Variable-pitch mechanism of a propeller

Abstract: A variable-pitch mechanism, for use in an airplane, a ship, or the like, for adjusting the pitch of a plurality of blades (8) of a propeller (4) in which attachment shafts (9) of a plurality of radial blades of a propeller are rotatably mounted on a tubular hub (3) which can be driven by a drive shaft (1), and eccentric pins (16) projecting from ends of the attachment shafts are held in an annular groove (15) defined in the outer periphery of an adjusting ring (14) which is disposed concentrically in the hub and axially movable. The attachment shafts can be turned about their own axes through the eccentric pins in response to axial displacement of the adjusting ring for adjusting the pitch of the propeller blades.

Description: The field of the present invention relates to a variable-pitch mechanism for use in an airplane, a ship, or the like, and more particularly to a mechanism for adjusting the pitch of a plurality of blades of a propeller. Heretofore there have been proposed various variable-pitch mechanisms employing a rack and pinion, a cam, a link, and the like, but the conventional mechanisms have been costly since they are complex in structure and difficult to machine. US-A-3567340 discloses a variable pitch mechanism in which the pitch of the propeller blades is adjusted in response to the axial movement of a rotationally fixed adjustment ring arranged in the propeller hub and having an annular groove on its outer surface for engagement with pins eccentrically located on the ends of attachment shafts of the blades. It is an object of the present invention to provide a variable-pitch mechanism which is of a simple structure and can be machined with ease. From a first aspect, the invention provides a variable-pitch mechanism of a propeller, wherein attachment shafts of a plurality of radial blades of the propeller are rotatably mounted on a tubular hub which can be driven by a drive shaft, and eccentric pins projecting from ends of the attachment shafts are held in an annular groove defined in the outer periphery of an adjusting ring which is disposed concentrically in the hub and is axially movable, the attachment shafts being turnable about their own axes through the eccentric pins in response to axial displacement of the adjusting ring, characterised in that said adjusting ring is rotatably mounted on an axially movable cylinder through a bearing, and is rotatable with the hub. It also extends to a variable-pitch mechanism of a propeller having a plurality of radial blades with attachment shafts rotatably mounted on a tubular hub driven to drive the propeller, eccentrically located means provided on each attachment shaft, an adjusting ring positioned within said tubular hub and axially movable with respect thereto, an annular groove defined in the adjusting ring, said eccentrically located means engaging said annular groove, and means for selectively moving said adjusting ring in an axial direction for causing the attachment shafts to turn about their own axes through the interengagement of the eccentrically located means and annular groove to adjust the pitch of the blades, characterised in that said adjusting ring is rotatably mounted on an axially movable cylinder through a bearing and is rotatable with said hub, and in that said hub is rotatably supported on a stationary support cylinder through bearings. Thus in accordance with the invention, and in contradistinction to the above mentioned prior art, the adjusting ring rotates with the hub and is rotatably mounted on an axially movable cylinder through bearings. According to a preferred feature of the present invention, one side wall of the annular groove has slots defined therein for allowing the eccentric pins to pass therethrough into the annular groove, and the adjusting ring has a retainer means for holding the eccentric pins in the annular grooves in positions displaced from the slots. Since the eccentric pins on the respective attachment shafts can be guided into the annular groove through the respective slots in the side wall of the annular groove, the variable-pitch mechanism can be assembled with ease. Inasmuch as the eccentric pins are normally held in positions displaced from the slots by the retainer means, the eccentric pins are reliably prevented from being removed from the annular groove. According to a further preferred feature of the present invention, the eccentric pins engage in the annular groove through sliders in which the eccentric pins are rotatably fitted. As such, the eccentric pins can smoothly be driven by the adjusting ring in response to relative rotation of the eccentric pins and