Elastic shaft coupling

Details Elastic shaft coupling Elastic shaft coupling

2001-02-05

2003-09-23

Binda, Greg (Department: 3679)

Rotary shafts, gudgeons, housings, and flexible couplings for ro

Having heating or cooling means

C464S092000

Reexamination Certificate

active

06623362

ABSTRACT:

BACKGROUND
The present invention relates to an elastic shaft coupling which, as a transmission element, has at least one torsion element with an elastically deformable elastomer body to which axial flange connections are attached in a fixed manner on the sides upon which force is applied and removed.
The transmission elements are subjected to substantial dynamical stress under the load changes typically occurring during operation. Such dynamical stress is reflected on the one hand by the considerable elongation stress of the connection between the connection flanges and the elastomer body. On the other hand, viscoelastic effects, i.e. inner friction of the elastomer materials, lead to conversion of mechanical energy into heat. This may lead to the occurrence of local thermal peaks, so called heat clusters because of the relatively low thermal conductivity of the rubber material. Material-specific limit temperatures should basically not be exceeded in this connection because that may otherwise lead to local damage. This applies to a special degree to the zone of the outer jacket surfaces because the expansion reached the highest values in said zone. The result thereof is particularly high load acting on the transition between the rubber-and-metal joint, which, of course, is noteworthy also because of the notch effect occurring on the outer limit edge. Furthermore, heating occurring on the surface of the material, which is accompanied by a mechanical load, should not exceed preset limit values because aging processes occurring there would otherwise be accelerated.
The problems explained above have been successfully counteracted in the prior art through constructional developments, so that rubber couplings are viewed since a fairly long time as entirely reliable construction elements with advantageous operating properties. Through particularly constructive developments, local loads are reduced in that connection to a harmless measure. For this purpose, the occurrence of local mechanical or thermal loads is either limited directly, and/or provision is made for effective cooling. A few measures that are advantageous in this regard are specified, for example in DE 37 10 390 C2, where the connection flanges are provided with the shape of the shell of a cone, so that the rubber body is provided with a V-shaped cross section that widens linearly outwards. Owing to the fact that the axial width of the elastomer body increases radially viewed from the inside to the outside, the outer fibers have a greater elastic length. The lower local expansion resulting therefrom is advantageous in view of the development of heat and the load to which the rubber-metal interfaces are subjected.
The collected lost heat is effectively dissipated via other measures such as a segmented design of the transmission elements, as well as by providing for through-extending cooling windows.
However, the trend to increasingly higher power densities, combined at the same time with a smaller installation space requires a more far-reaching optimization of the elastomer couplings known in the prior art.
An elastic shaft coupling is known from U.S. Pat. No. 2,742,769 which has an elastomer body between two connection flanges. However, it has been found that such elastomer bodies quickly fail in the presence of varying torques mainly on the outer radius even though the torque to be withstood stationarily is not reached.
An elastic shaft coupling with elastomer bodies of the type used in smaller mechanical drives is introduced also in U.S. Pat. No. 2,295,316. However, the shape of the elastomer bodies between the ends of the shaft leads to the fact that the elastomer body is destroyed by local overloads especially at the elastomer-metal interface.
For solving said problem the invention proposes that the axial width of the elastomer body be increased viewed radially from the inside to the outside more than proportionally at least by sections whereby the axial connection flanges (
2
) have chalice- or bell-shaped shapes in a continuously sweeping form relative to each other without a bend in the elastomer-metal interface.
According to the invention, the cross section of the elastomer body has at least an inner and one outer radial zone, whereby the radial width grows sooner in the outer than in the inner zone as the radius increases. While the width of the elastomer body in the prior art increases only linearly over the entire cross section because of the cone shell-shaped connection flanges, and therefore proportionally, the effective elastic width increases more rapidly to the outside according to the invention, at least by sections.
According to a particularly advantageous embodiment of the invention, provision is made that the cross section of the elastomer body is widened in the form of a bell viewed radially from the inside to the outside. The bell-shaped design, which could be called also chalice- or tulip-shaped, means there is a continuously curved, rounded transition between the individual zones. Avoiding a bent expanse of the connection flanges leads to a uniform load acting on the rubber-metal interface, and unsteadiness is avoided to the greatest possible extent.
The invention, of course, can be realized in the same way both on a through-extending, ring-shaped and a segmented elastomer body.
The special advantage of the invention ensues from the fact that the elastic length in the path in the outer zones is coordinated in a superior way with the mechanical and thermal load occurring there more than proportionally with the radius. Furthermore, the outer jacket surface of the elastomer body is enlarged in this connection to an extent such that lower local elongations issue, and superior dissipation of heat into the ambient air takes place at the same time. The aging effects mentioned above are clearly reduced in this way. The given amount of the overall cross sectional area of the elastomer body results overall in a more homogeneous load. Therefore, the transmittable power density is increased as compared to the designs of couplings known, for example from DE 37 10 390 C2 already cited above, and also DE 33 10 695 C2. This means that the coupling can be designed smaller for a given torque and consequently takes up less installation space. As an alternative it is possible in connection with a coupling with unchanged dimensions to transmit an accordingly high power.
For solving the problems explained above, provision is made according to a particularly advantageous, alternative embodiment that the transmission element has at least one inner elastomer body and at least one outer elastomer body, whereby the elastomer bodies are arranged coaxially with the axis of the coupling and with a radial spacing from each other and have a common connection flange on the driving side and the driven side.
Such an embodiment as defined by the invention can be realized in the same way with couplings according to the prior art cited above, and in conjunction with the elastomer bodies that widen toward the outside more than proportionally as defined by the invention.
As opposed to the prior art, a torsion element designed as defined by the invention has one-piece elastomer bodies not only in the radial direction, but at least two or more ring- or segment-shaped separate elastomer bodies that have a radial spacing from each other, whereby said elastomer bodies each have a radially through-extending, common connection flange both on the driving side and the driven side. This means that the outer elastomer bodies surround the inner elastomer bodies, thereby forming cooling channels that extend through in the peripheral direction.
A special advantage of the invention issues from the fact that the air-flushed cooling channels extending through in the peripheral direction are axially limited by the metallic connection flanges. The heat collected under dynamic load in the poorly thermally conductive rubber material of the elastomer bodies is dissipated in a particularly good way in this manner on account of the fact that air flowing along

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