from the first propeller and mounted on a common axis to turn as a unit therewith is in every respect identical with the first propeller, except that the second propeller is mounted so that it faces in the opposite direction with respect to the common axis. With the two propellers in position, it will be noted that the inwardly facing surfaces of the two propellers are of the same hand and are pitched at the same angle with relation to the common axis. Foreither direction of rotation the inwardly facing surfaces of the blades of the leading propeller provide the principal driving thrust of the dual propeller unit. The outwardly facing surfaces of the two propellers are also of the same hand and have the same higher pitch so that the trailing propeller of the pair for either direction of rotation of the dual propeller unit will provide an additional increment of thrust for the propeller unit in the direction of drive of the unit.

It is a further object of the invention to provide an improved propeller particularly adapted for use in the dual propeller unit herein disclosed which will develop the same maximum thrust during rotation of the propeller unit in either direction.

With the above and other objects in View as may hereinafter appear the several features of the invention consist also in the devices, combinations, and arrangement of parts hereinafter described and claimed, which, together with the advantages to be obtained thereby, will be readily understood by one skilled in the art from the following description taken in connection with the accompanying drawings in which:

Fig. 1 is a somewhat fragmentary view of an outboard dual propeller unit driven from a vertical shaft and illustrating in a preferred form the several features of the invention;

2,921,635 Patented. an. 19,1960

Fig. 2 is a perspective view of the dual of Fig. 1; a

Figs. 3 and 4 are sections taken respectively on lines 3-3 and 4-4 of Fig. 2;

Fig. 3 being a section of a blade of the left hand propeller; and

Fig. 4 being a corresponding section of a blade of the right hand propeller;

Fig. 5 is a diagrammatic view of the disclosure of Figs. 3 and 4 in whichthe dual propeller unit is shown as being driven in one direction, and in which the angle of the relatively inclined surfaces ofthe blades as shown in section has been exaggerated for purposes of illustration; and i Fig. 6 is a view similar to Fig. 5 in which the propeller assembly is being driven in the opposite direction from the direction of drive in Fig. 5.

The invention is herein disclosed in a preferred form as embodied in-an outboard dual propeller unit which comprises a horizontally disposed propeller shaft 10 mounted in suitable bearings, not shown, in a downwardly extending housing 12and two

propellers

14 and 16 mounted respectively on each end of the shaft 10*. The

propellers

14 and 16 andshaft 10 are adapted to be driven in either direction from any suitable reversible source of power not shown, through a vertical drive shaft 18 which is housed in a vertical extension of the housing 12 and is connected with the propeller shaft 10 by means of bevel gears 20, 22.

The

propellers

14 and 16 areso constructed and arranged that for one direction ofdrive the dual propeller unit one propeller of the pair will act as the primary propelling unit, while the second propeller acts as an auxiliary propelling element, and for the other direction of the drive the second propeller of the pair will act as the primary propelling element and the first propeller becomes an auxiliary propelling element. The dual propeller unit is arranged to deliver exactly the same amount of power for either direction of drive.

Referring to the drawings, the propeller 16 is formed with three blades which are of the same hand. Each blade is formed With two oppositely disposed flat surfaces which are inclined with relation to one another and are spaced apart along one edge to provide a thick blade section as indicated at 26 which tapers off to a relatively thin section at the opposite edge as indicated at 28. The propeller 16 is constructed and arranged to be driven in a clockwise direction, as shown in Fig. 2 in the diagrammatic Fig. 5, to produce a thrust to the left and a corresponding direction of travel to the right. The surface 30 of each blade of the propeller 16 which faces inwardly toward the propeller 14 has a pitch angle which is adjusted to generate a maximum thrust when the propeller 16 is in the lead position working in still Water.

It will be noted from Fig. 4 for example that the right hand or outside surface of each blade of the propeller 16 as indicated at 32 is a flat or substantially flat surface which is of the same hand and which has a substantially greater pitch angle than the primary driving surface 30 of the propeller 16. The sectional Fig. 4 indicates that each of the blades of the propeller 16 is shaped to provide an airfoil type cross section which is substantially thicker at the leading edge 26 and tapers to a relatively thin section 28 at the trailing edge of the blade.

