Patent GB-350943-A (GB)
Title: Improvements in or relating to couplings for conveying rotary motion
IPC: F16D3/80
Filed: 1930-03-17
Abstract: 350,943. Flexible couplings. CARTER, B. C., Royal Aircraft Establishment, South Farnborough, Hampshire. March 17, 1930, No. 8549. [Class 80 (ii).] A resilient coupling, more particularly for reducing liability to synchronous torsional vibrations such as of a crank-shaft air screw system at normal engine speeds, comprises radiating spring arms which transmit t h e drive and lower the natural frequency of the system, and a solid friction or hydraulic damper arranged in parallel between driving and driven members. The friction damper may comprise flat, conical or spherical plates and its effect may be influenced by the speed of rotation centrifugally or by end thrust of the driven member in one or either direction, or by springs. In some cases relative axial, radial or universal movement is permitted, the latter being accommodated by twisting of the blade spring arms. Where more than one mode of vibration is present, more than one coupling unit may be used. In the coupling shown in Fig. 5 tapering blade springs 1, radiating from a boss 2 bolted to a driven member 4, movably engage at their outer ends slots in bifurcated pins 18 rotatably mounted in bearings in the rim 15 of a flange 14 bolted to a driving member 3. Friction damping means comprises a series of blocks 23 embracing and guided radially by externally circular guide spokes 22 radiating from a boss 6 and housing helical springs 24 which, assisted by centrifugal force, press the blocks 23 against a member 7 rotatable with the driver. Double conical engaging surfaces lines with ferobestos or like friction material 27 are provided. Stops 20, 21 limit relative rotary movement. Brake linings having flat outer faces are also arranged between the blocks 23 and the sides of the guides and these serve also to damp the relative universal movement permitted by twisting of the springs. Relative axial movement is possible and relative radial movement is permitted by an Oldham coupling comprising a ring 30 having parallel-sided inward projections engaging grooves on the ring 7 and similar outward projections in a plane at rightangles engaging grooves in the rim 15. The springs 24 serve also to centralize the coupling. A coverplate 28 is provided. In a modification of this arrangement the part 7 is rigidly mounted on the rim 15 of the flange 14, relative axial movement only being permitted. The flange 14 carries a central boss projecting into the boss 2, two sets of roller bearings being interposed to maintain axial alignment. The deflection limiting stops are on the end of this added boss and co-operate with stops on the boss 6. The brake linings between the blocks 23 and guides 22 are omitted, the guides 22 are rectangular externally and the cover-plate is mounted on them. In the form utilizing hydraulic damping, Fig. 11, the rim 15 carries an endplate, forming together with the flange 14 a chamber closely fitting the spring arms 1. This chamber is divided by a series of inwardly projecting, rigid arms 42 so that each spring arm 1 can move in a space 41 containing oil or other liquid, such movement entailing the transference of liquid from chamber to chamber by way of a restricted passage 43, whereby a damping action is produced. The boss 2 is keyed to the driven member 4 which bears on a white metal bearing 11 between it and an inner extension 12 of the flange 14 attached to the driving shaft. As shown in Fig. 16 applied to driving an airscrew 61 from a crank shaft 3, the spring arms 1 project into the hollow blades 61 and engage at their ends the flat inner faces of hemispherical members 18 located on the spring ends by a pin 62. Roller bearings 48 are interposed between the boss 2 and the hub 4 which is made in halves united by bolts 63. A conical damper 6, 7, influenced by the thrust of the airscrew, is provided and a brake lining dust-excluding washer 64 is placed between member 6 and the crank case. Deflection of the springs 1 is limited by their contact with the walls of the airscrew. Slight axial movement is permitted by compression of the damper lining 27. In the form shown in Fig. 19 for driving a metal airscrew, the spring arms 1, one on each side of each blade, pass radially through slots in the airscrew hub 4 and are thereafter curved inwards to engage the usual pins 18 carried in lateral enlargements of bolts 63 forming the two securing parts of a four-piece ring 66 fitting in a groove in the hub 4 and uniting its two halves. The damping members 6, 7 are part spherical about the centre point of the airscrew hub which is mounted on spherical bearings 48, which may be of brake lining material, on the boss 2. Universal movement of the airscrew is accommodated by compression of the material 48 and the damper 6, 7 serves also to damp this movement. In another form for driving a metal or wooden airscrew the coupling is separate from the screw and the damper is of the conical form shown in Fig. 16. The spring boss 2 is carried by the crank shaft and the airscrew is mounted on a boss carried by the member 15 which also carries a boss extending rearwardly into the hollow crank shaft in which it has a roller bearing. The thrust action of the airscrew on the damper is further increased by a spring plate carried on the boss 2 and pressing rearwardly by contact of its outer part with the inner face of the flange part of the rim 15, a brake lining being interposed therebetween. In a drive for a wooden airscrew a double-acting friction damper is shown, the member 15 carrying two friction-lined conical surfaces gripping between them a single conical plate on the driver. This form is affected by thrust in either direction. The spring-engaging pins 18 may be lubricated which action may be assisted by centrifugal force, and may slide axially and the springs may radiate from an outer instead of an inner member. The spring ends may engage plain recesses in the member 15 or alternatively recesses of gear tooth form, the outer spring ends being then shaped to tooth form having a pinion centre at a calculated point in the spring arm. The springs may radiate outwards in conical form when they may have bevel toothed ends. The damper may be of the viscous type and comprise a multiplate coupling working in oil. The shaft 3 may in some cases be geared to the crank shaft and the invention is applicable to the spring drive described in Specification 292,276, [Class 80 (ii), Gearing, Variable-speed &c.].