GB2311116A

GB2311116A - Torsionally rigid, flexurally elastic shaft coupling

Info

Publication number: GB2311116A
Application number: GB9704764A
Authority: GB
Inventors: Gunter Klingler; Christoph Dropmann; Johann Huber
Original assignee: Chr Mayr GmbH and Co KG
Current assignee: Chr Mayr GmbH and Co KG
Priority date: 1996-03-12
Filing date: 1997-03-07
Publication date: 1997-09-17
Anticipated expiration: 2017-03-07
Also published as: DE29604609U1; DE19709951C2; ITMI970542A1; GB2311116B; IT1290053B1; GB9704764D0; DE19709951C5; DE19709951A1

Abstract

The coupling comprises an assembly of axially clamped lamellae (5) at least one of which is surface-treated or surface-formed on one or both sides in order to increase the frictional torque with constant surface pressure and a given number of screws (7). The surface treatment may be carried out by abrasive blasting (using glass splinters or beads, sand or metal shot), rolling, corrugating or stamping and may be applied only to part of the area of a lamella.

Description

Torsionally rigid, flexural elastic shaft coupling The invention relates to a torsionally rigid, flexural elastic shaft coupling, in particular all-steel shaft coupling, having the features of the preamble of Patent Claim 1, as is known from the documents of DE-U 93 05 154.

In this type of shaft coupling, it is necessary to distinguish between two torque regions: 1. purely frictional torque transmission, in which case the torque is transmitted from hub to hub completely without play; 2. mixed positive and frictional torque transmission, in which case the frictional resistance is overcome and the torque is transmitted with play as a function of the tolerances designed. This is generally the case for torques which are greater than the corresponding nominal moment of the coupling.

With the second kind of torque transmission (mixed positive and frictional transmission), fatigue cracks were observed in the lamellae transversely through the holes of the connecting locations, since here unfavourable force rearrangements or stress concentrations are produced at the edge of the lamella holes.

In principle, it is sought to configure the frictional torque to be just as high as possible in couplings of the type mentioned above.

The amount of torque which can be transmitted frictionally depends on the number of screws, the pitch diameter of the lamella connection and on the maximum frictional shearing stress Tnx which can be transmitted in the region of the connection. This is determined by the coefficient of friction and the compressive stress p, in accordance with the equation T = x p.

The influence of tribocorrosion results in a fall in the stress which the lamellae can withstand in the long term.

The level of the tribocorrosion becomes greater as the microslippage and/or surface pressure increase.

Both a relatively high surface pressure and also microslippage (due to displacement of the coupling) are present at the edges of the clamping locations of a lamella assembly. Tribocorrosion is thus produced here, in the event of large displacements, and at the same time the permissible material stresses fall.

The object of the invention is to increase the frictionally transmissible torque of the coupling; at the same time, the surface pressure (screw preloading force) and the number of screws should be kept constant and the coefficient of friction between the lamellae and the adjacent components collar bush and ring should be increased.

This object is achieved by the characterizing features of Patent Claim 1. Further features of the invention emerge from the subclaims.

Abrasive blasting is known from the article by E. Spielvogel n Strahlmittel als Werkzeug" [Blasting agents as a tool), Part I in I-Lack, 50, 5/1982, pages 181 to 184.

By means of the surface treatment, in particular the glass-blasting, sand-blasting or shot-peening, at least a partial region of one or more lamellae is provided on one or both sides with a roughened surface, in the region of which the coefficient of friction and thus also the frictionally transmissible torque are increased as a result.

The surface treatment methods, and also the abrasive material, the operating pressure and the duration of the abrasive operation are selected such that there is a slight material deformation (material rearrangement) in the treated region. In the process, the thickness of the lamella increases in the treated region by (up to) several hundredths of a millimetre. This increase in thickness has a positive effect during the subsequent assembly of the lamella assembly.

In the process, the coefficient of friction, and with it also the frictionally transmissible torque, rise by a factor of 2 to 3. A coupling designed in this way is able to transmit purely frictionally a torque which is superproportionally high based on its size, without the risk of increasing the influence of tribocorrosion by increasing the screw preloading force.

An exemplary embodiment of the invention is shown in the drawings, in which: Figure la shows a diagrammatic longitudinal section through two flexural elastic, torsionally rigid couplings, Figure Ib shows a detail from Figure la; Figure 2 shows a front view of an annular-disc lamella according to the invention.

In accordance with Figure la, a hub 1 is coupled to a hub 9 via two lamella couplings A, B according to the invention and a sleeve 8 arranged between them in a torsionally rigid but angularly, axially and laterally mobile manner. Since the two lamella couplings A and B are identical, it is sufficient to describe one of them.

