GB2151327A - Power gearing - Google Patents

Abstract

Power gearing (10) includes an input pinion (80) journalled in bearings (87) which may move in a direction generally parallel to the line of action (83) between the pinion and a pair of meshing idler gears (70) and (75) for the uniform distribution of input torque to the idler gears. Movement of the bearings in a normal direction is restrained for system stability. <IMAGE>

Description

SPECIFICATION Power gearing Technical Field This invention relates generally to compound power gearing and more specifically to uniform load distribution within such power gearing.

Background Art In compound gearing such as is employed to transmit power from an aircraft engine to a propeller, the driving of a single output gear by a pair of idler gears which are in turn driven from a single input pinion has been found desirable for reducing gear tooth load ing as well as minimizing gear and gear box size with a resulting reduction in weight of the gearing in toto. To achieve such advantages, the uniform distribution of torque by the input pinion to the idler gears is essential. However, with present-day gear mountings, normal manufacturing tolerances make such uniform load distribution between the pinion and idler gears difficult to achieve.One solution, when the input pinion center is offset from the line of the idler gear center lies in a pivotal yoke which rotatably supports the input pinion and allows the pinion to center itself between the idler gears for the uniform distribution of loading thereto. An example of such an arrangement is found in U.S. Patent No.

4,312,244 to Barnes et al. However, such a pinion mounting arrangement is impractical in situations where the center of the input pinion is essentially colinear with the centers of the idler gears or where reaction of gear loading to a fixed structural member of the gearing such as the gear box, is undesirable.

Disclosure of Invention Accordingly, it is among the objects of the present invention to provide an improved power gearing capable of the uniform distribution of loading from an input pinion to a pair of idler gears aligned therewith.

In accordance with the present invention, such uniform load distribution is achieved by floating one or more pinion bearings in a direction parallel to the line of action between the pinion and the idler gears while restrain -ing motion of the pinion in a direction normal thereto. A number of structures which achieve such results are proposed. In one preferred embodiment, a pinion bearing is disposed in a block slideably mounted in a channel member fixed to a stationary structural member such as a bulkhead provided in a housing for the gearing. In another preferred embodiment, the block is attached to the structural member of alternating layers of elastomeric and nonelastomeric material, the members having parallel major surfaces in planes parallel to the line of action between the pinion and idler gears.In a third alternate embodiment, the bearing block is mounted to the stationary structure by means of beams which are flexibly bendable in a direction parallel to the gear line of action and rigid in directions normal thereto.

Brief Description of Drawings Fig. 1 is an end elevation of a power gearing embodying the present invention, portions thereof being sectioned and broken away to show details of construction; Fig. 2 is a side, partially sectioned elevation of the power gearing shown in Fig. 1; Fig. 3 is an enlarged, partially sectioned plan view of the bearings which support an input pinion of the gearing as well as the arrangement for mounting the bearings within the gearing housing.

Fig. 4 is a frontal elevation of an alternate means for mounting the input pinion bearings shown in Fig. 3; and Fig. 5 is a frontal elevation of a second alternate means for mounting the bearings shown in Fig. 3.

Best Mode for Carrying Out The Invention and Industrial Applicability Thereof Referring to the drawings, and particularly to Figs. 1-3 thereof, the power gearing of the present invention is shown generally at 10 comprising a casing 1 5 and a gear train 20 therewithin. Gear train 20 is useful in any desired application such as for reducing the speed of an engine to a value compatible with the operating characteristics of an aircraft propeller. In such instance, the engine would be connected to the gear train at input shaft 25 thereof by any suitable means such as a splined connection (not shown) thereto and the propeller connected to an output shaft 30 by any suitable coupling such as that partially shown at 35.As best seen in Fig. 2, output shaft 30 is supported on roller bearing set 37 and ball bearing set 40 the bearing sets comprising the usual arrangement of ball or roller bearing elements in a circular race, and lubricated as required.

Output shaft 30 carries an output gear 45 thereof, shaft 30 and gear 45 being driven by gears 50 and 55 meshing therewith. Gears 50 and 55 are mounted on shafts 60 and 65, respectively, whichare journaled as at 57 to opposite ends of the housing in a manner similar to that described hereinabove with respect to output shaft 30. Shafts 60 and 65 also carry idler gears 70 and 75 thereon, axially spaced from gears 50 and 55, respectively. Idler gears 70 and 75 are driven by input pinion 80 which meshes therewith along lines of action (tangents to the pinion) 83 and is fixed to input shaft 25 for rotation therewith. Accordingly, it is seen that rotation of input shaft 25 by the engine will in turn rotate input pinion 80 which, by meshing with gears 70 and 75 drives shafts 60 and 65 and thus, gears 50 and 55.Rotation of gears 50 and 55, by the meshing of these gears with output gear 45, drives output shaft 30 and hence the device being driven through coupling 35.

