Rotary shafts – gudgeons – housings – and flexible couplings for ro – Coupling accommodates drive between members having... – Torque transmitted via intermediate element
Reexamination Certificate
1999-03-17
2001-01-09
Browne, Lynne H. (Department: 3629)
Rotary shafts, gudgeons, housings, and flexible couplings for ro
Coupling accommodates drive between members having...
Torque transmitted via intermediate element
C464S904000, C464S158000
Reexamination Certificate
active
06171197
ABSTRACT:
The present invention relates to a coupling for transmitting a torque between a drive shaft and a receiving shaft,
designed to allow an angular and/or radial misalignment and/or an axial displacement between the two shafts,
comprising:
two hubs each of which has external toothing usually symmetrically convex with respect to a plane perpendicular to the axis of rotation of the hub and called the plane of symmetry, and which are to be fixed, one to the drive shaft and the other to the receiving shaft,
a sleeve tube which has internal toothing cooperating with each aforementioned external toothing for transmitting torque between the shafts and which can slide longitudinally along these shafts, and
stop means designed to limit the longitudinal sliding of the sleeve tube with respect to at least one of the hubs.
Couplings of this kind, which are known at the present time, exhibit significant drawbacks which greatly limit their life and/or which lead to short service intervals or service costs which are considerable compared with the cost of the coupling itself.
In certain known couplings, the locating of the sleeve tube with respect to the hubs is achieved using springs. These cause contact corrosion at critical points of the coupling, and this reduces its life, among other things by contaminating the lubricant used therein. Springs can also cause an imbalance which is harmful not only to the coupling but also to the mechanisms connected to or by the coupling. This phenomenon is further amplified by any breakage and/or wearing of the springs. Another harmful effect also arises out of the natural frequency of undamped axial vibration originating from the system of moving masses and springs and which may generate axial forces which are harmful not only to the coupling itself but also to the mechanisms connected. Furthermore, the size of a system that contains springs limits the displacements and misalignment allowed by the couplings compared to a total given size thereof.
In other known couplings, the said locating of the sleeve tube is achieved using stops, but it has been found that their usual positions in the couplings cause, in the event of misalignment, a relatively large radial movement between the stop(s) on the sleeve tube and the stop(s) on the hub or hubs, and this results in contact corrosion, abrasion and therefore, in this case too, significant wear and harmful contamination of the lubricant. In the case of these couplings, it has also been found that the volume available for lubricant is limited and poorly designed to the extent that this lubricant can easily spill out, sometimes during rotation but especially when stationary.
The present invention is intended to overcome the aforementioned drawbacks, firstly by avoiding the use of springs, and secondly by analysing the operation of a coupling of the kind described hereinabove in an entirely new way and thereby determining a favourable location for the stops.
To this end, in the coupling according to the invention:
at least one of the hubs has an annular space which is centred on the axis of rotation of the hub and which extends substantially parallel to this axis between a wall bearing the external toothing and a part of the hub which is intended to attach this hub to the corresponding shaft, a web connecting the wall to the hub part, while the annular space is open at least on the same side as one of the two lateral faces of the hub, and
the stop means are arranged in the annular space and therein comprise:
an annular stop which is fixed to the hub at right angles to the axis of rotation thereof, and which is located substantially in the region of the aforementioned plane of symmetry, and,
at least on one side of the annular stop when considering the direction of its axis of rotation, an end stop associated with the stop, which is arranged in the form of a ring of a diameter similar to that of the annular stop, at right angles to the longitudinal axis of the sleeve tube and which is fixed thereto for example by a carrier.
In the known couplings described hereinabove, significant wear originates from a lack of sealing both insofar as there is a loss of lubricant escaping from the coupling and insofar as there is the ingress of contaminants. This lack of sealing stems, among other things, from significant radial movements which are imposed on the seals and make them ineffective, and from the wear of seals placed at the usual locations for such seals in the known couplings.
The same analysis as mentioned above has resulted in a solution to the ineffectiveness and wear of the seals mounted in the coupling of the invention being found, so that these seals no longer experience any radial displacement.
To this end, in the coupling according to the invention, a sealing ring is arranged between the hub part and the aforementioned carrier, preferably substantially at the location of the aforementioned plane of symmetry, and the said carrier also has a flange which closes the corresponding end of the sleeve tube and has an orifice through which the corresponding shaft and/or hub can pass.
Other details and features of the invention will emerge from the secondary claims and from the description of the drawings which are appended to this text and which illustrate, by way of non-limiting example, one advantageous embodiment of a coupling according to the invention.
REFERENCES:
patent: 3673814 (1972-07-01), Carman
patent: 4443205 (1984-04-01), Grant
patent: 5393267 (1995-02-01), Munyon
patent: 5911630 (1999-06-01), Shigeura
patent: 677 674 (1995-10-01), None
patent: 676 555 (1995-10-01), None
Browne Lynne H.
Esco Transmissions
Sughrue Mion Zinn Macpeak & Seas, PLLC
Thompson Kenneth
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