The propeller 14 is identical in construction 'with the propeller 16, but is mounted on the common axis. to face in the opposite direction from the propeller 16. A section through one of the blades of propeller 14, specifically shown in Fig. 3, discloses that the two oppositely disposed substantially flat surfaces 40 and 42 of each blade are disposed to form, along the lower or leading edge of propeller unit the blade, a thick section 44 which tapers gradually to a thinsection 46 at the upper or trailing edge of the blade. It 'will'beunderstood that each'of the blades of the propeller 14 is formed in an identical manner. Propeller 14 when driven in a counterclockwise direction as shown in Fig. 2 and asdllus'tfatbd 'in the diagrammatic" lfig. 6 produces a thrust to the right and a corresponding di rection'of travel'to the 'left. l

The relationship of the inner and outer propelling surfaces of the blades of the'two propellers willbe readily apparent from a consideration of Figs. 3 to 6 inclusive of the drawing. The inwardly facing surface 30 of the propeller 16, and surface 40 of the propeller 14 when placed in position on the propeller shaft 10' are of the same hand and have the same pitch angle 'with'relation to the rotational axis provided by the propeller shaft 19. When the unit is driven in a clockwise direction, the principal thrust load is taken by the inwardly facing surfaces 30 of the blades of thepropcller 16 which occupies the leading position for this direction of rotation of the unit. The propeller 14 is driven in a reverse direction. inwardly facing surface 40 of the propeller 14 is therefore inoperative. Whenever the dualpropeller unit is driven in a counterclockwise direction, the principal thrust load is taken by the inwardly facing surfaces 40 ofthe blades of propeller 14 and the inwardly facing surfaces 30 of the blades of propeller 16 are inoperative. As best shown in the somewhat diagrammatic views Figs. and 6 the outwardly facing surfaces 32 of the blades of propeller 16 and the outwardly facing surfaces 42 of the blades of propeller 14 have the same hand as the inwardly facing

surfaces

30 and 40 above described and are at a substantially steeper angle with relation to the axis of rotation provided by the propeller shaft 10. For a clockwise direction of rotation of the propeller unit the trailing propeller 14 will be traveling in the quick water provided by the operation of the leading propeller 16. The more steeply pitched outwardly facing-surfaces 42 of the blades of propeller 14 will develop an additional thrust in the direction of travel of the propeller unit to the right. Assuming a counterclockwise direction of rotation of the propeller unit in which the principal thrust is developed by the inwardly facing propelling surfaces 40 of the blades of propeller 14, the propeller 16 will be traveling in a reverse direction so that the outwardly facing surface 32 of each propeller blade of propeller 16, being more steeply angled than the thrust producing surfaces '40, will tend to develop some additional thrust in the quick water produced by the action of the propeller 14. A feature of the illustrated construction which is believed to contribute substantially to the eflicient utilization of the trailing propeller of the dual propeller unit for each direction of rotation of the unit consists in the use'ofpropeller blades having substantially the air foil cross section.

Each individual propeller may be regarded as a highly efiicient propulsion element when driven in a forward direction to load the lower pitched working surface of the propeller. The use of theairfoil section, utilizing two fiat or substantially flatpropelling surfaces inclined with relation to one another, is of especial value, however,in that'it-permits either propeller in turn to be-driven in what is in effect a reverse direction when in the trailing position and at the same time to pickup a substantial increment of thrust from the quick water developed by the thrust of the leading propeller. i

The invention having been-described what is claimed is:

A dual propeller unit which comprises with a supporting structure, a pair of propellers supported from said structure in spaced-relation to one another to turn on a common axis, driving means connected with said propellers to drive the same as a unit reversibly in either direction, each propeller having a hub and blade portions projecting outwardly from the hub formed with oppositely disposed propelling surfaces; those surfaces of the blades of the two. propellers in facing relation being of the same hand and having the same pitch angle with relation to said common axis, said pitch angle being adjusted for efficient operation of the blades of the leading propeller of the pair foreither direction of rotation of the 'dual propeller unit, and the opposite outwardly facing surfaces of the blades of the two propellers being of the same hand and having an identical substantially higher pitch angle with relation to said' common axis,' said lat' ter pitch angle being adjusted to produce from the 'trail ing propeller an additional increment of thrustin the quick water produced by the leading propeller, the lead ing edge of each blade of the leading propeller for either one direction of rotation of the dual propeller unit being formed with a relatively thick section which tapers gradually to a thin section at the trailing edge of said blade, and the leading edge of each blade of the trailing propeller for the same one direction of rotation of the dual propeller unit being formed with a thin section which widens gradually to a thick section at the trailing 5 edge of said blade.