FR2523921A1 - GEAR HOUSING FOR A MARINE PROPULSION DEVICE - Google Patents

Abstract

THE MARINE PROPULSION DEVICE INCLUDES A LOWER GROUP 12 WHICH INCLUDES A GEAR HOUSING 16, NORMALLY SUBMERSIBLE IN WATER, AGENCY TO EVACUATE THE ENGINE EXHAUST GAS THROUGH THE HUB 54 OF THE PROPELLER 23. THE END LEADING OF THE GEAR HOUSING HAS A TAPERED NOSE AND THE REAR END OF THE GEAR HOUSING HAS A GENERAL CIRCULAR SHAPE SECTION AND ENDS WITH A REAR EDGE IN THE VERTICAL ASSEMBLY 21 LOCATED IN FRONT OF THE PROPELLER HUB 54. THE OUTSIDE DIAMETER OF THE REAR END 20 OF THE GEAR HOUSING IS SIGNIFICANTLY LARGER THAN THE OUTSIDE DIAMETER OF THE PROPELLER HUB 54 TO HOUSE WITH THIS A ABRUPT RETRACTABLE GRADIN, AND THE OUTSIDE SURFACE OF THE GEAR HOUSING REINFORCED. 'EXTERIOR FROM NOSE 18 TO REAR EDGE 21.IN ONE EMBODIMENT, THE NOSE EXTENDS FORWARD BEYOND LEADING EDGE 17 OF THE DRIVE SHAFT.

Description

The present invention relates to marine propulsion devices, such as

  as outboard motors and stern power units and, more particularly, to marine propulsion devices comprising an exhaust by the hub and means for increasing the propeller thrust. According to another aspect, the invention relates to such marine propulsion devices comprising means for controlling the

hydrodynamic stall.

  Outboard motors and stern motor groups may include an exhaust system called by the hub comprising a massage of engine exhaust gas which

  extends through the drive shaft housing, the gear housing

  swimming and an internal annular passage to the propeller hub.

  We are constantly looking for ways to increase

  the thrust provided by the propeller of such propulsion devices

marine sion.

  At high speeds, there may be cavitation and separation of the current along the outer surface of the gear case, which causes air to reach the low pressure side of the propeller. When large amounts of air are present, a sudden loss may appear

  thrust and load capacity of the propeller, current state

  said hydrodynamic stall.

  Attention is drawn to the following US patents Holder patent number publication date Linthwaite 2,111,325 March 15, 1938 Irgens 2,564,903 August 21, 1951 Strang 2,791,196 May 7, 1957 Shimanckas 3,310,021 March 21, 1967

Shimanckas 3,467,051 Sept 16, 1969.

  Kiekhaefer 3,492,966 Feb 3, 1970 Granholm 3,799,103 March 26, 1974 rlapes et al 4,295,835 Oct 20, 1981 Attention is also drawn to a patent application filed in the United States of America in the name of HENRICH and dealing with

marine gear housing.

  The invention provides a marine propulsion device comprising a lower group which has an exhaust gas passage terminated by an O 'ceô ci Fement, N through rotary propeller shaft /' orifice of dchal 'e a propeller mounted on the 'propeller shaft to rotate ojointly with him and comprisingh a hub which has an outer surface of generally circular shape as well as a -assassement of exhaust gases by which the exhaust gases escape backwards in water, and a gear case in which the propeller shaft revolves The gear case has

  a leading end which has a tapered nose and a straight end

  ending with a rear edge in the vertical assembly if

  killed in front of the propeller hub The outside diameter of the section

  Less rear end of the gear housing is significantly greater than the outer diameter of the propeller hub to define with it a steep step, and the outer surface of the

  gear casing swells substantially continuously, radiates

  outwards from the nose to the rear edge

  In one embodiment, the tapered nose of the gear housing

  ge extends some distance forward beyond the leading edge of the drive shaft housing to make the outer surface of the gear case sharper, which reduces cavitation and separation of current along the area

  outside the gear case at high speed.

  The object of the present invention is to provide a device

  marine propulsion system: which includes an exhaust system through the hub and a simple means for increasing the propeller thrust; which has an exhaust system through the hub

  and a simple means for controlling the hydrodyna- dropout

mique;

  which has an outer surface gear case

  higher configured so that pressure conditions favoring increased propeller thrust appear in the vicinity of the propeller; which has a gear case configured to reduce cavitation and detachment of the flowing current

  the outer surface at high speeds.

  Other characteristics, aspects and advantages of the

  vention will appear to the technician on review of the description

  tion detailed below, drawing and claims

attached. In the attached drawing

  Figure 1 is a detail view with section and cutaway

  ment of the lower group of a marine propulsion device comprising various characteristics according to the invention; Figure 2 is a detail view of the lower group of a marine propulsion device comprising a casing

  structure gear according to a variant.

  Before describing in detail at least one of the realizations

  tions of the invention, it should be noted that the invention is not li-

  limited in its application to structural details and

  component arrangements indicated in the description below

  below or shown in the drawing The invention lends itself to various other embodiments In addition, the terminology adopted here is chosen for descriptive purposes and has no

limiting character.

  Figure 1 is a detail view of a marine propulsion device 10, which may be either a power unit of

  stern, or an outboard motor, comprising a group of prop

  drive or lower 12 which includes a drive shaft housing

  14 and a gear case 16 normally immersed in water.