The lamella coupling A or B has an assembly of annular or segment-shaped lamellae 5, which are axially clamped together. To this end, the lamellae have a plurality of axial bores 5a which are distributed over the periphery and into which the clamping bushes 6 are inserted. The lamella assembly 5 bears on one side against an end-side collar 6b of the clamping bush 6, which collar is of shallow conical form on its other side. On the other side, the lamella assembly bears against a ring 4 placed on the clamping bush 6. If the free end of the clamping bush 6 is flanged at the edges, as shown, then the lamella assembly 5 is fixed on the clamping bushes 6 and the whole can be installed as a unit or treated as a replacement part. The lamella assembly 5 is installed in the coupling by means of the screws 7 and the nuts 2.

Washers 3 may be arranged between the screw head 7 and the ring 4.

As shown in Fig. lb, a flange la of the hub 1 has recesses lb, the head of the screw 7 being situated in one of these recesses lb, an undamaged section of a flange 8a of the sleeve 8 being situated opposite each of these recesses as a bearing surface for the nut 2; for the next screw 7 in the peripheral direction, the conditions are mirror-inverted, i.e. its head lies in a recess of this type of the flange 8a as is shown, for example, on the lower edge of the diagram in Fig. la on the radially opposite side of the coupling A.

According to the invention, at least one lamella 5 is surface-treated or surface-formed on one or both sides.

The surface treatment may be limited to a partial region 5b. In accordance with Figure 2, such a partial region is designed in the region of, preferably provided annularly concentrically around the bore 5a, with the diameter of the ring 4 or of the clamping bush 6. In the event of an increase in thickness of the lamellae due to the surface treatment, for example the blasting operation, the partial region 5b may also be designed with a smaller diameter than that of the ring 4 or of the collar 6b. A likewise surface-treated region Sc with particular surface hardening may extend around the region Sb. The region Sc has an external diameter which is greater than the diameter of the ring 4 or of the collar 6b.

Processes which can be used for the surface treatment and/or forming are abrasive blasting, rolling, corrugating or stamping, or also any other equivalent mechanical process or chemical process (e.g. chemical nickelizing) by means of which a suitable surface structure can be achieved.

In the event of high displacement values and long operating time of the coupling, tribocorrosion preferentially occurs at the edges of the clamping locations of a lamella assembly. This leads to the permissible material stresses of the lamellae falling. This fall in the fatigue strength values can be reduced or prevented by increasing the surface hardness and by induced residual compressive stress.

Those locations of the lamellae which are subject to severe tribocorrosion in the immediate vicinity of the clamping must additionally, due to the displacement of the coupling, withstand the highest material stresses.

Owing to the high tensile stress component of the edge lamellae, these edge lamellae of the lamella assembly often break. The displaceability of such a lamella assembly can be increased by induced residual compressive stresses on the individual lamellae, since the tensile stresses effective in the lamellae (in the event of displacement of the coupling), in particular in the edge lamellae, are reduced by the surface treatment, for example the abrasive blasting.

By extending the surface-treated area of the lamella by the region Sc, the displaceability of such a coupling can be increased for the reasons mentioned above.

Claims

CLAIMS: 1. A torsionally rigid, flexurally elastic shaft coupling, having an assembly of lamellae which are axially clamped together, wherein at least one of the lamellae is surface-treated or surface-formed on one or both sides.
2. A coupling according to claim 1, wherein the surface treatment is carried out by abrasive blasting.
3. A coupling according to claim 1, wherein the surface treatment is carried out by rolling.
4. A coupling according to claim 1, wherein the surface treatment is carried out by corrugating.
5. A coupling according to claim 1, wherein the surface treatment is carried out by stamping.
6. A coupling according to one of claims 1, 2, 3, 4 or 5, wherein the surface treatment is carried out on only a partial area of the lamella.
7. A coupling according to one of claims 1 to 6, including axial bores in the lamellae, through which bores clamping bushes and/or screws extend, wherein the partial area of the surface treatment lies in the region of the bore.
8. A coupling according to claim 7, wherein the partial area concentrically surrounds the bore.
9. A coupling according to claim 7 or 8, wherein a likewise surface-treated region of particular surface hardening and/or deformation surrounds the partial area.
10. A coupling according to one of claim 2 and 6 to 9, wherein the abrasive blasting treatment is carried out by means of glass splinters, glass beads, sand or metal shot.
11. A coupling according to one of claims 1 to 10, wherein an application of material and thus an increase in thickness of the lamella is effected by material rearrangement in the region of the surface treatment, in particular abrasive blasting.
12. A coupling according to claims 1 to 11, wherein the lamellae are annular or segment-shaped.
13. A coupling according to any preceding claim, wherein the coupling is an all-steel shaft coupling.
14. A torsionally rigid flexurally elastic shaft coupling, substantially as hereinbefore described, or as illustrated in, the accompanying drawings.