Rotary shafts – gudgeons – housings – and flexible couplings for ro – Having heating or cooling means
Reexamination Certificate
1999-09-27
2001-05-22
Browne, Lynne H. (Department: 3629)
Rotary shafts, gudgeons, housings, and flexible couplings for ro
Having heating or cooling means
C403S220000, C464S096000
Reexamination Certificate
active
06234903
ABSTRACT:
The invention relates to a shaft coupling with at least one single-piece elastic transmission element for transmitting the torque, to which connecting elements are fixed on the driving and the driven sides.
Such couplings, which are typically arranged in the drivetrain between the engine and the transmission for transmitting the torque, are known in the state of the art by a multitude of different designs. Said designs, which may considerably deviate from each other in some cases with respect to their concrete technical embodiment, have the common feature that the torque is transmitted between the drive and the driven elements exclusively via elastically deformable transmission elements such as, for example rubber elements. For mounting between the halves of the coupling, such rubber elements are, as a rule, provided on both sides with metallic connection elements such as connection flanges or the like.
In addition to transmitting a mean driving torque, one of the important functions of such an elastic shaft coupling is to decouple the drivetrain from damaging torque peaks of the driving motor. Such variations in the torque are caused, for example by rotational vibrations, which are stimulated especially in the crankshafts of large low-inertia mass diesel engines. The elastic transmission elements are designed with respect to their elasticity and damping effect in such a way that they absorb said dynamic disturbances for the most part, so that the torque is provided with an even curve on the driven side.
A basic problem arises from the fact that the dynamic stresses described above are converted into heat when the elastic element is flexed, which may lead to local overheating because the employed elastomer materials such as, for example rubber have a distinctly low thermal conductivity. If the permissible limit temperature of the elastic material is exceeded due to such thermal load, damages occur that load to premature wear of the coupling.
Controlling the thermal problems in the face of increasing torques is made more difficult in light of the fact that the ratio of thermal stressability to mechanical stressability becomes more and more unfavorable as the dimensions of the elastic transmission element increase. The danger of local thermal overloads and of damage resulting therefrom exists especially in the core regions.
In order to achieve higher thermal stressability, it has already been proposed in DE 3710390 C2 to provide the elastic rubber elements including the connecting plates with through-extending windows, with the window openings extending through the core regions that were earlier subjected to the highest thermal stress. The rubber element is additionally cooled by the air circulating through the openings, so that the coupling overall can be stressed to a higher degree.
The solution described above does in fact offer distinct advantages versus single-piece solid rubber elements, however, it, too, is restricted by limit values conditioned by the principle, because the cross section of the window openings cannot be provided with any desired size, as this would reduce by the same measure the cross section of the elastic element, which absorbs the total dynamic load. For this reason, any further enlargement of the windows beyond the optimal size would again lead to reduced strassability.
However, even if the windows are designed in the optimal way, it was found that small core zones, or so-called heat foci, remain nonetheless. Such core zones are in fact shifted in terms of location as compared to the solid designs, and they do appear only in the presence of higher stresses; however, they nonetheless mark a limit which, if exceeded, leads again to damage.
A basic problem arises from the fact that there is a tendency in the direction of higher and even higher power densities combined with a structural volume as small as possible, but that it is not possible with the measures known according to the prior art to increase the stressability of couplings because of the thermal stress acting on the elastic transmission elements.
For solving said problem, the invention proposes for a shaft coupling of the type specified above that at least one cooling element made of a material with good thermal conductivity is nondetachably embedded in the transmission element, whereby such cooling element extends through a core zone of maximum heat generation and through a relatively cooler outer zone of the transmission element.
The cooling element as defined by the invention is an elastically deformable element consisting of a material with good thermal conductivity, i.e., which at least has a better thermal conductivity than the material of the elastic transmission element, e.g. rubber. According to the invention, said cooling element is arranged in the transmission element in such a way that it forms a heat bridge between the core zones in which maximum thermal stress occurs due to high dynamic loads, i.e., in the heat foci and in the outer zones of the transmission element, which are by nature cooler due to the dissipation of heat to the outside.
The special advantage of the invention results from the fact that owing to the arrangement of the cooling element, or cooling elements or heat conductors, the heat is dissipated from the critical zones into cooler zones in a targeted manner. In this connection, the mechanical and thermal properties of the cooling element may be adapted to the elastic material of the transmission element in such a way that no substantial change occurs in the elastic transmission properties of the coupling, i.e., that no undesirable weakening or hardening will occur. This can be accomplished in that the cooling element is elastically deformable to such an extent that it is capable of following the deformation of the transmission element.
Due to the fact that the cooling element overall provides for a more uniform temperature distribution within the elastic element, i.e., that fewer temperature gradients occur, the thermal wear, which rises overproportionately with the temperature, is significantly reduced, and the useful life of the transmission elements is thus distinctly prolonged.
The transmission elements designed as defined by the invention basically may be elements made of any desired material. However, according to the state of the art, particularly efficient transmission elements are known, which consist of a vulcanized rubber element to which metallic connecting elements are attached by vulcanizing. Such rubber elements are known, for example from the above-cited document DE 3710390 C2, and are characterized in general by special reliability. According to the invention, the cooling element is preferably vulcanized into the rubber as well, which ensures a safe support and good heat transfer from the heat foci.
According to an advantageous embodiment, provision is made that the cooling element is a cooling metal sheet with bending elasticity. It is preferably a thin metal sheet with good thermal conductivity which can be well-integrated in the transmission elemt with respect to its mechanical properties and dimensions.
According to an alternative embodiment, provision is made that the cooling element has a multitude of thermally conductive fibers. This may be either a flat or three-dimensional bundle of heat-conducting fibers arranged in parallel, or of thermally donductive fingers, for example wires, bands, flat sections, bars or the like, or also lamellae aligned like a comb, as well as also mats, net-like structures or the like. Such designs offer the advantage that they are mechanically particularly flexible.
Provision is made according to advantageous further developments of the invention that one side edge of the cooling element ends flush with the surface of the transmission element, i.e., that it terminates flush on said surface, or projects outwardly beyond the surface. In this way, it is accomplished that the heat withdrawn by the cooling element from the core zone is directly dissipated into the environment, resulting in a particularly efficie
Falz Ulrich
Walter Jurgen
Browne Lynne H.
Collard & Roe P.C.
Hackforth GmbH & Co. KG
Thompson Kenn
LandOfFree
Shaft coupling with cooling elements does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Shaft coupling with cooling elements, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Shaft coupling with cooling elements will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2530280