the sliders. According to another preferred feature of the present invention, the sliders are each of a square cross section held in face-to-face contact with opposite side wall surfaces defining the annular groove. As such, the sliders are held against the side wall surfaces of the annular groove through wide contact areas, and hence the pressure applied to the contact areas is low. An embodiment of the invention will now be described by way of example and with reference to the accompanying drawings, in which:- FIG. 1 is a vertical cross-sectional view of a rotating propeller propulsion system with a variable-pitch mechanism according to the present invention; FIG. 1A is a detailed view of the variable-pitch mechanism portion of the system of FIG. 1; FIG. 2 is a cross-sectional view of the system in FIG. 1 taken along line II-II of FIG. 1; and FIG. 3 is an enlarged cross-sectional view taken along line III-III of FIG. 1. Referring to the drawings, a rotating propeller propulsion system of an airplane is shown in FIGS. 1, 1A and 2, in which output power from a drive shaft 1 of a gas turbine engine or the like is transmitted through a speed reducer gear mechanism 2 to a tubular hub 3 to drive the hub 3 to rotate a propeller 4. The hub 3 is supported by a pair of bearings 6, 6′ on the outer periphery of a support cylinder 5 joined to a supporting structural body (not shown) of the engine and surrounding the drive shaft 1. An annular array of support tubes 7 is fixedly mounted on the hub 3, with the support tubes 7 extending radially through the peripheral wall of the hub 3. The propeller 4 comprises a plurality of blades 8 having respective attachment shafts 9 rotatably fitted respectively in the support tubes 7. Thrust bearings 10 are interposed between flanges 9a on the inner ends of the attachment shafts 9 and the support tubes 7. Therefore, when the hub 3 is driven to rotate around the support cylinder 5 in one direction, the blades 8, i.e., the propeller can be rotated in the same direction through the support tubes 7 and shafts 9. The pitch of the blades 8 can be varied by turning the attachment shafts 9 thereof through a variable-pitch mechanism 11 which is constructed as follows. The variable-pitch mechanism 11 comprises a movable cylinder 12 disposed between the bearings 6, 6′ in surrounding relation to the support cylinder 5 and reciprocally operable in the axial direction, and an adjusting ring 14 surrounding the movable cylinder 12 and coupled thereto through a bearing 13. The adjusting ring 14 is disposed concentrically in the hub 3 and is axially immovable, but rotatable with respect to the movable cylinder 12. The adjusting ring 14 has an annular groove 15 defined in an outer peripheral surface thereof. Eccentric pins 16 projecting respectively from the radially inner ends of the flanges 9a of the attachment shafts 9 are slidably held in the annular groove 15 through sliders 17 mounted on the respective eccentric pins 16. Each of the sliders 17 is of a square cross section having sides held in face-to-face contact with opposite surfaces defining the annular groove 15 (see FIG. 3). The sliders 17 have pin holes 18 defined centrally therein with the eccentric pins 16 being rotatably fitted respectively in the pin holes 18. The eccentric pins 16 have end flanges 16a of a larger diameter for preventing the sliders 17 from being dislodged therefrom. The sliders 17 can simultaneously be guided into the annular groove 15 through a number of respective slots 19 defined in a rear side wall of ring 14 which defines the annular groove 15. Retainer pins 20 fixed as retainer means centrally on the respective attachment shafts 9 are fitted respectively in positioning holes 21 defined in the adjusting ring 14 for retaining the sliders 17 in the annular groove 15 in positions displaced from the respective slots 19. The positioning holes 21 are in the form of oblong holes with their longer or major axes directed axially of the adjusting ring 14 to allow the adjusting ring 14 to move axially without being obstructed by the retainer pins 20. The movable cylinder 12 is slidably fitted over a pair of front and rear fixed pistons 22, 23 formed on the outer periphery of the support cylinder 5. The movable cylinder 12 has a partition 24 on a central portion of an inner wall surface thereof. The fixed cylinders 22, 23 and the partition 24 positioned therebetween jointly define front and rear oil chambers 25, 26 around the support cylinder 5. The peripheral wall of the support cylinder 5 has first and second oil passages 27, 28 defined therein and communicating with the first and second oil chambers 25, 26, respectively, for supplying