As set forth hereinabove, while compound gearing of the type described herein is compact and lightweight, for proper operation, input torque must be applied evenly to gears 70 and 75 from input pinion 80. However, due to normal manufacturing tolerances, such uniform torque distribution to the idler gears is not achievable with an input pinion movable only in rotation. Therefore, in accordance with the present invention the input pinion is movable in a direction generally parallel to lines of action 83.

Referring again to the drawings, input shaft 25, at an end thereof which connects to the engine, is supported on bearing set 85 and at an opposite end, on bearings 87 received in a circular race 90 which is accommodated within block 95. Block 95, as shown herein, may be of solid rectangular shape and is slideably received within a channel member 100 defined by bracket 102 and plate 104 secured to housing bulkhead 105 by any suitable means such as bolts 110 and nuts 11 5. It will be appreciated that channel member 100 allows relatively free movement of the input pinion bearings in a direction generally parallel to the lines ofaction of the input pinion and idler gears 70 and 75.As illustrated, bearing block 95 may be radially loaded by a spring 1 20 received between retainers 1 25 and 130, such loading reducing any tendency of the roller elements to skid in the race. It has been found that an input pinion in alignment with meshing idler gears as is the case herein, may exhibit instability in a direction generally normal to the lines of action between the gears, such instability if unchecked, causing the pinion to mesh with one idler gear more tightly than with the other. Accordingly, it is seen that by the present invention, the input pinion is allowed free travel in a direction generally parallel to the gear lines of action for a uniform distribution of input torque to the two idler gears yet is restrained in directions generally normal to the lines of action for purposes of stability.

Referring to Figs. 4 and 5, alternate means for achieving the uniform load distribution and stability of the power gearing of the present invention are shown. Referring to Fig. 4, rather than being received within the channel member, bearing block 95 may be supported on a mounting means comprising alternate joined layers 1 35 and 140 of elastomeric and nonelastomeric material, respectively. Those skilled in the art will recognize such mounting means as being flexible in a vertical direction when loaded in shear, yet very rigid in a horizontal direction when loaded in compression thereby allowing the movement of the input pinion bearings in a direction generally parallel to the gear lines of action while restraining the pinion in normal direction.

Referring to Fig. 5, another mounting means is shown, this means comprising beams 145 which are vertically flexible and horizontally rigid, thereby allowing bearing movement parallel to the gear lines of action while restraining the pinion in normal directions. As the mounting means shown in Fig.

4, the beams may be secured to the bulkhead in any of numerous known techniques such as the bolted connection discussed hereinabove.

It will be understood that vertical movement of the input pinion bearings will result in a cocking or angular displacement of the input pinion and input shaft. While such angular displacement of the pinion may be accommodated by flexibility between the pinion and idler gears, it is contemplated, although not shown, that further accommodation of such angular displacement of the input pinion may be accommodated by a crowning of the gear(s) or by utilizing splined connections at both ends of input shaft 25, thereby allowing vertical translation of the pinion without angularity.

While a particular embodiment of the power gearing of the present invention has been shown, it will be understood that various modifications of this gearing will, from the disclosure herein, suggest themselves to those skilled in the art. For example, while vertical lines of action (tangent to both pinion and idler gears) have been illustrated, it will be understood that the angular orientation of the lines of action may vary from those illustrated by as much as 30 without departing from the present invention. Accordingly, the present invention contemplates as much as a 30 variation between the directions of pinion movement and the lines of action within the meaning of the general parallelism between these two directions described herein. Likewise, while the pinion and idler gears are shown to be colinear, a moderate amount of perpendicular displacement of the pinion can be tolerated with only a negligible effect on the equal load distribution described herein. It is intended by the following claims to cover these and any other such modifications as fall within the true spirit and scope of this invention.

Having thus described the invention, what

Claims (4)

is claimed is: CLAIMS

1. A compound power gearing including a stationary support structure, an input pinion mounted on bearings therefor, a pair of idler gears meshing with said input pinion along lines of action therebetween and being driven by said input pinion, the centers of said input pinion and said idler gears being substantially colinear; and an output gear driven by said idler gears; said power gearing being characterized by: means accommodating said input pinion bearings and movable with respect to said support structure; and means fixed to said support structure for mounting said bearing accommodating means thereto, and allowing limited travel of said bearing accomodating means in a direction generally parallel to said lines of action of said input pinion and idler gears while restraining movement of said bearing accommodating means in a direction generally normal to said lines of action.

2. The compound power gearing of Claim 1 characterized by said bearing accommodating means comprising a block and said mounting means comprising a channel member generally conforming to the shape of said block, said block being slidably received within said channel member.

3. The compound power gearing of Claim 1 characterized by said mounting means comprising alternate, joined elastomeric and nonelastomeric members having generally parallel opposed major surfaces in planes parallel to said lines of action.

4. The compound power gearing of Claim 1 characterized by said mounting means comprising elongate beams flexible in a direction parallel to said lines of action and rigid in a direction normal thereto.