BR-102022003349-B1 - LINEAR ACTUATOR

BR102022003349B1BR 102022003349 B1BR102022003349 B1BR 102022003349B1BR-102022003349-B1

Abstract

BEARING ASSEMBLY, LINEAR ACTUATOR, AND MAINTENANCE METHOD FOR BEARING ASSEMBLY. This is a bearing assembly. The assembly comprises a housing, a spherical bearing located in the housing, and two outer races positioned between the spherical bearing and the housing. The outer races are configured in sliding engagement with the spherical bearing to allow the spherical bearing to rotate relative to the housing. The assembly comprises a clamping element configured to engage a first race between the two outer races and clamp the outer races against the spherical bearing, wherein the assembly is configured to provide a primary load path from the clamping element to the housing, wherein the primary load path leads from the clamping element to the housing via the outer races while deflecting the spherical bearing.

Inventors

Dario MOLINELLI
Franco Maino
Michele RESTUCCIA

Assignees

MICROTECNICA S.R.L

Dates

Publication Date: 20260317
Application Date: 20220222
Priority Date: 20210518

Claims (9)

1. Linear actuator for a helicopter rotor, comprising: a bearing assembly (24) comprising: a housing (32); a spherical bearing (26) located in the housing (32); two outer raceways (34, 36) positioned between the spherical bearing (26) and the housing (32), wherein the outer raceways (34, 36) are configured in sliding engagement with the spherical bearing (26) to allow the spherical bearing (26) to rotate relative to the housing (32); a clamping element (44) configured to engage a first track between the two outer tracks (34, 36) and clamp the outer tracks (34, 36) against the spherical bearing (26), wherein the assembly is configured to provide a primary load path (98) from the clamping element (44) to the housing (32), wherein the primary load path (98) leads from the clamping element (44) to the housing (32) by means of the outer tracks (34, 36) while bypassing the spherical bearing (26), characterized in that: the bearing assembly (24) comprises a shim (56) between the first and second outer tracks (34, 36), and the primary load path (98) leads through the shim (56); the linear actuator (18) further comprises a rod (28) extending through it and configured to move with the spherical bearing (26); a first portion (26a) of the spherical bearing (26) is configured to be in sliding engagement with a first (34) of the two outer races (34, 36), a second portion (26b) of the spherical bearing (26) is configured to be in sliding engagement with a second (36) of the two outer races (34, 36), and the spherical bearing (26) has a third portion (26c) between the first and second portions (26a, 26b), the third portion (26c) of the spherical bearing (26) having a curved cross-sectional profile such that a cross-sectional profile of the first, second and third portions (26a, 26b, 26c) of the spherical bearing (26) follows a continuous curve with a constant radius of curvature.
2. Linear actuator according to claim 1, characterized in that the wedge (56) makes contact with the first and second outer tracks (34, 36) to transfer load between them.
3. Linear actuator according to claim 1, characterized in that the first and second outer races (34, 36) and the shim (56) are positioned concentrically between the spherical bearing (26) and the housing (32).
4. Linear actuator according to claim 1, characterized in that the clamping element (44) is configured to clamp so as to press the first outer race (34) against the shim (56) which, in turn, presses the second outer race (36) against a portion of the housing (32) so as to provide the primary load path (98).
5. Linear actuator according to claim 1, characterized in that the shim (56) is an annular piece.
6. Linear actuator according to claim 1, characterized in that the clamping element (44) is configured to clamp the outer races (34, 36) against the spherical bearing (26) to provide a preload of the bearing assembly (24).
7. Linear actuator according to claim 1, characterized in that the clamping element (44) is a screw.
8. Linear actuator according to claim 1, characterized in that the housing (32) comprises a surface, optionally a shoulder (54), against which the second outer track is configured to be contiguously in use.
9. Linear actuator according to claim 1, characterized in that the housing (32) comprises an internal cylindrical bore with a screw thread that engages with a screw thread of the clamping element (44).