the first and second oil chambers 25, 26 with oil under pressure from an oil pressure source through a control valve (not shown). The operation of the variable-pitch mechanism according to this embodiment will now be described. FIGS. 1 and 3 show that the blades 8 are in a medium pitch condition. In this condition, the partition 24 of the movable cylinder 12 is held in an intermediate position centrally between the front and rear pistons 22, 23. The eccentric pins 16 are positioned rearwardly of the respective attachment shafts 9 and are spaced at about 45° from the axis A of the adjusting ring 14 in the direction (indicated by the arrow B) in which the propeller 4 rotates. The non-illustrated control valve is now operated to release oil pressure from the rear oil chamber 26 and supply oil pressure into the front oil chamber 25, thus moving the movable cylinder 12 with the adjusting ring 14 in the rearward direction (to the right in FIG. 1). Since the adjusting ring 14 then displaces all the eccentric pins 16 rearwardly and laterally through the sliders 17 slidably engaging in the common annular groove 15, the attachment shafts 9 are rotated about their own axes to angularly displace all the blades 8 for a lower pitch. Conversely, when the front oil chamber 25 is released from oil pressure and the rear oil chamber 26 is supplied with oil pressure, the movable cylinder 12 and the adjusting ring 14 are moved forwardly (to the left in FIG. 1) to cause the sliders 17 to drive the eccentric pins 16 forwardly and laterally to turn the attachment shafts 9 about their own axes. All the blades 8 are now angularly displaced for a higher pitch. During such pitch adjustment, the sliders 17 slide in the annular groove 15, and the eccentric pins 16 are rotated with respect to the sliders 17. Therefore, the eccentric pins 16 are smoothly driven in response to axial movement of the adjusting ring 14. Since the sliders 17 of a square cross section are held against the side wall surfaces of the annular groove 15 through wide contact areas, the pressure applied to the contact areas of the sliders 17 is low and hence wear on the sliders 17 is small, making the sliders 17 highly durable. While the propeller 4 is being rotated by the hub 3, the adjusting ring 14 is rotated in unison with the propeller 4 by the retainer pins 20. Inasmuch as the adjusting ring 14 is coupled to the movable cylinder 12 only through the bearing 13, the movable cylinder 12 is not rotated upon the rotation of the propeller 4. Certain of the advantages achieved by the present invention, at least in its preferred embodiments, will now be described. It is a first advantage that the attachment shafts of a plurality of radial blades of a propeller are rotatably mounted on a tubular hub which can be driven by a drive shaft, and eccentric pins projecting from ends of the attachment shafts are held in an annular groove defined in the outer periphery of an adjusting ring which is disposed concentrically in the hub and axially movable. The attachment shafts can be turned about their own axes through the eccentric pins in response to axial displacement of the adjusting ring. Therefore, the pitch of all the propeller blades can simultaneously be adjusted by axially moving the adjusting ring. Since the annular groove of the adjusting ring is of a simple shape with only the eccentric pins on the blade attachment shafts slidably engaging in the annular groove, the variable-pitch mechanism is simple in structure, can be machined with ease, and is of a low cost. It is a second advantage that one side wall of the annular groove has slots defined therein for allowing the eccentric pins to pass therethrough into the annular groove, and the adjusting ring has a retainer means for holding the eccentric pins in the annular grooves in positions displaced from the slots. Therefore, the eccentric pins can be placed in the annular groove of the adjusting ring while the eccentric pins are being mounted on the attachment shafts. Consequently, the variable-pitch mechanism can be assembled with ease. It is a third advantage that the eccentric pins engage in the annular groove through sliders in which the eccentric pins are rotatably fitted, so that the eccentric pins can smoothly be driven by the adjusting ring for reliable operation. It is a fourth advantage that the sliders are each of a square cross section held in face-to-face contact with opposite side wall surfaces defining the annular groove. Consequently, the pressure applied to contact areas between the slider and the side wall surfaces of the annular groove is kept at a lower level, reducing wear on the sliders and making the sliders durable.

