A gas turbine engine for an aircraft has an engine core including a turbine, a compressor, and a core shaft connecting the turbine to the compressor, the turbine being the lowest pressure turbine of the engine and the compressor being the lowest pressure compressor of the engine; a fan located upstream of the engine core; and a gearbox that receives an input from the core shaft and outputs drive to the fan. The engine core further has three bearings arranged to support the core shaft, and two rearward bearings, and wherein the forward most rearward bearing has a bearing stiffness defined by the radial displacement caused by the application of a radial force at the axial centerpoint of the bearing, and wherein a stiffness ratio of the bearing stiffness at the forward most rearward bearing to the minor span is in the range from 0.08 to 0.5 kN/mm.sup.2.

The present invention relates to internal combustion engines, and discloses a double-cylinder internal combustion engine. The double-cylinder internal combustion engine of the present invention adopts a curved groove ball bearing mechanism to replace crank-connecting rod mechanisms since traditional internal combustion engines have a complicated structure, high material requirements, high processing difficulty, and the inertia effect and noises thereof are hard to be eliminated. Two inner rings of the curved groove ball bearing mechanism are fixedly connected, and a valve mechanism and an ignition mechanism are driven through a gear pair, so that the two sets of cylinders and pistons reciprocate in opposite directions to automatically balance reciprocating inertia thereof. Compared with the prior art, the present invention has simple motion forms which only consist of the rotary motion and the reciprocating motion, and low noises are produced. The inertia of the reciprocating motion is automatically offset, causing small vibrations.

The present invention relates to internal combustion engines, and discloses a double-cylinder internal combustion engine. The double-cylinder internal combustion engine of the present invention adopts a curved groove ball bearing mechanism to replace crank-connecting rod mechanisms since traditional internal combustion engines have a complicated structure, high material requirements, high processing difficulty, and the inertia effect and noises thereof are hard to be eliminated. Two inner rings of the curved groove ball bearing mechanism are fixedly connected, and a valve mechanism and an ignition mechanism are driven through a gear pair, so that the two sets of cylinders and pistons reciprocate in opposite directions to automatically balance reciprocating inertia thereof. Compared with the prior art, the present invention has simple motion forms which only consist of the rotary motion and the reciprocating motion, and low noises are produced. The inertia of the reciprocating motion is automatically offset, causing small vibrations.

An outer-ring lubrication groove pattern formed in an outer-race raceway surface and an inner-race lubrication groove pattern formed in an inner-race raceway surface of a wave generator bearing of a strain wave gearing device are patterns in which linear lubrication grooves having very small widths and depths of several micrometers or less are arranged at fine pitches of several micrometers or less. The inner-race lubrication groove pattern includes a second groove pattern formed in long-axis-side inner-race raceway surface portions to hold the lubricant, and a first groove pattern formed in short-axis-side inner-race raceway surface portions to hold the lubricant and guide the lubricant to the second groove pattern. This configuration improves the contact state between balls and the inner-race and outer-race raceway surfaces of the wave generator bearing, thus reducing the coefficient of friction therebetween.

An outer-ring lubrication groove pattern formed in an outer-race raceway surface and an inner-race lubrication groove pattern formed in an inner-race raceway surface of a wave generator bearing of a strain wave gearing device are patterns in which linear lubrication grooves having very small widths and depths of several micrometers or less are arranged at fine pitches of several micrometers or less. The inner-race lubrication groove pattern includes a second groove pattern formed in long-axis-side inner-race raceway surface portions to hold the lubricant, and a first groove pattern formed in short-axis-side inner-race raceway surface portions to hold the lubricant and guide the lubricant to the second groove pattern. This configuration improves the contact state between balls and the inner-race and outer-race raceway surfaces of the wave generator bearing, thus reducing the coefficient of friction therebetween.

Only an outer spacer (33) is cooled by an outer spacer cooling structure, thereby causing a temperature difference between an inner spacer (32) and the outer spacer (33). According to this temperature difference, an inner ring (37) of a bearing (31) is displaced relatively to an outer ring (38) in a direction in which a preload inside the bearing (31) decreases.

A backstop of a torque transmission device of an aircraft steering system includes input and output sections of a drive shaft. Torque is transmitted from the input to the output, but is prevented from being transferred from the output back into the input. The input is limited from rotating coaxially relative to the output by more than a predetermined angle. The input stops at a first rotary position relative to the output upon rotating in a first rotary direction. The input stops at a second rotary position upon rotating in the opposite direction. The output is blocked from rotating in the second direction while the input is at the first rotary position and is blocked from rotating in the first direction while the input is at the second rotary position. The output is blocked from rotating by dissipating any torque acting upon the output into the housing of the backstop.

A backstop of a torque transmission device of an aircraft steering system includes input and output sections of a drive shaft. Torque is transmitted from the input to the output, but is prevented from being transferred from the output back into the input. The input is limited from rotating coaxially relative to the output by more than a predetermined angle. The input stops at a first rotary position relative to the output upon rotating in a first rotary direction. The input stops at a second rotary position upon rotating in the opposite direction. The output is blocked from rotating in the second direction while the input is at the first rotary position and is blocked from rotating in the first direction while the input is at the second rotary position. The output is blocked from rotating by dissipating any torque acting upon the output into the housing of the backstop.

A safety catch assembly design to prevent loss of drilling components during downhole operation is disclosed. The safety catch assembly can include a lower inner radial bearing comprising a catch ring retention zone. The safety catch assembly can also include one or more catch rings removably disposed in the catch ring retention zone, including a first catch ring having one or more ridges about its inner diameter and a second catch ring having one or more ridges about its inner diameter. In a locked position, the catch rings can retain the drilling components during a failure event.

A safety catch assembly design to prevent loss of drilling components during downhole operation is disclosed. The safety catch assembly can include a lower inner radial bearing comprising a catch ring retention zone. The safety catch assembly can also include one or more catch rings removably disposed in the catch ring retention zone, including a first catch ring having one or more ridges about its inner diameter and a second catch ring having one or more ridges about its inner diameter. In a locked position, the catch rings can retain the drilling components during a failure event.