Rotary shafts – gudgeons – housings – and flexible couplings for ro – Torque transmitted via flexible element – Element is plate with external edge completely surrounding...
Reexamination Certificate
1998-06-10
2001-03-13
Browne, Lynne H. (Department: 3629)
Rotary shafts, gudgeons, housings, and flexible couplings for ro
Torque transmitted via flexible element
Element is plate with external edge completely surrounding...
C244S215000, C403S220000, C403S337000
Reexamination Certificate
active
06200223
ABSTRACT:
PRIORITY CLAIM
This application is based on and claims the priority under 35 U.S.C. §119 of German Patent Application 197 24 772.5-12, filed on Jun. 12, 1997.
FIELD OF THE INVENTION
The invention relates to a flexible coupling for connecting two rotary drive shafts, especially in a transmission system that is driven by a central drive unit in an aircraft.
BACKGROUND INFORMATION
It is generally known and typical in the construction and operation of aircraft, that the high lift landing flaps and slats arranged on the wings are driven by means of a transmission system from a centrally arranged drive unit. In this manner, the drive power of a single drive unit can be used to operate a plurality of flaps and slats or the like, without requiring a plurality of separate drive motors. In this context, the overall drive system comprises a drive motor, redirecting or transfer transmissions, actuators, and plural transmissions shafts, as well as support bearings, articulated joints, and shaft couplings associated with the shafts.
FIG. 1
schematically shows a general overview of a known arrangement of a drive system for driving the flaps
51
and slats
52
arranged in a wing
5
of an aircraft
50
. The flap and slat drive system includes a transmission system
1
that is driven or powered by a central drive unit
25
. The transmission system
1
includes transmission shafts
8
respectively coupled together by coupling elements
2
at locations where the shaft run is substantially straight, and by articulated joint elements
4
at locations where the shaft run passes through a bend or the like. Additionally, respective coupling elements
2
, which may also provide a limited flexibility, and the articulated joint elements
4
must respectively be arranged at each location where the transmission system
1
is supported by support bearings
3
or connected to redirecting or transfer transmissions
26
or to actuators
27
. In this context, the particular type of coupling element or joint element is selected depending on the magnitude of the bend or redirection of the shaft line at that location. It is necessary to provide a flexible joint at each support bearing, in order to avoid the introduction of external bending forces into the shafts due to the flexing of the wing
5
.
Although flexible shaft couplings in general are known in the art, there has been a continuing need for improving the safety, reliability, and simplicity, and reducing the size and weight of such couplings, while achieving a more robust arrangement with a reduced need for maintenance, which may be used uniformly for many different installation situations throughout the transmission system.
OBJECTS OF THE INVENTION
In view of the above it is an object of the invention to provide an improved flexible shaft coupling that is relatively simple, cost economical, and failure tolerant relative to prior art shaft couplings, while fulfilling all strength and safety standards applicable to the construction and operation of aircraft. The invention further aims to provide a flexible coupling that has a fail-safe operation mode, whereby the coupling will still achieve its flexible coupling functions even in the event of a failure of one of the connecting bolts or of the flexible disk of the coupling. The invention further aims to overcome or avoid the other disadvantages of the prior art, and to achieve additional advantages, as apparent from the present description.
SUMMARY OF THE INVENTION
The above objects have been achieved in a flexible coupling for drive shafts according to the invention, comp rising first and second coupling flanges respectively connected to the ends of two shafts that are to be connected, and a flexible disk arranged and interconnected between the two coupling flanges by means of bolts and bushings, in such a manner that the two shafts are flexibly joined together. Particularly according to the invention, each of the bolt connections is respectively embodied to be securely fastened to a respective one of the coupling flanges while allowing free play relative to the other one of the coupling flanges.
Namely, at least one first bolt is secured to a first flange and has play relative to a second flange, while at least one second bolt is secured to a second flange and has play relative to the first flange. Bushings are arranged on the bolt, between the flanges and the flexible disk, so that each bolt securely clampingly holds the flexible disk and respectively connects the flexible disk securely to one or the other of the coupling flanges. In this manner, the force or torque transmission in normal operation is from the first coupling flange, through the first bolt(s) secured to the first flange, from there into the flexible disk, from the flexible disk into and through the second bolt(s) secured to the second coupling flange, and from there to the second coupling flange, or entirely vice versa.
The first and second coupling flanges may be respective rigid plates. Nonetheless, the overall coupling joint is flexible to a defined degree, due to the flexibility of the flexible disk through which the rigid flanges are interconnected and the power is transmitted, and due to the respective play of each one of the connecting bolts, respectively relative to one or the other of the coupling flanges. In the event of a failure, whereby one or two of the four bolts have failed, and/or the flexible disk itself has failed, the overall flexible coupling will remain operable in a fail-safe operating mode. In this condition, the force or torque transmission is carried out directly from one coupling flange to the other coupling flange through the remaining bolts therebetween. A slight relative rotation of the coupling flanges will cause the free-playing ends of the respective bolts to engage or bear against the respective flanges to which they are not securely fastened, to achieve a direct torque transmitting connection from one coupling flange through the bolts to the other coupling flange, while the free-playing contact between the free ends of the bolts and the flanges still allows the required flexibility. While this fail-safe operating mode will not be as smooth in operation, and will suffer relatively rapid wear, as compared to the normal operating condition, it will allow safe operation of the shaft drive system until the failed coupling can be repaired or replaced.
According to a preferred particular embodiment of the invention, a total of four bolt connections are provided, whereby two first bolts are secured without play to the first coupling flange and arranged with play relative to the second coupling flange, and two second bolts are secured without play to the second coupling flange and arranged with play relative to the first coupling flange. Preferably, three bushing members are arranged on each connecting bolt to achieve the above described rigid clamping of the flexible disk and one of the coupling flanges on the one hand, as well as the free play between the bolt and the other coupling flange on the other hand. For example, a first bushing member with a protruding rim or lip clamps the first coupling flange tightly against the bolt head, a second bushing member with a protruding rim or lip clamps the flexible disk tightly against the first bushing member, and a third bushing member with a protruding rim or lip braces against the threaded nut and transmits the clamping force applied by the nut through the second bushing member to the flexible disk, the third bushing member, and the first coupling flange. The second coupling flange is received with play around the second and third bushing members and respectively between the protruding rims or lips of the second and third bushing members.
The flexible coupling according to the invention can be used in any application in which it is necessary to couple two shafts, but is particularly suitable for use in transmission systems for driving the flaps and slats on a wing of an aircraft. The invention provides an improved system in this regard.
The invention achieves the
Binda Greg
Browne Lynne H.
DaimlerChrysler Aerospace Airbus GbmH
Fasse W. F.
Fasse W. G.
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