Claims: A variable-pitch mechanism of a propeller (4), wherein attachment shafts (9) of a plurality of radial blades (8) of the propeller are rotatably mounted on a tubular hub (3) which can be driven by a drive shaft (1), and eccentric pins (16) projecting from ends of the attachment shafts are held in an annular groove (15) defined in the outer periphery of an adjusting ring (14) which is disposed concentrically in the hub (3) and is axially movable, the attachment shafts (9) being turnable about their own axes through the eccentric pins (16) in response to axial displacement of the adjusting ring (14), characterised in that said adjusting ring (14) is rotatably mounted on an axially movable cylinder (12) through a bearing (13), and is rotatable with the hub (3). A variable-pitch mechanism according to claim 1, wherein one side wall of the annular groove (15) has slots (19) defined therein for allowing the eccentric pins (16) to pass therethrough into the annular groove, and the adjusting ring (14) has a retainer means (20) for holding the eccentric pins in the annular groove (15) in positions displaced from the slots. A variable-pitch mechanism according to claim 1 or 2, wherein the eccentric pins (16) engage in the annular groove (15) through sliders (17) in which the eccentric pins are rotatably fitted. A variable-pitch mechanism according to claim 3, wherein each of the sliders (17) has a square cross section held in face-to-face contact with opposite side wall surfaces defining the annular groove (15). A variable-pitch mechanism of a propeller (4) having a plurality of radial blades (8) with attachment shafts (9) rotatably mounted on a tubular hub (3) driven to drive the propeller, eccentrically located means (16) provided on each attachment shaft, an adjusting ring (14) positioned within said tubular hub (3) and axially movable with respect thereto, an annular groove (15) defined in the adjusting ring, said eccentrically located means (16) engaging said annular groove (15), and means for selectively moving said adjusting ring in an axial direction for causing the attachment shafts to turn about their own axes through the interengagement of the eccentrically located means (16) and annular groove (15) to adjust the pitch of the blades, characterised in that said adjusting ring (14) is rotatably mounted on an axially movable cylinder (12) through a bearing (13) and is rotatable with said hub (3), and in that said hub (3) is rotatably supported on a stationary support cylinder (5) through bearings (6). A variable-pitch mechanism according to claim 5, wherein the eccentrically located means comprise an eccentric pin (16) projecting from an end of each attachment shaft (9). A variable-pitch mechanism according to claim 6, wherein the eccentric pins (16) engage in the annular groove (15) through sliders (17) in which the eccentric pins are rotatably fitted. A variable-pitch mechanism according to claim 7, wherein each of the sliders (17) has a square cross section held in face-to-face contact with opposite side wall surfaces defining the annular grove (15). A variable-pitch mechanism according to any of claims 5 to 8 further comprising means restricting relative axial movement between the tubular hub (3) and the axially movable cylinder (12), said movable cylinder (12) having hydraulic means cooperating with the stationary support cylinder (5) for selectively moving the cylinder in an axial direction. A variable-pitch mechanism according to any of claims 1 to 4 wherein said hub (3) is concentric with said drive shaft (1) and is mounted on a stationary support cylinder (5) through bearings (6), said axially movable cylinder (12) being supported on, and axially movable with respect to, said stationary support cylinder (5), and having a plurality of tubular supports (7) spaced about and extending radially outwardly from said hub (3), and attached thereto, said attachment shafts (9) being rotatably mounted within said supports (7).

Inventors: BANNAI TAKESHI, KOMURA TAKASHI, BANNAI, TAKASHI, KOMURA, TAKASHI
Applicants: HONDA MOTOR CO LTD, HONDA GIKEN KOGYO KABUSHIKI KAISHA
Application year: 1991
Main classification: B64C11
IPC codes: B64C11, B63H3