Description

TECHNICAL FIELD [001] This disclosure relates to a bearing assembly, in particular for use in an actuator for a helicopter main rotor, although other applications are foreseen. FUNDAMENTALS [002] Figure 1 illustrates a side view of a helicopter main rotor 2. The main rotor 2 comprises four blades 4, each connected to a hub 6 that rotates around a central geometric axis 8. The main rotor 2 also comprises an upper swashplate 10 and a lower swashplate 12, wherein the upper swashplate 10 rotates relative to the lower swashplate 12 by means of bearings. Multiple pitch control rods 16 attach each blade to the upper swashplate 10, wherein each pitch control rod 16 is hinged at its top and bottom. The main rotor 2 also comprises a plurality (e.g., three) of actuators 18 connected to the lower sway plate 12, and the extension or retraction of the main rotor actuators 18 causes the lower sway plate 12 to be moved up or down (or tilted) relative to a main helicopter body 20, thus enabling the pilot to steer the helicopter. The main rotor actuators 18 are pivotally fixed to the lower sway plate 12 and are in the form of linear actuators. At the lower end of each of the main rotor actuators 18 there is a bearing assembly 24, which allows angular rotation of the actuator 18 in two orthogonal directions. [003] It should be understood that the bearing assembly 24 of this disclosure can be applied to any type of helicopter, and to other locations on a helicopter. The bearing assembly described herein is also not limited to use on a helicopter and may be applicable to other systems, and is also not necessarily limited to use with linear actuators. [004] Figure 2 illustrates a conventional bearing assembly 24 that can be used in the main rotor 2 of a helicopter (such as that illustrated in Figure 1). The bearing assembly 24 comprises a spherical bearing 26 that is located around a lower rod 28 of a main rotor actuator 18 as defined above. [005] The spherical bearing 26 comprises a cylindrical passage through its center, through which the lower rod 28 extends. The spherical bearing 26 is secured in place at one end by a shoulder 30 located on the lower rod 28. An internal thread 27 is screwed into a screw thread 46 of the lower rod 28 in order to secure the spherical bearing 26 in place. Consequently, the spherical bearing 26 is held between the shoulder 30 of the lower rod 28 and the internal thread 27. This method for retaining the spherical bearing 26 is not essential and any suitable method may be used. [006] The bearing assembly 24 comprises a static housing 32 which is fitted around the spherical bearing 26 and is configured to remain stationary as the lower rod 28 and the spherical bearing 26 move in use. The housing comprises a hollow interior within which the spherical bearing is located. Two outer races 34, 36 are located between the housing 32 and the spherical bearing 26. The outer races 34, 36 are generally annular and each has a curved inner surface 38, 40 which complements the curved outer surface 42 of the spherical bearing 26. In this way, the inner surface 38, 40 of each outer race is configured to make sliding contact with the outer surface 42 of the spherical bearing 26 in use. [007] Thus, a first portion 26a of the spherical bearing 26 is configured to be in sliding engagement with a first 34 of the two outer races 34, 36, a second portion 26b of the spherical bearing 26 is configured to be in sliding engagement with a second 36 of the two outer races 34, 36, and the spherical bearing 26 has a third portion 26c between the first and second portions 26a, 26b, the third portion 26c of the spherical bearing 26 having a curved cross-sectional profile such that a cross-sectional profile of the first, second and third portions 26a, 26b, 26c of the spherical bearing 26 follows a continuous curve with a constant radius of curvature. [008] An external thread 44 is configured to screw into a thread 48 located in an internal cylindrical hole of the housing 32, and press against the right external race 34 (as illustrated in Figure 2). The right external race 34 is wedge-shaped between the spherical bearing 26 and the housing 32. This means that, in turn, the external thread 44 presses the spherical bearing 26 towards the left external race 36, which is itself wedge-shaped between the spherical bearing 26 and the housing 32. Consequently, the external thread 44 cooperates with the external races 34, 36 to retain the spherical bearing 26 in place. [009] The external thread 44 is hollow so that the lower shank 28 and the internal thread 27 can extend through the external thread 44 as illustrated. [0010] More specifically, the external thread 44 comprises a surface configured to engage with an opposite surface 52 of the right external race 34. The right external race 34 further comprises a bearing surface 38 configured to engage the cooperating bearing surface 42 of the spherical bearing 26 and which is in sliding contact