Rotary shafts – gudgeons – housings – and flexible couplings for ro – Housing – With rolling body supporting shaft in housing
Utility Patent
1998-12-15
2001-01-02
Browne, Lynne H. (Department: 3629)
Rotary shafts, gudgeons, housings, and flexible couplings for ro
Housing
With rolling body supporting shaft in housing
C384S536000, C384S498000
Utility Patent
active
06168530
ABSTRACT:
This latter relates to a device for coaxially coupling two shafts, comprising a support at this coupling and a single system for flexibly linking the ends of these two shafts, said support including near this system a bearing block equipped with a single-row ball bearing and mounted in a fixed housing so that it can withstand slight radial and angular displacements with respect to this housing. It has been stated that in a preferential manner an annular cushion of elastic material was interposed between a swiveling exterior surface, with a relatively significant radius of curvature, of the bearing block and the fixed housing, this cushion being able to include for example two rubber rings. The value of said radius of curvature is related to the dimensions of the bearing contained inside the annular cushion.
Such a coupling device, by a self-alignment of the shafts, corrects the possible mis-alignments caused by positionning gaps between the concerned mechanical elements.
As for the fixed housing, intended to contain the annular cushion of elastic material and to hold it pressed on the bearing block, it was constituted from a globally cylindrical bearing body, closed by a cap fixed on the body for example by screws.
These basic features have been improved by taking into consideration the following requirements.
First of all, a clear need has arisen to be able to adjust more exactly the tightening of the transmission bearings in helicopters, taking account of the relatively significant deformations of the tail beams in flight, these beams supporting the corresponding transmission. This operation imposes a sufficient tightening for blocking said annular cushion and so prevent its rotation, which otherwise would lead to a premature wearing of the bearing. However, this tightening must remain limited to avoid damages to said annular cushion.
With previous devices the tightening of the transmission bearings was not able to be sufficiently exact because it was dependent upon the extremely variable compression and the deformation—significant—of the annular cushion of elastic material. Moreover, this deformation was determined by the direct abutment of the aforementioned cap against the bearing body after locking the fixing screws, and this mandatory abutment did not leave either the possibility of adjustment of this compression of the annular cushion of elastic material, nor the possibility of modifying, during maintenance and servicing operations, the initial adjustment in order to compensate for wear and play, or again to modify the initial adjustments of the bearing block in order to adapt them to different running conditions.
In other terms, there was on the one hand a genuine positional locking fault of the bearing, and on the other hand a deficiency in terms of the possibilities of adjusting the relative position of the different components and of the stresses in the bearing.
Another drawback of the annular cushion lay moreover in the fact that the elastomer or similar constituting the cushion, absorbing the noises and the vibrations, made difficult the detection of the bearing faults, like a wear or an excessive matting of the contact surfaces, or again of other abnormal operating conditions such as excessive vibration level of the coupling or the significant loss of grease.
The present improvements, which enable these drawbacks to be avoided, include the following features.
First of all, the annular cushion of elastic material has been replaced by an annular cushion of relatively rigid and incompressible material and the surface of which has a low friction coefficient, this annular cushion consisting of two rings spaced apart and arranged on each side of said transverse median plane of said swiveling exterior surface.
Since the cushion is rigid and relatively non-deformable, it is understood indeed that it must consist of two separated rings, arranged on each side of the transverse plane of symmetry of said swiveling exterior surface, failing which it would not be able to be mounted on it.
For the composition of these rings, particularly PTFE, PVC or other similar materials will be able to be used, whether they are solid, or used to constitute the coating of a rigid material, for example a metal such as steel or aluminum, this cushion possessing in any case a transverse section wholly adapted to the section of the annular space arranged between the inner surface of said fixed housing and said swiveling exterior surface of the bearing block. Another variant would be to use composite materials, constituted of metallic sheets inserted between elastomeric sheets.
All the drawbacks mentioned above, connected to the high compressibility of the elastomers and to their qualities, particularly the absorbing of vibrations, will in this way be overcome together.
In order to be able to conveniently adjust the radial compression of said relatively rigid annular cushion on said swiveling exterior surface of the bearing block, provision will moreover be made for said fixed housing to comprise means of adjusting the amplitude of axial engagement of said cover on said body, and means of adjustment of the tightening of said fixing screws.
In this way there will be no longer a dependency upon the uncontrollable compression of the elastomer of the cushion, and on the other hand it will be possible to exactly control this radial pressure exerted on the annular cushion, for example as a function of the manufacturing tolerances, and even to modify the adjustments during the lifetime of the coupling device, in order to take account, particularly, of wear, this by progressively absorbing the relatively significant axial clearances, initially provided between the cover and the housing body.
The reason for which these axial clearances must be relatively significant lies in the fact that, as mentioned above, the radius of curvature of the swiveling exterior surface of the bearing block is relatively large, since it is a matter of compensating only small possible misalignments of the shafts in relation to the bearing axis.
The result is that the appearance of a small radial clearance, for example in the bearing, will manifest itself in a relatively significant axial displacement of the cover of the fixed housing relative to its body. That will be better understood by the following, but it can also be noted here that it is also the relative significance of the radius of curvature of said swiveling exterior surface which makes appropriate the implementation of an annular cushion in PTFE or with a PTFE coating or other material with low coefficient of friction, in order to avoid its wedging, on dismantling, between the swiveling surface in question and the inner surface of the fixed housing.
It has been seen above that the rigid annular cushion had to consist of two separated rings in order to be able to be mounted on said swiveling exterior surface.
According to an additional characteristic of the present invention, the distance between these two rings is such that, seen from the center (C) of symmetry of said swiveling exterior surface, the angle (&phgr;) between these two rings is greater than the wedging angle (&agr;) of these two rings between said swiveling surface and said inner surface of the fixed housing.
This is indeed the necessary condition for the two rings to be able to be dismantled without being wedged by friction between the two aforementioned surfaces.
Given that the two rings are in PTFE or are coated with PTFE or any other material with a small or very small coefficient of friction, the wedging angle &agr; is very small, and it will therefore be the same for the angle &phgr;, which signifies that the distance between the two rings will be able to be very small. This enables all its compactness to be retained during mounting, in spite of the division of the annular cushion into two rings.
On these common bases, the invention can be implemented according to different embodiments, as far as the composition of the adjustment and tightening means mentioned above are concerned.
In a first emb
Guimbal Bruno
Jalaguier Jean-Pierre
Zoppitelli Elio
Browne Lynne H.
Eurocopter
Henderson & Sturm LLP
Thompson Kenneth
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