  The driving shaft casing 14 has a leading edge 17 The gear housing 16 has a leading end formed by a tapered nose 18, a torpedo-shaped outer surface 19 and a rear end section 20 with a section of

general circular shape.

  In the gear case 16, a propeller shaft 22 is journalled carrying a propeller 23 located behind it.

  the drive shaft housing 14 extends transversely to the rear

  propeller bre 22, a swiveling drive shaft 24, coupled by its upper end to an internal combustion engine (not shown) and by its lower end to the shaft

  propeller 22 via coupling or transmission

  Current type reverse gear 26 From the gear housing 16, a vertical fin or heel goes down

keel 28.

  The drive shaft housing 14 is traversed by an exhaust gas passage 30 terminated by an outlet orifice

  exhaust gas 32 at the rear end 20 of the intake housing

shot 16.

  The propeller shaft 22 has a rear section 36 which extends rearwards beyond the gear case 16 and a front section 38 which passes through the exhaust orifice 32 and pivots inside the gear case 16 thanks to a

  bearing retainer 40 suitably fixed internally

  inside of the gear case 16 The bearing retainer 40 has a central hub section 42 which carries a rolling bearing 44 and a lubricant seal

  46 The bearing retainer also includes a

  annular outer cap 48 which bears against the inside of the gear housing 16 and a series of spokes or ribs 50 directed radially and angularly spaced connecting one to

  the other the hub section 42 and the sleeve 48 The openings

  res 52 defined between the ribs 50 are part of the passage

engine exhaust 30.

  The propeller 23 comprises a hollow hub 54 whose outer surface 55 is of generally circular shape and carries a

  series of blades 56 The propeller 23 also has an internal sleeve

  laugher 58 which is connected to the hub 54 by a series of radially and angularly spaced directed ribs 60 The sleeve 58 is mounted on the rear section 36 of the propeller shaft 20 to rotate jointly with the latter, for example by means of splines 62 The openings 64 separating the ribs 60 define with the interior of the hub 54 a gas exhaust passage or conduit 66 which extends axially through the hub 54 The conduit 66 has an inlet communication with the orifice exhaust 32 and an outlet, located behind

  the propeller blades 56, through which the exhaust gases

  ment are discharged into the water. Such an exhaust system for the gases from the engine is commonly referred to as "through the hub" exhaust.

  The thrust generated by the helicopter is increased

  ce 23 by choosing the outside diameter of the circular rear end section 20 of the gear case 16 so that it is substantially greater than the outside diameter of the propeller hub 54, by arranging the rear edge 21 of the gear case 16 generally vertically so that there is a steep re-entrant step between the rear end section of the gear case 16 and the propeller hub 54, and by configuring the outer surface 19 of the gear case 16

  so that it swells substantially continuously, radial-

  outwards, from the nose 18 to the rear edge 21 This particular arrangement establishes in the vicinity of the propeller blades 56 pressure conditions which are favorable to the increase in the characteristics of energy transmission

of the propeller 23.

  According to the variant illustrated in Figure 2, the nose effi-

  the 70 of the gear housing 72 protrudes some distance forward the leading edge 17 of the drive shaft housing 14 to make the outer surface 74 of the gear housing 72 more pointed As in the embodiment illustrated in FIG. 1 , the outside diameter of the rear terminal section

  76 of the gear case 72 is substantially higher than

  lower than the outside diameter of the propeller hub 54, the rear edge

  78 of gear case 72 is generally vertical

  to provide a steep re-entering shelf between the rear end

  era 76 of the gear case and the propeller hub 54, and the

  outer surface 74 of the gear housing 72 swells

  continuously, radially outward between the

  nose 70 and rear edge 78 This arrangement, in addition to increasing

  lies in the propeller thrust, reduces the tendency to cavitate

  tion and separation of the current along the outer surface

  re of gear case 72 at high speeds, which minimizes

  is the amount of air, present in the vicinity of the low side

  propeller 56, capable of causing a hydrodyna-

  mique. RE VEDCA Ti Oh S 1 Marine propulsion device comprising a lower group (12) having an isch gas passage (30) terminated by an exhaust orifice (32), a rotating propeller shaft (22) passing through this exhaust orifice, a propeller (23) normally immersed in water and mounted on the propeller shaft to rotate jointly with it, this propeller comprising a hub (54) which has an outer surface of generally circular shape (55) and an exhaust gas passageway (66) which has a communicating inlet

  with said exhaust port (32) and an outlet communicating

  as for water, and a gear housing (16; 72) in which the propeller shaft journals, characterized in that this gear housing having a front end which has a tapered nose (18; 70) , a rear end (20; 76) of generally circular cross section whose outside diameter is substantially greater than the outside diameter of said propeller hub (54) and which ends in a rear edge (21; 78) overall vertical located in the propeller hub (54), and an outer surface (19; 74) swollen substantially continuously, radially outward, from said nose to said

rear edge.

  2 marine propulsion device according to claim 1, characterized in that said lower group (12) comprises a driving shaft housing (14) having a leading edge (17) and in that said nose (70) of the housing gear (72), extends towards

  the front beyond said leading edge of the driving shaft housing.